The Giardia cell cycle progresses independently of the anaphase-promoting complex

PubMed Central

Gourguechon, Stéphane; Holt, Liam J.; Cande, W. Zacheus

2013-01-01

Summary Most cell cycle regulation research has been conducted in model organisms representing a very small part of the eukaryotic domain. The highly divergent human pathogen Giardia intestinalis is ideal for studying the conservation of eukaryotic pathways. Although Giardia has many cell cycle regulatory components, its genome lacks all anaphase-promoting complex (APC) components. In the present study, we show that a single mitotic cyclin in Giardia is essential for progression into mitosis. Strikingly, Giardia cyclin B lacks the conserved N-terminal motif required for timely degradation mediated by the APC and ubiquitin conjugation. Expression of Giardia cyclin B in fission yeast is toxic, leading to a prophase arrest, and this toxicity is suppressed by the addition of a fission yeast degradation motif. Cyclin B is degraded during mitosis in Giardia cells, but this degradation appears to be independent of the ubiquitination pathway. Other putative APC substrates, aurora and polo-like kinases, also show no evidence of ubiquitination. This is the first example of mitosis not regulated by the APC and might reflect an evolutionary ancient form of cell cycle regulation. PMID:23525017

The Rho GTPase effector ROCK regulates cyclin A, cyclin D1, and p27Kip1 levels by distinct mechanisms.

PubMed

Croft, Daniel R; Olson, Michael F

2006-06-01

The members of the Rho GTPase family are well known for their regulation of actin cytoskeletal structures. In addition, they influence progression through the cell cycle. The RhoA and RhoC proteins regulate numerous effector proteins, with a central and vital signaling role mediated by the ROCK I and ROCK II serine/threonine kinases. The requirement for ROCK function in the proliferation of numerous cell types has been revealed by studies utilizing ROCK-selective inhibitors such as Y-27632. However, the mechanisms by which ROCK signaling promotes cell cycle progression have not been thoroughly characterized. Using a conditionally activated ROCK-estrogen receptor fusion protein, we found that ROCK activation is sufficient to stimulate G1/S cell cycle progression in NIH 3T3 mouse fibroblasts. Further analysis revealed that ROCK acts via independent pathways to alter the levels of cell cycle regulatory proteins: cyclin D1 and p21(Cip1) elevation via Ras and the mitogen-activated protein kinase pathway, increased cyclin A via LIM kinase 2, and reduction of p27(Kip1) protein levels. Therefore, the influence of ROCK on cell cycle regulatory proteins occurs by multiple independent mechanisms.

Glucose Regulates Cyclin D2 Expression in Quiescent and Replicating Pancreatic β-Cells Through Glycolysis and Calcium Channels

PubMed Central

Salpeter, Seth J.; Klochendler, Agnes; Weinberg-Corem, Noa; Porat, Shay; Granot, Zvi; Shapiro, A. M. James; Magnuson, Mark A.; Eden, Amir; Grimsby, Joseph; Glaser, Benjamin

2011-01-01

Understanding the molecular triggers of pancreatic β-cell proliferation may facilitate the development of regenerative therapies for diabetes. Genetic studies have demonstrated an important role for cyclin D2 in β-cell proliferation and mass homeostasis, but its specific function in β-cell division and mechanism of regulation remain unclear. Here, we report that cyclin D2 is present at high levels in the nucleus of quiescent β-cells in vivo. The major regulator of cyclin D2 expression is glucose, acting via glycolysis and calcium channels in the β-cell to control cyclin D2 mRNA levels. Furthermore, cyclin D2 mRNA is down-regulated during S-G2-M phases of each β-cell division, via a mechanism that is also affected by glucose metabolism. Thus, glucose metabolism maintains high levels of nuclear cyclin D2 in quiescent β-cells and modulates the down-regulation of cyclin D2 in replicating β-cells. These data challenge the standard model for regulation of cyclin D2 during the cell division cycle and suggest cyclin D2 as a molecular link between glucose levels and β-cell replication. PMID:21521747

Disruption of the G1/S Transition in Human Papillomavirus Type 16 E7-Expressing Human Cells Is Associated with Altered Regulation of Cyclin E

PubMed Central

Martin, Larry G.; Demers, G. William; Galloway, Denise A.

1998-01-01

The development of neoplasia frequently involves inactivation of the p53 and retinoblastoma (Rb) tumor suppressor pathways and disruption of cell cycle checkpoints that monitor the integrity of replication and cell division. The human papillomavirus type 16 (HPV-16) oncoproteins, E6 and E7, have been shown to bind p53 and Rb, respectively. To further delineate the mechanisms by which E6 and E7 affect cell cycle control, we examined various aspects of the cell cycle machinery. The low-risk HPV-6 E6 and E7 proteins did not cause any significant change in the levels of cell cycle proteins analyzed. HPV-16 E6 resulted in very low levels of p53 and p21 and globally elevated cyclin-dependent kinase (CDK) activity. In contrast, HPV-16 E7 had a profound effect on several aspects of the cell cycle machinery. A number of cyclins and CDKs were elevated, and despite the elevation of the levels of at least two CDK inhibitors, p21 and p16, CDK activity was globally increased. Most strikingly, cyclin E expression was deregulated both transcriptionally and posttranscriptionally and persisted at high levels in S and G2/M. Transit through G1 was shortened by the premature activation of cyclin E-associated kinase activity. Elevation of cyclin E levels required both the CR1 and CR2 domains of E7. These data suggest that cyclin E may be a critical target of HPV-16 E7 in the disruption of G1/S cell cycle progression and that the ability of E7 to regulate cyclin E involves activities in addition to the release of E2F. PMID:9444990

Correlation between Cyclin Dependent Kinases and Artemisinin-Induced Dormancy in Plasmodium falciparum In Vitro

PubMed Central

Gray, Karen-Ann; Gresty, Karryn J.; Chen, Nanhua; Zhang, Veronica; Gutteridge, Clare E.; Peatey, Christopher L.; Chavchich, Marina; Waters, Norman C.; Cheng, Qin

2016-01-01

Background Artemisinin-induced dormancy provides a plausible explanation for recrudescence following artemisinin monotherapy. This phenomenon shares similarities with cell cycle arrest where cyclin dependent kinases (CDKs) and cyclins play an important role. Methods Transcription profiles of Plasmodium falciparum CDKs and cyclins before and after dihydroartemisinin (DHA) treatment in three parasite lines, and the effect of CDK inhibitors on parasite recovery from DHA-induced dormancy were investigated. Results After DHA treatment, parasites enter a dormancy phase followed by a recovery phase. During the dormancy phase parasites up-regulate pfcrk1, pfcrk4, pfcyc2 and pfcyc4, and down-regulate pfmrk, pfpk5, pfpk6, pfcrk3, pfcyc1 and pfcyc3. When entering the recovery phase parasites immediately up-regulate all CDK and cyclin genes. Three CDK inhibitors, olomoucine, WR636638 and roscovitine, produced distinct effects on different phases of DHA-induced dormancy, blocking parasites recovery. Conclusions The up-regulation of PfCRK1 and PfCRK4, and down regulation of other CDKs and cyclins correlate with parasite survival in the dormant state. Changes in CDK expression are likely to negatively regulate parasite progression from G1 to S phase. These findings provide new insights into the mechanism of artemisinin-induced dormancy and cell cycle regulation of P. falciparum, opening new opportunities for preventing recrudescence following artemisinin treatment. PMID:27326764

Cyclin A recruits p33cdk2 to the cellular transcription factor DRTF1.

PubMed

Bandara, L R; Adamczewski, J P; Zamanian, M; Poon, R Y; Hunt, T; Thangue, N B

1992-01-01

Cyclins are regulatory molecules that undergo periodic accumulation and destruction during each cell cycle. By activating p34cdc2 and related kinase subunits they control important events required for normal cell cycle progression. Cyclin A, for example, regulates at least two distinct kinase subunits, the mitotic kinase subunit p34cdc2 and related subunit p33cdk2, and is widely believed to be necessary for progression through S phase. However, cyclin A also forms a stable complex with the cellular transcription factor DRTF1 and thus may perform other functions during S phase. DRTF1, in addition, associates with the tumour suppressor retinoblastoma (Rb) gene product and the Rb-related protein p107. We now show, using biologically active fusion proteins, that cyclin A can direct the binding of the cdc2-like kinase subunit, p33cdk2, to complexed DRTF1, containing either Rb or p107, as well as activate its histone H1 kinase activity. Cyclin A cannot, however, direct p34cdc2 to the DRTF1 complex and we present evidence suggesting that the stability of the cyclin A-p33cdk2 complex is influenced by DRTF1 or an associated protein. Cyclin A, therefore, serves as an activating and targeting subunit of p33cdk2. The ability of cyclin A to activate and recruit p33cdk2 to DRTF1 may play an important role in regulating cell cycle progression and moreover defines a mechanism for coupling cell-cycle events to transcriptional initiation.

Cyclin A and the retinoblastoma gene product complex with a common transcription factor.

PubMed

Bandara, L R; Adamczewski, J P; Hunt, T; La Thangue, N B

1991-07-18

The retinoblastoma gene (Rb) product is a negative regulator of cellular proliferation, an effect that could be mediated in part at the transcriptional level through its ability to complex with the sequence-specific transcription factor DRTF1. This interaction is modulated by adenovirus E1a, which sequesters the Rb protein and several other cellular proteins, including cyclin A, a molecule that undergoes cyclical accumulation and destruction during each cell cycle and which is required for cell cycle progression. Cyclin A, which also complexes with DRTF1, facilitates the efficient assembly of the Rb protein into the complex. This suggests a role for cyclin A in regulating transcription and defines a transcription factor through which molecules that regulate the cell cycle in a negative fashion, such as Rb, and in a positive fashion, such as cyclin A, interact. Mutant loss-of-function Rb alleles, which occur in a variety of tumour cells, also fail to complex with E1a and large T antigen. Here we report on a naturally occurring loss-of-function Rb allele encoding a protein that fails to complex with DRTF1. This might explain how mutation in the Rb gene prevents negative growth control.

Enterolactone induces G1-phase cell cycle arrest in non-small cell lung cancer cells by down-regulating cyclins and cyclin-dependent kinases

PubMed Central

Chikara, Shireen; Lindsey, Kaitlin; Dhillon, Harsharan; Mamidi, Sujan; Kittilson, Jeffrey; Christofidou-Solomidou, Melpo; Reindl, Katie M.

2017-01-01

Flaxseed is a rich source of the plant lignan secoisolariciresinol diglucoside (SDG) which is metabolized into mammalian lignans enterodiol (ED) and enterolactone (EL) in the digestive tract. The anti-cancer properties of these lignans have been demonstrated for various cancer types, but have not been studied for lung cancer. In this study we investigated the anti-cancer effects of EL for several non-small cell lung cancer (NSCLC) cell lines of various genetic backgrounds. EL inhibited the growth of A549, H441, and H520 lung cancer cells in concentration- and time-dependent manners. The anti-proliferative effects of EL for lung cancer cells were not due to enhanced cell death, but rather due to G1-phase cell cycle arrest. Molecular studies revealed that EL- decreased mRNA or protein expression levels of the G1-phase promoters cyclin D1, cyclin E, cyclin-dependent kinases (CDK)-2, -4, and -6, and p-cdc25A; decreased phosphorylated retinoblastoma (p-pRb) protein levels; and simultaneously increased levels of p21WAF1/CIP1, a negative regulator of the G1-phase. The results suggest that EL inhibits the growth of NSCLC cell lines by down-regulating G1-phase cyclins and CDKs, and up-regulating p21WAF1/CIP1, which leads to G1-phase cell cycle arrest. Therefore, EL may hold promise as an adjuvant treatment for lung cancer therapy. PMID:28323486

miR-340 inhibits glioblastoma cell proliferation by suppressing CDK6, cyclin-D1 and cyclin-D2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Xuesong; Gong, Xuhai; Chen, Jing

Glioblastoma development is often associated with alteration in the activity and expression of cell cycle regulators, such as cyclin-dependent kinases (CKDs) and cyclins, resulting in aberrant cell proliferation. Recent studies have highlighted the pivotal roles of miRNAs in controlling the development and growth of glioblastoma. Here, we provide evidence for a function of miR-340 in the inhibition of glioblastoma cell proliferation. We found that miR-340 is downregulated in human glioblastoma tissue samples and several established glioblastoma cell lines. Proliferation and neurosphere formation assays revealed that miR-340 plays an oncosuppressive role in glioblastoma, and that its ectopic expression causes significant defectmore » in glioblastoma cell growth. Further, using bioinformatics, luciferase assay and western blot, we found that miR-340 specifically targets the 3′UTRs of CDK6, cyclin-D1 and cyclin-D2, leading to the arrest of glioblastoma cells in the G0/G1 cell cycle phase. Confirming these results, we found that re-introducing CDK6, cyclin-D1 or cyclin-D2 expression partially, but significantly, rescues cells from the suppression of cell proliferation and cell cycle arrest mediated by miR-340. Collectively, our results demonstrate that miR-340 plays a tumor-suppressive role in glioblastoma and may be useful as a diagnostic biomarker and/or a therapeutic avenue for glioblastoma. - Highlights: • miR-340 is downregulated in glioblastoma samples and cell lines. • miR-340 inhibits glioblastoma cell proliferation. • miR-340 directly targets CDK6, cyclin-D1, and cyclin-D2. • miR-340 regulates glioblastoma cell proliferation via CDK6, cyclin-D1 and cyclin-D2.« less

Low concentrations of methylmercury inhibit neural progenitor cell proliferation associated with up-regulation of glycogen synthase kinase 3β and subsequent degradation of cyclin E in rats

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fujimura, Masatake, E-mail: fujimura@nimd.go.jp; Usuki, Fusako

2015-10-01

Methylmercury (MeHg) is an environmental neurotoxicant. The developing nervous system is susceptible to low concentrations of MeHg; however, the effect of MeHg on neural progenitor cell (NPC) proliferation, a key stage of neurogenesis during development, remains to be clarified. In this study, we investigated the effect of low concentrations of MeHg on NPCs by using a primary culture system developed using the embryonic rat cerebral cortex. NPC proliferation was suppressed 48 h after exposure to 10 nM MeHg, but cell death was not observed. Western blot analyses for cyclins A, B, D1, and E demonstrated that MeHg down-regulated cyclin E,more » a promoter of the G1/S cell cycle transition. Cyclin E has been shown to be degraded following the phosphorylation by glycogen synthase kinase 3β (GSK-3β). The time course study showed that GSK-3β was up-regulated 3 h after exposure to 10 nM MeHg, and cyclin E degradation 48 h after MeHg exposure. We further demonstrated that GSK-3β inhibitors, lithium and SB-415286, suppressed MeHg-induced inhibition of NPC proliferation by preventing cyclin E degradation. These results suggest that the inhibition of NPC proliferation induced by low concentration of MeHg was associated with up-regulation of GSK-3β at the early stage and subsequent degeneration of cyclin E. - Highlights: • NPC proliferation was suppressed by 10 nM MeHg, but cell death was not observed. • MeHg induced down-regulation of cyclin E, a promoter of cell cycle progression. • GSK-3β was up-regulated by 10 nM MeHg, leading to cyclin E degradation. • GSK-3β inhibitors suppressed MeHg-induced degradation of cyclin E.« less

The Kinetics of G2 and M Transitions Regulated by B Cyclins

PubMed Central

Huang, Yehong; Sramkoski, R. Michael; Jacobberger, James W.

2013-01-01

B cyclins regulate G2-M transition. Because human somatic cells continue to cycle after reduction of cyclin B1 (cycB1) or cyclin B2 (cycB2) by RNA interference (RNAi), and because cycB2 knockout mice are viable, the existence of two genes should be an optimization. To explore this idea, we generated HeLa BD™ Tet-Off cell lines with inducible cyclin B1- or B2-EGFP that were RNAi resistant. Cultures were treated with RNAi and/or doxycycline (Dox) and bromodeoxyuridine. We measured G2 and M transit times and 4C cell accumulation. In the absence of ectopic B cyclin expression, knockdown (kd) of either cyclin increased G2 transit. M transit was increased by cycB1 kd but decreased by cycB2 depletion. This novel difference was further supported by time-lapse microscopy. This suggests that cycB2 tunes mitotic timing, and we speculate that this is through regulation of a Golgi checkpoint. In the presence of endogenous cyclins, expression of active B cyclin-EGFPs did not affect G2 or M phase times. As previously shown, B cyclin co-depletion induced G2 arrest. Expression of either B cyclin-EGFP completely rescued knockdown of the respective endogenous cyclin in single kd experiments, and either cyclin-EGFP completely rescued endogenous cyclin co-depletion. Most of the rescue occurred at relatively low levels of exogenous cyclin expression. Therefore, cycB1 and cycB2 are interchangeable for ability to promote G2 and M transition in this experimental setting. Cyclin B1 is thought to be required for the mammalian somatic cell cycle, while cyclin B2 is thought to be dispensable. However, residual levels of cyclin B1 or cyclin B2 in double knockdown experiments are not sufficient to promote successful mitosis, yet residual levels are sufficient to promote mitosis in the presence of the dispensible cyclin B2. We discuss a simple model that would explain most data if cyclin B1 is necessary. PMID:24324638

Transcriptional and post-transcriptional down-regulation of cyclin D1 contributes to C6 glioma cell differentiation induced by forskolin.

PubMed

He, Songmin; Zhu, Wenbo; Zhou, Yuxi; Huang, Yijun; Ou, Yanqiu; Li, Yan; Yan, Guangmei

2011-09-01

Malignant gliomas are the most common and lethal intracranial tumors, and differentiation therapy shows great potential to be a promising candidate for their treatment. Here, we have elaborated that a PKA activator, forskolin, represses cell growth via cell cycle arrest in the G0/G1 phase and induces cell differentiation characteristic with elongated processes and restoration of GFAP expression. In mechanisms, we verified that forskolin significantly diminishes the mRNA and protein level of a key cell cycle regulator cyclin D1, and maintenance of low cyclin D1 expression level was required for forskolin-induced proliferation inhibition and differentiation by gain and loss of function approaches. In addition, that forskolin down-regulated the cyclin D1 by proteolytic (post-transcriptional) mechanisms was dependent on GSK-3β activation at Ser9. The pro-differentiation activity of forskolin and related molecular mechanisms imply that forskolin can be developed into a candidate for the future in differentiation therapy of glioma, and cyclin D1 is a promising target for pro-differentiation strategy. Copyright © 2011 Wiley-Liss, Inc.

Inhibition of Rac1 activity induces G1/S phase arrest through the GSK3/cyclin D1 pathway in human cancer cells.

PubMed

Liu, Linna; Zhang, Hongmei; Shi, Lei; Zhang, Wenjuan; Yuan, Juanli; Chen, Xiang; Liu, Juanjuan; Zhang, Yan; Wang, Zhipeng

2014-10-01

Rac1 has been shown to regulate the cell cycle in cancer cells. Yet, the related mechanism remains unclear. Thus, the present study aimed to investigate the mechanism involved in the regulation of G1/S phase transition by Rac1 in cancer cells. Inhibition of Rac1 by inhibitor NSC23766 induced G1/S phase arrest and inhibited the proliferation of A431, SW480 and U2-OS cells. Suppression of GSK3 by shRNA partially rescued G1/S phase arrest and inhibition of proliferation. Incubation of cells with NSC23766 reduced p-AKT and inactivated p-GSK3α and p-GSK3β, increased p-cyclin D1 expression and decreased the level of cyclin D1 protein. Consequently, cyclin D1 targeting transcriptional factor E2F1 expression, which promotes G1 to S phase transition, was also reduced. In contrast, constitutive active Rac1 resulted in increased p-AKT and inactivated p-GSK3α and p-GSK3β, decreased p-cyclin D1 expression and enhanced levels of cyclin D1 and E2F1 expression. Moreover, suppression of GSK3 did not alter p-AKT or Rac1 activity, but decreased p-cyclin D1 and increased total cyclin D1 protein. However, neither Rac1 nor GSK3 inhibition altered cyclin D1 at the RNA level. Moreover, after inhibition of Rac1 or GSK3 following proteasome inhibitor MG132 treatment, cyclin D1 expression at the protein level remained constant, indicating that Rac1 and GSK3 may regulate cyclin D1 turnover through phosphorylation and degradation. Therefore, our findings suggest that inhibition of Rac1 induces cell cycle G1/S arrest in cancer cells by regulation of the GSK3/cyclin D1 pathway.

Menadione induces G2/M arrest in gastric cancer cells by down-regulation of CDC25C and proteasome mediated degradation of CDK1 and cyclin B1

PubMed Central

Lee, Min Ho; Cho, Yoonjung; Kim, Do Hyun; Woo, Hyun Jun; Yang, Ji Yeong; Kwon, Hye Jin; Yeon, Min Ji; Park, Min; Kim, Sa-Hyun; Moon, Cheol; Tharmalingam, Nagendran; Kim, Tae Ue; Kim, Jong-Bae

2016-01-01

Menadione (vitamin K3) has been reported to induce apoptotic cell death and growth inhibition in various types of cancer cells. However, involvement of menadione in cell cycle control has not been considered in gastric cancer cells yet. In the current study, we have investigated whether menadione is involved in the cell cycle regulation and suppression of growth in gastric cancer cells. In the cell cycle analysis, we found that menadione induced G2/M cell cycle arrest in AGS cells. To elucidate the underlying mechanism, we investigated the cell cycle regulatory molecules involved in the G2/M cell cycle transition. After 24 h of menadione treatment, the protein level of CDK1, CDC25C and cyclin B1 in AGS cells was decreased in a menadione dose-dependent manner. In the time course experiment, the protein level of CDC25C decreased in 6 h, and CDK1and cyclin B1 protein levels began to decrease after 18 h of menadione treatment. We found that mRNA level of CDC25C decreased by menadione treatment in 6 h. Menadione did not have an influence on mRNA level of CDK1 and cyclin B1 though the protein levels were decreased. However, the decreased protein levels of CDK1 and cyclin B1 were recovered by inhibition of proteasome. Collectively, these results suggest that menadione inhibits growth of gastric cancer cells by reducing expression of CDC25C and promoting proteasome mediated degradation of CDK1 and cyclin B1 thereby blocking transition of the cell cycle from G2 phase to M phase. PMID:28077999

New roles for p21 and p27 cell-cycle inhibitors: a function for each cell compartment?

PubMed

Coqueret, Olivier

2003-02-01

Cell division relies on the activation of cyclins, which bind to cyclin-dependent kinases (CDKs) to induce cell-cycle progression towards S phase and later to initiate mitosis. Since uncontrolled cyclin-dependent kinase activity is often the cause of human cancer, their function is tightly regulated by cell-cycle inhibitors such as the p21 and p27 Cip/Kip proteins. Following anti-mitogenic signals or DNA damage, p21 and p27 bind to cyclin-CDK complexes to inhibit their catalytic activity and induce cell-cycle arrest. Interestingly, recent discoveries suggest that p21 and p27 might have new activities that are unrelated to their function as CDK inhibitors. The identification of new targets of Cip/Kip proteins as well as evidence of Cip/Kip cytoplasmic relocalization have revealed unexpected functions for these proteins in the control of CDK activation, in the regulation of apoptosis and in transcriptional activation. This article discusses recent insights into these possible additional functions of p21 and p27.

Phosphorylation of eukaryotic elongation factor 2 (eEF2) by cyclin A-cyclin-dependent kinase 2 regulates its inhibition by eEF2 kinase.

PubMed

Hizli, Asli A; Chi, Yong; Swanger, Jherek; Carter, John H; Liao, Yi; Welcker, Markus; Ryazanov, Alexey G; Clurman, Bruce E

2013-02-01

Protein synthesis is highly regulated via both initiation and elongation. One mechanism that inhibits elongation is phosphorylation of eukaryotic elongation factor 2 (eEF2) on threonine 56 (T56) by eEF2 kinase (eEF2K). T56 phosphorylation inactivates eEF2 and is the only known normal eEF2 functional modification. In contrast, eEF2K undergoes extensive regulatory phosphorylations that allow diverse pathways to impact elongation. We describe a new mode of eEF2 regulation and show that its phosphorylation by cyclin A-cyclin-dependent kinase 2 (CDK2) on a novel site, serine 595 (S595), directly regulates T56 phosphorylation by eEF2K. S595 phosphorylation varies during the cell cycle and is required for efficient T56 phosphorylation in vivo. Importantly, S595 phosphorylation by cyclin A-CDK2 directly stimulates eEF2 T56 phosphorylation by eEF2K in vitro, and we suggest that S595 phosphorylation facilitates T56 phosphorylation by recruiting eEF2K to eEF2. S595 phosphorylation is thus the first known eEF2 modification that regulates its inhibition by eEF2K and provides a novel mechanism linking the cell cycle machinery to translational control. Because all known eEF2 regulation is exerted via eEF2K, S595 phosphorylation may globally couple the cell cycle machinery to regulatory pathways that impact eEF2K activity.

Phosphorylation of Eukaryotic Elongation Factor 2 (eEF2) by Cyclin A–Cyclin-Dependent Kinase 2 Regulates Its Inhibition by eEF2 Kinase

PubMed Central

Hizli, Asli A.; Chi, Yong; Swanger, Jherek; Carter, John H.; Liao, Yi; Welcker, Markus; Ryazanov, Alexey G.

2013-01-01

Protein synthesis is highly regulated via both initiation and elongation. One mechanism that inhibits elongation is phosphorylation of eukaryotic elongation factor 2 (eEF2) on threonine 56 (T56) by eEF2 kinase (eEF2K). T56 phosphorylation inactivates eEF2 and is the only known normal eEF2 functional modification. In contrast, eEF2K undergoes extensive regulatory phosphorylations that allow diverse pathways to impact elongation. We describe a new mode of eEF2 regulation and show that its phosphorylation by cyclin A–cyclin-dependent kinase 2 (CDK2) on a novel site, serine 595 (S595), directly regulates T56 phosphorylation by eEF2K. S595 phosphorylation varies during the cell cycle and is required for efficient T56 phosphorylation in vivo. Importantly, S595 phosphorylation by cyclin A-CDK2 directly stimulates eEF2 T56 phosphorylation by eEF2K in vitro, and we suggest that S595 phosphorylation facilitates T56 phosphorylation by recruiting eEF2K to eEF2. S595 phosphorylation is thus the first known eEF2 modification that regulates its inhibition by eEF2K and provides a novel mechanism linking the cell cycle machinery to translational control. Because all known eEF2 regulation is exerted via eEF2K, S595 phosphorylation may globally couple the cell cycle machinery to regulatory pathways that impact eEF2K activity. PMID:23184662

D-type Cyclins are important downstream effectors of cytokine signaling that regulate the proliferation of normal and neoplastic mammary epithelial cells

PubMed Central

Zhang, Qian; Sakamoto, Kazuhito; Wagner, Kay-Uwe

2013-01-01

In response to the ligand-mediated activation of cytokine receptors, cells decide whether to proliferate or to undergo differentiation. D-type Cyclins (Cyclin D1, D2, or D3) and their associated Cyclin-dependent Kinases (CDK4, CDK6) connect signals from cytokines to the cell cycle machinery, and they propel cells through the G1 restriction point and into the S phase, after which growth factor stimulation is no longer essential to complete cell division. D-type Cyclins are upregulated in many human malignancies including breast cancer to promote an uncontrolled proliferation of cancer cells. After summarizing important aspects of the cytokine-mediated transcriptional regulation and the posttranslational modification of D-type Cyclins, this review will highlight the physiological significance of these cell cycle regulators during normal mammary gland development as well as the initiation and promotion of breast cancer. Although the vast majority of published reports focus almost exclusively on the role of Cyclin D1 in breast cancer, we summarize here previous and recent findings that demonstrate an important contribution of the remaining two members of this Cyclin family, in particular Cyclin D3, for the growth of ErbB2-associated breast cancer cells in humans and in mouse models. New data from genetically engineered models as well as the pharmacological inhibition of CDK4/6 suggest that targeting the combined functions of D-type Cyclins could be a suitable strategy for the treatment of ErbB2-positive and potentially other types of breast cancer. PMID:23562856

A cdk1 gradient guides surface contraction waves in oocytes.

PubMed

Bischof, Johanna; Brand, Christoph A; Somogyi, Kálmán; Májer, Imre; Thome, Sarah; Mori, Masashi; Schwarz, Ulrich S; Lénárt, Péter

2017-10-11

Surface contraction waves (SCWs) in oocytes and embryos lead to large-scale shape changes coupled to cell cycle transitions and are spatially coordinated with the cell axis. Here, we show that SCWs in the starfish oocyte are generated by a traveling band of myosin II-driven cortical contractility. At the front of the band, contractility is activated by removal of cdk1 inhibition of the RhoA/RhoA kinase/myosin II signaling module, while at the rear, contractility is switched off by negative feedback originating downstream of RhoA kinase. The SCW's directionality and speed are controlled by a spatiotemporal gradient of cdk1-cyclinB. This gradient is formed by the release of cdk1-cyclinB from the asymmetrically located nucleus, and progressive degradation of cyclinB. By combining quantitative imaging, biochemical and mechanical perturbations with mathematical modeling, we demonstrate that the SCWs result from the spatiotemporal integration of two conserved regulatory modules, cdk1-cyclinB for cell cycle regulation and RhoA/Rok/NMYII for actomyosin contractility.Surface contraction waves (SCWs) are prominent shape changes coupled to cell cycle transitions in oocytes. Here the authors show that SCWs are patterned by the spatiotemporal integration of two conserved modules, cdk1-cyclinB for cell cycle regulation and RhoA/Rok/NMYII for actomyosin contractility.

Gene structure, expression, and DNA methylation characteristics of sea cucumber cyclin B gene during aestivation.

PubMed

Zhu, Aijun; Chen, Muyan; Zhang, Xiumei; Storey, Kenneth B

2016-12-05

The sea cucumber, Apostichopus japonicus, is a good model for studying environmentally-induced aestivation by a marine invertebrate. One of the central requirements of aestivation is the repression of energy-expensive cellular processes such as cell cycle progression. The present study identified the gene structure of the cell cycle regulator, cyclin B, and detected the expression levels of this gene over three stages of the annual aestivation-arousal cycle. Furthermore, the DNA methylation characteristics of cyclin B were analyzed in non-aestivation and deep-aestivation stages of sea cucumbers. We found that the cyclin B promoter contains a CpG island, three CCAAT-boxes and three cell cycle gene homology regions (CHRs). Application of qRT-PCR analysis showed significant downregulation of cyclin B transcript levels during deep-aestivation in comparison with non-aestivation in both intestine and longitudinal muscle, and these returned to basal levels after arousal from aestivation. Methylation analysis of the cyclin B core promoter revealed that its methylation level showed significant differences between non-aestivation and deep-aestivation stages (p<0.05) and interestingly, a positive correlation between Cyclin B transcripts expression and methylation levels of the core promoter was also observed. Our findings suggest that cell cycle progression may be reversibly arrested during aestivation as indicated by the changes in cyclin B expression levels and we propose that DNA methylation is one of the regulatory mechanisms involved in cyclin B transcriptional variation. Copyright © 2016 Elsevier B.V. All rights reserved.

The cell cycle of early mammalian embryos: lessons from genetic mouse models.

PubMed

Artus, Jérôme; Babinet, Charles; Cohen-Tannoudji, Michel

2006-03-01

Genes coding for cell cycle components predicted to be essential for its regulation have been shown to be dispensable in mice, at the whole organism level. Such studies have highlighted the extraordinary plasticity of the embryonic cell cycle and suggest that many aspects of in vivo cell cycle regulation remain to be discovered. Here, we discuss the particularities of the mouse early embryonic cell cycle and review the mutations that result in cell cycle defects during mouse early embryogenesis, including deficiencies for genes of the cyclin family (cyclin A2 and B1), genes involved in cell cycle checkpoints (Mad2, Bub3, Chk1, Atr), genes involved in ubiquitin and ubiquitin-like pathways (Uba3, Ubc9, Cul1, Cul3, Apc2, Apc10, Csn2) as well as genes the function of which had not been previously ascribed to cell cycle regulation (Cdc2P1, E4F and Omcg1).

c-Jun induces apoptosis of starved BM2 monoblasts by activating cyclin A-CDK2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vanhara, Petr; Bryja, Vitezslav; Horvath, Viktor

2007-02-02

c-Jun is one of the major components of the activating protein-1 (AP-1), the transcription factor that participates in regulation of proliferation, differentiation, and apoptosis. In this study, we explored functional interactions of the c-Jun protein with several regulators of the G1/S transition in serum-deprived v-myb-transformed chicken monoblasts BM2. We show that the c-Jun protein induces expression of cyclin A, thus up-regulating activity of cyclin A-associated cyclin-dependent kinase 2 (CDK2), and causing massive programmed cell death of starved BM2cJUN cells. Specific inhibition of CDK2 suppresses frequency of apoptosis of BM2cJUN cells. We conclude that up-regulation of cyclin A expression and CDK2more » activity can represent important link between the c-Jun protein, cell cycle machinery, and programmed cell death pathway in leukemic cells.« less

ClC-3 Chloride Channel Proteins Regulate the Cell Cycle by Up-regulating cyclin D1-CDK4/6 through Suppressing p21/p27 Expression in Nasopharyngeal Carcinoma Cells

PubMed Central

Ye, Dong; Luo, Hai; Lai, Zhouyi; Zou, Lili; Zhu, Linyan; Mao, Jianwen; Jacob, Tim; Ye, Wencai; Wang, Liwei; Chen, Lixin

2016-01-01

It was shown in this study that knockdown of ClC-3 expression by ClC-3 siRNA prevented the activation of hypotonicity-induced chloride currents, and arrested cells at the G0/G1 phase in nasopharyngeal carcinoma CNE-2Z cells. Reconstitution of ClC-3 expression with ClC-3 expression plasmids could rescue the cells from the cell cycle arrest caused by ClC-3 siRNA treatments. Transfection of cells with ClC-3 siRNA decreased the expression of cyclin D1, cyclin dependent kinase 4 and 6, and increased the expression of cyclin dependent kinase inhibitors (CDKIs), p21 and p27. Pretreatments of cells with p21 and p27 siRNAs depleted the inhibitory effects of ClC-3 siRNA on the expression of CDK4 and CDK6, but not on that of cyclin D1, indicating the requirement of p21 and p27 for the inhibitory effects of ClC-3 siRNA on CDK4 and CDK6 expression. ClC-3 siRNA inhibited cells to progress from the G1 phase to the S phase, but pretreatments of cells with p21 and p27 siRNAs abolished the inhibitory effects of ClC-3 siRNA on the cell cycle progress. Our data suggest that ClC-3 may regulate cell cycle transition between G0/G1 and S phases by up-regulation of the expression of CDK4 and CDK6 through suppression of p21 and p27 expression. PMID:27451945

Mechanisms involved in regulating DNA replication origins during the cell cycle and in response to DNA damage.

PubMed Central

Early, Anne; Drury, Lucy S; Diffley, John F X

2004-01-01

Replication origins in eukaryotic cells never fire more than once in a given S phase. Here, we summarize the role of cyclin-dependent kinases in limiting DNA replication origin usage to once per cell cycle in the budding yeast Saccharomyces cerevisiae. We have examined the role of different cyclins in the phosphorylation and regulation of several replication/regulatory factors including Cdc6, Sic1, ORC and DNA polymerase alpha-primase. In addition to being regulated by the cell cycle machinery, replication origins are also regulated by the genome integrity checkpoint kinases, Mec1 and Rad53. In response to DNA damage or drugs which interfere with the progression of replication forks, the activation of late-firing replication origins is inhibited. There is evidence indicating that the temporal programme of origin firing depends upon the local histone acetylation state. We have attempted to test the possibility that checkpoint regulation of late-origin firing operates through the regulation of the acetylation state. We found that overexpression of the essential histone acetylase, Esal, cannot override checkpoint regulation of origin firing. We have also constructed a temperature-sensitive esa1 mutant. This mutant is unable to resume cell cycle progression after alpha-factor arrest. This can be overcome by overexpression of the G1 cyclin, Cln2, revealing a novel role for Esal in regulating Start. PMID:15065654

HCdc14A is involved in cell cycle regulation of human brain vascular endothelial cells following injury induced by high glucose, free fatty acids and hypoxia.

PubMed

Su, Jingjing; Zhou, Houguang; Tao, Yinghong; Guo, Zhuangli; Zhang, Shuo; Zhang, Yu; Huang, Yanyan; Tang, Yuping; Hu, Renming; Dong, Qiang

2015-01-01

Cell cycle processes play a vital role in vascular endothelial proliferation and dysfunction. Cell division cycle protein 14 (Cdc14) is an important cell cycle regulatory phosphatase. Previous studies in budding yeast demonstrated that Cdc14 could trigger the inactivation of mitotic cyclin-dependent kinases (Cdks), which are required for mitotic exit and cytokinesis. However, the exact function of human Cdc14 (hCdc14) in cell cycle regulation during vascular diseases is yet to be elucidated. There are two HCdc14 homologs: hCdc14A and hCdc14B. In the current study, we investigated the potential role of hCdc14A in high glucose-, free fatty acids (FFAs)-, and hypoxia-induced injury in cultured human brain vascular endothelial cells (HBVECs). Data revealed that high glucose, FFA, and hypoxia down-regulated hCdc14A expression remarkably, and also affected the expression of other cell cycle-related proteins such as cyclin B, cyclin D, cyclin E, and p53. Furthermore, the combined addition of the three stimuli largely blocked cell cycle progression, decreased cell proliferation, and increased apoptosis. We also determined that hCdc14A was localized mainly to centrosomes during interphase and spindles during mitosis using confocal microscopy, and that it could affect the expression of other cycle-related proteins. More importantly, the overexpression of hCdc14A accelerated cell cycle progression, enhanced cell proliferation, and promoted neoplastic transformation, whereas the knockdown of hCdc14A using small interfering RNA produced the opposite effects. Therefore, these findings provide novel evidence that hCdc14A might be involved in cell cycle regulation in cultured HBVECs during high glucose-, FFA-, and hypoxia-induced injury. Copyright © 2014 Elsevier Inc. All rights reserved.

c-Myc plays a key role in TADs-induced apoptosis and cell cycle arrest in human hepatocellular carcinoma cells.

PubMed

Zhang, Dongdong; Qi, Junpeng; Liu, Rui; Dai, Bingling; Ma, Weina; Zhan, Yingzhuan; Zhang, Yanmin

2015-01-01

Cancer cell growth is complicated progression which is regulated and controlled by multiple factors including cell cycle, migration and apoptosis. In present study, we report that TADs, a novel derivative of taspine, has an essential role in resisting hepatocellular carcinoma growth (including arrest cell cycle) and migration, and inducing cell apoptosis. Our findings demonstrated that the TADs showed good inhibition on the hepatoma cell growth and migration, and good action on apoptosis induction. Using genome-wide microarray analysis, we found the down-regulated growth and apoptosis factors, and selected down-regulated genes were confirmed by Western blot. Knockdown of a checkpoint c-Myc by siRNA significantly attenuated tumor inhibition and apoptosis effects of TADs. Moreover, our results indicated TADs could simultaneously increase cyclin D1 protein levels and decrease amount of cyclin E, cyclin B1 and cdc2 of the cycle proteins, and also TADs reduced Bcl-2 expression, and upregulated Bad, Bak and Bax activities. In conclusion, these results illustrated that TADs is a key factor in growth and apoptosis signaling inhibitor, has potential in cancer therapy.

Circadian clock regulation of the cell cycle in the zebrafish intestine.

PubMed

Peyric, Elodie; Moore, Helen A; Whitmore, David

2013-01-01

The circadian clock controls cell proliferation in a number of healthy tissues where cell renewal and regeneration are critical for normal physiological function. The intestine is an organ that typically undergoes regular cycles of cell division, differentiation and apoptosis as part of its role in digestion and nutrient absorption. The aim of this study was to explore circadian clock regulation of cell proliferation and cell cycle gene expression in the zebrafish intestine. Here we show that the zebrafish gut contains a directly light-entrainable circadian pacemaker, which regulates the daily timing of mitosis. Furthermore, this intestinal clock controls the expression of key cell cycle regulators, such as cdc2, wee1, p21, PCNA and cdk2, but only weakly influences cyclin B1, cyclin B2 and cyclin E1 expression. Interestingly, food deprivation has little impact on circadian clock function in the gut, but dramatically reduces cell proliferation, as well as cell cycle gene expression in this tissue. Timed feeding under constant dark conditions is able to drive rhythmic expression not only of circadian clock genes, but also of several cell cycle genes, suggesting that food can entrain the clock, as well as the cell cycle in the intestine. Rather surprisingly, we found that timed feeding is critical for high amplitude rhythms in cell cycle gene expression, even when zebrafish are maintained on a light-dark cycle. Together these results suggest that the intestinal clock integrates multiple rhythmic cues, including light and food, to function optimally.

Circadian Clock Regulation of the Cell Cycle in the Zebrafish Intestine

PubMed Central

Peyric, Elodie; Moore, Helen A.; Whitmore, David

2013-01-01

The circadian clock controls cell proliferation in a number of healthy tissues where cell renewal and regeneration are critical for normal physiological function. The intestine is an organ that typically undergoes regular cycles of cell division, differentiation and apoptosis as part of its role in digestion and nutrient absorption. The aim of this study was to explore circadian clock regulation of cell proliferation and cell cycle gene expression in the zebrafish intestine. Here we show that the zebrafish gut contains a directly light-entrainable circadian pacemaker, which regulates the daily timing of mitosis. Furthermore, this intestinal clock controls the expression of key cell cycle regulators, such as cdc2, wee1, p21, PCNA and cdk2, but only weakly influences cyclin B1, cyclin B2 and cyclin E1 expression. Interestingly, food deprivation has little impact on circadian clock function in the gut, but dramatically reduces cell proliferation, as well as cell cycle gene expression in this tissue. Timed feeding under constant dark conditions is able to drive rhythmic expression not only of circadian clock genes, but also of several cell cycle genes, suggesting that food can entrain the clock, as well as the cell cycle in the intestine. Rather surprisingly, we found that timed feeding is critical for high amplitude rhythms in cell cycle gene expression, even when zebrafish are maintained on a light-dark cycle. Together these results suggest that the intestinal clock integrates multiple rhythmic cues, including light and food, to function optimally. PMID:24013905

A Clb/Cdk1-mediated regulation of Fkh2 synchronizes CLB expression in the budding yeast cell cycle.

PubMed

Linke, Christian; Chasapi, Anastasia; González-Novo, Alberto; Al Sawad, Istabrak; Tognetti, Silvia; Klipp, Edda; Loog, Mart; Krobitsch, Sylvia; Posas, Francesc; Xenarios, Ioannis; Barberis, Matteo

2017-01-01

Precise timing of cell division is achieved by coupling waves of cyclin-dependent kinase (Cdk) activity with a transcriptional oscillator throughout cell cycle progression. Although details of transcription of cyclin genes are known, it is unclear which is the transcriptional cascade that modulates their expression in a timely fashion. Here, we demonstrate that a Clb/Cdk1-mediated regulation of the Fkh2 transcription factor synchronizes the temporal mitotic CLB expression in budding yeast. A simplified kinetic model of the cyclin/Cdk network predicts a linear cascade where a Clb/Cdk1-mediated regulation of an activator molecule drives CLB3 and CLB2 expression. Experimental validation highlights Fkh2 as modulator of CLB3 transcript levels, besides its role in regulating CLB2 expression. A Boolean model based on the minimal number of interactions needed to capture the information flow of the Clb/Cdk1 network supports the role of an activator molecule in the sequential activation, and oscillatory behavior, of mitotic Clb cyclins. This work illustrates how transcription and phosphorylation networks can be coupled by a Clb/Cdk1-mediated regulation that synchronizes them.

Rapamycin ameliorates IgA nephropathy via cell cycle-dependent mechanisms

PubMed Central

Tian, Jihua; Wang, Yanhong; Liu, Xinyan; Zhou, Xiaoshuang

2014-01-01

IgA nephropathy is the most frequent type of glomerulonephritis worldwide. The role of cell cycle regulation in the pathogenesis of IgA nephropathy has been studied. The present study was designed to explore whether rapamycin ameliorates IgA nephropathy via cell cycle-dependent mechanisms. After establishing an IgA nephropathy model, rats were randomly divided into four groups. Coomassie Brilliant Blue was used to measure the 24-h urinary protein levels. Renal function was determined using an autoanalyzer. Proliferation was assayed via Proliferating Cell Nuclear Antigen (PCNA) immunohistochemistry. Rat mesangial cells were cultured and divided into the six groups. Methylthiazolyldiphenyl-tetrazolium bromide (MTT) and flow cytometry were used to detect cell proliferation and the cell cycle phase. Western blotting was performed to determine cyclin E, cyclin-dependent kinase 2, p27Kip1, p70S6K/p-p70S6K, and extracellular signal-regulated kinase 1/2/p- extracellular signal-regulated kinase 1/2 protein expression. A low dose of the mammalian target of rapamycin (mTOR) inhibitor rapamycin prevented an additional increase in proteinuria, protected kidney function, and reduced IgA deposition in a model of IgA nephropathy. Rapamycin inhibited mesangial cell proliferation and arrested the cell cycle in the G1 phase. Rapamycin did not affect the expression of cyclin E and cyclin-dependent kinase 2. However, rapamycin upregulated p27Kip1 at least in part via AKT (also known as protein kinase B)/mTOR. In conclusion, rapamycin can affect cell cycle regulation to inhibit mesangial cell proliferation, thereby reduce IgA deposition, and slow the progression of IgAN. PMID:25349217

Rapamycin ameliorates IgA nephropathy via cell cycle-dependent mechanisms.

PubMed

Tian, Jihua; Wang, Yanhong; Liu, Xinyan; Zhou, Xiaoshuang; Li, Rongshan

2015-07-01

IgA nephropathy is the most frequent type of glomerulonephritis worldwide. The role of cell cycle regulation in the pathogenesis of IgA nephropathy has been studied. The present study was designed to explore whether rapamycin ameliorates IgA nephropathy via cell cycle-dependent mechanisms. After establishing an IgA nephropathy model, rats were randomly divided into four groups. Coomassie Brilliant Blue was used to measure the 24-h urinary protein levels. Renal function was determined using an autoanalyzer. Proliferation was assayed via Proliferating Cell Nuclear Antigen (PCNA) immunohistochemistry. Rat mesangial cells were cultured and divided into the six groups. Methylthiazolyldiphenyl-tetrazolium bromide (MTT) and flow cytometry were used to detect cell proliferation and the cell cycle phase. Western blotting was performed to determine cyclin E, cyclin-dependent kinase 2, p27(Kip1), p70S6K/p-p70S6K, and extracellular signal-regulated kinase 1/2/p- extracellular signal-regulated kinase 1/2 protein expression. A low dose of the mammalian target of rapamycin (mTOR) inhibitor rapamycin prevented an additional increase in proteinuria, protected kidney function, and reduced IgA deposition in a model of IgA nephropathy. Rapamycin inhibited mesangial cell proliferation and arrested the cell cycle in the G1 phase. Rapamycin did not affect the expression of cyclin E and cyclin-dependent kinase 2. However, rapamycin upregulated p27(Kip1) at least in part via AKT (also known as protein kinase B)/mTOR. In conclusion, rapamycin can affect cell cycle regulation to inhibit mesangial cell proliferation, thereby reduce IgA deposition, and slow the progression of IgAN. © 2014 by the Society for Experimental Biology and Medicine.

Targeted interactomics reveals a complex core cell cycle machinery in Arabidopsis thaliana.

PubMed

Van Leene, Jelle; Hollunder, Jens; Eeckhout, Dominique; Persiau, Geert; Van De Slijke, Eveline; Stals, Hilde; Van Isterdael, Gert; Verkest, Aurine; Neirynck, Sandy; Buffel, Yelle; De Bodt, Stefanie; Maere, Steven; Laukens, Kris; Pharazyn, Anne; Ferreira, Paulo C G; Eloy, Nubia; Renne, Charlotte; Meyer, Christian; Faure, Jean-Denis; Steinbrenner, Jens; Beynon, Jim; Larkin, John C; Van de Peer, Yves; Hilson, Pierre; Kuiper, Martin; De Veylder, Lieven; Van Onckelen, Harry; Inzé, Dirk; Witters, Erwin; De Jaeger, Geert

2010-08-10

Cell proliferation is the main driving force for plant growth. Although genome sequence analysis revealed a high number of cell cycle genes in plants, little is known about the molecular complexes steering cell division. In a targeted proteomics approach, we mapped the core complex machinery at the heart of the Arabidopsis thaliana cell cycle control. Besides a central regulatory network of core complexes, we distinguished a peripheral network that links the core machinery to up- and downstream pathways. Over 100 new candidate cell cycle proteins were predicted and an in-depth biological interpretation demonstrated the hypothesis-generating power of the interaction data. The data set provided a comprehensive view on heterodimeric cyclin-dependent kinase (CDK)-cyclin complexes in plants. For the first time, inhibitory proteins of plant-specific B-type CDKs were discovered and the anaphase-promoting complex was characterized and extended. Important conclusions were that mitotic A- and B-type cyclins form complexes with the plant-specific B-type CDKs and not with CDKA;1, and that D-type cyclins and S-phase-specific A-type cyclins seem to be associated exclusively with CDKA;1. Furthermore, we could show that plants have evolved a combinatorial toolkit consisting of at least 92 different CDK-cyclin complex variants, which strongly underscores the functional diversification among the large family of cyclins and reflects the pivotal role of cell cycle regulation in the developmental plasticity of plants.

Correlations between radiation-induced double strand breaks, cell division delay, and cyclin-dependent signaling in x-irradiated NIH3T3 fibroblasts

NASA Astrophysics Data System (ADS)

Cariveau, Mickael J.

2005-07-01

Molecular responses to radiation-induced DNA double strand breaks (DSB) are mediated by the phosphorylation of the histone variant H2AX which forms identifiable gamma-H2AX foci at the site of the DSB. This event is thought to be linked with the down-regulation of signaling proteins contributing to the checkpoints regulating cell cycle progression and, vis-a-vis , the induction of cell division delay. However, it is unclear whether this division delay is directly related to the number of DSB (gamma-H2AX foci) sustained by an irradiated cell and, if so, whether this number drives cells into cell cycle delay or apoptosis. For this reason, studies were conducted in the immortalized NIH/3T3 fibroblast cell in order to establish correlations between the temporal appearance of the gamma-H2AX foci (a DSB) and the expression of the cell cycle regulatory proteins, cyclin E, A, B1, and their cyclin kinase inhibitor, p21. Cell cycle kinetics and flow cytometry were used to establish radiation-induced division delay over a dose range of 1--6 Gy where a mitotic delay of 2.65 min/cGy was established. Correlations between the expression of cyclin E, A, B1, p21, and the generation of DSB were established in NIH/3T3 cells exposed to 2 or 4 Gy x-irradiation. The data suggest that the G1/S and S phase delay (cyclin E and cyclin A protein levels) are dependent on the dose of radiation while the G2/M (cyclin B1 protein levels) delay is dependent on the quantity of DSB sustained by the irradiated cell.

Cyclin K dependent regulation of Aurora B affects apoptosis and proliferation by induction of mitotic catastrophe in prostate cancer.

PubMed

Schecher, Sabrina; Walter, Britta; Falkenstein, Michael; Macher-Goeppinger, Stephan; Stenzel, Philipp; Krümpelmann, Kristina; Hadaschik, Boris; Perner, Sven; Kristiansen, Glen; Duensing, Stefan; Roth, Wilfried; Tagscherer, Katrin E

2017-10-15

Cyclin K plays a critical role in transcriptional regulation as well as cell development. However, the role of Cyclin K in prostate cancer is unknown. Here, we describe the impact of Cyclin K on prostate cancer cells and examine the clinical relevance of Cyclin K as a biomarker for patients with prostate cancer. We show that Cyclin K depletion in prostate cancer cells induces apoptosis and inhibits proliferation accompanied by an accumulation of cells in the G2/M phase. Moreover, knockdown of Cyclin K causes mitotic catastrophe displayed by multinucleation and spindle multipolarity. Furthermore, we demonstrate a Cyclin K dependent regulation of the mitotic kinase Aurora B and provide evidence for an Aurora B dependent induction of mitotic catastrophe. In addition, we show that Cyclin K expression is associated with poor biochemical recurrence-free survival in patients with prostate cancer treated with an adjuvant therapy. In conclusion, targeting Cyclin K represents a novel, promising anti-cancer strategy to induce cell cycle arrest and apoptotic cell death through induction of mitotic catastrophe in prostate cancer cells. Moreover, our results indicate that Cyclin K is a putative predictive biomarker for clinical outcome and therapy response for patients with prostate cancer. © 2017 UICC.

Characterization of cyclin-dependent kinases and Cdc2/Cdc28 kinase subunits in Trichomonas vaginalis.

PubMed

Amador, Erick; López-Pacheco, Karla; Morales, Nataly; Coria, Roberto; López-Villaseñor, Imelda

2017-04-01

Cyclin-dependent kinases (CDKs) have important roles in regulating key checkpoints between stages of the cell cycle. Their activity is tightly regulated through a variety of mechanisms, including through binding with cyclin proteins and the Cdc2/Cdc28 kinase subunit (CKS), and their phosphorylation at specific amino acids. Studies of the components involved in cell cycle control in parasitic protozoa are limited. Trichomonas vaginalis is the causative agent of trichomoniasis in humans and is therefore important in public health; however, some of the basic biological processes used by this organism have not been defined. Here, we characterized proteins potentially involved in cell cycle regulation in T. vaginalis. Three genes encoding protein kinases were identified in the T. vaginalis genome, and the corresponding recombinant proteins (TvCRK1, TvCRK2, TvCRK5) were studied. These proteins displayed similar sequence features to CDKs. Two genes encoding CKSs were also identified, and the corresponding recombinant proteins were found to interact with TvCRK1 and TvCRK2 by a yeast two-hybrid system. One putative cyclin B protein from T. vaginalis was found to bind to and activate the kinase activities of TvCRK1 and TvCRK5, but not TvCRK2. This work is the first characterization of proteins involved in cell cycle control in T. vaginalis.

Protein expression patterns of cell cycle regulators in operable breast cancer.

PubMed

Zagouri, Flora; Kotoula, Vassiliki; Kouvatseas, George; Sotiropoulou, Maria; Koletsa, Triantafyllia; Gavressea, Theofani; Valavanis, Christos; Trihia, Helen; Bobos, Mattheos; Lazaridis, Georgios; Koutras, Angelos; Pentheroudakis, George; Skarlos, Pantelis; Bafaloukos, Dimitrios; Arnogiannaki, Niki; Chrisafi, Sofia; Christodoulou, Christos; Papakostas, Pavlos; Aravantinos, Gerasimos; Kosmidis, Paris; Karanikiotis, Charisios; Zografos, George; Papadimitriou, Christos; Fountzilas, George

2017-01-01

To evaluate the prognostic role of elaborate molecular clusters encompassing cyclin D1, cyclin E1, p21, p27 and p53 in the context of various breast cancer subtypes. Cyclin E1, cyclin D1, p53, p21 and p27 were evaluated with immunohistochemistry in 1077 formalin-fixed paraffin-embedded tissues from breast cancer patients who had been treated within clinical trials. Jaccard distances were computed for the markers and the resulted matrix was used for conducting unsupervised hierarchical clustering, in order to identify distinct groups correlating with prognosis. Luminal B and triple-negative (TNBC) tumors presented with the highest and lowest levels of cyclin D1 expression, respectively. By contrast, TNBC frequently expressed Cyclin E1, whereas ER-positive tumors did not. Absence of Cyclin D1 predicted for worse OS, while absence of Cyclin E1 for poorer DFS. The expression patterns of all examined proteins yielded 3 distinct clusters; (1) Cyclin D1 and/or E1 positive with moderate p21 expression; (2) Cyclin D1 and/or E1, and p27 positive, p53 protein negative; and, (3) Cyclin D1 or E1 positive, p53 positive, p21 and p27 negative or moderately positive. The 5-year DFS rates for clusters 1, 2 and 3 were 70.0%, 79.1%, 67.4% and OS 88.4%, 90.4%, 78.9%, respectively. It seems that the expression of cell cycle regulators in the absence of p53 protein is associated with favorable prognosis in operable breast cancer.

The G1/S Specific Cyclin D2 Is a Regulator of HIV-1 Restriction in Non-proliferating Cells

PubMed Central

Badia, Roger; Pujantell, Maria; Riveira-Muñoz, Eva; Puig, Teresa; Torres-Torronteras, Javier; Martí, Ramón; Clotet, Bonaventura; Ampudia, Rosa M.; Ballana, Ester

2016-01-01

Macrophages are a heterogeneous cell population strongly influenced by differentiation stimuli that become susceptible to HIV-1 infection after inactivation of the restriction factor SAMHD1 by cyclin-dependent kinases (CDK). Here, we have used primary human monocyte-derived macrophages differentiated through different stimuli to evaluate macrophage heterogeneity on cell activation and proliferation and susceptibility to HIV-1 infection. Stimulation of monocytes with GM-CSF induces a non-proliferating macrophage population highly restrictive to HIV-1 infection, characterized by the upregulation of the G1/S-specific cyclin D2, known to control early steps of cell cycle progression. Knockdown of cyclin D2, enhances HIV-1 replication in GM-CSF macrophages through inactivation of SAMHD1 restriction factor by phosphorylation. Co-immunoprecipitation experiments show that cyclin D2 forms a complex with CDK4 and p21, a factor known to restrict HIV-1 replication by affecting the function of the downstream cascade that leads to SAMHD1 deactivation. Thus, we demonstrate that cyclin D2 acts as regulator of cell cycle proteins affecting SAMHD1-mediated HIV-1 restriction in non-proliferating macrophages. PMID:27541004

The Anaphase-Promoting Complex is a dual integrator that regulates both microRNA-mediated transcriptional regulation of Cyclin B1 and degradation of Cyclin B1 during Arabidopsis male gametophyte development

USDA-ARS?s Scientific Manuscript database

The anaphase-promoting complex/cyclosome (APC/C), an essential ubiquitin protein ligase, regulates mitotic progression and exit by enhancing degradation of cell cycle regulatory proteins, such as CYCB1;1, whose transcripts are upregulated by DUO POLLEN1 (DUO1). DUO1 is required for cell division in ...

The Anaphase-Promoting Complex Is a Dual Integrator That Regulates Both MicroRNA-Mediated Transcriptional Regulation of Cyclin B1 and Degradation of Cyclin B1 during Arabidopsis Male Gametophyte Development

USDA-ARS?s Scientific Manuscript database

The anaphase-promoting complex/cyclosome (APC/C), an essential ubiquitin protein ligase, regulates mitotic progression and exit by enhancing degradation of cell cycle regulatory proteins, such as CYCB1;1, whose transcripts are upregulated by DUO POLLEN1 (DUO1). DUO1 is required for cell division in ...

Cell-cycle regulation of formin-mediated actin cable assembly

PubMed Central

Miao, Yansong; Wong, Catherine C. L.; Mennella, Vito; Michelot, Alphée; Agard, David A.; Holt, Liam J.; Yates, John R.; Drubin, David G.

2013-01-01

Assembly of appropriately oriented actin cables nucleated by formin proteins is necessary for many biological processes in diverse eukaryotes. However, compared with knowledge of how nucleation of dendritic actin filament arrays by the actin-related protein-2/3 complex is regulated, the in vivo regulatory mechanisms for actin cable formation are less clear. To gain insights into mechanisms for regulating actin cable assembly, we reconstituted the assembly process in vitro by introducing microspheres functionalized with the C terminus of the budding yeast formin Bni1 into extracts prepared from yeast cells at different cell-cycle stages. EM studies showed that unbranched actin filament bundles were reconstituted successfully in the yeast extracts. Only extracts enriched in the mitotic cyclin Clb2 were competent for actin cable assembly, and cyclin-dependent kinase 1 activity was indispensible. Cyclin-dependent kinase 1 activity also was found to regulate cable assembly in vivo. Here we present evidence that formin cell-cycle regulation is conserved in vertebrates. The use of the cable-reconstitution system to test roles for the key actin-binding proteins tropomyosin, capping protein, and cofilin provided important insights into assembly regulation. Furthermore, using mass spectrometry, we identified components of the actin cables formed in yeast extracts, providing the basis for comprehensive understanding of cable assembly and regulation. PMID:24133141

Cyclin D regulation of a sexually dimorphic asymmetric cell division

PubMed Central

Tilmann, Christopher; Kimble, Judith

2006-01-01

SUMMARY The C. elegans somatic gonadal precursor cell (SGP) divides asymmetrically to establish gonad-specific coordinates in both sexes. In addition, the SGP division is sexually dimorphic and initiates sex-specific programs of gonadogenesis. Wnt/MAPK signaling determines the gonadal axes, and the FKH-6 transcription factor specifies the male mode of SGP division. In this paper, we demonstrate that C. elegans cyclin D controls POP-1/TCF asymmetry in the SGP daughters as well as fkh-6 and rnr expression in the SGPs. Although cyclin D mutants have delayed SGP divisions, the cyclin D defects are not mimicked by other methods of retarding the SGP division. We find that EFL-1/E2F has an antagonistic effect on fkh-6 expression and gonadogenesis, which is relieved by cyclin D activity. We propose that cyclin D and other canonical regulators of the G1/S transition coordinate key regulators of axis formation and sex determination with cell cycle progression to achieve the sexually dimorphic SGP asymmetric division. PMID:16198291

Direct trans-activation of the human cyclin D2 gene by the oncogene product Tax of human T-cell leukemia virus type I.

PubMed

Huang, Y; Ohtani, K; Iwanaga, R; Matsumura, Y; Nakamura, M

2001-03-01

Cyclins are one of the pivotal determinants regulating cell cycle progression. We previously reported that the trans-activator Tax of human T-cell leukemia virus type I (HTLV-I) induces endogenous cyclin D2 expression along with cell cycle progression in a resting human T-cell line, Kit 225, suggesting a role of cyclin D2 in Tax-mediated cell cycle progression. The cyclin D2 gene has a typical E2F binding element, raising the possibility that induction of cyclin D2 expression is a consequence of cell cycle progression. In this study, we examined the role and molecular mechanism of induction of the endogenous human cyclin D2 gene by Tax. Introduction of p19(INK4d), a cyclin dependent kinase (CDK) inhibitor of the INK4 family specific for D-type CDK, inhibited Tax-mediated activation of E2F, indicating requirement of D-type CDK in Tax-mediated activation of E2F. Previously indicated E2F binding element and two NF-kappaB-like binding elements in the 1.6 kbp cyclin D2 promoter fragment had little, if any, effect on responsiveness to Tax. We found that trans-activation of the cyclin D2 promoter by Tax was mainly mediated by a newly identified NF-kappaB-like element with auxiliary contribution of a CRE-like element residing in sequences downstream of -444 which were by themselves sufficient for trans-activation by Tax. These results indicate that Tax directly trans-activates the cyclin D2 gene, resulting in growth promotion and perhaps leukemogenesis through activation of D-type CDK.

Nitric oxide is involved in hydrogen gas-induced cell cycle activation during adventitious root formation in cucumber.

PubMed

Zhu, Yongchao; Liao, Weibiao; Niu, Lijuan; Wang, Meng; Ma, Zhanjun

2016-06-28

Adventitious root development is a complex process regulated through a variety of signaling molecules. Hydrogen gas (H2) and nitric oxide (NO), two new signaling molecules are both involved in plant development and stress tolerance. To investigate the mechanism of adventitious root development induced by hydrogen-rich water (HRW), a combination of fluorescence microscopy and molecular approaches was used to study cell cycle activation and cell cycle-related gene expression in cucumber (Cucumis sativus 'Xinchun 4') explants. The results revealed that the effect of HRW on adventitious root development was dose-dependent, with maximal biological responses at 50 % HRW. HRW treatment increased NO content in a time-dependent fashion. The results also indicated that HRW and NO promoted the G1-to-S transition and up-regulated cell cycle-related genes: CycA (A-type cyclin), CycB (B-type cyclin), CDKA (cyclin-dependent kinase A) and CDKB (cyclin-dependent kinase B) expression. Additionally, target genes related to adventitious rooting were up-regulated by HRW and NO in cucumber explants. While, the responses of HRW-induced adventitious root development and increase of NO content were partially blocked by a specific NO scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide potassium salt, NO synthase (NOS)-like enzyme inhibitor N(G) -nitro-L-arginine methylester hydrochloride, or nitrate reductase inhibitors tungstate and NaN3. These chemicals also partially reversed the effect of HRW on cell cycle activation and the transcripts of cell cycle regulatory genes and target genes related adventitious root formation. Together, NO may emerge as a downstream signaling molecule in H2-induced adventitious root organogenesis. Additionally, H2 mediated cell cycle activation via NO pathway during adventitious root formation.

Targeted interactomics reveals a complex core cell cycle machinery in Arabidopsis thaliana

PubMed Central

Van Leene, Jelle; Hollunder, Jens; Eeckhout, Dominique; Persiau, Geert; Van De Slijke, Eveline; Stals, Hilde; Van Isterdael, Gert; Verkest, Aurine; Neirynck, Sandy; Buffel, Yelle; De Bodt, Stefanie; Maere, Steven; Laukens, Kris; Pharazyn, Anne; Ferreira, Paulo C G; Eloy, Nubia; Renne, Charlotte; Meyer, Christian; Faure, Jean-Denis; Steinbrenner, Jens; Beynon, Jim; Larkin, John C; Van de Peer, Yves; Hilson, Pierre; Kuiper, Martin; De Veylder, Lieven; Van Onckelen, Harry; Inzé, Dirk; Witters, Erwin; De Jaeger, Geert

2010-01-01

Cell proliferation is the main driving force for plant growth. Although genome sequence analysis revealed a high number of cell cycle genes in plants, little is known about the molecular complexes steering cell division. In a targeted proteomics approach, we mapped the core complex machinery at the heart of the Arabidopsis thaliana cell cycle control. Besides a central regulatory network of core complexes, we distinguished a peripheral network that links the core machinery to up- and downstream pathways. Over 100 new candidate cell cycle proteins were predicted and an in-depth biological interpretation demonstrated the hypothesis-generating power of the interaction data. The data set provided a comprehensive view on heterodimeric cyclin-dependent kinase (CDK)–cyclin complexes in plants. For the first time, inhibitory proteins of plant-specific B-type CDKs were discovered and the anaphase-promoting complex was characterized and extended. Important conclusions were that mitotic A- and B-type cyclins form complexes with the plant-specific B-type CDKs and not with CDKA;1, and that D-type cyclins and S-phase-specific A-type cyclins seem to be associated exclusively with CDKA;1. Furthermore, we could show that plants have evolved a combinatorial toolkit consisting of at least 92 different CDK–cyclin complex variants, which strongly underscores the functional diversification among the large family of cyclins and reflects the pivotal role of cell cycle regulation in the developmental plasticity of plants. PMID:20706207

The Yeast Cyclin-Dependent Kinase Routes Carbon Fluxes to Fuel Cell Cycle Progression.

PubMed

Ewald, Jennifer C; Kuehne, Andreas; Zamboni, Nicola; Skotheim, Jan M

2016-05-19

Cell division entails a sequence of processes whose specific demands for biosynthetic precursors and energy place dynamic requirements on metabolism. However, little is known about how metabolic fluxes are coordinated with the cell division cycle. Here, we examine budding yeast to show that more than half of all measured metabolites change significantly through the cell division cycle. Cell cycle-dependent changes in central carbon metabolism are controlled by the cyclin-dependent kinase (Cdk1), a major cell cycle regulator, and the metabolic regulator protein kinase A. At the G1/S transition, Cdk1 phosphorylates and activates the enzyme Nth1, which funnels the storage carbohydrate trehalose into central carbon metabolism. Trehalose utilization fuels anabolic processes required to reliably complete cell division. Thus, the cell cycle entrains carbon metabolism to fuel biosynthesis. Because the oscillation of Cdk activity is a conserved feature of the eukaryotic cell cycle, we anticipate its frequent use in dynamically regulating metabolism for efficient proliferation. Copyright © 2016 Elsevier Inc. All rights reserved.

Role of Cyclin E as an Early Event in Ovarian Carcinogenesis

DTIC Science & Technology

2012-04-01

degradation . P27 is a powerful negative regulator of the cell cycle, preventing activation of cyclin E- cdk2 or cyclin D-cdk4 complexes and cell cycle...Ahmed M, Bavi P, et al. Bortezomib (Velcade) induces p27Kip1 expression through S-phase kinase protein 2 degradation in colorectal cancer. Cancer Res...CA1251CA72·4 CA 125 CA72-4 M-CSF CA 125/CA 72-4/M-CSFICA 15-3 CA125 CA 125/mesothelin CA 125/IL·6JIL·8NEGF;EGF CA 125/IL-6,G-CSFNEGF/EGF Leptin

Foci of cyclin A2 interact with actin and RhoA in mitosis.

PubMed

Loukil, Abdelhalim; Izard, Fanny; Georgieva, Mariya; Mashayekhan, Shaereh; Blanchard, Jean-Marie; Parmeggiani, Andrea; Peter, Marion

2016-06-09

Cyclin A2 is a key player in the regulation of the cell cycle. Its degradation in mid-mitosis depends primarily on the ubiquitin-proteasome system (UPS), while autophagy also contributes. However, a fraction of cyclin A2 persists beyond metaphase. In this work, we focus on cyclin A2-rich foci detected in mitosis by high resolution imaging and analyse their movements. We demonstrate that cyclin A2 interacts with actin and RhoA during mitosis, and that cyclin A2 depletion induces a dramatic decrease in active RhoA in mitosis. Our data suggest cyclin A2 participation in RhoA activation in late mitosis.

c-Myc plays a key role in TADs-induced apoptosis and cell cycle arrest in human hepatocellular carcinoma cells

PubMed Central

Zhang, Dongdong; Qi, Junpeng; Liu, Rui; Dai, Bingling; Ma, Weina; Zhan, Yingzhuan; Zhang, Yanmin

2015-01-01

Cancer cell growth is complicated progression which is regulated and controlled by multiple factors including cell cycle, migration and apoptosis. In present study, we report that TADs, a novel derivative of taspine, has an essential role in resisting hepatocellular carcinoma growth (including arrest cell cycle) and migration, and inducing cell apoptosis. Our findings demonstrated that the TADs showed good inhibition on the hepatoma cell growth and migration, and good action on apoptosis induction. Using genome-wide microarray analysis, we found the down-regulated growth and apoptosis factors, and selected down-regulated genes were confirmed by Western blot. Knockdown of a checkpoint c-Myc by siRNA significantly attenuated tumor inhibition and apoptosis effects of TADs. Moreover, our results indicated TADs could simultaneously increase cyclin D1 protein levels and decrease amount of cyclin E, cyclin B1 and cdc2 of the cycle proteins, and also TADs reduced Bcl-2 expression, and upregulated Bad, Bak and Bax activities. In conclusion, these results illustrated that TADs is a key factor in growth and apoptosis signaling inhibitor, has potential in cancer therapy. PMID:26045987

MicroRNA let-7b regulates neural stem cell proliferation and differentiation by targeting nuclear receptor TLX signaling

PubMed Central

Zhao, Chunnian; Sun, GuoQiang; Li, Shengxiu; Lang, Ming-Fei; Yang, Su; Li, Wendong; Shi, Yanhong

2010-01-01

Neural stem cell self-renewal and differentiation is orchestrated by precise control of gene expression involving nuclear receptor TLX. Let-7b, a member of the let-7 microRNA family, is expressed in mammalian brains and exhibits increased expression during neural differentiation. However, the role of let-7b in neural stem cell proliferation and differentiation remains unknown. Here we show that let-7b regulates neural stem cell proliferation and differentiation by targeting the stem cell regulator TLX and the cell cycle regulator cyclin D1. Overexpression of let-7b led to reduced neural stem cell proliferation and increased neural differentiation, whereas antisense knockdown of let-7b resulted in enhanced proliferation of neural stem cells. Moreover, in utero electroporation of let-7b to embryonic mouse brains led to reduced cell cycle progression in neural stem cells. Introducing an expression vector of Tlx or cyclin D1 that lacks the let-7b recognition site rescued let-7b-induced proliferation deficiency, suggesting that both TLX and cyclin D1 are important targets for let-7b-mediated regulation of neural stem cell proliferation. Let-7b, by targeting TLX and cyclin D1, establishes an efficient strategy to control neural stem cell proliferation and differentiation. PMID:20133835

MicroRNA let-7b regulates neural stem cell proliferation and differentiation by targeting nuclear receptor TLX signaling.

PubMed

Zhao, Chunnian; Sun, GuoQiang; Li, Shengxiu; Lang, Ming-Fei; Yang, Su; Li, Wendong; Shi, Yanhong

2010-02-02

Neural stem cell self-renewal and differentiation is orchestrated by precise control of gene expression involving nuclear receptor TLX. Let-7b, a member of the let-7 microRNA family, is expressed in mammalian brains and exhibits increased expression during neural differentiation. However, the role of let-7b in neural stem cell proliferation and differentiation remains unknown. Here we show that let-7b regulates neural stem cell proliferation and differentiation by targeting the stem cell regulator TLX and the cell cycle regulator cyclin D1. Overexpression of let-7b led to reduced neural stem cell proliferation and increased neural differentiation, whereas antisense knockdown of let-7b resulted in enhanced proliferation of neural stem cells. Moreover, in utero electroporation of let-7b to embryonic mouse brains led to reduced cell cycle progression in neural stem cells. Introducing an expression vector of Tlx or cyclin D1 that lacks the let-7b recognition site rescued let-7b-induced proliferation deficiency, suggesting that both TLX and cyclin D1 are important targets for let-7b-mediated regulation of neural stem cell proliferation. Let-7b, by targeting TLX and cyclin D1, establishes an efficient strategy to control neural stem cell proliferation and differentiation.

Alteration of cell cycle progression by Sindbis virus infection

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yi, Ruirong; Saito, Kengo; Isegawa, Naohisa

We examined the impact of Sindbis virus (SINV) infection on cell cycle progression in a cancer cell line, HeLa, and a non-cancerous cell line, Vero. Cell cycle analyses showed that SINV infection is able to alter the cell cycle progression in both HeLa and Vero cells, but differently, especially during the early stage of infection. SINV infection affected the expression of several cell cycle regulators (CDK4, CDK6, cyclin E, p21, cyclin A and cyclin B) in HeLa cells and caused HeLa cells to accumulate in S phase during the early stage of infection. Monitoring SINV replication in HeLa and Veromore » cells expressing cell cycle indicators revealed that SINV which infected HeLa cells during G{sub 1} phase preferred to proliferate during S/G{sub 2} phase, and the average time interval for viral replication was significantly shorter in both HeLa and Vero cells infected during G{sub 1} phase than in cells infected during S/G{sub 2} phase. - Highlights: • SINV infection was able to alter the cell cycle progression of infected cancer cells. • SINV infection can affect the expression of cell cycle regulators. • SINV infection exhibited a preference for the timing of viral replication among the cell cycle phases.« less

Complexes of D-type cyclins with CDKs during maize germination

PubMed Central

Vázquez-Ramos, Jorge M.

2013-01-01

The importance of cell proliferation in plant growth and development has been well documented. The majority of studies on basic cell cycle mechanisms in plants have been at the level of gene expression and much less knowledge has accumulated in terms of protein interactions and activation. Two key proteins, cyclins and cyclin-dependent kinases (CDKs) are fundamental for cell cycle regulation and advancement. Our aim has been to understand the role of D-type cyclins and type A and B CDKs in the cell cycle taking place during a developmental process such as maize seed germination. Results indicate that three maize D-type cyclins—D2;2, D4;2, and D5;3—(G1-S cyclins by definition) bind and activate two different types of CDK—A and B1;1—in a differential way during germination. Whereas CDKA–D-type cyclin complexes are more active at early germination times than at later times, it was surprising to observe that CDKB1;1, a supposedly G2-M kinase, bound in a differential way to all D-type cyclins tested during germination. Binding to cyclin D2;2 was detectable at all germination times, forming a complex with kinase activity, whereas binding to D4;2 and D5;3 was more variable; in particular, D5;3 was only detected at late germination times. Results are discussed in terms of cell cycle advancement and its importance for seed germination. PMID:24127516

Long noncoding RNA SNHG7 accelerates prostate cancer proliferation and cycle progression through cyclin D1 by sponging miR-503.

PubMed

Qi, Honggang; Wen, Bifeng; Wu, Qihang; Cheng, Wei; Lou, Jiangyong; Wei, Junjun; Huang, Jianjun; Yao, Xuping; Weng, Guobin

2018-06-01

Increasing evidence has indicated the important roles of long non-coding RNAs (lncRNAs) in tumorigenesis and cellular progression, including prostate cancer. In this study, we aim to investigate the expression level of SNHG7 and its biological functions on prostate cancer cells. Results indicated that SNHG7 expression was significantly up-regulated in prostate cancer tissue and cell lines. Besides, the overexpression of SNHG7 was closely correlated with the poor prognosis. In vitro and in vivo, experiments demonstrated that SNHG7 knockdown markedly inhibited prostate cancer proliferation and cycle-related protein (CDK4, CDK6, Cyclin D1), induced cell cycle arrest at G0/G1 phase and suppressed tumor growth. Moreover, miR-503 was predicted by bioinformatics tools and validated using luciferase reporter assay to both directly inhibited SNHG7 and Cyclin D1 expression by targeting their RNA 3'-UTR. In conclusion, results present that SNHG7 regulates the cycle progression and acts as an oncogenic gene in the prostate cancer tumorigenesis via miR-503/Cyclin D1 pathway, revealing the vital role of lncRNA/miRNA/mRNA axis in prostate cancer carcinogenesis. Copyright © 2018 Elsevier Masson SAS. All rights reserved.

Cyclin D1 in the Liver: Role of Noncanonical Signaling in Liver Steatosis and Hormone Regulation

PubMed Central

Núñez, Kelley G.; Gonzalez-Rosario, Janet; Thevenot, Paul T.; Cohen, Ari J.

2017-01-01

Background: Cyclin D1 is an important protein for cell cycle progression; however, functions independent of the cell cycle have been described in the liver. Cyclin D1 is also involved in DNA repair, is overexpressed in many cancers, and functions as a proto-oncogene. The lesser-known roles of Cyclin D1, specifically in hepatocytes, impact liver steatosis and hormone regulation in the liver. Methods: A comprehensive search of PubMed was conducted using the keywords Cyclin D1, steatosis, lipogenesis, and liver transplantation. In this article, we review the results from this literature search, with a focus on the role of Cyclin D1 in hepatic lipogenesis and gluconeogenesis, as well as the impact and function of this protein in hepatic steatosis. Results: Cyclin D1 represses carbohydrate response element binding protein (ChREBP) and results in a decrease in transcription of fatty acid synthase (FAS) and acetyl-coenzyme A carboxylase (ACC). Cyclin D1 also inhibits peroxisome proliferator-activated receptor gamma (PPARγ) which is involved in hepatic lipogenesis. Cyclin D1 inhibits both hepatocyte nuclear factor 4 alpha (HNF4α) and peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC1α) and represses transcription of lipogenic genes FAS and liver-type pyruvate kinase (Pklr), along with the gluconeogenic genes phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase (G6Pase). Conclusion: Cyclin D1 represses multiple proteins involved in both lipogenesis and gluconeogenesis in the liver. Targeting Cyclin D1 to decrease hepatic steatosis in patients with nonalcoholic fatty liver disease or alcoholic fatty liver disease may help improve patient health and the quality of the donor liver pool. PMID:28331449

Porcine epidemic diarrhea virus through p53-dependent pathway causes cell cycle arrest in the G0/G1 phase.

PubMed

Sun, Pei; Wu, Haoyang; Huang, Jiali; Xu, Ying; Yang, Feng; Zhang, Qi; Xu, Xingang

2018-05-22

Porcine epidemic diarrhea virus (PEDV), an enteropathogenic Alphacoronavirus, has caused enormous economic losses in the swine industry. p53 protein exists in a wide variety of animal cells, which is involved in cell cycle regulation, apoptosis, cell differentiation and other biological functions. In this study, we investigated the effects of PEDV infection on the cell cycle of Vero cells and p53 activation. The results demonstrated that PEDV infection induces cell cycle arrest at G0/G1 phase in Vero cells, while UV-inactivated PEDV does not cause cell cycle arrest. PEDV infection up-regulates the levels of p21, cdc2, cdk2, cdk4, Cyclin A protein and down-regulates Cyclin E protein. Further research results showed that inhibition of p53 signaling pathway can reverse the cell cycle arrest in G0/G1 phase induced by PEDV infection and cancel out the up-regulation of p21 and corresponding Cyclin/cdk mentioned above. In addition, PEDV infection of the cells synchronized in various stages of cell cycle showed that viral subgenomic RNA and virus titer were higher in the cells released from G0/G1 phase synchronized cells than that in the cells released from the G1/S phase and G2/M phase synchronized or asynchronous cells after 18 h p.i.. This is the first report to demonstrate that the p53-dependent pathway plays an important role in PEDV induced cell cycle arrest and beneficially contributes to viral infection. Copyright © 2018 Elsevier B.V. All rights reserved.

Protein tyrosine phosphatase of liver regeneration-1 is required for normal timing of cell cycle progression during liver regeneration

PubMed Central

Jiao, Yang; Ye, Diana Z.; Li, Zhaoyu; Teta-Bissett, Monica; Peng, Yong; Taub, Rebecca; Greenbaum, Linda E.

2014-01-01

Protein tyrosine phosphatase of liver regeneration-1 (Prl-1) is an immediate-early gene that is significantly induced during liver regeneration. Several in vitro studies have suggested that Prl-1 is important for the regulation of cell cycle progression. To evaluate its function in liver regeneration, we ablated the Prl-1 gene specifically in mouse hepatocytes using the Cre-loxP system. Prl-1 mutant mice (Prl-1loxP/loxP;AlfpCre) appeared normal and fertile. Liver size and metabolic function in Prl-1 mutants were comparable to controls, indicating that Prl-1 is dispensable for liver development, postnatal growth, and hepatocyte differentiation. Mutant mice demonstrated a delay in DNA synthesis after 70% partial hepatectomy, although ultimate liver mass restoration was not affected. At 40 h posthepatectomy, reduced protein levels of the cell cycle regulators cyclin E, cyclin A2, cyclin B1, and cyclin-dependent kinase 1 were observed in Prl-1 mutant liver. Investigation of the major signaling pathways involved in liver regeneration demonstrated that phosphorylation of protein kinase B (AKT) and signal transducer and activator of transcription (STAT) 3 were significantly reduced at 40 h posthepatectomy in Prl-1 mutants. Taken together, this study provides evidence that Prl-1 is required for proper timing of liver regeneration after partial hepatectomy. Prl-1 promotes G1/S progression via modulating expression of several cell cycle regulators through activation of the AKT and STAT3 signaling pathway. PMID:25377314

Experimental study on inhibitory effects of histone deacetylase inhibitor MS-275 and TSA on bladder cancer cells.

PubMed

Qu, Wei; Kang, Yin-Dong; Zhou, Mei-Sheng; Fu, Li-Li; Hua, Zhen-Hao; Wang, Li-Ming

2010-01-01

To investigate the inhibitory effect of histone deacetylase (HDAC) inhibitors (MS-275 and TSA) on T24 human bladder cancer cells in vitro, and explore the possible mechanism. The MTT assay was employed to evaluate the inhibitory effect of MS-275 and TSA on T24 cell growth. FCM was used to analyze the variation of T24 cell cycle distribution and the apoptotic ratio after T24 cells were treated with MS-275 and TSA. Histone acetylation level was detected by Western blot. mRNA expression of p21 WAF1/CIP1, cyclin A, and cyclin E was measured by FQ-PCR. Dynamic changes of Bcl-2 and bax expression were detected by FCM. MS-275 and TSA inhibited T24 cell growth in a concentration and time-dependent manner. Treatment with 4 μmol/l MS-275 or 0.4 μmol/l TSA blocked cell cycling in the G0/G1 phase and induced a significant increase in cell apoptosis. MS-275 and TSA significantly increased the level of histone acetylation, induced p21CIP1WAF1 mRNA expression, and inhibited cyclin A mRNA expression, though no significant effect was observed on cyclin E. Bcl-2 expression was down-regulated, while bax expression was up-regulated. HDAC inhibitors can block bladder cancer cell cycle in vitro and induce apoptosis. The molecular mechanism may be associated with increased level of histone acetylation, down-regulation of p21WAF1/CIP1 expression, up-regulation of cyclin A expression, and dynamic change of bcl-2 and bax expression. Copyright © 2010 Elsevier Inc. All rights reserved.

The Malaria Parasite Cyclin H Homolog PfCyc1 Is Required for Efficient Cytokinesis in Blood-Stage Plasmodium falciparum.

PubMed

Robbins, Jonathan A; Absalon, Sabrina; Streva, Vincent A; Dvorin, Jeffrey D

2017-06-13

All well-studied eukaryotic cell cycles are driven by cyclins, which activate cyclin-dependent kinases (CDKs), and these protein kinase complexes are viable drug targets. The regulatory control of the Plasmodium falciparum cell division cycle remains poorly understood, and the roles of the various CDKs and cyclins remain unclear. The P. falciparum genome contains multiple CDKs, but surprisingly, it does not contain any sequence-identifiable G 1 -, S-, or M-phase cyclins. We demonstrate that P. falciparum Cyc1 (PfCyc1) complements a G 1 cyclin-depleted Saccharomyces cerevisiae strain and confirm that other identified malaria parasite cyclins do not complement this strain. PfCyc1, which has the highest sequence similarity to the conserved cyclin H, cannot complement a temperature-sensitive yeast cyclin H mutant. Coimmunoprecipitation of PfCyc1 from P. falciparum parasites identifies PfMAT1 and PfMRK as specific interaction partners and does not identify PfPK5 or other CDKs. We then generate an endogenous conditional allele of PfCyc1 in blood-stage P. falciparum using a destabilization domain (DD) approach and find that PfCyc1 is essential for blood-stage proliferation. PfCyc1 knockdown does not impede nuclear division, but it prevents proper cytokinesis. Thus, we demonstrate that PfCyc1 has a functional divergence from bioinformatic predictions, suggesting that the malaria parasite cell division cycle has evolved to use evolutionarily conserved proteins in functionally novel ways. IMPORTANCE Human infection by the eukaryotic parasite Plasmodium falciparum causes malaria. Most well-studied eukaryotic cell cycles are driven by cyclins, which activate cyclin-dependent kinases (CDKs) to promote essential cell division processes. Remarkably, there are no identifiable cyclins that are predicted to control the cell cycle in the malaria parasite genome. Thus, our knowledge regarding the basic mechanisms of the malaria parasite cell cycle remains unsatisfactory. We demonstrate that P. falciparum Cyc1 (PfCyc1), a transcriptional cyclin homolog, complements a cell cycle cyclin-deficient yeast strain but not a transcriptional cyclin-deficient strain. We show that PfCyc1 forms a complex in the parasite with PfMRK and the P. falciparum MAT1 homolog. PfCyc1 is essential and nonredundant in blood-stage P. falciparum PfCyc1 knockdown causes a stage-specific arrest after nuclear division, demonstrating morphologically aberrant cytokinesis. This work demonstrates a conserved PfCyc1/PfMAT1/PfMRK complex in malaria and suggests that it functions as a schizont stage-specific regulator of the P. falciparum life cycle. Copyright © 2017 Robbins et al.

AMP-activated protein kinase is involved in neural stem cell growth suppression and cell cycle arrest by 5-aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside and glucose deprivation by down-regulating phospho-retinoblastoma protein and cyclin D.

PubMed

Zang, Yi; Yu, Li-Fang; Nan, Fa-Jun; Feng, Lin-Yin; Li, Jia

2009-03-06

The fate of neural stem cells (NSCs), including their proliferation, differentiation, survival, and death, is regulated by multiple intrinsic signals and the extrinsic environment. We had previously reported that 5-aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside (AICAR) directly induces astroglial differentiation of NSCs by activation of the Janus kinase (JAK)/Signal transducer and activator of transcription 3 (STAT3) pathway independently of AMP-activated protein kinase (AMPK). Here, we reported the observation that AICAR inhibited NSC proliferation and its underlying mechanism. Analysis of caspase activity and cell cycle showed that AICAR induced G1/G0 cell cycle arrest in NSCs, associated with decreased levels of poly(ADP-ribose) polymerase, phospho-retinoblastoma protein (Rb), and cyclin D but did not cause apoptosis. Iodotubericidin and Compound C, inhibitors of adenosine kinase and AMPK, respectively, or overexpression of a dominant-negative mutant of AMPK, but not JAK inhibitor, were able to reverse the anti-proliferative effect of AICAR. Glucose deprivation also activated the AMPK pathway, induced G0/G1 arrest, and suppressed the proliferation of NSCs, an effect associated with decreased levels of phospho-Rb and cyclin D protein. Furthermore, Compound C and overexpression of dominant-negative AMPK in C17.2 NSCs could block the glucose deprivation-mediated down-regulation of cyclin D and partially reverse the suppression of proliferation. These results suggest that AICAR and glucose deprivation might induce G1/G0 cell cycle arrest and suppress proliferation of NSCs via phospho-Rb and cyclin D down-regulation. AMPK, but not JAK/STAT3, activation is key for this inhibitory effect and may play an important role in the responses of NSCs to metabolic stresses such as glucose deprivation.

Rational design of a cyclin A fluorescent peptide sensor.

PubMed

Pazos, Elena; Pérez, Miguel; Gutiérrez-de-Terán, Hugo; Orzáez, Mar; Guevara, Tatiana; Mascareñas, José L; Vázquez, M Eugenio

2011-10-26

We report the design and development of a fluorescent sensor specifically designed to target cyclin A, a protein that plays a key role in the regulation of the cell cycle. Computational studies provide a molecular picture that explains the observed emission increase, suggesting that the 4-DMAP fluorophore in the peptide is protected from the bulk solvent when inserted into the hydrophobic binding groove of cyclin A.

Temporal self-organization of the cyclin/Cdk network driving the mammalian cell cycle

PubMed Central

Gérard, Claude; Goldbeter, Albert

2009-01-01

We propose an integrated computational model for the network of cyclin-dependent kinases (Cdks) that controls the dynamics of the mammalian cell cycle. The model contains four Cdk modules regulated by reversible phosphorylation, Cdk inhibitors, and protein synthesis or degradation. Growth factors (GFs) trigger the transition from a quiescent, stable steady state to self-sustained oscillations in the Cdk network. These oscillations correspond to the repetitive, transient activation of cyclin D/Cdk4–6 in G1, cyclin E/Cdk2 at the G1/S transition, cyclin A/Cdk2 in S and at the S/G2 transition, and cyclin B/Cdk1 at the G2/M transition. The model accounts for the following major properties of the mammalian cell cycle: (i) repetitive cell cycling in the presence of suprathreshold amounts of GF; (ii) control of cell-cycle progression by the balance between antagonistic effects of the tumor suppressor retinoblastoma protein (pRB) and the transcription factor E2F; and (iii) existence of a restriction point in G1, beyond which completion of the cell cycle becomes independent of GF. The model also accounts for endoreplication. Incorporating the DNA replication checkpoint mediated by kinases ATR and Chk1 slows down the dynamics of the cell cycle without altering its oscillatory nature and leads to better separation of the S and M phases. The model for the mammalian cell cycle shows how the regulatory structure of the Cdk network results in its temporal self-organization, leading to the repetitive, sequential activation of the four Cdk modules that brings about the orderly progression along cell-cycle phases. PMID:20007375

MAT1, cdk7 and cyclin H form a kinase complex which is UV light-sensitive upon association with TFIIH.

PubMed

Adamczewski, J P; Rossignol, M; Tassan, J P; Nigg, E A; Moncollin, V; Egly, J M

1996-04-15

MAT1, cyclin H and cdk7 are part of TFIIH, a class II transcription factor which possesses numerous subunits of which several have been shown to be involved in processes other than transcription. Two of them, XPD (ERCC2) and XPB (ERCC3), are helicases involved in nucleotide excision repair (NER), whereas cdk7, cyclin H and MAT1 are thought to participate in cell cycle regulation. MAT1, cyclin H and cdk7 exist as a ternary complex either free or associated with TFIIH from which the latter can be dissociated at high salt concentration. MAT1 is strongly associated with cdk7 and cyclin H. Although not strictly required for the formation and activity of the complex, it stimulates its kinase activity. The kinase activity of TFIIH, which is constant during the cell cycle, is reduced after UV light irradiation.

MAT1, cdk7 and cyclin H form a kinase complex which is UV light-sensitive upon association with TFIIH.

PubMed Central

Adamczewski, J P; Rossignol, M; Tassan, J P; Nigg, E A; Moncollin, V; Egly, J M

1996-01-01

MAT1, cyclin H and cdk7 are part of TFIIH, a class II transcription factor which possesses numerous subunits of which several have been shown to be involved in processes other than transcription. Two of them, XPD (ERCC2) and XPB (ERCC3), are helicases involved in nucleotide excision repair (NER), whereas cdk7, cyclin H and MAT1 are thought to participate in cell cycle regulation. MAT1, cyclin H and cdk7 exist as a ternary complex either free or associated with TFIIH from which the latter can be dissociated at high salt concentration. MAT1 is strongly associated with cdk7 and cyclin H. Although not strictly required for the formation and activity of the complex, it stimulates its kinase activity. The kinase activity of TFIIH, which is constant during the cell cycle, is reduced after UV light irradiation. Images PMID:8617234

Cyclin D1 Downregulation Contributes to Anti-Cancer Effect of Isorhapontigenin (ISO) on Human Bladder Cancer Cells

PubMed Central

Fang, Yong; Cao, Zipeng; Hou, Qi; Ma, Chen; Yao, Chunsuo; Li, Jingxia; Wu, Xue-Ru; Huang, Chuanshu

2013-01-01

Isorhapontigenin (ISO) is a new derivative of stilbene compound that was isolated from the Chinese herb Gnetum Cleistostachyum, and has been used for treatment of bladder cancers for centuries. In our current studies, we have explored the potential inhibitory effect and molecular mechanisms underlying ISO anti-cancer effects on anchorage-independent growth of human bladder cancer cell lines. We found that ISO showed a significant inhibitory effect on human bladder cancer cell growth and was accompanied with related cell cycle G0/G1 arrest as well as downregulation of Cyclin D1 expression at the transcriptional level in UMUC3 and RT112 cells. Further studies identified that ISO down-regulated Cyclin D1 gene transcription via inhibition of SP1 transactivation. Moreover, ectopic expression of GFP-Cyclin D1 rendered UMUC3 cells resistant to induction of cell cycle G0/G1 arrest and inhibition of cancer cell anchorage-independent growth by ISO treatment. Together, our studies demonstrate that ISO is an active compound that mediates for Gnetum Cleistostachyum’s induction of cell cycle G0/G1 arrest and inhibition of cancer cell anchorage-independent growth through down-regulating SP1/Cyclin D1 axis in bladder cancer cells. Our studies provide a novel insight into understanding the anti-cancer activity of the Chinese herb Gnetum Cleistostachyum and its isolate ISO. PMID:23723126

A minimal mathematical model combining several regulatory cycles from the budding yeast cell cycle.

PubMed

Sriram, K; Bernot, G; Képès, F

2007-11-01

A novel topology of regulatory networks abstracted from the budding yeast cell cycle is studied by constructing a simple nonlinear model. A ternary positive feedback loop with only positive regulations is constructed with elements that activates the subsequent element in a clockwise fashion. A ternary negative feedback loop with only negative regulations is constructed with the elements that inhibit the subsequent element in an anticlockwise fashion. Positive feedback loop exhibits bistability, whereas the negative feedback loop exhibits limit cycle oscillations. The novelty of the topology is that the corresponding elements in these two homogeneous feedback loops are linked by the binary positive feedback loops with only positive regulations. This results in the emergence of mixed feedback loops in the network that displays complex behaviour like the coexistence of multiple steady states, relaxation oscillations and chaos. Importantly, the arrangement of the feedback loops brings in the notion of checkpoint in the model. The model also exhibits domino-like behaviour, where the limit cycle oscillations take place in a stepwise fashion. As the aforementioned topology is abstracted from the budding yeast cell cycle, the events that govern the cell cycle are considered for the present study. In budding yeast, the sequential activation of the transcription factors, cyclins and their inhibitors form mixed feedback loops. The transcription factors that involve in the positive regulation in a clockwise orientation generates ternary positive feedback loop, while the cyclins and their inhibitors that involve in the negative regulation in an anticlockwise orientation generates ternary negative feedback loop. The mutual regulation between the corresponding elements in the transcription factors and the cyclins and their inhibitors generates binary positive feedback loops. The bifurcation diagram constructed for the whole system can be related to the different events of the cell cycle in terms of dynamical system theory. The checkpoint mechanism that plays an important role in different phases of the cell cycle are accounted for by silencing appropriate feedback loops in the model.

E2F1-mediated upregulation of p19INK4d determines its periodic expression during cell cycle and regulates cellular proliferation.

PubMed

Carcagno, Abel L; Marazita, Mariela C; Ogara, María F; Ceruti, Julieta M; Sonzogni, Silvina V; Scassa, María E; Giono, Luciana E; Cánepa, Eduardo T

2011-01-01

A central aspect of development and disease is the control of cell proliferation through regulation of the mitotic cycle. Cell cycle progression and directionality requires an appropriate balance of positive and negative regulators whose expression must fluctuate in a coordinated manner. p19INK4d, a member of the INK4 family of CDK inhibitors, has a unique feature that distinguishes it from the remaining INK4 and makes it a likely candidate for contributing to the directionality of the cell cycle. p19INK4d mRNA and protein levels accumulate periodically during the cell cycle under normal conditions, a feature reminiscent of cyclins. In this paper, we demonstrate that p19INK4d is transcriptionally regulated by E2F1 through two response elements present in the p19INK4d promoter. Ablation of this regulation reduced p19 levels and restricted its expression during the cell cycle, reflecting the contribution of a transcriptional effect of E2F1 on p19 periodicity. The induction of p19INK4d is delayed during the cell cycle compared to that of cyclin E, temporally separating the induction of these proliferative and antiproliferative target genes. Specific inhibition of the E2F1-p19INK4d pathway using triplex-forming oligonucleotides that block E2F1 binding on p19 promoter, stimulated cell proliferation and increased the fraction of cells in S phase. The results described here support a model of normal cell cycle progression in which, following phosphorylation of pRb, free E2F induces cyclin E, among other target genes. Once cyclinE/CDK2 takes over as the cell cycle driving kinase activity, the induction of p19 mediated by E2F1 leads to inhibition of the CDK4,6-containing complexes, bringing the G1 phase to an end. This regulatory mechanism constitutes a new negative feedback loop that terminates the G1 phase proliferative signal, contributing to the proper coordination of the cell cycle and provides an additional mechanism to limit E2F activity.

E2F1-Mediated Upregulation of p19INK4d Determines Its Periodic Expression during Cell Cycle and Regulates Cellular Proliferation

PubMed Central

Carcagno, Abel L.; Marazita, Mariela C.; Ogara, María F.; Ceruti, Julieta M.; Sonzogni, Silvina V.; Scassa, María E.; Giono, Luciana E.; Cánepa, Eduardo T.

2011-01-01

Background A central aspect of development and disease is the control of cell proliferation through regulation of the mitotic cycle. Cell cycle progression and directionality requires an appropriate balance of positive and negative regulators whose expression must fluctuate in a coordinated manner. p19INK4d, a member of the INK4 family of CDK inhibitors, has a unique feature that distinguishes it from the remaining INK4 and makes it a likely candidate for contributing to the directionality of the cell cycle. p19INK4d mRNA and protein levels accumulate periodically during the cell cycle under normal conditions, a feature reminiscent of cyclins. Methodology/Principal Findings In this paper, we demonstrate that p19INK4d is transcriptionally regulated by E2F1 through two response elements present in the p19INK4d promoter. Ablation of this regulation reduced p19 levels and restricted its expression during the cell cycle, reflecting the contribution of a transcriptional effect of E2F1 on p19 periodicity. The induction of p19INK4d is delayed during the cell cycle compared to that of cyclin E, temporally separating the induction of these proliferative and antiproliferative target genes. Specific inhibition of the E2F1-p19INK4d pathway using triplex-forming oligonucleotides that block E2F1 binding on p19 promoter, stimulated cell proliferation and increased the fraction of cells in S phase. Conclusions/Significance The results described here support a model of normal cell cycle progression in which, following phosphorylation of pRb, free E2F induces cyclin E, among other target genes. Once cyclinE/CDK2 takes over as the cell cycle driving kinase activity, the induction of p19 mediated by E2F1 leads to inhibition of the CDK4,6-containing complexes, bringing the G1 phase to an end. This regulatory mechanism constitutes a new negative feedback loop that terminates the G1 phase proliferative signal, contributing to the proper coordination of the cell cycle and provides an additional mechanism to limit E2F activity. PMID:21765927

Controlling the response to DNA damage by the APC/C-Cdh1.

PubMed

de Boer, H Rudolf; Guerrero Llobet, S; van Vugt, Marcel A T M

2016-03-01

Proper cell cycle progression is safeguarded by the oscillating activities of cyclin/cyclin-dependent kinase complexes. An important player in the regulation of mitotic cyclins is the anaphase-promoting complex/cyclosome (APC/C), a multi-subunit E3 ubiquitin ligase. Prior to entry into mitosis, the APC/C remains inactive, which allows the accumulation of mitotic regulators. APC/C activation requires binding to either the Cdc20 or Cdh1 adaptor protein, which sequentially bind the APC/C and facilitate targeting of multiple mitotic regulators for proteasomal destruction, including Securin and Cyclin B, to ensure proper chromosome segregation and mitotic exit. Emerging data have indicated that the APC/C, particularly in association with Cdh1, also functions prior to mitotic entry. Specifically, the APC/C-Cdh1 is activated in response to DNA damage in G2 phase cells. These observations are in line with in vitro and in vivo genetic studies, in which cells lacking Cdh1 expression display various defects, including impaired DNA repair and aberrant cell cycle checkpoints. In this review, we summarize the current literature on APC/C regulation in response to DNA damage, the functions of APC/C-Cdh1 activation upon DNA damage, and speculate how APC/C-Cdh1 can control cell fate in the context of persistent DNA damage.

Nicotine induces cell proliferation in association with cyclin D1 up-regulation and inhibits cell differentiation in association with p53 regulation in a murine pre-osteoblastic cell line

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sato, Tsuyoshi; Abe, Takahiro; Nakamoto, Norimichi

Recent studies have suggested that nicotine critically affects bone metabolism. Many studies have examined the effects of nicotine on proliferation and differentiation, but the underlying molecular mechanisms remain unclear. We examined cell cycle regulators involved in the proliferation and differentiation of MC3T3-E1 cells. Nicotine induced cell proliferation in association with p53 down-regulation and cyclin D1 up-regulation. In differentiated cells, nicotine reduced alkaline phosphatase activity and mineralized nodule formation in dose-dependent manners. Furthermore, p53 expression was sustained in nicotine-treated cells during differentiation. These findings indicate that nicotine promotes the cell cycle and inhibits differentiation in association with p53 regulation in pre-osteoblasticmore » cells.« less

A Transcriptome-based Perspective of Cell Cycle Regulation in Dinoflagellates.

PubMed

Morse, David; Daoust, Philip; Benribague, Siham

2016-12-01

Dinoflagellates are a group of unicellular and generally marine protists, of interest to many because of their ability to form the large algal blooms commonly called "red tides". The large algal concentrations in these blooms require sustained cell replication, yet to date little is known about cell cycle regulation in these organisms. To address this issue, we have screened the transcriptomes of two dinoflagellates, Lingulodinium polyedrum and Symbiodinium sp., with budding yeast cell cycle pathway components. We find most yeast cell cycle regulators have homologs in these dinoflagellates, suggesting that the yeast model is appropriate for understanding regulation of the dinoflagellate cell cycle. The dinoflagellates are lacking several components essential in yeast, but a comparison with a broader phylogenetic range of protists reveals these components are usually also missing in other organisms. Lastly, phylogenetic analyses show that the dinoflagellates contain at least three cyclin-dependent kinase (CDK) homologs (belonging to the CDK1, CDK5 and CDK8 families), and that the dinoflagellate cyclins belong exclusively to the A/B type. This suggests that dinoflagellate CDKs likely play a limited role outside regulation of the cell cycle. Copyright © 2016 Elsevier GmbH. All rights reserved.

A map of protein dynamics during cell-cycle progression and cell-cycle exit

PubMed Central

Gookin, Sara; Min, Mingwei; Phadke, Harsha; Chung, Mingyu; Moser, Justin; Miller, Iain; Carter, Dylan

2017-01-01

The cell-cycle field has identified the core regulators that drive the cell cycle, but we do not have a clear map of the dynamics of these regulators during cell-cycle progression versus cell-cycle exit. Here we use single-cell time-lapse microscopy of Cyclin-Dependent Kinase 2 (CDK2) activity followed by endpoint immunofluorescence and computational cell synchronization to determine the temporal dynamics of key cell-cycle proteins in asynchronously cycling human cells. We identify several unexpected patterns for core cell-cycle proteins in actively proliferating (CDK2-increasing) versus spontaneously quiescent (CDK2-low) cells, including Cyclin D1, the levels of which we find to be higher in spontaneously quiescent versus proliferating cells. We also identify proteins with concentrations that steadily increase or decrease the longer cells are in quiescence, suggesting the existence of a continuum of quiescence depths. Our single-cell measurements thus provide a rich resource for the field by characterizing protein dynamics during proliferation versus quiescence. PMID:28892491

Altered miRNA expression in aniline-mediated cell cycle progression in rat spleen.

PubMed

Wang, Gangduo; Wang, Jianling; Khan, M Firoze

2017-09-01

Aniline exposure is associated with toxicity to the spleen, however, early molecular events in aniline-induced cell cycle progression in the spleen remain unknown. MicroRNAs (miRNAs) have been implicated in tumor development by modulating key cell cycle regulators and controlling cell proliferation. This study was, therefore, undertaken on the expression of miRNAs, regulation of cyclins and cyclin-dependent kinases (CDKs) in an experimental condition that precedes a tumorigenic response. Male SD rats were treated with aniline (1 mmol/kg/day by gavage) for 7 days, and expression of miRNAs, cyclins and CDKs in rat spleens were analyzed. Microarray and/or qPCR analyses showed that aniline exposure led to significantly decreased miRNA expression of let-7a, miR-24, miR-34c, miR-100, miR-125b, and greatly increased miR-181a. The aberrant expression of miRNAs was associated with significantly increased protein expression of cyclins A, B1, D3 and E. Furthermore, remarkably enhanced expression of CDKs like CDK1, CDK2, CDK4, CDK6, especially p-CDK1 and p-CDK2 as well as alternations in the expression of pRB, p27, and CDC25A in the spleens of aniline-treated rats was also observed. The data suggest that aniline exposure leads to aberrant expression of miRNAs in the spleen which could be important in the regulation of cell cycle proteins. Our findings, thus, provide new insight into the role of miRNAs in cell cycle progression, which may contribute to aniline-induced tumorigenic response in the spleen.

Cell Cycle Regulators Guide Mitochondrial Activity in Radiation-Induced Adaptive Response

PubMed Central

Alexandrou, Aris T.

2014-01-01

Abstract Significance: There are accruing concerns on potential genotoxic agents present in the environment including low-dose ionizing radiation (LDIR) that naturally exists on earth's surface and atmosphere and is frequently used in medical diagnosis and nuclear industry. Although its long-term health risk is being evaluated and remains controversial, LDIR is shown to induce temporary but significant adaptive responses in mammalian cells and animals. The mechanisms guiding the mitochondrial function in LDIR-induced adaptive response represent a unique communication between DNA damage and cellular metabolism. Elucidation of the LDIR-regulated mitochondrial activity may reveal new mechanisms adjusting cellular function to cope with hazardous environmental stress. Recent Advances: Key cell cycle regulators, including Cyclin D1/CDK4 and Cyclin B1/cyclin-dependent kinase 1 (CDK1) complexes, are actively involved in the regulation of mitochondrial functions via phosphorylation of their mitochondrial targets. Accumulating new evidence supports a concept that the Cyclin B1/CDK1 complex acts as a mediator in the cross talk between radiation-induced DNA damage and mitochondrial functions to coordinate cellular responses to low-level genotoxic stresses. Critical Issues: The LDIR-mediated mitochondrial activity via Cyclin B1/CDK1 regulation is an irreplaceable network that is able to harmonize vital cellular functions with adjusted mitochondrial metabolism to enhance cellular homeostasis. Future Directions: Further investigation of the coordinative mechanism that regulates mitochondrial activities in sublethal stress conditions, including LDIR, will reveal new insights of how cells cope with genotoxic injury and will be vital for future targeted therapeutic interventions that reduce environmental injury and cancer risk. Antioxid. Redox Signal. 20, 1463–1480. PMID:24180340

Analysis of cell cycle-related proteins in gastric intramucosal differentiated-type cancers based on mucin phenotypes: a novel hypothesis of early gastric carcinogenesis based on mucin phenotype

PubMed Central

2010-01-01

Background Abnormalities of cell cycle regulators are common features in human cancers, and several of these factors are associated with the early development of gastric cancers. However, recent studies have shown that gastric cancer tumorigenesis was characterized by mucin expression. Thus, expression patterns of cell cycle-related proteins were investigated in the early phase of differentiated-type gastric cancers to ascertain any mechanistic relationships with mucin phenotypes. Methods Immunostaining for Cyclins D1, A, E, and p21, p27, p53 and β-catenin was used to examine impairments of the cell cycle in 190 gastric intramucosal differentiated-type cancers. Mucin phenotypes were determined by the expressions of MUC5AC, MUC6, MUC2 and CD10. A Ki-67 positive rate (PR) was also examined. Results Overexpressions of p53, cyclin D1 and cyclin A were significantly more frequent in a gastric phenotype than an intestinal phenotype. Cyclin A was overexpressed in a mixed phenotype compared with an intestinal phenotype, while p27 overexpression was more frequent in an intestinal phenotype than in a mixed phenotype. Reduction of p21 was a common feature of the gastric intramucosal differentiated-type cancers examined. Conclusions Our results suggest that the levels of some cell cycle regulators appear to be associated with mucin phenotypes of early gastric differentiated-type cancers. PMID:20525401

Cyclin-dependent kinase inhibitor p20 controls circadian cell-cycle timing

PubMed Central

Laranjeiro, Ricardo; Tamai, T. Katherine; Peyric, Elodie; Krusche, Peter; Ott, Sascha; Whitmore, David

2013-01-01

Specific stages of the cell cycle are often restricted to particular times of day because of regulation by the circadian clock. In zebrafish, both mitosis (M phase) and DNA synthesis (S phase) are clock-controlled in cell lines and during embryo development. Despite the ubiquitousness of this phenomenon, relatively little is known about the underlying mechanism linking the clock to the cell cycle. In this study, we describe an evolutionarily conserved cell-cycle regulator, cyclin-dependent kinase inhibitor 1d (20 kDa protein, p20), which along with p21, is a strongly rhythmic gene and directly clock-controlled. Both p20 and p21 regulate the G1/S transition of the cell cycle. However, their expression patterns differ, with p20 predominant in developing brain and peak expression occurring 6 h earlier than p21. p20 expression is also p53-independent in contrast to p21 regulation. Such differences provide a unique mechanism whereby S phase is set to different times of day in a tissue-specific manner, depending on the balance of these two inhibitors. PMID:23569261

Cyclin-dependent kinase inhibitor p20 controls circadian cell-cycle timing.

PubMed

Laranjeiro, Ricardo; Tamai, T Katherine; Peyric, Elodie; Krusche, Peter; Ott, Sascha; Whitmore, David

2013-04-23

Specific stages of the cell cycle are often restricted to particular times of day because of regulation by the circadian clock. In zebrafish, both mitosis (M phase) and DNA synthesis (S phase) are clock-controlled in cell lines and during embryo development. Despite the ubiquitousness of this phenomenon, relatively little is known about the underlying mechanism linking the clock to the cell cycle. In this study, we describe an evolutionarily conserved cell-cycle regulator, cyclin-dependent kinase inhibitor 1d (20 kDa protein, p20), which along with p21, is a strongly rhythmic gene and directly clock-controlled. Both p20 and p21 regulate the G1/S transition of the cell cycle. However, their expression patterns differ, with p20 predominant in developing brain and peak expression occurring 6 h earlier than p21. p20 expression is also p53-independent in contrast to p21 regulation. Such differences provide a unique mechanism whereby S phase is set to different times of day in a tissue-specific manner, depending on the balance of these two inhibitors.

A novel quantitative model of cell cycle progression based on cyclin-dependent kinases activity and population balances.

PubMed

Pisu, Massimo; Concas, Alessandro; Cao, Giacomo

2015-04-01

Cell cycle regulates proliferative cell capacity under normal or pathologic conditions, and in general it governs all in vivo/in vitro cell growth and proliferation processes. Mathematical simulation by means of reliable and predictive models represents an important tool to interpret experiment results, to facilitate the definition of the optimal operating conditions for in vitro cultivation, or to predict the effect of a specific drug in normal/pathologic mammalian cells. Along these lines, a novel model of cell cycle progression is proposed in this work. Specifically, it is based on a population balance (PB) approach that allows one to quantitatively describe cell cycle progression through the different phases experienced by each cell of the entire population during its own life. The transition between two consecutive cell cycle phases is simulated by taking advantage of the biochemical kinetic model developed by Gérard and Goldbeter (2009) which involves cyclin-dependent kinases (CDKs) whose regulation is achieved through a variety of mechanisms that include association with cyclins and protein inhibitors, phosphorylation-dephosphorylation, and cyclin synthesis or degradation. This biochemical model properly describes the entire cell cycle of mammalian cells by maintaining a sufficient level of detail useful to identify check point for transition and to estimate phase duration required by PB. Specific examples are discussed to illustrate the ability of the proposed model to simulate the effect of drugs for in vitro trials of interest in oncology, regenerative medicine and tissue engineering. Copyright © 2015 Elsevier Ltd. All rights reserved.

MINA controls proliferation and tumorigenesis of glioblastoma by epigenetically regulating cyclins and CDKs via H3K9me3 demethylation.

PubMed

Huang, M-Y; Xuan, F; Liu, W; Cui, H-J

2017-01-19

It is generally known that histone demethylases regulate gene transcription by altering the methylate status on histones, but their roles in cancers and the underlying molecular mechanisms still remain unclear. MYC-induced nuclear antigen (MINA) is reported to be a histone demethylase and highly expressed in many cancers. Here, for the first time, we show that MINA is involved in glioblastoma carcinogenesis and reveal the probable mechanisms of it in cell-cycle control. Kaplan-Meier analysis of progression-free survival showed that high MINA expression was strongly correlated with poor outcome and advancing tumor stage. MINA knockdown significantly repressed the cell proliferation and tumorigenesis abilities of glioblastoma cells in vitro and in vivo that were rescued by overexpressing the full-length MINA afterwards. Microarray analysis after knockdown of MINA revealed that MINA probably regulated glioblastoma carcinogenesis through the predominant cell-cycle pathways. Further investigation showed that MINA deficiency led to a cell-cycle arrest in G1 and G2 phases. And among the downstream genes, we found that cyclins and cyclin-dependent kinases were directly activated by MINA via the demethylation of H3K9me3.

Msx homeobox genes inhibit differentiation through upregulation of cyclin D1.

PubMed

Hu, G; Lee, H; Price, S M; Shen, M M; Abate-Shen, C

2001-06-01

During development, patterning and morphogenesis of tissues are intimately coordinated through control of cellular proliferation and differentiation. We describe a mechanism by which vertebrate Msx homeobox genes inhibit cellular differentiation by regulation of the cell cycle. We show that misexpression of Msx1 via retroviral gene transfer inhibits differentiation of multiple mesenchymal and epithelial progenitor cell types in culture. This activity of Msx1 is associated with its ability to upregulate cyclin D1 expression and Cdk4 activity, while Msx1 has minimal effects on cellular proliferation. Transgenic mice that express Msx1 under the control of the mouse mammary tumor virus long terminal repeat (MMTV LTR) display impaired differentiation of the mammary epithelium during pregnancy, which is accompanied by elevated levels of cyclin D1 expression. We propose that Msx1 gene expression maintains cyclin D1 expression and prevents exit from the cell cycle, thereby inhibiting terminal differentiation of progenitor cells. Our model provides a framework for reconciling the mutant phenotypes of Msx and other homeobox genes with their functions as regulators of cellular proliferation and differentiation during embryogenesis.

HIRA, the Human Homologue of Yeast Hir1p and Hir2p, Is a Novel Cyclin-cdk2 Substrate Whose Expression Blocks S-Phase Progression

PubMed Central

Hall, Caitlin; Nelson, David M.; Ye, Xiaofen; Baker, Kayla; DeCaprio, James A.; Seeholzer, Steven; Lipinski, Marc; Adams, Peter D.

2001-01-01

Substrates of cyclin-cdk2 kinases contain two distinct primary sequence motifs: a cyclin-binding RXL motif and one or more phosphoacceptor sites (consensus S/TPXK/R or S/TP). To identify novel cyclin-cdk2 substrates, we searched the database for proteins containing both of these motifs. One such protein is human HIRA, the homologue of two cell cycle-regulated repressors of histone gene expression in Saccharomyces cerevisiae, Hir1p and Hir2p. Here we demonstrate that human HIRA is an in vivo substrate of a cyclin-cdk2 kinase. First, HIRA bound to and was phosphorylated by cyclin A- and E-cdk2 in vitro in an RXL-dependent manner. Second, HIRA was phosphorylated in vivo on two consensus cyclin-cdk2 phosphoacceptor sites and at least one of these, threonine 555, was phosphorylated by cyclin A-cdk2 in vitro. Third, phosphorylation of HIRA in vivo was blocked by cyclin-cdk2 inhibitor p21cip1. Fourth, HIRA became phosphorylated on threonine 555 in S phase when cyclin-cdk2 kinases are active. Fifth, HIRA was localized preferentially to the nucleus, where active cyclin A- and E-cdk2 are located. Finally, ectopic expression of HIRA in cells caused arrest in S phase and this is consistent with the notion that it is a cyclin-cdk2 substrate that has a role in control of the cell cycle. PMID:11238922

Identification of an hexapeptide that binds to a surface pocket in cyclin A and inhibits the catalytic activity of the complex cyclin-dependent kinase 2-cyclin A.

PubMed

Canela, Núria; Orzáez, Mar; Fucho, Raquel; Mateo, Francesca; Gutierrez, Ricardo; Pineda-Lucena, Antonio; Bachs, Oriol; Pérez-Payá, Enrique

2006-11-24

The protein-protein complexes formed between different cyclins and cyclin-dependent kinases (CDKs) are central to cell cycle regulation. These complexes represent interesting points of chemical intervention for the development of antineoplastic molecules. Here we describe the identification of an all d-amino acid hexapeptide, termed NBI1, that inhibits the kinase activity of the cyclin-dependent kinase 2 (cdk2)-cyclin A complex through selective binding to cyclin A. The mechanism of inhibition is non-competitive for ATP and non-competitive for protein substrates. In contrast to the existing CDKs peptide inhibitors, the hexapeptide NBI1 interferes with the formation of the cdk2-cyclin A complex. Furthermore, a cell-permeable derivative of NBI1 induces apoptosis and inhibits proliferation of tumor cell lines. Thus, the NBI1-binding site on cyclin A may represent a new target site for the selective inhibition of activity cdk2-cyclin A complex.

Nuclear accumulation of cyclin D1 following long-term fractionated exposures to low-dose ionizing radiation in normal human diploid cells.

PubMed

Shimura, Tsutomu; Hamada, Nobuyuki; Sasatani, Megumi; Kamiya, Kenji; Kunugita, Naoki

2014-01-01

Cyclin D1 is a mitogenic sensor that responds to growth signals from the extracellular environment and regulates the G 1-to-S cell cycle transition. When cells are acutely irradiated with a single dose of 10 Gy, cyclin D1 is degraded, causing cell cycle arrest at the G 1/S checkpoint. In contrast, cyclin D1 accumulates in human tumor cells that are exposed to long-term fractionated radiation (0.5 Gy/fraction of X-rays). In this study we investigated the effect of fractionated low-dose radiation exposure on cyclin D1 localization in 3 strains of normal human fibroblasts. To specifically examine the nuclear accumulation of cyclin D1, cells were treated with a hypotonic buffer containing detergent to remove cytoplasmic cyclin D1. Proliferating cell nuclear antigen (PCNA) immunofluorescence was used to identify cells in S phase. With this approach, we observed S-phase nuclear retention of cyclin D1 following low-dose fractionated exposures, and found that cyclin D1 nuclear retention increased with exposure time. Cells that retained nuclear cyclin D1 were more likely to have micronuclei than non-retaining cells, indicating that the accumulation of nuclear cyclin D1 was associated with genomic instability. Moreover, inhibition of the v-akt murine thymoma viral oncogene homolog (AKT) pathway facilitated cyclin D1 degradation and eliminated cyclin D1 nuclear retention in cells exposed to fractionated radiation. Thus, cyclin D1 may represent a useful marker for monitoring long-term effects associated with exposure to low levels of radiation.

Nuclear accumulation of cyclin D1 following long-term fractionated exposures to low-dose ionizing radiation in normal human diploid cells

PubMed Central

Shimura, Tsutomu; Hamada, Nobuyuki; Sasatani, Megumi; Kamiya, Kenji; Kunugita, Naoki

2014-01-01

Cyclin D1 is a mitogenic sensor that responds to growth signals from the extracellular environment and regulates the G1-to-S cell cycle transition. When cells are acutely irradiated with a single dose of 10 Gy, cyclin D1 is degraded, causing cell cycle arrest at the G1/S checkpoint. In contrast, cyclin D1 accumulates in human tumor cells that are exposed to long-term fractionated radiation (0.5 Gy/fraction of X-rays). In this study we investigated the effect of fractionated low-dose radiation exposure on cyclin D1 localization in 3 strains of normal human fibroblasts. To specifically examine the nuclear accumulation of cyclin D1, cells were treated with a hypotonic buffer containing detergent to remove cytoplasmic cyclin D1. Proliferating cell nuclear antigen (PCNA) immunofluorescence was used to identify cells in S phase. With this approach, we observed S-phase nuclear retention of cyclin D1 following low-dose fractionated exposures, and found that cyclin D1 nuclear retention increased with exposure time. Cells that retained nuclear cyclin D1 were more likely to have micronuclei than non-retaining cells, indicating that the accumulation of nuclear cyclin D1 was associated with genomic instability. Moreover, inhibition of the v-akt murine thymoma viral oncogene homolog (AKT) pathway facilitated cyclin D1 degradation and eliminated cyclin D1 nuclear retention in cells exposed to fractionated radiation. Thus, cyclin D1 may represent a useful marker for monitoring long-term effects associated with exposure to low levels of radiation. PMID:24583467

Ubiquitin specific protease 2 acts as a key modulator for the regulation of cell cycle by adiponectin and leptin in cancer cells.

PubMed

Nepal, Saroj; Shrestha, Anup; Park, Pil-Hoon

2015-09-05

Adiponectin and leptin, both produced from adipose tissue, cause cell cycle arrest and progression, respectively in cancer cells. Ubiquitin specific protease-2 (USP-2), a deubiquitinating enzyme, is known to impair proteasome-induced degradation of cyclin D1, a critical cell cycle regulator. Herein, we investigated the effects of these adipokines on USP-2 expression and its potential role in the modulation of cell cycle. Treatment with globular adiponectin (gAcrp) decreased, whereas leptin increased USP-2 expression both in human hepatoma and breast cancer cells. In addition, overexpression or gene silencing of USP-2 affected cyclin D1 expression and cell cycle progression/arrest by adipokines. Adiponectin and leptin also modulated in vitro proteasomal activity, which was partially dependent on USP-2 expression. Taken together, our results reveal that modulation of USP-2 expression plays a crucial role in cell cycle regulation by adipokines. Thus, USP-2 would be a promising therapeutic target for the modulation of cancer cell growth by adipokines. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

Two inhibitory systems and CKIs regulate cell cycle exit of mammalian cardiomyocytes after birth

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tane, Shoji; Okayama, Hitomi; Ikenishi, Aiko

Mammalian cardiomyocytes actively proliferate during embryonic stages, following which they exit their cell cycle after birth, and the exit is maintained. Previously, we showed that two inhibitory systems (the G1-phase inhibitory system: repression of cyclin D1 expression; the M-phase inhibitory system: inhibition of CDK1 activation) maintain the cell cycle exit of mouse adult cardiomyocytes. We also showed that two CDK inhibitors (CKIs), p21{sup Cip1} and p27{sup Kip1}, regulate the cell cycle exit in a portion of postnatal cardiomyocytes. It remains unknown whether the two inhibitory systems are involved in the cell cycle exit of postnatal cardiomyocytes and whether p21{sup Cip1}more » and p27{sup Kip1} also inhibit entry to M-phase. Here, we showed that more than 40% of cardiomyocytes entered an additional cell cycle by induction of cyclin D1 expression at postnatal stages, but M-phase entry was inhibited in the majority of cardiomyocytes. Marked cell cycle progression and endoreplication were observed in cardiomyocytes of p21{sup Cip1} knockout mice at 4 weeks of age. In addition, tri- and tetranucleated cardiomyocytes increased significantly in p21{sup Cip1} knockout mice. These data showed that the G1-phase inhibitory system and two CKIs (p21{sup Cip1} and p27{sup Kip1}) inhibit entry to an additional cell cycle in postnatal cardiomyocytes, and that the M-phase inhibitory system and p21{sup Cip1} inhibit M-phase entry of cardiomyocytes which have entered the additional cell cycle. - Highlights: • Many postnatal cardiomyocytes entered an additional cell cycle by cyclin D1 induction. • The majority of cardiomyocytes could not enter M-phase after cyclin D1 induction. • Cell cycle progressed markedly in p21{sup Cip1} knockout mice after postnatal day 14. • Tri- and tetranucleated cardiomyocytes increased in p21{sup Cip1} knockout mice.« less

The cell-cycle interactome: a source of growth regulators?

PubMed

Blomme, Jonas; Inzé, Dirk; Gonzalez, Nathalie

2014-06-01

When plants develop, cell proliferation and cell expansion are tightly controlled in order to generate organs with a determinate final size such as leaves. Several studies have demonstrated the importance of the cell proliferation phase for leaf growth, illustrating that cell-cycle regulation is crucial for correct leaf development. A large and complex set of interacting proteins that constitute the cell-cycle interactome controls the transition from one cell-cycle phase to another. Here, we review the current knowledge on cell-cycle regulators from this interactome affecting final leaf size when their expression is altered, mainly in Arabidopsis. In addition to the description of mutants of CYCLIN-DEPENDENT KINASES (CDKs), CYCLINS (CYCs), and their transcriptional and post-translational regulators, a phenotypic analysis of gain- and loss-of-function mutants for 27 genes encoding proteins that interact with cell-cycle proteins is presented. This compilation of information shows that when cell-cycle-related genes are mis-expressed, leaf growth is often altered and that, seemingly, three main trends appear to be crucial in the regulation of final organ size by cell-cycle-related genes: (i) cellular compensation; (ii) gene dosage; and (iii) correct transition through the G2/M phase by ANAPHASE PROMOTING COMPLEX/CYCLOSOME (APC/C) activation. In conclusion, this meta-analysis shows that the cell-cycle interactome is enriched in leaf growth regulators, and illustrates the potential to identify new leaf growth regulators among putative new cell-cycle regulators. © The Author 2013. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. For permissions, please email: journals.permissions@oup.com.

Chromosome Instability Underlies Hematopoietic Stem Cell Dysfunction and Lymphoid Neoplasia Associated with Impaired Fbw7-Mediated Cyclin E Regulation

PubMed Central

Siu, Ka Tat; Xu, Yanfei; Swartz, Kelsey L.; Bhattacharyya, Mitra; Gurbuxani, Sandeep; Hua, Youjia

2014-01-01

The Fbw7 ubiquitin ligase critically regulates hematopoietic stem cell (HSC) function, though the precise contribution of individual substrate ubiquitination pathways to HSC homeostasis is unknown. In the work reported here, we used a mouse model in which we introduced two knock-in mutations (T74A and T393A [changes of T to A at positions 74 and 393]) to disrupt Fbw7-dependent regulation of cyclin E, its prototypic substrate, and to examine the consequences of cyclin E dysregulation for HSC function. Serial transplantation revealed that cyclin ET74A T393A HSCs self-renewed normally; however, we identified defects in their multilineage reconstituting capacity. By inducing hematologic stress, we exposed an impaired self-renewal phenotype in cyclin E knock-in HSCs that was associated with defective cell cycle exit and the emergence of chromosome instability (CIN). Importantly, p53 deletion induced both defects in self-renewal and multilineage reconstitution in cyclin E knock-in HSCs with serial transplantation and CIN in hematopoietic stem and progenitor cells. Moreover, CIN was a feature of fatal T-cell malignancies that ultimately developed in recipients of cyclin ET74A T393A; p53-null HSCs. Together, our findings demonstrate the importance of Fbw7-dependent cyclin E control to the hematopoietic system and highlight CIN as a characteristic feature of HSC dysfunction and malignancy induced by deregulated cyclin E. PMID:24958101

Downregulation of telomerase activity by diclofenac and curcumin is associated with cell cycle arrest and induction of apoptosis in colon cancer.

PubMed

Rana, Chandan; Piplani, Honit; Vaish, Vivek; Nehru, Bimla; Sanyal, S N

2015-08-01

Uncontrolled cell proliferation is the hallmark of cancer, and cancer cells have typically acquired damage to genes that directly regulate their cell cycles. The synthesis of DNA onto the end of chromosome during the replicative phase of cell cycle by telomerase may be necessary for unlimited proliferation of cells. Telomerase, a ribonucleoprotein enzyme is considered as a universal therapeutic target of cancer because of its preferential expression in cancer cells and its presence in 90 % of tumors. We studied the regulation of telomerase and telomerase reverse transcriptase catalytic subunit (TERT) by diclofenac and curcumin, alone and also in combination, in 1, 2-dimethylhydrazine dihydrochloride-induced colorectal cancer in rats. The relationship of telomerase activity with tumors suppressor proteins (p51, Rb, p21), cell cycle machinery, and apoptosis was also studied. Telomerase is highly expressed in DMH group and its high activity is associated with increased TERT expression. However, telomerase is absent or is present at lower levels in normal tissue. CDK4, CDK2, cyclin D1, and cyclin E are highly expressed in DMH as assessed by RT-PCR, qRT-PCR, Western blot, and immunofluorescence analysis. Diclofenac and curcumin overcome these carcinogenic effects by downregulating telomerase activity, diminishing the expression of TERT, CDK4, CDK2, cyclin D1, and cyclin E. The anticarcinogenic effects shown after the inhibition of telomerase activity by diclofenac and curcumin may be associated with upregulation of tumor suppressor proteins p51, Rb, and p21, whose activation induces the cells cycle arrest and apoptosis.

The Rts1 Regulatory Subunit of Protein Phosphatase 2A Is Required for Control of G1 Cyclin Transcription and Nutrient Modulation of Cell Size

PubMed Central

Artiles, Karen; Anastasia, Stephanie; McCusker, Derek; Kellogg, Douglas R.

2009-01-01

The key molecular event that marks entry into the cell cycle is transcription of G1 cyclins, which bind and activate cyclin-dependent kinases. In yeast cells, initiation of G1 cyclin transcription is linked to achievement of a critical cell size, which contributes to cell-size homeostasis. The critical cell size is modulated by nutrients, such that cells growing in poor nutrients are smaller than cells growing in rich nutrients. Nutrient modulation of cell size does not work through known critical regulators of G1 cyclin transcription and is therefore thought to work through a distinct pathway. Here, we report that Rts1, a highly conserved regulatory subunit of protein phosphatase 2A (PP2A), is required for normal control of G1 cyclin transcription. Loss of Rts1 caused delayed initiation of bud growth and delayed and reduced accumulation of G1 cyclins. Expression of the G1 cyclin CLN2 from an inducible promoter rescued the delayed bud growth in rts1Δ cells, indicating that Rts1 acts at the level of transcription. Moreover, loss of Rts1 caused altered regulation of Swi6, a key component of the SBF transcription factor that controls G1 cyclin transcription. Epistasis analysis revealed that Rts1 does not work solely through several known critical upstream regulators of G1 cyclin transcription. Cells lacking Rts1 failed to undergo nutrient modulation of cell size. Together, these observations demonstrate that Rts1 is a key player in pathways that link nutrient availability, cell size, and G1 cyclin transcription. Since Rts1 is highly conserved, it may function in similar pathways in vertebrates. PMID:19911052

Spatial Reorganization of the Endoplasmic Reticulum during Mitosis Relies on Mitotic Kinase Cyclin A in the Early Drosophila Embryo

PubMed Central

Bergman, Zane J.; Mclaurin, Justin D.; Eritano, Anthony S.; Johnson, Brittany M.; Sims, Amanda Q.; Riggs, Blake

2015-01-01

Mitotic cyclin-dependent kinase with their cyclin partners (cyclin:Cdks) are the master regulators of cell cycle progression responsible for regulating a host of activities during mitosis. Nuclear mitotic events, including chromosome condensation and segregation have been directly linked to Cdk activity. However, the regulation and timing of cytoplasmic mitotic events by cyclin:Cdks is poorly understood. In order to examine these mitotic cytoplasmic events, we looked at the dramatic changes in the endoplasmic reticulum (ER) during mitosis in the early Drosophila embryo. The dynamic changes of the ER can be arrested in an interphase state by inhibition of either DNA or protein synthesis. Here we show that this block can be alleviated by micro-injection of Cyclin A (CycA) in which defined mitotic ER clusters gathered at the spindle poles. Conversely, micro-injection of Cyclin B (CycB) did not affect spatial reorganization of the ER, suggesting CycA possesses the ability to initiate mitotic ER events in the cytoplasm. Additionally, RNAi-mediated simultaneous inhibition of all 3 mitotic cyclins (A, B and B3) blocked spatial reorganization of the ER. Our results suggest that mitotic ER reorganization events rely on CycA and that control and timing of nuclear and cytoplasmic events during mitosis may be defined by release of CycA from the nucleus as a consequence of breakdown of the nuclear envelope. PMID:25689737

Human cytomegalovirus tegument protein pp150 acts as a cyclin A2-CDK-dependent sensor of the host cell cycle and differentiation state.

PubMed

Bogdanow, Boris; Weisbach, Henry; von Einem, Jens; Straschewski, Sarah; Voigt, Sebastian; Winkler, Michael; Hagemeier, Christian; Wiebusch, Lüder

2013-10-22

Upon cell entry, herpesviruses deliver a multitude of premade virion proteins to their hosts. The interplay between these incoming proteins and cell-specific regulatory factors dictates the outcome of infections at the cellular level. Here, we report a unique type of virion-host cell interaction that is essential for the cell cycle and differentiation state-dependent onset of human cytomegalovirus (HCMV) lytic gene expression. The major tegument 150-kDa phosphoprotein (pp150) of HCMV binds to cyclin A2 via a functional RXL/Cy motif resulting in its cyclin A2-dependent phosphorylation. Alanine substitution of the RXL/Cy motif prevents this interaction and allows the virus to fully escape the cyclin-dependent kinase (CDK)-mediated block of immediate early (IE) gene expression in S/G2 phase that normally restricts the onset of the HCMV replication cycle to G0/G1. Furthermore, the cyclin A2-CDK-pp150 axis is also involved in the establishment of HCMV quiescence in NTera2 cells, showing the importance of this molecular switch for differentiation state-dependent regulation of IE gene expression. Consistent with the known nucleocapsid-binding function of pp150, its RXL/Cy-dependent phosphorylation affects gene expression of the parental virion only, suggesting a cis-acting, virus particle-associated mechanism of control. The pp150 homologs of other primate and mammalian CMVs lack an RXL/Cy motif and accordingly even the nearest relative of HCMV, chimpanzee CMV, starts its lytic cycle in a cell cycle-independent manner. Thus, HCMV has evolved a molecular sensor for cyclin A2-CDK activity to restrict its IE gene expression program as a unique level of self-limitation and adaptation to its human host.

Natural Compounds as Modulators of Cell Cycle Arrest: Application for Anticancer Chemotherapies

PubMed Central

Bailon-Moscoso, Natalia; Cevallos-Solorzano, Gabriela; Romero-Benavides, Juan Carlos; Orellana, Maria Isabel Ramirez

2017-01-01

Natural compounds from various plants, microorganisms and marine species play an important role in the discovery novel components that can be successfully used in numerous biomedical applications, including anticancer therapeutics. Since uncontrolled and rapid cell division is a hallmark of cancer, unraveling the molecular mechanisms underlying mitosis is key to understanding how various natural compounds might function as inhibitors of cell cycle progression. A number of natural compounds that inhibit the cell cycle arrest have proven effective for killing cancer cells in vitro, in vivo and in clinical settings. Significant advances that have been recently made in the understanding of molecular mechanisms underlying the cell cycle regulation using the chemotherapeutic agents is of great importance for improving the efficacy of targeted therapeutics and overcoming resistance to anticancer drugs, especially of natural origin, which inhibit the activities of cyclins and cyclin-dependent kinases, as well as other proteins and enzymes involved in proper regulation of cell cycle leading to controlled cell proliferation. PMID:28367072

p21 stability: linking chaperones to a cell cycle checkpoint.

PubMed

Liu, Geng; Lozano, Guillermina

2005-02-01

Progression through the cell cycle is regulated by numerous proteins, one of which is the cyclin-dependent kinase inhibitor, p21. A new study identifies a novel protein complex that stabilizes p21. The stability of this complex is critical in effecting the p53-mediated cell cycle checkpoint.

Suppression of Akt-mediated HDAC3 expression and CDK2 T39 phosphorylation by a bichalcone analog contributes to S phase retardation of cancer cells.

PubMed

Hung, Kuang-Chen; Lin, Meng-Liang; Hsu, Shih-Wei; Lee, Chuan-Chun; Huang, Ren-Yu; Wu, Tian-Shung; Chen, Shih-Shun

2018-06-15

Targeting cell cycle regulators has been a suggested mechanism for therapeutic cancer strategies. We report here that the bichalcone analog TSWU-CD4 induces S phase arrest of human cancer cells by inhibiting the formation of cyclin A-phospho (p)-cyclin-dependent kinase 2 (CDK2, threonine [Thr] 39) complexes, independent of mutant p53 expression. Ectopic expression of CDK2 (T39E), which mimics phosphorylation of the Thr 39 residue of CDK2, partially rescues the cells from TSWU-CD4-induced S phase arrest, whereas phosphorylation-deficient CDK2 (T39A) expression regulates cell growth with significant S phase arrest and enhances TSWU-CD4-triggered S phase arrest. Decreased histone deacetylase 3 (HDAC3) expression after TSWU-CD4 treatment was demonstrated, and TSWU-CD4 induced S phase arrest and inhibitory effects on cyclin A expression and CDK2 Thr 39 phosphorylation, while cyclin A-p-CDK2 (Thr 39) complex formation was suppressed by ectopic wild-type HDAC3 expression. The co-transfection of CDK2 (T39E) along with HDAC3 completely restored cyclin A expression, Thr 39-phosphorylated CDK2, cyclin A-p-CDK2 (Thr 39) complex formation, and the S phase population to normal levels. Protein kinase B (Akt) inactivation was required for TSWU-CD4-induced S phase cell cycle arrest, because constitutively active Akt1 blocks the induction of S phase arrest and the suppression of cyclin A and HDAC3 expression, CDK2 Thr 39 phosphorylation, and cyclin A-p-CDK2 (Thr 39) complex formation by TSWU-CD4. Taken together, our results indicate that TSWU-CD4 induces S phase arrest by inhibiting Akt-mediated HDAC3 expression and CDK2 Thr 39 phosphorylation to suppress the formation of cyclin A-p-CDK2 (Thr 39) complexes. Copyright © 2018 Elsevier B.V. All rights reserved.

Cyclin A2 promotes DNA repair in the brain during both development and aging.

PubMed

Gygli, Patrick E; Chang, Joshua C; Gokozan, Hamza N; Catacutan, Fay P; Schmidt, Theresa A; Kaya, Behiye; Goksel, Mustafa; Baig, Faisal S; Chen, Shannon; Griveau, Amelie; Michowski, Wojciech; Wong, Michael; Palanichamy, Kamalakannan; Sicinski, Piotr; Nelson, Randy J; Czeisler, Catherine; Otero, José J

2016-07-01

Various stem cell niches of the brain have differential requirements for Cyclin A2. Cyclin A2 loss results in marked cerebellar dysmorphia, whereas forebrain growth is retarded during early embryonic development yet achieves normal size at birth. To understand the differential requirements of distinct brain regions for Cyclin A2, we utilized neuroanatomical, transgenic mouse, and mathematical modeling techniques to generate testable hypotheses that provide insight into how Cyclin A2 loss results in compensatory forebrain growth during late embryonic development. Using unbiased measurements of the forebrain stem cell niche, we parameterized a mathematical model whereby logistic growth instructs progenitor cells as to the cell-types of their progeny. Our data was consistent with prior findings that progenitors proliferate along an auto-inhibitory growth curve. The growth retardation inCCNA2-null brains corresponded to cell cycle lengthening, imposing a developmental delay. We hypothesized that Cyclin A2 regulates DNA repair and that CCNA2-null progenitors thus experienced lengthened cell cycle. We demonstrate that CCNA2-null progenitors suffer abnormal DNA repair, and implicate Cyclin A2 in double-strand break repair. Cyclin A2's DNA repair functions are conserved among cell lines, neural progenitors, and hippocampal neurons. We further demonstrate that neuronal CCNA2 ablation results in learning and memory deficits in aged mice.

Nuclear receptor TLX regulates cell cycle progression in neural stem cells of the developing brain.

PubMed

Li, Wenwu; Sun, Guoqiang; Yang, Su; Qu, Qiuhao; Nakashima, Kinichi; Shi, Yanhong

2008-01-01

TLX is an orphan nuclear receptor that is expressed exclusively in vertebrate forebrains. Although TLX is known to be expressed in embryonic brains, the mechanism by which it influences neural development remains largely unknown. We show here that TLX is expressed specifically in periventricular neural stem cells in embryonic brains. Significant thinning of neocortex was observed in embryonic d 14.5 TLX-null brains with reduced nestin labeling and decreased cell proliferation in the germinal zone. Cell cycle analysis revealed both prolonged cell cycles and increased cell cycle exit in TLX-null embryonic brains. Increased expression of a cyclin-dependent kinase inhibitor p21 and decreased expression of cyclin D1 provide a molecular basis for the deficiency of cell cycle progression in embryonic brains of TLX-null mice. Furthermore, transient knockdown of TLX by in utero electroporation led to precocious cell cycle exit and differentiation of neural stem cells followed by outward migration. Together these results indicate that TLX plays an important role in neural development by regulating cell cycle progression and exit of neural stem cells in the developing brain.

Nuclear Receptor TLX Regulates Cell Cycle Progression in Neural Stem Cells of the Developing Brain

PubMed Central

Li, Wenwu; Sun, Guoqiang; Yang, Su; Qu, Qiuhao; Nakashima, Kinichi; Shi, Yanhong

2008-01-01

TLX is an orphan nuclear receptor that is expressed exclusively in vertebrate forebrains. Although TLX is known to be expressed in embryonic brains, the mechanism by which it influences neural development remains largely unknown. We show here that TLX is expressed specifically in periventricular neural stem cells in embryonic brains. Significant thinning of neocortex was observed in embryonic d 14.5 TLX-null brains with reduced nestin labeling and decreased cell proliferation in the germinal zone. Cell cycle analysis revealed both prolonged cell cycles and increased cell cycle exit in TLX-null embryonic brains. Increased expression of a cyclin-dependent kinase inhibitor p21 and decreased expression of cyclin D1 provide a molecular basis for the deficiency of cell cycle progression in embryonic brains of TLX-null mice. Furthermore, transient knockdown of TLX by in utero electroporation led to precocious cell cycle exit and differentiation of neural stem cells followed by outward migration. Together these results indicate that TLX plays an important role in neural development by regulating cell cycle progression and exit of neural stem cells in the developing brain. PMID:17901127

Aspirin regulation of c-myc and cyclinD1 proteins to overcome tamoxifen resistance in estrogen receptor-positive breast cancer cells.

PubMed

Cheng, Ran; Liu, Ya-Jing; Cui, Jun-Wei; Yang, Man; Liu, Xiao-Ling; Li, Peng; Wang, Zhan; Zhu, Li-Zhang; Lu, Si-Yi; Zou, Li; Wu, Xiao-Qin; Li, Yu-Xia; Zhou, You; Fang, Zheng-Yu; Wei, Wei

2017-05-02

Tamoxifen is still the most commonly used endocrine therapy drug for estrogen receptor (ER)-positive breast cancer patients and has an excellent outcome, but tamoxifen resistance remains a great impediment to successful treatment. Recent studies have prompted an anti-tumor effect of aspirin. Here, we demonstrated that aspirin not only inhibits the growth of ER-positive breast cancer cell line MCF-7, especially when combined with tamoxifen, but also has a potential function to overcome tamoxifen resistance in MCF-7/TAM. Aspirin combined with tamoxifen can down regulate cyclinD1 and block cell cycle in G0/G1 phase. Besides, tamoxifen alone represses c-myc, progesterone receptor (PR) and cyclinD1 in MCF-7 cell line but not in MCF-7/TAM, while aspirin combined with tamoxifen can inhibit the expression of these proteins in the resistant cell line. When knocking down c-myc in MCF-7/TAM, cells become more sensitive to tamoxifen, cell cycle is blocked as well, indicating that aspirin can regulate c-myc and cyclinD1 proteins to overcome tamoxifen resistance. Our study discovered a novel role of aspirin based on its anti-tumor effect, and put forward some kinds of possible mechanisms of tamoxifen resistance in ER-positive breast cancer cells, providing a new strategy for the treatment of ER-positive breast carcinoma.

Cell type-specific translational repression of Cyclin B during meiosis in males.

PubMed

Baker, Catherine Craig; Gim, Byung Soo; Fuller, Margaret T

2015-10-01

The unique cell cycle dynamics of meiosis are controlled by layers of regulation imposed on core mitotic cell cycle machinery components by the program of germ cell development. Although the mechanisms that regulate Cdk1/Cyclin B activity in meiosis in oocytes have been well studied, little is known about the trans-acting factors responsible for developmental control of these factors in male gametogenesis. During meiotic prophase in Drosophila males, transcript for the core cell cycle protein Cyclin B1 (CycB) is expressed in spermatocytes, but the protein does not accumulate in spermatocytes until just before the meiotic divisions. Here, we show that two interacting proteins, Rbp4 and Fest, expressed at the onset of spermatocyte differentiation under control of the developmental program of male gametogenesis, function to direct cell type- and stage-specific repression of translation of the core G2/M cell cycle component cycB during the specialized cell cycle of male meiosis. Binding of Fest to Rbp4 requires a 31-amino acid region within Rbp4. Rbp4 and Fest are required for translational repression of cycB in immature spermatocytes, with Rbp4 binding sequences in a cell type-specific shortened form of the cycB 3' UTR. Finally, we show that Fest is required for proper execution of meiosis I. © 2015. Published by The Company of Biologists Ltd.

Robust mitotic entry is ensured by a latching switch.

PubMed

Tuck, Chloe; Zhang, Tongli; Potapova, Tamara; Malumbres, Marcos; Novák, Béla

2013-01-01

Cell cycle events are driven by Cyclin dependent kinases (CDKs) and by their counter-acting phosphatases. Activation of the Cdk1:Cyclin B complex during mitotic entry is controlled by the Wee1/Myt1 inhibitory kinases and by Cdc25 activatory phosphatase, which are themselves regulated by Cdk1:Cyclin B within two positive circuits. Impairing these two feedbacks with chemical inhibitors induces a transient entry into M phase referred to as mitotic collapse. The pathology of mitotic collapse reveals that the positive circuits play a significant role in maintaining the M phase state. To better understand the function of these feedback loops during G2/M transition, we propose a simple model for mitotic entry in mammalian cells including spatial control over Greatwall kinase phosphorylation. After parameter calibration, the model is able to recapture the complex and non-intuitive molecular dynamics reported by Potapova et al. (Potapova et al., 2011). Moreover, it predicts the temporal patterns of other mitotic regulators which have not yet been experimentally tested and suggests a general design principle of cell cycle control: latching switches buffer the cellular stresses which accompany cell cycle processes to ensure that the transitions are smooth and robust.

Overexpression of the Ubiquilin-4 (UBQLN4) is Associated with Cell Cycle Arrest and Apoptosis in Human Normal Gastric Epithelial Cell Lines GES-1 Cells by Activation of the ERK Signaling Pathway

PubMed Central

Huang, Shengkai; Dong, Xin; Wang, Jia; Ding, Jie; Li, Yan; Li, Dongdong; Lin, Hong; Wang, Wenjie; Zhao, Mei

2018-01-01

Background Ubiquilin-4 (UBQLN4) is a component of the ubiquitin-proteasome system and regulates the degradation of many proteins implicated in pathological conditions. The aim of this study was to determine the role of UBQLN4 in regulating the proliferation and survival of the normal gastric epithelial cell line GES-1. Material/Methods We constructed GES-1 lines stably overexpressing UBQLN4 by lentiviral infection. Cell proliferation, apoptosis, and the cell cycle were analyzed using the MTT assay and flow cytometric assays. Phosphorylation of ERK, JNK, p38, and expression of cyclin D1 were detected by western blot analysis. Results Overexpression of UBQLN4 significantly reduced proliferation and induced G2/M phase arrest and apoptosis in GES-1 cells. Moreover, upregulation of UBQLN4 increased the expression of cyclin D1 and phosphorylated ERK, but not JNK or p38. Conclusions These data suggest that UBQLN4 may induce cell cycle arrest and apoptosis via activation of the ERK pathway and upregulation of cyclin D1 in GES-1 cells. PMID:29807370

Phloretin induces cell cycle arrest and apoptosis of human glioblastoma cells through the generation of reactive oxygen species.

PubMed

Liu, Yuanyuan; Fan, Chenghe; Pu, Lv; Wei, Cui; Jin, Haiqiang; Teng, Yuming; Zhao, Mingming; Yu, Albert Cheung Hoi; Jiang, Feng; Shu, Junlong; Li, Fan; Peng, Qing; Kong, Jian; Pan, Bing; Zheng, Lemin; Huang, Yining

2016-06-01

Phloretin, a flavonoid present in various plants, has been reported to exert anticarcinogenic effects. However, the mechanism of its chemo-preventive effect on human glioblastoma cells is not fully understood. This study aimed to investigate the molecular mechanism of phloretin and its associated chemo-preventive effect in human glioblastoma cells. The results indicate that phloretin inhibited cell proliferation by inducing cell cycle arrest at the G0-G1 phase and induced apoptosis of human glioblastoma cells. Phloretin-induced cell cycle arrest was associated with increased expression of p27 and decreased expression of cdk2, cdk4, cdk6, cyclinD and cyclinE. Moreover, the PI3K/AKT/mTOR signaling cascades were suppressed by phloretin in a dose-dependent manner. In addition, phloretin triggered the mitochondrial apoptosis pathway and generated reactive oxygen species (ROS). This was accompanied by the up-regulation of Bax, Bak and c-PARP and the down-regulation of Bcl-2. The antioxidant agents N-acetyl-L-cysteine and glutathione weakened the effect of phloretin on glioblastoma cells. In conclusion, these results demonstrate that phloretin exerts potent chemo-preventive activity in human glioblastoma cells through the generation of ROS.

The therapeutic potential of cell cycle targeting in multiple myeloma.

PubMed

Maes, Anke; Menu, Eline; Veirman, Kim De; Maes, Ken; Vand Erkerken, Karin; De Bruyne, Elke

2017-10-27

Proper cell cycle progression through the interphase and mitosis is regulated by coordinated activation of important cell cycle proteins (including cyclin-dependent kinases and mitotic kinases) and several checkpoint pathways. Aberrant activity of these cell cycle proteins and checkpoint pathways results in deregulation of cell cycle progression, which is one of the key hallmarks of cancer. Consequently, intensive research on targeting these cell cycle regulatory proteins identified several candidate small molecule inhibitors that are able to induce cell cycle arrest and even apoptosis in cancer cells. Importantly, several of these cell cycle regulatory proteins have also been proposed as therapeutic targets in the plasma cell malignancy multiple myeloma (MM). Despite the enormous progress in the treatment of MM the past 5 years, MM still remains most often incurable due to the development of drug resistance. Deregulated expression of the cyclins D is observed in virtually all myeloma patients, emphasizing the potential therapeutic interest of cyclin-dependent kinase inhibitors in MM. Furthermore, other targets have also been identified in MM, such as microtubules, kinesin motor proteins, aurora kinases, polo-like kinases and the anaphase promoting complex/cyclosome. This review will provide an overview of the cell cycle proteins and checkpoint pathways deregulated in MM and discuss the therapeutic potential of targeting proteins or protein complexes involved in cell cycle control in MM.

Cyclin D1b splice variant promotes αvβ3-mediated adhesion and invasive migration of breast cancer cells.

PubMed

Wu, Feng-Hua; Luo, Li-Qiong; Liu, Yi; Zhan, Qiu-Xiao; Luo, Chao; Luo, Jing; Zhang, Gui-Mei; Feng, Zuo-Hua

2014-12-01

Cyclin D1b, a splice variant of the cell cycle regulator cyclin D1, holds oncogenic functions in human cancer. However, the mechanisms underlying cyclin D1b function remain poorly understood. Here we introduced wild-type cyclin D1a or cyclin D1b variant into non-metastatic MCF-7 cells. Our results show that ectopic expression of cyclin D1b promotes invasiveness of the cancer cells in a cyclin D1a independent manner. Specifically, cyclin D1b is found to modulate the expression of αvβ3, which characterizes the metastatic phenotype, and enhance tumor cell invasive potential in cooperating with HoxD3. Notably, cyclin D1b promotes αvβ3-mediated adhesion and invasive migration, which are associated with invasive potential of breast cancer cells. Further exploration indicates that cyclin D1b makes breast cancer cells more sensitive to toll-like receptor 4 ligand released from damaged tumor cells. These findings reveal a role of cyclin D1b as a possible mediator of αvβ3 transcription to promote tumor metastasis. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

Cdc2/cyclin B1 regulates centrosomal Nlp proteolysis and subcellular localization.

PubMed

Zhao, Xuelian; Jin, Shunqian; Song, Yongmei; Zhan, Qimin

2010-11-01

The formation of proper mitotic spindles is required for appropriate chromosome segregation during cell division. Aberrant spindle formation often causes aneuploidy and results in tumorigenesis. However, the underlying mechanism of regulating spindle formation and chromosome separation remains to be further defined. Centrosomal Nlp (ninein-like protein) is a recently characterized BRCA1-regulated centrosomal protein and plays an important role in centrosome maturation and spindle formation. In this study, we show that Nlp can be phosphorylated by cell cycle protein kinase Cdc2/cyclin B1. The phosphorylation sites of Nlp are mapped at Ser185 and Ser589. Interestingly, the Cdc2/cyclin B1 phosphorylation site Ser185 of Nlp is required for its recognition by PLK1, which enable Nlp depart from centrosomes to allow the establishment of a mitotic scaffold at the onset of mitosis . PLK1 fails to dissociate the Nlp mutant lacking Ser185 from centrosome, suggesting that Cdc2/cyclin B1 might serve as a primary kinase of PLK1 in regulating Nlp subcellular localization. However, the phosphorylation at the site Ser589 by Cdc2/cyclin B1 plays an important role in Nlp protein stability probably due to its effect on protein degradation. Furthermore, we show that deregulated expression or subcellular localization of Nlp lead to multinuclei in cells, indicating that scheduled levels of Nlp and proper subcellular localization of Nlp are critical for successful completion of normal cell mitosis, These findings demonstrate that Cdc2/cyclin B1 is a key regulator in maintaining appropriate degradation and subcellular localization of Nlp, providing novel insights into understanding on the role of Cdc2/cyclin B1 in mitotic progression.

Problem-Solving Test: Analysis of the Role of Cyclin B

ERIC Educational Resources Information Center

Szeberenyi, Jozsef

2011-01-01

An experiment is described in this test that was designed to study the role of the cyclin B protein in a cell-free system. The work was performed in the lab of Tim Hunt who, together with Hartwell and Nurse, received the Nobel Prize in Physiology or Medicine in 2001 "for their discoveries of key chemicals that regulate the cell division cycle." It…

Cyclin C influences the timing of mitosis in fission yeast

PubMed Central

Banyai, Gabor; Szilagyi, Zsolt; Baraznenok, Vera; Khorosjutina, Olga; Gustafsson, Claes M.

2017-01-01

The multiprotein Mediator complex is required for the regulated transcription of nearly all RNA polymerase II–dependent genes. Mediator contains the Cdk8 regulatory subcomplex, which directs periodic transcription and influences cell cycle progression in fission yeast. Here we investigate the role of CycC, the cognate cyclin partner of Cdk8, in cell cycle control. Previous reports suggested that CycC interacts with other cellular Cdks, but a fusion of CycC to Cdk8 reported here did not cause any obvious cell cycle phenotypes. We find that Cdk8 and CycC interactions are stabilized within the Mediator complex and the activity of Cdk8-CycC is regulated by other Mediator components. Analysis of a mutant yeast strain reveals that CycC, together with Cdk8, primarily affects M-phase progression but mutations that release Cdk8 from CycC control also affect timing of entry into S phase. PMID:28515143

A nontranscriptional role for Oct4 in the regulation of mitotic entry

PubMed Central

Zhao, Rui; Deibler, Richard W.; Lerou, Paul H.; Ballabeni, Andrea; Heffner, Garrett C.; Cahan, Patrick; Unternaehrer, Juli J.; Kirschner, Marc W.; Daley, George Q.

2014-01-01

Rapid progression through the cell cycle and a very short G1 phase are defining characteristics of embryonic stem cells. This distinct cell cycle is driven by a positive feedback loop involving Rb inactivation and reduced oscillations of cyclins and cyclin-dependent kinase (Cdk) activity. In this setting, we inquired how ES cells avoid the potentially deleterious consequences of premature mitotic entry. We found that the pluripotency transcription factor Oct4 (octamer-binding transcription factor 4) plays an unappreciated role in the ES cell cycle by forming a complex with cyclin–Cdk1 and inhibiting Cdk1 activation. Ectopic expression of Oct4 or a mutant lacking transcriptional activity recapitulated delayed mitotic entry in HeLa cells. Reduction of Oct4 levels in ES cells accelerated G2 progression, which led to increased chromosomal missegregation and apoptosis. Our data demonstrate an unexpected nontranscriptional function of Oct4 in the regulation of mitotic entry. PMID:25324523

Mapping of CIP/KIP inhibitors, G1 cyclins D1, D3, E and p53 proteins in the rat term placenta.

PubMed

Korgun, Emin Turkay; Unek, Gozde; Herrera, Emilio; Jones, Carolyn J; Wadsack, Christian; Kipmen-Korgun, Dijle; Desoye, Gernot

2011-09-01

As cell cycle regulation is fundamental to the normal growth and development of the placenta, the aim of the present study was to determine the immunolocalizations of cell cycle related proteins, which have key roles in proliferation, differentiation and apoptosis during the development of the rat placenta. Here immunohistochemistry has been used to localize G1 cyclins (D1, D3, E), which are major determinants of proliferation, CIP/KIP inhibitors (p21, p27, p57), p53 as a master regulator and proliferating cell nuclear antigen in all cell types of the rat term placenta. The proportion of each cell type immunolabeled was counted. Cyclin D1 and cyclin D3 were present mostly in cells of the fetal aspect of the placenta, whereas the G1/S cyclin E was present only in the spongio- and labyrinthine trophoblast populations. Among the CIP/KIP inhibitors, p21 was present only in cells of the fetal aspect whereas p27 and p57 were found in all cell types studied. p53 was only found in a small proportion of cells with no co-localization of p53 and p21. The data suggest that the cells of the fetal side of the rat placenta still have some proliferation potential which is kept in check by expression of the CIP/KIP cell cycle inhibitors, whereas cells of the maternal aspect have lost this potential. Apoptosis is only marginal in the term rat placenta. In conclusion, proliferation and apoptosis in rat placental cells appears controlled mostly by the CIP/KIP inhibitors in late pregnancy.

Enterolactone Induces G1-phase Cell Cycle Arrest in Nonsmall Cell Lung Cancer Cells by Downregulating Cyclins and Cyclin-dependent Kinases.

PubMed

Chikara, Shireen; Lindsey, Kaitlin; Dhillon, Harsharan; Mamidi, Sujan; Kittilson, Jeffrey; Christofidou-Solomidou, Melpo; Reindl, Katie M

2017-01-01

Flaxseed is a rich source of the plant lignan secoisolariciresinol diglucoside (SDG), which is metabolized into mammalian lignans enterodiol (ED) and enterolactone (EL) in the digestive tract. The anticancer properties of these lignans have been demonstrated for various cancer types, but have not been studied for lung cancer. In this study, we investigated the anticancer effects of EL for several nonsmall cell lung cancer (NSCLC) cell lines of various genetic backgrounds. EL inhibited the growth of A549, H441, and H520 lung cancer cells in concentration- and time-dependent manners. The antiproliferative effects of EL for lung cancer cells were not due to enhanced cell death, but rather due to G 1 -phase cell cycle arrest. Molecular studies revealed that EL decreased mRNA or protein expression levels of the G 1 -phase promoters cyclin D1, cyclin E, cyclin-dependent kinases (CDK)-2, -4, and -6, and p-cdc25A; decreased phosphorylated retinoblastoma (p-pRb) protein levels; and simultaneously increased levels of p21 WAF1/CIP1 , a negative regulator of the G 1 phase. The results suggest that EL inhibits the growth of NSCLC cell lines by downregulating G 1 -phase cyclins and CDKs, and upregulating p21 WAF1/CIP1 , which leads to G 1 -phase cell cycle arrest. Therefore, EL may hold promise as an adjuvant treatment for lung cancer therapy.

Cyclin D-Cdk4 is regulated by GATA-1 and required for megakaryocyte growth and polyploidization.

PubMed

Muntean, Andrew G; Pang, Liyan; Poncz, Mortimer; Dowdy, Steven F; Blobel, Gerd A; Crispino, John D

2007-06-15

Endomitosis is a unique form of cell cycle used by megakaryocytes, in which the latter stages of mitosis are bypassed so that the cell can increase its DNA content and size. Although several transcription factors, including GATA-1 and RUNX-1, have been implicated in this process, the link between transcription factors and polyploidization remains undefined. Here we show that GATA-1-deficient megakaryocytes, which display reduced size and polyploidization, express nearly 10-fold less cyclin D1 and 10-fold increased levels of p16 compared with their wild-type counterparts. We further demonstrate that cyclin D1 is a direct GATA-1 target in megakaryocytes, but not erythroid cells. Restoration of cyclin D1 expression, when accompanied by ectopic overexpression of its partner Cdk4, resulted in a dramatic increase in megakaryocyte size and DNA content. However, terminal differentiation was not rescued. Of note, polyploidization was only modestly reduced in cyclin D1-deficient mice, likely due to compensation by elevated cyclin D3 expression. Finally, consistent with an additional defect conferred by increased levels of p16, inhibition of cyclin D-Cdk4 complexes with a TAT-p16 fusion peptide significantly blocked polyploidization of wild-type megakaryocytes. Together, these data show that GATA-1 controls growth and polyploidization by regulating cyclin D-Cdk4 kinase activity.

Cyclin D–Cdk4 is regulated by GATA-1 and required for megakaryocyte growth and polyploidization

PubMed Central

Muntean, Andrew G.; Pang, Liyan; Poncz, Mortimer; Dowdy, Steven F.; Blobel, Gerd A.

2007-01-01

Endomitosis is a unique form of cell cycle used by megakaryocytes, in which the latter stages of mitosis are bypassed so that the cell can increase its DNA content and size. Although several transcription factors, including GATA-1 and RUNX-1, have been implicated in this process, the link between transcription factors and polyploidization remains undefined. Here we show that GATA-1–deficient megakaryocytes, which display reduced size and polyploidization, express nearly 10-fold less cyclin D1 and 10-fold increased levels of p16 compared with their wild-type counterparts. We further demonstrate that cyclin D1 is a direct GATA-1 target in megakaryocytes, but not erythroid cells. Restoration of cyclin D1 expression, when accompanied by ectopic overexpression of its partner Cdk4, resulted in a dramatic increase in megakaryocyte size and DNA content. However, terminal differentiation was not rescued. Of note, polyploidization was only modestly reduced in cyclin D1–deficient mice, likely due to compensation by elevated cyclin D3 expression. Finally, consistent with an additional defect conferred by increased levels of p16, inhibition of cyclin D-Cdk4 complexes with a TAT-p16 fusion peptide significantly blocked polyploidization of wild-type megakaryocytes. Together, these data show that GATA-1 controls growth and polyploidization by regulating cyclin D-Cdk4 kinase activity. PMID:17317855

The absence of p27Kip1, an inhibitor of G1 cyclin-dependent kinases, uncouples differentiation and growth arrest during the granulosa->luteal transition.

PubMed

Tong, W; Kiyokawa, H; Soos, T J; Park, M S; Soares, V C; Manova, K; Pollard, J W; Koff, A

1998-09-01

The involvement of cyclin-dependent kinase inhibitors in differentiation remains unclear: are the roles of cyclin-dependent kinase inhibitors restricted to cell cycle arrest; or also required for completion of the differentiation program; or both? Here, we report that differentiation of luteal cells can be uncoupled from growth arrest in p27-deficient mice. In these mice, female-specific infertility correlates with a failure of embryos to implant at embryonic day 4.5. We show by ovarian transplant and hormone reconstitution experiments that failure to regulate luteal cell estradiol is one physiological mechanism for infertility in these mice. This failure is not due to a failure of p27-deficient granulosa cells to differentiate after hormonal stimulation; P450scc, a marker for luteal progesterone biosynthesis, is expressed and granulosa cell-specific cyclin D2 expression is reduced. However, unlike their wild-type counterparts, p27-deficient luteal cells continue to proliferate for up to 3.5 days after hormonal stimulation. By day 5.5, however, these cells withdraw from the cell cycle, suggesting that p27 plays a role in the early events regulating withdrawal of cells from the cell cycle. We have further shown that in the absence of this timely withdrawal, estradiol regulation is perturbed, explaining in part how fertility is compromised at the level of implantation. These data support the interpretation of our previous observations on oligodendrocyte differentiation about a role for p27 in establishing the nonproliferative state, which in some cases (oligodendrocytes) is required for differentiation, whereas in other cases it is required for the proper functioning of a differentiated cell (luteal cell).

Cyc17, a meiosis-specific cyclin, is essential for anaphase initiation and chromosome segregation in Tetrahymena thermophila.

PubMed

Yan, Guan-Xiong; Dang, Huai; Tian, Miao; Zhang, Jing; Shodhan, Anura; Ning, Ying-Zhi; Xiong, Jie; Miao, Wei

2016-07-17

Although the role of cyclins in controlling nuclear division is well established, their function in ciliate meiosis remains unknown. In ciliates, the cyclin family has undergone massive expansion which suggests that diverse cell cycle systems exist, and this warrants further investigation. A screen for cyclins in the model ciliate Tetrahymena thermophila showed that there are 34 cyclins in this organism. Only 1 cyclin, Cyc17, contains the complete cyclin core and is specifically expressed during meiosis. Deletion of CYC17 led to meiotic arrest at the diakinesis-like metaphase I stage. Expression of genes involved in DNA metabolism and chromosome organization (chromatin remodeling and basic chromosomal structure) was repressed in cyc17 knockout matings. Further investigation suggested that Cyc17 is involved in regulating spindle pole attachment, and is thus essential for chromosome segregation at meiosis. These findings suggest a simple model in which chromosome segregation is influenced by Cyc17.

F-box protein FBXL2 targets cyclin D2 for ubiquitination and degradation to inhibit leukemic cell proliferation

PubMed Central

Chen, Bill B.; Glasser, Jennifer R.; Coon, Tiffany A.; Zou, Chunbin; Miller, Hannah L.; Fenton, Moon; McDyer, John F.; Boyiadzis, Michael

2012-01-01

Hematologic maligancies exhibit a growth advantage by up-regulation of components within the molecular apparatus involved in cell-cycle progression. The SCF (Skip-Cullin1-F-box protein) E3 ligase family provides homeostatic feedback control of cell division by mediating ubiquitination and degradation of cell-cycle proteins. By screening several previously undescribed E3 ligase components, we describe the behavior of a relatively new SCF subunit, termed FBXL2, that ubiquitinates and destabilizes cyclin D2 protein leading to G0 phase arrest and apoptosis in leukemic and B-lymphoblastoid cell lines. FBXL2 expression was strongly suppressed, and yet cyclin D2 protein levels were robustly expressed in acute myelogenous leukemia (AML) and acute lymphoblastic leukemia (ALL) patient samples. Depletion of endogenous FBXL2 stabilized cyclin D2 levels, whereas ectopically expressed FBXL2 decreased cyclin D2 lifespan. FBXL2 did not bind a phosphodegron within its substrate, which is typical of other F-box proteins, but uniquely targeted a calmodulin-binding signature within cyclin D2 to facilitate its polyubiquitination. Calmodulin competes with the F-box protein for access to this motif where it bound and protected cyclin D2 from FBXL2. Calmodulin reversed FBXL2-induced G0 phase arrest and attenuated FBXL2-induced apoptosis of lymphoblastoid cells. These results suggest an antiproliferative effect of SCFFBXL2 in lymphoproliferative malignancies. PMID:22323446

A non-redundant function of cyclin E1 in hematopoietic stem cells.

PubMed

Campaner, Stefano; Viale, Andrea; De Fazio, Serena; Doni, Mirko; De Franco, Francesca; D'Artista, Luana; Sardella, Domenico; Pelicci, Pier Giuseppe; Amati, Bruno

2013-12-01

A precise balance between quiescence and proliferation is crucial for the lifelong function of hematopoietic stem cells (HSCs). Cyclins E1 and E2 regulate exit from quiescence in fibroblasts, but their role in HSCs remains unknown. Here, we report a non-redundant role for cyclin E1 in mouse HSCs. A long-term culture-initiating cell (LTC-IC) assay indicated that the loss of cyclin E1, but not E2, compromised the colony-forming activity of primitive hematopoietic progenitors. Ccne1(-/-) mice showed normal hematopoiesis in vivo under homeostatic conditions but a severe impairment following myeloablative stress induced by 5-fluorouracil (5-FU). Under these conditions, Ccne1(-/-) HSCs were less efficient in entering the cell cycle, resulting in decreased hematopoiesis and reduced survival of mutant mice upon weekly 5-FU treatment. The role of cyclin E1 in homeostatic conditions became apparent in aged mice, where HSC quiescence was increased in Ccne1(-/-) animals. On the other hand, loss of cyclin E1 provided HSCs with a competitive advantage in bone marrow serial transplantation assays, suggesting that a partial impairment of cell cycle entry may exert a protective role by preventing premature depletion of the HSC compartment. Our data support a role for cyclin E1 in controlling the exit from quiescence in HSCs. This activity, depending on the physiological context, can either jeopardize or protect the maintenance of hematopoiesis.

Cdc20 hypomorphic mice fail to counteract de novo synthesis of cyclin B1 in mitosis

PubMed Central

Malureanu, Liviu; Jeganathan, Karthik B.; Jin, Fang; Baker, Darren J.; van Ree, Janine H.; Gullon, Oliver; Chen, Zheyan; Henley, John R.

2010-01-01

Cdc20 is an activator of the anaphase-promoting complex/cyclosome that initiates anaphase onset by ordering the destruction of cyclin B1 and securin in metaphase. To study the physiological significance of Cdc20 in higher eukaryotes, we generated hypomorphic mice that express small amounts of this essential cell cycle regulator. In this study, we show that these mice are healthy and not prone to cancer despite substantial aneuploidy. Cdc20 hypomorphism causes chromatin bridging and chromosome misalignment, revealing a requirement for Cdc20 in efficient sister chromosome separation and chromosome–microtubule attachment. We find that cyclin B1 is newly synthesized during mitosis via cytoplasmic polyadenylation element–binding protein-dependent translation, causing its rapid accumulation between prometaphase and metaphase of Cdc20 hypomorphic cells. Anaphase onset is significantly delayed in Cdc20 hypomorphic cells but not when translation is inhibited during mitosis. These data reveal that Cdc20 is particularly rate limiting for cyclin B1 destruction because of regulated de novo synthesis of this cyclin after prometaphase onset. PMID:20956380

Increase in Ara-C cytotoxicity in the presence of valproate, a histone deacetylase inhibitor, is associated with the concurrent expression of cyclin D1 and p27(Kip 1) in acute myeloblastic leukemia cells.

PubMed

Siitonen, Timo; Koistinen, Pirjo; Savolainen, Eeva-Riitta

2005-11-01

The effects of valproate and butyrate were investigated in an acute myeloblastic cell line (OCI/AML-2) on cytotoxicity, cell cycle profile and expression of cell cycle regulating proteins in the presence of cytarabine (Ara-C) and etoposide. As a single agent valproate and butyrate inhibited AML cell growth but did not significantly induce cell death. A dramatic increase in cytotoxicity was observed when combining valproate or butyrate with Ara-C, whereas, co-addition of them with etoposide had much smaller effect on cell death. Valproate induced a clear G1 phase arrest and up-regulated cyclin D1 expression in the presence of Ara-C and etoposide. In addition, valporate was able to block the Ara-C-induced down-regulation of p27(Kip1) expression but not that induced by etoposide.

Cyclin E-Mediated Human Proopiomelanocortin Regulation as a Therapeutic Target for Cushing Disease.

PubMed

Liu, Ning-Ai; Araki, Takako; Cuevas-Ramos, Daniel; Hong, Jiang; Ben-Shlomo, Anat; Tone, Yukiko; Tone, Masahide; Melmed, Shlomo

2015-07-01

Cushing disease, due to pituitary corticotroph tumor ACTH hypersecretion, drives excess adrenal cortisol production with adverse morbidity and mortality. Loss of glucocorticoid negative feedback on the hypothalamic-pituitary-adrenal axis leads to autonomous transcription of the corticotroph precursor hormone proopiomelanocortin (POMC), consequent ACTH overproduction, and adrenal hypercortisolism. We previously reported that R-roscovitine (CYC202, seliciclib), a 2,6,9-trisubstituted purine analog, suppresses cyclin-dependent-kinase 2/cyclin E and inhibits ACTH in mice and zebrafish. We hypothesized that intrapituitary cyclin E signaling regulates corticotroph tumor POMC transcription independently of cell cycle progression. The aim was to investigate whether R-roscovitine inhibits human ACTH in corticotroph tumors by targeting the cyclin-dependent kinase 2/cyclin E signaling pathway. Primary cell cultures of surgically resected human corticotroph tumors were treated with or without R-roscovitine, ACTH measured by RIA and quantitative PCR, and/or Western blot analysis performed to investigate ACTH and lineage-specific transcription factors. Cyclin E and E2F transcription factor 1 (E2F1) small interfering RNA (siRNA) transfection was performed in murine corticotroph tumor AtT20 cells to elucidate mechanisms for drug action. POMC gene promoter activity in response to R-roscovitine treatment was analyzed using luciferase reporter and chromatin immunoprecipitation assays. R-roscovitine inhibits human corticotroph tumor POMC and Tpit/Tbx19 transcription with decreased ACTH expression. Cyclin E and E2F1 exhibit reciprocal positive regulation in corticotroph tumors. R-roscovitine disrupts E2F1 binding to the POMC gene promoter and suppresses Tpit/Tbx19 and other lineage-specific POMC transcription cofactors via E2F1-dependent and -independent pathways. R-roscovitine inhibits human pituitary corticotroph tumor ACTH by targeting the cyclin E/E2F1 pathway. Pituitary cyclin E/E2F1 signaling is a previously unappreciated molecular mechanism underlying neuroendocrine regulation of the hypothalamic-pituitary-adrenal axis, providing a subcellular therapeutic target for small molecule cyclin-dependent kinase 2 inhibitors of pituitary ACTH-dependent hypercortisolism, ie, Cushing disease.

α-Phellandrene alters expression of genes associated with DNA damage, cell cycle, and apoptosis in murine leukemia WEHI-3 cells.

PubMed

Lin, Jen-Jyh; Yu, Chien-Chih; Lu, Kung-Wen; Chang, Shu-Jen; Yu, Fu-Shun; Liao, Ching-Lung; Lin, Jaung-Geng; Chung, Jing-Gung

2014-08-01

α-phellandrene (α-PA) is a cyclic monoterpene, present in natural plants such as Schinus molle L. α-PA promotes immune responses in mice in vivo. However, there is no available information on whether α-PA affects gene expression in leukemia cells. The present study determined effects of α-PA on expression levels of genes associated with DNA damage, cell cycle and apoptotic cell death in mouse leukemia WEHI-3 cells. WEHI-3 cells were treated with 10 μM α-PA for 24 h, cells were harvested and total RNA was extracted, and gene expression was analyzed by cDNA microarray. Results indicated that α-PA up-regulated 10 genes 4-fold, 13 by over 3-fold and 175 by over 2-fold; 21 genes were down-regulated by over 4-fold, 26 genes by over 3-fold and expression of 204 genes was altered by at leas 2-fold compared with the untreated control cells. DNA damage-associated genes such as DNA damage-inducer transcript 4 and DNA fragmentation factor were up-regulated by 4-fold and over 2-fold, respectively; cell-cycle check point genes such as cyclin G2 and cyclin-dependent kinases inhibitor 2D and IA (p21) were up-regulated by over 3-fold and over 2-fold, respectively; apoptosis-associated genes such as BCL2/adenovirus EIB interacting protein 3, XIAP-associated factor 1, BCL2 modifying factor, caspase-8 and FADD-like apoptosis regulator were over 2-fold up-regulated. Furthermore, DNA damage-associated gene TATA box binding protein was over 4-fold down-regulated, and D19Ertd652c (DNA segment) over 2-fold down-regulated; cell cycle-associated gene cyclin E2 was over 2-fold down-regulated; apoptosis associated gene growth arrest-specific 5 was over 9-fold down-regulated, Gm5426 (ATP synthase) was over 3-fold down-regulated, and death box polypeptide 33 was over 2-fold down-regulated. Based on these observations, α-PA altered gene expression in WEHI-3 cells in vitro. Copyright© 2014 International Institute of Anticancer Research (Dr. John G. Delinassios), All rights reserved.

Cyclin E-p27 opposition and regulation of the G1 phase of the cell cycle in the murine neocortical PVE: a quantitative analysis of mRNA in situ hybridization

NASA Technical Reports Server (NTRS)

Delalle, I.; Takahashi, T.; Nowakowski, R. S.; Tsai, L. H.; Caviness, V. S. Jr

1999-01-01

We have analyzed the expression patterns of mRNAs of five cell cycle related proteins in the ventricular zone of the neocortical cerebral wall over the course of the neuronogenetic interval in the mouse. One set of mRNAs (cyclin E and p21) are initially expressed at high levels but expression then falls to a low asymptote. A second set (p27, cyclin B and cdk2) are initially expressed at low levels but ascend to peak levels only to decline again. These patterns divide the overall neuronogenetic interval into three phases. In phase 1 cyclin E and p21 levels of mRNA expression are high, while those of mRNAs of p27, cdk2 and cyclin B are low. In this phase the fraction of cells leaving the cycle after each mitosis, Q, is low and the duration of the G1 phase, TG1, is short. In phase 2 levels of expression of cyclin E and p21 fall to asymptote while levels of expression of mRNA of the other three proteins reach their peaks. Q increases to approach 0.5 and TG1 increases even more rapidly to approach its maximum length. In phase 3 levels of expression of cyclin E and p21 mRNAs remain low and those of the mRNAs of the other three proteins fall. TG1 becomes maximum and Q rapidly increases to 1.0. The character of these phases can be understood in part as consequences of the reciprocal regulatory influence of p27 and cyclin E and of the rate limiting functions of p27 at the restriction point and of cyclin E at the G1 to S transition.

Oxygen-Glucose Deprivation Induces G2/M Cell Cycle Arrest in Brain Pericytes Associated with ERK Inactivation.

PubMed

Wei, Wenjie; Yu, Zhiyuan; Xie, Minjie; Wang, Wei; Luo, Xiang

2017-01-01

Growing evidence has revealed that brain pericytes are multifunctional and contribute to the pathogenesis of a number of neurological disorders. However, the role of pericytes in cerebral ischemia, and especially the pathophysiological alterations in pericytes, remains unclear. In the present study, our aim was to determine whether the proliferation of pericytes is affected by cerebral ischemia and, if so, to identify the underlying mechanism(s). Cultured brain pericytes subjected to oxygen-glucose deprivation (OGD) were used as our model of cerebral ischemia; the protein expression levels of cyclin D1, cyclin E, cdk4, and cyclin B1 were determined by Western blot analysis, and cell cycle analysis was assessed by flow cytometry. The OGD treatment reduced the brain pericyte proliferation by causing G2/M phase arrest and downregulating the protein levels of cyclin D1, cyclin E, cdk4, and cyclin B1. Further studies demonstrated a simultaneous decrease in the activity of extracellular regulated protein kinases (ERK), suggesting a critical role of the ERK signaling cascade in the inhibition of OGD-induced pericyte proliferation. We suggest that OGD inhibition of the proliferation of brain pericytes is associated with the inactivation of the ERK signaling pathway, which arrests them in the G2/M phase.

Tax-dependent stimulation of G1 phase-specific cyclin-dependent kinases and increased expression of signal transduction genes characterize HTLV type 1-transformed T cells.

PubMed

Haller, K; Ruckes, T; Schmitt, I; Saul, D; Derow, E; Grassmann, R

2000-11-01

Human T cell leukemia virus protein induces T cells to permanent IL-2-dependent growth. These cells occasionally convert to factor independence. The viral oncoprotein Tax acts as an essential growth factor of transformed lymphocytes and stimulates the cell cycle in the G(1) phase. In T cells and fibroblasts Tax enhances the activity of the cyclin-dependent kinases (CDK) CDK4 and CDK6. These kinases, which require binding to cyclin D isotypes for their activity, control the G(1) phase. Coimmunoprecipitation from these cells revealed that Tax associates with cyclin D3/CDK6, suggesting a direct activation of this kinase. The CDK stimulation may account in part for the mitogenic Tax effect, which causes IL-2-dependent T cell growth by Tax. To address the conversion to IL-2-independent proliferation and to identify overexpressed genes, which contribute to the transformed growth, the gene expression patterns of HTLV-1-transformed T cells were compared with that of peripheral blood lymphocytes. Potentially overexpressed cDNAs were cloned, sequenced, and used to determine the RNA expression. Genes found to be up-regulated are involved in signal transduction (STAT5a, cyclin G(1), c-fgr, hPGT) and also glycoprotein synthesis (LDLC, ribophorin). Many of these are also activated during T cell activation and implicated in the regulation of growth and apoptosis. The transcription factor STAT5a, which is involved in IL-2 signaling, was strongly up-regulated only in IL-2-independent cells, thus suggesting that it contributes to factor-independent growth. Thus, the differentially expressed genes could cooperate with the Tax-induced cell cycle stimulation in the maintenance of IL-2-dependent and IL-2-independent growth of HTLV-transformed lymphocytes.

Regulation of tomato fruit pericarp development by an interplay between CDKB and CDKA1 cell cycle genes

PubMed Central

Czerednik, Anna; Busscher, Marco; Bielen, Bram A.M.; Wolters-Arts, Mieke; de Maagd, Ruud A.; Angenent, Gerco C.

2012-01-01

Growth of tomato fruits is determined by cell division and cell expansion, which are tightly controlled by factors that drive the core cell cycle. The cyclin-dependent kinases (CDKs) and their interacting partners, the cyclins, play a key role in the progression of the cell cycle. In this study the role of CDKA1, CDKB1, and CDKB2 in fruit development was characterized by fruit-specific overexpression and down-regulation. CDKA1 is expressed in the pericarp throughout development, but is strongly up-regulated in the outer pericarp cell layers at the end of the growth period, when CDKB gene expression has ceased. Overexpression of the CDKB genes at later stages of development and the down-regulation of CDKA1 result in a very similar fruit phenotype, showing a reduction in the number of cell layers in the pericarp and alterations in the desiccation of the fruits. Expression studies revealed that CDKA1 is down-regulated by the expression of CDKB1/2 in CDKB1 and CDKB2 overexpression mutants, suggesting opposite roles for these types of CDK proteins in tomato pericarp development. PMID:22282536

Cyclin Polynucleotides, Polypeptides And Uses Thereof.

DOEpatents

Lowe, Keith S.; Tao, Yumin; Gordon-Kamm, William J.; Gregory, Carolyn A.; Hoerster, George J.; McElver, John A.

2003-02-11

The invention provides isolated polynucleotides and their encoded proteins that are involved in cell cycle regulation. The invention further provides recombinant expression cassettes, host cells, transgenic plants, and antibody compositions. The present invention provides methods and compositions relating to altering cell cycle protein content and/or composition of plants.

Modifications in cell cycle kinetics and in expression of G1 phase-regulating proteins in human amniotic cells after exposure to electromagnetic fields and ionizing radiation.

PubMed

Lange, S; Viergutz, T; Simkó, M

2004-10-01

Low-frequency electromagnetic fields are suspected of being involved in carcinogenesis, particularly in processes that could be related to cancer promotion. Because development of cancer is associated with deregulated cell growth and we previously observed a magnetic field-induced decrease in DNA synthesis [Lange et al. (2002) Alterations in the cell cycle and in the protein level of cyclin D1p, 21CIP1, and p16INK4a after exposure to 50 HZ. MF in human cells. Radiat. Environ. Biophys.41, 131], this study aims to document the influence of 50 Hz, 1 mT magnetic fields (MF), with or without initial gamma-ionizing radiation (IR), on the following cell proliferation-relevant parameters in human amniotic fluid cells (AFC): cell cycle distribution, expression of the G1 phase-regulating proteins Cdk4, cyclin D1, p21CIP1 and p16INK4a, and Cdk4 activity. While IR induced a G1 delay and a dose-dependent G2 arrest, no discernible changes in cell cycle kinetics were observed due to MF exposure. However, a significant decrease in the protein expression of cyclin D1 and an increase in p21CIP1- and p16INK4a-expression could be detected after exposure to MF alone. IR-exposure caused an augmentation of p21CIP1- and p16INK4a- levels as well, but did not alter cyclin D1 expression. A slight diminution of Cdk4 activity was noticed after MF exposure only, indicating that Cdk4 appears not to act as a mediator of MF- or IR-induced changes in the cell cycle of AFC cells. Co-exposure to MF/IR affected neither cell cycle distribution nor protein expression or kinase activity additionally or synergistically, and therefore MF seems not to modify the mutagenic potency of IR.

Ran GTPase protein promotes human pancreatic cancer proliferation by deregulating the expression of Survivin and cell cycle proteins

DOE Office of Scientific and Technical Information (OSTI.GOV)

Deng, Lin; Department of Oncology, Tangdu Hospital, Fourth Military Medical University, Xi’an, Shaanxi 710038; Lu, Yuanyuan

2013-10-18

Highlights: •Overexpression of Ran in pancreatic cancer was correlated with histological grade. •Downregulation of Ran could induce cell apoptosis and inhibit cell proliferation. •The effects were mediated by cell cycle proteins, Survivin and cleaved Caspase-3. -- Abstract: Ran, a member of the Ras GTPase family, has important roles in nucleocytoplasmic transport. Herein, we detected Ran expression in pancreatic cancer and explored its potential role on tumour progression. Overexpressed Ran in pancreatic cancer tissues was found highly correlated with the histological grade. Downregulation of Ran led to significant suppression of cell proliferation, cell cycle arrest at the G1/S phase and inductionmore » of apoptosis. In vivo studies also validated that result. Further studies revealed that those effects were at least partly mediated by the downregulation of Cyclin A, Cyclin D1, Cyclin E, CDK2, CDK4, phospho-Rb and Survivin proteins and up regulation of cleaved Caspase-3.« less

CAK-Cyclin-dependent Activating Kinase: a key kinase in cell cycle control and a target for drugs?

PubMed

Lolli, Graziano; Johnson, Louise N

2005-04-01

The Cyclin-dependent kinase (CDK) Activating Kinase (CAK) is responsible for the activating phosphorylation of CDK1, CDK2, CDK4 and CDK6 and regulation of the cell cycle. The kinase is composed of three subunits: CDK7, Cyclin H and MAT1 (ménage a trois). Together with six other subunits, CAK is also part of the general transcription factor TFIIH where it is involved in promoter clearance and progression of transcription from the preinitiation to the initiation stage. CAK is required for cell cycle progression, which suggests that CDK7 could be a target for cancer therapy. However its role in transcription and its ubiquitous presence raise sensible concerns about possible toxicity of its inhibitors. The recently determined structure of CDK7 allows the design of inhibitors with differential specificity for the different CDKs. We review the role of CAK in different biological processes and evaluate the biological evidence for CDK7 as a possible pharmacological target.

Synchronous and Time-Dependent Expression of Cyclins, Cyclin-Dependant Kinases, and Apoptotic Genes in the Rumen Epithelia of Butyrate-Infused Goats

PubMed Central

Soomro, Jamila; Lu, Zhongyan; Gui, Hongbing; Zhang, Bei; Shen, Zanming

2018-01-01

In our previous study, we demonstrated that butyrate induced ruminal epithelial growth through cyclin D1 upregulation. Here, we investigated the influence of butyrate on the expression of genes associated with cell cycle and apoptosis in rumen epithelium. Goats (n = 24) were given an intra ruminal infusion of sodium butyrate at 0.3 (group B, n = 12) or 0 (group A, n = 12) g/kg of body weight (BW) per day before morning feeding for 28 days and were slaughtered (4 goat/group) at 5,7 and 9 h after butyrate infusion. Rumen fluid was analyzed for short chain fatty acids (SCFAs) concentration. Ruminal tissues were analyzed for morpho-histrometry and the expressions of genes associated with cell cycle and apoptosis. The results revealed that the ruminal butyrate concentration increased (P < 0.05) in B compared to group A. Morphometric analysis showed increased (P < 0.05) papillae size associated with higher number of cell layers in epithelial strata in B compared to A. Butyrate-induced papillae enlargement was coupled with enhanced mRNA expression levels (P < 0.05) of cyclin D1, CDK2, CDK4, and CDK6 (G0/G1 phase regulators) at 5 h, cyclin E1 (G1/S phase regulator) at 7 h and cyclin A and CDK1 (S phase regulators) at 9 h post-infusion compared to A group. In addition, the mRNA expression levels of apoptotic genes, i.e., caspase 3, caspase 9 and Bax at 5 h post-infusion were upregulated (P < 0.05) in group B compared to group A. The present study demonstrated that butyrate improved ruminal epithelial growth through concurrent and time-dependent changes in the expressions of genes involved in cell proliferation and apoptosis. It seems that the rate of proliferation was higher than the apoptosis which was reflected in epithelial growth. PMID:29875672

Expression of p21Waf1/Cip1 and cyclin D1 is increased in butyrate-resistant HeLa cells.

PubMed

Derjuga, A; Richard, C; Crosato, M; Wright, P S; Chalifour, L; Valdez, J; Barraso, A; Crissman, H A; Nishioka, W; Bradbury, E M; Th'ng, J P

2001-10-12

Sodium butyrate induced cell cycle arrest in mammalian cells through an increase in p21Waf1/Cip1, although another study showed that this arrest is related to pRB signaling. We isolated variants of HeLa cells adapted to growth in 5 mm butyrate. One of these variants, clone 5.1, constitutively expressed elevated levels of p21Waf1/Cip1 when incubated in regular growth medium and in the presence of butyrate. Despite this elevated level of p21Waf1/Cip1, the cells continue to proliferate, albeit at a slower rate than parental HeLa cells. Western blot analyses showed that other cell cycle regulatory proteins were not up-regulated to compensate for the elevated expression of p21Waf1/Cip1. However, cyclin D1 was down-regulated by butyrate in HeLa cells but not in clone 5.1. We conclude that continued expression of cyclin D1 allowed clone 5.1 to grow in the presence of butyrate and elevated levels of p21Waf1/Cip1.

Cyclin D1 negatively regulates the expression of differentiation genes in HT-29 M6 mucus-secreting colon cancer cells.

PubMed

Mayo, Clara; Mayol, Xavier

2009-08-28

HT-29 M6 colon cancer cells differentiate to a mucus-secreting phenotype in culture. We found that the pattern of cyclin D1 expression in HT-29 M6 cells did not correlate with instances of cell proliferation but was specifically induced during a dedifferentiation process following disaggregation of epithelial cell layers, even under conditions that did not allow cell cycle reentrance. Interestingly, ectopic expression of cyclin D1 in differentiated cells led to the inhibition of the transcriptional activity of differentiation gene promoters, such as the mucin MUC1. We thus propose that the overexpression of cyclin D1 found in colon cancer favours tumour dedifferentiation as one mechanism of tumour progression.

Cyclin B Translation Depends on mTOR Activity after Fertilization in Sea Urchin Embryos

PubMed Central

Boulben, Sandrine; Glippa, Virginie; Morales, Julia; Cormier, Patrick

2016-01-01

The cyclin B/CDK1 complex is a key regulator of mitotic entry. Using PP242, a specific ATP-competitive inhibitor of mTOR kinase, we provide evidence that the mTOR signalling pathway controls cyclin B mRNA translation following fertilization in Sphaerechinus granularis and Paracentrotus lividus. We show that PP242 inhibits the degradation of the cap-dependent translation repressor 4E-BP (eukaryotic initiation factor 4E-Binding Protein). PP242 inhibits global protein synthesis, delays cyclin B accumulation, cyclin B/CDK1 complex activation and consequently entry into the mitotic phase of the cell cycle triggered by fertilization. PP242 inhibits cyclin B mRNA recruitment into active polysomes triggered by fertilization. An amount of cyclin B mRNA present in active polysomes appears to be insensitive to PP242 treatment. Taken together, our results suggest that, following sea urchin egg fertilization, cyclin B mRNA translation is controlled by two independent mechanisms: a PP242-sensitive and an additional PP242-insentitive mechanism. PMID:26962866

Function of cell-cycle regulators in predicting silent pituitary adenoma progression following surgical resection

PubMed Central

Park, Sung Hyun; Jang, Ji Hwan; Lee, Young Min; Kim, Joon Soo; Kim, Kyu Hong; Kim, Young Zoon

2017-01-01

The present study investigated the use of cell-cycle regulators for predicting the progression of silent pituitary adenoma (SPA) following surgical resection, via immunohistochemical analysis of tumor samples obtained by surgical resection. The medical records of patients diagnosed with SPA between January 2000 and December 2013 in the Samsung Changwon Hospital, Sungkyunkwan University School of Medicine (Changwon, South Korea) were reviewed. Immunohistochemical staining was performed on sections of the archived, paraffin-embedded tissues obtained by surgery, with all tissues stained for cell-cycle regulatory proteins p16, p15, p21, cyclin-dependent kinase (CDK)4, CDK6, retinoblastoma protein (pRb) and cyclin D1, as well as E3 ubiquitin-protein ligase mib1 (MIB-1) antigen and p53. The primary end-point was to investigate the expression of cell-cycle regulatory proteins in SPA. The secondary end-point was to estimate the progression-free survival of patients with SPA following surgical resection and to identify its association with the expression of cell-cycle regulatory proteins. Of the 127 SPA samples, 44 (34.6%) were from patients with progression during a mean follow-up period of 62.4 months (range, 24.2–118.9 months). Immunohistochemical overexpression was identified in 61 samples (48.0%) for p16, 38 samples (29.9%) for p15, 19 samples (15.0%) for p21, 49 samples (38.6%) for CDK4, 17 samples (13.4%) for CDK6, 57 samples (44.9%) for pRb and in 65 samples (51.2%) for cyclin D1. Multivariate analysis revealed that null cell adenoma [95% confidence interval (CI), 0.276–0.808], somatotroph SPAs (95% CI, 1.296–3.121), corticotroph SPAs (95% CI, 1.811–4.078), pluripotent SPAs (95% CI, 2.264–5.194), decreased expression of p16 (95% CI, 2.724–5.588), overexpression of pRb (95% CI, 2.557–5.333), cyclin D1 (95% CI, 1.894–4.122) and MIB-1 (95% CI, 1.561–4.133), increased mitotic index (95% CI, 1.228–4.079), increased p53 expression (95% CI, 1.307–4.065) and invasion into the cavernous sinus (95% CI, 3.842–7.502) predicted SPA progression following resection. The results of the present study suggested that specific cell-cycle regulators, including p16, cyclin D1 and pRb, were associated with SPA progression. PMID:29344143

The activity and stability of the intrinsically disordered Cip/Kip protein family are regulated by non-receptor tyrosine kinases

PubMed Central

Otieno, Steve; Lelli, Moreno; Kriwacki, Richard W.

2014-01-01

The Cip/Kip family of cyclin-dependent kinase (Cdk) inhibitors includes p21Cip1, p27Kip1 and p57Kip2. Their kinase inhibitory activities are mediated by a homologous N-terminal kinase-inhibitory domain (KID). The Cdk inhibitory activity and stability of p27 have been shown to be regulated by a two-step phosphorylation mechanism involving a tyrosine residue within the KID and a threonine residue within the flexible C-terminus. We show that these residues are conserved in p21 and p57, suggesting that a similar phosphorylation cascade regulates these Cdk inhibitors. However, the presence of a cyclin binding motif within its C-terminus alters the regulatory interplay between p21 and Cdk2/cyclin A, and its responses to tyrosine phosphorylation and altered p21:Cdk2/cyclin A stoichiometry. We also show that the Cip/Kip proteins can be phosphorylated in vitro by representatives of many non-receptor tyrosine kinase (NRTK) sub-families, suggesting that NRTKs may generally regulate the activity and stability of these Cdk inhibitors. Our results further suggest that the Cip/Kip proteins integrate signals from various NRTK pathways and cell cycle regulation. PMID:25463440

The activity and stability of the intrinsically disordered Cip/Kip protein family are regulated by non-receptor tyrosine kinases.

PubMed

Huang, Yongqi; Yoon, Mi-Kyung; Otieno, Steve; Lelli, Moreno; Kriwacki, Richard W

2015-01-30

The Cip/Kip family of cyclin-dependent kinase (Cdk) inhibitors includes p21(Cip1), p27(Kip1) and p57(Kip2). Their kinase inhibitory activities are mediated by a homologous N-terminal kinase inhibitory domain. The Cdk inhibitory activity and stability of p27 have been shown to be regulated by a two-step phosphorylation mechanism involving a tyrosine residue within the kinase inhibitory domain and a threonine residue within the flexible C-terminus. We show that these residues are conserved in p21 and p57, suggesting that a similar phosphorylation cascade regulates these Cdk inhibitors. However, the presence of a cyclin binding motif within its C-terminus alters the regulatory interplay between p21 and Cdk2/cyclin A, as well as its responses to tyrosine phosphorylation and altered p21:Cdk2/cyclin A stoichiometry. We also show that the Cip/Kip proteins can be phosphorylated in vitro by representatives of many non-receptor tyrosine kinase (NRTK) sub-families, suggesting that NRTKs may generally regulate the activity and stability of these Cdk inhibitors. Our results further suggest that the Cip/Kip proteins integrate signals from various NRTK pathways and cell cycle regulation. Copyright © 2014 Elsevier Ltd. All rights reserved.

p14ARF Post-Transcriptional Regulation of Nuclear Cyclin D1 in MCF-7 Breast Cancer Cells: Discrimination between a Good and Bad Prognosis?

PubMed Central

McGowan, Eileen M.; Tran, Nham; Alling, Nikki; Yagoub, Daniel; Sedger, Lisa M.; Martiniello-Wilks, Rosetta

2012-01-01

As part of a cell’s inherent protection against carcinogenesis, p14ARF is upregulated in response to hyperproliferative signalling to induce cell cycle arrest. This property makes p14ARF a leading candidate for cancer therapy. This study explores the consequences of reactivating p14ARF in breast cancer and the potential of targeting p14ARF in breast cancer treatment. Our results show that activation of the p14ARF-p53-p21-Rb pathway in the estrogen sensitive MCF-7 breast cancer cells induces many hallmarks of senescence including a large flat cell morphology, multinucleation, senescence-associated-β-gal staining, and rapid G1 and G2/M phase cell cycle arrest. P14ARF also induces the expression of the proto-oncogene cyclin D1, which is most often associated with a transition from G1-S phase and is highly expressed in breast cancers with poor clinical prognosis. In this study, siRNA knockdown of cyclin D1, p21 and p53 show p21 plays a pivotal role in the maintenance of high cyclin D1 expression, cell cycle and growth arrest post-p14ARF induction. High p53 and p14ARF expression and low p21/cyclin D1 did not cause cell-cycle arrest. Knockdown of cyclin D1 stops proliferation but does not reverse senescence-associated cell growth. Furthermore, cyclin D1 accumulation in the nucleus post-p14ARF activation correlated with a rapid loss of nucleolar Ki-67 protein and inhibition of DNA synthesis. Latent effects of the p14ARF-induced cellular processes resulting from high nuclear cyclin D1 accumulation included a redistribution of Ki-67 into the nucleoli, aberrant nuclear growth (multinucleation), and cell proliferation. Lastly, downregulation of cyclin D1 through inhibition of ER abrogated latent recurrence. The mediation of these latent effects by continuous expression of p14ARF further suggests a novel mechanism whereby dysregulation of cyclin D1 could have a double-edged effect. Our results suggest that p14ARF induced-senescence is related to late-onset breast cancer in estrogen responsive breast cancers and/or the recurrence of more aggressive breast cancer post-therapy. PMID:22860097

Cyclin-dependent kinase inhibitor p21(Waf1): contemporary view on its role in senescence and oncogenesis.

PubMed

Romanov, V S; Pospelov, V A; Pospelova, T V

2012-06-01

p21(Waf1) was identified as a protein suppressing cyclin E/A-CDK2 activity and was originally considered as a negative regulator of the cell cycle and a tumor suppressor. It is now considered that p21(Waf1) has alternative functions, and the view of its role in cellular processes has begun to change. At present, p21(Waf1) is known to be involved in regulation of fundamental cellular programs: cell proliferation, differentiation, migration, senescence, and apoptosis. In fact, it not only exhibits antioncogenic, but also oncogenic properties. This review provides a contemporary understanding of the functions of p21(Waf1) depending on its intracellular localization. On one hand, when in the nucleus, it serves as a negative cell cycle regulator and tumor suppressor, in particular by participating in the launch of a senescence program. On the other hand, when p21(Waf1) is localized in the cytoplasm, it acts as an oncogene by regulating migration, apoptosis, and proliferation.

Di(2-ethylhexyl) phthalate inhibits antral follicle growth, induces atresia, and inhibits steroid hormone production in cultured mouse antral follicles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hannon, Patrick R., E-mail: phannon2@illinois.edu; Brannick, Katherine E., E-mail: kbran@illinois.edu; Wang, Wei, E-mail: Wei.Wang2@covance.com

Di(2-ethylhexyl) phthalate (DEHP) is a ubiquitous environmental toxicant found in consumer products that causes ovarian toxicity. Antral follicles are the functional ovarian units and must undergo growth, survival from atresia, and proper regulation of steroidogenesis to ovulate and produce hormones. Previous studies have determined that DEHP inhibits antral follicle growth and decreases estradiol levels in vitro; however, the mechanism by which DEHP elicits these effects is unknown. The present study tested the hypothesis that DEHP directly alters regulators of the cell cycle, apoptosis, and steroidogenesis to inhibit antral follicle functionality. Antral follicles from adult CD-1 mice were cultured with vehiclemore » control or DEHP (1–100 μg/ml) for 24–96 h to establish the temporal effects of DEHP on the follicle. Following 24–96 h of culture, antral follicles were subjected to gene expression analysis, and media were subjected to measurements of hormone levels. DEHP increased the mRNA levels of cyclin D2, cyclin dependent kinase 4, cyclin E1, cyclin A2, and cyclin B1 and decreased the levels of cyclin-dependent kinase inhibitor 1A prior to growth inhibition. Additionally, DEHP increased the mRNA levels of BCL2-associated agonist of cell death, BCL2-associated X protein, BCL2-related ovarian killer protein, B-cell leukemia/lymphoma 2, and Bcl2-like 10, leading to an increase in atresia. Further, DEHP decreased the levels of progesterone, androstenedione, and testosterone prior to the decrease in estradiol levels, with decreased mRNA levels of side-chain cleavage, 17α-hydroxylase-17,20-desmolase, 17β-hydroxysteroid dehydrogenase, and aromatase. Collectively, DEHP directly alters antral follicle functionality by inhibiting growth, inducing atresia, and inhibiting steroidogenesis. - Highlights: • DEHP inhibits antral follicle growth by dysregulating cell cycle regulators. • DEHP induces antral follicle atresia by dysregulating apoptosis regulators. • DEHP inhibits the production of antral follicle produced sex steroid hormones.« less

EMODIN DOWNREGULATES CELL PROLIFERATION MARKERS DURING DMBA INDUCED ORAL CARCINOGENESIS IN GOLDEN SYRIAN HAMSTERS.

PubMed

Manimaran, Asokan; Buddhan, Rajamanickam; Manoharan, Shanmugam

2017-01-01

Cell-cycle disruption is the major characteristic features of neoplastic transformation and the status of cell-cycle regulators can thus be utilized to assess the prognostic significance in patients with cancer. The PCNA, cyclin D1, CDK4, CDK6 and survivin expression in the buccal mucosa was utilized to evaluate the Emodin efficacy on abnormal cell proliferation during 7,12-dimethylbenz(a)anthracene (DMBA) induced oral carcinogenesis in golden Syrian hamsters. Topical application of DMBA, three times a week for 14 weeks, on the hamsters' buccal pouches developed well differentiated squamous cell carcinoma. Cyclin D1 and PCNA over-expression and up-regulation of CDK4, CDK6 and survivin were noticed in the buccal mucosa of hamsters treated with DMBA alone. Emodin administration (50mg/kg b.w) orally to hamsters treated with DMBA down-regulated the expression of cell proliferation markers in the buccal mucosa. The anti-cell proliferative role of Emodin is owing to its modulating efficacy on cell-cycle markers towards the tumor suppression during DMBA induced oral carcinogenesis.

Inhibitor of DNA binding 1 regulates cell cycle progression of endothelial progenitor cells through induction of Wnt2 expression

PubMed Central

Xia, Xi; Yu, Yang; Zhang, Li; Ma, Yang; Wang, Hong

2016-01-01

Endothelial injury is a risk factor for atherosclerosis. Endothelial progenitor cell (EPC) proliferation contributes to vascular injury repair. Overexpression of inhibitor of DNA binding 1 (Id1) significantly promotes EPC proliferation; however, the underlying molecular mechanism remains to be fully elucidated. The present study investigated the role of Id1 in cell cycle regulation of EPCs, which is closely associated with proliferation. Overexpression of Id1 increased the proportion of EPCs in the S/G2M phase and significantly increased cyclin D1 expression levels, while knockdown of Id1 arrested the cell cycle progression of EPCs in the G1 phase and inhibited cyclin D1 expression levels. In addition, it was demonstrated that Id1 upregulated wingless-type mouse mammary tumor virus integration site family member 2 (Wnt2) expression levels and promoted β-catenin accumulation and nuclear translocation. Furthermore, Wnt2 knockdown counteracted the effects of Id1 on cell cycle progression of EPCs. In conclusion, the results of the present study indicate that Id1 promoted Wnt2 expression, which accelerated cell cycle progression from G1 to S phase. This suggests that Id1 may promote cell cycle progression of EPCs, and that Wnt2 may be important in Id1 regulation of the cell cycle of EPCs. PMID:27432753

The AhR is involved in the regulation of LoVo cell proliferation through cell cycle-associated proteins.

PubMed

Yin, Jiuheng; Sheng, Baifa; Han, Bin; Pu, Aimin; Yang, Kunqiu; Li, Ping; Wang, Qimeng; Xiao, Weidong; Yang, Hua

2016-05-01

Some ingredients in foods can activate the aryl hydrocarbon receptor (AhR) and arrest cell proliferation. In this study, we hypothesized that 6-formylindolo [3, 2-b] carbazole (FICZ) arrests the cell cycle in LoVo cells (a colon cancer line) through the AhR. The AhR agonist FICZ and the AhR antagonist CH223191 were used to treat LoVo cells. Real-time PCR and Western blot analyses were performed to detect the expression of the AhR, CYP1A1, CDK4, cyclinD1, cyclin E, CDK2, P27, and pRb. The distribution and activation of the AhR were detected with immunofluorescence. A 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) assay and flow cytometric analysis were performed to measure cell viability, cell cycle stage, and apoptosis. Our results show that FICZ inhibited LoVo cell proliferation by inducing G1 cell cycle arrest but had no effect on epithelial apoptosis. Further analysis found that FICZ downregulated cyclinD1 and upregulated p27 expression to arrest Rb phosphorylation. The downregulation of cyclinD1 and upregulation of p27 were abolished by co-treatment with CH223191. We conclude that the AhR, when activated by FICZ (an endogenous AhR ligand), can arrest the cell cycle and block LoVo cell proliferation. © 2016 International Federation for Cell Biology.

The Septins Function in G1 Pathways that Influence the Pattern of Cell Growth in Budding Yeast

PubMed Central

Egelhofer, Thea A.; Villén, Judit; McCusker, Derek; Gygi, Steven P.; Kellogg, Douglas R.

2008-01-01

The septins are a conserved family of proteins that have been proposed to carry out diverse functions. In budding yeast, the septins become localized to the site of bud emergence in G1 but have not been thought to carry out important functions at this stage of the cell cycle. We show here that the septins function in redundant mechanisms that are required for formation of the bud neck and for the normal pattern of cell growth early in the cell cycle. The Shs1 septin shows strong genetic interactions with G1 cyclins and is directly phosphorylated by G1 cyclin-dependent kinases, consistent with a role in early cell cycle events. However, Shs1 phosphorylation site mutants do not show genetic interactions with the G1 cyclins or obvious defects early in the cell cycle. Rather, they cause an increased cell size and aberrant cell morphology that are dependent upon inhibitory phosphorylation of Cdk1 at the G2/M transition. Shs1 phosphorylation mutants also show defects in interaction with the Gin4 kinase, which associates with the septins during G2/M and plays a role in regulating inhibitory phosphorylation of Cdk1. Phosphorylation of Shs1 by G1 cyclin-dependent kinases plays a role in events that influence Cdk1 inhibitory phosphorylation. PMID:18431499

Plasmodium P-Type Cyclin CYC3 Modulates Endomitotic Growth during Oocyst Development in Mosquitoes

PubMed Central

Ferguson, David J. P.; Kaindama, Mbinda L.; Brusini, Lorenzo; Joshi, Nimitray; Rchiad, Zineb; Brady, Declan; Guttery, David S.; Wheatley, Sally P.; Yamano, Hiroyuki; Holder, Anthony A.; Pain, Arnab; Wickstead, Bill; Tewari, Rita

2015-01-01

Cell-cycle progression and cell division in eukaryotes are governed in part by the cyclin family and their regulation of cyclin-dependent kinases (CDKs). Cyclins are very well characterised in model systems such as yeast and human cells, but surprisingly little is known about their number and role in Plasmodium, the unicellular protozoan parasite that causes malaria. Malaria parasite cell division and proliferation differs from that of many eukaryotes. During its life cycle it undergoes two types of mitosis: endomitosis in asexual stages and an extremely rapid mitotic process during male gametogenesis. Both schizogony (producing merozoites) in host liver and red blood cells, and sporogony (producing sporozoites) in the mosquito vector, are endomitotic with repeated nuclear replication, without chromosome condensation, before cell division. The role of specific cyclins during Plasmodium cell proliferation was unknown. We show here that the Plasmodium genome contains only three cyclin genes, representing an unusual repertoire of cyclin classes. Expression and reverse genetic analyses of the single Plant (P)-type cyclin, CYC3, in the rodent malaria parasite, Plasmodium berghei, revealed a cytoplasmic and nuclear location of the GFP-tagged protein throughout the lifecycle. Deletion of cyc3 resulted in defects in size, number and growth of oocysts, with abnormalities in budding and sporozoite formation. Furthermore, global transcript analysis of the cyc3-deleted and wild type parasites at gametocyte and ookinete stages identified differentially expressed genes required for signalling, invasion and oocyst development. Collectively these data suggest that cyc3 modulates oocyst endomitotic development in Plasmodium berghei. PMID:26565797

The mechanistic effects of the dioxonaphthoimidazolium analog YM155 in renal cell carcinoma cell cycling and apoptosis.

PubMed

Sim, Mei Yi; Go, Mei Lin; Yuen, John Shyi Peng

2018-06-15

To investigate the effect of dioxonaphthoimidazolium analog YM155 on cell cycle progression of the clear-cell variant of renal cell carcinoma (ccRCC). Cell cycle analysis was performed using bromodeoxyuridine (BrdU) and PI, apoptosis initiation was monitored using Annexin V and proteins expression was determined using western immunoblotting. Here, we showed that YM155 activated stress-related molecules (histone H2AX, checkpoint kinases Chk1 and Chk2, p53) that mediate DNA damage checkpoint responses. The coordinated activation of these effector molecules disrupts progression of the cell cycle at the S phase as deduced from BrdU pulsing experiments and the ensuing changes in the levels of proteins (cyclins, CDKs, CDK inhibitors, phosphatases) that control cell cycle progression. Notably, we found increases in cyclin E and Cdc2 which regulate transition of cells from G1 to S, even as losses were observed for other CDKs and their cyclin partners. Furthermore, by inducing a loss in total pRb possibly by promoting its degradation, YM155 promoted the E2F transcription of genes that regulate entry into the S phase. After 24 h, cell cycle arrest to repair YM155-inflicted DNA damage was overtaken by p53-mediated apoptosis. YM155 induced increases in pro-apoptotic proteins (Bax and Bad), diminished anti-apoptotic proteins (Mcl-1, Bcl-xl, XIAP, survivin) and initiated cleavage of apoptotic marker proteins caspase 3 and PARP. Taken together, the added insight provided on the cell cycle perturbative effects of YM155 may assist clinicians in framing rational choices for combining YM155 with other anti-cancer drugs or treatment modalities in ccRCC. Copyright © 2018 Elsevier Inc. All rights reserved.

Regulation of steroid hormone receptors and coregulators during the cell cycle highlights potential novel function in addition to roles as transcription factors

PubMed Central

Zheng, Yingfeng; Murphy, Leigh C.

2016-01-01

Cell cycle progression is tightly controlled by several kinase families including Cyclin-Dependent Kinases, Polo-Like Kinases, and Aurora Kinases. A large amount of data show that steroid hormone receptors and various components of the cell cycle, including cell cycle regulated kinases, interact, and this often results in altered transcriptional activity of the receptor. Furthermore, steroid hormones, through their receptors, can also regulate the transcriptional expression of genes that are required for cell cycle regulation. However, emerging data suggest that steroid hormone receptors may have roles in cell cycle progression independent of their transcriptional activity. The following is a review of how steroid receptors and their coregulators can regulate or be regulated by the cell cycle machinery, with a particular focus on roles independent of transcription in G2/M. PMID:26778927

Copper Uptake in Mammary Epithelial Cells Activates Cyclins and Triggers Antioxidant Response

PubMed Central

dos Santos, Nathália Villa; Matias, Andreza Cândido; Higa, Guilherme Shigueto Vilar; Kihara, Alexandre Hiroaki; Cerchiaro, Giselle

2015-01-01

The toxicologic effects of copper (Cu) on tumor cells have been studied during the past decades, and it is suggested that Cu ion may trigger antiproliferative effects in vitro. However, in normal cells the toxicologic effects of high exposures of free Cu are not well understood. In this work, Cu uptake, the expression of genes associated with cell cycle regulation, and the levels of ROS production and related oxidative processes were evaluated in Cu-treated mammary epithelial MCF10A nontumoral cells. We have shown that the Cu additive is associated with the activation of cyclin D1 and cyclin B1, as well as cyclin-dependent kinase 2 (CDK2). These nontumor cells respond to Cu-induced changes in the oxidative balance by increase of the levels of reduced intracellular glutathione (GSH), decrease of reactive oxygen species (ROS) generation, and accumulation during progression of the cell cycle, thus preventing the cell abnormal proliferation or death. Taken together, our findings revealed an effect that contributes to prevent a possible damage of normal cells exposed to chemotherapeutic effects of drugs containing the Cu ion. PMID:26583055

Cyclin D1 in ASM Cells from Asthmatics Is Insensitive to Corticosteroid Inhibition.

PubMed

Allen, Jodi C; Seidel, Petra; Schlosser, Tobias; Ramsay, Emma E; Ge, Qi; Ammit, Alaina J

2012-01-01

Hyperplasia of airway smooth muscle (ASM) is a feature of the remodelled airway in asthmatics. We examined the antiproliferative effectiveness of the corticosteroid dexamethasone on expression of the key regulator of G(1) cell cycle progression-cyclin D1-in ASM cells from nonasthmatics and asthmatics stimulated with the mitogen platelet-derived growth factor BB. While cyclin D1 mRNA and protein expression were repressed in cells from nonasthmatics in contrast, cyclin D1 expression in asthmatics was resistant to inhibition by dexamethasone. This was independent of a repressive effect on glucocorticoid receptor translocation. Our results corroborate evidence demonstrating that corticosteroids inhibit mitogen-induced proliferation only in ASM cells from subjects without asthma and suggest that there are corticosteroid-insensitive proliferative pathways in asthmatics.

Cyclin-dependent kinases: engines, clocks, and microprocessors.

PubMed

Morgan, D O

1997-01-01

Cyclin-dependent kinases (Cdks) play a well-established role in the regulation of the eukaryotic cell division cycle and have also been implicated in the control of gene transcription and other processes. Cdk activity is governed by a complex network of regulatory subunits and phosphorylation events whose precise effects on Cdk conformation have been revealed by recent crystallographic studies. In the cell, these regulatory mechanisms generate an interlinked series of Cdk oscillators that trigger the events of cell division.

Plant hormone cytokinins control cell cycle progression and plastid replication in apicomplexan parasites.

PubMed

Andrabi, Syed Bilal Ahmad; Tahara, Michiru; Matsubara, Ryuma; Toyama, Tomoko; Aonuma, Hiroka; Sakakibara, Hitoshi; Suematsu, Makoto; Tanabe, Kazuyuki; Nozaki, Tomoyoshi; Nagamune, Kisaburo

2018-02-01

Cytokinins are plant hormones that are involved in regulation of cell proliferation, cell cycle progression, and cell and plastid development. Here, we show that the apicomplexan parasites Toxoplasma gondii and Plasmodium berghei, an opportunistic human pathogen and a rodent malaria agent, respectively, produce cytokinins via a biosynthetic pathway similar to that in plants. Cytokinins regulate the growth and cell cycle progression of T. gondii by mediating expression of the cyclin gene TgCYC4. A natural form of cytokinin, trans-zeatin (t-zeatin), upregulated expression of this cyclin, while a synthetic cytokinin, thidiazuron, downregulated its expression. Immunofluorescence microscopy and quantitative PCR analysis showed that t-zeatin increased the genome-copy number of apicoplast, which are non-photosynthetic plastid, in the parasite, while thidiazuron led to their disappearance. Thidiazuron inhibited growth of T. gondii and Plasmodium falciparum, a human malaria parasite, suggesting that thidiazuron has therapeutic potential as an inhibitor of apicomplexan parasites. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.

ROCK inhibition with Y27632 promotes the proliferation and cell cycle progression of cultured astrocyte from spinal cord.

PubMed

Yu, Zhiyuan; Liu, Miao; Fu, Peicai; Xie, Minjie; Wang, Wei; Luo, Xiang

2012-12-01

Rho-associated Kinase (ROCK) has been identified as an important regulator of proliferation and cell cycle progression in a number of cell types. Although its effects on astrocyte proliferation have not been well characterized, ROCK has been reported to play important roles in gap junction formation, morphology, and migration of astrocytes. In the present study, our aim was to investigate the effect of ROCK inhibition by [(+)-(R)-trans-4-(1-aminoethyl)-N-(4-pyridyl) cyclohexanecarboxamide dihydrochloride] (Y27632) on proliferation and DNA synthesis in cultured astrocytes from rat spinal cord and the possible mechanism involved. Western blots showed that treatment of astrocytes with Y27632 increased their expression of cyclin D1, CDK4, and cyclin E, thereby causing cell cycle progression. Furthermore, Y27632-induced astrocyte proliferation was mediated through the extracellular-signal-regulated kinase signaling cascade. These results indicate the importance of ROCK in astrocyte proliferation. Copyright © 2012 Elsevier Ltd. All rights reserved.

Implications of caspase-dependent proteolytic cleavage of cyclin A1 in DNA damage-induced cell death

DOE Office of Scientific and Technical Information (OSTI.GOV)

Woo, Sang Hyeok; Seo, Sung-Keum; An, Sungkwan

Highlights: • Caspase-1 mediates doxorubicin-induced downregulation of cyclin A1. • Active caspase-1 effectively cleaved cyclin A1 at D165. • Cyclin A1 expression is involved in DNA damage-induced cell death. - Abstract: Cyclin A1 is an A-type cyclin that directly binds to CDK2 to regulate cell-cycle progression. In the present study, we found that doxorubicin decreased the expression of cyclin A1 at the protein level in A549 lung cancer cells, while markedly downregulating its mRNA levels. Interestingly, doxorubicin upregulated caspase-1 in a concentration-dependent manner, and z-YAVD-fmk, a specific inhibitor of caspase-1, reversed the doxorubicin-induced decrease in cyclin A1 in A549 lungmore » cancer and MCF7 breast cancer cells. Active caspase-1 effectively cleaved cyclin A1 at D165 into two fragments, which in vitro cleavage assays showed were further cleaved by caspase-3. Finally, we found that overexpression of cyclin A1 significantly reduced the cytotoxicity of doxorubicin, and knockdown of cyclin A1 by RNA interference enhanced the sensitivity of cells to ionizing radiation. Our data suggest a new mechanism for the downregulation of cyclin A1 by DNA-damaging stimuli that could be intimately involved in the cell death induced by DNA damage-inducing stimuli, including doxorubicin and ionizing radiation.« less

Oncogenic collaboration of the cyclin D1 (PRAD1, bcl-1) gene with a mutated p53 and an activated ras oncogene in neoplastic transformation.

PubMed

Uchimaru, K; Endo, K; Fujinuma, H; Zukerberg, L; Arnold, A; Motokura, T

1996-05-01

Cyclin D1 is one of the key regulators in G1 progression in the cell cycle and is also a candidate oncogene (termed PRAD1 or bcl-1) in several types of human tumors. We report a collaboration of the cyclin D1 gene with ras and a mutated form of p53 (p53-mt) in neoplastic transformation. Transfection of cyclin D1 alone or in combination with ras or with p53-mt was not sufficient for focus formation of rat embryonic fibroblasts. However, focus formation induced by co-transfection of ras and p53-mt was enhanced in the presence of the cyclin D1-expression plasmid. Co-transfection of ras- and p53-mt-transformants with the cyclin D1-expression plasmid resulted in reduced serum dependency in vitro. Furthermore, the transformants expressing exogenous cyclin D1 grew faster than those without the cyclin D1 plasmid when injected into nude mice. These observations strengthen the significance of cyclin D1 overexpression through gene rearrangement or gene amplification observed in human tumors as a step in multistep oncogenesis; deregulated expression of cyclin D1 may reduce the requirement for growth factors and may stimulate in vivo growth.

Isorhapontigenin (ISO) inhibited cell transformation by inducing G0/G1 phase arrest via increasing MKP-1 mRNA Stability.

PubMed

Gao, Guangxun; Chen, Liang; Li, Jingxia; Zhang, Dongyun; Fang, Yong; Huang, Haishan; Chen, Xiequn; Huang, Chuanshu

2014-05-15

The cancer chemopreventive property of Chinese herb new isolate isorhapontigenin (ISO) and mechanisms underlying its activity have never been explored. Here we demonstrated that ISO treatment with various concentrations for 3 weeks could dramatically inhibit TPA/EGF-induced cell transformation of Cl41 cells in Soft Agar assay, whereas co-incubation of cells with ISO at the same concentrations could elicit G0/G1 cell-cycle arrest without redundant cytotoxic effects on non-transformed cells. Further studies showed that ISO treatment resulted in cyclin D1 downregulation in dose- and time-dependent manner. Our results indicated that ISO regulated cyclin D1 at transcription level via targeting JNK/C-Jun/AP-1 activation. Moreover, we found that ISO-inhibited JNK/C-Jun/AP-1 activation was mediated by both upregulation of MKP-1 expression through increasing its mRNA stability and deactivating MKK7. Most importantly, MKP-1 knockdown could attenuate ISO-mediated suppression of JNK/C-Jun activation and cyclin D1 expression, as well as G0/G1 cell cycle arrest and cell transformation inhibition, while ectopic expression of FLAG-cyclin D1 T286A mutant also reversed ISO-induced G0/G1 cell-cycle arrest and inhibition of cell transformation. Our results demonstrated that ISO is a promising chemopreventive agent via upregulating mkp-1 mRNA stability, which is distinct from its cancer therapeutic effect with downregulation of XIAP and cyclin D1 expression.

Prognostic value of cell cycle regulatory proteins in muscle-infiltrating bladder cancer.

PubMed

Galmozzi, Fabia; Rubagotti, Alessandra; Romagnoli, Andrea; Carmignani, Giorgio; Perdelli, Luisa; Gatteschi, Beatrice; Boccardo, Francesco

2006-12-01

The aims of this study were to investigate the expression levels of proteins involved in cell cycle regulation in specimens of bladder cancer and to correlate them with the clinicopathological characteristics, proliferative activity and survival. Eighty-two specimens obtained from patients affected by muscle-invasive bladder cancer were evaluated immunohistochemically for p53, p21 and cyclin D1 expression, as well as for the tumour proliferation index, Ki-67. The statistical analysis included Kaplan-Meier curves with log-rank test and Cox proportional hazards models. In univariate analyses, low Ki-67 proliferation index (P = 0.045) and negative p21 immunoreactivity (P = 0.04) were associated to patient's overall survival (OS), but in multivariate models p21 did not reach statistical significance. When the combinations of the variables were assessed in two separate multivariate models that included tumour stage, grading, lymph node status, vascular invasion and perineural invasion, the combined variables p21/Ki-67 or p21/cyclin D1 expression were independent predictors for OS; in particular, patients with positive p21/high Ki-67 (P = 0.015) or positive p21/negative cyclin D1 (P = 0.04) showed the worst survival outcome. Important alterations in the cell cycle regulatory pathways occur in muscle-invasive bladder cancer and the combined use of cell cycle regulators appears to provide significant prognostic information that could be used to select the patients most suitable for multimodal therapeutic approaches.

Redox regulation of cardiomyocyte cell cycling via an ERK1/2 and c-Myc-dependent activation of cyclin D2 transcription

PubMed Central

Murray, Thomas V.A.; Smyrnias, Ioannis; Schnelle, Moritz; Mistry, Rajesh K.; Zhang, Min; Beretta, Matteo; Martin, Daniel; Anilkumar, Narayana; de Silva, Shana M.; Shah, Ajay M.; Brewer, Alison C.

2015-01-01

Adult mammalian cardiomyocytes have a very limited capacity to proliferate, and consequently the loss of cells after cardiac stress promotes heart failure. Recent evidence suggests that administration of hydrogen peroxide (H2O2), can regulate redox-dependent signalling pathway(s) to promote cardiomyocyte proliferation in vitro, but the potential relevance of such a pathway in vivo has not been tested. We have generated a transgenic (Tg) mouse model in which the H2O2-generating enzyme, NADPH oxidase 4 (Nox4), is overexpressed within the postnatal cardiomyocytes, and observed that the hearts of 1–3 week old Tg mice pups are larger in comparison to wild type (Wt) littermate controls. We demonstrate that the cardiomyocytes of Tg mouse pups have increased cell cycling capacity in vivo as determined by incorporation of 5-bromo-2′-deoxyuridine. Further, microarray analyses of the transcriptome of these Tg mouse hearts suggested that the expression of cyclin D2 is significantly increased. We investigated the molecular mechanisms which underlie this more proliferative phenotype in isolated neonatal rat cardiomyocytes (NRCs) in vitro, and demonstrate that Nox4 overexpression mediates an H2O2-dependent activation of the ERK1/2 signalling pathway, which in turn phosphorylates and activates the transcription factor c-myc. This results in a significant increase in cyclin D2 expression, which we show to be mediated, at least in part, by cis-acting c-myc binding sites within the proximal cyclin D2 promoter. Overexpression of Nox4 in NRCs results in an increase in their proliferative capacity that is ablated by the silencing of cyclin D2. We further demonstrate activation of the ERK1/2 signalling pathway, increased phosphorylation of c-myc and significantly increased expression of cyclin D2 protein in the Nox4 Tg hearts. We suggest that this pathway acts to maintain the proliferative capacity of cardiomyocytes in Nox4 Tg pups in vivo and so delays their exit from the cell cycle after birth. PMID:25450615

Cell cycle regulation by the intrinsically disordered proteins p21 and p27.

PubMed

Yoon, Mi-Kyung; Mitrea, Diana M; Ou, Li; Kriwacki, Richard W

2012-10-01

Today, it is widely accepted that proteins that lack highly defined globular three-dimensional structures, termed IDPs (intrinsically disordered proteins), play key roles in myriad biological processes. Our understanding of how intrinsic disorder mediates biological function is, however, incomplete. In the present paper, we review disorder-mediated cell cycle regulation by two intrinsically disordered proteins, p21 and p27. A structural adaptation mechanism involving a stretchable dynamic linker helix allows p21 to promiscuously recognize the various Cdk (cyclin-dependent kinase)-cyclin complexes that regulate cell division. Disorder within p27 mediates transmission of an N-terminal tyrosine phosphorylation signal to a C-terminal threonine phosphorylation, constituting a signalling conduit. These mechanisms are mediated by folding upon binding p21/p27's regulatory targets. However, residual disorder within the bound state contributes critically to these functional mechanisms. Our studies provide insights into how intrinsic protein disorder mediates regulatory processes and opportunities for designing drugs that target cancer-associated IDPs.

The A- and B-type cyclin associated cdc2 kinases in Xenopus turn on and off at different times in the cell cycle.

PubMed Central

Minshull, J; Golsteyn, R; Hill, C S; Hunt, T

1990-01-01

Cyclins play a key role in the induction of mitosis. In this paper we report the isolation of a cyclin A cDNA clone from Xenopus eggs. Its cognate mRNA encodes a protein that shows characteristic accumulation and destruction during mitotic cell cycles. The cyclin A polypeptide is associated with a protein that cross-reacts with an antibody against the conserved 'PSTAIR' epitope of p34cdc2, and the cyclin A-cdc2 complex exhibits protein kinase activity that oscillates with the cell cycle. This kinase activity rises more smoothly than that of the cyclin B-cdc2 complexes and reaches a peak earlier in the cell cycle; indeed, cyclin A is destroyed before nuclear envelope breakdown. None of the cyclin-cdc2 complexes show simple relationships between the concentration of the cyclin moiety and the kinase activity. All three cyclin associated kinases (A, B1 and B2) phosphorylate identical sites on histones with the consensus XSPXK/R, although they show significant differences in their substrate preferences. We discuss possible models for the different roles of the A- and B-type cyclins in the control of cell division. Images Fig. 3. Fig. 4. Fig. 5. Fig. 6. Fig. 7. Fig. 8. Fig. 9. PMID:2143983

Molecular mechanisms of celery seed extract induced apoptosis via s phase cell cycle arrest in the BGC-823 human stomach cancer cell line.

PubMed

Gao, Lin-Lin; Feng, Lei; Yao, Shu-Tong; Jiao, Peng; Qin, Shu-Cun; Zhang, Wei; Zhang, Ya-Bin; Li, Fu-Rong

2011-01-01

Mechanisms of apoptosis in tumor cells is an important field of tumor therapy and cancer molecular biology. Loss of cell cycle control, leading to uncontrolled proliferation, is common in cancer. Therefore, the identification of potent and selective cyclin dependent kinase inhibitors is a priority for anti-cancer drug discovery. There are at least two major apoptotic pathways, initiated by caspase-8 and caspase-9, respectively, which can activate caspase cascades. Apoptosis triggered by activation of the mitochondrial-dependent caspase pathway represents the main programmed cell death mechanism. This is activated by various intracellular stresses that induce permeabilization of the mitochondrial membrane. Anti-tumor effects of celery seed extract (CSE) and related mechanisms regarding apoptosis were here investigated in human gastric cancer BGC-823 cells. CSE was produced by supercritical fluid extraction. Cell viability was analyzed by 3-(4,5-dimethylthiazol-2-yl)- 2,5-diphenyl-tetrazolium bromide (MTT) assay and apoptosis by flow cytometry using Annexin/PI staining and DAPI staining and a laser scanning confocal microscope (LSCM). Cell cycling was evaluated using PI staining with flow cytometry and expression of cell cycle and apoptosis-related proteins cyclin A, CDK2, bcl-2 and bax was assessed by immunohistochemical staining. CSE had an anti-proliferation effect on human gastric cancer BGC-823 cells in a dose- and time-dependent manner. After treatment, the apoptotic rate significantly increased, with morphological changes typical of apoptosis observed with LSCM by DAPI staining. Cell cycle and apoptosis related proteins, such as cyclin A, CDK2 and bcl-2 were all down-regulated, whereas bax was up-regulated. The molecular determinants of inhibition of cell proliferation as well as apoptosis of CSE may be associated with cycle arrest in the S phase.

CDK inhibitors, p21{sup Cip1} and p27{sup Kip1}, participate in cell cycle exit of mammalian cardiomyocytes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tane, Shoji; Ikenishi, Aiko; Okayama, Hitomi

2014-01-17

Highlights: •Expression of p21 and p27 in the hearts showed a peak during postnatal stages. •p21 and p27 bound to cyclin E, cyclin A and CDK2 in the hearts at postnatal stages. •Cardiomyocytes in both KO mice showed failure in the cell cycle exit at G1-phase. •These data show the first apparent phenotypes in the hearts of Cip/Kip KO mice. -- Abstract: Mammalian cardiomyocytes actively proliferate during embryonic stages, following which cardiomyocytes exit their cell cycle after birth. The irreversible cell cycle exit inhibits cardiac regeneration by the proliferation of pre-existing cardiomyocytes. Exactly how the cell cycle exit occurs remainsmore » largely unknown. Previously, we showed that cyclin E- and cyclin A-CDK activities are inhibited before the CDKs levels decrease in postnatal stages. This result suggests that factors such as CDK inhibitors (CKIs) inhibit CDK activities, and contribute to the cell cycle exit. In the present study, we focused on a Cip/Kip family, which can inhibit cyclin E- and cyclin A-CDK activities. Expression of p21{sup Cip1} and p27{sup Kip1} but not p57{sup Kip2} showed a peak around postnatal day 5, when cyclin E- and cyclin A-CDK activities start to decrease. p21{sup Cip1} and p27{sup Kip1} bound to cyclin E, cyclin A and CDK2 at postnatal stages. Cell cycle distribution patterns of postnatal cardiomyocytes in p21{sup Cip1} and p27{sup Kip1} knockout mice showed failure in the cell cycle exit at G1-phase, and endoreplication. These results indicate that p21{sup Cip1} and p27{sup Kip} play important roles in the cell cycle exit of postnatal cardiomyocytes.« less

CARMA3 is overexpressed in colon cancer and regulates NF-{kappa}B activity and cyclin D1 expression

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miao, Zhifeng; Zhao, Tingting; Wang, Zhenning

2012-09-07

Highlights: Black-Right-Pointing-Pointer CARMA3 expression is elevated in colon cancers. Black-Right-Pointing-Pointer CARMA3 promotes proliferation and cell cycle progression in colon cancer cells. Black-Right-Pointing-Pointer CARMA3 upregulates cyclinD1 through NF-{kappa}B activation. -- Abstract: CARMA3 was recently reported to be overexpressed in cancers and associated with the malignant behavior of cancer cells. However, the expression of CARMA3 and its biological roles in colon cancer have not been reported. In the present study, we analyzed the expression pattern of CARMA3 in colon cancer tissues and found that CARMA3 was overexpressed in 30.8% of colon cancer specimens. There was a significant association between CARMA3 overexpression andmore » TNM stage (p = 0.0383), lymph node metastasis (p = 0.0091) and Ki67 proliferation index (p = 0.0035). Furthermore, knockdown of CARMA3 expression in HT29 and HCT116 cells with high endogenous expression decreased cell proliferation and cell cycle progression while overexpression of CARMA3 in LoVo cell line promoted cell proliferation and facilitated cell cycle transition. Further analysis showed that CARMA3 knockdown downregulated and its overexpression upregulated cyclin D1 expression and phospho-Rb levels. In addition, we found that CARMA3 depletion inhibited p-I{kappa}B levels and NF-{kappa}B activity and its overexpression increased p-I{kappa}B expression and NF-{kappa}B activity. NF-{kappa}B inhibitor BAY 11-7082 reversed the role of CARMA3 on cyclin D1 upregulation. In conclusion, our study found that CARMA3 is overexpressed in colon cancers and contributes to malignant cell growth by facilitating cell cycle progression through NF-{kappa}B mediated upregulation of cyclin D1.« less

Stress and developmental regulation of the yeast C-type cyclin Ume3p (Srb11p/Ssn8p).

PubMed Central

Cooper, K F; Mallory, M J; Smith, J B; Strich, R

1997-01-01

The ume3-1 allele was identified as a mutation that allowed the aberrant expression of several meiotic genes (e.g. SPO11, SPO13) during mitotic cell division in Saccharomyces cerevisiae. Here we report that UME3 is also required for the full repression of the HSP70 family member SSA1. UME3 encodes a non-essential C-type cyclin (Ume3p) whose levels do not vary through the mitotic cell cycle. However, Ume3p is destroyed during meiosis or when cultures are subjected to heat shock. Ume3p mutants resistant to degradation resulted in a 2-fold reduction in SPO13 mRNA levels during meiosis, indicating that the down-regulation of this cyclin is important for normal meiotic gene expression. Mutational analysis identified two regions (PEST-rich and RXXL) that mediate Ume3p degradation. A third destruction signal lies within the highly conserved cyclin box, a region that mediates cyclin-cyclin-dependent kinase (Cdk) interactions. However, the Cdk activated by Ume3p (Ume5p) is not required for the rapid destruction of this cyclin. Finally, Ume3p destruction was not affected in mutants defective for ubiquitin-dependent proteolysis. These results support a model in which Ume3p, when exposed to heat shock or sporulation conditions, is targeted for destruction to allow the expression of genes necessary for the cell to respond correctly to these environmental cues. PMID:9303311

Physalis angulata induced G2/M phase arrest in human breast cancer cells.

PubMed

Hsieh, Wen-Tsong; Huang, Kuan-Yuh; Lin, Hui-Yi; Chung, Jing-Gung

2006-07-01

Physalis angulata (PA) is employed in herbal medicine around the world. It is used to treat diabetes, hepatitis, asthma and malaria in Taiwan. We have evaluated PA as a cancer chemopreventive agent in vitro by studying the role of PA in regulation of proliferation, cell cycle and apoptosis in human breast cancer cell lines. PA inhibited cell proliferation and induced G2/M arrest and apoptosis in human breast cancer MAD-MB 231 and MCF-7 cell lines. In this study, under treatment with various concentrations of PA in MDA-MB 231 cell line, we checked mRNA levels for cyclin A and cyclin B1 and the protein levels of cyclin A and cyclin B1, Cdc2 (cyclin-dependent kinases), p21(waf1/cip1) and P27(Kip1) (cyclin-dependent kinase inhibitors), Cdc25C, Chk2 and Wee1 kinase (cyclin-dependent kinase relative factors) in cell cycle G2/M phase. From those results, we determined that PA arrests MDA-MB 231 cells at the G2/M phase by (i) inhibiting synthesis or stability of mRNA and their downstream protein levels of cyclin A and cyclin B1, (ii) increasing p21(waf1/cip1) and P27(kip1) levels, (iii) increasing Chk2, thus causing an increase in Cdc25C phosphorylation/inactivation and inducing a decrease in Cdc2 levels and an increase in Wee1 level. According to the results obtained, PA appears to possess anticarcinogenic properties; these results suggest that the effect of PA on the levels of phosphorylated/inactivated Cdc25C are mediated by Chk2 activation, at least in part, via p21(waf1/cip1) and P27(kip1) cyclin-dependent kinase inhibitors pathway to arrest cells at G2/M phase in breast cancer carcinoma cells.

Cell cycle control, checkpoint mechanisms, and genotoxic stress.

PubMed Central

Shackelford, R E; Kaufmann, W K; Paules, R S

1999-01-01

The ability of cells to maintain genomic integrity is vital for cell survival and proliferation. Lack of fidelity in DNA replication and maintenance can result in deleterious mutations leading to cell death or, in multicellular organisms, cancer. The purpose of this review is to discuss the known signal transduction pathways that regulate cell cycle progression and the mechanisms cells employ to insure DNA stability in the face of genotoxic stress. In particular, we focus on mammalian cell cycle checkpoint functions, their role in maintaining DNA stability during the cell cycle following exposure to genotoxic agents, and the gene products that act in checkpoint function signal transduction cascades. Key transitions in the cell cycle are regulated by the activities of various protein kinase complexes composed of cyclin and cyclin-dependent kinase (Cdk) molecules. Surveillance control mechanisms that check to ensure proper completion of early events and cellular integrity before initiation of subsequent events in cell cycle progression are referred to as cell cycle checkpoints and can generate a transient delay that provides the cell more time to repair damage before progressing to the next phase of the cycle. A variety of cellular responses are elicited that function in checkpoint signaling to inhibit cyclin/Cdk activities. These responses include the p53-dependent and p53-independent induction of Cdk inhibitors and the p53-independent inhibitory phosphorylation of Cdk molecules themselves. Eliciting proper G1, S, and G2 checkpoint responses to double-strand DNA breaks requires the function of the Ataxia telangiectasia mutated gene product. Several human heritable cancer-prone syndromes known to alter DNA stability have been found to have defects in checkpoint surveillance pathways. Exposures to several common sources of genotoxic stress, including oxidative stress, ionizing radiation, UV radiation, and the genotoxic compound benzo[a]pyrene, elicit cell cycle checkpoint responses that show both similarities and differences in their molecular signaling. Images Figure 3 PMID:10229703

Senescence and quiescence in adipose-derived stromal cells: Effects of human platelet lysate, fetal bovine serum and hypoxia.

PubMed

Søndergaard, Rebekka Harary; Follin, Bjarke; Lund, Lisbeth Drozd; Juhl, Morten; Ekblond, Annette; Kastrup, Jens; Haack-Sørensen, Mandana

2017-01-01

Adipose-derived stromal cells (ASCs) are attractive sources for cell-based therapies. The hypoxic niche of ASCs in vivo implies that cells will benefit from hypoxia during in vitro expansion. Human platelet lysate (hPL) enhances ASC proliferation rates, compared with fetal bovine serum (FBS) at normoxia. However, the low proliferation rates of FBS-expanded ASCs could be signs of senescence or quiescence. We aimed to determine the effects of hypoxia and hPL on the expansion of ASCs and whether FBS-expanded ASCs are senescent or quiescent. ASCs expanded in FBS or hPL at normoxia or hypoxia until passage 7 (P7), or in FBS until P5 followed by culture in hPL until P7, were evaluated by proliferation rates, cell cycle analyses, gene expression and β-galactosidase activity. hPL at normoxia and hypoxia enhanced proliferation rates and expression of cyclins, and decreased G0/G1 fractions and expression of p21 and p27, compared with FBS. The shift from FBS to hPL enhanced cyclin levels, decreased p21 and p27 levels and tended to decrease G0/G1 fractions. Hypoxia does not add to the effect of hPL during ASC expansion with regard to proliferation, cell cycle regulation and expression of cyclins, p21 and p27. hPL rejuvenates FBS-expanded ASCs with regard to cell cycle regulation and expression of cyclins, p21 and p27. This indicates a reversible arrest. Therefore, we conclude that ASCs expanded until P7 are not senescent regardless of culture conditions. Copyright © 2017 International Society for Cellular Therapy. Published by Elsevier Inc. All rights reserved.

PRMT5 is essential for the eIF4E-mediated 5′-cap dependent translation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lim, Ji-Hong; Lee, Yoon-Mi; Lee, Gibok

2014-10-03

Highlights: • PRMT5 participates in syntheses of HIF-1α, c-Myc and cyclin D1 proteins. • PRMT5 promotes the 5′-cap dependent translation. • PRMT5 is required for eIF4E binding to mRNA 5′-cap. • PRMT5 is essential for eIF4E-dependent cell proliferation. - Abstract: It is becoming clear that PRMT5 plays essential roles in cell cycle progression, survival, and responses to external stresses. However, the precise mechanisms underlying such roles of PRMT5 have not been clearly understood. Previously, we have demonstrated that PRMT5 participates in cellular adaptation to hypoxia by ensuring 5′-cap dependent translation of HIF-1α. Given that c-Myc and cyclin D1 expressions aremore » also tightly regulated in 5′-cap dependent manner, we here tested the possibility that PRMT5 promotes cell proliferation by increasing de novo syntheses of the oncoproteins. c-Myc and cyclin D1 were found to be noticeably downregulated by PRMT5 knock-down. A RNA immunoprecipitation analysis, which can identify RNA–protein interactions, showed that PRMT5 is required for the interaction among eIF4E and 5′-UTRs of HIF-1α, c-Myc and cyclin D1 mRNAs. In addition, PRMT5 knock-down inhibited cell proliferation by inducing cell cycle arrest at the G1 phase. More importantly, ectopic expression of eIF4E significantly rescued the cell cycle progression and cell proliferation even in PRMT5-deficeint condition. Based on these results, we propose that PRMT5 determines cell fate by regulating 5′-cap dependent translation of proteins essential for proliferation and survival.« less

P276-00, a cyclin-dependent kinase inhibitor, modulates cell cycle and induces apoptosis in vitro and in vivo in mantle cell lymphoma cell lines

PubMed Central

2012-01-01

Background Mantle cell lymphoma (MCL) is a well-defined aggressive lymphoid neoplasm characterized by proliferation of mature B-lymphocytes that have a remarkable tendency to disseminate. This tumor is considered as one of the most aggressive lymphoid neoplasms with poor responses to conventional chemotherapy and relatively short survival. Since cyclin D1 and cell cycle control appears as a natural target, small-molecule inhibitors of cyclin-dependent kinases (Cdks) and cyclins may play important role in the therapy of this disorder. We explored P276-00, a novel selective potent Cdk4-D1, Cdk1-B and Cdk9-T1 inhibitor discovered by us against MCL and elucidated its potential mechanism of action. Methods The cytotoxic effect of P276-00 in three human MCL cell lines was evaluated in vitro. The effect of P276-00 on the regulation of cell cycle, apoptosis and transcription was assessed, which are implied in the pathogenesis of MCL. Flow cytometry, western blot, immunoflourescence and siRNA studies were performed. The in vivo efficacy and effect on survival of P276-00 was evaluated in a Jeko-1 xenograft model developed in SCID mice. PK/PD analysis of tumors were performed using LC-MS and western blot analysis. Results P276-00 showed a potent cytotoxic effect against MCL cell lines. Mechanistic studies confirmed down regulation of cell cycle regulatory proteins with apoptosis. P276-00 causes time and dose dependent increase in the sub G1 population as early as from 24 h. Reverse transcription PCR studies provide evidence that P276-00 treatment down regulated transcription of antiapoptotic protein Mcl-1 which is a potential pathogenic protein for MCL. Most importantly, in vivo studies have revealed significant efficacy as a single agent with increased survival period compared to vehicle treated. Further, preliminary combination studies of P276-00 with doxorubicin and bortezomib showed in vitro synergism. Conclusion Our studies thus provide evidence and rational that P276-00 alone or in combination is a potential therapeutic molecule to improve patients’ outcome in mantle cell lymphoma. PMID:23075291

Progress with palbociclib in breast cancer: latest evidence and clinical considerations

PubMed Central

Rocca, Andrea; Schirone, Alessio; Maltoni, Roberta; Bravaccini, Sara; Cecconetto, Lorenzo; Farolfi, Alberto; Bronte, Giuseppe; Andreis, Daniele

2016-01-01

Deregulation of the cell cycle is a hallmark of cancer, and research on cell cycle control has allowed identification of potential targets for anticancer treatment. Palbociclib is a selective inhibitor of the cyclin-dependent kinases 4 and 6 (CDK4/6), which are involved, with their coregulatory partners cyclin D, in the G1-S transition. Inhibition of this step halts cell cycle progression in cells in which the involved pathway, including the retinoblastoma protein (Rb) and the E2F family of transcription factors, is functioning, although having been deregulated. Among breast cancers, those with functioning cyclin D-CDK4/6-Rb-E2F are mainly hormone-receptor (HR) positive, with some HER2-positive and rare triple-negative cases. Deregulation results from genetic or otherwise occurring hyperactivation of molecules subtending cell cycle progression, or inactivation of cell cycle inhibitors. Based on results of randomized clinical trials, palbociclib was granted accelerated approval by the US Food and Drug Administration (FDA) for use in combination with letrozole as initial endocrine-based therapy for metastatic disease in postmenopausal women with HR-positive, HER2-negative breast cancer, and was approved for use in combination with fulvestrant in women with HR-positive, HER2-negative advanced breast cancer with disease progression following endocrine therapy. This review provides an update of the available knowledge on the cell cycle and its regulation, on the alterations in cyclin D-CDK4/6-Rb-E2F axis in breast cancer and their roles in endocrine resistance, on the preclinical activity of CDK4/6 inhibitors in breast cancer, both as monotherapy and as partners of combinatorial synergic treatments, and on the clinical development of palbociclib in breast cancer. PMID:28203301

DOE Office of Scientific and Technical Information (OSTI.GOV)

Peek, Gregory W.; Tollefsbol, Trygve O., E-mail: trygve@uab.edu; Comprehensive Cancer Center, University of Alabama at Birmingham, Birmingham, AL

Human telomerase reverse transcriptase (hTERT) is the catalytic and limiting component of telomerase and also a transcription factor. It is critical to the integrity of the ends of linear chromosomes and to the regulation, extent and rate of cell cycle progression in multicellular eukaryotes. The level of hTERT expression is essential to a wide range of bodily functions and to avoidance of disease conditions, such as cancer, that are mediated in part by aberrant level and regulation of cell cycle proliferation. Value of a gene in regulation depends on its ability to both receive input from multiple sources and transmitmore » signals to multiple effectors. The expression of hTERT and the progression of the cell cycle have been shown to be regulated by an extensive network of gene products and signaling pathways, including the PI3K/Akt and TGF-β pathways. The PI3K inhibitor PX-866 and the competitive estrogen receptor ligand raloxifene have been shown to modify progression of those pathways and, in combination, to decrease proliferation of estrogen receptor positive (ER+) MCF-7 breast cancer cells. We found that combinations of modulators of those pathways decreased not only hTERT transcription but also transcription of additional essential cell cycle regulators such as Cyclin D1. By evaluating known expression profile signatures for TGF-β pathway diversions, we confirmed additional genes such as heparin-binding epidermal growth factor-like growth factor (HB EGF) by which those pathways and their perturbations may also modify cell cycle progression. - Highlights: • PX-866 and raloxifene affect the PI3K/Akt and TGF-β pathways. • PX-866 and raloxifene down-regulate genes up-regulated in cancer. • PX-866 and raloxifene decrease transcription of hTERT and Cyclin D1. • Pathological transcription signatures can identify new defense mechanisms.« less

Human Cpr (Cell Cycle Progression Restoration) Genes Impart a Far(-) Phenotype on Yeast Cells

PubMed Central

Edwards, M. C.; Liegeois, N.; Horecka, J.; DePinho, R. A.; Sprague-Jr., G. F.; Tyers, M.; Elledge, S. J.

1997-01-01

Regulated cell cycle progression depends on the proper integration of growth control pathways with the basic cell cycle machinery. While many of the central molecules such as cyclins, CDKs, and CKIs are known, and many of the kinases and phosphatases that modify the CDKs have been identified, little is known about the additional layers of regulation that impinge upon these molecules. To identify new regulators of cell proliferation, we have selected for human and yeast cDNAs that when overexpressed were capable of specifically overcoming G(1) arrest signals from the cell cycle branch of the mating pheromone pathway, while still maintaining the integrity of the transcriptional induction branch. We have identified 13 human CPR (cell cycle progression restoration) genes and 11 yeast OPY (overproduction-induced pheromone-resistant yeast) genes that specifically block the G(1) arrest by mating pheromone. The CPR genes represent a variety of biochemical functions including a new cyclin, a tumor suppressor binding protein, chaperones, transcription factors, translation factors, RNA-binding proteins, as well as novel proteins. Several CPR genes require individual CLNs to promote pheromone resistance and those that require CLN3 increase the basal levels of Cln3 protein. Moreover, several of the yeast OPY genes have overlapping functions with the human CPR genes, indicating a possible conservation of roles. PMID:9383053

S phase entry causes homocysteine-induced death while ataxia telangiectasia and Rad3 related protein functions anti-apoptotically to protect neurons.

PubMed

Ye, Weizhen; Blain, Stacy W

2010-08-01

A major phenotype seen in neurodegenerative disorders is the selective loss of neurons due to apoptotic death and evidence suggests that inappropriate re-activation of cell cycle proteins in post-mitotic neurons may be responsible. To investigate whether reactivation of the G1 cell cycle proteins and S phase entry was linked with apoptosis, we examined homocysteine-induced neuronal cell death in a rat cortical neuron tissue culture system. Hyperhomocysteinaemia is a physiological risk factor for a variety of neurodegenerative diseases, including Alzheimer's disease. We found that in response to homocysteine treatment, cyclin D1, and cyclin-dependent kinases 4 and 2 translocated to the nucleus, and p27 levels decreased. Both cyclin-dependent kinases 4 and 2 regained catalytic activity, the G1 gatekeeper retinoblastoma protein was phosphorylated and DNA synthesis was detected, suggesting transit into S phase. Double-labelling immunofluorescence showed a 95% co-localization of anti-bromodeoxyuridine labelling with apoptotic markers, demonstrating that those cells that entered S phase eventually died. Neurons could be protected from homocysteine-induced death by methods that inhibited G1 phase progression, including down-regulation of cyclin D1 expression, inhibition of cyclin-dependent kinases 4 or 2 activity by small molecule inhibitors, or use of the c-Abl kinase inhibitor, Gleevec, which blocked cyclin D and cyclin-dependent kinase 4 nuclear translocation. However, blocking cell cycle progression post G1, using DNA replication inhibitors, did not prevent apoptosis, suggesting that death was not preventable post the G1-S phase checkpoint. While homocysteine treatment caused DNA damage and activated the DNA damage response, its mechanism of action was distinct from that of more traditional DNA damaging agents, such as camptothecin, as it was p53-independent. Likewise, inhibition of the DNA damage sensors, ataxia-telangiectasia mutant and ataxia telangiectasia and Rad3 related proteins, did not rescue apoptosis and in fact exacerbated death, suggesting that the DNA damage response might normally function neuroprotectively to block S phase-dependent apoptosis induction. As cell cycle events appear to be maintained in vivo in affected neurons for weeks to years before apoptosis is observed, activation of the DNA damage response might be able to hold cell cycle-induced death in check.

A Stochastic Model of the Yeast Cell Cycle Reveals Roles for Feedback Regulation in Limiting Cellular Variability.

PubMed

Barik, Debashis; Ball, David A; Peccoud, Jean; Tyson, John J

2016-12-01

The cell division cycle of eukaryotes is governed by a complex network of cyclin-dependent protein kinases (CDKs) and auxiliary proteins that govern CDK activities. The control system must function reliably in the context of molecular noise that is inevitable in tiny yeast cells, because mistakes in sequencing cell cycle events are detrimental or fatal to the cell or its progeny. To assess the effects of noise on cell cycle progression requires not only extensive, quantitative, experimental measurements of cellular heterogeneity but also comprehensive, accurate, mathematical models of stochastic fluctuations in the CDK control system. In this paper we provide a stochastic model of the budding yeast cell cycle that accurately accounts for the variable phenotypes of wild-type cells and more than 20 mutant yeast strains simulated in different growth conditions. We specifically tested the role of feedback regulations mediated by G1- and SG2M-phase cyclins to minimize the noise in cell cycle progression. Details of the model are informed and tested by quantitative measurements (by fluorescence in situ hybridization) of the joint distributions of mRNA populations in yeast cells. We use the model to predict the phenotypes of ~30 mutant yeast strains that have not yet been characterized experimentally.

A Stochastic Model of the Yeast Cell Cycle Reveals Roles for Feedback Regulation in Limiting Cellular Variability

PubMed Central

Ball, David A.

2016-01-01

The cell division cycle of eukaryotes is governed by a complex network of cyclin-dependent protein kinases (CDKs) and auxiliary proteins that govern CDK activities. The control system must function reliably in the context of molecular noise that is inevitable in tiny yeast cells, because mistakes in sequencing cell cycle events are detrimental or fatal to the cell or its progeny. To assess the effects of noise on cell cycle progression requires not only extensive, quantitative, experimental measurements of cellular heterogeneity but also comprehensive, accurate, mathematical models of stochastic fluctuations in the CDK control system. In this paper we provide a stochastic model of the budding yeast cell cycle that accurately accounts for the variable phenotypes of wild-type cells and more than 20 mutant yeast strains simulated in different growth conditions. We specifically tested the role of feedback regulations mediated by G1- and SG2M-phase cyclins to minimize the noise in cell cycle progression. Details of the model are informed and tested by quantitative measurements (by fluorescence in situ hybridization) of the joint distributions of mRNA populations in yeast cells. We use the model to predict the phenotypes of ~30 mutant yeast strains that have not yet been characterized experimentally. PMID:27935947

[Promoting effect of cyclin D1 overexpression on proliferation and epithelial mesenchymal transition of cervical squamous cell carcinoma SiHa cells].

PubMed

Wang, P; Liu, S; Cheng, B; Wu, X Z; Ding, S S; Xu, L; Liu, Y; Duan, L; Sun, S Z

2017-03-08

Objective: To study effects of cyclin D1 overexpression on the proliferation and differentiation of cervical squamous cell carcinoma SiHa cells and to investigate related signaling molecules. Methods: Primers were designed to amplify the full length of cyclin D1 gene and cyclin D1 gene was amplified by PCR for constructing pcDNA3.1 plasmid vector. The construct was then transfected into SiHa cells, and the cells with stable overexpression of cyclin D1 were established, cyclin D1 gene and protein expression were detected by RT-PCR and Western blot, respectively. Cell growth curve was documented by MTT assay. CK7, E-cadherin, vimentin, Snail gene and protein expression in transfected cells were detected by RT-PCR and Western blot. RT-PCR was used to detect the mRNA expression of proliferation and differentiation-related genes like CDK4, CDK2, p21, p27, cyclin E, Rb, E2F, E6/E7 and Ki-67. After synchronization of cells, RT-PCR was used to detect of cyclin D1 and p21 mRNA expression at different time points of the cell cycle. Results: The G-3 cells with cyclin D1 overexpression were successfully established. The growth curve and Ki-67 mRNA expression accelerated in G-3 cells.Vimentin and Snail expression significantly increased at both gene and protein levels, while E-cadherin, CK7 gene and protein expression significantly decreased, indicating epithelial mesenchymal transitionoccurred in G-3 cells.Meanwhile, mRNA expression of cyclin D1, CDK4, CDK2, p21, p27, cyclin E, E2F and Rb increased, while E6/E7 and p16 showed no significant change. The expression trends of p21 and cyclin D1 were almost identical with fluctuation at different time points in the cell cycle. Conclusions: Overexpression of cyclin D1 induced by gene transfection promotes proliferation and epithelial mesenchymal transition in SiHa cells.The process is accompanied by up-regulation of CDK4, CDK2, p21, p27 and cyclin E genes.p21 expression increases synchronously with cyclin D1, suggesting a regulatory role in epithelial mesenchymal transition by affecting expression of vimentin in G-3 cells.

Altered expression of key cell cycle regulators in renal cell carcinoma associated with Xp11.2 translocation.

PubMed

Barroca, H; Castedo, S; Vieira, J; Teixeira, M; Müller-Höcker, J

2009-01-01

Renal cell carcinoma (RCC) is a rare tumor in the pediatric population. Recently, a phenotypically and genetically distinct kidney carcinoma, mainly prevalent in children and associated with an Xp11.2 translocation or TFE3 gene fusion, has been described. It has been advanced that in this subtype of RCC, there is an accumulation of cyclin D1, cyclin D3, and p21 ((wafl/cip1)). The aim of the present study was to figure out in two pediatric RCC recently diagnosed in our department (one clear cell-type RCC and one TFE3-positive RCC) whether those features are indeed specific of the latter tumor or occur in pediatric RCC irrespective of the tumor type. The following immunostains were performed in both cases: Ki67, p16(ink4a), p21 ((wafl/cip1)), p27(kip1), p53, p63, mdm2, cyclin D1, cyclin D3, TFE3, CD10, vimentin, E-cadherin, and RCC-antigen. We observed in the TFE3-positive carcinoma an intense immunoreaction for p21 ((wafl/cip1)), cyclin D1, and cyclin D3, without expression for p53, p16, p27(kip1), and mdm2, whereas the immunoexpression profile observed in the classic RCC was similar to that of clear cell, adult-type RCC. Our study confirms that TFE3-positive RCC exhibits a deregulation of the cell cycle apparently unrelated to the young age of the patients.

BRCA1-IRIS regulates cyclin D1 expression in breast cancer cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nakuci, Enkeleda; Mahner, Sven; DiRenzo, James

2006-10-01

The regulator of cell cycle progression, cyclin D1, is up-regulated in breast cancer cells; its expression is, in part, dependent on ER{alpha} signaling. However, many ER{alpha}-negative tumors and tumor cell lines (e.g., SKBR3) also show over-expression of cyclin D1. This suggests that, in addition to ER{alpha} signaling, cyclin D1 expression is under the control of other signaling pathways; these pathways may even be over-expressed in the ER{alpha}-negative cells. We previously noticed that both ER{alpha}-positive and -negative cell lines over-express BRCA1-IRIS mRNA and protein. Furthermore, the level of over-expression of BRCA1-IRIS in ER{alpha}-negative cell lines even exceeded its over-expression level inmore » ER{alpha}-positive cell lines. In this study, we show that: (1) BRCA1-IRIS forms complex with two of the nuclear receptor co-activators, namely, SRC1 and SRC3 (AIB1) in an ER{alpha}-independent manner. (2) BRCA1-IRIS alone, or in connection with co-activators, is recruited to the cyclin D1 promoter through its binding to c-Jun/AP1 complex; this binding activates the cyclin D1 expression. (3) Over-expression of BRCA1-IRIS in breast cells over-activates JNK/c-Jun; this leads to the induction of cyclin D1 expression and cellular proliferation. (4) BRCA1-IRIS activation of JNK/c-Jun/AP1 appears to account for this, because in cells that were depleted from BRCA1-IRIS, JNK remained inactive. However, depletion of SRC1 or SRC3 instead reduced c-Jun expression. Our data suggest that this novel signaling pathway links BRCA1-IRIS to cellular proliferation through c-Jun/AP1 nuclear pathway; finally, this culminates in the increased expression of the cyclin D1 gene.« less

The integration of HR-HPV increases the expression of cyclins A and E in cytologies with and without low-grade lesions.

PubMed

Zubillaga-Guerrero, M I; Illades-Aguiar, B; Leyva-Vazquez, M A; Flores-Alfaro, E; Castañeda-Saucedo, E; Muñoz-Valle, J F; Alarcón-Romero, L C

2013-01-01

Cyclin-A and cyclin-E are regulators of G1-S phase of normal cell cycle. Integration of human papilloma virus high-risk (HR-HPV) could alter this mechanism, and its overexpression has been associated with poor prognosis in cervical cancer. To determine the expression of cyclin-A and cyclin-E, types of HR-HPV and physical state of DNA in cytologies with the diagnosis of low-grade squamous intraepithelial lesion (LSIL). 115 cytological specimens in liquid base (liquid-PREP(™)) were analyzed. 25 specimens were with no signs of SIL (NSIL) and without HPV; 30 with NSIL with low-risk HPV (LR-HPV); 30 with NSIL with HR-HPV; and 30 with both LSIL and HR-HPV. The expression of cyclins was evaluated by immunocytochemistry; and the detection of viral DNA was done by polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLPs) for genotyping or sequencing of HPV. The physical state of HPV was evaluated by in situ hybridization with amplification with tyramide. In the cytologies NSIL with LR-HPV, the expression of cyclin-A and cyclin-E was found respectively in 23.3% and 33.3% of the specimens. Among the specimens of NSIL with HR-HPV, 33.3% expressed cyclin-A and 40% cyclin-E, while 100% of the LSILs expressed the 2 cyclins. On the other hand, 100% of the samples NSIL with LR-HPV presented an episomal pattern. Of the specimens of NSIL with HR-HPV, 56.6% exhibited an episomal pattern, 23.3% integrated and 20%, mixed. Among the LSILs, 90% were mixed and 10% integrated. The cyclins A and E are present in the LSILs that occur predominantly in mixed state in the presence of HR-HPV.

Interplay between cancer cell cycle and metabolism: Challenges, targets and therapeutic opportunities.

PubMed

Roy, Debmalya; Sheng, Gao Ying; Herve, Semukunzi; Carvalho, Evandro; Mahanty, Arpan; Yuan, Shengtao; Sun, Li

2017-05-01

A growing interest has emerged in the field of studying the cross-talk between cancer cell cycle and metabolism. In this review, we aimed to present how metabolism and cell cycle are correlated and how cancer cells get energy to drive cell cycle. Cell proliferation and cell death largely depend on the metabolic activity of the cell. Cell cycle proteins, e.g. cyclin D, cyclin dependent kinase (CDK), some pro-apoptotic and anti-apoptotic proteins, and P53 have been shown to be regulated by metabolic crosstalk. Dysregulation of this cross-talk between metabolism and cell cycle leads to degenerative disorder(s) and cancer. It is not fully understood the actual reason of aberration between metabolism and cell cycle, but it is a hallmark of cancer research. Herein, we discussed the role of some regulatory molecules relative of cell cycle and metabolism and highlight how they control the function of each other. We also pointed out, current therapeutic opportunities and some additional crucial therapeutic targets on these fields that could be a breakthrough in cancer research. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

The ciliary margin zone of the mammalian retina generates retinal ganglion cells

PubMed Central

Marcucci, Florencia; Murcia-Belmonte, Veronica; Coca, Yaiza; Ferreiro-Galve, Susana; Wang, Qing; Kuwajima, Takaaki; Khalid, Sania; Ross, M. Elizabeth; Herrera, Eloisa; Mason, Carol

2016-01-01

Summary The retina of lower vertebrates grows continuously by integrating new neurons generated from progenitors in the ciliary margin zone (CMZ). Whether the mammalian CMZ provides the neural retina with retinal cells is controversial. Live-imaging of embryonic retina expressing eGFP in the CMZ shows that cells migrate laterally from the CMZ to the neural retina where differentiated retinal ganglion cells (RGCs) reside. As Cyclin D2, a cell-cycle regulator, is enriched in ventral CMZ, we analyzed Cyclin D2−/− mice to test whether the CMZ is a source of retinal cells. Neurogenesis is diminished in Cyclin D2 mutants, leading to a reduction of RGCs in the ventral retina. In line with these findings, in the albino retina, the decreased production of ipsilateral RGCs is correlated with fewer Cyclin D2+ cells. Together, these results implicate the mammalian CMZ as a neurogenic site that produces RGCs and whose proper generation depends on Cyclin D2 activity. PMID:28009286

The Ciliary Margin Zone of the Mammalian Retina Generates Retinal Ganglion Cells.

PubMed

Marcucci, Florencia; Murcia-Belmonte, Veronica; Wang, Qing; Coca, Yaiza; Ferreiro-Galve, Susana; Kuwajima, Takaaki; Khalid, Sania; Ross, M Elizabeth; Mason, Carol; Herrera, Eloisa

2016-12-20

The retina of lower vertebrates grows continuously by integrating new neurons generated from progenitors in the ciliary margin zone (CMZ). Whether the mammalian CMZ provides the neural retina with retinal cells is controversial. Live imaging of embryonic retina expressing eGFP in the CMZ shows that cells migrate laterally from the CMZ to the neural retina where differentiated retinal ganglion cells (RGCs) reside. Because Cyclin D2, a cell-cycle regulator, is enriched in ventral CMZ, we analyzed Cyclin D2 -/- mice to test whether the CMZ is a source of retinal cells. Neurogenesis is diminished in Cyclin D2 mutants, leading to a reduction of RGCs in the ventral retina. In line with these findings, in the albino retina, the decreased production of ipsilateral RGCs is correlated with fewer Cyclin D2 + cells. Together, these results implicate the mammalian CMZ as a neurogenic site that produces RGCs and whose proper generation depends on Cyclin D2 activity. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

Checkpoints couple transcription network oscillator dynamics to cell-cycle progression.

PubMed

Bristow, Sara L; Leman, Adam R; Simmons Kovacs, Laura A; Deckard, Anastasia; Harer, John; Haase, Steven B

2014-09-05

The coupling of cyclin dependent kinases (CDKs) to an intrinsically oscillating network of transcription factors has been proposed to control progression through the cell cycle in budding yeast, Saccharomyces cerevisiae. The transcription network regulates the temporal expression of many genes, including cyclins, and drives cell-cycle progression, in part, by generating successive waves of distinct CDK activities that trigger the ordered program of cell-cycle events. Network oscillations continue autonomously in mutant cells arrested by depletion of CDK activities, suggesting the oscillator can be uncoupled from cell-cycle progression. It is not clear what mechanisms, if any, ensure that the network oscillator is restrained when progression in normal cells is delayed or arrested. A recent proposal suggests CDK acts as a master regulator of cell-cycle processes that have the potential for autonomous oscillatory behavior. Here we find that mitotic CDK is not sufficient for fully inhibiting transcript oscillations in arrested cells. We do find that activation of the DNA replication and spindle assembly checkpoints can fully arrest the network oscillator via overlapping but distinct mechanisms. Further, we demonstrate that the DNA replication checkpoint effector protein, Rad53, acts to arrest a portion of transcript oscillations in addition to its role in halting cell-cycle progression. Our findings indicate that checkpoint mechanisms, likely via phosphorylation of network transcription factors, maintain coupling of the network oscillator to progression during cell-cycle arrest.

The CDK-APC/C Oscillator Predominantly Entrains Periodic Cell-Cycle Transcription

PubMed Central

Rahi, Sahand Jamal; Pecani, Kresti; Ondracka, Andrej; Oikonomou, Catherine; Cross, Frederick R.

2016-01-01

Throughout cell cycle progression, the expression of multiple transcripts oscillate, and whether these are under the centralized control of the CDK-APC/C proteins or can be driven by a de-centralized transcription factor (TF) cascade is a fundamental question for understanding cell cycle regulation. In budding yeast, we find that the transcription of nearly all genes, as assessed by RNA-seq or fluorescence microscopy in single cells, is dictated by CDK-APC/C. Three exceptional genes are transcribed in a pulsatile pattern in a variety of CDK-APC/C arrests. Pursuing one of these transcripts, the SIC1 inhibitor of B-type cyclins, we use a combination of mathematical modeling and experimentation to provide evidence that, counter-intuitively, Sic1 provides a failsafe mechanism promoting nuclear division when levels of mitotic cyclins are low. PMID:27058667

Inefficient differentiation response to cell cycle stress leads to genomic instability and malignant progression of squamous carcinoma cells

PubMed Central

Alonso-Lecue, Pilar; de Pedro, Isabel; Coulon, Vincent; Molinuevo, Rut; Lorz, Corina; Segrelles, Carmen; Ceballos, Laura; López-Aventín, Daniel; García-Valtuille, Ana; Bernal, José M; Mazorra, Francisco; Pujol, Ramón M; Paramio, Jesús; Ramón Sanz, J; Freije, Ana; Toll, Agustí; Gandarillas, Alberto

2017-01-01

Squamous cell carcinoma (SCC) or epidermoid cancer is a frequent and aggressive malignancy. However in apparent paradox it retains the squamous differentiation phenotype except for very dysplastic lesions. We have shown that cell cycle stress in normal epidermal keratinocytes triggers a squamous differentiation response involving irreversible mitosis block and polyploidisation. Here we show that cutaneous SCC cells conserve a partial squamous DNA damage-induced differentiation response that allows them to overcome the cell division block. The capacity to divide in spite of drug-induced mitotic stress and DNA damage made well-differentiated SCC cells more genomically instable and more malignant in vivo. Consistently, in a series of human biopsies, non-metastatic SCCs displayed a higher degree of chromosomal alterations and higher expression of the S phase regulator Cyclin E and the DNA damage signal γH2AX than the less aggressive, non-squamous, basal cell carcinomas. However, metastatic SCCs lost the γH2AX signal and Cyclin E, or accumulated cytoplasmic Cyclin E. Conversely, inhibition of endogenous Cyclin E in well-differentiated SCC cells interfered with the squamous phenotype. The results suggest a dual role of cell cycle stress-induced differentiation in squamous cancer: the resulting mitotic blocks would impose, when irreversible, a proliferative barrier, when reversible, a source of genomic instability, thus contributing to malignancy. PMID:28661481

Prognostic significance of cell cycle proteins and genomic instability in borderline, early and advanced stage ovarian carcinomas.

PubMed

Blegen, H.; Einhorn, N.; Sjövall, K.; Roschke, A.; Ghadimi, B. M.; McShane, L. M.; Nilsson, B.; Shah, K.; Ried, T.; Auer, G.

2000-11-01

Disturbed cell cycle-regulating checkpoints and impairment of genomic stability are key events during the genesis and progression of malignant tumors. We analyzed 80 epithelial ovarian tumors of benign (n = 10) and borderline type (n = 18) in addition to carcinomas of early (n = 26) and advanced (n = 26) stages for the expression of Ki67, cyclin A and cyclin E, p21WAF-1, p27KIP-1 and p53 and correlated the results with the clinical course. Genomic instability was assessed by DNA ploidy measurements and, in 35 cases, by comparative genomic hybridization. Overexpression of cyclin A and cyclin E was observed in the majority of invasive carcinomas, only rarely in borderline tumors and in none of the benign tumors. Similarly, high expression of p53 together with undetectable p21 or loss of chromosome arm 17p were frequent events only in adenocarcinomas. Both borderline tumors and adenocarcinomas revealed a high number of chromosomal gains and losses. However, regional chromosomal amplifications were found to occur 13 times more frequently in the adenocarcinomas than in the borderline tumors. The expression pattern of low p27 together with high Ki67 was found to be an independent predictor of poor outcome in invasive carcinomas. The results provide a link between disturbed cell cycle regulatory proteins, chromosomal aberrations and survival in ovarian carcinomas.

Epigenetic regulation of vascular smooth muscle cell proliferation and neointima formation by histone deacetylase inhibition.

PubMed

Findeisen, Hannes M; Gizard, Florence; Zhao, Yue; Qing, Hua; Heywood, Elizabeth B; Jones, Karrie L; Cohn, Dianne; Bruemmer, Dennis

2011-04-01

Proliferation of smooth muscle cells (SMC) in response to vascular injury is central to neointimal vascular remodeling. There is accumulating evidence that histone acetylation constitutes a major epigenetic modification for the transcriptional control of proliferative gene expression; however, the physiological role of histone acetylation for proliferative vascular disease remains elusive. In the present study, we investigated the role of histone deacetylase (HDAC) inhibition in SMC proliferation and neointimal remodeling. We demonstrate that mitogens induce transcription of HDAC 1, 2, and 3 in SMC. Short interfering RNA-mediated knockdown of either HDAC 1, 2, or 3 and pharmacological inhibition of HDAC prevented mitogen-induced SMC proliferation. The mechanisms underlying this reduction of SMC proliferation by HDAC inhibition involve a growth arrest in the G(1) phase of the cell cycle that is due to an inhibition of retinoblastoma protein phosphorylation. HDAC inhibition resulted in a transcriptional and posttranscriptional regulation of the cyclin-dependent kinase inhibitors p21(Cip1) and p27(Kip). Furthermore, HDAC inhibition repressed mitogen-induced cyclin D1 mRNA expression and cyclin D1 promoter activity. As a result of this differential cell cycle-regulatory gene expression by HDAC inhibition, the retinoblastoma protein retains a transcriptional repression of its downstream target genes required for S phase entry. Finally, we provide evidence that these observations are applicable in vivo by demonstrating that HDAC inhibition decreased neointima formation and expression of cyclin D1 in a murine model of vascular injury. These findings identify HDAC as a critical component of a transcriptional cascade regulating SMC proliferation and suggest that HDAC might play a pivotal role in the development of proliferative vascular diseases, including atherosclerosis and in-stent restenosis.

Epigenetic Regulation of Vascular Smooth Muscle Cell Proliferation and Neointima Formation by Histone Deacetylase Inhibition

PubMed Central

Findeisen, Hannes M.; Gizard, Florence; Zhao, Yue; Qing, Hua; Heywood, Elizabeth B.; Jones, Karrie L.; Cohn, Dianne; Bruemmer, Dennis

2011-01-01

Objective Proliferation of smooth muscle cells (SMC) in response to vascular injury is central to neointimal vascular remodeling. There is accumulating evidence that histone acetylation constitutes a major epigenetic modification for the transcriptional control of proliferative gene expression; however, the physiological role of histone acetylation for proliferative vascular disease remains elusive. Methods and Results In the present study, we investigated the role of histone deacetylase (HDAC) inhibition in SMC proliferation and neointimal remodeling. We demonstrate that mitogens induce transcription of HDAC 1, 2 and 3 in SMC. siRNA-mediated knock-down of either HDAC 1, 2 or 3 and pharmacologic inhibition of HDAC prevented mitogen-induced SMC proliferation. The mechanisms underlying this reduction of SMC proliferation by HDAC inhibition involve a growth arrest in the G1-phase of the cell cycle due to an inhibition of retinoblastoma protein phosphorylation. HDAC inhibition resulted in a transcriptional and posttranscriptional regulation of the cyclin-dependent kinase inhibitors p21Cip1 and p27Kip. Furthermore, HDAC inhibition repressed mitogen-induced cyclin D1 mRNA expression and cyclin D1 promoter activity. As a result of this differential cell cycle-regulatory gene expression by HDAC inhibition, the retinoblastoma protein retains a transcriptional repression of its downstream target genes required for S phase entry. Finally, we provide evidence that these observations are applicable in vivo by demonstrating that HDAC inhibition decreased neointima formation and expression of cyclin D1 in a murine model of vascular injury. Conclusion These findings identify HDAC as a critical component of a transcriptional cascade regulating SMC proliferation and suggest that HDAC might play a pivotal role in the development of proliferative vascular diseases, including atherosclerosis and in-stent restenosis. PMID:21233448

TNF-α sensitizes chemotherapy and radiotherapy against breast cancer cells.

PubMed

Wu, Xiao; Wu, Meng-Yao; Jiang, Min; Zhi, Qiaoming; Bian, Xiaojie; Xu, Meng-Dan; Gong, Fei-Ran; Hou, Juan; Tao, Min; Shou, Liu-Mei; Duan, Weiming; Chen, Kai; Shen, Meng; Li, Wei

2017-01-01

Despite new developments in cancer therapy, chemotherapy and radiotherapy remain the cornerstone of breast cancer treatment. Therefore, finding ways to reduce the toxicity and increase sensitivity is particularly important. Tumor necrosis factor alpha (TNF-α) exerts multiple functions in cell proliferation, differentiation and apoptosis. In the present study, we investigated whether TNF-α could enhance the effect of chemotherapy and radiotherapy against breast cancer cells. Cell growth was determined by MTT assay in vitro, and by using nude mouse tumor xenograft model in vivo. Cell cycle and apoptosis/necrosis were evaluated by flow cytometry. DNA damage was visualized by phospho-Histone H2A.X staining. mRNA expression was assessed by using real-time PCR. Protein expression was tested by Western blot assay. TNF-α strengthened the cytotoxicity of docetaxel, 5-FU and cisplatin against breast cancer cells both in vitro and in vivo. TNF-α activated NF-κB pathway and dependently up-regulated expressions of CyclinD1, CyclinD2, CyclinE, CDK2, CDK4 and CDK6, the key regulators participating in G1→S phase transition. As a result, TNF-α drove cells out of quiescent G0/G1 phase, entering vulnerable proliferating phases. Treatment of TNF-α brought more DNA damage after Cs 137 -irradiation and strengthened G2/M and S phase cell cycle arrest induced by docetaxel and cisplatin respectively. Moreover, the up-regulation of RIP3 (a necroptosis marker) by 5-FU, and the activation of RIP3 by TNF-α, synergistically triggered necroptosis (programmed necrosis). Knockdown of RIP3 attenuated the synergetic effect of TNF-α and 5-FU. TNF-α presented radiotherapy- and chemotherapy-sensitizing effects against breast cancer cells.

Mechanistic insights into avian reovirus p17-modulated suppression of cell-cycle CDK/cyclin complexes and enhancement of p53 and cyclin H interaction.

PubMed

Chiu, Hung-Chuan; Huang, Wei-Ru; Liao, Tsai-Ling; Chi, Pei-I; Nielsen, Brent L; Liu, Jyung-Hurng; Liu, Hung-Jen

2018-06-15

The avian reovirus (ARV) p17 protein is a nucleocytoplasmic shuttling protein. Although we have demonstrated that p17 causes cell growth retardation via activation of p53, the precise mechanisms remains unclear. This is the first report that ARV p17 possesses broad inhibitory effects on cell-cycle CDKs, cyclins, CDK/cyclin complexes, and CDK activating kinase (CAK) activity in various mammalian, avian, and cancer cell lines. Suppression of CDK activity by p17 occurs by direct binding to CDKs, cyclins, and CDK/cyclin complexes, transcriptional downregulation of CDKs, cytoplasmic retention of CDKs and cyclins, and inhibition of CAK activity by promoting p53/cyclin H interaction. p17 binds to CDK/cyclin except for CDK1/cyclin B1 and CDK7/cyclin H complexes. We have determined that the negatively charged 151 LAVxDxDxE/DDGADPN 165 motif in cyclin B1 interacts with a positively charged region of CDK1. p17 mimics the cyclin B1 sequence to compete for CDK1 binding. The PSTAIRE motif is not required for interaction of CDK1/cyclin B1, but is required for other CDK/cyclin complexes. p17 interacts with cyclins by its cyclin-binding motif 125 RXL 127 Sequence and mutagenic analyses of p17 indicated that a 140 WXFD 143 motif and residues D113 and K122 in p17 are critical for CDK2 and CDK6 binding, leading to their sequestration in the cytoplasm. Exogenous expression of p17 significantly enhanced virus replication while p17 mutants with low binding ability to cell-cycle CDKs have no effect on virus yield, suggesting that p17 inhibits cell growth and the cell cycle benefiting virus replication. An in vivo tumorigenesis assay also showed a significant reduction in tumor size. Published under license by The American Society for Biochemistry and Molecular Biology, Inc.

Multiple degradation pathways regulate versatile CIP/KIP CDK inhibitors.

PubMed

Starostina, Natalia G; Kipreos, Edward T

2012-01-01

The mammalian CIP/KIP family of cyclin-dependent kinase (CDK) inhibitors (CKIs) comprises three proteins--p21(Cip1/WAF1), p27(Kip1), and p57(Kip2)--that bind and inhibit cyclin-CDK complexes, which are key regulators of the cell cycle. CIP/KIP CKIs have additional independent functions in regulating transcription, apoptosis and actin cytoskeletal dynamics. These divergent functions are performed in distinct cellular compartments and contribute to the seemingly contradictory observation that the CKIs can both suppress and promote cancer. Multiple ubiquitin ligases (E3s) direct the proteasome-mediated degradation of p21, p27 and p57. This review analyzes recent data highlighting our current understanding of how distinct E3 pathways regulate subpopulations of the CKIs to control their diverse functions. Copyright © 2011 Elsevier Ltd. All rights reserved.

Silymarin induces cyclin D1 proteasomal degradation via its phosphorylation of threonine-286 in human colorectal cancer cells.

PubMed

Eo, Hyun Ji; Park, Gwang Hun; Song, Hun Min; Lee, Jin Wook; Kim, Mi Kyoung; Lee, Man Hyo; Lee, Jeong Rak; Koo, Jin Suk; Jeong, Jin Boo

2015-01-01

Silymarin from milk thistle (Silybum marianum) plant has been reported to show anti-cancer, anti-inflammatory, antioxidant and hepatoprotective effects. For anti-cancer activity, silymarin is known to regulate cell cycle progression through cyclin D1 downregulation. However, the mechanism of silymarin-mediated cyclin D1 downregulation still remains unanswered. The current study was performed to elucidate the molecular mechanism of cyclin D1 downregulation by silymarin in human colorectal cancer cells. The treatment of silymarin suppressed the cell proliferation in HCT116 and SW480 cells and decreased cellular accumulation of exogenously-induced cyclin D1 protein. However, silymarin did not change the level of cyclin D1 mRNA. Inhibition of proteasomal degradation by MG132 attenuated silymarin-mediated cyclin D1 downregulation and the half-life of cyclin D1 was decreased in the cells treated with silymarin. In addition, silymarin increased phosphorylation of cyclin D1 at threonine-286 and a point mutation of threonine-286 to alanine attenuated silymarin-mediated cyclin D1 downregulation. Inhibition of NF-κB by a selective inhibitor, BAY 11-7082 suppressed cyclin D1 phosphorylation and downregulation by silymarin. From these results, we suggest that silymarin-mediated cyclin D1 downregulation may result from proteasomal degradation through its threonine-286 phosphorylation via NF-κB activation. The current study provides new mechanistic link between silymarin, cyclin D1 downregulation and cell growth in human colorectal cancer cells. Copyright © 2014 Elsevier B.V. All rights reserved.

Baicalein induces G1 arrest in oral cancer cells by enhancing the degradation of cyclin D1 and activating AhR to decrease Rb phosphorylation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cheng, Ya-Hsin, E-mail: yhcheng@mail.cmu.edu.tw; Li, Lih-Ann; Lin, Pinpin

Baicalein is a flavonoid, known to have anti-inflammatory and anti-cancer effects. As an aryl hydrocarbon receptor (AhR) ligand, baicalein at high concentrations blocks AhR-mediated dioxin toxicity. Because AhR had been reported to play a role in regulating the cell cycle, we suspected that the anti-cancer effect of baicalein is associated with AhR. This study investigated the molecular mechanism involved in the anti-cancer effect of baicalein in oral cancer cells HSC-3, including whether such effect would be AhR-mediated. Results revealed that baicalein inhibited cell proliferation and increased AhR activity in a dose-dependent manner. Cell cycle was arrested at the G1 phasemore » and the expression of CDK4, cyclin D1, and phosphorylated retinoblastoma (pRb) was decreased. When the AhR was suppressed by siRNA, the reduction of pRb was partially reversed, accompanied by a decrease of cell population at G1 phase and an increase at S phase, while the reduction of cyclin D1 and CDK4 did not change. This finding suggests that the baicalein activation of AhR is indeed associated with the reduction of pRb, but is independent of the reduction of cyclin D1 and CDK4. When cells were pre-treated with LiCl, the inhibitor of GSK-3β, the decrease of cyclin D1 was blocked and the reduction of pRb was recovered. The data indicates that in HSC-3 the reduction of pRb is both mediated by baicalein through activation of AhR and facilitation of cyclin D1 degradation, which causes cell cycle arrest at the G1 phase, and results in the inhibition of cell proliferation. -- Highlights: ► Baicalein causes the G1 phase arrest by decreasing Rb phosphorylation. ► Baicalein modulates AhR-mediated cell proliferation. ► Both AhR activation and cyclin D1 degradation results in hypophosphorylation of Rb. ► Baicalein facilitates cyclin D1 degradation by signalling the GSK-3β pathway.« less

Pax6 Exerts Regional Control of Cortical Progenitor Proliferation via Direct Repression of Cdk6 and Hypophosphorylation of pRb

PubMed Central

Mi, Da; Carr, Catherine B.; Georgala, Petrina A.; Huang, Yu-Ting; Manuel, Martine N.; Jeanes, Emily; Niisato, Emi; Sansom, Stephen N.; Livesey, Frederick J.; Theil, Thomas; Hasenpusch-Theil, Kerstin; Simpson, T. Ian; Mason, John O.; Price, David J.

2013-01-01

Summary The mechanisms by which early spatiotemporal expression patterns of transcription factors such as Pax6 regulate cortical progenitors in a region-specific manner are poorly understood. Pax6 is expressed in a gradient across the developing cortex and is essential for normal corticogenesis. We found that constitutive or conditional loss of Pax6 increases cortical progenitor proliferation by amounts that vary regionally with normal Pax6 levels. We compared the gene expression profiles of equivalent Pax6-expressing progenitors isolated from Pax6+/+ and Pax6−/− cortices and identified many negatively regulated cell-cycle genes, including Cyclins and Cdks. Biochemical assays indicated that Pax6 directly represses Cdk6 expression. Cyclin/Cdk repression inhibits retinoblastoma protein (pRb) phosphorylation, thereby limiting the transcription of genes that directly promote the mechanics of the cell cycle, and we found that Pax6 inhibits pRb phosphorylation and represses genes involved in DNA replication. Our results indicate that Pax6’s modulation of cortical progenitor cell cycles is regional and direct. PMID:23622063

Enhanced expression of cyclins and cyclin-dependent kinases in aniline-induced cell proliferation in rat spleen

PubMed Central

Wang, Jianling; Wang, Gangduo; Ma, Huaxian; Khan, M. Firoze

2010-01-01

Aniline exposure is associated with toxicity to the spleen leading to splenomegaly, hyperplasia, fibrosis and a variety of sarcomas of the spleen on chronic exposure. In earlier studies, we have shown that aniline exposure leads to iron overload, oxidative stress and activation of redox-sensitive transcription factors, which could regulate various genes leading to a tumorigenic response in the spleen. However, molecular mechanisms leading to aniline-induced cellular proliferation in the spleen remain largely unknown. This study was, therefore, undertaken on the regulation of G1 phase cell cycle proteins (cyclins), expression of cyclin-dependent kinases (CDKs), phosphorylation of retinoblastoma protein (pRB) and cell proliferation in the spleen, in an experimental condition preceding a tumorigenic response. Male SD rats were treated with aniline (0.5 mmol/kg/day via drinking water) for 30 days (controls received drinking water only), and splenocyte proliferation, protein expression of G1 phase cyclins, CDKs and pRB were measured. Aniline treatment resulted in significant increases in splenocyte proliferation, based on cell counts, cell proliferation markers including proliferating cell nuclear antigen (PCNA), nuclear Ki67 protein (Ki67) and minichromosome maintenance (MCM), MTT assay and flow cytometric analysis. Western blot analysis of splenocyte proteins from aniline-treated rats showed significantly increased expression of cyclins D1, D2, D3 and cyclin E, as compared to the controls. Similarly, real-time PCR analysis showed significantly increased mRNA expression for cyclins D1, D2, D3 and E in the spleens of aniline-treated rats. The overexpression of these cyclins was associated with increases in the expression of CDK4, CDK6, CDK2 as well as phosphorylation of pRB protein. Our data suggest that increased expression of cyclins, CDKs and phosphorylation of pRB protein could be critical in cell proliferation, and may contribute to aniline-induced tumorigenic response in the spleen. PMID:21070798

HTLV-I Tax and cell cycle progression.

PubMed

Neuveut, C; Jeang, K T

2000-01-01

Human T-cell leukemia virus type I (HTLV-I) is the etiological agent for adult T-cell leukemia (ATL) and various human myopathies/neuropathies. HTLV-I encodes a 40 kDa phosphoprotein, Tax, which has been implicated in cellular transformation. In similarity with several other oncoproteins such as Myc, Jun, and Fos, Tax is a transcriptional activator. How Tax mechanistically dysregulates the cell cycle remains unclear. Recent findings from us and others have shown that Tax targets key regulators of G1/S and M progression such as p16INK4a, cyclin D1, cyclin D3-cdk, and the mitotic spindle checkpoint apparatus. Thus, Tax influences the progression of cells in various phases of the cell cycle. In this regard, we will discuss three distinct mechanisms through which Tax affects cell-cycling: a) through direct association Tax can abrogate the inhibitory function of p16INK4a on the G1-cdks, b) Tax can also directly influence cyclin D-cdk activities by a protein-protein interaction, and c) Tax targets the HsMAD1 mitotic spindle-assembly checkpoint protein. Through these varied routes, the HTLV-I oncoprotein dysregulates cellular growth controls and engenders a proclivity of cells toward a loss of DNA-damage surveillance.

Meier-Gorlin syndrome mutations disrupt an Orc1 CDK inhibitory domain and cause centrosome reduplication.

PubMed

Hossain, Manzar; Stillman, Bruce

2012-08-15

Like DNA replication, centrosomes are licensed to duplicate once per cell division cycle to ensure genetic stability. In addition to regulating DNA replication, the Orc1 subunit of the human origin recognition complex controls centriole and centrosome copy number. Here we report that Orc1 harbors a PACT centrosome-targeting domain and a separate domain that differentially inhibits the protein kinase activities of Cyclin E-CDK2 and Cyclin A-CDK2. A cyclin-binding motif (Cy motif) is required for Orc1 to bind Cyclin A and inhibit Cyclin A-CDK2 kinase activity but has no effect on Cyclin E-CDK2 kinase activity. In contrast, Orc1 inhibition of Cyclin E-CDK2 kinase activity occurs by a different mechanism that is affected by Orc1 mutations identified in Meier-Gorlin syndrome patients. The cyclin/CDK2 kinase inhibitory domain of Orc1, when tethered to the PACT domain, localizes to centrosomes and blocks centrosome reduplication. Meier-Gorlin syndrome mutations that disrupt Cyclin E-CDK2 kinase inhibition also allow centrosome reduplication. Thus, Orc1 contains distinct domains that control centrosome copy number and DNA replication. We suggest that the Orc1 mutations present in some Meier-Gorlin syndrome patients contribute to the pronounced microcephaly and dwarfism observed in these individuals by altering centrosome duplication in addition to DNA replication defects.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pang, Xiaojuan; Shu, Yuxin; Niu, Zhiyuan

Post-translational regulation plays a critical role in the control of cell growth and proliferation. The phosphorylation of peroxisome proliferator-activated receptor γ (PPARγ) is the most important post-translational modification. The function of PPARγ phosphorylation has been studied extensively in the past. However, the relationship between phosphorylated PPARγ1 and tumors remains unclear. Here we investigated the role of PPARγ1 phosphorylation in human fibrosarcoma HT1080 cell line. Using the nonphosphorylation (Ser84 to alanine, S84A) and phosphorylation (Ser84 to aspartic acid, S84D) mutant of PPARγ1, the results suggested that phosphorylation attenuated PPARγ1 transcriptional activity. Meanwhile, we demonstrated that phosphorylated PPARγ1 promoted HT1080 cell proliferationmore » and this effect was dependent on the regulation of cell cycle arrest. The mRNA levels of cyclin-dependent kinase inhibitor (CKI) p21{sup Waf1/Cip1} and p27{sup Kip1} descended in PPARγ1{sup S84D} stable HT1080 cell, whereas the expression of p18{sup INK4C} was not changed. Moreover, compared to the PPARγ1{sup S84A}, PPARγ1{sup S84D} up-regulated the expression levels of cyclin D1 and cyclin A. Finally, PPARγ1 phosphorylation reduced sensitivity to agonist rosiglitazone and increased resistance to anticancer drug 5-fluorouracil (5-FU) in HT1080 cell. Our findings establish PPARγ1 phosphorylation as a critical event in human fibrosarcoma growth. These findings raise the possibility that chemical compounds that prevent the phosphorylation of PPARγ1 could act as anticancer drugs. - Highlights: • Phosphorylation attenuates PPARγ1 transcriptional activity. • Phosphorylated PPARγ1 promotes HT1080 cells proliferation. • PPARγ1 phosphorylation regulates cell cycle by mediating expression of cell cycle regulators. • PPARγ1 phosphorylation reduces sensitivity to agonist and anticancer drug. • Our findings establish PPARγ1 phosphorylation as a critical event in HT1080 cells growth.« less

Choline availability modulates human neuroblastoma cell proliferation and alters the methylation of the promoter region of the cyclin-dependent kinase inhibitor 3 gene

PubMed Central

Niculescu, Mihai D.; Yamamuro, Yutaka; Zeisel, Steven H.

2006-01-01

Choline is an important methyl donor and a component of membrane phospholipids. In this study, we tested the hypothesis that choline availability can modulate cell proliferation and the methylation of genes that regulate cell cycling. In several other model systems, hypomethylation of cytosine bases that are followed by a guanosine (CpG) sites in the promoter region of a gene is associated with increased gene expression. We found that in choline-deficient IMR-32 neuroblastoma cells, the promoter of the cyclin-dependent kinase inhibitor 3 gene (CDKN3) was hypomethylated. This change was associated with increased expression of CDKN3 and increased levels of its gene product, kinase-associated phosphatase (KAP), which inhibits the G1/S transition of the cell cycle by dephosphorylating cyclin-dependent kinases. Choline deficiency also reduced global DNA methylation. The percentage of cells that accumulated bromodeoxyuridine (proportional to cell proliferation) was 1.8 times lower in the choline-deficient cells than in the control cells. Phosphorylated retinoblastoma (p110) levels were 3 times lower in the choline-deficient cells than in control cells. These findings suggest that the mechanism whereby choline deficiency inhibits cell proliferation involves hypomethylation of key genes regulating cell cycling. This may be a mechanism for our previously reported observation that stem cell proliferation in hippocampus neuroepithelium is decreased in choline-deficient rat and mouse fetuses. PMID:15147518

Restrictions in Cell Cycle Progression of Adult Vestibular Supporting Cells in Response to Ectopic Cyclin D1 Expression

PubMed Central

Loponen, Heidi; Ylikoski, Jukka; Albrecht, Jeffrey H.; Pirvola, Ulla

2011-01-01

Sensory hair cells and supporting cells of the mammalian inner ear are quiescent cells, which do not regenerate. In contrast, non-mammalian supporting cells have the ability to re-enter the cell cycle and produce replacement hair cells. Earlier studies have demonstrated cyclin D1 expression in the developing mouse supporting cells and its downregulation along maturation. In explant cultures of the mouse utricle, we have here focused on the cell cycle control mechanisms and proliferative potential of adult supporting cells. These cells were forced into the cell cycle through adenoviral-mediated cyclin D1 overexpression. Ectopic cyclin D1 triggered robust cell cycle re-entry of supporting cells, accompanied by changes in p27Kip1 and p21Cip1 expressions. Main part of cell cycle reactivated supporting cells were DNA damaged and arrested at the G2/M boundary. Only small numbers of mitotic supporting cells and rare cells with signs of two successive replications were found. Ectopic cyclin D1-triggered cell cycle reactivation did not lead to hyperplasia of the sensory epithelium. In addition, a part of ectopic cyclin D1 was sequestered in the cytoplasm, reflecting its ineffective nuclear import. Combined, our data reveal intrinsic barriers that limit proliferative capacity of utricular supporting cells. PMID:22073316

Restrictions in cell cycle progression of adult vestibular supporting cells in response to ectopic cyclin D1 expression.

PubMed

Loponen, Heidi; Ylikoski, Jukka; Albrecht, Jeffrey H; Pirvola, Ulla

2011-01-01

Sensory hair cells and supporting cells of the mammalian inner ear are quiescent cells, which do not regenerate. In contrast, non-mammalian supporting cells have the ability to re-enter the cell cycle and produce replacement hair cells. Earlier studies have demonstrated cyclin D1 expression in the developing mouse supporting cells and its downregulation along maturation. In explant cultures of the mouse utricle, we have here focused on the cell cycle control mechanisms and proliferative potential of adult supporting cells. These cells were forced into the cell cycle through adenoviral-mediated cyclin D1 overexpression. Ectopic cyclin D1 triggered robust cell cycle re-entry of supporting cells, accompanied by changes in p27(Kip1) and p21(Cip1) expressions. Main part of cell cycle reactivated supporting cells were DNA damaged and arrested at the G2/M boundary. Only small numbers of mitotic supporting cells and rare cells with signs of two successive replications were found. Ectopic cyclin D1-triggered cell cycle reactivation did not lead to hyperplasia of the sensory epithelium. In addition, a part of ectopic cyclin D1 was sequestered in the cytoplasm, reflecting its ineffective nuclear import. Combined, our data reveal intrinsic barriers that limit proliferative capacity of utricular supporting cells.

Cypermethrin Induces Macrophages Death through Cell Cycle Arrest and Oxidative Stress-Mediated JNK/ERK Signaling Regulated Apoptosis

PubMed Central

Huang, Fang; Liu, Qiaoyun; Xie, Shujun; Xu, Jian; Huang, Bo; Wu, Yihua; Xia, Dajing

2016-01-01

Cypermethrin is one of the most highly effective synthetic pyrethroid insecticides. The toxicity of cypermethrin to the reproductive and nervous systems has been well studied. However, little is known about the toxic effect of cypermethrin on immune cells such as macrophages. Here, we investigated the cytotoxicity of cypermethrin on macrophages and the underlying molecular mechanisms. We found that cypermethrin reduced cell viability and induced apoptosis in RAW 264.7 cells. Cypermethrin also increased reactive oxygen species (ROS) production and DNA damage in a dose-dependent manner. Moreover, cypermethrin-induced G1 cell cycle arrest was associated with an enhanced expression of p21, wild-type p53, and down-regulation of cyclin D1, cyclin E and CDK4. In addition, cypermethrin treatment activated MAPK signal pathways by inducing c-Jun N-terminal kinase (JNK) and extracellular regulated protein kinases 1/2 ERK1/2 phosphorylation, and increased the cleaved poly ADP-ribose polymerase (PARP). Further, pretreatment with antioxidant N-acetylcysteine (NAC) effectively abrogated cypermethrin-induced cell cytotoxicity, G1 cell cycle arrest, DNA damage, PARP activity, and JNK and ERK1/2 activation. The specific JNK inhibitor (SP600125) and ERK1/2 inhibitor (PD98059) effectively reversed the phosphorylation level of JNK and ERK1/2, and attenuated the apoptosis. Taken together, these data suggested that cypermethrin caused immune cell death via inducing cell cycle arrest and apoptosis regulated by ROS-mediated JNK/ERK pathway. PMID:27322250

American cranberry (Vaccinium macrocarpon) extract affects human prostate cancer cell growth via cell cycle arrest by modulating expression of cell cycle regulators.

PubMed

Déziel, Bob; MacPhee, James; Patel, Kunal; Catalli, Adriana; Kulka, Marianna; Neto, Catherine; Gottschall-Pass, Katherine; Hurta, Robert

2012-05-01

Prostate cancer is one of the most common cancers in the world, and its prevalence is expected to increase appreciably in the coming decades. As such, more research is necessary to understand the etiology, progression and possible preventative measures to delay or to stop the development of this disease. Recently, there has been interest in examining the effects of whole extracts from commonly harvested crops on the behaviour and progression of cancer. Here, we describe the effects of whole cranberry extract (WCE) on the behaviour of DU145 human prostate cancer cells in vitro. Following treatment of DU145 human prostate cancer cells with 10, 25 and 50 μg ml⁻¹ of WCE, respectively for 6 h, WCE significantly decreased the cellular viability of DU145 cells. WCE also decreased the proportion of cells in the G2-M phase of the cell cycle and increased the proportion of cells in the G1 phase of the cell cycle following treatment of cells with 25 and 50 μg ml⁻¹ treatment of WCE for 6 h. These alterations in cell cycle were associated with changes in cell cycle regulatory proteins and other cell cycle associated proteins. WCE decreased the expression of CDK4, cyclin A, cyclin B1, cyclin D1 and cyclin E, and increased the expression of p27. Changes in p16(INK4a) and pRBp107 protein expression levels also were evident, however, the changes noted in p16(INK4a) and pRBp107 protein expression levels were not statistically significant. These findings demonstrate that phytochemical extracts from the American cranberry (Vaccinium macrocarpon) can affect the behaviour of human prostate cancer cells in vitro and further support the potential health benefits associated with cranberries.

The all-trans retinoic acid (atRA)-regulated gene Calmin (Clmn) regulates cell cycle exit and neurite outgrowth in murine neuroblastoma (Neuro2a) cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marzinke, Mark A.; Clagett-Dame, Margaret, E-mail: dame@biochem.wisc.edu; Pharmaceutical Science Division, University of Wisconsin-Madison, Madison, WI 53705-2222

2012-01-01

The vitamin A metabolite all-trans retinoic acid (atRA) functions in nervous system development and regulates cell proliferation and differentiation. Neuroblastoma cells (SH-SY5Y and Neuro2a or N2A) exposed to atRA undergo growth inhibition and neuronal differentiation, both of which are preceded by an increase in Clmn mRNA. Treatment of N2A cells with atRA produces a reduction in phosphohistone 3 immunostaining and BrdU incorporation, both indicators of a reduction in cell proliferation. These effects are nearly eliminated in atRA-treated shClmn knockdown cells. Loss of Clmn in the mouse N2A cell line also results in a significant reduction of atRA-mediated neurite outgrowth, amore » response that can be rescued by reintroduction of the Clmn sequence. In contrast, ectopic overexpression of Clmn produces an increase in the cyclin dependent kinase inhibitor, p21{sup Cip1}, a decrease in cyclin D1 protein and an increase in hypophosphorylated Rb, showing that Clmn participates in G{sub 1}/S arrest. Clmn overexpression alone is sufficient to inhibit N2A cell proliferation, whereas both Clmn and atRA must be present to induce neurite outgrowth. This study shows that the atRA-responsive gene Clmn promotes exit from the cell cycle, a requisite event for neuronal differentiation. -- Highlights: Black-Right-Pointing-Pointer Calmin is a retinoic acid-responsive gene. Black-Right-Pointing-Pointer Calmin promotes cell cycle exit in N2A cells. Black-Right-Pointing-Pointer Calmin overexpression increases p21Cip1 and decreases cyclin D1. Black-Right-Pointing-Pointer Calmin is required for RA-induced growth inhibition and neurite outgrowth.« less

PKCeta enhances cell cycle progression, the expression of G1 cyclins and p21 in MCF-7 cells.

PubMed

Fima, E; Shtutman, M; Libros, P; Missel, A; Shahaf, G; Kahana, G; Livneh, E

2001-10-11

Protein kinase C encodes a family of enzymes implicated in cellular differentiation, growth control and tumor promotion. However, not much is known with respect to the molecular mechanisms that link protein kinase C to cell cycle control. Here we report that the expression of PKCeta in MCF-7 cells, under the control of a tetracycline-responsive inducible promoter, enhanced cell growth and affected the cell cycle at several points. The induced expression of another PKC isoform, PKCdelta, in MCF-7 cells had opposite effects and inhibited their growth. PKCeta expression activated cellular pathways in these cells that resulted in the increased expression of the G1 phase cyclins, cyclin D and cyclin E. Expression of the cyclin-dependent kinase inhibitor p21(WAF1) was also specifically elevated in PKCeta expressing cells, but its overall effects were not inhibitory. Although, the protein levels of the cyclin-dependent kinase inhibitor p27(KIP1) were not altered by the induced expression of PKCeta, the cyclin E associated Cdk2 kinase activity was in correlation with the p27(KIP1) bound to the cyclin E complex and not by p21(WAF1) binding. PKCeta expression enhanced the removal of p27(KIP1) from this complex, and its re-association with the cyclin D/Cdk4 complex. Reduced binding of p27(KIP1) to the cyclin D/Cdk4 complex at early time points of the cell cycle also enhanced the activity of this complex, while at later time points the decrease in bound p21(WAF1) correlated with its increased activity in PKCeta-expressing cells. Thus, PKCeta induces altered expression of several cell cycle functions, which may contribute to its ability to affect cell growth.

6-Gingerol Inhibits Growth of Colon Cancer Cell LoVo via Induction of G2/M Arrest

PubMed Central

Lin, Ching-Bin; Lin, Chun-Che; Tsay, Gregory J.

2012-01-01

6-Gingerol, a natural component of ginger, has been widely reported to possess antiinflammatory and antitumorigenic activities. Despite its potential efficacy against cancer, the anti-tumor mechanisms of 6-gingerol are complicated and remain sketchy. In the present study, we aimed to investigate the anti-tumor effects of 6-gingerol on colon cancer cells. Our results revealed that 6-gingerol treatment significantly reduced the cell viability of human colon cancer cell, LoVo, in a dose-dependent manner. Further flow cytometric analysis showed that 6-gingerol induced significant G2/M phase arrest and had slight influence on sub-G1 phase in LoVo cells. Therefore, levels of cyclins, cyclin-dependent kinases (CDKs), and their regulatory proteins involved in S-G2/M transition were investigated. Our findings revealed that levels of cyclin A, cyclin B1, and CDK1 were diminished; in contrast, levels of the negative cell cycle regulators p27Kip1 and p21Cip1 were increased in response to 6-gingerol treatment. In addition, 6-gingerol treatment elevated intracellular reactive oxygen species (ROS) and phosphorylation level of p53. These findings indicate that exposure of 6-gingerol may induce intracellular ROS and upregulate p53, p27Kip1, and p21Cip1 levels leading to consequent decrease of CDK1, cyclin A, and cyclin B1 as result of cell cycle arrest in LoVo cells. It would be suggested that 6-gingerol should be beneficial to treatment of colon cancer. PMID:22719783

6-Gingerol Inhibits Growth of Colon Cancer Cell LoVo via Induction of G2/M Arrest.

PubMed

Lin, Ching-Bin; Lin, Chun-Che; Tsay, Gregory J

2012-01-01

6-Gingerol, a natural component of ginger, has been widely reported to possess antiinflammatory and antitumorigenic activities. Despite its potential efficacy against cancer, the anti-tumor mechanisms of 6-gingerol are complicated and remain sketchy. In the present study, we aimed to investigate the anti-tumor effects of 6-gingerol on colon cancer cells. Our results revealed that 6-gingerol treatment significantly reduced the cell viability of human colon cancer cell, LoVo, in a dose-dependent manner. Further flow cytometric analysis showed that 6-gingerol induced significant G2/M phase arrest and had slight influence on sub-G1 phase in LoVo cells. Therefore, levels of cyclins, cyclin-dependent kinases (CDKs), and their regulatory proteins involved in S-G2/M transition were investigated. Our findings revealed that levels of cyclin A, cyclin B1, and CDK1 were diminished; in contrast, levels of the negative cell cycle regulators p27(Kip1) and p21(Cip1) were increased in response to 6-gingerol treatment. In addition, 6-gingerol treatment elevated intracellular reactive oxygen species (ROS) and phosphorylation level of p53. These findings indicate that exposure of 6-gingerol may induce intracellular ROS and upregulate p53, p27(Kip1), and p21(Cip1) levels leading to consequent decrease of CDK1, cyclin A, and cyclin B1 as result of cell cycle arrest in LoVo cells. It would be suggested that 6-gingerol should be beneficial to treatment of colon cancer.

Plasmin-clipped beta(2)-glycoprotein-I inhibits endothelial cell growth by down-regulating cyclin A, B and D1 and up-regulating p21 and p27.

PubMed

Beecken, Wolf-Dietrich C; Ringel, Eva Maria; Babica, Jan; Oppermann, Elsie; Jonas, Dietger; Blaheta, Roman A

2010-10-28

beta(2)-Glycoprotein-I (beta(2)gpI), an abundant plasma glycoprotein, functions as a regulator of thrombosis. Previously, we demonstrated that plasmin-clipped beta(2)gpI (cbeta(2)gpI) exerts an anti-angiogenic effect on human umbilical vein endothelial cells (HUVEC). The present study was focused on the molecular background responsible for this phenomenon. cbeta(2)gpI strongly reduced HUVEC growth and proliferation as evidenced by the MTT and BrdU assay and delayed cell cycle progression arresting HUVEC in the S-and G2/M-phase. Western blot analysis indicated that cbeta(2)gpI inhibited cyclin A, B and D1, and enhanced p21 and p27 expression. Activity of p38 was down-regulated independently from the cbeta(2)gpI incubation time. Phosphorylation of ERK1/2 was not changed early (30 and 60 min) but became enhanced later (90 min, 4h). JNK activity was reduced rapidly after cbeta(2)gpI treatment but compared to controls, increased thereafter. Annexin II blockade prevented growth inhibition and cell cycle delay evoked by cbeta(2)gpI. We assume that cbeta(2)gpI's effects on HUVEC growth is mediated via cyclin A, B and D1 suppression, up-regulation of p21 and p27 and coupled to modifications of the mitogen-activated protein (MAP) kinase signalling pathway. cbeta(2)gpI may represent a potential endogenous angiogenesis-targeted compound, opening the possibility of a novel tool to treat cancer. 2010 Elsevier Ireland Ltd. All rights reserved.

Knockdown of human deubiquitinase PSMD14 induces cell cycle arrest and senescence

DOE Office of Scientific and Technical Information (OSTI.GOV)

Byrne, Ann; McLaren, Rajashree P.; Mason, Paul

2010-01-15

The PSMD14 (POH1, also known as Rpn11/MPR1/S13/CepP1) protein within the 19S complex (19S cap; PA700) is responsible for substrate deubiquitination during proteasomal degradation. The role of PSMD14 in cell proliferation and senescence was explored using siRNA knockdown in carcinoma cell lines. Our results reveal that down-regulation of PSMD14 by siRNA transfection had a considerable impact on cell viability causing cell arrest in the G0-G1 phase, ultimately leading to senescence. The molecular events associated with decreased cell proliferation, cell cycle arrest and senescence include down-regulation of cyclin B1-CDK1-CDC25C, down-regulation of cyclin D1 and up-regulation of p21{sup /Cip} and p27{sup /Kip1}. Mostmore » notably, phosphorylation of the retinoblastoma protein was markedly reduced in PSMD14 knockdown cells. A comparative study with PSMB5, a subunit of the 20S proteasome, revealed that PSMB5 and PSMD14 have different effects on cell cycle, senescence and associated molecular events. These data support the view that the 19S and 20S subunits of the proteasome have distinct biological functions and imply that targeting 19S and 20S would have distinct molecular consequences on tumor cells.« less

Inhibition of MDA-MB-231 breast cancer cell proliferation and tumor growth by apigenin through induction of G2/M arrest and histone H3 acetylation-mediated p21WAF1/CIP1 expression.

PubMed

Tseng, Tsui-Hwa; Chien, Ming-Hsien; Lin, Wea-Lung; Wen, Yu-Ching; Chow, Jyh-Ming; Chen, Chi-Kuan; Kuo, Tsang-Chih; Lee, Wei-Jiunn

2017-02-01

Apigenin (4',5,7-trihydroxyflavone), a flavonoid commonly found in fruits and vegetables, has anticancer properties in various malignant cancer cells. However, the molecular basis of the anticancer effect remains to be elucidated. In this study, we investigated the cellular mechanisms underlying the induction of cell cycle arrest by apigenin. Our results showed that apigenin at the nonapoptotic induction concentration inhibited cell proliferation and induced cell cycle arrest at the G2/M phase in the MDA-MB-231 breast cancer cell line. Immunoblot analysis indicated that apigenin suppressed the expression of cyclin A, cyclin B, and cyclin-dependent kinase-1 (CDK1), which control the G2-to-M phase transition in the cell cycle. In addition, apigenin upregulated p21 WAF1/CIP1 and increased the interaction of p21 WAF1/CIP1 with proliferating cell nuclear antigen (PCNA), which inhibits cell cycle progression. Furthermore, apigenin significantly inhibited histone deacetylase (HDAC) activity and induced histone H3 acetylation. The subsequent chromatin immunoprecipitation (ChIP) assay indicated that apigenin increased acetylation of histone H3 in the p21 WAF1/CIP1 promoter region, resulting in the increase of p21 WAF1/CIP1 transcription. In a tumor xenograft model, apigenin effectively delayed tumor growth. In these apigenin-treated tumors, we also observed reductions in the levels of cyclin A and cyclin B and increases in the levels of p21 WAF1/CIP1 and acetylated histone H3. These findings demonstrate for the first time that apigenin can be used in breast cancer prevention and treatment through epigenetic regulation. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 434-444, 2017. © 2016 Wiley Periodicals, Inc.

Cooperation of p27Kip1 and p18INK4c in Progestin-Mediated Cell Cycle Arrest in T-47D Breast Cancer Cells

PubMed Central

Swarbrick, Alexander; Lee, Christine S. L.; Sutherland, Robert L.; Musgrove, Elizabeth A.

2000-01-01

The steroid hormone progesterone regulates proliferation and differentiation in the mammary gland and uterus by cell cycle phase-specific actions. The long-term effect of progestins on T-47D breast cancer cells is inhibition of cellular proliferation. This is accompanied by decreased G1 cyclin-dependent kinase (CDK) activities, redistribution of the CDK inhibitor p27Kip1 among these CDK complexes, and alterations in the elution profile of cyclin E-Cdk2 upon gel filtration chromatography, such that high-molecular-weight complexes predominate. This study aimed to determine the relative contribution of CDK inhibitors to these events. Following progestin treatment, the majority of cyclin E- and D-CDK complexes were bound to p27Kip1 and few were bound to p21Cip1. In vitro, recombinant His6-p27 could quantitatively reproduce the effects on cyclin E-Cdk2 kinase activity and the shift in molecular weight observed following progestin treatment. In contrast, cyclin D-Cdk4 was not inhibited by His6-p27 in vitro or p27Kip1 in vivo. However, an increase in the expression of the Cdk4/6 inhibitor p18INK4c and its extensive association with Cdk4 and Cdk6 were apparent following progestin treatment. Recombinant p18INK4c led to the reassortment of cyclin-CDK-CDK inhibitor complexes in vitro, with consequent decrease in cyclin E-Cdk2 activity. These results suggest a concerted model of progestin action whereby p27Kip1 and p18INK4c cooperate to inhibit cyclin E-Cdk2 and Cdk4. Since similar models have been developed for growth inhibition by transforming growth factor β and during adipogenesis, interaction between the Cip/Kip and INK4 families of inhibitors may be a common theme in physiological growth arrest and differentiation. PMID:10713180

Cyclin D2 induces proliferation of cardiac myocytes and represses hypertrophy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Busk, Peter K.; Hinrichsen, Rebecca; Bartkova, Jirina

2005-03-10

The myocytes of the adult mammalian heart are considered unable to divide. Instead, mitogens induce cardiomyocyte hypertrophy. We have investigated the effect of adenoviral overexpression of cyclin D2 on myocyte proliferation and morphology. Cardiomyocytes in culture were identified by established markers. Cyclin D2 induced DNA synthesis and proliferation of cardiomyocytes and impaired hypertrophy induced by angiotensin II and serum. At the molecular level, cyclin D2 activated CDK4/6 and lead to pRB phosphorylation and downregulation of the cell cycle inhibitors p21{sup Waf1/Cip1} and p27{sup Kip1}. Expression of the CDK4/6 inhibitor p16 inhibited proliferation and cyclin D2 overexpressing myocytes became hypertrophic undermore » such conditions. Inhibition of hypertrophy by cyclin D2 correlated with downregulation of p27{sup Kip1}. These data show that hypertrophy and proliferation are highly related processes and suggest that cardiomyocyte hypertrophy is due to low amounts of cell cycle activators unable to overcome the block imposed by cell cycle inhibitors. Cell cycle entry upon hypertrophy may be converted to cell division by increased expression of activators such as cyclin D2.« less

Interaction between ROCK II and nucleophosmin/B23 in the regulation of centrosome duplication.

PubMed

Ma, Zhiyong; Kanai, Masayuki; Kawamura, Kenji; Kaibuchi, Kozo; Ye, Keqiang; Fukasawa, Kenji

2006-12-01

Nucleophosmin (NPM)/B23 has been implicated in the regulation of centrosome duplication. NPM/B23 localizes between two centrioles in the unduplicated centrosome. Upon phosphorylation on Thr(199) by cyclin-dependent kinase 2 (CDK2)/cyclin E, the majority of centrosomal NPM/B23 dissociates from centrosomes, but some NPM/B23 phosphorylated on Thr(199) remains at centrosomes. It has been shown that Thr(199) phosphorylation of NPM/B23 is critical for the physical separation of the paired centrioles, an initial event of the centrosome duplication process. Here, we identified ROCK II kinase, an effector of Rho small GTPase, as a protein that localizes to centrosomes and physically interacts with NPM/B23. Expression of the constitutively active form of ROCK II promotes centrosome duplication, while down-regulation of ROCK II expression results in the suppression of centrosome duplication, especially delaying the initiation of centrosome duplication during the cell cycle. Moreover, ROCK II regulates centrosome duplication in its kinase and centrosome localization activity-dependent manner. We further found that ROCK II kinase activity is significantly enhanced by binding to NPM/B23 and that NPM/B23 acquires a higher binding affinity to ROCK II upon phosphorylation on Thr(199). Moreover, physical interaction between ROCK II and NPM/B23 in vivo occurs in association with CDK2/cyclin E activation and the emergence of Thr(199)-phosphorylated NPM/B23. All these findings point to ROCK II as the effector of the CDK2/cyclin E-NPM/B23 pathway in the regulation of centrosome duplication.

Cell cycle accumulation of the proliferating cell nuclear antigen PCN-1 transitions from continuous in the adult germline to intermittent in the early embryo of C. elegans.

PubMed

Kocsisova, Zuzana; Kornfeld, Kerry; Schedl, Tim

2018-05-30

The proliferating cell nuclear antigen (PCNA or PCN-1 in C. elegans), an essential processivity factor for DNA polymerase δ, has been widely used as a marker of S-phase. In C. elegans early embryos, PCN-1 accumulation is cyclic, localizing to the nucleus during S-phase and the cytoplasm during the rest of the cell cycle. The C. elegans larval and adult germline is an important model systems for studying cell cycle regulation, and it was observed that the cell cycle regulator cyclin E (CYE-1 in C. elegans) displays a non-cyclic, continuous accumulation pattern in this tissue. The accumulation pattern of PCN-1 has not been well defined in the larval and adult germline, and the objective of this study was to determine if the accumulation pattern is cyclic, as in other cells and organisms, or continuous, similar to cyclin E. To study the larval and adult germline accumulation of PCN-1 expressed from its native locus, we used CRISPR/Cas9 technology to engineer a novel allele of pcn-1 that encodes an epitope-tagged protein. S-phase nuclei were labeled using EdU nucleotide incorporation, and FLAG::PCN-1 was detected by antibody staining. All progenitor zone nuclei, including those that were not in S-phase (as they were negative for EdU staining) showed PCN-1 accumulation, indicating that PCN-1 accumulated during all cell cycle phases in the germline progenitor zone. The same result was observed with a GFP::PCN-1 fusion protein expressed from a transgene. pcn-1 loss-of-function mutations were analyzed, and pcn-1 was necessary for robust fertility and embryonic development. In the C. elegans early embryo as well as other organisms, PCN-1 accumulates in nuclei only during S-phase. By contrast, in the progenitor zone of the germline of C. elegans, PCN-1 accumulated in nuclei during all cell cycle stages. This pattern is similar to accumulation pattern of cyclin E. These observations support the model that mitotic cell cycle regulation in the germline stem and progenitor cells is distinct from somatic cells, as it does not heavily rely on cyclic accumulation of classic cell cycle proteins.

Synergistic cooperation of Sall4 and Cyclin D1 in transcriptional repression

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boehm, Johann; Kaiser, Frank J.; Borozdin, Wiktor

2007-05-11

Loss of function mutations in SALL4 cause Okihiro syndrome, an autosomal dominant disorder characterised by radial ray malformations associated with Duane anomaly. In zebrafish and mouse Sall4 interacts with TBX5 during limb and heart development and plays a crucial role for embryonic stem (ES) cell pluripotency. Here we report the nuclear interaction of murine Sall4 with Cyclin D1, one of the main regulators of G{sub 1} to S phase transition in cell cycle, verified by yeast two-hybrid assay, co-immunoprecipitation and intracellular co-localisation. Furthermore, using luciferase reporter gene assays we demonstrate that Sall4 operates as a transcriptional repressor located to heterochromatinmore » and that this activity is modulated by Cyclin D1.« less

Limb-bud and Heart Overexpression Inhibits the Proliferation and Migration of PC3M Cells.

PubMed

Liu, Qicai; Li, Ermao; Huang, Long; Cheng, Minsheng; Li, Li

2018-01-01

Background: The limb-bud and heart gene ( LBH ) was discovered in the early 21st century and is specifically expressed in the mouse embryonic limb and heart development. Increasing evidences have indicated that LBH not only plays an important role in embryo development, it is also closely correlated with the occurance and progression of many tumors. However, its function in prostate cancer (PCa) is still not well understood. Here, we explored the effects of LBH on the proliferation and migration of the PCa cell line PC3M. Methods: LBH expression in tissues and cell lines of PCa was detected by immunohistochemistry and Western blotting. Lentivirus was used to transduct the LBH gene into the PC3M cells. Stable LBH-overexpressing PC3M-LBH cells and PC3M-NC control cells were obtained via puromycin screening. Cell proliferation was examined using the 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay. Cell cycle distribution and apoptosis rate were investigated using flow cytometry. Cell migration was studied using the Transwell assay. Results: LBH expression level was down-regulated in 3 different PCa cell lines, especially in PC3M cells, compared with the normal prostate epithelial cells(RWPE-1). Cell lines of LBH-upregulated PC3M-LBH and PC3M-NC control were successfully constructed. Significantly increased LBH expression level and decreased cyclin D1 and cyclin E2 expression level was found in PC3M-LBH cells as compared to the PC3M-NC cells. The overexpression of LBH significantly inhibited PC3M cell proliferation in vitro and tumor growth in nude mice. LBH overexpression in PC3M cell, also induced cell cycle G0/G1 phase arrest and decreased the migration of PC3M cells. Conclusions : Our results reveal that LBH expression is down-regulated in the tissue and cell lines of PCa. LBH overexpression inhibits PC3M cell proliferation and tumor growth by inducing cell cycle arrest through down-regulating cyclin D1and cyclin E2 expression. LBH might be a therapeutic target and potential diagnostic marker in PCa.

Transforming Growth Factor β Inhibits Platelet Derived Growth Factor-Induced Vascular Smooth Muscle Cell Proliferation via Akt-Independent, Smad-Mediated Cyclin D1 Downregulation

PubMed Central

Martin-Garrido, Abel; Williams, Holly C.; Lee, Minyoung; Seidel-Rogol, Bonnie; Ci, Xinpei; Dong, Jin-Tang; Lassègue, Bernard; Martín, Alejandra San; Griendling, Kathy K.

2013-01-01

In adult tissue, vascular smooth muscle cells (VSMCs) exist in a differentiated phenotype, which is defined by the expression of contractile proteins and lack of proliferation. After vascular injury, VSMC adopt a synthetic phenotype associated with proliferation, migration and matrix secretion. The transition between phenotypes is a consequence of the extracellular environment, and in particular, is regulated by agonists such as the pro-differentiating cytokine transforming growth factor β (TGFβ) and the pro-proliferative cytokine platelet derived growth factor (PDGF). In this study, we investigated the interplay between TGFβ and PDGF with respect to their ability to regulate VSMC proliferation. Stimulation of human aortic VSMC with TGFβ completely blocked proliferation induced by all isoforms of PDGF, as measured by DNA synthesis and total cell number. Mechanistically, PDGF-induced Cyclin D1 mRNA and protein expression was inhibited by TGFβ. TGFβ had no effect on PDGF activation of its receptor and ERK1/2, but inhibited Akt activation. However, constitutively active Akt did not reverse the inhibitory effect of TGFβ on Cyclin D1 expression even though inhibition of the proteasome blocked the effect of TGFβ. siRNA against Smad4 completely reversed the inhibitory effect of TGFβ on PDGF-induced Cyclin D1 expression and restored proliferation in response to PDGF. Moreover, siRNA against KLF5 prevented Cyclin D1 upregulation by PDGF and overexpression of KLF5 partially reversed TGFβ-induced inhibition of Cyclin D1 expression. Taken together, our results demonstrate that KLF5 is required for PDGF-induced Cyclin D1 expression, which is inhibited by TGFβ via a Smad dependent mechanism, resulting in arrest of VSMCs in the G1 phase of the cell cycle. PMID:24236150

Transforming growth factor β inhibits platelet derived growth factor-induced vascular smooth muscle cell proliferation via Akt-independent, Smad-mediated cyclin D1 downregulation.

PubMed

Martin-Garrido, Abel; Williams, Holly C; Lee, Minyoung; Seidel-Rogol, Bonnie; Ci, Xinpei; Dong, Jin-Tang; Lassègue, Bernard; Martín, Alejandra San; Griendling, Kathy K

2013-01-01

In adult tissue, vascular smooth muscle cells (VSMCs) exist in a differentiated phenotype, which is defined by the expression of contractile proteins and lack of proliferation. After vascular injury, VSMC adopt a synthetic phenotype associated with proliferation, migration and matrix secretion. The transition between phenotypes is a consequence of the extracellular environment, and in particular, is regulated by agonists such as the pro-differentiating cytokine transforming growth factor β (TGFβ) and the pro-proliferative cytokine platelet derived growth factor (PDGF). In this study, we investigated the interplay between TGFβ and PDGF with respect to their ability to regulate VSMC proliferation. Stimulation of human aortic VSMC with TGFβ completely blocked proliferation induced by all isoforms of PDGF, as measured by DNA synthesis and total cell number. Mechanistically, PDGF-induced Cyclin D1 mRNA and protein expression was inhibited by TGFβ. TGFβ had no effect on PDGF activation of its receptor and ERK1/2, but inhibited Akt activation. However, constitutively active Akt did not reverse the inhibitory effect of TGFβ on Cyclin D1 expression even though inhibition of the proteasome blocked the effect of TGFβ. siRNA against Smad4 completely reversed the inhibitory effect of TGFβ on PDGF-induced Cyclin D1 expression and restored proliferation in response to PDGF. Moreover, siRNA against KLF5 prevented Cyclin D1 upregulation by PDGF and overexpression of KLF5 partially reversed TGFβ-induced inhibition of Cyclin D1 expression. Taken together, our results demonstrate that KLF5 is required for PDGF-induced Cyclin D1 expression, which is inhibited by TGFβ via a Smad dependent mechanism, resulting in arrest of VSMCs in the G1 phase of the cell cycle.

Cyclin B in mouse oocytes and embryos: importance for human reproduction and aneuploidy.

PubMed

Polański, Zbigniew; Homer, Hayden; Kubiak, Jacek Z

2012-01-01

Oocyte maturation and early embryo development require precise coordination between cell cycle progression and the developmental programme. Cyclin B plays a major role in this process: its accumulation and degradation is critical for driving the cell cycle through activation and inactivation of the major cell cycle kinase, CDK1. CDK1 activation is required for M-phase entry whereas its inactivation leads to exit from M-phase. The tempo of oocyte meiotic and embryonic mitotic divisions is set by the rate of cyclin B accumulation and the timing of its destruction. By controlling when cyclin B destruction is triggered and by co-ordinating this with the completion of chromosome alignment, the spindle assembly checkpoint (SAC) is a critical quality control system important for averting aneuploidy and for building in the flexibility required to better integrate cell cycle progression with development. In this review we focus on cyclin B metabolism in mouse oocytes and embryos and illustrate how the cell cycle-powered clock (in fact cyclin B-powered clock) controls oocyte maturation and early embryo development, thereby providing important insight into human reproduction and potential causes of Down syndrome.

The Potential Role of As-sumo-1 in the Embryonic Diapause Process and Early Embryo Development of Artemia sinica

PubMed Central

Chu, Bing; Yao, Feng; Cheng, Cheng; Wu, Yang; Mei, Yanli; Li, Xuejie; Liu, Yan; Wang, Peisheng; Hou, Lin; Zou, Xiangyang

2014-01-01

During embryonic development of Artemia sinica, environmental stresses induce the embryo diapause phenomenon, required to resist apoptosis and regulate cell cycle activity. The small ubiquitin-related modifier-1 (SUMO), a reversible post-translational protein modifier, plays an important role in embryo development. SUMO regulates multiple cellular processes, including development and other biological processes. The molecular mechanism of diapause, diapause termination and the role of As-sumo-1 in this processes and in early embryo development of Artemia sinica still remains unknown. In this study, the complete cDNA sequences of the sumo-1 homolog, sumo ligase homolog, caspase-1 homolog and cyclin B homolog from Artemia sinica were cloned. The mRNA expression patterns of As-sumo-1, sumo ligase, caspase-1, cyclin B and the location of As-sumo-1 were investigated. SUMO-1, p53, Mdm2, Caspase-1, Cyclin B and Cyclin E proteins were analyzed during different developmental stages of the embryo of A. sinica. Small interfering RNA (siRNA) was used to verify the function of sumo-1 in A. sinica. The full-length cDNA of As-sumo-1 was 476 bp, encoding a 92 amino acid protein. The As-caspases-1 cDNA was 966 bp, encoding a 245 amino-acid protein. The As-sumo ligase cDNA was 1556 bp encoding, a 343 amino acid protein, and the cyclin B cDNA was 739 bp, encoding a 133 amino acid protein. The expressions of As-sumo-1, As-caspase-1 and As-cyclin B were highest at the 10 h stage of embryonic development, and As-sumo ligase showed its highest expression at 0 h. The expression of As-SUMO-1 showed no tissue or organ specificity. Western blotting showed high expression of As-SUMO-1, p53, Mdm2, Caspase-1, Cyclin B and Cyclin E at the 10 h stage. The siRNA caused abnormal development of the embryo, with increased malformation and mortality. As-SUMO-1 is a crucial regulation and modification protein resumption of embryonic diapause and early embryo development of A. sinica. PMID:24404204

Cytotoxicity of diacetoxyscirpenol is associated with apoptosis by activation of caspase-8 and interruption of cell cycle progression by down-regulation of cdk4 and cyclin B1 in human Jurkat T cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jun, Do Youn; Institute of Genetic Engineering, Kyungpook National University, Daegu; Kim, Jun Seok

2007-07-15

To understand the mechanism underlying T-cell toxicity of diacetoxyscirpenol (DAS) from Fusarium sambucinum, its apoptogenic as well as growth retardation activity was investigated in human Jurkat T cells. Exposure to DAS (0.01-0.15 {mu}M) caused apoptotic DNA fragmentation along with caspase-8 activation, Bid cleavage, mitochondrial cytochrome c release, activation of caspase-9 and caspase-3, and PARP degradation, without any alteration in the levels of Fas or FasL. Under these conditions, necrosis was not accompanied. The cytotoxicity of DAS was not blocked by the anti-Fas neutralizing antibody ZB-4. Although the DAS-induced apoptotic events were completely prevented by overexpression of Bcl-xL, the cells overexpressingmore » Bcl-xL were unable to divide in the presence of DAS, resulting from the failure of cell cycle progression possibly due to down-regulation in the protein levels of cdk4 and cyclin B1. The DAS-mediated apoptosis and activation of caspase-8, -9, and -3 were abrogated by either pan-caspase inhibitor (z-VAD-fmk) or caspase-8 inhibitor (z-IETD-fmk). While the DAS-mediated apoptosis and activation of caspase-9 and caspase-3 were slightly suppressed by the mitochondrial permeability transition pore inhibitor (CsA), both caspase-8 activation and Bid cleavage were not affected by CsA. The activated normal peripheral T cells possessed a similar susceptibility to the cytotoxicity of DAS. These results demonstrate that the T-cell toxicity of DAS is attributable to not only apoptosis initiated by caspase-8 activation and subsequent mitochondrion-dependent or -independent activation of caspase cascades, which can be regulated by Bcl-xL, but also interruption of cell cycle progression caused by down-regulation of cdk4 and cyclin B1 proteins.« less

Phenethyl isothiocyanate alters the gene expression and the levels of protein associated with cell cycle regulation in human glioblastoma GBM 8401 cells.

PubMed

Chou, Yu-Cheng; Chang, Meng-Ya; Wang, Mei-Jen; Liu, Hsin-Chung; Chang, Shu-Jen; Harnod, Tomor; Hung, Chih-Huang; Lee, Hsu-Tung; Shen, Chiung-Chyi; Chung, Jing-Gung

2017-01-01

Glioblastoma is the most common and aggressive primary brain malignancy. Phenethyl isothiocyanate (PEITC), a member of the isothiocyanate family, can induce apoptosis in many human cancer cells. Our previous study disclosed that PEITC induces apoptosis through the extrinsic pathway, dysfunction of mitochondria, reactive oxygen species (ROS)-induced endoplasmic reticulum (ER) stress, and intrinsic (mitochondrial) pathway in human brain glioblastoma multiforme (GBM) 8401 cells. To the best of our knowledge, we first investigated the effects of PEITC on the genetic levels of GBM 8401 cells in vitro. PEITC may induce G0/G1 cell-cycle arrest through affecting the proteins such as cdk2, cyclin E, and p21 in GBM 8401 cells. Many genes associated with cell-cycle regulation of GBM 8401 cells were changed after PEITC treatment: 48 genes were upregulated and 118 were downregulated. The cell-division cycle protein 20 (CDC20), Budding uninhibited by benzimidazole 1 homolog beta (BUB1B), and cyclin B1 were downregulated, and clusterin was upregulated in GBM 8401 cells treated with PEITC. These changes of gene expression can provide the effects of PEITC on the genetic levels and potential biomarkers for glioblastoma. © 2015 Wiley Periodicals, Inc. Environ Toxicol 32: 176-187, 2017. © 2015 Wiley Periodicals, Inc.

CDK1 Prevents Unscheduled PLK4-STIL Complex Assembly in Centriole Biogenesis.

PubMed

Zitouni, Sihem; Francia, Maria E; Leal, Filipe; Montenegro Gouveia, Susana; Nabais, Catarina; Duarte, Paulo; Gilberto, Samuel; Brito, Daniela; Moyer, Tyler; Kandels-Lewis, Steffi; Ohta, Midori; Kitagawa, Daiju; Holland, Andrew J; Karsenti, Eric; Lorca, Thierry; Lince-Faria, Mariana; Bettencourt-Dias, Mónica

2016-05-09

Centrioles are essential for the assembly of both centrosomes and cilia. Centriole biogenesis occurs once and only once per cell cycle and is temporally coordinated with cell-cycle progression, ensuring the formation of the right number of centrioles at the right time. The formation of new daughter centrioles is guided by a pre-existing, mother centriole. The proximity between mother and daughter centrioles was proposed to restrict new centriole formation until they separate beyond a critical distance. Paradoxically, mother and daughter centrioles overcome this distance in early mitosis, at a time when triggers for centriole biogenesis Polo-like kinase 4 (PLK4) and its substrate STIL are abundant. Here we show that in mitosis, the mitotic kinase CDK1-CyclinB binds STIL and prevents formation of the PLK4-STIL complex and STIL phosphorylation by PLK4, thus inhibiting untimely onset of centriole biogenesis. After CDK1-CyclinB inactivation upon mitotic exit, PLK4 can bind and phosphorylate STIL in G1, allowing pro-centriole assembly in the subsequent S phase. Our work shows that complementary mechanisms, such as mother-daughter centriole proximity and CDK1-CyclinB interaction with centriolar components, ensure that centriole biogenesis occurs once and only once per cell cycle, raising parallels to the cell-cycle regulation of DNA replication and centromere formation. Copyright © 2016 Elsevier Ltd. All rights reserved.

Human transcription factor hTAF(II)150 (CIF150) is involved in transcriptional regulation of cell cycle progression.

PubMed

Martin, J; Halenbeck, R; Kaufmann, J

1999-08-01

Here we present evidence that CIF150 (hTAF(II)150), the human homolog of Drosophila TAF(II)150, plays an important and selective role in establishing gene expression patterns necessary for progression through the cell cycle. Gel filtration experiments demonstrate that CIF150 (hTAF(II)150) seems to be less tightly associated with human transcription factor IID than hTAF(II)130 is associated with hTAF(II)250. The transient functional knockout of CIF150 (hTAF(II)150) protein led to cell cycle arrest at the G(2)/M transition in mammalian cell lines. PCR display analysis with the RNA derived from CIF150-depleted cells indicated that CIF150 (hTAF(II)150) is required for the transcription of only a subset of RNA polymerase II genes. CIF150 (hTAF(II)150) directly stimulated cyclin B1 and cyclin A transcription in cotransfection assays and in vitro assays, suggesting that the expression of these genes is dependent on CIF150 (hTAF(II)150) function. We defined a CIF150 (hTAF(II)150) consensus binding site and demonstrated that a CIF150-responsive cis element is present in the cyclin B1 core promoter. These results suggest that one function of CIF150 (hTAF(II)150) is to select specific RNA polymerase II core promoter elements involved in cell cycle progression.

Human Transcription Factor hTAFII150 (CIF150) Is Involved in Transcriptional Regulation of Cell Cycle Progression

PubMed Central

Martin, Jay; Halenbeck, Robert; Kaufmann, Jörg

1999-01-01

Here we present evidence that CIF150 (hTAFII150), the human homolog of Drosophila TAFII150, plays an important and selective role in establishing gene expression patterns necessary for progression through the cell cycle. Gel filtration experiments demonstrate that CIF150 (hTAFII150) seems to be less tightly associated with human transcription factor IID than hTAFII130 is associated with hTAFII250. The transient functional knockout of CIF150 (hTAFII150) protein led to cell cycle arrest at the G2/M transition in mammalian cell lines. PCR display analysis with the RNA derived from CIF150-depleted cells indicated that CIF150 (hTAFII150) is required for the transcription of only a subset of RNA polymerase II genes. CIF150 (hTAFII150) directly stimulated cyclin B1 and cyclin A transcription in cotransfection assays and in vitro assays, suggesting that the expression of these genes is dependent on CIF150 (hTAFII150) function. We defined a CIF150 (hTAFII150) consensus binding site and demonstrated that a CIF150-responsive cis element is present in the cyclin B1 core promoter. These results suggest that one function of CIF150 (hTAFII150) is to select specific RNA polymerase II core promoter elements involved in cell cycle progression. PMID:10409744

Role of insulin-like growth factor-1 (IGF-1) in regulating cell cycle progression

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ma, Qi-lin; Yang, Tian-lun; Yin, Ji-ye

2009-11-06

Aims: Insulin-like growth factor-1 (IGF-1) is a polypeptide protein hormone, similar in molecular structure to insulin, which plays an important role in cell migration, cell cycle progression, cell survival and proliferation. In this study, we investigated the possible mechanisms of IGF-1 mediated cell cycle redistribution and apoptosis of vascular endothelial cells. Method: Human umbilical vein endothelial cells (HUVECs) were pretreated with 0.1, 0.5, or 2.5 {mu}g/mL of IGF-1 for 30 min before the addition of Ang II. Cell cycle redistribution and apoptosis were examined by flow cytometry. Expression of Ang II type 1 (AT{sub 1}) mRNA and cyclin E proteinmore » were determined by RT-PCR and Western blot, respectively. Results: Ang II (1 {mu}mol/L) induced HUVECs arrested at G{sub 0}/G{sub 1}, enhanced the expression level of AT{sub 1} mRNA in a time-dependent manner, reduced the enzymatic activity of nitric oxide synthase (NOS) and nitric oxide (NO) content as well as the expression level of cyclin E protein. However, IGF-1 enhanced NOS activity, NO content, and the expression level of cyclin E protein, and reduced the expression level of AT{sub 1} mRNA. L-NAME significantly counteracted these effects of IGF-1. Conclusions: Our data suggests that IGF-1 can reverse vascular endothelial cells arrested at G{sub 0}/G{sub 1} and apoptosis induced by Ang II, which might be mediated via a NOS-NO signaling pathway and is likely associated with the expression levels of AT1 mRNA and cyclin E proteins.« less

Cyclin A1 shows age-related expression in benign tonsils, HPV16-dependent overexpression in HNSCC and predicts lower recurrence rate in HNSCC independently of HPV16

PubMed Central

2012-01-01

Background Promoter methylation of the tumor suppressor gene Cyclin A1 could be associated with Human Papillomavirus 16 (HPV16) induced Head and Neck Squamous Cell Carcinoma (HNSCC) and Cervical Carcinoma. There is disagreement about the impact of this epigenetic event on protein expression of Cyclin A1 in malignant and non-malignant tissue and there hardly exists any information about possible relationships between Cyclin A1 expression and clinicopathological characteristics in HNSCC. Methods We analyzed protein expression of Cyclin A1 in 81 HNSCC and 74 benign tonsils by immunohistochemistry and correlated it to Cyclin A1 methylation status, presence of HPV16 infection and other clinicopathological characteristics. Results Overexpression of Cyclin A1 was more present in HNSCC than in tonsils (p < 0.001). In both entities, HNSCC and benign tonsils, expression of Cyclin A1 significantly correlated with the expression of Cyclin-dependent kinase-inhibitor p16 (p = 0.000672 and 0.00495). In tonsils, expression of Cyclin A1 was inversely proportional to age (p = 0.00000396), and further correlated with expression of tumor suppressor gene p53 (p = 0.000228). In HNSCC Cyclin A1 expression was associated with the presence of HPV16 DNA (p = 0.0014) and a lower recurrence rate in univariate and multivariate analysis (p = 0.002 and 0.013). Neither in HNSCC nor in tonsils Cyclin A1 expression correlated with promoter methylation. Conclusions Cyclin A1 is an important cell cycle regulator with age-related increased expression in tonsils of children. HPV16 induces overexpression of Cyclin A1 in HNSCC despite promoter methylation. Overexpression of Cyclin A1 predicts a lower recurrence rate in HNSCC independently of HPV16. PMID:22712549

Akt-mediated phosphorylation of CDK2 regulates its dual role in cell cycle progression and apoptosis.

PubMed

Maddika, Subbareddy; Ande, Sudharsana Rao; Wiechec, Emilia; Hansen, Lise Lotte; Wesselborg, Sebastian; Los, Marek

2008-04-01

Here, we show that CDK2, an S-phase cyclin-dependent kinase, is a novel target for Akt during cell cycle progression and apoptosis. Akt phosphorylates CDK2 at threonine 39 residue both in vitro and in vivo. Although CDK2 threonine 39 phosphorylation mediated by Akt enhances cyclin-A binding, it is dispensable for its basal binding and the kinase activity. In addition, for the first time, we report a transient nucleo-cytoplasmic shuttling of Akt during specific stages of the cell cycle, in particular during the late S and G2 phases. The Akt that is re-localized to the nucleus phosphorylates CDK2 and causes the temporary cytoplasmic localization of the CDK2-cyclin-A complex. The CDK2 cytoplasmic redistribution is required for cell progression from S to G2-M phase, because the CDK2 T39A mutant, which lacks the phosphorylation site and is defective in cytoplasmic localization, severely affects cell cycle progression at the transition from S to G2-M. Interestingly, we also show that the Akt/CDK2 pathway is constitutively activated by some anticancer drugs, such as methotrexate and docetaxel, and under these conditions it promotes, rather than represses, cell death. Thus, the constitutive activation of the Akt/CDK2 pathway and changed subcellular localization promotes apoptosis. By contrast, the transient, physiological Akt/CDK2 activation is necessary for cell cycle progression.

PP2ARts1 is a master regulator of pathways that control cell size

PubMed Central

Zapata, Jessica; Dephoure, Noah; MacDonough, Tracy; Yu, Yaxin; Parnell, Emily J.; Mooring, Meghan; Gygi, Steven P.; Stillman, David J.

2014-01-01

Cell size checkpoints ensure that passage through G1 and mitosis occurs only when sufficient growth has occurred. The mechanisms by which these checkpoints work are largely unknown. PP2A associated with the Rts1 regulatory subunit (PP2ARts1) is required for cell size control in budding yeast, but the relevant targets are unknown. In this paper, we used quantitative proteome-wide mass spectrometry to identify proteins controlled by PP2ARts1. This revealed that PP2ARts1 controls the two key checkpoint pathways thought to regulate the cell cycle in response to cell growth. To investigate the role of PP2ARts1 in these pathways, we focused on the Ace2 transcription factor, which is thought to delay cell cycle entry by repressing transcription of the G1 cyclin CLN3. Diverse experiments suggest that PP2ARts1 promotes cell cycle entry by inhibiting the repressor functions of Ace2. We hypothesize that control of Ace2 by PP2ARts1 plays a role in mechanisms that link G1 cyclin accumulation to cell growth. PMID:24493588

Characterisation of cell cycle arrest and terminal differentiation in a maximally proliferative human epithelial tissue: Lessons from the human hair follicle matrix.

PubMed

Purba, Talveen S; Brunken, Lars; Peake, Michael; Shahmalak, Asim; Chaves, Asuncion; Poblet, Enrique; Ceballos, Laura; Gandarillas, Alberto; Paus, Ralf

2017-09-01

Human hair follicle (HF) growth and hair shaft formation require terminal differentiation-associated cell cycle arrest of highly proliferative matrix keratinocytes. However, the regulation of this complex event remains unknown. CIP/KIP family member proteins (p21 CIP1 , p27 KIP1 and p57 KIP2 ) regulate cell cycle progression/arrest, endoreplication, differentiation and apoptosis. Since they have not yet been adequately characterized in the human HF, we asked whether and where CIP/KIP proteins localise in the human hair matrix and pre-cortex in relation to cell cycle activity and HF-specific epithelial cell differentiation that is marked by keratin 85 (K85) protein expression. K85 expression coincided with loss or reduction in cell cycle activity markers, including in situ DNA synthesis (EdU incorporation), Ki-67, phospho-histone H3 and cyclins A and B1, affirming a post-mitotic state of pre-cortical HF keratinocytes. Expression of CIP/KIP proteins was found abundantly within the proliferative hair matrix, concomitant with a role in cell cycle checkpoint control. p21 CIP1 , p27 KIP1 and cyclin E persisted within post-mitotic keratinocytes of the pre-cortex, whereas p57 KIP2 protein decreased but became nuclear. These data imply a supportive role for CIP/KIP proteins in maintaining proliferative arrest, differentiation and anti-apoptotic pathways, promoting continuous hair bulb growth and hair shaft formation in anagen VI. Moreover, post-mitotic hair matrix regions contained cells with enlarged nuclei, and DNA in situ hybridisation showed cells that were >2N in the pre-cortex. This suggests that CIP/KIP proteins might counterbalance cyclin E to control further rounds of DNA replication in a cell population that has a propensity to become tetraploid. These data shed new light on the in situ-biography of human hair matrix keratinocytes on their path of active cell cycling, arrest and terminal differentiation, and showcase the human HF as an excellent, clinically relevant model system for cell cycle physiology research of human epithelial cells within their natural tissue habitat. Crown Copyright © 2017. Published by Elsevier GmbH. All rights reserved.

Coordinating cell proliferation and differentiation: Antagonism between cell cycle regulators and cell type-specific gene expression

PubMed Central

Ruijtenberg, Suzan; van den Heuvel, Sander

2016-01-01

ABSTRACT Cell proliferation and differentiation show a remarkable inverse relationship. Precursor cells continue division before acquiring a fully differentiated state, while terminal differentiation usually coincides with proliferation arrest and permanent exit from the division cycle. Mechanistic insight in the temporal coordination between cell cycle exit and differentiation has come from studies of cells in culture and genetic animal models. As initially described for skeletal muscle differentiation, temporal coordination involves mutual antagonism between cyclin-dependent kinases that promote cell cycle entry and transcription factors that induce tissue-specific gene expression. Recent insights highlight the contribution of chromatin-regulating complexes that act in conjunction with the transcription factors and determine their activity. In particular SWI/SNF chromatin remodelers contribute to dual regulation of cell cycle and tissue-specific gene expression during terminal differentiation. We review the concerted regulation of the cell cycle and cell type-specific transcription, and discuss common mutations in human cancer that emphasize the clinical importance of proliferation versus differentiation control. PMID:26825227

An attempt to evaluate the effect of vitamin K3 using as an enhancer of anticancer agents.

PubMed

Matzno, Sumio; Yamaguchi, Yuka; Akiyoshi, Takeshi; Nakabayashi, Toshikatsu; Matsuyama, Kenji

2008-06-01

The possibility of vitamin K3 (VK3) as an anticancer agent was assessed. VK3 dose-dependently diminished the cell viability (measured as esterase activity) with IC50 of 13.7 microM and Hill coefficient of 3.1 in Hep G2 cells. It also decreased the population of S phase and arrested cell cycle in the G2/M phase in a dose-dependent manner. G2/M arrest was regulated by the increment of cyclin A/cdk1 and cyclin A/cdk2 complex, and contrasting cyclin B/cdk1 complex decrease. Finally, combined application demonstrated that VK3 significantly enhanced the cytotoxicity of etoposide, a G2 phase-dependent anticancer agent, whereas it reduced the cytotoxic activity of irinotecan, a S phase-dependent agent. These findings suggest that VK3 induces G2/M arrest by inhibition of cyclin B/cdk1 complex formation, and is thus useful as an enhancer of G2 phase-dependent drugs in hepatic cancer chemotherapy.

Loss of DLK expression in WI-38 human diploid fibroblasts induces a senescent-like proliferation arrest

DOE Office of Scientific and Technical Information (OSTI.GOV)

Daviau, Alex; Couture, Jean-Philippe; Blouin, Richard, E-mail: Richard.Blouin@USherbrooke.ca

Highlights: {yields} Role of DLK in cell proliferation. {yields} Modulation of DLK expression during cell cycle progression. {yields} DLK knockdown induces proliferation arrest and senescence. {yields} DLK-depleted cells display loss of cyclin D1 and up-regulation of p21. {yields} DLK participates in cell proliferation by modulating cell cycle regulator expression. -- Abstract: DLK, a serine/threonine kinase that functions as an upstream activator of the mitogen-activated protein kinase (MAPK) pathways, has been shown to play a role in development, cell differentiation, apoptosis and neuronal response to injury. Interestingly, recent studies have shown that DLK may also be required for cell proliferation, althoughmore » little is known about its specific functions. To start addressing this issue, we studied how DLK expression is modulated during cell cycle progression and what effect DLK depletion has on cell proliferation in WI-38 fibroblasts. Our results indicate that DLK protein levels are low in serum-starved cells, but that serum addition markedly stimulated it. Moreover, RNA interference experiments demonstrate that DLK is required for ERK activity, expression of the cell cycle regulator cyclin D1 and proliferation of WI-38 cells. DLK-depleted cells also show a senescent phenotype as revealed by senescence-associated galactosidase activity and up-regulation of the senescence pathway proteins p53 and p21. Consistent with a role for p53 in this response, inhibition of p53 expression by RNA interference significantly alleviated senescence induced by DLK knockdown. Together, these findings indicate that DLK participates in cell proliferation and/or survival, at least in part, by modulating the expression of cell cycle regulatory proteins.« less

ATP depletion during mitotic arrest induces mitotic slippage and APC/CCdh1-dependent cyclin B1 degradation.

PubMed

Park, Yun Yeon; Ahn, Ju-Hyun; Cho, Min-Guk; Lee, Jae-Ho

2018-04-27

ATP depletion inhibits cell cycle progression, especially during the G1 phase and the G2 to M transition. However, the effect of ATP depletion on mitotic progression remains unclear. We observed that the reduction of ATP after prometaphase by simultaneous treatment with 2-deoxyglucose and NaN 3 did not arrest mitotic progression. Interestingly, ATP depletion during nocodazole-induced prometaphase arrest resulted in mitotic slippage, as indicated by a reduction in mitotic cells, APC/C-dependent degradation of cyclin B1, increased cell attachment, and increased nuclear membrane reassembly. Additionally, cells successfully progressed through the cell cycle after mitotic slippage, as indicated by EdU incorporation and time-lapse imaging. Although degradation of cyclin B during normal mitotic progression is primarily regulated by APC/C Cdc20 , we observed an unexpected decrease in Cdc20 prior to degradation of cyclin B during mitotic slippage. This decrease in Cdc20 was followed by a change in the binding partner preference of APC/C from Cdc20 to Cdh1; consequently, APC/C Cdh1 , but not APC/C Cdc20 , facilitated cyclin B degradation following ATP depletion. Pulse-chase analysis revealed that ATP depletion significantly abrogated global translation, including the translation of Cdc20 and Cdh1. Additionally, the half-life of Cdh1 was much longer than that of Cdc20. These data suggest that ATP depletion during mitotic arrest induces mitotic slippage facilitated by APC/C Cdh1 -dependent cyclin B degradation, which follows a decrease in Cdc20 resulting from reduced global translation and the differences in the half-lives of the Cdc20 and Cdh1 proteins.

Functional synergy between DP-1 and E2F-1 in the cell cycle-regulating transcription factor DRTF1/E2F.

PubMed Central

Bandara, L R; Buck, V M; Zamanian, M; Johnston, L H; La Thangue, N B

1993-01-01

It is widely believed that the cellular transcription factor DRTF1/E2F integrates cell cycle events with the transcription apparatus because during cell cycle progression in mammalian cells it interacts with molecules that are important regulators of cellular proliferation, such as the retinoblastoma tumour suppressor gene product (pRb), p107, cyclins and cyclin-dependent kinases. Thus, pRb, which negatively regulates early cell cycle progression and is frequently mutated in tumour cells, and the Rb-related protein p107, bind to and repress the transcriptional activity of DRTF1/E2F. Viral oncoproteins, such as adenovirus E1a and SV40 large T antigen, overcome such repression by sequestering pRb and p107 and in so doing are likely to activate genes regulated by DRTF1/E2F, such as cdc2, c-myc and DHFR. Two sequence-specific DNA binding proteins, E2F-1 and DP-1, which bind to the E2F site, contain a small region of similarity. The functional relationship between them has, however, been unclear. We report here that DP-1 and E2F-1 exist in a DNA binding complex in vivo and that they bind efficiently and preferentially as a heterodimer to the E2F site. Moreover, studies in yeast and Drosophila cells indicate that DP-1 and E2F-1 interact synergistically in E2F site-dependent transcriptional activation. Images PMID:8223441

Chromosome Association of Minichromosome Maintenance Proteins in Drosophila Mitotic Cycles

PubMed Central

Su, Tin Tin; O'Farrell, Patrick H.

1997-01-01

Minichromosome maintenance (MCM) proteins are essential DNA replication factors conserved among eukaryotes. MCMs cycle between chromatin bound and dissociated states during each cell cycle. Their absence on chromatin is thought to contribute to the inability of a G2 nucleus to replicate DNA. Passage through mitosis restores the ability of MCMs to bind chromatin and the ability to replicate DNA. In Drosophila early embryonic cell cycles, which lack a G1 phase, MCMs reassociate with condensed chromosomes toward the end of mitosis. To explore the coupling between mitosis and MCM–chromatin interaction, we tested whether this reassociation requires mitotic degradation of cyclins. Arrest of mitosis by induced expression of nondegradable forms of cyclins A and/or B showed that reassociation of MCMs to chromatin requires cyclin A destruction but not cyclin B destruction. In contrast to the earlier mitoses, mitosis 16 (M16) is followed by G1, and MCMs do not reassociate with chromatin at the end of M16. dacapo mutant embryos lack an inhibitor of cyclin E, do not enter G1 quiescence after M16, and show mitotic reassociation of MCM proteins. We propose that cyclin E, inhibited by Dacapo in M16, promotes chromosome binding of MCMs. We suggest that cyclins have both positive and negative roles in controlling MCM–chromatin association. PMID:9314525

Gene expression of cyclin-dependent kinase inhibitors and effect of heparin on their expression in mice with hypoxia-induced pulmonary hypertension

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yu Lunyin; Quinn, Deborah A.; Garg, Hari G.

The balance between cell proliferation and cell quiescence is regulated delicately by a variety of mediators, in which cyclin-dependent kinases (CDK) and CDK inhibitors (CDKI) play a very important role. Heparin which inhibits pulmonary artery smooth muscle cell (PASMC) proliferation increases the levels of two CDKIs, p21 and p27, although only p27 is important in inhibition of PASMC growth in vitro and in vivo. In the present study we investigated the expression profile of all the cell cycle regulating genes, including all seven CDKIs (p21, p27, p57, p15, p16, p18, and p19), in the lungs of mice with hypoxia-induced pulmonarymore » hypertension. A cell cycle pathway specific gene microarray was used to profile the 96 genes involved in cell cycle regulation. We also observed the effect of heparin on gene expression. We found that (a) hypoxic exposure for two weeks significantly inhibited p27 expression and stimulated p18 activity, showing a 98% decrease in p27 and 81% increase in p18; (b) other CDKIs, p21, p57, p15, p16, and p19 were not affected significantly in response to hypoxia; (c) heparin treatment restored p27 expression, but did not influence p18; (d) ERK1/2 and p38 were mediators in heparin upregulation of p27. This study provides an expression profile of cell cycle regulating genes under hypoxia in mice with hypoxia-induced pulmonary hypertension and strengthens the previous finding that p27 is the only CDKI involved in heparin regulation of PASMC proliferation and hypoxia-induced pulmonary hypertension.« less

Cell cycle proteins as promising targets in cancer therapy.

PubMed

Otto, Tobias; Sicinski, Piotr

2017-01-27

Cancer is characterized by uncontrolled tumour cell proliferation resulting from aberrant activity of various cell cycle proteins. Therefore, cell cycle regulators are considered attractive targets in cancer therapy. Intriguingly, animal models demonstrate that some of these proteins are not essential for proliferation of non-transformed cells and development of most tissues. By contrast, many cancers are uniquely dependent on these proteins and hence are selectively sensitive to their inhibition. After decades of research on the physiological functions of cell cycle proteins and their relevance for cancer, this knowledge recently translated into the first approved cancer therapeutic targeting of a direct regulator of the cell cycle. In this Review, we focus on proteins that directly regulate cell cycle progression (such as cyclin-dependent kinases (CDKs)), as well as checkpoint kinases, Aurora kinases and Polo-like kinases (PLKs). We discuss the role of cell cycle proteins in cancer, the rationale for targeting them in cancer treatment and results of clinical trials, as well as the future therapeutic potential of various cell cycle inhibitors.

Chikusetsusaponin IVa methyl ester induces cell cycle arrest by the inhibition of nuclear translocation of β-catenin in HCT116 cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Kyung-Mi; Yun, Ji Ho; Lee, Dong Hwa

2015-04-17

We demonstrate that chikusetsusaponin IVa methyl ester (CME), a triterpenoid saponin from the root of Achyranthes japonica, has an anticancer activity. We investigate its molecular mechanism in depth in HCT116 cells. CME reduces the amount of β-catenin in nucleus and inhibits the binding of β-catenin to specific DNA sequences (TCF binding elements, TBE) in target gene promoters. Thus, CME appears to decrease the expression of cell cycle regulatory proteins such as Cyclin D1, as a representative target for β-catenin, as well as CDK2 and CDK4. As a result of the decrease of the cell cycle regulatory proteins, CME inhibits cellmore » proliferation by arresting the cell cycle at the G0/G1 phase. Therefore, we suggest that CME as a novel Wnt/β-catenin inhibitor can be a putative agent for the treatment of colorectal cancers. - Highlights: • CME inhibits cell proliferation in HCT116 cells. • CME increases cell cycle arrest at G0/G1 phase and apoptosis. • CME attenuates cyclin D1 and regulates cell cycle regulatory proteins. • CME inhibits β-catenin translocation to nucleus.« less

Estrogen and progesterone promote breast cancer cell proliferation by inducing cyclin G1 expression.

PubMed

Tian, J-M; Ran, B; Zhang, C-L; Yan, D-M; Li, X-H

2018-01-23

Breast cancer is the most common cause of cancer among women in most countries (WHO). Ovarian hormone disorder is thought to be associated with breast tumorigenesis. The present study investigated the effects of estrogen and progesterone administration on cell proliferation and underlying mechanisms in breast cancer MCF-7 cells. It was found that a single administration of estradiol (E2) or progesterone increased MCF-7 cell viability in a dose-dependent manner and promoted cell cycle progression by increasing the percentage of cells in the G2/M phase. A combination of E2 and progesterone led to a stronger effect than single treatment. Moreover, cyclin G1 was up-regulated by E2 and/or progesterone in MCF-7 cells. After knockdown of cyclin G1 in MCF-7 cells using a specific shRNA, estradiol- and progesterone-mediated cell viability and clonogenic ability were significantly limited. Additionally, estradiol- and progesterone-promoted cell accumulation in the G2/M phase was reversed after knockdown of cyclin G1. These data indicated that estrogen and progesterone promoted breast cancer cell proliferation by inducing the expression of cyclin G1. Our data indicated that novel therapeutics against cyclin G1 are promising for the treatment of estrogen- and progesterone-mediated breast cancer progression.

MicroRNA-195 inhibits proliferation of cervical cancer cells by targeting cyclin D1a.

PubMed

Wang, Ning; Wei, Heng; Yin, Duo; Lu, Yanming; Zhang, Yao; Zhang, Qiao; Ma, Xiaoxin; Zhang, Shulan

2016-04-01

Cervical cancer is one of the most frequent gynecological malignancies in women worldwide. MicroRNA-195 (miR-195) was recently found highly expressed in cervical cancer. However, the role of miR-195 in the pathology of cervical cancer remains poorly understood. In this study, we first confirmed the downregulation of miR-195 in primary cervical cancer tissues. For the functional study, we introduced the sequences of miR-195 or miR-195 inhibitor into Hela and SiHa cervical cancer cell lines. Overexpression of miR-195 inhibited the proliferation of both Hela and SiHa cells. In contrast, reducing the endogenous miR-195 level by miR-195 inhibitor promoted the proliferation of cervical cancer cells. Flow cytometric assay showed that overexpression of miR-195 induced G1 phase arrest, whereas miR-195 inhibitor shortened G1 phase of cervical cancer cells. In addition, the suppressive role of miR-195 in cell cycle was also demonstrated by the western blot results of various cell cycle indicators, such as phosphorylated retinoblastoma (p-Rb) and proliferating cell nuclear antigen (PCNA), in the gain and loss of function experiments. Furthermore, Dual-Luciferase Reporter Assay revealed that miR-195 targeted the 3'-untranslated region of cyclin D1a transcript, such as to regulate cyclin D1 expression. In summary, our results suggest that miR-195 acts as a suppressor in the proliferation and cell cycle of cervical cancer cells by directly targeting cyclin D1a mRNA.

A Protein Encoded by the Latency-Related Gene of Bovine Herpesvirus 1 Is Expressed in Trigeminal Ganglionic Neurons of Latently Infected Cattle and Interacts with Cyclin-Dependent Kinase 2 during Productive Infection

PubMed Central

Jiang, Yunquan; Hossain, Ashfaque; Winkler, Maria Teresa; Holt, Todd; Doster, Alan; Jones, Clinton

1998-01-01

Despite productive viral gene expression in the peripheral nervous system during acute infection, the bovine herpesvirus 1 (BHV-1) infection cycle is blocked in sensory ganglionic neurons and consequently latency is established. The only abundant viral transcript expressed during latency is the latency-related (LR) RNA. LR gene products inhibit S-phase entry, and binding of the LR protein (LRP) to cyclin A was hypothesized to block cell cycle progression. This study demonstrates LRP is a nuclear protein which is expressed in neurons of latently infected cattle. Affinity chromatography indicated that LRP interacts with cyclin-dependent kinase 2 (cdk2)-cyclin complexes or cdc2-cyclin complexes in transfected human cells or infected bovine cells. After partial purification using three different columns (DEAE-Sepharose, Econo S, and heparin-agarose), LRP was primarily associated with cdk2-cyclin E complexes, an enzyme which is necessary for G1-to-S-phase cell cycle progression. During acute infection of trigeminal ganglia or following dexamethasone-induced reactivation, BHV-1 induces expression of cyclin A in neurons (L. M. Schang, A. Hossain, and C. Jones, J. Virol. 70:3807–3814, 1996). Expression of S-phase regulatory proteins (cyclin A, for example) leads to neuronal apoptosis. Consequently, we hypothesize that interactions between LRP and cell cycle regulatory proteins promote survival of postmitotic neurons during acute infection and/or reactivation. PMID:9733854

A protein encoded by the latency-related gene of bovine herpesvirus 1 is expressed in trigeminal ganglionic neurons of latently infected cattle and interacts with cyclin-dependent kinase 2 during productive infection.

PubMed

Jiang, Y; Hossain, A; Winkler, M T; Holt, T; Doster, A; Jones, C

1998-10-01

Despite productive viral gene expression in the peripheral nervous system during acute infection, the bovine herpesvirus 1 (BHV-1) infection cycle is blocked in sensory ganglionic neurons and consequently latency is established. The only abundant viral transcript expressed during latency is the latency-related (LR) RNA. LR gene products inhibit S-phase entry, and binding of the LR protein (LRP) to cyclin A was hypothesized to block cell cycle progression. This study demonstrates LRP is a nuclear protein which is expressed in neurons of latently infected cattle. Affinity chromatography indicated that LRP interacts with cyclin-dependent kinase 2 (cdk2)-cyclin complexes or cdc2-cyclin complexes in transfected human cells or infected bovine cells. After partial purification using three different columns (DEAE-Sepharose, Econo S, and heparin-agarose), LRP was primarily associated with cdk2-cyclin E complexes, an enzyme which is necessary for G1-to-S-phase cell cycle progression. During acute infection of trigeminal ganglia or following dexamethasone-induced reactivation, BHV-1 induces expression of cyclin A in neurons (L. M. Schang, A. Hossain, and C. Jones, J. Virol. 70:3807-3814, 1996). Expression of S-phase regulatory proteins (cyclin A, for example) leads to neuronal apoptosis. Consequently, we hypothesize that interactions between LRP and cell cycle regulatory proteins promote survival of postmitotic neurons during acute infection and/or reactivation.

The Down syndrome-related protein kinase DYRK1A phosphorylates p27Kip1 and Cyclin D1 and induces cell cycle exit and neuronal differentiation

PubMed Central

Soppa, Ulf; Schumacher, Julian; Florencio Ortiz, Victoria; Pasqualon, Tobias; Tejedor, Francisco J; Becker, Walter

2014-01-01

A fundamental question in neurobiology is how the balance between proliferation and differentiation of neuronal precursors is maintained to ensure that the proper number of brain neurons is generated. Substantial evidence implicates DYRK1A (dual specificity tyrosine-phosphorylation-regulated kinase 1A) as a candidate gene responsible for altered neuronal development and brain abnormalities in Down syndrome. Recent findings support the hypothesis that DYRK1A is involved in cell cycle control. Nonetheless, how DYRK1A contributes to neuronal cell cycle regulation and thereby affects neurogenesis remains poorly understood. In the present study we have investigated the mechanisms by which DYRK1A affects cell cycle regulation and neuronal differentiation in a human cell model, mouse neurons, and mouse brain. Dependent on its kinase activity and correlated with the dosage of overexpression, DYRK1A blocked proliferation of SH-SY5Y neuroblastoma cells within 24 h and arrested the cells in G1 phase. Sustained overexpression of DYRK1A induced G0 cell cycle exit and neuronal differentiation. Furthermore, we provide evidence that DYRK1A modulated protein stability of cell cycle-regulatory proteins. DYRK1A reduced cellular Cyclin D1 levels by phosphorylation on Thr286, which is known to induce proteasomal degradation. In addition, DYRK1A phosphorylated p27Kip1 on Ser10, resulting in protein stabilization. Inhibition of DYRK1A kinase activity reduced p27Kip1 Ser10 phosphorylation in cultured hippocampal neurons and in embryonic mouse brain. In aggregate, these results suggest a novel mechanism by which overexpression of DYRK1A may promote premature neuronal differentiation and contribute to altered brain development in Down syndrome. PMID:24806449

Molecular mechanisms of cisplatin cytotoxicity in acute promyelocytic leukemia cells.

PubMed

Kumar, Sanjay; Tchounwou, Paul B

2015-12-01

Cis-diamminedichloroplatinum (II) (cisplatin) is a widely used anti-tumor drug for the treatment of a broad range of human malignancies with successful therapeutic outcomes for head and neck, ovarian, and testicular cancers. It has been found to inhibit cell cycle progression and to induce oxidative stress and apoptosis in acute promyelocytic leukemia (APL) cells. However, its molecular mechanisms of cytotoxic action are poorly understood. We hypothesized that cisplatin induces cytotoxicity through DNA adduct formation, oxidative stress, transcriptional factors (p53 and AP-1), cell cycle regulation, stress signaling and apoptosis in APL cells. We used the APL cell line as a model, and applied a variety of molecular tools to elucidate the cytotoxic mode of action of cisplatin. We found that cisplatin inhibited cell proliferation by a cytotoxicity, characterized by DNA damage and modulation of oxidative stress. Cisplatin also activated p53 and phosphorylated activator protein (AP-1) component, c-Jun at serine (63, 73) residue simultaneously leading to cell cycle arrest through stimulation of p21 and down regulation of cyclins and cyclin dependent kinases in APL cell lines. It strongly activated the intrinsic pathway of apoptosis through alteration of the mitochondrial membrane potential, release of cytochrome C, and up-regulation of caspase 3 activity. It also down regulated the p38MAPK pathway. Overall, this study highlights the molecular mechanisms that underline cisplatin toxicity to APL cells, and provides insights into selection of novel targets and/or design of therapeutic agents to treat APL.

Microsporidia infection impacts the host cell's cycle and reduces host cell apoptosis

PubMed Central

Higes, Mariano; Sagastume, Soledad; Juarranz, Ángeles; Dias-Almeida, Joyce; Budge, Giles E.; Meana, Aránzazu; Boonham, Neil

2017-01-01

Intracellular parasites can alter the cellular machinery of host cells to create a safe haven for their survival. In this regard, microsporidia are obligate intracellular fungal parasites with extremely reduced genomes and hence, they are strongly dependent on their host for energy and resources. To date, there are few studies into host cell manipulation by microsporidia, most of which have focused on morphological aspects. The microsporidia Nosema apis and Nosema ceranae are worldwide parasites of honey bees, infecting their ventricular epithelial cells. In this work, quantitative gene expression and histology were studied to investigate how these two parasites manipulate their host’s cells at the molecular level. Both these microsporidia provoke infection-induced regulation of genes involved in apoptosis and the cell cycle. The up-regulation of buffy (which encodes a pro-survival protein) and BIRC5 (belonging to the Inhibitor Apoptosis protein family) was observed after infection, shedding light on the pathways that these pathogens use to inhibit host cell apoptosis. Curiously, different routes related to cell cycle were modified after infection by each microsporidia. In the case of N. apis, cyclin B1, dacapo and E2F2 were up-regulated, whereas only cyclin E was up-regulated by N. ceranae, in both cases promoting the G1/S phase transition. This is the first report describing molecular pathways related to parasite-host interactions that are probably intended to ensure the parasite’s survival within the cell. PMID:28152065

Microsporidia infection impacts the host cell's cycle and reduces host cell apoptosis.

PubMed

Martín-Hernández, Raquel; Higes, Mariano; Sagastume, Soledad; Juarranz, Ángeles; Dias-Almeida, Joyce; Budge, Giles E; Meana, Aránzazu; Boonham, Neil

2017-01-01

Intracellular parasites can alter the cellular machinery of host cells to create a safe haven for their survival. In this regard, microsporidia are obligate intracellular fungal parasites with extremely reduced genomes and hence, they are strongly dependent on their host for energy and resources. To date, there are few studies into host cell manipulation by microsporidia, most of which have focused on morphological aspects. The microsporidia Nosema apis and Nosema ceranae are worldwide parasites of honey bees, infecting their ventricular epithelial cells. In this work, quantitative gene expression and histology were studied to investigate how these two parasites manipulate their host's cells at the molecular level. Both these microsporidia provoke infection-induced regulation of genes involved in apoptosis and the cell cycle. The up-regulation of buffy (which encodes a pro-survival protein) and BIRC5 (belonging to the Inhibitor Apoptosis protein family) was observed after infection, shedding light on the pathways that these pathogens use to inhibit host cell apoptosis. Curiously, different routes related to cell cycle were modified after infection by each microsporidia. In the case of N. apis, cyclin B1, dacapo and E2F2 were up-regulated, whereas only cyclin E was up-regulated by N. ceranae, in both cases promoting the G1/S phase transition. This is the first report describing molecular pathways related to parasite-host interactions that are probably intended to ensure the parasite's survival within the cell.

Minichromosome maintenance (Mcm) proteins, cyclin B1 and D1, phosphohistone H3 and in situ DNA replication for functional analysis of vulval intraepithelial neoplasia.

PubMed

Davidson, E J; Morris, L S; Scott, I S; Rushbrook, S M; Bird, K; Laskey, R A; Wilson, G E; Kitchener, H C; Coleman, N; Stern, P L

2003-01-27

Vulval intraepithelial neoplasia (VIN) is defined histopathologically by distinctive abnormalities of cellular maturation and differentiation. To investigate the functional properties of VIN, the expression of several proteins involved in the regulation of the cell cycle as well as in situ DNA replication competence was analysed by immunohistochemistry. Snap-frozen vulval biopsies were graded as normal squamous epithelium (n=6), undifferentiated HPV positive VIN 1 (n=3), VIN 2 (n=8) and VIN 3 (n=20). Immunohistochemistry was performed using the following markers: cyclin D1 (expressed in middle/late G1), cyclin B1 (expressed in G2/early M), phosphorylated histone H3 (expressed during mitosis) and minichromosome maintenance (Mcm) proteins 2 and 5 (expressed during the cell cycle, but not in differentiated or quiescent cells). In situ DNA replication competence was used to identify S-phase cells. The percentage of positively stained nuclei in three representative microscopic fields was calculated per biopsy. In normal vulva, the expression of all markers was restricted to the proliferative compartment of the basal layer of the epithelium. In contrast in high-grade VIN, the majority of epithelial cells expressed the Mcm proteins from basal to superficial layer. The detection of cyclins B1 and D1, phospho-histone H3 and in situ DNA replication was also found through the full thickness of these lesions but by a lower proportion of the cells. This is consistent with these markers providing a series of 'snapshots' of the cell cycle status of individual cells. The low-grade VIN showed reduced expression of the cell cycle markers in relation to the level of dysplasia. The combination of these analyses establishes that the majority of VIN cells remain in a functional replicative or prereplicative state of the cell cycle. Clinical application of these analyses may provide a basis for improved diagnosis of VIN.

Down-regulation of microRNA-135b inhibited growth of cervical cancer cells by targeting FOXO1.

PubMed

Xu, Yue; Zhao, Shuhua; Cui, Manhua; Wang, Qiang

2015-01-01

More and more evidence has confirmed that dysregulation of microRNAs (miRNAs) can conduce to the progression of human cancers. Previous studied have shown that dysregulation of miR-135b is in varieties of tumors. However, the roles of miR-135b in cervical cancer remain unknown. Therefore, our aim of this study was to explore the biological function and molecular mechanism of miR-135b in cervical cancer cell lines, discussing whether it could be a therapeutic biomarker of cervical cancer in the future. The MTT assay and ELISA-Brdu assay were used to assess cell proliferation. Cell cycle was detected by flow cytometry. Real-time quantitative polymerase chain reaction (PCR) and Western blot analyses were used to detect expressions of cyclin D1, p21, p27 and FOXO1. In our study, we found that miR-135b is up-regulated in cervical cancer cell lines. Down-regulation of miR-135b evidently inhibited proliferation and arrested cell cycle in cervical cancer cells. Bioinformatics analysis predicted that the FOXO1 was a potential target gene of miR-135b. Besides, miR-135b inhibition significantly increased expressions of the cyclin-dependent kinase inhibitors, p21(/CIP1) and p27(/KIP1), and decreased expression of cyclin D1. However, the high level of miR-135b was associated with increased expression of FOXO1 in cervical cancer cells. Further study by luciferase reporter assay demonstrated that miR-135b could directly target FOXO1. Down-regulation of FOXO1 in cervical cancer cells transfected with miR-135b inhibitor partially reversed its inhibitory effects. In conclusion, down-regulation of miR-135b inhibited cell growth in cervical cancer cells by up-regulation of FOXO1.

cDNA Microarray Gene Expression Profiling of Hedgehog Signaling Pathway Inhibition in Human Colon Cancer Cells

PubMed Central

Shi, Ting; Mazumdar, Tapati; DeVecchio, Jennifer; Duan, Zhong-Hui; Agyeman, Akwasi; Aziz, Mohammad; Houghton, Janet A.

2010-01-01

Background Hedgehog (HH) signaling plays a critical role in normal cellular processes, in normal mammalian gastrointestinal development and differentiation, and in oncogenesis and maintenance of the malignant phenotype in a variety of human cancers. Increasing evidence further implicates the involvement of HH signaling in oncogenesis and metastatic behavior of colon cancers. However, genomic approaches to elucidate the role of HH signaling in cancers in general are lacking, and data derived on HH signaling in colon cancer is extremely limited. Methodology/Principal Findings To identify unique downstream targets of the GLI genes, the transcriptional regulators of HH signaling, in the context of colon carcinoma, we employed a small molecule inhibitor of both GLI1 and GLI2, GANT61, in two human colon cancer cell lines, HT29 and GC3/c1. Cell cycle analysis demonstrated accumulation of GANT61-treated cells at the G1/S boundary. cDNA microarray gene expression profiling of 18,401 genes identified Differentially Expressed Genes (DEGs) both common and unique to HT29 and GC3/c1. Analyses using GenomeStudio (statistics), Matlab (heat map), Ingenuity (canonical pathway analysis), or by qRT-PCR, identified p21Cip1 (CDKN1A) and p15Ink4b (CDKN2B), which play a role in the G1/S checkpoint, as up-regulated genes at the G1/S boundary. Genes that determine further cell cycle progression at G1/S including E2F2, CYCLIN E2 (CCNE2), CDC25A and CDK2, and genes that regulate passage of cells through G2/M (CYCLIN A2 [CCNA2], CDC25C, CYCLIN B2 [CCNB2], CDC20 and CDC2 [CDK1], were down-regulated. In addition, novel genes involved in stress response, DNA damage response, DNA replication and DNA repair were identified following inhibition of HH signaling. Conclusions/Significance This study identifies genes that are involved in HH-dependent cellular proliferation in colon cancer cells, and following its inhibition, genes that regulate cell cycle progression and events downstream of the G1/S boundary. PMID:20957031

CDK activity provides temporal and quantitative cues for organizing genome duplication

PubMed Central

Perrot, Anthony; Millington, Christopher Lee; Gómez-Escoda, Blanca; Schausi-Tiffoche, Diane

2018-01-01

In eukaryotes, the spatial and temporal organization of genome duplication gives rise to distinctive profiles of replication origin usage along the chromosomes. While it has become increasingly clear that these programs are important for cellular physiology, the mechanisms by which they are determined and modulated remain elusive. Replication initiation requires the function of cyclin-dependent kinases (CDKs), which associate with various cyclin partners to drive cell proliferation. Surprisingly, although we possess detailed knowledge of the CDK regulators and targets that are crucial for origin activation, little is known about whether CDKs play a critical role in establishing the genome-wide pattern of origin selection. We have addressed this question in the fission yeast, taking advantage of a simplified cell cycle network in which cell proliferation is driven by a single cyclin-CDK module. This system allows us to precisely control CDK activity in vivo using chemical genetics. First, in contrast to previous reports, our results clearly show that distinct cyclin-CDK pairs are not essential for regulating specific subsets of origins and for establishing a normal replication program. Importantly, we then demonstrate that the timing at which CDK activity reaches the S phase threshold is critical for the organization of replication in distinct efficiency domains, while the level of CDK activity at the onset of S phase is a dose-dependent modulator of overall origin efficiencies. Our study therefore implicates these different aspects of CDK regulation as versatile mechanisms for shaping the architecture of DNA replication across the genome. PMID:29466359

TGEV nucleocapsid protein induces cell cycle arrest and apoptosis through activation of p53 signaling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ding, Li; College of Life Sciences, Hainan Normal University, Haikou, Hainan 571158; Huang, Yong

2014-03-07

Highlights: • TGEV N protein reduces cell viability by inducing cell cycle arrest and apoptosis. • TGEV N protein induces cell cycle arrest and apoptosis by regulating p53 signaling. • TGEV N protein plays important roles in TGEV-induced cell cycle arrest and apoptosis. - Abstract: Our previous studies showed that TGEV infection could induce cell cycle arrest and apoptosis via activation of p53 signaling in cultured host cells. However, it is unclear which viral gene causes these effects. In this study, we investigated the effects of TGEV nucleocapsid (N) protein on PK-15 cells. We found that TGEV N protein suppressedmore » cell proliferation by causing cell cycle arrest at the S and G2/M phases and apoptosis. Characterization of various cellular proteins that are involved in regulating cell cycle progression demonstrated that the expression of N gene resulted in an accumulation of p53 and p21, which suppressed cyclin B1, cdc2 and cdk2 expression. Moreover, the expression of TGEV N gene promoted translocation of Bax to mitochondria, which in turn caused the release of cytochrome c, followed by activation of caspase-3, resulting in cell apoptosis in the transfected PK-15 cells following cell cycle arrest. Further studies showed that p53 inhibitor attenuated TGEV N protein induced cell cycle arrest at S and G2/M phases and apoptosis through reversing the expression changes of cdc2, cdk2 and cyclin B1 and the translocation changes of Bax and cytochrome c induced by TGEV N protein. Taken together, these results demonstrated that TGEV N protein might play an important role in TGEV infection-induced p53 activation and cell cycle arrest at the S and G2/M phases and apoptosis occurrence.« less

MAP kinase dependent cyclinE/cdk2 activity promotes DNA replication in early sea urchin embryos

PubMed Central

Kisielewska, J.; Philipova, R.; Huang, J.-Y.; Whitaker, M.

2009-01-01

Sea urchins provide an excellent model for studying cell cycle control mechanisms governing DNA replication in vivo. Fertilization and cell cycle progression are tightly coordinated by Ca2+ signals, but the mechanisms underlying the onset of DNA replication after fertilization remain less clear. In this study we demonstrate that calcium-dependent activation of ERK1 promotes accumulation of cyclinE/cdk2 into the male and female pronucleus and entry into first S-phase. We show that cdk2 activity rises quickly after fertilization to a maximum at 4 min, corresponding in timing to the early ERK1 activity peak. Abolishing MAP kinase activity after fertilization with MEK inhibitor, U0126, substantially reduces the early peak of cdk2 activity and prevents cyclinE and cdk2 accumulation in both sperm pronucleus and zygote nucleus in vivo. Both p27kip1 and roscovitine, cdk2 inhibitors, prevented DNA replication suggesting cdk2 involvement in this process in sea urchin. Inhibition of cdk2 activity using p27kip1 had no effect on the phosphorylation of MBP by ERK, but completely abolished phosphorylation of retinoblastoma protein, a cdk2 substrate, indicating that cdk2 activity is downstream of ERK1 activation. This pattern of regulation of DNA synthesis conforms to the pattern observed in mammalian somatic cells. PMID:19665013

Cdk7 mediates RPB1-driven mRNA synthesis in Toxoplasma gondii

PubMed Central

Deshmukh, Abhijit S.; Mitra, Pallabi; Maruthi, Mulaka

2016-01-01

Cyclin-dependent kinase 7 in conjunction with CyclinH and Mat1 activates cell cycle CDKs and is a part of the general transcription factor TFIIH. Role of Cdk7 is well characterized in model eukaryotes however its relevance in protozoan parasites has not been investigated. This important regulator of key processes warrants closer examination particularly in this parasite given its unique cell cycle progression and flexible mode of replication. We report functional characterization of TgCdk7 and its partners TgCyclinH and TgMat1. Recombinant Cdk7 displays kinase activity upon binding its cyclin partner and this activity is further enhanced in presence of Mat1. The activated kinase phosphorylates C-terminal domain of TgRPB1 suggesting its role in parasite transcription. Therefore, the function of Cdk7 in CTD phosphorylation and RPB1 mediated transcription was investigated using Cdk7 inhibitor. Unphosphorylated CTD binds promoter DNA while phosphorylation by Cdk7 triggers its dissociation from DNA with implications for transcription initiation. Inhibition of Cdk7 in the parasite led to strong reduction in Serine 5 phosphorylation of TgRPB1-CTD at the promoters of constitutively expressed actin1 and sag1 genes with concomitant reduction of both nascent RNA synthesis and 5′-capped transcripts. Therefore, we provide compelling evidence for crucial role of TgCdk7 kinase activity in mRNA synthesis. PMID:27759017

Gossypol inhibition of mitosis, cyclin D1 and Rb protein in human mammary cancer cells and cyclin-D1 transfected human fibrosarcoma cells.

PubMed Central

Ligueros, M.; Jeoung, D.; Tang, B.; Hochhauser, D.; Reidenberg, M. M.; Sonenberg, M.

1997-01-01

The antiproliferative effects of gossypol on human MCF-7 mammary cancer cells and cyclin D1-transfected HT-1060 human fibrosarcoma cells were investigated by cell cycle analysis and effects on the cell cycle regulatory proteins Rb and cyclin D1. Flow cytometry of MCF-7 cells at 24 h indicated that 10 microM gossypol inhibited DNA synthesis by producing a G1/S block. Western blot analysis using anti-human Rb antibodies and anti-human cyclin D1 antibodies in MCF-7 cells and high- and low-expression cyclin D1-transfected fibrosarcoma cells indicated that, after 6 h exposure, gossypol decreased the expression levels of these proteins in a dose-dependent manner. Gossypol also decreased the ratio of phosphorylated to unphosphorylated Rb protein in human mammary cancer and fibrosarcoma cell lines. Gossypol (10 microM) treated also decreased cyclin D1-associated kinase activity on histone H1 used as a substrate in MCF-7 cells. These results suggest that gossypol might suppress growth by modulating the expression of cell cycle regulatory proteins Rb and cyclin D1 and the phosphorylation of Rb protein. Images Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 PMID:9218727

Osthole induces G2/M arrest and apoptosis in lung cancer A549 cells by modulating PI3K/Akt pathway

PubMed Central

2011-01-01

Background To explore the effects of Osthole on the proliferation, cell cycle and apoptosis of human lung cancer A549 cells. Methods Human lung cancer A549 cells were treated with Osthole at different concentrations. Cell proliferation was measured using the MTT assay. Cell cycle was evaluated using DNA flow cytometry analysis. Induction of apoptosis was determined by flow cytometry and fluorescent microscopy. The expressions of Cyclin B1, p-Cdc2, Bcl-2, Bax, t-Akt and p-Akt were evaluated by Western blotting. Results Osthole inhibited the growth of human lung cancer A549 cells by inducing G2/M arrest and apoptosis. Western blotting demonstrated that Osthole down-regulated the expressions of Cyclin B1, p-Cdc2 and Bcl-2 and up-regulated the expressions of Bax in A549 cells. Inhibition of PI3K/Akt signaling pathway was also observed after treating A549 cells with Osthole. Conclusions Our findings suggest that Osthole may have a therapeutic application in the treatment of human lung cancer. PMID:21447176

[Circadian rhythm variation of the clock genes Per1 and cell cycle related genes in different stages of carcinogenesis of buccal mucosa in animal model].

PubMed

Tan, Xuemei; Ye, Hua; Yang, Kai; Chen, Dan; Tang, Hong

2015-07-01

To investigate the expression and circadian rhythm variation of biological clock gene Per1 and cell cycle genes p53, CyclinD1, cyclin-dependent kinases (CDK1), CyclinB1 in different stages of carcinogenesis in buccal mucosa and its relationship with the development of buccal mucosa carcinoma. Ninety golden hamsters were housed under 12 hours light-12 hours dark cycles, and the model of buccal squamous cell carcinoma was established by using the dimethylbenzanthracene (DMBA) to smear the golden hamster buccal mucosa. Before the DMBA was used and after DMBA was used 6 weeks and 14 weeks respectively, the golden hamsters were sacrificed at 6 different time points (5 rats per time point) within 24 hour, including 4, 8, 12, 16, 20 and 24 hour after lights onset (HALO), and the normal buccal mucosa, precancerous lesions and cancer tissue were obtained, respectively. HE stained sections were prepared to observe the canceration of each tissue. Real time RT-PCR was used to detect the mRNA expression of Per1, p53, CyclinD1, CDK1 and CyclinB1, and a cosine analysis method was applied to determine the circadian rhythm variation of Per1, p53, CyclinD1, CDK1 and CyclinB1 mRNA expression, which were characterized by median, amplitude and acrophase. The expression of Per1, p53, CDK1 and CyclinD1 mRNA in 6 different time points within 24 hours in the tissues of three different stages of carcinogenesis had circadian rhythm, respectively. However, the CyclinB1 mRNA was expressed with circadian rhythm just in normal and cancer tissue (P < 0.05), while in precancerous lesions the circadian rhythm was in disorder (P > 0.05). As the development of carcinoma, the median of Per1 and p53 mRNA expression were significantly decreased (P < 0.05), yet the median of CDK1, CyclinB1 and CyclinD1 mRNA expression were significantly increased (P < 0.05). The amplitude of Per1, p53 and CyclinD1 mRNA expression was significantly decreased as the development of carcinoma (P < 0.05), however the amplitude of CDK1 mRNA expression was significantly increased (P < 0.05). In addition, there was no significant difference in the amplitude of CyclinB1 mRNA expression. The time that the peak expression value of Per1 and CDK1 mRNA appeared (Acrophase) in precancerous lesions was remarkably earlier than that in normal tissues, but the acrophase of p53 and CyclinD1 mRNA expression was remarkably delayed. Moreover, the acrophase of CDK1 and CyclinB1 mRNA expression in cancer tissues was obviously earlier than that in normal tissues, yet there was no significant variation in acrophase of Per1, p53, CyclinD1 mRNA expression between normal tissues and cancer tissues. The circadian rhythm of clock gene Per1 and cell cycle genes p53, CyclinD1, CDK1, CyclinB1 expression remarkably varied with the occurrence and development of carcinoma. Further research into the interaction between circadian and cell cycle of two cycle activity and relationship with the carcinogenesis may providenew ideas and methods of individual treatment and the mechanism of carcinogenesis.

Deficiency of the NR4A Orphan Nuclear Receptor NOR1 attenuates Neointima Formation Following Vascular Injury

PubMed Central

Nomiyama, Takashi; Zhao, Yue; Gizard, Florence; Findeisen, Hannes M.; Heywood, Elizabeth B.; Jones, Karrie L.; Conneely, Orla M.; Bruemmer, Dennis

2009-01-01

Background The neuron-derived orphan receptor-1 (NOR1) belongs to the evolutionary highly conserved and most ancient NR4A subfamily of the nuclear hormone receptor superfamily. Members of this subfamily function as early response genes regulating key cellular processes including proliferation, differentiation, and survival. Although NOR1 has previously been demonstrated to be required for smooth muscle cell (SMC) proliferation in vitro, the role of this nuclear receptor for the proliferative response underlying neointima formation and target genes trans-activated by NOR1 remain to be defined. Methods and Results Using a model of guide wire-induced arterial injury, we demonstrate decreased neointima formation in NOR1-/- mice compared to wildtype mice. In vitro, NOR1-deficient SMC exhibit decreased proliferation due to a G1→S phase arrest of the cell cycle and increased apoptosis in response to serum deprivation. NOR1-deficiency alters phosphorylation of the retinoblastoma protein by preventing mitogen-induced cyclin D1 and D2 expression. Conversely, overexpression of NOR1 induces cyclin D1 expression and the transcriptional activity of the cyclin D1 promoter in transient reporter assays. Gel shift and chromatin immunoprecipitation assays identified a putative response element for NR4A receptors in the cyclin D1 promoter, to which NOR1 is recruited in response to mitogenic stimulation. Finally, we provide evidence that these observations are applicable in vivo by demonstrating decreased cyclin D1 expression during neointima formation in NOR1-deficient mice. Conclusions These experiments characterize cyclin D1 as a NOR1-regulated target gene in SMC and demonstrate that NOR1 deficiency decreases neointima formation in response to vascular injury. PMID:19153266

Cyclin D1-Cdk4 controls glucose metabolism independently of cell cycle progression.

PubMed

Lee, Yoonjin; Dominy, John E; Choi, Yoon Jong; Jurczak, Michael; Tolliday, Nicola; Camporez, Joao Paulo; Chim, Helen; Lim, Ji-Hong; Ruan, Hai-Bin; Yang, Xiaoyong; Vazquez, Francisca; Sicinski, Piotr; Shulman, Gerald I; Puigserver, Pere

2014-06-26

Insulin constitutes a principal evolutionarily conserved hormonal axis for maintaining glucose homeostasis; dysregulation of this axis causes diabetes. PGC-1α (peroxisome-proliferator-activated receptor-γ coactivator-1α) links insulin signalling to the expression of glucose and lipid metabolic genes. The histone acetyltransferase GCN5 (general control non-repressed protein 5) acetylates PGC-1α and suppresses its transcriptional activity, whereas sirtuin 1 deacetylates and activates PGC-1α. Although insulin is a mitogenic signal in proliferative cells, whether components of the cell cycle machinery contribute to its metabolic action is poorly understood. Here we report that in mice insulin activates cyclin D1-cyclin-dependent kinase 4 (Cdk4), which, in turn, increases GCN5 acetyltransferase activity and suppresses hepatic glucose production independently of cell cycle progression. Through a cell-based high-throughput chemical screen, we identify a Cdk4 inhibitor that potently decreases PGC-1α acetylation. Insulin/GSK-3β (glycogen synthase kinase 3-beta) signalling induces cyclin D1 protein stability by sequestering cyclin D1 in the nucleus. In parallel, dietary amino acids increase hepatic cyclin D1 messenger RNA transcripts. Activated cyclin D1-Cdk4 kinase phosphorylates and activates GCN5, which then acetylates and inhibits PGC-1α activity on gluconeogenic genes. Loss of hepatic cyclin D1 results in increased gluconeogenesis and hyperglycaemia. In diabetic models, cyclin D1-Cdk4 is chronically elevated and refractory to fasting/feeding transitions; nevertheless further activation of this kinase normalizes glycaemia. Our findings show that insulin uses components of the cell cycle machinery in post-mitotic cells to control glucose homeostasis independently of cell division.

The cyclin-dependent kinase inhibitor p57Kip2 regulates cell cycle exit, differentiation, and migration of embryonic cerebral cortical precursors.

PubMed

Tury, Anna; Mairet-Coello, Georges; DiCicco-Bloom, Emanuel

2011-08-01

Mounting evidence indicates cyclin-dependent kinase (CDK) inhibitors (CKIs) of the Cip/Kip family, including p57(Kip2) and p27(Kip1), control not only cell cycle exit but also corticogenesis. Nevertheless, distinct activities of p57(Kip2) remain poorly defined. Using in vivo and culture approaches, we show p57(Kip2) overexpression at E14.5-15.5 elicits precursor cell cycle exit, promotes transition from proliferation to neuronal differentiation, and enhances process outgrowth, while opposite effects occur in p57(Kip2)-deficient precursors. Studies at later ages indicate p57(Kip2) overexpression also induces precocious glial differentiation, suggesting stage-dependent effects. In embryonic cortex, p57(Kip2) overexpression advances cell radial migration and alters postnatal laminar positioning. While both CKIs induce differentiation, p57(Kip2) was twice as effective as p27(Kip1) in inducing neuronal differentiation and was not permissive to astrogliogenic effects of ciliary neurotrophic factor, suggesting that the CKIs differentially modulate cell fate decisions. At molecular levels, although highly conserved N-terminal regions of both CKIs elicit cycle withdrawal and differentiation, the C-terminal region of p57(Kip2) alone inhibits in vivo migration. Furthermore, p57(Kip2) effects on neurogenesis and gliogenesis require the N-terminal cyclin/CDK binding/inhibitory domains, while previous p27(Kip1) studies report cell cycle-independent functions. These observations suggest p57(Kip2) coordinates multiple stages of corticogenesis and exhibits distinct and common activities compared with related family member p27(Kip1).

Inhibition effects of scorpion venom extracts (Buthus matensii Karsch) on the growth of human breast cancer MCF-7 cells.

PubMed

Li, Weiling; Li, Ye; Zhao, Yuwan; Yuan, Jieli; Mao, Weifeng

2014-01-01

To observe the inhibition effects of the Buthus matensii Karsch (BmK) scorpion venom extracts on the growth of human breast cancer MCF-7 cells, and to explore its mechanisms. Two common tumor cells (SMMC7721, MCF-7) were examined for the one which wasmore sensitivity to scorpion venom by MTT method. Cell cycle was determined by flow cytometry. Immunocytochemistry was applied to detect apoptosis-related protein Caspase-3 and Bcl-2 levels, while the expression of cell cycle-related protein Cyclin D1 was shown by Western blotting. Our data indicated that MCF-7 was the more sensitive cell line to scorpion venom. The extracts of scorpion venom could inhibit the growth and proliferation of MCF-7 cells. Furthermore, the extract of scorpion venom induced apoptosis through Caspase-3 up-regulation while Bcl-2 down-regulation in MCF-7 cells. In addition, the extracts of scorpion venom blocked the cells from G0/G1 phase to S phase and decreased cell cycle-related protein Cyclin D1 level after drug intervention compared with the negative control group. These results showed that the BmK scorpion venom extracts could inhibit the growth of MCF-7 cells by inducing apoptosis and blocking cell cycle in G0/G1 phase. The BmK scorpion venom extracts will be very valuable for the treatment of breast cancer.

Effects of Different Zinc Species on Cellar Zinc Distribution, Cell Cycle, Apoptosis and Viability in MDAMB231 Cells.

PubMed

Wang, Yan-hong; Zhao, Wen-jie; Zheng, Wei-juan; Mao, Li; Lian, Hong-zhen; Hu, Xin; Hua, Zi-chun

2016-03-01

Intracellular metal elements exist in mammalian cells with the concentration range from picomoles per litre to micromoles per litre and play a considerable role in various biological procedures. Element provided by different species can influence the availability and distribution of the element in a cell and could lead to different biological effects on the cell's growth and function. Zinc as an abundant and widely distributed essential trace element, is involved in numerous and relevant physiological functions. Zinc homeostasis in cells, which is regulated by metallothioneins, zinc transporter/SLC30A, Zrt-/Irt-like proteins/SLC39A and metal-response element-binding transcription factor-1 (MTF-1), is crucial for normal cellular functioning. In this study, we investigated the influences of different zinc species, zinc sulphate, zinc gluconate and bacitracin zinc, which represented inorganic, organic and biological zinc species, respectively, on cell cycle, viability and apoptosis in MDAMB231 cells. It was found that the responses of cell cycle, apoptosis and death to different zinc species in MDAMB231 cells are different. Western blot analysis of the expression of several key proteins in regulating zinc-related transcription, cell cycle, apoptosis, including MTF-1, cyclin B1, cyclin D1, caspase-8 and caspase-9 in treated cells further confirmed the observed results on cell level.

Requirement of ClC-3 in G0/G1 to S Phase Transition Induced by IGF-1 via ERK1/2-Cyclins Cascade in Multiple Myeloma Cells.

PubMed

Du, Yu; Tu, Yong-Sheng; Tang, Yong-Bo; Huang, Yun-Ying; Zhou, Fang-Min; Tian, Tian; Li, Xiao-Yan

2018-06-01

ClC-3 is involved in the proliferation and migration of several cancer cells. However, ClC-3 expression and its role of cell-cycle control in multiple myeloma (MM) has not yet been investigated. MM cells were treated with different concentrations of IGF (30, 100, 300 ng/mL), and their proliferation was examined by CCK-8. The effects of ClC-3 on cell cycle progression was detected by flow cytometry. Western blot was used to analyze the relative levels of ClC3, CD138, P21, P27, CDK, p-Erk1/2, and t-Erk1/2 protein expression. Transfection of RPMI8226 with gpClC-3 cDNA and siRNA alters the expression of ClC-3. We compared the expression of ClC-3 in primary myeloma cells and in MM cell lines (U266 and RPMI8266) with that in normal plasma cells (PCs) from normal subjects and found that myeloma cells from patients and MM cell lines had significantly higher expression of ClC-3. Additionally, silencing of ClC-3 with the small interfering RNA (siRNA) that targets human ClC-3 decreased proliferation of RPMI8226 after IGF-1 treatment and slowed cell cycle progression from G0/G1 to S phase, which was associated with diminished phosphorylation of ERK1/2, down-expression of cyclin E, cyclin D1 and up-regulation of p27 and p21. By contrast, overexpression of ClC-3 potentiated cell proliferation induced by IGF-1, raised the percentage of S phase cells, enhanced phosphorylation of ERK1/2, downregulated p27 and p21 and upregulated cyclin E and cyclin D1. ClC-3 accelerated G0/G1 to S phase transition in the cell cycle by modulating ERK1/2 kinase activity and expression of G1/S transition related proteins, making ClC-3 an attractive therapeutic target in MM.

D-type cyclins in adult human testis and testicular cancer: relation to cell type, proliferation, differentiation, and malignancy.

PubMed

Bartkova, J; Rajpert-de Meyts, E; Skakkebaek, N E; Bartek, J

1999-04-01

D-type cyclins are proto-oncogenic components of the 'RB pathway', a G1/S regulatory mechanism centred around the retinoblastoma tumour suppressor (pRB) implicated in key cellular decisions that control cell proliferation, cell-cycle arrest, quiescence, and differentiation. This study focused on immunohistochemical and immunochemical analysis of human adult testis and 32 testicular tumours to examine the differential expression and abundance of cyclins D1, D2, and D3 in relation to cell type, proliferation, differentiation, and malignancy. In normal testis, the cell type-restricted expression patterns were dominated by high levels of cyclin D3 in quiescent Leydig cells and the lack of any D-type cyclin in the germ cells, the latter possibly representing the only example of normal mammalian cells proliferating in the absence of these cyclins. Most carcinoma-in-situ lesions appeared to gain expression of cyclin D2 but not D1 or D3, while the invasive testicular tumours showed variable positivity for cyclins D2 and D3, but rarely D1. An unexpected correlation with differentiation rather than proliferation was found particularly for cyclin D3 in teratomas, a conceptually significant observation confirmed by massive up-regulation of cyclin D3 in the human teratocarcinoma cell line NTera2/D1 induced to differentiate along the neuronal lineage. These results suggest a possible involvement of cyclin D2 in the early stages of testicular oncogenesis and the striking examples of proliferation-independent expression point to potential dual or multiple roles of the D-type cyclins, particularly of cyclin D3. These findings extend current concepts of the biology of the cyclin D subfamily, as well as of the biology and oncopathology of the human adult testis. Apart from practical implications for the assessment of proliferation and oncogenic aberrations in human tissues and tumours, this study may inspire further research into the emerging role of the cyclin D proteins in the establishment and/or maintenance of the differentiated phenotypes. Copyright 1999 John Wiley & Sons, Ltd.

Ghrelin augments murine T-cell proliferation by activation of the phosphatidylinositol-3-kinase, extracellular signal-regulated kinase and protein kinase C signaling pathways

PubMed Central

Lee, Jun Ho; Patel, Kalpesh; Tae, Hyun Jin; Lustig, Ana; Kim, Jie Wan; Mattson, Mark P.; Taub, Dennis D.

2014-01-01

Thymic atrophy occurs during normal aging, and is accelerated by exposure to chronic stressors that elevate glucocorticoid levelsand impair the naïve T cell output. The orexigenic hormone ghrelin was recently shown to attenuate age-associated thymic atrophy. Here, we report that ghrelin enhances the proliferation of murine CD4+ primary T cells and a CD4+ T-cell line. Ghrelin induced activation of the ERK1/2 and Akt signaling pathways, via upstream activation of phosphatidylinositol-3-kinase and protein kinase C, to enhance T-cell proliferation. Moreover, ghrelin induced expression of the cell cycle proteins cyclin D1, cyclin E, cyclin-dependent kinase 2 (CDK2) and retinoblastoma phosphorylation. Finally, ghrelin activated the above-mentioned signaling pathways and stimulated thymocyte proliferation in young and older mice in vivo. PMID:25447526

Novel Synthetic Mono-triazole Glycosides Induce G0/G1 Cell-cycle Arrest and Apoptosis in Cholangiocarcinoma Cells.

PubMed

Obchoei, Sumalee; Saeeng, Rungnapha; Wongkham, Chaisiri; Wongkham, Sopit

2016-11-01

The treatment of cholangiocarcinoma (CCA) is still ineffective and the search for a novel treatment is needed. In this study, eight novel mono-triazole glycosides (W1-W8) were synthesized and tested for their anticancer activities in CCA cell lines. The anti-proliferation effect and the underlying mechanisms of the triazole glycosides were explored. Viable cells were determined using the MTT test. Among glycosides tested, W4 and W5 exhibited the most potent anticancer activity in a dose- and time-dependent fashion. Flow cytometry and wstern blot analysis revealed that W4 and W5 induced G 0 /G 1 phase cell-cycle arrest through down-regulation of cyclin D1, cyclin E and induction of cyclin-dependent kinase inhibitors, p27 and p21 protein expression. Annexin V/propidium iodide (PI) staining demonstrated that W4 and W5 also induced apoptotic cells in a dose-dependent manner via caspase signaling cascade. Together, these findings imply that the novel synthetic glycosides might be a promising anticancer agent for CCA. Copyright© 2016 International Institute of Anticancer Research (Dr. John G. Delinassios), All rights reserved.

Predicting network modules of cell cycle regulators using relative protein abundance statistics.

PubMed

Oguz, Cihan; Watson, Layne T; Baumann, William T; Tyson, John J

2017-02-28

Parameter estimation in systems biology is typically done by enforcing experimental observations through an objective function as the parameter space of a model is explored by numerical simulations. Past studies have shown that one usually finds a set of "feasible" parameter vectors that fit the available experimental data equally well, and that these alternative vectors can make different predictions under novel experimental conditions. In this study, we characterize the feasible region of a complex model of the budding yeast cell cycle under a large set of discrete experimental constraints in order to test whether the statistical features of relative protein abundance predictions are influenced by the topology of the cell cycle regulatory network. Using differential evolution, we generate an ensemble of feasible parameter vectors that reproduce the phenotypes (viable or inviable) of wild-type yeast cells and 110 mutant strains. We use this ensemble to predict the phenotypes of 129 mutant strains for which experimental data is not available. We identify 86 novel mutants that are predicted to be viable and then rank the cell cycle proteins in terms of their contributions to cumulative variability of relative protein abundance predictions. Proteins involved in "regulation of cell size" and "regulation of G1/S transition" contribute most to predictive variability, whereas proteins involved in "positive regulation of transcription involved in exit from mitosis," "mitotic spindle assembly checkpoint" and "negative regulation of cyclin-dependent protein kinase by cyclin degradation" contribute the least. These results suggest that the statistics of these predictions may be generating patterns specific to individual network modules (START, S/G2/M, and EXIT). To test this hypothesis, we develop random forest models for predicting the network modules of cell cycle regulators using relative abundance statistics as model inputs. Predictive performance is assessed by the areas under receiver operating characteristics curves (AUC). Our models generate an AUC range of 0.83-0.87 as opposed to randomized models with AUC values around 0.50. By using differential evolution and random forest modeling, we show that the model prediction statistics generate distinct network module-specific patterns within the cell cycle network.

P21 and p27: roles in carcinogenesis and drug resistance.

PubMed

Abukhdeir, Abde M; Park, Ben Ho

2008-07-01

Human cancers arise from an imbalance of cell growth and cell death. Key proteins that govern this balance are those that mediate the cell cycle. Several different molecular effectors have been identified that tightly regulate specific phases of the cell cycle, including cyclins, cyclin-dependent kinases (CDKs) and CDK inhibitors. Notably, loss of expression or function of two G1-checkpoint CDK inhibitors - p21 (CDKN1A) and p27 (CDKN1B) - has been implicated in the genesis or progression of many human malignancies. Additionally, there is a growing body of evidence suggesting that functional loss of p21 or p27 can mediate a drug-resistance phenotype. However, reports in the literature have also suggested p21 and p27 can promote tumours, indicating a paradoxical effect. Here, we review historic and recent studies of these two CDK inhibitors, including their identification, function, importance to carcinogenesis and finally their roles in drug resistance.

Developmental regulation of CYCA2s contributes to tissue-specific proliferation in Arabidopsis

PubMed Central

Vanneste, Steffen; Coppens, Frederik; Lee, EunKyoung; Donner, Tyler J; Xie, Zidian; Van Isterdael, Gert; Dhondt, Stijn; De Winter, Freya; De Rybel, Bert; Vuylsteke, Marnik; De Veylder, Lieven; Friml, Jiří; Inzé, Dirk; Grotewold, Erich; Scarpella, Enrico; Sack, Fred; Beemster, Gerrit T S; Beeckman, Tom

2011-01-01

In multicellular organisms, morphogenesis relies on a strict coordination in time and space of cell proliferation and differentiation. In contrast to animals, plant development displays continuous organ formation and adaptive growth responses during their lifespan relying on a tight coordination of cell proliferation. How developmental signals interact with the plant cell-cycle machinery is largely unknown. Here, we characterize plant A2-type cyclins, a small gene family of mitotic cyclins, and show how they contribute to the fine-tuning of local proliferation during plant development. Moreover, the timely repression of CYCA2;3 expression in newly formed guard cells is shown to require the stomatal transcription factors FOUR LIPS/MYB124 and MYB88, providing a direct link between developmental programming and cell-cycle exit in plants. Thus, transcriptional downregulation of CYCA2s represents a critical mechanism to coordinate proliferation during plant development. PMID:21772250

Cyclin C influences the timing of mitosis in fission yeast.

PubMed

Banyai, Gabor; Szilagyi, Zsolt; Baraznenok, Vera; Khorosjutina, Olga; Gustafsson, Claes M

2017-07-01

The multiprotein Mediator complex is required for the regulated transcription of nearly all RNA polymerase II-dependent genes. Mediator contains the Cdk8 regulatory subcomplex, which directs periodic transcription and influences cell cycle progression in fission yeast. Here we investigate the role of CycC, the cognate cyclin partner of Cdk8, in cell cycle control. Previous reports suggested that CycC interacts with other cellular Cdks, but a fusion of CycC to Cdk8 reported here did not cause any obvious cell cycle phenotypes. We find that Cdk8 and CycC interactions are stabilized within the Mediator complex and the activity of Cdk8-CycC is regulated by other Mediator components. Analysis of a mutant yeast strain reveals that CycC, together with Cdk8, primarily affects M-phase progression but mutations that release Cdk8 from CycC control also affect timing of entry into S phase. © 2017 Banyai et al. This article is distributed by The American Society for Cell Biology under license from the author(s). Two months after publication it is available to the public under an Attribution–Noncommercial–Share Alike 3.0 Unported Creative Commons License (http://creativecommons.org/licenses/by-nc-sa/3.0).

Cyclin A2 and CDK2 as Novel Targets of Aspirin and Salicylic acid: a Potential Role in Cancer Prevention

PubMed Central

Dachineni, Rakesh; Ai, Guoqiang; Kumar, D. Ramesh; Sadhu, Satya S.; Tummala, Hemachand; Bhat, G. Jayarama

2015-01-01

Data emerging from the past 10 years have consolidated the rationale for investigating the use of aspirin as a chemopreventive agent; however, the mechanisms leading to its anti-cancer effects are still being elucidated. We hypothesized that aspirin’s chemopreventive actions may involve cell cycle regulation through modulation of the levels or activity of cyclin A2/cyclin dependent kinase-2 (CDK2). In this study, HT-29 and other diverse panel of cancer cells were used to demonstrate that both aspirin and its primary metabolite, salicylic acid, decreased cyclin A2 (CCNA2) and CDK2 protein and mRNA levels. The down regulatory effect of either drugs on cyclin A2 levels was prevented by pretreatment with lactacystin, an inhibitor of proteasomes, suggesting the involvement of 26S proteasomes. In-vitro kinase assays showed that lysates from cells treated with salicylic acid had lower levels of CDK2 activity. Importantly, three independent experiments revealed that salicylic acid directly binds to CDK2. Firstly, inclusion of salicylic acid in naïve cell lysates, or in recombinant CDK2 preparations, increased the ability of the anti-CDK2 antibody to immunoprecipitate CDK2, suggesting that salicylic acid may directly bind and alter its conformation. Secondly, in 8-anilino-1-naphthalene-sulfonate (ANS)-CDK2 fluorescence assays, pre-incubation of CDK2 with salicylic acid, dose-dependently quenched the fluorescence due to ANS. Thirdly, computational analysis using molecular docking studies identified Asp145 and Lys33 as the potential sites of salicylic acid interactions with CDK2. These results demonstrate that aspirin and salicylic acid down-regulate cyclin A2/CDK2 proteins in multiple cancer cell lines, suggesting a novel target and mechanism of action in chemoprevention. Implications Biochemical and structural studies indicate that the anti-proliferative actions of aspirin are mediated through cyclin A2/CDK2. PMID:26685215

BAG3 regulates cell proliferation, migration, and invasion in human colorectal cancer.

PubMed

Shi, Huiyong; Xu, Haidong; Li, Zengjun; Zhen, Yanan; Wang, Bin; Huo, Shoujun; Xiao, Ruixue; Xu, Zhongfa

2016-04-01

Bcl2-associated athanogene 3 (BAG3) has been reported to be elevated in various tumors. However, it is unclear whether BAG3 has a functional role in the initiation and progression of colorectal cancer (CRC). Here, we collected CRC samples and cell lines to validate the pathway by using gene and protein assays. RT-PCR showed that the expression of BAG3 mRNA in CRC tissues was obviously higher than that in non-tumor tissues (p < 0.001). Immunohistochemical analysis showed that immunoreactivity of BAG3 was found in most CRC tissues and strongly correlated with TNM stage (p = 0.001), differentiation (p = 0.003), and metastasis (p = 0.010). Low expression of BAG3 in HCT-8 significantly reduced cellular proliferation, migration, and invasion. The analysis of in vitro cell showed that HCT-8 cells were exposed to si-BAG3, and its growth was inhibited depending on modulation of cell cycle G1/S checkpoints and cell cycle regulators, involving cyclin D1, cyclin A2, and cyclin B1. Furthermore, suppression of the epithelial-mesenchymal transition (EMT) by si-BAG3 is linked to the decreased expression of E-cadherin and the increased expression of N-cadherin, vimentin, and MMP9. In conclusion, in the present study, we demonstrated that BAG3 overexpression plays a critical role in cell proliferation, migration, and invasion of colorectal cancer. Our data suggests targeted inhibition of BAG3 may be useful for patients with CRC.

Clinicopathological and prognostic significance of cyclin D1 amplification in patients with breast cancer: a meta-analysis.

PubMed

He, Qi; Wu, Jingxun; Liu, Xin-Li; Ma, Yi-Han; Wu, Xiao-Ting; Wang, Wen-Yi; An, Han-Xiang

2017-01-01

Cyclin D1 plays a critical role in tumorigenesis and the regulation of the G1/S transition in the cell cycle. The relationship between cyclin D1 amplification and clinicopathological parameters in patients with breast cancer remains controversial and its impact on survival outcome is not completely clear. We conducted a meta-analysis to investigate the associations between cyclin D1 gene amplification and certain clinicopathological characteristics and the prognosis in breast cancer. Literature search of PubMed (up to August 3, 2016) was performed. We used Stata 12.0 (Stata Corporation, Texas, US) to analyze the correlations between cyclin D1 amplification and clinicopathological features and the prognostic indicator relapse free survival (RFS) and overall survival (OS) in patients with breast cancer. Publication bias analysis and sensitivity analysis were performed. A total of 9,238 breast cancer patients from 21 studies were included. The pooled odds ratios (ORs) indicated that cyclin D1 amplification was significantly associated with estrogen receptor (ER), progesterone receptor (PR), histological grade and lymph node status, but not associated with human epidermal growth factor receptor-2 (HER2) and tumor size. The combined hazard ratios (HRs) for RFS and OS showed that patients with cyclin D1 amplification displayed a 1.31-fold higher risk of recurrence (HR =1.31, 95% confidence interval (95% CI):1.02-1.60, p<0.01), and a risk of mortality 1.22-fold higher times greater than those without cyclin D1 amplification (HR=1.22, 95% CI:0.99- 1.44, p<0.01), respectively. Our meta-analysis indicated that cyclin D1 amplification is significantly associated with established clinicopathological variables and can be used as a poor prognostic indicator for patients with breast cancer.

Murrayafoline A Induces a G0/G1-Phase Arrest in Platelet-Derived Growth Factor-Stimulated Vascular Smooth Muscle Cells

PubMed Central

Han, Joo-Hui; Kim, Yohan; Jung, Sang-Hyuk; Lee, Jung-Jin; Park, Hyun-Soo; Song, Gyu-Yong; Cuong, Nguyen Manh; Kim, Young Ho

2015-01-01

The increased potential for vascular smooth muscle cell (VSMC) growth is a key abnormality in the development of atherosclerosis and post-angioplasty restenosis. Abnormally high activity of platelet-derived growth factor (PDGF) is believed to play a central role in the etiology of these pathophysiological situations. Here, we investigated the anti-proliferative effects and possible mechanism(s) of murrayafoline A, a carbazole alkaloid isolated from Glycosmis stenocarpa Guillamin (Rutaceae), on PDGF-BB-stimulated VSMCs. Murrayafoline A inhibited the PDGF-BB-stimulated proliferation of VSMCs in a concentration-dependent manner, as measured using a non-radioactive colorimetric WST-1 assay and direct cell counting. Furthermore, murrayafoline A suppressed the PDGF-BB-stimulated progression through G0/G1 to S phase of the cell cycle, as measured by [3H]-thymidine incorporation assay and cell cycle progression analysis. This anti-proliferative action of murrayafoline A, arresting cell cycle progression at G0/G1 phase in PDGF-BB-stimulated VSMCs, was mediated via down-regulation of the expression of cyclin D1, cyclin E, cyclin-dependent kinase (CDK)2, CDK4, and proliferating cell nuclear antigen (PCNA), and the phosphorylation of retinoblastoma protein (pRb). These results indicate that murrayafoline A may be useful in preventing the progression of vascular complications such as restenosis after percutaneous transluminal coronary angioplasty and atherosclerosis. PMID:26330754

CYCLIN-DEPENDENT KINASE G1 Is Associated with the Spliceosome to Regulate CALLOSE SYNTHASE5 Splicing and Pollen Wall Formation in Arabidopsis[C][W][OA

PubMed Central

Huang, Xue-Yong; Niu, Jin; Sun, Ming-Xi; Zhu, Jun; Gao, Ju-Fang; Yang, Jun; Zhou, Que; Yang, Zhong-Nan

2013-01-01

Arabidopsis thaliana CYCLIN-DEPEDENT KINASE G1 (CDKG1) belongs to the family of cyclin-dependent protein kinases that were originally characterized as cell cycle regulators in eukaryotes. Here, we report that CDKG1 regulates pre-mRNA splicing of CALLOSE SYNTHASE5 (CalS5) and, therefore, pollen wall formation. The knockout mutant cdkg1 exhibits reduced male fertility with impaired callose synthesis and abnormal pollen wall formation. The sixth intron in CalS5 pre-mRNA, a rare type of intron with a GC 5′ splice site, is abnormally spliced in cdkg1. RNA immunoprecipitation analysis suggests that CDKG1 is associated with this intron. CDKG1 contains N-terminal Ser/Arg (RS) motifs and interacts with splicing factor Arginine/Serine-Rich Zinc Knuckle-Containing Protein33 (RSZ33) through its RS region to regulate proper splicing. CDKG1 and RS-containing Zinc Finger Protein22 (SRZ22), a splicing factor interacting with RSZ33 and U1 small nuclear ribonucleoprotein particle (snRNP) component U1-70k, colocalize in nuclear speckles and reside in the same complex. We propose that CDKG1 is recruited to U1 snRNP through RSZ33 to facilitate the splicing of the sixth intron of CalS5. PMID:23404887

Immunohistochemical estimation of cell cycle phase in laryngeal neoplasia

PubMed Central

Chatrath, P; Scott, I S; Morris, L S; Davies, R J; Bird, K; Vowler, S L; Coleman, N

2006-01-01

We previously developed an immunohistochemical method for estimating cell cycle state and phase in tissue samples, including biopsies that are too small for flow cytometry. We have used our technique to examine whether primary abnormalities of the cell cycle exist in laryngeal neoplasia. Antibodies against the markers of cell cycle entry, minichromosome maintenance protein-2 (Mcm-2) and Ki67, and putative markers of cell cycle phase, cyclin D1 (G1-phase), cyclin A (S-phase), cyclin B1 (G2-phase) and phosphohistone H3 (Mitosis) were applied to paraffin-embedded sections of normal larynx (n=8), laryngeal dysplasia (n=10) and laryngeal squamous cell carcinoma (n=10). Cells expressing each marker were determined as a percentage of total cells, termed the labelling index (LI), and as a percentage of Mcm-2-positive cells, termed the labelling fraction (LF). The frequency of coexpression of each putative phase marker was investigated by confocal microscopy. There was a correlation between Mcm-2 and Ki67 LIs (ρ=0.93) but Mcm-2 LIs were consistently higher. All cells expressing a phase marker coexpressed Mcm-2, whereas Ki67 was not expressed in a proportion of these cells. The putative phase markers showed little coexpression. Labelling index values increased on progression from normal larynx through laryngeal dysplasia to squamous cell carcinoma for Mcm-2 (P=0.001), Ki67 (P=0.0002), cyclin D1 (P=0.015), cyclin A (P=0.0001) and cyclin B1 (P=0.0004). There was no evidence of an increase in the LF for any phase marker. Immunohistochemistry can be used to estimate cell cycle state and phase in laryngeal biopsies. Our data argues against primary cell cycle phase abnormalities in laryngeal neoplasia. PMID:16832409

CCDC106 promotes non-small cell lung cancer cell proliferation.

PubMed

Zhang, Xiupeng; Zheng, Qin; Wang, Chen; Zhou, Haijing; Jiang, Guiyang; Miao, Yuan; Zhang, Yong; Liu, Yang; Li, Qingchang; Qiu, Xueshan; Wang, Enhua

2017-04-18

Coiled-coil domain containing (CCDC) family members enhance tumor cell proliferation, and high CCDC protein levels correlate with unfavorable prognoses. Limited research demonstrated that CCDC106 may promote the degradation of p53/TP53 protein and inhibit its transactivity. The present study demonstrated that CCDC106 expression correlates with advanced TNM stage (P = 0.008), positive regional lymph node metastasis (P < 0.001), and poor overall survival (P < 0.001) in 183 non-small cell lung cancer cases. A549 and H1299 cells were selected as representative of CCDC106-low and CCDC106-high expressing cell lines, respectively. CCDC106 overexpression promoted A549 cell proliferation and xenograft tumor growth in nude mice, while siRNA-mediated CCDC106 knockdown inhibited H1299 cell proliferation. CCDC106 promoted AKT phosphorylation and upregulated the cell cycle-regulating proteins Cyclin A2 and Cyclin B1. Cell proliferation promoted by CCDC106 via Cyclin A2 and Cyclin B1 was rescued by treatment with the AKT inhibitor, LY294002. Our studies revealed that CCDC106 is associated with non-small cell lung cancer progression and unfavorable prognosis. CCDC106 enhanced Cyclin A2 and Cyclin B1 expression and promoted A549 and H1299 cell proliferation, which depended on AKT signaling. These results suggest that CCDC106 may be a novel target for lung cancer treatment.

The alpha-fetoprotein (AFP) third domain: a search for AFP interaction sites of cell cycle proteins.

PubMed

Mizejewski, G J

2016-09-01

The carboxy-terminal third domain of alpha-fetoprotein (AFP-3D) is known to harbor binding and/or interaction sites for hydrophobic ligands, receptors, and binding proteins. Such reports have established that AFP-3D consists of amino acid (AA) sequence stretches on the AFP polypeptide that engages in protein-to-protein interactions with various ligands and receptors. Using a computer software program specifically designed for such interactions, the present report identified AA sequence fragments on AFP-3D that could potentially interact with a variety of cell cycle proteins. The cell cycle proteins identified were (1) cyclins, (2) cyclin-dependent kinases, (3) cell cycle-associated proteins (inhibitors, checkpoints, initiators), and (4) ubiquitin ligases. Following detection of the AFP-3D to cell cycle protein interaction sites, the computer-derived AFP localization AA sequences were compared and aligned with previously reported hydrophobic ligand and receptor interaction sites on AFP-3D. A literature survey of the association of cell cycle proteins with AFP showed both positive relationships and correlations. Previous reports of experimental AFP-derived peptides effects on various cell cycle proteins served to confirm and verify the present computer cell cycle protein identifications. Cell cycle protein interactions with AFP-CD peptides have been reported in cultured MCF-7 breast cancer cells subjected to mRNA microarray analysis. After 7 days in culture with MCF-7 cells, the AFP-derived peptides were shown to downregulate cyclin E, SKP2, checkpoint suppressors, cyclin-dependent kinases, and ubiquitin ligases that modulate cyclin E/CdK2 transition from the G1 to the S-phase of the cell cycle. Thus, the experimental data on AFP-CD interaction with cell cycle proteins were consistent with the "in silico" findings.

CYCD3 D-type cyclins regulate cambial cell proliferation and secondary growth in Arabidopsis

PubMed Central

Collins, Carl; Maruthi, N. M.; Jahn, Courtney E.

2015-01-01

A major proportion of plant biomass is derived from the activity of the cambium, a lateral meristem responsible for vascular tissue formation and radial organ enlargement in a process termed secondary growth. In contrast to our relatively good understanding of the regulation of primary meristems, remarkably little is known concerning the mechanisms controlling secondary growth, particularly how cambial cell divisions are regulated and integrated with vascular differentiation. A genetic loss-of-function approach was used here to reveal a rate-limiting role for the Arabidopsis CYCLIN D3 (CYCD3) subgroup of cell-cycle genes in the control of cambial cell proliferation and secondary growth, providing conclusive evidence of a direct link between the cell cycle and vascular development. It is shown that all three CYCD3 genes are specifically expressed in the cambium throughout vascular development. Analysis of a triple loss-of-function CYCD3 mutant revealed a requirement for CYCD3 in promoting the cambial cell cycle since mutant stems and hypocotyls showed a marked reduction in diameter linked to reduced mitotic activity in the cambium. Conversely, loss of CYCD3 provoked an increase in xylem cell size and the expression of differentiation markers, showing that CYCD3 is required to restrain the differentiation of xylem precursor cells. Together, our data show that tight control of cambial cell division through developmental- and cell type-specific regulation of CYCD3 is required for normal vascular development, constituting part of a novel mechanism controlling organ growth in higher plants. PMID:26022252

Mangiferin Facilitates Islet Regeneration and β-Cell Proliferation through Upregulation of Cell Cycle and β-Cell Regeneration Regulators

PubMed Central

Wang, Hai-Lian; Li, Chun-Yang; Zhang, Bin; Liu, Yuan-De; Lu, Bang-Min; Shi, Zheng; An, Na; Zhao, Liang-Kai; Zhang, Jing-Jing; Bao, Jin-Ku; Wang, Yi

2014-01-01

Mangiferin, a xanthonoid found in plants including mangoes and iris unguicularis, was suggested in previous studies to have anti-hyperglycemic function, though the underlying mechanisms are largely unknown. This study was designed to determine the therapeutic effect of mangiferin by the regeneration of β-cells in mice following 70% partial pancreatectomy (PPx), and to explore the mechanisms of mangiferin-induced β-cell proliferation. For this purpose, adult C57BL/6J mice after 7–14 days post-PPx, or a sham operation were subjected to mangiferin (30 and 90 mg/kg body weight) or control solvent injection. Mangiferin-treated mice exhibited an improved glycemia and glucose tolerance, increased serum insulin levels, enhanced β-cell hyperplasia, elevated β-cell proliferation and reduced β-cell apoptosis. Further dissection at the molecular level showed several key regulators of cell cycle, such as cyclin D1, D2 and cyclin-dependent kinase 4 (Cdk4) were significantly up-regulated in mangiferin-treated mice. In addition, critical genes related to β-cell regeneration, such as pancreatic and duodenal homeobox 1 (PDX-1), neurogenin 3 (Ngn3), glucose transporter 2 (GLUT-2), Forkhead box protein O1 (Foxo-1), and glucokinase (GCK), were found to be promoted by mangiferin at both the mRNA and protein expression level. Thus, mangiferin administration markedly facilitates β-cell proliferation and islet regeneration, likely by regulating essential genes in the cell cycle and the process of islet regeneration. These effects therefore suggest that mangiferin bears a therapeutic potential in preventing and/or treating the diabetes. PMID:24853132

Mangiferin facilitates islet regeneration and β-cell proliferation through upregulation of cell cycle and β-cell regeneration regulators.

PubMed

Wang, Hai-Lian; Li, Chun-Yang; Zhang, Bin; Liu, Yuan-De; Lu, Bang-Min; Shi, Zheng; An, Na; Zhao, Liang-Kai; Zhang, Jing-Jing; Bao, Jin-Ku; Wang, Yi

2014-05-20

Mangiferin, a xanthonoid found in plants including mangoes and iris unguicularis, was suggested in previous studies to have anti-hyperglycemic function, though the underlying mechanisms are largely unknown. This study was designed to determine the therapeutic effect of mangiferin by the regeneration of β-cells in mice following 70% partial pancreatectomy (PPx), and to explore the mechanisms of mangiferin-induced β-cell proliferation. For this purpose, adult C57BL/6J mice after 7-14 days post-PPx, or a sham operation were subjected to mangiferin (30 and 90 mg/kg body weight) or control solvent injection. Mangiferin-treated mice exhibited an improved glycemia and glucose tolerance, increased serum insulin levels, enhanced β-cell hyperplasia, elevated β-cell proliferation and reduced β-cell apoptosis. Further dissection at the molecular level showed several key regulators of cell cycle, such as cyclin D1, D2 and cyclin-dependent kinase 4 (Cdk4) were significantly up-regulated in mangiferin-treated mice. In addition, critical genes related to β-cell regeneration, such as pancreatic and duodenal homeobox 1 (PDX-1), neurogenin 3 (Ngn3), glucose transporter 2 (GLUT-2), Forkhead box protein O1 (Foxo-1), and glucokinase (GCK), were found to be promoted by mangiferin at both the mRNA and protein expression level. Thus, mangiferin administration markedly facilitates β-cell proliferation and islet regeneration, likely by regulating essential genes in the cell cycle and the process of islet regeneration. These effects therefore suggest that mangiferin bears a therapeutic potential in preventing and/or treating the diabetes.

Candidate genes and pathogenesis investigation for sepsis-related acute respiratory distress syndrome based on gene expression profile.

PubMed

Wang, Min; Yan, Jingjun; He, Xingxing; Zhong, Qiang; Zhan, Chengye; Li, Shusheng

2016-04-18

Acute respiratory distress syndrome (ARDS) is a potentially devastating form of acute inflammatory lung injury as well as a major cause of acute respiratory failure. Although researchers have made significant progresses in elucidating the pathophysiology of this complex syndrome over the years, the absence of a universal detail disease mechanism up until now has led to a series of practical problems for a definitive treatment. This study aimed to predict some genes or pathways associated with sepsis-related ARDS based on a public microarray dataset and to further explore the molecular mechanism of ARDS. A total of 122 up-regulated DEGs and 91 down-regulated differentially expressed genes (DEGs) were obtained. The up- and down-regulated DEGs were mainly involved in functions like mitotic cell cycle and pathway like cell cycle. Protein-protein interaction network of ARDS analysis revealed 20 hub genes including cyclin B1 (CCNB1), cyclin B2 (CCNB2) and topoisomerase II alpha (TOP2A). A total of seven transcription factors including forkhead box protein M1 (FOXM1) and 30 target genes were revealed in the transcription factor-target gene regulation network. Furthermore, co-cited genes including CCNB2-CCNB1 were revealed in literature mining for the relations ARDS related genes. Pathways like mitotic cell cycle were closed related with the development of ARDS. Genes including CCNB1, CCNB2 and TOP2A, as well as transcription factors like FOXM1 might be used as the novel gene therapy targets for sepsis related ARDS.

Vitex rotundifolia Fruit Suppresses the Proliferation of Human Colorectal Cancer Cells through Down-regulation of Cyclin D1 and CDK4 via Proteasomal-Dependent Degradation and Transcriptional Inhibition.

PubMed

Song, Hun Min; Park, Gwang Hun; Park, Su Bin; Kim, Hyun-Seok; Son, Ho-Jun; Um, Yurry; Jeong, Jin Boo

2018-01-01

Viticis Fructus (VF) as the dried fruit from Vitex rotundifolia L. used as a traditional medicine for treating inflammation, headache, migraine, chronic bronchitis, eye pain, and gastrointestinal infections has been reported to have antiproliferative effects against various cancer cells, including breast, lung and colorectal cancer cells. However, the molecular mechanisms by which VF mediates the inhibitory effect of the proliferation of cancer cells have not been elucidated in detail. In this study, we investigated the molecular mechanism of VF on the down-regulation of cyclin D1 and CDK4 level associated with cancer cell proliferation. VF suppressed the proliferation of human colorectal cancer cell lines such as HCT116 and SW480. VF induced decrease in cyclin D1 and CDK4 in both protein and mRNA levels. However, the protein levels of cyclin D1 and CDK4 were decreased by VF at an earlier time than the change of mRNA levels; rather it suppressed the expression of cyclin D1 and CDK4 via the proteasomal degradation. In cyclin D1 and CDK4 degradation, we found that Thr286 phosphorylation of cyclin D1 plays a pivotal role in VF-mediated cyclin D1 degradation. Subsequent experiments with several kinase inhibitors suggest that VF-mediated degradation of cyclin D1 may be dependent on GSK3[Formula: see text] and VF-mediated degradation of CDK4 is dependent on ERK1/2, p38 and GSK3[Formula: see text]. In the transcriptional regulation of cyclin D1 and CDK4, we found that VF inhibited Wnt activation associated with cyclin D1 transcriptional regulation through TCF4 down-regulation. In addition, VF treatment down-regulated c-myc expression associated CDK4 transcriptional regulation. Our results suggest that VF has potential to be a candidate for the development of chemoprevention or therapeutic agents for human colorectal cancer.

βTrCP controls the lysosome-mediated degradation of CDK1, whose accumulation correlates with tumor malignancy.

PubMed

Herrero-Ruiz, Joaquín; Mora-Santos, Mar; Giráldez, Servando; Sáez, Carmen; Japón, Miguel A; Tortolero, Maria; Romero, Francisco

2014-09-15

In mammals, cell cycle progression is controlled by cyclin-dependent kinases, among which CDK1 plays important roles in the regulation of the G2/M transition, G1 progression and G1/S transition. CDK1 is highly regulated by its association to cyclins, phosphorylation and dephosphorylation, changes in subcellular localization, and by direct binding of CDK inhibitor proteins. CDK1 steady-state protein levels are held constant throughout the cell cycle by a coordinated regulation of protein synthesis and degradation. We show that CDK1 is ubiquitinated by the E3 ubiquitin ligase SCFβTrCP and degraded by the lysosome. Furthermore, we found that DNA damage not only triggers the stabilization of inhibitory phosphorylation sites on CDK1 and repression of CDK1 gene expression, but also regulates βTrCP-induced CDK1 degradation in a cell type-dependent manner. Specifically, treatment with the chemotherapeutic agent doxorubicin in certain cell lines provokes CDK1 degradation and induces apoptosis, whereas in others it inhibits destruction of the protein. These observations raise the possibility that different tumor types, depending on their pathogenic spectrum mutations, may display different sensitivity to βTrCP-induced CDK1 degradation after DNA damage. Finally, we found that CDK1 accumulation in patients' tumors shows a negative correlation with βTrCP and a positive correlation with the degree of tumor malignancy.

Cyclin D1 down-regulation is essential for DBC2's tumor suppressor function

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yoshihara, Takashi; Collado, Denise; Hamaguchi, Masaaki

2007-07-13

The expression of tumor suppressor gene DBC2 causes certain breast cancer cells to stop growing [M. Hamaguchi, J.L. Meth, C. Von Klitzing, W. Wei, D. Esposito, L. Rodgers, T. Walsh, P. Welcsh, M.C. King, M.H. Wigler, DBC2, a candidate for a tumor suppressor gene involved in breast cancer, Proc. Natl. Acad. Sci. USA 99 (2002) 13647-13652]. Recently, DBC2 was found to participate in diverse cellular functions such as protein transport, cytoskeleton regulation, apoptosis, and cell cycle control [V. Siripurapu, J.L. Meth, N. Kobayashi, M. Hamaguchi, DBC2 significantly influences cell cycle, apoptosis, cytoskeleton, and membrane trafficking pathways. J. Mol. Biol. 346more » (2005) 83-89]. Its tumor suppression mechanism, however, remains unclear. In this paper, we demonstrate that DBC2 suppresses breast cancer proliferation through down-regulation of Cyclin D1 (CCND1). Additionally, the constitutional overexpression of CCND1 prevented the negative impact of DBC2 expression on their growth. Under a CCND1 promoter, the expression of CCNE1 exhibited the same protective effect. Our results indicate that the down-regulation of CCND1 is an essential step for DBC2's growth suppression of cancer cells. We believe that this discovery contributes to a better understanding of DBC2's tumor suppressor function.« less

Decursin inhibits growth of human bladder and colon cancer cells via apoptosis, G1-phase cell cycle arrest and extracellular signal-regulated kinase activation.

PubMed

Kim, Wun-Jae; Lee, Se-Jung; Choi, Young Deuk; Moon, Sung-Kwon

2010-04-01

Decursin, a pyranocoumarin isolated from the Korean Angelica gigas root, has demonstrated anti-cancer properties. In the present study, we found that decursin inhibited cell viability in cultured human urinary bladder cancer 235J cells and colon cancer HCT116 cells. The inhibited proliferation was due to apoptotic induction, because both cells treated with decursin dose-dependently showed a sub-G1 phase accumulation and an increased cytoplasmic DNA-histone complex. Cell death caused by decursin was also associated with the down-regulation of anti-apoptotic factor Bcl-2 and the up-regulation of pro-apoptotic molecules cytochrome c, caspase 3 and Bax. Treatment of both types of cancer cells with decursin resulted in G1-phase cell cycle arrest, as revealed by FACS analyses. In addition, decursin increased protein levels of p21WAF1 with a decrease in cyclins and cyclin dependent kinases (CDKs). Furthermore, decursin induced the activation of extracellular signal-regulated kinases (ERK) in both cancer cell lines, with the notable exceptions of c-Jun N-terminal kinase (JNK) and p38 mitogen activated protein (MAP) kinase. Finally, pretreatment with ERK-specific inhibitor PD98059 reversed decursin-induced p21WAF1 expression and decursin-inhibited cell growth. Thus, these findings suggest that decursin has potential therapeutic efficacy for the treatment of bladder and colon cancer.

FGF inhibits the activity of the cyclin B1/CDK1 kinase to induce a transient G₂arrest in RCS chondrocytes.

PubMed

Tran, Tri; Kolupaeva, Victoria; Basilico, Claudio

2010-11-01

Fibroblast growth factors (FGFs) negatively regulate long bone development by inhibiting the proliferation of chondrocytes that accumulate in the G₁ phase of the cycle following FGF treatment. Here we report that FGF also causes a striking but transient delay in mitotic entry in RCS chondrocytes by inactivating the cyclin B1-associated CDK1(CDC2) kinase. As a consequence of this inactivation, cells accumulate in the G₂ phase of the cycle for the first 4-6 hours of the treatment. Cyclin B1/CDK1 activity is then restored and cells reach a G₁ arrest. The reduced cyclin B1/CDK1 activity was accompanied by increased CDK1 inhibitory phosphorylation, likely caused by increased activity and expression of the Myt1 kinase. FGF1 also caused dephosphorylation of the CDC25C phosphatase, that however appears due the inactivation of cyclin B1/CDK1 complex in the CDK1 feedback loop, and not the activation of specific phosphatases. the inactivation of the cyclin B1/CDK1 complex is a direct effect of FGF signaling, and not a consequence of the G₂ arrest as it can be observed also in cells blocked at mitosis by Nocodazole. The Chk1 and AtM/ATR kinase are known to play essential roles in the G₂ checkpoint induced by DNA damage/genotoxic stress, but inhibition of Chk1 or ATM/ATR not only did not prevent, but rather potentiated the FGF-induced G₂ arrest. Additionally our results indicate that the transient G₂ arrest is induced by FGF in RCS cell through mechanisms that are independent of the G₁ arrest, and that the G₂ block is not strictly required for the sustained G₁ arrest but may provide a pausing mechanism that allows the FGF response to be fully established.

From quiescence to proliferation: Cdk oscillations drive the mammalian cell cycle

PubMed Central

Gérard, Claude; Goldbeter, Albert

2012-01-01

We recently proposed a detailed model describing the dynamics of the network of cyclin-dependent kinases (Cdks) driving the mammalian cell cycle (Gérard and Goldbeter, 2009). The model contains four modules, each centered around one cyclin/Cdk complex. Cyclin D/Cdk4–6 and cyclin E/Cdk2 promote progression in G1 and elicit the G1/S transition, respectively; cyclin A/Cdk2 ensures progression in S and the transition S/G2, while the activity of cyclin B/Cdk1 brings about the G2/M transition. This model shows that in the presence of sufficient amounts of growth factor the Cdk network is capable of temporal self-organization in the form of sustained oscillations, which correspond to the ordered, sequential activation of the various cyclin/Cdk complexes that control the successive phases of the cell cycle. The results suggest that the switch from cellular quiescence to cell proliferation corresponds to the transition from a stable steady state to sustained oscillations in the Cdk network. The transition depends on a finely tuned balance between factors that promote or hinder progression in the cell cycle. We show that the transition from quiescence to proliferation can occur in multiple ways that alter this balance. By resorting to bifurcation diagrams, we analyze the mechanism of oscillations in the Cdk network. Finally, we show that the complexity of the detailed model can be greatly reduced, without losing its key dynamical properties, by considering a skeleton model for the Cdk network. Using such a skeleton model for the mammalian cell cycle we show that positive feedback (PF) loops enhance the amplitude and the robustness of Cdk oscillations with respect to molecular noise. We compare the relative merits of the detailed and skeleton versions of the model for the Cdk network driving the mammalian cell cycle. PMID:23130001

Parvovirus-Induced Depletion of Cyclin B1 Prevents Mitotic Entry of Infected Cells

PubMed Central

Adeyemi, Richard O.; Pintel, David J.

2014-01-01

Parvoviruses halt cell cycle progression following initiation of their replication during S-phase and continue to replicate their genomes for extended periods of time in arrested cells. The parvovirus minute virus of mice (MVM) induces a DNA damage response that is required for viral replication and induction of the S/G2 cell cycle block. However, p21 and Chk1, major effectors typically associated with S-phase and G2-phase cell cycle arrest in response to diverse DNA damage stimuli, are either down-regulated, or inactivated, respectively, during MVM infection. This suggested that parvoviruses can modulate cell cycle progression by another mechanism. In this work we show that the MVM-induced, p21- and Chk1-independent, cell cycle block proceeds via a two-step process unlike that seen in response to other DNA-damaging agents or virus infections. MVM infection induced Chk2 activation early in infection which led to a transient S-phase block associated with proteasome-mediated CDC25A degradation. This step was necessary for efficient viral replication; however, Chk2 activation and CDC25A loss were not sufficient to keep infected cells in the sustained G2-arrested state which characterizes this infection. Rather, although the phosphorylation of CDK1 that normally inhibits entry into mitosis was lost, the MVM induced DDR resulted first in a targeted mis-localization and then significant depletion of cyclin B1, thus directly inhibiting cyclin B1-CDK1 complex function and preventing mitotic entry. MVM infection thus uses a novel strategy to ensure a pseudo S-phase, pre-mitotic, nuclear environment for sustained viral replication. PMID:24415942

Parvovirus-induced depletion of cyclin B1 prevents mitotic entry of infected cells.

PubMed

Adeyemi, Richard O; Pintel, David J

2014-01-01

Parvoviruses halt cell cycle progression following initiation of their replication during S-phase and continue to replicate their genomes for extended periods of time in arrested cells. The parvovirus minute virus of mice (MVM) induces a DNA damage response that is required for viral replication and induction of the S/G2 cell cycle block. However, p21 and Chk1, major effectors typically associated with S-phase and G2-phase cell cycle arrest in response to diverse DNA damage stimuli, are either down-regulated, or inactivated, respectively, during MVM infection. This suggested that parvoviruses can modulate cell cycle progression by another mechanism. In this work we show that the MVM-induced, p21- and Chk1-independent, cell cycle block proceeds via a two-step process unlike that seen in response to other DNA-damaging agents or virus infections. MVM infection induced Chk2 activation early in infection which led to a transient S-phase block associated with proteasome-mediated CDC25A degradation. This step was necessary for efficient viral replication; however, Chk2 activation and CDC25A loss were not sufficient to keep infected cells in the sustained G2-arrested state which characterizes this infection. Rather, although the phosphorylation of CDK1 that normally inhibits entry into mitosis was lost, the MVM induced DDR resulted first in a targeted mis-localization and then significant depletion of cyclin B1, thus directly inhibiting cyclin B1-CDK1 complex function and preventing mitotic entry. MVM infection thus uses a novel strategy to ensure a pseudo S-phase, pre-mitotic, nuclear environment for sustained viral replication.

Tubulin polymerization promoting protein 1 (Tppp1) phosphorylation by Rho-associated coiled-coil kinase (rock) and cyclin-dependent kinase 1 (Cdk1) inhibits microtubule dynamics to increase cell proliferation.

PubMed

Schofield, Alice V; Gamell, Cristina; Suryadinata, Randy; Sarcevic, Boris; Bernard, Ora

2013-03-15

Tubulin polymerization promoting protein 1 (Tppp1) regulates microtubule (MT) dynamics via promoting MT polymerization and inhibiting histone deacetylase 6 (Hdac6) activity to increase MT acetylation. Our results reveal that as a consequence, Tppp1 inhibits cell proliferation by delaying the G1/S-phase and the mitosis to G1-phase transitions. We show that phosphorylation of Tppp1 by Rho-associated coiled-coil kinase (Rock) prevents its Hdac6 inhibitory activity to enable cells to enter S-phase. Whereas, our analysis of the role of Tppp1 during mitosis revealed that inhibition of its MT polymerizing and Hdac6 regulatory activities were necessary for cells to re-enter the G1-phase. During this investigation, we also discovered that Tppp1 is a novel Cyclin B/Cdk1 (cyclin-dependent kinase) substrate and that Cdk phosphorylation of Tppp1 inhibits its MT polymerizing activity. Overall, our results show that dual Rock and Cdk phosphorylation of Tppp1 inhibits its regulation of the cell cycle to increase cell proliferation.

Putting one step before the other: distinct activation pathways for Cdk1 and Cdk2 bring order to the mammalian cell cycle

PubMed Central

Merrick, Karl A.; Fisher, Robert P.

2010-01-01

Eukaryotic cell division is controlled by the activity of cyclin-dependent kinases (CDKs). Cdk1 and Cdk2, which function at different stages of the mammalian cell cycle, both require cyclin-binding and phosphorylation of the activation (T-) loop for full activity, but differ with respect to the order in which the two steps occur in vivo. To form stable complexes with either of its partners—cyclins A and B—Cdk1 must be phosphorylated on its T-loop, but that phosphorylation in turn depends on the presence of cyclin. Cdk2 can follow a kinetically distinct path to activation in which T-loop phosphorylation precedes cyclin-binding, and thereby out-compete the more abundant Cdk1 for limiting amounts of cyclin A. Mathematical modeling suggests this could be a principal basis for the temporal ordering of CDK activation during S phase, which may dictate the sequence in which replication origins fire. Still to be determined are how: 1) the activation machinery discriminates between closely related CDKs, and 2) coordination of the cell cycle is affected when this mechanism of pathway insulation breaks down. PMID:20139727

Identification of Cyclin-dependent Kinase 1 Specific Phosphorylation Sites by an In Vitro Kinase Assay.

PubMed

Cui, Heying; Loftus, Kyle M; Noell, Crystal R; Solmaz, Sozanne R

2018-05-03

Cyclin-dependent kinase 1 (Cdk1) is a master controller for the cell cycle in all eukaryotes and phosphorylates an estimated 8 - 13% of the proteome; however, the number of identified targets for Cdk1, particularly in human cells is still low. The identification of Cdk1-specific phosphorylation sites is important, as they provide mechanistic insights into how Cdk1 controls the cell cycle. Cell cycle regulation is critical for faithful chromosome segregation, and defects in this complicated process lead to chromosomal aberrations and cancer. Here, we describe an in vitro kinase assay that is used to identify Cdk1-specific phosphorylation sites. In this assay, a purified protein is phosphorylated in vitro by commercially available human Cdk1/cyclin B. Successful phosphorylation is confirmed by SDS-PAGE, and phosphorylation sites are subsequently identified by mass spectrometry. We also describe purification protocols that yield highly pure and homogeneous protein preparations suitable for the kinase assay, and a binding assay for the functional verification of the identified phosphorylation sites, which probes the interaction between a classical nuclear localization signal (cNLS) and its nuclear transport receptor karyopherin α. To aid with experimental design, we review approaches for the prediction of Cdk1-specific phosphorylation sites from protein sequences. Together these protocols present a very powerful approach that yields Cdk1-specific phosphorylation sites and enables mechanistic studies into how Cdk1 controls the cell cycle. Since this method relies on purified proteins, it can be applied to any model organism and yields reliable results, especially when combined with cell functional studies.

Effect of berberine on cell cycle arrest and cell survival during cerebral ischemia and reperfusion and correlations with p53/cyclin D1 and PI3K/Akt.

PubMed

Chai, Yu-Shuang; Hu, Jun; Lei, Fan; Wang, Yu-Gang; Yuan, Zhi-Yi; Lu, Xi; Wang, Xin-Pei; Du, Feng; Zhang, Dong; Xing, Dong-Ming; Du, Li-Jun

2013-05-15

Berberine acted as a natural medicine with multiple pharmacological activities. In the present study, we examined the effect of berberine against cerebral ischemia damage from cell cycle arrest and cell survival. Oxygen-glucose deprivation of PC12 cells and primary neurons, and carotid artery ligation in mice were used as in vitro and in vivo cerebral ischemia models. We found that the effect of berberine on cell cycle arrest during ischemia was mediated by decreased p53 and cyclin D1, increased phosphorylation of Bad (higher expression of p-Bad and higher ratio of p-Bad to Bad) and decreased cleavage of caspase 3. Meanwhile, berberine activated the PI3K/Akt pathway during the reperfusion, especially the phosphor-activation of Akt, to promote the cell survival. The neural protective effect of berberine was remained in the presence of inhibitor of mitogen-activated protein/extracellular signal-regulated kinase (MEK), but was suppressed by the inhibitors of PI3K and Akt. We demonstrated that berberine induced cell cycle arrest and cell survival to resist cerebral ischemia injury. Copyright © 2013 Elsevier B.V. All rights reserved.

Cyclic phosphatidic acid induces G0/G1 arrest, inhibits AKT phosphorylation, and downregulates cyclin D1 expression in colorectal cancer cells.

PubMed

Tsukahara, Tamotsu; Haniu, Hisao; Matsuda, Yoshikazu

2015-03-01

Lysophosphatidic acid (LPA) and its analogs are well-known mitogens for various cell types. Many reports have confirmed that several types of cancer cell produce LPA to promote survival, growth and tumorigenesis. This indicates that the interface between the LPA signaling pathway and the cell cycle signaling system is critical to the control of cancer cell proliferation. However, our previous study indicated that cyclic phosphatidic acid (cPA), which is structurally similar to LPA, inhibits the proliferation and migration of colon cancer cells. It has been reported that cPA shows several biological activities not shown by LPA. However, understanding of the detailed molecular and cellular mechanism underlying the regulation of the cell cycle by cPA is still in its infancy. In this study, we investigated the effect of cPA treatment on human DLD-1 colon cancer cells by analyzing cell cycle dynamics, gene expression, and AKT phosphorylation. Our findings indicate that cPA inhibits cell cycle progression in DLD-1 colon cancer cells via the downregulation of cyclin D1 and the inhibition of AKT phosphorylation.

Berberine Induces Cell Cycle Arrest in Cholangiocarcinoma Cell Lines via Inhibition of NF-κB and STAT3 Pathways.

PubMed

Puthdee, Nattapong; Seubwai, Wunchana; Vaeteewoottacharn, Kulthida; Boonmars, Thidarut; Cha'on, Ubon; Phoomak, Chatchai; Wongkham, Sopit

2017-01-01

Berberine is a natural compound found in several herbs. Anticancer activity of berberine was reported in several cancers, however, little is known regarding the effects of berberine against cholangiocarcinoma (CCA). In this study, the growth inhibitory effects of berberine on CCA cell lines and its molecular mechanisms were explored. Cell growth and cell cycle distribution were examined by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and flow cytometry. The expression levels of cell cycle regulatory proteins were determined by Western blot analysis. Berberine significantly inhibited growth of CCA cell lines in a dose and time dependent fashion. The inhibition was largely attributed to cell cycle arrest at the G1 phase through the reduction of cyclin D1, and cyclin E. Moreover, berberine could reduce the expression and activation of signal transducers and activator of transcription 3 (STAT3) and probably nuclear factor-kappaB (NF-κB) via suppression of extracellular signal-regulated kinase (ERK) 1/2 action. These results highlight the potential of berberine to be a multi-target agent for CCA treatment.

MLL5, a trithorax homolog, indirectly regulates H3K4 methylation, represses cyclin A2 expression, and promotes myogenic differentiation

PubMed Central

Sebastian, Soji; Sreenivas, Prethish; Sambasivan, Ramkumar; Cheedipudi, Sirisha; Kandalla, Prashanth; Pavlath, Grace K.; Dhawan, Jyotsna

2009-01-01

Most cells in adult tissues are nondividing. In skeletal muscle, differentiated myofibers have exited the cell cycle permanently, whereas satellite stem cells withdraw transiently, returning to active proliferation to repair damaged myofibers. We have examined the epigenetic mechanisms operating in conditional quiescence by analyzing the function of a predicted chromatin regulator mixed lineage leukemia 5 (MLL5) in a culture model of reversible arrest. MLL5 is induced in quiescent myoblasts and regulates both the cell cycle and differentiation via a hierarchy of chromatin and transcriptional regulators. Knocking down MLL5 delays entry of quiescent myoblasts into S phase, but hastens S-phase completion. Cyclin A2 (CycA) mRNA is no longer restricted to S phase, but is induced throughout G0/G1, with activation of the cell cycle regulated element (CCRE) in the CycA promoter. Overexpressed MLL5 physically associates with the CCRE and impairs its activity. MLL5 also regulates CycA indirectly: Cux, an activator of CycA promoter and S phase is induced in RNAi cells, and Brm/Brg1, CCRE-binding repressors that promote differentiation are repressed. In knockdown cells, H3K4 methylation at the CCRE is reduced, reflecting quantitative global changes in methylation. MLL5 appears to lack intrinsic histone methyl transferase activity, but regulates expression of histone-modifying enzymes LSD1 and SET7/9, suggesting an indirect mechanism. Finally, expression of muscle regulators Pax7, Myf5, and myogenin is impaired in MLL5 knockdown cells, which are profoundly differentiation defective. Collectively, our results suggest that MLL5 plays an integral role in novel chromatin regulatory mechanisms that suppress inappropriate expression of S-phase-promoting genes and maintain expression of determination genes in quiescent cells. PMID:19264965

From Normalcy to Neoplasia. The Role of Epithelial-Stromal Interactions in Regulating Mammary Growth and Differentiation

DTIC Science & Technology

2000-08-01

through the cell Fantl V, Stamp G, Andrews A, Rosewell I, Dickson C. 1995. Mice cycle are able to die. The local concentrations of inhibi- lacking...Cyclin DI provides a link between development and oncogenesis in the retina and breast. Cell 82:621-630. 29. V. Fantl, G. Stamp, A. Andrews, I. Rosewell

Animal Models for Studying the In Vivo Functions of Cell Cycle CDKs.

PubMed

Risal, Sanjiv; Adhikari, Deepak; Liu, Kui

2016-01-01

Multiple Cdks (Cdk4, Cdk6, and Cdk2) and a mitotic Cdk (Cdk1) are involved in cell cycle progression in mammals. Cyclins, Cdk inhibitors, and phosphorylations (both activating and inhibitory) at different cellular levels tightly modulate the activities of these kinases. Based on the results of biochemical studies, it was long believed that different Cdks functioned at specific stages during cell cycle progression. However, deletion of all three interphase Cdks in mice affected cell cycle entry and progression only in certain specialized cells such as hematopoietic cells, beta cells of the pancreas, pituitary lactotrophs, and cardiomyocytes. These genetic experiments challenged the prevailing biochemical model and established that Cdks function in a cell-specific, but not a stage-specific, manner during cell cycle entry and the progression of mitosis. Recent in vivo studies have further established that Cdk1 is the only Cdk that is both essential and sufficient for driving the resumption of meiosis during mouse oocyte maturation. These genetic studies suggest a minimal-essential cell cycle model in which Cdk1 is the central regulator of cell cycle progression. Cdk1 can compensate for the loss of the interphase Cdks by forming active complexes with A-, B-, E-, and D-type Cyclins in a stepwise manner. Thus, Cdk1 plays an essential role in both mitosis and meiosis in mammals, whereas interphase Cdks are dispensable.

Cell Type-Specific Gene Expression Analyses by RNA Sequencing Reveal Local High Nitrate-Triggered Lateral Root Initiation in Shoot-Borne Roots of Maize by Modulating Auxin-Related Cell Cycle Regulation1[OPEN

PubMed Central

Yu, Peng; Eggert, Kai; von Wirén, Nicolaus; Li, Chunjian; Hochholdinger, Frank

2015-01-01

Plants have evolved a unique plasticity of their root system architecture to flexibly exploit heterogeneously distributed mineral elements from soil. Local high concentrations of nitrate trigger lateral root initiation in adult shoot-borne roots of maize (Zea mays) by increasing the frequency of early divisions of phloem pole pericycle cells. Gene expression profiling revealed that, within 12 h of local high nitrate induction, cell cycle activators (cyclin-dependent kinases and cyclin B) were up-regulated, whereas repressors (Kip-related proteins) were down-regulated in the pericycle of shoot-borne roots. In parallel, a ubiquitin protein ligase S-Phase Kinase-Associated Protein1-cullin-F-box proteinS-Phase Kinase-Associated Protein 2B-related proteasome pathway participated in cell cycle control. The division of pericycle cells was preceded by increased levels of free indole-3-acetic acid in the stele, resulting in DR5-red fluorescent protein-marked auxin response maxima at the phloem poles. Moreover, laser-capture microdissection-based gene expression analyses indicated that, at the same time, a significant local high nitrate induction of the monocot-specific PIN-FORMED9 gene in phloem pole cells modulated auxin efflux to pericycle cells. Time-dependent gene expression analysis further indicated that local high nitrate availability resulted in PIN-FORMED9-mediated auxin efflux and subsequent cell cycle activation, which culminated in the initiation of lateral root primordia. This study provides unique insights into how adult maize roots translate information on heterogeneous nutrient availability into targeted root developmental responses. PMID:26198256

Silkworm Pupa Protein Hydrolysate Induces Mitochondria-Dependent Apoptosis and S Phase Cell Cycle Arrest in Human Gastric Cancer SGC-7901 Cells.

PubMed

Li, Xiaotong; Xie, Hongqing; Chen, Yajie; Lang, Mingzi; Chen, Yuyin; Shi, Liangen

2018-03-28

Silkworm pupae ( Bombyx mori ) are a high-protein nutrition source consumed in China since more than 2 thousand years ago. Recent studies revealed that silkworm pupae have therapeutic benefits to treat many diseases. However, the ability of the compounds of silkworm pupae to inhibit tumourigenesis remains to be elucidated. Here, we separated the protein of silkworm pupae and performed alcalase hydrolysis. Silkworm pupa protein hydrolysate (SPPH) can specifically inhibit the proliferation and provoke abnormal morphologic features of human gastric cancer cells SGC-7901 in a dose- and time-dependent manner. Moreover, flow cytometry indicated that SPPH can induce apoptosis and arrest the cell-cycle in S phase. Furthermore, SPPH was shown to provoke accumulation of reactive oxygen species (ROS) and depolarization of mitochondrial membrane potential. Western blotting analysis indicated that SPPH inhibited Bcl-2 expression and promoted Bax expression, and subsequently induced apoptosis-inducing factor and cytochrome C release, which led to the activation of initiator caspase-9 and executioner caspase-3, cleavage of poly (ADP-ribose) polymerase (PARP), eventually caused cell apoptosis. Moreover, SPPH-induced S-phase arrest was mediated by up-regulating the expression of E2F1 and down-regulating those of cyclin E, CDK2 and cyclin A2. Transcriptome sequencing and gene set enrichment analysis (GSEA) also revealed that SPPH treatment could affect gene expression and pathway regulation related to tumourigenesis, apoptosis and cell cycle. In summary, our results suggest that SPPH could specifically suppress cell growth of SGC-7901 through an intrinsic apoptotic pathway, ROS accumulation and cell cycle arrest, and silkworm pupae have a potential to become a source of anticancer agents in the future.

A single cyclin–CDK complex is sufficient for both mitotic and meiotic progression in fission yeast

PubMed Central

Gutiérrez-Escribano, Pilar; Nurse, Paul

2015-01-01

The dominant model for eukaryotic cell cycle control proposes that cell cycle progression is driven by a succession of CDK complexes with different substrate specificities. However, in fission yeast it has been shown that a single CDK complex generated by the fusion of the Cdc13 cyclin with the CDK protein Cdc2 can drive the mitotic cell cycle. Meiosis is a modified cell cycle programme in which a single S-phase is followed by two consecutive rounds of chromosome segregation. Here we systematically analyse the requirements of the different fission yeast cyclins for meiotic cell cycle progression. We also show that a single Cdc13–Cdc2 complex, in the absence of the other cyclins, can drive the meiotic cell cycle. We propose that qualitatively different CDK complexes are not absolutely required for cell cycle progression either during mitosis or meiosis, and that a single CDK complex can drive both cell cycle programmes. PMID:25891897

Up-Regulation of Long Noncoding RNA SRA Promotes Cell Growth, Inhibits Cell Apoptosis, and Induces Secretion of Estradiol and Progesterone in Ovarian Granular Cells of Mice.

PubMed

Li, Yan; Wang, Haixu; Zhou, Dangxia; Shuang, Ting; Zhao, Haibo; Chen, Biliang

2018-04-20

BACKGROUND Increasing evidence indicates that long noncoding RNAs (LncRNAs) play a key role in multiple pathological processes. It has been shown that LncRNA steroid receptor RNA activator (SRA) is elevated in peripheral blood of patients with polycystic ovary syndrome (PCOS). The aim of this study was to assess the effect of elevated LncRNA SRA on ovarian granular cells of mice in vitro. MATERIAL AND METHODS We firstly isolated granular cells from mouse ovaries and over-expressed the LncRNA SRA by means of lentiviral transfection in this cell line. Then, we assessed the effects of LncRNA SRA on granular cells through real-time PCR, CCK-8 assay, flow cytometry, Hoechst staining, and Western blot assay. RESULTS We demonstrated that elevated LncRNA SRA stimulated cell growth, changed distribution of cell cycle phases with increase of Cyclin B, Cyclin E, and Cyclin D1, and inhibited cell apoptosis with up-regulation of bcl2 and down-regulation of bax, cleaved-caspase 3, and cleaved-PARP. Moreover, the contents of estradiol (E2) and progesterone (PG) and expressions of their key enzymes (CYP19A1 and CYP11A1) were up-regulated following over-expression of LncRNA SRA. CONCLUSIONS Taken together, our results indicate that abnormal LncRNA SRA may be a risk factor for evoking PCOS.

Repair of oxidative DNA damage, cell-cycle regulation and neuronal death may influence the clinical manifestation of Alzheimer's disease.

PubMed

Silva, Aderbal R T; Santos, Ana Cecília Feio; Farfel, Jose M; Grinberg, Lea T; Ferretti, Renata E L; Campos, Antonio Hugo Jose Froes Marques; Cunha, Isabela Werneck; Begnami, Maria Dirlei; Rocha, Rafael M; Carraro, Dirce M; de Bragança Pereira, Carlos Alberto; Jacob-Filho, Wilson; Brentani, Helena

2014-01-01

Alzheimer's disease (AD) is characterized by progressive cognitive decline associated with a featured neuropathology (neuritic plaques and neurofibrillary tangles). Several studies have implicated oxidative damage to DNA, DNA repair, and altered cell-cycle regulation in addition to cell death in AD post-mitotic neurons. However, there is a lack of studies that systematically assess those biological processes in patients with AD neuropathology but with no evidence of cognitive impairment. We evaluated markers of oxidative DNA damage (8-OHdG, H2AX), DNA repair (p53, BRCA1, PTEN), and cell-cycle (Cdk1, Cdk4, Cdk5, Cyclin B1, Cyclin D1, p27Kip1, phospho-Rb and E2F1) through immunohistochemistry and cell death through TUNEL in autopsy hippocampal tissue samples arrayed in a tissue microarray (TMA) composed of three groups: I) "clinical-pathological AD" (CP-AD)--subjects with neuropathological AD (Braak ≥ IV and CERAD = B or C) and clinical dementia (CDR ≥ 2, IQCODE>3.8); II) "pathological AD" (P-AD)--subjects with neuropathological AD (Braak ≥ IV and CERAD = B or C) and without cognitive impairment (CDR 0, IQCODE<3.2); and III) "normal aging" (N)--subjects without neuropathological AD (Braak ≤ II and CERAD 0 or A) and with normal cognitive function (CDR 0, IQCODE<3.2). Our results show that high levels of oxidative DNA damage are present in all groups. However, significant reductions in DNA repair and cell-cycle inhibition markers and increases in cell-cycle progression and cell death markers in subjects with CP-AD were detected when compared to both P-AD and N groups, whereas there were no significant differences in the studied markers between P-AD individuals and N subjects. This study indicates that, even in the setting of pathological AD, healthy cognition may be associated with a preserved repair to DNA damage, cell-cycle regulation, and cell death in post-mitotic neurons.

Whether to target single or multiple CDKs for therapy? That is the question.

PubMed

Węsierska-Gądek, Józefa; Maurer, Margarita; Zulehner, Nora; Komina, Oxana

2011-02-01

Complexes consisting of cyclin-dependent kinases (CDKs) and their regulatory subunits (the cyclins) control the progression of normal mammalian cells through the cell cycle. However, during malignant transformation this regulatory apparatus malfunctions, allowing cells to undergo unchecked proliferation. In many cases, the high mitotic potential of malignant cells is due to the constitutive activation of CDK-cyclin complexes, facilitated by the inactivation of cellular CDK inhibitors, such as p16(INK4A) or p27(Kip1), and the loss of functional tumor suppressors, such as the p53 and pRb proteins. It has recently been suggested that pharmacological intervention based on remedying the deficiency or loss of activity of these negative regulators of the cell cycle could be a very effective therapeutic option in the treatment of cancer. Multiple CDK inhibitors have been synthesized over the last two decades, spanning at least five classes of compounds. While these inhibitors can be classified on the basis of their chemical structure, it may be more interesting to categorize them according to their pharmacological nature, as broad-spectrum unspecific, pan-specific, or very selective antagonists. This review offers a critical assessment of the advantages and disadvantages of both pan-specific and highly selective CDK inhibitors in therapy. © 2010 Wiley-Liss, Inc.

PAC exhibits potent anti-colon cancer properties through targeting cyclin D1 and suppressing epithelial-to-mesenchymal transition.

PubMed

Al-Qasem, Abeer; Al-Howail, Huda A; Al-Swailem, Mashael; Al-Mazrou, Amer; Al-Otaibi, Basem; Al-Jammaz, Ibrahim; Al-Khalaf, Huda H; Aboussekhra, Abdelilah

2016-03-01

Colorectal cancer (CRC) is a major cause of cancer morbidity and mortality worldwide. Although response rates and overall survival have been improved in recent years, resistance to multiple drug combinations is inevitable. Therefore, the development of more efficient drugs, with fewer side effects is urgently needed. To this end, we have investigated in the present report the effect of PAC, a novel cucumin analogue, on CRC cells both in vitro and in vivo. We have shown that PAC induces apoptosis, mainly via the internal mitochondrial route, and inhibits cell proliferation through delaying the cell cycle at G2/M phase. Interestingly, the pro-apoptotic effect was mediated through STAT3-dependent down-regulation of cyclin D1 and its downstream target survivin. Indeed, change in the expression level of cyclin D1 modulated the expression of survivin and the response of CRC cells to PAC. Furthermore, using the ChIP assay, we have shown PAC-dependent reduction in the binding of STAT3 to the cyclin D1 promoter in vivo. Additionally, PAC suppressed the epithelial-to-mesenchymal process through down-regulating the mesenchymal markers (N-cadherin, vimentin and Twist1) and inhibiting the invasion/migration abilities of the CRC cells via repressing the pro-migration/invasion protein kinases AKT and ERK1/2. In addition, PAC inhibited tumor growth and repressed the JAK2/STAT3, AKT/mTOR and MEK/ERK pathways as well as their common downstream effectors cyclin D1 and survivin in humanized CRC xenografts. Collectively, these results indicate that PAC has potent anti-CRC effects, and therefore could constitute an effective alternative chemotherapeutic agent, which may consolidate the adjuvant treatment of colon cancer. © 2015 Wiley Periodicals, Inc.

Cyclin-Dependent Kinase Inhibitors for the Treatment of Breast Cancer: Past, Present, and Future.

PubMed

DiPippo, Adam J; Patel, Neelam K; Barnett, Chad M

2016-06-01

Treatment of metastatic breast cancer (MBC) that is resistant to endocrine therapy presents a significant clinical challenge. The well-known role of cell cycle dysregulation in these patients is partly mediated by cyclin-dependent kinase (CDK) activity. Specific cyclin and CDK complexes regulate cell cycle progression by managing the transition through the cell cycle, and inhibition of CDKs represents an important target for novel agents. First-generation CDK inhibitors (e.g., flavopiridol) were relatively nonselective and had an unacceptable toxicity profile in early trials. Second-generation CDK inhibitors were designed to target the CDK4 and CDK6 (CDK4/6) pathway and have shown promising clinical activity with an acceptable toxicity profile in patients with MBC. Palbociclib is a first-in-class CDK4/6 inhibitor that was granted accelerated U.S. Food and Drug Administration approval in combination with letrozole for the treatment of MBC in the first-line setting (February 2015) as well as in combination with fulvestrant for MBC that had progressed on previous endocrine therapy (February 2016). Other CDK4/6 inhibitors, including ribociclib and abemaciclib, are under investigation as monotherapy and in combination with endocrine or anti-human epidermal growth receptor 2 therapy for the treatment of MBC. Ongoing clinical trials should provide additional information to guide the appropriate use of these agents and identify patient populations that could derive the most benefit. © 2016 Pharmacotherapy Publications, Inc.

Intact follicular maturation and defective luteal function in mice deficient for cyclin- dependent kinase-4.

PubMed

Moons, David S; Jirawatnotai, Siwanon; Tsutsui, Tateki; Franks, Roberta; Parlow, A F; Hales, Dale B; Gibori, Geula; Fazleabas, Asgerally T; Kiyokawa, Hiroaki

2002-02-01

Cell cycle progression of granulosa cells is critical for ovarian function, especially follicular maturation. During follicular maturation, FSH induces cyclin D2, which promotes G1 progression by activating cyclin-dependent kinase-4 (Cdk4). Because cyclin D2-deficient mice exhibit a block in follicular growth, cyclin D2/Cdk4 has been hypothesized to be required for FSH-dependent proliferation of granulosa cells. Here we investigate ovarian function in Cdk4-knockout mice we recently generated. Cdk4(-/-) females were sterile, but the morphology of their ovaries appeared normal before sexual maturation. The number of preovulatory follicles and the ovulation efficiency were modestly reduced in gonadotropin-treated Cdk4(-/-) mice. However, unlike cyclin D2-deficient mice, Cdk4(-/-) mice showed no obvious defect in FSH-induced proliferation of granulosa cells. Cdk4(-/-) ovaries displayed normal preovulatory expression of aromatase, PR, and cyclooxygenase-2. Postovulatory progesterone secretion was markedly impaired in Cdk4(-/-) mice, although granulosa cells initiated luteinization with induction of p450 side-chain cleavage cytochrome and p27(Kip1). Progesterone treatment rescued implantation and restored fertility in Cdk4(-/-) mice. Serum PRL levels after mating were significantly reduced in Cdk4(-/-) mice, suggesting the involvement of perturbed PRL regulation in luteal failure. Thus, Cdk4 is critical for luteal function, and some redundant protein(s) can compensate for the absence of Cdk4 in proliferation of granulosa cells.

Differential response of cell-cycle and cell-expansion regulators to heat stress in apple (Malus domestica) fruitlets.

PubMed

Flaishman, Moshe A; Peles, Yuval; Dahan, Yardena; Milo-Cochavi, Shira; Frieman, Aviad; Naor, Amos

2015-04-01

Temperature is one of the most significant factors affecting physiological and biochemical aspects of fruit development. Current and progressing global warming is expected to change climate in the traditional deciduous fruit tree cultivation regions. In this study, 'Golden Delicious' trees, grown in a controlled environment or commercial orchard, were exposed to different periods of heat treatment. Early fruitlet development was documented by evaluating cell number, cell size and fruit diameter for 5-70 days after full bloom. Normal activities of molecular developmental and growth processes in apple fruitlets were disrupted under daytime air temperatures of 29°C and higher as a result of significant temporary declines in cell-production and cell-expansion rates, respectively. Expression screening of selected cell cycle and cell expansion genes revealed the influence of high temperature on genetic regulation of apple fruitlet development. Several core cell-cycle and cell-expansion genes were differentially expressed under high temperatures. While expression levels of B-type cyclin-dependent kinases and A- and B-type cyclins declined moderately in response to elevated temperatures, expression of several cell-cycle inhibitors, such as Mdwee1, Mdrbr and Mdkrps was sharply enhanced as the temperature rose, blocking the cell-cycle cascade at the G1/S and G2/M transition points. Moreover, expression of several expansin genes was associated with high temperatures, making them potentially useful as molecular platforms to enhance cell-expansion processes under high-temperature regimes. Understanding the molecular mechanisms of heat tolerance associated with genes controlling cell cycle and cell expansion may lead to the development of novel strategies for improving apple fruit productivity under global warming. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

TORC1 and class I HDAC inhibitors synergize to suppress mature B cell neoplasms.

PubMed

Simmons, John K; Patel, Jyoti; Michalowski, Aleksandra; Zhang, Shuling; Wei, Bih-Rong; Sullivan, Patrick; Gamache, Ben; Felsenstein, Kenneth; Kuehl, W Michael; Simpson, R Mark; Zingone, Adriana; Landgren, Ola; Mock, Beverly A

2014-03-01

Enhanced proliferative signaling and loss of cell cycle regulation are essential for cancer progression. Increased mitogenic signaling through activation of the mTOR pathway, coupled with deregulation of the Cyclin D/retinoblastoma (Rb) pathway is a common feature of lymphoid malignancies, including plasmacytoma (PCT), multiple myeloma (MM), Burkitt's lymphoma (BL), and mantle cell lymphoma (MCL). Here we evaluate the synergy of pharmacologically affecting both of these critical pathways using the mTOR inhibitor sirolimus and the histone deacetylase inhibitor entinostat. A dose-matrix screening approach found this combination to be highly active and synergistic in a panel of genetically diverse human MM cell lines. Synergy and activity was observed in mouse PCT and human BL and MCL cell lines tested in vitro, as well as in freshly isolated primary MM patient samples tested ex vivo. This combination had minimal effects on healthy donor cells and retained activity when tested in a co-culture system simulating the protective interaction of cancer cells with the tumor microenvironment. Combining sirolimus with entinostat enhanced cell cycle arrest and apoptosis. At the molecular level, entinostat increased the expression of cell cycle negative regulators including CDKN1A (p21) and CDKN2A (p16), while the combination decreased critical growth and survival effectors including Cyclin D, BCL-XL, BIRC5, and activated MAPK. Published by Elsevier B.V.

A novel pyrazolo[1,5-a]pyrimidine is a potent inhibitor of cyclin-dependent protein kinases 1, 2, and 9, which demonstrates antitumor effects in human tumor xenografts following oral administration.

PubMed

Heathcote, Dean A; Patel, Hetal; Kroll, Sebastian H B; Hazel, Pascale; Periyasamy, Manikandan; Alikian, Mary; Kanneganti, Seshu K; Jogalekar, Ashutosh S; Scheiper, Bodo; Barbazanges, Marion; Blum, Andreas; Brackow, Jan; Siwicka, Alekasandra; Pace, Robert D M; Fuchter, Matthew J; Snyder, James P; Liotta, Dennis C; Freemont, Paul S; Aboagye, Eric O; Coombes, R Charles; Barrett, Anthony G M; Ali, Simak

2010-12-23

Cyclin-dependent protein kinases (CDKs) are central to the appropriate regulation of cell proliferation, apoptosis, and gene expression. Abnormalities in CDK activity and regulation are common features of cancer, making CDK family members attractive targets for the development of anticancer drugs. Here, we report the identification of a pyrazolo[1,5-a]pyrimidine derived compound, 4k (BS-194), as a selective and potent CDK inhibitor, which inhibits CDK2, CDK1, CDK5, CDK7, and CDK9 (IC₅₀= 3, 30, 30, 250, and 90 nmol/L, respectively). Cell-based studies showed inhibition of the phosphorylation of CDK substrates, Rb and the RNA polymerase II C-terminal domain, down-regulation of cyclins A, E, and D1, and cell cycle block in the S and G₂/M phases. Consistent with these findings, 4k demonstrated potent antiproliferative activity in 60 cancer cell lines tested (mean GI₅₀= 280 nmol/L). Pharmacokinetic studies showed that 4k is orally bioavailable, with an elimination half-life of 178 min following oral dosing in mice. When administered at a concentration of 25 mg/kg orally, 4k inhibited human tumor xenografts and suppressed CDK substrate phosphorylation. These findings identify 4k as a novel, potent CDK selective inhibitor with potential for oral delivery in cancer patients.

Ubiquitylation and proteasomal degradation of the p21(Cip1), p27(Kip1) and p57(Kip2) CDK inhibitors.

PubMed

Lu, Zhimin; Hunter, Tony

2010-06-15

The expression levels of the p21(Cip1) family CDK inhibitors (CKIs), p21(Cip1), p27(Kip1) and p57(Kip2), play a pivotal role in the precise regulation of cyclin-dependent kinase (CDK) activity, which is instrumental to proper cell cycle progression. The stabilities of p21(Cip1), p27(Kip1) and p57(Kip2) are all tightly and differentially regulated by ubiquitylation and proteasome-mediated degradation during various stages of the cell cycle, either in steady state or in response to extracellular stimuli, which often elicit site-specific phosphorylation of CKIs triggering their degradation.

Cut2 proteolysis required for sister-chromatid seperation in fission yeast.

PubMed

Funabiki, H; Yamano, H; Kumada, K; Nagao, K; Hunt, T; Yanagida, M

1996-05-30

Although mitotic cyclins are well-known substrates for ubiquitin-mediated proteolysis at the metaphase-anaphase transition, their degradation is not essential for separation of sister chromatids; several lines of evidence suggest that proteolysis of other protein(s) is required, however. Here we report the anaphase-specific proteolysis of the Schizosaccharomyces pombe Cut2 protein, which is essential for sister-chromatid separation. Cut2 is located in the nucleus, where it is concentrated along the short metaphase spindle. The rapid degradation of Cut2 at anaphase requires its amino-terminal region and the activity of Cut9 (ref. 14), a component of the 20S cyclosome/anaphase-promoting complex (APC), which is necessary for cyclin destruction. Expression of non-degradable Cut2 blocks sister-chromatid separation but not cell-cycle progression. This defect can be overcome by grafting the N terminus of cyclin B onto the truncated Cut2, demonstrating that the regulated proteolysis of Cut2 is essential for sister-chromatid separation.

Inhibition of CDC25B Phosphatase Through Disruption of Protein–Protein Interaction

DOE PAGES

Lund, George; Dudkin, Sergii; Borkin, Dmitry; ...

2014-11-25

CDC25 phosphatases are key cell cycle regulators and represent very attractive but challenging targets for anticancer drug discovery. Here in this paper, we explored whether fragment-based screening represents a valid approach to identify inhibitors of CDC25B. This resulted in identification of 2-fluoro-4-hydroxybenzonitrile, which directly binds to the catalytic domain of CDC25B. Interestingly, NMR data and the crystal structure demonstrate that this compound binds to the pocket distant from the active site and adjacent to the protein–protein interaction interface with CDK2/Cyclin A substrate. Furthermore, we developed a more potent analogue that disrupts CDC25B interaction with CDK2/Cyclin A and inhibits dephosphorylation ofmore » CDK2. Based on these studies, we provide a proof of concept that targeting CDC25 phosphatases by inhibiting their protein–protein interactions with CDK2/Cyclin A substrate represents a novel, viable opportunity to target this important class of enzymes.« less

Anti-tumor effect of emodin on gynecological cancer cells.

PubMed

Wang, Yaoxian; Yu, Hui; Zhang, Jin; Ge, Xin; Gao, Jing; Zhang, Yunyan; Lou, Ge

2015-10-01

Although an anti-tumor effect of emodin has been reported before, its effect on human gynecological cancer cells has so far not been studied. Here, we assessed the effect of emodin on cervical cancer-derived (Hela), choriocarcinoma-derived (JAR) and ovarian cancer-derived (HO-8910) cells, and investigated the possible underlying molecular and cellular mechanisms. The respective cells were treated with 0, 5, 10 or 15 μM emodin for 72 h. Subsequently, MTT and Transwell in vitro migration assays revealed that emodin significantly decreased the viability and invasive capacity of the gynecological cancer-derived cells tested. We found that emodin induced apoptosis and significantly decreased mitochondrial membrane potential and ATP release in these cells. We also found that emodin may exert its apoptotic effects via regulating the activity of caspase-9 and the expression of cleaved-caspase-3. Moreover, we found that emodin induced a cell cycle arrest at the G0/G1 phase, possibly through down-regulating the key cell cycle regulators Cyclin D and Cyclin E. Interestingly, emodin also led to autophagic cell death, as revealed by increased MAP LC3 expression, a marker of the autophagosome, and decreased expression of the autophagy regulators Beclin-1 and Atg12-Atg5. Finally, we found that the protein levels of both VEGF and VEGFR-2 were significantly decreased in emodin-treated cells, suggesting an anti-angiogenic effect of emodin on gynecological cancer-derived cells. Our results suggest that emodin exhibits an anti-tumor effect on gynecological cancer-derived cells, possibly through multiple mechanisms including the induction of apoptosis and autophagy, the arrest of the cell cycle, and the inhibition of angiogenesis. Our findings may provide a basis for the design of potential emodin-based strategies for the treatment of gynecological tumors.

Probing the Role of Nascent Helicity in p27 Function as a Cell Cycle Regulator

PubMed Central

Otieno, Steve; Kriwacki, Richard

2012-01-01

p27 regulates the activity of Cdk complexes which are the principal governors of phase transitions during cell division. Members of the p27 family of proteins, which also includes p21 and p57, are called the Cip/Kip cyclin-dependent kinase regulators (CKRs). Interestingly, the Cip/Kip CKRs play critical roles in cell cycle regulation by being intrinsically unstructured, a characteristic contrary to the classical structure-function paradigm. They exhibit nascent helicity which has been localized to a segment referred to as sub-domain LH. The nascent helicity of this sub-domain is conserved and we hypothesize that it is an important determinant of their functional properties. To test this hypothesis, we successfully designed and prepared p27 variants in which domain LH was either more or less helical with respect to the wild-type protein. Thermal denaturation experiments showed that the ternary complexes of the p27 variants bound to Cdk2/Cyclin A were less stable compared to the wild-type complex. Isothermal titration calorimetry experiments showed a decrease in the enthalpy of binding for all the mutants with respect to p27. The free energies of binding varied within a much narrower range. In vitro Cdk2 inhibition assays showed that the p27 variants exhibited disparate inhibitory potencies. Furthermore, when over-expressed in NIH 3T3 mouse fibroblast cells, the less helical p27 variants were less effective in causing cell cycle arrest relative to the wild-type p27. Our results indicate that the nascent helicity of sub-domain LH plays a key role mediating the biological function of p27. PMID:23071750

The MO15 cell cycle kinase is associated with the TFIIH transcription-DNA repair factor.

PubMed

Roy, R; Adamczewski, J P; Seroz, T; Vermeulen, W; Tassan, J P; Schaeffer, L; Nigg, E A; Hoeijmakers, J H; Egly, J M

1994-12-16

A protein kinase activity that phosphorylates the C-terminal domain (CTD) of RNA polymerase II and is associated with the basal transcription-repair factor TFIIH (also called BTF2) resides with MO15, a cyclin-dependent protein kinase that was first found to be involved in cell cycle regulation. Using in vivo and in vitro repair assays, we show that MO15 is important for nucleotide excision repair, most likely through its association with TFIIH, thus providing an unexpected link among three important cellular mechanisms.

Pirfenidone Induces G1 Arrest in Human Tenon's Fibroblasts In Vitro Involving AKT and MAPK Signaling Pathways.

PubMed

Guo, Xiujuan; Yang, Yangfan; Liu, Liling; Liu, Xiaoan; Xu, Jiangang; Wu, Kaili; Yu, Minbin

2017-06-01

To investigate the underlying mechanism by which pirfenidone blocks the transition from the G1 to S phase in primary human Tenon's fibroblasts. Primary human Tenon's fibroblasts were characterized by immunocytofluorescence staining with vimentin, fibroblast surface protein, and cytokeratin. After treating Tenon's fibroblasts with pirfenidone under proliferation conditions (10% fetal bovine serum), cell proliferation was measured using a WST-1 assay. Progression through the cell cycle was analyzed by flow cytometry. The expression of CDK2, CDK6, cyclinD1, cyclinD3, and cyclinE and the phosphorylation of AKT, ERK1/2/MAPK, JNK/MAPK, and p38 MAPK were estimated using western blot analysis. Under proliferative conditions, pirfenidone inhibited Tenon's fibroblasts proliferation and arrested the cell cycle at the G1 phase; decreased the phosphorylation of AKT, GSK3β, ERK1/2/MAPK, and JNK/MAPK; increased the phosphorylation of p38 MAPK; and inhibited CDK2, CDK6, cyclin D1, cyclin D3, and cyclin E in a dose-dependent manner. Inhibitors of AKT (LY294002), ERK1/2 (U0126), and JNK (SP600125) arrested the G1/S transition, similar to the effect of pirfenidone. The p38 inhibitor (SB202190) decreased the G1-blocking effect of pirfenidone. The expression of CDK2, CDK6, cyclin D1, and cyclin D3 were inhibited by LY294002, U0126, and SP600125. SB202190 attenuated the pirfenidone-induced reduction of CDK2, CDK6, cyclin D1, cyclin D3, and cyclin E. Pirfenidone inhibited HTFs proliferation and induced G1 arrest by downregulating CDKs and cyclins involving the AKT/GSK3β and MAPK signaling pathways.

Modulatory effect of phytoglycoprotein (38 kDa) on cyclin D1/CDK4 in BNL CL.2 cells induced by N-methyl-N'-nitro-N-nitrosoguanidine.

PubMed

Lee, Jin; Lim, Kye-Taek

2012-02-01

In the developmental stages of cancer, cell transformation occurs after the promotion stage and is a marker of cancer progression. This cell transformation is related to abnormal proliferation during the cancer initiation stage. The purpose of this study was to evaluate the effect of Styrax japonica Siebold et al. Zuccarin (SJSZ) glycoprotein on cell transformation in murine embryonic liver cells (BNL CL.2) following N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) treatment. To determine abnormal proliferation during the initiation stage, intracellular reactive oxygen species (ROS), phosphorylation of extracellular signal-regulated kinase (ERK), p38 mitogen-activated protein kinase (MAPK), activities of cell cycle-related factors [cyclin D1/cyclin dependent kinase (CDK) 4], cell cycle inhibitors (p53, p21, and p27), nuclear factor (NF)-κB, and proliferating cell nuclear antigen (PCNA) were evaluated using Western blot analysis and real-time PCR. Our study demonstrated that SJSZ glycoprotein (50 μg/ml) reduces foci formation with combined treatment [MNNG and 12-O-tetradecanoyl phorbol-13-acetate] of BNL CL.2 cells. With regard to proliferation-related signals, our finding indicated that SJSZ glycoprotein (50 μg/ml) diminished the production of intracellular ROS, activity of phosphorylated ERK, p38 MAPK, NF-κB (p50 and p65), PCNA, and cyclin D1/CDK4 in MNNG-induced BNL CL.2 cells. Taken together, these results lead us to speculate that SJSZ glycoprotein can inhibit abnormal cell proliferation at the initiation stage of hepatocarcinogenesis.

Global increase in replication fork speed during a p57KIP2-regulated erythroid cell fate switch

PubMed Central

Hwang, Yung; Futran, Melinda; Hidalgo, Daniel; Pop, Ramona; Iyer, Divya Ramalingam; Scully, Ralph; Rhind, Nicholas; Socolovsky, Merav

2017-01-01

Cell cycle regulators are increasingly implicated in cell fate decisions, such as the acquisition or loss of pluripotency and self-renewal potential. The cell cycle mechanisms that regulate these cell fate decisions are largely unknown. We studied an S phase–dependent cell fate switch, in which murine early erythroid progenitors transition in vivo from a self-renewal state into a phase of active erythroid gene transcription and concurrent maturational cell divisions. We found that progenitors are dependent on p57KIP2-mediated slowing of replication forks for self-renewal, a novel function for cyclin-dependent kinase inhibitors. The switch to differentiation entails rapid down-regulation of p57KIP2 with a consequent global increase in replication fork speed and an abruptly shorter S phase. Our work suggests that cell cycles with specialized global DNA replication dynamics are integral to the maintenance of specific cell states and to cell fate decisions. PMID:28560351

Cdk1 activity acts as a quantitative platform for coordinating cell cycle progression with periodic transcription

PubMed Central

Banyai, Gabor; Baïdi, Feriel; Coudreuse, Damien; Szilagyi, Zsolt

2016-01-01

Cell proliferation is regulated by cyclin-dependent kinases (Cdks) and requires the periodic expression of particular gene clusters in different cell cycle phases. However, the interplay between the networks that generate these transcriptional oscillations and the core cell cycle machinery remains largely unexplored. In this work, we use a synthetic regulable Cdk1 module to demonstrate that periodic expression is governed by quantitative changes in Cdk1 activity, with different clusters directly responding to specific activity levels. We further establish that cell cycle events neither participate in nor interfere with the Cdk1-driven transcriptional program, provided that cells are exposed to the appropriate Cdk1 activities. These findings contrast with current models that propose self-sustained and Cdk1-independent transcriptional oscillations. Our work therefore supports a model in which Cdk1 activity serves as a quantitative platform for coordinating cell cycle transitions with the expression of critical genes to bring about proper cell cycle progression. PMID:27045731

Sepsis reveals compartment-specific responses in intestinal proliferation and apoptosis in transgenic mice whose enterocytes re-enter the cell cycle.

PubMed

Lyons, John D; Klingensmith, Nathan J; Otani, Shunsuke; Mittal, Rohit; Liang, Zhe; Ford, Mandy L; Coopersmith, Craig M

2017-12-01

Cell production and death are tightly regulated in the rapidly renewing gut epithelium, with proliferation confined to crypts and apoptosis occurring in villi and crypts. This study sought to determine how stress alters these compartmentalized processes. Wild-type mice made septic via cecal ligation and puncture had decreased crypt proliferation and increased crypt and villus apoptosis. Fabpi -TAg mice expressing large T-antigen solely in villi had ectopic enterocyte proliferation with increased villus apoptosis in unmanipulated animals. Septic fabpi -TAg mice had an unexpected increase in villus proliferation compared with unmanipulated littermates, whereas crypt proliferation was decreased. Cell cycle regulators cyclin D1 and cyclin D2 were decreased in jejunal tissue in septic transgenic mice. In contrast, villus and crypt apoptosis were increased in septic fabpi -TAg mice. To examine the relationship between apoptosis and proliferation in a compartment-specific manner, fabpi -TAg mice were crossed with fabpl -Bcl-2 mice, resulting in expression of both genes in the villus but Bcl-2 alone in the crypt. Septic bi-transgenic animals had decreased crypt apoptosis but had a paradoxical increase in villus apoptosis compared with septic fabpi -TAg mice, associated with decreased proliferation in both compartments. Thus, sepsis unmasks compartment-specific proliferative and apoptotic regulation that is not present under homeostatic conditions.-Lyons, J. D., Klingensmith, N. J., Otani, S., Mittal, R., Liang, Z., Ford, M. L., Coopersmith, C. M. Sepsis reveals compartment-specific responses in intestinal proliferation and apoptosis in transgenic mice whose enterocytes re-enter the cell cycle. © FASEB.

Cortactin modulates RhoA activation and expression of Cip/Kip cyclin-dependent kinase inhibitors to promote cell cycle progression in 11q13-amplified head and neck squamous cell carcinoma cells.

PubMed

Croucher, David R; Rickwood, Danny; Tactacan, Carole M; Musgrove, Elizabeth A; Daly, Roger J

2010-11-01

The cortactin oncoprotein is frequently overexpressed in head and neck squamous cell carcinoma (HNSCC), often due to amplification of the encoding gene (CTTN). While cortactin overexpression enhances invasive potential, recent research indicates that it also promotes cell proliferation, but how cortactin regulates the cell cycle machinery is unclear. In this article we report that stable short hairpin RNA-mediated cortactin knockdown in the 11q13-amplified cell line FaDu led to increased expression of the Cip/Kip cyclin-dependent kinase inhibitors (CDKIs) p21(WAF1/Cip1), p27(Kip1), and p57(Kip2) and inhibition of S-phase entry. These effects were associated with increased binding of p21(WAF1/Cip1) and p27(Kip1) to cyclin D1- and E1-containing complexes and decreased retinoblastoma protein phosphorylation. Cortactin regulated expression of p21(WAF1/Cip1) and p27(Kip1) at the transcriptional and posttranscriptional levels, respectively. The direct roles of p21(WAF1/Cip1), p27(Kip1), and p57(Kip2) downstream of cortactin were confirmed by the transient knockdown of each CDKI by specific small interfering RNAs, which led to partial rescue of cell cycle progression. Interestingly, FaDu cells with reduced cortactin levels also exhibited a significant diminution in RhoA expression and activity, together with decreased expression of Skp2, a critical component of the SCF ubiquitin ligase that targets p27(Kip1) and p57(Kip2) for degradation. Transient knockdown of RhoA in FaDu cells decreased expression of Skp2, enhanced the level of Cip/Kip CDKIs, and attenuated S-phase entry. These findings identify a novel mechanism for regulation of proliferation in 11q13-amplified HNSCC cells, in which overexpressed cortactin acts via RhoA to decrease expression of Cip/Kip CDKIs, and highlight Skp2 as a downstream effector for RhoA in this process.

βTrCP controls the lysosome-mediated degradation of CDK1, whose accumulation correlates with tumor malignancy

PubMed Central

Herrero-Ruiz, Joaquín; Mora-Santos, Mar; Giráldez, Servando; Sáez, Carmen; Japón, Miguel Á.; Tortolero, Maria; Romero, Francisco

2014-01-01

In mammals, cell cycle progression is controlled by cyclin-dependent kinases, among which CDK1 plays important roles in the regulation of the G2/M transition, G1 progression and G1/S transition. CDK1 is highly regulated by its association to cyclins, phosphorylation and dephosphorylation, changes in subcellular localization, and by direct binding of CDK inhibitor proteins. CDK1 steady-state protein levels are held constant throughout the cell cycle by a coordinated regulation of protein synthesis and degradation. We show that CDK1 is ubiquitinated by the E3 ubiquitin ligase SCFβTrCP and degraded by the lysosome. Furthermore, we found that DNA damage not only triggers the stabilization of inhibitory phosphorylation sites on CDK1 and repression of CDK1 gene expression, but also regulates βTrCP-induced CDK1 degradation in a cell type-dependent manner. Specifically, treatment with the chemotherapeutic agent doxorubicin in certain cell lines provokes CDK1 degradation and induces apoptosis, whereas in others it inhibits destruction of the protein. These observations raise the possibility that different tumor types, depending on their pathogenic spectrum mutations, may display different sensitivity to βTrCP-induced CDK1 degradation after DNA damage. Finally, we found that CDK1 accumulation in patients’ tumors shows a negative correlation with βTrCP and a positive correlation with the degree of tumor malignancy. PMID:25149538

Characterization of the Regulation and Function of Zinc-Dependent Histone Deacetylases During Mouse Liver Regeneration

PubMed Central

Huang, Jiansheng; Barr, Emily; Rudnick, David A.

2013-01-01

The studies reported here were undertaken to define the regulation and functional importance of zinc-dependent histone deacetylase (Zn-HDAC) activity during liver regeneration using the mouse partial hepatectomy (PH) model. The results showed that hepatic HDAC activity was significantly increased in nuclear and cytoplasmic fractions following PH. Further analyses showed isoform-specific effects of PH on HDAC mRNA and protein expression, with increased expression of the class I HDACs, 1 and 8, and class II HDAC4 in regenerating liver. Hepatic expression of (class II) HDAC5 was unchanged after PH; however HDAC5 exhibited transient nuclear accumulation in regenerating liver. These changes in hepatic HDAC expression, subcellular localization, and activity coincided with diminished histone acetylation in regenerating liver. The significance of these events was investigated by determining the effects of suberoylanilide hydroxyamic acid (SAHA, a specific inhibitor of Zn-HDAC activity) on hepatic regeneration. The results showed that SAHA-treatment suppressed the effects of PH on histone deacetylation and hepatocellular BrdU incorporation. Further examination showed that SAHA blunted hepatic expression and activation of cell cycle signals downstream of induction of cyclin D1 expression in mice subjected to PH. Conclusion The data reported here demonstrate isoform-specific regulation of Zn-HDAC expression, subcellular localization, and activity in regenerating liver. These studies also indicate that HDAC activity promotes liver regeneration by regulating hepatocellular cell cycle progression at a step downstream of cyclin D1 induction. PMID:23258575

Cytotoxicity of flavones and flavonols to a human esophageal squamous cell carcinoma cell line (KYSE-510) by induction of G2/M arrest and apoptosis.

PubMed

Zhang, Qiang; Zhao, Xin-Huai; Wang, Zhu-Jun

2009-08-01

In this study, cytotoxic effects of structurally related flavones and flavonols on a human esophageal squamous cell carcinoma cell line (KYSE-510) were determined, and the molecular mechanisms responsible for their cytotoxic effects were studied. The results of MTT assay showed that flavones (luteolin, apigenin, chrysin) and flavonols (quercetin, kaempferol, myricetin) were able to induce cytotoxicity in KYSE-510 cells in a dose- and time-dependent manner, and the cytotoxic potency of these compounds was in the order of: luteolin>quercetin>chrysin>kaempferol>apigenin>myricetin. Flow cytometry and DNA fragmentation analysis indicated that the cytotoxicity induced by flavones and flavonols was mediated by G(2)/M cell cycle arrest and apoptosis. Furthermore, the expression of genes related to cell cycle arrest and apoptosis was assessed by oligonucleotide microarray, real-time RT-PCR and Western blot. It was shown that the treatment of KYSE-510 cells with these compounds caused G(2)/M arrest through up-regulation of p21(waf1) and down-regulation of cyclin B1 at the mRNA and protein levels, and induced p53-independent mitochondrial-mediated apoptosis through up-regulation of PIG3 and cleavage of caspase-9 and caspase-3. The results of western blot analysis further showed that increases of p63 and p73 protein translation or stability might be contributed to the regulation of p21(waf1), cyclin B1 and PIG3.

High glucose concentration induces endothelial cell proliferation by regulating cyclin-D2-related miR-98.

PubMed

Li, Xin-Xin; Liu, Yue-Mei; Li, You-Jie; Xie, Ning; Yan, Yun-Fei; Chi, Yong-Liang; Zhou, Ling; Xie, Shu-Yang; Wang, Ping-Yu

2016-06-01

Cyclin D2 is involved in the pathology of vascular complications of type 2 diabetes mellitus (T2DM). This study investigated the role of cyclin-D2-regulated miRNAs in endothelial cell proliferation of T2DM. Results showed that higher glucose concentration (4.5 g/l) significantly promoted the proliferation of rat aortic endothelial cells (RAOECs), and significantly increased the expression of cyclin D2 and phosphorylation of retinoblastoma 1 (p-RB1) in RAOECs compared with those under low glucose concentration. The cyclin D2-3' untranslated region is targeted by miR-98, as demonstrated by miRNA analysis software. Western blot also confirmed that cyclin D2 and p-RB1 expression was regulated by miR-98. The results indicated that miR-98 treatment can induce RAOEC apoptosis. The suppression of RAOEC growth by miR-98 might be related to regulation of Bcl-2, Bax and Caspase 9 expression. Furthermore, the expression levels of miR-98 decreased in 4.5 g/l glucose-treated cells compared with those treated by low glucose concentration. Similarly, the expression of miR-98 significantly decreased in aortas of established streptozotocin (STZ)-induced diabetic rat model compared with that in control rats; but cyclin D2 and p-RB1 levels remarkably increased in aortas of STZ-induced diabetic rats compared with those in healthy control rats. In conclusion, this study demonstrated that high glucose concentration induces cyclin D2 up-regulation and miR-98 down-regulation in the RAOECs. By regulating cyclin D2, miR-98 can inhibit human endothelial cell growth, thereby providing novel therapeutic targets for vascular complication of T2DM. © 2016 The Authors. Journal of Cellular and Molecular Medicine published by John Wiley & Sons Ltd and Foundation for Cellular and Molecular Medicine.

Problem-Solving Test: The Mechanism of Action of a Human Papilloma Virus Oncoprotein

ERIC Educational Resources Information Center

Szeberenyi, Jozsef

2009-01-01

Terms to be familiar with before you start to solve the test: human papilloma virus; cervical cancer; oncoproteins; malignant transformation; retinoblastoma protein; cell cycle; quiescent and cycling cells; cyclin/cyclin-dependent kinase (Cdk) complexes; E2F; S-phase genes; enhancer element; proto-oncogenes; tumor suppressor genes; radioactive…

Two cell cycle blocks caused by iron chelation of neuroblastoma cells: separating cell cycle events associated with each block.

PubMed

Siriwardana, Gamini; Seligman, Paul A

2013-12-01

Studies have presented evidence that besides the well described S phase block, treatment of cancer cell lines with the iron chelator deferrioxamine (DFO) also results in an earlier block in G1 phase. In this article, measurements of cell cycle regulatory proteins define this block at a very specific point in G1. DFO treatment results in markedly decreased cyclin A protein levels. Cyclin E levels that accumulate in early to mid-G1 are increased in cells treated with DFO as compared to the resting cells. The DFO S phase block is shown after cells are arrested at G1/S by (aphidicolin) then released into DFO. The same S phase block occurs with DFO treatment of a neuroblastoma cell line relatively resistant to the G1 DFO block. These experiments clearly differentiate the S phase DFO block from the earlier block pinpointed to a point in mid-G1, before G1/S when cyclin E protein increases but before increased cyclin A synthesis. Apoptosis was observed in cells inhibited by DFO at both cell cycle arrest points.

Silibinin Inhibits Platelet-Derived Growth Factor-Driven Cell Proliferation via Downregulation of N-Glycosylation in Human Tenon's Fibroblasts in a Proteasome-Dependent Manner.

PubMed

Chen, Yi-Hao; Chen, Ching-Long; Lu, Da-Wen; Liang, Chang-Min; Tai, Ming-Cheng; Chen, Jiann-Torng

2016-01-01

The objective of this study was to evaluate the effects of silibinin on cell proliferation in platelet-derived growth factor (PDGF)-treated human Tenon's fibroblasts (HTFs). The effect of silibinin on cell proliferation in PDGF-treated HTFs was determined by examining the expression of proliferating cell nuclear antigen (PCNA) and performing WST-1 assays. Cell cycle progression was evaluated using flow cytometry. The related cyclins and cyclin-dependent kinases (CDKs) were also analyzed using western blot. A modified rat trabeculectomy model was established to evaluate the effect of silibinin on cell proliferation in vivo. Western blot analysis was carried out to determine the effect of silibinin on the expression of PDGF receptor and on the downstream signaling pathways regulated by PDGF receptor. PDGF elevated the expression of PCNA in HTFs, and this elevation was inhibited by silibinin. The inhibitory effect of silibinin on cell proliferation was also confirmed via WST-1 assay. PDGF-stimulated cell cycle in HTFs was delayed by silibinin, and the related cyclin D1 and CDK4 were also suppressed by silibinin. In the rat model of trabeculectomy, silibinin reduced the expression of PCNA at the site of blebs in vivo. The effects of silibinin on PDGF-stimulated HTFs were mediated via the downregulation of PDGF receptor-regulated signaling pathways, such as ERKs and STATs, which may be partially caused by the downregulation of N-glycosylation of PDGF receptor beta (PDGFRβ). The effect of silibinin on modulation of N-glycosylation of PDGFRβ was mediated in a proteasome-dependent manner. Silibinin inhibited cell proliferation and delayed cell cycle progression in PDGF-treated HTFs in vitro. PDGF also modulated the process of N-glycosylation of the PDGFRβ in a proteasome-dependent manner. Our findings suggest that silibinin has potential therapeutic applications in glaucoma filtering surgery.

Silibinin Inhibits Platelet-Derived Growth Factor-Driven Cell Proliferation via Downregulation of N-Glycosylation in Human Tenon's Fibroblasts in a Proteasome-Dependent Manner

PubMed Central

Chen, Yi-Hao; Chen, Ching-Long; Lu, Da-Wen; Liang, Chang-Min; Tai, Ming-Cheng; Chen, Jiann-Torng

2016-01-01

The objective of this study was to evaluate the effects of silibinin on cell proliferation in platelet-derived growth factor (PDGF)-treated human Tenon's fibroblasts (HTFs). The effect of silibinin on cell proliferation in PDGF-treated HTFs was determined by examining the expression of proliferating cell nuclear antigen (PCNA) and performing WST-1 assays. Cell cycle progression was evaluated using flow cytometry. The related cyclins and cyclin-dependent kinases (CDKs) were also analyzed using western blot. A modified rat trabeculectomy model was established to evaluate the effect of silibinin on cell proliferation in vivo. Western blot analysis was carried out to determine the effect of silibinin on the expression of PDGF receptor and on the downstream signaling pathways regulated by PDGF receptor. PDGF elevated the expression of PCNA in HTFs, and this elevation was inhibited by silibinin. The inhibitory effect of silibinin on cell proliferation was also confirmed via WST-1 assay. PDGF-stimulated cell cycle in HTFs was delayed by silibinin, and the related cyclin D1 and CDK4 were also suppressed by silibinin. In the rat model of trabeculectomy, silibinin reduced the expression of PCNA at the site of blebs in vivo. The effects of silibinin on PDGF-stimulated HTFs were mediated via the downregulation of PDGF receptor-regulated signaling pathways, such as ERKs and STATs, which may be partially caused by the downregulation of N-glycosylation of PDGF receptor beta (PDGFRβ). The effect of silibinin on modulation of N-glycosylation of PDGFRβ was mediated in a proteasome-dependent manner. Silibinin inhibited cell proliferation and delayed cell cycle progression in PDGF-treated HTFs in vitro. PDGF also modulated the process of N-glycosylation of the PDGFRβ in a proteasome-dependent manner. Our findings suggest that silibinin has potential therapeutic applications in glaucoma filtering surgery. PMID:28030611

Multiple functions of p21 in cell cycle, apoptosis and transcriptional regulation after DNA damage.

PubMed

Karimian, Ansar; Ahmadi, Yasin; Yousefi, Bahman

2016-06-01

An appropriate control over cell cycle progression depends on many factors. Cyclin-dependent kinase (CDK) inhibitor p21 (also known as p21(WAF1/Cip1)) is one of these factors that promote cell cycle arrest in response to a variety of stimuli. The inhibitory effect of P21 on cell cycle progression correlates with its nuclear localization. P21 can be induced by both p53-dependent and p53-independent mechanisms. Some other important functions attributed to p21 include transcriptional regulation, modulation or inhibition of apoptosis. These functions are largely dependent on direct p21/protein interactions and also on p21 subcellular localizations. In addition, p21 can play a role in DNA repair by interacting with proliferating cell nuclear antigen (PCNA). In this review, we will focus on the multiple functions of p21 in cell cycle regulation, apoptosis and gene transcription after DNA damage and briefly discuss the pathways and factors that have critical roles in p21 expression and activity. Copyright © 2016 Elsevier B.V. All rights reserved.

AS160 controls eukaryotic cell cycle and proliferation by regulating the CDK inhibitor p21.

PubMed

Gongpan, Pianchou; Lu, Yanting; Wang, Fang; Xu, Yuhui; Xiong, Wenyong

2016-07-02

AS160 (TBC1D4) has been implicated in multiple biological processes. However, the role and the mechanism of action of AS160 in the regulation of cell proliferation remain unclear. In this study, we demonstrated that AS160 knockdown led to blunted cell proliferation in multiple cell types, including fibroblasts and cancer cells. The results of cell cycle analysis showed that these cells were arrested in the G1 phase. Intriguingly, this inhibition of cell proliferation and the cell cycle arrest caused by AS160 depletion were glucose independent. Moreover, AS160 silencing led to a marked upregulation of the expression of the cyclin-dependent kinase inhibitor p21. Furthermore, whereas AS160 overexpression resulted in p21 downregulation and rescued the arrested cell cycle in AS160-depeleted cells, p21 silencing rescued the inhibited cell cycle and proliferation in the cells. Thus, our results demonstrated that AS160 regulates glucose-independent eukaryotic cell proliferation through p21-dependent control of the cell cycle, and thereby revealed a molecular mechanism of AS160 modulation of cell cycle and proliferation that is of general physiological significance.

Overexpression of Transcription Factor Sp1 Leads to Gene Expression Perturbations and Cell Cycle Inhibition

PubMed Central

Deniaud, Emmanuelle; Baguet, Joël; Chalard, Roxane; Blanquier, Bariza; Brinza, Lilia; Meunier, Julien; Michallet, Marie-Cécile; Laugraud, Aurélie; Ah-Soon, Claudette; Wierinckx, Anne; Castellazzi, Marc; Lachuer, Joël; Gautier, Christian

2009-01-01

Background The ubiquitous transcription factor Sp1 regulates the expression of a vast number of genes involved in many cellular functions ranging from differentiation to proliferation and apoptosis. Sp1 expression levels show a dramatic increase during transformation and this could play a critical role for tumour development or maintenance. Although Sp1 deregulation might be beneficial for tumour cells, its overexpression induces apoptosis of untransformed cells. Here we further characterised the functional and transcriptional responses of untransformed cells following Sp1 overexpression. Methodology and Principal Findings We made use of wild-type and DNA-binding-deficient Sp1 to demonstrate that the induction of apoptosis by Sp1 is dependent on its capacity to bind DNA. Genome-wide expression profiling identified genes involved in cancer, cell death and cell cycle as being enriched among differentially expressed genes following Sp1 overexpression. In silico search to determine the presence of Sp1 binding sites in the promoter region of modulated genes was conducted. Genes that contained Sp1 binding sites in their promoters were enriched among down-regulated genes. The endogenous sp1 gene is one of the most down-regulated suggesting a negative feedback loop induced by overexpressed Sp1. In contrast, genes containing Sp1 binding sites in their promoters were not enriched among up-regulated genes. These results suggest that the transcriptional response involves both direct Sp1-driven transcription and indirect mechanisms. Finally, we show that Sp1 overexpression led to a modified expression of G1/S transition regulatory genes such as the down-regulation of cyclin D2 and the up-regulation of cyclin G2 and cdkn2c/p18 expression. The biological significance of these modifications was confirmed by showing that the cells accumulated in the G1 phase of the cell cycle before the onset of apoptosis. Conclusion This study shows that the binding to DNA of overexpressed Sp1 induces an inhibition of cell cycle progression that precedes apoptosis and a transcriptional response targeting genes containing Sp1 binding sites in their promoter or not suggesting both direct Sp1-driven transcription and indirect mechanisms. PMID:19753117

P53-dependent antiproliferative and pro-apoptotic effects of trichostatin A (TSA) in glioblastoma cells.

PubMed

Bajbouj, K; Mawrin, C; Hartig, R; Schulze-Luehrmann, J; Wilisch-Neumann, A; Roessner, A; Schneider-Stock, R

2012-05-01

Glioblastomas are known to be highly chemoresistant, but HDAC inhibitors (HDACi) have been shown to be of therapeutic relevance for this aggressive tumor type. We treated U87 glioblastoma cells with trichostatin A (TSA) to define potential epigenetic targets for HDACi-mediated antitumor effects. Using a cDNA array analysis covering 96 cell cycle genes, cyclin-dependent kinase inhibitor p21(WAF1) was identified as the major player in TSA-induced cell cycle arrest. TSA slightly inhibited proliferation and viability of U87 cells, cumulating in a G1/S cell cycle arrest. This effect was accompanied by a significant up-regulation of p53 and its transcriptional target p21(WAF1) and by down-regulation of key G1/S regulators, such as cdk4, cdk6, and cyclin D1. Nevertheless, TSA did not induce apoptosis in U87 cells. As expected, TSA promoted the accumulation of total acetylated histones H3 and H4 and a decrease in endogenous HDAC activity. Characterizing the chromatin modulation around the p21(WAF1) promoter after TSA treatment using chromatin immunoprecipitation, we found (1) a release of HDAC1, (2) an increase of acetylated H4 binding, and (3) enhanced recruitment of p53. p53-depleted U87 cells showed an abrogation of the G1/S arrest and re-entered the cell cycle. Immunofluorescence staining revealed that TSA induced the nuclear translocation of p21(WAF1) verifying a cell cycle arrest. On the other hand, a significant portion of p21(WAF1) was present in the cytoplasmic compartment causing apoptosis resistance. Furthermore, TSA-treated p53-mutant cell line U138 failed to show an induction in p21(WAF1), showed a deficient G2/M checkpoint, and underwent mitotic catastrophe. We suggest that HDAC inhibition in combination with other clinically used drugs may be considered an effective strategy to overcome chemoresistance in glioblastoma cells.

Effect on intensity of treadmill running on learning, memory and expressions of cell cycle-related proteins in rats with cerebral ischemia.

PubMed

Zhao, Ya-Ning; Li, Jian-Min; Chen, Chang-Xiang; Li, Shu-Xing; Xue, Cheng-Jing

2017-06-20

We discussed the intensity of treadmill running on learning, memory and expression of cell cycle-related proteins in rats with cerebral ischemia. Eighty healthy male SD rats were randomly divided into normal group, model group, intensity I group and intensity II group, with 20 rats in each group. The four-vessel occlusion method of Pulsinelli (4-VO) was used to induce global cerebral ischemia. Brain neuronal morphology was observed by hematoxylin-eosin (HE) staining at 3h, 6h, 24h and 48h after modeling, respectively. Hippocampal expressions of cyclin A and cyclin E were detected by immunohistochemistry. At 48h after modeling, the learning and memory performance of rats was tested by water maze experiment. Compared with the normal group, the other three groups had a significant reduction in surviving neurons, prolonging of escape latency and decreased number of passes over the former position of the platform (P<0.05). The number of surviving neurons and the number of passes over the former position of the platform were obviously lower in the model group than in intensity I group (P<0.05), but significantly higher compared with intensity II group (P<0.05). Escape latency of the model group was obviously prolonged as compared with intensity I group (P<0.05), but much shorter than that of intensity II group (P<0.05). Compared with the normal group, the expressions of cyclin A and cyclin E were significantly upregulated at different time points after modeling (P<0.05). The expression of the model group was higher than that of intensity I group, but lower than that of intensity II group (P<0.05). Moderate intensity of treadmill running can help protect brain neurons and improve learning and memory performance of rats with global cerebral ischemia. But high intensity of treadmill running has a negative impact, possibly through the regulation of cell cycle-related proteins in ischemia/reperfusion injury.

Quantitative Cell Cycle Analysis Based on an Endogenous All-in-One Reporter for Cell Tracking and Classification.

PubMed

Zerjatke, Thomas; Gak, Igor A; Kirova, Dilyana; Fuhrmann, Markus; Daniel, Katrin; Gonciarz, Magdalena; Müller, Doris; Glauche, Ingmar; Mansfeld, Jörg

2017-05-30

Cell cycle kinetics are crucial to cell fate decisions. Although live imaging has provided extensive insights into this relationship at the single-cell level, the limited number of fluorescent markers that can be used in a single experiment has hindered efforts to link the dynamics of individual proteins responsible for decision making directly to cell cycle progression. Here, we present fluorescently tagged endogenous proliferating cell nuclear antigen (PCNA) as an all-in-one cell cycle reporter that allows simultaneous analysis of cell cycle progression, including the transition into quiescence, and the dynamics of individual fate determinants. We also provide an image analysis pipeline for automated segmentation, tracking, and classification of all cell cycle phases. Combining the all-in-one reporter with labeled endogenous cyclin D1 and p21 as prime examples of cell-cycle-regulated fate determinants, we show how cell cycle and quantitative protein dynamics can be simultaneously extracted to gain insights into G1 phase regulation and responses to perturbations. Copyright © 2017 The Author(s). Published by Elsevier Inc. All rights reserved.

Differential regulation of the cell cycle by alpha1-adrenergic receptor subtypes.

PubMed

Gonzalez-Cabrera, Pedro J; Shi, Ting; Yun, June; McCune, Dan F; Rorabaugh, Boyd R; Perez, Dianne M

2004-11-01

Alpha(1)-Adrenergic receptors have been implicated in growth-promoting pathways. A microarray study of individual alpha(1)-adrenergic receptor subtypes (alpha(1A), alpha(1B), and alpha(1D)) expressed in Rat-1 fibroblasts revealed that epinephrine altered the transcription of several cell cycle regulatory genes in a direction consistent with the alpha(1A)- and alpha(1D)-adrenergic receptors mediating G(1)-S cell cycle arrest and the alpha(1B-)mediating cell-cycle progression. A time course indicated that in alpha(1A) cells, epinephrine stimulated a G(1)-S arrest, which began after 8 h of stimulation and maximized at 16 h, at which point was completely blocked with cycloheximide. The alpha(1B)-adrenergic receptor profile also showed unchecked cell cycle progression, even under low serum conditions and induced foci formation. The G(1)-S arrest induced by alpha(1A)- and alpha(1D)-adrenergic receptors was associated with decreased cyclin-dependent kinase-6 and cyclin E-associated kinase activities and increased expression of the cyclin-dependent kinase inhibitor p27(Kip1), all of which were blocked by prazosin. There were no differences in kinase activities and/or expression of p27(Kip1) in epinephrine alpha(1B)-AR fibroblasts, although the microarray did indicate differences in p27(Kip1) RNA levels. Cell counts proved the antimitotic effect of epinephrine in alpha(1A) and alpha(1D) cells and indicated that alpha(1B)-adrenergic receptor subtype expression was sufficient to cause proliferation of Rat-1 fibroblasts independent of agonist stimulation. Analysis in transfected PC12 cells also confirmed the alpha(1A)- and alpha(1B)-adrenergic receptor effect. The alpha(1B)-subtype native to DDT1-MF2 cells, a smooth muscle cell line, caused progression of the cell cycle. These results indicate that the alpha(1A)- and alpha(1D)-adrenergic receptors mediate G(1)-S cell-cycle arrest, whereas alpha(1B)-adrenergic receptor expression causes a cell cycle progression and may induce transformation in sensitive cell lines.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guo, Zheng; Guangdong Provincial Key Laboratory of Gastroenterology, Department of Gastroenterology, Nanfang Hospital, Southern Medical University, 1838 Guangzhou Dadao Bei, Guangzhou 510515; Zhou, Yuning

Highlights: Black-Right-Pointing-Pointer Rictor associates with FBXW7 to form an E3 complex. Black-Right-Pointing-Pointer Knockdown of rictor decreases ubiquitination of c-Myc and cylin E. Black-Right-Pointing-Pointer Knockdown of rictor increases protein levels of c-Myc and cylin E. Black-Right-Pointing-Pointer Overexpression of rictor induces the degradation of c-Myc and cyclin E proteins. Black-Right-Pointing-Pointer Rictor regulation of c-Myc and cyclin E requires FBXW7. -- Abstract: Rictor (Rapamycin-insensitive companion of mTOR) forms a complex with mTOR and phosphorylates and activates Akt. Activation of Akt induces expression of c-Myc and cyclin E, which are overexpressed in colorectal cancer and play an important role in colorectal cancer cell proliferation.more » Here, we show that rictor associates with FBXW7 to form an E3 complex participating in the regulation of c-Myc and cyclin E degradation. The Rictor-FBXW7 complex is biochemically distinct from the previously reported mTORC2 and can be immunoprecipitated independently of mTORC2. Moreover, knocking down of rictor in serum-deprived colorectal cancer cells results in the decreased ubiquitination and increased protein levels of c-Myc and cyclin E while overexpression of rictor induces the degradation of c-Myc and cyclin E proteins. Genetic knockout of FBXW7 blunts the effects of rictor, suggesting that rictor regulation of c-Myc and cyclin E requires FBXW7. Our findings identify rictor as an important component of FBXW7 E3 ligase complex participating in the regulation of c-Myc and cyclin E protein ubiquitination and degradation. Importantly, our results suggest that elevated growth factor signaling may contribute to decrease rictor/FBXW7-mediated ubiquitination of c-Myc and cyclin E, thus leading to accumulation of cyclin E and c-Myc in colorectal cancer cells.« less

Modulated Expression of Genes Encoding Estrogen Metabolizing Enzymes by G1-Phase Cyclin-Dependent Kinases 6 and 4 in Human Breast Cancer Cells

PubMed Central

Jia, Yi; Domenico, Joanne; Swasey, Christina; Wang, Meiqin; Gelfand, Erwin W.; Lucas, Joseph J.

2014-01-01

G1-phase cell cycle defects, such as alterations in cyclin D1 or cyclin-dependent kinase (cdk) levels, are seen in most tumors. For example, increased cyclin D1 and decreased cdk6 levels are seen in many human breast tumors. Overexpression of cdk6 in breast tumor cells in culture has been shown to suppress proliferation, unlike the growth stimulating effects of its close homolog, cdk4. In addition to directly affecting proliferation, alterations in cdk6 or cdk4 levels in breast tumor cells also differentially influence levels of numerous steroid metabolic enzymes (SMEs), including those involved in estrogen metabolism. Overexpression of cdk6 in tumor cell lines having low cdk6 resulted in decreased levels of mRNAs encoding aldo-keto reductase (AKR)1C1, AKR1C2 and AKR1C3, which are hydroxysteroid dehydrogenases (HSDs) involved in steroid hormone metabolism. In contrast, increasing cdk4 dramatically increased these transcript levels, especially those encoding AKR1C3, an enzyme that converts estrone to 17β-estradiol, a change that could result in a pro-estrogenic state favoring tumor growth. Effects on other estrogen metabolizing enzymes, including cytochrome P450 (CYP) 19 aromatase, 17β-HSD2, and CYP1B1 transcripts, were also observed. Interactions of cdk6 and cdk4, but not cyclin D1, with the promoter region of a cdk-regulated gene, 17β-HSD2, were detected. The results uncover a previously unsuspected link between the cell cycle and hormone metabolism and differential roles for cdk6 and cdk4 in a novel mechanism for pre-receptor control of steroid hormone action, with important implications for the origin and treatment of steroid hormone-dependent cancers. PMID:24848372

SALL2 represses cyclins D1 and E1 expression and restrains G1/S cell cycle transition and cancer-related phenotypes.

PubMed

E Hermosilla, Viviana; Salgado, Ginessa; Riffo, Elizabeth; Escobar, David; Hepp, Matías I; Farkas, Carlos; Galindo, Mario; Morín, Violeta; García-Robles, María A; Castro, Ariel F; Pincheira, Roxana

2018-04-24

SALL2 is a poorly characterized transcription factor that belongs to the Spalt-like family involved in development. Mutations on SALL2 have been associated with ocular coloboma and cancer. In cancers, SALL2 is deregulated and is proposed as a tumor suppressor in ovarian cancer. SALL2 has been implicated in stemness, cell death, proliferation, and quiescence. However, mechanisms underlying roles of SALL2 related to cancer remain largely unknown. Here, we investigated the role of SALL2 in cell proliferation using mouse embryo fibroblasts (MEFs) derived from Sall2 -/- mice. Compared to Sall2 +/+ MEFs, Sall2 -/- MEFs exhibit enhanced cell proliferation and faster postmitotic progression through G1 and S phases. Accordingly, Sall2 -/- MEFs exhibit higher mRNA and protein levels of cyclins D1 and E1. Chromatin immunoprecipitation and promoter reporter assays showed that SALL2 binds and represses CCND1 and CCNE1 promoters, identifying a novel mechanism by which SALL2 may control cell cycle. In addition, the analysis of tissues from Sall2 +/+ and Sall2 -/- mice confirmed the inverse correlation between expression of SALL2 and G1-S cyclins. Consistent with an antiproliferative function of SALL2, immortalized Sall2 -/- MEFs showed enhanced growth rate, foci formation, and anchorage-independent growth, confirming tumor suppressor properties for SALL2. Finally, cancer data analyses show negative correlations between SALL2 and G1-S cyclins' mRNA levels in several cancers. Altogether, our results demonstrated that SALL2 is a negative regulator of cell proliferation, an effect mediated in part by repression of G1-S cyclins' expression. Our results have implications for the understanding and significance of SALL2 role under physiological and pathological conditions. © 2018 The Authors. Published by FEBS Press and John Wiley & Sons Ltd.

Alpinia oxyphylla Miq. fruit extract activates IGFR-PI3K/Akt signaling to induce Schwann cell proliferation and sciatic nerve regeneration.

PubMed

Chang, Yung-Ming; Chang, Hen-Hong; Tsai, Chin-Chuan; Lin, Hung-Jen; Ho, Tsung-Jung; Ye, Chi-Xin; Chiu, Ping-Ling; Chen, Yueh-Sheng; Chen, Ray-Jade; Huang, Chih-Yang; Lin, Chien-Chung

2017-03-31

It is known that the medicinal herb Alpinia oxyphylla Miq. is widely used as a remedy for diarrhea as well as the symptoms accompanying hypertension and cerebrovascular disorders. Moreover, it has also been reported that Alpinia oxyphylla Miq. has beneficial effects on anti-senescence and neuro-protection. This study focuses on the molecular mechanisms by which the Alpinia oxyphylla Miq. fruits promote neuron regeneration. A piece of silicone rubber was guided across a 15 mm gap in the sciatic nerve of a rat. This nerve gap was then filled with various doses of Alpinia oxyphylla Miq. fruits to assess their regenerative effect on damaged nerves. Further, we investigated the role of Alpinia oxyphylla Miq. fruits in RSC96 Schwann cell proliferation. Our current results showed that treatment with the extract of Alpinia oxyphylla Miq. fruits triggers the phosphorylated insulin-like growth factor-1 receptor- phosphatidylinositol 3-kinase/serine-threonine kinase pathway, and up-regulated the proliferating cell nuclear antigen in a dose-dependent manner. Cell cycle analysis on RSC96 Schwann cells showed that, after exposure to Alpinia oxyphylla Miq. fruit extract, the transition from the first gap phase to the synthesis phase occurs in 12-18 h. The expression of the cell cycle regulatory proteins cyclin D1, cyclin E and cyclin A increased in a dose-dependent manner. Transfection with a small interfering RNA blocked the expression of phosphatidylinositol 3-kinase and induced down-regulation both on the mRNA and protein levels, which resulted in a reduction of the expression of the survival factor B-cell lymphoma 2. We provide positive results that demonstrate that Alpinia oxyphylla Miq. fruits facilitate the survival and proliferation of RSC96 cells via insulin-like growth factor-1 signaling.

Betacellulin ameliorates hyperglycemia in obese diabetic db/db mice.

PubMed

Oh, Yoon Sin; Shin, Seungjin; Li, Hui Ying; Park, Eun-Young; Lee, Song Mi; Choi, Cheol Soo; Lim, Yong; Jung, Hye Seung; Jun, Hee-Sook

2015-11-01

We found that administration of a recombinant adenovirus (rAd) expressing betacellulin (BTC) into obese diabetic db/db mice ameliorated hyperglycemia. Exogenous glucose clearance was significantly improved, and serum insulin levels were significantly higher in rAd-BTC-treated mice than rAd-β-gal-treated control mice. rAd-BTC treatment increased insulin/bromodeoxyuridine double-positive cells in the islets, and islets from rAd-BTC-treated mice exhibited a significant increase in the level of G1-S phase-related cyclins as compared with control mice. In addition, BTC treatment increased messenger RNA (mRNA) and protein levels of these cyclins and cyclin-dependent kinases in MIN-6 cells. BTC treatment induced intracellular Ca(2+) levels through phospholipase C-γ1 activation, and upregulated calcineurin B (CnB1) levels as well as calcineurin activity. Upregulation of CnB1 by BTC treatment was observed in isolated islet cells from db/db mice. When treated with CnB1 small interfering RNA (siRNA) in MIN-6 cells and isolated islets, induction of cell cycle regulators by BTC treatment was blocked and consequently reduced BTC-induced cell viability. As well as BTC's effects on cell survival and insulin secretion, our findings demonstrate a novel pathway by which BTC controls beta-cell regeneration in the obese diabetic condition by regulating G1-S phase cell cycle expression through Ca(2+) signaling pathways. Administration of BTC to db/db mice results in amelioration of hyperglycemia. BTC stimulates beta-cell proliferation in db/db mice. Ca(2+) signaling was involved in BTC-induced beta-cell proliferation. BTC has an anti-apoptotic effect and potentiates glucose-stimulated insulin secretion.

MUC4 Regulates Cellular Senescence in Head and Neck Squamous Cell Carcinoma (HNSCC) through p16/Rb Pathway

PubMed Central

Macha, Muzafar A.; Rachagani, Satyanarayana; Pai, Priya; Gupta, Suprit; Lydiatt, Williams M.; Smith, Russell B.; Johansson, Sonny L.; Lele, Subodh M.; Kakar, Sham S.; Lee, John H.; Meza, Jane; Ganti, Apar K.; Jain, Maneesh; Batra, Surinder K.

2014-01-01

The limited effectiveness of therapy for patients with advanced stage Head and Neck Squamous Cell Carcinoma (HNSCC) or recurrent disease is a reflection of an incomplete understanding of the molecular basis of HNSCC pathogenesis. MUC4, a high molecular weight glycoprotein, is differentially overexpressed in many human cancers and implicated in cancer progression and resistance to several chemotherapies. However its clinical relevance and the molecular mechanisms through which it mediates HNSCC progression are not well understood. The present study revealed a significant up-regulation of MUC4 in 78% (68/87) of HNSCC tissues compared to 10% (1/10) in benign samples [p= 0.006, OR (95% C.I) = 10.74 (2.0 - 57.56)]. MUC4 knockdown (KD) in SCC1 and SCC10B HNSCC cell lines resulted in significant inhibition of growth in vitro and in vivo, increased senescence as indicated by an increase in the number of flat, enlarged and senescence-associated β-galactosidase (SA-β-Gal) positive cells. Decreased cellular proliferation was associated with G0/G1 cell cycle arrest and decrease expression of cell cycle regulatory proteins like cyclin E, cyclin D1 and decrease in BrdU incorporation. Mechanistic studies revealed upregulation of p16, pRb dephosphorylation and its interaction with HDAC1/2. This resulted in decreased histone acetylation (H3K9) at Cyclin E promoter leading to its downregulation. Orthotropic implantation of MUC4 KD SCC1 cells into the floor of the mouth of nude mice resulted in the formation of significantly small tumors (170±18.30 mg) compared to bigger tumors (375 ±17.29 mg) formed by control cells (p= 0.00007). In conclusion, our findings showed that MUC4 overexpression plays a critical role by regulating proliferation and cellular senescence of HNSCC cells. Downregulation of MUC4 may be a promising therapeutic approach for treating HNSCC patients. PMID:24747969

Interplay between cell cycle and autophagy induced by boswellic acid analog

PubMed Central

Pathania, Anup S.; Guru, Santosh K.; Kumar, Suresh; Kumar, Ashok; Ahmad, Masroor; Bhushan, Shashi; Sharma, Parduman R.; Mahajan, Priya; Shah, Bhahwal A.; Sharma, Simmi; Nargotra, Amit; Vishwakarma, Ram; Korkaya, Hasan; Malik, Fayaz

2016-01-01

In this study, we investigated the role of autophagy induced by boswellic acid analog BA145 on cell cycle progression in pancreatic cancer cells. BA145 induced robust autophagy in pancreatic cancer cell line PANC-1 and exhibited cell proliferation inhibition by inducing cells to undergo G2/M arrest. Inhibition of G2/M progression was associated with decreased expression of cyclin A, cyclin B, cyclin E, cdc2, cdc25c and CDK-1. Pre-treatment of cells with autophagy inhibitors or silencing the expression of key autophagy genes abrogated BA145 induced G2/M arrest and downregulation of cell cycle regulatory proteins. It was further observed that BA145 induced autophagy by targeting mTOR kinase (IC50 1 μM), leading to reduced expression of p-mTOR, p-p70S6K (T389), p-4EBP (T37/46) and p-S6 (S240/244). Notably, inhibition of mTOR signalling by BA145 was followed by attendant activation of AKT and its membrane translocation. Inhibition of Akt through pharmacological inhibitors or siRNAs enhanced BA145 mediated autophagy, G2/M arrest and reduced expression of G2/M regulators. Further studies revealed that BA145 arbitrated inhibition of mTOR led to the activation of Akt through IGFR/PI3k/Akt feedback loop. Intervention in IGFR/PI3k/Akt loop further depreciated Akt phosphorylation and its membrane translocation that culminates in augmented autophagy with concomitant G2/M arrest and cell death. PMID:27680387

TOFA suppresses ovarian cancer cell growth in vitro and in vivo.

PubMed

Li, Shu; Qiu, Lihua; Wu, Buchu; Shen, Haoran; Zhu, Jing; Zhou, Liang; Gu, Liying; Di, Wen

2013-08-01

A characteristic feature of cancer cells is the activation of de novo fatty acid synthesis. Acetyl‑CoA carboxylase (ACC) is a key enzyme in fatty acid synthesis, accelerating the reaction that carboxylates cytosolic acetyl‑CoA to form malonyl‑CoA. ACC is highly expressed in several types of human cancer and is important in breast and prostate cancer cell growth. The aim of the present study was to investigate the effects of 5‑tetradecyloxy‑2‑furoic acid (TOFA), an allosteric inhibitor of ACC, on the proliferation and cell cycle progression of the ovarian cancer cell lines COC1 and COC1/DDP. TOFA was found to be cytotoxic to COC1 and COC1/DDP cells with a 50% inhibitory concentration (IC50) of ~26.1 and 11.6 µg/ml, respectively. TOFA inhibited the proliferation of the cancer cells examined in a time‑ and dose‑dependent manner, arrested the cells in the G0/G1 cell cycle phase and induced apoptosis. The expression of the cell cycle regulating proteins cyclin D1 and cyclin-dependent kinase (CDK) 4, as well as the expression of the apoptosis‑related proteins caspase‑3 and Bcl‑2, were detected by western blot analysis. Cyclin D1, CDK4 and Bcl‑2 protein expression was inhibited by TOFA, while caspase‑3 was cleaved and activated. To the best of our knowledge, the present study demonstrated for the first time that TOFA inhibits COC1/DDP cell growth in ovarian tumor mouse xenografts. By inhibiting ACC, TOFA may be a promising small molecule agent for ovarian cancer therapy.

S100A8/A9 (Calprotectin) Negatively Regulates G2/M Cell Cycle Progression and Growth of Squamous Cell Carcinoma

PubMed Central

Khammanivong, Ali; Wang, Chengxing; Sorenson, Brent S.; Ross, Karen F.; Herzberg, Mark C.

2013-01-01

Malignant transformation results in abnormal cell cycle regulation and uncontrolled growth in head and neck squamous cell carcinoma (HNSCC) and other cancers. S100A8/A9 (calprotectin) is a calcium-binding heterodimeric protein complex implicated in cell cycle regulation, but the specific mechanism and role in cell cycle control and carcinoma growth are not well understood. In HNSCC, S100A8/A9 is downregulated at both mRNA and protein levels. We now report that downregulation of S100A8/A9 correlates strongly with a loss of cell cycle control and increased growth of carcinoma cells. To show its role in carcinogenesis in an in vitro model, S100A8/A9 was stably expressed in an S100A8/A9-negative human carcinoma cell line (KB cells, HeLa-like). S100A8/A9 expression increases PP2A phosphatase activity and p-Chk1 (Ser345) phosphorylation, which appears to signal inhibitory phosphorylation of mitotic p-Cdc25C (Ser216) and p-Cdc2 (Thr14/Tyr15) to inactivate the G2/M Cdc2/cyclin B1 complex. Cyclin B1 expression then downregulates and the cell cycle arrests at the G2/M checkpoint, reducing cell division. As expected, S100A8/A9-expressing cells show both decreased anchorage-dependent and -independent growth and mitotic progression. Using shRNA, silencing of S100A8/A9 expression in the TR146 human HNSCC cell line increases growth and survival and reduces Cdc2 inhibitory phosphorylation at Thr14/Tyr15. The level of S100A8/A9 endogenous expression correlates strongly with the reduced p-Cdc2 (Thr14/Tyr14) level in HNSCC cell lines, SCC-58, OSCC-3 and UMSCC-17B. S100A8/A9-mediated control of the G2/M cell cycle checkpoint is, therefore, a likely suppressive mechanism in human squamous cell carcinomas and may suggest new therapeutic approaches. PMID:23874958

GPER mediates the inhibitory actions of estrogen on adipogenesis in 3T3-L1 cells through perturbation of mitotic clonal expansion.

PubMed

Zhu, Pei; Yuen, Jacky M L; Sham, Kathy W Y; Cheng, Christopher H K

2013-11-01

G-protein-coupled estrogen receptor 1 (GPER) mediates non-genomic signaling of estrogenic events. Here we showed for the first time that Gper/GPER is expressed in Swiss 3T3 mouse embryo preadipocytes 3T3-L1, and that Gper/GPER is up-regulated during differentiation of the cells induced by monocyte differentiation-inducing (MDI) cocktail. Activation of GPER by the natural ligand 17β-estradiol (E2), and the specific agonist G1, was shown to inhibit lipid accumulation in 3T3-L1 cells, while such inhibition was reversed upon knockdown of GPER using specific siRNA. GPER was also found to mediate perturbation of mitotic clonal expansion (MCE) in these cells by inhibiting cell cycle arrest during MDI cocktail-induced differentiation. Persistent activation of cell cycle regulating factors cyclin-dependant kinase (CDK) 4, CDK6 and cyclin D1, and phosphorylation of retinoblastoma (Rb) protein at serine 795 was observed in the G1-treated cells. Taken together, our results indicate that E2-GPER signaling leads to an inhibition of adipogenesis in 3T3-L1 cells via perturbation of MCE. Copyright © 2013 Elsevier Inc. All rights reserved.

Rho-associated kinase (ROCK) inhibition reverses low cell activity on hydrophobic surfaces.

PubMed

Tian, Yu Shun; Kim, Hyun Jung; Kim, Hyun-Man

2009-08-28

Hydrophobic polymers do not offer an adequate scaffold surface for cells to attach, migrate, proliferate, and differentiate. Thus, hydrophobic scaffolds for tissue engineering have traditionally been physicochemically modified to enhance cellular activity. However, modifying the surface by chemical or physical treatment requires supplementary engineering procedures. In the present study, regulation of a cell signal transduction pathway reversed the low cellular activity on a hydrophobic surface without surface modification. Inhibition of Rho-associated kinase (ROCK) by Y-27632 markedly enhanced adhesion, migration, and proliferation of osteoblastic cells cultured on a hydrophobic polystyrene surface. ROCK inhibition regulated cell-cycle-related molecules on the hydrophobic surface. This inhibition also decreased expression of the inhibitors of cyclin-dependent kinases such as p21(cip1) and p27(kip1) and increased expression of cyclin A and D. These results indicate that defective cellular activity on the hydrophobic surface can be reversed by the control of a cell signal transduction pathway without physicochemical surface modification.

Direct binding of the N-terminus of HTLV-1 tax oncoprotein to cyclin-dependent kinase 4 is a dominant path to stimulate the kinase activity.

PubMed

Li, Junan; Li, Hongyuan; Tsai, Ming-Daw

2003-06-10

The involvement of Tax oncoprotein in the INK4-CDK4/6-Rb pathway has been regarded as a key factor for immortalization and transformation of human T-cell leukemia virus 1 (HTLV-1) infected cells. In both p16 -/- and +/+ cells, expression of Tax has been correlated with an increase in CDK4 activity, which subsequently increases the phosphorylation of Rb and drives the infected cells into cell cycle progression. In relation to these effects, Tax has been shown to interact with two components of the INK4-CDK4/6-Rb pathway, p16 and cyclin D(s). While Tax competes with CDK4 for p16 binding, thus suppressing p16 inhibition of CDK4, Tax also binds to cyclin D(s) with concomitant increases in both CDK4 activity and the phosphorylation of cyclin D(s). Here we show that both Tax and residues 1-40 of the N-terminus of Tax, Tax40N, bind to and activate CDK4 in vitro. In the presence of INK4 proteins, binding of Tax and Tax40N to CDK4 counteracts against the inhibition of p16 and p18 and acts as the major path to regulate Tax-mediated activation of CDK4. We also report that Tax40N retains the transactivation ability. These results of in vitro studies demonstrate a potentially novel, p16-independent route to regulate CDK4 activity by the Tax oncoprotein in HTLV-1 infected cells.

Down-regulation of NTCP expression by cyclin D1 in hepatitis B virus-related hepatocellular carcinoma has clinical significance

PubMed Central

Kang, Jingting; Wang, Jie; Cheng, Jin; Cao, Zhiliang; Chen, Ran; Li, Huiyu; Liu, Shuang; Chen, Xiangmei; Sui, Jianhua; Lu, Fengmin

2017-01-01

The sodium-dependent taurocholate cotransporter polypeptide (NTCP) has been identified as a liver specific functional receptor for the hepatitis B virus (HBV). Previous studies indicated that the expression of NTCP may be associated with the proliferation status of hepatocytes. However, the involvement of NTCP in hepatocellular carcinoma (HCC) cells proliferation remains unclear. In this study, we confirmed that NTCP was down-regulated in HCC tumor tissues compared with that in the adjacent non-tumor tissues (P < 0.0001). Clinically, lower expression of NTCP was correlated with poor post-surgery survival rate (P = 0.0009) and larger tumor tissue mass (P = 0.003) of HCC patients. This was supported by the finding that ectopic expression of NTCP in both HepG2 and Huh-7 cells could significantly suppress hepatocytes growth by arresting cells in G0/G1 phase. We also discovered that cyclin D1 could transcriptionally suppress NTCP expression by inhibiting the activity of NTCP promoter, while arresting HCC cells in G0/G1 phase by serum starvation could upregulate NTCP mRNA levels. This is the first study to report that the transcriptional inhibition of NTCP expression during cell cycle progression was mediated by cyclin D1. The down-regulated NTCP expression was associated with poor prognosis and lower HBV cccDNA level in HCC patients. Therefore, NTCP expression levels might serve as a novel prognostic predictive marker for post-surgery survival rate of HCC patients. PMID:28915572

Down-regulation of NTCP expression by cyclin D1 in hepatitis B virus-related hepatocellular carcinoma has clinical significance.

PubMed

Kang, Jingting; Wang, Jie; Cheng, Jin; Cao, Zhiliang; Chen, Ran; Li, Huiyu; Liu, Shuang; Chen, Xiangmei; Sui, Jianhua; Lu, Fengmin

2017-08-22

The sodium-dependent taurocholate cotransporter polypeptide (NTCP) has been identified as a liver specific functional receptor for the hepatitis B virus (HBV). Previous studies indicated that the expression of NTCP may be associated with the proliferation status of hepatocytes. However, the involvement of NTCP in hepatocellular carcinoma (HCC) cells proliferation remains unclear. In this study, we confirmed that NTCP was down-regulated in HCC tumor tissues compared with that in the adjacent non-tumor tissues ( P < 0.0001). Clinically, lower expression of NTCP was correlated with poor post-surgery survival rate ( P = 0.0009) and larger tumor tissue mass ( P = 0.003) of HCC patients. This was supported by the finding that ectopic expression of NTCP in both HepG2 and Huh-7 cells could significantly suppress hepatocytes growth by arresting cells in G0/G1 phase. We also discovered that cyclin D1 could transcriptionally suppress NTCP expression by inhibiting the activity of NTCP promoter, while arresting HCC cells in G0/G1 phase by serum starvation could upregulate NTCP mRNA levels. This is the first study to report that the transcriptional inhibition of NTCP expression during cell cycle progression was mediated by cyclin D1. The down-regulated NTCP expression was associated with poor prognosis and lower HBV cccDNA level in HCC patients. Therefore, NTCP expression levels might serve as a novel prognostic predictive marker for post-surgery survival rate of HCC patients.

Heterogeneous expression and biological function of ubiquitin carboxy-terminal hydrolase-L1 in osteosarcoma.

PubMed

Zheng, Shuier; Qiao, Guanglei; Min, Daliu; Zhang, Zhichang; Lin, Feng; Yang, Qingcheng; Feng, Tao; Tang, Lina; Sun, Yuanjue; Zhao, Hui; Li, Hongtao; Yu, Wenxi; Yang, Yumei; Shen, Zan; Yao, Yang

2015-04-01

Ubiquitin carboxyl terminal hydrolase 1 (UCHL1), a member of the UCH class of DUBs, has been reported as either an oncogene or a tumor suppressor. However, the molecular mechanism underlying the biological function of UCHL1 in osteosarcoma is still unclear. This study was aimed at elucidating the roles of UCHL1 in regulating the biological behavior of osteosarcoma cells. In this study, we found that UCHL1 was elevated in osteosarcoma compared with normal bone tissue. Moreover, UCHL1 expression level was correlated with tumor maximum diameter, high rate of lung metastases and short survival time. Then, we found that knockdown of UCHL1 in osteosarcoma cell MG63 inhibited cell proliferation and significantly increased cell population in the G1 phase. Several cyclins promoting G1/S phase transition were reduced after UCHL1 knockdown, including cell cycle regulator cyclin D1, cyclin E1 and CDK6. Moreover, inhibition of UCHL1 in MG63 cells dramatically induced cell apoptosis. We also found that down-regulation of UCHL1 in MG63 significantly inhibited cell invasion. Then, we found that there was a positive correlation between UCHL1 expression level and the Akt and ERK phosphorylation status. Finally, in vivo data showed that knockdown of UCHL1 inhibited osteosarcoma growth in nude mice. These results indicate that UCHL1 could work as an oncogene and may serve as a promising therapeutic strategy for osteosarcoma. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

Comparative analysis of Homo sapiens and Mus musculus cyclin-dependent kinase (CDK) inhibitor genes p16 (MTS1) and p15 (MTS2).

PubMed

Jiang, P; Stone, S; Wagner, R; Wang, S; Dayananth, P; Kozak, C A; Wold, B; Kamb, A

1995-12-01

Cyclin-dependent kinase inhibitors are a growing family of molecules that regulate important transitions in the cell cycle. At least one of these molecules, p16, has been implicated in human tumorigenesis while its close homolog, p15, is induced by cell contact and transforming growth factor-beta (TGF-beta). To investigate the evolutionary and functional features of p15 and p16, we have isolated mouse (Mus musculus) homologs of each gene. Comparative analysis of these sequences provides evidence that the genes have similar functions in mouse and human. In addition, the comparison suggests that a gene conversion event is part of the evolution of the human p15 and p16 genes.

Icaritin enhances mESC self-renewal through upregulating core pluripotency transcription factors mediated by ERα

PubMed Central

Tsang, Wing Pui; Zhang, Fengjie; He, Qiling; Cai, Waijiao; Huang, Jianhua; Chan, Wai Yee; Shen, Ziyin; Wan, Chao

2017-01-01

Utilization of small molecules in modulation of stem cell self-renewal is a promising approach to expand stem cells for regenerative therapy. Here, we identify Icaritin, a phytoestrogen molecule enhances self-renewal of mouse embryonic stem cells (mESCs). Icaritin increases mESCs proliferation while maintains their self-renewal capacity in vitro and pluripotency in vivo. This coincides with upregulation of key pluripotency transcription factors OCT4, NANOG, KLF4 and SOX2. The enhancement of mESCs self-renewal is characterized by increased population in S-phase of cell cycle, elevation of Cylin E and Cyclin-dependent kinase 2 (CDK2) and downregulation of p21, p27 and p57. PCR array screening reveals that caudal-related homeobox 2 (Cdx2) and Rbl2/p130 are remarkably suppressed in mESCs treated with Icaritin. siRNA knockdown of Cdx2 or Rbl2/p130 upregulates the expression of Cyclin E, OCT4 and SOX2, and subsequently increases cell proliferation and colony forming efficiency of mESCs. We then demonstrate that Icaritin co-localizes with estrogen receptor alpha (ERα) and activates its nuclear translocation in mESCs. The promotive effect of Icaritin on cell cycle and pluripotency regulators are eliminated by siRNA knockdown of ERα in mESCs. The results suggest that Icaritin enhances mESCs self-renewal by regulating cell cycle machinery and core pluripotency transcription factors mediated by ERα. PMID:28091581

Icaritin enhances mESC self-renewal through upregulating core pluripotency transcription factors mediated by ERα.

PubMed

Tsang, Wing Pui; Zhang, Fengjie; He, Qiling; Cai, Waijiao; Huang, Jianhua; Chan, Wai Yee; Shen, Ziyin; Wan, Chao

2017-01-16

Utilization of small molecules in modulation of stem cell self-renewal is a promising approach to expand stem cells for regenerative therapy. Here, we identify Icaritin, a phytoestrogen molecule enhances self-renewal of mouse embryonic stem cells (mESCs). Icaritin increases mESCs proliferation while maintains their self-renewal capacity in vitro and pluripotency in vivo. This coincides with upregulation of key pluripotency transcription factors OCT4, NANOG, KLF4 and SOX2. The enhancement of mESCs self-renewal is characterized by increased population in S-phase of cell cycle, elevation of Cylin E and Cyclin-dependent kinase 2 (CDK2) and downregulation of p21, p27 and p57. PCR array screening reveals that caudal-related homeobox 2 (Cdx2) and Rbl2/p130 are remarkably suppressed in mESCs treated with Icaritin. siRNA knockdown of Cdx2 or Rbl2/p130 upregulates the expression of Cyclin E, OCT4 and SOX2, and subsequently increases cell proliferation and colony forming efficiency of mESCs. We then demonstrate that Icaritin co-localizes with estrogen receptor alpha (ERα) and activates its nuclear translocation in mESCs. The promotive effect of Icaritin on cell cycle and pluripotency regulators are eliminated by siRNA knockdown of ERα in mESCs. The results suggest that Icaritin enhances mESCs self-renewal by regulating cell cycle machinery and core pluripotency transcription factors mediated by ERα.

Seed Germination and Seedling Growth under Simulated Microgravity Causes Alterations in Plant Cell Proliferation and Ribosome Biogenesis

NASA Astrophysics Data System (ADS)

Matía, Isabel; van Loon, Jack W. A.; Carnero-Díaz, Eugénie; Marco, Roberto; Medina, Francisco Javier

2009-01-01

The study of the modifications induced by altered gravity in functions of plant cells is a valuable tool for the objective of the survival of terrestrial organisms in conditions different from those of the Earth. We have used the system "cell proliferation-ribosome biogenesis", two inter-related essential cellular processes, with the purpose of studying these modifications. Arabidopsis seedlings belonging to a transformed line containing the reporter gene GUS under the control of the promoter of the cyclin gene CYCB1, a cell cycle regulator, were grown in a Random Positioning Machine, a device known to accurately simulate microgravity. Samples were taken at 2, 4 and 8 days after germination and subjected to biometrical analysis and cellular morphometrical, ultrastructural and immunocytochemical studies in order to know the rates of cell proliferation and ribosome biogenesis, plus the estimation of the expression of the cyclin gene, as an indication of the state of cell cycle regulation. Our results show that cells divide more in simulated microgravity in a Random Positioning Machine than in control gravity, but the cell cycle appears significantly altered as early as 2 days after germination. Furthermore, higher proliferation is not accompanied by an increase in ribosome synthesis, as is the rule on Earth, but the functional markers of this process appear depleted in simulated microgravity-grown samples. Therefore, the alteration of the gravitational environmental conditions results in a considerable stress for plant cells, including those not specialized in gravity perception.

Modelling the CDK-dependent transcription cycle in fission yeast.

PubMed

Sansó, Miriam; Fisher, Robert P

2013-12-01

CDKs (cyclin-dependent kinases) ensure directionality and fidelity of the eukaryotic cell division cycle. In a similar fashion, the transcription cycle is governed by a conserved subfamily of CDKs that phosphorylate Pol II (RNA polymerase II) and other substrates. A genetic model organism, the fission yeast Schizosaccharomyces pombe, has yielded robust models of cell-cycle control, applicable to higher eukaryotes. From a similar approach combining classical and chemical genetics, fundamental principles of transcriptional regulation by CDKs are now emerging. In the present paper, we review the current knowledge of each transcriptional CDK with respect to its substrate specificity, function in transcription and effects on chromatin modifications, highlighting the important roles of CDKs in ensuring quantity and quality control over gene expression in eukaryotes.

5-epi-Sinuleptolide induces cell cycle arrest and apoptosis through tumor necrosis factor/mitochondria-mediated caspase signaling pathway in human skin cancer cells.

PubMed

Liang, Chia-Hua; Wang, Guey-Horng; Chou, Tzung-Han; Wang, Shih-Hao; Lin, Rong-Jyh; Chan, Leong-Perng; So, Edmund Cheung; Sheu, Jyh-Horng

2012-07-01

Skin cancers are reportedly increasing worldwide. Developing novel anti-skin cancer drugs with minimal side effects is necessary to address this public health issue. Sinuleptolide has been demonstrated to possess anti-cancer cell activities; however, the mechanisms underlying the anti-skin cancer effects of 5-epi-sinuleptolide and sinuleptolide remain poorly understood. Apoptosis cell, cell-cycle-related regulatory factors, and mitochondria- and death receptor-dependent caspase pathway in 5-epi-sinuleptolide-induced cell apoptosis were examined using SCC25 cells. 5-epi-Sinuleptolide inhibited human skin cancer cell growth more than did sinuleptolide. Treatment of SCC25 cells with 5-epi-sinuleptolide increased apoptotic body formation, and induced cell-cycle arrest during the G2/M phase. Notably, 5-epi-sinuleptolide up-regulated p53 and p21 expression and inhibited G2/M phase regulators of cyclin B1 and cyclin-dependent kinease 1 (CDK1) in SCC25 cells. Additionally, 5-epi-sinuleptolide induced apoptosis by mitochondria-mediated cytochrome c and Bax up-expression, down-regulated Bcl-2, and activated caspase-9 and -3. 5-epi-Sinuleptolide also up-regulated tBid, which is associated with up-regulation of tumor necrosis factor-α (TNF-α) and Fas ligand (FasL) and their cognate receptors (i.e., TNF-RI, TNF-R2 and Fas), downstream adaptor TNF-R1-associated death domain (TRADD) and Fas-associated death domain (FADD), and activated caspase-8 in SCC25 cells. The analytical results indicate that the death receptor- and mitochondria-mediated caspase pathway is critical in 5-epi-sinuleptolide-induced apoptosis of skin cancer cells. This is the first report suggesting that the apoptosis mediates the anti-tumor effect of 5-epi-sinuleptolide. The results of this study might provide useful suggestions for designing of anti-tumor drugs for skin cancer patients. Copyright © 2012 Elsevier B.V. All rights reserved.

Novel Pactamycin Analogs Induce p53 Dependent Cell-Cycle Arrest at S-Phase in Human Head and Neck Squamous Cell Carcinoma (HNSCC) Cells

PubMed Central

Guha, Gunjan; Liang, Xiaobo; Kulesz-Martin, Molly F.; Mahmud, Taifo; Indra, Arup Kumar; Ganguli-Indra, Gitali

2015-01-01

Pactamycin, although putatively touted as a potent antitumor agent, has never been used as an anticancer drug due to its high cytotoxicity. In this study, we characterized the effects of two novel biosynthetically engineered analogs of pactamycin, de-6MSA-7-demethyl-7-deoxypactamycin (TM-025) and 7-demethyl-7-deoxypactamycin (TM-026), in head and neck squamous cell carcinoma (HNSCC) cell lines SCC25 and SCC104. Both TM-025 and TM-026 exert growth inhibitory effects on HNSCC cells by inhibiting cell proliferation. Interestingly, unlike their parent compound pactamycin, the analogs do not inhibit synthesis of nascent protein in a cell-based assay. Furthermore, they do not induce apoptosis or autophagy in a dose- or a time-dependent manner, but induce mild senescence in the tested cell lines. Cell cycle analysis demonstrated that both analogs significantly induce cell cycle arrest of the HNSCC cells at S-phase resulting in reduced accumulation of G2/M-phase cells. The pactamycin analogs induce expression of cell cycle regulatory proteins including master regulator p53, its downstream target p21Cip1/WAF1, p27kip21, p19, cyclin E, total and phospho Cdc2 (Tyr15) and Cdc25C. Besides, the analogs mildly reduce cyclin D1 expression without affecting expression of cyclin B, Cdk2 and Cdk4. Specific inhibition of p53 by pifithrin-α reduces the percentage of cells accumulated in S-phase, suggesting contribution of p53 to S-phase increase. Altogether, our results demonstrate that Pactamycin analogs TM-025 and TM-026 induce senescence and inhibit proliferation of HNSCC cells via accumulation in S-phase through possible contribution of p53. The two PCT analogs can be widely used as research tools for cell cycle inhibition studies in proliferating cancer cells with specific mechanisms of action. PMID:25938491

Two cell cycle blocks caused by iron chelation of neuroblastoma cells: separating cell cycle events associated with each block

PubMed Central

Siriwardana, Gamini; Seligman, Paul A.

2013-01-01

Abstract Studies have presented evidence that besides the well described S phase block, treatment of cancer cell lines with the iron chelator deferrioxamine (DFO) also results in an earlier block in G1 phase. In this article, measurements of cell cycle regulatory proteins define this block at a very specific point in G1. DFO treatment results in markedly decreased cyclin A protein levels. Cyclin E levels that accumulate in early to mid‐G1 are increased in cells treated with DFO as compared to the resting cells. The DFO S phase block is shown after cells are arrested at G1/S by (aphidicolin) then released into DFO. The same S phase block occurs with DFO treatment of a neuroblastoma cell line relatively resistant to the G1 DFO block. These experiments clearly differentiate the S phase DFO block from the earlier block pinpointed to a point in mid‐G1, before G1/S when cyclin E protein increases but before increased cyclin A synthesis. Apoptosis was observed in cells inhibited by DFO at both cell cycle arrest points. PMID:24744856

p21 in cancer: intricate networks and multiple activities.

PubMed

Abbas, Tarek; Dutta, Anindya

2009-06-01

One of the main engines that drives cellular transformation is the loss of proper control of the mammalian cell cycle. The cyclin-dependent kinase inhibitor p21 (also known as p21WAF1/Cip1) promotes cell cycle arrest in response to many stimuli. It is well positioned to function as both a sensor and an effector of multiple anti-proliferative signals. This Review focuses on recent advances in our understanding of the regulation of p21 and its biological functions with emphasis on its p53-independent tumour suppressor activities and paradoxical tumour-promoting activities, and their implications in cancer.

Increased expression of cyclin B1 mRNA coincides with diminished G{sub 2}-phase arrest in irradiated HeLa cells treated with staurosporine or caffeine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bernhard, E.J.; Maity, A.; McKenna, W.G.

1994-12-01

The irradiation of cells results in delayed progression through the G{sub 2} phase of the cell cycle. Treatment of irradiated HeLa cells with caffeine greatly reduces the G{sub 2}-phase delay, while caffeine does not alter progression of cells through the cell cycle in unirradiated cells. In this report we demonstrate that treatment of HeLa cells with the kinase inhibitor staurosporine, but not with the inhibitor H7, also results in a reduction of the G{sub 2}-phase arrest after irradiation. Cell cycle progression in unirradiated cells is unaffected by 4.4 nM (2ng/ml) staurosporine, which releases the radiation-induced G{sub 2}-phase arrest. In HeLamore » cells, the G{sub 2}-phase delay after irradiation in S phase is accompanied by decreased expression of cyclin B1 mRNA. Coincident with the reduction in G{sub 2}-phase delay, we observed an increase in cyclin B1 mRNA accumulation in irradiated, staurosporine-treated cells compared to cells treated with irradiation alone. Caffeine treatment of irradiated HeLa cells also resulted in an elevation in the levels of cyclin B1 message. These results support the hypothesis that diminished cyclin B1 mRNA levels influence G{sub 2}-phase arrest to some degree. The findings that both staurosporine and caffeine treatments reverse the depression in cyclin B1 expression suggest that these two compounds may act on a common pathway of cell cycle control in response to radiation injury. 33 refs., 6 figs.« less

Formononetin induces cell cycle arrest of human breast cancer cells via IGF1/PI3K/Akt pathways in vitro and in vivo.

PubMed

Chen, J; Zeng, J; Xin, M; Huang, W; Chen, X

2011-09-01

Formononetin is one of the main components of red clover plants, and is considered as a typical phytoestrogen. This study further investigated that formononetin inactivated IGF1/IGF1R-PI3K/Akt pathways and decreased cyclin D1 mRNA and protein expression in human breast cancer cells in vitro and in vivo. MCF-7 cells were treated with different concentrations of formononetin. The proliferation of the cells treated with formononetin was tested by MTT assay. The cell cycle in the treated cells was examined by flow cytometry. The levels of p-IGF-1 R, p-Akt, and cyclin D1 protein expression and cyclin D1 mRNA expression in the treated cells were determined by Western blot and RT-PCR, respectively. In addition, the antitumor activity of formononetin was evaluated in nude mice bearing orthotopic tumor implants. Compared with the control, formononetin inhibited the proliferation of MCF-7 cells and effectively induced cell cycle arrest. The levels of p-IGF-1 R, p-Akt, cyclin D1 protein expression, and cyclin D1 mRNA expression were also downregulated. On the other hand, formononetin also prevented the tumor growth of human breast cancer cells in nude mouse xenografts. These results show that formononetin causes cell cycle arrest at the G0/G1 phase by inactivating IGF1/IGF1R-PI3K/Akt pathways and decreasing cyclin D1 mRNA and protein expression, indicating the use of formononetin in the prevention of breast cancer carcinogenesis. Georg Thieme Verlag KG Stuttgart · New York.

Disorder of G2-M Checkpoint Control in Aniline-Induced Cell Proliferation in Rat Spleen.

PubMed

Wang, Jianling; Wang, Gangduo; Khan, M Firoze

2015-01-01

Aniline, a toxic aromatic amine, is known to cause hemopoietic toxicity both in humans and animals. Aniline exposure also leads to toxic response in spleen which is characterized by splenomegaly, hyperplasia, fibrosis and the eventual formation of tumors on chronic in vivo exposure. Previously, we have shown that aniline exposure leads to iron overload, oxidative DNA damage, and increased cell proliferation, which could eventually contribute to a tumorigenic response in the spleen. Despite our demonstration that cell proliferation was associated with deregulation of G1 phase cyclins and increased expression of G1 phase cyclin-dependent kinases (CDKs), molecular mechanisms, especially the regulation of G2 phase and contribution of epigenetic mechanisms in aniline-induced splenic cellular proliferation remain largely unclear. This study therefore, mainly focused on the regulation of G2 phase in an animal model preceding a tumorigenic response. Male Sprague-Dawley rats were given aniline (0.5 mmol/kg/day) in drinking water or drinking water only (controls) for 30 days, and expression of G2 phase cyclins, CDK1, CDK inhibitors and miRNAs were measured in the spleen. Aniline treatment resulted in significant increases in cell cycle regulatory proteins, including cyclins A, B and CDK1, particularly phosphor-CDK1, and decreases in CDK inhibitors p21 and p27, which could promote the splenocytes to go through G2/M transition. Our data also showed upregulation of tumor markers Trx-1 and Ref-1 in rats treated with aniline. More importantly, we observed lower expression of miRNAs including Let-7a, miR-15b, miR24, miR-100 and miR-125, and greater expression of CDK inhibitor regulatory miRNAs such as miR-181a, miR-221 and miR-222 in the spleens of aniline-treated animals. Our findings suggest that significant increases in the expression of cyclins, CDK1 and aberrant regulation of miRNAs could lead to an accelerated G2/M transition of the splenocytes, and potentially to a tumorigenic response on chronic aniline exposure.

Disorder of G2-M Checkpoint Control in Aniline-Induced Cell Proliferation in Rat Spleen

PubMed Central

Wang, Jianling; Wang, Gangduo; Khan, M. Firoze

2015-01-01

Aniline, a toxic aromatic amine, is known to cause hemopoietic toxicity both in humans and animals. Aniline exposure also leads to toxic response in spleen which is characterized by splenomegaly, hyperplasia, fibrosis and the eventual formation of tumors on chronic in vivo exposure. Previously, we have shown that aniline exposure leads to iron overload, oxidative DNA damage, and increased cell proliferation, which could eventually contribute to a tumorigenic response in the spleen. Despite our demonstration that cell proliferation was associated with deregulation of G1 phase cyclins and increased expression of G1 phase cyclin-dependent kinases (CDKs), molecular mechanisms, especially the regulation of G2 phase and contribution of epigenetic mechanisms in aniline-induced splenic cellular proliferation remain largely unclear. This study therefore, mainly focused on the regulation of G2 phase in an animal model preceding a tumorigenic response. Male Sprague-Dawley rats were given aniline (0.5 mmol/kg/day) in drinking water or drinking water only (controls) for 30 days, and expression of G2 phase cyclins, CDK1, CDK inhibitors and miRNAs were measured in the spleen. Aniline treatment resulted in significant increases in cell cycle regulatory proteins, including cyclins A, B and CDK1, particularly phosphor-CDK1, and decreases in CDK inhibitors p21 and p27, which could promote the splenocytes to go through G2/M transition. Our data also showed upregulation of tumor markers Trx-1 and Ref-1 in rats treated with aniline. More importantly, we observed lower expression of miRNAs including Let-7a, miR-15b, miR24, miR-100 and miR-125, and greater expression of CDK inhibitor regulatory miRNAs such as miR-181a, miR-221 and miR-222 in the spleens of aniline-treated animals. Our findings suggest that significant increases in the expression of cyclins, CDK1 and aberrant regulation of miRNAs could lead to an accelerated G2/M transition of the splenocytes, and potentially to a tumorigenic response on chronic aniline exposure. PMID:26192324

Identification of human cyclin-dependent kinase 8, a putative protein kinase partner for cyclin C.

PubMed Central

Tassan, J P; Jaquenoud, M; Léopold, P; Schultz, S J; Nigg, E A

1995-01-01

Metazoan cyclin C was originally isolated by virtue of its ability to rescue Saccharomyces cerevisiae cells deficient in G1 cyclin function. This suggested that cyclin C might play a role in cell cycle control, but progress toward understanding the function of this cyclin has been hampered by the lack of information on a potential kinase partner. Here we report the identification of a human protein kinase, K35 [cyclin-dependent kinase 8 (CDK8)], that is likely to be a physiological partner of cyclin C. A specific interaction between K35 and cyclin C could be demonstrated after translation of CDKs and cyclins in vitro. Furthermore, cyclin C could be detected in K35 immunoprecipitates prepared from HeLa cells, indicating that the two proteins form a complex also in vivo. The K35-cyclin C complex is structurally related to SRB10-SRB11, a CDK-cyclin pair recently shown to be part of the RNA polymerase II holoenzyme of S. cerevisiae. Hence, we propose that human K35(CDK8)-cyclin C might be functionally associated with the mammalian transcription apparatus, perhaps involved in relaying growth-regulatory signals. Images Fig. 2 Fig. 3 PMID:7568034

miR-26a regulates mouse hepatocyte proliferation via directly targeting the 3' untranslated region of CCND2 and CCNE2.

PubMed

Zhou, Jian; Ju, Wei-Qiang; Yuan, Xiao-Peng; Zhu, Xiao-Feng; Wang, Dong-Ping; He, Xiao-Shun

2016-02-01

The deficiency of liver regeneration needs to be addressed in the fields of liver surgery, split liver transplantation and living donor liver transplantation. Researches of microRNAs would broaden our understandings on the mechanisms of various diseases. Our previous research confirmed that miR-26a regulated liver regeneration in mice; however, the relationship between miR-26a and its target, directly or indirectly, remains unclear. Therefore, the present study further investigated the mechanism of miR-26a in regulating mouse hepatocyte proliferation. An established mouse liver cell line, Nctc-1469, was transfected with Ad5-miR-26a-EGFP, Ad5-anti-miR-26a-EGFP or Ad5-EGFP vector. Cell proliferation was assessed by MTS, cell apoptosis and cell cycle by flow cytometry, and gene expression by Western blotting and quantitative real-time PCR. Dual-luciferase reporter assays were used to test targets of miR-26a. Compared with the Ad5-EGFP group, Ad5-anti-miR-26a-EGFP down-regulated miR-26a and increased proliferation of hepatocytes, with more cells entering the G1 phase of cell cycle (82.70%+/-1.45% vs 75.80%+/-3.92%), and decreased apoptosis (5.50%+/-0.35% vs 6.73%+/-0.42%). CCND2 and CCNE2 were the direct targeted genes of miR-26a. miR-26a down-regulation up-regulated CCND2 and CCNE2 expressions and down-regulated p53 expression in Nctc-1469 cells. On the contrary, miR-26a over-expression showed the opposite results. miR-26a regulated mouse hepatocyte proliferation by directly targeting the 3' untranslated regions of cyclin D2/cyclin E2; miR-26a also regulated p53-mediated apoptosis. Our data suggested that miR-26a may be a promising regulator in liver regeneration.

Celecoxib prevents colitis associated colon carcinogenesis: an upregulation of apoptosis.

PubMed

Setia, Shruti; Nehru, Bimla; Sanyal, Sankar N

2014-12-01

Uncontrolled cell proliferation and suppressed apoptosis are the critical events transforming a normal cell to a cancerous one wherein the inflammatory microenvironment supports this oncogenic transformation. The process of colon carcinogenesis may be aggravated in chronic inflammatory conditions such as ulcerative colitis where non-steroidal anti-inflammatory drugs (NSAIDs) may effectively prevent the cellular and molecular events. Western blots and immunofluorescent analysis of DNA mismatch repair enzymes, cell cycle regulators and pro- and anti-apoptotic proteins were performed in dextran sulfate sodium (DSS)-induced ulcerative colitis and 1,2-dimethyl benz(a)anthracene (DMH)-induced colon cancer. Also, apoptotic studies were done in isolated colonocytes using fluorescent staining and in paraffin sections using TUNEL assay. An upregulation of cell cycle regulators: cyclin D1/cdk4 and cyclin E/cdk2 and anti-apoptotic Bcl-2, along with the suppression of DNA repair enzymes: MLH1 and MSH2; tumour suppressors: p53, p21and Rb and pro-apoptotic proteins: Bax and Bad were observed in the DSS, DMH and DSS+DMH groups. Proliferating cell nuclear antigen (PCNA) was also overexpressed in these groups. The ultimate executioner of the apoptotic pathway; caspase-3, was suppressed in these groups. Apoptotic studies in colonocytes and paraffin sections revealed suppressed apoptosis in these groups. These effects were corrected with the administration of a second generation NSAID, celecoxib along with the treatment of DSS and DMH. The chemopreventive action of celecoxib in colitis mediated colon carcinogenesis may include the regulation of DNA mismatch repair enzymes, cell cycle check points, cell proliferation and apoptosis. Copyright © 2014 Institute of Pharmacology, Polish Academy of Sciences. Published by Elsevier Urban & Partner Sp. z o.o. All rights reserved.

Transcription factor FBI-1 acts as a dual regulator in adipogenesis by coordinated regulation of cyclin-A and E2F-4.

PubMed

Laudes, Matthias; Bilkovski, Roman; Oberhauser, Frank; Droste, Andrea; Gomolka, Matthias; Leeser, Uschi; Udelhoven, Michael; Krone, Wilhelm

2008-05-01

Generation of new adipocytes plays a major role in the development of obesity. We previously have shown that transcriptional repressor factor that binds to IST (FBI)-1 exerts a dual effect in the process of adipogenesis by inhibiting proliferation and promoting differentiation of preadipocytes. The aim of the present study was to identify FBI-1 regulated molecular effectors that could account for these effects. Overexpressing FBI-1 in preadipocytes resulted in reduced expression of the cell cycle regulator cyclin A, which may explain FBI-1 induced inhibition of proliferation. Interestingly, FBI-1 repressed cyclin A promoter activity through an indirect mechanisms that did not involve direct binding of FBI-1 to the promoter sequence, but rather FBI-1 inhibition of transcriptional activator Sp1 binding to a regulatory element at -452 to -443. We also show that FBI-1 promotes terminal preadipocyte differentiation through a mechanism involving decreased levels of expression of the PPARgamma inhibitor E2F-4. FBI-1 significantly reduced E2F-4 promoter activity. Contrary to cyclin A, we found FBI-1-induced repression of E2F-4 is mediated by a direct mechanism via a FBI-1 regulatory element at -11 to -5. As function of transcriptional repressors normally depends on the presence of regulatory co-factors we also performed expression profiling of potential FBI-1 co-repressors throughout adipogenesis. In these experiments Sin3A and histon deacetylase (HDAC)-1 showed a similar expression pattern compared to FBI-1. Strikingly, co-immunoprecipitation studies revealed that FBI-1 binds Sin3A and HDAC-1 to form a repressor complex. Furthermore, by mutational analysis the amino terminal Poxvirus (POZ) domain of FBI-1 was found to be important for Sin3A and HDAC-1 binding. Taken together, FBI-1 is the first transcriptional repressor shown to act as a dual regulator in adipogenesis exerting repressor activities on target genes by both, direct and indirect mechanisms.

Wnt signaling regulates pancreatic β cell proliferation

PubMed Central

Rulifson, Ingrid C.; Karnik, Satyajit K.; Heiser, Patrick W.; ten Berge, Derk; Chen, Hainan; Gu, Xueying; Taketo, Makoto M.; Nusse, Roel; Hebrok, Matthias; Kim, Seung K.

2007-01-01

There is widespread interest in defining factors and mechanisms that stimulate proliferation of pancreatic islet cells. Wnt signaling is an important regulator of organ growth and cell fates, and genes encoding Wnt-signaling factors are expressed in the pancreas. However, it is unclear whether Wnt signaling regulates pancreatic islet proliferation and differentiation. Here we provide evidence that Wnt signaling stimulates islet β cell proliferation. The addition of purified Wnt3a protein to cultured β cells or islets promoted expression of Pitx2, a direct target of Wnt signaling, and Cyclin D2, an essential regulator of β cell cycle progression, and led to increased β cell proliferation in vitro. Conditional pancreatic β cell expression of activated β-catenin, a crucial Wnt signal transduction protein, produced similar phenotypes in vivo, leading to β cell expansion, increased insulin production and serum levels, and enhanced glucose handling. Conditional β cell expression of Axin, a potent negative regulator of Wnt signaling, led to reduced Pitx2 and Cyclin D2 expression by β cells, resulting in reduced neonatal β cell expansion and mass and impaired glucose tolerance. Thus, Wnt signaling is both necessary and sufficient for islet β cell proliferation, and our study provides previously unrecognized evidence of a mechanism governing endocrine pancreas growth and function. PMID:17404238

Effects of magnolol on UVB-induced skin cancer development in mice and its possible mechanism of action.

PubMed

Chilampalli, Chandeshwari; Guillermo, Ruth; Zhang, Xiaoying; Kaushik, Radhey S; Young, Alan; Zeman, David; Hildreth, Michael B; Fahmy, Hesham; Dwivedi, Chandradhar

2011-10-20

Magnolol, a plant lignan isolated from the bark and seed cones of Magnolia officinalis, has been shown to have chemopreventive effects on chemically-induced skin cancer development. The objectives of this investigation are to study the anticarcinogenic effects of magnolol on UVB-induced skin tumor development in SKH-1 mice, a model relevant to humans, and determine the possible role of apoptosis and cell cycle arrest involved in the skin tumor development. UVB-induced skin carcinogenesis model in SKH-1 mice was used for determining the preventive effects of magnolol on skin cancer development. Western blottings and flow cytometric analysis were used to study the effects of magnolol on apoptosis and cell cycle. Magnolol pretreated groups (30, 60 μ g) before UVB treatments (30 mJ/cm2, 5 days/week) resulted in 27-55% reduction in tumor multiplicity as compared to control group in SKH-1 mice. Magnolol pretreatment increased the cleavage of caspase-8 and poly-(-ADP-ribose) polymerase (PARP), increased the expression of p21, a cell cycle inhibitor, and decreased the expression of proteins involved in the G2/M phase of cell cycle in skin samples from SKH-1 mice.Treatment of A431 cells with magnolol decreased cell viability and cell proliferation in a concentration dependent manner. Magnolol induced G2/M phase cell cycle arrest in A431 cells at 12 h with a decreased expression of cell cycle proteins such as cyclin B1, cyclin A, CDK4, Cdc2 and simultaneous increase in the expression of Cip/p21, a cyclin-dependent kinase inhibitor. Magnolol induced apoptosis in vivo and in vitro with an increased cleavage of caspase-8 and PARP. Phospho-signal transducers and activators of transcription 3 (Tyr705), B-Raf, p-MEK, and p-AKT were down-regulated, whereas phosphorylation of ERK was induced by magnolol in A431 cells. Magnolol pretreatments prevent UVB-induced skin cancer development by enhancing apoptosis, causing cell cycle arrest at G2/M phase, and affecting various signaling pathways. Magnolol could be a potentially safe and potent anticarcinogenic agent against skin cancer.

Effects of magnolol on UVB-induced skin cancer development in mice and its possible mechanism of action

PubMed Central

2011-01-01

Background Magnolol, a plant lignan isolated from the bark and seed cones of Magnolia officinalis, has been shown to have chemopreventive effects on chemically-induced skin cancer development. The objectives of this investigation are to study the anticarcinogenic effects of magnolol on UVB-induced skin tumor development in SKH-1 mice, a model relevant to humans, and determine the possible role of apoptosis and cell cycle arrest involved in the skin tumor development. Methods UVB-induced skin carcinogenesis model in SKH-1 mice was used for determining the preventive effects of magnolol on skin cancer development. Western blottings and flow cytometric analysis were used to study the effects of magnolol on apoptosis and cell cycle. Results Magnolol pretreated groups (30, 60 μ g) before UVB treatments (30 mJ/cm2, 5 days/week) resulted in 27-55% reduction in tumor multiplicity as compared to control group in SKH-1 mice. Magnolol pretreatment increased the cleavage of caspase-8 and poly-(-ADP-ribose) polymerase (PARP), increased the expression of p21, a cell cycle inhibitor, and decreased the expression of proteins involved in the G2/M phase of cell cycle in skin samples from SKH-1 mice. Treatment of A431 cells with magnolol decreased cell viability and cell proliferation in a concentration dependent manner. Magnolol induced G2/M phase cell cycle arrest in A431 cells at 12 h with a decreased expression of cell cycle proteins such as cyclin B1, cyclin A, CDK4, Cdc2 and simultaneous increase in the expression of Cip/p21, a cyclin-dependent kinase inhibitor. Magnolol induced apoptosis in vivo and in vitro with an increased cleavage of caspase-8 and PARP. Phospho-signal transducers and activators of transcription 3 (Tyr705), B-Raf, p-MEK, and p-AKT were down-regulated, whereas phosphorylation of ERK was induced by magnolol in A431 cells. Conclusions Magnolol pretreatments prevent UVB-induced skin cancer development by enhancing apoptosis, causing cell cycle arrest at G2/M phase, and affecting various signaling pathways. Magnolol could be a potentially safe and potent anticarcinogenic agent against skin cancer. PMID:22014088

Scalloped and Yorkie are required for cell cycle re-entry of quiescent cells after tissue damage.

PubMed

Meserve, Joy H; Duronio, Robert J

2015-08-15

Regeneration of damaged tissues typically requires a population of active stem cells. How damaged tissue is regenerated in quiescent tissues lacking a stem cell population is less well understood. We used a genetic screen in the developing Drosophila melanogaster eye to investigate the mechanisms that trigger quiescent cells to re-enter the cell cycle and proliferate in response to tissue damage. We discovered that Hippo signaling regulates compensatory proliferation after extensive cell death in the developing eye. Scalloped and Yorkie, transcriptional effectors of the Hippo pathway, drive Cyclin E expression to induce cell cycle re-entry in cells that normally remain quiescent in the absence of damage. Ajuba, an upstream regulator of Hippo signaling that functions as a sensor of epithelial integrity, is also required for cell cycle re-entry. Thus, in addition to its well-established role in modulating proliferation during periods of tissue growth, Hippo signaling maintains homeostasis by regulating quiescent cell populations affected by tissue damage. © 2015. Published by The Company of Biologists Ltd.

Differential regulation of cyclin-dependent kinase inhibitors in neuroblastoma cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Qiao, Lan; Department of Pharmaceutical Sciences, Jilin University, Changchun 130021; Paul, Pritha

2013-05-31

Highlights: •GRP-R signaling differentially regulated the expression of p21 and p27. •Silencing GRP/GRP-R downregulated p21, while p27 expression was upregulated. •Inhibition of GRP/GRP-R signaling enhanced PTEN expression, correlative to the increased expression of p27. •PTEN and p27 co-localized in cytoplasm and silencing PTEN decreased p27 expression. -- Abstract: Gastrin-releasing peptide (GRP) and its receptor (GRP-R) are highly expressed in undifferentiated neuroblastoma, and they play critical roles in oncogenesis. We previously reported that GRP activates the PI3K/AKT signaling pathway to promote DNA synthesis and cell cycle progression in neuroblastoma cells. Conversely, GRP-R silencing induces cell cycle arrest. Here, we speculated thatmore » GRP/GRP-R signaling induces neuroblastoma cell proliferation via regulation of cyclin-dependent kinase (CDK) inhibitors. Surprisingly, we found that GRP/GRP-R differentially induced expressions of p21 and p27. Silencing GRP/GRP-R decreased p21, but it increased p27 expressions in neuroblastoma cells. Furthermore, we found that the intracellular localization of p21 and p27 in the nuclear and cytoplasmic compartments, respectively. In addition, we found that GRP/GRP-R silencing increased the expression and accumulation of PTEN in the cytoplasm of neuroblastoma cells where it co-localized with p27, thus suggesting that p27 promotes the function of PTEN as a tumor suppressor by stabilizing PTEN in the cytoplasm. GRP/GRP-R regulation of CDK inhibitors and tumor suppressor PTEN may be critical for tumoriogenesis of neuroblastoma.« less

Characterization of the regulation and function of zinc-dependent histone deacetylases during rodent liver regeneration.

PubMed

Huang, Jiansheng; Barr, Emily; Rudnick, David A

2013-05-01

The studies reported here were undertaken to define the regulation and functional importance of zinc-dependent histone deacetylase (Zn-HDAC) activity during liver regeneration using the mouse partial hepatectomy (PH) model. The results showed that hepatic HDAC activity was significantly increased in nuclear and cytoplasmic fractions following PH. Further analyses showed isoform-specific effects of PH on HDAC messenger RNA (mRNA) and protein expression, with increased expression of the class I HDACs, 1 and 8, and class II HDAC4 in regenerating liver. Hepatic expression of (class II) HDAC5 was unchanged after PH; however, HDAC5 exhibited transient nuclear accumulation in regenerating liver. These changes in hepatic HDAC expression, subcellular localization, and activity coincided with diminished histone acetylation in regenerating liver. The significance of these events was investigated by determining the effects of suberoylanilide hydroxyamic acid (SAHA, a specific inhibitor of Zn-HDAC activity) on hepatic regeneration. The results showed that SAHA treatment suppressed the effects of PH on histone deacetylation and hepatocellular bromodeoxyuridine (BrdU) incorporation. Further examination showed that SAHA blunted hepatic expression and activation of cell cycle signals downstream of induction of cyclin D1 expression in mice subjected to PH. The data reported here demonstrate isoform-specific regulation of Zn-HDAC expression, subcellular localization, and activity in regenerating liver. These studies also indicate that HDAC activity promotes liver regeneration by regulating hepatocellular cell cycle progression at a step downstream of cyclin D1 induction. Copyright © 2012 American Association for the Study of Liver Diseases.

[Long-term expansion of multipotent mesenchymal stromal cells under reduced oxygen tension].

PubMed

Rylova, Iu V; Buravkova, L B

2013-01-01

We have shown that the decrease in oxygen tension in the culture medium of multipotent mesenchymal stromal cells (MMSCs) results in a short-term reduction in the proportion of CD73(+)-cells in the population, without effecting the number of cells expressing other constitutive surface markers (CD90 and CD105). In this case, the heterogeneity of the cell population declined: large spread cells disappeared. The proliferative activity of MMSCs significantly increased and remained stable in conditions in which the oxygen content was close to the tissue oxygen levels (5% O2). At lower oxygen concentration, proliferative activity of the cells gradually reduced from passages 3-4. The increase in proliferative activity was not accompanied by increased expression of telomerase gene indicateding the alsance of cell transformation. However, genome-wide analysis of MMSC gene expression level revealed changes in expression of cyclins (CCND2 and PCNA), regulatory subunit cyclin-dependent kinase (CKS2) and an inhibitor of cyclin-dependent kinase (CDKN2C), regulating the cell cycle, which is obviously facilitated the increase in the proliferative capacity of cells at lower oxygen tension.

The negative cell cycle regulators, p27Kip1, p18Ink4c, and GSK-3, play critical role in maintaining quiescence of adult human pancreatic β-cells and restrict their ability to proliferate

PubMed Central

Stein, Jeffrey; Milewski, Wieslawa M; Dey, Arunangsu

2013-01-01

Adult human pancreatic β-cells are primarily quiescent (G0) yet the mechanisms controlling their quiescence are poorly understood. Here, we demonstrate, by immunofluorescence and confocal microscopy, abundant levels of the critical negative cell cycle regulators, p27(Kip1) and p18(Ink4c), 2 key members of cyclin-dependent kinase (CDK) inhibitor family, and glycogen synthase kinase-3 (GSK-3), a serine-threonine protein kinase, in islet β-cells of adult human pancreatic tissue. Our data show that p27(Kip1) localizes primarily in β-cell nuclei, whereas, p18(Ink4c) is mostly present in β-cell cytosol. Additionally, p-p27(S10), a phosphorylated form of p27(Kip1), which was shown to interact with and to sequester cyclinD-CDK4/6 in the cytoplasm, is present in substantial amounts in β-cell cytosol. Our immunofluorescence analysis displays similar distribution pattern of p27(Kip1), p-p27(S10), p18(Ink4c) and GSK-3 in islet β-cells of adult mouse pancreatic tissue. We demonstrate marked interaction of p27(Kip1) with cyclin D3, an abundant D-type cyclin in adult human islets, and vice versa as well as with its cognate kinase partners, CDK4 and CDK6. Likewise, we show marked interaction of p18(Ink4c) with CDK4. The data collectively suggest that inhibition of CDK function by p27(Kip1) and p18(Ink4c) contributes to human β-cell quiescence. Consistent with this, we have found by BrdU incorporation assay that combined treatments of small molecule GSK-3 inhibitor and mitogen/s lead to elevated proliferation of human β-cells, which is caused partly due to p27(Kip1) downregulation. The results altogether suggest that ex vivo expansion of human β-cells is achievable via increased proliferation for β-cell replacement therapy in diabetes. PMID:23896637

The Concerted Action of Type 2 and Type 3 Deiodinases Regulates the Cell Cycle and Survival of Basal Cell Carcinoma Cells.

PubMed

Miro, Caterina; Ambrosio, Raffaele; De Stefano, Maria Angela; Di Girolamo, Daniela; Di Cicco, Emery; Cicatiello, Annunziata Gaetana; Mancino, Giuseppina; Porcelli, Tommaso; Raia, Maddalena; Del Vecchio, Luigi; Salvatore, Domenico; Dentice, Monica

2017-04-01

Thyroid hormones (THs) mediate pleiotropic cellular processes involved in metabolism, cellular proliferation, and differentiation. The intracellular hormonal environment can be tailored by the type 1 and 2 deiodinase enzymes D2 and D3, which catalyze TH activation and inactivation respectively. In many cellular systems, THs exert well-documented stimulatory or inhibitory effects on cell proliferation; however, the molecular mechanisms by which they control rates of cell cycle progression have not yet been entirely clarified. We previously showed that D3 depletion or TH treatment influences the proliferation and survival of basal cell carcinoma (BCC) cells. Surprisingly, we also found that BCC cells express not only sustained levels of D3 but also robust levels of D2. The aim of the present study was to dissect the contribution of D2 to TH metabolism in the BCC context, and to identify the molecular changes associated with cell proliferation and survival induced by TH and mediated by D2 and D3. We used the CRISPR/Cas9 technology to genetically deplete D2 and D3 in BCC cells and studied the consequences of depletion on cell cycle progression and on cell death. Cell cycle progression was analyzed by fluorescence activated cell sorting analysis of synchronized cells, and the apoptosis rate by annexin V incorporation. Mechanistic investigations revealed that D2 inactivation accelerates cell cycle progression thereby enhancing the proportion of S-phase cells and cyclin D1 expression. Conversely, D3 mutagenesis drastically suppressed cell proliferation and enhanced apoptosis of BCC cells. Furthermore, the basal apoptotic rate was oppositely regulated in D2- and D3-depleted cells. Our results indicate that BCC cells constitute an example in which the TH signal is finely tuned by the concerted expression of opposite-acting deiodinases. The dual regulation of D2 and D3 expression plays a critical role in cell cycle progression and cell death by influencing cyclin D1-mediated entry into the G1-S phase. These findings reinforce the concept that TH is a potential therapeutic target in human BCC.

Transient inhibition of cell proliferation does not compromise self-renewal of mouse embryonic stem cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Ruoxing; Guo, Yan-Lin, E-mail: yanlin.guo@usm.edu

2012-10-01

Embryonic stem cells (ESCs) have unlimited capacity for self-renewal and can differentiate into various cell types when induced. They also have an unusual cell cycle control mechanism driven by constitutively active cyclin dependent kinases (Cdks). In mouse ESCs (mESCs). It is proposed that the rapid cell proliferation could be a necessary part of mechanisms that maintain mESC self-renewal and pluripotency, but this hypothesis is not in line with the finding in human ESCs (hESCs) that the length of the cell cycle is similar to differentiated cells. Therefore, whether rapid cell proliferation is essential for the maintenance of mESC state remainsmore » unclear. We provide insight into this uncertainty through chemical intervention of mESC cell cycle. We report here that inhibition of Cdks with olomoucine II can dramatically slow down cell proliferation of mESCs with concurrent down-regulation of cyclin A, B and E, and the activation of the Rb pathway. However, mESCs display can recover upon the removal of olomoucine II and are able to resume normal cell proliferation without losing self-renewal and pluripotency, as demonstrated by the expression of ESC markers, colony formation, embryoid body formation, and induced differentiation. We provide a mechanistic explanation for these observations by demonstrating that Oct4 and Nanog, two major transcription factors that play critical roles in the maintenance of ESC properties, are up-regulated via de novo protein synthesis when the cells are exposed to olomoucine II. Together, our data suggest that short-term inhibition of cell proliferation does not compromise the basic properties of mESCs. -- Highlights: Black-Right-Pointing-Pointer Inhibition of Cdks slows down mESCs proliferation. Black-Right-Pointing-Pointer mESCs display remarkable recovery capacity from short-term cell cycle interruption. Black-Right-Pointing-Pointer Short-term cell cycle interruption does not compromise mESC self-renewal. Black-Right-Pointing-Pointer Oct4 and Nanog are up-regulated via de novo synthesis by cell cycle interruption.« less

Cyclin D1 in well differentiated thyroid tumour of uncertain malignant potential.

PubMed

Lamba Saini, Monika; Weynand, Birgit; Rahier, Jacques; Mourad, Michel; Hamoir, Marc; Marbaix, Etienne

2015-04-18

Encapsulated follicular tumours with equivocal papillary thyroid carcinoma (PTC) type nuclear features continue to remain a challenge despite the recent attempts to classify these borderline lesions. The term 'well differentiated tumour of uncertain malignant potential (WDT-UMP)' was introduced to classify these tumours. The present study aimed to evaluate the role of a cell cycle regulator like cyclin D1 in these tumours along with assessment of other well established PTC markers like galectin-3, HBME-1, CK19. Thirteen cases of metastatic PTC, papillary microcarcinoma and follicular variant of PTC (FVPTC) were identified from a histological review of 510 cases. In addition, 13 cases of a subset of follicular adenomatoid nodules with focal areas showing nuclear features characteristic of PTC, identified as WDT-UMP, were also analyzed. Immunohistochemical analysis of galectin-3, HBME-1, CK19 and the proliferation markers Ki67 and cyclin D1 was performed. Lesions were analyzed for cyclin D1 gene amplification by fluorescent in-situ hybridization. All WDT-UMP lesions showed immunolabelling of cyclin D1, Ki67; 11/ 13 cases showed immunolabelling of CK19; 10/13 cases showed immunolabelling of HBME-1 and 4/13 cases showed immunolabelling of galectin-3. Surrounding benign adenomatoid areas showed no to faint focal staining in all thirteen cases of cyclin D1, HBME-1 and galectin-3. A low rate of cyclin D1 gene amplification was identified in a significant proportion of cells in the WDT-UMP lesions as compared to surrounding benign adenomatoid areas. Increased expression of cyclin D1 and amplification of its gene along with immunolabelling of HBME-1 in WDT-UMP lesions showing cytological features of papillary thyroid carcinoma within follicular adenomatoid nodules suggest that these areas could correspond to a precursor lesion of follicular variant of PTC. Overexpression of cyclin D1, associated with the amplification of the gene suggests that these WDT-UMP lesions are an intermediate between the benign and malignant groups making this group of lesions a reliable precursor of FVPTC. The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1851820807142117.

FLASH is essential during early embryogenesis and cooperates with p73 to regulate histone gene transcription.

PubMed

De Cola, A; Bongiorno-Borbone, L; Bianchi, E; Barcaroli, D; Carletti, E; Knight, R A; Di Ilio, C; Melino, G; Sette, C; De Laurenzi, V

2012-02-02

Replication-dependent histone gene expression is a fundamental process occurring in S-phase under the control of the cyclin-E/CDK2 complex. This process is regulated by a number of proteins, including Flice-Associated Huge Protein (FLASH) (CASP8AP2), concentrated in specific nuclear organelles known as HLBs. FLASH regulates both histone gene transcription and mRNA maturation, and its downregulation in vitro results in the depletion of the histone pull and cell-cycle arrest in S-phase. Here we show that the transcription factor p73 binds to FLASH and is part of the complex that regulates histone gene transcription. Moreover, we created a novel gene trap to disrupt FLASH in mice, and we show that homozygous deletion of FLASH results in early embryonic lethality, owing to arrest of FLASH(-/-) embryos at the morula stage. These results indicate that FLASH is an essential, non-redundant regulator of histone transcription and cell cycle during embryogenesis.

Osthole inhibits gastric cancer cell proliferation through regulation of PI3K/AKT

PubMed Central

Zhang, Yan

2018-01-01

Osthole is an active compound isolated from Chinese herb Cnidium monnieri (L.) Cusson, and had been reported to possess antitumor effect. However, the effect of osthole on the gastric cancer cells has not been investigated. In this study, the effects of osthole on the proliferation of human gastric cancer cells were tested. The data showed that osthole treatment significantly inhibited the proliferation of gastric cancer cells and resulted in the cell cycle arrest at G2/M phase in a dose-dependent manner. Western-blot study showed that the expression of cyclin B1 and cdc2 was markedly reduced by osthole. Moreover, expression of PI3K and pAKT was also significantly suppressed, and the results indicated that the inhibition of pAKT, cyclin B1, and cdc2 levels by osthole was notably enhanced by a PI3K inhibitor. These results demonstrate that osthole could inhibit gastric cancer cells proliferation via induction of cell cycle arrest at G2/M phase by the reduction of PI3K/AKT. PMID:29590128

Osthole inhibits gastric cancer cell proliferation through regulation of PI3K/AKT.

PubMed

Xu, Xiaojun; Liu, Xiaoyuan; Zhang, Yan

2018-01-01

Osthole is an active compound isolated from Chinese herb Cnidium monnieri (L.) Cusson, and had been reported to possess antitumor effect. However, the effect of osthole on the gastric cancer cells has not been investigated. In this study, the effects of osthole on the proliferation of human gastric cancer cells were tested. The data showed that osthole treatment significantly inhibited the proliferation of gastric cancer cells and resulted in the cell cycle arrest at G2/M phase in a dose-dependent manner. Western-blot study showed that the expression of cyclin B1 and cdc2 was markedly reduced by osthole. Moreover, expression of PI3K and pAKT was also significantly suppressed, and the results indicated that the inhibition of pAKT, cyclin B1, and cdc2 levels by osthole was notably enhanced by a PI3K inhibitor. These results demonstrate that osthole could inhibit gastric cancer cells proliferation via induction of cell cycle arrest at G2/M phase by the reduction of PI3K/AKT.

Overexpression of Cdk5 or non-phosphorylatable retinoblastoma protein protects septal neurons from oxygen-glucose deprivation.

PubMed

Panickar, Kiran S; Nonner, Doris; White, Michael G; Barrett, John N

2008-09-01

Activation of cyclin dependent kinases (Cdks) contributes to neuronal death following ischemia. We used oxygen-glucose deprivation (OGD) in septal neuronal cultures to test for possible roles of cell cycle proteins in neuronal survival. Increased cdc2-immunoreactive neurons were observed at 24 h after the end of 5 h OGD. Green fluorescent protein (GFP) or GFP along with a wild type or dominant negative form of the retinoblastoma protein (Rb), or cyclin-dependent kinase5 (Cdk5), were overexpressed using plasmid constructs. Following OGD, when compared to controls, neurons expressing both GFP and dominant negative Rb, RbDeltaK11, showed significantly less damage using microscopy imaging. Overexpression of Rb-wt did not affect survival. Surprisingly, overexpression of Cdk5-wild type significantly protected neurons from process disintegration but Cdk5T33, a dominant negative Cdk5, gave little or no protection. Thus phosphorylation of the cell cycle regulator, Rb, contributes to death in OGD in septal neurons but Cdk5 can have a protective role.

A novel function for Foxm1 in interkinetic nuclear migration in the developing telencephalon and anxiety-related behavior.

PubMed

Wu, Xiaojing; Gu, Xiaochun; Han, Xiaoning; Du, Ailing; Jiang, Yan; Zhang, Xiaoyun; Wang, Yanjie; Cao, Guangliang; Zhao, Chunjie

2014-01-22

Interkinetic nuclear migration (INM) is a key feature of cortical neurogenesis. INM functions to maximize the output of the neuroepithelium, and more importantly, balance the self-renewal and differentiation of the progenitors. Although INM has been reported to be highly correlated with the cell cycle, little is known about the effects of cell cycle regulators on INM. In this study, by crossing Foxm1(fl/fl) mice with Emx1-Cre line, we report that a conditional disruption of forkhead transcription factor M1 (Foxm1) in dorsal telencephalon results in abnormal cell cycle progression, leading to impaired INM through the downregulation of Cyclin b1 and Cdc25b. The impairment of INM disturbs the synchronization of apical progenitors (APs) and promotes the transition from APs to basal progenitors (BPs) in a cell-autonomous fashion. Moreover, ablation of Foxm1 causes anxiety-related behaviors in adulthood. Thus, this study provides evidence of linkages among the cell cycle regulator Foxm1, INM, and adult behavior.

Anticancer effect of PP31J isolated from Physalis pubescens L. in human cervical carcinoma cells

PubMed Central

Zeng, Wenjie; Wang, Qianqian; Chen, Lifeng; Huang, Lu; Zhao, Xiaofeng

2017-01-01

Extracts derived from Physalis pubescens L. may function as cancer therapies. The pharmacological effects of PP31J on human cervical carcinoma cells (HeLa cells) were investigated in this study. HeLa cells were treated with PP31J, and then cell proliferation, apoptosis, and cell cycle distribution were measured using a cell counting kit-8 (CCK-8) assay and flow cytometry. Protein expression levels of regulators of cell apoptosis and cell cycle were also examined using western blotting. Our data show that PP31J inhibited the growth of HeLa cells. Significant growth inhibition compared to the vehicle-treated group was observed using a concentration of 5 μM PP31J at 24, 48, and 72 h. PP31J also selectively arrested cell cycle progression in the G1 phase at 40 μM (P < 0.05) and in the G2/M phase at 20 μM (P < 0.01) and 40 μM (P < 0.001). Our results further demonstrate a significant increase in cell apoptosis (P < 0.001) following PP31J treatment (10, 20, and 40 μM). Immunoblotting data show that PP31J downregulated (P < 0.01) the expression of Bcl-xL and decreased (P < 0.05) the expression of Survivin and Cyclin D1 at 20 and 40 μM. This study shows the anti-tumor activity of PP31J in HeLa cells and that the effects of PP31J on cell cycle distribution and apoptosis induction were partially attributed to the regulation of Cyclin D1, Survivin, and Bcl-xL. PMID:28559997

Cyclin D2 is sufficient to drive β cell self-renewal and regeneration.

PubMed

Tschen, Shuen-Ing; Zeng, Chun; Field, Loren; Dhawan, Sangeeta; Bhushan, Anil; Georgia, Senta

2017-01-01

Diabetes results from an inadequate mass of functional β cells, due to either β cell loss caused by autoimmune destruction (type I diabetes) or β cell failure in response to insulin resistance (type II diabetes). Elucidating the mechanisms that regulate β cell mass may be key to developing new techniques that foster β cell regeneration as a cellular therapy to treat diabetes. While previous studies concluded that cyclin D2 is required for postnatal β cell self-renewal in mice, it is not clear if cyclin D2 is sufficient to drive β cell self-renewal. Using transgenic mice that overexpress cyclin D2 specifically in β cells, we show that cyclin D2 overexpression increases β cell self-renewal post-weaning and results in increased β cell mass. β cells that overexpress cyclin D2 are responsive to glucose stimulation, suggesting they are functionally mature. β cells that overexpress cyclin D2 demonstrate an enhanced regenerative capacity after injury induced by streptozotocin toxicity. To understand if cyclin D2 overexpression is sufficient to drive β cell self-renewal, we generated a novel mouse model where cyclin D2 is only expressed in β cells of cyclin D2 -/- mice. Transgenic overexpression of cyclin D2 in cyclin D2 - / - β cells was sufficient to restore β cell mass, maintain normoglycaemia, and improve regenerative capacity when compared with cyclin D2 -/- littermates. Taken together, our results indicate that cyclin D2 is sufficient to regulate β cell self-renewal and that manipulation of its expression could be used to enhance β cell regeneration.

Role of melatonin in the epigenetic regulation of breast cancer.

PubMed

Korkmaz, Ahmet; Sanchez-Barcelo, Emilio J; Tan, Dun-Xian; Reiter, Russel J

2009-05-01

The oncostatic properties of melatonin as they directly or indirectly involve epigenetic mechanisms of cancer are reviewed with a special focus on breast cancer. Five lines of evidence suggest that melatonin works via epigenetic processes: (1) melatonin influences transcriptional activity of nuclear receptors (ERalpha, GR and RAR) involved in the regulation of breast cancer cell growth; (2) melatonin down-regulates the expression of genes responsible for the local synthesis or activation of estrogens including aromatase, an effect which may be mediated by methylation of the CYP19 gene or deacetylation of CYP19 histones; (3) melatonin inhibits telomerase activity and expression induced by either natural estrogens or xenoestrogens; (4) melatonin modulates the cell cycle through the inhibition of cyclin D1 expression; (5) melatonin influences circadian rhythm disturbances dependent on alterations of the light/dark cycle (i.e., light at night) with the subsequent deregulation of PER2 which acts as a tumor suppressor gene.

FAK Regulates Intestinal Epithelial Cell Survival and Proliferation during Mucosal Wound Healing

PubMed Central

Tilghman, Robert W.; Casanova, James E.; Bouton, Amy H.

2011-01-01

Background Following damage to the intestinal epithelium, restoration of epithelial barrier integrity is triggered by a robust proliferative response. In other tissues, focal adhesion kinase (FAK) regulates many of the cellular processes that are critical for epithelial homeostasis and restitution, including cell migration, proliferation and survival. However, few studies to date have determined how FAK contributes to mucosal wound healing in vivo. Methodology and Principal Findings To examine the role of FAK in intestinal epithelial homeostasis and during injury, we generated intestinal epithelium (IE)-specific conditional FAK knockout mice. Colitis was induced with dextran-sulfate-sodium (DSS) and intestinal tissues were analyzed by immunohistochemistry and immunoblotting. While intestinal development occurred normally in mice lacking FAK, FAK-deficient animals were profoundly susceptible to colitis. The loss of epithelial FAK resulted in elevated p53 expression and an increased sensitivity to apoptosis, coincident with a failure to upregulate epithelial cell proliferation. FAK has been reported to function as a mechanosensor, inducing cyclin D1 expression and promoting cell cycle progression under conditions in which tissue/matrix stiffness is increased. Collagen deposition, a hallmark of inflammatory injury resulting in increased tissue rigidity, was observed in control and FAK knockout mice during colitis. Despite this fibrotic response, the colonic epithelium in FAK-deficient mice exhibited significantly reduced cyclin D1 expression, suggesting that proliferation is uncoupled from fibrosis in the absence of FAK. In support of this hypothesis, proliferation of Caco-2 cells increased proportionally with matrix stiffness in vitro only under conditions of normal FAK expression; FAK depleted cells exhibited reduced proliferation concomitant with attenuated cyclin D1 expression. Conclusions In the colon, FAK functions as a regulator of epithelial cell survival and proliferation under conditions of mucosal injury and a mechanosensor of tissue compliance, inducing repair-driven proliferation in the colonic epithelium through upregulation of cyclin D1. PMID:21887232

The Hog1 MAP Kinase Promotes the Recovery from Cell Cycle Arrest Induced by Hydrogen Peroxide in Candida albicans

PubMed Central

Correia, Inês; Alonso-Monge, Rebeca; Pla, Jesús

2017-01-01

Eukaryotic cell cycle progression in response to environmental conditions is controlled via specific checkpoints. Signal transduction pathways mediated by MAPKs play a crucial role in sensing stress. For example, the canonical MAPKs Mkc1 (of the cell wall integrity pathway), and Hog1 (of the HOG pathway), are activated upon oxidative stress. In this work, we have analyzed the effect of oxidative stress induced by hydrogen peroxide on cell cycle progression in Candida albicans. Hydrogen peroxide was shown to induce a transient arrest at the G1 phase of the cell cycle. Specifically, a G1 arrest was observed, although phosphorylation of Mkc1 and Hog1 MAPKs can take place at all stages of the cell cycle. Interestingly, hog1 (but not mkc1) mutants required a longer time compared to wild type cells to resume growth after hydrogen peroxide challenge. Using GFP-labeled cells and mixed cultures of wild type and hog1 cells we were able to show that hog1 mutants progress faster through the cell cycle under standard growth conditions in the absence of stress (YPD at 37°C). Consequently, hog1 mutants exhibited a smaller cell size. The altered cell cycle progression correlates with altered expression of the G1 cyclins Cln3 and Pcl2 in hog1 cells compared to the wild type strain. In addition, Hgc1 (a hypha-specific G1 cyclin) as well as Cln3 displayed a different kinetics of expression in the presence of hydrogen peroxide in hog1 mutants. Collectively, these results indicate that Hog1 regulates the expression of G1 cyclins not only in response to oxidative stress, but also under standard growth conditions. Hydrogen peroxide treated cells did not show fluctuations in the mRNA levels for SOL1, which are observed in untreated cells during cell cycle progression. In addition, treatment with hydrogen peroxide prevented degradation of Sol1, an effect which was enhanced in hog1 mutants. Therefore, in C. albicans, the MAPK Hog1 mediates cell cycle progression in response to oxidative stress, and further participates in the cell size checkpoint during vegetative growth. PMID:28111572

The soy-derived peptide Vglycin inhibits the growth of colon cancer cells in vitro and in vivo.

PubMed

Gao, Chang; Sun, Rui; Xie, Ya-Rong; Jiang, An-Li; Lin, Mei; Li, Min; Chen, Zheng-Wang; Zhang, Ping; Jin, Honglin; Feng, Jue-Ping

2017-05-01

Vglycin, a novel natural polypeptide isolated from pea seeds, possesses antidiabetic properties. Our previous studies have shown that Vglycin can induce the differentiation of human colon adenocarcinoma cells. We aimed to determine the anticancer activity of Vglycin against colon cancer cells and to elucidate related apoptosis-inducing mechanisms. Treatment with purified Vglycin significantly reduced growth, viability, and colony formation of CT-26, SW480, and NCL-H716 colon cancer cells in a dose-dependent manner while down-regulating the expression of proliferating cell nuclear antigen. Mouse xenograft studies showed a 38% inhibition of colon cancer growth in mice treated with Vglycin (20 mg/kg/day) at day 21. Furthermore, the potential mechanisms involved in Vglycin-induced cell apoptosis were examined using cell cycle studies, ultrastructural examination, as well as apoptosis-associated pathway analysis. The results showed that Vglycin significantly promoted apoptosis and G1/S phase cell cycle arrest. As revealed by Western blot, the expression of CDK2 and Cyclin D1 was down-regulated in all three Vglycin-treated colon cancer cells, indicating that the CDK2/Cyclin D1 cell cycle pathway involved in the initiation and progression of colon cancer. Moreover, the inhibition of Vglycin-induced cell proliferation in colon cancer cells was accompanied by alteration of the expression levels of the apoptosis-related proteins Bax, Bcl-2 and Mcl-1, and an increase of caspase-3 activity. Together, our results suggest that Vglycin may be another plant-derived peptide that suppresses colon cancer, supporting the continued investigation of Vglycin as therapeutic agent for colon cancer. Impact statement The antidiabetic properties and the capability of inducing differentiation of human colon adenocarcinoma cells of Vglycin have been reported in our previous studies. However, the anticancer potential of Vglycin on colon cancer cells and its possible related mechanisms were still unknown. In this study, we found that Vglycin could reduce growth, viability, and colony formation or colony size of CT-26, SW480, and NCL-H716 colon cancer cells. Moreover, Vglycin decreased tumor volume by 38% in xenograft mice transplanted with CT-26 cells. The mechanisms of these phenomena may be due to the down-regulated CDK2 and Cyclin D1, G1/S phase cell cycle arrest, and the dysregulated expression of Bax, Bcl-2, and Mcl-1. The findings highlight the anticancer potential of Vglycin against colon cancer cells, and suggest Vglycin may be another colon cancer potential suppressive component of plant-derived peptides.

Effects of Long-Term 50Hz Power-Line Frequency Electromagnetic Field on Cell Behavior in Balb/c 3T3 Cells

PubMed Central

An, Guang-Zhou; Xu, Hui; Zhou, Yan; Du, Le; Miao, Xia; Jiang, Da-Peng; Li, Kang-Chu; Guo, Guo-Zhen; Zhang, Chen; Ding, Gui-Rong

2015-01-01

Power-line frequency electromagnetic field (PF-EMF) was reported as a human carcinogen by some epidemiological research, but the conclusion is lack of robust experiment evidence. To identify the effects of long-term PF-EMF exposure on cell behavior, Balb/c 3T3 cells in exponential growth phase were exposed or sham-exposed to 50 Hertz (Hz) PF-EMF at 2.3 mT for 2 hours (h) one day, 5 days every week. After 11 weeks exposure, cells were collected instantly. Cell morphology was observed under invert microscope and Giemsa staining, cell viability was detected by 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay, cell cycle and apoptosis was examined by flow cytometry, the protein level of Proliferating Cell Nuclear Antigen (PCNA) and CyclinD1 was detected by western blot, cell transformation was examined by soft agar clone assay and plate clone forming test, and cell migration ability was observed by scratch adhesion test. It was found that after PF-EMF exposure, cell morphology, apoptosis, cell migration ability and cell transformation didn’t change. However, compared with sham group, cell viability obviously decreased and cell cycle distribution also changed after 11 weeks PF-EMF exposure. Meanwhile, the protein level of PCNA and CyclinD1 significantly decreased after PF-EMF exposure. These data suggested that although long-term 50Hz PF-EMF exposure under this experimental condition had no effects on apoptosis, cell migration ability and cell transformation, it could affect cell proliferation and cell cycle by down-regulation the expression of PCNA and CyclinD1 protein. PMID:25695503

Effects of long-term 50Hz power-line frequency electromagnetic field on cell behavior in Balb/c 3T3 cells.

PubMed

An, Guang-Zhou; Xu, Hui; Zhou, Yan; Du, Le; Miao, Xia; Jiang, Da-Peng; Li, Kang-Chu; Guo, Guo-Zhen; Zhang, Chen; Ding, Gui-Rong

2015-01-01

Power-line frequency electromagnetic field (PF-EMF) was reported as a human carcinogen by some epidemiological research, but the conclusion is lack of robust experiment evidence. To identify the effects of long-term PF-EMF exposure on cell behavior, Balb/c 3T3 cells in exponential growth phase were exposed or sham-exposed to 50 Hertz (Hz) PF-EMF at 2.3 mT for 2 hours (h) one day, 5 days every week. After 11 weeks exposure, cells were collected instantly. Cell morphology was observed under invert microscope and Giemsa staining, cell viability was detected by 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay, cell cycle and apoptosis was examined by flow cytometry, the protein level of Proliferating Cell Nuclear Antigen (PCNA) and CyclinD1 was detected by western blot, cell transformation was examined by soft agar clone assay and plate clone forming test, and cell migration ability was observed by scratch adhesion test. It was found that after PF-EMF exposure, cell morphology, apoptosis, cell migration ability and cell transformation didn't change. However, compared with sham group, cell viability obviously decreased and cell cycle distribution also changed after 11 weeks PF-EMF exposure. Meanwhile, the protein level of PCNA and CyclinD1 significantly decreased after PF-EMF exposure. These data suggested that although long-term 50Hz PF-EMF exposure under this experimental condition had no effects on apoptosis, cell migration ability and cell transformation, it could affect cell proliferation and cell cycle by down-regulation the expression of PCNA and CyclinD1 protein.

Progesterone-induced miR-133a inhibits the proliferation of endometrial epithelial cells.

PubMed

Pan, J-L; Yuan, D-Z; Zhao, Y-B; Nie, L; Lei, Y; Liu, M; Long, Y; Zhang, J-H; Blok, L J; Burger, C W; Yue, L-M

2017-03-01

This study aimed to understand the role of miR-133a in progesterone actions, explore the regulative mechanism of the progesterone receptor, and investigate the effects of miR-133a on the progesterone-inhibited proliferation of mouse endometrial epithelial cells. The expression of miR-133a induced by progesterone was detected by quantitative real-time PCR both in vivo and in vitro. Ishikawa subcell lines stably transfected with progesterone receptor subtypes were used to determine the receptor mechanism of progesterone inducing miR-133a. Specific miR-133a mimics or inhibitors were transfected into mouse uteri and primary cultured endometrial epithelial cells to overexpress or downregulate the miR-133a. The roles of miR-133a in the cell cycle and proliferation of endometrial epithelial cells were analysed by flow cytometry and Edu incorporation analysis. The protein levels of cyclinD2 in uterine tissue sections and primary cultured endometrial epithelial cells were determined by immunohistochemistry and Western blot analysis. Progesterone could induce miR-133a expression in a PRB-dependent manner in endometrial epithelial cells. miR-133a inhibited endometrial epithelial cell proliferation by arresting cell cycle at the G 1 -S transition. Moreover, miR-133a acted as an inhibitor in downregulating cyclinD2 in endometrial epithelial cells. We showed for the first time that progesterone-induced miR-133a inhibited the proliferation of endometrial epithelial cells by downregulating cyclinD2. Our research indicated an important mechanism for progesterone inhibiting the proliferation of endometrial epithelial cells by inducing special miRNAs to inhibit positive regulatory proteins in the cell cycle. © 2016 Scandinavian Physiological Society. Published by John Wiley & Sons Ltd.

The inhibition of PI3K and NFκB promoted curcumin-induced cell cycle arrest at G2/M via altering polyamine metabolism in Bcl-2 overexpressing MCF-7 breast cancer cells.

PubMed

Berrak, Özge; Akkoç, Yunus; Arısan, Elif Damla; Çoker-Gürkan, Ajda; Obakan-Yerlikaya, Pınar; Palavan-Ünsal, Narçin

2016-02-01

Bcl-2 protein has been contributed with number of genes which are involved in oncogenesis. Among the many targets of Bcl-2, NFκB have potential role in induction of cell cycle arrest. Curcumin has potential therapeutic effects against breast cancer through multiple signaling pathways. In this study, we investigated the role of curcumin in induction of cell cycle arrest via regulating of NFκB and polyamine biosynthesis in wt and Bcl-2+ MCF-7 cells. To examine the effect of curcumin on cell cycle regulatory proteins, PI3K/Akt, NFκB pathways and polyamine catabolism, we performed immunoblotting assay. In addition, cell cycle analysis was performed by flow cytometry. The results indicated that curcumin induced cell cycle arrest at G2/M phase by downregulation of cyclin B1 and Cdc2 and inhibited colony formation in MCF-7wt cells. However, Bcl-2 overexpression prevented the inhibition of cell cycle associated proteins after curcumin treatment. The combination of LY294002, PI3K inhibitor, and curcumin induced cell cycle arrest by decreasing CDK4, CDK2 and cyclin E2 in Bcl-2+ MCF-7 cells. Moreover, LY294002 further inhibited the phosphorylation of Akt in Bcl-2+ MCF-7 cells. Curcumin could suppress the nuclear transport of NFκB through decreasing the interaction of P-IκB-NFκB. The combination of wedelolactone, NFκB inhibitor, and curcumin acted different on SSAT expression in wt MCF-7 and Bcl-2+ MCF-7 cells. NFκB inhibition increased the SSAT after curcumin treatment in Bcl-2 overexpressed MCF-7 cells. Inhibition of NFκB activity as well as suppression of ROS generation with NAC resulted in the partial relief of cells from G2/M checkpoint after curcumin treatment in wt MCF-7 cells. In conclusion, the potential role of curcumin in induction of cell cycle arrest is related with NFκB-regulated polyamine biosynthesis. Copyright © 2015 Elsevier Masson SAS. All rights reserved.

Daughter-Specific Transcription Factors Regulate Cell Size Control in Budding Yeast

PubMed Central

Di Talia, Stefano; Wang, Hongyin; Skotheim, Jan M.; Rosebrock, Adam P.; Futcher, Bruce; Cross, Frederick R.

2009-01-01

In budding yeast, asymmetric cell division yields a larger mother and a smaller daughter cell, which transcribe different genes due to the daughter-specific transcription factors Ace2 and Ash1. Cell size control at the Start checkpoint has long been considered to be a main regulator of the length of the G1 phase of the cell cycle, resulting in longer G1 in the smaller daughter cells. Our recent data confirmed this concept using quantitative time-lapse microscopy. However, it has been proposed that daughter-specific, Ace2-dependent repression of expression of the G1 cyclin CLN3 had a dominant role in delaying daughters in G1. We wanted to reconcile these two divergent perspectives on the origin of long daughter G1 times. We quantified size control using single-cell time-lapse imaging of fluorescently labeled budding yeast, in the presence or absence of the daughter-specific transcriptional regulators Ace2 and Ash1. Ace2 and Ash1 are not required for efficient size control, but they shift the domain of efficient size control to larger cell size, thus increasing cell size requirement for Start in daughters. Microarray and chromatin immunoprecipitation experiments show that Ace2 and Ash1 are direct transcriptional regulators of the G1 cyclin gene CLN3. Quantification of cell size control in cells expressing titrated levels of Cln3 from ectopic promoters, and from cells with mutated Ace2 and Ash1 sites in the CLN3 promoter, showed that regulation of CLN3 expression by Ace2 and Ash1 can account for the differential regulation of Start in response to cell size in mothers and daughters. We show how daughter-specific transcriptional programs can interact with intrinsic cell size control to differentially regulate Start in mother and daughter cells. This work demonstrates mechanistically how asymmetric localization of cell fate determinants results in cell-type-specific regulation of the cell cycle. PMID:19841732

A Presumptive Developmental Role for a Sea Urchin Cyclin B Splice Variant

PubMed Central

Lozano, Jean-Claude; Schatt, Philippe; Marquès, François; Peaucellier, Gérard; Fort, Philippe; Féral, Jean-Pierre; Genevière, Anne-Marie; Picard, André

1998-01-01

We show that a splice variant–derived cyclin B is produced in sea urchin oocytes and embryos. This splice variant protein lacks highly conserved sequences in the COOH terminus of the protein. It is found strikingly abundant in growing oocytes and cells committed to differentiation during embryogenesis. Cyclin B splice variant (CBsv) protein associates weakly in the cell with Xenopus cdc2 and with budding yeast CDC28p. In contrast to classical cyclin B, CBsv very poorly complements a triple CLN deletion in budding yeast, and its microinjection prevents an initial step in MPF activation, leading to an important delay in oocyte meiosis reinitiation. CBsv microinjection in fertilized eggs induces cell cycle delay and abnormal development. We assume that CBsv is produced in growing oocytes to keep them in prophase, and during embryogenesis to slow down cell cycle in cells that will be committed to differentiation. PMID:9442104

Taraxasterol suppresses the growth of human liver cancer by upregulating Hint1 expression.

PubMed

Bao, Tianhao; Ke, Yang; Wang, Yifan; Wang, Weiwei; Li, Yuehua; Wang, Yan; Kui, Xiang; Zhou, Qixin; Zhou, Han; Zhang, Cheng; Zhou, Dongming; Wang, Lin; Xiao, Chunjie

2018-07-01

Taraxasterol has potent anti-inflammatory and anti-tumor activity. However, the effect and potential mechanisms of Taraxasterol on the growth of human liver cancer have not been clarified. Histidine triad nucleotide-binding protein 1 (Hint1) is a tumor suppressor and its downregulated expression is associated with the development of cancer. Here, we report that Taraxasterol treatment significantly suppressed cell proliferation and induced cell cycle arrest at G0/G1 phase and apoptosis in liver cancer cells, but not in non-tumor hepatocytes. Furthermore, Taraxasterol upregulated Hint1 and Bax, but downregulated Bcl2 and cyclin D1 expression, accompanied by promoting the demethylation in the Hint1 promoter region in liver cancer cells. The effects of Taraxasterol were abrogated by Hint1 silencing and partially mitigated by Bax silencing, Bcl2 or cyclin D1 over-expression in HepG2 cells. Moreover, oral administration with Taraxasterol did not affect body weight, urinary protein levels, and the heart, liver, and kidney morphology in BALB/c mice but effectively inhibited the growth of implanted SK-Hep1 tumor in vivo. Collectively, we demonstrate that Taraxasterol inhibits the growth of liver cancer at least partially by enhancing Hint1 expression to regulate Bax, Bcl2, and cyclin D1 expression. Taraxasterol may be a drug candidate for the treatment of human liver cancer. Taraxasterol inhibits growth and induces apoptosis in human liver cancer cells. Taraxasterol enhances Hint1 expression by promoting demethylation in Hint1 promoter. Taraxasterol increases Hint1 levels to regulate Bax, Bcl2, and cyclinD1 expression. The effects of Taraxasterol are abrogated by Hint1 silencing in liver cancer cells. Taraxasterol inhibits the growth of subcutaneously implanted liver cancers in mice.

Synergistic Effect of TPD7 and Berberine against Leukemia Jurkat Cell Growth through Regulating Ephrin-B2 Signaling.

PubMed

Ma, Weina; Zhu, Man; Yang, Liu; Yang, Tianfeng; Zhang, Yanmin

2017-09-01

TPD7, a novel biphenyl urea taspine derivative, and berberine have presented inhibition on VEGFR2 that can be regulated by ephrin-B2 reverse signaling through interactions with the PDZ domain. The purpose of this study is to investigate the inhibitory effect of the combination of TPD7 and berberine (TAB) on T-cell acute lymphoblastic leukemia cell growth. TPD7 and berberine together synergistically inhibited the proliferation of Jurkat cells. Also, the combination of TAB induced G 1 -phase cell-cycle arrest by downregulating the level of cyclin D1, cyclin E, and CDC2. Furthermore, the combination of TAB significantly enhanced apoptosis in Jurkat cells, and the apoptosis most likely resulted from the modulation of the level of Bcl-2 family members. Most importantly, the concomitant treatment simultaneously regulated the ephrin-B2 and VEGFR2 signaling, as well as modulated the MEK/ERK and PTEN/PI3K/AKT/mTOR signaling. Therefore, the combination treatment of TAB may be a promising therapeutic method in treating T-cell acute lymphoblastic leukemia. Copyright © 2017 John Wiley & Sons, Ltd. Copyright © 2017 John Wiley & Sons, Ltd.

Cellular effects of olomoucine, an inhibitor of cyclin-dependent kinases.

PubMed

Abraham, R T; Acquarone, M; Andersen, A; Asensi, A; Bellé, R; Berger, F; Bergounioux, C; Brunn, G; Buquet-Fagot, C; Fagot, D

1995-01-01

Olomoucine (2-(2-hydroxyethylamino)-6-benzylamino-9-methylpurine) has been recently described as a competitive inhibitor (ATP-binding site) of the cell cycle regulating p34cdc2/cyclin B, p33cdk2/cyclin A and p33cdk2/cyclin E kinases, the brain p33cdk5/p35 kinase and the ERK1/MAP-kinase. The unusual specificity of this compound towards cell cycle regulating enzymes suggests that it could inhibit certain steps of the cell cycle. The cellular effects of olomoucine were investigated in a large variety of plant and animal models. This compound inhibits the G1/S transition of unicellular algae (dinoflagellate and diatom). It blocks Fucus zygote cleavage and development of Laminaria gametophytes. Stimulated Petunia mesophyl protoplasts are arrested in G1 by olomoucine. By arresting cleavage it blocks the Laminaria gametophytes. Stimulated Petunia mesophyl protoplasts are arrested in G1 by olomoucine. By arresting cleavage it blocks the development of Calanus copepod larvae. It reversibly inhibits the early cleavages of Caenorhabditis elegans embryos and those of ascidian embryos. Olomoucine inhibits the serotonin-induced prophase/metaphase transition of clam oocytes; furthermore, it triggers the the release of these oocytes from their meiotic metaphase I arrest, and induces nuclei reformation. Olomoucine slows down the prophase/metaphase transition in cleaving sea urchin embryos, but does not affect the duration of the metaphase/anaphase and anaphase/telophase transitions. It also inhibits the prophase/metaphase transition of starfish oocytes triggered by various agonists. Xenopus oocyte maturation, the in vivo and in vitro phosphorylation of elongation factor EF-1 are inhibited by olomoucine. Mouse oocyte maturation is delayed by this compound, whereas parthenogenetic release from metaphase II arrest is facilitated. Growth of a variety of human cell lines (rhabdomyosarcoma cell lines Rh1, Rh18, Rh28 and Rh30; MCF-7, KB-3-1 and their adriamycin-resistant counterparts; National Cancer Institute 60 human tumor cell lines comprising nine tumor types) is inhibited by olomoucine. Cell cycle parameter analysis of the non-small cell lung cancer cell line MR65 shows that olomoucine affects G1 and S phase transits. Olomoucine inhibits DNA synthesis in interleukin-2-stimulated T lymphocytes (CTLL-2 cells) and triggers a G1 arrest similar to interleukin-2 deprivation. Both cdc2 and cdk2 kinases (immunoprecipitated from nocodazole- and hydroxyurea-treated CTLL-2 cells, respectively) are inhibited by olomoucine. Both yeast and Drosophila embryos were insensitive to olomoucine. Taken together the results of this Noah's Ark approach show that olomoucine arrests cells both at the G1/S and the G2/M boundaries, consistent with the hypothesis of a prevalent effect on the cdk2 and cdc2 kinases, respectively.

Structural and functional analysis of cyclin D1 reveals p27 and substrate inhibitor binding requirements.

PubMed

Liu, Shu; Bolger, Joshua K; Kirkland, Lindsay O; Premnath, Padmavathy N; McInnes, Campbell

2010-12-17

An alternative strategy for inhibition of the cyclin dependent kinases (CDKs) in antitumor drug discovery is afforded through the substrate recruitment site on the cyclin positive regulatory subunit. Critical CDK substrates such as the Rb and E2F families must undergo cyclin groove binding before phosphorylation, and hence inhibitors of this interaction also block substrate specific kinase activity. This approach offers the potential to generate highly selective and cell cycle specific CDK inhibitors and to reduce the inhibition of transcription mediated through CDK7 and 9, commonly observed with ATP competitive compounds. While highly potent peptide and small molecule inhibitors of CDK2/cyclin A, E substrate recruitment have been reported, little information has been generated on the determinants of inhibitor binding to the cyclin groove of the CDK4/cyclin D1 complex. CDK4/cyclin D is a validated anticancer drug target and continues to be widely pursued in the development of new therapeutics based on cell cycle blockade. We have therefore investigated the structural basis for peptide binding to its cyclin groove and have examined the features contributing to potency and selectivity of inhibitors. Peptidic inhibitors of CDK4/cyclin D of pRb phosphorylation have been synthesized, and their complexes with CDK4/cyclin D1 crystal structures have been generated. Based on available structural information, comparisons of the cyclin grooves of cyclin A2 and D1 are presented and provide insights into the determinants for peptide binding and the basis for differential binding and inhibition. In addition, a complex structure has been generated in order to model the interactions of the CDKI, p27(KIP)¹, with cyclin D1. This information has been used to shed light onto the endogenous inhibition of CDK4 and also to identify unique aspects of cyclin D1 that can be exploited in the design of cyclin groove based CDK inhibitors. Peptidic and nonpeptidic compounds have been synthesized in order to explore structure-activity relationship for binding to the cyclin D1 groove, which to date has not been carried out in a systematic fashion. Collectively, the data presented provide new insights into how compounds can be developed that function as chemical biology probes to determine the cellular and antitumor effects of CDK inhibition. Furthermore, such compounds will serve as templates for structure-guided efforts to develop potential therapeutics based on selective inhibition of CDK4/cyclin D activity.

Coordinated Expression of Cyclin-dependent Kinase-4 and its Regulators in Human Oral Tumors

PubMed Central

POI, MING J.; KNOBLOCH, THOMAS J.; SEARS, MARTA T.; UHRIG, LANA K.; WARNER, BLAKE M.; WEGHORST, CHRISTOPHER M.; LI, JUNAN

2014-01-01

Background/Aim While aberrant expression of cyclin-dependent kinase-4 (CDK4) has been found in squamous cell carcinoma of the head and neck (SCCHN), the associations between CDK4 and its regulators, namely, cyclin D1, cyclin E, gankyrin, SEI1, and BMI1 in gene expression remain to be explored. Herein we investigated the mRNA profiles of these oncogenes and their interrelations in different oral lesion tissues. Materials and Methods Thirty SCCHN specimens and patient-matched high at-risk mucosa (HARM) and 16 healthy control specimens were subjected to quantitative reverse transcription-polymerase chain reaction (qRT-PCR) analyses. Results The mRNA levels of CDK4, cyclin D1, gankyrin, SEI1, BMI1 were significantly elevated in both HARM and SCCHN (in comparison with control specimens), and statistically significant correlations were found among these markers in gene expression. Conclusion Up-regulation of CDK4 and its regulators takes place in oral cancer progression in a coordinate manner, and HARM and SCCHN share a similar molecular signature within the CDK4-pRB pathway. PMID:24982332

Retroviruses Hijack Chromatin Loops to Drive Oncogene Expression and Highlight the Chromatin Architecture around Proto-Oncogenic Loci

PubMed Central

Pattison, Jillian M.; Wright, Jason B.; Cole, Michael D.

2015-01-01

The majority of the genome consists of intergenic and non-coding DNA sequences shown to play a major role in different gene regulatory networks. However, the specific potency of these distal elements as well as how these regions exert function across large genomic distances remains unclear. To address these unresolved issues, we closely examined the chromatin architecture around proto-oncogenic loci in the mouse and human genomes to demonstrate a functional role for chromatin looping in distal gene regulation. Using cell culture models, we show that tumorigenic retroviral integration sites within the mouse genome occur near existing large chromatin loops and that this chromatin architecture is maintained within the human genome as well. Significantly, as mutagenesis screens are not feasible in humans, we demonstrate a way to leverage existing screens in mice to identify disease relevant human enhancers and expose novel disease mechanisms. For instance, we characterize the epigenetic landscape upstream of the human Cyclin D1 locus to find multiple distal interactions that contribute to the complex cis-regulation of this cell cycle gene. Furthermore, we characterize a novel distal interaction upstream of the Cyclin D1 gene which provides mechanistic evidence for the abundant overexpression of Cyclin D1 occurring in multiple myeloma cells harboring a pathogenic translocation event. Through use of mapped retroviral integrations and translocation breakpoints, our studies highlight the importance of chromatin looping in oncogene expression, elucidate the epigenetic mechanisms crucial for distal cis-regulation, and in one particular instance, explain how a translocation event drives tumorigenesis through upregulation of a proto-oncogene. PMID:25799187

Activation of G-protein coupled estrogen receptor inhibits the proliferation of cervical cancer cells via sustained activation of ERK1/2.

PubMed

Zhang, Qiong; Wu, Yuan-Zhe; Zhang, Yan-Mei; Ji, Xiao-Hong; Hao, Qun

2015-04-01

Cervical cancer is one of the most common gynaecological women cancer and suggested to be modulated by estrogenic signals. G protein-coupled receptor (GPER), a seven-transmembrane G protein-coupled receptor, has been reported to regulate the cell proliferation of various cancers. But there is no study investigating the effects of GPER on the progression of cervical cancer. In the present study, we revealed for the first time that GPER was also highly expressed in various human cervical cancer cells. Activation of GPER via its specific agonist G-1 induced G2/M cell cycle arrest and down regulation of cyclin B via a time dependent manner. Furthermore, G-1 treatment induced sustained activation of extracellular-signal-regulated kinases (ERK)1/2 via epidermal growth factor receptor (EGFR) signals. Both inhibitors of ERK1/2 and EGFR significantly abolished G-1-induced suppression of cell proliferation and down regulation of cyclin B. Generally, our study revealed that GPER is highly expressed in human cervical cancer cells and its activation inhibits cell proliferation via EGFR/ERK1/2 signals. It suggested that G-1 can be considered as a potential new pharmacological tool to reduce the growth of cervical cancer. Copyright © 2015 John Wiley & Sons, Ltd.

The ethanol extract from Artemisia princeps Pampanini induces p53-mediated G1 phase arrest in A172 human neuroblastoma cells.

PubMed

Park, Eun Young; Lee, Kyung-Won; Lee, Heon-Woo; Cho, Young-Wuk; Baek, Nam-In; Chung, Hae-Gon; Jeong, Tae-Sook; Choi, Myung-Sook; Lee, Kyung-Tae

2008-06-01

In the present study, the antiproliferative effects of the ethanol extract of Artemisia princeps Pampanini (EAPP) and the mechanism involved were investigated. Of the various cancer cells examined, human neuroblastoma A172 cells were most sensitive to EAPP, and their proliferation was dose- and time-dependently inhibited by EAPP. DNA flow cytometry analysis indicated that EAPP notably induced the G(1) phase arrest in A172 cells. Of the G(1) phase cycle-related proteins examined, the expressions of cyclin-dependent kinase (CDK) 2, CDK4, and CDK6 and of cyclin D(1), D(2), and D(3) were found to be markedly reduced by EAPP, whereas cyclin E was unaffected. Moreover, the protein and mRNA levels of the CDK inhibitors p16(INK4a), p21(CIP1/WAF1), and p27(KIP1) were increased, and the activities of CDK2, CDK4, and CDK6 were reduced. Furthermore, the expressions of E2F-1 and of phosphorylated pRb were also decreased, and the protein levels of p53 and pp53 (Ser15) were increased. Up-regulation of p21(CIP1/WAF1) was found to be mediated by a p53-dependent pathway in EAPP-induced G(1)-arrested A172 cells. When these data are taken together, the EAPP was found to potently inhibit the proliferation of human neuroblastoma A172 cells via G(1) phase cell cycle arrest.

Cyclin-dependent kinase inhibitor Cdkn2c regulates B cell homeostasis and function in the NZM2410-derived murine lupus susceptibility locus Sle2c1

PubMed Central

Xu, Zhiwei; Potula, Hari-Hara SK; Vallurupalli, Anusha; Perry, Daniel; Baker, Henry; Croker, Byron P.; Dozmorov, Igor; Morel, Laurence

2013-01-01

Sle2c1 is an NZM2410 and NZB-derived lupus susceptibility locus that induces an expansion of the B1a cell compartment. B1a cells have a repertoire enriched for autoreactivity, and an expansion of this B cell subset occurs in several mouse models of lupus. A combination of genetic mapping and candidate gene analysis presents Cdkn2c, a gene encoding for cyclin-dependent kinase inhibitor p18INK4c (p18), as the top candidate gene for inducing the Slec2c1 associated expansion of B1a cells. A novel SNP in the NZB allele of the Cdkn2c promoter is associated with a significantly reduced Cdkn2c expression in the splenic B cells and Pc B1a cells from Sle2c1-carrying mice, which leads to a defective G1 cell cycle arrest in splenic B cells and increased proliferation of Pc B1a cells. As cell cycle is differentially regulated in B1a and B2 cells, these results suggest that Cdkn2c plays a critical role in B1a cell self-renewal, and that its impaired expression leads to an accumulation of these cells with high autoreactive potential. PMID:21543644

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cheng, Jing; Du, Yi-Fang; Xiao, Zhi-Yi

KYKZL-1, a newly synthesized compound with COX/5-LOX dual inhibition, was subjected to the inhibitory activity test on Hep G{sub 2} growth. We found that KYKZL-1 inhibited the growth of Hep G{sub 2} cells via inducing apoptosis. Further studies showed that KYKZL-1 activated caspase-3 through cytochrome c release from mitochondria and down regulation of Bcl-2/Bax ratio and reduced the high level of COX-2 and 5-LOX. As shown in its anti-inflammatory effect, KYKZL-1 also exhibited inhibitory effect on the PGE{sub 2} and LTB{sub 4} production in Hep G{sub 2} cells. Accordingly, exogenous addition of PGE{sub 2} or LTB{sub 4} reversed the decreasesmore » in cell viability. In addition, KYKZL-1 caused cell cycle arrest at the S–G{sub 2} checkpoint via the activation of p21{sup CIP1} protein and down-regulation of cyclin A expression. These data indicate that the growth inhibitory effect of KYKZL-1 is associated with inhibition of AA metabolites and caspase-3 pathway and cell cycle arrest. Combined with our previous findings, KYKZL-1 exhibiting COX/5-LOX inhibition may be a promising potential agent not only for inflammation control but also for cancer prevention/therapy with an enhanced gastric safety profile. - Highlights: • KYKZL-1 is designed to exhibit COX/5-LOX dual inhibition. • KYKZL-1 resulted in apoptosis of Hep G{sub 2} cells. • KYKZL-1 activated caspase-3 through cytochrome c and bcl-2/bax ratio. • KYKZL-1 caused cell cycle arrest via modulation of p21{sup CIP1} and cyclin A level.« less

Prevention of chemotherapy-induced alopecia in rats by CDK inhibitors.

PubMed

Davis, S T; Benson, B G; Bramson, H N; Chapman, D E; Dickerson, S H; Dold, K M; Eberwein, D J; Edelstein, M; Frye, S V; Gampe, R T; Griffin, R J; Harris, P A; Hassell, A M; Holmes, W D; Hunter, R N; Knick, V B; Lackey, K; Lovejoy, B; Luzzio, M J; Murray, D; Parker, P; Rocque, W J; Shewchuk, L; Veal, J M; Walker, D H; Kuyper, L F

2001-01-05

Most traditional cytotoxic anticancer agents ablate the rapidly dividing epithelium of the hair follicle and induce alopecia (hair loss). Inhibition of cyclin-dependent kinase 2 (CDK2), a positive regulator of eukaryotic cell cycle progression, may represent a therapeutic strategy for prevention of chemotherapy-induced alopecia (CIA) by arresting the cell cycle and reducing the sensitivity of the epithelium to many cell cycle-active antitumor agents. Potent small-molecule inhibitors of CDK2 were developed using structure-based methods. Topical application of these compounds in a neonatal rat model of CIA reduced hair loss at the site of application in 33 to 50% of the animals. Thus, inhibition of CDK2 represents a potentially useful approach for the prevention of CIA in cancer patients.

Protoparvovirus Interactions with the Cellular DNA Damage Response

PubMed Central

Majumder, Kinjal; Etingov, Igor

2017-01-01

Protoparvoviruses are simple single-stranded DNA viruses that infect many animal species. The protoparvovirus minute virus of mice (MVM) infects murine and transformed human cells provoking a sustained DNA damage response (DDR). This DDR is dependent on signaling by the ATM kinase and leads to a prolonged pre-mitotic cell cycle block that features the inactivation of ATR-kinase mediated signaling, proteasome-targeted degradation of p21, and inhibition of cyclin B1 expression. This review explores how protoparvoviruses, and specifically MVM, co-opt the common mechanisms regulating the DDR and cell cycle progression in order to prepare the host nuclear environment for productive infection. PMID:29088070

Protoparvovirus Interactions with the Cellular DNA Damage Response.

PubMed

Majumder, Kinjal; Etingov, Igor; Pintel, David J

2017-10-31

Protoparvoviruses are simple single-stranded DNA viruses that infect many animal species. The protoparvovirus minute virus of mice (MVM) infects murine and transformed human cells provoking a sustained DNA damage response (DDR). This DDR is dependent on signaling by the ATM kinase and leads to a prolonged pre-mitotic cell cycle block that features the inactivation of ATR-kinase mediated signaling, proteasome-targeted degradation of p21, and inhibition of cyclin B1 expression. This review explores how protoparvoviruses, and specifically MVM, co-opt the common mechanisms regulating the DDR and cell cycle progression in order to prepare the host nuclear environment for productive infection.

Cyclin D2 is sufficient to drive β cell self-renewal and regeneration

PubMed Central

2017-01-01

ABSTRACT Diabetes results from an inadequate mass of functional β cells, due to either β cell loss caused by autoimmune destruction (type I diabetes) or β cell failure in response to insulin resistance (type II diabetes). Elucidating the mechanisms that regulate β cell mass may be key to developing new techniques that foster β cell regeneration as a cellular therapy to treat diabetes. While previous studies concluded that cyclin D2 is required for postnatal β cell self-renewal in mice, it is not clear if cyclin D2 is sufficient to drive β cell self-renewal. Using transgenic mice that overexpress cyclin D2 specifically in β cells, we show that cyclin D2 overexpression increases β cell self-renewal post-weaning and results in increased β cell mass. β cells that overexpress cyclin D2 are responsive to glucose stimulation, suggesting they are functionally mature. β cells that overexpress cyclin D2 demonstrate an enhanced regenerative capacity after injury induced by streptozotocin toxicity. To understand if cyclin D2 overexpression is sufficient to drive β cell self-renewal, we generated a novel mouse model where cyclin D2 is only expressed in β cells of cyclin D2−/− mice. Transgenic overexpression of cyclin D2 in cyclin D2−/− β cells was sufficient to restore β cell mass, maintain normoglycaemia, and improve regenerative capacity when compared with cyclin D2−/− littermates. Taken together, our results indicate that cyclin D2 is sufficient to regulate β cell self-renewal and that manipulation of its expression could be used to enhance β cell regeneration. PMID:28763258

A Minimal Anaphase Promoting Complex/Cyclosome (APC/C) in Trypanosoma brucei

PubMed Central

Bessat, Mohamed; Knudsen, Giselle; Burlingame, Alma L.; Wang, Ching C.

2013-01-01

The anaphase-promoting complex/cyclosome (APC/C) is a multi-subunit E3 ubiquitin ligase that initiates chromosome segregation and mitotic exit by targeting critical cell-cycle regulators for proteolytic destruction. Previously, seven APC/C subunit homologues were identified in the genome of Trypanosoma brucei. In the present study, we tested five of them in yeast complementation studies and found none of them capable of complementing the yeast mutants lacking the corresponding subunits, suggesting significant discrepancies between the two APC/C’s. Subunit homologues of mitotic checkpoint complex (MCC) have not yet been identified in T. brucei, raising the possibility that a MCC-APC/C complex equivalent may not exist in T. brucei. We performed tandem affinity purification of the protein complex containing a APC1 fusion protein expressed in the cells enriched in different phases of the cell cycle of procyclic form T. brucei, and compared their protein profiles using LC-MS/MS analyses. The seven putative APC/C subunits were identified in the protein complex throughout the cell cycle together with three additional proteins designated the associated proteins (AP) AP1, AP2 and AP3. Abundance of the 10 proteins remained relatively unchanged throughout the cell cycle, suggesting that they are the core subunits of APC/C. AP1 turned out to be a homologue of APC4. An RNAi knockdown of APC4 and AP3 showed no detectable cellular phenotype, whereas an AP2 knockdown enriched the cells in G2/M phase. The AP2-depleted cells showed stabilized mitotic cyclin B. An accumulation of poly-ubiquitinated cyclin B was indicated in the cells treated with the proteasome inhibitor MG132, demonstrating the involvement of proteasome in degrading poly-ubiquitinated cyclin B. In all, a 10-subunit APC/C machinery with a conserved function is identified in T. brucei without linking to a MCC-like complex, thus indicating a unique T. brucei APC/C. PMID:23533609

Geraniol and beta-ionone inhibit proliferation, cell cycle progression, and cyclin-dependent kinase 2 activity in MCF-7 breast cancer cells independent of effects on HMG-CoA reductase activity.

PubMed

Duncan, Robin E; Lau, Dominic; El-Sohemy, Ahmed; Archer, Michael C

2004-11-01

3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase catalyzes the formation of mevalonate, a precursor of cholesterol that is also required for cell proliferation. Mevalonate depletion results in a G1 phase cell cycle arrest that is mediated in part by impaired activity of cyclin-dependent kinase (CDK) 2, and decreased expression of positive regulators of G1 to S phase progression. Inhibition of mevalonate synthesis may, therefore, be a useful strategy to impair the growth of malignant cells. Plant isoprenoids, including beta-ionone and geraniol, have previously been shown to inhibit rodent mammary tumor development, and rodent and avian hepatic HMG-CoA reductase activity. We hypothesized that the putative anti-proliferative and cell cycle inhibitory effects of beta-ionone and geraniol on MCF-7 human breast cancer cells in culture are mediated by mevalonate depletion resulting from inhibition of HMG-CoA reductase activity. Flow cytometric analysis showed a G1 arrest in isoprenoid-treated MCF-7 cells, and also a G2/M arrest at higher concentrations of isoprenoids. These compounds minimally affected the growth of MCF-10F normal breast epithelial cells. Both beta-ionone and geraniol inhibited CDK 2 activity and dose-dependently decreased the expression of cyclins D1, E, and A, and CDK 2 and 4, without changing the expression of p21cip1 or p27kip1. Although both beta-ionone and geraniol also inhibited MCF-7 proliferation, only geraniol inhibited HMG-CoA reductase activity. While these effects were significantly correlated (r2=0.89, P <0.01), they were not causally related, since exogenous mevalonate did not restore growth in geraniol-inhibited cells. These findings indicate that mechanisms other than impaired mevalonate synthesis mediate the anti-proliferative and cell cycle regulatory effects of beta-ionone and geraniol in human breast cancer cells.

Cell wall mannoprotein of Candida albicans induces cell cycle alternation and inhibits apoptosis of HaCaT cells via NF-κB signal pathway.

PubMed

Han, Yang; Jiang, Hang-Hang; Zhang, Yu-Jing; Hao, Xing-Jia; Sun, Yu-Zhe; Qi, Rui-Qun; Chen, Hong-Duo; Gao, Xing-Hua

2017-10-01

Candida albicans (C. albicans) is a commensal organism in human and a well-known dimorphic opportunistic pathogenic fungus. Though plenty of researches on the pathogenesis of C. albicans have been performed, the mechanism is not fully understood. The cell wall components of C. albicans have been documented to play important roles in its pathogenic processes. To further study the infectious mechanism of C. albicans, we investigated the potential functional role of its cell wall mannoprotein in cell cycle and apoptosis of HaCaT cells. We found that mannoprotein could promote the transition of cell cycle from G1/G0 to S phase, in which Cyclin D1, CDK4 and p-Rb, the major regulators of the cell cycle progression, showed significant upregulation, and CDKN1A (cyclin dependent kinase inhibitor 1A (p21)) showed significant downregulation. Mannoprotein also could inhibit apoptosis of HaCaT cells, which was well associated with increased expression of BCL2 (Bcl-2). Moreover, mannoprotein could increase the phosphorylation levels of RELA (p65) and NFKBIA (IκBα), as the key factors of NF-κB signal pathway in HaCaT cells, suggesting the activation of NF-κB signal pathway. Additionally, a NF-κB specific inhibitor, PDTC, could rescue the effect of mannoprotein on cell cycle and apoptosis of HaCaT cells, which suggested that mannoprotein could activate NF-κB signal pathway to mediate cell cycle alternation and inhibit apoptosis. Copyright © 2017. Published by Elsevier Ltd.

Regulation of D-cyclin translation inhibition in myeloma cells treated with mTOR inhibitors: Rationale for combined treatment with ERK inhibitors and rapamycin

PubMed Central

Frost, Patrick; Shi, Yijiang; Hoang, Bao; Gera, Joseph; Lichtenstein, Alan

2009-01-01

We have shown that heightened AKT activity sensitized multiple myeloma (MM) cells to the anti-tumor effects of the mTOR-inhibitor, CCI-779. To test the mechanism of AKT’s regulatory role, we stably transfected U266 MM cell lines with an activated AKT allele or empty vector. The AKT-transfected cells were more sensitive to cytostasis induced in vitro by rapamycin or in vivo by its analog, CCI-779, whereas cells with quiescent AKT were resistant. The ability of mTOR inhibitors to downregulate D-cyclin expression was significantly greater in AKT-transfected MM cells, due in part, to AKT’s ability to curtail cap-independent translation and internal ribosome entry site (IRES) activity of D-cyclin transcripts. Similar AKT-dependent regulation of rapamycin responsiveness was demonstrated in a second myeloma model: the PTEN-null OPM-2 cell line transfected with wild type PTEN. As ERK/p38 activity facilitates IRES-mediated translation of some transcripts, we investigated ERK/p38 as regulators of AKT-dependent effects on rapamycin sensitivity. AKT-transfected U266 cells demonstrated significantly decreased ERK and p38 activity. However, only an ERK inhibitor prevented D-cyclin IRES activity in resistant “low AKT” myeloma cells. Furthermore, the ERK inhibitor successfully sensitized myeloma cells to rapamycin in terms of down regulated D-cyclin protein expression and G1 arrest. However, ectopic over-expression of an activated MEK gene did not increase cap-independent translation of D-cyclin in “high AKT” myeloma cells indicating that MEK/ERK activity was required but not sufficient for activation of the IRES. These data support a scenario where heightened AKT activity down-regulates D-cyclin IRES function in MM cells and ERK facilitates activity. PMID:19139116

p21/Cyclin E pathway modulates anticlastogenic function of Bmi-1 in cancer cells

PubMed Central

Deng, Wen; Zhou, Yuan; Tiwari, Agnes FY; Su, Hang; Yang, Jie; Zhu, Dandan; Lau, Victoria Ming Yi; Hau, Pok Man; Yip, Yim Ling; Cheung, Annie LM; Guan, Xin-Yuan; Tsao, Sai Wah

2015-01-01

Apart from regulating stem cell self-renewal, embryonic development and proliferation, Bmi-1 has been recently reported to be critical in the maintenance of genome integrity. In searching for novel mechanisms underlying the anticlastogenic function of Bmi-1, we observed, for the first time, that Bmi-1 positively regulates p21 expression. We extended the finding that Bmi-1 deficiency induced chromosome breaks in multiple cancer cell models. Interestingly, we further demonstrated that knockdown of cyclin E or ectopic overexpression of p21 rescued Bmi-1 deficiency-induced chromosome breaks. We therefore conclude that p21/cyclin E pathway is crucial in modulating the anticlastogenic function of Bmi-1. As it is well established that the overexpression of cyclin E potently induces genome instability and p21 suppresses the function of cyclin E, the novel and important implication from our findings is that Bmi-1 plays an important role in limiting genomic instability in cylin E-overexpressing cancer cells by positive regulation of p21. PMID:25131797

A Novel, Non-Apoptotic Role for Scythe/BAT3: A Functional Switch between the Pro- and Anti-Proliferative Roles of p21 during the Cell Cycle

PubMed Central

Yong, Sheila T.; Wang, Xiao-Fan

2012-01-01

Background Scythe/BAT3 is a member of the BAG protein family whose role in apoptosis has been extensively studied. However, since the developmental defects observed in Bat3-null mouse embryos cannot be explained solely by defects in apoptosis, we investigated whether BAT3 is also involved in cell-cycle progression. Methods/Principal Findings Using a stable-inducible Bat3-knockdown cellular system, we demonstrated that reduced BAT3 protein level causes a delay in both G1/S transition and G2/M progression. Concurrent with these changes in cell-cycle progression, we observed a reduction in the turnover and phosphorylation of the CDK inhibitor p21, which is best known as an inhibitor of DNA replication; however, phosphorylated p21 has also been shown to promote G2/M progression. Our findings indicate that in Bat3-knockdown cells, p21 continues to be synthesized during cell-cycle phases that do not normally require p21, resulting in p21 protein accumulation and a subsequent delay in cell-cycle progression. Finally, we showed that BAT3 co-localizes with p21 during the cell cycle and is required for the translocation of p21 from the cytoplasm to the nucleus during the G1/S transition and G2/M progression. Conclusion: Our study reveals a novel, non-apoptotic role for BAT3 in cell-cycle regulation. By maintaining a low p21 protein level during the G1/S transition, BAT3 counteracts the inhibitory effect of p21 on DNA replication and thus enables the cells to progress from G1 to S phase. Conversely, during G2/M progression, BAT3 facilitates p21 phosphorylation by cyclin A/Cdk2, an event required for G2/M progression. BAT3 modulates these pro- and anti-proliferative roles of p21 at least in part by regulating cyclin A abundance, as well as p21 translocation between the cytoplasm and the nucleus to ensure that it functions in the appropriate intracellular compartment during each phase of the cell cycle. PMID:22761665

The human HECA interacts with cyclins and CDKs to antagonize Wnt-mediated proliferation and chemoresistance of head and neck cancer cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dowejko, Albert, E-mail: Albert.Dowejko@klinik.uni-regensburg.de; Bauer, Richard; Bauer, Karin

2012-03-10

There is a growing evidence that the human homologue of the Drosophila headcase (HECA) plays an important role in human carcinogenesis. So far specific protein interaction partners and affected signaling pathways of HECA are still elusive. In a recent study we showed that HECA overexpression in oral squamous-cell carcinoma (OSCC) keratinocytes has tumor suppressive effects resulting in a recuperation of cell cycle control concerning the entry and progression of S-phase, G2- and M-phase. Currently, quantitative RT-PCR and immunohistochemical analysis of primary tumor tissue from OSCC patients demonstrate that HECA expression is markedly decreased compared to normal control patients with abundantmore » HECA expression. Additionally, there is nearly no HECA expression in OSCC metastases. Here, we show that HECA expression is negatively controlled by the Wnt-pathway and TCF4, a Wnt related transcription factor, binds to the HECA promoter. Furthermore, immunocytochemistry reveals colocalization of HECA with the cyclin dependent kinase CDK9. Immunoprecipitation experiments and proximity ligation assays further reveal an interaction of HECA with CDK2, CDK9, Cyclin A and Cyclin K, a direct transcriptional target of the p53 tumor suppressor. Silencing HECA in OSCC cell lines leads to a significant increase of cell division and a markedly increased resistance against the chemotherapeutic cisplatin. On the contrary, HECA overexpressing OSCC cell lines show decreased resistance of OSCC cells against cisplatin. Therefore, HECA could be considered as future therapeutic agent against Wnt-dependent tumor progression. -- Highlights: Black-Right-Pointing-Pointer HECA is a new cell cycle regulator with anti-tumor features in head and neck cancer. Black-Right-Pointing-Pointer During tumor progression HECA mRNA and protein expression decrease. Black-Right-Pointing-Pointer The HECA promotor is a direct target of the Wnt/beta-catenin/TCF-pathway. Black-Right-Pointing-Pointer The HECA protein antagonizes Wnt-mediated cell proliferation through interaction with major cell cycle factors. Black-Right-Pointing-Pointer Modulating HECA level confers benefits for engaging tumor cells with cisplatin.« less

Regulation of the Anaphase-promoting Complex–Separase Cascade by Transforming Growth Factor-β Modulates Mitotic Progression in Bone Marrow Stromal Cells

PubMed Central

Fujita, Takeo; Epperly, Michael W.; Zou, Hui; Greenberger, Joel S.

2008-01-01

Alteration of the tumor microenvironment by aberrant stromal cells influences many aspects of cell biology, including differentiation of stem cells and tumor metastasis. The role of transforming growth factor (TGF)-β signaling in stromal cells of the tissue microenvironment is critical to both pathways. We examined murine marrow stromal cells with deletion of Smad3 and found that they have an altered cell cycle profile, with a higher fraction of cells in G2/M phase. Deletion of Smad3 significantly abrogates TGF-β signaling and suppresses phosphorylation of CDC27–anaphase-promoting complex (APC) during mitosis, thereby resulting in elevated cyclin-dependent kinase (CDK)1 activity via increased levels of cyclin B. Enhanced CDK1 activity due to deregulation of APC leads in turn to hyperphosphorylation of separase, impeding chromatid separation. A residue Ser1126Ala mutation in separase specifically abolished separase hyperphosphorylation in Smad3-deficient cells. The present results unveil a new function for the TGF-β pathway in the regulation of APC to mediate chromatid separation during mitosis. PMID:18843049

A new class of cyclin dependent kinase in Chlamydomonas is required for coupling cell size to cell division

PubMed Central

Li, Yubing; Liu, Dianyi; López-Paz, Cristina; Olson, Bradley JSC; Umen, James G

2016-01-01

Proliferating cells actively control their size by mechanisms that are poorly understood. The unicellular green alga Chlamydomonas reinhardtii divides by multiple fission, wherein a ‘counting’ mechanism couples mother cell-size to cell division number allowing production of uniform-sized daughters. We identified a sizer protein, CDKG1, that acts through the retinoblastoma (RB) tumor suppressor pathway as a D-cyclin-dependent RB kinase to regulate mitotic counting. Loss of CDKG1 leads to fewer mitotic divisions and large daughters, while mis-expression of CDKG1 causes supernumerous mitotic divisions and small daughters. The concentration of nuclear-localized CDKG1 in pre-mitotic cells is set by mother cell size, and its progressive dilution and degradation with each round of cell division may provide a link between mother cell-size and mitotic division number. Cell-size-dependent accumulation of limiting cell cycle regulators such as CDKG1 is a potentially general mechanism for size control. DOI: http://dx.doi.org/10.7554/eLife.10767.001 PMID:27015111

Effects of tanshinone nanoemulsion and extract on inhibition of lung cancer cells A549

NASA Astrophysics Data System (ADS)

Lee, W. D.; Liang, Y. J.; Chen, B. H.

2016-12-01

Danshen (Salvia miltiorrhiza), a Chinese medicinal herb, consists of several functional components including tanshinones responsible for prevention of several chronic diseases. This study intends to prepare tanshinone extract and nanoemulsion from danshen and determine their inhibition effect on lung cancer cells A549. A highly stable tanshinone nanoemulsion composed of Capryol 90, Tween 80, ethanol and deionized water with the mean particle size of 14.2 nm was successfully prepared. Tanshinone nanoemulsion was found to be more effective in inhibiting A549 proliferation than tanshinone extract. Both nanoemulsion and extract could penetrate into cytoplasm through endocytosis, with the former being more susceptible than the latter. A dose-dependent response in up-regulation of p-JNK, p53 and p21 and down-regulation of CDK2, cyclin D1 and cyclin E1 expressions was observed with the cell cycle arrested at G0/G1 phase. The cellular microcompartment change of A549 was also investigated. The study demonstrated that tanshinone nanoemulsion may be used as a botanic drug for treatment of lung cancer.

MicroRNA let-7c Inhibits Cell Proliferation and Induces Cell Cycle Arrest by Targeting CDC25A in Human Hepatocellular Carcinoma

PubMed Central

Zhu, Xiuming; Wu, Lingjiao; Yao, Jian; Jiang, Han; Wang, Qiangfeng; Yang, Zhijian; Wu, Fusheng

2015-01-01

Down-regulation of the microRNA let-7c plays an important role in the pathogenesis of human hepatocellular carcinoma (HCC). The aim of the present study was to determine whether the cell cycle regulator CDC25A is involved in the antitumor effect of let-7c in HCC. The expression levels of let-7c in HCC cell lines were examined by quantitative real-time PCR, and a let-7c agomir was transfected into HCC cells to overexpress let-7c. The effects of let-7c on HCC proliferation, apoptosis and cell cycle were analyzed. The in vivo tumor-inhibitory efficacy of let-7c was evaluated in a xenograft mouse model of HCC. Luciferase reporter assays and western blotting were conducted to identify the targets of let-7c and to determine the effects of let-7c on CDC25A, CyclinD1, CDK6, pRb and E2F2 expression. The results showed that the expression levels of let-7c were significantly decreased in HCC cell lines. Overexpression of let-7c repressed cell growth, induced cell apoptosis, led to G1 cell cycle arrest in vitro, and suppressed tumor growth in a HepG2 xenograft model in vivo. The luciferase reporter assay showed that CDC25A was a direct target of let-7c, and that let-7c inhibited the expression of CDC25A protein by directly targeting its 3ʹ UTR. Restoration of CDC25A induced a let-7c-mediated G1-to-S phase transition. Western blot analysis demonstrated that overexpression of let-7c decreased CyclinD1, CDK6, pRb and E2F2 protein levels. In conclusion, this study indicates that let-7c suppresses HCC progression, possibly by directly targeting the cell cycle regulator CDC25A and indirectly affecting its downstream target molecules. Let-7c may therefore be an effective therapeutic target for HCC. PMID:25909324

E-type cyclins modulate telomere integrity in mammalian male meiosis.

PubMed

Manterola, Marcia; Sicinski, Piotr; Wolgemuth, Debra J

2016-06-01

We have shown that E-type cyclins are key regulators of mammalian male meiosis. Depletion of cyclin E2 reduced fertility in male mice due to meiotic defects, involving abnormal pairing and synapsis, unrepaired DNA, and loss of telomere structure. These defects were exacerbated by additional loss of cyclin E1, and complete absence of both E-type cyclins produces a meiotic catastrophe. Here, we investigated the involvement of E-type cyclins in maintaining telomere integrity in male meiosis. Spermatocytes lacking cyclin E2 and one E1 allele (E1+/-E2-/-) displayed a high rate of telomere abnormalities but can progress to pachytene and diplotene stages. We show that their telomeres exhibited an aberrant DNA damage repair response during pachynema and that the shelterin complex proteins TRF2 and RAP2 were significantly decreased in the proximal telomeres. Moreover, the insufficient level of these proteins correlated with an increase of γ-H2AX foci in the affected telomeres and resulted in telomere associations involving TRF1 and telomere detachment in later prophase-I stages. These results suggest that E-type cyclins are key modulators of telomere integrity during meiosis by, at least in part, maintaining the balance of shelterin complex proteins, and uncover a novel role of E-type cyclins in regulating chromosome structure during male meiosis.

Expression of retinoblastoma gene product (pRb) in mantle cell lymphomas. Correlation with cyclin D1 (PRAD1/CCND1) mRNA levels and proliferative activity.

PubMed Central

Jares, P.; Campo, E.; Pinyol, M.; Bosch, F.; Miquel, R.; Fernandez, P. L.; Sanchez-Beato, M.; Soler, F.; Perez-Losada, A.; Nayach, I.; Mallofré, C.; Piris, M. A.; Montserrat, E.; Cardesa, A.

1996-01-01

Mantle cell lymphomas (MCLs) are molecularly characterized by bcl-1 rearrangement and constant cyclin D1 (PRAD-1/CCND1) gene overexpression. Cyclin D1 is a G1 cyclin that participates in the control of the cell cycle progression by interacting with the retinoblastoma gene product (pRb). Inactivation of the Rb tumor suppressor gene has been implicated in the development of different types of human tumors including some high grade non-Hodgkin's lymphomas. To determine the role of the retinoblastoma gene in the pathogenesis of MCLs and its possible interaction with cyclin D1, pRb expression was examined in 23 MCLs including 17 typical and 6 blastic variants by immunohistochemistry and Western blot. Rb gene structure was studied in 13 cases by Southern blot. Cytogenetic analysis was performed in 5 cases. The results were compared with the cyclin D1 mRNA levels examined by Northern analysis, and the proliferative activity of the tumors was measured by Ki-67 growth fraction and flow cytometry. pRb was expressed in all MCLs. The expression varied from case to case (mean, 14.1% of positive cells; range, 1.3 to 42%) with a significant correlation with the proliferative activity of the tumors (mitotic index r = 0.85; Ki-67 r = 0.7; S phase = 0.73). Blastic variants showed higher numbers of pRb-positive cells (mean, 29%) than the typical cases (10%; P < 0.005) by immunohistochemistry and, concordantly, higher levels of expression by Western blot. In addition, the blastic cases also had an increased expression of the phosphorylated protein. No alterations in Rb gene structure were observed by Southern blot analysis. Cyclin D1 mRNA levels were independent of pRb expression and the proliferative activity of the tumors. These findings suggest that pRb in MCLs is normally regulated in relation to the proliferative activity of the tumors. Cyclin D1 overexpression may play a role in the maintenance of cell proliferation by overcoming the suppressive growth control of pRb. Images Figure 1 Figure 2 Figure 4 PMID:8623927

Cyclin D1 Determines Mitochondrial Function In Vivo†

PubMed Central

Sakamaki, Toshiyuki; Casimiro, Mathew C.; Ju, Xiaoming; Quong, Andrew A.; Katiyar, Sanjay; Liu, Manran; Jiao, Xuanmao; Li, Anping; Zhang, Xueping; Lu, Yinan; Wang, Chenguang; Byers, Stephen; Nicholson, Robert; Link, Todd; Shemluck, Melvin; Yang, Jianguo; Fricke, Stanley T.; Novikoff, Phyllis M.; Papanikolaou, Alexandros; Arnold, Andrew; Albanese, Christopher; Pestell, Richard

2006-01-01

The cyclin D1 gene encodes a regulatory subunit of the holoenzyme that phosphorylates and inactivates the pRb tumor suppressor to promote nuclear DNA synthesis. cyclin D1 is overexpressed in human breast cancers and is sufficient for the development of murine mammary tumors. Herein, cyclin D1 is shown to perform a novel function, inhibiting mitochondrial function and size. Mitochondrial activity was enhanced by genetic deletion or antisense or small interfering RNA to cyclin D1. Global gene expression profiling and functional analysis of mammary epithelial cell-targeted cyclin D1 antisense transgenics demonstrated that cyclin D1 inhibits mitochondrial activity and aerobic glycolysis in vivo. Reciprocal regulation of these genes was observed in cyclin D1-induced mammary tumors. Cyclin D1 thus integrates nuclear DNA synthesis and mitochondrial function. PMID:16809779

A Noncanonical Role for the CKI-RB-E2F Cell Cycle Signaling Pathway in Plant Effector-Triggered Immunity

PubMed Central

Wang, Shui; Gu, Yangnan; Zebell, Sophia G.; Anderson, Lisa K.; Wang, Wei; Mohan, Rajinikanth; Dong, Xinnian

2014-01-01

SUMMARY Effector-triggered immunity (ETI), the major host defense mechanism in plants, is often associated with programmed cell death (PCD). Plants lack close homologs of caspases, the key mediators of PCD in animals. So although the NB-LRR receptors involved in ETI are well studied, how they activate PCD and confer disease resistance remains elusive. We show that the Arabidopsis nuclear envelope protein, CPR5, negatively regulates ETI and the associated PCD through a physical interaction with CYCLIN-DEPENDENT KINASE INHIBITORs (CKIs). Upon ETI induction, CKIs are released from CPR5 to cause over-activation of another core cell cycle regulator, E2F. In cki and e2f mutants, ETI responses induced by both TIR-NB-LRR and CC-NB-LRR classes of immune receptors are compromised. We further show that E2F is deregulated during ETI probably through CKI-mediated hyperphosphorylation of RETINOBLASTOMA-RELATED 1 (RBR1). This study demonstrates that canonical cell cycle regulators also play important noncanonical roles in plant immunity. PMID:25455564

Antitumorigenic effect of atmospheric-pressure dielectric barrier discharge on human colorectal cancer cells via regulation of Sp1 transcription factor

NASA Astrophysics Data System (ADS)

Han, Duksun; Cho, Jin Hyoung; Lee, Ra Ham; Bang, Woong; Park, Kyungho; Kim, Minseok S.; Shim, Jung-Hyun; Chae, Jung-Il; Moon, Se Youn

2017-02-01

Human colorectal cancer cell lines (HT29 and HCT116) were exposed to dielectric barrier discharge (DBD) plasma at atmospheric pressure to investigate the anticancer capacity of the plasma. The dose- and time-dependent effects of DBDP on cell viability, regulation of transcription factor Sp1, cell-cycle analysis, and colony formation were investigated by means of MTS assay, DAPI staining, propidium iodide staining, annexin V-FITC staining, Western blot analysis, RT-PCR analysis, fluorescence microscopy, and anchorage-independent cell transformation assay. By increasing the duration of plasma dose times, significant reductions in the levels of both Sp1 protein and Sp1 mRNA were observed in both cell lines. Also, expression of negative regulators related to the cell cycle (such as p53, p21, and p27) was increased and of the positive regulator cyclin D1 was decreased, indicating that the plasma treatment led to apoptosis and cell-cycle arrest. In addition, the sizes and quantities of colony formation were significantly suppressed even though two cancer promoters, such as TPA and epidermal growth factor, accompanied the plasma treatment. Thus, plasma treatment inhibited cell viability and colony formation by suppressing Sp1, which induced apoptosis and cell-cycle arrest in these two human colorectal cancer cell lines.

p21 induction plays a dual role in anti-cancer activity of ursolic acid

PubMed Central

Zhang, Xudong; Song, Xinhua; Yin, Shutao; Zhao, Chong; Fan, Lihong

2015-01-01

Previous studies have shown that induction of G1 arrest and apoptosis by ursolic acid is associated with up-regulation of cyclin-dependent kinase inhibitor (CDKI) protein p21 in multiple types of cancer cells. However, the functional role of p21 induction in G1 cell cycle arrest and apoptosis, and the mechanisms of p21 induction by ursolic acid have not been critically addressed. In the current study, we demonstrated that p21 played a mediator role in G1 cell cycle arrest by ursolic acid, whereas p21-mediated up-regulation of Mcl-1 compromised apoptotic effect of ursolic acid. These results suggest that p21 induction plays a dual role in the anti-cancer activity of ursolic acid in terms of cell cycle and apoptosis regulation. p21 induction by ursolic acid was attributed to p53 transcriptional activation. Moreover, we found that ursolic acid was able to inhibit murine double minute-2 protein (MDM2) and T-LAK cell-originated protein kinase (TOPK), the two negative regulator of p53, which in turn contributed to ursolic acid-induced p53 activation. Our findings provided novel insights into understanding of the mechanisms involved in cell cycle arrest and apoptosis induction in response to ursolic acid exposure. PMID:26582056

Lupeol induces p53 and cyclin-B-mediated G2/M arrest and targets apoptosis through activation of caspase in mouse skin

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nigam, Nidhi; Prasad, Sahdeo; George, Jasmine

2009-04-03

Lupeol, present in fruits and medicinal plants, is a biologically active compound that has been shown to have various pharmacological properties in experimental studies. In the present study, we demonstrated the modulatory effect of lupeol on 7,12-dimethylbenz[a]anthracene (DMBA)-induced alterations on cell proliferation in the skin of Swiss albino mice. Lupeol treatment showed significant (p < 0.05) preventive effects with marked inhibition at 48, 72, and 96 h against DMBA-mediated neoplastic events. Cell-cycle analysis showed that lupeol-induced G2/M-phase arrest (16-37%) until 72 h, and these inhibitory effects were mediated through inhibition of the cyclin-B-regulated signaling pathway involving p53, p21/WAF1, cdc25C, cdc2,more » and cyclin-B gene expression. Further lupeol-induced apoptosis was observed, as shown by an increased sub-G1 peak (28%) at 96 h, with upregulation of bax and caspase-3 genes and downregulation of anti-apoptotic bcl-2 and survivin genes. Thus, our results indicate that lupeol has novel anti-proliferative and apoptotic potential that may be helpful in designing strategies to fight skin cancer.« less

Cellular conservation of endangered midget buffalo (Lowland Anoa, Bubalus quarlesi) by establishment of primary cultured cell, and its immortalization with expression of cell cycle regulators.

PubMed

Fukuda, Tomokazu; Iino, Yuuka; Eitsuka, Takahiro; Onuma, Manabu; Katayama, Masafumi; Murata, Koichi; Inoue-Murayama, Miho; Hara, Kumiko; Isogai, Emiko; Kiyono, Tohru

2016-10-01

Lowland Anoa has become endangered due to hunting and human activity. Protection and breeding of endangered species in a controlled environment is the best way of conservation. However, it is not possible to adopt this approach for all endangered species because of the cost involved and the ever-increasing number of critically endangered species. In consideration of these limitations to the conventional conservation methods, we established a primary cell culture of endangered buffalo (Lowland Anoa, Bubalus quarlesi), for the preservation of this biological resource. In addition, we introduced human derived, mutant cyclin dependent kinase 4 (CDK4), Cyclin D, and telomerase reverse transcriptase (TERT) into the primary cells. The successful introduction of these three genes was confirmed by western blot with specific antibodies, and enzymatic activity. We also showed that the expression of mutant CDK4, Cyclin D, and TERT allows us to efficiently establish an immortalized cell line, with an intact chromosome pattern, from Lowland Anoa. To the best of our knowledge, this study is the first investigation that established an immortalized cell line of an endangered wild animal species.

Insight into the mechanisms of action of estrogen receptor β in the breast, prostate, colon, and CNS.

PubMed

Dey, Prasenjit; Barros, Rodrigo P A; Warner, Margaret; Ström, Anders; Gustafsson, Jan-Åke

2013-12-01

Estrogen and its receptors (ERs) influence many biological processes in physiology and pathology in men and women. ERs are involved in the etiology and/or progression of cancers of the prostate, breast, uterus, ovary, colon, lung, stomach, and malignancies of the immune system. In estrogen-sensitive malignancies, ERβ usually is a tumor suppressor and ERα is an oncogene. ERβ regulates genes in several key pathways including tumor suppression (p53, PTEN); metabolism (PI3K); survival (Akt); proliferation pathways (p45(Skp2), cMyc, and cyclin E); cell-cycle arresting factors (p21(WAF1), cyclin-dependent kinase inhibitor 1 (CDKN1A)), p27(Kip1), and cyclin-dependent kinases (CDKs); protection from reactive oxygen species, glutathione peroxidase. Because they are activated by small molecules, ERs are excellent targets for pharmaceuticals. ERα antagonists have been used for many years in the treatment of breast cancer and more recently pharmaceutical companies have produced agonists which are very selective for ERα or ERβ. ERβ agonists are being considered for preventing progression of cancer, treatment of anxiety and depression, as anti-inflammatory agents and as agents, which prevent or reduce the severity of neurodegenerative diseases.

A novel miRNA-mediated STOP sign in lung cancer: miR-340 inhibits the proliferation of lung cancer cells through p27KIP1

PubMed Central

Fernandez, Serena; Risolino, Maurizio; Verde, Pasquale

2015-01-01

Oncosuppressor miRNAs inhibit cancer cell proliferation by targeting key components of the cell cycle machinery. In our recent report we showed that miR-340 is a novel tumor suppressor in non-small cell lung cancer. miR-340 inhibits neoplastic cell proliferation and induces p27KIP1 by targeting multiple translational and post-translational regulators of this cyclin-dependent kinase inhibitor. PMID:27308439

MUC4 regulates cellular senescence in head and neck squamous cell carcinoma through p16/Rb pathway.

PubMed

Macha, M A; Rachagani, S; Pai, P; Gupta, S; Lydiatt, W M; Smith, R B; Johansson, S L; Lele, S M; Kakar, S S; Farghaly, H; Lee, J H; Meza, J; Ganti, A K; Jain, M; Batra, S K

2015-03-26

The limited effectiveness of therapy for patients with advanced stage head and neck squamous cell carcinoma (HNSCC) or recurrent disease is a reflection of an incomplete understanding of the molecular basis of HNSCC pathogenesis. MUC4, a high molecular weight glycoprotein, is differentially overexpressed in many human cancers and implicated in cancer progression and resistance to several chemotherapies. However, its clinical relevance and the molecular mechanisms through which it mediates HNSCC progression are not well understood. This study revealed a significant upregulation of MUC4 in 78% (68/87) of HNSCC tissues compared with 10% positivity (1/10) in benign samples (P=0.006, odds ratio (95% confidence interval)=10.74 (2.0-57.56). MUC4 knockdown (KD) in SCC1 and SCC10B HNSCC cell lines resulted in significant inhibition of growth in vitro and in vivo, increased senescence as indicated by an increase in the number of flat, enlarged and senescence-associated β-galactosidase (SA-β-Gal)-positive cells. Decreased cellular proliferation was associated with G0/G1 cell cycle arrest and decrease expression of cell cycle regulatory proteins like cyclin E, cyclin D1 and decrease in BrdU incorporation. Mechanistic studies revealed upregulation of p16, pRb dephosphorylation and its interaction with histone deacetylase 1/2. This resulted in decreased histone acetylation (H3K9) at cyclin E promoter leading to its downregulation. Orthotopic implantation of MUC4 KD SCC1 cells into the floor of the mouth in nude mice resulted in the formation of significantly smaller tumors (170±18.30 mg) compared to those (375±17.29 mg) formed by control cells (P=0.00007). In conclusion, our findings showed that MUC4 overexpression has a critical role by regulating proliferation and cellular senescence of HNSCC cells. Downregulation of MUC4 may be a promising therapeutic approach for treating HNSCC patients.

Incarvine C suppresses proliferation and vasculogenic mimicry of hepatocellular carcinoma cells via targeting ROCK inhibition.

PubMed

Zhang, Ji-Gang; Zhang, Dan-Dan; Wu, Xin; Wang, Yu-Zhu; Gu, Sheng-Ying; Zhu, Guan-Hua; Li, Xiao-Yu; Li, Qin; Liu, Gao-Lin

2015-10-28

Studies have described vasculogenic mimicry (VM) as an alternative circulatory system to blood vessels in multiple malignant tumor types, including hepatocellular carcinoma (HCC). In the current study, we aimed to seek novel and more efficient treatment strategies by targeting VM and explore the underlying mechanisms in HCC cells. Cell counting kit-8 (CCK-8) assay and colony survival assay were performed to explore the inhibitory effect of incarvine C (IVC) on human cancer cell proliferation. Flow cytometry was performed to analyze the cell cycle distribution after DNA staining and cell apoptosis by the Annexin V-PE and 7-AAD assay. The effect of IVC on Rho-associated, coiled-coil-containing protein kinase (ROCK) was determined by western blotting and stress fiber formation assay. The inhibitory role of IVC on MHCC97H cell VM formation was determined by formation of tubular network structures on Matrigel in vitro, real time-qPCR, confocal microscopy and western blotting techniques. We explored an anti-metastatic HCC agent, IVC, derived from traditional Chinese medicinal herbs, and found that IVC dose-dependently inhibited the growth of MHCC97H cells. IVC induced MHCC97H cell cycle arrest at G1 transition, which was associated with cyclin-dependent kinase 2 (CDK-2)/cyclin-E1 degradation and p21/p53 up-regulation. In addition, IVC induced apoptotic death of MHCC97H cells. Furthermore, IVC strongly suppressed the phosphorylation of the ROCK substrate myosin phosphatase target subunit-1 (MYPT-1) and ROCK-mediated actin fiber formation. Finally, IVC inhibited cell-dominant tube formation in vitro, which was accompanied with the down-regulation of VM-key factors as detected by real time-qPCR and immunofluorescence. Taken together, the effective inhibitory effect of IVC on MHCC97H cell proliferation and neovascularization was associated with ROCK inhibition, suggesting that IVC may be a new potential drug candidate for the treatment of HCC.

Maternal gestational betaine supplementation-mediated suppression of hepatic cyclin D2 and presenilin1 gene in newborn piglets is associated with epigenetic regulation of the STAT3-dependent pathway.

PubMed

Cai, Demin; Yuan, Mengjie; Jia, Yimin; Liu, Haoyu; Hu, Yun; Zhao, Ruqian

2015-12-01

Betaine, which donates methyl groups through methionine metabolism for DNA and protein methylation, is critical for epigenetic gene regulation, especially during fetal development. Here we fed gestational sows with control or betaine supplemented diets (3 g/kg) throughout the pregnancy to explore the effects of maternal betaine on hepatic cell proliferation in neonatal piglets. Neonatal piglets born to betaine-supplemented sows demonstrated a reduction of cell number and DNA content in the liver, which was associated with significantly down-regulated hepatic expression of cell cycle regulatory genes, cyclin D2 (CCND2) and presenilin1 (PSEN1). Moreover, STAT3 binding to the promoter of CCND2 and PSEN1 was also lower in betaine-exposed piglets, accompanied by strong reduction of STAT3 mRNA and protein expression, along with its phosphorylation at Tyr705 and Ser727 residues. Also, prenatal betaine exposure significantly attenuated upstream kinases of STAT3 signaling pathway (phospho-ERK1/2, phospho-SRC and phospho-JAK2) in the livers of neonates. Furthermore, the repressed STAT3 expression in the liver of betaine-exposed piglets was associated with DNA hypermethylation and more enriched repression histone mark H3K27me3 on its promoter, together with significantly up-regulated expression of H3K27me3 and enhancer of zeste homolog 2 (EZH2) proteins, as well as miR-124a, which targets STAT3. Taken together, our results suggest that maternal dietary betaine supplementation during gestation inhibits hepatic cell proliferation in neonatal piglets, at least partly, through epigenetic regulation of hepatic CCND2 and PSEN1 genes via a STAT3-dependent pathway. These neonatal changes in cell cycle and proliferation regulation may lead to lower liver weight and hepatic DNA content at weaning. Copyright © 2015 Elsevier Inc. All rights reserved.

Octyl gallate and gallic acid isolated from Terminalia bellarica regulates normal cell cycle in human breast cancer cell lines.

PubMed

Sales, Mary Selesty; Roy, Anita; Antony, Ludas; Banu, Sakhila K; Jeyaraman, Selvaraj; Manikkam, Rajalakshmi

2018-07-01

Herbal medicines stand unique and effective in treating human diseases. Terminalia bellarica (T. bellarica) is a potent medicinal herb, with a wide range of pharmacological activities. The present study was aimed to evaluate the effect of octyl gallate (OG) and gallic acid (GA) isolated from methanolic fruit extract of T. bellirica to inhibit the survival of breast cancer cells (MCF-7 & MDA-MB-231). Both OG & GA exhibited decreased MCF-7 & MDA-MB-231 survival and induced apoptosis, with IC 50 value of OG and GA as 40 μM and 80 μM respectively. No toxic effect was observed on normal breast cells (MCF-10A). The compounds inhibited cell cycle progression by altering the expression of the cell cycle regulators (Cyclin D1, D3, CDK-4, CDK-6, p18 INK4, p21Waf-1 and p27 KIP). Octyl gallate was more effective at low concentrations than GA. In-silico results provided stable interactions between the compounds and target proteins. The present investigation proved the downregulation of positive cell cycle regulators and upregulation of negative cell cycle regulators inducing apoptosis in compound-treated breast cancer cells. Hence, both the compounds may serve as potential anticancer agents and could be developed as breast cancer drugs, with further explorations. Copyright © 2018 Elsevier Masson SAS. All rights reserved.

Regulation of a transcription factor network by Cdk1 coordinates late cell cycle gene expression

PubMed Central

Landry, Benjamin D; Mapa, Claudine E; Arsenault, Heather E; Poti, Kristin E; Benanti, Jennifer A

2014-01-01

To maintain genome stability, regulators of chromosome segregation must be expressed in coordination with mitotic events. Expression of these late cell cycle genes is regulated by cyclin-dependent kinase (Cdk1), which phosphorylates a network of conserved transcription factors (TFs). However, the effects of Cdk1 phosphorylation on many key TFs are not known. We find that elimination of Cdk1-mediated phosphorylation of four S-phase TFs decreases expression of many late cell cycle genes, delays mitotic progression, and reduces fitness in budding yeast. Blocking phosphorylation impairs degradation of all four TFs. Consequently, phosphorylation-deficient mutants of the repressors Yox1 and Yhp1 exhibit increased promoter occupancy and decreased expression of their target genes. Interestingly, although phosphorylation of the transcriptional activator Hcm1 on its N-terminus promotes its degradation, phosphorylation on its C-terminus is required for its activity, indicating that Cdk1 both activates and inhibits a single TF. We conclude that Cdk1 promotes gene expression by both activating transcriptional activators and inactivating transcriptional repressors. Furthermore, our data suggest that coordinated regulation of the TF network by Cdk1 is necessary for faithful cell division. PMID:24714560

Regulation of a transcription factor network by Cdk1 coordinates late cell cycle gene expression.

PubMed

Landry, Benjamin D; Mapa, Claudine E; Arsenault, Heather E; Poti, Kristin E; Benanti, Jennifer A

2014-05-02

To maintain genome stability, regulators of chromosome segregation must be expressed in coordination with mitotic events. Expression of these late cell cycle genes is regulated by cyclin-dependent kinase (Cdk1), which phosphorylates a network of conserved transcription factors (TFs). However, the effects of Cdk1 phosphorylation on many key TFs are not known. We find that elimination of Cdk1-mediated phosphorylation of four S-phase TFs decreases expression of many late cell cycle genes, delays mitotic progression, and reduces fitness in budding yeast. Blocking phosphorylation impairs degradation of all four TFs. Consequently, phosphorylation-deficient mutants of the repressors Yox1 and Yhp1 exhibit increased promoter occupancy and decreased expression of their target genes. Interestingly, although phosphorylation of the transcriptional activator Hcm1 on its N-terminus promotes its degradation, phosphorylation on its C-terminus is required for its activity, indicating that Cdk1 both activates and inhibits a single TF. We conclude that Cdk1 promotes gene expression by both activating transcriptional activators and inactivating transcriptional repressors. Furthermore, our data suggest that coordinated regulation of the TF network by Cdk1 is necessary for faithful cell division.

Cancer dormancy and cell signaling: Induction of p21waf1 initiated by membrane IgM engagement increases survival of B lymphoma cells

PubMed Central

Marches, Radu; Hsueh, Robert; Uhr, Jonathan W.

1999-01-01

The p21WAF1 (p21) cyclin-dependent kinase inhibitor plays a major role in regulating cell cycle arrest. It was recently reported that the p53-independent elevation of p21 protein levels is essential in mediating the G1 arrest resulting from signal transduction events initiated by the crosslinking of membrane IgM on Daudi Burkitt lymphoma cells. Although the role of p21 in cell cycle regulation is well documented, there is little information concerning its role in antibody-mediated apoptosis. In the present study, we examined the involvement of p21 in the regulation of apoptosis by suppressing its induction in anti-IgM-treated Daudi cells through a p21 antisense expression construct approach. Reduction in induced p21 protein levels resulted in diminished G1 arrest and increased apoptosis. The increased susceptibility to anti-IgM-mediated apoptosis was associated with increased caspase-3-like activity and poly-(ADP)ribose polymerase cleavage. These data suggest that p21 may directly interfere with the caspase cascade, thus playing a dual role in regulating both cell cycle progression and apoptosis. PMID:10411940

AMPKα1 controls hepatocyte proliferation independently of energy balance by regulating Cyclin A2 expression.

PubMed

Merlen, Grégory; Gentric, Géraldine; Celton-Morizur, Séverine; Foretz, Marc; Guidotti, Jacques-Emmanuel; Fauveau, Véronique; Leclerc, Jocelyne; Viollet, Benoit; Desdouets, Chantal

2014-01-01

AMP-activated protein kinase (AMPK) is an evolutionarily conserved sensor of cellular energy status that contributes to restoration of energy homeostasis by slowing down ATP-consuming pathways and activating ATP-producing pathways. Unexpectedly, in different systems, AMPK is also required for proper cell division. In the current study, we evaluated the potential effect of the AMPK catalytic subunit, AMPKα1, on hepatocyte proliferation. Hepatocyte proliferation was determined in AMPKα1 knockout and wild-type mice in vivo after two thirds partial hepatectomy, and in vitro in primary hepatocyte cultures. The activities of metabolic and cell cycle-related signaling pathways were measured. After partial hepatectomy, hepatocytes proliferated rapidly, correlating with increased AMPK phosphorylation. Deletion of AMPKα1 delayed liver regeneration by impacting on G1/S transition phase. The proliferative defect of AMPKα1-deficient hepatocytes was cell autonomous, and independent of energy balance. The priming phase, lipid droplet accumulation, protein anabolic responses and growth factor activation after partial hepatectomy occurred normally in the absence of AMPKα1 activity. By contrast, mRNA and protein expression of cyclin A2, a key driver of S phase progression, were compromised in the absence of AMPK activity. Importantly, AMPKα1 controlled cyclin A2 transcription mainly through the ATF/CREB element. Our study highlights a novel role for AMPKα1 as a positive regulator of hepatocyte division occurring independently of energy balance. Copyright © 2013 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved.

Pause, play, repeat

PubMed Central

Sansó, Miriam; Fisher, Robert P

2013-01-01

Cyclin-dependent kinases (CDKs) play a central role in governing eukaryotic cell division. It is becoming clear that the transcription cycle of RNA polymerase II (RNAP II) is also regulated by CDKs; in metazoans, the cell cycle and transcriptional CDK networks even share an upstream activating kinase, which is itself a CDK. From recent chemical-genetic analyses we know that CDKs and their substrates control events both early in transcription (the transition from initiation to elongation) and late (3′ end formation and transcription termination). Moreover, mutual dependence on CDK activity might couple the “beginning” and “end” of the cycle, to ensure the fidelity of mRNA maturation and the efficient recycling of RNAP II from sites of termination to the transcription start site (TSS). As is the case for CDKs involved in cell cycle regulation, different transcriptional CDKs act in defined sequence on multiple substrates. These phosphorylations are likely to influence gene expression by several mechanisms, including direct, allosteric effects on the transcription machinery, co-transcriptional recruitment of proteins needed for mRNA-capping, splicing and 3′ end maturation, dependent on multisite phosphorylation of the RNAP II C-terminal domain (CTD) and, perhaps, direct regulation of RNA-processing or histone-modifying machinery. Here we review these recent advances, and preview the emerging challenges for transcription-cycle research. PMID:23756342

Kaposi's Sarcoma-Associated Herpesvirus Viral Interferon Regulatory Factor 4 (vIRF4) Perturbs the G1-S Cell Cycle Progression via Deregulation of the cyclin D1 Gene.

PubMed

Lee, Hye-Ra; Mitra, Jaba; Lee, Stacy; Gao, Shou-Jiang; Oh, Tae-Kwang; Kim, Myung Hee; Ha, Taekjip; Jung, Jae U

2016-01-15

Kaposi's sarcoma-associated herpesvirus (KSHV) infection modulates the host cell cycle to create an environment optimal for its viral-DNA replication during the lytic life cycle. We report here that KSHV vIRF4 targets the β-catenin/CBP cofactor and blocks its occupancy on the cyclin D1 promoter, suppressing the G1-S cell cycle progression and enhancing KSHV replication. This shows that KSHV vIRF4 suppresses host G1-S transition, possibly providing an intracellular milieu favorable for its replication. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

Overexpression of TRPV3 Correlates with Tumor Progression in Non-Small Cell Lung Cancer.

PubMed

Li, Xiaolei; Zhang, Qianhui; Fan, Kai; Li, Baiyan; Li, Huifeng; Qi, Hanping; Guo, Jing; Cao, Yonggang; Sun, Hongli

2016-03-24

(1) BACKGROUND: Transient receptor potential vanilloid 3 (TRPV3) is a member of the TRP channels family of Ca(2+)-permeant channels. The proteins of some TRP channels are highly expressed in cancer cells. This study aimed to assess the clinical significance and biological functions of TRPV3 in non-small cell lung cancer (NSCLC); (2) METHODS: Immunohistochemistry was used to detect the expression of TRPV3 in NSCLC tissues and adjacent noncancerous lung tissues. Western blot was used to detect the protein expressions of TRPV3, CaMKII, p-CaMKII, CyclinA, CyclinD, CyclinE1, CDK2, CDK4, and P27. Small interfering RNA was used to deplete TRPV3 expression. A laser scanning confocal microscope was used to measure intracellular calcium concentration ([Ca(2+)]i). Flow cytometry was used to analyze cell cycle; (3) RESULTS: TRPV3 was overexpressed in 65 of 96 (67.7%) human lung cancer cases and correlated with differentiation (p = 0.001) and TNM stage (p = 0.004). Importantly, TRPV3 expression was associated with short overall survival. In addition, blocking or knockdown of TRPV3 could inhibit lung cancer cell proliferation. Moreover, TRPV3 inhibition could decrease [Ca(2+)]i of lung cancer cells and arrest cell cycle at the G1/S boundary. Further results revealed that TRPV3 inhibition decreased expressions of p-CaMKII, CyclinA, CyclinD1, CyclinE, and increased P27 level; (4) CONCLUSIONS: Our findings demonstrate that TRPV3 was overexpressed in NSCLC and correlated with lung cancer progression. TRPV3 activation could promote proliferation of lung cancer cells. TRPV3 might serve as a potential companion drug target in NSCLC.

Overexpression of TRPV3 Correlates with Tumor Progression in Non-Small Cell Lung Cancer

PubMed Central

Li, Xiaolei; Zhang, Qianhui; Fan, Kai; Li, Baiyan; Li, Huifeng; Qi, Hanping; Guo, Jing; Cao, Yonggang; Sun, Hongli

2016-01-01

(1) Background: Transient receptor potential vanilloid 3 (TRPV3) is a member of the TRP channels family of Ca2+-permeant channels. The proteins of some TRP channels are highly expressed in cancer cells. This study aimed to assess the clinical significance and biological functions of TRPV3 in non-small cell lung cancer (NSCLC); (2) Methods: Immunohistochemistry was used to detect the expression of TRPV3 in NSCLC tissues and adjacent noncancerous lung tissues. Western blot was used to detect the protein expressions of TRPV3, CaMKII, p-CaMKII, CyclinA, CyclinD, CyclinE1, CDK2, CDK4, and P27. Small interfering RNA was used to deplete TRPV3 expression. A laser scanning confocal microscope was used to measure intracellular calcium concentration ([Ca2+]i). Flow cytometry was used to analyze cell cycle; (3) Results: TRPV3 was overexpressed in 65 of 96 (67.7%) human lung cancer cases and correlated with differentiation (p = 0.001) and TNM stage (p = 0.004). Importantly, TRPV3 expression was associated with short overall survival. In addition, blocking or knockdown of TRPV3 could inhibit lung cancer cell proliferation. Moreover, TRPV3 inhibition could decrease [Ca2+]i of lung cancer cells and arrest cell cycle at the G1/S boundary. Further results revealed that TRPV3 inhibition decreased expressions of p-CaMKII, CyclinA, CyclinD1, CyclinE, and increased P27 level; (4) Conclusions: Our findings demonstrate that TRPV3 was overexpressed in NSCLC and correlated with lung cancer progression. TRPV3 activation could promote proliferation of lung cancer cells. TRPV3 might serve as a potential companion drug target in NSCLC. PMID:27023518

The neem limonoids azadirachtin and nimbolide induce cell cycle arrest and mitochondria-mediated apoptosis in human cervical cancer (HeLa) cells.

PubMed

Priyadarsini, R Vidya; Murugan, R Senthil; Sripriya, P; Karunagaran, D; Nagini, S

2010-06-01

Limonoids from the neem tree (Azadirachta indica) have attracted considerable research attention in recent years owing to their potent antioxidant and anti-proliferative effects. The present study was designed to investigate the cellular and molecular mechanisms by which azadirachtin and nimbolide exert cytotoxic effects in the human cervical cancer (HeLa) cell line. Both azadirachtin and nimbolide significantly suppressed the viability of HeLa cells in a dose-dependent manner by inducing cell cycle arrest at G0/G1 phase accompanied by p53-dependent p21 accumulation and down-regulation of the cell cycle regulatory proteins cyclin B, cyclin D1 and PCNA. Characteristic changes in nuclear morphology, presence of a subdiploid peak and annexin-V staining pointed to apoptosis as the mode of cell death. Increased generation of reactive oxygen species with decline in the mitochondrial transmembrane potential and release of cytochrome c confirmed that the neem limonoids transduced the apoptotic signal via the mitochondrial pathway. Altered expression of the Bcl-2 family of proteins, inhibition of NF-kappaB activation and over-expression of caspases and survivin provide compelling evidence that azadirachtin and nimbolide induce a shift of balance toward a pro-apoptotic phenotype. Antioxidants such as azadirachtin and nimbolide that can simultaneously arrest the cell cycle and target multiple molecules involved in mitochondrial apoptosis offer immense potential as anti-cancer therapeutic drugs.

Arctigenin induces cell cycle arrest by blocking the phosphorylation of Rb via the modulation of cell cycle regulatory proteins in human gastric cancer cells.

PubMed

Jeong, Jin Boo; Hong, Se Chul; Jeong, Hyung Jin; Koo, Jin Suk

2011-10-01

Gastric cancer is a leading cause of cancer-related deaths, worldwide being second only to lung cancer as a cause of death. Arctigenin, a representative dibenzylbutyrolactone lignan, occurs in a variety of plants. However, the molecular mechanisms of arctigenin for anti-tumor effect on gastric cancer have not been examined. This study examined the biological effects of arctigenin on the human gastric cancer cell line SNU-1 and AGS. Cell proliferation was determined by MTT assay. In MTT assay, the proliferation of SNU-1 and AGS cells was significantly inhibited by arctigenin in a time and dose dependent manner, as compared with SNU-1 and AGS cells cultured in the absence of arctigenin. Inhibition of cell proliferation by arctigenin was in part associated with apoptotic cell death, as shown by changes in the expression ratio of Bcl-2 to Bax by arctigenin. Also, arctigenin blocked cell cycle arrest from G(1) to S phase by regulating the expression of cell cycle regulatory proteins such as Rb, cyclin D1, cyclin E, CDK4, CDK2, p21Waf1/Cip1 and p15 INK4b. The antiproliferative effect of arctigenin on SNU-1 and AGS gastric cancer cells revealed in this study suggests that arctigenin has intriguing potential as a chemopreventive or chemotherapeutic agent. Crown Copyright © 2011. Published by Elsevier B.V. All rights reserved.

Centriole overduplication through the concurrent formation of multiple daughter centrioles at single maternal templates.

PubMed

Duensing, A; Liu, Y; Perdreau, S A; Kleylein-Sohn, J; Nigg, E A; Duensing, S

2007-09-20

Abnormal centrosome numbers are detected in virtually all cancers. The molecular mechanisms that underlie centrosome amplification, however, are poorly characterized. Based on the model that each maternal centriole serves as a template for the formation of one and only one daughter centriole per cell division cycle, the prevailing view is that centriole overduplication arises from successive rounds of centriole reproduction. Here, we provide evidence that a single maternal centriole can concurrently generate multiple daughter centrioles. This mechanism was initially identified in cells treated with the peptide vinyl sulfone proteasome inhibitor Z-L(3)VS. We subsequently found that the formation of more than one daughter at maternal centrioles requires cyclin E/cyclin-dependent kinase 2 as well as Polo-like kinase 4 and that overexpression of these proteins mimics this phenotype in the absence of a proteasome inhibitor. Moreover, we show that the human papillomavirus type 16 E7 oncoprotein stimulates aberrant daughter centriole numbers in part through the formation of more than one daughter centriole at single maternal templates. These results help to explain how oncogenic stimuli can rapidly induce abnormal centriole numbers within a single cell-division cycle and provide insights into the regulation of centriole duplication.

Veterinary drug, 17β-trenbolone promotes the proliferation of human prostate cancer cell line through the Akt/AR signaling pathway.

PubMed

Lee, Hee-Seok; Jung, Da-Woon; Han, Songyi; Kang, Hui-Seung; Suh, Jin-Hyang; Oh, Hyun-Suk; Hwang, Myung-Sil; Moon, Guiim; Park, Yooheon; Hong, Jin-Hwan; Koo, Yong Eui

2018-05-01

Trenbolone acetate (TBA) is a synthetic anabolic steroidal growth factor that is used for rapid muscle development in cattle. The absorbed TBA is hydrolyzed to the active form, 17β-trenbolone (17 TB; 17β-hydroxy-estra-4,9,11-trien-3-one) in meat and milk products, which can cause adverse health effects in humans. Similar to 5α-dihydrotestosterone (DHT), 17 TB was reported to exhibit endocrine disrupting effects on animals and humans due to its androgenic effect via binding to the androgen receptor. The purpose of this study is to investigate the molecular mechanism of cell proliferation in prostate cancer (PCa) cells treated with 17 TB. We found that 17 TB induces AR-dependent cell proliferation in the human prostate cancer cell line, 22Rv1 in a concentration dependent manner. Treatment with 17 TB increased the expression of cell cycle regulatory proteins, cyclin D2/CDK-4 and cyclin E/CDK-2, whereas the expression of p27 was down-regulated. Furthermore, phosphorylation of Rb and activation of E2F were also induced, which suggests the activation of cyclin D2/CDK-4 and cyclin E/CDK-2 in the cells. When 22Rv1 cells were exposed to 30 pM of 17 TB, which is the effective concentration (EC 50 ) value required to observe proliferative effects on 22Rv1 cells, the expression levels of the phosphorylated forms of Akt and GSK3β were increased. This study demonstrates that 17 TB induces AR-dependent proliferation through the modulation of cell cycle-related proteins in the Akt signaling pathway. The present study provides an effective methodology for identifying cell proliferation signaling of veterinary drugs that exert AR agonistic effects. Copyright © 2018 Elsevier Ltd. All rights reserved.

CDC25B and p53 are independently implicated in radiation sensitivity for human esophageal cancers.

PubMed

Miyata, H; Doki, Y; Shiozaki, H; Inoue, M; Yano, M; Fujiwara, Y; Yamamoto, H; Nishioka, K; Kishi, K; Monden, M

2000-12-01

Ionized radiation leads to G1 arrest and apoptosis by a p53-dependent pathway and G2-M arrest through a p53-independent pathway. In this study, we evaluated the role of cell cycle-regulating molecules in the sensitivity of cancer cells for radiation therapy. Forty-seven patients with squamous cell carcinomas of the esophagus had undergone radiation therapy, followed by surgical resection. They were classified as sensitive to radiation (SR, 14 cases) with no residual tumor in the surgical specimen or as resistant to radiation (RR, 33 cases) with viable residual tumors. Their preradiation biopsy samples were immunohistochemically investigated for the expressions of cell cycle-related molecules, including p53, CDC25A, CDC25B, cyclin D1, cyclin B1, and Ki-67. p53 expression was negative in 71% (10 of 14) of SR and positive in 91% (30 of 33) of RR. The association was strong between high radiation sensitivity and negative p53 expression (P < 0.0001). CDC25B, which is not expressed in normal epithelium but is in the cytoplasm of esophageal cancers, was strongly expressed (2+) in 46% (6 of 14) of SR and in 6% (2 of 23) of RR. Thus, the sensitivity for radiation therapy was significantly correlated with CDC25B overexpression. With respect to CDC25A, cyclin D1, cyclin B1, and Ki-67, no statistically significant differences were found in their expressions between SR and RR tumors. p53 and CDC25B expressions showed no significant associations, and multivariate analysis revealed that both p53 and CDC25B are significant independent markers for predicting radiation sensitivity. CDC25B was revealed to be a novel predictor of radiation sensitivity in esophageal cancers. Because CDC25B is an oncogene, which affects G2-M progression, these results suggest the importance of a p53-independent G2-M checkpoint in radiation therapy.

Tangeretin, a citrus flavonoid, inhibits PGDF-BB-induced proliferation and migration of aortic smooth muscle cells by blocking AKT activation.

PubMed

Seo, Juhee; Lee, Hyun Sun; Ryoo, Sungwoo; Seo, Jee Hee; Min, Byung-Sun; Lee, Jeong-Hyung

2011-12-30

Tangeretin, a natural polymethoxylated flavone concentrated in the peel of citrus fruits, is known to have antiproliferative, antiinvasive, antimetastatic and antioxidant activities. However, the effect of tangeretin on vascular smooth muscle cells (VSMCs) is unknown. This study examined the effect of tangeretin on platelet-derived growth factor (PDGF)-BB-induced proliferation and migration of rat aortic smooth muscle cells (RASMCs) as well as its underlying mechanisms. Tangeretin significantly inhibited proliferation, DNA synthesis and migration of PDGF-BB-stimulated RASMCs without inducing cell death. Treatment with tangeretin-induced cell-cycle arrest in the G₀/G₁ phase was associated with down-regulation of cyclin D1 and cyclin E in addition to up-regulation of p27(kip1). We also showed that tangeretin inhibited PDGF-BB-induced phosphorylation of AKT, while it had no effect on the phosphorylation of phospholipase Cγ (PLCγ), PDGF receptor β-chain (PDGF-Rβ) and extracellular signal-regulated kinase 1/2 (ERK1/2), c-Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinases (MAPKs). An in vitro kinase assay revealed that tangeretin inhibited AKT activity in a dose-dependent manner. Moreover, treatment of LY294002, a phosphoinositide 3-kinase (PI3K) inhibitor, had similar effects than that of tangeretin on the expression of p27(kip1) and cyclin D1, as well as cell migration in PDFG-BB-stimulated RASMCs. Taken together, these findings suggest that tangeretin could suppress PDGF-BB-induced proliferation and migration of RASMCs through the suppression of PI3K/AKT signaling pathway, and may be a potential candidate for preventing or treating vascular diseases, such as atherosclerosis and restenosis. Copyright © 2011 Elsevier B.V. All rights reserved.

A Cyclin Dependent Kinase Regulatory Subunit (CKS) Gene of Pigeonpea Imparts Abiotic Stress Tolerance and Regulates Plant Growth and Development in Arabidopsis

PubMed Central

Tamirisa, Srinath; Vudem, Dashavantha R.; Khareedu, Venkateswara R.

2017-01-01

Frequent climatic changes in conjunction with other extreme environmental factors are known to affect growth, development and productivity of diverse crop plants. Pigeonpea, a major grain legume of the semiarid tropics, endowed with an excellent deep-root system, is known as one of the important drought tolerant crop plants. Cyclin dependent kinases (CDKs) are core cell cycle regulators and play important role in different aspects of plant growth and development. The cyclin-dependent kinase regulatory subunit gene (CKS) was isolated from the cDNA library of pigeonpea plants subjected to drought stress. Pigeonpea CKS (CcCKS) gene expression was detected in both the root and leaf tissues of pigeonpea and was upregulated by polyethylene glycol (PEG), mannitol, NaCl and abscisic acid (ABA) treatments. The overexpression of CcCKS gene in Arabidopsis significantly enhanced tolerance of transgenics to drought and salt stresses as evidenced by different physiological parameters. Under stress conditions, transgenics showed higher biomass, decreased rate of water loss, decreased MDA levels, higher free proline contents, and glutathione levels. Moreover, under stress conditions transgenics exhibited lower stomatal conductance, lower transpiration, and higher photosynthetic rates. However, under normal conditions, CcCKS-transgenics displayed decreased plant growth rate, increased cell size and decreased stomatal number compared to those of wild-type plants. Real-time polymerase chain reaction revealed that CcCKS could regulate the expression of both ABA-dependent and ABA-independent genes associated with abiotic stress tolerance as well as plant growth and development. As such, the CcCKS seems promising and might serve as a potential candidate gene for enhancing the abiotic stress tolerance of crop plants. PMID:28239388

A Cyclin Dependent Kinase Regulatory Subunit (CKS) Gene of Pigeonpea Imparts Abiotic Stress Tolerance and Regulates Plant Growth and Development in Arabidopsis.

PubMed

Tamirisa, Srinath; Vudem, Dashavantha R; Khareedu, Venkateswara R

2017-01-01

Frequent climatic changes in conjunction with other extreme environmental factors are known to affect growth, development and productivity of diverse crop plants. Pigeonpea, a major grain legume of the semiarid tropics, endowed with an excellent deep-root system, is known as one of the important drought tolerant crop plants. Cyclin dependent kinases (CDKs) are core cell cycle regulators and play important role in different aspects of plant growth and development. The cyclin-dependent kinase regulatory subunit gene ( CKS ) was isolated from the cDNA library of pigeonpea plants subjected to drought stress. Pigeonpea CKS ( CcCKS ) gene expression was detected in both the root and leaf tissues of pigeonpea and was upregulated by polyethylene glycol (PEG), mannitol, NaCl and abscisic acid (ABA) treatments. The overexpression of CcCKS gene in Arabidopsis significantly enhanced tolerance of transgenics to drought and salt stresses as evidenced by different physiological parameters. Under stress conditions, transgenics showed higher biomass, decreased rate of water loss, decreased MDA levels, higher free proline contents, and glutathione levels. Moreover, under stress conditions transgenics exhibited lower stomatal conductance, lower transpiration, and higher photosynthetic rates. However, under normal conditions, CcCKS -transgenics displayed decreased plant growth rate, increased cell size and decreased stomatal number compared to those of wild-type plants. Real-time polymerase chain reaction revealed that Cc CKS could regulate the expression of both ABA-dependent and ABA-independent genes associated with abiotic stress tolerance as well as plant growth and development. As such, the CcCKS seems promising and might serve as a potential candidate gene for enhancing the abiotic stress tolerance of crop plants.

Regulation of proliferation in developing human tooth germs by MSX homeodomain proteins and cyclin-dependent kinase inhibitor p19INK4d.

PubMed

Kero, Darko; Vukojevic, Katarina; Stazic, Petra; Sundov, Danijela; Mardesic Brakus, Snjezana; Saraga-Babic, Mirna

2017-10-02

Before the secretion of hard dental tissues, tooth germs undergo several distinctive stages of development (dental lamina, bud, cap and bell). Every stage is characterized by specific proliferation patterns, which is regulated by various morphogens, growth factors and homeodomain proteins. The role of MSX homeodomain proteins in odontogenesis is rather complex. Expression domains of genes encoding for murine Msx1/2 during development are observed in tissues containing highly proliferative progenitor cells. Arrest of tooth development in Msx knockout mice can be attributed to impaired proliferation of progenitor cells. In Msx1 knockout mice, these progenitor cells start to differentiate prematurely as they strongly express cyclin-dependent kinase inhibitor p19 INK4d . p19 INK4d induces terminal differentiation of cells by blocking the cell cycle in mitogen-responsive G1 phase. Direct suppression of p19 INK4d by Msx1 protein is, therefore, important for maintaining proliferation of progenitor cells at levels required for the normal progression of tooth development. In this study, we examined the expression patterns of MSX1, MSX2 and p19 INK4d in human incisor tooth germs during the bud, cap and early bell stages of development. The distribution of expression domains of p19 INK4d throughout the investigated period indicates that p19 INK4d plays active role during human tooth development. Furthermore, comparison of expression domains of p19 INK4d with those of MSX1, MSX2 and proliferation markers Ki67, Cyclin A2 and pRb, indicates that MSX-mediated regulation of proliferation in human tooth germs might not be executed by the mechanism similar to one described in developing tooth germs of wild-type mouse.

Molecular evolution of cyclin proteins in animals and fungi

PubMed Central

2011-01-01

Background The passage through the cell cycle is controlled by complexes of cyclins, the regulatory units, with cyclin-dependent kinases, the catalytic units. It is also known that cyclins form several families, which differ considerably in primary structure from one eukaryotic organism to another. Despite these lines of evidence, the relationship between the evolution of cyclins and their function is an open issue. Here we present the results of our study on the molecular evolution of A-, B-, D-, E-type cyclin proteins in animals and fungi. Results We constructed phylogenetic trees for these proteins, their ancestral sequences and analyzed patterns of amino acid replacements. The analysis of infrequently fixed atypical amino acid replacements in cyclins evidenced that accelerated evolution proceeded predominantly during paralog duplication or after it in animals and fungi and that it was related to aromorphic changes in animals. It was shown also that evolutionary flexibility of cyclin function may be provided by consequential reorganization of regions on protein surface remote from CDK binding sites in animal and fungal cyclins and by functional differentiation of paralogous cyclins formed in animal evolution. Conclusions The results suggested that changes in the number and/or nature of cyclin-binding proteins may underlie the evolutionary role of the alterations in the molecular structure of cyclins and their involvement in diverse molecular-genetic events. PMID:21798004

Magnolol attenuates neointima formation by inducing cell cycle arrest via inhibition of ERK1/2 and NF-kappaB activation in vascular smooth muscle cells.

PubMed

Karki, Rajendra; Ho, Oak-Min; Kim, Dong-Wook

2013-03-01

Endovascular injury induces switching of contractile phenotype of vascular smooth muscle cells (VSMCs) to synthetic phenotype, thereby causing proliferation of VSMCs leading to intimal thickening. The purpose of this study was to assess the effect of magnolol on the proliferation of VSMCs in vitro and neointima formation in vivo, as well as the related cell signaling mechanisms. Tumor necrosis factor alpha (TNF-alpha) induced proliferation ofVSMCs was assessed using colorimetric assay. Cell cycle progression and mRNA expression of cell cycle associated molecules were determined by flow cytometry and reverse transcription polymerase chain reaction (RT-PCR) respectively. The signaling molecules such as ERK1/2,JNK, P38 and NF-kappaB were determined by Western blot analysis. In addition, rat carotid artery balloon injury model was performed to assess the effect of magnolol on neointima formation in vivo. Oral administration of magnolol significantly inhibited intimal area and intimal/medial ratio (I/M). Our in vitro assays revealed magnolol dose dependently induced cell cycle arrest at G0/G1. Also, magnolol inhibited mRNA and protein expression of cyclin D1, cyclin E, CDK4 and CDK2 in vitro and in vivo. The cell cycle arrest was associated with inhibition of ERK1/2 phosphorylation and NF-kappaB translocation. Magnolol suppressed proliferation of VSMCs in vitro and attenuated neointima formation in vivo by inducing cell cycle arrest at G0/G1 through modulation of cyclin D1, cyclin E, CDK4 and CDK2 expression. Thus, the results suggest that magnolol could be a potential therapeutic candidate for the prevention of restenosis and atherosclerosis.

Differentiation of C2C12 myoblasts expressing lamin A mutated at a site responsible for Emery-Dreifuss muscular dystrophy is improved by inhibition of the MEK-ERK pathway and stimulation of the PI3-kinase pathway

DOE Office of Scientific and Technical Information (OSTI.GOV)

Favreau, Catherine; Delbarre, Erwan; Courvalin, Jean-Claude

2008-04-01

Mutation R453W in A-type lamins, that are major nuclear envelope proteins, generates Emery-Dreifuss muscular dystrophy. We previously showed that mouse myoblasts expressing R453W-lamin A incompletely exit the cell cycle and differentiate into myocytes with a low level of multinucleation. Here we attempted to improve differentiation by treating these cells with a mixture of PD98059, an extracellular-regulated kinase (ERK) kinase (also known as mitogen-activated kinase, MEK) inhibitor, and insulin-like growth factor-II, an activator of phosphoinositide 3-kinase. We show that mouse myoblasts expressing R453W-lamin A were sensitive to the drug treatment as shown by (i) an increase in multinucleation, (ii) downregulation ofmore » proliferation markers (cyclin D1, hyperphosphorylated Rb), (iii) upregulation of myogenin, and (iv) sustained activation of p21 and cyclin D3. However, nuclear matrix anchorage of p21 and cyclin D3 in a complex with hypophosphorylated Rb that is critical to trigger cell cycle arrest and myogenin induction was deficient and incompletely restored by drug treatment. As the turn-over of R453W-lamin A at the nuclear envelope was greatly enhanced, we propose that R453W-lamin A impairs the capacity of the nuclear lamina to serve as scaffold for substrates of the MEK-ERK pathway and for MyoD-induced proteins that play a role in the differentiation process.« less

Targeting the cyclin D-cyclin-dependent kinase (CDK) 4/6-retinoblastoma pathway with selective CDK 4/6 inhibitors in hormone receptor-positive breast cancer: rationale, current status, and future directions.

PubMed

Spring, Laura; Bardia, Aditya; Modi, Shanu

2016-01-01

Dysregulation of the cyclin D-cyclin-dependent kinase (CDK) 4/6-INK4-retinoblastoma (Rb) pathway is an important contributor to endocrine therapy resistance. Recent clinical development of selective inhibitors of CDK4 and CDK6 kinases has led to renewed interest in cell cycle regulators, following experience with relatively non-selective pan-CDK inhibitors that often resulted in limited activity and poor safety profiles in the clinic. The highly selective oral CDK 4/6 inhibitors palbociclib (PD0332991), ribociclib (LEE011), and abemaciclib (LY2835219) are able to inhibit the proliferation of Rb-positive tumor cells and have demonstrated dose-dependent growth inhibition in ER+ breast cancer models. In metastatic breast cancer, all three agents are being explored in combination with endocrine therapy in Phase III studies. Results so far indicated promising efficacy and manageable safety profiles, and led to the FDA approval of palbociclib. Phase II-III studies of these agents, in combination with endocrine therapy, are also underway in early breast cancer in the neoadjuvant and adjuvant settings. Selective CDK 4/6 inhibitors are also being investigated with other targeted agents or chemotherapy in the advanced setting. This article reviews the rationale for targeting cyclin D-CDK 4/6 in hormone receptor-positive (HR+) breast cancer, provides an overview of the available preclinical and clinical data with CDK 4/6 inhibitors in breast cancer to date, and summarizes the main features of ongoing clinical trials of these new agents in breast cancer. Future trials evaluating further combination strategies with CDK 4/6 backbone and translational studies refining predictive biomarkers are needed to help personalize the optimal treatment regimen for individual patients with ER+ breast cancer.

Extracellular guanosine and GTP promote expression of differentiation markers and induce S-phase cell-cycle arrest in human SH-SY5Y neuroblastoma cells.

PubMed

Guarnieri, S; Pilla, R; Morabito, C; Sacchetti, S; Mancinelli, R; Fanò, G; Mariggiò, M A

2009-04-01

SH-SY5Y neuroblastoma cells, a model for studying neuronal differentiation, are able to differentiate into either cholinergic or dopaminergic/adrenergic phenotypes depending on media conditions. Using this system, we asked whether guanosine (Guo) or guanosine-5'-triphosphate (GTP) are able to drive differentiation towards one particular phenotype. Differentiation was determined by evaluating the frequency of cells bearing neurites and assessing neurite length after exposure to different concentrations of Guo or GTP for different durations. After 6 days, 0.3 mM Guo or GTP induced a significant increase in the number of cells bearing neurites and increased neurite length. Western blot analyses confirmed that purines induced differentiation; cells exposed to purines showed increases in the levels of GAP43, MAP2, and tyrosine hydroxylase. Proliferation assays and cytofluorimetric analyses indicated a significant anti-proliferative effect of purines, and a concentration-dependent accumulation of cells in S-phase, starting after 24 h of purine exposure and extending for up to 6 days. A transcriptional profile analysis using gene arrays showed that an up-regulation of cyclin E2/cdk2 evident after 24 h was responsible for S-phase entry, and a concurrent down-regulation of cell-cycle progression-promoting cyclin B1/B2 prevented S-phase exit. In addition, patch-clamp recordings revealed that 0.3 mM Guo or GTP, after 6 day incubation, significantly decreased Na(+) currents. In conclusion, we showed Guo- and GTP-induced cell-cycle arrest in neuroblastoma cells and suggest that this makes these cells more responsive to differentiation processes that favor the dopaminergic/adrenergic phenotype.

Antitumor effects with apoptotic death in human promyelocytic leukemia HL-60 cells and suppression of leukemia xenograft tumor growth by irinotecan HCl.

PubMed

Chen, Yung-Liang; Chueh, Fu-Shin; Yang, Jai-Sing; Hsueh, Shu-Ching; Lu, Chi-Cheng; Chiang, Jo-Hua; Lee, Ching-Sung; Lu, Hsu-Feng; Chung, Jing-Gung

2015-07-01

Irinotecan HCl (CPT-11) is an anticancer prodrug, but there is no available information addressing CPT-11-inhibited leukemia cells in in vitro and in vivo studies. Therefore, we investigated the cytotoxic effects of CPT-11 in promyelocytic leukemia HL-60 cells and in vivo and tumor growth in a leukemia xenograft model. Effects of CPT-11 on HL-60 cells were determined using flow cytometry, immunofluorescence staining, comet assay, real-time PCR, and Western blotting. CPT-11 demonstrated a dose- and time-dependent inhibition of cell growth, induction of apoptosis, and cell-cycle arrest at G0/G1 phase in HL-60 cells. CPT-11 promoted the release of AIF from mitochondria and its translocation to the nucleus. Bid, Bax, Apaf-1, caspase-9, AIF, Endo G, caspase-12, ATF-6b, Grp78, CDK2, Chk2, and cyclin D were all significantly upregulated and Bcl-2 was down-regulated by CPT-11 in HL-60 cells. Induction of cell-cycle arrest by CPT-11 was associated with changes in expression of key cell-cycle regulators such as CDK2, Chk2, and cyclin D in HL-60 cells. To test whether CPT-11 could augment antitumor activity in vivo, athymic BALB/c(nu/nu) nude mice were inoculated with HL-60 cells, followed by treatment with either CPT-11. The treatments significantly inhibited tumor growth and reduced tumor weight and volume in the HL-60 xenograft mice. The present study demonstrates the schedule-dependent antileukemia effect of CPT-11 using both in vitro and in vivo models. CPT-11 could potentially be a promising agent for the treatment of promyelocytic leukemia and requires further investigation. © 2014 Wiley Periodicals, Inc.

Sulforaphane inhibits PDGF-induced proliferation of rat aortic vascular smooth muscle cell by up-regulation of p53 leading to G1/S cell cycle arrest.

PubMed

Yoo, Su-Hyang; Lim, Yong; Kim, Seung-Jung; Yoo, Kyu-Dong; Yoo, Hwan-Soo; Hong, Jin-Tae; Lee, Mi-Yea; Yun, Yeo-Pyo

2013-01-01

Vascular diseases such as atherosclerosis and restenosis artery angioplasty are associated with vascular smooth muscle cell (VSMC) proliferation and intimal thickening arterial walls. In the present study, we investigated the inhibitory effects of sulforaphane, an isothiocyanate produced in cruciferous vegetables, on VSMC proliferation and neointimal formation in a rat carotid artery injury model. Sulforaphane at the concentrations of 0.5, 1.0, and 2.0 μM significantly inhibited platelet-derived growth factor (PDGF)-BB-induced VSMC proliferation in a concentration-dependent manner, determined by cell count. The IC50 value of sulforaphane-inhibited VSMC proliferation was 0.8 μM. Sulforaphane increased the cyclin-dependent kinase inhibitor p21 and p53 levels, while it decreased CDK2 and cyclin E expression. The effects of sulforaphane on vascular thickening were determined 14 days after the injury to the rat carotid artery. The angiographic mean luminary diameters of the group treated with 2 and 4 μM sulforaphane were 0.25±0.1 and 0.09±0.1 mm², respectively, while the value of the control groups was 0.40±0.1 mm², indicating that sulforaphane may inhibit neointimal formation. The expression of PCNA, maker for cell cycle arrest, was decreased, while that of p53 and p21 was increased, which showed the same pattern as one in in-vitro study. These results suggest that sulforaphane-inhibited VSMC proliferation may occur through the G1/S cell cycle arrest by up-regulation of p53 signaling pathway, and then lead to the decreased neointimal hyperplasia thickening. Thus, sulforaphane may be a promising candidate for the therapy of atherosclerosis and post-angiography restenosis. © 2013.

Transient inhibition of cell proliferation does not compromise self-renewal of mouse embryonic stem cells.

PubMed

Wang, Ruoxing; Guo, Yan-Lin

2012-10-01

Embryonic stem cells (ESCs) have unlimited capacity for self-renewal and can differentiate into various cell types when induced. They also have an unusual cell cycle control mechanism driven by constitutively active cyclin dependent kinases (Cdks). In mouse ESCs (mESCs). It is proposed that the rapid cell proliferation could be a necessary part of mechanisms that maintain mESC self-renewal and pluripotency, but this hypothesis is not in line with the finding in human ESCs (hESCs) that the length of the cell cycle is similar to differentiated cells. Therefore, whether rapid cell proliferation is essential for the maintenance of mESC state remains unclear. We provide insight into this uncertainty through chemical intervention of mESC cell cycle. We report here that inhibition of Cdks with olomoucine II can dramatically slow down cell proliferation of mESCs with concurrent down-regulation of cyclin A, B and E, and the activation of the Rb pathway. However, mESCs display can recover upon the removal of olomoucine II and are able to resume normal cell proliferation without losing self-renewal and pluripotency, as demonstrated by the expression of ESC markers, colony formation, embryoid body formation, and induced differentiation. We provide a mechanistic explanation for these observations by demonstrating that Oct4 and Nanog, two major transcription factors that play critical roles in the maintenance of ESC properties, are up-regulated via de novo protein synthesis when the cells are exposed to olomoucine II. Together, our data suggest that short-term inhibition of cell proliferation does not compromise the basic properties of mESCs. Copyright © 2012 Elsevier Inc. All rights reserved.

Lebein, a snake venom disintegrin, suppresses human colon cancer cells proliferation and tumor-induced angiogenesis through cell cycle arrest, apoptosis induction and inhibition of VEGF expression.

PubMed

Zakraoui, Ons; Marcinkiewicz, Cezary; Aloui, Zohra; Othman, Houcemeddine; Grépin, Renaud; Haoues, Meriam; Essafi, Makram; Srairi-Abid, Najet; Gasmi, Ammar; Karoui, Habib; Pagès, Gilles; Essafi-Benkhadir, Khadija

2017-01-01

Lebein, is an heterodimeric disintegrin isolated from Macrovipera lebetina snake venom that was previously characterized as an inhibitor of ADP-induced platelet aggregation. In this study, we investigated the effect of Lebein on the p53-dependent growth of human colon adenocarcinoma cell lines. We found that Lebein significantly inhibited LS174 (p53wt), HCT116 (p53wt), and HT29 (p53mut) colon cancer cell viability by inducing cell cycle arrest through the modulation of expression levels of the tumor suppression factor p53, cell cycle regulating proteins cyclin D1, CDK2, CDK4, retinoblastoma (Rb), CDK1, and cyclin-dependent kinase inhibitors p21 and p27. Interestingly, Lebein-induced apoptosis of colon cancer cells was dependent on their p53 status. Thus, in LS174 cells, cell death was associated with PARP cleavage and the activation of caspases 3 and 8 while in HCT116 cells, Lebein induced caspase-independent apoptosis through increased expression of apoptosis inducing factor (AIF). In LS174 cells, Lebein triggers the activation of the MAPK ERK1/2 pathway through induction of reactive oxygen species (ROS). It also decreased cell adhesion and migration to fibronectin through down regulation of α5β1 integrin. Moreover, Lebein significantly reduced the expression of two angiogenesis stimulators, Vascular Endothelial Growth Factor (VEGF) and Neuropilin 1 (NRP1). It inhibited the VEGF-induced neovascularization process in the quail embryonic CAM system and blocked the development of human colon adenocarcinoma in nude mice. Overall, our work indicates that Lebein may be useful to design a new therapy against colon cancer. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Saito, Yuri, E-mail: saito-yu@bldon.med.osaka-u.ac.jp; Shibayama, Hirohiko; Tanaka, Hirokazu

Research highlights: {yields} Anamorsin (AM) (also called CIAPIN-1) is a cell-death-defying factor. {yields} Biological mechanisms of AM functions have not been elucidated yet. {yields} PKC{theta} , PKC{delta} and p38MAPK were more phosphorylated in AM deficient MEF cells. {yields} AM may negatively regulates PKCs and p38MAPK in MEF cells. -- Abstract: Anamorsin (AM) plays crucial roles in hematopoiesis and embryogenesis. AM deficient (AM KO) mice die during late gestation; AM KO embryos are anemic and very small compared to wild type (WT) embryos. To determine which signaling pathways AM utilizes for these functions, we used murine embryonic fibroblast (MEF) cells generatedmore » from E-14.5 AM KO or WT embryos. Proliferation of AM KO MEF cells was markedly retarded, and PKC{theta}, PKC{delta}, and p38MAPK were more highly phosphorylated in AM KO MEF cells. Expression of cyclinD1, the target molecule of p38MAPK, was down-regulated in AM KO MEF cells. p38MAPK inhibitor as well as PKC inhibitor restored expression of cyclinD1 and cell growth in AM KO MEF cells. These data suggest that PKC{theta}, PKC{delta}, and p38MAPK activation lead to cell cycle retardation in AM KO MEF cells, and that AM may negatively regulate novel PKCs and p38MAPK in MEF cells.« less

PD 0332991, a selective cyclin D kinase 4/6 inhibitor, sensitizes lung cancer cells to treatment with epidermal growth factor receptor tyrosine kinase inhibitors

PubMed Central

Li, Ying; Li, Yongwen; Zhang, Hongbing; Liu, Hongyu; Chen, Jun

2016-01-01

Acquired resistance to epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) is a major challenge to targeted therapy for non-small cell lung cancer (NSCLC). We investigated whether a cyclin D kinase 4/6 (CDK4/6) inhibitor, PD 0332991, could reverse EGFR-TKI resistance in human lung cancer cells and explored the underlying mechanisms. We found that PD 0332991 potentiated gefitinib-induced growth inhibition in both EGFR-TKI-sensitive (PC-9) and EGFR-TKI-resistant (PC-9/AB2) cells by down-regulating proliferation and inducing apoptosis and G0/G1 cell cycle arrest. Tumor xenografts were then used to verify the effects of PD 0332991 in vivo. Mice treated with a combination of PD 0332991 and gefitinib had the fastest tumor regression and delayed relapse. Tumors from mice receiving the combination treatment exhibited down-regulated proliferation, up-regulated apoptosis, and less angiogenesis. Finally, lung adenocarcinoma patients with acquired resistance to EGFR-TKIs were given an exploratory treatment of PD 0332991. One patient with gefitinib resistance exhibited clinical remission after treatment with PD 0332991. These findings suggest PD 0332991 reverses acquired EGFR-TKI-resistance in NSCLC cells, and may provide a novel treatment strategy for NSLSC patients with EGFR-TKI resistance. PMID:27825114

Cell cycle-regulated proteolysis of mitotic target proteins.

PubMed

Bastians, H; Topper, L M; Gorbsky, G L; Ruderman, J V

1999-11-01

The ubiquitin-dependent proteolysis of mitotic cyclin B, which is catalyzed by the anaphase-promoting complex/cyclosome (APC/C) and ubiquitin-conjugating enzyme H10 (UbcH10), begins around the time of the metaphase-anaphase transition and continues through G1 phase of the next cell cycle. We have used cell-free systems from mammalian somatic cells collected at different cell cycle stages (G0, G1, S, G2, and M) to investigate the regulated degradation of four targets of the mitotic destruction machinery: cyclins A and B, geminin H (an inhibitor of S phase identified in Xenopus), and Cut2p (an inhibitor of anaphase onset identified in fission yeast). All four are degraded by G1 extracts but not by extracts of S phase cells. Maintenance of destruction during G1 requires the activity of a PP2A-like phosphatase. Destruction of each target is dependent on the presence of an N-terminal destruction box motif, is accelerated by additional wild-type UbcH10 and is blocked by dominant negative UbcH10. Destruction of each is terminated by a dominant activity that appears in nuclei near the start of S phase. Previous work indicates that the APC/C-dependent destruction of anaphase inhibitors is activated after chromosome alignment at the metaphase plate. In support of this, we show that addition of dominant negative UbcH10 to G1 extracts blocks destruction of the yeast anaphase inhibitor Cut2p in vitro, and injection of dominant negative UbcH10 blocks anaphase onset in vivo. Finally, we report that injection of dominant negative Ubc3/Cdc34, whose role in G1-S control is well established and has been implicated in kinetochore function during mitosis in yeast, dramatically interferes with congression of chromosomes to the metaphase plate. These results demonstrate that the regulated ubiquitination and destruction of critical mitotic proteins is highly conserved from yeast to humans.

Effects of the Kava Chalcone Flavokawain A Differ in Bladder Cancer Cells with Wild-type versus Mutant p53

PubMed Central

Tang, Yaxiong; Simoneau, Anne R.; Xie, Jun; Shahandeh, Babbak; Zi, Xiaolin

2010-01-01

Flavokawain A is the predominant chalcone from kava extract. We have assessed the mechanisms of flavokawain A's action on cell cycle regulation. In a p53 wild-type, low-grade, and papillary bladder cancer cell line (RT4), flavokawain A increased p21/WAF1 and p27/KIP1, which resulted in a decrease in cyclin-dependent kinase-2 (CDK2) kinase activity and subsequent G1 arrest. The increase of p21/WAF1 protein corresponded to an increased mRNA level, whereas p27/KIP1 accumulation was associated with the down-regulation of SKP2 and then increased the stability of the p27/KIP1 protein. The accumulation of p21/WAF1 and p27/KIP1 was independent of cell cycle position and thus not a result of the cell cycle arrest. In contrast, flavokawain A induced a G2-M arrest in six p53 mutant-type, high-grade bladder cancer cell lines (T24, UMUC3, TCCSUP, 5637, HT1376, and HT1197). Flavokawain A significantly reduced the expression of CDK1-inhibitory kinases, Myt1 and Wee1, and caused cyclin B1 protein accumulation leading to CDK1 activation in T24 cells. Suppression of p53 expression by small interfering RNA in RT4 cells restored Cdc25C expression and down-regulated p21/WAF1 expression, which allowed Cdc25C and CDK1 activation and then led to a G2-M arrest and an enhanced growth-inhibitory effect by flavokawain A. Consistently, flavokawain A also caused a pronounced CDK1 activation and G2-M arrest in p53 knockout but not in p53 wild-type HCT116 cells. This selectivity of flavokawain A for inducing a G2-M arrest in p53-defective cells deserves further investigation as a new mechanism for the prevention and treatment of bladder cancer. PMID:19138991

MicroRNA-188 suppresses G1/S transition by targeting multiple cyclin/CDK complexes.

PubMed

Wu, Jiangbin; Lv, Qing; He, Jie; Zhang, Haoxiang; Mei, Xueshuang; Cui, Kai; Huang, Nunu; Xie, Weidong; Xu, Naihan; Zhang, Yaou

2014-10-11

Accelerated cell cycle progression is the common feature of most cancers. MiRNAs can act as oncogenes or tumor suppressors by directly modulating cell cycle machinery. It has been shown that miR-188 is upregulated in UVB-irradiated mouse skin and human nasopharyngeal carcinoma CNE cells under hypoxic stress. However, little is known about the function of miR-188 in cell proliferation and growth control. Overexpression of miR-188 inhibits cell proliferation, tumor colony formation and G1/S cell cycle transition in human nasopharyngeal carcinoma CNE cells. Using bioinformatics approach, we identify a series of genes regulating G1/S transition as putative miR-188 targets. MiR-188 inhibits both mRNA and protein expression of CCND1, CCND3, CCNE1, CCNA2, CDK4 and CDK2, suppresses Rb phosphorylation and downregulates E2F transcriptional activity. The expression level of miR-188 also inversely correlates with the expression of miR-188 targets in human nasopharyngeal carcinoma (NPC) tissues. Moreover, studies in xenograft mouse model reveal that miR-188 is capable of inhibiting tumor initiation and progression by suppressing target genes expression and Rb phosphorylation. This study demonstrates that miR-188 exerts anticancer effects, via downregulation of multiple G1/S related cyclin/CDKs and Rb/E2F signaling pathway.

The multifunctional RNA-binding protein hnRNPK is critical for the proliferation and differentiation of myoblasts.

PubMed

Xu, Yongjie; Li, Rui; Zhang, Kaili; Wu, Wei; Wang, Suying; Zhang, Pengpeng; Xu, Haixia

2018-06-14

HnRNPK is a multifunctional protein that participates in chromatin remodeling, transcrip-tion, RNA splicing, mRNA stability and translation. Here, we uncovered the function of hnRNPK in regulating the proliferation and differentiation of myoblasts. hnRNPK was mutated in the C2C12 myoblast cell line using the CRISPR/Cas9 system. A decreased proliferation rate was observed in hnRNPK-mutated cells, suggesting an impaired prolif-eration phenotype. Furthermore, increased G2/M phase, decreased S phase and increased sub-G1 phase cells were detected in the hnRNPK-mutated cell lines. The expression analysis of key cell cycle regulators indicated mRNA of Cyclin A2 was significantly in-creased in the mutant myoblasts compared to the control cells, while Cyclin B1, Cdc25b and Cdc25c were decreased sharply. In addition to the myoblast proliferation defect, the mutant cells exhibited defect in myotube formation. The myotube formation marker, my-osin heavy chain (MHC), was decreased sharply in hnRNPK-mutated cells compared to control myoblasts during differentiation. The deficiency in hnRNPK also resulted in the repression of Myog expression, a key myogenic regulator during differentiation. Together, our data demonstrate that hnRNPK is required for myoblast proliferation and differentia-tion and may be an essential regulator of myoblast function.

Distinct Signaling Pathways Mediate Stimulation of Cell Cycle Progression and Prevention of Apoptotic Cell Death by Estrogen in Rat Pituitary Tumor PR1 Cells

PubMed Central

Caporali, Simona; Imai, Manami; Altucci, Lucia; Cancemi, Massimo; Caristi, Silvana; Cicatiello, Luigi; Matarese, Filomena; Penta, Roberta; Sarkar, Dipak K.; Bresciani, Francesco; Weisz, Alessandro

2003-01-01

Estrogens control cell growth and viability in target cells via an interplay of genomic and extragenomic pathways not yet elucidated. Here, we show evidence that cell proliferation and survival are differentially regulated by estrogen in rat pituitary tumor PR1 cells. Pico- to femtomolar concentrations of 17β-estradiol (E2) are sufficient to foster PR1 cell proliferation, whereas nanomolar concentrations of the same are needed to prevent cell death that occurs at a high rate in these cells in the absence of hormone. Activation of endogenous (PRL) or transfected estrogen-responsive genes occurs at the same, higher concentrations of E2 required to promote cell survival, whereas stimulation of cyclin D3 expression and DNA synthesis occur at lower E2 concentrations. Similarly, the pure antiestrogen ICI 182,780 inhibits estrogen response element-dependent trans-activation and cell death more effectively than cyclin-cdk activity, G1-S transition, or DNA synthesis rate. In antiestrogen-treated and/or estrogen-deprived cells, death is due predominantly to apoptosis. Estrogen-induced cell survival, but not E2-dependent cell cycle progression, can be prevented by an inhibitor of c-Src kinase or by blockade of the mitogen-activated protein kinase kinase/extracellular signal-regulated kinase signaling pathway. These data indicate the coexistence of two distinguishable estrogen signaling pathways in PR1 cells, characterized by different functions and sensitivity to hormones and antihormones. PMID:12960425

Retinoic acid receptor alpha drives cell cycle progression and is associated with increased sensitivity to retinoids in T-cell lymphoma.

PubMed

Wang, Xueju; Dasari, Surendra; Nowakowski, Grzegorz S; Lazaridis, Konstantinos N; Wieben, Eric D; Kadin, Marshall E; Feldman, Andrew L; Boddicker, Rebecca L

2017-04-18

Peripheral T-cell lymphomas (PTCLs) are aggressive non-Hodgkin lymphomas with generally poor outcomes following standard therapy. Few candidate therapeutic targets have been identified to date. Retinoic acid receptor alpha (RARA) is a transcription factor that modulates cell growth and differentiation in response to retinoids. While retinoids have been used to treat some cutaneous T-cell lymphomas (CTCLs), their mechanism of action and the role of RARA in CTCL and other mature T-cell lymphomas remain poorly understood. After identifying a PTCL with a RARAR394Q mutation, we sought to characterize the role of RARA in T-cell lymphoma cells. Overexpressing wild-type RARA or RARAR394Q significantly increased cell growth in RARAlow cell lines, while RARA knockdown induced G1 arrest and decreased expression of cyclin-dependent kinases CDK2/4/6 in RARAhigh cells. The retinoids, AM80 (tamibarotene) and all-trans retinoic acid, caused dose-dependent growth inhibition, G1 arrest, and CDK2/4/6 down-regulation. Genes down-regulated in transcriptome data were enriched for cell cycle and G1-S transition. Finally, RARA overexpression augmented chemosensitivity to retinoids. In conclusion, RARA drives cyclin-dependent kinase expression, G1-S transition, and cell growth in T-cell lymphoma. Synthetic retinoids inhibit these functions in a dose-dependent fashion and are most effective in cells with high RARA expression, indicating RARA may represent a therapeutic target in some PTCLs.

Hcm1 integrates signals from Cdk1 and calcineurin to control cell proliferation

PubMed Central

Arsenault, Heather E.; Roy, Jagoree; Mapa, Claudine E.; Cyert, Martha S.; Benanti, Jennifer A.

2015-01-01

Cyclin-dependent kinase (Cdk1) orchestrates progression through the cell cycle by coordinating the activities of cell-cycle regulators. Although phosphatases that oppose Cdk1 are likely to be necessary to establish dynamic phosphorylation, specific phosphatases that target most Cdk1 substrates have not been identified. In budding yeast, the transcription factor Hcm1 activates expression of genes that regulate chromosome segregation and is critical for maintaining genome stability. Previously we found that Hcm1 activity and degradation are stimulated by Cdk1 phosphorylation of distinct clusters of sites. Here we show that, upon exposure to environmental stress, the phosphatase calcineurin inhibits Hcm1 by specifically removing activating phosphorylations and that this regulation is important for cells to delay proliferation when they encounter stress. Our work identifies a mechanism by which proliferative signals from Cdk1 are removed in response to stress and suggests that Hcm1 functions as a rheostat that integrates stimulatory and inhibitory signals to control cell proliferation. PMID:26269584

Distinct mechanisms act in concert to mediate cell cycle arrest.

PubMed

Toettcher, Jared E; Loewer, Alexander; Ostheimer, Gerard J; Yaffe, Michael B; Tidor, Bruce; Lahav, Galit

2009-01-20

In response to DNA damage, cells arrest at specific stages in the cell cycle. This arrest must fulfill at least 3 requirements: it must be activated promptly; it must be sustained as long as damage is present to prevent loss of genomic information; and after the arrest, cells must re-enter into the appropriate cell cycle phase to ensure proper ploidy. Multiple molecular mechanisms capable of arresting the cell cycle have been identified in mammalian cells; however, it is unknown whether each mechanism meets all 3 requirements or whether they act together to confer specific functions to the arrest. To address this question, we integrated mathematical models describing the cell cycle and the DNA damage signaling networks and tested the contributions of each mechanism to cell cycle arrest and re-entry. Predictions from this model were then tested with quantitative experiments to identify the combined action of arrest mechanisms in irradiated cells. We find that different arrest mechanisms serve indispensable roles in the proper cellular response to DNA damage over time: p53-independent cyclin inactivation confers immediate arrest, whereas p53-dependent cyclin downregulation allows this arrest to be sustained. Additionally, p21-mediated inhibition of cyclin-dependent kinase activity is indispensable for preventing improper cell cycle re-entry and endoreduplication. This work shows that in a complex signaling network, seemingly redundant mechanisms, acting in a concerted fashion, can achieve a specific cellular outcome.

CCS52A2/FZR1, a cell cycle regulator, is an essential factor for shoot apical meristem maintenance in Arabidopsis thaliana.

PubMed

Liu, Yajie; Ye, Wei; Li, Beibei; Zhou, Xiaojing; Cui, Yuhai; Running, Mark P; Liu, Kede

2012-08-08

Cell division and cell fate decisions regulate organ formation and function in plant growth and development. It is still unclear how specific meristematic regulatory networks operate with the cell cycle machinery to translate stem cell identity and maintenance into cellular behavior. In this study, we address these questions by analysis of a shoot apex defective mutant, namely xcm9. Phenotypic analysis of the xcm9 mutant reveals concomitant premature termination of floral shoots with frequent bifurcation of the shoot apices, stems, and flowers. Microscopic observations show irregular cell organization in shoot apical meristems of xcm9. Positional cloning revealed that xcm9 is a loss of function allele of the CCS52A2/FZR1 gene, which has previously been implicated in root development. Expression analysis demonstrated that CCS52A2 maintains a higher transcriptional expression level in actively dividing tissue. Genetic studies indicated that the CCS52A2 gene functions together with WUSCHEL (WUS) and CLAVATA3 (CLV3) in regulating the development of the shoot meristem, and also contributes to this regulation together with the chromatin remodeling pathway. In addition, fewer xcm9 cells express CYCLIN B1:1, showing that cell cycle progression is disrupted in the mutant. We propose that the CCS52A2 gene is a mediator that functions together with meristematic genes to regulate meristem organization, and cross-functions with chromatin regulators in cell cycle progression during shoot apical meristem development.

Cell Signalling Through Covalent Modification and Allostery

NASA Astrophysics Data System (ADS)

Johnson, Louise N.

Phosphorylation plays essential roles in nearly every aspect of cell life. Protein kinases catalyze the transfer of the γ-phosphate of ATP to a serine, threonine or tyrosine residue in protein substrates. This covalent modification allows activation or inhibition of enzyme activity, creates recognition sites for other proteins and promotes order/disorder or disorder/order transitions. These properties regulate ­signalling pathways and cellular processes that mediate metabolism, transcription, cell cycle progression, differentiation, cytoskeleton arrangement and cell movement, apoptosis, intercellular communication, and neuronal and immunological functions. In this lecture I shall review the structural consequences of protein phosphorylation using our work on glycogen phosphorylase and the cell cycle cyclin dependent protein kinases as illustrations. Regulation of protein phosphorylation may be disrupted in the diseased state and protein kinases have become high profile targets for drug development. To date there are 11 compounds that have been approved for clinical use in the treatment of cancer.

Obatoclax, a Pan-BCL-2 Inhibitor, Targets Cyclin D1 for Degradation to Induce Antiproliferation in Human Colorectal Carcinoma Cells.

PubMed

Or, Chi-Hung R; Chang, Yachu; Lin, Wei-Cheng; Lee, Wee-Chyan; Su, Hong-Lin; Cheung, Muk-Wing; Huang, Chang-Po; Ho, Cheesang; Chang, Chia-Che

2016-12-27

Colorectal cancer is the third most common cancer worldwide. Aberrant overexpression of antiapoptotic BCL-2 (B-cell lymphoma 2) family proteins is closely linked to tumorigenesis and poor prognosis in colorectal cancer. Obatoclax is an inhibitor targeting all antiapoptotic BCL-2 proteins. A previous study has described the antiproliferative action of obatoclax in one human colorectal cancer cell line without elucidating the underlying mechanisms. We herein reported that, in a panel of human colorectal cancer cell lines, obatoclax inhibits cell proliferation, suppresses clonogenicity, and induces G₁-phase cell cycle arrest, along with cyclin D1 downregulation. Notably, ectopic cyclin D1 overexpression abrogated clonogenicity suppression but also G₁-phase arrest elicited by obatoclax. Mechanistically, pre-treatment with the proteasome inhibitor MG-132 restored cyclin D1 levels in all obatoclax-treated cell lines. Cycloheximide chase analyses further revealed an evident reduction in the half-life of cyclin D1 protein by obatoclax, confirming that obatoclax downregulates cyclin D1 through induction of cyclin D1 proteasomal degradation. Lastly, threonine 286 phosphorylation of cyclin D1, which is essential for initiating cyclin D1 proteasomal degradation, was induced by obatoclax in one cell line but not others. Collectively, we reveal a novel anticancer mechanism of obatoclax by validating that obatoclax targets cyclin D1 for proteasomal degradation to downregulate cyclin D1 for inducing antiproliferation.

Glycyrrhetinic acid induces G1-phase cell cycle arrest in human non-small cell lung cancer cells through endoplasmic reticulum stress pathway

PubMed Central

ZHU, JIE; CHEN, MEIJUAN; CHEN, NING; MA, AIZHEN; ZHU, CHUNYAN; ZHAO, RUOLIN; JIANG, MIAO; ZHOU, JING; YE, LIHONG; FU, HAIAN; ZHANG, XU

2015-01-01

Glycyrrhetinic acid (GA) is a natural compound extracted from liquorice, which is often used in traditional Chinese medicine. The purpose of the present study was to investigate the antitumor effect of GA in human non-small cell lung cancer (NSCLC), and its underlying mechanisms in vitro. We have shown that GA suppressed the proliferation of A549 and NCI-H460 cells. Flow cytometric analysis showed that GA arrested cell cycle in G0/G1 phase without inducing apoptosis. Western blot analysis indicated that GA mediated G1-phase cell cycle arrest by upregulation of cyclin-dependent kinase inhibitors (CKIs) (p18, p16, p27 and p21) and inhibition of cyclins (cyclin-D1, -D3 and -E) and cyclin-dependent kinases (CDKs) (CDK4, 6 and 2). GA also maintained pRb phosphorylation status, and inhibited E2F transcription factor 1 (E2F-1) in both cell lines. GA upregulated the unfolded proteins, Bip, PERK and ERP72. Accumulation of unfolded proteins in the endoplasmic reticulum (ER) triggered the unfolded protein response (UPR), which could be the mechanism by which GA inhibited cell proliferation in NSCLC cells. GA then coordinated the induction of ER chaperones, which decreased protein synthesis and induced cell cycle arrest in the G1 phase. This study provides experimental evidence to support the development of GA as a chemotherapeutic agent for NSCLC. PMID:25573651

RBP-J-interacting and tubulin-associated protein induces apoptosis and cell cycle arrest in human hepatocellular carcinoma by activating the p53–Fbxw7 pathway

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Haihe; Yang, Zhanchun; Liu, Chunbo

2014-11-07

Highlights: • RITA overexpression increased protein expression of p53 and Fbxw7 and downregulated the expression of cyclin D1, cyclin E, CDK2, Hes-1 and NF-κB p65. • RITA can significantly inhibit the in vitro growth of SMMC7721 and HepG2 cells. • RITA exerts tumor-suppressive effects in hepatocarcinogenesis through induction of G0/G1 cell cycle arrest and apoptosis and suggest a therapeutic application of RITA in HCC. - Abstract: Aberrant Notch signaling is observed in human hepatocellular carcinoma (HCC) and has been associated with the modulation of cell growth. However, the role of Notch signaling in HCC and its underlying mechanism remain elusive.more » RBP-J-interacting and tubulin-associated (RITA) mediates the nuclear export of RBP-J to tubulin fibers and downregulates Notch-mediated transcription. In this study, we found that RITA overexpression increased protein expression of p53 and Fbxw7 and downregulated the expression of cyclin D1, cyclin E, CDK2, Hes-1 and NF-κB p65. These changes led to growth inhibition and induced G0/G1 cell cycle arrest and apoptosis in SMMC7721 and HepG2 cells. Our findings indicate that RITA exerts tumor-suppressive effects in hepatocarcinogenesis through induction of G0/G1 cell cycle arrest and apoptosis and suggest a therapeutic application of RITA in HCC.« less

Proteomic analysis of cell cycle arrest and differentiation induction caused by ATPR, a derivative of all-trans retinoic acid, in human gastric cancer SGC-7901 cells.

PubMed

Xia, Quan; Zhao, Yingli; Wang, Jiali; Qiao, Wenhao; Zhang, Dongling; Yin, Hao; Xu, Dujuan; Chen, Feihu

2017-07-01

4-amino-2-trifluoromethyl-phenyl retinate (ATPR) was reported to potentially inhibit proliferation and induce differentiation activity in some tumor cells. In this study, a proteomics approach was used to investigate the possible mechanism by screening the differentially expressed protein profiles of SGC-7901 cells before and after ATPR-treatment in vitro. Peptides digested from the total cellular proteins were analyzed by reverse phase LC-MS/MS followed by a label-free quantification analysis. The SEQUEST search engine was used to identify proteins and bioinformatics resources were used to investigate the involved pathways for the differentially expressed proteins. Thirteen down-regulated proteins were identified in the ATPR-treated group. Bioinformatics analysis showed that the effects of ATPR on 14-3-3ε might potentially involve the PI3K-AKT-FOXO pathway and P27Kip1 expression. Western blot and RT-PCR analysis showed that ATPR could inhibit AKT phosphorylation, up-regulate the expression of FOXO1A and P27Kip1 at both the protein and mRNA levels, and down-regulate the cytoplasmic expression of cyclin E and CDK2. ATPR-induced G0/G1 phase arrest and differentiation can be ablated if the P27kip1 gene is silenced with sequence-specific siRNA or in 14-3-3ε overexpression of SGC-7901 cells. ATPR might cause cell cycle arrest and differentiation in SGC-7901 cells by simultaneously inhibiting the phosphorylation of AKT and down-regulating 14-3-3ε. This change would then enhance the inhibition of cyclin E/CDK2 by up-regulating FOXO1A and P27Kip1. Our findings could be of value for finding new drug targets and for developing more effective differentiation inducer. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Mangiferin induces islet regeneration in aged mice through regulating p16INK4a

PubMed Central

Liu, Yilong; Huai, Guoli; Sun, Minghan; Deng, Shaoping; Yang, Hongji; Tong, Rongsheng; Wang, Yi

2018-01-01

Previous studies by our group on mangiferin demonstrated that it exerts an antihyperglycemic effect through the regulation of cell cycle proteins in 3-month-old, partially pancreatectomized (PPx) mice. However, β-cell proliferation is known to become severely restricted with advanced age. Therefore, it is unknown whether mangiferin is able to reverse the diabetic condition and retain β-cell regeneration capability in aged mice. In the present study, 12-month-old C57BL/6J mice that had undergone PPx were subjected to mangiferin treatment (90 mg/kg) for 28 days. Mangiferin-treated aged mice exhibited decreased blood glucose levels and increased glucose tolerance, which was accompanied with higher serum insulin levels when compared with those in untreated PPx control mice. In addition, islet hyperplasia, elevated β-cell proliferation and reduced β-cell apoptosis were also identified in the mice that received mangiferin treatment. Further studies on the mRNA transcript and protein expression levels indicated comparatively increased levels of cyclins D1 and D2 and cyclin-dependent kinase 4 in mangiferin-treated mice, while the levels of p27Kip1 and p16INK4a were decreased relative to those in the untreated PPx controls. Of note, mangiferin treatment improved the proliferation rate of islet β-cells in adult mice overexpressing p16INK4a, suggesting that mangiferin induced β-cell proliferation via the regulation of p16INK4a. In addition, the mRNA transcription levels of critical genes associated with insulin secretion, including pancreatic and duodenal homeobox 1, glucose transporter 2 and glucokinase, were observed to be upregulated after mangiferin treatment. Taken together, it was indicated that mangiferin treatment significantly induced β-cell proliferation and inhibited β-cell apoptosis by regulating cell cycle checkpoint proteins. Furthermore, mangiferin was also demonstrated to regulate genes associated with insulin secretion. Collectively these, results suggest the therapeutic potential of mangiferin in the treatment of diabetes in aged individuals. PMID:29512742

Proteomic analysis of the response to cell cycle arrests in human myeloid leukemia cells.

PubMed

Ly, Tony; Endo, Aki; Lamond, Angus I

2015-01-02

Previously, we analyzed protein abundance changes across a 'minimally perturbed' cell cycle by using centrifugal elutriation to differentially enrich distinct cell cycle phases in human NB4 cells (Ly et al., 2014). In this study, we compare data from elutriated cells with NB4 cells arrested at comparable phases using serum starvation, hydroxyurea, or RO-3306. While elutriated and arrested cells have similar patterns of DNA content and cyclin expression, a large fraction of the proteome changes detected in arrested cells are found to reflect arrest-specific responses (i.e., starvation, DNA damage, CDK1 inhibition), rather than physiological cell cycle regulation. For example, we show most cells arrested in G2 by CDK1 inhibition express abnormally high levels of replication and origin licensing factors and are likely poised for genome re-replication. The protein data are available in the Encyclopedia of Proteome Dynamics (

Effects of histone acetylation and DNA methylation on p21( WAF1) regulation.

PubMed

Fang, Jing-Yuan; Lu, You-Yong

2002-06-01

Cell cycle progression is regulated by interactions between cyclins and cyclin-dependent kinases (CDKs). p21(WAF1) is one of the CIP/KIP family which inhibits CDKs activity. Increased expression of p21(WAF1) may play an important role in the growth arrest induced in transformed cells. Although the stability of the p21( WAF1) mRNA could be altered by different signals, cell differentiation and numerous influencing factors. However, recent studies suggest that two known mechanisms of epigenesis, i.e.gene inactivation by methylation in promoter region and changes to an inactive chromatin by histone deacetylation, seem to be the best candidate mechanisms for inactivation of p21( WAF1). To date, almost no coding region p21(WAF1) mutations have been found in tumor cells, despite extensive screening of hundreds of various tumors. Hypermethylation of the p21(WAF1) promoter region may represent an alternative mechanism by which the p21(WAF1/CIP1) gene can be inactivated. The reduction of cellular DNMT protein levels also induces a corresponding rapid increase in the cell cycle regulator p21(WAF1) protein demonstrating a regulatory link between DNMT and p21(WAF1) which is independent of methylation of DNA. Both histone hyperacetylation and hypoacetylation appear to be important in the carcinoma process, and induction of the p21(WAF1) gene by histone hyperacetylation may be a mechanism by which dietary fiber prevents carcinogenesis. Here, we review the influence of histone acetylation and DNA methylation on p21(WAF1) transcription, and affection of pathways or factors associated such as p 53, E2A, Sp1 as well as several histone deacetylation inhibitors.

The M-phase specific hyperphosphorylation of Staufen2 involved the cyclin-dependent kinase CDK1.

PubMed

Beaujois, Rémy; Ottoni, Elizabeth; Zhang, Xin; Gagnon, Christina; HSine, Sami; Mollet, Stéphanie; Viranaicken, Wildriss; DesGroseillers, Luc

2017-07-14

Staufen2 (STAU2) is an RNA-binding protein involved in the post-transcriptional regulation of gene expression. This protein was shown to be required for organ formation and cell differentiation. Although STAU2 functions have been reported in neuronal cells, its role in dividing cells remains deeply uncharacterized. Especially, its regulation during the cell cycle is completely unknown. In this study, we showed that STAU2 isoforms display a mitosis-specific slow migration pattern on SDS-gels in all tested transformed and untransformed cell lines. Deeper analyses in hTert-RPE1 and HeLa cells further indicated that the slow migration pattern of STAU2 isoforms is due to phosphorylation. Time course studies showed that STAU2 phosphorylation occurs before prometaphase and terminates as cells exit mitosis. Interestingly, STAU2 isoforms were phosphorylated on several amino acid residues in the C-terminal half via the cyclin-dependent kinase 1 (Cdk1), an enzyme known to play crucial roles during mitosis. Introduction of phospho-mimetic or phospho-null mutations in STAU2 did not impair its RNA-binding capacity, its stability, its interaction with protein co-factors or its sub-cellular localization, suggesting that STAU2 phosphorylation in mitosis does not regulate these functions. Similarly, STAU2 phosphorylation is not likely to be crucial for cell cycle progression since expression of phosphorylation mutants in hTert-RPE1 cells did not impair cell proliferation. Altogether, these results indicate that STAU2 isoforms are phosphorylated during mitosis and that the phosphorylation process involves Cdk1. The meaning of this post-translational modification is still elusive.