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Sample records for quercetin-mediated cell cycle

  1. The roles of endoplasmic reticulum stress and mitochondrial apoptotic signaling pathway in quercetin-mediated cell death of human prostate cancer PC-3 cells.

    PubMed

    Liu, Kuo-Ching; Yen, Chun-Yi; Wu, Rick Sai-Chuen; Yang, Jai-Sing; Lu, Hsu-Feng; Lu, Kung-Wen; Lo, Chyi; Chen, Hung-Yi; Tang, Nou-Ying; Wu, Chih-Chung; Chung, Jing-Gung

    2014-04-01

    Prostate cancer has its highest incidence and is becoming a major concern. Many studies have shown that traditional Chinese medicine exhibited antitumor responses. Quercetin, a natural polyphenolic compound, has been shown to induce apoptosis in many human cancer cell lines. Although numerous evidences show multiple possible signaling pathways of quercetin in apoptosis, there is no report to address the role of endoplasmic reticulum (ER) stress in quercetin-induced apoptosis in PC-3 cells. The purpose of this study was to investigate the effects of quercetin on the induction of the apoptotic pathway in human prostate cancer PC-3 cells. Cells were treated with quercetin for 24 and 48 h and at various doses (50-200 μM), and cell morphology and viability decreased significantly in dose-dependent manners. Flow cytometric assay indicated that quercetin at 150 μM caused G0/G1 phase arrest (31.4-49.7%) and sub-G1 phase cells (19.77%) for 36 h treatment and this effect is a time-dependent manner. Western blotting analysis indicated that quercetin induces the G0/G1 phase arrest via decreasing the levels of CDK2, cyclins E, and D proteins. Quercetin also stimulated the protein expression of ATF, GRP78, and GADD153 which is a hall marker of ER stress. Furthermore, PC-3 cells after incubation with quercetin for 48 h showed an apoptotic cell death and DNA damage which are confirmed by DAPI and Comet assays, leading to decrease the antiapoptotic Bcl-2 protein and level of ΔΨm , and increase the proapoptotic Bax protein and the activations of caspase-3, -8, and -9. Moreover, quercetin promoted the trafficking of AIF protein released from mitochondria to nuclei. These data suggest that quercetin may induce apoptosis by direct activation of caspase cascade through mitochondrial pathway and ER stress in PC-3 cells. Copyright © 2012 Wiley Periodicals, Inc.

  2. Examination of KNK437- and quercetin-mediated inhibition of heat shock-induced heat shock protein gene expression in Xenopus laevis cultured cells.

    PubMed

    Manwell, Laurie A; Heikkila, John J

    2007-11-01

    We examined the effect of quercetin (3,3',4',5,7-pentahydroxyflavon) and KNK437 (N-formyl-3,4-methylenedioxy-benzylidene-gamma-butyrolactam), a benzylidene lactam compound, on heat-induced heat shock protein (hsp) gene expression in Xenopus laevis A6 kidney epithelial cells. In previous studies, both quercetin and KNK437 inhibited heat shock factor activity resulting in a repression of hsp mRNA and protein accumulation in human cultured cells. In this first study of the effect of these hsp gene expression inhibitors in a non-mammalian cell line, we report that both quercetin and KNK437 reduced the heat shock-induced accumulation of hsp30, hsp47 and hsp70 mRNA in X. laevis cultured cells. However, these inhibitors had no effect on the relative level of a non-heat shock protein mRNA, ef1alpha, in either control or heat shocked cells. Western blot and immunocytochemical analyses revealed that quercetin partially inhibited HSP30 protein accumulation. In contrast, HSP30 protein was not detectable in KNK437-treated cells. Finally, treatment of A6 cells with KNK437 inhibited the heat shock-induced acquisition of thermotolerance, as determined by preservation of actin filaments and cellular morphology using immunocytochemistry and laser scanning confocal microscopy.

  3. Quercetin-mediated Mcl-1 and survivin downregulation restores TRAIL-induced apoptosis in non-Hodgkin’s lymphoma B cells

    PubMed Central

    Jacquemin, Guillaume; Granci, Virginie; Gallouet, Anne Sophie; Lalaoui, Najoua; Morlé, Aymeric; Iessi, Elisabetta; Morizot, Alexandre; Garrido, Carmen; Guillaudeux, Thierry; Micheau, Olivier

    2012-01-01

    Background Non-Hodgkin's B-cell lymphomas account for approximately 70% of B-cell lymphomas. While its incidence is dramatically increasing worldwide, the disease is still associated with high morbidity due to ineffectiveness of conventional therapies, creating an urgent need for novel therapeutic approaches. Unconventional compounds, including polyphenols and the cytokine TRAIL, are being extensively studied for their capacity to restore apoptosis in a large number of tumors, including lymphomas. Design and Methods Molecular mechanisms of TRAIL-resistance and reactivation of the apoptotic machinery by quercetin in non-Hodgkin’s lymphoma cell lines were determined by Hoescht, flow cytometry, Western blot, qPCR, by use of siRNA or pharmacological inhibitors of the mitochondrial pathway and by immunoprecipitation followed by post-translational modification analysis. Results Results demonstrate that quercetin, a natural flavonoid, restores TRAIL-induced cell death in resistant transformed follicular lymphoma B-cell lines, despite high Bcl-2 expression levels due to the chromosomal translocation t(14;18). Quercetin rescues mitochondrial activation by inducing the proteasomal degradation of Mcl-1 and by inhibiting survivin expression at the mRNA level, irrespective of p53. Restoration of the TRAIL pathway requires Bax and Bak but is independent of enhanced TRAIL DISC formation. Conclusions We demonstrate that inactivation of survivin and Mcl-1 expression by quercetin is sufficient to restore TRAIL sensitivity in resistant non–Hodgkin’s lymphoma B cells. Our results suggest, therefore, that combining quercetin with TRAIL treatments may be useful in the treatment of non–Hodgkin’s lymphoma. PMID:21933852

  4. The microbial cell cycle

    SciTech Connect

    Nurse, P.; Streiblova, E.

    1984-01-01

    This book concentrates on the major problems of cell cycle control in microorganisms. A wide variety of microorganisms, ranging from bacteria and yeasts to hyphal fungi, algae, and ciliates are analyzed, with emphasis on the basic similarities among the organisms. Different ways of looking at cell cycle control which emphasize aspects of the problem such as circadian rhythms, limit cycle oscillators, and cell size models, are considered. New approaches such as the study of cell cycle mutants, and cloning of cell cycle control genes are also presented.

  5. The Chlamydomonas cell cycle.

    PubMed

    Cross, Frederick R; Umen, James G

    2015-05-01

    The position of Chlamydomonas within the eukaryotic phylogeny makes it a unique model in at least two important ways: as a representative of the critically important, early-diverging lineage leading to plants; and as a microbe retaining important features of the last eukaryotic common ancestor (LECA) that has been lost in the highly studied yeast lineages. Its cell biology has been studied for many decades and it has well-developed experimental genetic tools, both classical (Mendelian) and molecular. Unlike land plants, it is a haploid with very few gene duplicates, making it ideal for loss-of-function genetic studies. The Chlamydomonas cell cycle has a striking temporal and functional separation between cell growth and rapid cell division, probably connected to the interplay between diurnal cycles that drive photosynthetic cell growth and the cell division cycle; it also exhibits a highly choreographed interaction between the cell cycle and its centriole-basal body-flagellar cycle. Here, we review the current status of studies of the Chlamydomonas cell cycle. We begin with an overview of cell-cycle control in the well-studied yeast and animal systems, which has yielded a canonical, well-supported model. We discuss briefly what is known about similarities and differences in plant cell-cycle control, compared with this model. We next review the cytology and cell biology of the multiple-fission cell cycle of Chlamydomonas. Lastly, we review recent genetic approaches and insights into Chlamydomonas cell-cycle regulation that have been enabled by a new generation of genomics-based tools. © 2015 The Authors The Plant Journal published by Society for Experimental Biology and John Wiley & Sons Ltd.

  6. Specific cell cycle synchronization with butyrate and cell cycle analysis

    USDA-ARS?s Scientific Manuscript database

    Synchronized cells have been invaluable for many kinds of cell cycle and cell proliferation studies. Butyrate induces cell cycle arrest and apoptosis in MDBK cells. To explore the possibility of using butyrate-blocked cells to obtain synchronized cells, we investigated the property of the cell cyc...

  7. Cell cycle effects of drugs

    SciTech Connect

    Dethlefsen, L.A.

    1986-01-01

    This book contains 11 chapters. Some of the chapter titles are: Cell Growth and Division Cycle; Cell Cycle Effects of Alkylating Agents; Biological Effects of Folic Acid Antagonists with Antineoplastic Activity; and Bleomycin-Mode of Action with Particular Reference to the Cell Cycle.

  8. Cell cycle in mouse development.

    PubMed

    Ciemerych, Maria A; Sicinski, Peter

    2005-04-18

    Mice likely represent the most-studied mammalian organism, except for humans. Genetic engineering in embryonic stem cells has allowed derivation of mouse strains lacking particular cell cycle proteins. Analyses of these mutant mice, and cells derived from them, facilitated the studies of the functions of cell cycle apparatus at the organismal and cellular levels. In this review, we give some background about the cell cycle progression during mouse development. We next discuss some insights about in vivo functions of the cell cycle proteins, gleaned from mouse knockout experiments. Our text is meant to provide examples of the recent experiments, rather than to supply an extensive and complete list.

  9. How do prokaryotic cells cycle?

    PubMed

    Margolin, William; Bernander, Rolf

    2004-09-21

    This issue of Current Biology features five reviews covering various key aspects of the eukaryotic cell cycle. The topics include initiation of chromosome replication, assembly of the mitotic spindle, cytokinesis, the regulation of cell-cycle progression, and cell-cycle modeling, focusing mainly on budding yeast, fission yeast and animal cell model systems. The reviews underscore common themes as well as key differences in the way these processes are carried out and regulated among the different model organisms. Consequently, an important question is how cell-cycle mechanisms and controls have evolved, particularly in the broader perspective of the three domains of life.

  10. NETs and cell cycle regulation.

    PubMed

    Robson, Michael I; Le Thanh, Phu; Schirmer, Eric C

    2014-01-01

    There are many ways that the nuclear envelope can influence the cell cycle. In addition to roles of lamins in regulating the master cell cycle regulator pRb and nuclear envelope breakdown in mitosis, many other nuclear envelope proteins influence the cell cycle through regulatory or structural functions. Of particular note among these are the nuclear envelope transmembrane proteins (NETs) that appear to influence cell cycle regulation through multiple separate mechanisms. Some NETs and other nuclear envelope proteins accumulate on the mitotic spindle, suggesting functional or structural roles in the cell cycle. In interphase exogenous overexpression of some NETs promotes an increase in G1 populations, while others promote an increase in G2/M populations, sometimes associated with the induction of senescence. Intriguingly, most of the NETs linked to the cell cycle are highly restricted in their tissue expression; thus, their misregulation in cancer could contribute to the many tissue-specific types of cancer.

  11. The Abbreviated Pluripotent Cell Cycle

    PubMed Central

    Kapinas, Kristina; Grandy, Rodrigo; Ghule, Prachi; Medina, Ricardo; Becker, Klaus; Pardee, Arthur; Zaidi, Sayyed K.; Lian, Jane; Stein, Janet; van Wijnen, Andre; Stein, Gary

    2013-01-01

    Human embryonic stem cells and induced pluripotent stem cells proliferate rapidly and divide symmetrically producing equivalent progeny cells. In contrast, lineage committed cells acquire an extended symmetrical cell cycle. Self-renewal of tissue-specific stem cells is sustained by asymmetric cell division where one progeny cell remains a progenitor while the partner progeny cell exits the cell cycle and differentiates. There are three principal contexts for considering the operation and regulation of the pluripotent cell cycle: temporal, regulatory andstructural. The primary temporal context that the pluripotent self-renewal cell cycle of human embryonic stem cells (hESCs) is a short G1 period without reducing periods of time allocated to S phase, G2, and mitosis. The rules that govern proliferation in hESCs remain to be comprehensively established. However, several lines of evidence suggest a key role for the naïve transcriptome of hESCs, which is competent to stringently regulate the ESC cell cycle. This supports the requirements of pluripotent cells to self propagate while suppressing expression of genes that confer lineage commitment and/or tissue specificity. However, for the first time, we consider unique dimensions to the architectural organization and assembly of regulatory machinery for gene expression in nuclear microenviornments that define parameters of pluripotency. From both fundamental biological and clinical perspectives, understanding control of the abbreviated embryonic stem cell cycle can provide options to coordinate control of proliferation versus differentiation. Wound healing, tissue engineering, and cell-based therapy to mitigate developmental aberrations illustrate applications that benefit from knowledge of the biology of the pluripotent cell cycle. PMID:22552993

  12. The abbreviated pluripotent cell cycle.

    PubMed

    Kapinas, Kristina; Grandy, Rodrigo; Ghule, Prachi; Medina, Ricardo; Becker, Klaus; Pardee, Arthur; Zaidi, Sayyed K; Lian, Jane; Stein, Janet; van Wijnen, Andre; Stein, Gary

    2013-01-01

    Human embryonic stem cells (hESCs) and induced pluripotent stem cells proliferate rapidly and divide symmetrically producing equivalent progeny cells. In contrast, lineage committed cells acquire an extended symmetrical cell cycle. Self-renewal of tissue-specific stem cells is sustained by asymmetric cell division where one progeny cell remains a progenitor while the partner progeny cell exits the cell cycle and differentiates. There are three principal contexts for considering the operation and regulation of the pluripotent cell cycle: temporal, regulatory, and structural. The primary temporal context that the pluripotent self-renewal cell cycle of hESCs is a short G1 period without reducing periods of time allocated to S phase, G2, and mitosis. The rules that govern proliferation in hESCs remain to be comprehensively established. However, several lines of evidence suggest a key role for the naïve transcriptome of hESCs, which is competent to stringently regulate the embryonic stem cell (ESC) cell cycle. This supports the requirements of pluripotent cells to self-propagate while suppressing expression of genes that confer lineage commitment and/or tissue specificity. However, for the first time, we consider unique dimensions to the architectural organization and assembly of regulatory machinery for gene expression in nuclear microenviornments that define parameters of pluripotency. From both fundamental biological and clinical perspectives, understanding control of the abbreviated ESC cycle can provide options to coordinate control of proliferation versus differentiation. Wound healing, tissue engineering, and cell-based therapy to mitigate developmental aberrations illustrate applications that benefit from knowledge of the biology of the pluripotent cell cycle.

  13. Cell cycle regulation in hematopoietic stem cells.

    PubMed

    Pietras, Eric M; Warr, Matthew R; Passegué, Emmanuelle

    2011-11-28

    Hematopoietic stem cells (HSCs) give rise to all lineages of blood cells. Because HSCs must persist for a lifetime, the balance between their proliferation and quiescence is carefully regulated to ensure blood homeostasis while limiting cellular damage. Cell cycle regulation therefore plays a critical role in controlling HSC function during both fetal life and in the adult. The cell cycle activity of HSCs is carefully modulated by a complex interplay between cell-intrinsic mechanisms and cell-extrinsic factors produced by the microenvironment. This fine-tuned regulatory network may become altered with age, leading to aberrant HSC cell cycle regulation, degraded HSC function, and hematological malignancy.

  14. The cell cycle and pluripotency.

    PubMed

    Hindley, Christopher; Philpott, Anna

    2013-04-15

    PSCs (pluripotent stem cells) possess two key properties that have made them the focus of global research efforts in regenerative medicine: they have unlimited expansion potential under conditions which favour their preservation as PSCs and they have the ability to generate all somatic cell types upon differentiation (pluripotency). Conditions have been defined in vitro in which pluripotency is maintained, or else differentiation is favoured and is directed towards specific somatic cell types. However, an unanswered question is whether or not the core cell cycle machinery directly regulates the pluripotency and differentiation properties of PSCs. If so, then manipulation of the cell cycle may represent an additional tool by which in vitro maintenance or differentiation of PSCs may be controlled in regenerative medicine. The present review aims to summarize our current understanding of links between the core cell cycle machinery and the maintenance of pluripotency in ESCs (embryonic stem cells) and iPSCs (induced PSCs).

  15. Cell Cycle Regulation by Checkpoints

    PubMed Central

    Barnum, Kevin J.; O’Connell, Matthew J.

    2016-01-01

    Cell cycle checkpoints are surveillance mechanisms that monitor the order, integrity, and fidelity of the major events of the cell cycle. These include growth to the appropriate cell size, the replication and integrity of the chromosomes, and their accurate segregation at mitosis. Many of these mechanisms are ancient in origin and highly conserved, and hence have been heavily informed by studies in simple organisms such as the yeasts. Others have evolved in higher organisms, and control alternative cell fates with significant impact on tumor suppression. Here, we consider these different checkpoint pathways and the consequences of their dysfunction on cell fate. PMID:24906307

  16. Cell cycle regulation by checkpoints.

    PubMed

    Barnum, Kevin J; O'Connell, Matthew J

    2014-01-01

    Cell cycle checkpoints are surveillance mechanisms that monitor the order, integrity, and fidelity of the major events of the cell cycle. These include growth to the appropriate cell size, the replication and integrity of the chromosomes, and their accurate segregation at mitosis. Many of these mechanisms are ancient in origin and highly conserved, and hence have been heavily informed by studies in simple organisms such as the yeasts. Others have evolved in higher organisms, and control alternative cell fates with significant impact on tumor suppression. Here, we consider these different checkpoint pathways and the consequences of their dysfunction on cell fate.

  17. Myc and cell cycle control.

    PubMed

    Bretones, Gabriel; Delgado, M Dolores; León, Javier

    2015-05-01

    Soon after the discovery of the Myc gene (c-Myc), it became clear that Myc expression levels tightly correlate to cell proliferation. The entry in cell cycle of quiescent cells upon Myc enforced expression has been described in many models. Also, the downregulation or inactivation of Myc results in the impairment of cell cycle progression. Given the frequent deregulation of Myc oncogene in human cancer it is important to dissect out the mechanisms underlying the role of Myc on cell cycle control. Several parallel mechanisms account for Myc-mediated stimulation of the cell cycle. First, most of the critical positive cell cycle regulators are encoded by genes induced by Myc. These Myc target genes include Cdks, cyclins and E2F transcription factors. Apart from its direct effects on the transcription, Myc is able to hyperactivate cyclin/Cdk complexes through the induction of Cdk activating kinase (CAK) and Cdc25 phosphatases. Moreover, Myc antagonizes the activity of cell cycle inhibitors as p21 and p27 through different mechanisms. Thus, Myc is able to block p21 transcription or to induce Skp2, a protein involved in p27 degradation. Finally, Myc induces DNA replication by binding to replication origins and by upregulating genes encoding proteins required for replication initiation. Myc also regulates genes involved in the mitotic control. A promising approach to treat tumors with deregulated Myc is the synthetic lethality based on the inhibition of Cdks. Thus, the knowledge of the Myc-dependent cell cycle regulatory mechanisms will help to discover new therapeutic approaches directed against malignancies with deregulated Myc. This article is part of a Special Issue entitled: Myc proteins in cell biology and pathology. Copyright © 2014 Elsevier B.V. All rights reserved.

  18. What cycles the cell? -Robust autonomous cell cycle models.

    PubMed

    Lavi, Orit; Louzoun, Yoram

    2009-12-01

    The cell cycle is one of the best studied cellular mechanisms at the experimental and theoretical levels. Although most of the important biochemical components and reactions of the cell cycle are probably known, the precise way the cell cycle dynamics are driven is still under debate. This phenomenon is not atypical to many other biological systems where the knowledge of the molecular building blocks and the interactions between them does not lead to a coherent picture of the appropriate dynamics. We here propose a methodology to develop plausible models for the driving mechanisms of embryonic and cancerous cell cycles. We first define a key property of the system (a cyclic behaviour in the case of the embryonic cell cycle) and set mathematical constraints on the types of two variable simplified systems robustly reproducing such a cyclic behaviour. We then expand these robust systems to three variables and reiterate the procedure. At each step, we further limit the type of expanded systems to fit the known microbiology until a detailed description of the system is obtained. This methodology produces mathematical descriptions of the required biological systems that are more robust to changes in the precise function and rate constants. This methodology can be extended to practically any type of subcellular mechanism.

  19. Autoradiography and the Cell Cycle.

    ERIC Educational Resources Information Center

    Jones, C. Weldon

    1992-01-01

    Outlines the stages of a cell biology "pulse-chase" experiment in which the students apply autoradiography techniques to learn about the concept of the cell cycle. Includes (1) seed germination and plant growth; (2) radioactive labeling and fixation of root tips; (3) feulgen staining of root tips; (4) preparation of autoradiograms; and…

  20. Autoradiography and the Cell Cycle.

    ERIC Educational Resources Information Center

    Jones, C. Weldon

    1992-01-01

    Outlines the stages of a cell biology "pulse-chase" experiment in which the students apply autoradiography techniques to learn about the concept of the cell cycle. Includes (1) seed germination and plant growth; (2) radioactive labeling and fixation of root tips; (3) feulgen staining of root tips; (4) preparation of autoradiograms; and…

  1. Cell Cycle Regulation and Melanoma.

    PubMed

    Xu, Wen; McArthur, Grant

    2016-06-01

    Dysregulation of cell cycle control is a hallmark of melanomagenesis. Agents targeting the G1-S and G2-M checkpoints, as well as direct anti-mitotic agents, have all shown promising preclinical activity in melanoma. However, in vivo, standalone single agents targeting cell cycle regulation have only demonstrated modest efficacy in unselected patients. The advent of specific CDK 4/6 inhibitors targeting the G1-S transition, with an improved therapeutic index, is a significant step forward. Potential synergy exists with the combination of CDK4/6 inhibitors with existing therapies targeting the MAPK pathway, particularly in subsets of metastatic melanomas such as NRAS and BRAF mutants. This reviews summaries of the latest developments in both preclinical and clinical data with cell cycle-targeted therapies in melanoma.

  2. Mitochondrial dynamics during cell cycling.

    PubMed

    Horbay, Rostyslav; Bilyy, Rostyslav

    2016-12-01

    Mitochondria are the cell's power plant that must be in a proper functional state in order to produce the energy necessary for basic cellular functions, such as proliferation. Mitochondria are 'dynamic' in that they are constantly undergoing fission and fusion to remain in a functional state throughout the cell cycle, as well as during other vital processes such as energy supply, cellular respiration and programmed cell death. The mitochondrial fission/fusion machinery is involved in generating young mitochondria, while eliminating old, damaged and non-repairable ones. As a result, the organelles change in shape, size and number throughout the cell cycle. Such precise and accurate balance is maintained by the cytoskeletal transporting system via microtubules, which deliver the mitochondrion from one location to another. During the gap phases G1 and G2, mitochondria form an interconnected network, whereas in mitosis and S-phase fragmentation of the mitochondrial network will take place. However, such balance is lost during neoplastic transformation and autoimmune disorders. Several proteins, such as Drp1, Fis1, Kif-family proteins, Opa1, Bax and mitofusins change in activity and might link the mitochondrial fission/fusion events with processes such as alteration of mitochondrial membrane potential, apoptosis, necrosis, cell cycle arrest, and malignant growth. All this indicates how vital proper functioning of mitochondria is in maintaining cell integrity and preventing carcinogenesis.

  3. Secretory leukoprotease inhibitor is required for efficient quercetin-mediated suppression of TNFα secretion

    PubMed Central

    Serino, Grazia; Galleggiante, Vanessa; Caruso, Maria Lucia; Mastronardi, Mauro; Cavalcanti, Elisabetta; Ranson, Nicole; Pinto, Aldo; Campiglia, Pietro; Santino, Angelo

    2016-01-01

    Dendritic cells (DCs) are professional antigen presenting cells (APCs) that in response to microbial infections generate long-lasting adaptive immune response. Following microbial uptake, DCs undergo a cascade of cellular differentiation that ultimately leads to “mature” DCs. Mature DCs produce a variety of inflammatory cytokines, including tumor necrosis factor-α (TNFα) a key cytokine for the inflammatory cascade. In numerous studies, polyphenols, including quercetin, demonstrated their ability to suppress TNFα secretion and protect from the onset of chronic inflammatory disorders. We show that murine bone marrow derived DCs express Slpi following quercetin exposure. Slpi is known to suppress LPS mediated NFκB activation, thus, it was hypothesized that its expression could be the key step for polyphenol induced inflammatory suppression. Slpi-KO DCs poorly respond to quercetin administration failing to reduce TNFα secretion in response to quercetin exposure. Supernatant from quercetin exposed DCs could also reduce LPS-mediated TNFα secretion by unrelated DCs, but this property is lost using an anti-Slpi antibody. In vivo, oral administration of quercetin is able to induce Slpi expression. Human biopsies from inflamed tract of the intestine reveal the presence of numerous SLPI+ cells and the expression level could be further increased by quercetin administration. We propose that quercetin induces Slpi expression that in turn reduces the inflammatory response. Our data encourages the development of nutritional strategies to improve the efficiency of current therapies for intestinal chronic inflammatory syndrome and reduce the risks of colorectal cancer development. PMID:27716626

  4. Cell cycle regulation and regeneration.

    PubMed

    Heber-Katz, Ellen; Zhang, Yong; Bedelbaeva, Khamila; Song, Fengyu; Chen, Xiaoping; Stocum, David L

    2013-01-01

    Regeneration of ear punch holes in the MRL mouse and amputated limbs of the axolotl show a number of similarities. A large proportion of the fibroblasts of the uninjured MRL mouse ear are arrested in G2 of the cell cycle, and enter nerve-dependent mitosis after injury to form a ring-shaped blastema that regenerates the ear tissue. Multiple cell types contribute to the establishment of the regeneration blastema of the urodele limb by dedifferentiation, and there is substantial reason to believe that the cells of this early blastema are also arrested in G2, and enter mitosis under the influence of nerve-dependent factors supplied by the apical epidermal cap. Molecular analysis reveals other parallels, such as; (1) the upregulation of Evi5, a centrosomal protein that prevents mitosis by stabilizing Emi1, a protein that inhibits the degradation of cyclins by the anaphase promoting complex and (2) the expression of sodium channels by the epidermis. A central feature in the entry into the cell cycle by MRL ear fibroblasts is a natural downregulation of p21, and knockout of p21 in wild-type mice confers regenerative capacity on non-regenerating ear tissue. Whether the same is true for entry into the cell cycle in regenerating urodele limbs is presently unknown.

  5. [Cell cycle regulation in cancer stem cells].

    PubMed

    Takeishi, Shoichiro

    2015-05-01

    In addition to the properties of self-renewal and multipotency, cancer stem cells share the characteristics of their distinct cell cycle status with somatic stem cells. Cancer stem cells (CSCs) are maintained in a quiescent state with this characteristic conferring resistance to anticancer therapies that target dividing cells. Elucidation of the mechanisms of CSC quiescence might therefore be expected to provide further insight into CSC behaviors and lead to the elimination of cancer. This review summarizes several key regulators of the cell cycle in CSCs as well as attempts to define future challenges in this field, especially from the point of view of the application of our current understandings to the clinical medicine.

  6. Virus manipulation of cell cycle.

    PubMed

    Nascimento, R; Costa, H; Parkhouse, R M E

    2012-07-01

    Viruses depend on host cell resources for replication and access to those resources may be limited to a particular phase of the cell cycle. Thus manipulation of cell cycle is a commonly employed strategy of viruses for achieving a favorable cellular environment. For example, viruses capable of infecting nondividing cells induce S phase in order to activate the host DNA replication machinery and provide the nucleotide triphosphates necessary for viral DNA replication (Flemington in J Virol 75:4475-4481, 2001; Sullivan and Pipas in Microbiol Mol Biol Rev 66:179-202, 2002). Viruses have developed several strategies to subvert the cell cycle by association with cyclin and cyclin-dependent kinase complexes and molecules that regulate their activity. Viruses tend to act on cellular proteins involved in a network of interactions in a way that minimal protein-protein interactions lead to a major effect. The complex and interactive nature of intracellular signaling pathways controlling cell division affords many opportunities for virus manipulation strategies. Taking the maxim "Set a thief to catch a thief" as a counter strategy, however, provides us with the very same virus evasion strategies as "ready-made tools" for the development of novel antivirus therapeutics. The most obvious are attenuated virus vaccines with critical evasion genes deleted. Similarly, vaccines against viruses causing cancer are now being successfully developed. Finally, as viruses have been playing chess with our cell biology and immune responses for millions of years, the study of their evasion strategies will also undoubtedly reveal new control mechanisms and their corresponding cellular intracellular signaling pathways.

  7. Cell cycle regulation by protein degradation.

    PubMed

    Koepp, Deanna M

    2014-01-01

    Cell division is controlled by a highly regulated program to accurately duplicate and segregate chromosomes. An important feature of the cell cycle regulatory program is that key cell cycle proteins are present and active during specific cell cycle stages but are later removed or inhibited to maintain appropriate timing. The ubiquitin-proteasome system has emerged as an important mechanism to target cell cycle proteins for degradation at critical junctures during cell division. Two key E3 ubiquitin ligase complexes that target key cell cycle proteins are the Skp1-Cul1-F-box protein complex and the anaphase-promoting complex/cyclosome. This chapter focuses on the role of these E3 ubiquitin ligases and how ubiquitin-dependent degradation of central cell cycle regulatory proteins advances the cell cycle.

  8. Cell cycle regulation during viral infection.

    PubMed

    Bagga, Sumedha; Bouchard, Michael J

    2014-01-01

    To replicate their genomes in cells and generate new progeny, viruses typically require factors provided by the cells that they have infected. Subversion of the cellular machinery that controls replication of the infected host cell is a common activity of many viruses. Viruses employ different strategies to deregulate cell cycle checkpoint controls and modulate cell proliferation pathways. A number of DNA and RNA viruses encode proteins that target critical cell cycle regulators to achieve cellular conditions that are beneficial for viral replication. Many DNA viruses induce quiescent cells to enter the cell cycle; this is thought to increase pools of deoxynucleotides and thus, facilitate viral replication. In contrast, some viruses can arrest cells in a particular phase of the cell cycle that is favorable for replication of the specific virus. Cell cycle arrest may inhibit early cell death of infected cells, allow the cells to evade immune defenses, or help promote virus assembly. Although beneficial for the viral life cycle, virus-mediated alterations in normal cell cycle control mechanisms could have detrimental effects on cellular physiology and may ultimately contribute to pathologies associated with the viral infection, including cell transformation and cancer progression and maintenance. In this chapter, we summarize various strategies employed by DNA and RNA viruses to modulate the replication cycle of the virus-infected cell. When known, we describe how these virus-associated effects influence replication of the virus and contribute to diseases associated with infection by that specific virus.

  9. "Constructing" the Cell Cycle in 3D

    ERIC Educational Resources Information Center

    Koc, Isil; Turan, Merve

    2012-01-01

    The cycle of duplication and division, known as the "cell cycle," is the essential mechanism by which all living organisms reproduce. This activity allows students to develop an understanding of the main events that occur during the typical eukaryotic cell cycle mostly in the process of mitotic phase that divides the duplicated genetic material…

  10. "Constructing" the Cell Cycle in 3D

    ERIC Educational Resources Information Center

    Koc, Isil; Turan, Merve

    2012-01-01

    The cycle of duplication and division, known as the "cell cycle," is the essential mechanism by which all living organisms reproduce. This activity allows students to develop an understanding of the main events that occur during the typical eukaryotic cell cycle mostly in the process of mitotic phase that divides the duplicated genetic material…

  11. Cytofluorometric assessment of cell cycle progression.

    PubMed

    Vitale, Ilio; Jemaà, Mohamed; Galluzzi, Lorenzo; Metivier, Didier; Castedo, Maria; Kroemer, Guido

    2013-01-01

    One of the most prominent features of cellular senescence, a stress response that prevents the propagation of cells that have accumulated potentially oncogenic alterations, is a permanent loss of proliferative potential. Thus, at odds with quiescent cells, which resume proliferation when stimulated to do so, senescent cells cannot proceed through the cell cycle even in the presence of mitogenic factors. Here, we describe a set of cytofluorometric techniques for studying how chemical and/or physical stimuli alter the cell cycle in vitro, in both qualitative and quantitative terms. Taken together, these methods allow for the identification of bona fide cytostatic effects as well as for a refined characterization of cell cycle distributions, providing information on proliferation, DNA content as well as on the presence of cell cycle phase-specific markers. At the end of the chapter, a set of guidelines is offered to assist researchers that approach the study of the cell cycle with the interpretation of results.

  12. Cell division cycle 45 promotes papillary thyroid cancer progression via regulating cell cycle.

    PubMed

    Sun, Jing; Shi, Run; Zhao, Sha; Li, Xiaona; Lu, Shan; Bu, Hemei; Ma, Xianghua

    2017-05-01

    Cell division cycle 45 was reported to be overexpressed in some cancer-derived cell lines and was predicted to be a candidate oncogene in cervical cancer. However, the clinical and biological significance of cell division cycle 45 in papillary thyroid cancer has never been investigated. We determined the expression level and clinical significance of cell division cycle 45 using The Cancer Genome Atlas, quantitative real-time polymerase chain reaction, and immunohistochemistry. A great upregulation of cell division cycle 45 was observed in papillary thyroid cancer tissues compared with adjacent normal tissues. Furthermore, overexpression of cell division cycle 45 positively correlates with more advanced clinical characteristics. Silence of cell division cycle 45 suppressed proliferation of papillary thyroid cancer cells via G1-phase arrest and inducing apoptosis. The oncogenic activity of cell division cycle 45 was also confirmed in vivo. In conclusion, cell division cycle 45 may serve as a novel biomarker and a potential therapeutic target for papillary thyroid cancer.

  13. Model Organisms for Studying the Cell Cycle.

    PubMed

    Tang, Zhaohua

    2016-01-01

    Regulation of the cell-division cycle is fundamental for the growth, development, and reproduction of all species of life. In the past several decades, a conserved theme of cell cycle regulation has emerged from research in diverse model organisms. A comparison of distinct features of several diverse model organisms commonly used in cell cycle studies highlights their suitability for various experimental approaches, and recaptures their contributions to our current understanding of the eukaryotic cell cycle. A historic perspective presents a recollection of the breakthrough upon unfolding the universal principles of cell cycle control by scientists working with diverse model organisms, thereby appreciating the discovery pathways in this field. A comprehensive understanding is necessary to address current challenging questions about cell cycle control. Advances in genomics, proteomics, quantitative methodologies, and approaches of systems biology are redefining the traditional concept of what constitutes a model organism and have established a new era for development of novel, and refinement of the established model organisms. Researchers working in the field are no longer separated by their favorite model organisms; they have become more integrated into a larger community for gaining greater insights into how a cell divides and cycles. The new technologies provide a broad evolutionary spectrum of the cell-division cycle and allow informative comparisons among different species at a level that has never been possible, exerting unimaginable impact on our comprehensive understanding of cell cycle regulation.

  14. Molecular mechanisms controlling the cell cycle in embryonic stem cells.

    PubMed

    Abdelalim, Essam M

    2013-12-01

    Embryonic stem (ES) cells are originated from the inner cell mass of a blastocyst stage embryo. They can proliferate indefinitely, maintain an undifferentiated state (self-renewal), and differentiate into any cell type (pluripotency). ES cells have an unusual cell cycle structure, consists mainly of S phase cells, a short G1 phase and absence of G1/S checkpoint. Cell division and cell cycle progression are controlled by mechanisms ensuring the accurate transmission of genetic information from generation to generation. Therefore, control of cell cycle is a complicated process, involving several signaling pathways. Although great progress has been made on the molecular mechanisms involved in the regulation of ES cell cycle, many regulatory mechanisms remain unknown. This review summarizes the current knowledge about the molecular mechanisms regulating the cell cycle of ES cells and describes the relationship existing between cell cycle progression and the self-renewal.

  15. Gene copy number and cell cycle arrest

    NASA Astrophysics Data System (ADS)

    Ghosh, Bhaswar; Bose, Indrani

    2006-03-01

    The cell cycle is an orderly sequence of events which ultimately lead to the division of a single cell into two daughter cells. In the case of DNA damage by radiation or chemicals, the damage checkpoints in the G1 and G2 phases of the cell cycle are activated. This results in an arrest of the cell cycle so that the DNA damage can be repaired. Once this is done, the cell continues with its usual cycle of activity. We study a mathematical model of the DNA damage checkpoint in the G2 phase which arrests the transition from the G2 to the M (mitotic) phase of the cell cycle. The tumor suppressor protein p53 plays a key role in activating the pathways leading to cell cycle arrest in mammalian systems. If the DNA damage is severe, the p53 proteins activate other pathways which bring about apoptosis, i.e., programmed cell death. Loss of the p53 gene results in the proliferation of cells containing damaged DNA, i.e., in the growth of tumors which may ultimately become cancerous. There is some recent experimental evidence which suggests that the mutation of a single copy of the p53 gene (in the normal cell each gene has two identical copies) is sufficient to trigger the formation of tumors. We study the effect of reducing the gene copy number of the p53 and two other genes on cell cycle arrest and obtain results consistent with experimental observations.

  16. Crosstalk between stem cell and cell cycle machineries.

    PubMed

    Kareta, Michael S; Sage, Julien; Wernig, Marius

    2015-12-01

    Pluripotent stem cells, defined by an unlimited self-renewal capacity and an undifferentiated state, are best typified by embryonic stem cells. These cells have a unique cell cycle compared to somatic cells as defined by a rapid progression through the cell cycle and a minimal time spent in G1. Recent reports indicate that pluripotency and cell cycle regulation are mechanistically linked. In this review, we discuss the reciprocal co-regulation of these processes, how this co-regulation may prevent differentiation, and how cellular reprogramming can re-establish the unique cell cycle regulation in induced pluripotent stem cells. Copyright © 2015. Published by Elsevier Ltd.

  17. Cell cycle control and seed development

    PubMed Central

    Dante, Ricardo A.; Larkins, Brian A.; Sabelli, Paolo A.

    2014-01-01

    Seed development is a complex process that requires coordinated integration of many genetic, metabolic, and physiological pathways and environmental cues. Different cell cycle types, such as asymmetric cell division, acytokinetic mitosis, mitotic cell division, and endoreduplication, frequently occur in sequential yet overlapping manner during the development of the embryo and the endosperm, seed structures that are both products of double fertilization. Asymmetric cell divisions in the embryo generate polarized daughter cells with different cell fates. While nuclear and cell division cycles play a key role in determining final seed cell numbers, endoreduplication is often associated with processes such as cell enlargement and accumulation of storage metabolites that underlie cell differentiation and growth of the different seed compartments. This review focuses on recent advances in our understanding of different cell cycle mechanisms operating during seed development and their impact on the growth, development, and function of seed tissues. Particularly, the roles of core cell cycle regulators, such as cyclin-dependent-kinases and their inhibitors, the Retinoblastoma-Related/E2F pathway and the proteasome-ubiquitin system, are discussed in the contexts of different cell cycle types that characterize seed development. The contributions of nuclear and cellular proliferative cycles and endoreduplication to cereal endosperm development are also discussed. PMID:25295050

  18. Cell cycle control and seed development.

    PubMed

    Dante, Ricardo A; Larkins, Brian A; Sabelli, Paolo A

    2014-01-01

    Seed development is a complex process that requires coordinated integration of many genetic, metabolic, and physiological pathways and environmental cues. Different cell cycle types, such as asymmetric cell division, acytokinetic mitosis, mitotic cell division, and endoreduplication, frequently occur in sequential yet overlapping manner during the development of the embryo and the endosperm, seed structures that are both products of double fertilization. Asymmetric cell divisions in the embryo generate polarized daughter cells with different cell fates. While nuclear and cell division cycles play a key role in determining final seed cell numbers, endoreduplication is often associated with processes such as cell enlargement and accumulation of storage metabolites that underlie cell differentiation and growth of the different seed compartments. This review focuses on recent advances in our understanding of different cell cycle mechanisms operating during seed development and their impact on the growth, development, and function of seed tissues. Particularly, the roles of core cell cycle regulators, such as cyclin-dependent-kinases and their inhibitors, the Retinoblastoma-Related/E2F pathway and the proteasome-ubiquitin system, are discussed in the contexts of different cell cycle types that characterize seed development. The contributions of nuclear and cellular proliferative cycles and endoreduplication to cereal endosperm development are also discussed.

  19. Cell cycle gene expression under clinorotation

    NASA Astrophysics Data System (ADS)

    Artemenko, Olga

    2016-07-01

    Cyclins and cyclin-dependent kinase (CDK) are main regulators of the cell cycle of eukaryotes. It's assumes a significant change of their level in cells under microgravity conditions and by other physical factors actions. The clinorotation use enables to determine the influence of gravity on simulated events in the cell during the cell cycle - exit from the state of quiet stage and promotion presynthetic phase (G1) and DNA synthesis phase (S) of the cell cycle. For the clinorotation effect study on cell proliferation activity is the necessary studies of molecular mechanisms of cell cycle regulation and development of plants under altered gravity condition. The activity of cyclin D, which is responsible for the events of the cell cycle in presynthetic phase can be controlled by the action of endogenous as well as exogenous factors, but clinorotation is one of the factors that influence on genes expression that regulate the cell cycle.These data can be used as a model for further research of cyclin - CDK complex for study of molecular mechanisms regulation of growth and proliferation. In this investigation we tried to summarize and analyze known literature and own data we obtained relatively the main regulators of the cell cycle in altered gravity condition.

  20. The peri-cell-cycle in Arabidopsis.

    PubMed

    Beeckman, T; Burssens, S; Inzé, D

    2001-03-01

    The root systems of plants proliferate via de novo formed meristems originating from differentiated pericycle cells. The identity of putative signals responsible for triggering some of the pericycle cells to re-enter the cell cycle remains unknown. Here, the cell cycle regulation in the pericycle of seedling roots of Arabidopsis thaliana (L.) HEYNH: is studied shortly after germination using various strategies. Based on the detailed analysis of the promoter-beta-glucuronidase activity of four key cell cycle regulatory genes, combined with cell length measurements, microdensitometry of DNA content, and experiments with a cell cycle-blocking agent, a model is proposed for cell cycle regulation in the pericycle at the onset of lateral root initiation. The results clearly show that before the first lateral root is initiated, the pericycle consists of dissimilar cell files in respect of their cell division history. Depending on the distance behind the root tip and on position in relation to the vascular tissue, particular pericycle cells remain in the G(2) phase of the cell cycle and are apparently more susceptible to lateral root initiation than others.

  1. Stretched cell cycle model for proliferating lymphocytes

    PubMed Central

    Dowling, Mark R.; Kan, Andrey; Heinzel, Susanne; Zhou, Jie H. S.; Marchingo, Julia M.; Wellard, Cameron J.; Markham, John F.; Hodgkin, Philip D.

    2014-01-01

    Stochastic variation in cell cycle time is a consistent feature of otherwise similar cells within a growing population. Classic studies concluded that the bulk of the variation occurs in the G1 phase, and many mathematical models assume a constant time for traversing the S/G2/M phases. By direct observation of transgenic fluorescent fusion proteins that report the onset of S phase, we establish that dividing B and T lymphocytes spend a near-fixed proportion of total division time in S/G2/M phases, and this proportion is correlated between sibling cells. This result is inconsistent with models that assume independent times for consecutive phases. Instead, we propose a stretching model for dividing lymphocytes where all parts of the cell cycle are proportional to total division time. Data fitting based on a stretched cell cycle model can significantly improve estimates of cell cycle parameters drawn from DNA labeling data used to monitor immune cell dynamics. PMID:24733943

  2. Protein tyrosine nitration in the cell cycle

    SciTech Connect

    Jia, Min; Mateoiu, Claudia; Souchelnytskyi, Serhiy

    2011-09-23

    Highlights: {yields} Enrichment of 3-nitrotyrosine containing proteins from cells synchronized in different phases of the cell cycle. {yields} Identification of 76 tyrosine nitrated proteins that change expression during the cell cycle. {yields} Nineteen identified proteins were previously described as regulators of cell proliferation. -- Abstract: Nitration of tyrosine residues in proteins is associated with cell response to oxidative/nitrosative stress. Tyrosine nitration is relatively low abundant post-translational modification that may affect protein functions. Little is known about the extent of protein tyrosine nitration in cells during progression through the cell cycle. Here we report identification of proteins enriched for tyrosine nitration in cells synchronized in G0/G1, S or G2/M phases of the cell cycle. We identified 27 proteins in cells synchronized in G0/G1 phase, 37 proteins in S phase synchronized cells, and 12 proteins related to G2/M phase. Nineteen of the identified proteins were previously described as regulators of cell proliferation. Thus, our data indicate which tyrosine nitrated proteins may affect regulation of the cell cycle.

  3. Lactobacillus Decelerates Cervical Epithelial Cell Cycle Progression

    PubMed Central

    Vielfort, Katarina; Weyler, Linda; Söderholm, Niklas; Engelbrecht, Mattias; Löfmark, Sonja; Aro, Helena

    2013-01-01

    We investigated cell cycle progression in epithelial cervical ME-180 cells during colonization of three different Lactobacillus species utilizing live cell microscopy, bromodeoxyuridine incorporation assays, and flow cytometry. The colonization of these ME-180 cells by L. rhamnosus and L. reuteri, originating from human gastric epithelia and saliva, respectively, was shown to reduce cell cycle progression and to cause host cells to accumulate in the G1 phase of the cell cycle. The G1 phase accumulation in L. rhamnosus-colonized cells was accompanied by the up-regulation and nuclear accumulation of p21. By contrast, the vaginal isolate L. crispatus did not affect cell cycle progression. Furthermore, both the supernatants from the lactic acid-producing L. rhamnosus colonies and lactic acid added to cell culture media were able to reduce the proliferation of ME-180 cells. In this study, we reveal the diversity of the Lactobacillus species to affect host cell cycle progression and demonstrate that L. rhamnosus and L. reuteri exert anti-proliferative effects on human cervical carcinoma cells. PMID:23675492

  4. Nucleosome architecture throughout the cell cycle.

    PubMed

    Deniz, Özgen; Flores, Oscar; Aldea, Martí; Soler-López, Montserrat; Orozco, Modesto

    2016-01-28

    Nucleosomes provide additional regulatory mechanisms to transcription and DNA replication by mediating the access of proteins to DNA. During the cell cycle chromatin undergoes several conformational changes, however the functional significance of these changes to cellular processes are largely unexplored. Here, we present the first comprehensive genome-wide study of nucleosome plasticity at single base-pair resolution along the cell cycle in Saccharomyces cerevisiae. We determined nucleosome organization with a specific focus on two regulatory regions: transcription start sites (TSSs) and replication origins (ORIs). During the cell cycle, nucleosomes around TSSs display rearrangements in a cyclic manner. In contrast to gap (G1 and G2) phases, nucleosomes have a fuzzier organization during S and M phases, Moreover, the choreography of nucleosome rearrangements correlate with changes in gene expression during the cell cycle, indicating a strong association between nucleosomes and cell cycle-dependent gene functionality. On the other hand, nucleosomes are more dynamic around ORIs along the cell cycle, albeit with tighter regulation in early firing origins, implying the functional role of nucleosomes on replication origins. Our study provides a dynamic picture of nucleosome organization throughout the cell cycle and highlights the subsequent impact on transcription and replication activity.

  5. Nucleosome architecture throughout the cell cycle

    PubMed Central

    Deniz, Özgen; Flores, Oscar; Aldea, Martí; Soler-López, Montserrat; Orozco, Modesto

    2016-01-01

    Nucleosomes provide additional regulatory mechanisms to transcription and DNA replication by mediating the access of proteins to DNA. During the cell cycle chromatin undergoes several conformational changes, however the functional significance of these changes to cellular processes are largely unexplored. Here, we present the first comprehensive genome-wide study of nucleosome plasticity at single base-pair resolution along the cell cycle in Saccharomyces cerevisiae. We determined nucleosome organization with a specific focus on two regulatory regions: transcription start sites (TSSs) and replication origins (ORIs). During the cell cycle, nucleosomes around TSSs display rearrangements in a cyclic manner. In contrast to gap (G1 and G2) phases, nucleosomes have a fuzzier organization during S and M phases, Moreover, the choreography of nucleosome rearrangements correlate with changes in gene expression during the cell cycle, indicating a strong association between nucleosomes and cell cycle-dependent gene functionality. On the other hand, nucleosomes are more dynamic around ORIs along the cell cycle, albeit with tighter regulation in early firing origins, implying the functional role of nucleosomes on replication origins. Our study provides a dynamic picture of nucleosome organization throughout the cell cycle and highlights the subsequent impact on transcription and replication activity. PMID:26818620

  6. Ubiquitin ligases and cell cycle control.

    PubMed

    Teixeira, Leonardo K; Reed, Steven I

    2013-01-01

    The ubiquitin-proteasome system plays a pivotal role in the sequence of events leading to cell division known as the cell cycle. Not only does ubiquitin-mediated proteolysis constitute a critical component of the core oscillator that drives the cell cycle in all eukaryotes, it is also central to the mechanisms that ensure that the integrity of the genome is maintained. These functions are primarily carried out by two families of E3 ubiquitin ligases, the Skp/cullin/F-box-containing and anaphase-promoting complex/cyclosome complexes. However, beyond those functions associated with regulation of central cell cycle events, many peripheral cell cycle-related processes rely on ubiquitylation for signaling, homeostasis, and dynamicity, involving additional types of ubiquitin ligases and regulators. We are only beginning to understand the diversity and complexity of this regulation.

  7. Cell Cycle Deregulation in Ewing's Sarcoma Pathogenesis

    PubMed Central

    Kowalewski, Ashley A.; Randall, R. Lor; Lessnick, Stephen L.

    2011-01-01

    Ewing's sarcoma is a highly aggressive pediatric tumor of bone that usually contains the characteristic chromosomal translocation t(11;22)(q24;q12). This translocation encodes the oncogenic fusion protein EWS/FLI, which acts as an aberrant transcription factor to deregulate target genes necessary for oncogenesis. One key feature of oncogenic transformation is dysregulation of cell cycle control. It is therefore likely that EWS/FLI and other cooperating mutations in Ewing's sarcoma modulate the cell cycle to facilitate tumorigenesis. This paper will summarize current published data associated with deregulation of the cell cycle in Ewing's sarcoma and highlight important questions that remain to be answered. PMID:21052502

  8. Cell cycle regulates cell type in the Arabidopsis sepal.

    PubMed

    Roeder, Adrienne H K; Cunha, Alexandre; Ohno, Carolyn K; Meyerowitz, Elliot M

    2012-12-01

    The formation of cellular patterns during development requires the coordination of cell division with cell identity specification. This coordination is essential in patterning the highly elongated giant cells, which are interspersed between small cells, in the outer epidermis of the Arabidopsis thaliana sepal. Giant cells undergo endocycles, replicating their DNA without dividing, whereas small cells divide mitotically. We show that distinct enhancers are expressed in giant cells and small cells, indicating that these cell types have different identities as well as different sizes. We find that members of the epidermal specification pathway, DEFECTIVE KERNEL1 (DEK1), MERISTEM LAYER1 (ATML1), Arabidopsis CRINKLY4 (ACR4) and HOMEODOMAIN GLABROUS11 (HDG11), control the identity of giant cells. Giant cell identity is established upstream of cell cycle regulation. Conversely, endoreduplication represses small cell identity. These results show not only that cell type affects cell cycle regulation, but also that changes in the cell cycle can regulate cell type.

  9. Transcriptional landscape of the human cell cycle.

    PubMed

    Liu, Yin; Chen, Sujun; Wang, Su; Soares, Fraser; Fischer, Martin; Meng, Feilong; Du, Zhou; Lin, Charles; Meyer, Clifford; DeCaprio, James A; Brown, Myles; Liu, X Shirley; He, Housheng Hansen

    2017-03-28

    Steady-state gene expression across the cell cycle has been studied extensively. However, transcriptional gene regulation and the dynamics of histone modification at different cell-cycle stages are largely unknown. By applying a combination of global nuclear run-on sequencing (GRO-seq), RNA sequencing (RNA-seq), and histone-modification Chip sequencing (ChIP-seq), we depicted a comprehensive transcriptional landscape at the G0/G1, G1/S, and M phases of breast cancer MCF-7 cells. Importantly, GRO-seq and RNA-seq analysis identified different cell-cycle-regulated genes, suggesting a lag between transcription and steady-state expression during the cell cycle. Interestingly, we identified genes actively transcribed at early M phase that are longer in length and have low expression and are accompanied by a global increase in active histone 3 lysine 4 methylation (H3K4me2) and histone 3 lysine 27 acetylation (H3K27ac) modifications. In addition, we identified 2,440 cell-cycle-regulated enhancer RNAs (eRNAs) that are strongly associated with differential active transcription but not with stable expression levels across the cell cycle. Motif analysis of dynamic eRNAs predicted Kruppel-like factor 4 (KLF4) as a key regulator of G1/S transition, and this identification was validated experimentally. Taken together, our combined analysis characterized the transcriptional and histone-modification profile of the human cell cycle and identified dynamic transcriptional signatures across the cell cycle.

  10. Targeting cell cycle regulation in cancer therapy.

    PubMed

    Diaz-Moralli, Santiago; Tarrado-Castellarnau, Míriam; Miranda, Anibal; Cascante, Marta

    2013-05-01

    Cell proliferation is an essential mechanism for growth, development and regeneration of eukaryotic organisms; however, it is also the cause of one of the most devastating diseases of our era: cancer. Given the relevance of the processes in which cell proliferation is involved, its regulation is of paramount importance for multicellular organisms. Cell division is orchestrated by a complex network of interactions between proteins, metabolism and microenvironment including several signaling pathways and mechanisms of control aiming to enable cell proliferation only in response to specific stimuli and under adequate conditions. Three main players have been identified in the coordinated variation of the many molecules that play a role in cell cycle: i) The cell cycle protein machinery including cyclin-dependent kinases (CDK)-cyclin complexes and related kinases, ii) The metabolic enzymes and related metabolites and iii) The reactive-oxygen species (ROS) and cellular redox status. The role of these key players and the interaction between oscillatory and non-oscillatory species have proved essential for driving the cell cycle. Moreover, cancer development has been associated to defects in all of them. Here, we provide an overview on the role of CDK-cyclin complexes, metabolic adaptations and oxidative stress in regulating progression through each cell cycle phase and transitions between them. Thus, new approaches for the design of innovative cancer therapies targeting crosstalk between cell cycle simultaneous events are proposed. Copyright © 2013 Elsevier Inc. All rights reserved.

  11. Interplay between cell growth and cell cycle in plants.

    PubMed

    Sablowski, Robert; Carnier Dornelas, Marcelo

    2014-06-01

    The growth of organs and whole plants depends on both cell growth and cell-cycle progression, but the interaction between both processes is poorly understood. In plants, the balance between growth and cell-cycle progression requires coordinated regulation of four different processes: macromolecular synthesis (cytoplasmic growth), turgor-driven cell-wall extension, mitotic cycle, and endocycle. Potential feedbacks between these processes include a cell-size checkpoint operating before DNA synthesis and a link between DNA contents and maximum cell size. In addition, key intercellular signals and growth regulatory genes appear to target at the same time cell-cycle and cell-growth functions. For example, auxin, gibberellin, and brassinosteroid all have parallel links to cell-cycle progression (through S-phase Cyclin D-CDK and the anaphase-promoting complex) and cell-wall functions (through cell-wall extensibility or microtubule dynamics). Another intercellular signal mediated by microtubule dynamics is the mechanical stress caused by growth of interconnected cells. Superimposed on developmental controls, sugar signalling through the TOR pathway has recently emerged as a central control point linking cytoplasmic growth, cell-cycle and cell-wall functions. Recent progress in quantitative imaging and computational modelling will facilitate analysis of the multiple interconnections between plant cell growth and cell cycle and ultimately will be required for the predictive manipulation of plant growth.

  12. Mechanics and regulation of cell shape during the cell cycle.

    PubMed

    Clark, Andrew G; Paluch, Ewa

    2011-01-01

    Many cell types undergo dramatic changes in shape throughout the cell cycle. For individual cells, a tight control of cell shape is crucial during cell division, but also in interphase, for example during cell migration. Moreover, cell cycle-related cell shape changes have been shown to be important for tissue morphogenesis in a number of developmental contexts. Cell shape is the physical result of cellular mechanical properties and of the forces exerted on the cell. An understanding of the causes and repercussions of cell shape changes thus requires knowledge of both the molecular regulation of cellular mechanics and how specific changes in cell mechanics in turn effect global shape changes. In this chapter, we provide an overview of the current knowledge on the control of cell morphology, both in terms of general cell mechanics and specifically during the cell cycle.

  13. Fuel cell and advanced turbine power cycle

    SciTech Connect

    White, D.J.

    1995-10-19

    Solar Turbines, Incorporated (Solar) has a vested interest in the integration of gas turbines and high temperature fuel cells and in particular, solid oxide fuel cells (SOFCs). Solar has identified a parallel path approach to the technology developments needed for future products. The primary approach is to move away from the simple cycle industrial machines of the past and develop as a first step more efficient recuperated engines. This move was prompted by the recognition that the simple cycle machines were rapidly approaching their efficiency limits. Improving the efficiency of simple cycle machines is and will become increasingly more costly. Each efficiency increment will be progressively more costly than the previous step.

  14. Cell cycle regulation of mitochondrial function.

    PubMed

    Lopez-Mejia, Isabel C; Fajas, Lluis

    2015-04-01

    Specific cellular functions, such as proliferation, survival, growth, or senescence, require a particular adaptive metabolic response, which is fine tuned by members of the cell cycle regulators families. Currently, proteins such as cyclins, CDKs, or E2Fs are being studied in the context of cell proliferation and survival, cell signaling, cell cycle regulation, and cancer. We show in this review that cellular, animal and molecular studies provided enough evidence to prove that these factors play, in addition, crucial roles in the control of mitochondrial function; finally resulting in a dual proliferative and metabolic response. Copyright © 2014 Elsevier Ltd. All rights reserved.

  15. Cell cycle regulated gene expression in yeasts.

    PubMed

    McInerny, Christopher J

    2011-01-01

    The regulation of gene expression through the mitotic cell cycle, so that genes are transcribed at particular cell cycle times, is widespread among eukaryotes. In some cases, it appears to be important for control mechanisms, as deregulated expression results in uncontrolled cell divisions, which can cause cell death, disease, and malignancy. In this review, I describe the current understanding of such regulated gene expression in two established simple eukaryotic model organisms, the budding yeast Saccharomyces cerevisiae and the fission yeast Schizosaccharomyces pombe. In these two yeasts, the global pattern of cell cycle gene expression has been well described, and most of the transcription factors that control the various waves of gene expression, and how they are in turn themselves regulated, have been characterized. As related mechanisms occur in all other eukaryotes, including humans, yeasts offer an excellent paradigm to understand this important molecular process. Copyright © 2011 Elsevier Inc. All rights reserved.

  16. Cell cycle regulation by microRNAs in stem cells.

    PubMed

    Wang, Yangming; Blelloch, Robert

    2011-01-01

    The ability to self-renew and to differentiate into at least one-cell lineage defines a stem cell. Self-renewal is a process by which stem cells proliferate without differentiation. Proliferation is achieved through a series of highly regulated events of the cell cycle. MicroRNAs (miRNAs) are a class of short noncoding RNAs whose importance in these events is becoming increasingly appreciated. In this chapter, we discuss the role of miRNAs in regulating the cell cycle in various stem cells with a focus on embryonic stem cells. We also present the evidence indicating that cell cycle-regulating miRNAs are incorporated into a large regulatory network to control the self-renewal of stem cells by inducing or inhibiting differentiation. In addition, we discuss the function of cell cycle-regulating miRNAs in cancer.

  17. Acanthamoeba induces cell-cycle arrest in host cells.

    PubMed

    Sissons, James; Alsam, Selwa; Jayasekera, Samantha; Kim, Kwang Sik; Stins, Monique; Khan, Naveed Ahmed

    2004-08-01

    Acanthamoeba can cause fatal granulomatous amoebic encephalitis (GAE) and eye keratitis. However, the pathogenesis and pathophysiology of these emerging diseases remain unclear. In this study, the effects of Acanthamoeba on the host cell cycle using human brain microvascular endothelial cells (HBMEC) and human corneal epithelial cells (HCEC) were determined. Two isolates of Acanthamoeba belonging to the T1 genotype (GAE isolate) and T4 genotype (keratitis isolate) were used, which showed severe cytotoxicity on HBMEC and HCEC, respectively. No tissue specificity was observed in their ability to exhibit binding to the host cells. To determine the effects of Acanthamoeba on the host cell cycle, a cell-cycle-specific gene array was used. This screened for 96 genes specific for host cell-cycle regulation. It was observed that Acanthamoeba inhibited expression of genes encoding cyclins F and G1 and cyclin-dependent kinase 6, which are proteins important for cell-cycle progression. Moreover, upregulation was observed of the expression of genes such as GADD45A and p130 Rb, associated with cell-cycle arrest, indicating cell-cycle inhibition. Next, the effect of Acanthamoeba on retinoblastoma protein (pRb) phosphorylation was determined. pRb is a potent inhibitor of G1-to-S cell-cycle progression; however, its function is inhibited upon phosphorylation, allowing progression into S phase. Western blotting revealed that Acanthamoeba abolished pRb phosphorylation leading to cell-cycle arrest at the G1-to-S transition. Taken together, these studies demonstrated for the first time that Acanthamoeba inhibits the host cell cycle at the transcriptional level, as well as by modulating pRb phosphorylation using host cell-signalling mechanisms. A complete understanding of Acanthamoeba-host cell interactions may help in developing novel strategies to treat Acanthamoeba infections.

  18. Decision for cell fate: deubiquitinating enzymes in cell cycle checkpoint.

    PubMed

    Lim, Key-Hwan; Song, Myoung-Hyun; Baek, Kwang-Hyun

    2016-04-01

    All organs consisting of single cells are consistently maintaining homeostasis in response to stimuli such as free oxygen, DNA damage, inflammation, and microorganisms. The cell cycle of all mammalian cells is regulated by protein expression in the right phase to respond to proliferation and apoptosis signals. Post-translational modifications (PTMs) of proteins by several protein-editing enzymes are associated with cell cycle regulation by their enzymatic functions. Ubiquitination, one of the PTMs, is also strongly related to cell cycle regulation by protein degradation or signal transduction. The importance of deubiquitinating enzymes (DUBs), which have a reversible function for ubiquitination, has recently suggested that the function of DUBs is also important for determining the fate of proteins during cell cycle processing. This article reviews and summarizes the diverse roles of DUBs, including DNA damage, cell cycle processing, and regulation of histone proteins, and also suggests the possibility for therapeutic targets.

  19. Cell cycle control across the eukaryotic kingdom.

    PubMed

    Harashima, Hirofumi; Dissmeyer, Nico; Schnittger, Arp

    2013-07-01

    Almost two billion years of evolution have generated a vast and amazing variety of eukaryotic life with approximately 8.7 million extant species. Growth and reproduction of all of these organisms depend on faithful duplication and distribution of their chromosomes to the newly forming daughter cells in a process called the cell cycle. However, most of what is known today about cell cycle control comes from a few model species that belong to the unikonts; that is, to only one of five 'supergroups' that comprise the eukaryotic kingdom. Recently, analyzing species from distantly related clades is providing insights into general principles of cell cycle regulation and shedding light on its evolution. Here, referring to animal and fungal as opposed to non-unikont systems, especially flowering plants from the archaeplastid supergroup, we compare the conservation of central cell cycle regulator functions, the structure of network topologies, and the evolutionary dynamics of substrates of core cell cycle kinases. Copyright © 2013 Elsevier Ltd. All rights reserved.

  20. Cycle life test of secondary spacecraft cells

    NASA Technical Reports Server (NTRS)

    Harkness, J. D.

    1980-01-01

    The results of the life cycling program on rechargeable calls are reported. Information on required data, the use of which the data will be put, application details, including orbital description, charge control methods, load rquirements, etc., are given. Cycle tests were performed on 660 sealed, nickel cadmium cells. The cells consisted of seven sample classifications ranging form 3.0 to 20 amp. hours. Nickel cadmium, silver cadmium, and silver zinc sealed cells, excluding synchronous orbit and accelerated test packs were added. The capacities of the nickel cadmium cells, the silver cadmium and the silver zinc cells differed in range of amp hrs. The cells were cylced under different load, charge control, and temperature conditions. All cell packs are recharged by use of a pack voltage limit. All charging is constant current until the voltage limit is reached.

  1. Cell cycle regulation of Rho signaling pathways.

    PubMed

    David, Muriel; Petit, Dominique; Bertoglio, Jacques

    2012-08-15

    The dynamics of the actin cytoskeleton and its regulation by Rho GTPases are essential to maintain cell shape, to allow cell motility and are also critical during cell cycle progression and mitosis. Rho GTPases and their effectors are involved in cell rounding at mitosis onset, in chromosomes alignment and are required for contraction of the actomyosin ring that separates daughter cells at the end of mitosis. Recent studies have revealed how a number of nucleotide exchange factors and GTPase-activating proteins regulate the activity of Rho GTPases during these processes. This review will focus on how the cell cycle machinery, in turn, regulates expression of proteins in the Rho signaling pathways through transcriptional activation, ubiquitylation and proteasomal degradation and modulates their activity through phosphorylation by mitotic kinases.

  2. Modeling of Sonos Memory Cell Erase Cycle

    NASA Technical Reports Server (NTRS)

    Phillips, Thomas A.; MacLeond, Todd C.; Ho, Fat D.

    2010-01-01

    Silicon-oxide-nitride-oxide-silicon (SONOS) nonvolatile semiconductor memories (NVSMS) have many advantages. These memories are electrically erasable programmable read-only memories (EEPROMs). They utilize low programming voltages, endure extended erase/write cycles, are inherently resistant to radiation, and are compatible with high-density scaled CMOS for low power, portable electronics. The SONOS memory cell erase cycle was investigated using a nonquasi-static (NQS) MOSFET model. The SONOS floating gate charge and voltage, tunneling current, threshold voltage, and drain current were characterized during an erase cycle. Comparisons were made between the model predictions and experimental device data.

  3. Parvovirus infection-induced cell death and cell cycle arrest

    PubMed Central

    Chen, Aaron Yun; Qiu, Jianming

    2011-01-01

    The cytopathic effects induced during parvovirus infection have been widely documented. Parvovirus infection-induced cell death is often directly associated with disease outcomes (e.g., anemia resulting from loss of erythroid progenitors during parvovirus B19 infection). Apoptosis is the major form of cell death induced by parvovirus infection. However, nonapoptotic cell death, namely necrosis, has also been reported during infection of the minute virus of mice, parvovirus H-1 and bovine parvovirus. Recent studies have revealed multiple mechanisms underlying the cell death during parvovirus infection. These mechanisms vary in different parvoviruses, although the large nonstructural protein (NS)1 and the small NS proteins (e.g., the 11 kDa of parvovirus B19), as well as replication of the viral genome, are responsible for causing infection-induced cell death. Cell cycle arrest is also common, and contributes to the cytopathic effects induced during parvovirus infection. While viral NS proteins have been indicated to induce cell cycle arrest, increasing evidence suggests that a cellular DNA damage response triggered by an invading single-stranded parvoviral genome is the major inducer of cell cycle arrest in parvovirus-infected cells. Apparently, in response to infection, cell death and cell cycle arrest of parvovirus-infected cells are beneficial to the viral cell lifecycle (e.g., viral DNA replication and virus egress). In this article, we will discuss recent advances in the understanding of the mechanisms underlying parvovirus infection-induced cell death and cell cycle arrest. PMID:21331319

  4. Role of transcription factor Sp1 in the quercetin-mediated inhibitory effect on human malignant pleural mesothelioma.

    PubMed

    Chae, Jung-Il; Cho, Jin Hyoung; Lee, Kyung-Ae; Choi, Nag-Jin; Seo, Kang Seok; Kim, Sang-Bum; Lee, Sang-Han; Shim, Jung-Hyun

    2012-10-01

    Quercetin (Qu) is found in plants, including red onions and in the skins of red apples, and induces the apoptosis of certain malignant cells. However, no report has been issued on the apoptotic effect of Qu on human malignant pleural mesothelioma. In the present study, it was found that MSTO-211H mesothelioma cell viability was reduced and apoptotic cell death was increased by Qu (20-80 µM), which was found to have an IC₅₀ of 58 µM. In addition, Qu increased the sub-G₁ cell population, and was found to interact with specificity protein 1 (Sp1) and significantly suppressed its expression at the protein and mRNA levels. Furthermore, Qu modulated the levels of Sp1 regulatory genes, such as cyclin D1, myeloid cell leukemia (Mcl)-1 and survivin in MSTO-211H cells. Apoptotic signaling cascades were activated by the cleavage of Bid, caspase-3 and PARP, and by the downregulation of Bcl-xL and the upregulation of Bax in MSTO-211H cells. Our results strongly suggest that Sp1 be considered as a novel molecular target of Qu in human malignant pleural mesothelioma.

  5. Cell Cycle Regulators and Cell Death in Immunity

    PubMed Central

    Zebell, Sophia G.; Dong, Xinnian

    2015-01-01

    Summary Various cell death mechanisms are integral to host defense in both plants and mammals. Plant defense against biotrophic pathogens is associated with programmed cell death (PCD) of the infected cell. This effector-triggered PCD is partly analogous to pyroptosis, an inflammatory host cell death process that plays a crucial role in defense against microbial infections in mammals. Plant effector-triggered PCD also shares with mammalian apoptosis the involvement of cell cycle regulators as signaling components. Here we explore the similarities between these different cell death programs as they relate to host defense and their relationship to the cell-cycle. PMID:26468745

  6. Cell-Cycle Regulators and Cell Death in Immunity.

    PubMed

    Zebell, Sophia G; Dong, Xinnian

    2015-10-14

    Various cell death mechanisms are integral to host defense in both plants and mammals. Plant defense against biotrophic pathogens is associated with programmed cell death (PCD) of the infected cell. This effector-triggered PCD is partly analogous to pyroptosis, an inflammatory host cell death process that plays a crucial role in defense against microbial infections in mammals. Plant effector-triggered PCD also shares with mammalian apoptosis the involvement of cell-cycle regulators as signaling components. Here we explore the similarities between these different cell death programs as they relate to host defense and their relationship to the cell cycle. Copyright © 2015 Elsevier Inc. All rights reserved.

  7. SAFT nickel hydrogen cell cycling status

    NASA Technical Reports Server (NTRS)

    Borthomieu, Yannick; Duquesne, Didier

    1994-01-01

    An overview of the NiH2 cell development is given. The NiH2 SAFT system is an electrochemical (single or dual) stack (IPV). The stack is mounted in an hydroformed Inconel 718 vessel operating at high pressure, equipped with 'rabbit ears' ceramic brazed electrical feedthroughs. The cell design is described: positive electrode, negative electrode, and stack configuration. Overviews of low earth orbit and geostationary earth orbit cyclings are provided. DPA results are also provided. The cycling and DPA results demonstrate that SAFT NiH2 is characterized by high reliability and very stable performances.

  8. Natural flavonoids targeting deregulated cell cycle progression in cancer cells.

    PubMed

    Singh, Rana Pratap; Agarwal, Rajesh

    2006-03-01

    The prolonged duration requiring alteration of multi-genetic and epigenetic molecular events for cancer development provides a strong rationale for cancer prevention, which is developing as a potential strategy to arrest or reverse carcinogenic changes before the appearance of the malignant disease. Cell cycle progression is an important biological event having controlled regulation in normal cells, which almost universally becomes aberrant or deregulated in transformed and neoplastic cells. In this regard, targeting deregulated cell cycle progression and its modulation by various natural and synthetic agents are gaining widespread attention in recent years to control the unchecked growth and proliferation in cancer cells. In fact, a vast number of experimental studies convincingly show that many phytochemicals halt uncontrolled cell cycle progression in cancer cells. Among these phytochemicals, natural flavonoids have been identified as a one of the major classes of natural anticancer agents exerting antineoplastic activity via cell cycle arrest as a major mechanism in various types of cancer cells. This review is focused at the modulatory effects of natural flavonoids on cell cycle regulators including cyclin-dependent kinases and their inhibitors, cyclins, p53, retinoblastoma family of proteins, E2Fs, check-point kinases, ATM/ATR and survivin controlling G1/S and G2/M check-point transitions in cell cycle progression, and discusses how these molecular changes could contribute to the antineoplastic effects of natural flavonoids.

  9. Control of cell cycle and cell growth by molecular chaperones.

    PubMed

    Aldea, Martí; Garí, Eloi; Colomina, Neus

    2007-11-01

    Cells adapt their size to both intrinsic and extrinsic demands and, among them, those that stem from growth and proliferation rates are crucial for cell size homeostasis. Here we revisit mechanisms that regulate cell cycle and cell growth in budding yeast. Cyclin Cln3, the most upstream activator of Start, is retained at the endoplasmic reticulum in early G(1) and released by specific chaperones in late G(1) to initiate the cell cycle. On one hand, these chaperones are rate-limiting for release of Cln3 and cell cycle entry and, on the other hand, they are required for key biosynthetic processes. We propose a model whereby the competition for specialized chaperones between growth and cycle machineries could gauge biosynthetic rates and set a critical size threshold at Start.

  10. Tumor cell "dead or alive": caspase and survivin regulate cell death, cell cycle and cell survival.

    PubMed

    Suzuki, A; Shiraki, K

    2001-04-01

    Cell death and cell cycle progression are two sides of the same coin, and these two different phenomenons are regulated moderately to maintain the cellular homeostasis. Tumor is one of the disease states produced as a result of the disintegrated regulation and is characterized as cells showing an irreversible progression of cell cycle and a resistance to cell death signaling. Several investigations have been performed for the understanding of cell death or cell cycle, and cell death research has remarkably progressed in these 10 years. Caspase is a nomenclature referring to ICE/CED-3 cysteine proteinase family and plays a central role during cell death. Recently, several investigations raised some possible hypotheses that caspase is also involved in cell cycle regulation. In this issue, therefore, we review the molecular basis of cell death and cell cycle regulated by caspase in tumor, especially hepatocellular carcinoma cells.

  11. Cell cycle regulation of glucocorticoid receptor function.

    PubMed Central

    Hsu, S C; Qi, M; DeFranco, D B

    1992-01-01

    Glucocorticoid receptor (GR) nuclear translocation, transactivation and phosphorylation were examined during the cell cycle in mouse L cell fibroblasts. Glucocorticoid-dependent transactivation of the mouse mammary tumor virus promoter was observed in G0 and S phase synchronized L cells, but not in G2 synchronized cells. G2 effects were selective on the glucocorticoid hormone signal transduction pathway, since glucocorticoid but not heavy metal induction of the endogenous Metallothionein-1 gene was also impaired in G2 synchronized cells. GRs that translocate to the nucleus of G2 synchronized cells in response to dexamethasone treatment were not efficiently retained there and redistributed to the cytoplasmic compartment. In contrast, GRs bound by the glucocorticoid antagonist RU486 were efficiently retained within nuclei of G2 synchronized cells. Inefficient nuclear retention was observed for both dexamethasone- and RU486-bound GRs in L cells that actively progress through G2 following release from an S phase arrest. Finally, site-specific alterations in GR phosphorylation were observed in G2 synchronized cells suggesting that cell cycle regulation of specific protein kinases and phosphatases could influence nuclear retention, recycling and transactivation activity of the GR. Images PMID:1505524

  12. Control points within the cell cycle

    SciTech Connect

    Van't Hof, J.

    1984-01-01

    Evidence of the temporal order of chromosomal DNA replication argues favorably for the view that the cell cycle is controlled by genes acting in sequence whose time of expression is determined by mitosis and the amount of nuclear DNA (2C vs 4C) in the cell. Gl and G2 appear to be carbohydrate dependent in that cells starved of either carbohydrate of phosphate fail to make these transitions. Cells deprived of nitrate, however, fail only at Gl to S transition indicating that the controls that operate in G1 differ from those that operate in G2. 46 references, 5 figures.

  13. Cell cycle regulation of human endometrial stromal cells during decidualization.

    PubMed

    Logan, Philip C; Steiner, Michael; Ponnampalam, Anna P; Mitchell, Murray D

    2012-08-01

    Differentiation of endometrial stromal cells into decidual cells is crucial for optimal endometrial receptivity. Data from our previous microarray study implied that expression of many cell cycle regulators are changed during decidualization and inhibition of DNA methylation in vitro. In this study, we hypothesized that both the classic progestin treatment and DNA methylation inhibition would inhibit stromal cell proliferation and cell cycle transition. The human endometrial stromal cell line (HESC) was treated from 2 days to 18 days with the DNA methylation inhibitor, 5-aza-2'-deoxycytidine (AZA), a mixture of estradiol/progestin/cyclic adenosine monophosphate ([cAMP]; medroxy-progesterone acetate [MPA mix]) or both. Cell growth was measured by cell counting, cell cycle transition and apoptosis were analyzed by flow cytometry, expression of cell cycle regulators were analyzed by quantitative polymerase chain reaction (qPCR) and Western blotting, and change in DNA methylation profiles were detected by methylation-specific PCR. Both AZA and MPA mix inhibited the proliferation of HESC for at least 7 days. Treatment with MPA mix resulted in an early G0/G1 inhibition followed by G2/M phase inhibition at 18 days. In contrast, AZA treatment inhibited cell cycle progression at the G2/M phase throughout. The protein levels of p21(Cip1)and 14-3-3σ were increased with both AZA and MPA mix treatments without any change in the DNA methylation profiles of the genes. Our data imply that the decidualization of HESC is associated with cell cycle arrest at G0/G1 phase initially and G2/M phase at later stages. Our results also suggest that p53 pathway members play a role in the cell cycle regulation of endometrial stromal cells.

  14. Quercetin-mediated synthesis of graphene oxide-silver nanoparticle nanocomposites: a suitable alternative nanotherapy for neuroblastoma.

    PubMed

    Yuan, Yu-Guo; Wang, Yan-Hong; Xing, Hui-Hui; Gurunathan, Sangiliyandi

    2017-01-01

    Graphene and graphene-related materials have gained substantial interest from both academia and industry for the development of unique nanomaterials for biomedical applications. Graphene oxide (GO) and silver nanoparticles (AgNPs) are a valuable platform for the development of nanocomposites, permitting the combination of nanomaterials with different physical and chemical properties to generate novel materials with improved and effective functionalities in a single platform. Therefore, this study was conducted to synthesize a graphene oxide-silver nanoparticle (GO-AgNPs) nanocomposite using the biomolecule quercetin and evaluate the potential cytotoxicity and mechanism of GO-AgNPs in human neuroblastoma cancer cells (SH-SY5Y). The synthesized GO-AgNPs were characterized using various analytical techniques. The potential toxicities of GO-AgNPs were evaluated using a series of biochemical and cellular assays. The expression of apoptotic and anti-apoptotic genes was measured by quantitative real-time reverse transcription polymerase chain reaction. Further, apoptosis was confirmed by caspase-9/3 activity and a terminal deoxynucleotidyl transferase dUTP nick end labeling assay, and GO-AgNPs-induced autophagy was also confirmed by transmission electron microscopy. The prepared GO-AgNPs exhibited significantly higher cytotoxicity toward SH-SY5Y cells than GO. GO-AgNPs induced significant cytotoxicity in SH-SY5Y cells by the loss of cell viability, inhibition of cell proliferation, increased leakage of lactate dehydrogenase, decreased level of mitochondrial membrane potential, reduced numbers of mitochondria, enhanced level of reactive oxygen species generation, increased expression of pro-apoptotic genes, and decreased expression of anti-apoptotic genes. GO-AgNPs induced caspase-9/3-dependent apoptosis via DNA fragmentation. Finally, GO-AgNPs induced accumulation of autophagosomes and autophagic vacuoles. In this study, we developed an environmentally friendly, facile

  15. Quercetin-mediated synthesis of graphene oxide–silver nanoparticle nanocomposites: a suitable alternative nanotherapy for neuroblastoma

    PubMed Central

    Yuan, Yu-Guo; Wang, Yan-Hong; Xing, Hui-Hui; Gurunathan, Sangiliyandi

    2017-01-01

    Background Graphene and graphene-related materials have gained substantial interest from both academia and industry for the development of unique nanomaterials for biomedical applications. Graphene oxide (GO) and silver nanoparticles (AgNPs) are a valuable platform for the development of nanocomposites, permitting the combination of nanomaterials with different physical and chemical properties to generate novel materials with improved and effective functionalities in a single platform. Therefore, this study was conducted to synthesize a graphene oxide–silver nanoparticle (GO-AgNPs) nanocomposite using the biomolecule quercetin and evaluate the potential cytotoxicity and mechanism of GO-AgNPs in human neuroblastoma cancer cells (SH-SY5Y). Methods The synthesized GO-AgNPs were characterized using various analytical techniques. The potential toxicities of GO-AgNPs were evaluated using a series of biochemical and cellular assays. The expression of apoptotic and anti-apoptotic genes was measured by quantitative real-time reverse transcription polymerase chain reaction. Further, apoptosis was confirmed by caspase-9/3 activity and a terminal deoxynucleotidyl transferase dUTP nick end labeling assay, and GO-AgNPs-induced autophagy was also confirmed by transmission electron microscopy. Results The prepared GO-AgNPs exhibited significantly higher cytotoxicity toward SH-SY5Y cells than GO. GO-AgNPs induced significant cytotoxicity in SH-SY5Y cells by the loss of cell viability, inhibition of cell proliferation, increased leakage of lactate dehydrogenase, decreased level of mitochondrial membrane potential, reduced numbers of mitochondria, enhanced level of reactive oxygen species generation, increased expression of pro-apoptotic genes, and decreased expression of anti-apoptotic genes. GO-AgNPs induced caspase-9/3-dependent apoptosis via DNA fragmentation. Finally, GO-AgNPs induced accumulation of autophagosomes and autophagic vacuoles. Conclusion In this study, we

  16. Mitochondrial dynamics and the cell cycle

    USDA-ARS?s Scientific Manuscript database

    Nuclear-mitochondrial (NM) communication impacts many aspects of plant development including vigor, sterility and viability. Dynamic changes in mitochondrial number, shape, size, and cellular location takes place during the cell cycle possibly impacting the process itself and leading to distribution...

  17. Dynamic ubiquitin signaling in cell cycle regulation.

    PubMed

    Gilberto, Samuel; Peter, Matthias

    2017-08-07

    The cell division cycle is driven by a collection of enzymes that coordinate DNA duplication and separation, ensuring that genomic information is faithfully and perpetually maintained. The activity of the effector proteins that perform and coordinate these biological processes oscillates by regulated expression and/or posttranslational modifications. Ubiquitylation is a cardinal cellular modification and is long known for driving cell cycle transitions. In this review, we emphasize emerging concepts of how ubiquitylation brings the necessary dynamicity and plasticity that underlie the processes of DNA replication and mitosis. New studies, often focusing on the regulation of chromosomal proteins like DNA polymerases or kinetochore kinases, are demonstrating that ubiquitylation is a versatile modification that can be used to fine-tune these cell cycle events, frequently through processes that do not involve proteasomal degradation. Understanding how the increasing variety of identified ubiquitin signals are transduced will allow us to develop a deeper mechanistic perception of how the multiple factors come together to faithfully propagate genomic information. Here, we discuss these and additional conceptual challenges that are currently under study toward understanding how ubiquitin governs cell cycle regulation. © 2017 Gilberto and Peter.

  18. Linking the Cell Cycle to Cell Fate Decisions.

    PubMed

    Dalton, Stephen

    2015-10-01

    Pluripotent stem cells (PSCs) retain the ability to differentiate into a wide range of cell types while undergoing self-renewal. They also exhibit an unusual mode of cell cycle regulation, reflected by a cell cycle structure where G1 and G2 phases are truncated. When individual PSCs are exposed to specification cues, they activate developmental programs and remodel the cell cycle so that the length of G1 and overall cell division times increase. The response of individual stem cells to pro-differentiation signals is strikingly heterogeneous, resulting in asynchronous differentiation. Recent evidence indicates that this phenomenon is due to cell cycle-dependent mechanisms that restrict the initial activation of developmental genes to the G1 phase. This suggests a broad biological mechanism where multipotent cells are 'primed' to initiate cell fate decisions during their transition through G1. Here, I discuss mechanisms underpinning the commitment towards the differentiated state and its relation to the cell cycle. Copyright © 2015 Elsevier Ltd. All rights reserved.

  19. FUEL CELL/MICRO-TURBINE COMBINED CYCLE

    SciTech Connect

    Larry J. Chaney; Mike R. Tharp; Tom W. Wolf; Tim A. Fuller; Joe J. Hartvigson

    1999-12-01

    A wide variety of conceptual design studies have been conducted that describe ultra-high efficiency fossil power plant cycles. The most promising of these ultra-high efficiency cycles incorporate high temperature fuel cells with a gas turbine. Combining fuel cells with a gas turbine increases overall cycle efficiency while reducing per kilowatt emissions. This study has demonstrated that the unique approach taken to combining a fuel cell and gas turbine has both technical and economic merit. The approach used in this study eliminates most of the gas turbine integration problems associated with hybrid fuel cell turbine systems. By using a micro-turbine, and a non-pressurized fuel cell the total system size (kW) and complexity has been reduced substantially from those presented in other studies, while maintaining over 70% efficiency. The reduced system size can be particularly attractive in the deregulated electrical generation/distribution environment where the market may not demand multi-megawatt central stations systems. The small size also opens up the niche markets to this high efficiency, low emission electrical generation option.

  20. Modeling of SONOS Memory Cell Erase Cycle

    NASA Technical Reports Server (NTRS)

    Phillips, Thomas A.; MacLeod, Todd C.; Ho, Fat H.

    2011-01-01

    Utilization of Silicon-Oxide-Nitride-Oxide-Silicon (SONOS) nonvolatile semiconductor memories as a flash memory has many advantages. These electrically erasable programmable read-only memories (EEPROMs) utilize low programming voltages, have a high erase/write cycle lifetime, are radiation hardened, and are compatible with high-density scaled CMOS for low power, portable electronics. In this paper, the SONOS memory cell erase cycle was investigated using a nonquasi-static (NQS) MOSFET model. Comparisons were made between the model predictions and experimental data.

  1. Solid oxide fuel cell combined cycles

    SciTech Connect

    Bevc, F.P.; Lundberg, W.L.; Bachovchin, D.M.

    1996-12-31

    The integration of the solid oxide fuel cell and combustion turbine technologies can result in combined-cycle power plants, fueled with natural gas, that have high efficiencies and clean gaseous emissions. Results of a study are presented in which conceptual designs were developed for 3 power plants based upon such an integration, and ranging in rating from 3 to 10 MW net ac. The plant cycles are described and characteristics of key components summarized. Also, plant design-point efficiency estimates are presented as well as values of other plant performance parameters.

  2. Cell Cycle Progression of Human Cells Cultured in Rotating Bioreactor

    NASA Technical Reports Server (NTRS)

    Parks, Kelsey

    2009-01-01

    Space flight has been shown to alter the astronauts immune systems. Because immune performance is complex and reflects the influence of multiple organ systems within the host, scientists sought to understand the potential impact of microgravity alone on the cellular mechanisms critical to immunity. Lymphocytes and their differentiated immature form, lymphoblasts, play an important and integral role in the body's defense system. T cells, one of the three major types of lymphocytes, play a central role in cell-mediated immunity. They can be distinguished from other lymphocyte types, such as B cells and natural killer cells by the presence of a special receptor on their cell surface called T cell receptors. Reported studies have shown that spaceflight can affect the expression of cell surface markers. Cell surface markers play an important role in the ability of cells to interact and to pass signals between different cells of the same phenotype and cells of different phenotypes. Recent evidence suggests that cell-cycle regulators are essential for T-cell function. To trigger an effective immune response, lymphocytes must proliferate. The objective of this project is to investigate the changes in growth of human cells cultured in rotating bioreactors and to measure the growth rate and the cell cycle distribution for different human cell types. Human lymphocytes and lymphoblasts will be cultured in a bioreactor to simulate aspects of microgravity. The bioreactor is a cylindrical culture vessel that incorporates the aspects of clinostatic rotation of a solid fluid body around a horizontal axis at a constant speed, and compensates gravity by rotation and places cells within the fluid body into a sustained free-fall. Cell cycle progression and cell proliferation of the lymphocytes will be measured for a number of days. In addition, RNA from the cells will be isolated for expression of genes related in cell cycle regulations.

  3. Cell Cycle Progression of Human Cells Cultured in Rotating Bioreactor

    NASA Technical Reports Server (NTRS)

    Parks, Kelsey

    2009-01-01

    Space flight has been shown to alter the astronauts immune systems. Because immune performance is complex and reflects the influence of multiple organ systems within the host, scientists sought to understand the potential impact of microgravity alone on the cellular mechanisms critical to immunity. Lymphocytes and their differentiated immature form, lymphoblasts, play an important and integral role in the body's defense system. T cells, one of the three major types of lymphocytes, play a central role in cell-mediated immunity. They can be distinguished from other lymphocyte types, such as B cells and natural killer cells by the presence of a special receptor on their cell surface called T cell receptors. Reported studies have shown that spaceflight can affect the expression of cell surface markers. Cell surface markers play an important role in the ability of cells to interact and to pass signals between different cells of the same phenotype and cells of different phenotypes. Recent evidence suggests that cell-cycle regulators are essential for T-cell function. To trigger an effective immune response, lymphocytes must proliferate. The objective of this project is to investigate the changes in growth of human cells cultured in rotating bioreactors and to measure the growth rate and the cell cycle distribution for different human cell types. Human lymphocytes and lymphoblasts will be cultured in a bioreactor to simulate aspects of microgravity. The bioreactor is a cylindrical culture vessel that incorporates the aspects of clinostatic rotation of a solid fluid body around a horizontal axis at a constant speed, and compensates gravity by rotation and places cells within the fluid body into a sustained free-fall. Cell cycle progression and cell proliferation of the lymphocytes will be measured for a number of days. In addition, RNA from the cells will be isolated for expression of genes related in cell cycle regulations.

  4. Cell cycle nucleic acids, polypeptides and uses thereof

    DOEpatents

    Gordon-Kamm, William J.; Lowe, Keith S.; Larkins, Brian A.; Dilkes, Brian R.; Sun, Yuejin

    2007-08-14

    The invention provides isolated nucleic acids 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, cell cycle progression, cell number and/or composition of plants.

  5. Westinghouse fuel cell combined cycle systems

    SciTech Connect

    Veyo, S.

    1996-12-31

    Efficiency (voltage) of the solid oxide fuel cell (SOFC) should increase with operating pressure, and a pressurized SOFC could function as the heat addition process in a Brayton cycle gas turbine (GT) engine. An overall cycle efficiency of 70% should be possible. In cogeneration, half of the waste heat from a PSOFC/GT should be able to be captured in process steam and hot water, leading to a fuel effectiveness of about 85%. In order to make the PSOFC/GT a commercial reality, satisfactory operation of the SOFC at elevated pressure must be verified, a pressurized SOFC generator module must be designed, built, and tested, and the combined cycle and parameters must be optimized. A prototype must also be demonstrated. This paper describes progress toward making the PSOFC/GT a reality.

  6. Cell shape dynamics during the staphylococcal cell cycle

    PubMed Central

    Monteiro, João M.; Fernandes, Pedro B.; Vaz, Filipa; Pereira, Ana R.; Tavares, Andreia C.; Ferreira, Maria T.; Pereira, Pedro M.; Veiga, Helena; Kuru, Erkin; VanNieuwenhze, Michael S.; Brun, Yves V.; Filipe, Sérgio R.; Pinho, Mariana G.

    2015-01-01

    Staphylococcus aureus is an aggressive pathogen and a model organism to study cell division in sequential orthogonal planes in spherical bacteria. However, the small size of staphylococcal cells has impaired analysis of changes in morphology during the cell cycle. Here we use super-resolution microscopy and determine that S. aureus cells are not spherical throughout the cell cycle, but elongate during specific time windows, through peptidoglycan synthesis and remodelling. Both peptidoglycan hydrolysis and turgor pressure are required during division for reshaping the flat division septum into a curved surface. In this process, the septum generates less than one hemisphere of each daughter cell, a trait we show is common to other cocci. Therefore, cell surface scars of previous divisions do not divide the cells in quadrants, generating asymmetry in the daughter cells. Our results introduce a need to reassess the models for division plane selection in cocci. PMID:26278781

  7. Cell cycle regulation of hematopoietic stem or progenitor cells.

    PubMed

    Hao, Sha; Chen, Chen; Cheng, Tao

    2016-05-01

    The highly regulated process of blood production is achieved through the hierarchical organization of hematopoietic stem cell (HSC) subsets and their progenies, which differ in self-renewal and differentiation potential. Genetic studies in mice have demonstrated that cell cycle is tightly controlled by the complex interplay between extrinsic cues and intrinsic regulatory pathways involved in HSC self-renewal and differentiation. Deregulation of these cellular programs may transform HSCs or hematopoietic progenitor cells (HPCs) into disease-initiating stem cells, and can result in hematopoietic malignancies such as leukemia. While previous studies have shown roles for some cell cycle regulators and related signaling pathways in HSCs and HPCs, a more complete picture regarding the molecular mechanisms underlying cell cycle regulation in HSCs or HPCs is lacking. Based on accumulated studies in this field, the present review introduces the basic components of the cell cycle machinery and discusses their major cellular networks that regulate the dormancy and cell cycle progression of HSCs. Knowledge on this topic would help researchers and clinicians to better understand the pathogenesis of relevant blood disorders and to develop new strategies for therapeutic manipulation of HSCs.

  8. 4D chromatin dynamics in cycling cells

    PubMed Central

    Strickfaden, Hilmar; Zunhammer, Andreas; van Koningsbruggen, Silvana; Köhler, Daniela

    2010-01-01

    This live cell study of chromatin dynamics in four dimensions (space and time) in cycling human cells provides direct evidence for three hypotheses first proposed by Theodor Boveri in seminal studies of fixed blastomeres from Parascaris equorum embryos: (I) Chromosome territory (CT) arrangements are stably maintained during interphase. (II) Chromosome proximity patterns change profoundly during prometaphase. (III) Similar CT proximity patterns in pairs of daughter nuclei reflect symmetrical chromosomal movements during anaphase and telophase, but differ substantially from the arrangement in mother cell nucleus. Hypothesis I could be confirmed for the majority of interphase cells. A minority, however, showed complex, rotational movements of CT assemblies with large-scale changes of CT proximity patterns, while radial nuclear arrangements were maintained. A new model of chromatin dynamics is proposed. It suggests that long-range DNA-DNA interactions in cell nuclei may depend on a combination of rotational CT movements and locally constrained chromatin movements. PMID:21327076

  9. Molecular regulation of the diatom cell cycle.

    PubMed

    Huysman, Marie J J; Vyverman, Wim; De Veylder, Lieven

    2014-06-01

    Accounting for almost one-fifth of the primary production on Earth, the unicellular eukaryotic group of diatoms plays a key ecological and biogeochemical role in our contemporary oceans. Furthermore, as producers of various lipids and pigments, and characterized by their finely ornamented silica cell wall, diatoms hold great promise for different industrial fields, including biofuel production, nanotechnology, and pharmaceutics. However, in spite of their major ecological importance and their high commercial value, little is known about the mechanisms that control the diatom life and cell cycle. To date, both microscopic and genomic analyses have revealed that diatoms exhibit specific and unique mechanisms of cell division compared with those found in the classical model organisms. Here, we review the structural peculiarities of diatom cell proliferation, highlight the regulation of their major cell cycle checkpoints by environmental factors, and discuss recent progress in molecular cell division research. © 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.

  10. A thermodynamic cycle for the solar cell

    NASA Astrophysics Data System (ADS)

    Alicki, Robert; Gelbwaser-Klimovsky, David; Jenkins, Alejandro

    2017-03-01

    A solar cell is a heat engine, but textbook treatments are not wholly satisfactory from a thermodynamic standpoint, since they present solar cells as directly converting the energy of light into electricity, and the current in the circuit as maintained by an electrostatic potential. We propose a thermodynamic cycle in which the gas of electrons in the p phase serves as the working substance. The interface between the p and n phases acts as a self-oscillating piston that modulates the absorption of heat from the photons so that it may perform a net positive work during a complete cycle of its motion, in accordance with the laws of thermodynamics. We draw a simple hydrodynamical analogy between this model and the ;putt-putt; engine of toy boats, in which the interface between the water's liquid and gas phases serves as the piston. We point out some testable consequences of this model.

  11. A metabolic thermodynamic theory of cell cycle

    NASA Astrophysics Data System (ADS)

    Kummer, A.; Ocone, R.

    2003-08-01

    Due to its intrinsic complexity, a complete mathematical description of the cell cycle appears a difficult task. Nevertheless, a preliminary analysis, based on molecular biology, can help in clarifying what are the reliable tools for a quantitative approach. In a previous paper [Physica A 321 (3-4) (2003) 587], the steps to be followed to formulate a metabolic statistical thermodynamics have been established. Here we present a simple mathematical model for the interaction of CyclinB and Cdh1 [The Cell Cycle. An Introduction, Oxford University Press, New York, 1993], with the aim of analysing the properties of the system from a thermodynamic viewpoint. The model is shown to define the Gibbs phase integral of the system and the general Gibbs energy function is obtained. This, together with the analogue of the temperature, defines the working tools indispensable for the formulation of a metabolic statistical thermodynamic-like theory.

  12. Cell cycle regulation in human embryonic stem cells: links to adaptation to cell culture.

    PubMed

    Barta, Tomas; Dolezalova, Dasa; Holubcova, Zuzana; Hampl, Ales

    2013-03-01

    Cell cycle represents not only a tightly orchestrated mechanism of cell replication and cell division but it also plays an important role in regulation of cell fate decision. Particularly in the context of pluripotent stem cells or multipotent progenitor cells, regulation of cell fate decision is of paramount importance. It has been shown that human embryonic stem cells (hESCs) show unique cell cycle characteristics, such as short doubling time due to abbreviated G1 phase; these properties change with the onset of differentiation. This review summarizes the current understanding of cell cycle regulation in hESCs. We discuss cell cycle properties as well as regulatory machinery governing cell cycle progression of undifferentiated hESCs. Additionally, we provide evidence that long-term culture of hESCs is accompanied by changes in cell cycle properties as well as configuration of several cell cycle regulatory molecules.

  13. Targeting cell cycle regulators in hematologic malignancies

    PubMed Central

    Aleem, Eiman; Arceci, Robert J.

    2015-01-01

    Hematologic malignancies represent the fourth most frequently diagnosed cancer in economically developed countries. In hematologic malignancies normal hematopoiesis is interrupted by uncontrolled growth of a genetically altered stem or progenitor cell (HSPC) that maintains its ability of self-renewal. Cyclin-dependent kinases (CDKs) not only regulate the mammalian cell cycle, but also influence other vital cellular processes, such as stem cell renewal, differentiation, transcription, epigenetic regulation, apoptosis, and DNA repair. Chromosomal translocations, amplification, overexpression and altered CDK activities have been described in different types of human cancer, which have made them attractive targets for pharmacological inhibition. Mouse models deficient for one or more CDKs have significantly contributed to our current understanding of the physiological functions of CDKs, as well as their roles in human cancer. The present review focuses on selected cell cycle kinases with recent emerging key functions in hematopoiesis and in hematopoietic malignancies, such as CDK6 and its role in MLL-rearranged leukemia and acute lymphocytic leukemia, CDK1 and its regulator WEE-1 in acute myeloid leukemia (AML), and cyclin C/CDK8/CDK19 complexes in T-cell acute lymphocytic leukemia. The knowledge gained from gene knockout experiments in mice of these kinases is also summarized. An overview of compounds targeting these kinases, which are currently in clinical development in various solid tumors and hematopoietic malignances, is presented. These include the CDK4/CDK6 inhibitors (palbociclib, LEE011, LY2835219), pan-CDK inhibitors that target CDK1 (dinaciclib, flavopiridol, AT7519, TG02, P276-00, terampeprocol and RGB 286638) as well as the WEE-1 kinase inhibitor, MK-1775. The advantage of combination therapy of cell cycle inhibitors with conventional chemotherapeutic agents used in the treatment of AML, such as cytarabine, is discussed. PMID:25914884

  14. Targeting cell cycle regulators in hematologic malignancies.

    PubMed

    Aleem, Eiman; Arceci, Robert J

    2015-01-01

    Hematologic malignancies represent the fourth most frequently diagnosed cancer in economically developed countries. In hematologic malignancies normal hematopoiesis is interrupted by uncontrolled growth of a genetically altered stem or progenitor cell (HSPC) that maintains its ability of self-renewal. Cyclin-dependent kinases (CDKs) not only regulate the mammalian cell cycle, but also influence other vital cellular processes, such as stem cell renewal, differentiation, transcription, epigenetic regulation, apoptosis, and DNA repair. Chromosomal translocations, amplification, overexpression and altered CDK activities have been described in different types of human cancer, which have made them attractive targets for pharmacological inhibition. Mouse models deficient for one or more CDKs have significantly contributed to our current understanding of the physiological functions of CDKs, as well as their roles in human cancer. The present review focuses on selected cell cycle kinases with recent emerging key functions in hematopoiesis and in hematopoietic malignancies, such as CDK6 and its role in MLL-rearranged leukemia and acute lymphocytic leukemia, CDK1 and its regulator WEE-1 in acute myeloid leukemia (AML), and cyclin C/CDK8/CDK19 complexes in T-cell acute lymphocytic leukemia. The knowledge gained from gene knockout experiments in mice of these kinases is also summarized. An overview of compounds targeting these kinases, which are currently in clinical development in various solid tumors and hematopoietic malignances, is presented. These include the CDK4/CDK6 inhibitors (palbociclib, LEE011, LY2835219), pan-CDK inhibitors that target CDK1 (dinaciclib, flavopiridol, AT7519, TG02, P276-00, terampeprocol and RGB 286638) as well as the WEE-1 kinase inhibitor, MK-1775. The advantage of combination therapy of cell cycle inhibitors with conventional chemotherapeutic agents used in the treatment of AML, such as cytarabine, is discussed.

  15. The cell cycle as a brake for β-cell regeneration from embryonic stem cells.

    PubMed

    El-Badawy, Ahmed; El-Badri, Nagwa

    2016-01-13

    The generation of insulin-producing β cells from stem cells in vitro provides a promising source of cells for cell transplantation therapy in diabetes. However, insulin-producing cells generated from human stem cells show deficiency in many functional characteristics compared with pancreatic β cells. Recent reports have shown molecular ties between the cell cycle and the differentiation mechanism of embryonic stem (ES) cells, assuming that cell fate decisions are controlled by the cell cycle machinery. Both β cells and ES cells possess unique cell cycle machinery yet with significant contrasts. In this review, we compare the cell cycle control mechanisms in both ES cells and β cells, and highlight the fundamental differences between pluripotent cells of embryonic origin and differentiated β cells. Through critical analysis of the differences of the cell cycle between these two cell types, we propose that the cell cycle of ES cells may act as a brake for β-cell regeneration. Based on these differences, we discuss the potential of modulating the cell cycle of ES cells for the large-scale generation of functionally mature β cells in vitro. Further understanding of the factors that modulate the ES cell cycle will lead to new approaches to enhance the production of functional mature insulin-producing cells, and yield a reliable system to generate bona fide β cells in vitro.

  16. Ionizing radiation damage to cells: effects of cell cycle redistribution.

    PubMed

    Chen, P L; Brenner, D J; Sachs, R K

    1995-04-01

    If a population of cycling cells is exposed to a fixed dose of ionizing radiation delivered over time T, it is sometimes observed that increasing T increases the amount of cell killing. This is essentially because at first the radiation preferentially kills cells in a sensitive portion of the cycle and the surviving, more resistant cells then have time to reach more sensitive stages. We refer to this effect as population resensitization, caused by redistribution within the cell cycle. We investigate the effect theoretically by employing the McKendrick-von Foerster equation for age-structured proliferating cell populations, generalized by introducing a radiation damage term. Within our formalism, we show that population resensitization occurs whenever: (a) prior to irradiation the cell population has the stable age-distribution approached asymptotically by an unirradiated population, and (b) T is sufficiently small. Examples and other cases are outlined. The methods of Volterra integral equations, renewal theory, and positive semigroup theory are applied. The effect of varying T is evaluated by considering the ultimate amplitude of the stable age-distribution population at times much greater than both the irradiation duration and the average cell-cycle time. The main biological limitations of the formalism are the following: considering only radiation damage which is not subject to enzymatic repair or quadratic misrepair, using an overly naive method of ensuring loss of cell cycle synchrony, neglecting nonlinear effects such as density inhibition of growth, and neglecting radiatively induced perturbations of the cell cycle. Possible methods for removing these limitations are briefly discussed.

  17. Reprogramming the Cell Cycle for Endoreduplication in Rodent Trophoblast Cells

    PubMed Central

    MacAuley, Alasdair; Cross, James C.; Werb, Zena

    1998-01-01

    Differentiation of trophoblast giant cells in the rodent placenta is accompanied by exit from the mitotic cell cycle and onset of endoreduplication. Commitment to giant cell differentiation is under developmental control, involving down-regulation of Id1 and Id2, concomitant with up-regulation of the basic helix-loop-helix factor Hxt and acquisition of increased adhesiveness. Endoreduplication disrupts the alternation of DNA synthesis and mitosis that maintains euploid DNA content during proliferation. To determine how the mammalian endocycle is regulated, we examined the expression of the cyclins and cyclin-dependent kinases during the transition from replication to endoreduplication in the Rcho-1 rat choriocarcinoma cell line. We cultured these cells under conditions that gave relatively synchronous endoreduplication. This allowed us to study the events that occur during the transition from the mitotic cycle to the first endocycle. With giant cell differentiation, the cells switched cyclin D isoform expression from D3 to D1 and altered several checkpoint functions, acquiring a relative insensitivity to DNA-damaging agents and a coincident serum independence. The initiation of S phase during endocycles appeared to involve cycles of synthesis of cyclins E and A, and termination of S was associated with abrupt loss of cyclin A and E. Both cyclins were absent from gap phase cells, suggesting that their degradation may be necessary to allow reinitiation of the endocycle. The arrest of the mitotic cycle at the onset of endoreduplication was associated with a failure to assemble cyclin B/p34cdk1 complexes during the first endocycle. In subsequent endocycles, cyclin B expression was suppressed. Together these data suggest several points at which cell cycle regulation could be targeted to shift cells from a mitotic to an endoreduplicative cycle. PMID:9529378

  18. Cell cycle regulation of Golgi membrane dynamics

    PubMed Central

    Tang, Danming; Wang, Yanzhuang

    2013-01-01

    The Golgi apparatus is a membranous organelle in the cell that plays essential roles in protein and lipid trafficking, sorting, processing and modification. Its basic structure is a stack of closely aligned flattened cisternae. In mammalian cells, dozens of Golgi stacks are often laterally linked into a ribbon-like structure. Biogenesis of the Golgi during cell division occurs through a sophisticated disassembly and reassembly process that can be divided into three distinct but cooperative steps, including the deformation and reformation of the Golgi cisternae, stacks and ribbon. Here, we review our current understanding of the protein machineries that control these three steps in the cycle of mammalian cell division: GRASP65 and GRASP55 in Golgi stack and ribbon formation; ubiquitin and AAA ATPases in post-mitotic Golgi membrane fusion; and golgins and cytoskeleton in Golgi ribbon formation. PMID:23453991

  19. Fuel cell and advanced turbine power cycle

    SciTech Connect

    White, D.J.

    1996-12-31

    Solar has a vested interest in integration of gas turbines and high temperature fuels (particularly solid oxide fuel cells[SOFC]); this would be a backup for achieving efficiencies on the order of 60% with low exhaust emissions. Preferred cycle is with the fuel cell as a topping system to the gas turbine; bottoming arrangements (fuel cells using the gas turbine exhaust as air supply) would likely be both larger and less efficient unless complex steam bottoming systems are added. The combined SOFC and gas turbine will have an advantage because it will have lower NOx emissions than any heat engine system. Market niche for initial product entry will be the dispersed or distributed power market in nonattainment areas. First entry will be of 1-2 MW units between the years 2000 and 2004. Development requirements are outlined for both the fuel cell and the gas turbine.

  20. Mir-33 regulates cell proliferation and cell cycle progression

    PubMed Central

    Allen, Ryan M; Salerno, Alessandro G; Ramírez, Cristina M; Chamorro-Jorganes, Aránzazu; Wanschel, Amarylis C; Lasunción, Miguel A; Morales-Ruiz, Manuel; Suárez, Yajaira; Baldán, Ángel; Esplugues, Enric

    2012-01-01

    Cholesterol metabolism is tightly regulated at the cellular level and is essential for cellular growth. MicroRNAs (miRNAs), a class of noncoding RNAs, have emerged as critical regulators of gene expression, acting predominantly at the posttranscriptional level. Recent work from our group and others has shown that hsa-miR-33a and hsa-miR-33b, miRNAs located within intronic sequences of the Srebp genes, regulate cholesterol and fatty acid metabolism in concert with their host genes. Here, we show that hsa-miR-33 family members modulate the expression of genes involved in cell cycle regulation and cell proliferation. MiR-33 inhibits the expression of the cyclin-dependent kinase 6 (CDK6) and cyclin D1 (CCND1), thereby reducing cell proliferation and cell cycle progression. Overexpression of miR-33 induces a significant G1 cell cycle arrest in Huh7 and A549 cell lines. Most importantly, inhibition of miR-33 expression using 2′fluoro/methoxyethyl-modified (2′F/MOE-modified) phosphorothioate backbone antisense oligonucleotides improves liver regeneration after partial hepatectomy (PH) in mice, suggesting an important role for miR-33 in regulating hepatocyte proliferation during liver regeneration. Altogether, these results suggest that Srebp/miR-33 locus may cooperate to regulate cell proliferation and cell cycle progression and may also be relevant to human liver regeneration. PMID:22333591

  1. Mir-33 regulates cell proliferation and cell cycle progression.

    PubMed

    Cirera-Salinas, Daniel; Pauta, Montse; Allen, Ryan M; Salerno, Alessandro G; Ramírez, Cristina M; Chamorro-Jorganes, Aranzazu; Wanschel, Amarylis C; Lasuncion, Miguel A; Morales-Ruiz, Manuel; Suarez, Yajaira; Baldan, Ángel; Esplugues, Enric; Fernández-Hernando, Carlos

    2012-03-01

    Cholesterol metabolism is tightly regulated at the cellular level and is essential for cellular growth. microRNAs (miRNAs), a class of noncoding RNAs, have emerged as critical regulators of gene expression, acting predominantly at posttranscriptional level. Recent work from our group and others has shown that hsa-miR-33a and hsa-miR-33b, miRNAs located within intronic sequences of the Srebp genes, regulate cholesterol and fatty acid metabolism in concert with their host genes. Here, we show that hsa-miR-33 family members modulate the expression of genes involved in cell cycle regulation and cell proliferation. MiR-33 inhibits the expression of the cyclin-dependent kinase 6 (CDK6) and cyclin D1 (CCND1), thereby reducing cell proliferation and cell cycle progression. Overexpression of miR-33 induces a significant G 1 cell cycle arrest in Huh7 and A549 cell lines. Most importantly, inhibition of miR-33 expression using 2'fluoro/methoxyethyl-modified (2'F/MOE-modified) phosphorothioate backbone antisense oligonucleotides improves liver regeneration after partial hepatectomy (PH) in mice, suggesting an important role for miR-33 in regulating hepatocyte proliferation during liver regeneration. Altogether, these results suggest that Srebp/miR-33 locus may cooperate to regulate cell proliferation, cell cycle progression and may also be relevant to human liver regeneration.

  2. Proliferation and cell cycle dynamics in the developing stellate ganglion.

    PubMed

    Gonsalvez, David G; Cane, Kylie N; Landman, Kerry A; Enomoto, Hideki; Young, Heather M; Anderson, Colin R

    2013-04-03

    Cell proliferation during nervous system development is poorly understood outside the mouse neocortex. We measured cell cycle dynamics in the embryonic mouse sympathetic stellate ganglion, where neuroblasts continue to proliferate following neuronal differentiation. At embryonic day (E) 9.5, when neural crest-derived cells were migrating and coalescing into the ganglion primordium, all cells were cycling, cell cycle length was only 10.6 h, and S-phase comprised over 65% of the cell cycle; these values are similar to those previously reported for embryonic stem cells. At E10.5, Sox10(+) cells lengthened their cell cycle to 38 h and reduced the length of S-phase. As cells started to express the neuronal markers Tuj1 and tyrosine hydroxylase (TH) at E10.5, they exited the cell cycle. At E11.5, when >80% of cells in the ganglion were Tuj1(+)/TH(+) neuroblasts, all cells were again cycling. Neuroblast cell cycle length did not change significantly after E11.5, and 98% of Sox10(-)/TH(+) cells had exited the cell cycle by E18.5. The cell cycle length of Sox10(+)/TH(-) cells increased during late embryonic development, and ∼25% were still cycling at E18.5. Loss of Ret increased neuroblast cell cycle length at E16.5 and decreased the number of neuroblasts at E18.5. A mathematical model generated from our data successfully predicted the relative change in proportions of neuroblasts and non-neuroblasts in wild-type mice. Our results show that, like other neurons, sympathetic neuron differentiation is associated with exit from the cell cycle; sympathetic neurons are unusual in that they then re-enter the cell cycle before later permanently exiting.

  3. Cell cycle of globose basal cells in rat olfactory epithelium.

    PubMed

    Huard, J M; Schwob, J E

    1995-05-01

    The olfactory epithelium of adult mammals has the unique property of generating olfactory sensory neurons throughout life. Cells of the basal compartment, which include horizontal and globose basal cells, are responsible for the ongoing process of neurogenesis in this system. We report here that the globose basal cells in olfactory epithelium of rats, as in mice, are the predominant type of proliferating cell, and account for 97.6% of the actively dividing cells in the basal compartment of the normal epithelium. Globose basal cells have not been fully characterized in terms of their proliferative properties, and the dynamic aspects of neurogenesis are not well understood. As a consequence, it is uncertain whether cell kinetic properties are under any regulation that could affect the rate of neurogenesis. To address this gap in our knowledge, we have determined the duration of both the synthesis phase (S-phase) and the full cell cycle of globose basal cells in adult rats. The duration of the S-phase was found to be 9 hr in experiments utilizing sequential injections of either IdU followed by BrdU or 3H-thy followed by BrdU. The duration of the cell cycle was determined by varying the time interval between the injections of 3H-thy and BrdU and tracking the set of cells that exit S shortly after the first injection. With this paradigm, the interval required for these cells to traverse G2, M, G1, and a second S-phase, is equivalent to the duration of one mitotic cycle and equals 17 hr. These observations serve as the foundation to assess whether the cell cycle duration is subject to regulation in response to experimental injury, and whether such regulation is partly responsible for changes in the rate of neurogenesis in such settings.

  4. Mitochondrial Regulation of Cell Cycle and Proliferation

    PubMed Central

    Antico Arciuch, Valeria Gabriela; Elguero, María Eugenia; Poderoso, Juan José

    2012-01-01

    Abstract Eukaryotic mitochondria resulted from symbiotic incorporation of α-proteobacteria into ancient archaea species. During evolution, mitochondria lost most of the prokaryotic bacterial genes and only conserved a small fraction including those encoding 13 proteins of the respiratory chain. In this process, many functions were transferred to the host cells, but mitochondria gained a central role in the regulation of cell proliferation and apoptosis, and in the modulation of metabolism; accordingly, defective organelles contribute to cell transformation and cancer, diabetes, and neurodegenerative diseases. Most cell and transcriptional effects of mitochondria depend on the modulation of respiratory rate and on the production of hydrogen peroxide released into the cytosol. The mitochondrial oxidative rate has to remain depressed for cell proliferation; even in the presence of O2, energy is preferentially obtained from increased glycolysis (Warburg effect). In response to stress signals, traffic of pro- and antiapoptotic mitochondrial proteins in the intermembrane space (B-cell lymphoma-extra large, Bcl-2-associated death promoter, Bcl-2 associated X-protein and cytochrome c) is modulated by the redox condition determined by mitochondrial O2 utilization and mitochondrial nitric oxide metabolism. In this article, we highlight the traffic of the different canonical signaling pathways to mitochondria and the contributions of organelles to redox regulation of kinases. Finally, we analyze the dynamics of the mitochondrial population in cell cycle and apoptosis. Antioxid. Redox Signal. 16, 1150–1180. PMID:21967640

  5. [Cell cycle, mitosis and therapeutic applications].

    PubMed

    Levy, Antonin; Albiges-Sauvin, Laurence; Massard, Christophe; Soria, Jean-Charles; Deutsch, Eric

    2011-10-01

    Genomic DNA is constantly under stress of endogenous and exogenous DNA damaging agents. Without proper care, the DNA damage causes an alteration of the genomic structure and can lead to cell death or the occurrence of mutations involved in tumorigenesis. During the process of evolution, organisms have acquired a series of response mechanisms and repair of DNA damage, thereby ensuring the maintenance of genome stability and faithful transmission of genetic information. The checkpoints are the major mechanisms by which a cell can respond to DNA damage, either by actively stopping the cell cycle or by induction of apoptosis. Two parallel signalling pathways, ATM and ATR respond to genotoxic stress by activating their downstream target proteins including the two effectors kinases CHK1 and CHK2. Promising preliminary data render these proteins potential targets for therapeutic development against cancer.

  6. The cell cycle rallies the transcription cycle: Cdc28/Cdk1 is a cell cycle-regulated transcriptional CDK.

    PubMed

    Chymkowitch, Pierre; Enserink, Jorrit M

    2013-01-01

    In the budding yeast Saccharomyces cerevisiae, the cyclin-dependent kinases (CDKs) Kin28, Bur1 and Ctk1 regulate basal transcription by phosphorylating the carboxyl-terminal domain (CTD) of RNA polymerase II. However, very little is known about the involvement of the cell cycle CDK Cdc28 in the transcription process. We have recently shown that, upon cell cycle entry, Cdc28 kinase activity boosts transcription of a subset of genes by directly stimulating the basal transcription machinery. Here, we discuss the biological significance of this finding and give our view of the kinase-dependent role of Cdc28 in regulation of RNA polymerase II.

  7. T Cell Receptor-induced Activation and Apoptosis In Cycling Human T Cells Occur throughout the Cell Cycle

    PubMed Central

    Karas, Michael; Zaks, Tal Z.; JL, Liu; LeRoith, Derek

    1999-01-01

    Previous studies have found conflicting associations between susceptibility to activation-induced cell death and the cell cycle in T cells. However, most of the studies used potentially toxic pharmacological agents for cell cycle synchronization. A panel of human melanoma tumor-reactive T cell lines, a CD8+ HER-2/neu-reactive T cell clone, and the leukemic T cell line Jurkat were separated by centrifugal elutriation. Fractions enriched for the G0–G1, S, and G2–M phases of the cell cycle were assayed for T cell receptor-mediated activation as measured by intracellular Ca2+ flux, cytolytic recognition of tumor targets, and induction of Fas ligand mRNA. Susceptibility to apoptosis induced by recombinant Fas ligand and activation-induced cell death were also studied. None of the parameters studied was specific to a certain phase of the cell cycle, leading us to conclude that in nontransformed human T cells, both activation and apoptosis through T cell receptor activation can occur in all phases of the cell cycle. PMID:10588669

  8. Fungal Cell Cycle: A Unicellular versus Multicellular Comparison.

    PubMed

    Dörter, Ilkay; Momany, Michelle

    2016-12-01

    All cells must accurately replicate DNA and partition it to daughter cells. The basic cell cycle machinery is highly conserved among eukaryotes. Most of the mechanisms that control the cell cycle were worked out in fungal cells, taking advantage of their powerful genetics and rapid duplication times. Here we describe the cell cycles of the unicellular budding yeast Saccharomyces cerevisiae and the multicellular filamentous fungus Aspergillus nidulans. We compare and contrast morphological landmarks of G1, S, G2, and M phases, molecular mechanisms that drive cell cycle progression, and checkpoints in these model unicellular and multicellular fungal systems.

  9. The cell-cycle state of stem cells determines cell fate propensity.

    PubMed

    Pauklin, Siim; Vallier, Ludovic

    2013-09-26

    Self-renewal and differentiation of stem cells are fundamentally associated with cell-cycle progression to enable tissue specification, organ homeostasis, and potentially tumorigenesis. However, technical challenges have impaired the study of the molecular interactions coordinating cell fate choice and cell-cycle progression. Here, we bypass these limitations by using the FUCCI reporter system in human pluripotent stem cells and show that their capacity of differentiation varies during the progression of their cell cycle. These mechanisms are governed by the cell-cycle regulators cyclin D1-3 that control differentiation signals such as the TGF-β-Smad2/3 pathway. Conversely, cell-cycle manipulation using a small molecule directs differentiation of hPSCs and provides an approach to generate cell types with a clinical interest. Our results demonstrate that cell fate decisions are tightly associated with the cell-cycle machinery and reveal insights in the mechanisms synchronizing differentiation and proliferation in developing tissues.

  10. Cell Cycle Regulators during Human Atrial Development

    PubMed Central

    Kim, Won Ho; Joo, Chan Uhng; Ku, Ja Hong; Ryu, Chul Hee; Koh, Keum Nim; Koh, Gou Young; Ko, Jae Ki

    1998-01-01

    Objectives The molecular mechanisms that regulate cardiomyocyte cell cycle and terminal differentiation in humans remain largely unknown. To determine which cyclins, cyclin dependent kinases (CDKs) and cyclin kinase inhibitors (CKIs) are important for cardiomyocyte proliferation, we have examined protein levels of cyclins, CDKs and CKIs during normal atrial development in humans. Methods Atrial tissues were obtained in the fetus from inevitable abortion and in the adult during surgery, Cyclin and CDK proteins were determined by Western blot analysis, CDK activities were determined by phosphorylation amount using specific substrate. Results Most cyclins and CDKs were high during the fetal period and their levels decreased at different rates during the adult period. While the protein levels of cyclin D1, cyclin D3, CDK4, CDK6 and CDK2 were still detectable in adult atria, the protein levels of cyclin E, cyclin A, cyclin B, cdc2 and PCNA were not detectable. Interestingly, p27KIP 1 protein increased markedly in the adult period, while p21C IP 1 protein in atria was detectable only in the fetal period. While the activities of CDK6, CDK2 and cdc2 decreased markedly, the activity of CDK4 did not change from the fetal period to the adult period. Conclusion These findings indicate that marked reduction of protein levels and activities of cyclins and CDKs, and marked induction of p27KIP 1 in atria, are associated with the withdrawal of cardiac cell cycle in adult humans. PMID:9735660

  11. Alteration of cell cycle progression by Sindbis virus infection

    SciTech Connect

    Yi, Ruirong; Saito, Kengo; Isegawa, Naohisa; Shirasawa, Hiroshi

    2015-07-10

    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 Vero 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.

  12. Cell cycle regulation by long non-coding RNAs.

    PubMed

    Kitagawa, Masatoshi; Kitagawa, Kyoko; Kotake, Yojiro; Niida, Hiroyuki; Ohhata, Tatsuya

    2013-12-01

    The mammalian cell cycle is precisely controlled by cyclin-dependent kinases (CDKs) and related pathways such as the RB and p53 pathways. Recent research on long non-coding RNAs (lncRNAs) indicates that many lncRNAs are involved in the regulation of critical cell cycle regulators such as the cyclins, CDKs, CDK inhibitors, pRB, and p53. These lncRNAs act as epigenetic regulators, transcription factor regulators, post-transcription regulators, and protein scaffolds. These cell cycle-regulated lncRNAs mainly control cellular levels of cell cycle regulators via various mechanisms, and may provide diversity and reliability to the general cell cycle. Interestingly, several lncRNAs are induced by DNA damage and participate in cell cycle arrest or induction of apoptosis as DNA damage responses. Therefore, deregulations of these cell cycle regulatory lncRNAs may be involved in tumorigenesis, and they are novel candidate molecular targets for cancer therapy and diagnosis.

  13. Cell cycle proliferation decisions: the impact of single cell analyses.

    PubMed

    Matson, Jacob P; Cook, Jeanette G

    2017-02-01

    Cell proliferation is a fundamental requirement for organismal development and homeostasis. The mammalian cell division cycle is tightly controlled to ensure complete and precise genome duplication and segregation of replicated chromosomes to daughter cells. The onset of DNA replication marks an irreversible commitment to cell division, and the accumulated efforts of many decades of molecular and cellular studies have probed this cellular decision, commonly called the restriction point. Despite a long-standing conceptual framework of the restriction point for progression through G1 phase into S phase or exit from G1 phase to quiescence (G0), recent technical advances in quantitative single cell analysis of mammalian cells have provided new insights. Significant intercellular heterogeneity revealed by single cell studies and the discovery of discrete subpopulations in proliferating cultures suggests the need for an even more nuanced understanding of cell proliferation decisions. In this review, we describe some of the recent developments in the cell cycle field made possible by quantitative single cell experimental approaches. © 2016 Federation of European Biochemical Societies.

  14. Metabolism, cell growth and the bacterial cell cycle

    PubMed Central

    Wang, Jue D.; Levin, Petra A.

    2010-01-01

    Adaptation to fluctuations in nutrient availability is a fact of life for single-celled organisms in the ‘wild’. A decade ago our understanding of how bacteria adjust cell cycle parameters to accommodate changes in nutrient availability stemmed almost entirely from elegant physiological studies completed in the 1960s. In this Opinion article we summarize recent groundbreaking work in this area and discuss potential mechanisms by which nutrient availability and metabolic status are coordinated with cell growth, chromosome replication and cell division. PMID:19806155

  15. Capacity fade of Sony 18650 cells cycled at elevated temperatures. Part I. Cycling performance

    NASA Astrophysics Data System (ADS)

    Ramadass, P.; Haran, Bala; White, Ralph; Popov, Branko N.

    The capacity fade of Sony 18650 Li-ion cells increases with increase in temperature. After 800 cycles, the cells cycled at RT and 45 °C showed a capacity fade of 30 and 36%, respectively. The cell cycled at 55 °C showed a capacity loss of about 70% after 490 cycles. The rate capability of the cells continues to decrease with cycling. Impedance measurements showed an overall increase in the cell resistance with cycling and temperature. Impedance studies of the electrode materials showed an increased positive electrode resistance when compared to that of the negative electrode for cells cycled at RT and 45 °C. However, cells cycled at 50 and 55 °C exhibit higher negative electrode resistance. The increased capacity fade for the cells cycled at high temperatures can be explained by taking into account the repeated film formation over the surface of anode, which results in increased rate of lithium loss and also in a drastic increase in the negative electrode resistance with cycling.

  16. Cell cycle dysregulation in pituitary oncogenesis.

    PubMed

    Muşat, Madalina; Vax, Vladimir V; Borboli, Ninetta; Gueorguiev, Maria; Bonner, Sarah; Korbonits, Márta; Grossman, Ashley B

    2004-01-01

    The cell cycle is the process by which cells grow, replicate their genome and divide. The cell cycle control system is a cyclically-operating biochemical device constructed from a set of interacting proteins that induce and coordinate proper progression through the cycle, and includes cyclins, cyclin-dependent kinases (CDK) and their inhibitors (CDKI). There are mainly two families of CDKI, the INK family (INK4a/p16; INK4b/p15; INK4c/p18 and INK4d/p19) and the WAF/KIP family (WAF1/p21; KIP1/p27; KIP2/p57). Progression through the cell cycle is mainly dependent on fluctuations in the concentration of cyclins and CDKI achieved through the programmed degradation of these proteins by proteolysis within the ubiquitin-proteasome system. There is also a transcriptional regulation of cyclin expression, probably dependent on CDK phosphorylation. The p53 family--p53, p63 and p73--function as transcription factors that play a major role in regulating the response of mammalian cells to stressors and damage, in part through the transcriptional activation of genes involved in cell cycle control (e.g. p21), DNA repair, senescence, angiogenesis and apoptosis. Essential for the maintenance of euploidy during mitosis is human securin, identical to the product of the pituitary tumour-transforming gene (PTTG). Loss of regulation at the G1/S transition appears to be a common event among virtually all types of human tumours. Aberrations of one or more components of the pRb/p16/cyclin D1/CDK4 pathway seem to be a frequent event (80%) in pituitary tumours. The role of p27 is rather that of a haploinsufficient gene. p27-/- mice show an increased growth rate, due to increased cellularity, testicular and ovarian cell hyperplasia and infertility, and hyperplasia of the pituitary intermediate lobe with nearly 100% mortality caused by such a benign pituitary tumour. Although the p27 gene was not found to be mutated in human pituitary tumours and its mRNA expression was similar in tumour samples

  17. Analysis of Cell Cycle Switches in Drosophila Oogenesis.

    PubMed

    Jia, Dongyu; Huang, Yi-Chun; Deng, Wu-Min

    2015-01-01

    The study of Drosophila oogenesis provides invaluable information about signaling pathway regulation and cell cycle programming. During Drosophila oogenesis, a string of egg chambers in each ovariole progressively develops toward maturity. Egg chamber development consists of 14 stages. From stage 1 to stage 6 (mitotic cycle), main-body follicle cells undergo mitotic divisions. From stage 7 to stage 10a (endocycle), follicle cells cease mitosis but continue three rounds of endoreduplication. From stage 10b to stage 13 (gene amplification), instead of whole genome duplication, follicle cells selectively amplify specific genomic regions, mostly for chorion production. So far, Drosophila oogenesis is one of the most well studied model systems used to understand cell cycle switches, which furthers our knowledge about cell cycle control machinery and sheds new light on potential cancer treatments. Here, we give a brief summary of cell cycle switches, the associated signaling pathways and factors, and the detailed experimental procedures used to study the cell cycle switches.

  18. Investigational cell cycle inhibitors in clinical trials for bladder cancer.

    PubMed

    Yun, Seok Joong; Moon, Sung-Kwon; Kim, Wun-Jae

    2013-03-01

    Cancer-related cell cycle defects are often mediated by alterations in activity of diverse cell cycle regulators. The development of cell cycle inhibitors has undergone a gradual evolution, and new investigational drugs have been extensively tested as a single agent or combination with conventional chemotherapeutic drugs. This review covers a broad perspective of how the cell cycle is deregulated in bladder cancer and discusses the clinical trials of cell cycle inhibitors. Although diverse cell cycle inhibitors have been considered as relevant drug candidates for cancer therapy owing to their potential role in restoring control of the cell cycle, these inhibitors have not been yet widely tested in human bladder cancer. Numerous studies already reported that deregulation of cell cycle controls has been commonly observed in bladder cancer cells, thus warranting clinical trials of these inhibitors in advanced bladder cancer patients. In addition, nonmuscle invasive bladder cancer (NMIBC) and muscle invasive bladder cancer (MIBC) show different clinical and molecular biological characteristics, although ∼ 10 - 20% of NMIBC will progress to MIBC. Therefore, adequate cell cycle inhibitors have to be chosen for bladder cancer treatment based on the different genetic features between NMIBC and MIBC related to cell cycle regulators.

  19. Classic "broken cell" techniques and newer live cell methods for cell cycle assessment.

    PubMed

    Henderson, Lindsay; Bortone, Dante S; Lim, Curtis; Zambon, Alexander C

    2013-05-15

    Many common, important diseases are either caused or exacerbated by hyperactivation (e.g., cancer) or inactivation (e.g., heart failure) of the cell division cycle. A better understanding of the cell cycle is critical for interpreting numerous types of physiological changes in cells. Moreover, new insights into how to control it will facilitate new therapeutics for a variety of diseases and new avenues in regenerative medicine. The progression of cells through the four main phases of their division cycle [G(0)/G(1), S (DNA synthesis), G(2), and M (mitosis)] is a highly conserved process orchestrated by several pathways (e.g., transcription, phosphorylation, nuclear import/export, and protein ubiquitination) that coordinate a core cell cycle pathway. This core pathway can also receive inputs that are cell type and cell niche dependent. "Broken cell" methods (e.g., use of labeled nucleotide analogs) to assess for cell cycle activity have revealed important insights regarding the cell cycle but lack the ability to assess living cells in real time (longitudinal studies) and with single-cell resolution. Moreover, such methods often require cell synchronization, which can perturb the pathway under study. Live cell cycle sensors can be used at single-cell resolution in living cells, intact tissue, and whole animals. Use of these more recently available sensors has the potential to reveal physiologically relevant insights regarding the normal and perturbed cell division cycle.

  20. The Cell Cycle Switch Computes Approximate Majority

    NASA Astrophysics Data System (ADS)

    Cardelli, Luca; Csikász-Nagy, Attila

    2012-09-01

    Both computational and biological systems have to make decisions about switching from one state to another. The `Approximate Majority' computational algorithm provides the asymptotically fastest way to reach a common decision by all members of a population between two possible outcomes, where the decision approximately matches the initial relative majority. The network that regulates the mitotic entry of the cell-cycle in eukaryotes also makes a decision before it induces early mitotic processes. Here we show that the switch from inactive to active forms of the mitosis promoting Cyclin Dependent Kinases is driven by a system that is related to both the structure and the dynamics of the Approximate Majority computation. We investigate the behavior of these two switches by deterministic, stochastic and probabilistic methods and show that the steady states and temporal dynamics of the two systems are similar and they are exchangeable as components of oscillatory networks.

  1. Local circadian clock gates cell cycle progression of transient amplifying cells during regenerative hair cycling

    PubMed Central

    Plikus, Maksim V.; Vollmers, Christopher; de la Cruz, Damon; Chaix, Amandine; Ramos, Raul; Panda, Satchidananda; Chuong, Cheng-Ming

    2013-01-01

    Regenerative cycling of hair follicles offers an unique opportunity to explore the role of circadian clock in physiological tissue regeneration. We focused on the role of circadian clock in actively proliferating transient amplifying cells, as opposed to quiescent stem cells. We identified two key sites of peripheral circadian clock activity specific to regenerating anagen hair follicles, namely epithelial matrix and mesenchymal dermal papilla. We showed that peripheral circadian clock in epithelial matrix cells generates prominent daily mitotic rhythm. As a consequence of this mitotic rhythmicity, hairs grow faster in the morning than in the evening. Because cells are the most susceptible to DNA damage during mitosis, this cycle leads to a remarkable time-of-day–dependent sensitivity of growing hair follicles to genotoxic stress. Same doses of γ-radiation caused dramatic hair loss in wild-type mice when administered in the morning, during mitotic peak, compared with the evening, when hair loss is minimal. This diurnal radioprotective effect becomes lost in circadian mutants, consistent with asynchronous mitoses in their hair follicles. Clock coordinates cell cycle progression with genotoxic stress responses by synchronizing Cdc2/Cyclin B-mediated G2/M checkpoint. Our results uncover diurnal mitotic gating as the essential protective mechanism in highly proliferative hair follicles and offer strategies for minimizing or maximizing cytotoxicity of radiation therapies. PMID:23690597

  2. Cell Cycle and Cell Size Dependent Gene Expression Reveals Distinct Subpopulations at Single-Cell Level

    PubMed Central

    Dolatabadi, Soheila; Candia, Julián; Akrap, Nina; Vannas, Christoffer; Tesan Tomic, Tajana; Losert, Wolfgang; Landberg, Göran; Åman, Pierre; Ståhlberg, Anders

    2017-01-01

    Cell proliferation includes a series of events that is tightly regulated by several checkpoints and layers of control mechanisms. Most studies have been performed on large cell populations, but detailed understanding of cell dynamics and heterogeneity requires single-cell analysis. Here, we used quantitative real-time PCR, profiling the expression of 93 genes in single-cells from three different cell lines. Individual unsynchronized cells from three different cell lines were collected in different cell cycle phases (G0/G1 – S – G2/M) with variable cell sizes. We found that the total transcript level per cell and the expression of most individual genes correlated with progression through the cell cycle, but not with cell size. By applying the random forests algorithm, a supervised machine learning approach, we show how a multi-gene signature that classifies individual cells into their correct cell cycle phase and cell size can be generated. To identify the most predictive genes we used a variable selection strategy. Detailed analysis of cell cycle predictive genes allowed us to define subpopulations with distinct gene expression profiles and to calculate a cell cycle index that illustrates the transition of cells between cell cycle phases. In conclusion, we provide useful experimental approaches and bioinformatics to identify informative and predictive genes at the single-cell level, which opens up new means to describe and understand cell proliferation and subpopulation dynamics. PMID:28179914

  3. SUMOylation-mediated regulation of cell cycle progression and cancer

    PubMed Central

    Eifler, Karolin; Vertegaal, Alfred C.O.

    2016-01-01

    SUMOylation plays critical roles during cell cycle progression. Many important cell cycle regulators, including many oncogenes and tumor suppressors, are functionally regulated via SUMOylation. The dynamic SUMOylation pattern observed throughout the cell cycle is ensured via distinct spatial and temporal regulation of the SUMO machinery. Additionally, SUMOylation cooperates with other post-translational modifications to mediate cell cycle progression. Deregulation of these SUMOylation and deSUMOylation enzymes causes severe defects in cell proliferation and genome stability. Different types of cancers were recently shown to be dependent on a functioning SUMOylation system, a finding that could potentially be exploited in anti-cancer therapies. PMID:26601932

  4. Indirect-fired gas turbine dual fuel cell power cycle

    DOEpatents

    Micheli, Paul L.; Williams, Mark C.; Sudhoff, Frederick A.

    1996-01-01

    A fuel cell and gas turbine combined cycle system which includes dual fuel cell cycles combined with a gas turbine cycle wherein a solid oxide fuel cell cycle operated at a pressure of between 6 to 15 atms tops the turbine cycle and is used to produce CO.sub.2 for a molten carbonate fuel cell cycle which bottoms the turbine and is operated at essentially atmospheric pressure. A high pressure combustor is used to combust the excess fuel from the topping fuel cell cycle to further heat the pressurized gas driving the turbine. A low pressure combustor is used to combust the excess fuel from the bottoming fuel cell to reheat the gas stream passing out of the turbine which is used to preheat the pressurized air stream entering the topping fuel cell before passing into the bottoming fuel cell cathode. The CO.sub.2 generated in the solid oxide fuel cell cycle cascades through the system to the molten carbonate fuel cell cycle cathode.

  5. Dynamic translation regulation in Caulobacter cell cycle control.

    PubMed

    Schrader, Jared M; Li, Gene-Wei; Childers, W Seth; Perez, Adam M; Weissman, Jonathan S; Shapiro, Lucy; McAdams, Harley H

    2016-11-01

    Progression of the Caulobacter cell cycle requires temporal and spatial control of gene expression, culminating in an asymmetric cell division yielding distinct daughter cells. To explore the contribution of translational control, RNA-seq and ribosome profiling were used to assay global transcription and translation levels of individual genes at six times over the cell cycle. Translational efficiency (TE) was used as a metric for the relative rate of protein production from each mRNA. TE profiles with similar cell cycle patterns were found across multiple clusters of genes, including those in operons or in subsets of operons. Collections of genes associated with central cell cycle functional modules (e.g., biosynthesis of stalk, flagellum, or chemotaxis machinery) have consistent but different TE temporal patterns, independent of their operon organization. Differential translation of operon-encoded genes facilitates precise cell cycle-timing for the dynamic assembly of multiprotein complexes, such as the flagellum and the stalk and the correct positioning of regulatory proteins to specific cell poles. The cell cycle-regulatory pathways that produce specific temporal TE patterns are separate from-but highly coordinated with-the transcriptional cell cycle circuitry, suggesting that the scheduling of translational regulation is organized by the same cyclical regulatory circuit that directs the transcriptional control of the Caulobacter cell cycle.

  6. Glyphosate-based pesticides affect cell cycle regulation.

    PubMed

    Marc, Julie; Mulner-Lorillon, Odile; Bellé, Robert

    2004-04-01

    Cell-cycle dysregulation is a hallmark of tumor cells and human cancers. Failure in the cell-cycle checkpoints leads to genomic instability and subsequent development of cancers from the initial affected cell. A worldwide used product Roundup 3plus, based on glyphosate as the active herbicide, was suggested to be of human health concern since it induced cell cycle dysfunction as judged from analysis of the first cell division of sea urchin embryos, a recognized model for cell cycle studies. Several glyphosate-based pesticides from different manufacturers were assayed in comparison with Roundup 3plus for their ability to interfere with the cell cycle regulation. All the tested products, Amega, Cargly, Cosmic, and Roundup Biovert induced cell cycle dysfunction. The threshold concentration for induction of cell cycle dysfunction was evaluated for each product and suggests high risk by inhalation for people in the vicinity of the pesticide handling sprayed at 500 to 4000 times higher dose than the cell-cycle adverse concentration.

  7. Calcium, a Cell Cycle Commander, Drives Colon Cancer Cell Diffpoptosis.

    PubMed

    Abd-Rabou, Ahmed A

    2017-03-01

    The story of the cell commonder, calcium, reaches into all corners of the cell and controls cell proliferation, differentiation, function, and even death. The calcium-driven eukaryotic revolution is one of the great turning points in the life history, happened about two billion years later when it was converted from a dangerous killer that had to be kept out of cell into the cell master which drives the cell. This review article will take the readers to a tour of tissues chosen to best show the calcium's many faces (proliferator, differentiator, and killer). The reader will first see calcium and its many helpers, such as the calcium-binding signaler protein calmodulin, directing the key events of the cell cycle. Then the tour will move onto the colon to show calcium driving the proliferation of progenitor cells, then the differentiation and ultimately the programmed death of their progeny. Moreover, the reader will learn of the striking disabling and bypassing of calcium-dependent control mechanisms during carcinogenesis. Finally, recommendations should be taken from the underlying mechanisms through which calcium masters the presistance, progression, and even apoptosis of colorectal cancer cells. Thus, this could be of great interest for designing of chemoprevention protocols.

  8. Drug-induced cell cycle modulation leading to cell-cycle arrest, nuclear mis-segregation, or endoreplication

    PubMed Central

    2011-01-01

    Background Cancer cell responses to chemotherapeutic agents vary, and this may reflect different defects in DNA repair, cell-cycle checkpoints, and apoptosis control. Cytometry analysis only quantifies dye-incorporation to examine DNA content and does not reflect the biological complexity of the cell cycle in drug discovery screens. Results Using population and time-lapse imaging analyses of cultured immortalized cells expressing a new version of the fluorescent cell-cycle indicator, Fucci (Fluorescent Ubiquitination-based Cell Cycle Indicator), we found great diversity in the cell-cycle alterations induced by two anticancer drugs. When treated with etoposide, an inhibitor of DNA topoisomerase II, HeLa and NMuMG cells halted at the G2/M checkpoint. HeLa cells remained there, but NMuMG cells then overrode the checkpoint and underwent nuclear mis-segregation or avoided the checkpoint and entered the endoreplication cycle in a drug concentration dependent manner. In contrast, an inhibitor of Cdk4 led to G1 arrest or endoreplication in NMuMG cells depending upon the initial cell-cycle phase of drug exposure. Conclusions Drug-induced cell cycle modulation varied not only between different cell types or following treatment with different drugs, but also between cells treated with different concentrations of the same drug or following drug addition during different phases of the cell cycle. By combining cytometry analysis with the Fucci probe, we have developed a novel assay that fully integrates the complexity of cell cycle regulation into drug discovery screens. This assay system will represent a powerful drug-discovery tool for the development of the next generation of anti-cancer therapies. PMID:21226962

  9. Basal p21 controls population heterogeneity in cycling and quiescent cell cycle states

    PubMed Central

    Overton, K. Wesley; Spencer, Sabrina L.; Noderer, William L.; Meyer, Tobias; Wang, Clifford L.

    2014-01-01

    Phenotypic heterogeneity within a population of genetically identical cells is emerging as a common theme in multiple biological systems, including human cell biology and cancer. Using live-cell imaging, flow cytometry, and kinetic modeling, we showed that two states—quiescence and cell cycling—can coexist within an isogenic population of human cells and resulted from low basal expression levels of p21, a Cyclin-dependent kinase (CDK) inhibitor (CKI). We attribute the p21-dependent heterogeneity in cell cycle activity to double-negative feedback regulation involving CDK2, p21, and E3 ubiquitin ligases. In support of this mechanism, analysis of cells at a point before cell cycle entry (i.e., before the G1/S transition) revealed a p21–CDK2 axis that determines quiescent and cycling cell states. Our findings suggest a mechanistic role for p21 in generating heterogeneity in both normal tissues and tumors. PMID:25267623

  10. Calcium signaling and cell cycle: Progression or death.

    PubMed

    Humeau, Juliette; Bravo-San Pedro, José Manuel; Vitale, Ilio; Nuñez, Lucia; Villalobos, Carlos; Kroemer, Guido; Senovilla, Laura

    2017-07-25

    Cytosolic Ca(2+) concentration levels fluctuate in an ordered manner along the cell cycle, in line with the fact that Ca(2+) is involved in the regulation of cell proliferation. Cell proliferation should be an error-free process, yet is endangered by mistakes. In fact, a complex network of proteins ensures that cell cycle does not progress until the previous phase has been successfully completed. Occasionally, errors occur during the cell cycle leading to cell cycle arrest. If the error is severe, and the cell cycle checkpoints work perfectly, this results into cellular demise by activation of apoptotic or non-apoptotic cell death programs. Cancer is characterized by deregulated proliferation and resistance against cell death. Ca(2+) is a central key to these phenomena as it modulates signaling pathways that control oncogenesis and cancer progression. Here, we discuss how Ca(2+) participates in the exogenous and endogenous signals controlling cell proliferation, as well as in the mechanisms by which cells die if irreparable cell cycle damage occurs. Moreover, we summarize how Ca(2+) homeostasis remodeling observed in cancer cells contributes to deregulated cell proliferation and resistance to cell death. Finally, we discuss the possibility to target specific components of Ca(2+) signal pathways to obtain cytostatic or cytotoxic effects. Copyright © 2017 Elsevier Ltd. All rights reserved.

  11. Identification of cell cycle-regulated genes in fission yeast.

    PubMed

    Peng, Xu; Karuturi, R Krishna Murthy; Miller, Lance D; Lin, Kui; Jia, Yonghui; Kondu, Pinar; Wang, Long; Wong, Lim-Soon; Liu, Edison T; Balasubramanian, Mohan K; Liu, Jianhua

    2005-03-01

    Cell cycle progression is both regulated and accompanied by periodic changes in the expression levels of a large number of genes. To investigate cell cycle-regulated transcriptional programs in the fission yeast Schizosaccharomyces pombe, we developed a whole-genome oligonucleotide-based DNA microarray. Microarray analysis of both wild-type and cdc25 mutant cell cultures was performed to identify transcripts whose levels oscillated during the cell cycle. Using an unsupervised algorithm, we identified 747 genes that met the criteria for cell cycle-regulated expression. Peaks of gene expression were found to be distributed throughout the entire cell cycle. Furthermore, we found that four promoter motifs exhibited strong association with cell cycle phase-specific expression. Examination of the regulation of MCB motif-containing genes through the perturbation of DNA synthesis control/MCB-binding factor (DSC/MBF)-mediated transcription in arrested synchronous cdc10 mutant cell cultures revealed a subset of functional targets of the DSC/MBF transcription factor complex, as well as certain gene promoter requirements. Finally, we compared our data with those for the budding yeast Saccharomyces cerevisiae and found approximately 140 genes that are cell cycle regulated in both yeasts, suggesting that these genes may play an evolutionarily conserved role in regulation of cell cycle-specific processes. Our complete data sets are available at http://giscompute.gis.a-star.edu.sg/~gisljh/CDC.

  12. From the cell cycle to population cycles in phytoplankton-nutrient interactions

    SciTech Connect

    Pascual, M.; Caswell, H.

    1997-04-01

    The internal demographic structure of a population influences its dynamics and its response to the environment. Most models for phytoplankton ignore internal structure and group all cells in a single variable such as total biomass or density. However, a cell does have a life history, the cell division cycle. We investigate the significance of the cell cycle to phytoplankton population dynamics in a variable nutrient environment, using chemostate models. Following the transition point hypothesis, nutrient uptake affects cell development only within a limited segment of the cell cycle. Simulation results demonstrate oscillations in cell numbers and population structure generated by this interaction. When nutrient input is varied periodically, the population displays an aperiodic response with frequencies different from that of the forcing. These results also hold for a model that includes nutrient storage by the cells. These dynamics differ from those of traditional chemostate models and from cell cycle models driven by light cycles. Resource control of cell cycle progression may explain the time delays previously postulated to explain oscillatory transients in chemostate experiments. 78 refs., 22 figs.

  13. Flow cytometry analysis of cell cycle and specific cell synchronization with butyrate

    USDA-ARS?s Scientific Manuscript database

    Synchronized cells have been invaluable in many kinds of cell cycle and cell proliferation studies. Butyrate induces cell cycle arrest and apoptosis in MDBK cells. The possibility of using butyrate-blocked cells to obtain synchronized cells was explored and the properties of butyrate-induced cell ...

  14. Cell cycle regulation of central spindle assembly.

    PubMed

    Mishima, Masanori; Pavicic, Visnja; Grüneberg, Ulrike; Nigg, Erich A; Glotzer, Michael

    2004-08-19

    The bipolar mitotic spindle is responsible for segregating sister chromatids at anaphase. Microtubule motor proteins generate spindle bipolarity and enable the spindle to perform mechanical work. A major change in spindle architecture occurs at anaphase onset when central spindle assembly begins. This structure regulates the initiation of cytokinesis and is essential for its completion. Central spindle assembly requires the centralspindlin complex composed of the Caenorhabditis elegans ZEN-4 (mammalian orthologue MKLP1) kinesin-like protein and the Rho family GAP CYK-4 (MgcRacGAP). Here we describe a regulatory mechanism that controls the timing of central spindle assembly. The mitotic kinase Cdk1/cyclin B phosphorylates the motor domain of ZEN-4 on a conserved site within a basic amino-terminal extension characteristic of the MKLP1 subfamily. Phosphorylation by Cdk1 diminishes the motor activity of ZEN-4 by reducing its affinity for microtubules. Preventing Cdk1 phosphorylation of ZEN-4/MKLP1 causes enhanced metaphase spindle localization and defects in chromosome segregation. Thus, phosphoregulation of the motor domain of MKLP1 kinesin ensures that central spindle assembly occurs at the appropriate time in the cell cycle and maintains genomic stability.

  15. Cell cycle controls stress response and longevity in C. elegans

    PubMed Central

    Dottermusch, Matthias; Lakner, Theresa; Peyman, Tobias; Klein, Marinella; Walz, Gerd; Neumann-Haefelin, Elke

    2016-01-01

    Recent studies have revealed a variety of genes and mechanisms that influence the rate of aging progression. In this study, we identified cell cycle factors as potent regulators of health and longevity in C. elegans. Focusing on the cyclin-dependent kinase 2 (cdk-2) and cyclin E (cye-1), we show that inhibition of cell cycle genes leads to tolerance towards environmental stress and longevity. The reproductive system is known as a key regulator of longevity in C. elegans. We uncovered the gonad as the central organ mediating the effects of cell cycle inhibition on lifespan. In particular, the proliferating germ cells were essential for conferring longevity. Steroid hormone signaling and the FOXO transcription factor DAF-16 were required for longevity associated with cell cycle inhibition. Furthermore, we discovered that SKN-1 (ortholog of mammalian Nrf proteins) activates protective gene expression and induces longevity when cell cycle genes are inactivated. We conclude that both, germline absence and inhibition through impairment of cell cycle machinery results in longevity through similar pathways. In addition, our studies suggest further roles of cell cycle genes beyond cell cycle progression and support the recently described connection of SKN-1/Nrf to signals deriving from the germline. PMID:27668945

  16. Thermal stress cycling of GaAs solar cells

    NASA Technical Reports Server (NTRS)

    Francis, Robert W.

    1987-01-01

    Thermal stress cycling was performed on gallium arsenide solar cells to investigate their electrical, mechanical, and structural integrity. Cells were cycled under low Earth orbit (LEO) simulated temperature conditions in vacuum. Cell evaluations consisted of power output values, spectral response, optical microscopy and ion microprobe mass analysis, and depth profiles on both front surface inter-grid areas and metallization contact grid lines. Cells were examined for degradation after 500, 5,000, 10,000 and 15,245 thermal cycles. No indication of performance degradation was found for any vendor's cell lot.

  17. The molecular basis of carcinogenesis: understanding the cell cycle clock.

    PubMed

    Weinberg, R A

    1996-06-01

    The cell cycle clock is the central controller of cell proliferation that governs the progress of the cell through its growth cycle, its exit from the active cycle, and its decision to differentiate. Components of the clock are found to be functioning in an aberrant fashion in many types of malignancies. Notable among these is the retinoblastoma protein, pRB, which acts to restrain proliferation in normal cells and suffers inactivation in many types of tumour cells. Its activity is controlled by D-type cyclins in various cell types. We have deleted one of these cyclins--cyclin D1--from the mouse germline and find that its absence leads to a limited range of defects including hypoplastic retinae and the inability of the mammary epithelium to respond to pregnancy-associated hormonal stimulation. Cyclin D1 is overexpressed in many human breast cancers, pointing to a highly specific association of this cell cycle clock component with mammary cell proliferation.

  18. Cell cycle analysis by flow cytometry: principles and applications.

    PubMed

    Jayat, C; Ratinaud, M H

    1993-01-01

    Numerous flow cytometric analyses are based on DNA content studies. We have considered firstly monoparametric cell cycle analyses, which only take DNA content into account, but are sometimes of limited interest. Then, we have presented multiparametric analyses, which can be used to improve cycle phase identification by taking simultaneously into account DNA and other cellular components, or by considering some events occurring during cell cycle. Finally, we have discussed monoparametric and multiparametric cell cycle analysis interest in various application fields, particularly in pharmacology, toxicology, tumoral pathology and higher plant system studies.

  19. Quantitative Characterization of Cell Behaviors through Cell Cycle Progression via Automated Cell Tracking

    PubMed Central

    Wang, Yuliang; Jeong, Younkoo; Jhiang, Sissy M.; Yu, Lianbo; Menq, Chia-Hsiang

    2014-01-01

    Cell behaviors are reflections of intracellular tension dynamics and play important roles in many cellular processes. In this study, temporal variations in cell geometry and cell motion through cell cycle progression were quantitatively characterized via automated cell tracking for MCF-10A non-transformed breast cells, MCF-7 non-invasive breast cancer cells, and MDA-MB-231 highly metastatic breast cancer cells. A new cell segmentation method, which combines the threshold method and our modified edge based active contour method, was applied to optimize cell boundary detection for all cells in the field-of-view. An automated cell-tracking program was implemented to conduct live cell tracking over 40 hours for the three cell lines. The cell boundary and location information was measured and aligned with cell cycle progression with constructed cell lineage trees. Cell behaviors were studied in terms of cell geometry and cell motion. For cell geometry, cell area and cell axis ratio were investigated. For cell motion, instantaneous migration speed, cell motion type, as well as cell motion range were analyzed. We applied a cell-based approach that allows us to examine and compare temporal variations of cell behavior along with cell cycle progression at a single cell level. Cell body geometry along with distribution of peripheral protrusion structures appears to be associated with cell motion features. Migration speed together with motion type and motion ranges are required to distinguish the three cell-lines examined. We found that cells dividing or overlapping vertically are unique features of cell malignancy for both MCF-7 and MDA-MB-231 cells, whereas abrupt changes in cell body geometry and cell motion during mitosis are unique to highly metastatic MDA-MB-231 cells. Taken together, our live cell tracking system serves as an invaluable tool to identify cell behaviors that are unique to malignant and/or highly metastatic breast cancer cells. PMID:24911281

  20. Genetic instability in cancer cells by impaired cell cycle checkpoints.

    PubMed

    Nakanishi, Makoto; Shimada, Midori; Niida, Hiroyuki

    2006-10-01

    Cells continuously encounter DNA damage caused either by damaging agents, including oxygen radicals and DNA replication errors caused by stalled replication forks, or by extracellular environments such as ultraviolet or ionizing irradiation. Such DNA damage poses a great threat to genome stability, potentially leading to loss or amplification of chromosome activity, which may result in cellular senescence, cancer or apoptosis. The DNA damage checkpoints coordinate an arrest in cell cycle progression with the DNA repair process, suppressing either mitotic catastrophe or proliferation of cells with damaged DNA. Numerous key players have been identified in terms of damage sensor proteins, transducer kinases and effectors, but their coordination and interconnectedness in damage control have only recently become evident. In this review, we discuss changes in chromatin structure, recruitment of mediator proteins and activation of transducer kinases in response to DNA damage. These cellular responses are important for determining the potential effects of current cancer therapies in terms of toxicity and efficacy.

  1. Cell shape, cytoskeletal mechanics, and cell cycle control in angiogenesis

    NASA Technical Reports Server (NTRS)

    Ingber, D. E.; Prusty, D.; Sun, Z.; Betensky, H.; Wang, N.

    1995-01-01

    Capillary endothelial cells can be switched between growth and differentiation by altering cell-extracellular matrix interactions and thereby, modulating cell shape. Studies were carried out to determine when cell shape exerts its growth-regulatory influence during cell cycle progression and to explore the role of cytoskeletal structure and mechanics in this control mechanism. When G0-synchronized cells were cultured in basic fibroblast growth factor (FGF)-containing defined medium on dishes coated with increasing densities of fibronectin or a synthetic integrin ligand (RGD-containing peptide), cell spreading, nuclear extension, and DNA synthesis all increased in parallel. To determine the minimum time cells must be adherent and spread on extracellular matrix (ECM) to gain entry into S phase, cells were removed with trypsin or induced to retract using cytochalasin D at different times after plating. Both approaches revealed that cells must remain extended for approximately 12-15 h and hence, most of G1, in order to enter S phase. After this restriction point was passed, normally 'anchorage-dependent' endothelial cells turned on DNA synthesis even when round and in suspension. The importance of actin-containing microfilaments in shape-dependent growth control was confirmed by culturing cells in the presence of cytochalasin D (25-1000 ng ml-1): dose-dependent inhibition of cell spreading, nuclear extension, and DNA synthesis resulted. In contrast, induction of microtubule disassembly using nocodazole had little effect on cell or nuclear spreading and only partially inhibited DNA synthesis. Interestingly, combination of nocodazole with a suboptimal dose of cytochalasin D (100 ng ml-1) resulted in potent inhibition of both spreading and growth, suggesting that microtubules are redundant structural elements which can provide critical load-bearing functions when microfilaments are partially compromised. Similar synergism between nocodazole and cytochalasin D was observed

  2. Cell shape, cytoskeletal mechanics, and cell cycle control in angiogenesis

    NASA Technical Reports Server (NTRS)

    Ingber, D. E.; Prusty, D.; Sun, Z.; Betensky, H.; Wang, N.

    1995-01-01

    Capillary endothelial cells can be switched between growth and differentiation by altering cell-extracellular matrix interactions and thereby, modulating cell shape. Studies were carried out to determine when cell shape exerts its growth-regulatory influence during cell cycle progression and to explore the role of cytoskeletal structure and mechanics in this control mechanism. When G0-synchronized cells were cultured in basic fibroblast growth factor (FGF)-containing defined medium on dishes coated with increasing densities of fibronectin or a synthetic integrin ligand (RGD-containing peptide), cell spreading, nuclear extension, and DNA synthesis all increased in parallel. To determine the minimum time cells must be adherent and spread on extracellular matrix (ECM) to gain entry into S phase, cells were removed with trypsin or induced to retract using cytochalasin D at different times after plating. Both approaches revealed that cells must remain extended for approximately 12-15 h and hence, most of G1, in order to enter S phase. After this restriction point was passed, normally 'anchorage-dependent' endothelial cells turned on DNA synthesis even when round and in suspension. The importance of actin-containing microfilaments in shape-dependent growth control was confirmed by culturing cells in the presence of cytochalasin D (25-1000 ng ml-1): dose-dependent inhibition of cell spreading, nuclear extension, and DNA synthesis resulted. In contrast, induction of microtubule disassembly using nocodazole had little effect on cell or nuclear spreading and only partially inhibited DNA synthesis. Interestingly, combination of nocodazole with a suboptimal dose of cytochalasin D (100 ng ml-1) resulted in potent inhibition of both spreading and growth, suggesting that microtubules are redundant structural elements which can provide critical load-bearing functions when microfilaments are partially compromised. Similar synergism between nocodazole and cytochalasin D was observed

  3. Life cycle testing of sodium/sulfur satellite battery cells

    NASA Astrophysics Data System (ADS)

    Flake, Richard A.

    Test results on sodium sulfur cells developed presently by the Air Force for NaS rechargeable batteries for baseload power applications are summarized. Cycle life data are presented on fourteen cells, some of which have accumulated more than 1900 days on test and/or more than 6000 cycles. Results demonstrated cycle life times to be sufficient for use on satellites in high-altitude orbits.

  4. Characteristics and Behavior of Cycled Aged Lithium Ion Cells

    DTIC Science & Technology

    2010-01-01

    service cycle and provide the cornerstone for safety analysis. 18650 Cells with representative chemistry of cells contained in current Army procured...their relevance to this effort warrants inclusion. 1-3 EXPERIMENTAL Representative 18650 cells were cycled at different rates and environmental...conditions. The 18650 chemistry used in this effort is a LiCoO2 lithium ion electrochemical cell. The bulk of this effort was conducted with 1.5 Amp-hr

  5. Why should we study the plant cell cycle?

    PubMed

    Inzé, Dirk

    2003-04-01

    Description of the molecular biology of plant and animal cell cycles highlights similarities and critical differences. The cell cycle is a point of control in both growth and development and deepening understanding of underlying processes and mechanisms may have many practical applications.

  6. Regulation of the Embryonic Cell Cycle During Mammalian Preimplantation Development.

    PubMed

    Palmer, N; Kaldis, P

    2016-01-01

    The preimplantation development stage of mammalian embryogenesis consists of a series of highly conserved, regulated, and predictable cell divisions. This process is essential to allow the rapid expansion and differentiation of a single-cell zygote into a multicellular blastocyst containing cells of multiple developmental lineages. This period of development, also known as the germinal stage, encompasses several important developmental transitions, which are accompanied by dramatic changes in cell cycle profiles and dynamics. These changes are driven primarily by differences in the establishment and enforcement of cell cycle checkpoints, which must be bypassed to facilitate the completion of essential cell cycle events. Much of the current knowledge in this area has been amassed through the study of knockout models in mice. These mouse models are powerful experimental tools, which have allowed us to dissect the relative dependence of the early embryonic cell cycles on various aspects of the cell cycle machinery and highlight the extent of functional redundancy between members of the same gene family. This chapter will explore the ways in which the cell cycle machinery, their accessory proteins, and their stimuli operate during mammalian preimplantation using mouse models as a reference and how this allows for the usually well-defined stages of the cell cycle to be shaped and transformed during this unique and critical stage of development. © 2016 Elsevier Inc. All rights reserved.

  7. Rethinking cell-cycle-dependent gene expression in Schizosaccharomyces pombe.

    PubMed

    Cooper, Stephen

    2017-06-21

    Three studies of gene expression during the division cycle of Schizosaccharomyces pombe led to the proposal that a large number of genes are expressed at particular times during the S. pombe cell cycle. Yet only a small fraction of genes proposed to be expressed in a cell-cycle-dependent manner are reproducible in all three published studies. In addition to reproducibility problems, questions about expression amplitudes, cell-cycle timing of expression, synchronization artifacts, and the problem with methods for synchronizing cells must be considered. These problems and complications prompt the idea that caution should be used before accepting the conclusion that there are a large number of genes expressed in a cell-cycle-dependent manner in S. pombe.

  8. Regulatory pathways coordinating cell cycle progression in early Xenopus development.

    PubMed

    Gotoh, Tetsuya; Villa, Linda M; Capelluto, Daniel G S; Finkielstein, Carla V

    2011-01-01

    The African clawed frog, Xenopus laevis, is used extensively as a model organism for studying both cell development and cell cycle regulation. For over 20 years now, this model organism has contributed to answering fundamental questions concerning the mechanisms that underlie cell cycle transitions--the cellular components that synthesize, modify, repair, and degrade nucleic acids and proteins, the signaling pathways that allow cells to communicate, and the regulatory pathways that lead to selective expression of subsets of genes. In addition, the remarkable simplicity of the Xenopus early cell cycle allows for tractable manipulation and dissection of the basic components driving each transition. In this organism, early cell divisions are characterized by rapid cycles alternating phases of DNA synthesis and division. The post-blastula stages incorporate gap phases, lengthening progression, and allowing more time for DNA repair. Various cyclin/Cdk complexes are differentially expressed during the early cycles with orderly progression being driven by both the combined action of cyclin synthesis and degradation and the appropriate selection of specific substrates by their Cdk components. Like other multicellular organisms, chief developmental events in early Xenopus embryogenesis coincide with profound remodeling of the cell cycle, suggesting that cell proliferation and differentiation events are linked and coordinated through crosstalk mechanisms acting on signaling pathways involving the expression of cell cycle control genes.

  9. The Cell Cycle: An Activity Using Paper Plates to Represent Time Spent in Phases of the Cell Cycle

    ERIC Educational Resources Information Center

    Scherer, Yvette D.

    2014-01-01

    In this activity, students are given the opportunity to combine skills in math and geometry for a biology lesson in the cell cycle. Students utilize the data they collect and analyze from an online onion-root-tip activity to create a paper-plate time clock representing a 24-hour cell cycle. By dividing the paper plate into appropriate phases of…

  10. The Cell Cycle: An Activity Using Paper Plates to Represent Time Spent in Phases of the Cell Cycle

    ERIC Educational Resources Information Center

    Scherer, Yvette D.

    2014-01-01

    In this activity, students are given the opportunity to combine skills in math and geometry for a biology lesson in the cell cycle. Students utilize the data they collect and analyze from an online onion-root-tip activity to create a paper-plate time clock representing a 24-hour cell cycle. By dividing the paper plate into appropriate phases of…

  11. Effect of immunosuppression on the human mesangial cell cycle

    PubMed Central

    ZHOU, XIAOSHUANG; WORKENEH, BIRUH; HU, ZHAOYONG; LI, RONGSHAN

    2015-01-01

    The present study investigated the effects of immunosuppressive agents [tacrolimus (Tac), cyclosporine A (CsA), mycophenolic acid (MMF) and methylprednisone (MP)] on the proliferation, cell cycle progression and apoptotic rate of human mesangial cells. Cultured human mesangial cells were treated with several concentrations of the immunosuppressive agents for 24, 48 or 72 h. Cell cycle progression, proliferation and apoptosis were analyzed using an MTT assay and flow cytometry. Tac and CsA significantly inhibited the proliferation of human mesangial cells in a dose- and time-dependent manner. Cell cycle analysis revealed that Tac and CsA arrested mesangial cells in the G0/G1 phase, preventing them from entering S phase. Similarly, MP inhibited human mesangial cell growth by causing cell cycle arrest in G0/G1 phase. MMF also inhibited mesangial cell proliferation, but accomplished this by preventing progression from S phase to the G2/M phase. The combination of MP and MMF synergistically inhibited mesangial cell proliferation. Tac, CsA, MP and MMF inhibited proliferation of human mesangial cells by blocking progression of the cell cycle. In conclusion, these agents, sequentially or in combination, may be used to effectively treat mesangial proliferative glomerular disease. PMID:25370945

  12. Cell cycle-dependent induction of autophagy, mitophagy and reticulophagy.

    PubMed

    Tasdemir, Ezgi; Maiuri, M Chiara; Tajeddine, Nicolas; Vitale, Ilio; Criollo, Alfredo; Vicencio, José Miguel; Hickman, John A; Geneste, Olivier; Kroemer, Guido

    2007-09-15

    When added to cells, a variety of autophagy inducers that operate through distinct mechanisms and target different organelles for autophagic destruction (mitochondria in mitophagy, endoplasmic reticulum in reticulophagy) rarely induce autophagic vacuolization in more than 50% or the cells. Here we show that this heterogeneity may be explained by cell cycle-specific effects. The BH3 mimetic ABT737, lithium, rapamycin, tunicamycin or nutrient depletion stereotypically induce autophagy preferentially in the G(1) and S phases of the cell cycle, as determined by simultaneous monitoring of cell cycle markers and the cytoplasmic aggregation of GFP-LC3 in autophagic vacuoles. These results point to a hitherto neglected crosstalk between autophagic vacuolization and cell cycle regulation.

  13. Brucella abortus Cell Cycle and Infection Are Coordinated.

    PubMed

    De Bolle, Xavier; Crosson, Sean; Matroule, Jean-Yves; Letesson, Jean-Jacques

    2015-12-01

    Brucellae are facultative intracellular pathogens. The recent development of methods and genetically engineered strains allowed the description of cell-cycle progression of Brucella abortus, including unipolar growth and the ordered initiation of chromosomal replication. B. abortus cell-cycle progression is coordinated with intracellular trafficking in the endosomal compartments. Bacteria are first blocked at the G1 stage, growth and chromosome replication being resumed shortly before reaching the intracellular proliferation compartment. The control mechanisms of cell cycle are similar to those reported for the bacterium Caulobacter crescentus, and they are crucial for survival in the host cell. The development of single-cell analyses could also be applied to other bacterial pathogens to investigate their cell-cycle progression during infection.

  14. Viral manipulation of DNA repair and cell cycle checkpoints

    PubMed Central

    Chaurushiya, Mira S.; Weitzman, Matthew D.

    2009-01-01

    Recognition and repair of DNA damage is critical for maintaining genomic integrity and suppressing tumorigenesis. In eukaryotic cells, the sensing and repair of DNA damage are exquisitely coordinated with cell cycle progression and checkpoints, in order to prevent the propagation of damaged DNA. The carefully maintained cellular response to DNA damage is challenged by viruses, which produce a large amount of exogenous DNA during infection. Viruses also express proteins that perturb cellular DNA repair and cell cycle pathways, promoting tumorigenesis in their quest for cellular domination. This review presents an overview of strategies employed by viruses to manipulate DNA damage responses and cell cycle checkpoints as they commandeer the cell to maximize their own viral replication. Studies of viruses have identified key cellular regulators and revealed insights into molecular mechanisms governing DNA repair, cell cycle checkpoints, and transformation. PMID:19473887

  15. Flow cytometry methods for the study of cell-cycle parameters of planarian stem cells.

    PubMed

    Kang, Hara; Sánchez Alvarado, Alejandro

    2009-05-01

    Due to their characteristic inaccessibility and low numbers, little is known about the cell-cycle dynamics of most stem cells in vivo. A powerful, established methodology to study cell-cycle dynamics is flow cytometry, which is used routinely to study the cell-cycle dynamics of proliferating cells in vitro. Its use in heterogeneous mixtures of cells obtained from whole animals, however, is complicated by the relatively low abundance of cycling to non-cycling cells. We report on flow cytometric methods that take advantage of the abundance of proliferating stem cells in the planarian Schmidtea mediterranea. The optimized protocols allow us to measure cell-cycle dynamics and follow BrdU-labeled cells specifically in complex mixtures of cells. These methods expand on the growing toolkit being developed to study stem cell biology in planarians, and open the door to detailed cytometric studies of a collectively totipotent population of adult stem cells in vivo.

  16. Cycle life test. [of secondary spacecraft cells

    NASA Technical Reports Server (NTRS)

    Harkness, J. D.

    1977-01-01

    Statistical information concerning cell performance characteristics and limitations of secondary spacecraft cells is presented. Weaknesses in cell design as well as battery weaknesses encountered in various satellite programs are reported. Emphasis is placed on improving the reliability of space batteries.

  17. 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

  18. The intestinal epithelial cell cycle: uncovering its 'cryptic' nature.

    PubMed

    McKernan, Declan P; Egan, Laurence J

    2015-03-01

    To discuss the recent landmark findings that have increased our understanding not only of the role of the epithelial cell cycle in the homeostasis of the small intestine, but also its relevance to inflammation and cancer. Recent data have unveiled novel information on protein interactions directly involved in the cell cycle as well as in the pathways that transduce external environmental signals to the cell cycle. A growing body of the recent evidence confirms the importance of food as well as hormonal regulation in the gut on cell cycle. Information on the contribution of the epithelial microenvironment, including the microbiota, has grown substantially in the recent years as well as on the gene-environment interactions and the multiple epigenetic mechanisms involved in regulating cell-cycle proteins and signalling. Finally, further studies investigating the dysregulation of the cell cycle during inflammation and proliferation have increased our understanding of the pathophysiology of chronic inflammatory diseases and cancer. This review highlights some of the most recent advances that further emphasize the importance of the cell cycle in the small intestine during homeostasis as well as in inflammation and cancer.

  19. Interplay between the cell cycle and double-strand break response in mammalian cells.

    PubMed

    Beishline, Kate; Azizkhan-Clifford, Jane

    2014-01-01

    The cell cycle is intimately associated with the ability of cells to sense and respond to and repair DNA damage. Understanding how cell cycle progression, particularly DNA replication and cell division, are regulated and how DNA damage can affect these processes has been the subject of intense research. Recent evidence suggests that the repair of DNA damage is regulated by the cell cycle, and that cell cycle factors are closely associated with repair factors and participate in cellular decisions regarding how to respond to and repair damage. Precise regulation of cell cycle progression in the presence of DNA damage is essential to maintain genomic stability and avoid the accumulation of chromosomal aberrations that can promote tumor formation. In this review, we discuss the current understanding of how mammalian cells induce cell cycle checkpoints in response to DNA double-strand breaks. In addition, we discuss how cell cycle factors modulate DNA repair pathways to facilitate proper repair of DNA lesions.

  20. Cell cycle transitions: a common role for stoichiometric inhibitors.

    PubMed

    Hopkins, Michael; Tyson, John J; Novák, Béla

    2017-09-20

    The cell division cycle is the process by which eukaryotic cells replicate their chromosomes and partition them to two daughter cells. To maintain the integrity of the genome, proliferating cells must be able to block progression through the division cycle at key transition points (called 'checkpoints'), if there have been problems in the replication of the chromosomes or their biorientation on the mitotic spindle. These checkpoints are governed by protein-interaction networks, composed of phase-specific cell-cycle activators and inhibitors. Examples include Cdk1:Clb5 and its inhibitor Sic1 at the G1/S checkpoint in budding yeast, APC:Cdc20 and its inhibitor MCC at the mitotic checkpoint, and PP2A:B55 and its inhibitor ENSA at the mitotic-exit checkpoint. Each of these inhibitors is a substrate as well as a stoichiometric inhibitor of the cell-cycle activator. Because the production of each inhibitor is promoted by a regulatory protein that is itself inhibited by the cell cycle activator, their interaction network presents a regulatory motif characteristic of a 'feedback-amplified domineering substrate' (FADS). We describe how the FADS motif responds to signals in the fashion of a bistable toggle switch, and then we discuss how this toggle switch accounts for the abrupt and irreversible nature of three specific cell-cycle checkpoints. © 2017 by The American Society for Cell Biology.

  1. Disconnected circadian and cell cycles in a tumor-driven cell line.

    PubMed

    Pendergast, Julie S; Yeom, Mijung; Reyes, Bryan A; Ohmiya, Yoshihiro; Yamazaki, Shin

    2010-11-01

    Cell division occurs at a specific time of day in numerous species, suggesting that the circadian and cell cycles are coupled in vivo. By measuring the cell cycle rhythm in real-time, we recently showed that the circadian and cell cycles are not coupled in immortalized fibroblasts, resulting in a rapid rate of cell division even though the circadian rhythm is normal in these cells. Here we report that tumor-driven Lewis lung carcinoma (LLC) cells have perfectly temperature compensated circadian clocks, but the periods of their cell cycle gene expression rhythms are temperature-dependent, suggesting that their circadian and cell cycles are not connected. These data support our hypothesis that decoupling of the circadian and cell cycles may underlie aberrant cell division in tumor cells.

  2. SUMOylation-Mediated Regulation of Cell Cycle Progression and Cancer.

    PubMed

    Eifler, Karolin; Vertegaal, Alfred C O

    2015-12-01

    Protein conjugation with Small ubiquitin-like modifier (SUMOylation) has critical roles during cell cycle progression. Many important cell cycle regulators, including many oncogenes and tumor suppressors, are functionally regulated via SUMOylation. The dynamic SUMOylation pattern observed throughout the cell cycle is ensured via distinct spatial and temporal regulation of the SUMO machinery. Additionally, SUMOylation cooperates with other post-translational modifications to mediate cell cycle progression. Deregulation of these SUMOylation and deSUMOylation enzymes causes severe defects in cell proliferation and genome stability. Different types of cancer were recently shown to be dependent on a functioning SUMOylation system, a finding that could be exploited in anticancer therapies. Copyright © 2015 Elsevier Ltd. All rights reserved.

  3. Cold nights impair leaf growth and cell cycle progression in maize through transcriptional changes of cell cycle genes.

    PubMed

    Rymen, Bart; Fiorani, Fabio; Kartal, Fatma; Vandepoele, Klaas; Inzé, Dirk; Beemster, Gerrit T S

    2007-03-01

    Low temperature inhibits the growth of maize (Zea mays) seedlings and limits yield under field conditions. To study the mechanism of cold-induced growth retardation, we exposed maize B73 seedlings to low night temperature (25 degrees C /4 degrees C, day/night) from germination until the completion of leaf 4 expansion. This treatment resulted in a 20% reduction in final leaf size compared to control conditions (25 degrees C/18 degrees C, day/night). A kinematic analysis of leaf growth rates in control and cold-treated leaves during daytime showed that cold nights affected both cell cycle time (+65%) and cell production (-22%). In contrast, the size of mature epidermal cells was unaffected. To analyze the effect on cell cycle progression at the molecular level, we identified through a bioinformatics approach a set of 43 cell cycle genes and analyzed their expression in proliferating, expanding, and mature cells of leaves exposed to either control or cold nights. This analysis showed that: (1) the majority of cell cycle genes had a consistent proliferation-specific expression pattern; and (2) the increased cell cycle time in the basal meristem of leaves exposed to cold nights was associated with differential expression of cell cycle inhibitors and with the concomitant down-regulation of positive regulators of cell division.

  4. Regulation of sister chromatid cohesion during the mitotic cell cycle.

    PubMed

    Zheng, Ge; Yu, HongTao

    2015-11-01

    Orderly execution of two critical events during the cell cycle--DNA replication and chromosome segregation--ensures the stable transmission of genetic materials. The cohesin complex physically connects sister chromatids during DNA replication in a process termed sister chromatid cohesion. Timely establishment and dissolution of sister chromatid cohesion is a prerequisite for accurate chromosome segregation, and is tight regulated by the cell cycle machinery and cohesin-associated proteins. In this review, we discuss recent progress in the molecular understanding of sister chromatid cohesion during the mitotic cell cycle.

  5. Cell Cycle Related Differentiation of Bone Marrow Cells into Lung Cells

    SciTech Connect

    Dooner, Mark; Aliotta, Jason M.; Pimental, Jeffrey; Dooner, Gerri J.; Abedi, Mehrdad; Colvin, Gerald; Liu, Qin; Weier, Heinz-Ulli; Dooner, Mark S.; Quesenberry, Peter J.

    2007-12-31

    Green-fluorescent protein (GFP) labeled marrow cells transplanted into lethally irradiated mice can be detected in the lungs of transplanted mice and have been shown to express lung specific proteins while lacking the expression of hematopoietic markers. We have studied marrow cells induced to transit cell cycle by exposure to IL-3, IL-6, IL-11 and steel factor at different times of culture corresponding to different phases of cell cycle. We have found that marrow cells at the G1/S interface have a 3-fold increase in cells which assume a lung phenotype and that this increase is no longer seen in late S/G2. These cells have been characterized as GFP{sup +} CD45{sup -} and GFP{sup +} cytokeratin{sup +}. Thus marrow cells with the capacity to convert into cells with a lung phenotype after transplantation show a reversible increase with cytokine induced cell cycle transit. Previous studies have shown the phenotype of bone marrow stem cells fluctuates reversibly as these cells traverse cell cycle, leading to a continuum model of stem cell regulation. The present studies indicate that marrow stem cell production of nonhematopoietic cells also fluctuates on a continuum.

  6. Impact of the cell division cycle on gene circuits

    NASA Astrophysics Data System (ADS)

    Bierbaum, Veronika; Klumpp, Stefan

    2015-12-01

    In growing cells, protein synthesis and cell growth are typically not synchronous, and, thus, protein concentrations vary over the cell division cycle. We have developed a theoretical description of genetic regulatory systems in bacteria that explicitly considers the cell division cycle to investigate its impact on gene expression. We calculate the cell-to-cell variations arising from cells being at different stages in the division cycle for unregulated genes and for basic regulatory mechanisms. These variations contribute to the extrinsic noise observed in single-cell experiments, and are most significant for proteins with short lifetimes. Negative autoregulation buffers against variation of protein concentration over the division cycle, but the effect is found to be relatively weak. Stronger buffering is achieved by an increased protein lifetime. Positive autoregulation can strongly amplify such variation if the parameters are set to values that lead to resonance-like behaviour. For cooperative positive autoregulation, the concentration variation over the division cycle diminishes the parameter region of bistability and modulates the switching times between the two stable states. The same effects are seen for a two-gene mutual-repression toggle switch. By contrast, an oscillatory circuit, the repressilator, is only weakly affected by the division cycle.

  7. Ca2+ signaling, genes and the cell cycle

    PubMed Central

    Machaca, Khaled

    2013-01-01

    Changes in the concentration and spatial distribution of Ca2+ ions in the cytoplasm constitute a ubiquitous intracellular signaling module in cellular physiology. With the advent of Ca2+ dyes that allow direct visualization of Ca2+ transients, combined with powerful experimental tools such as electrophysiological recordings, intracellular Ca2+ transients have been implicated in practically every aspect of cellular physiology, including cellular proliferation. Ca2+ signals are associated with different phases of the cell cycle and interfering with Ca2+ signaling or downstream pathways often disrupts progression of the cell cycle. Although there exists a dependence between Ca2+ signals and the cell cycle the mechanisms involved are not well defined and given the cross-talk between Ca2+ and other signaling modules, it is difficult to assess the exact role of Ca2+ signals in cell cycle progression. Two exceptions however, include fertilization and T-cell activation, where well-defined roles for Ca2+ signals in mediating progression through specific stages of the cell cycle have been clearly established. In the case of T-cell activation Ca2+ regulates entry into the cell cycle through the induction of gene transcription. PMID:21084120

  8. The Mammalian Cell Cycle Regulates Parvovirus Nuclear Capsid Assembly

    PubMed Central

    Riolobos, Laura; Domínguez, Carlos; Kann, Michael; Almendral, José M.

    2015-01-01

    It is unknown whether the mammalian cell cycle could impact the assembly of viruses maturing in the nucleus. We addressed this question using MVM, a reference member of the icosahedral ssDNA nuclear parvoviruses, which requires cell proliferation to infect by mechanisms partly understood. Constitutively expressed MVM capsid subunits (VPs) accumulated in the cytoplasm of mouse and human fibroblasts synchronized at G0, G1, and G1/S transition. Upon arrest release, VPs translocated to the nucleus as cells entered S phase, at efficiencies relying on cell origin and arrest method, and immediately assembled into capsids. In synchronously infected cells, the consecutive virus life cycle steps (gene expression, proteins nuclear translocation, capsid assembly, genome replication and encapsidation) proceeded tightly coupled to cell cycle progression from G0/G1 through S into G2 phase. However, a DNA synthesis stress caused by thymidine irreversibly disrupted virus life cycle, as VPs became increasingly retained in the cytoplasm hours post-stress, forming empty capsids in mouse fibroblasts, thereby impairing encapsidation of the nuclear viral DNA replicative intermediates. Synchronously infected cells subjected to density-arrest signals while traversing early S phase also blocked VPs transport, resulting in a similar misplaced cytoplasmic capsid assembly in mouse fibroblasts. In contrast, thymidine and density arrest signals deregulating virus assembly neither perturbed nuclear translocation of the NS1 protein nor viral genome replication occurring under S/G2 cycle arrest. An underlying mechanism of cell cycle control was identified in the nuclear translocation of phosphorylated VPs trimeric assembly intermediates, which accessed a non-conserved route distinct from the importin α2/β1 and transportin pathways. The exquisite cell cycle-dependence of parvovirus nuclear capsid assembly conforms a novel paradigm of time and functional coupling between cellular and virus life

  9. Krebs cycle rewired for macrophage and dendritic cell effector functions.

    PubMed

    Ryan, Dylan Gerard; O'Neill, Luke A J

    2017-07-07

    The Krebs cycle is an amphibolic pathway operating in the mitochondrial matrix of all eukaryotic organisms. In response to proinflammatory stimuli, macrophages and dendritic cells undergo profound metabolic remodelling to support the biosynthetic and bioenergetic requirements of the cell. Recently, it has been discovered that this metabolic shift also involves the rewiring of the Krebs cycle to regulate cellular metabolic flux and the accumulation of Krebs cycle intermediates, notably, citrate, succinate and fumarate. Interestingly, a new role for Krebs cycle intermediates as signalling molecules and immunomodulators that dictate the inflammatory response has begun to emerge. This review will discuss the latest developments in Krebs cycle rewiring and immune cell effector functions, with a particular focus on the regulation of cytokine production. © 2017 Federation of European Biochemical Societies.

  10. Adenosine induces G2/M cell-cycle arrest by inhibiting cell mitosis progression.

    PubMed

    Jia, Kun-Zhi; Tang, Bo; Yu, Lu; Cheng, Wei; Zhang, Rong; Zhang, Jian-Fa; Hua, Zi-Chun

    2009-12-16

    Cellular adenosine accumulates under stress conditions. Few papers on adenosine are concerned with its function in the cell cycle. The cell cycle is the essential mechanism by which all living things reproduce and the target machinery when cells encounter stresses, so it is necessary to examine the relationship between adenosine and the cell cycle. In the present study, adenosine was found to induce G-2/M cell-cycle arrest. Furthermore, adenosine was found to modulate the expression of some important proteins in the cell cycle, such as cyclin B and p21, and to inhibit the transition of metaphase to anaphase in mitosis.

  11. Mechanisms of sulindac-induced apoptosis and cell cycle arrest.

    PubMed

    Jung, Barbara; Barbier, Valerie; Brickner, Howard; Welsh, John; Fotedar, Arun; McClelland, Michael

    2005-02-28

    The mechanism underlying the chemopreventive effects of the non-steroidal anti-inflammatory drug sulindac remains unclear. Its active metabolite, sulindac sulfide, induces cell cycle arrest as well as apoptosis in mammalian cell lines. We now show that in murine thymocytes, sulindac sulfide-induced cell death is p53, bax, Fas, and FasL independent. In contrast, bcl2 transgenic thymocytes are resistant to sulindac sulfide-induced apoptosis. In addition, we demonstrate that sulindac sulfide-induced cell cycle arrest in mouse embryonic fibroblasts (MEFs) is partly mediated by the retinoblastoma tumor suppressor protein (Rb) and the cyclin kinase inhibitor p21waf1/cip1. Furthermore, MEFs deficient in p21 or Rb are more susceptible to sulindac sulfide-induced cell death. These results suggest that sulindac may selectively target premalignant cells with cell cycle checkpoint deficits.

  12. Cell cycle progression in response to oxygen levels.

    PubMed

    Ortmann, Brian; Druker, Jimena; Rocha, Sonia

    2014-09-01

    Hypoxia' or decreases in oxygen availability' results in the activation of a number of different responses at both the whole organism and the cellular level. These responses include drastic changes in gene expression, which allow the organism (or cell) to cope efficiently with the stresses associated with the hypoxic insult. A major breakthrough in the understanding of the cellular response to hypoxia was the discovery of a hypoxia sensitive family of transcription factors known as the hypoxia inducible factors (HIFs). The hypoxia response mounted by the HIFs promotes cell survival and energy conservation. As such, this response has to deal with important cellular process such as cell division. In this review, the integration of oxygen sensing with the cell cycle will be discussed. HIFs, as well as other components of the hypoxia pathway, can influence cell cycle progression. The role of HIF and the cell molecular oxygen sensors in the control of the cell cycle will be reviewed.

  13. Configuration and performance of fuel cell-combined cycle options

    SciTech Connect

    Rath, L.K.; Le, P.H.; Sudhoff, F.A.

    1995-12-31

    The natural gas, indirect-fired, carbonate fuel-cell-bottomed, combined cycle (NG-IFCFC) and the topping natural-gas/solid-oxide fuel-cell combined cycle (NG-SOFCCC) are introduced as novel power-plant systems for the distributed power and on-site markets in the 20-200 mega-watt (MW) size range. The novel NG-IFCFC power-plant system configures the ambient pressure molten-carbonate fuel cell (MCFC) with a gas turbine, air compressor, combustor, and ceramic heat exchanger: The topping solid-oxide fuel-cell (SOFC) combined cycle is not new. The purpose of combining a gas turbine with a fuel cell was to inject pressurized air into a high-pressure fuel cell and to reduce the size, and thereby, to reduce the cost of the fuel cell. Today, the SOFC remains pressurized, but excess chemical energy is combusted and the thermal energy is utilized by the Carnot cycle heat engine to complete the system. ASPEN performance results indicate efficiencies and heat rates for the NG-IFCFC or NG-SOFCCC are better than conventional fuel cell or gas turbine steam-bottomed cycles, but with smaller and less expensive components. Fuel cell and gas turbine systems should not be viewed as competitors, but as an opportunity to expand to markets where neither gas turbines nor fuel cells alone would be commercially viable. Non-attainment areas are the most likely markets.

  14. Estrogen receptor alpha is cell cycle-regulated and regulates the cell cycle in a ligand-dependent fashion.

    PubMed

    JavanMoghadam, Sonia; Weihua, Zhang; Hunt, Kelly K; Keyomarsi, Khandan

    2016-06-17

    Estrogen receptor alpha (ERα) has been implicated in several cell cycle regulatory events and is an important predictive marker of disease outcome in breast cancer patients. Here, we aimed to elucidate the mechanism through which ERα influences proliferation in breast cancer cells. Our results show that ERα protein is cell cycle-regulated in human breast cancer cells and that the presence of 17-β-estradiol (E2) in the culture medium shortened the cell cycle significantly (by 4.5 hours, P < 0.05) compared with unliganded conditions. The alterations in cell cycle duration were observed in the S and G2/M phases, whereas the G1 phase was indistinguishable under liganded and unliganded conditions. In addition, ERα knockdown in MCF-7 cells accelerated mitotic exit, whereas transfection of ERα-negative MDA-MB-231 cells with exogenous ERα significantly shortened the S and G2/M phases (by 9.1 hours, P < 0.05) compared with parental cells. Finally, treatment of MCF-7 cells with antiestrogens revealed that tamoxifen yields a slower cell cycle progression through the S and G2/M phases than fulvestrant does, presumably because of the destabilizing effect of fulvestrant on ERα protein. Together, these results show that ERα modulates breast cancer cell proliferation by regulating events during the S and G2/M phases of the cell cycle in a ligand-dependent fashion. These results provide the rationale for an effective treatment strategy that includes a cell cycle inhibitor in combination with a drug that lowers estrogen levels, such as an aromatase inhibitor, and an antiestrogen that does not result in the degradation of ERα, such as tamoxifen.

  15. Intercellular Coupling of the Cell Cycle and Circadian Clock in Adult Stem Cell Culture.

    PubMed

    Matsu-Ura, Toru; Dovzhenok, Andrey; Aihara, Eitaro; Rood, Jill; Le, Hung; Ren, Yan; Rosselot, Andrew E; Zhang, Tongli; Lee, Choogon; Obrietan, Karl; Montrose, Marshall H; Lim, Sookkyung; Moore, Sean R; Hong, Christian I

    2016-12-01

    Circadian clock-gated cell division cycles are observed from cyanobacteria to mammals via intracellular molecular connections between these two oscillators. Here we demonstrate WNT-mediated intercellular coupling between the cell cycle and circadian clock in 3D murine intestinal organoids (enteroids). The circadian clock gates a population of cells with heterogeneous cell-cycle times that emerge as 12-hr synchronized cell division cycles. Remarkably, we observe reduced-amplitude oscillations of circadian rhythms in intestinal stem cells and progenitor cells, indicating an intercellular signal arising from differentiated cells governing circadian clock-dependent synchronized cell division cycles. Stochastic simulations and experimental validations reveal Paneth cell-secreted WNT as the key intercellular coupling component linking the circadian clock and cell cycle in enteroids.

  16. Interaction of the Circadian Cycle with the Cell Cycle in Pyrocystis fusiformis.

    PubMed

    Sweeney, B M

    1982-07-01

    Dividing pairs or single cells of the large dinoflagellate, Pyrocystis fusiformis Murray, were isolated in capillary tubes and their morphology was observed over a number of days, either in a light-dark cycle or in constant darkness. Morphological stages were correlated with the first growth stage, G(1), DNA synthesis, S, the second growth stage, G(2), mitosis, M, and cytokinesis, C, segments of the cell division cycle. The S phase was identified by measuring the nuclear DNA content of cells of different morphologies by the fluorescence of 4', 6-diamidino-2-phenylindole dichloride.Cells changed from one morphological stage to the next only during the night phase of the circadian cycle, both under light-dark conditions and in continuous darkness. Cells in all segments of the cell division cycle displayed a circadian rhythm in bioluminescence. These findings are incompatible with a mechanism for circadian oscillations that invokes cycling in G(q), an hypothesized side loop from G(1). All morphological stages, not only division, appear to be phased by the circadian clock.

  17. Interaction of the Circadian Cycle with the Cell Cycle in Pyrocystis fusiformis12

    PubMed Central

    Sweeney, Beatrice M.

    1982-01-01

    Dividing pairs or single cells of the large dinoflagellate, Pyrocystis fusiformis Murray, were isolated in capillary tubes and their morphology was observed over a number of days, either in a light-dark cycle or in constant darkness. Morphological stages were correlated with the first growth stage, G1, DNA synthesis, S, the second growth stage, G2, mitosis, M, and cytokinesis, C, segments of the cell division cycle. The S phase was identified by measuring the nuclear DNA content of cells of different morphologies by the fluorescence of 4′, 6-diamidino-2-phenylindole dichloride. Cells changed from one morphological stage to the next only during the night phase of the circadian cycle, both under light-dark conditions and in continuous darkness. Cells in all segments of the cell division cycle displayed a circadian rhythm in bioluminescence. These findings are incompatible with a mechanism for circadian oscillations that invokes cycling in Gq, an hypothesized side loop from G1. All morphological stages, not only division, appear to be phased by the circadian clock. PMID:16662459

  18. Apicomplexan cell cycle flexibility: centrosome controls the clutch

    PubMed Central

    Chen, Chun-Ti; Gubbels, Marc-Jan

    2015-01-01

    The centrosome serves as a central hub coordinating multiple cellular events in eukaryotes. A recent study in Toxoplasma gondii revealed a unique bipartite structure of the centrosome, which coordinates the nuclear cycle (S-phase and mitosis) and budding cycle (cytokinesis) of the parasite, and deciphers the principle behind flexible apicomplexan cell division modes. PMID:25899747

  19. Regulation of the Chlamydomonas cell cycle by light and dark

    PubMed Central

    1980-01-01

    By growing cells in alternating periods of light and darkness, we have found that the synchronization of phototrophically grown Chlamydomonas populations is regulated at two specific points in the cell cycle: the primary arrest (A) point, located in early G1, and the transition (T) point, located in mid-G1. At the A point, cell cycle progression becomes light dependent. At the T point, completion of the cycle becomes independent of light. Cells transferred from light to dark at cell cycle position between the two regulatory points enter a reversible resting state in which they remain viable and metabolically active, but do not progress through their cycles. The photosystem II inhibitor dichlorophenyldimethylurea (DCMU) mimics the A point block induced by darkness. This finding indicates that the A point block is mediated by a signal that operates through photosynthetic electron transport. Cells short of the T point will arrest in darkness although they contain considerable carbohydrate reserves. After the T point, a sharp increase occurs in starch degradation and in the endogenous respiration rate, indicating that some internal block to the availability of stored energy reserves has now been released, permitting cell cycle progression. PMID:6767730

  20. Phosphorylation network dynamics in the control of cell cycle transitions.

    PubMed

    Fisher, Daniel; Krasinska, Liliana; Coudreuse, Damien; Novák, Béla

    2012-10-15

    Fifteen years ago, it was proposed that the cell cycle in fission yeast can be driven by quantitative changes in the activity of a single protein kinase complex comprising a cyclin - namely cyclin B - and cyclin dependent kinase 1 (Cdk1). When its activity is low, Cdk1 triggers the onset of S phase; when its activity level exceeds a specific threshold, it promotes entry into mitosis. This model has redefined our understanding of the essential functional inputs that organize cell cycle progression, and its main principles now appear to be applicable to all eukaryotic cells. But how does a change in the activity of one kinase generate ordered progression through the cell cycle in order to separate DNA replication from mitosis? To answer this question, we must consider the biochemical processes that underlie the phosphorylation of Cdk1 substrates. In this Commentary, we discuss recent findings that have shed light on how the threshold levels of Cdk1 activity that are required for progression through each phase are determined, how an increase in Cdk activity generates directionality in the cell cycle, and why cell cycle transitions are abrupt rather than gradual. These considerations lead to a general quantitative model of cell cycle control, in which opposing kinase and phosphatase activities have an essential role in ensuring dynamic transitions.

  1. Effects of HMGB-1 Overexpression on Cell-Cycle Progression in MCF-7 Cells

    PubMed Central

    Yoon, Sarah; Lee, Jin Young; Yoon, Byung-Koo; Bae, DukSoo

    2004-01-01

    High mobility group-1 (HMGB-1) enhances the DNA interactions and possesses a transcriptional activation potential for several families of sequence-specific transcriptional activators. In order to examine the effect of HMGB-1 on the cell cycle progression in MCF-7 cells, the HMGB-1 expression vector was transfected into synchronized MCF-7 cells, and the effect of HMGB-1 overexpression on the cell cycle was examined. The HMGB-1 protein level in the transfected cells increased 4.87-fold compared to the non-transfected cells. There were few changes in the cell cycle phase distribution after HMGB-1 overexpression in the MCF-7 cells. Following the estrogen treatment, the cell cycle progressed in both the HMGB-1 overexpressed MCF-7 and the mock-treated cells. However, a larger proportion of HMGB-1 overexpressing MCF-7 cells progressed to the either S or G2 phase than the mock-treated cells. The mRNA levels of the cell cycle regulators changed after being treated with estrogen in both the HMGB-1 overexpressing MCF-7 and the mock-treated cells, but the changes in the expression level of the cell cycle regulator genes were more prominent in the HMGB-1 overexpressing MCF-7 cells than in the mock-treated cells. In conclusion, HMGB-1 overexpression itself does not alter the MCF-7 cell cycle progression, but the addition of estrogen to the HMGB-1 overexpressing MCF-7 cells appears to accelerate the cell cycle progression. PMID:15201494

  2. Mathematical model of the cell division cycle of fission yeast

    NASA Astrophysics Data System (ADS)

    Novak, Bela; Pataki, Zsuzsa; Ciliberto, Andrea; Tyson, John J.

    2001-03-01

    Much is known about the genes and proteins controlling the cell cycle of fission yeast. Can these molecular components be spun together into a consistent mechanism that accounts for the observed behavior of growth and division in fission yeast cells? To answer this question, we propose a mechanism for the control system, convert it into a set of 14 differential and algebraic equations, study these equations by numerical simulation and bifurcation theory, and compare our results to the physiology of wild-type and mutant cells. In wild-type cells, progress through the cell cycle (G1→S→G2→M) is related to cyclic progression around a hysteresis loop, driven by cell growth and chromosome alignment on the metaphase plate. However, the control system operates much differently in double-mutant cells, wee1- cdc25Δ, which are defective in progress through the latter half of the cell cycle (G2 and M phases). These cells exhibit "quantized" cycles (interdivision times clustering around 90, 160, and 230 min). We show that these quantized cycles are associated with a supercritical Hopf bifurcation in the mechanism, when the wee1 and cdc25 genes are disabled.

  3. Cell-cycle involvement in autophagy and apoptosis in yeast.

    PubMed

    Azzopardi, Maria; Farrugia, Gianluca; Balzan, Rena

    2017-01-01

    Regulation of the cell cycle and apoptosis are two eukaryotic processes required to ensure maintenance of genomic integrity, especially in response to DNA damage. The ease with which yeast, amongst other eukaryotes, can switch from cellular proliferation to cell death may be the result of a common set of biochemical factors which play dual roles depending on the cell's physiological state. A wide variety of homologues are shared between different yeasts and metazoans and this conservation confirms their importance. This review gives an overview of key molecular players involved in yeast cell-cycle regulation, and those involved in mechanisms which are induced by cell-cycle dysregulation. One such mechanism is autophagy which, depending on the severity and type of DNA damage, may either contribute to the cell's survival or death. Cell-cycle dysregulation due to checkpoint deficiency leads to mitotic catastrophe which in turn leads to programmed cell death. Molecular players implicated in the yeast apoptotic pathway were shown to play important roles in the cell cycle. These include the metacaspase Yca1p, the caspase-like protein Esp1p, the cohesin subunit Mcd1p, as well as the inhibitor of apoptosis protein Bir1p. The roles of these molecular players are discussed. Copyright © 2016 The Author(s). Published by Elsevier B.V. All rights reserved.

  4. Genome-wide examination of myoblast cell cycle withdrawal duringdifferentiation

    SciTech Connect

    Shen, Xun; Collier, John Michael; Hlaing, Myint; Zhang, Leanne; Delshad, Elizabeth H.; Bristow, James; Bernstein, Harold S.

    2002-12-02

    Skeletal and cardiac myocytes cease division within weeks of birth. Although skeletal muscle retains limited capacity for regeneration through recruitment of satellite cells, resident populations of adult myocardial stem cells have not been identified. Because cell cycle withdrawal accompanies myocyte differentiation, we hypothesized that C2C12 cells, a mouse myoblast cell line previously used to characterize myocyte differentiation, also would provide a model for studying cell cycle withdrawal during differentiation. C2C12 cells were differentiated in culture medium containing horse serum and harvested at various time points to characterize the expression profiles of known cell cycle and myogenic regulatory factors by immunoblot analysis. BrdU incorporation decreased dramatically in confluent cultures 48 hr after addition of horse serum, as cells started to form myotubes. This finding was preceded by up-regulation of MyoD, followed by myogenin, and activation of Bcl-2. Cyclin D1 was expressed in proliferating cultures and became undetectable in cultures containing 40 percent fused myotubes, as levels of p21(WAF1/Cip1) increased and alpha-actin became detectable. Because C2C12 myoblasts withdraw from the cell cycle during myocyte differentiation following a course that recapitulates this process in vivo, we performed a genome-wide screen to identify other gene products involved in this process. Using microarrays containing approximately 10,000 minimally redundant mouse sequences that map to the UniGene database of the National Center for Biotechnology Information, we compared gene expression profiles between proliferating, differentiating, and differentiated C2C12 cells and verified candidate genes demonstrating differential expression by RT-PCR. Cluster analysis of differentially expressed genes revealed groups of gene products involved in cell cycle withdrawal, muscle differentiation, and apoptosis. In addition, we identified several genes, including DDAH2 and Ly

  5. Grow₂: the HIF system, energy homeostasis and the cell cycle.

    PubMed

    Moniz, Sónia; Biddlestone, John; Rocha, Sónia

    2014-05-01

    Cell cycle progression is an energy demanding process and requires fine-tuned metabolic regulation. Cells must overcome an energy restriction checkpoint before becoming committed to progress through the cell cycle. Aerobic organisms need oxygen for the metabolic conversion of nutrients into energy. As such, environmental oxygen is a critical signalling molecule regulating cell fate. The Hypoxia Inducible Factors (HIFs) are a family of transcription factors that respond to changes in environmental oxygen and cell energy and coordinate a transcriptional program which forms an important part of the cellular response to a hostile environment. A significant proportion of HIF-dependent transcriptional target genes, code for proteins that are involved in energy homeostasis. In this review we discuss the role of the HIF system in the regulation of energy homeostasis in response to changes in environmental oxygen and the impact on cell cycle control, and address the implications of the deregulation of this effect in cancer.

  6. Large scale spontaneous synchronization of cell cycles in amoebae

    NASA Astrophysics Data System (ADS)

    Segota, Igor; Boulet, Laurent; Franck, Carl

    2014-03-01

    Unicellular eukaryotic amoebae Dictyostelium discoideum are generally believed to grow in their vegetative state as single cells until starvation, when their collective aspect emerges and they differentiate to form a multicellular slime mold. While major efforts continue to be aimed at their starvation-induced social aspect, our understanding of population dynamics and cell cycle in the vegetative growth phase has remained incomplete. We show that substrate-growtn cell populations spontaneously synchronize their cell cycles within several hours. These collective population-wide cell cycle oscillations span millimeter length scales and can be completely suppressed by washing away putative cell-secreted signals, implying signaling by means of a diffusible growth factor or mitogen. These observations give strong evidence for collective proliferation behavior in the vegetative state and provide opportunities for synchronization theories beyond classic Kuramoto models.

  7. Variety in intracellular diffusion during the cell cycle

    NASA Astrophysics Data System (ADS)

    Selhuber-Unkel, Christine; Yde, Pernille; Berg-Sørensen, Kirstine; Oddershede, Lene B.

    2009-06-01

    During the cell cycle, the organization of the cytoskeletal network undergoes dramatic changes. In order to reveal possible changes of the viscoelastic properties in the intracellular space during the cell cycle we investigated the diffusion of endogenous lipid granules within the fission yeast Schizosaccharomyces Pombe using optical tweezers. The cell cycle was divided into interphase and mitotic cell division, and the mitotic cell division was further subdivided in its stages. During all stages of the cell cycle, the granules predominantly underwent subdiffusive motion, characterized by an exponent α that is also linked to the viscoelastic moduli of the cytoplasm. The exponent α was significantly smaller during interphase than during any stage of the mitotic cell division, signifying that the cytoplasm was more elastic during interphase than during division. We found no significant differences in the subdiffusive exponents from granules measured in different stages of cell division. Also, our results for the exponent displayed no significant dependence on the position of the granule within the cell. The observation that the cytoplasm is more elastic during interphase than during mitotic cell division is consistent with the fact that elastic cytoskeletal elements such as microtubules are less abundantly present during cell division than during interphase.

  8. Variety in intracellular diffusion during the cell cycle.

    PubMed

    Selhuber-Unkel, Christine; Yde, Pernille; Berg-Sørensen, Kirstine; Oddershede, Lene B

    2009-07-01

    During the cell cycle, the organization of the cytoskeletal network undergoes dramatic changes. In order to reveal possible changes of the viscoelastic properties in the intracellular space during the cell cycle we investigated the diffusion of endogenous lipid granules within the fission yeast Schizosaccharomyces Pombe using optical tweezers. The cell cycle was divided into interphase and mitotic cell division, and the mitotic cell division was further subdivided in its stages. During all stages of the cell cycle, the granules predominantly underwent subdiffusive motion, characterized by an exponent alpha that is also linked to the viscoelastic moduli of the cytoplasm. The exponent alpha was significantly smaller during interphase than during any stage of the mitotic cell division, signifying that the cytoplasm was more elastic during interphase than during division. We found no significant differences in the subdiffusive exponents from granules measured in different stages of cell division. Also, our results for the exponent displayed no significant dependence on the position of the granule within the cell. The observation that the cytoplasm is more elastic during interphase than during mitotic cell division is consistent with the fact that elastic cytoskeletal elements such as microtubules are less abundantly present during cell division than during interphase.

  9. Thermally regenerative hydrogen/oxygen fuel cell power cycles

    NASA Astrophysics Data System (ADS)

    Morehouse, J. H.

    1986-07-01

    Two innovative thermodynamic power cycles are analytically examined for future engineering feasibility. The power cycles use a hydrogen-oxygen fuel cell for electrical energy production and use the thermal dissociation of water for regeneration of the hydrogen and oxygen. The TDS (thermal dissociation system) uses a thermal energy input at over 2000 K to thermally dissociate the water. The other cycle, the HTE (high temperature electrolyzer) system, dissociates the water using an electrolyzer operating at high temperature (1300 K) which receives its electrical energy from the fuel cell. The primary advantages of these cycles is that they are basically a no moving parts system, thus having the potential for long life and high reliability, and they have the potential for high thermal efficiency. Both cycles are shown to be classical heat engines with ideal efficiency close to Carnot cycle efficiency. The feasibility of constructing actual cycles is investigated by examining process irreversibilities and device efficiencies for the two types of cycles. The results show that while the processes and devices of the 2000 K TDS exceed current technology limits, the high temperature electrolyzer system appears to be a state-of-the-art technology development. The requirements for very high electrolyzer and fuel cell efficiencies are seen as determining the feasbility of the HTE system, and these high efficiency devices are currently being developed. It is concluded that a proof-of-concept HTE system experiment can and should be conducted.

  10. Thermally regenerative hydrogen/oxygen fuel cell power cycles

    NASA Technical Reports Server (NTRS)

    Morehouse, J. H.

    1986-01-01

    Two innovative thermodynamic power cycles are analytically examined for future engineering feasibility. The power cycles use a hydrogen-oxygen fuel cell for electrical energy production and use the thermal dissociation of water for regeneration of the hydrogen and oxygen. The TDS (thermal dissociation system) uses a thermal energy input at over 2000 K to thermally dissociate the water. The other cycle, the HTE (high temperature electrolyzer) system, dissociates the water using an electrolyzer operating at high temperature (1300 K) which receives its electrical energy from the fuel cell. The primary advantages of these cycles is that they are basically a no moving parts system, thus having the potential for long life and high reliability, and they have the potential for high thermal efficiency. Both cycles are shown to be classical heat engines with ideal efficiency close to Carnot cycle efficiency. The feasibility of constructing actual cycles is investigated by examining process irreversibilities and device efficiencies for the two types of cycles. The results show that while the processes and devices of the 2000 K TDS exceed current technology limits, the high temperature electrolyzer system appears to be a state-of-the-art technology development. The requirements for very high electrolyzer and fuel cell efficiencies are seen as determining the feasbility of the HTE system, and these high efficiency devices are currently being developed. It is concluded that a proof-of-concept HTE system experiment can and should be conducted.

  11. Keith's MAGIC: Cloning and the Cell Cycle.

    PubMed

    Wells, D N

    2013-10-01

    Abstract Professor Keith Campbell's critical contribution to the discovery that a somatic cell from an adult animal can be fully reprogrammed by oocyte factors to form a cloned individual following nuclear transfer (NT)(Wilmut et al., 1997 ) overturned a dogma concerning the reversibility of cell fate that many scientists had considered to be biologically impossible. This seminal experiment proved the totipotency of adult somatic nuclei and finally confirmed that adult cells could differentiate without irreversible changes to the genetic material.

  12. Duplication of the genome in normal and cancer cell cycles.

    PubMed

    Bandura, Jennifer L; Calvi, Brian R

    2002-01-01

    It is critical to discover the mechanisms of normal cell cycle regulation if we are to fully understand what goes awry in cancer cells. The normal eukaryotic cell tightly regulates the activity of origins of DNA replication so that the genome is duplicated exactly once per cell cycle. Over the last ten years much has been learned concerning the cell cycle regulation of origin activity. It is now clear that the proteins and cell cycle mechanisms that control origin activity are largely conserved from yeast to humans. Despite this conservation, the composition of origins of DNA replication in higher eukaryotes remains ill defined. A DNA consensus for predicting origins has yet to emerge, and it is of some debate whether primary DNA sequence determines where replication initiates. In this review we outline what is known about origin structure and the mechanism of once per cell cycle DNA replication with an emphasis on recent advances in mammalian cells. We discuss the possible relevance of these regulatory pathways for cancer biology and therapy.

  13. Cell cycle deregulation by methyl isocyanate: Implications in liver carcinogenesis.

    PubMed

    Panwar, Hariom; Raghuram, Gorantla V; Jain, Deepika; Ahirwar, Alok K; Khan, Saba; Jain, Subodh K; Pathak, Neelam; Banerjee, Smita; Maudar, Kewal K; Mishra, Pradyumna K

    2014-03-01

    Liver is often exposed to plethora of chemical toxins. Owing to its profound physiological role and central function in metabolism and homeostasis, pertinent succession of cell cycle in liver epithelial cells is of prime importance to maintain cellular proliferation. Although recent evidence has displayed a strong association between exposures to methyl isocyanate (MIC), one of the most toxic isocyanates, and neoplastic transformation, molecular characterization of the longitudinal effects of MIC on cell cycle regulation has never been performed. Here, we sequentially delineated the status of different proteins arbitrating the deregulation of cell cycle in liver epithelial cells treated with MIC. Our data reaffirms the oncogenic capability of MIC with elevated DNA damage response proteins pATM and γ-H2AX, deregulation of DNA damage check point genes CHK1 and CHK2, altered expression of p53 and p21 proteins involved in cell cycle arrest with perturbation in GADD-45 expression in the treated cells. Further, alterations in cyclin A, cyclin E, CDK2 levels along with overexpression of mitotic spindle checkpoints proteins Aurora A/B, centrosomal pericentrin protein, chromosomal aberrations, and loss of Pot1a was observed. Thus, MIC impacts key proteins involved in cell cycle regulation to trigger genomic instability as a possible mechanism of developmental basis of liver carcinogenesis.

  14. Combined cycle phosphoric acid fuel cell electric power system

    SciTech Connect

    Mollot, D.J.; Micheli, P.L.

    1995-12-31

    By arranging two or more electric power generation cycles in series, combined cycle systems are able to produce electric power more efficiently than conventional single cycle plants. The high fuel to electricity conversion efficiency results in lower plant operating costs, better environmental performance, and in some cases even lower capital costs. Despite these advantages, combined cycle systems for the 1 - 10 megawatt (MW) industrial market are rare. This paper presents a low noise, low (oxides of nitrogen) NOx, combined cycle alternative for the small industrial user. By combining a commercially available phosphoric acid fuel cell (PAFC) with a low-temperature Rankine cycle (similar to those used in geothermal applications), electric conversion efficiencies between 45 and 47 percent are predicted. While the simple cycle PAFC is competitive on a cost of energy basis with gas turbines and diesel generators in the 1 to 2 MW market, the combined cycle PAFC is competitive, on a cost of energy basis, with simple cycle diesel generators in the 4 to 25 MW market. In addition, the efficiency and low-temperature operation of the combined cycle PAFC results in a significant reduction in carbon dioxide emissions with NO{sub x} concentration on the order of 1 parts per million (per weight) (ppmw).

  15. Global Dynamical Properties of the Yeast Cell Cycle Network

    NASA Astrophysics Data System (ADS)

    Tang, Chao

    2004-03-01

    The interactions between proteins, DNA, and RNA in living cells constitute molecular networks that govern various cellular functions. To investigate the global dynamical properties and stabilities of such networks, we studied the network regulating the cell division (cell cycle) of the budding yeast. With the use of both discrete (Boolean) and continuous (ODEs) dynamical models, it was demonstrated that the cell-cycle network is extremely stable and robust for its function. The biological stationary state--the G1 state--is a global attractor of the dynamics. The biological pathway--the cell-cycle sequence of protein states--is a globally attracting trajectory of the dynamics. These properties are largely preserved with respect to small perturbations to the network. These results suggest that cellular regulatory networks are robustly designed for their functions.

  16. The Timing of T Cell Priming and Cycling

    PubMed Central

    Obst, Reinhard

    2015-01-01

    The proliferation of specific lymphocytes is the central tenet of the clonal selection paradigm. Antigen recognition by T cells triggers a series of events that produces expanded clones of differentiated effector cells. TCR signaling events are detectable within seconds and minutes and are likely to continue for hours and days in vivo. Here, I review the work done on the importance of TCR signals in the later part of the expansion phase of the primary T cell response, primarily regarding the regulation of the cell cycle in CD4+ and CD8+ cells. The results suggest a degree of programing by early signals for effector differentiation, particularly in the CD8+ T cell compartment, with optimal expansion supported by persistent antigen presentation later on. Differences to CD4+ T cell expansion and new avenues toward a molecular understanding of cell cycle regulation in lymphocytes are discussed. PMID:26594213

  17. NONO couples the circadian clock to the cell cycle.

    PubMed

    Kowalska, Elzbieta; Ripperger, Juergen A; Hoegger, Dominik C; Bruegger, Pascal; Buch, Thorsten; Birchler, Thomas; Mueller, Anke; Albrecht, Urs; Contaldo, Claudio; Brown, Steven A

    2013-01-29

    Mammalian circadian clocks restrict cell proliferation to defined time windows, but the mechanism and consequences of this interrelationship are not fully understood. Previously we identified the multifunctional nuclear protein NONO as a partner of circadian PERIOD (PER) proteins. Here we show that it also conveys circadian gating to the cell cycle, a connection surprisingly important for wound healing in mice. Specifically, although fibroblasts from NONO-deficient mice showed approximately normal circadian cycles, they displayed elevated cell doubling and lower cellular senescence. At a molecular level, NONO bound to the p16-Ink4A cell cycle checkpoint gene and potentiated its circadian activation in a PER protein-dependent fashion. Loss of either NONO or PER abolished this activation and circadian expression of p16-Ink4A and eliminated circadian cell cycle gating. In vivo, lack of NONO resulted in defective wound repair. Because wound healing defects were also seen in multiple circadian clock-deficient mouse lines, our results therefore suggest that coupling of the cell cycle to the circadian clock via NONO may be useful to segregate in temporal fashion cell proliferation from tissue organization.

  18. NONO couples the circadian clock to the cell cycle

    PubMed Central

    Kowalska, Elzbieta; Ripperger, Juergen A.; Hoegger, Dominik C.; Bruegger, Pascal; Buch, Thorsten; Birchler, Thomas; Mueller, Anke; Albrecht, Urs; Contaldo, Claudio; Brown, Steven A.

    2013-01-01

    Mammalian circadian clocks restrict cell proliferation to defined time windows, but the mechanism and consequences of this interrelationship are not fully understood. Previously we identified the multifunctional nuclear protein NONO as a partner of circadian PERIOD (PER) proteins. Here we show that it also conveys circadian gating to the cell cycle, a connection surprisingly important for wound healing in mice. Specifically, although fibroblasts from NONO-deficient mice showed approximately normal circadian cycles, they displayed elevated cell doubling and lower cellular senescence. At a molecular level, NONO bound to the p16-Ink4A cell cycle checkpoint gene and potentiated its circadian activation in a PER protein-dependent fashion. Loss of either NONO or PER abolished this activation and circadian expression of p16-Ink4A and eliminated circadian cell cycle gating. In vivo, lack of NONO resulted in defective wound repair. Because wound healing defects were also seen in multiple circadian clock-deficient mouse lines, our results therefore suggest that coupling of the cell cycle to the circadian clock via NONO may be useful to segregate in temporal fashion cell proliferation from tissue organization. PMID:23267082

  19. Post-transcriptional RNA Regulons Affecting Cell Cycle and Proliferation

    PubMed Central

    Blackinton, Jeff G.

    2014-01-01

    The cellular growth cycle is initiated and maintained by punctual, yet agile, regulatory events involving modifications of cell cycle proteins as well as coordinated gene expression to support cyclic checkpoint decisions. Recent evidence indicates that post-transcriptional partitioning of messenger RNA subsets by RNA-binding proteins help physically localize, temporally coordinate, and efficiently translate cell cycle proteins. This dynamic organization of mRNAs encoding cell cycle components contributes to the overall economy of the cell cycle consistent with the post-transcriptional RNA regulon model of gene expression. This review examines several recent studies demonstrating the coordination of mRNA subsets encoding cell cycle proteins during nuclear export and subsequent coupling to protein synthesis, and discusses evidence for mRNA coordination of p53 targets and the DNA damage response pathway. We consider how these observations may connect to upstream and downstream post-transcriptional coordination and coupling of splicing, export, localization, and translation. Published examples from yeast, nematode, insect, and mammalian systems are discussed, and we consider genetic evidence supporting the conclusion that dysregulation of RNA regulons may promote pathogenic states of growth such as carcinogenesis. PMID:24882724

  20. Bax alpha perturbs T cell development and affects cell cycle entry of T cells.

    PubMed Central

    Brady, H J; Gil-Gómez, G; Kirberg, J; Berns, A J

    1996-01-01

    Bax alpha can heterodimerize with Bcl-2 and Bcl-X(L), countering their effects, as well as promoting apoptosis on overexpression. We show that bax alpha transgenic mice have greatly reduced numbers of mature T cells, which results from an impaired positive selection in the thymus. This perturbation in positive selection is accompanied by an increase in the number of cycling thymocytes. Further to this, mature T cells overexpressing Bax alpha have lower levels of p27Kip1 and enter S phase more rapidly in response to interleukin-2 stimulation than do control T cells, while the converse is true of bcl-2 transgenic T cells. These data indicate that apoptotic regulatory proteins can modulate the level of cell cycle-controlling proteins and thereby directly impact on the cell cycle. Images PMID:9003775

  1. The Dynamical Mechanisms of the Cell Cycle Size Checkpoint

    NASA Astrophysics Data System (ADS)

    Feng, Shi-Fu; Yan, Jie; Liu, Zeng-Rong; Yang, Ling

    2012-10-01

    Cell division must be tightly coupled to cell growth in order to maintain cell size, whereas the mechanisms of how initialization of mitosis is regulated by cell size remain to be elucidated. We develop a mathematical model of the cell cycle, which incorporates cell growth to investigate the dynamical properties of the size checkpoint in embryos of Xenopus laevis. We show that the size checkpoint is naturally raised from a saddle-node bifurcation, and in a mutant case, the cell loses its size control ability due to the loss of this saddle-node point.

  2. Creatine kinase in cell cycle regulation and cancer.

    PubMed

    Yan, Yong-Bin

    2016-08-01

    The phosphocreatine-creatine kinase (CK) shuttle system is increasingly recognized as a fundamental mechanism for ATP homeostasis in both excitable and non-excitable cells. Many intracellular processes are ATP dependent. Cell division is a process requiring a rapid rate of energy turnover. Cell cycle regulation is also a key point to understanding the mechanisms underlying cancer progression. It has been known for about 40 years that aberrant CK levels are associated with various cancers and for over 30 years that CK is involved in mitosis regulation. However, the underlying molecular mechanisms have not been investigated sufficiently until recently. By maintaining ATP at sites of high-energy demand, CK can regulate cell cycle progression by affecting the intracellular energy status as well as by influencing signaling pathways that are essential to activate cell division and cytoskeleton reorganization. Aberrant CK levels may impair cell viability under normal or stressed conditions and induce cell death. The involvement of CK in cell cycle regulation and cellular energy metabolism makes it a potential diagnostic biomarker and therapeutic target in cancer. To understand the multiple physiological/pathological functions of CK, it is necessary to identify CK-binding partners and regulators including proteins, non-coding RNAs and participating endogenous small molecular weight chemical compounds. This review will focus on molecular mechanisms of CK in cell cycle regulation and cancer progression. It will also discuss the implications of recent mechanistic studies, the emerging problems and future challenges of the multifunctional enzyme CK.

  3. Nanosecond pulsed electric fields and the cell cycle

    NASA Astrophysics Data System (ADS)

    Mahlke, Megan A.

    Exposure to nanosecond pulsed electrical fields (nsPEFs) can cause poration of external and internal cell membranes, DNA damage, and disassociation of cytoskeletal components, all of which are capable of disrupting a cell's ability to replicate. The phase of the cell cycle at the time of exposure is linked to differential sensitivities to nsPEFs across cell lines, as DNA structure, membrane elasticity, and cytoskeletal structure change dramatically during the cell cycle. Additionally, nsPEFs are capable of activating cell cycle checkpoints, which could lead to apoptosis or slow population growth. NsPEFs are emerging as a method for treating tumors via apoptotic induction; therefore, investigating the relevance of nsPEFs and the cell cycle could translate into improved efficacy in tumor treatment. Populations of Jurkat and Chinese Hamster Ovary (CHO) cells were examined post-exposure (10 ns pulse trains at 150kV/cm) by analysis of DNA content via propidium iodide staining and flow cytometric analysis at various time points (1, 6, and 12h post-exposure) to determine population distribution in cell cycle phases. Additionally, CHO and Jurkat cells were synchronized in G1/S and G2/M phases, pulsed, and analyzed to evaluate the role of cell cycle phase in survival of nsPEFs. CHO populations appeared similar to sham populations post-nsPEFs but exhibited arrest in the G1 phase at 6h after exposure. Jurkat cells exhibited increased cell death after nsPEFs compared to CHO cells but did not exhibit checkpoint arrest at any observed time point. The G1/S phase checkpoint is partially controlled by the action of p53; the lack of an active p53 response in Jurkat cells could contribute to their ability to pass this checkpoint and resist cell cycle arrest. Both cell lines exhibited increased sensitivity to nsPEFs in G2/M phase. Live imaging of CHO cells after nsPEF exposure supports the theory of G1/S phase arrest, as a reduced number of cells undergo mitosis within 24 h when

  4. Cell cycles and proliferation patterns in Haematococcus pluvialis

    NASA Astrophysics Data System (ADS)

    Zhang, Chunhui; Liu, Jianguo; Zhang, Litao

    2016-09-01

    Most studies on Haematococcus pluvialis have been focused on cell growth and astaxanthin accumulation; far less attention has been paid to cell cycles and proliferation patterns. The purpose of this study was to clarify cell cycles and proliferation patterns in H. pluvialis microscopically using a camera and video recorder system. The complicated life history of H. pluvialis can be divided into two stages: the motile stage and the non-motile stage. All the cells can be classified into forms as follows: motile cell, non-motile cell, zoospore and aplanospore. The main cell proliferation, both in the motile phase and non-motile phase in H. pluvialis, is by asexual reproduction. Under normal growth conditions, a motile cell usually produces two, sometimes four, and exceptionally eight zoospores. Under unfavorable conditions, the motile cell loses its flagella and transforms into a non-motile cell, and the non-motile cell usually produces 2, 4 or 8 aplanospores, and occasionally 20-32 aplanospores, which further develop into non-motile cells. Under suitable conditions, the non-motile cell is also able to release zoospores. The larger non-motile cells produce more than 16 zoospores, and the smaller ones produce 4 or 8 zoospores. Vegetative reproduction is by direct cell division in the motile phase and by occasional cell budding in the non-motile phase. There is, as yet, no convincing direct evidence for sexual reproduction.

  5. Cell cycles and proliferation patterns in Haematococcus pluvialis

    NASA Astrophysics Data System (ADS)

    Zhang, Chunhui; Liu, Jianguo; Zhang, Litao

    2017-09-01

    Most studies on Haematococcus pluvialis have been focused on cell growth and astaxanthin accumulation; far less attention has been paid to cell cycles and proliferation patterns. The purpose of this study was to clarify cell cycles and proliferation patterns in H. pluvialis microscopically using a camera and video recorder system. The complicated life history of H. pluvialis can be divided into two stages: the motile stage and the non-motile stage. All the cells can be classified into forms as follows: motile cell, nonmotile cell, zoospore and aplanospore. The main cell proliferation, both in the motile phase and non-motile phase in H. pluvialis, is by asexual reproduction. Under normal growth conditions, a motile cell usually produces two, sometimes four, and exceptionally eight zoospores. Under unfavorable conditions, the motile cell loses its flagella and transforms into a non-motile cell, and the non-motile cell usually produces 2, 4 or 8 aplanospores, and occasionally 20-32 aplanospores, which further develop into non-motile cells. Under suitable conditions, the non-motile cell is also able to release zoospores. The larger non-motile cells produce more than 16 zoospores, and the smaller ones produce 4 or 8 zoospores. Vegetative reproduction is by direct cell division in the motile phase and by occasional cell budding in the non-motile phase. There is, as yet, no convincing direct evidence for sexual reproduction.

  6. Cycle life characteristics of Li-TiS2 cells

    NASA Technical Reports Server (NTRS)

    Deligiannis, Frank; Shen, D.; Huang, C. K.; Surampudi, S.

    1991-01-01

    The development of lithium ambient temperature rechargeable cells is discussed. During the development process, we hope to gain a greater understanding of the materials and the properties of the Li-TiS2 cell and its components. The design will meet the requirements of 100 Wh/Kg and 1000 cycles, at 50 percent depth-of-discharge, by 1995.

  7. Regulation of the cell cycle and centrosome biology by deubiquitylases.

    PubMed

    Darling, Sarah; Fielding, Andrew B; Sabat-Pośpiech, Dorota; Prior, Ian A; Coulson, Judy M

    2017-09-12

    Post-translational modification of proteins by ubiquitylation is increasingly recognised as a highly complex code that contributes to the regulation of diverse cellular processes. In humans, a family of almost 100 deubiquitylase enzymes (DUBs) are assigned to six subfamilies and many of these DUBs can remove ubiquitin from proteins to reverse signals. Roles for individual DUBs have been delineated within specific cellular processes, including many that are dysregulated in diseases, particularly cancer. As potentially druggable enzymes, disease-associated DUBs are of increasing interest as pharmaceutical targets. The biology, structure and regulation of DUBs have been extensively reviewed elsewhere, so here we focus specifically on roles of DUBs in regulating cell cycle processes in mammalian cells. Over a quarter of all DUBs, representing four different families, have been shown to play roles either in the unidirectional progression of the cell cycle through specific checkpoints, or in the DNA damage response and repair pathways. We catalogue these roles and discuss specific examples. Centrosomes are the major microtubule nucleating centres within a cell and play a key role in forming the bipolar mitotic spindle required to accurately divide genetic material between daughter cells during cell division. To enable this mitotic role, centrosomes undergo a complex replication cycle that is intimately linked to the cell division cycle. Here, we also catalogue and discuss DUBs that have been linked to centrosome replication or function, including centrosome clustering, a mitotic survival strategy unique to cancer cells with supernumerary centrosomes. © 2017 The Author(s).

  8. Bridges between Cell Cycle Regulation and Self-Renewal Maintenance.

    PubMed

    Viatour, Patrick

    2012-11-01

    Stem cells are a unique population that lies at the summit of any, or at least most, biological systems. They can differentiate in a variety of mature cell types, but they also have the ability to self-renew, that is, the capacity to divide and retain all the features of the mother cell. The regulation of self-renewal has been studied for many years, but several aspects of this regulation are still vague. The combined decision to divide and self-renew or differentiate suggests that the mechanisms that regulate self-renewal and cell cycle activity are intermingled. While inactivation of many cell cycle regulators impacts the physiological and pathological biology of stem cells, the exact mechanisms that link the decision to enter the cell cycle and the choice of the cellular fate are poorly understood. The multiplicity of signals and pathways regulating self-renewal add to the complexity of the phenomenon. Here, I will review the described links between the cell cycle and self-renewal and discuss the role of the niche in the regulation of both mechanisms.

  9. Cycle life characteristics of Li-TiS2 cells

    NASA Technical Reports Server (NTRS)

    Deligiannis, Frank; Shen, D.; Huang, C. K.; Surampudi, S.

    1991-01-01

    The development of lithium ambient temperature rechargeable cells is discussed. During the development process, we hope to gain a greater understanding of the materials and the properties of the Li-TiS2 cell and its components. The design will meet the requirements of 100 Wh/Kg and 1000 cycles, at 50 percent depth-of-discharge, by 1995.

  10. Live Cell Imaging of the Schizosaccharomyces pombe Sexual Life Cycle.

    PubMed

    Merlini, Laura; Vjestica, Aleksandar; Dudin, Omaya; Bendezú, Felipe; Martin, Sophie G

    2017-07-21

    The fission yeast Schizosaccharomyces pombe is an invaluable model system for studying the principles that drive sexual differentiation and the meiotic cell division cycle. We describe a simple protocol for microscopic observation of the entire sexual life cycle that can be adapted to focus on specific stages of sexual differentiation. After growth to exponential phase in a nitrogen-rich medium, cell cultures are switched to a nitrogen-deprived medium until the population is enriched for the specific stage of the sexual lifecycle to be studied. Cells are then mounted in easily constructed customized agarose pad chambers for imaging. © 2017 Cold Spring Harbor Laboratory Press.

  11. Analyzing transcription dynamics during the budding yeast cell cycle.

    PubMed

    Leman, Adam R; Bristow, Sara L; Haase, Steven B

    2014-01-01

    Assaying global cell cycle-regulated transcription in budding yeast involves extracting RNA from a synchronous population and proper normalization of detected transcript levels. Here, we describe synchronization of Saccharomyces cerevisiae cell populations by centrifugal elutriation, followed by the isolation of RNA for microarray analysis. Further, we outline the computational methods required to directly compare RNA abundance from individual time points within an experiment and to compare independent experiments. Together, these methods describe the complete workflow necessary to observe RNA abundance during the cell cycle.

  12. The yeast cell-cycle network is robustly designed

    NASA Astrophysics Data System (ADS)

    Li, Fangting; Long, Tao; Lu, Ying; Ouyang, Qi; Tang, Chao

    2004-04-01

    The interactions between proteins, DNA, and RNA in living cells constitute molecular networks that govern various cellular functions. To investigate the global dynamical properties and stabilities of such networks, we studied the cell-cycle regulatory network of the budding yeast. With the use of a simple dynamical model, it was demonstrated that the cell-cycle network is extremely stable and robust for its function. The biological stationary state, the G1 state, is a global attractor of the dynamics. The biological pathway, the cell-cycle sequence of protein states, is a globally attracting trajectory of the dynamics. These properties are largely preserved with respect to small perturbations to the network. These results suggest that cellular regulatory networks are robustly designed for their functions.

  13. Cell cycling with the SEB: a personal view.

    PubMed

    Bryant, John

    2014-06-01

    This review, written from a personal perspective, traces firstly the development of plant cell cycle research from the 1970s onwards, with some focus on the work of the author and of Dr Dennis Francis. Secondly there is a discussion of the support for and discussion of plant cell cycle research in the SEB, especially through the activities of the Cell Cycle Group within the Society's Cell Biology Section. In the main part of the review, selected aspects of DNA replication that have of been of special interest to the author are discussed. These are DNA polymerases and associated proteins, pre-replication events, regulation of enzymes and other proteins, nature and activation of DNA replication origins, and DNA endoreduplication. For all these topics, there is mention of the author's own work, followed by a brief synthesis of current understanding and a look to possible future developments.

  14. Cdks, cyclins and CKIs: roles beyond cell cycle regulation.

    PubMed

    Lim, Shuhui; Kaldis, Philipp

    2013-08-01

    Cyclin-dependent kinases (Cdks) are serine/threonine kinases and their catalytic activities are modulated by interactions with cyclins and Cdk inhibitors (CKIs). Close cooperation between this trio is necessary for ensuring orderly progression through the cell cycle. In addition to their well-established function in cell cycle control, it is becoming increasingly apparent that mammalian Cdks, cyclins and CKIs play indispensable roles in processes such as transcription, epigenetic regulation, metabolism, stem cell self-renewal, neuronal functions and spermatogenesis. Even more remarkably, they can accomplish some of these tasks individually, without the need for Cdk/cyclin complex formation or kinase activity. In this Review, we discuss the latest revelations about Cdks, cyclins and CKIs with the goal of showcasing their functional diversity beyond cell cycle regulation and their impact on development and disease in mammals.

  15. Cyclin and DNA Distributed Cell Cycle Model for GS-NS0 Cells

    PubMed Central

    García Münzer, David G.; Kostoglou, Margaritis; Georgiadis, Michael C.; Pistikopoulos, Efstratios N.; Mantalaris, Athanasios

    2015-01-01

    Mammalian cell cultures are intrinsically heterogeneous at different scales (molecular to bioreactor). The cell cycle is at the centre of capturing heterogeneity since it plays a critical role in the growth, death, and productivity of mammalian cell cultures. Current cell cycle models use biological variables (mass/volume/age) that are non-mechanistic, and difficult to experimentally determine, to describe cell cycle transition and capture culture heterogeneity. To address this problem, cyclins—key molecules that regulate cell cycle transition—have been utilized. Herein, a novel integrated experimental-modelling platform is presented whereby experimental quantification of key cell cycle metrics (cell cycle timings, cell cycle fractions, and cyclin expression determined by flow cytometry) is used to develop a cyclin and DNA distributed model for the industrially relevant cell line, GS-NS0. Cyclins/DNA synthesis rates were linked to stimulatory/inhibitory factors in the culture medium, which ultimately affect cell growth. Cell antibody productivity was characterized using cell cycle-specific production rates. The solution method delivered fast computational time that renders the model’s use suitable for model-based applications. Model structure was studied by global sensitivity analysis (GSA), which identified parameters with a significant effect on the model output, followed by re-estimation of its significant parameters from a control set of batch experiments. A good model fit to the experimental data, both at the cell cycle and viable cell density levels, was observed. The cell population heterogeneity of disturbed (after cell arrest) and undisturbed cell growth was captured proving the versatility of the modelling approach. Cell cycle models able to capture population heterogeneity facilitate in depth understanding of these complex systems and enable systematic formulation of culture strategies to improve growth and productivity. It is envisaged that this

  16. Digital Holographic Microscopy for Non-Invasive Monitoring of Cell Cycle Arrest in L929 Cells

    PubMed Central

    Falck Miniotis, Maria; Mukwaya, Anthonny; Gjörloff Wingren, Anette

    2014-01-01

    Digital holographic microscopy (DHM) has emerged as a powerful non-invasive tool for cell analysis. It has the capacity to analyse multiple parameters simultaneously, such as cell- number, confluence and phase volume. This is done while cells are still adhered and growing in their culture flask. The aim of this study was to investigate whether DHM was able to monitor drug-induced cell cycle arrest in cultured cells and thus provide a non-disruptive alternative to flow cytometry. DHM parameters from G1 and G2/M cell cycle arrested L929 mouse fibroblast cells were collected. Cell cycle arrest was verified with flow cytometry. This study shows that DHM is able to monitor phase volume changes corresponding to either a G1 or G2/M cell cycle arrest. G1-phase arrest with staurosporine correlated with a decrease in the average cell phase volume and G2/M-phase arrest with colcemid and etoposide correlated with an increase in the average cell phase volume. Importantly, DHM analysis of average cell phase volume was of comparable accuracy to flow cytometric measurement of cell cycle phase distribution as recorded following dose-dependent treatment with etoposide. Average cell phase volume changes in response to treatment with cell cycle arresting compounds could therefore be used as a DHM marker for monitoring cell cycle arrest in cultured mammalian cells. PMID:25208094

  17. Cell cycle regulation by the bacterial nucleoid.

    PubMed

    Adams, David William; Wu, Ling Juan; Errington, Jeff

    2014-12-01

    Division site selection presents a fundamental challenge to all organisms. Bacterial cells are small and the chromosome (nucleoid) often fills most of the cell volume. Thus, in order to maximise fitness and avoid damaging the genetic material, cell division must be tightly co-ordinated with chromosome replication and segregation. To achieve this, bacteria employ a number of different mechanisms to regulate division site selection. One such mechanism, termed nucleoid occlusion, allows the nucleoid to protect itself by acting as a template for nucleoid occlusion factors, which prevent Z-ring assembly over the DNA. These factors are sequence-specific DNA-binding proteins that exploit the precise organisation of the nucleoid, allowing them to act as both spatial and temporal regulators of bacterial cell division. The identification of proteins responsible for this process has provided a molecular understanding of nucleoid occlusion but it has also prompted the realisation that substantial levels of redundancy exist between the diverse systems that bacteria employ to ensure that division occurs in the right place, at the right time.

  18. CIRCADIAN CLOCK AND CELL CYCLE GENE EXPRESSION

    PubMed Central

    Metz, Richard P.; Qu, Xiaoyu; Laffin, Brian; Earnest, David; Porter, Weston W.

    2009-01-01

    Mouse mammary epithelial cells (HC-11) and mammary tissues were analyzed for developmental changes in circadian clock, cellular proliferation and differentiation marker genes. Expression of the clock genes, Per1 and Bmal1, were elevated in differentiated HC-11 cells whereas Per2 mRNA levels were higher in undifferentiated cells. This differentiation-dependent profile of clock gene expression was consistent with that observed in mouse mammary glands as Per1 and Bmal1 mRNA levels were elevated in late pregnant and lactating mammary tissues, while Per2 expression was higher in proliferating virgin and early pregnant glands. In both HC-11 cells and mammary glands, elevated Per2 expression was positively correlated with c-Myc and Cyclin D1 mRNA levels while Per1 and Bmal1 expression changed in conjunction with ß-casein mRNA levels. Interestingly, developmental stage had differential effects on rhythms of clock gene expression in the mammary gland. These data suggest that circadian clock genes may play a role in mouse mammary gland development and differentiation. PMID:16261617

  19. Regulation of the cell division cycle in Trypanosoma brucei.

    PubMed

    Li, Ziyin

    2012-10-01

    The cell division cycle is tightly regulated by the activation and inactivation of a series of proteins that control the replication and segregation of organelles to the daughter cells. During the past decade, we have witnessed significant advances in our understanding of the cell cycle in Trypanosoma brucei and how the cycle is regulated by various regulatory proteins. However, many other regulators, especially those unique to trypanosomes, remain to be identified, and we are just beginning to delineate the signaling pathways that drive the transitions through different cell cycle stages, such as the G(1)/S transition, G(2)/M transition, and mitosis-cytokinesis transition. Trypanosomes appear to employ both evolutionarily conserved and trypanosome-specific molecules to regulate the various stages of its cell cycle, including DNA replication initiation, spindle assembly, chromosome segregation, and cytokinesis initiation and completion. Strikingly, trypanosomes lack some crucial regulators that are well conserved across evolution, such as Cdc6 and Cdt1, which are involved in DNA replication licensing, the spindle motor kinesin-5, which is required for spindle assembly, the central spindlin complex, which has been implicated in cytokinesis initiation, and the actomyosin contractile ring, which is located at the cleavage furrow. Conversely, trypanosomes possess certain regulators, such as cyclins, cyclin-dependent kinases, and mitotic centromere-associated kinesins, that are greatly expanded and likely play diverse cellular functions. Overall, trypanosomes apparently have integrated unique regulators into the evolutionarily conserved pathways to compensate for the absence of those conserved molecules and, additionally, have evolved certain cell cycle regulatory pathways that are either different from its human host or distinct between its own life cycle forms.

  20. Metformin inhibits cell cycle progression of B-cell chronic lymphocytic leukemia cells

    PubMed Central

    Bruno, Silvia; Ledda, Bernardetta; Tenca, Claudya; Ravera, Silvia; Orengo, Anna Maria; Mazzarello, Andrea Nicola; Pesenti, Elisa; Casciaro, Salvatore; Racchi, Omar; Ghiotto, Fabio; Marini, Cecilia; Sambuceti, Gianmario; DeCensi, Andrea; Fais, Franco

    2015-01-01

    B-cell chronic lymphocytic leukemia (CLL) was believed to result from clonal accumulation of resting apoptosis-resistant malignant B lymphocytes. However, it became increasingly clear that CLL cells undergo, during their life, iterative cycles of re-activation and subsequent clonal expansion. Drugs interfering with CLL cell cycle entry would be greatly beneficial in the treatment of this disease. 1, 1-Dimethylbiguanide hydrochloride (metformin), the most widely prescribed oral hypoglycemic agent, inexpensive and well tolerated, has recently received increased attention for its potential antitumor activity. We wondered whether metformin has apoptotic and anti-proliferative activity on leukemic cells derived from CLL patients. Metformin was administered in vitro either to quiescent cells or during CLL cell activation stimuli, provided by classical co-culturing with CD40L-expressing fibroblasts. At doses that were totally ineffective on normal lymphocytes, metformin induced apoptosis of quiescent CLL cells and inhibition of cell cycle entry when CLL were stimulated by CD40-CD40L ligation. This cytostatic effect was accompanied by decreased expression of survival- and proliferation-associated proteins, inhibition of signaling pathways involved in CLL disease progression and decreased intracellular glucose available for glycolysis. In drug combination experiments, metformin lowered the apoptotic threshold and potentiated the cytotoxic effects of classical and novel antitumor molecules. Our results indicate that, while CLL cells after stimulation are in the process of building their full survival and cycling armamentarium, the presence of metformin affects this process. PMID:26265439

  1. Alteration of Cell Cycle Mediated by Zinc in Human Bronchial ...

    EPA Pesticide Factsheets

    Zinc (Zn2+), a ubiquitous ambient air contaminant, presents an oxidant challenge to the human lung and is linked to adverse human health effects. To further elucidate the adaptive and apoptotic cellular responses of human airway cells to Zn2+, we performed pilot studies to examine cell cycle perturbation upon exposure using a normal human bronchial epithelial cell culture (BEAS-2B). BEAS-2B cells were treated with low (0, 1, 2 µM) and apoptotic (3 µM) doses of Zn2+ plus 1 µM pyrithione, a Zn2+-specific ionophore facilitating cellular uptake, for up to 24 h. Fixed cells were then stained with propidium iodine (PI) and cell cycle phase was determined by fluorescent image cytometry. Initial results report the percentage of cells in the S phase after 18 h exposure to 1, 2, and 3 µM Zn2+ were similar (8%, 7%, and 12%, respectively) compared with 7% in controls. Cells exposed to 3 µM Zn2+ increased cell populations in G2/M phase (76% versus 68% in controls). Interestingly, exposure to 1 µM Zn2+ resulted in decreased (59%) cells in G2/M. While preliminary, these pilot studies suggest Zn2+ alters cell cycle in BEAS-2B cells, particularly in the G2/M phase. The G2/M checkpoint maintains DNA integrity by enabling initiation of DNA repair or apoptosis. Our findings suggest that the adaptive and apoptotic responses to Zn2+ exposure may be mediated via perturbation of the cell cycle at the G2/M checkpoint. This work was a collaborative summer student project. The st

  2. Choreography of the Mycobacterium replication machinery during the cell cycle.

    PubMed

    Trojanowski, Damian; Ginda, Katarzyna; Pióro, Monika; Hołówka, Joanna; Skut, Partycja; Jakimowicz, Dagmara; Zakrzewska-Czerwińska, Jolanta

    2015-02-17

    It has recently been demonstrated that bacterial chromosomes are highly organized, with specific positioning of the replication initiation region. Moreover, the positioning of the replication machinery (replisome) has been shown to be variable and dependent on species-specific cell cycle features. Here, we analyzed replisome positions in Mycobacterium smegmatis, a slow-growing bacterium that exhibits characteristic asymmetric polar cell extension. Time-lapse fluorescence microscopy analyses revealed that the replisome is slightly off-center in mycobacterial cells, a feature that is likely correlated with the asymmetric growth of Mycobacterium cell poles. Estimates of the timing of chromosome replication in relation to the cell cycle, as well as cell division and chromosome segregation events, revealed that chromosomal origin-of-replication (oriC) regions segregate soon after the start of replication. Moreover, our data demonstrate that organization of the chromosome by ParB determines the replisome choreography. Despite significant progress in elucidating the basic processes of bacterial chromosome replication and segregation, understanding of chromosome dynamics during the mycobacterial cell cycle remains incomplete. Here, we provide in vivo experimental evidence that replisomes in Mycobacterium smegmatis are highly dynamic, frequently splitting into two distinct replication forks. However, unlike in Escherichia coli, the forks do not segregate toward opposite cell poles but remain in relatively close proximity. In addition, we show that replication cycles do not overlap. Finally, our data suggest that ParB participates in the positioning of newly born replisomes in M. smegmatis cells. The present results broaden our understanding of chromosome segregation in slow-growing bacteria. In view of the complexity of the mycobacterial cell cycle, especially for pathogenic representatives of the genus, understanding the mechanisms and factors that affect chromosome

  3. Establishment of Human Papillomavirus Infection Requires Cell Cycle Progression

    PubMed Central

    Pyeon, Dohun; Pearce, Shane M.; Lank, Simon M.; Ahlquist, Paul; Lambert, Paul F.

    2009-01-01

    Human papillomaviruses (HPVs) are DNA viruses associated with major human cancers. As such there is a strong interest in developing new means, such as vaccines and microbicides, to prevent HPV infections. Developing the latter requires a better understanding of the infectious life cycle of HPVs. The HPV infectious life cycle is closely linked to the differentiation state of the stratified epithelium it infects, with progeny virus only made in the terminally differentiating suprabasal compartment. It has long been recognized that HPV must first establish its infection within the basal layer of stratified epithelium, but why this is the case has not been understood. In part this restriction might reflect specificity of expression of entry receptors. However, this hypothesis could not fully explain the differentiation restriction of HPV infection, since many cell types can be infected with HPVs in monolayer cell culture. Here, we used chemical biology approaches to reveal that cell cycle progression through mitosis is critical for HPV infection. Using infectious HPV16 particles containing the intact viral genome, G1-synchronized human keratinocytes as hosts, and early viral gene expression as a readout for infection, we learned that the recipient cell must enter M phase (mitosis) for HPV infection to take place. Late M phase inhibitors had no effect on infection, whereas G1, S, G2, and early M phase cell cycle inhibitors efficiently prevented infection. We conclude that host cells need to pass through early prophase for successful onset of transcription of the HPV encapsidated genes. These findings provide one reason why HPVs initially establish infections in the basal compartment of stratified epithelia. Only this compartment of the epithelium contains cells progressing through the cell cycle, and therefore it is only in these cells that HPVs can establish their infection. By defining a major condition for cell susceptibility to HPV infection, these results also have

  4. Real-Time Cell Cycle Imaging in a 3D Cell Culture Model of Melanoma.

    PubMed

    Spoerri, Loredana; Beaumont, Kimberley A; Anfosso, Andrea; Haass, Nikolas K

    2017-01-01

    Aberrant cell cycle progression is a hallmark of solid tumors; therefore, cell cycle analysis is an invaluable technique to study cancer cell biology. However, cell cycle progression has been most commonly assessed by methods that are limited to temporal snapshots or that lack spatial information. Here, we describe a technique that allows spatiotemporal real-time tracking of cell cycle progression of individual cells in a multicellular context. The power of this system lies in the use of 3D melanoma spheroids generated from melanoma cells engineered with the fluorescent ubiquitination-based cell cycle indicator (FUCCI). This technique allows us to gain further and more detailed insight into several relevant aspects of solid cancer cell biology, such as tumor growth, proliferation, invasion, and drug sensitivity.

  5. Periodic gene expression program of the fission yeast cell cycle.

    PubMed

    Rustici, Gabriella; Mata, Juan; Kivinen, Katja; Lió, Pietro; Penkett, Christopher J; Burns, Gavin; Hayles, Jacqueline; Brazma, Alvis; Nurse, Paul; Bähler, Jürg

    2004-08-01

    Cell-cycle control of transcription seems to be universal, but little is known about its global conservation and biological significance. We report on the genome-wide transcriptional program of the Schizosaccharomyces pombe cell cycle, identifying 407 periodically expressed genes of which 136 show high-amplitude changes. These genes cluster in four major waves of expression. The forkhead protein Sep1p regulates mitotic genes in the first cluster, including Ace2p, which activates transcription in the second cluster during the M-G1 transition and cytokinesis. Other genes in the second cluster, which are required for G1-S progression, are regulated by the MBF complex independently of Sep1p and Ace2p. The third cluster coincides with S phase and a fourth cluster contains genes weakly regulated during G2 phase. Despite conserved cell-cycle transcription factors, differences in regulatory circuits between fission and budding yeasts are evident, revealing evolutionary plasticity of transcriptional control. Periodic transcription of most genes is not conserved between the two yeasts, except for a core set of approximately 40 genes that seem to be universally regulated during the eukaryotic cell cycle and may have key roles in cell-cycle progression.

  6. Microgravity modifies the cell cycle in the lentil root meristem

    NASA Astrophysics Data System (ADS)

    Driss-Ecole, D.; Yu, F.; Legué, V.; Perbal, G.

    In order to investigate the effects of microgravity on the cell cycle, lentil seedlings were grown in space as follows: 1 - in microgravity for 29h (Fmug), 2 - on the 1g centrifuge (F1g), 3 - in microgravity for 25h and then on the 1g centrifuge for 4h (Fmug+1g), 4 - on the 1g centrifuge for 25h and then in microgravity for 4h (F1g+mug). There were no statistical differences in mean root length after 29h in the four samples. The DNA content of nuclei in the root meristem was estimated by image analysis after sectioning and staining by the Feulgen technique. Three different regions, each of 0.2mm length (a, b, c), were distinguished basal to the root cap junction (RCJ). No difference in the distribution of nuclear DNA contents was found in region c (the furthest from the RCJ) in all four growth conditions. However, the nuclear DNA distributions were different in regions a and b in microgravity and on the 1g centrifuge (there were more cycling cells in 1g than in 1mug). When roots were grown in 1g and transferred to microgravity (F1g+mug), the proportion of cycling cells was increased. In the (Fmug+1g) sample, by contrast, the cell cycle was not modified by the transfer from 1mug to 1g. Microgravity perturbed the cell cycle by lengthening the G1 phase in the lentil root meristem.

  7. Optical measurement of cycle-dependent cell growth.

    PubMed

    Mir, Mustafa; Wang, Zhuo; Shen, Zhen; Bednarz, Michael; Bashir, Rashid; Golding, Ido; Prasanth, Supriya G; Popescu, Gabriel

    2011-08-09

    Determining the growth patterns of single cells offers answers to some of the most elusive questions in contemporary cell biology: how cell growth is regulated and how cell size distributions are maintained. For example, a linear growth in time implies that there is no regulation required to maintain homeostasis; an exponential pattern indicates the opposite. Recently, there has been great effort to measure single cells using microelectromechanical systems technology, and several important questions have been explored. However, a unified, easy-to-use methodology to measure the growth rate of individual adherent cells of various sizes has been lacking. Here we demonstrate that a newly developed optical interferometric technique, known as spatial light interference microscopy, can measure the cell dry mass of many individual adherent cells in various conditions, over spatial scales from micrometers to millimeters, temporal scales ranging from seconds to days, and cell types ranging from bacteria to mammalian cells. We found evidence of exponential growth in Escherichia coli, which agrees very well with other recent reports. Perhaps most importantly, combining spatial light interference microscopy with fluorescence imaging provides a unique method for studying cell cycle-dependent growth. Thus, by using a fluorescent reporter for the S phase, we measured single cell growth over each phase of the cell cycle in human osteosarcoma U2OS cells and found that the G2 phase exhibits the highest growth rate, which is mass-dependent and can be approximated by an exponential.

  8. Optical measurement of cycle-dependent cell growth

    PubMed Central

    Mir, Mustafa; Wang, Zhuo; Shen, Zhen; Bednarz, Michael; Bashir, Rashid; Golding, Ido; Prasanth, Supriya G.; Popescu, Gabriel

    2011-01-01

    Determining the growth patterns of single cells offers answers to some of the most elusive questions in contemporary cell biology: how cell growth is regulated and how cell size distributions are maintained. For example, a linear growth in time implies that there is no regulation required to maintain homeostasis; an exponential pattern indicates the opposite. Recently, there has been great effort to measure single cells using microelectromechanical systems technology, and several important questions have been explored. However, a unified, easy-to-use methodology to measure the growth rate of individual adherent cells of various sizes has been lacking. Here we demonstrate that a newly developed optical interferometric technique, known as spatial light interference microscopy, can measure the cell dry mass of many individual adherent cells in various conditions, over spatial scales from micrometers to millimeters, temporal scales ranging from seconds to days, and cell types ranging from bacteria to mammalian cells. We found evidence of exponential growth in Escherichia coli, which agrees very well with other recent reports. Perhaps most importantly, combining spatial light interference microscopy with fluorescence imaging provides a unique method for studying cell cycle-dependent growth. Thus, by using a fluorescent reporter for the S phase, we measured single cell growth over each phase of the cell cycle in human osteosarcoma U2OS cells and found that the G2 phase exhibits the highest growth rate, which is mass-dependent and can be approximated by an exponential. PMID:21788503

  9. Arresting cell cycles and the effect on wound healing.

    PubMed

    Vande Berg, Jerry S; Robson, Martin C

    2003-06-01

    Wounds that contain a significant number of fibroblasts that are arrested because of senescence, damaged DNA, or enduring quiescence do not heal. As the arrested population of cells decreases and more cells that divide and contribute to wound repair populate the wound, the wound is more likely to achieve closure. Having an understanding of the regulatory mechanisms within the cell cycle is important to wound repair, particularly chronic wounds. The theory of cellular senescence in chronic wounds is new and has never been tested. Studies seem to show that senescent cells in chronic wounds are a significant part of the wounding process. Senescence is irreversible, and senescent cells are refractory to growth factor therapy. Future growth factor therapies or genetic transfections that are capable of repairing the short circuit in cycling cells or overriding the senescent condition will be important partners in the successful treatment of chronic wound patients.

  10. Changing gears in the cell cycle: histoblasts and beyond.

    PubMed

    Ninov, Nikolay; Martín-Blanco, Enrique

    2009-01-01

    Although the molecular elements controlling cell cycle progression are well established, the mechanisms regulating how cell proliferation is triggered in response to extrinsic stimuli and how cell divisions change speed, particularly in stem or tumor cells or regenerative tissues, are poorly understood. One exceptional model system in which these events are precisely defined is Drosophila abdominal morphogenesis, in which stem-like histoblasts build the adult epidermis at metamorphosis by undergoing a series of sequential transitions from a non-proliferative to a growing, and finally to an invasive epithelium. We have recently uncovered in histoblasts an internal logic modulating cell cycle transitions that should constitute a reference paradigm for the study of other equivalent processes in stem cell, cancer or developmental biology.

  11. Neuronal cell cycle: the neuron itself and its circumstances.

    PubMed

    Frade, José M; Ovejero-Benito, María C

    2015-01-01

    Neurons are usually regarded as postmitotic cells that undergo apoptosis in response to cell cycle reactivation. Nevertheless, recent evidence indicates the existence of a defined developmental program that induces DNA replication in specific populations of neurons, which remain in a tetraploid state for the rest of their adult life. Similarly, de novo neuronal tetraploidization has also been described in the adult brain as an early hallmark of neurodegeneration. The aim of this review is to integrate these recent developments in the context of cell cycle regulation and apoptotic cell death in neurons. We conclude that a variety of mechanisms exists in neuronal cells for G1/S and G2/M checkpoint regulation. These mechanisms, which are connected with the apoptotic machinery, can be modulated by environmental signals and the neuronal phenotype itself, thus resulting in a variety of outcomes ranging from cell death at the G1/S checkpoint to full proliferation of differentiated neurons.

  12. Divide or Conquer: Cell Cycle Regulation of Invasive Behavior.

    PubMed

    Kohrman, Abraham Q; Matus, David Q

    2017-01-01

    Cell invasion through the basement membrane (BM) occurs during normal embryonic development and is a fundamental feature of cancer metastasis. The underlying cellular and genetic machinery required for invasion has been difficult to identify, due to a lack of adequate in vivo models to accurately examine invasion in single cells at subcellular resolution. Recent evidence has documented a functional link between cell cycle arrest and invasive activity. While cancer progression is traditionally thought of as a disease of uncontrolled cell proliferation, cancer cell dissemination, a critical aspect of metastasis, may require a switch from a proliferative to an invasive state. In this work, we review evidence that BM invasion requires cell cycle arrest and discuss the implications of this concept with regard to limiting the lethality associated with cancer metastasis. Copyright © 2016 Elsevier Ltd. All rights reserved.

  13. Choreography of the Mycobacterium Replication Machinery during the Cell Cycle

    PubMed Central

    Trojanowski, Damian; Ginda, Katarzyna; Pióro, Monika; Hołówka, Joanna; Skut, Partycja; Jakimowicz, Dagmara

    2015-01-01

    ABSTRACT It has recently been demonstrated that bacterial chromosomes are highly organized, with specific positioning of the replication initiation region. Moreover, the positioning of the replication machinery (replisome) has been shown to be variable and dependent on species-specific cell cycle features. Here, we analyzed replisome positions in Mycobacterium smegmatis, a slow-growing bacterium that exhibits characteristic asymmetric polar cell extension. Time-lapse fluorescence microscopy analyses revealed that the replisome is slightly off-center in mycobacterial cells, a feature that is likely correlated with the asymmetric growth of Mycobacterium cell poles. Estimates of the timing of chromosome replication in relation to the cell cycle, as well as cell division and chromosome segregation events, revealed that chromosomal origin-of-replication (oriC) regions segregate soon after the start of replication. Moreover, our data demonstrate that organization of the chromosome by ParB determines the replisome choreography. PMID:25691599

  14. Bcl-2 delays cell cycle through mitochondrial ATP and ROS.

    PubMed

    Du, Xing; Fu, Xufeng; Yao, Kun; Lan, Zhenwei; Xu, Hui; Cui, Qinghua; Yang, Elizabeth

    2017-02-22

    Bcl-2 inhibits cell proliferation by delaying G0/G1 to S phase entry. We tested the hypothesis that Bcl-2 regulates S phase entry through mitochondrial pathways. Existing evidence indicates mitochondrial adenosine tri-phosphate (ATP) and reactive oxygen species (ROS) are important signals in cell survival and cell death, however, the molecular details of how these 2 processes are linked remain unknown. In this study, 2 cell lines stably expressing Bcl-2, 3T3Bcl-2 and C3HBcl-2, and vector-alone PB controls were arrested in G0/G1 phase by serum starvation and contact inhibition, and ATP and ROS were measured during re-stimulation of cell cycle entry. Both ATP and ROS levels were decreased in G0/G1 arrested cells compared with normal growing cells. In addition, ROS levels were significant lower in synchronized Bcl-2 cells than those in PB controls. After re-stimulation, ATP levels increased with time, reaching peak value 1-3 hours ahead of S phase entry for both Bcl-2 cells and PB controls. Consistent with 2 hours of S phase delay, Bcl-2 cells reached ATP peaks 2 hours later than PB control, which suggests a rise in ATP levels is required for S phase entry. To examine the role of ATP and ROS in cell cycle regulation, ATP and ROS level were changed. We observed that elevation of ATP accelerated cell cycle progression in both PB and Bcl-2 cells, and decrease of ATP and ROS to the level equivalent to Bcl-2 cells delayed S phase entry in PB cells. Our results support the hypothesis that Bcl-2 protein regulates mitochondrial metabolism to produce less ATP and ROS, which contributes to S phase entry delay in Bcl-2 cells. These findings reveal a novel mechanistic basis for understanding the link between mitochondrial metabolism and tumor-suppressive function of Bcl-2.

  15. Life-cycle costs of high-performance cells

    NASA Technical Reports Server (NTRS)

    Daniel, R.; Burger, D.; Reiter, L.

    1985-01-01

    A life cycle cost analysis of high efficiency cells was presented. Although high efficiency cells produce more power, they also cost more to make and are more susceptible to array hot-spot heating. Three different computer analysis programs were used: SAMICS (solar array manufacturing industry costing standards), PVARRAY (an array failure mode/degradation simulator), and LCP (lifetime cost and performance). The high efficiency cell modules were found to be more economical in this study, but parallel redundancy is recommended.

  16. A role for homologous recombination proteins in cell cycle regulation.

    PubMed

    Kostyrko, Kaja; Bosshard, Sandra; Urban, Zuzanna; Mermod, Nicolas

    2015-01-01

    Eukaryotic cells respond to DNA breaks, especially double-stranded breaks (DSBs), by activating the DNA damage response (DDR), which encompasses DNA repair and cell cycle checkpoint signaling. The DNA damage signal is transmitted to the checkpoint machinery by a network of specialized DNA damage-recognizing and signal-transducing molecules. However, recent evidence suggests that DNA repair proteins themselves may also directly contribute to the checkpoint control. Here, we investigated the role of homologous recombination (HR) proteins in normal cell cycle regulation in the absence of exogenous DNA damage. For this purpose, we used Chinese Hamster Ovary (CHO) cells expressing the Fluorescent ubiquitination-based cell cycle indicators (Fucci). Systematic siRNA-mediated knockdown of HR genes in these cells demonstrated that the lack of several of these factors alters cell cycle distribution, albeit differentially. The knock-down of MDC1, Rad51 and Brca1 caused the cells to arrest in the G2 phase, suggesting that they may be required for the G2/M transition. In contrast, inhibition of the other HR factors, including several Rad51 paralogs and Rad50, led to the arrest in the G1/G0 phase. Moreover, reduced expression of Rad51B, Rad51C, CtIP and Rad50 induced entry into a quiescent G0-like phase. In conclusion, the lack of many HR factors may lead to cell cycle checkpoint activation, even in the absence of exogenous DNA damage, indicating that these proteins may play an essential role both in DNA repair and checkpoint signaling.

  17. A combined gas cooled nuclear reactor and fuel cell cycle

    NASA Astrophysics Data System (ADS)

    Palmer, David J.

    Rising oil costs, global warming, national security concerns, economic concerns and escalating energy demands are forcing the engineering communities to explore methods to address these concerns. It is the intention of this thesis to offer a proposal for a novel design of a combined cycle, an advanced nuclear helium reactor/solid oxide fuel cell (SOFC) plant that will help to mitigate some of the above concerns. Moreover, the adoption of this proposal may help to reinvigorate the Nuclear Power industry while providing a practical method to foster the development of a hydrogen economy. Specifically, this thesis concentrates on the importance of the U.S. Nuclear Navy adopting this novel design for its nuclear electric vessels of the future with discussion on efficiency and thermodynamic performance characteristics related to the combined cycle. Thus, the goals and objectives are to develop an innovative combined cycle that provides a solution to the stated concerns and show that it provides superior performance. In order to show performance, it is necessary to develop a rigorous thermodynamic model and computer program to analyze the SOFC in relation with the overall cycle. A large increase in efficiency over the conventional pressurized water reactor cycle is realized. Both sides of the cycle achieve higher efficiencies at partial loads which is extremely important as most naval vessels operate at partial loads as well as the fact that traditional gas turbines operating alone have poor performance at reduced speeds. Furthermore, each side of the cycle provides important benefits to the other side. The high temperature exhaust from the overall exothermic reaction of the fuel cell provides heat for the reheater allowing for an overall increase in power on the nuclear side of the cycle. Likewise, the high temperature helium exiting the nuclear reactor provides a controllable method to stabilize the fuel cell at an optimal temperature band even during transients helping

  18. Cell-cycle regulation in embryonic stem cells: centrosomal decisions on self-renewal.

    PubMed

    Koledova, Zuzana; Krämer, Alwin; Kafkova, Leona Raskova; Divoky, Vladimir

    2010-11-01

    Embryonic stem cells seem to have the intriguing capacity to divide indefinitely while retaining their pluripotency. This self-renewal is accomplished by specialized mechanisms of cell-cycle control. In the last few years, several studies have provided evidence for a direct link between cell-cycle regulation and cell-fate decisions in stem cells. In this review, we discuss the peculiarities of embryonic stem cell-cycle control mechanisms, implicate their involvement in cell-fate decisions, and distinguish centrosomes as important players in the self-renewal versus differentiation roulette.

  19. Thermal stress cycling of GaAs solar cells

    NASA Technical Reports Server (NTRS)

    Janousek, B. K.; Francis, R. W.; Wendt, J. P.

    1985-01-01

    A thermal cycling experiment was performed on GaAs solar cells to establish the electrical and structural integrity of these cells under the temperature conditions of a simulated low-Earth orbit of 3-year duration. Thirty single junction GaAs cells were obtained and tests were performed to establish the beginning-of-life characteristics of these cells. The tests consisted of cell I-V power output curves, from which were obtained short-circuit current, open circuit voltage, fill factor, and cell efficiency, and optical micrographs, spectral response, and ion microprobe mass analysis (IMMA) depth profiles on both the front surfaces and the front metallic contacts of the cells. Following 5,000 thermal cycles, the performance of the cells was reexamined in addition to any factors which might contribute to performance degradation. It is established that, after 5,000 thermal cycles, the cells retain their power output with no loss of structural integrity or change in physical appearance.

  20. Identification of a novel EGF-sensitive cell cycle checkpoint

    SciTech Connect

    Walker, Francesca . E-mail: francesca.walker@ludwig.edu.au; Zhang Huihua; Burgess, Antony W.

    2007-02-01

    The site of action of growth factors on mammalian cell cycle has been assigned to the boundary between the G1 and S phases. We show here that Epidermal Growth Factor (EGF) is also required for mitosis. BaF/3 cells expressing the EGFR (BaF/wtEGFR) synthesize DNA in response to EGF, but arrest in S-phase. We have generated a cell line (BaF/ERX) with defective downregulation of the EGFR and sustained activation of EGFR signalling pathways: these cells undergo mitosis in an EGF-dependent manner. The transit of BaF/ERX cells through G2/M strictly requires activation of EGFR and is abolished by AG1478. This phenotype is mimicked by co-expression of ErbB2 in BaF/wtEGFR cells, and abolished by inhibition of the EGFR kinase, suggesting that sustained signalling of the EGFR, through impaired downregulation of the EGFR or heterodimerization, is required for completion of the cycle. We have confirmed the role of EGFR signalling in the G2/M phase of the cell cycle using a human tumor cell line which overexpresses the EGFR and is dependent on EGFR signalling for growth. These findings unmask an EGF-sensitive checkpoint, helping to understand the link between sustained EGFR signalling, proliferation and the acquisition of a radioresistant phenotype in cancer cells.

  1. Labeling of lectin receptors during the cell cycle.

    PubMed

    Garrido, J

    1976-12-01

    Labeling of lectin receptors during the cell cycle. (Localizabión de receptores para lectinas durante el ciclo celular). Arch. Biol. Med. Exper. 10: 100-104, 1976. The topographic distribution of specific cell surface receptors for concanavalin A and wheat germ agglutinin was studied by ultrastructural labeling in the course of the cell cycle. C12TSV5 cells were synchronized by double thymidine block or mechanical selection (shakeoff). They were labeled by means of lectin-peroxidase techniques while in G1 S, G2 and M phases of the cycle. The results obtained were similar for both lectins employed. Interphase cells (G1 S, G2) present a stlihtly discontinous labeling pattern that is similar to the one observed on unsynchronized cells of the same line. Cells in mitosis, on the contrary, present a highly discontinous distribution of reaction product. This pattern disappears after the cells enters G1 and is not present on mitotic cells fixed in aldehyde prior to labeling.

  2. Computation Molecular Kinetics Model of HZE Induced Cell Cycle Arrest

    NASA Technical Reports Server (NTRS)

    Cucinotta, Francis A.; Ren, Lei

    2004-01-01

    Cell culture models play an important role in understanding the biological effectiveness of space radiation. High energy and charge (HZE) ions produce prolonged cell cycle arrests at the G1/S and G2/M transition points in the cell cycle. A detailed description of these phenomena is needed to integrate knowledge of the expression of DNA damage in surviving cells, including the determination of relative effectiveness factors between different types of radiation that produce differential types of DNA damage and arrest durations. We have developed a hierarchical kinetics model that tracks the distribution of cells in various cell phase compartments (early G1, late G1, S, G2, and M), however with transition rates that are controlled by rate-limiting steps in the kinetics of cyclin-cdk's interactions with their families of transcription factors and inhibitor molecules. The coupling of damaged DNA molecules to the downstream cyclin-cdk inhibitors is achieved through a description of the DNA-PK and ATM signaling pathways. For HZE irradiations we describe preliminary results, which introduce simulation of the stochastic nature of the number of direct particle traversals per cell in the modulation of cyclin-cdk and cell cycle population kinetics. Comparison of the model to data for fibroblast cells irradiated photons or HZE ions are described.

  3. Thermal stress cycling of GaAs solar cells

    NASA Astrophysics Data System (ADS)

    Janousek, B. K.; Francis, R. W.; Wendt, J. P.

    A thermal cycling experiment was performed on GaAs solar cells to establish the electrical and structural integrity of these cells under the temperature conditions of a simulated low-Earth orbit of 3-year duration. Thirty single junction GaAs cells were obtained and tests were performed to establish the beginning-of-life characteristics of these cells. The tests consisted of cell I-V power output curves, from which were obtained short-circuit current, open circuit voltage, fill factor, and cell efficiency, and optical micrographs, spectral response, and ion microprobe mass analysis (IMMA) depth profiles on both the front surfaces and the front metallic contacts of the cells. Following 5,000 thermal cycles, the performance of the cells was reexamined in addition to any factors which might contribute to performance degradation. It is established that, after 5,000 thermal cycles, the cells retain their power output with no loss of structural integrity or change in physical appearance.

  4. Computation Molecular Kinetics Model of HZE Induced Cell Cycle Arrest

    NASA Technical Reports Server (NTRS)

    Cucinotta, Francis A.; Ren, Lei

    2004-01-01

    Cell culture models play an important role in understanding the biological effectiveness of space radiation. High energy and charge (HZE) ions produce prolonged cell cycle arrests at the G1/S and G2/M transition points in the cell cycle. A detailed description of these phenomena is needed to integrate knowledge of the expression of DNA damage in surviving cells, including the determination of relative effectiveness factors between different types of radiation that produce differential types of DNA damage and arrest durations. We have developed a hierarchical kinetics model that tracks the distribution of cells in various cell phase compartments (early G1, late G1, S, G2, and M), however with transition rates that are controlled by rate-limiting steps in the kinetics of cyclin-cdk's interactions with their families of transcription factors and inhibitor molecules. The coupling of damaged DNA molecules to the downstream cyclin-cdk inhibitors is achieved through a description of the DNA-PK and ATM signaling pathways. For HZE irradiations we describe preliminary results, which introduce simulation of the stochastic nature of the number of direct particle traversals per cell in the modulation of cyclin-cdk and cell cycle population kinetics. Comparison of the model to data for fibroblast cells irradiated photons or HZE ions are described.

  5. Regulation of mammalian cell cycle progression in the regenerating liver.

    PubMed

    Chauhan, Anuradha; Lorenzen, Stephan; Herzel, Hanspeter; Bernard, Samuel

    2011-08-21

    The process of cell division in mammalian cells is orchestrated by cell-cycle-dependent oscillations of cyclin protein levels. Cyclin levels are controlled by redundant transcriptional, post-translational and degradation feedback loops. How each of these separate loops contributes to the regulation of the key cell cycle events and to the connection between the G1-S transition and the subsequent mitotic events is under investigation. Here, we present an integrated computational model of the mammalian cell cycle based on the sequential activation of cyclins. We validate the model against experimental data on liver cells (hepatocytes), which undergo one or two rounds of synchronous circadian-clock gated cell divisions during liver regeneration, after partial hepatectomy (PH). The model exhibits bandpass filter properties that allow the system to ignore strong but transient, or sustained but weak damages after PH. Bifurcation analysis of the model suggests two different threshold mechanisms for the progression of the cell through mitosis. These results are coherent with the notion that the mitotic exit in mammalian cells is bistable, and suggests that Cdc20 homologue 1 (Cdh1) is an important regulator of mitosis. Regulation by Cdh1 also explains the observed G2/M phase prolongation after hepatocyte growth factor (HGF) stimulation during S phase. Copyright © 2011 Elsevier Ltd. All rights reserved.

  6. Entrainability of cell cycle oscillator models with exponential growth of cell mass.

    PubMed

    Nakao, Mitsuyuki; Enkhkhudulmur, Tsog-Erdene; Katayama, Norihiro; Karashima, Akihiro

    2014-01-01

    Among various aspects of cell cycle, understanding synchronization mechanism of cell cycle is important because of the following reasons. (1)Cycles of cell assembly should synchronize to form an organ. (2) Synchronizing cell cycles are required to experimental analysis of regulatory mechanisms of cell cycles. (3) Cell cycle has a distinct phase relationship with the other biological rhythms such as circadian rhythm. However, forced as well as mutual entrainment mechanisms are not clearly known. In this study, we investigated entrainability of cell cycle models of yeast cell under the periodic forcing to both of the cell mass and molecular dynamics. Dynamics of models under study involve the cell mass growing exponentially. In our result, they are shown to allow only a limited frequency range for being entrained by the periodic forcing. In contrast, models with linear growth are shown to be entrained in a wider frequency range. It is concluded that if the cell mass is included in the cell cycle regulation, its entrainability is sensitive to a shape of growth curve assumed in the model.

  7. Cell Division, a new open access online forum for and from the cell cycle community.

    PubMed

    Kaldis, Philipp; Pagano, Michele

    2006-04-03

    Cell Division is a new, open access, peer-reviewed online journal that publishes cutting-edge articles, commentaries and reviews on all exciting aspects of cell cycle control in eukaryotes. A major goal of this new journal is to publish timely and significant studies on the aberrations of the cell cycle network that occur in cancer and other diseases.

  8. The enigmatic effects of caffeine in cell cycle and cancer

    PubMed Central

    Bode, Ann M.

    2010-01-01

    Caffeine may very well be the most frequently ingested neuroactive drug in the world. Mechanistically, caffeine has been reported to affect cell cycle function, induce programmed cell death or apoptosis and perturb key cell cycle regulatory proteins. Although the effects of caffeine have been heavily investigated, much of the research data regarding caffeine's effects on cell cycle and proliferation seem ambiguous. One important factor may be that caffeine has been used experimentally in numerous cell types under a variety of conditions at concentrations ranging from micromolar to high millimolar. Physiologically, achieving experimental blood levels of caffeine would be extremely difficult without adverse side effects. Therefore, the relevance of experimental data obtained by using high concentrations of caffeine is not clear and may account for some of the discrepancies in the literature. This review attempts to reconcile data regarding the cellular effects of caffeine by examining reported effects on cell cycle, proliferation and apoptosis with careful attention to differences in experimental conditions and caffeine concentration utilized. PMID:16709440

  9. Vertebrate Cell Cycle Modulates Infection by Protozoan Parasites

    NASA Astrophysics Data System (ADS)

    Dvorak, James A.; Crane, Mark St. J.

    1981-11-01

    Synchronized HeLa cell populations were exposed to Trypanosoma cruzi or Toxoplasma gondii, obligate intracellular protozoan parasites that cause Chagas' disease and toxoplasmosis, respectively, in humans. The ability of the two parasites to infect HeLa cells increased as the HeLa cells proceeded from the G1 phase to the S phase of their growth cycle and decreased as the cells entered G2-M. Characterization of the S-phase cell surface components responsible for this phenomenon could be beneficial in the development of vaccines against these parasitic diseases.

  10. High efficiency fuel cell/advanced turbine power cycles

    SciTech Connect

    Morehead, H.

    1995-10-19

    An outline of the Westinghouse high-efficiency fuel cell/advanced turbine power cycle is presented. The following topics are discussed: The Westinghouse SOFC pilot manufacturing facility, cell scale-up plan, pressure effects on SOFC power and efficiency, sureCell versus conventional gas turbine plants, sureCell product line for distributed power applications, 20 MW pressurized-SOFC/gas turbine power plant, 10 MW SOFC/CT power plant, sureCell plant concept design requirements, and Westinghouse SOFC market entry.

  11. The reproductive-cell cycle theory of aging: an update.

    PubMed

    Atwood, Craig S; Bowen, Richard L

    2011-01-01

    The Reproductive-Cell Cycle Theory posits that the hormones that regulate reproduction act in an antagonistic pleiotrophic manner to control aging via cell cycle signaling; promoting growth and development early in life in order to achieve reproduction, but later in life, in a futile attempt to maintain reproduction, become dysregulated and drive senescence. Since reproduction is the most important function of an organism from the perspective of the survival of the species, if reproductive-cell cycle signaling factors determine the rate of growth, determine the rate of development, determine the rate of reproduction, and determine the rate of senescence, then by definition they determine the rate of aging and thus lifespan. The theory is able to explain: 1) the simultaneous regulation of the rate of aging and reproduction as evidenced by the fact that environmental conditions and experimental interventions known to extend longevity are associated with decreased reproductive-cell cycle signaling factors, thereby slowing aging and preserving fertility in a hostile reproductive environment; 2) two phenomena that are closely related to species lifespan-the rate of growth and development and the ultimate size of the animal; 3). the apparent paradox that size is directly proportional to lifespan and inversely proportional to fertility between species but vice versa within a species; 4). how differing rates of reproduction between species is associated with differences in their lifespan; 5). why we develop aging-related diseases; and 6). an evolutionarily credible reason for why and how aging occurs-these hormones act in an antagonistic pleiotrophic manner via cell cycle signaling; promoting growth and development early in life in order to achieve reproduction, but later in life, in a futile attempt to maintain reproduction, become dysregulated and drive senescence (dyosis). In essence, the Reproductive-Cell Cycle Theory can explain aging in all sexually reproductive life

  12. Coordinating cell polarity and cell cycle progression: what can we learn from flies and worms?

    PubMed

    Noatynska, Anna; Tavernier, Nicolas; Gotta, Monica; Pintard, Lionel

    2013-08-07

    Spatio-temporal coordination of events during cell division is crucial for animal development. In recent years, emerging data have strengthened the notion that tight coupling of cell cycle progression and cell polarity in dividing cells is crucial for asymmetric cell division and ultimately for metazoan development. Although it is acknowledged that such coupling exists, the molecular mechanisms linking the cell cycle and cell polarity machineries are still under investigation. Key cell cycle regulators control cell polarity, and thus influence cell fate determination and/or differentiation, whereas some factors involved in cell polarity regulate cell cycle timing and proliferation potential. The scope of this review is to discuss the data linking cell polarity and cell cycle progression, and the importance of such coupling for asymmetric cell division. Because studies in model organisms such as Caenorhabditis elegans and Drosophila melanogaster have started to reveal the molecular mechanisms of this coordination, we will concentrate on these two systems. We review examples of molecular mechanisms suggesting a coupling between cell polarity and cell cycle progression.

  13. Coordinating cell polarity and cell cycle progression: what can we learn from flies and worms?

    PubMed Central

    Noatynska, Anna; Tavernier, Nicolas; Gotta, Monica; Pintard, Lionel

    2013-01-01

    Spatio-temporal coordination of events during cell division is crucial for animal development. In recent years, emerging data have strengthened the notion that tight coupling of cell cycle progression and cell polarity in dividing cells is crucial for asymmetric cell division and ultimately for metazoan development. Although it is acknowledged that such coupling exists, the molecular mechanisms linking the cell cycle and cell polarity machineries are still under investigation. Key cell cycle regulators control cell polarity, and thus influence cell fate determination and/or differentiation, whereas some factors involved in cell polarity regulate cell cycle timing and proliferation potential. The scope of this review is to discuss the data linking cell polarity and cell cycle progression, and the importance of such coupling for asymmetric cell division. Because studies in model organisms such as Caenorhabditis elegans and Drosophila melanogaster have started to reveal the molecular mechanisms of this coordination, we will concentrate on these two systems. We review examples of molecular mechanisms suggesting a coupling between cell polarity and cell cycle progression. PMID:23926048

  14. Modelling cell cycle synchronisation in networks of coupled radial glial cells.

    PubMed

    Barrack, Duncan S; Thul, Rüdiger; Owen, Markus R

    2015-07-21

    Radial glial cells play a crucial role in the embryonic mammalian brain. Their proliferation is thought to be controlled, in part, by ATP mediated calcium signals. It has been hypothesised that these signals act to locally synchronise cell cycles, so that clusters of cells proliferate together, shedding daughter cells in uniform sheets. In this paper we investigate this cell cycle synchronisation by taking an ordinary differential equation model that couples the dynamics of intracellular calcium and the cell cycle and extend it to populations of cells coupled via extracellular ATP signals. Through bifurcation analysis we show that although ATP mediated calcium release can lead to cell cycle synchronisation, a number of other asynchronous oscillatory solutions including torus solutions dominate the parameter space and cell cycle synchronisation is far from guaranteed. Despite this, numerical results indicate that the transient and not the asymptotic behaviour of the system is important in accounting for cell cycle synchronisation. In particular, quiescent cells can be entrained on to the cell cycle via ATP mediated calcium signals initiated by a driving cell and crucially will cycle in near synchrony with the driving cell for the duration of neurogenesis. This behaviour is highly sensitive to the timing of ATP release, with release at the G1/S phase transition of the cell cycle far more likely to lead to near synchrony than release during mid G1 phase. This result, which suggests that ATP release timing is critical to radial glia cell cycle synchronisation, may help us to understand normal and pathological brain development.

  15. FOXM1 participates in PLK1-regulated cell cycle progression in renal cell cancer cells

    PubMed Central

    ZHANG, ZHE; ZHANG, GUOJUN; KONG, CHUIZE

    2016-01-01

    The regulation of entry into and progression through mitosis is important for cell proliferation. Polo-like kinase 1 (PLK1) is involved in multiple stages of mitosis. Forkhead box protein M1 (FOXM1) has multiple functions in tumorigenesis and, in elevated levels, is frequently associated with cancer progression. The present study reports that FOXM1, a substrate of PLK1, controls the transcription mechanism that mediates the PLK1-dependent regulation of the cell cycle. The present study investigated the expression of PLK1 and FOXM1 in the clear renal cell carcinoma 769-P and ACHN cell lines, and indicated that the expression of PLK1 and FOXM1 are correlated in human renal cell cancer cell lines and that the suppression of PLK1 may decrease the expression of FOXM1. The knockdown of FOXM1 or PLK1 in renal cell cancer cell lines caused cell cycle progression to be blocked. As a result, the present study indicated the involvement of FOXM1 in PLK1-regulated cell cycle progression. PMID:27073539

  16. Long Cycle Life Secondary Lithium Cells Utilizing Tetrahydrofuran.

    DTIC Science & Technology

    1984-04-01

    11D-Ri49 762 LONG CYCLE LIFE SECONDARY LITHIUM CELLS UTILIZING 1/1 TETRRHYDROFURAN(U) EIC LABS INC NORWOOD MR K M ABRAHAM ET AL. APR 84 TR-12 N80914...Contract No. N00014-77-C-0155 TECHNICAL REPORT NO. 12 I LONG CYCLE LIFE SECONDARY LITHIUM CELLS UTILIZING TETRAHYDROFURAN By K. M. Abraham J. S. Foos...CONTRACT OF GRANT NUMBER(s) K. 14. Abraham , j. S. Foos and J. L. Goldman N00014-77-C-0155 9. PERFORMING ORGANIZATION NAME AND ADDRESS 10PRAM ELEORMNT

  17. Regulated protein kinases and phosphatases in cell cycle decisions.

    PubMed

    Novak, Bela; Kapuy, Orsolya; Domingo-Sananes, Maria Rosa; Tyson, John J

    2010-12-01

    Many aspects of cell physiology are controlled by protein kinases and phosphatases, which together determine the phosphorylation state of targeted substrates. Some of these target proteins are themselves kinases or phosphatases or other components of a regulatory network characterized by feedback and feed-forward loops. In this review we describe some common regulatory motifs involving kinases, phosphatases, and their substrates, focusing particularly on bistable switches involved in cellular decision processes. These general principles are applied to cell cycle transitions, with special emphasis on the roles of regulated phosphatases in orchestrating progression from one phase to the next of the DNA replication-division cycle.

  18. Regulated protein kinases and phosphatases in cell cycle decisions

    PubMed Central

    Novak, Bela; Kapuy, Orsolya; Domingo-Sananes, Maria Rosa; Tyson, John J

    2013-01-01

    Many aspects of cell physiology are controlled by protein kinases and phosphatases, which together determine the phosphorylation state of targeted substrates. Some of these target proteins are themselves kinases or phosphatases or other components of a regulatory network characterized by feedback and feed-forward loops. In this review we describe some common regulatory motifs involving kinases, phosphatases, and their substrates, focusing particularly on bistable switches involved in cellular decision processes. These general principles are applied to cell cycle transitions, with special emphasis on the roles of regulated phosphatases in orchestrating progression from one phase to the next of the DNA replication-division cycle. PMID:20678910

  19. Computation intelligent for eukaryotic cell-cycle gene network.

    PubMed

    Wu, Shinq-Jen; Wu, Cheng-Tao; Lee, Tsu-Tian

    2006-01-01

    Computational intelligent approaches is adopted to construct the S-system of eukaryotic cell cycle for further analysis of genetic regulatory networks. A highly nonlinear power-law differential equation is constructed to describe the transcriptional regulation of gene network from the time-courses dataset. Global artificial algorithm, based on hybrid differential evolution, can achieve global optimization for the highly nonlinear differential gene network modeling. The constructed gene regulatory networks will be a reference for researchers to realize the inhibitory and activatory operator for genes synthesis and decomposition in Eukaryotic cell cycle.

  20. How does a bacterium grow during its cell cycle?

    PubMed

    Burdett, I D; Kirkwood, T B

    1983-07-07

    Rod-shaped bacteria such as Escherichia coli and Bacillus subtilis appear to extend continuously in length between divisions. However, the kinetics of growth of the individual cell in the steady state is still unknown. A brief, critical account of the main approaches used to determine the pattern of surface extension is given. In general, these approaches are of three types. Firstly, attempts have been made to relate average cell size to growth rate of the culture and to determine possible stages in the cell cycle at which the rate of length extension might change. Secondly, comparisons have been made between the measured length distribution of cells and theoretical distributions, based on three primary hypotheses (linear, bilinear and exponential growth). Thirdly, the principle of Collins and Richmond, involving the calculation of growth rate from the length distributions of extant, separating and new-born cells, is described. It is emphasized that there is a strong element of variation in size at different stages of the cell cycle. This variation imposes severe limitations on models which utilize only average cellular dimensions. We conclude that the Collins-Richmond principle affords the most powerful approach to the analysis of bacterial growth kinetics. However, we propose that the method be modified to permit calculation of separate rates of growth of cells between discernible events in the cell cycle, as well as simply between birth and division.

  1. Impact of cell cycle delay on micronucleus frequency in TK6 cells.

    PubMed

    Sobol, Zhanna; Spellman, Richard A; Thiffeault, Catherine; Dobo, Krista L; Schuler, Maik

    2014-01-01

    Previous studies with TK6 cells have shown that extending the recovery period after pulse treatment allows for greater micronucleus expression for some compounds. This study explores the role of cell cycle delay in micronucleus expression after pulse treatment with three model genotoxins [mitomycin C, etoposide (ETOP), vinblastine]. Cells were treated for 4 hr and allowed to recover for 36 hr with samples removed at various time points during the recovery period and analyzed for cell cycle distribution, apoptosis and micronucleus frequency. Our results show that mitomycin C causes cell cycle delay for 20 hr after pulse treatment and cell cycle perturbation is no longer evident after 36 hr of recovery. The micronucleus frequency of cells sampled at 36 hr is doubled when compared with cells sampled at 20 hr after mitomycin C removal. When cells were treated with indirect acting genotoxins (ETOP, vinblastine), cell cycle perturbation was not observed at the 20 hr time point. Micronucleus frequency after treatment with either ETOP or vinblastine did not differ between the 20 hr and the 36 hr time point. All three compounds induced similar levels of apoptosis ranging from 4.5 to 5.6% with maximum induction occurring at the 36-hr time point. We conclude that TK6 cells exhibit extended cell cycle arrest after exposure to MMC and can go on to express micronuclei, after overcoming cell cycle arrest.

  2. Visualisation of cell cycle modifications by X-ray irradiation of single HeLa cells using fluorescent ubiquitination-based cell cycle indicators.

    PubMed

    Kaminaga, K; Noguchi, M; Narita, A; Sakamoto, Y; Kanari, Y; Yokoya, A

    2015-09-01

    To explore the effects of X-ray irradiation on mammalian cell cycle dynamics, single cells using the fluorescent ubiquitination-based cell cycle indicator (Fucci) technique were tracked. HeLa cells expressing Fucci were used to visualise cell cycle modifications induced by irradiation. After cultured HeLa-Fucci cells were exposed to 5 Gy X-rays, fluorescent cell images were captured every 20 min for 48 h using a fluorescent microscope. Time dependence of the fluorescence intensity of S/G2 cells was analysed to examine the cell cycle dynamics of irradiated and non-irradiated control cells. The results showed that irradiated cells could be divided into two populations: one with similar cell cycle dynamics to that of non-irradiated cells, and another displaying a prolonged G2 phase. Based on these findings, it is proposed in this article that an underlying switch mechanism is involved in cell cycle regulation and the G2/M checkpoint of HeLa cells. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  3. UV-induced changes in cell cycle and gene expression within rabbit lens epithelial cells

    SciTech Connect

    Sidjanin, D.; Grdina, D.; Woloschak, G.E.

    1994-11-01

    Damage to lens epithelial cells is a probable initiation process in cataract formation induced by ultraviolet radiation. These experiments investigated the ability of 254 nm radiation on cell cycle progression and gene expression in rabbit lens epithelial cell line N/N1003A. No changes in expression of c-fos, c-jun, alpha- tubulin, or vimentin was observed following UV exposure. Using flow cytometry, an accumulation of cells in G1/S phase of the cell cycle 1 hr following exposure. The observed changes in gene expression, especially the decreased histone transcripts reported here may play a role in UV induced inhibition of cell cycle progression.

  4. DREAMs make plant cells to cycle or to become quiescent.

    PubMed

    Magyar, Zoltán; Bögre, László; Ito, Masaki

    2016-12-01

    Cell cycle phase specific oscillation of gene transcription has long been recognized as an underlying principle for ordered processes during cell proliferation. The G1/S-specific and G2/M-specific cohorts of genes in plants are regulated by the E2F and the MYB3R transcription factors. Mutant analysis suggests that activator E2F functions might not be fully required for cell cycle entry. In contrast, the two activator-type MYB3Rs are part of positive feedback loops to drive the burst of mitotic gene expression, which is necessary at least to accomplish cytokinesis. Repressor MYB3Rs act outside the mitotic time window during cell cycle progression, and are important for the shutdown of mitotic genes to impose quiescence in mature organs. The two distinct classes of E2Fs and MYB3Rs together with the RETINOBLATOMA RELATED are part of multiprotein complexes that may be evolutionary related to what is known as DREAM complex in animals. In plants, there are multiple such complexes with distinct compositions and functions that may be involved in the coordinated cell cycle and developmental regulation of E2F targets and mitotic genes. Copyright © 2016 Elsevier Ltd. All rights reserved.

  5. Histone supply regulates S phase timing and cell cycle progression

    PubMed Central

    Günesdogan, Ufuk; Jäckle, Herbert; Herzig, Alf

    2014-01-01

    Eukaryotes package DNA into nucleosomes that contain a core of histone proteins. During DNA replication, nucleosomes are disrupted and re-assembled with newly synthesized histones and DNA. Despite much progress, it is still unclear why higher eukaryotes contain multiple core histone genes, how chromatin assembly is controlled, and how these processes are coordinated with cell cycle progression. We used a histone null mutation of Drosophila melanogaster to show that histone supply levels, provided by a defined number of transgenic histone genes, regulate the length of S phase during the cell cycle. Lack of de novo histone supply not only extends S phase, but also causes a cell cycle arrest during G2 phase, and thus prevents cells from entering mitosis. Our results suggest a novel cell cycle surveillance mechanism that monitors nucleosome assembly without involving the DNA repair pathways and exerts its effect via suppression of CDC25 phosphatase String expression. DOI: http://dx.doi.org/10.7554/eLife.02443.001 PMID:25205668

  6. Canthin-6-one induces cell death, cell cycle arrest and differentiation in human myeloid leukemia cells.

    PubMed

    Vieira Torquato, Heron F; Ribeiro-Filho, Antonio C; Buri, Marcus V; Araújo Júnior, Roberto T; Pimenta, Renata; de Oliveira, José Salvador R; Filho, Valdir C; Macho, Antonio; Paredes-Gamero, Edgar J; de Oliveira Martins, Domingos T

    2017-04-01

    Canthin-6-one is a natural product isolated from various plant genera and from fungi with potential antitumor activity. In the present study, we evaluate the antitumor effects of canthin-6-one in human myeloid leukemia lineages. Kasumi-1 lineage was used as a model for acute myeloid leukemia. Cells were treated with canthin-6-one and cell death, cell cycle and differentiation were evaluated in both total cells (Lin(+)) and leukemia stem cell population (CD34(+)CD38(-)Lin(-/low)). Among the human lineages tested, Kasumi-1 was the most sensitive to canthin-6-one. Canthin-6-one induced cell death with apoptotic (caspase activation, decrease of mitochondrial potential) and necrotic (lysosomal permeabilization, double labeling of annexin V/propidium iodide) characteristics. Moreover, canthin-6-one induced cell cycle arrest at G0/G1 (7μM) and G2 (45μM) evidenced by DNA content, BrdU incorporation and cyclin B1/histone 3 quantification. Canthin-6-one also promoted differentiation of Kasumi-1, evidenced by an increase in the expression of myeloid markers (CD11b and CD15) and the transcription factor PU.1. Furthermore, a reduction of the leukemic stem cell population and clonogenic capability of stem cells were observed. These results show that canthin-6-one can affect Kasumi-1 cells by promoting cell death, cell cycle arrest and cell differentiation depending on concentration used. Canthin-6-one presents an interesting cytotoxic activity against leukemic cells and represents a promising scaffold for the development of molecules for anti-leukemic applications, especially by its anti-leukemic stem cell activity. Copyright © 2017 Elsevier B.V. All rights reserved.

  7. RAD001 (everolimus) induces dose-dependent changes to cell cycle regulation and modifies the cell cycle response to vincristine.

    PubMed

    Saunders, P O; Weiss, J; Welschinger, R; Baraz, R; Bradstock, K F; Bendall, L J

    2013-10-01

    More than 50% of adults and ~20% of children with pre-B acute lymphoblastic leukemia (ALL) relapse following treatment. Dismal outcomes for patients with relapsed or refractory disease mandate novel approaches to therapy. We have previously shown that the combination of the mTOR inhibitor RAD001 (everolimus) and the chemotherapeutic agent vincristine increases the survival of non-obese diabetic/severe combined immuno-deficient (NOD/SCID) mice bearing human ALL xenografts. We have also shown that 16 μM RAD001 synergized with agents that cause DNA damage or microtubule disruption in pre-B ALL cells in vitro. Here, we demonstrate that RAD001 has dose-dependent effects on the cell cycle in ALL cells, with 1.5 μM RAD001 inhibiting pRb, Ki67 and PCNA expression and increasing G0/1 cell cycle arrest, whereas 16 μM RAD001 increases pRb, cyclin D1, Ki67 and PCNA, with no evidence of an accumulation of cells in G0/1. Transition from G2 into mitosis was promoted by 16 μM RAD001 with reduced phosphorylation of cdc2 in cells with 4 N DNA content. However, 16 μM RAD001 preferentially induced cell death in cells undergoing mitosis. When combined with vincristine, 16 μM RAD001 reduced the vincristine-induced accumulation of cells in mitosis, probably as a result of increased death in this population. Although 16 μM RAD001 weakly activated Chk1 and Chk2, it suppressed strong vincristine-induced activation of these cell cycle checkpoint regulators. We conclude that RAD001 enhances chemosensitivity at least in part through suppression of cell cycle checkpoint regulation in response to vincristine and increased progression from G2 into mitosis.

  8. High-resolution timing of cell cycle-regulated gene expression

    PubMed Central

    Rowicka, Maga; Kudlicki, Andrzej; Tu, Benjamin P.; Otwinowski, Zbyszek

    2007-01-01

    The eukaryotic cell division cycle depends on an intricate sequence of transcriptional events. Using an algorithm based on maximum-entropy deconvolution, and expression data from a highly synchronized yeast culture, we have timed the peaks of expression of transcriptionally regulated cell cycle genes to an accuracy of 2 min (≈1% of the cell cycle time). The set of 1,129 cell cycle-regulated genes was identified by a comprehensive analysis encompassing all available cell cycle yeast data sets. Our results reveal distinct subphases of the cell cycle undetectable by morphological observation, as well as the precise timeline of macromolecular complex assembly during key cell cycle events. PMID:17827275

  9. The Effect of Spaceflight on Cartilage Cell Cycle and Differentiation

    NASA Technical Reports Server (NTRS)

    Doty, Stephen B.; Stiner, Dalina; Telford, William G.

    2000-01-01

    In vivo studies have shown that spaceflight results in loss of bone and muscle. In an effort to understand the mechanisms of these changes, cell cultures of cartilage, bone and muscle have been subjected to spaceflight to study the microgravity effects on differentiated cells. However it now seems possible that the cell differentiation process itself may be the event(s) most affected by spaceflight. For example, osteoblast-like cells have been shown to have reduced cellular activity in microgravity due to an underdifferentiated state (Carmeliet, et al, 1997). And reduced human lymphocyte growth in spaceflight was related to increased apoptosis (Lewis, et al, 1998). Which brings us to the question of whether reduced cellular activity in space is due to an effect on the differentiated cell, an effect on the cell cycle and cell proliferation, or an effect on cell death. This question has not been specifically addressed on previous flights and was the question behind die present study.

  10. Meta-analysis reveals conserved cell cycle transcriptional network across multiple human cell types.

    PubMed

    Giotti, Bruno; Joshi, Anagha; Freeman, Tom C

    2017-01-05

    Cell division is central to the physiology and pathology of all eukaryotic organisms. The molecular machinery underpinning the cell cycle has been studied extensively in a number of species and core aspects of it have been found to be highly conserved. Similarly, the transcriptional changes associated with this pathway have been studied in different organisms and different cell types. In each case hundreds of genes have been reported to be regulated, however there seems to be little consensus in the genes identified across different studies. In a recent comparison of transcriptomic studies of the cell cycle in different human cell types, only 96 cell cycle genes were reported to be the same across all studies examined. Here we perform a systematic re-examination of published human cell cycle expression data by using a network-based approach to identify groups of genes with a similar expression profile and therefore function. Two clusters in particular, containing 298 transcripts, showed patterns of expression consistent with cell cycle occurrence across the four human cell types assessed. Our analysis shows that there is a far greater conservation of cell cycle-associated gene expression across human cell types than reported previously, which can be separated into two distinct transcriptional networks associated with the G1/S-S and G2-M phases of the cell cycle. This work also highlights the benefits of performing a re-analysis on combined datasets.

  11. α-Mangostin Induces Apoptosis and Cell Cycle Arrest in Oral Squamous Cell Carcinoma Cell

    PubMed Central

    Kwak, Hyun-Ho; Park, Bong-Soo

    2016-01-01

    Mangosteen has long been used as a traditional medicine and is known to have antibacterial, antioxidant, and anticancer effects. Although the effects of α-mangostin, a natural compound extracted from the pericarp of mangosteen, have been investigated in many studies, there is limited data on the effects of the compound in human oral squamous cell carcinoma (OSCC). In this study, α-mangostin was assessed as a potential anticancer agent against human OSCC cells. α-Mangostin inhibited cell proliferation and induced cell death in OSCC cells in a dose- and time-dependent manner with little to no effect on normal human PDLF cells. α-Mangostin treatment clearly showed apoptotic evidences such as nuclear fragmentation and accumulation of annexin V and PI-positive cells on OSCC cells. α-Mangostin treatment also caused the collapse of mitochondrial membrane potential and the translocation of cytochrome c from the mitochondria into the cytosol. The expressions of the mitochondria-related proteins were activated by α-mangostin. Treatment with α-mangostin also induced G1 phase arrest and downregulated cell cycle-related proteins (CDK/cyclin). Hence, α-mangostin specifically induces cell death and inhibits proliferation in OSCC cells via the intrinsic apoptosis pathway and cell cycle arrest at the G1 phase, suggesting that α-mangostin may be an effective agent for the treatment of OSCC. PMID:27478478

  12. Effects of cell cycle noise on excitable gene circuits

    NASA Astrophysics Data System (ADS)

    Veliz-Cuba, Alan; Gupta, Chinmaya; Bennett, Matthew R.; Josić, Krešimir; Ott, William

    2016-12-01

    We assess the impact of cell cycle noise on gene circuit dynamics. For bistable genetic switches and excitable circuits, we find that transitions between metastable states most likely occur just after cell division and that this concentration effect intensifies in the presence of transcriptional delay. We explain this concentration effect with a three-states stochastic model. For genetic oscillators, we quantify the temporal correlations between daughter cells induced by cell division. Temporal correlations must be captured properly in order to accurately quantify noise sources within gene networks.

  13. Cell cycle-dependent control of homologous recombination.

    PubMed

    Zhao, Xin; Wei, Chengwen; Li, Jingjing; Xing, Poyuan; Li, Jingyao; Zheng, Sihao; Chen, Xuefeng

    2017-08-01

    DNA double-strand breaks (DSBs) are among the most deleterious type of DNA lesions threatening genome integrity. Homologous recombination (HR) and non-homologous end joining (NHEJ) are two major pathways to repair DSBs. HR requires a homologous template to direct DNA repair, and is generally recognized as a high-fidelity pathway. In contrast, NHEJ directly seals broken ends, but the repair product is often accompanied by sequence alterations. The choice of repair pathways is strictly controlled by the cell cycle. The occurrence of HR is restricted to late S to G2 phases while NHEJ operates predominantly in G1 phase, although it can act throughout most of the cell cycle. Deregulation of repair pathway choice can result in genotoxic consequences associated with cancers. How the cell cycle regulates the choice of HR and NHEJ has been extensively studied in the past decade. In this review, we will focus on the current progresses on how HR is controlled by the cell cycle in both Saccharomyces cerevisiae and mammals. Particular attention will be given to how cyclin-dependent kinases modulate DSB end resection, DNA damage checkpoint signaling, repair and processing of recombination intermediates. In addition, we will discuss recent findings on how HR is repressed in G1 and M phases by the cell cycle. © The Author 2017. Published by Oxford University Press on behalf of the Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  14. Mammalian interphase cdks: dispensable master regulators of the cell cycle.

    PubMed

    Enders, Greg H

    2012-11-01

    Cyclin-dependent kinases (Cdks) drive cell cycle progression in all eukaryotes. Yeasts have a single major Cdk that mediates distinct cell cycle transitions via association with different cyclins. The closest homolog in mammals, Cdk1, drives mitosis. Mammals have additional Cdks-Cdk2, Cdk4, and Cdk6-that represent the major Cdks activated during interphase (iCdks). A large body of evidence has accrued that suggests that activation of iCdks dictates progression though interphase. In apparent contradiction, deficiency in each individual iCdk, respectively, in knockout mice proved to be compatible with live birth and in some instances fertility. Moreover, murine embryos could be derived with Cdk1 as the only functional Cdk. Thus, none of the iCdks is strictly essential for mammalian cell cycle progression, raising the possibility that Cdk1 is the dominant regulator in interphase. However, an absence of iCdks has been accompanied by major shifts in cyclin association to Cdk1, suggesting gain in function. After considerable tweaking, a chemical genetic approach has recently been able to examine the impact of acute inhibition of Cdk2 activity without marked distortion of cyclin/Cdk complex formation. The results suggest that, when expressed at its normal levels, Cdk2 performs essential roles in driving human cells into S phase and maintaining genomic stability. These new findings appear to have restored order to the cell cycle field, bringing it full circle to the view that iCdks indeed play important roles. They also underscore the caveat in knockdown and knockout approaches that protein underexpression can significantly perturb a protein interaction network. We discuss the implications of the new synthesis for future cell cycle studies and anti-Cdk-based therapy of cancer and other diseases.

  15. Concise Review: Control of Cell Fate Through Cell Cycle and Pluripotency Networks.

    PubMed

    Boward, Ben; Wu, Tianming; Dalton, Stephen

    2016-06-01

    Pluripotent stem cells (PSCs) proliferate rapidly with a characteristic cell cycle structure consisting of short G1- and G2-gap phases. This applies broadly to PSCs of peri-implantation stage embryos, cultures of embryonic stem cells, induced pluripotent stem cells, and embryonal carcinoma cells. During the early stages of PSC differentiation however, cell division times increase as a consequence of cell cycle remodeling. Most notably, this is indicated by elongation of the G1-phase. Observations linking changes in the cell cycle with exit from pluripotency have raised questions about the role of cell cycle control in maintenance of the pluripotent state. Until recently however, this has been a difficult question to address because of limitations associated with experimental tools. Recent studies now show that pluripotency and cell cycle regulatory networks are intertwined and that cell cycle control mechanisms are an integral, mechanistic part of the PSC state. Studies in embryonal carcinoma, some 30 years ago, first suggested that pluripotent cells initiate differentiation when in the G1-phase. More recently, a molecular "priming" mechanism has been proposed to explain these observations in human embryonic stem cells. Complexity in this area has been increased by the realization that pluripotent cells exist in multiple developmental states and that in addition to each having their own characteristic gene expression and epigenetic signatures, they potentially have alternate modes of cell cycle regulation. This review will summarize current knowledge in these areas and will highlight important aspects of interconnections between the cell cycle, self-renewal, pluripotency, and cell fate decisions. Stem Cells 2016;34:1427-1436. © 2016 AlphaMed Press.

  16. Cell cycle-arrested tumor cells exhibit increased sensitivity towards TRAIL-induced apoptosis

    PubMed Central

    Ehrhardt, H; Wachter, F; Grunert, M; Jeremias, I

    2013-01-01

    Resting tumor cells represent a huge challenge during anticancer therapy due to their increased treatment resistance. TNF-related apoptosis-inducing ligand (TRAIL) is a putative future anticancer drug, currently in phases I and II clinical studies. We recently showed that TRAIL is able to target leukemia stem cell surrogates. Here, we tested the ability of TRAIL to target cell cycle-arrested tumor cells. Cell cycle arrest was induced in tumor cell lines and xenografted tumor cells in G0, G1 or G2 using cytotoxic drugs, phase-specific inhibitors or RNA interference against cyclinB and E. Biochemical or molecular arrest at any point of the cell cycle increased TRAIL-induced apoptosis. Accordingly, when cell cycle arrest was disabled by addition of caffeine, the antitumor activity of TRAIL was reduced. Most important for clinical translation, tumor cells from three children with B precursor or T cell acute lymphoblastic leukemia showed increased TRAIL-induced apoptosis upon knockdown of either cyclinB or cyclinE, arresting the cell cycle in G2 or G1, respectively. Taken together and in contrast to most conventional cytotoxic drugs, TRAIL exerts enhanced antitumor activity against cell cycle-arrested tumor cells. Therefore, TRAIL might represent an interesting drug to treat static-tumor disease, for example, during minimal residual disease. PMID:23744361

  17. Cell-cycle synchronisation of bloodstream forms of Trypanosoma brucei using Vybrant DyeCycle Violet-based sorting.

    PubMed

    Kabani, Sarah; Waterfall, Martin; Matthews, Keith R

    2010-01-01

    Studies on the cell-cycle of Trypanosoma brucei have revealed several unusual characteristics that differ from the model eukaryotic organisms. However, the inability to isolate homogenous populations of parasites in distinct cell-cycle stages has limited the analysis of trypanosome cell division and complicated the understanding of mutant phenotypes with possible impact on cell-cycle related events. Although hydroxyurea-induced cell-cycle arrest in procyclic and bloodstream forms has been applied recently with success, such block-release protocols can complicate the analysis of cell-cycle regulated events and have the potential to disrupt important cell-cycle checkpoints. An alternative approach based on flow cytometry of parasites stained with Vybrant DyeCycle Orange circumvents this problem, but is restricted to procyclic form parasites. Here, we apply Vybrant Dyecycle Violet staining coupled with flow cytometry to effectively select different cell-cycle stages of bloodstream form trypanosomes. Moreover, the sorted parasites remain viable, although synchrony is rapidly lost. This method enables cell-cycle enrichment of populations of trypanosomes in their mammal infective stage, particularly at the G1 phase.

  18. Understanding cell cycle and cell death regulation provides novel weapons against human diseases.

    PubMed

    Wiman, K G; Zhivotovsky, B

    2017-05-01

    Cell division, cell differentiation and cell death are the three principal physiological processes that regulate tissue homoeostasis in multicellular organisms. The growth and survival of cells as well as the integrity of the genome are regulated by a complex network of pathways, in which cell cycle checkpoints, DNA repair and programmed cell death have critical roles. Disruption of genomic integrity and impaired regulation of cell death may both lead to uncontrolled cell growth. Compromised cell death can also favour genomic instability. It is becoming increasingly clear that dysregulation of cell cycle and cell death processes plays an important role in the development of major disorders such as cancer, cardiovascular disease, infection, inflammation and neurodegenerative diseases. Research achievements in these fields have led to the development of novel approaches for treatment of various conditions associated with abnormalities in the regulation of cell cycle progression or cell death. A better understanding of how cellular life-and-death processes are regulated is essential for this development. To highlight these important advances, the Third Nobel Conference entitled 'The Cell Cycle and Cell Death in Disease' was organized at Karolinska Institutet in 2016. In this review we will summarize current understanding of cell cycle progression and cell death and discuss some of the recent advances in therapeutic applications in pathological conditions such as cancer, neurological disorders and inflammation. © 2017 The Association for the Publication of the Journal of Internal Medicine.

  19. Hydrogenosome behavior during the cell cycle in Tritrichomonas foetus.

    PubMed

    Benchimol, Marlene; Engelke, Flávio

    2003-07-01

    The hydrogenosome is an unusual organelle found in several trichomonad species and other protists living in oxygen poor or anoxic environments. The hydrogenosome behavior in the protist Tritrichomonas foetus, parasite of the urogenital tract of cattle, is reported here. The hydrogenosomes were followed by light and transmission electron microscopy during the whole cell cycle. Videomicroscopy, immunofluorescence microscopy, and immunocytochemistry were also used. It is shown that the hydrogenosomes divide at any phase of the cell cycle and that the organellar division is not synchronized. During the interphase the hydrogenosomes are distributed mainly along the axostyle and costa, and at the beginning of mitosis migrate to around the nucleus. Three forms of hydrogenosome division were seen: (1). segmentation, where elongated hydrogenosomes are further separated by external membranous profiles; (2). partition, where rounded hydrogenosomes, in a bulky form, are further separated by a membranous internal septum and, (3). a new dividing form: heart-shaped hydrogenosomes, which gradually present a membrane invagination leading to the organelle division. The hydrogenosomes divide at any phase of the cell cycle. A necklace of intramembranous particles delimiting the outer hydrogenosomal membrane in the region of organelle division was observed by freeze-etching. Similarities between hydrogenosomes and mitochondria behavior during the cell cycle are discussed.

  20. An adaptor hierarchy regulates proteolysis during a bacterial cell cycle

    PubMed Central

    Joshi, Kamal Kishore; Bergé, Matthieu; Radhakrishnan, Sunish Kumar; Viollier, Patrick Henri; Chien, Peter

    2015-01-01

    Summary Regulated protein degradation is essential. The timed destruction of crucial proteins by the ClpXP protease drives cell-cycle progression in the bacterium Caulobacter crescentus. Although ClpXP is active alone, additional factors are inexplicably required for cell-cycle dependent proteolysis. Here, we show that these factors constitute an adaptor hierarchy where different substrates are destroyed based on the degree of adaptor assembly. The hierarchy builds upon priming of ClpXP by the adaptor CpdR, which promotes degradation of one class of substrates and also recruits the adaptor RcdA to degrade a second class of substrates. Adding the PopA adaptor promotes destruction of a third class of substrates, while inhibiting degradation of the second class. We dissect RcdA to generate bespoke adaptors, identifying critical substrate elements needed for RcdA recognition and uncovering additional cell-cycle dependent ClpXP substrates. Our work reveals how hierarchical adaptors and primed proteases orchestrate regulated proteolysis during bacterial cell-cycle progression. PMID:26451486

  1. Cycle life status of SAFT VOS nickel-cadmium cells

    NASA Technical Reports Server (NTRS)

    Goualard, Jacques

    1993-01-01

    The SAFT prismatic VOS Ni-Cd cells have been flown in geosynchronous orbit since 1977 and in low earth orbit since 1983. Parallel cycling tests are performed by several space agencies in order to determine the cycle life for a wide range of temperature and depth of discharge (DOD). In low Earth orbit (LEO), the ELAN program is conducted on 24 Ah cells by CNES and ESA at the European Battery Test Center at temperatures ranging from 0 to 27 C and DOD from 10 to 40 percent. Data are presented up to 37,000 cycles. One pack (X-80) has achieved 49,000 cycles at 10 C and 23 percent DOD. The geosynchronous orbit simulation of a high DOD test is conducted by ESA on 3 batteries at 10 C and 70, 90, and 100 percent DOD. Thirty-one eclipse seasons are completed, and no signs of degradation have been found. The Air Force test at CRANE on 24 Ah and 40 Ah cells at 20 C and 80 percent DOD has achieved 19 shadow periods. Life expectancy is discussed. The VOS cell technology could be used for the following: (1) in geosynchronous conditions--15 yrs at 10-15 C and 80 percent DOD; and (2) in low earth orbit--10 yrs at 5-15 C and 25-30 percent DOD.

  2. Evaluation program for secondary spacecraft cells: Cycle life test

    NASA Technical Reports Server (NTRS)

    Harkness, J. D.

    1979-01-01

    The service life and storage stability for several storage batteries were determined. The batteries included silver-zinc batteries, nickel-cadmium batteries, and silver-cadmium batteries. The cell performance characteristics and limitations are to be used by spacecraft power systems planners and designers. A statistical analysis of the life cycle prediction and cause of failure versus test conditions is presented.

  3. Sonoporation-Induced Apoptosis and Cell Cycle Arrest: Initial Findings

    NASA Astrophysics Data System (ADS)

    Zhong, Wenjing; Sit, Wai Hung; Wan, Jennifer M. F.; Yu, Alfred C. H.

    2011-09-01

    Sonoporation is known to be able to temporarily permeabilize cells, but during this process it may have traumatic impact on cell viability. In this work, we found that sonoporation may induce apoptosis and G2/M-phase cell cycle arrest in some cells hours after ultrasonic exposure in vitro. Methods: Suspensions of HL-60 leukemia cells were prepared (106 cells/ml), and a 1% v/v microbubble solution was added to induce sonoporation during ultrasound exposure. They were then placed 7 cm away from a 2.54 cm-diameter, 1 MHz unfocused ultrasound probe, and these samples were insonated for 1 min with ultrasound pulses (10% duty cycle, 1 kHz pulse repetition frequency). In this study, two levels of peak negative ultrasound pressure were used: 0.3 MPa and 0.5 MPa. After exposure, the cell suspensions were further incubated. They were harvested after 4 h, 8 h, 12 h and 24 h to analyze the cell-cycle distribution (sub-G1, G0/G1, S, G2/M) at these time points using propidium iodide staining and flow cytometry. Results: Some sonoporation-treated cells had undergone apoptosis by 4h, and the largest number of apoptotic cells (sub-G1 phase) was observed after 12h (0.3 MPa group: 25.0%; 0.5 MPa group: 27.2%). Also, after experiencing sonoporation, some viable cells were stopped in the G2/M phase without undergoing cytokinesis, and the maximum G2/M population rise was seen after 12h (0.3 MPa group: +12.2%; 0.5 MPa group: +14.7%). This was accompanied by decreases in the populations of G0/G1-phase and S-phase.

  4. Visualizing cell-cycle kinetics after hypoxia/reoxygenation in HeLa cells expressing fluorescent ubiquitination-based cell cycle indicator (Fucci).

    PubMed

    Goto, Tatsuaki; Kaida, Atsushi; Miura, Masahiko

    2015-12-10

    Hypoxia induces G1 arrest in many cancer cell types. Tumor cells are often exposed to hypoxia/reoxygenation, especially under acute hypoxic conditions in vivo. In this study, we investigated cell-cycle kinetics and clonogenic survival after hypoxia/reoxygenation in HeLa cells expressing fluorescent ubiquitination-based cell cycle indicator (Fucci). Hypoxic treatment halted cell-cycle progression during mid-S to G2 phase, as determined by the cell cycle-regulated E3 ligase activities of SCF(Skp2) and APC/C(Cdh1), which are regulators of the Fucci probes; however, the DNA content of the arrested cells was equivalent to that in G1 phase. After reoxygenation, time-lapse imaging and DNA content analysis revealed that all cells reached G2 phase, and that Fucci fluorescence was distinctly separated into two fractions 24h after reoxygenation: red cells that released from G2 arrest after repairing DNA double-strand breaks (DSBs) exhibited higher clonogenic survival, whereas most cells that stayed green contained many DSBs and exhibited lower survival. We conclude that hypoxia disrupts coordination of DNA synthesis and E3 ligase activities associated with cell-cycle progression, and that DSB repair could greatly influence cell-cycle kinetics and clonogenic survival after hypoxia/reoxygenation. Copyright © 2015 Elsevier Inc. All rights reserved.

  5. Cell cycle-dependent radiosensitivity in two-cell mouse embryos in culture

    SciTech Connect

    Domon, M.

    1980-02-01

    The radiosensitivity in embryo systems varies depending on factors such as genetic background, oxygen environment, developmental stage, and age of the embryo in cell cycle. This paper is concerned with the involvement of cell cycle age in radiosensitivity of two-cell mouse embryos. Thus the doses needed for 50% killing of blastocyst formation in vitro (LD/sub 50/) of X rays for the two-cell mouse embryos in culture were measured during their cell cycle. The cell cycle in the two-cell embryos was quite peculiar; the cell cycle time of 18 h was divided into a long DNA post synthesis phase (G/sub 2/) plus mitosis (M) of 14 h and a short DNA synthesis phase (S) of 4 h. Results indicate that the LD/sub 50/ varies roughly from 100 to 600 rad within the cell cycle. Thus a major factor in determining the sensitivity to ionizing radiation of two-cell mouse embryos in vitro and perhaps in vivo is their position in the cell division cycle at the time of irradiation.

  6. Protein turnover in the cell cycle of Escherichia coli.

    PubMed

    Nishi, A; Kogoma, T

    1965-10-01

    Nishi, Arasuke (University of Tokyo, Tokyo, Japan), and Tokio Kogoma. Protein turnover in the cell cycle of Escherichia coli. J. Bacteriol. 90:884-890. 1965.-Protein metabolism and enzyme formation throughout the cell cycle were investigated in synchronized cultures of Escherichia coli. The cells showed a temporary cessation of the net increase of bulk protein and of constitutive beta-galactosidase activity during the division period. By contrast, when tested by short-term experiments performed with cells at different growth stages, the bacteria displayed a constant incorporation of labeled protein precursors into the protein fraction, even during the fission period. Similar results were obtained with respect to the capacities for induced enzyme formation. On the other hand, when the cells were previously labeled and then subjected to synchronization in a nonradioactive medium, the radioactivity of the protein fraction decreased temporarily by nearly 10% during the fission period and then regained its previous level at the beginning of the ensuing phase of growth. This indicates that the products of partial degradation of protein were again utilized for protein synthesis in the next cell cycle. It was concluded that the temporary lagging of net increase of bulk protein may be due to the partial breakdown of protein occurring during the fission period.

  7. Cell cycle analysis of fetal germ cells during sex differentiation in mice

    PubMed Central

    Spiller, Cassy; Wilhelm, Dagmar; Koopman, Peter

    2009-01-01

    Background information. Primordial germ cells in developing male and female gonads are responsive to somatic cell cues that direct their sex-specific differentiation into functional gametes. The first divergence of the male and female pathways is a change in cell cycle state observed from 12.5 dpc (days post coitum) in mice. At this time XY and XX germ cells cease mitotic division and enter G1/G0 arrest and meiosis prophase I respectively. Aberrant cell cycle regulation at this time can lead to disrupted ovarian development, germ cell apoptosis, reduced fertility and/or the formation of germ cell tumours. Results. In order to unravel the mechanisms utilized by germ cells to achieve and maintain the correct cell cycle states, we analysed the expression of a large number of cell cycle genes in purified germ cells across the crucial time of sex differentiation. Our results revealed common signalling for both XX and XY germ cell survival involving calcium signalling. A robust mechanism for apoptosis and checkpoint control was observed in XY germ cells, characterized by p53 and Atm (ataxia telangiectasia mutated) expression. Additionally, a member of the retinoblastoma family and p21 were identified, linking these factors to XY germ cell G1/G0 arrest. Lastly, in XX germ cells we observed a down-regulation of genes involved in both G1- and G2-phases of the cell cycle consistent with their entry into meiosis. Conclusion. The present study has provided a detailed analysis of cell cycle gene expression during fetal germ cell development and identified candidate factors warranting further investigation in order to understand cases of aberrant cell cycle control in these specialized cells. PMID:19419345

  8. A Coarse Estimation of Cell Size Region from a Mesoscopic Stochastic Cell Cycle Model

    NASA Astrophysics Data System (ADS)

    Yi, Ming; Jia, Ya; Liu, Quan; Zhu, Chun-Lian; Yang, Li-Jian

    2007-07-01

    Based on a deterministic cell cycle model of fission yeast, the effects of the finite cell size on the cell cycle regulation in wee1- cdc25Δ double mutant type are numerically studied by using of the chemical Langevin equations. It is found that at a certain region of cell size, our numerical results from the chemical Langevin equations are in good qualitative agreement with the experimental observations. The two resettings to the G2 phase from early stages of mitosis can be induced under the moderate cell size. The quantized cycle times can be observed during such a cell size region. Therefore, a coarse estimation of cell size is obtained from the mesoscopic stochastic cell cycle model.

  9. Lipoxygenase inhibitors induce arrest of tumor cells in S-phase of the cell cycle.

    PubMed

    Hofmanová, J; Soucek, K; Pacherník, J; Kovaríková, M; Hoferová, Z; Minksová, K; Netíková, J; Kozubík, A

    2002-01-01

    Inhibitors of the lipoxygenase pathway of arachidonic acid metabolism represent a potential anti-tumor drugs. These compounds have been found to inhibit the growth and induce the apoptosis of various tumor cells both in vitro and in vivo. In this study, the effects of the lipoxygenase inhibitors esculetin and nordihydroguaiaretic acid (NDGA) on the progression of the cell cycle were investigated in eight mammalian cell lines of different origin. Flow cytometric analyses of cell cycle distribution after staining of DNA with propidium iodide or 7-aminoactinomycin D and DNA synthesis using incorporation of 5-bromo-2'-deoxy-uridine showed that both esculetin and NDGA suppress cell growth by interrupting the progression of cells through S-phase that results in their accumulation in this phase of the cell cycle. The possible mechanisms of these effects and the significance of the findings for the improvement of anticancer therapy targeted on cell cycle is discussed.

  10. Cell-cycle quiescence maintains Caenorhabditis elegans germline stem cells independent of GLP-1/Notch.

    PubMed

    Seidel, Hannah S; Kimble, Judith

    2015-11-09

    Many types of adult stem cells exist in a state of cell-cycle quiescence, yet it has remained unclear whether quiescence plays a role in maintaining the stem cell fate. Here we establish the adult germline of Caenorhabditis elegans as a model for facultative stem cell quiescence. We find that mitotically dividing germ cells--including germline stem cells--become quiescent in the absence of food. This quiescence is characterized by a slowing of S phase, a block to M-phase entry, and the ability to re-enter M phase rapidly in response to re-feeding. Further, we demonstrate that cell-cycle quiescence alters the genetic requirements for stem cell maintenance: The signaling pathway required for stem cell maintenance under fed conditions--GLP-1/Notch signaling--becomes dispensable under conditions of quiescence. Thus, cell-cycle quiescence can itself maintain stem cells, independent of the signaling pathway otherwise essential for such maintenance.

  11. Existence of Corneal Endothelial Slow-Cycling Cells

    PubMed Central

    Espana, Edgar M.; Sun, Mei; Birk, David E.

    2015-01-01

    Purpose. To demonstrate the presence and location of corneal endothelial progenitor cells. Methods. Progenitor cell markers nestin, leucine-rich repeat-containing G-protein–coupled receptor 5, Sox9, and nerve growth factor receptor p75, as well as proliferation marker Ki-67, were examined on postnatal day (P)3, P30, and P90 corneas using immunofluorescence microscopy. Mice (P3) were pulsed with 5-bromo-2′-deoxyuridine (BrdU) and chased. Results. Cell proliferation was observed in all layers of P3 corneas. No posterior stromal cell proliferation was noted in P30 corneas. Progenitor cell markers were expressed in the P3 cornea, but were downregulated during maturation with minimal or no expression in P90 central corneas. In contrast, cells expressing progenitor markers were located exclusively at the corneal periphery at P90. Clusters of cells reactive for progenitor markers were in the endothelial and subendothelial space in the P90 peripheral cornea. Reactivity against BrdU was localized to the central and peripheral cornea at 1 week, and to the extreme periphery 3 weeks following a BrdU pulse. Cells reactive for both BrdU and progenitor markers were localized to the peripheral endothelium. At 3 weeks, cells reactive for BrdU and the progenitor markers were localized in the peripheral endothelium. Approximately, 20% to 45% of the progenitor marker positive cells also were labeled with BrdU. Conclusions. During development, the murine corneal endothelium is composed of proliferating cells expressing progenitor markers. In contrast, in the mature endothelium slow-cycling cells, cells expressing progenitor markers and a subpopulation of slow-cycling cells expressing progenitor makers are restricted to the endothelial periphery. PMID:26066751

  12. The influence of reactive oxygen species on cell cycle progression in mammalian cells.

    PubMed

    Verbon, Eline Hendrike; Post, Jan Andries; Boonstra, Johannes

    2012-12-10

    Cell cycle regulation is performed by cyclins and cyclin dependent kinases (CDKs). Recently, it has become clear that reactive oxygen species (ROS) influence the presence and activity of these enzymes and thereby control cell cycle progression. In this review, we first describe the discovery of enzymes specialized in ROS production: the NADPH oxidase (NOX) complexes. This discovery led to the recognition of ROS as essential players in many cellular processes, including cell cycle progression. ROS influence cell cycle progression in a context-dependent manner via phosphorylation and ubiquitination of CDKs and cell cycle regulatory molecules. We show that ROS often regulate ubiquitination via intermediate phosphorylation and that phosphorylation is thus the major regulatory mechanism influenced by ROS. In addition, ROS have recently been shown to be able to activate growth factor receptors. We will illustrate the diverse roles of ROS as mediators in cell cycle regulation by incorporating phosphorylation, ubiquitination and receptor activation in a model of cell cycle regulation involving EGF-receptor activation. We conclude that ROS can no longer be ignored when studying cell cycle progression. Copyright © 2012 Elsevier B.V. All rights reserved.

  13. Single cell studies of the cell cycle and some models

    PubMed Central

    Mitchison, JM

    2005-01-01

    Analysis of growth and division often involves measurements made on cell populations, which tend to average data. The value of single cell analysis needs to be appreciated, and models based on findings from single cells should be taken into greater consideration in our understanding of the way in which cell size and division are co-ordinated. Examples are given of some single cell analyses in mammalian cells, yeast and other microorganisms. There is also a short discussion on how far the results are in accord with simple models. PMID:15703075

  14. Autophagy and the Cell Cycle: A Complex Landscape

    PubMed Central

    Mathiassen, Søs Grønbæk; De Zio, Daniela; Cecconi, Francesco

    2017-01-01

    Autophagy is a self-degradation pathway, in which cytoplasmic material is sequestered in double-membrane vesicles and delivered to the lysosome for degradation. Under basal conditions, autophagy plays a homeostatic function. However, in response to various stresses, the pathway can be further induced to mediate cytoprotection. Defective autophagy has been linked to a number of human pathologies, including neoplastic transformation, even though autophagy can also sustain the growth of tumor cells in certain contexts. In recent years, a considerable correlation has emerged between autophagy induction and stress-related cell-cycle responses, as well as unexpected roles for autophagy factors and selective autophagic degradation in the process of cell division. These advances have obvious implications for our understanding of the intricate relationship between autophagy and cancer. In this review, we will discuss our current knowledge of the reciprocal regulation connecting the autophagy pathway and cell-cycle progression. Furthermore, key findings involving nonautophagic functions for autophagy-related factors in cell-cycle regulation will be addressed. PMID:28409123

  15. Cell Cycle Programs of Gene Expression Control Morphogenetic Protein Localization

    PubMed Central

    Lord, Matthew; Yang, Melody C.; Mischke, Michelle; Chant, John

    2000-01-01

    Genomic studies in yeast have revealed that one eighth of genes are cell cycle regulated in their expression. Almost without exception, the significance of cell cycle periodic gene expression has not been tested. Given that many such genes are critical to cellular morphogenesis, we wanted to examine the importance of periodic gene expression to this process. The expression profiles of two genes required for the axial pattern of cell division, BUD3 and BUD10/AXL2/SRO4, are strongly cell cycle regulated. BUD3 is expressed close to the onset of mitosis. BUD10 is expressed in late G1. Through promotor-swap experiments, the expression profile of each gene was altered and the consequences examined. We found that an S/G2 pulse of BUD3 expression controls the timing of Bud3p localization, but that this timing is not critical to Bud3p function. In contrast, a G1 pulse of BUD10 expression plays a direct role in Bud10p localization and function. Bud10p, a membrane protein, relies on the polarized secretory machinery specific to G1 to be delivered to its proper location. Such a secretion-based targeting mechanism for membrane proteins provides cells with flexibility in remodeling their architecture or evolving new forms. PMID:11134078

  16. Instructive simulation of the bacterial cell division cycle.

    PubMed

    Zaritsky, Arieh; Wang, Ping; Vischer, Norbert O E

    2011-07-01

    The coupling between chromosome replication and cell division includes temporal and spatial elements. In bacteria, these have globally been resolved during the last 40 years, but their full details and action mechanisms are still under intensive study. The physiology of growth and the cell cycle are reviewed in the light of an established dogma that has formed a framework for development of new ideas, as exemplified here, using the Cell Cycle Simulation (CCSim) program. CCSim, described here in detail for the first time, employs four parameters related to time (replication, division and inter-division) and size (cell mass at replication initiation) that together are sufficient to describe bacterial cells under various conditions and states, which can be manipulated environmentally and genetically. Testing the predictions of CCSim by analysis of time-lapse micrographs of Escherichia coli during designed manipulations of the rate of DNA replication identified aspects of both coupling elements. Enhanced frequencies of cell division were observed following an interval of reduced DNA replication rate, consistent with the prediction of a minimum possible distance between successive replisomes (an eclipse). As a corollary, the notion that cell poles are not always inert was confirmed by observed placement of division planes at perpendicular planes in monstrous and cuboidal cells containing multiple, segregating nucleoids.

  17. Dynamics of gene regulatory networks with cell division cycle

    NASA Astrophysics Data System (ADS)

    Chen, Luonan; Wang, Ruiqi; Kobayashi, Tetsuya J.; Aihara, Kazuyuki

    2004-07-01

    This paper focuses on modeling and analyzing the nonlinear dynamics of gene regulatory networks with the consideration of a cell division cycle with duplication process of DNA , in particular for switches and oscillators of synthetic networks. We derive two models that may correspond to the eukaryotic and prokaryotic cells, respectively. A biologically plausible three-gene model ( lac,tetR , and cI ) and a repressilator as switch and oscillator examples are used to illustrate our theoretical results. We show that the cell cycle may play a significant role in gene regulation due to the nonlinear dynamics of a gene regulatory network although gene expressions are usually tightly controlled by transcriptional factors.

  18. Cell-cycle analyses using thymidine analogues in fission yeast.

    PubMed

    Anda, Silje; Boye, Erik; Grallert, Beata

    2014-01-01

    Thymidine analogues are powerful tools when studying DNA synthesis including DNA replication, repair and recombination. However, these analogues have been reported to have severe effects on cell-cycle progression and growth, the very processes being investigated in most of these studies. Here, we have analyzed the effects of 5-ethynyl-2'-deoxyuridine (EdU) and 5-Chloro-2'-deoxyuridine (CldU) using fission yeast cells and optimized the labelling procedure. We find that both analogues affect the cell cycle, but that the effects can be mitigated by using the appropriate analogue, short pulses of labelling and low concentrations. In addition, we report sequential labelling of two consecutive S phases using EdU and 5-bromo-2'-deoxyuridine (BrdU). Furthermore, we show that detection of replicative DNA synthesis is much more sensitive than DNA-measurements by flow cytometry.

  19. Pseudolaric acid B induced cell cycle arrest, autophagy and senescence in murine fibrosarcoma l929 cell.

    PubMed

    Yu, Jing hua; Liu, Chun yu; Zheng, Gui bin; Zhang, Li Ying; Yan, Ming hui; Zhang, Wen yan; Meng, Xian ying; Yu, Xiao fang

    2013-01-01

    PAB induced various cancer cell apoptosis, cell cycle arrest and senescence. But in cell line murine fibrosarcoma L929, PAB did not induce apoptosis, but autophagy, therefore it was thought by us as a good model to research the relationship of cell cycle arrest, autophagy and senescence bypass apoptosis. Inhibitory ratio was assessed by 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) analysis. Phase contrast microscopy visualized cell morphology. Hoechst 33258 staining for nuclear change, propidium iodode (PI) staining for cell cycle, monodansylcadaverine (MDC) staining for autophagy, and rodanmine 123 staining for mitochondrial membrane potential (MMP) were measured by fluorescence microscopy or flowcytometry. Apoptosis was determined by DNA ladder test. Protein kinase C (PKC) activity was detected by PKC assay kit. SA-β-galactosidase assay was used to detect senescence. Protein expression was examined by western blot. PAB inhibited L929 cell growth in time-and dose-dependent manner. At 12 h, 80 μmol/L PAB induced obvious mitotic arrest; at 24 h, PAB began to induce autophagy; at 36 h, cell-treated with PAB slip into G1 cell cycle; and 3 d PAB induced senescence. In time sequence PAB induced firstly cell cycle arrest, then autophagy, then slippage into G1 phase, lastly senescence. Senescent cells had high level of autophagy, inhibiting autophagy led to apoptosis, and no senescence. PAB activated PKC activity to induce cell cycle arrest, autophagy and senescence, inhibiting PKC activity suppressed cell cycle arrest, autophagy and senescence. PAB induced cell cycle arrest, autophagy and senescence in murine fibrosarcoma L929 cell through PKC.

  20. Effects of c-myc expression on cell cycle progression.

    PubMed Central

    Hanson, K D; Shichiri, M; Follansbee, M R; Sedivy, J M

    1994-01-01

    We used targeted homologous recombination to disrupt one c-myc gene copy in a diploid fibroblast cell line and found that a twofold reduction in Myc expression resulted in lower exponential growth rates and a lengthening of the G0-to-S-phase transition (M. Shichiri, K. D. Hanson and J. M. Sedivy, Cell Growth Differ. 4:93-104, 1993). Myc is a transcription factor, and the number of target genes whose regulation could result in differential growth rates may be very large. We have approached this problem by examining effects of reduced c-myc expression in three broad areas: (i) secretion of growth factors, (ii) expression of growth factor receptors, and (iii) intracellular signal transduction between Myc and components of the intrinsic cell cycle clock. We have found no evidence that differential medium conditioning can account for the growth phenotypes. Likewise, the expression of receptors for platelet-derived growth factor, epidermal growth factor, basic fibroblast growth factor, and insulin-like growth factor I was the same in diploid and heterozygous cells (platelet-derived growth factor, epidermal growth factor, fibroblast growth factor, and insulin-like growth factor are the sole growth factors required by these cells for growth in serum-free medium). In contrast, expression of cyclin E, cyclin A, and Rb phosphorylation were delayed when quiescent c-myc heterozygous cells were stimulated to enter the cell cycle. Expression of cyclin D1, cyclin D3, and Cdk2 was not affected. The timing of cyclin E induction was the earliest observable effect of reduced Myc expression. Our data indicate that Myc contributes to regulation of proliferation by a cell-autonomous mechanism that involves the modulation of cyclin E expression and, consequently, progression through the restriction point of the cell cycle. Images PMID:8065309

  1. Piperlongumine Suppresses Proliferation of Human Oral Squamous Cell Carcinoma through Cell Cycle Arrest, Apoptosis and Senescence.

    PubMed

    Chen, San-Yuan; Liu, Geng-Hung; Chao, Wen-Ying; Shi, Chung-Sheng; Lin, Ching-Yen; Lim, Yun-Ping; Lu, Chieh-Hsiang; Lai, Peng-Yeh; Chen, Hau-Ren; Lee, Ying-Ray

    2016-04-23

    Oral squamous cell carcinoma (OSCC), an aggressive cancer originating in the oral cavity, is one of the leading causes of cancer deaths in males worldwide. This study investigated the antitumor activity and mechanisms of piperlongumine (PL), a natural compound isolated from Piper longum L., in human OSCC cells. The effects of PL on cell proliferation, the cell cycle, apoptosis, senescence and reactive oxygen species (ROS) levels in human OSCC cells were investigated. PL effectively inhibited cell growth, caused cell cycle arrest and induced apoptosis and senescence in OSCC cells. Moreover, PL-mediated anti-human OSCC behavior was inhibited by an ROS scavenger N-acetyl-l-cysteine (NAC) treatment, suggesting that regulation of ROS was involved in the mechanism of the anticancer activity of PL. These findings suggest that PL suppresses tumor growth by regulating the cell cycle and inducing apoptosis and senescence and is a potential chemotherapy agent for human OSCC cells.

  2. NSA2, a novel nucleolus protein regulates cell proliferation and cell cycle

    SciTech Connect

    Zhang, Heyu; Ma, Xi; Shi, Taiping; Song, Quansheng; Zhao, Hongshan; Ma, Dalong

    2010-01-01

    NSA2 (Nop seven-associated 2) was previously identified in a high throughput screen of novel human genes associated with cell proliferation, and the NSA2 protein is evolutionarily conserved across different species. In this study, we revealed that NSA2 is broadly expressed in human tissues and cultured cell lines, and located in the nucleolus of the cell. Both of the putative nuclear localization signals (NLSs) of NSA2, also overlapped with nucleolar localization signals (NoLSs), are capable of directing nucleolar accumulation. Moreover, over-expression of the NSA2 protein promoted cell growth in different cell lines and regulated the G1/S transition in the cell cycle. SiRNA silencing of the NSA2 transcript attenuated the cell growth and dramatically blocked the cell cycle in G1/S transition. Our results demonstrated that NSA2 is a nucleolar protein involved in cell proliferation and cell cycle regulation.

  3. Relation Between the Cell Volume and the Cell Cycle Dynamics in Mammalian cell

    NASA Astrophysics Data System (ADS)

    Magno, A. C. G.; Oliveira, I. L.; Hauck, J. V. S.

    2016-08-01

    The main goal of this work is to add and analyze an equation that represents the volume in a dynamical model of the mammalian cell cycle proposed by Gérard and Goldbeter (2011) [1]. The cell division occurs when the cyclinB/Cdkl complex is totally degraded (Tyson and Novak, 2011)[2] and it reaches a minimum value. At this point, the cell is divided into two newborn daughter cells and each one will contain the half of the cytoplasmic content of the mother cell. The equations of our base model are only valid if the cell volume, where the reactions occur, is constant. Whether the cell volume is not constant, that is, the rate of change of its volume with respect to time is explicitly taken into account in the mathematical model, then the equations of the original model are no longer valid. Therefore, every equations were modified from the mass conservation principle for considering a volume that changes with time. Through this approach, the cell volume affects all model variables. Two different dynamic simulation methods were accomplished: deterministic and stochastic. In the stochastic simulation, the volume affects every model's parameters which have molar unit, whereas in the deterministic one, it is incorporated into the differential equations. In deterministic simulation, the biochemical species may be in concentration units, while in stochastic simulation such species must be converted to number of molecules which are directly proportional to the cell volume. In an effort to understand the influence of the new equation a stability analysis was performed. This elucidates how the growth factor impacts the stability of the model's limit cycles. In conclusion, a more precise model, in comparison to the base model, was created for the cell cycle as it now takes into consideration the cell volume variation

  4. Cell cycle regulation during proliferation and differentiation of mammalian muscle precursor cells.

    PubMed

    Ciemerych, Maria A; Archacka, Karolina; Grabowska, Iwona; Przewoźniak, Marta

    2011-01-01

    Proliferation and differentiation of muscle precursor cells are intensively studied not only in the developing mouse embryo but also using models of skeletal muscle regeneration or analyzing in vitro cultured cells. These analyses allowed to show the universality of the cell cycle regulation and also uncovered tissue-specific interplay between major cell cycle regulators and factors crucial for the myogenic differentiation. Examination of the events accompanying proliferation and differentiation leading to the formation of functional skeletal muscle fibers allows understanding the molecular basis not only of myogenesis but also of skeletal muscle regeneration. This chapter presents the basis of the cell cycle regulation in proliferating and differentiating muscle precursor cells during development and after muscle injury. It focuses at major cell cycle regulators, myogenic factors, and extracellular environment impacting on the skeletal muscle.

  5. High efficiency carbonate fuel cell/turbine hybrid power cycles

    SciTech Connect

    Steinfeld, G.

    1995-10-19

    Carbonate fuel cells developed by Energy Research Corporation, in commercial 2.85 MW size, have an efficiency of 57.9 percent. Studies of higher efficiency hybrid power cycles were conducted in cooperation with METC to identify an economically competitive system with an efficiency in excess of 65 percent. A hybrid power cycle was identified that includes a direct carbonate fuel cell, a gas turbine and a steam cycle, which generates power at a LHV efficiency in excess of 70 percent. This new system is called a Tandem Technology Cycle (TTC). In a TTC operating on natural gas fuel, 95 percent of the fuel is mixed with recycled fuel cell anode exhaust, providing water for the reforming of the fuel, and flows to a direct carbonate fuel cell system which generates 72 percent of the power. The portion of the fuel cell anode exhaust which is not recycled, is burned and heat is transferred to the compressed air from a gas turbine, raising its temperature to 1800{degrees}F. The stream is then heated to 2000{degrees}F in the gas turbine burner and expands through the turbine generating 13 percent of the power. Half the exhaust from the gas turbine flows to the anode exhaust burner, and the remainder flows to the fuel cell cathodes providing the O{sub 2} and CO{sub 2} needed in the electrochemical reaction. Exhaust from the fuel cells flows to a steam system which includes a heat recovery steam generator and stages steam turbine which generates 15 percent of the TTC system power. Studies of the TTC for 200-MW and 20-MW size plants quantified performance, emissions and cost-of-electricity, and compared the characteristics of the TTC to gas turbine combined cycles. A 200-MW TTC plant has an efficiency of 72.6 percent, and is relatively insensitive to ambient temperature, but requires a heat exchanger capable of 2000{degrees}F. The estimated cost of electricity is 45.8 mills/kWhr which is not competitive with a combined cycle in installations where fuel cost is under $5.8/MMBtu.

  6. Cell-size dependent progression of the cell cycle creates homeostasis and flexibility of plant cell size

    PubMed Central

    R. Jones, Angharad; Forero-Vargas, Manuel; Withers, Simon P.; Smith, Richard S.; Traas, Jan; Dewitte, Walter; Murray, James A. H.

    2017-01-01

    Mean cell size at division is generally constant for specific conditions and cell types, but the mechanisms coupling cell growth and cell cycle control with cell size regulation are poorly understood in intact tissues. Here we show that the continuously dividing fields of cells within the shoot apical meristem of Arabidopsis show dynamic regulation of mean cell size dependent on developmental stage, genotype and environmental signals. We show cell size at division and cell cycle length is effectively predicted using a two-stage cell cycle model linking cell growth and two sequential cyclin dependent kinase (CDK) activities, and experimental results concur in showing that progression through both G1/S and G2/M is size dependent. This work shows that cell-autonomous co-ordination of cell growth and cell division previously observed in unicellular organisms also exists in intact plant tissues, and that cell size may be an emergent rather than directly determined property of cells. PMID:28447614

  7. Modeling circadian clock-cell cycle interaction effects on cell population growth rates.

    PubMed

    El Cheikh, R; Bernard, S; El Khatib, N

    2014-12-21

    The circadian clock and the cell cycle are two tightly coupled oscillators. Recent analytical studies have shown counter-intuitive effects of circadian gating of the cell cycle on growth rates of proliferating cells which cannot be explained by a molecular model or a population model alone. In this work, we present a combined molecular-population model that studies how coupling the circadian clock to the cell cycle, through the protein WEE1, affects a proliferating cell population. We show that the cell cycle can entrain to the circadian clock with different rational period ratios and characterize multiple domains of entrainment. We show that coupling increases the growth rate for autonomous periods of the cell cycle around 24 h and above 48 h. We study the effect of mutation of circadian genes on the growth rate of cells and show that disruption of the circadian clock can lead to abnormal proliferation. Particularly, we show that Cry 1, Cry 2 mutations decrease the growth rate of cells, Per 2 mutation enhances it and Bmal 1 knockout increases it for autonomous periods of the cell cycle less than 21 h and decreases it elsewhere. Combining a molecular model to a population model offers new insight on the influence of the circadian clock on the growth of a cell population. This can help chronotherapy which takes benefits of physiological rhythms to improve anti-cancer efficacy and tolerance to drugs by administering treatments at a specific time of the day. Copyright © 2014 Elsevier Ltd. All rights reserved.

  8. CELL CYCLE SYNCHRONIZATION OF MOUSE LIVER EPITHELIAL CELLS BY ELUTRIATION CENTRIFUGATION

    SciTech Connect

    Pearlman, Andrew L.; Bartholomew, James C.

    1980-06-01

    Detailed methods are described for the sorting and cell cycle synchronization by means of centrifugal elutriation of an established mouse liver epithelial cell line(NMuLi). In a comparison between three different elutriation media and between two different temperatures(4° and 20° C), the NMuLi cells were found to be most reproducibly sorted in the cell cycle when run in growth medium in the absence of serum and at the lower temperature. Under these conditions. and using decrements of rotor speed calculated from an empirically derived algorithm as described in the text an initially asynchronous population (38% G{sub 1}, 36% S, and 28% G{sub 2}M) was sorted into fractions enriched to 60% G{sub 1}, 75% S, and 50% G{sub 2}M. Of the cells loaded into the rotor, 30% were lost in the elutriation process, and about 20% recovered as aggregates. The remainder appeared in the various synchronized fractions. Epithelial cells sorted in this manner demonstrated no loss of viability, and upon replating showed significant movement in the cell cycle by 6 hrs post elutriation. The degree of synchronous movement through the cell cycle achieved by elutriation depended on the part of the cell cycle from which the original elutriated fraction came. Cells collected as late S and G{sub 2}M moved through the cell cycle with the tightest sychrony.

  9. Short-Stalked Prosthecomicrobium hirschii Cells Have a Caulobacter-Like Cell Cycle

    PubMed Central

    Williams, Michelle; Hoffman, Michelle D.; Daniel, Jeremy J.; Madren, Seth M.; Dhroso, Andi; Korkin, Dmitry; Givan, Scott A.; Jacobson, Stephen C.

    2016-01-01

    ABSTRACT The dimorphic alphaproteobacterium Prosthecomicrobium hirschii has both short-stalked and long-stalked morphotypes. Notably, these morphologies do not arise from transitions in a cell cycle. Instead, the maternal cell morphology is typically reproduced in daughter cells, which results in microcolonies of a single cell type. In this work, we further characterized the short-stalked cells and found that these cells have a Caulobacter-like life cycle in which cell division leads to the generation of two morphologically distinct daughter cells. Using a microfluidic device and total internal reflection fluorescence (TIRF) microscopy, we observed that motile short-stalked cells attach to a surface by means of a polar adhesin. Cells attached at their poles elongate and ultimately release motile daughter cells. Robust biofilm growth occurs in the microfluidic device, enabling the collection of synchronous motile cells and downstream analysis of cell growth and attachment. Analysis of a draft P. hirschii genome sequence indicates the presence of CtrA-dependent cell cycle regulation. This characterization of P. hirschii will enable future studies on the mechanisms underlying complex morphologies and polymorphic cell cycles. IMPORTANCE Bacterial cell shape plays a critical role in regulating important behaviors, such as attachment to surfaces, motility, predation, and cellular differentiation; however, most studies on these behaviors focus on bacteria with relatively simple morphologies, such as rods and spheres. Notably, complex morphologies abound throughout the bacteria, with striking examples, such as P. hirschii, found within the stalked Alphaproteobacteria. P. hirschii is an outstanding candidate for studies of complex morphology generation and polymorphic cell cycles. Here, the cell cycle and genome of P. hirschii are characterized. This work sets the stage for future studies of the impact of complex cell shapes on bacterial behaviors. PMID:26833409

  10. 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 (

  11. Astaxanthin Inhibits Proliferation and Induces Apoptosis and Cell Cycle Arrest of Mice H22 Hepatoma Cells

    PubMed Central

    Shao, Yiye; Ni, Yanbo; Yang, Jing; Lin, Xutao; Li, Jun; Zhang, Lixia

    2016-01-01

    Background It is widely recognized that astaxanthin (ASX), a member of the carotenoid family, has strong biological activities including antioxidant, anti-inflammation, and immune-modulation activities. Previous studies have confirmed that ASX can effectively inhibit hepatoma cells in vitro. Material/Methods MTT was used to assay proliferation of mice H22 cells, and flow cytometry was used to determine apoptosis and cell cycle arrest of H22 cells in vitro and in vivo. Moreover, anti-tumor activity of ASX was observed in mice. Results ASX inhibited the proliferation of H22 cells, promoted cell necrosis, and induced cell cycle arrest in G2 phase in vitro and in vivo. Conclusions This study indicated that ASX can inhibit proliferation and induce apoptosis and cell cycle arrest in mice H22 hepatoma cells in vitro and in vivo. PMID:27333866

  12. Molecular ties between the cell cycle and differentiation in embryonic stem cells

    PubMed Central

    Li, Victor C.; Kirschner, Marc W.

    2014-01-01

    Attainment of the differentiated state during the final stages of somatic cell differentiation is closely tied to cell cycle progression. Much less is known about the role of the cell cycle at very early stages of embryonic development. Here, we show that molecular pathways involving the cell cycle can be engineered to strongly affect embryonic stem cell differentiation at early stages in vitro. Strategies based on perturbing these pathways can shorten the rate and simplify the lineage path of ES differentiation. These results make it likely that pathways involving cell proliferation intersect at various points with pathways that regulate cell lineages in embryos and demonstrate that this knowledge can be used profitably to guide the path and effectiveness of cell differentiation of pluripotent cells. PMID:24979803

  13. Molecular ties between the cell cycle and differentiation in embryonic stem cells.

    PubMed

    Li, Victor C; Kirschner, Marc W

    2014-07-01

    Attainment of the differentiated state during the final stages of somatic cell differentiation is closely tied to cell cycle progression. Much less is known about the role of the cell cycle at very early stages of embryonic development. Here, we show that molecular pathways involving the cell cycle can be engineered to strongly affect embryonic stem cell differentiation at early stages in vitro. Strategies based on perturbing these pathways can shorten the rate and simplify the lineage path of ES differentiation. These results make it likely that pathways involving cell proliferation intersect at various points with pathways that regulate cell lineages in embryos and demonstrate that this knowledge can be used profitably to guide the path and effectiveness of cell differentiation of pluripotent cells.

  14. Bioelectrical Regulation of Cell Cycle and the Planarian Model System

    PubMed Central

    Barghouth, Paul G.; Thiruvalluvan, Manish; Oviedo, Néstor J.

    2015-01-01

    Cell cycle regulation through the manipulation of endogenous membrane potentials offers tremendous opportunities to control cellular processes during tissue repair and cancer formation. However, the molecular mechanisms by which biophysical signals modulate the cell cycle remain underappreciated and poorly understood. Cells in complex organisms generate and maintain a constant voltage gradient across the plasma membrane known as the transmembrane potential. This potential, generated through the combined efforts of various ion transporters, pumps and channels, is known to drive a wide range of cellular processes such as cellular proliferation, migration and tissue regeneration while its deregulation can lead to tumorigenesis. These cellular regulatory events, coordinated by ionic flow, correspond to a new and exciting field termed molecular bioelectricity. We aim to present a brief discussion on the biophysical machinery involving membrane potential and the mechanisms mediating cell cycle progression and cancer transformation. Furthermore, we present the planarian Schmidtea mediterranea as a tractable model system for understanding principles behind molecular bioelectricity at both the cellular and organismal level. PMID:25749155

  15. Size sensors in bacteria, cell cycle control, and size control

    PubMed Central

    Robert, Lydia

    2015-01-01

    Bacteria proliferate by repetitive cycles of cellular growth and division. The progression into the cell cycle is admitted to be under the control of cell size. However, the molecular basis of this regulation is still unclear. Here I will discuss which mechanisms could allow coupling growth and division by sensing size and transmitting this information to the division machinery. Size sensors could act at different stages of the cell cycle. During septum formation, mechanisms controlling the formation of the Z ring, such as MinCD inhibition or Nucleoid Occlusion (NO) could participate in the size-dependence of the division process. In addition or alternatively, the coupling of growth and division may occur indirectly through the control of DNA replication initiation. The relative importance of these different size-sensing mechanisms could depend on the environmental and genetic context. The recent demonstration of an incremental strategy of size control in bacteria, suggests that DnaA-dependent control of replication initiation could be the major size control mechanism limiting cell size variation. PMID:26074903

  16. Size sensors in bacteria, cell cycle control, and size control.

    PubMed

    Robert, Lydia

    2015-01-01

    Bacteria proliferate by repetitive cycles of cellular growth and division. The progression into the cell cycle is admitted to be under the control of cell size. However, the molecular basis of this regulation is still unclear. Here I will discuss which mechanisms could allow coupling growth and division by sensing size and transmitting this information to the division machinery. Size sensors could act at different stages of the cell cycle. During septum formation, mechanisms controlling the formation of the Z ring, such as MinCD inhibition or Nucleoid Occlusion (NO) could participate in the size-dependence of the division process. In addition or alternatively, the coupling of growth and division may occur indirectly through the control of DNA replication initiation. The relative importance of these different size-sensing mechanisms could depend on the environmental and genetic context. The recent demonstration of an incremental strategy of size control in bacteria, suggests that DnaA-dependent control of replication initiation could be the major size control mechanism limiting cell size variation.

  17. Cell cycle regulation by the NEK family of protein kinases.

    PubMed

    Fry, Andrew M; O'Regan, Laura; Sabir, Sarah R; Bayliss, Richard

    2012-10-01

    Genetic screens for cell division cycle mutants in the filamentous fungus Aspergillus nidulans led to the discovery of never-in-mitosis A (NIMA), a serine/threonine kinase that is required for mitotic entry. Since that discovery, NIMA-related kinases, or NEKs, have been identified in most eukaryotes, including humans where eleven genetically distinct proteins named NEK1 to NEK11 are expressed. Although there is no evidence that human NEKs are essential for mitotic entry, it is clear that several NEK family members have important roles in cell cycle control. In particular, NEK2, NEK6, NEK7 and NEK9 contribute to the establishment of the microtubule-based mitotic spindle, whereas NEK1, NEK10 and NEK11 have been implicated in the DNA damage response. Roles for NEKs in other aspects of mitotic progression, such as chromatin condensation, nuclear envelope breakdown, spindle assembly checkpoint signalling and cytokinesis have also been proposed. Interestingly, NEK1 and NEK8 also function within cilia, the microtubule-based structures that are nucleated from basal bodies. This has led to the current hypothesis that NEKs have evolved to coordinate microtubule-dependent processes in both dividing and non-dividing cells. Here, we review the functions of the human NEKs, with particular emphasis on those family members that are involved in cell cycle control, and consider their potential as therapeutic targets in cancer.

  18. Bioelectrical regulation of cell cycle and the planarian model system.

    PubMed

    Barghouth, Paul G; Thiruvalluvan, Manish; Oviedo, Néstor J

    2015-10-01

    Cell cycle regulation through the manipulation of endogenous membrane potentials offers tremendous opportunities to control cellular processes during tissue repair and cancer formation. However, the molecular mechanisms by which biophysical signals modulate the cell cycle remain underappreciated and poorly understood. Cells in complex organisms generate and maintain a constant voltage gradient across the plasma membrane known as the transmembrane potential. This potential, generated through the combined efforts of various ion transporters, pumps and channels, is known to drive a wide range of cellular processes such as cellular proliferation, migration and tissue regeneration while its deregulation can lead to tumorigenesis. These cellular regulatory events, coordinated by ionic flow, correspond to a new and exciting field termed molecular bioelectricity. We aim to present a brief discussion on the biophysical machinery involving membrane potential and the mechanisms mediating cell cycle progression and cancer transformation. Furthermore, we present the planarian Schmidtea mediterranea as a tractable model system for understanding principles behind molecular bioelectricity at both the cellular and organismal level. This article is part of a Special Issue entitled: Membrane channels and transporters in cancers. Copyright © 2015 Elsevier B.V. All rights reserved.

  19. SAMHD1 controls cell cycle status, apoptosis and HIV-1 infection in monocytic THP-1 cells.

    PubMed

    Bonifati, Serena; Daly, Michele B; St Gelais, Corine; Kim, Sun Hee; Hollenbaugh, Joseph A; Shepard, Caitlin; Kennedy, Edward M; Kim, Dong-Hyun; Schinazi, Raymond F; Kim, Baek; Wu, Li

    2016-08-01

    SAMHD1 limits HIV-1 infection in non-dividing myeloid cells by decreasing intracellular dNTP pools. HIV-1 restriction by SAMHD1 in these cells likely prevents activation of antiviral immune responses and modulates viral pathogenesis, thus highlighting a critical role of SAMHD1 in HIV-1 physiopathology. Here, we explored the function of SAMHD1 in regulating cell proliferation, cell cycle progression and apoptosis in monocytic THP-1 cells. Using the CRISPR/Cas9 technology, we generated THP-1 cells with stable SAMHD1 knockout. We found that silencing of SAMHD1 in cycling cells stimulates cell proliferation, redistributes cell cycle population in the G1/G0 phase and reduces apoptosis. These alterations correlated with increased dNTP levels and more efficient HIV-1 infection in dividing SAMHD1 knockout cells relative to control. Our results suggest that SAMHD1, through its dNTPase activity, affects cell proliferation, cell cycle distribution and apoptosis, and emphasize a key role of SAMHD1 in the interplay between cell cycle regulation and HIV-1 infection. Copyright © 2016 Elsevier Inc. All rights reserved.

  20. SAMHD1 controls cell cycle status, apoptosis and HIV-1 infection in monocytic THP-1 cells

    SciTech Connect

    Bonifati, Serena; Daly, Michele B.; St Gelais, Corine; Kim, Sun Hee; Hollenbaugh, Joseph A.; Shepard, Caitlin; Kennedy, Edward M.; Kim, Dong-Hyun; Schinazi, Raymond F.; Kim, Baek; Wu, Li

    2016-08-15

    SAMHD1 limits HIV-1 infection in non-dividing myeloid cells by decreasing intracellular dNTP pools. HIV-1 restriction by SAMHD1 in these cells likely prevents activation of antiviral immune responses and modulates viral pathogenesis, thus highlighting a critical role of SAMHD1 in HIV-1 physiopathology. Here, we explored the function of SAMHD1 in regulating cell proliferation, cell cycle progression and apoptosis in monocytic THP-1 cells. Using the CRISPR/Cas9 technology, we generated THP-1 cells with stable SAMHD1 knockout. We found that silencing of SAMHD1 in cycling cells stimulates cell proliferation, redistributes cell cycle population in the G{sub 1}/G{sub 0} phase and reduces apoptosis. These alterations correlated with increased dNTP levels and more efficient HIV-1 infection in dividing SAMHD1 knockout cells relative to control. Our results suggest that SAMHD1, through its dNTPase activity, affects cell proliferation, cell cycle distribution and apoptosis, and emphasize a key role of SAMHD1 in the interplay between cell cycle regulation and HIV-1 infection.

  1. G2/M cell cycle arrest in the life cycle of viruses.

    PubMed

    Davy, Clare; Doorbar, John

    2007-11-25

    There is increasing evidence that viral infection, expression of viral protein or the presence of viral DNA causes the host cell cycle to arrest during G2/M. The mechanisms used by viruses to cause arrest vary widely; some involve the activation of the cellular pathways that induce arrest in response to DNA damage, while others use completely novel means. The analysis of virus-mediated arrest has not been proven easy, and in most cases the consequences of arrest for the virus life cycle are not well defined. However, a number of effects of arrest are being investigated and it will be interesting to see to what extent perturbation of the G2/M transition is involved in viral infections.

  2. Cell Cycle Dependence of TRAIL Sensitivity in Prostate Cancer Cells

    DTIC Science & Technology

    2006-11-01

    or presence of proteasome inhibitors and measured HIF-1α levels by immunoblotting. We also incubated cells in cobalt chloride (to mimic hypoxia) in...Indistinguishable results were obtained in cells exposed to cobalt chloride . Figure 5: Effects of proteasome inhibitors on HIF- 1α promoter activity (LNCaP...havegenerated luciferase-transduced variants of our human prostate cancer cell lines in order touse them to generate orthotopic tumors in nude mice that can

  3. Differential expression and alternative splicing of cell cycle genes in imatinib-treated K562 cells.

    PubMed

    Liu, Jing; Lin, Jin; Huang, Lin-Feng; Huang, Bo; Xu, Yan-Mei; Li, Jing; Wang, Yan; Zhang, Jing; Yang, Wei-Ming; Min, Qing-Hua; Wang, Xiao-Zhong

    2015-09-01

    Cancer progression often involves the disorder of the cell cycle, and a number of effective chemotherapeutic drugs have been shown to induce cell cycle arrest. The purpose of this study was to comprehensively investigate the effects of imatinib on the expression profile of cell cycle genes in the chronic myeloid leukemia (CML) K562 cell line. In addition, we also investigated alternative splicing of the cell cycle genes affected by imatinib, since an important relationship has been shown to exist between RNA splicing and cell cycle progression. Exon array analysis was performed using total RNA purified from normal and imatinib-treated K562 cells. We identified 185 differentially expressed genes and 277 alternative splicing events between the two cell groups. A detailed analysis by reverse transcription-PCR (RT-PCR) of key genes confirmed the experimental results of the exon array. These results suggested that treatment of K562 cells with imatinib shifts the expression and alternative splicing profiles of several cell cycle-related genes. Importantly, these findings may help improve imatinib treatment strategies in patients with CML and may be useful for imatinib resistance research and CML drug development.

  4. Cell cycle regulation by MicroRNAs in embryonic stem cells.

    PubMed

    Wang, Yangming; Blelloch, Robert

    2009-05-15

    The cell cycle is tightly orchestrated during normal development. Embryonic stem (ES) cells have a unique cell cycle structure, in which the G1/S restriction is largely absent, enabling cells to rapidly move through the G1 phase and enter the S phase. This hastened cell cycle allows the early embryo to rapidly grow. Recent experiments suggest that small noncoding RNAs, the microRNAs (miRNAs), play a central role in achieving this unique cell cycle structure. The responsible miRNAs function by suppressing multiple inhibitors of the G1/S transition. Expression of these miRNAs drops dramatically as the ES cells differentiate and as the G1 phase extends. Some of the same miRNAs are overexpressed in cancers, in which they can promote tumor growth, suggesting common mechanisms of miRNA-regulated cell cycle control in ES cells and cancers. This review discusses these recent findings in the context of broader knowledge of cell cycle control in normal and abnormal development.

  5. Tangeretin induces cell cycle arrest and apoptosis through upregulation of PTEN expression in glioma cells.

    PubMed

    Ma, Li-Li; Wang, Da-Wei; Yu, Xu-Dong; Zhou, Yan-Ling

    2016-07-01

    Tangeretin (TANG), present in peel of citrus fruits, has been shown to various medicinal properties such as chemopreventive and neuroprotective. However, the chemopreventive effect of TANG on glioblastoma cells has not been examined. The present study was designed to explore the anticancer potential of TANG in glioblastoma cells and to investigate the related mechanism. Human glioblastoma U-87MG and LN-18 cells were treated with 45μM concentration of TANG and cell growth was measured by MTT assay. The cell cycle distribution and cell death were measured by flow cytometry. The expression of cell cycle and apoptosis related genes were analyzed by quantitative RT-PCR and western blot. The cells treated with TANG were significantly increased cell growth suppression and cell death effects than vehicle treated cells. Further, TANG treatment increases G2/M arrest and apoptosis by modulating PTEN and cell-cycle regulated genes such as cyclin-D and cdc-2 mRNA and protein expressions. Moreover, the ability of TANG to decrease cell growth and to induce cell death was compromised when PTEN was knockdown by siRNA. Taken together, the chemopreventive effect of TANG is associated with regulation of cell-cycle and apoptosis in glioblastoma, thereby attenuating glioblastoma cell growth. Hence, the present findings suggest that TANG may be a therapeutic agent for glioblastoma treatment. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

  6. Live fast, die soon: cell cycle progression and lifespan in yeast cells

    PubMed Central

    Jiménez, Javier; Bru, Samuel; Ribeiro, Mariana; Clotet, Josep

    2015-01-01

    Our understanding of lifespan has benefited enormously from the study of a simple model, the yeast Saccharomyces cerevisiae. Although a unicellular organism, yeasts undergo many of the processes directly related with aging that to some extent are conserved in mammalian cells. Nutrient-limiting conditions have been involved in lifespan extension, especially in the case of caloric restriction, which also has a direct impact on cell cycle progression. In fact, other environmental stresses (osmotic, oxidative) that interfere with normal cell cycle progression also influence the lifespan of cells, indicating a relationship between lifespan and cell cycle control. In the present review we compile and discuss new findings related to how cell cycle progression is regulated by other nutrients. We centred this review on the analysis of phosphate, also give some attention to nitrogen, and the impact of these nutrients on lifespan. PMID:28357278

  7. Polydatin inhibits growth of lung cancer cells by inducing apoptosis and causing cell cycle arrest.

    PubMed

    Zhang, Yusong; Zhuang, Zhixiang; Meng, Qinghui; Jiao, Yang; Xu, Jiaying; Fan, Saijun

    2014-01-01

    Polydatin (PD), a small natural compound from Polygonum cuspidatum, has a number of biological functions. However, the anticancer activity of PD has been poorly investigated. In the present study, thiazolyl blue tetrazolium bromide assay was used to evaluate the inhibitory effect of PD on cell growth. Cell cycle distribution and apoptosis were investigated by flow cytometry. In addition, the expression of several proteins associated with apoptosis and cell cycle were analyzed by western blot analysis. The results demonstrated that PD significantly inhibits the proliferation of A549 and NCI-H1975 lung cancer cell lines and causes dose-dependent apoptosis. Cell cycle analysis revealed that PD induces S phase cell cycle arrest. Western blot analysis showed that the expression of Bcl-2 decreased as that of Bax increased, and the expression of cyclin D1 was also suppressed. The results suggest that PD has potential therapeutic applications in the treatment of lung cancer.

  8. Polydatin inhibits growth of lung cancer cells by inducing apoptosis and causing cell cycle arrest

    PubMed Central

    ZHANG, YUSONG; ZHUANG, ZHIXIANG; MENG, QINGHUI; JIAO, YANG; XU, JIAYING; FAN, SAIJUN

    2014-01-01

    Polydatin (PD), a small natural compound from Polygonum cuspidatum, has a number of biological functions. However, the anticancer activity of PD has been poorly investigated. In the present study, thiazolyl blue tetrazolium bromide assay was used to evaluate the inhibitory effect of PD on cell growth. Cell cycle distribution and apoptosis were investigated by flow cytometry. In addition, the expression of several proteins associated with apoptosis and cell cycle were analyzed by western blot analysis. The results demonstrated that PD significantly inhibits the proliferation of A549 and NCI-H1975 lung cancer cell lines and causes dose-dependent apoptosis. Cell cycle analysis revealed that PD induces S phase cell cycle arrest. Western blot analysis showed that the expression of Bcl-2 decreased as that of Bax increased, and the expression of cyclin D1 was also suppressed. The results suggest that PD has potential therapeutic applications in the treatment of lung cancer. PMID:24348867

  9. Interference of peritoneal dialysis fluids with cell cycle mechanisms.

    PubMed

    Büchel, Janine; Bartosova, Maria; Eich, Gwendolyn; Wittenberger, Timo; Klein-Hitpass, Ludger; Steppan, Sonja; Hackert, Thilo; Schaefer, Franz; Passlick-Deetjen, Jutta; Schmitt, Claus P

    2015-01-01

    Peritoneal dialysis fluids (PDF) differ with respect to osmotic and buffer compound, and pH and glucose degradation products (GDP) content. The impact on peritoneal membrane integrity is still insufficiently described. We assessed global genomic effects of PDF in primary human peritoneal mesothelial cells (PMC) by whole genome analyses, quantitative real-time polymerase chain reaction (RT-PCR) and functional measurements. PMC isolated from omentum of non-uremic patients were incubated with conventional single chamber PDF (CPDF), lactate- (LPDF), bicarbonate- (BPDF) and bicarbonate/lactate-buffered double-chamber PDF (BLPDF), icodextrin (IPDF) and amino acid PDF (APDF), diluted 1:1 with medium. Affymetrix GeneChip U133Plus2.0 (Affymetrix, CA, USA) and quantitative RT-PCR were applied; cell viability was assessed by proliferation assays. The number of differentially expressed genes compared to medium was 464 with APDF, 208 with CPDF, 169 with IPDF, 71 with LPDF, 45 with BPDF and 42 with BLPDF. Out of these genes 74%, 73%, 79%, 72%, 47% and 57% were downregulated. Gene Ontology (GO) term annotations mainly revealed associations with cell cycle (p = 10(-35)), cell division, mitosis, and DNA replication. One hundred and eighteen out of 249 probe sets detecting genes involved in cell cycle/division were suppressed, with APDF-treated PMC being affected the most regarding absolute number and degree, followed by CPDF and IPDF. Bicarbonate-containing PDF and BLPDF-treated PMC were affected the least. Quantitative RT-PCR measurements confirmed microarray findings for key cell cycle genes (CDK1/CCNB1/CCNE2/AURKA/KIF11/KIF14). Suppression was lowest for BPDF and BLPDF, they upregulated CCNE2 and SMC4. All PDF upregulated 3 out of 4 assessed cell cycle repressors (p53/BAX/p21). Cell viability scores confirmed gene expression results, being 79% of medium for LPDF, 101% for BLPDF, 51% for CPDF and 23% for IPDF. Amino acid-containing PDF (84%) incubated cells were as viable as BPDF

  10. Interference of Peritoneal Dialysis Fluids with Cell Cycle Mechanisms

    PubMed Central

    Büchel, Janine; Bartosova, Maria; Eich, Gwendolyn; Wittenberger, Timo; Klein-Hitpass, Ludger; Steppan, Sonja; Hackert, Thilo; Schaefer, Franz; Passlick-Deetjen, Jutta; Schmitt, Claus P.

    2015-01-01

    ♦ Introduction: Peritoneal dialysis fluids (PDF) differ with respect to osmotic and buffer compound, and pH and glucose degradation products (GDP) content. The impact on peritoneal membrane integrity is still insufficiently described. We assessed global genomic effects of PDF in primary human peritoneal mesothelial cells (PMC) by whole genome analyses, quantitative real-time polymerase chain reaction (RT-PCR) and functional measurements. ♦ Methods: PMC isolated from omentum of non-uremic patients were incubated with conventional single chamber PDF (CPDF), lactate- (LPDF), bicarbonate- (BPDF) and bicarbonate/lactate-buffered double-chamber PDF (BLPDF), icodextrin (IPDF) and amino acid PDF (APDF), diluted 1:1 with medium. Affymetrix GeneChip U133Plus2.0 (Affymetrix, CA, USA) and quantitative RT-PCR were applied; cell viability was assessed by proliferation assays. ♦ Results: The number of differentially expressed genes compared to medium was 464 with APDF, 208 with CPDF, 169 with IPDF, 71 with LPDF, 45 with BPDF and 42 with BLPDF. Out of these genes 74%, 73%, 79%, 72%, 47% and 57% were downregulated. Gene Ontology (GO) term annotations mainly revealed associations with cell cycle (p = 10-35), cell division, mitosis, and DNA replication. One hundred and eighteen out of 249 probe sets detecting genes involved in cell cycle/division were suppressed, with APDF-treated PMC being affected the most regarding absolute number and degree, followed by CPDF and IPDF. Bicarbonate-containing PDF and BLPDF-treated PMC were affected the least. Quantitative RT-PCR measurements confirmed microarray findings for key cell cycle genes (CDK1/CCNB1/CCNE2/AURKA/KIF11/KIF14). Suppression was lowest for BPDF and BLPDF, they upregulated CCNE2 and SMC4. All PDF upregulated 3 out of 4 assessed cell cycle repressors (p53/BAX/p21). Cell viability scores confirmed gene expression results, being 79% of medium for LPDF, 101% for BLPDF, 51% for CPDF and 23% for IPDF. Amino acid-containing PDF

  11. Evidence for an interplay between cell cycle progression and the initiation of differentiation between life cycle forms of African trypanosomes

    PubMed Central

    1994-01-01

    Successful transmission of the African trypanosome between the mammalian host blood-stream and the tsetse fly vector involves dramatic alterations in the parasite's morphology and biochemistry. This differentiation through to the tsetse midgut procyclic form is accompanied by re-entry into a proliferative cell cycle. Using a synchronous differentiation model and a variety of markers diagnostic for progress through both differentiation and the cell cycle, we have investigated the interplay between these two processes. Our results implicate a relationship between the trypanosome cell cycle position and the perception of the differentiation signal and demonstrate that irreversible commitment to the differentiation occurs rapidly after induction. Furthermore, we show that re-entry into the cell cycle in the differentiating population is synchronous, and that once initiated, progress through the differentiation pathway can be uncoupled from progress through the cell cycle. PMID:8195296

  12. Pharmacodynamic Modeling of Cell Cycle Effects for Gemcitabine and Trabectedin Combinations in Pancreatic Cancer Cells

    PubMed Central

    Miao, Xin; Koch, Gilbert; Ait-Oudhia, Sihem; Straubinger, Robert M.; Jusko, William J.

    2016-01-01

    Combinations of gemcitabine and trabectedin exert modest synergistic cytotoxic effects on two pancreatic cancer cell lines. Here, systems pharmacodynamic (PD) models that integrate cellular response data and extend a prototype model framework were developed to characterize dynamic changes in cell cycle phases of cancer cell subpopulations in response to gemcitabine and trabectedin as single agents and in combination. Extensive experimental data were obtained for two pancreatic cancer cell lines (MiaPaCa-2 and BxPC-3), including cell proliferation rates over 0–120 h of drug exposure, and the fraction of cells in different cell cycle phases or apoptosis. Cell cycle analysis demonstrated that gemcitabine induced cell cycle arrest in S phase, and trabectedin induced transient cell cycle arrest in S phase that progressed to G2/M phase. Over time, cells in the control group accumulated in G0/G1 phase. Systems cell cycle models were developed based on observed mechanisms and were used to characterize both cell proliferation and cell numbers in the sub G1, G0/G1, S, and G2/M phases in the control and drug-treated groups. The proposed mathematical models captured well both single and joint effects of gemcitabine and trabectedin. Interaction parameters were applied to quantify unexplainable drug-drug interaction effects on cell cycle arrest in S phase and in inducing apoptosis. The developed models were able to identify and quantify the different underlying interactions between gemcitabine and trabectedin, and captured well our large datasets in the dimensions of time, drug concentrations, and cellular subpopulations. PMID:27895579

  13. [Integrins and cell cycle control by the environment].

    PubMed

    Bernard, A; Bernard, G

    2000-04-01

    Integrins insure cell adhesion to extra-cellular matrix components; they are thus involved in tissue architecture. They also can insure intercellular adhesions by binding to surface molecules from the immunoglobulin superfamily. Integrins binding to their ligands induce cytoskeleton reorganisation and, consequently, they gather into focal adhesion contacts. This greatly strenghthens mechanical forces. Nevertheless, integrins can also participate in cell locomotion and, moreover, tranduce within cells signals that can extensively influence cell metabolism, cell cycle and apoptosis. Doing so, they can interact with signals from other cellular receptors, such as soluble growth factors. They are therefore key molecules to integrate intrinsic and extrinsic events of the cellular behavior. They profoundly influence oncogenesis and the metastatic process.

  14. Adolescent binge alcohol exposure alters hippocampal progenitor cell proliferation in rats: effects on cell cycle kinetics.

    PubMed

    McClain, Justin A; Hayes, Dayna M; Morris, Stephanie A; Nixon, Kimberly

    2011-09-01

    Binge alcohol exposure in adolescent rats potently inhibits adult hippocampal neurogenesis by altering neural progenitor cell (NPC) proliferation and survival; however, it is not clear whether alcohol results in an increase or decrease in net proliferation. Thus, the effects of alcohol on hippocampal NPC cell cycle phase distribution and kinetics were assessed in an adolescent rat model of an alcohol use disorder. Cell cycle distribution was measured using a combination of markers (Ki-67, bromodeoxyuridine incorporation, and phosphohistone H3) to determine the proportion of NPCs within G1, S, and G2/M phases of the cell cycle. Cell cycle kinetics were calculated using a cumulative bromodeoxyuridine injection protocol to determine the effect of alcohol on cell cycle length and S-phase duration. Binge alcohol exposure reduced the proportion of NPCs in S-phase, but had no effect on G1 or G2/M phases, indicating that alcohol specifically targets S-phase of the cell cycle. Cell cycle kinetics studies revealed that alcohol reduced NPC cell cycle duration by 36% and shortened S-phase by 62%, suggesting that binge alcohol exposure accelerates progression through the cell cycle. This effect would be expected to increase NPC proliferation, which was supported by a slight, but significant increase in the number of Sox-2+ NPCs residing in the hippocampal subgranular zone following binge alcohol exposure. These studies suggest the mechanism of alcohol inhibition of neurogenesis and also reveal the earliest evidence of the compensatory neurogenesis reaction that has been observed a week after binge alcohol exposure.

  15. Computational analysis of mammalian cell division gated by a circadian clock: quantized cell cycles and cell size control.

    PubMed

    Zámborszky, Judit; Hong, Christian I; Csikász Nagy, Attila

    2007-12-01

    Cell cycle and circadian rhythms are conserved from cyanobacteria to humans with robust cyclic features. Recently, molecular links between these two cyclic processes have been discovered. Core clock transcription factors, Bmal1 and Clock (Clk), directly regulate Wee1 kinase, which inhibits entry into the mitosis. We investigate the effect of this connection on the timing of mammalian cell cycle processes with computational modeling tools. We connect a minimal model of circadian rhythms, which consists of transcription-translation feedback loops, with a modified mammalian cell cycle model from Novak and Tyson (2004). As we vary the mass doubling time (MDT) of the cell cycle, stochastic simulations reveal quantized cell cycles when the activity of Wee1 is influenced by clock components. The quantized cell cycles disappear in the absence of coupling or when the strength of this link is reduced. More intriguingly, our simulations indicate that the circadian clock triggers critical size control in the mammalian cell cycle. A periodic brake on the cell cycle progress via Wee1 enforces size control when the MDT is quite different from the circadian period. No size control is observed in the absence of coupling. The issue of size control in the mammalian system is debatable, whereas it is well established in yeast. It is possible that the size control is more readily observed in cell lines that contain circadian rhythms, since not all cell types have a circadian clock. This would be analogous to an ultradian clock intertwined with quantized cell cycles (and possibly cell size control) in yeast. We present the first coupled model between the mammalian cell cycle and circadian rhythms that reveals quantized cell cycles and cell size control influenced by the clock.

  16. The Toxoplasma Centrocone Houses Cell Cycle Regulatory Factors.

    PubMed

    Naumov, Anatoli; Kratzer, Stella; Ting, Li-Min; Kim, Kami; Suvorova, Elena S; White, Michael W

    2017-08-22

    Our knowledge of cell cycle regulatory mechanisms in apicomplexan parasites is very limited. In this study, we describe a novel Toxoplasma gondii factor that has a vital role in chromosome replication and the regulation of cytoplasmic and nuclear mitotic structures, and we named this factor ECR1 for essential for chromosome replication 1. ECR1 was discovered by complementation of a temperature-sensitive (ts) mutant that suffers lethal, uncontrolled chromosome replication at 40°C similar to a ts mutant carrying a defect in topoisomerase. ECR1 is a 52-kDa protein containing divergent RING and TRAF-Sina-like zinc binding domains that are dynamically expressed in the tachyzoite cell cycle. ECR1 first appears in the unique spindle compartment of the Apicomplexa (centrocone) of the nuclear envelope in early S phase and then in the nucleus in late S phase where it reaches maximum expression. Following nuclear division, but before daughter parasites separate from the mother parasite, ECR1 is downregulated and is absent in new daughter parasites. The proteomics of ECR1 identified interactions with the ubiquitin-mediated protein degradation machinery and the minichromosome maintenance complex, and the loss of ECR1 led to increased stability of a key member of this complex, MCM2. ECR1 also forms a stable complex with the cyclin-dependent kinase (CDK)-related kinase, Tgondii Crk5 (TgCrk5), which displays a similar cell cycle expression and localization during tachyzoite replication. Importantly, the localization of ECR1/TgCrk5 in the centrocone indicates that this Apicomplexa-specific spindle compartment houses important regulatory factors that control the parasite cell cycle.IMPORTANCE Parasites of the apicomplexan family are important causes of human disease, including malaria, toxoplasmosis, and cryptosporidiosis. Parasite growth is the underlying cause of pathogenesis, yet despite this importance, the molecular basis for parasite replication is poorly understood. Filling

  17. Cell cycle dependent changes in the plasma membrane organization of mammalian cells.

    PubMed

    Denz, Manuela; Chiantia, Salvatore; Herrmann, Andreas; Mueller, Peter; Korte, Thomas; Schwarzer, Roland

    2017-03-01

    Lipid membranes are major structural elements of all eukaryotic and prokaryotic organisms. Although many aspects of their biology have been studied extensively, their dynamics and lateral heterogeneity are still not fully understood. Recently, we observed a cell-to-cell variability in the plasma membrane organization of CHO-K1 cells (Schwarzer et al., 2014). We surmised that cell cycle dependent changes of the individual cells from our unsynchronized cell population account for this phenomenon. In the present study, this hypothesis was tested. To this aim, CHO-K1 cells were arrested in different cell cycle phases by chemical treatments, and the order of their plasma membranes was determined by various fluorescent lipid analogues using fluorescence lifetime imaging microscopy. Our experiments exhibit significant differences in the membrane order of cells arrested in the G2/M or S phase compared to control cells. Our single-cell analysis also enabled the specific selection of mitotic cells, which displayed a significant increase of the membrane order compared to the control. In addition, the lipid raft marker GPImYFP was used to study the lateral organization of cell cycle arrested cells as well as mitotic cells and freely cycling samples. Again, significant differences were found between control and arrested cells and even more pronounced between control and mitotic cells. Our data demonstrate a direct correlation between cell cycle progression and plasma membrane organization, underlining that cell-to-cell heterogeneities of membrane properties have to be taken into account in cellular studies especially at the single-cell level.

  18. Lineage correlations of single cell division time as a probe of cell-cycle dynamics.

    PubMed

    Sandler, Oded; Mizrahi, Sivan Pearl; Weiss, Noga; Agam, Oded; Simon, Itamar; Balaban, Nathalie Q

    2015-03-26

    Stochastic processes in cells are associated with fluctuations in mRNA, protein production and degradation, noisy partition of cellular components at division, and other cell processes. Variability within a clonal population of cells originates from such stochastic processes, which may be amplified or reduced by deterministic factors. Cell-to-cell variability, such as that seen in the heterogeneous response of bacteria to antibiotics, or of cancer cells to treatment, is understood as the inevitable consequence of stochasticity. Variability in cell-cycle duration was observed long ago; however, its sources are still unknown. A central question is whether the variance of the observed distribution originates from stochastic processes, or whether it arises mostly from a deterministic process that only appears to be random. A surprising feature of cell-cycle-duration inheritance is that it seems to be lost within one generation but to be still present in the next generation, generating poor correlation between mother and daughter cells but high correlation between cousin cells. This observation suggests the existence of underlying deterministic factors that determine the main part of cell-to-cell variability. We developed an experimental system that precisely measures the cell-cycle duration of thousands of mammalian cells along several generations and a mathematical framework that allows discrimination between stochastic and deterministic processes in lineages of cells. We show that the inter- and intra-generation correlations reveal complex inheritance of the cell-cycle duration. Finally, we build a deterministic nonlinear toy model for cell-cycle inheritance that reproduces the main features of our data. Our approach constitutes a general method to identify deterministic variability in lineages of cells or organisms, which may help to predict and, eventually, reduce cell-to-cell heterogeneity in various systems, such as cancer cells under treatment.

  19. Cell cycle in the fucus zygote parallels a somatic cell cycle but displays a unique translational regulation of cyclin-dependent kinases.

    PubMed

    Corellou, F; Brownlee, C; Detivaud, L; Kloareg, B; Bouget, F Y

    2001-03-01

    In eukaryotic cells, the basic machinery of cell cycle control is highly conserved. In particular, many cellular events during cell cycle progression are controlled by cyclin-dependent kinases (CDKs). The cell cycle in animal early embryos, however, differs substantially from that of somatic cells or yeasts. For example, cell cycle checkpoints that ensure that the sequence of cell cycle events is correct have been described in somatic cells and yeasts but are largely absent in embryonic cells. Furthermore, the regulation of CDKs is substantially different in the embryonic and somatic cells. In this study, we address the nature of the first cell cycle in the brown alga Fucus, which is evolutionarily distant from the model systems classically used for cell cycle studies in embryos. This cycle consists of well-defined G1, S, G2, and M phases. The purine derivative olomoucine inhibited CDKs activity in vivo and in vitro and induced different cell cycle arrests, including at the G1/S transition, suggesting that, as in somatic cells, CDKs tightly control cell cycle progression. The cell cycle of Fucus zygotes presented the other main features of a somatic cell cycle, such as a functional spindle assembly checkpoint that targets CDKs and the regulation of the early synthesis of two PSTAIRE CDKs, p32 and p34, and the associated histone H1 kinase activity as well as the regulation of CDKs by tyrosine phosphorylation. Surprisingly, the synthesis after fertilization of p32 and p34 was translationally regulated, a regulation not described previously for CDKs. Finally, our results suggest that the activation of mitotic CDKs relies on an autocatalytic amplification mechanism.

  20. Nuclear size, nuclear pore number and cell cycle.

    PubMed

    Maeshima, Kazuhiro; Iino, Haruki; Hihara, Saera; Imamoto, Naoko

    2011-01-01

    In eukaryotic cells, the nucleus is a complex and sophisticated organelle containing genomic DNA and supports essential cellular activities. Its surface contains many nuclear pore complexes (NPCs), channels for macromolecular transport between the cytoplasm and nucleus. It has been observed that the nuclear volume and the number of NPCs almost doubles during interphase in dividing cells, but the coordination of these events with the cell cycle was poorly understood, particularly in mammalian cells. Recently, we demonstrated that cyclin-dependent protein kinases (Cdks) control interphase NPC formation in dividing human cells. Cdks drive the very early step of NPC formation because Cdk inhibition suppressed the generation of "nascent pores," which are considered to be immature NPCs, and disturbed expression and localization of some nucleoporins. Cdk inhibition did not affect nuclear volume, suggesting that these two processes have distinct regulatory mechanisms in the cell cycle. The details of our experimental systems and finding are discussed in more depth. With new findings recently reported, we also discuss possible molecular mechanisms of interphase NPC formation.

  1. Cell reprogramming modelled as transitions in a hierarchy of cell cycles

    NASA Astrophysics Data System (ADS)

    Hannam, Ryan; Annibale, Alessia; Kühn, Reimer

    2017-10-01

    We construct a model of cell reprogramming (the conversion of fully differentiated cells to a state of pluripotency, known as induced pluripotent stem cells, or iPSCs) which builds on key elements of cell biology viz. cell cycles and cell lineages. Although reprogramming has been demonstrated experimentally, much of the underlying processes governing cell fate decisions remain unknown. This work aims to bridge this gap by modelling cell types as a set of hierarchically related dynamical attractors representing cell cycles. Stages of the cell cycle are characterised by the configuration of gene expression levels, and reprogramming corresponds to triggering transitions between such configurations. Two mechanisms were found for reprogramming in a two level hierarchy: cycle specific perturbations and a noise induced switching. The former corresponds to a directed perturbation that induces a transition into a cycle-state of a different cell type in the potency hierarchy (mainly a stem cell) whilst the latter is a priori undirected and could be induced, e.g. by a (stochastic) change in the cellular environment. These reprogramming protocols were found to be effective in large regimes of the parameter space and make specific predictions concerning reprogramming dynamics which are broadly in line with experimental findings.

  2. Cell cycle regulation of embryonic stem cells and mouse embryonic fibroblasts lacking functional Pax7.

    PubMed

    Czerwinska, Areta M; Nowacka, Joanna; Aszer, Magdalena; Gawrzak, Sylwia; Archacka, Karolina; Fogtman, Anna; Iwanicka-Nowicka, Roksana; Jańczyk-Ilach, Katarzyna; Koblowska, Marta; Ciemerych, Maria A; Grabowska, Iwona

    2016-11-01

    The transcription factor Pax7 plays a key role during embryonic myogenesis and in adult organisms in that it sustains the proper function of satellite cells, which serve as adult skeletal muscle stem cells. Recently we have shown that lack of Pax7 does not prevent the myogenic differentiation of pluripotent stem cells. In the current work we show that the absence of functional Pax7 in differentiating embryonic stem cells modulates cell cycle facilitating their proliferation. Surprisingly, deregulation of Pax7 function also positively impacts at the proliferation of mouse embryonic fibroblasts. Such phenotypes seem to be executed by modulating the expression of positive cell cycle regulators, such as cyclin E.

  3. Circular piecewise regression with applications to cell-cycle data.

    PubMed

    Rueda, Cristina; Fernández, Miguel A; Barragán, Sandra; Mardia, Kanti V; Peddada, Shyamal D

    2016-12-01

    Applications of circular regression models appear in many different fields such as evolutionary psychology, motor behavior, biology, and, in particular, in the analysis of gene expressions in oscillatory systems. Specifically, for the gene expression problem, a researcher may be interested in modeling the relationship among the phases of cell-cycle genes in two species with differing periods. This challenging problem reduces to the problem of constructing a piecewise circular regression model and, with this objective in mind, we propose a flexible circular regression model which allows different parameter values depending on sectors along the circle. We give a detailed interpretation of the parameters in the model and provide maximum likelihood estimators. We also provide a model selection procedure based on the concept of generalized degrees of freedom. The model is then applied to the analysis of two different cell-cycle data sets and through these examples we highlight the power of our new methodology.

  4. Mitochondria. Cell cycle-dependent regulation of mitochondrial preprotein translocase.

    PubMed

    Harbauer, Angelika B; Opalińska, Magdalena; Gerbeth, Carolin; Herman, Josip S; Rao, Sanjana; Schönfisch, Birgit; Guiard, Bernard; Schmidt, Oliver; Pfanner, Nikolaus; Meisinger, Chris

    2014-11-28

    Mitochondria play central roles in cellular energy conversion, metabolism, and apoptosis. Mitochondria import more than 1000 different proteins from the cytosol. It is unknown if the mitochondrial protein import machinery is connected to the cell division cycle. We found that the cyclin-dependent kinase Cdk1 stimulated assembly of the main mitochondrial entry gate, the translocase of the outer membrane (TOM), in mitosis. The molecular mechanism involved phosphorylation of the cytosolic precursor of Tom6 by cyclin Clb3-activated Cdk1, leading to enhanced import of Tom6 into mitochondria. Tom6 phosphorylation promoted assembly of the protein import channel Tom40 and import of fusion proteins, thus stimulating the respiratory activity of mitochondria in mitosis. Tom6 phosphorylation provides a direct means for regulating mitochondrial biogenesis and activity in a cell cycle-specific manner.

  5. Coherent regulation in yeast’s cell-cycle network

    NASA Astrophysics Data System (ADS)

    Aral, Neşe; Kabakçıoğlu, Alkan

    2015-05-01

    We define a measure of coherent activity for gene regulatory networks, a property that reflects the unity of purpose between the regulatory agents with a common target. We propose that such harmonious regulatory action is desirable under a demand for energy efficiency and may be selected for under evolutionary pressures. We consider two recent models of the cell-cycle regulatory network of the yeast, Saccharomyces cerevisiae as a case study and calculate their degree of coherence. A comparison with random networks of similar size and composition reveals that the yeast’s cell-cycle regulation is wired to yield an exceptionally high level of coherent regulatory activity. We also investigate the mean degree of coherence as a function of the network size, connectivity and the fraction of repressory/activatory interactions.

  6. Coherent regulation in yeast's cell-cycle network.

    PubMed

    Aral, Neşe; Kabakçıoğlu, Alkan

    2015-05-13

    We define a measure of coherent activity for gene regulatory networks, a property that reflects the unity of purpose between the regulatory agents with a common target. We propose that such harmonious regulatory action is desirable under a demand for energy efficiency and may be selected for under evolutionary pressures. We consider two recent models of the cell-cycle regulatory network of the yeast, Saccharomyces cerevisiae as a case study and calculate their degree of coherence. A comparison with random networks of similar size and composition reveals that the yeast's cell-cycle regulation is wired to yield an exceptionally high level of coherent regulatory activity. We also investigate the mean degree of coherence as a function of the network size, connectivity and the fraction of repressory/activatory interactions.

  7. Local homogeneity of cell cycle length in developing mouse cortex

    NASA Technical Reports Server (NTRS)

    Cai, L.; Hayes, N. L.; Nowakowski, R. S.

    1997-01-01

    We have measured the amount of variation in the length of the cell cycle for cells in the pseudostratified ventricular epithelium (PVE) of the developing cortex of mice on embryonic day 14. Our measurements were made in three cortical regions (i.e., the neocortex, archicortex, and periarchicortex) using three different methods: the cumulative labeling method (CLM), the percent labeled mitoses (PLM) method, and a comparison of the time needed for the PLM to ascend from 0 to 100% with the time needed for the PLM to descend from 100 to 0%. These 3 different techniques provide different perspectives on the cytokinetic parameters. Theoretically, CLM gives an estimate for a maximum value of the total length of the cell cycle (TC), whereas PLM gives an estimate of a minimum value of TC. The difference between these two estimates indicates that the range for TC is +/-1% of the mean TC for periarchicortex, +/-7% for neocortex, and +/-8% for archicortex. This was confirmed by a lengthening of the PLM descent time in comparison with its ascent time. The sharpness of the transitions and the flatness of the plateau of the PLM curves indicate that 99% of the proliferating cells are within this narrow estimated range for TC; hence, only approximately 1% deviate outside of a relatively restricted range from the average TC of the population. In the context of the possible existence within the cortical PVE of two populations with markedly dissimilar cell cycle kinetics from the mean, one such population must comprise approximately 99% of the total population, and the other, if it exists, is only approximately 1% of the total. This seems to be true for all three cortical regions. The narrow range of TC indicates a homogeneity in the cell cycle length for proliferating cells in three different cortical regions, despite the fact that progenitor cells of different lineages may be present. It further predicts the existence of almost synchronous interkinetic nuclear movements of the

  8. Local homogeneity of cell cycle length in developing mouse cortex

    NASA Technical Reports Server (NTRS)

    Cai, L.; Hayes, N. L.; Nowakowski, R. S.

    1997-01-01

    We have measured the amount of variation in the length of the cell cycle for cells in the pseudostratified ventricular epithelium (PVE) of the developing cortex of mice on embryonic day 14. Our measurements were made in three cortical regions (i.e., the neocortex, archicortex, and periarchicortex) using three different methods: the cumulative labeling method (CLM), the percent labeled mitoses (PLM) method, and a comparison of the time needed for the PLM to ascend from 0 to 100% with the time needed for the PLM to descend from 100 to 0%. These 3 different techniques provide different perspectives on the cytokinetic parameters. Theoretically, CLM gives an estimate for a maximum value of the total length of the cell cycle (TC), whereas PLM gives an estimate of a minimum value of TC. The difference between these two estimates indicates that the range for TC is +/-1% of the mean TC for periarchicortex, +/-7% for neocortex, and +/-8% for archicortex. This was confirmed by a lengthening of the PLM descent time in comparison with its ascent time. The sharpness of the transitions and the flatness of the plateau of the PLM curves indicate that 99% of the proliferating cells are within this narrow estimated range for TC; hence, only approximately 1% deviate outside of a relatively restricted range from the average TC of the population. In the context of the possible existence within the cortical PVE of two populations with markedly dissimilar cell cycle kinetics from the mean, one such population must comprise approximately 99% of the total population, and the other, if it exists, is only approximately 1% of the total. This seems to be true for all three cortical regions. The narrow range of TC indicates a homogeneity in the cell cycle length for proliferating cells in three different cortical regions, despite the fact that progenitor cells of different lineages may be present. It further predicts the existence of almost synchronous interkinetic nuclear movements of the

  9. [Cell cycle arrest at M phase induced by vinblastine in MOLT-4 cells].

    PubMed

    Zhong, Yi-Sheng; Pan, Chang-Chuan; Jin, Chang-Nan; Li, Jian-Jun; Xiong, Gong-Peng; Zhang, Jian-Xi; Gong, Jian-Ping

    2009-04-01

    This study was purposed to investigate the biological effect of vinblastine (VLS), usually known as inductor of mitotic arrest, on MOLT-4 of ALL cells and to evaluate its significance. The cell arrest in M phase and/or cell apoptosis were induced by treatment of MOLT-4 cells with 0.05 microg/ml VLS for 0 - 12 hours; the DNA histogram was detected by flow cytometry; the morphological changes of cells were observed by confocal microscopy; the cell cycle distribution, cell apoptosis and morphological changes of cells before and after arrest were analyzed by using arrest increasing rate (AIR), arrest efficiency (AE), apoptosis rate (AR) and morphologic parameters respectively. The results indicated that the cell arrest did not accompanied by significant increase of apoptosis rate; the DNA histogram of cell arrest showed dynamic change of cell cycle in time-dependent manner; the arrest efficiency could be quantified. The cell arrest at M phase was accompanied by cell stack in S phase, the cell proliferation rate dropped after cell arrest occurred. The cells arrested at M phase possessed of characteristic morphologic features in cell mitosis. It is concluded that the vinblastine can solely induce arrest of MOLT-4 cells at M phase. This study provides experimental basis for further investigating the relation of cell cycle arrest to apoptosis, mechanism of checkpoint and development of new anticancer drugs.

  10. The cell cycle regulator protein P16 and the cellular senescence of dental follicle cells.

    PubMed

    Morsczeck, Christian; Hullmann, Markus; Reck, Anja; Reichert, Torsten E

    2017-08-02

    Cellular senescence is a restricting factor for regenerative therapies with somatic stem cells. We showed previously that the onset of cellular senescence inhibits the osteogenic differentiation in stem cells of the dental follicle (DFCs), although the mechanism remains elusive. Two different pathways are involved in the induction of the cellular senescence, which are driven either by the cell cycle protein P21 or by the cell cycle protein P16. In this study, we investigated the expression of cell cycle proteins in DFCs after the induction of cellular senescence. The induction of cellular senescence was proved by an increased expression of β-galactosidase and an increased population doubling time after a prolonged cell culture. Cellular senescence regulated the expression of cell cycle proteins. The expression of cell cycle protein P16 was up-regulated, which correlates with the induction of cellular senescence markers in DFCs. However, the expression of cyclin-dependent kinases (CDK)2 and 4 and the expression of the cell cycle protein P21 were successively decreased in DFCs. In conclusion, our data suggest that a P16-dependent pathway drives the induction of cellular senescence in DFCs.

  11. Cell cycle arrest and clonogenic tumor cell kill by divergent chemotherapeutic drugs.

    PubMed

    Mastbergen, S C; Duivenvoorden, I; Versteegh, R T; Geldof, A A

    2000-01-01

    Regulators of cell cycle phase transitions could be important targets for cancer treatment using cytostatic chemotherapy. Therefore, the extent of cell cycle arrest induced by different cytostatic agents has to be correlated with ultimate clonogenic tumor cell death. Especially the value of early cell cycle perturbations as indicators for the clinical efficacy of drugs should be a matter of investigation. In vitro PC-3 human prostate carcinoma cells were incubated for 24 hours with a panel of six different chemotherapeutic drugs in various concentrations (Aplidine, Cisplatin, Isohomohalichondrin B (IHB), Taxol, Vincristine and Vinorelbine). The short term effects on the cell cycle distribution were determined by DNA flowcytometry while the clonogenic capacity of these cells was quantitated to measure the cytotoxic treatment efficacy. Significant decreases of clonogenic survival proved to be strongly correlated with cell cycle perturbations. IHB, Taxol, Vincristine and Vinorelbine resulted in accumulation (up to 87-92%) in the G2M phase, while Cisplatin and Aplidine led to increases in the S-phase fraction and in both G2M- as well as S-phase fractions, respectively. Cell cycle phase perturbations appear to be suitable, early markers for cytotoxic drug efficacy.

  12. Ecdysone signaling induces two phases of cell cycle exit in Drosophila cells

    PubMed Central

    Guo, Yongfeng; Flegel, Kerry; Kumar, Jayashree; McKay, Daniel J.

    2016-01-01

    ABSTRACT During development, cell proliferation and differentiation must be tightly coordinated to ensure proper tissue morphogenesis. Because steroid hormones are central regulators of developmental timing, understanding the links between steroid hormone signaling and cell proliferation is crucial to understanding the molecular basis of morphogenesis. Here we examined the mechanism by which the steroid hormone ecdysone regulates the cell cycle in Drosophila. We find that a cell cycle arrest induced by ecdysone in Drosophila cell culture is analogous to a G2 cell cycle arrest observed in the early pupa wing. We show that in the wing, ecdysone signaling at the larva-to-puparium transition induces Broad which in turn represses the cdc25c phosphatase String. The repression of String generates a temporary G2 arrest that synchronizes the cell cycle in the wing epithelium during early pupa wing elongation and flattening. As ecdysone levels decline after the larva-to-puparium pulse during early metamorphosis, Broad expression plummets, allowing String to become re-activated, which promotes rapid G2/M progression and a subsequent synchronized final cell cycle in the wing. In this manner, pulses of ecdysone can both synchronize the final cell cycle and promote the coordinated acquisition of terminal differentiation characteristics in the wing. PMID:27737823

  13. Predicting Cell Cycle Regulated Genes by Causal Interactions

    PubMed Central

    Emmert-Streib, Frank; Dehmer, Matthias

    2009-01-01

    The fundamental difference between classic and modern biology is that technological innovations allow to generate high-throughput data to get insights into molecular interactions on a genomic scale. These high-throughput data can be used to infer gene networks, e.g., the transcriptional regulatory or signaling network, representing a blue print of the current dynamical state of the cellular system. However, gene networks do not provide direct answers to biological questions, instead, they need to be analyzed to reveal functional information of molecular working mechanisms. In this paper we propose a new approach to analyze the transcriptional regulatory network of yeast to predict cell cycle regulated genes. The novelty of our approach is that, in contrast to all other approaches aiming to predict cell cycle regulated genes, we do not use time series data but base our analysis on the prior information of causal interactions among genes. The major purpose of the present paper is to predict cell cycle regulated genes in S. cerevisiae. Our analysis is based on the transcriptional regulatory network, representing causal interactions between genes, and a list of known periodic genes. No further data are used. Our approach utilizes the causal membership of genes and the hierarchical organization of the transcriptional regulatory network leading to two groups of periodic genes with a well defined direction of information flow. We predict genes as periodic if they appear on unique shortest paths connecting two periodic genes from different hierarchy levels. Our results demonstrate that a classical problem as the prediction of cell cycle regulated genes can be seen in a new light if the concept of a causal membership of a gene is applied consequently. This also shows that there is a wealth of information buried in the transcriptional regulatory network whose unraveling may require more elaborate concepts than it might seem at first. PMID:19688096

  14. The Cell Cycle Timing of Human Papillomavirus DNA Replication.

    PubMed

    Reinson, Tormi; Henno, Liisi; Toots, Mart; Ustav, Mart; Ustav, Mart

    2015-01-01

    Viruses manipulate the cell cycle of the host cell to optimize conditions for more efficient viral genome replication. One strategy utilized by DNA viruses is to replicate their genomes non-concurrently with the host genome; in this case, the viral genome is amplified outside S phase. This phenomenon has also been described for human papillomavirus (HPV) vegetative genome replication, which occurs in G2-arrested cells; however, the precise timing of viral DNA replication during initial and stable replication phases has not been studied. We developed a new method to quantitate newly synthesized DNA levels and used this method in combination with cell cycle synchronization to show that viral DNA replication is initiated during S phase and is extended to G2 during initial amplification but follows the replication pattern of cellular DNA during S phase in the stable maintenance phase. E1 and E2 protein overexpression changes the replication time from S only to both the S and G2 phases in cells that stably maintain viral episomes. These data demonstrate that the active synthesis and replication of the HPV genome are extended into the G2 phase to amplify its copy number and the duration of HPV genome replication is controlled by the level of the viral replication proteins E1 and E2. Using the G2 phase for genome amplification may be an important adaptation that allows exploitation of changing cellular conditions during cell cycle progression. We also describe a new method to quantify newly synthesized viral DNA levels and discuss its benefits for HPV research.

  15. Cell cycle and centromere FISH studies in premature centromere division.

    PubMed

    Corona-Rivera, Alfredo; Salamanca-Gomez, Fabio; Bobadilla-Morales, Lucina; Corona-Rivera, Jorge R; Palomino-Cueva, Cesar; Garcia-Cobian, Teresa A; Corona-Rivera, Enrique

    2005-09-20

    Mitotic configurations consistent in split centromeres and splayed chromatids in all or most of the chromosomes or premature centromere division (PCD) have been described in three categories. (1) Low frequency of PCD observed in colchicines-treated lymphocyte cultures from normal individuals. (2) High frequency of PCD with mosaic variegated aneuploidy. (3) High frequency of PCD as a sole chromosome abnormality observed in individuals with no recognizable clinical pattern. We report four members of a family with the third category of PCD. Cell cycle duration assessed by average generation time using differential sister chromatid stain analysis and FISH studies of DNA centromere sequences in PCD individuals, are included and compared with previously reported PCD individuals from 9 families. We observed PCD in colchicine-treated cultures from the propositus, his father, and two paternal aunts but not in his mother and four other paternal and maternal family members, as well as in untreated cultures from the propositus and his father. We observed cytological evidence of active centromeres by Cd stain. Significative cell cycle time reduction in anaphases of PCD individuals (average generation time of 21.8 h;SD 0.4) with respect to individuals without PCD (average generation time of 31.8 h;SD 3.9) was observed (P < 0.005, Student t-test for independent samples). Increased cell proliferation kinetics was observed in anaphasic cells of individuals with PCD, by differential sister chromatid stain analysis. FISH studies revealed the presence of alpha satellite DNA from chromosomes 1, 13, 21/18, X, all centromeres, and CENP-B box sequences in metaphasic and anaphasic cells from PCD individuals. This report examines evidences of a functional relationship between PCD and cell cycle impairment. It seems that essential centromere integrity is present in these cases.

  16. Cell cycle and centromere FISH studies in premature centromere division

    PubMed Central

    Corona-Rivera, Alfredo; Salamanca-Gomez, Fabio; Bobadilla-Morales, Lucina; Corona-Rivera, Jorge R; Palomino-Cueva, Cesar; Garcia-Cobian, Teresa A; Corona-Rivera, Enrique

    2005-01-01

    Background Mitotic configurations consistent in split centromeres and splayed chromatids in all or most of the chromosomes or premature centromere division (PCD) have been described in three categories. (1) Low frequency of PCD observed in colchicines-treated lymphocyte cultures from normal individuals. (2) High frequency of PCD with mosaic variegated aneuploidy. (3) High frequency of PCD as a sole chromosome abnormality observed in individuals with no recognizable clinical pattern. We report four members of a family with the third category of PCD. Methods Cell cycle duration assessed by average generation time using differential sister chromatid stain analysis and FISH studies of DNA centromere sequences in PCD individuals, are included and compared with previously reported PCD individuals from 9 families. Results We observed PCD in colchicine-treated cultures from the propositus, his father, and two paternal aunts but not in his mother and four other paternal and maternal family members, as well as in untreated cultures from the propositus and his father. We observed cytological evidence of active centromeres by Cd stain. Significative cell cycle time reduction in anaphases of PCD individuals (average generation time of 21.8 h;SD 0.4) with respect to individuals without PCD (average generation time of 31.8 h;SD 3.9) was observed (P < 0.005, Student t-test for independent samples). Increased cell proliferation kinetics was observed in anaphasic cells of individuals with PCD, by differential sister chromatid stain analysis. FISH studies revealed the presence of alpha satellite DNA from chromosomes 1, 13, 21/18, X, all centromeres, and CENP-B box sequences in metaphasic and anaphasic cells from PCD individuals. Conclusion This report examines evidences of a functional relationship between PCD and cell cycle impairment. It seems that essential centromere integrity is present in these cases. PMID:16174301

  17. Cell cycle regulation of homologous recombination in Saccharomyces cerevisiae.

    PubMed

    Mathiasen, David P; Lisby, Michael

    2014-03-01

    Homologous recombination (HR) contributes to maintaining genome integrity by facilitating error-free repair of DNA double-strand breaks (DSBs) primarily during the S and G2 phases of the mitotic cell cycle, while nonhomologous end joining (NHEJ) is the preferred pathway for DSB repair in G1 phase. The decision to repair a DSB by NHEJ or HR is made primarily at the level of DSB end resection, which is inhibited by the Ku complex in G1 and promoted by the Sae2 and Mre11 nucleases in S/G2 . The cell cycle regulation of HR is accomplished both at the transcription level and at the protein level through post-translational modification, degradation and subcellular localization. Cyclin-dependent kinase Cdc28 plays an established key role in these events, while the role of transcriptional regulation and protein degradation are less well understood. Here, the cell cycle regulatory mechanisms for mitotic HR in Saccharomyces cerevisiae are reviewed, and evolutionarily conserved principles are highlighted. © 2014 Federation of European Microbiological Societies. Published by John Wiley & Sons Ltd. All rights reserved.

  18. Tracking of Normal and Malignant Progenitor Cell Cycle Transit in a Defined Niche

    PubMed Central

    Pineda, Gabriel; Lennon, Kathleen M.; Delos Santos, Nathaniel P.; Lambert-Fliszar, Florence; Riso, Gennarina L.; Lazzari, Elisa; Marra, Marco A.; Morris, Sheldon; Sakaue-Sawano, Asako; Miyawaki, Atsushi; Jamieson, Catriona H. M.

    2016-01-01

    While implicated in therapeutic resistance, malignant progenitor cell cycle kinetics have been difficult to quantify in real-time. We developed an efficient lentiviral bicistronic fluorescent, ubiquitination-based cell cycle indicator reporter (Fucci2BL) to image live single progenitors on a defined niche coupled with cell cycle gene expression analysis. We have identified key differences in cell cycle regulatory gene expression and transit times between normal and chronic myeloid leukemia progenitors that may inform cancer stem cell eradication strategies. PMID:27041210

  19. The ORC1 cycle in human cells: II. Dynamic changes in the human ORC complex during the cell cycle.

    PubMed

    Ohta, Satoshi; Tatsumi, Yasutoshi; Fujita, Masatoshi; Tsurimoto, Toshiki; Obuse, Chikashi

    2003-10-17

    The origin recognition complex (ORC) plays a central role in regulating the initiation of DNA replication in eukaryotes. The level of the ORC1 subunit oscillates throughout the cell cycle, defining an ORC1 cycle. ORC1 accumulates in G1 and is degraded in S phase, although other ORC subunits (ORCs 2-5) remain at almost constant levels. The behavior of ORC components in human cell nuclei with respect to the ORC1 cycle demonstrates that ORCs 2-5 form a complex that is present throughout the cell cycle and that associates with ORC1 when it accumulates in G1 nuclei. ORCs 2-5 are found in both nuclease-insoluble and -soluble fractions. The appearance of nuclease-insoluble ORCs 2-5 parallels the increase in the level of ORC1 associating with nuclease-insoluble, non-chromatin nuclear structures. Thus, ORCs 2-5 are temporally recruited to nuclease-insoluble structures by formation of the ORC1-5 complex. An artificial reduction in the level of ORC1 in human cells by RNA interference results in a shift of ORC2 to the nuclease-soluble fraction, and the association of MCM proteins with chromatin fractions is also blocked by this treatment. These results indicate that ORC1 regulates the status of the ORC complex in human nuclei by tethering ORCs 2-5 to nuclear structures. This dynamic shift is further required for the loading of MCM proteins onto chromatin. Thus, the pre-replication complex in human cells may be regulated by the temporal accumulation of ORC1 in G1 nuclei.

  20. A Novel Bipartite Centrosome Coordinates the Apicomplexan Cell Cycle

    PubMed Central

    Suvorova, Elena S.; Francia, Maria; Striepen, Boris; White, Michael W.

    2015-01-01

    Apicomplexan parasites can change fundamental features of cell division during their life cycles, suspending cytokinesis when needed and changing proliferative scale in different hosts and tissues. The structural and molecular basis for this remarkable cell cycle flexibility is not fully understood, although the centrosome serves a key role in determining when and how much replication will occur. Here we describe the discovery of multiple replicating core complexes with distinct protein composition and function in the centrosome of Toxoplasma gondii. An outer core complex distal from the nucleus contains the TgCentrin1/TgSfi1 protein pair, along with the cartwheel protein TgSas-6 and a novel Aurora-related kinase, while an inner core closely aligned with the unique spindle pole (centrocone) holds distant orthologs of the CEP250/C-Nap protein family. This outer/inner spatial relationship of centrosome cores is maintained throughout the cell cycle. When in metaphase, the duplicated cores align to opposite sides of the kinetochores in a linear array. As parasites transition into S phase, the cores sequentially duplicate, outer core first and inner core second, ensuring that each daughter parasite inherits one copy of each type of centrosome core. A key serine/threonine kinase distantly related to the MAPK family is localized to the centrosome, where it restricts core duplication to once per cycle and ensures the proper formation of new daughter parasites. Genetic analysis of the outer core in a temperature-sensitive mutant demonstrated this core functions primarily in cytokinesis. An inhibition of ts-TgSfi1 function at high temperature caused the loss of outer cores and a severe block to budding, while at the same time the inner core amplified along with the unique spindle pole, indicating the inner core and spindle pole are independent and co-regulated. The discovery of a novel bipartite organization in the parasite centrosome that segregates the functions of

  1. Role of key regulators of the cell cycle in maintenance of hematopoietic stem cells.

    PubMed

    Matsumoto, Akinobu; Nakayama, Keiichi I

    2013-02-01

    Hematopoietic stem cells (HSCs) are characterized by pluripotentiality and self-renewal ability. To maintain a supply of mature blood cells and to avoid HSC exhaustion during the life span of an organism, most HSCs remain quiescent, with only a limited number entering the cell cycle. The molecular mechanisms by which quiescence is maintained in HSCs are addressed, with recent genetic studies having provided important insight into the relation between the cell cycle activity and stemness of HSCs. The cell cycle is tightly regulated in HSCs by complex factors. Key regulators of the cell cycle in other cell types-including cyclins, cyclin-dependent kinases (CDKs), the retinoblastoma protein family, the transcription factor E2F, and CDK inhibitors-also contribute to such regulation in HSCs. Most, but not all, of these regulators are necessary for maintenance of HSCs, with abnormal activation or suppression of the cell cycle resulting in HSC exhaustion. The cell cycle in HSCs is also regulated by external factors such as cytokines produced by niche cells as well as by the ubiquitin-proteasome pathway. Studies of the cell cycle in HSCs may shed light on the pathogenesis of hematopoietic disorders, serve as a basis for the development of new therapeutic strategies for such disorders, prove useful for the expansion of HSCs in vitro as a possible replacement for blood transfusion, and provide insight into stem cell biology in general. This article is part of a Special Issue entitled Biochemistry of Stem Cells. Copyright © 2012 Elsevier B.V. All rights reserved.

  2. Nuclear incorporation of iron during the eukaryotic cell cycle

    DOE PAGES

    Robinson, Ian; Yang, Yang; Zhang, Fucai; ...

    2016-10-18

    Scanning X-ray fluorescence microscopy has been used to probe the distribution of S, P and Fe within cell nuclei. Nuclei, which may have originated at different phases of the cell cycle, are found to show very different levels of Fe present with a strongly inhomogeneous distribution. P and S signals, presumably from DNA and associated nucleosomes, are high and relatively uniform across all the nuclei; these agree with X-ray phase contrast projection microscopy images of the same samples. Finally, we discuss possible reasons for the Fe incorporation.

  3. Nuclear incorporation of iron during the eukaryotic cell cycle

    PubMed Central

    Robinson, Ian; Yang, Yang; Zhang, Fucai; Lynch, Christophe; Yusuf, Mohammed; Cloetens, Peter

    2016-01-01

    Scanning X-ray fluorescence microscopy has been used to probe the distribution of S, P and Fe within cell nuclei. Nuclei, which may have originated at different phases of the cell cycle, are found to show very different levels of Fe present with a strongly inhomogeneous distribution. P and S signals, presumably from DNA and associated nucleosomes, are high and relatively uniform across all the nuclei; these agree with X-ray phase contrast projection microscopy images of the same samples. Possible reasons for the Fe incorporation are discussed. PMID:27787255

  4. Nuclear incorporation of iron during the eukaryotic cell cycle

    SciTech Connect

    Robinson, Ian; Yang, Yang; Zhang, Fucai; Lynch, Christophe; Yusuf, Mohammed; Cloetens, Peter

    2016-10-18

    Scanning X-ray fluorescence microscopy has been used to probe the distribution of S, P and Fe within cell nuclei. Nuclei, which may have originated at different phases of the cell cycle, are found to show very different levels of Fe present with a strongly inhomogeneous distribution. P and S signals, presumably from DNA and associated nucleosomes, are high and relatively uniform across all the nuclei; these agree with X-ray phase contrast projection microscopy images of the same samples. Finally, we discuss possible reasons for the Fe incorporation.

  5. Cinobufacini induced MDA-MB-231 cell apoptosis-associated cell cycle arrest and cytoskeleton function.

    PubMed

    Ma, Lina; Song, Bing; Jin, Hua; Pi, Jiang; Liu, Li; Jiang, Jinhuan; Cai, Jiye

    2012-02-01

    Cinobufacini is a traditional Chinese anti-tumor drug and widely used in clinic experiences. But little is known about its effect on the cells. In this study, the effects of cinobufacini on breast cancer MDA-MB-231 cell were evaluated by CCK-8 assay, and the data showed cinobufacini could inhibit the MDA-MB-231 cells growth effectively in dose-dependent and time-dependent manners. Cell apoptosis and cell cycle were detected by flow cytometry analysis. After the cells being treated with 50 μg/mL cinobufacini for 48 h, the early apoptosis percentage (20.45 ± 1.46%) is much higher than the normal group (7.73 ± 1.21%). The cell cycle data indicated that cinobufacini caused a cell cycle arrest at S phase. What's more, cinobufacini can affect the disruption of cytoskeleton, and these alterations changed the cell-surface ultrastructure and the cell morphology which were detected by atomic force microscopy (AFM) at nanoscale level. It indicated that the cell membrane structure and cytoskeleton networks were destroyed and the cell tails were narrowed after the cell being treated with cinobufacini. The present study is to provide valuable new insights to understand the mechanism of the drug in anti-tumor process. Furthermore, the knowledge concerning the signaling of cell cycle is potentially important to clinical utility. Copyright © 2011 Elsevier Ltd. All rights reserved.

  6. Cell cycle arrest induced by MPPa-PDT in MDA-MB-231 cells

    NASA Astrophysics Data System (ADS)

    Liang, Liming; Bi, Wenxiang; Tian, Yuanyuan

    2016-05-01

    Photodynamic therapy (PDT) is a medical treatment using a photosensitizing agent and light source to treat cancers. Pyropheophorbidea methyl ester (MPPa), a derivative of chlorophyll, is a novel potent photosensitizer. To learn more about this photosensitizer, we examined the cell cycle arrest in MDA-MB-231. Cell cycle and apoptosis were measured by flow cytometer. Checkpoints of the cell cycle were measured by western blot. In this study, we found that the expression of Cyclin D1 was obviously decreased, while the expression of Chk2 and P21 was increased after PDT treatment. This study showed that MPPa-PDT affected the checkpoints of the cell cycle and led the cells to apoptosis.

  7. Synchronization of Green Algae by Light and Dark Regimes for Cell Cycle and Cell Division Studies.

    PubMed

    Hlavová, Monika; Vítová, Milada; Bišová, Kateřina

    2016-01-01

    A synchronous population of cells is one of the prerequisites for studying cell cycle processes such as DNA replication, nuclear and cellular division. Green algae dividing by multiple fission represent a unique single cell system enabling the preparation of highly synchronous cultures by application of a light-dark regime similar to what they experience in nature. This chapter provides detailed protocols for synchronization of different algal species by alternating light-dark cycles; all critical points are discussed extensively. Moreover, detailed information on basic analysis of cell cycle progression in such cultures is presented, including analyses of nuclear, cellular, and chloroplast divisions. Modifications of basic protocols that enable changes in cell cycle progression are also suggested so that nuclear or chloroplast divisions can be followed separately.

  8. Cell-cycle research with synchronous cultures: an evaluation

    NASA Technical Reports Server (NTRS)

    Helmstetter, C. E.; Thornton, M.; Grover, N. B.

    2001-01-01

    The baby-machine system, which produces new-born Escherichia coli cells from cultures immobilized on a membrane, was developed many years ago in an attempt to attain optimal synchrony with minimal disturbance of steady-state growth. In the present article, we put forward a model to describe the behaviour of cells produced by this method, and provide quantitative evaluation of the parameters involved, at each of four different growth rates. Considering the high level of selection achievable with this technique and the natural dispersion in interdivision times, we believe that the output of the baby machine is probably close to optimal in terms of both quality and persistence of synchrony. We show that considerable information on events in the cell cycle can be obtained from populations with age distributions very much broader than those achieved with the baby machine and differing only modestly from steady state. The data presented here, together with the long and fruitful history of findings employing the baby-machine technique, suggest that minimisation of stress on cells is the single most important factor for successful cell-cycle analysis.

  9. Cell-cycle research with synchronous cultures: an evaluation

    NASA Technical Reports Server (NTRS)

    Helmstetter, C. E.; Thornton, M.; Grover, N. B.

    2001-01-01

    The baby-machine system, which produces new-born Escherichia coli cells from cultures immobilized on a membrane, was developed many years ago in an attempt to attain optimal synchrony with minimal disturbance of steady-state growth. In the present article, we put forward a model to describe the behaviour of cells produced by this method, and provide quantitative evaluation of the parameters involved, at each of four different growth rates. Considering the high level of selection achievable with this technique and the natural dispersion in interdivision times, we believe that the output of the baby machine is probably close to optimal in terms of both quality and persistence of synchrony. We show that considerable information on events in the cell cycle can be obtained from populations with age distributions very much broader than those achieved with the baby machine and differing only modestly from steady state. The data presented here, together with the long and fruitful history of findings employing the baby-machine technique, suggest that minimisation of stress on cells is the single most important factor for successful cell-cycle analysis.

  10. Allyl isothiocyanate affects the cell cycle of Arabidopsis thaliana

    PubMed Central

    Åsberg, Signe E.; Bones, Atle M.; Øverby, Anders

    2015-01-01

    Isothiocyanates (ITCs) are degradation products of glucosinolates present in members of the Brassicaceae family acting as herbivore repellents and antimicrobial compounds. Recent results indicate that allyl ITC (AITC) has a role in defense responses such as glutathione depletion, ROS generation and stomatal closure. In this study we show that exposure to non-lethal concentrations of AITC causes a shift in the cell cycle distribution of Arabidopsis thaliana leading to accumulation of cells in S-phases and a reduced number of cells in non-replicating phases. Furthermore, transcriptional analysis revealed an AITC-induced up-regulation of the gene encoding cyclin-dependent kinase A while several genes encoding mitotic proteins were down-regulated, suggesting an inhibition of mitotic processes. Interestingly, visualization of DNA synthesis indicated that exposure to AITC reduced the rate of DNA replication. Taken together, these results indicate that non-lethal concentrations of AITC induce cells of A. thaliana to enter the cell cycle and accumulate in S-phases, presumably as a part of a defensive response. Thus, this study suggests that AITC has several roles in plant defense and add evidence to the growing data supporting a multifunctional role of glucosinolates and their degradation products in plants. PMID:26042144

  11. Computational Cell Cycle Profiling of Cancer Cells for Prioritizing FDA-Approved Drugs with Repurposing Potential.

    PubMed

    Lo, Yu-Chen; Senese, Silvia; France, Bryan; Gholkar, Ankur A; Damoiseaux, Robert; Torres, Jorge Z

    2017-09-12

    Discovery of first-in-class medicines for treating cancer is limited by concerns with their toxicity and safety profiles, while repurposing known drugs for new anticancer indications has become a viable alternative. Here, we have developed a new approach that utilizes cell cycle arresting patterns as unique molecular signatures for prioritizing FDA-approved drugs with repurposing potential. As proof-of-principle, we conducted large-scale cell cycle profiling of 884 FDA-approved drugs. Using cell cycle indexes that measure changes in cell cycle profile patterns upon chemical perturbation, we identified 36 compounds that inhibited cancer cell viability including 6 compounds that were previously undescribed. Further cell cycle fingerprint analysis and 3D chemical structural similarity clustering identified unexpected FDA-approved drugs that induced DNA damage, including clinically relevant microtubule destabilizers, which was confirmed experimentally via cell-based assays. Our study shows that computational cell cycle profiling can be used as an approach for prioritizing FDA-approved drugs with repurposing potential, which could aid the development of cancer therapeutics.

  12. Cell cycle characteristics of crenarchaeota: unity among diversity.

    PubMed

    Lundgren, Magnus; Malandrin, Laurence; Eriksson, Stefan; Huber, Harald; Bernander, Rolf

    2008-08-01

    The hyperthermophilic archaea Acidianus hospitalis, Aeropyrum pernix, Pyrobaculum aerophilum, Pyrobaculum calidifontis, and Sulfolobus tokodaii representing three different orders in the phylum Crenarchaeota were analyzed by flow cytometry and combined phase-contrast and epifluorescence microscopy. The overall organization of the cell cycle was found to be similar in all species, with a short prereplicative period and a dominant postreplicative period that accounted for 64 to 77% of the generation time. Thus, in all Crenarchaeota analyzed to date, cell division and initiation of chromosome replication occur in close succession, and a long time interval separates termination of replication from cell division. In Pyrobaculum, chromosome segregation overlapped with or closely followed DNA replication, and further genome separation appeared to occur concomitant with cellular growth. Cell division in P. aerophilum took place without visible constriction.

  13. Cell Cycle Characteristics of Crenarchaeota: Unity among Diversity▿

    PubMed Central

    Lundgren, Magnus; Malandrin, Laurence; Eriksson, Stefan; Huber, Harald; Bernander, Rolf

    2008-01-01

    The hyperthermophilic archaea Acidianus hospitalis, Aeropyrum pernix, Pyrobaculum aerophilum, Pyrobaculum calidifontis, and Sulfolobus tokodaii representing three different orders in the phylum Crenarchaeota were analyzed by flow cytometry and combined phase-contrast and epifluorescence microscopy. The overall organization of the cell cycle was found to be similar in all species, with a short prereplicative period and a dominant postreplicative period that accounted for 64 to 77% of the generation time. Thus, in all Crenarchaeota analyzed to date, cell division and initiation of chromosome replication occur in close succession, and a long time interval separates termination of replication from cell division. In Pyrobaculum, chromosome segregation overlapped with or closely followed DNA replication, and further genome separation appeared to occur concomitant with cellular growth. Cell division in P. aerophilum took place without visible constriction. PMID:18502873

  14. Single-cell dynamics of the chromosome replication and cell division cycles in mycobacteria.

    PubMed

    Santi, Isabella; Dhar, Neeraj; Bousbaine, Djenet; Wakamoto, Yuichi; McKinney, John D

    2013-01-01

    During the bacterial cell cycle, chromosome replication and cell division must be coordinated with overall cell growth in order to maintain the correct ploidy and cell size. The spatial and temporal coordination of these processes in mycobacteria is not understood. Here we use microfluidics and time-lapse fluorescence microscopy to measure the dynamics of cell growth, division and chromosome replication in single cells of Mycobacterium smegmatis. We find that single-cell growth is size-dependent (large cells grow faster than small cells), which implicates a size-control mechanism in cell-size homoeostasis. Asymmetric division of mother cells gives rise to unequally sized sibling cells that grow at different velocities but show no differential sensitivity to antibiotics. Individual cells are restricted to one round of chromosome replication per cell division cycle, although replication usually initiates in the mother cell before cytokinesis and terminates in the daughter cells after cytokinesis. These studies reveal important differences between cell cycle organization in mycobacteria compared with better-studied model organisms.

  15. Effects of mimosine on Wolbachia in mosquito cells: cell cycle suppression reduces bacterial abundance.

    PubMed

    Fallon, Ann M

    2015-10-01

    The plant allelochemical L-mimosine (β-[N-(3-hydroxy-4-pyridone)]-α-aminopropionic acid; leucenol) resembles the nonessential amino acid, tyrosine. Because the obligate intracellular alphaproteobacterium, Wolbachia pipientis, metabolizes amino acids derived from host cells, the effects of mimosine on infected and uninfected mosquito cells were investigated. The EC50 for mimosine was 6-7 μM with Aedes albopictus C7-10 and C/wStr cell lines, and was not influenced by infection status. Mosquito cells responded to concentrations of mimosine substantially lower than those used to synchronize the mammalian cell cycle; at concentrations of 30-35 μM, mimosine reversibly arrested the mosquito cell cycle at the G1/S boundary and inhibited growth of Wolbachia strain wStr. Although lower concentrations of mimosine slightly increased wStr abundance, concentrations that suppressed the cell cycle reduced Wolbachia levels.

  16. Model scenarios for evolution of the eukaryotic cell cycle.

    PubMed Central

    Novak, B; Csikasz-Nagy, A; Gyorffy, B; Nasmyth, K; Tyson, J J

    1998-01-01

    Progress through the division cycle of present day eukaryotic cells is controlled by a complex network consisting of (i) cyclin-dependent kinases (CDKs) and their associated cyclins, (ii) kinases and phosphatases that regulate CDK activity, and (iii) stoichiometric inhibitors that sequester cyclin-CDK dimers. Presumably regulation of cell division in the earliest ancestors of eukaryotes was a considerably simpler affair. Nasmyth (1995) recently proposed a mechanism for control of a putative, primordial, eukaryotic cell cycle, based on antagonistic interactions between a cyclin-CDK and the anaphase promoting complex (APC) that labels the cyclin subunit for proteolysis. We recast this idea in mathematical form and show that the model exhibits hysteretic behaviour between alternative steady states: a Gl-like state (APC on, CDK activity low, DNA unreplicated and replication complexes assembled) and an S/M-like state (APC off, CDK activity high, DNA replicated and replication complexes disassembled). In our model, the transition from G1 to S/M ('Start') is driven by cell growth, and the reverse transition ('Finish') is driven by completion of DNA synthesis and proper alignment of chromosomes on the metaphase plate. This simple and effective mechanism for coupling growth and division and for accurately copying and partitioning a genome consisting of numerous chromosomes, each with multiple origins of replication, could represent the core of the eukaryotic cell cycle. Furthermore, we show how other controls could be added to this core and speculate on the reasons why stoichiometric inhibitors and CDK inhibitory phosphorylation might have been appended to the primitive alternation between cyclin accumulation and degradation. PMID:10098216

  17. Dopamine Modulates Cell Cycle in the Lateral Ganglionic Eminence

    PubMed Central

    Ohtani, Nobuyo; Goto, Tomohide; Waeber, Christian; Bhide, Pradeep G.

    2005-01-01

    Dopamine is a neuromodulator the functions of which in the regulation of complex behaviors such as mood, motivation, and attention are well known. Dopamine appears in the brain early in the embryonic period when none of those behaviors is robust, raising the possibility that dopamine may influence brain development. The effects of dopamine on specific developmental processes such as neurogenesis are not fully characterized. The neostriatum is a dopamine-rich region of the developing and mature brain. If dopamine influenced neurogenesis, the effects would likely be pronounced in the neostriatum. Therefore, we examined whether dopamine influenced neostriatal neurogenesis by influencing the cell cycle of progenitor cells in the lateral ganglionic eminence (LGE), the neuroepithelial precursor of the neostriatum. We show that dopamine arrives in the LGE via the nigrostriatal pathway early in the embryonic period and that neostriatal neurogenesis progresses in a dopamine-rich milieu. Dopamine D1-like receptor activation reduces entry of progenitor cells from the G1-to S-phase of the cell cycle, whereas D2-like receptor activation produces the opposite effects by promoting G1- to S-phase entry. D1-like effects are prominent in the ventricular zone, and D2-like effects are prominent in the subventricular zone. The overall effects of dopamine on the cell cycle are D1-like effects, most likely because of the preponderance of D1-like binding sites in the embryonic neostriatum. These data reveal a novel developmental role for dopamine and underscore the relevance of dopaminergic signaling in brain development. PMID:12684471

  18. Nonylphenol decreases viability and arrests cell cycle via reactive oxygen species in Raji cells.

    PubMed

    Qi, Yongmei; Zhang, Yingmei; Liu, Yingxia; Zhang, Wenya

    2013-01-01

    4-Nonylphenol (NP), an environmental contaminant commonly found in water systems, has been documented to have adverse effects on human health. In the current study, the effects of NP on the survival, reactive oxygen species (ROS) production and cell cycle distribution of human Raji cells, a human lymphoblastoid cell line with B cell characteristics, were investigated. Furthermore, N-Acetyl-Cysteine (NAC) was used to explore the underlying mechanisms. The results showed that NP dramatically reduced cell viability along with the induction of ROS in a dose dependent manner, and cell survival was recovered by NAC pretreatment. Most strikingly, NP exposure altered the cell cycle profile, mainly leading to the accumulation of cells in the G2/M phase. Pretreatment of Raji cells with NAC attenuated the NP-induced G2/M cell cycle arrest. Taken together, the results suggest NP exhibits cytotoxic effects on Raji cells by decreasing cell viability and inducing G2/M cell cycle arrest, in a ROS dependent manner. Copyright © 2011 Elsevier GmbH. All rights reserved.

  19. Effects of trichostatin A on HDAC8 expression, proliferation and cell cycle of Molt-4 cells.

    PubMed

    He, Jing; Liu, Hongli; Chen, Yan

    2006-01-01

    The effects of Trichostatin A (TSA) on histone deacetylase 8 (HDAC8) expression, proliferation and cell cycle arrest in T-lymphoblastic leukemia cell line Molt-4 cells in vitro were investigated. The effect of TSA on the growth of Molt-4 cells was studied by MTT assay. Flow cytometry was used to examine the cell cycle. The expression of HDAC8 was detected by using immunocytochemistry and Western blot. The results showed that proliferation of Molt-4 cells was inhibited in TSA-treated group in a time- and dose-dependent manner. The IC50 of TSA exposures for 24 h and 36 h were 254.3236 and 199.257 microg/L respectively. The cell cycle analysis revealed that Molt-4 was mostly in G0/G1 phase, and after treatment with TSA from 50 to 400 microg/L for 24 h, the percents of G0/G1 cells were decreased and cells were arrested in G2/M phase. Treatment of TSA for 24 h could significantly inhibit the expression of HDAC8 protein in Molt-4 cells (P<0.01). It was concluded that TSA could decrease the expression of HDAC8 in Molt-4 cells, which contributed to the inhibition of proliferation and induction of cell cycle arrest in Molt-4 cells.

  20. Linalool Induces Cell Cycle Arrest and Apoptosis in Leukemia Cells and Cervical Cancer Cells through CDKIs.

    PubMed

    Chang, Mei-Yin; Shieh, Den-En; Chen, Chung-Chi; Yeh, Ching-Sheng; Dong, Huei-Ping

    2015-11-26

    Plantaginaceae, a popular traditional Chinese medicine, has long been used for treating various diseases from common cold to cancer. Linalool is one of the biologically active compounds that can be isolated from Plantaginaceae. Most of the commonly used cytotoxic anticancer drugs have been shown to induce apoptosis in susceptible tumor cells. However, the signaling pathway for apoptosis remains undefined. In this study, the cytotoxic effect of linalool on human cancer cell lines was investigated. Water-soluble tetrazolium salts (WST-1) based colorimetric cellular cytotoxicity assay, was used to test the cytotoxic ability of linalool against U937 and HeLa cells, and flow cytometry (FCM) and genechip analysis were used to investigate the possible mechanism of apoptosis. These results demonstrated that linalool exhibited a good cytotoxic effect on U937 and HeLa cells, with the IC50 value of 2.59 and 11.02 μM, respectively, compared with 5-FU with values of 4.86 and 12.31 μM, respectively. After treating U937 cells with linalool for 6 h, we found an increased sub-G1 peak and a dose-dependent phenomenon, whereby these cells were arrested at the G0/G1 phase. Furthermore, by using genechip analysis, we observed that linalool can promote p53, p21, p27, p16, and p18 gene expression. Therefore, this study verified that linalool can arrest the cell cycle of U937 cells at the G0/G1 phase and can arrest the cell cycle of HeLa cells at the G2/M phase. Its mechanism facilitates the expression of the cyclin-dependent kinases inhibitors (CDKIs) p53, p21, p27, p16, and p18, as well as the non-expression of cyclin-dependent kinases (CDKs) activity.

  1. Linalool Induces Cell Cycle Arrest and Apoptosis in Leukemia Cells and Cervical Cancer Cells through CDKIs

    PubMed Central

    Chang, Mei-Yin; Shieh, Den-En; Chen, Chung-Chi; Yeh, Ching-Sheng; Dong, Huei-Ping

    2015-01-01

    Plantaginaceae, a popular traditional Chinese medicine, has long been used for treating various diseases from common cold to cancer. Linalool is one of the biologically active compounds that can be isolated from Plantaginaceae. Most of the commonly used cytotoxic anticancer drugs have been shown to induce apoptosis in susceptible tumor cells. However, the signaling pathway for apoptosis remains undefined. In this study, the cytotoxic effect of linalool on human cancer cell lines was investigated. Water-soluble tetrazolium salts (WST-1) based colorimetric cellular cytotoxicity assay, was used to test the cytotoxic ability of linalool against U937 and HeLa cells, and flow cytometry (FCM) and genechip analysis were used to investigate the possible mechanism of apoptosis. These results demonstrated that linalool exhibited a good cytotoxic effect on U937 and HeLa cells, with the IC50 value of 2.59 and 11.02 μM, respectively, compared with 5-FU with values of 4.86 and 12.31 μM, respectively. After treating U937 cells with linalool for 6 h, we found an increased sub-G1 peak and a dose-dependent phenomenon, whereby these cells were arrested at the G0/G1 phase. Furthermore, by using genechip analysis, we observed that linalool can promote p53, p21, p27, p16, and p18 gene expression. Therefore, this study verified that linalool can arrest the cell cycle of U937 cells at the G0/G1 phase and can arrest the cell cycle of HeLa cells at the G2/M phase. Its mechanism facilitates the expression of the cyclin-dependent kinases inhibitors (CDKIs) p53, p21, p27, p16, and p18, as well as the non-expression of cyclin-dependent kinases (CDKs) activity. PMID:26703569

  2. A conserved DNA damage response pathway responsible for coupling the cell division cycle to the circadian and metabolic cycles.

    PubMed

    Chen, Zheng; McKnight, Steven L

    2007-12-01

    The circadian clock drives endogenous oscillations of cellular and physiological processes with a periodicity of approximately 24 h. Progression of the cell division cycle (CDC) has been found to be coupled to the circadian clock, and it has been postulated that gating of the CDC by the circadian cycle may have evolved to protect DNA from the mutagenic effects of ultraviolet light. When grown under nutrient-limiting conditions in a chemostat, prototrophic strains of budding yeast, Saccharomyces cerevisiae, adopt a robust metabolic cycle of ultradian dimensions that temporally compartmentalizes essential cellular events. The CDC is gated by this yeast metabolic cycle (YMC), with DNA replication strictly segregated away from the oxidative phase when cells are actively respiring. Mutants impaired in such gating allow DNA replication to take place during the respiratory phase of the YMC and have been found to suffer significantly elevated rates of spontaneous mutation. Analogous to the circadian cycle, the YMC also employs the conserved DNA checkpoint kinase Rad53/Chk2 to facilitate coupling with the CDC. These studies highlight an evolutionarily conserved mechanism that seems to confine cell division to particular temporal windows to prevent DNA damage. We hypothesize that DNA damage itself might constitute a "zeitgeber", or time giver, for both the circadian cycle and the metabolic cycle. We discuss these findings in the context of a unifying theme underlying the circadian and metabolic cycles, and explore the relevance of cell cycle gating to human diseases including cancer.

  3. Hubble Space Telescope solar cell module thermal cycle test

    NASA Technical Reports Server (NTRS)

    Douglas, Alexander; Edge, Ted; Willowby, Douglas; Gerlach, Lothar

    1992-01-01

    The Hubble Space Telescope (HST) solar array consists of two identical double roll-out wings designed after the Hughes flexible roll-up solar array (FRUSA) and was developed by the European Space Agency (ESA) to meet specified HST power output requirements at the end of 2 years, with a functional lifetime of 5 years. The requirement that the HST solar array remain functional both mechanically and electrically during its 5-year lifetime meant that the array must withstand 30,000 low Earth orbit (LEO) thermal cycles between approximately +100 and -100 C. In order to evaluate the ability of the array to meet this requirement, an accelerated thermal cycle test in vacuum was conducted at NASA's Marshall Space Flight Center (MSFC), using two 128-cell solar array modules which duplicated the flight HST solar array. Several other tests were performed on the modules. The thermal cycle test was interrupted after 2,577 cycles, and a 'cold-roll' test was performed on one of the modules in order to evaluate the ability of the flight array to survive an emergency deployment during the dark (cold) portion of an orbit. A posttest static shadow test was performed on one of the modules in order to analyze temperature gradients across the module. Finally, current in-flight electrical performance data from the actual HST flight solar array will be tested.

  4. Cell Division and Targeted Cell Cycle Arrest Opens and Stabilizes Basement Membrane Gaps

    PubMed Central

    Matus, David Q.; Chang, Emily; Makohon-Moore, Sasha C.; Hagedorn, Mary A.; Chi, Qiuyi; Sherwood, David R.

    2014-01-01

    Large gaps in basement membrane (BM) occur during organ remodeling and cancer cell invasion. Whether dividing cells, which temporarily reduce their attachment to BM, influence these breaches is unknown. Here we analyse uterine-vulval attachment during development across 21 species of rhabditid nematodes and find that the BM gap that forms between these organs is always bounded by a non-dividing vulval cell. Through cell cycle manipulation and live cell imaging in Caenorhabditis elegans, we show that actively dividing vulval cells facilitate enlargement of this breach by promoting BM movement. In contrast, targeted cell-cycle arrest halts BM movement and limits gap opening. Further, we demonstrate that the BM component laminin accumulates at the BM gap edge and promotes increased integrin levels in non-dividing vulval cells, stabilizing gap position. Together, these studies reveal that cell division can be used as a mechanism to regulate BM breaches, thus controlling the exchange of cells between tissues. PMID:24924309

  5. Preparative electrophoresis of cultured human cells: Effect of cell cycle phase

    NASA Technical Reports Server (NTRS)

    Kunze, M. E.; Todd, P. W.; Goolsby, C. L.; Walker, J. T.

    1985-01-01

    Human epithelioid T-1E cells were cultured in suspension and subjected to density gradient electrophoresis upward in a vertical column. It is indicated that the most rapidly migrating cells were at the beginning of the cell cycle and the most slowly migrating cells were at the end of the cell cycle. The fastest migrating cells divided 24 hr later than the slowest migrating cells. Colonies developing from slowly migrating cells had twice as many cells during exponential growth as did the most rapidly migrating cells, and the numbers of cells per colony at any time was inversely related to the electrophoretic migration rate. The DNA measurements by fluorescence flow cytometry indicates that the slowest migrating cell populations are enriched in cells that have twice as much DNA as the fastest migrating cells. It is concluded that electrophoretic mobility of these cultured human cells declines steadily through the cell cycle and that the mobility is lowest at the end of G sub 2 phase and highest at the beginning of G sub 1 phase.

  6. Identification of Tympanic Border Cells as Slow-Cycling Cells in the Cochlea

    PubMed Central

    Taniguchi, Mirei; Yamamoto, Norio; Nakagawa, Takayuki; Ogino, Eriko; Ito, Juichi

    2012-01-01

    Mammalian cochlear sensory epithelial cells are believed to possess minimal regenerative potential because they halt proliferation during late stage of embryogenesis and never regenerate after birth. This means that sensorineural hearing loss caused by the death of cochlear sensory epithelial cells is a permanent condition. However, stem cells were recently identified in neonatal mice following dissociation of their inner ear organs. This suggests that regenerative therapy for sensorineural hearing loss may be possible. Unfortunately, dissociation distorts the microanatomy of the inner ear, making it difficult to determine the precise location of stem cells in unaltered specimens. To develop new therapeutic approaches based on sensory epithelial cell regeneration, the location of these stem cells must be elucidated. Stem cells normally proliferate at a slow rate in adult organs. In fact, so-called label-retaining cells, or slow-cycling cells, of the brain and skin are recognized as stem cells. In this study, using the exogenous proliferation marker, 5′-bromo-2′-deoxyuridine (BrdU) in combination with the endogenous proliferation marker Ki-67, we identified tympanic border cells. These cells, which are located beneath the basilar membrane in vivo, represent slow-cycling cells of the murine cochlea. Immunohistochemically, these cells stained positive for the immature cell marker Nestin. But it will be difficult to achieve regeneration of the cochlear function because these slow-cycling cells disappear in the mature murine cochlea. PMID:23119055

  7. Preparative electrophoresis of cultured human cells: Effect of cell cycle phase

    NASA Technical Reports Server (NTRS)

    Kunze, M. E.; Todd, P. W.; Goolsby, C. L.; Walker, J. T.

    1985-01-01

    Human epithelioid T-1E cells were cultured in suspension and subjected to density gradient electrophoresis upward in a vertical column. It is indicated that the most rapidly migrating cells were at the beginning of the cell cycle and the most slowly migrating cells were at the end of the cell cycle. The fastest migrating cells divided 24 hr later than the slowest migrating cells. Colonies developing from slowly migrating cells had twice as many cells during exponential growth as did the most rapidly migrating cells, and the numbers of cells per colony at any time was inversely related to the electrophoretic migration rate. The DNA measurements by fluorescence flow cytometry indicates that the slowest migrating cell populations are enriched in cells that have twice as much DNA as the fastest migrating cells. It is concluded that electrophoretic mobility of these cultured human cells declines steadily through the cell cycle and that the mobility is lowest at the end of G sub 2 phase and highest at the beginning of G sub 1 phase.

  8. HDAC2 regulates cell proliferation, cell cycle progression and cell apoptosis in esophageal squamous cell carcinoma EC9706 cells

    PubMed Central

    Li, Shenglei; Wang, Feng; Qu, Yunhui; Chen, Xiaoqi; Gao, Ming; Yang, Jianping; Zhang, Dandan; Zhang, Na; Li, Wencai; Liu, Hongtao

    2017-01-01

    Increasing evidence has demonstrated that histone deacetylase 2 (HDAC2) participates in the regulation of a variety of biological processes in numerous tumors. However, the potential role of HDAC2 in the development and progression of esophageal squamous cell carcinoma (ESCC) remains elusive. Immunohistochemistry was utilized to detect the expression of HDAC2, Cell Counting Kit-8 was used to determine the cell proliferation, and flow cytometry was employed to investigate cell cycle and cell apoptosis. Finally, western blotting was employed to detect the protein expression of cyclin D1, p21, B cell lymphoma-2 (Bcl-2) and Bcl-2-associated X protein (Bax). The present study found that expression of HDAC2 protein in ESCC tissues was significantly increased compared with atypical hyperplasia tissues and normal esophageal mucosa (P<0.001). The expression of HDAC2 was not associated with the age or gender of patients (P>0.05), but was closely associated with the histological grade, invasion depth, tumor-node-metastasis stage and lymph node metastasis, respectively (all P<0.001). HDAC2 small interfering RNA effectively downregulated the expression of HDAC2 protein in ESCC EC9706 cells. Downregulation of HDAC2 expression evidently inhibited cell proliferation, arrested cell cycle at the G0/G1 phase and induced cell apoptosis in ESCC EC9706 cells, coupled with increased expression of p21 and Bax proteins and decreased expression of cyclin D1 and Bcl-2 proteins. Overall, the present findings suggest that HDAC2 may play an important role in the development and progression of ESCC and be considered as a novel molecular target for the treatment of ESCC. PMID:28123574

  9. Modeling metaphase to anaphase transition of budding yeast cell cycle

    NASA Astrophysics Data System (ADS)

    Qin, Shanshan; Tang, Chao

    2014-03-01

    One of the interesting questions in cell cycle is how the sister chromosomes separate in an abrupt and irreversible manner. Anaphase is initiated when the anaphase-promoting complex (APC) triggers the destruction of securin (Pds1), allowing separase (Esp1) to cut the sister-chromatid cohesion. In experiment,we observed the degradation timing were different among cycling protein Clb5, Clb2 and Pds1. Phosphorylation of these proteins by APC dramaticaly affect their degradation. To fully understand the role of activation and degradation timing and coordination these cell cycle associated proteins,we build a simplified ordinary differential equations model. Simulation results suggest that the phosphorylation of protein do delay its degradation by APC, which agree with our experiment results. The positive feedback loop between Cdc14 and Pds1 is responsible for the abrupt separation of sister-chromatid. When varying each parameter up and down for ten fold, similar results can still be produced, suggest that this network is robustly designed for its function.

  10. Flow cytometric analysis of the cell cycle in chronic gastritis.

    PubMed

    Guerci, A; Chambre, J F; Franck, P; Floquet, J; Gaucher, P; Guerci, O

    1992-09-01

    Flow cytometric cell cycle analysis was recorded in gastric biopsy specimens from patients with normal gastric mucosa (GM), superficial gastritis (SG) and chronic atrophic gastritis (CAG). Cell-cycle analysis showed significantly higher percentages of cells in S- and S+G2/M-phase in CAG than in SG and normal GM (P < 0.0001). Moreover, CAG with severe or moderate atrophy showed significantly higher percentages of cells in S-phase (P < 0.05) and S+G2/M-phase (P < 0.02) than CAG with mild atrophy in antrum. In fundus, even if this increase was observed, it did not reach statistical significance. Consideration of concomitant pathologic findings such as oesophagite, gastric or duodenal ulcer, duodenite or benign polyp allowed a better differentiation of CAG both in antrum and in fundus. Significantly higher S-phase was observed in CAG with severe or moderate atrophy than in CAG with mild atrophy (P < 0.05). No statistically significant results were observed in patients with normal gastric mucosa or chronic gastritis and a concomitant pathologic finding.

  11. Modeling cell-cycle synchronization during embryogenesis in Xenopus laevis

    NASA Astrophysics Data System (ADS)

    McIsaac, R. Scott; Huang, K. C.; Sengupta, Anirvan; Wingreen, Ned

    2010-03-01

    A widely conserved aspect of embryogenesis is the ability to synchronize nuclear divisions post-fertilization. How is synchronization achieved? Given a typical protein diffusion constant of 10 μm^2sec, and an embryo length of 1mm, it would take diffusion many hours to propagate a signal across the embryo. Therefore, synchrony cannot be attained by diffusion alone. We hypothesize that known autocatalytic reactions of cell-cycle components make the embryo an ``active medium'' in which waves propagate much faster than diffusion, enforcing synchrony. We report on robust spatial synchronization of components of the core cell cycle circuit based on a mathematical model previously determined by in vitro experiments. In vivo, synchronized divisions are preceded by a rapid calcium wave that sweeps across the embryo. Experimental evidence supports the hypothesis that increases in transient calcium levels lead to derepression of a negative feedback loop, allowing cell divisions to start. Preliminary results indicate a novel relationship between the speed of the initial calcium wave and the ability to achieve synchronous cell divisions.

  12. Stressing the cell cycle in senescence and aging.

    PubMed

    Chandler, Hollie; Peters, Gordon

    2013-12-01

    Senescence represents a permanent exit from the cell cycle and its role in curtailing the proliferation of damaged and potentially oncogenic cells has relevance both as a front-line defense against cancer and as an underlying cause of aging. The retinoblastoma protein (RB) and p53 tumor suppressors are central to the process and the growth arrest is primarily implemented by the cyclin-dependent kinase (CDK) inhibitors, p16INK4a and p21CIP1. In contrast to terminal differentiation, senescence is a general response to a diverse range of cellular stresses and is typically accompanied by a characteristic set of phenotypic changes. Of particular note is a secretory program whose autocrine and paracrine effects can advertize the presence of senescent cells within a tissue and promote their clearance by the immune system. In this short review, we will highlight recent advances in understanding the relationship between senescence and aging and the distinction between senescence and terminal differentiation, from a cell cycle perspective. Copyright © 2013 Elsevier Ltd. All rights reserved.

  13. [From ovocyte to biochemistry of the cell cycle].

    PubMed

    Ozon, R

    1991-01-01

    The cell division cycle in eukaryotes contains up to three major transition points; the conversion of quiescent cells to a stage of active proliferation, the initiation of DNA synthesis (S phase) and the induction of mitosis in cells with newly replicated genome (M phase). Within the past years two strategies, have converged to identify, genetically and biochemically a key protein kinase p34 cdc2 that governs the entry into mitosis. In the fission yeast Schizosaccharomyces pombe a number of mutants in the mitotic regulatory circuit have been isolated. A central gene in the network is cdc2 which is essential for the proper execution of mitosis. The cdc2 gene interacts with a number of other genes for correct mitotic control. The Amphibian oocyte, the oocyte from Xenopus laevis particularly, is arrested at the G2 phase of the first meiotic division; when it enters M phase, it contains a dominant regulatory factor known as MPF (M-phase or maturation promoting factor). Purified MPF is an heterodimer formed of two polypeptides p34cdc2 an homologue of the product of the gene cdc2 and p45cdc13 or cyclin an homologue of the product of the gene cdc13. Biochemical studies have revealed that p34cdc2 is a phosphotyrosine protein during the G2 phase of the cell cycle, both mitotic and meiotic. The tyrosine phosphorylation of p34cdc2 is regulated by the gradual accumulation of cyclin. At the onset of M phase, the complex p34cdc2/cyclin is activated as an histone H1 kinase, and p34cdc2 is tyrosine dephosphorylated. The mechanism of activation of p34cdc2 is negatively regulated by a form of protein phosphatase 2A. Ovulated vertebrate oocytes are arrested at metaphase of the second meiotic division (M II) under the control of the proto-oncogene c-mos a protein kinase. The exit of M II phase and the initiation of early embryonic mitotic cell cycles are physiologically induced by the spermatozoa at the time of fertilization. They requires the degradation of c-mos by a Ca2+ dependent

  14. Exosomes Secreted by Toxoplasma gondii-Infected L6 Cells: Their Effects on Host Cell Proliferation and Cell Cycle Changes.

    PubMed

    Kim, Min Jae; Jung, Bong-Kwang; Cho, Jaeeun; Song, Hyemi; Pyo, Kyung-Ho; Lee, Ji Min; Kim, Min-Kyung; Chai, Jong-Yil

    2016-04-01

    Toxoplasma gondii infection induces alteration of the host cell cycle and cell proliferation. These changes are not only seen in directly invaded host cells but also in neighboring cells. We tried to identify whether this alteration can be mediated by exosomes secreted by T. gondii-infected host cells. L6 cells, a rat myoblast cell line, and RH strain of T. gondii were selected for this study. L6 cells were infected with or without T. gondii to isolate exosomes. The cellular growth patterns were identified by cell counting with trypan blue under confocal microscopy, and cell cycle changes were investigated by flow cytometry. L6 cells infected with T. gondii showed decreased proliferation compared to uninfected L6 cells and revealed a tendency to stay at S or G2/M cell phase. The treatment of exosomes isolated from T. gondii-infected cells showed attenuation of cell proliferation and slight enhancement of S phase in L6 cells. The cell cycle alteration was not as obvious as reduction of the cell proliferation by the exosome treatment. These changes were transient and disappeared at 48 hr after the exosome treatment. Microarray analysis and web-based tools indicated that various exosomal miRNAs were crucial for the regulation of target genes related to cell proliferation. Collectively, our study demonstrated that the exosomes originating from T. gondii could change the host cell proliferation and alter the host cell cycle.

  15. Cell and nuclei separation from tissue and from various phases of the cell cycle. Final report

    SciTech Connect

    Pipkin, J.

    1982-05-01

    The Cell Biology laboratory has developed practical methods for routine electrostatic separation of nuclei. Specially designed collection chambers facilitate the capture of sufficient numbers of cells and/or nuclei from precise areas of the cell cycle for biochemical analysis. These analyses include: one- and two-dimensional gel electrophoresis, isoelectric focusing, amino acid analysis and capillary isotachophoretic techniques that are used to demonstrate nuclear regulatory protein synthesis during the in vivo cell cycle after administration of various compounds. Separation of nuclei into homogeneous populations simplifies the detection of biochemical events that transpire in both cycling and non-cycling tissue into more discrete stages for analysis, thus uncluttering the more complex overall picture seen so commonly in generalized proliferating tissue.

  16. Effects of suppressed autophagy on mitochondrial dynamics and cell cycle of N2a cells.

    PubMed

    Gui, Meng-cui; Chen, Bo; Yu, Shan-shan; Bu, Bi-tao

    2014-04-01

    Autophagy dysregulation, mitochondrial dynamic abnormality and cell cycle re-entry are implicated in the vulnerable neurons of patients with Alzheimer's disease. This study was designed to testify the association among autophagy, mitochondrial dynamics and cell cycle in dividing neuroblastoma (N2a) cells. The N2a cells were cultured in vitro and treated with different concentrations of 3-methyladenine (3-MA). The cell viability was detected by methyl thiazolyl tetrazolium (MTT) assay. They were randomly divided into control group (cells cultured in normal culture medium) and 3-MA group (cells treated with 10 mmol/L 3-MA). The cell cycle was analyzed in the two groups 3, 6, 12, and 24 h after treatment by flow cytometry. Western blotting was used to evaluate the expression levels of mitofission 1 (Fis1), mitofusin 2 (Mfn2), microtubule-associated protein 1 light chain 3 (LC3), cell cycle-dependent kinase 4 (CDK4) and cdc2. The flow cytometry revealed that the proportion of cells in G(2)/M was significantly increased, and that in G0/G1 was significantly reduced in the 3-MA group as compared with the control group. Western blotting showed that the expression levels of Fis1, LC3, and CDK4 were significantly up-regulated in the 3-MA group at the four indicated time points as compared with the control group. Mfn2 was initially decreased in the 3-MA group, and then significantly increased at 6 h or 12 h. Cdc2 was significantly increased in the 3-MA group at 3 h and 6 h, and then dropped significantly at 12 h and 24 h. Our data indicated that 3-MA-induced suppressed autophagy may interfere with the cell cycle progression and mitochondrial dynamics, and cause cell death. There are interactions among cell cycle, mitochondrial dynamics and autophagy in neurons.

  17. Maintenance of imprinting and nuclear architecture in cycling cells.

    PubMed

    Teller, Kathrin; Solovei, Irina; Buiting, Karin; Horsthemke, Bernhard; Cremer, Thomas

    2007-09-18

    Dynamic gene repositioning has emerged as an additional level of epigenetic gene regulation. An early example was the report of a transient, spatial convergence (< or =2 microm) of oppositely imprinted regions ("kissing"), including the Angelman syndrome/Prader-Willi syndrome (AS/PWS) locus and the Beckwith-Wiedemann syndrome locus in human lymphocytes during late S phase. It was argued that kissing is required for maintaining opposite imprints in cycling cells. Employing 3D-FISH with a BAC contig covering the AS/PWS region, light optical, serial sectioning, and quantitative 3D-image analysis, we observed that both loci always retained a compact structure and did not form giant loops. Three-dimensional distances measured among various, homologous AS/PWS segments in 393 human lymphocytes, 132 human fibroblasts, and 129 lymphoblastoid cells from Gorilla gorilla revealed a wide range of distances at any stage of interphase and in G(0). At late S phase, 4% of nuclei showed distances < or =2 microm, 49% showed distances >6 microm, and 18% even showed distances >8 microm. A similar distance variability was found for Homo sapiens (HSA) 15 centromeres in a PWS patient with a deletion of the maternal AS/PWS locus and for the Beckwith-Wiedemann syndrome loci in human lymphocytes. A transient kiss during late S phase between loci widely separated at other stages of the cell cycle seems incompatible with known global constraints of chromatin movements in cycling cells. Further experiments suggest that the previously observed convergence of AS/PWS loci during late S phase was most likely a side effect of the convergence of nucleolus organizer region-bearing acrocentric human chromosomes, including HSA 15.

  18. Cell cycle reentry from the late S phase: implications from stem cell formation in the moss Physcomitrella patens.

    PubMed

    Ishikawa, Masaki; Hasebe, Mitsuyasu

    2015-05-01

    Differentiated cells are in a non-dividing, quiescent state, but some differentiated cells can reenter the cell cycle in response to appropriate stimuli. Quiescent cells are generally arrested at the G0/G1 phase, reenter the cell cycle, and progress to the S phase to replicate their genomic DNA. On the other hand, some types of cells are arrested at the different phase and reenter the cell cycle from there. In the moss Physcomitrella patens, the differentiated leaf cells of gametophores formed in the haploid generation contain approximately 2C DNA content, and DNA synthesis is necessary for reentry into the cell cycle, which is suggested to be arrested at late S phase. Here we review various cell-division reactivation processes in which cells reenter the cell cycle from the late S phase, and discuss possible mechanisms of such unusual cell cycle reentries with special emphasis on Physcomitrella.

  19. Human pancreatic β-cell G1/S molecule cell cycle atlas.

    PubMed

    Fiaschi-Taesch, Nathalie M; Kleinberger, Jeffrey W; Salim, Fatimah G; Troxell, Ronnie; Wills, Rachel; Tanwir, Mansoor; Casinelli, Gabriella; Cox, Amy E; Takane, Karen K; Scott, Donald K; Stewart, Andrew F

    2013-07-01

    Expansion of pancreatic β-cells is a key goal of diabetes research, yet induction of adult human β-cell replication has proven frustratingly difficult. In part, this reflects a lack of understanding of cell cycle control in the human β-cell. Here, we provide a comprehensive immunocytochemical "atlas" of G1/S control molecules in the human β-cell. This atlas reveals that the majority of these molecules, previously known to be present in islets, are actually present in the β-cell. More importantly, and in contrast to anticipated results, the human β-cell G1/S atlas reveals that almost all of the critical G1/S cell cycle control molecules are located in the cytoplasm of the quiescent human β-cell. Indeed, the only nuclear G1/S molecules are the cell cycle inhibitors, pRb, p57, and variably, p21: none of the cyclins or cdks necessary to drive human β-cell proliferation are present in the nuclear compartment. This observation may provide an explanation for the refractoriness of human β-cells to proliferation. Thus, in addition to known obstacles to human β-cell proliferation, restriction of G1/S molecules to the cytoplasm of the human β-cell represents an unanticipated obstacle to therapeutic human β-cell expansion.

  20. Human Pancreatic β-Cell G1/S Molecule Cell Cycle Atlas

    PubMed Central

    Fiaschi-Taesch, Nathalie M.; Kleinberger, Jeffrey W.; Salim, Fatimah G.; Troxell, Ronnie; Wills, Rachel; Tanwir, Mansoor; Casinelli, Gabriella; Cox, Amy E.; Takane, Karen K.; Scott, Donald K.; Stewart, Andrew F.

    2013-01-01

    Expansion of pancreatic β-cells is a key goal of diabetes research, yet induction of adult human β-cell replication has proven frustratingly difficult. In part, this reflects a lack of understanding of cell cycle control in the human β-cell. Here, we provide a comprehensive immunocytochemical “atlas” of G1/S control molecules in the human β-cell. This atlas reveals that the majority of these molecules, previously known to be present in islets, are actually present in the β-cell. More importantly, and in contrast to anticipated results, the human β-cell G1/S atlas reveals that almost all of the critical G1/S cell cycle control molecules are located in the cytoplasm of the quiescent human β-cell. Indeed, the only nuclear G1/S molecules are the cell cycle inhibitors, pRb, p57, and variably, p21: none of the cyclins or cdks necessary to drive human β-cell proliferation are present in the nuclear compartment. This observation may provide an explanation for the refractoriness of human β-cells to proliferation. Thus, in addition to known obstacles to human β-cell proliferation, restriction of G1/S molecules to the cytoplasm of the human β-cell represents an unanticipated obstacle to therapeutic human β-cell expansion. PMID:23493570

  1. Cell-cycle-independent transitions in temporal identity of mammalian neural progenitor cells.

    PubMed

    Okamoto, Mayumi; Miyata, Takaki; Konno, Daijiro; Ueda, Hiroki R; Kasukawa, Takeya; Hashimoto, Mitsuhiro; Matsuzaki, Fumio; Kawaguchi, Ayano

    2016-04-20

    During cerebral development, many types of neurons are sequentially generated by self-renewing progenitor cells called apical progenitors (APs). Temporal changes in AP identity are thought to be responsible for neuronal diversity; however, the mechanisms underlying such changes remain largely unknown. Here we perform single-cell transcriptome analysis of individual progenitors at different developmental stages, and identify a subset of genes whose expression changes over time but is independent of differentiation status. Surprisingly, the pattern of changes in the expression of such temporal-axis genes in APs is unaffected by cell-cycle arrest. Consistent with this, transient cell-cycle arrest of APs in vivo does not prevent descendant neurons from acquiring their correct laminar fates. Analysis of cultured APs reveals that transitions in AP gene expression are driven by both cell-intrinsic and -extrinsic mechanisms. These results suggest that the timing mechanisms controlling AP temporal identity function independently of cell-cycle progression and Notch activation mode.

  2. Function of cyclins in regulating the mitotic and meiotic cell cycles in male germ cells

    PubMed Central

    Wolgemuth, Debra J.

    2014-01-01

    The specialized cell cycles that characterize various aspects of the differentiation of germ cells provide a unique opportunity to understand heretofore elusive aspects of the in vivo function of cell cycle regulators. Key components of the cell cycle machinery are the regulatory sub-units, the cyclins, and their catalytic partners, the cyclin-dependent kinases. Some of the cyclins exhibit unique patterns of expression in germ cells that suggest possible concomitant distinct functions, predictions that are being explored by targeted mutagenesis in mouse models. A novel, meiosis-specific function has been shown for one of the A-type cyclins, cyclin A1. Embryonic lethality has obviated understanding of the germline functions of cyclin A2 and cyclin B1, while yet other cyclins, although expressed at specific stages of germ cell development, may have less essential function in the male germline. PMID:19001847

  3. Reverse the curse - the role of deubiquitination in cell cycle control

    PubMed Central

    Song, Ling; Rape, Michael

    2008-01-01

    Reversible protein ubiquitination is a crucial mechanism regulating the progression through the eukaryotic cell cycle. Ubiquitin-dependent signaling is terminated by specific deubiquitinating enzymes (DUBs), which now are known to be integral components of the core cell cycle machinery and cell cycle checkpoints. The importance of DUBs for cell cycle control is underscored by their frequent misregulation in cancer. Here, we discuss the role of deubiquitinating enzymes in controlling proliferation. PMID:18346885

  4. Follicular Dendritic Cells Retain Infectious HIV in Cycling Endosomes.

    PubMed

    Heesters, Balthasar A; Lindqvist, Madelene; Vagefi, Parsia A; Scully, Eileen P; Schildberg, Frank A; Altfeld, Marcus; Walker, Bruce D; Kaufmann, Daniel E; Carroll, Michael C

    2015-12-01

    Despite the success of antiretroviral therapy (ART), it does not cure Human Immunodeficiency Virus (HIV) and discontinuation results in viral rebound. Follicular dendritic cells (FDC) are in direct contact with CD4+ T cells and they retain intact antigen for prolonged periods. We found that human FDC isolated from patients on ART retain infectious HIV within a non-degradative cycling compartment and transmit infectious virus to uninfected CD4 T cells in vitro. Importantly, treatment of the HIV+ FDC with a soluble complement receptor 2 purges the FDC of HIV virions and prevents viral transmission in vitro. Our results provide an explanation for how FDC can retain infectious HIV for extended periods and suggest a therapeutic strategy to achieve cure in HIV-infected humans.

  5. Selective cell cycle transcription requires membrane synthesis in Caulobacter

    PubMed Central

    Brassinga, Ann Karen C.; Gorbatyuk, Boris; Ouimet, Marie–Claude; Marczynski, Gregory T.

    2000-01-01

    Caulobacter crescentus divides asymmetrically and creates distinct polar membrane surfaces that partition during the cell cycle to distinct cell progeny. Blocking membrane synthesis prevented transcription from selective promoters involved in asymmetric cell division. Transcription from sigma-54-dependent flagellar promoters was blocked completely; however, transcription from the CtrA response regulator-dependent flagellar promoters was activated but reduced. Transcription from the ccrM (DNA methylation) promoter and the che (chemosensory) promoter was also blocked completely. Transcription from a strong promoter at the chromosome replication origin was first stopped then induced by blocked membrane synthesis. We propose a feedback control coupling membrane synthesis to transcription that selectively supports membrane-associated processes such as flagellar assembly, chemosensory biogenesis and chromosome replication. PMID:10675339

  6. Cell cycle RNA regulons coordinating early lymphocyte development.

    PubMed

    Galloway, Alison; Turner, Martin

    2017-09-01

    Lymphocytes undergo dynamic changes in gene expression as they develop from progenitor cells lacking antigen receptors, to mature cells that are prepared to mount immune responses. While transcription factors have established roles in lymphocyte development, they act in concert with post-transcriptional and post-translational regulators to determine the proteome. Furthermore, the post-transcriptional regulation of RNA regulons consisting of mRNAs whose protein products act cooperatively allows RNA binding proteins to exert their effects at multiple points in a pathway. Here, we review recent evidence demonstrating the importance of RNA binding proteins that control the cell cycle in lymphocyte development and discuss the implications for tumorigenesis. WIREs RNA 2017, 8:e1419. doi: 10.1002/wrna.1419 For further resources related to this article, please visit the WIREs website. © 2017 The Authors. WIREs RNA published by Wiley Periodicals, Inc.

  7. Monitoring of dynamin during the Toxoplasma gondii cell cycle.

    PubMed

    Caldas, Lucio Ayres; Soares, Leandro Lemgruber; Henrique Seabra, Sergio; Attias, Marcia; de Souza, Wanderley

    2016-12-01

    The obligate intracellular protozoan parasite Toxoplasma gondii actively invades virtually all warm-blooded nucleated cells. This process results in a non-fusogenic vacuole, inside which the parasites replicate continuously until egress signaling is triggered. In this work, we investigated the role of the large GTPase dynamin in the interaction of T. gondii with the host cell by using laser and electron microscopy during three key stages: invasion, development and egress. The detection of dynamin during invasion indicates the occurrence of endocytosis, while T. gondii egress appeared to be independent of dynamin participation. However, the presence of dynamin during T. gondii development suggests that this molecule plays undescribed roles in the tachyzoite's cell cycle. © FEMS 2016. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  8. Effects of simulated microgravity on cell cycle in human endothelial cells

    NASA Astrophysics Data System (ADS)

    Sokolovskaya, Alisa A.; Ignashkova, Tatiana I.; Bochenkova, Anna V.; Moskovtsev, Aleksey A.; Baranov, Victor M.; Kubatiev, Aslan A.

    2014-06-01

    The aim of the current study is to investigate effects of simulated microgravity on the cell cycle of endothelial cells. We analyze changes in the cell cycle after exposure of endothelial-like EA.hy 926 cells to simulated microgravity using a Desktop random positioning machine (RPM). Cell cycle profiles determined by flow cytometry show, that the percentage of the cells in the G0/G1 phase after 24 and 96 h of RPM-simulated microgravity is significantly increased as compared to the control group. However, no significant difference is observed after 120 h of RPM-simulated microgravity. In regard to S phase, the percentage of cells is significantly decreased after 24 and 96 h of RPM, respectively; whereas 120 h later, the number of S-phase cells is comparable to the control group. Thus, we show that simulated microgravity inhibits cell cycle progression of human EA.hy 926 cells from the G0/G1 phase to the S phase. We observe an effect of a hibernation-like state, when the growth of the cells in the RPM group slows down, but does not stop. Our results further show that simulated microgravity can affect adhesion of endothelial cells, and alpha-tubulin expression, as most cells begin to detach from the surface of OptiCell unit after 24 h, form aggregates after 48 h, and exhibit accumulation of alpha-tubulin around the nucleus after 48 h of exposure to simulated microgravity conditions. Our results demonstrate a chance in the cell cycle in a low gravitational field.

  9. Differential expression of cell-cycle regulators in human beta-cells derived from insulinoma tissue.

    PubMed

    Ueberberg, Sandra; Tannapfel, Andrea; Schenker, Peter; Viebahn, Richard; Uhl, Waldemar; Schneider, Stephan; Meier, Juris J

    2016-05-01

    The low frequency of beta-cell replication in the adult human pancreas limits beta-cell regeneration. A better understanding of the regulation of human beta-cell proliferation is crucial to develop therapeutic strategies aiming to enhance beta-cell mass. To identify factors that control beta-cell proliferation, cell-cycle regulation was examined in human insulinomas as a model of increased beta-cell proliferation (n=11) and healthy pancreatic tissue from patients with benign pancreatic tumors (n=9). Tissue sections were co-stained for insulin and cell-cycle proteins. Transcript levels of selected cell-cycle factors in beta-cells were determined by qRT-PCR after performing laser-capture microdissection. The frequency of beta-cell replication was 3.74±0.92% in the insulinomas and 0.11±0.04% in controls (p=0.0016). p21 expression was higher in insulinomas (p=0.0058), and Rb expression was higher by trend (p=0.085), whereas p16 (p<0.0001), Cyclin C (p<0.0001), and p57 (p=0.018) expression levels were lower. The abundance of Cyclin D3 (p=0.62) and p27 (p=0.68) was not different between the groups. The reduced expression of p16 (p<0.0001) and p57 (p=0.012) in insulinomas and the unchanged expression of Cyclin D3 (p=0.77) and p27 (p=0.55) were confirmed using qRT-PCR. The expression of certain cell-cycle factors in beta-cells derived from insulinomas and healthy adults differs markedly. Targeting such differentially regulated cell-cycle proteins may evolve as a future strategy to enhance beta-cell regeneration. Copyright © 2016 Elsevier Inc. All rights reserved.

  10. Coupling between the Circadian Clock and Cell Cycle Oscillators: Implication for Healthy Cells and Malignant Growth.

    PubMed

    Feillet, Celine; van der Horst, Gijsbertus T J; Levi, Francis; Rand, David A; Delaunay, Franck

    2015-01-01

    Uncontrolled cell proliferation is one of the key features leading to cancer. Seminal works in chronobiology have revealed that disruption of the circadian timing system in mice, either by surgical, genetic, or environmental manipulation, increased tumor development. In humans, shift work is a risk factor for cancer. Based on these observations, the link between the circadian clock and cell cycle has become intuitive. But despite identification of molecular connections between the two processes, the influence of the clock on the dynamics of the cell cycle has never been formally observed. Recently, two studies combining single live cell imaging with computational methods have shed light on robust coupling between clock and cell cycle oscillators. We recapitulate here these novel findings and integrate them with earlier results in both healthy and cancerous cells. Moreover, we propose that the cell cycle may be synchronized or slowed down through coupling with the circadian clock, which results in reduced tumor growth. More than ever, systems biology has become instrumental to understand the dynamic interaction between the circadian clock and cell cycle, which is critical in cellular coordination and for diseases such as cancer.

  11. Oscillatory Dynamics of Cell Cycle Proteins in Single Yeast Cells Analyzed by Imaging Cytometry

    PubMed Central

    Ball, David A.; Marchand, Julie; Poulet, Magaly; Baumann, William T.; Chen, Katherine C.; Tyson, John J.; Peccoud, Jean

    2011-01-01

    Progression through the cell division cycle is orchestrated by a complex network of interacting genes and proteins. Some of these proteins are known to fluctuate periodically during the cell cycle, but a systematic study of the fluctuations of a broad sample of cell-cycle proteins has not been made until now. Using time-lapse fluorescence microscopy, we profiled 16 strains of budding yeast, each containing GFP fused to a single gene involved in cell cycle regulation. The dynamics of protein abundance and localization were characterized by extracting the amplitude, period, and other indicators from a series of images. Oscillations of protein abundance could clearly be identified for Cdc15, Clb2, Cln1, Cln2, Mcm1, Net1, Sic1, and Whi5. The period of oscillation of the fluorescently tagged proteins is generally in good agreement with the inter-bud time. The very strong oscillations of Net1 and Mcm1 expression are remarkable since little is known about the temporal expression of these genes. By collecting data from large samples of single cells, we quantified some aspects of cell-to-cell variability due presumably to intrinsic and extrinsic noise affecting the cell cycle. PMID:22046265

  12. Effects of cell cycle on the uptake of water soluble quantum dots by cells

    NASA Astrophysics Data System (ADS)

    Zheng, Shen; Chen, Ji-Yao; Wang, Jun-Yong; Zhou, Lu-Wei; Peng, Qian

    2011-12-01

    Quantum dots (QDs) with excellent optical properties have become powerful candidates for cell imaging. Although numerous reports have studied the uptake of QDs by cells, little information exists on the effects of cell cycle on the cellular QD uptake. In this report, the effects of cell cycle on the uptake of water soluble thiol-capped CdTe QDs by the human cervical carcinoma Hela cell line, human hepatocellular carcinoma QGY7701 cell line, and human embryonic kidney 293T cell line were studied by means of laser scanning confocal microscopy and flow cytometry. All three cell lines show to take up CdTe QDs via endocytosis. After arresting cells at specific phases with pharmacological agents, the cells in G2/M phase take up the most CdTe QDs, probably due to an increased membrane expansion during mitosis; whereas the cells in G1 phase do the least. A mathematical physics model was built to calculate the relative uptake rates of CdTe QDs by cells in different phases of the cell cycle, with the result as the uptake rate in G2/M phase is 2-4 times higher than that in G1 phase for these three cell lines. The results obtained from this study may provide the information useful for intracellular delivery of QDs.

  13. Selection of mammalian cells based on their cell-cycle phase using dielectrophoresis

    PubMed Central

    Kim, Unyoung; Shu, Chih-Wen; Dane, Karen Y.; Daugherty, Patrick S.; Wang, Jean Y. J.; Soh, H. T.

    2007-01-01

    An effective, noninvasive means of selecting cells based on their phase within the cell cycle is an important capability for biological research. Current methods of producing synchronous cell populations, however, tend to disrupt the natural physiology of the cell or suffer from low synchronization yields. In this work, we report a microfluidic device that utilizes the dielectrophoresis phenomenon to synchronize cells by exploiting the relationship between the cell's volume and its phase in the cell cycle. The dielectrophoresis activated cell synchronizer (DACSync) device accepts an asynchronous mixture of cells at the inlet, fractionates the cell populations according to the cell-cycle phase (G1/S and G2/M), and elutes them through different outlets. The device is gentle and efficient; it utilizes electric fields that are 1–2 orders of magnitude below those used in electroporation and enriches asynchronous tumor cells in the G1 phase to 96% in one round of sorting, in a continuous flow manner at a throughput of 2 × 105 cells per hour per microchannel. This work illustrates the feasibility of using laminar flow and electrokinetic forces for the efficient, noninvasive separation of living cells. PMID:18093921

  14. Impairment of cell cycle progression by sterigmatocystin in human pulmonary cells in vitro.

    PubMed

    Huang, Shujuan; Wang, Juan; Xing, Lingxiao; Shen, Haitao; Yan, Xia; Wang, Junling; Zhang, Xianghong

    2014-04-01

    Sterigmatocystin (ST) is a carcinogenic mycotoxin that is commonly found in human food, animal feed and in the indoor environment. Although the correlation between ST exposure and lung cancer has been widely reported in many studies, the cytotoxicity of ST on human pulmonary cells is not yet fully understood. In the current study, we found that ST could induce DNA double-strand breaks in a human immortalized bronchial epithelial cell line (BEAS-2B cells) and a human lung cancer cell line (A549 cells). In addition, the effects of ST on cell cycle arrest were complex and dependent on the tested ST concentration and cell type. Low concentrations of ST arrested cells in the G2/M phase in BEAS-2B cells and in the S phase in A549 cells, while at high concentration both cells lines were arrested in S and G2/M phases. Furthermore, we observed that the modulation of cyclins and CDK expression showed concomitant changes with cell cycle arrest upon ST exposure in BEAS-2B and A549 cells. In conclusion, ST induced DNA damage and affected key proteins involved in cell cycle regulation to trigger genomic instability, which may be a potential mechanism underlying the developmental basis of lung carcinogenesis.

  15. Chromosome replication status and DNA content at any cell age in a bacterial cell cycle.

    PubMed

    Jiménez-Sánchez, Alfonso

    2015-09-07

    An algorithm is presented to determine the chromosome replication status, the rate of DNA synthesis per fork, and the amount of DNA in chromosome equivalents (G) per chromosome, per cell and per age throughout a bacterial cell cycle. This algorithm is the only attempt to study replication and the G value at any cell age since the general model of the bacterial cell cycle by Cooper and Helmstetter (1968, J. Mol. Biol. 31, 619-644). To help using it, two implementations are provided. Copyright © 2015 Elsevier Ltd. All rights reserved.

  16. Cell cycle regulatory E3 ubiquitin ligases as anticancer targets.

    PubMed

    Pray, Todd R; Parlati, Francesco; Huang, Jianing; Wong, Brian R; Payan, Donald G; Bennett, Mark K; Issakani, Sarkiz Daniel; Molineaux, Susan; Demo, Susan D

    2002-12-01

    Disregulation of the cell cycle and proliferation play key roles in cellular transformation and tumorigenesis. Such processes are intimately tied to the concentration, localization and activity of enzymes, adapters, receptors, and structural proteins in cells. Ubiquitination of these cellular regulatory proteins, governed by specific enzymes in the ubiquitin (Ub) conjugation cascade, has profound effects on their various functions, most commonly through proteasome targeting and degradation. This review will focus on a variety of E3 Ub ligases as potential oncology drug targets, with particular emphasis on the role of these molecules in the regulation of stability, localization, and activity of key proteins such as tumor suppressors and oncoproteins. E3 ubiquitin ligases that have established roles in cell cycle and apoptosis, such as the anaphase-promoting complex (APC), the Skp-1-Cul1-F-box class, and the murine double minute 2 (MDM2) protein, in addition to more recently discovered E3 ubiquitin ligases which may be similarly important in tumorigenesis, (e.g. Smurf family, CHFR, and Efp), will be discussed. We will present evidence to support E3 ligases as good biological targets in the development of anticancer therapeutics and address challenges in drug discovery for these targets.

  17. Effects of heavy ions on cycling stem cells

    NASA Astrophysics Data System (ADS)

    Hagan, Michael P.; Holahan, E. Vincent; Ainsworth, E. John

    Murine marrow stem cells assayed with the spleen colony assay have been shown to be largely in a noncycling state, Go. In the unirradiated animal where these spleen-colony forming units (CFUs) transit normally between a non-proliferative state and active proliferation, exposure to a sufficient dose of ionizing radiation increases the frequency (probability) of this transition. For low-LET irradiation, marrow stem cells are not induced into cycle until a threshold dose is achieved. This dose appears to be in the range 50 to 100 cGy, inducing proliferation in an all-or-nothing manner. For irradiation with heavy charged-particles, however, the threshold dose is dependent on mass and energy. Irradiation with particles of sufficient mass and energy stimulates active proliferation even at the smallest doses tested, 5 cGy. Further, this response does not appear to result from an all-or-nothing effect. Rather, individual animals with intermediate levels of stem cell cycling have been observed. These data support the notion that locally controlled hemopoiesis can be affected by local deposition of radiation damage.

  18. Distinct Effects of Inorganic Phosphate on Cell Cycle and Apoptosis in Human Vascular Smooth Muscle Cells.

    PubMed

    Rahabi-Layachi, Haifa; Ourouda, Roger; Boullier, Agnes; Massy, Ziad A; Amant, Carole

    2015-02-01

    Inorganic phosphate (Pi) is an essential nutrient to all living organisms. Nevertheless, hyperphosphatemia is now recognized as a risk factor for cardiovascular events and mortality in chronic kidney disease (CKD) patients. To our knowledge, the mechanisms by which elevated Pi alters smooth muscle cell proliferation have been poorly addressed. Therefore, in this study, we investigated the effects of Pi on cell cycle regulation and apoptosis in human aortic smooth muscle cells (HAoSMC). HAoSMC were treated with physiologic (1 mM) or high (2 and 3 mM) Pi concentrations. We showed that Pi not only decreased significantly cell viability (P < 0.001) but also induced apoptosis of HAoSMC. Moreover, Pi treatment blocked G1/S cell cycle progression by increasing cell number in G0/G1 phase up to 82.4 ± 3.4% for 3 mM vs 76.2 ± 3.1% for control (P < 0.01) while decreasing cell number in S phase. Accordingly, this was associated with a decrease protein expression of cyclin E and its associated CDK (CDK2), and phosphorylated retinoblastoma protein. Moreover, we observed an increase of protein expression of cell cycle inhibitors p15, p21, and p27. Interestingly, we also found that induction of cell cycle arrest was partially dependent on phosphate uptake. Our results demonstrated that Pi reduced HAoSMC proliferation by inducing apoptosis and cell cycle arrest. Indeed, we showed for the first time that Pi affected HAoSMC cell cycle by blocking G1/S progression. These findings would be useful for a better understanding of molecular mechanisms involved in vascular complications observed in CKD patients. © 2014 Wiley Periodicals, Inc.

  19. Chemosensitization of cancer cells via gold nanoparticle-induced cell cycle regulation.

    PubMed

    Mackey, Megan A; El-Sayed, Mostafa A

    2014-01-01

    We have previously shown that plasmonic nanoparticles conjugated with nuclear-targeting and cytoplasm-targeting peptides (NLS and RGD, respectively) are capable of altering the cell cycle of human oral squamous carcinoma cells (HSC-3). In the present work, we show that this regulation of the cell cycle can be exploited to enhance the efficacy of a common chemotherapeutic agent, 5-Fluorouracil, by pretreating cells with gold nanoparticles. Utilizing flow cytometry cell cycle analysis, we were able to quantify the 5-Fluorouracil efficacy as an accumulation of cells in the S phase with a depletion of cells in the G2/M phase. Two gold nanoparticle sizes were tested in this work; 30 nm with a surface plasmon resonance at 530 nm and 15 nm with a surface plasmon resonance at 520 nm. The 30 nm nuclear-targeted gold nanoparticles (NLS-AuNPs) showed the greatest 5-Fluorouracil efficacy enhancement when 5-Fluorouracil treatment (500 μm, 48 h) is preceded by a 24-h treatment with nanoparticles. In conclusion, we show that nuclear-targeted 30 nm gold nanoparticles enhance 5-Fluorouracil drug efficacy in HSC-3 cells via regulation of the cell cycle, a chemosensitization technique that could potentially be expanded to different cell lines and different chemotherapies. © 2013 The American Society of Photobiology.

  20. Chemosensitization of Cancer Cells via Gold Nanoparticle-Induced Cell Cycle Regulation

    PubMed Central

    Mackey, Megan A.; El-Sayed, Mostafa A.

    2015-01-01

    We have previously shown that plasmonic nanoparticles conjugated with nuclear-targeting and cytoplasm-targeting peptides (NLS and RGD, respectively) are capable of altering the cell cycle of human oral squamous carcinoma cells (HSC-3). In the present work, we show that this regulation of the cell cycle can be exploited to enhance the efficacy of a common chemotherapeutic agent, 5-Fluorouracil, by pre-treating cells with gold nanoparticles. Utilizing flow cytometry cell cycle analysis, we were able to quantify the 5-Fluorouracil efficacy as an accumulation of cells in the S phase with a depletion of cells in the G2/M phase. Two gold nanoparticle sizes were tested in this work; 30 nm with a surface plasmon resonance at 530 nm and 15 nm with a surface plasmon resonance at 520 nm. The 30 nm nuclear-targeted gold nanoparticles (NLS-AuNPs) showed the greatest 5-Fluorouracil efficacy enhancement when 5-Fluorouracil treatment (500 μM, 48 h) is preceded by a 24 h treatment with nanoparticles. In conclusion, we show that nuclear-targeted 30 nm gold nanoparticles enhance 5-Fluorouracil drug efficacy in HSC-3 cells via regulation of the cell cycle, a chemosensitization technique that could potentially be expanded to different cell lines and different chemotherapies. PMID:24329577

  1. Dihydromyricetin induces cell cycle arrest and apoptosis in melanoma SK-MEL-28 cells.

    PubMed

    Zeng, Guofang; Liu, Jie; Chen, Hege; Liu, Bin; Zhang, Qingyu; Li, Mingyi; Zhu, Runzhi

    2014-06-01

    Dihydromyricetin (DHM) exhibits multiple pharmacological activities; however, the role of DHM in anti-melanoma activities and the underlying molecular mechanisms are unclear. The aim of the present study was to evaluate the effects of DHM on cell proliferation, cell cycle distribution and apoptosis in the human melanoma SK-MEL-28 cell line, and to explore the related mechanisms. The effect of DHM on cell proliferation was investigated by MTT assay, and cell cycle distribution was determined by flow cytometry. TUNEL assay was used to evaluate DHM-mediated apoptosis, and western blotting was applied to examine expression levels of p53, p21, Cdc25A, Cdc2, P-Cdc2, Bax, IKK-α, NF-κB p65, p38 and P-p38 proteins. The results revealed that DHM suppressed cell proliferation of SK-MEL-28 cells in a concentration- and time-dependent manner, and caused cell cycle arrest at the G1/S phase. DHM increased the production of p53 and p21 proteins and downregulated the production of Cdc25A, Cdc2 and P-Cdc2 proteins, which induced cell cycle arrest. Additionally, DHM significantly induced the apoptosis of SK-MEL-28 cells, and enhanced the expression levels of Bax proteins and decreased the protein levels of IKK-α, NF-κB (p65) and P-p38. The results suggest that DHM may be a novel and effective candidate agent to inhibit the growth of melanoma.

  2. Smoc2 potentiates proliferation of hepatocellular carcinoma cells via promotion of cell cycle progression

    PubMed Central

    Su, Jing-Ran; Kuai, Jing-Hua; Li, Yan-Qing

    2016-01-01

    AIM To determine the influence of Smoc2 on hepatocellular carcinoma (HCC) cell proliferation and to find a possible new therapeutic target for preventing HCC progression. METHODS We detected expression of Smoc2 in HCC tissues and corresponding non-tumor liver (CNL) tissues using PCR, western blot, and immunohistochemistry methods. Subsequently, we down-regulated and up-regulated Smoc2 expression using siRNA and lentivirus transfection assay, respectively. Then, we identified the effect of Smoc2 on cell proliferation and cell cycle using CCK-8 and flow cytometry, respectively. The common cell growth signaling influenced by Smoc2 was detected by western blot assay. RESULTS The expression of Smoc2 was significantly higher in HCC tissues compared with CNL tissues. Overexpression of Smoc2 promoted HCC cell proliferation and cell cycle progression. Down-regulation of Smoc2 led to inhibition of cell proliferation and cell cycle progression. Smoc2 had positive effect on ERK and AKT signaling. CONCLUSION Smoc2 promotes the proliferation of HCC cells through accelerating cell cycle progression and might act as an anti-cancer therapeutic target in the future. PMID:28018113

  3. Progenitor/Stem Cell Fate Determination: Interactive Dynamics of Cell Cycle and Microvesicles

    PubMed Central

    Lee, David; Puente, Napoleon; Faradyan, Sam; Sears, Edmund H.; Amaral, Ashley; Goldberg, Laura; Dooner, Mark S.; Pereira, Mandy; Quesenberry, Peter J.

    2012-01-01

    We have shown that hematopoietic stem/progenitor cell phenotype and differentiative potential change throughout cell cycle. Lung-derived microvesicles (LDMVs) also change marrow cell phenotype by inducing them to express pulmonary epithelial cell-specific mRNA and protein. These changes are accentuated when microvesicles isolated from injured lung. We wish to determine if microvesicle-treated stem/progenitor cell phenotype is linked to cell cycle and to the injury status of the lung providing microvesicles. Lineage depleted, Sca-1+ (Lin-/Sca-1+) marrow isolated from mice were cultured with interleukin 3 (IL-3), IL-6, IL-11, and stem cell factor (cytokine-cultured cells), removed at hours zero (cell cycle phase G0/G1), 24 (late G1/early S), and 48 (late S/early G2/M), and cocultured with lung tissue, lung conditioned media (LCM), or LDMV from irradiated or nonirradiated mice. Alternatively, Lin-/Sca-1+ cells not exposed to exogenous cytokines were separated into G0/G1 and S/G2/M cell cycle phase populations by fluorescence-activated cell sorting (FACS) and used in coculture. Separately, LDMV from irradiated and nonirradiated mice were analyzed for the presence of adhesion proteins. Peak pulmonary epithelial cell-specific mRNA expression was seen in G0/G1 cytokine-cultured cells cocultured with irradiated lung and in late G1/early S cells cocultured with nonirradiated lung. The same pattern was seen in cytokine-cultured Lin-/Sca-1 cells cocultured with LCM and LDMV and when FACS-separated Lin-/Sca-1 cells unexposed to exogenous cytokines were used in coculture. Cells and LDMV expressed adhesion proteins whose levels differed based on cycle status (cells) or radiation injury (LDMV), suggesting a mechanism for microvesicle entry. These data demonstrate that microvesicle modification of progenitor/stem cells is influenced by cell cycle and the treatment of the originator lung tissue. PMID:22214238

  4. Flagellar duplication and migration during the Trichomonas vaginalis cell cycle.

    PubMed

    Zuo, Y; Riley, D E; Krieger, J N

    1999-04-01

    Trichomonas vaginalis is a flagellated protozoan, a representative of 1 of the earliest known eukaryotic lineages. Trichomonas vaginalis lacks centrioles but possesses basal bodies. We report here the cell cycle-dependent flagellar dynamics of T. vaginalis. By immunofluorescence, we found that T. vaginalis flagella duplicated during S-phase, segregated toward the nuclear poles, and then emanated from the spindle poles at mitosis. This behavior strongly parallels that of centrioles and other spindle pole-associated structures variously termed centrosomes, spindle pole bodies, or microtubule organizing centers. These observations support the hypothesis that flagellar forces may have provided motile forces for spindle pole alignment in an ancestral eukaryote.

  5. Forty-five years of cell-cycle genetics

    PubMed Central

    Reid, Brian J.; Culotti, Joseph G.; Nash, Robert S.; Pringle, John R.

    2015-01-01

    In the early 1970s, studies in Leland Hartwell’s laboratory at the University of Washington launched the genetic analysis of the eukaryotic cell cycle and set the path that has led to our modern understanding of this centrally important process. This 45th-anniversary Retrospective reviews the steps by which the project took shape, the atmosphere in which this happened, and the possible morals for modern times. It also provides an up-to-date look at the 35 original CDC genes and their human homologues. PMID:26628751

  6. Prp19 Arrests Cell Cycle via Cdc5L in Hepatocellular Carcinoma Cells

    PubMed Central

    Huang, Renzheng; Xue, Ruyi; Qu, Di; Yin, Jie; Shen, Xi-Zhong

    2017-01-01

    Pre-mRNA processing factor 19 (Prp19) is involved in many cellular events including pre-mRNA processing and DNA damage response. Recently, it has been identified as a candidate oncogene in hepatocellular carcinoma (HCC). However, the role of Prp19 in tumor biology is still elusive. Here, we reported that Prp19 arrested cell cycle in HCC cells via regulating G2/M transition. Mechanistic insights revealed that silencing Prp19 inhibited the expression of cell division cycle 5-like (Cdc5L) via repressing the translation of Cdc5L mRNA and facilitating lysosome-mediated degradation of Cdc5L in HCC cells. Furthermore, we found that silencing Prp19 induced cell cycle arrest could be partially resumed by overexpressing Cdc5L. This work implied that Prp19 participated in mitotic progression and thus could be a promising therapeutic target of HCC. PMID:28387715

  7. Pathobiology of Pneumocystis pneumonia: life cycle, cell wall and cell signal transduction.

    PubMed

    Skalski, Joseph H; Kottom, Theodore J; Limper, Andrew H

    2015-09-01

    Pneumocystis is a genus of ascomycetous fungi that are highly morbid pathogens in immunosuppressed humans and other mammals. Pneumocystis cannot easily be propagated in culture, which has greatly hindered understanding of its pathobiology. The Pneumocystis life cycle is intimately associated with its mammalian host lung environment, and life cycle progression is dependent on complex interactions with host alveolar epithelial cells and the extracellular matrix. The Pneumocystis cell wall is a varied and dynamic structure containing a dominant major surface glycoprotein, β-glucans and chitins that are important for evasion of host defenses and stimulation of the host immune system. Understanding of Pneumocystis cell signaling pathways is incomplete, but much has been deduced by comparison of the Pneumocystis genome with homologous genes and proteins in related fungi. In this mini-review, the pathobiology of Pneumocystis is reviewed, with particular focus on the life cycle, cell wall components and cell signal transduction.

  8. Salidroside induces cell-cycle arrest and apoptosis in human breast cancer cells

    SciTech Connect

    Hu, Xiaolan; Zhang, Xianqi; Qiu, Shuifeng; Yu, Daihua; Lin, Shuxin

    2010-07-16

    Research highlights: {yields} Salidroside inhibits the growth of human breast cancer cells. {yields} Salidroside induces cell-cycle arrest of human breast cancer cells. {yields} Salidroside induces apoptosis of human breast cancer cell lines. -- Abstract: Recently, salidroside (p-hydroxyphenethyl-{beta}-D-glucoside) has been identified as one of the most potent compounds isolated from plants of the Rhodiola genus used widely in traditional Chinese medicine, but pharmacokinetic data on the compound are unavailable. We were the first to report the cytotoxic effects of salidroside on cancer cell lines derived from different tissues, and we found that human breast cancer MDA-MB-231 cells (estrogen receptor negative) were sensitive to the inhibitory action of low-concentration salidroside. To further investigate the cytotoxic effects of salidroside on breast cancer cells and reveal possible ER-related differences in response to salidroside, we used MDA-MB-231 cells and MCF-7 cells (estrogen receptor-positive) as models to study possible molecular mechanisms; we evaluated the effects of salidroside on cell growth characteristics, such as proliferation, cell cycle duration, and apoptosis, and on the expression of apoptosis-related molecules. Our results demonstrated for the first time that salidroside induces cell-cycle arrest and apoptosis in human breast cancer cells and may be a promising candidate for breast cancer treatment.

  9. Cell cycle synchronization of animal cells and nuclei by centrifugal elutriation.

    PubMed

    Banfalvi, Gaspar

    2008-01-01

    Synchronization of cells and nuclei is a powerful technique for the exact study of regulatory mechanisms and for understanding cell cycle events. Counterflow centrifugal elutriation is a biophysical cell separation technique in which cell size and sedimentation density differences of living cells are exploited to isolate subpopulations in various stages of cell cycle. Here, a protocol is described for the separation of phase-enriched subpopulations from exponentially growing Chinese hamster ovary cells at high-resolution power of elutriation. The efficiency of elutriation is confirmed by measuring the DNA content fluorimetrically and by flow cytometry. The resolution power of elutriation is demonstrated by the ability to fractionate nuclei of murine pre-B cells. The installation and elutriation by collecting 16-30 synchronized fractions, including particle size analysis, can be achieved in 4-5 h.

  10. Naphthoquinones from Onosma paniculata induce cell-cycle arrest and apoptosis in melanoma Cells.

    PubMed

    Kretschmer, Nadine; Rinner, Beate; Deutsch, Alexander J A; Lohberger, Birgit; Knausz, Heike; Kunert, Olaf; Blunder, Martina; Boechzelt, Herbert; Schaider, Helmut; Bauer, Rudolf

    2012-05-25

    Activity-guided fractionation of a petroleum ether-soluble extract of the roots of Onosma paniculata, which has been shown to affect the cell cycle and to induce apoptosis in melanoma cells, led to the isolation of several shikonin derivatives, namely, β-hydroxyisovalerylshikonin (1), acetylshikonin (2), dimethylacrylshikonin (3), and a mixture of α-methylbutyrylshikonin and isovalerylshikonin (4+5). All compounds exhibited strong cytotoxicity against eight cancer cell lines and MRC-5 lung fibroblasts, with 3 found to possess the most potent cytotoxicity toward four melanoma cell lines (SBcl2, WM35, WM9, and WM164). Furthermore, 3 and the mixture of 4+5 were found to interfere with cell-cycle progression in these cell lines and led to an increasing number of cells in the subG1 region as well as to caspase-3/7 activation, indicating apoptotic cell death.

  11. Distinct modes of centromere protein dynamics during cell cycle progression in Drosophila S2R+ cells.

    PubMed

    Lidsky, Peter V; Sprenger, Frank; Lehner, Christian F

    2013-10-15

    Centromeres are specified epigenetically in animal cells. Therefore, faithful chromosome inheritance requires accurate maintenance of epigenetic centromere marks during progression through the cell cycle. Clarification of the mechanisms that control centromere protein behavior during the cell cycle should profit from the relatively simple protein composition of Drosophila centromeres. Thus we have analyzed the dynamics of the three key players Cid/Cenp-A, Cenp-C and Cal1 in S2R+ cells using quantitative microscopy and fluorescence recovery after photobleaching, in combination with novel fluorescent cell cycle markers. As revealed by the observed protein abundances and mobilities, centromeres proceed through at least five distinct states during the cell cycle, distinguished in part by unexpected Cid behavior. In addition to the predominant Cid loading onto centromeres during G1, a considerable but transient increase was detected during early mitosis. A low level of Cid loading was detected in late S and G2, starting at the reported time of centromere DNA replication. Our results reveal the complexities of Drosophila centromere protein dynamics and its intricate coordination with cell cycle progression.

  12. Ethanol Metabolism Activates Cell Cycle Checkpoint Kinase, Chk2

    PubMed Central

    Clemens, Dahn L.; Mahan Schneider, Katrina J.; Nuss, Robert F.

    2011-01-01

    Chronic ethanol abuse results in hepatocyte injury and impairs hepatocyte replication. We have previously shown that ethanol metabolism results in cell cycle arrest at the G2/M transition, which is partially mediated by inhibitory phosphorylation of the cyclin-dependent kinase, Cdc2. To further delineate the mechanisms by which ethanol metabolism mediates this G2/M arrest, we investigated the involvement of upstream regulators of Cdc2 activity. Cdc2 is activated by the phosphatase Cdc25C. The activity of Cdc25C can, in turn, be regulated by the checkpoint kinase, Chk2, which is regulated by the kinase ataxia telangiectasia mutated (ATM). To investigate the involvement of these regulators of Cdc2 activity, VA-13 cells, which are Hep G2 cells modified to efficiently express alcohol dehydrogenase, were cultured in the presence or absence of 25 mM ethanol. Immunoblots were performed to determine the effects of ethanol metabolism on the activation of Cdc25C, Chk2, and ATM. Ethanol metabolism increased the active forms of ATM, and Chk2, as well as the phosphorylated form of Cdc25C. Additionally, inhibition of ATM resulted in approximately 50% of the cells being rescued from the G2/M cell cycle arrest, and ameliorated the inhibitory phosphorylation of Cdc2. Our findings demonstrate that ethanol metabolism activates ATM. ATM can activate the checkpoint kinase Chk2, resulting in phosphorylation of Cdc25C, and ultimately in the accumulation of inactive Cdc2. This may, in part, explain the ethanol metabolism-mediated impairment in hepatocyte replication, which may be important in the initiation and progression of alcoholic liver injury. PMID:21924579

  13. Magnolol causes alterations in the cell cycle in androgen insensitive human prostate cancer cells in vitro by affecting expression of key cell cycle regulatory proteins.

    PubMed

    McKeown, Brendan T; McDougall, Luke; Catalli, Adriana; Hurta, Robert A R

    2014-01-01

    Prostate cancer, one of the most common cancers in the Western world, affects many men worldwide. This study investigated the effects of magnolol, a compound found in the roots and bark of the magnolia tree Magnolia officinalis, on the behavior of 2 androgen insensitive human prostate cancer cell lines, DU145 and PC3, in vitro. Magnolol, in a 24-h exposure at 40 and 80 μM, was found to be cytotoxic to cells. Magnolol also affected cell cycle progression of DU145 and PC3 cells, resulting in alterations to the cell cycle and subsequently decreasing the proportion of cells entering the G2/M-phase of the cell cycle. Magnolol inhibited the expression of cell cycle regulatory proteins including cyclins A, B1, D1, and E, as well as CDK2 and CDK4. Protein expression levels of pRBp107 decreased and pRBp130 protein expression levels increased in response to magnolol exposure, whereas p16(INK4a), p21, and p27 protein expression levels were apparently unchanged post 24-h exposure. Magnolol exposure at 6 h did increase p27 protein expression levels. This study has demonstrated that magnolol can alter the behavior of androgen insensitive human prostate cancer cells in vitro and suggests that magnolol may have potential as a novel anti-prostate cancer agent.

  14. Berberine induces cell cycle arrest and apoptosis in human gastric carcinoma SNU-5 cell line

    PubMed Central

    Lin, Jing-Pin; Yang, Jai-Sing; Lee, Jau-Hong; Hsieh, Wen-Tsong; Chung, Jing-Gung

    2006-01-01

    AIM: To investigate the relationship between the inhibited growth (cytotoxic activity) of berberine and apoptotic pathway with its molecular mechanism of action. METHODS: The in vitro cytotoxic techniques were complemented by cell cycle analysis and determination of sub-G1 for apoptosis in human gastric carcinoma SNU-5 cells. Percentage of viable cells, cell cycle, and sub-G1 group (apoptosis) were examined and determined by the flow cytometric methods. The associated proteins for cell cycle arrest and apoptosis were examined by Western blotting. RESULTS: For SNU-5 cell line, the IC (50) was found to be 48 μmol/L of berberine. In SNU-5 cells treated with 25-200 μmol/L berberine, G2/M cell cycle arrest was observed which was associated with a marked increment of the expression of p53, Wee1 and CDk1 proteins and decreased cyclin B. A concentration-dependent decrease of cells in G0/G1 phase and an increase in G2/M phase were detected. In addition, apoptosis detected as sub-G0 cell population in cell cycle measurement was proved in 25-200 μmol/L berberine-treated cells by monitoring the apoptotic pathway. Apoptosis was identified by sub-G0 cell population, and upregulation of Bax, downregulation of Bcl-2, release of Ca2+, decreased the mitochondrial membrane potential and then led to the release of mitochondrial cytochrome C into the cytoplasm and caused the activation of caspase-3, and finally led to the occurrence of apoptosis. CONCLUSION: Berberine induces p53 expression and leads to the decrease of the mitochondrial membrane potential, Cytochrome C release and activation of caspase-3 for the induction of apoptosis. PMID:16440412

  15. 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.

  16. Global control of cell growth in fission yeast and its coordination with the cell cycle.

    PubMed

    Navarro, Francisco J; Weston, Louise; Nurse, Paul

    2012-12-01

    Cell growth is a fundamental process for every cell but its pleiotropic complexity makes it difficult to comprehend. Global aspects of cellular growth, like the overall determinants of growth rate are not well understood. Here we examine the cell growth pattern of the fission yeast Schizosaccharomyces pombe during the mitotic and meiotic cell cycles. We also explore recent findings illuminating aspects of cell size homeostasis and cell growth regulation, and propose that there are global controls over growth acting at the level of the cell. Copyright © 2012 Elsevier Ltd. All rights reserved.

  17. Induction of G1 cell cycle arrest and apoptosis by berberine in bladder cancer cells.

    PubMed

    Yan, Keqiang; Zhang, Cheng; Feng, Jinbo; Hou, Lifang; Yan, Lei; Zhou, Zunlin; Liu, Zhaoxu; Liu, Cheng; Fan, Yidon; Zheng, Baozhong; Xu, Zhonghua

    2011-07-01

    Bladder cancer is the ninth most common type of cancer, and its surgery is always followed by chemotherapy to prevent recurrence. Berberine is non-toxic to normal cells but has anti-cancer effects in many cancer cell lines. This study was aimed to determine whether berberine inhibits the cell proliferation and induces cell cycle arrest and apoptosis in BIU-87 and T24 bladder cancer cell line. The superficial bladder cancer cell line BIU-87 and invasive T24 bladder cancer cells were treated with different concentrations of berberine. MTT assay was used to determine the effects of berberine on the viability of these cells. The cell cycle arrest was detected through propidium iodide (PI) staining. The induction of apoptosis was determined through Annexin V-conjugated Alexa Fluor 488 (Alexa488) staining. Berberine inhibited the viability of BIU-87 and T24 cells in a dose- and time-dependent manner. It also promoted cell cycle arrest at G0/G1 in a dose-dependent manner and induced apoptosis. We observed that H-Ras and c-fos mRNA and protein expressionswere dose-dependently and time-dependently decreased by berberine treatment. Also, we investigated the cleaved caspase-3 and caspase-9 protein expressions increased in a dose-dependent manner. Berberine inhibits the cell proliferation and induces cell cycle arrest and apoptosis in BIU-87, bladder cancer cell line and T24, invasive bladder cancer cell line. Berberine can inhibit the oncogentic H-Ras and c-fos in T24 cells, and can induce the activation of the caspase-3 and caspase-9 apoptosis. Therefore, berberine has the potential to be a novel chemotherapy drug to treat the bladder cancer by suppressing tumor growth. Copyright © 2011 Elsevier B.V. All rights reserved.

  18. Kinetic cell-cycle analysis of a cultured mammalian cell population.

    PubMed

    Bronk, B V; Dienes, G J; Schindler, R; Gautschi, J R

    1974-08-01

    The parameters of the cell cycle are analyzed in terms of the stochastic theory of cell proliferation for a murine mastocytoma line. The cells were grown in suspension culture under steady-state conditions in a chemostat. Initial estimates of the parameters from synchronous growth indicate that agreement of the data with the model is obtained only if the model is modified to include an initial proliferating fraction of less than 100%, and a cell loss continuing throughout the course of the experiment. The analysis verifies that the modified theory adequately describes the data, and that similar parameters are obtained from both desynchronization and percent labeled mitosis experiments. The average cycle time from 10 desynchronization experiments was 8.24 +/- 0.52 h with a cellular standard deviation of 1.28 +/- 0.18. The combined parameter obtained by dividing the cellular standard deviation by the cycle time is shown to be a useful measure of biological variability well defined over many different experiments. The rate constant for cell loss is about 0.009 which gives an 8% cell loss per cycle. The cell loss is sufficient to account for the apparent deficit in initially proliferating cells. The initial distribution of the synchronous cells is qualitatively examined and is found to be peaked late in G(1) or early in S.

  19. INTEGRATED GASIFICATION COMBINED CYCLE PROJECT 2 MW FUEL CELL DEMONSTRATION

    SciTech Connect

    FuelCell Energy

    2005-05-16

    With about 50% of power generation in the United States derived from coal and projections indicating that coal will continue to be the primary fuel for power generation in the next two decades, the Department of Energy (DOE) Clean Coal Technology Demonstration Program (CCTDP) has been conducted since 1985 to develop innovative, environmentally friendly processes for the world energy market place. The 2 MW Fuel Cell Demonstration was part of the Kentucky Pioneer Energy (KPE) Integrated Gasification Combined Cycle (IGCC) project selected by DOE under Round Five of the Clean Coal Technology Demonstration Program. The participant in the CCTDP V Project was Kentucky Pioneer Energy for the IGCC plant. FuelCell Energy, Inc. (FCE), under subcontract to KPE, was responsible for the design, construction and operation of the 2 MW fuel cell power plant. Duke Fluor Daniel provided engineering design and procurement support for the balance-of-plant skids. Colt Engineering Corporation provided engineering design, fabrication and procurement of the syngas processing skids. Jacobs Applied Technology provided the fabrication of the fuel cell module vessels. Wabash River Energy Ltd (WREL) provided the test site. The 2 MW fuel cell power plant utilizes FuelCell Energy's Direct Fuel Cell (DFC) technology, which is based on the internally reforming carbonate fuel cell. This plant is capable of operating on coal-derived syngas as well as natural gas. Prior testing (1992) of a subscale 20 kW carbonate fuel cell stack at the Louisiana Gasification Technology Inc. (LGTI) site using the Dow/Destec gasification plant indicated that operation on coal derived gas provided normal performance and stable operation. Duke Fluor Daniel and FuelCell Energy developed a commercial plant design for the 2 MW fuel cell. The plant was designed to be modular, factory assembled and truck shippable to the site. Five balance-of-plant skids incorporating fuel processing, anode gas oxidation, heat recovery, water

  20. Methods of Synchronization of Yeast Cells for the Analysis of Cell Cycle Progression.

    PubMed

    Juanes, M Angeles

    2017-01-01

    Cell division is a fascinating and fundamental process that sustains life. By this process, unicellular organisms reproduce and multicellular organisms sustain development, growth, and tissue repair. Division of a mother cell gives rise to two daughter cells according to an ordered set of events within four successive phases called G1 (gap1), S (DNA Synthesis), G2 (gap2), and M (Mitosis) phase. How these different phases are orchestrated to ensure the physical separation of the two daughter cells is a tightly regulated process. Indeed, inappropriate cell division could lead to uncontrolled cell proliferation and ultimately to cancer. Saccharomyces cerevisiae is an excellent model system for unraveling the secrets of cell division. A large community of researchers has chosen budding yeast as a model because of its advantages: rapid growth in simple and economical media, tractable genetics, powerful biochemistry, cell biology, and proteomics approaches. Furthermore, the cell cycle mechanisms, as elucidated in yeast, are conserved in higher eukaryotes. The ability to synchronize and get large numbers of cells in a particular stage of the cell cycle is crucial to properly explore the mechanisms of the cell cycle. An overview of the most common yeast synchronization techniques has been compiled in this chapter.

  1. Cell-cycle analysis of fission yeast cells by flow cytometry.

    PubMed

    Knutsen, Jon Halvor Jonsrud; Rein, Idun Dale; Rothe, Christiane; Stokke, Trond; Grallert, Beáta; Boye, Erik

    2011-02-28

    The cell cycle of the fission yeast, Schizosaccharomyces pombe, does not easily lend itself to analysis by flow cytometry, mainly because cells in G(1) and G(2) phase contain the same amount of DNA. This occurs because fission yeast cells under standard growth conditions do not complete cytokinesis until after G(1) phase. We have devised a flow cytometric method exploiting the fact that cells in G(1) phase contain two nuclei, whereas cells in G(2) are mononuclear. Measurements of the width as well as the total area of the DNA-associated fluorescence signal allows the discrimination between cells in G(1) and in G(2) phase and the cell-cycle progression of fission yeast can be followed in detail by flow cytometry. Furthermore, we show how this method can be used to monitor the timing of cell entry into anaphase. Fission yeast cells tend to form multimers, which represents another problem of flow cytometry-based cell-cycle analysis. Here we present a method employing light-scatter measurements to enable the exclusion of cell doublets, thereby further improving the analysis of fission yeast cells by flow cytometry.

  2. Arecoline suppresses HaCaT cell proliferation through cell cycle regulatory molecules.

    PubMed

    Zhou, Zhong-Su; Li, Ming; Gao, Feng; Peng, Jie-Ying; Xiao, Hai-Bo; Dai, Li-Xia; Lin, Shi-Rong; Zhang, Rui; Jin, Long-Yu

    2013-06-01

    Betel nut chewing is the most common cause of oral submucous fibrosis (OSF). Arecoline is the main component of the betel nut, and is associated with the occurrence and development of OSF through cytotoxicity, genotoxicity and DNA damage. Similar types of stimuli elicit differential responses in different cells. In the present study, we investigated the effects of arecoline on the HaCaT epithelial and Hel fibroblast cell lines. The data showed that arecoline affected HaCaT cell morphology. MTT assay revealed that arecoline suppressed HaCaT cell proliferation. Furthermore, we found that arecoline induced the cell cycle arrest of HaCaT cells. In comparison with the untreated control cells, following treatment with ≥75 µg/ml arecoline an increased percentage of HaCaT cells remained at the G0/G1 phase of the cell cycle, accompanied by a reduced percentage of cells in the S phase. However, arecoline treatment did not significantly alter Hel cell cycle distribution. In the HaCaT epithelial cells, arecoline downregulated expression of the G1/S phase regulatory proteins cyclin D1, CDK4, CDK2, E2F1 as determined by reverse transcription-PCR analysis and western blotting. In summary, arecoline inhibits HaCaT epithelial cell proliferation and survival, in a dose-dependent manner, and cell cycle arrest in the G1/S phase, while this is not obvious in the Hel fibroblast cells. Potentially, our findings may aid in the prevention of arecoline-associated human OSF.

  3. A genetic interaction map of cell cycle regulators

    PubMed Central

    Billmann, Maximilian; Horn, Thomas; Fischer, Bernd; Sandmann, Thomas; Huber, Wolfgang; Boutros, Michael

    2016-01-01

    Cell-based RNA interference (RNAi) is a powerful approach to screen for modulators of many cellular processes. However, resulting candidate gene lists from cell-based assays comprise diverse effectors, both direct and indirect, and further dissecting their functions can be challenging. Here we screened a genome-wide RNAi library for modulators of mitosis and cytokinesis in Drosophila S2 cells. The screen identified many previously known genes as well as modulators that have previously not been connected to cell cycle control. We then characterized ∼300 candidate modifiers further by genetic interaction analysis using double RNAi and a multiparametric, imaging-based assay. We found that analyzing cell cycle–relevant phenotypes increased the sensitivity for associating novel gene function. Genetic interaction maps based on mitotic index and nuclear size grouped candidates into known regulatory complexes of mitosis or cytokinesis, respectively, and predicted previously uncharacterized components of known processes. For example, we confirmed a role for the Drosophila CCR4 mRNA processing complex component l(2)NC136 during the mitotic exit. Our results show that the combination of genome-scale RNAi screening and genetic interaction analysis using process-directed phenotypes provides a powerful two-step approach to assigning components to specific pathways and complexes. PMID:26912791

  4. Stochastic model of yeast cell-cycle network

    NASA Astrophysics Data System (ADS)

    Zhang, Yuping; Qian, Minping; Ouyang, Qi; Deng, Minghua; Li, Fangting; Tang, Chao

    2006-07-01

    Biological functions in living cells are controlled by protein interaction and genetic networks. These molecular networks should be dynamically stable against various fluctuations which are inevitable in the living world. In this paper, we propose and study a stochastic model for the network regulating the cell cycle of the budding yeast. The stochasticity in the model is controlled by a temperature-like parameter β. Our simulation results show that both the biological stationary state and the biological pathway are stable for a wide range of “temperature”. There is, however, a sharp transition-like behavior at βc, below which the dynamics are dominated by noise. We also define a pseudo energy landscape for the system in which the biological pathway can be seen as a deep valley.

  5. Positive-feedback loops in cell cycle progression.

    PubMed

    Pomerening, Joseph R

    2009-11-03

    A positive-feedback loop is a simple motif that is ubiquitous to the modules and networks that comprise cellular signaling systems. Signaling behaviors that are synonymous with positive feedback include amplification and rapid switching, maintenance, and the coherence of outputs. Recent advances have been made towards understanding how positive-feedback loops function, as well as their mechanistic basis in controlling eukaryotic cell cycle progression. Some of these advances will be reviewed here, including: how cyclin controls passage through Start and maintains coherence of G1/S regulon expression in yeast; how Polo-like kinase 1 activation is driven by Bora and Aurora A, and its expression is stimulated by Forkhead Box M1 in mammalian cells; and how some of the various dynamic behaviors of spindle assembly and anaphase onset can be produced.

  6. Cell cycle progression score predicts metastatic progression of clear cell renal cell carcinoma after resection.

    PubMed

    Askeland, Eric J; Chehval, Vincent A; Askeland, Ryan W; Fosso, Placede G; Sangale, Zaina; Xu, Nafei; Rajamani, Saradha; Stone, Steven; Brown, James A

    2015-01-01

    The outcome of surgically resected, apparently localized, clear cell renal carcinoma (ccRCC) is uncertain. To evaluate if cell cycle progression (CCP) gene expression can predict future metastasis. Pathologic T2a-T3b tumors at University of Iowa were reviewed. Patients with known or suspected metastasis, lymph node involvement or who received neoadjuvant or adjuvant radiation, chemotherapy or immunotherapy were excluded. Case and control cohorts were defined as those who did or did not develop metastatic disease within 5 years. Measured levels of 31 cell cycle genes and 15 control genes from the tumor were calculated as a CCP score. Additionally, gene expression data for a separate ccRCC cohort was downloaded from The Cancer Genome Atlas (TCGA). Univariate analysis of 26 cases and 38 controls revealed that the CCP score predicted progression to metastasis (OR 2.65, p = 0.0091). In multivariate logistic regression modeling, CCP expression remained a significant independent predictor for progression (p = 0.026). The CCP score was also significantly associated with distant metastasis in the TCGA renal cancer cohort in both univariate (p = 1.0 × 10-9) and multivariate (p = 5.6 × 10-3) analysis. The CCP score has prognostic value in predicting metastatic progression after resection of organ-confined ccRCC.

  7. The cell cycle: A critical therapeutic target to prevent vascular proliferative disease

    PubMed Central

    Charron, Thierry; Nili, Nafiseh; Strauss, Bradley H

    2006-01-01

    Percutaneous coronary intervention is the preferred revascularization approach for most patients with coronary artery disease. However, this strategy is limited by renarrowing of the vessel by neointimal hyperplasia within the stent lumen (in-stent restenosis). Vascular smooth muscle cell proliferation is a major component in this healing process. This process is mediated by multiple cytokines and growth factors, which share a common pathway in inducing cell proliferation: the cell cycle. The cell cycle is highly regulated by numerous mechanisms ensuring orderly and coordinated cell division. The present review discusses current concepts related to regulation of the cell cycle and new therapeutic options that target aspects of the cell cycle. PMID:16498512

  8. Microarray analysis of cell cycle gene expression in adult human corneal endothelial cells.

    PubMed

    Ha Thi, Binh Minh; Campolmi, Nelly; He, Zhiguo; Pipparelli, Aurélien; Manissolle, Chloé; Thuret, Jean-Yves; Piselli, Simone; Forest, Fabien; Peoc'h, Michel; Garraud, Olivier; Gain, Philippe; Thuret, Gilles

    2014-01-01

    Corneal endothelial cells (ECs) form a monolayer that controls the hydration of the cornea and thus its transparency. Their almost nil proliferative status in humans is responsible, in several frequent diseases, for cell pool attrition that leads to irreversible corneal clouding. To screen for candidate genes involved in cell cycle arrest, we studied human ECs subjected to various environments thought to induce different proliferative profiles compared to ECs in vivo. Donor corneas (a few hours after death), organ-cultured (OC) corneas, in vitro confluent and non-confluent primary cultures, and an immortalized EC line were compared to healthy ECs retrieved in the first minutes of corneal grafts. Transcriptional profiles were compared using a cDNA array of 112 key genes of the cell cycle and analysed using Gene Ontology classification; cluster analysis and gene map presentation of the cell cycle regulation pathway were performed by GenMAPP. Results were validated using qRT-PCR on 11 selected genes. We found several transcripts of proteins implicated in cell cycle arrest and not previously reported in human ECs. Early G1-phase arrest effectors and multiple DNA damage-induced cell cycle arrest-associated transcripts were found in vivo and over-represented in OC and in vitro ECs. Though highly proliferative, immortalized ECs also exhibited overexpression of transcripts implicated in cell cycle arrest. These new effectors likely explain the stress-induced premature senescence that characterizes human adult ECs. They are potential targets for triggering and controlling EC proliferation with a view to increasing the cell pool of stored corneas or facilitating mass EC culture for bioengineered endothelial grafts.

  9. Microarray Analysis of Cell Cycle Gene Expression in Adult Human Corneal Endothelial Cells

    PubMed Central

    Ha Thi, Binh Minh; Campolmi, Nelly; He, Zhiguo; Pipparelli, Aurélien; Manissolle, Chloé; Thuret, Jean-Yves; Piselli, Simone; Forest, Fabien; Peoc'h, Michel; Garraud, Olivier; Gain, Philippe; Thuret, Gilles

    2014-01-01

    Corneal endothelial cells (ECs) form a monolayer that controls the hydration of the cornea and thus its transparency. Their almost nil proliferative status in humans is responsible, in several frequent diseases, for cell pool attrition that leads to irreversible corneal clouding. To screen for candidate genes involved in cell cycle arrest, we studied human ECs subjected to various environments thought to induce different proliferative profiles compared to ECs in vivo. Donor corneas (a few hours after death), organ-cultured (OC) corneas, in vitro confluent and non-confluent primary cultures, and an immortalized EC line were compared to healthy ECs retrieved in the first minutes of corneal grafts. Transcriptional profiles were compared using a cDNA array of 112 key genes of the cell cycle and analysed using Gene Ontology classification; cluster analysis and gene map presentation of the cell cycle regulation pathway were performed by GenMAPP. Results were validated using qRT-PCR on 11 selected genes. We found several transcripts of proteins implicated in cell cycle arrest and not previously reported in human ECs. Early G1-phase arrest effectors and multiple DNA damage-induced cell cycle arrest-associated transcripts were found in vivo and over-represented in OC and in vitro ECs. Though highly proliferative, immortalized ECs also exhibited overexpression of transcripts implicated in cell cycle arrest. These new effectors likely explain the stress-induced premature senescence that characterizes human adult ECs. They are potential targets for triggering and controlling EC proliferation with a view to increasing the cell pool of stored corneas or facilitating mass EC culture for bioengineered endothelial grafts. PMID:24747418

  10. Robust synchronization of coupled circadian and cell cycle oscillators in single mammalian cells.

    PubMed

    Bieler, Jonathan; Cannavo, Rosamaria; Gustafson, Kyle; Gobet, Cedric; Gatfield, David; Naef, Felix

    2014-07-15

    Circadian cycles and cell cycles are two fundamental periodic processes with a period in the range of 1 day. Consequently, coupling between such cycles can lead to synchronization. Here, we estimated the mutual interactions between the two oscillators by time-lapse imaging of single mammalian NIH3T3 fibroblasts during several days. The analysis of thousands of circadian cycles in dividing cells clearly indicated that both oscillators tick in a 1:1 mode-locked state, with cell divisions occurring tightly 5 h before the peak in circadian Rev-Erbα-YFP reporter expression. In principle, such synchrony may be caused by either unidirectional or bidirectional coupling. While gating of cell division by the circadian cycle has been most studied, our data combined with stochastic modeling unambiguously show that the reverse coupling is predominant in NIH3T3 cells. Moreover, temperature, genetic, and pharmacological perturbations showed that the two interacting cellular oscillators adopt a synchronized state that is highly robust over a wide range of parameters. These findings have implications for circadian function in proliferative tissues, including epidermis, immune cells, and cancer.

  11. Robust synchronization of coupled circadian and cell cycle oscillators in single mammalian cells

    PubMed Central

    Bieler, Jonathan; Cannavo, Rosamaria; Gustafson, Kyle; Gobet, Cedric; Gatfield, David; Naef, Felix

    2014-01-01

    Circadian cycles and cell cycles are two fundamental periodic processes with a period in the range of 1 day. Consequently, coupling between such cycles can lead to synchronization. Here, we estimated the mutual interactions between the two oscillators by time-lapse imaging of single mammalian NIH3T3 fibroblasts during several days. The analysis of thousands of circadian cycles in dividing cells clearly indicated that both oscillators tick in a 1:1 mode-locked state, with cell divisions occurring tightly 5 h before the peak in circadian Rev-Erbα-YFP reporter expression. In principle, such synchrony may be caused by either unidirectional or bidirectional coupling. While gating of cell division by the circadian cycle has been most studied, our data combined with stochastic modeling unambiguously show that the reverse coupling is predominant in NIH3T3 cells. Moreover, temperature, genetic, and pharmacological perturbations showed that the two interacting cellular oscillators adopt a synchronized state that is highly robust over a wide range of parameters. These findings have implications for circadian function in proliferative tissues, including epidermis, immune cells, and cancer. PMID:25028488

  12. Control of sleep by a network of cell cycle genes.

    PubMed

    Afonso, Dinis J S; Machado, Daniel R; Koh, Kyunghee

    2015-01-01

    Sleep is essential for health and cognition, but the molecular and neural mechanisms of sleep regulation are not well understood. We recently reported the identification of TARANIS (TARA) as a sleep-promoting factor that acts in a previously unknown arousal center in Drosophila. tara mutants exhibit a dose-dependent reduction in sleep amount of up to ∼60%. TARA and its mammalian homologs, the Trip-Br (Transcriptional Regulators Interacting with PHD zinc fingers and/or Bromodomains) family of proteins, are primarily known as transcriptional coregulators involved in cell cycle progression, and contain a conserved Cyclin-A (CycA) binding homology domain. We found that tara and CycA synergistically promote sleep, and CycA levels are reduced in tara mutants. Additional data demonstrated that Cyclin-dependent kinase 1 (Cdk1) antagonizes tara and CycA to promote wakefulness. Moreover, we identified a subset of CycA expressing neurons in the pars lateralis, a brain region proposed to be analogous to the mammalian hypothalamus, as an arousal center. In this Extra View article, we report further characterization of tara mutants and provide an extended discussion of our findings and future directions within the framework of a working model, in which a network of cell cycle genes, tara, CycA, and Cdk1, interact in an arousal center to regulate sleep.

  13. Control of sleep by a network of cell cycle genes

    PubMed Central

    Afonso, Dinis J. S.; Machado, Daniel R.; Koh, Kyunghee

    2015-01-01

    ABSTRACT Sleep is essential for health and cognition, but the molecular and neural mechanisms of sleep regulation are not well understood. We recently reported the identification of TARANIS (TARA) as a sleep-promoting factor that acts in a previously unknown arousal center in Drosophila. tara mutants exhibit a dose-dependent reduction in sleep amount of up to ∼60%. TARA and its mammalian homologs, the Trip-Br (Transcriptional Regulators Interacting with PHD zinc fingers and/or Bromodomains) family of proteins, are primarily known as transcriptional coregulators involved in cell cycle progression, and contain a conserved Cyclin-A (CycA) binding homology domain. We found that tara and CycA synergistically promote sleep, and CycA levels are reduced in tara mutants. Additional data demonstrated that Cyclin-dependent kinase 1 (Cdk1) antagonizes tara and CycA to promote wakefulness. Moreover, we identified a subset of CycA expressing neurons in the pars lateralis, a brain region proposed to be analogous to the mammalian hypothalamus, as an arousal center. In this Extra View article, we report further characterization of tara mutants and provide an extended discussion of our findings and future directions within the framework of a working model, in which a network of cell cycle genes, tara, CycA, and Cdk1, interact in an arousal center to regulate sleep. PMID:26925838

  14. Host cell kinases and the hepatitis C virus life cycle.

    PubMed

    Colpitts, Che C; Lupberger, Joachim; Doerig, Christian; Baumert, Thomas F

    2015-10-01

    Hepatitis C virus (HCV) infection relies on virus-host interactions with human hepatocytes, a context in which host cell kinases play critical roles in every step of the HCV life cycle. During viral entry, cellular kinases, including EGFR, EphA2 and PKA, regulate the localization of host HCV entry factors and induce receptor complex assembly. Following virion internalization, viral genomes replicate on endoplasmic reticulum-derived membranous webs. The formation of membranous webs depends on interactions between the HCV NS5a protein and PI4KIIIα. The phosphorylation status of NS5a, regulated by PI4KIIIα, CKI and other kinases, also acts as a molecular switch to virion assembly, which takes place on lipid droplets. The formation of lipid droplets is enhanced by HCV activation of IKKα. In view of the multiple crucial steps in the viral life cycle that are mediated by host cell kinases, these enzymes also represent complementary targets for antiviral therapy. This article is part of a Special Issue entitled: Inhibitors of Protein Kinases. Copyright © 2015 Elsevier B.V. All rights reserved.

  15. Dynamics of Cdk1 substrate specificity during the cell cycle.

    PubMed

    Kõivomägi, Mardo; Valk, Ervin; Venta, Rainis; Iofik, Anna; Lepiku, Martin; Morgan, David O; Loog, Mart

    2011-06-10

    Cdk specificity is determined by the intrinsic selectivity of the active site and by substrate docking sites on the cyclin subunit. There is a long-standing debate about the relative importance of these factors in the timing of Cdk1 substrate phosphorylation. We analyzed major budding yeast cyclins (the G1/S-cyclin Cln2, S-cyclin Clb5, G2/M-cyclin Clb3, and M-cyclin Clb2) and found that the activity of Cdk1 toward the consensus motif increased gradually in the sequence Cln2-Clb5-Clb3-Clb2, in parallel with cell cycle progression. Further, we identified a docking element that compensates for the weak intrinsic specificity of Cln2 toward G1-specific targets. In addition, Cln2-Cdk1 showed distinct consensus site specificity, suggesting that cyclins do not merely activate Cdk1 but also modulate its active-site specificity. Finally, we identified several Cln2-, Clb3-, and Clb2-specific Cdk1 targets. We propose that robust timing and ordering of cell cycle events depend on gradual changes in the substrate specificity of Cdk1. Copyright © 2011 Elsevier Inc. All rights reserved.

  16. Dynamics of Cdk1 Substrate Specificity during the Cell Cycle

    PubMed Central

    Kõivomägi, Mardo; Valk, Ervin; Venta, Rainis; Iofik, Anna; Lepiku, Martin; Morgan, David O.; Loog, Mart

    2011-01-01

    Summary Cdk specificity is determined by the intrinsic selectivity of the active site and by substrate docking sites on the cyclin subunit. There is a long-standing debate about the relative importance of these factors in the timing of Cdk1 substrate phosphorylation. We analyzed major budding yeast cyclins (the G1/S-cyclin Cln2, S-cyclin Clb5, G2/M-cyclin Clb3, and M-cyclin Clb2) and found that the activity of Cdk1 toward the consensus motif increased gradually in the sequence Cln2-Clb5-Clb3-Clb2, in parallel with cell cycle progression. Further, we identified a docking element that compensates for the weak intrinsic specificity of Cln2 toward G1-specific targets. In addition, Cln2-Cdk1 showed distinct consensus site specificity, suggesting that cyclins do not merely activate Cdk1 but also modulate its active-site specificity. Finally, we identified several Cln2-, Clb3-, and Clb2-specific Cdk1 targets. We propose that robust timing and ordering of cell cycle events depend on gradual changes in the substrate specificity of Cdk1. PMID:21658602

  17. Cell Cycle Synchronization of HeLa Cells to Assay EGFR Pathway Activation.

    PubMed

    Wee, Ping; Wang, Zhixiang

    2017-01-01

    Progression through the cell cycle causes changes in the cell's signaling pathways that can alter EGFR signal transduction. Here, we describe drug-derived protocols to synchronize HeLa cells in various phases of the cell cycle, including G1 phase, S phase, G2 phase, and mitosis, specifically in the mitotic stages of prometaphase, metaphase, and anaphase/telophase. The synchronization procedures are designed to allow synchronized cells to be treated for EGF and collected for the purpose of Western blotting for EGFR signal transduction components.S phase synchronization is performed by thymidine block, G2 phase with roscovitine, prometaphase with nocodazole, metaphase with MG132, and anaphase/telophase with blebbistatin. G1 phase synchronization is performed by culturing synchronized mitotic cells obtained by mitotic shake-off. We also provide methods to validate the synchronization methods. For validation by Western blotting, we provide the temporal expression of various cell cycle markers that are used to check the quality of the synchronization. For validation of mitotic synchronization by microscopy, we provide a guide that describes the physical properties of each mitotic stage, using their cellular morphology and DNA appearance. For validation by flow cytometry, we describe the use of imaging flow cytometry to distinguish between the phases of the cell cycle, including between each stage of mitosis.

  18. Valproic acid induces apoptosis and cell cycle arrest in poorly differentiated thyroid cancer cells.

    PubMed

    Catalano, Maria G; Fortunati, Nicoletta; Pugliese, Mariateresa; Costantino, Lucia; Poli, Roberta; Bosco, Ornella; Boccuzzi, Giuseppe

    2005-03-01

    Poorly differentiated thyroid carcinoma is an aggressive human cancer that is resistant to conventional therapy. Histone deacetylase inhibitors are