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Sample records for microtubule-and cell cycle

  1. Dynamic microtubules and the texture of plant cell walls.

    PubMed

    Lloyd, Clive

    2011-01-01

    The relationship between microtubules and cell-wall texture has had a fitful history in which progress in one area has not been matched by progress in the other. For example, the idea that wall texture arises entirely from self-assembly, independently of microtubules, originated with electron microscopic analyses of fixed cells that gave no clue to the ability of microtubules to reorganize. Since then, live-cell studies have established the surprising dynamicity of plant microtubules involving collisions, changes in angle, parallelization, and rotation of microtubule tracks. Combined with proof that cellulose synthases do track along shifting microtubules, this offers more realistic models for the dynamic influence of microtubules on wall texture than could have been imagined in the electron microscopic era-the era from which most ideas on wall texture originate. This review revisits the classical literature on wall organization from the vantage point of current knowledge of microtubule dynamics.

  2. Biophysical measurements of cells, microtubules, and DNA with an atomic force microscope

    NASA Astrophysics Data System (ADS)

    Devenica, Luka M.; Contee, Clay; Cabrejo, Raysa; Kurek, Matthew; Deveney, Edward F.; Carter, Ashley R.

    2016-04-01

    Atomic force microscopes (AFMs) are ubiquitous in research laboratories and have recently been priced for use in teaching laboratories. Here, we review several AFM platforms and describe various biophysical experiments that could be done in the teaching laboratory using these instruments. In particular, we focus on experiments that image biological materials (cells, microtubules, and DNA) and quantify biophysical parameters including membrane tension, persistence length, contour length, and the drag force.

  3. Interactions among endoplasmic reticulum, microtubules, and retrograde movements of the cell surface.

    PubMed

    Terasaki, M; Reese, T S

    1994-01-01

    Relationships among the endoplasmic reticulum (ER), microtubules, and bead movements on the cell surface were investigated in the thin peripheral region of A6 cells, a frog kidney cell line. ER tubules were often aligned with microtubules, as shown by double-labeling with DiOC6(3) and anti-tubulin in fixed cells. In living cells stained with DiOC6(3) and observed in time lapse, there were frequent extensions, but few retractions, of ER tubules. In addition, there was a steady retrograde (towards the cell center) movement of all of the ER at approximately 0.3 microns/min. Since microtubules are often aligned with the ER, microtubules must also be moving retrogradely. By simultaneous imaging, it was found that the ER moves retrogradely at the same rate as aminated latex beads on the cell surface. This indicates that the mechanisms for ER and bead movement are closely related. Cytochalasin B stopped bead and ER movement in most of the cells, providing evidence that actin is involved in both retrograde movements. The ER retracted towards the cell center in nocodazole while both ER and microtubules retracted in taxol. Time lapse observations showed that for both drugs, the retraction of the ER is the result of retrograde movement in the absence of new ER extensions. Presumably, ER extensions do not occur in nocodazole because of the absence of microtubules, and do not occur in taxol because taxol-stabilized microtubules move retrogradely and there is no polymerization of new microtubule tracks for ER elongation. PMID:7859292

  4. Microtubules and actin filaments are not critically involved in the biogenesis of epithelial cell surface polarity.

    PubMed

    Salas, P J; Misek, D E; Vega-Salas, D E; Gundersen, D; Cereijido, M; Rodriguez-Boulan, E

    1986-05-01

    We have studied the role of microtubules and actin filaments in the biogenesis of epithelial cell surface polarity, using influenza hemagglutinin and vesicular stomatitis G protein as model apical and basolateral proteins in infected Madin-Darby canine kidney cells. Addition of colchicine or nocodazole to confluent monolayers at concentrations sufficient to completely disassemble microtubules did not affect the asymmetric budding of influenza or vesicular stomatitis virus and only slightly reduced the typical asymmetric surface distribution of their envelope proteins, despite extensive cytoplasmic redistribution of the Golgi apparatus. Alteration of microtubular function by taxol or dissociation of actin filaments by cytochalasin D also failed to have a significant effect. Furthermore, neither colchicine nor cytochalasin D pretreatment blocked the ability of subconfluent Madin-Darby canine kidney cells to sustain polarized budding of influenza virus a few hours after attachment to the substrate. Our results indicate that domain-specific microtubule or actin filament "tracks" are not responsible for the vectorial delivery of apically or basolaterally directed transport vesicles. In conjunction with currently available evidence, they are compatible with a model in which receptors in the cytoplasmic aspect of apical or basolateral regions provide vectoriality to the transport of vesicles carrying plasma membrane proteins to their final surface localization. PMID:2871031

  5. Microtubule and Cell Contact Dependency of ER-bound PTP1B Localization in Growth Cones

    PubMed Central

    Fuentes, Federico

    2009-01-01

    PTP1B is an ER-bound protein tyrosine phosphatase implied in the regulation of cell adhesion. Here we investigated mechanisms involved in the positioning and dynamics of PTP1B in axonal growth cones and evaluated the role of this enzyme in axons. In growth cones, PTP1B consistently localizes in the central domain, and occasionally at the peripheral region and filopodia. Live imaging of GFP-PTP1B reveals dynamic excursions of fingerlike processes within the peripheral region and filopodia. PTP1B and GFP-PTP1B colocalize with ER markers and coalign with microtubules at the peripheral region and redistribute to the base of the growth cone after treatment with nocodazole, a condition that is reversible. Growth cone contact with cellular targets is accompanied by invasion of PTP1B and stable microtubules in the peripheral region aligned with the contact axis. Functional impairment of PTP1B causes retardation of axon elongation, as well as reduction of growth cone filopodia lifetime and Src activity. Our results highlight the role of microtubules and cell contacts in the positioning of ER-bound PTP1B to the peripheral region of growth cones, which may be required for the positive role of PTP1B in axon elongation, filopodia stabilization, and Src activity. PMID:19158394

  6. Complex relationship between TCTP, microtubules and actin microfilaments regulates cell shape in normal and cancer cells

    PubMed Central

    Bazile, Franck; Pascal, Aude; Arnal, Isabelle; Le Clainche, Christophe; Chesnel, Franck; Kubiak, Jacek Z.

    2009-01-01

    Translationally Controlled Tumor-associated Protein (TCTP) is a ubiquitous and highly conserved protein implicated in cancers. Here we demonstrate that interactions of TCTP with microtubules (MTs) are functionally important but indirect, and we reveal novel interaction of TCTP with the actin cytoskeleton. Firstly, immunofluorescence in Xenopus XL2 cells revealed cytoplasmic fibers stained with TCTP but not with tubulin antibodies, as well as MT-free of TCTP. Furthermore, TCTP localized to a subset of actin-rich fibers in migrating cells. Secondly XlTCTP did not affect in vitro assembly/disassembly of MTs, and lacked MT binding affinity both in pull-down assays and in cell-free extracts. Although TCTP also failed to bind to purified F-actin, it associated with microfilaments in cell-free extracts. Thirdly, TCTP concentrated in mitotic spindle did not colocalize with MTs, and was easily dissociated from these structures except at the poles. Finally, RNAi knockdown of TCTP in XL2 and HeLa cells provoked drastic, MT-dependent, shape change. These data show that although TCTP interacts with MTs it does not behave as classic MT Associated Protein (MAP). Our evidence for an association of TCTP with F-actin structures, and for an involvement in cell shape regulation, implicates this protein in integrating cytoskeletal interations both in interphase and mitosis providing a new avenue to fully understand the role of TCTP. PMID:19168579

  7. Drug Discovery Targeting Cell Division Proteins, Microtubules and FtsZ

    PubMed Central

    Kumar, Kunal; Awasthi, Divya; Vineberg, Jacob G.

    2014-01-01

    Eukaryotic cell division or cytokinesis has been a major target for anticancer drug discovery. After the huge success of paclitaxel and docetaxel, microtubule-stabilizing agents (MSAs) appear to have gained a premier status in the discovery of next-generation anticancer agents. However, the drug resistance caused by MDR, point mutations, and overexpression of tubulin subtypes, etc., is a serious issue associated with these agents. Accordingly, the discovery and development of new-generation MSAs that can obviate various drug resistances has a significant meaning. In sharp contrast, prokaryotic cell division has been largely unexploited for the discovery and development of antibacterial drugs. However, recent studies on the mechanism of bacterial cytokinesis revealed that the most abundant and highly conserved cell division protein, FtsZ, would be an excellent new target for the drug discovery of next-generation antibacterial agents that can circumvent drug-resistances to the commonly used drugs for tuberculosis, MRSA and other infections. This review describes an account of our research on these two fronts in drug discovery, targeting eukaryotic as well as prokaryotic cell division. PMID:24680057

  8. Regulation of developmental and environmental signaling by interaction between microtubules and membranes in plant cells.

    PubMed

    Zhang, Qun; Zhang, Wenhua

    2016-02-01

    Cell division and expansion require the ordered arrangement of microtubules, which are subject to spatial and temporal modifications by developmental and environmental factors. Understanding how signals translate to changes in cortical microtubule organization is of fundamental importance. A defining feature of the cortical microtubule array is its association with the plasma membrane; modules of the plasma membrane are thought to play important roles in the mediation of microtubule organization. In this review, we highlight advances in research on the regulation of cortical microtubule organization by membrane-associated and membrane-tethered proteins and lipids in response to phytohormones and stress. The transmembrane kinase receptor Rho-like guanosine triphosphatase, phospholipase D, phosphatidic acid, and phosphoinositides are discussed with a focus on their roles in microtubule organization. PMID:26687389

  9. Molecular mechanisms of Tau binding to microtubules and its role in microtubule dynamics in live cells.

    PubMed

    Breuzard, Gilles; Hubert, Pierre; Nouar, Roqiya; De Bessa, Tiphany; Devred, François; Barbier, Pascale; Sturgis, James N; Peyrot, Vincent

    2013-07-01

    Despite extensive studies, the molecular mechanisms of Tau binding to microtubules (MTs) and its consequences on MT stability still remain unclear. It is especially true in cells where the spatiotemporal distribution of Tau-MT interactions is unknown. Using Förster resonance energy transfer (FRET), we showed that the Tau-MT interaction was distributed along MTs in periodic hotspots of high and low FRET intensities. Fluorescence recovery after photobleaching (FRAP) revealed a two-phase exchange of Tau with MTs as a rapid diffusion followed by a slower binding phase. A real-time FRET assay showed that high FRET occurred simultaneously with rescue and pause transitions at MT ends. To further explore the functional interaction of Tau with MTs, the binding of paclitaxel (PTX), tubulin acetylation induced by trichostatin A (TSA), and the expression of non-acetylatable tubulin were used. With PTX and TSA, FRAP curves best fitted a single phase with a long time constant, whereas with non-acetylatable α-tubulin, curves best fitted a two phase recovery. Upon incubation with PTX and TSA, the number of high and low FRET hotspots decreased by up to 50% and no hotspot was observed during rescue and pause transitions. In the presence of non-acetylatable α-tubulin, a 34% increase in low FRET hotspots occurred, and our real-time FRET assay revealed that low FRET hotspots appeared with MTs recovering growth. In conclusion, we have identified, by FRET and FRAP, a discrete Tau-MT interaction, in which Tau could induce conformational changes of MTs, favoring recovery of MT self-assembly. PMID:23659998

  10. 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.

  11. Bisphenol A disrupts microtubules and induces multipolar spindles in dividing root tip cells of the gymnosperm Abies cephalonica.

    PubMed

    Adamakis, Ioannis-Dimosthenis S; Panteris, Emmanuel; Eleftheriou, Eleftherios P

    2016-04-01

    The effects of bisphenol A (BPA), an endocrine chemical disruptor extensively used in the plastic and epoxy resin industry, on dividing root tip cells of the gymnosperm Abies cephalonica Loudon were investigated by confocal laser scanning microscopy after tubulin and endoplasmic reticulum immunolocalization and DNA staining. Microtubule arrays of all mitotic stages were disrupted within a few hours of treatment: preprophase bands exhibited asymmetric width; prometaphase, metaphase and anaphase spindles appeared sharply pointed, sigmoid or multipolar; phragmoplast microtubules were elongated and occasionally bended toward the daughter nuclei. Depending on the mitotic stage, the chromosomes appeared condensed at prophase, as a compact mass at metaphase and anaphase, unsegregated or bridged at telophase. Endoplasmic reticulum patterns were also affected, reflecting those of the respective microtubule arrays. Recovery of the microtubules after oryzalin treatment was more effective in a BPA solution than in water. It is concluded that the plant mitotic apparatus microtubules are very sensitive to BPA, the effect of which depends on the specific cell cycle stage. The formation of multipolar spindles is reminiscent of animal cells and is ascribed to the induction of multiple microtubule nucleation sites, deriving from the centrosomal properties of gymnosperms. PMID:26855225

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

    PubMed

    Li, Congjun

    2011-01-01

    Synchronized cells have been invaluable in many kinds of cell cycle and cell proliferation studies. Butyrate induces cell cycle arrest and apoptosis in Madin Darby Bovine Kidney (MDBK) cells. We explore the possibility of using butyrate-blocked cells to obtain synchronized cells and we characterize the properties of butyrate-induced cell cycle arrest. The site of growth inhibition and cell cycle arrest was analyzed using 5-bromo-2'-deoxyuridine (BrdU) incorporation and flow cytometry analyses. Exposure of MDBK cells to 10 mM butyrate caused growth inhibition and cell cycle arrest in a reversible manner. Butyrate affected the cell cycle at a specific point both immediately after mitosis and at a very early stage of the G1 phase. After release from butyrate arrest, MDBK cells underwent synchronous cycles of DNA synthesis and transited through the S phase. It takes at least 8 h for butyrate-induced G1-synchronized cells to begin the progression into the S phase. One cycle of cell division for MDBK cells is about 20 h. By combining BrdU incorporation and DNA content analysis, not only can the overlapping of different cell populations be eliminated, but the frequency and nature of individual cells that have synthesized DNA can also be determined.

  13. 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.

  14. A Barley ROP GTPase ACTIVATING PROTEIN Associates with Microtubules and Regulates Entry of the Barley Powdery Mildew Fungus into Leaf Epidermal Cells[C][W

    PubMed Central

    Hoefle, Caroline; Huesmann, Christina; Schultheiss, Holger; Börnke, Frederik; Hensel, Götz; Kumlehn, Jochen; Hückelhoven, Ralph

    2011-01-01

    Little is known about the function of host factors involved in disease susceptibility. The barley (Hordeum vulgare) ROP (RHO of plants) G-protein RACB is required for full susceptibility of the leaf epidermis to invasion by the biotrophic fungus Blumeria graminis f. sp hordei. Stable transgenic knockdown of RACB reduced the ability of barley to accommodate haustoria of B. graminis in intact epidermal leaf cells and to form hairs on the root epidermis, suggesting that RACB is a common element of root hair outgrowth and ingrowth of haustoria in leaf epidermal cells. We further identified a barley MICROTUBULE-ASSOCIATED ROP-GTPASE ACTIVATING PROTEIN (MAGAP1) interacting with RACB in yeast and in planta. Fluorescent MAGAP1 decorated cortical microtubules and was recruited by activated RACB to the cell periphery. Under fungal attack, MAGAP1-labeled microtubules built a polarized network at sites of successful defense. By contrast, microtubules loosened where the fungus succeeded in penetration. Genetic evidence suggests a function of MAGAP1 in limiting susceptibility to penetration by B. graminis. Additionally, MAGAP1 influenced the polar organization of cortical microtubules. These results add to our understanding of how intact plant cells accommodate fungal infection structures and suggest that RACB and MAGAP1 might be antagonistic players in cytoskeleton organization for fungal entry. PMID:21685259

  15. Microtubule-associated Protein 2c Reorganizes Both Microtubules and Microfilaments into Distinct Cytological Structures in an Actin-binding Protein-280–deficient Melanoma Cell Line

    PubMed Central

    Cunningham, C. Casey; Leclerc, Nicole; Flanagan, Lisa A.; Lu, Mei; Janmey, Paul A.; Kosik, Kenneth S.

    1997-01-01

    The emergence of processes from cells often involves interactions between microtubules and microfilaments. Interactions between these two cytoskeletal systems are particularly apparent in neuronal growth cones. The juvenile isoform of the neuronal microtubule-associated protein 2 (MAP2c) is present in growth cones, where we hypothesize it mediates interactions between microfilaments and microtubules. To approach this problem in vivo, we used the human melanoma cell, M2, which lacks actin-binding protein-280 (ABP-280) and forms membrane blebs, which are not seen in wild-type or ABP-transfected cells. The microinjection of tau or mature MAP2 rescued the blebbing phenotype; MAP2c not only caused cessation of blebbing but also induced the formation of two distinct cellular structures. These were actin-rich lamellae, which often included membrane ruffles, and microtubule-bearing processes. The lamellae collapsed after treatment with cytochalasin D, and the processes retracted after treatment with colchicine. MAP2c was immunocytochemically visualized in zones of the cell that were devoid of tubulin, such as regions within the lamellae and in association with membrane ruffles. In vitro rheometry confirmed that MAP2c is an efficient actin gelation protein capable of organizing actin filaments into an isotropic array at very low concentrations; tau and mature MAP2 do not share this rheologic property. These results suggest that MAP2c engages in functionally specific interactions not only with microtubules but also with microfilaments. PMID:9049250

  16. 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.

  17. Polyploidisation of metastatic colon carcinoma cells by microtubule and tubulin interacting drugs: effect on proteolytic activity and invasiveness.

    PubMed

    Seiler, Nikolaus; Schneider, Yann; Gossé, Francine; Schleiffer, René; Raul, Francis

    2004-10-01

    When SW620 colon cancer-derived metastatic cells were exposed to nanomolar concentrations of Taxol, colchicine or (Z)-3,5,4'-trimethoxystilbene (R3), huge aneuploid, polynuclear cells survived the treatment. These cells released considerable amounts of the matrix metalloproteinase matrilysin (MMP-7), and tissue-type plasminogen activator (tPA) into the surrounding culture medium. MMP-7, and other proteolytic enzymes were highly expressed by these cells. In spite of their enormous size, the polyploid cells exhibited a considerable migratory capacity, as was demonstrated by their migration through an artificial basement membrane. While colchicine and R3-treated cells showed an inverse relationship between drug concentration and invasiveness, treatment with Taxol increased the capacity of the SW620 cells to penetrate through the membrane. The invasive capacity was not correlated with the induction and release of proteolytic enzymes. The idea that expression and release of proteolytic enzymes is a fundamental prerequisite of tumour cell invasiveness is generally accepted. The ability of the cells to respond to chemotactic signalling, and the filamentous structures of the cells, together with several cell adhesion factors, which are the basis of cell migration, are prerequisites of invasiveness. These factors are presumably different in the aneuploid cells produced by Taxol, colchicine and R3, and await scrutiny. PMID:15375554

  18. P-glycoprotein (ABCB1) inhibited network of mitochondrion transport along microtubule and BMP signal-induced cell shape in chimpanzee left cerebrum by systems-theoretical analysis.

    PubMed

    Lin, Hong; Wang, Lin; Jiang, Minghu; Huang, Juxiang; Qi, Lianxiu

    2012-10-01

    We constructed the significant low-expression P-glycoprotein (ABCB1) inhibited transport and signal network in chimpanzee compared with high-expression (fold change ≥2) the human left cerebrum in GEO data set, by using integration of gene regulatory activated and inhibited network inference method with gene ontology (GO) analysis. Our result showed that ABCB1 transport and signal upstream network RAB2A inhibited ABCB1, and downstream ABCB1-inhibited SMAD1_2, NCK2, SLC25A46, GDF10, RASGRP1, EGFR, LRPPRC, RASSF2, RASA4, CA2, CBLB, UBR5, SLC25A16, ITGB3BP, DDIT4, PDPN, RAB2A in chimpanzee left cerebrum. We obtained that the different biological processes of ABCB1 inhibited transport and signal network repressed carbon dioxide transport, ER to Golgi vesicle-mediated transport, folic acid transport, mitochondrion transport along microtubule, water transport, BMP signaling pathway, Ras protein signal transduction, transforming growth factor beta receptor signaling pathway in chimpanzee compared with the inhibited network of the human left cerebrum, as a result of inducing inhibition of mitochondrion transport along microtubule and BMP signal-induced cell shape in chimpanzee left cerebrum. Our hypothesis was verified by the same and different biological processes of ABCB1 inhibited transport and signal network of chimpanzee compared with the corresponding activated network of chimpanzee and the human left cerebrum, respectively.

  19. Complementary roles of microtubules and microfilaments in the lung fibroblast-mediated contraction of collagen gels: Dynamics and the influence of cell density.

    PubMed

    Redden, Robert A; Doolin, Edward J

    2006-01-01

    Fibroblasts are important cellular components in wound healing, scar formation, and fibrotic disorders; and the fibroblast-populated collagen-gel (FPCG) model allows examination of fibroblast behavior in an in vitro three-dimensional environment similar to that in vivo. Contraction of free-floating FPCGs depends on an active and dynamic cytoskeleton, and the contraction dynamics are highly influenced by cell density. We investigated mechanistic differences between high- and low-cell density FPCG contraction by evaluating contraction dynamics in detail, using specific cytoskeletal disruptors. Collagen gels were seeded with human lung fibroblasts at either high (HD) or low (LD) density, and incubated with or without cytoskeletal disruptors colchicine (microtubules) or cytochalasin D (microfilaments). Gel area was measured daily. FPCG contraction curves were essentially sigmoidal, featuring an initial period of no contraction (lag phase), followed by a period of rapid contraction (log phase). Contraction curves of HD-FPCGs were distinct from those of LD-FPCGs. For example, HD-FPCGs had a negligible lag phase (compared with 3 d for LD-FPCGs) and exhibited a higher rate of log-phase contraction. Both colchicine and cytochalasin dose-dependently inhibited contraction but specifically affected different phases of contraction in HD- and LD-FPCGs; and colchicine inhibited LD-FPCGs much more than HD-FPCGs. The data indicate that LD- and HD-FPCGs contract through different primary mechanisms. Microtubules and microfilaments are both complementarily and dynamically involved in the contraction of FPCGs, and cell density influences primary cytoskeletal mechanisms. These results provide valuable information about fibroblast behavior in healing and fibrosis, and may suggest novel treatment options. PMID:16759151

  20. Orchestration of microtubules and the actin cytoskeleton in trichome cell shape determination by a plant-unique kinesin

    PubMed Central

    Tian, Juan; Han, Libo; Feng, Zhidi; Wang, Guangda; Liu, Weiwei; Ma, Yinping; Yu, Yanjun; Kong, Zhaosheng

    2015-01-01

    Microtubules (MTs) and actin filaments (F-actin) function cooperatively to regulate plant cell morphogenesis. However, the mechanisms underlying the crosstalk between these two cytoskeletal systems, particularly in cell shape control, remain largely unknown. In this study, we show that introduction of the MyTH4-FERM tandem into KCBP (kinesin-like calmodulin-binding protein) during evolution conferred novel functions. The MyTH4 domain and the FERM domain in the N-terminal tail of KCBP physically bind to MTs and F-actin, respectively. During trichome morphogenesis, KCBP distributes in a specific cortical gradient and concentrates at the branching sites and the apexes of elongating branches, which lack MTs but have cortical F-actin. Further, live-cell imaging and genetic analyses revealed that KCBP acts as a hub integrating MTs and actin filaments to assemble the required cytoskeletal configuration for the unique, polarized diffuse growth pattern during trichome cell morphogenesis. Our findings provide significant insights into the mechanisms underlying cytoskeletal regulation of cell shape determination. DOI: http://dx.doi.org/10.7554/eLife.09351.001 PMID:26287478

  1. Disassembly of microtubules and inhibition of neurite outgrowth, neuroblastoma cell proliferation, and MAP kinase tyrosine dephosphorylation by dibenzyl trisulphide.

    PubMed

    Rösner, H; Williams, L A; Jung, A; Kraus, W

    2001-08-22

    Dibenzyl trisulphide (DTS), a main lipophilic compound in Petiveria alliacea L. (Phytolaccaceae), was identified as one of the active immunomodulatory compounds in extracts of the plant. To learn more about its biological activities and molecular mechanisms, we conducted one-dimensional NMR interaction studies with bovine serum albumin (BSA) and tested DTS and related compounds in two well-established neuronal cell-and-tissue culture systems. We found that DTS preferentially binds to an aromatic region of BSA which is rich in tyrosyl residues. In SH-SY5Y neuroblastoma cells, DTS attenuates the dephosphorylation of tyrosyl residues of MAP kinase (erk1/erk2). In the same neuroblastoma cell line and in Wistar 38 human lung fibroblasts, DTS causes a reversible disassembly of microtubules, but it did not affect actin dynamics. Probably due to the disruption of the microtubule dynamics, DTS also inhibits neuroblastoma cell proliferation and neurite outgrowth from spinal cord explants. Related dibenzyl compounds with none, one, or two sulphur atoms were found to be significantly less effective. These data confirmed that the natural compound DTS has a diverse spectrum of biological properties, including cytostatic and neurotoxic actions in addition to immunomodulatory activities.

  2. 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 (5)…

  3. 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. PMID:27106898

  4. Analysis of the Schizosaccharomyces pombe Cell Cycle.

    PubMed

    Hagan, Iain M; Grallert, Agnes; Simanis, Viesturs

    2016-01-01

    Schizosaccharomyces pombe cells are rod shaped, and they grow by tip elongation. Growth ceases during mitosis and cell division; therefore, the length of a septated cell is a direct measure of the timing of mitotic commitment, and the length of a wild-type cell is an indicator of its position in the cell cycle. A large number of documented stage-specific changes can be used as landmarks to characterize cell cycle progression under specific experimental conditions. Conditional mutations can permanently or transiently block the cell cycle at almost any stage. Large, synchronously dividing cell populations, essential for the biochemical analysis of cell cycle events, can be generated by induction synchrony (arrest-release of a cell cycle mutant) or selection synchrony (centrifugal elutriation or lactose-gradient centrifugation). Schizosaccharomyces pombe cell cycle studies routinely combine particular markers, mutants, and synchronization procedures to manipulate the cycle. We describe these techniques and list key landmarks in the fission yeast mitotic cell division cycle.

  5. Artelastin is a cytotoxic prenylated flavone that disturbs microtubules and interferes with DNA replication in MCF-7 human breast cancer cells.

    PubMed

    Pedro, Madalena; Ferreira, Maria Manuel; Cidade, Honorina; Kijjoa, Anake; Bronze-da-Rocha, Elsa; Nascimento, Maria São José

    2005-06-01

    Artelastin, a novel prenylated flavone, previously isolated from the wood bark of Artocarpus elasticus, was evaluated for its capacity to inhibit the growth of fifty-two human tumor cell lines, representing nine different tumor types. A pronounced dose-dependent growth inhibitory effect was detected in all the cell lines, with GI50 values ranging from 0.8-20.8 microM. Studies to elucidate the basis of the growth inhibitory activity of artelastin were performed in the MCF-7 human breast cancer cell line (GI50 = 6.0 microM). We show that artelastin exerts a biphasic effect in the DNA synthesis of MCF-7 cells, a stimulatory effect at low concentrations (below GI50) for short times of exposition (6 h and 24 h), and an inhibitory effect at high concentrations (above GI50). Remarkably, treated cells that have DNA synthesis affected could be viable and metabolically active. Furthermore, artelastin acts as a cytotoxic rather than a cytostatic compound. Massive cytoplasmatic vacuoles were detected in cells after artelastin treatment. Together with these morphological alterations, cells show the presence of abnormal nuclear morphologies, and occasionally nuclear condensation, which were identified as apoptotic by TUNEL assay. Moreover, artelastin was shown to disturb the microtubule network while no effect was observed on the kinetochores. Flow cytometry analysis of cells treated with artelastin reveal an accumulation in S phase that interferes with the cell cycle progression. Additionally, according to BrdU patterns, studies with synchronized cells at G0 and at G1/S transition also suggest that artelastin delays DNA replication since progression of cells trough S-phase is perturbed.

  6. "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…

  7. Microtubules and cellulose biosynthesis: the emergence of new players.

    PubMed

    Li, Shundai; Lei, Lei; Yingling, Yaroslava G; Gu, Ying

    2015-12-01

    Microtubules determine the orientation of newly formed cellulose microfibrils in expanding cells. There are many hypotheses regarding how the information is transduced across the plasma membrane from microtubules to cellulose microfibrils. However, the molecular mechanisms underlying the co-alignment between microtubules and cellulose microfibrils were not revealed until the recent discovery of cellulose synthase interacting (CSI) proteins. Characterization of CSIs and additional cellulose synthase-associated proteins will greatly advance the knowledge of how cellulose microfibrils are organized.

  8. Analysis of the Schizosaccharomyces pombe Cell Cycle.

    PubMed

    Hagan, Iain M; Grallert, Agnes; Simanis, Viesturs

    2016-01-01

    Schizosaccharomyces pombe cells are rod shaped, and they grow by tip elongation. Growth ceases during mitosis and cell division; therefore, the length of a septated cell is a direct measure of the timing of mitotic commitment, and the length of a wild-type cell is an indicator of its position in the cell cycle. A large number of documented stage-specific changes can be used as landmarks to characterize cell cycle progression under specific experimental conditions. Conditional mutations can permanently or transiently block the cell cycle at almost any stage. Large, synchronously dividing cell populations, essential for the biochemical analysis of cell cycle events, can be generated by induction synchrony (arrest-release of a cell cycle mutant) or selection synchrony (centrifugal elutriation or lactose-gradient centrifugation). Schizosaccharomyces pombe cell cycle studies routinely combine particular markers, mutants, and synchronization procedures to manipulate the cycle. We describe these techniques and list key landmarks in the fission yeast mitotic cell division cycle. PMID:27587785

  9. 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.

  10. 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.

  11. Cell cycle restriction is more important than apoptosis induction for RASSF1A protein tumor suppression.

    PubMed

    Donninger, Howard; Clark, Jennifer A; Monaghan, Megan K; Schmidt, M Lee; Vos, Michele; Clark, Geoffrey J

    2014-11-01

    The Ras association domain family protein 1A (RASSF1A) is arguably one of the most frequently inactivated tumor suppressors in human cancer. RASSF1A modulates apoptosis via the Hippo and Bax pathways but also modulates the cell cycle. In part, cell cycle regulation appears to be dependent upon the ability of RASSF1A to complex with microtubules and regulate their dynamics. Which property of RASSF1A, apoptosis induction or microtubule regulation, is responsible for its tumor suppressor function is not known. We have identified a short conserved motif that is essential for the binding of RASSF family proteins with microtubule-associated proteins. By making a single point mutation in the motif, we were able to generate a RASSF1A variant that retains wild-type apoptotic properties but completely loses the ability to bind microtubule-associated proteins and complex with microtubules. Comparison of this mutant to wild-type RASSF1A showed that, despite retaining its proapoptotic properties, the mutant was completely unable to induce cell cycle arrest or suppress the tumorigenic phenotype. Therefore, it appears that the cell cycle/microtubule effects of RASSF1A are key to its tumor suppressor function rather than its apoptotic effects.

  12. 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.

  13. 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

  14. Metabolic control of the cell cycle

    PubMed Central

    Kalucka, Joanna; Missiaen, Rindert; Georgiadou, Maria; Schoors, Sandra; Lange, Christian; De Bock, Katrien; Dewerchin, Mieke; Carmeliet, Peter

    2015-01-01

    Cell division is a metabolically demanding process, requiring the production of large amounts of energy and biomass. Not surprisingly therefore, a cell's decision to initiate division is co-determined by its metabolic status and the availability of nutrients. Emerging evidence reveals that metabolism is not only undergoing substantial changes during the cell cycle, but it is becoming equally clear that metabolism regulates cell cycle progression. Here, we overview the emerging role of those metabolic pathways that have been best characterized to change during or influence cell cycle progression. We then studied how Notch signaling, a key angiogenic pathway that inhibits endothelial cell (EC) proliferation, controls EC metabolism (glycolysis) during the cell cycle. PMID:26431254

  15. Random transitions and cell cycle control.

    PubMed

    Brooks, R F

    1981-01-01

    Differences between the cycle times of sister cells are exponentially distributed, which means that these differences can be explained entirely by the existence of a single critical step in the cell cycle which occurs at random. Cycle times as a whole are not exponentially distributed, indicating an additional source of variation in the cell cycle. It follows that this additional variation must affect sister cells identically; ie, sister cell cycle times are correlated. This correlation and the overall distribution of cycle times can be predicted quantitatively by a model that was developed initially in order to explain certain problematic features of the response of quiescent cells to mitogenic stimulation - in particular, the significance of the lag that almost invariably occurs between stimulation and the onset of DNA synthesis. This model proposes that each cell cycle depends not on one but two random transitions, one of which (at reasonably high growth rates) occurs in the mother cell, its effects being inherited equally by the two daughter cells. The fundamental timing element in the cell cycle is proposed to be a lengthy process, called L, which accounts for most of the lag on mitogenic stimulation and also for the minimum cycle time in growing cultures. One of the random transitions is concerned with the initiation of L, whereas the other becomes possible on completion of L. The latter transition has two consequences: the first is the initiation of a sequence of events which includes S, G2 and M; the second is the restoration of the state from which L may be initiated once more. As a result, L may begin (at random) at any stage of the conventional cycle, ie, S, G2, M, or G1. There are marked similarities between the hypothetical process L and the biogenesis of mitotic centres - the structures responsible for organising the spindle poles. PMID:7312875

  16. 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.

  17. High-Cycle-Life Lithium Cell

    NASA Technical Reports Server (NTRS)

    Yen, S. P. S.; Carter, B.; Shen, D.; Somoano, R.

    1985-01-01

    Lithium-anode electrochemical cell offers increased number of charge/ discharge cycles. Cell uses components selected for compatibility with electrolyte solvent: These materials are wettable and chemically stable. Low vapor pressure and high electrochemical stability of solvent improve cell packaging, handling, and safety. Cell operates at modest temperatures - less than 100 degrees C - and is well suited to automotive, communications, and other applications.

  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.

  19. 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.

  20. Dynamic changes in microtubules and early development of reconstructed embryos after somatic cell nuclear transfer in a non-human primate.

    PubMed

    Chen, Naiqing; Liow, Swee-Lian; Yip, Wan-Yue; Tan, Lay-Geok; Tong, Guo-Qing; Ng, Soon-Chye

    2006-01-01

    In order to improve somatic cell nuclear transfer (SCNT) efficiency and to understand cellular changes in SCNT, the dynamic changes in microtubules/DNA and early development of SCNT embryos with single or multiple pronuclei were investigated, along with activation timing on efficiency of SCNT, were studied in the Cynomolgus monkey. The confocal images showed that microtubules assembled around condensed DNA at 1h after cell injection; normal or abnormal reconstructed spindle formed at 2 h after cell injection; and reconstructed spindle separated at 2 h after activation. The results of nuclear formation showed that 61.3% of the reconstructed embryos did not form pronuclei; 19.3% formed a single nucleus, and 11.9% and 7.5% formed two and more than two reconstructed pronuclei, respectively. The cleavage and 8-cell development rates of SCNT embryos with pronuclei were significantly higher than those without pronuclei, but there was no difference in development rates among NT embryos with single, two and more then two pronuclei. Activation at 2 h after cell injection yielded more embryos with pronuclei and yielded 8-cell NT embryos more reliably than did activation at 3-4 h. In conclusion, microtubules assembled around condensed DNA at 1-2 h after cell injection, and formed a spindle at 2 h after SCNT, which separated at 2 h after activation; early development was affected by activation time, but no different between single and multiple pronuclei.

  1. Analysis of Cell Cycle Status of Murine Hematopoietic Stem Cells.

    PubMed

    Szade, Krzysztof; Bukowska-Strakova, Karolina; Zukowska, Monika; Jozkowicz, Alicja; Dulak, Józef

    2016-01-01

    Hematopoietic stem cells (HSC) act as paradigmatic tissue-specific adult stem cells. While they are quiescent in steady-state conditions, they enter the cell cycle and proliferate in stress conditions and during tissue regeneration. Therefore, analysis of cell cycle status of HSC is crucial for understanding their biology. However, due to low number of HSC in tissue and need to use many surface markers for their identification, analysis of their cycle status is technically complicated. Here, we presented our simple strategy to analyze cell cycle of strictly defined LKS CD48(-)CD150(+)CD34(-) HSC, together with Ki67 and DAPI staining by flow cytometry.

  2. Dynein interacts with the neural cell adhesion molecule (NCAM180) to tether dynamic microtubules and maintain synaptic density in cortical neurons.

    PubMed

    Perlson, Eran; Hendricks, Adam G; Lazarus, Jacob E; Ben-Yaakov, Keren; Gradus, Tal; Tokito, Mariko; Holzbaur, Erika L F

    2013-09-27

    Cytoplasmic dynein is well characterized as an organelle motor, but dynein also acts to tether and stabilize dynamic microtubule plus-ends in vitro. Here we identify a novel and direct interaction between dynein and the 180-kDa isoform of the neural cell adhesion molecule (NCAM). Optical trapping experiments indicate that dynein bound to beads via the NCAM180 interaction domain can tether projecting microtubule plus-ends. Live cell assays indicate that the NCAM180-dependent recruitment of dynein to the cortex leads to the selective stabilization of microtubules projecting to NCAM180 patches at the cell periphery. The dynein-NCAM180 interaction also enhances cell-cell adhesion in heterologous cell assays. Dynein and NCAM180 co-precipitate from mouse brain extract and from synaptosomal fractions, consistent with an endogenous interaction in neurons. Thus, we examined microtubule dynamics and synaptic density in primary cortical neurons. We find that depletion of NCAM, inhibition of the dynein-NCAM180 interaction, or dampening of microtubule dynamics with low dose nocodazole all result in significantly decreased in synaptic density. Based on these observations, we propose a working model for the role of dynein at the synapse, in which the anchoring of the motor to the cortex via binding to an adhesion molecule mediates the tethering of dynamic microtubule plus-ends to potentiate synaptic stabilization.

  3. A festival of cell-cycle controls.

    PubMed

    Haase, S B; Clarke, D J

    2001-11-01

    The second biennial Salk Cell Cycle meeting convened on 22 June 2001 in San Diego, California. Organized by Tony Hunter and Susan Forsburg of the Salk Institute, the five-day conference was highlighted by enlightening science and plenty of San Diego sunshine. Presentations covered a broad range of contemporary cell-cycle topics, ranging from regulation of DNA replication and mitosis to DNA damage recognition and checkpoint control.

  4. The NFL-TBS.40-63 anti-glioblastoma peptide disrupts microtubule and mitochondrial networks in the T98G glioma cell line.

    PubMed

    Rivalin, Romain; Lepinoux-Chambaud, Claire; Eyer, Joël; Savagner, Frédérique

    2014-01-01

    Despite aggressive therapies, including combinations of surgery, radiotherapy and chemotherapy, glioblastoma remains a highly aggressive brain cancer with the worst prognosis of any central nervous system disease. We have previously identified a neurofilament-derived cell-penetrating peptide, NFL-TBS.40-63, that specifically enters by endocytosis in glioblastoma cells, where it induces microtubule destruction and inhibits cell proliferation. Here, we explore the impact of NFL-TBS.40-63 peptide on the mitochondrial network and its functions by using global cell respiration, quantitative PCR analysis of the main actors directing mitochondrial biogenesis, western blot analysis of the oxidative phosphorylation (OXPHOS) subunits and confocal microscopy. We show that the internalized peptide disturbs mitochondrial and microtubule networks, interferes with mitochondrial dynamics and induces a rapid depletion of global cell respiration. This effect may be related to reduced expression of the NRF-1 transcription factor and of specific miRNAs, which may impact mitochondrial biogenesis, in regard to default mitochondrial mobility.

  5. 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.

  6. Cell Cycle Synchronization in Xenopus Egg Extracts.

    PubMed

    Gillespie, Peter J; Neusiedler, Julia; Creavin, Kevin; Chadha, Gaganmeet Singh; Blow, J Julian

    2016-01-01

    Many important discoveries in cell cycle research have been made using cell-free extracts prepared from the eggs of the South African clawed frog Xenopus laevis. These extracts efficiently support the key nuclear functions of the eukaryotic cell cycle in vitro under apparently the same controls that exist in vivo. The Xenopus cell-free system is therefore uniquely suited to the study of the mechanisms, dynamics and integration of cell cycle regulated processes at a biochemical level. Here, we describe methods currently in use in our laboratory for the preparation of Xenopus egg extracts and demembranated sperm nuclei. We detail how these extracts can be used to study the key transitions of the eukaryotic cell cycle and describe conditions under which these transitions can be manipulated by addition of drugs that either retard or advance passage. In addition, we describe in detail essential techniques that provide a practical starting point for investigating the function of proteins involved in the operation of the eukaryotic cell cycle.

  7. The cell cycle and acute kidney injury.

    PubMed

    Price, Peter M; Safirstein, Robert L; Megyesi, Judit

    2009-09-01

    Acute kidney injury (AKI) activates pathways of cell death and cell proliferation. Although seemingly discrete and unrelated mechanisms, these pathways can now be shown to be connected and even to be controlled by similar pathways. The dependence of the severity of renal-cell injury on cell cycle pathways can be used to control and perhaps to prevent acute kidney injury. This review is written to address the correlation between cellular life and death in kidney tubules, especially in acute kidney injury.

  8. The cell cycle DB: a systems biology approach to cell cycle analysis

    PubMed Central

    Alfieri, Roberta; Merelli, Ivan; Mosca, Ettore; Milanesi, Luciano

    2008-01-01

    The cell cycle database is a biological resource that collects the most relevant information related to genes and proteins involved in human and yeast cell cycle processes. The database, which is accessible at the web site http://www.itb.cnr.it/cellcycle, has been developed in a systems biology context, since it also stores the cell cycle mathematical models published in the recent years, with the possibility to simulate them directly. The aim of our resource is to give an exhaustive view of the cell cycle process starting from its building-blocks, genes and proteins, toward the pathway they create, represented by the models. PMID:18160409

  9. 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.

  10. Helicobacter pylori inhibits gastric cell cycle progression.

    PubMed

    Ahmed, A; Smoot, D; Littleton, G; Tackey, R; Walters, C S; Kashanchi, F; Allen, C R; Ashktorab, H

    2000-08-01

    Helicobacter pylori infection of the gastric mucosa is associated with changes in gastric epithelial cell proliferation. In vitro studies have shown that exposure to H. pylori inhibits proliferation of gastric cells. This study sought to investigate the cell cycle progression of gastric epithelial cell lines in the presence and absence of H. pylori. Unsynchronized and synchronized gastric epithelial cell lines AGS and KatoIII were exposed to H. pylori over a 24-h period. Cell cycle progression was determined by flow cytometry using propidium iodide (PI), and by analysis of cyclin E, p21, and p53 protein expression using Western blots. In the absence of H. pylori 40, 45, and 15% of unsynchronized AGS cells were in G(0)-G(1), S, and G(2)-M phases, respectively, by flow cytometry analysis. When AGS cells were cultured in the presence of H. pylori, the S phase decreased 10% and the G(0)-G(1) phase increased 17% after 24 h compared with the controls. KatoIII cells, which have a deleted p53 gene, showed little or no response to H. pylori. When G1/S synchronized AGS cells were incubated with media containing H. pylori, the G(1) phase increased significantly (25%, P < 0.05) compared with controls after 24 h. In contrast, the control cells were able to pass through S phase. The inhibitory effects of H. pylori on the cell cycle of AGS cells were associated with a significant increase in p53 and p21 expression after 24 h. The expression of cyclin E was downregulated in AGS cells following exposure of AGS cells to H. pylori for 24 h. This study shows that H. pylori-induced growth inhibition in vitro is predominantly at the G(0)-G(1) checkpoint. Our results suggest that p53 may be important in H. pylori-induced cell cycle arrest. These results support a role for cyclin-dependent kinase inhibitors in the G(1) cell cycle arrest exerted by H. pylori and its involvement in changing the regulatory proteins, p53, p21, and cyclin E in the cell cycle. PMID:11008106

  11. Cell-cycle-specific initiation of replication.

    PubMed

    Nordström, K; Austin, S J

    1993-11-01

    The following characteristics are relevant when replication of chromosomes and plasmids is discussed in relation to the cell cycle: the timing or replication, the selection of molecules for replication, and the coordination of multiple initiation events within a single cell cycle. Several fundamentally different methods have been used to study these processes: Meselson-Stahl density-shift experiments, experiments with the so-called 'baby machine', sorting of cells according to size, and flow cytometry. The evidence for precise timing and co-ordination of chromosome replication in Escherichia coli is overwhelming. Similarly, the high-copy-number plasmid ColE1 and the low-copy-number plasmids R1/R100 without any doubt replicate randomly throughout the cell cycle. Data about the low-copy-number plasmids F and P1 are conflicting. This calls for new types of experiments and for a better understanding of how these plasmids control their replication and partitioning.

  12. Flavonoids: from cell cycle regulation to biotechnology.

    PubMed

    Woo, Ho-Hyung; Jeong, Byeong Ryong; Hawes, Martha C

    2005-03-01

    Flavonoids have been proposed to play diverse roles in plant growth and development, including defense, symbiosis, pollen development and male fertility, polar auxin transport, and protection against ultraviolet radiation. Recently, a new role in cell cycle regulation has emerged. Genetic alteration of glucuronide metabolism by altered expression of a Pisum sativum UDP-glucuronosyltransferase (PsUGT1) results in an altered cell cycle in pea, alfalfa, and Arabidopsis. In alfalfa, altered expression of PsUGT1 results in accumulation of a flavonoid-like compound that suppresses growth of cultured cells. The results are consistent with the hypothesis that PsUGT1 functions by controlling cellular levels of a factor controlling cell cycle (FCC). PMID:15834800

  13. Cell cycle-specific effects of lovastatin.

    PubMed Central

    Jakóbisiak, M; Bruno, S; Skierski, J S; Darzynkiewicz, Z

    1991-01-01

    Lovastatin (LOV), the drug recently introduced to treat hypercholesteremia, inhibits the synthesis of mevalonic acid. The effects of LOV on the cell cycle progression of the human bladder carcinoma T24 cell line expressing activated p21ras were investigated. At a concentration of 2-10 microM, LOV arrested cells in G1 and also prolonged--or arrested a minor fraction of cells in--the G2 phase of the cell cycle; at a concentration of 50 microM, LOV was cytotoxic. The cytostatic effects were reversed by addition of exogenous mevalonate. Cells arrested in the cycle by LOV were viable for up to 72 hr and did not show any changes in RNA or protein content or chromatin condensation, which would be typical of either unbalanced growth or deep quiescence. The expression of the proliferation-associated nuclear proteins Ki-67 and p105 in these cells was reduced by up to 72% and 74%, respectively, compared with exponentially growing control cells. After removal of LOV, the cells resumed progression through the cycle; they entered S phase asynchronously after a lag of approximately 6 hr. Because mevalonate is essential for the posttranslational modification (isoprenylation) of p21ras, which in turn allows this protein to become attached to the cell membrane, the data suggest that the LOV-induced G1 arrest may be a consequence of the loss of the signal transduction capacity of p21ras. Indeed, while exposure of cells to LOV had no effect on the cellular content of p21ras (detected immunocytochemically), it altered the intracellular location of this protein, causing its dissociation from the cell membrane and translocation toward the cytoplasm and nucleus. However, it is also possible that inhibition of isoprenylation of proteins other than p21ras (e.g., nuclear lamins) by LOV may be responsible for the observed suppression of growth of T24 cells. Images PMID:1673788

  14. 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

  15. 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.

  16. 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.

  17. Cell Cycle Regulation of DNA Replication

    PubMed Central

    Sclafani, R. A.; Holzen, T. M.

    2008-01-01

    Eukaryotic DNA replication is regulated to ensure all chromosomes replicate once and only once per cell cycle. Replication begins at many origins scattered along each chromosome. Except for budding yeast, origins are not defined DNA sequences and probably are inherited by epigenetic mechanisms. Initiation at origins occurs throughout the S phase according to a temporal program that is important in regulating gene expression during development. Most replication proteins are conserved in evolution in eukaryotes and archaea, but not in bacteria. However, the mechanism of initiation is conserved and consists of origin recognition, assembly of pre-replication (pre-RC) initiative complexes, helicase activation, and replisome loading. Cell cycle regulation by protein phosphorylation ensures that pre-RC assembly can only occur in G1 phase, whereas helicase activation and loading can only occur in S phase. Checkpoint regulation maintains high fidelity by stabilizing replication forks and preventing cell cycle progression during replication stress or damage. PMID:17630848

  18. Synchronized Cell Cycle Arrest Promotes Osteoclast Differentiation

    PubMed Central

    Kwon, Minsuk; Kim, Jin-Man; Lee, Kyunghee; Park, So-Young; Lim, Hyun-Sook; Kim, Taesoo; Jeong, Daewon

    2016-01-01

    Osteoclast progenitors undergo cell cycle arrest before differentiation into osteoclasts, induced by exposure to macrophage colony-stimulating factor (M-CSF) and receptor activator of nuclear factor-κB ligand (RANKL). The role of such cell cycle arrest in osteoclast differentiation has remained unclear, however. We here examined the effect of synchronized cell cycle arrest on osteoclast formation. Osteoclast progenitors deprived of M-CSF in culture adopted a uniform morphology and exhibited cell cycle arrest at the G0–G1 phase in association with both down-regulation of cyclins A and D1 as well as up-regulation of the cyclin-dependent kinase inhibitor p27Kip1. Such M-CSF deprivation also promoted the differentiation of osteoclast progenitors into multinucleated osteoclasts expressing high levels of osteoclast marker proteins such as NFATc1, c-Fos, Atp6v0d2, cathepsin K, and integrin β3 on subsequent exposure to M-CSF and RANKL. Our results suggest that synchronized arrest and reprogramming of osteoclast progenitors renders them poised to respond to inducers of osteoclast formation. Further characterization of such effects may facilitate induction of the differentiation of heterogeneous and multipotent cells into desired cell lineages. PMID:27517906

  19. Synchronized Cell Cycle Arrest Promotes Osteoclast Differentiation.

    PubMed

    Kwon, Minsuk; Kim, Jin-Man; Lee, Kyunghee; Park, So-Young; Lim, Hyun-Sook; Kim, Taesoo; Jeong, Daewon

    2016-01-01

    Osteoclast progenitors undergo cell cycle arrest before differentiation into osteoclasts, induced by exposure to macrophage colony-stimulating factor (M-CSF) and receptor activator of nuclear factor-κB ligand (RANKL). The role of such cell cycle arrest in osteoclast differentiation has remained unclear, however. We here examined the effect of synchronized cell cycle arrest on osteoclast formation. Osteoclast progenitors deprived of M-CSF in culture adopted a uniform morphology and exhibited cell cycle arrest at the G₀-G₁ phase in association with both down-regulation of cyclins A and D1 as well as up-regulation of the cyclin-dependent kinase inhibitor p27(Kip1). Such M-CSF deprivation also promoted the differentiation of osteoclast progenitors into multinucleated osteoclasts expressing high levels of osteoclast marker proteins such as NFATc1, c-Fos, Atp6v0d2, cathepsin K, and integrin β3 on subsequent exposure to M-CSF and RANKL. Our results suggest that synchronized arrest and reprogramming of osteoclast progenitors renders them poised to respond to inducers of osteoclast formation. Further characterization of such effects may facilitate induction of the differentiation of heterogeneous and multipotent cells into desired cell lineages. PMID:27517906

  20. Cell cycle checkpoint regulators reach a zillion

    PubMed Central

    Yasutis, Kimberly M.; Kozminski, Keith G.

    2013-01-01

    Entry into mitosis is regulated by a checkpoint at the boundary between the G2 and M phases of the cell cycle (G2/M). In many organisms, this checkpoint surveys DNA damage and cell size and is controlled by both the activation of mitotic cyclin-dependent kinases (Cdks) and the inhibition of an opposing phosphatase, protein phosphatase 2A (PP2A). Misregulation of mitotic entry can often lead to oncogenesis or cell death. Recent research has focused on discovering the signaling pathways that feed into the core checkpoint control mechanisms dependent on Cdk and PP2A. Herein, we review the conserved mechanisms of the G2/M transition, including recently discovered upstream signaling pathways that link cell growth and DNA replication to cell cycle progression. Critical consideration of the human, frog and yeast models of mitotic entry frame unresolved and emerging questions in this field, providing a prediction of signaling molecules and pathways yet to be discovered. PMID:23598718

  1. 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.

  2. Potassium channels in cell cycle and cell proliferation

    PubMed Central

    Urrego, Diana; Tomczak, Adam P.; Zahed, Farrah; Stühmer, Walter; Pardo, Luis A.

    2014-01-01

    Normal cell-cycle progression is a crucial task for every multicellular organism, as it determines body size and shape, tissue renewal and senescence, and is also crucial for reproduction. On the other hand, dysregulation of the cell-cycle progression leading to uncontrolled cell proliferation is the hallmark of cancer. Therefore, it is not surprising that it is a tightly regulated process, with multifaceted and very complex control mechanisms. It is now well established that one of those mechanisms relies on ion channels, and in many cases specifically on potassium channels. Here, we summarize the possible mechanisms underlying the importance of potassium channels in cell-cycle control and briefly review some of the identified channels that illustrate the multiple ways in which this group of proteins can influence cell proliferation and modulate cell-cycle progression. PMID:24493742

  3. Primary Cilia and the Cell Cycle

    PubMed Central

    Plotnikova, Olga V.; Pugacheva, Elena N.; Golemis, Erica A.

    2009-01-01

    Cilia are microtubule-based structures that protrude from the cell surface, and function as sensors for mechanical and chemical environmental cues that regulate cellular differentiation or division. In metazoans, ciliary signaling is important both during organismal development and in the homeostasis controls of adult tissues, with receptors for the Hedgehog, PDGF, Wnt, and other signaling cascades arrayed and active along the ciliary membrane. In normal cells, cilia are dynamically regulated during cell cycle progression: present in G0 and G1 cells, and usually in S/G2 cells, but almost invariably resorbed before mitotic entry, to re-appear post-cytokinesis. This periodic resorption and reassembly of cilia, specified by interaction with the intrinsic cell cycle machinery, influences the susceptibility of cells to the influence of extrinsic signals with cilia-associated receptors. Pathogenic conditions of mammals associated with loss of or defects in ciliary integrity include a number of developmental disorders, cystic syndromes in adults, and some cancers. With the continuing expansion of the list of human diseases associated with ciliary abnormalities, the identification of the cellular mechanisms regulating ciliary growth and disassembly has become a topic of intense research interest. Although these mechanisms are far from being understood, a number of recent studies have begun to identify key regulatory factors that may begin to offer insight into disease pathogenesis and treatment. In this chapter we will discuss the current state of knowledge regarding cell cycle control of ciliary dynamics, and provide general methods that can be applied to investigate cell cycle-dependent ciliary growth and disassembly. PMID:20362089

  4. Regulation of Melanosome Movement in the Cell Cycle by Reversible Association with Myosin V

    PubMed Central

    Rogers, Stephen L.; Karcher, Ryan L.; Roland, Joseph T.; Minin, Alexander A.; Steffen, Walter; Gelfand, Vladimir I.

    1999-01-01

    Previously, we have shown that melanosomes of Xenopus laevis melanophores are transported along both microtubules and actin filaments in a coordinated manner, and that myosin V is bound to purified melanosomes (Rogers, S., and V.I. Gelfand. 1998. Curr. Biol. 8:161–164). In the present study, we have demonstrated that myosin V is the actin-based motor responsible for melanosome transport. To examine whether myosin V was regulated in a cell cycle-dependent manner, purified melanosomes were treated with interphase- or metaphase-arrested Xenopus egg extracts and assayed for in vitro motility along Nitella actin filaments. Motility of organelles treated with mitotic extract was found to decrease dramatically, as compared with untreated or interphase extract-treated melanosomes. This mitotic inhibition of motility correlated with the dissociation of myosin V from melanosomes, but the activity of soluble motor remained unaffected. Furthermore, we find that myosin V heavy chain is highly phosphorylated in metaphase extracts versus interphase extracts. We conclude that organelle transport by myosin V is controlled by a cell cycle-regulated association of this motor to organelles, and that this binding is likely regulated by phosphorylation of myosin V during mitosis. PMID:10491390

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. Cell proliferation and cell cycle control: a mini review.

    PubMed

    Golias, C H; Charalabopoulos, A; Charalabopoulos, K

    2004-12-01

    Tumourigenesis is the result of cell cycle disorganisation, leading to an uncontrolled cellular proliferation. Specific cellular processes-mechanisms that control cell cycle progression and checkpoint traversation through the intermitotic phases are deregulated. Normally, these events are highly conserved due to the existence of conservatory mechanisms and molecules such as cell cycle genes and their products: cyclins, cyclin dependent kinases (Cdks), Cdk inhibitors (CKI) and extra cellular factors (i.e. growth factors). Revolutionary techniques using laser cytometry and commercial software are available to quantify and evaluate cell cycle processes and cellular growth. S-phase fraction measurements, including ploidy values, using histograms and estimation of indices such as the mitotic index and tumour-doubling time indices, provide adequate information to the clinician to evaluate tumour aggressiveness, prognosis and the strategies for radiotherapy and chemotherapy in experimental researches.

  10. The Cell Cycle Ontology: an application ontology for the representation and integrated analysis of the cell cycle process

    PubMed Central

    Antezana, Erick; Egaña, Mikel; Blondé, Ward; Illarramendi, Aitzol; Bilbao, Iñaki; De Baets, Bernard; Stevens, Robert; Mironov, Vladimir; Kuiper, Martin

    2009-01-01

    The Cell Cycle Ontology ( is an application ontology that automatically captures and integrates detailed knowledge on the cell cycle process. Cell Cycle Ontology is enabled by semantic web technologies, and is accessible via the web for browsing, visualizing, advanced querying, and computational reasoning. Cell Cycle Ontology facilitates a detailed analysis of cell cycle-related molecular network components. Through querying and automated reasoning, it may provide new hypotheses to help steer a systems biology approach to biological network building. PMID:19480664

  11. 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.

  12. 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.

  13. Cell shape dynamics during the staphylococcal cell cycle.

    PubMed

    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

    2015-08-17

    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.

  14. 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.

  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. 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.

  17. Metabolism, cell growth and the bacterial cell cycle.

    PubMed

    Wang, Jue D; Levin, Petra A

    2009-11-01

    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.

  18. [Motor Proteins of Microtubules and Mechanisms of Synaptic Plasticity].

    PubMed

    Vasilyeva, N A; Pivovarov, A S

    2016-01-01

    Motor proteins of microtubules, kinesin and dynein superfamily proteins play an important role in the intracellular transport. Inside a neuron they are involved in the transport of organelles, proteins and mRNAs along the axons and dendrites to the nerve terminals and back to the cell bodies. Disturbance of axonal transport may affect neurotransmitter release and short-term presynaptic plasticity. Disturbance of dendritic transport, in particular the recycling of synaptic receptors, affects postsynaptic plasticity. The review attempts to trace the connections between the motor proteins of microtubules and mechanisms of synaptic plasticity from the perspective of their involvement in the intracellular transport of proteins and organelles, which play role in the mechanisms of synaptic plasticity. PMID:27538280

  19. 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. PMID:25914884

  20. 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

  1. Tau co-organizes dynamic microtubule and actin networks

    PubMed Central

    Elie, Auréliane; Prezel, Elea; Guérin, Christophe; Denarier, Eric; Ramirez-Rios, Sacnicte; Serre, Laurence; Andrieux, Annie; Fourest-Lieuvin, Anne; Blanchoin, Laurent; Arnal, Isabelle

    2015-01-01

    The crosstalk between microtubules and actin is essential for cellular functions. However, mechanisms underlying the microtubule-actin organization by cross-linkers remain largely unexplored. Here, we report that tau, a neuronal microtubule-associated protein, binds to microtubules and actin simultaneously, promoting in vitro co-organization and coupled growth of both networks. By developing an original assay to visualize concomitant microtubule and actin assembly, we show that tau can induce guided polymerization of actin filaments along microtubule tracks and growth of single microtubules along actin filament bundles. Importantly, tau mediates microtubule-actin co-alignment without changing polymer growth properties. Mutagenesis studies further reveal that at least two of the four tau repeated motifs, primarily identified as tubulin-binding sites, are required to connect microtubules and actin. Tau thus represents a molecular linker between microtubule and actin networks, enabling a coordination of the two cytoskeletons that might be essential in various neuronal contexts. PMID:25944224

  2. Elutriation for Cell Cycle Synchronization in Fission Yeast.

    PubMed

    Kume, Kazunori

    2016-01-01

    Cell synchronization is a powerful technique for studying the eukaryotic cell cycle events precisely. The fission yeast is a rod-shaped cell whose growth is coordinated with the cell cycle. Monitoring the cellular growth of fission yeast is a relatively simple way to measure the cell cycle stage of a cell. Here, we describe a detailed method of unperturbed cell synchronization, named centrifugal elutriation, for fission yeast. PMID:26254921

  3. Microtubule organization during the cell cycle of the primitive eukaryote dinoflagellate Crypthecodinium cohnii.

    PubMed

    Perret, E; Davoust, J; Albert, M; Besseau, L; Soyer-Gobillard, M O

    1993-03-01

    The complete microtubular system of the dinoflagellate Crypthecodinium cohnii Biecheler is described, as seen by confocal laser scanning fluorescence microscopy and labelling with anti-beta-tubulin antibody. This technique allowed us to observe the organization of the subcortical and internal cytoskeletons and the mitotic microtubular system, and their changes during the cell cycle. These observations are compared with those made in cryosections by light microscopy and in fast-freeze-fixed, cryosubstituted cells by electron microscopy. We show the organization of the cortical microtubules, and in particular of the thick microtubular bundles arranged as a three-pronged fork from which they seem to emanate. This fork emerges from a peculiar cytoplasmic zone at the pole of the cell and is in contact with the region of the kinetosomes, at the cingulum. During the G1 phase, only a single, radial microtubular bundle (a "desmose") is observable in the inner part of the cytoplasm. One of its ends is near the flagellar bases and the other end is close to the nucleus in the centrosome region. During the S phase, the flagella drop off, the cell encysts and the kinetosomes duplicate. In mitosis, the cortical microtubules and the intracytoplasmic microtubular bundles do not depolymerize. The microtubular fork, desmose and centrosome double and migrate, while the divided kinetosomes stay in the same place. Later, the centrosomes organize the extranuclear spindle, which is connected to the kinetosome region by the microtubular desmose. The convergent end of the three-pronged fork seems to be in contact with the centrosome region. In early and mid-prophase, thick microtubular bundles pass through the nucleus in cytoplasmic channels and converge towards the two poles. Asters were never seen at the spindle poles. The channels and microtubular bundles in the spindle double in number during late prophase and lengthen in early anaphase. The spindle bundles diverge in late anaphase

  4. The Cell Cycle Ontology: an application ontology for the representation and integrated analysis of the cell cycle process.

    PubMed

    Antezana, Erick; Egaña, Mikel; Blondé, Ward; Illarramendi, Aitzol; Bilbao, Iñaki; De Baets, Bernard; Stevens, Robert; Mironov, Vladimir; Kuiper, Martin

    2009-01-01

    The Cell Cycle Ontology (http://www.CellCycleOntology.org) is an application ontology that automatically captures and integrates detailed knowledge on the cell cycle process. Cell Cycle Ontology is enabled by semantic web technologies, and is accessible via the web for browsing, visualizing, advanced querying, and computational reasoning. Cell Cycle Ontology facilitates a detailed analysis of cell cycle-related molecular network components. Through querying and automated reasoning, it may provide new hypotheses to help steer a systems biology approach to biological network building.

  5. 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

  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. A genomic multi-process survey of the machineries that control and link cell shape, microtubule organisation and cell cycle progression

    PubMed Central

    Geymonat, Marco; Bortfeld-Miller, Miriam; Walter, Thomas; Wagstaff, Laura; Piddini, Eugenia; Carazo Salas, Rafael E.

    2015-01-01

    SUMMARY Understanding cells as integrated systems requires that we systematically decipher how single genes affect multiple biological processes and how processes are functionally linked. Here, we used multi-process phenotypic profiling, combining high-resolution 3D confocal microscopy and multi-parametric image analysis, to simultaneously survey the fission yeast genome with respect to three key cellular processes: cell shape, microtubule organisation and cell cycle progression. We identify, validate and functionally annotate 262 genes controlling specific aspects of those processes. Of these 62% had not been linked to these processes before and 35% are implicated in multiple processes. Importantly, we identify a conserved role for DNA-damage responses in controlling microtubule stability. In addition, we investigate how the processes are functionally linked. We show unexpectedly that disruption of cell cycle progression does not necessarily impact on cell size control and that distinct aspects of cell shape regulate microtubules and vice-versa, identifying important systems-level links across these processes. PMID:25373780

  8. Feedback and Modularity in Cell Cycle Control

    NASA Astrophysics Data System (ADS)

    Skotheim, Jan

    2009-03-01

    Underlying the wonderful diversity of natural forms is the ability of an organism to grow into its appropriate shape. Regulation ensures that cells grow, divide and differentiate so that the organism and its constitutive parts are properly proportioned and of suitable size. Although the size-control mechanism active in an individual cell is of fundamental importance to this process, it is difficult to isolate and study in complex multi-cellular systems and remains poorly understood. This motivates our use of the budding yeast model organism, whose Start checkpoint integrates multiple internal (e.g. cell size) and external signals into an irreversible decision to enter the cell cycle. We have endeavored to address the following two questions: What makes the Start transition irreversible? How does a cell compute its own size? I will report on the progress we have made. Our work is part of an emerging framework for understanding biological control circuits, which will allow us to discern the function of natural systems and aid us in engineering synthetic systems.

  9. 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.

  10. Self-organization of microtubules and motors

    NASA Astrophysics Data System (ADS)

    Ndlec, F. J.; Surrey, T.; Maggs, A. C.; Leibler, S.

    1997-09-01

    Cellular structures are established and maintained through a dynamic interplay between assembly and regulatory processes. Self-organization of molecular components provides a variety of possible spatial structures: the regulatory machinery chooses the most appropriate to express a given cellular function. Here we study the extent and the characteristics of self-organization using microtubules and molecular motors as a model system. These components are known to participate in the formation of many cellular structures, such as the dynamic asters found in mitotic and meiotic spindles. Purified motors and microtubules have previously been observed to form asters in vitro. We have reproduced this result with a simple system consisting solely of multi-headed constructs of the motor protein kinesin and stabilized microtubules. We show that dynamic asters can also be obtained from a homogeneous solution of tubulin and motors. By varying the relative concentrations of the components, we obtain a variety of self-organized structures. Further, by studying this process in a constrained geometry of micro-fabricated glass chambers, we demonstrate that the same final structure can be reached through different assembly `pathways'.

  11. PLK-1: Angel or devil for cell cycle progression.

    PubMed

    Kumar, Shiv; Sharma, Ashish Ranjan; Sharma, Garima; Chakraborty, Chiranjib; Kim, Jaebong

    2016-04-01

    PLK-1 is a key player in the eukaryotic cell cycle. Cell cycle progression is precisely controlled by cell cycle regulatory kinases. PLK-1 is a mitotic kinase that actively regulates the G2/M transition, mitosis, mitotic exit, and cytokinesis. During cell cycle progression, PLK-1 controls various events related to the cell cycle maturation, directly and/or indirectly. On the contrary, aberrant expression of PLK-1 is strongly associated with tumorigenesis and its poor prognosis. The misexpression of PLK-1 causes the abnormalities including aneuploidy, mitotic defects, leading to tumorigenesis through inhibiting the p53 and pRB genes. Therefore, we reviewed the role of PLK-1 in the cell cycle progression and in the tumorigenesis either as a cell cycle regulator or on an attractive anti-cancer drug target. PMID:26899266

  12. Cell cycle measurement of mouse hematopoietic stem/progenitor cells.

    PubMed

    Chitteti, Brahmananda Reddy; Srour, Edward F

    2014-01-01

    Lifelong production of blood cells is sustained by hematopoietic stem cells (HSC). HSC reside in a mitotically quiescent state within specialized areas of the bone marrow (BM) microenvironment known as the hematopoietic niche (HN). HSC enter into active phases of cell cycle in response to intrinsic and extrinsic biological cues thereby undergoing differentiation or self-renewal divisions. Quiescent and mitotically active HSC have different metabolic states and different functional abilities such as engraftment and BM repopulating potential following their transplantation into conditioned recipients. Recent studies reveal that various cancers also utilize the same mechanisms of quiescence as normal stem cells and preserve the root of malignancy thus contributing to relapse and metastasis. Therefore, exploring the stem cell behavior and function in conjunction with their cell cycle status has significant clinical implications in HSC transplantation and in treating cancers. In this chapter, we describe methodologies to isolate or analytically measure the frequencies of quiescent (G0) and active (G1, S, and G2-M) hematopoietic progenitor and stem cells among murine BM cells.

  13. Distinct localization and cell cycle dependence of COOH terminally tyrosinolated alpha-tubulin in the microtubules of Trypanosoma brucei brucei

    PubMed Central

    1987-01-01

    alpha-Tubulin can be posttranslationally modified in that its COOH- terminal amino acid residue, tyrosine, can be selectively removed and replaced again. This reaction cycle involves two enzymes, tubulin carboxypeptidase and tubulin tyrosine ligase. The functional significance of this unusual modification is unclear. The present study demonstrates that posttranslational tyrosinolation of alpha-tubulin does occur in the parasitic hemoflagellate Trypanosoma brucei brucei and that posttranslational tyrosinolation can be detected in both alpha- tubulin isoforms found in this organism. Trypanosomes contain a number of microtubular structures: the flagellar axoneme; the subpellicular layer of singlet microtubules which are closely associated with the cell membrane; the basal bodies; and a cytoplasmic pool of soluble tubulin. Tyrosinolated alpha-tubulin is present in all these populations. However, immunofluorescence studies demonstrate a distinct localization of tyrosinolated alpha-tubulin within individual microtubules and organelles. This localization is subject to a temporal modulation that correlates strongly with progress of a cell through the cell cycle. Our results indicate that the presence of tyrosinolated alpha-tubulin is a marker for newly formed microtubules. PMID:3546334

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

    PubMed

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

    2013-06-01

    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.

  15. 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

  16. 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.

  17. Modeling the fission yeast cell cycle: Quantized cycle times in wee1 cdc25 mutant cells

    NASA Astrophysics Data System (ADS)

    Sveiczer, Akos; Csikasz-Nagy, Attila; Gyorffy, Bela; Tyson, John J.; Novak, Bela

    2000-07-01

    A detailed mathematical model for the fission yeast mitotic cycle is developed based on positive and negative feedback loops by which Cdc13/Cdc2 kinase activates and inactivates itself. Positive feedbacks are created by Cdc13/Cdc2-dependent phosphorylation of specific substrates: inactivating its negative regulators (Rum1, Ste9 and Wee1/Mik1) and activating its positive regulator (Cdc25). A slow negative feedback loop is turned on during mitosis by activation of Slp1/anaphase-promoting complex (APC), which indirectly re-activates the negative regulators, leading to a drop in Cdc13/Cdc2 activity and exit from mitosis. The model explains how fission yeast cells can exit mitosis in the absence of Ste9 (Cdc13 degradation) and Rum1 (an inhibitor of Cdc13/Cdc2). We also show that, if the positive feedback loops accelerating the G2/M transition (through Wee1 and Cdc25) are weak, then cells can reset back to G2 from early stages of mitosis by premature activation of the negative feedback loop. This resetting can happen more than once, resulting in a quantized distribution of cycle times, as observed experimentally in wee1- cdc25Delta mutant cells. Our quantitative description of these quantized cycles demonstrates the utility of mathematical modeling, because these cycles cannot be understood by intuitive arguments alone.

  18. Spindle microtubules and their mechanical associations after micromanipulation in anaphase.

    PubMed

    Nicklas, R B; Kubai, D F; Hays, T S

    1982-10-01

    Micromanipulation of living grasshopper spermatocytes in anaphase has been combined with electron microscopy to reveal otherwise obscure features of spindle organization. A chromosome is pushed laterally outside the spindle and stretched, and the cell is fixed with a novel, agar-treated glutaraldehyde solution. Two- and three-dimensional reconstructions from serial sections of seven cells show that kinetochore microtubules of the manipulated chromosome are shifted outside the confusing thicket of spindle microtubules and mechanical associations among microtubules are revealed by bent or shifted microtubules. These are the chief results: (a) The disposition of microtubules invariably is consistent with a skeletal role for spindle microtubules. (b) The kinetochore microtubule bundle is composed of short and long microtubules, with weak but recognizable mechanical associations among them. Some kinetochore microtubules are more tightly linked to one other microtubule within the bundle. (c) Microtubules of the kinetochore microtubule bundle are firmly connected to other spindle microtubules only near the pole, although some nonkinetochore microtubules of uncertain significance enter the bundle nearer to the kinetochore. (d) The kinetochore microtubules of adjacent chromosomes are mechanically linked, which provides an explanation for interdependent chromosome movement in "hinge anaphases." In the region of the spindle open to analysis after chromosome micromanipulation, microtubules may be linked mechanically by embedment in a gel, rather than by dynein or other specific, cross-bridging molecules.

  19. 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

  20. 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.

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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 ...

  2. Cyclic AMP, a nonessential regulator of the cell cycle.

    PubMed Central

    Coffino, P; Gray, J W; Tomkins, G M

    1975-01-01

    Flow-microfluorimetric analysis has been carried out on populations of exponentially growing S49 mouse lymphoma cells treated with dibutyryl cyclic AMP. The drug produces a specific concentration-dependent block in the G-1 phase of the cell cycle while other phases of the cycle are not perceptibly altered. The cell cycle of a line of mutant cells lacking the cyclic AMP-dependent protein kinase is not affected by the drug. Since these mutant cells have been shown to maintain a normal cell cycle, even in the presence of high levels of cyclic AMP, periodic fluctuations in the levels of the cyclic nucleotide cannot be required for or determine progression through the cell cycle. PMID:165491

  3. 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

  4. Cell cycle control by oscillating regulatory proteins in Caulobacter crescentus.

    PubMed

    Holtzendorff, Julia; Reinhardt, Jens; Viollier, Patrick H

    2006-04-01

    Significant strides have been made in recent years towards understanding the molecular basis of cell cycle progression in the model bacterium Caulobacter crescentus. At the heart of cell cycle regulation is a multicomponent transcriptional feedback loop, governing the production of successive regulatory waves or pulses of at least three master regulatory proteins. These oscillating master regulators direct the execution of phase-specific events and, importantly, through intrinsic genetic switches not only determine the length of a given phase, but also provide the driving force that catapults the cell into the next stage of the cell cycle. The genetic switches act as fail safe mechanisms that prevent the cell cycle from relapsing and thus govern the ordered production and the periodicity of these regulatory waves. Here, we detail how the master regulators CtrA, GcrA and DnaA coordinate cell cycle progression and polar development in Caulobacter. PMID:16547950

  5. Cell cycle control by oscillating regulatory proteins in Caulobacter crescentus.

    PubMed

    Holtzendorff, Julia; Reinhardt, Jens; Viollier, Patrick H

    2006-04-01

    Significant strides have been made in recent years towards understanding the molecular basis of cell cycle progression in the model bacterium Caulobacter crescentus. At the heart of cell cycle regulation is a multicomponent transcriptional feedback loop, governing the production of successive regulatory waves or pulses of at least three master regulatory proteins. These oscillating master regulators direct the execution of phase-specific events and, importantly, through intrinsic genetic switches not only determine the length of a given phase, but also provide the driving force that catapults the cell into the next stage of the cell cycle. The genetic switches act as fail safe mechanisms that prevent the cell cycle from relapsing and thus govern the ordered production and the periodicity of these regulatory waves. Here, we detail how the master regulators CtrA, GcrA and DnaA coordinate cell cycle progression and polar development in Caulobacter.

  6. 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

  7. 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.

  8. 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. PMID:27475848

  9. Capacity-cycle life behavior in secondary lithium cells

    NASA Technical Reports Server (NTRS)

    Somoano, R. B.; Carter, B. J.; Shen, D.; Yen, S. P. S.

    1985-01-01

    The practical utilization of high energy density rechargeable lithium cells is dependent upon maintaining high capacity for the duration of the required cycle life. However, a critical, yet generic problem with room temperature lithium systems is that the capacity often declines considerably during the early stages of cycling. The results of our studies are reported on electrolyte degradation which is observed after cells have undergone 300 and 700 deep cycles with 3-methylsulfolane- and 2-methyltetrahydrofuran-LiAsF6 electrolytes, respectively.

  10. Segmentation and classification of cell cycle phases in fluorescence imaging.

    PubMed

    Ersoy, Ilker; Bunyak, Filiz; Chagin, Vadim; Cardoso, M Christina; Palaniappan, Kannappan

    2009-01-01

    Current chemical biology methods for studying spatiotemporal correlation between biochemical networks and cell cycle phase progression in live-cells typically use fluorescence-based imaging of fusion proteins. Stable cell lines expressing fluorescently tagged protein GFP-PCNA produce rich, dynamically varying sub-cellular foci patterns characterizing the cell cycle phases, including the progress during the S-phase. Variable fluorescence patterns, drastic changes in SNR, shape and position changes and abundance of touching cells require sophisticated algorithms for reliable automatic segmentation and cell cycle classification. We extend the recently proposed graph partitioning active contours (GPAC) for fluorescence-based nucleus segmentation using regional density functions and dramatically improve its efficiency, making it scalable for high content microscopy imaging. We utilize surface shape properties of GFP-PCNA intensity field to obtain descriptors of foci patterns and perform automated cell cycle phase classification, and give quantitative performance by comparing our results to manually labeled data.

  11. Connecting the nucleolus to the cell cycle and human disease.

    PubMed

    Tsai, Robert Y L; Pederson, Thoru

    2014-08-01

    Long known as the center of ribosome synthesis, the nucleolus is connected to cell cycle regulation in more subtle ways. One is a surveillance system that reacts promptly when rRNA synthesis or processing is impaired, halting cell cycle progression. Conversely, the nucleolus also acts as a first-responder to growth-related stress signals. Here we review emerging concepts on how these "infraribosomal" links between the nucleolus and cell cycle progression operate in both forward and reverse gears. We offer perspectives on how new cancer therapeutic designs that target this infraribosomal mode of cell growth control may shape future clinical progress.

  12. 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…

  13. Different cell cycle modulation by celecoxib at different concentrations.

    PubMed

    Kim, Young-Mee; Pyo, Hongryull

    2013-03-01

    Abstract Different cyclooxygenase (COX)-2 inhibitors were known to cause different cell cycle changes. We investigated whether this different effect on cell cycle change was due to concentration-dependent effect. We investigated the effects of celecoxib, a COX-2 selective inhibitor, on cell cycle regulation in irradiated cancer cells that express high or low levels of COX-2. Four stably COX-2 knocked-down or overexpressed cell lines were treated with various concentrations of celecoxib with or without radiation. Celecoxib differentially modulated the cell cycle according to the concentrations applied. G1 arrest was induced at lower concentrations, whereas G2/M arrest was induced at higher concentrations in each cell line tested. Radiation-induced G2/M arrest was enhanced at lower concentrations but reduced at higher concentrations. The cutoff values to divide lower and higher concentrations were cell-type specific. Celecoxib treatment activated Cdc25C and inhibited p21 expression in both unirradiated and irradiated cells, regardless of COX-2 expression. Apoptosis was induced in irradiated cells 48 hours after treatment with celecoxib dependent of COX-2. These results imply that celecoxib deactivates the G2 checkpoint via both Cdc25C- and p21-dependent pathways in irradiated cells, which subsequently die by secondary apoptosis. Cell cycle modulating effects in irradiated cells resulting from treatment with celecoxib may have clinical importance with regard to the potential application of celecoxib in cancer patients undergoing radiotherapy. PMID:23268707

  14. 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.

  15. 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.

  16. 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.

  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. Landscape of Pin1 in the cell cycle

    PubMed Central

    Lin, Cheng-Han; Li, Hao-Yi; Lee, Yu-Cheng; Calkins, Marcus J; Lee, Kuen-Haur

    2015-01-01

    Pin1 is a peptidyl-prolyl isomerase which plays a critical role in many diseases including cancer and Alzheimer's disease. The essential role of Pin1 is to affect stability, localization or function of phosphoproteins by catalyzing structural changes. Among the collection of Pin1 substrates, many have been shown to be involved in regulating cell cycle progression. The cell cycle disorder caused by dysregulation of these substrates is believed to be a common phenomenon in cancer. A number of recent studies have revealed possible functions of several important Pin1-binding cell cycle regulators. Investigating the involvement of Pin1 in the cell cycle may assist in the development of future cancer therapeutics. In this review, we summarize current knowledge regarding the network of Pin1 substrates and Pin1 regulators in cell cycle progression. In G1/S progression, cyclin D1, RB, p53, p27, and cyclin E are all well-known cell cycle regulators that are modulated by Pin1. During G2/M transition, our lab has shown that Aurora A suppresses Pin1 activity through phosphorylation at Ser16 and cooperates with hBora to modulate G2/M transition. We conclude that Pin1 may be thought of as a molecular timer which modulates cell cycle progression networks. PMID:25662955

  19. Staphylococcal Enterotoxin O Exhibits Cell Cycle Modulating Activity

    PubMed Central

    Hodille, Elisabeth; Alekseeva, Ludmila; Berkova, Nadia; Serrier, Asma; Badiou, Cedric; Gilquin, Benoit; Brun, Virginie; Vandenesch, François; Terman, David S.; Lina, Gerard

    2016-01-01

    Maintenance of an intact epithelial barrier constitutes a pivotal defense mechanism against infections. Staphylococcus aureus is a versatile pathogen that produces multiple factors including exotoxins that promote tissue alterations. The aim of the present study is to investigate the cytopathic effect of staphylococcal exotoxins SEA, SEG, SEI, SElM, SElN and SElO on the cell cycle of various human cell lines. Among all tested exotoxins only SEIO inhibited the proliferation of a broad panel of human tumor cell lines in vitro. Evaluation of a LDH release and a DNA fragmentation of host cells exposed to SEIO revealed that the toxin does not induce necrosis or apoptosis. Analysis of the DNA content of tumor cells synchronized by serum starvation after exposure to SEIO showed G0/G1 cell cycle delay. The cell cycle modulating feature of SEIO was confirmed by the flow cytometry analysis of synchronized cells exposed to supernatants of isogenic S. aureus strains wherein only supernatant of the SElO producing strain induced G0/G1 phase delay. The results of yeast-two-hybrid analysis indicated that SEIO’s potential partner is cullin-3, involved in the transition from G1 to S phase. In conclusion, we provide evidence that SEIO inhibits cell proliferation without inducing cell death, by delaying host cell entry into the G0/G1 phase of the cell cycle. We speculate that this unique cell cycle modulating feature allows SEIO producing bacteria to gain advantage by arresting the cell cycle of target cells as part of a broader invasive strategy. PMID:27148168

  20. Redistribution of microtubules and pericentriolar material during the development of polarity in mouse blastomeres

    PubMed Central

    1987-01-01

    The distribution of microtubules and microtubule organizing centers (MTOCs) during the development of cell polarity in eight-cell mouse blastomeres was studied by immunofluorescence and immunoelectron microscopy using monoclonal anti-tubulin antibodies and an anti- pericentriolar material (PCM) serum. In early eight-cell blastomeres microtubules were found mainly around the nucleus and in the cell cortex, whereas PCM foci were observed dispersed in the cytoplasm. During the eight-cell stage, microtubules disappeared from the area adjacent to the zone of intercellular contact and accumulated in the apical part of the cell while their number decreased in the basal domain. The PCM also relocalized to the apical domain of the cell, but this occurred after the redistribution of the microtubules by a mechanism that involved the microtubule network. The possible roles of both MTOCs and microtubules in establishing cell polarity are discussed. PMID:3571331

  1. 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.

  2. Impact of the cell division cycle on gene circuits.

    PubMed

    Bierbaum, Veronika; Klumpp, Stefan

    2015-09-25

    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.

  3. 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

  4. Cell-Cycle Inhibition by Helicobacter pylori L-Asparaginase

    PubMed Central

    Scotti, Claudia; Sommi, Patrizia; Pasquetto, Maria Valentina; Cappelletti, Donata; Stivala, Simona; Mignosi, Paola; Savio, Monica; Chiarelli, Laurent Roberto; Valentini, Giovanna; Bolanos-Garcia, Victor M.; Merrell, Douglas Scott; Franchini, Silvia; Verona, Maria Luisa; Bolis, Cristina; Solcia, Enrico; Manca, Rachele; Franciotta, Diego; Casasco, Andrea; Filipazzi, Paola; Zardini, Elisabetta; Vannini, Vanio

    2010-01-01

    Helicobacter pylori (H. pylori) is a major human pathogen causing chronic gastritis, peptic ulcer, gastric cancer, and mucosa-associated lymphoid tissue lymphoma. One of the mechanisms whereby it induces damage depends on its interference with proliferation of host tissues. We here describe the discovery of a novel bacterial factor able to inhibit the cell-cycle of exposed cells, both of gastric and non-gastric origin. An integrated approach was adopted to isolate and characterise the molecule from the bacterial culture filtrate produced in a protein-free medium: size-exclusion chromatography, non-reducing gel electrophoresis, mass spectrometry, mutant analysis, recombinant protein expression and enzymatic assays. L-asparaginase was identified as the factor responsible for cell-cycle inhibition of fibroblasts and gastric cell lines. Its effect on cell-cycle was confirmed by inhibitors, a knockout strain and the action of recombinant L-asparaginase on cell lines. Interference with cell-cycle in vitro depended on cell genotype and was related to the expression levels of the concurrent enzyme asparagine synthetase. Bacterial subcellular distribution of L-asparaginase was also analysed along with its immunogenicity. H. pylori L-asparaginase is a novel antigen that functions as a cell-cycle inhibitor of fibroblasts and gastric cell lines. We give evidence supporting a role in the pathogenesis of H. pylori-related diseases and discuss its potential diagnostic application. PMID:21085483

  5. 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.

  6. Two cell cycle blocks caused by iron chelation of neuroblastoma cells: separating cell cycle events associated with each block

    PubMed Central

    Siriwardana, Gamini; Seligman, Paul A.

    2013-01-01

    Abstract Studies have presented evidence that besides the well described S phase block, treatment of cancer cell lines with the iron chelator deferrioxamine (DFO) also results in an earlier block in G1 phase. In this article, measurements of cell cycle regulatory proteins define this block at a very specific point in G1. DFO treatment results in markedly decreased cyclin A protein levels. Cyclin E levels that accumulate in early to mid‐G1 are increased in cells treated with DFO as compared to the resting cells. The DFO S phase block is shown after cells are arrested at G1/S by (aphidicolin) then released into DFO. The same S phase block occurs with DFO treatment of a neuroblastoma cell line relatively resistant to the G1 DFO block. These experiments clearly differentiate the S phase DFO block from the earlier block pinpointed to a point in mid‐G1, before G1/S when cyclin E protein increases but before increased cyclin A synthesis. Apoptosis was observed in cells inhibited by DFO at both cell cycle arrest points. PMID:24744856

  7. Two cell cycle blocks caused by iron chelation of neuroblastoma cells: separating cell cycle events associated with each block.

    PubMed

    Siriwardana, Gamini; Seligman, Paul A

    2013-12-01

    Studies have presented evidence that besides the well described S phase block, treatment of cancer cell lines with the iron chelator deferrioxamine (DFO) also results in an earlier block in G1 phase. In this article, measurements of cell cycle regulatory proteins define this block at a very specific point in G1. DFO treatment results in markedly decreased cyclin A protein levels. Cyclin E levels that accumulate in early to mid-G1 are increased in cells treated with DFO as compared to the resting cells. The DFO S phase block is shown after cells are arrested at G1/S by (aphidicolin) then released into DFO. The same S phase block occurs with DFO treatment of a neuroblastoma cell line relatively resistant to the G1 DFO block. These experiments clearly differentiate the S phase DFO block from the earlier block pinpointed to a point in mid-G1, before G1/S when cyclin E protein increases but before increased cyclin A synthesis. Apoptosis was observed in cells inhibited by DFO at both cell cycle arrest points.

  8. 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.

  9. 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

  10. Downregulation of Protein 4.1R, a Mature Centriole Protein, Disrupts Centrosomes, Alters Cell Cycle Progression, and Perturbs Mitotic Spindles and Anaphase▿

    PubMed Central

    Krauss, Sharon Wald; Spence, Jeffrey R.; Bahmanyar, Shirin; Barth, Angela I. M.; Go, Minjoung M.; Czerwinski, Debra; Meyer, Adam J.

    2008-01-01

    Centrosomes nucleate and organize interphase microtubules and are instrumental in mitotic bipolar spindle assembly, ensuring orderly cell cycle progression with accurate chromosome segregation. We report that the multifunctional structural protein 4.1R localizes at centrosomes to distal/subdistal regions of mature centrioles in a cell cycle-dependent pattern. Significantly, 4.1R-specific depletion mediated by RNA interference perturbs subdistal appendage proteins ninein and outer dense fiber 2/cenexin at mature centrosomes and concomitantly reduces interphase microtubule anchoring and organization. 4.1R depletion causes G1 accumulation in p53-proficient cells, similar to depletion of many other proteins that compromise centrosome integrity. In p53-deficient cells, 4.1R depletion delays S phase, but aberrant ninein distribution is not dependent on the S-phase delay. In 4.1R-depleted mitotic cells, efficient centrosome separation is reduced, resulting in monopolar spindle formation. Multipolar spindles and bipolar spindles with misaligned chromatin are also induced by 4.1R depletion. Notably, all types of defective spindles have mislocalized NuMA (nuclear mitotic apparatus protein), a 4.1R binding partner essential for spindle pole focusing. These disruptions contribute to lagging chromosomes and aberrant microtubule bridges during anaphase/telophase. Our data provide functional evidence that 4.1R makes crucial contributions to the structural integrity of centrosomes and mitotic spindles which normally enable mitosis and anaphase to proceed with the coordinated precision required to avoid pathological events. PMID:18212055

  11. 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.

  12. Molecular markers and cell cycle inhibitors show the importance of cell cycle progression in nematode-induced galls and syncytia.

    PubMed Central

    de Almeida Engler, J; De Vleesschauwer, V; Burssens, S; Celenza, J L; Inzé, D; Van Montagu, M; Engler, G; Gheysen, G

    1999-01-01

    Root knot and cyst nematodes induce large multinucleated cells, designated giant cells and syncytia, respectively, in plant roots. We have used molecular markers to study cell cycle progression in these specialized feeding cells. In situ hybridization with two cyclin-dependent kinases and two cyclins showed that these genes were induced very early in galls and syncytia and that the feeding cells progressed through the G2 phase. By using cell cycle blockers, DNA synthesis and progression through the G2 phase, or mitosis, were shown to be essential for gall and syncytium establishment. When mitosis was blocked, further gall development was arrested. This result demonstrates that cycles of endoreduplication or other methods of DNA amplification are insufficient to drive giant cell expansion. On the other hand, syncytium development was much less affected by a mitotic block; however, syncytium expansion was inhibited. PMID:10330466

  13. 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.

  14. Manganese Superoxide Dismutase Regulates a Redox Cycle Within the Cell Cycle

    PubMed Central

    Sarsour, Ehab H.; Kalen, Amanda L.

    2014-01-01

    Abstract Significance: Manganese superoxide dismutase (MnSOD) is a nuclear-encoded and mitochondria-matrix-localized oxidation-reduction (redox) enzyme that regulates cellular redox homeostasis. Cellular redox processes are known to regulate proliferative and quiescent growth states. Therefore, MnSOD and mitochondria-generated reactive oxygen species (ROS) are believed to be critical regulators of quiescent cells' entry into the cell cycle and exit from the proliferative cycle back to the quiescent state. Recent Advances/Critical Issues: Recent evidence suggests that the intracellular redox environment fluctuates during the cell cycle, shifting toward a more oxidized status during mitosis. MnSOD activity is higher in G0/G1 cells compared with S, G2 and M phases. After cell division, MnSOD activity increases in the G1 phase of the daughter generation. The periodic fluctuation in MnSOD activity during the cell cycle inversely correlates with cellular superoxide levels as well as glucose and oxygen consumption. Based on an inverse correlation between MnSOD activity and glucose consumption during the cell cycle, it is proposed that MnSOD is a central molecular player for the “Warburg effect.” Future Directions: In general, loss of MnSOD activity results in aberrant proliferation. A better understanding of the MnSOD and mitochondrial ROS-dependent cell cycle processes may lead to novel approaches to overcome aberrant proliferation. Since ROS have both deleterious (pathological) and beneficial (physiological) effects, it is proposed that “eustress” should be used when discussing ROS processes that regulate normal physiological functions, while “oxidative stress” should be used to discuss the deleterious effects of ROS. Antioxid. Redox Signal. 20, 1618–1627. PMID:23590434

  15. 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.

  16. 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.

  17. 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.

  18. Modeling the cell division cycle: cdc2 and cyclin interactions.

    PubMed Central

    Tyson, J J

    1991-01-01

    The proteins cdc2 and cyclin form a heterodimer (maturation promoting factor) that controls the major events of the cell cycle. A mathematical model for the interactions of cdc2 and cyclin is constructed. Simulation and analysis of the model show that the control system can operate in three modes: as a steady state with high maturation promoting factor activity, as a spontaneous oscillator, or as an excitable switch. We associate the steady state with metaphase arrest in unfertilized eggs, the spontaneous oscillations with rapid division cycles in early embryos, and the excitable switch with growth-controlled division cycles typical of nonembryonic cells. PMID:1831270

  19. p53 and Cell Cycle Effects After DNA Damage

    PubMed Central

    Senturk, Emir; Manfredi, James J.

    2016-01-01

    Flow cytometry, a valuable technique that employs the principles of light scattering, light excitation, and emission of fluorochrome molecules, can be used to assess the cell cycle position of individual cells based on DNA content. After the permeabilization of cells, the DNA can be stained with a fluorescent dye. Cells which have a 2N amount of DNA can be distinguished from cells with a 4N amount of DNA, making flow cytometry a very useful tool for the analysis of cell cycle checkpoints following DNA damage. A critical feature of the cellular response to DNA damage is the ability to pause and repair the damage so that consequential mutations are not passed along to daughter generations of cells. If cells arrest prior to DNA replication, they will contain a 2N amount of DNA, whereas arrest after replication but before mitosis will result in a 4N amount of DNA. Using this technique, the role that p53 plays in cell cycle checkpoints following DNA damage can be evaluated based on changes in the profile of the G1, S, and G2/M phases of the cell cycle. PMID:23150436

  20. NUTRIENT REGULATION OF CELL CYCLE PROGRESSION

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Cell replication is tightly controlled in normal tissues and aberrant during disease progression, such as in tumorigenesis. The replication of cells can be divided into four distinct phases: Gap 1 (G1), synthesis (S), gap 2 (G2), and mitosis (M). The progression from one phase to the next is intrica...

  1. Targeting the cancer cell cycle by cold atmospheric plasma

    NASA Astrophysics Data System (ADS)

    Volotskova, O.; Hawley, T. S.; Stepp, M. A.; Keidar, M.

    2012-09-01

    Cold atmospheric plasma (CAP), a technology based on quasi-neutral ionized gas at low temperatures, is currently being evaluated as a new highly selective alternative addition to existing cancer therapies. Here, we present a first attempt to identify the mechanism of CAP action. CAP induced a robust ~2-fold G2/M increase in two different types of cancer cells with different degrees of tumorigenicity. We hypothesize that the increased sensitivity of cancer cells to CAP treatment is caused by differences in the distribution of cancer cells and normal cells within the cell cycle. The expression of γH2A.X (pSer139), an oxidative stress reporter indicating S-phase damage, is enhanced specifically within CAP treated cells in the S phase of the cell cycle. Together with a significant decrease in EdU-incorporation after CAP, these data suggest that tumorigenic cancer cells are more susceptible to CAP treatment.

  2. The Timing of T Cell Priming and Cycling.

    PubMed

    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

  3. Interplay between flagellation and cell cycle control in Caulobacter.

    PubMed

    Ardissone, Silvia; Viollier, Patrick H

    2015-12-01

    The assembly of the flagellum, a sophisticated nanomachine powering bacterial locomotion in liquids and across surfaces, is highly regulated. In the synchronizable α-Proteobacterium Caulobacter crescentus, the flagellum is built at a pre-selected cell pole and flagellar transcript abundance oscillates during the cell cycle. Conserved regulators not only dictate when the transcripts encoding flagellar structural proteins peak, but also those encoding polarization factors. Additionally, post-transcriptional cell cycle cues facilitate flagellar (dis-)assembly at the new cell pole. Because of this regulatory complexity and the power of bacterial genetics, motility is a suitable and simple proxy for dissecting how bacteria implement cell cycle progression and polarity, while also providing clues on how bacteria might decide when and where to display other surface structures. PMID:26476805

  4. 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.

  5. 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

  6. 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).

  7. 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

  8. How the cell cycle impacts chromatin architecture and influences cell fate

    PubMed Central

    Ma, Yiqin; Kanakousaki, Kiriaki; Buttitta, Laura

    2015-01-01

    Since the earliest observations of cells undergoing mitosis, it has been clear that there is an intimate relationship between the cell cycle and nuclear chromatin architecture. The nuclear envelope and chromatin undergo robust assembly and disassembly during the cell cycle, and transcriptional and post-transcriptional regulation of histone biogenesis and chromatin modification is controlled in a cell cycle-dependent manner. Chromatin binding proteins and chromatin modifications in turn influence the expression of critical cell cycle regulators, the accessibility of origins for DNA replication, DNA repair, and cell fate. In this review we aim to provide an integrated discussion of how the cell cycle machinery impacts nuclear architecture and vice-versa. We highlight recent advances in understanding cell cycle-dependent histone biogenesis and histone modification deposition, how cell cycle regulators control histone modifier activities, the contribution of chromatin modifications to origin firing for DNA replication, and newly identified roles for nucleoporins in regulating cell cycle gene expression, gene expression memory and differentiation. We close with a discussion of how cell cycle status may impact chromatin to influence cell fate decisions, under normal contexts of differentiation as well as in instances of cell fate reprogramming. PMID:25691891

  9. 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. PMID:27020776

  10. 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

  11. 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.

  12. Cell cycle arrest is not yet senescence, which is not just cell cycle arrest: terminology for TOR-driven aging.

    PubMed

    Blagosklonny, Mikhail V

    2012-03-01

    Cell cycle arrest is not yet senescence. When the cell cycle is arrested, an inappropriate growth-promotion converts an arrest into senescence (geroconversion). By inhibiting the growth-promoting mTOR pathway, rapamycin decelerates geroconversion of the arrested cells. And as a striking example, while causing arrest, p53 may decelerate or suppress geroconversion (in some conditions). Here I discuss the meaning of geroconversion and also the terms gerogenes, gerossuppressors, gerosuppressants, gerogenic pathways, gero-promoters, hyperfunction and feedback resistance, regenerative potential, hypertrophy and secondary atrophy, pro-gerogenic and gerogenic cells. PMID:22394614

  13. 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

  14. The architectural organization of human stem cell cycle regulatory machinery.

    PubMed

    Stein, Gary S; Stein, Janet L; van J Wijnen, Andre; Lian, Jane B; Montecino, Martin; Medina, Ricardo; Kapinas, Kristie; Ghule, Prachi; Grandy, Rodrigo; Zaidi, Sayyed K; Becker, Klaus A

    2012-01-01

    Two striking features of human embryonic stem cells that support biological activity are an abbreviated cell cycle and reduced complexity to nuclear organization. The potential implications for rapid proliferation of human embryonic stem cells within the context of sustaining pluripotency, suppressing phenotypic gene expression and linkage to simplicity in the architectural compartmentalization of regulatory machinery in nuclear microenvironments is explored. Characterization of the molecular and architectural commitment steps that license human embryonic stem cells to initiate histone gene expression is providing understanding of the principal regulatory mechanisms that control the G1/S phase transition in primitive pluripotent cells. From both fundamental regulatory and clinical perspectives, further understanding of the pluripotent cell cycle in relation to compartmentalization of regulatory machinery in nuclear microenvironments is relevant to applications of stem cells for regenerative medicine and new dimensions to therapy where traditional drug discovery strategies have been minimally effective.

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

    PubMed

    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

    2015-09-01

    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.

  16. Molecular mechanisms creating bistable switches at cell cycle transitions

    PubMed Central

    Verdugo, Anael; Vinod, P. K.; Tyson, John J.; Novak, Bela

    2013-01-01

    Progression through the eukaryotic cell cycle is characterized by specific transitions, where cells move irreversibly from stage i−1 of the cycle into stage i. These irreversible cell cycle transitions are regulated by underlying bistable switches, which share some common features. An inhibitory protein stalls progression, and an activatory protein promotes progression. The inhibitor and activator are locked in a double-negative feedback loop, creating a one-way toggle switch that guarantees an irreversible commitment to move forward through the cell cycle, and it opposes regression from stage i to stage i−1. In many cases, the activator is an enzyme that modifies the inhibitor in multiple steps, whereas the hypo-modified inhibitor binds strongly to the activator and resists its enzymatic activity. These interactions are the basis of a reaction motif that provides a simple and generic account of many characteristic properties of cell cycle transitions. To demonstrate this assertion, we apply the motif in detail to the G1/S transition in budding yeast and to the mitotic checkpoint in mammalian cells. Variations of the motif might support irreversible cellular decision-making in other contexts. PMID:23486222

  17. 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.

  18. Downregulation of cell cycle-related proteins in ovarian cancer line and cell cycle arrest induced by microRNA

    PubMed Central

    Yuan, Jian-Mei; Shi, Xue-Jun; Sun, Ping; Liu, Jun-Xia; Wang, Wei; Li, Ming; Ling, Feng-Yu

    2015-01-01

    Objective: The effect of miR-449 and miR-34 on the growth, cell cycle and target gene expressions of ovarian cancer cell line SKOV3 and SKOV3-ipl was discussed. Method: Real-time quantitative reverse transcription PCR was employed to detect the expressions of miR-449a/b and miR-34b, c in SKOV3 and SKOV3-ipl cells. The two miRNAs were successfully expressed in SKOV3-ipl cells by transfection. The variations in cell growth rate and cell cycle were determined by MTS assay and flow cytometry, respectively. The expressions of cell cycle-related proteins were detected by Western Blot. Results: miR-449b and miR-34c induced the decline of the adhesiveness of SKOV3-ipl cells by 20%-30%. The number of cells arrested in G1-phase increased and the number of cells arrested in S-phase decreased significantly. The cell cycle-related proteins CDK6 and CDC254 were downregulated. miR-449b caused the expression of CDK6 and CDC25A to decrease. After the co-transfection with miR-449b and miR-34c, the relevant proteins were downregulated more significantly. The expressions of CDK6, CDC25A and cyclin A were decreased significantly. Conclusion: miR-449b and miR-34c can induce cell cycle arrest in SKOV3-ipl cells and the downregulation of CDK6, CDC25A and cyclin A. PMID:26770455

  19. Redox Control of the Cell Cycle in Health and Disease

    PubMed Central

    Sarsour, Ehab H.; Kumar, Maneesh G.; Chaudhuri, Leena; Kalen, Amanda L.

    2009-01-01

    Abstract The cellular oxidation and reduction (redox) environment is influenced by the production and removal of reactive oxygen species (ROS). In recent years, several reports support the hypothesis that cellular ROS levels could function as “second messengers” regulating numerous cellular processes, including proliferation. Periodic oscillations in the cellular redox environment, a redox cycle, regulate cell-cycle progression from quiescence (G0) to proliferation (G1, S, G2, and M) and back to quiescence. A loss in the redox control of the cell cycle could lead to aberrant proliferation, a hallmark of various human pathologies. This review discusses the literature that supports the concept of a redox cycle controlling the mammalian cell cycle, with an emphasis on how this control relates to proliferative disorders including cancer, wound healing, fibrosis, cardiovascular diseases, diabetes, and neurodegenerative diseases. We hypothesize that reestablishing the redox control of the cell cycle by manipulating the cellular redox environment could improve many aspects of the proliferative disorders. Antioxid. Redox Signal. 11, 2985–3011. PMID:19505186

  20. 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.

  1. Regulation of the Cell Division Cycle in Trypanosoma brucei

    PubMed Central

    2012-01-01

    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 G1/S transition, G2/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. PMID:22865501

  2. Cell cycle regulation of human WEE1.

    PubMed Central

    McGowan, C H; Russell, P

    1995-01-01

    WEE1 kinase negatively regulates entry into mitosis by catalyzing the inhibitory tyrosine phosphorylation of CDC2/cyclin B kinase. We report here an investigation of human WEE1. Endogenous WEE1 migrates as an approximately 94 kDa protein in SDS-PAGE, substantially larger than the 49 kDa protein encoded by the original human WEE1 cDNA clone that was truncated at the 5'-end. Antibody depletion experiments demonstrate that WEE1 accounts for most of the activity that phosphorylates CDC2 on Tyr15 in an in vitro assay of HeLa cell lysates, hence it is likely to have an important role in the mitotic control of human cells. WEE1 activity was not found to be elevated in HeLa cells arrested in S phase, suggesting that unreplicated DNA does not delay M phase by hyperactivating WEE1. WEE1 activity is strongly suppressed during M phase, suggesting that negative regulation of WEE1 could be part of the mechanism by which activation of CDC2/cyclin B kinase is promoted during the G2/M transition. M phase WEE1 is re-activated in samples prepared in the absence of protein phosphatase inhibitors, demonstrating that WEE1 is inhibited by a mechanism that requires protein phosphorylation. Images PMID:7774574

  3. 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.

  4. Ionizing radiation and cell cycle progression in ataxia telangiectasia

    SciTech Connect

    Beamish, H.; Khanna, K.K.; Lavin, M.F.

    1994-04-01

    Exposure of mammalian cells to ionizing radiation causes delay in normal progress through the cell cycle at a number of different checkpoints. Abnormalities in these checkpoints have been described for ataxia telangiectasia cells after irradiation. In this report we show that these abnormalities occur at different phases in the cell cycle in several ataxia telangiectasia lymphoblastoid cells. Ataxia telangiectasia cells, synchronized in late G{sub 1} phase with either mimosine or aphidicolin and exposed to radiation, showed a reduced delay in entering S phase compared to irradiated control cells. Failure to exhibit G{sub 1}-phase delay in ataxia telangiectasia cells is accompanied by a reduced ability of radiation to activate the product of the tumor suppressor gene p53, a protein involved in G{sub 1}/S-phase delay. When the progress of irradiated G{sub 1}-phase cells was followed into the subsequent G{sub 2} and G{sub 1} phases ataxia telangiectasia cells showed a more pronounced accumulation in G{sub 2} phase than control cells. When cells were irradiated in S phase and extent of delay was more evident in G{sub 2} phase and ataxia telangiectasia cells were delayed to a greater extent. These results suggest that the lack of initial delay in both G{sub 1} and S phases to the radiosensitivity observed in this syndrome. 26 refs., 3 figs., 2 tabs.

  5. 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

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

    PubMed Central

    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. PMID:26125600

  7. 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.

  8. 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.

  9. 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. PMID:1030938

  10. 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.

  11. 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.

  12. 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.

  13. 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

  14. 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.

  15. 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.

  16. WWP2 is required for normal cell cycle progression.

    PubMed

    Choi, Byeong Hyeok; Che, Xun; Chen, Changyan; Lu, Luo; Dai, Wei

    2015-09-01

    WWP2 is a ubiquitin E3 ligase belonging to the Nedd4-like family. Given that WWP2 target proteins including PTEN that are crucial for regulating cell proliferation or suppressing tumorigenesis, we have asked whether WWP2 plays a role in controlling cell cycle progression. Here we report that WWP2 is necessary for normal cell cycle progression as its silencing significantly reduces the cell proliferation rate. We have identified that an isoform of WWP2 (WWP2-V4) is highly expressed in the M phase of the cell cycle. Silencing of WWP2 accelerates the turnover of cyclin E, which is accompanied by increased levels of phospho-histone H3 (p-H3) and cyclin B. Moreover, silencing of WWP2 results in compromised phosphorylation of Akt(S473), a residue whose phosphorylation is tightly associated with the activation of the kinase. Combined, these results strongly suggest that WWP2 is an important component in regulating the Akt signaling cascade, as well as cell cycle progression. PMID:26622940

  17. WWP2 is required for normal cell cycle progression

    PubMed Central

    Choi, Byeong Hyeok; Che, Xun; Chen, Changyan; Lu, Luo; Dai, Wei

    2015-01-01

    WWP2 is a ubiquitin E3 ligase belonging to the Nedd4-like family. Given that WWP2 target proteins including PTEN that are crucial for regulating cell proliferation or suppressing tumorigenesis, we have asked whether WWP2 plays a role in controlling cell cycle progression. Here we report that WWP2 is necessary for normal cell cycle progression as its silencing significantly reduces the cell proliferation rate. We have identified that an isoform of WWP2 (WWP2-V4) is highly expressed in the M phase of the cell cycle. Silencing of WWP2 accelerates the turnover of cyclin E, which is accompanied by increased levels of phospho-histone H3 (p-H3) and cyclin B. Moreover, silencing of WWP2 results in compromised phosphorylation of AktS473, a residue whose phosphorylation is tightly associated with the activation of the kinase. Combined, these results strongly suggest that WWP2 is an important component in regulating the Akt signaling cascade, as well as cell cycle progression. PMID:26622940

  18. Human Fucci Pancreatic Beta Cell Lines: New Tools to Study Beta Cell Cycle and Terminal Differentiation

    PubMed Central

    Carlier, Géraldine; Maugein, Alicia; Cordier, Corinne; Pechberty, Séverine; Garfa-Traoré, Meriem; Martin, Patrick; Scharfmann, Raphaël; Albagli, Olivier

    2014-01-01

    Regulation of cell cycle in beta cells is poorly understood, especially in humans. We exploited here the recently described human pancreatic beta cell line EndoC-βH2 to set up experimental systems for cell cycle studies. We derived 2 populations from EndoC-βH2 cells that stably harbor the 2 genes encoding the Fucci fluorescent indicators of cell cycle, either from two vectors, or from a unique bicistronic vector. In proliferating non-synchronized cells, the 2 Fucci indicators revealed cells in the expected phases of cell cycle, with orange and green cells being in G1 and S/G2/M cells, respectively, and allowed the sorting of cells in different substeps of G1. The Fucci indicators also faithfully red out alterations in human beta cell proliferative activity since a mitogen-rich medium decreased the proportion of orange cells and inflated the green population, while reciprocal changes were observed when cells were induced to cease proliferation and increased expression of some beta cell genes. In the last situation, acquisition of a more differentiated beta cell phenotype correlates with an increased intensity in orange fluorescence. Hence Fucci beta cell lines provide new tools to address important questions regarding human beta cell cycle and differentiation. PMID:25259951

  19. 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

  20. Does prolonged cycling of moderate intensity affect immune cell function?

    PubMed Central

    Scharhag, J; Meyer, T; Gabriel, H; Schlick, B; Faude, O; Kindermann, W; Shephard, R

    2005-01-01

    Background: Prolonged exercise may induce temporary immunosuppression with a presumed increased susceptibility for infection. However, there are only few data on immune cell function after prolonged cycling at moderate intensities typical for road cycling training sessions. Methods: The present study examined the influence on immune cell function of 4 h of cycling at a constant intensity of 70% of the individual anaerobic threshold. Interleukin-6 (IL-6) and C-reactive protein (CRP), leukocyte and lymphocyte populations, activities of natural killer (NK), neutrophils, and monocytes were examined before and after exercise, and also on a control day without exercise. Results: Cycling for 4 h induced a moderate acute phase response with increases in IL-6 from 1.0 (SD 0.5) before to 9.6 (5.6) pg/ml 1 h after exercise and CRP from 0.5 (SD 0.4) before to 1.8 (1.3) mg/l 1 day after exercise. Although absolute numbers of circulating NK cells, monocytes, and neutrophils increased during exercise, on a per cell basis NK cell activity, neutrophil and monocyte phagocytosis, and monocyte oxidative burst did not significantly change after exercise. However, a minor effect over time for neutrophil oxidative burst was noted, tending to decrease after exercise. Conclusions: Prolonged cycling at moderate intensities does not seem to seriously alter the function of cells of the first line of defence. Therefore, the influence of a single typical road cycling training session on the immune system is only moderate and appears to be safe from an immunological point of view. PMID:15728699

  1. 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.

  2. Multistage carcinogenesis modeling including cell cycle and DNA damage states

    NASA Astrophysics Data System (ADS)

    Hazelton, W.; Moolgavkar, S.

    The multistage clonal expansion model of carcinogenesis is generalized to include cell cycle states and corresponding DNA damage states with imperfect repair for normal and initiated stem cells. Initiated cells may undergo transformation to a malignant state, eventually leading to cancer incidence or death. The model allows oxidative or radiation induced DNA damage, checkpoint delay, DNA repair, apoptosis, and transformation rates to depend on the cell cycle state or DNA damage state of normal and initiated cells. A probability generating function approach is used to represent the time dependent probability distribution for cells in all states. The continuous time coupled Markov system representing this joint distribution satisfies a partial differential equation (pde). Time dependent survival and hazard functions are found through numerical solution of the characteristic equations for the pde. Although the hazard and survival can be calculated numerically, number and size distributions of pre-malignant lesions from models that are developed will be approximated through simulation. We use the model to explore predictions for hazard and survival as parameters representing cell cycle regulation and arrest are modified. Modification of these parameters may influence rates for cell division, apoptosis and malignant transformation that are important in carcinogenesis. We also explore enhanced repair that may be important for low-dose hypersensitivity and adaptive response, and degradation of repair processes or loss of checkpoint control that may drive genetic instability.

  3. 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.

  4. 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

  5. Cyclin G2 is a centrosome-associated nucleocytoplasmic shuttling protein that influences microtubule stability and induces a p53-dependent cell cycle arrest

    SciTech Connect

    Arachchige Don, Aruni S.; Dallapiazza, Robert F.; Bennin, David A.; Brake, Tiffany; Cowan, Colleen E.; Horne, Mary C. . E-mail: mary-horne@uiowa.edu

    2006-12-10

    , the mature centriole present at microtubule foci, indicates that cyclin G2 resides primarily on the mother centriole. Copurification of cyclin G2 and PP2A subunits with microtubules and centrosomes, together with the effects of ectopic cyclin G2 on cell cycle progression, nuclear morphology and microtubule growth and stability, suggests that cyclin G2 may modulate the cell cycle and cellular division processes through modulation of PP2A and centrosomal associated activities.

  6. 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

  7. Protection of renal cells from cisplatin toxicity by cell cycle inhibitors.

    PubMed

    Price, Peter M; Safirstein, Robert L; Megyesi, Judit

    2004-02-01

    The optimal use of cisplatin as a chemotherapeutic drug has been limited by its nephrotoxicity. Murine models have been used to study cisplatin-induced acute renal failure. After cisplatin administration, cells of the S3 segment in the renal proximal tubule are especially sensitive and undergo extensive necrosis in vivo. Similarly, cultured proximal tubule cells undergo apoptosis in vitro after cisplatin exposure. We have shown in vivo that kidney cells enter the cell cycle after cisplatin administration but that cell cycle-inhibitory proteins p21 and 14-3-3sigma are also upregulated. These proteins coordinate the cell cycle, and deletion of either of the genes resulted in increased nephrotoxicity in vivo or increased cell death in vitro after exposure to cisplatin. However, it was not known whether cell cycle inhibition before acute renal failure could protect from cisplatin-induced cell death, especially in cells with functional p21 and 14-3-3sigma genes. Using several cell cycle inhibitors, including a p21 adenovirus, and the drugs roscovitine and olomoucine, we have been able to completely protect a mouse kidney proximal tubule cell culture from cisplatin-induced apoptosis. The protection by p21 was independent of an effect on the cell cycle and was likely caused by selective inhibition of caspase-dependent and -independent cell death pathways in the cells.

  8. Arginine starvation in colorectal carcinoma cells: Sensing, impact on translation control and cell cycle distribution.

    PubMed

    Vynnytska-Myronovska, Bozhena O; Kurlishchuk, Yuliya; Chen, Oleh; Bobak, Yaroslav; Dittfeld, Claudia; Hüther, Melanie; Kunz-Schughart, Leoni A; Stasyk, Oleh V

    2016-02-01

    Tumor cells rely on a continued exogenous nutrient supply in order to maintain a high proliferative activity. Although a strong dependence of some tumor types on exogenous arginine sources has been reported, the mechanisms of arginine sensing by tumor cells and the impact of changes in arginine availability on translation and cell cycle regulation are not fully understood. The results presented herein state that human colorectal carcinoma cells rapidly exhaust the internal arginine sources in the absence of exogenous arginine and repress global translation by activation of the GCN2-mediated pathway and inhibition of mTOR signaling. Tumor suppressor protein p53 activation and G1/G0 cell cycle arrest support cell survival upon prolonged arginine starvation. Cells with the mutant or deleted TP53 fail to stop cell cycle progression at defined cell cycle checkpoints which appears to be associated with reduced recovery after durable metabolic stress triggered by arginine withdrawal.

  9. Association between microtubules and Golgi vesicles isolated from rat parotid glands.

    PubMed

    Coffe, G; Raymond, M N

    1990-01-01

    We report an isolation procedure of trans-Golgi vesicles (GVs) from rat parotid glands. Various organelle markers were used, particularly galactosyl transferase as a trans-Golgi marker, to test the purity of the GV fraction. A quantitative in vitro binding assay between microtubules and GVs is described. The vesicles were incubated with taxol-induced microtubules, layered between 50% and 43% sucrose cushions and subjected to centrifugation. Unlike free microtubules which were sedimented, the GV-bound microtubules co-migrated upward with GVs. Quantification of these bound microtubules was carried out by densitometric scanning of Coomassie blue-stained gels. The association between microtubules and GVs followed a saturation curve, with a plateau value of 20 micrograms of microtubule protein bound to 500 micrograms of GV fraction. The half-saturation of the GV sites was obtained with a microtubule concentration of 20 micrograms/ml. Electron microscopy of negatively stained re-floated material showed numerous microtubule-vesicle complexes. Coating of microtubules with an excess of brain microtubule-associated proteins (MAPs) abolished binding. In the absence of exogenous microtubules, we showed that the GV fraction was already interacting with a class of endogenous rat parotid microtubules. This class of colcemid and cold-stable microtubules represents 10-20% of the total tubulin content of the parotid cell. PMID:1983303

  10. The complex dynamic network of microtubule and microfilament cytasters of the leech zygote.

    PubMed

    Cantillana, V; Urrutia, M; Ubilla, A; Fernández, J

    2000-12-01

    The organization of the cytoskeleton in the early first interphase zygote and its involvement in organelle redistribution were studied in the glossiphoniid leech Theromyzon trizonare by confocal and electron microscopy, immunofluorescence, and time-lapse video imaging after microinjection of labeled tubulin and/or actin and loading with a mitotracker. The cytoskeleton consists of an inner or endoplasmic and an outer or ectoplasmic domain. The inner domain consists of a monaster whose fibers retract from the zygote periphery by the end of the early first interphase. The outer domain is built upon a network of microtubules and microfilaments cytasters. Short pulses of microinjected labeled actin or tubulin and Taxol treatment demonstrate that cytasters are centers of microtubule and microfilament nucleation. Immunostaining with anti-centrophilin, anti-BX-63, and anti-AH-6 indicates that the network of cytasters includes centrosomal antigens. Cytasters move in an orderly fashion at speeds of 0.5-2 micrometer/min, in an energy-dependent process retarded and finally blocked by the ATP analogue AMP-PNP and high concentrations of Taxol. Colliding cytasters fuse and form larger cytoskeletal nucleation centers. The leech zygote is a highly compartmentalized cell whose cytasters function as articulated components of a very dynamic cytoskeletal system engaged in bulk transportation of organelles during ooplasmic segregation. PMID:11087633

  11. Lithium/disulfide cells capable of long cycle life

    SciTech Connect

    Kaun, T.D.; Holifield, T.F.; DeLuca, W.H.

    1988-01-01

    The lithium-alloy/disulfide cell has undergone improvements to provide a very stable, high performance upper-plateau (UP) FeS/sub 2/ electrode. Prismatic UP FeS/sub 2/ cell tests (12--24 Ah capacity) with a LiCl-LiBr-KBr eutectic electrolyte have demonstrated 1000 deep discharge cycles at 400/degree/C with less than a 20% drop in capacity and without reduced power capability. Previous lithium-alloy/disulfide cells, which were based on a two voltage-plateau FeS/sub 2/ electrode and LiCl-KCl eutectic electrolyte had a life expectancy of only 100 cycles. Both time- and cycle-related capacity loss mechanisms have been eliminated with the improved cell design. In addition, new cell design features of overcharge tolerance and overdischarge safeguarding enhance battery durability. The performance prospects of a Li-alloy/UP FeS/sub 2/ battery for an IDSEP van application are discussed. A specific energy of 150 Wh/kg for this battery after 1000 cycles of operation is projected. 8 refs., 5 figs., 1 tab.

  12. Lithium/disulfide cells capable of long cycle life

    NASA Astrophysics Data System (ADS)

    Kaun, T. D.; Holifield, T. F.; Deluca, W. H.

    The lithium-alloy/disulfide cell has undergone improvements to provide a very stable, high performance Upper-Plateau (UP) FeS2 electrode. Prismatic UP FeS2 cell tests (12 to 24 Ah capacity) with a LiCl-LiBr-KBr eutectic electrolyte have demonstrated 1000 deep discharge cycles at 400 C with less than a 20 percent drop in capacity and without reduced power capability. Previous lithium-alloy/disulfide cells, which were based on a two voltage-plateau FeS2 electrode and LiCl-KCl eutectic electrolyte had a life expectancy of only 100 cycles. Both time- and cycle-related capacity loss mechanisms have been eliminated with the improved cell design. In addition, new cell design features of overcharge tolerance and overdischarge safeguarding enhance battery durability. The performance prospects of a Li-alloy/UP FeS2 battery for an IDSEP van application are discussed. A specific energy of 150 Wh/kg for this battery after 1000 cycles of operation is projected.

  13. 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.

  14. [Dynamics of the cell cycle in human endothelial cell culture infected with influenza virus].

    PubMed

    Prochukhanova, A R; Lyublinskaya, O G; Azarenok, A A; Nazarova, A V; Zenin, V V; Zhilinskaya, I N

    2015-01-01

    Cell cycle in a culture of endothelial cells EAhy 926 infected with influenza virus was investigated. Cytometric analysis of culture, synchronized using contact inhibition, has shown that the exposure to the influenza virus in cells EAhy 926 lengthened S-phase of the cell cycle. This result has been tested and proven on culture EAhy 926 treated with nocodazole. Compared with lung carcinoma cells A549, in which influenza virus provokes the arrest of G0/G1 phase of the cycle, elongation of S-phase of cycle at a similar infection of endothelial culture EAhy 926 indicates that the influenza virus differently affects the dynamics of the cell cycle according to the origin of the infected culture.

  15. Cell cycle control of DNA joint molecule resolution.

    PubMed

    Wild, Philipp; Matos, Joao

    2016-06-01

    The establishment of stable interactions between chromosomes underpins vital cellular processes such as recombinational DNA repair and bipolar chromosome segregation. On the other hand, timely disengagement of persistent connections is necessary to assure efficient partitioning of the replicated genome prior to cell division. Whereas great progress has been made in defining how cohesin-mediated chromosomal interactions are disengaged as cells prepare to undergo chromosome segregation, little is known about the metabolism of DNA joint molecules (JMs), generated during the repair of chromosomal lesions. Recent work on Mus81 and Yen1/GEN1, two conserved structure-selective endonucleases, revealed unforeseen links between JM-processing and cell cycle progression. Cell cycle kinases and phosphatases control Mus81 and Yen1/GEN1 to restrain deleterious JM-processing during S-phase, while safeguarding chromosome segregation during mitosis.

  16. 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.

  17. 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.

  18. 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.

  19. Thrombospondin-1 signaling through CD47 inhibits cell cycle progression and induces senescence in endothelial cells

    PubMed Central

    Gao, Qi; Chen, Kexin; Gao, Lu; Zheng, Yang; Yang, Yong-Guang

    2016-01-01

    CD47 signaling in endothelial cells has been shown to suppress angiogenesis, but little is known about the link between CD47 and endothelial senescence. Herein, we demonstrate that the thrombospondin-1 (TSP1)-CD47 signaling pathway is a major mechanism for driving endothelial cell senescence. CD47 deficiency in endothelial cells significantly improved their angiogenic function and attenuated their replicative senescence. Lack of CD47 also suppresses activation of cell cycle inhibitors and upregulates the expression of cell cycle promoters, leading to increased cell cycle progression. Furthermore, TSP1 significantly accelerates replicative senescence and associated cell cycle arrest in a CD47-dependent manner. These findings demonstrate that TSP1-CD47 signaling is an important mechanism driving endothelial cell senescence. Thus, TSP1 and CD47 provide attractive molecular targets for treatment of aging-associated cardiovascular dysfunction and diseases involving endothelial dysregulation. PMID:27607583

  20. Cell Cycle Control by a Minimal Cdk Network

    PubMed Central

    Gérard, Claude; Tyson, John J.; Coudreuse, Damien; Novák, Béla

    2015-01-01

    In present-day eukaryotes, the cell division cycle is controlled by a complex network of interacting proteins, including members of the cyclin and cyclin-dependent protein kinase (Cdk) families, and the Anaphase Promoting Complex (APC). Successful progression through the cell cycle depends on precise, temporally ordered regulation of the functions of these proteins. In light of this complexity, it is surprising that in fission yeast, a minimal Cdk network consisting of a single cyclin-Cdk fusion protein can control DNA synthesis and mitosis in a manner that is indistinguishable from wild type. To improve our understanding of the cell cycle regulatory network, we built and analysed a mathematical model of the molecular interactions controlling the G1/S and G2/M transitions in these minimal cells. The model accounts for all observed properties of yeast strains operating with the fusion protein. Importantly, coupling the model’s predictions with experimental analysis of alternative minimal cells, we uncover an explanation for the unexpected fact that elimination of inhibitory phosphorylation of Cdk is benign in these strains while it strongly affects normal cells. Furthermore, in the strain without inhibitory phosphorylation of the fusion protein, the distribution of cell size at division is unusually broad, an observation that is accounted for by stochastic simulations of the model. Our approach provides novel insights into the organization and quantitative regulation of wild type cell cycle progression. In particular, it leads us to propose a new mechanistic model for the phenomenon of mitotic catastrophe, relying on a combination of unregulated, multi-cyclin-dependent Cdk activities. PMID:25658582

  1. 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.

  2. 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.

  3. 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.

  4. Cell Cycle Regulatory Functions of the KSHV Oncoprotein LANA

    PubMed Central

    Wei, Fang; Gan, Jin; Wang, Chong; Zhu, Caixia; Cai, Qiliang

    2016-01-01

    Manipulation of cell cycle is a commonly employed strategy of viruses for achieving a favorable cellular environment during infection. Kaposi’s sarcoma-associated herpesvirus (KSHV), the primary etiological agent of several human malignancies including Kaposi’s sarcoma, and primary effusion lymphoma, encodes several oncoproteins that deregulate normal physiology of cell cycle machinery to persist with endothelial cells and B cells and subsequently establish a latent infection. During latency, only a small subset of viral proteins is expressed. Latency-associated nuclear antigen (LANA) is one of the latent antigens shown to be essential for transformation of endothelial cells in vitro. It has been well demonstrated that LANA is critical for the maintenance of latency, episome DNA replication, segregation and gene transcription. In this review, we summarize recent studies and address how LANA functions as an oncoprotein to steer host cell cycle-related events including proliferation and apoptosis by interacting with various cellular and viral factors, and highlight the potential therapeutic strategy of disrupting LANA-dependent signaling as targets in KSHV-associated cancers. PMID:27065950

  5. 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

  6. 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.

  7. Pseudolaric Acid B Induced Cell Cycle Arrest, Autophagy and Senescence in Murine Fibrosarcoma L929 Cell

    PubMed Central

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

    2013-01-01

    Objective: 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. Methods: 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. Results: 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. Conclusion: PAB induced cell cycle arrest, autophagy and senescence in murine fibrosarcoma L929 cell through PKC. PMID:23630435

  8. Characterization of high-power lithium-ion cells during constant current cycling. Part I. Cycle performance and electrochemical diagnostics

    SciTech Connect

    Shim, Joongpyo; Striebel, Kathryn A.

    2003-01-24

    Twelve-cm{sup 2} pouch type lithium-ion cells were assembled with graphite anodes, LiNi{sub 0.8}Co{sub 0.15}Al{sub 0.05}O{sub 2} cathodes and 1M LiPF{sub 6}/EC/DEC electrolyte. These pouch cells were cycled at different depths of discharge (100 percent and 70 percent DOD) at room temperature to investigate cycle performance and pulse power capability. The capacity loss and power fade of the cells cycled over 100 percent DOD was significantly faster than the cell cycled over 70 percent DOD. The overall cell impedance increased with cycling, although the ohmic resistance from the electrolyte was almost constant. From electrochemical analysis of each electrode after cycling, structural and/or impedance changes in the cathode are responsible for most of the capacity and power fade, not the consumption of cycleable Li from side-reactions.

  9. Periodic synthesis of phospholipids during the Caulobacter crescentus cell cycle.

    PubMed Central

    O'Neill, E A; Bender, R A

    1987-01-01

    Net phospholipid synthesis is discontinuous during the Caulobacter crescentus cell cycle with synthesis restricted to two discrete periods. The first period of net phospholipid synthesis begins in the swarmer cell shortly after cell division and ends at about the time when DNA replication initiates. The second period of phospholipid synthesis begins at a time when DNA replication is about two-thirds complete and ends at about the same time that DNA replication terminates. Thus, considerable DNA replication, growth, and differentiation (stalk growth) occur in the absence of net phospholipid synthesis. In fact, when net phospholipid synthesis was inhibited by the antibiotic cerulenin through the entire cell cycle, both the initiation and the elongation phases of DNA synthesis occurred normally. An analysis of the kinetics of incorporation of radioactive phosphate into macromolecules showed that the periodicity of phospholipid synthesis could not have been detected by pulse-labeling techniques, and only an analysis of cells prelabeled to equilibrium allowed detection of the periodicity. Equilibrium-labeled cells also allowed determination of the absolute amount of phosphorus-containing macromolecules in newborn swarmer cells. These cells contain about as much DNA as one Escherichia coli chromosome and about four times as much RNA as DNA. The amount of phosphorus in phospholipids is about one-seventh of that in DNA, or about 3% of the total macromolecular phosphorus. PMID:3584065

  10. 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

  11. Flow cytometric cell cycle analysis of somatic cells primary cultures established for bovine cloning.

    PubMed

    Katska, L; Bochenek, M; Kania, G; Ryñska, B; Smorag, Z

    2002-12-01

    An important factor governing developmental rates of somatic cloned embryos is the phase of the cell cycle of donor nuclei. The aim of this experiment was to investigate the distribution of cell cycle phases in bovine cumulus and fibroblast cells cultured using routine treatment, and under cell cycle-arresting treatments. The highest percentages of cumulus cells in the G0 + G1 stage were observed in uncultured, frozen/thawed cells originating from immature oocytes (79.8 +/- 2.2%), fresh and frozen/thawed cells from in vitro matured oocytes (84.1 +/- 6.2 and 77.8 +/- 5.7%, respectively), and in cycling cells (72.7 +/- 16.3 and 78.4 +/- 11.2%, respectively for cumulus cells from immature and in vitro matured oocytes). Serum starvation of cumulus cultures markedly decreased percentages of cells in G0 + G1, and prolonged starvation significantly increased (P < 0.05) percentages of cells in G2 + M phase. Culture of cumulus cells to confluency did not increase percentages of cells in G0 + G1. Contrary to findings in cumulus cells, significantly higher percentages of cells in G0 + G1 were apparent when fibroblast cells were cultured to confluency or serum starved, and significantly increased (P < 0.01) as the starvation period was prolonged. It is concluded that for particular cell types specific strategies should be used to attain improvements in the efficiency of cloning procedures.

  12. Cell cycle constraints on capsulation and bacteriophage susceptibility

    PubMed Central

    Ardissone, Silvia; Fumeaux, Coralie; Bergé, Matthieu; Beaussart, Audrey; Théraulaz, Laurence; Radhakrishnan, Sunish Kumar; Dufrêne, Yves F; Viollier, Patrick H

    2014-01-01

    Despite the crucial role of bacterial capsules in pathogenesis, it is still unknown if systemic cues such as the cell cycle can control capsule biogenesis. In this study, we show that the capsule of the synchronizable model bacterium Caulobacter crescentus is cell cycle regulated and we unearth a bacterial transglutaminase homolog, HvyA, as restriction factor that prevents capsulation in G1-phase cells. This capsule protects cells from infection by a generalized transducing Caulobacter phage (φCr30), and the loss of HvyA confers insensitivity towards φCr30. Control of capsulation during the cell cycle could serve as a simple means to prevent steric hindrance of flagellar motility or to ensure that phage-mediated genetic exchange happens before the onset of DNA replication. Moreover, the multi-layered regulatory circuitry directing HvyA expression to G1-phase is conserved during evolution, and HvyA orthologues from related Sinorhizobia can prevent capsulation in Caulobacter, indicating that alpha-proteobacteria have retained HvyA activity. DOI: http://dx.doi.org/10.7554/eLife.03587.001 PMID:25421297

  13. Effects of Roundup and glyphosate formulations on intracellular transport, microtubules and actin filaments in Xenopus laevis melanophores.

    PubMed

    Hedberg, Daniel; Wallin, Margareta

    2010-04-01

    Glyphosate containing herbicides, such as Roundup, are commonly used and generally considered to be safe. However, some toxic effects are found on amphibians in vivo and human and mouse cells in vitro. In this study the effects of Roundup, glyphosate, glyphosateisopropylamine and isopropylamine were studied on intracellular transport by measuring aggregation capacity in Xenopus laevis melanophores. The chemicals inhibited retrograde transport of melanosomes in the range of 0.5-5mM. Cellular morphology and localization of microtubules and actin filaments were affected as determined by immunocytochemistry. Both glyphosate and Roundup decreased pH in the media. Acidic pH inhibited melanosome transport and altered microtubule and actin morphology in the absence of chemicals, while transport inhibiting concentrations of glyphosate, Roundup and glyphosateisopropylamine disassembled both microtubules and actin filaments. At physiological pH the effects of Roundup decreased whereas glyphosate failed to inhibit transport. Physiological pH decreases glyphosate lipophilicity and its diffusion into the cytoplasm. The Roundup formulation contains surfactants, such as POEA (polyetylated tallow amine) that increases membrane permeability allowing cellular uptake at physiological pH. Our results show that the effects of glyphosate containing compounds are pH-dependent and that they inhibit intracellular transport through disassembly of the cytoskeleton possibly by interfering with intracellular Ca(2+)-balance.

  14. 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.

  15. Cell-Cycle Analyses Using Thymidine Analogues in Fission Yeast

    PubMed Central

    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. PMID:24551125

  16. Cyclin G2 is a Centrosome-associated Nucleocytoplasmic Shuttling Protein that Influences Microtubule Stability and Induces a p53-dependent Cell Cycle Arrest

    PubMed Central

    Arachchige Don, Aruni S.; Dallapiazza, Robert F.; Bennin, David A.; Brake, Tiffany; Cowan, Colleen E.; Horne, Mary C.

    2007-01-01

    Cyclin G2 is an atypical cyclin that associates with active protein phosphatase 2A. Cyclin G2 gene expression correlates with cell cycle inhibition; it is significantly upregulated in response to DNA damage and diverse growth inhibitory stimuli, but repressed by mitogenic signals. Ectopic expression of cyclin G2 promotes cell cycle arrest, cyclin dependent kinase 2 inhibition, and the formation of aberrant nuclei [1]. Here we report that endogenous cyclin G2 copurifies with centrosomes and microtubules (MT), and that ectopic G2 expression alters microtubule stability. We find exogenous and endogenous cyclin G2 present at microtubule organizing centers (MTOCs) where it colocalizes with centrosomal markers in a variety of cell lines. We previously reported that cyclin G2 forms complexes with active protein phosphatase 2A (PP2A) and colocalizes with PP2A in a detergent resistant compartment. We now show that cyclin G2 and PP2A colocalize at MTOCs in transfected cells, and that the endogenous proteins copurify with isolated centrosomes. Displacement of the endogenous centrosomal scaffolding protein AKAP450 that anchors PP2A at the centrosome, resulted in the depletion of centrosomal cyclin G2. We find that ectopic expression of cyclin G2 induces microtubule bundling and resistance to depolymerization, inhibition of polymer regrowth from MTOCs, and a p53 dependent cell cycle arrest. Furthermore, we determined that a 100 amino acid carboxy-terminal region of cyclin G2 is sufficient to both direct GFP localization to centrosomes and induce cell cycle inhibition. Colocalization of endogenous cyclin G2 with only one of two GFP-centrin tagged centrioles, the mature centriole present at microtubule foci, indicate that cyclin G2 resides primarily on the mother centriole. Copurification of cyclin G2 and PP2A subunits with microtubules and centrosomes, together with the effects of ectopic cyclin G2 on cell cycle progression, nuclear morphology, and microtubule growth and

  17. 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

  18. 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.

  19. 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

  20. Chemical dissection of the cell cycle: probes for cell biology and anti-cancer drug development.

    PubMed

    Senese, S; Lo, Y C; Huang, D; Zangle, T A; Gholkar, A A; Robert, L; Homet, B; Ribas, A; Summers, M K; Teitell, M A; Damoiseaux, R; Torres, J Z

    2014-01-01

    Cancer cell proliferation relies on the ability of cancer cells to grow, transition through the cell cycle, and divide. To identify novel chemical probes for dissecting the mechanisms governing cell cycle progression and cell division, and for developing new anti-cancer therapeutics, we developed and performed a novel cancer cell-based high-throughput chemical screen for cell cycle modulators. This approach identified novel G1, S, G2, and M-phase specific inhibitors with drug-like properties and diverse chemotypes likely targeting a broad array of processes. We further characterized the M-phase inhibitors and highlight the most potent M-phase inhibitor MI-181, which targets tubulin, inhibits tubulin polymerization, activates the spindle assembly checkpoint, arrests cells in mitosis, and triggers a fast apoptotic cell death. Importantly, MI-181 has broad anti-cancer activity, especially against BRAF(V600E) melanomas.

  1. 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. PMID:27183329

  2. Polyamines and the Cell Cycle of Catharanthus roseus Cells in Culture 1

    PubMed Central

    Maki, Hisae; Ando, Satoshi; Kodama, Hiroaki; Komamine, Atsushi

    1991-01-01

    Investigation was made on the effect of partial depletion of polyamines (PAs), induced by treatment with inhibitors of the biosynthesis of PAs, on the distribution of cells at each phase of the cell cycle in Catharanthus roseus (L.) G. Don. cells in suspension cultures, using flow cytometry. More cells treated with inhibitors of arginine decarboxylase (ADC) and ornithine decarboxylase (ODC) were accumulated in the G1 phase than those in the control, while the treatment with an inhibitor of spermidine (SPD) synthase showed no effect on the distribution of cells. The endogenous levels of the PAs, putrescine (PUT), SPD, and spermine (SPM), were determined during the cell cycle in synchronous cultures of C. roseus. Two peaks of endogenous level of PAs, in particular, of PUT and SPD, were observed during the cell cycle. Levels of PAs increased markedly prior to synthesis of DNA in the S phase and prior to cytokinesis. Activities of ADC and ODC were also assayed during the cell cycle. Activities of ADC was much higher than that of ODC throughout the cell cycle, but both activities of ODC and ADC changed in concert with changes in levels of PAs. Therefore, it is suggested that these enzymes may regulate PA levels during the cell cycle. These results indicate that inhibitors of PUT biosynthesis caused the suppression of cell proliferation by prevention of the progression of the cell cycle, probably from the G1 to the S phase, and PUT may play more important roles in the progression of the cell cycle than other PAs. PMID:16668290

  3. Characterization of Fuel Cell Vehicle Duty Cycle Elements

    SciTech Connect

    MAISH, ALEXANDER B.; NILAN, ERIC J.; BACA, PAUL M.

    2002-12-01

    This report covers research done as part of US Department of Energy contract DE-PS26-99FT14299 with the Fuel Cell Propulsion Institute on the fuel cell RATLER{trademark} vehicle, Lurch, as well as work done on the fuel cells designed for the vehicle. All work contained within this report was conducted at the Robotic Vehicle Range at Sandia National Laboratories in Albuquerque New Mexico. The research conducted includes characterization of the duty cycle of the robotic vehicle. This covers characterization of its various abilities such as hill climbing and descending, spin-turns, and driving on level ground. This was accomplished with the use of current sensors placed in the vehicle in conjunction with a Data Acquisition System (DAS), which was also created at Sandia Labs. Characterization of the two fuel cells was accomplished using various measuring instruments and techniques that will be discussed later in the report. A Statement of Work for this effort is included in Appendix A. This effort was able to complete characterization of vehicle duty cycle elements using battery power, but problems with the fuel cell control systems prevented completion of the characterization of the fuel cell operation on the benchtop and in the vehicle. Some data was obtained characterizing the fuel cell current-voltage performance and thermal rise rate by bypassing elements of the control system.

  4. 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. PMID:24348867

  5. 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

  6. Boolean Network Model Predicts Cell Cycle Sequence of Fission Yeast

    PubMed Central

    Davidich, Maria I.; Bornholdt, Stefan

    2008-01-01

    A Boolean network model of the cell-cycle regulatory network of fission yeast (Schizosaccharomyces Pombe) is constructed solely on the basis of the known biochemical interaction topology. Simulating the model in the computer faithfully reproduces the known activity sequence of regulatory proteins along the cell cycle of the living cell. Contrary to existing differential equation models, no parameters enter the model except the structure of the regulatory circuitry. The dynamical properties of the model indicate that the biological dynamical sequence is robustly implemented in the regulatory network, with the biological stationary state G1 corresponding to the dominant attractor in state space, and with the biological regulatory sequence being a strongly attractive trajectory. Comparing the fission yeast cell-cycle model to a similar model of the corresponding network in S. cerevisiae, a remarkable difference in circuitry, as well as dynamics is observed. While the latter operates in a strongly damped mode, driven by external excitation, the S. pombe network represents an auto-excited system with external damping. PMID:18301750

  7. 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.

  8. 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

  9. ADOLESCENT BINGE ALCOHOL EXPOSURE ALTERS HIPPOCAMPAL PROGENITOR CELL PROLIFERATION IN RATS: EFFECTS ON CELL CYCLE KINETICS

    PubMed Central

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

    2012-01-01

    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, bromo-deoxy-uridine incorporation, and phospho-histone 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 bromo-deoxy-uridine 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 but also reveal the earliest evidence of the compensatory neurogenesis reaction that has been observed a week after binge alcohol exposure. PMID:21484803

  10. Cell cycle-dependent regulation of pyrimidine biosynthesis.

    PubMed

    Sigoillot, Frederic D; Berkowski, J Andrew; Sigoillot, Severine M; Kotsis, Damian H; Guy, Hedeel I

    2003-01-31

    De novo pyrimidine biosynthesis is activated in proliferating cells in response to an increased demand for nucleotides needed for DNA synthesis. The pyrimidine biosynthetic pathway in baby hamster kidney cells, synchronized by serum deprivation, was found to be up-regulated 1.9-fold during S phase and subsequently down-regulated as the cells progressed through the cycle. The nucleotide pools were depleted by serum starvation and were not replenished during the first round of cell division, suggesting that the rate of utilization of the newly synthesized nucleotides closely matched their rate of formation. The activation and subsequent down-regulation of the pathway can be attributed to altered allosteric regulation of the carbamoyl-phosphate synthetase activity of CAD (carbamoyl-phosphate synthetase-aspartate carbamoyltransferase-dihydroorotase), a multifunctional protein that initiates mammalian pyrimidine biosynthesis. As the culture approached S-phase there was an increased sensitivity to the allosteric activator, 5-phosphoribosyl-1-pyrophosphate, and a loss of UTP inhibition, changes that were reversed when cells emerged from S phase. The allosteric regulation of CAD is known to be modulated by MAP kinase (MAPK) and protein kinase A (PKA)-mediated phosphorylations as well as by autophosphorylation. CAD was found to be fully autophosphorylated in the synchronized cells, but the level remained invariant throughout the cycle. Although the MAPK activity increased early in G(1), the phosphorylation of the CAD MAPK site was delayed until just before the onset of S phase, probably due to antagonistic phosphorylation by PKA that persisted until late G(1). Once activated, pyrimidine biosynthesis remained elevated until rephosphorylation of CAD by PKA and dephosphorylation of the CAD MAPK site late in S phase. Thus, the cell cycle-dependent regulation of pyrimidine biosynthesis results from the sequential phosphorylation and dephosphorylation of CAD under the control of

  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. 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

  13. Analysis of simple sequence repeats in mammalian cell cycle genes.

    PubMed

    Trivedi, Seema; Wills, Christopher; Metzgar, David

    2014-01-01

    Simple sequence repeats (SSRs), or microsatellites are hyper-mutable and can lead to disorders. Here we explore SSR distribution in cell cycle-associated genes [grouped into: checkpoint; regulation; replication, repair, and recombination (RRR); and transition] in humans and orthologues of eight mammals. Among the gene groups studied, transition genes have the highest SSR density. Trinucleotide repeats are not abundant and introns have higher repeat density than exons. Many repeats in human genes are conserved; however, CG motifs are conserved only in regulation genes. SSR variability in cell cycle genes represents a genetic Achilles' heel, yet SSRs are common in all groups of genes. This tolerance many be due to i) positions in introns where they do not disrupt gene function, ii) essential roles in regulation, iii) specific value of adaptability, and/or iv) lack of negative selection pressure. Present study may be useful for further exploration of their medical relevance and potential functionality.

  14. 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.

  15. Cell cycle regulation: repair and regeneration in acute renal failure.

    PubMed

    Price, Peter M; Megyesi, Judit; Safirstein, Robert L

    2003-09-01

    Research into mechanisms of acute renal failure has begun to reveal molecular targets for possible therapeutic intervention. Much useful knowledge into the causes and prevention of this syndrome has been gained by the study of animal models. Most recently, investigation of the effects on acute renal failure of selected gene knock-outs in mice has contributed to our recognition of many previously unappreciated molecular pathways. Particularly, experiments have revealed the protective nature of 2 highly induced genes whose functions are to inhibit and control the cell cycle after acute renal failure. By use of these models we have started to understand the role of increased cell cycle activity after renal stress and the role of proteins induced by these stresses that limit this proliferation.

  16. Cell cycle regulation: repair and regeneration in acute renal failure.

    PubMed

    Price, Peter M; Megyesi, Judit; Saf Irstein, Robert L

    2004-08-01

    Research into mechanisms of acute renal failure has begun to reveal molecular targets for possible therapeutic intervention. Much useful knowledge into the causes and prevention of this syndrome has been gained by the study of animal models. Most recently, investigation of the effects on acute renal failure of selected gene knock-outs in mice has contributed to our recognition of many previously unappreciated molecular pathways. Particularly, experiments have revealed the protective nature of two highly induced genes whose functions are to inhibit and control the cell cycle after acute renal failure. By use of these models we have started to understand the role of increased cell cycle activity after renal stress, and the role of proteins induced by these stresses that limit this proliferation.

  17. The role of microtubules and microtubule-organising centres during the migration of mitochondria.

    PubMed

    Knabe, W; Kuhn, H J

    1996-10-01

    The translocation of mitochondria towards the primitive inner segment of the cones in the tree shrew Tupaia belangeri was investigated by transmission electron microscopy. Throughout ontogeny the migrating mitochondria were codistributed with cytoplasmic microtubules which were preserved after the application of conventional preparation techniques for transmission electron microscopy. Both the basal body of the connecting cilium and the second centriole located in the vicinity of the basal body were demonstrated to act as microtubule-organising centres (MTOCs) from which axonemal and cytoplasmic microtubules originated. The megamitochondria in the inner segment of the retinal cones of Tupaia are unique among mammals with respect to their extraordinary size and to their ordered distribution characterised by longitudinal and radial size-gradients within developing and mature cone inner segments. Thus the consistent finding of microtubules and MTOCs in the structurally polarised cones represents an extreme example of the capacity of cells to regulate the transport and distribution of organelles.

  18. 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.

  19. 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.

  20. 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

  1. 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

    2015-01-01

    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.

  2. 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

  3. The Cell Cycle Timing of Human Papillomavirus DNA Replication

    PubMed Central

    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. PMID:26132923

  4. 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

  5. Cycle reset in a melanoma cell line caused by cooling.

    PubMed

    Dewey, D L

    1987-11-01

    When cells in culture are released from G0 into cycle by diluting into fresh medium there is a delay of many hours before they re-enter the cycle and start DNA synthesis. A mouse melanoma cell line designated HP2 has been used to investigate the effects of non-standard temperatures between the time of plating and DNA synthesis. When the cells were incubated in a 5% CO2 box at 8 degrees C for periods during the G0-G1 transition there was an extra delay before the start of S, approximately equal to the time that the cells were held at 8 degrees C and independent of the time when the cold pulse was administered. When the cells were cooled to 25 degrees C the delay was longer than the time for which the cells had been kept at 25 degrees C, and this extra delay was also dependent on the point in G0-G1 when the cells were cooled, as though the cells could be reset to an earlier time by this treatment. It is suggested that a labile substance required for progression is destroyed faster than it is made at 25 degrees C but at 8 degrees C the rate of destruction is very low. Another phenomenon noted during these cooling experiments was that the peak height of the S phase profile, as measured by frequent pulse-thymidine incorporation experiments, was substantially higher for cells which had been cooled at a later stage in the G0-G1 transition, even though the overall times at 37 degrees C and at the colder temperature were identical. By varying the temperature of the cold pulse it was possible to separate the change in the peak height and the delay as separate entities. PMID:3502929

  6. A DNA-damage-induced cell cycle checkpoint in Arabidopsis.

    PubMed Central

    Preuss, S B; Britt, A B

    2003-01-01

    Although it is well established that plant seeds treated with high doses of gamma radiation arrest development as seedlings, the cause of this arrest is unknown. The uvh1 mutant of Arabidopsis is defective in a homolog of the human repair endonuclease XPF, and uvh1 mutants are sensitive to both the toxic effects of UV and the cytostatic effects of gamma radiation. Here we find that gamma irradiation of uvh1 plants specifically triggers a G(2)-phase cell cycle arrest. Mutants, termed suppressor of gamma (sog), that suppress this radiation-induced arrest and proceed through the cell cycle unimpeded were recovered in the uvh1 background; the resulting irradiated plants are genetically unstable. The sog mutations fall into two complementation groups. They are second-site suppressors of the uvh1 mutant's sensitivity to gamma radiation but do not affect the susceptibility of the plant to UV radiation. In addition to rendering the plants resistant to the growth inhibitory effects of gamma radiation, the sog1 mutation affects the proper development of the pollen tetrad, suggesting that SOG1 might also play a role in the regulation of cell cycle progression during meiosis. PMID:12750343

  7. Development of cell-cycle checkpoint therapy for solid tumors.

    PubMed

    Tamura, Kenji

    2015-12-01

    Cellular proliferation is tightly controlled by several cell-cycle checkpoint proteins. In cancer, the genes encoding these proteins are often disrupted and cause unrestrained cancer growth. The proteins are over-expressed in many malignancies; thus, they are potential targets for anti-cancer therapies. These proteins include cyclin-dependent kinase, checkpoint kinase, WEE1 kinase, aurora kinase and polo-like kinase. Cyclin-dependent kinase inhibitors are the most advanced cell-cycle checkpoint therapeutics available. For instance, palbociclib (PD0332991) is a first-in-class, oral, highly selective inhibitor of CDK4/6 and, in combination with letrozole (Phase II; PALOMA-1) or with fulvestrant (Phase III; PALOMA-3), it has significantly prolonged progression-free survival, in patients with metastatic estrogen receptor-positive, HER2-negative breast cancer, in comparison with that observed in patients using letrozole, or fulvestrant alone, respectively. In this review, we provide an overview of the current compounds available for cell-cycle checkpoint protein-directed therapy for solid tumors. PMID:26486823

  8. Effects of mimosine on Wolbachia in mosquito cells: cell cycle suppression reduces bacterial abundance

    PubMed Central

    Fallon, Ann M.

    2016-01-01

    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. PMID:26019119

  9. Spaceflight alters microtubules and increases apoptosis in human lymphocytes (Jurkat)

    NASA Technical Reports Server (NTRS)

    Lewis, M. L.; Reynolds, J. L.; Cubano, L. A.; Hatton, J. P.; Lawless, B. D.; Piepmeier, E. H.

    1998-01-01

    Alteration in cytoskeletal organization appears to underlie mechanisms of gravity sensitivity in space-flown cells. Human T lymphoblastoid cells (Jurkat) were flown on the Space Shuttle to test the hypothesis that growth responsiveness is associated with microtubule anomalies and mediated by apoptosis. Cell growth was stimulated in microgravity by increasing serum concentration. After 4 and 48 h, cells filtered from medium were fixed with formalin. Post-flight, confocal microscopy revealed diffuse, shortened microtubules extending from poorly defined microtubule organizing centers (MTOCs). In comparable ground controls, discrete microtubule filaments radiated from organized MTOCs and branched toward the cell membrane. At 4 h, 30% of flown, compared to 17% of ground, cells showed DNA condensation characteristic of apoptosis. Time-dependent increase of the apoptosis-associated Fas/ APO-1 protein in static flown, but not the in-flight 1 g centrifuged or ground controls, confirmed microgravity-associated apoptosis. By 48 h, ground cultures had increased by 40%. Flown populations did not increase, though some cells were cycling and actively metabolizing glucose. We conclude that cytoskeletal alteration, growth retardation, and metabolic changes in space-flown lymphocytes are concomitant with increased apoptosis and time-dependent elevation of Fas/APO-1 protein. We suggest that reduced growth response in lymphocytes during spaceflight is linked to apoptosis.

  10. Cell-Cycle Control of Developmentally Regulated Transcription Factors Accounts for Heterogeneity in Human Pluripotent Cells

    PubMed Central

    Singh, Amar M.; Chappell, James; Trost, Robert; Lin, Li; Wang, Tao; Tang, Jie; Wu, Hao; Zhao, Shaying; Jin, Peng; Dalton, Stephen

    2013-01-01

    Summary Heterogeneity within pluripotent stem cell (PSC) populations is indicative of dynamic changes that occur when cells drift between different states. Although the role of metastability in PSCs is unclear, it appears to reflect heterogeneity in cell signaling. Using the Fucci cell-cycle indicator system, we show that elevated expression of developmental regulators in G1 is a major determinant of heterogeneity in human embryonic stem cells. Although signaling pathways remain active throughout the cell cycle, their contribution to heterogeneous gene expression is restricted to G1. Surprisingly, we identify dramatic changes in the levels of global 5-hydroxymethylcytosine, an unanticipated source of epigenetic heterogeneity that is tightly linked to cell-cycle progression and the expression of developmental regulators. When we evaluated gene expression in differentiating cells, we found that cell-cycle regulation of developmental regulators was maintained during lineage specification. Cell-cycle regulation of developmentally regulated transcription factors is therefore an inherent feature of the mechanisms underpinning differentiation. PMID:24371808

  11. 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.

  12. 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

  13. Exosomes Secreted by Toxoplasma gondii-Infected L6 Cells: Their Effects on Host Cell Proliferation and Cell Cycle Changes

    PubMed Central

    Kim, Min Jae; Jung, Bong-Kwang; Cho, Jaeeun; Song, Hyemi; Pyo, Kyung-Ho; Lee, Ji Min; Kim, Min-Kyung; Chai, Jong-Yil

    2016-01-01

    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. PMID:27180572

  14. Cell cycle switch to endocycle: the nucleolus lends a hand.

    PubMed

    Martindill, David M J; Riley, Paul R

    2008-01-01

    The bHLH transcription factor Hand1 is essential for placentation and cardiac morphogenesis but how its developmental activity is regulated is largely unknown. We recently showed that Hand1 is sequestered in the nucleoli of rodent trophoblast stem (TS) cells by the I-mfa domain-containing protein HICp40 and that this is associated with their proliferation and continuing self-renewal. However when these cells commit to differentiate into trophoblast giant (TG) cells, Hand1 is phosphorylated by the polo-like kinase Plk4 (Sak) and released into the nucleus to activate downstream target genes. This event underlies the release of Hand1 from the nucleolus and represents the 'molecular switch' that promotes mitotic cell cycle exit and the onset of endoreduplication. In this brief discussion we examine the wider implications of these findings and address some of the unanswered questions that remain.

  15. 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.

  16. Multiscale Polar Theory of Microtubule and Motor-Protein Assemblies

    PubMed Central

    Gao, Tong; Blackwell, Robert; Glaser, Matthew A.; Betterton, M. D.; Shelley, Michael J.

    2015-01-01

    Microtubules and motor proteins are building blocks of self-organized subcellular biological structures such as the mitotic spindle and the centrosomal microtubule array. These same ingredients can form new “bioactive” liquid-crystalline fluids that are intrinsically out of equilibrium and which display complex flows and defect dynamics. It is not yet well understood how microscopic activity, which involves polarity-dependent interactions between motor proteins and microtubules, yields such larger-scale dynamical structures. In our multiscale theory, Brownian dynamics simulations of polar microtubule ensembles driven by cross-linking motors allow us to study microscopic organization and stresses. Polarity sorting and cross-link relaxation emerge as two polar-specific sources of active destabilizing stress. On larger length scales, our continuum Doi-Onsager theory captures the hydrodynamic flows generated by polarity-dependent active stresses. The results connect local polar structure to flow structures and defect dynamics. PMID:25679909

  17. Sodium butyrate regulates androgen receptor expression and cell cycle arrest in human prostate cancer cells.

    PubMed

    Kim, Jeonga; Park, Hyeyoung; Im, Ji Young; Choi, Wahn Soo; Kim, Hyung Sik

    2007-01-01

    Histone deacetylase (HDAC) inhibitors have been shown to modify the expression of a variety of genes related to cell cycle regulation and apoptosis in several cancer cells. However, the precise mode of action of HDAC inhibitors in prostate cancer cells is not completely understood. This study examined whether an HDAC inhibitor affects cell death in human prostate cancer cells through the epigenetic regulation of androgen receptor (AR) expression. The molecular mechanism of the HDAC inhibitor, sodium butyrate, on the epigenetic alterations of cell cycle regulators was evaluated in androgen-dependent human prostate cancer LNCaP cells. The expression levels of acetylated histone H3 and H4 increased significantly after 48 h treatment with sodium butyrate. Sodium butyrate induced the expression of AR after 48 h treatment. In addition, immunofluorescence assay revealed the nuclear localization of the AR after sodium butyrate treatment. Sodium butyrate also significantly decreased the expression of the cell cycle regulatory proteins (cyclin D1/cyclin dependent kinase (CDK)4, CDK6, and cyclin E/CDK2) in the LNCaP cells after 48 h treatment. Furthermore, p21Waf1/Cip1 and p27Kip1 were upregulated as a result of the sodium butyrate treatment. These results suggest that sodium butyrate effectively inhibited cell proliferation and induced apoptosis of human prostate cancer cells by altering the expression of cell cycle regulators and AR. This study indicated that sodium butyrate may be a potential agent in prostate cancer treatment.

  18. Regulation of Sp1 by cell cycle related proteins

    PubMed Central

    Tapias, Alicia; Ciudad, Carlos J.; Roninson, Igor B.; Noé, Véronique

    2009-01-01

    Sp1 transcription factor regulates the expression of multiple genes, including the Sp1 gene itself. We analyzed the ability of different cell cycle regulatory proteins to interact with Sp1 and to affect Sp1 promoter activity. Using an antibody array, we observed that CDK4, SKP2, Rad51, BRCA2 and p21 could interact with Sp1 and we confirmed these interactions by co-immunoprecipitation. CDK4, SKP2, Rad51, BRCA2 and p21 also activated the Sp1 promoter. Among the known Sp1-interacting proteins, E2F-DP1, Cyclin D1, Stat3 and Rb activated the Sp1 promoter, whereas p53 and NFκB inhibited it. The proteins that regulated Sp1 gene expression were shown by positive chromatin immunoprecipitation to be bound to the Sp1 promoter. Moreover, SKP2, BRCA2, p21, E2F-DP1, Stat3, Rb, p53 and NFκB had similar effects on an artificial promoter containing only Sp1 binding sites. Transient transfections of CDK4, Rad51, E2F-DP1, p21 and Stat3 increased mRNA expression from the endogenous Sp1 gene in HeLa cells whereas overexpression of NFκB, and p53 decreased Sp1 mRNA levels. p21 expression from a stably integrated inducible promoter in HT1080 cells activated Sp1 expression at the promoter and mRNA levels, but at the same time it decreased Sp1 protein levels due to the activation of Sp1 degradation. The observed multiple effects of cell cycle regulators on Sp1 suggest that Sp1 may be a key mediator of cell cycle associated changes in gene expression. PMID:18769160

  19. Pitx2 expression promotes p21 expression and cell cycle exit in neural stem cells.

    PubMed

    Heldring, Nina; Joseph, Bertrand; Hermanson, Ola; Kioussi, Chrissa

    2012-11-01

    Cortical development is a complex process that involves many events including proliferation, cell cycle exit and differentiation that need to be appropriately synchronized. Neural stem cells (NSCs) isolated from embryonic cortex are characterized by their ability of self-renewal under continued maintenance of multipotency. Cell cycle progression and arrest during development is regulated by numerous factors, including cyclins, cyclin dependent kinases and their inhibitors. In this study, we exogenously expressed the homeodomain transcription factor Pitx2, usually expressed in postmitotic progenitors and neurons of the embryonic cortex, in NSCs with low expression of endogenous Pitx2. We found that Pitx2 expression induced a rapid decrease in proliferation associated with an accumulation of NSCs in G1 phase. A search for potential cell cycle inhibitors responsible for such cell cycle exit of NSCs revealed that Pitx2 expression caused a rapid and dramatic (≉20-fold) increase in expression of the cell cycle inhibitor p21 (WAF1/Cip1). In addition, Pitx2 bound directly to the p21 promoter as assessed by chromatin immunoprecipitation (ChIP) in NSCs. Surprisingly, Pitx2 expression was not associated with an increase in differentiation markers, but instead the expression of nestin, associated with undifferentiated NSCs, was maintained. Our results suggest that Pitx2 promotes p21 expression and induces cell cycle exit in neural progenitors.

  20. 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.

  1. Pneumococcal Pneumolysin Induces DNA Damage and Cell Cycle Arrest

    PubMed Central

    Rai, Prashant; He, Fang; Kwang, Jimmy; Engelward, Bevin P.; Chow, Vincent T.K.

    2016-01-01

    Streptococcus pneumoniae produces pneumolysin toxin as a key virulence factor against host cells. Pneumolysin is a cholesterol-dependent cytolysin (CDC) toxin that forms lytic pores in host membranes and mediates pneumococcal disease pathogenesis by modulating inflammatory responses. Here, we show that pneumolysin, which is released during bacterial lysis, induces DNA double strand breaks (DSBs), as indicated by ataxia telangiectasia mutated (ATM)-mediated H2AX phosphorylation (γH2AX). Pneumolysin-induced γH2AX foci recruit mediator of DNA damage checkpoint 1 (MDC1) and p53 binding protein 1 (53BP1), to sites of DSBs. Importantly, results show that toxin-induced DNA damage precedes cell cycle arrest and causes apoptosis when DNA-dependent protein kinase (DNA-PK)-mediated non-homologous end joining is inhibited. Further, we observe that cells that were undergoing DNA replication harbored DSBs in greater frequency during pneumolysin treatment. This observation raises the possibility that DSBs might be arising as a result of replication fork breakdown. Additionally, neutralizing the oligomerization domain of pneumolysin with monoclonal antibody suppresses DNA damage and also cell cycle arrest, indicating that pneumolysin oligomerization is important for causing DNA damage. Taken together, this study reveals a previously unidentified ability of pneumolysin to induce cytotoxicity via DNA damage, with implications in the pathophysiology of S. pneumoniae infection. PMID:27026501

  2. 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.

  3. (p)ppGpp and the bacterial cell cycle.

    PubMed

    Nazir, Aanisa; Harinarayanan, Rajendran

    2016-06-01

    Genes of the Rel/Spo homolog (RSH) superfamily synthesize and/or hydrolyse the modified nucleotides pppGpp/ ppGpp (collectively referred to as (p)ppGpp) and are prevalent across diverse bacteria and in plant chloroplasts. Bacteria accumulate (p)ppGpp in response to nutrient deprivation (generically called the stringent response) and elicit appropriate adaptive responses mainly through the regulation of transcription. Although at different concentrations (p)ppGpp affect the expression of distinct set of genes, the two well-characterized responses are reduction in expression of the protein synthesis machinery and increase in the expression of genes coding for amino acid biosynthesis. In Escherichia coli, the cellular (p)ppGpp level inversely correlates with the growth rate and increasing its concentration decreases the steady state growth rate in a defined growth medium. Since change in growth rate must be accompanied by changes in cell cycle parameters set through the activities of the DNA replication and cell division apparatus, (p)ppGpp could coordinate protein synthesis (cell mass increase) with these processes. Here we review the role of (p)ppGpp in bacterial cell cycle regulation.

  4. Pneumococcal Pneumolysin Induces DNA Damage and Cell Cycle Arrest.

    PubMed

    Rai, Prashant; He, Fang; Kwang, Jimmy; Engelward, Bevin P; Chow, Vincent T K

    2016-01-01

    Streptococcus pneumoniae produces pneumolysin toxin as a key virulence factor against host cells. Pneumolysin is a cholesterol-dependent cytolysin (CDC) toxin that forms lytic pores in host membranes and mediates pneumococcal disease pathogenesis by modulating inflammatory responses. Here, we show that pneumolysin, which is released during bacterial lysis, induces DNA double strand breaks (DSBs), as indicated by ataxia telangiectasia mutated (ATM)-mediated H2AX phosphorylation (γH2AX). Pneumolysin-induced γH2AX foci recruit mediator of DNA damage checkpoint 1 (MDC1) and p53 binding protein 1 (53BP1), to sites of DSBs. Importantly, results show that toxin-induced DNA damage precedes cell cycle arrest and causes apoptosis when DNA-dependent protein kinase (DNA-PK)-mediated non-homologous end joining is inhibited. Further, we observe that cells that were undergoing DNA replication harbored DSBs in greater frequency during pneumolysin treatment. This observation raises the possibility that DSBs might be arising as a result of replication fork breakdown. Additionally, neutralizing the oligomerization domain of pneumolysin with monoclonal antibody suppresses DNA damage and also cell cycle arrest, indicating that pneumolysin oligomerization is important for causing DNA damage. Taken together, this study reveals a previously unidentified ability of pneumolysin to induce cytotoxicity via DNA damage, with implications in the pathophysiology of S. pneumoniae infection. PMID:27026501

  5. (p)ppGpp and the bacterial cell cycle.

    PubMed

    Nazir, Aanisa; Harinarayanan, Rajendran

    2016-06-01

    Genes of the Rel/Spo homolog (RSH) superfamily synthesize and/or hydrolyse the modified nucleotides pppGpp/ ppGpp (collectively referred to as (p)ppGpp) and are prevalent across diverse bacteria and in plant chloroplasts. Bacteria accumulate (p)ppGpp in response to nutrient deprivation (generically called the stringent response) and elicit appropriate adaptive responses mainly through the regulation of transcription. Although at different concentrations (p)ppGpp affect the expression of distinct set of genes, the two well-characterized responses are reduction in expression of the protein synthesis machinery and increase in the expression of genes coding for amino acid biosynthesis. In Escherichia coli, the cellular (p)ppGpp level inversely correlates with the growth rate and increasing its concentration decreases the steady state growth rate in a defined growth medium. Since change in growth rate must be accompanied by changes in cell cycle parameters set through the activities of the DNA replication and cell division apparatus, (p)ppGpp could coordinate protein synthesis (cell mass increase) with these processes. Here we review the role of (p)ppGpp in bacterial cell cycle regulation. PMID:27240988

  6. Novel antiproliferative flavonoids induce cell cycle arrest in human prostate cancer cell lines.

    PubMed

    Haddad, A Q; Venkateswaran, V; Viswanathan, L; Teahan, S J; Fleshner, N E; Klotz, L H

    2006-01-01

    Epidemiologic studies have demonstrated an inverse association between flavonoid intake and prostate cancer (PCa) risk. The East Asian diet is very high in flavonoids and, correspondingly, men in China and Japan have the lowest incidence of PCa worldwide. There are thousands of different naturally occurring and synthetic flavonoids. However, only a few have been studied in PCa. Our aim was to identify novel flavonoids with antiproliferative effect in PCa cell lines, as well as determine their effects on cell cycle. We have screened a representative subgroup of 26 flavonoids for antiproliferative effect on the human PCa (LNCaP and PC3), breast cancer (MCF-7), and normal prostate stromal cell lines (PrSC). Using a fluorescence-based cell proliferation assay (Cyquant), we have identified five flavonoids, including the novel compounds 2,2'-dihydroxychalcone and fisetin, with antiproliferative and cell cycle arresting properties in human PCa in vitro. Most of the flavonoids tested exerted antiproliferative effect at lower doses in the PCa cell lines compared to the non-PCa cells. Flow cytometry was used as a means to determine the effects on cell cycle. PC3 cells were arrested in G2/M phase by flavonoids. LNCaP cells demonstrated different cell cycle profiles. Further studies are warranted to determine the molecular mechanism of action of 2,2'-DHC and fisetin in PCa, and to establish their effectiveness in vivo.

  7. 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.

  8. 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

  9. 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.

  10. Coupling between the Circadian Clock and Cell Cycle Oscillators: Implication for Healthy Cells and Malignant Growth

    PubMed Central

    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. PMID:26029155

  11. 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.

  12. Impairment of cell cycle progression by aflatoxin B1 in human cell lines.

    PubMed

    Ricordy, R; Gensabella, G; Cacci, E; Augusti-Tocco, G

    2002-05-01

    Aflatoxin B1 is a mycotoxin produced by Aspergillus flavus and Aspergillus parasiticum, which may be present as a food contaminant. It is known to cause acute toxic effects and act as a carcinogenic agent. The carcinogenic action has been related to its ability to form unstable adducts with DNA, which represent possible mutagenic sites. On the other hand, the primary cellular target responsible for its toxic action has not yet been clearly identified. Previous data suggested a possible correlation between cell proliferation and responsiveness to aflatoxin toxicity. These observations led us to investigate the effect of the toxin on cell cycle progression of three human cell lines (HepG2, SK-N-MC and SK-N-SH derived from liver and nervous tissue tumours); they were shown to display different responses to toxin exposure and have different growth kinetics. We performed analysis of the cell cycle, DNA synthesis and expression of p21 and p53 in the presence and absence of the toxin in all cell lines exposed. The results of cell cycle cytofluorometric analysis show significant alterations of cell cycle progression as a result of toxin treatment. In all cell lines exposure to a 24 h toxin treatment causes a dose-dependent accumulation in S phase, however, the ability to recover from impairment to traverse S phase varies in the cell lines under study. SK-N-MC cells appear more prone to resume DNA synthesis when the toxin is removed, while the other two cell lines maintain a significant inhibition of DNA synthesis, as indicated by cytofluorimetry and [(3)H]dTR incorporation. The level of p53 and p21 expression in the three cell lines was examined by western blot analysis and significant differences were detected. The ready resumption of DNA synthesis displayed by SK-N-MC cells could possibly be related to the absence of p53 control of cell cycle progression.

  13. 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.

  14. Procollagen mRNA metabolism during the fibroblast cell cycle and its synthesis in transformed cells.

    PubMed

    Parker, I; Fitschen, W

    1980-06-25

    Procollagen mRNA was isolated from mouse embryos and used for the synthesis of a highly labelled cDNA probe complementary to collagen mRNA. This probe was used for the investigation of procollagen mRNA metabolism during the cell cycle of 3T6 mouse embryo fibroblasts in culture. Titration hybridization experiments revealed that procollagen mRNA was present throughout the cell cycle following stumulation of confluent monolayers. Procollagen mRNA levels of sparse cultures appeared similar to those of unstimulated monolayers. The fluctuating levels of collagen synthesis during the cell cycle can be ascribed to changes in the amount of collagen mRNA present. In mouse sarcoma virus transformed 3T3 cells only 20--30% of the amount of procollagen mRNA in 3T3 cells is present indicating that the decline in collagen synthesis is due to mRNA availability.

  15. MYC-repressed long noncoding RNAs antagonize MYC-induced cell proliferation and cell cycle progression

    PubMed Central

    Jeon, Young-Jun; Fadda, Paolo; Alder, Hansjuerg; Croce, Carlo M.

    2015-01-01

    The transcription factor MYC is a proto-oncogene regulating cell proliferation, cell cycle, apoptosis and metabolism. The recent identification of MYC-regulated long noncoding RNAs (lncRNAs) expands our knowledge of the role of lncRNAs in MYC functions. Here, we identify MYC-repressed lncRNAs named MYCLo-4, -5 and -6 by comparing 3 categories of lncRNAs (downregulated in highly MYC-expressing colorectal cancer, up-regulated by MYC knockdown in HCT116, upregulated by MYC knockdown in RKO). The MYC-repressed MYCLos are implicated in MYC-modulated cell proliferation through cell cycle regulation. By screening cell cycle-related genes regulated by MYC and the MYC-repressed MYCLos, we identified the MYC-repressed gene GADD45A as a target gene of the MYC-repressed MYCLos such as MYCLo-4 and MYCLo-6. PMID:26003165

  16. 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.

  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. 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.

  19. Metformin impairs growth of endometrial cancer cells via cell cycle arrest and concomitant autophagy and apoptosis

    PubMed Central

    2014-01-01

    Background Effective therapies for early endometrial cancer usually involve surgical excision and consequent infertility Therefore, new treatment approaches that preserve fertility should be developed. Metformin, a well-tolerated anti-diabetic drug, can inhibit cancer cell growth. However, the mechanism of metformin action is not well understood. Here we investigate the roles of autophagy and apoptosis in the anti-cancer effects of metformin on endometrial cancer cells. Methods Ishikawa endometrial cancer cells were treated with metformin. WST-8 assays, colony formation assays, flow cytometry, caspase luminescence measurement, immunofluorescence, and western blots were used to assess the effects of metformin on cell viability, proliferation, cell cycle progression, apoptosis, and autophagy. Results Metformin-treated cells exhibited significantly lower viability and proliferation and significantly more cell cycle arrest in G1 and G2/M than control cells. These cells also exhibited significantly more apoptosis via both intrinsic and extrinsic pathways. In addition, metformin treatment induced autophagy. Inhibition of autophagy, either by Beclin1 knockdown or by 3-methyladenine-mediated inhibition of caspase-3/7, suppressed the anti-proliferative effects of metformin on endometrial cancer cells. These findings indicate that the anti-proliferative effects and apoptosis caused by metformin are partially or completely dependent on autophagy. Conclusions We showed that metformin suppresses endometrial cancer cell growth via cell cycle arrest and concomitant autophagy and apoptosis. PMID:24966801

  20. 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

  1. Hsp90 phosphorylation, Wee1 and the cell cycle.

    PubMed

    Mollapour, Mehdi; Tsutsumi, Shinji; Neckers, Len

    2010-06-15

    Heat Shock Protein 90 (Hsp90) is an essential molecular chaperone in eukaryotic cells, and it maintains the functional conformation of a subset of proteins that are typically key components of multiple regulatory and signaling networks mediating cancer cell proliferation, survival, and metastasis. It is possible to selectively inhibit Hsp90 using natural products such as geldanamycin (GA) or radicicol (RD), which have served as prototypes for development of synthetic Hsp90 inhibitors. These compounds bind within the ADP/ATP-binding site of the Hsp90 N-terminal domain to inhibit its ATPase activity. As numerous N-terminal domain inhibitors are currently undergoing extensive clinical evaluation, it is important to understand the factors that may modulate in vivo susceptibility to these drugs. We recently reported that Wee1Swe1-mediated, cell cycle-dependent, tyrosine phosphorylation of Hsp90 affects GA binding and impacts cancer cell sensitivity to Hsp90 inhibition. This phosphorylation also affects Hsp90 ATPase activity and its ability to chaperone a selected group of clients, comprised primarily of protein kinases. Wee1 regulates the G2/M transition. Here we present additional data demonstrating that tyrosine phosphorylation of Hsp90 by Wee1Swe1 is important for Wee1Swe1 association with Hsp90 and for Wee1Swe1 stability. Yeast expressing non-phosphorylatable yHsp90-Y24F, like swe1∆ yeast, undergo premature nuclear division that is insensitive to G2/M checkpoint arrest. These findings demonstrate the importance of Hsp90 phosphorylation for proper cell cycle regulation. PMID:20519952

  2. 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

  3. 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

  4. 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

  5. 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.

  6. Evaluation of effect of triterpenes and limonoids on cell growth, cell cycle and apoptosis in human tumor cell line.

    PubMed

    Cazal, Cristiane M; Choosang, Kantima; Severino, Vanessa Gisele P; Soares, Marcio S; Sarria, Andre Lucio F; Fernandes, Joao B; Silva, Maria Fatima G F; Vieira, Paulo Cezar; Pakkong, Pannee; Almeida, Gabriela M; Vasconcelos, M Helena; Nascimento, Maria S J; Pinto, Madalena M M

    2010-12-01

    Six triterpenes and eight limonoids were evaluated for their capacity to inhibit the growth of three human tumour cell lines, breast adenocarcinoma (MCF-7), non-small cell lung cancer (NCI-H460) and melanoma (A375-C5). The mechanisms involved in the observed cell growth arrest of the four most potent compounds were carried out by studying their effect in cell cycle profile and programmed cell death. The results showed that one triterpene (odoratol) and two limonoids (gedunin and cedrelone) caused cell cycle arrest while only the limonoids gedunin and cedrelone were found to be very potent inducers of apoptosis. PMID:21269253

  7. Induction of cell cycle arrest in prostate cancer cells by the dietary compound isoliquiritigenin.

    PubMed

    Lee, Yeo Myeong; Lim, Do Young; Choi, Hyun Ju; Jung, Jae In; Chung, Won-Yoon; Park, Jung Han Yoon

    2009-02-01

    Isoliquiritigenin (ISL), a flavonoid chalcone that is present in licorice, shallot, and bean sprouts, is known to have antitumorigenic activities. The present study examined whether ISL alters prostate cancer cell cycle progression. DU145 human and MatLyLu (MLL) rat prostate cancer cells were cultured with various concentrations of ISL. In both DU145 and MLL cells treated with ISL, the percentage of cells in the G1 phase increased, and the incorporation of [(3)H]thymidine decreased. ISL decreased the protein levels of cyclin D1, cyclin E, and cyclin-dependent kinase (CDK) 4, whereas cyclin A and CDK2 expressions were unaltered in cells treated with ISL. The expression of the CDK inhibitor p27(KIP1) was increased in cells treated with 20 micromol/L ISL. In addition, treatment of cells with 20 micromol/L ISL for 24 hours led to G2/M cell cycle arrest. Cell division control (CDC) 2 protein levels remained unchanged. The protein levels of phospho-CDC2 (Tyr15) and cyclin B1 were increased, and the CDC25C level was decreased by ISL dose-dependently. We demonstrate that ISL promotes cell cycle arrest in DU145 and MLL cells, thereby providing insights into the mechanisms underlying its antitumorigenic activities.

  8. Induction of cell cycle arrest in prostate cancer cells by the dietary compound isoliquiritigenin.

    PubMed

    Lee, Yeo Myeong; Lim, Do Young; Choi, Hyun Ju; Jung, Jae In; Chung, Won-Yoon; Park, Jung Han Yoon

    2009-02-01

    Isoliquiritigenin (ISL), a flavonoid chalcone that is present in licorice, shallot, and bean sprouts, is known to have antitumorigenic activities. The present study examined whether ISL alters prostate cancer cell cycle progression. DU145 human and MatLyLu (MLL) rat prostate cancer cells were cultured with various concentrations of ISL. In both DU145 and MLL cells treated with ISL, the percentage of cells in the G1 phase increased, and the incorporation of [(3)H]thymidine decreased. ISL decreased the protein levels of cyclin D1, cyclin E, and cyclin-dependent kinase (CDK) 4, whereas cyclin A and CDK2 expressions were unaltered in cells treated with ISL. The expression of the CDK inhibitor p27(KIP1) was increased in cells treated with 20 micromol/L ISL. In addition, treatment of cells with 20 micromol/L ISL for 24 hours led to G2/M cell cycle arrest. Cell division control (CDC) 2 protein levels remained unchanged. The protein levels of phospho-CDC2 (Tyr15) and cyclin B1 were increased, and the CDC25C level was decreased by ISL dose-dependently. We demonstrate that ISL promotes cell cycle arrest in DU145 and MLL cells, thereby providing insights into the mechanisms underlying its antitumorigenic activities. PMID:19298190

  9. Platinum-zoledronate complex blocks gastric cancer cell proliferation by inducing cell cycle arrest and apoptosis.

    PubMed

    Yang, Hui; Qiu, Ling; Zhang, Li; Lv, Gaochao; Li, Ke; Yu, Huixin; Xie, Minhao; Lin, Jianguo

    2016-08-01

    A series of novel dinuclear platinum complexes based on the bisphosphonate ligands have been synthesized and characterized in our recent study. For the purpose of discovering the pharmacology and action mechanisms of this kind of compounds, the most potent compound [Pt(en)]2ZL was selected for systematic investigation. In the present study, the inhibition effect on the human gastric cancer cell lines SGC7901 and action mechanism of [Pt(en)]2ZL were investigated. The traditional 3-[4,5-dimethyl-2-thiazolyl]-2,5-diphenyl-2-tetrazolium bromide (MTT) assay and colony formation assay were carried out to study the effect of [Pt(en)]2ZL on the cell viability and proliferation capacity, respectively. The senescence-associated β-galactosidase staining and immunofluorescence staining were also performed to assess the cell senescence and microtubule polymerization. Fluorescence staining and flow cytometry (FCM) were used to monitor the cell cycle distribution and apoptosis, and Western blot analysis was applied to examine the expression of several apoptosis-related proteins. The results demonstrated that [Pt(en)]2ZL exhibited remarkable cytotoxicity and anti-proliferative effects on the SGC7901 cells in a dose- and time-dependent manner, and it also induced cell senescence and abnormal microtubule assembly. The cell apoptosis and cell cycle arrest induced by [Pt(en)]2ZL were also observed with the fluorescence staining and FCM. The expressions of cell cycle regulators (p53, p21, cyclin D1, cyclin E, and cyclin-dependent kinase (CDK)2) and apoptosis-related proteins (Bcl-2, Bax, caspase-3, poly ADP ribose polymerase (PARP), and survivin) were regulated by the treatment of [Pt(en)]2ZL, resulting in the cell cycle arrest and apoptosis. Therefore, [Pt(en)]2ZL exerted anti-tumor effect on the gastric cancer via inducing cell cycle arrest at G1/S phase and apoptosis. PMID:26891667

  10. Ghrelin regulates cell cycle-related gene expression in cultured hippocampal neural stem cells.

    PubMed

    Chung, Hyunju; Park, Seungjoon

    2016-08-01

    We have previously demonstrated that ghrelin stimulates the cellular proliferation of cultured adult rat hippocampal neural stem cells (NSCs). However, little is known about the molecular mechanisms by which ghrelin regulates cell cycle progression. The purpose of this study was to investigate the potential effects of ghrelin on cell cycle regulatory molecules in cultured hippocampal NSCs. Ghrelin treatment increased proliferation assessed by CCK-8 proliferation assay. The expression levels of proliferating cell nuclear antigen and cell division control 2, well-known cell-proliferating markers, were also increased by ghrelin. Fluorescence-activated cell sorting analysis revealed that ghrelin promoted progression of cell cycle from G0/G1 to S phase, whereas this progression was attenuated by the pretreatment with specific inhibitors of MEK/extracellular signal-regulated kinase 1/2, phosphoinositide 3-kinase/Akt, mammalian target of rapamycin, and janus kinase 2/signal transducer and activator of transcription 3. Ghrelin-induced proliferative effect was associated with increased expression of E2F1 transcription factor in the nucleus, as determined by Western blotting and immunofluorescence. We also found that ghrelin caused an increase in protein levels of positive regulators of cell cycle, such as cyclin A and cyclin-dependent kinase (CDK) 2. Moreover, p27(KIP1) and p57(KIP2) protein levels were reduced when cell were exposed to ghrelin, suggesting downregulation of CDK inhibitors may contribute to proliferative effect of ghrelin. Our data suggest that ghrelin targets both cell cycle positive and negative regulators to stimulate proliferation of cultured hippocampal NSCs. PMID:27325242

  11. 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

  12. EDD induces cell cycle arrest by increasing p53 levels.

    PubMed

    Smits, Veronique A J

    2012-02-15

    Tight regulation of p53 is essential for its central role in maintaining genome stability and tumor prevention. Here, EDD/ UBR5/hHyd, hereafter called EDD, is identified as a novel regulator of p53. Downregulation of EDD results in elevated p53 protein levels both in transformed and untransformed cells. Concomitant with a rise in p53, the levels of p21, a critical p53 target, are also elevated in these conditions. Surprisingly, EDD knockdown does not affect p53 protein stability, and p53 mRNA levels do not increase significantly upon EDD depletion. Consistent with the function of p53, EDD downregulation triggers a senescent phenotype in fibroblasts at later time points. In addition, the increased p53 levels upon EDD depletion cause a G(1) arrest, as co-depletion of EDD and p53 completely rescues this effect on cell cycle progression. PMID:22374670

  13. 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. PMID:26925838

  14. Alterations in cell cycle regulation in mouse skin tumors.

    PubMed

    Balasubramanian, S; Ahmad, N; Jeedigunta, S; Mukhtar, H

    1998-02-24

    The connection between cell cycle and cancer has become obvious in as much as it is considered that dysregulated cellular proliferation is a hallmark of cancer. In many studies, the dysregulation of the cyclin-cdk-cki network has been reported in experimental animal and human tumors, but to our knowledge a complete profile of alterations in regulatory molecules in any tumor model system is lacking. In this study, we assessed the expression of various cyclins, cyclin dependent kinases, and cyclin kinase inhibitors in chemically induced squamous papillomas in SENCAR mouse skin. Western blot analysis data showed a significant upregulation of cyclins (31, 6, 19, and 12 folds elevation for cyclin-D1, D2, E, and A, respectively) in tumors compared to the normal skin. The protein expression of the cdk (1, 2, and 4) was also found to be elevated in tumors compared to normal skin (33 fold for cdk1, 14 fold for cdk2, and 9 fold for cdk4). In tumors, compared to the normal skin, a significant increase in the level of protein expression of p27 and p57 (4 and 3 fold, respectively) was evident. In normal skin, p16 and p21 were not detectable but significant expression of these proteins was detected in tumors. Taken together, these data provide evidence that cell cycle deregulation in G1-phase is a critical event during the course of two stage skin carcinogenesis. This may have relevance to epithelial cancers in general.

  15. Anillin interacts with microtubules and is part of the astral pathway that defines cortical domains.

    PubMed

    van Oostende Triplet, Chloe; Jaramillo Garcia, Melina; Haji Bik, Husni; Beaudet, Daniel; Piekny, Alisa

    2014-09-01

    Cytokinesis occurs by the ingression of an actomyosin ring that separates the cell into two daughter cells. The mitotic spindle, comprising astral and central spindle microtubules, couples contractile ring ingression with DNA segregation. Cues from the central spindle activate RhoA, the upstream regulator of the contractile ring. However, additional cues from the astral microtubules also reinforce the localization of active RhoA. Using human cells, we show that astral and central spindle microtubules independently control the localization of contractile proteins during cytokinesis. Astral microtubules restrict the accumulation and localization of contractile proteins during mitosis, whereas the central spindle forms a discrete ring by directing RhoA activation in the equatorial plane. Anillin stabilizes the contractile ring during cytokinesis. We show that human anillin interacts with astral microtubules and that this interaction is competed by the cortical recruitment of anillin by active RhoA. Anillin restricts the localization of myosin to the equatorial cortex and that of NuMA (part of the microtubule-tethering complex that regulates spindle position) to the polar cortex. The sequestration of anillin by astral microtubules might alter the organization of cortical proteins to polarize cells for cytokinesis. PMID:24994938

  16. Expression of Cell Cycle–Related Genes With Cytokine-Induced Cell Cycle Progression of Primitive Hematopoietic Stem Cells

    PubMed Central

    Dooner, Gerri J.; Del Tatto, Michael; Colvin, Gerald A.; Johnson, Kevin; Dooner, Mark S.

    2010-01-01

    Primitive marrow lineage-negative rhodamine low and Hoechst low (LRH) stem cells isolated on the basis of quiescence respond to the cytokines thrombopoietin, FLT3L, and steel factor by synchronously progressing through cell cycle. We have now profiled the mRNA expression, as determined by real-time RT-PCR, of 47 hematopoietic or cell cycle-related genes, focusing on the variations in the cell cycle regulators with cycle transit. LRH stem cells, at isolation, showed expression of all interrogated genes, but at relatively low levels. In our studies, there was a good deal of consistency with regard to cell cycle regulatory genes involved in the G1/S progression point of LRH murine stem cells. The observed pattern of expression of cyclin A2 is consistent with actions at these phases of cell cycle. Minimal elevations were seen at 16 h with higher elevations at 24, 32, 40, and 48 h times encompassing S, G2, and M phases. CDK2 expression pattern was also consistent with a role in G1/S transition with a modest elevation at 24 h and more substantial elevation at 32 h. The observed pattern of expression of cyclin F mRNA with marked elevations at 16–40 h was also consistent with actions in S and G2 phases. Cyclin D1 expression pattern was less consistent with its known role in G1 progression. The alterations in multiple other cell cycle regulators were consistent with previous information obtained in other cell systems. The cycle regulatory mechanics appears to be preserved across broad ranges of cell types. PMID:19788373

  17. The Analysis of Cell Cycle, Proliferation, and Asymmetric Cell Division by Imaging Flow Cytometry.

    PubMed

    Filby, Andrew; Day, William; Purewal, Sukhveer; Martinez-Martin, Nuria

    2016-01-01

    Measuring cellular DNA content by conventional flow cytometry (CFC) and fluorescent DNA-binding dyes is a highly robust method for analysing cell cycle distributions within heterogeneous populations. However, any conclusions drawn from single-parameter DNA analysis alone can often be confounded by the asynchronous nature of cell proliferation. We have shown that by combining fluorescent DNA stains with proliferation tracking dyes and antigenic staining for mitotic cells one can elucidate the division history and cell cycle position of any cell within an asynchronously dividing population. Furthermore if one applies this panel to an imaging flow cytometry (IFC) system then the spatial information allows resolution of the four main mitotic phases and the ability to study molecular distributions within these populations. We have employed such an approach to study the prevalence of asymmetric cell division (ACD) within activated immune cells by measuring the distribution of key fate determining molecules across the plane of cytokinesis in a high-throughput, objective, and internally controlled manner. Moreover the ability to perform high-resolution, temporal dissection of the cell division process lends itself perfectly to investigating the influence chemotherapeutic agents exert on the proliferative capacity of transformed cell lines. Here we describe the method in detail and its application to both ACD and general cell cycle analysis. PMID:27460238

  18. Coordination between donor cell type and cell cycle stage improves nuclear cloning efficiency in cattle.

    PubMed

    Wells, D N; Laible, G; Tucker, F C; Miller, A L; Oliver, J E; Xiang, T; Forsyth, J T; Berg, M C; Cockrem, K; L'Huillier, P J; Tervit, H R; Oback, B

    2003-01-01

    Several studies have shown that both quiescent and proliferating somatic donor cells can be fully reprogrammed after nuclear transfer (NT) and result in viable offspring. So far, however, no comparative study has conclusively demonstrated the relative importance of donor cell cycle stage on nuclear cloning efficiency. Here, we compare two different types of bovine fetal fibroblasts (BFFs) that were synchronized in G(0), G(1), and different phases within G(1). We show that for non-transgenic (non-TG) fibroblasts, serum starvation into G(0) results in a significantly higher percentage of viable calves at term than synchronization in early G(1) or late G(1). For transgenic fibroblasts, however, cells selected in G(1) show significantly higher development to calves at term and higher post-natal survival to weaning than cells in G(0). This suggests that it may be necessary to coordinate donor cell type and cell cycle stage to maximize overall cloning efficiency.

  19. Lineage-specific interface proteins match up the cell cycle and differentiation in embryo stem cells.

    PubMed

    Re, Angela; Workman, Christopher T; Waldron, Levi; Quattrone, Alessandro; Brunak, Søren

    2014-09-01

    The shortage of molecular information on cell cycle changes along embryonic stem cell (ESC) differentiation prompts an in silico approach, which may provide a novel way to identify candidate genes or mechanisms acting in coordinating the two programs. We analyzed germ layer specific gene expression changes during the cell cycle and ESC differentiation by combining four human cell cycle transcriptome profiles with thirteen in vitro human ESC differentiation studies. To detect cross-talk mechanisms we then integrated the transcriptome data that displayed differential regulation with protein interaction data. A new class of non-transcriptionally regulated genes was identified, encoding proteins which interact systematically with proteins corresponding to genes regulated during the cell cycle or cell differentiation, and which therefore can be seen as interface proteins coordinating the two programs. Functional analysis gathered insights in fate-specific candidates of interface functionalities. The non-transcriptionally regulated interface proteins were found to be highly regulated by post-translational ubiquitylation modification, which may synchronize the transition between cell proliferation and differentiation in ESCs. PMID:25173649

  20. Gold nanoparticle sensitize radiotherapy of prostate cancer cells by regulation of the cell cycle

    NASA Astrophysics Data System (ADS)

    Roa, Wilson; Zhang, Xiaojing; Guo, Linghong; Shaw, Andrew; Hu, Xiuying; Xiong, Yeping; Gulavita, Sunil; Patel, Samir; Sun, Xuejun; Chen, Jie; Moore, Ronald; Xing, James Z.

    2009-09-01

    Glucose-capped gold nanoparticles (Glu-GNPs) have been used to improve cellular targeting and radio-sensitization. In this study, we explored the mechanism of Glu-GNP enhanced radiation sensitivity in radiation-resistant human prostate cancer cells. Cell survival and proliferation were measured using MTT and clonogenic assay. Flow cytometry with staining by propidium iodide (PI) was performed to study the cell cycle changes induced by Glu-GNPs, and western blotting was used to determine the expression of p53 and cyclin proteins that correlated to cell cycle regulation. With 2 Gy of ortho-voltage irradiation, Glu-GNP showed a 1.5-2.0 fold enhancement in growth inhibition when compared to x-rays alone. Comparing the cell cycle change, Glu-GNPs induced acceleration in the G0/G1 phase and accumulation of cells in the G2/M phase at 29.8% versus 18.4% for controls at 24 h. G2/M arrest was accompanied by decreased expression of p53 and cyclin A, and increased expression of cyclin B1 and cyclin E. In conclusion, Glu-GNPs trigger activation of the CDK kinases leading to cell cycle acceleration in the G0/G1 phase and accumulation in the G2/M phase. This activation is accompanied by a striking sensitization to ionizing radiation, which may have clinical implications.

  1. [Variability of the duration of the cell cycle in pig embryo kidney cells in monolayer culture and correlation of the cycle duration in sister cells].

    PubMed

    Blokhin, A V; Voronkova, L N; Sakharov, V N

    1985-07-01

    The distribution of generation time of sister cells for the exponentially proliferating monolayer SPEV culture was obtained with time lapse cinemicrographic technique. The distribution is characterized by the average generation time equal to 24.3 hour, with the variation coefficient, asymmetry coefficient and correlation coefficient for sister pair cell being, respectively, 17%, 0.2 and 0.78. The results obtained are compared with the prediction of "a random transition" in the cell cycle. PMID:3901449

  2. Transgenerational cell fate profiling: a method for the graphical presentation of complex cell cycle alterations.

    PubMed

    Jemaà, Mohamed; Galluzzi, Lorenzo; Kepp, Oliver; Castedo, Maria; Rello-Varona, Santiago; Vitale, Ilio; Kroemer, Guido

    2013-01-01

    The illicit generation of tetraploid cells constitutes a prominent driver of oncogenesis, as it often precedes the development of aneuploidy and genomic instability. In addition, tetraploid (pre-)malignant cells display an elevated resistance against radio- and chemotherapy. Here, we report a strategy to preferentially kill tetraploid tumor cells based on the broad-spectrum kinase inhibitor SP600125. Live videomicroscopy revealed that SP600125 affects the execution of mitosis, impedes proper cell division and/or activates apoptosis in near-to-tetraploid, though less so in parental, cancer cells. We propose a novel graphical model to quantify the differential response of diploid and tetraploid cells to mitotic perturbators, including SP600125, which we baptized "transgenerational cell fate profiling." We speculate that this representation constitutes a valid alternative to classical "single-cell fate" and "genealogical" profiling and, hence, may facilitate the analysis of cell fate within a heterogeneous population as well as the visual examination of cell cycle alterations.

  3. Sparstolonin B Inhibits Pro-Angiogenic Functions and Blocks Cell Cycle Progression in Endothelial Cells

    PubMed Central

    Bateman, Henry R.; Liang, Qiaoli; Fan, Daping; Rodriguez, Vanessa; Lessner, Susan M.

    2013-01-01

    Sparstolonin B (SsnB) is a novel bioactive compound isolated from Sparganium stoloniferum, an herb historically used in Traditional Chinese Medicine as an anti-tumor agent. Angiogenesis, the process of new capillary formation from existing blood vessels, is dysregulated in many pathological disorders, including diabetic retinopathy, tumor growth, and atherosclerosis. In functional assays, SsnB inhibited endothelial cell tube formation (Matrigel method) and cell migration (Transwell method) in a dose-dependent manner. Microarray experiments with human umbilical vein endothelial cells (HUVECs) and human coronary artery endothelial cells (HCAECs) demonstrated differential expression of several hundred genes in response to SsnB exposure (916 and 356 genes, respectively, with fold change ≥2, p<0.05, unpaired t-test). Microarray data from both cell types showed significant overlap, including genes associated with cell proliferation and cell cycle. Flow cytometric cell cycle analysis of HUVECs treated with SsnB showed an increase of cells in the G1 phase and a decrease of cells in the S phase. Cyclin E2 (CCNE2) and Cell division cycle 6 (CDC6) are regulatory proteins that control cell cycle progression through the G1/S checkpoint. Both CCNE2 and CDC6 were downregulated in the microarray data. Real Time quantitative PCR confirmed that gene expression of CCNE2 and CDC6 in HUVECs was downregulated after SsnB exposure, to 64% and 35% of controls, respectively. The data suggest that SsnB may exert its anti-angiogenic properties in part by downregulating CCNE2 and CDC6, halting progression through the G1/S checkpoint. In the chick chorioallantoic membrane (CAM) assay, SsnB caused significant reduction in capillary length and branching number relative to the vehicle control group. Overall, SsnB caused a significant reduction in angiogenesis (ANOVA, p<0.05), demonstrating its ex vivo efficacy. PMID:23940584

  4. Helicobacter pylori interferes with an embryonic stem cell micro RNA cluster to block cell cycle progression

    PubMed Central

    2011-01-01

    Background MicroRNAs, post-transcriptional regulators of eukaryotic gene expression, are implicated in host defense against pathogens. Viruses and bacteria have evolved strategies that suppress microRNA functions, resulting in a sustainable infection. In this work we report that Helicobacter pylori, a human stomach-colonizing bacterium responsible for severe gastric inflammatory diseases and gastric cancers, downregulates an embryonic stem cell microRNA cluster in proliferating gastric epithelial cells to achieve cell cycle arrest. Results Using a deep sequencing approach in the AGS cell line, a widely used cell culture model to recapitulate early events of H. pylori infection of gastric mucosa, we reveal that hsa-miR-372 is the most abundant microRNA expressed in this cell line, where, together with hsa-miR-373, it promotes cell proliferation by silencing large tumor suppressor homolog 2 (LATS2) gene expression. Shortly after H. pylori infection, miR-372 and miR-373 synthesis is highly inhibited, leading to the post-transcriptional release of LATS2 expression and thus, to a cell cycle arrest at the G1/S transition. This downregulation of a specific cell-cycle-regulating microRNA is dependent on the translocation of the bacterial effector CagA into the host cells, a mechanism highly associated with the development of severe atrophic gastritis and intestinal-type gastric carcinoma. Conclusions These data constitute a novel example of host-pathogen interplay involving microRNAs, and unveil the couple LATS2/miR-372 and miR-373 as an unexpected mechanism in infection-induced cell cycle arrest in proliferating gastric cells, which may be relevant in inhibition of gastric epithelium renewal, a major host defense mechanism against bacterial infections. PMID:22027184

  5. (Z)-3,5,4'-Trimethoxystilbene Limits Hepatitis C and Cancer Pathophysiology by Blocking Microtubule Dynamics and Cell-Cycle Progression.

    PubMed

    Nguyen, Charles B; Kotturi, Hari; Waris, Gulam; Mohammed, Altaf; Chandrakesan, Parthasarathy; May, Randal; Sureban, Sripathi; Weygant, Nathaniel; Qu, Dongfeng; Rao, Chinthalapally V; Dhanasekaran, Danny N; Bronze, Michael S; Houchen, Courtney W; Ali, Naushad

    2016-08-15

    Hepatocellular carcinoma (HCC) is the third most common cause of cancer-related deaths worldwide. Chronic hepatitis C virus (HCV) infection causes induction of several tumors/cancer stem cell (CSC) markers and is known to be a major risk factor for development of HCC. Therefore, drugs that simultaneously target viral replication and CSC properties are needed for a risk-free treatment of advanced stage liver diseases, including HCC. Here, we demonstrated that (Z)-3,5,4'-trimethoxystilbene (Z-TMS) exhibits potent antitumor and anti-HCV activities without exhibiting cytotoxicity to human hepatocytes in vitro or in mice livers. Diethylnitrosamine (DEN)/carbon tetrachloride (CCl4) extensively induced expression of DCLK1 (a CSC marker) in the livers of C57BL/6 mice following hepatic injury. Z-TMS exhibited hepatoprotective effects against DEN/CCl4-induced injury by reducing DCLK1 expression and improving histologic outcomes. The drug caused bundling of DCLK1 with microtubules and blocked cell-cycle progression at G2-M phase in hepatoma cells via downregulation of CDK1, induction of p21(cip1/waf1) expression, and inhibition of Akt (Ser(473)) phosphorylation. Z-TMS also inhibited proliferation of erlotinib-resistant lung adenocarcinoma cells (H1975) bearing the T790M EGFR mutation, most likely by promoting autophagy and nuclear fragmentation. In conclusion, Z-TMS appears to be a unique therapeutic agent targeting HCV and concurrently eliminating cells with neoplastic potential during chronic liver diseases, including HCC. It may also be a valuable drug for targeting drug-resistant carcinomas and cancers of the lungs, pancreas, colon, and intestine, in which DCLK1 is involved in tumorigenesis. Cancer Res; 76(16); 4887-96. ©2016 AACR. PMID:27287718

  6. Cycle life test and failure model of nickel-hydrogen cells

    NASA Technical Reports Server (NTRS)

    Smithrick, J. J.

    1983-01-01

    Six ampere hour individual pressure vessel nickel hydrogen cells were charge/discharge cycled to failure. Failure as used here is defined to occur when the end of discharge voltage degraded to 0.9 volts. They were cycled under a low earth orbit cycle regime to a deep depth of discharge (80 percent of rated ampere hour capacity). Both cell designs were fabricated by the same manufacturer and represent current state of the art. A failure model was advanced which suggests both cell designs have inadequate volume tolerance characteristics. The limited existing data base at a deep depth of discharge (DOD) was expanded. Two cells of each design were cycled. One COMSAT cell failed at cycle 1712 and the other failed at cycle 1875. For the Air Force/Hughes cells, one cell failed at cycle 2250 and the other failed at cycle 2638. All cells, of both designs, failed due to low end of discharge voltage (0.9 volts). No cell failed due to electrical shorts. After cell failure, three different reconditioning tests (deep discharge, physical reorientation, and open circuit voltage stand) were conducted on all cells of each design. A fourth reconditioning test (electrolyte addition) was conducted on one cell of each design. In addition post cycle cell teardown and failure analysis were performed on the one cell of each design which did not have electrolyte added after failure.

  7. Tcf3 and cell cycle factors contribute to butyrate resistance in colorectal cancer cells

    SciTech Connect

    Chiaro, Christopher; Lazarova, Darina L.; Bordonaro, Michael

    2012-11-09

    Highlights: Black-Right-Pointing-Pointer We investigate mechanisms responsible for butyrate resistance in colon cancer cells. Black-Right-Pointing-Pointer Tcf3 modulates butyrate's effects on Wnt activity and cell growth in resistant cells. Black-Right-Pointing-Pointer Tcf3 modulation of butyrate's effects differ by cell context. Black-Right-Pointing-Pointer Cell cycle factors are overexpressed in the resistant cells. Black-Right-Pointing-Pointer Reversal of altered gene expression can enhance the anti-cancer effects of butyrate. -- Abstract: Butyrate, a fermentation product of dietary fiber, inhibits clonal growth in colorectal cancer (CRC) cells dependent upon the fold induction of Wnt activity. We have developed a CRC cell line (HCT-R) that, unlike its parental cell line, HCT-116, does not respond to butyrate exposure with hyperactivation of Wnt signaling and suppressed clonal growth. PCR array analyses revealed Wnt pathway-related genes, the expression of which differs between butyrate-sensitive HCT-116 CRC cells and their butyrate-resistant HCT-R cell counterparts. We identified overexpression of Tcf3 as being partially responsible for the butyrate-resistant phenotype, as this DNA-binding protein suppresses the hyperinduction of Wnt activity by butyrate. Consequently, Tcf3 knockdown in HCT-R cells restores their sensitivity to the effects of butyrate on Wnt activity and clonal cell growth. Interestingly, the effects of overexpressed Tcf3 differ between HCT-116 and HCT-R cells; thus, in HCT-116 cells Tcf3 suppresses proliferation without rendering the cells resistant to butyrate. In HCT-R cells, however, the overexpression of Tcf3 inhibits Wnt activity, and the cells are still able to proliferate due to the higher expression levels of cell cycle factors, particularly those driving the G{sub 1} to S transition. Knowledge of the molecular mechanisms determining the variable sensitivity of CRC cells to butyrate may assist in developing approaches that prevent or

  8. The cell-cycle dependence of the spectra of proliferating normal and neoplastic single cells using confocal resonance Raman microspectroscopy

    NASA Astrophysics Data System (ADS)

    Boydston-White, Susie; Liu, Cheng-Hui; Alfano, Robert R.

    2013-03-01

    Confocal resonance Raman (RR) spectra were collected from single proliferating cells and analyzed to detect spectral patterns that are cell-cycle dependent, as a consequence of cellular proliferation — normal or abnormal. The cells' biochemical age at each time point was confirmed by immunohistochemical staining to identify the presence or absence of cellular components that appear and/or disappear as the cells proceed through the cell-cycle. The RR spectra were collected and compared for each time point as the cells proceeded through the cell cycle to determine what spectral vibrational patterns are cell-cycle dependent. In this study, the question is whether the cell-cycle dependent RR spectral patterns of the vibrational modes observed in proliferating normal and neoplastic single cells are due to a state of cancer or are simply the consequences of the cells' changing internal biochemistry due to the process of cellular proliferation --- normal or abnormal.

  9. SPARC expression induces cell cycle arrest via STAT3 signaling pathway in medulloblastoma cells

    SciTech Connect

    Chetty, Chandramu; Dontula, Ranadheer; Gujrati, Meena; Lakka, Sajani S.

    2012-01-13

    Highlights: Black-Right-Pointing-Pointer Ectopic expression of SPARC impaired cell proliferation in medulloblastoma cells. Black-Right-Pointing-Pointer SPARC expression induces STAT3 mediated cell cycle arrest in medulloblastoma cells. Black-Right-Pointing-Pointer SPARC expression significantly inhibited pre-established tumor growth in nude-mice. -- Abstract: Dynamic cell interaction with ECM components has profound influence in cancer progression. SPARC is a component of the ECM, impairs the proliferation of different cell types and modulates tumor cell aggressive features. We previously reported that SPARC expression significantly impairs medulloblastoma tumor growth in vivo. In this study, we demonstrate that expression of SPARC inhibits medulloblastoma cell proliferation. MTT assay indicated a dose-dependent reduction in tumor cell proliferation in adenoviral mediated expression of SPARC full length cDNA (Ad-DsRed-SP) in D425 and UW228 cells. Flow cytometric analysis showed that Ad-DsRed-SP-infected cells accumulate in the G2/M phase of cell cycle. Further, immunoblot and immunoprecipitation analyses revealed that SPARC induced G2/M cell cycle arrest was mediated through inhibition of the Cyclin-B-regulated signaling pathway involving p21 and Cdc2 expression. Additionally, expression of SPARC decreased STAT3 phosphorylation at Tyr-705; constitutively active STAT3 expression reversed SPARC induced G2/M arrest. Ad-DsRed-SP significantly inhibited the pre-established orthotopic tumor growth and tumor volume in nude-mice. Immunohistochemical analysis of tumor sections from mice treated with Ad-DsRed-SP showed decreased immunoreactivity for pSTAT3 and increased immunoreactivity for p21 compared to tumor section from mice treated with mock and Ad-DsRed. Taken together our studies further reveal that STAT3 plays a key role in SPARC induced G2/M arrest in medulloblastoma cells. These new findings provide a molecular basis for the mechanistic understanding of the

  10. Anti-hepatoma cells function of luteolin through inducing apoptosis and cell cycle arrest.

    PubMed

    Ding, Shixiong; Hu, Airong; Hu, Yaoren; Ma, Jianbo; Weng, Pengjian; Dai, Jinhua

    2014-04-01

    The aim of this study is to explore the apoptotic induction and cell cycle arrest function of luteolin on the liver cancer cells and the related mechanism. The liver cancer cell line SMMC-7721, BEL-7402, and normal liver cells HL-7702 were treated with different concentrations of luteolin. Cell proliferation ability was tested. Morphological changes of the apoptotic cells were observed under inverted fluorescence microscope after Hoechst33342 staining. We investigated the effect of luteolin on cell cycling and apoptosis with flow cytometry. The mitochondrial membrane potential changes were analyzed after JC-1 staining. Caspases-3 and Bcl-2 family proteins expression were analyzed by real-time PCR. Cell proliferation of SMMC-7721 and BEL-7402 were inhibited by luteolin, and the inhibition was dose-time-dependent. Luteolin could arrest the cells at G1/S stage, reduce mitochondrial membrane potential, and induce higher apoptosis rate and the typical apoptotic morphological changes of the liver carcinoma cells. Q-RT-PCR results also showed that luteolin increased Bax and caspase-3 expression significantly and upregulated Bcl-2 expression in a dose-dependent manner in liver carcinoma cells. However, the normal liver cells HL-7702 was almost not affected by luteolin treatment. Luteolin can inhibit SMMC-7721 and BEL-7402 cell proliferation in a time- and dose-dependent manner. And the mechanism maybe through arresting cell cycle at phase G1/S, enhancing Bax level, reducing anti-apoptotic protein Bcl-2 level, resulting in activating caspase-3 enzyme and decrease of mitochondrial membrane potential, and finally leading to cell apoptosis.

  11. Cell cycle progression in glioblastoma cells is unaffected by pathophysiological levels of hypoxia

    PubMed Central

    Richards, Rosalie; Jenkinson, Michael D.; Haylock, Brian J.

    2016-01-01

    Hypoxia is associated with the increased malignancy of a broad range of solid tumours. While very severe hypoxia has been widely shown to induce cell cycle arrest, the impact of pathophysiological hypoxia on tumour cell proliferation is poorly understood. The aim of this study was to investigate the effect of different oxygen levels on glioblastoma (GBM) cell proliferation and survival. GBM is an extremely aggressive brain tumour with a heterogeneous oxygenation pattern. The effects of a range of oxygen tensions on GBM cell lines and primary cells were assessed using flow cytometry. Results indicate that cell cycle distribution and viability are unaffected by long term exposure (24–96 h) to pathophysiological levels of oxygen (1–8% O2). Both transient cell cycle arrest and small amounts of cell death could only be detected when cells were exposed to severe hypoxia (0.1% O2). No significant changes in p21 protein expression levels were detected. These findings reinforce the importance of using physiologically relevant oxygen tensions when investigating tumour hypoxia, and help to explain how solid tumours can be both hypoxic and highly proliferative, as is the case with GBM. PMID:26966676

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

    PubMed Central

    Seidel, Hannah S; Kimble, Judith

    2015-01-01

    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. DOI: http://dx.doi.org/10.7554/eLife.10832.001 PMID:26551561

  13. Discovery of a Splicing Regulator Required for Cell Cycle Progression

    SciTech Connect

    Suvorova, Elena S.; Croken, Matthew; Kratzer, Stella; Ting, Li-Min; Conde de Felipe, Magnolia; Balu, Bharath; Markillie, Lye Meng; Weiss, Louis M.; Kim, Kami; White, Michael W.

    2013-02-01

    In the G1 phase of the cell division cycle, eukaryotic cells prepare many of the resources necessary for a new round of growth including renewal of the transcriptional and protein synthetic capacities and building the machinery for chromosome replication. The function of G1 has an early evolutionary origin and is preserved in single and multicellular organisms, although the regulatory mechanisms conducting G1 specific functions are only understood in a few model eukaryotes. Here we describe a new G1 mutant from an ancient family of apicomplexan protozoans. Toxoplasma gondii temperature-sensitive mutant 12-109C6 conditionally arrests in the G1 phase due to a single point mutation in a novel protein containing a single RNA-recognition-motif (TgRRM1). The resulting tyrosine to asparagine amino acid change in TgRRM1 causes severe temperature instability that generates an effective null phenotype for this protein when the mutant is shifted to the restrictive temperature. Orthologs of TgRRM1 are widely conserved in diverse eukaryote lineages, and the human counterpart (RBM42) can functionally replace the missing Toxoplasma factor. Transcriptome studies demonstrate that gene expression is downregulated in the mutant at the restrictive temperature due to a severe defect in splicing that affects both cell cycle and constitutively expressed mRNAs. The interaction of TgRRM1 with factors of the tri-SNP complex (U4/U6 & U5 snRNPs) indicate this factor may be required to assemble an active spliceosome. Thus, the TgRRM1 family of proteins is an unrecognized and evolutionarily conserved class of splicing regulators. This study demonstrates investigations into diverse unicellular eukaryotes, like the Apicomplexa, have the potential to yield new insights into important mechanisms conserved across modern eukaryotic kingdoms.

  14. Self-Sustained Oscillatory Sliding Movement of Doublet Microtubules and Flagellar Bend Formation.

    PubMed

    Ishijima, Sumio

    2016-01-01

    It is well established that the basis for flagellar and ciliary movements is ATP-dependent sliding between adjacent doublet microtubules. However, the mechanism for converting microtubule sliding into flagellar and ciliary movements has long remained unresolved. The author has developed new sperm models that use bull spermatozoa divested of their plasma membrane and midpiece mitochondrial sheath by Triton X-100 and dithiothreitol. These models enable the observation of both the oscillatory sliding movement of activated doublet microtubules and flagellar bend formation in the presence of ATP. A long fiber of doublet microtubules extruded by synchronous sliding of the sperm flagella and a short fiber of doublet microtubules extruded by metachronal sliding exhibited spontaneous oscillatory movements and constructed a one beat cycle of flagellar bending by alternately actuating. The small sliding displacement generated by metachronal sliding formed helical bends, whereas the large displacement by synchronous sliding formed planar bends. Therefore, the resultant waveform is a half-funnel shape, which is similar to ciliary movements. PMID:26863204

  15. Self-Sustained Oscillatory Sliding Movement of Doublet Microtubules and Flagellar Bend Formation

    PubMed Central

    Ishijima, Sumio

    2016-01-01

    It is well established that the basis for flagellar and ciliary movements is ATP-dependent sliding between adjacent doublet microtubules. However, the mechanism for converting microtubule sliding into flagellar and ciliary movements has long remained unresolved. The author has developed new sperm models that use bull spermatozoa divested of their plasma membrane and midpiece mitochondrial sheath by Triton X-100 and dithiothreitol. These models enable the observation of both the oscillatory sliding movement of activated doublet microtubules and flagellar bend formation in the presence of ATP. A long fiber of doublet microtubules extruded by synchronous sliding of the sperm flagella and a short fiber of doublet microtubules extruded by metachronal sliding exhibited spontaneous oscillatory movements and constructed a one beat cycle of flagellar bending by alternately actuating. The small sliding displacement generated by metachronal sliding formed helical bends, whereas the large displacement by synchronous sliding formed planar bends. Therefore, the resultant waveform is a half-funnel shape, which is similar to ciliary movements. PMID:26863204

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

    PubMed

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

    2016-05-19

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

  17. Dynamical modeling of the cell cycle and cell fate emergence in Caulobacter crescentus.

    PubMed

    Quiñones-Valles, César; Sánchez-Osorio, Ismael; Martínez-Antonio, Agustino

    2014-01-01

    The division of Caulobacter crescentus, a model organism for studying cell cycle and differentiation in bacteria, generates two cell types: swarmer and stalked. To complete its cycle, C. crescentus must first differentiate from the swarmer to the stalked phenotype. An important regulator involved in this process is CtrA, which operates in a gene regulatory network and coordinates many of the interactions associated to the generation of cellular asymmetry. Gaining insight into how such a differentiation phenomenon arises and how network components interact to bring about cellular behavior and function demands mathematical models and simulations. In this work, we present a dynamical model based on a generalization of the Boolean abstraction of gene expression for a minimal network controlling the cell cycle and asymmetric cell division in C. crescentus. This network was constructed from data obtained from an exhaustive search in the literature. The results of the simulations based on our model show a cyclic attractor whose configurations can be made to correspond with the current knowledge of the activity of the regulators participating in the gene network during the cell cycle. Additionally, we found two point attractors that can be interpreted in terms of the network configurations directing the two cell types. The entire network is shown to be operating close to the critical regime, which means that it is robust enough to perturbations on dynamics of the network, but adaptable to environmental changes.

  18. Dynamical Modeling of the Cell Cycle and Cell Fate Emergence in Caulobacter crescentus

    PubMed Central

    Quiñones-Valles, César; Sánchez-Osorio, Ismael; Martínez-Antonio, Agustino

    2014-01-01

    The division of Caulobacter crescentus, a model organism for studying cell cycle and differentiation in bacteria, generates two cell types: swarmer and stalked. To complete its cycle, C. crescentus must first differentiate from the swarmer to the stalked phenotype. An important regulator involved in this process is CtrA, which operates in a gene regulatory network and coordinates many of the interactions associated to the generation of cellular asymmetry. Gaining insight into how such a differentiation phenomenon arises and how network components interact to bring about cellular behavior and function demands mathematical models and simulations. In this work, we present a dynamical model based on a generalization of the Boolean abstraction of gene expression for a minimal network controlling the cell cycle and asymmetric cell division in C. crescentus. This network was constructed from data obtained from an exhaustive search in the literature. The results of the simulations based on our model show a cyclic attractor whose configurations can be made to correspond with the current knowledge of the activity of the regulators participating in the gene network during the cell cycle. Additionally, we found two point attractors that can be interpreted in terms of the network configurations directing the two cell types. The entire network is shown to be operating close to the critical regime, which means that it is robust enough to perturbations on dynamics of the network, but adaptable to environmental changes. PMID:25369202

  19. Quantitative imaging with Fucci and mathematics to uncover temporal dynamics of cell cycle progression.

    PubMed

    Saitou, Takashi; Imamura, Takeshi

    2016-01-01

    Cell cycle progression is strictly coordinated to ensure proper tissue growth, development, and regeneration of multicellular organisms. Spatiotemporal visualization of cell cycle phases directly helps us to obtain a deeper understanding of controlled, multicellular, cell cycle progression. The fluorescent ubiquitination-based cell cycle indicator (Fucci) system allows us to monitor, in living cells, the G1 and the S/G2/M phases of the cell cycle in red and green fluorescent colors, respectively. Since the discovery of Fucci technology, it has found numerous applications in the characterization of the timing of cell cycle phase transitions under diverse conditions and various biological processes. However, due to the complexity of cell cycle dynamics, understanding of specific patterns of cell cycle progression is still far from complete. In order to tackle this issue, quantitative approaches combined with mathematical modeling seem to be essential. Here, we review several studies that attempted to integrate Fucci technology and mathematical models to obtain quantitative information regarding cell cycle regulatory patterns. Focusing on the technological development of utilizing mathematics to retrieve meaningful information from the Fucci producing data, we discuss how the combined methods advance a quantitative understanding of cell cycle regulation.

  20. Cell Cycle Arrest by a Natural Product via G2/M Checkpoint

    PubMed Central

    2005-01-01

    CKBM is a natural product that exhibits a novel anti-tumor activity through the induction of cell cycle arrest and apoptosis. We have investigated its effects on cell cycle regulation using a gastric cancer cell line, AGS. The effects of CKBM on cell proliferation, cell cycle regulation and apoptosis were analyzed using BrdU (5-bromo-2'-deoxyuridine) cell proliferation assay and flow cytometric analysis, respectively. Specific cellular protein expressions were measured using Western blot analysis. Flow cytometric analysis indicated that CKBM induced G2/M cell cycle arrest and apoptosis, whereas differential protein expressions of p21, p53 and 14-3-3σ (stratifin) using Western blot analysis were enhanced. The differential expressions of p21, p53 and 14-3-3σ in AGS cancer cells after CKBM treatment may play critical roles in the G2/M cell cycle arrest that blocks cell proliferation and induces apoptosis. PMID:15968342

  1. Imaging Nuclear Morphology and Organization in Cleared Plant Tissues Treated with Cell Cycle Inhibitors.

    PubMed

    de Souza Junior, José Dijair Antonino; de Sa, Maria Fatima Grossi; Engler, Gilbert; Engler, Janice de Almeida

    2016-01-01

    Synchronization of root cells through chemical treatment can generate a large number of cells blocked in specific cell cycle phases. In plants, this approach can be employed for cell suspension cultures and plant seedlings. To identify plant cells in the course of the cell cycle, especially during mitosis in meristematic tissues, chemical inhibitors can be used to block cell cycle progression. Herein, we present a simplified and easy-to-apply protocol to visualize mitotic figures, nuclei morphology, and organization in whole Arabidopsis root apexes. The procedure is based on tissue clearing, and fluorescent staining of nuclear DNA with DAPI. The protocol allows carrying out bulk analysis of nuclei and cell cycle phases in root cells and will be valuable to investigate mutants like overexpressing lines of genes disturbing the plant cell cycle.

  2. Dihydroartemisinin (DHA) induces ferroptosis and causes cell cycle arrest in head and neck carcinoma cells.

    PubMed

    Lin, Renyu; Zhang, Ziheng; Chen, Lingfeng; Zhou, Yunfang; Zou, Peng; Feng, Chen; Wang, Li; Liang, Guang

    2016-10-10

    Head and neck cancer is the sixth most common cancer worldwide. Dihydroartemisinin (DHA), a semi-synthetic derivative of artemisinin, exhibits a wide range of biological roles including a highly efficient and specific anti-tumor activity. Here, we aimed to examine the effect of DHA on head and neck carcinoma cells and elucidate the potential mechanisms. We used five head and neck carcinoma cell lines and two non-tumorigenic normal epithelial cell lines to achieve our goals. Cells were exposed to DHA and subjected to cellular activity assays including viability, cell cycle analysis, cell death, and angiogenic phenotype. Our results show that DHA causes cell cycle arrest which is mediated through Forkhead box protein M1 (FOXM1). We also demonstrate that DHA induces ferroptosis and apoptosis in head and neck carcinoma cells. Lastly, our results show that DHA alters the angiogenic phenotype of cancer cells by reducing the expression of angiogenic factors and the ability of cancer cells to support endothelial cell tubule formation. Our study suggests that DHA specifically causes head and neck cancer cell death through contribution from both ferroptosis and apoptosis. DHA may represent an effective strategy in head and neck cancer treatment.

  3. Measuring cell cycle progression kinetics with metabolic labeling and flow cytometry.

    PubMed

    Fleisig, Helen; Wong, Judy

    2012-01-01

    Precise control of the initiation and subsequent progression through the various phases of the cell cycle are of paramount importance in proliferating cells. Cell cycle division is an integral part of growth and reproduction and deregulation of key cell cycle components have been implicated in the precipitating events of carcinogenesis. Molecular agents in anti-cancer therapies frequently target biological pathways responsible for the regulation and coordination of cell cycle division. Although cell cycle kinetics tend to vary according to cell type, the distribution of cells amongst the four stages of the cell cycle is rather consistent within a particular cell line due to the consistent pattern of mitogen and growth factor expression. Genotoxic events and other cellular stressors can result in a temporary block of cell cycle progression, resulting in arrest or a temporary pause in a particular cell cycle phase to allow for instigation of the appropriate response mechanism. The ability to experimentally observe the behavior of a cell population with reference to their cell cycle progression stage is an important advance in cell biology. Common procedures such as mitotic shake off, differential centrifugation or flow cytometry-based sorting are used to isolate cells at specific stages of the cell cycle. These fractionated, cell cycle phase-enriched populations are then subjected to experimental treatments. Yield, purity and viability of the separated fractions can often be compromised using these physical separation methods. As well, the time lapse between separation of the cell populations and the start of experimental treatment, whereby the fractionated cells can progress from the selected cell cycle stage, can pose significant challenges in the successful implementation and interpretation of these experiments. Other approaches to study cell cycle stages include the use of chemicals to synchronize cells. Treatment of cells with chemical inhibitors of key

  4. Differences in CART expression and cell cycle behavior discriminate sympathetic neuroblast from chromaffin cell lineages in mouse sympathoadrenal cells.

    PubMed

    Chan, Wing Hei; Gonsalvez, David G; Young, Heather M; Southard-Smith, E Michelle; Cane, Kylie N; Anderson, Colin R

    2016-02-01

    Adrenal medullary chromaffin cells and peripheral sympathetic neurons originate from a common sympathoadrenal (SA) progenitor cell. The timing and phenotypic changes that mark this lineage diversification are not fully understood. The present study investigated the expression patterns of phenotypic markers, and cell cycle dynamics, in the adrenal medulla and the neighboring suprarenal ganglion of embryonic mice. The noradrenergic marker, tyrosine hydroxylase (TH), was detected in both presumptive adrenal medulla and sympathetic ganglion cells, but with significantly stronger immunostaining in the former. There was intense cocaine and amphetamine-regulated transcript (CART) peptide immunostaining in most neuroblasts, whereas very few adrenal chromaffin cells showed detectable CART immunostaining. This phenotypic segregation appeared as early as E12.5, before anatomical segregation of the two cell types. Cell cycle dynamics were also examined. Initially, 88% of Sox10 positive (+) neural crest progenitors were proliferating at E10.5. Many SA progenitor cells withdrew from the cell cycle at E11.5 as they started to express TH. Whereas 70% of neuroblasts (TH+/CART+ cells) were back in the cell cycle at E12.5, only around 20% of chromaffin (CART negative) cells were in the cell cycle at E12.5 and subsequent days. Thus, chromaffin cell and neuroblast lineages showed differences in proliferative behavior from their earliest appearance. We conclude that the intensity of TH immunostaining and the expression of CART permit early discrimination of chromaffin cells and sympathetic neuroblasts, and that developing chromaffin cells exhibit significantly lower proliferative activity relative to sympathetic neuroblasts.

  5. Boron neutron capture therapy induces cell cycle arrest and cell apoptosis of glioma stem/progenitor cells in vitro

    PubMed Central

    2013-01-01

    Background Glioma stem cells in the quiescent state are resistant to clinical radiation therapy. An almost inevitable glioma recurrence is due to the persistence of these cells. The high linear energy transfer associated with boron neutron capture therapy (BNCT) could kill quiescent and proliferative cells. Methods The present study aimed to evaluate the effects of BNCT on glioma stem/progenitor cells in vitro. The damage induced by BNCT was assessed using cell cycle progression, apoptotic cell ratio and apoptosis-associated proteins expression. Results The surviving fraction and cell viability of glioma stem/progenitor cells were decreased compared with differentiated glioma cells using the same boronophenylalanine pretreatment and the same dose of neutron flux. BNCT induced cell cycle arrest in the G2/M phase and cell apoptosis via the mitochondrial pathway, with changes in the expression of associated proteins. Conclusions Glioma stem/progenitor cells, which are resistant to current clinical radiotherapy, could be effectively killed by BNCT in vitro via cell cycle arrest and apoptosis using a prolonged neutron irradiation, although radiosensitivity of glioma stem/progenitor cells was decreased compared with differentiated glioma cells when using the same dose of thermal neutron exposure and boronophenylalanine pretreatment. Thus, BNCT could offer an appreciable therapeutic advantage to prevent tumor recurrence, and may become a promising treatment in recurrent glioma. PMID:23915425

  6. Identifying and removing the cell-cycle effect from single-cell RNA-Sequencing data

    PubMed Central

    Barron, Martin; Li, Jun

    2016-01-01

    Single-cell RNA-Sequencing (scRNA-Seq) is a revolutionary technique for discovering and describing cell types in heterogeneous tissues, yet its measurement of expression often suffers from large systematic bias. A major source of this bias is the cell cycle, which introduces large within-cell-type heterogeneity that can obscure the differences in expression between cell types. The current method for removing the cell-cycle effect is unable to effectively identify this effect and has a high risk of removing other biological components of interest, compromising downstream analysis. We present ccRemover, a new method that reliably identifies the cell-cycle effect and removes it. ccRemover preserves other biological signals of interest in the data and thus can serve as an important pre-processing step for many scRNA-Seq data analyses. The effectiveness of ccRemover is demonstrated using simulation data and three real scRNA-Seq datasets, where it boosts the performance of existing clustering algorithms in distinguishing between cell types. PMID:27670849

  7. Single-cell analysis of transcription kinetics across the cell cycle

    PubMed Central

    Skinner, Samuel O; Xu, Heng; Nagarkar-Jaiswal, Sonal; Freire, Pablo R; Zwaka, Thomas P; Golding, Ido

    2016-01-01

    Transcription is a highly stochastic process. To infer transcription kinetics for a gene-of-interest, researchers commonly compare the distribution of mRNA copy-number to the prediction of a theoretical model. However, the reliability of this procedure is limited because the measured mRNA numbers represent integration over the mRNA lifetime, contribution from multiple gene copies, and mixing of cells from different cell-cycle phases. We address these limitations by simultaneously quantifying nascent and mature mRNA in individual cells, and incorporating cell-cycle effects in the analysis of mRNA statistics. We demonstrate our approach on Oct4 and Nanog in mouse embryonic stem cells. Both genes follow similar two-state kinetics. However, Nanog exhibits slower ON/OFF switching, resulting in increased cell-to-cell variability in mRNA levels. Early in the cell cycle, the two copies of each gene exhibit independent activity. After gene replication, the probability of each gene copy to be active diminishes, resulting in dosage compensation. DOI: http://dx.doi.org/10.7554/eLife.12175.001 PMID:26824388

  8. Single-cell analysis of transcription kinetics across the cell cycle.

    PubMed

    Skinner, Samuel O; Xu, Heng; Nagarkar-Jaiswal, Sonal; Freire, Pablo R; Zwaka, Thomas P; Golding, Ido

    2016-01-01

    Transcription is a highly stochastic process. To infer transcription kinetics for a gene-of-interest, researchers commonly compare the distribution of mRNA copy-number to the prediction of a theoretical model. However, the reliability of this procedure is limited because the measured mRNA numbers represent integration over the mRNA lifetime, contribution from multiple gene copies, and mixing of cells from different cell-cycle phases. We address these limitations by simultaneously quantifying nascent and mature mRNA in individual cells, and incorporating cell-cycle effects in the analysis of mRNA statistics. We demonstrate our approach on Oct4 and Nanog in mouse embryonic stem cells. Both genes follow similar two-state kinetics. However, Nanog exhibits slower ON/OFF switching, resulting in increased cell-to-cell variability in mRNA levels. Early in the cell cycle, the two copies of each gene exhibit independent activity. After gene replication, the probability of each gene copy to be active diminishes, resulting in dosage compensation. PMID:26824388

  9. Simvastatin induces cell cycle arrest and inhibits proliferation of bladder cancer cells via PPARγ signalling pathway

    PubMed Central

    Wang, Gang; Cao, Rui; Wang, Yongzhi; Qian, Guofeng; Dan, Han C.; Jiang, Wei; Ju, Lingao; Wu, Min; Xiao, Yu; Wang, Xinghuan

    2016-01-01

    Simvastatin is currently one of the most common drugs for old patients with hyperlipidemia, hypercholesterolemia and atherosclerotic diseases by reducing cholesterol level and anti-lipid properties. Importantly, simvastatin has also been reported to have anti-tumor effect, but the underlying mechanism is largely unknown. We collected several human bladder samples and performed microarray. Data analysis suggested bladder cancer (BCa) was significantly associated with fatty acid/lipid metabolism via PPAR signalling pathway. We observed simvastatin did not trigger BCa cell apoptosis, but reduced cell proliferation in a dose- and time-dependent manner, accompanied by PPARγ-activation. Moreover, flow cytometry analysis indicated that simvastatin induced cell cycle arrest at G0/G1 phase, suggested by downregulation of CDK4/6 and Cyclin D1. Furthermore, simvastatin suppressed BCa cell metastasis by inhibiting EMT and affecting AKT/GSK3β. More importantly, we found that the cell cycle arrest at G0/G1 phase and the alterations of CDK4/6 and Cyclin D1 triggered by simvastatin could be recovered by PPARγ-antagonist (GW9662), whereas the treatment of PPARα-antagonist (GW6471) shown no significant effects on the BCa cells. Taken together, our study for the first time revealed that simvastatin inhibited bladder cancer cell proliferation and induced cell cycle arrest at G1/G0 phase via PPARγ signalling pathway. PMID:27779188

  10. Mast cells as modulators of hair follicle cycling.

    PubMed

    Maurer, M; Paus, R; Czarnetzki, B M

    1995-08-01

    While the central role of mast cells (MC) in allergy and inflammation is well-appreciated, much less is known about their physiological functions. The impressive battery of potent growth modulatory MC products, and increasing evidence of MC involvement in hyperproliferative and fibrotic disorders suggest that tissue remodelling may be one of those, namely in the skin. Here, we delineate why this may best be studied by analysing the potential role of MC in hair growth regulation. On the background of numerous, yet widely under-appreciated hints from the older literature, we summarize and discuss our recent observations from the C57BL/6 mouse model for hair research which support the concept that MC are functionally important modulators of hair follicle cycling, specifically during anagen development. This invites to exploit the murine hair cycle as a model for dissecting the physiological growth modulatory functions of MC and encourages the exploration of MC-targeting pharmaceutical strategies for the treatment of hair growth disorders.

  11. Origin of bistability underlying mammalian cell cycle entry.

    PubMed

    Yao, Guang; Tan, Cheemeng; West, Mike; Nevins, Joseph R; You, Lingchong

    2011-04-26

    Precise control of cell proliferation is fundamental to tissue homeostasis and differentiation. Mammalian cells commit to proliferation at the restriction point (R-point). It has long been recognized that the R-point is tightly regulated by the Rb-E2F signaling pathway. Our recent work has further demonstrated that this regulation is mediated by a bistable switch mechanism. Nevertheless, the essential regulatory features in the Rb-E2F pathway that create this switching property have not been defined. Here we analyzed a library of gene circuits comprising all possible link combinations in a simplified Rb-E2F network. We identified a minimal circuit that is able to generate robust, resettable bistability. This minimal circuit contains a feed-forward loop coupled with a mutual-inhibition feedback loop, which forms an AND-gate control of the E2F activation. Underscoring its importance, experimental disruption of this circuit abolishes maintenance of the activated E2F state, supporting its importance for the bistability of the Rb-E2F system. Our findings suggested basic design principles for the robust control of the bistable cell cycle entry at the R-point. PMID:21525871

  12. Origin of bistability underlying mammalian cell cycle entry

    PubMed Central

    Yao, Guang; Tan, Cheemeng; West, Mike; Nevins, Joseph R; You, Lingchong

    2011-01-01

    Precise control of cell proliferation is fundamental to tissue homeostasis and differentiation. Mammalian cells commit to proliferation at the restriction point (R-point). It has long been recognized that the R-point is tightly regulated by the Rb–E2F signaling pathway. Our recent work has further demonstrated that this regulation is mediated by a bistable switch mechanism. Nevertheless, the essential regulatory features in the Rb–E2F pathway that create this switching property have not been defined. Here we analyzed a library of gene circuits comprising all possible link combinations in a simplified Rb–E2F network. We identified a minimal circuit that is able to generate robust, resettable bistability. This minimal circuit contains a feed-forward loop coupled with a mutual-inhibition feedback loop, which forms an AND-gate control of the E2F activation. Underscoring its importance, experimental disruption of this circuit abolishes maintenance of the activated E2F state, supporting its importance for the bistability of the Rb–E2F system. Our findings suggested basic design principles for the robust control of the bistable cell cycle entry at the R-point. PMID:21525871

  13. Fanconi anemia and the cell cycle: new perspectives on aneuploidy

    PubMed Central

    2014-01-01

    Fanconi anemia (FA) is a complex heterogenic disorder of genomic instability, bone marrow failure, cancer predisposition, and congenital malformations. The FA signaling network orchestrates the DNA damage recognition and repair in interphase as well as proper execution of mitosis. Loss of FA signaling causes chromosome instability by weakening the spindle assembly checkpoint, disrupting centrosome maintenance, disturbing resolution of ultrafine anaphase bridges, and dysregulating cytokinesis. Thus, the FA genes function as guardians of genome stability throughout the cell cycle. This review discusses recent advances in diagnosis and clinical management of Fanconi anemia and presents the new insights into the origins of genomic instability in FA. These new discoveries may facilitate the development of rational therapeutic strategies for FA and for FA-deficient malignancies in the general population. PMID:24765528

  14. Cell cycle kinetics in pterygium at three latitudes.

    PubMed

    Karukonda, S R; Thompson, H W; Beuerman, R W; Lam, D S; Wilson, R; Chew, S J; Steinemann, T L

    1995-04-01

    The cell cycle kinetics of 93 specimens of pterygial tissue, as well as 19 specimens of normal conjunctiva, from patients at three sites representing three different latitudes (Singapore, 1 degree; Hong Kong, 22 degrees; and Little Rock, Arkansas, 34 degrees) were evaluated by flow cytometry. The results showed no difference in cellular proliferation patterns between pterygial and conjunctival tissue at any of the sites, suggesting that pterygium is not a disorder of excess cellular proliferation. Transmission electron microscopy showed extracellular matrix to be a prominent component of pterygium. Cellular proliferation patterns of primary and recurrent pterygium were not significantly different from each other. Factors associated with increased incidence of pterygium included male sex, outdoor occupation, and advanced age.

  15. Astaxanthin Inhibits Proliferation of Human Gastric Cancer Cell Lines by Interrupting Cell Cycle Progression

    PubMed Central

    Kim, Jung Ha; Park, Jong-Jae; Lee, Beom Jae; Joo, Moon Kyung; Chun, Hoon Jai; Lee, Sang Woo; Bak, Young-Tae

    2016-01-01

    Background/Aims Astaxanthin is a carotenoid pigment that has antioxidant, antitumoral, and anti-inflammatory properties. In this in vitro study, we investigated the mechanism of anticancer effects of astaxanthin in gastric carcinoma cell lines. Methods The human gastric adenocarcinoma cell lines AGS, KATO-III, MKN-45, and SNU-1 were treated with various concentrations of astaxanthin. A cell viability test, cell cycle analysis, and immunoblotting were performed. Results The viability of each cancer cell line was suppressed by astaxanthin in a dose-dependent manner with significantly decreased proliferation in KATO-III and SNU-1 cells. Astaxanthin increased the number of cells in the G0/G1 phase but reduced the proportion of S phase KATO-III and SNU-1 cells. Phosphorylated extracellular signal-regulated kinase (ERK) was decreased in an inverse dose-dependent correlation with astaxanthin concentration, and the expression of p27kip-1 increased the KATO-III and SNU-1 cell lines in an astaxanthin dose-dependent manner. Conclusions Astaxanthin inhibits proliferation by interrupting cell cycle progression in KATO-III and SNU-1 gastric cancer cells. This may be caused by the inhibition of the phosphorylation of ERK and the enhanced expression of p27kip-1. PMID:26470770

  16. Abnormal mitosis triggers p53-dependent cell cycle arrest in human tetraploid cells.

    PubMed

    Kuffer, Christian; Kuznetsova, Anastasia Yurievna; Storchová, Zuzana

    2013-08-01

    Erroneously arising tetraploid mammalian cells are chromosomally instable and may facilitate cell transformation. An increasing body of evidence shows that the propagation of mammalian tetraploid cells is limited by a p53-dependent arrest. The trigger of this arrest has not been identified so far. Here we show by live cell imaging of tetraploid cells generated by an induced cytokinesis failure that most tetraploids arrest and die in a p53-dependent manner after the first tetraploid mitosis. Furthermore, we found that the main trigger is a mitotic defect, in particular, chromosome missegregation during bipolar mitosis or spindle multipolarity. Both a transient multipolar spindle followed by efficient clustering in anaphase as well as a multipolar spindle followed by multipolar mitosis inhibited subsequent proliferation to a similar degree. We found that the tetraploid cells did not accumulate double-strand breaks that could cause the cell cycle arrest after tetraploid mitosis. In contrast, tetraploid cells showed increased levels of oxidative DNA damage coinciding with the p53 activation. To further elucidate the pathways involved in the proliferation control of tetraploid cells, we knocked down specific kinases that had been previously linked to the cell cycle arrest and p53 phosphorylation. Our results suggest that the checkpoint kinase ATM phosphorylates p53 in tetraploid cells after abnormal mitosis and thus contributes to proliferation control of human aberrantly arising tetraploids.

  17. Cell Cycle-Dependent Mechanisms Underlie Vincristine-Induced Death of Primary Acute Lymphoblastic Leukemia Cells.

    PubMed

    Kothari, Anisha; Hittelman, Walter N; Chambers, Timothy C

    2016-06-15

    Microtubule-targeting agents (MTA), such as the taxanes and vinca alkaloids, are used to treat a variety of cancers due to their ability to perturb microtubule dynamics. In cell culture, MTAs exert their anticancer effects primarily by causing mitotic arrest and cell death. However, accumulating indirect evidence suggests that MTAs may exert their cytotoxicity in human tumors by interfering with interphase microtubules. In this study, we sought to develop and characterize an experimental system in which to test the hypothesis that MTAs induce cell death during interphase. Primary adult acute lymphoblastic leukemia (ALL) cells treated with vincristine only weakly exhibited colocalization between mitotic and apoptotic markers and major characteristics of mitotic death, such as an increase in cells with 4N DNA content before the appearance of cells with <2N DNA content, suggesting a mixed response. Therefore, we separated ALL cells into distinct phases of the cell cycle by centrifugal elutriation, labeled cells with 5-ethynyl-2'-deoxyuridine (EdU), and then treated each population with vincristine. Cells isolated during G1 underwent cell death without evidence of EdU uptake, indicating that the cytotoxic effects of vincristine took place during G1 Conversely, cells isolated during S or G2-M phases underwent death following mitotic arrest. Thus, vincristine induces distinct death programs in primary ALL cells depending on cell-cycle phase, and cells in G1 are particularly susceptible to perturbation of interphase microtubules. Primary ALL cells may therefore provide a powerful model system in which to study the multimodal mechanisms underlying MTA-induced cell death. Cancer Res; 76(12); 3553-61. ©2016 AACR. PMID:27197148

  18. Cell Cycle-Dependent Mechanisms Underlie Vincristine-Induced Death of Primary Acute Lymphoblastic Leukemia Cells.

    PubMed

    Kothari, Anisha; Hittelman, Walter N; Chambers, Timothy C

    2016-06-15

    Microtubule-targeting agents (MTA), such as the taxanes and vinca alkaloids, are used to treat a variety of cancers due to their ability to perturb microtubule dynamics. In cell culture, MTAs exert their anticancer effects primarily by causing mitotic arrest and cell death. However, accumulating indirect evidence suggests that MTAs may exert their cytotoxicity in human tumors by interfering with interphase microtubules. In this study, we sought to develop and characterize an experimental system in which to test the hypothesis that MTAs induce cell death during interphase. Primary adult acute lymphoblastic leukemia (ALL) cells treated with vincristine only weakly exhibited colocalization between mitotic and apoptotic markers and major characteristics of mitotic death, such as an increase in cells with 4N DNA content before the appearance of cells with <2N DNA content, suggesting a mixed response. Therefore, we separated ALL cells into distinct phases of the cell cycle by centrifugal elutriation, labeled cells with 5-ethynyl-2'-deoxyuridine (EdU), and then treated each population with vincristine. Cells isolated during G1 underwent cell death without evidence of EdU uptake, indicating that the cytotoxic effects of vincristine took place during G1 Conversely, cells isolated during S or G2-M phases underwent death following mitotic arrest. Thus, vincristine induces distinct death programs in primary ALL cells depending on cell-cycle phase, and cells in G1 are particularly susceptible to perturbation of interphase microtubules. Primary ALL cells may therefore provide a powerful model system in which to study the multimodal mechanisms underlying MTA-induced cell death. Cancer Res; 76(12); 3553-61. ©2016 AACR.

  19. Life cycle assessment of fuel cell vehicles: Dealing with uncertainties

    NASA Astrophysics Data System (ADS)

    Contadini, Jose Fernando

    Life cycle assessment (LCA), or "well to wheels" in transportation terms, involves some subjectivity and uncertainty, especially with new technologies and future scenarios. To analyze lifecycle impacts of future fuel cell vehicles and fuels, I developed the Fuel Upstream Energy and Emission Model (FUEEM). The FUEEM project pioneered two specific new ways to incorporate and propagate uncertainty within an LCA analysis. First, the model uses probabilistic curves generated by experts as inputs and then employs Monte Carlo simulation techniques to propagate these uncertainties throughout the full chain of fuel production and use. Second, the FUEEM process explicitly involves the interested parties in the entire analysis process, not only in the critical final review phase. To demonstrate the FUEEM process, an analysis has been made for the use of three different fuel cell vehicle technologies (direct hydrogen, indirect methanol, and indirect hydrocarbon) in 2010 within the South Coast Air Basin (SCAB) of California (Los Angeles). The analysis covered topics such as the requirement of non-renewable energy sources, emissions of CO2 and other greenhouse gases, and emissions of several criteria pollutants generated within SCAB and within other regions. The results obtained from this example show that the hydrogen option has the potential to have the most efficient energy life cycle for the SCAB, followed by the methanol and finally by the Fisher-Tropsch naphtha option. A similar pattern is observed for the greenhouse gas emissions. The results showing criteria pollutants emitted within SCAB highlight the importance of having a flexible model that is responsive to local considerations. This dissertation demonstrates that explicit recognition and quantitative analysis of the inherent uncertainty in the LCA process generates richer information, explains many of the discrepancies between results of previous studies, and enhances the robustness and credibility of LCA analyses.

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

    PubMed Central

    Ruijtenberg, Suzan; van den Heuvel, Sander

    2016-01-01

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

  1. Microtubule and Actin Interplay Drive Intracellular c-Src Trafficking.

    PubMed

    Arnette, Christopher; Frye, Keyada; Kaverina, Irina

    2016-01-01

    The proto-oncogene c-Src is involved in a variety of signaling processes. Therefore, c-Src spatiotemporal localization is critical for interaction with downstream targets. However, the mechanisms regulating this localization have remained elusive. Previous studies have shown that c-Src trafficking is a microtubule-dependent process that facilitates c-Src turnover in neuronal growth cones. As such, microtubule depolymerization lead to the inhibition of c-Src recycling. Alternatively, c-Src trafficking was also shown to be regulated by RhoB-dependent actin polymerization. Our results show that c-Src vesicles primarily exhibit microtubule-dependent trafficking; however, microtubule depolymerization does not inhibit vesicle movement. Instead, vesicular movement becomes both faster and less directional. This movement was associated with actin polymerization directly at c-Src vesicle membranes. Interestingly, it has been shown previously that c-Src delivery is an actin polymerization-dependent process that relies on small GTPase RhoB at c-Src vesicles. In agreement with this finding, microtubule depolymerization induced significant activation of RhoB, together with actin comet tail formation. These effects occurred downstream of GTP-exchange factor, GEF-H1, which was released from depolymerizing MTs. Accordingly, GEF-H1 activity was necessary for actin comet tail formation at the Src vesicles. Our results indicate that regulation of c-Src trafficking requires both microtubules and actin polymerization, and that GEF-H1 coordinates c-Src trafficking, acting as a molecular switch between these two mechanisms. PMID:26866809

  2. Microtubule and Actin Interplay Drive Intracellular c-Src Trafficking

    PubMed Central

    Arnette, Christopher; Frye, Keyada; Kaverina, Irina

    2016-01-01

    The proto-oncogene c-Src is involved in a variety of signaling processes. Therefore, c-Src spatiotemporal localization is critical for interaction with downstream targets. However, the mechanisms regulating this localization have remained elusive. Previous studies have shown that c-Src trafficking is a microtubule-dependent process that facilitates c-Src turnover in neuronal growth cones. As such, microtubule depolymerization lead to the inhibition of c-Src recycling. Alternatively, c-Src trafficking was also shown to be regulated by RhoB-dependent actin polymerization. Our results show that c-Src vesicles primarily exhibit microtubule-dependent trafficking; however, microtubule depolymerization does not inhibit vesicle movement. Instead, vesicular movement becomes both faster and less directional. This movement was associated with actin polymerization directly at c-Src vesicle membranes. Interestingly, it has been shown previously that c-Src delivery is an actin polymerization-dependent process that relies on small GTPase RhoB at c-Src vesicles. In agreement with this finding, microtubule depolymerization induced significant activation of RhoB, together with actin comet tail formation. These effects occurred downstream of GTP-exchange factor, GEF-H1, which was released from depolymerizing MTs. Accordingly, GEF-H1 activity was necessary for actin comet tail formation at the Src vesicles. Our results indicate that regulation of c-Src trafficking requires both microtubules and actin polymerization, and that GEF-H1 coordinates c-Src trafficking, acting as a molecular switch between these two mechanisms. PMID:26866809

  3. Cell Cycle Arrest and Cell Survival Induce Reverse Trends of Cardiolipin Remodeling

    PubMed Central

    Chao, Yu-Jen; Chang, Wan-Hsin; Ting, Hsiu-Chi; Chao, Wei-Ting; Hsu, Yuan-Hao Howard

    2014-01-01

    Cell survival from the arrested state can be a cause of the cancer recurrence. Transition from the arrest state to the growth state is highly regulated by mitochondrial activity, which is related to the lipid compositions of the mitochondrial membrane. Cardiolipin is a critical phospholipid for the mitochondrial integrity and functions. We examined the changes of cardiolipin species by LC-MS in the transition between cell cycle arrest and cell reviving in HT1080 fibrosarcoma cells. We have identified 41 cardiolipin species by MS/MS and semi-quantitated them to analyze the detailed changes of cardiolipin species. The mass spectra of cardiolipin with the same carbon number form an envelope, and the C64, C66, C68, C70 C72 and C74 envelopes in HT1080 cells show a normal distribution in the full scan mass spectrum. The cardiolipin quantity in a cell decreases while entering the cell cycle arrest, but maintains at a similar level through cell survival. While cells awakening from the arrested state and preparing itself for replication, the groups with short acyl chains, such as C64, C66 and C68 show a decrease of cardiolipin percentage, but the groups with long acyl chains, such as C70 and C72 display an increase of cardiolipin percentage. Interestingly, the trends of the cardiolipin species changes during the arresting state are completely opposite to cell growing state. Our results indicate that the cardiolipin species shift from the short chain to long chain cardiolipin during the transition from cell cycle arrest to cell progression. PMID:25422939

  4. Heterochronic misexpression of Ascl1 in the Atoh7 retinal cell lineage blocks cell cycle exit

    PubMed Central

    Hufnagel, Robert B.; Riesenberg, Amy N.; Quinn, Malgorzata; Brzezinski, Joseph A.; Glaser, Tom; Brown, Nadean L.

    2013-01-01

    Retinal neurons and glia arise from a common progenitor pool in a temporal order, with retinal ganglion cells (RGCs) appearing first, and Müller glia last. The transcription factors Atoh7/Math5 and Ascl1/Mash1 represent divergent bHLH clades, and exhibit distinct spatial and temporal retinal expression patterns, with little overlap during early development. Here, we tested the ability of Ascl1 to change the fate of cells in the Atoh7 lineage when misexpressed from the Atoh7 locus, using an Ascl1-IRES-DsRed2 knock-in allele. In Atoh7Ascl1KI/+ and Atoh7Ascl1KI/Ascl1KI embryos, ectopic Ascl1 delayed cell cycle exit and differentiation, even in cells coexpressing Atoh7. The heterozygous retinas recovered, and eventually produced a normal complement of RGCs, while homozygous substitution of Ascl1 for Atoh7 did not promote postnatal retinal fates precociously, nor rescue Atoh7 mutant phenotypes. However, our analyses revealed two unexpected findings. First, ectopic Ascl1 disrupted cell cycle progression within the marked Atoh7 lineage, but also nonautonomously in other retinal cells. Second, the size of the Atoh7 retinal lineage was unaffected, supporting the idea of a compensatory shift of the non-proliferative cohort to maintain lineage size. Overall, we conclude that Ascl1 acts dominantly to block cell cycle exit, but is incapable of redirecting the fates of early RPCs. PMID:23481413

  5. Ras-mediated cell cycle arrest is altered by nuclear oncogenes to induce Schwann cell transformation.

    PubMed Central

    Ridley, A J; Paterson, H F; Noble, M; Land, H

    1988-01-01

    The cellular responses to ras and nuclear oncogenes were investigated in purified populations of rat Schwann cells. v-Ha-ras and SV40 large T cooperate to transform Schwann cells, inducing growth in soft agar and allowing proliferation in the absence of added mitogens. Expression of large T alone reduces their growth factor requirements but is insufficient to induce full transformation. In contrast, expression of v-Ha-ras leads to proliferation arrest in Schwann cells expressing a temperature-sensitive mutant of large T at the restrictive temperature. Cells arrest in either the G1 or G2/M phases of the cell cycle, and can re-enter cell division at the permissive temperature even after prolonged periods at the restrictive conditions. Oncogenic ras proteins also inhibit DNA synthesis when microinjected into Schwann cells. Adenovirus E1a and c-myc oncogenes behave similarly to SV40 large T. They cooperate with Ha-ras oncogenes to transform Schwann cells, and prevent ras-induced growth arrest. Thus nuclear oncogenes fundamentally alter the response of Schwann cells to a ras oncogene from cell cycle arrest to transformation. Images PMID:3049071

  6. Induction of apoptosis and cell-cycle arrest in human colon cancer cells by meclizine.

    PubMed

    Lin, Jiunn-Chang; Ho, Yuan-Soon; Lee, Jie-Jen; Liu, Chien-Liang; Yang, Tsen-Long; Wu, Chih-Hsiung

    2007-06-01

    Meclizine (MEC), a histamine H1 antagonist, is used for the treatment of motion sickness and vertigo. In this study, we demonstrate that MEC dose-dependently induced apoptosis in human colon cancer cell lines (COLO 205 and HT 29 cells). Results of a DNA ladder assay revealed that DNA ladders appeared with MEC treatment in COLO 205 cells at dosage of >50 microM. In addition, the total cell number decreased dose-dependently after treatment with MEC in COLO 205 and HT 29 cells. Using flow cytometry, the percentage of COLO 205 cells arrested at G0/G1 phase increased dose-dependently. Analysis of changes in cell-cycle arrest-associated proteins with Western blotting showed that p53 and p21 were upregulated after treatment with MEC. The kinase activities of cyclin-dependent kinase 2 (CDK2) and CDK4 were suppressed in MEC-treated cells. As for apoptosis, MEC may induce upregulation of p53 and downregulation of Bcl-2, thus causing the release of cytochrome C from mitochondria and the translocation of apoptosis-inducing factor (AIF) to the nucleus. This resulted in the activation of caspase 3, 8, and 9. Our results provide the molecular basis of MEC-induced apoptosis and cell-cycle arrest in human colon cancer cells. PMID:17222494

  7. In vivo and Ex vivo MR Imaging of Slowly Cycling Melanoma Cells

    PubMed Central

    Magnitsky, S.; Roesch, A.; Herlyn, M.; Glickson, J.D.

    2011-01-01

    Slowly cycling cells are believed to play a critical role in tumor progression and metastatic dissemination. The goal of this study was to develop a method for in vivo detection of slowly cycling cells. To distinguish these cells from more rapidly proliferating cells that constitute the vast majority of cells in tumors, we utilized the well-known effect of label dilution due to division of cells with normal cycle and retention of contrast agent in slowly dividing cells. To detect slowly cycling cells melanoma cells were labeled with iron oxide particles. After labeling, we observed dilution of contrast agent in parallel with cell proliferation in the vast majority of normally cycling cells. A small and distinct sub-population of iron-retaining cells was detected by flow cytometry after 20 days of in vitro proliferation. These iron-retaining cells exhibited high expression of a biological marker of slowly cycling cells, JARID1B. After implantation of labeled cells as xenografts into immunocompromised mice, iron-retaining cells were detected in vivo and ex vivo by MRI that was confirmed by Prussian Blue staining. MR imaging detects not only iron retaining melanoma cells but also iron positive macrophages. Proposed method opens up opportunities to image subpopulation of melanoma cells, which is critical for continuous tumor growth. PMID:21523820

  8. The Schaechter-Bentzon-Maaløe experiment and the analysis of cell cycle events in eukaryotic cells.

    PubMed

    Cooper, Stephen

    2002-04-01

    The Schaechter-Bentzon-Maaløe (SBM) experiment, performed more than 40 years ago, provides an important lesson for the analysis of the eukaryotic cell cycle. Before this experiment, temperature shifts had been used to synchronize bacteria and determine the pattern of DNA synthesis during the bacterial division cycle. These experiments indicated that DNA replication occurred during a fraction of the division cycle with gaps before and after DNA synthesis, a pattern similar to the eukaryotic division cycle. The SBM experiment studied DNA replication during the division cycle by labeling an unperturbed culture with a short pulse of tritiated thymidine. All cells were found to be labeled, indicating that unperturbed cells synthesize DNA throughout the division cycle. Thus, the SBM experiment was a control experiment demonstrating that artifacts can be introduced by synchronization methods. The idea of an control experiment under unperturbed conditions is proposed for the analysis of data on cell-cycle-specific gene expression in yeast and mammalian cells.

  9. The cell cycle of the planctomycete Gemmata obscuriglobus with respect to cell compartmentalization

    PubMed Central

    Lee, Kuo-Chang; Webb, Rick I; Fuerst, John A

    2009-01-01

    Background Gemmata obscuriglobus is a distinctive member of the divergent phylum Planctomycetes, all known members of which are peptidoglycan-less bacteria with a shared compartmentalized cell structure and divide by a budding process. G. obscuriglobus in addition shares the unique feature that its nucleoid DNA is surrounded by an envelope consisting of two membranes forming an analogous structure to the membrane-bounded nucleoid of eukaryotes and therefore G. obscuriglobus forms a special model for cell biology. Draft genome data for G. obscuriglobus as well as complete genome sequences available so far for other planctomycetes indicate that the key bacterial cell division protein FtsZ is not present in these planctomycetes, so the cell division process in planctomycetes is of special comparative interest. The membrane-bounded nature of the nucleoid in G. obscuriglobus also suggests that special mechanisms for the distribution of this nuclear body to the bud and for distribution of chromosomal DNA might exist during division. It was therefore of interest to examine the cell division cycle in G. obscuriglobus and the process of nucleoid distribution and nuclear body formation during division in this planctomycete bacterium via light and electron microscopy. Results Using phase contrast and fluorescence light microscopy, and transmission electron microscopy, the cell division cycle of G. obscuriglobus was determined. During the budding process, the bud was formed and developed in size from one point of the mother cell perimeter until separation. The matured daughter cell acted as a new mother cell and started its own budding cycle while the mother cell can itself initiate budding repeatedly. Fluorescence microscopy of DAPI-stained cells of G. obscuriglobus suggested that translocation of the nucleoid and formation of the bud did not occur at the same time. Confocal laser scanning light microscopy applied to cells stained for membranes as well as DNA confirmed the

  10. Methamphetamine is not Toxic but Disrupts the Cell Cycle of Blood-Brain Barrier Endothelial Cells.

    PubMed

    Fisher, D; Gamieldien, K; Mafunda, P S

    2015-07-01

    The cytotoxic effects of methamphetamine (MA) are well established to be caused via induced oxidative stress which in turn compromises the core function of the blood-brain barrier (BBB) by reducing its ability to regulate the homeostatic environment of the brain. While most studies were conducted over a period of 24-48 h, this study investigated the mechanisms by which chronic exposure of MA adversely affect the endothelial cells of BBB over an extended period of 96 h. MA induced significant depression of cell numbers at 96 h. This result was supported by flow cytometric data on the cell cycle which showed that brain endothelial cells (bEnd5) at 96 h were significantly suppressed in the S-phase of the cell cycle. In contrast, at 24-72 h control cell numbers for G1, S and G2-M phases were similar to MA-exposed cells. MA (0-1,000 µM) did not, however, statistically affect the viability and cytotoxicity of the bEnd5 cells, and the profile of ATP production and DNA synthesis (BrdU) across 96 h did not provide a rationale for the suppression of cell division. Our study reports for the first time that chronic exposure to MA results in long-term disruption of the cell cycle phases which eventuates in the attenuation of brain capillary endothelial cell growth after 96 h, compounding and contributing to the already well-known adverse short-term permeability effects of MA exposure on the BBB.

  11. Cell cycle regulation and apoptotic cell death in experimental colon carcinogenesis: intervening with cyclooxygenase-2 inhibitors.

    PubMed

    Saini, Manpreet Kaur; Sanyal, Sankar Nath

    2015-01-01

    Relative imbalance in the pathways regulating cell cycle, cell proliferation, or cell death marks a prerequisite for neoplasm. C-phycocyanin, a biliprotein from Spirulina platensis and a selective COX-2 inhibitor along with piroxicam, a traditional nonsteroidal antiinflammatory drug was used to investigate the role of cell cycle regulatory proteins and proinflammatory transcription factor NFκB in 1,2-dimethylhydrazine dihydrochloride (DMH)-induced rat colon carcinogenesis. Cell cycle regulators [cyclin D1, cyclin E, cyclin dependent kinase 2 (CDK2), CDK4, and p53], NFκB (p65) pathway, and proliferating cell nuclear antigen (PCNA) were evaluated by gene and protein expression, whereas apoptosis was studied by terminal deoxynucleotidyl transferase dUTP nick end labeling and apoptotic bleb assay. Molecular docking of ligand protein interaction was done to validate the in vivo results. Cyclin D1, cyclin E, CDK2, and CDK4 were overexpressed in DMH, whereas piroxicam and c-phycocyanin promoted the cell cycle arrest by downregulating them. Both drugs mediated apoptosis through p53 activation. Piroxicam and c-phycocyanin also stimulated antiproliferation by restraining PCNA expression and reduced cell survival via inhibiting NFκB (p65) pathway. Molecular docking revealed that phycocyanobilin (a chromophore of c-phycocyanin) interact with DNA binding site of NFκB. Inhibition of cyclin/CDK complex by piroxicam and c-phycocyanin affects the expression of p53 in colon cancer followed by downregulation of NFκB and PCNA levels, thus substantiating the antineoplastic role of these agents. PMID:25825916

  12. Dynamics of the cell-cycle network under genome-rewiring perturbations.

    PubMed

    Katzir, Yair; Elhanati, Yuval; Averbukh, Inna; Braun, Erez

    2013-12-01

    The cell-cycle progression is regulated by a specific network enabling its ordered dynamics. Recent experiments supported by computational models have shown that a core of genes ensures this robust cycle dynamics. However, much less is known about the direct interaction of the cell-cycle regulators with genes outside of the cell-cycle network, in particular those of the metabolic system. Following our recent experimental work, we present here a model focusing on the dynamics of the cell-cycle core network under rewiring perturbations. Rewiring is achieved by placing an essential metabolic gene exclusively under the regulation of a cell-cycle's promoter, forcing the cell-cycle network to function under a multitasking challenging condition; operating in parallel the cell-cycle progression and a metabolic essential gene. Our model relies on simple rate equations that capture the dynamics of the relevant protein-DNA and protein-protein interactions, while making a clear distinction between these two different types of processes. In particular, we treat the cell-cycle transcription factors as limited 'resources' and focus on the redistribution of resources in the network during its dynamics. This elucidates the sensitivity of its various nodes to rewiring interactions. The basic model produces the correct cycle dynamics for a wide range of parameters. The simplicity of the model enables us to study the interface between the cell-cycle regulation and other cellular processes. Rewiring a promoter of the network to regulate a foreign gene, forces a multitasking regulatory load. The higher the load on the promoter, the longer is the cell-cycle period. Moreover, in agreement with our experimental results, the model shows that different nodes of the network exhibit variable susceptibilities to the rewiring perturbations. Our model suggests that the topology of the cell-cycle core network ensures its plasticity and flexible interface with other cellular processes, without a

  13. Dynamics of the cell-cycle network under genome-rewiring perturbations

    NASA Astrophysics Data System (ADS)

    Katzir, Yair; Elhanati, Yuval; Averbukh, Inna; Braun, Erez

    2013-12-01

    The cell-cycle progression is regulated by a specific network enabling its ordered dynamics. Recent experiments supported by computational models have shown that a core of genes ensures this robust cycle dynamics. However, much less is known about the direct interaction of the cell-cycle regulators with genes outside of the cell-cycle network, in particular those of the metabolic system. Following our recent experimental work, we present here a model focusing on the dynamics of the cell-cycle core network under rewiring perturbations. Rewiring is achieved by placing an essential metabolic gene exclusively under the regulation of a cell-cycle's promoter, forcing the cell-cycle network to function under a multitasking challenging condition; operating in parallel the cell-cycle progression and a metabolic essential gene. Our model relies on simple rate equations that capture the dynamics of the relevant protein-DNA and protein-protein interactions, while making a clear distinction between these two different types of processes. In particular, we treat the cell-cycle transcription factors as limited ‘resources’ and focus on the redistribution of resources in the network during its dynamics. This elucidates the sensitivity of its various nodes to rewiring interactions. The basic model produces the correct cycle dynamics for a wide range of parameters. The simplicity of the model enables us to study the interface between the cell-cycle regulation and other cellular processes. Rewiring a promoter of the network to regulate a foreign gene, forces a multitasking regulatory load. The higher the load on the promoter, the longer is the cell-cycle period. Moreover, in agreement with our experimental results, the model shows that different nodes of the network exhibit variable susceptibilities to the rewiring perturbations. Our model suggests that the topology of the cell-cycle core network ensures its plasticity and flexible interface with other cellular processes, without

  14. DNA Damage, Cell Cycle Arrest, and Apoptosis Induction Caused by Lead in Human Leukemia Cells

    PubMed Central

    Yedjou, Clement G.; Tchounwou, Hervey M.; Tchounwou, Paul B.

    2015-01-01

    In recent years, the industrial use of lead has been significantly reduced from paints and ceramic products, caulking, and pipe solder. Despite this progress, lead exposure continues to be a significant public health concern. The main goal of this research was to determine the in vitro mechanisms of lead nitrate [Pb(NO3)2] to induce DNA damage, apoptosis, and cell cycle arrest in human leukemia (HL-60) cells. To reach our goal, HL-60 cells were treated with different concentrations of Pb(NO3)2 for 24 h. Live cells and necrotic death cells were measured by the propidium idiode (PI) assay using the cellometer vision. Cell apoptosis was measured by the flow cytometry and DNA laddering. Cell cycle analysis was evaluated by the flow cytometry. The result of the PI demonstrated a significant (p < 0.05) increase of necrotic cell death in Pb(NO3)2-treated cells, indicative of membrane rupture by Pb(NO3)2 compared to the control. Data generated from the comet assay indicated a concentration-dependent increase in DNA damage, showing a significant increase (p < 0.05) in comet tail-length and percentages of DNA cleavage. Data generated from the flow cytometry assessment indicated that Pb(NO3)2 exposure significantly (p < 0.05) increased the proportion of caspase-3 positive cells (apoptotic cells) compared to the control. The flow cytometry assessment also indicated Pb(NO3)2 exposure caused cell cycle arrest at the G0/G1 checkpoint. The result of DNA laddering assay showed presence of DNA smear in the agarose gel with little presence of DNA fragments in the treated cells compared to the control. In summary, Pb(NO3)2 inhibits HL-60 cells proliferation by not only inducing DNA damage and cell cycle arrest at the G0/G1 checkpoint but also triggering the apoptosis through caspase-3 activation and nucleosomal DNA fragmentation accompanied by secondary necrosis. We believe that our study provides a new insight into the mechanisms of Pb(NO3)2 exposure and its associated adverse health

  15. DNA Damage, Cell Cycle Arrest, and Apoptosis Induction Caused by Lead in Human Leukemia Cells.

    PubMed

    Yedjou, Clement G; Tchounwou, Hervey M; Tchounwou, Paul B

    2016-01-01

    In recent years, the industrial use of lead has been significantly reduced from paints and ceramic products, caulking, and pipe solder. Despite this progress, lead exposure continues to be a significant public health concern. The main goal of this research was to determine the in vitro mechanisms of lead nitrate [Pb(NO₃)₂] to induce DNA damage, apoptosis, and cell cycle arrest in human leukemia (HL-60) cells. To reach our goal, HL-60 cells were treated with different concentrations of Pb(NO₃)₂ for 24 h. Live cells and necrotic death cells were measured by the propidium idiode (PI) assay using the cellometer vision. Cell apoptosis was measured by the flow cytometry and DNA laddering. Cell cycle analysis was evaluated by the flow cytometry. The result of the PI demonstrated a significant (p < 0.05) increase of necrotic cell death in Pb(NO₃)₂-treated cells, indicative of membrane rupture by Pb(NO₃)₂ compared to the control. Data generated from the comet assay indicated a concentration-dependent increase in DNA damage, showing a significant increase (p < 0.05) in comet tail-length and percentages of DNA cleavage. Data generated from the flow cytometry assessment indicated that Pb(NO₃)₂ exposure significantly (p < 0.05) increased the proportion of caspase-3 positive cells (apoptotic cells) compared to the control. The flow cytometry assessment also indicated Pb(NO₃)₂ exposure caused cell cycle arrest at the G₀/G₁ checkpoint. The result of DNA laddering assay showed presence of DNA smear in the agarose gel with little presence of DNA fragments in the treated cells compared to the control. In summary, Pb(NO₃)₂ inhibits HL-60 cells proliferation by not only inducing DNA damage and cell cycle arrest at the G₀/G₁ checkpoint but also triggering the apoptosis through caspase-3 activation and nucleosomal DNA fragmentation accompanied by secondary necrosis. We believe that our study provides a new insight into the mechanisms of Pb

  16. DNA Damage, Cell Cycle Arrest, and Apoptosis Induction Caused by Lead in Human Leukemia Cells.

    PubMed

    Yedjou, Clement G; Tchounwou, Hervey M; Tchounwou, Paul B

    2015-12-22

    In recent years, the industrial use of lead has been significantly reduced from paints and ceramic products, caulking, and pipe solder. Despite this progress, lead exposure continues to be a significant public health concern. The main goal of this research was to determine the in vitro mechanisms of lead nitrate [Pb(NO₃)₂] to induce DNA damage, apoptosis, and cell cycle arrest in human leukemia (HL-60) cells. To reach our goal, HL-60 cells were treated with different concentrations of Pb(NO₃)₂ for 24 h. Live cells and necrotic death cells were measured by the propidium idiode (PI) assay using the cellometer vision. Cell apoptosis was measured by the flow cytometry and DNA laddering. Cell cycle analysis was evaluated by the flow cytometry. The result of the PI demonstrated a significant (p < 0.05) increase of necrotic cell death in Pb(NO₃)₂-treated cells, indicative of membrane rupture by Pb(NO₃)₂ compared to the control. Data generated from the comet assay indicated a concentration-dependent increase in DNA damage, showing a significant increase (p < 0.05) in comet tail-length and percentages of DNA cleavage. Data generated from the flow cytometry assessment indicated that Pb(NO₃)₂ exposure significantly (p < 0.05) increased the proportion of caspase-3 positive cells (apoptotic cells) compared to the control. The flow cytometry assessment also indicated Pb(NO₃)₂ exposure caused cell cycle arrest at the G₀/G₁ checkpoint. The result of DNA laddering assay showed presence of DNA smear in the agarose gel with little presence of DNA fragments in the treated cells compared to the control. In summary, Pb(NO₃)₂ inhibits HL-60 cells proliferation by not only inducing DNA damage and cell cycle arrest at the G₀/G₁ checkpoint but also triggering the apoptosis through caspase-3 activation and nucleosomal DNA fragmentation accompanied by secondary necrosis. We believe that our study provides a new insight into the mechanisms of Pb

  17. A primer for studying cell cycle dynamics of the human hair follicle.

    PubMed

    Purba, Talveen S; Brunken, Lars; Hawkshaw, Nathan J; Peake, Michael; Hardman, Jonathan; Paus, Ralf

    2016-09-01

    The cell cycle is of major importance to human hair follicle (HF) biology. Not only is continuously active cell cycling required to facilitate healthy hair growth in anagen VI HFs, but perturbations in the cell cycle are likely to be of significance in HF pathology (i.e. in scarring, non-scarring, chemotherapy-induced and androgenic alopecias). However, cell cycle dynamics of the human hair follicle (HF) are poorly understood in contrast to what is known in mouse. The current Methods Review aims at helping to close this gap by presenting a primer that introduces immunohistological/immunofluorescent techniques to study the cell cycle in the human HF. Moreover, this primer encourages the exploitation of the human HF as a powerful and clinically relevant tool to investigate mammalian cell cycle biology in situ. To achieve this, we describe methods to study markers of general 'proliferation' (nuclei count, Ki-67 expression), apoptosis (terminal deoxynucleotidyl transferase dUTP nick-end labelling, cleaved caspase 3), mitosis (phospho-histone H3, 'pS780'), DNA synthesis (5-ethynyl-2'-deoxyuridine) and cell cycle regulation (cyclins) in the human HF. In addition, we provide specific examples of dual immunolabelling for instructive cell cycle analyses and for investigating the cell cycle behaviour of specific HF keratinocyte subpopulations, such as keratin 15+ stem/progenitor cells.

  18. The Global Regulatory Architecture of Transcription during the Caulobacter Cell Cycle

    PubMed Central

    Zhou, Bo; Schrader, Jared M.; Kalogeraki, Virginia S.; Abeliuk, Eduardo; Dinh, Cong B.; Pham, James Q.; Cui, Zhongying Z.; Dill, David L.; McAdams, Harley H.; Shapiro, Lucy

    2015-01-01

    Each Caulobacter cell cycle involves differentiation and an asymmetric cell division driven by a cyclical regulatory circuit comprised of four transcription factors (TFs) and a DNA methyltransferase. Using a modified global 5′ RACE protocol, we globally mapped transcription start sites (TSSs) at base-pair resolution, measured their transcription levels at multiple times in the cell cycle, and identified their transcription factor binding sites. Out of 2726 TSSs, 586 were shown to be cell cycle-regulated and we identified 529 binding sites for the cell cycle master regulators. Twenty-three percent of the cell cycle-regulated promoters were found to be under the combinatorial control of two or more of the global regulators. Previously unknown features of the core cell cycle circuit were identified, including 107 antisense TSSs which exhibit cell cycle-control, and 241 genes with multiple TSSs whose transcription levels often exhibited different cell cycle timing. Cumulatively, this study uncovered novel new layers of transcriptional regulation mediating the bacterial cell cycle. PMID:25569173

  19. Arctigenin induces cell cycle arrest by blocking the phosphorylation of Rb via the modulation of cell cycle regulatory proteins in human gastric cancer cells.

    PubMed

    Jeong, Jin Boo; Hong, Se Chul; Jeong, Hyung Jin; Koo, Jin Suk

    2011-10-01

    Gastric cancer is a leading cause of cancer-related deaths, worldwide being second only to lung cancer as a cause of death. Arctigenin, a representative dibenzylbutyrolactone lignan, occurs in a variety of plants. However, the molecular mechanisms of arctigenin for anti-tumor effect on gastric cancer have not been examined. This study examined the biological effects of arctigenin on the human gastric cancer cell line SNU-1 and AGS. Cell proliferation was determined by MTT assay. In MTT assay, the proliferation of SNU-1 and AGS cells was significantly inhibited by arctigenin in a time and dose dependent manner, as compared with SNU-1 and AGS cells cultured in the absence of arctigenin. Inhibition of cell proliferation by arctigenin was in part associated with apoptotic cell death, as shown by changes in the expression ratio of Bcl-2 to Bax by arctigenin. Also, arctigenin blocked cell cycle arrest from G(1) to S phase by regulating the expression of cell cycle regulatory proteins such as Rb, cyclin D1, cyclin E, CDK4, CDK2, p21Waf1/Cip1 and p15 INK4b. The antiproliferative effect of arctigenin on SNU-1 and AGS gastric cancer cells revealed in this study suggests that arctigenin has intriguing potential as a chemopreventive or chemotherapeutic agent.

  20. Mps1 is SUMO-modified during the cell cycle.

    PubMed

    Restuccia, Agnese; Yang, Feikun; Chen, Changyan; Lu, Lou; Dai, Wei

    2016-01-19

    Mps1 is a dual specificity protein kinase that regulates the spindle assembly checkpoint and mediates proper microtubule attachment to chromosomes during mitosis. However, the molecular mechanism that controls Mps1 protein level and its activity during the cell cycle remains unclear. Given that sumoylation plays an important role in mitotic progression, we investigated whether Mps1 was SUMO-modified and whether sumoylation affects its activity in mitosis. Our results showed that Mps1 was sumoylated in both asynchronized and mitotic cell populations. Mps1 was modified by both SUMO-1 and SUMO-2. Our further studies revealed that lysine residues including K71, K287, K367 and K471 were essential for Mps1 sumoylation. Sumoylation appeared to play a role in mediating kinetochore localization of Mps1, thus affecting normal mitotic progression. Furthermore, SUMO-resistant mutants of Mps1 interacted with BubR1 more efficiently than it did with the wild-type control. Combined, our results indicate that Mps1 is SUMO-modified that plays an essential role in regulating Mps1 functions during mitosis. PMID:26675261

  1. Mps1 is SUMO-modified during the cell cycle

    PubMed Central

    Chen, Changyan; Lu, Lou; Dai, Wei

    2016-01-01

    Mps1 is a dual specificity protein kinase that regulates the spindle assembly checkpoint and mediates proper microtubule attachment to chromosomes during mitosis. However, the molecular mechanism that controls Mps1 protein level and its activity during the cell cycle remains unclear. Given that sumoylation plays an important role in mitotic progression, we investigated whether Mps1 was SUMO-modified and whether sumoylation affects its activity in mitosis. Our results showed that Mps1 was sumoylated in both asynchronized and mitotic cell populations. Mps1 was modified by both SUMO-1 and SUMO-2. Our further studies revealed that lysine residues including K71, K287, K367 and K471 were essential for Mps1 sumoylation. Sumoylation appeared to play a role in mediating kinetochore localization of Mps1, thus affecting normal mitotic progression. Furthermore, SUMO-resistant mutants of Mps1 interacted with BubR1 more efficiently than it did with the wild-type control. Combined, our results indicate that Mps1 is SUMO-modified that plays an essential role in regulating Mps1 functions during mitosis. PMID:26675261

  2. Cell-cycle-independent transitions in temporal identity of mammalian neural progenitor cells

    PubMed Central

    Okamoto, Mayumi; Miyata, Takaki; Konno, Daijiro; Ueda, Hiroki R.; Kasukawa, Takeya; Hashimoto, Mitsuhiro; Matsuzaki, Fumio; Kawaguchi, Ayano

    2016-01-01

    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. PMID:27094546

  3. Tcf3 and cell cycle factors contribute to butyrate resistance in colorectal cancer cells.

    PubMed

    Chiaro, Christopher; Lazarova, Darina L; Bordonaro, Michael

    2012-11-01

    Butyrate, a fermentation product of dietary fiber, inhibits clonal growth in colorectal cancer (CRC) cells dependent upon the fold induction of Wnt activity. We have developed a CRC cell line (HCT-R) that, unlike its parental cell line, HCT-116, does not respond to butyrate exposure with hyperactivation of Wnt signaling and suppressed clonal growth. PCR array analyses revealed Wnt pathway-related genes, the expression of which differs between butyrate-sensitive HCT-116 CRC cells and their butyrate-resistant HCT-R cell counterparts. We identified overexpression of Tcf3 as being partially responsible for the butyrate-resistant phenotype, as this DNA-binding protein suppresses the hyperinduction of Wnt activity by butyrate. Consequently, Tcf3 knockdown in HCT-R cells restores their sensitivity to the effects of butyrate on Wnt activity and clonal cell growth. Interestingly, the effects of overexpressed Tcf3 differ between HCT-116 and HCT-R cells; thus, in HCT-116 cells Tcf3 suppresses proliferation without rendering the cells resistant to butyrate. In HCT-R cells, however, the overexpression of Tcf3 inhibits Wnt activity, and the cells are still able to proliferate due to the higher expression levels of cell cycle factors, particularly those driving the G(1) to S transition. Knowledge of the molecular mechanisms determining the variable sensitivity of CRC cells to butyrate may assist in developing approaches that prevent or reverse butyrate resistance.

  4. Chinese medicinal herb, Acanthopanax gracilistylus, extract induces cell cycle arrest of human tumor cells in vitro.

    PubMed

    Shan, B E; Zeki, K; Sugiura, T; Yoshida, Y; Yamashita, U

    2000-04-01

    We investigated the effect of a Chinese medicinal herb, Acanthopanax gracilistylus (AG), extract (E) on the growth of human tumor cell lines in vitro. AGE markedly inhibited the proliferation of several tumor cell lines such as MT-2, Raji, HL-60, TMK-1 and HSC-2. The activity was associated with a protein of 60 kDa, which was purified by gel-filtration chromatography. Cell viability analyses indicated that the treatment with AGE inhibits cell proliferation, but does not induce cell death. The mechanism of AGE-induced inhibition of tumor cell growth involves arrest of the cell cycle at the G(0) / G(1) stage without a direct cytotoxic effect. The cell cycle arrest induced by AGE was accompanied by a decrease of phosphorylated retinoblastoma (Rb) protein. Furthermore, cyclin-dependent kinases 2 and 4 (Cdk2 and Cdk4), which are involved in the phosphorylation of Rb, were also decreased. These results suggest that AGE inhibits tumor cell growth by affecting phosphorylated Rb proteins and Cdks. PMID:10804285

  5. Diosgenin induces G2/M cell cycle arrest and apoptosis in human hepatocellular carcinoma cells.

    PubMed

    Li, Yongjian; Wang, Xiaorong; Cheng, Silu; Du, Juan; Deng, Zhengting; Zhang, Yani; Liu, Qun; Gao, Jingdong; Cheng, Binbin; Ling, Changquan

    2015-02-01

    Diosgenin is a major compound of Dioscoreaceae plants such as yam, which is used as a drug in Traditional Chinese Medicine, and a common vegetable worldwide. The anticancer effect of diosgenin has been reported in various tumor cells, including leukemia, gastric, colorectal, and breast cancer. However, the activity of diosgenin on hepatocellular carcinoma (HCC) and the underlying mechanism have not been completely investigated. Therefore, we investigated the efficacy and associated mechanisms of diosgenin in HCC cells. Flow cytometric analysis was performed to determine the presence of cell cycle arrest and apopotic cells. Diosgenin significantly inhibited the growth of Bel-7402, SMMC-7721 and HepG2 HCC cells in a concentration-dependent manner. Diosgenin treatment for 24 h induced G2/M cell cycle arrest and apoptosis of hepatoma cells. Diosgenin inhibited Akt phosphorylation and upregulated p21 and p27 expression, but did not alter the expression of p53, suggesting diosgenin-induced upregulation of p21 and p57 is p53-independent in HCC cells. Diosgenin induced HCC cell apoptosis by activating caspase cascades -3, -8 and -9. However, diosgenin did not affect Bcl-2 and Bax levels. In conclusion, results of the present study suggest that diosgenin may be an active anti-HCC agent obtained from natural plants and provide new insights in understanding the mechanisms of diosgenin. PMID:25434486

  6. Apoptosis and cell-cycle arrest in human and murine tumor cells are initiated by isoprenoids.

    PubMed

    Mo, H; Elson, C E

    1999-04-01

    Diverse classes of phytochemicals initiate biological responses that effectively lower cancer risk. One class of phytochemicals, broadly defined as pure and mixed isoprenoids, encompasses an estimated 22,000 individual components. A representative mixed isoprenoid, gamma-tocotrienol, suppresses the growth of murine B16(F10) melanoma cells, and with greater potency, the growth of human breast adenocarcinoma (MCF-7) and human leukemic (HL-60) cells. beta-Ionone, a pure isoprenoid, suppresses the growth of B16 cells and with greater potency, the growth of MCF-7, HL-60 and human colon adenocarcinoma (Caco-2) cells. Results obtained with diverse cell lines differing in ras and p53 status showed that the isoprenoid-mediated suppression of growth is independent of mutated ras and p53 functions. beta-Ionone suppressed the growth of human colon fibroblasts (CCD-18Co) but only when present at three-fold the concentration required to suppress the growth of Caco-2 cells. The isoprenoids initiated apoptosis and, concomitantly arrested cells in the G1 phase of the cell cycle. Both suppress 3-hydroxy-3-methylglutaryl CoA reductase activity. beta-Ionone and lovastatin interfered with the posttranslational processing of lamin B, an activity essential to assembly of daughter nuclei. This interference, we postulate, renders neosynthesized DNA available to the endonuclease activities leading to apoptotic cell death. Lovastatin-imposed mevalonate starvation suppressed the glycosylation and translocation of growth factor receptors to the cell surface. As a consequence, cells were arrested in the G1 phase of the cell cycle. This rationale may apply to the isoprenoid-mediated G1-phase arrest of tumor cells. The additive and potentially synergistic actions of these isoprenoids in the suppression of tumor cell proliferation and initiation of apoptosis coupled with the mass action of the diverse isoprenoid constituents of plant products may explain, in part, the impact of fruit, vegetable

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

    PubMed

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

    2013-01-01

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

  8. Programmed cell cycle arrest is required for infection of corn plants by the fungus Ustilago maydis.

    PubMed

    Castanheira, Sónia; Mielnichuk, Natalia; Pérez-Martín, José

    2014-12-01

    Ustilago maydis is a plant pathogen that requires a specific structure called infective filament to penetrate the plant tissue. Although able to grow, this filament is cell cycle arrested on the plant surface. This cell cycle arrest is released once the filament penetrates the plant tissue. The reasons and mechanisms for this cell cycle arrest are unknown. Here, we have tried to address these questions. We reached three conclusions from our studies. First, the observed cell cycle arrest is the result of the cooperation of at least two distinct mechanisms: one involving the activation of the DNA damage response (DDR) cascade; and the other relying on the transcriptional downregulation of Hsl1, a kinase that modulates the G2/M transition. Second, a sustained cell cycle arrest during the infective filament step is necessary for the virulence in U. maydis, as a strain unable to arrest the cell cycle was severely impaired in its ability to infect corn plants. Third, production of the appressorium, a structure required for plant penetration, is incompatible with an active cell cycle. The inability to infect plants by strains defective in cell cycle arrest seems to be caused by their failure to induce the appressorium formation process. In summary, our findings uncover genetic circuits to arrest the cell cycle during the growth of this fungus on the plant surface, thus allowing the penetration into plant tissue.

  9. A marginal band-associated protein has properties of both microtubule- and microfilament-associated proteins

    PubMed Central

    1989-01-01

    The marginal band of nucleated erythrocytes is a microtubule organelle under rigorous quantitative and spatial control, with properties quite different from those of the microtubule organelles of cultured cells. Previous results suggest that proteins other than tubulin may participate in organizing the marginal band, and may interact with elements of the erythrocyte cytoskeleton in addition to microtubules. To identify such species, we raised mAbs against the proteins that assemble from chicken brain homogenates with tubulin. One such antibody binds to a single protein in chicken erythrocytes, and produces an immunofluorescence pattern colocalizing with marginal band microtubules. Several properties of this protein are identical to those of ezrin, a protein isolated from brush border and localized to motile elements of cultured cells. A significant proportion of the antigen is not soluble in erythrocytes, as determined by extraction with nonionic detergent. This cytoskeleton-associated fraction is unaffected by treatments that solubilize the marginal band microtubules. The protein has properties of both microtubule- and microfilament-associated proteins. In the accompanying manuscript (Goslin, K., E. Birgbauer, G. Banker, and F. Solomon. 1989. J. Cell Biol. 109:1621-1631), we show that the same antibody recognizes a component of growth cones with a similar dual nature. In early embryonic red blood cells, the antigen is dispersed throughout the cell and does not colocalize with assembled tubulin. Its confinement to the marginal band during development follows rather than precedes that of microtubules. These results, along with previous work, suggest models for the formation of the marginal band. PMID:2677023

  10. Synchronization of Caulobacter crescentus for investigation of the bacterial cell cycle.

    PubMed

    Schrader, Jared M; Shapiro, Lucy

    2015-04-08

    The cell cycle is important for growth, genome replication, and development in all cells. In bacteria, studies of the cell cycle have focused largely on unsynchronized cells making it difficult to order the temporal events required for cell cycle progression, genome replication, and division. Caulobacter crescentus provides an excellent model system for the bacterial cell cycle whereby cells can be rapidly synchronized in a G0 state by density centrifugation. Cell cycle synchronization experiments have been used to establish the molecular events governing chromosome replication and segregation, to map a genetic regulatory network controlling cell cycle progression, and to identify the establishment of polar signaling complexes required for asymmetric cell division. Here we provide a detailed protocol for the rapid synchronization of Caulobacter NA1000 cells. Synchronization can be performed in a large-scale format for gene expression profiling and western blot assays, as well as a small-scale format for microscopy or FACS assays. The rapid synchronizability and high cell yields of Caulobacter make this organism a powerful model system for studies of the bacterial cell cycle.

  11. Visualizing spatiotemporal dynamics of multicellular cell-cycle progressions with fucci technology.

    PubMed

    Sakaue-Sawano, Asako; Miyawaki, Atsushi

    2014-05-01

    The visualization of cell-cycle behavior of individual cells within complex tissues presents an irresistible challenge to biologists studying multicellular structures. However, the transition from G1 to S in the cell cycle is difficult to monitor despite the fact that the process involves the critical decision to initiate a new round of DNA replication. Here, we use ubiquitination oscillators that control cell-cycle transitions to develop genetically encoded fluorescent probes for cell-cycle progression. Fucci (fluorescent ubiquitination-based cell-cycle indicator) probes exploit the regulation of cell-cycle-dependent ubiquitination to effectively label individual nuclei in G1 phase red, and those in S/G2/M phases green. Cultured cells and transgenic mice constitutively expressing the probes have been generated, such that every cell nucleus shows either red or green fluorescence. This protocol details two experiments that use biological samples expressing Fucci probes. One experiment involves time-lapse imaging of cells stably expressing a Fucci derivative (Fucci2), which allows for the exploration of the spatiotemporal patterns of cell-cycle dynamics during structural and behavioral changes of cultured cells. The other experiment involves large-field, high-resolution imaging of fixed sections of Fucci transgenic mouse embryos, which provides maps that illustrate cell proliferation versus differentiation in various developing organs.

  12. Physiology of Saccharomyces cerevisiae during cell cycle oscillations.

    PubMed

    Duboc, P; Marison, I; von Stockar, U

    1996-10-18

    Synchronized populations of Saccharomyces cerevisiae CBS 426 are characterized by autonomous oscillations of process variables. CO2 evolution rate, O2 uptake rate and heat production rate varied by a factor of 2 for a continuous culture grown at a dilution rate of 0.10 h-1. Elemental analysis showed that the carbon mass fraction of biomass did not change. Since the reactor is not at steady state, the elemental and energy balances were calculated on cumulated quantities, i.e. the integral of the reaction rates. It was possible to show that carbon, degree of reduction and energy balances matched. Application of simple mass balance principles for non-steady state systems indicated that oscillations were basically characterized by changes in biomass production rate. In addition, the amount of intermediates, e.g. ethanol or acetate, produced or consumed was negligible. Growth rate was low during the S-phase (0.075 h-1) and high during the G2, M and G1 phases (0.125 h-1) for a constant dilution rate of 0.10 h-1. However, nitrogen, ash, sulfur and potassium content showed systematic increases during the S-phase (bud initiation). Cell component analyses showed that changes in cellular fractions during oscillations (storage carbohydrate content decreased during the S-phase) were due to changes in production rates, particularly for protein and carbohydrates. Nevertheless, using the data evaluation techniques for dynamic systems presented here, it was shown that storage carbohydrates are not consumed during the S-phase. Only the synthesis rate of the different cell components changed depending on position in cell cycle. The growth process may be divided into two phenomena: the formation of new cells during mitosis with a low yield, and size increase of new born cells with high yield. Both kinetic and stoichiometric coefficients varied with the position in the oscillation: the results showed that biomass structure changed and that specific growth rate, as well as biomass yield

  13. The marine-derived fungal metabolite, terrein, inhibits cell proliferation and induces cell cycle arrest in human ovarian cancer cells.

    PubMed

    Chen, Yi-Fei; Wang, Shu-Ying; Shen, Hong; Yao, Xiao-Fen; Zhang, Feng-Li; Lai, Dongmei

    2014-12-01

    The difficulties faced in the effective treatment of ovarian cancer are multifactorial, but are mainly associated with relapse and drug resistance. Cancer stem-like cells have been reported to be an important contributor to these hindering factors. In this study, we aimed to investigate the anticancer activities of a bioactive fungal metabolite, namely terrein, against the human epithelial ovarian cancer cell line, SKOV3, primary human ovarian cancer cells and ovarian cancer stem-like cells. Terrein was separated and purified from the fermentation metabolites of the marine sponge-derived fungus, Aspergillus terreus strain PF26. Its anticancer activities against ovarian cancer cells were investigated by cell proliferation assay, cell migration assay, cell apoptosis and cell cycle assays. The ovarian cancer stem-like cells were enriched and cultured in a serum-free in vitro suspension system. Terrein inhibited the proliferation of the ovarian cancer cells by inducing G2/M phase cell cycle arrest. The underlying mechanisms involved the suppression of the expression of LIN28, an important marker gene of stemness in ovarian cancer stem cells. Of note, our study also demonstrated the ability of terrein to inhibit the proliferation of ovarian cancer stem-like cells, in which the expression of LIN28 was also downregulated. Our findings reveal that terrein (produced by fermention) may prove to be a promising drug candidate for the treatment of ovarian cancer by inhibiting the proliferation of cancer stem-like cells.

  14. Cancer cell(s) cycle sequencing reveals universal mechanisms of apoptosis.

    PubMed

    Marretta, R M Ardito; Ales, F

    2010-12-01

    In this paper, cell cycle in higher eukaryotes and their molecular networks signals both in G1/S and G2/M transitions are replicated in silico. Biochemical kinetics, converted into a set of differential equations, and system control theory are employed to design multi-nested digital layers to simulate protein-to-protein activation and inhibition for cell cycle dynamics in the presence of damaged genomes. Sequencing and controlling the digital process of four micro-scale species networks (p53/Mdm2/DNA damage, p21mRNA/cyclin-CDK complex, CDK/CDC25/weel/SKP2/APC/CKI and apoptosis target genes system) not only allows the comprehension of the mechanisms of these molecule interactions but paves the way for unraveling the participants and their by-products, until now quite unclear, which have the task of carrying out (or not) cell death. Whatever the running simulations (e.g., different species signals, mutant cells and different DNA damage levels), the results of the proposed cell digital multi-layers give reason to believe in the existence of a universal apoptotic mechanism. As a consequence, we identified and selected cell check points, sizers, timers and specific target genes dynamic both for influencing mitotic process and avoiding cancer proliferation as much as for leading the cancer cell(s) to collapse into a steady stable apoptosis phase. PMID:21141676

  15. A stochastic spatiotemporal model of a response-regulator network in the Caulobacter crescentus cell cycle

    NASA Astrophysics Data System (ADS)

    Li, Fei; Subramanian, Kartik; Chen, Minghan; Tyson, John J.; Cao, Yang

    2016-06-01

    The asymmetric cell division cycle in Caulobacter crescentus is controlled by an elaborate molecular mechanism governing the production, activation and spatial localization of a host of interacting proteins. In previous work, we proposed a deterministic mathematical model for the spatiotemporal dynamics of six major regulatory proteins. In this paper, we study a stochastic version of the model, which takes into account molecular fluctuations of these regulatory proteins in space and time during early stages of the cell cycle of wild-type Caulobacter cells. We test the stochastic model with regard to experimental observations of increased variability of cycle time in cells depleted of the divJ gene product. The deterministic model predicts that overexpression of the divK gene blocks cell cycle progression in the stalked stage; however, stochastic simulations suggest that a small fraction of the mutants cells do complete the cell cycle normally.

  16. Cdk1 activity acts as a quantitative platform for coordinating cell cycle progression with periodic transcription

    PubMed Central

    Banyai, Gabor; Baïdi, Feriel; Coudreuse, Damien; Szilagyi, Zsolt

    2016-01-01

    Cell proliferation is regulated by cyclin-dependent kinases (Cdks) and requires the periodic expression of particular gene clusters in different cell cycle phases. However, the interplay between the networks that generate these transcriptional oscillations and the core cell cycle machinery remains largely unexplored. In this work, we use a synthetic regulable Cdk1 module to demonstrate that periodic expression is governed by quantitative changes in Cdk1 activity, with different clusters directly responding to specific activity levels. We further establish that cell cycle events neither participate in nor interfere with the Cdk1-driven transcriptional program, provided that cells are exposed to the appropriate Cdk1 activities. These findings contrast with current models that propose self-sustained and Cdk1-independent transcriptional oscillations. Our work therefore supports a model in which Cdk1 activity serves as a quantitative platform for coordinating cell cycle transitions with the expression of critical genes to bring about proper cell cycle progression. PMID:27045731

  17. The retinoblastoma family of proteins and their regulatory functions in the mammalian cell division cycle

    PubMed Central

    2012-01-01

    The retinoblastoma (RB) family of proteins are found in organisms as distantly related as humans, plants, and insects. These proteins play a key role in regulating advancement of the cell division cycle from the G1 to S-phases. This is achieved through negative regulation of two important positive regulators of cell cycle entry, E2F transcription factors and cyclin dependent kinases. In growth arrested cells transcriptional activity by E2Fs is repressed by RB proteins. Stimulation of cell cycle entry by growth factor signaling leads to activation of cyclin dependent kinases. They in turn phosphorylate and inactivate the RB family proteins, leading to E2F activation and additional cyclin dependent kinase activity. This propels the cell cycle irreversibly forward leading to DNA synthesis. This review will focus on the basic biochemistry and cell biology governing the regulation and activity of mammalian RB family proteins in cell cycle control. PMID:22417103

  18. Transcriptomic profiling of human embryonic stem cells upon cell cycle manipulation during pluripotent state dissolution.

    PubMed

    Gonzales, Kevin Andrew Uy; Liang, Hongqing

    2015-12-01

    While distinct cell cycle structures have been known to correlate with pluripotent or differentiated cell states [1], there is no evidence on how the cell cycle machinery directly contributes to human embryonic stem cell (hESC) pluripotency. We established a determinant role of cell cycle machineries on the pluripotent state by demonstrating that the specific perturbation of the S and G2 phases can prevent pluripotent state dissolution (PSD) [2]. Active mechanisms in these phases, such as the DNA damage checkpoint and Cyclin B1, promote the pluripotent state [2]. To understand the mechanisms behind the effect on PSD by these pathways in hESCs, we performed comprehensive gene expression analysis by time-course microarray experiments. From these datasets, we observed expression changes in genes involved in the TGFβ signaling pathway, which has a well-established role in hESC maintenance [3], [4], [5]. The microarray data have been deposited in NCBI's Gene Expression Omnibus (GEO) and can be accessed through GEO Series accession numbers GSE62062 and GSE63215.

  19. A proteomic chronology of gene expression through the cell cycle in human myeloid leukemia cells

    PubMed Central

    Ly, Tony; Ahmad, Yasmeen; Shlien, Adam; Soroka, Dominique; Mills, Allie; Emanuele, Michael J; Stratton, Michael R; Lamond, Angus I

    2014-01-01

    Technological advances have enabled the analysis of cellular protein and RNA levels with unprecedented depth and sensitivity, allowing for an unbiased re-evaluation of gene regulation during fundamental biological processes. Here, we have chronicled the dynamics of protein and mRNA expression levels across a minimally perturbed cell cycle in human myeloid leukemia cells using centrifugal elutriation combined with mass spectrometry-based proteomics and RNA-Seq, avoiding artificial synchronization procedures. We identify myeloid-specific gene expression and variations in protein abundance, isoform expression and phosphorylation at different cell cycle stages. We dissect the relationship between protein and mRNA levels for both bulk gene expression and for over ∼6000 genes individually across the cell cycle, revealing complex, gene-specific patterns. This data set, one of the deepest surveys to date of gene expression in human cells, is presented in an online, searchable database, the Encyclopedia of Proteome Dynamics (http://www.peptracker.com/epd/). DOI: http://dx.doi.org/10.7554/eLife.01630.001 PMID:24596151

  20. Cytoplasmic sequestration of cyclin D1 associated with cell cycle withdrawal of neuroblastoma cells

    SciTech Connect

    Sumrejkanchanakij, Piyamas; Eto, Kazuhiro; Ikeda, Masa-Aki . E-mail: mikeda.emb@tmd.ac.jp

    2006-02-03

    The regulation of D-type cyclin-dependent kinase activity is critical for neuronal differentiation and apoptosis. We recently showed that cyclin D1 is sequestered in the cytoplasm and that its nuclear localization induces apoptosis in postmitotic primary neurons. Here, we further investigated the role of the subcellular localization of cyclin D1 in cell cycle withdrawal during the differentiation of N1E-115 neuroblastoma cells. We show that cyclin D1 became predominantly cytoplasmic after differentiation. Targeting cyclin D1 expression to the nucleus induced phosphorylation of Rb and cdk2 kinase activity. Furthermore, cyclin D1 nuclear localization promoted differentiated N1E-115 cells to reenter the cell cycle, a process that was inhibited by p16{sup INK4a}, a specific inhibitor of D-type cyclin activity. These results indicate that cytoplasmic sequestration of cyclin D1 plays a role in neuronal cell cycle withdrawal, and suggests that the abrogation of machinery involved in monitoring aberrant nuclear cyclin D1 activity contributes to neuronal tumorigenesis.

  1. Effects of storage on the cycle life of nickel hydrogen battery cells

    NASA Astrophysics Data System (ADS)

    Zimmerman, A. H.; Matsumoto, J.; Poston, T.; Prater, A.; Barrera, T.

    The cycle life of a nickel hydrogen cell has been evaluated at 80 percent depth of discharge after nearly 5 years of cell storage, including two years of shorted storage. After this storage the cycle life was found to be about 1200 cycles, compared to 5000-9000 cycles for typical unstored cells. Cell analyses before cycling indicated significant segregation of cobalt additive in the nickel electrodes, as well as a small amount of sinter corrosion. The large decrease in cycle life after storage is attributed primarily to the loss of about one-third of the active cobalt from the active material during the discharged storage of these hydrogen precharged cells, and to the formation of inactive cobalt oxides in the nickel electrodes. Storage methods capable of eliminating problems from both sinter corrosion and cobalt segregation are discussed.

  2. Apigenin inhibits pancreatic cancer cell proliferation through G2/M cell cycle arrest

    PubMed Central

    Ujiki, Michael B; Ding, Xian-Zhong; Salabat, M Reza; Bentrem, David J; Golkar, Laleh; Milam, Ben; Talamonti, Mark S; Bell, Richard H; Iwamura, Takeshi; Adrian, Thomas E

    2006-01-01

    Background Many chemotherapeutic agents have been used to treat pancreatic cancer without success. Apigenin, a naturally occurring flavonoid, has been shown to inhibit growth in some cancer cell lines but has not been studied in pancreatic cancer. We hypothesized that apigenin would inhibit pancreatic cancer cell growth in vitro. Results Apigenin caused both time- and concentration-dependent inhibition of DNA synthesis and cell proliferation in four pancreatic cancer cell lines. Apigenin induced G2/M phase cell cycle arrest. Apigenin reduced levels of cyclin A, cyclin B, phosphorylated forms of cdc2 and cdc25, which are all proteins required for G2/M transition. Conclusion Apigenin inhibits growth of pancreatic cancer cells through suppression of cyclin B-associated cdc2 activity and G2/M arrest, and may be a valuable drug for the treatment or prevention of pancreatic cancer. PMID:17196098

  3. Modelling the coupling between intracellular calcium release and the cell cycle during cortical brain development.

    PubMed

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

    2014-04-21

    Most neocortical neurons formed during embryonic brain development arise from radial glial cells which communicate, in part, via ATP mediated calcium signals. Although the intercellular signalling mechanisms that regulate radial glia proliferation are not well understood, it has recently been demonstrated that ATP dependent intracellular calcium release leads to an increase of nearly 100% in overall cellular proliferation. It has been hypothesised that cytoplasmic calcium accelerates entry into S phase of the cell cycle and/or acts to recruit otherwise quiescent cells onto the cell cycle. In this paper we study this cell cycle acceleration and recruitment by forming a differential equation model for ATP mediated calcium-cell cycle coupling via Cyclin D in a single radial glial cell. Bifurcation analysis and numerical simulations suggest that the cell cycle period depends only weakly on cytoplasmic calcium. Therefore, the accelerative impact of calcium on the cell cycle can only account for a small fraction of the large increase in proliferation observed experimentally. Crucially however, our bifurcation analysis reveals that stable fixed point and stable limit cycle solutions can coexist, and that calcium dependent Cyclin D dynamics extend the oscillatory region to lower Cyclin D synthesis rates, thus rendering cells more susceptible to cycling. This supports the hypothesis that cycling glial cells recruit quiescent cells (in G0 phase) onto the cell cycle, via a calcium signalling mechanism, and that this may be the primary means by which calcium augments proliferation rates at the population scale. Numerical simulations of two coupled cells demonstrate that such a scenario is indeed feasible.

  4. Model-Based Analysis of Cell Cycle Responses to Dynamically Changing Environments

    PubMed Central

    Seaton, Daniel D; Krishnan, J

    2016-01-01

    Cell cycle progression is carefully coordinated with a cell’s intra- and extracellular environment. While some pathways have been identified that communicate information from the environment to the cell cycle, a systematic understanding of how this information is dynamically processed is lacking. We address this by performing dynamic sensitivity analysis of three mathematical models of the cell cycle in Saccharomyces cerevisiae. We demonstrate that these models make broadly consistent qualitative predictions about cell cycle progression under dynamically changing conditions. For example, it is shown that the models predict anticorrelated changes in cell size and cell cycle duration under different environments independently of the growth rate. This prediction is validated by comparison to available literature data. Other consistent patterns emerge, such as widespread nonmonotonic changes in cell size down generations in response to parameter changes. We extend our analysis by investigating glucose signalling to the cell cycle, showing that known regulation of Cln3 translation and Cln1,2 transcription by glucose is sufficient to explain the experimentally observed changes in cell cycle dynamics at different glucose concentrations. Together, these results provide a framework for understanding the complex responses the cell cycle is capable of producing in response to dynamic environments. PMID:26741131

  5. PDK1 regulates VDJ recombination, cell-cycle exit and survival during B-cell development.

    PubMed

    Venigalla, Ram K C; McGuire, Victoria A; Clarke, Rosemary; Patterson-Kane, Janet C; Najafov, Ayaz; Toth, Rachel; McCarthy, Pierre C; Simeons, Frederick; Stojanovski, Laste; Arthur, J Simon C

    2013-04-01

    Phosphoinositide-dependent kinase-1 (PDK1) controls the activation of a subset of AGC kinases. Using a conditional knockout of PDK1 in haematopoietic cells, we demonstrate that PDK1 is essential for B cell development. B-cell progenitors lacking PDK1 arrested at the transition of pro-B to pre-B cells, due to a cell autonomous defect. Loss of PDK1 decreased the expression of the IgH chain in pro-B cells due to impaired recombination of the IgH distal variable segments, a process coordinated by the transcription factor Pax5. The expression of Pax5 in pre-B cells was decreased in PDK1 knockouts, which correlated with reduced expression of the Pax5 target genes IRF4, IRF8 and Aiolos. As a result, Ccnd3 is upregulated in PDK1 knockout pre-B cells and they have an impaired ability to undergo cell-cycle arrest, a necessary event for Ig light chain rearrangement. Instead, these cells underwent apoptosis that correlated with diminished expression of the pro-survival gene Bcl2A1. Reintroduction of both Pax5 and Bcl2A1 together into PDK1 knockout pro-B cells restored their ability to differentiate in vitro into mature B cells.

  6. PDK1 regulates VDJ recombination, cell-cycle exit and survival during B-cell development.

    PubMed

    Venigalla, Ram K C; McGuire, Victoria A; Clarke, Rosemary; Patterson-Kane, Janet C; Najafov, Ayaz; Toth, Rachel; McCarthy, Pierre C; Simeons, Frederick; Stojanovski, Laste; Arthur, J Simon C

    2013-04-01

    Phosphoinositide-dependent kinase-1 (PDK1) controls the activation of a subset of AGC kinases. Using a conditional knockout of PDK1 in haematopoietic cells, we demonstrate that PDK1 is essential for B cell development. B-cell progenitors lacking PDK1 arrested at the transition of pro-B to pre-B cells, due to a cell autonomous defect. Loss of PDK1 decreased the expression of the IgH chain in pro-B cells due to impaired recombination of the IgH distal variable segments, a process coordinated by the transcription factor Pax5. The expression of Pax5 in pre-B cells was decreased in PDK1 knockouts, which correlated with reduced expression of the Pax5 target genes IRF4, IRF8 and Aiolos. As a result, Ccnd3 is upregulated in PDK1 knockout pre-B cells and they have an impaired ability to undergo cell-cycle arrest, a necessary event for Ig light chain rearrangement. Instead, these cells underwent apoptosis that correlated with diminished expression of the pro-survival gene Bcl2A1. Reintroduction of both Pax5 and Bcl2A1 together into PDK1 knockout pro-B cells restored their ability to differentiate in vitro into mature B cells. PMID:23463102

  7. M2 receptor activation inhibits cell cycle progression and survival in human glioblastoma cells.

    PubMed

    Ferretti, Michela; Fabbiano, Cinzia; Di Bari, Maria; Conte, Claudia; Castigli, Emilia; Sciaccaluga, Miriam; Ponti, Donatella; Ruggieri, Paola; Raco, Antonino; Ricordy, Ruggero; Calogero, Antonella; Tata, Ada Maria

    2013-04-01

    Muscarinic receptors, expressed in several primary and metastatic tumours, appear to be implicated in their growth and propagation. In this work we have demonstrated that M2 muscarinic receptors are expressed in glioblastoma human specimens and in glioblastoma cell lines. Moreover, we have characterized the effects of the M2 agonist arecaidine on cell growth and survival both in two different glioblastoma cell lines (U251MG and U87MG) and in primary cultures obtained from different human biopsies. Cell growth analysis has demonstrated that the M2 agonist arecaidine strongly decreased cell proliferation in both glioma cell lines and primary cultures. This effect was dose and time dependent. FACS analysis has confirmed cell cycle arrest at G1/S and at G2/M phase in U87 cells and U251 respectively. Cell viability analysis has also shown that arecaidine induced severe apoptosis, especially in U251 cells. Chemosensitivity assays have, moreover, shown arecaidine and temozolomide similar effects on glioma cell lines, although IC50 value for arecaidine was significantly lower than temozolomide. In conclusion, we report for the first time that M2 receptor activation has a relevant role in the inhibition of glioma cell growth and survival, suggesting that M2 may be a new interesting therapeutic target to investigate for glioblastoma therapy.

  8. Nitrogen-containing bisphosphonates inhibit cell cycle progression in human melanoma cells.

    PubMed

    Forsea, A-M; Müller, C; Riebeling, C; Orfanos, C E; Geilen, C C

    2004-08-16

    Cutaneous melanoma is one of the highly malignant human tumours, due to its tendency to generate early metastases and its resistance to classical chemotherapy. We recently demonstrated that pamidronate, a nitrogen-containing bisphosphonate, has an antiproliferative and proapoptotic effect on different melanoma cell lines. In the present study, we compared the in vitro effects of three different bisphosphonates on human melanoma cell lines and we demonstrated that the two nitrogen-containing bisphosphonates pamidronate and zoledronate inhibited the proliferation of melanoma cells and induced apoptosis in a dose- and time-dependent manner. Moreover, cell cycle progression was altered, the two compounds causing accumulation of the cells in the S phase of the cycle. In contrast, the nonaminobisphosphonate clodronate had no effect on melanoma cells. These findings suggest a direct antitumoural effect of bisphosphonates on melanoma cells in vitro and further support the hypothesis of different intracellular mechanisms of action for nitrogen-containing and nonaminobisphosphonates. Our data indicate that nitrogen-containing bisphosphonates may be a useful novel therapeutic class for treatment and/or prevention of melanoma metastases.

  9. Cell cycle arrest in a model of colistin nephrotoxicity.

    PubMed

    Eadon, Michael T; Hack, Bradley K; Alexander, Jessy J; Xu, Chang; Dolan, M Eileen; Cunningham, Patrick N

    2013-10-01

    Colistin (polymixin E) is an antibiotic prescribed with resurging frequency for multidrug resistant gram negative bacterial infections. It is associated with nephrotoxicity in humans in up to 55% of cases. Little is known regarding genes involved in colistin nephrotoxicity. A murine model of colistin-mediated kidney injury was developed. C57/BL6 mice were administered saline or colistin at a dose of 16 mg/kg/day in 2 divided intraperitoneal doses and killed after either 3 or 15 days of colistin. After 15 days, mice exposed to colistin had elevated blood urea nitrogen (BUN), creatinine, and pathologic evidence of acute tubular necrosis and apoptosis. After 3 days, mice had neither BUN elevation nor substantial pathologic injury; however, urinary neutrophil gelatinase-associated lipocalin was elevated (P = 0.017). An Illumina gene expression array was performed on kidney RNA harvested 72 h after first colistin dose to identify differentially expressed genes early in drug treatment. Array data revealed 21 differentially expressed genes (false discovery rate < 0.1) between control and colistin-exposed mice, including LGALS3 and CCNB1. The gene signature was significantly enriched for genes involved in cell cycle proliferation. RT-PCR, immunoblot, and immunostaining validated the relevance of key genes and proteins. This murine model offers insights into the potential mechanism of colistin-mediated nephrotoxicity. Further studies will determine whether the identified genes play a causative or protective role in colistin-induced nephrotoxicity.

  10. Entropic Biological Score: a cell cycle investigation for GRNs inference.

    PubMed

    Lopes, Fabrício M; Ray, Shubhra Sankar; Hashimoto, Ronaldo F; Cesar, Roberto M

    2014-05-15

    Inference of gene regulatory networks (GRNs) is one of the most challenging research problems of Systems Biology. In this investigation, a new GRNs inference methodology, called Entropic Biological Score (EBS), which linearly combines the mean conditional entropy (MCE) from expression levels and a Biological Score (BS), obtained by integrating different biological data sources, is proposed. The EBS is validated with the Cell Cycle related functional annotation information, available from Munich Information Center for Protein Sequences (MIPS), and compared with some existing methods like MRNET, ARACNE, CLR and MCE for GRNs inference. For real networks, the performance of EBS, which uses the concept of integrating different data sources, is found to be superior to the aforementioned inference methods. The best results for EBS are obtained by considering the weights w1=0.2 and w2=0.8 for MCE and BS values, respectively, where approximately 40% of the inferred connections are found to be correct and significantly better than related methods. The results also indicate that expression profile is able to recover some true connections, that are not present in biological annotations, thus leading to the possibility of discovering new relations between its genes. PMID:24631265

  11. A Strong Nucleotypic Effect on the Cell Cycle Regardless of Ploidy Level

    PubMed Central

    Francis, Dennis; Davies, M. Stuart; Barlow, Peter W.

    2008-01-01

    Background and Aims In published studies, positive relationships between nucleotype and the duration of the mitotic cell cycle in angiosperms have been reported but the highest number of species analyzed was approx. 60. Here an analysis is presented of DNA C-values and cell cycle times in root apical meristems of angiosperms comprising 110 measurements, including monocots and eudicots within a set temperature range, and encompassing an approx. 290-fold variation in DNA C-values. Methods Data for 110 published cell cycle times of seedlings grown at temperatures between 20–25 °C were compared with DNA C-values (58 values for monocots and 52 for eudicots). Regression analyses were undertaken for all species, and separately for monocots and eudicots, diploids and polyploids, and annuals and perennials. Cell cycle times were plotted against the nuclear DNA C-values. Key Results A positive relationship was observed between DNA C-value and cell cycle time for all species and for eudicots and monocots separately, regardless of the presence or absence of polyploid values. In this sample, among 52 eudicots the maximum cell cycle length was 18 h, whereas the 58 monocot values ranged from 8–120 h. There was a striking additional increase in cell cycle duration in perennial monocots with C-values greater than 25 pg. Indeed, the most powerful relationship between DNA C-value and cell cycle time and the widest range of cell cycle times was in perennials regardless of ploidy level. Conclusions DNA replication is identified as a rate limiting step in the cell cycle, the flexibility of DNA replication is explored, and we speculate on how the licensing of initiation points of DNA replication may be a responsive component of the positive nucleotypic effect of C-value on the duration of the mitotic cell cycle. PMID:18339642

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

    SciTech Connect

    Ding, Li; Huang, Yong; Du, Qian; Dong, Feng; Zhao, Xiaomin; Zhang, Wenlong; Xu, Xingang; Tong, Dewen

    2014-03-07

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

  13. Arecoline induced cell cycle arrest, apoptosis, and cytotoxicity to human endothelial cells.

    PubMed

    Tseng, Shuei-Kuen; Chang, Mei-Chi; Su, Cheng-Yao; Chi, Lin-Yang; Chang, Jenny Zwei-Ching; Tseng, Wan-Yu; Yeung, Sin-Yuet; Hsu, Ming-Lun; Jeng, Jiiang-Huei

    2012-08-01

    Betel quid (BQ) chewing is a common oral habit in South Asia and Taiwan. BQ consumption may increase the risk of oral squamous cell carcinoma (OSCC), oral submucous fibrosis (OSF), and periodontitis as well as systemic diseases (atherosclerosis, hypertension, etc.). However, little is known about the toxic effect of BQ components on endothelial cells that play important roles for angiogenesis, carcinogenesis, tissue fibrosis, and cardiovascular diseases. EAhy 926 (EAHY) endothelial cells were exposed to arecoline, a major BQ alkaloid, for various time periods. Cytotoxicity was estimated by 3-(4, 5- dimethylthiazol-2-yl)-2, 5-diphenyl tetrazolium bromide assay. The cell cycle distribution of EAHY cells residing in sub-G0/G1, G0/G1, S-, and G2/M phases was analyzed by propidium iodide staining of cellular DNA content and flow cytometry. Some EAHY cells retracted, became round-shaped in appearance, and even detached from the culture plate after exposure to higher concentrations of arecoline (> 0.4 mM). At concentrations of 0.4 and 0.8 mM, arecoline induced significant cytotoxicity to EAHY cells. At similar concentrations, arecoline induced G2/M cell cycle arrest and increased sub-G0/G1 population, a hallmark of apoptosis. Interestingly, prolonged exposure to arecoline (0.1 mM) for 12 and 21 days significantly suppressed the proliferation of EAHY cells, whereas EAHY cells showed adaptation and survived when exposed to 0.05 mM arecoline. These results suggest that BQ components may contribute to the pathogenesis of OSF and BQ chewing-related cardiovascular diseases via toxicity to oral or systemic endothelial cells, leading to impairment of vascular function. During BQ chewing, endothelial damage may be induced by areca nut components and associate with the pathogenesis of OSF, periodontitis, and cardiovascular diseases.

  14. Analysis of cell-cycle regulation following exposure of lung-derived cells to γ-rays

    NASA Astrophysics Data System (ADS)

    Trani, D.; Lucchetti, C.; Cassone, M.; D'Agostino, L.; Caputi, M.; Giordano, A.

    Acute exposure of mammalian cells to ionizing radiation results in a delay of cell-cycle progression and/or augmentation of apoptosis. Following ionizing radiation-induced DNA damage, cell-cycle arrest in the G1- or G2-phase of the cell-cycle prevents or delays DNA replication or mitosis, providing time for the DNA repair machinery to exert its function. Deregulation or failing of cell-cycle checkpoints and/or DNA repair mechanisms may lead normal cells bearing chromosome mutations to acquire neoplastic autonomy, which in turn can trigger the onset of cancer. Existing studies have focused on the impact of p53 status on the radiation response of lung cancer (LC) cell lines in terms of both cell-cycle regulation and apoptosis, while no comparative studies have been performed on the radiation response of lung derived normal and cancerous epithelial cells. To investigate the radiation response in normal and cancerous phenotypes, along with the role and impact of p53 status, and possible correlations with pRb/p105 or other proteins involved in carcinogenesis and cell-cycle regulation, we selected two lung-derived epithelial cell lines, one normal (NL20, p53 wild-type) and one non-small cell lung cancer (NSCLC), H358 (known to be p53-deficient). We compared the levels of γ-induced cell proliferation ability, cell-cycle arrest, apoptotic index, and expression levels of cell-cycle regulating and regulated proteins. The different cell sensitivity, apoptotic response and protein expression profiles resulting from our study for NL20 and H358 cells suggest that still unknown mechanisms involving p53, pRb/p105 and their target molecules might play a pivotal role in determining cell sensitivity and resistance upon exposure to ionizing radiation.

  15. CONDENSED MATTER: STRUCTURE, MECHANICAL AND THERMAL PROPERTIES: A Method to Design Synthetic Cell-Cycle Networks

    NASA Astrophysics Data System (ADS)

    Miao, Ke-Ke

    2009-07-01

    The interactions among proteins, DNA and RNA in an organism form elaborate cell-cycle networks which govern cell growth and proliferation. Understanding the common structure of cell-cycle networks will be of great benefit to science research. Here, inspired by the importance of the cell-cycle regulatory network of yeast which has been studied intensively, we focus on small networks with 11 nodes, equivalent to that of the cell-cycle regulatory network used by Li et al. [Proc. Natl. Acad. Sci. USA 101(2004)4781] Using a Boolean model, we study the correlation between structure and function, and a possible common structure. It is found that cascade-like networks with a great number of interactions between nodes are stable. Based on these findings, we are able to construct synthetic networks that have the same functions as the cell-cycle regulatory network.

  16. Treatment-induced cell cycle kinetics dictate tumor response to chemotherapy

    PubMed Central

    Hallett, Robin M.; Huang, Cheng; Motazedian, Ali; Auf der Mauer, Stefanie; Pond, Gregory R.; Hassell, John A.; Nordon, Robert E.; Draper, Jonathan S.

    2015-01-01

    Chemotherapy fails to provide durable cure for the majority of cancer patients. To identify mechanisms associated with chemotherapy resistance, we identified genes differentially expressed before and after chemotherapeutic treatment of breast cancer patients. Treatment response resulted in either increased or decreased cell cycle gene expression. Tumors in which cell cycle gene expression was increased by chemotherapy were likely to be chemotherapy sensitive, whereas tumors in which cell cycle gene transcripts were decreased by chemotherapy were resistant to these agents. A gene expression signature that predicted these changes proved to be a robust and novel index that predicted the response of patients with breast, ovarian, and colon tumors to chemotherapy. Investigations in tumor cell lines supported these findings, and linked treatment induced cell cycle changes with p53 signaling and G1/G0 arrest. Hence, chemotherapy resistance, which can be predicted based on dynamics in cell cycle gene expression, is associated with TP53 integrity. PMID:25749523

  17. Cell cycle gene expression networks discovered using systems biology: Significance in carcinogenesis.

    PubMed

    Scott, Robert E; Ghule, Prachi N; Stein, Janet L; Stein, Gary S

    2015-10-01

    The early stages of carcinogenesis are linked to defects in the cell cycle. A series of cell cycle checkpoints are involved in this process. The G1/S checkpoint that serves to integrate the control of cell proliferation and differentiation is linked to carcinogenesis and the mitotic spindle checkpoint is associated with the development of chromosomal instability. This paper presents the outcome of systems biology studies designed to evaluate if networks of covariate cell cycle gene transcripts exist in proliferative mammalian tissues including mice, rats, and humans. The GeneNetwork website that contains numerous gene expression datasets from different species, sexes, and tissues represents the foundational resource for these studies (www.genenetwork.org). In addition, WebGestalt, a gene ontology tool, facilitated the identification of expression networks of genes that co-vary with key cell cycle targets, especially Cdc20 and Plk1 (www.bioinfo.vanderbilt.edu/webgestalt). Cell cycle expression networks of such covariate mRNAs exist in multiple proliferative tissues including liver, lung, pituitary, adipose, and lymphoid tissues among others but not in brain or retina that have low proliferative potential. Sixty-three covariate cell cycle gene transcripts (mRNAs) compose the average cell cycle network with P = e(-13) to e(-36) . Cell cycle expression networks show species, sex and tissue variability, and they are enriched in mRNA transcripts associated with mitosis, many of which are associated with chromosomal instability. PMID:25808367

  18. The oncogene c-Myc coordinates regulation of metabolic networks to enable rapid cell cycle entry.

    PubMed

    Morrish, Fionnuala; Neretti, Nicola; Sedivy, John M; Hockenbery, David M

    2008-04-15

    The c-myc proto-oncogene is rapidly activated by serum and regulates genes involved in metabolism and cell cycle progression. This gene is thereby uniquely poised to coordinate both the metabolic and cell cycle regulatory events required for cell cycle entry. However, this function of Myc has not been evaluated. Using a rat fibroblast model of isogenic cell lines, myc(-/-), myc(+/-), myc(+/+) and myc(-/-) cells with an inducible c-myc transgene (mycER), we show that the Myc protein programs cells to utilize both oxidative phosphorylation and glycolysis to drive cell cycle progression. We demonstrate this coordinate regulation of metabolic networks is essential, as specific inhibitors of these pathways block Myc-induced proliferation. Metabolic events temporally correlated with cell cycle entry include increased oxygen consumption, mitochondrial function, pyruvate and lactate production, and ATP generation. Treatment of normal cells with inhibitors of oxidative phosphorylation recapitulates the myc(-/-) phenotype, resulting in impaired cell cycle entry and reduced metabolism. Combined with a kinetic expression profiling analysis of genes linked to mitochondrial function, our study indicates that Myc's ability to coordinately regulate the mitochondrial metabolic network transcriptome is required for rapid cell cycle entry. This function of Myc may underlie the pervasive presence of Myc in many human cancers.

  19. Vitisin A inhibits adipocyte differentiation through cell cycle arrest in 3T3-L1 cells

    SciTech Connect

    Kim, Soon-hee; Park, Hee-Sook; Lee, Myoung-su; Cho, Yong-Jin; Kim, Young-Sup; Hwang, Jin-Taek; Sung, Mi Jeong; Kim, Myung Sunny; Kwon, Dae Young

    2008-07-18

    Inhibition of adipocyte differentiation is one approach among the anti-obesity strategies. This study demonstrates that vitisin A, a resveratrol tetramer, inhibits adipocyte differentiation most effectively of 18 stilbenes tested. Fat accumulation and PPAR{gamma} expression were decreased by vitisin A in a dose-dependent manner. Vitisin A significantly inhibited preadipocyte proliferation and consequent differentiation within the first 2 days of treatment, indicating that the anti-adipogenic effect of vitisin A was derived from anti-proliferation. Based on cell cycle analysis, vitisin A blocked the cell cycle at the G1-S phase transition, causing cells to remain in the preadipocyte state. Vitisin A increased p21 expression, while the Rb phosphorylation level was reduced. Therefore, vitisin A seems to induce G1 arrest through p21- and consequent Rb-dependent suppression of transcription. On the other hand, ERK and Akt signaling pathways were not involved in the anti-mitotic regulation by vitisin A. Taken together, these results suggest that vitisin A inhibits adipocyte differentiation through preadipocyte cell cycle arrest.

  20. Effect of KOH concentration on LEO cycle life of IPV nickel-hydrogen flight battery cells

    NASA Technical Reports Server (NTRS)

    Smithrick, John J.; Hall, Stephen W.

    1990-01-01

    A breakthrough in low earth orbit (LEO) cycle life of individual pressure vessel (IPV) nickel hydrogen battery cells was reported. The cycle life of boiler plate cells containing 26 percent potassium hydroxide (KOH) electrolyte was about 40,000 LEO cycles compared to 3500 cycles for cells containing 31 percent KOH. The effect of KOH concentration on cycle life was studied. The cycle regime was a stressful accelerated LEO, which consisted of a 27.5 min charge followed by a 17.5 min charge (2 x normal rate). The depth of discharge (DOD) was 80 percent. The cell temperature was maintained at 23 C. The next step is to validate these results using flight hardware and a real time LEO test. NASA Lewis has a contract with the Naval Weapons Support Center (NWSC), Crane, Indiana, to validate the boiler plate test results. Six 48 A-hr Hughes recirculation design IPV nickel-hydrogen flight battery cells are being evaluated. Three of the cells contain 26 percent KOH (test cells) and three contain 31 percent KOH (control cells). They are undergoing real time LEO cycle life testing. The cycle regime is a 90-min LEO orbit consisting of a 54-min charge followed by a 36-min discharge. The depth-of-discharge is 80 percent. The cell temperature is maintained at 10 C. The cells were cycled for over 8000 cycles in the continuing test. There were no failures for the cells containing 26 percent KOH. There was two failures, however, for the cells containing 31 percent KOH.

  1. Effect of KOH concentration on LEO cycle life of IPV nickel-hydrogen flight battery cells

    NASA Technical Reports Server (NTRS)

    Smithrick, John J.; Hall, Stephen W.

    1990-01-01

    A breakthrough in the low-earth-orbit (LEO) cycle life of individual pressure vessel (IPV) nickel hydrogen battery cells is reported. The cycle life of boiler plate cells containing 26 percent potassium hydroxide (KOH) electrolyte was about 40,000 LEO cycles compared to 3500 cycles for cells containing 31 percent KOH. The effect of KOH concentration on cycle life was studied. The cycle regime was a stressful accelerated LEO, which consisted of a 27.5 min charge followed by a 17.5 min charge (2 x normal rate). The depth of discharge (DOD) was 80 percent. The cell temperature was maintained at 23 C. The next step is to validate these results using flight hardware and real time LEO test. NASA Lewis has a contract with the Naval Weapons Support Center (NWSC), Crane, Indiana to validate the boiler plate test results. Six 48 A-hr Hughes recirculation design IPV nickel-hydrogen flight battery cells are being evaluated. Three of the cells contain 26 percent KOH (test cells) and three contain 31 percent KOH (control cells). They are undergoing real time LEO cycle life testing. The cycle regime is a 90-min LEO orbit consisting of a 54-min charge followed by a 36-min discharge. The depth-of-discharge is 80 percent. The cell temperature is maintained at 10 C. The cells were cycled for over 8000 cycles in the continuing test. There were no failures for the cells containing 26 percent KOH. There were two failures, however, for the cells containing 31 percent KOH.

  2. Radioprotection and Cell Cycle Arrest of Intestinal Epithelial Cells by Darinaparsin, a Tumor Radiosensitizer

    SciTech Connect

    Tian, Junqiang; Doi, Hiroshi; Saar, Matthias; Santos, Jennifer; Li, Xuejun; Peehl, Donna M.; Knox, Susan J.

    2013-12-01

    Purpose: It was recently reported that the organic arsenic compound darinaparsin (DPS) is a cytotoxin and radiosensitizer of tumor cells in vitro and in subcutaneous xenograft tumors. Surprisingly, it was also found that DPS protects normal intestinal crypt epithelial cells (CECs) from clonogenic death after ionizing radiation (IR). Here we tested the DPS radiosensitizing effect in a clinically relevant model of prostate cancer and explored the radioprotective effect and mechanism of DPS on CECs. Methods and Materials: The radiation modification effect of DPS was tested in a mouse model of orthotopic xenograft prostate cancer and of IR-induced acute gastrointestinal syndrome. The effect of DPS on CEC DNA damage and DNA damage responses was determined by immunohistochemistry. Results: In the mouse model of IR-induced gastrointestinal syndrome, DPS treatment before IR accelerated recovery from body weight loss and increased animal survival. DPS decreased post-IR DNA damage and cell death, suggesting that the radioprotective effect was mediated by enhanced DNA damage repair. Shortly after DPS injection, significant cell cycle arrest was observed in CECs at both G1/S and G2/M checkpoints, which was accompanied by the activation of cell cycle inhibitors p21 and growth arrest and DNA-damage-inducible protein 45 alpha (GADD45A). Further investigation revealed that DPS activated ataxia telangiectasia mutated (ATM), an important inducer of DNA damage repair and cell cycle arrest. Conclusions: DPS selectively radioprotected normal intestinal CECs and sensitized prostate cancer cells in a clinically relevant model. This effect may be, at least in part, mediated by DNA damage response activation and has the potential to significantly increase the therapeutic index of radiation therapy.

  3. Knockdown of the Cell Cycle Inhibitor p21 Enhances Cartilage Formation by Induced Pluripotent Stem Cells

    PubMed Central

    Diekman, Brian O.; Thakore, Pratiksha I.; O'Connor, Shannon K.; Willard, Vincent P.; Brunger, Jonathan M.; Christoforou, Nicolas; Leong, Kam W.

    2015-01-01

    The limited regenerative capacity of articular cartilage contributes to progressive joint dysfunction associated with cartilage injury or osteoarthritis. Cartilage tissue engineering seeks to provide a biological substitute for repairing damaged or diseased cartilage, but requires a cell source with the capacity for extensive expansion without loss of chondrogenic potential. In this study, we hypothesized that decreased expression of the cell cycle inhibitor p21 would enhance the proliferative and chondrogenic potential of differentiated induced pluripotent stem cells (iPSCs). Murine iPSCs were directed to differentiate toward the chondrogenic lineage with an established protocol and then engineered to express a short hairpin RNA (shRNA) to reduce the expression of p21. Cells expressing the p21 shRNA demonstrated higher proliferative potential during monolayer expansion and increased synthesis of glycosaminoglycans (GAGs) in pellet cultures. Furthermore, these cells could be expanded ∼150-fold over three additional passages without a reduction in the subsequent production of GAGs, while control cells showed reduced potential for GAG synthesis with three additional passages. In pellets from extensively passaged cells, knockdown of p21 attenuated the sharp decrease in cell number that occurred in control cells, and immunohistochemical analysis showed that p21 knockdown limited the production of type I and type X collagen while maintaining synthesis of cartilage-specific type II collagen. These findings suggest that manipulating the cell cycle can augment the monolayer expansion and preserve the chondrogenic capacity of differentiated iPSCs, providing a strategy for enhancing iPSC-based cartilage tissue engineering. PMID:25517798

  4. Knockdown of the cell cycle inhibitor p21 enhances cartilage formation by induced pluripotent stem cells.

    PubMed

    Diekman, Brian O; Thakore, Pratiksha I; O'Connor, Shannon K; Willard, Vincent P; Brunger, Jonathan M; Christoforou, Nicolas; Leong, Kam W; Gersbach, Charles A; Guilak, Farshid

    2015-04-01

    The limited regenerative capacity of articular cartilage contributes to progressive joint dysfunction associated with cartilage injury or osteoarthritis. Cartilage tissue engineering seeks to provide a biological substitute for repairing damaged or diseased cartilage, but requires a cell source with the capacity for extensive expansion without loss of chondrogenic potential. In this study, we hypothesized that decreased expression of the cell cycle inhibitor p21 would enhance the proliferative and chondrogenic potential of differentiated induced pluripotent stem cells (iPSCs). Murine iPSCs were directed to differentiate toward the chondrogenic lineage with an established protocol and then engineered to express a short hairpin RNA (shRNA) to reduce the expression of p21. Cells expressing the p21 shRNA demonstrated higher proliferative potential during monolayer expansion and increased synthesis of glycosaminoglycans (GAGs) in pellet cultures. Furthermore, these cells could be expanded ∼150-fold over three additional passages without a reduction in the subsequent production of GAGs, while control cells showed reduced potential for GAG synthesis with three additional passages. In pellets from extensively passaged cells, knockdown of p21 attenuated the sharp decrease in cell number that occurred in control cells, and immunohistochemical analysis showed that p21 knockdown limited the production of type I and type X collagen while maintaining synthesis of cartilage-specific type II collagen. These findings suggest that manipulating the cell cycle can augment the monolayer expansion and preserve the chondrogenic capacity of differentiated iPSCs, providing a strategy for enhancing iPSC-based cartilage tissue engineering.

  5. Vincristine induces cell cycle arrest and apoptosis in SH-SY5Y human neuroblastoma cells.

    PubMed

    Tu, Yue; Cheng, Shixiang; Zhang, Sai; Sun, Hongtao; Xu, Zhongwei

    2013-01-01

    Neuroblastoma is a common childhood tumor. Vincristine (VCR), an alkaloid extracted from Catharanthus roseus, is commonly used in combination chemotherapy. However, the mechanisms of VCR-induced neuroblastoma cell death are not clear. The aim of this study was to investigate the impact of VCR on mitosis and apoptosis of SH-SY5Y neuroblastoma cells and the underlying mechanisms. SH-SY5Y cells were treated with increasing VCR doses for different time points. Cell proliferation was detected using the MTT assay. Mitotic rate was quantified by immunofluorescence. Cell cycle and apoptosis were analyzed by flow cytometry. The mRNA and protein expression of caspase-3 and -9 (apoptotic factors), as well as cyclin B and D (cell cycle factors), was evaluated by real-time (RT)-PCR and western blot analysis, respectively. VCR inhibited SH-SY5Y cell proliferation in a time- and dose-dependent manner (P<0.05). The IC50 of VCR in SH-SY5Y cells was determined as 0.1 µM. VCR at 0.1 µM induced mitotic arrest and apoptosis, promoted the expression of caspase-3 and -9 and cyclin B, while decreasing the expression of cyclin D at 6, 12, 18 and 24 h. Except for the mRNA expression of cyclin D at 6 h, these changes were significant at both the mRNA and protein levels (P<0.05). VCR induces mitotic arrest of SH-SY5Y cells by regulating cyclin B and D. It further induces apoptosis in these cells through the activation of caspase-3 and -9. This study provides fundamental evidence for the application of VCR in neuroblastoma chemotherapy.

  6. A role for novel cell-cycle proteins in podocyte biology.

    PubMed

    Price, Peter M

    2010-04-01

    Cell-cycle proteins influence almost all aspects of embryogenesis and differentiation. In adults, these proteins control cell division and regeneration after injury. During the past several years, their roles in controlling reaction to stress have been demonstrated in several organ systems. In the kidney, the cell types affected include both tubular and glomerular compartments. Now a novel cell cycle-related protein is shown to influence podocyte biology.

  7. Middle infrared radiation induces G2/M cell cycle arrest in A549 lung cancer cells.

    PubMed

    Chang, Hsin-Yi; Shih, Meng-Her; Huang, Hsuan-Cheng; Tsai, Shang-Ru; Juan, Hsueh-Fen; Lee, Si-Chen

    2013-01-01

    There were studies investigating the effects of broadband infrared radiation (IR) on cancer cell, while the influences of middle-infrared radiation (MIR) are still unknown. In this study, a MIR emitter with emission wavelength band in the 3-5 µm region was developed to irradiate A549 lung adenocarcinoma cells. It was found that MIR exposure inhibited cell proliferation and induced morphological changes by altering the cellular distribution of cytoskeletal components. Using quantitative PCR, we found that MIR promoted the expression levels of ATM (ataxia telangiectasia mutated), ATR (ataxia-telangiectasia and Rad3-related and Rad3-related), TP53 (tumor protein p53), p21 (CDKN1A, cyclin-dependent kinase inhibitor 1A) and GADD45 (growth arrest and DNA-damage inducible), but decreased the expression levels of cyclin B coding genes, CCNB1 and CCNB2, as well as CDK1 (Cyclin-dependent kinase 1). The reduction of protein expression levels of CDC25C, cyclin B1 and the phosphorylation of CDK1 at Thr-161 altogether suggest G(2)/M arrest occurred in A549 cells by MIR. DNA repair foci formation of DNA double-strand breaks (DSB) marker γ-H2AX and sensor 53BP1 was induced by MIR treatment, it implies the MIR induced G(2)/M cell cycle arrest resulted from DSB. This study illustrates a potential role for the use of MIR in lung cancer therapy by initiating DSB and blocking cell cycle progression.

  8. Evaluation of rapid cell division in non-uniform cell cycles.

    PubMed

    Lee, Juyun; Jeon, Wonju; Chang, Man; Han, Myung-Soo

    2015-10-01

    To better understand the mechanisms of development of harmful algal blooms (HABs), accurate estimates of species-specific in situ growth rates are needed. HABs are caused by rapid cell division by the causative microorganisms. To accurately estimate the in situ growth rates of harmful algae having non-uniform and/or irregular cell cycles, we modified a standard equation based on the cell cycle, and calculated the in situ growth rate to describe the process of bloom development in nature. Sampling of a developing bloom of Heterosigma akashiwo in Pohang Bay, Korea, was conducted every 3 h from 15:00 on August 2 to 07:00 on August 4, 2006. The amount of H. akashiwo DNA was measured using flow cytometry following tyramide signal amplification-fluorescence in situ hybridization. On August 2, the percentage of G1 phase cells decreased from 15:00 to 19:00 then increased until 22:00; it then decreased until 07:00 on August 3, followed by an increase to 10:00. This indicates the ability of the cells in nature to undergo more than one round of division per day. During the following night two rounds of division did not occur. The in situ growth rates estimated using the modified equation ranged from 0.31 to 0.53 d(-1) . We conclude that the use of this equation enables more accurate estimates of bloom formation by rapidly dividing cells.

  9. TRAP1 regulates cell cycle and apoptosis in thyroid carcinoma cells.

    PubMed

    Palladino, Giuseppe; Notarangelo, Tiziana; Pannone, Giuseppe; Piscazzi, Annamaria; Lamacchia, Olga; Sisinni, Lorenza; Spagnoletti, Girolamo; Toti, Paolo; Santoro, Angela; Storto, Giovanni; Bufo, Pantaleo; Cignarelli, Mauro; Esposito, Franca; Landriscina, Matteo

    2016-09-01

    Tumor necrosis factor receptor-associated protein 1 (TRAP1) is a heat shock protein 90 (HSP90) molecular chaperone upregulated in several human malignancies and involved in protection from apoptosis and drug resistance, cell cycle progression, cell metabolism and quality control of specific client proteins. TRAP1 role in thyroid carcinoma (TC), still unaddressed at present, was investigated by analyzing its expression in a cohort of 86 human TCs and evaluating its involvement in cancer cell survival and proliferation in vitro Indeed, TRAP1 levels progressively increased from normal peritumoral thyroid gland, to papillary TCs (PTCs), follicular variants of PTCs (FV-PTCs) and poorly differentiated TCs (PDTCs). By contrast, anaplastic thyroid tumors exhibited a dual pattern, the majority being characterized by high TRAP1 levels, while a small subgroup completely negative. Consistently with a potential involvement of TRAP1 in thyroid carcinogenesis, TRAP1 silencing resulted in increased sensitivity to paclitaxel-induced apoptosis, inhibition of cell cycle progression and attenuation of ERK signaling. Noteworthy, the inhibition of TRAP1 ATPase activity by pharmacological agents resulted in attenuation of cell proliferation, inhibition of ERK signaling and reversion of drug resistance. These data suggest that TRAP1 inhibition may be regarded as potential strategy to target specific features of human TCs, i.e., cell proliferation and resistance to apoptosis. PMID:27422900

  10. Circadian Clock Genes Modulate Human Bone Marrow Mesenchymal Stem Cell Differentiation, Migration and Cell Cycle

    PubMed Central

    Boucher, Helene; Vanneaux, Valerie; Domet, Thomas; Parouchev, Alexandre; Larghero, Jerome

    2016-01-01

    Many of the components that regulate the circadian clock have been identified in organisms and humans. The influence of circadian rhythm (CR) on the regulation of stem cells biology began to be evaluated. However, little is known on the role of CR on human mesenchymal stem cell (hMSCs) properties. The objective of this study was to investigate the influence of CR on the differentiation capacities of bone marrow hMSCs, as well as the regulation of cell cycle and migration capabilities. To that, we used both a chemical approach with a GSK-3β specific inhibitor (2’E,3’Z-6-bromoindirubin-3’-oxime, BIO) and a knockdown of CLOCK and PER2, two of the main genes involved in CR regulation. In these experimental conditions, a dramatic inhibition of adipocyte differentiation was observed, while osteoblastic differentiation capacities were not modified. In addition, cell migration was decreased in PER2-/- cells. Lastly, downregulation of circadian clock genes induced a modification of the hMSCs cell cycle phase distribution, which was shown to be related to a change of the cyclin expression profile. Taken together, these data showed that CR plays a role in the regulation of hMSCs differentiation and division, and likely represent key factor in maintaining hMSCs properties. PMID:26741371

  11. Estrogen inhibits cell cycle progression and retinoblastoma phosphorylation in rhesus ovarian surface epithelial cell culture

    SciTech Connect

    Wright, Jay W.; Stouffer, Richard L.; Rodland, Karin D.

    2003-10-31

    Estrogen promotes the growth of some ovarian cancer cells at nanomolar concentrations, but has been shown to inhibit growth of normal ovarian surface epithelial (OSE) cells at micromolar concentrations (1μg/ml). OSE cells express the estrogen receptor (ER)-α, and are the source of 90% of various cancers. The potential sensitivity of OSE cells to estrogen stresses the importance of understanding the estrogen-dependent mechanisms at play in OSE proliferation and transformation, as well as in anticancer treatment. We investigated the effects of estradiol on cell proliferation in vitro, and demonstrate an intracellular locus of action of estradiol in cultured rhesus ovarian surface epithelial (RhOSE) cells. We show that ovarian and breast cells are growth-inhibited by micromolar concentration of estradiol and that this inhibition correlates with estrogen receptor expression. We further show that normal rhesus OSE cells do not activate ERK or Akt in response to estradiol nor does estradiol block the ability of serum to stimulate ERK or induce cyclin D expression. Contrarily, estradiol inhibits serum-dependent retinoblastoma protein (Rb) phosphorylation and blocks DNA synthesis. This inhibition does not formally arrest cells and is reversible within hours of estrogen withdrawal. Our data are consistent with growth inhibition by activation of Rb and indicate that sensitivity to hormone therapy in anticancer treatment can be modulated by cell cycle regulators downstream of the estrogen receptor.

  12. NAC, Tiron and Trolox Impair Survival of Cell Cultures Containing Glioblastoma Tumorigenic Initiating Cells by Inhibition of Cell Cycle Progression

    PubMed Central

    Stigliani, Sara; Carra, Elisa; Monteghirfo, Stefano; Longo, Luca; Daga, Antonio; Dono, Mariella; Zupo, Simona; Giaretti, Walter; Castagnola, Patrizio

    2014-01-01

    Reactive oxygen species (ROS) are metabolism by-products that may act as signaling molecules to sustain tumor growth. Antioxidants have been used to impair cancer cell survival. Our goal was to determine the mechanisms involved in the response to antioxidants of a human cell culture (PT4) containing glioblastoma (GBM) tumorigenic initiating cells (TICs). ROS production in the absence or presence of N-acetyl-L-cysteine (NAC), tiron, and trolox was evaluated by flow cytometry (FCM). The effects of these antioxidants on cell survival and apoptosis were evaluated by 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay (MTT) and FCM. The biological processes modulated by these drugs were determined by oligonucleotide microarray gene expression profiling. Our results showed that NAC, tiron and trolox impaired PT4 cell survival, had minor effects on ROS levels and caused wide deregulation of cell cycle genes. Furthermore, tiron and trolox caused inhibition of cell survival in two additional cell cultures containing TICs, FO-1 and MM1, established from a melanoma and a mesothelioma patient, respectively. NAC, instead, impaired survival of the MM1 cells but not of the FO-1 cells. However, when used in combination, NAC enhanced the inhibitory effect of PLX4032 (BRAF V600E inhibitor) and Gefitinib (EGFR inhibitor), on FO-1 and PT4 cell survival. Collectively, NAC, tiron and trolox modulated gene expression and impaired the growth of cultures containing TICs primarily by inhibiting cell cycle progression. PMID:24587218

  13. Flexural rigidity of microtubules and actin filaments measured from thermal fluctuations in shape

    PubMed Central

    1993-01-01

    Microtubules are long, proteinaceous filaments that perform structural functions in eukaryotic cells by defining cellular shape and serving as tracks for intracellular motor proteins. We report the first accurate measurements of the flexural rigidity of microtubules. By analyzing the thermally driven fluctuations in their shape, we estimated the mean flexural rigidity of taxol-stabilized microtubules to be 2.2 x 10(-23) Nm2 (with 6.4% uncertainty) for seven unlabeled microtubules and 2.1 x 10(-23) Nm2 (with 4.7% uncertainty) for eight rhodamine-labeled microtubules. These values are similar to earlier, less precise estimates of microtubule bending stiffness obtained by modeling flagellar motion. A similar analysis on seven rhodamine-phalloidin- labeled actin filaments gave a flexural rigidity of 7.3 x 10(-26) Nm2 (with 6% uncertainty), consistent with previously reported results. The flexural rigidity of these microtubules corresponds to a persistence length of 5,200 microns showing that a microtubule is rigid over cellular dimensions. By contrast, the persistence length of an actin filament is only approximately 17.7 microns, perhaps explaining why actin filaments within cells are usually cross-linked into bundles. The greater flexural rigidity of a microtubule compared to an actin filament mainly derives from the former's larger cross-section. If tubulin were homogeneous and isotropic, then the microtubule's Young's modulus would be approximately 1.2 GPa, similar to Plexiglas and rigid plastics. Microtubules are expected to be almost inextensible: the compliance of cells is due primarily to filament bending or sliding between filaments rather than the stretching of the filaments themselves. PMID:8432732

  14. An extensive program of periodic alternative splicing linked to cell cycle progression

    PubMed Central

    Dominguez, Daniel; Tsai, Yi-Hsuan; Weatheritt, Robert; Wang, Yang; Blencowe, Benjamin J; Wang, Zefeng

    2016-01-01

    Progression through the mitotic cell cycle requires periodic regulation of gene function at the levels of transcription, translation, protein-protein interactions, post-translational modification and degradation. However, the role of alternative splicing (AS) in the temporal control of cell cycle is not well understood. By sequencing the human transcriptome through two continuous cell cycles, we identify ~1300 genes with cell cycle-dependent AS changes. These genes are significantly enriched in functions linked to cell cycle control, yet they do not significantly overlap genes subject to periodic changes in steady-state transcript levels. Many of the periodically spliced genes are controlled by the SR protein kinase CLK1, whose level undergoes cell cycle-dependent fluctuations via an auto-inhibitory circuit. Disruption of CLK1 causes pleiotropic cell cycle defects and loss of proliferation, whereas CLK1 over-expression is associated with various cancers. These results thus reveal a large program of CLK1-regulated periodic AS intimately associated with cell cycle control. DOI: http://dx.doi.org/10.7554/eLife.10288.001 PMID:27015110

  15. Overexpression of Cell Cycle Proteins of Peripheral Lymphocytes in Patients with Alzheimer's Disease

    PubMed Central

    Kim, Hyeran; Kwon, Young-Ah; Ahn, Inn Sook; Kim, Sangha; Kim, Seonwoo; Jo, Sangmee Ahn

    2016-01-01

    Objective Biological markers for Alzheimer's disease (AD) will help clinicians make objective diagnoses early during the course of dementia. Previous studies have suggested that cell cycle dysregulation begins earlier than the onset of clinical manifestations in AD. Methods We examined the lymphocyte expression of cell cycle proteins in AD patients, dementia controls (DC), and normal controls (NC). One-hundred seventeen subjects (36 AD, 31 DC, and 50 NC) were recruited. The cell cycle proteins CDK2, CDK4, CDK6, cyclin B, and cyclin D were measured in peripheral lymphocytes. Cell cycle protein expression in the three groups was compared after adjusting for age and sex. Results The levels of cell cycle proteins CDK2, CDK4, CDK6, cyclin B, and cyclin D were significantly higher in AD patients than in the NC subjects. The DC group manifested intermediate levels of cell cycle proteins compared with the AD patients and the NC subjects. The present study indicates that cell cycle proteins are upregulated in the peripheral lymphocytes of AD patients. Conclusion Cell cycle dysregulation in peripheral lymphocytes may present a promising starting point for identifying peripheral biomarkers of AD. PMID:26766955

  16. Regulation of Neuronal Cell Cycle and Apoptosis by MicroRNA 34a

    PubMed Central

    Modi, Prashant Kumar; Jaiswal, Surbhi

    2015-01-01

    The cell cycle of neurons remains suppressed to maintain the state of differentiation and aberrant cell cycle reentry results in loss of neurons, which is a feature in neurodegenerative disorders like Alzheimer's disease (AD). Present studies revealed that the expression of microRNA 34a (miR-34a) needs to be optimal in neurons, as an aberrant increase or decrease in its expression causes apoptosis. miR-34a keeps the neuronal cell cycle under check by preventing the expression of cyclin D1 and promotes cell cycle arrest. Neurotoxic amyloid β1–42 peptide (Aβ42) treatment of cortical neurons suppressed miR-34a, resulting in unscheduled cell cycle reentry, which resulted in apoptosis. The repression of miR-34a was a result of degradation of TAp73, which was mediated by aberrant activation of the MEK extracellular signal-regulated kinase (ERK) pathway by Aβ42. A significant decrease in miR-34a and TAp73 was observed in the cortex of a transgenic (Tg) mouse model of AD, which correlated well with cell cycle reentry observed in the neurons of these animals. Importantly, the overexpression of TAp73α and miR-34a reversed cell cycle-related neuronal apoptosis (CRNA). These studies provide novel insights into how modulation of neuronal cell cycle machinery may lead to neurodegeneration and may contribute to the understanding of disorders like AD. PMID:26459758

  17. RPS27a promotes proliferation, regulates cell cycle progression and inhibits apoptosis of leukemia cells

    SciTech Connect

    Wang, Houcai; Yu, Jing; Zhang, Lixia; Xiong, Yuanyuan; Chen, Shuying; Xing, Haiyan; Tian, Zheng; Tang, Kejing; Wei, Hui; Rao, Qing; Wang, Min; Wang, Jianxiang

    2014-04-18

    Highlights: • RPS27a expression was up-regulated in advanced-phase CML and AL patients. • RPS27a knockdown changed biological property of K562 and K562/G01 cells. • RPS27a knockdown affected Raf/MEK/ERK, P21 and BCL-2 signaling pathways. • RPS27a knockdown may be applicable for new combination therapy in CML patients. - Abstract: Ribosomal protein S27a (RPS27a) could perform extra-ribosomal functions besides imparting a role in ribosome biogenesis and post-translational modifications of proteins. The high expression level of RPS27a was reported in solid tumors, and we found that the expression level of RPS27a was up-regulated in advanced-phase chronic myeloid leukemia (CML) and acute leukemia (AL) patients. In this study, we explored the function of RPS27a in leukemia cells by using CML cell line K562 cells and its imatinib resistant cell line K562/G01 cells. It was observed that the expression level of RPS27a was high in K562 cells and even higher in K562/G01 cells. Further analysis revealed that RPS27a knockdown by shRNA in both K562 and K562G01 cells inhibited the cell viability, induced cell cycle arrest at S and G2/M phases and increased cell apoptosis induced by imatinib. Combination of shRNA with imatinib treatment could lead to more cleaved PARP and cleaved caspase-3 expression in RPS27a knockdown cells. Further, it was found that phospho-ERK(p-ERK) and BCL-2 were down-regulated and P21 up-regulated in RPS27a knockdown cells. In conclusion, RPS27a promotes proliferation, regulates cell cycle progression and inhibits apoptosis of leukemia cells. It appears that drugs targeting RPS27a combining with tyrosine kinase inhibitor (TKI) might represent a novel therapy strategy in TKI resistant CML patients.

  18. Targeting of cytosolic phospholipase A2α impedes cell cycle re-entry of quiescent prostate cancer cells

    PubMed Central

    Yao, Mu; Xie, Chanlu; Kiang, Mei-Yee; Teng, Ying; Harman, David; Tiffen, Jessamy; Wang, Qian; Sved, Paul; Bao, Shisan; Witting, Paul; Holst, Jeff; Dong, Qihan

    2015-01-01

    Cell cycle re-entry of quiescent cancer cells has been proposed to be involved in cancer progression and recurrence. Cytosolic phospholipase A2α (cPLA2α) is an enzyme that hydrolyzes membrane glycerophospholipids to release arachidonic acid and lysophospholipids that are implicated in cancer cell proliferation. The aim of this study was to determine the role of cPLA2α in cell cycle re-entry of quiescent prostate cancer cells. When PC-3 and LNCaP cells were rendered to a quiescent state, the active form of cPLA2α with a phosphorylation at Ser505 was lower compared to their proliferating state. Conversely, the phospho-cPLA2α levels were resurgent during the induction of cell cycle re-entry. Pharmacological inhibition of cPLA2α with Efipladib upon induction of cell cycle re-entry inhibited the re-entry process, as manifested by refrained DNA synthesis, persistent high proportion of cells in G0/G1 and low percentage of cells in S and G2/M phases, together with a stagnant recovery of Ki-67 expression. Simultaneously, Efipladib prohibited the emergence of Skp2 while maintained p27 at a high level in the nuclear compartment during cell cycle re-entry. Inhibition of cPLA2α also prevented an accumulation of cyclin D1/CDK4, cyclin E/CDK2, phospho-pRb, pre-replicative complex proteins CDC6, MCM7, ORC6 and DNA synthesis-related protein PCNA during induction of cell cycle re-entry. Moreover, a pre-treatment of the prostate cancer cells with Efipladib during induction of cell cycle re-entry subsequently compromised their tumorigenic capacity in vivo. Hence, cPLA2α plays an important role in cell cycle re-entry by quiescent prostate cancer cells. PMID:26416244

  19. The human papillomavirus type 58 E7 oncoprotein modulates cell cycle regulatory proteins and abrogates cell cycle checkpoints

    SciTech Connect

    Zhang Weifang; Li Jing; Kanginakudru, Sriramana; Zhao Weiming; Yu Xiuping; Chen, Jason J.

    2010-02-05

    HPV type 58 (HPV-58) is the third most common HPV type in cervical cancer from Eastern Asia, yet little is known about how it promotes carcinogenesis. In this study, we demonstrate that HPV-58 E7 significantly promoted the proliferation and extended the lifespan of primary human keratinocytes (PHKs). HPV-58 E7 abrogated the G1 and the postmitotic checkpoints, although less efficiently than HPV-16 E7. Consistent with these observations, HPV-58 E7 down-regulated the cellular tumor suppressor pRb to a lesser extent than HPV-16 E7. Similar to HPV-16 E7 expressing PHKs, Cdk2 remained active in HPV-58 E7 expressing PHKs despite the presence of elevated levels of p53 and p21. Interestingly, HPV-58 E7 down-regulated p130 more efficiently than HPV-16 E7. Our study demonstrates a correlation between the ability of down-regulating pRb/p130 and abrogating cell cycle checkpoints by HPV-58 E7, which also correlates with the biological risks of cervical cancer progression associated with HPV-58 infection.

  20. Cell Inquiry: A 5E Learning Cycle Lesson

    ERIC Educational Resources Information Center

    Wilder, Melinda; Shuttleworth, Phyllis

    2004-01-01

    One dilemma science teachers face every day is balancing the content demands of state and federal testing requirements while providing opportunities for inquiry. Using the 5E learning cycle is a realistic, constructivist way to address this dilemma. The 5E learning cycle leads students through a sequence of learning in which they become engaged in…

  1. Cell Inquiry: A 5E Learning Cycle Lesson

    ERIC Educational Resources Information Center

    Wilder, Melinda; Shuttleworth, Phyllis

    2005-01-01

    One dilemma science teachers face every day is balancing the content demands of state and federal testing requirements while providing opportunities for inquiry. Using the 5E learning cycle is a realistic, constructivist way to address this dilemma. The 5E learning cycle leads students through a sequence of learning in which they become engaged in…

  2. Effect of KOH concentration on LEO cycle life of IPV nickel-hydrogen flight cells. An update

    NASA Technical Reports Server (NTRS)

    Smithrick, John J.; Hall, Stephen W.

    1991-01-01

    An update of validation test results confirming the breakthrough in LEO cycle life of nickel-hydrogen cells containing 26 percent potassium hydroxide (KOH) electrolyte is presented. A breakthrough in the LEO cycle life of individual pressure vessel nickel-hydrogen cells is reported. The cycle life of boiler plate cells containing 26 percent KOH electrolyte was about 40,000 LEO cycles compared to 3500 cycles for cells containing 31 percent KOH.

  3. Longitudinal tracking of single live cancer cells to understand cell cycle effects of the nuclear export inhibitor, selinexor

    PubMed Central

    Marcus, Joshua M.; Burke, Russell T.; DeSisto, John A.; Landesman, Yosef; Orth, James D.

    2015-01-01

    Longitudinal tracking is a powerful approach to understand the biology of single cells. In cancer therapy, outcome is determined at the molecular and cellular scale, yet relationships between cellular response and cell fate are often unknown. The selective inhibitor of nuclear export, selinexor, is in development for the treatment of various cancers. Selinexor covalently binds exportin-1, causing nuclear sequestration of cargo proteins, including key regulators of the cell cycle and apoptosis. The cell cycle effects of selinexor and the relationships between cell cycle effects and cell fates, has not been described for individual cells. Using fluorescent cell cycle indicators we report the majority of cell death after selinexor treatment occurs from a protracted G1-phase and early S-phase. G1- or early S-phase treated cells show the strongest response and either die or arrest, while those treated in late S- or G2-phase progress to mitosis and divide. Importantly, the progeny of cell divisions also die or arrest, mostly in the next G1-phase. Cells that survive selinexor are negative for multiple proliferation biomarkers, indicating a penetrant, arrested state. Selinexor acts quickly, shows strong cell cycle selectivity, and is highly effective at arresting cell growth and inducing death in cancer-derived cells. PMID:26399741

  4. SON controls cell-cycle progression by coordinated regulation of RNA splicing.

    PubMed

    Ahn, Eun-Young; DeKelver, Russell C; Lo, Miao-Chia; Nguyen, Tuyet Ann; Matsuura, Shinobu; Boyapati, Anita; Pandit, Shatakshi; Fu, Xiang-Dong; Zhang, Dong-Er

    2011-04-22

    It has been suspected that cell-cycle progression might be functionally coupled with RNA processing. However, little is known about the role of the precise splicing control in cell-cycle progression. Here, we report that SON, a large Ser/Arg (SR)-related protein, is a splicing cofactor contributing to efficient splicing of cell-cycle regulators. Downregulation of SON leads to severe impairment of spindle pole separation, microtubule dynamics, and genome integrity. These molecular defects result from inadequate RNA splicing of a specific set of cell-cycle-related genes that possess weak splice sites. Furthermore, we show that SON facilitates the interaction of SR proteins with RNA polymerase II and other key spliceosome components, suggesting its function in efficient cotranscriptional RNA processing. These results reveal a mechanism for controlling cell-cycle progression through SON-dependent constitutive splicing at suboptimal splice sites, with strong implications for its role in cancer and other human diseases.

  5. Punctuated evolution and transitional hybrid network in an ancestral cell cycle of fungi.

    PubMed

    Medina, Edgar M; Turner, Jonathan J; Gordân, Raluca; Skotheim, Jan M; Buchler, Nicolas E

    2016-01-01

    Although cell cycle control is an ancient, conserved, and essential process, some core animal and fungal cell cycle regulators share no more sequence identity than non-homologous proteins. Here, we show that evolution along the fungal lineage was punctuated by the early acquisition and entrainment of the SBF transcription factor through horizontal gene transfer. Cell cycle evolution in the fungal ancestor then proceeded through a hybrid network containing both SBF and its ancestral animal counterpart E2F, which is still maintained in many basal fungi. We hypothesize that a virally-derived SBF may have initially hijacked cell cycle control by activating transcription via the cis-regulatory elements targeted by the ancestral cell cycle regulator E2F, much like extant viral oncogenes. Consistent with this hypothesis, we show that SBF can regulate promoters with E2F binding sites in budding yeast. PMID:27162172

  6. Feedback loops and reciprocal regulation: recurring motifs in the systems biology of the cell cycle

    PubMed Central

    Ferrell, James E.

    2013-01-01

    The study of eukaryotic cell cycle regulation over the last several decades has led to a remarkably detailed understanding of the complex regulatory system that drives this fundamental process. This allows us to now look for recurring motifs in the regulatory system. Among these are negative feedback loops, which underpin checkpoints and generate cell cycle oscillations; positive feedback loops, which promote oscillations and make cell cycle transitions switch-like and unidirectional; and reciprocal regulation, which can increase the control a key regulator exerts. These simple motifs are found at multiple points in the cell cycle (e.g., S-phase and M-phase control) and are conserved in diverse organisms. These findings argue for an underlying unity in the principles of cell cycle control. PMID:23927869

  7. Punctuated evolution and transitional hybrid network in an ancestral cell cycle of fungi

    PubMed Central

    Medina, Edgar M; Turner, Jonathan J; Gordân, Raluca; Skotheim, Jan M; Buchler, Nicolas E

    2016-01-01

    Although cell cycle control is an ancient, conserved, and essential process, some core animal and fungal cell cycle regulators share no more sequence identity than non-homologous proteins. Here, we show that evolution along the fungal lineage was punctuated by the early acquisition and entrainment of the SBF transcription factor through horizontal gene transfer. Cell cycle evolution in the fungal ancestor then proceeded through a hybrid network containing both SBF and its ancestral animal counterpart E2F, which is still maintained in many basal fungi. We hypothesize that a virally-derived SBF may have initially hijacked cell cycle control by activating transcription via the cis-regulatory elements targeted by the ancestral cell cycle regulator E2F, much like extant viral oncogenes. Consistent with this hypothesis, we show that SBF can regulate promoters with E2F binding sites in budding yeast. DOI: http://dx.doi.org/10.7554/eLife.09492.001 PMID:27162172

  8. Activation of the methylation cycle in cells reprogrammed into a stem cell-like state

    PubMed Central

    Bosch-Barrera, Joaquim; Alarcón, Tomás; Joven, Jorge; Menendez, Javier A.

    2015-01-01

    Generation of induced pluripotent stem (iPS) cells and cancer biogenesis share similar metabolic switches. Most studies have focused on how the establishment of a cancer-like glycolytic phenotype is necessary for the optimal routing of somatic cells for achieving stemness. However, relatively little effort has been dedicated towards elucidating how one-carbon (1C) metabolism is retuned during acquisition of stem cell identity. Here we used ultra-high pressure liquid chromatography coupled to an electrospray ionization source and a triple-quadrupole mass spectrometer [UHPLC-ESI-QqQ-MS/MS] to quantitatively examine the methionine/folate bi-cyclic 1C metabolome during nuclear reprogramming of somatic cells into iPS cells. iPS cells optimize the synthesis of the universal methyl donor S-adenosylmethionine (SAM), apparently augment the ability of the redox balance regulator NADPH in SAM biosynthesis, and greatly increase their methylation potential by triggering a high SAM:S-adenosylhomocysteine (SAH) ratio. Activation of the methylation cycle in iPS cells efficiently prevents the elevation of homocysteine (Hcy), which could alter global DNA methylation and induce mitochondrial toxicity, oxidative stress and inflammation. In this regard, the methyl donor choline is also strikingly accumulated in iPS cells, suggesting perhaps an overactive intersection of the de novo synthesis of choline with the methionine-Hcy cycle. Activation of methylogenesis and maintenance of an optimal SAM:Hcy ratio might represent an essential function of 1C metabolism to provide a labile pool of methyl groups and NADPH-dependent redox products required for successfully establishing and maintaining an embryonic-like DNA methylation imprint in stem cell states. PMID:26909364

  9. Transcriptional modulator ZBED6 affects cell cycle and growth of human colorectal cancer cells.

    PubMed

    Akhtar Ali, Muhammad; Younis, Shady; Wallerman, Ola; Gupta, Rajesh; Andersson, Leif; Sjöblom, Tobias

    2015-06-23

    The transcription factor ZBED6 (zinc finger, BED-type containing 6) is a repressor of IGF2 whose action impacts development, cell proliferation, and growth in placental mammals. In human colorectal cancers, IGF2 overexpression is mutually exclusive with somatic mutations in PI3K signaling components, providing genetic evidence for a role in the PI3K pathway. To understand the role of ZBED6 in tumorigenesis, we engineered and validated somatic cell ZBED6 knock-outs in the human colorectal cancer cell lines RKO and HCT116. Ablation of ZBED6 affected the cell cycle and led to increased growth rate in RKO cells but reduced growth in HCT116 cells. This striking difference was reflected in the transcriptome analyses, which revealed enrichment of cell-cycle-related processes among differentially expressed genes in both cell lines, but the direction of change often differed between the cell lines. ChIP sequencing analyses displayed enrichment of ZBED6 binding at genes up-regulated in ZBED6-knockout clones, consistent with the view that ZBED6 modulates gene expression primarily by repressing transcription. Ten differentially expressed genes were identified as putative direct gene targets, and their down-regulation by ZBED6 was validated experimentally. Eight of these genes were linked to the Wnt, Hippo, TGF-β, EGF receptor, or PI3K pathways, all involved in colorectal cancer development. The results of this study show that the effect of ZBED6 on tumor development depends on the genetic background and the transcriptional state of its target genes.

  10. Monitoring cell-cycle-related viscoelasticity by a quartz crystal microbalance

    NASA Astrophysics Data System (ADS)

    Alessandrini, A.; Croce, M. A.; Tiozzo, R.; Facci, P.

    2006-02-01

    We have monitored viscoelasticity variation of a cell population during the cell cycle by a Quartz Crystal Microbalance (QCM). Balb 3T3 fibroblasts were synchronized in the G0/G1 phase and seeded in a QCM chamber placed in a cell incubator. After cell sedimentation, the frequency signal was characterized by an amplitude modulation attributed to the viscoelasticity variation of the cells proliferating in phase. A control experiment with nonsynchronized cells showed a similar signal trend, but without significant modulation. Interestingly, the system resulted also to perform as a device sensitive to the effect of drugs affecting the cell cycle, such as colchicine.

  11. Furrow microtubules and localized exocytosis in cleaving Xenopus laevis embryos

    NASA Technical Reports Server (NTRS)

    Danilchik, Michael V.; Bedrick, Steven D.; Brown, Elizabeth E.; Ray, Kimberly

    2003-01-01

    microtubules near the surface is sufficient to mobilize them for exocytosis at the end of the cell cycle.

  12. Tumorigenicity of hypoxic respiring cancer cells revealed by a hypoxia–cell cycle dual reporter

    PubMed Central

    Le, Anne; Stine, Zachary E.; Nguyen, Christopher; Afzal, Junaid; Sun, Peng; Hamaker, Max; Siegel, Nicholas M.; Gouw, Arvin M.; Kang, Byung-hak; Yu, Shu-Han; Cochran, Rory L.; Sailor, Kurt A.; Song, Hongjun; Dang, Chi V.

    2014-01-01

    Although aerobic glycolysis provides an advantage in the hypoxic tumor microenvironment, some cancer cells can also respire via oxidative phosphorylation. These respiring (“non-Warburg”) cells were previously thought not to play a key role in tumorigenesis and thus fell from favor in the literature. We sought to determine whether subpopulations of hypoxic cancer cells have different metabolic phenotypes and gene-expression profiles that could influence tumorigenicity and therapeutic response, and we therefore developed a dual fluorescent protein reporter, HypoxCR, that detects hypoxic [hypoxia-inducible factor (HIF) active] and/or cycling cells. Using HEK293T cells as a model, we identified four distinct hypoxic cell populations by flow cytometry. The non-HIF/noncycling cell population expressed a unique set of genes involved in mitochondrial function. Relative to the other subpopulations, these hypoxic “non-Warburg” cells had highest oxygen consumption rates and mitochondrial capacity consistent with increased mitochondrial respiration. We found that these respiring cells were unexpectedly tumorigenic, suggesting that continued respiration under limiting oxygen conditions may be required for tumorigenicity. PMID:25114222

  13. Cell-cycle distribution of urothelial tumour cells as measured by flow cytometry.

    PubMed Central

    Collste, L. G.; Darzynkiewicz, Z.; Traganos, F.; Sharpless, T. K.; Devonec, M.; Claps, M. L.; Whitmore, W. F.; Melamed, M. R.

    1979-01-01

    The fraction of cells in S + G2 + mitosis from 54 urothelial tumours was calculated by flow cytometry after acridine orange (AO) staining of cells obtained by bladder irrigation or biopsy. Fluorescence signals emitted by the AO-stained DNA and RNA of each cell were separated optically and measured for 5,000 cells per specimen. The patients were classified by the histology of their tumours and clinical data into 5 diagnostic categories: NED (no evidence of disease, but history of bladder tumour), 3; papilloma, 8; non-invasive papillary carcinoma, 8; carcinoma in situ, 17 and invasive carcinoma, 18. The fraction of cells with DNA values in S + G2 + M of the cell cycle varied between 7 and 57% of the total, with a wide range within each diagnostic category, but no statistically significant differences between the groups. The proportion of cells in S + G2 + M from an individual tumour was not correlated with histologic grade or clinical behaviour. The possibility that some tumour cells with DNA values above G1 level are quiescent cells arrested at S or G2 is discussed. PMID:526428

  14. Intermittent Stem Cell Cycling Balances Self-Renewal and Senescence of the C. elegans Germ Line.

    PubMed

    Cinquin, Amanda; Chiang, Michael; Paz, Adrian; Hallman, Sam; Yuan, Oliver; Vysniauskaite, Indre; Fowlkes, Charless C; Cinquin, Olivier

    2016-04-01

    Self-renewing organs often experience a decline in function in the course of aging. It is unclear whether chronological age or external factors control this decline, or whether it is driven by stem cell self-renewal-for example, because cycling cells exhaust their replicative capacity and become senescent. Here we assay the relationship between stem cell cycling and senescence in the Caenorhabditis elegans reproductive system, defining this senescence as the progressive decline in "reproductive capacity," i.e. in the number of progeny that can be produced until cessation of reproduction. We show that stem cell cycling diminishes remaining reproductive capacity, at least in part through the DNA damage response. Paradoxically, gonads kept under conditions that preclude reproduction keep cycling and producing cells that undergo apoptosis or are laid as unfertilized gametes, thus squandering reproductive capacity. We show that continued activity is in fact beneficial inasmuch as gonads that are active when reproduction is initiated have more sustained early progeny production. Intriguingly, continued cycling is intermittent-gonads switch between active and dormant states-and in all likelihood stochastic. Other organs face tradeoffs whereby stem cell cycling has the beneficial effect of providing freshly-differentiated cells and the detrimental effect of increasing the likelihood of cancer or senescence; stochastic stem cell cycling may allow for a subset of cells to preserve proliferative potential in old age, which may implement a strategy to deal with uncertainty as to the total amount of proliferation to be undergone over an organism's lifespan. PMID:27077385

  15. Intermittent Stem Cell Cycling Balances Self-Renewal and Senescence of the C. elegans Germ Line.

    PubMed

    Cinquin, Amanda; Chiang, Michael; Paz, Adrian; Hallman, Sam; Yuan, Oliver; Vysniauskaite, Indre; Fowlkes, Charless C; Cinquin, Olivier

    2016-04-01

    Self-renewing organs often experience a decline in function in the course of aging. It is unclear whether chronological age or external factors control this decline, or whether it is driven by stem cell self-renewal-for example, because cycling cells exhaust their replicative capacity and become senescent. Here we assay the relationship between stem cell cycling and senescence in the Caenorhabditis elegans reproductive system, defining this senescence as the progressive decline in "reproductive capacity," i.e. in the number of progeny that can be produced until cessation of reproduction. We show that stem cell cycling diminishes remaining reproductive capacity, at least in part through the DNA damage response. Paradoxically, gonads kept under conditions that preclude reproduction keep cycling and producing cells that undergo apoptosis or are laid as unfertilized gametes, thus squandering reproductive capacity. We show that continued activity is in fact beneficial inasmuch as gonads that are active when reproduction is initiated have more sustained early progeny production. Intriguingly, continued cycling is intermittent-gonads switch between active and dormant states-and in all likelihood stochastic. Other organs face tradeoffs whereby stem cell cycling has the beneficial effect of providing freshly-differentiated cells and the detrimental effect of increasing the likelihood of cancer or senescence; stochastic stem cell cycling may allow for a subset of cells to preserve proliferative potential in old age, which may implement a strategy to deal with uncertainty as to the total amount of proliferation to be undergone over an organism's lifespan.

  16. Nonlinear Optical Imaging and Raman Microspectrometry of the Cell Nucleus throughout the Cell Cycle

    PubMed Central

    Pliss, Artem; Kuzmin, Andrey N.; Kachynski, Aliaksandr V.; Prasad, Paras N.

    2010-01-01

    Fundamental understanding of cellular processes at molecular level is of considerable importance in cell biology as well as in biomedical disciplines for early diagnosis of infection and cancer diseases, and for developing new molecular medicine-based therapies. Modern biophotonics offers exclusive capabilities to obtain information on molecular composition, organization, and dynamics in a cell by utilizing a combination of optical spectroscopy and optical imaging. We introduce here a combination of Raman microspectrometry, together with coherent anti-Stokes Raman scattering (CARS) and two-photon excited fluorescence (TPEF) nonlinear optical microscopy, to study macromolecular organization of the nucleus throughout the cell cycle. Site-specific concentrations of proteins, DNA, RNA, and lipids were determined in nucleoli, nucleoplasmic transcription sites, nuclear speckles, constitutive heterochromatin domains, mitotic chromosomes, and extrachromosomal regions of mitotic cells by quantitative confocal Raman microspectrometry. A surprising finding, obtained in our study, is that the local concentration of proteins does not increase during DNA compaction. We also demonstrate that postmitotic DNA decondensation is a gradual process, continuing for several hours. The quantitative Raman spectroscopic analysis was corroborated with CARS/TPEF multimodal imaging to visualize the distribution of protein, DNA, RNA, and lipid macromolecules throughout the cell cycle. PMID:21081098

  17. p205, a potential tumor suppressor, inhibits cell proliferation via multiple pathways of cell cycle regulation.

    PubMed

    Asefa, Benyam; Dermott, Jonathan M; Kaldis, Philipp; Stefanisko, Karen; Garfinkel, David J; Keller, Jonathan R

    2006-02-20

    p205 is a member of the interferon-inducible p200 family of proteins that regulate cell proliferation. Over-expression of p205 inhibits cell growth, although its mechanism of action is currently unknown. Therefore, we evaluated the effect of p205 on the p53 and Rb-dependent pathways of cell cycle regulation. p205 expression results in elevated levels of p21, and activates the p21 promoter in vitro in a p53-dependent manner. In addition, p205 induces increased expression of Rb, and binds directly to Rb and p53. Interestingly, p205 also induces growth inhibition independent of p53 and Rb by delaying G2/M progression in proliferating cells, and is a substrate for Cdk2 kinase activity. Finally, we have identified other binding partners of p205 by a yeast two-hybrid screen, including the paired homeodomain protein HoxB2. Taken together, our results indicate that p205 induces growth arrest by interaction with multiple transcription factors that regulate the cell cycle, including but not entirely dependent on the Rb- and p53-mediated pathways of growth inhibition. PMID:16458891

  18. Nonlinear optical imaging and Raman microspectrometry of the cell nucleus throughout the cell cycle.

    PubMed

    Pliss, Artem; Kuzmin, Andrey N; Kachynski, Aliaksandr V; Prasad, Paras N

    2010-11-17

    Fundamental understanding of cellular processes at molecular level is of considerable importance in cell biology as well as in biomedical disciplines for early diagnosis of infection and cancer diseases, and for developing new molecular medicine-based therapies. Modern biophotonics offers exclusive capabilities to obtain information on molecular composition, organization, and dynamics in a cell by utilizing a combination of optical spectroscopy and optical imaging. We introduce here a combination of Raman microspectrometry, together with coherent anti-Stokes Raman scattering (CARS) and two-photon excited fluorescence (TPEF) nonlinear optical microscopy, to study macromolecular organization of the nucleus throughout the cell cycle. Site-specific concentrations of proteins, DNA, RNA, and lipids were determined in nucleoli, nucleoplasmic transcription sites, nuclear speckles, constitutive heterochromatin domains, mitotic chromosomes, and extrachromosomal regions of mitotic cells by quantitative confocal Raman microspectrometry. A surprising finding, obtained in our study, is that the local concentration of proteins does not increase during DNA compaction. We also demonstrate that postmitotic DNA decondensation is a gradual process, continuing for several hours. The quantitative Raman spectroscopic analysis was corroborated with CARS/TPEF multimodal imaging to visualize the distribution of protein, DNA, RNA, and lipid macromolecules throughout the cell cycle.

  19. Protein kinase C signaling mediates a program of cell cycle withdrawal in the intestinal epithelium.

    PubMed

    Frey, M R; Clark, J A; Leontieva, O; Uronis, J M; Black, A R; Black, J D

    2000-11-13

    Members of the protein kinase C (PKC) family of signal transduction molecules have been widely implicated in regulation of cell growth and differentiation, although the underlying molecular mechanisms involved remain poorly defined. Using combined in vitro and in vivo intestinal epithelial model systems, we demonstrate that PKC signaling can trigger a coordinated program of molecular events leading to cell cycle withdrawal into G(0). PKC activation in the IEC-18 intestinal crypt cell line resulted in rapid downregulation of D-type cyclins and differential induction of p21(waf1/cip1) and p27(kip1), thus targeting all of the major G(1)/S cyclin-dependent kinase complexes. These events were associated with coordinated alterations in expression and phosphorylation of the pocket proteins p107, pRb, and p130 that drive cells to exit the cell cycle into G(0) as indicated by concomitant downregulation of the DNA licensing factor cdc6. Manipulation of PKC isozyme levels in IEC-18 cells demonstrated that PKCalpha alone can trigger hallmark events of cell cycle withdrawal in intestinal epithelial cells. Notably, analysis of the developmental control of cell cycle regulatory molecules along the crypt-villus axis revealed that PKCalpha activation is appropriately positioned within intestinal crypts to trigger this program of cell cycle exit-specific events in situ. Together, these data point to PKCalpha as a key regulator of cell cycle withdrawal in the intestinal epithelium.

  20. Tumor-suppressor Genes, Cell Cycle Regulatory Checkpoints, and the Skin.

    PubMed

    Abreu Velez, Ana Maria; Howard, Michael S

    2015-05-01

    The cell cycle (or cell-division cycle) is a series of events that take place in a cell, leading to its division and duplication. Cell division requires cell cycle checkpoints (CPs) that are used by the cell to both monitor and regulate the progress of the cell cycle. Tumor-suppressor genes (TSGs) or antioncogenes are genes that protect the cell from a single event or multiple events leading to cancer. When these genes mutate, the cell can progress to a cancerous state. We aimed to perform a narrative review, based on evaluation of the manuscripts published in MEDLINE-indexed journals using the Medical Subject Headings (MeSH) terms "tumor suppressor's genes," "skin," and "cell cycle regulatory checkpoints." We aimed to review the current concepts regarding TSGs, CPs, and their association with selected cutaneous diseases. It is important to take into account that in some cell cycle disorders, multiple genetic abnormalities may occur simultaneously. These abnormalities may include intrachromosomal insertions, unbalanced division products, recombinations, reciprocal deletions, and/or duplication of the inserted segments or genes; thus, these presentations usually involve several genes. Due to their complexity, these disorders require specialized expertise for proper diagnosis, counseling, personal and family support, and genetic studies. Alterations in the TSGs or CP regulators may occur in many benign skin proliferative disorders, neoplastic processes, and genodermatoses.

  1. Tumor-suppressor Genes, Cell Cycle Regulatory Checkpoints, and the Skin

    PubMed Central

    Velez, Ana Maria Abreu; Howard, Michael S.

    2015-01-01

    The cell cycle (or cell-division cycle) is a series of events that take place in a cell, leading to its division and duplication. Cell division requires cell cycle checkpoints (CPs) that are used by the cell to both monitor and regulate the progress of the cell cycle. Tumor-suppressor genes (TSGs) or antioncogenes are genes that protect the cell from a single event or multiple events leading to cancer. When these genes mutate, the cell can progress to a cancerous state. We aimed to perform a narrative review, based on evaluation of the manuscripts published in MEDLINE-indexed journals using the Medical Subject Headings (MeSH) terms “tumor suppressor's genes,” “skin,” and “cell cycle regulatory checkpoints.” We aimed to review the current concepts regarding TSGs, CPs, and their association with selected cutaneous diseases. It is important to take into account that in some cell cycle disorders, multiple genetic abnormalities may occur simultaneously. These abnormalities may include intrachromosomal insertions, unbalanced division products, recombinations, reciprocal deletions, and/or duplication of the inserted segments or genes; thus, these presentations usually involve several genes. Due to their complexity, these disorders require specialized expertise for proper diagnosis, counseling, personal and family support, and genetic studies. Alterations in the TSGs or CP regulators may occur in many benign skin proliferative disorders, neoplastic processes, and genodermatoses. PMID:26110128

  2. Cyclin A2: At the crossroads of cell cycle and cell invasion

    PubMed Central

    Loukil, Abdelhalim; Cheung, Caroline T; Bendris, Nawal; Lemmers, Bénédicte; Peter, Marion; Blanchard, Jean Marie

    2015-01-01

    Cyclin A2 is an essential regulator of the cell division cycle through the activation of kinases that participate to the regulation of S phase as well as the mitotic entry. However, whereas its degradation by the proteasome in mid mitosis was thought to be essential for mitosis to proceed, recent observations show that a small fraction of cyclin A2 persists beyond metaphase and is degraded by autophagy. Its implication in the control of cytoskeletal dynamics and cell movement has unveiled its role in the modulation of RhoA activity. Since this GTPase is involved in both cell rounding early in mitosis and later, in the formation of the cleavage furrow, this suggests that cyclin A2 is a novel actor in cytokinesis. Taken together, these data point to this cyclin as a potential mediator of cell-niche interactions whose dysregulation could be taken as a hallmark of metastasis. PMID:26629317

  3. Cyclin A2: At the crossroads of cell cycle and cell invasion.

    PubMed

    Loukil, Abdelhalim; Cheung, Caroline T; Bendris, Nawal; Lemmers, Bénédicte; Peter, Marion; Blanchard, Jean Marie

    2015-11-26

    Cyclin A2 is an essential regulator of the cell division cycle through the activation of kinases that participate to the regulation of S phase as well as the mitotic entry. However, whereas its degradation by the proteasome in mid mitosis was thought to be essential for mitosis to proceed, recent observations show that a small fraction of cyclin A2 persists beyond metaphase and is degraded by autophagy. Its implication in the control of cytoskeletal dynamics and cell movement has unveiled its role in the modulation of RhoA activity. Since this GTPase is involved in both cell rounding early in mitosis and later, in the formation of the cleavage furrow, this suggests that cyclin A2 is a novel actor in cytokinesis. Taken together, these data point to this cyclin as a potential mediator of cell-niche interactions whose dysregulation could be taken as a hallmark of metastasis.

  4. Resveratrol causes cell cycle arrest, decreased collagen synthesis, and apoptosis in rat intestinal smooth muscle cells.

    PubMed

    Garcia, Patricia; Schmiedlin-Ren, Phyllissa; Mathias, Jason S; Tang, Huaijing; Christman, Gregory M; Zimmermann, Ellen M

    2012-02-01

    One of the most difficult and treatment-resistant complications of Crohn's disease is the development of fibrotic intestinal strictures due to mesenchymal cell hyperplasia and collagen deposition. Resveratrol, a phytoalexin found in berries, peanuts, grapes, and red wine, has been shown to inhibit fibrosis in vasculature, heart, lung, kidney, liver, and esophagus in animal models. Resveratrol has also been shown to inhibit oxidation, inflammation, and cell proliferation and to decrease collagen synthesis in several cell types or animal models. The aim of this study was to determine whether resveratrol has antifibrotic effects on intestinal smooth muscle cells. Responses to resveratrol by cultured smooth muscle cells isolated from colons of untreated Lewis rats were examined; this rat strain is used in a model of Crohn's disease with prominent intestinal fibrosis. A relative decrease in cell numbers following treatment with 50 and 100 μM resveratrol was evident at 24 h (P ≤ 0.005). This effect was largely due to cell cycle arrest, with an increase in the percent of cells in S phase from 8 to 25-35% (P < 0.05). Cell viability was unchanged until 2-3 days of treatment when there was a 1.2- to 5.0-fold increase in the percent of apoptotic cells, depending on the assay (P < 0.05). Expression of collagen type I protein was decreased following treatment with resveratrol for 24 h (to 44 and 25% of control levels with 50 and 100 μM resveratrol, respectively; P < 0.05). Expression of procollagen types I and III mRNA was also decreased with resveratrol treatment. Resveratrol (50 μM) diminished the proliferative response to TGF-β₁ (P = 0.02) as well as IGF-I-stimulated collagen production (P = 0.02). Thus resveratrol decreases intestinal smooth muscle cell numbers through its effects on cell cycle arrest and apoptosis and also decreases collagen synthesis by the cells. These effects could be useful in preventing the smooth muscle cell hyperplasia and collagen

  5. Altered Cell Cycle Arrest by Multifunctional Drug-Loaded Enzymatically-Triggered Nanoparticles.

    PubMed

    Huang, Can; Sun, Ying; Shen, Ming; Zhang, Xiangyu; Gao, Pei; Duan, Yourong

    2016-01-20

    cRGD-targeting matrix metalloproteinase (MMP)-sensitive nanoparticles [PLGA-PEG1K-cRGD/PLGA-peptide-PEG5K (NPs-cRGD)] were successfully developed. Au-Pt(IV) nanoparticles, PTX, and ADR were encapsulated into NPs-RGD separately. The effects of the drug-loaded nanoparticles on the cell cycle were investigated. Here, we showed that higher cytotoxicity of drug-loaded nanoparticles was related to the cell cycle arrest, compared to that of free drugs. The NPs-cRGD studied here did not disrupt cell cycle progression. The cell cycle of Au-Pt(IV)@NPs-cRGD showed a main S phase arrest in all phases of the cell cycle phase, especially in G0/G1 phase. PTX@NPs-cRGD and ADR@NPs-cRGD showed a higher ratio of G2/M and S phase arrest than the free drugs, respectively. Cells in G0/G1 and S phases of the cell cycle had a higher uptake ratio of NPs-cRGD. A nutrient deprivation or an increase in the requirement of nutrients in tumor cells could promote the uptake of nanoparticles from the microenvironments. In vivo, NPs-cRGD could efficiently accumulate at tumor sites. The inhibition of tumor growth coupled with cell cycle arrest is in line with that in vitro. On the basis of our results, we propose that future studies on nanoparticle action mechanism should consider the cell cycle, which could be different from free drugs. Understanding the actions of cell cycle arrest could affect the application of nanomedicine in the clinic.

  6. Effect of Handling, Storage and Cycling on Ni-H2 Cells: Second Plateau Phenomenon

    NASA Technical Reports Server (NTRS)

    Vaidyanathan, Hari; Rao, Gopalakrishna M.; Day, John H. (Technical Monitor)

    2000-01-01

    A viewgraph presentation outlines the effects of handling, storing, and cycling of NiH2 cells, particularly the second plateau phenomenon. Details are given on the criteria for cell selection, cell history, the second plateau capacity at C/2 discharge, and cell reversal test conditions. Tables display a gas analysis and nickel precharge.

  7. Cell cycle Start is coupled to entry into the yeast metabolic cycle across diverse strains and growth rates.

    PubMed

    Burnetti, Anthony J; Aydin, Mert; Buchler, Nicolas E

    2016-01-01

    Cells have evolved oscillators with different frequencies to coordinate periodic processes. Here we studied the interaction of two oscillators, the cell division cycle (CDC) and the yeast metabolic cycle (YMC), in budding yeast. Previous work suggested that the CDC and YMC interact to separate high oxygen consumption (HOC) from DNA replication to prevent genetic damage. To test this hypothesis, we grew diverse strains in chemostat and measured DNA replication and oxygen consumption with high temporal resolution at different growth rates. Our data showed that HOC is not strictly separated from DNA replication; rather, cell cycle Start is coupled with the initiation of HOC and catabolism of storage carbohydrates. The logic of this YMC-CDC coupling may be to ensure that DNA replication and cell division occur only when sufficient cellular energy reserves have accumulated. Our results also uncovered a quantitative relationship between CDC period and YMC period across different strains. More generally, our approach shows how studies in genetically diverse strains efficiently identify robust phenotypes and steer the experimentalist away from strain-specific idiosyncrasies. PMID:26538026

  8. Cell cycle Start is coupled to entry into the yeast metabolic cycle across diverse strains and growth rates

    PubMed Central

    Burnetti, Anthony J.; Aydin, Mert; Buchler, Nicolas E.

    2016-01-01

    Cells have evolved oscillators with different frequencies to coordinate periodic processes. Here we studied the interaction of two oscillators, the cell division cycle (CDC) and the yeast metabolic cycle (YMC), in budding yeast. Previous work suggested that the CDC and YMC interact to separate high oxygen consumption (HOC) from DNA replication to prevent genetic damage. To test this hypothesis, we grew diverse strains in chemostat and measured DNA replication and oxygen consumption with high temporal resolution at different growth rates. Our data showed that HOC is not strictly separated from DNA replication; rather, cell cycle Start is coupled with the initiation of HOC and catabolism of storage carbohydrates. The logic of this YMC–CDC coupling may be to ensure that DNA replication and cell division occur only when sufficient cellular energy reserves have accumulated. Our results also uncovered a quantitative relationship between CDC period and YMC period across different strains. More generally, our approach shows how studies in genetically diverse strains efficiently identify robust phenotypes and steer the experimentalist away from strain-specific idiosyncrasies. PMID:26538026

  9. PVM/MA-shelled selol nanocapsules promote cell cycle arrest in A549 lung adenocarcinoma cells

    PubMed Central

    2014-01-01

    Background Selol is an oily mixture of selenitetriacylglycerides that was obtained as a semi-synthetic compound containing selenite. Selol is effective against cancerous cells and less toxic to normal cells compared with inorganic forms of selenite. However, Selol’s hydrophobicity hinders its administration in vivo. Therefore, the present study aimed to produce a formulation of Selol nanocapsules (SPN) and to test its effectiveness against pulmonary adenocarcinoma cells (A549). Results Nanocapsules were produced through an interfacial nanoprecipitation method. The polymer shell was composed of poly(methyl vinyl ether-co-maleic anhydride) (PVM/MA) copolymer. The obtained nanocapsules were monodisperse and stable. Both free Selol (S) and SPN reduced the viability of A549 cells, whereas S induced a greater reduction in non-tumor cell viability than SPN. The suppressor effect of SPN was primarily associated to the G2/M arrest of the cell cycle, as was corroborated by the down-regulations of the CCNB1 and CDC25C genes. Apoptosis and necrosis were induced by Selol in a discrete percentage of A549 cells. SPN also increased the production of reactive oxygen species, leading to oxidative cellular damage and to the overexpression of the GPX1, CYP1A1, BAX and BCL2 genes. Conclusions This study presents a stable formulation of PVM/MA-shelled Selol nanocapsules and provides the first demonstration that Selol promotes G2/M arrest in cancerous cells. PMID:25149827

  10. Cell cycle-dependent modulation of FtsZ expression in synchronized tobacco BY2 cells.

    PubMed

    El-Shami, M; El-Kafafi, S; Falconet, D; Lerbs-Mache, S

    2002-04-01

    In higher plants, the FtsZ protein, the ancestor of tubulin, has been shown to be implicated in both proplastid division, which occurs in dividing cells and in the division of the differentiated plastids present in non-dividing cells. Here we report studies on the expression of the two FtsZ gene families in higher plants, FtsZ1 and FtsZ2, in non-synchronized and synchronized tobacco BY2 cells. We have isolated and characterized members of each gene family from Nicotiana tabacum. Specific cDNA probes for each tobacco FtsZ gene family and polyclonal antibodies specific for the FtsZ1 and FtsZ2 proteins were obtained in order to determine mRNA and protein levels. A constant level of FtsZ1 and FtsZ2 transcripts and proteins was observed in non-synchronized cell cultures. However, a complex pattern of expression of both gene families was observed during the cell cycle in synchronized cells, with mRNA and protein levels peaking during cell division, thus implying that the FtsZ proteins may be involved in plastid transmission to the two daughter cells.

  11. Cell cycle dependent regulation of deoxycytidine kinase, deoxyguanosine kinase, and cytosolic 5'-nucleotidase I activity in MOLT-4 cells.

    PubMed

    Fyrberg, A; Mirzaee, S; Lotfi, K

    2006-01-01

    Activation of nucleoside analogues is dependent on kinases and 5'-nucleotidases and the balance between the activity of these enzymes. The purpose of this study was to analyze deoxycytidine kinase, deoxyguanosine kinase, and 4 different 5'-nucleotidases during cell cycle progression in MOLT-4 cells. The activity of both kinases was cell cycle dependent and increased during proliferation while the activity of cytosolic 5'-nucleotidase I decreased. We could show that the kinase activity was higher than the total nucleotidase activity, which was unchanged or decreased during cell cycle progression. These data may be important in designing modern combination therapy with nucleoside analogues.

  12. Mnt-Max to Myc-Max complex switching regulates cell cycle entry.

    PubMed

    Walker, William; Zhou, Zi-Qiang; Ota, Sara; Wynshaw-Boris, Anthony; Hurlin, Peter J

    2005-05-01

    The c-Myc oncoprotein is strongly induced during the G0 to S-phase transition and is an important regulator of cell cycle entry. In contrast to c-Myc, the putative Myc antagonist Mnt is maintained at a constant level during cell cycle entry. Mnt and Myc require interaction with Max for specific DNA binding at E-box sites, but have opposing transcriptional activities. Here, we show that c-Myc induction during cell cycle entry leads to a transient decrease in Mnt-Max complexes and a transient switch in the ratio of Mnt-Max to c-Myc-Max on shared target genes. Mnt overexpression suppressed cell cycle entry and cell proliferation, suggesting that the ratio of Mnt-Max to c-Myc-Max is critical for cell cycle entry. Furthermore, simultaneous Cre-Lox mediated deletion of Mnt and c-Myc in mouse embryo fibroblasts rescued the cell cycle entry and proliferative block caused by c-Myc ablation alone. These results demonstrate that Mnt-Myc antagonism plays a fundamental role in regulating cell cycle entry and proliferation.

  13. Identification of essential Alphaproteobacterial genes reveals operational variability in conserved developmental and cell cycle systems

    PubMed Central

    Curtis, Patrick D.; Brun, Yves V.

    2014-01-01

    Summary The cell cycle of Caulobacter crescentus is controlled by a complex signaling network that coordinates events. Genome sequencing has revealed many C. crescentus cell cycle genes are conserved in other Alphaproteobacteria, but it is not clear to what extent their function is conserved. As many cell cycle regulatory genes are essential in C. crescentus, the essential genes of two Alphaproteobacteria, Agrobacterium tumefaciens (Rhizobiales) and Brevundimonas subvibrioides (Caulobacterales), were elucidated to identify changes in cell cycle protein function over different phylogenetic distances as demonstrated by changes in essentiality. The results show the majority of conserved essential genes are involved in critical cell cycle processes. Changes in component essentiality reflect major changes in lifestyle, such as divisome components in A. tumefaciens resulting from that organism’s different growth pattern. Larger variability of essentiality was observed in cell cycle regulators, suggesting regulatory mechanisms are more customizable than the processes they regulate. Examples include variability in the essentiality of divJ and divK spatial cell cycle regulators, and non-essentiality of the highly conserved and usually essential DNA methyltransferase CcrM. These results show that while essential cell functions are conserved across varying genetic distance, much of a given organism’s essential gene pool is specific to that organism. PMID:24975755

  14. Pravastatin induces cell cycle arrest and decreased production of VEGF and bFGF in multiple myeloma cell line.

    PubMed

    Trojan, P J J; Bohatch-Junior, M S; Otuki, M F; Souza-Fonseca-Guimarães, F; Svidnicki, P V; Nogaroto, V; Fernandes, D; Krum, E A; Favero, G M

    2016-02-01

    Multiple myeloma (MM) is a B cell bone marrow neoplasia characterized by inflammation with an intense secretion of growth factors that promote tumor growth, cell survival, migration and invasion. The aim of this study was to evaluate the effects of pravastatin, a drug used to reduce cholesterol, in a MM cell line.Cell cycle and viability were determinate by Trypan Blue and Propidium Iodide. IL6, VEGF, bFGF and TGFβ were quantified by ELISA and qRT-PCR including here de HMG CoA reductase. It was observed reduction of cell viability, increase of cells in G0/G1 phase of the cell cycle and reducing the factors VEGF and bFGF without influence on 3-Methyl-Glutaryl Coenzyme A reductase expression.The results demonstrated that pravastatin induces cell cycle arrest in G0/G1 and decreased production of growth factors in Multiple Myeloma cell line. PMID:26909624

  15. Animal Models for Studying the In Vivo Functions of Cell Cycle CDKs.

    PubMed

    Risal, Sanjiv; Adhikari, Deepak; Liu, Kui

    2016-01-01

    Multiple Cdks (Cdk4, Cdk6, and Cdk2) and a mitotic Cdk (Cdk1) are involved in cell cycle progression in mammals. Cyclins, Cdk inhibitors, and phosphorylations (both activating and inhibitory) at different cellular levels tightly modulate the activities of these kinases. Based on the results of biochemical studies, it was long believed that different Cdks functioned at specific stages during cell cycle progression. However, deletion of all three interphase Cdks in mice affected cell cycle entry and progression only in certain specialized cells such as hematopoietic cells, beta cells of the pancreas, pituitary lactotrophs, and cardiomyocytes. These genetic experiments challenged the prevailing biochemical model and established that Cdks function in a cell-specific, but not a stage-specific, manner during cell cycle entry and the progression of mitosis. Recent in vivo studies have further established that Cdk1 is the only Cdk that is both essential and sufficient for driving the resumption of meiosis during mouse oocyte maturation. These genetic studies suggest a minimal-essential cell cycle model in which Cdk1 is the central regulator of cell cycle progression. Cdk1 can compensate for the loss of the interphase Cdks by forming active complexes with A-, B-, E-, and D-type Cyclins in a stepwise manner. Thus, Cdk1 plays an essential role in both mitosis and meiosis in mammals, whereas interphase Cdks are dispensable.

  16. Does the Potential for Chaos Constrain the Embryonic Cell-Cycle Oscillator?

    PubMed Central

    Sengupta, Anirvan; Wingreen, Ned S.

    2011-01-01

    Although many of the core components of the embryonic cell-cycle network have been elucidated, the question of how embryos achieve robust, synchronous cellular divisions post-fertilization remains unexplored. What are the different schemes that could be implemented by the embryo to achieve synchronization? By extending a cell-cycle model previously developed for embryos of the frog Xenopus laevis to include the spatial dimensions of the embryo, we establish a novel role for the rapid, fertilization-initiated calcium wave that triggers cell-cycle oscillations. Specifically, in our simulations a fast calcium wave results in synchronized cell cycles, while a slow wave results in full-blown spatio-temporal chaos. We show that such chaos would ultimately lead to an unpredictable patchwork of cell divisions across the embryo. Given this potential for chaos, our results indicate a novel design principle whereby the fast calcium-wave trigger following embryo fertilization synchronizes cell divisions. PMID:21779158

  17. Cell-Cycle Control of Bivalent Epigenetic Domains Regulates the Exit from Pluripotency

    PubMed Central

    Singh, Amar M.; Sun, Yuhua; Li, Li; Zhang, Wenjuan; Wu, Tianming; Zhao, Shaying; Qin, Zhaohui; Dalton, Stephen

    2015-01-01

    Summary Here we show that bivalent domains and chromosome architecture for bivalent genes are dynamically regulated during the cell cycle in human pluripotent cells. Central to this is the transient increase in H3K4-trimethylation at developmental genes during G1, thereby creating a “window of opportunity” for cell-fate specification. This mechanism is controlled by CDK2-dependent phosphorylation of the MLL2 (KMT2B) histone methyl-transferase, which facilitates its recruitment to developmental genes in G1. MLL2 binding is required for changes in chromosome architecture around developmental genes and establishes promoter-enhancer looping interactions in a cell-cycle-dependent manner. These cell-cycle-regulated loops are shown to be essential for activation of bivalent genes and pluripotency exit. These findings demonstrate that bivalent domains are established to control the cell-cycle-dependent activation of developmental genes so that differentiation initiates from the G1 phase. PMID:26278042

  18. Centriole maturation requires regulated Plk1 activity during two consecutive cell cycles.

    PubMed

    Kong, Dong; Farmer, Veronica; Shukla, Anil; James, Jana; Gruskin, Richard; Kiriyama, Shigeo; Loncarek, Jadranka

    2014-09-29

    Newly formed centrioles in cycling cells undergo a maturation process that is almost two cell cycles long before they become competent to function as microtubule-organizing centers and basal bodies. As a result, each cell contains three generations of centrioles, only one of which is able to form cilia. It is not known how this long and complex process is regulated. We show that controlled Plk1 activity is required for gradual biochemical and structural maturation of the centrioles and timely appendage assembly. Inhibition of Plk1 impeded accumulation of appendage proteins and appendage formation. Unscheduled Plk1 activity, either in cycling or interphase-arrested cells, accelerated centriole maturation and appendage and cilia formation on the nascent centrioles, erasing the age difference between centrioles in one cell. These findings provide a new understanding of how the centriole cycle is regulated and how proper cilia and centrosome numbers are maintained in the cells.

  19. Cell-Cycle Control of Bivalent Epigenetic Domains Regulates the Exit from Pluripotency.

    PubMed

    Singh, Amar M; Sun, Yuhua; Li, Li; Zhang, Wenjuan; Wu, Tianming; Zhao, Shaying; Qin, Zhaohui; Dalton, Stephen

    2015-09-01

    Here we show that bivalent domains and chromosome architecture for bivalent genes are dynamically regulated during the cell cycle in human pluripotent cells. Central to this is the transient increase in H3K4-trimethylation at developmental genes during G1, thereby creating a "window of opportunity" for cell-fate specification. This mechanism is controlled by CDK2-dependent phosphorylation of the MLL2 (KMT2B) histone methyl-transferase, which facilitates its recruitment to developmental genes in G1. MLL2 binding is required for changes in chromosome architecture around developmental genes and establishes promoter-enhancer looping interactions in a cell-cycle-dependent manner. These cell-cycle-regulated loops are shown to be essential for activation of bivalent genes and pluripotency exit. These findings demonstrate that bivalent domains are established to control the cell-cycle-dependent activation of developmental genes so that differentiation initiates from the G1 phase. PMID:26278042

  20. Overexpression of AQP3 Modifies the Cell Cycle and the Proliferation Rate of Mammalian Cells in Culture.

    PubMed

    Galán-Cobo, Ana; Ramírez-Lorca, Reposo; Serna, Ana; Echevarría, Miriam

    2015-01-01

    Abnormal AQP3 overexpression in tumor cells of different origins has been reported and a role for this enhanced AQP3 expression in cell proliferation and tumor processess has been indicated. To further understand the role AQP3 plays in cell proliferation we explore the effect that stable over expression of AQP3 produces over the proliferation rate and cell cycle of mammalian cells. The cell cycle was analyzed by flow cytometry with propidium iodide (PI) and the cell proliferation rate measured through cell counting and BrdU staining. Cells with overexpression of AQP3 (AQP3-o) showed higher proliferation rate and larger percentage of cells in phases S and G2/M, than wild type cells (wt). Evaluation of the cell response against arresting the cell cycle with Nocodazole showed that AQP3-o exhibited a less modified cell cycle pattern and lower Annexin V specific staining than wt, consistently with a higher resistance to apoptosis of AQP3-overexpressing cells. The cell volume and complexity were also larger in AQP3-o compared to wt cells. After transcriptomic analysis, RT-qPCR was performed to highlight key molecules implicated in cell proliferation which expression may be altered by overexpression of AQP3 and the comparative analysis between both type of cells showed significant changes in the expression of Zeb2, Jun, JunB, NF-kβ, Cxcl9, Cxcl10, TNF, and TNF receptors. We conclude that the role of AQP3 in cell proliferation seems to be connected to increments in the cell cycle turnover and changes in the expression levels of relevant genes for this process. Larger expression of AQP3 may confer to the cell a more tumor like phenotype and contributes to explain the presence of this protein in many different tumors.

  1. Overexpression of AQP3 Modifies the Cell Cycle and the Proliferation Rate of Mammalian Cells in Culture

    PubMed Central

    Galán-Cobo, Ana; Ramírez-Lorca, Reposo; Serna, Ana; Echevarría, Miriam

    2015-01-01

    Abnormal AQP3 overexpression in tumor cells of different origins has been reported and a role for this enhanced AQP3 expression in cell proliferation and tumor processess has been indicated. To further understand the role AQP3 plays in cell proliferation we explore the effect that stable over expression of AQP3 produces over the proliferation rate and cell cycle of mammalian cells. The cell cycle was analyzed by flow cytometry with propidium iodide (PI) and the cell proliferation rate measured through cell counting and BrdU staining. Cells with overexpression of AQP3 (AQP3-o) showed higher proliferation rate and larger percentage of