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  • Role of histone modifications in marking and activating genes through mitosis. 16199528

    The global inhibition of transcription at the mitotic phase of the cell cycle occurs together with the general displacement of transcription factors from the mitotic chromatin. Nevertheless, the DNase- and potassium permanganate-hypersensitive sites are maintained on potentially active promoters during mitosis, helping to mark active genes at this stage of the cell cycle. Our study focuses on the role of histone acetylation and H3 (Lys-4) methylation in the maintenance of the competency of these active genes during mitosis. To this end we have analyzed histone modifications across the promoters and coding regions of constitutively active, inducible, and inactive genes in mitotic arrested cells. Our results show that basal histone modifications are maintained during mitosis at promoters and coding regions of the active and inducible RNA polymerase II-transcribed genes. In addition we have demonstrated that, together with H3 acetylation and H3 (Lys-4) methylation, H4 (Lys-12) acetylation at the coding regions contributes to the formation of a stable mark on active genes at this stage of the cell cycle. Finally, analysis of cyclin B1 gene activation during mitosis revealed that the former occurs with a strong increase of H3 (Lys-4) trimethylation but not H3 or H4 acetylation, suggesting that histone methyltransferases are active during this stage. These data demonstrate a critical role of histone acetylation and H3 (Lys-4) methylation during mitosis in marking and activating genes during the mitotic stage of the cell cycle.
    Tipo de documento:
    Referencia
    Referencia del producto:
    Múltiplo
    Nombre del producto:
    Múltiplo

  • Studies on the mechanism of resistance to rapamycin in human cancer cells. 9804616

    Rapamycin is a potent cytostatic agent that arrests cells in the G1 phase of the cell cycle. The relationships between cellular sensitivity to rapamycin, drug accumulation, expression of mammalian target of rapamycin (mTOR), and inhibition of growth factor activation of ribosomal p70S6 kinase (p70(S6k)) and dephosphorylation of pH acid stable protein I (eukaryotic initiation factor 4E binding protein) were examined. We show that some cell lines derived from childhood tumors are highly sensitive to growth inhibition by rapamycin, whereas others have high intrinsic resistance (>1000-fold). Accumulation and retention of [14C]rapamycin were similar in sensitive and resistant cells, with all cells examined demonstrating a stable tight binding component. Western analysis showed levels of mTOR were similar in each cell line (<2-fold variation). The activity of p70(S6k), activated downstream of mTOR, was similar in four cell lines (range, 11.75-41. 8 pmol/2 x 10(6) cells/30 min), but activity was equally inhibited in cells that were highly resistant to rapamycin-induced growth arrest. Rapamycin equally inhibited serum-induced phosphorylation of pH acid stable protein I in Rh1 (intrinsically resistant) and sensitive Rh30 cells. In serum-fasted Rh30 and Rh1 cells, the addition of serum rapidly induced c-MYC (protein) levels. Rapamycin blocked induction in Rh30 cells but not in Rh1 cells. Serum-fasted Rh30/rapa10K cells, selected for high level acquired resistance to rapamycin, showed >/=10-fold increased c-MYC compared with Rh30. These results suggest that the ability of rapamycin to inhibit c-MYC induction correlates with intrinsic sensitivity, whereas failure of rapamycin to inhibit induction or overexpression of c-MYC correlates with intrinsic and acquired resistance, respectively.
    Tipo de documento:
    Referencia
    Referencia del producto:
    MABS196
    Nombre del producto:
    Anti-mTOR/FRAP Antibody, clone 22C2

  • PLK-1 asymmetry contributes to asynchronous cell division of C. elegans embryos. 18305005

    Acquisition of lineage-specific cell cycle duration is an important feature of metazoan development. In Caenorhabditis elegans, differences in cell cycle duration are already apparent in two-cell stage embryos, when the larger anterior blastomere AB divides before the smaller posterior blastomere P1. This time difference is under the control of anterior-posterior (A-P) polarity cues set by the PAR proteins. The mechanisms by which these cues regulate the cell cycle machinery differentially in AB and P1 are incompletely understood. Previous work established that retardation of P1 cell division is due in part to preferential activation of an ATL-1/CHK-1 dependent checkpoint in P1, but how the remaining time difference is controlled is not known. Here, we establish that differential timing relies also on a mechanism that promotes mitosis onset preferentially in AB. The polo-like kinase PLK-1, a positive regulator of mitotic entry, is distributed in an asymmetric manner in two-cell stage embryos, with more protein present in AB than in P1. We find that PLK-1 asymmetry is regulated by A-P polarity cues through preferential protein retention in the embryo anterior. Importantly, mild inactivation of plk-1 by RNAi delays entry into mitosis in P1, but not in AB, in a manner that is independent of ATL-1/CHK-1. Together, our findings support a model in which differential timing of mitotic entry in C. elegans embryos relies on two complementary mechanisms: ATL-1/CHK-1-dependent preferential retardation in P1 and PLK-1-dependent preferential promotion in AB, which together couple polarity cues and cell cycle progression during early development.
    Tipo de documento:
    Referencia
    Referencia del producto:
    MAB3580

  • Regulation of cyclin D2 gene expression by the Myc/Max/Mad network: Myc-dependent TRRAP recruitment and histone acetylation at the cyclin D2 promoter. 11511535

    Myc oncoproteins promote cell cycle progression in part through the transcriptional up-regulation of the cyclin D2 gene. We now show that Myc is bound to the cyclin D2 promoter in vivo. Binding of Myc induces cyclin D2 expression and histone acetylation at a single nucleosome in a MycBoxII/TRRAP-dependent manner. Down-regulation of cyclin D2 mRNA expression in differentiating HL60 cells is preceded by a switch of promoter occupancy from Myc/Max to Mad/Max complexes, loss of TRRAP binding, increased HDAC1 binding, and histone deacetylation. Thus, recruitment of TRRAP and regulation of histone acetylation are critical for transcriptional activation by Myc.
    Tipo de documento:
    Referencia
    Referencia del producto:
    Múltiplo
    Nombre del producto:
    Múltiplo

  • The Spy1/RINGO family represents a novel mechanism regulating mammary growth and tumorigenesis. 18483240

    Spy1A is a unique cell cycle activator known to mediate cell cycle progression and override the DNA damage response. This study focused on determining the role of this protein on postnatal mammary gland morphogenesis and neoplasia. Herein, we show that Spy1A levels are tightly regulated during mammary gland development and that ectopic expression stimulates precocious development and results in disrupted morphology of the gland. This follows the same trend as the oncogene c-Myc, and we show that Spy1A expression is regulated downstream of c-Myc signaling. Importantly, we show that overexpression of Spy1A accelerates tumorigenesis in vivo. Collectively, this work is the first report that the Spy1/RINGO family of proteins may play an essential role in regulating both normal and abnormal growth processes in the breast.
    Tipo de documento:
    Referencia
    Referencia del producto:
    MAB1501R
    Nombre del producto:
    Anti-Actin Antibody,clone C4

  • HNF1B Loss Exacerbates the Development of Chromophobe Renal Cell Carcinomas. 28807937

    Chromophobe renal cell carcinoma (ChRCC) is characterized by major changes in chromosomal copy number (CN). No model is available to precisely elucidate the molecular drivers of this tumor type. HNF1B is a master regulator of gene expression. Here, we report that the transcription factor HNF1B is downregulated in the majority of ChRCC and that the magnitude of HNF1B loss is unique to ChRCC. We also observed a strong correlation between reduced HNF1B expression and aneuploidy in ChRCC patients. In murine embryonic fibroblasts or ACHN cells, HNF1B deficiency reduced expression of the spindle checkpoint proteins MAD2L1 and BUB1B, and the cell-cycle checkpoint proteins RB1 and p27. Furthermore, it altered the chromatin accessibility of Mad2l1, Bub1b, and Rb1 genes and triggered aneuploidy development. Analysis of The Cancer Genome Atlas database revealed TP53 mutations in 33% of ChRCC where HNF1B expression was repressed. In clinical specimens, combining HNF1B loss with TP53 mutation produced an association with poor patient prognosis. In cells, combining HNF1B loss and TP53 mutation increased cell proliferation and aneuploidy. Our results show how HNF1B loss leads to abnormal mitotic protein regulation and induction of aneuploidy. We propose that coordinate loss of HNF1B and TP53 may enhance cellular survival and confer an aggressive phenotype in ChRCC. Cancer Res; 77(19); 5313-26. ©2017 AACR.
    Tipo de documento:
    Referencia
    Referencia del producto:
    17-10085
    Nombre del producto:
    Magna ChIP™ A/G Chromatin Immunoprecipitation Kit

  • ES cell cycle progression and differentiation require the action of the histone methyltransferase Dot1L. 19544450

    Mouse embryonic stem cells (ESCs) proliferate with rapid cell cycle kinetics but without loss of pluripotency. The histone methyltransferase Dot1L is responsible for methylation of histone H3 at lysine 79 (H3K79me). We investigated whether ESCs require Dot1L for proper stem cell behavior. ESCs deficient in Dot1L tolerate a nearly complete loss of H3K79 methylation without a substantial impact on proliferation or morphology. However, shortly after differentiation is induced, Dot1L-deficient cells cease proliferating and arrest in G2/M-phase of the cell cycle, with increased levels of aneuploidy. In addition, many aberrant mitotic spindles occur in Dot1L-deficient cells. Surprisingly, these mitotic and cell cycle defects fail to trigger apoptosis, indicating that mouse ESCs lack stringent cell cycle checkpoint control during initial stages of differentiation. Transcriptome analysis indicates that Dot1L deficiency causes the misregulation of a select set of genes, including many with known roles in cell cycle control and cellular proliferation as well as markers of endoderm differentiation. The data indicate a requirement for Dot1L function for early stages of ESC differentiation where Dot1L is necessary for faithful execution of mitosis and proper transcription of many genes throughout the genome.
    Tipo de documento:
    Referencia
    Referencia del producto:
    17-295
    Nombre del producto:
    Chromatin Immunoprecipitation (ChIP) Assay Kit

  • Splicing of histone deacetylase 7 modulates smooth muscle cell proliferation and neointima formation through nuclear β-catenin translocation. 21836063

    Vascular smooth muscle cell (SMC) proliferation has an indispensable role in the pathogenesis of vascular disease, but the mechanism is not fully elucidated. The epigenetic enzyme histone deacetylase 7 (HDAC7) is involved in endothelial homeostasis and SMC differentiation and could have a role in SMC proliferation. In this study, we sought to examine the effect of 2 HDAC7 isoforms on SMC proliferation and neointima formation.We demonstrated that overexpression of unspliced HDAC7 (HDAC7u) could suppress SMC proliferation through downregulation of cyclin D1 and cell cycle arrest, whereas spliced HDAC7 (HDAC7s) could not. Small interfering RNA (siRNA)-mediated knockdown of HDAC7 increased SMC proliferation and induced nuclear translocation of β-catenin. Additional experiments showed that only HDAC7u could bind to β-catenin and retain it in the cytoplasm. Reporter gene assay and reverse transcription polymerase chain reaction revealed a reduction of β-catenin activity in cells overexpressing HDAC7u but not HDAC7s. Deletion studies indicated that the C-terminal region of HDAC7u is responsible for the interaction with β-catenin. However, the addition of amino acids to the N terminus of HDAC7u disrupted the binding, further strengthening our hypothesis that HDAC7s does not interact with β-catenin. The growth factor platelet-derived growth factor-BB increased the splicing of HDAC7 while simultaneously decreasing the expression of HDAC7u. Importantly, in an animal model of femoral artery wire injury, we demonstrated that knockdown of HDAC7 by siRNA aggravates neointima formation in comparison with control siRNA.Our findings demonstrate that splicing of HDAC7 modulates SMC proliferation and neointima formation through β-catenin nuclear translocation, which provides a potential therapeutic target in vascular disease.
    Tipo de documento:
    Referencia
    Referencia del producto:
    Múltiplo
    Nombre del producto:
    Múltiplo

  • Distinct populations of human PCNA are required for initiation of chromosomal DNA replication and concurrent DNA repair. 16226749

    The integrity of genomic DNA during the cell division cycle in eukaryotic cells is maintained by regulated chromosomal DNA replication and repair of damaged DNA. We have used fractionation and reconstitution experiments to purify essential factors for the initiation of human chromosomal DNA replication in late G1 phase template nuclei from human cells. Here, we report the identification of soluble PCNA as an essential initiation factor in this system. Recombinant histidine-tagged human PCNA can substitute for purified endogenous human PCNA to initiate human chromosomal DNA replication. It is recruited specifically to discrete DNA replication foci formed during initiation in vitro. The template nuclei also contain DNA breaks as result of the synchronisation procedure. A separate population of chromatin-bound PCNA is already present in these template nuclei at discrete DNA damage foci, co-localising with gamma-H2AX, RPA and Rad51. This DNA damage-associated PCNA population is marked by mono-ubiquitination, suggesting that it is involved in DNA repair. Importantly, the population of damage focus-associated PCNA is neither involved in, nor required for, the initiation of chromosomal DNA replication in the same nuclei.
    Tipo de documento:
    Referencia
    Referencia del producto:
    07-164
    Nombre del producto:
    Anti-phospho-H2A.X (Ser139) Antibody

  • A nucleocytoplasmic malate dehydrogenase regulates p53 transcriptional activity in response to metabolic stress. 19229245

    Metabolic enzymes have been shown to function as transcriptional regulators. p53, a tumor-suppressive transcription factor, was recently found to regulate energy metabolism. These combined facts raise the possibility that metabolic enzymes may directly regulate p53 function. Here, we discover that nucleocytoplasmic malate dehydrogenase-1 (MDH1) physically associates with p53. Upon glucose deprivation, MDH1 stabilizes and transactivates p53 by binding to p53-responsive elements in the promoter of downstream genes. Knockdown of MDH1 significantly reduces binding of acetylated-p53 and transcription-active histone codes to the promoter upon glucose depletion. MDH1 regulates p53-dependent cell-cycle arrest and apoptosis in response to glucose deprivation, suggesting that MDH1 functions as a transcriptional regulator for a p53-dependent metabolic checkpoint. Our findings provide insight into how metabolism is directly linked to gene expression for controlling cellular events in response to metabolic stress.
    Tipo de documento:
    Referencia
    Referencia del producto:
    07-473
    Nombre del producto:
    Anti-trimethyl-Histone H3 (Lys4) Antibody