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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

  • Estrogen-induced activation of Cdk4 and Cdk2 during G1-S phase progression is accompanied by increased cyclin D1 expression and decreased cyclin-dependent kinase inhibito ... 9099745

    Estrogens induce cell proliferation in target tissues by stimulating progression through G1 phase of the cell cycle, but the underlying molecular targets remain undefined. To determine the role of the cyclin/cyclin-dependent kinase (CDK)/retinoblastoma protein (pRB) pathway in this response we treated MCF-7 breast cancer cells with the pure estrogen antagonist ICI 182780 to inhibit estrogen-induced gene expression and induce G1 phase arrest. Subsequent treatment with 17beta-estradiol resulted in the synchronous entry of cells into S phase commencing at 12 h. The proportion of cells in S phase reached a maximum of 60% at 21-24 h. Cells subsequently completed mitosis and entered a second semisynchronous round of replication. Entry into S phase was preceded by increased activity of both Cdk4 and cyclin E-Cdk2 and hyperphosphorylation of pRB, all within the first 3-6 h of estradiol treatment. The increase in Cdk4 activity was accompanied by increases in cyclin D1 mRNA and protein, indicating that an initiating event in the activation of Cdk4 was increased cyclin D1 gene expression. In contrast, the levels of Cdk2 and the CDK inhibitors p21 (WAF1/CIP1/SDI1) and p27 (KIP1) in total cell lysates and in cyclin E immunoprecipitates were unaltered at these early time points. However, an inhibitory activity was present in antiestrogen-pretreated cell lysates toward recombinant cyclin E-Cdk2 and was relieved by estradiol treatment. This activity was attributable predominantly to p21. These apparently conflicting data were resolved by performing gel filtration chromatography, which revealed that only a minority of cyclin E-Cdk2 complexes were active following estradiol treatment. Active complexes eluted at a higher molecular weight than inactive complexes, were relatively deficient in both p21 and p27, and contained Cdk2 with increased threonine 160 phosphorylation, consistent with a mechanism of activation of cyclin E-Cdk2 involving both reduced CDK inhibitor association and CDK-activating kinase-mediated phosphorylation of Cdk2. These results provide an explanation for the early activation of both cyclin D1-Cdk4 and cyclin E-Cdk2 complexes that accompany G1-S phase progression in response to estradiol.
    Tipo de documento:
    Referencia
    Referencia del producto:
    07-687
    Nombre del producto:
    Anti-Cyclin E Antibody

  • Apc10 and Ste9/Srw1, two regulators of the APC-cyclosome, as well as the CDK inhibitor Rum1 are required for G1 cell-cycle arrest in fission yeast. 9736616

    Many eukaryotic cells arrest the cell cycle at G1 phase upon nutrient deprivation. In fission yeast, during nitrogen starvation, cells divide twice and arrest at G1. We have isolated a novel type of sterile mutant, which undergoes one additional S phase upon starvation and, as a result, arrests at G2. Three loci (apc10, ste9/srw1 and rum1) were identified. The apc10 mutants, previously unidentified, show, in addition to sterility, temperature-sensitive growth with defects in chromosome segregation. apc10(+) is essential for viability, encodes a conserved protein (a homologue of budding yeast Apc10/Doc1) and is required for ubiquitination and degradation of mitotic B-type cyclins. Apc10 does not co-sediment with the 20S APC-cyclosome, a ubiquitin ligase for B-type cyclins, and in the apc10 mutant the 20S complex is intact, suggesting that it is a novel regulator for this complex. A subpopulation of Apc10 does co-immunoprecipitate with the anaphase-promoting complex (APC). A second gene, ste9(+)/srw1(+), encodes a member of the fizzy-related family, also regulators of the APC. Finally, Rum1 is a cyclin-dependent kinase (CDK) inhibitor which exists only in G1. The results suggest that dual downregulation of CDK, one via the APC and the other via the CDK inhibitor, is a universal mechanism that is used to arrest cell cycle progression at G1.
    Tipo de documento:
    Referencia
    Referencia del producto:
    MAB1510

  • MAP kinase regulation of the mitotic spindle checkpoint. 20812004

    Maintaining the integrity of the cell cycle is critical for ensuring that cells only undergo DNA replication and proliferation under controlled conditions in response to discrete stimuli. One mechanism by which the fidelity of this process is guaranteed is through the activation of cell cycle checkpoints. The mitotic spindle checkpoint, which is regulated by Aurora B kinase, ensures proper kinetochore attachment to chromosomes leading to equal distribution of chromosomes to daughter cells. We demonstrated that the mitogen-activated protein kinase (MAPK) cascade regulates mitotic progression and the spindle checkpoint. As demonstrated by immunofluorescence at kinetochores, depletion of Raf Kinase Inhibitory Protein (RKIP), an inhibitor of Raf/MEK/ERK signaling, causes an increase in MAPK activity that inhibits Aurora B kinase activity. By monitoring mitotic index and transit time from nuclear envelope breakdown to anaphase, we demonstrated that RKIP depletion leads to a defective spindle checkpoint and genomic instability, particularly in response to drugs that disrupt microtubule function.
    Tipo de documento:
    Referencia
    Referencia del producto:
    07-232

  • G1 phase regulation, area-specific cell cycle control, and cytoarchitectonics in the primate cortex. 16055060

    We have investigated the cell cycle-related mechanisms that lead to the emergence of primate areas 17 and 18. These areas are characterized by striking differences in cytoarchitectonics and neuron number. We show in vivo that (1) area 17 precursors of supragranular neurons exhibit a shorter cell cycle duration, a reduced G1 phase, and a higher rate of cell cycle reentry than area 18 precursors; (2) area 17 and area 18 precursors show contrasting and specific levels of expression of cyclin E (high in area 17, low in area 18) and p27Kip1 (low in area 17, high in area 18); (3) ex vivo up- and downmodulation of cyclin E and p27Kip1 show that both regulators influence cell cycle kinetics by modifying rates of cell cycle progression and cell cycle reentry; (4) modeling the areal differences in cell cycle parameters suggests that they contribute to areal differences in numbers of precursors and neuron production.
    Tipo de documento:
    Referencia
    Referencia del producto:
    07-145
    Nombre del producto:
    Anti-phospho-Histone H3 (Ser28) Antibody

  • Transcription factor Sp3 represses expression of p21CIP¹ via inhibition of productive elongation by RNA polymerase II. 23401853

    Like that of many protein-coding genes, expression of the p21(CIP1) cell cycle inhibitor is regulated at the level of transcription elongation. While many transcriptional activators have been shown to stimulate elongation, the mechanisms by which promoter-specific repressors regulate pausing and elongation by RNA polymerase II (RNA PolII) are not well described. Here we report that the transcription factor Sp3 inhibits basal p21(CIP1) gene expression by promoter-bound RNA PolII. Knockdown of Sp3 led to increased p21(CIP1) mRNA levels and reduced occupancy of the negative elongation factor (NELF) at the p21(CIP1) promoter, although the level of binding of the positive transcription elongation factor b (P-TEFb) kinase was not increased. Sp3 depletion correlated with increased H3K36me3 and H2Bub1, two histone modifications associated with transcription elongation. Further, Sp3 was shown to promote the binding of protein phosphatase 1 (PP1) to the p21(CIP1) promoter, leading to reduced H3S10 phosphorylation, a finding consistent with Sp3-dependent regulation of the local balance between kinase and phosphatase activities. Analysis of other targets of Sp3-mediated repression suggests that, in addition to previously described SUMO modification-dependent chromatin-silencing mechanisms, inhibition of the transition of paused RNA PolII to productive elongation, described here for p21(CIP1), is a general mechanism by which transcription factor Sp3 fine-tunes gene expression.
    Tipo de documento:
    Referencia
    Referencia del producto:
    Múltiplo
    Nombre del producto:
    Múltiplo

  • LINC00037 Inhibits Proliferation of Renal Cell Carcinoma Cells in an Epidermal Growth Factor Receptor-Dependent Way. 29393141

    LINC00037 has previously been reported to be up-regulated in clear cell renal cell carcinoma (ccRCC), however, the underlying mechanism remained unknown. In this study, we designed to investigate the functional role of LINC00037 in ccRCC Methods: LINC00037 knockdown and re-expressing 786-O and A498 cells were established. CCK8 assay and EdU assay were performed to evaluate the proliferation rates of ccRCC cells. Flow cytometry assay was performed to detect the cell apoptosis and cell cycle. Subcutaneous injection xenotransplantation mouse model was used to observe the role of LINC00037 in tumor growth in vivo. Mass spectrometry (MS) was performed to find the interacting partner of LINC00037 and RNA immunoprecipitation (RIP) was carried out to validate their interaction.We found that knockdown of LINC00037 resulted in inhibited cell proliferation with activated apoptosis and cell cycle arrest in vitro. Over-expression of LINC00037 in LINC00037 knockdown cells restored and enhanced cell proliferation. In vivo mouse model indicated reduced tumor progression by LINC00037 depletion and promoted tumor progression by LINC00037 overexpression. LINC00037 could bind to epidermal growth factor receptor (EGFR) and increase the protein level of EGFR.LINC00037 could inhibit proliferation of ccRCC in an epidermal growth factor receptor-dependent way.
    Tipo de documento:
    Referencia
    Referencia del producto:
    17-700
    Nombre del producto:
    Magna RIP™ RNA-Binding Protein Immunoprecipitation Kit

  • Degradation of cyclin D3 independent of Thr-283 phosphorylation. 16331257

    Cyclin D3 has been shown to play a major role in the regulation of cell cycle progression in lymphocytes. It is therefore important to understand the mechanisms involved in the regulation of this protein. We have previously shown that both basal and cAMP-induced degradation of cyclin D3 in Reh cells is dependent on Thr-283 phosphorylation by glycogen synthase kinase-3beta (GSK-3beta). We now provide evidence of an alternative mechanism being involved in the regulation of cyclin D3 degradation. Treatment of lymphoid cells with okadaic acid (OA), an inhibitor of protein phosphatases 1 and 2A (PP1 and PP2A), induces rapid phosphorylation and proteasomal degradation of cyclin D3. This degradation is not inhibited by the GSK-3beta inhibitors lithium or Kenpaullone, or by substitution of Thr-283 with Ala on cyclin D3, indicating that cyclin D3 can be degraded independently of Thr-283 phosphorylation and GSK-3beta activity. Interestingly, in vitro experiments revealed that PP1, but not PP2A, was able to dephosphorylate cyclin D3 efficiently, and PP1 was found to associate with His-tagged cyclin D3. These results support the hypothesis that PP1 constitutively keeps cyclin D3 in a stable, dephosphorylated state, and that treatment of cells with OA leads to phosphorylation and degradation of cyclin D3 through inhibition of PP1.
    Tipo de documento:
    Referencia
    Referencia del producto:
    06-221

  • Thyroid hormone, retinoic acid, and testosterone suppress proliferation and induce markers of differentiation in cultured rat sertoli cells. 12933640

    This study uses a high purity cell culture system to extend previous observations of factors controlling the end of the Sertoli cell proliferative phase. Thyroid hormone, retinoic acid, and testosterone were assessed for their ability to halt the proliferative phase and regulate the expression of markers associated with maturation of the Sertoli cell. We show that these hormones share similar suppressive effects on the rate of Sertoli cell division without any apparent additive effects. We demonstrate that these hormones induce the progressive accumulation of cell cycle inhibitors p27Kip1 and p21Cip1 in Sertoli cells, a likely regulatory mechanism controlling the suppression of proliferation. We used real-time RT-PCR to examine the effects of these factors on the expression of mRNA encoding the Id proteins, demonstrating an increase in Id2 and Id3 expression in Sertoli cells treated with thyroid hormone, retinoic acid, or testosterone. Finally, we examined the expression of a number of genes that have been implicated in the Sertoli cell differentiation process. Our results suggest that these hormones can induce aspects of Sertoli cell differentiation in vitro, providing a valuable in vitro model for studying Sertoli cell function.
    Tipo de documento:
    Referencia
    Referencia del producto:
    MAB3408
    Nombre del producto:
    Anti-Tubulin Antibody, beta, clone KMX-1

  • Involvement of glycogen synthase kinase-3beta signaling and aberrant nucleocytoplasmic localization of retinoblastoma protein in tumor promotion in a rat two-stage thyroi ... 19505811

    To investigate the cell cycle kinetics during the tumor promotion process induced by hypothyroidism in a rat model of thyroid follicular cell carcinogenesis, immunohistochemical analysis of cell cycle molecules and related signaling molecules was performed in conjunction with analysis of cell proliferation activity in an initiation-promotion model. Male F344 rats were injected with N-bis(2-hydroxypropyl)nitrosamine, and one week later treated with 6-propyl-2-thiouracil (PTU) at 12ppm in the drinking water for 4, 10 or 15 weeks. At each time point, proliferative lesions increased the expression of cyclin A, cyclin D, cyclin E and cyclin-dependent kinase (Cdk)-2, in association with the development of lesion stages from the early focal hyperplasia to the late carcinoma, while a subpopulation of proliferative lesions showed decreased numbers of both cell division cycle-2- and Ki-67-positive cells at week 15 compared with that at week 10, suggesting a reduced promoting effect of serum thyroid-stimulating hormone in the sensitive cellular population after long-term exposure to PTU. On the other hand, increased immunolocalization of phosphorylated and inactive glycogen synthase kinase (GSK)-3beta was observed in a subpopulation of proliferative lesions, in parallel with the cyclins and Cdk2. Nuclear immunoreactivity of phosphorylated and inactive retinoblastoma (Rb) protein was also increased in association with lesion development, with carcinomas showing increased cytoplasmic localization. The results suggest that proliferative lesions activate the cell cycle machinery following tumor promotion via a regulatory mechanism involving inactivation of GSK3beta and Rb protein, the latter signaling mechanism involving its aberrant nucleocytoplasmic transport for the acquisition of a malignant phenotype.
    Tipo de documento:
    Referencia
    Referencia del producto:
    06-137