Mus musculus
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PROVIDER: PRJNA243360 | ENA |
REPOSITORIES: ENA
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Project description:The retinoblastoma tumor suppressor protein (Rb) regulates early G1 phase checkpoints, including the DNA damage response, as well as cell cycle exit and differentiation. The widely accepted model of G1 cell cycle progression proposes that cyclin D:Cdk4/6 partially inactivates the Rb tumor suppressor during early G1 phase by progressive multi-phosphorylation, termed hypo-phosphorylation, resulting in release of E2F transcription factors. However, this model remains largely unproven biochemically and the biologically active form(s) of Rb remains unknown. Here we find that Rb is un-phosphorylated in G0 cells and becomes exclusively mono-phosphorylated throughout all of early G1 phase by cyclin D:Cdk4/6. Early G1 phase mono-phosphorylated Rb is composed of 14 independent isoforms that are all targeted by the E1a oncoprotein, but each shows a preferential binding pattern to specific E2F1-4 transcription factors. At the late G1 Restriction Point, cyclin E:Cdk2 inactivates Rb by a quantum hyper-phosphorylation (>12 phosphates/Rb). Cells undergoing a DNA damage response activate cyclin D:Cdk4/6 to generate mono-phosphorylated Rb that regulates global transcription. In contrast, a non-phosphorylatable ?Cdk-Rb allele was non-functional for regulating a DNA damage response, but functional for driving cell cycle exit and differentiation during myogenesis. These observations fundamentally change our understanding of G1 cell cycle progression and show that there is no progressive multi-phosphorylation or hypo-phosphorylation inactivation of Rb during early G1 phase by cyclin D:Cdk4/6. Instead, cyclin D:Cdk4/6 generates functionally active, mono-phosphorylated Rb that is the only Rb isoform present in cells during early G1 phase. Global transcriptional analysis of murine embryonic fibroblasts (MEFs) with conditional deletion of the endogenous RB gene by treatment with cell permeable TAT-Cre. Comparison to unaltered MEFs and MEFs with physiological level of exogenous wildtype or phospho-mutant RB expressed at time of RB gene deletion.
2014-04-03 | E-GEOD-56453 | biostudies-arrayexpress
Project description:The retinoblastoma tumor suppressor protein (Rb) regulates early G1 phase checkpoints, including the DNA damage response, as well as cell cycle exit and differentiation. The widely accepted model of G1 cell cycle progression proposes that cyclin D:Cdk4/6 partially inactivates the Rb tumor suppressor during early G1 phase by progressive multi-phosphorylation, termed hypo-phosphorylation, resulting in release of E2F transcription factors. However, this model remains largely unproven biochemically and the biologically active form(s) of Rb remains unknown. Here we find that Rb is un-phosphorylated in G0 cells and becomes exclusively mono-phosphorylated throughout all of early G1 phase by cyclin D:Cdk4/6. Early G1 phase mono-phosphorylated Rb is composed of 14 independent isoforms that are all targeted by the E1a oncoprotein, but each shows a preferential binding pattern to specific E2F1-4 transcription factors. At the late G1 Restriction Point, cyclin E:Cdk2 inactivates Rb by a quantum hyper-phosphorylation (>12 phosphates/Rb). Cells undergoing a DNA damage response activate cyclin D:Cdk4/6 to generate mono-phosphorylated Rb that regulates global transcription. In contrast, a non-phosphorylatable ?Cdk-Rb allele was non-functional for regulating a DNA damage response, but functional for driving cell cycle exit and differentiation during myogenesis. These observations fundamentally change our understanding of G1 cell cycle progression and show that there is no progressive multi-phosphorylation or hypo-phosphorylation inactivation of Rb during early G1 phase by cyclin D:Cdk4/6. Instead, cyclin D:Cdk4/6 generates functionally active, mono-phosphorylated Rb that is the only Rb isoform present in cells during early G1 phase.
2014-04-03 | GSE56453 | GEO
Project description:The length of the G1 phase in the cell cycle shows significant variability in different cell types and tissue types. To gain insights into the control of G1 length, we generated an E2F activity reporter that captures free E2F activity after dissociation from Rb sequestration and followed its kinetics of activation at the single-cell level, in real time. Our results demonstrate that its activity is precisely coordinated with S phase progression. Quantitative analysis indicates that there is a pre-S phase delay between E2F transcriptional dynamic and activity dynamics. This delay is variable among different cell types and is strongly modulated by the cyclin D/CDK4/6 complex activity through Rb phosphorylation. Our findings suggest that the main function of this complex is to regulate the appropriate timing of G1 length.
2018-11-07 | MODEL1811050001 | BioModels
Project description:Circadian disruption has multiple pathological consequences, but the underlying mechanisms are largely unclear. To address such mechanisms, we subjected cultured cells to chronic circadian desynchrony (CCD), mimicking a chronic jet-lag paradigm, and assayed a range of cellular functions. The results indicated a specific circadian clock-dependent increase in cell proliferation. Transcriptome analysis revealed upregulation of G1-S-phase transition genes (cMyc, CyclinD1/3, Cdt1), concomitant with increased phosphorylation of the Retinoblastoma protein (Rb) by Cyclin D kinase 4/6 (CDK4/6) and increased G1-S progression. Phospho-Rb (Ser807/811) was found to oscillate in a circadian fashion and exhibit phase-shifted rhythms in circadian desynchronized cells. A CDK4/6 inhibitor approved for cancer treatment reduced growth of cultured cells and mouse tumors in a time-of-day specific manner, but the time dependence was lost with CCD. Our study identifies a mechanism that underlies effects of circadian disruption on tumor growth and underscores the importance of treatment timed to endogenous circadian rhythms.
2019-05-14 | GSE119668 | GEO
Project description:Cyclin dependent kinase 4 and 6 (CDK4/6) in complex with D-type cyclins promote cell cycle entry, at least in part through phosphorylation of the retinoblastoma tumor suppressor protein (Rb). The CDK4/6-cyclin D-Rb pathway is commonly deregulated in human cancer, often through CDK4/6 or D-type cyclin overexpression, or inactivation of the CDK4/6 antagonist p16/CDKN2A. Importantly, a substantial fraction of cancers depend on continuous CDK4/6-cyclin D kinase activity and are sensitive to CDK4/6-specific inhibitors. Here, we investigate critical CDK4/6-cyclin D functions that may determine the sensitivity to CDK4/6 inhibitors, making use of the essential roles of CDK4/6 (CDK-4) and cyclin D (CYD-1) in the nematode C. elegans. In an unbiased screen, we found that simultaneous loss of C. elegans Rb (lin-35) and down-regulation of the APC/C substrate specificity factor FZR1/Cdh1 completely overcomes CDK-4/CYD-1 requirement. Furthermore, CDK-4/CYD-1 phosphorylates specific residues in the LIN-35 Rb spacer domain and FZR-1 N-terminus that correspond to inactivating phosphorylations of the human homologs. Thus, CDK-4/CYD-1 appears to promote cell cycle entry by antagonizing not only transcriptional repression by LIN-35 Rb but also protein degradation by APC/CFZR-1. Simultaneous knockdown of Rb and FZR1 in human breast cancer cells synergistically overcomes arrest by the CDK4/6-specific inhibitor PD 00332991. These results reveal APC/CFZR1 as a putative CDK4/6-Cyclin D target and important contributing factor in the response to CDK4/6-inhibitor treatment.
2016-07-05 | PXD001501 | Pride
Project description:Hyper-phosphorylation of RB controls its interaction with E2F and inhibits its tumor suppressor properties. However, during G1 active RB can be mono-phosphorylated on any one of 14 CDK phosphorylation sites. Here we used quantitative proteomics to profile protein complexes formed by each mono-phosphorylated RB isoform (mP-RB) and identified the associated transcriptional outputs. The results show that the 14 sites of mono-phosphorylation co-ordinate RB’s interactions and confer functional specificity. All 14 mP-RBs interact with E2F/DP proteins but they provide different shades of E2F regulation. RB mono-phosphorylation at S811, for example, alters RB transcriptional activity by promoting its association with NuRD complexes. The greatest functional differences between mP-RBs are evident beyond the cell cycle machinery. RB mono-phosphorylation at S811 or T826 stimulates the expression of oxidative phosphorylation genes, increasing cellular oxygen consumption. These results indicate that RB activation signals are integrated in a phosphorylation code that determines the diversity of RB activity.
2019-02-01 | GSE116346 | GEO
Project description:Genomic aberrations of Cyclin D1 (CCND1) and CDK4 in neuroblastoma indicate that dysregulation of the G1 entry checkpoint is an important cell cycle aberration in this pediatric tumor. Here we report that analysis of Affymetrix expression data of primary neuroblastic tumors shows an extensive over-expression of Cyclin D1 and CDK4 which correlates with histological subgroups and prognosis respectively. Immunohistochemical analysis demonstrated an over-expression of Cyclin D1 in neuroblasts and a low Cyclin D1 expression in all cell types in ganglioneuroma. This suggests an involvement of G1 regulating genes in neuronal differentiation processes which we further evaluated using RNA interference against Cyclin D1 and its kinase partner CDK4 in several neuroblastoma cell lines. This resulted in pRb pathway inhibition as shown by an almost complete disappearance of CDK4 specific pRb phosphorylation; reduction of E2F transcriptional activity and a decrease of Cyclin A protein levels. The Cyclin D1 and CDK4 knock-down resulted in a significant reduction in cell proliferation, a G1 specific cell cycle arrest and moreover an extensive neuronal differentiation. Affymetrix microarray profiling of siRNA treated cells revealed a shift in expression profile towards a neuronal phenotype. Several new potential downstream players are identified. We conclude that neuroblastoma functionally depend on over-expression of G1 regulating genes to maintain their undifferentiated phenotype. Experiment Overall Design: The Cell line IMR-32 at time point 0 and transiently transfected with siRNA against GFP, Cyclin D1 and CDK4 at time point 48 hours. All experiments are biological triplicates.
2008-10-25 | E-GEOD-8866 | biostudies-arrayexpress
Project description:The combination of CDK4/6 inhibitors (CDK4/6i) and endocrine therapy (ET) has significantly improved outcomes for patients with hormone receptor-positive (HR+) metastatic breast cancer. However, most patients eventually develop resistance, leading to treatment discontinuation. The therapeutic benefits of maintaining CDK4/6i or transitioning to CDK2 inhibitors (CDK2i) beyond disease progression remain unclear. Here, we show that maintaining CDK4/6i and ET or combining them with CDK2i effectively suppresses the growth of drug-resistant HR+ breast cancer cells by prolonging G1-phase progression. CDK4/6i maintenance triggers a non-canonical pathway for Rb inactivation through post-translational degradation, resulting in attenuated E2F activity and slowed G1 progression. ET further augments this effect by inhibiting c-Myc-mediated E2F amplification. Although the maintenance of CDK4/6i and ET outperforms CDK2i with ET, the triple combination of CDK4/6i, CDK2i, and ET most effectively suppresses both E2F activity and tumor growth. Moreover, while overexpression of both cyclin E and A can promote resistance to the CDK4/6i and CDK2i combination, cyclin E plays a more pivotal role in developing resistance. These findings highlight the potential of sustained CDK4/6i therapy and the incorporation of CDK2i to mitigate resistance in HR+ breast cancer.
2024-10-10 | GSE279160 | GEO
Project description:Genomic aberrations of Cyclin D1 (CCND1) and CDK4 in neuroblastoma indicate that dysregulation of the G1 entry checkpoint is an important cell cycle aberration in this pediatric tumor. Here we report that analysis of Affymetrix expression data of primary neuroblastic tumors shows an extensive over-expression of Cyclin D1 and CDK4 which correlates with histological subgroups and prognosis respectively. Immunohistochemical analysis demonstrated an over-expression of Cyclin D1 in neuroblasts and a low Cyclin D1 expression in all cell types in ganglioneuroma. This suggests an involvement of G1 regulating genes in neuronal differentiation processes which we further evaluated using RNA interference against Cyclin D1 and its kinase partner CDK4 in several neuroblastoma cell lines. This resulted in pRb pathway inhibition as shown by an almost complete disappearance of CDK4 specific pRb phosphorylation; reduction of E2F transcriptional activity and a decrease of Cyclin A protein levels. The Cyclin D1 and CDK4 knock-down resulted in a significant reduction in cell proliferation, a G1 specific cell cycle arrest and moreover an extensive neuronal differentiation. Affymetrix microarray profiling of siRNA treated cells revealed a shift in expression profile towards a neuronal phenotype. Several new potential downstream players are identified. We conclude that neuroblastoma functionally depend on over-expression of G1 regulating genes to maintain their undifferentiated phenotype. Keywords: Neuroblastoma, CCND1, Cyclin D1, CDK4
2008-08-20 | GSE8866 | GEO
Project description:PD-0332991 is a selective inhibitor of the CDK4/6 kinases with the ability to block retinoblastoma (Rb) phosphorylation in the low nanomolar range. Here we investigate the role of CDK4/6 inhibition in human ovarian cancer. We examined the effects of PD-0332991 on proliferation, cell-cycle, apoptosis, and Rb phosphorylation using a panel of 40 established human ovarian cancer cell lines. Molecular markers for response prediction, including p16 and Rb, were studied using gene expression profiling, Western blot, and arrayCGH. Multiple drug effect analysis was used to study interactions with chemotherapeutic drugs. Expression of p16 and Rb was studied using immunohistochemistry in a large clinical cohort ovarian cancer patients. Concentration-dependent anti-proliferative effects of PD-0332991were seen in all ovarian cancer cell lines, but varied significantly between individual lines. Rb proficient cell lines with low p16 expression were most responsive to CDK4/6 inhibition. Copy number variations of CDKN2A, Rb, CCNE1, and CCND1 were associated with response to PD-0332991. CDK4/6 inhibition induced G0/G1 cell cycle arrest, blocked Rb phosphorylation in a concentration and time dependent manner, and enhanced the effects of chemotherapy. Rb proficiency with low p16 expression was seen in 97/262 (37%) of ovarian cancer patients and associated with adverse clinical outcome (progression free survival, adjusted relative risk 1.49, 95%CI 0.99-2.22, p =0.054). PD-0332991 shows promising biologic activity in ovarian cancer cell lines. Assessment of Rb and p16 expression may help select patients most likely to benefit from CDK4/6 inhibition in ovarian cancer. Gene expression of 40 individual ovarian cell lines relative to an ovarian cell line reference mix containing equal amounts of 41 ovarian cell lines (including OCC-1 which was later identified as originating from mouse). The expression data was correllated with cell line growth response to CDK 4/6 inhibitor PD-0332991 to identify genes associated with drug sensitivity and resistance.
2011-01-22 | E-GEOD-26805 | biostudies-arrayexpress