Localized phosphorylation of RNA Polymerase II by G1 cyclin-Cdk promotes cell cycle entry
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ABSTRACT:
PROVIDER: PRJNA716055 | ENA |
REPOSITORIES: ENA
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Project description:The cell cycle is thought to be initiated by cyclin-dependent kinases (Cdk) inactivating transcriptional inhibitors of cell cycle gene-expression. In budding yeast, the G1 cyclin Cln3-Cdk1 complex is thought to directly phosphorylate Whi5, thereby releasing the transcription factor SBF and committing cells to division. Here, we report that Cln3-Cdk1 does not phosphorylate Whi5, but instead phosphorylates the RNA Polymerase II subunit Rpb1’s C-terminal domain (CTD) on S5 of its heptapeptide repeats. Cln3-Cdk1 binds SBF-regulated promoters(8) and Cln3’s function can be performed by the canonical S5 kinase Ccl1-Kin28 when synthetically recruited to SBF. Thus, Cln3-Cdk1 triggers cell division by phosphorylating Rpb1 at SBF-regulated promoters to promote transcription. Our findings blur the distinction between cell cycle and transcriptional Cdks to highlight the ancient relationship between these processes.
2021-12-01 | GSE169271 | GEO
Project description:In eukaryotes, cyclin/CDK complexes drive cells through DNA replication and mitosis, establising cell cycle temporal order. The fission yeast S. pombe is able to function with a single cyclin/CDK complex, with cell cycle order emerging from differential substrate sensitivities to CDK activity. What influence cyclin specificity has upon the cell cycle in this situation is currently unknown. Here we show that in a system that is reliant on a single cyclin for both the G1/S and G2/M transition, cyclin specificity is not needed for the G1/S transition, but instead is required for the G2/M transition and correct localisation of cyclin/CDK to the yeast centrosome equivalent, the SPB. This loss of centrosome localisation was also seen in human cells expressing mutant Cyclin B1, suggesting conservation of function. In fission yeast, although interphase centrosomal localisation is lost, mitotic SPB localisation remains. This hitherto unknown second localisation method is dependent on Polo kinase, suggesting a finer spatiotemporal control of cyclin/CDK during cell cycle progression than previously known. Thus, cyclin specificity is intrinsically twinned with spatial control of cyclin/CDK, and we suggest that this regulation may be conserved through evolution.
2019-05-27 | PXD011987 | Pride
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 appropriate ordering of the cell cycle events in eukaryoates is thought to be brought about by qualitative differences in the substrate specificity of multiple differentially expression Cyclin-CDK complexes. Our analysis of fission yeast supports an alternative quantitative model. Here we report a phosphoproteomics based global analysis of CDK substrate phosphorylation. We show that the phosphorylation of different CDK substrates is precisely ordered during the cell cycle by a single Cyclin-CDK complex. This is achieved by the differential sensitivity of substrates to a progressively rising CDK-to-phosphatase activity ratio, with early-phosphorylated substrates more sensitive to CDK activity than late substrates. This is combined with a rapid substrate phosphorylation turnover to generate clearly resolved substrate-specific thresholds, which in turn ensures the temporal ordering of downstream cell cycle events. These observations can also explain the major genetic redundancies between different cyclins and CDKs in higher eukaryotes.
2018-04-11 | PXD003598 | Pride
Project description: Not available
| S-EPMC8608368 | biostudies-literature
Project description: Not available
| S-EPMC3778871 | biostudies-literature
Project description:Cell-cycle transitions are generally triggered by variations in the activity of cyclin-dependent kinases (CDKs) bound to cyclins. Malaria-causing parasites have evolved unique cell-cycles with a repertoire of ancestral CDKs and cyclins whose functions and interdependency remain elusive. Here, we show that the divergent Plasmodium berghei CDK-related kinase 5 (CRK5), is a critical cell-cycle regulator of gametogony required for transmission to the mosquito. It phosphorylates canonical CDK motifs on components of the pre-replicative complex and is essential for DNA replication. We also provide evidence for indirect regulation of the concomitant progression through M-phase. Over a replicative cycle, CRK5 stably interacts with a single Plasmodium-specific cyclin (SOC2) with no evidence of SOC2 cycling through transcription, translation nor degradation. Our results present evidence that during Plasmodium gametogony, a unique and divergent cyclin/CDK pair evolved to fulfil the functional space of multiple eukaryotic cell-cycle kinases controlling S-phase entry and progression through M-phase.
2020-06-17 | GSE144743 | GEO
Project description:Cyclin-dependent kinases (CDKs) complexed with cyclins drive progression through the eukaryotic cell cycle. From yeast to human cells, cyclin-CDK localises to the centrosome, but the importance of this localisation is unclear. The conserved ‘hydrophobic patch’ substrate docking site on human Cyclin B1 and on the equivalent fission yeast Cdc13 mediates their localisation to the centrosome and the spindle-pole body (SPB, yeast centrosome equivalent). A hydrophobic patch mutant (HPM) of Cdc13 cannot enter mitosis, but whether this mitotic defect is due to defective SPB localisation or defective cyclin-substrate docking is unknown. Here we show that artificially restoring Cdc13HPM SPB localisation in fission yeast partially rescues both mitosis and defective CDK substrate phosphorylation at both the SPB and within the cytoplasm. In addition, we found that an HPM of the S-phase cyclin Cig2 has defective SPB localisation but is still able to perform bulk DNA synthesis. Our results demonstrate that the hydrophobic patch mediates the SPB localisation of both S- and M-phase cyclins, and that Cdc13 SPB localisation is essential for mitotic entry and for full phosphorylation of CDK substrates, supporting the view that the centrosome plays a role as a signalling hub regulating CDK cell cycle control.
2024-04-04 | PXD044732 | Pride
Project description:Two models have been put forward for cyclin-dependent kinase (Cdk) control of the cell cycle. In the qualitative model, cell cycle events are ordered by distinct substrate specificities associated with successive waves of G1, S and mitotic cyclins. Alternatively, the gradual quantitative rise of Cdk activity from G1 phase to mitosis could lead to ordered substrate phosphorylation at sequential thresholds. Here, we study the relative contributions of qualitative and quantitative Cdk control in the budding yeast S. cerevisiae. S-phase cyclins can be replaced by a single mitotic cyclin, albeit at the cost of reduced fitness. The single cyclin can in addition replace G1 cyclins to support ordered cell cycle progression, fulfilling key predictions of the quantitative model. However, single-cyclin cells fail to polarize or grow buds and thus cannot sustain proliferation. Our results suggest that budding yeast has become dependent on G1 cyclin specificity to couple cell cycle progression to essential morphogenetic events.
2021-08-23 | PXD022757 | Pride