Differential contribution of the chromatin-associated PP1 binding proteins PNUTS, Repo-Man and Ki-67 to mitotic exit and G1 re-establishment.
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ABSTRACT:
PROVIDER: PRJEB72791 | ENA |
REPOSITORIES: ENA
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Project description:Mitotic exit is an important part of the cell cycle that requires coordination of many chromatin and cytoskeleton remodelling events to successfully complete cell division and maintain cell identity. Protein de-phosphorylation is a key step in directing mitotic exit and protein phosphatase 1 (PP1) is essential to this process. However, the specific contribution of its numerous targeting subunits is still unknown. Here we have investigated the function of three chromatin-associated PP1 targeting subunits in exiting mitosis: Repo-Man, Ki-67 and PNUTS. We have generated endogenously tagged, auxin-degradable alleles for each subunit and used a multi-omic approach to address their specific contribution to transcription resumption, chromatin accessibility and protein phosphorylation at the transition from mitosis to G1. This approach has identified their distinct role in mitotic exit, provided unique datasets for the cell cycle community, and highlighted specific and novel functions for Ki-67 and Repo-Man in genome stability and organisation.
2025-01-01 | E-MTAB-13827 | biostudies-arrayexpress
Project description:Mitotic exit is an important part of the cell cycle that requires coordination of many chromatin and cytoskeleton remodelling events to successfully complete cell division and maintain cell identity. Protein de-phosphorylation is a key step in directing mitotic exit and protein phosphatase 1 (PP1) is essential to this process. However, the specific contribution of its numerous targeting subunits is still unknown. Here we have investigated the function of three chromatin-associated PP1 targeting subunits in exiting mitosis: Repo-Man, Ki-67 and PNUTS. We have generated endogenously tagged, auxin-degradable alleles for each subunit and used a multi-omic approach to address their specific contribution to transcription resumption, chromatin accessibility and protein phosphorylation at the transition from mitosis to G1. This approach has identified their distinct role in mitotic exit, provided unique datasets for the cell cycle community, and highlighted specific and novel functions for Ki-67 and Repo-Man in genome stability and organisation.
2025-01-01 | E-MTAB-13826 | biostudies-arrayexpress
Project description:Differential contribution of the chromatin-associated PP1 binding proteins PNUTS, Repo-Man and Ki-67 to mitotic exit and G1 re-establishment.
| PRJEB72792 | ENA
Project description:Ki-67 molecular functions and properties have remained quite obscure for a long time, despite its importance as a major proliferation marker in clinic. Only recently it has been shown that Ki-67 has a major role in the formation of the mitotic chromosome periphery compartment, and it is a protein phosphatase 1 (PP1) binding protein. Understanding Ki-67 functions at different stages of the cell cycle has been so far hindered by the fact that the different phenotypes observed in cells upon Ki-67 depletion could be the outcome of secondary effects. Here, by using Auxin-inducible-degron (AID) system, we show that Ki-67 degradation at the G1/S boundary causes the disassembly of the replication machinery and leads to DNA damage. This triggers the interferon response and causes replication delay. Our results support the model whereby Ki-67 contributes to replication forks protection, and it is important for timely DNA replication and genome maintenance.
2024-04-13 | PXD037513 | Pride
Project description:Antigen Ki-67 is a nuclear protein expressed in proliferating mammalian cells. It is widely used in cancer histopathology but its functions remain unclear. Here, we show that Ki-67 controls heterochromatin organisation. Altering Ki-67 expression levels did not significantly affect cell proliferation in vivo. Ki-67 mutant mice developed normally and cells lacking Ki-67 proliferated efficiently. Conversely, upregulation of Ki-67 expression in differentiated tissues did not inhibit cell cycle arrest. Ki-67 interactors included proteins involved in nucleolar processes and chromatin regulators. Ki-67 depletion disrupted nucleologenesis but did not inhibit pre-rRNA processing. In contrast, it altered gene expression. Ki-67 silencing also had wide-ranging effects on chromatin organisation, disrupting heterochromatin compaction and long-range genomic interactions. Trimethylation of histone H3K9 and H4K20 at heterochromatin was strongly reduced. Overexpression of human or Xenopus Ki-67 induced ectopic heterochromatin formation. Altogether, our results suggest that Ki-67 expression in proliferating cells spatially organises heterochromatin, thereby controlling gene expression.
2018-10-26 | PXD003551 | Pride
Project description:Ki-67 is highly expressed in proliferating cells, characteristic that made the protein a very important marker widely used in the clinic. However, its molecular functions and properties have remained quite obscure for a long time. Only recently important discoveries have shed some light on Ki-67 function and shown that Ki-67 has a major role in the formation of mitotic chromosome periphery compartment, it is associated with protein phosphatase one (PP1) and regulates chromatin structure in both interphase and mitosis. However, it is still difficult to understand the specific molecular function of this protein since the different phenotypes could be the outcome of secondary effects. In fact, the studies so far conducted have used either RNAi or knock-out cells: the former could lead to phenotypes which are the sum of a cascade of complex events while the latter could be the outcome of compensatory mechanisms taking place. To address these problems, we have generated a cell line system for the rapid manipulation of Ki-67 by introducing an Auxin-inducible-degron (AID) tag in both alleles of the endogenous Ki-67 gene in HCT116 cells. This AID system allows rapid protein depletion by the addition of Auxin.
2024-04-07 | E-MTAB-12279 | biostudies-arrayexpress
Project description:Control of transcription speed, which influences many co-transcriptional processes, is poorly understood. We report that PNUTS-PP1 phosphatase is a negative regulator of RNA pol II elongation rate. The PNUTS W401A mutation, which disrupts PP1 binding, causes genome-wide acceleration of transcription associated with hyper-phosphorylation of the Spt5 elongation factor. Immediately downstream of poly(A) sites, pol II decelerates from >2kb/min to <1 kb/min, which correlates with Spt5 dephosphorylation. Pol II deceleration and Spt5 dephosphorylation require poly(A) site recognition and the PNUTS-PP1 complex, which is in turn necessary for transcription termination. These results lead to a new model for termination, the “sitting duck torpedo” mechanism, where poly(A) site-dependent deceleration caused by PNUTS-PP1 and Spt5 dephosphorylation is required to convert pol II into a viable target for the Xrn2 terminator exonuclease. Spt5 and its bacterial homologue NusG therefore have related functions controlling kinetic competition between RNA polymerases and the termination factors that pursue them.
2019-10-30 | GSE134198 | GEO
Project description:Transcriptional profiling of isogenic human cervical cancer cell line HCT-116, comparing cells treated with control shRNA or with Ki-67 shRNA, grown either in vitro or as tumours in nude mice. The aim was to assess effects of loss of Ki-67 on gene expression during exponential cell growth and in tumours
2021-02-18 | GSE162365 | GEO
Project description:RNA polymerase II progression from initiation to elongation is driven in part by a cascade of protein kinases acting on the core transcription machinery. Conversely, the corresponding phosphatases, notably PP2A and PP1—the most abundant serine-threonine phosphatases in cells—are thought to mainly impede polymerase progression, respectively restraining pause release at promoters and polymerase elongation at terminators. Here we reveal an unexpected role of PP1, within the PNUTS-PP1 complex, in sustaining global transcriptional activation. Acute disruption of PNUTS-PP1 leads to severe defects in the release of paused polymerase and subsequent downregulation for the majority of transcribed genes. Mechanistically, PNUTS-PP1 promotes pause release by dephosphorylating multiple substrates, including the 7SK snRNP subunit MEPCE, a known regulator of pause release. PNUTS-PP1 exhibits antagonistic functions compared to INTAC phosphatase, which generally inhibits pause release. Our research thus highlights the opposing roles of PP1 and PP2A in modulating genome-wide transcriptional pausing and gene expression.
2024-12-02 | GSE279151 | GEO
Project description:RNA polymerase II progression from initiation to elongation is driven in part by a cascade of protein kinases acting on the core transcription machinery. Conversely, the corresponding phosphatases, notably PP2A and PP1—the most abundant serine-threonine phosphatases in cells—are thought to mainly impede polymerase progression, respectively restraining pause release at promoters and polymerase elongation at terminators. Here we reveal an unexpected role of PP1, within the PNUTS-PP1 complex, in sustaining global transcriptional activation. Acute disruption of PNUTS-PP1 leads to severe defects in the release of paused polymerase and subsequent downregulation for the majority of transcribed genes. Mechanistically, PNUTS-PP1 promotes pause release by dephosphorylating multiple substrates, including the 7SK snRNP subunit MEPCE, a known regulator of pause release. PNUTS-PP1 exhibits antagonistic functions compared to INTAC phosphatase, which generally inhibits pause release. Our research thus highlights the opposing roles of PP1 and PP2A in modulating genome-wide transcriptional pausing and gene expression.
2024-12-02 | GSE279150 | GEO