Dynamic phosphorylation of G9a by Plk1 and PP2A modulates its catalytic activity and chromosome accessibility during mitosis
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PROVIDER: PRJNA925867 | ENA |
REPOSITORIES: ENA
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Project description:Phosphorylation of Ser10 of histone H3 (H3S10p), together with the adjacent dimethylation of Lys9 (H3K9me2), has been proposed to function as a ‘phospho-methyl switch’ to regulate mitotic chromosome dynamics and control peripheral heterochromatin localization (1, 2). Despite of immensely understanding the regulation of H3S10 phosphorylation, how this modification temporarily masks the H3K9me2 mark during mitosis is poorly understood. Herein, we report that the master mitotic kinase Plk1 phosphorylates G9a at Thr1045 (pT1045) in vitro and in vivo at early mitosis. T1045p inhibits G9a catalytic activity, leading to decrease H3K9me2 levels. RNA-sequencing analysis showed that the phospho-mimic T1045 mutant of G9a (T1045E) compromised its repressive activity on several targeted genes, which was confirmed by luciferase reporter assays. Using genome-wide epigenomic technologies, we found that T1045E mutant displayed reduced H3K9me2 level, accompanied with increased chromatin accessibility, compared to the wild-type G9a cells. Finally, we found that T1045 phosphorylation could be removed by the phosphatase PP2A at late mitosis, which inversely reactivated G9a activity on H3K9me2 level, correlated with lower levels of H3S10p. Therefore, our result may provide a mechanistic explanation for ‘phospho-methyl switch’ and highlight the importance of Plk1 and PP2A-mediated dynamic regulation of G9a during mitosis.
2023-07-17 | GSE223359 | GEO
Project description:Plk1 is a key mitotic kinase that localizes to distinct subcellular structures to promote accurate mitotic progression. Plk1 recruitment depends on direct interaction between polo-box domain (PBD) on Plk1 and PBD binding motif (PBD BM) on the interactors. However, recent study showed that PBD BM alone is not enough for stable binding between CENP-U and Plk1 highlighting the complexity of the interaction which warrants further investigation. An important interactor for Plk1 during mitosis is the checkpoint protein BubR1. Plk1 bound to BubR1 via PBD interaction with pT620 phosphorylates BubR1 S676/T680 to promote BubR1-PP2A/B56 interaction. The BubR1-PP2A/B56 complex counteracts the destablizing effect on kinetochore-microtubule attachments by mitotic kinases to promote mitotic progression.
Here we show that Plk1 phosphorylates T600/T608 on BubR1 and the double phosphorylation is critical for BubR1-Plk1 interaction. A similar mechanism for Plk1-Bub1 interaction also exists indicating a general principle for Plk1 kinetochore recruitment through self-priming. Mechanistically preventing BubR1 T600/T608 phosphorylation impairs chromosome congression and checkpoint silencing by reducing Plk1 and PP2A/B56 binding to BubR1. Increasing the binding affinity towards Plk1 and PP2A/B56 in BubR1 through protein engineering bypasses the requirement of T600/T608 phosphorylation for mitotic progression. These results reveal a new layer of regulation for accurate mitotic progression.
2024-10-31 | MSV000096264 | MassIVE
Project description:Gene expression in eukaryotes is tightly linked to the methylation state of specific lysine residues within the N-terminal region of the core histone proteins. While the mechanisms connecting histone lysine methylation to effector protein recruitment and control of gene activity are increasingly well understood, it remains unknown whether non-histone chromatin proteins are targets for similar modification-recognition systems. Here we show that histone H3 and the H3 methyltransferase G9a share a conserved methylation motif that is both necessary and sufficient to mediate in vivo interaction with the potent epigenetic regulator Heterochromatin Protein 1 (HP1). As with H3, G9a-HP1 interaction is dependent on lysine methylation and can be reversed by adjacent phosphorylation. NMR analysis demonstrates that the HP1 chromodomain recognizes methyl-G9a through a binding mode similar to that used in recognition of methyl-H3, and that adjacent phosphorylation directly antagonizes G9a-HP1 interaction. In addition to uncovering the chromodomain as a generalized methyl-lysine binding module, these data identify histone-like modification cassettes (or âhistone mimicsâ) as an entirely new class of non-histone methylation targets, and directly demonstrate the relevance of the principles underlying the histone code to the regulation of non-histone proteins. Experiment Overall Design: Two independent Affymetrix gene expression microarray analyses were performed on samples from G9a-deleted MEFs reconstituted with empty vector (delta), wild type FLAG-G9a (WT), FLAG-G9a K165A (K165A) or FLAG-G9a H1093K catalytic mutant (H1093K).
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Project description:Phosphatase PP2A expression level is positively correlated to the clinical severity of systemic lupus erythematosus (SLE) and IL17A cytokine overproduction, indicating a potential role of PP2A in controlling TH17 differentiation and inflammation. By generating a mouse strain with the ablation of the catalytic subunit α of PP2A in peripheral mature T cells (PP2A cKO), we provide evidence here that PP2A complex is essential in TH17 differentiation. Hence, PP2A cKO mice exhibited a selective reduction of TH17 cell numbers and an attenuated disease severity in an experimental autoimmune encephalomyelitis (EAE) model. Importantly, PP2A deficiency ablated c-terminal phosphorylation of SMAD2 whereas increased c-terminal phosphorylation of SMAD3. Through direct binding to and regulating the activity of RORγt, the phosphorylational changes of these R-SMADs subsequently reduced Il17a transcription. Finally, PP2A inhibitors recapitulated the phenotype of PP2A cKO mice, i.e., inhibiting TH17 differentiation and protecting mice from EAE. Together, the current study proves that phosphatase PP2A is essential for TH17 differentiation, and inhibition of PP2A could be a possible therapeutic approach for the controlling of TH17-driven autoimmune diseases.
2018-09-13 | GSE119836 | GEO
Project description:The shugoshin proteins are universal protectors of centromeric cohesin during mitosis and meiosis. The binding of human hSgo1 to the PP2A-B56 phosphatase through a coiled coil (CC) region mediates cohesion protection during mitosis. Here we undertook a structure function analysis of the PP2A-B56-hSgo1 complex, revealing unanticipated aspects of complex formation and function. We establish that a highly conserved pocket on the B56 regulatory subunit is required for hSgo1 binding and cohesion protection during mitosis in human somatic cells. Consistent with this, we show that hSgo1 blocks the binding of PP2A-B56 substrates containing a canonical B56 binding motif. We find that PP2A-B56 bound to hSgo1 dephosphorylates Cdk1 sites on hSgo1 itself to modulate cohesin interactions. Collectively our work provides important insight into cohesion protection during mitosis.
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Project description:Polo-like kinase 1 (PLK1) is a serine/threonine kinase required for mitosis and cytokinesis. As cancer cells are often hypersensitive to partial PLK1 inactivation, chemical inhibitors of PLK1 have been developed and tested in clinical trials. However, these molecules alone were not completely effective. PLK1 promotes numerous molecular and cellular events in the cell division cycle. To date, it is unclear which of these events most crucially depend on PLK1 activity. We used a CRISPR-based genome-wide screening strategy to identify genes whose inactivation enhances cell proliferation defects upon partial chemical inhibition of PLK1. Genes identified encode proteins that are functionally linked to PLK1 in multiple ways. Among them, factors that promote centromere and kinetochore function were clearly enriched. In particular, inactivation of the kinesin KIF18A or SKA1 in PLK1-compromised cells results in mitotic defects, activation of the spindle assembly checkpoint and nuclear reassembly defects. Our results suggest that functions of PLK1 at kinetochores are most sensitive to its inhibition, and point at KIF18A as a possible target for combinatorial therapies using existing PLK1 inhibitors.
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Project description:Polo-like kinase 1 (PLK1) protects against genome instability by ensuring timely and accurate mitotic cell division, and its activity is tightly regulated throughout the cell cycle. Although the pathways that initially activate PLK1 in G2 are well-characterized, the factors that directly regulate PLK1 in mitosis remain poorly understood. Here, we identify that human PLK1 activity is sustained by the DNA damage response kinase Checkpoint kinase 2 (Chk2) in mitosis. Chk2 directly phosphorylates PLK1 T210, a residue on its T-loop whose phosphorylation is essential for full PLK1 kinase activity. Loss of Chk2-dependent PLK1 activity causes increased mitotic errors, including chromosome misalignment, chromosome missegregation, and cytokinetic defects. Moreover, Chk2 deficiency increases sensitivity to PLK1 inhibitors, suggesting that Chk2 status may be an informative biomarker for PLK1 inhibitor efficacy. This work demonstrates that Chk2 sustains mitotic PLK1 activity and protects genome stability through discrete functions in interphase DNA damage repair and mitotic chromosome segregation.
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Project description:The Eyes Absent family of proteins (EYA1-4) are a biochemically unique group of tyrosine phosphatases known to be tumour promoting across a range of cancer types. To date, the molecular targets of EYA phosphatase activity remain largely uncharacterised. Here, we identify Polo-like kinase 1 (PLK1) as a direct interactor and phosphatase substrate of both EYA4 and EYA1, with pY445 on PLK1 being the primary target site. EYA-mediated dephosphorylation of PLK1 in the G2 phase of the cell cycle is required for centrosome maturation, PLK1 localization to centrosomes, and polo-box domain (PBD) dependent interactions between PLK1 and the PLK1-activating proteins BORA and CEP192. Molecular dynamics simulations support the rationale that pY445 confers a structural impairment to PBD-substrate interactions that is relieved by EYA-mediated dephosphorylation. Depletion of EYA4 or EYA1, or chemical inhibition of EYA phosphatase activity, dramatically reduces PLK1 activation, causing mitotic defects and cell death. Overall, we have characterized a novel phosphotyrosine signalling network governing PLK1 and mitosis. This work provides a mechanism of cell killing for EYA phosphatase inhibitors with important therapeutic implications.
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Project description:We found that synergy between the antiandrogen abiraterone and Plk1 inhibitors was completely independent of abiraterone's effects on AR signaling. To identify AR-independent effects of abiraterone we designed a comprehensive RNA seq experiment. This identified an AR-independent synergy-specific gene set signature that was induced by abiraterone treatment and was dominated by gene sets related to mitosis and the mitotic spindle. AR-independent effects of abiraterone were isolated by including an enzalutamide treatment arm and by utilizing cancer cell lines that do not express the AR. Synergy-specific gene expression changes were identified by using cell lines that responded synergistically or non-synergistically to combined abiraterone and onvansertib.
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Project description:Transcriptional profiling of HEK293T cells following treatment with a small molecule inhibitor of catalytic activity of the G9a lysine methyltransferase (UNC0638, 1 micromolar, 48 hours), or siRNA against WIZ or G9a (72 hours treatment).
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