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Fesquet D, Llères D, Grimaud C, Viganò C, Méchali F, Boulon S, Coux O, Bonne-Andrea C, Baldin V. The 20S proteasome activator PA28γ controls the compaction of chromatin. J Cell Sci 2021; 134:134/3/jcs257717. [PMID: 33526472 DOI: 10.1242/jcs.257717] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2020] [Accepted: 12/03/2020] [Indexed: 12/16/2022] Open
Abstract
PA28γ (also known as PSME3), a nuclear activator of the 20S proteasome, is involved in the degradation of several proteins regulating cell growth and proliferation and in the dynamics of various nuclear bodies, but its precise cellular functions remain unclear. Here, using a quantitative FLIM-FRET based microscopy assay monitoring close proximity between nucleosomes in living human cells, we show that PA28γ controls chromatin compaction. We find that its depletion induces a decompaction of pericentromeric heterochromatin, which is similar to what is observed upon the knockdown of HP1β (also known as CBX1), a key factor of the heterochromatin structure. We show that PA28γ is present at HP1β-containing repetitive DNA sequences abundant in heterochromatin and, importantly, that HP1β on its own is unable to drive chromatin compaction without the presence of PA28γ. At the molecular level, we show that this novel function of PA28γ is independent of its stable interaction with the 20S proteasome, and most likely depends on its ability to maintain appropriate levels of H3K9me3 and H4K20me3, histone modifications that are involved in heterochromatin formation. Overall, our results implicate PA28γ as a key factor involved in the regulation of the higher order structure of chromatin.
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Affiliation(s)
- Didier Fesquet
- Centre de Recherche de Biologie cellulaire de Montpellier (CRBM), Université de Montpellier, CNRS, 34293 Montpellier, France
| | - David Llères
- Institut de Génétique Moléculaire de Montpellier (IGMM), Université de Montpellier, CNRS, 34293 Montpellier, France
| | - Charlotte Grimaud
- Institut de Recherche en Cancérologie de Montpellier (IRCM), INSERM U1194, Institut Régional du Cancer (ICM), Université de Montpellier, CNRS Route de Mende, 34293 Montpellier, France
| | - Cristina Viganò
- Centre de Recherche de Biologie cellulaire de Montpellier (CRBM), Université de Montpellier, CNRS, 34293 Montpellier, France
| | - Francisca Méchali
- Centre de Recherche de Biologie cellulaire de Montpellier (CRBM), Université de Montpellier, CNRS, 34293 Montpellier, France
| | - Séverine Boulon
- Centre de Recherche de Biologie cellulaire de Montpellier (CRBM), Université de Montpellier, CNRS, 34293 Montpellier, France
| | - Olivier Coux
- Centre de Recherche de Biologie cellulaire de Montpellier (CRBM), Université de Montpellier, CNRS, 34293 Montpellier, France
| | - Catherine Bonne-Andrea
- Centre de Recherche de Biologie cellulaire de Montpellier (CRBM), Université de Montpellier, CNRS, 34293 Montpellier, France
| | - Véronique Baldin
- Centre de Recherche de Biologie cellulaire de Montpellier (CRBM), Université de Montpellier, CNRS, 34293 Montpellier, France
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Ong JY, Bradley MC, Torres JZ. Phospho-regulation of mitotic spindle assembly. Cytoskeleton (Hoboken) 2020; 77:558-578. [PMID: 33280275 PMCID: PMC7898546 DOI: 10.1002/cm.21649] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2020] [Revised: 10/08/2020] [Accepted: 12/02/2020] [Indexed: 12/23/2022]
Abstract
The assembly of the bipolar mitotic spindle requires the careful orchestration of a myriad of enzyme activities like protein posttranslational modifications. Among these, phosphorylation has arisen as the principle mode for spatially and temporally activating the proteins involved in early mitotic spindle assembly processes. Here, we review key kinases, phosphatases, and phosphorylation events that regulate critical aspects of these processes. We highlight key phosphorylation substrates that are important for ensuring the fidelity of centriole duplication, centrosome maturation, and the establishment of the bipolar spindle. We also highlight techniques used to understand kinase-substrate relationships and to study phosphorylation events. We conclude with perspectives on the field of posttranslational modifications in early mitotic spindle assembly.
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Affiliation(s)
- Joseph Y Ong
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California, USA
| | - Michelle C Bradley
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California, USA
| | - Jorge Z Torres
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California, USA.,Molecular Biology Institute, University of California, Los Angeles, California, USA.,Jonsson Comprehensive Cancer Center, University of California, Los Angeles, California, USA
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Yabuno Y, Uchihashi T, Sasakura T, Shimizu H, Naito Y, Fukushima K, Ota K, Kogo M, Nojima H, Yabuta N. Clathrin heavy chain phosphorylated at T606 plays a role in proper cell division. Cell Cycle 2019; 18:1976-1994. [PMID: 31272276 PMCID: PMC6681784 DOI: 10.1080/15384101.2019.1637201] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2018] [Revised: 06/13/2019] [Accepted: 06/24/2019] [Indexed: 10/26/2022] Open
Abstract
Clathrin regulates mitotic progression, in addition to membrane trafficking. However, the detailed regulatory mechanisms of clathrin during mitosis remain elusive. Here, we demonstrate novel regulation of clathrin during mitotic phase of the cell cycle. Clathrin heavy chain (CHC) was phosphorylated at T606 by its association partner cyclin G-associated kinase (GAK). This phosphorylation was required for proper cell proliferation and tumor growth of cells implanted into nude mice. Immunofluorescence analysis showed that the localization of CHC-pT606 signals changed during mitosis. CHC-pT606 signals localized in the nucleus and at the centrosome during interphase, whereas CHC signals were mostly cytoplasmic. Co-immunoprecipitation suggested that CHC formed a complex with GAK and polo-like kinase 1 (PLK1). Depletion of GAK using siRNA induced metaphase arrest and aberrant localization of CHC-pT606, which abolished Kiz-pT379 (as a phosphorylation target of PLK1) signals on chromatin at metaphase. Taken together, we propose that the GAK_CHC-pT606_PLK1_Kiz-pT379 axis plays a role in proliferation of cancer cells.
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Affiliation(s)
- Yusuke Yabuno
- First Department of Oral and Maxillofacial Surgery, Graduate School of Dentistry, Osaka University, Osaka, Japan
| | - Toshihiro Uchihashi
- First Department of Oral and Maxillofacial Surgery, Graduate School of Dentistry, Osaka University, Osaka, Japan
| | - Towa Sasakura
- Department of Molecular Genetics, Research Institute for Microbial Diseases, Osaka University, Osaka, Japan
| | - Hiroyuki Shimizu
- Department of Molecular Genetics, Research Institute for Microbial Diseases, Osaka University, Osaka, Japan
| | - Yoko Naito
- Department of Molecular Genetics, Research Institute for Microbial Diseases, Osaka University, Osaka, Japan
- Division of Cancer Cell Regulation, Aichi Cancer Center Research Institute, Aichi, Japan
| | - Kohshiro Fukushima
- Department of Molecular Genetics, Research Institute for Microbial Diseases, Osaka University, Osaka, Japan
| | - Kaori Ota
- Department of Molecular Genetics, Research Institute for Microbial Diseases, Osaka University, Osaka, Japan
| | - Mikihiko Kogo
- First Department of Oral and Maxillofacial Surgery, Graduate School of Dentistry, Osaka University, Osaka, Japan
| | - Hiroshi Nojima
- Department of Molecular Genetics, Research Institute for Microbial Diseases, Osaka University, Osaka, Japan
| | - Norikazu Yabuta
- Department of Molecular Genetics, Research Institute for Microbial Diseases, Osaka University, Osaka, Japan
- Department of Oncogene Research, Research Institute for Microbial Diseases, Osaka University, Suita, Osaka, Japan
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4
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Bonnet F, Molina A, Roussat M, Azais M, Bel-Vialar S, Gautrais J, Pituello F, Agius E. Neurogenic decisions require a cell cycle independent function of the CDC25B phosphatase. eLife 2018; 7:32937. [PMID: 29969095 PMCID: PMC6051746 DOI: 10.7554/elife.32937] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2017] [Accepted: 06/08/2018] [Indexed: 01/06/2023] Open
Abstract
A fundamental issue in developmental biology and in organ homeostasis is understanding the molecular mechanisms governing the balance between stem cell maintenance and differentiation into a specific lineage. Accumulating data suggest that cell cycle dynamics play a major role in the regulation of this balance. Here we show that the G2/M cell cycle regulator CDC25B phosphatase is required in mammals to finely tune neuronal production in the neural tube. We show that in chick neural progenitors, CDC25B activity favors fast nuclei departure from the apical surface in early G1, stimulates neurogenic divisions and promotes neuronal differentiation. We design a mathematical model showing that within a limited period of time, cell cycle length modifications cannot account for changes in the ratio of the mode of division. Using a CDC25B point mutation that cannot interact with CDK, we show that part of CDC25B activity is independent of its action on the cell cycle.
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Affiliation(s)
- Frédéric Bonnet
- Centre de Biologie du Développement, Centre de Biologie Intégrative, Université de Toulouse, CNRS, UPS, Toulouse, France
| | - Angie Molina
- Centre de Biologie du Développement, Centre de Biologie Intégrative, Université de Toulouse, CNRS, UPS, Toulouse, France
| | - Mélanie Roussat
- Centre de Biologie du Développement, Centre de Biologie Intégrative, Université de Toulouse, CNRS, UPS, Toulouse, France
| | - Manon Azais
- Centre de Recherches sur la Cognition Animale, Centre de Biologie Intégrative., Université de Toulouse, CNRS, UPS, Toulouse, France
| | - Sophie Bel-Vialar
- Centre de Biologie du Développement, Centre de Biologie Intégrative, Université de Toulouse, CNRS, UPS, Toulouse, France
| | - Jacques Gautrais
- Centre de Recherches sur la Cognition Animale, Centre de Biologie Intégrative., Université de Toulouse, CNRS, UPS, Toulouse, France
| | - Fabienne Pituello
- Centre de Biologie du Développement, Centre de Biologie Intégrative, Université de Toulouse, CNRS, UPS, Toulouse, France
| | - Eric Agius
- Centre de Biologie du Développement, Centre de Biologie Intégrative, Université de Toulouse, CNRS, UPS, Toulouse, France
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Zitouni S, Méchali F, Papin C, Choquet A, Roche D, Baldin V, Coux O, Bonne-Andrea C. The stability of Fbw7α in M-phase requires its phosphorylation by PKC. PLoS One 2017; 12:e0183500. [PMID: 28850619 PMCID: PMC5574586 DOI: 10.1371/journal.pone.0183500] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2017] [Accepted: 08/05/2017] [Indexed: 12/21/2022] Open
Abstract
Fbw7 is a tumor suppressor often deleted or mutated in human cancers. It serves as the substrate-recruiting subunit of a SCF ubiquitin ligase that targets numerous critical proteins for degradation, including oncoproteins and master transcription factors. Cyclin E was the first identified substrate of the SCFFbw7 ubiquitin ligase. In human cancers bearing FBXW7-gene mutations, deregulation of cyclin E turnover leads to its aberrant expression in mitosis. We investigated Fbw7 regulation in Xenopus eggs, which, although arrested in a mitotic-like phase, naturally express high levels of cyclin E. Here, we report that Fbw7α, the only Fbw7 isoform detected in eggs, is phosphorylated by PKC (protein kinase C) at a key residue (S18) in a manner coincident with Fbw7α inactivation. We show that this PKC-dependent phosphorylation and inactivation of Fbw7α also occurs in mitosis during human somatic cell cycles, and importantly is critical for Fbw7α stabilization itself upon nuclear envelope breakdown. Finally, we provide evidence that S18 phosphorylation, which lies within the intrinsically disordered N-terminal region specific to the α-isoform reduces the capacity of Fbw7α to dimerize and to bind cyclin E. Together, these findings implicate PKC in an evolutionarily-conserved pathway that aims to protect Fbw7α from degradation by keeping it transiently in a resting, inactive state.
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Affiliation(s)
- Sihem Zitouni
- Centre de Recherche de Biologie Cellulaire de Montpellier, CNRS, UMR 5237, Université de Montpellier, Montpellier, France
| | - Francisca Méchali
- Centre de Recherche de Biologie Cellulaire de Montpellier, CNRS, UMR 5237, Université de Montpellier, Montpellier, France
| | - Catherine Papin
- Institut de Génétique Humaine, CNRS, UMR 9002, Université de Montpellier, Montpellier, France
| | - Armelle Choquet
- Institut de Génomique Fonctionnelle, CNRS UMR 5203, Université de Montpellier, Montpellier, France
| | - Daniel Roche
- Centre de Recherche de Biologie Cellulaire de Montpellier, CNRS, UMR 5237, Université de Montpellier, Montpellier, France
- Institut de Biologie Computationnelle, LIRMM, CNRS, Université de Montpellier, Montpellier, France
| | - Véronique Baldin
- Centre de Recherche de Biologie Cellulaire de Montpellier, CNRS, UMR 5237, Université de Montpellier, Montpellier, France
| | - Olivier Coux
- Centre de Recherche de Biologie Cellulaire de Montpellier, CNRS, UMR 5237, Université de Montpellier, Montpellier, France
| | - Catherine Bonne-Andrea
- Centre de Recherche de Biologie Cellulaire de Montpellier, CNRS, UMR 5237, Université de Montpellier, Montpellier, France
- * E-mail:
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