Mécanisme de répression par les protéines polycomb

Publications de l’équipe

Année de publication : 2014

Chiara Mozzetta, Julien Pontis, Lauriane Fritsch, Philippe Robin, Manuela Portoso, Caroline Proux, Raphaël Margueron, Slimane Ait-Si-Ali (2014 Jan 7)

The histone H3 lysine 9 methyltransferases G9a and GLP regulate polycomb repressive complex 2-mediated gene silencing.

Molecular cell : 277-89 : DOI : 10.1016/j.molcel.2013.12.005 En savoir plus
Résumé

G9a/GLP and Polycomb Repressive Complex 2 (PRC2) are two major epigenetic silencing machineries, which in particular methylate histone H3 on lysines 9 and 27 (H3K9 and H3K27), respectively. Although evidence of a crosstalk between H3K9 and H3K27 methylations has started to emerge, their actual interplay remains elusive. Here, we show that PRC2 and G9a/GLP interact physically and functionally. Moreover, combining different genome-wide approaches, we demonstrate that Ezh2 and G9a/GLP share an important number of common genomic targets, encoding developmental and neuronal regulators. Furthermore, we show that G9a enzymatic activity modulates PRC2 genomic recruitment to a subset of its target genes. Taken together, our findings demonstrate an unanticipated interplay between two main histone lysine methylation mechanisms, which cooperate to maintain silencing of a subset of developmental genes.

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Année de publication : 2013

Jinsook Son, Steven S Shen, Raphael Margueron, Danny Reinberg (2013 Dec 20)

Nucleosome-binding activities within JARID2 and EZH1 regulate the function of PRC2 on chromatin.

Genes & development : 2663-77 : DOI : 10.1101/gad.225888.113 En savoir plus
Résumé

Polycomb-repressive complex 2 (PRC2) comprises specific members of the Polycomb group of epigenetic modulators. PRC2 catalyzes methylation of histone H3 at Lys 27 (H3K27me3) through its Enhancer of zeste (Ezh) constituent, of which there are two mammalian homologs: Ezh1 and Ezh2. Several ancillary factors, including Jarid2, modulate PRC2 function, with Jarid2 facilitating its recruitment to target genes. Jarid2, like Ezh2, is present in poorly differentiated and actively dividing cells, while Ezh1 associates with PRC2 in all cells, including resting cells. We found that Jarid2 exhibits nucleosome-binding activity that contributes to PRC2 stimulation. Moreover, such nucleosome-binding activity is exhibited by PRC2 comprising Ezh1 (PRC2-Ezh1), in contrast to PRC2-Ezh2. The presence of Ezh1 helps to maintain PRC2 occupancy on its target genes in myoblasts where Jarid2 is not expressed. Our findings allow us to propose a model in which PRC2-Ezh2 is important for the de novo establishment of H3K27me3 in dividing cells, whereas PRC2-Ezh1 is required for its maintenance in resting cells.

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Monica Rolando, Christophe Rusniok, Raphael Margueron, Carmen Buchrieser (2013 Oct 24)

[Host epigenetic targeting by Legionella pneumophila].

Médecine sciences : M/S : 843-5 : DOI : 10.1051/medsci/20132910010 En savoir plus
Résumé

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M Escamilla-Del-Arenal, S T da Rocha, C G Spruijt, O Masui, O Renaud, Arne H Smits, R Margueron, M Vermeulen, E Heard (2013 Oct 23)

Cdyl, a new partner of the inactive X chromosome and potential reader of H3K27me3 and H3K9me2.

Molecular and cellular biology : 5005-20 : DOI : 10.1128/MCB.00866-13 En savoir plus
Résumé

X chromosome inactivation is a remarkable example of chromosome-wide gene silencing and facultative heterochromatin formation. Numerous histone posttranslational modifications, including H3K9me2 and H3K27me3, accompany this process, although our understanding of the enzymes that lay down these marks and the factors that bind to them is still incomplete. Here we identify Cdyl, a chromodomain-containing transcriptional corepressor, as a new chromatin-associated protein partner of the inactive X chromosome (Xi). Using mouse embryonic stem cell lines with mutated histone methyltransferase activities, we show that Cdyl relies on H3K9me2 for its general association with chromatin in vivo. For its association with Xi, Cdyl requires the process of differentiation and the presence of H3K9me2 and H3K27me3, which both become chromosomally enriched following Xist RNA coating. We further show that the removal of the PRC2 component Eed and subsequent loss of H3K27me3 lead to a reduction of both Cdyl and H3K9me2 enrichment on inactive Xi. Finally, we show that Cdyl associates with the H3K9 histone methyltransferase G9a and the MGA protein, both of which are also found on Xi. We propose that the combination of H3K9me2 and H3K27me3 recruits Cdyl to Xi, and this, in turn, may facilitate propagation of the H3K9me2 mark by anchoring G9a.

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Année de publication : 2012

Monica Rolando, Serena Sanulli, Christophe Rusniok, Laura Gomez-Valero, Clement Bertholet, Tobias Sahr, Raphael Margueron, Carmen Buchrieser (2012 Dec 10)

Legionella pneumophila effector RomA uniquely modifies host chromatin to repress gene expression and promote intracellular bacterial replication.

Cell host & microbe : 395-405 : DOI : 10.1016/j.chom.2013.03.004 En savoir plus
Résumé

Histone posttranslational modifications control eukaryotic gene expression and regulate many biological processes including immunity. Pathogens alter host epigenetic control to aid pathogenesis. We find that the intracellular bacterial pathogen Legionella pneumophila uses a Dot/Icm type IV secreted effector, RomA, to uniquely modify the host chromatin landscape. RomA, a SET domain-containing methyltransferase, trimethylates K14 of histone H3, a histone mark not previously described in mammals. RomA localizes to the infected cell nucleus where it promotes a burst of H3K14 methylation and consequently decreases H3K14 acetylation, an activating histone mark, to repress host gene expression. ChIP-seq analysis identified 4,870 H3K14 methylated promoter regions, including innate immune genes. Significantly reduced replication of a RomA-deleted strain in host cells was trans-complemented by wild-type, but not by catalytically inactive, RomA. Thus, a secreted L. pneumophila effector targets the host cell nucleus and modifies histones to repress gene expression and promote efficient intracellular replication.

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Inês Pinheiro, Raphaël Margueron, Nicholas Shukeir, Michael Eisold, Christoph Fritzsch, Florian M Richter, Gerhard Mittler, Christel Genoud, Susumu Goyama, Mineo Kurokawa, Jinsook Son, Danny Reinberg, Monika Lachner, Thomas Jenuwein (2012 Sep 4)

Prdm3 and Prdm16 are H3K9me1 methyltransferases required for mammalian heterochromatin integrity.

Cell : 948-60 : DOI : 10.1016/j.cell.2012.06.048 En savoir plus
Résumé

Heterochromatin serves important functions, protecting genome integrity and stabilizing gene expression programs. Although the Suv39h methyltransferases (KMTs) are known to ensure pericentric H3K9me3 methylation, the mechanisms that initiate and maintain mammalian heterochromatin organization remain elusive. We developed a biochemical assay and used in vivo analyses in mouse embryonic fibroblasts to identify Prdm3 and Prdm16 as redundant H3K9me1-specific KMTs that direct cytoplasmic H3K9me1 methylation. The H3K9me1 is converted in the nucleus to H3K9me3 by the Suv39h enzymes to reinforce heterochromatin. Simultaneous depletion of Prdm3 and Prdm16 abrogates H3K9me1 methylation, prevents Suv39h-dependent H3K9me3 trimethylation, and derepresses major satellite transcription. Most strikingly, DNA-FISH and electron microscopy reveal that combined impairment of Prdm3 and Prdm16 results in disintegration of heterochromatic foci and disruption of the nuclear lamina. Our data identify Prdm3 and Prdm16 as H3K9me1 methyltransferases and expose a functional framework in which anchoring to the nuclear periphery helps maintain the integrity of mammalian heterochromatin.

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Philipp Tropberger, Sebastian Pott, Claudia Keller, Kinga Kamieniarz-Gdula, Matthieu Caron, Florian Richter, Guohong Li, Gerhard Mittler, Edison T Liu, Marc Bühler, Raphael Margueron, Robert Schneider (2012 Apr 4)

Regulation of transcription through acetylation of H3K122 on the lateral surface of the histone octamer.

Cell : 859-72 : DOI : 10.1016/j.cell.2013.01.032 En savoir plus
Résumé

Histone modifications are key regulators of chromatin function. However, little is known to what extent histone modifications can directly impact on chromatin. Here, we address how a modification within the globular domain of histones regulates chromatin function. We demonstrate that H3K122ac can be sufficient to stimulate transcription and that mutation of H3K122 impairs transcriptional activation, which we attribute to a direct effect of H3K122ac on histone-DNA binding. In line with this, we find that H3K122ac defines genome-wide genetic elements and chromatin features associated with active transcription. Furthermore, H3K122ac is catalyzed by the coactivators p300/CBP and can be induced by nuclear hormone receptor signaling. Collectively, this suggests that transcriptional regulators elicit their effects not only via signaling to histone tails but also via direct structural perturbation of nucleosomes by directing acetylation to their lateral surface.

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Jon Mallen-St Clair, Rengin Soydaner-Azeloglu, Kyoung Eun Lee, Laura Taylor, Alexandra Livanos, Yuliya Pylayeva-Gupta, George Miller, Raphaël Margueron, Danny Reinberg, Dafna Bar-Sagi (2012 Mar 7)

EZH2 couples pancreatic regeneration to neoplastic progression.

Genes & development : 439-44 : DOI : 10.1101/gad.181800.111 En savoir plus
Résumé

Although the polycomb group protein Enhancer of Zeste Homolog 2 (EZH2) is well recognized for its role as a key regulator of cell differentiation, its involvement in tissue regeneration is largely unknown. Here we show that EZH2 is up-regulated following cerulein-induced pancreatic injury and is required for tissue repair by promoting the regenerative proliferation of progenitor cells. Loss of EZH2 results in impaired pancreatic regeneration and accelerates KRas(G12D)-driven neoplasia. Our findings implicate EZH2 in constraining neoplastic progression through homeostatic mechanisms that control pancreatic regeneration and provide insights into the documented link between chronic pancreatic injury and an increased risk for pancreatic cancer.

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Année de publication : 2011

Lovorka Stojic, Zuzana Jasencakova, Carolina Prezioso, Alexandra Stützer, Beatrice Bodega, Diego Pasini, Rebecca Klingberg, Chiara Mozzetta, Raphael Margueron, Pier Lorenzo Puri, Dirk Schwarzer, Kristian Helin, Wolfgang Fischle, Valerio Orlando (2011 Sep 7)

Chromatin regulated interchange between polycomb repressive complex 2 (PRC2)-Ezh2 and PRC2-Ezh1 complexes controls myogenin activation in skeletal muscle cells.

Epigenetics & chromatin : 16 : DOI : 10.1186/1756-8935-4-16 En savoir plus
Résumé

Polycomb group (PcG) genes code for chromatin multiprotein complexes that are responsible for maintaining gene silencing of transcriptional programs during differentiation and in adult tissues. Despite the large amount of information on PcG function during development and cell identity homeostasis, little is known regarding the dynamics of PcG complexes and their role during terminal differentiation.

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D B Beck, R Bonasio, S Kaneko, G Li, G Li, R Margueron, H Oda, K Sarma, R J Sims, J Son, P Trojer, D Reinberg (2011 Apr 20)

Chromatin in the nuclear landscape.

Cold Spring Harbor symposia on quantitative biology : 11-22 : DOI : 10.1101/sqb.2010.75.052 En savoir plus
Résumé

Chromatin affects many, if not all aspects, of nuclear organization and function. For this reason, we have focused our attention on elucidating some of the basic mechanisms regulating the formation and maintenance of chromatin, specifically concerning Polycomb repressive complex 2 (PRC2) and PR-Set7. PRC2 is responsible for catalyzing trimethylation of lysine 27 of histone H3 and thus has a critical role in the formation of facultative heterochromatin. PR-Set7 is responsible for catalyzing monomethylation of lysine 20 of histone H4 and is required for proper cell cycle progression and DNA damage response. We have also expanded our work to establish novel techniques and approaches to determine how chromatin is spatially regulated within the nuclear landscape.

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Raphaël Margueron, Danny Reinberg (2011 Jan 21)

The Polycomb complex PRC2 and its mark in life.

Nature : 343-9 : DOI : 10.1038/nature09784 En savoir plus
Résumé

Polycomb group proteins maintain the gene-expression pattern of different cells that is set during early development by regulating chromatin structure. In mammals, two main Polycomb group complexes exist – Polycomb repressive complex 1 (PRC1) and 2 (PRC2). PRC1 compacts chromatin and catalyses the monoubiquitylation of histone H2A. PRC2 also contributes to chromatin compaction, and catalyses the methylation of histone H3 at lysine 27. PRC2 is involved in various biological processes, including differentiation, maintaining cell identity and proliferation, and stem-cell plasticity. Recent studies of PRC2 have expanded our perspectives on its function and regulation, and uncovered a role for non-coding RNA in the recruitment of PRC2 to target genes.

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Année de publication : 2010

Syuzo Kaneko, Gang Li, Jinsook Son, Chong-Feng Xu, Raphael Margueron, Thomas A Neubert, Danny Reinberg (2010 Dec 3)

Phosphorylation of the PRC2 component Ezh2 is cell cycle-regulated and up-regulates its binding to ncRNA.

Genes & development : 2615-20 : DOI : 10.1101/gad.1983810 En savoir plus
Résumé

Ezh2 functions as a histone H3 Lys 27 (H3K27) methyltransferase when comprising the Polycomb-Repressive Complex 2 (PRC2). Trimethylation of H3K27 (H3K27me3) correlates with transcriptionally repressed chromatin. The means by which PRC2 targets specific chromatin regions is currently unclear, but noncoding RNAs (ncRNAs) have been shown to interact with PRC2 and may facilitate its recruitment to some target genes. Here we show that Ezh2 interacts with HOTAIR and Xist. Ezh2 is phosphorylated by cyclin-dependent kinase 1 (CDK1) at threonine residues 345 and 487 in a cell cycle-dependent manner. A phospho-mimic at residue 345 increased HOTAIR ncRNA binding to Ezh2, while the phospho-mimic at residue 487 was ineffectual. An Ezh2 domain comprising T345 was found to be important for binding to HOTAIR and the 5′ end of Xist.

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Guohong Li, Raphael Margueron, Guobin Hu, David Stokes, Yuh-Hwa Wang, Danny Reinberg (2010 Apr 14)

Highly compacted chromatin formed in vitro reflects the dynamics of transcription activation in vivo.

Molecular cell : 41-53 : DOI : 10.1016/j.molcel.2010.01.042 En savoir plus
Résumé

High-order chromatin was reconstituted in vitro. This species reflects the criteria associated with transcriptional regulation in vivo. Histone H1 was determinant to formation of condensed structures, with deacetylated histones giving rise to highly compacted chromatin that approximated 30 nm fibers as evidenced by electron microscopy. Using the PEPCK promoter, we validated the integrity of these templates that were refractory to transcription by attaining transcription through the progressive action of the pertinent factors. The retinoic acid receptor binds to highly compacted chromatin, but the NF1 transcription factor binds only after histone acetylation by p300 and SWI/SNF-mediated nucleosome mobilization, reflecting the in vivo case. Mapping studies revealed the same pattern of nucleosomal repositioning on the PEPCK promoter in vitro and in vivo, correlating with NF1 binding and transcription. The reconstitution of such highly compacted « 30 nm » chromatin that mimics in vivo characteristics should advance studies of its conversion to a transcriptionally active form.

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Raphaël Margueron, Danny Reinberg (2010 Mar 20)

Chromatin structure and the inheritance of epigenetic information.

Nature reviews. Genetics : 285-96 : DOI : 10.1038/nrg2752 En savoir plus
Résumé

Although it is widely accepted that the regulation of the chromatin landscape is pivotal to conveying the epigenetic program, it is still unclear how a defined chromatin domain is reproduced following DNA replication and transmitted from one cell generation to the next. Here, we review the multiple mechanisms that potentially affect the inheritance of epigenetic information in somatic cells. We consider models of how histones might be recycled following replication, and discuss the importance of positive-feedback loops, long-range gene interactions and the complex network of trans-acting factors in the transmission of chromatin states.

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Gang Li, Raphael Margueron, Manching Ku, Pierre Chambon, Bradley E Bernstein, Danny Reinberg (2010 Feb 4)

Jarid2 and PRC2, partners in regulating gene expression.

Genes & development : 368-80 : DOI : 10.1101/gad.1886410 En savoir plus
Résumé

The Polycomb group proteins foster gene repression profiles required for proper development and unimpaired adulthood, and comprise the components of the Polycomb-Repressive Complex 2 (PRC2) including the histone H3 Lys 27 (H3K27) methyltransferase Ezh2. How mammalian PRC2 accesses chromatin is unclear. We found that Jarid2 associates with PRC2 and stimulates its enzymatic activity in vitro. Jarid2 contains a Jumonji C domain, but is devoid of detectable histone demethylase activity. Instead, its artificial recruitment to a promoter in vivo resulted in corecruitment of PRC2 with resultant increased levels of di- and trimethylation of H3K27 (H3K27me2/3). Jarid2 colocalizes with Ezh2 and MTF2, a homolog of Drosophila Pcl, at endogenous genes in embryonic stem (ES) cells. Jarid2 can bind DNA and its recruitment in ES cells is interdependent with that of PRC2, as Jarid2 knockdown reduced PRC2 at its target promoters, and ES cells devoid of the PRC2 component EED are deficient in Jarid2 promoter access. In addition to the well-documented defects in embryonic viability upon down-regulation of Jarid2, ES cell differentiation is impaired, as is Oct4 silencing.

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