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Paramecium Polycomb Repressive Complex 2 physically interacts with the small RNA binding PIWI protein to repress transposable elements

ABSTRACT: Polycomb Repressive Complex 2 (PRC2) maintains transcriptionally silent genes in a repressed state via deposition of histone H3 K27 trimethyl (me3) marks. PRC2 has also been implicated in silencing transposable elements (TEs) yet how PRC2 is targeted to TEs remains unclear. To address this question, we performed tandem affinity purification combined with mass spectrometry and identified proteins that physically interact with the Paramecium Enhancer-of-zeste Ezl1 enzyme, which catalyzes H3K9me3 and H3K27me3 deposition at TEs. We show that the Paramecium PRC2 core complex comprises four subunits, each required in vivo for catalytic activity. We also identify PRC2 cofactors, including the RNA interference (RNAi) effector Ptiwi09, which are necessary to target H3K9me3 and H3K27me3 to TEs. We find that the physical interaction between PRC2 and the RNAi pathway is mediated by a RING finger protein and that small RNA recruitment of PRC2 to TEs is analogous to the small RNA recruitment of H3K9 methylation SU(VAR)3-9 enzymes.

INSTRUMENT(S): LTQ Orbitrap Velos

ORGANISM(S): Paramecium Tetraurelia

TISSUE(S): Cell Culture

SUBMITTER: Laurent Lignières

LAB HEAD: Guillaume Chevreux

PROVIDER: PXD031335 | Pride | 2022-04-06

REPOSITORIES: Pride

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			Action	DRS
	35830_64366.pep.xml	Pepxml
	35831_64367.pep.xml	Pepxml
	35832_64368.pep.xml	Pepxml
	35833_64369.pep.xml	Pepxml
	40556_67749.pep.xml	Pepxml

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Investigation of small RNA biogenesis and turnover in the absence of the PRC2 associated protein Ded2p

Project description:Heterochromatic histone H3 methylation at lysine 9 (H3K9me2/3) and lysine 27 (H3K27me3) is generally catalyzed by SUV39 and EZH family methyltransferases, respectively, and has distinct functions in most eukaryotes. In contrast, the ciliated protozoan Tetrahymena lacks the SUV39 enzyme, and the EZH enzyme Ezl1p is responsible for the deposition of both H3K9me3 and H3K27me3 during Piwi-directed DNA elimination. Understanding how both modifications are catalyzed by the EZH enzyme should shed light on the mechanism and the evolution of the division of labor between the two heterochromatic histone methyltransferase families in eukaryotes. Here, we show that loss of the novel protein Ded2p abolishes the accumulation of H3K9me3 but not H3K27me3 in Tetrahymena. The phenotypes of DED2 KO cells revealed that H3K27me3 is sufficient for promoting secondary small RNA biogenesis but not for suppressing TEs, assembling heterochromatin bodies and completing DNA elimination. Ded2p associates with Ezl1p through Rnf2p, a component of Tetrahymena Polycomb Repressive Complex 2 (PRC2) to promote the accumulation of H3K9me3. Our results indicate that there are functional distinctions between H3K9me3 and H3K27me3 in different steps of the DNA elimination process and the specificity of the methyltransferase activity of PRC2 can be modulated by its associated factor to catalyze H3K9me3.

2023-04-01 | GSE190308 | GEO

The PIWI-interacting protein Gtsf1 controls the selective degradation of small RNAs in Paramecium

Project description:Ciliates undergo developmentally programmed genome elimination, in which small RNAs direct the removal of target DNA segments, including transposable elements. At each sexual generation, the development of the macronucleus (MAC) requires massive and reproducible elimination of a large proportion of the germline micronuclear (MIC) genome, leading to a highly streamlined somatic MAC genome. 25-nt long scnRNAs are produced from the entire germline MIC genome during meiosis, and this initial complex small RNA population is then transported to the maternal MAC, where selection of scnRNAs corresponding to germline (MIC)-specific sequences is thought to take place. Selected scnRNAs, loaded onto the PIWI protein Ptiwi09, guide the deposition of histone H3 post-translational modifications (H3K9me3 and H3K27me3) onto transposable elements in the developing macronucleus, ultimately triggering their specific elimination. How germline-specific MIC scnRNAs are selected remains to be determined. Here, we provide important mechanistic insights into the scnRNA selection pathway by identifying a Paramecium homolog of Gametocyte specific factor 1 (Gtsf1) as essential for the selective degradation of scnRNAs corresponding to retained somatic MAC sequences. Consistently, we also show that Gstf1 is exclusively localized in the maternal macronucleus, where scnRNA selection is presumed to occur, and associates with the scnRNA-binding protein Ptiwi09. Furthermore, Gtsf1 is necessary for DNA elimination and correct H3K9me3 and H3K27me3 localization in the new developing macronucleus, demonstrating that the scnRNA selection process is important for genome elimination. We propose that Gtsf1 is required for the coordinated degradation of Ptiwi09-scnRNA complexes that pair with nascent RNA transcribed from the maternal MAC genome, similarly to the mechanism suggested for microRNA target-directed degradation in metazoans.

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Paramecium Gtsf1 is an essential nuclear PIWI-interacting protein controlling the selective degradation of small RNAs during programmed DNA elimination

2024-10-17 | PXD045266 | Pride

Reader interactome of epigenetic histone marks in birds

Project description:Lysine methylation is part of the posttranscriptional histone code employed to recruit modification specific readers to chromatin. Unbiased, quantitative mass spectrometry approaches combined with peptide pull-downs have been used to study histone methylation-dependent binders in mammalian cells. Here, we extend the study to birds by investigating the interaction partners for H3K4me3, H3K9me3, H3K27me3 and H3K36me3 in chicken (gallus gallus) and zebra finch (taeniopygia guttata) using label free quantitative proteomics. In general, we find very strong overlap in interaction partners for the trimethyl marks in birds compared to mammals, underscoring the known conserved function of these modifications. In agreement with their epigenetic role, we find binding of PHF2 and members of the TFIID, SAGA, SET1 and NURF complex to the activation mark H3K4me3. Our data furthermore supports the existence of a LID complex in vertebrates recruited to the H3K4me3. The repressive marks are bound by the HP1 proteins and the EED subunit of the PRC2 complex as well as by WIZ. Like the screens in mammals, we found ZNF462, ZNF828 and POGZ enriched at H3K9me3. However, we noted some unexpected differences. First, we did not observe the enrichment of CDYL and CDYL2 at the repressive marks. Second N-PAC (also known as GLYR1), an H3K36me3 interactor in mammals, is not binding to this modification in our screen. This suggests that despite strong conservation of the histone tail sequence, species-specific differences in epigenetic readers may have evolved.

2016-01-04 | PXD002282 | Pride

Genome-wide maps of chromatin state in wild-type and SetDB1 induced knockout mESCs

Project description:We report the application of single-molecule-based sequencing technology for high-throughput profiling of histone modifications in mammalian cells and characterized genome-wide SetDB1 binding and H3K9 trimethylation (H3K9me3) profiles in mouse ES cells and uncovered two distinct classes of SetDB1 binding sites, termed solo and ensemble peaks. The solo peaks were devoid of H3K9me3 and enriched near developmental regulators while the ensemble peaks were associated with H3K9me3. A subset of the SetDB1 solo peaks, particularly those near neural development related genes, was found to be associated with Polycomb Repressive Complex 2 (PRC2) as well as PRC2-interacting proteins Jarid2 and Mtf2. Genetic deletion of Setdb1 dramatically reduced Ezh2 binding as well as histone 3 lysine 27 (H3K27) trimethylation level at SetDB1 solo peaks and facilitated neural differentiation. Furthermore, we found that H3K27me3 inhibits SetDB1 methyltransferase activity in vitro. The currently identified reciprocal action between SetDB1 and PRC2 reveals a novel mechanism underlying ES cell pluripotency and differentiation regulation. Examination of 2 different histone modifications in 2 cell status.

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piRNA production requires heterochromatin formation in Drosophila

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Project description:Polycomb repression of gene expression is critical for development, with a pivotal role for trimethylation of lysine 27 of histone H3 (H3K27me3) deposited by Polycomb Repressive Complex 2 (PRC2). While the function and regulation of PRC2 have been extensively studied, the mechanism(s) by which it is recruited to specific genomic targets has remained largely elusive, in particular in vertebrates. Here we identify the PRC2-associated protein Mtf2 as a novel DNA methylation-sensitive PRC2 recruiter in mouse embryonic stem cells (mESCs). Mtf2 directly binds to DNA and is essential for recruitment of PRC2 both in vitro and in vivo. Genome-wide recruitment of the PRC2 catalytic subunit Ezh2 to genomic targets is drastically impaired in Mtf2 knock-out mESCs, resulting in largely reduced H3K27me3 deposition. Mtf2 selectively binds regions with high density of closely spaced unmethylated CpG-containing motifs with a locally unwound helical structure. This binding is dependent on one of the Mtf2 PHD domains, a protein domain shared among Pcl homologs, and an Mtf2-specific domain. The sequences bound by Mtf2 are enriched in PRC2-repressed CpG island-containing targets in zebrafish, Xenopus, mouse and human, suggesting that Mtf2-mediated PRC2 recruitment to unmethylated genomic regions is conserved among vertebrates.

2018-05-07 | PXD005821 | Pride

Natural variation of H3K27me3 determines genes important for cell fate in the unicellular eukaryotic model Phaeodactylum tricornutum

Project description:In multicellular organisms, tri-methylation of lysine 27 of histone H3 (H3K27me3) was shown to be deposited by Polycomb Repressive Complex 2 (PRC2) to establish and maintain silencing, critical for cell fate and developmentally regulated processes. PRC2 complex is absent in both yeast Saccharomyces cerevisiae and S. pombe which initially suggested that PRC2 arose with the emergence of multicellularity. However, its discovery in several microalgae questions its role in this important class of organisms. Here, we show using mutants of the homologue of catalytic unit of PRC2, enhancer of zeste E(z) in the model diatom P. tricornutum (Pt), which presents different morphotypes (fusiform, triradiate, oval and cruciform) that Pt E(z) is responsible of di and tri-methylation of lysine 27. Indeed, H3K27me3 depletion causes the distortion of the morphology providing evidence for a role of H3K27me3 in cell differentiation in unicellular species. H3K27me3 genome wide profiling in fusiform and triradiate further revealed genes important for cell identity. These results suggest a role of PRC2 and its associated mark in cell fate in unicellular species and their ancestral function in a broad evolutionary context.

2020-12-07 | PXD012347 | Pride

Integrative proteomics reveals a protective role of PRC2 for the ground state pluripotent epigenome

Project description:The ground state of pluripotency is defined as a basal proliferative state free of epigenetic restriction, represented by mouse embryonic stem cells (ESCs) cultured with two kinase inhibitors (so-called “2i”). Through comparison with serum-grown ESCs, we identify epigenetic features characterizing 2i ESCs by proteome profiling of chromatin including post-translational histone modifications. The most prominent difference is H3K27me3 and its enzymatic writer complex PRC2 that are highly abundant on eu- and heterochromatin in 2i ESCs, with H3K27me3 redistributing outside canonical PRC2 targets in a CpG-dependent fashion. Using PRC2-deficient 2i ESCs, we identify epigenetic crosstalk with H3K27me3, including significant increases in H4 acetylation and DNA methylation. This suggests that the unique H3K27me3 configuration protects 2i ESCs from preparation to lineage priming. Interestingly, removal of DNA methylation in PRC2-deficient 2i ESCs lacking H3K27me3 using 5-azacytidine hardly affected ESC viability and transcriptome, showing that ESCs are independent of both major repressive epigenetic marks.

2018-11-21 | PXD007154 | Pride

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