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Cell reprogramming requires silencing of a core subset of Polycomb targets.

ABSTRACT: Transcription factor (TF)-induced reprogramming of somatic cells into induced pluripotent stem cells (iPSC) is associated with genome-wide changes in chromatin modifications. Polycomb-mediated histone H3 lysine-27 trimethylation (H3K27me3) has been proposed as a defining mark that distinguishes the somatic from the iPSC epigenome. Here, we dissected the functional role of H3K27me3 in TF-induced reprogramming through the inactivation of the H3K27 methylase EZH2 at the onset of reprogramming. Our results demonstrate that surprisingly the establishment of functional iPSC proceeds despite global loss of H3K27me3. iPSC lacking EZH2 efficiently silenced the somatic transcriptome and differentiated into tissues derived from the three germ layers. Remarkably, the genome-wide analysis of H3K27me3 in Ezh2 mutant iPSC cells revealed the retention of this mark on a highly selected group of Polycomb targets enriched for developmental regulators controlling the expression of lineage specific genes. Erasure of H3K27me3 from these targets led to a striking impairment in TF-induced reprogramming. These results indicate that PRC2-mediated H3K27 trimethylation is required on a highly selective core of Polycomb targets whose repression enables TF-dependent cell reprogramming.

ORGANISM(S): Mus musculus

PROVIDER: GSE44972 | GEO | 2013/03/09

SECONDARY ACCESSION(S): PRJNA192668

REPOSITORIES: GEO

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Cell reprogramming requires silencing of a core subset of Polycomb targets.

Project description:Transcription factor (TF)-induced reprogramming of somatic cells into induced pluripotent stem cells (iPSC) is associated with genome-wide changes in chromatin modifications. Polycomb-mediated histone H3 lysine-27 trimethylation (H3K27me3) has been proposed as a defining mark that distinguishes the somatic from the iPSC epigenome. Here, we dissected the functional role of H3K27me3 in TF-induced reprogramming through the inactivation of the H3K27 methylase EZH2 at the onset of reprogramming. Our results demonstrate that surprisingly the establishment of functional iPSC proceeds despite global loss of H3K27me3. iPSC lacking EZH2 efficiently silenced the somatic transcriptome and differentiated into tissues derived from the three germ layers. Remarkably, the genome-wide analysis of H3K27me3 in Ezh2 mutant iPSC cells revealed the retention of this mark on a highly selected group of Polycomb targets enriched for developmental regulators controlling the expression of lineage specific genes. Erasure of H3K27me3 from these targets led to a striking impairment in TF-induced reprogramming. These results indicate that PRC2-mediated H3K27 trimethylation is required on a highly selective core of Polycomb targets whose repression enables TF-dependent cell reprogramming. Genechip microarray analysis was performed respectively on 4 Ezh2 +/+ iPSC clones (control), 4 Ezh2 M-bM-^HM-^FSET/M-bM-^HM-^FSET iPSC clones (experimental), 3 independent preparations of wild type MEF (reference) and one sample of E14Tg2a embryonic stem cells (reference) using Affymetrix Mouse Gene 1.0 ST arrays. Labeling, hybridization, and washing were performed according to Affymetrix guidelines

2013-03-09 | E-GEOD-44972 | biostudies-arrayexpress

Chip-chip from HepG2 cells with EZH2, SUZ12 and H3K27me3

Project description:Polycomb group (PcG) proteins including EZH2, SUZ12 and so on, which specifically catalyze trimethylation of histone 3 lysine 27 (H3K27me3), and methylated H3K27 can be recognized by other specific binding proteins to compress chromatin structure, leading to the transcriptional repression of the target genes. To completely understand the epigenetic profile and molecular network of PcG in HCC, we performed ChIP-on-chip screens with EZH2, SUZ12 and H3K27me3 antibodies in HepG2 cells. Comparison of ChIP-on-chip results from EZH2, SUZ12 and H3K27me3.

2013-11-13 | E-GEOD-52300 | biostudies-arrayexpress

EZHIP / CXorf67 mimics K27M mutated oncohistones and functions as an intrinsic inhibitor of PRC2 function in aggressive posterior fossa ependymoma

Project description:Posterior fossa A (PFA) ependymomas comprise one out of nine molecular groups of ependymoma. PFA tumors are mainly diagnosed in infants and young children, show a poor prognosis and are characterized by a lack of the repressive histone H3 lysine 27 trimethylation (H3K27me3) mark. Recently, we reported CXorf67 overexpression as hallmark of PFA ependymoma and showed that CXorf67 can interact with EZH2 thereby inhibiting polycomb repressive complex 2 (PRC2). Here, we report that the inhibitory mechanism of this interaction is similar as in diffuse midline gliomas harboring H3K27M mutations. A small, highly conserved peptide sequence located in the C-terminal region of CXorf67 mimics the H3K27M peptide and binds to the SET domain of EZH2. This interaction blocks EZH2 methyltransferase activity and causes H3K27 hypomethylation, an oncogenic mechanism that may be exploited for targeted therapy in PFA ependymoma. Based on its function, we have renamed CXorf67 into EZH2 Inhibitory Protein (EZHIP).

2019-07-08 | PXD012318 | Pride

EZH1 and H3K27me3 ChIP-chip data from mouse embryonic stem cells

Project description:Trimethylation on H3K27 (H3K27me3) mediated by Polycomb repressive complex 2 (PRC2) has been linked to embryonic stem cell (ESC) identity and pluripotency. EZH2, the catalytic subunit of PRC2, has been reported as the sole histone methyltransferase that methylates H3K27 and mediates transcriptional silencing. Analysis of Ezh2(-/-) ESCs suggests existence of an additional enzyme(s) catalyzing H3K27 methylation. We have identified EZH1, a homolog of EZH2 that is physically present in a noncanonical PRC2 complex, as an H3K27 methyltransferase in vivo and in vitro. EZH1 colocalizes with the H3K27me3 mark on chromatin and preferentially preserves this mark on development-related genes in Ezh2(-/-) ESCs. Depletion of Ezh1 in cells lacking Ezh2 abolishes residual methylation on H3K27 and derepresses H3K27me3 target genes, demonstrating a role of EZH1 in safeguarding ESC identity. Ezh1 partially complements Ezh2 in executing pluripotency during ESC differentiation, suggesting that cell-fate transitions require epigenetic specificity.

2009-03-25 | GSE15388 | GEO

Chip-chip from HepG2 cells with EZH2, SUZ12 and H3K27me3

2013-11-13 | GSE52300 | GEO

An oncogenic Ezh2 mutation cooperates with particular genetic alterations to induce tumors in mice and redistributes H3K27m3 through the genome [RNA-seq]

Project description:B-cell lymphoma and melanoma harbor recurrent mutations in the gene encoding the EZH2 histone methyltransferase, but the carcinogenic role of these mutations is unclear. Here we describe a mouse model in which the most common somatic EZH2 gain-of-function mutation (Y646F in human, Y641F in the mouse) can be conditionally expressed. Expression of Ezh2Y641F in mouse B-cells or melanocytes caused high-penetrance lymphoma or melanoma, respectively. Bcl2 overexpression or p53 loss, but not c-Myc overexpression, further accelerated lymphoma progression, and expression of mutant B-Raf but not mutant N-Ras further accelerated melanoma progression. Although expression of Ezh2Y641F increased abundance of global H3K27 trimethylation (H3K27me3), it also caused a widespread redistribution of this repressive mark, including a loss of H3K27me3 associated with increased transcription at many loci. These results suggest that Ezh2Y641F induces lymphoma and melanoma through a vast reorganization of chromatin structure inducing both repression and activation of polycomb-regulated loci. B cells: 4 WT vs 4 Y641F samples, Melanoma: WT (480, 855) vs Y641F (480D, 855D) isogenic cell lines differing only for the presence of WT vs Y641F Ezh2.

2016-05-13 | E-GEOD-79035 | biostudies-arrayexpress

Bottom-up proteomics of EZH2 mutants in isogenic cells

Project description:The Enhancer of Zeste 2 Polycomb Repressive Complex 2 Subunit (EZH2) is an essential epigenetic modifier able to methylate lysine 27 on histone H3 (H3K27) to induce chromatin compaction, protein complex recruitment and ultimately transcriptional repression. Hematologic malignancies, including Diffuse Large B cell lymphoma (DLBCL) and Acute myeloid leukemia (AML) have shown a high EZH2-mutation frequency (>20%) associated with poor clinical outcomes. Particularly, two distinct oncogenic mutations, so-called gain-of-function (Y641F and A677G) and loss-of-function (H689A and F667I) are found in the catalytic domain of EZH2. In this study, a comprehensive multi-omics approach was employed to characterize downstream effects of H3K27me3 deposition driven by EZH2 mutations. Human embryonic kidney cells (HEK293T) were transfected to generate three stable EZH2 mutants: EZH2(Y641F), EZH2(A677G), and EZH2(H689A/F667I), which were validated via immunoblotting and DIA-MS-based histone profiling assay. Subsequently, constructs were analyzed under a comprehensive multi-omics approach including label-free whole-cell proteomics, acquired with a Bruker timsTOF Pro HPLC-MS/MS with Ion Mobility. Important protein interactors at nuclear level were dysregulated, such as SMYD3 (SET and MYND domain containing 3), NSD2 (nuclear receptor binding SET domain protein 2) and CHD7 (chromodomain helicase DNA binding protein 7), suggesting a cooperative network of chromatin remodelers for gene expression reprogramming.

2023-10-24 | PXD042875 | Pride

Repressive and active histone methylation mark distinct promoters in human and mouse spermatozoa (Illumina)

Project description:In higher eukaryotes, histone methylation is involved in the maintenance of cellular identity during somatic development. During spermatogenesis, Since most nucleosomes are replaced by protamines during spermatogenesis . Iit is therefore unclear whether if histone modifications function in paternal transmission of epigenetic information. Here we show that H3K4 di-methylation (H3K4me2) and H3K27 tri-methylation (H3K27me3), two modifications important for Trithorax and Polycomb-mediated gene regulation, display methylation-specific distributions at regulatory regions in human spermatozoa. H3K4 dimethylation H3K4me2-marksed promoters of genes relevant control gene functions in spermatogenesis and cellular homeostasis suggesting that this mark reflects germline transcription. In contrast, H3K27 trimethylation (H3K27me3) marks promoters of key developmental regulators in sperm like in somatic cells. Promoters of orthologous genes are similarly modified in mouse spermatozoa. Further, particularly genes with extensive H3K27me3 coverage around transcriptional start sites are never expressed during male and female gametogenesis, nor in pre-implantation embryos. These data are compatible with a function for Polycomb in repressing somatic determinants across generations. Importantly, however, we observe only modest selective retention of nucleosomes at regulatory regions in human sperm suggesting that paternal transmission of H3K27me3-encoded epigenetic information may be subjected to variegation. Identification of nucleosome containing regions in 6 human sperm samples

2010-05-16 | E-GEOD-19889 | biostudies-arrayexpress

A cDNA microarray analysis was performed on shRNA KDs of EZH2, SUZ12, BMI1, or CBX8 HepG2 cells.

Project description:Polycomb group (PcG) proteins including EZH2, SUZ12 ,BMI1,CBX8 and so on, which specifically catalyze trimethylation of histone 3 lysine 27 (H3K27me3), and methylated H3K27 can be recognized by other specific binding proteins to compress chromatin structure, leading to the transcriptional repression of the target genes. To explore a potential functional implication of PcG components in HCC, we stably transfected HepG2 cells with either vectors or constructs expressing shRNA that specifically targets EZH2, SUZ12, BMI1, or CBX8. A cDNA microarray analysis was performed on shRNA KDs of EZH2, SUZ12, BMI1, or CBX8 HepG2 cells. To obtain a broader understanding of the molecular network of PcG in HCC, the whole genome microarray expression profiling was performed on shRNA KDs of EZH2, SUZ12, BMI1, or CBX8 HepG2 cells. Comparison of gene expression results from shRNA KDs of EZH2, SUZ12, BMI1 or CBX8 HepG2 cells.

2014-01-16 | E-GEOD-54108 | biostudies-arrayexpress

EZH2-mediated H3K27 trimethylation mediates neurodegeneration in ataxia-telangiectasia

Project description:The symptoms of ataxia-telangiectasia (A-T) include a progressive neurodegeneration caused by ATM protein deficiency. We previously found that nuclear accumulation of histone deacetylase-4, HDAC4, contributes to this degeneration; we now report that increased histone H3K27 trimethylation (H3K27me3) mediated by polycomb repressive complex 2 (PRC2) also plays an important role in the A-T phenotype. Enhancer of zeste homolog 2 (EZH2), a core catalytic component of PRC2, is identified as a new ATM kinase target, and its S734 phosphorylation reduces protein stability. Thus, PRC2 formation is elevated along with H3K27me3in ATM deficiency. ChIP-sequencing shows a significant increase in H3K27me3 ‘marks’ and a dramatic shift in their location. The change of H3K27me3 chromatin-binding pattern is directly related to cell cycle re-entry and cell death of ATM-deficient neurons. Lentiviral knockdown of EZH2 rescues Purkinje cell degeneration and behavioral abnormalities in Atm / mice, demonstrating that EZH2-mediated H3K27me3 is another key factor in A-T neurodegeneration. Two samples each were run of brain total RNA from Atm+/+ and Atm-/- mice.

2013-10-25 | E-GEOD-50951 | biostudies-arrayexpress

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