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The Polycomb group protein CBX6 is an essential regulator of embryonic stem cell identity

ABSTRACT: Polycomb group proteins are transcriptional repressors that control cell identity and development. In mammals, at least five different CBX proteins are believed to associate with the core Polycomb repressive complex 1 (PRC1). CBX6 and CBX7 are the most highly expressed CBX proteins in embryonic stem cells (ESCs), yet little is known about the function of CBX6 in these cells. Here we show that CBX6 is an essential regulator of ESC identity, since ablation of CBX6 function destabilizes the pluripotency network and triggers differentiation. At the molecular level, CBX6 is linked to the canonical PRC1 (cPRC1) complex; however, contrary to expectations, our results indicate that CBX6 also has a non-canonical PRC1 function. Taken together, our findings reveal that CBX6 is an essential component for ESC biology and contributes to the structural and functional complexity of the PRC1 complex.

ORGANISM(S): Mus musculus

PROVIDER: GSE98723 | GEO | 2017/09/15

SECONDARY ACCESSION(S): PRJNA386280

REPOSITORIES: GEO

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The Polycomb group protein CBX6 is an essential regulator of embryonic stem cell identity

Project description:Polycomb group proteins are transcriptional repressors that control cell identity and development. In mammals, at least five different CBX proteins are believed to associate with the core Polycomb repressive complex 1 (PRC1). CBX6 and CBX7 are the most highly expressed CBX proteins in embryonic stem cells (ESCs), yet little is known about the function of CBX6 in these cells. Here we show that CBX6 is an essential regulator of ESC identity, since ablation of CBX6 function destabilizes the pluripotency network and triggers differentiation. At the molecular level, CBX6 is linked to the canonical PRC1 (cPRC1) complex; however, contrary to expectations, our results indicate that CBX6 also has a non-canonical PRC1 function. Taken together, our findings reveal that CBX6 is an essential component for ESC biology and contributes to the structural and functional complexity of the PRC1 complex.

2017-09-25 | PXD007577 | Pride

PRC2.1 and PRC2.2 Specific Accessory Proteins Drive Recruitment of Different Forms of Canonical PRC1 [RNA-seq]

Project description:Polycomb repressive complex 2 (PRC2) mediates H3K27me3 deposition, which is thought to recruit canonical PRC1 (cPRC1) via chromodomain-containing CBX proteins to promote stable repression of developmental genes. PRC2 forms two major subcomplexes, PRC2.1 and PRC2.2, but their specific roles remain unclear. Through genetic knockout and replacement of PRC2 subcomplex-specific subunits in naïve and primed pluripotent cells, we uncover distinct roles for PRC2.1 and PRC2.2 in mediating the recruitment of different forms of cPRC1. PRC2.1 catalyses the majority of H3K27me3 at Polycomb target genes and is sufficient to promote recruitment of CBX2/4-cPRC1, but not CBX7-cPRC1. Conversely, while PRC2.2 is poor at catalysing H3K27me3, we find that its accessory protein JARID2 is essential for recruitment of CBX7-cPRC1 and the consequent 3D chromatin interactions at Polycomb target genes. We therefore define distinct contributions of PRC2.1 and PRC2.2 specific accessory proteins to Polycomb mediated repression and uncover a new mechanism for cPRC1 recruitment.

2023-04-06 | GSE199528 | GEO

PRC2.1 and PRC2.2 Specific Accessory Proteins Drive Recruitment of Different Forms of Canonical PRC1 [ChIP]

2023-04-06 | GSE199527 | GEO

PRC2.1 and PRC2.2 Specific Accessory Proteins Drive Recruitment of Different Forms of Canonical PRC1

2023-04-06 | GSE199530 | GEO

PRC2.1 and PRC2.2 Specific Accessory Proteins Drive Recruitment of Different Forms of Canonical PRC1 [4C-seq]

2023-04-06 | GSE199529 | GEO

CBX7 is a tumour suppressor that inhibits bladder cancer

Project description:The Polycomb Group Proteins (PcG) are epigenetic regulatory complexes, dysregulation of which has been associated with multiple biological processes, including maintenance of cell identity, differentiation, proliferation, and cancer progression.PcGs form two multiprotein complexes, Polycomb repressive complex 1 (PRC1) and PRC2(1).The PRC2 protein complex mainly consists of Early embryonic deficient (EED), Suppressor of Zeste (SUZ12) and Enhancer of Zeste (EZH), which can catalyzes the trimethylation of histone H3 lysine 27 (H3K27me3), thereby leaving a transcriptionally repressive mark on the chromatin . Such alterations are recognized and read by canonical PRC1 which is composed of CBX (polycomb), PCGF (polycomb group factor), HPH (human polyhomeotic homolog), and the E3-ligase protein (RING) that catalyzes the monoubiquitination of histone H2A on lysine 119 (H2AK119ub1). The H3K27me3 mark is identified by and binds to the chromodomain within the CBX protein in PRC1, thereby ubiquitinating H2AK119 via the RING proteins. The interaction of PRC2 and PRC1 in chromatin contributes to chromatin compaction and transcriptional silencing of target genes.There are five chromobox proteins in humans, CBX2, 4, 6, 7 and 8. Increasing evidence supports essential roles of CBX proteins in tumorigenesis. Remarkably, CBX proteins have shown an opposite function in distinct cancer types in tumor development. For example, CBX7 is overexpressed in ovarian and prostate cancer , implying its oncogenic role in these tumor types. In contrast, CBX7 functions as a tumor suppressor and loss of CBX7 has been associated with increasing the malignancy grade in bladder, breast, pancreatic, glioma, and colon carcinomas (3 4 5 6 7), but its tumor suppression mechanism is unclear.

2021-06-15 | GSE158244 | GEO

The HDAC inhibitor SAHA regulates CBX2 stability via a SUMO-triggered ubiquitin-mediated pathway in leukemia

Project description:Leukemias are characterized by bone marrow failure due to oncogenic mutations of hematopoietic stem cells (HSC) or blood precursor cells. HSC differentiation and self-renewal properties are tightly regulated by Polycomb group (PcG) proteins, a well-characterized family of transcriptional epigenetic regulators. PcG proteins form two canonical complexes: Polycomb repressive complex 1 (PRC1), and Polycomb repressive complex 2 (PRC2).CBX proteins link the activity of PRC1 with PRC2, serving as critical regulators of PcG-mediating activity. While the functional role of some CBX proteins in cancer has been largely explored, recent reports support the specific role of CBX2 in human tumors, thus it represent a promising new target for anti-cancer strategies. To date, chromodomain inhibitors have been identified for CBX7 , but no molecules inhibiting CBX2 have been described. Nevertheless, different chromatin-modulating drugs such as histone deacetylase inhibitors (HDACi) are reported to regulate CBX2 targets on chromatin, suggesting that HDACi might be used to indirectly modulate aberrant effects of CBX2 in cancer. We describe a novel SAHA-mediated mechanism of CBX2 post-translational regulation. We found that CBX2 undergoes SAHA-induced SUMO2/3 modification and that CBX2 SUMOylation promotes its ubiquitination and proteasome-dependent degradation. We also identified the specific molecular pathway and key players regulating CBX2 stability, demonstrating that CBX4 and RNF4 act as the E3 SUMO and E3 ubiquitin ligase, respectively. Additionally, CBX2-depleted leukemic cells display impaired proliferation, showing that CBX2 is required for leukemia cell clonogenicity. Our study provides the first evidence of a non-canonical SAHA-mediated anti-tumorigenic activity via CBX2 SUMOylation and degradation

2018-02-27 | PXD008287 | Pride

LFQMS of RING2 (RING1B, RNF2) immunoprecipitation from MDA-MB-231 and T47D breast cancer cells

Project description:Polycomb repressive complex PRC1 is essential for gene regulation in numerous cell fate decisions. We show that RING1B (RING2, RNF2) and canonical PRC1 (cPRC1) genes are amplified and overexpressed in breast cancer (BC). Moreover, cPRC1 complexes functionally associate with genes regulated by cell type specific key transcription factors such as estrogen receptor (ER) in ER+ tumor cells and BRD4 in triple negative BC cells. cPRC1 is recruited to active enhancers in a manner independent of PRC2 and RING1B enzymatic activity. RING1B regulates enhancer activity and gene transcription not only by promoting the expression of BC oncogenes but also by regulating chromatin accessibility for oncogenic transcription factors. RING1B recruitment, and thus PRC1 association, to active enhancers occurs in multiple cancers.

2018-10-19 | PXD009570 | Pride

Functional Dissection of Variant Polycomb Repressive Complex 1 Subunits RYBP and YAF2 during Neural Differentiation of Embryonic Stem Cells

Project description:Polycomb repressive complex 1 (PRC1) comprises two different complexes: CBX-containing canonical PRC1 (cPRC1) and RYBP/YAF2-containing variant PRC1 (vPRC1). RYBP-vPRC1 or YAF2-vPRC1 catalyzes H2AK119ub through a positive-feedback model; however, whether RYBP and YAF2 have different regulatory functions is still unclear. Here, we show that the expression of RYBP and YAF2 decreases and increases, respectively, during neural differentiation of embryonic stem cells (ESCs). Rybp knockout impairs neural differentiation by activating Wnt signaling and derepressing nonneuroectoderm-associated genes. However, Yaf2 knockout promotes neural differentiation and leads to redistribution of RYBP binding, increases enrichment of RYBP and H2AK119ub on the RYBP-YAF2 cotargeted genes, and prevents ectopic derepression of nonneuroectoderm-associated genes in neural-differentiated cells. Taken together, this study reveals that RYBP and YAF2 function differentially in regulating mESC neural differentiation.

2023-10-07 | GSE213416 | GEO

Gene expression of mesothelioma cell line ACC-Meso-4 treated with shRNA targeting chromobox (CBX) 6, 7, and 8.

Project description:Chromobox (CBX) family proteins are components in polycomb repressive complex 1 (PRC1), responsible for targeting PRC1 to the chromatin. We studied genes regulated by CBX6, 7, or 8 in human ACC-Meso-4 mesothelioma cell line by microarray analysis of ACC-Meso-4 cells stably expressing short hairpin RNA (shRNA) targeting CBX-6, 7, 8, or control nontarget shRNA.

2019-02-22 | GSE126605 | GEO

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