A Central Role for PRC1 in Shaping the 3D Nuclear Landscape
Ontology highlight
ABSTRACT: 1. Loss of RING1B substantially disrupts nuclear architecture. 2. PRC1 mediated looping can occur at a Mb scale and is independent of CTCF. 3. Polycomb mediated looping is driven by canonical PRC1 complexes. 4. Trimeric PRC1-mediated interactions occur in vitro and in vivo. 5. Gene up-regulation does not directly lead to the loss of PRC1 loops.
Project description:Polycomb repressive complex 1 (PRC1) catalyzes H2A monoubiquitination (uH2A) and regulates pluripotency in embryonic stem cells (ESCs). However the mechanisms controlling PRC1 recruitment and activity are largely unknown. Here we show that Fbxl10 interacts with Ring1B and Nspc1, forming a non-canonical PRC1. We demonstrate that Fbxl10-PRC1 is essential for H2A ubiquitination in mouse ESCs. Genome-wide analyses reveal that Fbxl10 preferentially binds to CpG islands and co-localizes with Ring1B on Polycomb target genes. Notably, Fbxl10 depletion causes modest dissociation of Ring1B but a major loss of uH2A on target genes. Furthermore rescue experiments for Fbxl10 reveal that its DNA binding capability and integration into PRC1 are required for proper H2A ubiquitination. ES cells lacking Fbxl10, like previously characterized Polycomb mutants, show a severely compromised capacity for successful differentiation. Our results shed light on a novel mechanism how CpG islands regulate chromatin function by affecting polycomb recruitment and activity. All ChIP-seq reactions were performed in either untransfected cells, cells expressing scrambled shRNA or Fbxl10 shRNA, Ring1b-/- or Suz12-/- mouse ES cells
Project description:Polycomb repressive complex 1 (PRC1) catalyzes H2A monoubiquitination (uH2A) and regulates pluripotency in embryonic stem cells (ESCs). However the mechanisms controlling PRC1 recruitment and activity are largely unknown. Here we show that Fbxl10 interacts with Ring1B and Nspc1, forming a non-canonical PRC1. We demonstrate that Fbxl10-PRC1 is essential for H2A ubiquitination in mouse ESCs. Genome-wide analyses reveal that Fbxl10 preferentially binds to CpG islands and co-localizes with Ring1B on Polycomb target genes. Notably, Fbxl10 depletion causes modest dissociation of Ring1B but a major loss of uH2A on target genes. Furthermore rescue experiments for Fbxl10 reveal that its DNA binding capability and integration into PRC1 are required for proper H2A ubiquitination. ES cells lacking Fbxl10, like previously characterized Polycomb mutants, show a severely compromised capacity for successful differentiation. Our results shed light on a novel mechanism how CpG islands regulate chromatin function by affecting polycomb recruitment and activity.
Project description:Polycomb repressive complexes (PRCs) play key roles in developmental epigenetic regulation. Yet the mechanisms that target PRCs to specific loci in mammalian cells remain incompletely understood. In this study, we show that Bmi1, a core component of Polycomb Repressive Complex 1 (PRC1), binds directly to the Runx1/CBFbeta transcription factor complex. Genome-wide studies in megakaryocytic cells demonstrate considerable chromatin occupancy overlap between the PRC1 core component Ring1b and Runx1/CBFbeta and functional regulation of a significant fraction of commonly bound genes. Bmi1/Ring1b and Runx1/CBFbeta deficiency generate partial phenocopies of one another in vivo. We also show that Ring1b occupies key Runx1 binding sites in primary murine thymocytes and that this occurs via Polycomb Repressive Complex 2 (PRC2) independent mechanisms. Genetic depletion of Runx1 results in reduced Ring1b binding at these sites in vivo. These findings provide evidence for site-specific PRC1 chromatin recruitment by core binding transcription factors in mammalian cells. shRNA mediated knockdown of CBFb, Ring1b and control in biological triplicate
Project description:Polycomb Repressive Complexes 1 and 2 (PRC1 and 2) play a critical role in the epigenetic regulation of transcription during cellular differentiation, stem cell pluripotency, and neoplastic progression1-3. Here we show that the Polycomb group protein EED, a core component of PRC2, physically interacts with and functions as part of the PRC1 complex. Components of PRC1 and PRC2 compete for EED binding. EED functions to recruit PRC1 to H3K27me3 loci and enhances PRC1 mediated H2A ubiquitin E3 ligase activity. Taken together, we uncover the integral role of EED as an epigenetic exchange factor coordinating the activities of PRC1 and 2. EED, uH2A, RING1A, RING1B, BMI1 and H3K27Me3 ChIP-seq in EED stable knockdown and control Scramble DU145 prostate cancer cell line
Project description:Polycomb repressive complexes (PRCs) play key roles in developmental epigenetic regulation. Yet the mechanisms that target PRCs to specific loci in mammalian cells remain incompletely understood. In this study, we show that Bmi1, a core component of Polycomb Repressive Complex 1 (PRC1), binds directly to the Runx1/CBFbeta transcription factor complex. Genome-wide studies in megakaryocytic cells demonstrate considerable chromatin occupancy overlap between the PRC1 core component Ring1b and Runx1/CBFbeta and functional regulation of a significant fraction of commonly bound genes. Bmi1/Ring1b and Runx1/CBFbeta deficiency generate partial phenocopies of one another in vivo. We also show that Ring1b occupies key Runx1 binding sites in primary murine thymocytes and that this occurs via Polycomb Repressive Complex 2 (PRC2) independent mechanisms. Genetic depletion of Runx1 results in reduced Ring1b binding at these sites in vivo. These findings provide evidence for site-specific PRC1 chromatin recruitment by core binding transcription factors in mammalian cells. ChIP-seq against Runx1, CBFb and Ring1b in L8057 cells (induced & uninduced with biological replicates) and thymocytes from control and Runx1 KO mice
Project description:Embryonic stem (ES) cells express pluripotency-associated genes and repress differentiation-inducible genes. The activities of these genes are coordinately reversed during differentiation. The changes in the transcriptome upon conditional KAP1 knockout in ES cells overlapped with the changes during embryoid body formation. KAP1 repressed differentiation-inducible genes and derepressed pluripotency-associated genes in ES cells. KAP1 formed complexes with polycomb repressive complexes 1 (PRC1) through an interaction that was mediated by the KAP1 coiled-coil region. KAP1 and PRC1 bound cooperatively at the promoters of differentiation-inducible genes and repressed their transcription. In contrast, KAP1 bound the transcribed and flanking sequences of pluripotency-associated genes, did not enhance PRC1 binding, and derepressed their transcription. KAP1 had opposite effects on differentiation-inducible and pluripotency-associated gene transcription both in ES cells and in differentiating embryoid bodies. The region of KAP1 that mediated the interaction with PRC1 was required for KAP1 enhancement of PRC1 binding and for KAP1 repression of transcription at differentiation-inducible promoters. This region of KAP1 was not required for KAP1 suppression of PRC1 binding or for KAP1 derepression of transcription at pluripotency-associated promoters. The opposite effects of KAP1 on transcription of differentiation-inducible versus pluripotency-associated genes contributed to the reciprocal changes in their transcription during differentiation. Analysis of the regions occupied by KAP1(TRIM28/TIF1beta) and by Ring1b(Rnf2) in mouse embryonic stem cells before and after conditional KAP fl/fl and Ring1b fl/fl knockout
Project description:The Polycomb repressive system is an essential chromatin-based regulator of gene expression. Despite being extensively studied, how it selects its target genes is poorly understood and whether its histone modifying activities are required for transcriptional repression remains controversial. Here, we directly test the requirement for PRC1 catalytic activity in Polycomb system function. To achieve this, we develop a new inducible mutation system in embryonic stem cells that completely removes PRC1 catalytic activity. Using this system, we demonstrate that catalysis by PRC1 is important for Polycomb chromatin domain formation and long-range chromatin interactions. Furthermore, we show that variant PRC1 complexes with DNA-binding activities occupy target sites independently of Polycomb chromatin domain formation, providing a putative mechanism for Polycomb target site selection. Finally, we discover that Polycomb-mediated gene repression requires PRC1 catalytic activity. Together these discoveries provide compelling new evidence that PRC1 catalysis is central to Polycomb system function and gene regulation.
Project description:The Polycomb repressive system is an essential chromatin-based regulator of gene expression. Despite being extensively studied, how it selects its target genes is poorly understood and whether its histone modifying activities are required for transcriptional repression remains controversial. Here, we directly test the requirement for PRC1 catalytic activity in Polycomb system function. To achieve this, we develop a new inducible mutation system in embryonic stem cells that completely removes PRC1 catalytic activity. Using this system, we demonstrate that catalysis by PRC1 is important for Polycomb chromatin domain formation and long-range chromatin interactions. Furthermore, we show that variant PRC1 complexes with DNA-binding activities occupy target sites independently of Polycomb chromatin domain formation, providing a putative mechanism for Polycomb target site selection. Finally, we discover that Polycomb-mediated gene repression requires PRC1 catalytic activity. Together these discoveries provide compelling new evidence that PRC1 catalysis is central to Polycomb system function and gene regulation.
Project description:The Polycomb repressive system is an essential chromatin-based regulator of gene expression. Despite being extensively studied, how it selects its target genes is poorly understood and whether its histone modifying activities are required for transcriptional repression remains controversial. Here, we directly test the requirement for PRC1 catalytic activity in Polycomb system function. To achieve this, we develop a new inducible mutation system in embryonic stem cells that completely removes PRC1 catalytic activity. Using this system, we demonstrate that catalysis by PRC1 is important for Polycomb chromatin domain formation and long-range chromatin interactions. Furthermore, we show that variant PRC1 complexes with DNA-binding activities occupy target sites independently of Polycomb chromatin domain formation, providing a putative mechanism for Polycomb target site selection. Finally, we discover that Polycomb-mediated gene repression requires PRC1 catalytic activity. Together these discoveries provide compelling new evidence that PRC1 catalysis is central to Polycomb system function and gene regulation.
Project description:Polycomb repressive complexes (PRCs) play key roles in developmental epigenetic regulation. Yet the mechanisms that target PRCs to specific loci in mammalian cells remain incompletely understood. In this study, we show that Bmi1, a core component of Polycomb Repressive Complex 1 (PRC1), binds directly to the Runx1/CBFbeta transcription factor complex. Genome-wide studies in megakaryocytic cells demonstrate considerable chromatin occupancy overlap between the PRC1 core component Ring1b and Runx1/CBFbeta and functional regulation of a significant fraction of commonly bound genes. Bmi1/Ring1b and Runx1/CBFbeta deficiency generate partial phenocopies of one another in vivo. We also show that Ring1b occupies key Runx1 binding sites in primary murine thymocytes and that this occurs via Polycomb Repressive Complex 2 (PRC2) independent mechanisms. Genetic depletion of Runx1 results in reduced Ring1b binding at these sites in vivo. These findings provide evidence for site-specific PRC1 chromatin recruitment by core binding transcription factors in mammalian cells.