The Experts below are selected from a list of 43806 Experts worldwide ranked by ideXlab platform
Robert J Klose - One of the best experts on this subject based on the ideXlab platform.
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PRC1 drives polycomb mediated gene repression by controlling transcription initiation and burst frequency
Nature Structural & Molecular Biology, 2021Co-Authors: Paula Dobrinic, Aleksander T Szczurek, Robert J KloseAbstract:The Polycomb repressive system plays a fundamental role in controlling gene expression during mammalian development. To achieve this, Polycomb repressive complexes 1 and 2 (PRC1 and PRC2) bind target genes and use histone modification-dependent feedback mechanisms to form Polycomb chromatin domains and repress transcription. The inter-relatedness of PRC1 and PRC2 activity at these sites has made it difficult to discover the specific components of Polycomb chromatin domains that drive gene repression and to understand mechanistically how this is achieved. Here, by exploiting rapid degron-based approaches and time-resolved genomics, we kinetically dissect Polycomb-mediated repression and discover that PRC1 functions independently of PRC2 to counteract RNA polymerase II binding and transcription initiation. Using single-cell gene expression analysis, we reveal that PRC1 acts uniformly within the cell population and that repression is achieved by controlling transcriptional burst frequency. These important new discoveries provide a mechanistic and conceptual framework for Polycomb-dependent transcriptional control. Here the authors find that Polycomb repressive complex PRC1 functions independently of PRC2 to counteract Pol II binding, regulating transcription initiation and burst frequency.
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live cell single particle tracking of PRC1 reveals a highly dynamic system with low target site occupancy
Nature Communications, 2021Co-Authors: Miles K Huseyin, Robert J KloseAbstract:Polycomb repressive complex 1 (PRC1) is an essential chromatin-based repressor of gene transcription. How PRC1 engages with chromatin to identify its target genes and achieve gene repression remains poorly defined, representing a major hurdle to our understanding of Polycomb system function. Here, we use genome engineering and single particle tracking to dissect how PRC1 binds to chromatin in live mouse embryonic stem cells. We observe that PRC1 is highly dynamic, with only a small fraction stably interacting with chromatin. By integrating subunit-specific dynamics, chromatin binding, and abundance measurements, we discover that PRC1 exhibits low occupancy at target sites. Furthermore, we employ perturbation approaches to uncover how specific components of PRC1 define its kinetics and chromatin binding. Together, these discoveries provide a quantitative understanding of chromatin binding by PRC1 in live cells, suggesting that chromatin modification, as opposed to PRC1 complex occupancy, is central to gene repression. How PRC1 recognises and interacts with its target genes remains poorly understood. Here, the authors use genome engineering and single particle tracking to dissect how PRC1 binds to chromatin in live mouse embryonic stem cells, revealing that this repressor is highly dynamic, with only a small fraction stably interacting with chromatin.
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PRC1 drives polycomb mediated gene repression by controlling transcription initiation and burst frequency
bioRxiv, 2020Co-Authors: Paula Dobrinic, Aleksander T Szczurek, Robert J KloseAbstract:The Polycomb repressive system plays a fundamental role in controlling gene expression during mammalian development. To achieve this, Polycomb repressive complexes 1 and 2 (PRC1 and PRC2) bind target genes and use histone modification-dependent feedback mechanisms to form Polycomb chromatin domains and repress transcription. The interrelatedness of PRC1 and PRC2 activity at these sites has made it difficult to discover the specific components of Polycomb chromatin domains that drive gene repression and to understand mechanistically how this is achieved. Here, by exploiting rapid degron-based approaches and time-resolved genomics we kinetically dissect Polycomb-mediated repression and discover that PRC1 functions independently of PRC2 to counteract RNA polymerase II binding and transcription initiation. Using single-cell gene expression analysis, we reveal that PRC1 acts uniformly within the cell population, and that repression is achieved by controlling transcriptional burst frequency. These important new discoveries provide a mechanistic and conceptual framework for Polycomb-dependent transcriptional control.
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live cell single particle tracking of PRC1 reveals a highly dynamic system with low target site occupancy
bioRxiv, 2020Co-Authors: Miles K Huseyin, Robert J KloseAbstract:Polycomb repressive complex 1 (PRC1) is an essential chromatin-based repressor of gene transcription. However, how PRC1 engages with chromatin to identify its target genes and achieve gene repression remains poorly defined, representing a major hurdle to our understanding of Polycomb system function. Here we use genome engineering and single particle tracking to dissect how PRC1 binds to chromatin in live mouse embryonic stem cells. We reveal that PRC1 is highly dynamic, with only a small fraction stably interacting with chromatin. By integrating subunit-specific dynamics, chromatin binding, and abundance measurements, we discover that PRC1 exhibits surprisingly low occupancy at target sites. Furthermore, we employ perturbation approaches to uncover how specific components of PRC1 define its kinetics and chromatin binding. Together, these discoveries provide a quantitative understanding of chromatin binding by PRC1 in live cells, and suggests that chromatin modification, as opposed to PRC1 complex occupancy, is central to gene repression.
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PRC1 catalytic activity is central to polycomb system function
Molecular Cell, 2020Co-Authors: Neil P Blackledge, Miles K Huseyin, Nadezda A Fursova, Jessica R Kelley, Angelika Feldmann, Robert J KloseAbstract:The Polycomb repressive system is an essential chromatin-based regulator of gene expression. Despite being extensively studied, how the Polycomb system 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 conditional mutation system in embryonic stem cells that completely removes PRC1 catalytic activity. Using this system, we demonstrate that catalysis by PRC1 drives 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 PRC1 catalytic activity, 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 evidence that PRC1 catalysis is central to Polycomb system function and gene regulation.
Wei Jiang - One of the best experts on this subject based on the ideXlab platform.
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Spatiotemporal control of spindle midzone formation by PRC1 in human cells
Proceedings of the National Academy of Sciences of the United States of America, 2006Co-Authors: Changjun Zhu, Eric H. Y. Lau, Robert Schwarzenbacher, Ella Bossy-wetzel, Wei JiangAbstract:We have examined the role of PRC1, a midzone-associated, microtubule bundling, Cdk substrate protein, in regulating the spatiotemporal formation of the midzone in HeLa cells. Cdk-mediated phosphorylation of PRC1 in early mitosis holds PRC1 in an inactive monomeric state. During the metaphase-to-anaphase transition, PRC1 is dephosphorylated, promoting PRC1 oligomerization. Using time-lapse video microscopy, RNA interference, 3D immunofluorescence reconstruction imaging, and rescue experiments, we demonstrate that the dephosphorylated form of PRC1 is essential for bundling antiparallel, nonkinetochore, interdigitating microtubules to establish the midzone that is necessary for cytokinesis. Our results thus indicate that PRC1 is an essential factor in controlling the spatiotemporal formation of the midzone in human cells.
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cell cycle dependent translocation of PRC1 on the spindle by kif4 is essential for midzone formation and cytokinesis
Proceedings of the National Academy of Sciences of the United States of America, 2005Co-Authors: Changjun Zhu, Wei JiangAbstract:The spindle midzone, a conspicuous network of antiparallel interdigitating nonkinetochore microtubules between separating chromosomes, plays a crucial role in regulating the initiation and completion of cytokinesis. In this study, we report the use of time-lapse microscopy and a human kinesin endoribonucleases RNase III-prepared short interfering RNA (esiRNA) library to identify Kif4 as a motor protein that translocates PRC1, a spindle midzone-associated cyclin-dependent kinase substrate protein, to the plus ends of interdigitating spindle microtubules during the metaphase-to-anaphase transition. We show that Kif4 binds to PRC1 through its “stalk plus tail” domains and Kif4 and PRC1 colocalize on the spindle midzone/midbody during anaphase and cytokinesis. Suppression of Kif4 expression by Kif4 esiRNA results in the inhibition of PRC1 translocation, a block of the midzone formation, and a failure of cytokinesis. PRC1 translocation and midzone formation can be restored, and the cytokinetic defects can be rescued in Kif4 esiRNA-treated cells by coexpression of Kif4 but not its motor dead mutant Kif4md. Furthermore, we show that cyclin-dependent kinase phosphorylation of PRC1 controls the timing of PRC1 translocation by Kif4. These results, in light of the crucial role of PRC1 in midzone formation, indicate that cell cycle-dependent translocation of PRC1 by Kif4 is essential for midzone formation and cytokinesis.
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PRC1 is a microtubule binding and bundling protein essential to maintain the mitotic spindle midzone
Journal of Cell Biology, 2002Co-Authors: Cristiana Mollinari, Jean-philippe Kleman, Wei Jiang, Tony Hunter, Guy Schoehn, Robert L MargolisAbstract:Midzone microtubules of mammalian cells play an essential role in the induction of cell cleavage, serving as a platform for a number of proteins that play a part in cytokinesis. We demonstrate that PRC1, a mitotic spindle-associated Cdk substrate that is essential to cell cleavage, is a microtubule binding and bundling protein both in vivo and in vitro. Overexpression of PRC1 extensively bundles interphase microtubules, but does not affect early mitotic spindle organization. PRC1 contains two Cdk phosphorylation motifs, and phosphorylation is possibly important to mitotic suppression of bundling, as a Cdk phosphorylation-null mutant causes extensive bundling of the prometaphase spindle. Complete suppression of PRC1 by siRNA causes failure of microtubule interdigitation between half spindles and the absence of a spindle midzone. Truncation mutants demonstrate that the NH 2 -terminal region of PRC1, rich in α-helical sequence, is important for localization to the cleavage furrow and to the center of the midbody, whereas the central region, with the highest sequence homology between species, is required for microtubule binding and bundling activity. We conclude that PRC1 is a microtubule-associated protein required to maintain the spindle midzone, and that distinct functions are associated with modular elements of the primary sequence.
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PRC1 a human mitotic spindle associated cdk substrate protein required for cytokinesis
Molecular Cell, 1998Co-Authors: Wei Jiang, Gretchen S Jimenez, Nicholas J Wells, Thomas J Hope, Geoffrey M Wahl, Tony Hunter, Rikiro FukunagaAbstract:Abstract We have identified a novel human protein, PRC1, that is involved in cytokinesis. PRC1 is a good substrate for several CDKs in vitro and is phosphorylated in vivo at sites that are phosphorylated by CDK in vitro, strongly suggesting that PRC1 is an in vivo CDK substrate. PRC1 has sequence homology to the budding yeast anaphase spindle elongation factor Ase1p. Like Ase1p, PRC1 protein levels are high during S and G2/M and drop dramatically after cells exit mitosis and enter G1. PRC1 is a nuclear protein in interphase, becomes associated with mitotic spindles in a highly dynamic manner during mitosis, and localizes to the cell midbody during cytokinesis. Microinjection of anti-PRC1 antibodies into HeLa cells blocked cellular cleavage, but not nuclear division, indicating a functional role for PRC1 in the process of cytokinesis.
Miles K Huseyin - One of the best experts on this subject based on the ideXlab platform.
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live cell single particle tracking of PRC1 reveals a highly dynamic system with low target site occupancy
Nature Communications, 2021Co-Authors: Miles K Huseyin, Robert J KloseAbstract:Polycomb repressive complex 1 (PRC1) is an essential chromatin-based repressor of gene transcription. How PRC1 engages with chromatin to identify its target genes and achieve gene repression remains poorly defined, representing a major hurdle to our understanding of Polycomb system function. Here, we use genome engineering and single particle tracking to dissect how PRC1 binds to chromatin in live mouse embryonic stem cells. We observe that PRC1 is highly dynamic, with only a small fraction stably interacting with chromatin. By integrating subunit-specific dynamics, chromatin binding, and abundance measurements, we discover that PRC1 exhibits low occupancy at target sites. Furthermore, we employ perturbation approaches to uncover how specific components of PRC1 define its kinetics and chromatin binding. Together, these discoveries provide a quantitative understanding of chromatin binding by PRC1 in live cells, suggesting that chromatin modification, as opposed to PRC1 complex occupancy, is central to gene repression. How PRC1 recognises and interacts with its target genes remains poorly understood. Here, the authors use genome engineering and single particle tracking to dissect how PRC1 binds to chromatin in live mouse embryonic stem cells, revealing that this repressor is highly dynamic, with only a small fraction stably interacting with chromatin.
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live cell single particle tracking of PRC1 reveals a highly dynamic system with low target site occupancy
bioRxiv, 2020Co-Authors: Miles K Huseyin, Robert J KloseAbstract:Polycomb repressive complex 1 (PRC1) is an essential chromatin-based repressor of gene transcription. However, how PRC1 engages with chromatin to identify its target genes and achieve gene repression remains poorly defined, representing a major hurdle to our understanding of Polycomb system function. Here we use genome engineering and single particle tracking to dissect how PRC1 binds to chromatin in live mouse embryonic stem cells. We reveal that PRC1 is highly dynamic, with only a small fraction stably interacting with chromatin. By integrating subunit-specific dynamics, chromatin binding, and abundance measurements, we discover that PRC1 exhibits surprisingly low occupancy at target sites. Furthermore, we employ perturbation approaches to uncover how specific components of PRC1 define its kinetics and chromatin binding. Together, these discoveries provide a quantitative understanding of chromatin binding by PRC1 in live cells, and suggests that chromatin modification, as opposed to PRC1 complex occupancy, is central to gene repression.
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PRC1 catalytic activity is central to polycomb system function
Molecular Cell, 2020Co-Authors: Neil P Blackledge, Miles K Huseyin, Nadezda A Fursova, Jessica R Kelley, Angelika Feldmann, Robert J KloseAbstract:The Polycomb repressive system is an essential chromatin-based regulator of gene expression. Despite being extensively studied, how the Polycomb system 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 conditional mutation system in embryonic stem cells that completely removes PRC1 catalytic activity. Using this system, we demonstrate that catalysis by PRC1 drives 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 PRC1 catalytic activity, 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 evidence that PRC1 catalysis is central to Polycomb system function and gene regulation.
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PRC1 catalytic activity is central to polycomb system function
bioRxiv, 2019Co-Authors: Neil P Blackledge, Miles K Huseyin, Nadezda A Fursova, Jessica R Kelley, Angelika Feldmann, Robert J KloseAbstract:Summary The Polycomb repressive system is an essential chromatin-based regulator of gene expression. Despite being extensively studied, how its target genes are selected 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. We demonstrate that a mutation widely used to disrupt PRC1 catalysis is hypomorphic, complicating the interpretation of previous studies. To overcome this, we develop a new inducible mutation system in embryonic stem cells that completely ablates PRC1 catalytic activity, revealing that catalysis by PRC1 drives Polycomb chromatin domain formation and higher-order chromatin interactions. In the absence of catalysis, we uncover the primary DNA-based targeting determinants that direct Polycomb target site selection. Finally, we discover that Polycomb-mediated gene repression requires PRC1 catalytic activity. Together these discoveries provide compelling new evidence supporting a PRC1-initiated pathway for Polycomb system function in gene regulation.
Neil P Blackledge - One of the best experts on this subject based on the ideXlab platform.
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PRC1 catalytic activity is central to polycomb system function
Molecular Cell, 2020Co-Authors: Neil P Blackledge, Miles K Huseyin, Nadezda A Fursova, Jessica R Kelley, Angelika Feldmann, Robert J KloseAbstract:The Polycomb repressive system is an essential chromatin-based regulator of gene expression. Despite being extensively studied, how the Polycomb system 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 conditional mutation system in embryonic stem cells that completely removes PRC1 catalytic activity. Using this system, we demonstrate that catalysis by PRC1 drives 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 PRC1 catalytic activity, 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 evidence that PRC1 catalysis is central to Polycomb system function and gene regulation.
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PRC1 catalytic activity is central to polycomb system function
bioRxiv, 2019Co-Authors: Neil P Blackledge, Miles K Huseyin, Nadezda A Fursova, Jessica R Kelley, Angelika Feldmann, Robert J KloseAbstract:Summary The Polycomb repressive system is an essential chromatin-based regulator of gene expression. Despite being extensively studied, how its target genes are selected 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. We demonstrate that a mutation widely used to disrupt PRC1 catalysis is hypomorphic, complicating the interpretation of previous studies. To overcome this, we develop a new inducible mutation system in embryonic stem cells that completely ablates PRC1 catalytic activity, revealing that catalysis by PRC1 drives Polycomb chromatin domain formation and higher-order chromatin interactions. In the absence of catalysis, we uncover the primary DNA-based targeting determinants that direct Polycomb target site selection. Finally, we discover that Polycomb-mediated gene repression requires PRC1 catalytic activity. Together these discoveries provide compelling new evidence supporting a PRC1-initiated pathway for Polycomb system function in gene regulation.
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Synergy between variant PRC1 complexes defines polycomb-mediated gene repression
'Elsevier BV', 2019Co-Authors: Na Fursova, Neil P Blackledge, Nakayama M, Ito S, Koseki Y, Am Farcas, Hw King, Koseki H, Rj KloseAbstract:The Polycomb system modifies chromatin and plays an essential role in repressing gene expression to control normal mammalian development. However, the components and mechanisms that define how Polycomb protein complexes achieve this remain enigmatic. Here, we use combinatorial genetic perturbation coupled with quantitative genomics to discover the central determinants of Polycomb-mediated gene repression in mouse embryonic stem cells. We demonstrate that canonical Polycomb repressive complex 1 (PRC1), which mediates higher-order chromatin structures, contributes little to gene repression. Instead, we uncover an unexpectedly high degree of synergy between variant PRC1 complexes, which is fundamental to gene repression. We further demonstrate that variant PRC1 complexes are responsible for distinct pools of H2A monoubiquitylation that are associated with repression of Polycomb target genes and silencing during X chromosome inactivation. Together, these discoveries reveal a new variant PRC1-dependent logic for Polycomb-mediated gene repression
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variant PRC1 complex dependent h2a ubiquitylation drives prc2 recruitment and polycomb domain formation
Cell, 2014Co-Authors: Neil P Blackledge, Joanna F. Mcgouran, Sarah Cooper, Anca M Farcas, Takashi Kondo, Hamish W King, Lars L P Hanssen, Shinsuke Ito, Kaori Kondo, Yoko KosekiAbstract:Chromatin modifying activities inherent to polycomb repressive complexes PRC1 and PRC2 play an essential role in gene regulation, cellular differentiation, and development. However, the mechanisms by which these complexes recognize their target sites and function together to form repressive chromatin domains remain poorly understood. Recruitment of PRC1 to target sites has been proposed to occur through a hierarchical process, dependent on prior nucleation of PRC2 and placement of H3K27me3. Here, using a de novo targeting assay in mouse embryonic stem cells we unexpectedly discover that PRC1-dependent H2AK119ub1 leads to recruitment of PRC2 and H3K27me3 to effectively initiate a polycomb domain. This activity is restricted to variant PRC1 complexes, and genetic ablation experiments reveal that targeting of the variant PCGF1/PRC1 complex by KDM2B to CpG islands is required for normal polycomb domain formation and mouse development. These observations provide a surprising PRC1-dependent logic for PRC2 occupancy at target sites in vivo.
Danny Reinberg - One of the best experts on this subject based on the ideXlab platform.
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USP7 cooperates with SCML2 to regulate the activity of PRC1.
Molecular and cellular biology, 2015Co-Authors: Emilio Lecona, Varun Narendra, Danny ReinbergAbstract:USP7 is a protein deubiquitinase with an essential role in development. Here, we provide evidence that USP7 regulates the activity of Polycomb repressive complex 1 (PRC1) in coordination with SCML2. There are six versions of PRC1 defined by the association of one of the PCGF homologues (PCGF1 to PCGF6) with the common catalytic subunit RING1B. First, we show that SCML2, a Polycomb group protein that associates with PRC1.2 (containing PCGF2/MEL18) and PRC1.4 (containing PCGF4/BMI1), modulates the localization of USP7 and bridges USP7 with PRC1.4, allowing for the stabilization of BMI1. Chromatin immunoprecipitation (ChIP) experiments demonstrate that USP7 is found at SCML2 and BMI1 target genes. Second, inhibition of USP7 leads to a reduction in the level of ubiquitinated histone H2A (H2Aub), the catalytic product of PRC1 and key for its repressive activity. USP7 regulates the posttranslational status of RING1B and BMI1, a specific component of PRC1.4. Thus, not only does USP7 stabilize PRC1 components, its catalytic activity is also necessary to maintain a functional PRC1, thereby ensuring appropriate levels of repressive H2Aub.
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an auts2 polycomb complex activates gene expression in the cns
Nature, 2014Co-Authors: Zhonghua Gao, Pedro Lee, James M Stafford, Melanie Von Schimmelmann, Anne Schaefer, Danny ReinbergAbstract:Naturally occurring variations of Polycomb repressive complex 1 (PRC1) comprise a core assembly of Polycomb group proteins and additional factors that include, surprisingly, autism susceptibility candidate 2 (AUTS2). Although AUTS2 is often disrupted in patients with neuronal disorders, the mechanism underlying the pathogenesis is unclear. We investigated the role of AUTS2 as part of a previously identified PRC1 complex (PRC1–AUTS2), and in the context of neurodevelopment. In contrast to the canonical role of PRC1 in gene repression, PRC1–AUTS2 activates transcription. Biochemical studies demonstrate that the CK2 component of PRC1–AUTS2 neutralizes PRC1 repressive activity, whereas AUTS2-mediated recruitment of P300 leads to gene activation. Chromatin immunoprecipitation followed by sequencing (ChIP-seq) demonstrated that AUTS2 regulates neuronal gene expression through promoter association. Conditional targeting of Auts2 in the mouse central nervous system (CNS) leads to various developmental defects. These findings reveal a natural means of subverting PRC1 activity, linking key epigenetic modulators with neuronal functions and diseases. Polycomb group proteins are known to maintain gene repression during development; however, when autism susceptibility candidate 2 (AUTS2) associates with some Polycomb group complexes, these complexes have an unexpected gene activation role, offering new insight into the role of AUTS2 in neurological disorders. Polycomb group proteins, which maintain gene repression during development, comprise two main complexes (PRC1 and PRC2), with distinct enzymatic activities. Some PRC1 complexes associate with autism susceptibility candidate 2 (AUTS2), the gene for which is often disrupted in neuronal disorders. Here, Danny Reinberg and colleagues find that AUTS2 confers an unexpected transcriptional activation function on PRC1, and the PRC1–AUTS2 complex regulates neuronal genes. Deletion of the Auts2 locus in the mouse central nervous system leads to developmental defects. AUTS2 may have a key role in modulating PRC1 activity during normal brain development.
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Interactions with RNA direct the Polycomb group protein SCML2 to chromatin where it represses target genes
eLife, 2014Co-Authors: Roberto Bonasio, Emilio Lecona, Varun Narendra, Philipp Voigt, Fabio Parisi, Yuval Kluger, Danny ReinbergAbstract:Polycomb repressive complex-1 (PRC1) is essential for the epigenetic regulation of gene expression. SCML2 is a mammalian homolog of Drosophila SCM, a Polycomb-group protein that associates with PRC1. In this study, we show that SCML2A, an SCML2 isoform tightly associated to chromatin, contributes to PRC1 localization and also directly enforces repression of certain Polycomb target genes. SCML2A binds to PRC1 via its SPM domain and interacts with ncRNAs through a novel RNA-binding region (RBR). Targeting of SCML2A to chromatin involves the coordinated action of the MBT domains, RNA binding, and interaction with PRC1 through the SPM domain. Deletion of the RBR reduces the occupancy of SCML2A at target genes and overexpression of a mutant SCML2A lacking the RBR causes defects in PRC1 recruitment. These observations point to a role for ncRNAs in regulating SCML2 function and suggest that SCML2 participates in the epigenetic control of transcription directly and in cooperation with PRC1.DOI: http://dx.doi.org/10.7554/eLife.02637.001.
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pcgf homologs cbx proteins and rybp define functionally distinct PRC1 family complexes
Molecular Cell, 2012Co-Authors: Zhonghua Gao, Roberto Bonasio, Fabio Parisi, Yuval Kluger, Jin Zhang, Francesco Strino, Ayana Sawai, Danny ReinbergAbstract:The heterogeneous nature of mammalian PRC1 complexes has hindered our understanding of their biological functions. Here, we present a comprehensive proteomic and genomic analysis that uncovered six major groups of PRC1 complexes, each containing a distinct PCGF subunit, a RING1A/B ubiquitin ligase, and a unique set of associated polypeptides. These PRC1 complexes differ in their genomic localization, and only a small subset colocalize with H3K27me3. Further biochemical dissection revealed that the six PCGF-RING1A/B combinations form multiple complexes through association with RYBP or its homolog YAF2, which prevents the incorporation of other canonical PRC1 subunits, such as CBX, PHC, and SCM. Although both RYBP/YAF2- and CBX/PHC/SCM-containing complexes compact chromatin, only RYBP stimulates the activity of RING1B toward H2AK119ub1, suggesting a central role in PRC1 function. Knockdown of RYBP in embryonic stem cells compromised their ability to form embryoid bodies, likely because of defects in cell proliferation and maintenance of H2AK119ub1 levels.
