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Thomas R. Cech - One of the best experts on this subject based on the ideXlab platform.
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RNA is essential for PRC2 chromatin occupancy and function in human pluripotent stem cells
Nature Genetics, 2020Co-Authors: Yicheng Long, Karen J. Goodrich, Anne R. Gooding, Taeyoung Hwang, John L. Rinn, Thomas R. CechAbstract:Perturbation of RNA–PRC2 interaction in human pluripotent stem cells disrupts PRC2 chromatin occupancy and localization genome wide. PRC2–RNA interactions contribute to cardiomyocyte differentiation. Many chromatin-binding proteins and protein complexes that regulate transcription also bind RNA. One of these, Polycomb repressive complex 2 (PRC2), deposits the H3K27me3 mark of facultative heterochromatin and is required for stem cell differentiation. PRC2 binds RNAs broadly in vivo and in vitro. Yet, the biological importance of this RNA binding remains unsettled. Here, we tackle this question in human induced pluripotent stem cells by using multiple complementary approaches. Perturbation of RNA–PRC2 interaction by RNase A, by a chemical inhibitor of transcription or by an RNA-binding-defective mutant all disrupted PRC2 chromatin occupancy and localization genome wide. The physiological relevance of PRC2–RNA interactions is further underscored by a cardiomyocyte differentiation defect upon genetic disruption. We conclude that PRC2 requires RNA binding for chromatin localization in human pluripotent stem cells and in turn for defining cellular state.
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RNA is essential for PRC2 chromatin occupancy and function in human pluripotent stem cells.
Nature genetics, 2020Co-Authors: Yicheng Long, Karen J. Goodrich, Anne R. Gooding, Taeyoung Hwang, John L. Rinn, Thomas R. CechAbstract:Many chromatin-binding proteins and protein complexes that regulate transcription also bind RNA. One of these, Polycomb repressive complex 2 (PRC2), deposits the H3K27me3 mark of facultative heterochromatin and is required for stem cell differentiation. PRC2 binds RNAs broadly in vivo and in vitro. Yet, the biological importance of this RNA binding remains unsettled. Here, we tackle this question in human induced pluripotent stem cells by using multiple complementary approaches. Perturbation of RNA-PRC2 interaction by RNase A, by a chemical inhibitor of transcription or by an RNA-binding-defective mutant all disrupted PRC2 chromatin occupancy and localization genome wide. The physiological relevance of PRC2-RNA interactions is further underscored by a cardiomyocyte differentiation defect upon genetic disruption. We conclude that PRC2 requires RNA binding for chromatin localization in human pluripotent stem cells and in turn for defining cellular state.
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Live-cell imaging reveals the dynamics of PRC2 and recruitment to chromatin by SUZ12-associated subunits
Genes & development, 2018Co-Authors: Daniel T. Youmans, Jens C. Schmidt, Thomas R. CechAbstract:Polycomb-repressive complex 2 (PRC2) is a histone methyltransferase that promotes epigenetic gene silencing, but the dynamics of its interactions with chromatin are largely unknown. Here we quantitatively measured the binding of PRC2 to chromatin in human cancer cells. Genome editing of a HaloTag into the endogenous EZH2 and SUZ12 loci and single-particle tracking revealed that ∼80% of PRC2 rapidly diffuses through the nucleus, while ∼20% is chromatin-bound. Short-term treatment with a small molecule inhibitor of the EED-H3K27me3 interaction had no immediate effect on the chromatin residence time of PRC2. In contrast, separation-of-function mutants of SUZ12, which still form the core PRC2 complex but cannot bind accessory proteins, revealed a major contribution of AEBP2 and PCL homolog proteins to chromatin binding. We therefore quantified the dynamics of this chromatin-modifying complex in living cells and separated the contributions of H3K27me3 histone marks and various PRC2 subunits to recruitment of PRC2 to chromatin.
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Molecular analysis of PRC2 recruitment to DNA in chromatin and its inhibition by RNA
Nature Structural & Molecular Biology, 2017Co-Authors: Xueyin Wang, Anne R. Gooding, Richard D. Paucek, Zachary Z Brown, Eva J Ge, Tom W Muir, Thomas R. CechAbstract:Many studies have revealed pathways of epigenetic gene silencing by Polycomb repressive complex 2 (PRC2) in vivo , but understanding the underlying molecular mechanisms requires biochemistry. Here we analyze interactions of reconstituted human PRC2 with nucleosome complexes. Histone modifications, the H3K27M cancer mutation, and inclusion of JARID2 or EZH1 in the PRC2 complex have unexpectedly minor effects on PRC2–nucleosome binding. Instead, protein-free linker DNA dominates the PRC2–nucleosome interaction. Specificity for CG-rich sequences is consistent with PRC2 occupying CG-rich DNA in vivo . PRC2 preferentially binds methylated DNA regulated by its AEBP2 subunit, suggesting how DNA and histone methylation collaborate to repress chromatin. We find that RNA, known to inhibit PRC2 activity, is not a methyltransferase inhibitor per se . Instead, RNA sequesters PRC2 from nucleosome substrates, because PRC2 binding requires linker DNA, and RNA and DNA binding are mutually exclusive. Together, we provide a model for PRC2 recruitment and an explanation for how actively transcribed genomic regions bind PRC2 but escape silencing. Biochemical reconstitution of PRC2 interactions with chromatinized templates demonstrates that protein-free linker DNA dominates the PRC2-nucleosome interaction, while RNA inhibits binding.
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Molecular analysis of PRC2 recruitment to DNA in chromatin and its inhibition by RNA.
Nature structural & molecular biology, 2017Co-Authors: Xueyin Wang, Anne R. Gooding, Richard D. Paucek, Zachary Z Brown, Tom W Muir, Thomas R. CechAbstract:Many studies have revealed pathways of epigenetic gene silencing by Polycomb repressive complex 2 (PRC2) in vivo, but understanding the underlying molecular mechanisms requires biochemistry. Here we analyze interactions of reconstituted human PRC2 with nucleosome complexes. Histone modifications, the H3K27M cancer mutation, and inclusion of JARID2 or EZH1 in the PRC2 complex have unexpectedly minor effects on PRC2-nucleosome binding. Instead, protein-free linker DNA dominates the PRC2-nucleosome interaction. Specificity for CG-rich sequences is consistent with PRC2 occupying CG-rich DNA in vivo. PRC2 preferentially binds methylated DNA regulated by its AEBP2 subunit, suggesting how DNA and histone methylation collaborate to repress chromatin. We find that RNA, known to inhibit PRC2 activity, is not a methyltransferase inhibitor per se. Instead, RNA sequesters PRC2 from nucleosome substrates, because PRC2 binding requires linker DNA, and RNA and DNA binding are mutually exclusive. Together, we provide a model for PRC2 recruitment and an explanation for how actively transcribed genomic regions bind PRC2 but escape silencing.
Jürg Müller - One of the best experts on this subject based on the ideXlab platform.
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DNA binding by PHF1 prolongs PRC2 residence time on chromatin and thereby promotes H3K27 methylation
Nature Structural & Molecular Biology, 2017Co-Authors: Jeongyoon Choi, Andreas Linus Bachmann, Katharina Tauscher, Christian Benda, Beat Fierz, Jürg MüllerAbstract:The DNA-binding activity of the winged-helix domain of PHF1 stabilizes PRC2 on chromatin, thereby permitting efficient H3K27 trimethylation. Polycomb repressive complex 2 (PRC2) trimethylates histone H3 at lysine 27 to mark genes for repression. We measured the dynamics of PRC2 binding on recombinant chromatin and free DNA at the single-molecule level using total internal reflection fluorescence (TIRF) microscopy. PRC2 preferentially binds free DNA with multisecond residence time and midnanomolar affinity. PHF1, a PRC2 accessory protein of the Polycomblike family, extends PRC2 residence time on DNA and chromatin. Crystallographic and functional studies reveal that Polycomblike proteins contain a winged-helix domain that binds DNA in a sequence-nonspecific fashion. DNA binding by this winged-helix domain accounts for the prolonged residence time of PHF1–PRC2 on chromatin and makes it a more efficient H3K27 methyltranferase than PRC2 alone. Together, these studies establish that interactions with DNA provide the predominant binding affinity of PRC2 for chromatin. Moreover, they reveal the molecular basis for how Polycomblike proteins stabilize PRC2 on chromatin and stimulate its activity.
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dna binding by phf1 prolongs PRC2 residence time on chromatin and thereby promotes h3k27 methylation
Nature Structural & Molecular Biology, 2017Co-Authors: Jeongyoon Choi, Katharina Tauscher, Christian Benda, Beat Fierz, Andreas Bachmann, Jürg MüllerAbstract:Polycomb repressive complex 2 (PRC2) trimethylates histone H3 at lysine 27 to mark genes for repression. We measured the dynamics of PRC2 binding on recombinant chromatin and free DNA at the single-molecule level using total internal reflection fluorescence (TIRF) microscopy. PRC2 preferentially binds free DNA with multisecond residence time and midnanomolar affinity. PHF1, a PRC2 accessory protein of the Polycomblike family, extends PRC2 residence time on DNA and chromatin. Crystallographic and functional studies reveal that Polycomblike proteins contain a winged-helix domain that binds DNA in a sequence-nonspecific fashion. DNA binding by this winged-helix domain accounts for the prolonged residence time of PHF1-PRC2 on chromatin and makes it a more efficient H3K27 methyltranferase than PRC2 alone. Together, these studies establish that interactions with DNA provide the predominant binding affinity of PRC2 for chromatin. Moreover, they reveal the molecular basis for how Polycomblike proteins stabilize PRC2 on chromatin and stimulate its activity.
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pcl PRC2 is needed to generate high levels of h3 k27 trimethylation at polycomb target genes
The EMBO Journal, 2007Co-Authors: Maxim Nekrasov, Tetyana Klymenko, Sven Fraterman, Bernadett Papp, Katarzyna Oktaba, Thomas Köcher, Adrian Cohen, Hendrik G. Stunnenberg, Matthias Wilm, Jürg MüllerAbstract:PRC2 is thought to be the histone methyltransferase (HMTase) responsible for H3-K27 trimethylation at Polycomb target genes. Here we report the biochemical purification and characterization of a distinct form of Drosophila PRC2 that contains the Polycomb group protein polycomblike (Pcl). Like PRC2, Pcl-PRC2 is an H3-K27-specific HMTase that mono-, di- and trimethylates H3-K27 in nucleosomes in vitro. Analysis of Drosophila mutants that lack Pcl unexpectedly reveals that Pcl-PRC2 is required to generate high levels of H3-K27 trimethylation at Polycomb target genes but is dispensable for the genome-wide H3-K27 mono- and dimethylation that is generated by PRC2. In Pcl mutants, Polycomb target genes become derepressed even though H3-K27 trimethylation at these genes is only reduced and not abolished, and even though targeting of the Polycomb protein complexes PhoRC and PRC1 to Polycomb response elements is not affected. Pcl-PRC2 is thus the HMTase that generates the high levels of H3-K27 trimethylation in Polycomb target genes that are needed to maintain a Polycomb-repressed chromatin state.
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Pcl‐PRC2 is needed to generate high levels of H3‐K27 trimethylation at Polycomb target genes
The EMBO journal, 2007Co-Authors: Maxim Nekrasov, Tetyana Klymenko, Sven Fraterman, Bernadett Papp, Katarzyna Oktaba, Thomas Köcher, Adrian Cohen, Hendrik G. Stunnenberg, Matthias Wilm, Jürg MüllerAbstract:PRC2 is thought to be the histone methyltransferase (HMTase) responsible for H3-K27 trimethylation at Polycomb target genes. Here we report the biochemical purification and characterization of a distinct form of Drosophila PRC2 that contains the Polycomb group protein polycomblike (Pcl). Like PRC2, Pcl-PRC2 is an H3-K27-specific HMTase that mono-, di- and trimethylates H3-K27 in nucleosomes in vitro. Analysis of Drosophila mutants that lack Pcl unexpectedly reveals that Pcl-PRC2 is required to generate high levels of H3-K27 trimethylation at Polycomb target genes but is dispensable for the genome-wide H3-K27 mono- and dimethylation that is generated by PRC2. In Pcl mutants, Polycomb target genes become derepressed even though H3-K27 trimethylation at these genes is only reduced and not abolished, and even though targeting of the Polycomb protein complexes PhoRC and PRC1 to Polycomb response elements is not affected. Pcl-PRC2 is thus the HMTase that generates the high levels of H3-K27 trimethylation in Polycomb target genes that are needed to maintain a Polycomb-repressed chromatin state.
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Nucleosome binding and histone methyltransferase activity of Drosophila PRC2.
EMBO reports, 2005Co-Authors: Maxim Nekrasov, Brigitte Wild, Jürg MüllerAbstract:The Drosophila Polycomb group protein E(z) is a histone methyltransferase (HMTase) that is essential for maintaining HOX gene silencing during development. E(z) exists in a multiprotein complex called Polycomb repressive complex 2 (PRC2) that also contains Su(z)12, Esc and Nurf55. Reconstituted recombinant PRC2 methylates nucleosomes in vitro, but recombinant E(z) on its own shows only poor HMTase activity on nucleosomes. Here, we investigate the function of the PRC2 subunits. We show that PRC2 binds to nucleosomes in vitro but that individual PRC2 subunits alone do not bind to nucleosomes. By analysing PRC2 subcomplexes, we show that Su(z)12–Nurf55 is the minimal nucleosome-binding module of PRC2 and that Esc contributes to high-affinity binding of PRC2 nucleosomes. We find that nucleosome binding of PRC2 is not sufficient for histone methylation and that only complexes that contain Esc protein show robust HMTase activity. These observations suggest that different subunits provide mechanistically distinct functions within the PRC2 HMTase: the nucleosome-binding subunits Su(z)12 and Nurf55 anchor the E(z) enzyme on chromatin substrates, whereas Esc is needed to boost enzymatic activity.
Anne R. Gooding - One of the best experts on this subject based on the ideXlab platform.
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RNA is essential for PRC2 chromatin occupancy and function in human pluripotent stem cells.
Nature genetics, 2020Co-Authors: Yicheng Long, Karen J. Goodrich, Anne R. Gooding, Taeyoung Hwang, John L. Rinn, Thomas R. CechAbstract:Many chromatin-binding proteins and protein complexes that regulate transcription also bind RNA. One of these, Polycomb repressive complex 2 (PRC2), deposits the H3K27me3 mark of facultative heterochromatin and is required for stem cell differentiation. PRC2 binds RNAs broadly in vivo and in vitro. Yet, the biological importance of this RNA binding remains unsettled. Here, we tackle this question in human induced pluripotent stem cells by using multiple complementary approaches. Perturbation of RNA-PRC2 interaction by RNase A, by a chemical inhibitor of transcription or by an RNA-binding-defective mutant all disrupted PRC2 chromatin occupancy and localization genome wide. The physiological relevance of PRC2-RNA interactions is further underscored by a cardiomyocyte differentiation defect upon genetic disruption. We conclude that PRC2 requires RNA binding for chromatin localization in human pluripotent stem cells and in turn for defining cellular state.
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RNA is essential for PRC2 chromatin occupancy and function in human pluripotent stem cells
Nature Genetics, 2020Co-Authors: Yicheng Long, Karen J. Goodrich, Anne R. Gooding, Taeyoung Hwang, John L. Rinn, Thomas R. CechAbstract:Perturbation of RNA–PRC2 interaction in human pluripotent stem cells disrupts PRC2 chromatin occupancy and localization genome wide. PRC2–RNA interactions contribute to cardiomyocyte differentiation. Many chromatin-binding proteins and protein complexes that regulate transcription also bind RNA. One of these, Polycomb repressive complex 2 (PRC2), deposits the H3K27me3 mark of facultative heterochromatin and is required for stem cell differentiation. PRC2 binds RNAs broadly in vivo and in vitro. Yet, the biological importance of this RNA binding remains unsettled. Here, we tackle this question in human induced pluripotent stem cells by using multiple complementary approaches. Perturbation of RNA–PRC2 interaction by RNase A, by a chemical inhibitor of transcription or by an RNA-binding-defective mutant all disrupted PRC2 chromatin occupancy and localization genome wide. The physiological relevance of PRC2–RNA interactions is further underscored by a cardiomyocyte differentiation defect upon genetic disruption. We conclude that PRC2 requires RNA binding for chromatin localization in human pluripotent stem cells and in turn for defining cellular state.
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Molecular analysis of PRC2 recruitment to DNA in chromatin and its inhibition by RNA
Nature Structural & Molecular Biology, 2017Co-Authors: Xueyin Wang, Anne R. Gooding, Richard D. Paucek, Zachary Z Brown, Eva J Ge, Tom W Muir, Thomas R. CechAbstract:Many studies have revealed pathways of epigenetic gene silencing by Polycomb repressive complex 2 (PRC2) in vivo , but understanding the underlying molecular mechanisms requires biochemistry. Here we analyze interactions of reconstituted human PRC2 with nucleosome complexes. Histone modifications, the H3K27M cancer mutation, and inclusion of JARID2 or EZH1 in the PRC2 complex have unexpectedly minor effects on PRC2–nucleosome binding. Instead, protein-free linker DNA dominates the PRC2–nucleosome interaction. Specificity for CG-rich sequences is consistent with PRC2 occupying CG-rich DNA in vivo . PRC2 preferentially binds methylated DNA regulated by its AEBP2 subunit, suggesting how DNA and histone methylation collaborate to repress chromatin. We find that RNA, known to inhibit PRC2 activity, is not a methyltransferase inhibitor per se . Instead, RNA sequesters PRC2 from nucleosome substrates, because PRC2 binding requires linker DNA, and RNA and DNA binding are mutually exclusive. Together, we provide a model for PRC2 recruitment and an explanation for how actively transcribed genomic regions bind PRC2 but escape silencing. Biochemical reconstitution of PRC2 interactions with chromatinized templates demonstrates that protein-free linker DNA dominates the PRC2-nucleosome interaction, while RNA inhibits binding.
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Molecular analysis of PRC2 recruitment to DNA in chromatin and its inhibition by RNA.
Nature structural & molecular biology, 2017Co-Authors: Xueyin Wang, Anne R. Gooding, Richard D. Paucek, Zachary Z Brown, Tom W Muir, Thomas R. CechAbstract:Many studies have revealed pathways of epigenetic gene silencing by Polycomb repressive complex 2 (PRC2) in vivo, but understanding the underlying molecular mechanisms requires biochemistry. Here we analyze interactions of reconstituted human PRC2 with nucleosome complexes. Histone modifications, the H3K27M cancer mutation, and inclusion of JARID2 or EZH1 in the PRC2 complex have unexpectedly minor effects on PRC2-nucleosome binding. Instead, protein-free linker DNA dominates the PRC2-nucleosome interaction. Specificity for CG-rich sequences is consistent with PRC2 occupying CG-rich DNA in vivo. PRC2 preferentially binds methylated DNA regulated by its AEBP2 subunit, suggesting how DNA and histone methylation collaborate to repress chromatin. We find that RNA, known to inhibit PRC2 activity, is not a methyltransferase inhibitor per se. Instead, RNA sequesters PRC2 from nucleosome substrates, because PRC2 binding requires linker DNA, and RNA and DNA binding are mutually exclusive. Together, we provide a model for PRC2 recruitment and an explanation for how actively transcribed genomic regions bind PRC2 but escape silencing.
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Targeting of Polycomb Repressive Complex 2 to RNA by Short Repeats of Consecutive Guanines
Molecular cell, 2017Co-Authors: Xueyin Wang, Karen J. Goodrich, Anne R. Gooding, Haroon Naeem, Stuart K. Archer, Richard D. Paucek, Daniel T. Youmans, Thomas R. Cech, Chen DavidovichAbstract:Polycomb repressive complex 2 (PRC2) is a histone methyltransferase that trimethylates H3K27, a mark of repressed chromatin. Mammalian PRC2 binds RNA promiscuously, with thousands of target transcripts in vivo. But what does PRC2 recognize in these RNAs? Here we show that purified human PRC2 recognizes G > C,U ≫ A in single-stranded RNA and has a high affinity for folded guanine quadruplex (G4) structures but little binding to duplex RNAs. Importantly, G-tract motifs are significantly enriched among PRC2-binding transcripts in vivo. DNA sequences coding for PRC2-binding RNA motifs are enriched at PRC2-binding sites on chromatin and H3K27me3-modified nucleosomes. Collectively, the abundance of PRC2-binding RNA motifs rationalizes the promiscuous RNA binding of PRC2, and their enrichment at Polycomb target genes provides a means for RNA-mediated regulation.
Karen J. Goodrich - One of the best experts on this subject based on the ideXlab platform.
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RNA is essential for PRC2 chromatin occupancy and function in human pluripotent stem cells
Nature Genetics, 2020Co-Authors: Yicheng Long, Karen J. Goodrich, Anne R. Gooding, Taeyoung Hwang, John L. Rinn, Thomas R. CechAbstract:Perturbation of RNA–PRC2 interaction in human pluripotent stem cells disrupts PRC2 chromatin occupancy and localization genome wide. PRC2–RNA interactions contribute to cardiomyocyte differentiation. Many chromatin-binding proteins and protein complexes that regulate transcription also bind RNA. One of these, Polycomb repressive complex 2 (PRC2), deposits the H3K27me3 mark of facultative heterochromatin and is required for stem cell differentiation. PRC2 binds RNAs broadly in vivo and in vitro. Yet, the biological importance of this RNA binding remains unsettled. Here, we tackle this question in human induced pluripotent stem cells by using multiple complementary approaches. Perturbation of RNA–PRC2 interaction by RNase A, by a chemical inhibitor of transcription or by an RNA-binding-defective mutant all disrupted PRC2 chromatin occupancy and localization genome wide. The physiological relevance of PRC2–RNA interactions is further underscored by a cardiomyocyte differentiation defect upon genetic disruption. We conclude that PRC2 requires RNA binding for chromatin localization in human pluripotent stem cells and in turn for defining cellular state.
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RNA is essential for PRC2 chromatin occupancy and function in human pluripotent stem cells.
Nature genetics, 2020Co-Authors: Yicheng Long, Karen J. Goodrich, Anne R. Gooding, Taeyoung Hwang, John L. Rinn, Thomas R. CechAbstract:Many chromatin-binding proteins and protein complexes that regulate transcription also bind RNA. One of these, Polycomb repressive complex 2 (PRC2), deposits the H3K27me3 mark of facultative heterochromatin and is required for stem cell differentiation. PRC2 binds RNAs broadly in vivo and in vitro. Yet, the biological importance of this RNA binding remains unsettled. Here, we tackle this question in human induced pluripotent stem cells by using multiple complementary approaches. Perturbation of RNA-PRC2 interaction by RNase A, by a chemical inhibitor of transcription or by an RNA-binding-defective mutant all disrupted PRC2 chromatin occupancy and localization genome wide. The physiological relevance of PRC2-RNA interactions is further underscored by a cardiomyocyte differentiation defect upon genetic disruption. We conclude that PRC2 requires RNA binding for chromatin localization in human pluripotent stem cells and in turn for defining cellular state.
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Targeting of Polycomb Repressive Complex 2 to RNA by Short Repeats of Consecutive Guanines
Molecular cell, 2017Co-Authors: Xueyin Wang, Karen J. Goodrich, Anne R. Gooding, Haroon Naeem, Stuart K. Archer, Richard D. Paucek, Daniel T. Youmans, Thomas R. Cech, Chen DavidovichAbstract:Polycomb repressive complex 2 (PRC2) is a histone methyltransferase that trimethylates H3K27, a mark of repressed chromatin. Mammalian PRC2 binds RNA promiscuously, with thousands of target transcripts in vivo. But what does PRC2 recognize in these RNAs? Here we show that purified human PRC2 recognizes G > C,U ≫ A in single-stranded RNA and has a high affinity for folded guanine quadruplex (G4) structures but little binding to duplex RNAs. Importantly, G-tract motifs are significantly enriched among PRC2-binding transcripts in vivo. DNA sequences coding for PRC2-binding RNA motifs are enriched at PRC2-binding sites on chromatin and H3K27me3-modified nucleosomes. Collectively, the abundance of PRC2-binding RNA motifs rationalizes the promiscuous RNA binding of PRC2, and their enrichment at Polycomb target genes provides a means for RNA-mediated regulation.
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toward a consensus on the binding specificity and promiscuity of PRC2 for rna
Molecular Cell, 2015Co-Authors: Chen Davidovich, Xueyin Wang, Karen J. Goodrich, Anne R. Gooding, Jeannie T. Lee, Catherine Cifuentesrojas, Thomas R. CechAbstract:Summary Polycomb repressive complex-2 (PRC2) is a histone methyltransferase required for epigenetic silencing during development and cancer. Early works suggested binding specificity of PRC2 to certain long non-coding RNAs for recruitment to chromatin. More recent studies provided evidence both in favor and against this idea. Here, we bridge the two existing models of PRC2-RNA interaction. RepA RNA is a good binding partner for PRC2, while multiple non-relevant RNAs, including bacterial mRNAs, also bind PRC2; K d s depend to some extent on the experimental conditions. Human and mouse PRC2 have broadly similar RNA-binding properties in vitro. Examination of evidence supporting an existing model for site-specific recruitment of PRC2 by a well-defined RNA motif in cells reveals that results are PRC2 independent. We conclude that promiscuous and specific RNA-binding activities of PRC2 in vitro are not mutually exclusive, and that binding specificity in vivo remains to be demonstrated.
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A dimeric state for PRC2
Nucleic acids research, 2014Co-Authors: Chen Davidovich, Karen J. Goodrich, Anne R. Gooding, Thomas R. CechAbstract:Polycomb repressive complex-2 (PRC2) is a histone methyltransferase required for epigenetic silencing during development and cancer. Long non-coding RNAs (lncRNAs) can recruit PRC2 to chromatin. Previous studies identified PRC2 subunits in a complex with the apparent molecular weight of a dimer, which might be accounted for by the incorporation of additional protein subunits or RNA rather than PRC2 dimerization. Here we show that reconstituted human PRC2 is in fact a dimer, using multiple independent approaches including analytical size exclusion chromatography (SEC), SEC combined with multi-angle light scattering and co-immunoprecipitation of differentially tagged subunits. Even though it contains at least two RNA-binding subunits, each PRC2 dimer binds only one RNA molecule. Yet, multiple PRC2 dimers bind a single RNA molecule cooperatively. These observations suggest a model in which the first RNA binding event promotes the recruitment of multiple PRC2 complexes to chromatin, thereby nucleating repression.
Jeongyoon Choi - One of the best experts on this subject based on the ideXlab platform.
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DNA binding by PHF1 prolongs PRC2 residence time on chromatin and thereby promotes H3K27 methylation
Nature Structural & Molecular Biology, 2017Co-Authors: Jeongyoon Choi, Andreas Linus Bachmann, Katharina Tauscher, Christian Benda, Beat Fierz, Jürg MüllerAbstract:The DNA-binding activity of the winged-helix domain of PHF1 stabilizes PRC2 on chromatin, thereby permitting efficient H3K27 trimethylation. Polycomb repressive complex 2 (PRC2) trimethylates histone H3 at lysine 27 to mark genes for repression. We measured the dynamics of PRC2 binding on recombinant chromatin and free DNA at the single-molecule level using total internal reflection fluorescence (TIRF) microscopy. PRC2 preferentially binds free DNA with multisecond residence time and midnanomolar affinity. PHF1, a PRC2 accessory protein of the Polycomblike family, extends PRC2 residence time on DNA and chromatin. Crystallographic and functional studies reveal that Polycomblike proteins contain a winged-helix domain that binds DNA in a sequence-nonspecific fashion. DNA binding by this winged-helix domain accounts for the prolonged residence time of PHF1–PRC2 on chromatin and makes it a more efficient H3K27 methyltranferase than PRC2 alone. Together, these studies establish that interactions with DNA provide the predominant binding affinity of PRC2 for chromatin. Moreover, they reveal the molecular basis for how Polycomblike proteins stabilize PRC2 on chromatin and stimulate its activity.
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dna binding by phf1 prolongs PRC2 residence time on chromatin and thereby promotes h3k27 methylation
Nature Structural & Molecular Biology, 2017Co-Authors: Jeongyoon Choi, Katharina Tauscher, Christian Benda, Beat Fierz, Andreas Bachmann, Jürg MüllerAbstract:Polycomb repressive complex 2 (PRC2) trimethylates histone H3 at lysine 27 to mark genes for repression. We measured the dynamics of PRC2 binding on recombinant chromatin and free DNA at the single-molecule level using total internal reflection fluorescence (TIRF) microscopy. PRC2 preferentially binds free DNA with multisecond residence time and midnanomolar affinity. PHF1, a PRC2 accessory protein of the Polycomblike family, extends PRC2 residence time on DNA and chromatin. Crystallographic and functional studies reveal that Polycomblike proteins contain a winged-helix domain that binds DNA in a sequence-nonspecific fashion. DNA binding by this winged-helix domain accounts for the prolonged residence time of PHF1-PRC2 on chromatin and makes it a more efficient H3K27 methyltranferase than PRC2 alone. Together, these studies establish that interactions with DNA provide the predominant binding affinity of PRC2 for chromatin. Moreover, they reveal the molecular basis for how Polycomblike proteins stabilize PRC2 on chromatin and stimulate its activity.
