Polycomb Repressive Complex 2 methylates Elongin A to regulate transcripiton [BrU-RNA-seq]
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ABSTRACT: Polycomb repressive complex 2 (PRC2-EZH2) methylates histone H3 at lysine 27 (H3K27) and is required to maintain gene repression during development. Misregulation of PRC2 is linked to a range of neoplastic malignancies, which is believed to involve methylation of H3K27. However, the full spectrum of non-histone substrates of PRC2 that might also contribute to PRC2 function is not known. We characterized the target recognition specificity of PRC2 and used the resultant data to screen for novel potential targets. The RNA polymerase II (Pol II) transcription factor, Elongin A (EloA), is methylated by PRC2 in vivo. Mutation of the methylated EloA residue decreased repression of many, but not all, PRC2 target genes as measured by both steady state and nascent RNA levels. We propose that PRC2 regulates transcription of a subset of target genes in part via methylation of EloA.
Project description:Polycomb repressive complex 2 (PRC2-EZH2) methylates histone H3 at lysine 27 (H3K27) and is required to maintain gene repression during development. Misregulation of PRC2 is linked to a range of neoplastic malignancies, which is believed to involve methylation of H3K27. However, the full spectrum of non-histone substrates of PRC2 that might also contribute to PRC2 function is not known. We characterized the target recognition specificity of PRC2 and used the resultant data to screen for novel potential targets. The RNA polymerase II (Pol II) transcription factor, Elongin A (EloA), is methylated by PRC2 in vivo. Mutation of the methylated EloA residue decreased repression of many, but not all, PRC2 target genes as measured by both steady state and nascent RNA levels. We propose that PRC2 regulates transcription of a subset of target genes in part via methylation of EloA.
Project description:Polycomb repressive complex 2 (PRC2-EZH2) methylates histone H3 at lysine 27 (H3K27). PRC2 is required to maintain gene repression during development and differentiation and misregulation of PRC2 is linked to a range of neoplastic malignancies, activities that are believed to involve H3K27 methylation. The full spectrum of non-histone substrates of PRC2, however, is not known, and it is not known which other substrates might also contribute to the biological functions of PRC2. We characterized the target recognition specificity and substrate diversity of PRC2, and identified more than one hundred potential novel nuclear targets of PRC2. The RNA polymerase II (Pol II) transcription elongation factor, Elongin A (EloA), is an in vivo target of PRC2. Mutation of the EloA residue that is methylated by PRC2 decreases repression of numerous PRC2 target genes. We propose that this functional crosstalk between PRC2 and EloA tunes the level of repression of targeted genes and contributes to the biological functions of PRC2.
Project description:The cellular plasticity of pluripotent stem cells is thought to be sustained by genomic regions that display both active and repressive chromatin properties. These regions exhibit low levels of gene expression, yet the mechanisms controlling these levels remain unknown. Here, we describe Elongin BC as a binding factor at the promoters of bivalent sites. Biochemical and genome-wide analysis shows that Elongin BC is associated with Polycomb Repressive Complex 2 (PRC2) in pluripotent stem cells. Elongin BC is recruited to chromatin by the PRC2-associated factor EPOP (Elongin- and POlycomb-associated Protein, also termed C17orf96, esPRC2p48, E130012A19Rik), a protein expressed in the inner cell mass of the mouse blastocyst. Both EPOP and Elongin BC are required to maintain low levels of expression at PRC2 genomic targets. Our results indicate that keeping the balance between activating and repressive cues is a more general feature of chromatin in pluripotent stem cells than previously appreciated.
Project description:Elongin is a hetero-trimeric elongation factor for RNA polymerase (Pol) II transcription that is conserved among metazoa. We solved three structures of human Elongin bound to transcribing Pol II using cryo-EM assisted by crosslinking mass spectrometry. The structures show that Elongin subunit ELOA binds the RPB2 side of Pol II and anchors the ELOB-8 ELOC subunit heterodimer. ELOA contains an N-terminal ‘latch’ that binds between the end of the RPB1 bridge helix and the funnel helices, thereby inducing a conformational change near the Pol II active center. The latch is strictly required for the elongation-stimulatory activity of Elongin, but not for its binding to Pol II, indicating that Elongin functions by allosterically influencing the conformational mobility of the active center. Structural comparisons show that Elongin binding to Pol II is incompatible with association of super elongation complex, the PAF1 complex, and RTF1, which also contains a latch element that stimulates Pol II.
Project description:To identify potential Elongin A targets during neuronal differentiation of ES cells, a cDNA microarray analysis comparing embryoid bodies (EBs) derived from Elongin A+/+ ES cells and Elongin A-/- ES cells was performed. Gene expression in EBs derived from Elongin A+/+ and Elongin A-/- ES cells was measured at day 4 after retinoic acid treatment (2 ?M).
Project description:The bZIP transcription factor ATF6α is a master regulator of endoplasmic reticulum (ER) stress response genes. In this report, we identify the multifunctional RNA polymerase II transcription factor Elongin as a cofactor for ATF6α-dependent transcription activation. Biochemical studies reveal that Elongin functions at least in part by facilitating ATF6α-dependent loading of Mediator at the promoters and enhancers of ER stress response genes. Depletion of Elongin from cells leads to impaired transcription of ER stress response genes and to defects in the recruitment of Mediator and, in particular, its CDK8 kinase subunit. Taken together, these findings bring to light a new role for Elongin as a loading factor for Mediator during the ER stress response.
Project description:The bZIP transcription factor ATF6α is a master regulator of endoplasmic reticulum (ER) stress response genes. In this report, we identify the multifunctional RNA polymerase II transcription factor Elongin as a cofactor for ATF6α-dependent transcription activation. Biochemical studies reveal that Elongin functions at least in part by facilitating ATF6α-dependent loading of Mediator at the promoters and enhancers of ER stress response genes. Depletion of Elongin from cells leads to impaired transcription of ER stress response genes and to defects in the recruitment of Mediator and, in particular, its CDK8 kinase subunit. Taken together, these findings bring to light a new role for Elongin as a loading factor for Mediator during the ER stress response.
Project description:To identify potential Elongin A targets during neuronal differentiation of ES cells, a cDNA microarray analysis comparing embryoid bodies (EBs) derived from Elongin A+/+ ES cells and Elongin A-/- ES cells was performed.