{"id":41,"date":"2016-11-28T14:07:51","date_gmt":"2016-11-28T21:07:51","guid":{"rendered":"https:\/\/blogs.ubc.ca\/cdrohanbiol463\/?p=41"},"modified":"2016-11-28T14:07:51","modified_gmt":"2016-11-28T21:07:51","slug":"41","status":"publish","type":"post","link":"https:\/\/blogs.ubc.ca\/cdrohanbiol463\/2016\/11\/28\/41\/","title":{"rendered":""},"content":{"rendered":"<p>Chromatin remodelling and bivalent histone modifications in ESCs. <em>EMBO Reports.<\/em><\/p>\n<ul>\n<li>Nucleosome formed by pair of each of the core histones &#8211; H2A, H2B, H3, H4<\/li>\n<li>Linked histones (H1) between the nucleosomes forms higher-order chromatin structure<\/li>\n<li>Histone modification can assist with transcriptional activation and repression<\/li>\n<li>Combination of H3K4me3 (activating) and H3K27me3 (repressive) found in some promoters, called<strong> bivalent modifications<\/strong><\/li>\n<li><strong>HCNEs<\/strong> (highly conserved noncoding elements) tend to be enriched with bivalent modifications<\/li>\n<li>WT conditions there was little activation of these bivalent promoters<\/li>\n<li>Depletion of PRC2 subunit leads to loss of H3K27me3, upregulation of genes<\/li>\n<li>Concluded that the promoters are &#8220;poised&#8221; for gene expression<\/li>\n<li>Bivalent domains tend to be developmentally regulated, although some have been found in terminally differentiated cells<\/li>\n<li>In ESCs, bivalent domains tend to be associated with CpG islands<\/li>\n<li><strong>Challenge:<\/strong> have yet to develop single nucleosome resolution technique, hard to determine function of these domains conclusively<\/li>\n<li>Trithorax group (TrxG) proteins deposit H3K4me3 &#8211; SETD1A, SETD1B, MLL complexes<\/li>\n<li>SET1A\/B &#8211; responsible for global deposition of H3K4me3<\/li>\n<li>MLL2 is the main methyltransferase at bivalent domains\n<ul>\n<li>Contains CXXC and ZF-CXXC domains, which recognize unmethylated CpGs<\/li>\n<li>MLL2 KO is embryonic lethal, shows developmentally important<\/li>\n<\/ul>\n<\/li>\n<li>PcG proteins (PRC2) mainly deposit H3K27me3 at bivalent promoters\n<ul>\n<li>Core PRC2 made up of EZH2 or EZH1, EED, SUZ12<\/li>\n<li>EZH2: enhancer of Zeste, catalytic subunit of the complex, methyltransferase for H3K27me3<\/li>\n<li>PRC2-specific bivalent domains are usually on promoters of not &#8220;bona fide&#8221; developmentally active genes<\/li>\n<li>PcG proteins are vital for ESC differentiation, depletion of PRC2 in ESCs shows aberrant differentiation potential<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<p>&nbsp;<\/p>\n<p>Key takeaways:<\/p>\n<p>Glossary:<br \/>\nHCNE: highly conserved noncoding elements, tend to be enriched with bivalent modifications<br \/>\nBivalent modifications: combination of both repressive and activating histone modifications<br \/>\nChromatin remodelling: any change or modification to chromatin<br \/>\nH2K27me3: trimethylated lysine 27 on histone 3, repressive mark<br \/>\nH3K4me3: trimethylated lysine 4 on histone 3, activating mark<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Chromatin remodelling and bivalent histone modifications in ESCs. EMBO Reports. Nucleosome formed by pair of each of the core histones &#8211; H2A, H2B, H3, H4 Linked histones (H1) between the nucleosomes forms higher-order chromatin structure Histone modification can assist with transcriptional activation and repression Combination of H3K4me3 (activating) and H3K27me3 (repressive) found in some promoters, [&hellip;]<\/p>\n","protected":false},"author":8192,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1788162],"tags":[],"class_list":["post-41","post","type-post","status-publish","format-standard","hentry","category-paper-summaries"],"_links":{"self":[{"href":"https:\/\/blogs.ubc.ca\/cdrohanbiol463\/wp-json\/wp\/v2\/posts\/41","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/blogs.ubc.ca\/cdrohanbiol463\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blogs.ubc.ca\/cdrohanbiol463\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blogs.ubc.ca\/cdrohanbiol463\/wp-json\/wp\/v2\/users\/8192"}],"replies":[{"embeddable":true,"href":"https:\/\/blogs.ubc.ca\/cdrohanbiol463\/wp-json\/wp\/v2\/comments?post=41"}],"version-history":[{"count":2,"href":"https:\/\/blogs.ubc.ca\/cdrohanbiol463\/wp-json\/wp\/v2\/posts\/41\/revisions"}],"predecessor-version":[{"id":69,"href":"https:\/\/blogs.ubc.ca\/cdrohanbiol463\/wp-json\/wp\/v2\/posts\/41\/revisions\/69"}],"wp:attachment":[{"href":"https:\/\/blogs.ubc.ca\/cdrohanbiol463\/wp-json\/wp\/v2\/media?parent=41"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blogs.ubc.ca\/cdrohanbiol463\/wp-json\/wp\/v2\/categories?post=41"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blogs.ubc.ca\/cdrohanbiol463\/wp-json\/wp\/v2\/tags?post=41"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}