E2F mediates cell cycle-dependent transcriptional repression in vivo by recruitment of an HDAC1/mSin3B corepressor complex
E2F mediates cell cycle-dependent transcriptional repression in vivo by recruitment of an HDAC1/mSin3B corepressor complex
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DOI：
10.1101/gad.969202
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发表时间：
2002-04-15
影响因子：
10.5
通讯作者：
Dynlacht, BD
中科院分区：
文献类型：
--
作者：
Rayman, JB;Takahashi, Y;Dynlacht, BD
尽管生化和遗传数据表明 E2F 和 pRB（口袋蛋白）家族通过染色质修饰因子调节转录，但这些蛋白质家族基因调控的精确机制尚未在生理环境中得到定义。在这项研究中，我们研究了野生型和口袋蛋白缺陷原代细胞中启动子的占据情况。我们发现，由组蛋白脱乙酰酶 (HDAC1) 和 mSin3B 组成的辅阻遏物复合物被特异性招募到静止细胞中内源性 E2F 调节的启动子中。一旦细胞到达 G(1) 晚期（与基因激活同时发生），这些复合物就会与启动子解离。有趣的是，HDAC1 复合物向启动子的募集完全依赖于 p107 和 p130，并且需要完整的 E2F 结合位点。相比之下，mSin3B 招募到某些启动子不需要 p107 或 p130，这表明该辅阻遏物的招募可以通过 E2F 依赖性和独立机制发生。值得注意的是，pRB 的丢失对 HDAC1 或 mSin3B 的募集没有影响。 p107/p130 缺陷引发 E2F4 核定位的急剧丧失以及转录去抑制，核小体作图研究表明这是 E2F 结合位点附近核小体局部超乙酰化的结果。总而言之，这些发现表明，当细胞退出细胞周期时，p130 护送 E2F4 进入细胞核，并与含有 mSin3B 和/或 HDAC1 的辅阻遏物复合物一起直接抑制靶基因的转录。
Despite biochemical and genetic data suggesting that E2F and pRB (pocket protein) families regulate transcription via chromatin-modifying factors, the precise mechanisms underlying gene regulation by these protein families have not yet been defined in a physiological setting. In this study, we have investigated promoter occupancy in wild-type and pocket protein-deficient primary cells. We show that corepressor complexes consisting of histone deacetylase (HDAC1) and mSin3B were specifically recruited to endogenous E2F-regulated promoters in quiescent cells. These complexes dissociated from promoters once cells reached late G(1), coincident with gene activation. Interestingly, recruitment of HDAC1 complexes to promoters depended absolutely on p107 and p130, and required an intact E2F-binding site. In contrast, mSin3B recruitment to certain promoters did not require p107 or p130, suggesting that recruitment of this corepressor can occur via E2F-dependent and -independent mechanisms. Remarkably, loss of pRB had no effect on HDAC1 or mSin3B recruitment. p107/p130 deficiency triggered a dramatic loss of E2F4 nuclear localization as well as transcriptional derepression, which is suggested by nucleosome mapping studies to be the result of localized hyperacetylation of nucleosomes proximal to E2F-binding sites. Taken together, these findings show that p130 escorts E2F4 into the nucleus and, together with corepressor complexes that contain mSin3B and/or HDAC1, directly represses transcription from target genes as cells withdraw from the cell cycle.