Moreland R J, Tirode F, Yan Q, Conaway J W, Egly J M, Conaway R C
Program in Molecular and Cell Biology, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma 73104, USA.
J Biol Chem. 1999 Aug 6;274(32):22127-30. doi: 10.1074/jbc.274.32.22127.
TFIIH is an RNA polymerase II transcription factor that performs ATP-dependent functions in both transcription initiation, where it catalyzes formation of the open complex, and in promoter escape, where it suppresses arrest of the early elongation complex at promoter-proximal sites. TFIIH possesses three known ATP-dependent activities: a 3' --> 5' DNA helicase catalyzed by its XPB subunit, a 5' --> 3' DNA helicase catalyzed by its XPD subunit, and a carboxyl-terminal domain (CTD) kinase activity catalyzed by its CDK7 subunit. In this report, we exploit TFIIH mutants to investigate the contributions of TFIIH DNA helicase and CTD kinase activities to efficient promoter escape by RNA polymerase II in a minimal transcription system reconstituted with purified polymerase and general initiation factors. Our findings argue that the TFIIH XPB DNA helicase is primarily responsible for preventing premature arrest of early elongation intermediates during exit of polymerase from the promoter.
TFIIH是一种RNA聚合酶II转录因子，在转录起始（催化开放复合物的形成）和启动子逃逸（抑制早期延伸复合物在启动子近端位点的停滞）过程中均发挥ATP依赖性功能。TFIIH具有三种已知的ATP依赖活性：由其XPB亚基催化的3'→5' DNA解旋酶活性、由其XPD亚基催化的5'→3' DNA解旋酶活性以及由其CDK7亚基催化的羧基末端结构域（CTD）激酶活性。在本报告中，我们利用TFIIH突变体，在由纯化的聚合酶和通用起始因子重构的最小转录系统中，研究TFIIH DNA解旋酶和CTD激酶活性对RNA聚合酶II有效启动子逃逸的贡献。我们的研究结果表明，TFIIH XPB DNA解旋酶主要负责防止聚合酶从启动子退出过程中早期延伸中间体的过早停滞。
