Human Mediator Enhances Activator-Facilitated Recruitment of RNA Polymerase II and Promoter Recognition by TATA-Binding Protein (TBP) Independently of TBP-Associated Factors
Human Mediator Enhances Activator-Facilitated Recruitment of RNA Polymerase II and Promoter Recognition by TATA-Binding Protein (TBP) Independently of TBP-Associated Factors
复制标题
DOI：
10.1128/mcb.23.17.6229-6242.2003
复制
发表时间：
2003-09
影响因子：
5.3
通讯作者：
Shwu‐Yuan Wu;T. Zhou;C. Chiang
中科院分区：
文献类型：
--
作者：
Shwu‐Yuan Wu;T. Zhou;C. Chiang
介体是一种参与多种转录激活因子功能的辅助因子。虽然已经分离出具有不同蛋白质组成的介体，但尚不清楚介体如何促进激活子依赖性转录，而不依赖于其对基础转录的一般刺激。为了确定介体功能的机制，我们分离了两种形式的人类介体复合物（介体-P.5和介体-P.85），并证明介体-P.5通过增强激活剂介导的RNA聚合酶II（pol II）的募集而明显起作用，而介体-P.85主要通过刺激总体基础转录起作用。当用TATA结合蛋白（TBP）代替TFIID时，介体-P.5的辅激活因子功能没有受损，但当另一种通用辅因子PC 4从反应中省略或当在pol II进入预起始复合物后加入介体-P.5时，其功能被废除。此外，介体-P. 5能够以激活剂依赖性方式增强TBP与TATA盒的结合。我们的数据提供了生物化学证据，介导的功能，促进激活剂介导的招聘pol II和启动子识别TBP，这两者都可以发生在TFIID中的TBP相关因子的情况下。
ABSTRACT Mediator is a general cofactor implicated in the functions of many transcriptional activators. Although Mediator with different protein compositions has been isolated, it remains unclear how Mediator facilitates activator-dependent transcription, independent of its general stimulation of basal transcription. To define the mechanisms of Mediator function, we isolated two forms of human Mediator complexes (Mediator-P.5 and Mediator-P.85) and demonstrated that Mediator-P.5 clearly functions by enhancing activator-mediated recruitment of RNA polymerase II (pol II), whereas Mediator-P.85 works mainly by stimulating overall basal transcription. The coactivator function of Mediator-P.5 was not impaired when TATA-binding protein (TBP) was used in place of TFIID, but it was abolished when another general cofactor, PC4, was omitted from the reaction or when Mediator-P.5 was added after pol II entry into the preinitiation complex. Moreover, Mediator- P.5 is able to enhance TBP binding to the TATA box in an activator-dependent manner. Our data provides biochemical evidence that Mediator functions by facilitating activator-mediated recruitment of pol II and also promoter recognition by TBP, both of which can occur in the absence of TBP-associated factors in TFIID.