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首页> 外文期刊>Molecular and Cellular Biology >Human Mediator Enhances Activator-Facilitated Recruitment of RNA Polymerase II and Promoter Recognition by TATA-Binding Protein (TBP) Independently of TBP-Associated Factors
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Human Mediator Enhances Activator-Facilitated Recruitment of RNA Polymerase II and Promoter Recognition by TATA-Binding Protein (TBP) Independently of TBP-Associated Factors

机译：人类介体增强激活剂促进的RNA聚合酶II的招募和TATA结合蛋白（TBP）的启动子识别，而与TBP相关因素无关

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摘要

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.
机译：介体是与许多转录激活因子的功能有关的一般辅助因子。尽管已分离出具有不同蛋白质组成的介体，但仍不清楚介体如何促进活化剂依赖性转录，而与其对基础转录的一般刺激无关。为了定义介体功能的机制，我们分离了两种形式的人类介体复合物（Mediator-P.5和Mediator-P.85），并证明了Mediator-P.5通过增强激活剂介导的RNA聚合酶II的募集而明显发挥了作用（ pol II），而Mediator-P.85主要通过刺激总体基础转录来发挥作用。当使用TATA结合蛋白（TBP）代替TFIID时，不会损害Mediator-P.5的共激活因子功能，但是当反应中省略了另一种通用辅助因子PC4或Mediator-P.5时，该因子被取消了。在pol II进入预初始化复合体后被添加。此外，Mediator-P.5能够以依赖于激活剂的方式增强TBP与TATA盒的结合。我们的数据提供了生化证据，表明介体通过促进激活剂介导的pol II募集以及TBP对启动子的识别而发挥功能，这两种情况都可能在TFIID中不存在TBP相关因子的情况下发生。

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