Activator-Mediator Binding Stabilizes RNA Polymerase II Orientation within the Human Mediator-RNA Polymerase II-TFIIF Assembly
Activator-Mediator Binding Stabilizes RNA Polymerase II Orientation within the Human Mediator-RNA Polymerase II-TFIIF Assembly
复制标题
DOI：
10.1016/j.jmb.2012.02.014
复制
发表时间：
2012-04-13
影响因子：
5.6
通讯作者：
Taatjes, Dylan J.
中科院分区：
文献类型：
--
作者：
Bernecky, Carrie;Taatjes, Dylan J.
人类介体复合体以尚不完全了解的方式控制RNA聚合酶II(PolII)的功能。激活剂介体结合改变介体结构，这些激活剂诱导的结构变化似乎在转录调控中起着关键作用。最近的一项冷冻电子显微镜(EM)分析表明，PolII在Mediator PolII TFIIF组件中具有稳定的取向，其中Mediator与病毒蛋白16(VP16)的激活结构域结合。尽管TFIIF被证明对在该组装中定位PolII很重要，但激活因子的潜在作用没有得到评估。为了确定激活剂结合如何影响PolII的定向，我们分离了介体不与激活剂结合的人介体PolII TFIIF复合体。对该组装件的冷冻-EM分析以及POLIT晶体结构对接表明，POLII在相同的一般位置与介体结合；然而，与VP16结合的介体相反，在没有激活剂的情况下，POLII似乎不能稳定定位。POLII定位的可变性可能在机制上很重要，可能使人类启动子的正义和反义转录成为可能。由于Mediator与PolII相互作用广泛，这些结果表明，激活子结合引起的介体结构变化有助于在转录启动之前稳定地定位PolII。(C)2012爱思唯尔有限公司。保留所有权利。
The human Mediator complex controls RNA polymerase II (pol II) function in ways that remain incompletely understood. Activator Mediator binding alters Mediator structure, and these activator-induced structural shifts appear to play key roles in regulating transcription. A recent cryo-electron microscopy (EM) analysis revealed that pol II adopted a stable orientation within a Mediator pol II TFIIF assembly in which Mediator was bound to the activation domain of viral protein 16 (VP16). Whereas TFIIF was shown to be important for orienting pol II within this assembly, the potential role of the activator was not assessed. To determine how activator binding might affect pol II orientation, we isolated human Mediator pol II TFIIF complexes in which Mediator was not bound to an activator. Cryo-EM analysis of this assembly, coupled with pol IT crystal structure docking, revealed that pol II binds Mediator at the same general location; however, in contrast to VP16-bound Mediator, pol II does not appear to stably orient in the absence of an activator. Variability in pol II orientation might be important mechanistically, perhaps to enable sense and antisense transcription at human promoters. Because Mediator interacts extensively with pol II, these results suggest that Mediator structural shifts induced by activator binding help stably orient pol II prior to transcription initiation. (C) 2012 Elsevier Ltd. All rights reserved.