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首页> 外文期刊>Journal of Molecular Biology >Activator-mediator binding stabilizes RNA polymerase II orientation within the human mediator-RNA polymerase II-TFIIF assembly
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Activator-mediator binding stabilizes RNA polymerase II orientation within the human mediator-RNA polymerase II-TFIIF assembly

机译：激活剂-介体结合可稳定人介体-RNA聚合酶II-TFIIF组装物中的RNA聚合酶II方向

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摘要

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 II 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.
机译：人类介体复合物以尚未完全了解的方式控制RNA聚合酶II（pol II）的功能。激活剂-介体结合改变了介体结构，这些激活剂诱导的结构转变似乎在调节转录中起关键作用。最近的低温电子显微镜（EM）分析显示，pol II在Mediator-pol II-TFIIF组件内采用了稳定的方向，其中Mediator与病毒蛋白16（VP16）的激活域结合。尽管TFIIF被证明对于在该装配中定向pol II很重要，但未评估活化剂的潜在作用。为了确定激活剂结合如何影响pol II方向，我们分离了其中Mediator未与激活剂结合的人类Mediator-pol II-TFIIF复合物。对该组件的Cryo-EM分析加上pol II晶体结构对接发现，pol II在相同的一般位置结合Mediator。但是，与结合VP16的介体相反，在没有激活剂的情况下，pol II似乎无法稳定地定向。 pol II方向的可变性在机械上可能很重要，也许可以在人类启动子上实现有义和反义转录。由于介体与pol II广泛相互作用，因此这些结果表明，由激活剂结合诱导的介体结构变化有助于在转录起始之前稳定地定向pol II。

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