Department of Biomedical Sciences, School of Public Health, University at Albany, Albany, United States.
Computational Biology Branch, National Center for Biotechnology Information, National Library of Medicine, Bethesda, United States.
Elife. 2018 Dec 12;7:e39633. doi: 10.7554/eLife.39633.
The Mediator complex stimulates the cooperative assembly of a pre-initiation complex (PIC) and recruitment of RNA Polymerase II (Pol II) for gene activation. The core Mediator complex is organized into head, middle, and tail modules, and in budding yeast (), Mediator recruitment has generally been ascribed to sequence-specific activators engaging the tail module triad of Med2-Med3-Med15 at upstream activating sequences (UASs). We show that yeast lacking Med2-Med3-Med15 are viable and that Mediator and PolII are recruited to promoters genome-wide in these cells, albeit at reduced levels. To test whether Mediator might alternatively be recruited via interactions with the PIC, we examined Mediator association genome-wide after depleting PIC components. We found that depletion of Taf1, Rpb3, and TBP profoundly affected Mediator association at active gene promoters, with TBP being critical for transit of Mediator from UAS to promoter, while Pol II and Taf1 stabilize Mediator association at proximal promoters.
中介复合物刺激起始前复合物（PIC）的协同组装，并募集 RNA 聚合酶 II（Pol II）以激活基因。核心中介复合物分为头部、中部和尾部模块，在芽殖酵母（）中，中介复合物的募集通常归因于序列特异性激活剂与上游激活序列（UAS）上的尾部模块三联体 Med2-Med3-Med15 结合。我们表明，缺乏 Med2-Med3-Med15 的酵母是可行的，并且 Mediator 和 PolII 在这些细胞中被募集到全基因组的启动子，尽管水平较低。为了测试 Mediator 是否可以通过与 PIC 的相互作用被募集，我们在耗尽 PIC 成分后检查了 Mediator 的全基因组关联。我们发现，Taf1、Rpb3 和 TBP 的耗竭严重影响了活性基因启动子上的 Mediator 关联，TBP 对于 Mediator 从 UAS 到启动子的转运至关重要，而 Pol II 和 Taf1 则稳定了近端启动子上的 Mediator 关联。
