美国西北大学何源和R. Tjian研究组合作揭示人类介体结合的转录预启动复合物（PIC）复合物结构。该项研究成果发表在2021年3月11日出版的《科学》杂志上。

他们介绍了在分辨率小于4Å处与人类介体结合的PIC的冷冻电镜镜结构。介体中的转录因子结合位点主要是灵活地拴在尾巴模块上。 通过与Mediator的多次接触，CDK7得以稳定。 RNA聚合酶II（Pol II）C末端结构域（CTD）有两个结合位点，一个在介体的头部和中间模块之间，另一个在CDK7的活性位点之间，为在介体结合的PIC中Pol II CTD磷酸化提供了结构性证据。

据了解，真核转录需要组装由Pol II和一般转录因子组成的多亚基PIC。辅助激活因子介体通过转录因子募集，促进PIC的组装，并通过TFIIH亚基CDK7刺激Pol II CTD磷酸化。

附：英文原文

Title: Structure of the human Mediator-bound transcription preinitiation complex

Author: R. Abdella, A. Talyzina, S. Chen, C. J. Inouye, R. Tjian, Y. He

Issue&Volume: 2021/03/11

Abstract: Eukaryotic transcription requires the assembly of a multi-subunit preinitiation complex (PIC) comprised of RNA polymerase II (Pol II) and the general transcription factors. The co-activator Mediator is recruited by transcription factors, facilitates the assembly of the PIC, and stimulates phosphorylation of the Pol II C-terminal domain (CTD) by the TFIIH subunit CDK7. Here, we present the cryo-electron microscopy structure of the human Mediator-bound PIC at sub-4 . Transcription factor binding sites within Mediator are primarily flexibly tethered to the tail module. CDK7 is stabilized by multiple contacts with Mediator. Two binding sites exist for the Pol II CTD, one between the head and middle modules of Mediator and the other in the active site of CDK7, providing structural evidence for Pol II CTD phosphorylation within the Mediator-bound PIC.

DOI: 10.1126/science.abg3074

Source: https://science.sciencemag.org/content/early/2021/03/10/science.abg3074