Department of Cell Biology, The Scripps Research Institute, La Jolla, CA 92037, USA.
Structure. 2012 May 9;20(5):899-910. doi: 10.1016/j.str.2012.02.023.
Mediator, a large (21 polypeptides, MW ∼1 MDa) complex conserved throughout eukaryotes, plays an essential role in control of gene expression by conveying regulatory signals that influence the activity of the preinitiation complex. However, the precise mode of interaction between Mediator and RNA polymerase II (RNAPII), and the mechanism of regulation by Mediator remain elusive. We used cryo-electron microscopy and reconstituted in vitro transcription assays to characterize a transcriptionally-active complex including the Mediator Head module and components of a minimum preinitiation complex (RNAPII, TFIIF, TFIIB, TBP, and promoter DNA). Our results reveal how the Head interacts with RNAPII, affecting its conformation and function.
中介体是一种广泛存在于真核生物中的大型复合物（21 个多肽，MW∼1 MDa），通过传递影响起始前复合物活性的调节信号，在基因表达的调控中发挥着重要作用。然而，中介体与 RNA 聚合酶 II（RNAPII）之间的确切相互作用模式以及中介体的调节机制仍不清楚。我们使用低温电子显微镜和体外重建转录实验来表征一个转录活性复合物，该复合物包括中介体头部模块和一个最小起始前复合物的成分（RNAPII、TFIIF、TFIIB、TBP 和启动子 DNA）。我们的结果揭示了头部如何与 RNAPII 相互作用，从而影响其构象和功能。
