Role for the MED21-MED7 Hinge in Assembly of the Mediator-RNA Polymerase II Holoenzyme.

Mediator plays an integral role in activation of RNA polymerase II (Pol II) transcription. A key step in activation is binding of Mediator to Pol II to form the Mediator-Pol II holoenzyme. Here, we exploit a combination of biochemistry and macromolecular EM to investigate holoenzyme assembly. We identify a subset of human Mediator head module subunits that bind Pol II independent of other subunits and thus probably contribute to a major Pol II binding site. In addition, we show that binding of human Mediator to Pol II depends on the integrity of a conserved "hinge" in the middle module MED21-MED7 heterodimer. Point mutations in the hinge region leave core Mediator intact but lead to increased disorder of the middle module and markedly reduced affinity for Pol II. These findings highlight the importance of Mediator conformation for holoenzyme assembly. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

Citation

Shigeo Sato, Chieri Tomomori-Sato, Kuang-Lei Tsai, Xiaodi Yu, Mihaela Sardiu, Anita Saraf, Michael P Washburn, Laurence Florens, Francisco J Asturias, Ronald C Conaway, Joan W Conaway. Role for the MED21-MED7 Hinge in Assembly of the Mediator-RNA Polymerase II Holoenzyme. The Journal of biological chemistry. 2016 Dec 23;291(52):26886-26898

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PMID: 27821593

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