Mediator independently orchestrates multiple steps of preinitiation complex assembly in vivo.

Nucleic acids research 2015 Oct 30

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Mediator is a large multiprotein complex conserved in all eukaryotes, which has a crucial coregulator function in transcription by RNA polymerase II (Pol II). However, the molecular mechanisms of its action in vivo remain to be understood. Med17 is an essential and central component of the Mediator head module. In this work, we utilised our large collection of conditional temperature-sensitive med17 mutants to investigate Mediator's role in coordinating preinitiation complex (PIC) formation in vivo at the genome level after a transfer to a non-permissive temperature for 45 minutes. The effect of a yeast mutation proposed to be equivalent to the human Med17-L371P responsible for infantile cerebral atrophy was also analyzed. The ChIP-seq results demonstrate that med17 mutations differentially affected the global presence of several PIC components including Mediator, TBP, TFIIH modules and Pol II. Our data show that Mediator stabilizes TFIIK kinase and TFIIH core modules independently, suggesting that the recruitment or the stability of TFIIH modules is regulated independently on yeast genome. We demonstrate that Mediator selectively contributes to TBP recruitment or stabilization to chromatin. This study provides an extensive genome-wide view of Mediator's role in PIC formation, suggesting that Mediator coordinates multiple steps of a PIC assembly pathway. © The Author(s) 2015. Published by Oxford University Press on behalf of Nucleic Acids Research.

Citation

Fanny Eyboulet, Sandra Wydau-Dematteis, Thomas Eychenne, Olivier Alibert, Helen Neil, Claire Boschiero, Marie-Claire Nevers, Hervé Volland, David Cornu, Virginie Redeker, Michel Werner, Julie Soutourina. Mediator independently orchestrates multiple steps of preinitiation complex assembly in vivo. Nucleic acids research. 2015 Oct 30;43(19):9214-31