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A study of Mediator subunit enhancer-promoter binding

ABSTRACT: Mediator is a transcriptional co-activator recruited to enhancers by DNA-binding activators, and it also interacts with RNA polymerase (Pol) II as part of the preinitiation complex (PIC). We demonstrate that a single Mediator complex associates with the enhancer and core promoter in vivo, indicating that it can physically bridge these transcriptional elements. However, the Mediator kinase module associates strongly with the enhancer, but not with the core promoter, and it dissociates from the enhancer upon depletion of the TFIIH kinase. Severing the kinase module from Mediator by removing the connecting subunit Med13 does not affect Mediator association at the core promoter, but increases occupancy at enhancers. Thus, Mediator undergoes a compositional change in which the kinase module, recruited via Mediator to the enhancer, dissociates from Mediator to permit association with Pol II and the PIC. As such, Mediator acts as a dynamic bridge between the enhancer and core promoter.

ORGANISM(S): Saccharomyces cerevisiae

PROVIDER: GSE82082 | GEO | 2016/10/31

SECONDARY ACCESSION(S): PRJNA323937

REPOSITORIES: GEO

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The Cdk8 kinase module regulates Mediator-RNA polymerase II interaction

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Evidence that Mediator is essential for Pol II transcription but not a required component of the preinitiation complex in vivo

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Project description:Cyclin Dependent Kinases CDK8 and CDK19 (Mediator kinase) are regulatory components of the Mediator complex, a highly conserved complex that fine tunes transcriptional output. While Mediator kinase has been implicated in the transcriptional control of key pathways necessary for development and growth, its function in vivo has not been well described. Herein, we report the consequences of complete ablation of both Cdk8/19 on tissue homeostasis. We show that intestinal epithelial specific deletion of Mediator kinase leads to a distinct defect in secretory progenitor differentiation with broad loss of the intestinal secretory cell types. Using a phospho-proteogenomic approach, we show that the Cdk8/19 kinase module interacts with and phosphorylates components of the chromatin remodeling complex Swi/Snf in intestinal epithelial cells. Genomic localisation of Swi/Snf and Mediator shows Cdk8/19-dependent genomic binding at distinct super-enhancer loci within key lineage specification genes, including the master regulator of secretory differentiation ATOH1. Using CRISPRi/CRISPRa, we identify a distinct Mediator-Swi/Snf bound enhancer element that is necessary and sufficient for ATOH1 expression in a Mediator-kinase dependent manner. As such, these studies uncover a newly described transcriptional mechanism of ATOH1-dependent intestinal cell specification that is dependent on the coordinated interaction of the chromatin remodeling complex Swi/Snf and Mediator complex.

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