Mediator Requirement for Both Recruitment and Postrecruitment Steps in Transcription Initiation

Molecular Biology Institute and Department of Microbiology, Immunology and Molecular Genetics, University of California Los Angeles, 611 Young Drive East, Los Angeles, California 90095, USA.
Molecular Cell (Impact Factor: 14.46). 04/2005; 17(5):683-94. DOI: 10.1016/j.molcel.2005.02.010
Source: PubMed

ABSTRACT Mediator complexes are required for activators to stimulate Pol II preinitiation complex assembly on an associated promoter. We show here that for the mouse Egr1 gene, controlled largely by MAP kinase phosphorylation of the ELK1 transcription factor, the MED23 Mediator subunit that interacts with phospho-ELK1 is also required to stimulate Pol II initiation at a step subsequent to preinitiation complex assembly. In Med23-/- cells, histone acetylation, methylation, and chromatin remodeling complex association at the Egr1 promoter were equivalent to that of wild-type cells, yet Egr1 induction was greatly reduced. MAP kinase activation stimulated Pol II and GTF promoter binding. However, the difference in factor binding between wild-type and mutant cells was much less than the difference in transcription, and Pol II remained localized to the promoter in mutant cells. These results indicate that an interaction with MED23 stimulates initiation by promoter bound Pol II in addition to Pol II and GTF recruitment.

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Available from: Hiroshi Handa, Aug 20, 2015
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    • "ChIP assays were performed as described previously (Wang et al., 2005), and immunoprecipitated DNA was quantified by real-time PCR. The following antibodies were used: anti-ETS1 (Santa Cruz, sc-350X; 1:100); anti-Pol II (Santa Cruz, sc-899; 1:100); anti-P300 (Santa Cruz, sc-585; 1:100); anti-H3K4me1 (Abcam, ab8895; 1:500) and anti- H3K27ac (Abcam, ab4729; 1:500). "
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    • "The authors concluded that the HSF- Mediator interaction triggered activation of paused pol II (Park et al., 2001b). In vitro studies by the Roeder lab and studies in murine embryonic stem cells by the Berk group showed further evidence for Mediator in ''post-recruitment'' or elongation events (Malik et al., 2002; Wang et al., 2005a). "
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