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Division of Molecular and Cellular Biology, International Graduate School of Arts and Sciences, Yokohama City University, Yokohama 230-0045, Japan
Mediator is one of the most important co-activators that function in eukaryotic transcriptional regulation. In Saccharomyces cerevisiae, Mediator is comprised of 25 subunits belonging to four structurally distinct modules: Head, Middle, Tail, and Cyc-C. Although each module plays a critical role in the regulation of a distinct set of genes, the precise molecular mechanisms remain unclear. To gain new insight into the role of the less-characterized Middle module, we analyzed the function of Med9 by constructing a set of mutants and subjecting them to a range of in vivo and in vitro assays. Our results demonstrate that Med9 has two functional domains. The species-specific amino-terminal half (aa 1–63) plays a regulatory role in transcriptional regulation in vivo and in vitro. In contrast, the well-conserved carboxy-terminal half (aa 64–149) has a more fundamental function involved in direct binding to the amino-terminal portions of Med4 and Med7 and the assembly of Med9 into the Middle module. Importantly, activator-dependent recruitment of TBP and Taf11 to the promoter is differentially affected in med9 extracts and in extracts lacking Mediator. Add-back experiments indicate that some unidentified factor(s) in med9 extracts may impact the binding of TFIID to the promoter.
* Correspondence: kokubo{at}tsurumi.yokohama-cu.ac.jp
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T. Koschubs, K. Lorenzen, S. Baumli, S. Sandstrom, A. J. R. Heck, and P. Cramer Preparation and topology of the Mediator middle module Nucleic Acids Res., January 31, 2010; (2010): gkq029v1 - gkq029. [Abstract] [Full Text] [PDF] |
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