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Med19(Rox3) regulates Intermodule interactions in the Saccharomyces cerevisiae mediator complex.
The Journal of Biological Chemistry (2007)
  • Shamara M Baidoobonso
  • Benjamin W Guidi
  • Lawrence C Myers
The Saccharomyces cerevisiae Mediator is a 25-subunit complex that facilitates both transcriptional activation and repression. Structural and functional studies have divided Mediator subunits into four distinct modules. The Head, Middle, and Tail modules form the core functional Mediator complex, whereas a fourth, the Cyc-C module, is variably associated with the core. By purifying Mediator from a strain lacking the Med19(Rox3) subunit, we have found that a complex missing only the Med19(Rox3) subunit can be isolated under mild conditions. Additionally, we have established that the entire Middle module is released when the Deltamed19(rox3) Mediator is purified under more stringent conditions. In contrast to most models of the modular structure of Mediator, we show that release of the Middle module in the Deltamed19(rox3) Mediator leaves a stable complex made up solely of Head and Tail subunits. Both the intact and Head-Tail Deltamed19(rox3) Mediator complexes have defects in enhanced basal transcription, enhanced TFIIH phosphorylation of the CTD, as well as binding of RNA Pol II and the CTD. The largely intact Deltamed19(rox3) complex facilitates activated transcription at levels similar to the wild type Mediator. In the absence of the Middle module, however, the Deltamed19(rox3) Mediator is unable to facilitate activated transcription. Although the Middle module is unnecessary for holding the Head and Tail modules together, it is required for the complex to function as a conduit between activators and the core transcription machinery.
  • Gene Expression Regulation,
  • Fungal/physiology,
  • Mediator Complex,
  • Multiprotein Complexes/genetics,
  • Multiprotein Complexes/metabolism,
  • RNA Polymerase II/genetics,
  • RNA Polymerase II/metabolism,
  • Saccharomyces cerevisiae/physiology,
  • Saccharomyces cerevisiae Proteins/genetics,
  • Saccharomyces cerevisiae Proteins/metabolism,
  • Transcription Factor TFIIH/genetics,
  • Transcription Factor TFIIH/metabolism,
  • Transcription Factors/genetics,
  • Transcription Factors/metabolism,
  • Transcription,
  • Genetic/physiology
Publication Date
February 23, 2007
Citation Information
Shamara M Baidoobonso, Benjamin W Guidi and Lawrence C Myers. "Med19(Rox3) regulates Intermodule interactions in the Saccharomyces cerevisiae mediator complex." The Journal of Biological Chemistry Vol. 282 Iss. 8 (2007)
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