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Site-specific Srb10-dependent phosphorylation of the yeast Mediator subunit Med2 regulates gene expression from the

Magnus Hallberg1, Gennady V Polozkov, Guo-Zhen Hu

  • 1Department of Medical Biochemistry and Biophysics, Umeå University, SE-901 87 Umeå, Sweden.

Proceedings of the National Academy of Sciences of the United States of America
|February 28, 2004
PubMed

Insights

The cyclin-dependent kinase Srb10 phosphorylates Med2, a subunit of the yeast Mediator complex. This posttranslational modification is crucial for regulating the expression of specific genes involved in transcriptional regulation.

Area of Science:

  • Molecular Biology
  • Gene Regulation
  • Biochemistry

Background:

  • The yeast Mediator complex is essential for transcriptional regulation, interacting with activators and RNA polymerase II.
  • The precise molecular mechanisms underlying Mediator complex function remain largely uncharacterized.

Purpose of the Study:

  • To investigate the molecular mechanisms of Mediator complex function.
  • To identify specific interactions and modifications affecting Mediator complex activity.

Main Methods:

  • In vivo and in vitro interaction and phosphorylation assays.
  • Site-directed mutagenesis of the Med2 phosphorylation site.
  • Analysis of gene expression for plasmid-encoded genes (REP1, REP2, FLP1, RAF1).

Main Results:

  • Srb10 kinase was found to interact with and phosphorylate the Med2 subunit of the Mediator complex.
  • Mutation of the single Med2 phosphorylation site led to significantly reduced expression of REP1, REP2, FLP1, and RAF1 genes.
  • These findings align with previous studies on Srb10/Srb11 deletions, implicating posttranslational modifications in Mediator function.

Conclusions:

  • Posttranslational modification, specifically phosphorylation of Med2 by Srb10, plays a critical role in regulating gene expression.
  • These modifications are vital for the Mediator complex's function in transcriptional regulation.
  • The study highlights the importance of understanding Mediator subunit modifications for comprehending gene expression control.

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