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Related Experiment Videos

Mediator as a general transcription factor.

Yuichiro Takagi1, Roger D Kornberg

  • 1Department of Structural Biology, Stanford University School of Medicine, Stanford, California 94305-5400, USA.

The Journal of Biological Chemistry
|November 3, 2005
PubMed
Summary

Mediator is essential for basal RNA polymerase II transcription. This general transcription factor is crucial for initiating transcription, similar to RNA polymerase II itself.

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Area of Science:

  • Molecular Biology
  • Gene Regulation
  • Biochemistry

Background:

  • Yeast strains with temperature-sensitive (ts) mutations in Mediator (Srb4 subunit) or RNA polymerase II cease mRNA transcription at restrictive temperatures.
  • Previous studies indicated a critical role for Mediator in transcription.
  • The precise function of Mediator in basal transcription remained to be fully elucidated.

Purpose of the Study:

  • To investigate the role of Mediator in basal RNA polymerase II transcription.
  • To determine if Mediator is required for the initiation of transcription in vivo.
  • To characterize the function of the Srb4 subunit of Mediator in transcription regulation.

Main Methods:

  • Utilized yeast strains with temperature-sensitive mutations in the Srb4 subunit of Mediator.
  • Performed in vitro transcription assays at restrictive temperatures.
  • Compared transcription defects in srb4ts strains to those with RNA polymerase II mutations.

Main Results:

  • Mediator (srb4ts) was found to be defective in stimulating basal RNA polymerase II transcription in vitro at restrictive temperatures.
  • The transcription defect observed in srb4ts Mediator strains was similar to that of RNA polymerase II mutant strains.
  • Mediator's role as an anti-inhibitor opposing negative regulators was largely excluded.

Conclusions:

  • Mediator is indispensable for basal RNA polymerase II transcription in vivo.
  • Mediator functions as a general transcription factor, critical for transcription initiation.
  • Mediator's importance is comparable to RNA polymerase II and other general transcription factors.

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