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Mediator protein mutations that selectively abolish activated transcription
L C Myers1, C M Gustafsson, K C Hayashibara
1Department of Structural Biology, Stanford University School of Medicine, Stanford, CA 94305, USA.
Summary
Deleting key subunits of the yeast Mediator complex (Med2, Pgd1, Sin4) blocked transcriptional activation in vitro. This highlights Mediator's crucial role as a global transcriptional coactivator in yeast.
Area of Science:
- Molecular Biology
- Yeast Genetics
- Transcriptional Regulation
Background:
- The Mediator complex is a crucial coactivator for RNA polymerase II transcription.
- Specific subunits of Mediator are known to be essential for certain activation processes.
Purpose of the Study:
- To investigate the role of specific Mediator subunits in transcriptional activation.
- To compare in vitro and in vivo requirements for Mediator function.
- To identify Mediator as a global transcriptional coactivator.
Main Methods:
- In vitro transcription assays using Gal4-VP16 and Gcn4 activators.
- Genetic deletion studies in yeast (Deltamed2 strain).
- Whole genome expression profiling.
Main Results:
- Deletion of Med2, Pgd1, or Sin4 abolished Gal4-VP16-mediated activation in vitro.
- Mediator subunit requirements differed for Gcn4 activation.
- In vivo genetic requirements mirrored in vitro findings.
- Deltamed2 strain showed reduced transcription of inducible genes.
Conclusions:
- Mediator subunits Med2, Pgd1, and Sin4 are essential for specific transcriptional activation events.
- Mediator functions as a global transcriptional coactivator in yeast.
- In vitro findings accurately reflect in vivo requirements for Mediator function.