Yeast Genetics and Molecular Biology 1998
College Park, Maryland
August 1998

Name: McVeigh, Richard
Mailing Address: LEGR-NICHD, National Institutes of Health, 6A/B1A-5 6 Center Dr, Bethesda, MD 20892, USA
Email Address: rmcveigh@aghmac1.nichd.nih.gov
Phone and Fax numbers: 301-594-7259, 301-496-8576

023

Gcn4p activation domain interacts specifically with components of TFIID, Holoenzyme Mediator and ADA/GCN5 complex: evidence for redundant pathways.


Richard McVeigh (1) , Belinda Jackson (1), Connie Drysdale (1), Yu Bai (2), Edward Klebanow (2), Christoph Hengartner (3), Tetsuro Kokubo (4), Mark Swanson (4), Richard Young (3), Yoshihiro Nakatani (4), Anthony Weil (2), and Alan Hinnebusch (1)
(1) LEGR-NICHD, National Institutes of Health, Bethesda, MD 20892; (2) Dept. of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN 37232-0615 (3) Whitehead Institute, Cambridge, MA 02142; (4) LMGR-NICHD, National Institutes of Health, Bethesda, MD 20892;

The transcriptional activator GCN4 contains clusters of hydrophobic residues that make additive contributions to transcription in vivo. We observed efficient binding of a GST-GCN4 fusion to components of TFIID, holoenzyme mediator and ADA/GCN5 complex in cell extracts, that was dependent on the hydrophobic clusters in the activation domain. There were additive effects of the mutations on binding of coactivator proteins in vitro that paralleled reductions in activation in vivo. Immunoprecipitation studies have revealed that components of the mediator are not associated with TFIID and the ADA/GCN5 complex in cell extracts. GCN4 is thus believed to interact independently with TFIID, ADA/GCN5 and mediator using nearly identical sets of hydrophobic clusters for all these interactions. Full activation is dependent upon interaction of GCN4 with all three complexes, as mutations in single components of the three complexes can have dramatic effects on the ability of GCN4 to function as a transcriptional activator in vivo. In vitro, GST-GCN4 fusion was able to bind to partially purified holoenzyme mediator in a manner similar that seen in cell extracts, suggesting that mediator is one of the direct contacts of GCN4.

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