Transcriptional activation by Gcn4p involves independent interactions with the SWI/SNF complex and the SRB/mediator.
Mutations in three subunits of the SWI/SNF complex and in the Med2p subunit of the SRB/mediator of pol II holoenzyme impaired Gcn4p-activated transcription of HIS3 without reducing Gcn4p-independent transcription of this gene. Recombinant Gcn4p interacted with SWI/SNF and SRB/mediator subunits in cell extracts in a manner dependent on the same hydrophobic clusters in the Gcn4p activation domain; however, higher concentrations of Gcn4p were required for binding to SWI/SNF versus SRB/mediator subunits. In addition, SRB/mediator and SWI/SNF subunits did not coimmunopreciptate from the extracts. These findings, together with the fact that Gcn4p specifically interacted with purified SWI/SNF, strongly suggest that Gcn4p independently recruits SWI/SNF and holoenzyme to its target promoters in the course of activating transcription.
Natarajan
K
K
Laboratory of Eukaryotic Gene Regulation, National Institute of Child Health and Human Development, Bethesda, Maryland 20892, USA.
Jackson
B M
BM
Zhou
H
H
Winston
F
F
Hinnebusch
A G
AG
D004257:DNA Polymerase II / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005656:Fungal Proteins / Q000378:metabolism*; D015966:Gene Expression Regulation, Fungal; D006836:Hydro-Lyases / Q000235:genetics; D056892:Mediator Complex; D009154:Mutation; D009687:Nuclear Proteins; D009707:Nucleosomes / Q000378:metabolism*; D011485:Protein Binding; D011494:Protein Kinases / Q000378:metabolism*; D011994:Recombinant Proteins; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors / Q000378:metabolism*; D015533:Transcriptional Activation; D015003:Yeasts / Q000378:metabolism
D004268:DNA-Binding Proteins; D005656:Fungal Proteins; D056892:Mediator Complex; D009687:Nuclear Proteins; D009707:Nucleosomes; D011994:Recombinant Proteins; C118425:SAGA protein, Emericella nidulans; C074748:SRB2 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D011494:Protein Kinases; D004257:DNA Polymerase II; D006836:Hydro-Lyases; C021434:imidazoleglycerolphosphate dehydratase