title: Interaction of Gcn4 with target gene chromatin is modulated by proteasome function.
abstract: The ubiquitin-proteasome system (UPS) influences gene transcription in multiple ways. One way in which the UPS affects transcription centers on transcriptional activators, the function of which can be stimulated by components of the UPS that also trigger their destruction. Activation of transcription by the yeast activator Gcn4, for example, is attenuated by mutations in the ubiquitin ligase that mediates Gcn4 ubiquitylation or by inhibition of the proteasome, leading to the idea that ubiquitin-mediated proteolysis of Gcn4 is required for its activity. Here we probe the steps in Gcn4 activity that are perturbed by disruption of the UPS. We show that the ubiquitylation machinery and the proteasome control different steps in Gcn4 function and that proteasome activity is required for the ability of Gcn4 to bind to its target genes in the context of chromatin. Curiously, the effect of proteasome inhibition on Gcn4 activity is suppressed by mutations in the ubiquitin-selective chaperone Cdc48, revealing that proteolysis per se is not required for Gcn4 activity. Our data highlight the role of Cdc48 in controlling promoter occupancy by Gcn4 and support a model in which ubiquitylation of activators-not their destruction-is important for function.
authors.affiliation: Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37232.
authors.forename: Gregory C
authors.initials: GC
authors.lastname: Howard
authors.affiliation: Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37232 william.p.tansey@vanderbilt.edu.
authors.forename: William P
authors.initials: WP
authors.lastname: Tansey
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D050976:Basic-Leucine Zipper Transcription Factors / Q000378:metabolism* / Q000502:physiology*; D018797:Cell Cycle Proteins / Q000378:metabolism; D002843:Chromatin / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D018832:Molecular Chaperones / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D059748:Proteolysis; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism* / Q000502:physiology*; D014157:Transcription Factors / Q000378:metabolism; D015533:Transcriptional Activation; D025801:Ubiquitin / Q000378:metabolism; D054875:Ubiquitination; D000074405:Valosin Containing Protein
chemical_list: D050976:Basic-Leucine Zipper Transcription Factors; D018797:Cell Cycle Proteins; D002843:Chromatin; D004268:DNA-Binding Proteins; C501391:GCN4 protein, S cerevisiae; D018832:Molecular Chaperones; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D025801:Ubiquitin; D046988:Proteasome Endopeptidase Complex; D000251:Adenosine Triphosphatases; C000614177:CDC48 protein, S cerevisiae; D000074405:Valosin Containing Protein