Negative regulation of Gcn4 and Msn2 transcription factors by Srb10 cyclin-dependent kinase

• Published in: Genes & development Vol. 15; no. 9; pp. 1078 - 1092
• Main Authors: Chi, Y, Huddleston, M J, Zhang, X, Young, R A, Annan, R S, Carr, S A, Deshaies, R J
• Format: Journal Article
• Language: English
• Published: United States Cold Spring Harbor Laboratory Press 01.05.2001
• Subjects: Amino Acids - metabolism; Cell Nucleus - metabolism; Culture Media; Cyclin-Dependent Kinase 8; Cyclin-Dependent Kinases - genetics; Cyclin-Dependent Kinases - metabolism; DNA-Binding Proteins - metabolism; Fungal Proteins - metabolism; Gcn4 protein; Msn2 protein; Mutation; Peptide Synthases - metabolism; Phosphorylation; Protein Kinases - metabolism; Protein Subunits; Protein-Serine-Threonine Kinases - metabolism; Research Paper; RNA Polymerase II - metabolism; Saccharomyces cerevisiae; Saccharomyces cerevisiae Proteins; SKP Cullin F-Box Protein Ligases; srb10 gene; Trans-Activators - metabolism; Transcription Factors - metabolism; Ubiquitins - metabolism; Yeasts - genetics; Yeasts - metabolism
• ISSN: 0890-9369; 1549-5477
• DOI: 10.1101/gad.867501

The budding yeast transcriptional activator Gcn4 is rapidly degraded in an SCF(Cdc4)-dependent manner in vivo. Upon fractionation of yeast extracts to identify factors that mediate Gcn4 ubiquitination, we found that Srb10 phosphorylates Gcn4 and thereby marks it for recognition by SCF(Cdc4) ubiquitin ligase. Srb10 is a physiological regulator of Gcn4 stability because both phosphorylation and turnover of Gcn4 are diminished in srb10 mutants. Gcn4 is almost completely stabilized in srb10Delta pho85Delta cells, or upon mutation of all Srb10 phosphorylation sites within Gcn4, suggesting that the Pho85 and Srb10 cyclin-dependent kinases (CDKs) conspire to limit the accumulation of Gcn4. The multistress response transcriptional regulator Msn2 is also a substrate for Srb10 and is hyperphosphorylated in an Srb10-dependent manner upon heat-stress-induced translocation into the nucleus. Whereas Msn2 is cytoplasmic in resting wild-type cells, its nuclear exclusion is partially compromised in srb10 mutant cells. Srb10 has been shown to repress a subset of genes in vivo, and has been proposed to inhibit transcription via phosphorylation of the C-terminal domain of RNA polymerase II. We propose that Srb10 also inhibits gene expression by promoting the rapid degradation or nuclear export of specific transcription factors. Simultaneous down-regulation of both transcriptional regulatory proteins and RNA polymerase may enhance the potency and specificity of transcriptional inhibition by Srb10.