The yeast cyclin-C-Cdk8p kinase complex represses the transcription of a subset of genes involved in the stress response. To relieve this repression, cyclin C is destroyed in cells exposed to H(2)O(2) by the 26S proteasome. This report identifies Not4p as the ubiquitin ligase mediating H(2)O(2)-induced cyclin C destruction. Not4p is required for H(2)O(2)-induced cyclin C destruction in vivo and polyubiquitylates cyclin C in vitro by utilizing Lys48, a ubiquitin linkage associated with directing substrates to the 26S proteasome. Before its degradation, cyclin C, but not Cdk8p, translocates from the nucleus to the cytoplasm. This translocation requires both the cell-wall-integrity MAPK module and phospholipase C, and these signaling pathways are also required for cyclin C destruction. In addition, blocking cytoplasmic translocation slows the mRNA induction kinetics of two stress response genes repressed by cyclin C. Finally, a cyclin C derivative restricted to the cytoplasm is still subject to Not4p-dependent destruction, indicating that the degradation signal does not occur in the nucleus. These results identify a stress-induced proteolytic pathway regulating cyclin C that requires nuclear to cytoplasmic relocalization and Not4p-mediated ubiquitylation.
|Evidence ID||Analyze ID||Interactor||Interactor Systematic Name||Interactor||Interactor Systematic Name||Type||Assay||Annotation||Action||Modification||Phenotype||Source||Reference||Note|
|Evidence ID||Analyze ID||Gene||Gene Systematic Name||Gene Ontology Term||Gene Ontology Term ID||Qualifier||Aspect||Method||Evidence||Source||Assigned On||Reference||Annotation Extension|
|Evidence ID||Analyze ID||Gene||Gene Systematic Name||Phenotype||Experiment Type||Experiment Type Category||Mutant Information||Strain Background||Chemical||Details||Reference|
|Evidence ID||Analyze ID||Regulator||Regulator Systematic Name||Target||Target Systematic Name||Experiment||Conditions||Strain||Source||Reference|