SIC1 is ubiquitinated in vitro by a pathway that requires CDC4, CDC34, and cyclin/CDK activities.
Traversal from G1 to S-phase in cycling cells of budding yeast is dependent on the destruction of the S-phase cyclin/CDK inhibitor SIC1. Genetic data suggest that SIC1 proteolysis is mediated by the ubiquitin pathway and requires the action of CDC34, CDC4, CDC53, SKP1, and CLN/CDC28. As a first step in ... defining the functions of the corresponding gene products, we have reconstituted SIC1 multiubiquitination in DEAE-fractionated yeast extract. Multiubiquitination depends on cyclin/CDC28 protein kinase and the CDC34 ubiquitin-conjugating enzyme. Ubiquitin chain formation is abrogated in cdc4ts mutant extracts and assembly restored by the addition of exogenous CDC4, suggesting a direct role for this protein in SIC1 multiubiquitination. Deletion analysis of SIC1 indicates that the N-terminal 160 residues are both necessary and sufficient to serve as substrate for CDC34-dependent ubiquitination. The complementary C-terminal segment of SIC1 binds to the S-phase cyclin CLB5, indicating a modular structure for SIC1.
Mesh Terms:
CDC28 Protein Kinase, S cerevisiae, Cell Cycle Proteins, Cyclin B, Cyclin-Dependent Kinase Inhibitor Proteins, Cyclins, Enzyme Inhibitors, F-Box Proteins, Fungal Proteins, Ligases, Phosphorylation, Saccharomyces cerevisiae Proteins, Ubiquitin-Protein Ligase Complexes, Ubiquitin-Protein Ligases, Ubiquitins, Yeasts
CDC28 Protein Kinase, S cerevisiae, Cell Cycle Proteins, Cyclin B, Cyclin-Dependent Kinase Inhibitor Proteins, Cyclins, Enzyme Inhibitors, F-Box Proteins, Fungal Proteins, Ligases, Phosphorylation, Saccharomyces cerevisiae Proteins, Ubiquitin-Protein Ligase Complexes, Ubiquitin-Protein Ligases, Ubiquitins, Yeasts
Mol. Biol. Cell
Date: Aug. 01, 1997
PubMed ID: 9285816
View in: Pubmed Google Scholar
Download Curated Data For This Publication
14866
Switch View:
- Interactions 4