A complex of Cdc4p, Skp1p, and Cdc53p/cullin catalyzes ubiquitination of the phosphorylated CDK inhibitor Sic1p.
In S. cerevisiae, the G1/S transition requires Cdc4p, Cdc34p, Cdc53p, Skp1p, and the Cln/Cdc28p cyclin-dependent kinase (Cdk). These proteins are thought to promote the proteolytic inactivation of the S-phase Cdk inhibitor Sic1p. We show here that Cdc4p, Cdc53p, and Skp1p assemble into a ubiquitin ligase complex named SCFCdc4p. When mixed ... together, SCFCdc4p subunits, E1 enzyme, the E2 enzyme Cdc34p, and ubiquitin are sufficient to reconstitute ubiquitination of Cdk-phosphorylated Sic1p. Phosphorylated Sic1p substrate is specifically targeted for ubiquitination by binding to a Cdc4p/Skp1p subcomplex. Taken together, these data illuminate the molecular basis for the G1/S transition in budding yeast and suggest a general mechanism for phosphorylation-targeted ubiquitination in eukaryotes.
Mesh Terms:
Animals, Cell Cycle Proteins, Cullin Proteins, Cyclin-Dependent Kinase Inhibitor Proteins, Enzyme Inhibitors, F-Box Proteins, Fungal Proteins, Insects, Phosphorylation, Proto-Oncogene Proteins c-myc, Recombinant Proteins, S-Phase Kinase-Associated Proteins, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins, Ubiquitin-Protein Ligases, Ubiquitins
Animals, Cell Cycle Proteins, Cullin Proteins, Cyclin-Dependent Kinase Inhibitor Proteins, Enzyme Inhibitors, F-Box Proteins, Fungal Proteins, Insects, Phosphorylation, Proto-Oncogene Proteins c-myc, Recombinant Proteins, S-Phase Kinase-Associated Proteins, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins, Ubiquitin-Protein Ligases, Ubiquitins
Cell
Date: Oct. 17, 1997
PubMed ID: 9346239
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