A Complex of Cdc4p, Skp1p, and Cdc53p/cullin Catalyzes Ubiquitination of the Phosphorylated CDK Inhibitor Sic1p

Cell. 1997 Oct 17;91(2):221-30. doi: 10.1016/s0092-8674(00)80404-3.

Abstract

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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Cell Cycle Proteins / genetics
  • Cell Cycle Proteins / isolation & purification
  • Cell Cycle Proteins / metabolism*
  • Cullin Proteins*
  • Cyclin-Dependent Kinase Inhibitor Proteins
  • Enzyme Inhibitors / isolation & purification
  • Enzyme Inhibitors / metabolism*
  • F-Box Proteins*
  • Fungal Proteins / isolation & purification
  • Fungal Proteins / metabolism*
  • Insecta
  • Phosphorylation
  • Proto-Oncogene Proteins c-myc / genetics
  • Proto-Oncogene Proteins c-myc / metabolism
  • Recombinant Proteins / metabolism
  • S-Phase Kinase-Associated Proteins
  • Saccharomyces cerevisiae
  • Saccharomyces cerevisiae Proteins*
  • Ubiquitin-Protein Ligases*
  • Ubiquitins / metabolism*

Substances

  • CDC4 protein, S cerevisiae
  • Cdc53 protein, S cerevisiae
  • Cell Cycle Proteins
  • Cullin Proteins
  • Cyclin-Dependent Kinase Inhibitor Proteins
  • Enzyme Inhibitors
  • F-Box Proteins
  • Fungal Proteins
  • Proto-Oncogene Proteins c-myc
  • Recombinant Proteins
  • S-Phase Kinase-Associated Proteins
  • SIC1 protein, S cerevisiae
  • Saccharomyces cerevisiae Proteins
  • Ubiquitins
  • Ubiquitin-Protein Ligases