Abstract
Cell cycle-specific proteolysis is critical for proper execution of mitosis in all eukaryotes. Ubiquitination and subsequent proteolysis of the mitotic regulators Clb2 and Pds1 depend on the cyclosome/APC and the 26S proteasome. We report here that components of the cell cycle machinery in yeast, specifically the cell cycle regulatory cyclin-dependent kinase Cdc28 and a conserved associated protein Cks1/Suc1, interact genetically, physically, and functionally with components of the 26S proteasome. A mutation in Cdc28 (cdc28-1N) that interferes with Cks1 binding, or inactivation of Cks1 itself, confers stabilization of Clb2, the principal mitotic B-type cyclin in budding yeast. Surprisingly, Clb2-ubiquitination in vivo and in vitro is not affected by mutations in cks1, indicating that Cks1 is not essential for cyclosome/APC activity. However, mutant Cks1 proteins no longer physically interact with the proteasome, suggesting that Cks1 is required for some aspect of proteasome function during M-phase-specific proteolysis. We further provide evidence that Cks1 function is required for degradation of the anaphase inhibitor Pds1. Stabilization of Pds1 is partially responsible for the metaphase arrest phenotype of cks1 mutants because deletion of PDS1 partially relieves the metaphase block in these mutants.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Adaptor Proteins, Signal Transducing
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Anaphase-Promoting Complex-Cyclosome
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Base Sequence
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CDC28 Protein Kinase, S cerevisiae / genetics
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CDC28 Protein Kinase, S cerevisiae / metabolism
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Cell Cycle Proteins*
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Cyclin B*
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Cyclin-Dependent Kinases / genetics
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Cyclin-Dependent Kinases / metabolism*
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Cyclins / genetics
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Cyclins / metabolism
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Cysteine Endopeptidases / genetics
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Cysteine Endopeptidases / metabolism*
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DNA Primers / genetics
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Endopeptidases / metabolism
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Enhancer Elements, Genetic
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Fungal Proteins / genetics
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Fungal Proteins / metabolism*
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Genes, Fungal
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Ligases / genetics
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Ligases / metabolism
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Metaphase
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Mitosis
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Multienzyme Complexes / genetics
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Multienzyme Complexes / metabolism*
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Mutation
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Nuclear Proteins / genetics
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Nuclear Proteins / metabolism
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Phenotype
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Proteasome Endopeptidase Complex
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Saccharomyces cerevisiae / cytology
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Saccharomyces cerevisiae / genetics
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Saccharomyces cerevisiae / metabolism*
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Saccharomyces cerevisiae Proteins*
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Schizosaccharomyces pombe Proteins*
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Securin
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Temperature
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Ubiquitin-Protein Ligase Complexes*
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Ubiquitin-Protein Ligases
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Ubiquitins / metabolism
Substances
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Adaptor Proteins, Signal Transducing
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CKS1 protein, S cerevisiae
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CLB2 protein, S cerevisiae
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Cell Cycle Proteins
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Cyclin B
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Cyclins
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DNA Primers
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Fungal Proteins
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Multienzyme Complexes
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Nuclear Proteins
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PDS1 protein, S cerevisiae
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Saccharomyces cerevisiae Proteins
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Schizosaccharomyces pombe Proteins
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Securin
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Suc1 protein, S pombe
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Ubiquitins
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Ubiquitin-Protein Ligase Complexes
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Anaphase-Promoting Complex-Cyclosome
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Ubiquitin-Protein Ligases
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CDC28 Protein Kinase, S cerevisiae
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Cyclin-Dependent Kinases
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Endopeptidases
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Cysteine Endopeptidases
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Proteasome Endopeptidase Complex
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Ligases