Cyclin-dependent kinase and Cks/Suc1 interact with the proteasome in yeast to control proteolysis of M-phase targets

Article Abstract:

Cks/Suc1 and cyclin-dependent kinase interact with the yeast proteasome to regulate proteolysis of M-phase targets. Components of the yeast cell cycle mechanism, more precisely a conserved associated protein Cks1/Suc1 and the cell cycle regulatory cyclin-dependent kinase Cdc28, interact genetically, functionally and physically with components of the 26S proteasome. A mutation in Cdc28 that interferes with Cks1 binding, or inactivation of Cks, gives stabilization of Clb2, the main mitotic B-type cyclin in budding yeast. Clb2-ubiquitination in vivo/vitro is not affected by mutations in cks1 (ital). So Cks1 is not necessary for cyclosome/APC activity. Mutant Cks1 proteins then no longer physically interact with the proteasome. Thus likely Cks1 is needed for some part of proteasome function in M-phase-specific proteolysis. Cks1 activity is apparently needed for degradation of anaphase inhibitor Pds1. Pds1 stabilization is partly responsible for the metaphase arrest phenotype of cks1 (ital) mutants because deletion of PCS1 (ital) partly cuts down the metaphase block in the mutants.

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Pds1p of budding yeast has dual roles: inhibition of anaphase initiation and regulation of mitotic exit

Article Abstract:

Budding yeast and its Pds1p are discussed with information about the two roles of Pds1p, regulating mitotic exit and inhibiting anaphase initiation. It is proposed that the two roles of Pds1p as inhibitor of anaphase and cyclin degradation let the cell link mitosis exit to already ended completion of anaphase. The observations give a novel regulatory paradigm with sequential degradation of two substrates determined by those substrates so that an early substrate inhibits degradation of a subsequent one.

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A role for the Cdc7 kinase regulatory subunit Dbf4p in the formation of initiation-competent origins of replication

Article Abstract:

Formation of initiation-competent origins of replication is discussed with consideration of the role for the Cdc7 kinase regulatory subunit Dbf4p. Two kinase complexes have been shown to be essential for promotion of replication in vitro through use of a reconstituted DNA replication assay from yeast.

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