P40SDB25, a putative CDK inhibitor, has a role in the M/G1 transition in Saccharomyces cerevisiae.

The Saccharomyces cerevisiae protein kinase Dbf2 carries out an essential function in late mitosis, and its kinase activity is cell-cycle regulated around anaphase/telophase. We have isolated SDB25, a high copy suppressor of temperature-sensitive dbf2 mutants, and genetic analysis suggests that the two proteins may function in parallel pathways in late ...
mitosis. SDB25 encodes p40, a previously characterized substrate and potent inhibitor of Cdc28 kinase activity. Sdb25 is a phosphoprotein, and Sdb25 immunoprecipitates have a histone H1 kinase activity that is CDC28-dependent. Remarkably, Sdb25 transcript levels, protein levels, and associated kinase activity are precisely cell-cycle regulated, sharing a common peak in late mitosis. Moreover, Sdb25 protein levels and associated kinase activity are sharply up-regulated at the peak of Dbf2 kinase activity in cells released from a dbf2 ts block. The Sdb25 protein then disappears around Start in the next cell cycle. This indicates that SDB25 function is confined to M/G1, and morphological analysis of sdb25 delta cells supports this conclusion. Our data suggest that Sdb25 functions in a pathway in late mitosis leading to the down-regulation of Cdc28 kinase activity as cells traverse the M/G1 boundary.
Mesh Terms:
Amino Acid Sequence, Base Sequence, Blotting, Northern, Blotting, Southern, CDC28 Protein Kinase, S cerevisiae, Cell Cycle, Cyclin-Dependent Kinase Inhibitor Proteins, DNA, Fungal, Fungal Proteins, G1 Phase, Gene Deletion, Gene Expression Regulation, Fungal, Genes, Fungal, Genes, Suppressor, Genotype, Mitosis, Molecular Sequence Data, Phenotype, Phosphoproteins, RNA, Fungal, Restriction Mapping, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins, Transcription, Genetic
Genes Dev.
Date: Jul. 15, 1994
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