Regulation of the G1 phase of the cell cycle by periodic stabilization and degradation of the p25rum1 CDK inhibitor.

摘要: In fission yeast, the cyclin‐dependent kinase (CDK) inhibitor p25 rum1 is a key regulator of progression through G 1 phase cell cycle. We show here that protein levels are sharply periodic. begins to accumulate at anaphase, persists in and destroyed during S phase. stabilized polyubiquitinated mutant defective 26S proteasome, suggesting its degradation normally occurs ubiquitin‐dependent proteasome pathway. Phosphorylation by cdc2–cyclin complexes residues T58 T62 important target for degradation. Mutation one or both these alanine causes stabilization induces cycle delay polyploidization due occasional re‐initiation DNA replication before mitosis. The CDK–cyclin complex cdc2–cig1, which insensitive inhibition, seems be main phosphorylates . 2 serves as trigger proteolysis. Thus, periodic accumulation CDK plays role setting threshold cyclin determining length pre‐Start ensuring correct order events.