MECHANISMS RESTRICTING DNA-REPLICATION TO ONCE PER CELL-CYCLE - MCMS,PRE-REPLICATIVE COMPLEXES AND KINASES

Art important aspect of cell behaviour is that DNA replication happens only once per cell cycle. Replicated DNA is unable to re-replicate un til cell division has occurred. Unreplicated DNA is in a replication-c ompetent or 'licensed' state. The ability to replicate is lost in S ph ase and regained following passage through mitosis. Recent evidence ha s implicated an MCM (minichromosome maintenance) protein complex and t he Cdc6 protein in determining replication competence. Regeneration of replication competence upon passage through mitosis entails changes i n protein kinase activity, of which the MCMs are a likely target. Feat ures of the mechanism that restricts DNA replication to once per cell cycle appear to be conserved throughout eukaryotes.