REGULATORY ROLES OF CYCLIN-DEPENDENT KINASE PHOSPHORYLATION IN CELL-CYCLE CONTROL

Cyclins and cyclin-dependent kinases (Cdks) are universal regulators o f cell cycle progression in eukaryotic cells. Cdk activity is controll ed by phosphorylation at three conserved sites, and many of the enzyme s that act on these sites have now been identified. Although the bioch emistry of Cdk phosphorylation is relatively well understood, the regu latory roles of such phosphorylation are, in many cases, obscure. Rece nt studies have uncovered new and unexpected potential roles, and prom pted re-examination of previously assumed roles, of Cdk phosphorylatio n.