Regulation of the eukaryotic cell cycle.

The sundry cellular processes required to successfully replicate and divide cells are driven by the sequential activation and inactivation of a family of cyclin dependent kinases. Activation is driven predominately by the periodic expression of the cyclin subunit and requires activating phosphorylation of the kinase subunit. Inactivation is controlled by inhibitory phosphorylation of the kinase subunit, by ubiquitin-mediated degradation of the cyclin subunit and by interaction of the complex with small inhibitory proteins. The mechanisms that coordinate cell cycle progression under favorable and adverse conditions are reviewed.