Ratchets and clocks: The cell cycle, ubiquitylation and protein turnover

Both the cell-cycle and ubiquitin-mediated-proteolysis fields have come of age over the past ten years. One byproduct of the impressive progress in these areas of investigation is the realization that they are intricately related: cell-cycle control is crucially dependent on the ubiquitin-mediated degradation of key regulatory proteins. Very recent advances have allowed an understanding of protein degradation and cell-cycle control at greatly enhanced levels of resolution. Consolidating these advances is likely to provide new insights into the regulatory biology of cell-cycle transitions.