The role of RB in cell cycle control.

The retinoblastoma protein is an inhibitor of cell cycle progression from the G1 to the S phase of the cell cycle. It acts through its ability to interact with cellular target molecules such as E2F transcription factors. The function of pRB is negatively regulated by a cell-cycle dependent phosphorylation catalyzed by cyclin-dependent kinases in the late G1 cell cycle phase. Recent evidence indicates that this pRB inactivation is a key molecular event leading to the S-phase commitment at the G1 restriction point in the cell cycle. Deregulated inactivation of pRB in G1 phase may be a universal mechanism underlying cellular transformation.