The retinoblastoma protein and cell cycle control

pRB, the product of the retinoblastoma tumor suppressor gene, operates in the midst of the cell cycle clock apparatus. Its main role is to act as a signal transducer connecting the cell cycle clock with the transcriptional machinery. In this role, pRB allows the clock to control the expression of banks of genes that mediate advance of the cell through a critical phase of its growth cycle. Loss of pRB function deprives the clock and thus the cell of an important mechanism for braking cell proliferation through modulation of gene expression.