Studies of the retinoblastoma gene (Rb) have shown that its protein product (pRb) acts to
restrict cell proliferation, inhibit apoptosis, and promote cell differentiation. The frequent
mutation of the Rb gene, and the functional inactivation of pRb in tumor cells, have spurred
interest in the mechanism of pRb action. Recently, much attention has focused on pRb's role
in the regulation of the E2F transcription factor. However, biochemical studies have
suggested that E2F is only one of many pRb-targets and, to date, at least 110 cellular …