Abstract
The E2F1 transcription factor is active in many types of solid tumors and can function as either an oncogene or tumor suppressor in vivo. E2F1 activity is connected with a variety of cell fates including proliferation, apoptosis, senescence, differentiation, and autophagy, and these effects are mediated through differential target gene expression. E2F1-induced cell death is an innate anti-cancer mechanism to kill cells with a spontaneous oncogenic mutation that might otherwise form a cancer. Relatively little is known about the molecular circuitry that tips E2F1 balance toward proliferation during normal growth versus apoptosis during oncogenic stress, and which pathways mediate this decision. To further explore these mechanisms, we utilized an unbiased shRNA screen to identify candidate genes that mediate E2F1-induced cell death. We identified the ubiquitin-like with PHD and ring finger domains 2 (UHRF2) gene as an important mediator of E2F1-induced cell death. UHRF2 encodes a nuclear protein involved in cell-cycle regulation. Several of these domains have been shown to be essential for the regulation of cell proliferation, and UHRF2 has been implicated as an oncogene in some settings. Other reports have suggested that UHRF2 causes growth arrest, functions as a tumor suppressor, and is deleted in a variety of tumors. We show that UHRF2 is a transcriptional target of E2F, that it directly interacts with E2F1, and is required for E2F1 induction of apoptosis and transcription of a number of important apoptotic regulators.