The pro-death role of Cited2 in stroke is regulated by E2F1/4 transcription factors.

We previously reported that the cell cycle-related cyclin-dependent kinase 4-retinoblastoma (RB) transcriptional corepressor pathway is essential for stroke-induced cell death both and However, how this signaling pathway induces cell death is unclear. Previously, we found that the cyclin-dependent kinase 4 pathway activates the pro-apoptotic transcriptional co-regulator Cited2 after DNA damage. In the present study, we report that Cited2 protein expression is also dramatically increased following stroke/ischemic insult. Critically, utilizing conditional knockout mice, we show that Cited2 is required for neuronal cell death, both in culture and in mice after ischemic insult. Importantly, determining the mechanism by which Cited2 levels are regulated, we found that E2F transcription factor (E2F) family members participate in Cited2 regulation. First, E2F1 expression induced transcription, and E2F1 deficiency reduced expression. Moreover, determining the potential E2F-binding regions on the gene regulatory sequence by ChIP analysis, we provide evidence that E2F1/4 proteins bind to this DNA region. A luciferase reporter assay to probe the functional outcomes of this interaction revealed that E2F1 activates and E2F4 inhibits transcription. Moreover, we identified the functional binding motif for E2F1 in the gene promoter by demonstrating that mutation of this site dramatically reduces E2F1-mediated transcription. Finally, E2F1 and E2F4 regulated expression in neurons after stroke-related insults. Taken together, these results indicate that the E2F- regulatory pathway is critically involved in stroke injury.