A role for E2F1 in Ras activation of p21(WAF1/CIP1) transcription

We recently reported that E2F1 could transactivate the p21 promoter via cis-acting elements between -119 to +16 bp of the p21 gene. Here we show that activated V12-H-Ras can induce the p21 promoter through the same region of the p21 promoter by a p53-independent mechanism in NIH3T3 cells. In contrast, activated Ras was not able to induce the p21 promoter in E2F1(-/-) fibroblasts, suggesting that E2F1 is required for induction of the p21 promoter by activated Ras, Cotransfection of increasing concentrations of dominant negative E2F1 alone, or with dominant negative DP1 into NIH3T3 cells suppressed induction of the p21 promoter by activated Pas. These data suggest that p53-independent induction of the p21 promoter by activated Ras is mediated at least in part by E2F1.