E2F-1 (Transcription factor E2F1) is a transcription activator that binds DNA cooperatively with DP proteins through the E2 recognition site, 5'-TTTC[CG]CGC-3' found in the promoter region of a number of genes whose products are involved in cell cycle regulation or in DNA replication. The DRTF1/E2F comple, Xenopus/Amphibian, functions in the control of cell-cycle progression from G1 to S phase. E2F-1 binds preferentially to RB1 protein in a cell-cycle dependent manner. E2F-1 can mediate both cell proliferation and p53-dependent apoptosis.