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 (PubMed:10675335, PubMed:12717439, PubMed:17050006, PubMed:17704056, PubMed:18625225, PubMed:28992046). The DRTF1/E2F complex functions in the control of cell-cycle progression from G1 to S phase (PubMed:10675335, PubMed:12717439, PubMed:17704056). E2F1 binds preferentially RB1 in a cell-cycle dependent manner (PubMed:10675335, PubMed:12717439, PubMed:17704056). It can mediate both cell proliferation and TP53/p53- dependent apoptosis (PubMed:8170954). Blocks adipocyte differentiation by binding to specific promoters repressing CEBPA binding to its target gene promoters (PubMed:20176812). Directly activates transcription of PEG10 (PubMed:17050006, PubMed:18625225, PubMed:28992046). Positively regulates transcription of RRP1B (PubMed:20040599). {ECO:0000269|PubMed:10675335, ECO:0000269|PubMed:12717439, ECO:0000269|PubMed:17050006, ECO:0000269|PubMed:17704056, ECO:0000269|PubMed:18625225, ECO:0000269|PubMed:20040599, ECO:0000269|PubMed:20176812, ECO:0000269|PubMed:28992046, ECO:0000269|PubMed:8170954}. This is the function of Ensembl gene identifier ENSG00000101412 (E2F1, E2F transcription factor 1).