E2F stimulates the XRCC1 promoter-luciferase reporter. A, relative light units, normalized to a β-galactosidase signal, of pGL3-XRCC1-(-881 to +158) (0.1 μg) co-transfected with increasing amounts of wild-type E2F1 or mutant E2F1(132E) expression plasmids (50-250 ng) into Saos2 cells. B, relative light units, normalized to a β-galactosidase signal, of pGL3-XRCC1-(-881 to +158) (0.1 μg) co-transfected with increasing amounts of the indicated E2F expression vectors (50-250 ng) into Saos2 cells. C, relative light units, normalized to a β-galactosidase signal, of the relative -fold change of the XRCC1-(-881 to +158) promoter-reporter versus an E2F binding site-deleted XRCC1 promoter-reporter (ΔE2F1-XRCC1), in response to increasing amounts of co-transfected wild-type E2F1 or mutant E2F1(132E) expression plasmids (50-250 ng). S.D. of triplicate experiments is shown.