To investigate the regulatory effect and significance of transcription factor E2F1 on X-ray repair cross2 complementing 1 (XRCC1).Saos2 cells were transfected with the E2F1 expression vectors (tet-E2F1) and mutated E2F1 expression vectors (tet-132E). XRCC1 promotor luciferase reporter vector was constructed and transfected into Saos2 cells together with E2F1, E2F2, E2F3 and E2F4 expression vectors at different amount. The cells were collected 36 hours post-transfection for luciferase assays and absorbance was read at 570 nm.Cotransfection of increasing amounts of E2F1 expression vector with the XRCC1 promoter-luciferase reporter caused a dose-dependent increase in luciferase activation. In contrast, DNA binding incompetent E2F1 (132E) could not activate the XRCC1 promoter-luciferase reporter.E2F1 could upregulate endogenous XRCC1 expression and stimulate the XRCC1 promoter.