Abstract: 【Abstract】 Objective To investigate the roles of enzyme DCAF proteinDNA damagebinding protein 1 (DDB1)/cullin4 (CRL4) complex family members CRL4WD40 repeat domain protein 70 (WDR70) in DNA repair process and its mutation in ovarian cancer. Methods Immunofluorescent assay was employed to measure H2AX（γH2AX） and phosphorylated replication protein A2 （RPA32） formed in siDDB1 or siWDR70 ovarian cancer cells after the treatments of chemical medicine and radioactive threapy. 5Brdu immunohistochemical staining was used to explore the function of WDR70 in DNA replication. The expressions of WDR70 and histone protein H2B monoubiquitination (uH2B) was measured by immunohistochemistry, the function of DNA repair, expression and mutations of CRL4 in ovarian cancer were detected by semiquantitative PCR and DNA sequencing. Results Immunofluorescent assay indicated that distinct subunits of CRL4 played different roles in checkpoint activation and H2Bmonoubiquitinationdepedendent homologous recombination, while the scaffold subunit DDB1 participated in both processes, WDR70 was only required for DNA end resection, chromatin loading of RPA32 and HR. The dose of WDR70 was not effect on DNA replication. Ovarian cancer had different expression of WDR70 and uH2B compared with normal tissue, transcripts of WDR70 was diminished or truncated in 50% of ovarian cancer, which corresponded to multiple mutations. Conclusion CRL4 ubiquitin ligase plays multiple roles in DNA repair and is critical for genome stability. It may be an potential anticancer barrier against ovarian malignancies.