RESUMO
Objective: To investigate the biological effects of ubiquitin-specific peptidase 39 (USP39) on the DNA damage response pathway of tumor cells. Methods: Tumor cells (293T, HeLa, U2OS, T47D) were cultured in DMEM medium or RPMI-1640 containing 100 mL/L FBS in a humidified atmosphere containing 50 mL/L CO2 at 37 ℃. The effect of knockdown of USP39 on the radiosensitivity of tumor cells was detected by MTS[3-(4,5-diethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-etrazolium, inner salt]. The efficiency of HR repair and NHEJ repair was detected by cytometry. The expression of DNA damage-responsive proteins by knockdown of USP39 was examined by Western blot. The proteins interacting with USP39 were detected by co-immunoprecipitation, protein purification and mass spectrometry, and then gene ontology analysis was performed. DNA damage was induced by micro-irradiation and its recruitment to DNA damage sites was detected by agonistic confocal microscopy. Results: Knockdown of USP39 resulted in increased radiosensitivity of tumor cells (P<0.05). Knockdown of USP39 inhibited homologous recombination and non-homologous end joining repair efficiency of tumor cells (P<0.05). Knockdown of USP39 promoted the expression of DNA damage response protein. USP39 aggregated to DNA damage sites; USP39 interacting proteins were involved in multiple signaling pathways associated with DNA damage response. Conclusion: USP39 plays an important role in the DNA damage response.