NEDDylation has been shown to participate in the DNA damage pathway,but the substrates of neural precursor cell expressed developmentally downregulated 8 (NEDD8) and the roles of NEDDylation involved in the DNA damage response (DDR) are largely unknown.Translesion synthesis (TLS) is a damage-tolerance mechanism,in which RAD18/RAD6-mediated monoubiquitinated proliferating cell nuclear antigen (PCNA) promotes recruitment of polymerase η (polη) to bypass lesions.Here we identify PCNA as a substrate of NEDD8,and show that E3 ligase RAD18-catalyzed PCNA NEDDylation antagonizes its ubiquitination.In addition,NEDP1 acts as the deNEDDylase of PCNA,and NEDP1 deletion enhances PCNA NEDDylation but reduces its ubiquitination.In response to H2O2 stimulation,NEDP1 disassociates from PCNA and RAD18-dependent PCNA NEDDylation increases markedly after its ubiquitination.Impairment of NEDDylation by Ubc12 knockout enhances PCNA ubiquitination and promotes PCNA-polη interaction,while up-regulation of NEDDylation by NEDD8 overexpression or NEDP1 deletion reduces the excessive accumulation of ubiquitinated PCNA,thus inhibits PCNA-polη interaction and blocks polη foci formation.Moreover,Ubc12 knockout decreases cell sensitivity to H2O2-induced oxidative stress,but NEDP1 deletion aggravates this sensitivity.Collectively,our study elucidates the important role of NEDDylation in the DDR as a modulator of PCNA monoubiquitination and polη recruitment.