Fig. 3
APE1 participates in the DDR and NHEJ repair after oxidative stress. a HeLa NC and shAPE1 cells were treated with TBHP for 1 h and allowed to recover for 5 min to 8 h. The γH2AX, DNA-PKcs pS2056 and ATM pS1981 level were assayed by immunoblotting and Ku80 was used as a loading control. b The interaction between Ku80 and DNA-PKcs is decreased in APE1 deficiency cells. Ku80 was immunoprecipitated from HeLa NC and shAPE1 cell lines 1 h after TBHP treated 1 h. The immunoprecipitates were analyzed by immunoblotting with anti-DNA-PKcs, Ku80 antibodies. c The interaction between APE1 and DNA-PKcs in HeLa WT cells, assayed by APE1 immunoprecipitation, was significantly increased post- TBHP treatment 1 h and allowed to recover 1 h. d–e HeLa NC and shAPE1 cells were treated with TBHP, the resolution of 53BP1 foci were assessed at 0.5, 3 and 7 h post-TBHP treatment. d The representative images are shown. e The statistical analysis of 53BP1 foci per nucleus are shown. f The recruitment of NHEJ factors to the chromatin after TBHP is attenuated in HeLa shAPE1 cells. HeLa NC and shAPE1 cells were treated with TBHP and allowed to recover for 1 and 4 h. Subsequently, the chromatin-enriched fractions were isolated for immunoblotting to assess the recruitment of key NHEJ proteins to chromatin. The p-values were determined using an unpaired Student’s t-test (*p < 0.05). The data are presented as the mean ± SEM from three independent experiments