Fig. 1.

DSBs trigger activation of APOBEC3B and lead to late-onset DSB formation mediated by BER. (A) Schematic representation of deamination reactions and the subsequent BER process. (B–C) HeLa cells were transfected with the pPM-APOBEC3B or negative control (NC) vector and treated as depicted in the upper boxes. The numbers of γH2AX foci in γ-irradiated HeLa cells were quantified via immunofluorescence (B). γH2AX foci merged with 53BP1 foci: 97% at 1 h, 90% at 24 h, and 84% at 48 h (C). (D) Cells were transfected with a negative control siRNA (siNC) or a siRNA against UNG (siUNG). (E) Cells were treated with or without the PARP inhibitor olaparib. Bars show means ± s.d. The numbers of cells counted in each condition are inserted in the graphs. Scale bars, 10 µm.