Fig. 4

The effect of ATM inhibition on the repair of DNA double-strand breaks in CBP-depleted cells. a Left panel: Representative immunofluorescence images showing γH2AX (red) and 53BP1 (green) foci at 24 h after 2 Gy ionizing radiation (IR) in T47D cells transfected with the indicated siRNAs and incubated with 5 µM of ATM inhibitor (ATMi). Scale bar, 100 µm. Right panel: Quantification of γH2AX/53BP1 foci at 1 and 24 h post-IR from 100 cells. b Upper panel: Representative images of the neutral comet assay performed after the indicated times following 40 Gy IR. Scale bar, 50 µm. Lower panel: Fold change of tail moment, calculated using OpenComet software, from 50 cells. c IR sensitivity of T47D cells transfected with negative control (siCtrl) or CBP (siCBP) siRNA for 48 h, followed by treatment with or without 2.5 or 5 µM of ATMi for 2 h prior to irradiation. d Colony formation assay of ATM-deficient SKX cells transfected with the indicated siRNAs for 48 h before irradiation. Data are represented as mean ± SEM, n = 3. P < 0.05 is considered significant, Mann–Whitney U test. ns, not significant