Fig. 6

CBP is required for recruitment and activation of ATM at sites of DNA double-strand breaks. a Upper panel: Proximity ligation assay (PLA) analysis for γH2AX and ATM colocalization after 5 min of 2 Gy IR in T47D cells transfected with the indicated siRNAs. Scale bar, 100 µm. Lower panel: Quantification of PLA signals from 100 cells. b Left panel: T47D wild-type (WT) and CBP knockout (KO) clones 1(CI #1) and 2 (CI #2) irradiated with 2 Gy. PLA analysis was performed 5 min post-irradiation using anti-γH2AX and anti-ATM antibodies. Scale bar, 100 µm. Right panel: Graph depicting PLA signal quantification from 100 cells. c Left panel: Representative immunoblot images for CBP, acetyl-p53 and p53 in T47D cells after incubation with ATM inhibitor (ATMi) for 2 h followed by Doxorubicin (DOX) exposure for 8 h. Right panel: Quantification of the band intensities for the indicated proteins, normalized to β-actin. d Left panel: T47D cells treated with ATMi 2 h before irradiation. PLA was performed using anti-γH2AX and anti-CBP antibodies. Scale bar, 100 µm. Right panel: Quantification of PLA signals using ImageJ software from 100 cells. Data are represented as mean ± SEM, n = 3. P < 0.05 is considered significant, Mann–Whitney U test. ns, not significant