Fig. 5

Role of CBP in DNA damage response is independent of ER. a Upper panel: T47D cells were treated with estrogen receptor inhibitor (ERi) 4 h before irradiation with 2 Gy. Proximity ligation assay (PLA) was performed to assess colocalization of γH2AX and CBP at 5 min post-2 Gy ionizing radiation (IR). Scale bar, 100 µm. Lower panel: Quantification of PLA signal for γH2AX and CBP using ImageJ software from 100 cells. b Upper panel: PLA for γH2AX and CBP colocalization after 5 min of 2 Gy IR in BT549 cells. Scale bar, 100 µm. Lower panel: Quantification of PLA signals from 100 cells. c, d Upper panel: Representative images of immunofluorescence staining with anti-γH2AX (Red) and anti-53BP1 (green) antibodies in T47D cells treated with 10 nM of ERi ICI 182780 at 24 h post-IR (c) and BT549 cells treated with 5 µM of ATM inhibitor (ATM) at 24 h after 2 Gy IR (d). Scale bar, 100 µm. Lower panel: Quantification data of colocalized γH2AX and 53BP1 at 1 and 24 h of IR in T47D cells (c) and BT549 cells (d). e, f IR sensitivity of T47D cells (e) and BT549 cells (f) transfected with negative control (siCtrl) or CBP (siCBP) siRNA for 48 h, followed by treatment with and without ERi or ATMi before irradiation with the indicated doses. Data are represented as mean ± SEM, n = 3. P < 0.05 is considered significant, Mann–Whitney U test. ns, not significant