Figure 3. Knockdown of endogenous TPD52 in SK-BR-3 cells improved ATM-mediated DDR post-IR. Cells were untreated or treated with 6 Gy IR 72 h post-transfection with non-targeting (Si-Con) or TPD52 (Si-D52-1, Si-D52-2) siRNAs. (A) Total protein were harvested and subjected to western blot analyses using antisera indicated. (B) γH2AX foci were visualized using immunofluorescence with co-staining of TPD52. Nuclei were counterstained using DAPI. Representative images from one of 3 independent experiments are shown. (C) γH2AX foci were quantitated using Metamorph. Scatter plots of the numbers of γH2AX foci/cell from 3 independent experiments obtained using GraphPad Prism 4.03. Horizontal bars indicate the median γH2AX foci/cell for each siRNA. ***P < 0.0001 (Si-Con v. Si-D52-1, n = 576; Si-Con v. Si-D52-2, n = 642); Mann–Whitney U test.