Confocal microscopy for the expression of γ-H2AX protein. (A-C) Phosphorylated γ-H2AX protein was detected with its antibody and then measured by confocal microscopy at different time points after 4-Gy of γ-irradiation (×40 magnification). (D) Fold change of fluorescence intensity. The intensity of Alexa 488–labeled γ-H2AX was measured by Adobe PhotoshopCS3 imaging process software (Adobe System Inc). The bars show the fold change of mean fluorescence intensity per cell (n = 50 cells picked randomly) compared with that of Puma^+/+ nonirradiated group. **P < .01.