A3G is required for DSB repair in H9 lymphoma cells. (A) Western blot showing A3G cellular protein level. PBMC(−) and PBMC(+), naive, and phytohemagglutinin-activated peripheral blood mononuclear cells, respectively. α-tubulin was used as a loading control. Molecular weights (kDa) are indicated on the left. (B) Cells were irradiated (4 Gy) or mock-irradiated and stained with anti–γ-H2AX antibody. A3G knockdown or control H9 (C) or ARH-77 (D) cells were preincubated with 20μM z-VAD-fmk or mock for 1 hour and treated as in panel B. Values represent mean ± SD from 3 independent experiments and at least 10 different fields for each time point analyzed. (E) Cell-cycle analysis after IR. (Left): Irradiated (4 Gy) or mock-irradiated (No IR) cells were stained after 20 hours with propidium iodide, and DNA content was determined by FACS (10 000 acquired events). (Right): Values represent mean ± SD from 3 independent experiments.