Flow cytometry
Log phase cells were irradiated at RT with a 60 Co γ-irradiator at doses of 6 or 12 Gy and incubated for 24 h. Cells were then pulse-labeled for 1 h with BrdU (10 μM), fixed in 70% ethanol, double-stained with FITC anti-BrdU and propidium iodide, then sorted by using a Becton Dickinson FACScan machine. Data were analyzed using Becton Dickinson Cellquest Pro.