A. FACS scans of γH2Ax versus propidium iodide (DNA content) in GM5659T, GM5659T plus shRNA against p53, and GM637 (normal SV40 transformed) cells that were unirradiated or irradiated with 20 J/m2 and harvested 4 hr later. B. p53-dependence of Mre11 foci in XPV and normal cells. Histograms of the percentage of XP-V and normal cells showing Mre11 foci after stable (left panel) or transient (right panel) infection with pSuper.Retro.p53.Neo.Gfp or its vector control. Open bars (1), vector-infected no irradiation control; grey bars (2), vector-infected cells after 13 J/m2 UV; hatched bars (3), unirradiated cells infected with pSuper.Retro.p53.Neo.Gfp; black bars (4), cells infected with pSuper.Retro.p53.Neo.Gfp after 13 J/m2 UV.