FIGURE 4.

Partial contribution of ATM to UV-induced H2AX phosphorylation and UV resistance in quiescent human cells. A, G₀-arrested TIG-120 cells were pretreated with ATMi as described in the legend to Fig. 2 and irradiated with 20 J/m² of UV. After incubation with ATMi for the indicated periods, cell lysates were prepared and analyzed by Western blotting with anti-γH2AX antibody. B, G₀-arrested AT2KY cells were treated with LY294002 as described in Fig. 2. The cells were irradiated with 20 J/m² of UV, and the phosphorylation of H2AX was analyzed by Western blotting. C, asynchronously growing (AS) or G₀-arrested SuSa/T-n or AT1OS/T-n cells were plated into 60-mm dishes and irradiated with the indicated doses of UV after 6-h incubation. The cells were further incubated for 2–3 weeks, and the resultant colonies were counted after ethanol fixation and Giemsa staining.