Figure 3

Inhibition of ATR or ATM does not abrogate PCNA ubiquitination. (A) A549 and (B) HeLa cells were incubated with the indicated doses of caffeine 1 h prior to UV irradiation. Six hours after irradiation cells were lysed followed by immunoblotting for PCNA. (C) A549 cells were treated as in A followed by immunoblotting for phosphorylated S15 on p53.