Fig. 3

CHK2 kinase maintains its own activity independently of ATM, ATR, and DNA-PKcs after DNA damage in G1. a G1-synchronized cells were left unirradiated (0 Gy) or irradiated (4Gy); irradiated cells were either left untreated (−) or treated (+) with inhibitors for ATM (ATMi), ATR (ATRi), or DNA-PKcs (DNA-PKi) kinases alone or in combination at the time of IR (0 h) and protein was harvested 1 h later (1 h post-damage, hpd) for western blot analysis. b Cells were treated as in a, but inhibitors were added 1 h after IR and harvested 2hpd (upper panel) or 16 h after IR and harvested 17hpd (lower panel). CDK4 served as a loading control for all experiments