Additional file 3 of Sustained CHK2 activity, but not ATM activity, is critical to maintain a G1 arrest after DNA damage in untransformed cells

Additional file 3: Fig. S3. Controls for ATR and DNA-PKcs inhibitors used in the present work. a RPE-1 cells were treated with hydroxyurea (HU) to induce ATR activation, or pre-treated with ATR inhibitor before HU treatment. Protein was harvested, and ATR activation status was checked by western blot using pCHK1 S345 phopshosite as a readout. CDK4 served as a loading control. ATRi effectively prevented HU-induced pCHK2 phosphorylation. b G1-synchronized RPE-1 cells grown onto coverslips were irradiated (4 Gy), and fixed for γH2AX and DAPI staining at the indicated timepoints; one sample was pretreated with DNA-PKcs inhibitor. Treatment with DNA-PKcsi prevented the foci resolution observed at 40 hours post-damage.