V3 clonal transfectants expressing wild-type human DNA-PKcs, no DNA-PKcs, or mutant DNA-PKcs as indicated were plated at cloning densities into complete medium with increasing doses of calicheamicin (A), etoposide (B), or camptothecin (in the presence of 20 μM KU55933) (C). Colonies were stained after eight days, and percent survival was calculated. Error bars represent the standard error of the means for six independent experiments. (D) Immunoblot for DNA-PKcs expression in V3 transfectants. (E) 2.5% agarose electrophoresis of PCR amplification of coding joints from AT coding joint substrate from V3 stable transfectants expressing or not wild-type or mutant DNA-PKcs and then transfected with substrate and RAG1 and RAG2 expression constructs.