Mouse embryonic fibroblasts (MEFs) were scored for proliferation 48 hours after x-ray exposure based on BrdU containing G1 cells relative to untreated controls. Cell line details are denoted in the legend by cell line number, mouse strain, and Artemis genotype. (A) Radiation sensitivity of GSE-22 transformed mArt+/+, mArt+/- and mArt-/- on 129/SvJ background. (B) Radiation sensitivity of GSE-22 transformed mArt+/+, mArt+/- and mArt-/- on B6 background. (C) Radiation sensitivity of SV40 transformed mArt+/+, mArt+/- and mArt-/- on 129/SvJ background, derived from different animals. (D) Radiation sensitivity of additional mArt-/- lines from additional animals of noted backgrounds immortalized with GSE-22 (top graph) or SV40 (lower graph).