Regulation of Noxa, Puma, and Bim following DNA damage. (A) rv c-MYC-driven Puma^−/−Bim^−/− and p53^−/− cell lines (derived from n = 3 independent lymphomas per genotype) were treated with etoposide (0.2 μg/mL) for 6 hours in the presence of QVD-OPH (25μM) and assessed for levels of mRNA of the genes indicated. Data represent mean ± SEM from 3 independent experiments. (B) Regulation of Noxa, Puma, and Bim following DNA damage: Regulation of Bim may be p53 dependent or independent. p53 activation directly induces the BH3-only genes, Noxa and Puma. p53 activation (possibly indirect) may also trigger the induction of C/EBP-homologous protein, which, in turn, may elevate Bim. X, Y, and Z represent unidentified potential regulators of Bim transcriptional induction.