Noxa mediates cell-cycle control of apoptosis. (A) qPCR analysis of relative Noxa mRNA in p18^+/+ and p18^−/− rBCs (A) before and after stimulation with BAFF or anti-IgM for 48 hours and (B) before and after stimulation with anti-IgM and anti-CD40 for 72 hours and infection with a Noxa shRNA- or nonsense shRNA (Cntl)-expressing retrovirus or left uninfected. (C) Total live cells from cultures in panel B at 48 and 72 hours after shRNA-retrovirus infection.