MyoD^−/− myoblasts up-regulate antiapoptotic proteins Bcl-2 and Bcl-xL and induce Cyt c release. (A) Expression of antiapoptotic proteins Bcl-2 and Bcl-xL and proapoptotic protein Bak in wild-type and MyoD^−/− myoblasts was assessed by Western blotting under growth conditions (control [Cont]) or after UV exposure or treatment with thapsigargin (Thap) for 1 d. Mitochondrial (Mito) and cytoplasmic (Cyto) protein extracts were also probed with antibodies against COX4, Cyt c, or β-actin. (B) Cyt c translocation into cytoplasm in MyoD^−/− myoblasts was assessed by Western blotting after infection with a lentivirus vector expressing MyoD or a control empty vector under growth conditions, differentiation conditions (Diff) for 3 d, or after UV exposure or treatment with thapsigargin for 1 d. (C) Cyt c translocation into cytoplasm in wild-type myoblasts was assessed by Western blotting after infection with a lentivirus vector expressing shRNA for MyoD or a control shRNA vector under growth conditions, differentiation conditions for 3 d, or after UV exposure or treatment with thapsigargin for 1 d. β-Actin was monitored as a loading control.