BCL-2 PREVENTS ACTIVATION OF CPP32 CYSTEINE PROTEASE AND CLEAVAGE OF POLY (ADP-RIBOSE) POLYMERASE AND U1-70 KD PROTEINS IN STAUROSPORINE-MEDIATED APOPTOSIS

Members of the the Bcl-2 and ICE/ced-3 gene families have been implica ted as essential components in the central of the cell death pathway. Bcl-2 overexpression can prevent programmed cell death (PCD) in differ ent cell types. ICE/ced-3-like proteases are synthesized as pro-enzyme s and are activated by limited proteolysis. When overexpressed in dive rse cell types, they trigger PCD. Bcl-2 can inhibit PCD mediated by th ese proteases, although as yet it is not clear at what specific step i n the cell death pathway the protein acts. Here, we demonstrate that C PP32/Yama/Apopain, a member of the ICE/Ced-3 gene family is processed during staurosporine-induced apoptosis in HeLa cells and that concomit ant with CPP32 activation, two other proteins, poly (ADP-ribose) polym erase (PARP) and the U1-70 K small ribonucleoprotein, also undergo pro teolysis. Overexpression of Bcl-2 prevents cleavage of CPP32, PARP and U1-70 K and protects HeLa cells from PCD. These results demonstrate t hat Bcl-2 controls PCD, by acting upstream of CPP32/Yama/Apopain.