Permeabilization of the outer mitochondrial membrane by pro-apoptotic BCL2 family members BAK and BAX allows release of direct IAP-binding protein with low pI (DIABLO, also known as SMAC) from the mitochondrial intermembrane space into the cytosol (Du C et al, 2000; Arnoult D et al. 2003). When released from mitochondria, DIABLO acts as a natural antagonist of inhibitor of apoptosis proteins (IAPs). DIABLO antagonistic activity is based on its N-terminal tetrapeptide (AVPI) that binds baculoviral IAP repeat (BIR) domains of IAPs, releasing their inhibitory effects on both initiator and effector caspases, thus promoting cell death (Du C et al. 2000; Gao Z et al. 2007). Binding of DIABLO (SMAC) to survivin leads to the inhibition of apoptosis (Song Z et al. 2003).