In mammalian cells, apoptosis comes in two forms, intrinsic and extrinsic, which are triggered by cell death stimuli from intraand extracellular environments, respectively (Figure 1). The intracellular stimuli, such as DNA damage, generally result in the activation of the BH3-only Bcl-2 family of proteins, which causes the release of proapoptotic factors from the intermembrane space of mitochondria into the cytoplasm (Cory & Adams 2002, Wang 2001). The release process is mediated by Bax and Bak and antagonized by the antiapoptotic proteins Bcl-2 and Bcl-xL. One of the released protein factors, cytochrome c, directly activates Apaf-1 and, in the presence of dATP or ATP, induces the formation of a multimeric complex dubbed the “apoptosome.” The apoptosome mediates the activation of the initiator caspase, caspase-9, which subsequently activates the effector caspases, caspase-3 and caspase- 7, which are responsible for the dismantling of an apoptotic cell. The active caspases are subject to inhibition by the inhibitor of apoptosis (IAP) family of proteins (Salvesen & Duckett 2002). Smac/DIABLO, another protein released from mitochondria during apoptosis, interacts with multiple IAPs and counters IAP-mediated caspase inhibition.