Stress-induced p53 runs a direct mitochondrial death program: its role in physiologic and pathophysiologic stress responses in vivo.

It is now well established that a fraction of stress-induced wtp53 protein rapidly translocates to mitochondria in immortalized and transformed cells in culture. Mitochondrial p53 interacts with anti-apoptotic proteins of the Bcl 2 family at the outer mitochondrial membrane, resulting in membrane permeabilization, release of death effectors such as cytochrome C and subsequent rapid apoptosis. The significance and relevance of this direct mitochondrial p53 program to the overall p53-mediated stress response in vivo is underlined by a number of recent studies in animals and primary cells. They all support a role for this direct pathway in the physiologic and pathophysiologic response to genotoxic and hypoxic insults and occur precisely in those tissues where p53 plays a critical role in mediating apotpotis rather than cell cycle arrest.