What's new in p53?

p53 is the main intrinsic factor inducing apoptosis by recognizing the external stimuli and activating the p53 responsive genes to an irreversible series of events. P53 activates the transcription of specific proapoptotic genes called p53 target genes. A growing number of p53 responsive genes have been identified and numerous studies have demonstrated that p53 proapoptotic factors such as Noxa, Puma and Perp play cell type specific roles in p53's mediated response to certain stimuli. Perp (p53 apoptosis effector related to PMP-22) is a direct proapoptotic target gene encoding a tetraspan protein. Perp is highly expressed in cells undergoing apoptosis compared to cells under G1 arrest and its overexpression is sufficient to cause cell death in fibroblasts. Noxa is another member of the preapoptotic p53 genes family. When expressed Noxa acts in a BH3 motif-dependent localization to mitochondria, causing structural changes, activation of caspase 9 and release of cytochrome c from mitochondria to cytosol. Puma (p53 mutant of apoptosis) is another critical mediator of p53-dependent apoptosis. P53 binds to Puma-promoter gene sites, leading to puma production. The mtCLIC, a member of intracellular chloride channels, is a cytoplasmic and mitochondrial protein positively regulated by p53. Caspase 10 is induced in p53-dependent manner leading to cellular apoptosis. Other newly announced factors are also involved in p53-regulated apoptosis such as brain-specific angiogenesis inhibitor-1 (BSAI1), MSOD and GPX genes. A global discussion on this topic is attempted in the present review article.