PUMA (p53 upregulated modulator of apoptosis) is one of the pro-apoptotic Bcl-2 family members which are also transcriptional targets of p53. PUMA gene encodes two BH3 domain-containing proteins termed PUMA-α and PUMA-β. PUMA proteins bind Bcl-2, localize to the mitochondria, and induce cytochrome c release and apoptosis in response to p53. PUMA may be a direct mediator of p53-induced apoptosis.