Pirh 2 (P53 induced RING-H2 protein) mediates E3-dependent ubiquitination and proteasomal degradation of proteins. Pirh2 has ubiquitin-protein ligase activity and binds to p53 and promotes the ubiquitin-mediated proteosomal degradation of p53. Pirh2 is oncogenic because loss of p53 function contributes directly to malignant tumor development. Pirh2 e, Xenopus/Amphibian,pression decreases the level of p53, and a decrease of endogenous Pirh2 e, Xenopus/Amphibian,pression increases p53 levels. Pirh2 is therefore considered together with MDM2, to act as a negative regulator of p53 function.