Pirh2, also known as Androgen receptor N-terminal-interacting protein (ARNIP), ZN363 or CHIMP, has p53-induced ubiquitin-protein ligase activity, promoting p53 degradation. The protein physically interacts with p53 and the resulting degradation of p53 renders Pirh2 an oncogenic protein as the loss of p53 function contributes to malignant tumor development. The gene encoding for the protein maps to chromosome 4q21.1 and transcription of this gene is regulated by p53. Pirh2 expression decreases the level of p53 and a decrease of endogenous Pirh2 expression ups p53 levels. Pirh2 is therefore considered, together with MDM2, to be acting as a negative regulator of p53 function.
