Identification of a region of p53 that confers lability.

Degradation provides one means for controlling the cellular level of the p53 tumor suppressor. Here we have determined a structural element of p53 required for degradation. To create a substrate amenable to in vitro analysis of proteolysis, we appended to p53 the N terminus of antizyme, a protein that binds to and induces degradation of mammalian ornithine decarboxylase (ODC). We found using deletion analysis that an element within amino acids 100-150 is required for degradation of the fusion protein. A monoclonal antibody (PAb246) that binds close to this region prevents the degradation induced by human papillomavirus 16 E6 protein. Furthermore, we found that amino acids 100-150 of p53 can function as an independent domain to induce Trypanosoma brucei ODC, a stable protein, to be degraded in vivo or, by cooperating with an antizyme binding domain of ODC, to confer polyamine-dependent regulation.