This project aims to develop an understanding of yet unknown molecular events involved in oncogenesis, specifically the role played by post-translational acetylation of the tumor suppressor p53 protein. Disruption of growth-arrest responses and apoptotic pathways by missense mutations of the p53 gene is known to confer a selective advantage to neoplastic clones and to render them refractory to several anti-neoplastic treatments. Such unresponsiveness is, at least partially, sustained by the fact that most of p53 mutants are incapable of binding to p53-specific DNA-binding sites and thus, of activating growth-regulatory genes. Direct gene therapy, by introduction of a normal p53 gene into tumor cells has been attempted but yielded inconclusive results, probably due to dominant negative activity(s) intrinsic to several p53 mutant proteins. Thus, the possibility of rescuing normal activity(s) from a p53 from a p53 mutant per se appears to attractive alternative approach. Studies showing that the DNA binding ability of p53 mutants can be reestablished in vitro by the addition of anti-p53 monoclonal antibodies, support this view and provide valuable evidence that the structure of p53 is flexible. I have now demonstrated that post-translational acetylation of p53 by the acetyl-transferase, P/CAF, restores sequence specific DNA-binding of p53 mutant proteins otherwise dysfunctional for binding to DNA. Furthermore, overexpression of P/CAF in transformed cell lines carrying mutations of the p53 gene rescues most phenotypes of transformed cells, including a normal morphotype and responsiveness to genotoxic agents, such as UV-irradiation. These findings implicate P/CAF as a crucial component of an intracellular pathway cascade which normally prevents oncogenesis. They also reveal the existence of a novel molecular mechanism whereby acetylation of p53, and perhaps of other regulatory proteins, micht determine the sensitivity of tumor cells to therapeutic agents. I propose here genetic and biochemical approaches to examine how P/CAF exerts its tumor-suppressive activity.
