Defining the minimal requirements for papilloma viral E6-mediated inhibition of human p53 activity in fission yeast.

The majority of human anogenital carcinomas show evidence of papillomavirus infection. To facilitate viral replication, viruses disable key cellular responses which would otherwise precipitate cell suicide. An obligate factor in one such response is the p53 tumour suppressor protein. p53 gene mutation is an infrequent event in anogenital cancer, apparently due to the action of HPV E6 protein, which inhibits wild-type p53 function by stimulating the degradation of p53 protein. p53 is required for the apoptotic response that is triggered in untransformed cells following inappropriate cell-cycling. E6 directed inhibition of p53 function thus facilitates the survival of transformed cells. We have developed a genetically tractable model that reports E6 protein-mediated human p53 inactivation in the fission yeast Schizosaccharomyces pombe. Functional dissection of the requirements for E6 directed inhibition in this system reveal an absolute requirement for the presence of both E6 protein and the human E3 ubiquitin ligase, E6-AP. Using a defined set of E6 mutants we show that degradation of p53 protein rather than E6/p53 association is likely required for E6-mediated inhibition. This S. pombe based system represents a candidate screen for novel antiviral agents that act by disrupting the E6/E6-AP/p53 interaction.