While infection with papillomaviruses (PV) results in the formation of warts, in some instances these can progress to cancer. This is most evident in the human uterine cervix, where specific types of human (H) PVs are limited to benign disease whereas others possess neoplastic potential. The molecular basis for the distinct biological implications of these viruses is unknown. Papillomaviruses encode several oncogenes, one of which, the E6 oncoprotein, is the focus of these studies. This small zinc finger protein is capable of transforming mouse fibroblasts and human keratinocytes in vitro, and along with the viral E7 gene, is selectively retained and expressed in human cervical tumors. We have now discovered a new function for E6: activation of transcription. When targeted to a promoter through a chimeric, functional DNA binding domain, expression of a reporter increased in S. cerevisiae and mouse cells. Furthermore, we detected synergistic stimulation of transcription when E6 and the viral enhancer E2 were co-transfected into mouse cells. In this grant application, we propose to develop a series of E6 mutants to determine what regions of E6 are required for transformation and transactivation and whether these are related. Does E6 have two distinct activities, one observed when localized to a promoter, the other through interactions with viral and cellular transcription factors? Does E6 bind DNA? What are the similarities and differences among E6 proteins from HPVs limited to benign disease and those that are capable of inducing cancer in transcription activation? Additionally, we will pursue investigations to correlate E6 functions with its physical characteristics including cellular and nuclear localization and zinc binding, and in later years, develop models to probe the molecular mechanisms through which it operates.
