High-risk strains of human papillomavirus (HPV), such as HPV 16, are causative agents in most cases of human cervical carcinoma. Worldwide, this disease is responsible for approximately 370,000 newly diagnosed cases each year, with about a 50% mortality rate. HPV 16, as well as other """"""""high risk"""""""" strains, codes for two oncogenes, E6 and E7. E7 functions by binding to and inactivating Rb, while E6 is best known for its ability to mediate the rapid degradation of p53. The accumulating evidence, however, indicates that this is not the only function of E6, and indeed, cannot completely explain its transforming potential. Previous work in our laboratory has shown that transfection of the E6 gene from HPV 16 into a number of cell lines, derived from two species and several tissue types, protects them from TNF-triggered apoptosis in a p53-independent manner. E6 was then shown to bind to TNF R1, resulting in impaired transmission of the apoptotic signal. Recently, we have found that E6 binds to FADD as well as to TNF R1, and can block apoptosis mediated by Fas as well as that mediated by TNF R1. This project integrates a variety of biochemical, genetic and cell biological approaches designed to achieve our overall goal of understanding the interactions of E6 with host apoptotic pathways at a molecular level, and of laying the groundwork for future novel therapeutic interventions. Specifically, four specific aims will address the following questions.1) What region(s) of TNF R1 are required for binding to E6? 2) What is the biological significance of E6-mediated protection from TNF in the contexts of virus survival and oncogenicity? 3) How generalized is the protection from apoptotic stimuli provided by HPV 16 E6? 4) What molecules can block this protective ability? The ability of papillomavirus-encoded proteins to interact with key regulators in receptor-triggered apoptotic pathways has not previously been described, and may contribute to the ability of the virus to evade the host immune system and/or to transform cells. A more complete understanding of such interactions will, therefore, enhance efforts to develop novel and effective preventive and therapeutic approaches to papillomavirus infection. ? ?
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