TARGETING AND DEGRADATION OF P53 BY E6 OF HUMAN PAPILLOMAVIRUS TYPE-16 IS PREFERENTIAL FOR THE 1620+ P53 CONFORMATION

E6-mediated degradation of p53 is believed to play a role in the trans formation of cells by high-risk types of human papillomavirus. In orde r to explore the structural requirements for targeting of p53 we have compared E6-mediated degradation of variant p53 forms expressed in vit ro. Complete degradation was observed in samples containing monomers, dimers and higher molecular weight structures of wild-type p53, indica ting that E6 targets all quaternary forms of wild-type p53. Wild-type human and murine p53s reactive with PAb 1620 (which recognizes a confo rmation-dependent epitope) were degraded when incubated with E6. Mutan t p53 proteins were variably resistant to E6-mediated degradation, and this correlated with PAb 1620 reactivity. Thus, mutants hp53Val-154, hp53Val-266 and hp53Pro-273 (1620-degrees) were completely resistant t o degradation, whereas hp53Ile-247 and hp53Trp-248 (1620+) were degrad ed. Mutants hp53Leu-273 and mp53Val-135, which are temperature sensiti ve for conformation, were completely degraded in the 1620+ form but de gradation resistant in the 1620-degrees form. Although the PAb 1620+ c onformation appeared important for recognition of p53 by E6, the epito pe itself is unlikely to be the actual recognition target since the PA b 1620 monoclonal antibody failed to protect against E6-mediated degra dation.