Complementation of a p300/CBP defective-binding mutant of adenovirus E1a by human papillomavirus E6 proteins

Previous studies have shown that the human papillomavirus type 16 (HPV-16) E6 protein binds to p300/CBP and abrogates its transcriptional coactivator function. However, there is little information on the biological consequences of this interaction and discrepancy as to whether the interaction is high-risk E6 specific or not. We performed a series of studies to compare the interactions of HPV-18 and HPV-11 EG with p300, and showed that both high- and low-risk E6 proteins bind p300. In addition, using a transformation-deficient mutant of adenovirus E1a, which cannot interact with p300, we demonstrated that HPV-16, HPV-18 and, to a lesser extent, HPV-11 EG, can complement this mutant in cell transformation assays. In contrast, a mutant of HPV-16 EG which does not bind p300 failed to rescue the E1a mutant. These results suggest that the E6-p300 interaction may be important for the ability of HPV E6 to contribute towards cell transformation.