Trans-activating activity of the E6 proteins of the human papillomavirus (HPV) type-11 and -16 on the PE1E4 promoter of HPV-11 in C33A cells.

We investigated trans-activating effects of the full-length E6 protein of HPV-16 (16E6) and the E6 protein of HPV-11 (11E6) on the PE1E4 promoter of HPV-11 in C33A cells which lack normal function of p53. 16E6 showed no significant activation of the reporter plasmid containing PE1E4 and the upstream sequence, including the long control region (LCR). In contrast, 11E6 activated the promoter in a dose dependent manner, while relatively high doses of 11E6 were required to activate the promoter. When a reporter plasmid, which lacked LCR was used, however, both 16E6 and 11E6 activated the promoter, though high doses of 16E6 suppressed activity. Using deletion plasmids we further showed that 11E6 activated transcriptions from any mutant reporter plasmids as far as the constructs have promoter activities. Finally, we showed that 11E6 enhanced the expression levels of c-fos protein by infection of C33A cells with 11E6-expressing recombinant adenovirus. These findings suggested that E6 proteins of both HPVs would induce similar protein(s) which is required for an efficient transcription of minimum promoter of viral and cellular genes, and that the 16E6 induce additional protein(s) which suppress PE1E4 in the presence or absence of LCR.