Transcription-modulatory activity of full-length E6 and E6*I proteins of human papillomavirus type 16

The E6 gene of human papillomavirus type 16 (HPV16) has the potential to encode full-length as well as truncated E6 proteins (E6*I and E6*II) by alternative splicings. Spliced ORF E6*I is considered to facilitate the translation of the neighboring E7 ORF; however, the putative E6*I protein is suspected to be functionless. In this study, the transcription-modulatory functions of full-length E6 and E6*I proteins were examined using cDNAs from a cervical carcinoma cell line. E6*I cDNA was able to trans-activate the autologous P97 promoter and the heterologous adenovirus E2 promoter. Full-length E6 was found to trans-activate the heterologous promoter, but repress transcription from the autologous P97 promoter. The transcription-modulatory functions of full-length E6 and E6*I proteins suggested that transcriptional regulation of HPVs associated with mucosal malignant lesions is complex.