Site-directed mutagenesis of human papillomavirus 18 promoter elements and tissue-specific expression in cervical carcinoma cells
In this study, the effect of mutations in transcription factor-binding elements was investigated in the human papillomavirus (HPV) 18 P(105) promoter. Site-directed mutagenesis activities, in the AP1/YY1-, KRF-1-, GRE/YY1-, Sp1- and the double mutation (AP1/YY1- and GRE/YY1)-binding sites were assessed in five human cell lines: HeLa (HPV18-positive cervical carcinoma), SiHa (HPV16-positive cervical carcinoma), C33A (HPV-negative cervical carcinoma), H1299 (non-small cell lung carcinoma) and MRC-5 (foetal lung fibroblast). The results indicated that the GRE/YY1 mutation increased the HPV18 P(105) promoter activity in the cervical cell lines by 53-135%. In HeLa and SiHa cells, mutations in the AP1/YY1, KRF-1 and Sp1 transcription factor-binding sites resulted in reduced promoter activity. For C33A, mutations in KRF-1 and Sp1 reduced the promoter activity, while the GRE/YY1 mutation increased the activity. The double mutation, AP1/YY1 and GRE/YY1, appeared to display an additive effect of the two individual mutations in cervical cells. Compared with HeLa cells, HPV18 P(105) promoter activity was more than 80-fold lower in H1299 cells and more than 500-fold lower in MRC-5 cells. Hence in this study, a comprehensive site-directed mutagenesis analysis, of important transcription factor-binding elements, in the HPV18 P(105) promoter was accomplished in a range of human cell lines. In particular, we concluded that HPV-induced factors were extremely important in the transcriptional activity of the HPV18 P(105) promoter.