Sequence variation and the transcriptional activity of the upstream regulatory region in human papillomavirus 16 E7 variants in cervical cancer of Korean women

In this study, we investigated the sequence variation and different transcriptional activities of the upstream regulatory region (URR) in HPV 16 E7 variants in cervical cancer tissue from Korean women. Using PCR-directed sequencing, the presence of sequence variations in URRs were analyzed and the sites of sequence variation were matched with the known transcriptional factor binding site (TFBS) in 26 HPV 16 E7 variants, 21 cases with A647G (KE7-1, high oncogenic potential) and 5 cases with T732C (KE7-2, low oncogenic potential). In addition, we determined the transcriptional activity of URR in a HPV 16 prototype, and in 4 cases of HPV 16 E7 variants, by using the functional chloramphenicol acetyl transferase (CAT) assay. The 26 HPV 16 E7 variants showed more than 11 sites of sequence variation in the URR. Ten sites of sequence variation were located in the known TFBS and the distribution of sequence variations in the URR showed clear differences between KE7-1 and KE7-2. The sequence variations T7781C and C7786T were matched with YY1 binding sites, G7193T and C7689A were matched with TEF1 binding sites, and C7394T and C7395T were matched with GRE binding sites. The other sequence variations, which were matched with the TFBS, were A7485C, G7489A, T7743G and G7842A. The URR activity of KE7-1 was significantly lower than that of the HPV 16 prototype, whilst KE7-2 was similar. Taken together with the results of the transcriptional activities of KE7-1 and KE7-2, our results suggest that the functional activity and sequence variations of HPV 16 URR may not be related to the oncogenic potential of HPV 16 E7 variants.