Human papillomaviruses (HPV) are small DNA viruses which induce benign lesions of squamous epithelia. More than 60 HPV genotypes are known, and the vast majority of genital infections contain DNA types 6, 11, 16 and 18. HPV 6 and 11 are most often associated with benign lesions. However, these two types are also closely associated with Buschke-Lowenstein verrucous carcinoma, an invasively growing, non-metastasizing lesion. The highly exophytic nature of HPV 6 induced benign tumors, the condyloma acuminata, and the aggressive phenotype of the verrucous carcinomas suggest an important viral role in the aberrant proliferation of infected epithelial cells. Recent studies have suggested an intimate relationship between HPV 6 gene expression and epithelial cell terminal differentiation. Although the mechanism of gene expression in high-risk HPV types is well understood, little is known about how the analogous HPV 6 genes are regulated. In fact, it appears that expression of E6 and E7 oncogenes may be regulated differently in genital HPV types of different oncogenic potential. In contrast to HPV 16 and 18, the so-called high oncogenic types, the putative gene regulatory sequences of HPV 6 appear to extend beyond the non-coding region (URR) into the E6, E7 and E1 open reading frames, because transcriptional promoters have been mapped to 3 distinct sites downstream of the 5' end of E6 ORF. The initial goal of this application is to understand the interaction among different HPV 6 promoters, their regulation by viral and cellular proteins, and their role in the immortalization of human keratinocytes. Because human papillomaviruses have a strict tropism for epithelial cells, it is essential that HPV 6 promoter activities be studied in the context of the natural host cell. Vectors carrying the HPV 6 regulatory fragment will be used as transcriptional templates in transient transfection assays in a variety of epithelial cells. Transcripts arising from individual promoters in transfected cells will be identified by S1 mapping and primer extension analysis of HPV 6 RNA. Comparative studies of transcription in different cell types will be carried out to identify cell-specific promoter(s). These assays will also be used in analysis of recombinant, deletion and linker-scanning mutants of the HPV 6 regulatory region to identify responsive elements involved in viral transcription. Because papillomaviruses also encode several regulatory proteins, the effect of different viral proteins on HPV 6 transcription will be analyzed. The role of HPV6 regulatory region on the immortalization potential will be studied by constructing recombinants between HPV6 and 18 and testing their ability to immortalize human foreskin keratinocytes. Through these studies, the applicant hopes to elucidate the mechanism of HPV 6 gene regulation.
| Sang, B C; Chen, J Y; Minna, J et al. (1994) Distinct regions of p53 have a differential role in transcriptional activation and repression functions. Oncogene 9:853-9 |
