BOTH CONSERVED REGION-1 (CR-1) AND CR-2 OF THE HUMAN PAPILLOMAVIRUS TYPE-16 E7 ONCOGENE ARE REQUIRED FOR INDUCTION OF EPIDERMAL HYPERPLASIAAND TUMOR-FORMATION IN TRANSGENIC MICE

High-risk human papillomavirus type 16 (HPV-16) and HPV-18 are associa ted with the majority of human cervical carcinomas, and two viral gene s, HPV E6 and E7, are commonly found to be expressed in these cancers. The presence of HPV-16 E7 is sufficient to induce epidermal hyperplas ia and epithelial tumors in transgenic mice. In this study, we have pe rformed experiments in transgenic mice to determine which domains of E 7 contribute to these in vivo properties. The human keratin 14 promote r was used to direct expression of mutant E7 genes to stratified squam ous epithelia in mice. The E7 mutants chosen had either an in-frame de letion in the conserved region 2 (CR2) domain, which is required for b inding of the retinoblastoma tumor suppressor protein (pRb) and pRb-li ke proteins, or an in-frame deletion in the E7 CR1 domain. The CR1 dom ain contributes to cellular transformation at a level other than pRb b inding. Four lines of animals transgenic for an HPV-16 E7 harboring a CR1 deletion and five lines harboring a CR2 deletion were generated an d were observed for overt and histological phenotypes. A detailed time course analysis was performed to monitor acute effects of wild-type v ersus mutant E7 on the epidermis, a site of high-level expression. In the transgenic mice ,vith the wild-type E7 gene, age-dependent express ion of HPV-16 E7 correlated with the severity of epidermal hyperplasia . Similar age-dependent patterns of expression of the mutant E7 genes failed to result in any phenotypes. In addition, the transgenic mice w ith a mutant E7 gene did not develop tumors. These experiments indicat e that binding and inactivation of pRb and pRb-like proteins through t he CR2 domain of E7 are necessary for induction of epidermal hyperplas ia and carcinogenesis in mouse shin and also suggest a role for the CR I domain in the induction of these phenotypes through as-yet-uncharact erized mechanisms.