ABSTRACT
The papillomaviruses infect and replicate in the stratified layers of skin and mucosa, giving rise to benign lesions called warts or papillomas. The viral E6 and E7 proteins overcome the obstacle by inducing cells to enter S-phase and by abrogating cell-cycle controls. In addition to their roles in DNA replication, the E1 and E2 proteins regulate viral gene expression, including the promoter that transcribes the E6 and E7 genes. This chapter describes the functions of the viral proteins and provides an integrated view of current theories concerning their role in viral replication and malignant progression. The majority of papillomaviruses induce self-limiting, benign, proliferative epithelial lesions. Papillomaviruses infect the basal layer of cells of a stratified epithelium. The a6b4 integrin protein, expressed exclusively in this cell layer, probably acts as a receptor for the virus. Damage to the superficial skin or mucosa is presumed necessary to allow access of virus to the basal layer.
