Structure, Activity, and Regulation of the Bovine Papillomavirus E5 Gene and Its Transforming Protein Product

Abstract

Transfected bovine papillomavirus type 1 (BPV) DNA can induce tumorigenic transformation of C127 cells, an established line of mouse cells (Dvoretsky et al. 1980; Lowy et al. 1980). By assaying the activity of constructed viral mutants, we and others have shown that an intact E5 gene is required for efficient C127 cell focus formation (DiMaio et al. 1986; Groff and Lancaster 1986; Rabson et al. 1986). Moreover, expression of the E5 gene in the absence of all other BPV genes is sufficient to induce focus formation (Schiller et al. 1986; Yang et al. 1985; Horwitz et al. 1988). Detailed mutational and biochemical analysis of this gene indicates that translation of the portion of open reading frame (ORF) E5 downstream of the first methionine codon results in the synthesis of a 7K polypeptide required for efficient transformation (DiMaio et al. 1986; Schlegel et al. 1986; Burkhardt et al. 1987).