Human papillomavirus type 16 transformation of primary human embryonic fibroblasts requires expression of open reading frames E6 and E7.

Human papillomavirus 16 (HPV-16) early genes were tested for their ability to transform primary human embryonic fibroblasts (WI38) or to extend the life span of the fibroblasts. The expression plasmids containing the transcriptional unit for the HPV-16 subgenomic DNA fragments controlled by the simian virus 40 promoter were introduced into WI38 cells with the aid of neomycin selection, and the drug-resistant cells that survived long-term culture were characterized. The fragments containing E6E7 open reading frames (ORFs) intact were found to be capable of extending the life span of WI38 cells. From the results obtained with frameshift mutations in either ORF and from those obtained by cotransfection with the separate plasmids containing E6 and E7 ORFs, it was concluded that HPV-16 transformation (extension of the life span) of human fibroblasts requires expression of genes E6 and E7.