Transformation of rat 3Y1 cells by human papillomavirus type-18 DNA

Rat 3Y1 cell cultures transfected with human papillomavirus type-18 (HPV 18) DNA produced foci of morphologically transformed cells capable of anchorage-independent growth. Analyses of the transformed cell clones obtained after transfection with EcoRI-cleaved linear HPV 18 DNA showed that, although the viral DNAs integrated in the cell DNA had rearrangements (probably around the sites of integration), they appeared to retain the putative transcriptional control region and the downstream area containing E6E7 open reading frames (ORF) intact, and to be transcriptionally active. The expression plasmids constructed from an SV40-derived expression vector (pSV2-0) and HPV 18 DNA fragments containing either E6 or E7 ORF intact were examined for their transforming capacity. HPV 18 E7 ORF was found to encode a transforming gene for rat 3Y1 cells.