A transformed cell line (RC335) showing higher saturation cell density was obtained from 3Y1 cells (a fibroblastic cell line of rat) transfected with DNA of human papillomavirus type 47 (HPV-47), an epidermodysplasia verruciformis-associated virus, which our laboratory reported previously. The cell line was found to produce a major and several minor species of viral RNAs. The primary structure of the major viral RNA in RC335 was extensively studied and found to consist of two exons and contain open reading frames (ORFs) E6, E7, and a fused ORF, E1/E4. The major RNA was indicated to play an important role in the transformation of RC335 by an experiment with the recombinant retrovirus designed to produce the RNA containing these ORFs, i.e., the recombinant virus induced transformation similar to that in RC335 upon infection of 3Y1 cells. Furthermore the experiments with recombinant viruses carrying a nonsense mutation or large deletion in the above ORF(s) indicated that E6 was necessary and sufficient for the transformation.