Viral DNA in transformed cells

Abstract

32P-labeled adenovirus 2 DNA was treated with restricting endonuclease from Escherichia coli strain RY-13 (Yoshimori, 1972) (EcoRI) or restricting endonuclease from Hemophilus parainfluenzae (Hpa I) and the resulting fragments of DNA were separated by gel electrophoresis. The kinetics of renaturation of each of the fragments and of complete adenovirus 2 DNA were measured in the presence of DNA extracted from nine lines of adenovirus 2-transformed rat cells and from control cells. Six of the transformed cell lines contained viral DNA sequences homologous to two of the seven Hpa I§ fragments and to part of one of the six EcoRI fragments. From the order of the fragments formed by EcoRI and Hpa I on the adenovirus 2 map we conclude that these cell lines contain only the segment of viral DNA that stretches from the left-hand end to a point about 14% along the viral genome. Thus, any viral function expressed in transformed cells must be coded by this small section of viral DNA. The three remaining lines of adenovirus 2-transformed rat cells are more complicated and contain not only the sequences from the left-hand end of the viral DNA, but also other segments of the viral genome. However, no adenovirus 2-transformed rat cell contained DNA sequences homologous to the complete viral genome.