Transformation of primary rat kidney cells by DNA fragments of weakly oncogenic adenoviruses.

Primary cultures of baby rat kidney (BRK) cells were transformed by intact DNA and DNA fragments of weakly oncogenic human adenovirus types 3 and 7. The smallest fragment found to contain transforming activity was the left-terminal 4% endo R.HindIII fragment (for both adenovirus type 3 and 7 DNAs). The efficiency of transformation of this fragment was low, and no permanent cell line could be established. Left-terminal fragments ranging from 84 to 4,5% of the viral genome could all transform BRK cells with the same efficiency as intact viral DNA. A number of adenovirus type 7 DNA fragment-transformed lines were established and were found to contain persistent viral DNA sequences and adenovirus subgroup B-specific T antigen. Consequently, the transforming functions of adenovirus types 3 and 7 are located at the extreme left-hand end of the genome, and the minimum size for a DNA fragment with transforming activity is 1.0 X 10(6) daltons. These results do not rule out the possibility that viral genes located outside the transforming region may also influence transformation.