Integrated viral sequences in adenovirus type 12-transformed hamster cells

The physical state of the viral genome in four lines of hamster cells transformed by adenovirus type 12 (Ad12) has been investigated. The four lines of transformed cells originated from hamster cells after infection with Ad12 at multiplicities ranging from 5-350 plaque-forming units per cell. The DNA from transformed cells has been restricted with the Sal I endonuclease from Streptomyces albus which cleaves adenovirus DNA more frequently than DNA from adenovirus-transformed hamster cells. Thus after cleavage by the Sal I enzyme, it is possible to separate free adenovirus DNA sequences from these which are covalently linked to cellular DNA in transformed hamster cells. The results of sequential hybridization experiments in which the Sal I-treated DNA from transformed cells is first annealed to Ad12 DNA on filters, then eluted, and finally hybridized to hamster cell DNA, support the model of Ad12 DNA integrated in multiple fragments into the host genome. Further experiments will be required to characterize the host sequences adjacent to adenovirus DNA and to compare these sequences in different lines of Ad12 transformed cells.