Structural analysis of integrated polyomavirus DNA in a polyomavirus-induced hamster tumor cell line

The nucleotide sequence and structural organization of integrated polyomavirus DNA and flanking host chromosomal DNA in a polyomavirus-induced hamster tumor cell line were evaluated. Although the proximal portion of the early transcriptional region was intact, the remainder of the integrated viral sequences was characterized by a series of rearrangements, including deletions, insertions, and a tandem duplication. Short direct repeats of different nucleotide sequences located on each side of the host-viral DNA junctions we examined were observed. Tumor cell chromosomal DNA flanking the integration site contained regions of patchy homology with viral DNA sequences which could have participated in the recombinational events leading to stable integration. The presence of several unusual structural features of tumor cell chromosomal DNA at the site of viral DNA integration, which were reminiscent of papovavirus DNA integrated into transformed cells, suggests that the recombinational mechanisms operative in vivo are accurately reflected by those functioning in vitro.