Recombination induces tandem repeats of integrated viral sequences in polyoma-transformed cells.

Transformed Fischer rat cells derived from coinfections with wild-type polyoma virus and transformation-deficient hr-t deletion mutants were studied. The structure of the integrated viral DNA was determined by Southern blot analysis of high-molecular-weight DNA. In several cases the two parental genomes were found cointegrated in a head-to-tail manner at a single site in the host DNA. The results indicate that parental viral genomes recombine in Fischer rat cells in the process of transformation, and that the commonly observed tandem integration of viral genomes in polyoma-transformed cells must be due, in part, to recombination events.