Rearrangements of viral and cellular DNA are often associated with expression of Rous sarcoma virus in rat cells.

Rous sarcoma virus (RSV) proviruses integrated within the DNA of transformed rat cells frequently display duplications of variable segments of proviral DNA upstream of an intact provirus. The rearrangement in the A11 clone of transformed rat cells consists of a partial duplication of both viral and cellular DNA segments whose origin is a region of approximately 4 kb encompassing the 3' virus-cell junction. Transposition of this DNA appears to have occurred at or after virus integration by a mechanism involving at least two recombination events. In every case examined, including A11, the transcriptional organization of the original provirus has been conserved and viral RNA expression appears to occur normally. The frequency of such rearranged proviruses in the DNA of transformed rat cells suggests that upstream rearrangements may influence provirus expression.