Differences between cellular integration sites of transcribed and nontranscribed Rous sarcoma proviruses.

Transcribed Rous sarcoma proviruses in Rat-1 DNA tend to integrate closely 3' to C-G-rich restriction enzyme sites, and 2 of 13 such proviruses were found to have inserted at the same locus. However, most integrated proviruses were transcriptionally silent insertions at sites indistinguishable from random. We conclude that Rous sarcoma proviruses in rat cells usually fail to integrate in a favorable site for transcription, in contrast to studies on proviral integration in permissive hosts.