Replication of the retroviral terminal repeat sequence during in vivo reverse transcription.

There is a copy of a short terminal repeat segment, r, at each end of the retroviral RNA genome. During reverse transcription, r is copied from the genomic RNA to form the R component of the long terminal repeat in viral DNA. Although our current model for reverse transcription suggests that the 5' r is copied, it is not known whether the 5' copy, the 3' copy, or part of each r in the genomic RNA serves as the template for the R region in the progeny viral DNA. To assess the relative contribution of the 5' and 3' r templates, we examined the effect of mutations located at the center of the 5' or 3' r of spleen necrosis virus and determined the sequence of the R region in the progeny proviruses after a single round of retroviral replication. In approximately 90% of the proviruses, the 5' r marker was copied, whereas 10% of the proviruses had derived the R marker from the 3' r.