HOMOLOGOUS RECOMBINATION PROMOTED BY REVERSE-TRANSCRIPTASE DURING COPYING OF 2 DISTINCT RNA TEMPLATES

Retroviruses are known to mutate at high rates. An important source of genetic variability is recombination taking place during reverse tran scription of internal regions of the two genomic RNAs. We have designe d an in vitro model system, involving genetic markers carried on two R NA templates, to allow a search for individual recombination events an d to score their frequency of occurrence. We show that Moloney murine leukemia virus reverse transcriptase alone promotes homologous recombi nation efficiently. While RNA concentration has little effect on recom bination frequency, there is a clear correlation between the amount of reverse transcriptase used in the assay and the extent of recombinati on observed. Under conditions mimicking the in vivo situation, a rate compatible with ex vivo estimates has been obtained.