Possible origin of murine AIDS-inducing sequence

The murine AIDS (MAIDS) virus has a unique sequence in its gag p12 region. A transcript which hybridizes with this sequence is expressed in normal C57BL/6 mice. This transcript has been proposed to be the origin of the MAIDS virus, since the virus was originally isolated from radiation-induced leukemic C57BL/6 mice. The transcript, designated Edv, was molecularly cloned and sequenced. Compared with the nucleotide sequence of the helper LP-BM5 ecotropic virus, the pathogenic defective MAIDS virus has 16-bp deletions and a 1-bp insertion in the 5' and 3' regions of the gag p12 sequence, respectively, and the Edv transcript contains only a 3-bp deletion. Therefore, the amino acid sequence of the gag p12 region of the MAIDS virus is less homologous to that of the helper virus and Edv transcript due to the frameshift mutations. This suggested that the MAIDS virus was generated by such frameshift mutations in the gag p12 region during recombination between the helper virus and the Edv or a related sequence.