Sequences homologous to retrovirus-like genes of the mouse are present in multiple copies in the Syrian hamster genome.

The genome of M. musculus contains many copies of DNA sequences homologous to the 35S RNA of intracisternal type-A particles (IAP) (1,2). A major class of IAP genes has been identified and isolated from a mouse library in Charon 4A (3). Cloned mouse IAP genes were used as probes to study homologous sequences in the DNA of other species. Sequences related to mouse IAP genes were detected in the DNAs from a variety of animal cells. DNAs from rat, gerbil, and hamster cells all gave strong reactions which could be localized to discrete restriction fragments on genomic blots. The reaction of Syrian hamster DNA was particularly strong. Fragments derived from different parts of the IAP gene all reacted with Syrian hamster DNA, and the reactive restriction fragments in the Syrian hamster DNA could be ordered with reference to the known restriction map of the IAP genes. The data suggest that sequences related to mouse IAP genes make up a 7 Kb unit in the Syrian hamster genome. Since the majority of the hamster sequences are quite divergent from those in the mouse, the ease with which they are detected suggests that they must be reiterated in the hamster genome.