Evolution of type C viral genes: origin of feline leukemia virus.

Reiterated gene sequences related to the RNA of feline leukemia virus (FeLV) are detected in all tissues of domestic cats and their close Felis relatives but not in more distantly related Felis species. Partially homologous viral gene sequences are found in rodent, and particularly rat, DNA. Together with the immunologic relationships observed between FeLV and endogenous rodent type C viruses, the results lead to the conclusion that FeLV-related genes were transmitted from a rodent to cat ancestor and have been perpetuated in the germ line of cats.