Abstract
The recently described amphotropic group of murine leukemia viruses constitutes a distinct biological group, differing from the ecotropic and xenotropic groups in host range, cross interference, and serological reactivity. Viruses of this group have been detected only in wild mice from certain areas in California. By using a [3H]DNA probe synthesized in an endogenous reaction from detergent-lysed amphotropic virus (strain 1504-A), it was demonstrated that the amphotropic murine leukemia viruses are distinct biochemically, in that 20% of the viral genome sequences are not shared by AKR-type ecotropic or nay of three types of xenotropic murine leukemia virus tested. A subset of these amphotropic unique sequences, comprising one half of them, is present in the genome of wild mouse ecotropic viruses and in Moloney and Rauscher viruses as well. Sequences homologous to the entire genome of 1504-A amphotropic virus are present in the cellular DNA of all eight inbred mouse strains tested, as well as in wild Mus in Asia, in amounts varying from three to six complete viral genomes per haploid cell genome. Evidence is presented that at least 20% of the DNA sequences in both mouse- and mink-grown murine leukemia virus probes are of host-cell origin.