Nucleotide sequence of the env-specific segment of NFS-Th-1 xenotropic murine leukemia virus.

The sequence of 863 contiguous nucleotides encompassing portions of the pol and env genes of NFS-Th-1 xenotropic proviral DNA was determined. This region of the xenotropic murine leukemia virus genome contains and env-specific segment that hybridizes exclusively to xenotropic and mink cell focus-forming but not to ecotropic proviral DNAs (C. E. Buckler et al., J. Virol. 41:228-236, 1982). The unique xenotropic env segment contained several characteristic deletions and insertions relative to the analogous region in AKR and Moloney ecotropic murine leukemia viruses. Portions of an endogenous env segment cloned from a BALB/c mouse embryo gene library that had a restriction map and hybridization properties typical of xenotropic viruses (A. S. Khan et al., J. Virol. 44:625-636, 1982) were also sequenced. The sequence of the endogenous env gene was very similar to the comparable region of the NFS-Th-1 xenotropic virus containing the characteristic deletions and insertions previously observed and could represent a segment of an endogenous xenotropic provirus.