Nucleotide sequences associated with differences in electrophoretic mobility of envelope glycoprotein gp70 and with G IX antigen phenotype of certain murine leukemia viruses

Previous genetic and biochemical studies led to the identification of two large RNase T1-resistant oligonucleotides, designated the GIX + and GIX - oligonucleotides, whose presence in the genomes of closely related murine leukemia viruses is mutually exclusive and predictive of two properties of the viral envelope glycoprotein gp70. Viruses harboring the GIX + oligonucleotide induce expression of the gp70-associated antigen GIX and possess gp70s with more rapid electrophoretic mobility on sodium dodecyl sulfate/polyacrylamide gels than viruses that possess the GIX - oligonucleotide. The latter viruses fail to induce GIX on infected fibroblasts. The GIX + and GIX - oligonucleotides lie in corresponding positions in the 3′ third of the oligonucleotide maps of their respective viruses. We have determined the nucleotide sequences of the GIX + and GIX - oligonucleotides. The sequence of the GIX - oligonucleotide is U-A-U-C-U-C-A-A-C-C-A-C-C-A-U-A-C-U-U-A-A-C-C-U-C-A-C-C-A-C-[unk]-G, and the sequence of the GIX + oligonucleotide is U-A-U-C-U-C-A-A-C-C-A-C-C-A-U-A-C-U-U-G. Thus, a single base change could result in the interconversion of the two oligonucleotides. Consideration of the amino acids specified by the two oligonucleotides suggests that this single base difference may result in the presence of an additional oligosaccharide chain in the gp70s of the GIX - viruses. Evidence supporting this prediction has been obtained by M. R. Rosner, J.-S. Tung, E. Fleissner, and P. W. Robbins (personal communication). It is entirely possible that the single nucleotide change that apparently results in a different electrophoretic mobility of the gp70s of the GIX + and GIX - viruses is also responsible for the presence or absence of the GIX antigenic determinant; however, the validity of this possibility awaits further investigation.