EIAV genomic organization: further characterization by sequencing of purified glycoproteins and cDNA

Nucleotide sequence analyses of two different proviral clones of equine infectious anemia virus (EIAV), designated lambda 12 (K. Rushlow et al., 1986, Virology 155, 309-321) and 1369 (T. Kawakami et al., 1987, Virology 158, 300-312), indicate significant differences in the organization of two critical regions of the viral genome, i.e., in the short open reading frames in the pol-env intergenic region and in the 5'-end of the env gene. To determine the correct structure of the EIAV genome, we have performed nucleotide sequence analyses of cDNA clones produced from viral RNA and direct sequencing of purified EIAV envelope glycoproteins (gp90 and gp45). The results of the cDNA sequencing confirm the presence of two short open reading frames in the pol-env intergenic region, as reported previously for the lambda 12 clone. The protein sequencing data correlated exactly with the amino-terminal sequences of gp90 and gp45 deduced from lambda 12 nucleotide sequences. However, the protein sequencing also revealed that the putative signal sequence of EIAV gp90 is not removed during processing. Thus, EIAV apparently contains short open reading frames analogous to human immunodeficiency virus, but differs in its mode of env polyprotein processing.