CLONING AND STRUCTURAL-ANALYSIS OF 4 GENES ENCODING INTERFERON-OMEGA IN RABBIT

By using an ovine interferon-tau (IFN-tau) cDNA probe, four recombinan t phages were isolated from a rabbit genomic library and sequenced fro m nucleotides -450 to 1,300 relative to the CAP site. Each of the four rabbit genes contains an open reading frame of 595 nucleotides and co de for proteins that exhibit structural characteristics of the interfe ron-omega (IFN-omega) family. They display more than 98% identity in t heir coding regions. The deduced amino acid sequences share >96% seque nce similarity. In contrast, the 5' and 3' noncoding regions have dive rged considerably (approximately 50% identity). Amino acid comparisons of rabbit IFN-omega with IFN-omega of other species reveal the highes t degree of identity with human (72%), followed by porcine (68%) IFN-o mega. Rabbit IFN-omega displays only 57% sequence similarity with ovin e IFN-tau. The coding regions of the four genes subcloned in a cytomeg alovirus eukaryotic expression vector and transfected in monkey COS-7 cells direct the production of proteins that protect bovine and rabbit cells against vesicular stomatitis virus infection, thus demonstratin g that these genes encode fully active IFN proteins. The expression of these genes was studied in Sendai-induced rabbit leukocytes. A single band of poly(A)+RNA hybridized with a rabbit IFN-omega probe under st ringent conditions, whereas no IFN-omega transcript was detected with RNA isolated from uninduced leukocytes. Southern blot analyses suggest the existence of at least eight IFN-omega genes or pseudogenes in the rabbit genome.