Cloning and characterization of cDNAs for a bovine (Bos taurus) Mx protein

Mr proteins are GTPases that are stringently induced in cells from many vertebrates on exposure to type I interferons (IFNs), and expression of some Mr proteins potently inhibits replication of specific viruses. Two cDNAs encoding bovine Mr proteins were isolated from an endometrial phage library. The open reading frames (ORFs) of these two clones predict proteins of 654 (Mx1) and 648 (Mx1-a) residues. Both possess the tripartite GTPase domains, dynamin signature, and leucine zipper motifs conserved in all other Mr proteins identified. The bovine protein sequences show highest identity to ovine Mr (93%) and are substantially similar to human MxA (73%) and mouse Mx1 (43%). Based on differences between the two bovine clones in the coding and 3'-untranslated regions, it was concluded that they represent two alleles of one gene, and heterozygous and homozygous cattle were identified. Expression of Mx mRNA was rapidly induced in cultured bovine cells by treatment with IFN.