Genetic polymorphisms and antiviral activity in the bovine MX1 gene

Bovine MX1 cDNAs consisting of 2280 bp from 11 animals of five breeds and from a cultured cell line were sequenced and compared with previously reported data. Ten nucleotide substitutions were synonymous mutations, and a single nucleotide substitution at 458 resulted in an amino acid exchange of Ile (ATT) and Met (ATG). A 13-bp deletion-insertion mutation was also found in the 3ʹ-UTR. Based on the nucleotide substitutions found in this study, bovine MX1 cDNA was classified into 11 genotypes. A phylogenetic tree of the 11 genotypes suggested that the genotypes observed in Brahman were a great genetic distance from other genotypes. An 18-bp deletioninsertion variation at position 171 was found to be the result of alternative splicing. The 18-bp deletion-insertion is located at the boundary between exon  3 and intron 3. Permanently transfected 3T3 cell lines expressing bovine MX1 mRNA were established to analyse the antiviral potential against VSV(DELTA)G*-G infection. Transfected cell clones expressing bovine MX1 mRNA showed a significantly smaller number of cells infected with VSV(DELTA)G*-G compared with the control cells. These results indicate that the bovine MX1 protein has potent antiviral activity.