Identification of the murine Mx2 gene: Interferon-induced expression of the Mx2 protein from the feral mouse gene confers resistance to vesicular stomatitis virus

The mouse genome contains two related interferon-regulated genes, Mx1 and M x2, Whereas Mx1 codes for the nuclear 72-kDa protein that interferes with i nfluenza virus replication after interferon treatment, the Mx2 gene is nonf unctional in all laboratory mouse strains examined, since its open reading frame (ORF) is interrupted by an insertional mutation and a subsequent fram eshift mutation. In the present study, we demonstrate that Mx2 mRNA of cell s from feral mouse strains NJL (Mus musculus musculus) and SPR (Mus spretus ) differs from that of the laboratory mouse strains tested. The Mx2 mRNA of the feral strains contains a single long ORF consisting of 656 amino acids . We further show that Mx2 protein in the feral strains is expressed upon i nterferon treatment and localizes to the cytoplasm much like the rat Mx2 pr otein, which inhibits vesicular stomatitis virus replication. Furthermore, transfected 3T3 cell lines of laboratory mouse origin expressing Mx2 from f eral strains acquire slight resistance to vesicular stomatitis virus.