Characterization of a mouse interferon gene locus II. Differential expression of alpha-interferon genes.

A cluster of four MuIFN-alpha genes was recently isolated and characterized (1); one of the genes in this cluster had, in the coding region, an internal deletion of 5 amino acids. Bacterial expression plasmids were constructed to examine the effect of this deletion on the antiviral activity of the MuIFN-alpha 4 peptide and it was found that the alpha 4 interferon peptide had a 100-fold lower antiviral activity than full length alpha-interferon proteins when expressed in E. coli. Three of the four MuIFN-alpha genes identified were expressed coordinately in L-cells infected with NDV. The relative levels of alpha 4 mRNA were substantially higher than the levels of the other alpha mRNAs. Comparison of the 5' end flanking sequences of these four alpha interferon genes revealed that the promoter sequences of alpha 1, alpha 5 and alpha 6 are more homologous to each other than to the alpha 4 promoter which also contains a G rich cluster not seen in the other three promoters.