Two Interferon mRNAs in Human Fibroblasts: In vitro Translation and Escherichia coli Cloning Studies

Two mRNA species that produce biologically active interferon were isolated from human fibroblasts and studied by size fractionation and cloning in Escherichia coli plasmid pBR322. The major fibroblast interferon (Hu IFN-β 1) is coded for by the smaller of the two mRNAs, an 11S species, 900 nucleotides long, which in cell-free systems yields a 20,000 Mrprotein. The second interferon mRNA species (Hu IFN-β 2) is 14S, about 1300 nucleotides long, and codes for another protein of 23,000-26,000 Mr. The two interferon mRNAs do not cross-hybridize. Both are induced by poly(rI· rC) but IFN-β 2 mRNA is induced to about 10% in cells by cycloheximide treatment alone whereas under these conditions IFN-β 1 is not induced.