Resolution of human fibroblast interferon into two distinct classes by thiol exchange chromatography

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-beta 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 Mr protein. The second interferon mRNA species (Hu IFN-beta 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-beta 2 mRNA is induced to about 10% in cells by cycloheximide treatment alone whereas under these conditions IFN-beta 1 is not induced.

Heterogeneity of poly(I) x poly(C)-induced human fibroblast interferon mRNA species

Three classes of human interferons (IFNs) have been defined on the basis of their immunological properties: the 'Le' or 'alpha' IFN, mainly derived from leukocyte or lymphoblastoid cells; the 'F' or 'beta' IFN, mainly derived from fibroblast cultures; and the 'T', 'immune' or 'gamma' IFN, mainly derived from mitogen- or antigen-stimulated lymphoid cells. Whereas several individual species of Le IFN have been purified to homogeneity, it is generally considered that F IFN represents a single protein. Thus current efforts to clone human fibroblast IFN mRNA sequences are based on the observation that F IFN mRNA sediments in sucrose gradients as a single RNA species of size corresponding to 12-14 S (refs 7-10). We show here, using gel electrohporesis of mRNA, that two populations of translationally active human fibroblast IFN mRNA molecules exist--an abundant '14 S' species and a scarce '11 S' species. Microinjection of either species of mRNA into Xenopus oocytes leads to the synthesis of biologically active F-type human IFN. These data agree with and complement recent RNA hybridization studies of Weissenbach et al.