Regulated expression of an extrachromosomal human β-interferon gene in mouse cells

β (fibroblast)-interferon mRNA and protein are induced by the synthetic double-stranded RNA poly(I)·poly(C) in cultured human fibroblasts. To study the mechanism of this induction, we have isolated a human β-interferon gene and inserted it in a vector plasmid containing DNA of the bovine papilloma virus. After removal of bacterial plasmid sequences, the bovine papilloma virus β-interferon recombinant was used to morphologically transform mouse fibroblasts. Analysis of DNA from the transformed cell lines indicated that this recombinant is propagated as a stable multicopy extrachromosomal element. Human β-interferon mRNA and protein are inducible by poly(I)·poly(C) in all of these cell lines, and the mRNA is indistinguishable from β-interferon mRNA synthesized by induced human cells