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Does the human "beta 2 interferon" (HuIFN-beta 2) mRNA of length 1.3 kb obtained from poly(I) X poly(C) and cycloheximide-induced human diploid fibroblasts (FS-4) code for an interferon per se, or for a protein which, in turn, induces IFN-beta in the cell culture assay that is usually used to detect the antiviral activity of the translation product (obtained from Xenopus laevis oocytes) of this mRNA? This question has been resolved by demonstrating that the IFN derived from the 1.3 kb mRNA can be detected by the direct assay of the oocyte translation product in a highly sensitive radioimmunoassay based on a high-affinity polyclonal antibody raised against N-terminal aminoacid sequence pure IFN-beta 1.

The chromatin structure of the human interferon (IFN) genes was evaluated during induction of human lymphoblastoid (Namalwa) cells by Sendai virus. Namalwa cells were treated with bromodeoxyuridine (BrdUrd) for 36-48 h and induced with Sendai virus for 7 h; the nuclear fraction was isolated and treated with low levels of either micrococcal nuclease or DNAse I. DNA was extracted from the nuclease-treated chromatin, restricted with Eco RI and analyzed by Southern blotting using IFN-alpha 1 and -beta 1 cDNA probes. An increase in the digestibility of the IFN-alpha 1-related genes and the IFN-beta 1 gene was observed in chromatin prepared from BrdUrd-treated, Sendai virus-induced Namalwa cells as compared with chromatin from uninduced Namalwa cells. Our results indicate that, during IFN induction in Namalwa cells by Sendai virus, the IFN genes assume a more open conformation consistent with increased transcriptional activity across these genes.

The Sellers TT algorithm has been used to conduct a detailed pattern search in the amino acid sequence of human and murine gamma-interferon. Each of these proteins contains two large repeats at the level of the primary amino acid sequence that divide each of these molecules into an aminoterminal and a related carboxyterminal segment.

The human interferon alpha 1 and beta 1 (IFN-alpha 1 and -beta 1) genes are approximately 56% identical in the nucleotide sequence across the regions coding for the mature proteins. An IFN-alpha 1 cDNA insert containing such sequences can be used to isolate 15 IFN-beta 1 cDNA colonies present in a 2600-strong library in Escherichia coli prepared from polyadenylated RNA extracted from human diploid fibroblasts (FS-4) induced with poly(I).poly(C). Conversely, a clone containing an IFN-alpha 1 cDNA exhibited detectable hybridization with an IFN-beta 1 probe. One of the IFN-beta 1 cDNA clones isolated in these experiments had lost the internal PstI and PvuII sites due to a change at nucleotide 277 from a C to an A. As a consequence, this allele codes for Met-47 instead of Leu-47. Suggestive evidence has been obtained for the presence of this allele in human genomic DNA (IFN-beta 1 Met-47).

Earlier studies showed that both tumor necrosis factor (TNF) and interleukin-1 (IL1) can inhibit virus replication in cultured cells. However, in human FS-4 fibroblasts, in which recombinant human TNF protected cells from encephalomyocarditis (EMC) virus infection, recombinant human IL1 alpha and IL1 beta failed to induce antiviral protection. Moreover, both forms of IL1 inhibited the development of the TNF-induced antiviral state. To elucidate the mechanism of this inhibition, we examined the effect of IL1 on the synthesis of interferon-beta (IFN-beta), stimulated with polyinosinate.polycytidylate [poly(I).poly(C)]. When added 2 h or more before poly(I).poly(C), both forms of IL1 had a strong inhibitory effect on IFN-beta synthesis, as determined by antiviral assay of the IFN-beta protein or by quantitation of IFN-beta mRNA levels in Northern blot analysis. However, when IL1 was added simultaneously with poly(I).poly(C), or 2 h after poly(I).poly(C), IFN-beta synthesis was increased. The inhibitory action of IL1 on poly(I).poly(C)-induced IFN-beta synthesis was abolished in the presence of cycloheximide, suggesting that it is mediated indirectly by an IL1-induced product in the FS-4 cells. In addition to its ability to inhibit IFN-beta synthesis, IL1 also caused a partial reversal of the antiviral action of IFN-beta. In contrast to IL1, TNF did not inhibit IFN-beta synthesis, nor did it interfere with the antiviral action of IFN-beta. Simultaneous addition of TNF and poly(I).poly(C) to FS-4 cells enhanced IFN-beta synthesis. Under proper conditions TNF and IFN-beta showed an additive antiviral effect.