Interferons-α/β- and -γ-Resistant Friend Cell Variants Exhibiting Receptor Sites for Interferons but No Induction of 2-5A Synthetase and 67K Protein Kinase

Abstract

A number of Friend leukemia cell variants with a interferon-gamma (IFN-gamma)-resistant phenotype have been isolated. They appear resistant to the antiproliferative action of IFN-gamma and to the induction of the antiviral state assessed by Friend leukemia virus release and vesicular stomatitis virus yield. Selection was performed via a prolonged exposure to increasing amounts of highly purified recombinant IFN-gamma of wild-type Friend cells or of variant clones thereof already resistant to IFN-alpha/beta (Affabris et al., 1982, Virology 120, 441-452). Only the clones derived from IFN-alpha/beta-resistant variants showed a phenotype fully resistant to IFN-gamma treatment while keeping their previously acquired resistance to IFN-alpha/beta. These cells are not deficient in high-affinity receptors for IFN-gamma so that their resistant phenotype appears to be mediated by events distal to binding of IFN-gamma to its receptors. Furthermore, analysis of IFN-induced dsRNA-dependent 2-5A synthetase and 67K protein kinase enzymatic activities, biochemical markers for cellular responses to IFN, showed that both these activities were not induced in IFN-alpha/beta and IFN-gamma-resistant clones when treated with either type of IFN. Accordingly, no increased expression of 2-5A synthetase mRNA(s) could be detected by probing poly(A)+-enriched RNA from cells exposed to IFN-alpha/beta or IFN-gamma treatment with murine or human specific cDNAs. On the other hand, no major changes in restriction patterns of 2-5A synthetase gene(s) were observed in these variant cells by restriction endonuclease digestion and Southern blotting. In addition, analysis of 2-5A synthetase mRNA induction, performed on wild-type cells, showed that the kinetic of induction due to IFN-gamma treatment is slower than that obtained with IFN-alpha/beta.

Activation and repression of the 2-5A synthetase and p21 gene promoters by IRF-1 and IRF-2

“…3Cl8 FLC clone (Coccia et al, 1988) was grown in RPMI 1640 supplemented with 5% fetal calf serum (FCS), penicillin (100 IU/ml) and streptomycin (100 mg/ml). L 929 cells were grown in Dulbecco supplemented with 10% FCS Figure 6 Schematic model of IRF target gene regulation and antibiotics.…”

Protein binding to the interferon response enhancer correlates with interferon induction of 2'-5'-oligoadenylate synthetase in normal and interferon-resistant Friend cells

“…IFN-resistant cell lines are an important tool in studying the mechanisms involved in the induction of gene expression by IFNs. We have isolated two such variants from Friend leukemia cells (FLC) (1,2,8,39): the 3C18 cloned variant, derived from wild-type (w.t.) FLC, is totally resistant to type I and partially resistant to type II IFN (1, 2, 39).…”

“…The 3-yR8 variant is derived from 3C18 cells and is resistant to both types of IFNs (8). This resistance is not mediated by changes in the IFN receptor number or affinity on the cell membrane (2,8,39). Therefore, the resistant cell clones appear to be deficient in intracellular factors which transduce the IFN signal (17).…”

Posttranscriptional regulation of beta interferon expression in erythroid Friend cells treated with gamma interferon

“…2, VSV yield is still reduced by 2.5 logs in wt cells treated with 50 U of IFN--y per ml in the presence of polyclonal antibodies to MuIFN-cx/1 or of MAbs to MuIFN-1. Accordingly, IFN--y induces a less pronounced antiviral state in FLC (clone 3Cl8) resistant to IFN-a/p (1,2,11,52) than in wt cells (2.8 versus 4.0 logs of reduction in VSV yield) (Fig. 2).…”

“…Murine IFN-a/, (MuIFN-o/,B) prepared and purified as described previously (11) to 107 U/mg of protein was used. Recombinant IFN--y (107 U/mg of protein) was produced by Genentech and kindly provided by Boehringer Ingelheim.…”