Interferon induction of fibroblast proteins with guanylate binding activity

Treatment of human diploid fibroblastic cells with interferon induces the synthesis of two guanylate binding proteins (GBP) with molecular weights of 67,000 and 56,000. The Mr = 67,000 protein (67K GBP) is synthesized upon treatment with either alpha-, beta-, or gamma-interferon. Among these interferons, gamma-interferon induces a higher level of 67K GBP synthesis. The 67K GBP synthesized in either beta- or gamma-interferon-treated cells has two charge forms with isoelectric points of 6.0 and 5.8, respectively. The synthesis of the Mr = 56,000 protein is induced by the treatment using either alpha- or beta-interferon, but its synthesis in gamma-interferon-treated cells is undetectable. The amounts of the radioactive GBPs synthesized in human fibroblasts are proportional to the amounts of the purified beta-interferon used for the inductions. Syntheses of GBPs require the transcription of cellular genes because their syntheses are completely blocked by actinomycin D treatments. The mRNA for the 67K GBP is found in fibroblasts that are treated by either alpha-, beta-, or gamma-interferon, but it is not detected in untreated cells. More 67K GBP mRNA is accumulated in the gamma-interferon-treated than in alpha- or beta-interferon-treated fibroblasts. This is consistent with more 67K GBP synthesis found in gamma-interferon-treated fibroblasts.