Molecular cloning of a gene selectively induced by gamma interferon from human macrophage cell line U937

A cDNA clone encoding a gamma interferon (IFN-gamma)-inducible mRNA in human cells of the macrophage lineage was isolated and characterized. The corresponding gene, gamma.1, was selectively induced by IFN-gamma, responding a hundredfold better to IFN-gamma than to IFN-alpha. The induction was rapid and transient, with maximal mRNA accumulation at about 3 h and decline to the basal level after 48 h. Transcriptional activation could be detected as early as 5 min after IFN-gamma stimulation and accounted entirely for the mRNA accumulation. The induction of gamma.1 by IFN-gamma was cell-type restricted, being seen only in macrophages and endothelial cells. In addition, phorbol ester-induced differentiation of promyelocytic HL-60 cells and promonocytic THP-1 cells rendered the gamma.1 gene inducible by IFN-gamma. The 1.0-kilobase gamma.1 cDNA sequence encoded a small predicted polypeptide of 38 amino acids and had a conserved sequence associated with rapidly turning over mRNAs. In vitro translation of the gamma.1 transcript yielded a 4,000-dalton polypeptide.