CIRF-3, A NEW MEMBER OF THE INTERFERON REGULATORY FACTOR (IRF) FAMILYTHAT IS RAPIDLY AND TRANSIENTLY INDUCED BY DSRNA

In mammals, some of the effects of interferon (IFN) on gene transcript ion are known to be mediated by a family of IFN-inducible DNA-binding proteins, the IFN regulatory factor (IRF) family, which includes both activators and repressors of transcription. Although IFN activities ha ve been described in many vertebrates, little is known about regulatio n of IFN- or IFN-stimulated genes in species other than human and mous e. Here, we report the cloning of a chicken cDNA, cIRF-3, encoding a p rotein with a DNA-binding domain similar to that found in the mammalia n IRF family of proteins. Similarity between cIRF-3 and the mammalian IRFs is comparable with that between known members of the family. It i s most similar to the IRF proteins ICSBP and ISGF3 gamma but is equall y divergent from both. Gel mobility shift assays indicate that cIRF-3 is capable of binding a known IFN-stimulated response element that is conserved between the mammalian and chicken Mx genes. Expression of th e cIRF-3 gene can be induced to high levels by poly(l). poly(C). Induc tion is rapid and transient with no requirement for protein synthesis. Co-treatment of cells with cycloheximide results in superinduction of cIRF-3 mRNA. The structural and regulatory characteristics of cIRF-3 indicate that it is the first example of a non-mammalian IRF protein.