PROMOTER STRUCTURES AND DIFFERENTIAL RESPONSES TO VIRAL AND NONVIRAL INDUCERS OF CHICKEN TYPE-I INTERFERON GENES

Two serologically distinct type I interferons (IFNs), designated ChIFN 1 and ChIFN2, are known in the chicken. ChIFN1 is encoded by a family of 10 or more genes, whereas ChIFN2 is encoded by a single gene. We sh ow here that ChIFN1 and ChIFN2 transcripts are both strongly induced b y Newcastle disease virus in primary chicken macrophages, By contrast, oral administration of the imidazoquinoline S-28463, which selectivel y induces IFN-alpha in mammals, led to a rapid accumulation of ChIFN1 (but not ChIFN2) transcripts in adult chicken spleen and thymus. The 5 '-upstream region of the ChIFN2 gene contains a NF-kappa B consensus m otif flanked by a sequence element that could serve as a binding site for transcription factor IRF-1, reminiscent of mammalian IFN-beta prom oters, and it mediated powerful virus inducibility in a duck fibroblas t cell line when cloned in front of a promoterless luciferase reporter gene. The 5'-upstream region of the cloned ChIFN1 gene contains two p utative binding sites for IRF-1, but lacks NF-kappa B-binding sites, a nd it did not respond well to virus in transfected cells, Thus, the pr omoters of ChIFN1 and ChIFN2 genes not only exhibited differential res ponses to nonviral inducers in vivo, but also differed in structure an d response to virus in transfected cells. These findings indicate that ChIFN2 represents the avian homolog of mammalian IFN-beta, whereas Ch IFN1 seems to correspond to mammalian IFN-alpha.