Cloning and promoter analysis of the chicken interferon regulatory factor-3 gene

Interferon regulatory factors (IRFs) are a family of DNA-binding proteins i nvolved in mediating the cellular response to interferons (IFNs) and viral infection. Although extensively studied in mammals, IRFs of other vertebrat es have been less well characterized. Previously, we cloned chicken interfe ron regulatory factor-3 (chIRF-3) mRNA, which is rapidly and transiently in duced by double-stranded (ds)RNA, The chIRF-3 mRNA encodes a protein distin ct from any known mammalian IRF. Here, we show that chIRF-3 is activated ad ditively by type I and type II IFNs, To delineate the sequence elements req uired to regulate chIRF-3 expression, we cloned chIRF-3 and 0.48 kb of 5' f lanking sequence. Computer analysis of the proximal promoter revealed three putative binding sites for nuclear factor (NF)-kappa B, two overlapping in terferon-stimulated response elements (ISREs), and an interferon gamma acti vating sequence (GAS). The presence of both GAS and ISRE consensus sequence s in the chIRF-3 promoter is unique among IRF family members. Both type I a nd II IFNs, as well as dsRNA and IRF-1, trans-activate the promoter in shor t-term transfection experiments. Mutational analysis of the promoter demons trated that the putative NF-kappa B binding sites are needed for stimulatio n by dsRNA but not by either type I or type II IFN and that both the overla pping ISREs and GAS are required for full induction by type I or type II IF N.