Gene induction pathways mediated by distinct IRFs during viral infection

During viral infection, interferon-alpha/beta (IFN-alpha/beta) and many IFN-inducible genes are induced to elicit antiviral responses of the host. Using cells with a gene disruption(s) for the IRF family of transcription factors, we provide evidence that these genes, containing similar IRF-binding cis-elements, are classified into distinct groups, based on the gene induction pathway(s), The IFN-beta gene induction is dependent on either IRF-3 or IRF-7, whereas induction of the IFN-alpha gene family is IRF-7-dependent. On the other hand, ISG15, ISG54 and IP-10 are induced by either IRF-3 or IFN stimulated gene factor 3 (ISGF3). We also show that another group of genes is totally dependent on ISGF3, Thus, during viral infection, a given gene responds either directly to a virus or virus-induced IFN-alpha/beta or both through distinct pathways, The differential utilization of these induction pathways for these genes during viral infection may reflect their distinct functional roles in the efficient antiviral response. (C) 2001 Academic Press.