Differential binding of interferon-induced factors to an oligonucleotide that mediates transcriptional activation.

Type I interferons elicit a number of biological responses by rapidly and transiently stimulating the transcriptional expression of a specific set of genes. The promoters of the inducible genes contain an enhancer element which is required for transcriptional activation. A specific oligonucleotide of 18 residues is sufficient for transcriptional induction when positioned in a heterologous promoter. Previous studies have identified three protein factors which can bind to the interferon stimulated enhancer. We show here that the binding of one of the interferon-induced factors requires specific nucleotides flanking the minimum recognition site for the other two factors. The distinct interaction of this factor with the response element is of significant importance since this factor is the sole candidate for a primary transcriptional activator of interferon-induced genes.