Characterization of Three Promoter Elements and Cognate DNA Binding Protein(s) Necessary for IFN-γ Induction of gp91-phox Transcription

The cytochrome b₅₅₈ heavy chain (gp91-phox) is expressed in terminally differentiated myelomonocytic cells. Three cis-elements located between -450 and -100 bp of the gp91-phox promoter are required for IFN-γ-induced transcription. Mutations that disrupt individual cis-elements incrementally decrease gp91-phox promoter activity, and one of the two proximal elements must be present for an IFN-γ response. The DNA-binding activities that interact with each of the cis-elements exhibit similar gel mobility and binding site specificity, although a consensus binding site common to the three elements is not apparent. An increased level of each DNA/protein complex is observed in myeloid cells following treatment with PMA, retinoic acid/dimethylformamide, or IFN-γ, but not in similarly treated HeLa cells. The myeloid-specific increase in the intensity of each complex is delayed 12 to 24 h following IFN-γ treatment, and the complexes are not immunoreactive with antisera directed against IFN-responsive factors such as IRF-1, IRF-2, IFN consensus sequence binding protein, Stat1, and IFN-stimulated gene factor-3γ, although IRF-2 is additionally detected as binding to the middle cis-element. These results reveal cis-elements and a DNA-binding factor(s) that participate in a common pathway in response to various stimuli that induce gp91-phox transcription.