STAT-1 and c-Fos interaction in nitric oxide synthase-2 gene activation

1 Pulmonary and Critical Care Medicine and Cancer Biology, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, Ohio 44195; and 2 Pulmonary-Critical Care Medicine Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892 Submitted 30 December 2002 ; accepted in final form 12 March 2003 Interferon- (IFN- ) is required for induction of the human nitric oxide synthase-2 ( NOS2 ) gene in lung epithelium. Although the human NOS2 promoter region contains many cytokine-responsive elements, the molecular basis of induction is only partially understood. Here, the major cis -regulatory elements that control IFN- -inducible NOS2 gene transcription in human lung epithelial cells are identified as composite response elements that bind signal transducer and activator of transcription 1 (STAT-1) and activator protein 1 (AP-1), which is comprised of c-Fos, Fra-2, c-Jun, and JunD. Notably, IFN- activation of the human NOS2 promoter is shown to require functional AP-1 regulatory region(s), suggesting a role for AP-1 activation/binding in the IFN- induction of genes. We show that c-Fos interacts with STAT-1 after IFN- activation and the c-Fos/STAT-1 complex binds to the -activated site (GAS) element in close proximity to AP-1 sites located at 4.9 kb upstream of the transcription start site. Taken together, our findings support a model in which a physical interaction between c-Fos and STAT-1 participates in NOS2 gene transcriptional activation. gene regulation; signal transduction Address for reprint requests and other correspondence: S. C. Erzurum, Cleveland Clinic Foundation, Lerner Research Institute, 9500 Euclid Ave./NB40, Cleveland, OH 44195 (E-mail: erzurus{at}ccf.org ).