title: Dominant-negative effect of the c-fos family gene products on inducible NO synthase expression in macrophages.
abstract: Activation of murine peritoneal macrophages or the macrophage cell line RAW264 with IFN-gamma and bacterial lipopolysaccharide promotes a transient up-regulation of c-fos family gene expression following inducible NO synthase (iNOS) production. Since introduction of a double mutation into the two AP-1-binding sites in the iNOS promoter region reduced the promoter activity to 25% of the authentic one in activated RAW264 cells, the induced c-Fos/AP-1 may promote iNOS expression in activated macrophages. Surprisingly, overexpression of c-fos in activated macrophages completely suppressed the production of iNOS, but not that of IL-6 and IL-1beta. The regulatory effect was also observed by overexpression of c-fos, c-jun or fosB on the promoter activity as deduced from transfection experiments. However, the mutation of AP-1-binding sites in the promoter region did not abrogate the regulatory effect of c-fos and the effect of c-fos was diminished by co-transfection with c-jun, but not with fosB, suggesting no relation between the regulatory effect and a c-Fos/AP-1 complex. Expression of NF-IL6 (C/EBPbeta), whose gene product can make a non-functional heterodimer with c-Fos family proteins, was transiently induced in activated macrophages. Overexpression of NF-IL6 in activated RAW264 cells augmented iNOS promoter activity and reduced the regulatory effect of c-fos overexpression. Thus, overproduction of c-Fos family proteins acts as a dominant-negative-type regulator on iNOS expression in activated macrophages.
authors.affiliation: Department of Developmental Genetics (H2), Graduate School of Medicine, Chiba University, Chiba 260-8670, Japan.
authors.forename: Seiji
authors.initials: S
authors.lastname: Okada
authors.forename: Shintaro
authors.initials: S
authors.lastname: Obata
authors.forename: Masahiko
authors.initials: M
authors.lastname: Hatano
authors.forename: Takeshi
authors.initials: T
authors.lastname: Tokuhisa
mesh_terms: D000818:Animals; D001665:Binding Sites; D022782:CCAAT-Enhancer-Binding Protein-beta / Q000378:metabolism; D002460:Cell Line; D015971:Gene Expression Regulation, Enzymologic; D016762:Genes, fos; D007371:Interferon-gamma / Q000502:physiology; D008070:Lipopolysaccharides / Q000378:metabolism; D008262:Macrophage Activation; D008264:Macrophages / Q000201:enzymology* / Q000276:immunology / Q000378:metabolism; D051379:Mice; D019001:Nitric Oxide Synthase / Q000235:genetics* / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II; D017354:Point Mutation; D011401:Promoter Regions, Genetic; D016760:Proto-Oncogene Proteins c-fos / Q000235:genetics / Q000378:metabolism*; D018808:Transcription Factor AP-1 / Q000235:genetics / Q000378:metabolism; D015854:Up-Regulation
chemical_list: D022782:CCAAT-Enhancer-Binding Protein-beta; D008070:Lipopolysaccharides; D016760:Proto-Oncogene Proteins c-fos; D018808:Transcription Factor AP-1; D007371:Interferon-gamma; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse