Selective interaction of a subset of interferon-gamma response element-binding proteins with the intercellular adhesion molecule-1 (ICAM-1) gene promoter controls the pattern of expression on epithelial cells.
Intercellular adhesion molecule-1 (ICAM-1) modulates epithelial and endothelial leukocyte adherence, but epithelial cell ICAM-1 levels (unlike endothelial cell levels) are selectively sensitive to interferon-gamma (IFN-gamma). Nuclear run-off assays indicated that IFN-gamma regulation of epithelial ICAM-1 levels occurs at a transcriptional level, so the basis for selective cytokine control of ICAM-1 expression was investigated using the ICAM-1 gene promoter region. A plasmid construct containing 5.0 kilobases of ICAM-1 gene 5'-flanking region fused to a reporter gene was selectively responsive to IFN-gamma in (human tracheal) epithelial cells but not in (human umbilical vein) endothelial cells, indicating that this region is sufficient to mediate proper cell-specific expression. An IFN-gamma response element (IRE) was localized to a DNA segment (nucleotides -130 to -94) in the ICAM-1 gene by comparisons of nested 5'-deletional constructs and by demonstrating that this segment confers IFN-gamma responsiveness on heterologous promoters. This same IRE formed a single major binding complex (IRE-BC) in gel retardation assays with nuclear proteins from IFN-gamma-stimulated but not unstimulated epithelial cells, and mutation of the IRE consensus motif (TTTCCGGGAAA at -116 to -106) resulted in loss of IRE-protein binding and abolished IFN-gamma responsiveness, indicating that this sequence is required for ICAM-1 IRE function. Comparison of the ICAM-1 IRE to DNA elements that confer IFN responsiveness in other human genes indicated similarity only to response regions in the Fc gamma RI and IRF-1 genes. The findings provide evidence for a distinct IRE subset that combines a DNA element common to all IFN-responsive genes (GAAA) with a distinct flanking sequence (the inverted repeat GAAA) in order to fine-tune IFN responses and activate a subset of immune response genes (ICAM-1, Fc gamma RI, and IRF-1).
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Department of Internal Medicine, Washington University School of Medicine, St. Louis, Missouri 63110.
Pelletier
M R
MR
Holtzman
M J
MJ
D001483:Base Sequence; D015815:Cell Adhesion Molecules / Q000235:genetics*; D004252:DNA Mutational Analysis; D017931:DNA Primers / Q000737:chemistry; D004268:DNA-Binding Proteins / Q000378:metabolism; D004730:Endothelium, Vascular / Q000378:metabolism; D004848:Epithelium / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000235:genetics; D005786:Gene Expression Regulation; D006801:Humans; D066298:In Vitro Techniques; D018799:Intercellular Adhesion Molecule-1; D007371:Interferon-gamma / Q000494:pharmacology*; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000378:metabolism; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000235:genetics; D017452:Receptors, IgG / Q000235:genetics; D014158:Transcription, Genetic
D015815:Cell Adhesion Molecules; D017931:DNA Primers; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D012333:RNA, Messenger; D017452:Receptors, IgG; D018799:Intercellular Adhesion Molecule-1; D007371:Interferon-gamma; D019204:GTP-Binding Proteins