Regulation of intercellular adhesion molecule-1 gene by tumor necrosis factor-alpha is mediated by the nuclear factor-kappaB heterodimers p65/p65 and p65/c-Rel in the absence of p50.
Human intercellular adhesion molecule-1 (ICAM-1) plays an important role in immune responses as the major specific ligand for the beta2-integrins LFA-1 and Mac-1. During the inflammatory process, ICAM-1 expression is stimulated by various proinflammatory cytokines. We have examined the mechanisms of transcriptional control involved in the stimulation of ICAM-1 gene expression by tumor necrosis factor-alpha (TNF-alpha) and by the nuclear factor-kappaB (NF-kappaB) family of transcription factors in the Ad5-transformed human embryonal kidney cell line 293. A proximal site (5'-TTGGAAATTCC-3') mapping at position -228 from the ATG and known to mediate TNF-alpha responsiveness in endothelial cells is also critical for TNF-alpha responsiveness in 293 cells. However, unlike endothelial cells, electrophoretic mobility shift assays, using whole-cell extracts prepared from TNF-alpha-treated cells, showed that TNF-alpha induces the formation of a specific kappaB binding complex, mainly composed of NF-kappaB subunits RelA and c-Rel. Electrophoretic mobility shift assays done with 293 cells transfected with p50, p65, or both subunits showed that p50 only has a weak ability to bind the proximal ICAM-1 NF-kappaB site. Another element exhibiting sequence homology with NF-kappaB binding sites and located at position -540 relative to the mRNA cap site was found to be involved in the basal activity of the ICAM-1 promoter, is not required for TNF-alpha responsiveness, and does not bind NF-kappaB subunits. Whereas transactivation of the ICAM-1 promoter by p65 requires the proximal NF-kappaB site, deletion mutant analysis showed that p50 and, to a greater extent, p52 transactivate reporter plasmids lacking NF-kappaB sites, suggesting the presence of other p50/p52 responsive element(s).
Aoudjit
F
F
Department of Biochemistry, Laval University, Quebec, Canada.
Brochu
N
N
Bélanger
B
B
Stratowa
C
C
Hiscott
J
J
Audette
M
M
D002135:Calcium-Binding Proteins; D002478:Cells, Cultured; D005786:Gene Expression Regulation; D017930:Genes, Reporter; D006801:Humans; D018799:Intercellular Adhesion Molecule-1 / Q000235:genetics*; D007668:Kidney / Q000166:cytology; D008562:Membrane Glycoproteins / Q000378:metabolism*; D016328:NF-kappa B / Q000378:metabolism*; D052002:NF-kappa B p50 Subunit; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D020569:Proto-Oncogene Proteins c-rel; D050863:Synaptotagmin I; D050857:Synaptotagmins; D014157:Transcription Factors / Q000378:metabolism; D015533:Transcriptional Activation; D014162:Transfection; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
D002135:Calcium-Binding Proteins; D008562:Membrane Glycoproteins; D016328:NF-kappa B; D052002:NF-kappa B p50 Subunit; D009419:Nerve Tissue Proteins; D011518:Proto-Oncogene Proteins; D020569:Proto-Oncogene Proteins c-rel; D050863:Synaptotagmin I; D014157:Transcription Factors; D014409:Tumor Necrosis Factor-alpha; D018799:Intercellular Adhesion Molecule-1; D050857:Synaptotagmins