Functional consequences of a polymorphism affecting NF-kappaB p50-p50 binding to the TNF promoter region.
Stimulation of the NF-kappaB pathway often causes p65-p50 and p50-p50 dimers to be simultaneously present in the cell nucleus. A natural polymorphism at nucleotide -863 in the human TNF promoter (encoding tumor necrosis factor [TNF]) region provides an opportunity to dissect the functional interaction of p65-p50 and p50-p50 at a single NF-kappaB binding site. We found that this site normally binds both p65-p50 and p50-p50, but a single base change specifically inhibits p50-p50 binding. Reporter gene analysis in COS-7 cells expressing both p65-p50 and p50-p50 shows that the ability to bind p50-p50 reduces the enhancer effect of this NF-kappaB site. Using an adenoviral reporter assay, we found that the variant which binds p50-p50 results in a reduction of lipopolysaccharide-inducible gene expression in primary human monocytes. This finding adds to a growing body of experimental evidence that p50-p50 can inhibit the transactivating effects of p65-p50 and illustrates the potential for genetic modulation of inflammatory gene regulation in humans by subtle nucleotide changes that alter the relative binding affinities of different forms of the NF-kappaB complex.
Udalova
I A
IA
Molecular Infectious Disease Group, Institute of Molecular Medicine, Oxford University, Oxford, United Kingdom. iudalova@molbiol.ox.ac.uk
Richardson
A
A
Denys
A
A
Smith
C
C
Ackerman
H
H
Foxwell
B
B
Kwiatkowski
D
D
D000256:Adenoviridae / Q000235:genetics; D000818:Animals; D001665:Binding Sites; D019556:COS Cells; D002458:Cell Fractionation; D002460:Cell Line; D002478:Cells, Cultured; D003001:Cloning, Molecular; D019281:Dimerization; D005786:Gene Expression Regulation; D017930:Genes, Reporter / Q000235:genetics; D006801:Humans; D008070:Lipopolysaccharides / Q000494:pharmacology; D008264:Macrophages / Q000166:cytology / Q000378:metabolism; D009000:Monocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D016328:NF-kappa B / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D052002:NF-kappa B p50 Subunit; D011110:Polymorphism, Genetic / Q000235:genetics*; D011401:Promoter Regions, Genetic / Q000235:genetics*; D015533:Transcriptional Activation / Q000502:physiology; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics*
D008070:Lipopolysaccharides; D016328:NF-kappa B; D052002:NF-kappa B p50 Subunit; D014409:Tumor Necrosis Factor-alpha