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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.

Type

Journal article

Journal

Mol Cell Biol

Publication Date

12/2000

Volume

20

Pages

9113 - 9119

Keywords

Adenoviridae, Animals, Binding Sites, COS Cells, Cell Fractionation, Cell Line, Cells, Cultured, Cloning, Molecular, Dimerization, Gene Expression Regulation, Genes, Reporter, Humans, Lipopolysaccharides, Macrophages, Monocytes, NF-kappa B, NF-kappa B p50 Subunit, Polymorphism, Genetic, Promoter Regions, Genetic, Transcriptional Activation, Tumor Necrosis Factor-alpha