Allele-specific chromatin remodeling of the tumor necrosis factor-alpha promoter

The -863 C/A polymorphism in the tumor necrosis factor-alpha (TNF-alpha) promoter has been suggested to influence TNF-alpha expression. Here we elucidated the molecular mechanisms underlying the allele-specific regulation of TNF-alpha gene expression under basal and LPS-stimulated conditions in THP-1 cells and in human primary macrophages. We show that the binding of two NF-kappaB complexes, the p50/p50 homodimer and the p50/p65 heterodimer, was upregulated upon LPS stimulation. Both complexes bound to the C-allele whereas the A-allele only bound the p50/p65 complex. Two DNase I hypersensitive sites appeared in the TNF-alpha promoter after LPS stimulation of THP-1 cells. DNase I hypersensitivity of the TNF-alpha promoter was also analyzed in human monocytes prepared from individuals of different -863C/A genotype. Hypersensitivity was increased in the promoter harboring the mutant A-allele, particularly after LPS stimulation. In summary, binding of transcription factor NF-kappaB to the TNF-alpha promoter is associated with allele-specific remodeling of chromatin structure.