The NF-κB-Like Site in the TNF-α Repressor Element Is Essential for Its Repressor Function

Abstract

We have previously identified a repressor element in the TNF-α promoter (−280 to −172) by deletion analysis. When this 108 bp repressor element was placed in front of a heterologous promoter containing an NF-κB binding site, less repression was observed. When this element was dimerized and placed in front of the positive element (−125 to −102) of the TNF-α promoter, instead of repression, activation was observed. There is an NF-κB-like site in the 108 bp repressor region (−211 to −202) and our gel retardation analysis showed that this site and a known NF-κB binding site both could compete for one of the specific protein complexes formed on the 108 bp probe. To test the functionality of this NF-κB-like site, we mutagenized the critical GGGG sequence to ATCC. Contrary to our prediction, such a mutation blocked the repressor function of the 108 bp element. This suggests that the NF-κB-like site is an essential sequence for the repressor function of the 108 bp repressor element.