TRIF [TIR (Toll/interleukin-1 receptor) domain-containing adaptor protein inducing interferon β; also known as TICAM-1 (TIR-containing adaptor molecule-1)] is a key adaptor for TLR3 (Toll-like receptor 3)- and TLR4-mediated signalling. We have performed a detailed annotation of the human TRIF gene and fine analysis of the basal and inducible promoter elements lying 5´ to the site of initiation of transcription. Human TRIF maps to chromosome 19p13.3 and is flanked upstream by TIP47, which encodes the mannose 6-phosphate receptor binding protein, and downstream by a gene encoding FEM1a, a human homologue of the Caenorhabditis elegans Feminisation-1 gene. Using promoter–reporter deletion constructs, we identified a distal region with the ability to negatively regulate basal transcription and a proximal region containing an Sp1 (stimulating protein 1) site that confers approx. 75% of basal transcriptional activity. TRIF expression can be induced by multiple stimuli, such as the ligands for TLR2, TLR3 and TLR4, and by the pro-inflammatory cytokines tumour necrosis factor α and interleukin-1α. All of these stimuli act via an NF-κB (nuclear factor-κB) motif at position −127. In spite of the presence of a STAT1 (signal transduction and activators of transcription 1) motif at position −330, the addition of type I or type II interferon had no effect on TRIF activity. The human TRIF gene would therefore appear to be regulated primarily by NF-κB.

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