PU.1 and Interferon Consensus Sequence-binding Protein Regulate the Myeloid Expression of the Human Toll-like Receptor 4 Gene

• Published in: The Journal of biological chemistry Vol. 275; no. 13; pp. 9773 - 9781
• Main Authors: Rehli, Michael, Poltorak, Alexander, Schwarzfischer, Lucia, Krause, Stefan W., Andreesen, Reinhard, Beutler, Bruce
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 31.03.2000; American Society for Biochemistry and Molecular Biology
• Subjects: Amino Acid Sequence; Animals; Base Sequence; Bone Marrow - metabolism; Cloning, Molecular; DNA; Drosophila Proteins; Ets protein; Gene Expression Regulation - physiology; Humans; Interferon Regulatory Factors; Membrane Glycoproteins - genetics; Mice; Molecular Sequence Data; Mutagenesis, Site-Directed; Promoter Regions, Genetic; Protein Binding; Proto-Oncogene Proteins - metabolism; Proto-Oncogene Proteins - physiology; PU.1 protein; Receptors, Cell Surface - genetics; Repressor Proteins - physiology; Sequence Homology, Nucleic Acid; TLR gene; Toll-Like Receptor 4; Toll-Like Receptors; Trans-Activators - metabolism; Trans-Activators - physiology
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.275.13.9773

The protein product of the Toll-like receptor (TLR) 4 gene has been implicated in the signal transduction events induced by lipopolysaccharide (LPS). In mice, destructive mutations ofTlr4 impede the normal response to LPS and cause a high susceptibility to Gram-negative infection. Expression of TLR4 mRNA in humans is restricted to a small number of cell types, including LPS-responsive myeloid cells, B-cells, and endothelial cells. To investigate the molecular basis for TLR4 expression in cells of myeloid origin, we cloned the human TLR4 gene and analyzed its putative 5′-proximal promoter. In transient transfections a region of only 75 base pairs upstream of the major transcription initiation site was sufficient to induce maximal luciferase activity in THP-1 cells. The sequence of this region is similar in human and mouse TLR4 genes and lacks a TATA box, typical Sp1-sites or CCAAT box sequences. Instead, it contains consensus-binding sites for Ets family transcription factors, octamer-binding factors, and a composite interferon response factor/Ets motif. The activity of the promoter in macrophages was strictly dependent on the integrity of both half sites of the composite interferon response factor/Ets motif, which was constitutively bound by the myeloid and B-cell-specific transcription factor PU.1 and interferon consensus sequence-binding protein. These results indicate that the two tissue-restricted transcription factors PU.1 and interferon consensus sequence-binding protein participate in the basal regulation of human TLR4 in myeloid cells. Cloning of the human TLR4 gene provides a basis for further investigation of the possible impact of genetic variations on the susceptibility to infection and sepsis.