PU.1 and interferon consensus sequence-binding protein regulate the myeloid expression of the human Toll-like receptor 4 gene.
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 of Tlr4 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.
Rehli
M
M
Department of Hematology and Oncology, University of Regensburg, 93042 Regensburg, Germany. Michael.Rehli@klinik.uni-regensburg.de
Poltorak
A
A
Schwarzfischer
L
L
Krause
S W
SW
Andreesen
R
R
Beutler
B
B
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001853:Bone Marrow / Q000378:metabolism*; D003001:Cloning, Molecular; D004247:DNA; D029721:Drosophila Proteins; D005786:Gene Expression Regulation / Q000502:physiology*; D006801:Humans; D050835:Interferon Regulatory Factors; D008562:Membrane Glycoproteins / Q000235:genetics*; D051379:Mice; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D011518:Proto-Oncogene Proteins / Q000378:metabolism / Q000502:physiology*; D011956:Receptors, Cell Surface / Q000235:genetics*; D012097:Repressor Proteins / Q000502:physiology*; D012689:Sequence Homology, Nucleic Acid; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors; D015534:Trans-Activators / Q000378:metabolism / Q000502:physiology*; D000099185:Interferon Regulatory Factor-8; D000099232:Proto-Oncogene Protein Spi-1
D004247:DNA; D029721:Drosophila Proteins; D050835:Interferon Regulatory Factors; D008562:Membrane Glycoproteins; D011518:Proto-Oncogene Proteins; D011956:Receptors, Cell Surface; D012097:Repressor Proteins; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors; D015534:Trans-Activators; D000099185:Interferon Regulatory Factor-8; D000099232:Proto-Oncogene Protein Spi-1; C495345:TLR4 protein, human