Inducible binding of PU.1 and interacting proteins to the Toll-like receptor 4 promoter during endotoxemia.
We hypothesized that PU.1 and PU.1 interacting proteins (PIP) binding to the Toll-like receptor 4 (TLR4) promoter is involved in endotoxin-induced upregulation of TLR4 gene expression. Our results employing chromatin immunoprecipitation assays indicate that PU.1 binds to the murine TLR4 promoter both in macrophage cells and, most importantly, in whole lung tissue. Treatment of RAW 264.7 cells with endotoxin induced the association of PU.1 and the TLR4 promoter in a time-dependent manner, and this was closely tied to interactions between the TLR4 promoter and the PIP interferon regulatory factors (IRF)4 and IRF8. PU.1 binding was related to increases in steady-state TLR4 mRNA and total TLR4 protein in RAW cells. Endotoxemia in animals caused the similar inducible interaction between PU.1 and IRF4 and the TLR4 promoter in lung tissue of mice that was treated with a single intraperitoneal injection of endotoxin. PU.1 binding to the TLR4 promoter was not enhanced in the lung tissue of endotoxin-resistant C3H/HeJ mice in response to endotoxemia. Transient transfection studies in RAW cells indicate that inducible binding of PU.1 to the TLR4 promoter is abrogated by a Ser148 to Ala mutation in PU.1. These data suggest that induction of PU.1/PIP binding to the TLR4 promoter is involved in endotoxin response in vivo and may mediate transcriptional changes in TLR4 gene expression.
Pedchenko
Tetyana V
TV
Division of Allergy, Department of Medicine, Pulmonary and Critical Care Medicine, Vanderbilt University Medical Center, Nashville, TN, USA.
Park
Gye Young
GY
Joo
Myungsoo
M
Blackwell
Timothy S
TS
Christman
John W
JW
D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000378:metabolism*; D019446:Endotoxemia / Q000235:genetics / Q000378:metabolism*; D004731:Endotoxins / Q000494:pharmacology; D066298:In Vitro Techniques; D050835:Interferon Regulatory Factors; D008168:Lung / Q000187:drug effects / Q000378:metabolism; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism; D051379:Mice; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D011971:Receptors, Immunologic / Q000235:genetics* / Q000378:metabolism*; D051197:Toll-Like Receptor 4; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic; D000099232:Proto-Oncogene Protein Spi-1; D000099218:Interferon Regulatory Factor-4
D004268:DNA-Binding Proteins; D004731:Endotoxins; D050835:Interferon Regulatory Factors; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; D011971:Receptors, Immunologic; D051197:Toll-Like Receptor 4; D015534:Trans-Activators; D000099232:Proto-Oncogene Protein Spi-1; D000099218:Interferon Regulatory Factor-4; C493487:Tlr4 protein, mouse