Identification of transactivation-responsive DNA-binding protein 43 (TARDBP43; TDP-43) as a novel factor for TNF-α expression upon lipopolysaccharide stimulation in human monocytes

H. Murata, Takako Hattori, H. Maeda, Shogo Takashiba, Masaharu Takigawa, J. Kido, T. Nagata

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

Background and Objective: Tumor necrosis factor alpha (TNF-α) is a major cytokine implicated in various inflammatory diseases. The nature of the nuclear factors associated with human TNF-α gene regulation is not well elucidated. We previously identified a novel region located from -550 to -487 in human TNF-α promoter that did not contain the reported binding sites for nuclear factor kappa B (NF-κB) but showed lipopolysaccharide (LPS)-induced transcriptional activity. The purpose of this study is to identify novel factors that bind to the promoter region and regulate TNF-α expression. Material and Methods: To identify DNA-binding proteins that bound to the target region of TNF-α promoter, a cDNA library from LPS-stimulated human monocytic cell line THP-1 was screened using a yeast one-hybrid system. Cellular localizations of the DNA-binding protein in the cells were examined by subcellular immunocytochemistry. Nuclear amounts of the protein in LPS-stimulated THP-1 cells were identified by western blot analysis. Expression of mRNA of the protein in the cells was quantified by real-time polymerase chain reaction. Electrophoretic mobility shift assays were performed to confirm the DNA-binding profile. Overexpression of the protein and knockdown of the gene were also performed to investigate the role for TNF-α expression. Results: Several candidates were identified from the cDNA library and transactivation-responsive DNA-binding protein 43 (TARDBP43; TDP-43) was focused on. Western blot analysis revealed that nuclear TDP-43 protein was increased in the LPS-stimulated THP-1 cells. Expression of TDP-43 mRNA was already enhanced before TNF-α induction by LPS. Electrophoretic mobility shift assay analysis showed that nuclear extracts obtained by overexpressing FLAG-tagged TDP-43 bound to the -550 to -487 TNF-α promoter fragments. Overexpression of TDP-43 in THP-1 cells resulted in an increase of TNF-α expression. Knockdown of TDP-43 in THP-1 cells downregulated TNF-α expression. Conclusion: We identified TDP-43 as one of the novel TNF-α factors and found that it bound to the LPS-responsive element in the TNF-α promoter to increase TNF-α expression.

Original languageEnglish
Pages (from-to)452-460
Number of pages9
JournalJournal of Periodontal Research
Volume50
Issue number4
DOIs
Publication statusPublished - Aug 1 2015

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Keywords

  • Lipopolysaccharide
  • Monocyte
  • TDP-43
  • Tumor necrosis factor alpha

ASJC Scopus subject areas

  • Periodontics

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