Transcription of Tnfaip3 is regulated by NF-κB and p38 via C/EBPβ in activated macrophages

• Published in: PloS one 2013, Vol.8 (9), p.e73153
• Main Authors: Lai, Ting-Yu, Wu, Shang-Duen, Tsai, Mong-Hsun, Chuang, Eric Y, Chuang, Li-Ling, Hsu, Li-Chung, Lai, Liang-Chuan
• Format: Article
• Language: English
• Subjects: Adapters; Animals; Bacteria; Binding sites; Bioinformatics; Biology; Bone marrow; Bone Marrow Cells - cytology; CCAAT-Enhancer-Binding Protein-beta - metabolism; Cell Line; Chromatin; Chromatin Immunoprecipitation; Cysteine Endopeptidases - genetics; Cytokines; DNA-Binding Proteins - genetics; Enzymes; Gene expression; Gene Expression Regulation - drug effects; Genes; Gram-negative bacteria; Gram-positive bacteria; Helicobacter pylori; Immune response; Immune system; Immunity; Immunoprecipitation; Innate immunity; Intracellular Signaling Peptides and Proteins - genetics; Kinases; Laboratory animals; Lipopolysaccharides; Lipopolysaccharides - pharmacology; Macrophage Activation - drug effects; Macrophages; Macrophages - cytology; Macrophages - drug effects; Macrophages - immunology; Macrophages - metabolism; Medicine; Mice; Microorganisms; NF-κB protein; p38 Mitogen-Activated Protein Kinases - metabolism; Promoter Regions, Genetic - genetics; Proteins; Receptors; Recruitment; Regulatory mechanisms (biology); Signal transduction; Signal Transduction - drug effects; Signaling; TLR4 protein; Toll-Like Receptor 4 - metabolism; Toll-like receptors; Transcription Factor RelA - metabolism; Transcription factors; Transcription, Genetic - drug effects; Tumor Necrosis Factor alpha-Induced Protein 3; Ubiquitin-Protein Ligases - genetics
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0073153

Macrophages play a pivotal role in the immune system through recognition and elimination of microbial pathogens. Toll-like receptors (TLRs) on macrophages interact with microbial substances and initiate signal transduction through intracellular adapters. TLR4, which recognizes the lipopolysaccharides (LPS) on Gram-positive and Gram-negative bacteria, triggers downstream signaling mediators and eventually activates IκB kinase (IKK) complex and mitogen-activated protein kinases (MAPKs) such as p38. Previous reports revealed that, in addition to NF-κB, a core transcription factor of the innate immune response, the induction of some LPS-induced genes in macrophages required another transcription factor whose activity depends on p38. However, these additional transcription factors remain to be identified. In order to identify p38-activated transcription factors that cooperate with NF-κB in response to LPS stimulation, microarrays were used to identify genes regulated by both NF-κB and p38 using wild-type, IKK-depleted, and p38 inhibitor-treated mouse bone marrow-derived macrophages (BMDMs). In silico analysis of transcription factor binding sites was used to predict the potential synergistic transcription factors from the co-expressed genes. Among these genes, NF-κB and C/EBPβ, a p38 downstream transcription factor, were predicted to co-regulate genes in LPS-stimulated BMDMs. Based on the subsequent results of a chromatin immunoprecipitation assay and TNFAIP3 expression in C/EBPβ-ablated macrophages, we demonstrated that Tnfaip3 is regulated by both NF-κB and p38-dependent C/EBPβ. These results identify a novel regulatory mechanism in TLR4-mediated innate immunity.