title: XBP-1 couples endoplasmic reticulum stress to augmented IFN-beta induction via a cis-acting enhancer in macrophages.
abstract: Perturbation of the endoplasmic reticulum (ER) results in a conserved stress response called the unfolded protein response (UPR). Macrophages undergoing a UPR respond to LPS with log-fold increased production of IFN-beta, a cytokine with diverse roles in innate and adaptive immunity. In this study, we found that thapsigargin-induced ER stress augmented recruitment of IFN regulatory factor-3, CREB binding protein/p300, and transcriptional machinery to the murine ifnb1 promoter during LPS stimulation. Although full synergistic IFN-beta production requires X-box binding protein 1 (XBP-1), this UPR-regulated transcription factor did not appreciably bind the ifnb1 promoter. However, XBP-1 bound a conserved site 6.1 kb downstream of ifnb1, along with IFN regulatory factor-3 and CREB binding protein only during concomitant UPR and LPS stimulation. XBP-1 physically associates with p300, suggesting a mechanism of multimolecular assembly at the +6.1 kb site. Luciferase reporter assays provide evidence this +6 kb region functions as an XBP-1-dependent enhancer of ifnb1 promoter activity. Thus, this study identifies a novel role for a UPR-dependent transcription factor in the regulation of an inflammatory cytokine. Our findings have broader mechanistic implications for the pathogenesis of diseases involving ER stress and type I IFN, including viral infection, ischemia-reperfusion injury, protein misfolding, and inflammatory diseases.
authors.affiliation: Department of Pediatrics, University of Wisconsin School of Medicine and Public Health, Madison, WI 53792, USA.
authors.forename: Ling
authors.initials: L
authors.lastname: Zeng
authors.forename: Yi-Ping
authors.initials: YP
authors.lastname: Liu
authors.forename: Haibo
authors.initials: H
authors.lastname: Sha
authors.forename: Hui
authors.initials: H
authors.lastname: Chen
authors.forename: Ling
authors.initials: L
authors.lastname: Qi
authors.forename: Judith A
authors.initials: JA
authors.lastname: Smith
mesh_terms: D000818:Animals; D002460:Cell Line; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D004742:Enhancer Elements, Genetic / Q000235:genetics*; D055786:Gene Knockout Techniques; D006801:Humans; D015151:Immunoblotting; D050838:Interferon Regulatory Factor-3 / Q000378:metabolism; D016899:Interferon-beta / Q000235:genetics* / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology; D008156:Luciferases / Q000235:genetics / Q000378:metabolism; D008264:Macrophages / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D008954:Models, Biological; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding / Q000187:drug effects; D000071701:Regulatory Factor X Transcription Factors; D020133:Reverse Transcriptase Polymerase Chain Reaction; D019284:Thapsigargin / Q000494:pharmacology; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation / Q000187:drug effects; D056811:Unfolded Protein Response / Q000187:drug effects; D000071717:X-Box Binding Protein 1; D050880:p300-CBP Transcription Factors / Q000378:metabolism
chemical_list: D004268:DNA-Binding Proteins; D050838:Interferon Regulatory Factor-3; D008070:Lipopolysaccharides; D000071701:Regulatory Factor X Transcription Factors; D014157:Transcription Factors; D000071717:X-Box Binding Protein 1; C000605543:XBP1 protein, human; C000605544:Xbp1 protein, mouse; D019284:Thapsigargin; D016899:Interferon-beta; D008156:Luciferases; D050880:p300-CBP Transcription Factors