title: Synergistic expression of the CXCL10 gene in response to IL-1β and IFN-γ involves NF-κB, phosphorylation of STAT1 at Tyr701, and acetylation of histones H3 and H4.
abstract: The CXCL10 gene encodes a peptide that chemoattracts a variety of leukocytes associated with type 1 and type 2 diabetes. The present study was undertaken to determine the molecular mechanisms required for expression of the CXCL10 gene in response to IL-1β and IFN-γ using rat islets and β cell lines. IL-1β induced the expression of the CXCL10 gene and promoter activity, whereas the combination of IL-1β plus IFN-γ was synergistic. Small interfering RNA-mediated suppression of NF-κB p65 markedly inhibited the ability of cytokines to induce the expression of the CXCL10 gene, whereas targeting STAT1 only diminished the synergy provided by IFN-γ. Furthermore, we found that a JAK1 inhibitor dose dependently reduced IFN-γ-controlled CXCL10 gene expression and promoter activity, concomitant with a decrease in STAT1 phosphorylation at Tyr(701). We further discovered that, although the Tyr(701) phosphorylation site is inducible (within 15 min of IFN-γ exposure), the Ser(727) site within STAT1 is constitutively phosphorylated. Thus, we generated single-mutant STAT1 Y701F and double-mutant STAT1 Y701F/S727A adenoviruses. Using these recombinant adenoviruses, we determined that overexpression of either the single- or double-mutant STAT1 decreased the IFN-γ-mediated potentiation of CXCL10 gene expression, promoter activity, and secretion of protein. Moreover, the Ser(727) phosphorylation was neither contingent on a functional Y701 site in β cells nor was it required for cytokine-mediated expression of the CXCL10 gene. We conclude that the synergism of IL-1β and IFN-γ to induce expression of the CXCL10 gene requires NF-κB, STAT1 phosphorylated at Tyr(701), recruitment of coactivators, and acetylation of histones H3 and H4.
authors.affiliation: Department of Nutrition, University of Tennessee, Knoxville, TN 37996-1920, USA.
authors.forename: Susan J
authors.initials: SJ
authors.lastname: Burke
authors.forename: Matthew R
authors.initials: MR
authors.lastname: Goff
authors.forename: Danhong
authors.initials: D
authors.lastname: Lu
authors.forename: David
authors.initials: D
authors.lastname: Proud
authors.forename: Michael D
authors.initials: MD
authors.lastname: Karlstad
authors.forename: J Jason
authors.initials: JJ
authors.lastname: Collier
mesh_terms: D000107:Acetylation; D000818:Animals; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D054357:Chemokine CXCL10 / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism; D005786:Gene Expression Regulation / Q000276:immunology*; D006657:Histones / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007371:Interferon-gamma / Q000037:antagonists & inhibitors / Q000502:physiology*; D053583:Interleukin-1beta / Q000502:physiology*; D016297:Mutagenesis, Site-Directed; D016328:NF-kappa B / Q000502:physiology*; D010766:Phosphorylation / Q000235:genetics / Q000276:immunology; D051381:Rats; D017208:Rats, Wistar; D050794:STAT1 Transcription Factor / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000235:genetics / Q000276:immunology; D014443:Tyrosine / Q000235:genetics / Q000378:metabolism
chemical_list: C114753:CXCL10 protein, human; D054357:Chemokine CXCL10; D006657:Histones; D053583:Interleukin-1beta; D016328:NF-kappa B; D050794:STAT1 Transcription Factor; C494079:STAT1 protein, human; D014443:Tyrosine; D007371:Interferon-gamma