title: A prominent role for Sp1 during lipopolysaccharide-mediated induction of the IL-10 promoter in macrophages.
abstract: IL-10 is an antiinflammatory cytokine secreted by activated macrophages and Th2 cells. IL-10 secretion promotes the down-regulation of proinflammatory cytokine synthesis and the development of Th2 responses. In macrophages, proinflammatory cytokines appear to be induced by similar mechanisms, but the IL-10 induction mechanisms have not been examined. We have analyzed the murine IL-10 promoter in the RAW264.7 macrophage line activated with LPS. A comprehensive mutant analysis revealed only one element upstream of the core promoter that was essential for promoter induction. A refined mutant analysis localized this element to nucleotides -89 to -78, and gel shift experiments revealed that it represents a nonconsensus binding site for Sp1. The functional relevance of Sp1 was supported by the high affinity of the interaction, the close correlation between the nucleotides required for Sp1 binding and promoter function, and the ability of an Sp1 consensus sequence to substitute for the -89/-78 promoter sequence. Evidence that Sp1 may be a target of signaling pathways involved in IL-10 induction was provided by the exclusive requirement for the Sp1 binding site, by the ability of the Sp1 site to confer induction to a heterologous promoter, and by the delineation of an Sp1 domain that can mediate induction. No relevant contribution from Rel, C/EBP (CCAAT/enhancer-binding protein), or AP-1 binding sites, which regulate most proinflammatory cytokine promoters, was observed. Together, these results demonstrate that IL-10 gene regulation is distinct from the regulation of proinflammatory cytokine genes, and suggest that Sp1 may be a central mediator of IL-10 induction.
authors.affiliation: Department of Microbiology, Division of Dermatology, University of California, Los Angeles, School of Medicine, Los Angeles, CA 90095, USA.
authors.forename: H D
authors.initials: HD
authors.lastname: Brightbill
authors.forename: S E
authors.initials: SE
authors.lastname: Plevy
authors.forename: R L
authors.initials: RL
authors.lastname: Modlin
authors.forename: S T
authors.initials: ST
authors.lastname: Smale
mesh_terms: D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D016384:Consensus Sequence; D004252:DNA Mutational Analysis / Q000379:methods; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D005786:Gene Expression Regulation / Q000276:immunology*; D016753:Interleukin-10 / Q000096:biosynthesis / Q000235:genetics*; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008264:Macrophages / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000502:physiology; D011401:Promoter Regions, Genetic / Q000276:immunology*; D012333:RNA, Messenger / Q000096:biosynthesis; D017422:Sequence Analysis, DNA; D016329:Sp1 Transcription Factor / Q000235:genetics / Q000502:physiology*; D014158:Transcription, Genetic / Q000276:immunology
chemical_list: D004268:DNA-Binding Proteins; D008070:Lipopolysaccharides; D010446:Peptide Fragments; D012333:RNA, Messenger; D016329:Sp1 Transcription Factor; D016753:Interleukin-10