title: IRF8 and IRF3 cooperatively regulate rapid interferon-β induction in human blood monocytes.
abstract: Robust and rapid induction of interferon-β (IFN-β) in monocytes after pathogenic stimulation is a hallmark of innate immune responses. Here, we reveal the molecular mechanism underlying this key property that is exclusive to human blood monocytes. We found that IFN-β was produced rapidly in primary human monocytes as a result of cooperation between the myeloid-specific transcription factor IRF8 and the ubiquitous transcription factor IRF3. Knockdown of IRF8 in monocytes abrogated IFN-β transcription, whereas reintroduction of IRF8 into the IRF8(-/-) 32Dcl3 murine myeloid cell line reinstated IFN-β transcription. Moreover, we provide evidence that IRF8 constitutively binds to the ETS/IRF composite element of the IFN-β promoter region together with PU.1 in vivo. Furthermore we uncovered a requirement for IRF3, a master regulator of IFN-β production, as a previously un-indentified interaction partner of IRF8. We mapped the protein-protein interacting regions of IRF3 and IRF8, and found that their interaction was independent of the DNA-binding domain and the IRF association domain of IRF8 and IRF3, respectively. Therefore, we propose a model for the rapid induction of IFN-β in monocytes, whereby IRF8 and PU.1 form a scaffold complex on the IFN-β promoter to facilitate the recruitment of IRF3, thus enabling rapid IFN-β transcription.
authors.affiliation: Laboratory of Gene Regulation and Inflammation, Singapore Immunology Network, Agency for Science, Technology and Research (A*STAR), Biopolis, Immunos #04-00, Singapore.
authors.forename: Peng
authors.initials: P
authors.lastname: Li
authors.forename: Joyce Jing-Yi
authors.initials: JJ
authors.lastname: Wong
authors.forename: Calvin
authors.initials: C
authors.lastname: Sum
authors.forename: Wei-Xiang
authors.initials: WX
authors.lastname: Sin
authors.forename: Kok-Quan
authors.initials: KQ
authors.lastname: Ng
authors.forename: Mickey B C
authors.initials: MB
authors.lastname: Koh
authors.forename: Keh-Chuang
authors.initials: KC
authors.lastname: Chin
mesh_terms: D000818:Animals; D001483:Base Sequence; D015153:Blotting, Western; D024202:Electrophoretic Mobility Shift Assay; D005434:Flow Cytometry; D015870:Gene Expression; D005786:Gene Expression Regulation / Q000235:genetics* / Q000276:immunology; D006801:Humans; D047468:Immunoprecipitation; D050838:Interferon Regulatory Factor-3 / Q000235:genetics* / Q000276:immunology / Q000378:metabolism; D050835:Interferon Regulatory Factors / Q000235:genetics* / Q000276:immunology / Q000378:metabolism; D016899:Interferon-beta / Q000096:biosynthesis* / Q000235:genetics / Q000276:immunology; D051379:Mice; D008969:Molecular Sequence Data; D009000:Monocytes / Q000276:immunology / Q000378:metabolism*; D020411:Oligonucleotide Array Sequence Analysis; D011401:Promoter Regions, Genetic / Q000235:genetics; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015534:Trans-Activators / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D014158:Transcription, Genetic; D000099185:Interferon Regulatory Factor-8; D000099232:Proto-Oncogene Protein Spi-1
chemical_list: D050838:Interferon Regulatory Factor-3; D050835:Interferon Regulatory Factors; D016899:Interferon-beta; D011518:Proto-Oncogene Proteins; D015534:Trans-Activators; D000099185:Interferon Regulatory Factor-8; D000099232:Proto-Oncogene Protein Spi-1; C494232:IRF3 protein, human