title: Human genome-wide RNAi screen identifies an essential role for inositol pyrophosphates in Type-I interferon response.
abstract: The pattern recognition receptor RIG-I is critical for Type-I interferon production. However, the global regulation of RIG-I signaling is only partially understood. Using a human genome-wide RNAi-screen, we identified 226 novel regulatory proteins of RIG-I mediated interferon-β production. Furthermore, the screen identified a metabolic pathway that synthesizes the inositol pyrophosphate 1-IP7 as a previously unrecognized positive regulator of interferon production. Detailed genetic and biochemical experiments demonstrated that the kinase activities of IPPK, PPIP5K1 and PPIP5K2 (which convert IP5 to1-IP7) were critical for both interferon induction, and the control of cellular infection by Sendai and influenza A viruses. Conversely, ectopically expressed inositol pyrophosphate-hydrolases DIPPs attenuated interferon transcription. Mechanistic experiments in intact cells revealed that the expression of IPPK, PPIP5K1 and PPIP5K2 was needed for the phosphorylation and activation of IRF3, a transcription factor for interferon. The addition of purified individual inositol pyrophosphates to a cell free reconstituted RIG-I signaling assay further identified 1-IP7 as an essential component required for IRF3 activation. The inositol pyrophosphate may act by β-phosphoryl transfer, since its action was not recapitulated by a synthetic phosphonoacetate analogue of 1-IP7. This study thus identified several novel regulators of RIG-I, and a new role for inositol pyrophosphates in augmenting innate immune responses to viral infection that may have therapeutic applications.
authors.affiliation: Program on Emerging Infectious Diseases, DUKE-NUS Graduate Medical School, Singapore.
authors.forename: Niyas Kudukkil
authors.initials: NK
authors.lastname: Pulloor
authors.affiliation: Program on Emerging Infectious Diseases, DUKE-NUS Graduate Medical School, Singapore.
authors.forename: Sajith
authors.initials: S
authors.lastname: Nair
authors.forename: Kathleen
authors.initials: K
authors.lastname: McCaffrey
authors.affiliation: Center for Computational and Integrative Biology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, United States of America.
authors.forename: Aleksandar D
authors.initials: AD
authors.lastname: Kostic
authors.affiliation: Program on Emerging Infectious Diseases, DUKE-NUS Graduate Medical School, Singapore.
authors.forename: Pradeep
authors.initials: P
authors.lastname: Bist
authors.affiliation: Inositol Signaling Group, Laboratory of Signal Transduction, National Institute of Environmental Health Sciences, NIH, DHHS, Research Triangle Park, North Carolina, United States of America.
authors.forename: Jeremy D
authors.initials: JD
authors.lastname: Weaver
authors.affiliation: Department of Pharmacy and Pharmacology, University of Bath, Claverton Down, Bath, United Kingdom.
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Riley
authors.affiliation: Solomon H. Snyder Department of Neuroscience and Departments of Psychiatry and Behavioral Sciences, The Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America.
authors.forename: Richa
authors.initials: R
authors.lastname: Tyagi
authors.affiliation: Section of Microbial Pathogenesis, Yale University School of Medicine, New Haven, Connecticut, United States of America.
authors.forename: Pradeep D
authors.initials: PD
authors.lastname: Uchil
authors.affiliation: Department of Biochemistry, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America.
authors.forename: John D
authors.initials: JD
authors.lastname: York
authors.affiliation: Solomon H. Snyder Department of Neuroscience and Departments of Psychiatry and Behavioral Sciences, The Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America.
authors.forename: Solomon H
authors.initials: SH
authors.lastname: Snyder
authors.affiliation: Department of Microbiology, Global Health and Emerging Pathogens Institute, Department of Medicine, Division of Infectious Diseases, Icahn School of Medicine at Mount Sinai, New York, New York, United States of America.
authors.forename: Adolfo
authors.initials: A
authors.lastname: García-Sastre
authors.affiliation: Department of Pharmacy and Pharmacology, University of Bath, Claverton Down, Bath, United Kingdom.
authors.forename: Barry V L
authors.initials: BV
authors.lastname: Potter
authors.affiliation: Lady Davis Institute for Medical Research, Jewish General Hospital, Montreal, Canada.
authors.forename: Rongtuan
authors.initials: R
authors.lastname: Lin
authors.affiliation: Inositol Signaling Group, Laboratory of Signal Transduction, National Institute of Environmental Health Sciences, NIH, DHHS, Research Triangle Park, North Carolina, United States of America.
authors.forename: Stephen B
authors.initials: SB
authors.lastname: Shears
authors.affiliation: Center for Computational and Integrative Biology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, United States of America.
authors.forename: Ramnik J
authors.initials: RJ
authors.lastname: Xavier
authors.affiliation: Program on Emerging Infectious Diseases, DUKE-NUS Graduate Medical School, Singapore.
authors.forename: Manoj N
authors.initials: MN
authors.lastname: Krishnan
mesh_terms: D005786:Gene Expression Regulation / Q000276:immunology*; D006801:Humans; D007113:Immunity, Innate / Q000276:immunology; D050838:Interferon Regulatory Factor-3 / Q000276:immunology; D007370:Interferon Type I / Q000276:immunology*; D010744:Phosphoric Monoester Hydrolases / Q000276:immunology*; D034741:RNA, Small Interfering; D018168:Receptors, Retinoic Acid / Q000276:immunology*; D015398:Signal Transduction / Q000276:immunology*
chemical_list: C494232:IRF3 protein, human; D050838:Interferon Regulatory Factor-3; D007370:Interferon Type I; C437968:PLAAT4 protein, human; D034741:RNA, Small Interfering; D018168:Receptors, Retinoic Acid; D010744:Phosphoric Monoester Hydrolases; C021822:myo-inositol-1 (or 4)-monophosphatase