title: Evolution of the DEAD box helicase family in chicken: chickens have no DHX9 ortholog.
abstract: Viral RNA represents a pattern molecule that can be recognized by RNA sensors in innate immunity. Humans and mice possess cytoplasmic DNA/RNA sensors for detecting viral replication. There are a number of DEAD (Asp-Glu-Ala-Asp; DExD/H) box-type helicases in mammals, among which retinoic acid-inducible gene 1 (RIG-I) and melanoma differentiation-associated protein 5 (MDA50) are indispensable for RNA sensing; however, they are functionally supported by a number of sensors that directly bind viral RNA or replicative RNA intermediates to convey signals to RIG-I and MDA5. Some DEAD box helicase members recognize DNA irrespective of the origin. These sensors transmit IFN-inducing signals through adaptors, including mitochondrial antiviral signaling. Viral double-stranded RNAs are reportedly sensed by the helicases DDX1, DDX21, DHX36, DHX9, DDX3, DDX41, LGP2 and DDX60, in addition to RIG-I and MDA5, and induce type I IFNs, thereby blocking viral replication. Humans and mice have all nucleic acid sensors listed here. In the RNA sensing system in chicken, it was found in the present study that most DEAD box helicases are conserved; however, DHX9 is genetically deficient in addition to reported RIG-I. Based on the current genome databases, similar DHX9 deficiency was observed in ducks and several other bird species. Because chicken, but not duck, was found to be deficient in RIG-I, the RNA-sensing system of chicken lacks RIG-I and DHX9 and is thus more fragile than that of duck or mammal. DHX9 may generally compensate for the function of RIG-I and deficiency of DHX9 possibly participates in exacerbations of viral infection such as influenza in chickens.
authors.affiliation: Department of Microbiology and Immunology, Hokkaido University Graduate School of Medicine, Kita-ku, Sapporo 060-8638.
authors.forename: Haruko
authors.initials: H
authors.lastname: Sato
authors.affiliation: Department of Microbiology and Immunology, Hokkaido University Graduate School of Medicine, Kita-ku, Sapporo 060-8638.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Oshiumi
authors.affiliation: Department of Microbiology and Immunology, Hokkaido University Graduate School of Medicine, Kita-ku, Sapporo 060-8638.
authors.forename: Hiromi
authors.initials: H
authors.lastname: Takaki
authors.affiliation: National Institute of Animal Health, National Agriculture and Food Research Organization (NARO), Tsukuba 305-8642, Japan.
authors.forename: Hirokazu
authors.initials: H
authors.lastname: Hikono
authors.affiliation: Department of Microbiology and Immunology, Hokkaido University Graduate School of Medicine, Kita-ku, Sapporo 060-8638.
authors.forename: Tsukasa
authors.initials: T
authors.lastname: Seya
mesh_terms: D000818:Animals; D002645:Chickens / Q000276:immunology*; D053487:DEAD-box RNA Helicases / Q000235:genetics*; D004372:Ducks / Q000276:immunology; D006801:Humans; D007113:Immunity, Innate / Q000276:immunology; D000072640:Interferon-Induced Helicase, IFIH1; D051379:Mice; D009363:Neoplasm Proteins / Q000235:genetics*; D012367:RNA, Viral / Q000235:genetics; D051192:Receptors, Pattern Recognition / Q000235:genetics / Q000276:immunology; D044767:Ubiquitin-Protein Ligases / Q000235:genetics*; D014777:Virus Diseases / Q000276:immunology*; D014779:Virus Replication / Q000235:genetics
chemical_list: D009363:Neoplasm Proteins; D012367:RNA, Viral; D051192:Receptors, Pattern Recognition; D044767:Ubiquitin-Protein Ligases; C098487:DHX9 protein, human; C452815:IFIH1 protein, human; D053487:DEAD-box RNA Helicases; D000072640:Interferon-Induced Helicase, IFIH1
keywords: DEAD box helicase; chicken innate immunity; phylogeny; type I interferon