title: Structural basis of double-stranded RNA recognition by the RIG-I like receptor MDA5.
abstract: RIG-I, MDA5 and LGP2 are cytosolic pattern recognition receptors detecting single-stranded or double-stranded RNA in virally infected cells. The activation of RIG-I or MDA5 stimulates the secretion of type I interferons that play key roles in antiviral immune responses. The C-terminal domains (CTD) of RIG-I and LGP2 are responsible for RNA binding; however, it is not clear how MDA5 binds RNA. To understand the structural basis of dsRNA recognition by MDA5, we have determined the 1.45A resolution structure of the C-terminal domain of human MDA5. The structure revealed a highly conserved fold similar to the structures of RIG-I and LGP2 CTDs. NMR titration of MDA5 CTD with dsRNA demonstrated that a positively charged surface is involved in dsRNA binding. Mutagenesis and RNA binding studies showed that electrostatic interactions play primary roles in dsRNA recognition by MDA5. Like RIG-I and LGP2, MDA5 CTD preferentially binds dsRNA with blunt ends, but does not associate with dsRNA with either 5' or 3' overhangs. Molecular modeling of MDA5 CTD/dsRNA complex suggests that MDA5 CTD may recognize the first turn of blunt-ended dsRNA in a similar manner as LGP2.
authors.affiliation: Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX 77843-2128, USA.
authors.forename: Xiaojun
authors.initials: X
authors.lastname: Li
authors.forename: Cheng
authors.initials: C
authors.lastname: Lu
authors.forename: Mikaela
authors.initials: M
authors.lastname: Stewart
authors.forename: Hengyu
authors.initials: H
authors.lastname: Xu
authors.forename: Roland K
authors.initials: RK
authors.lastname: Strong
authors.forename: Tatyana
authors.initials: T
authors.lastname: Igumenova
authors.forename: Pingwei
authors.initials: P
authors.lastname: Li
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D018360:Crystallography, X-Ray; D000071457:DEAD Box Protein 58; D053487:DEAD-box RNA Helicases / Q000737:chemistry* / Q000378:metabolism*; D006801:Humans; D000072640:Interferon-Induced Helicase, IFIH1; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D020365:RNA Helicases / Q000737:chemistry / Q000378:metabolism; D012330:RNA, Double-Stranded / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D011971:Receptors, Immunologic; D017386:Sequence Homology, Amino Acid; D055672:Static Electricity; D013499:Surface Properties
chemical_list: D012330:RNA, Double-Stranded; D011971:Receptors, Immunologic; C520569:DHX58 protein, human; C452820:RIGI protein, human; C452815:IFIH1 protein, human; D000071457:DEAD Box Protein 58; D053487:DEAD-box RNA Helicases; D000072640:Interferon-Induced Helicase, IFIH1; D020365:RNA Helicases