Structural and functional insights into 5'-ppp RNA pattern recognition by the innate immune receptor RIG-I.
RIG-I is a cytosolic helicase that senses 5'-ppp RNA contained in negative-strand RNA viruses and triggers innate antiviral immune responses. Calorimetric binding studies established that the RIG-I C-terminal regulatory domain (CTD) binds to blunt-end double-stranded 5'-ppp RNA a factor of 17 more tightly than to its single-stranded counterpart. Here we report on the crystal structure of RIG-I CTD bound to both blunt ends of a self-complementary 5'-ppp dsRNA 12-mer, with interactions involving 5'-pp clearly visible in the complex. The structure, supported by mutation studies, defines how a lysine-rich basic cleft within the RIG-I CTD sequesters the observable 5'-pp of the bound RNA, with a stacked phenylalanine capping the terminal base pair. Key intermolecular interactions observed in the crystalline state are retained in the complex of 5'-ppp dsRNA 24-mer and full-length RIG-I under in vivo conditions, as evaluated from the impact of binding pocket RIG-I mutations and 2'-OCH(3) RNA modifications on the interferon response.
Wang
Yanli
Y
Structural Biology Program, Memorial Sloan-Kettering Cancer Center, New York, New York, USA.
Ludwig
Janos
J
Schuberth
Christine
C
Goldeck
Marion
M
Schlee
Martin
M
Li
Haitao
H
Juranek
Stefan
S
Sheng
Gang
G
Micura
Ronald
R
Tuschl
Thomas
T
Hartmann
Gunther
G
Patel
Dinshaw J
DJ
D000595:Amino Acid Sequence; D001665:Binding Sites; D018360:Crystallography, X-Ray; D000071457:DEAD Box Protein 58; D053487:DEAD-box RNA Helicases / Q000737:chemistry* / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D006801:Humans; D007113:Immunity, Innate; D000072640:Interferon-Induced Helicase, IFIH1; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D017354:Point Mutation; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D020365:RNA Helicases / Q000737:chemistry / Q000378:metabolism; D012330:RNA, Double-Stranded / Q000737:chemistry / Q000378:metabolism*; D011971:Receptors, Immunologic; D016415:Sequence Alignment
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