The C-terminal regulatory domain is the RNA 5'-triphosphate sensor of RIG-I.
The ATPase RIG-I senses viral RNAs that contain 5'-triphosphates in the cytoplasm. It initiates a signaling cascade that activates innate immune response by interferon and cytokine production, providing essential antiviral protection for the host. The mode of RNA 5'-triphosphate sensing by RIG-I remains elusive. We show that the C-terminal regulatory domain RD of RIG-I binds viral RNA in a 5'-triphosphate-dependent manner and activates the RIG-I ATPase by RNA-dependent dimerization. The crystal structure of RD reveals a zinc-binding domain that is structurally related to GDP/GTP exchange factors of Rab-like GTPases. The zinc coordination site is essential for RIG-I signaling and is also conserved in MDA5 and LGP2, suggesting related RD domains in all three enzymes. Structure-guided mutagenesis identifies a positively charged groove as likely 5'-triphosphate-binding site of RIG-I. This groove is distinct in MDA5 and LGP2, raising the possibility that RD confers ligand specificity.
Cui
Sheng
S
Gene Center, Department of Chemistry and Biochemistry, Ludwig-Maximilians-University of Munich, Feodor-Lynen-Strasse 25, 81377 Munich, Germany.
Eisenächer
Katharina
K
Kirchhofer
Axel
A
Brzózka
Krzysztof
K
Lammens
Alfred
A
Lammens
Katja
K
Fujita
Takashi
T
Conzelmann
Karl-Klaus
KK
Krug
Anne
A
Hopfner
Karl-Peter
KP
D000251:Adenosine Triphosphatases / Q000737:chemistry / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D000818:Animals; D001665:Binding Sites / Q000235:genetics; D002460:Cell Line; D000071457:DEAD Box Protein 58; D053487:DEAD-box RNA Helicases / Q000737:chemistry / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D019281:Dimerization; D006801:Humans; D007113:Immunity, Innate / Q000502:physiology; D000072640:Interferon-Induced Helicase, IFIH1; D007372:Interferons / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D011122:Polyphosphates / Q000737:chemistry / Q000276:immunology / Q000378:metabolism*; D017434:Protein Structure, Tertiary / Q000235:genetics; D012315:RNA Caps / Q000737:chemistry / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D020365:RNA Helicases / Q000737:chemistry / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D012367:RNA, Viral / Q000737:chemistry / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D011971:Receptors, Immunologic; D040681:Structural Homology, Protein; D013329:Structure-Activity Relationship; D013379:Substrate Specificity / Q000235:genetics; D015032:Zinc / Q000737:chemistry / Q000276:immunology / Q000378:metabolism; D020691:rab GTP-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology / Q000378:metabolism
D011122:Polyphosphates; D012315:RNA Caps; D012367:RNA, Viral; D011971:Receptors, Immunologic; D007372:Interferons; C520569:DHX58 protein, human; D000251:Adenosine Triphosphatases; 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; D020691:rab GTP-Binding Proteins; D015032:Zinc; C005692:triphosphoric acid