regulatory domain of the RIG-I family ATPase LGP2 senses double-stranded RNA

• Published in: Nucleic acids research Vol. 37; no. 6; pp. 2014 - 2025
• Main Authors: Pippig, Diana A, Hellmuth, Johannes C, Cui, Sheng, Kirchhofer, Axel, Lammens, Katja, Lammens, Alfred, Schmidt, Andreas, Rothenfusser, Simon, Hopfner, Karl-Peter
• Format: Journal Article
• Language: English
• Published: England Oxford University Press 01.04.2009; Oxford Publishing Limited (England)
• Subjects: Amino Acid Sequence; Binding Sites; Cell Line; Crystallography, X-Ray; DEAD Box Protein 58; DEAD-box RNA Helicases - chemistry; DEAD-box RNA Helicases - metabolism; Humans; Interferon-Induced Helicase, IFIH1; Models, Molecular; Molecular Sequence Data; Mutagenesis, Site-Directed; Polyphosphates - chemistry; Protein Binding; Protein Structure, Tertiary; Receptors, Immunologic; RNA Helicases - chemistry; RNA Helicases - genetics; RNA Helicases - metabolism; RNA, Double-Stranded - chemistry; RNA, Double-Stranded - metabolism; RNA-Binding Proteins - chemistry; Scattering, Small Angle; Signal Transduction; Structural Biology; X-Ray Diffraction
• ISSN: 0305-1048; 1362-4962
• DOI: 10.1093/nar/gkp059

RIG-I and MDA5 sense cytoplasmic viral RNA and set-off a signal transduction cascade, leading to antiviral innate immune response. The third RIG-I-like receptor, LGP2, differentially regulates RIG-I- and MDA5-dependent RNA sensing in an unknown manner. All three receptors possess a C-terminal regulatory domain (RD), which in the case of RIG-I senses the viral pattern 5′-triphosphate RNA and activates ATP-dependent signaling by RIG-I. Here we report the 2.6 Å crystal structure of LGP2 RD along with in vitro and in vivo functional analyses and a homology model of MDA5 RD. Although LGP2 RD is structurally related to RIG-I RD, we find it rather binds double-stranded RNA (dsRNA) and this binding is independent of 5′-triphosphates. We identify conserved and receptor-specific parts of the RNA binding site. Latter are required for specific dsRNA binding by LGP2 RD and could confer pattern selectivity between RIG-I-like receptors. Our data furthermore suggest that LGP2 RD modulates RIG-I-dependent signaling via competition for dsRNA, another pattern sensed by RIG-I, while a fully functional LGP2 is required to augment MDA5-dependent signaling.