Structural Analysis of dsRNA Binding to Anti-viral Pattern Recognition Receptors LGP2 and MDA5

• Published in: Molecular cell Vol. 62; no. 4; pp. 586 - 602
• Main Authors: Uchikawa, Emiko, Lethier, Mathilde, Malet, Hélène, Brunel, Joanna, Gerlier, Denis, Cusack, Stephen
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 19.05.2016; Cell Press
• Subjects: Adenosine Diphosphate - metabolism; Adenosine Triphosphatases - chemistry; Adenosine Triphosphatases - genetics; Adenosine Triphosphatases - metabolism; Adenosine Triphosphate - metabolism; Animals; Avian Proteins - chemistry; Avian Proteins - genetics; Avian Proteins - metabolism; Binding Sites; Cell Line; Chickens; DEAD Box Protein 58 - chemistry; DEAD Box Protein 58 - genetics; DEAD Box Protein 58 - metabolism; Humans; Hydrolysis; Immunology; Interferon-Induced Helicase, IFIH1 - chemistry; Interferon-Induced Helicase, IFIH1 - genetics; Interferon-Induced Helicase, IFIH1 - metabolism; Life Sciences; Models, Molecular; Nucleic Acid Conformation; Protein Binding; Protein Interaction Domains and Motifs; Receptors, Pattern Recognition - chemistry; Receptors, Pattern Recognition - genetics; Receptors, Pattern Recognition - metabolism; RNA, Double-Stranded - chemistry; RNA, Double-Stranded - genetics; RNA, Double-Stranded - metabolism; RNA-Binding Proteins - chemistry; RNA-Binding Proteins - genetics; RNA-Binding Proteins - metabolism; Structure-Activity Relationship; Transfection
• ISSN: 1097-2765; 1097-4164
• DOI: 10.1016/j.molcel.2016.04.021

RIG-I and MDA5 sense virus-derived short 5′ppp blunt-ended or long dsRNA, respectively, causing interferon production. Non-signaling LGP2 appears to positively and negatively regulate MDA5 and RIG-I signaling, respectively. Co-crystal structures of chicken (ch) LGP2 with dsRNA display a fully or semi-closed conformation depending on the presence or absence of nucleotide. LGP2 caps blunt, 3′ or 5′ overhang dsRNA ends with 1 bp longer overall footprint than RIG-I. Structures of 1:1 and 2:1 complexes of chMDA5 with short dsRNA reveal head-to-head packing rather than the polar head-to-tail orientation described for long filaments. chLGP2 and chMDA5 make filaments with a similar axial repeat, although less co-operatively for chLGP2. Overall, LGP2 resembles a chimera combining a MDA5-like helicase domain and RIG-I like CTD supporting both stem and end binding. Functionally, RNA binding is required for LGP2-mediated enhancement of MDA5 activation. We propose that LGP2 end-binding may promote nucleation of MDA5 oligomerization on dsRNA. [Display omitted] •chLPG2-dsRNA structures reveal RIG-I like end binding, but overhangs are possible•chMDA5-dsRNA complex structures show head-to-head packing on short dsRNAs•LGP2 also has MDA5-like behavior, coating dsRNA but with less cooperativity•Both human and chicken LGP2 enhance MDA5 signaling in an RNA-dependent manner Uchikawa et al. reveal structural details of dsRNA recognition by MDA5 and LGP2 that synergistically sense viral RNA and activate interferon expression. LGP2 is primarily a dsRNA end binder but can also coat dsRNA, but less co-operatively than MDA5. Functional studies show that LGP2 enhancement of MDA5 signaling is RNA dependent.