Abstract
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.
Copyright © 2016 The Author(s). Published by Elsevier Inc. All rights reserved.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Adenosine Diphosphate / metabolism
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Adenosine Triphosphatases / chemistry
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Adenosine Triphosphatases / genetics
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Adenosine Triphosphatases / metabolism*
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Adenosine Triphosphate / metabolism
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Animals
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Avian Proteins / chemistry
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Avian Proteins / genetics
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Avian Proteins / metabolism*
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Binding Sites
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Cell Line
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Chickens
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DEAD Box Protein 58 / chemistry
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DEAD Box Protein 58 / genetics
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DEAD Box Protein 58 / metabolism*
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Humans
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Hydrolysis
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Interferon-Induced Helicase, IFIH1 / chemistry
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Interferon-Induced Helicase, IFIH1 / genetics
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Interferon-Induced Helicase, IFIH1 / metabolism*
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Models, Molecular
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Nucleic Acid Conformation
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Protein Binding
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Protein Interaction Domains and Motifs
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RNA, Double-Stranded / chemistry
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RNA, Double-Stranded / genetics
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RNA, Double-Stranded / metabolism*
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RNA-Binding Proteins / chemistry
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RNA-Binding Proteins / genetics
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RNA-Binding Proteins / metabolism*
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Receptors, Pattern Recognition / chemistry
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Receptors, Pattern Recognition / genetics
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Receptors, Pattern Recognition / metabolism*
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Structure-Activity Relationship
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Transfection
Substances
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Avian Proteins
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RNA, Double-Stranded
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RNA-Binding Proteins
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Receptors, Pattern Recognition
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Adenosine Diphosphate
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Adenosine Triphosphate
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Adenosine Triphosphatases
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DEAD Box Protein 58
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Interferon-Induced Helicase, IFIH1