Double-stranded RNA (dsRNA) is a potent proinflammatory signature of viral infection. Long cytosolic dsRNA is recognized by MDA5. The cooperative assembly of MDA5 into helical filaments on dsRNA nucleates the assembly of a multiprotein type I interferon signaling platform. Here, we determined cryoelectron microscopy (cryo-EM) structures of MDA5-dsRNA filaments with different helical twists and bound nucleotide analogs at resolutions sufficient to build and refine atomic models. The structures identify the filament-forming interfaces, which encode the dsRNA binding cooperativity and length specificity of MDA5. The predominantly hydrophobic interface contacts confer flexibility, reflected in the variable helical twist within filaments. Mutation of filament-forming residues can result in loss or gain of signaling activity. Each MDA5 molecule spans 14 or 15 RNA base pairs, depending on the twist. Variations in twist also correlate with variations in the occupancy and type of nucleotide in the active site, providing insights on how ATP hydrolysis contributes to MDA5-dsRNA recognition.
Pubmed ID: 30449722 RIS Download
Mesh terms: Adenosine Triphosphate | Cryoelectron Microscopy | HEK293 Cells | Humans | Hydrolysis | Hydrophobic and Hydrophilic Interactions | Interferon-Induced Helicase, IFIH1 | Interferon-beta | Molecular Docking Simulation | Mutation | Nucleic Acid Conformation | Protein Conformation | RNA, Double-Stranded | Signal Transduction | Structure-Activity Relationship
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The MRC Laboratory of Molecular Biology (LMB) has long been, and remains, a world-class research laboratory. Our primary goal is to understand biological processes at the molecular level, through the application of methods drawn from physics, chemistry and genetics. This quest extends from structural studies of individual macromolecules, through their interactions and beyond to the functioning of subcellular systems, cells and multicellular systems in whole organisms, with the ultimate aim of using this knowledge to tackle specific problems in human health and disease. The LMB is one of the birthplaces of modern molecular biology. Many techniques were pioneered at the laboratory, most notably methods for determining the three-dimensional structure of proteins and DNA sequencing. Whole genome sequencing was initiated at the LMB. Another landmark discovery was the invention of monoclonal antibodies. Over the years, the work of LMB scientists has attracted 9 Nobel Prizes, shared between 13 LMB scientists, as well as numerous other prizes and scientific awards.View all literature mentions
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