Cell Reports
Volume 2, Issue 5, 29 November 2012, Pages 1187-1196
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MDA5 Detects the Double-Stranded RNA Replicative Form in Picornavirus-Infected Cells

https://doi.org/10.1016/j.celrep.2012.10.005Get rights and content
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Summary

RIG-I and MDA5 are cytosolic RNA sensors that play a critical role in innate antiviral responses. Major advances have been made in identifying RIG-I ligands, but our knowledge of the ligands for MDA5 remains restricted to data from transfection experiments mostly using poly(I:C), a synthetic dsRNA mimic. Here, we dissected the IFN-α/β-stimulatory activity of different viral RNA species produced during picornavirus infection, both by RNA transfection and in infected cells in which specific steps of viral RNA replication were inhibited. Our results show that the incoming genomic plus-strand RNA does not activate MDA5, but minus-strand RNA synthesis and production of the 7.5 kbp replicative form trigger a strong IFN-α/β response. IFN-α/β production does not rely on plus-strand RNA synthesis and thus generation of the partially double-stranded replicative intermediate. This study reports MDA5 activation by a natural RNA ligand under physiological conditions.

Highlights

► Viral ssRNA, with or without the 5′ VPg peptide, does not induce IFN-α/β ► Synthesis of minus-strand—but not plus-strand—RNA is crucial for MDA5 activation ► The picornavirus RF activates MDA5 both in vitro and in vivo ► MDA5 activation by viral replicative form is independent of the terminal groups of this RNA

Cited by (0)

4

These authors contributed equally to this work

5

Present address: Virology Division, Department of Infectious Diseases and Immunology, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 1, 3584 CL Utrecht, The Netherlands

6

Present address: Department of Tumor Immunology, Radboud University Nijmegen Medical Centre, Nijmegen, PO Box 9101, 6500 HB, The Netherlands