title: Molecular mechanism of signal perception and integration by the innate immune sensor retinoic acid-inducible gene-I (RIG-I).
abstract: RIG-I is a major innate immune sensor for viral infection, triggering an interferon (IFN)-mediated antiviral response upon cytosolic detection of viral RNA. Double-strandedness and 5'-terminal triphosphates were identified as motifs required to elicit optimal immunological signaling. However, very little is known about the response dynamics of the RIG-I pathway, which is crucial for the ability of the cell to react to diverse classes of viral RNA while maintaining self-tolerance. In the present study, we addressed the molecular mechanism of RIG-I signal detection and its translation into pathway activation. By employing highly quantitative methods, we could establish the length of the double-stranded RNA (dsRNA) to be the most critical determinant of response strength. Size exclusion chromatography and direct visualization in scanning force microscopy suggested that this was due to cooperative oligomerization of RIG-I along dsRNA. The initiation efficiency of this oligomerization process critically depended on the presence of high affinity motifs, like a 5'-triphosphate. It is noteworthy that for dsRNA longer than 200 bp, internal initiation could effectively compensate for a lack of terminal triphosphates. In summary, our data demonstrate a very flexible response behavior of the RIG-I pathway, in which sensing and integration of at least two distinct signals, initiation efficiency and double strand length, allow the host cell to mount an antiviral response that is tightly adjusted to the type of the detected signal, such as viral genomes, replication intermediates, or small by-products.
authors.affiliation: Department of Infectious Diseases, Molecular Virology, Heidelberg University, Im Neuenheimer Feld 345, 69120 Heidelberg, Germany. marco_binder@med.uni-heidelberg.de
authors.forename: Marco
authors.initials: M
authors.lastname: Binder
authors.forename: Florian
authors.initials: F
authors.lastname: Eberle
authors.forename: Stefan
authors.initials: S
authors.lastname: Seitz
authors.forename: Norbert
authors.initials: N
authors.lastname: Mücke
authors.forename: Christian M
authors.initials: CM
authors.lastname: Hüber
authors.forename: Narsis
authors.initials: N
authors.lastname: Kiani
authors.forename: Lars
authors.initials: L
authors.lastname: Kaderali
authors.forename: Volker
authors.initials: V
authors.lastname: Lohmann
authors.forename: Alexander
authors.initials: A
authors.lastname: Dalpke
authors.forename: Ralf
authors.initials: R
authors.lastname: Bartenschlager
mesh_terms: D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D000071457:DEAD Box Protein 58; D053487:DEAD-box RNA Helicases / Q000502:physiology*; D017931:DNA Primers; D006801:Humans; D007113:Immunity, Innate; D051379:Mice; D018625:Microscopy, Atomic Force; D010766:Phosphorylation; D012330:RNA, Double-Stranded / Q000502:physiology; D011971:Receptors, Immunologic; D015398:Signal Transduction
chemical_list: D017931:DNA Primers; D012330:RNA, Double-Stranded; D011971:Receptors, Immunologic; C452820:RIGI protein, human; D000071457:DEAD Box Protein 58; D053487:DEAD-box RNA Helicases