RNase L releases a small RNA from HCV RNA that refolds into a potent PAMP.
Triggering and propagating an intracellular innate immune response is essential for control of viral infections. RNase L is a host endoribonuclease and a pivotal component of innate immunity that cleaves viral and cellular RNA within single-stranded loops releasing small structured RNAs with 5'-hydroxyl (5'-OH) and 3'-monophosphoryl (3'-p) groups. In 2007, we reported that RNase L cleaves self RNA to produce small RNAs that function as pathogen-associated molecular patterns (PAMPs). However, the precise sequence and structure of PAMP RNAs produced by RNase L is unknown. Here we used hepatitis C virus RNA as substrate to characterize RNase L mediated cleavage products [named suppressor of virus RNA (svRNA)] for their ability to activate RIG-I like receptors (RLR). The NS5B region of HCV RNA was cleaved by RNase L to release an svRNA that bound to RIG-I, displacing its repressor domain and stimulating its ATPase activity while signaling to the IFN-β gene in intact cells. All three of these RIG-I functions were dependent on the presence in svRNA of the 3'-p. Furthermore, svRNA suppressed HCV replication in vitro through a mechanism involving IFN production and triggered a RIG-I-dependent hepatic innate immune response in mice. RNase L and OAS (required for its activation) were both expressed in hepatocytes from HCV-infected patients, raising the possibility that the OAS/RNase L pathway might suppress HCV replication in vivo. It is proposed that RNase L mediated cleavage of HCV RNA generates svRNA that activates RIG-I, thus propagating innate immune signaling to the IFN-β gene.
Malathi
Krishnamurthy
K
Department of Cancer Biology, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio 44195, USA.
Saito
Takeshi
T
Crochet
Nannette
N
Barton
David J
DJ
Gale
Michael
M
Silverman
Robert H
RH
D000818:Animals; D001483:Base Sequence; D045744:Cell Line, Tumor; D000071457:DEAD Box Protein 58; D053487:DEAD-box RNA Helicases / Q000378:metabolism; D004722:Endoribonucleases / Q000378:metabolism*; D016174:Hepacivirus / Q000737:chemistry* / Q000276:immunology / Q000378:metabolism*; D006801:Humans; D007113:Immunity, Innate; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism; D009690:Nucleic Acid Conformation; D011485:Protein Binding; D012367:RNA, Viral / Q000737:chemistry* / Q000276:immunology / Q000378:metabolism*; D011956:Receptors, Cell Surface; D011971:Receptors, Immunologic; D013379:Substrate Specificity; D014779:Virus Replication; D000097905:Roundabout Proteins
D000071457:DEAD Box Protein 58; D053487:DEAD-box RNA Helicases; D004722:Endoribonucleases; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D012367:RNA, Viral; D011956:Receptors, Cell Surface; D011971:Receptors, Immunologic; C118348:Robo3 protein, mouse; D000097905:Roundabout Proteins; C031956:2-5A-dependent ribonuclease; C452820:RIGI protein, human