RNA with an exposed 5’-triphosphate (5’-ppp) and terminal double-stranded structures as found in cells during infection with many viruses, constitutes a strong activating ligand for the cytosolic pathogen sensor RIG-I. RNA binding and subsequent ATP hydrolysis by RIG-I are believed to be critical for downstream signaling. During its ligand-mediated activation, RIG-I has been suggested to form multimers but there is insufficient evidence on whether RIG-I is able to form higher-order oligomers on RNA and how multimerization affects signaling. In addition, RIG-I has been shown to translocate on 5’-ppp-dsRNA in an ATP-dependent manner and a precise role for the ATPase and associated RNA translocase activities in RIG-I activation has not been established. Using biochemical analyses of native RIG-I-RNA complexes, we show that RIG-I oligomerizes on this 5’-ppp dsRNA in an ATP hydrolysis-dependent manner. Importantly, there is a drastic reduction in ATP-dependent oligomerization of RIG-I on DI RNA with shorter dsRNA stems, correlating with the level of IFN-I activation by these RNAs. These results demonstrate a clear role for RIG-I ATPase in dsRNA length-dependent oligomer formation and provide a rationale for the ATP-driven translocase activity of RIG-I in stimulation of the IFN response.
- Copyright © 2013 by The American Association of Immunologists, Inc.