The lock-washer: a reconciliation of the RIG-I activation models

RIG-I belongs to a type of intracellular pattern recognition receptors involved in the recognition of viral RNA by the innate immune system. A report by Peisley et al. published in Nature provides the crystal structure of human RIG-I revealing a tetrameric architecture of the RIG-I 2-CARD domain bound by three K63-linked ubiquitin chains, uncovering its activation mechanism for downstream signaling.