Structure and dynamics of the second CARD of human RIG-I provide mechanistic insights into regulation of RIG-I activation

Structure. 2012 Dec 5;20(12):2048-61. doi: 10.1016/j.str.2012.09.003. Epub 2012 Oct 11.


RIG-I is a cytosolic sensor of viral RNA, comprised of two N-terminal CARDs followed by helicase and C-terminal regulatory domains (helicase-CTD). Viral RNA binds to the helicase-CTD and "exposes" the CARDs for downstream signaling. The role of the second CARD (CARD2) is essential as RIG-I activation requires dephosphorylation of Thr170 followed by ubiquitination at Lys172. Here, we present the solution structure and dynamics of human RIG-I CARD2. Surprisingly, we find that Thr170 is mostly buried. Parallel studies on the phosphomimetic T170E mutant suggest that the loss of function upon Thr170 phosphorylation is likely associated with changes in the CARD1-CARD2 interface that may prevent Lys172 ubiquitination and/or binding to free K63-linked polyubiquitin. We also demonstrate a strong interaction between CARD2 and the helicase-CTD, and show that mutations at the interface result in constitutive activation of RIG-I. Collectively, our data suggests a close interplay between phosphorylation, ubiquitination, and activation of human RIG-I, all mediated by CARD2.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Substitution
  • Catalytic Domain
  • DEAD Box Protein 58
  • DEAD-box RNA Helicases / chemistry*
  • DEAD-box RNA Helicases / genetics
  • DEAD-box RNA Helicases / metabolism
  • HEK293 Cells
  • Humans
  • Interferon-beta / genetics
  • Models, Molecular*
  • Mutagenesis, Site-Directed
  • Nuclear Magnetic Resonance, Biomolecular
  • Phosphoproteins / chemistry
  • Phosphorylation
  • Promoter Regions, Genetic
  • Protein Interaction Domains and Motifs
  • Protein Structure, Secondary
  • Receptors, Immunologic
  • Surface Properties
  • Transcriptional Activation
  • Ubiquitination


  • Phosphoproteins
  • Receptors, Immunologic
  • Interferon-beta
  • RIGI protein, human
  • DEAD Box Protein 58
  • DEAD-box RNA Helicases

Associated data

  • PDB/2LWD
  • PDB/2LWE