Characterization of RNA driven structural changes in full length RIG-I leading to its agonism or antagonism

Area of Science:

• Immunology
• Molecular Biology
• Structural Biology

Background:

• RIG-I is a key cytoplasmic sensor for viral RNA, initiating innate immune responses via type I interferon induction.
• Its mechanism involves RNA recognition by the C-terminal domain (CTD) and signaling via CARD domains, but the role of ATP in CARD ejection remains debated.

Purpose of the Study:

• To investigate the role of ATP and RNA binding in RIG-I activation using NMR spectroscopy.
• To elucidate the conformational changes in RIG-I upon binding different RNA types and nucleotides.

Main Methods:

• Utilized NMR spectroscopy on full-length, selectively methionine-labeled RIG-I.
• Studied interactions with 5'-triphosphate and 5'-OH dsRNA in the presence and absence of nucleotides.

Main Results:

• Identified specific residues in CTD, helicase, and CARD domains sensitive to RNA-induced conformational changes.
• Results support a model where RNA binding, rather than ATP, is the primary driver for CARD domain release.

Conclusions:

• RNA binding is the principal event triggering RIG-I activation and downstream signaling.
• This clarifies the mechanism of RIG-I's antiviral immune response initiation.