Human IFIT3 Modulates IFIT1 RNA Binding Specificity and Protein Stability

Britney Johnson, Laura A. VanBlargan, Wei Xu, James P. White, Chao Shan, Pei Yong Shi, Rong Zhang, Jagat Adhikari, Michael L. Gross, Daisy W. Leung, Michael S. Diamond, Gaya K. Amarasinghe

Research output: Contribution to journalArticlepeer-review

33 Scopus citations


Although interferon-induced proteins with tetratricopeptide repeats (IFIT proteins) inhibit infection of many viruses by recognizing their RNA, the regulatory mechanisms involved remain unclear. Here we report a crystal structure of cap 0 (m7GpppN) RNA bound to human IFIT1 in complex with the C-terminal domain of human IFIT3. Structural, biochemical, and genetic studies suggest that IFIT3 binding to IFIT1 has dual regulatory functions: (1) extending the half-life of IFIT1 and thereby increasing its steady-state amounts in cells; and (2) allosterically regulating the IFIT1 RNA-binding channel, thereby enhancing the specificity of recognition for cap 0 but not cap 1 (m7GpppNm) or 5′-ppp RNA. Mouse Ifit3 lacks this key C-terminal domain and does not bind mouse Ifit1. The IFIT3 interaction with IFIT1 is important for restricting infection of viruses lacking 2′-O methylation in their RNA cap structures. Our experiments establish differences in the regulation of IFIT1 orthologs and define targets for modulation of human IFIT protein activity. Prior studies have suggested that human IFIT1, unlike its mouse ortholog, might not recognize viral RNA molecules lacking 2′-O methylation on their cap structures. Johnson et al. report a crystal structure between cap 0 (m7GpppN) RNA bound to human IFIT1 in complex with the C-terminal domain (CTD) of human IFIT3. The CTD of IFIT3 bound to IFIT1 and allosterically regulated the IFIT1 RNA-binding channel and promoted selective recognition of cap 0 RNA.

Original languageEnglish (US)
Pages (from-to)487-499.e5
Issue number3
StatePublished - Mar 20 2018


  • RNA-binding protein
  • X-ray
  • antiviral
  • crystallography
  • flavivirus
  • host defense
  • innate immunity
  • interferon stimulated genes
  • pathogen associated molecular patterns
  • self/non-self RNA recognition

ASJC Scopus subject areas

  • Immunology and Allergy
  • Immunology
  • Infectious Diseases


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