Combined structural, biochemical and cellular evidence demonstrates that both FGDF motifs in alphavirus nsP3 are required for efficient replication

Open Biol. 2016 Jul;6(7):160078. doi: 10.1098/rsob.160078.


Recent findings have highlighted the role of the Old World alphavirus non-structural protein 3 (nsP3) as a host defence modulator that functions by disrupting stress granules, subcellular phase-dense RNA/protein structures formed upon environmental stress. This disruption mechanism was largely explained through nsP3-mediated recruitment of the host G3BP protein via two tandem FGDF motifs. Here, we present the 1.9 Å resolution crystal structure of the NTF2-like domain of G3BP-1 in complex with a 25-residue peptide derived from Semliki Forest virus nsP3 (nsP3-25). The structure reveals a poly-complex of G3BP-1 dimers interconnected through the FGDF motifs in nsP3-25. Although in vitro and in vivo binding studies revealed a hierarchical interaction of the two FGDF motifs with G3BP-1, viral growth curves clearly demonstrated that two intact FGDF motifs are required for efficient viral replication. Chikungunya virus nsP3 also binds G3BP dimers via a hierarchical interaction, which was found to be critical for viral replication. These results highlight a conserved molecular mechanism in host cell modulation.

Keywords: innate immunity; protein structure–function; stress response; virus–host interaction.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Motifs
  • Cell Line
  • Chikungunya virus / metabolism
  • Chikungunya virus / physiology
  • Conserved Sequence
  • Crystallography, X-Ray
  • DNA Helicases / chemistry*
  • DNA Helicases / metabolism*
  • HEK293 Cells
  • Humans
  • Models, Molecular
  • Poly-ADP-Ribose Binding Proteins / chemistry*
  • Poly-ADP-Ribose Binding Proteins / metabolism*
  • Protein Binding
  • Protein Multimerization
  • Protein Structure, Tertiary
  • RNA Helicases / chemistry*
  • RNA Helicases / metabolism*
  • RNA Recognition Motif Proteins / chemistry*
  • RNA Recognition Motif Proteins / metabolism*
  • RNA-Binding Proteins / chemistry*
  • RNA-Binding Proteins / metabolism*
  • Semliki forest virus / metabolism
  • Semliki forest virus / physiology*
  • Viral Nonstructural Proteins / chemistry*
  • Viral Nonstructural Proteins / metabolism*
  • Virus Replication


  • Nsp3 protein, semliki forest virus
  • Poly-ADP-Ribose Binding Proteins
  • RNA Recognition Motif Proteins
  • RNA-Binding Proteins
  • Viral Nonstructural Proteins
  • DNA Helicases
  • G3BP1 protein, human
  • RNA Helicases

Associated data

  • Dryad/10.5061/dryad.d69r2