Stress granule formation, disassembly, and composition are regulated by alphavirus ADP-ribosylhydrolase activity

Proc Natl Acad Sci U S A. 2021 Feb 9;118(6):e2021719118. doi: 10.1073/pnas.2021719118.


While biomolecular condensates have emerged as an important biological phenomenon, mechanisms regulating their composition and the ways that viruses hijack these mechanisms remain unclear. The mosquito-borne alphaviruses cause a range of diseases from rashes and arthritis to encephalitis, and no licensed drugs are available for treatment or vaccines for prevention. The alphavirus virulence factor nonstructural protein 3 (nsP3) suppresses the formation of stress granules (SGs)-a class of cytoplasmic condensates enriched with translation initiation factors and formed during the early stage of infection. nsP3 has a conserved N-terminal macrodomain that hydrolyzes ADP-ribose from ADP-ribosylated proteins and a C-terminal hypervariable domain that binds the essential SG component G3BP1. Here, we show that macrodomain hydrolase activity reduces the ADP-ribosylation of G3BP1, disassembles virus-induced SGs, and suppresses SG formation. Expression of nsP3 results in the formation of a distinct class of condensates that lack translation initiation factors but contain G3BP1 and other SG-associated RNA-binding proteins. Expression of ADP-ribosylhydrolase-deficient nsP3 results in condensates that retain translation initiation factors as well as RNA-binding proteins, similar to SGs. Therefore, our data reveal that ADP-ribosylation controls the composition of biomolecular condensates, specifically the localization of translation initiation factors, during alphavirus infection.

Keywords: ADP-ribosylation; alphavirus; biomolecular condensates; macrodomain; stress granules.

Publication types

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

MeSH terms

  • Alphavirus / genetics*
  • Alphavirus / pathogenicity
  • Animals
  • Arthritis / virology
  • Culicidae / virology
  • DNA Helicases / genetics*
  • Encephalitis / virology
  • Exanthema / virology
  • Gene Expression Regulation, Viral / genetics
  • HeLa Cells
  • Humans
  • N-Glycosyl Hydrolases / genetics*
  • Poly-ADP-Ribose Binding Proteins / genetics*
  • RNA Helicases / genetics*
  • RNA Recognition Motif Proteins / genetics*
  • RNA-Binding Proteins / genetics
  • Viral Nonstructural Proteins / genetics*


  • Poly-ADP-Ribose Binding Proteins
  • RNA Recognition Motif Proteins
  • RNA-Binding Proteins
  • Viral Nonstructural Proteins
  • N-Glycosyl Hydrolases
  • ADP-ribosylarginine hydrolase
  • DNA Helicases
  • G3BP1 protein, human
  • RNA Helicases