Viral tegument proteins restrict cGAS-DNA phase separation to mediate immune evasion

Mol Cell. 2021 Jul 1;81(13):2823-2837.e9. doi: 10.1016/j.molcel.2021.05.002. Epub 2021 May 19.

Abstract

DNA-induced liquid-liquid phase separation of cyclic GMP-AMP synthase (cGAS) triggers a potent response to detect pathogen infection and promote innate immune signaling. Whether and how pathogens manipulate cGAS-DNA condensation to mediate immune evasion is unknown. We report the identification of a structurally related viral tegument protein family, represented by ORF52 and VP22 from gamma- and alpha-herpesvirinae, respectively, that employs a conserved mechanism to restrict cGAS-DNA phase separation. ORF52/VP22 proteins accumulate into, and effectively disrupt, the pre-formed cGAS-DNA condensation both in vitro and in cells. The inhibition process is dependent on DNA-induced liquid-liquid phase separation of the viral protein rather than a direct interaction with cGAS. Moreover, highly abundant ORF52 proteins carried within viral particles are able to target cGAS-DNA phase separation in early infection stage. Our results define ORF52/VP22-type tegument proteins as a family of inhibitors targeting cGAS-DNA phase separation and demonstrate a mechanism for how viruses overcome innate immunity.

Keywords: ORF52; ORF9; VP22; cGAS; cGAS-STING pathway; herpesvirus; host-pathogen interaction; phase separation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alphaherpesvirinae* / chemistry
  • Alphaherpesvirinae* / genetics
  • Alphaherpesvirinae* / immunology
  • Betaherpesvirinae* / chemistry
  • Betaherpesvirinae* / genetics
  • Betaherpesvirinae* / immunology
  • DNA* / chemistry
  • DNA* / genetics
  • DNA* / immunology
  • HEK293 Cells
  • HeLa Cells
  • Herpesviridae Infections* / genetics
  • Herpesviridae Infections* / immunology
  • Humans
  • Immune Evasion*
  • Immunity, Innate
  • Nucleotidyltransferases* / chemistry
  • Nucleotidyltransferases* / genetics
  • Nucleotidyltransferases* / immunology
  • Viral Structural Proteins* / chemistry
  • Viral Structural Proteins* / genetics
  • Viral Structural Proteins* / immunology

Substances

  • Viral Structural Proteins
  • DNA
  • Nucleotidyltransferases
  • cGAS protein, human