The tegument protein VP22 of pseudorabies virus inhibits cGAS condensation by inducing nuclear-to-cytoplasmic translocation of DDX21.

Abstract

Cyclic GMP-AMP synthase (cGAS) is a pivotal DNA sensor that initiates antiviral responses, yet the mechanisms by which viruses evade cGAS-mediated innate immunity remain poorly understood. Here, we identified VP22, a tegument protein of pseudorabies virus (PRV), a member of the Alphaherpesvirinae subfamily, as a viral antagonist of the type I interferon (IFN-I) response through hijacking the host RNA helicase DDX21. Specifically, VP22 impairs 2'3'-cyclic GMP-AMP (cGAMP) synthesis by disrupting cGAS condensation. In vivo, cGAS restricts the replication of VP22-deficient PRV and attenuates its pathogenicity, an effect neutralized by VP22. Notably, DDX21 is essential for VP22-mediated inhibition of cGAS activity. Mechanistically, VP22 stabilizes DDX21 protein level and enhances its interaction with cGAS. Furthermore, VP22 promotes the translocation of DDX21 from the nucleus to the cytoplasm, a process required for inhibition of cGAS condensation and activation. Collectively, these findings reveal a previously unrecognized, host-dependent mechanism by which PRV subverts cGAS signaling, shedding light on viral strategies to subvert host DNA sensing and innate immunity.