Human cytomegalovirus long non-coding RNA counteracts nuclear cGAS to facilitate immune evasion.

Viruses have evolved diverse immune evasion strategies, including the targeting of host pattern recognition receptors. The role of viral non-coding RNAs in modulating pattern recognition receptor activity is unclear. Here we show that human cytomegalovirus (HCMV) produces long non-coding RNA4.9 that counteracts the nuclear cyclic GMP-AMP synthase (cGAS)-mediated immune response to facilitate viral infection in human foreskin fibroblasts. RNA4.9 interacts with host cGAS via its 75-nucleotide RNA region with predicted hairpin loops. Binding of RNA4.9 to cGAS inhibits cGAS enzymatic activity as well as downstream interferon response and facilitates productive viral replication. Sterically blocking the folding of the 75-nucleotide region with antisense oligonucleotides during HCMV infection restores cGAS activity and impairs viral replication. In addition, we found that the specific localization of RNA4.9, which concentrates near HCMV DNA, is correlated with its efficient binding to cGAS and subsequent immune suppression. Our findings identify viral non-coding RNAs as key regulators of cGAS and highlight their potential as therapeutic targets.