Helicase-independent function of RIG-I against murine gammaherpesvirus 68 via blocking the nuclear translocation of viral proteins

Yang Xu; Guoli Hou; Qizhi Liu; Qiushi Zhang; Chun Li; Liang Hu; Xiaoying Chen; Rui Chen; Chengming Ding; Deliang Li; Junhua Li

doi:10.1016/j.ijbiomac.2023.126527

Helicase-independent function of RIG-I against murine gammaherpesvirus 68 via blocking the nuclear translocation of viral proteins

Int J Biol Macromol. 2023 Oct 1:250:126527. doi: 10.1016/j.ijbiomac.2023.126527. Epub 2023 Aug 24.

Authors

Yang Xu¹, Guoli Hou¹, Qizhi Liu², Qiushi Zhang¹, Chun Li¹, Liang Hu¹, Xiaoying Chen¹, Rui Chen¹, Chengming Ding³, Deliang Li⁴, Junhua Li⁵

Affiliations

¹ College of Animal Science and Technology, Hunan Agricultural University, Changsha 410128, China.
² Department of Surgery, Samuel Oschin Cancer Institute, Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA.
³ The First Affiliated Hospital, Department of Hepatopancreatobiliary Surgery, Hengyang Medical School, University of South China, Hengyang, Hunan 421001, China.
⁴ College of Animal Science and Technology, Hunan Agricultural University, Changsha 410128, China. Electronic address: lidl@hunau.edu.cn.
⁵ College of Animal Science and Technology, Hunan Agricultural University, Changsha 410128, China. Electronic address: lijunhua@hunau.edu.cn.

PMID: 37633553
DOI: 10.1016/j.ijbiomac.2023.126527

Abstract

Innate immunity is the first line of defense against viral pathogens. Retinoic Acid-Inducible Gene 1 (RIG-I) is a pattern recognition receptor that recognizes virus-associated double-stranded RNA and initiates the interferon responses. Besides signal transduction, RIG-I exerts direct antiviral functions to displace viral proteins on dsRNA via its Helicase activity. Nevertheless, this effector-like activity of RIG-I against herpesviruses remains largely unexplored. It has been previously reported that herpesviruses deamidate RIG-I, resulting in the abolishment of its Helicase activity and signal transduction. In this study, we discovered that RIG-I possessed signaling-independent antiviral activities against murine gamma herpesviruses 68 (γHV68, murid herpesvirus 4). Importantly, a Helicase-dead mutant of RIG-I (K270A) demonstrated comparable inhibition on herpesviruses lytic replication, indicating that this antiviral activity is Helicase-independent. Mechanistically, RIG-I bound the Replication and Transcription Activator (RTA) and diminished its nuclear localization to repress viral transcription. We further demonstrated that RIG-I blocked the nuclear translocation of ORF21 (Thymidine Kinase), ORF75c (vGAT), both of which form a nuclear complex with RTA and RNA polymerase II (Pol II) to facilitate viral transcription. Moreover, RIG-I retained ORF59 (DNA processivity factor) in the cytoplasm to repress viral DNA replication. Altogether, we illuminated a previously unidentified, Helicase-independent effector-like function of RIG-I against γHV68, representing an exquisite host strategy to counteract viral manipulations on innate immune signaling. IMPORTANCE: Retinoic acid-inducible gene I (RIG-I), a member of DExD/H box RNA helicase family, functions as a key pattern recognition receptor (PRR) responsible for the detection of intracellular double-stranded RNA (dsRNA) from virus-infected cells and induction of type I interferon (IFN) responses. Nevertheless, our understanding of the helicase-independent effector-like activity of RIG-I against virus infection, especially herpesvirus infection, remains largely unknown. Herein, by deploying murine gamma herpesviruses 68 (γHV68) as a model system, we demonstrated that RIG-I possessed an interferon and helicase-independent antiviral activity against γHV68 via blocking the nuclear trafficking of viral proteins, which concomitantly repressed the viral early transcription and genome replication thereof. Our work illuminates a previously unidentified antiviral strategy of RIG-I against herpesvirus infection.

Keywords: Gamma herpesviruses 68; Helicase-independent; Nuclear translocation; RIG-I; RTA.