ZAP Inhibits Murine Gammaherpesvirus 68 ORF64 Expression and Is Antagonized by RTA

Abstract

bZinc finger antiviral protein (ZAP) is an interferon-inducible host antiviral factor that specifically inhibits the replication of certain viruses, including HIV-1 and Ebola virus. ZAP functions as a dimer formed through intermolecular interactions of its N-terminal tails. ZAP binds directly to specific viral mRNAs and inhibits their expression by repressing translation and/or promoting degradation of the target mRNA. ZAP is not a universal antiviral factor, since some viruses grow normally in ZAP-expressing cells. It is not fully understood what determines whether a virus is susceptible to ZAP. We explored the interaction between ZAP and murine gammaherpesvirus 68 (MHV-68), whose life cycle has latent and lytic phases. We previously reported that ZAP inhibits the expression of M2, which is expressed mainly in the latent phase, and regulates MHV-68 latency in cultured cells. Here, we report that ZAP inhibits the expression of ORF64, a tegument protein that is expressed in the lytic phase and is essential for lytic replication. MHV-68 infection induced ZAP expression. However, ZAP did not inhibit lytic replication of MHV-68. We provide evidence showing that the antiviral activity of ZAP is antagonized by MHV-68 RTA, a critical viral transactivator expressed in the lytic phase. We further show that RTA inhibits the antiviral activity of ZAP by disrupting the N-terminal intermolecular interaction of ZAP. Our results provide an example of how a virus can escape ZAP-mediated immunity.

The impact of PARPs and ADP-ribosylation on inflammation and host–pathogen interactions

“…As such, most of its antiviral activity is independent of ADP-ribosylation. Since its discovery, ZAP has been shown to inhibit the replication of several viral families, including retroviruses, alphaviruses, filoviruses, picornaviruses, herpesviruses, arteriviruses, orthomyxoviruses, flaviviruses, and hepatitis B virus (Bick et al 2003;Muller et al 2007;Zhu et al 2011;Wang et al 2012;Xuan et al 2012;Mao et al 2013;Xuan et al 2013;Li et al 2015Li et al , 2015aChiu et al 2018;Xie et al 2018;Zhao et al 2019). ZAP is transcribed into four different isoforms, with ZAPL and ZAPS being the most studied .…”

The Short Form of the Zinc Finger Antiviral Protein Inhibits Influenza A Virus Protein Expression and Is Antagonized by the Virus-Encoded NS1

“…RNA binding is the first step for ZAPS to inhibit target mRNA expression. We thus analyzed the effect of NS1 expression on ZAPS binding to the target RNA using the RNA immunoprecipitation assay we previously reported (15). The N-terminal domain of ZAPS, which is the major RNA-binding domain of the protein, and a ZAP-responsive reporter, MK-fLuc (10), were coexpressed in HEK293 cells, together with NS1 or the NS1 mutants.…”

“…In the C-terminal domain of the long isoform (ZAPL), there is a poly(ADP-ribose) polymerase (PARP) domain, which is missing in the short isoform (ZAPS). Most of the previously reported studies on the antiviral activities of ZAP and the underlying mechanisms were performed with ZAPS (4,6,7,(10)(11)(12)(13)(14)(15). Nonetheless, given that ZAPL contains all the sequences of ZAPS, it would be reasonable to expect that ZAPL shares these antiviral activities and mechanisms with ZAPS.…”

“…The presence of a ZRE in the viral mRNA does not guarantee sensitivity of a virus to ZAPS. We previously reported that ZAPS inhibited murine gammaherpesvirus 68 open reading frame 64 (ORF64) expression but had little effect on the lytic replication of the virus because ZAPS was antagonized by the viral protein RTA (15). Given the lack of predictable target sequences in viruses and possible antagonism by viral proteins, whether a virus is sensitive to ZAPS can only be tested experimentally.…”

HIV-1 Exploits the Host Factor RuvB-like 2 to Balance Viral Protein Expression

“…The RNA was reverse transcribed and detected by PCR. The method for detecting protein-associated mRNA has been described previously (Xuan et al, 2013). Briefly, HeLa cells were transfected with plasmids expressing Flag-tagged RVB2 and the luciferase reporter.…”