DNA Sensing-Independent Inhibition of Herpes Simplex Virus 1 Replication by DAI/ZBP1

Abstract

DNA-dependent activator of interferon regulatory factor (DAI) acts as a cytosolic B-form DNA sensor that induces type I interferons. However, DAI is not required for DNA sensing in certain cell types due to redundancy of the DNA sensing system. Here, we investigated the effect of DAI on herpes simplex virus 1 (HSV-1) infection in HepG2 hepatocellular carcinoma cells. DAI transcription was induced after gamma interferon (IFN-␥) treatment or HSV-1 infection. HSV-1 replication was enhanced by DAI knockdown, and ectopic DAI expression repressed viral replication in a manner requiring the Z␤ and D3 domains, but not the Z␣ domain. This activity of DAI was more prominent at low multiplicity of infection (MOI) and correlated with the reduced expression of viral immediate-early genes. Consistently, DAI repressed the activation of ICP0 promoter in reporter gene assays. DNA-dependent activator of interferon (IFN) regulatory factor (DAI), which is also referred to as Z-DNA binding protein 1 (ZBP1) or DLM-1, was initially identified as a highly upregulated protein in mouse tumor stromal cells and in macrophages treated by gamma IFN (IFN-␥) or lipopolysaccharide (1). Structural analyses have revealed that DAI/ZBP1/DLM-1 (referred to as DAI hereafter) contains the amino-terminal Z-form DNA-binding domains, Z␣ and Z␤, which are homologous to those of adenosine deaminase that acts on RNA (ADAR1), an RNA editing enzyme (2-5). Since Z-DNA is located near the transcription start sites of certain genes in the genome, a role of DAI in transcriptional regulation has been suggested (6, 7). Induction of DAI was also observed in mouse hepatocytes infected with hepatitis B virus (HBV) (8) and in mouse embryonic fibroblasts (MEFs) stimulated by B-form DNA (9).Recently, DAI was shown to act as a cytosolic B-form DNA sensor that initiates IFN responses via activation of the nuclear factor-B (NF-B) and interferon regulatory transcription factor 3 (IRF3) pathways in mice (10). In addition to the Z-DNA-binding domains, a region termed the D3 domain was demonstrated to primarily contribute to the recognition of B-DNA in vitro (10). However, all of the Z␣, Z␤, and D3 domains were required for efficient B-DNA binding in vivo and DAI was suggested to undergo DNA-mediated multimerization to evoke activation of IFN responses (11). The carboxyl-terminal region of DAI was responsible for recruitment of both IRF3 and TANK-binding kinase 1 (TBK1), an IB kinase that activates IRF3 (10). The mechanism by which DAI activates the NF-B pathway was shown to involve recruitment of receptor-interacting protein kinase 1 (RIP1) and RIP3 through a RIP homotypic interaction motif (RHIM)-dependent interaction with DAI (12, 13). Recently, the binding of DAI with RIP3 was shown to mediate virus-induced programmed necrosis (14).The requirement of DAI in induction of IFN response by cytosolic stimulation of B-DNA is dependent on cell type. DAI played a role in the DNA-mediated IFN production in mouse fibroblast L929 (10, 12, 15) and mouse SVEC4-10 endothelial cells (12)...

Pattern Recognition Receptor–Initiated Innate Antiviral Responses in Mouse Epididymal Epithelial Cells

“…In contrast, DAI is dispensable for the DNA-triggered IFN production in mouse embryo fibroblasts and dendritic cells (44). Recent studies showed that DAI initiates necroposis of 3T3 cells in response to mouse CMV infection (47), and it inhibits HSV-1 replication by suppressing the expression of the viral ICP0 protein in hepatocellular carcinoma cells (48). These observations suggest that DAI can be involved in the antiviral responses through different mechanisms dependent on cell and virus types.…”

Herpes Simplex Virus 1 Infection Induces Activation and Subsequent Inhibition of the IFI16 and NLRP3 Inflammasomes

“…The different topology of HSV-1 DNA may release structural constraints on IFI16, making it accessible to bind ASC. Additional extensive studies beyond the scope of the present study are required to further examine the interactions of IFI16 with host and viral DNA and to determine if there is a direct interaction of IFI16 with the HSV-1 genome or if the interaction occurs through other proteins known to interact with IFI16 and HSV-1 DNA, such as p53 (21), BRCA1 (73), or proteins in ND10 domains (74).…”

Type I Interferon and NF-κB Activation Elicited by Herpes Simplex Virus gH/gL via αvβ3 Integrin in Epithelial and Neuronal Cell Lines

“…Until recently, the prevalent paradigm has been that the IFN production occurs in response to activation of the cytosolic sensors, whereas the TLRs located at the plasma membrane elicit a predominantly inflammatory response (4)(5)(6). In particular, until recently, TLR2 was known to sense bacteria and was thought not to be involved in recognition of viruses.…”