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Dynamic Response of IFI16 and Promyelocytic Leukemia Nuclear Body Components to Herpes Simplex Virus 1 Infection.

ABSTRACT:

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Intrinsic immunity is an aspect of antiviral defense that operates through diverse mechanisms at the intracellular level through a wide range of constitutively expressed cellular proteins. In the case of herpesviruses, intrinsic resistance involves the repression of viral gene expression during the very early stages of infection, a process that is normally overcome by viral tegument and/or immediate-early proteins. Thus, the balance between cellular repressors and virus-counteracting proteins determines whether or not a cell becomes productively infected. One aspect of intrinsic resistance to herpes simplex virus 1 (HSV-1) is conferred by components of promyelocytic leukemia nuclear bodies (PML NBs), which respond to infection by accumulating at sites that are closely associated with the incoming parental HSV-1 genomes. Other cellular proteins, including IFI16, which has been implicated in sensing pathogen DNA and initiating signaling pathways that lead to an interferon response, also respond to viral genomes in this manner. Here, studies of the dynamics of the response of PML NB components and IFI16 to invading HSV-1 genomes demonstrated that this response is extremely rapid, occurring within the first hour after addition of the virus, and that human Daxx (hDaxx) and IFI16 respond more rapidly than PML. In the absence of HSV-1 regulatory protein ICP0, which counteracts the recruitment process, the newly formed, viral-genome-induced PML NB-like foci can fuse with existing PML NBs. These data are consistent with a model involving viral genome sequestration into such structures, thereby contributing to the low probability of initiation of lytic infection in the absence of ICP0.

Importance

Herpesviruses have intimate interactions with their hosts, with infection leading either to the productive lytic cycle or to a quiescent infection in which viral gene expression is suppressed while the viral genome is maintained in the host cell nucleus. Whether a cell becomes lytically or quiescently infected can be determined through the competing activities of cellular repressors and viral activators, some of which counteract cell-mediated repression. Therefore, the events that occur within the earliest stages of infection can be of crucial importance. This paper describes the extremely rapid response to herpes simplex virus 1 infection of cellular protein IFI16, a sensor of pathogen DNA, and also of the PML nuclear body proteins PML and hDaxx, as revealed by live-cell microscopy. The data imply that these proteins can accumulate on or close to the viral genomes in a sequential manner which may lead to their sequestration and repression.

SUBMITTER: Everett RD

PROVIDER: S-EPMC4702556 | biostudies-literature | 2016 Jan

REPOSITORIES: biostudies-literature

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Dynamic Response of IFI16 and Promyelocytic Leukemia Nuclear Body Components to Herpes Simplex Virus 1 Infection.

Everett Roger D RD

Journal of virology 20151014 1

<h4>Unlabelled</h4>Intrinsic immunity is an aspect of antiviral defense that operates through diverse mechanisms at the intracellular level through a wide range of constitutively expressed cellular proteins. In the case of herpesviruses, intrinsic resistance involves the repression of viral gene expression during the very early stages of infection, a process that is normally overcome by viral tegument and/or immediate-early proteins. Thus, the balance between cellular repressors and virus-counte ...[more]

PMID: 26468536

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Project description:Aspects of intrinsic antiviral immunity are mediated by promyelocytic leukemia nuclear body (PML-NB) constituent proteins. During herpesvirus infection, these antiviral proteins are independently recruited to nuclear domains that contain infecting viral genomes to cooperatively promote viral genome silencing. Central to the execution of this particular antiviral response is the small ubiquitin-like modifier (SUMO) signaling pathway. However, the participating SUMOylation enzymes are not fully characterized. We identify the SUMO ligase protein inhibitor of activated STAT1 (PIAS1) as a constituent PML-NB protein. We show that PIAS1 localizes at PML-NBs in a SUMO interaction motif (SIM)-dependent manner that requires SUMOylated or SUMOylation-competent PML. Following infection with herpes simplex virus 1 (HSV-1), PIAS1 is recruited to nuclear sites associated with viral genome entry in a SIM-dependent manner, consistent with the SIM-dependent recruitment mechanisms of other well-characterized PML-NB proteins. In contrast to that of Daxx and Sp100, however, the recruitment of PIAS1 is enhanced by PML. PIAS1 promotes the stable accumulation of SUMO1 at nuclear sites associated with HSV-1 genome entry, whereas the accumulation of other evaluated PML-NB proteins occurs independently of PIAS1. We show that PIAS1 cooperatively contributes to HSV-1 restriction through mechanisms that are additive to those of PML and cooperative with those of PIAS4. The antiviral mechanisms of PIAS1 are counteracted by ICP0, the HSV-1 SUMO-targeted ubiquitin ligase, which disrupts the recruitment of PIAS1 to nuclear domains that contain infecting HSV-1 genomes through mechanisms that do not directly result in PIAS1 degradation.Adaptive, innate, and intrinsic immunity cooperatively and efficiently restrict the propagation of viral pathogens. Intrinsic immunity mediated by constitutively expressed cellular proteins represents the first line of intracellular defense against infection. PML-NB constituent proteins mediate aspects of intrinsic immunity to restrict herpes simplex virus 1 (HSV-1) as well as other viruses. These proteins repress viral replication through mechanisms that rely on SUMO signaling. However, the participating SUMOylation enzymes are not known. We identify the SUMO ligase PIAS1 as a constituent PML-NB antiviral protein. This finding distinguishes a SUMO ligase that may mediate signaling events important in PML-NB-mediated intrinsic immunity. Moreover, this research complements the recent identification of PIAS4 as an intrinsic antiviral factor, supporting a role for PIAS proteins as both positive and negative regulators of host immunity to virus infection.

Project description:Proliferating cell nuclear antigen (PCNA) forms a homotrimer that encircles replicating DNA and is bound by DNA polymerases to add processivity to cellular DNA synthesis. In addition, PCNA acts as a scaffold to recruit DNA repair and chromatin remodeling proteins to replicating DNA via its interdomain connecting loop (IDCL). Despite encoding a DNA polymerase processivity factor UL42, it was previously found that PCNA associates with herpes simplex virus type 1 (HSV-1) replication forks and is necessary for productive HSV-1 infection. To define the role that PCNA plays during viral DNA replication or a replication-coupled process, we investigated the effects that two mechanistically distinct PCNA inhibitors, PCNA-I1 and T2AA, have on the HSV-1 infectious cycle. PCNA-I1 binds at the interface between PCNA monomers, stabilizes the homotrimer, and may interfere with protein-protein interactions. T2AA inhibits select protein-protein interactions within the PCNA IDCL. Here we demonstrate that PCNA-I1 treatment results in reduced HSV-1 DNA replication, late gene expression, and virus production, while T2AA treatment results in reduced late viral gene expression and infectious virus production. To pinpoint the mechanisms by which PCNA inhibitors affect viral processes and protein recruitment to replicated viral DNA, we performed accelerated native isolation of proteins on nascent DNA (aniPOND). Results indicate that T2AA inhibits recruitment of the viral uracil glycosylase UL2 and transcription regulatory factors to viral DNA, likely leading to a defect in viral base excision repair and the observed defect in late viral gene expression and infectious virus production. In addition, PCNA-I1 treatment results in decreased association of the viral DNA polymerase UL30 and known PCNA-interacting proteins with viral DNA, consistent with the observed block in viral DNA replication and subsequent processes. Together, we conclude that inhibitors of cellular PCNA block recruitment of key viral and cellular factors to viral DNA to inhibit viral DNA synthesis and coupled processes.

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Dataset Information

Dynamic Response of IFI16 and Promyelocytic Leukemia Nuclear Body Components to Herpes Simplex Virus 1 Infection.

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Importance

Publications

Dynamic Response of IFI16 and Promyelocytic Leukemia Nuclear Body Components to Herpes Simplex Virus 1 Infection.

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