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Cytoplasmic ATR Activation Promotes Vaccinia Virus Genome Replication.

ABSTRACT: In contrast to most DNA viruses, poxviruses replicate their genomes in the cytoplasm without host involvement. We find that vaccinia virus induces cytoplasmic activation of ATR early during infection, before genome uncoating, which is unexpected because ATR plays a fundamental nuclear role in maintaining host genome integrity. ATR, RPA, INTS7, and Chk1 are recruited to cytoplasmic DNA viral factories, suggesting canonical ATR pathway activation. Consistent with this, pharmacological and RNAi-mediated inhibition of canonical ATR signaling suppresses genome replication. RPA and the sliding clamp PCNA interact with the viral polymerase E9 and are required for DNA replication. Moreover, the ATR activator TOPBP1 promotes genome replication and associates with the viral replisome component H5. Our study suggests that, in contrast to long-held beliefs, vaccinia recruits conserved components of the eukaryote DNA replication and repair machinery to amplify its genome in the host cytoplasm.

SUBMITTER: Postigo A

PROVIDER: S-EPMC5437729 | biostudies-literature | 2017 May

REPOSITORIES: biostudies-literature

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Cytoplasmic ATR Activation Promotes Vaccinia Virus Genome Replication.

Postigo Antonio A Ramsden Amy E AE Howell Michael M Way Michael M

Cell reports 20170501 5

In contrast to most DNA viruses, poxviruses replicate their genomes in the cytoplasm without host involvement. We find that vaccinia virus induces cytoplasmic activation of ATR early during infection, before genome uncoating, which is unexpected because ATR plays a fundamental nuclear role in maintaining host genome integrity. ATR, RPA, INTS7, and Chk1 are recruited to cytoplasmic DNA viral factories, suggesting canonical ATR pathway activation. Consistent with this, pharmacological and RNAi-med ...[more]

PMID: 28467896

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Project description:Vaccinia virus has recently been used as an expression vector for gene delivery and an oncolytic agent for cancer therapy. Although it has been established that interferon-induced double-stranded RNA (dsRNA)-activated protein kinase (PKR) and RNase L interfere with viral replication, little else is known about the other host factors that might affect viral replication and virus-mediated host cell killing. In this study, we evaluated the roles of c-Jun NH2-terminal kinase (JNK) in oncolytic vaccinia virus replication and vaccinia virus-mediated host cell killing. We found that JNK knockout mouse embryonic fibroblasts (MEFs) were more susceptible to oncolytic vaccinia virus infection than wild-type MEFs. Moreover, viral replication and the production of infectious viral progeny were up to 100-fold greater in JNK-deficient MEFs than in wild-type MEFs. A similar result was observed for wild-type vaccinia virus. The increased killing of infected cells and the production of viral progeny was also observed in wild-type MEFs that had been treated with JNK inhibitors and in human colon cancer cells that had been transfected with dominant-negative JNK constructs. Moreover, testing on several human lung cancer cell lines and HeLa cells showed an inverse correlation between levels of JNK expression and susceptibility to oncolytic vaccinia virus. Our study also revealed that oncolytic virus infection-mediated PKR activation was blocked or diminished in JNK-deficient MEFs. The adenovirus-mediated ectopic expression of human PKR in JNK-deficient MEFs reduced vaccinia virus replication to the levels observed in wild-type MEFs, indicating that JNK is required for vaccinia virus to efficiently activate PKR. Our results demonstrated that the cellular status of JNK function can dramatically affect oncolytic vaccinia virus replication and vaccinia virus-mediated host cell killing. This finding may enable further improvements in oncolytic virotherapy using vaccinia virus.

Project description:UnlabelledViruses require host cell metabolism to provide the necessary energy and biosynthetic precursors for successful viral replication. Vaccinia virus (VACV) is a member of the Poxviridae family, and its use as a vaccine enabled the eradication of variola virus, the etiologic agent of smallpox. A global metabolic screen of VACV-infected primary human foreskin fibroblasts suggested that glutamine metabolism is altered during infection. Glutamine and glucose represent the two main carbon sources for mammalian cells. Depriving VACV-infected cells of exogenous glutamine led to a substantial decrease in infectious virus production, whereas starving infected cells of exogenous glucose had no significant impact on replication. Viral yield in glutamine-deprived cells or in cells treated with an inhibitor of glutaminolysis, the pathway of glutamine catabolism, could be rescued by the addition of multiple tricarboxylic acid (TCA) cycle intermediates. Thus, VACV infection induces a metabolic alteration to fully rely on glutamine to anaplerotically maintain the TCA cycle. VACV protein synthesis, but not viral transcription, was decreased in glutamine-deprived cells, which corresponded with a dramatic reduction in all VACV morphogenetic intermediates. This study reveals the unique carbon utilization program implemented during poxvirus infection and provides a potential metabolic pathway to target viral replication.ImportanceViruses are dependent on the metabolic machinery of the host cell to supply the energy and molecular building blocks needed for critical processes including genome replication, viral protein synthesis, and membrane production. This study investigates how vaccinia virus (VACV) infection alters global cellular metabolism, providing the first metabolomic analysis for a member of the poxvirus family. Unlike most viruses examined to date, VACV does not activate glycolysis, and exogenous glucose is not required for maximal virus production. Instead, VACV requires exogenous glutamine for efficient replication, and inhibition of glutamine metabolism effectively blocks VACV protein synthesis. This study defines a major metabolic perturbation essential for the replication of a poxvirus and may lead to the discovery of novel antiviral therapies based on metabolic inhibitors.

Dataset Information

Cytoplasmic ATR Activation Promotes Vaccinia Virus Genome Replication.

Publications

Cytoplasmic ATR Activation Promotes Vaccinia Virus Genome Replication.

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