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Herpes simplex virus 2 expresses a novel form of ICP34.5, a major viral neurovirulence factor, through regulated alternative splicing.

ABSTRACT: Herpes simplex virus 1 (HSV-1) and HSV-2, two closely related neurotropic human herpesviruses, achieve neurotropism through ICP34.5, a major viral neurovirulence factor. In this report, in addition to the full-length 38-kDa protein (ICP34.5?), we identified a 28-kDa novel form of ICP34.5 (ICP34.5?) in HSV-2-infected cells. ICP34.5? is translated from unspliced ICP34.5 mRNA, with the retained intron introducing a premature stop codon. Thus, ICP34.5? lacks the C-terminal conserved GADD34 domain but includes 19 additional amino acids encoded by the intron. Although a fraction of both HSV-2 ICP34.5 proteins are detected in the nucleolus, ICP34.5? is predominantly located in cytoplasm, and ICP34.5? is mainly detected more diffusely in the nucleus. ICP34.5? is unable to counteract PKR-mediated eIF2 phosphorylation but does not interfere with ICP34.5?'s function in this process. Efficient expression of ICP34.5? in cell culture assays is dependent on viral infection or expression of ICP27, a multifunctional immediate-early gene. The effect of ICP27 on the ICP34.5? protein level is attributed to its selective inhibition of ICP34.5 splicing, which results in increased expression of ICP34.5? but a reduced level of ICP34.5?. The C- terminal KH3 domain but not the RNA binding domain of ICP27 is required for its specific inhibition of ICP34.5 splicing and promotion of ICP34.5? expression. Our results suggest that the expression of ICP34.5? and ICP34.5? is tightly regulated in HSV-2 and likely contributes to viral pathogenesis.

SUBMITTER: Tang S

PROVIDER: S-EPMC3648131 | biostudies-literature | 2013 May

REPOSITORIES: biostudies-literature

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Herpes simplex virus 2 expresses a novel form of ICP34.5, a major viral neurovirulence factor, through regulated alternative splicing.

Tang Shuang S Guo Nini N Patel Amita A Krause Philip R PR

Journal of virology 20130313 10

Herpes simplex virus 1 (HSV-1) and HSV-2, two closely related neurotropic human herpesviruses, achieve neurotropism through ICP34.5, a major viral neurovirulence factor. In this report, in addition to the full-length 38-kDa protein (ICP34.5α), we identified a 28-kDa novel form of ICP34.5 (ICP34.5β) in HSV-2-infected cells. ICP34.5β is translated from unspliced ICP34.5 mRNA, with the retained intron introducing a premature stop codon. Thus, ICP34.5β lacks the C-terminal conserved GADD34 domain bu ...[more]

PMID: 23487469

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Project description:Expression of viral genes and activation of innate antiviral responses during infection result in an increase in reactive oxygen species (ROS) and toxic by-products of energy metabolism which can lead to cell death. The mitochondrion and its associated proteins are crucial regulators of these responses and related pathways such as autophagy and apoptosis. Through a mass spectrometry approach, we have shown that the herpes simplex virus 1 (HSV-1) neurovirulence- and autophagy-modulating protein ICP34.5 interacts with numerous mitochondrion-associated factors. Specifically, we showed that amino acids 68 to 87 of ICP34.5, the domain that binds beclin1 and controls neurovirulence, are necessary for interactions with PGAM5, KEAP1, and other regulators of the antioxidant response, mitochondrial trafficking, and programmed cell death. We further show that while this domain interacts with multiple cellular stress response factors, it does not alter apoptosis or antioxidant gene expression. That said, the attenuated replication of a recombinant virus lacking residues 68 to 87 (termed Δ68-87) in primary human fibroblasts was restored by addition of ferric nitrate. Furthermore, in primary mouse neurons, the perinuclear localization of mitochondria that follows infection with HSV-1 was notably absent following Δ68-87 infection. Through this 20-amino-acid domain, ICP34.5 significantly reduces mitochondrial motility in axons of neurons. We propose the hypothesis that ICP34.5 promotes perinuclear mitochondrial localization by modulating transport of mitochondria through interaction with PGAM5. These data expand upon previous observations of altered mitochondrial dynamics following alphaherpesvirus infections and identify a key determinant of this activity during HSV-1 infections.IMPORTANCE Herpes simplex virus persists lifelong in neurons and can reactivate to cause recurrent lesions in mucosal tissues. A key determinant of virulence is the viral protein ICP34.5, of which residues 68 to 87 significantly contribute to neurovirulence through an unknown mechanism. Our report provides evidence that residues 68 to 87 of ICP34.5 are required for binding mitochondrion-associated factors. These interactions alter mitochondrial dynamics in neurons, thereby facilitating viral replication and pathogenesis.

Project description:We described previously an African swine fever virus (ASFV) open reading frame, 23-NL, in the African isolate Malawi Lil 20/1 whose product shared significant similarity in a carboxyl-terminal domain with those of a mouse myeloid differentiation primary response gene, MyD116, and the herpes simplex virus neurovirulence-associated gene, ICP34.5 (M. D. Sussman, Z. Lu, G. Kutish, C. L. Afonso, P. Roberts, and D. L. Rock, J. Virol. 66:5586-5589, 1992). The similarity of 23-NL to these genes suggested that this gene may function in some aspect of ASFV virulence and/or host range. Sequence analysis of additional pathogenic viral isolates demonstrates that this gene is highly conserved among diverse ASFV isolates and that the gene product exists in either a long (184 amino acids as in 23-NL) or a short form (70 to 72 amino acids in other examined ASFV isolates). The short form of the gene, NL-S, encodes the complete highly conserved, hydrophilic, carboxyl-terminal domain of 56 amino acids common to 23-NL, MyD116, and ICP34.5. Recombinant NL-S gene deletion mutants and their revertants were constructed from the pathogenic ASFV isolate E70 and an E70 monkey cell culture-adapted virus, MS44, to study gene function. Although deletion of NL-S did not affect viral growth in primary swine macrophages or Vero cell cultures in vitro, the null mutant, E70/43, exhibited a marked reduction in pig virulence. In contrast to revertant or parental E70 where mortality was 100%, all E70/43-infected animals survived infection. With the exception of a transient fever response, E70/43-infected animals remained clinically normal and exhibited a 1,000-fold reduction in both mean and maximum viremia titers. All convalescent E70/43-infected animals survived infection when challenged with parental E70 at 30 days postinfection. These data indicate that the highly conserved NL-S gene of ASFV, while nonessential for growth in swine macrophages in vitro, is a significant viral virulence factor and may function as a host range gene.

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Dataset Information

Herpes simplex virus 2 expresses a novel form of ICP34.5, a major viral neurovirulence factor, through regulated alternative splicing.

Publications

Herpes simplex virus 2 expresses a novel form of ICP34.5, a major viral neurovirulence factor, through regulated alternative splicing.

Similar Datasets

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