Virus-Mediated Compartmentalization of the Host Translational Machinery

ABSTRACT Viruses require the host translational apparatus to synthesize viral proteins. Host stress response mechanisms that suppress translation, therefore, represent a significant obstacle that viruses must overcome. Here, we report a strategy whereby the mammalian orthoreoviruses compartmentalize...

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Autores principales:	Emily A. Desmet, Lynne J. Anguish, John S. L. Parker
Formato:	article
Lenguaje:	EN
Publicado:	American Society for Microbiology 2014
Materias:	Microbiology QR1-502
Acceso en línea:	https://doaj.org/article/ad60cb2f176f47c5a4123bd278849a61
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spelling	oai:doaj.org-article:ad60cb2f176f47c5a4123bd278849a612021-11-15T15:45:54ZVirus-Mediated Compartmentalization of the Host Translational Machinery10.1128/mBio.01463-142150-7511https://doaj.org/article/ad60cb2f176f47c5a4123bd278849a612014-10-01T00:00:00Zhttps://journals.asm.org/doi/10.1128/mBio.01463-14https://doaj.org/toc/2150-7511ABSTRACT Viruses require the host translational apparatus to synthesize viral proteins. Host stress response mechanisms that suppress translation, therefore, represent a significant obstacle that viruses must overcome. Here, we report a strategy whereby the mammalian orthoreoviruses compartmentalize the translational machinery within virus-induced inclusions known as viral factories (VF). VF are the sites of reovirus replication and assembly but were thought not to contain ribosomes. It was assumed viral mRNAs exited the VF to undergo translation by the cellular machinery, and proteins reentered the factory to participate in assembly. Here, we used ribopuromycylation to visualize active translation in infected cells. These studies revealed that active translation occurs within VF and that ribosomal subunits and proteins required for translation initiation, elongation, termination, and recycling localize to the factory. Interestingly, we observed components of the 43S preinitiation complex (PIC) concentrating primarily at factory margins, suggesting a spatial and/or dynamic organization of translation within the VF. Similarly, the viral single-stranded RNA binding protein σNS localized to the factory margins and had a tubulovesicular staining pattern that extended a short distance from the margins of the factories and colocalized with endoplasmic reticulum (ER) markers. Consistent with these colocalization studies, σNS was found to associate with both eukaryotic translation initiation factor 3 subunit A (eIF3A) and the ribosomal subunit pS6R. Together, these findings indicate that σNS functions to recruit 43S PIC machinery to the primary site of viral translation within the viral factory. Pathogen-mediated compartmentalization of the translational apparatus provides a novel mechanism by which viruses might avoid host translational suppression. IMPORTANCE Viruses lack biosynthetic capabilities and depend upon the host for protein synthesis. This dependence requires viruses to evolve mechanisms to coerce the host translational machinery into synthesizing viral proteins in the face of ongoing cellular stress responses that suppress global protein synthesis. Reoviruses replicate and assemble within cytoplasmic inclusions called viral factories. However, synthesis of viral proteins was thought to occur in the cytosol. To identify the site(s) of viral translation, we undertook a microscopy-based approach using ribopuromycylation to detect active translation. Here, we report that active translation occurs within viral factories and that translational factors are compartmentalized within factories. Furthermore, we find that the reovirus nonstructural protein σNS associates with 43S preinitiation complexes at the factory margins, suggesting a role for σNS in translation. Together, virus-induced compartmentalization of the host translational machinery represents a strategy for viruses to spatiotemporally couple viral protein synthesis with viral replication and assembly.Emily A. DesmetLynne J. AnguishJohn S. L. ParkerAmerican Society for MicrobiologyarticleMicrobiologyQR1-502ENmBio, Vol 5, Iss 5 (2014)
institution	DOAJ
collection	DOAJ
language	EN
topic	Microbiology QR1-502
spellingShingle	Microbiology QR1-502 Emily A. Desmet Lynne J. Anguish John S. L. Parker Virus-Mediated Compartmentalization of the Host Translational Machinery
description	ABSTRACT Viruses require the host translational apparatus to synthesize viral proteins. Host stress response mechanisms that suppress translation, therefore, represent a significant obstacle that viruses must overcome. Here, we report a strategy whereby the mammalian orthoreoviruses compartmentalize the translational machinery within virus-induced inclusions known as viral factories (VF). VF are the sites of reovirus replication and assembly but were thought not to contain ribosomes. It was assumed viral mRNAs exited the VF to undergo translation by the cellular machinery, and proteins reentered the factory to participate in assembly. Here, we used ribopuromycylation to visualize active translation in infected cells. These studies revealed that active translation occurs within VF and that ribosomal subunits and proteins required for translation initiation, elongation, termination, and recycling localize to the factory. Interestingly, we observed components of the 43S preinitiation complex (PIC) concentrating primarily at factory margins, suggesting a spatial and/or dynamic organization of translation within the VF. Similarly, the viral single-stranded RNA binding protein σNS localized to the factory margins and had a tubulovesicular staining pattern that extended a short distance from the margins of the factories and colocalized with endoplasmic reticulum (ER) markers. Consistent with these colocalization studies, σNS was found to associate with both eukaryotic translation initiation factor 3 subunit A (eIF3A) and the ribosomal subunit pS6R. Together, these findings indicate that σNS functions to recruit 43S PIC machinery to the primary site of viral translation within the viral factory. Pathogen-mediated compartmentalization of the translational apparatus provides a novel mechanism by which viruses might avoid host translational suppression. IMPORTANCE Viruses lack biosynthetic capabilities and depend upon the host for protein synthesis. This dependence requires viruses to evolve mechanisms to coerce the host translational machinery into synthesizing viral proteins in the face of ongoing cellular stress responses that suppress global protein synthesis. Reoviruses replicate and assemble within cytoplasmic inclusions called viral factories. However, synthesis of viral proteins was thought to occur in the cytosol. To identify the site(s) of viral translation, we undertook a microscopy-based approach using ribopuromycylation to detect active translation. Here, we report that active translation occurs within viral factories and that translational factors are compartmentalized within factories. Furthermore, we find that the reovirus nonstructural protein σNS associates with 43S preinitiation complexes at the factory margins, suggesting a role for σNS in translation. Together, virus-induced compartmentalization of the host translational machinery represents a strategy for viruses to spatiotemporally couple viral protein synthesis with viral replication and assembly.
format	article
author	Emily A. Desmet Lynne J. Anguish John S. L. Parker
author_facet	Emily A. Desmet Lynne J. Anguish John S. L. Parker
author_sort	Emily A. Desmet
title	Virus-Mediated Compartmentalization of the Host Translational Machinery
title_short	Virus-Mediated Compartmentalization of the Host Translational Machinery
title_full	Virus-Mediated Compartmentalization of the Host Translational Machinery
title_fullStr	Virus-Mediated Compartmentalization of the Host Translational Machinery
title_full_unstemmed	Virus-Mediated Compartmentalization of the Host Translational Machinery
title_sort	virus-mediated compartmentalization of the host translational machinery
publisher	American Society for Microbiology
publishDate	2014
url	https://doaj.org/article/ad60cb2f176f47c5a4123bd278849a61
work_keys_str_mv	AT emilyadesmet virusmediatedcompartmentalizationofthehosttranslationalmachinery AT lynnejanguish virusmediatedcompartmentalizationofthehosttranslationalmachinery AT johnslparker virusmediatedcompartmentalizationofthehosttranslationalmachinery
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Virus-Mediated Compartmentalization of the Host Translational Machinery

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