Reovirus Nonstructural Protein σNS Recruits Viral RNA to Replication Organelles
ABSTRACT The function of the mammalian orthoreovirus (reovirus) σNS nonstructural protein is enigmatic. σNS is an RNA-binding protein that forms oligomers and enhances the stability of bound RNAs, but the mechanisms by which it contributes to reovirus replication are unknown. To determine the functi...
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American Society for Microbiology
2021
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oai:doaj.org-article:fbf6adbb4e59406fb675881fcf04dd692021-11-10T18:37:51ZReovirus Nonstructural Protein σNS Recruits Viral RNA to Replication Organelles10.1128/mBio.01408-212150-7511https://doaj.org/article/fbf6adbb4e59406fb675881fcf04dd692021-08-01T00:00:00Zhttps://journals.asm.org/doi/10.1128/mBio.01408-21https://doaj.org/toc/2150-7511ABSTRACT The function of the mammalian orthoreovirus (reovirus) σNS nonstructural protein is enigmatic. σNS is an RNA-binding protein that forms oligomers and enhances the stability of bound RNAs, but the mechanisms by which it contributes to reovirus replication are unknown. To determine the function of σNS-RNA binding in reovirus replication, we engineered σNS mutants deficient in RNA-binding capacity. We found that alanine substitutions of positively charged residues in a predicted RNA-binding domain decrease RNA-dependent oligomerization. To define steps in reovirus replication facilitated by the RNA-binding property of σNS, we established a complementation system in which wild-type or mutant forms of σNS could be tested for the capacity to overcome inhibition of σNS expression. Mutations in σNS that disrupt RNA binding also diminish viral replication and σNS distribution to viral factories. Moreover, viral mRNAs only incorporate into viral factories or factory-like structures (formed following expression of nonstructural protein μNS) when σNS is present and capable of binding RNA. Collectively, these findings indicate that σNS requires positively charged residues in a putative RNA-binding domain to recruit viral mRNAs to sites of viral replication and establish a function for σNS in reovirus replication. IMPORTANCE Viral replication requires the formation of neoorganelles in infected cells to concentrate essential viral and host components. However, for many viruses, it is unclear how these components coalesce into neoorganelles to form factories for viral replication. We discovered that two mammalian reovirus nonstructural proteins act in concert to form functioning viral factories. Reovirus μNS proteins assemble into exclusive factory scaffolds that require reovirus σNS proteins for efficient viral mRNA incorporation. Our results demonstrate a role for σNS in RNA recruitment to reovirus factories and, more broadly, show how a cytoplasmic non-membrane-enclosed factory is formed by an RNA virus. Understanding the mechanisms of viral factory formation will help identify new targets for antiviral therapeutics that disrupt assembly of these structures and inform the use of nonpathogenic viruses for biotechnological applications.Christopher H. LeeKrishnan RaghunathanGwen M. TaylorAndrea J. FrenchRaquel TenorioIsabel Fernández de CastroCristina RiscoJohn S. L. ParkerTerence S. DermodyAmerican Society for MicrobiologyarticlereovirusσNSμNSviral RNA-binding proteinsviral factoriesviral geneticsMicrobiologyQR1-502ENmBio, Vol 12, Iss 4 (2021) |
| institution |
DOAJ |
| collection |
DOAJ |
| language |
EN |
| topic |
reovirus σNS μNS viral RNA-binding proteins viral factories viral genetics Microbiology QR1-502 |
| spellingShingle |
reovirus σNS μNS viral RNA-binding proteins viral factories viral genetics Microbiology QR1-502 Christopher H. Lee Krishnan Raghunathan Gwen M. Taylor Andrea J. French Raquel Tenorio Isabel Fernández de Castro Cristina Risco John S. L. Parker Terence S. Dermody Reovirus Nonstructural Protein σNS Recruits Viral RNA to Replication Organelles |
| description |
ABSTRACT The function of the mammalian orthoreovirus (reovirus) σNS nonstructural protein is enigmatic. σNS is an RNA-binding protein that forms oligomers and enhances the stability of bound RNAs, but the mechanisms by which it contributes to reovirus replication are unknown. To determine the function of σNS-RNA binding in reovirus replication, we engineered σNS mutants deficient in RNA-binding capacity. We found that alanine substitutions of positively charged residues in a predicted RNA-binding domain decrease RNA-dependent oligomerization. To define steps in reovirus replication facilitated by the RNA-binding property of σNS, we established a complementation system in which wild-type or mutant forms of σNS could be tested for the capacity to overcome inhibition of σNS expression. Mutations in σNS that disrupt RNA binding also diminish viral replication and σNS distribution to viral factories. Moreover, viral mRNAs only incorporate into viral factories or factory-like structures (formed following expression of nonstructural protein μNS) when σNS is present and capable of binding RNA. Collectively, these findings indicate that σNS requires positively charged residues in a putative RNA-binding domain to recruit viral mRNAs to sites of viral replication and establish a function for σNS in reovirus replication. IMPORTANCE Viral replication requires the formation of neoorganelles in infected cells to concentrate essential viral and host components. However, for many viruses, it is unclear how these components coalesce into neoorganelles to form factories for viral replication. We discovered that two mammalian reovirus nonstructural proteins act in concert to form functioning viral factories. Reovirus μNS proteins assemble into exclusive factory scaffolds that require reovirus σNS proteins for efficient viral mRNA incorporation. Our results demonstrate a role for σNS in RNA recruitment to reovirus factories and, more broadly, show how a cytoplasmic non-membrane-enclosed factory is formed by an RNA virus. Understanding the mechanisms of viral factory formation will help identify new targets for antiviral therapeutics that disrupt assembly of these structures and inform the use of nonpathogenic viruses for biotechnological applications. |
| format |
article |
| author |
Christopher H. Lee Krishnan Raghunathan Gwen M. Taylor Andrea J. French Raquel Tenorio Isabel Fernández de Castro Cristina Risco John S. L. Parker Terence S. Dermody |
| author_facet |
Christopher H. Lee Krishnan Raghunathan Gwen M. Taylor Andrea J. French Raquel Tenorio Isabel Fernández de Castro Cristina Risco John S. L. Parker Terence S. Dermody |
| author_sort |
Christopher H. Lee |
| title |
Reovirus Nonstructural Protein σNS Recruits Viral RNA to Replication Organelles |
| title_short |
Reovirus Nonstructural Protein σNS Recruits Viral RNA to Replication Organelles |
| title_full |
Reovirus Nonstructural Protein σNS Recruits Viral RNA to Replication Organelles |
| title_fullStr |
Reovirus Nonstructural Protein σNS Recruits Viral RNA to Replication Organelles |
| title_full_unstemmed |
Reovirus Nonstructural Protein σNS Recruits Viral RNA to Replication Organelles |
| title_sort |
reovirus nonstructural protein σns recruits viral rna to replication organelles |
| publisher |
American Society for Microbiology |
| publishDate |
2021 |
| url |
https://doaj.org/article/fbf6adbb4e59406fb675881fcf04dd69 |
| work_keys_str_mv |
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