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Zhou X, Hou X, Xiao G, Liu B, Jia H, Wei J, Mi X, Guo Q, Wei Y, Zhai SL. Emergence of a Novel G4P[6] Porcine Rotavirus with Unique Sequence Duplication in NSP5 Gene in China. Animals (Basel) 2024; 14:1790. [PMID: 38929409 PMCID: PMC11200575 DOI: 10.3390/ani14121790] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2024] [Revised: 06/12/2024] [Accepted: 06/13/2024] [Indexed: 06/28/2024] Open
Abstract
Rotavirus is a major causative agent of diarrhoea in children, infants, and young animals around the world. The associated zoonotic risk necessitates the serious consideration of the complete genetic information of rotavirus. A segmented genome makes rotavirus prone to rearrangement and the formation of a new viral strain. Monitoring the molecular epidemiology of rotavirus is essential for its prevention and control. The quantitative RT-PCR targeting the NSP5 gene was used to detect rotavirus group A (RVA) in pig faecal samples, and two pairs of universal primers and protocols were used for amplifying the G and P genotype. The genotyping and phylogenetic analysis of 11 genes were performed by RT-PCR and a basic bioinformatics method. A unique G4P[6] rotavirus strain, designated S2CF (RVA/Pig-tc/CHN/S2CF/2023/G4P[6]), was identified in one faecal sample from a piglet with severe diarrhoea in Guangdong, China. Whole genome sequencing and analysis suggested that the 11 segments of the S2CF strain showed a unique Wa-like genotype constellation and a typical porcine RVA genomic configuration of G4-P[6]-I1-R1-C1-M1-A8-N1-T1-E1-H1. Notably, 4 of the 11 gene segments (VP4, VP6, VP2, and NSP5) clustered consistently with human-like RVAs, suggesting independent human-to-porcine interspecies transmission. Moreover, a unique 344-nt duplicated sequence was identified for the first time in the untranslated region of NSP5. This study further reveals the genetic diversity and potential inter-species transmission of porcine rotavirus.
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Affiliation(s)
- Xia Zhou
- Guangdong Provincial Key Laboratory of Livestock Disease Prevention, Institute of Animal Health, Guangdong Academy of Agricultural Sciences, Scientific Observation and Experiment Station of Veterinary Drugs and Diagnostic Techniques of Guangdong Province, Guangzhou 510640, China; (X.Z.); (X.H.); (G.X.); (B.L.); (H.J.)
| | - Xueyan Hou
- Guangdong Provincial Key Laboratory of Livestock Disease Prevention, Institute of Animal Health, Guangdong Academy of Agricultural Sciences, Scientific Observation and Experiment Station of Veterinary Drugs and Diagnostic Techniques of Guangdong Province, Guangzhou 510640, China; (X.Z.); (X.H.); (G.X.); (B.L.); (H.J.)
- College of Veterinary Medicine, Xinjiang Agricultural University, Urumqi 830052, China;
| | - Guifa Xiao
- Guangdong Provincial Key Laboratory of Livestock Disease Prevention, Institute of Animal Health, Guangdong Academy of Agricultural Sciences, Scientific Observation and Experiment Station of Veterinary Drugs and Diagnostic Techniques of Guangdong Province, Guangzhou 510640, China; (X.Z.); (X.H.); (G.X.); (B.L.); (H.J.)
| | - Bo Liu
- Guangdong Provincial Key Laboratory of Livestock Disease Prevention, Institute of Animal Health, Guangdong Academy of Agricultural Sciences, Scientific Observation and Experiment Station of Veterinary Drugs and Diagnostic Techniques of Guangdong Province, Guangzhou 510640, China; (X.Z.); (X.H.); (G.X.); (B.L.); (H.J.)
| | - Handuo Jia
- Guangdong Provincial Key Laboratory of Livestock Disease Prevention, Institute of Animal Health, Guangdong Academy of Agricultural Sciences, Scientific Observation and Experiment Station of Veterinary Drugs and Diagnostic Techniques of Guangdong Province, Guangzhou 510640, China; (X.Z.); (X.H.); (G.X.); (B.L.); (H.J.)
| | - Jie Wei
- Xinjiang Key Laboratory of Animal Infectious Diseases, Institute of Veterinary Medicine, Xinjiang Academy of Animal Sciences, Urumqi 830013, China; (J.W.); (X.M.)
| | - Xiaoyun Mi
- Xinjiang Key Laboratory of Animal Infectious Diseases, Institute of Veterinary Medicine, Xinjiang Academy of Animal Sciences, Urumqi 830013, China; (J.W.); (X.M.)
| | - Qingyong Guo
- College of Veterinary Medicine, Xinjiang Agricultural University, Urumqi 830052, China;
| | - Yurong Wei
- Xinjiang Key Laboratory of Animal Infectious Diseases, Institute of Veterinary Medicine, Xinjiang Academy of Animal Sciences, Urumqi 830013, China; (J.W.); (X.M.)
| | - Shao-Lun Zhai
- Guangdong Provincial Key Laboratory of Livestock Disease Prevention, Institute of Animal Health, Guangdong Academy of Agricultural Sciences, Scientific Observation and Experiment Station of Veterinary Drugs and Diagnostic Techniques of Guangdong Province, Guangzhou 510640, China; (X.Z.); (X.H.); (G.X.); (B.L.); (H.J.)
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Bracci N, Baer A, Flor R, Petraccione K, Stocker T, Zhou W, Ammosova T, Dinglasan RR, Nekhai S, Kehn-Hall K. CK1 and PP1 regulate Rift Valley fever virus genome replication through L protein phosphorylation. Antiviral Res 2024; 226:105895. [PMID: 38679165 DOI: 10.1016/j.antiviral.2024.105895] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2024] [Revised: 04/15/2024] [Accepted: 04/22/2024] [Indexed: 05/01/2024]
Abstract
Rift Valley fever virus (RVFV) is an arbovirus in the Phenuiviridae family identified initially by the large 'abortion storms' observed among ruminants; RVFV can also infect humans. In humans, there is a wide variation of clinical symptoms ranging from subclinical to mild febrile illness to hepatitis, retinitis, delayed-onset encephalitis, or even hemorrhagic fever. The RVFV is a tri-segmented negative-sense RNA virus consisting of S, M, and L segments. The L segment encodes the RNA-dependent RNA polymerase (RdRp), termed the L protein, which is responsible for both viral mRNA synthesis and genome replication. Phosphorylation of viral RdRps is known to regulate viral replication. This study shows that RVFV L protein is serine phosphorylated and identified Casein Kinase 1 alpha (CK1α) and protein phosphatase 1 alpha (PP1α) as L protein binding partners. Inhibition of CK1 and PP1 through small molecule inhibitor treatment, D4476 and 1E7-03, respectively, caused a change in the phosphorylated status of the L protein. Inhibition of PP1α resulted in increased L protein phosphorylation whereas inhibition of CK1α decreased L protein phosphorylation. It was also found that in RVFV infected cells, PP1α localized to the cytoplasmic compartment. Treatment of RVFV infected cells with CK1 inhibitors reduced virus production in both mammalian and mosquito cells. Lastly, inhibition of either CK1 or PP1 reduced viral genomic RNA levels. These data indicate that L protein is phosphorylated and that CK1 and PP1 play a crucial role in regulating the L protein phosphorylation cycle, which is critical to viral RNA production and viral replication.
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Affiliation(s)
- Nicole Bracci
- Department of Biomedical Sciences and Pathobiology, Virginia-Maryland College of Veterinary Medicine, Virginia Polytechnic Institute and State University, Virginia, USA; Center for Emerging, Zoonotic, and Arthropod-borne Pathogens, Virginia Polytechnic Institute and State University, Virginia, USA
| | - Alan Baer
- National Center for Biodefense and Infectious Diseases, School of Systems Biology, George Mason University, Manassas, VA, USA
| | - Rafaela Flor
- Department of Biomedical Sciences and Pathobiology, Virginia-Maryland College of Veterinary Medicine, Virginia Polytechnic Institute and State University, Virginia, USA; Center for Emerging, Zoonotic, and Arthropod-borne Pathogens, Virginia Polytechnic Institute and State University, Virginia, USA
| | - Kaylee Petraccione
- Department of Biomedical Sciences and Pathobiology, Virginia-Maryland College of Veterinary Medicine, Virginia Polytechnic Institute and State University, Virginia, USA; Center for Emerging, Zoonotic, and Arthropod-borne Pathogens, Virginia Polytechnic Institute and State University, Virginia, USA
| | - Timothy Stocker
- Department of Biomedical Sciences and Pathobiology, Virginia-Maryland College of Veterinary Medicine, Virginia Polytechnic Institute and State University, Virginia, USA; Center for Emerging, Zoonotic, and Arthropod-borne Pathogens, Virginia Polytechnic Institute and State University, Virginia, USA
| | - Weidong Zhou
- Center for Applied Proteomics and Molecular Medicine, School of Systems Biology, George Mason University, Manassas, VA, USA
| | - Tatiana Ammosova
- Center for Sickle Cell Disease, Department of Medicine, Howard University, Washington D.C., USA
| | - Rhoel R Dinglasan
- Emerging Pathogens Institute, University of Florida, Florida, USA; Department of Infectious Diseases & Immunology, College of Veterinary Medicine, University of Florida, Florida, USA
| | - Sergei Nekhai
- Center for Sickle Cell Disease, Department of Medicine, Howard University, Washington D.C., USA
| | - Kylene Kehn-Hall
- Department of Biomedical Sciences and Pathobiology, Virginia-Maryland College of Veterinary Medicine, Virginia Polytechnic Institute and State University, Virginia, USA; Center for Emerging, Zoonotic, and Arthropod-borne Pathogens, Virginia Polytechnic Institute and State University, Virginia, USA.
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3
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Nichols SL, Haller C, Borodavka A, Esstman SM. Rotavirus NSP2: A Master Orchestrator of Early Viral Particle Assembly. Viruses 2024; 16:814. [PMID: 38932107 PMCID: PMC11209291 DOI: 10.3390/v16060814] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2024] [Revised: 05/06/2024] [Accepted: 05/16/2024] [Indexed: 06/28/2024] Open
Abstract
Rotaviruses (RVs) are 11-segmented, double-stranded (ds) RNA viruses and important causes of acute gastroenteritis in humans and other animal species. Early RV particle assembly is a multi-step process that includes the assortment, packaging and replication of the 11 genome segments in close connection with capsid morphogenesis. This process occurs inside virally induced, cytosolic, membrane-less organelles called viroplasms. While many viral and cellular proteins play roles during early RV assembly, the octameric nonstructural protein 2 (NSP2) has emerged as a master orchestrator of this key stage of the viral replication cycle. NSP2 is critical for viroplasm biogenesis as well as for the selective RNA-RNA interactions that underpin the assortment of 11 viral genome segments. Moreover, NSP2's associated enzymatic activities might serve to maintain nucleotide pools for use during viral genome replication, a process that is concurrent with early particle assembly. The goal of this review article is to summarize the available data about the structures, functions and interactions of RV NSP2 while also drawing attention to important unanswered questions in the field.
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Affiliation(s)
- Sarah L. Nichols
- Department of Biology, Wake Forest University, Wake Downtown, 455 Vine Street, Winston-Salem, NC 27106, USA;
| | - Cyril Haller
- Department of Chemical Engineering and Biotechnology, Cambridge University, Philippa Fawcett Drive, Cambridge CB3 0AS, UK;
| | - Alexander Borodavka
- Department of Chemical Engineering and Biotechnology, Cambridge University, Philippa Fawcett Drive, Cambridge CB3 0AS, UK;
| | - Sarah M. Esstman
- Department of Biology, Wake Forest University, Wake Downtown, 455 Vine Street, Winston-Salem, NC 27106, USA;
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Vetter J, Lee M, Eichwald C. The Role of the Host Cytoskeleton in the Formation and Dynamics of Rotavirus Viroplasms. Viruses 2024; 16:668. [PMID: 38793550 PMCID: PMC11125917 DOI: 10.3390/v16050668] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2024] [Revised: 04/22/2024] [Accepted: 04/23/2024] [Indexed: 05/26/2024] Open
Abstract
Rotavirus (RV) replicates within viroplasms, membraneless electron-dense globular cytosolic inclusions with liquid-liquid phase properties. In these structures occur the virus transcription, replication, and packaging of the virus genome in newly assembled double-layered particles. The viroplasms are composed of virus proteins (NSP2, NSP5, NSP4, VP1, VP2, VP3, and VP6), single- and double-stranded virus RNAs, and host components such as microtubules, perilipin-1, and chaperonins. The formation, coalescence, maintenance, and perinuclear localization of viroplasms rely on their association with the cytoskeleton. A stabilized microtubule network involving microtubules and kinesin Eg5 and dynein molecular motors is associated with NSP5, NSP2, and VP2, facilitating dynamic processes such as viroplasm coalescence and perinuclear localization. Key post-translation modifications, particularly phosphorylation events of RV proteins NSP5 and NSP2, play pivotal roles in orchestrating these interactions. Actin filaments also contribute, triggering the formation of the viroplasms through the association of soluble cytosolic VP4 with actin and the molecular motor myosin. This review explores the evolving understanding of RV replication, emphasizing the host requirements essential for viroplasm formation and highlighting their dynamic interplay within the host cell.
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Affiliation(s)
| | | | - Catherine Eichwald
- Institute of Virology, University of Zurich, 8057 Zurich, Switzerland; (J.V.); (M.L.)
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5
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Vetter J, Papa G, Tobler K, Rodriguez JM, Kley M, Myers M, Wiesendanger M, Schraner EM, Luque D, Burrone OR, Fraefel C, Eichwald C. The recruitment of TRiC chaperonin in rotavirus viroplasms correlates with virus replication. mBio 2024; 15:e0049924. [PMID: 38470055 PMCID: PMC11005421 DOI: 10.1128/mbio.00499-24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2024] [Accepted: 02/22/2024] [Indexed: 03/13/2024] Open
Abstract
Rotavirus (RV) replication takes place in the viroplasms, cytosolic inclusions that allow the synthesis of virus genome segments and their encapsidation in the core shell, followed by the addition of the second layer of the virion. The viroplasms are composed of several viral proteins, including NSP5, which serves as the main building block. Microtubules, lipid droplets, and miRNA-7 are among the host components recruited in viroplasms. We investigated the interaction between RV proteins and host components of the viroplasms by performing a pull-down assay of lysates from RV-infected cells expressing NSP5-BiolD2. Subsequent tandem mass spectrometry identified all eight subunits of the tailless complex polypeptide I ring complex (TRiC), a cellular chaperonin responsible for folding at least 10% of the cytosolic proteins. Our confirmed findings reveal that TRiC is brought into viroplasms and wraps around newly formed double-layered particles. Chemical inhibition of TRiC and silencing of its subunits drastically reduced virus progeny production. Through direct RNA sequencing, we show that TRiC is critical for RV replication by controlling dsRNA genome segment synthesis, particularly negative-sense single-stranded RNA. Importantly, cryo-electron microscopy analysis shows that TRiC inhibition results in defective virus particles lacking genome segments and polymerase complex (VP1/VP3). Moreover, TRiC associates with VP2 and NSP5 but not with VP1. Also, VP2 is shown to be essential for recruiting TRiC in viroplasms and preserving their globular morphology. This study highlights the essential role of TRiC in viroplasm formation and in facilitating virion assembly during the RV life cycle. IMPORTANCE The replication of rotavirus takes place in cytosolic inclusions termed viroplasms. In these inclusions, the distinct 11 double-stranded RNA genome segments are co-packaged to complete a genome in newly generated virus particles. In this study, we show for the first time that the tailless complex polypeptide I ring complex (TRiC), a cellular chaperonin responsible for the folding of at least 10% of the cytosolic proteins, is a component of viroplasms and is required for the synthesis of the viral negative-sense single-stranded RNA. Specifically, TRiC associates with NSP5 and VP2, the cofactor involved in RNA replication. Our study adds a new component to the current model of rotavirus replication, where TRiC is recruited to viroplasms to assist replication.
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Affiliation(s)
- Janine Vetter
- Institute of Virology, University of Zurich, Zurich, Switzerland
| | - Guido Papa
- Molecular Immunology Lab, International Centre for Genetic Engineering and Biotechnology, Trieste, Italy
| | - Kurt Tobler
- Institute of Virology, University of Zurich, Zurich, Switzerland
| | - Javier M. Rodriguez
- Department of Structure of Macromolecules, Centro Nacional de Biotecnología/CSIC, Cantoblanco, Madrid, Spain
| | - Manuel Kley
- Institute of Virology, University of Zurich, Zurich, Switzerland
| | - Michael Myers
- Proteomics Lab, International Centre for Genetic Engineering and Biotechnology, Trieste, Italy
| | - Mahesa Wiesendanger
- Institute of Virology, University of Zurich, Zurich, Switzerland
- Institute of Veterinary Anatomy, University of Zurich, Zurich, Switzerland
| | - Elisabeth M. Schraner
- Institute of Virology, University of Zurich, Zurich, Switzerland
- Institute of Veterinary Anatomy, University of Zurich, Zurich, Switzerland
| | - Daniel Luque
- School of Biomedical Sciences, The University of New South Wales, Sydney, New South Wales, Australia
- Electron Microscope Unit, Mark Wainwright Analytical Centre, The University of New South Wales, Sydney, New South Wales, Australia
| | - Oscar R. Burrone
- Molecular Immunology Lab, International Centre for Genetic Engineering and Biotechnology, Trieste, Italy
| | - Cornel Fraefel
- Institute of Virology, University of Zurich, Zurich, Switzerland
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Zhao B, Hu L, Kaundal S, Neetu N, Lee CH, Somoulay X, Sankaran B, Taylor GM, Dermody TS, Venkataram Prasad BV. Structure of orthoreovirus RNA chaperone σNS, a component of viral replication factories. Nat Commun 2024; 15:2460. [PMID: 38503747 PMCID: PMC10950856 DOI: 10.1038/s41467-024-46627-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2023] [Accepted: 02/29/2024] [Indexed: 03/21/2024] Open
Abstract
The mammalian orthoreovirus (reovirus) σNS protein is required for formation of replication compartments that support viral genome replication and capsid assembly. Despite its functional importance, a mechanistic understanding of σNS is lacking. We conducted structural and biochemical analyses of a σNS mutant that forms dimers instead of the higher-order oligomers formed by wildtype (WT) σNS. The crystal structure shows that dimers interact with each other using N-terminal arms to form a helical assembly resembling WT σNS filaments in complex with RNA observed using cryo-EM. The interior of the helical assembly is of appropriate diameter to bind RNA. The helical assembly is disrupted by bile acids, which bind to the same site as the N-terminal arm. This finding suggests that the N-terminal arm functions in conferring context-dependent oligomeric states of σNS, which is supported by the structure of σNS lacking an N-terminal arm. We further observed that σNS has RNA chaperone activity likely essential for presenting mRNA to the viral polymerase for genome replication. This activity is reduced by bile acids and abolished by N-terminal arm deletion, suggesting that the activity requires formation of σNS oligomers. Our studies provide structural and mechanistic insights into the function of σNS in reovirus replication.
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Affiliation(s)
- Boyang Zhao
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, TX, USA
| | - Liya Hu
- Verna and Marrs Mclean Department of Biochemistry and Molecular Pharmacology, Baylor College of Medicine, Houston, TX, USA
| | - Soni Kaundal
- Verna and Marrs Mclean Department of Biochemistry and Molecular Pharmacology, Baylor College of Medicine, Houston, TX, USA
| | - Neetu Neetu
- Verna and Marrs Mclean Department of Biochemistry and Molecular Pharmacology, Baylor College of Medicine, Houston, TX, USA
| | - Christopher H Lee
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburg, PA, USA
- Institute of Infection, Inflammation, and Immunity, UPMC Children's Hospital of Pittsburgh, Pittsburg, PA, USA
| | - Xayathed Somoulay
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburg, PA, USA
- Institute of Infection, Inflammation, and Immunity, UPMC Children's Hospital of Pittsburgh, Pittsburg, PA, USA
| | - Banumathi Sankaran
- Berkeley Center for Structural Biology, Molecular Biophysics and Integrated Bioimaging, Lawrence Berkeley Laboratory, Berkeley, CA, USA
| | - Gwen M Taylor
- Institute of Infection, Inflammation, and Immunity, UPMC Children's Hospital of Pittsburgh, Pittsburg, PA, USA
- Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburg, PA, USA
| | - Terence S Dermody
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburg, PA, USA.
- Institute of Infection, Inflammation, and Immunity, UPMC Children's Hospital of Pittsburgh, Pittsburg, PA, USA.
- Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburg, PA, USA.
| | - B V Venkataram Prasad
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, TX, USA.
- Verna and Marrs Mclean Department of Biochemistry and Molecular Pharmacology, Baylor College of Medicine, Houston, TX, USA.
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Liu Z, Smith H, Criglar JM, Valentin AJ, Karandikar U, Zeng XL, Estes MK, Crawford SE. Rotavirus-mediated DGAT1 degradation: A pathophysiological mechanism of viral-induced malabsorptive diarrhea. Proc Natl Acad Sci U S A 2023; 120:e2302161120. [PMID: 38079544 PMCID: PMC10743370 DOI: 10.1073/pnas.2302161120] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2023] [Accepted: 10/11/2023] [Indexed: 12/18/2023] Open
Abstract
Gastroenteritis is among the leading causes of mortality globally in infants and young children, with rotavirus (RV) causing ~258 million episodes of diarrhea and ~128,000 deaths annually in infants and children. RV-induced mechanisms that result in diarrhea are not completely understood, but malabsorption is a contributing factor. RV alters cellular lipid metabolism by inducing lipid droplet (LD) formation as a platform for replication factories named viroplasms. A link between LD formation and gastroenteritis has not been identified. We found that diacylglycerol O-acyltransferase 1 (DGAT1), the terminal step in triacylglycerol synthesis required for LD biogenesis, is degraded in RV-infected cells by a proteasome-mediated mechanism. RV-infected DGAT1-silenced cells show earlier and increased numbers of LD-associated viroplasms per cell that translate into a fourfold-to-fivefold increase in viral yield (P < 0.05). Interestingly, DGAT1 deficiency in children is associated with diarrhea due to altered trafficking of key ion transporters to the apical brush border of enterocytes. Confocal microscopy and immunoblot analyses of RV-infected cells and DGAT1-/- human intestinal enteroids (HIEs) show a decrease in expression of nutrient transporters, ion transporters, tight junctional proteins, and cytoskeletal proteins. Increased phospho-eIF2α (eukaryotic initiation factor 2 alpha) in DGAT1-/- HIEs, and RV-infected cells, indicates a mechanism for malabsorptive diarrhea, namely inhibition of translation of cellular proteins critical for nutrient digestion and intestinal absorption. Our study elucidates a pathophysiological mechanism of RV-induced DGAT1 deficiency by protein degradation that mediates malabsorptive diarrhea, as well as a role for lipid metabolism, in the pathogenesis of gastroenteritis.
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Affiliation(s)
- Zheng Liu
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, TX77030
- Department of Biosciences, Rice University, Houston, TX77005
| | - Hunter Smith
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, TX77030
| | - Jeanette M. Criglar
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, TX77030
| | - Antonio J. Valentin
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, TX77030
| | - Umesh Karandikar
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, TX77030
| | - Xi-Lei Zeng
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, TX77030
| | - Mary K. Estes
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, TX77030
- Department of Medicine, Baylor College of Medicine, Houston, TX77030
| | - Sue E. Crawford
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, TX77030
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Borodavka A, Acker J. Seeing Biomolecular Condensates Through the Lens of Viruses. Annu Rev Virol 2023; 10:163-182. [PMID: 37040799 DOI: 10.1146/annurev-virology-111821-103226] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/13/2023]
Abstract
Phase separation of viral biopolymers is a key factor in the formation of cytoplasmic viral inclusions, known as sites of virus replication and assembly. This review describes the mechanisms and factors that affect phase separation in viral replication and identifies potential areas for future research. Drawing inspiration from studies on cellular RNA-rich condensates, we compare the hierarchical coassembly of ribosomal RNAs and proteins in the nucleolus to the coordinated coassembly of viral RNAs and proteins taking place within viral factories in viruses containing segmented RNA genomes. We highlight the common characteristics of biomolecular condensates in viral replication and how this new understanding is reshaping our views of virus assembly mechanisms. Such studies have the potential to uncover unexplored antiviral strategies targeting these phase-separated states.
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Affiliation(s)
- Alexander Borodavka
- Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom;
| | - Julia Acker
- Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom;
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Zhao B, Hu L, Kuandal S, Neetu N, Lee C, Somoulay X, Sankaran B, Taylor GM, Dermody TS, Prasad BVV. Structure of Orthoreovirus RNA Chaperone σNS, a Component of Viral Replication Factories. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.07.31.551319. [PMID: 37577609 PMCID: PMC10418060 DOI: 10.1101/2023.07.31.551319] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/15/2023]
Abstract
The reovirus σNS RNA-binding protein is required for formation of intracellular compartments during viral infection that support viral genome replication and capsid assembly. Despite its functional importance, a mechanistic understanding of σNS is lacking. We conducted structural and biochemical analyses of an R6A mutant of σNS that forms dimers instead of the higher-order oligomers formed by wildtype (WT) σNS. The crystal structure of selenomethionine-substituted σNS-R6A reveals that the mutant protein forms a stable antiparallel dimer, with each subunit having a well-folded central core and a projecting N-terminal arm. The dimers interact with each other by inserting the N-terminal arms into a hydrophobic pocket of the neighboring dimers on either side to form a helical assembly that resembles filaments of WT σNS in complex with RNA observed using cryo-EM. The interior of the crystallographic helical assembly is positively charged and of appropriate diameter to bind RNA. The helical assembly is disrupted by bile acids, which bind to the same hydrophobic pocket as the N-terminal arm, as demonstrated in the crystal structure of σNS-R6A in complex with bile acid, suggesting that the N-terminal arm functions in conferring context-dependent oligomeric states of σNS. This idea is supported by the structure of σNS lacking the N-terminal arm. We discovered that σNS displays RNA helix destabilizing and annealing activities, likely essential for presenting mRNA to the viral RNA-dependent RNA polymerase for genome replication. The RNA chaperone activity is reduced by bile acids and abolished by N-terminal arm deletion, suggesting that the activity requires formation of σNS oligomers. Our studies provide structural and mechanistic insights into the function of σNS in reovirus replication.
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10
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Asensio-Cob D, Rodríguez JM, Luque D. Rotavirus Particle Disassembly and Assembly In Vivo and In Vitro. Viruses 2023; 15:1750. [PMID: 37632092 PMCID: PMC10458742 DOI: 10.3390/v15081750] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2023] [Revised: 08/11/2023] [Accepted: 08/14/2023] [Indexed: 08/27/2023] Open
Abstract
Rotaviruses (RVs) are non-enveloped multilayered dsRNA viruses that are major etiologic agents of diarrheal disease in humans and in the young in a large number of animal species. The viral particle is composed of three different protein layers that enclose the segmented dsRNA genome and the transcriptional complexes. Each layer defines a unique subparticle that is associated with a different phase of the replication cycle. Thus, while single- and double-layered particles are associated with the intracellular processes of selective packaging, genome replication, and transcription, the viral machinery necessary for entry is located in the third layer. This modular nature of its particle allows rotaviruses to control its replication cycle by the disassembly and assembly of its structural proteins. In this review, we examine the significant advances in structural, molecular, and cellular RV biology that have contributed during the last few years to illuminating the intricate details of the RV particle disassembly and assembly processes.
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Affiliation(s)
- Dunia Asensio-Cob
- Department of Molecular Medicine, Peter Gilgan Centre for Research and Learning, The Hospital for Sick Children, 686 Bay Street, Toronto, ON M5G0A4, Canada;
| | - Javier M. Rodríguez
- Department of Structure of Macromolecules, Centro Nacional de Biotecnología/CSIC, Cantoblanco, 28049 Madrid, Spain
| | - Daniel Luque
- Electron Microscopy Unit UCCT/ISCIII, 28220 Majadahonda, Spain
- School of Biomedical Sciences, The University of New South Wales, Sydney, NSW 2052, Australia
- Electron Microscope Unit, Mark Wainwright Analytical Centre, The University of New South Wales, Sydney, NSW 2052, Australia
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11
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Flexibility of the Rotavirus NSP2 C-Terminal Region Supports Factory Formation via Liquid-Liquid Phase Separation. J Virol 2023; 97:e0003923. [PMID: 36749077 PMCID: PMC9973012 DOI: 10.1128/jvi.00039-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Many viruses sequester the materials needed for their replication into discrete subcellular factories. For rotaviruses (RVs), these factories are called viroplasms, and they are formed in the host cell cytosol via the process of liquid-liquid phase separation (LLPS). The nonstructural protein 2 (NSP2) and its binding partner, nonstructural protein 5 (NSP5), are critical for viroplasm biogenesis. Yet it is not fully understood how NSP2 and NSP5 cooperate to form factories. The C-terminal region (CTR) of NSP2 (residues 291 to 317) is flexible, allowing it to participate in domain-swapping interactions that promote interoctamer interactions and, presumably, viroplasm formation. Molecular dynamics simulations showed that a lysine-to-glutamic acid change at position 294 (K294E) reduces NSP2 CTR flexibility in silico. To test the impact of reduced NSP2 CTR flexibility during infection, we engineered a mutant RV bearing this change (rRV-NSP2K294E). Single-cycle growth assays revealed a >1.2-log reduction in endpoint titers for rRV-NSP2K294E versus the wild-type control (rRV-WT). Using immunofluorescence assays, we found that rRV-NSP2K294E formed smaller, more numerous viroplasms than rRV-WT. Live-cell imaging experiments confirmed these results and revealed that rRV-NSP2K294E factories had delayed fusion kinetics. Moreover, NSP2K294E and several other CTR mutants formed fewer viroplasm-like structures in NSP5 coexpressing cells than did control NSP2WT. Finally, NSP2K294E exhibited defects in its capacity to induce LLPS droplet formation in vitro when incubated alongside NSP5. These results underscore the importance of NSP2 CTR flexibility in supporting the biogenesis of RV factories. IMPORTANCE Viruses often condense the materials needed for their replication into discrete intracellular factories. For rotaviruses, agents of severe gastroenteritis in children, factory formation is mediated in part by an octameric protein called NSP2. A flexible C-terminal region of NSP2 has been proposed to link several NSP2 octamers together, a feature that might be important for factory formation. Here, we created a change in NSP2 that reduced C-terminal flexibility and analyzed the impact on rotavirus factories. We found that the change caused the formation of smaller and more numerous factories that could not readily fuse together like those of the wild-type virus. The altered NSP2 protein also had a reduced capacity to form factory-like condensates in a test tube. Together, these results add to our growing understanding of how NSP2 supports rotavirus factory formation-a key step of viral replication.
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12
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Strauss S, Acker J, Papa G, Desirò D, Schueder F, Borodavka A, Jungmann R. Principles of RNA recruitment to viral ribonucleoprotein condensates in a segmented dsRNA virus. eLife 2023; 12:e68670. [PMID: 36700549 PMCID: PMC9925054 DOI: 10.7554/elife.68670] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2021] [Accepted: 01/26/2023] [Indexed: 01/27/2023] Open
Abstract
Rotaviruses transcribe 11 distinct RNAs that must be co-packaged prior to their replication to make an infectious virion. During infection, nontranslating rotavirus transcripts accumulate in cytoplasmic protein-RNA granules known as viroplasms that support segmented genome assembly and replication via a poorly understood mechanism. Here, we analysed the RV transcriptome by combining DNA-barcoded smFISH of rotavirus-infected cells. Rotavirus RNA stoichiometry in viroplasms appears to be distinct from the cytoplasmic transcript distribution, with the largest transcript being the most enriched in viroplasms, suggesting a selective RNA enrichment mechanism. While all 11 types of transcripts accumulate in viroplasms, their stoichiometry significantly varied between individual viroplasms. Accumulation of transcripts requires the presence of 3' untranslated terminal regions and viroplasmic localisation of the viral polymerase VP1, consistent with the observed lack of polyadenylated transcripts in viroplasms. Our observations reveal similarities between viroplasms and other cytoplasmic RNP granules and identify viroplasmic proteins as drivers of viral RNA assembly during viroplasm formation.
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Affiliation(s)
| | - Julia Acker
- Department of Biochemistry, University of CambridgeCambridgeUnited Kingdom
| | - Guido Papa
- Molecular Immunology Laboratory, International Centre for Genetic Engineering and BiotechnologyTriesteItaly
| | - Daniel Desirò
- Department of Biochemistry, University of CambridgeCambridgeUnited Kingdom
| | - Florian Schueder
- Max Planck Institute of BiochemistryMunichGermany
- Department of Physics and Center for Nanoscience, Ludwig Maximilian UniversityMunichGermany
| | | | - Ralf Jungmann
- Max Planck Institute of BiochemistryMunichGermany
- Department of Physics and Center for Nanoscience, Ludwig Maximilian UniversityMunichGermany
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13
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Rahman SK, Ampah KK, Roy P. Role of NS2 specific RNA binding and phosphorylation in liquid-liquid phase separation and virus assembly. Nucleic Acids Res 2022; 50:11273-11284. [PMID: 36259663 DOI: 10.1093/nar/gkac904] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2022] [Revised: 09/28/2022] [Accepted: 10/08/2022] [Indexed: 11/13/2022] Open
Abstract
Liquid-liquid phase separation (LLPS) has assumed a prominent role in biological cell systems, where it underpins the formation of subcellular compartments necessary for cell function. We investigated the underlying mechanism of LLPS in virus infected cells, where virus inclusion bodies are formed by an RNA-binding phosphoprotein (NS2) of Bluetongue virus to serve as sites for subviral particle assembly and virus maturation. We show that NS2 undergoes LLPS that is dependent on protein phosphorylation and RNA-binding and that LLPS occurrence is accompanied by a change in protein secondary structure. Site-directed mutagenesis identified two critical arginine residues in NS2 responsible for specific RNA binding and thus for NS2-RNA complex driven LLPS. Reverse genetics identified the same residues as essential for VIB assembly in infected cells and virus viability. Our findings suggest that a specific arginine-RNA interaction in the context of a phosphorylated state drives LLPS in this, and possibly other, virus infections.
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Affiliation(s)
- Shah Kamranur Rahman
- Department of Infection Biology, London School of Hygiene and Tropical Medicine, London WC1E 7HT UK
| | - Khamal Kwesi Ampah
- Department of Infection Biology, London School of Hygiene and Tropical Medicine, London WC1E 7HT UK
| | - Polly Roy
- Department of Infection Biology, London School of Hygiene and Tropical Medicine, London WC1E 7HT UK
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14
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Chandra P, Banerjee S, Saha P, Chawla-Sarkar M, Patra U. Sneaking into the viral safe-houses: Implications of host components in regulating integrity and dynamics of rotaviral replication factories. Front Cell Infect Microbiol 2022; 12:977799. [PMID: 36189370 PMCID: PMC9515456 DOI: 10.3389/fcimb.2022.977799] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2022] [Accepted: 08/18/2022] [Indexed: 11/13/2022] Open
Abstract
The biology of the viral life cycle essentially includes two structural and functional entities—the viral genome and protein machinery constituting the viral arsenal and an array of host cellular components which the virus closely associates with—to ensure successful perpetuation. The obligatory requirements of the virus to selectively evade specific host cellular factors while exploiting certain others have been immensely important to provide the platform for designing host-directed antiviral therapeutics. Although the spectrum of host-virus interaction is multifaceted, host factors that particularly influence viral replication have immense therapeutic importance. During lytic proliferation, viruses usually form replication factories which are specialized subcellular structures made up of viral proteins and replicating nucleic acids. These viral niches remain distinct from the rest of the cellular milieu, but they effectively allow spatial proximity to selective host determinants. Here, we will focus on the interaction between the replication compartments of a double stranded RNA virus rotavirus (RV) and the host cellular determinants of infection. RV, a diarrheagenic virus infecting young animals and children, forms replication bodies termed viroplasms within the host cell cytoplasm. Importantly, viroplasms also serve as the site for transcription and early morphogenesis of RVs and are very dynamic in nature. Despite advances in the understanding of RV components that constitute the viroplasmic architecture, knowledge of the contribution of host determinants to viroplasm dynamicity has remained limited. Emerging evidence suggests that selective host determinants are sequestered inside or translocated adjacent to the RV viroplasms. Functional implications of such host cellular reprogramming are also ramifying—disarming the antiviral host determinants and usurping the pro-viral components to facilitate specific stages of the viral life cycle. Here, we will provide a critical update on the wide variety of host cellular pathways that have been reported to regulate the spatial and temporal dynamicity of RV viroplasms. We will also discuss the methods used so far to study the host-viroplasm interactions and emphasize on the potential host factors which can be targeted for therapeutic intervention in the future.
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Affiliation(s)
- Pritam Chandra
- Division of Virology, Indian Council of Medical Research National Institute of Cholera and Enteric Diseases, Kolkata, India
| | - Shreya Banerjee
- Division of Virology, Indian Council of Medical Research National Institute of Cholera and Enteric Diseases, Kolkata, India
| | - Priyanka Saha
- Division of Virology, Indian Council of Medical Research National Institute of Cholera and Enteric Diseases, Kolkata, India
| | - Mamta Chawla-Sarkar
- Division of Virology, Indian Council of Medical Research National Institute of Cholera and Enteric Diseases, Kolkata, India
- *Correspondence: Mamta Chawla-Sarkar, , ; Upayan Patra,
| | - Upayan Patra
- Institute of Biochemistry II, Faculty of Medicine, Goethe University, Frankfurt, Germany
- *Correspondence: Mamta Chawla-Sarkar, , ; Upayan Patra,
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15
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Wang J, Yang J, Lei C, Sun X, Hu J. Phosphorylation of the Autographa californica multiple nucleopolyhedrovirus polyhedron envelope protein plays an important role in the formation of the occlusion body envelope. J Gen Virol 2022; 103. [PMID: 35737520 DOI: 10.1099/jgv.0.001759] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
During the life cycle of a baculovirus, a crystallized protein matrix, formed by polyhedrin (POLH), is produced. The protein matrix is surrounded by a multilayered protein/carbohydrate envelope, and matrix and envelope together form a mature occlusion body (OB). The polyhedron envelope plays an important role in resistance against adverse external environments. The polyhedron envelope protein (PEP) is the main protein that forms the polyhedron envelope, but the mechanism of formation of the polyhedron envelope is unclear. Here, through immunofluorescence localization observations, we found that PEP interacted with both POLH and P10 during formation of the polyhedron envelope in the late stages of infection, and PEP was also required for P10 incorporation on the surface of OBs. In this process, the phosphorylation of PEP played an important role. PEP was determined to be a phosphorylated protein using the Phos-tag technique, and PK1 was determined to be the phosphokinase of PEP by co-immunoprecipitation and in vitro phosphorylation. Immunofluorescence localization revealed that PEP was continuously phosphorylated by PK1 after PEP entered the nucleus until PEP was correctly packaged on the OB surface. Multi-point mutations of PEP conservative potential phosphorylation sites showed that the simultaneous mutation of S85, T86 and Y92 caused changes in the location of PEP and P10 in the late stages of infection, and resulted in an OB surface that lacked the polyhedron envelope. These data suggested that the phosphorylation of PEP at particular sites, i.e. S85, T86 and Y92, plays an important role in the formation of the polyhedron envelope.
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Affiliation(s)
- Jia Wang
- Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, PR China.,University of Chinese Academy of Sciences, Beijing 100049, PR China
| | - Jian Yang
- Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, PR China.,University of Chinese Academy of Sciences, Beijing 100049, PR China
| | - Chengfeng Lei
- Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, PR China
| | - Xiulian Sun
- Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, PR China
| | - Jia Hu
- Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, PR China
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16
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Caragliano E, Brune W, Bosse JB. Herpesvirus Replication Compartments: Dynamic Biomolecular Condensates? Viruses 2022; 14:960. [PMID: 35632702 PMCID: PMC9147375 DOI: 10.3390/v14050960] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2022] [Revised: 04/29/2022] [Accepted: 05/01/2022] [Indexed: 02/01/2023] Open
Abstract
Recent progress has provided clear evidence that many RNA-viruses form cytoplasmic biomolecular condensates mediated by liquid-liquid phase separation to facilitate their replication. In contrast, seemingly contradictory data exist for herpesviruses, which replicate their DNA genomes in nuclear membrane-less replication compartments (RCs). Here, we review the current literature and comment on nuclear condensate formation by herpesviruses, specifically with regard to RC formation. Based on data obtained with human cytomegalovirus (human herpesvirus 5), we propose that liquid and homogenous early RCs convert into more heterogeneous RCs with complex properties over the course of infection. We highlight how the advent of DNA replication leads to the maturation of these biomolecular condensates, likely by adding an additional DNA scaffold.
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Affiliation(s)
- Enrico Caragliano
- Leibniz Institute for Experimental Virology (HPI), 20251 Hamburg, Germany;
- Centre for Structural Systems Biology, 22607 Hamburg, Germany
- Institute of Virology, Hannover Medical School, 30625 Hannover, Germany
- Cluster of Excellence RESIST (EXC 2155), Hannover Medical School, 30625 Hannover, Germany
| | - Wolfram Brune
- Leibniz Institute for Experimental Virology (HPI), 20251 Hamburg, Germany;
- German Center for Infection Research (DZIF), Partner Site Hamburg-Lübeck-Borstel-Riems, 38124 Braunschweig, Germany
| | - Jens B. Bosse
- Leibniz Institute for Experimental Virology (HPI), 20251 Hamburg, Germany;
- Centre for Structural Systems Biology, 22607 Hamburg, Germany
- Institute of Virology, Hannover Medical School, 30625 Hannover, Germany
- Cluster of Excellence RESIST (EXC 2155), Hannover Medical School, 30625 Hannover, Germany
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17
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Criglar JM, Estes MK, Crawford SE. Rotavirus-Induced Lipid Droplet Biogenesis Is Critical for Virus Replication. Front Physiol 2022; 13:836870. [PMID: 35492603 PMCID: PMC9040889 DOI: 10.3389/fphys.2022.836870] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2021] [Accepted: 03/02/2022] [Indexed: 01/14/2023] Open
Abstract
A variety of pathogens, including viruses, bacteria and parasites, target cellular lipid droplets for their replication. Rotaviruses (RVs) infect the villous epithelium of the small intestine and are a major cause of acute gastroenteritis in infants and young children worldwide. RVs induce and require lipid droplets for the formation of viroplasms, sites of virus genome replication, and nascent particle assembly. Here we review the role of lipid droplets in RV replication. Inhibitors of fatty acid synthesis or chemicals that interfere with lipid droplet homeostasis decrease the number and size of viroplasms and the yield of infectious virus. We used a genetically engineered RV, delayed in viroplasm assembly, to show an early interaction of RV nonstructural protein NSP2 and the lipid droplet-associated protein phospho-PLIN1. The interaction between NSP2 and phospho-PLIN1 suggests that we have identified part of the mechanism of RV-induced lipid droplet formation. These studies demonstrate that RV is an excellent model to dissect the cellular process of lipid droplet formation and to determine how RV induces and usurps lipid droplet biogenesis to form viroplasm/lipid droplets for virus replication.
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Affiliation(s)
- Jeanette M Criglar
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, TX, United States
| | - Mary K Estes
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, TX, United States.,Department of Medicine, Baylor College of Medicine, Houston, TX, United States
| | - Sue E Crawford
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, TX, United States
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18
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Geiger F, Acker J, Papa G, Wang X, Arter WE, Saar KL, Erkamp NA, Qi R, Bravo JPK, Strauss S, Krainer G, Burrone OR, Jungmann R, Knowles TPJ, Engelke H, Borodavka A. Liquid-liquid phase separation underpins the formation of replication factories in rotaviruses. EMBO J 2021; 40:e107711. [PMID: 34524703 PMCID: PMC8561643 DOI: 10.15252/embj.2021107711] [Citation(s) in RCA: 51] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2021] [Revised: 08/23/2021] [Accepted: 08/27/2021] [Indexed: 12/29/2022] Open
Abstract
RNA viruses induce the formation of subcellular organelles that provide microenvironments conducive to their replication. Here we show that replication factories of rotaviruses represent protein-RNA condensates that are formed via liquid-liquid phase separation of the viroplasm-forming proteins NSP5 and rotavirus RNA chaperone NSP2. Upon mixing, these proteins readily form condensates at physiologically relevant low micromolar concentrations achieved in the cytoplasm of virus-infected cells. Early infection stage condensates could be reversibly dissolved by 1,6-hexanediol, as well as propylene glycol that released rotavirus transcripts from these condensates. During the early stages of infection, propylene glycol treatments reduced viral replication and phosphorylation of the condensate-forming protein NSP5. During late infection, these condensates exhibited altered material properties and became resistant to propylene glycol, coinciding with hyperphosphorylation of NSP5. Some aspects of the assembly of cytoplasmic rotavirus replication factories mirror the formation of other ribonucleoprotein granules. Such viral RNA-rich condensates that support replication of multi-segmented genomes represent an attractive target for developing novel therapeutic approaches.
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Affiliation(s)
- Florian Geiger
- Department of ChemistryLudwig‐Maximilians‐Universität MünchenMunichGermany
| | - Julia Acker
- Department of BiochemistryUniversity of CambridgeCambridgeUK
| | - Guido Papa
- International Center for Genetic Engineering and BiotechnologyTriesteItaly
- Present address:
Medical Research Council Laboratory of Molecular Biology (MRC LMB)CambridgeUK
| | - Xinyu Wang
- Department of BiochemistryUniversity of CambridgeCambridgeUK
| | | | - Kadi L Saar
- Department of ChemistryUniversity of CambridgeCambridgeUK
| | - Nadia A Erkamp
- Department of ChemistryUniversity of CambridgeCambridgeUK
| | - Runzhang Qi
- Department of ChemistryUniversity of CambridgeCambridgeUK
| | - Jack PK Bravo
- Department of BiochemistryUniversity of CambridgeCambridgeUK
- Present address:
Department of Molecular BiosciencesUniversity of Texas at AustinAustinTXUSA
| | - Sebastian Strauss
- Department of Physics and Center for NanoscienceMax Planck Institute of BiochemistryMunichGermany
| | - Georg Krainer
- Department of ChemistryUniversity of CambridgeCambridgeUK
| | - Oscar R Burrone
- International Center for Genetic Engineering and BiotechnologyTriesteItaly
| | - Ralf Jungmann
- Department of Physics and Center for NanoscienceMax Planck Institute of BiochemistryMunichGermany
| | | | - Hanna Engelke
- Department of ChemistryLudwig‐Maximilians‐Universität MünchenMunichGermany
- Institute of Pharmaceutical SciencesKarl‐Franzens‐Universität GrazGrazAustria
| | - Alexander Borodavka
- Department of ChemistryLudwig‐Maximilians‐Universität MünchenMunichGermany
- Department of BiochemistryUniversity of CambridgeCambridgeUK
- Department of Physics and Center for NanoscienceMax Planck Institute of BiochemistryMunichGermany
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19
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Rotaviral nonstructural protein 5 (NSP5) promotes proteasomal degradation of up-frameshift protein 1 (UPF1), a principal mediator of nonsense-mediated mRNA decay (NMD) pathway, to facilitate infection. Cell Signal 2021; 89:110180. [PMID: 34718106 DOI: 10.1016/j.cellsig.2021.110180] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2021] [Revised: 10/22/2021] [Accepted: 10/25/2021] [Indexed: 11/23/2022]
Abstract
Nonsense-mediated mRNA decay (NMD), a cellular RNA quality system, has been shown to be an ancestral form of cellular antiviral response that can restrict viral infection by targeting viral RNA for degradation or other various mechanisms. In support to this hypothesis, emerging evidences unraveled that viruses have evolved numerous mechanisms to circumvent or modulate the NMD pathway to ensure unhindered replication within the host cell. In this study, we investigated the potential interplay between the cellular NMD pathway and rotavirus (RV). Our data suggested that rotavirus infection resulted in global inhibition of NMD pathway by downregulating the expression of UPF1 in a strain independent manner. UPF1 expression was found to be regulated at the post-transcriptional level by ubiquitin-proteasome mediated degradation pathway. Subsequent studies revealed rotaviral non-structural protein 5 (NSP5) associates with UPF1 and promotes its cullin-dependent proteasome mediated degradation. Furthermore, ectopic expression of UPF1 during RV infection resulted in reduced expression of viral proteins and viral RNAs leading to diminished production of infective rotavirus particles, suggesting the anti-rotaviral role of UPF1. Finally, the delayed degradation kinetics of transfected rotaviral RNA in UPF1 and UPF2 depleted cells and the association of UPF1 and UPF2 with viral RNAs suggested that NMD targets rotaviral RNAs for degradation. Collectively, the present study demonstrates the antiviral role of NMD pathway during rotavirus infection and also reveals the underlying mechanism by which rotavirus overwhelms NMD pathway to establish successful replication.
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20
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Caddy S, Papa G, Borodavka A, Desselberger U. Rotavirus research: 2014-2020. Virus Res 2021; 304:198499. [PMID: 34224769 DOI: 10.1016/j.virusres.2021.198499] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2021] [Revised: 06/24/2021] [Accepted: 06/25/2021] [Indexed: 02/09/2023]
Abstract
Rotaviruses are major causes of acute gastroenteritis in infants and young children worldwide and also cause disease in the young of many other mammalian and of avian species. During the recent 5-6 years rotavirus research has benefitted in a major way from the establishment of plasmid only-based reverse genetics systems, the creation of human and other mammalian intestinal enteroids, and from the wide application of structural biology (cryo-electron microscopy, cryo-EM tomography) and complementary biophysical approaches. All of these have permitted to gain new insights into structure-function relationships of rotaviruses and their interactions with the host. This review follows different stages of the viral replication cycle and summarizes highlights of structure-function studies of rotavirus-encoded proteins (both structural and non-structural), molecular mechanisms of viral replication including involvement of cellular proteins and lipids, the spectrum of viral genomic and antigenic diversity, progress in understanding of innate and acquired immune responses, and further developments of prevention of rotavirus-associated disease.
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Affiliation(s)
- Sarah Caddy
- Cambridge Institute for Therapeutic Immunology and Infectious Disease Jeffery Cheah Biomedical Centre, Cambridge, CB2 0AW, UK.
| | - Guido Papa
- MRC Laboratory of Molecular Biology, Cambridge Biomedical Campus Francis Crick Avenue, Cambridge, CB2 0QH, UK.
| | - Alexander Borodavka
- Department of Biochemistry, University of Cambridge, Cambridge, CB2 1QW, UK.
| | - Ulrich Desselberger
- Department of Medicine, University of Cambridge, Addenbrooke's Hospital, Cambridge CB2 0QQ, UK.
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21
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Bravo JPK, Bartnik K, Venditti L, Acker J, Gail EH, Colyer A, Davidovich C, Lamb DC, Tuma R, Calabrese AN, Borodavka A. Structural basis of rotavirus RNA chaperone displacement and RNA annealing. Proc Natl Acad Sci U S A 2021; 118:e2100198118. [PMID: 34615715 PMCID: PMC8521686 DOI: 10.1073/pnas.2100198118] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/12/2021] [Indexed: 01/13/2023] Open
Abstract
Rotavirus genomes are distributed between 11 distinct RNA molecules, all of which must be selectively copackaged during virus assembly. This likely occurs through sequence-specific RNA interactions facilitated by the RNA chaperone NSP2. Here, we report that NSP2 autoregulates its chaperone activity through its C-terminal region (CTR) that promotes RNA-RNA interactions by limiting its helix-unwinding activity. Unexpectedly, structural proteomics data revealed that the CTR does not directly interact with RNA, while accelerating RNA release from NSP2. Cryo-electron microscopy reconstructions of an NSP2-RNA complex reveal a highly conserved acidic patch on the CTR, which is poised toward the bound RNA. Virus replication was abrogated by charge-disrupting mutations within the acidic patch but completely restored by charge-preserving mutations. Mechanistic similarities between NSP2 and the unrelated bacterial RNA chaperone Hfq suggest that accelerating RNA dissociation while promoting intermolecular RNA interactions may be a widespread strategy of RNA chaperone recycling.
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Affiliation(s)
- Jack P K Bravo
- Department of Biochemistry, University of Cambridge, Cambridge CB2 1QW, United Kingdom
- Astbury Centre for Structural Molecular Biology, School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, LS2 9JT Leeds, United Kingdom
| | - Kira Bartnik
- Department of Chemistry, Center for NanoScience, Nanosystems Initiative Munich, Centre for Integrated Protein Science Munich, Ludwig Maximilian University of Munich, D-81377 Munich, Germany
| | - Luca Venditti
- Department of Biochemistry, University of Cambridge, Cambridge CB2 1QW, United Kingdom
| | - Julia Acker
- Department of Biochemistry, University of Cambridge, Cambridge CB2 1QW, United Kingdom
| | - Emma H Gail
- Department of Biochemistry and Molecular Biology, Biomedicine Discovery Institute, Faculty of Medicine, Nursing and Health Sciences, Monash University, Clayton, VIC 3800, Australia
- Australian Research Council (ARC) Centre of Excellence in Advanced Molecular Imaging, European Molecular Biology Laboratory (EMBL) Australia, Clayton, VIC 3800, Australia
| | - Alice Colyer
- Astbury Centre for Structural Molecular Biology, School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, LS2 9JT Leeds, United Kingdom
| | - Chen Davidovich
- Department of Biochemistry and Molecular Biology, Biomedicine Discovery Institute, Faculty of Medicine, Nursing and Health Sciences, Monash University, Clayton, VIC 3800, Australia
- Australian Research Council (ARC) Centre of Excellence in Advanced Molecular Imaging, European Molecular Biology Laboratory (EMBL) Australia, Clayton, VIC 3800, Australia
| | - Don C Lamb
- Department of Chemistry, Center for NanoScience, Nanosystems Initiative Munich, Centre for Integrated Protein Science Munich, Ludwig Maximilian University of Munich, D-81377 Munich, Germany
| | - Roman Tuma
- Astbury Centre for Structural Molecular Biology, School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, LS2 9JT Leeds, United Kingdom
- Faculty of Science, University of South Bohemia, 370 05 Ceske Budejovice, Czech Republic
| | - Antonio N Calabrese
- Astbury Centre for Structural Molecular Biology, School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, LS2 9JT Leeds, United Kingdom
| | - Alexander Borodavka
- Department of Biochemistry, University of Cambridge, Cambridge CB2 1QW, United Kingdom;
- Astbury Centre for Structural Molecular Biology, School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, LS2 9JT Leeds, United Kingdom
- Department of Chemistry, Center for NanoScience, Nanosystems Initiative Munich, Centre for Integrated Protein Science Munich, Ludwig Maximilian University of Munich, D-81377 Munich, Germany
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22
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Development of Nanobodies against Mal de Río Cuarto virus major viroplasm protein P9-1 for diagnostic sandwich ELISA and immunodetection. Sci Rep 2021; 11:20013. [PMID: 34625580 PMCID: PMC8501053 DOI: 10.1038/s41598-021-99275-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2021] [Accepted: 09/13/2021] [Indexed: 02/08/2023] Open
Abstract
Mal de Río Cuarto virus (MRCV) is a member of the genus Fijivirus of the family Reoviridae that causes a devastating disease in maize and is persistently and propagatively transmitted by planthopper vectors. Virus replication and assembly occur within viroplasms formed by viral and host proteins. This work describes the isolation and characterization of llama-derived Nanobodies (Nbs) recognizing the major viral viroplasm component, P9-1. Specific Nbs were selected against recombinant P9-1, with affinities in the nanomolar range as measured by surface plasmon resonance. Three selected Nbs were fused to alkaline phosphatase and eGFP to develop a sandwich ELISA test which showed a high diagnostic sensitivity (99.12%, 95% CI 95.21-99.98) and specificity (100%, 95% CI 96.31-100) and a detection limit of 0.236 ng/ml. Interestingly, these Nanobodies recognized different P9-1 conformations and were successfully employed to detect P9-1 in pull-down assays of infected maize extracts. Finally, we demonstrated that fusions of the Nbs to eGFP and RFP allowed the immunodetection of virus present in phloem cells of leaf thin sections. The Nbs developed in this work will aid the study of MRCV epidemiology, assist maize breeding programs, and be valuable tools to boost fundamental research on viroplasm structure and maturation.
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RNA Origami: Packaging a Segmented Genome in Orbivirus Assembly and Replication. Viruses 2021; 13:v13091841. [PMID: 34578422 PMCID: PMC8473007 DOI: 10.3390/v13091841] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2021] [Revised: 09/07/2021] [Accepted: 09/11/2021] [Indexed: 01/04/2023] Open
Abstract
Understanding how viruses with multi-segmented genomes incorporate one copy of each segment into their capsids remains an intriguing question. Here, we review our recent progress and describe the advancements made in understanding the genome packaging mechanism of a model nonenveloped virus, Bluetongue virus (BTV), with a 10-segment (S1–S10) double-strand RNA (dsRNA) genome. BTV (multiple serotypes), a member of the Orbivirus genus in the Reoviridae family, is a notable pathogen for livestock and is responsible for significant economic losses worldwide. This has enabled the creation of an extensive set of reagents and assays, including reverse genetics, cell-free RNA packaging, and bespoke bioinformatics approaches, which can be directed to address the packaging question. Our studies have shown that (i) UTRs enable the conformation of each segment necessary for the next level of RNA–RNA interaction; (ii) a specific order of intersegment interactions leads to a complex RNA network containing all the active components in sorting and packaging; (iii) networked segments are recruited into nascent assembling capsids; and (iv) select capsid proteins might be involved in the packaging process. The key features of genome packaging mechanisms for BTV and related dsRNA viruses are novel and open up new avenues of potential intervention.
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Rotavirus viroplasm biogenesis involves microtubule-based dynein transport mediated by an interaction between NSP2 and dynein intermediate chain. J Virol 2021; 95:e0124621. [PMID: 34379449 DOI: 10.1128/jvi.01246-21] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Rotaviruses are the causative agents of severe and dehydrating gastroenteritis in children, piglets, and many other young animals. They replicate their genomes and assemble double-layered particles in cytoplasmic electron-dense inclusion bodies called 'viroplasms'. The formation of viroplasms is reportedly associated with the stability of microtubules. Although material transport is an important function of microtubules, whether and how microtubule-based transport influences the formation of viroplasms is still unclear. Here, we demonstrate that the small viroplasms move and fuse in living cells. We show that microtubule-based dynein transport affects rotavirus infection, viroplasm formation, and the assembly of transient enveloped particles (TEPs) and triple-layered particles (TLPs). The dynein intermediate chain (DIC) is shown to localize in the viroplasm and to interact directly with non-structural protein 2 (NSP2), indicating that DIC is responsible for connecting the viroplasm to dynein. The WD40 repeat domain of DIC regulates the interaction between DIC and NSP2, and the knockdown of DIC inhibited rotaviral infection, viroplasm formation, and the assembly of TEPs and TLPs. Our findings show that rotavirus viroplasms hijack dynein transport for fusion events, required for maximal assembly of infectious viral progeny. This study provides novel insights into the intracellular transport of viroplasms, which is involved in their biogenesis. Importance Because the viroplasm is the viral factory for rotavirus replication, viroplasm formation undoubtedly determines the effective production of progeny rotavirus. Therefore, understanding the virus-host interactions involved in the biogenesis of the viroplasm is critical for the future development of prophylactic and therapeutic strategies. Previous studies have reported that the formation of viroplasms is associated with the stability of microtubules, whereas little is known about its specific mechanism. Here, we demonstrate that rotavirus viroplasm formation takes advantage of microtubule-based dynein transport mediated by an interaction between NSP2 and DIC. These findings provide new insight into the intracellular transport of viroplasms.
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Papa G, Borodavka A, Desselberger U. Viroplasms: Assembly and Functions of Rotavirus Replication Factories. Viruses 2021; 13:1349. [PMID: 34372555 PMCID: PMC8310052 DOI: 10.3390/v13071349] [Citation(s) in RCA: 37] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2021] [Revised: 07/08/2021] [Accepted: 07/09/2021] [Indexed: 02/07/2023] Open
Abstract
Viroplasms are cytoplasmic, membraneless structures assembled in rotavirus (RV)-infected cells, which are intricately involved in viral replication. Two virus-encoded, non-structural proteins, NSP2 and NSP5, are the main drivers of viroplasm formation. The structures (as far as is known) and functions of these proteins are described. Recent studies using plasmid-only-based reverse genetics have significantly contributed to elucidation of the crucial roles of these proteins in RV replication. Thus, it has been recognized that viroplasms resemble liquid-like protein-RNA condensates that may be formed via liquid-liquid phase separation (LLPS) of NSP2 and NSP5 at the early stages of infection. Interactions between the RNA chaperone NSP2 and the multivalent, intrinsically disordered protein NSP5 result in their condensation (protein droplet formation), which plays a central role in viroplasm assembly. These droplets may provide a unique molecular environment for the establishment of inter-molecular contacts between the RV (+)ssRNA transcripts, followed by their assortment and equimolar packaging. Future efforts to improve our understanding of RV replication and genome assortment in viroplasms should focus on their complex molecular composition, which changes dynamically throughout the RV replication cycle, to support distinct stages of virion assembly.
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Affiliation(s)
- Guido Papa
- MRC Laboratory of Molecular Biology, Cambridge Biomedical Campus, Cambridge CB2 0QH, UK;
| | | | - Ulrich Desselberger
- Department of Medicine, Addenbrooke’s Hospital, University of Cambridge, Cambridge CB2 0QQ, UK
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Patra U, Mukhopadhyay U, Mukherjee A, Dutta S, Chawla-Sarkar M. Treading a HOSTile path: Mapping the dynamic landscape of host cell-rotavirus interactions to explore novel host-directed curative dimensions. Virulence 2021; 12:1022-1062. [PMID: 33818275 PMCID: PMC8023246 DOI: 10.1080/21505594.2021.1903198] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Viruses are intracellular pathogens and are dependent on host cellular resources to carry out their cycles of perpetuation. Obtaining an integrative view of host-virus interaction is of utmost importance to understand the complex and dynamic interplay between viral components and host machineries. Besides its obvious scholarly significance, a comprehensive host-virus interaction profile also provides a platform where from host determinants of pro-viral and antiviral importance can be identified and further be subjected to therapeutic intervention. Therefore, adjunct to conventional methods of prophylactic vaccination and virus-directed antivirals, this host-targeted antiviral approach holds promising therapeutic potential. In this review, we present a comprehensive landscape of host cellular reprogramming in response to infection with rotavirus (RV) which causes profuse watery diarrhea in neonates and infants. In addition, an emphasis is given on how host determinants are either usurped or subverted by RV in course of infection and how therapeutic manipulation of specific host factors can effectively modulate the RV life cycle.
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Affiliation(s)
- Upayan Patra
- Division of Virology, National Institute of Cholera and Enteric Diseases, Beliaghata, Kolkata, India
| | - Urbi Mukhopadhyay
- Division of Virology, National Institute of Cholera and Enteric Diseases, Beliaghata, Kolkata, India
| | - Arpita Mukherjee
- Division of Virology, National Institute of Cholera and Enteric Diseases, Beliaghata, Kolkata, India
| | - Shanta Dutta
- Division of Bacteriology, National Institute of Cholera and Enteric Diseases, Beliaghata, Kolkata, India
| | - Mamta Chawla-Sarkar
- Division of Virology, National Institute of Cholera and Enteric Diseases, Beliaghata, Kolkata, India
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Kanai Y, Kobayashi T. Rotavirus reverse genetics systems: Development and application. Virus Res 2021; 295:198296. [PMID: 33440223 DOI: 10.1016/j.virusres.2021.198296] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2020] [Revised: 12/31/2020] [Accepted: 01/05/2021] [Indexed: 12/14/2022]
Abstract
Rotaviruses (RVs) cause acute gastroenteritis in infants and young children. Since 2006, live-attenuated vaccines have reduced the number of RV-associated deaths; however, RV is still responsible for an estimated 228,047 annual deaths worldwide. RV, a member of the family Reoviridae, has an 11-segmented double-stranded RNA genome contained within a non-enveloped, triple layered virus particle. In 2017, a long-awaited helper virus-free reverse genetics system for RV was established. Since then, numerous studies have reported the generation of recombinant RVs; these studies verify the robustness of reverse genetics systems. This review provides technical insight into current reverse genetics systems for RVs, as well as discussing basic and applied studies that have used these systems.
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Affiliation(s)
- Yuta Kanai
- Department of Virology, Research Institute for Microbial Diseases, Osaka University, 3-1 Yamadaoka, Suita, Osaka, 565-0871, Japan.
| | - Takeshi Kobayashi
- Department of Virology, Research Institute for Microbial Diseases, Osaka University, 3-1 Yamadaoka, Suita, Osaka, 565-0871, Japan.
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Criglar JM, Crawford SE, Estes MK. Plasmid-based reverse genetics for probing phosphorylation-dependent viroplasm formation in rotaviruses. Virus Res 2020; 291:198193. [PMID: 33053412 DOI: 10.1016/j.virusres.2020.198193] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2020] [Revised: 10/02/2020] [Accepted: 10/07/2020] [Indexed: 01/15/2023]
Abstract
Rotavirus (RV) replication occurs in cytoplasmic compartments, known as viroplasms, that are composed of viral and cellular proteins. Viroplasm formation requires RV nonstructural proteins NSP2 and NSP5 and cellular lipid droplets (LDs); however, the mechanisms required for viroplasm assembly remain largely unknown. We previously identified two conformationally-distinct forms of NSP2 (dNSP2, vNSP2) found in RV-infected cells that interact differentially with hypo- and hyperphosphorylated NSP5, respectively, and indicate a coordinated phosphorylation-dependent mechanism regulating viroplasm assembly. We also reported that phosphorylation of dNSP2 on serine 313 by the cellular kinase CK1α triggers the localization of vNSP2 to sites of viroplasm assembly and its association with hyperphosphorylated NSP5. To directly evaluate the role of CK1α-mediated NSP2 phosphorylation on viroplasm formation, we used a recently published plasmid-based reverse genetics method to generate a recombinant rotavirus (rRV) with a phosphomimetic NSP2 mutation (rRV NSP2 S313D). The rRV NSP2 S313D virus is significantly delayed in viroplasm formation, virus replication, and interferes with wild type RV replication during co-infection. The rRV NSP2 S313A virus was not rescued. Taking advantage of the delay in viroplasm formation, the NSP2 S313D phosphomimetic mutant was used as a tool to observe very early events in viroplasm assembly. We show that (1) viroplasm assembly correlates with NSP5 hyperphosphorylation, and (2) that vNSP2 S313D co-localizes with RV-induced LDs without NSP5, suggesting that vNSP2 phospho-S313 is sufficient for interacting with LDs and may be the virus factor required for RV-induced LD formation. Further studies with the rRV NSP2 S313D virus are expected to reveal new aspects of viroplasm and LD initiation and assembly.
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Affiliation(s)
- Jeanette M Criglar
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, TX 77030, United States
| | - Sue E Crawford
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, TX 77030, United States
| | - Mary K Estes
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, TX 77030, United States; Department of Medicine, Divisions of Gastroenterology and Hepatology and Infectious Diseases, Baylor College of Medicine, Houston, TX 77030, United States.
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A Calcium Sensor Discovered in Bluetongue Virus Nonstructural Protein 2 Is Critical for Virus Replication. J Virol 2020; 94:JVI.01099-20. [PMID: 32759321 PMCID: PMC7527055 DOI: 10.1128/jvi.01099-20] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2020] [Accepted: 07/29/2020] [Indexed: 12/20/2022] Open
Abstract
After entering the host cells, viruses use cellular host factors to ensure a successful virus replication process. For replication in infected cells, members of the Reoviridae family form inclusion body-like structures known as viral inclusion bodies (VIB) or viral factories. Bluetongue virus (BTV) forms VIBs in infected cells through nonstructural protein 2 (NS2), a phosphoprotein. An important regulatory factor critical for VIB formation is phosphorylation of NS2. In our study, we discovered a characteristic calcium-binding EF-hand-like motif in NS2 and found that the calcium binding preferentially affects phosphorylation level of the NS2 and has a role in regulating VIB assembly. Many viruses use specific viral proteins to bind calcium ions (Ca2+) for stability or to modify host cell pathways; however, to date, no Ca2+ binding protein has been reported in bluetongue virus (BTV), the causative agent of bluetongue disease in livestock. Here, using a comprehensive bioinformatics screening, we identified a putative EF-hand-like Ca2+ binding motif in the carboxyl terminal region of BTV nonstructural phosphoprotein 2 (NS2). Subsequently, using a recombinant NS2, we demonstrated that NS2 binds Ca2+ efficiently and that Ca2+ binding was perturbed when the Asp and Glu residues in the motif were substituted by alanine. Using circular dichroism analysis, we found that Ca2+ binding by NS2 triggered a helix-to-coil secondary structure transition. Further, cryo-electron microscopy in the presence of Ca2+ revealed that NS2 forms helical oligomers which, when aligned with the N-terminal domain crystal structure, suggest an N-terminal domain that wraps around the C-terminal domain in the oligomer. Further, an in vitro kinase assay demonstrated that Ca2+ enhanced the phosphorylation of NS2 significantly. Importantly, mutations introduced at the Ca2+ binding site in the viral genome by reverse genetics failed to allow recovery of viable virus, and the NS2 phosphorylation level and assembly of viral inclusion bodies (VIBs) were reduced. Together, our data suggest that NS2 is a dedicated Ca2+ binding protein and that calcium sensing acts as a trigger for VIB assembly, which in turn facilitates virus replication and assembly. IMPORTANCE After entering the host cells, viruses use cellular host factors to ensure a successful virus replication process. For replication in infected cells, members of the Reoviridae family form inclusion body-like structures known as viral inclusion bodies (VIB) or viral factories. Bluetongue virus (BTV) forms VIBs in infected cells through nonstructural protein 2 (NS2), a phosphoprotein. An important regulatory factor critical for VIB formation is phosphorylation of NS2. In our study, we discovered a characteristic calcium-binding EF-hand-like motif in NS2 and found that the calcium binding preferentially affects phosphorylation level of the NS2 and has a role in regulating VIB assembly.
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Yun T, Hua J, Ye W, Ni Z, Chen L, Zhang C. The phosphoproteomic responses of duck (Cairna moschata) to classical/novel duck reovirus infections in the spleen tissue. Sci Rep 2020; 10:15315. [PMID: 32943705 PMCID: PMC7499213 DOI: 10.1038/s41598-020-72311-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2019] [Accepted: 08/05/2020] [Indexed: 12/18/2022] Open
Abstract
Duck reovirus (DRV) is a fatal member of the genus Orthoreovirus in the family Reoviridae. The disease caused by DRV leads to huge economic losses to the duck industry. Post-translational modification is an efficient strategy to enhance the immune responses to virus infection. However, the roles of protein phosphorylation in the responses of ducklings to Classic/Novel DRV (C/NDRV) infections are largely unknown. Using a high-resolution LC–MS/MS integrated to highly sensitive immune-affinity antibody method, phosphoproteomes of Cairna moschata spleen tissues under the C/NDRV infections were analyzed, producing a total of 8,504 phosphorylation sites on 2,853 proteins. After normalization with proteomic data, 392 sites on 288 proteins and 484 sites on 342 proteins were significantly changed under the C/NDRV infections, respectively. To characterize the differentially phosphorylated proteins (DPPs), a systematic bioinformatics analyses including Gene Ontology annotation, domain annotation, subcellular localization, and Kyoto Encyclopedia of Genes and Genomes pathway annotation were performed. Two important serine protease system-related proteins, coagulation factor X and fibrinogen α-chain, were identified as phosphorylated proteins, suggesting an involvement of blood coagulation under the C/NDRV infections. Furthermore, 16 proteins involving the intracellular signaling pathways of pattern-recognition receptors were identified as phosphorylated proteins. Changes in the phosphorylation levels of MyD88, NF-κB, RIP1, MDA5 and IRF7 suggested a crucial role of protein phosphorylation in host immune responses of C. moschata. Our study provides new insights into the responses of ducklings to the C/NDRV infections at PTM level.
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Affiliation(s)
- Tao Yun
- Institute of Animal Husbandry and Veterinary Sciences, Zhejiang Academy of Agricultural Sciences, Hangzhou, 310021, China
| | - Jionggang Hua
- Institute of Animal Husbandry and Veterinary Sciences, Zhejiang Academy of Agricultural Sciences, Hangzhou, 310021, China
| | - Weicheng Ye
- Institute of Animal Husbandry and Veterinary Sciences, Zhejiang Academy of Agricultural Sciences, Hangzhou, 310021, China
| | - Zheng Ni
- Institute of Animal Husbandry and Veterinary Sciences, Zhejiang Academy of Agricultural Sciences, Hangzhou, 310021, China
| | - Liu Chen
- Institute of Animal Husbandry and Veterinary Sciences, Zhejiang Academy of Agricultural Sciences, Hangzhou, 310021, China
| | - Cun Zhang
- Institute of Animal Husbandry and Veterinary Sciences, Zhejiang Academy of Agricultural Sciences, Hangzhou, 310021, China.
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Criglar JM, Crawford SE, Zhao B, Smith HG, Stossi F, Estes MK. A Genetically Engineered Rotavirus NSP2 Phosphorylation Mutant Impaired in Viroplasm Formation and Replication Shows an Early Interaction between vNSP2 and Cellular Lipid Droplets. J Virol 2020; 94:e00972-20. [PMID: 32461314 PMCID: PMC7375380 DOI: 10.1128/jvi.00972-20] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2020] [Accepted: 05/21/2020] [Indexed: 12/18/2022] Open
Abstract
Many RNA viruses replicate in cytoplasmic compartments (virus factories or viroplasms) composed of viral and cellular proteins, but the mechanisms required for their formation remain largely unknown. Rotavirus (RV) replication in viroplasms requires interactions between virus nonstructural proteins NSP2 and NSP5, which are associated with components of lipid droplets (LDs). We previously identified two forms of NSP2 in RV-infected cells, a cytoplasmically dispersed form (dNSP2) and a viroplasm-specific form (vNSP2), which interact with hypophosphorylated and hyperphosphorylated NSP5, respectively, indicating that a coordinated phosphorylation cascade controls viroplasm assembly. The cellular kinase CK1α phosphorylates NSP2 on serine 313, triggering the localization of vNSP2 to sites of viroplasm assembly and its association with hyperphosphorylated NSP5. Using reverse genetics, we generated a rotavirus with a phosphomimetic NSP2 (S313D) mutation to directly evaluate the role of CK1α NSP2 phosphorylation in viroplasm formation. Recombinant rotavirus NSP2 S313D (rRV NSP2 S313D) is significantly delayed in viroplasm formation and in virus replication and interferes with wild-type RV replication in coinfection. Taking advantage of the delay in viroplasm formation, the NSP2 phosphomimetic mutant was used as a tool to observe very early events in viroplasm assembly. We show that (i) viroplasm assembly correlates with NSP5 hyperphosphorylation and (ii) vNSP2 S313D colocalizes with RV-induced LDs without NSP5, suggesting that vNSP2 phospho-S313 is sufficient for interacting with LDs and may be the virus factor required for RV-induced LD formation. Further studies with the rRV NSP2 S313D virus are expected to reveal new aspects of viroplasm and LD initiation and assembly.IMPORTANCE Reverse genetics was used to generate a recombinant rotavirus with a single phosphomimetic mutation in nonstructural protein 2 (NSP2 S313D) that exhibits delayed viroplasm formation, delayed replication, and an interfering phenotype during coinfection with wild-type rotavirus, indicating the importance of this amino acid during virus replication. Exploiting the delay in viroplasm assembly, we found that viroplasm-associated NSP2 colocalizes with rotavirus-induced lipid droplets prior to the accumulation of other rotavirus proteins that are required for viroplasm formation and that NSP5 hyperphosphorylation is required for viroplasm assembly. These data suggest that NSP2 phospho-S313 is sufficient for interaction with lipid droplets and may be the virus factor that induces lipid droplet biogenesis in rotavirus-infected cells. Lipid droplets are cellular organelles critical for the replication of many viral and bacterial pathogens, and thus, understanding the mechanism of NSP2-mediated viroplasm/lipid droplet initiation and interaction will lead to new insights into this important host-pathogen interaction.
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Affiliation(s)
- Jeanette M Criglar
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas, USA
| | - Sue E Crawford
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas, USA
| | - Boyang Zhao
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas, USA
| | - Hunter G Smith
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas, USA
| | - Fabio Stossi
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, Texas, USA
- Integrated Microscopy Core, Baylor College of Medicine, Houston, Texas, USA
| | - Mary K Estes
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas, USA
- Department of Medicine, Division of Gastroenterology and Hepatology, Baylor College of Medicine, Houston, Texas, USA
- Department of Medicine, Division of Infectious Diseases, Baylor College of Medicine, Houston, Texas, USA
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Differential Localization of Structural and Non-Structural Proteins during the Bluetongue Virus Replication Cycle. Viruses 2020; 12:v12030343. [PMID: 32245145 PMCID: PMC7150864 DOI: 10.3390/v12030343] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2020] [Revised: 03/13/2020] [Accepted: 03/19/2020] [Indexed: 12/12/2022] Open
Abstract
Members of the Reoviridae family assemble virus factories within the cytoplasm of infected cells to replicate and assemble virus particles. Bluetongue virus (BTV) forms virus inclusion bodies (VIBs) that are aggregates of viral RNA, certain viral proteins, and host factors, and have been shown to be sites of the initial assembly of transcriptionally active virus-like particles. This study sought to characterize the formation, composition, and ultrastructure of VIBs, particularly in relation to virus replication. In this study we have utilized various microscopic techniques, including structured illumination microscopy, and virological assays to show for the first time that the outer capsid protein VP5, which is essential for virus maturation, is also associated with VIBs. The addition of VP5 to assembled virus cores exiting VIBs is required to arrest transcriptionally active core particles, facilitating virus maturation. Furthermore, we observed a time-dependent association of the glycosylated non-structural protein 3 (NS3) with VIBs, and report on the importance of the two polybasic motifs within NS3 that facilitate virus trafficking and egress from infected cells at the plasma membrane. Thus, the presence of VP5 and the dynamic nature of NS3 association with VIBs that we report here provide novel insight into these previously less well-characterized processes.
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Conserved Rotavirus NSP5 and VP2 Domains Interact and Affect Viroplasm. J Virol 2020; 94:JVI.01965-19. [PMID: 31915278 DOI: 10.1128/jvi.01965-19] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2019] [Accepted: 12/21/2019] [Indexed: 01/15/2023] Open
Abstract
One step of the life cycle common to all rotaviruses (RV) studied so far is the formation of viroplasms, membrane-less cytosolic inclusions providing a microenvironment for early morphogenesis and RNA replication. Viroplasm-like structures (VLS) are simplified viroplasm models consisting of complexes of nonstructural protein 5 (NSP5) with the RV core shell VP2 or NSP2. We identified and characterized the domains required for NSP5-VP2 interaction and VLS formation. VP2 mutations L124A, V865A, and I878A impaired both NSP5 hyperphosphorylation and NSP5/VP2 VLS formation. Moreover, NSP5-VP2 interaction does not depend on NSP5 hyperphosphorylation. The NSP5 tail region is required for VP2 interaction. Notably, VP2 L124A expression acts as a dominant-negative element by disrupting the formation of either VLS or viroplasms and blocking RNA synthesis. In silico analyses revealed that VP2 L124, V865, and I878 are conserved among RV species A to H. Detailed knowledge of the protein interaction interface required for viroplasm formation may facilitate the design of broad-spectrum antivirals to block RV replication.IMPORTANCE Alternative treatments to combat rotavirus infection are a requirement for susceptible communities where vaccines cannot be applied. This demand is urgent for newborn infants, immunocompromised patients, adults traveling to high-risk regions, and even for the livestock industry. Aside from structural and physiological divergences among RV species studied before now, all replicate within cytosolic inclusions termed viroplasms. These inclusions are composed of viral and cellular proteins and viral RNA. Viroplasm-like structures (VLS), composed of RV protein NSP5 with either NSP2 or VP2, are models for investigating viroplasms. In this study, we identified a conserved amino acid in the VP2 protein, L124, necessary for its interaction with NSP5 and the formation of both VLSs and viroplasms. As RV vaccines cover a narrow range of viral strains, the identification of VP2 L124 residue lays the foundations for the design of drugs that specifically block NSP5-VP2 interaction as a broad-spectrum RV antiviral.
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Hervás M, Ciordia S, Navajas R, García JA, Martínez-Turiño S. Common and Strain-Specific Post-Translational Modifications of the Potyvirus Plum pox virus Coat Protein in Different Hosts. Viruses 2020; 12:E308. [PMID: 32178365 PMCID: PMC7150786 DOI: 10.3390/v12030308] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2020] [Revised: 03/05/2020] [Accepted: 03/09/2020] [Indexed: 01/04/2023] Open
Abstract
Phosphorylation and O-GlcNAcylation are widespread post-translational modifications (PTMs), often sharing protein targets. Numerous studies have reported the phosphorylation of plant viral proteins. In plants, research on O-GlcNAcylation lags behind that of other eukaryotes, and information about O-GlcNAcylated plant viral proteins is extremely scarce. The potyvirus Plum pox virus (PPV) causes sharka disease in Prunus trees and also infects a wide range of experimental hosts. Capsid protein (CP) from virions of PPV-R isolate purified from herbaceous plants can be extensively modified by O-GlcNAcylation and phosphorylation. In this study, a combination of proteomics and biochemical approaches was employed to broaden knowledge of PPV CP PTMs. CP proved to be modified regardless of whether or not it was assembled into mature particles. PTMs of CP occurred in the natural host Prunus persica, similarly to what happens in herbaceous plants. Additionally, we observed that O-GlcNAcylation and phosphorylation were general features of different PPV strains, suggesting that these modifications contribute to general strategies deployed during plant-virus interactions. Interestingly, phosphorylation at a casein kinase II motif conserved among potyviral CPs exhibited strain specificity in PPV; however, it did not display the critical role attributed to the same modification in the CP of another potyvirus, Potato virus A.
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Affiliation(s)
- Marta Hervás
- Department of Plant Molecular Genetics, Centro Nacional de Biotecnología (CNB-CSIC), Campus Universidad Autónoma de Madrid, 28049 Madrid, Spain;
| | - Sergio Ciordia
- Proteomics Unit, Centro Nacional de Biotecnología (CNB-CSIC), ProteoRed ISCIII, 28049 Madrid, Spain; (S.C.); (R.N.)
| | - Rosana Navajas
- Proteomics Unit, Centro Nacional de Biotecnología (CNB-CSIC), ProteoRed ISCIII, 28049 Madrid, Spain; (S.C.); (R.N.)
| | - Juan Antonio García
- Department of Plant Molecular Genetics, Centro Nacional de Biotecnología (CNB-CSIC), Campus Universidad Autónoma de Madrid, 28049 Madrid, Spain;
| | - Sandra Martínez-Turiño
- Department of Plant Molecular Genetics, Centro Nacional de Biotecnología (CNB-CSIC), Campus Universidad Autónoma de Madrid, 28049 Madrid, Spain;
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COPII Vesicle Transport Is Required for Rotavirus NSP4 Interaction with the Autophagy Protein LC3 II and Trafficking to Viroplasms. J Virol 2019; 94:JVI.01341-19. [PMID: 31597778 DOI: 10.1128/jvi.01341-19] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2019] [Accepted: 10/03/2019] [Indexed: 11/20/2022] Open
Abstract
Many viruses that replicate in the cytoplasm dramatically remodel and stimulate the accumulation of host cell membranes for efficient replication by poorly understood mechanisms. For rotavirus, a critical step in virion assembly requires the accumulation of membranes adjacent to virus replication centers called viroplasms. Early electron microscopy studies describe viroplasm-associated membranes as "swollen" endoplasmic reticulum (ER). We previously demonstrated that rotavirus infection initiates cellular autophagy and that membranes containing the autophagy marker protein LC3 and the rotavirus ER-synthesized transmembrane glycoprotein NSP4 traffic to viroplasms, suggesting that NSP4 must exit the ER. This study aimed to address the mechanism of NSP4 exit from the ER and determine whether the viroplasm-associated membranes are ER derived. We report that (i) NSP4 exits the ER in COPII vesicles, resulting in disrupted COPII vesicle transport and ER exit sites; (ii) COPII vesicles are hijacked by LC3 II, which interacts with NSP4; and (iii) NSP4/LC3 II-containing membranes accumulate adjacent to viroplasms. In addition, the ER transmembrane proteins SERCA and calnexin were not detected in viroplasm-associated membranes, providing evidence that the rotavirus maturation process of "budding" occurs through autophagy-hijacked COPII vesicle membranes. These findings reveal a new mechanism for rotavirus maturation dependent on intracellular host protein transport and autophagy for the accumulation of membranes required for virus replication.IMPORTANCE In a morphogenic step that is exceedingly rare for nonenveloped viruses, immature rotavirus particles assemble in replication centers called viroplasms, and bud through cytoplasmic cellular membranes to acquire the outer capsid proteins for infectious particle assembly. Historically, the intracellular membranes used for particle budding were thought to be endoplasmic reticulum (ER) because the rotavirus nonstructural protein NSP4, which interacts with the immature particles to trigger budding, is synthesized as an ER transmembrane protein. This present study shows that NSP4 exits the ER in COPII vesicles and that the NSP4-containing COPII vesicles are hijacked by the cellular autophagy machinery, which mediates the trafficking of NSP4 to viroplasms. Changing the paradigm for rotavirus maturation, we propose that the cellular membranes required for immature rotavirus particle budding are not an extension of the ER but are COPII-derived autophagy isolation membranes.
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Recombinant Rotaviruses Rescued by Reverse Genetics Reveal the Role of NSP5 Hyperphosphorylation in the Assembly of Viral Factories. J Virol 2019; 94:JVI.01110-19. [PMID: 31619556 PMCID: PMC6912106 DOI: 10.1128/jvi.01110-19] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2019] [Accepted: 09/30/2019] [Indexed: 12/24/2022] Open
Abstract
The rotavirus (RV) double-stranded RNA genome is replicated and packaged into virus progeny in cytoplasmic structures termed viroplasms. The nonstructural protein NSP5, which undergoes a complex hyperphosphorylation process during RV infection, is required for the formation of these virus-induced organelles. However, its roles in viroplasm formation and RV replication have never been directly assessed due to the lack of a fully tractable reverse-genetics (RG) system for rotaviruses. Here, we show a novel application of a recently developed RG system by establishing a stable trans-complementing NSP5-producing cell line required to rescue rotaviruses with mutations in NSP5. This approach allowed us to provide the first direct evidence of the pivotal role of this protein during RV replication. Furthermore, using recombinant RV mutants, we shed light on the molecular mechanism of NSP5 hyperphosphorylation during infection and its involvement in the assembly and maturation of replication-competent viroplasms. Rotavirus (RV) replicates in round-shaped cytoplasmic viral factories, although how they assemble remains unknown. During RV infection, NSP5 undergoes hyperphosphorylation, which is primed by the phosphorylation of a single serine residue. The role of this posttranslational modification in the formation of viroplasms and its impact on virus replication remain obscure. Here, we investigated the role of NSP5 during RV infection by taking advantage of a modified fully tractable reverse-genetics system. A trans-complementing cell line stably producing NSP5 was used to generate and characterize several recombinant rotaviruses (rRVs) with mutations in NSP5. We demonstrate that an rRV lacking NSP5 was completely unable to assemble viroplasms and to replicate, confirming its pivotal role in rotavirus replication. A number of mutants with impaired NSP5 phosphorylation were generated to further interrogate the function of this posttranslational modification in the assembly of replication-competent viroplasms. We showed that the rRV mutant strains exhibited impaired viral replication and the ability to assemble round-shaped viroplasms in MA104 cells. Furthermore, we investigated the mechanism of NSP5 hyperphosphorylation during RV infection using NSP5 phosphorylation-negative rRV strains, as well as MA104-derived stable transfectant cell lines expressing either wild-type NSP5 or selected NSP5 deletion mutants. Our results indicate that NSP5 hyperphosphorylation is a crucial step for the assembly of round-shaped viroplasms, highlighting the key role of the C-terminal tail of NSP5 in the formation of replication-competent viral factories. Such a complex NSP5 phosphorylation cascade may serve as a paradigm for the assembly of functional viral factories in other RNA viruses. IMPORTANCE The rotavirus (RV) double-stranded RNA genome is replicated and packaged into virus progeny in cytoplasmic structures termed viroplasms. The nonstructural protein NSP5, which undergoes a complex hyperphosphorylation process during RV infection, is required for the formation of these virus-induced organelles. However, its roles in viroplasm formation and RV replication have never been directly assessed due to the lack of a fully tractable reverse-genetics (RG) system for rotaviruses. Here, we show a novel application of a recently developed RG system by establishing a stable trans-complementing NSP5-producing cell line required to rescue rotaviruses with mutations in NSP5. This approach allowed us to provide the first direct evidence of the pivotal role of this protein during RV replication. Furthermore, using recombinant RV mutants, we shed light on the molecular mechanism of NSP5 hyperphosphorylation during infection and its involvement in the assembly and maturation of replication-competent viroplasms.
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Tenorio R, Fernández de Castro I, Knowlton JJ, Zamora PF, Sutherland DM, Risco C, Dermody TS. Function, Architecture, and Biogenesis of Reovirus Replication Neoorganelles. Viruses 2019; 11:v11030288. [PMID: 30901959 PMCID: PMC6466366 DOI: 10.3390/v11030288] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2019] [Revised: 03/17/2019] [Accepted: 03/19/2019] [Indexed: 02/06/2023] Open
Abstract
Most viruses that replicate in the cytoplasm of host cells form neoorganelles that serve as sites of viral genome replication and particle assembly. These highly specialized structures concentrate viral proteins and nucleic acids, prevent the activation of cell-intrinsic defenses, and coordinate the release of progeny particles. Reoviruses are common pathogens of mammals that have been linked to celiac disease and show promise for oncolytic applications. These viruses form nonenveloped, double-shelled virions that contain ten segments of double-stranded RNA. Replication organelles in reovirus-infected cells are nucleated by viral nonstructural proteins µNS and σNS. Both proteins partition the endoplasmic reticulum to form the matrix of these structures. The resultant membranous webs likely serve to anchor viral RNA⁻protein complexes for the replication of the reovirus genome and the assembly of progeny virions. Ongoing studies of reovirus replication organelles will advance our knowledge about the strategies used by viruses to commandeer host biosynthetic pathways and may expose new targets for therapeutic intervention against diverse families of pathogenic viruses.
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Affiliation(s)
- Raquel Tenorio
- Cell Structure Laboratory, National Center for Biotechnology, CNB-CSIC, Cantoblanco Campus, 28049 Madrid, Spain.
| | - Isabel Fernández de Castro
- Cell Structure Laboratory, National Center for Biotechnology, CNB-CSIC, Cantoblanco Campus, 28049 Madrid, Spain.
| | - Jonathan J Knowlton
- Department of Pathology, Microbiology, and Immunology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA.
| | - Paula F Zamora
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, PA 15219, USA.
| | - Danica M Sutherland
- Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, PA 15224, USA.
- Center for Microbial Pathogenesis, UPMC Children's Hospital of Pittsburgh, Pittsburgh, PA 15224, USA.
| | - Cristina Risco
- Cell Structure Laboratory, National Center for Biotechnology, CNB-CSIC, Cantoblanco Campus, 28049 Madrid, Spain.
| | - Terence S Dermody
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, PA 15219, USA.
- Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, PA 15224, USA.
- Center for Microbial Pathogenesis, UPMC Children's Hospital of Pittsburgh, Pittsburgh, PA 15224, USA.
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The 13th International Double-Stranded RNA Virus Symposium, Houffalize, Belgium, 24 to 28 September 2018. J Virol 2019; 93:JVI.01964-18. [PMID: 30723139 DOI: 10.1128/jvi.01964-18] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2018] [Accepted: 11/20/2018] [Indexed: 11/20/2022] Open
Abstract
The triennial International Double-Stranded RNA Virus Symposium, this year organized by J. Matthijnssens, J. S. L. Parker, P. Danthi, and P. Van Damme in Belgium, gathered over 200 scientists to discuss novel observations and hypotheses in the field. The keynote lecture on functional interactions of bacteria and viruses in the gut microbiome was presented by Julie Pfeiffer. Workshops were held on viral diversity, molecular epidemiology, molecular virology, immunity and pathogenesis, virus structure, the viral use and abuse of cellular pathways, and applied double-stranded RNA (dsRNA) virology. The establishment of a plasmid only-based reverse genetics system for rotaviruses by several Japanese research groups in 2017 has now been reproduced by various other research groups and was discussed in detail. The visualization of dsRNA virus replication steps in living cells received much attention. Mechanisms of the cellular innate immune response to virus infection and of viral pathogenesis were explored. Knowledge of the gut microbiome's influence on specific immune responses has increased rapidly, also due to the availability of relevant animal models of virus infection. The method of cryo-electron microscopic (cryo-EM) tomography has elucidated various asymmetric structures in viral particles. The use of orthoreoviruses for oncolytic virotherapy was critically assessed. The application of llama-derived single chain nanobodies for passive immunotherapy was considered attractive. In a satellite symposium the introduction, impact and further developments of rotavirus vaccines were reviewed. The Jean Cohen Lecturer of this meeting was Harry B. Greenberg, who presented aspects of his research on rotaviruses over a period of more than 40 years. He was also interviewed at the meeting by Vincent Racaniello for the 513th session of This Week in Virology.
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