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Nouwen LV, Breeuwsma M, Zaal EA, van de Lest CHA, Buitendijk I, Zwaagstra M, Balić P, Filippov DV, Berkers CR, van Kuppeveld FJM. Modulation of nucleotide metabolism by picornaviruses. PLoS Pathog 2024; 20:e1012036. [PMID: 38457376 PMCID: PMC10923435 DOI: 10.1371/journal.ppat.1012036] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2023] [Accepted: 02/08/2024] [Indexed: 03/10/2024] Open
Abstract
Viruses actively reprogram the metabolism of the host to ensure the availability of sufficient building blocks for virus replication and spreading. However, relatively little is known about how picornaviruses-a large family of small, non-enveloped positive-strand RNA viruses-modulate cellular metabolism for their own benefit. Here, we studied the modulation of host metabolism by coxsackievirus B3 (CVB3), a member of the enterovirus genus, and encephalomyocarditis virus (EMCV), a member of the cardiovirus genus, using steady-state as well as 13C-glucose tracing metabolomics. We demonstrate that both CVB3 and EMCV increase the levels of pyrimidine and purine metabolites and provide evidence that this increase is mediated through degradation of nucleic acids and nucleotide recycling, rather than upregulation of de novo synthesis. Finally, by integrating our metabolomics data with a previously acquired phosphoproteomics dataset of CVB3-infected cells, we identify alterations in phosphorylation status of key enzymes involved in nucleotide metabolism, providing insight into the regulation of nucleotide metabolism during infection.
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Affiliation(s)
- Lonneke V. Nouwen
- Section of Virology, Division of Infectious Diseases & Immunology, Department of Biomolecular Health Sciences, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands
| | - Martijn Breeuwsma
- Section of Virology, Division of Infectious Diseases & Immunology, Department of Biomolecular Health Sciences, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands
| | - Esther A. Zaal
- Division Cell Biology, Metabolism & Cancer, Department of Biomolecular Health Sciences, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands
| | - Chris H. A. van de Lest
- Division Cell Biology, Metabolism & Cancer, Department of Biomolecular Health Sciences, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands
| | - Inge Buitendijk
- Section of Virology, Division of Infectious Diseases & Immunology, Department of Biomolecular Health Sciences, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands
| | - Marleen Zwaagstra
- Section of Virology, Division of Infectious Diseases & Immunology, Department of Biomolecular Health Sciences, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands
| | - Pascal Balić
- Gorlaeus Laboratories, Leiden Institute of Chemistry, Universiteit Leiden, Leiden, The Netherlands
| | - Dmitri V. Filippov
- Gorlaeus Laboratories, Leiden Institute of Chemistry, Universiteit Leiden, Leiden, The Netherlands
| | - Celia R. Berkers
- Division Cell Biology, Metabolism & Cancer, Department of Biomolecular Health Sciences, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands
| | - Frank J. M. van Kuppeveld
- Section of Virology, Division of Infectious Diseases & Immunology, Department of Biomolecular Health Sciences, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands
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2
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Mondal S, Sarvari G, Boehr DD. Picornavirus 3C Proteins Intervene in Host Cell Processes through Proteolysis and Interactions with RNA. Viruses 2023; 15:2413. [PMID: 38140654 PMCID: PMC10747604 DOI: 10.3390/v15122413] [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: 10/15/2023] [Revised: 12/07/2023] [Accepted: 12/09/2023] [Indexed: 12/24/2023] Open
Abstract
The Picornaviridae family comprises a large group of non-enveloped viruses with enormous impact on human and animal health. The picornaviral genome contains one open reading frame encoding a single polyprotein that can be processed by viral proteases. The picornaviral 3C proteases share similar three-dimensional structures and play a significant role in the viral life cycle and virus-host interactions. Picornaviral 3C proteins also have conserved RNA-binding activities that contribute to the assembly of the viral RNA replication complex. The 3C protease is important for regulating the host cell response through the cleavage of critical host cell proteins, acting to selectively 'hijack' host factors involved in gene expression, promoting picornavirus replication, and inactivating key factors in innate immunity signaling pathways. The protease and RNA-binding activities of 3C are involved in viral polyprotein processing and the initiation of viral RNA synthesis. Most importantly, 3C modifies critical molecules in host organelles and maintains virus infection by subtly subverting host cell death through the blocking of transcription, translation, and nucleocytoplasmic trafficking to modulate cell physiology for viral replication. Here, we discuss the molecular mechanisms through which 3C mediates physiological processes involved in promoting virus infection, replication, and release.
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Affiliation(s)
| | | | - David D. Boehr
- Department of Chemistry, The Pennsylvania State University, University Park, PA 16802, USA
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3
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Wu J, Lu J, Mao L, Xu M, Dai L, Wang Y. Targeting HNRNPA2B1 inhibits enterovirus 71 replication in SK-N-SH cells. Virus Res 2023; 336:199224. [PMID: 37716669 PMCID: PMC10511483 DOI: 10.1016/j.virusres.2023.199224] [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: 05/31/2023] [Revised: 09/06/2023] [Accepted: 09/13/2023] [Indexed: 09/18/2023]
Abstract
OBJECTIVE To investigate the effect of heterogeneous nuclear ribonucleoprotein A2B1 (HNRNPA2B1) on the replication of enterovirus 71 (EV-71) in SK-N-SH cells. METHODS The mRNA and protein expression of HNRNPA2B1 in SK-N-SH cells were detected by real-time quantitative PCR (qRT-PCR) and western blotting (WB), respectively. WB was used to detect HNRNPA2B1 protein expression in the nucleus and cytosol. The localization of HNRNPA2B1 protein in the nucleus and cytosol was detected by immunofluorescence (IF). The expression of HNRNPA2B1 was inhibited by small interfering RNA (si-HNRNPA2B1). Viral RNA, viral structural protein VP1, and viral titer were detected by qRT-PCR, WB, and viral dilution counting, respectively. RESULTS EV-71 infection significantly upregulates the expression of HNRNPA2B1 in SK-N-SH cells. EV-71 infection promotes HNRNPA2B1 nucleus-cytoplasm redistribution. Down-regulation of HNRNPA2B1 expression significantly inhibited EV-71 replication. CONCLUSION HNRNPA2B1 protein redistributed from nucleus to cytoplasm and is highly expressed in the cytoplasm during EV-71 infection. Inhibition of HNRNPA2B1 levels effectively inhibits EV-71 replication in SK-N-SH cells.
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Affiliation(s)
- Jing Wu
- Department of Laboratory Medicine, the Affiliated Guangji Hospital of Soochow University, Suzhou Mental Health Center, Suzhou, Jiangsu 215137, China.
| | - Jian Lu
- Department of Laboratory Medicine, the Second Affiliated Hospital of Soochow University, Suzhou, Jiangsu 215008, China
| | - Lingxiang Mao
- Department of Laboratory Medicine, the Affiliated Kunshan Hospital of Jiangsu University, Kunshan, Jiangsu 215300, China
| | - Meiqin Xu
- Department of Laboratory Medicine, the Affiliated Guangji Hospital of Soochow University, Suzhou Mental Health Center, Suzhou, Jiangsu 215137, China
| | - Lu Dai
- Department of Laboratory Medicine, the Affiliated Guangji Hospital of Soochow University, Suzhou Mental Health Center, Suzhou, Jiangsu 215137, China
| | - Yun Wang
- Department of Laboratory Medicine, the Affiliated Guangji Hospital of Soochow University, Suzhou Mental Health Center, Suzhou, Jiangsu 215137, China
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4
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Li R, Gao S, Chen H, Zhang X, Yang X, Zhao J, Wang Z. Virus usurps alternative splicing to clear the decks for infection. Virol J 2023; 20:131. [PMID: 37340420 DOI: 10.1186/s12985-023-02098-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2023] [Accepted: 06/12/2023] [Indexed: 06/22/2023] Open
Abstract
Since invasion, there will be a tug-of-war between host and virus to scramble cellular resources, for either restraining or facilitating infection. Alternative splicing (AS) is a conserved and critical mechanism of processing pre-mRNA into mRNAs to increase protein diversity in eukaryotes. Notably, this kind of post-transcriptional regulatory mechanism has gained appreciation since it is widely involved in virus infection. Here, we highlight the important roles of AS in regulating viral protein expression and how virus in turn hijacks AS to antagonize host immune response. This review will widen the understandings of host-virus interactions, be meaningful to innovatively elucidate viral pathogenesis, and provide novel targets for developing antiviral drugs in the future.
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Affiliation(s)
- Ruixue Li
- College of Veterinary Medicine, Henan Agricultural University, Zhengzhou, People's Republic of China
| | - Shenyan Gao
- College of Veterinary Medicine, Henan Agricultural University, Zhengzhou, People's Republic of China
| | - Huayuan Chen
- College of Veterinary Medicine, Henan Agricultural University, Zhengzhou, People's Republic of China
| | - Xiaozhan Zhang
- College of Veterinary Medicine, Henan University of Animal Husbandry and Economy, Zhengzhou, People's Republic of China
| | - Xia Yang
- College of Veterinary Medicine, Henan Agricultural University, Zhengzhou, People's Republic of China
| | - Jun Zhao
- College of Veterinary Medicine, Henan Agricultural University, Zhengzhou, People's Republic of China
| | - Zeng Wang
- College of Veterinary Medicine, Henan Agricultural University, Zhengzhou, People's Republic of China.
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5
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Jia R, Zheng ZM. Oncogenic SRSF3 in health and diseases. Int J Biol Sci 2023; 19:3057-3076. [PMID: 37416784 PMCID: PMC10321290 DOI: 10.7150/ijbs.83368] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2023] [Accepted: 05/30/2023] [Indexed: 07/08/2023] Open
Abstract
Serine/arginine rich splicing factor 3 (SRSF3) is an important multi-functional splicing factor, and has attracted increasing attentions in the past thirty years. The importance of SRSF3 is evidenced by its impressively conserved protein sequences in all animals and alternative exon 4 which represents an autoregulatory mechanism to maintain its proper cellular expression level. New functions of SRSF3 have been continuously discovered recently, especially its oncogenic function. SRSF3 plays essential roles in many cellular processes by regulating almost all aspects of RNA biogenesis and processing of many target genes, and thus, contributes to tumorigenesis when overexpressed or disregulated. This review updates and highlights the gene, mRNA, and protein structure of SRSF3, the regulatory mechanisms of SRSF3 expression, and the characteristics of SRSF3 targets and binding sequences that contribute to SRSF3's diverse molecular and cellular functions in tumorigenesis and human diseases.
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Affiliation(s)
- Rong Jia
- The State Key Laboratory Breeding Base of Basic Science of Stomatology & Key Laboratory of Oral Biomedicine Ministry of Education, School & Hospital of Stomatology, Wuhan University, Wuhan, Hubei, China
| | - Zhi-Ming Zheng
- Tumor Virus RNA Biology Section, HIV Dynamics and Replication Program, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Frederick, Maryland, USA
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6
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Mann JT, Riley BA, Baker SF. All differential on the splicing front: Host alternative splicing alters the landscape of virus-host conflict. Semin Cell Dev Biol 2023; 146:40-56. [PMID: 36737258 DOI: 10.1016/j.semcdb.2023.01.013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2022] [Revised: 01/24/2023] [Accepted: 01/25/2023] [Indexed: 02/05/2023]
Abstract
Alternative RNA splicing is a co-transcriptional process that richly increases proteome diversity, and is dynamically regulated based on cell species, lineage, and activation state. Virus infection in vertebrate hosts results in rapid host transcriptome-wide changes, and regulation of alternative splicing can direct a combinatorial effect on the host transcriptome. There has been a recent increase in genome-wide studies evaluating host alternative splicing during viral infection, which integrates well with prior knowledge on viral interactions with host splicing proteins. A critical challenge remains in linking how these individual events direct global changes, and whether alternative splicing is an overall favorable pathway for fending off or supporting viral infection. Here, we introduce the process of alternative splicing, discuss how to analyze splice regulation, and detail studies on genome-wide and splice factor changes during viral infection. We seek to highlight where the field can focus on moving forward, and how incorporation of a virus-host co-evolutionary perspective can benefit this burgeoning subject.
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Affiliation(s)
- Joshua T Mann
- Infectious Disease Program, Lovelace Biomedical Research Institute, Albuquerque, NM, USA
| | - Brent A Riley
- Infectious Disease Program, Lovelace Biomedical Research Institute, Albuquerque, NM, USA
| | - Steven F Baker
- Infectious Disease Program, Lovelace Biomedical Research Institute, Albuquerque, NM, USA.
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7
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Yang X, Aloise C, van Vliet ALW, Zwaagstra M, Lyoo H, Cheng A, van Kuppeveld FJM. Proteolytic Activities of Enterovirus 2A Do Not Depend on Its Interaction with SETD3. Viruses 2022; 14:v14071360. [PMID: 35891342 PMCID: PMC9318592 DOI: 10.3390/v14071360] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2022] [Revised: 06/13/2022] [Accepted: 06/20/2022] [Indexed: 11/28/2022] Open
Abstract
Enterovirus 2Apro is a protease that proteolytically processes the viral polyprotein and cleaves several host proteins to antagonize host responses during enteroviral infection. Recently, the host protein actin histidine methyltransferase SET domain containing 3 (SETD3) was identified to interact with 2Apro and to be essential for virus replication. The role of SETD3 and its interaction with 2Apro remain unclear. In this study, we investigated the potential involvement of SETD3 in several functions of 2Apro. For this, we introduced the 2Apro from coxsackievirus B3 (CVB3) in a mutant of encephalomyocarditis virus (EMCV) containing an inactivated Leader protein (EMCV-Lzn) that is unable to shut down host mRNA translation, to trigger nucleocytoplasmic transport disorder (NCTD), and to suppress stress granule (SG) formation and type I interferon (IFN) induction. Both in wt HeLa cells and in HeLa SETD3 knockout (SETD3KO) cells, the virus containing active 2Apro (EMCV-2Apro) efficiently cleaved eukaryotic translation initiation factor 4 gamma (eIF4G) to shut off host mRNA translation, cleaved nucleoporins to trigger NCTD, and actively suppressed SG formation and IFN gene transcription, arguing against a role of SETD3 in these 2Apro-mediated functions. Surprisingly, we observed that the catalytic activity of enteroviral 2A is not crucial for triggering NCTD, as a virus containing an inactive 2Apro (EMCV-2Am) induced NCTD in both wt and SETD3KO cells, albeit delayed, challenging the idea that the NCTD critically depends on nucleoporin cleavage by this protease. Taken together, our results do not support a role of SETD3 in the proteolytic activities of enterovirus 2Apro.
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Affiliation(s)
- Xiaoyao Yang
- Virology Section, Infectious Diseases and Immunology Division, Department of Biomolecular Health Sciences, Faculty of Veterinary Medicine, Utrecht University, 3584 CL Utrecht, The Netherlands; (X.Y.); (C.A.); (A.L.W.v.V.); (M.Z.); (H.L.)
- Institute of Preventive Veterinary Medicine, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu 611130, China
| | - Chiara Aloise
- Virology Section, Infectious Diseases and Immunology Division, Department of Biomolecular Health Sciences, Faculty of Veterinary Medicine, Utrecht University, 3584 CL Utrecht, The Netherlands; (X.Y.); (C.A.); (A.L.W.v.V.); (M.Z.); (H.L.)
| | - Arno L. W. van Vliet
- Virology Section, Infectious Diseases and Immunology Division, Department of Biomolecular Health Sciences, Faculty of Veterinary Medicine, Utrecht University, 3584 CL Utrecht, The Netherlands; (X.Y.); (C.A.); (A.L.W.v.V.); (M.Z.); (H.L.)
| | - Marleen Zwaagstra
- Virology Section, Infectious Diseases and Immunology Division, Department of Biomolecular Health Sciences, Faculty of Veterinary Medicine, Utrecht University, 3584 CL Utrecht, The Netherlands; (X.Y.); (C.A.); (A.L.W.v.V.); (M.Z.); (H.L.)
| | - Heyrhyoung Lyoo
- Virology Section, Infectious Diseases and Immunology Division, Department of Biomolecular Health Sciences, Faculty of Veterinary Medicine, Utrecht University, 3584 CL Utrecht, The Netherlands; (X.Y.); (C.A.); (A.L.W.v.V.); (M.Z.); (H.L.)
| | - Anchun Cheng
- Institute of Preventive Veterinary Medicine, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu 611130, China
- Correspondence: (A.C.); (F.J.M.v.K.)
| | - Frank J. M. van Kuppeveld
- Virology Section, Infectious Diseases and Immunology Division, Department of Biomolecular Health Sciences, Faculty of Veterinary Medicine, Utrecht University, 3584 CL Utrecht, The Netherlands; (X.Y.); (C.A.); (A.L.W.v.V.); (M.Z.); (H.L.)
- Correspondence: (A.C.); (F.J.M.v.K.)
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8
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Persistent Enterovirus Infection: Little Deletions, Long Infections. Vaccines (Basel) 2022; 10:vaccines10050770. [PMID: 35632526 PMCID: PMC9143164 DOI: 10.3390/vaccines10050770] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2022] [Revised: 05/04/2022] [Accepted: 05/10/2022] [Indexed: 01/27/2023] Open
Abstract
Enteroviruses have now been shown to persist in cell cultures and in vivo by a novel mechanism involving the deletion of varying amounts of the 5′ terminal genomic region termed domain I (also known as the cloverleaf). Molecular clones of coxsackievirus B3 (CVB3) genomes with 5′ terminal deletions (TD) of varying length allow the study of these mutant populations, which are able to replicate in the complete absence of wildtype virus genomes. The study of TD enteroviruses has revealed numerous significant differences from canonical enteroviral biology. The deletions appear and become the dominant population when an enterovirus replicates in quiescent cell populations, but can also occur if one of the cis-acting replication elements of the genome (CRE-2C) is artificially mutated in the element’s stem and loop structures. This review discusses how the TD genomes arise, how they interact with the host, and their effects on host biology.
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9
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RNA-Binding Proteins as Regulators of Internal Initiation of Viral mRNA Translation. Viruses 2022; 14:v14020188. [PMID: 35215780 PMCID: PMC8879377 DOI: 10.3390/v14020188] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Revised: 01/03/2022] [Accepted: 01/14/2022] [Indexed: 12/17/2022] Open
Abstract
Viruses are obligate intracellular parasites that depend on the host’s protein synthesis machinery for translating their mRNAs. The viral mRNA (vRNA) competes with the host mRNA to recruit the translational machinery, including ribosomes, tRNAs, and the limited eukaryotic translation initiation factor (eIFs) pool. Many viruses utilize non-canonical strategies such as targeting host eIFs and RNA elements known as internal ribosome entry sites (IRESs) to reprogram cellular gene expression, ensuring preferential translation of vRNAs. In this review, we discuss vRNA IRES-mediated translation initiation, highlighting the role of RNA-binding proteins (RBPs), other than the canonical translation initiation factors, in regulating their activity.
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10
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Filipe IC, Guedes MS, Zdobnov EM, Tapparel C. Enterovirus D: A Small but Versatile Species. Microorganisms 2021; 9:1758. [PMID: 34442837 PMCID: PMC8400195 DOI: 10.3390/microorganisms9081758] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2021] [Revised: 08/09/2021] [Accepted: 08/10/2021] [Indexed: 12/13/2022] Open
Abstract
Enteroviruses (EVs) from the D species are the causative agents of a diverse range of infectious diseases in spite of comprising only five known members. This small clade has a diverse host range and tissue tropism. It contains types infecting non-human primates and/or humans, and for the latter, they preferentially infect the eye, respiratory tract, gastrointestinal tract, and nervous system. Although several Enterovirus D members, in particular EV-D68, have been associated with neurological complications, including acute myelitis, there is currently no effective treatment or vaccine against any of them. This review highlights the peculiarities of this viral species, focusing on genome organization, functional elements, receptor usage, and pathogenesis.
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Affiliation(s)
- Ines Cordeiro Filipe
- Department of Microbiology and Molecular Medicine, University of Geneva, 1206 Geneva, Switzerland;
| | - Mariana Soares Guedes
- Department of Microbiology and Molecular Medicine, University of Geneva, 1206 Geneva, Switzerland;
| | - Evgeny M. Zdobnov
- Department of Genetic Medicine and Development, Switzerland and Swiss Institute of Bioinformatics, University of Geneva, 1206 Geneva, Switzerland;
| | - Caroline Tapparel
- Department of Microbiology and Molecular Medicine, University of Geneva, 1206 Geneva, Switzerland;
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11
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Embarc-Buh A, Francisco-Velilla R, Martinez-Salas E. RNA-Binding Proteins at the Host-Pathogen Interface Targeting Viral Regulatory Elements. Viruses 2021; 13:952. [PMID: 34064059 PMCID: PMC8224014 DOI: 10.3390/v13060952] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2021] [Revised: 05/10/2021] [Accepted: 05/17/2021] [Indexed: 12/16/2022] Open
Abstract
Viral RNAs contain the information needed to synthesize their own proteins, to replicate, and to spread to susceptible cells. However, due to their reduced coding capacity RNA viruses rely on host cells to complete their multiplication cycle. This is largely achieved by the concerted action of regulatory structural elements on viral RNAs and a subset of host proteins, whose dedicated function across all stages of the infection steps is critical to complete the viral cycle. Importantly, not only the RNA sequence but also the RNA architecture imposed by the presence of specific structural domains mediates the interaction with host RNA-binding proteins (RBPs), ultimately affecting virus multiplication and spreading. In marked difference with other biological systems, the genome of positive strand RNA viruses is also the mRNA. Here we focus on distinct types of positive strand RNA viruses that differ in the regulatory elements used to promote translation of the viral RNA, as well as in the mechanisms used to evade the series of events connected to antiviral response, including translation shutoff induced in infected cells, assembly of stress granules, and trafficking stress.
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Affiliation(s)
| | | | - Encarnacion Martinez-Salas
- Centro de Biología Molecular Severo Ochoa, CSIC-UAM, Nicolás Cabrera 1, 28049 Madrid, Spain; (A.E.-B.); (R.F.-V.)
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12
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Barrera A, Olguín V, Vera-Otarola J, López-Lastra M. Cap-independent translation initiation of the unspliced RNA of retroviruses. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2020; 1863:194583. [PMID: 32450258 DOI: 10.1016/j.bbagrm.2020.194583] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 04/08/2020] [Revised: 05/12/2020] [Accepted: 05/18/2020] [Indexed: 12/12/2022]
Abstract
Retroviruses are a unique family of RNA viruses that utilize a virally encoded reverse transcriptase (RT) to replicate their genomic RNA (gRNA) through a proviral DNA intermediate. The provirus is permanently integrated into the host cell chromosome and is expressed by the host cell transcription, RNA processing, and translation machinery. Retroviral messenger RNAs (mRNAs) entirely resemble a cellular mRNA as they have a 5'cap structure, 5'untranslated region (UTR), an open reading frame (ORF), 3'UTR, and a 3'poly(A) tail. The primary transcription product interacts with the cellular RNA processing machinery and is spliced, exported to the cytoplasm, and translated. However, a proportion of the pre-mRNA subverts typical RNA processing giving rise to the full-length RNA. In the cytoplasm, the full-length retroviral RNA fulfills a dual role acting as mRNA and as the gRNA. Simple retroviruses generate two pools of full-length RNA, one for each purpose. However, complex retroviruses have a single pool of full-length RNA, which is destined for translation or encapsidation. As for eukaryotic mRNAs, translational control of retroviral protein synthesis is mostly exerted at the step of initiation. Interestingly, some retroviral mRNAs, both simple and complex, use a dual mechanism to initiate protein synthesis, a cap-dependent initiation mechanism, or via internal initiation using an internal ribosome entry site (IRES). In this review, we describe and discuss data regarding the molecular mechanism driving the canonical cap-dependent and IRES-mediated translation initiation for retroviral mRNA, focusing the discussion mainly on the most studied retroviral mRNA, the HIV-1 mRNA.
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Affiliation(s)
- Aldo Barrera
- Laboratorio de Virología Molecular, Instituto Milenio de Inmunología e Inmunoterapia, Centro de Investigaciones Médicas, Departamento de Enfermedades Infecciosas e Inmunología Pediátrica, Escuela de Medicina, Pontificia Universidad Católica de Chile, Marcoleta 391, Santiago, Chile
| | - Valeria Olguín
- Laboratorio de Virología Molecular, Instituto Milenio de Inmunología e Inmunoterapia, Centro de Investigaciones Médicas, Departamento de Enfermedades Infecciosas e Inmunología Pediátrica, Escuela de Medicina, Pontificia Universidad Católica de Chile, Marcoleta 391, Santiago, Chile
| | - Jorge Vera-Otarola
- Laboratorio de Virología Molecular, Instituto Milenio de Inmunología e Inmunoterapia, Centro de Investigaciones Médicas, Departamento de Enfermedades Infecciosas e Inmunología Pediátrica, Escuela de Medicina, Pontificia Universidad Católica de Chile, Marcoleta 391, Santiago, Chile
| | - Marcelo López-Lastra
- Laboratorio de Virología Molecular, Instituto Milenio de Inmunología e Inmunoterapia, Centro de Investigaciones Médicas, Departamento de Enfermedades Infecciosas e Inmunología Pediátrica, Escuela de Medicina, Pontificia Universidad Católica de Chile, Marcoleta 391, Santiago, Chile.
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13
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Holmes AC, Semler BL. Picornaviruses and RNA Metabolism: Local and Global Effects of Infection. J Virol 2019; 93:e02088-17. [PMID: 31413128 PMCID: PMC6803262 DOI: 10.1128/jvi.02088-17] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2019] [Accepted: 08/06/2019] [Indexed: 11/20/2022] Open
Abstract
Due to the limiting coding capacity for members of the Picornaviridae family of positive-strand RNA viruses, their successful replication cycles require complex interactions with host cell functions. These interactions span from the down-modulation of many aspects of cellular metabolism to the hijacking of specific host functions used during viral translation, RNA replication, and other steps of infection by picornaviruses, such as human rhinovirus, coxsackievirus, poliovirus, foot-and-mouth disease virus, enterovirus D-68, and a wide range of other human and nonhuman viruses. Although picornaviruses replicate exclusively in the cytoplasm of infected cells, they have extensive interactions with host cell nuclei and the proteins and RNAs that normally reside in this compartment of the cell. This review will highlight some of the more recent studies that have revealed how picornavirus infections impact the RNA metabolism of the host cell posttranscriptionally and how they usurp and modify host RNA binding proteins as well as microRNAs to potentiate viral replication.
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Affiliation(s)
- Autumn C Holmes
- Department of Microbiology & Molecular Genetics, University of California, Irvine, California, USA
- Center for Virus Research, University of California, Irvine, California, USA
| | - Bert L Semler
- Department of Microbiology & Molecular Genetics, University of California, Irvine, California, USA
- Center for Virus Research, University of California, Irvine, California, USA
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14
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Dumont AA, Dumont L, Berthiaume J, Auger-Messier M. p38α MAPK proximity assay reveals a regulatory mechanism of alternative splicing in cardiomyocytes. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2019; 1866:118557. [PMID: 31505169 DOI: 10.1016/j.bbamcr.2019.118557] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/14/2019] [Revised: 08/30/2019] [Accepted: 09/05/2019] [Indexed: 11/26/2022]
Abstract
The p38 mitogen-activated protein kinase (MAPK) signaling pathway is essential for normal heart function. However, p38 also contributes to heart failure pathogenesis by affecting cardiomyocytes contractility and survival. To unravel part of the complex role of p38 in cardiac function, we performed an APEX2-based proximity assay in cultured neonatal rat ventricular myocytes and identified the protein interaction networks (interactomes) of two highly expressed p38 isoforms in the heart. We found that p38α and p38γ have distinct interactomes in cardiomyocytes under both basal and osmotic stress-activated states. Interestingly, the activated p38α interactome contains many RNA-binding proteins implicated in splicing, including the serine/arginine-rich splicing factor 3 (SRSF3). Its interaction with the activated p38α was validated by co-immunoprecipitation. The cytoplasmic abundance and alternative splicing function of SRSF3 are also both modulated by the p38 signaling pathway. Our findings reveal a new function for p38 as a specific regulator of SRSF3 in cardiomyocytes.
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Affiliation(s)
- Audrey-Ann Dumont
- Département de Médecine, Service de Cardiologie, Centre de Recherche du CHUS, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Sherbrooke, QC, Canada
| | - Lauralyne Dumont
- Département de Médecine, Service de Cardiologie, Centre de Recherche du CHUS, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Sherbrooke, QC, Canada
| | - Jonathan Berthiaume
- Département de Médecine, Service de Cardiologie, Centre de Recherche du CHUS, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Sherbrooke, QC, Canada
| | - Mannix Auger-Messier
- Département de Médecine, Service de Cardiologie, Centre de Recherche du CHUS, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Sherbrooke, QC, Canada.
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15
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Dave P, George B, Raheja H, Rani P, Behera P, Das S. The mammalian host protein DAP5 facilitates the initial round of translation of Coxsackievirus B3 RNA. J Biol Chem 2019; 294:15386-15394. [PMID: 31455634 DOI: 10.1074/jbc.ra119.009000] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2019] [Revised: 08/18/2019] [Indexed: 11/06/2022] Open
Abstract
During enteroviral infections, the canonical translation factor eukaryotic translation initiation factor 4 γ I (eIF4GI) is cleaved by viral protease 2A. The resulting C-terminal fragment is recruited by the viral internal ribosome entry site (IRES) for efficient translation of the viral RNA. However, the 2A protease is not present in the viral capsid and is synthesized only after the initial round of translation. This presents the conundrum of how the initial round of translation occurs in the absence of the C-terminal eIF4GI fragment. Interestingly, the host protein DAP5 (also known as p97, eIF4GIII, and eIF4G2), an isoform of eIF4GI, closely resembles the eIF4GI C-terminal fragment produced after 2A protease-mediated cleavage. Using the Coxsackievirus B3 (CVB3) IRES as a model system, here we demonstrate that DAP5, but not the full-length eIF4GI, is required for CVB3 IRES activity for translation of input viral RNA. Additionally, we show that DAP5 is specifically required by type I IRES but not by type II or type III IRES, in which cleavage of eIF4GI has not been observed. We observed that both DAP5 and C-terminal eIF4GI interact with CVB3 IRES in the same region, but DAP5 exhibits a lower affinity for CVB3 IRES compared with the C-terminal eIF4GI fragment. It appears that DAP5 is required for the initial round of viral RNA translation by sustaining a basal level of CVB3 IRES activity. This activity leads to expression of 2A protease and consequent robust CVB3 IRES-mediated translation by the C-terminal eIF4GI fragment.
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Affiliation(s)
- Pratik Dave
- Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore 560012, India
| | - Biju George
- Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore 560012, India
| | - Harsha Raheja
- Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore 560012, India
| | - Priya Rani
- Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore 560012, India
| | - Padmanava Behera
- Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore 560012, India
| | - Saumitra Das
- Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore 560012, India .,Center for Infectious Disease Research, Indian Institute of Science, Bangalore 560012, India.,National Institute of Biomedical Genomics, Kalyani, West Bengal 741251, India
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16
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Hanson PJ, Hossain AR, Qiu Y, Zhang HM, Zhao G, Li C, Lin V, Sulaimon S, Vlok M, Fung G, Chen VH, Jan E, McManus BM, Granville DJ, Yang D. Cleavage and Sub-Cellular Redistribution of Nuclear Pore Protein 98 by Coxsackievirus B3 Protease 2A Impairs Cardioprotection. Front Cell Infect Microbiol 2019; 9:265. [PMID: 31396490 PMCID: PMC6667557 DOI: 10.3389/fcimb.2019.00265] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2019] [Accepted: 07/08/2019] [Indexed: 01/15/2023] Open
Abstract
Myocarditis, inflammation of the heart muscle, affects all demographics and is a major cause of sudden and unexpected death in young people. It is most commonly caused by viral infections of the heart, with coxsackievirus B3 (CVB3) being among the most prevalent pathogens. To understand the molecular pathogenesis of CVB3 infection and provide strategies for developing treatments, we examined the role of a key nuclear pore protein 98 (NUP98) in the setting of viral myocarditis. NUP98 was cleaved as early as 2 h post-CVB3 infection. This cleavage was further verified through both the ectopic expression of viral proteases and in vitro using purified recombinant CVB3 proteases (2A and 3C), which demonstrated that CVB3 2A but not 3C is responsible for this cleavage. By immunostaining and confocal imaging, we observed that cleavage resulted in the redistribution of NUP98 to punctate structures in the cytoplasm. Targeted siRNA knockdown of NUP98 during infection further increased viral protein expression and viral titer, and reduced cell viability, suggesting a potential antiviral role of NUP98. Moreover, we discovered that expression levels of neuregulin-1 (NRG1), a cardioprotective gene, and presenilin-1 (PSEN1), a cellular protease processing the tyrosine kinase receptor ERBB4 of NRG1, were reliant upon NUP98 and were downregulated during CVB3 infection. In addition, expression of these NUP98 target genes in myocardium tissue not only occurred at an earlier phase of infection, but also appeared in areas away from the initial inflammatory regions. Collectively, CVB3-induced cleavage of NUP98 and subsequent impairment of the cardioprotective NRG1-ERBB4/PSEN1 signaling cascade may contribute to increased myocardial damage in the context of CVB3-induced myocarditis. To our knowledge, this is the first study to demonstrate the link between NUP98 and the NRG1 signaling pathway in viral myocarditis.
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Affiliation(s)
- Paul J Hanson
- Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, BC, Canada.,UBC Centre for Heart Lung Innovation, St. Paul's Hospital, Vancouver, BC, Canada
| | - Al Rohet Hossain
- Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, BC, Canada.,UBC Centre for Heart Lung Innovation, St. Paul's Hospital, Vancouver, BC, Canada
| | - Ye Qiu
- Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, BC, Canada.,UBC Centre for Heart Lung Innovation, St. Paul's Hospital, Vancouver, BC, Canada
| | - Huifang M Zhang
- Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, BC, Canada.,UBC Centre for Heart Lung Innovation, St. Paul's Hospital, Vancouver, BC, Canada
| | - Guangze Zhao
- Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, BC, Canada.,UBC Centre for Heart Lung Innovation, St. Paul's Hospital, Vancouver, BC, Canada
| | - Cheng Li
- UBC Centre for Heart Lung Innovation, St. Paul's Hospital, Vancouver, BC, Canada
| | - Veena Lin
- UBC Centre for Heart Lung Innovation, St. Paul's Hospital, Vancouver, BC, Canada
| | - Saheedat Sulaimon
- UBC Centre for Heart Lung Innovation, St. Paul's Hospital, Vancouver, BC, Canada.,Jefferson College of Population Health, Thomas Jefferson University, Philadelphia, PA, United States
| | - Marli Vlok
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, BC, Canada
| | - Gabriel Fung
- Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, BC, Canada.,UBC Centre for Heart Lung Innovation, St. Paul's Hospital, Vancouver, BC, Canada
| | - Victoria H Chen
- UBC Centre for Heart Lung Innovation, St. Paul's Hospital, Vancouver, BC, Canada.,Faculty of Medicine, University of British Columbia, Vancouver, BC, Canada
| | - Eric Jan
- Jefferson College of Population Health, Thomas Jefferson University, Philadelphia, PA, United States
| | - Bruce M McManus
- Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, BC, Canada.,UBC Centre for Heart Lung Innovation, St. Paul's Hospital, Vancouver, BC, Canada.,Faculty of Medicine, University of British Columbia, Vancouver, BC, Canada
| | - David J Granville
- Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, BC, Canada.,UBC Centre for Heart Lung Innovation, St. Paul's Hospital, Vancouver, BC, Canada
| | - Decheng Yang
- Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, BC, Canada.,UBC Centre for Heart Lung Innovation, St. Paul's Hospital, Vancouver, BC, Canada
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17
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Boudreault S, Roy P, Lemay G, Bisaillon M. Viral modulation of cellular RNA alternative splicing: A new key player in virus-host interactions? WILEY INTERDISCIPLINARY REVIEWS-RNA 2019; 10:e1543. [PMID: 31034770 PMCID: PMC6767064 DOI: 10.1002/wrna.1543] [Citation(s) in RCA: 50] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/13/2018] [Revised: 03/25/2019] [Accepted: 04/08/2019] [Indexed: 12/26/2022]
Abstract
Upon viral infection, a tug of war is triggered between host cells and viruses to maintain/gain control of vital cellular functions, the result of which will ultimately dictate the fate of the host cell. Among these essential cellular functions, alternative splicing (AS) is an important RNA maturation step that allows exons, or parts of exons, and introns to be retained in mature transcripts, thereby expanding proteome diversity and function. AS is widespread in higher eukaryotes, as it is estimated that nearly all genes in humans are alternatively spliced. Recent evidence has shown that upon infection by numerous viruses, the AS landscape of host‐cells is affected. In this review, we summarize recent advances in our understanding of how virus infection impacts the AS of cellular transcripts. We also present various molecular mechanisms allowing viruses to modulate cellular AS. Finally, the functional consequences of these changes in the RNA splicing signatures during virus–host interactions are discussed. This article is categorized under:RNA in Disease and Development > RNA in Disease RNA Processing > Splicing Regulation/Alternative Splicing
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Affiliation(s)
- Simon Boudreault
- Département de biochimie, Faculté de médecine et des sciences de la santé, Université de Sherbrooke, Sherbrooke, Québec, Canada
| | - Patricia Roy
- Département de biochimie, Faculté de médecine et des sciences de la santé, Université de Sherbrooke, Sherbrooke, Québec, Canada
| | - Guy Lemay
- Département de microbiologie, infectiologie et immunologie, Faculté de médecine, Université de Montréal, Montréal, Québec, Canada
| | - Martin Bisaillon
- Département de biochimie, Faculté de médecine et des sciences de la santé, Université de Sherbrooke, Sherbrooke, Québec, Canada
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18
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Meng W, Wang XJ, Wang HCR. Targeting nuclear proteins for control of viral replication. Crit Rev Microbiol 2019; 45:495-513. [DOI: 10.1080/1040841x.2018.1553848] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Affiliation(s)
- Wen Meng
- Key Laboratory of Animal Epidemiology of the Ministry of Agriculture, College of Veterinary Medicine, China Agricultural University, Beijing, China
| | - Xiao-Jia Wang
- Key Laboratory of Animal Epidemiology of the Ministry of Agriculture, College of Veterinary Medicine, China Agricultural University, Beijing, China
| | - Hwa-Chain Robert Wang
- Department of Biomedical and Diagnostic Sciences, College of Veterinary Medicine, The University of Tennessee, Knoxville, USA
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19
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Ashraf U, Benoit-Pilven C, Lacroix V, Navratil V, Naffakh N. Advances in Analyzing Virus-Induced Alterations of Host Cell Splicing. Trends Microbiol 2018; 27:268-281. [PMID: 30577974 DOI: 10.1016/j.tim.2018.11.004] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2018] [Revised: 10/19/2018] [Accepted: 11/09/2018] [Indexed: 12/14/2022]
Abstract
Alteration of host cell splicing is a common feature of many viral infections which is underappreciated because of the complexity and technical difficulty of studying alternative splicing (AS) regulation. Recent advances in RNA sequencing technologies revealed that up to several hundreds of host genes can show altered mRNA splicing upon viral infection. The observed changes in AS events can be either a direct consequence of viral manipulation of the host splicing machinery or result indirectly from the virus-induced innate immune response or cellular damage. Analysis at a higher resolution with single-cell RNAseq, and at a higher scale with the integration of multiple omics data sets in a systems biology perspective, will be needed to further comprehend this complex facet of virus-host interactions.
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Affiliation(s)
- Usama Ashraf
- Institut Pasteur, Unité de Génétique Moléculaire des Virus à ARN, Département de Virologie, F-75015 Paris, France; CNRS UMR3569, F-75015 Paris, France; Université Paris Diderot, Sorbonne Paris Cité EA302, F-75015 Paris, France
| | - Clara Benoit-Pilven
- INSERM U1028; CNRS UMR5292, Lyon Neuroscience Research Center, Genetic of Neuro-development Anomalies Team, F-69000 Lyon, France; Université Claude Bernard Lyon 1, CNRS UMR5558, Laboratoire de Biométrie et Biologie Evolutive, F-69622 Villeurbanne, France; EPI ERABLE, INRIA Grenoble Rhône-Alpes, F-38330 Montbonnot Saint-Martin, France
| | - Vincent Lacroix
- Université Claude Bernard Lyon 1, CNRS UMR5558, Laboratoire de Biométrie et Biologie Evolutive, F-69622 Villeurbanne, France; EPI ERABLE, INRIA Grenoble Rhône-Alpes, F-38330 Montbonnot Saint-Martin, France
| | - Vincent Navratil
- PRABI, Rhône Alpes Bioinformatics Center, UCBL, Université Claude Bernard Lyon 1, F-69000 Lyon, France; European Virus Bioinformatics Center, Leutragraben 1, D-07743 Jena, Germany
| | - Nadia Naffakh
- Institut Pasteur, Unité de Génétique Moléculaire des Virus à ARN, Département de Virologie, F-75015 Paris, France; CNRS UMR3569, F-75015 Paris, France; Université Paris Diderot, Sorbonne Paris Cité EA302, F-75015 Paris, France.
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20
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Lozano G, Francisco-Velilla R, Martinez-Salas E. Deconstructing internal ribosome entry site elements: an update of structural motifs and functional divergences. Open Biol 2018; 8:rsob.180155. [PMID: 30487301 PMCID: PMC6282068 DOI: 10.1098/rsob.180155] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2018] [Accepted: 10/30/2018] [Indexed: 12/16/2022] Open
Abstract
Beyond the general cap-dependent translation initiation, eukaryotic organisms use alternative mechanisms to initiate protein synthesis. Internal ribosome entry site (IRES) elements are cis-acting RNA regions that promote internal initiation of translation using a cap-independent mechanism. However, their lack of primary sequence and secondary RNA structure conservation, as well as the diversity of host factor requirement to recruit the ribosomal subunits, suggest distinct types of IRES elements. In spite of this heterogeneity, conserved motifs preserve sequences impacting on RNA structure and RNA–protein interactions important for IRES-driven translation. This conservation brings the question of whether IRES elements could consist of basic building blocks, which upon evolutionary selection result in functional elements with different properties. Although RNA-binding proteins (RBPs) perform a crucial role in the assembly of ribonucleoprotein complexes, the versatility and plasticity of RNA molecules, together with their high flexibility and dynamism, determines formation of macromolecular complexes in response to different signals. These properties rely on the presence of short RNA motifs, which operate as modular entities, and suggest that decomposition of IRES elements in short modules could help to understand the different mechanisms driven by these regulatory elements. Here we will review evidence suggesting that model IRES elements consist of the combination of short modules, providing sites of interaction for ribosome subunits, eIFs and RBPs, with implications for definition of criteria to identify novel IRES-like elements genome wide.
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Affiliation(s)
- Gloria Lozano
- Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid, Nicolás Cabrera 1, 28049 Madrid, Spain
| | - Rosario Francisco-Velilla
- Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid, Nicolás Cabrera 1, 28049 Madrid, Spain
| | - Encarnacion Martinez-Salas
- Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid, Nicolás Cabrera 1, 28049 Madrid, Spain
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21
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Flather D, Nguyen JHC, Semler BL, Gershon PD. Exploitation of nuclear functions by human rhinovirus, a cytoplasmic RNA virus. PLoS Pathog 2018; 14:e1007277. [PMID: 30142213 PMCID: PMC6126879 DOI: 10.1371/journal.ppat.1007277] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2018] [Revised: 09/06/2018] [Accepted: 08/11/2018] [Indexed: 12/17/2022] Open
Abstract
Protein production, genomic RNA replication, and virion assembly during infection by picornaviruses like human rhinovirus and poliovirus take place in the cytoplasm of infected human cells, making them the quintessential cytoplasmic pathogens. However, a growing body of evidence suggests that picornavirus replication is promoted by a number of host proteins localized normally within the host cell nucleus. To systematically identify such nuclear proteins, we focused on those that appear to re-equilibrate from the nucleus to the cytoplasm during infection of HeLa cells with human rhinovirus via quantitative protein mass spectrometry. Our analysis revealed a highly selective re-equilibration of proteins with known mRNA splicing and transport-related functions over nuclear proteins of all other functional classes. The multifunctional splicing factor proline and glutamine rich (SFPQ) was identified as one such protein. We found that SFPQ is targeted for proteolysis within the nucleus by viral proteinase 3CD/3C, and a fragment of SFPQ was shown to migrate to the cytoplasm at mid-to-late times of infection. Cells knocked down for SFPQ expression showed significantly reduced rhinovirus titers, viral protein production, and viral RNA accumulation, consistent with SFPQ being a pro-viral factor. The SFPQ fragment that moved into the cytoplasm was able to bind rhinovirus RNA either directly or indirectly. We propose that the truncated form of SFPQ promotes viral RNA stability or replication, or virion morphogenesis. More broadly, our findings reveal dramatic changes in protein compartmentalization during human rhinovirus infection, allowing the virus to systematically hijack the functions of proteins not normally found at its cytoplasmic site of replication. We explored the dynamics of host cell protein relocalization from the nucleus to the cytoplasm during an infection by human rhinovirus using quantitative mass spectrometry, confocal imaging, and Western blot analysis. We discovered a highly selective re-equilibration of proteins with known mRNA splicing and transport-related functions, including splicing factor proline and glutamine rich (SFPQ). Using RNAi experiments and viral replication assays, we demonstrated that SFPQ is a pro-viral factor required for rhinovirus growth. Our studies provide new insights into how this cytoplasmic RNA virus is able to alter and hijack the functions of host proteins that normally reside in the nucleus.
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Affiliation(s)
- Dylan Flather
- Department of Microbiology and Molecular Genetics, School of Medicine, University of California, Irvine, California, United States of America
- Center for Virus Research, University of California, Irvine, California, United States of America
| | - Joseph H. C. Nguyen
- Department of Microbiology and Molecular Genetics, School of Medicine, University of California, Irvine, California, United States of America
- Center for Virus Research, University of California, Irvine, California, United States of America
| | - Bert L. Semler
- Department of Microbiology and Molecular Genetics, School of Medicine, University of California, Irvine, California, United States of America
- Center for Virus Research, University of California, Irvine, California, United States of America
- * E-mail: (BLS); (PDG)
| | - Paul D. Gershon
- Center for Virus Research, University of California, Irvine, California, United States of America
- Department of Molecular Biology and Biochemistry, University of California, Irvine, California, United States of America
- * E-mail: (BLS); (PDG)
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22
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Wong KZ, Chu JJH. The Interplay of Viral and Host Factors in Chikungunya Virus Infection: Targets for Antiviral Strategies. Viruses 2018; 10:E294. [PMID: 29849008 PMCID: PMC6024654 DOI: 10.3390/v10060294] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2018] [Revised: 05/13/2018] [Accepted: 05/28/2018] [Indexed: 12/14/2022] Open
Abstract
Chikungunya virus (CHIKV) has re-emerged as one of the many medically important arboviruses that have spread rampantly across the world in the past decade. Infected patients come down with acute fever and rashes, and a portion of them suffer from both acute and chronic arthralgia. Currently, there are no targeted therapeutics against this debilitating virus. One approach to develop potential therapeutics is by understanding the viral-host interactions. However, to date, there has been limited research undertaken in this area. In this review, we attempt to briefly describe and update the functions of the different CHIKV proteins and their respective interacting host partners. In addition, we also survey the literature for other reported host factors and pathways involved during CHIKV infection. There is a pressing need for an in-depth understanding of the interaction between the host environment and CHIKV in order to generate potential therapeutics.
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Affiliation(s)
- Kai Zhi Wong
- Laboratory of Molecular RNA Virology & Antiviral Strategies, Department of Microbiology & Immunology, Yong Loo Lin School of Medicine, National University Health System, 5 Science Drive 2, National University of Singapore, Singapore 117597, Singapore.
| | - Justin Jang Hann Chu
- Laboratory of Molecular RNA Virology & Antiviral Strategies, Department of Microbiology & Immunology, Yong Loo Lin School of Medicine, National University Health System, 5 Science Drive 2, National University of Singapore, Singapore 117597, Singapore.
- Institute of Molecular & Cell Biology, Agency for Science, Technology & Research (A*STAR), 61 Biopolis Drive, Proteos #06-05, Singapore 138673, Singapore.
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23
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Abstract
Infected cells can undergo apoptosis as a protective response to viral infection, thereby limiting viral infection. As viruses require a viable cell for replication, the death of the cell limits cellular functions that are required for virus replication and propagation. Picornaviruses are single-stranded RNA viruses that modify the host cell apoptotic response, probably in order to promote viral replication, largely as a function of the viral proteases 2A, 3C, and 3CD. These proteases are essential for viral polyprotein processing and also cleave cellular proteins. Picornavirus proteases cleave proapoptotic adaptor proteins, resulting in downregulation of apoptosis. Picornavirus proteases also cleave nucleoporins, disrupting the orchestrated manner in which signaling pathways use active nucleocytoplasmic trafficking, including those involved in apoptosis. In addition to viral proteases, the transmembrane 2B protein alters intracellular ion signaling, which may also modulate apoptosis. Overall, picornaviruses, via the action of virally encoded proteins, exercise intricate control over and subvert cell death pathways, specifically apoptosis, thereby allowing viral replication to continue.
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24
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Yang X, Cheng A, Wang M, Jia R, Sun K, Pan K, Yang Q, Wu Y, Zhu D, Chen S, Liu M, Zhao XX, Chen X. Structures and Corresponding Functions of Five Types of Picornaviral 2A Proteins. Front Microbiol 2017; 8:1373. [PMID: 28785248 PMCID: PMC5519566 DOI: 10.3389/fmicb.2017.01373] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2017] [Accepted: 07/06/2017] [Indexed: 11/27/2022] Open
Abstract
Among the few non-structural proteins encoded by the picornaviral genome, the 2A protein is particularly special, irrespective of structure or function. During the evolution of the Picornaviridae family, the 2A protein has been highly non-conserved. We believe that the 2A protein in this family can be classified into at least five distinct types according to previous studies. These five types are (A) chymotrypsin-like 2A, (B) Parechovirus-like 2A, (C) hepatitis-A-virus-like 2A, (D) Aphthovirus-like 2A, and (E) 2A sequence of the genus Cardiovirus. We carried out a phylogenetic analysis and found that there was almost no homology between each type. Subsequently, we aligned the sequences within each type and found that the functional motifs in each type are highly conserved. These different motifs perform different functions. Therefore, in this review, we introduce the structures and functions of these five types of 2As separately. Based on the structures and functions, we provide suggestions to combat picornaviruses. The complexity and diversity of the 2A protein has caused great difficulties in functional and antiviral research. In this review, researchers can find useful information on the 2A protein and thus conduct improved antiviral research.
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Affiliation(s)
- Xiaoyao Yang
- Institute of Preventive Veterinary Medicine, Sichuan Agricultural UniversityChengdu, China.,Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural UniversityChengdu, China.,Avian Disease Research Center, College of Veterinary Medicine, Sichuan Agricultural UniversityChengdu, China
| | - Anchun Cheng
- Institute of Preventive Veterinary Medicine, Sichuan Agricultural UniversityChengdu, China.,Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural UniversityChengdu, China.,Avian Disease Research Center, College of Veterinary Medicine, Sichuan Agricultural UniversityChengdu, China
| | - Mingshu Wang
- Institute of Preventive Veterinary Medicine, Sichuan Agricultural UniversityChengdu, China.,Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural UniversityChengdu, China.,Avian Disease Research Center, College of Veterinary Medicine, Sichuan Agricultural UniversityChengdu, China
| | - Renyong Jia
- Institute of Preventive Veterinary Medicine, Sichuan Agricultural UniversityChengdu, China.,Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural UniversityChengdu, China.,Avian Disease Research Center, College of Veterinary Medicine, Sichuan Agricultural UniversityChengdu, China
| | - Kunfeng Sun
- Institute of Preventive Veterinary Medicine, Sichuan Agricultural UniversityChengdu, China.,Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural UniversityChengdu, China.,Avian Disease Research Center, College of Veterinary Medicine, Sichuan Agricultural UniversityChengdu, China
| | - Kangcheng Pan
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural UniversityChengdu, China
| | - Qiao Yang
- Institute of Preventive Veterinary Medicine, Sichuan Agricultural UniversityChengdu, China.,Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural UniversityChengdu, China.,Avian Disease Research Center, College of Veterinary Medicine, Sichuan Agricultural UniversityChengdu, China
| | - Ying Wu
- Institute of Preventive Veterinary Medicine, Sichuan Agricultural UniversityChengdu, China.,Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural UniversityChengdu, China.,Avian Disease Research Center, College of Veterinary Medicine, Sichuan Agricultural UniversityChengdu, China
| | - Dekang Zhu
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural UniversityChengdu, China.,Avian Disease Research Center, College of Veterinary Medicine, Sichuan Agricultural UniversityChengdu, China
| | - Shun Chen
- Institute of Preventive Veterinary Medicine, Sichuan Agricultural UniversityChengdu, China.,Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural UniversityChengdu, China.,Avian Disease Research Center, College of Veterinary Medicine, Sichuan Agricultural UniversityChengdu, China
| | - Mafeng Liu
- Institute of Preventive Veterinary Medicine, Sichuan Agricultural UniversityChengdu, China.,Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural UniversityChengdu, China.,Avian Disease Research Center, College of Veterinary Medicine, Sichuan Agricultural UniversityChengdu, China
| | - Xin-Xin Zhao
- Institute of Preventive Veterinary Medicine, Sichuan Agricultural UniversityChengdu, China.,Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural UniversityChengdu, China.,Avian Disease Research Center, College of Veterinary Medicine, Sichuan Agricultural UniversityChengdu, China
| | - Xiaoyue Chen
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural UniversityChengdu, China.,Avian Disease Research Center, College of Veterinary Medicine, Sichuan Agricultural UniversityChengdu, China
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25
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A Cytoplasmic RNA Virus Alters the Function of the Cell Splicing Protein SRSF2. J Virol 2017; 91:JVI.02488-16. [PMID: 28077658 DOI: 10.1128/jvi.02488-16] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2016] [Accepted: 01/05/2017] [Indexed: 11/20/2022] Open
Abstract
To replicate efficiently, viruses must create favorable cell conditions and overcome cell antiviral responses. We previously reported that the reovirus protein μ2 from strain T1L, but not strain T3D, represses one antiviral response: alpha/beta interferon signaling. We report here that T1L, but not T3D, μ2 localizes to nuclear speckles, where it forms a complex with the mRNA splicing factor SRSF2 and alters its subnuclear localization. Reovirus replicates in cytoplasmic viral factories, and there is no evidence that reovirus genomic or messenger RNAs are spliced, suggesting that T1L μ2 might target splicing of cell RNAs. Indeed, RNA sequencing revealed that reovirus T1L, but not T3D, infection alters the splicing of transcripts for host genes involved in mRNA posttranscriptional modifications. Moreover, depletion of SRSF2 enhanced reovirus replication and cytopathic effect, suggesting that T1L μ2 modulation of splicing benefits the virus. This provides the first report of viral antagonism of the splicing factor SRSF2 and identifies the viral protein that determines strain-specific differences in cell RNA splicing.IMPORTANCE Efficient viral replication requires that the virus create favorable cell conditions. Many viruses accomplish this by repressing specific antiviral responses. We demonstrate here that some mammalian reoviruses, RNA viruses that replicate strictly in the cytoplasm, express a protein variant that localizes to nuclear speckles, where it targets a cell mRNA splicing factor. Infection with a reovirus strain that targets this splicing factor alters splicing of cell mRNAs involved in the maturation of many other cell mRNAs. Depletion of this cell splicing factor enhances reovirus replication and cytopathic effect. Our results provide the first evidence of viral antagonism of this splicing factor and suggest that downstream consequences to the cell are global and benefit the virus.
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26
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Regulation Mechanisms of Viral IRES-Driven Translation. Trends Microbiol 2017; 25:546-561. [PMID: 28242053 DOI: 10.1016/j.tim.2017.01.010] [Citation(s) in RCA: 103] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2016] [Revised: 01/10/2017] [Accepted: 01/30/2017] [Indexed: 02/06/2023]
Abstract
Internal ribosome entry sites (IRESs) can be found in the mRNA of many viruses as well as in cellular genes involved in the stress response, cell cycle, and apoptosis. IRES-mediated translation can occur when dominant cap-dependent translation is inhibited, and viruses can take advantage of this to subvert host translation machinery. In this review, we focus on the four major types of IRES identified in RNA viruses, and outline their distinct structural properties and requirements of translational factors. We further discuss auxiliary host factors known as IRES trans-acting factors (ITAFs), which are involved in the modulation of optimal IRES activity. Currently known strategies employed by viruses to harness ITAFs and regulate IRES activity are also highlighted.
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27
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Serine/Arginine-Rich Splicing Factor 3 and Heterogeneous Nuclear Ribonucleoprotein A1 Regulate Alternative RNA Splicing and Gene Expression of Human Papillomavirus 18 through Two Functionally Distinguishable cis Elements. J Virol 2016; 90:9138-52. [PMID: 27489271 DOI: 10.1128/jvi.00965-16] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2016] [Accepted: 07/25/2016] [Indexed: 12/15/2022] Open
Abstract
UNLABELLED Human papillomavirus 18 (HPV18) is the second most common oncogenic HPV type associated with cervical, anogenital, and oropharyngeal cancers. Like other oncogenic HPVs, HPV18 encodes two major (one early and one late) polycistronic pre-mRNAs that are regulated by alternative RNA splicing to produce a repertoire of viral transcripts for the expression of individual viral genes. However, RNA cis-regulatory elements and trans-acting factors contributing to HPV18 alternative RNA splicing remain unknown. In this study, an exonic splicing enhancer (ESE) in the nucleotide (nt) 3520 to 3550 region in the HPV18 genome was identified and characterized for promotion of HPV18 929^3434 splicing and E1^E4 production through interaction with SRSF3, a host oncogenic splicing factor differentially expressed in epithelial cells and keratinocytes. Introduction of point mutations in the SRSF3-binding site or knockdown of SRSF3 expression in cells reduces 929^3434 splicing and E1^E4 production but activates other, minor 929^3465 and 929^3506 splicing. Knockdown of SRSF3 expression also enhances the expression of E2 and L1 mRNAs. An exonic splicing silencer (ESS) in the HPV18 nt 612 to 639 region was identified as being inhibitory to the 233^416 splicing of HPV18 E6E7 pre-mRNAs via binding to hnRNP A1, a well-characterized, abundantly and ubiquitously expressed RNA-binding protein. Introduction of point mutations into the hnRNP A1-binding site or knockdown of hnRNP A1 expression promoted 233^416 splicing and reduced E6 expression. These data provide the first evidence that the alternative RNA splicing of HPV18 pre-mRNAs is subject to regulation by viral RNA cis elements and host trans-acting splicing factors. IMPORTANCE Expression of HPV18 genes is regulated by alternative RNA splicing of viral polycistronic pre-mRNAs to produce a repertoire of viral early and late transcripts. RNA cis elements and trans-acting factors contributing to HPV18 alternative RNA splicing have been discovered in this study for the first time. The identified ESS at the E7 open reading frame (ORF) prevents HPV18 233^416 splicing in the E6 ORF through interaction with a host splicing factor, hnRNP A1, and regulates E6 and E7 expression of the early E6E7 polycistronic pre-mRNA. The identified ESE at the E1^E4 ORF promotes HPV18 929^3434 splicing of both viral early and late pre-mRNAs and E1^E4 production through interaction with SRSF3. This study provides important observations on how alternative RNA splicing of HPV18 pre-mRNAs is subject to regulation by viral RNA cis elements and host splicing factors and offers potential therapeutic targets to overcome HPV-related cancer.
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28
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Laitinen OH, Svedin E, Kapell S, Nurminen A, Hytönen VP, Flodström-Tullberg M. Enteroviral proteases: structure, host interactions and pathogenicity. Rev Med Virol 2016; 26:251-67. [PMID: 27145174 PMCID: PMC7169145 DOI: 10.1002/rmv.1883] [Citation(s) in RCA: 59] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2015] [Revised: 03/22/2016] [Accepted: 03/23/2016] [Indexed: 12/22/2022]
Abstract
Enteroviruses are common human pathogens, and infections are particularly frequent in children. Severe infections can lead to a variety of diseases, including poliomyelitis, aseptic meningitis, myocarditis and neonatal sepsis. Enterovirus infections have also been implicated in asthmatic exacerbations and type 1 diabetes. The large disease spectrum of the closely related enteroviruses may be partially, but not fully, explained by differences in tissue tropism. The molecular mechanisms by which enteroviruses cause disease are poorly understood, but there is increasing evidence that the two enteroviral proteases, 2Apro and 3Cpro, are important mediators of pathology. These proteases perform the post‐translational proteolytic processing of the viral polyprotein, but they also cleave several host‐cell proteins in order to promote the production of new virus particles, as well as to evade the cellular antiviral immune responses. Enterovirus‐associated processing of cellular proteins may also contribute to pathology, as elegantly demonstrated by the 2Apro‐mediated cleavage of dystrophin in cardiomyocytes contributing to Coxsackievirus‐induced cardiomyopathy. It is likely that improved tools to identify targets for these proteases will reveal additional host protein substrates that can be linked to specific enterovirus‐associated diseases. Here, we discuss the function of the enteroviral proteases in the virus replication cycle and review the current knowledge regarding how these proteases modulate the infected cell in order to favour virus replication, including ways to avoid detection by the immune system. We also highlight new possibilities for the identification of protease‐specific cellular targets and thereby a way to discover novel mechanisms contributing to disease. Copyright © 2016 John Wiley & Sons, Ltd.
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Affiliation(s)
- Olli H Laitinen
- BioMediTech, Finland and Fimlab Laboratories, University of Tampere, Tampere, Finland
| | - Emma Svedin
- The Center for Infectious Medicine, Department of Medicine HS, Karolinska Institutet, Stockholm, Sweden
| | - Sebastian Kapell
- The Center for Infectious Medicine, Department of Medicine HS, Karolinska Institutet, Stockholm, Sweden
| | - Anssi Nurminen
- BioMediTech, Finland and Fimlab Laboratories, University of Tampere, Tampere, Finland
| | - Vesa P Hytönen
- BioMediTech, Finland and Fimlab Laboratories, University of Tampere, Tampere, Finland
| | - Malin Flodström-Tullberg
- BioMediTech, Finland and Fimlab Laboratories, University of Tampere, Tampere, Finland.,The Center for Infectious Medicine, Department of Medicine HS, Karolinska Institutet, Stockholm, Sweden
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29
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Selective Removal of FG Repeat Domains from the Nuclear Pore Complex by Enterovirus 2A(pro). J Virol 2015; 89:11069-79. [PMID: 26311873 DOI: 10.1128/jvi.00956-15] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2015] [Accepted: 08/20/2015] [Indexed: 12/31/2022] Open
Abstract
UNLABELLED Enteroviruses proteolyze nuclear pore complex (NPC) proteins (Nups) during infection, leading to disruption of host nuclear transport pathways and alterations in nuclear permeability. To better understand how enteroviruses exert these effects on nuclear transport, the mechanisms and consequences of Nup98 proteolysis were examined. The results indicate that Nup98 is rapidly targeted for degradation following enterovirus infection and that this is mediated by the enterovirus 2A protease (2A(pro)). Incubation of bacterially expressed or in vitro-translated Nup98 with 2A(pro) results in proteolytic cleavage at multiple sites in vitro, indicating that 2A(pro) cleaves Nup98 directly. Site-directed mutagenesis of putative cleavage sites identified Gly374 and Gly552 as the sites of 2A(pro) proteolysis in Nup98 in vitro and in infected cells. Indirect immunofluorescence assays using an antibody that recognizes the N terminus of Nup98 revealed that proteolysis releases the N-terminal FG-rich region from the NPC. In contrast, similar analyses using an antibody to the C terminus indicated that this region is retained at the nuclear rim. Nup88, a core NPC component that serves as a docking site for Nup98, also remains at the NPC in infected cells. These findings support a model whereby the selective removal of Nup FG repeat domains leads to increased NPC permeability and inhibition of certain transport pathways, while retention of structural domains maintains the overall NPC structure and leaves other transport pathways unaffected. IMPORTANCE Enteroviruses are dependent upon host nuclear RNA binding proteins for efficient replication. This study examines the mechanisms responsible for alterations in nuclear transport in enterovirus-infected cells that lead to the cytoplasmic accumulation of these proteins. The results demonstrate that the enterovirus 2A protease directly cleaves the nuclear pore complex (NPC) protein, Nup98, at amino acid positions G374 and G552 both in vitro and in infected cells. Cleavage at these positions results in the selective removal of the FG-containing N terminus of Nup98 from the NPC, while the C terminus remains associated. Nup88, a core component of the NPC that serves as a docking site for the C terminus of Nup98, remains associated with the NPC in infected cells. These findings help to explain the alterations in permeability and nuclear transport in enterovirus-infected cells and how NPCs remain functional for certain trafficking pathways despite significant alterations to their compositions.
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30
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Flather D, Semler BL. Picornaviruses and nuclear functions: targeting a cellular compartment distinct from the replication site of a positive-strand RNA virus. Front Microbiol 2015; 6:594. [PMID: 26150805 PMCID: PMC4471892 DOI: 10.3389/fmicb.2015.00594] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2015] [Accepted: 05/29/2015] [Indexed: 11/13/2022] Open
Abstract
The compartmentalization of DNA replication and gene transcription in the nucleus and protein production in the cytoplasm is a defining feature of eukaryotic cells. The nucleus functions to maintain the integrity of the nuclear genome of the cell and to control gene expression based on intracellular and environmental signals received through the cytoplasm. The spatial separation of the major processes that lead to the expression of protein-coding genes establishes the necessity of a transport network to allow biomolecules to translocate between these two regions of the cell. The nucleocytoplasmic transport network is therefore essential for regulating normal cellular functioning. The Picornaviridae virus family is one of many viral families that disrupt the nucleocytoplasmic trafficking of cells to promote viral replication. Picornaviruses contain positive-sense, single-stranded RNA genomes and replicate in the cytoplasm of infected cells. As a result of the limited coding capacity of these viruses, cellular proteins are required by these intracellular parasites for both translation and genomic RNA replication. Being of messenger RNA polarity, a picornavirus genome can immediately be translated upon entering the cell cytoplasm. However, the replication of viral RNA requires the activity of RNA-binding proteins, many of which function in host gene expression, and are consequently localized to the nucleus. As a result, picornaviruses disrupt nucleocytoplasmic trafficking to exploit protein functions normally localized to a different cellular compartment from which they translate their genome to facilitate efficient replication. Furthermore, picornavirus proteins are also known to enter the nucleus of infected cells to limit host-cell transcription and down-regulate innate antiviral responses. The interactions of picornavirus proteins and host-cell nuclei are extensive, required for a productive infection, and are the focus of this review.
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Affiliation(s)
- Dylan Flather
- Department of Microbiology and Molecular Genetics, Center for Virus Research, School of Medicine, University of California, Irvine Irvine, CA, USA
| | - Bert L Semler
- Department of Microbiology and Molecular Genetics, Center for Virus Research, School of Medicine, University of California, Irvine Irvine, CA, USA
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31
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Kuo RL, Lin YH, Wang RYL, Hsu CW, Chiu YT, Huang HI, Kao LT, Yu JS, Shih SR, Wu CC. Proteomics analysis of EV71-infected cells reveals the involvement of host protein NEDD4L in EV71 replication. J Proteome Res 2015; 14:1818-30. [PMID: 25785312 DOI: 10.1021/pr501199h] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Enterovirus 71 (EV71) is a human enterovirus that has seriously affected the Asia-Pacific area for the past two decades. EV71 infection can result in mild hand-foot-and-mouth disease and herpangina and may occasionally lead to severe neurological complications in children. However, the specific biological processes that become altered during EV71 infection remain unclear. To further explore host responses upon EV71 infection, we identified proteins differentially expressed in EV71-infected human glioblastoma SF268 cells using isobaric mass tag (iTRAQ) labeling coupled with multidimensional liquid chromatography-mass spectrometry (LC-MS/MS). Network analysis of proteins altered in cells infected with EV71 revealed that the changed biological processes are related to protein and ion transport, regulation of protein degradation, and homeostatic processes. We confirmed that the levels of NEDD4L and PSMF1 were increased and reduced, respectively, in EV71-infected cells compared to mock-infected control cells. To determine the physiological relevance of our findings, we investigated the consequences of EV71 infection in cells with NEDD4L or PSMF1 depletion. We found that the depletion of NEDD4L significantly reduced the replication of EV71, whereas PSMF1 knockdown enhanced EV71 replication. Collectively, our findings provide the first evidence of proteome-wide dysregulation by EV71 infection and suggest a novel role for the host protein NEDD4L in the replication of this virus.
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Affiliation(s)
- Rei-Lin Kuo
- †Department of Medical Biotechnology and Laboratory Science, College of Medicine, Chang Gung University, Tao-Yuan 333, Taiwan.,‡Research Center for Emerging Viral Infections, College of Medicine, Chang Gung University, Tao-Yuan 333, Taiwan
| | - Ya-Han Lin
- †Department of Medical Biotechnology and Laboratory Science, College of Medicine, Chang Gung University, Tao-Yuan 333, Taiwan.,‡Research Center for Emerging Viral Infections, College of Medicine, Chang Gung University, Tao-Yuan 333, Taiwan
| | - Robert Yung-Liang Wang
- ‡Research Center for Emerging Viral Infections, College of Medicine, Chang Gung University, Tao-Yuan 333, Taiwan.,§Department of Biomedical Sciences, College of Medicine, Chang Gung University, Tao-Yuan 333, Taiwan
| | - Chia-Wei Hsu
- ∥Molecular Medicine Research Center, Chang Gung University, Tao-Yuan 333, Taiwan
| | - Yi-Ting Chiu
- †Department of Medical Biotechnology and Laboratory Science, College of Medicine, Chang Gung University, Tao-Yuan 333, Taiwan
| | - Hsing-I Huang
- †Department of Medical Biotechnology and Laboratory Science, College of Medicine, Chang Gung University, Tao-Yuan 333, Taiwan.,‡Research Center for Emerging Viral Infections, College of Medicine, Chang Gung University, Tao-Yuan 333, Taiwan
| | - Li-Ting Kao
- †Department of Medical Biotechnology and Laboratory Science, College of Medicine, Chang Gung University, Tao-Yuan 333, Taiwan.,‡Research Center for Emerging Viral Infections, College of Medicine, Chang Gung University, Tao-Yuan 333, Taiwan
| | - Jau-Song Yu
- ∥Molecular Medicine Research Center, Chang Gung University, Tao-Yuan 333, Taiwan
| | - Shin-Ru Shih
- †Department of Medical Biotechnology and Laboratory Science, College of Medicine, Chang Gung University, Tao-Yuan 333, Taiwan.,‡Research Center for Emerging Viral Infections, College of Medicine, Chang Gung University, Tao-Yuan 333, Taiwan.,⊥Clinical Virology Laboratory, Linkou Chang Gung Memorial Hospital, Tao-Yuan 333, Taiwan
| | - Chih-Ching Wu
- †Department of Medical Biotechnology and Laboratory Science, College of Medicine, Chang Gung University, Tao-Yuan 333, Taiwan.,∥Molecular Medicine Research Center, Chang Gung University, Tao-Yuan 333, Taiwan
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32
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Martínez-Salas E, Francisco-Velilla R, Fernandez-Chamorro J, Lozano G, Diaz-Toledano R. Picornavirus IRES elements: RNA structure and host protein interactions. Virus Res 2015; 206:62-73. [PMID: 25617758 DOI: 10.1016/j.virusres.2015.01.012] [Citation(s) in RCA: 98] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2014] [Revised: 01/05/2015] [Accepted: 01/12/2015] [Indexed: 01/26/2023]
Abstract
Internal ribosome entry site (IRES) elements were discovered in picornaviruses. These elements are cis-acting RNA sequences that adopt diverse three-dimensional structures and recruit the translation machinery using a 5' end-independent mechanism assisted by a subset of translation initiation factors and various RNA binding proteins termed IRES transacting factors (ITAFs). Many of these factors suffer important modifications during infection including cleavage by picornavirus proteases, changes in the phosphorylation level and/or redistribution of the protein from the nuclear to the cytoplasm compartment. Picornavirus IRES are amongst the most potent elements described so far. However, given their large diversity and complexity, the mechanistic basis of its mode of action is not yet fully understood. This review is focused to describe recent advances on the studies of RNA structure and RNA-protein interactions modulating picornavirus IRES activity.
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Affiliation(s)
- Encarnación Martínez-Salas
- Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas - Universidad Autónoma de Madrid, Nicolas Cabrera 1, 28049 Madrid, Spain.
| | - Rosario Francisco-Velilla
- Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas - Universidad Autónoma de Madrid, Nicolas Cabrera 1, 28049 Madrid, Spain
| | - Javier Fernandez-Chamorro
- Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas - Universidad Autónoma de Madrid, Nicolas Cabrera 1, 28049 Madrid, Spain
| | - Gloria Lozano
- Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas - Universidad Autónoma de Madrid, Nicolas Cabrera 1, 28049 Madrid, Spain
| | - Rosa Diaz-Toledano
- Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas - Universidad Autónoma de Madrid, Nicolas Cabrera 1, 28049 Madrid, Spain
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33
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Abstract
Human rhinoviruses (HRV) are the major etiological agents of the common cold and asthma exacerbations, with significant worldwide health and economic impact. Although large-scale population vaccination has proved successful in limiting or even eradicating many viruses, the more than 100 distinct serotypes mean that conventional vaccination is not a feasible strategy to combat HRV. An alternative strategy is to target conserved viral proteins such as the HRV proteases, 2A(pro) and 3C(pro), the focus of this review. Necessary for host cell shutoff, virus replication, and pathogenesis, 2A(pro) and 3C(pro) are clearly viable drug targets, and indeed, 3C(pro) has been successfully targeted for treating the common cold in experimental infection. 2A(pro) and 3C(pro) are crucial for virus replication due to their role in polyprotein processing as well as cleavage of key cellular proteins to inhibit cellular transcription and translation. Intriguingly, the action of the HRV proteases also disrupts nucleocytoplasmic trafficking, contributing to HRV cytopathic effects. Improved understanding of the protease-cell interactions should enable new therapeutic approaches to be identified for drug development.
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Affiliation(s)
- Lora M Jensen
- Faculty of Education, Science, Technology and Mathematics, Centre for Research in Therapeutic Solutions, University of Canberra, 1 Kirinari Street, Bruce, Canberra, ACT, 2601, Australia
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34
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Wu S, Wang Y, Lin L, Si X, Wang T, Zhong X, Tong L, Luan Y, Chen Y, Li X, Zhang F, Zhao W, Zhong Z. Protease 2A induces stress granule formation during coxsackievirus B3 and enterovirus 71 infections. Virol J 2014; 11:192. [PMID: 25410318 PMCID: PMC4247557 DOI: 10.1186/s12985-014-0192-1] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2014] [Accepted: 10/26/2014] [Indexed: 02/02/2023] Open
Abstract
Background Stress granules (SGs) are granular aggregates in the cytoplasm that are formed under a variety of stress situations including viral infection. Previous studies indicate that poliovirus, a member of Picornaviridae, can induce SG formation. However, the exact mechanism by which the picornaviruses induce SG formation is unknown. Method The localization of SG markers in cells infected with coxsackievirus B3 (CVB3) or enterovirus 71 (EV71) and in cells expressing each viral protein was determined via immunofluorescence assays or plasmid transfection. Eight plasmids expressing mutants of the 2A protease (2Apro) of CVB3 were generated using a site-directed mutagenesis strategy. The cleavage efficiencies of eIF4G by CVB3 2Apro and its mutants were determined via western blotting assays. Results In this study, we found that CVB3 infection induced SG formation, as evidenced by the co-localization of some accepted SG markers in viral infection-induced granules. Furthermore, we identified that 2Apro of CVB3 was the key viral component that triggered SG formation. A 2Apro mutant with the G122E mutation, which exhibited very low cleavage efficiency toward eIF4G, significantly attenuated its capacity for SG induction, indicating that the protease activity was required for 2Apro to initiate SG formation. Finally, we observed that SGs also formed in EV71-infected cells. Expression of EV71 2Apro alone was also sufficient to cause SG formation. Conclusion Both CVB3 and EV71 infections can induce SG formation, and 2Apro plays a crucial role in the induction of SG formation during these infections. This finding may help us to better understand how picornaviruses initiate the SG response. Electronic supplementary material The online version of this article (doi:10.1186/s12985-014-0192-1) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Shuo Wu
- Department of Microbiology, Harbin Medical University, Harbin, 150081, China.
| | - Yan Wang
- Department of Microbiology, Harbin Medical University, Harbin, 150081, China.
| | - Lexun Lin
- Department of Microbiology, Harbin Medical University, Harbin, 150081, China.
| | - Xiaoning Si
- Department of Microbiology, Harbin Medical University, Harbin, 150081, China.
| | - Tianying Wang
- Department of Microbiology, Harbin Medical University, Harbin, 150081, China.
| | - Xiaoyan Zhong
- Department of Microbiology, Harbin Medical University, Harbin, 150081, China.
| | - Lei Tong
- Department of Microbiology, Harbin Medical University, Harbin, 150081, China.
| | - Ying Luan
- Department of Microbiology, Harbin Medical University, Harbin, 150081, China.
| | - Yang Chen
- Department of Microbiology, Harbin Medical University, Harbin, 150081, China.
| | - Xiaoyu Li
- Division of Gastroenterology and Hepatology, Department of Medicine, University of Florida-Jacksonville, Jacksonville, FL, 32206, USA.
| | - Fengmin Zhang
- Department of Microbiology, Harbin Medical University, Harbin, 150081, China.
| | - Wenran Zhao
- Department of Cell Biology, Harbin Medical University, Harbin, 150081, China.
| | - Zhaohua Zhong
- Department of Microbiology, Harbin Medical University, Harbin, 150081, China.
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35
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Wu S, Lin L, Zhao W, Li X, Wang Y, Si X, Wang T, Wu H, Zhai X, Zhong X, Gao S, Tong L, Xu Z, Zhong Z. AUF1 is recruited to the stress granules induced by coxsackievirus B3. Virus Res 2014; 192:52-61. [PMID: 25148713 DOI: 10.1016/j.virusres.2014.08.003] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2014] [Revised: 08/05/2014] [Accepted: 08/11/2014] [Indexed: 11/18/2022]
Abstract
Stress granules (SGs) are cytoplasmic granules that are formed in cells when stress occurs. In this study, we found that SGs formed in cells infected with coxsackievirus B3 (CVB3), evidenced with the co-localization of some accepted SG markers in the viral infection-induced granules. We further discovered that adenosine-uridine (AU)-rich element RNA binding factor 1 (AUF1), which can bind to mRNAs and regulate their translation, was recruited to the SGs in response to high dose of CVB3 by detecting the co-localization of AUF1 with SG markers. Similar results were also observed in the enterovirus 71 (EV71)-infected cells. Finally, we demonstrated that AUF1 was also recruited to arsenite-induced SGs, suggesting that the recruitment of AUF1 to SG is not a specific response to viral infection. In summary, our data indicate that both CVB3 and EV71 infections can induce SG formation, and AUF1 is a novel SG component upon the viral infections. Our findings may shed light on understanding the picornavirus-host interaction.
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Affiliation(s)
- Shuo Wu
- Department of Microbiology, Harbin Medical University, Harbin 150081, China
| | - Lexun Lin
- Department of Microbiology, Harbin Medical University, Harbin 150081, China
| | - Wenran Zhao
- Department of Cell Biology, Harbin Medical University, Harbin 150081, China
| | - Xiaobo Li
- Department of Pathology, Harbin Medical University, Harbin 150081, China
| | - Yan Wang
- Department of Microbiology, Harbin Medical University, Harbin 150081, China
| | - Xiaoning Si
- Department of Microbiology, Harbin Medical University, Harbin 150081, China
| | - Tianying Wang
- Department of Microbiology, Harbin Medical University, Harbin 150081, China
| | - Heng Wu
- Department of Microbiology, Harbin Medical University, Harbin 150081, China
| | - Xia Zhai
- Department of Microbiology, Harbin Medical University, Harbin 150081, China
| | - Xiaoyan Zhong
- Department of Microbiology, Harbin Medical University, Harbin 150081, China
| | - Shuoyang Gao
- Department of Microbiology, Harbin Medical University, Harbin 150081, China
| | - Lei Tong
- Department of Microbiology, Harbin Medical University, Harbin 150081, China
| | - Zhikai Xu
- Department of Microbiology, School of Basic Medicine, Fourth Military Medical University, Xi'an 710032, China.
| | - Zhaohua Zhong
- Department of Microbiology, Harbin Medical University, Harbin 150081, China.
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36
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Cathcart AL, Rozovics JM, Semler BL. Cellular mRNA decay protein AUF1 negatively regulates enterovirus and human rhinovirus infections. J Virol 2013; 87:10423-34. [PMID: 23903828 PMCID: PMC3807403 DOI: 10.1128/jvi.01049-13] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2013] [Accepted: 07/19/2013] [Indexed: 01/12/2023] Open
Abstract
To successfully complete their replication cycles, picornaviruses modify several host proteins to alter the cellular environment to favor virus production. One such target of viral proteinase cleavage is AU-rich binding factor 1 (AUF1), a cellular protein that binds to AU-rich elements, or AREs, in the 3' noncoding regions (NCRs) of mRNAs to affect the stability of the RNA. Previous studies found that, during poliovirus or human rhinovirus infection, AUF1 is cleaved by the viral proteinase 3CD and that AUF1 can interact with the long 5' NCR of these viruses in vitro. Here, we expand on these initial findings to demonstrate that all four isoforms of AUF1 bind directly to stem-loop IV of the poliovirus 5' NCR, an interaction that is inhibited through proteolytic cleavage of AUF1 by the viral proteinase 3CD. Endogenous AUF1 was observed to relocalize to the cytoplasm of infected cells in a viral protein 2A-driven manner and to partially colocalize with the viral protein 3CD. We identify a negative role for AUF1 in poliovirus infection, as AUF1 inhibited viral translation and, ultimately, overall viral titers. Our findings also demonstrate that AUF1 functions as an antiviral factor during infection by coxsackievirus or human rhinovirus, suggesting a common mechanism that targets these related picornaviruses.
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Affiliation(s)
- Andrea L Cathcart
- Department of Microbiology and Molecular Genetics, School of Medicine, University of California, Irvine, CA 92697 USA
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Álvarez E, Castelló A, Carrasco L, Izquierdo JM. Poliovirus 2A protease triggers a selective nucleo-cytoplasmic redistribution of splicing factors to regulate alternative pre-mRNA splicing. PLoS One 2013; 8:e73723. [PMID: 24066065 PMCID: PMC3774746 DOI: 10.1371/journal.pone.0073723] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2013] [Accepted: 07/30/2013] [Indexed: 12/31/2022] Open
Abstract
Poliovirus protease 2A (2Apro) obstructs host gene expression by reprogramming transcriptional and post-transcriptional regulatory events during infection. Here we demonstrate that expression of 2Apro induces a selective nucleo-cytoplasm translocation of several important RNA binding proteins and splicing factors. Subcellular fractionation studies, together with immunofluorescence microscopy revealed an asymmetric distribution of HuR and TIA1/TIAR in 2Apro expressing cells, which modulates splicing of the human Fas exon 6. Consistent with this result, knockdown of HuR or overexpression of TIA1/TIAR, leads to Fas exon 6 inclusion in 2Apro-expressing cells. Therefore, poliovirus 2Apro can target alternative pre-mRNA splicing by regulating protein shuttling between the nucleus and the cytoplasm.
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Affiliation(s)
- Enrique Álvarez
- Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid (CSIC-UAM), Madrid, Spain
- * E-mail: (EA); (JMI)
| | - Alfredo Castelló
- European Molecular Biology Laboratory (EMBL), Heidelberg, Germany
| | - Luis Carrasco
- Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid (CSIC-UAM), Madrid, Spain
| | - José M. Izquierdo
- Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid (CSIC-UAM), Madrid, Spain
- * E-mail: (EA); (JMI)
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Fitzgerald KD, Semler BL. Poliovirus infection induces the co-localization of cellular protein SRp20 with TIA-1, a cytoplasmic stress granule protein. Virus Res 2013; 176:223-31. [PMID: 23830997 PMCID: PMC3742715 DOI: 10.1016/j.virusres.2013.06.012] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2013] [Revised: 06/21/2013] [Accepted: 06/21/2013] [Indexed: 12/18/2022]
Abstract
Different types of environmental stress cause mammalian cells to form cytoplasmic foci, termed stress granules, which contain mRNPs that are translationally silenced. These foci are transient and dynamic, and contain components of the cellular translation machinery as well as certain mRNAs and RNA binding proteins. Stress granules are known to be induced by conditions such as hypoxia, nutrient deprivation, and oxidative stress, and a number of cellular factors have been identified that are commonly associated with these foci. More recently it was discovered that poliovirus infection also induces the formation of stress granules, although these cytoplasmic foci appear to be somewhat compositionally unique. Work described here examined the punctate pattern of SRp20 (a host cell mRNA splicing protein) localization in the cytoplasm of poliovirus-infected cells, demonstrating the partial co-localization of SRp20 with the stress granule marker protein TIA-1. We determined that SRp20 does not co-localize with TIA-1, however, under conditions of oxidative stress, indicating that the close association of these two proteins during poliovirus infection is not representative of a general response to cellular stress. We confirmed that the expression of a dominant negative version of TIA-1 (TIA-1-PRD) results in the dissociation of stress granules. Finally, we demonstrated that expression of wild type TIA-1 or dominant negative TIA-1-PRD in cells during poliovirus infection does not dramatically affect viral translation. Taken together, these studies provide a new example of the unique cytoplasmic foci that form during poliovirus infection.
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Affiliation(s)
| | - Bert L. Semler
- Corresponding author. Tel.: +1 949 824 7573; fax: +1 949 824 2694.
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