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Gottipati K, McNeme SC, Tipo J, White MA, Choi K. Structural basis for cloverleaf RNA-initiated viral genome replication. Nucleic Acids Res 2023; 51:8850-8863. [PMID: 37486760 PMCID: PMC10484678 DOI: 10.1093/nar/gkad618] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2023] [Revised: 07/07/2023] [Accepted: 07/18/2023] [Indexed: 07/25/2023] Open
Abstract
The genomes of positive-strand RNA viruses serve as a template for both protein translation and genome replication. In enteroviruses, a cloverleaf RNA structure at the 5' end of the genome functions as a switch to transition from viral translation to replication by interacting with host poly(C)-binding protein 2 (PCBP2) and the viral 3CDpro protein. We determined the structures of cloverleaf RNA from coxsackievirus and poliovirus. Cloverleaf RNA folds into an H-type four-way junction and is stabilized by a unique adenosine-cytidine-uridine (A•C-U) base triple involving the conserved pyrimidine mismatch region. The two PCBP2 binding sites are spatially proximal and are located on the opposite end from the 3CDpro binding site on cloverleaf. We determined that the A•C-U base triple restricts the flexibility of the cloverleaf stem-loops resulting in partial occlusion of the PCBP2 binding site, and elimination of the A•C-U base triple increases the binding affinity of PCBP2 to the cloverleaf RNA. Based on the cloverleaf structures and biophysical assays, we propose a new mechanistic model by which enteroviruses use the cloverleaf structure as a molecular switch to transition from viral protein translation to genome replication.
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Affiliation(s)
- Keerthi Gottipati
- Department of Biochemistry and Molecular Biology, Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, 301 University Boulevard, Galveston, TX 77555, USA
- Department of Molecular and Cellular Biochemistry, Indiana University, 212 S. Hawthorne Drive, Bloomington, IN 47405, USA
| | - Sean C McNeme
- Department of Biochemistry and Molecular Biology, Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, 301 University Boulevard, Galveston, TX 77555, USA
| | - Jerricho Tipo
- Department of Pharmacology and Toxicology, Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, 301 University Boulevard, Galveston, TX 77555, USA
| | - Mark A White
- Department of Biochemistry and Molecular Biology, Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, 301 University Boulevard, Galveston, TX 77555, USA
| | - Kyung H Choi
- Department of Biochemistry and Molecular Biology, Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, 301 University Boulevard, Galveston, TX 77555, USA
- Department of Molecular and Cellular Biochemistry, Indiana University, 212 S. Hawthorne Drive, Bloomington, IN 47405, USA
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Wang J, Sun D, Wang M, Cheng A, Zhu Y, Mao S, Ou X, Zhao X, Huang J, Gao Q, Zhang S, Yang Q, Wu Y, Zhu D, Jia R, Chen S, Liu M. Multiple functions of heterogeneous nuclear ribonucleoproteins in the positive single-stranded RNA virus life cycle. Front Immunol 2022; 13:989298. [PMID: 36119073 PMCID: PMC9478383 DOI: 10.3389/fimmu.2022.989298] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2022] [Accepted: 08/12/2022] [Indexed: 11/13/2022] Open
Abstract
The heterogeneous nuclear ribonucleoproteins (hnRNPs) are a diverse family of RNA binding proteins that are implicated in RNA metabolism, such as alternative splicing, mRNA stabilization and translational regulation. According to their different cellular localization, hnRNPs display multiple functions. Most hnRNPs were predominantly located in the nucleus, but some of them could redistribute to the cytoplasm during virus infection. HnRNPs consist of different domains and motifs that enable these proteins to recognize predetermined nucleotide sequences. In the virus-host interactions, hnRNPs specifically bind to viral RNA or proteins. And some of the viral protein-hnRNP interactions require the viral RNA or other host factors as the intermediate. Through various mechanisms, hnRNPs could regulate viral translation, viral genome replication, the switch of translation to replication and virion release. This review highlights the common features and the distinguish roles of hnRNPs in the life cycle of positive single-stranded RNA viruses.
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Affiliation(s)
- Jingming Wang
- Institute of Preventive Veterinary Medicine, Sichuan Agricultural University, Chengdu City, China
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Chengdu City, China
- Avian Disease Research Center, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu City, China
| | - Di Sun
- Institute of Preventive Veterinary Medicine, Sichuan Agricultural University, Chengdu City, China
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Chengdu City, China
- Avian Disease Research Center, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu City, China
| | - Mingshu Wang
- Institute of Preventive Veterinary Medicine, Sichuan Agricultural University, Chengdu City, China
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Chengdu City, China
- Avian Disease Research Center, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu City, China
| | - Anchun Cheng
- Institute of Preventive Veterinary Medicine, Sichuan Agricultural University, Chengdu City, China
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Chengdu City, China
- Avian Disease Research Center, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu City, China
- *Correspondence: Anchun Cheng,
| | - Yukun Zhu
- Institute of Preventive Veterinary Medicine, Sichuan Agricultural University, Chengdu City, China
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Chengdu City, China
- Avian Disease Research Center, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu City, China
| | - Sai Mao
- Institute of Preventive Veterinary Medicine, Sichuan Agricultural University, Chengdu City, China
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Chengdu City, China
- Avian Disease Research Center, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu City, China
| | - Xuming Ou
- Institute of Preventive Veterinary Medicine, Sichuan Agricultural University, Chengdu City, China
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Chengdu City, China
- Avian Disease Research Center, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu City, China
| | - Xinxin Zhao
- Institute of Preventive Veterinary Medicine, Sichuan Agricultural University, Chengdu City, China
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Chengdu City, China
- Avian Disease Research Center, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu City, China
| | - Juan Huang
- Institute of Preventive Veterinary Medicine, Sichuan Agricultural University, Chengdu City, China
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Chengdu City, China
- Avian Disease Research Center, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu City, China
| | - Qun Gao
- Institute of Preventive Veterinary Medicine, Sichuan Agricultural University, Chengdu City, China
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Chengdu City, China
- Avian Disease Research Center, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu City, China
| | - Shaqiu Zhang
- Institute of Preventive Veterinary Medicine, Sichuan Agricultural University, Chengdu City, China
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Chengdu City, China
- Avian Disease Research Center, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu City, China
| | - Qiao Yang
- Institute of Preventive Veterinary Medicine, Sichuan Agricultural University, Chengdu City, China
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Chengdu City, China
- Avian Disease Research Center, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu City, China
| | - Ying Wu
- Institute of Preventive Veterinary Medicine, Sichuan Agricultural University, Chengdu City, China
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Chengdu City, China
- Avian Disease Research Center, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu City, China
| | - Dekang Zhu
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Chengdu City, China
- Avian Disease Research Center, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu City, China
| | - Renyong Jia
- Institute of Preventive Veterinary Medicine, Sichuan Agricultural University, Chengdu City, China
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Chengdu City, China
- Avian Disease Research Center, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu City, China
| | - Shun Chen
- Institute of Preventive Veterinary Medicine, Sichuan Agricultural University, Chengdu City, China
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Chengdu City, China
- Avian Disease Research Center, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu City, China
| | - Mafeng Liu
- Institute of Preventive Veterinary Medicine, Sichuan Agricultural University, Chengdu City, China
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Chengdu City, China
- Avian Disease Research Center, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu City, China
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Asnani M, Pestova TV, Hellen CUT. PCBP2 enables the cadicivirus IRES to exploit the function of a conserved GRNA tetraloop to enhance ribosomal initiation complex formation. Nucleic Acids Res 2016; 44:9902-9917. [PMID: 27387282 PMCID: PMC5175331 DOI: 10.1093/nar/gkw609] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2016] [Revised: 06/24/2016] [Accepted: 06/24/2016] [Indexed: 12/22/2022] Open
Abstract
The cadicivirus IRES diverges structurally from canonical Type 1 IRESs (e.g. poliovirus) but nevertheless also contains an essential GNRA tetraloop in a subdomain (d10c) that is homologous to poliovirus dIVc. In addition to canonical initiation factors, the canonical Type 1 and divergent cadicivirus IRESs require the same IRES trans-acting factor, poly(C)-binding protein 2 (PCBP2). PCBP2 has three KH domains and binds poliovirus IRES domain dIV in the vicinity of the tetraloop. How PCBP2 binds the cadicivirus IRES, and the roles of PCBP2 and the tetraloop in Type 1 IRES function are unknown. Here, directed hydroxyl radical probing showed that KH1 also binds near the cadicivirus tetraloop. KH2 and KH3 bind adjacently to an IRES subdomain (d10b) that is unrelated to dIV, with KH3 in an inverted orientation. KH3 is critical for PCBP2's binding to this IRES whereas KH1 is essential for PCBP2's function in promoting initiation. PCBP2 enforced the wild-type structure of d10c when it contained minor destabilizing substitutions, exposing the tetraloop. Strikingly, PCBP2 enhanced initiation on mutant IRESs that retained consensus GNRA tetraloops, whereas mutants with divergent sequences did not respond to PCBP2. These studies show that PCBP2 enables the IRES to exploit the GNRA tetraloop to enhance initiation.
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Affiliation(s)
- Mukta Asnani
- Department of Cell Biology, SUNY Downstate Medical Center, 450 Clarkson Avenue, MSC 44, Brooklyn, NY 11203, USA
| | - Tatyana V Pestova
- Department of Cell Biology, SUNY Downstate Medical Center, 450 Clarkson Avenue, MSC 44, Brooklyn, NY 11203, USA
| | - Christopher U T Hellen
- Department of Cell Biology, SUNY Downstate Medical Center, 450 Clarkson Avenue, MSC 44, Brooklyn, NY 11203, USA
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Asnani M, Pestova TV, Hellen CUT. Initiation on the divergent Type I cadicivirus IRES: factor requirements and interactions with the translation apparatus. Nucleic Acids Res 2016; 44:3390-407. [PMID: 26873921 PMCID: PMC4838371 DOI: 10.1093/nar/gkw074] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2015] [Accepted: 01/29/2016] [Indexed: 01/03/2023] Open
Abstract
Cadicivirus (CDV) is unique amongst picornaviruses in having a dicistronic genome with internal ribosomal entry sites (IRESs) preceding both open reading frames. Here, we investigated initiation on the 5'-terminal IRES. We report that the 982-nt long 5'UTR comprises 12 domains (d1-d12), five of which (d8-d12, nts 341-950) constitute a divergent Type I IRES. It comprises central elements (the apex of d10, d11 and the following polypyrimidine tract) that are homologous to corresponding elements in canonical Type 1 IRESs, and non-canonical flanking domains (d8, d9 and d12). In vitro reconstitution revealed that as with canonical Type I IRESs, 48S complex formation requires eukaryotic initiation factors (eIFs) 1, 1A, 2, 3, 4A, 4B and 4G, and the poly(C) binding protein 2 (PCBP2), and starts with specific binding of eIF4G/eIF4A to d11. However, in contrast to canonical Type I IRESs, subsequent recruitment of 43S ribosomal complexes does not require direct interaction of their eIF3 constituent with the IRES-bound eIF4G. On the other hand, the CDV IRES forms a 40S/eIF3/IRES ternary complex, with multiple points of contact. These additional interactions with translational components could potentially stimulate recruitment of the 43S complex and alleviate the necessity for direct eIF4G/eIF3 interaction.
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Affiliation(s)
- Mukta Asnani
- Department of Cell Biology, SUNY Downstate Medical Center, 450 Clarkson Avenue, MSC44, Brooklyn, NY 11203, USA
| | - Tatyana V Pestova
- Department of Cell Biology, SUNY Downstate Medical Center, 450 Clarkson Avenue, MSC44, Brooklyn, NY 11203, USA
| | - Christopher U T Hellen
- Department of Cell Biology, SUNY Downstate Medical Center, 450 Clarkson Avenue, MSC44, Brooklyn, NY 11203, USA
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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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Sweeney TR, Abaeva IS, Pestova TV, Hellen CUT. The mechanism of translation initiation on Type 1 picornavirus IRESs. EMBO J 2013; 33:76-92. [PMID: 24357634 DOI: 10.1002/embj.201386124] [Citation(s) in RCA: 119] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Picornavirus Type 1 IRESs comprise five principal domains (dII-dVI). Whereas dV binds eIF4G, a conserved AUG in dVI was suggested to stimulate attachment of 43S ribosomal preinitiation complexes, which then scan to the initiation codon. Initiation on Type 1 IRESs also requires IRES trans-acting factors (ITAFs), and several candidates have been proposed. Here, we report the in vitro reconstitution of initiation on three Type 1 IRESs: poliovirus (PV), enterovirus 71 (EV71), and bovine enterovirus (BEV). All of them require eIF2, eIF3, eIF4A, eIF4G, eIF4B, eIF1A, and a single ITAF, poly(C) binding protein 2 (PCBP2). In each instance, initiation starts with binding of eIF4G/eIF4A. Subsequent recruitment of 43S complexes strictly requires direct interaction of their eIF3 constituent with eIF4G. The following events can differ between IRESs, depending on the stability of dVI. If it is unstructured (BEV), all ribosomes scan through dVI to the initiation codon, requiring eIF1 to bypass its AUG. If it is structured (PV, EV71), most initiation events occur without inspection of dVI, implying that its AUG does not determine ribosomal attachment.
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Affiliation(s)
- Trevor R Sweeney
- Department of Cell Biology, SUNY Downstate Medical Center, Brooklyn, NY, USA
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