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Vincent HA, Ziehr B, Lenarcic EM, Moorman NJ. Human cytomegalovirus pTRS1 stimulates cap-independent translation. Virology 2019; 537:246-253. [PMID: 31539772 PMCID: PMC8281606 DOI: 10.1016/j.virol.2019.08.026] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2019] [Revised: 08/28/2019] [Accepted: 08/28/2019] [Indexed: 01/08/2023]
Abstract
Human cytomegalovirus (HCMV) manipulates multiple cellular processes to facilitate virus replication, including the control of mRNA translation. We previously showed that the HCMV TRS1 protein (pTRS1) promotes cap-dependent mRNA translation independent of its ability to antagonize the antiviral protein PKR. Here we find that pTRS1 enhances internal ribosome entry site (IRES) activity using a novel circular RNA reporter that lacks an mRNA cap and poly(A) tail. Additionally, pTRS1 expression increases the activity of cellular IRESs that control the expression of proteins needed for efficient HCMV replication. We find that the ability of pTRS1 to enhance cap-independent translation is separable from its ability to antagonize PKR, but requires the pTRS1 RNA binding domain. Together these data show that pTRS1 stimulates cap-independent translation and suggest a role for pTRS1 in alternative translation initiation pathways during HCMV infection.
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Affiliation(s)
- Heather A Vincent
- Department of Microbiology & Immunology, Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Benjamin Ziehr
- Department of Microbiology & Immunology, Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Erik M Lenarcic
- Department of Microbiology & Immunology, Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Nathaniel J Moorman
- Department of Microbiology & Immunology, Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
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Cencic R, Pelletier J. A cautionary note on the use of cap analogue affinity resins. Anal Biochem 2018; 560:24-29. [PMID: 30193929 DOI: 10.1016/j.ab.2018.09.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2018] [Revised: 09/02/2018] [Accepted: 09/03/2018] [Indexed: 10/28/2022]
Abstract
All cellular cytoplasmic mRNAs are capped at their 5' ends with an m7GpppN group. Several proteins that mediate cap function have been identified by cap affinity purification, enabling their characterization in a number of biological processes. Among these, eukaryotic initiation factor (eIF) 4E is the best characterized and plays a critical role in regulating ribosome recruitment to mRNAs during translation initiation. Cap affinity chromatography is often used to identify eIF4E-interacting proteins, which could play critical roles in molding the eIF4E-interactome and impacting on eIF4E-directed translation. Here we address how improper implementation of this technology can lead to false conclusions and provide recommendations to ensure correct interpretation of data obtained by this approach.
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Affiliation(s)
- Regina Cencic
- Department of Biochemistry, McGill University, Montreal, Quebec, H3G 1Y6, Canada
| | - Jerry Pelletier
- Department of Biochemistry, McGill University, Montreal, Quebec, H3G 1Y6, Canada; Rosalind and Morris Goodman Cancer Research Center, McGill University, Montreal, Quebec, H3G 1Y6, Canada; Department of Oncology, McGill University, Montreal, Quebec, H3G 1Y6, Canada.
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3
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Kumar P, Hellen CUT, Pestova TV. Toward the mechanism of eIF4F-mediated ribosomal attachment to mammalian capped mRNAs. Genes Dev 2017; 30:1573-88. [PMID: 27401559 PMCID: PMC4949329 DOI: 10.1101/gad.282418.116] [Citation(s) in RCA: 83] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2016] [Accepted: 06/01/2016] [Indexed: 11/24/2022]
Abstract
Ribosomal attachment to mammalian capped mRNAs is achieved through the cap-eukaryotic initiation factor 4E (eIF4E)-eIF4G-eIF3-40S chain of interactions, but the mechanism by which mRNA enters the mRNA-binding channel of the 40S subunit remains unknown. To investigate this process, we recapitulated initiation on capped mRNAs in vitro using a reconstituted translation system. Formation of initiation complexes at 5'-terminal AUGs was stimulated by the eIF4E-cap interaction and followed "the first AUG" rule, indicating that it did not occur by backward scanning. Initiation complexes formed even at the very 5' end of mRNA, implying that Met-tRNAi (Met) inspects mRNA from the first nucleotide and that initiation does not have a "blind spot." In assembled initiation complexes, the cap was no longer associated with eIF4E. Omission of eIF4A or disruption of eIF4E-eIF4G-eIF3 interactions converted eIF4E into a specific inhibitor of initiation on capped mRNAs. Taken together, these results are consistent with the model in which eIF4E-eIF4G-eIF3-40S interactions place eIF4E at the leading edge of the 40S subunit, and mRNA is threaded into the mRNA-binding channel such that Met-tRNAi (Met) can inspect it from the first nucleotide. Before entering, eIF4E likely dissociates from the cap to overcome steric hindrance. We also found that the m(7)G cap specifically interacts with eIF3l.
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Affiliation(s)
- Parimal Kumar
- Department of Cell Biology, State University of New York Downstate Medical Center, Brooklyn, New York 11203, USA
| | - Christopher U T Hellen
- Department of Cell Biology, State University of New York Downstate Medical Center, Brooklyn, New York 11203, USA
| | - Tatyana V Pestova
- Department of Cell Biology, State University of New York Downstate Medical Center, Brooklyn, New York 11203, USA
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4
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Vincent HA, Ziehr B, Moorman NJ. Human Cytomegalovirus Strategies to Maintain and Promote mRNA Translation. Viruses 2016; 8:97. [PMID: 27089357 PMCID: PMC4848592 DOI: 10.3390/v8040097] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2016] [Revised: 03/25/2016] [Accepted: 03/31/2016] [Indexed: 02/02/2023] Open
Abstract
mRNA translation requires the ordered assembly of translation initiation factors and ribosomal subunits on a transcript. Host signaling pathways regulate each step in this process to match levels of protein synthesis to environmental cues. In response to infection, cells activate multiple defenses that limit viral protein synthesis, which viruses must counteract to successfully replicate. Human cytomegalovirus (HCMV) inhibits host defenses that limit viral protein expression and manipulates host signaling pathways to promote the expression of both host and viral proteins necessary for virus replication. Here we review key regulatory steps in mRNA translation, and the strategies used by HCMV to maintain protein synthesis in infected cells.
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Affiliation(s)
- Heather A Vincent
- Department of Microbiology & Immunology, Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
| | - Benjamin Ziehr
- Department of Microbiology & Immunology, Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
| | - Nathaniel J Moorman
- Department of Microbiology & Immunology, Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
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Mitchell SF, Walker SE, Algire MA, Park EH, Hinnebusch AG, Lorsch JR. The 5'-7-methylguanosine cap on eukaryotic mRNAs serves both to stimulate canonical translation initiation and to block an alternative pathway. Mol Cell 2010; 39:950-62. [PMID: 20864040 DOI: 10.1016/j.molcel.2010.08.021] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2010] [Revised: 05/20/2010] [Accepted: 08/02/2010] [Indexed: 10/19/2022]
Abstract
Translational control is frequently exerted at the stage of mRNA recruitment to the initiating ribosome. We have reconstituted mRNA recruitment to the 43S preinitiation complex (PIC) using purified S. cerevisiae components. We show that eIF3 and the eIF4 factors not only stabilize binding of mRNA to the PIC, they also dramatically increase the rate of recruitment. Although capped mRNAs require eIF3 and the eIF4 factors for efficient recruitment to the PIC, uncapped mRNAs can be recruited in the presence of eIF3 alone. The cap strongly inhibits this alternative recruitment pathway, imposing a requirement for the eIF4 factors for rapid and stable binding of natural mRNA. Our data suggest that the 5' cap serves as both a positive and negative element in mRNA recruitment, promoting initiation in the presence of the canonical group of mRNA handling factors while preventing binding to the ribosome via an aberrant, alternative pathway requiring only eIF3.
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Affiliation(s)
- Sarah F Mitchell
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
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Yan Y, Svitkin Y, Lee JM, Bisaillon M, Pelletier J. Ribavirin is not a functional mimic of the 7-methyl guanosine mRNA cap. RNA (NEW YORK, N.Y.) 2005; 11:1238-44. [PMID: 16043507 PMCID: PMC1370807 DOI: 10.1261/rna.2930805] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Ribavirin is a guanosine ribonucleoside analog that displays broad-spectrum anti-viral activity and is currently used for the treatment of some viral infections. Ribavirin has recently been proposed to also be a mimic of the 7-methyl guanosine cap found at the 5' end of mRNAs. To obtain supporting functional data for this hypothesis, we assessed the ability of ribavirin triphosphate to interfere with the interaction between eIF4E and 7-methyl guanosine capped mRNA. In chemical cross-linking assays, cap-affinity chromatography, and cap-dependent translation assays, ribavirin was unable to function as a cap analog.
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Affiliation(s)
- Yifei Yan
- Department of Biochemistry, McIntyre Medical Sciences Building, McGill University, Montreal, Québec H3G 1Y6, Canada
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Abstract
Protein synthesis in both eukaryotic and prokaryotic cells is a complex process requiring a large number of macromolecules: initiation factors, elongation factors, termination factors, ribosomes, mRNA, amino-acylsynthetases and tRNAs. This review focuses on our current knowledge of protein synthesis in higher plants.
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Affiliation(s)
- K S Browning
- Department of Chemistry and Biochemistry, University of Texas at Austin 78712, USA
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Sonenberg N. Cap-binding proteins of eukaryotic messenger RNA: functions in initiation and control of translation. PROGRESS IN NUCLEIC ACID RESEARCH AND MOLECULAR BIOLOGY 1988; 35:173-207. [PMID: 3065823 DOI: 10.1016/s0079-6603(08)60614-5] [Citation(s) in RCA: 230] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
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Bielka H. Properties and spatial arrangement of components in preinitiation complexes of eukaryotic protein synthesis. PROGRESS IN NUCLEIC ACID RESEARCH AND MOLECULAR BIOLOGY 1985; 32:267-89. [PMID: 3911277 DOI: 10.1016/s0079-6603(08)60351-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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Characterization of eukaryotic initiation factor 4A, a protein involved in ATP-dependent binding of globin mRNA. J Biol Chem 1982. [DOI: 10.1016/s0021-9258(18)34662-3] [Citation(s) in RCA: 118] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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Sonenberg N, Trachsel H. Probing the function of the eukaryotic 5'-cap structure using monoclonal antibodies to cap-binding proteins. CURRENT TOPICS IN CELLULAR REGULATION 1982; 21:65-88. [PMID: 6754270 DOI: 10.1016/b978-0-12-152821-8.50007-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
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