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Zhang L, More KR, Ojha A, Jackson CB, Quinlan BD, Li H, He W, Farzan M, Pardi N, Choe H. Effect of mRNA-LNP components of two globally-marketed COVID-19 vaccines on efficacy and stability. NPJ Vaccines 2023; 8:156. [PMID: 37821446 PMCID: PMC10567765 DOI: 10.1038/s41541-023-00751-6] [Citation(s) in RCA: 19] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2023] [Accepted: 09/25/2023] [Indexed: 10/13/2023] Open
Abstract
During the COVID-19 pandemic, Pfizer-BioNTech and Moderna successfully developed nucleoside-modified mRNA lipid nanoparticle (LNP) vaccines. SARS-CoV-2 spike protein expressed by those vaccines are identical in amino acid sequence, but several key components are distinct. Here, we compared the effect of ionizable lipids, untranslated regions (UTRs), and nucleotide composition of the two vaccines, focusing on mRNA delivery, antibody generation, and long-term stability. We found that the ionizable lipid, SM-102, in Moderna's vaccine performs better than ALC-0315 in Pfizer-BioNTech's vaccine for intramuscular delivery of mRNA and antibody production in mice and long-term stability at 4 °C. Moreover, Pfizer-BioNTech's 5' UTR and Moderna's 3' UTR outperform their counterparts in their contribution to transgene expression in mice. We further found that varying N1-methylpseudouridine content at the wobble position of mRNA has little effect on vaccine efficacy. These findings may contribute to the further improvement of nucleoside-modified mRNA-LNP vaccines and therapeutics.
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Affiliation(s)
- Lizhou Zhang
- Division of Infectious Disease, Boston Children's Hospital, Boston, MA, USA.
- Department of Pediatrics, Harvard Medical School, Boston, MA, USA.
- Department of Immunology and Microbiology, UF Scripps Institute for Biomedical Innovation & Technology, Jupiter, FL, USA.
| | - Kunal R More
- Department of Immunology and Microbiology, UF Scripps Institute for Biomedical Innovation & Technology, Jupiter, FL, USA
| | - Amrita Ojha
- Department of Immunology and Microbiology, UF Scripps Institute for Biomedical Innovation & Technology, Jupiter, FL, USA
| | - Cody B Jackson
- Division of Infectious Disease, Boston Children's Hospital, Boston, MA, USA
- Department of Pediatrics, Harvard Medical School, Boston, MA, USA
- Department of Immunology and Microbiology, UF Scripps Institute for Biomedical Innovation & Technology, Jupiter, FL, USA
| | - Brian D Quinlan
- Department of Immunology and Microbiology, UF Scripps Institute for Biomedical Innovation & Technology, Jupiter, FL, USA
| | - Hao Li
- Division of Infectious Disease, Boston Children's Hospital, Boston, MA, USA
- Department of Pediatrics, Harvard Medical School, Boston, MA, USA
- Department of Immunology and Microbiology, UF Scripps Institute for Biomedical Innovation & Technology, Jupiter, FL, USA
- Skaggs Graduate School, The Scripps Research Institute, La Jolla, CA, USA
| | - Wenhui He
- Division of Infectious Disease, Boston Children's Hospital, Boston, MA, USA
- Department of Pediatrics, Harvard Medical School, Boston, MA, USA
- Department of Immunology and Microbiology, UF Scripps Institute for Biomedical Innovation & Technology, Jupiter, FL, USA
- Center For Integrated Solutions for Infectious Diseases, The Broad Institute of MIT and Harvard, Cambridge, MA, USA
| | - Michael Farzan
- Division of Infectious Disease, Boston Children's Hospital, Boston, MA, USA
- Department of Pediatrics, Harvard Medical School, Boston, MA, USA
- Department of Immunology and Microbiology, UF Scripps Institute for Biomedical Innovation & Technology, Jupiter, FL, USA
- Skaggs Graduate School, The Scripps Research Institute, La Jolla, CA, USA
- Center For Integrated Solutions for Infectious Diseases, The Broad Institute of MIT and Harvard, Cambridge, MA, USA
| | - Norbert Pardi
- Department of Microbiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Hyeryun Choe
- Division of Infectious Disease, Boston Children's Hospital, Boston, MA, USA.
- Department of Pediatrics, Harvard Medical School, Boston, MA, USA.
- Department of Immunology and Microbiology, UF Scripps Institute for Biomedical Innovation & Technology, Jupiter, FL, USA.
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Targeting the DEAD-Box RNA Helicase eIF4A with Rocaglates-A Pan-Antiviral Strategy for Minimizing the Impact of Future RNA Virus Pandemics. Microorganisms 2021; 9:microorganisms9030540. [PMID: 33807988 PMCID: PMC8001013 DOI: 10.3390/microorganisms9030540] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2021] [Revised: 03/01/2021] [Accepted: 03/02/2021] [Indexed: 12/17/2022] Open
Abstract
The increase in pandemics caused by RNA viruses of zoonotic origin highlights the urgent need for broad-spectrum antivirals against novel and re-emerging RNA viruses. Broad-spectrum antivirals could be deployed as first-line interventions during an outbreak while virus-specific drugs and vaccines are developed and rolled out. Viruses depend on the host’s protein synthesis machinery for replication. Several natural compounds that target the cellular DEAD-box RNA helicase eIF4A, a key component of the eukaryotic translation initiation complex eIF4F, have emerged as potential broad-spectrum antivirals. Rocaglates, a group of flavaglines of plant origin that clamp mRNAs with highly structured 5′ untranslated regions (5′UTRs) onto the surface of eIF4A through specific stacking interactions, exhibit the largest selectivity and potential therapeutic indices among all known eIF4A inhibitors. Their unique mechanism of action limits the inhibitory effect of rocaglates to the translation of eIF4A-dependent viral mRNAs and a minor fraction of host mRNAs exhibiting stable RNA secondary structures and/or polypurine sequence stretches in their 5′UTRs, resulting in minimal potential toxic side effects. Maintaining a favorable safety profile while inducing efficient inhibition of a broad spectrum of RNA viruses makes rocaglates into primary candidates for further development as pan-antiviral therapeutics.
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Abstract
The stage at which ribosomes are recruited to messenger RNAs (mRNAs) is an elaborate and highly regulated phase of protein synthesis. Upon completion of this step, a ribosome is positioned at an appropriate initiation codon and primed to synthesize the encoded polypeptide product. In most circumstances, this step commits the ribosome to translate the mRNA. We summarize the knowledge regarding the initiation factors implicated in this activity as well as review different mechanisms by which this process is conducted.
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Affiliation(s)
- Jerry Pelletier
- Department of Biochemistry, McGill University, Montreal, Quebec H3G 1Y6, Canada; , .,Rosalind and Morris Goodman Cancer Research Center, McGill University, Montreal, Quebec H3A 1A3, Canada.,Department of Oncology, McGill University, Montreal, Quebec H4A 3T2, Canada
| | - Nahum Sonenberg
- Department of Biochemistry, McGill University, Montreal, Quebec H3G 1Y6, Canada; , .,Rosalind and Morris Goodman Cancer Research Center, McGill University, Montreal, Quebec H3A 1A3, Canada
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Abstract
Gapmers are antisense oligonucleotides composed of a central DNA segment flanked by nucleotides of modified chemistry. Hybridizing with transcripts by sequence complementarity, gapmers recruit ribonuclease H and induce target RNA degradation. Since its concept first emerged in the 1980s, much work has gone into developing gapmers for use in basic research and therapy. These include improvements in gapmer chemistry, delivery, and therapeutic safety. Gapmers have also successfully entered clinical trials for various genetic disorders, with two already approved by the U.S. Food and Drug Administration for the treatment of familial hypercholesterolemia and transthyretin amyloidosis-associated polyneuropathy. Here, we review the events surrounding the early development of gapmers, from conception to their maturity, and briefly conclude with perspectives on their use in therapy.
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Affiliation(s)
- Kenji Rowel Q Lim
- Department of Medical Genetics, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada
| | - Toshifumi Yokota
- Department of Medical Genetics, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada.
- The Friends of Garrett Cumming Research and Muscular Dystrophy Canada HM Toupin Neurological Science Research Chair, Edmonton, AB, Canada.
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Abstract
The eukaryotic translation pathway has been studied for more than four decades, but the molecular mechanisms that regulate each stage of the pathway are not completely defined. This is in part because we have very little understanding of the kinetic framework for the assembly and disassembly of pathway intermediates. Steps of the pathway are thought to occur in the subsecond to second time frame, but most assays to monitor these events require minutes to hours to complete. Understanding translational control in sufficient detail will therefore require the development of assays that can precisely monitor the kinetics of the translation pathway in real time. Here, we describe the translation pathway from the perspective of its kinetic parameters, discuss advances that are helping us move toward the goal of a rigorous kinetic understanding, and highlight some of the challenges that remain.
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Liang XH, Sun H, Shen W, Wang S, Yao J, Migawa MT, Bui HH, Damle SS, Riney S, Graham MJ, Crooke RM, Crooke ST. Antisense oligonucleotides targeting translation inhibitory elements in 5' UTRs can selectively increase protein levels. Nucleic Acids Res 2017; 45:9528-9546. [PMID: 28934489 PMCID: PMC5766168 DOI: 10.1093/nar/gkx632] [Citation(s) in RCA: 74] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Revised: 07/05/2017] [Accepted: 07/10/2017] [Indexed: 12/31/2022] Open
Abstract
A variety of diseases are caused by deficiencies in amounts or activity of key proteins. An approach that increases the amount of a specific protein might be of therapeutic benefit. We reasoned that translation could be specifically enhanced using trans-acting agents that counter the function of negative regulatory elements present in the 5' UTRs of some mRNAs. We recently showed that translation can be enhanced by antisense oligonucleotides (ASOs) that target upstream open reading frames. Here we report the amount of a protein can also be selectively increased using ASOs designed to hybridize to other translation inhibitory elements in 5' UTRs. Levels of human RNASEH1, LDLR, and ACP1 and of mouse ACP1 and ARF1 were increased up to 2.7-fold in different cell types and species upon treatment with chemically modified ASOs targeting 5' UTR inhibitory regions in the mRNAs encoding these proteins. The activities of ASOs in enhancing translation were sequence and position dependent and required helicase activity. The ASOs appear to improve the recruitment of translation initiation factors to the target mRNA. Importantly, ASOs targeting ACP1 mRNA significantly increased the level of ACP1 protein in mice, suggesting that this approach has therapeutic and research potentials.
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Affiliation(s)
- Xue-hai Liang
- Department of Core Antisense Research, Ionis Pharmaceuticals, Inc., Carlsbad, CA, USA
| | - Hong Sun
- Department of Core Antisense Research, Ionis Pharmaceuticals, Inc., Carlsbad, CA, USA
| | - Wen Shen
- Department of Core Antisense Research, Ionis Pharmaceuticals, Inc., Carlsbad, CA, USA
| | - Shiyu Wang
- Department of Core Antisense Research, Ionis Pharmaceuticals, Inc., Carlsbad, CA, USA
| | - Joyee Yao
- Department of Core Antisense Research, Ionis Pharmaceuticals, Inc., Carlsbad, CA, USA
| | - Michael T. Migawa
- Department of Medicinal Chemistry, Ionis Pharmaceuticals, Inc., Carlsbad, CA, USA
| | - Huynh-Hoa Bui
- Department of Antisense Drug Discovery, Ionis Pharmaceuticals, Inc., Carlsbad, CA, USA
| | - Sagar S. Damle
- Department of Antisense Drug Discovery, Ionis Pharmaceuticals, Inc., Carlsbad, CA, USA
| | - Stan Riney
- Department of Antisense Drug Discovery, Ionis Pharmaceuticals, Inc., Carlsbad, CA, USA
| | - Mark J. Graham
- Department of Antisense Drug Discovery, Ionis Pharmaceuticals, Inc., Carlsbad, CA, USA
| | - Rosanne M. Crooke
- Department of Antisense Drug Discovery, Ionis Pharmaceuticals, Inc., Carlsbad, CA, USA
| | - Stanley T. Crooke
- Department of Core Antisense Research, Ionis Pharmaceuticals, Inc., Carlsbad, CA, USA
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Steinberger J, Chu J, Maïga RI, Sleiman K, Pelletier J. Developing anti-neoplastic biotherapeutics against eIF4F. Cell Mol Life Sci 2017; 74:1681-1692. [PMID: 28004147 PMCID: PMC11107644 DOI: 10.1007/s00018-016-2430-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2016] [Revised: 11/16/2016] [Accepted: 12/01/2016] [Indexed: 02/08/2023]
Abstract
Biotherapeutics have revolutionized modern medicine by providing medicines that would not have been possible with small molecules. With respect to cancer therapies, this represents the current sector of the pharmaceutical industry having the largest therapeutic impact, as exemplified by the development of recombinant antibodies and cell-based therapies. In cancer, one of the most common regulatory alterations is the perturbation of translational control. Among these, changes in eukaryotic initiation factor 4F (eIF4F) are associated with tumor initiation, progression, and drug resistance in a number of settings. This, coupled with the fact that systemic suppression of eIF4F appears well tolerated, indicates that therapeutic agents targeting eIF4F hold much therapeutic potential. Here, we discuss opportunities offered by biologicals for this purpose.
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Affiliation(s)
- Jutta Steinberger
- Department of Biochemistry, McGill University, McIntyre Medical Sciences Building, Rm 810, 3655 Drummond St., Montreal, QC, H3G 1Y6, Canada
| | - Jennifer Chu
- Department of Biochemistry, McGill University, McIntyre Medical Sciences Building, Rm 810, 3655 Drummond St., Montreal, QC, H3G 1Y6, Canada
| | - Rayelle Itoua Maïga
- Department of Biochemistry, McGill University, McIntyre Medical Sciences Building, Rm 810, 3655 Drummond St., Montreal, QC, H3G 1Y6, Canada
| | - Katia Sleiman
- Department of Biochemistry, McGill University, McIntyre Medical Sciences Building, Rm 810, 3655 Drummond St., Montreal, QC, H3G 1Y6, Canada
| | - Jerry Pelletier
- Department of Biochemistry, McGill University, McIntyre Medical Sciences Building, Rm 810, 3655 Drummond St., Montreal, QC, H3G 1Y6, Canada.
- The Rosalind and Morris Goodman Cancer Research Center, McGill University, Montreal, QC, H3G 1Y6, Canada.
- Department of Oncology, McGill University, Montreal, QC, H3G 1Y6, Canada.
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Pelletier J, Graff J, Ruggero D, Sonenberg N. Targeting the eIF4F translation initiation complex: a critical nexus for cancer development. Cancer Res 2015; 75:250-63. [PMID: 25593033 DOI: 10.1158/0008-5472.can-14-2789] [Citation(s) in RCA: 265] [Impact Index Per Article: 29.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Elevated protein synthesis is an important feature of many cancer cells and often arises as a consequence of increased signaling flux channeled to eukaryotic initiation factor 4F (eIF4F), the key regulator of the mRNA-ribosome recruitment phase of translation initiation. In many cellular and preclinical models of cancer, eIF4F deregulation results in changes in translational efficiency of specific mRNA classes. Importantly, many of these mRNAs code for proteins that potently regulate critical cellular processes, such as cell growth and proliferation, enhanced cell survival and cell migration that ultimately impinge on several hallmarks of cancer, including increased angiogenesis, deregulated growth control, enhanced cellular survival, epithelial-to-mesenchymal transition, invasion, and metastasis. By being positioned as the molecular nexus downstream of key oncogenic signaling pathways (e.g., Ras, PI3K/AKT/TOR, and MYC), eIF4F serves as a direct link between important steps in cancer development and translation initiation. Identification of mRNAs particularly responsive to elevated eIF4F activity that typifies tumorigenesis underscores the critical role of eIF4F in cancer and raises the exciting possibility of developing new-in-class small molecules targeting translation initiation as antineoplastic agents.
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Affiliation(s)
- Jerry Pelletier
- Department of Biochemistry, McGill University, Montreal, Québec, Canada. The Rosalind and Morris Goodman Cancer Research Center, McGill University, Montreal, Québec, Canada. Department of Oncology, McGill University, Montreal, Québec, Canada.
| | - Jeremy Graff
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana
| | - Davide Ruggero
- School of Medicine and Department of Urology, Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, California
| | - Nahum Sonenberg
- Department of Biochemistry, McGill University, Montreal, Québec, Canada. The Rosalind and Morris Goodman Cancer Research Center, McGill University, Montreal, Québec, Canada
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Abstract
A challenge in cancer therapy is to selectively target activities that are essential for survival of malignant cells while sparing normal cells. Translational control represents a potential anti-neoplastic target because it is exerted by major signaling pathways that are often usurped in cancers. Herein we describe approaches being developed that target eukaryotic initiation factor (eIF) 4F, a heterotrimeric complex that integrates multiple signaling inputs to the translation apparatus.
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Zhang Y, Wang Q, Guo X, Miller R, Guo Y, Yang HS. Activation and up-regulation of translation initiation factor 4B contribute to arsenic-induced transformation. Mol Carcinog 2011; 50:528-38. [PMID: 21268130 PMCID: PMC3110507 DOI: 10.1002/mc.20733] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2010] [Revised: 12/03/2010] [Accepted: 12/08/2010] [Indexed: 01/23/2023]
Abstract
Arsenic is a known human carcinogen. However, the mechanism of how arsenic induces cell transformation remains unclear. In this study, we demonstrated that long-term exposure to sodium arsenite at low-dose (2 µM) increases cell proliferation and neoplastic transformation in a mouse epidermal cell model, JB6 promotion-susceptible cells. The phosphorylation of AKT and its downstream targets, 70-kDa ribosomal protein S6 kinase (p70S6K) and translation initiation factor 4B (eIF4B), are increased in the arsenite treated cells, indicating that long-term arsenite treatment activates AKT-p70S6K signaling pathway. In addition, long-term exposure to arsenite up-regulates eIF4B expression and increases the rate of translation. Knockdown of eIF4B expression resulted in inhibition of arsenic-induced cell proliferation, transformation, and translation. Moreover, the expression of c-Myc which is up-regulated by long-term arsenite treatment is inhibited by eIF4B knockdown. Taken together, these results indicate that activation and up-regulation of eIF4B contributes to arsenic-induced transformation in JB6 cells.
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Affiliation(s)
- Yong Zhang
- Graduate Center for Toxicology, College of Medicine, University of Kentucky, Lexington, KY40536, USA
- Institute and Department of Urology, Peking University First Hospital, Beijing, China
| | - Qing Wang
- Graduate Center for Toxicology, College of Medicine, University of Kentucky, Lexington, KY40536, USA
| | - Xiaoling Guo
- Graduate Center for Toxicology, College of Medicine, University of Kentucky, Lexington, KY40536, USA
- Department of Oral and Maxillofacial Surgery, and School and Hospital of Stomatology, Shandong University, Jinan, Shandong Province, China
| | - Robert Miller
- Graduate Center for Toxicology, College of Medicine, University of Kentucky, Lexington, KY40536, USA
| | - Yinglu Guo
- Institute and Department of Urology, Peking University First Hospital, Beijing, China
| | - Hsin-Sheng Yang
- Graduate Center for Toxicology, College of Medicine, University of Kentucky, Lexington, KY40536, USA
- Markey Cancer Center, College of Medicine, University of Kentucky, Lexington, KY40536, 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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Jenkins RH, Bennagi R, Martin J, Phillips AO, Redman JE, Fraser DJ. A conserved stem loop motif in the 5'untranslated region regulates transforming growth factor-β(1) translation. PLoS One 2010; 5:e12283. [PMID: 20865036 PMCID: PMC2928724 DOI: 10.1371/journal.pone.0012283] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2010] [Accepted: 07/16/2010] [Indexed: 01/10/2023] Open
Abstract
Transforming growth factor-β1 (TGF-β1) regulates cellular proliferation, differentiation, migration, and survival. The human TGF-β1 transcript is inherently poorly translated, and translational activation has been documented in relation to several stimuli. In this paper, we have sought to identify in cis regulatory elements within the TGF-β1 5′Untranslated Region (5′UTR). In silico analysis predicted formation of stable secondary structure in a G/C-rich element between nucleotides +77 to +106, and demonstrated that this element is highly conserved across species. Circular dichroism spectroscopy confirmed the presence of secondary structure in this region. The proximal 5′UTR was inhibitory to translation in reporter gene experiments, and mutation of the secondary structure motif increased translational efficiency. Translational regulation of TGF-β1 mRNA is linked to altered binding of YB-1 protein to its 5′UTR. Immunoprecipitation-RT-qPCR demonstrated a high basal association of YB-1 with TGF-β1 mRNA. However, mutation of the secondary structure motif did not prevent interaction of YB-1 with the 5′UTR, suggesting that YB-1 binds to this region due to its G/C-rich composition, rather than a specific, sequence-dependent, binding site. These data identify a highly conserved element within the TGF-β1 5′UTR that forms stable secondary structure, and is responsible for the inherent low translation efficiency of this cytokine.
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Affiliation(s)
- Robert H. Jenkins
- Institute of Nephrology, School of Medicine, Cardiff University, Heath Park, Cardiff, Wales, United Kingdom
| | - Rasha Bennagi
- Institute of Nephrology, School of Medicine, Cardiff University, Heath Park, Cardiff, Wales, United Kingdom
| | - John Martin
- Institute of Nephrology, School of Medicine, Cardiff University, Heath Park, Cardiff, Wales, United Kingdom
| | - Aled O. Phillips
- Institute of Nephrology, School of Medicine, Cardiff University, Heath Park, Cardiff, Wales, United Kingdom
| | - James E. Redman
- School of Chemistry, Cardiff University, Park Place, Cardiff, Wales, United Kingdom
| | - Donald J. Fraser
- Institute of Nephrology, School of Medicine, Cardiff University, Heath Park, Cardiff, Wales, United Kingdom
- * E-mail:
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Fraser CS. The molecular basis of translational control. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2009; 90:1-51. [PMID: 20374738 DOI: 10.1016/s1877-1173(09)90001-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Our current understanding of eukaryotic protein synthesis has emerged from many years of biochemical, genetic and biophysical approaches. Significant insight into the molecular details of the mechanism has been obtained, although there are clearly many aspects of the process that remain to be resolved. Importantly, our understanding of the mechanism has identified a number of key stages in the pathway that contribute to the regulation of general and gene-specific translation. Not surprisingly, translational control is now widely accepted to play a role in aspects of cell stress, growth, development, synaptic function, aging, and disease. This chapter reviews the mechanism of eukaryotic protein synthesis and its relevance to translational control.
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Affiliation(s)
- Christopher S Fraser
- Department of Molecular and Cellular Biology, University of California at Davis, Davis, California 95616, USA
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14
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Vesely PW, Staber PB, Hoefler G, Kenner L. Translational regulation mechanisms of AP-1 proteins. MUTATION RESEARCH-REVIEWS IN MUTATION RESEARCH 2009; 682:7-12. [DOI: 10.1016/j.mrrev.2009.01.001] [Citation(s) in RCA: 344] [Impact Index Per Article: 22.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/22/2008] [Revised: 01/05/2009] [Accepted: 01/05/2009] [Indexed: 11/29/2022]
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15
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Kaye NM, Emmett KJ, Merrick WC, Jankowsky E. Intrinsic RNA binding by the eukaryotic initiation factor 4F depends on a minimal RNA length but not on the m7G cap. J Biol Chem 2009; 284:17742-50. [PMID: 19414591 DOI: 10.1074/jbc.m109.009001] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The eukaryotic initiation factor 4F (eIF4F) is thought to be the first factor to bind mRNA during 7-methylguanosine (m7G) cap-dependent translation initiation. The multipartite eIF4F contains the cap-binding protein eIF4E, and it is assumed that eIF4F binds mRNAs primarily at the 5' m7G cap structure. We have analyzed equilibrium binding of rabbit eIF4F to a series of diverse RNAs and found no impact of the 5'-cap on the stability of eIF4F-RNA complexes. However, eIF4F preferentially and cooperatively binds to RNAs with a minimum length of approximately 60 nucleotides in vitro. Furthermore, translation activity in rabbit reticulocyte lysate is strongly inhibited by RNAs exceeding this length, but not by shorter ones, consistent with the notion that eIF4F in its physiological environment preferentially binds longer RNAs, too. Collectively, our results indicate that intrinsic RNA binding by eIF4F depends on a minimal RNA length, rather than on cap recognition. The nonetheless essential m7G cap may either function at steps subsequent to eIF4F-RNA binding, or other factors facilitate preferential binding of eIF4F to the m7G cap.
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Affiliation(s)
- Nicholas M Kaye
- Department of Biochemistry, Center for RNA Molecular Biology, School of Medicine, Case Western Reserve University, Cleveland, OH 44106, USA
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16
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Santhanam AN, Bindewald E, Rajasekhar VK, Larsson O, Sonenberg N, Colburn NH, Shapiro BA. Role of 3'UTRs in the translation of mRNAs regulated by oncogenic eIF4E--a computational inference. PLoS One 2009; 4:e4868. [PMID: 19290046 PMCID: PMC2654073 DOI: 10.1371/journal.pone.0004868] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2008] [Accepted: 02/01/2009] [Indexed: 01/07/2023] Open
Abstract
Eukaryotic cap-dependent mRNA translation is mediated by the initiation factor eIF4E, which binds mRNAs and stimulates efficient translation initiation. eIF4E is often overexpressed in human cancers. To elucidate the molecular signature of eIF4E target mRNAs, we analyzed sequence and structural properties of two independently derived polyribosome recruited mRNA datasets. These datasets originate from studies of mRNAs that are actively being translated in response to cells over-expressing eIF4E or cells with an activated oncogenic AKT: eIF4E signaling pathway, respectively. Comparison of eIF4E target mRNAs to mRNAs insensitive to eIF4E-regulation has revealed surprising features in mRNA secondary structure, length and microRNA-binding properties. Fold-changes (the relative change in recruitment of an mRNA to actively translating polyribosomal complexes in response to eIF4E overexpression or AKT upregulation) are positively correlated with mRNA G+C content and negatively correlated with total and 3'UTR length of the mRNAs. A machine learning approach for predicting the fold change was created. Interesting tendencies of secondary structure stability are found near the start codon and at the beginning of the 3'UTR region. Highly upregulated mRNAs show negative selection (site avoidance) for binding sites of several microRNAs. These results are consistent with the emerging model of regulation of mRNA translation through a dynamic balance between translation initiation at the 5'UTR and microRNA binding at the 3'UTR.
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Affiliation(s)
- Arti N. Santhanam
- Gene Regulation Section, Laboratory of Cancer Prevention, National Cancer Institute, Frederick, Maryland, United States of America
| | - Eckart Bindewald
- Basic Research Program, SAIC-Frederick, Inc., National Cancer Institute-Frederick, Frederick, Maryland, United States of America
| | - Vinagolu K. Rajasekhar
- Developmental Biology Program, Memorial Sloan Kettering Cancer Center, New York, New York, United States of America
| | - Ola Larsson
- Department of Biochemistry and McGill Cancer Center, McGill University, Montreal, Quebec, Canada
| | - Nahum Sonenberg
- Department of Biochemistry and McGill Cancer Center, McGill University, Montreal, Quebec, Canada
| | - Nancy H. Colburn
- Basic Research Program, SAIC-Frederick, Inc., National Cancer Institute-Frederick, Frederick, Maryland, United States of America
| | - Bruce A. Shapiro
- Center for Cancer Research, Nanobiology Program, National Cancer Institute, Frederick, Maryland, United States of America
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17
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Zenkova MA, Karpova GG. Imperfectly matched nucleic acid complexes and their biochemical manifestation. RUSSIAN CHEMICAL REVIEWS 2007. [DOI: 10.1070/rc1993v062n04abeh000023] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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18
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Boiziau C, Boutorine AS, Loreau N, Verspieren P, Thuong NT, Toulmé JJ. Effect of Antisense Oligonucleotides Linked to Alkylating Agents on In Vitro Translation of Rabbit β-Globin andTypuaosomu bruceimRNAs. ACTA ACUST UNITED AC 2007. [DOI: 10.1080/07328319108046451] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- C. Boiziau
- a INSERM U201, Muséum National d'Histoire Naturelle , 43 rue Cuvier, F-75005 , Paris , France
- d Laboratoire de Biophysique MolCculaire , Universite de Bordeaux II , Bat 3A, 146 rue Léo Saignat, 33076 , Bordeaux Cedex , France
| | - A. S. Boutorine
- a INSERM U201, Muséum National d'Histoire Naturelle , 43 rue Cuvier, F-75005 , Paris , France
- b Institute of BioOrganic Chemistry, Siberian Division of the USSR Academy of Sciences , 630090 , Novosibirsk , USSR
| | - N. Loreau
- a INSERM U201, Muséum National d'Histoire Naturelle , 43 rue Cuvier, F-75005 , Paris , France
| | - P. Verspieren
- a INSERM U201, Muséum National d'Histoire Naturelle , 43 rue Cuvier, F-75005 , Paris , France
- d Laboratoire de Biophysique MolCculaire , Universite de Bordeaux II , Bat 3A, 146 rue Léo Saignat, 33076 , Bordeaux Cedex , France
| | - N. T. Thuong
- c Centre de Biophysique Moléculaire, CNRS , F-45071 , Orléans cedex , France
| | - J. J. Toulmé
- a INSERM U201, Muséum National d'Histoire Naturelle , 43 rue Cuvier, F-75005 , Paris , France
- d Laboratoire de Biophysique MolCculaire , Universite de Bordeaux II , Bat 3A, 146 rue Léo Saignat, 33076 , Bordeaux Cedex , France
- e Laboratoire de Biophysique Molbculaire , Universite de Bordeaux 11 , Bat 3A, 146 rue Léo Saignat, 33076 , Bordeaux Cedex , France
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19
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Kamura N, Sawasaki T, Kasahara Y, Takai K, Endo Y. Selection of 5'-untranslated sequences that enhance initiation of translation in a cell-free protein synthesis system from wheat embryos. Bioorg Med Chem Lett 2005; 15:5402-6. [PMID: 16213724 DOI: 10.1016/j.bmcl.2005.09.013] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2005] [Revised: 08/31/2005] [Accepted: 09/01/2005] [Indexed: 11/24/2022]
Abstract
Random libraries of mRNA 5'-leader sequences were screened to obtain some sequences that can stimulate the translation initiation in a cell-free translation system from wheat embryos as efficiently as the Omega sequence from tobacco mosaic virus. Several sequences that are as useful as the Omega sequence and are homologous to no known sequences survived the screening. We expect that these sequences add useful options to the cell-free protein synthesis system that is becoming a powerful tool in the post-genomic researches.
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Affiliation(s)
- Nami Kamura
- Department of Applied Chemistry, Faculty of Engineering, Ehime University, 3, Bunkyo-cho, Matsuyama, Ehime 790-8577, Japan
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20
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Abstract
Great advances have been made in the past three decades in understanding the molecular mechanics underlying protein synthesis in bacteria, but our understanding of the corresponding events in eukaryotic organisms is only beginning to catch up. In this review we describe the current state of our knowledge and ignorance of the molecular mechanics underlying eukaryotic translation. We discuss the mechanisms conserved across the three kingdoms of life as well as the important divergences that have taken place in the pathway.
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Affiliation(s)
- Lee D Kapp
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, 725 North Wolfe Street, Baltimore, Maryland 21205-2185, USA.
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21
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Dmitriev SE, Terenin IM, Dunaevsky YE, Merrick WC, Shatsky IN. Assembly of 48S translation initiation complexes from purified components with mRNAs that have some base pairing within their 5' untranslated regions. Mol Cell Biol 2004; 23:8925-33. [PMID: 14645505 PMCID: PMC309656 DOI: 10.1128/mcb.23.24.8925-8933.2003] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The reconstitution of translation initiation complexes from purified components is a reliable approach to determine the complete set of essential canonical initiation factors and auxiliary proteins required for the 40S ribosomal subunit to locate the initiation codon on individual mRNAs. Until now, it has been successful mostly for formation of 48S translation initiation complexes with viral IRES elements. Among cap-dependent mRNAs, only globin mRNAs and transcripts with artificial 5' leaders were amenable to this assembly. Here, with modified conditions for the reconstitution, 48S complexes have been successfully assembled with the 5' UTR of beta-actin mRNA (84 nucleotides) and the tripartite leader of adenovirus RNAs (232 nucleotides), though the latter has been able to use only the scanning rather then the shunting model of translation initiation with canonical initiation factors. We show that initiation factor 4B is essential for mRNAs that have even a rather moderate base pairing within their 5' UTRs (with the cumulative stability of the secondary structure within the entire 5' UTR < -13 kcal/mol) and not essential for beta-globin mRNA. A recombinant eIF4B poorly substitutes for the native factor. The 5' UTRs with base-paired G residues reveal a very sharp dependence on the eIF4B concentration to form the 48S complex. The data suggest that even small variations in concentration or activity of eIF4B in mammalian cells may differentially affect the translation of different classes of cap-dependent cellular mRNAs.
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Affiliation(s)
- Sergei E Dmitriev
- A. N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, 119899 Moscow, Russia
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22
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Yang HS, Jansen AP, Komar AA, Zheng X, Merrick WC, Costes S, Lockett SJ, Sonenberg N, Colburn NH. The transformation suppressor Pdcd4 is a novel eukaryotic translation initiation factor 4A binding protein that inhibits translation. Mol Cell Biol 2003; 23:26-37. [PMID: 12482958 PMCID: PMC140682 DOI: 10.1128/mcb.23.1.26-37.2003] [Citation(s) in RCA: 401] [Impact Index Per Article: 19.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2002] [Revised: 09/19/2002] [Accepted: 10/02/2002] [Indexed: 12/16/2022] Open
Abstract
Pdcd4 is a novel transformation suppressor that inhibits tumor promoter-induced neoplastic transformation and the activation of AP-1-dependent transcription required for transformation. A yeast two-hybrid analysis revealed that Pdcd4 associates with the eukaryotic translation initiation factors eIF4AI and eIF4AII. Immunofluorescent confocal microscopy showed that Pdcd4 colocalizes with eIF4A in the cytoplasm. eIF4A is an ATP-dependent RNA helicase needed to unwind 5' mRNA secondary structure. Recombinant Pdcd4 specifically inhibited the helicase activity of eIF4A and eIF4F. In vivo translation assays showed that Pdcd4 inhibited cap-dependent but not internal ribosome entry site (IRES)-dependent translation. In contrast, Pdcd4(D418A), a mutant inactivated for binding to eIF4A, failed to inhibit cap-dependent or IRES-dependent translation or AP-1 transactivation. Recombinant Pdcd4 prevented eIF4A from binding to the C-terminal region of eIF4G (amino acids 1040 to 1560) but not to the middle region of eIF4G(amino acids 635 to 1039). In addition, both Pdcd4 and Pdcd4(D418A) bound to the middle region of eIF4G. The mechanism by which Pdcd4 inhibits translation thus appears to involve inhibition of eIF4A helicase, interference with eIF4A association-dissociation from eIF4G, and inhibition of eIF4A binding to the C-terminal domain of eIF4G. Pdcd4 binding to eIF4A is linked to its transformation-suppressing activity, as Pdcd4-eIF4A binding and consequent inhibition of translation are required for Pdcd4 transrepression of AP-1.
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Affiliation(s)
- Hsin-Sheng Yang
- Gene Regulation Section, Center for Cancer Research, National Cancer Institute, Frederick, Maryland 21702, USA.
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23
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Stacey SN, Jordan D, Williamson AJ, Brown M, Coote JH, Arrand JR. Leaky scanning is the predominant mechanism for translation of human papillomavirus type 16 E7 oncoprotein from E6/E7 bicistronic mRNA. J Virol 2000; 74:7284-97. [PMID: 10906182 PMCID: PMC112249 DOI: 10.1128/jvi.74.16.7284-7297.2000] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2000] [Accepted: 05/19/2000] [Indexed: 11/20/2022] Open
Abstract
Human papillomaviruses (HPV) are unique in that they generate mRNAs that apparently can express multiple proteins from tandemly arranged open reading frames. The mechanisms by which this is achieved are uncertain and are at odds with the basic predictions of the scanning model for translation initiation. We investigated the unorthodox mechanism by which the E6 and E7 oncoproteins from human papillomavirus type 16 (HPV-16) can be translated from a single, bicistronic mRNA. The short E6 5' untranslated region (UTR) was shown to promote translation as efficiently as a UTR from Xenopus beta-globin. Insertion of a secondary structural element into the UTR inhibited both E6 and E7 expression, suggesting that E7 expression depends on ribosomal scanning from the 5' end of the mRNA. E7 translation was found to be cap dependent, but E6 was more dependent on capping and eIF4F activity than E7. Insertion of secondary structural elements at various points in the region upstream of E7 profoundly inhibited translation, indicating that scanning was probably continuous. Insertion of the E6 region between Renilla and firefly luciferase genes revealed little or no internal ribosomal entry site activity. However when E6 was located at the 5' end of the mRNA, it permitted over 100-fold-higher levels of downstream cistron translation than did the Renilla open reading frame. Internal AUGs in the E6 region with strong or intermediate Kozak sequence contexts were unable to inhibit E7 translation, but initiation at the E7 AUG was efficient and accurate. These data support a model in which E7 translation is facilitated by an extreme degree of leaky scanning, requiring the negotiation of 13 upstream AUGs. Ribosomal initiation complexes which fail to initiate at the E6 start codon can scan through to the E7 AUG without initiating translation, but competence to initiate is achieved once the E7 AUG is reached. These findings suggest that the E6 region of HPV-16 comprises features that sponsor both translation of the E6 protein and enhancement of translation at a downstream site.
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MESH Headings
- 5' Untranslated Regions
- Base Sequence
- Codon, Initiator
- Hot Temperature
- Humans
- Models, Molecular
- Molecular Sequence Data
- Oncogene Proteins, Viral/biosynthesis
- Oncogene Proteins, Viral/genetics
- Oncogene Proteins, Viral/metabolism
- Open Reading Frames/genetics
- Papillomaviridae/genetics
- Papillomaviridae/metabolism
- Papillomavirus E7 Proteins
- Potassium Chloride/metabolism
- Protein Biosynthesis
- Protein Structure, Secondary
- RNA Caps/genetics
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- RNA, Viral/genetics
- RNA, Viral/metabolism
- Repressor Proteins
- Ribosomes/genetics
- Ribosomes/metabolism
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Affiliation(s)
- S N Stacey
- Cancer Research Campaign, Department of Molecular Biology, Paterson Institute for Cancer Research, Christie Hospital, Manchester M20 4BX, United Kingdom.
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24
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Abstract
As obligate intracellular parasites, viruses rely exclusively on the translational machinery of the host cell for the synthesis of viral proteins. This relationship has imposed numerous challenges on both the infecting virus and the host cell. Importantly, viruses must compete with the endogenous transcripts of the host cell for the translation of viral mRNA. Eukaryotic viruses have thus evolved diverse mechanisms to ensure translational efficiency of viral mRNA above and beyond that of cellular mRNA. Mechanisms that facilitate the efficient and selective translation of viral mRNA may be inherent in the structure of the viral nucleic acid itself and can involve the recruitment and/or modification of specific host factors. These processes serve to redirect the translation apparatus to favor viral transcripts, and they often come at the expense of the host cell. Accordingly, eukaryotic cells have developed antiviral countermeasures to target the translational machinery and disrupt protein synthesis during the course of virus infection. Not to be outdone, many viruses have answered these countermeasures with their own mechanisms to disrupt cellular antiviral pathways, thereby ensuring the uncompromised translation of virion proteins. Here we review the varied and complex translational programs employed by eukaryotic viruses. We discuss how these translational strategies have been incorporated into the virus life cycle and examine how such programming contributes to the pathogenesis of the host cell.
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Affiliation(s)
- M Gale
- University of Texas Southwestern Medical Center, Dallas, Texas, USA.
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25
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Kwon CS, Chung WI. Differential roles of the 5' untranslated regions of cucumber mosaic virus RNAs 1, 2, 3 and 4 in translational competition. Virus Res 2000; 66:175-85. [PMID: 10725550 DOI: 10.1016/s0168-1702(00)00120-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
RNA species of plant tripartite RNA viruses show distinct translational activities in vitro when the viral RNA concentration is high. However, it is not known what causes the differential translation of virion RNAs. Using an in vitro wheat germ translation system, we investigated the translation efficiencies and competitive activities of chimeric cucumber mosaic virus (CMV) RNAs that contained viral untranslated regions (UTRs) and a luciferase-coding sequence. The chimeric RNAs exhibited distinct translation efficiencies and competitive activities. For example, the translation of chimeric CMV RNA 4 was about 40-fold higher than that of chimeric CMV RNA 3 in a competitive environment. The distinct translation resulted mainly from differences in competitive activities rather than translation efficiencies of the chimeric RNAs. The differential competitive activities were specified by viral 5 UTRs, but not by 3 UTRs or viral proteins. The competitive translational activities of the 5 UTRs were as follows: RNA 4 (coat protein)>RNAs 2 and 1 (2a and 1a protein, or replicase )> RNA 3 (3a protein).
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Affiliation(s)
- C S Kwon
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology, 373-1 Kusong-dong, Yusong-ku, Taejon, South Korea
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26
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Kwon CS, Chung W. A single-stranded loop in the 5' untranslated region of cucumber mosaic virus RNA 4 contributes to competitive translational activity. FEBS Lett 1999; 462:161-6. [PMID: 10580112 DOI: 10.1016/s0014-5793(99)01522-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The 5' untranslated region (UTR) of cucumber mosaic virus (CMV) RNA 4 confers a highly competitive translational advantage on a heterologous luciferase open reading frame. Here we investigated whether secondary structure in the 5' UTR contributes to this translational advantage. Stabilization of the 5' UTR RNA secondary structure inhibited competitive translational activity. Alteration of a potential single-stranded loop to a stem by substitution mutations greatly inhibited the competitive translational activity. Tobacco plants infected with wild type virus showed a 2.5-fold higher accumulation of maximal coat protein than did plants infected with a loop-mutant virus. Amplification of viral RNA in these plants could not explain the difference in accumulation of coat protein. Phylogenetic comparison showed that potential single-stranded loops of 12-23 nucleotides in length exist widely in subgroups of CMV.
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Affiliation(s)
- C S Kwon
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Taejon, South Korea
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27
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Daga RR, Jimenez J. Translational control of the cdc25 cell cycle phosphatase: a molecular mechanism coupling mitosis to cell growth. J Cell Sci 1999; 112 Pt 18:3137-46. [PMID: 10462529 DOI: 10.1242/jcs.112.18.3137] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The eukaryotic translation initiation factor 4A (eIF4A) is an RNA helicase required for translation initiation of eukaryotic mRNAs. By engineering fission yeast mutants with diminished eIF4A activity, we have found that translation of cdc25 mRNAs (a dosage-dependent activator of mitosis in all eukaryotic cells) is particularly sensitive to limitations of protein synthesis mediated by limited eIF4A activity. Genetic and biochemical analysis indicated that a rate-limited translation initiation of cdc25 mRNAs, exerted throughout its unusual 5′ untranslated leader, acts as a molecular sensor to ensure that a minimum cell mass (protein synthesis) is attained before mitosis occurs. The Cdc13 cyclin B is also among the limited pool of proteins whose translation is sensitive to reduced translation initiation activity. Interestingly, the 5′ leader sequences of cdc25 and cdc13 mRNAs have conserved features which are unusual in other yeast mRNAs, suggesting that common mechanisms operate in the expression of these two key mitotic activators at the translational level.
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Affiliation(s)
- R R Daga
- Unidad de Genética, Facultad de Ciencias, Universidad de Málaga, Campus Universitario de Teatinos, Spain
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28
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Rogers GW, Richter NJ, Merrick WC. Biochemical and kinetic characterization of the RNA helicase activity of eukaryotic initiation factor 4A. J Biol Chem 1999; 274:12236-44. [PMID: 10212190 DOI: 10.1074/jbc.274.18.12236] [Citation(s) in RCA: 247] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Eukaryotic initiation factor (eIF) 4A is the prototypic member of the DEAD box family of proteins and has been proposed to act as an RNA helicase to unwind secondary structure in the 5'-untranslated region of eukaryotic mRNAs. Previous studies have shown that the RNA helicase activity of eIF4A is dependent on the presence of a second initiation factor, eIF4B. In this report, eIF4A has been demonstrated to function independently of eIF4B as an ATP-dependent RNA helicase. The biochemical and kinetic properties of this activity were examined. By using a family of RNA duplexes with an unstructured single-stranded region followed by a duplex region of increasing length and stability, it was observed that the initial rate of duplex unwinding decreased with increasing stability of the duplex. Furthermore, the maximum amount of duplex unwound also decreased with increasing stability. Results suggest that eIF4A acts in a non-processive manner. eIF4B and eIF4H were shown to stimulate the helicase activity of eIF4A, allowing eIF4A to unwind longer, more stable duplexes with both an increase in initial rate and maximum amount of duplex unwound. A simple kinetic model is proposed to explain the mechanism by which eIF4A unwinds RNA duplex structures in an ATP-dependent manner.
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Affiliation(s)
- G W Rogers
- Department of Biochemistry, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106-4935, USA
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29
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Novoa I, Carrasco L. Cleavage of eukaryotic translation initiation factor 4G by exogenously added hybrid proteins containing poliovirus 2Apro in HeLa cells: effects on gene expression. Mol Cell Biol 1999; 19:2445-54. [PMID: 10082510 PMCID: PMC84037 DOI: 10.1128/mcb.19.4.2445] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Efficient cleavage of both forms of eukaryotic initiation factor 4G (eIF4G-1 and eIF4G-2) has been achieved in HeLa cells by incubation with hybrid proteins containing poliovirus 2Apro. Entry of these proteins into cells is promoted by adenovirus particles. Substantial levels of ongoing translation on preexisting cellular mRNAs still continue for several hours after eIF4G degradation. Treatment of control HeLa cells with hypertonic medium causes an inhibition of translation that is reversed upon restoration of cells to normal medium. Protein synthesis is not restored in cells lacking intact eIF4G after hypertonic treatment. Notably, induction of synthesis of heat shock proteins still occurs in cells pretreated with poliovirus 2Apro, suggesting that transcription and translation of these mRNAs takes place even in the presence of cleaved eIF4G. Finally, the synthesis of luciferase was examined in a HeLa cell line bearing the luciferase gene under control of a tetracycline-regulated promoter. Transcription of the luciferase gene and transport of the mRNA to the cytoplasm occurs at control levels in eIF4G-deficient cells. However, luciferase synthesis is strongly inhibited in these cells. These findings indicate that intact eIF4G is necessary for the translation of mRNAs not engaged in translation with the exception of heat shock mRNAs but is not necessary for the translation of mRNAs that are being translated.
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Affiliation(s)
- I Novoa
- Centro de Biología Molecular, UAM-CSIC, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain
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30
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Abstract
Regulation of translation initiation is a central control point in animal cells. We review our current understanding of the mechanisms of regulation, drawing particularly on examples in which the biological consequences of the regulation are clear. Specific mRNAs can be controlled via sequences in their 5' and 3' untranslated regions (UTRs) and by alterations in the translation machinery. The 5'UTR sequence can determine which initiation pathway is used to bring the ribosome to the initiation codon, how efficiently initiation occurs, and which initiation site is selected. 5'UTR-mediated control can also be accomplished via sequence-specific mRNA-binding proteins. Sequences in the 3' untranslated region and the poly(A) tail can have dramatic effects on initiation frequency, with particularly profound effects in oogenesis and early development. The mechanism by which 3'UTRs and poly(A) regulate initiation may involve contacts between proteins bound to these regions and the basal translation apparatus. mRNA localization signals in the 3'UTR can also dramatically influence translational activation and repression. Modulations of the initiation machinery, including phosphorylation of initiation factors and their regulated association with other proteins, can regulate both specific mRNAs and overall translation rates and thereby affect cell growth and phenotype.
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Affiliation(s)
- N K Gray
- Department of Biochemistry, University of Wisconsin, Madison 53706, USA
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31
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Gavin AC, Schorderet-Slatkine S. Ribosomal S6 kinase p90rsk and mRNA cap-binding protein eIF4E phosphorylations correlate with MAP kinase activation during meiotic reinitiation of mouse oocytes. Mol Reprod Dev 1997; 46:383-91. [PMID: 9041142 DOI: 10.1002/(sici)1098-2795(199703)46:3<383::aid-mrd18>3.0.co;2-#] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
During meiotic reinitiation of the mouse oocyte, entry into M-phase is regulated by changes of protein phosphorylation and by the stimulation of selective mRNA translation following the nuclear membrane dissolution. Our results reveal that M-phase kinases (MAP kinase and histone H1 kinase) are being activated together with S6 kinase and with the phosphorylation of eIF4E, the cap-binding subunit of the initiation factor eIF-4F. In order to test which signaling pathway(s) is(are) involved, okadaic acid and cycloheximide have been used as tools for differentially modulating MAP and histone H1 kinase activities. A role for MAP kinases in the phosphorylation of eIF4E and the activation of S6 kinase is suggested. The possible implication of p90rsk and/or of p70s6k in the overall increase in S6 kinase activity has been examined. p70s6k does not appear to be involved since phosphorylated forms are found in prophase and maturing oocytes. In contrast, p90rsk is phosphorylated and activated in maturing oocytes. p90rSk phosphorylation correlates with the activation of S6 kinase. These results suggest that the overall increase of S6 kinase activity is mostly due to p90rsk activation. The roles of eIF4E phosphorylation and S6 kinase activation in the physiological induction of M-phase and in the okadaic acid-induced premature mitotic events are discussed.
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Affiliation(s)
- A C Gavin
- Clinique de Stérilité et d'Endocrinologie Gynécologique, Department of Obstetrics and Gynaecology, Hôpital Cantonal Universitaire, Geneva,Switzerland
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32
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Yueh A, Schneider RJ. Selective translation initiation by ribosome jumping in adenovirus-infected and heat-shocked cells. Genes Dev 1996; 10:1557-67. [PMID: 8666238 DOI: 10.1101/gad.10.12.1557] [Citation(s) in RCA: 161] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Translation initiation on eukaryotic mRNAs usually occurs by 5'-processive scanning of 40S ribosome subunits from the m7GTP-cap to the initiating AUG. In contrast, picornavirus and some specialized mRNAS initiate translation by internally binding ribosomes. A poorly described third mechanism of initiation, referred to as ribosome shunting or jumping, involves discontinuous scanning by 40S ribosome subunits, in which large segments of the 5' noncoding region are bypassed. Ribosome shunting has only been observed to date on a cauliflower mosaic virus mRNA. In this report we show that the family of adenovirus late mRNAs, which are preferentially translated during infection, use a ribosome jumping mechanism to initiate protein synthesis. Late adenovirus mRNAs contain a common 5'-noncoding region known as the tripartite leader, which confers preferential translation by reducing the requirement for the rate-limiting initiation factor eIF-4F (cap-binding protein complex). Adenovirus inhibits cell protein synthesis largely by inactivating eIF-4F. We show that the tripartite leader directs both 5' linear ribosome scanning and ribosome jumping when eIF-4F is abundant but exclusively uses a ribosome jumping mechanism during late adenovirus infection or heat shock (stress) of mammalian cells, when eIF-4F is altered or inactivated. Shunting is directed by a complex group of secondary structures in the tripartite leader and is facilitated by one or more unidentified viral late gene products. We propose that shunting may represent a widespread mechanism to facilitate selective translation of specialized classes of capped mRNAs, including some stress and developmentally regulated mRNAs, which possess little requirement for eIF-4F but do not initiate by internal ribosome binding.
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Affiliation(s)
- A Yueh
- Department of Biochemistry and Kaplan Cancer Center, New York University Medical School, New York 10016, USA
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33
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Abstract
The cap-binding complex eIF-4F plays a major role in the control of translation initiation, and overexpression of its limiting subunit, eIF-4E, leads to the deregulation of cellular growth. The recent cloning of eIF-4E binding proteins (4E-BPs) has uncovered a previously unsuspected pathway for the regulation of eIF-4E activity, through sequestration of eIF-4E as a complex with 4E-BPs.
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Affiliation(s)
- S Mader
- Department of Biochemistry, McGill University, Montreal, Quebec, Canada
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34
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Affiliation(s)
- R J Schneider
- Department of Biochemistry, New York University Medical School, New York 10016, USA
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35
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Zhang Y, Feigenblum D, Schneider RJ. A late adenovirus factor induces eIF-4E dephosphorylation and inhibition of cell protein synthesis. J Virol 1994; 68:7040-50. [PMID: 7933086 PMCID: PMC237141 DOI: 10.1128/jvi.68.11.7040-7050.1994] [Citation(s) in RCA: 53] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Adenovirus prevents host cell protein synthesis during its late phase of replication in large part by causing the underphosphorylation of translation initiation factor eIF-4E, a component of initiation factor eIF-4F (cap-binding protein complex). Late adenovirus mRNAs are preferentially translated because they possess a reduced requirement for eIF-4F. This study continues the characterization of the mechanism by which adenovirus inhibits cellular protein synthesis. First it is shown that adenovirus blocks the addition of phosphate to eIF-4E rather than enhancing its removal, establishing that the virus impairs a signalling pathway or protein kinase activity involved in eIF-4E phosphorylation. It is then shown that shutoff of cell protein synthesis and translation of late viral mRNAs are uncoupled, in that shutoff actually occurs a short time (1 to 3 h) after late adenovirus mRNAs are already undergoing translation. Finally, by using a variety of genetic mutants stalled at different stages in the viral life cycle, it was found that dephosphorylation of eIF-4E and inhibition of cell translation are not caused by early adenovirus gene products acting at late times or by events related to viral DNA replication. Instead, it is shown that inhibition of eIF-4E phosphorylation and cell translation are mediated upon activation of the viral major late transcription unit. These and other results presented indicate that the adenovirus signal which induces eIF-4E dephosphorylation and shutoff of cell protein synthesis is linked either to an activity of one or more late viral polypeptides, to double-stranded RNA produced by opposition of the early and late viral transcription units, or to both.
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Affiliation(s)
- Y Zhang
- Department of Biochemistry, New York University Medical Center, New York 10016
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36
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Abstract
Control of polypeptide synthesis plays an important role in cell proliferation and translation rates generally reflect the growth state of the cultured eukaryotic cell. Physiological regulation of protein synthesis is almost always exerted at the level of polypeptide chain initiation, with the binding of mRNA to the small ribosomal subunit a rate-limiting step in many cell systems. Studies have indicated key roles in the regulation of protein synthesis for the structural features of mRNA molecules and phosphorylation of initiation factors which catalyse this process. This review focuses on translational regulation at the level of mRNA binding to the ribosome and the role of phosphorylation of initiation factors in mediating both quantitative and qualitative control. The identity of putative kinases which may mediate these processes is addressed and a possible model for the role of a transient activation of initiation factors in cell growth or differentiation is presented.
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Affiliation(s)
- S J Morley
- Department of Biochemistry, School of Biological Sciences, University of Sussex, Falmer, Brighton, UK
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37
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Abstract
In addition to the m7G cap structure, the length of the 5' UTR and the position and context of the AUG initiator codon (which have been discussed elsewhere in this volume), higher order structures within mRNA represent a critical parameter for translation. The role of RNA structure in translation initiation will be considered primarily, although structural elements have also been found to affect translation elongation and termination. We will first describe the different effects of higher order RNA structures per se, and then consider specific examples of RNA structural elements which control translation initiation by providing binding sites for regulatory proteins.
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Affiliation(s)
- N K Gray
- Gene Expression Programme, European Molecular Biology Laboratory, Heidelberg, Germany
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38
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Hess M, Duncan R. RNA/protein interactions in the 5'-untranslated leader of HSP70 mRNA in Drosophila lysates. Lack of evidence for specific protein binding. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)34145-5] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
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39
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Rao G, Griendling K, Frederickson R, Sonenberg N, Alexander R. Angiotensin II induces phosphorylation of eukaryotic protein synthesis initiation factor 4E in vascular smooth muscle cells. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)37265-4] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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40
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Cocuzzi ET, Walther SE, Denhardt DT. Expression and secretion of active mouse TIMP-1 using a baculovirus expression vector. Inflammation 1994; 18:35-43. [PMID: 8206645 DOI: 10.1007/bf01534596] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Mouse TIMP-1, one of the tissue inhibitors of metalloproteinases important in regulating turnover of extracellular matrix in both normal and pathological tissues, was previously expressed in E. coli in an inactive, nonglycosylated state that required refolding to become functional. Due to the difficulty of renaturation, an alternative to the prokaryotic expression system was sought. Since we are interested in studying the pharmacodynamics and pharmacokinetics of TIMP locally administered by controlled delivery to mice with experimentally induced arthritis, we also needed an efficient way of producing active TIMP in large quantities. Using the pBlueBacII transfer vector, we generated a recombinant baculovirus that in Sf9 cells could express glycosylated mouse TIMP-1 to about 3 mg of active protein/liter conditioned medium.
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Affiliation(s)
- E T Cocuzzi
- Department of Biological Sciences, Rutgers University, Piscataway, New Jersey 08855
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41
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Pantopoulos K, Johansson HE, Hentze MW. The role of the 5' untranslated region of eukaryotic messenger RNAs in translation and its investigation using antisense technologies. PROGRESS IN NUCLEIC ACID RESEARCH AND MOLECULAR BIOLOGY 1994; 48:181-238. [PMID: 7938549 PMCID: PMC7133200 DOI: 10.1016/s0079-6603(08)60856-9] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
This chapter discusses the recent advances in the field of translational control and the possibility of applying the powerful antisense technology to investigate some of the unanswered questions, especially those pertaining to the role of the 5’untranslated region ( UTR) on translation initiation. Translational regulation is predominantly exerted during the initiation phase that is considered to be the rate-limiting step. Two types of translational regulation can be distinguished: global, in which the initiation rate of (nearly) all cellular messenger RNA (mRNA) is controlled and selective, in which the translation rate of specific mRNAs varies in response to the biological stimuli. In most cases of global regulation, control is exerted via the phosphorylation state of certain initiation factors, whereas only a few examples of selective regulation have been characterized well enough to define the underlying molecular events. Interestingly, cis-acting regulatory sequences, affecting translation initiation, have been found not only in the 5’UTRs of selectively regulated mRNAs, but also in the 3’UTRs. Thus, in addition to the protein encoding open reading frames, both the 5’ and 3’UTRs of mRNAs must be considered for their effect on translation.
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Key Words
- alas, 5-aminolevulinate synthase
- bfgf, basic fibroblast growth factor
- bip, immunoglobulin-binding protein
- cat, chloramphenicol acetyltransferase
- dai, double-stranded rna-activated inhibitor
- ealas, erythroid-specific form of alas
- frp, ferritin repressor protein
- gcd, general control derepressible
- gcn, general control nonderepressible
- gef, guanine-nucleotide exchange factor
- grp, glucose-regulated protein
- hgh, human growth hormone
- icam, intracellular adhesion molecule
- ire, iron-responsive element
- ire-bp, iron-responsive element-binding protein
- ires, internal ribosomal entry site
- irf, iron regulatory factor
- irp, iron regulatory protein
- la, lupus erythematosus antigen
- lap, liver-enriched activating protein
- lip, liver-enriched inhibitory protein
- mep, methyl phosphonate
- pa, phosphoramidate
- pdgf, platelet-derived growth factor
- pest, phosphotriester
- pll, poly(1-lysine)
- po, phosphodiester
- ps, phosphorothioate
- ps2, phosphorodithioate
- ssl, suppressor of stem-loop
- tce, translational control element
- tgf, transforming growth factor
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Affiliation(s)
- K Pantopoulos
- Gene Expression Programme, European Molecular Biology Laboratory, Heidelberg, Germany
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42
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Kleene KC, Smith J. Translational activity of mouse protamine 1 messenger ribonucleoprotein particles in the reticulocyte and wheat germ cell-free translation systems. Mol Reprod Dev 1994; 37:12-20. [PMID: 7907489 DOI: 10.1002/mrd.1080370103] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Protamine 1 mRNAs are inactivated by a block to the initiation of translation in early spermatids and are translationally active in late spermatids in mice. To determine whether translation of protamine 1 mRNAs is inhibited by a protein repressor, the translational activity of ribonucleoprotein particles and deproteinized RNAs were compared in the reticulocyte and wheat germ cell-free translation lysates. To isolate RNPs, cytoplasmic extracts of total testes were fractionated by large-pore gel filtration chromatography. Ribonucleoprotein particles in the excluded fractions stimulated synthesis of radiolabeled translation products for protamine 1 about twofold less effectively than deproteinized RNAs in the reticulocyte lysate, but were inactive in the wheat germ lysate. The ability of translationally repressed protamine 1 ribonucleoprotein particles to form initiation complexes with 80S ribosomes in the reticulocyte lysate was also measured. Protamine 1 ribonucleoprotein particles isolated by gel filtration and in unfractionated cytoplasmic extracts of early spermatids were nearly as active in forming initiation complexes as deproteinized mRNAs. The isolation of ribonucleoprotein particles in buffers of varying ionic strength, protease inhibitors, and several other variables had no major effect on the ability of protamine 1 ribonucleoprotein particles to form initiation complexes in the reticulocyte lysate. These results can be explained by artifacts in the isolation or assay of ribonucleoprotein particles or by postulating that protamine 1 mRNAs are inactivated by a mechanism that does not involve protein repressors, such as sequestration.
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Affiliation(s)
- K C Kleene
- Department of Biology, University of Massachusetts at Boston 02125-33943
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43
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Levis C, Astier-Manifacier S. The 5' untranslated region of PVY RNA, even located in an internal position, enables initiation of translation. Virus Genes 1993; 7:367-79. [PMID: 8122396 DOI: 10.1007/bf01703392] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Potato virus Y (PVY) is the type member of the potyvirus group. Potyviruses, like picorna-, como-, and nepoviruses, belong to the picornavirus-like supergroup. All these viral RNAs have a VPg at their 5' end, and for four picornaviruses and one comovirus internal initiation of translation has been reported. To know if such a translational mechanism holds true for potyviral RNAs, the 5' nontranslated region (NTR) of PVY RNA was placed in an internal position, either by adding 91 bases upstream of the PVY 5'NTR or by inserting the PVY 5'NTR into an intercistronic region. The addition of extra bases stimulates translation in a rabbit reticulocyte lysate, and the presence of the PVY 5'NTR in the intercistronic region allows the synthesis of the second cistron. These findings strongly suggest that PVY RNA initiates translation by an internal ribosome-binding mechanism. Furthermore, the use of antisense oligodeoxynucleotides indicates that the entire 5'NTR seems to be involved in such a mechanism.
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Affiliation(s)
- C Levis
- Station de Phytopathologie, Institut National de la Recherche Agronomique, Versailles, France
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44
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Jaroszewski JW, Syi JL, Ghosh M, Ghosh K, Cohen JS. Targeting of antisense DNA: comparison of activity of anti-rabbit beta-globin oligodeoxyribonucleoside phosphorothioates with computer predictions of mRNA folding. ANTISENSE RESEARCH AND DEVELOPMENT 1993; 3:339-48. [PMID: 8155975 DOI: 10.1089/ard.1993.3.339] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
To assess the usefulness of computer-assisted modeling of mRNA as an aid in design of antisense DNA, the efficiency of inhibition of translation of rabbit beta-globin mRNA by various antisense sequences was compared with calculated structures of the mRNA. The model obtained by consideration of 30 lowest-energy computer-simulated structures is consistent with the high accessibility of the AUG initiation codon region known from digestion with nucleases and with previous antisense inhibition studies reported in the literature. Additional antisense inhibition data were obtained with 20-mer phosphorothioate oligonucleotides, targeted to regions of beta-globin mRNA differing moderately in their degree of participation in intramolecular folding. The efficiency of translation arrest by the oligonucleotides in cell-free expression systems (wheat germ extract and rabbit reticulocyte lysate) was obtained by measuring incorporation of [35S]methionine into total protein, and corrected for sequence-nonspecific inhibition using brome mosaic virus mRNA. In the presence of RNase H (wheat germ system), the inhibitory activity of the oligonucleotides showed correlation with the calculated secondary structure of mRNA, in particular at low oligonucleotide-to-mRNA ratios (correlation coefficient, 0.95). No correlation was observed in the reticulocyte lysate system, in which the inhibition is mediated by translational arrest.
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Affiliation(s)
- J W Jaroszewski
- Department of Organic Chemistry, Royal Danish School of Pharmacy, Copenhagen
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45
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Xu Z, Dholakia JN, Hille MB. Maturation hormone induced an increase in the translational activity of starfish oocytes coincident with the phosphorylation of the mRNA cap binding protein, eIF-4E, and the activation of several kinases. DEVELOPMENTAL GENETICS 1993; 14:424-39. [PMID: 8111971 DOI: 10.1002/dvg.1020140604] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The stimulation of translation in starfish oocytes by the maturation hormone, 1-methyladenine (1-MA), requires the activation or mobilization of both initiation factors and mRNAs [Xu and Hille, Cell Regul. 1:1057, 1990]. We identify here the translational initiation complex, eIF-4F, and the guanine nucleotide exchange factor for eIF-2, eIF-2B, as the rate controlling components of protein synthesis in immature oocytes of the starfish, Pisaster orchraceus. Increased phosphorylation of eIF-4E, the cap binding subunit of the eIF-4F complex, is coincident with the initial increase in translational activity during maturation of these oocytes. Significantly, protein kinase C activity increased during oocyte maturation in parallel with the increase in eIF-4E phosphorylation and protein synthesis. An increase in the activities of cdc2 kinase and mitogen-activated myelin basic protein kinase (MBP kinase) similarly coincide with the increase in eIF-4E phosphorylation. However, neither cdc2 kinase nor MBP kinase phosphorylates eIF-4E in vitro. Casein kinase II activity does not change during oocyte maturation, and therefore, cannot be responsible for the activation of translation. Treatment of oocytes with phorbol 12-myristate 13-acetate, an activator of protein kinase C, for 30 min prior to the addition of 1-MA resulted in the inhibition of 1-MA-induced phosphorylation of eIF-4E, translational activation, and germinal vesicle breakdown. Therefore, protein kinase C may phosphorylate eIF-4E, after very early events of maturation. Another possibility is that eIF-4E is phosphorylated by an unknown kinase that is activated by the cascade of reactions stimulated by 1-MA. In conclusion, our results suggest a role for the phosphorylation of eIF-4E in the activation of translation during maturation, similar to translational regulation during the stimulation of growth in mammalian cells.
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Affiliation(s)
- Z Xu
- Department of Zoology, University of Washington, Seattle 98195
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46
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Berben-Bloemheuvel G, Kasperaitis MA, van Heugten H, Thomas AA, van Steeg H, Voorma HO. Interaction of initiation factors with the cap structure of chimaeric mRNA containing the 5'-untranslated regions of Semliki Forest virus RNA is related to translational efficiency. EUROPEAN JOURNAL OF BIOCHEMISTRY 1992; 208:581-7. [PMID: 1396664 DOI: 10.1111/j.1432-1033.1992.tb17222.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Chimaeric chloramphenicol acetyltransferase (CAT) mRNA, containing the leader sequences of genomic 42S RNA and subgenomic 26S RNA of Semliki Forest virus (SFV) were synthesized by in-vitro transcription. These transcripts were translated with different efficiencies, as the authentic mRNA in SFV-infected cells. Therefore, they can be used as model mRNA species to study the mechanism underlying SFV-directed shut off of host protein synthesis. The interaction of translation initiation factors with the 5' cap structure was studied. Transcripts prepared in vitro using T7 RNA polymerase were capped and methylated posttranscriptionally with [32P]-GTP and S-adenosyl-L-methionine to yield cap-labelled mRNA species. Irradiation with ultraviolet light of 26S CAT and 42S CAT transcripts, together with crude rabbit reticulocyte initiation factors, resulted in the cap-specific cross-linking of eukaryotic initiation factors (eIF) eIF-4E and eIF-4B. The relative binding efficiency of these two factors to the cap structure of the various transcripts was, however, markedly different; the cap structure present in 26S CAT mRNA interacted efficiently with cap-binding proteins, whereas the cap structure of 42S CAT mRNA hardly bound to these proteins. Comparable results were obtained under competitive conditions. Data are presented that the secondary structure close to the 5' cap structure determines the efficiency of recognition of the mRNA by these initiation factors. Using a chemical cross-linking assay, it was demonstrated that eIF-4F, and also eIF-4E, differentially interacted with the cap structure of the various transcripts. The data are discussed with respect to the possible mechanisms involved in SFV-induced shut off of host cell protein synthesis.
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47
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Ricker RD, Kaji A. Studies on antisense inhibition of translation in vitro. Anomalies and re-evaluation. FEBS Lett 1992; 309:363-70. [PMID: 1516711 DOI: 10.1016/0014-5793(92)80808-t] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Experiments were carried out to better characterize antisense control of translation. Results in an E. coli system confirmed specific inhibition of poly(U) translation. At low concentrations, certain homopolymers (including poly(rA)) stimulated translation. Oligo(dA(n)) was inhibitory at n less than or equal to 8. Translation of globin mRNA in reticulocyte lysates indicated that ssDNA 15-mers targeted at beta-globin mRNA inhibited both alpha- and beta-globin production. Sequences targeted immediately downstream of the AUG were the least effective in inhibition. These and other anomalies are discussed here in relation to those of others, emphasizing caution in performing antisense experiments.
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Affiliation(s)
- R D Ricker
- Department of Microbiology, University of Pennsylvania, School of Medicine, Philadelphia 19104-6076
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48
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Baker B, Miraglia L, Hagedorn C. Modulation of eucaryotic initiation factor-4E binding to 5'-capped oligoribonucleotides by modified anti-sense oligonucleotides. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(19)49937-7] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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49
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van Heugten HA, Thomas AA, Voorma HO. Interaction of protein synthesis initiation factors with the mRNA cap structure. Biochimie 1992; 74:463-75. [PMID: 1637872 DOI: 10.1016/0300-9084(92)90087-u] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The mechanism of mRNA recognition by proteins interacting with the mRNA cap structure was investigated by photochemical cross-linking of proteins with 32P-labelled reoviral RNAs. Using ribosomal washes as a source of eukaryotic protein synthesis initiation factors, we identified the well-known cap binding proteins eIF-4B and -4E, but eIF-2 and eIF-3 as well. The interplay of purified eIF-4A, -4B, and -4F was studied in relation to ATP dependence and cap analogue sensitivity of cap binding. Next to their well-known roles in the initiation process, eIF-2 and eIF-3 also cross-linked to the 5' cap. eIF-2 stimulated eIF-4B and -4E cross-linking, an observation that has been previously described more extensively. The interaction of eIF-2 with the 5' end of mRNA was extremely sensitive to K(+)-ions and was resistant to a high concentration of Mg(2+)-ions; this influence of mono- and divalent ions was in contrast with the cross-linking of eIF-4B and -4E. Optimal interaction of these factors was obtained at moderate K+ concentration and low Mg(2+)-ion concentrations. eIF-2 cross-linking was sensitive to high protein to mRNA ratios indicating a weak affinity as compared to eIF-4E and -4B. The interaction of eIF-3 with the cap of mRNA is also weak as it was counteracted by all other cap binding proteins, leading to an inability to detect the cross-linking of this protein in crude eIF preparations. Time kinetics of formation of complexes suggested eIF-2 to be one of the first factors to interact with mRNA. Preformed RNA-protein complexes were dissociated after cap analogue addition, suggesting reversible interactions between RNA and proteins.
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Affiliation(s)
- H A van Heugten
- Department of Molecular Cell Biology, University of Utrecht, The Netherlands
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50
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Affiliation(s)
- C G Proud
- Department of Biochemistry, School of Medical Sciences, University of Bristol, England
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