1
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Mars JC, Culjkovic-Kraljacic B, Borden KL. eIF4E orchestrates mRNA processing, RNA export and translation to modify specific protein production. Nucleus 2024; 15:2360196. [PMID: 38880976 PMCID: PMC11185188 DOI: 10.1080/19491034.2024.2360196] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2024] [Accepted: 05/22/2024] [Indexed: 06/18/2024] Open
Abstract
The eukaryotic translation initiation factor eIF4E acts as a multifunctional factor that simultaneously influences mRNA processing, export, and translation in many organisms. Its multifactorial effects are derived from its capacity to bind to the methyl-7-guanosine cap on the 5'end of mRNAs and thus can act as a cap chaperone for transcripts in the nucleus and cytoplasm. In this review, we describe the multifactorial roles of eIF4E in major mRNA-processing events including capping, splicing, cleavage and polyadenylation, nuclear export and translation. We discuss the evidence that eIF4E acts at two levels to generate widescale changes to processing, export and ultimately the protein produced. First, eIF4E alters the production of components of the mRNA processing machinery, supporting a widescale reprogramming of multiple mRNA processing events. In this way, eIF4E can modulate mRNA processing without physically interacting with target transcripts. Second, eIF4E also physically interacts with both capped mRNAs and components of the RNA processing or translation machineries. Further, specific mRNAs are sensitive to eIF4E only in particular mRNA processing events. This selectivity is governed by the presence of cis-acting elements within mRNAs known as USER codes that recruit relevant co-factors engaging the appropriate machinery. In all, we describe the molecular bases for eIF4E's multifactorial function and relevant regulatory pathways, discuss the basis for selectivity, present a compendium of ~80 eIF4E-interacting factors which play roles in these activities and provide an overview of the relevance of its functions to its oncogenic potential. Finally, we summarize early-stage clinical studies targeting eIF4E in cancer.
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Affiliation(s)
- Jean-Clément Mars
- Institute of Research in Immunology and Cancer, Department of Pathology and Cell Biology, Université de Montréal, Montréal, QC, Canada
| | - Biljana Culjkovic-Kraljacic
- Institute of Research in Immunology and Cancer, Department of Pathology and Cell Biology, Université de Montréal, Montréal, QC, Canada
| | - Katherine L.B. Borden
- Institute of Research in Immunology and Cancer, Department of Pathology and Cell Biology, Université de Montréal, Montréal, QC, Canada
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2
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Bollu A, Schepers H, Klöcker N, Erguven M, Lawrence-Dörner AM, Rentmeister A. Visible Light Activates Coumarin-Caged mRNA for Cytoplasmic Cap Methylation in Cells. Chemistry 2024; 30:e202303174. [PMID: 37883670 DOI: 10.1002/chem.202303174] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2023] [Accepted: 10/23/2023] [Indexed: 10/28/2023]
Abstract
Protein synthesis is important and regulated by various mechanisms in the cell. Translation initiation in eukaryotes starts at the 5' cap and is the most complex of the three phases of mRNA translation. It requires methylation of the N7 position of the terminal guanosine (m7 G). The canonical capping occurs in the nucleus, however, cytoplasmic recapping has been discovered. It functions in switching mRNAs between translating and non-translating states, but the individual steps are difficult to dissect. We targeted cytoplasmic cap methylation as the ultimate step of cytoplasmic recapping. We present an N7G photocaged 5' cap that can be activated for cytoplasmic methylation by visible light. We report chemical and chemo-enzymatic synthesis of this 5' cap with 7-(diethylamino)-4-methyl-coumarin (DEACM) at the N7G and validate that it is not bound by translation initiation factor 4E (eIF4E). We demonstrate incorporation into mRNA, the release of unmethylated cap analog and enzymatic remethylation to functional cap 0 after irradiation at 450 nm. In cells, irradiation triggers translation of mRNAs with the N7G photocaged 5' cap via cytoplasmic cap methylation.
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Affiliation(s)
- Amarnath Bollu
- Department of Chemistry, Institute of Biochemistry, University of Münster, Corrensstraße 36, 48149, Münster, Germany
| | - Helena Schepers
- Department of Chemistry, Institute of Biochemistry, University of Münster, Corrensstraße 36, 48149, Münster, Germany
| | - Nils Klöcker
- Department of Chemistry, Institute of Biochemistry, University of Münster, Corrensstraße 36, 48149, Münster, Germany
| | - Mehmet Erguven
- Department of Chemistry, Institute of Biochemistry, University of Münster, Corrensstraße 36, 48149, Münster, Germany
- Cells in Motion Interfaculty Centre, University of Münster, Waldeyerstraße 15, 48149, Münster, Germany
| | - Ann-Marie Lawrence-Dörner
- Department of Chemistry, Institute of Biochemistry, University of Münster, Corrensstraße 36, 48149, Münster, Germany
| | - Andrea Rentmeister
- Department of Chemistry, Institute of Biochemistry, University of Münster, Corrensstraße 36, 48149, Münster, Germany
- Cells in Motion Interfaculty Centre, University of Münster, Waldeyerstraße 15, 48149, Münster, Germany
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3
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Hernández G, Vazquez-Pianzola P. eIF4E as a molecular wildcard in metazoans RNA metabolism. Biol Rev Camb Philos Soc 2023; 98:2284-2306. [PMID: 37553111 DOI: 10.1111/brv.13005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2023] [Revised: 07/01/2023] [Accepted: 07/25/2023] [Indexed: 08/10/2023]
Abstract
The evolutionary origin of eukaryotes spurred the transition from prokaryotic-like translation to a more sophisticated, eukaryotic translation. During this process, successive gene duplication of a single, primordial eIF4E gene encoding the mRNA cap-binding protein eukaryotic translation initiation factor 4E (eIF4E) gave rise to a plethora of paralog genes across eukaryotes that underwent further functional diversification in RNA metabolism. The ability to take different roles is due to eIF4E promiscuity in binding many partner proteins, rendering eIF4E a highly versatile and multifunctional player that functions as a molecular wildcard. Thus, in metazoans, eIF4E paralogs are involved in various processes, including messenger RNA (mRNA) processing, export, translation, storage, and decay. Moreover, some paralogs display differential expression in tissues and developmental stages and show variable biochemical properties. In this review, we discuss recent advances shedding light on the functional diversification of eIF4E in metazoans. We emphasise humans and two phylogenetically distant species which have become paradigms for studies on development, namely the fruit fly Drosophila melanogaster and the roundworm Caenorhabditis elegans.
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Affiliation(s)
- Greco Hernández
- mRNA and Cancer Laboratory, Unit of Biomedical Research on Cancer, National Institute of Cancer (Instituto Nacional de Cancerología, INCan), 22 San Fernando Ave., Tlalpan, Mexico City, 14080, Mexico
| | - Paula Vazquez-Pianzola
- Institute of Cell Biology, University of Bern, Baltzerstrasse 4, Berne, 3012, Switzerland
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4
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Kurpiejewski K, Jankowska-Anyszka M, Grzela R. N2 modified cap analogues as translation inhibitors and substrates for preparation of therapeutic mRNA. EUROPEAN BIOPHYSICS JOURNAL : EBJ 2023; 52:511-519. [PMID: 37656232 PMCID: PMC10618310 DOI: 10.1007/s00249-023-01676-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/23/2023] [Revised: 07/04/2023] [Accepted: 07/21/2023] [Indexed: 09/02/2023]
Abstract
In recent years many scientists have begun to focus on the mRNA molecule's emeregence as a new type of drug. Its fast-moving and successful career as a vaccine technology cannot be underestimated. mRNA provides new opportunities and allows for the rapid preparation of effective drugs at low cost. These extensive possibilities stem from a number of factors, but the small cap structure located at the 5' end of the mRNA is one contributing factor. Cap protects mRNA and ensures efficient recruitment to the biosynthesis machinery. Furthermore, it allows for the easy introduction of various modifications that influence the activity of the entire mRNA. Among the many different cap analogues that have been reported, those modified at the N2 position of guanosine have been systematically developed. N2-modified caps in the form of nucleoside monophosphates or dinucleotides show favorable biological properties, as well as a high capacity to inhibit the translation process in the cell-free RRL system. Modified N2 dinucleotides are efficiently incorporated into the structure of the mRNA transcript, and in specific circumstances with the correct orientation, making them an interesting alternative for ARCA-type analogues. Moreover, mRNA transcripts containing cap structures modified within the exocyclic amino group show very high translational activity. Therefore, analogues modified at the N2 position may have future applications as therapeutics against various manifestations of cancer and as desirable tools in RNA engineering.
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Affiliation(s)
| | | | - Renata Grzela
- Division of Biophysics, Institute of Experimental Physics, University of Warsaw, 02-093, Warsaw, Poland.
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5
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Calcineurin Inhibitor CN585 Exhibits Off-Target Effects in the Human Fungal Pathogen Aspergillus fumigatus. J Fungi (Basel) 2022; 8:jof8121281. [PMID: 36547614 PMCID: PMC9788591 DOI: 10.3390/jof8121281] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2022] [Revised: 11/29/2022] [Accepted: 12/03/2022] [Indexed: 12/12/2022] Open
Abstract
Calcineurin (CN) is an attractive antifungal target as it is critical for growth, stress response, drug resistance, and virulence in fungal pathogens. The immunosuppressive drugs, tacrolimus (FK506) and cyclosporin A (CsA), are fungistatic and specifically inhibit CN through binding to their respective immunophilins, FK506-binding protein (FKBP12), and cyclophilin (CypA). We are focused on CN structure-based approaches for the development of non-immunosuppressive FK506 analogs as antifungal therapeutics. Here, we examined the effect of the novel CN inhibitor, CN585, on the growth of the human pathogen Aspergillus fumigatus, the most common cause of invasive aspergillosis. Unexpectedly, in contrast to FK506, CN585 exhibited off-target effect on A. fumigatus wild-type and the azole- and echinocandin-resistant strains. Unlike with FK506 and CsA, the A. fumigatus CN, FKBP12, CypA mutants (ΔcnaA, Δfkbp12, ΔcypA) and various FK506-resistant mutants were all sensitive to CN585. Furthermore, in contrast to FK506 the cytosolic to nuclear translocation of the CN-dependent transcription factor (CrzA-GFP) was not inhibited by CN585. Molecular docking of CN585 onto human and A. fumigatus CN complexes revealed differential potential binding sites between human CN versus A. fumigatus CN. Our results indicate CN585 may be a non-specific inhibitor of CN with a yet undefined antifungal mechanism of activity.
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6
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Photocaged 5' cap analogues for optical control of mRNA translation in cells. Nat Chem 2022; 14:905-913. [PMID: 35725774 PMCID: PMC7613264 DOI: 10.1038/s41557-022-00972-7] [Citation(s) in RCA: 23] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2021] [Accepted: 05/11/2022] [Indexed: 11/08/2022]
Abstract
The translation of messenger RNA (mRNA) is a fundamental process in gene expression, and control of translation is important to regulate protein synthesis in cells. The primary hallmark of eukaryotic mRNAs is their 5′ cap, whose molecular contacts to the eukaryotic translation initiation factor eIF4E govern the initiation of translation. Here we report 5′ cap analogues with photo-cleavable groups (FlashCaps) that prohibit binding to eIF4E and resist cleavage by decapping enzymes. These compounds are compatible with the general and efficient production of mRNAs by in vitro transcription. In FlashCap-mRNAs, the single photocaging group abrogates translation in vitro and in mammalian cells without increasing immunogenicity. Irradiation restores the native cap, triggering efficient translation. FlashCaps overcome the problem of remaining sequence or structure changes in mRNA after irradiation that limited previous designs. Together, these results demonstrate that FlashCaps offer a route to regulate the expression of any given mRNA and to dose mRNA therapeutics with spatio-temporal control. ![]()
Analogues of mRNA 5′ caps containing a photo-cleavable group have now been developed. These so-called FlashCaps can be used for routine in vitro transcription to make long mRNAs containing a cap. In cells, the capped mRNAs are translationally muted; however, upon irradiation by light, the photo-cleavable group is removed without leaving any remaining modification and mRNA is then translated into the corresponding protein.
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7
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Borden K, Culjkovic-Kraljacic B, Cowling VH. To cap it all off, again: dynamic capping and recapping of coding and non-coding RNAs to control transcript fate and biological activity. Cell Cycle 2021; 20:1347-1360. [PMID: 34241559 PMCID: PMC8344758 DOI: 10.1080/15384101.2021.1930929] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
The addition of the methyl-7-guanosine (m7G) “cap” on the 5' ends of coding and some non-coding RNAs is essential for their protein coding capacity and biochemical activity, respectively. It was previously considered that capping was a constitutive process that generates a complete cap on all transcripts at steady-state. However, development of new methodologies demonstrated that steady-state capping is a dynamic and regulatable feature of many coding and non-coding RNAs. Indeed, capping status of specific RNAs can flux during differentiation and development, thereby impacting on their protein-coding capacity and activity. Moreover, in some primary cancer specimens, capping can be elevated for transcripts encoding proteins involved in proliferation and survival corresponding to their increased protein levels. Overexpression of one of the capping enzymes (RNMT), the transcription factor MYC or the eukaryotic translation initiation factor eIF4E all led to increased levels of steady-state capping of selected transcripts. Additionally, transcripts can be decapped and recapped, allowing these to be sequestered until needed. This review provides a summary of the major advances in enzymatic and affinity-based approaches to quantify m7G capping. Further, we summarize the evidence for regulation of capping. Capping has emerged as a significant regulatory step in RNA metabolism which is poised to impact a myriad of biological processes.
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Affiliation(s)
- Klb Borden
- Department of Pathology and Cell Biology, Institute of Research in Immunology and Cancer, University of Montreal, Montreal, Canada
| | - B Culjkovic-Kraljacic
- Department of Pathology and Cell Biology, Institute of Research in Immunology and Cancer, University of Montreal, Montreal, Canada
| | - V H Cowling
- Centre for Gene Regulation and Expression, School of Life Sciences, University of Dundee, Dundee, UK, UK
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8
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de Lima GB, de Lima Cavalcanti TYV, de Brito ANALM, de Assis LA, Andrade-Vieira RP, Freire ER, da Silva Assunção TR, de Souza Reis CR, Zanchin NIT, Guimarães BG, de-Melo-Neto OP. The translation initiation factor EIF4E5 from Leishmania: crystal structure and interacting partners. RNA Biol 2021; 18:2433-2449. [PMID: 33945405 DOI: 10.1080/15476286.2021.1918919] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
The mRNA cap-binding protein, eIF4E, mediates the recognition of the mRNA 5' end and, as part of the heterotrimeric eIF4F complex, facilitates the recruitment of the ribosomal subunits to initiate eukaryotic translation. Various regulatory events involving eIF4E and a second eIF4F subunit, eIF4G, are required for proper control of translation initiation. In pathogenic trypanosomatids, six eIF4Es and five eIF4Gs have been described, several forming different eIF4F-like complexes with yet unresolved roles. EIF4E5 is one of the least known of the trypanosomatid eIF4Es and has not been characterized in Leishmania species. Here, we used immunoprecipitation assays, combined with mass-spectrometry, to identify major EIF4E5 interacting proteins in L. infantum. A constitutively expressed, HA-tagged, EIF4E5 co-precipitated mainly with EIF4G1 and binding partners previously described in Trypanosoma brucei, EIF4G1-IP, RBP43 and the 14-3-3 proteins. In contrast, no clear co-precipitation with EIF4G2, also previously reported, was observed. EIF4E5 also co-precipitated with protein kinases, possibly associated with cell-cycle regulation, selected RNA binding proteins and histones. Phosphorylated residues were identified and mapped to the Leishmania-specific C-terminal end. Mutagenesis of the tryptophan residue (W53) postulated to mediate interactions with protein partners or of a neighbouring tryptophan conserved in Leishmania (W45) did not substantially impair the identified interactions. Finally, the crystal structure of Leishmania EIF4E5 evidences remarkable differences in the eIF4G interfacing region, when compared with human eIF4E-1 and with its Trypanosoma orthologue. Mapping of its C-terminal end near the cap-binding site also imply relevant differences in cap-binding function and/or regulation.
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Affiliation(s)
- Gustavo Barbosa de Lima
- Departamento de Microbiologia, Instituto Aggeu Magalhães, FIOCRUZ-PE, Av. Moraes Rego s/n, Recife-PE, Brazil
| | - Thaíse Yasmine Vasconcelos de Lima Cavalcanti
- Departamento de Microbiologia, Instituto Aggeu Magalhães, FIOCRUZ-PE, Av. Moraes Rego s/n, Recife-PE, Brazil.,Programa de Pós-Graduação em Genética, Universidade Federal de Pernambuco, Recife-PE, Brazil
| | - Adriana Neuman Albuquerque Lins Moura de Brito
- Departamento de Microbiologia, Instituto Aggeu Magalhães, FIOCRUZ-PE, Av. Moraes Rego s/n, Recife-PE, Brazil.,Programa de Pós-Graduação em Genética, Universidade Federal de Pernambuco, Recife-PE, Brazil
| | - Ludmilla Arruda de Assis
- Departamento de Microbiologia, Instituto Aggeu Magalhães, FIOCRUZ-PE, Av. Moraes Rego s/n, Recife-PE, Brazil
| | | | - Eden Ribeiro Freire
- Departamento de Microbiologia, Instituto Aggeu Magalhães, FIOCRUZ-PE, Av. Moraes Rego s/n, Recife-PE, Brazil.,Laboratório de Biologia Estrutural e Engenharia de Proteínas, Instituto Carlos Chagas, FIOCRUZ-PR, Curitiba-PR, Brazil
| | | | | | - Nilson Ivo Tonin Zanchin
- Laboratório de Biologia Estrutural e Engenharia de Proteínas, Instituto Carlos Chagas, FIOCRUZ-PR, Curitiba-PR, Brazil
| | - Beatriz Gomes Guimarães
- Laboratório de Biologia Estrutural e Engenharia de Proteínas, Instituto Carlos Chagas, FIOCRUZ-PR, Curitiba-PR, Brazil
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9
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Pelletier J, Schmeing TM, Sonenberg N. The multifaceted eukaryotic cap structure. WILEY INTERDISCIPLINARY REVIEWS-RNA 2020; 12:e1636. [PMID: 33300197 DOI: 10.1002/wrna.1636] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2020] [Revised: 10/16/2020] [Accepted: 11/03/2020] [Indexed: 12/13/2022]
Abstract
The 5' cap structure is added onto RNA polymerase II transcripts soon after initiation of transcription and modulates several post-transcriptional regulatory events involved in RNA maturation. It is also required for stimulating translation initiation of many cytoplasmic mRNAs and serves to protect mRNAs from degradation. These functional properties of the cap are mediated by several cap binding proteins (CBPs) involved in nuclear and cytoplasmic gene expression steps. The role that CBPs play in gene regulation, as well as the biophysical nature by which they recognize the cap, is quite intricate. Differences in mechanisms of capping as well as nuances in cap recognition speak to the potential of targeting these processes for drug development. In this review, we focus on recent findings concerning the cap epitranscriptome, our understanding of cap binding by different CBPs, and explore therapeutic targeting of CBP-cap interaction. This article is categorized under: RNA Interactions with Proteins and Other Molecules > Protein-RNA Recognition RNA Processing > Capping and 5' End Modifications Translation > Translation Mechanisms.
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Affiliation(s)
- Jerry Pelletier
- Department of Biochemistry, McGill University, Montreal, Quebec, Canada.,Department of Oncology, McGill University, Montreal, Quebec, Canada.,Rosalind and Morris Goodman Cancer Research Centre, McGill University, Montreal, Quebec, Canada.,Centre de Recherche en Biologie Structurale, McGill University, Montreal, Quebec, Canada
| | - T Martin Schmeing
- Department of Biochemistry, McGill University, Montreal, Quebec, Canada.,Centre de Recherche en Biologie Structurale, McGill University, Montreal, Quebec, Canada
| | - Nahum Sonenberg
- Department of Biochemistry, McGill University, Montreal, Quebec, Canada.,Rosalind and Morris Goodman Cancer Research Centre, McGill University, Montreal, Quebec, Canada
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10
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Cheng L, Zhang Y, Zhang Y, Chen T, Xu YZ, Rong YS. Loss of the RNA trimethylguanosine cap is compatible with nuclear accumulation of spliceosomal snRNAs but not pre-mRNA splicing or snRNA processing during animal development. PLoS Genet 2020; 16:e1009098. [PMID: 33085660 PMCID: PMC7605716 DOI: 10.1371/journal.pgen.1009098] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2020] [Revised: 11/02/2020] [Accepted: 09/07/2020] [Indexed: 12/31/2022] Open
Abstract
The 2,2,7-trimethylguanosine (TMG) cap is one of the first identified modifications on eukaryotic RNAs. TMG, synthesized by the conserved Tgs1 enzyme, is abundantly present on snRNAs essential for pre-mRNA splicing. Results from ex vivo experiments in vertebrate cells suggested that TMG ensures nuclear localization of snRNAs. Functional studies of TMG using tgs1 mutations in unicellular organisms yield results inconsistent with TMG being indispensable for either nuclear import or splicing. Utilizing a hypomorphic tgs1 mutation in Drosophila, we show that TMG reduction impairs germline development by disrupting the processing, particularly of introns with smaller sizes and weaker splice sites. Unexpectedly, loss of TMG does not disrupt snRNAs localization to the nucleus, disputing an essential role of TMG in snRNA transport. Tgs1 loss also leads to defective 3' processing of snRNAs. Remarkably, stronger tgs1 mutations cause lethality without severely disrupting splicing, likely due to the preponderance of TMG-capped snRNPs. Tgs1, a predominantly nucleolar protein in Drosophila, likely carries out splicing-independent functions indispensable for animal development. Taken together, our results suggest that nuclear import is not a conserved function of TMG. As a distinctive structure on RNA, particularly non-coding RNA, we suggest that TMG prevents spurious interactions detrimental to the function of RNAs that it modifies.
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Affiliation(s)
- Lin Cheng
- School of Life Sciences, Sun Yat-sen University, Guangzhou, China
- Hengyang College of Medicine, University of South China, Hengyang, China
| | - Yu Zhang
- Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai, China
- College of Life Sciences, Wuhan University, Wuhan, China
| | - Yi Zhang
- Laboratory of Biochemistry and Molecular Biology, National Cancer Institute, Bethesda, United States of America
| | - Tao Chen
- School of Life Sciences, Sun Yat-sen University, Guangzhou, China
- Hengyang College of Medicine, University of South China, Hengyang, China
| | - Yong-Zhen Xu
- College of Life Sciences, Wuhan University, Wuhan, China
| | - Yikang S. Rong
- Hengyang College of Medicine, University of South China, Hengyang, China
- * E-mail:
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11
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Borden KLB, Volpon L. The diversity, plasticity, and adaptability of cap-dependent translation initiation and the associated machinery. RNA Biol 2020; 17:1239-1251. [PMID: 32496897 PMCID: PMC7549709 DOI: 10.1080/15476286.2020.1766179] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Translation initiation is a critical facet of gene expression with important impacts that underlie cellular responses to stresses and environmental cues. Its dysregulation in many diseases position this process as an important area for the development of new therapeutics. The gateway translation factor eIF4E is typically considered responsible for ‘global’ or ‘canonical’ m7G cap-dependent translation. However, eIF4E impacts translation of specific transcripts rather than the entire translatome. There are many alternative cap-dependent translation mechanisms that also contribute to the translation capacity of the cell. We review the diversity of these, juxtaposing more recently identified mechanisms with eIF4E-dependent modalities. We also explore the multiplicity of functions played by translation factors, both within and outside protein synthesis, and discuss how these differentially contribute to their ultimate physiological impacts. For comparison, we discuss some modalities for cap-independent translation. In all, this review highlights the diverse mechanisms that engage and control translation in eukaryotes.
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Affiliation(s)
- Katherine L B Borden
- Institute of Research in Immunology and Cancer (IRIC), Department of Pathology and Cell Biology, Université de Montréal , Montreal, Québec, Canada
| | - Laurent Volpon
- Institute of Research in Immunology and Cancer (IRIC), Department of Pathology and Cell Biology, Université de Montréal , Montreal, Québec, Canada
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12
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Reolon LW, Vichier-Guerre S, de Matos BM, Dugué L, Assunção TRDS, Zanchin NIT, Pochet S, Guimarães BG. Crystal structure of the Trypanosoma cruzi EIF4E5 translation factor homologue in complex with mRNA cap-4. Nucleic Acids Res 2019; 47:5973-5987. [PMID: 31066441 PMCID: PMC6582342 DOI: 10.1093/nar/gkz339] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2019] [Revised: 04/18/2019] [Accepted: 04/24/2019] [Indexed: 12/20/2022] Open
Abstract
Association of the initiation factor eIF4E with the mRNA cap structure is a key step for translation. Trypanosomatids present six eIF4E homologues, showing a low conservation and also differing significantly from the IF4Es of multicellular eukaryotes. On the mRNA side, while in most eukaryotes the mRNA contains cap-0 (7-methyl-GTP), the trypanosomatid mRNA features a cap-4, which is formed by a cap-0, followed by the AACU sequence containing 2′-O-ribose methylations and base methylations on nucleotides 1 and 4. The studies on eIF4E-cap-4 interaction have been hindered by the difficulty to synthesize this rather elaborated cap-4 sequence. To overcome this problem, we applied a liquid-phase oligonucleotide synthesis strategy and describe for the first time the crystal structure of a trypanosomatid eIF4E (T. cruzi EIF4E5) in complex with cap-4. The TcEIF4E5-cap-4 structure allowed a detailed description of the binding mechanism, revealing the interaction mode for the AACU sequence, with the bases packed in a parallel stacking conformation and involved, together with the methyl groups, in hydrophobic contacts with the protein. This binding mechanism evidences a distinct cap interaction mode in comparison with previously described eIF4E structures and may account for the difference of TcEIF4E5-cap-4 dissociation constant in comparison with other eIF4E homologues.
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Affiliation(s)
- Lidia Watanabe Reolon
- Carlos Chagas Institute, Oswaldo Cruz Foundation, FIOCRUZ-PR, Curitiba, Paraná 81350-010, Brazil.,Biochemistry Postgraduate Program, Federal University of Parana, Curitiba, Paraná 81530-000, Brazil
| | | | - Bruno Moisés de Matos
- Carlos Chagas Institute, Oswaldo Cruz Foundation, FIOCRUZ-PR, Curitiba, Paraná 81350-010, Brazil.,Biochemistry Postgraduate Program, Federal University of Parana, Curitiba, Paraná 81530-000, Brazil
| | - Laurence Dugué
- Unité de Chimie et Biocatalyse, Institut Pasteur, UMR3523 CNRS, Paris 75015, France
| | | | - Nilson Ivo Tonin Zanchin
- Carlos Chagas Institute, Oswaldo Cruz Foundation, FIOCRUZ-PR, Curitiba, Paraná 81350-010, Brazil
| | - Sylvie Pochet
- Unité de Chimie et Biocatalyse, Institut Pasteur, UMR3523 CNRS, Paris 75015, France
| | - Beatriz Gomes Guimarães
- Carlos Chagas Institute, Oswaldo Cruz Foundation, FIOCRUZ-PR, Curitiba, Paraná 81350-010, Brazil.,Biochemistry Postgraduate Program, Federal University of Parana, Curitiba, Paraná 81530-000, Brazil
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13
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Santos Pereira-Dutra F, Cancela M, Valandro Meneghetti B, Bunselmeyer Ferreira H, Mariante Monteiro K, Zaha A. Functional characterization of the translation initiation factor eIF4E of Echinococcus granulosus. Parasitol Res 2019; 118:2843-2855. [PMID: 31401657 DOI: 10.1007/s00436-019-06421-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2019] [Accepted: 08/02/2019] [Indexed: 01/24/2023]
Abstract
The eukaryotic initiation factor 4E (eIF4E) specifically recognizes the 5' mRNA cap, a rate-limiting step in the translation initiation process. Although the 7-methylguanosine cap (MMGcap) is the most common 5' cap structure in eukaryotes, the trans-splicing process that occurs in several organism groups, including nematodes and flatworms, leads to the addition of a trimethylguanosine cap (TMGcap) to some RNA transcripts. In some helminths, eIF4E can have a dual capacity to bind both MMGcap and TMGcap. In the present work, we evaluated the distribution of eIF4E protein sequences in platyhelminths and we showed that only one gene coding for eIF4E is present in most parasitic flatworms. Based on this result, we cloned the Echinococcus granulosus cDNA sequence encoding eIF4E in Escherichia coli, expressed the recombinant eIF4E as a fusion protein to GST, and tested its ability to capture mRNAs through the 5' cap using pull-down assay and qPCR. Our results indicate that the recombinant eIF4E was able to bind preferentially 5'-capped mRNAs compared with rRNAs from total RNA preparations of E. granulosus. By qPCR, we observed an enrichment in MMG-capped mRNA compared with TMG-capped mRNAs among Eg-eIF4E-GST pull-down RNAs. Eg-eIF4E structural model using the Schistosoma mansoni eIF4E as template showed to be well preserved with only a few differences between chemically similar amino acid residues at the binding sites. These data showed that E. granulosus eIF4E can be used as a potential tool to study full-length 5'-capped mRNA, besides being a potential drug target against parasitic flatworms.
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Affiliation(s)
- Filipe Santos Pereira-Dutra
- Laboratório de Biologia Molecular de Cestodeos, Centro de Biotecnologia, Universidade Federal do Rio Grande do Sul, UFRGS, Avenida Bento Gonçalves, 9500, Caixa Postal 15053, Porto Alegre, RS, CEP 91501-970, Brazil.,Programa de Pós-Graduação em Biologia Celular e Molecular, Centro de Biotecnologia, UFRGS, Porto Alegre, Brazil
| | - Martin Cancela
- Laboratório de Biologia Molecular de Cestodeos, Centro de Biotecnologia, Universidade Federal do Rio Grande do Sul, UFRGS, Avenida Bento Gonçalves, 9500, Caixa Postal 15053, Porto Alegre, RS, CEP 91501-970, Brazil.,Programa de Pós-Graduação em Biologia Celular e Molecular, Centro de Biotecnologia, UFRGS, Porto Alegre, Brazil
| | - Bruna Valandro Meneghetti
- Laboratório de Biologia Molecular de Cestodeos, Centro de Biotecnologia, Universidade Federal do Rio Grande do Sul, UFRGS, Avenida Bento Gonçalves, 9500, Caixa Postal 15053, Porto Alegre, RS, CEP 91501-970, Brazil.,Programa de Pós-Graduação em Biologia Celular e Molecular, Centro de Biotecnologia, UFRGS, Porto Alegre, Brazil
| | - Henrique Bunselmeyer Ferreira
- Laboratório de Biologia Molecular de Cestodeos, Centro de Biotecnologia, Universidade Federal do Rio Grande do Sul, UFRGS, Avenida Bento Gonçalves, 9500, Caixa Postal 15053, Porto Alegre, RS, CEP 91501-970, Brazil.,Programa de Pós-Graduação em Biologia Celular e Molecular, Centro de Biotecnologia, UFRGS, Porto Alegre, Brazil.,Departamento de Biologia Molecular e Biotecnologia, Instituto de Biociências, UFRGS, Porto Alegre, Brazil
| | - Karina Mariante Monteiro
- Laboratório de Biologia Molecular de Cestodeos, Centro de Biotecnologia, Universidade Federal do Rio Grande do Sul, UFRGS, Avenida Bento Gonçalves, 9500, Caixa Postal 15053, Porto Alegre, RS, CEP 91501-970, Brazil.,Programa de Pós-Graduação em Biologia Celular e Molecular, Centro de Biotecnologia, UFRGS, Porto Alegre, Brazil.,Departamento de Biologia Molecular e Biotecnologia, Instituto de Biociências, UFRGS, Porto Alegre, Brazil
| | - Arnaldo Zaha
- Laboratório de Biologia Molecular de Cestodeos, Centro de Biotecnologia, Universidade Federal do Rio Grande do Sul, UFRGS, Avenida Bento Gonçalves, 9500, Caixa Postal 15053, Porto Alegre, RS, CEP 91501-970, Brazil. .,Programa de Pós-Graduação em Biologia Celular e Molecular, Centro de Biotecnologia, UFRGS, Porto Alegre, Brazil. .,Departamento de Biologia Molecular e Biotecnologia, Instituto de Biociências, UFRGS, Porto Alegre, Brazil.
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14
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Volpon L, Osborne MJ, Borden KL. Biochemical and Structural Insights into the Eukaryotic Translation Initiation Factor eIF4E. Curr Protein Pept Sci 2019; 20:525-535. [DOI: 10.2174/1389203720666190110142438] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2018] [Revised: 11/26/2018] [Accepted: 01/04/2019] [Indexed: 12/18/2022]
Abstract
A major question in cell and cancer biology is concerned with understanding the flow of
information from gene to protein. Indeed, many studies indicate that the proteome can be decoupled
from the transcriptome. A major source of this decoupling is post-transcriptional regulation. The eukaryotic
translation initiation factor eIF4E serves as an excellent example of a protein that can modulate
the proteome at the post-transcriptional level. eIF4E is elevated in many cancers thus highlighting
the relevance of this mode of control to biology. In this review, we provide a brief overview of various
functions of eIF4E in RNA metabolism e.g. in nuclear-cytoplasmic RNA export, translation,
RNA stability and/or sequestration. We focus on the modalities of eIF4E regulation at the biochemical
and particularly structural level. In this instance, we describe not only the importance for the m7Gcap
eIF4E interaction but also of recently discovered non-traditional RNA-eIF4E interactions as well
as cap-independent activities of eIF4E. Further, we describe several distinct structural modalities used
by the cell and some viruses to regulate or co-opt eIF4E, substantially extending the types of proteins
that can regulate eIF4E from the traditional eIF4E-binding proteins (e.g. 4E-BP1 and eIF4G). Finally,
we provide an overview of the results of targeting eIF4E activity in the clinic.
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Affiliation(s)
- Laurent Volpon
- Institute for Research in Immunology and Cancer (IRIC), Department of Pathology and Cell Biology, Universite de Montreal, Pavillion Marcelle-Coutu, Chemin Polytechnique, Montreal, Quebec, Canada
| | - Michael J. Osborne
- Institute for Research in Immunology and Cancer (IRIC), Department of Pathology and Cell Biology, Universite de Montreal, Pavillion Marcelle-Coutu, Chemin Polytechnique, Montreal, Quebec, Canada
| | - Katherine L.B. Borden
- Institute for Research in Immunology and Cancer (IRIC), Department of Pathology and Cell Biology, Universite de Montreal, Pavillion Marcelle-Coutu, Chemin Polytechnique, Montreal, Quebec, Canada
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15
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Lin J, Ye R, Thekke-Veetil T, Staton ME, Arelli PR, Bernard EC, Hewezi T, Domier LL, Hajimorad MR. A novel picornavirus-like genome from transcriptome sequencing of sugar beet cyst nematode represents a new putative genus. J Gen Virol 2018; 99:1418-1424. [PMID: 30156527 DOI: 10.1099/jgv.0.001139] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Analysis of transcriptome sequence data from eggs and second-stage juveniles (J2s) of sugar beet cyst nematode (SBCN, Heterodera schachtii) identified the full-length genome of a positive-sense single-stranded RNA virus, provisionally named sugar beet cyst nematode virus 1 (SBCNV1). The SBCNV1 sequence was detected in both eggs and J2s, indicating its possible vertical transmission. The 9503-nucleotide genome sequence contains a single long open reading frame, which was predicted to encode a polyprotein with conserved domains for picornaviral structural proteins proximal to its amino terminus and RNA helicase, cysteine proteinase and RNA-dependent RNA polymerase (RdRp) conserved domains proximal to its carboxyl terminus, hallmarks of viruses belonging to the order Picornavirales. Phylogenetic analysis of the predicted SBCNV1 RdRp amino acid sequence indicated that the SBCNV1 sequence is most closely related to members of the family Secoviridae, which includes genera of nematode-transmitted plant-infecting viruses. SBCNV1 represents the first fully sequenced viral genome from SBCN.
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Affiliation(s)
- Jingyu Lin
- 1Department of Entomology and Plant Pathology, University of Tennessee, Knoxville, TN 37996, USA
| | - Rongjian Ye
- 1Department of Entomology and Plant Pathology, University of Tennessee, Knoxville, TN 37996, USA.,†Present address: Life Science and Technology Center, China National Seed Group Company Limited, Wuhan 430075, PR China
| | | | - Margaret E Staton
- 1Department of Entomology and Plant Pathology, University of Tennessee, Knoxville, TN 37996, USA
| | - Prakash R Arelli
- 3Crop Genetics Research Unit, USDA-ARS, 605 Airways Blvd., Jackson, TN 38301, USA
| | - Ernest C Bernard
- 1Department of Entomology and Plant Pathology, University of Tennessee, Knoxville, TN 37996, USA
| | - Tarek Hewezi
- 4Department of Plant Sciences, University of Tennessee, Knoxville, TN 37996, USA
| | - Leslie L Domier
- 2Department of Crop Sciences, University of Illinois, Urbana, IL 61801, USA.,5Soybean/Maize Germplasm, Pathology, and Genetics Research Unit, USDA-ARS, Urbana, IL 61801, USA
| | - M R Hajimorad
- 1Department of Entomology and Plant Pathology, University of Tennessee, Knoxville, TN 37996, USA
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16
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Piserà A, Campo A, Campo S. Structure and functions of the translation initiation factor eIF4E and its role in cancer development and treatment. J Genet Genomics 2018; 45:13-24. [DOI: 10.1016/j.jgg.2018.01.003] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2017] [Revised: 01/12/2018] [Accepted: 01/15/2018] [Indexed: 12/22/2022]
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17
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Borden KLB. The eukaryotic translation initiation factor eIF4E wears a "cap" for many occasions. ACTA ACUST UNITED AC 2016; 4:e1220899. [PMID: 28090419 PMCID: PMC5173310 DOI: 10.1080/21690731.2016.1220899] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2016] [Revised: 07/12/2016] [Accepted: 08/02/2016] [Indexed: 01/11/2023]
Abstract
The eukaryotic translation initiation factor eIF4E plays important roles in controlling the composition of the proteome. Indeed, dysregulation of eIF4E is associated with poor prognosis cancers. The traditional view has been that eIF4E acts solely in translation. However, over the last ∼25 years, eIF4E was found in the nucleus where it acts in mRNA export and in the last ∼10 years, eIF4E was found in cytoplasmic processing bodies (P-bodies) where it functions in mRNA sequestration and stability. The common biochemical thread for these activities is the ability of eIF4E to bind the 7-methylguanosine cap on the 5′ end of mRNAs. Recently, the possibility that eIF4E directly binds some mRNA elements independently of the cap has also been raised. Importantly, the effects of eIF4E are not genome-wide with a subset of transcripts targeted depending on the presence of specific mRNA elements and context-dependent regulatory factors. Indeed, eIF4E governs RNA regulons through co-regulating the expression of groups of transcripts acting in the same biochemical pathways. In addition, studies over the past ∼15 years indicate that there are multiple strategies that regulatory factors employ to modulate eIF4E activities in context-dependent manners. This perspective focuses on these new findings and incorporates them into a broader model for eIF4E function.
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Affiliation(s)
- Katherine L B Borden
- Department of Pathology and Cell Biology, Institute of Research in Immunology and Cancer (IRIC), Université de Montréal , Montreal, Québec, Canada
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18
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Molecular recognition of mRNA 5' cap by 3' poly(A)-specific ribonuclease (PARN) differs from interactions known for other cap-binding proteins. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2016; 1864:331-45. [PMID: 26772900 DOI: 10.1016/j.bbapap.2016.01.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 09/30/2015] [Revised: 12/23/2015] [Accepted: 01/05/2016] [Indexed: 12/30/2022]
Abstract
The mRNA 5' cap structure plays a pivotal role in coordination of eukaryotic translation and mRNA degradation. Poly(A)-specific ribonuclease (PARN) is a dimeric exoribonuclease that efficiently degrades mRNA 3' poly(A) tails while also simultaneously interacting with the mRNA 5' cap. The cap binding amplifies the processivity of PARN action. We used surface plasmon resonance kinetic analysis, quantitative equilibrium fluorescence titrations and circular dichroism to study the cap binding properties of PARN. The molecular mechanism of 5' cap recognition by PARN has been demonstrated to differ from interactions seen for other known cap-binding proteins in that: i) the auxiliary biological function of 5' cap binding by the 3' degrading enzyme is accomplished by negative cooperativity of PARN dimer subunits; ii) non-coulombic interactions are major factors in the complex formation; and iii) PARN has versatile activity toward alternative forms of the cap. These characteristics contribute to stabilization of the PARN-cap complex needed for the deadenylation processivity. Our studies provide a consistent biophysical basis for elucidation of the processive mechanism of PARN-mediated 3' mRNA deadenylation and provide a new framework to interpret the role of the 5' cap in mRNA degradation.
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19
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Structural and biochemical insights into the degradation mechanism of chitosan by chitosanase OU01. Biochim Biophys Acta Gen Subj 2015; 1850:1953-61. [DOI: 10.1016/j.bbagen.2015.06.011] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2015] [Revised: 06/16/2015] [Accepted: 06/30/2015] [Indexed: 01/02/2023]
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20
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Piecyk K, Niedzwiecka A, Ferenc-Mrozek A, Lukaszewicz M, Darzynkiewicz E, Jankowska-Anyszka M. How to find the optimal partner--studies of snurportin 1 interactions with U snRNA 5' TMG-cap analogues containing modified 2-amino group of 7-methylguanosine. Bioorg Med Chem 2015; 23:4660-4668. [PMID: 26118337 DOI: 10.1016/j.bmc.2015.05.054] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2015] [Revised: 05/26/2015] [Accepted: 05/29/2015] [Indexed: 10/23/2022]
Abstract
Snurportin 1 is an adaptor protein that mediates the active nuclear import of uridine-rich small nuclear RNAs (U snRNA) by the importin-β receptor pathway. Its cellular activity influences the overall transport yield of small ribonucleoprotein complexes containing N(2),N(2),7-trimethylguanosine (TMG) capped U snRNA. So far little is still known about structural requirements related to molecular recognition of the trimethylguanosine moiety by snurportin in solution. Since these interactions are of a great biomedical importance, we synthesized a series of new 7-methylguanosine cap analogues with extended substituents at the exocyclic 2-amino group to gain a deeper insight into how the TMG-cap is adapted into the snurportin cap-binding pocket. Prepared chemical tools were applied in binding assays using emission spectroscopy. Surprisingly, our results revealed strict selectivity of snurportin towards the TMG-cap structure that relied mainly on its structural stiffness and compactness.
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Affiliation(s)
- Karolina Piecyk
- Faculty of Chemistry, University of Warsaw, 1 Pasteura St., 02-093 Warsaw, Poland
| | - Anna Niedzwiecka
- Laboratory of Biological Physics, Institute of Physics, Polish Academy of Sciences, 32/46 Lotników Ave., 02-668 Warsaw, Poland; Division of Biophysics, Institute of Experimental Physics, Faculty of Physics, University of Warsaw, 93 Żwirki I Wigury St., 02-089 Warsaw, Poland
| | | | - Maciej Lukaszewicz
- Division of Biophysics, Institute of Experimental Physics, Faculty of Physics, University of Warsaw, 93 Żwirki I Wigury St., 02-089 Warsaw, Poland
| | - Edward Darzynkiewicz
- Division of Biophysics, Institute of Experimental Physics, Faculty of Physics, University of Warsaw, 93 Żwirki I Wigury St., 02-089 Warsaw, Poland; Centre of New Technologies, University of Warsaw, 2C Banacha St., 02-097 Warsaw, Poland
| | - Marzena Jankowska-Anyszka
- Faculty of Chemistry, University of Warsaw, 1 Pasteura St., 02-093 Warsaw, Poland; Department of Biochemistry, Second Faculty of Medicine, Medical University of Warsaw, 101 Zwirki & Wigury Str., 02-089 Warsaw, Poland.
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21
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Kubacka D, Miguel RN, Minshall N, Darzynkiewicz E, Standart N, Zuberek J. Distinct features of cap binding by eIF4E1b proteins. J Mol Biol 2014; 427:387-405. [PMID: 25463438 PMCID: PMC4306533 DOI: 10.1016/j.jmb.2014.11.009] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2014] [Revised: 11/05/2014] [Accepted: 11/10/2014] [Indexed: 02/06/2023]
Abstract
eIF4E1b, closely related to the canonical translation initiation factor 4E (eIF4E1a), cap-binding protein is highly expressed in mouse, Xenopus and zebrafish oocytes. We have previously characterized eIF4E1b as a component of the CPEB mRNP translation repressor complex along with the eIF4E-binding protein 4E-Transporter, the Xp54/DDX6 RNA helicase and additional RNA-binding proteins. eIF4E1b exhibited only very weak interactions with m7GTP-Sepharose and, rather than binding eIF4G, interacted with 4E-T. Here we undertook a detailed examination of both Xenopus and human eIF4E1b interactions with cap analogues using fluorescence titration and homology modeling. The predicted structure of eIF4E1b maintains the α + β fold characteristic of eIF4E proteins and its cap-binding pocket is similarly arranged by critical amino acids: Trp56, Trp102, Glu103, Trp166, Arg112, Arg157 and Lys162 and residues of the C-terminal loop. However, we demonstrate that eIF4E1b is 3-fold less well able to bind the cap than eIF4E1a, both proteins being highly stimulated by methylation at N7 of guanine. Moreover, eIF4E1b proteins are distinguishable from eIF4E1a by a set of conserved amino acid substitutions, several of which are located near to cap-binding residues. Indeed, eIF4E1b possesses several distinct features, namely, enhancement of cap binding by a benzyl group at N7 position of guanine, a reduced response to increasing length of the phosphate chain and increased binding to a cap separated by a linker from Sepharose, suggesting differences in the arrangement of the protein's core. In agreement, mutagenesis of the amino acids differentiating eIF4E1b from eIF4E1a reduces cap binding by eIF4E1a 2-fold, demonstrating their role in modulating cap binding. Sequence analysis of vertebrate eIF4E1a and eIF4E1b proteins identified a set of conserved substitutions, including those near to cap-binding residues. The fluorescence titration assay revealed that human and Xenopus eIF4E1b have 3-fold lower affinity for m7GTP than the eIF4E1a proteins. Additional distinct features of cap binding by eIF4E1b suggest differences in the arrangement of the protein's core and its C-terminal loop. Mutagenesis of the distinguishing amino acids reduced cap binding by eIF4E1a 2-fold, demonstrating their role in modulating affinity to m7GTP.
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Affiliation(s)
- Dorota Kubacka
- Division of Biophysics, Institute of Experimental Physics, Faculty of Physics, University of Warsaw, Warsaw 02-089, Poland.
| | - Ricardo Núñez Miguel
- Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1QW, UK.
| | - Nicola Minshall
- Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1QW, UK.
| | - Edward Darzynkiewicz
- Division of Biophysics, Institute of Experimental Physics, Faculty of Physics, University of Warsaw, Warsaw 02-089, Poland; Centre of New Technologies, University of Warsaw, Warsaw 02-089, Poland.
| | - Nancy Standart
- Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1QW, UK.
| | - Joanna Zuberek
- Division of Biophysics, Institute of Experimental Physics, Faculty of Physics, University of Warsaw, Warsaw 02-089, Poland.
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22
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Abstract
We present the first chitosanase–substrate complex structure, and, in combination with a mutagenesis and thermal stability assay, we elucidate the chitosanase–substrate binding mechanism precisely for the first time. The structural basis for chitosanase cleavage specificity is analysed as well.
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23
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Coffman K, Yang B, Lu J, Tetlow AL, Pelliccio E, Lu S, Guo DC, Tang C, Dong MQ, Tamanoi F. Characterization of the Raptor/4E-BP1 interaction by chemical cross-linking coupled with mass spectrometry analysis. J Biol Chem 2014; 289:4723-34. [PMID: 24403073 DOI: 10.1074/jbc.m113.482067] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
mTORC1 plays critical roles in the regulation of protein synthesis, growth, and proliferation in response to nutrients, growth factors, and energy conditions. One of the substrates of mTORC1 is 4E-BP1, whose phosphorylation by mTORC1 reverses its inhibitory action on eIF4E, resulting in the promotion of protein synthesis. Raptor in mTOR complex 1 is believed to recruit 4E-BP1, facilitating phosphorylation of 4E-BP1 by the kinase mTOR. We applied chemical cross-linking coupled with mass spectrometry analysis to gain insight into interactions between mTORC1 and 4E-BP1. Using the cross-linking reagent bis[sulfosuccinimidyl] suberate, we showed that Raptor can be cross-linked with 4E-BP1. Mass spectrometric analysis of cross-linked Raptor-4E-BP1 led to the identification of several cross-linked peptide pairs. Compilation of these peptides revealed that the most N-terminal Raptor N-terminal conserved domain (in particular residues from 89 to 180) of Raptor is the major site of interaction with 4E-BP1. On 4E-BP1, we found that cross-links with Raptor were clustered in the central region (amino acid residues 56-72) we call RCR (Raptor cross-linking region). Intramolecular cross-links of Raptor suggest the presence of two structured regions of Raptor: one in the N-terminal region and the other in the C-terminal region. In support of the idea that the Raptor N-terminal conserved domain and the 4E-BP1 central region are closely located, we found that peptides that encompass the RCR of 4E-BP1 inhibit cross-linking and interaction of 4E-BP1 with Raptor. Furthermore, mutations of residues in the RCR decrease the ability of 4E-BP1 to serve as a substrate for mTORC1 in vitro and in vivo.
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Affiliation(s)
- Kimberly Coffman
- From the Department of Microbiology, Immunology, and Molecular Genetics, Jonsson Comprehensive Cancer Center, Molecular Biology Institute, University of California, Los Angeles, California 90095
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24
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Modrak-Wojcik A, Gorka M, Niedzwiecka K, Zdanowski K, Zuberek J, Niedzwiecka A, Stolarski R. Eukaryotic translation initiation is controlled by cooperativity effects within ternary complexes of 4E-BP1, eIF4E, and the mRNA 5' cap. FEBS Lett 2013; 587:3928-34. [PMID: 24211447 DOI: 10.1016/j.febslet.2013.10.043] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2013] [Revised: 10/29/2013] [Accepted: 10/29/2013] [Indexed: 10/26/2022]
Abstract
Initiation is the rate-limiting step during mRNA 5' cap-dependent translation, and thus a target of a strict control in the eukaryotic cell. It is shown here by analytical ultracentrifugation and fluorescence spectroscopy that the affinity of the human translation inhibitor, eIF4E-binding protein (4E-BP1), to the translation initiation factor 4E is significantly higher when eIF4E is bound to the cap. The 4E-BP1 binding stabilizes the active eIF4E conformation and, on the other hand, can facilitate dissociation of eIF4E from the cap. These findings reveal the particular allosteric effects forming a thermodynamic cycle for the cooperative regulation of the translation initiation inhibition.
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Affiliation(s)
- Anna Modrak-Wojcik
- Division of Biophysics, Institute of Experimental Physics, Faculty of Physics, University of Warsaw, 93 Zwirki & Wigury St., 02-089 Warszawa, Poland
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25
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Rossi A, Ross EJ, Jack A, Sánchez Alvarado A. Molecular cloning and characterization of SL3: a stem cell-specific SL RNA from the planarian Schmidtea mediterranea. Gene 2013; 533:156-67. [PMID: 24120894 DOI: 10.1016/j.gene.2013.09.101] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2013] [Revised: 08/26/2013] [Accepted: 09/26/2013] [Indexed: 01/03/2023]
Abstract
Spliced leader (SL) trans-splicing is a biological phenomenon, common among many metazoan taxa, consisting in the transfer of a short leader sequence from a small SL RNA to the 5' end of a subset of pre-mRNAs. While knowledge of the biochemical mechanisms driving this process has accumulated over the years, the functional consequences of such post-transcriptional event at the organismal level remain unclear. In addition, the fact that functional analyses have been undertaken mainly in trypanosomes and nematodes leaves a somehow fragmented picture of the possible biological significance and evolution of SL trans-splicing in eukaryotes. Here, we analyzed the spatial expression of SL RNAs in the planarian flatworm Schmidtea mediterranea, with the goal of identifying novel developmental paradigms for the study of trans-splicing in metazoans. Besides the previously identified SL1 and SL2, S. mediterranea expresses a third SL RNA described here as SL3. While, SL1 and SL2 are collectively expressed in a broad range of planarian cell types, SL3 is highly enriched in a subset of the planarian stem cells engaged in regenerative responses. Our findings provide new opportunities to study how trans-splicing may regulate the phenotype of a cell.
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Affiliation(s)
- Alessandro Rossi
- Stowers Institute for Medical Research, 1000 E 50th St., Kansas City, MO 64110, USA.
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26
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Conformational changes induced in the eukaryotic translation initiation factor eIF4E by a clinically relevant inhibitor, ribavirin triphosphate. Biochem Biophys Res Commun 2013; 434:614-9. [PMID: 23583375 DOI: 10.1016/j.bbrc.2013.03.125] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2013] [Accepted: 03/26/2013] [Indexed: 12/23/2022]
Abstract
The eukaryotic translation initiation factor eIF4E is highly elevated in human cancers including acute myeloid leukemia (AML). A potential anticancer agent, ribavirin, targets eIF4E activity in AML patients corresponding to clinical responses. To date, ribavirin is the only direct inhibitor of eIF4E to reach clinical trials. We showed that ribavirin acts as a competitive inhibitor of the methyl 7-guanosine (m(7)G) cap, the natural ligand of eIF4E. Here we examine the conformational changes occurring in human eIF4E upon binding the active metabolite of ribavirin, ribavirin triphosphate (RTP). Our NMR data revealed an unexpected concentration dependence on RTP affinity for eIF4E. We observed NMR spectra characteristic of tight binding at low micromolar concentrations (2-5 μM eIF4E) but much weaker affinity at more typical NMR concentrations (50- ). Comparison of chemical shift perturbation and line broadening suggest that the two eIF4E-RTP complexes differ in the precise positioning of RTP within the cap binding pocket, with the high affinity complex showing more extensive changes to the central β-sheet and dorsal surface of eIF4E, similar to m(7)G cap. The differences between high and low affinity complexes arise due to concentration dependent aggregation of eIF4E and RTP. Given the intracellular concentrations of eIF4E and RTP and the differential binding toward the W56A eIF4E mutant the high affinity complex is the most physiologically relevant. In summary, these findings demonstrate that RTP binds in the cap-binding site but also suggests new features of this pocket that should be considered in drug design efforts and reveal new insights into ligand eIF4E recognition.
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27
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Carroll M, Borden KLB. The oncogene eIF4E: using biochemical insights to target cancer. J Interferon Cytokine Res 2013; 33:227-38. [PMID: 23472659 DOI: 10.1089/jir.2012.0142] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The eukaryotic translation initiation factor eIF4E is overexpressed in many human malignancies where it is typically a harbinger of poor prognosis. eIF4E is positioned as a nexus in post-transcriptional gene expression. To carry out these functions, eIF4E needs to bind the m(7)G cap moiety on mRNAs. It plays critical roles in mRNA translation, mRNA export, and most likely in mRNA stability as well. Through these activities, eIF4E coordinately modulates the expression of many transcripts involved in proliferation and survival. eIF4E function is controlled by interactions with protein cofactors in concert with many signaling pathways, including Ras, Mnk, Erk, MAPK, PI3K, mTOR, and Akt. This review describes the eIF4E activity and provides several examples of cellular control mechanisms. Further, we describe some therapeutic strategies in preclinical and clinical development.
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Affiliation(s)
- Martin Carroll
- Division of Hematology and Oncology, University of Pennsylvania, Philadelphia, PA 19104, USA.
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28
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eIF4E3 acts as a tumor suppressor by utilizing an atypical mode of methyl-7-guanosine cap recognition. Proc Natl Acad Sci U S A 2013; 110:3877-82. [PMID: 23431134 DOI: 10.1073/pnas.1216862110] [Citation(s) in RCA: 84] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Recognition of the methyl-7-guanosine (m(7)G) cap structure on mRNA is an essential feature of mRNA metabolism and thus gene expression. Eukaryotic translation initiation factor 4E (eIF4E) promotes translation, mRNA export, proliferation, and oncogenic transformation dependent on this cap-binding activity. eIF4E-cap recognition is mediated via complementary charge interactions of the positively charged m(7)G cap between the negative π-electron clouds from two aromatic residues. Here, we demonstrate that a variant subfamily, eIF4E3, specifically binds the m(7)G cap in the absence of an aromatic sandwich, using instead a different spatial arrangement of residues to provide the necessary electrostatic and van der Waals contacts. Contacts are much more extensive between eIF4E3-cap than other family members. Structural analyses of other cap-binding proteins indicate this recognition mode is atypical. We demonstrate that eIF4E3 relies on this cap-binding activity to act as a tumor suppressor, competing with the growth-promoting functions of eIF4E. In fact, reduced eIF4E3 in high eIF4E cancers suggests that eIF4E3 underlies a clinically relevant inhibitory mechanism that is lost in some malignancies. Taken together, there is more structural plasticity in cap recognition than previously thought, and this is physiologically relevant.
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29
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Kinkelin K, Veith K, Grünwald M, Bono F. Crystal structure of a minimal eIF4E-Cup complex reveals a general mechanism of eIF4E regulation in translational repression. RNA (NEW YORK, N.Y.) 2012; 18:1624-34. [PMID: 22832024 PMCID: PMC3425778 DOI: 10.1261/rna.033639.112] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Cup is an eIF4E-binding protein (4E-BP) that plays a central role in translational regulation of localized mRNAs during early Drosophila development. In particular, Cup is required for repressing translation of the maternally contributed oskar, nanos, and gurken mRNAs, all of which are essential for embryonic body axis determination. Here, we present the 2.8 Å resolution crystal structure of a minimal eIF4E-Cup assembly, consisting of the interacting regions of the two proteins. In the structure, two separate segments of Cup contact two orthogonal faces of eIF4E. The eIF4E-binding consensus motif of Cup (YXXXXLΦ) binds the convex side of eIF4E similarly to the consensus of other eIF4E-binding proteins, such as 4E-BPs and eIF4G. The second, noncanonical, eIF4E-binding site of Cup binds laterally and perpendicularly to the eIF4E β-sheet. Mutations of Cup at this binding site were shown to reduce binding to eIF4E and to promote the destabilization of the associated mRNA. Comparison with the binding mode of eIF4G to eIF4E suggests that Cup and eIF4G binding would be mutually exclusive at both binding sites. This shows how a common molecular surface of eIF4E might recognize different proteins acting at different times in the same pathway. The structure provides insight into the mechanism by which Cup disrupts eIF4E-eIF4G interaction and has broader implications for understanding the role of 4E-BPs in translational regulation.
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Affiliation(s)
- Kerstin Kinkelin
- Max-Planck-Institute for Developmental Biology, 71076 Tübingen, Germany
| | - Katharina Veith
- Max-Planck-Institute for Developmental Biology, 71076 Tübingen, Germany
| | - Marlene Grünwald
- Max-Planck-Institute for Developmental Biology, 71076 Tübingen, Germany
| | - Fulvia Bono
- Max-Planck-Institute for Developmental Biology, 71076 Tübingen, Germany
- Corresponding authorE-mail
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30
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Piecyk K, Davis RE, Jankowska-Anyszka M. Synthesis of N²-modified 7-methylguanosine 5'-monophosphates as nematode translation inhibitors. Bioorg Med Chem 2012; 20:4781-9. [PMID: 22748379 PMCID: PMC3636719 DOI: 10.1016/j.bmc.2012.05.078] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2012] [Revised: 05/25/2012] [Accepted: 05/30/2012] [Indexed: 10/28/2022]
Abstract
Preparative scale synthesis of 14 new N(2)-modified mononucleotide 5' mRNA cap analogues was achieved. The key step involved use of an S(N)Ar reaction with protected 2-fluoro inosine and various primary and secondary amines. The derivatives were tested in a parasitic nematode, Ascaris suum, cell-free system as translation inhibitors. The most effective compound with IC(50) ∼0.9μM was a N(2)-p-metoxybenzyl-7-methylguanosine-5'-monophosphate 35.
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Affiliation(s)
- Karolina Piecyk
- Faculty of Chemistry, University of Warsaw, 02-093 Warsaw, Poland
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31
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Piecyk K, Davis RE, Jankowska-Anyszka M. 5'-Terminal chemical capping of spliced leader RNAs. Tetrahedron Lett 2012; 53:4843-4847. [PMID: 23175583 DOI: 10.1016/j.tetlet.2012.06.127] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Spliced leader (SL) RNA trans-splicing adds a 2,2,7-trimethylguanosine cap (TMG) and a 22-nucleotide sequence, the SL, to the 5' end of mRNAs. Both non-trans-spliced with a monomethylguanosine cap (MMG) and trans-spliced mRNAs co-exist in trans-splicing metazoan cells. Efficient translation of TMG-capped mRNAs in nematodes requires a defined core of nucleotides within the SL sequence. Here we present a chemical procedure for the preparation and purification of 5'-terminal capped MMG and TMG wild-type, and mutant 22 nt spliced leader RNAs (GGU/ACUUAAUUACCCAAGUUUGAG) with or without a 3' biotin tag.
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Affiliation(s)
- Karolina Piecyk
- Faculty of Chemistry, University of Warsaw, 02-093, Warsaw, Poland
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32
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Piecyk K, Davis RE, Jankowska-Anyszka M. Synthesis of ¹³C- and ¹⁴C-labeled dinucleotide mRNA cap analogues for structural and biochemical studies. Bioorg Med Chem Lett 2012; 22:4391-5. [PMID: 22658555 PMCID: PMC3652009 DOI: 10.1016/j.bmcl.2012.04.120] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2012] [Revised: 04/26/2012] [Accepted: 04/29/2012] [Indexed: 12/13/2022]
Abstract
Herein we describe the first simple and short method for specific labeling of mono- and trimethylated dinucleotide mRNA cap analogues with (13)C and (14)C isotopes. The labels were introduced within the cap structures either at the N7 for monomethylguanosine cap or N7 and N2 position for trimethylguanosine cap. The compounds designed for structural and biochemical studies will be useful tools for better understanding the role of the mRNA cap structures in pre-mRNA splicing, nucleocytoplasmic transport, translation initiation and mRNA degradation.
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Affiliation(s)
- Karolina Piecyk
- Faculty of Chemistry, University of Warsaw, Pasteura 1, 02-093 Warsaw, Poland
| | - Richard E. Davis
- Department of Biochemistry and Molecular Genetics, University of Colorado, School of Medicine, Aurora, CO 80045, USA
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