1
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Saha U, Gaine R, Paira S, Das S, Das B. RRM1 and PAB domains of translation initiation factor eIF4G (Tif4631p) play a crucial role in the nuclear degradation of export-defective mRNAs in Saccharomyces cerevisiae. FEBS J 2024; 291:897-926. [PMID: 37994298 DOI: 10.1111/febs.17016] [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: 03/07/2023] [Revised: 10/02/2023] [Accepted: 11/21/2023] [Indexed: 11/24/2023]
Abstract
In Saccharomyces cerevisiae, the CBC-Tif4631p-dependent exosomal targeting (CTEXT) complex consisting of Cbc1/2p, Tif4631p and Upf3p promotes the exosomal degradation of aberrantly long 3'-extended, export-defective transcripts and a small group of normal (termed 'special') mRNAs. We carried out a systematic analysis of all previously characterized functional domains of the major CTEXT component Tif4631p by deleting each of them and interrogating their involvement in the nuclear surveillance of abnormally long 3'-extended and export-defective messages. Our analyses show that the N-terminal RNA recognition motif 1 (RRM1) and poly(A)-binding protein (PAB) domains of Tif4631p, spanning amino acid residues, 1-82 and 188-299 in its primary structure, respectively, play a crucial role in degrading these aberrant messages. Furthermore, the physical association of the nuclear exosome with the altered/variant CTEXT complex harboring any of the mutant Tif4631p proteins lacking either the RRM1 or PAB domain becomes abolished. This finding indicates that the association between CTEXT and the exosome is accomplished via interaction between these Tif4631p domains with the major exosome component, Rrp6p. Abolition of interaction between altered CTEXT (harboring any of the RRM1/PAB-deleted versions of Tif4631p) and the exosome further leads to the impaired recruitment of the RNA targets to the Rrp6p subunit of the exosome carried out by the RRM1/PAB domains of Tif4631p. When analyzing the Tif4631p-interacting proteins, we identified a DEAD-box RNA helicase (Dbp2p), as an interacting partner that turned out to be a previously unknown component of CTEXT. The present study provides a more complete description of the CTEXT complex and offers insight into the functional relationship of this complex with the nuclear exosome.
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Grants
- BT/PR27917/BRB/10/1673/2018 Department of Biotechnology, Ministry of Science and Technology, India
- BT/PR6078/BRB/10/1114/2012 Department of Biotechnology, Ministry of Science and Technology, India
- 38/1427/16/EMR-II Council of Scientific and Industrial Research, India
- 38/1280/11/EMR-II Council of Scientific and Industrial Research, India
- SR/SO/BB/0066/2012 Department of Science and Technology, Ministry of Science and Technology, India
- Department of Science & Technology and Biotechnology, Government of West Bengal
- SR/WOS-A/LS-1067/2014 Department of Science and Technology, India, WOS-A
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Affiliation(s)
- Upasana Saha
- Department of Life Science and Biotechnology, Jadavpur University, Kolkata, India
| | - Rajlaxmi Gaine
- Department of Life Science and Biotechnology, Jadavpur University, Kolkata, India
| | - Sunirmal Paira
- Department of Life Science and Biotechnology, Jadavpur University, Kolkata, India
| | - Satarupa Das
- Department of Life Science and Biotechnology, Jadavpur University, Kolkata, India
| | - Biswadip Das
- Department of Life Science and Biotechnology, Jadavpur University, Kolkata, India
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2
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Wang J, Zhang G, Qian W, Li K. Decoding the Heterogeneity and Specialized Function of Translation Machinery Through Ribosome Profiling in Yeast Mutants of Initiation Factors. Adv Biol (Weinh) 2024; 8:e2300494. [PMID: 37997253 DOI: 10.1002/adbi.202300494] [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: 09/13/2023] [Revised: 09/24/2023] [Indexed: 11/25/2023]
Abstract
The nuanced heterogeneity and specialized functions of translation machinery are increasingly recognized as crucial for precise translational regulation. Here, high-throughput ribosomal profiling (ribo-seq) is used to analyze the specialized roles of eukaryotic initiation factors (eIFs) in the budding yeast. By examining changes in ribosomal distribution across the genome resulting from knockouts of eIF4A, eIF4B, eIF4G1, CAF20, or EAP1, or knockdowns of eIF1, eIF1A, eIF4E, or PAB1, two distinct initiation-factor groups, the "looping" and "scanning" groups are discerned, based on similarities in the ribosomal landscapes their perturbation induced. The study delves into the cis-regulatory sequence features of genes influenced predominantly by each group, revealing that genes more dependent on the looping-group factors generally have shorter transcripts and poly(A) tails. In contrast, genes more dependent on the scanning-group factors often possess upstream open reading frames and exhibit a higher GC content in their 5' untranslated regions. From the ribosomal RNA fragments identified in the ribo-seq data, ribosomal heterogeneity associated with perturbation of specific initiation factors is further identified, suggesting their potential roles in regulating ribosomal components. Collectively, the study illuminates the complexity of translational regulation driven by heterogeneity and specialized functions of translation machinery, presenting potential approaches for targeted gene translation manipulation.
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Affiliation(s)
- Jia Wang
- State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, Innovation Academy for Seed Design, Chinese Academy of Sciences, Beijing, 100101, China
| | - Geyu Zhang
- State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, Innovation Academy for Seed Design, Chinese Academy of Sciences, Beijing, 100101, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Wenfeng Qian
- State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, Innovation Academy for Seed Design, Chinese Academy of Sciences, Beijing, 100101, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Ke Li
- State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, Innovation Academy for Seed Design, Chinese Academy of Sciences, Beijing, 100101, China
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3
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Li S, Chen JS, Li X, Bai X, Shi D. MNK, mTOR or eIF4E-selecting the best anti-tumor target for blocking translation initiation. Eur J Med Chem 2023; 260:115781. [PMID: 37669595 DOI: 10.1016/j.ejmech.2023.115781] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2023] [Revised: 08/29/2023] [Accepted: 08/29/2023] [Indexed: 09/07/2023]
Abstract
Overexpression of eIF4E is common in patients with various solid tumors and hematologic cancers. As a potential anti-cancer target, eIF4E has attracted extensive attention from researchers. At the same time, mTOR kinases inhibitors and MNK kinases inhibitors, which are directly related to regulation of eIF4E, have been rapidly developed. To explore the optimal anti-cancer targets among MNK, mTOR, and eIF4E, this review provides a detailed classification and description of the anti-cancer activities of promising compounds. In addition, the structures and activities of some dual-target inhibitors are briefly described. By analyzing the different characteristics of the inhibitors, it can be concluded that MNK1/2 and eIF4E/eIF4G interaction inhibitors are superior to mTOR inhibitors. Simultaneous inhibition of MNK and eIF4E/eIF4G interaction may be the most promising anti-cancer method for targeting translation initiation.
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Affiliation(s)
- Shuo Li
- State Key Laboratory of Microbial Technology, Shandong University, Qingdao, 266237, Shandong, PR China.
| | - Jia-Shu Chen
- State Key Laboratory of Microbial Technology, Shandong University, Qingdao, 266237, Shandong, PR China.
| | - Xiangqian Li
- State Key Laboratory of Microbial Technology, Shandong University, Qingdao, 266237, Shandong, PR China.
| | - Xiaoyi Bai
- State Key Laboratory of Microbial Technology, Shandong University, Qingdao, 266237, Shandong, PR China.
| | - Dayong Shi
- State Key Laboratory of Microbial Technology, Shandong University, Qingdao, 266237, Shandong, PR China.
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4
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Pugsley L, Naineni SK, Amiri M, Yanagiya A, Cencic R, Sonenberg N, Pelletier J. C8ORF88: A Novel eIF4E-Binding Protein. Genes (Basel) 2023; 14:2076. [PMID: 38003019 PMCID: PMC10670996 DOI: 10.3390/genes14112076] [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: 08/04/2023] [Revised: 11/03/2023] [Accepted: 11/09/2023] [Indexed: 11/26/2023] Open
Abstract
Translation initiation in eukaryotes is regulated at several steps, one of which involves the availability of the cap binding protein to participate in cap-dependent protein synthesis. Binding of eIF4E to translational repressors (eIF4E-binding proteins [4E-BPs]) suppresses translation and is used by cells to link extra- and intracellular cues to protein synthetic rates. The best studied of these interactions involves repression of translation by 4E-BP1 upon inhibition of the PI3K/mTOR signaling pathway. Herein, we characterize a novel 4E-BP, C8ORF88, whose expression is predominantly restricted to early spermatids. C8ORF88:eIF4E interaction is dependent on the canonical eIF4E binding motif (4E-BM) present in other 4E-BPs. Whereas 4E-BP1:eIF4E interaction is dependent on the phosphorylation of 4E-BP1, these sites are not conserved in C8ORF88 indicating a different mode of regulation.
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Affiliation(s)
- Lauren Pugsley
- Department of Biochemistry, McGill University, Montreal, QC H3G 1Y6, Canada; (L.P.); (S.K.N.); (M.A.); (N.S.)
| | - Sai Kiran Naineni
- Department of Biochemistry, McGill University, Montreal, QC H3G 1Y6, Canada; (L.P.); (S.K.N.); (M.A.); (N.S.)
| | - Mehdi Amiri
- Department of Biochemistry, McGill University, Montreal, QC H3G 1Y6, Canada; (L.P.); (S.K.N.); (M.A.); (N.S.)
| | | | - Regina Cencic
- Department of Biochemistry, McGill University, Montreal, QC H3G 1Y6, Canada; (L.P.); (S.K.N.); (M.A.); (N.S.)
| | - Nahum Sonenberg
- Department of Biochemistry, McGill University, Montreal, QC H3G 1Y6, Canada; (L.P.); (S.K.N.); (M.A.); (N.S.)
- Rosalind and Morris Goodman Cancer Institute, McGill University, Montreal, QC H3A 1A3, Canada
| | - Jerry Pelletier
- Department of Biochemistry, McGill University, Montreal, QC H3G 1Y6, Canada; (L.P.); (S.K.N.); (M.A.); (N.S.)
- Rosalind and Morris Goodman Cancer Institute, McGill University, Montreal, QC H3A 1A3, Canada
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5
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Kamada Y, Ando R, Izawa S, Matsuura A. Yeast Tor complex 1 phosphorylates eIF4E-binding protein, Caf20. Genes Cells 2023; 28:789-799. [PMID: 37700444 DOI: 10.1111/gtc.13067] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2023] [Revised: 08/24/2023] [Accepted: 08/29/2023] [Indexed: 09/14/2023]
Abstract
Tor complex 1 (TORC1), a master regulator of cell growth, is an evolutionarily conserved protein kinase within eukaryotic organisms. To control cell growth, TORC1 governs translational processes by phosphorylating its substrate proteins in response to cellular nutritional cues. Mammalian TORC1 (mTORC1) assumes the responsibility of phosphorylating the eukaryotic translation initiation factor 4E (eIF4E)-binding protein 1 (4E-BP1) to regulate its interaction with eIF4E. The budding yeast Saccharomyces cerevisiae possesses a pair of 4E-BP genes, CAF20 and EAP1. However, the extent to which the TORC1-4E-BP axis regulates translational initiation in yeast remains uncertain. In this study, we demonstrated the influence of TORC1 on the phosphorylation status of Caf20 in vivo, as well as the direct phosphorylation of Caf20 by TORC1 in vitro. Furthermore, we found the TORC1-dependent recruitment of Caf20 to the 80S ribosome. Consequently, our study proposes a plausible involvement of yeast's 4E-BP in the efficacy of translation initiation, an aspect under the control of TORC1.
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Affiliation(s)
- Yoshiaki Kamada
- National Institute for Basic Biology, Okazaki, Japan
- Graduate University for Advanced Studies (SOKENDAI), Hayama, Kanagawa, Japan
| | - Ryoko Ando
- Department of Applied Biology, Graduate School of Science and Technology, Kyoto Institute of Technology, Kyoto, Japan
| | - Shingo Izawa
- Department of Applied Biology, Graduate School of Science and Technology, Kyoto Institute of Technology, Kyoto, Japan
| | - Akira Matsuura
- Department of Biology, Graduate School of Science, Chiba University, Chiba, Japan
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6
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Kershaw CJ, Nelson MG, Castelli LM, Jennings MD, Lui J, Talavera D, Grant CM, Pavitt GD, Hubbard SJ, Ashe MP. Translation factor and RNA binding protein mRNA interactomes support broader RNA regulons for posttranscriptional control. J Biol Chem 2023; 299:105195. [PMID: 37633333 PMCID: PMC10562868 DOI: 10.1016/j.jbc.2023.105195] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2023] [Revised: 08/18/2023] [Accepted: 08/20/2023] [Indexed: 08/28/2023] Open
Abstract
The regulation of translation provides a rapid and direct mechanism to modulate the cellular proteome. In eukaryotes, an established model for the recruitment of ribosomes to mRNA depends upon a set of conserved translation initiation factors. Nevertheless, how cells orchestrate and define the selection of individual mRNAs for translation, as opposed to other potential cytosolic fates, is poorly understood. We have previously found significant variation in the interaction between individual mRNAs and an array of translation initiation factors. Indeed, mRNAs can be separated into different classes based upon these interactions to provide a framework for understanding different modes of translation initiation. Here, we extend this approach to include new mRNA interaction profiles for additional proteins involved in shaping the cytoplasmic fate of mRNAs. This work defines a set of seven mRNA clusters, based on their interaction profiles with 12 factors involved in translation and/or RNA binding. The mRNA clusters share both physical and functional characteristics to provide a rationale for the interaction profiles. Moreover, a comparison with mRNA interaction profiles from a host of RNA binding proteins suggests that there are defined patterns in the interactions of functionally related mRNAs. Therefore, this work defines global cytoplasmic mRNA binding modules that likely coordinate the synthesis of functionally related proteins.
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Affiliation(s)
- Christopher J Kershaw
- Division of Molecular and Cellular Function, School of Biological Sciences, The University of Manchester, Manchester, UK
| | - Michael G Nelson
- Division of Molecular and Cellular Function, School of Biological Sciences, The University of Manchester, Manchester, UK
| | - Lydia M Castelli
- Division of Molecular and Cellular Function, School of Biological Sciences, The University of Manchester, Manchester, UK
| | - Martin D Jennings
- Division of Molecular and Cellular Function, School of Biological Sciences, The University of Manchester, Manchester, UK
| | - Jennifer Lui
- Division of Molecular and Cellular Function, School of Biological Sciences, The University of Manchester, Manchester, UK
| | - David Talavera
- Division of Cardiovascular Sciences, School of Medical Sciences, The University of Manchester, Manchester, UK
| | - Chris M Grant
- Division of Molecular and Cellular Function, School of Biological Sciences, The University of Manchester, Manchester, UK
| | - Graham D Pavitt
- Division of Molecular and Cellular Function, School of Biological Sciences, The University of Manchester, Manchester, UK.
| | - Simon J Hubbard
- Division of Molecular and Cellular Function, School of Biological Sciences, The University of Manchester, Manchester, UK.
| | - Mark P Ashe
- Division of Molecular and Cellular Function, School of Biological Sciences, The University of Manchester, Manchester, UK.
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7
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Tseng YT, Sung YC, Liu CY, Lo KY. Translation initiation factor eIF4G1 modulates assembly of the polypeptide exit tunnel region in yeast ribosome biogenesis. J Cell Sci 2022; 135:275526. [PMID: 35615984 DOI: 10.1242/jcs.259540] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Accepted: 05/12/2022] [Indexed: 01/24/2023] Open
Abstract
eIF4G is an important eukaryotic translation initiation factor. In this study, eIF4G1, one of the eIF4G isoforms, was shown to directly participate in biogenesis of the large (60S) ribosomal subunit in Saccharomyces cerevisiae cells. Mutation of eIF4G1 decreased the amount 60S ribosomal subunits significantly. The C-terminal fragment of eIF4G1 could complement the function in 60S biogenesis. Analyses of its purified complex with mass spectrometry indicated that eIF4G1 associated with the pre-60S form directly. Strong genetic and direct protein-protein interactions were observed between eIF4G1 and Ssf1 protein. Upon deletion of eIF4G1, Ssf1, Rrp15, Rrp14 and Mak16 were abnormally retained on the pre-60S complex. This purturbed the loading of Arx1 and eL31 at the polypeptide exit tunnel (PET) site and the transition to a Nog2 complex. Our data indicate that eIF4G1 is important in facilitating PET maturation and 27S processing correctly. This article has an associated First Person interview with the first author of the paper.
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Affiliation(s)
- Yun-Ting Tseng
- Department of Agricultural Chemistry, College of Bioresources and Agriculture, National Taiwan University, Taipei 10617, Taiwan
| | - Yu-Cheng Sung
- Department of Agricultural Chemistry, College of Bioresources and Agriculture, National Taiwan University, Taipei 10617, Taiwan
| | - Ching-Yu Liu
- Department of Agricultural Chemistry, College of Bioresources and Agriculture, National Taiwan University, Taipei 10617, Taiwan
| | - Kai-Yin Lo
- Department of Agricultural Chemistry, College of Bioresources and Agriculture, National Taiwan University, Taipei 10617, Taiwan
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8
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González-Catrilelbún S, Cartagena J, Vargas D, Breguel-Serrano P, Sandino AM, Rivas-Aravena A. The RNA-dependent RNA polymerase of the infectious pancreatic necrosis virus is linked to viral mRNA acting as a cap substitute. J Gen Virol 2022; 103. [DOI: 10.1099/jgv.0.001729] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The infectious pancreatic necrosis virus (IPNV) is responsible for significant economic losses in the aquaculture industry. It is an unenveloped virus with an icosahedral capsid. Its viral genome comprises two dsRNA segments, A and B. Segment A contains a small ORF, which encodes VP5, and a large ORF, which encodes a polyprotein that generates the structural proteins and the viral protease. Segment B encodes the RNA-dependent RNA polymerase (RdRp), called VP1 in this free form, or Vpg when it covalently attaches to the viral RNA. The viral genome does not have cap or poly(A). Instead, each 5′ end is linked to the Vpg. Recently, we demonstrated that mRNA-A contains an internal ribosome entry site (IRES) to command polyprotein synthesis. However, the presence of Vpg on IPNV mRNAs and its impact on cellular translation has not been investigated. This research demonstrates that IPNV mRNAs are linked to Vpg and that this protein inhibits cap-dependent translation on infected cells. Also, it is demonstrated that Vpg interacts with eIF4E and that rapamycin treatment partially diminishes the viral protein synthesis. In addition, we determined that an IRES does not command translation of IPNV mRNA-B. We show that VPg serves as a cap substitute during the initiation of IPNV translation, contributing to understanding the replicative cycle of Birnaviruses. Our results indicate that the viral protein VP1/Vpg is multifunctional, having a significant role during IPNV RNA synthesis as the RdRp and the primer for IPNV RNA synthesis and translation as the viral protein genome, acting as a cap substitute.
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Affiliation(s)
| | - Julio Cartagena
- Laboratorio de Virología, Centro de Biotecnología Acuícola, Universidad de Santiago de Chile, Santiago, Chile
| | - Deborah Vargas
- Laboratorio de Virología, Centro de Biotecnología Acuícola, Universidad de Santiago de Chile, Santiago, Chile
| | - Pamela Breguel-Serrano
- Laboratorio de Virología, Facultad de Medicina y Ciencia, Universidad San Sebastián, Santiago, Chile
| | - Ana María Sandino
- Laboratorio de Virología, Centro de Biotecnología Acuícola, Universidad de Santiago de Chile, Santiago, Chile
| | - Andrea Rivas-Aravena
- Laboratorio de Virología, Facultad de Medicina y Ciencia, Universidad San Sebastián, Santiago, Chile
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9
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Ram AK, Mallik M, Reddy RR, Suryawanshi AR, Alone PV. Altered proteome in translation initiation fidelity defective eIF5 G31R mutant causes oxidative stress and DNA damage. Sci Rep 2022; 12:5033. [PMID: 35322093 PMCID: PMC8943034 DOI: 10.1038/s41598-022-08857-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2021] [Accepted: 03/07/2022] [Indexed: 12/15/2022] Open
Abstract
The recognition of the AUG start codon and selection of an open reading frame (ORF) is fundamental to protein biosynthesis. Defect in the fidelity of start codon selection adversely affect proteome and have a pleiotropic effect on cellular function. Using proteomic techniques, we identified differential protein abundance in the translation initiation fidelity defective eIF5G31R mutant that initiates translation using UUG codon in addition to the AUG start codon. Consistently, the eIF5G31R mutant altered proteome involved in protein catabolism, nucleotide biosynthesis, lipid biosynthesis, carbohydrate metabolism, oxidation–reduction pathway, autophagy and re-programs the cellular pathways. The utilization of the upstream UUG codons by the eIF5G31R mutation caused downregulation of uridylate kinase expression, sensitivity to hydroxyurea, and DNA damage. The eIF5G31R mutant cells showed lower glutathione levels, high ROS activity, and sensitivity to H2O2.
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Affiliation(s)
- Anup Kumar Ram
- School of Biological Sciences, National Institute of Science Education and Research Bhubaneswar, P.O Jatni, Khurda, 752050, India.,Homi Bhabha National Institute (HBNI), Anushakti Nagar, Mumbai, 400094, India
| | - Monalisha Mallik
- School of Biological Sciences, National Institute of Science Education and Research Bhubaneswar, P.O Jatni, Khurda, 752050, India.,Homi Bhabha National Institute (HBNI), Anushakti Nagar, Mumbai, 400094, India
| | - R Rajendra Reddy
- Clinical Proteomics, DBT-Institute of Life Sciences, Bhubaneswar, Odisha, 751023, India
| | | | - Pankaj V Alone
- School of Biological Sciences, National Institute of Science Education and Research Bhubaneswar, P.O Jatni, Khurda, 752050, India. .,Homi Bhabha National Institute (HBNI), Anushakti Nagar, Mumbai, 400094, India.
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10
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Jennifer S, Corinna R, Thomas D, Nils L, Diethard M, Brigitte G. Going beyond the limit: Increasing global translation activity leads to increased productivity of recombinant secreted proteins in Pichia pastoris. Metab Eng 2022; 70:181-195. [DOI: 10.1016/j.ymben.2022.01.010] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2021] [Revised: 01/12/2022] [Accepted: 01/20/2022] [Indexed: 01/06/2023]
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11
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Control of the eIF4E activity: structural insights and pharmacological implications. Cell Mol Life Sci 2021; 78:6869-6885. [PMID: 34541613 PMCID: PMC8558276 DOI: 10.1007/s00018-021-03938-z] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2021] [Revised: 08/28/2021] [Accepted: 09/08/2021] [Indexed: 12/17/2022]
Abstract
The central role of eukaryotic translation initiation factor 4E (eIF4E) in controlling mRNA translation has been clearly assessed in the last decades. eIF4E function is essential for numerous physiological processes, such as protein synthesis, cellular growth and differentiation; dysregulation of its activity has been linked to ageing, cancer onset and progression and neurodevelopmental disorders, such as autism spectrum disorder (ASD) and Fragile X Syndrome (FXS). The interaction between eIF4E and the eukaryotic initiation factor 4G (eIF4G) is crucial for the assembly of the translational machinery, the initial step of mRNA translation. A well-characterized group of proteins, named 4E-binding proteins (4E-BPs), inhibits the eIF4E–eIF4G interaction by competing for the same binding site on the eIF4E surface. 4E-BPs and eIF4G share a single canonical motif for the interaction with a conserved hydrophobic patch of eIF4E. However, a second non-canonical and not conserved binding motif was recently detected for eIF4G and several 4E-BPs. Here, we review the structural features of the interaction between eIF4E and its molecular partners eIF4G and 4E-BPs, focusing on the implications of the recent structural and biochemical evidence for the development of new therapeutic strategies. The design of novel eIF4E-targeting molecules that inhibit translation might provide new avenues for the treatment of several conditions.
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12
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Rana A, Gupta N, Thakur A. Post-transcriptional and translational control of the morphology and virulence in human fungal pathogens. Mol Aspects Med 2021; 81:101017. [PMID: 34497025 DOI: 10.1016/j.mam.2021.101017] [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: 02/11/2021] [Revised: 08/13/2021] [Accepted: 08/20/2021] [Indexed: 11/17/2022]
Abstract
Host-pathogen interactions at the molecular level are the key to fungal pathogenesis. Fungal pathogens utilize several mechanisms such as adhesion, invasion, phenotype switching and metabolic adaptations, to survive in the host environment and respond. Post-transcriptional and translational regulations have emerged as key regulatory mechanisms ensuring the virulence and survival of fungal pathogens. Through these regulations, fungal pathogens effectively alter their protein pool, respond to various stress, and undergo morphogenesis, leading to efficient and comprehensive changes in fungal physiology. The regulation of virulence through post-transcriptional and translational regulatory mechanisms is mediated through mRNA elements (cis factors) or effector molecules (trans factors). The untranslated regions upstream and downstream of the mRNA, as well as various RNA-binding proteins involved in translation initiation or circularization of the mRNA, play pivotal roles in the regulation of morphology and virulence by influencing protein synthesis, protein isoforms, and mRNA stability. Therefore, post-transcriptional and translational mechanisms regulating the morphology, virulence and drug-resistance processes in fungal pathogens can be the target for new therapeutics. With improved "omics" technologies, these regulatory mechanisms are increasingly coming to the forefront of basic biology and drug discovery. This review aims to discuss various modes of post-transcriptional and translation regulations, and how these mechanisms exert influence in the virulence and morphogenesis of fungal pathogens.
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Affiliation(s)
- Aishwarya Rana
- Regional Centre for Biotechnology, 3rd Milestone Gurgaon-Faridabad Expressway, Faridabad 121001, India
| | - Nidhi Gupta
- Regional Centre for Biotechnology, 3rd Milestone Gurgaon-Faridabad Expressway, Faridabad 121001, India
| | - Anil Thakur
- Regional Centre for Biotechnology, 3rd Milestone Gurgaon-Faridabad Expressway, Faridabad 121001, India.
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13
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Nwokoye EC, AlNaseem E, Crawford RA, Castelli LM, Jennings MD, Kershaw CJ, Pavitt GD. Overlapping regions of Caf20 mediate its interactions with the mRNA-5'cap-binding protein eIF4E and with ribosomes. Sci Rep 2021; 11:13467. [PMID: 34188131 PMCID: PMC8242001 DOI: 10.1038/s41598-021-92931-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2021] [Accepted: 06/03/2021] [Indexed: 02/06/2023] Open
Abstract
By interacting with the mRNA 5' cap, the translation initiation factor eIF4E plays a critical role in selecting mRNAs for protein synthesis in eukaryotic cells. Caf20 is a member of the family of proteins found across eukaryotes termed 4E-BPs, which compete with eIF4G for interaction with eIF4E. Caf20 independently interacts with ribosomes. Thus, Caf20 modulates the mRNA selection process via poorly understood mechanisms. Here we performed unbiased mutagenesis across Caf20 to characterise which regions of Caf20 are important for interaction with eIF4E and with ribosomes. Caf20 binding to eIF4E is entirely dependent on a canonical motif shared with other 4E-BPs. However, binding to ribosomes is weakened by mutations throughout the protein, suggesting an extended binding interface that partially overlaps with the eIF4E-interaction region. By using chemical crosslinking, we identify a potential ribosome interaction region on the ribosome surface that spans both small and large subunits and is close to a known interaction site of eIF3. The function of ribosome binding by Caf20 remains unclear.
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Affiliation(s)
- Ebelechukwu C Nwokoye
- Division of Molecular and Cellular Function, School of Biological Sciences, Faculty of Biology, Medicine and Health, Manchester Academic Health Science Centre, The University of Manchester, Manchester, M13 9PT, UK.,Department of Botany, Nnamdi Azikiwe University, Awka, Nigeria
| | - Eiman AlNaseem
- Division of Molecular and Cellular Function, School of Biological Sciences, Faculty of Biology, Medicine and Health, Manchester Academic Health Science Centre, The University of Manchester, Manchester, M13 9PT, UK
| | - Robert A Crawford
- Division of Molecular and Cellular Function, School of Biological Sciences, Faculty of Biology, Medicine and Health, Manchester Academic Health Science Centre, The University of Manchester, Manchester, M13 9PT, UK
| | - Lydia M Castelli
- Division of Molecular and Cellular Function, School of Biological Sciences, Faculty of Biology, Medicine and Health, Manchester Academic Health Science Centre, The University of Manchester, Manchester, M13 9PT, UK.,Department of Neuroscience, Sheffield Institute for Translational Neuroscience (SITraN), University of Sheffield, Sheffield, S10 2HQ, UK
| | - Martin D Jennings
- Division of Molecular and Cellular Function, School of Biological Sciences, Faculty of Biology, Medicine and Health, Manchester Academic Health Science Centre, The University of Manchester, Manchester, M13 9PT, UK
| | - Christopher J Kershaw
- Division of Molecular and Cellular Function, School of Biological Sciences, Faculty of Biology, Medicine and Health, Manchester Academic Health Science Centre, The University of Manchester, Manchester, M13 9PT, UK
| | - Graham D Pavitt
- Division of Molecular and Cellular Function, School of Biological Sciences, Faculty of Biology, Medicine and Health, Manchester Academic Health Science Centre, The University of Manchester, Manchester, M13 9PT, UK.
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14
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Higuchi Y, Fujii S, Valderrama AL, Irie K, Suda Y, Mizuno T, Irie K. The eIF4E-binding protein Eap1 has similar but independent roles in cell growth and gene expression with the cytoplasmic deadenylase Ccr4. Biosci Biotechnol Biochem 2021; 85:1452-1459. [PMID: 33784392 DOI: 10.1093/bbb/zbab056] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2021] [Accepted: 03/24/2021] [Indexed: 11/12/2022]
Abstract
eIF4E-binding proteins (4E-BPs) are translational repressors that compete with eIF4G for binding to eIF4E. Here we investigated the roles of yeast 4E-BPs, Eap1, and Caf20 in cell wall integrity pathway and gene expression. We found that eap1∆ mutation, but not caf20∆ mutation, showed synthetic growth defect with mutation in ROM2 gene encoding Rho1 GEF. The eap1∆ mutation also showed synthetic lethality with mutation in CCR4 gene encoding cytoplasmic deadenylase. Ccr4 functions in the degradation of LRG1 mRNA encoding Rho1 GAP. Eap1-Y109A L114A, which could not bind to eIF4E, did not suppress the synthetic lethality of eap1∆ ccr4∆ mutant, suggesting that 4E-binding of Eap1 is important for its function. We also found that eap1∆ mutant showed the derepression of stress response gene HSP12. 4E-binding of Eap1 was also required for the repression of HSP12 expression. Our results indicate that Eap1 has similar but independent roles in cell growth and gene expression with Ccr4.
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Affiliation(s)
- Yudai Higuchi
- Department of Molecular Cell Biology, Graduate School of Comprehensive Human Sciences and Faculty of Medicine, University of Tsukuba, Tsukuba, Japan
| | - Shiori Fujii
- Department of Molecular Cell Biology, Graduate School of Comprehensive Human Sciences and Faculty of Medicine, University of Tsukuba, Tsukuba, Japan
| | - Arvin Lapiz Valderrama
- Department of Molecular Cell Biology, Graduate School of Comprehensive Human Sciences and Faculty of Medicine, University of Tsukuba, Tsukuba, Japan.,Ph.D. Program in Human Biology, School of Integrative and Global Majors, University of Tsukuba, Tsukuba, Japan
| | - Kaoru Irie
- Department of Molecular Cell Biology, Graduate School of Comprehensive Human Sciences and Faculty of Medicine, University of Tsukuba, Tsukuba, Japan
| | - Yasuyuki Suda
- Department of Molecular Cell Biology, Graduate School of Comprehensive Human Sciences and Faculty of Medicine, University of Tsukuba, Tsukuba, Japan.,Live Cell Super-resolution Imaging Research Team, RIKEN Center for Advanced Photonics, Wako, Saitama, Japan
| | - Tomoaki Mizuno
- Department of Molecular Cell Biology, Graduate School of Comprehensive Human Sciences and Faculty of Medicine, University of Tsukuba, Tsukuba, Japan
| | - Kenji Irie
- Department of Molecular Cell Biology, Graduate School of Comprehensive Human Sciences and Faculty of Medicine, University of Tsukuba, Tsukuba, Japan.,Ph.D. Program in Human Biology, School of Integrative and Global Majors, University of Tsukuba, Tsukuba, Japan
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15
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Batool W, Shabbir A, Lin L, Chen X, An Q, He X, Pan S, Chen S, Chen Q, Wang Z, Norvienyeku J. Translation Initiation Factor eIF4E Positively Modulates Conidiogenesis, Appressorium Formation, Host Invasion and Stress Homeostasis in the Filamentous Fungi Magnaporthe oryzae. FRONTIERS IN PLANT SCIENCE 2021; 12:646343. [PMID: 34220879 PMCID: PMC8244596 DOI: 10.3389/fpls.2021.646343] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/07/2021] [Accepted: 05/21/2021] [Indexed: 05/14/2023]
Abstract
Translation initiation factor eIF4E generally mediates the recognition of the 5'cap structure of mRNA during the recruitment of the ribosomes to capped mRNA. Although the eIF4E has been shown to regulate stress response in Schizosaccharomyces pombe positively, there is no direct experimental evidence for the contributions of eIF4E to both physiological and pathogenic development of filamentous fungi. We generated Magnaporthe oryzae eIF4E (MoeIF4E3) gene deletion strains using homologous recombination strategies. Phenotypic and biochemical analyses of MoeIF4E3 defective strains showed that the deletion of MoeIF4E3 triggered a significant reduction in growth and conidiogenesis. We also showed that disruption of MoeIF4E3 partially impaired conidia germination, appressorium integrity and attenuated the pathogenicity of ΔMoeif4e3 strains. In summary, this study provides experimental insights into the contributions of the eIF4E3 to the development of filamentous fungi. Additionally, these observations underscored the need for a comprehensive evaluation of the translational regulatory machinery in phytopathogenic fungi during pathogen-host interaction progression.
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Affiliation(s)
- Wajjiha Batool
- Fujian University Key Laboratory for Plant-Microbe Interaction, College of Plant Protection, Fujian Agriculture and Forestry University, Fuzhou, China
- State Key Laboratory for Ecological Pest Control of Fujian and Taiwan Crops, The School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Ammarah Shabbir
- Fujian University Key Laboratory for Plant-Microbe Interaction, College of Plant Protection, Fujian Agriculture and Forestry University, Fuzhou, China
- State Key Laboratory for Ecological Pest Control of Fujian and Taiwan Crops, The School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Lili Lin
- Fujian University Key Laboratory for Plant-Microbe Interaction, College of Plant Protection, Fujian Agriculture and Forestry University, Fuzhou, China
- State Key Laboratory for Ecological Pest Control of Fujian and Taiwan Crops, The School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Xiaomin Chen
- Fujian University Key Laboratory for Plant-Microbe Interaction, College of Plant Protection, Fujian Agriculture and Forestry University, Fuzhou, China
- State Key Laboratory for Ecological Pest Control of Fujian and Taiwan Crops, The School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Qiuli An
- Fujian University Key Laboratory for Plant-Microbe Interaction, College of Plant Protection, Fujian Agriculture and Forestry University, Fuzhou, China
- State Key Laboratory for Ecological Pest Control of Fujian and Taiwan Crops, The School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Xiongjie He
- Fujian University Key Laboratory for Plant-Microbe Interaction, College of Plant Protection, Fujian Agriculture and Forestry University, Fuzhou, China
- State Key Laboratory for Ecological Pest Control of Fujian and Taiwan Crops, The School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Shu Pan
- Fujian University Key Laboratory for Plant-Microbe Interaction, College of Plant Protection, Fujian Agriculture and Forestry University, Fuzhou, China
- State Key Laboratory for Ecological Pest Control of Fujian and Taiwan Crops, The School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Shuzun Chen
- Fujian University Key Laboratory for Plant-Microbe Interaction, College of Plant Protection, Fujian Agriculture and Forestry University, Fuzhou, China
- State Key Laboratory for Ecological Pest Control of Fujian and Taiwan Crops, The School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Qinghe Chen
- Fujian University Key Laboratory for Plant-Microbe Interaction, College of Plant Protection, Fujian Agriculture and Forestry University, Fuzhou, China
- State Key Laboratory for Ecological Pest Control of Fujian and Taiwan Crops, The School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
- Key Laboratory of Green Prevention and Control of Tropical Plant Diseases and Pests, Ministry of Education, College of Plant Protection, Hainan University, Haikou, China
| | - Zonghua Wang
- Fujian University Key Laboratory for Plant-Microbe Interaction, College of Plant Protection, Fujian Agriculture and Forestry University, Fuzhou, China
- Key Laboratory of Green Prevention and Control of Tropical Plant Diseases and Pests, Ministry of Education, College of Plant Protection, Hainan University, Haikou, China
- Institute of Oceanography, Minjiang University, Fuzhou, China
- *Correspondence: Zonghua Wang,
| | - Justice Norvienyeku
- Fujian University Key Laboratory for Plant-Microbe Interaction, College of Plant Protection, Fujian Agriculture and Forestry University, Fuzhou, China
- State Key Laboratory for Ecological Pest Control of Fujian and Taiwan Crops, The School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
- Key Laboratory of Green Prevention and Control of Tropical Plant Diseases and Pests, Ministry of Education, College of Plant Protection, Hainan University, Haikou, China
- Justice Norvienyeku, ;
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16
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Calafí C, López-Malo M, Velázquez D, Zhang C, Fernández-Fernández J, Rodríguez-Galán O, de la Cruz J, Ariño J, Casamayor A. Overexpression of budding yeast protein phosphatase Ppz1 impairs translation. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2020; 1867:118727. [DOI: 10.1016/j.bbamcr.2020.118727] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/27/2019] [Revised: 04/09/2020] [Accepted: 04/16/2020] [Indexed: 12/25/2022]
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17
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eIF4E and Interactors from Unicellular Eukaryotes. Int J Mol Sci 2020; 21:ijms21062170. [PMID: 32245232 PMCID: PMC7139794 DOI: 10.3390/ijms21062170] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2020] [Revised: 03/12/2020] [Accepted: 03/18/2020] [Indexed: 12/22/2022] Open
Abstract
eIF4E, the mRNA cap-binding protein, is well known as a general initiation factor allowing for mRNA-ribosome interaction and cap-dependent translation in eukaryotic cells. In this review we focus on eIF4E and its interactors in unicellular organisms such as yeasts and protozoan eukaryotes. In a first part, we describe eIF4Es from yeast species such as Saccharomyces cerevisiae, Candida albicans, and Schizosaccharomyces pombe. In the second part, we will address eIF4E and interactors from parasite unicellular species—trypanosomatids and marine microorganisms—dinoflagellates. We propose that different strategies have evolved during evolution to accommodate cap-dependent translation to differing requirements. These evolutive “adjustments” involve various forms of eIF4E that are not encountered in all microorganismic species. In yeasts, eIF4E interactors, particularly p20 and Eap1 are found exclusively in Saccharomycotina species such as S. cerevisiae and C. albicans. For protozoan parasites of the Trypanosomatidae family beside a unique cap4-structure located at the 5′UTR of all mRNAs, different eIF4Es and eIF4Gs are active depending on the life cycle stage of the parasite. Additionally, an eIF4E-interacting protein has been identified in Leishmania major which is important for switching from promastigote to amastigote stages. For dinoflagellates, little is known about the structure and function of the multiple and diverse eIF4Es that have been identified thanks to widespread sequencing in recent years.
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18
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T Magalhães B, Lourenço A, Azevedo NF. Computational resources and strategies to assess single-molecule dynamics of the translation process in S. cerevisiae. Brief Bioinform 2019; 22:219-231. [PMID: 31879749 DOI: 10.1093/bib/bbz149] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2019] [Revised: 10/16/2019] [Accepted: 10/30/2019] [Indexed: 11/13/2022] Open
Abstract
This work provides a systematic and comprehensive overview of available resources for the molecular-scale modelling of the translation process through agent-based modelling. The case study is the translation in Saccharomyces cerevisiae, one of the most studied yeasts. The data curation workflow encompassed structural information about the yeast (i.e. the simulation environment), and the proteins, ribonucleic acids and other types of molecules involved in the process (i.e. the agents). Moreover, it covers the main process events, such as diffusion (i.e. motion of molecules in the environment) and collision efficiency (i.e. interaction between molecules). Data previously determined by wet-lab techniques were preferred, resorting to computational predictions/extrapolations only when strictly necessary. The computational modelling of the translation processes is of added industrial interest, since it may bring forward knowledge on how to control such phenomena and enhance the production of proteins of interest in a faster and more efficient manner.
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Affiliation(s)
| | - Anália Lourenço
- Department of Computer Science, University of Vigo, Spain, Centre of Biological Engineering, University of Minho, Portugal
| | - Nuno F Azevedo
- Department of Chemical Engineering, Faculty of Engineering of the University of Porto, Portugal
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19
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Toribio R, Muñoz A, Castro-Sanz AB, Merchante C, Castellano MM. A novel eIF4E-interacting protein that forms non-canonical translation initiation complexes. NATURE PLANTS 2019; 5:1283-1296. [PMID: 31819221 PMCID: PMC6914366 DOI: 10.1038/s41477-019-0553-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/29/2018] [Accepted: 10/14/2019] [Indexed: 06/10/2023]
Abstract
Translation is a fundamental step in gene expression that regulates multiple developmental and stress responses. One key step of translation initiation is the association between eIF4E and eIF4G. This process is regulated in different eukaryotes by proteins that bind to eIF4E; however, evidence of eIF4E-interacting proteins able to regulate translation is missing in plants. Here, we report the discovery of CERES, a plant eIF4E-interacting protein. CERES contains an LRR domain and a canonical eIF4E-binding site. Although the CERES-eIF4E complex does not include eIF4G, CERES forms part of cap-binding complexes, interacts with eIF4A, PABP and eIF3, and co-sediments with translation initiation complexes in vivo. Moreover, CERES promotes translation in vitro and general translation in vivo, while it modulates the translation of specific mRNAs related to light and carbohydrate response. These data suggest that CERES is a non-canonical translation initiation factor that modulates translation in plants.
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Affiliation(s)
- René Toribio
- Centro de Biotecnología y Genómica de Plantas, Universidad Politécnica de Madrid (UPM) - Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (INIA), Madrid, Spain
| | - Alfonso Muñoz
- Centro de Biotecnología y Genómica de Plantas, Universidad Politécnica de Madrid (UPM) - Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (INIA), Madrid, Spain
- Departamento de Botánica, Ecología y Fisiología Vegetal, Universidad de Córdoba, Cordova, Spain
| | - Ana B Castro-Sanz
- Centro de Biotecnología y Genómica de Plantas, Universidad Politécnica de Madrid (UPM) - Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (INIA), Madrid, Spain
| | - Catharina Merchante
- Instituto de Hortofruticultura Subtropical y Mediterránea "La Mayora" - Universidad de Málaga- Consejo Superior de Investigaciones Científicas (IHSM-UMA-CSIC), Departamento de Biología Molecular y Bioquímica, Málaga, Spain
| | - M Mar Castellano
- Centro de Biotecnología y Genómica de Plantas, Universidad Politécnica de Madrid (UPM) - Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (INIA), Madrid, Spain.
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20
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Mechanisms by which PE21, an extract from the white willow Salix alba, delays chronological aging in budding yeast. Oncotarget 2019; 10:5780-5816. [PMID: 31645900 PMCID: PMC6791382 DOI: 10.18632/oncotarget.27209] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2019] [Accepted: 08/27/2019] [Indexed: 01/05/2023] Open
Abstract
We have recently found that PE21, an extract from the white willow Salix alba, slows chronological aging and prolongs longevity of the yeast Saccharomyces cerevisiae more efficiently than any of the previously known pharmacological interventions. Here, we investigated mechanisms through which PE21 delays yeast chronological aging and extends yeast longevity. We show that PE21 causes a remodeling of lipid metabolism in chronologically aging yeast, thereby instigating changes in the concentrations of several lipid classes. We demonstrate that such changes in the cellular lipidome initiate three mechanisms of aging delay and longevity extension. The first mechanism through which PE21 slows aging and prolongs longevity consists in its ability to decrease the intracellular concentration of free fatty acids. This postpones an age-related onset of liponecrotic cell death promoted by excessive concentrations of free fatty acids. The second mechanism of aging delay and longevity extension by PE21 consists in its ability to decrease the concentrations of triacylglycerols and to increase the concentrations of glycerophospholipids within the endoplasmic reticulum membrane. This activates the unfolded protein response system in the endoplasmic reticulum, which then decelerates an age-related decline in protein and lipid homeostasis and slows down an aging-associated deterioration of cell resistance to stress. The third mechanisms underlying aging delay and longevity extension by PE21 consists in its ability to change lipid concentrations in the mitochondrial membranes. This alters certain catabolic and anabolic processes in mitochondria, thus amending the pattern of aging-associated changes in several key aspects of mitochondrial functionality.
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21
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Leipheimer J, Bloom ALM, Panepinto JC. Protein Kinases at the Intersection of Translation and Virulence. Front Cell Infect Microbiol 2019; 9:318. [PMID: 31572689 PMCID: PMC6749009 DOI: 10.3389/fcimb.2019.00318] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2019] [Accepted: 08/26/2019] [Indexed: 12/14/2022] Open
Abstract
As free living organisms, fungi are challenged with a variety of environmental insults that threaten their cellular processes. In some cases, these challenges mimic conditions present within mammals, resulting in the accidental selection of virulence factors over evolutionary time. Be it within a host or the soil, fungi must contend with environmental challenges through the production of stress effector proteins while maintaining factors required for viability in any condition. Initiation and upkeep of this balancing act is mainly under the control of kinases that affect the propensity and selectivity of protein translation. This review will focus on kinases in pathogenic fungi that facilitate a virulence phenotype through translational control.
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Affiliation(s)
- Jay Leipheimer
- Department of Microbiology and Immunology, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, NY, United States
| | - Amanda L M Bloom
- Department of Microbiology and Immunology, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, NY, United States
| | - John C Panepinto
- Department of Microbiology and Immunology, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, NY, United States
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22
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Control of Translation at the Initiation Phase During Glucose Starvation in Yeast. Int J Mol Sci 2019; 20:ijms20164043. [PMID: 31430885 PMCID: PMC6720308 DOI: 10.3390/ijms20164043] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2019] [Revised: 08/10/2019] [Accepted: 08/15/2019] [Indexed: 12/13/2022] Open
Abstract
Glucose is one of the most important sources of carbon across all life. Glucose starvation is a key stress relevant to all eukaryotic cells. Glucose starvation responses have important implications in diseases, such as diabetes and cancer. In yeast, glucose starvation causes rapid and dramatic effects on the synthesis of proteins (mRNA translation). Response to glucose deficiency targets the initiation phase of translation by different mechanisms and with diverse dynamics. Concomitantly, translationally repressed mRNAs and components of the protein synthesis machinery may enter a variety of cytoplasmic foci, which also form with variable kinetics and may store or degrade mRNA. Much progress has been made in understanding these processes in the last decade, including with the use of high-throughput/omics methods of RNA and RNA:protein detection. This review dissects the current knowledge of yeast reactions to glucose starvation systematized by the stage of translation initiation, with the focus on rapid responses. We provide parallels to mechanisms found in higher eukaryotes, such as metazoans, for the most critical responses, and point out major remaining gaps in knowledge and possible future directions of research on translational responses to glucose starvation.
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23
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Chang Y, Huh WK. Ksp1-dependent phosphorylation of eIF4G modulates post-transcriptional regulation of specific mRNAs under glucose deprivation conditions. Nucleic Acids Res 2019; 46:3047-3060. [PMID: 29438499 PMCID: PMC5888036 DOI: 10.1093/nar/gky097] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2017] [Accepted: 02/05/2018] [Indexed: 12/31/2022] Open
Abstract
Post-transcriptional regulation is an important mechanism for modulating gene expression and is performed by numerous mRNA-binding proteins. To understand the mechanisms underlying post-transcriptional regulation, we investigated the phosphorylation status of 32 mRNA-binding proteins under glucose deprivation conditions in Saccharomyces cerevisiae. We identified 17 glucose-sensitive phosphoproteins and signal pathways implicated in their phosphorylation. Notably, phosphorylation of the eukaryotic translation initiation factor 4G (eIF4G) was regulated by both the Snf1/AMPK pathway and the target of rapamycin complex 1 (TORC1) pathway. The serine/threonine protein kinase Ksp1 has previously been suggested to be a downstream effector of TORC1, but its detailed function has rarely been discussed. We identified that Snf1/AMPK and TORC1 signalings converge on Ksp1, which phosphorylates eIF4G under glucose deprivation conditions. Ksp1-dependent phosphorylation of eIF4G regulates the degradation of specific mRNAs (e.g. glycolytic mRNAs and ribosomal protein mRNAs) under glucose deprivation conditions likely through the recruitment of Dhh1. Taken together, our results suggest that Ksp1 functions as a novel modulator of post-transcriptional regulation in yeast.
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Affiliation(s)
- Yeonji Chang
- Department of Biological Sciences, Seoul National University, Seoul 08826, Republic of Korea
| | - Won-Ki Huh
- Department of Biological Sciences, Seoul National University, Seoul 08826, Republic of Korea.,Institute of Microbiology, Seoul National University, Seoul 08826, Republic of Korea
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24
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Grüner S, Weber R, Peter D, Chung MY, Igreja C, Valkov E, Izaurralde E. Structural motifs in eIF4G and 4E-BPs modulate their binding to eIF4E to regulate translation initiation in yeast. Nucleic Acids Res 2019; 46:6893-6908. [PMID: 30053226 PMCID: PMC6061780 DOI: 10.1093/nar/gky542] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2018] [Accepted: 06/02/2018] [Indexed: 12/13/2022] Open
Abstract
The interaction of the eukaryotic initiation factor 4G (eIF4G) with the cap-binding protein eIF4E initiates cap-dependent translation and is regulated by the 4E-binding proteins (4E-BPs), which compete with eIF4G to repress translation. Metazoan eIF4G and 4E-BPs interact with eIF4E via canonical and non-canonical motifs that bind to the dorsal and lateral surface of eIF4E in a bipartite recognition mode. However, previous studies pointed to mechanistic differences in how fungi and metazoans regulate protein synthesis. We present crystal structures of the yeast eIF4E bound to two yeast 4E-BPs, p20 and Eap1p, as well as crystal structures of a fungal eIF4E–eIF4G complex. We demonstrate that the core principles of molecular recognition of eIF4E are in fact highly conserved among translational activators and repressors in eukaryotes. Finally, we reveal that highly specialized structural motifs do exist and serve to modulate the affinity of protein-protein interactions that regulate cap-dependent translation initiation in fungi.
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Affiliation(s)
- Stefan Grüner
- Department of Biochemistry, Max Planck Institute for Developmental Biology, Max-Planck-Ring 5, D-72076 Tübingen, Germany
| | - Ramona Weber
- Department of Biochemistry, Max Planck Institute for Developmental Biology, Max-Planck-Ring 5, D-72076 Tübingen, Germany
| | - Daniel Peter
- Department of Biochemistry, Max Planck Institute for Developmental Biology, Max-Planck-Ring 5, D-72076 Tübingen, Germany
| | - Min-Yi Chung
- Department of Biochemistry, Max Planck Institute for Developmental Biology, Max-Planck-Ring 5, D-72076 Tübingen, Germany
| | - Cátia Igreja
- Department of Biochemistry, Max Planck Institute for Developmental Biology, Max-Planck-Ring 5, D-72076 Tübingen, Germany
| | - Eugene Valkov
- Department of Biochemistry, Max Planck Institute for Developmental Biology, Max-Planck-Ring 5, D-72076 Tübingen, Germany
| | - Elisa Izaurralde
- Department of Biochemistry, Max Planck Institute for Developmental Biology, Max-Planck-Ring 5, D-72076 Tübingen, Germany
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25
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Crawford RA, Pavitt GD. Translational regulation in response to stress in Saccharomyces cerevisiae. Yeast 2018; 36:5-21. [PMID: 30019452 PMCID: PMC6492140 DOI: 10.1002/yea.3349] [Citation(s) in RCA: 51] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2018] [Revised: 06/08/2018] [Accepted: 06/25/2018] [Indexed: 12/19/2022] Open
Abstract
The budding yeast Saccharomyces cerevisiae must dynamically alter the composition of its proteome in order to respond to diverse stresses. The reprogramming of gene expression during stress typically involves initial global repression of protein synthesis, accompanied by the activation of stress‐responsive mRNAs through both translational and transcriptional responses. The ability of specific mRNAs to counter the global translational repression is therefore crucial to the overall response to stress. Here we summarize the major repressive mechanisms and discuss mechanisms of translational activation in response to different stresses in S. cerevisiae. Taken together, a wide range of studies indicate that multiple elements act in concert to bring about appropriate translational responses. These include regulatory elements within mRNAs, altered mRNA interactions with RNA‐binding proteins and the specialization of ribosomes that each contribute towards regulating protein expression to suit the changing environmental conditions.
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Affiliation(s)
- Robert A Crawford
- Division of Molecular and Cellular Function, School of Biological Sciences, Faculty of Biology, Medicine and Health, Manchester Academic Health Science Centre, The University of Manchester, Michael Smith Building, Dover Street, Manchester, M13 9PT, UK
| | - Graham D Pavitt
- Division of Molecular and Cellular Function, School of Biological Sciences, Faculty of Biology, Medicine and Health, Manchester Academic Health Science Centre, The University of Manchester, Michael Smith Building, Dover Street, Manchester, M13 9PT, UK
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26
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Park K, Lee YS, Jung D, Kim J. Roles of eIF4E-binding protein Caf20 in Ste12 translation and P-body formation in yeast. J Microbiol 2018; 56:744-747. [PMID: 30136257 DOI: 10.1007/s12275-018-8230-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2018] [Revised: 07/09/2018] [Accepted: 07/10/2018] [Indexed: 12/20/2022]
Abstract
Translation initiation factor eIF4E forms eIF4E-eIF4G complex at the 5' cap of mRNA. This interaction can be inhibited by the family of 4E-binding proteins (4E-BP). In yeast Saccharomyces cerevisiae, two 4E-BPs, Caf20 and Eap1, compete with eIF4G for binding to eIF4E via the shared conserved interaction motif. In order to investigate the roles of Caf20 in gene-specific translational regulation and the formation of mRNA granules (P-bodies), we introduced substitution mutations, caf20-Y4A or caf20-L9A, in the eIF4E-binding motif for CAF20. Overexpression of the wild-type CAF20 showed an increased protein level of Ste12 transcription factor as well as highly developed P-body formation. However, 4E-binding site mutations of CAF20 led to a reduced number of P-body foci and decreased levels of Ste12 protein. The phenotypes of the caf20 deletion mutation were also analyzed, and we suggest that Caf20 plays a critical role in Ste12 protein expression and in the control of P-body formation.
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Affiliation(s)
- Kiyoung Park
- Department of Microbiology and Molecular Biology, College of Bioscience and Biotechnology, Chungnam National University, Daejeon, 34134, Republic of Korea
| | - Yu-Seon Lee
- Department of Microbiology and Molecular Biology, College of Bioscience and Biotechnology, Chungnam National University, Daejeon, 34134, Republic of Korea
| | - Daehee Jung
- Department of Microbiology and Molecular Biology, College of Bioscience and Biotechnology, Chungnam National University, Daejeon, 34134, Republic of Korea
| | - Jinmi Kim
- Department of Microbiology and Molecular Biology, College of Bioscience and Biotechnology, Chungnam National University, Daejeon, 34134, Republic of Korea.
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Fonseca BD, Lahr RM, Damgaard CK, Alain T, Berman AJ. LARP1 on TOP of ribosome production. WILEY INTERDISCIPLINARY REVIEWS-RNA 2018; 9:e1480. [PMID: 29722158 DOI: 10.1002/wrna.1480] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/31/2017] [Revised: 03/06/2018] [Accepted: 03/07/2018] [Indexed: 12/27/2022]
Abstract
The ribosome is an essential unit of all living organisms that commands protein synthesis, ultimately fuelling cell growth (accumulation of cell mass) and cell proliferation (increase in cell number). The eukaryotic ribosome consists of 4 ribosomal RNAs (rRNAs) and 80 ribosomal proteins (RPs). Despite its fundamental role in every living organism, our present understanding of how higher eukaryotes produce the various ribosome components is incomplete. Uncovering the mechanisms utilized by human cells to generate functional ribosomes will likely have far-reaching implications in human disease. Recent biochemical and structural studies revealed La-related protein 1 (LARP1) as a key new player in RP production. LARP1 is an RNA-binding protein that belongs to the LARP superfamily; it controls the translation and stability of the mRNAs that encode RPs and translation factors, which are characterized by a 5' terminal oligopyrimidine (5'TOP) motif and are thus known as TOP mRNAs. The activity of LARP1 is regulated by the mammalian target of rapamycin complex 1 (mTORC1): a eukaryotic protein kinase complex that integrates nutrient sensing with mRNA translation, particularly that of TOP mRNAs. In this review, we provide an overview of the role of LARP1 in the control of ribosome production in multicellular eukaryotes. This article is categorized under: Translation > Translation Regulation RNA Interactions with Proteins and Other Molecules > Protein-RNA Interactions: Functional Implications RNA Processing > Capping and 5' End Modifications.
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Affiliation(s)
- Bruno D Fonseca
- Children's Hospital of Eastern Ontario, Ottawa, Ontario, Canada
| | - Roni M Lahr
- University of Pittsburgh, Pittsburgh, Pennsylvania, United States
| | | | - Tommy Alain
- Children's Hospital of Eastern Ontario, Ottawa, Ontario, Canada
| | - Andrea J Berman
- University of Pittsburgh, Pittsburgh, Pennsylvania, United States
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28
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Properties of the ternary complex formed by yeast eIF4E, p20 and mRNA. Sci Rep 2018; 8:6707. [PMID: 29712996 PMCID: PMC5928113 DOI: 10.1038/s41598-018-25273-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2018] [Accepted: 04/17/2018] [Indexed: 11/25/2022] Open
Abstract
Yeast p20 is a small, acidic protein that binds eIF4E, the cap-binding protein. It has been proposed to affect mRNA translation and degradation, however p20′s function as an eIF4E-binding protein (4E-BP) and its physiological significance has not been clearly established. In this paper we present data demonstrating that p20 is capable of binding directly to mRNA due to electrostatic interaction of a stretch of arginine and histidine residues in the protein with negatively charged phosphates in the mRNA backbone. This interaction contributes to formation of a ternary eIF4E/p20/capped mRNA complex that is more stable than complexes composed of capped mRNA bound to eIF4E in the absence of p20. eIF4E/p20 complex was found to have a more pronounced stimulatory effect on capped mRNA translation than purified eIF4E alone. Addition of peptides containing the eIF4E-binding domains present in p20 (motif YTIDELF), in eIF4G (motif YGPTFLL) or Eap1 (motif YSMNELY) completely inhibited eIF4E-dependent capped mRNA translation (in vitro), but had a greatly reduced inhibitory effect when eIF4E/p20 complex was present. We propose that the eIF4E/p20/mRNA complex serves as a stable depository of mRNAs existing in a dynamic equilibrium with other complexes such as eIF4E/eIF4G (required for translation) and eIF4E/Eap1 (required for mRNA degradation).
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29
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Gottier P, Serricchio M, Vitale R, Corcelli A, Bütikofer P. Cross-species complementation of bacterial- and eukaryotic-type cardiolipin synthases. MICROBIAL CELL 2017; 4:376-383. [PMID: 29167800 PMCID: PMC5695855 DOI: 10.15698/mic2017.11.598] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The glycerophospholipid cardiolipin is a unique constituent of bacterial and mitochondrial membranes. It is involved in forming and stabilizing high molecular mass membrane protein complexes and in maintaining membrane architecture. Absence of cardiolipin leads to reduced efficiency of the electron transport chain, decreased membrane potential, and, ultimately, impaired respiratory metabolism. For the protozoan parasite Trypanosoma brucei cardiolipin synthesis is essential for survival, indicating that the enzymes involved in cardiolipin production represent potential drug targets. T. brucei cardiolipin synthase (TbCLS) is unique as it belongs to the family of phospholipases D (PLD), harboring a prokaryotic-type cardiolipin synthase (CLS) active site domain. In contrast, most other eukaryotic CLS, including the yeast ortholog ScCrd1, are members of the CDP-alcohol phosphatidyltransferase family. To study if these mechanistically distinct CLS enzymes are able to catalyze cardiolipin production in a cell that normally expresses a different type of CLS, we expressed TbCLS and ScCrd1 in CLS-deficient yeast and trypanosome strains, respectively. Our results show that TbCLS complemented cardiolipin production in CRD1 knockout yeast and partly restored wild-type colony forming capability under stress conditions. Remarkably, CL remodeling appeared to be impaired in the transgenic construct, suggesting that CL production and remodeling are tightly coupled processes that may require a clustering of the involved proteins into specific CL-synthesizing domains. In contrast, no complementation was observed by heterologous expression of ScCrd1 in conditional TbCLS knockout trypanosomes, despite proper mitochondrial targeting of the protein.
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Affiliation(s)
- Petra Gottier
- Institute for Biochemistry and Molecular Medicine, University of Bern, Bern, Switzerland
| | - Mauro Serricchio
- Institute for Biochemistry and Molecular Medicine, University of Bern, Bern, Switzerland
| | - Rita Vitale
- School of Medicine: Basic Medical Sciences, Neuroscience and Sense Organs, University of Bari Aldo Moro, Bari, Italy
| | - Angela Corcelli
- School of Medicine: Basic Medical Sciences, Neuroscience and Sense Organs, University of Bari Aldo Moro, Bari, Italy
| | - Peter Bütikofer
- Institute for Biochemistry and Molecular Medicine, University of Bern, Bern, Switzerland
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Sekiyama N, Boeszoermenyi A, Arthanari H, Wagner G, Léger-Abraham M. 1H, 13C, and 15N backbone chemical shift assignments of 4E-BP1 44-87 and 4E-BP1 44-87 bound to eIF4E. BIOMOLECULAR NMR ASSIGNMENTS 2017; 11:187-191. [PMID: 28589219 PMCID: PMC5693643 DOI: 10.1007/s12104-017-9744-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2017] [Accepted: 05/26/2017] [Indexed: 06/07/2023]
Abstract
The eukaryotic translational initiation factor 4G (eIF4G) interacts with the cap-binding protein eIF4E through a consensus binding motif, Y(X)4LΦ (where X is any amino acid and Φ is a hydrophobic residue). 4E binding proteins (4E-BPs), which also contain a Y(X)4LΦ motif, regulate the eIF4E/eIF4G interaction. The non- or minimally-phosphorylated form of 4E-BP1 binds eIF4E, preventing eIF4E from interacting with eIF4G, thus inhibiting translation initiation. 4EGI-1, a small molecule inhibitor of the eIF4E/eIF4G interaction that is under investigation as a novel anti-cancer drug, has a dual activity; it disrupts the eIF4E/eIF4G interaction and stabilizes the binding of 4E-BP1 to eIF4E. Here, we report the complete backbone NMR resonance assignment of an unliganded 4E-BP1 fragment (4E-BP144-87). We also report the near complete backbone assignment of the same fragment in complex to eIF4E/m7GTP (excluding the assignment of the last C-terminus residue, D87). The chemical shift data constitute a prerequisite to understanding the mechanism of action of translation initiation inhibitors, including 4EGI-1, that modulate the eIF4E/4E-BP1 interaction.
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Affiliation(s)
- Naotaka Sekiyama
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, 02115, USA
- Department of Biophysics, Graduate School of Science, Kyoto University, Oiwake-cho, Kitashirakawa, Sakyo-Ku, Kyoto, 606-8502, Japan
| | - Andras Boeszoermenyi
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, 02115, USA
| | - Haribabu Arthanari
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, 02115, USA
| | - Gerhard Wagner
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, 02115, USA.
| | - Mélissa Léger-Abraham
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, 02115, USA.
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31
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Mechanism and Regulation of Protein Synthesis in Saccharomyces cerevisiae. Genetics 2017; 203:65-107. [PMID: 27183566 DOI: 10.1534/genetics.115.186221] [Citation(s) in RCA: 100] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2015] [Accepted: 02/24/2016] [Indexed: 12/18/2022] Open
Abstract
In this review, we provide an overview of protein synthesis in the yeast Saccharomyces cerevisiae The mechanism of protein synthesis is well conserved between yeast and other eukaryotes, and molecular genetic studies in budding yeast have provided critical insights into the fundamental process of translation as well as its regulation. The review focuses on the initiation and elongation phases of protein synthesis with descriptions of the roles of translation initiation and elongation factors that assist the ribosome in binding the messenger RNA (mRNA), selecting the start codon, and synthesizing the polypeptide. We also examine mechanisms of translational control highlighting the mRNA cap-binding proteins and the regulation of GCN4 and CPA1 mRNAs.
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32
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Das S, Das B. eIF4G—an integrator of mRNA metabolism? FEMS Yeast Res 2016; 16:fow087. [DOI: 10.1093/femsyr/fow087] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/29/2016] [Indexed: 11/14/2022] Open
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Burger VM, Nolasco DO, Stultz CM. Expanding the Range of Protein Function at the Far End of the Order-Structure Continuum. J Biol Chem 2016; 291:6706-13. [PMID: 26851282 PMCID: PMC4807258 DOI: 10.1074/jbc.r115.692590] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The traditional view of the structure-function paradigm is that a protein's function is inextricably linked to a well defined, three-dimensional structure, which is determined by the protein's primary amino acid sequence. However, it is now accepted that a number of proteins do not adopt a unique tertiary structure in solution and that some degree of disorder is required for many proteins to perform their prescribed functions. In this review, we highlight how a number of protein functions are facilitated by intrinsic disorder and introduce a new protein structure taxonomy that is based on quantifiable metrics of a protein's disorder.
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Affiliation(s)
- Virginia M Burger
- From the Research Laboratory for Electronics, Department of Electrical Engineering & Computer Science, and
| | - Diego O Nolasco
- From the Research Laboratory for Electronics, Department of Electrical Engineering & Computer Science, and
| | - Collin M Stultz
- From the Research Laboratory for Electronics, Department of Electrical Engineering & Computer Science, and the Institute for Medical Engineering and Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02138
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Alonso-Rodríguez E, Fernández-Piñar P, Sacristán-Reviriego A, Molina M, Martín H. An Analog-sensitive Version of the Protein Kinase Slt2 Allows Identification of Novel Targets of the Yeast Cell Wall Integrity Pathway. J Biol Chem 2016; 291:5461-5472. [PMID: 26786099 DOI: 10.1074/jbc.m115.683680] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2015] [Indexed: 12/12/2022] Open
Abstract
The yeast cell wall integrity MAPK Slt2 mediates the transcriptional response to cell wall alterations through phosphorylation of transcription factors Rlm1 and SBF. However, the variety of cellular functions regulated by Slt2 suggests the existence of a significant number of still unknown substrates for this kinase. To identify novel Slt2 targets, we generated and characterized an analog-sensitive mutant of Slt2 (Slt2-as) that can be specifically inhibited by bulky kinase inhibitor analogs. We demonstrated that Slt2-as is able to use adenosine 5'-[γ-thio]triphosphate analogs to thiophosphorylate its substrates in yeast cell extracts as well as when produced as recombinant proteins in Escherichia coli. Taking advantage of this chemical-genetic approach, we found that Slt2 phosphorylates the MAPK phosphatase Msg5 both in the N-terminal regulatory and C-terminal catalytic domains. Moreover, we identified the calcineurin regulator Rcn2, the 4E-BP (translation initiation factor eIF4E-binding protein) translation repressor protein Caf20, and the Golgi-associated adaptor Gga1 as novel targets for Slt2. The Slt2 phosphorylation sites on Rcn2 and Caf20 were determined. We also demonstrated that, in the absence of SLT2, the GGA1 paralog GGA2 is essential for cells to survive under cell wall stress and for proper protein sorting through the carboxypeptidase Y pathway. Therefore, Slt2-as provides a powerful tool that can expand our knowledge of the outputs of the cell wall integrity MAPK pathway.
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Affiliation(s)
- Esmeralda Alonso-Rodríguez
- From the Departamento de Microbiología II, Facultad de Farmacia, Universidad Complutense de Madrid and Instituto Ramón y Cajal de Investigaciones Sanitarias (IRYCIS), 28040 Madrid, Spain
| | - Pablo Fernández-Piñar
- From the Departamento de Microbiología II, Facultad de Farmacia, Universidad Complutense de Madrid and Instituto Ramón y Cajal de Investigaciones Sanitarias (IRYCIS), 28040 Madrid, Spain
| | - Almudena Sacristán-Reviriego
- From the Departamento de Microbiología II, Facultad de Farmacia, Universidad Complutense de Madrid and Instituto Ramón y Cajal de Investigaciones Sanitarias (IRYCIS), 28040 Madrid, Spain
| | - María Molina
- From the Departamento de Microbiología II, Facultad de Farmacia, Universidad Complutense de Madrid and Instituto Ramón y Cajal de Investigaciones Sanitarias (IRYCIS), 28040 Madrid, Spain.
| | - Humberto Martín
- From the Departamento de Microbiología II, Facultad de Farmacia, Universidad Complutense de Madrid and Instituto Ramón y Cajal de Investigaciones Sanitarias (IRYCIS), 28040 Madrid, Spain
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The 4E-BP Caf20p Mediates Both eIF4E-Dependent and Independent Repression of Translation. PLoS Genet 2015; 11:e1005233. [PMID: 25973932 PMCID: PMC4431810 DOI: 10.1371/journal.pgen.1005233] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2014] [Accepted: 04/21/2015] [Indexed: 11/19/2022] Open
Abstract
Translation initiation factor eIF4E mediates mRNA selection for protein synthesis via the mRNA 5'cap. A family of binding proteins, termed the 4E-BPs, interact with eIF4E to hinder ribosome recruitment. Mechanisms underlying mRNA specificity for 4E-BP control remain poorly understood. Saccharomyces cerevisiae 4E-BPs, Caf20p and Eap1p, each regulate an overlapping set of mRNAs. We undertook global approaches to identify protein and RNA partners of both 4E-BPs by immunoprecipitation of tagged proteins combined with mass spectrometry or next-generation sequencing. Unexpectedly, mass spectrometry indicated that the 4E-BPs associate with many ribosomal proteins. 80S ribosome and polysome association was independently confirmed and was not dependent upon interaction with eIF4E, as mutated forms of both Caf20p and Eap1p with disrupted eIF4E-binding motifs retain ribosome interaction. Whole-cell proteomics revealed Caf20p mutations cause both up and down-regulation of proteins and that many changes were independent of the 4E-binding motif. Investigations into Caf20p mRNA targets by immunoprecipitation followed by RNA sequencing revealed a strong association between Caf20p and mRNAs involved in transcription and cell cycle processes, consistent with observed cell cycle phenotypes of mutant strains. A core set of over 500 Caf20p-interacting mRNAs comprised of both eIF4E-dependent (75%) and eIF4E-independent targets (25%), which differ in sequence attributes. eIF4E-independent mRNAs share a 3' UTR motif. Caf20p binds all tested motif-containing 3' UTRs. Caf20p and the 3'UTR combine to influence ERS1 mRNA polysome association consistent with Caf20p contributing to translational control. Finally ERS1 3'UTR confers Caf20-dependent repression of expression to a heterologous reporter gene. Taken together, these data reveal conserved features of eIF4E-dependent Caf20p mRNA targets and uncover a novel eIF4E-independent mode of Caf20p binding to mRNAs that extends the regulatory role of Caf20p in the mRNA-specific repression of protein synthesis beyond its interaction with eIF4E.
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36
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Abstract
Dysregulation of mRNA translation is a frequent feature of neoplasia. Many oncogenes and tumour suppressors affect the translation machinery, making aberrant translation a widespread characteristic of tumour cells, independent of the genetic make-up of the cancer. Therefore, therapeutic agents that target components of the protein synthesis apparatus hold promise as novel anticancer drugs that can overcome intra-tumour heterogeneity. In this Review, we discuss the role of translation in cancer, with a particular focus on the eIF4F (eukaryotic translation initiation factor 4F) complex, and provide an overview of recent efforts aiming to 'translate' these results to the clinic.
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Jones GD, Williams EP, Place AR, Jagus R, Bachvaroff TR. The alveolate translation initiation factor 4E family reveals a custom toolkit for translational control in core dinoflagellates. BMC Evol Biol 2015; 15:14. [PMID: 25886308 PMCID: PMC4330643 DOI: 10.1186/s12862-015-0301-9] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2014] [Accepted: 01/29/2015] [Indexed: 01/27/2023] Open
Abstract
Background Dinoflagellates are eukaryotes with unusual cell biology and appear to rely on translational rather than transcriptional control of gene expression. The eukaryotic translation initiation factor 4E (eIF4E) plays an important role in regulating gene expression because eIF4E binding to the mRNA cap is a control point for translation. eIF4E is part of an extended, eukaryote-specific family with different members having specific functions, based on studies of model organisms. Dinoflagellate eIF4E diversity could provide a mechanism for dinoflagellates to regulate gene expression in a post-transcriptional manner. Accordingly, eIF4E family members from eleven core dinoflagellate transcriptomes were surveyed to determine the diversity and phylogeny of the eIF4E family in dinoflagellates and related lineages including apicomplexans, ciliates and heterokonts. Results The survey uncovered eight to fifteen (on average eleven) different eIF4E family members in each core dinoflagellate species. The eIF4E family members from heterokonts and dinoflagellates segregated into three clades, suggesting at least three eIF4E cognates were present in their common ancestor. However, these three clades are distinct from the three previously described eIF4E classes, reflecting diverse approaches to a central eukaryotic function. Heterokonts contain four clades, ciliates two and apicomplexans only a single recognizable eIF4E clade. In the core dinoflagellates, the three clades were further divided into nine sub-clades based on the phylogenetic analysis and species representation. Six of the sub-clades included at least one member from all eleven core dinoflagellate species, suggesting duplication in their shared ancestor. Conservation within sub-clades varied, suggesting different selection pressures. Conclusions Phylogenetic analysis of eIF4E in core dinoflagellates revealed complex layering of duplication and conservation when compared to other eukaryotes. Our results suggest that the diverse eIF4E family in core dinoflagellates may provide a toolkit to enable selective translation as a strategy for controlling gene expression in these enigmatic eukaryotes. Electronic supplementary material The online version of this article (doi:10.1186/s12862-015-0301-9) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Grant D Jones
- Institute of Marine and Environmental Technology, University of Maryland Center for Environmental Science, Baltimore, USA. .,University of Maryland, Baltimore, Graduate School, Baltimore, USA.
| | - Ernest P Williams
- Institute of Marine and Environmental Technology, University of Maryland Center for Environmental Science, Baltimore, USA.
| | - Allen R Place
- Institute of Marine and Environmental Technology, University of Maryland Center for Environmental Science, Baltimore, USA.
| | - Rosemary Jagus
- Institute of Marine and Environmental Technology, University of Maryland Center for Environmental Science, Baltimore, USA.
| | - Tsvetan R Bachvaroff
- Institute of Marine and Environmental Technology, University of Maryland Center for Environmental Science, Baltimore, USA.
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38
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An eIF4E-interacting peptide induces cell death in cancer cell lines. Cell Death Dis 2014; 5:e1500. [PMID: 25356869 PMCID: PMC4237268 DOI: 10.1038/cddis.2014.457] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2014] [Revised: 09/09/2014] [Accepted: 09/16/2014] [Indexed: 12/22/2022]
Abstract
The eukaryotic initiation factor eIF4E is essential for cap-dependent initiation of translation in eukaryotes. Abnormal regulation of eIF4E has been implicated in oncogenic transformation. We developed an eIF4E-binding peptide derived from Angel1, a partner of eIF4E that we recently identified. We show here that this peptide fused to a penetratin motif causes drastic and rapid cell death in several epithelial cancer cell lines. This necrotic cell death was characterized by a drop in ATP levels with F-actin network injury being a key step in extensive plasma membrane blebbing and membrane permeabilization. This synthetic eIF4E-binding peptide provides a candidate pharmacophore for a promising new cancer therapy strategy.
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39
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Igreja C, Peter D, Weiler C, Izaurralde E. 4E-BPs require non-canonical 4E-binding motifs and a lateral surface of eIF4E to repress translation. Nat Commun 2014; 5:4790. [PMID: 25179781 PMCID: PMC4164784 DOI: 10.1038/ncomms5790] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2014] [Accepted: 07/24/2014] [Indexed: 12/01/2022] Open
Abstract
eIF4E-binding proteins (4E-BPs) are a widespread class of translational regulators that share a canonical (C) eIF4E-binding motif (4E-BM) with eIF4G. Consequently, 4E-BPs compete with eIF4G for binding to the dorsal surface on eIF4E to inhibit translation initiation. Some 4E-BPs contain non-canonical 4E-BMs (NC 4E-BMs), but the contribution of these motifs to the repressive mechanism—and whether these motifs are present in all 4E-BPs—remains unknown. Here, we show that the three annotated Drosophila melanogaster 4E-BPs contain NC 4E-BMs. These motifs bind to a lateral surface on eIF4E that is not used by eIF4G. This distinct molecular recognition mode is exploited by 4E-BPs to dock onto eIF4E–eIF4G complexes and effectively displace eIF4G from the dorsal surface of eIF4E. Our data reveal a hitherto unrecognized role for the NC4E-BMs and the lateral surface of eIF4E in 4E-BP-mediated translational repression, and suggest that bipartite 4E-BP mimics might represent efficient therapeutic tools to dampen translation during oncogenic transformation. eIF4E-binding proteins (4E-BPs) are a conserved class of translational repressors that play essential roles in the regulation of protein expression. Here, Igreja et al. indentify non-canonical interactions between 4E-BPs and eIF4E that are required to effectively displace eIF4G and inhibit translation.
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Affiliation(s)
- Cátia Igreja
- Department of Biochemistry, Max Planck Institute for Developmental Biology, Spemannstrasse 35, 72076 Tübingen, Germany
| | - Daniel Peter
- Department of Biochemistry, Max Planck Institute for Developmental Biology, Spemannstrasse 35, 72076 Tübingen, Germany
| | - Catrin Weiler
- Department of Biochemistry, Max Planck Institute for Developmental Biology, Spemannstrasse 35, 72076 Tübingen, Germany
| | - Elisa Izaurralde
- Department of Biochemistry, Max Planck Institute for Developmental Biology, Spemannstrasse 35, 72076 Tübingen, Germany
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Senissar M, Le Saux A, Belgareh-Touzé N, Adam C, Banroques J, Tanner NK. The DEAD-box helicase Ded1 from yeast is an mRNP cap-associated protein that shuttles between the cytoplasm and nucleus. Nucleic Acids Res 2014; 42:10005-22. [PMID: 25013175 PMCID: PMC4150762 DOI: 10.1093/nar/gku584] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2013] [Revised: 06/02/2014] [Accepted: 06/17/2014] [Indexed: 01/13/2023] Open
Abstract
The DEAD-box helicase Ded1 is an essential yeast protein that is closely related to mammalian DDX3 and to other DEAD-box proteins involved in developmental and cell cycle regulation. Ded1 is considered to be a translation-initiation factor that helps the 40S ribosome scan the mRNA from the 5' 7-methylguanosine cap to the AUG start codon. We used IgG pull-down experiments, mass spectrometry analyses, genetic experiments, sucrose gradients, in situ localizations and enzymatic assays to show that Ded1 is a cap-associated protein that actively shuttles between the cytoplasm and the nucleus. NanoLC-MS/MS analyses of purified complexes show that Ded1 is present in both nuclear and cytoplasmic mRNPs. Ded1 physically interacts with purified components of the nuclear CBC and the cytoplasmic eIF4F complexes, and its enzymatic activity is stimulated by these factors. In addition, we show that Ded1 is genetically linked to these factors. Ded1 comigrates with these proteins on sucrose gradients, but treatment with rapamycin does not appreciably alter the distribution of Ded1; thus, most of the Ded1 is in stable mRNP complexes. We conclude that Ded1 is an mRNP cofactor of the cap complex that may function to remodel the different mRNPs and thereby regulate the expression of the mRNAs.
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Affiliation(s)
- Meriem Senissar
- Expression Génétique Microbienne, CNRS FRE3630 (UPR9073), in association with Université Paris Diderot, Sorbonne Paris Cité, Paris 75005, France Université Paris-Sud, Ecole Doctorale 426 GGC, Orsay, France
| | - Agnès Le Saux
- Expression Génétique Microbienne, CNRS FRE3630 (UPR9073), in association with Université Paris Diderot, Sorbonne Paris Cité, Paris 75005, France
| | - Naïma Belgareh-Touzé
- Laboratoire de Biologie Moléculaire et Cellulaire des Eucaryotes, CNRS UMR8226 (FRE3354), UPMC, Paris 75005, France
| | - Céline Adam
- Expression Génétique Microbienne, CNRS FRE3630 (UPR9073), in association with Université Paris Diderot, Sorbonne Paris Cité, Paris 75005, France
| | - Josette Banroques
- Expression Génétique Microbienne, CNRS FRE3630 (UPR9073), in association with Université Paris Diderot, Sorbonne Paris Cité, Paris 75005, France
| | - N Kyle Tanner
- Expression Génétique Microbienne, CNRS FRE3630 (UPR9073), in association with Université Paris Diderot, Sorbonne Paris Cité, Paris 75005, France
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Ostareck DH, Naarmann-de Vries IS, Ostareck-Lederer A. DDX6 and its orthologs as modulators of cellular and viral RNA expression. WILEY INTERDISCIPLINARY REVIEWS-RNA 2014; 5:659-78. [PMID: 24788243 DOI: 10.1002/wrna.1237] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/04/2013] [Revised: 03/19/2014] [Accepted: 03/21/2014] [Indexed: 12/21/2022]
Abstract
DDX6 (Rck/p54), a member of the DEAD-box family of helicases, is highly conserved from unicellular eukaryotes to vertebrates. Functions of DDX6 and its orthologs in dynamic ribonucleoproteins contribute to global and transcript-specific messenger RNA (mRNA) storage, translational repression, and decay during development and differentiation in the germline and somatic cells. Its role in pathways that promote mRNA-specific alternative translation initiation has been shown to be linked to cellular homeostasis, deregulated tissue development, and the control of gene expression in RNA viruses. Recently, DDX6 was found to participate in mRNA regulation mediated by miRNA-mediated silencing. DDX6 and its orthologs have versatile functions in mRNA metabolism, which characterize them as important post-transcriptional regulators of gene expression.
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Affiliation(s)
- Dirk H Ostareck
- Experimental Research Unit, Department of Intensive Care and Intermediate Care, University Hospital, RWTH Aachen University, Aachen, Germany
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eIF4E is an important determinant of adhesion and pseudohyphal growth of the yeast S. cerevisiae. PLoS One 2012; 7:e50773. [PMID: 23226381 PMCID: PMC3511313 DOI: 10.1371/journal.pone.0050773] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2012] [Accepted: 10/24/2012] [Indexed: 01/09/2023] Open
Abstract
eIF4E, the cytoplasmatic cap-binding protein, is required for efficient cap-dependent translation. We have studied the influence of mutations that alter the activity and/or expression level of eIF4E on haploid and diploid cells in the yeast S. cerevisiae. Temperature-sensitive eIF4E mutants with reduced levels of expression and reduced cap-binding affinity clearly show a loss in haploid adhesion and diploid pseudohyphenation upon starvation for nitrogen. Some of these mutations affect the interaction of the cap-structure of mRNAs with the cap-binding groove of eIF4E. The observed reduction in adhesive and pseudohyphenating properties is less evident for an eIF4E mutant that shows reduced interaction with p20 (an eIF4E-binding protein) or for a p20-knockout mutant. Loss of adhesive and pseudohyphenating properties was not only observed for eIF4E mutants but also for knockout mutants of components of eIF4F such as eIF4B and eIF4G1. We conclude from these experiments that mutations that affect components of the eIF4F-complex loose properties such as adhesion and pseudohyphal differentiation, most likely due to less effective translation of required mRNAs for such processes.
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Rendl LM, Bieman MA, Vari HK, Smibert CA. The eIF4E-binding protein Eap1p functions in Vts1p-mediated transcript decay. PLoS One 2012; 7:e47121. [PMID: 23071728 PMCID: PMC3468468 DOI: 10.1371/journal.pone.0047121] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2012] [Accepted: 09/10/2012] [Indexed: 01/06/2023] Open
Abstract
Sequence-specific RNA binding proteins can induce the degradation of mRNAs through their ability to recruit proteins that trigger transcript destabilization. For example, Vts1p, the S. cerevisiae member of the Smaug family of RNA binding proteins, is thought to induce transcript decay by recruiting the Ccr4p-Pop2p-Not deadenylase complex to target mRNAs. The resulting deadenylation triggers transcript decapping followed by 5′-to-3′ exonucleolytic decay. Here we show that the eIF4E-binding protein, Eap1p, is required for efficient degradation of Vts1p target transcripts and that this role involves the ability of Eap1p to interact with eIF4E. Eap1p does not stimulate deadenylation of Vts1p target transcripts but is instead involved in decapping. Eap1p interacts with Vts1p and mediates an indirect interaction between Vts1p and eIF4E. Taken together these data suggest a model whereby the interaction of Vts1p with Eap1p at target mRNAs stimulates decapping.
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Affiliation(s)
- Laura M. Rendl
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
| | - Melissa A. Bieman
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
| | - Heli K. Vari
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
| | - Craig A. Smibert
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
- * E-mail:
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A eukaryotic translation initiation factor 4E-binding protein promotes mRNA decapping and is required for PUF repression. Mol Cell Biol 2012; 32:4181-94. [PMID: 22890846 DOI: 10.1128/mcb.00483-12] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
PUF proteins are eukaryotic RNA-binding proteins that repress specific mRNAs. The mechanisms and corepressors involved in PUF repression remain to be fully identified. Here, we investigated the mode of repression by Saccharomyces cerevisiae Puf5p and Puf4p and found that Puf5p specifically requires Eap1p to repress mRNAs, whereas Puf4p does not. Surprisingly, we observed that Eap1p, which is a member of the eukaryotic translation initiation factor 4E (eIF4E)-binding protein (4E-BP) class of translational inhibitors, does not inhibit the efficient polyribosome association of a Puf5p target mRNA. Rather, we found that Eap1p accelerates mRNA degradation by promoting decapping, and the ability of Eap1p to interact with eIF4E facilitates this activity. Deletion of EAP1 dramatically reduces decapping, resulting in accumulation of deadenylated, capped mRNA. In support of this phenotype, Eap1p associates both with Puf5p and the Dhh1p decapping factor. Furthermore, recruitment of Eap1p to downregulated mRNA is mediated by Puf5p. On the basis of these results, we propose that Puf5p promotes decapping by recruiting Eap1p and associated decapping factors to mRNAs. The implication of these findings is that a 4E-BP can repress protein expression by promoting specific mRNA degradation steps in addition to or in lieu of inhibiting translation initiation.
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Regulation of Translation Initiation under Abiotic Stress Conditions in Plants: Is It a Conserved or Not so Conserved Process among Eukaryotes? Comp Funct Genomics 2012; 2012:406357. [PMID: 22593661 PMCID: PMC3347718 DOI: 10.1155/2012/406357] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2011] [Accepted: 02/08/2012] [Indexed: 11/30/2022] Open
Abstract
For years, the study of gene expression regulation of plants in response to stress conditions has been focused mainly on the analysis of transcriptional changes. However, the knowledge on translational regulation is very scarce in these organisms, despite in plants, as in the rest of the eukaryotes, translational regulation has been proven to play a pivotal role in the response to different stresses. Regulation of protein synthesis under abiotic stress was thought to be a conserved process, since, in general, both the translation factors and the translation process are basically similar in eukaryotes. However, this conservation is not so clear in plants as the knowledge of the mechanisms that control translation is very poor. Indeed, some of the basic regulators of translation initiation, well characterised in other systems, are still to be identified in plants. In this paper we will focus on both the regulation of different initiation factors and the mechanisms that cellular mRNAs use to bypass the translational repression established under abiotic stresses. For this purpose, we will review the knowledge from different eukaryotes but paying special attention to the information that has been recently published in plants.
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PAS kinase: integrating nutrient sensing with nutrient partitioning. Semin Cell Dev Biol 2012; 23:626-30. [PMID: 22245833 DOI: 10.1016/j.semcdb.2011.12.007] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2011] [Accepted: 12/23/2011] [Indexed: 11/21/2022]
Abstract
Recent data suggests that PAS kinase acts as a signal integrator to adjust metabolic behavior in response to nutrient conditions. Specifically, PAS kinase controls the partitioning of nutrient resources between the myriad of possible fates. In this capacity, PAS kinase elicits a pro-growth program, which includes both signaling and metabolic control, both in yeast and in mammals. We propose that, like other kinases possessing these properties-AMPK and TOR, PAS kinase might be target for therapy of diabetes, obesity and cancer.
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A conserved motif within the flexible C-terminus of the translational regulator 4E-BP is required for tight binding to the mRNA cap-binding protein eIF4E. Biochem J 2011; 441:237-45. [DOI: 10.1042/bj20101481] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Although the central α-helical Y(X)4LΦ motif (X, variable amino acid; Φ, hydrophobic amino acid) of the translational regulator 4E-BP [eIF (eukaryotic initiation factor) 4E-binding protein] is the core binding region for the mRNA cap-binding protein eIF4E, the functions of its N- and C-terminal flexible regions for interaction with eIF4E remain to be elucidated. To identify the role for the C-terminal region in such an interaction, the binding features of full-length and sequential C-terminal deletion mutants of 4E-BPn (n=1–3) subtypes were investigated by SPR (surface plasmon resonance) analysis and ITC (isothermal titration calorimetry). Consequently, the conserved PGVTS/T motif within the C-terminal region was shown to act as the second binding region and to play an important role in the tight binding to eIF4E. The 4E-BP subtypes increased the association constant with eIF4E by approximately 1000-fold in the presence of this conserved region compared with that in the absence of this region. The sequential deletion of this conserved region in 4E-BP1 showed that deletion of Val81 leads to a considerable decrease in the binding ability of 4E-BP. Molecular dynamics simulation suggested that the conserved PGVTS/T region functions as a kind of paste, adhering the root of both the eIF4E N-terminal and 4E-BP C-terminal flexible regions through a hydrophobic interaction, where valine is located at the crossing position of both flexible regions. It is concluded that the conserved PGVTS/T motif within the flexible C-terminus of 4E-BP plays an auxiliary, but indispensable, role in strengthening the binding of eIF4E to the core Y(X)4LΦ motif.
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Igreja C, Izaurralde E. CUP promotes deadenylation and inhibits decapping of mRNA targets. Genes Dev 2011; 25:1955-67. [PMID: 21937713 DOI: 10.1101/gad.17136311] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
CUP is an eIF4E-binding protein (4E-BP) that represses the expression of specific maternal mRNAs prior to their posterior localization. Here, we show that CUP employs multiple mechanisms to repress the expression of target mRNAs. In addition to inducing translational repression, CUP maintains mRNA targets in a repressed state by promoting their deadenylation and protects deadenylated mRNAs from further degradation. Translational repression and deadenylation are independent of eIF4E binding and require both the middle and C-terminal regions of CUP, which collectively we termed the effector domain. This domain associates with the deadenylase complex CAF1-CCR4-NOT and decapping activators. Accordingly, in isolation, the effector domain is a potent trigger of mRNA degradation and promotes deadenylation, decapping and decay. However, in the context of the full-length CUP protein, the decapping and decay mediated by the effector domain are inhibited, and target mRNAs are maintained in a deadenylated, repressed form. Remarkably, an N-terminal regulatory domain containing a noncanonical eIF4E-binding motif is required to protect CUP-associated mRNAs from decapping and further degradation, suggesting that this domain counteracts the activity of the effector domain. Our findings indicate that the mode of action of CUP is more complex than previously thought and provide mechanistic insight into the regulation of mRNA expression by 4E-BPs.
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Affiliation(s)
- Catia Igreja
- Max Planck Institute for Developmental Biology, Tübingen, Germany
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49
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Umenaga Y, Paku KS, In Y, Ishida T, Tomoo K. Identification and function of the second eIF4E-binding region in N-terminal domain of eIF4G: Comparison with eIF4E-binding protein. Biochem Biophys Res Commun 2011; 414:462-7. [DOI: 10.1016/j.bbrc.2011.09.084] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2011] [Accepted: 09/14/2011] [Indexed: 10/17/2022]
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Abstract
The AKT signalling pathway is a major regulator of protein synthesis that impinges on multiple cellular processes frequently altered in cancer, such as proliferation, cell growth, survival, and angiogenesis. AKT controls protein synthesis by regulating the multistep process of mRNA translation at every stage from ribosome biogenesis to translation initiation and elongation. Recent studies have highlighted the ability of oncogenic AKT to drive cellular transformation by altering gene expression at the translational level. Oncogenic AKT signalling leads to both global changes in protein synthesis as well as specific changes in the translation of select mRNAs. New and developing technologies are significantly advancing our ability to identify and functionally group these translationally controlled mRNAs into gene networks based on their modes of regulation. How oncogenic AKT activates ribosome biogenesis, translation initiation, and translational elongation to regulate these translational networks is an ongoing area of research. Currently, the majority of therapeutics targeting translational control are focused on blocking translation initiation through inhibition of eIF4E hyperactivity. However, it will be important to determine whether combined inhibition of ribosome biogenesis, translation initiation, and translation elongation can demonstrate improved therapeutic efficacy in tumours driven by oncogenic AKT.
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Affiliation(s)
- A C Hsieh
- Department of Urology, School of Medicine, Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, Helen Diller Family Cancer Research Building, Room 386, 1450 3rd Street, San Francisco, CA 94158-3110, USA
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