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Dasgupta A, Prensner JR. Upstream open reading frames: new players in the landscape of cancer gene regulation. NAR Cancer 2024; 6:zcae023. [PMID: 38774471 PMCID: PMC11106035 DOI: 10.1093/narcan/zcae023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2023] [Revised: 04/29/2024] [Accepted: 05/07/2024] [Indexed: 05/24/2024] Open
Abstract
The translation of RNA by ribosomes represents a central biological process and one of the most dysregulated processes in cancer. While translation is traditionally thought to occur exclusively in the protein-coding regions of messenger RNAs (mRNAs), recent transcriptome-wide approaches have shown abundant ribosome activity across diverse stretches of RNA transcripts. The most common type of this kind of ribosome activity occurs in gene leader sequences, also known as 5' untranslated regions (UTRs) of the mRNA, that precede the main coding sequence. Translation of these upstream open reading frames (uORFs) is now known to occur in upwards of 25% of all protein-coding genes. With diverse functions from RNA regulation to microprotein generation, uORFs are rapidly igniting a new arena of cancer biology, where they are linked to cancer genetics, cancer signaling, and tumor-immune interactions. This review focuses on the contributions of uORFs and their associated 5'UTR sequences to cancer biology.
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Affiliation(s)
- Anwesha Dasgupta
- Chad Carr Pediatric Brain Tumor Center, University of Michigan Medical School, Ann Arbor, MI 48109, USA
- Department of Pediatrics, Division of Pediatric Hematology/Oncology, University of Michigan Medical School, Ann Arbor, MI 48109, USA
- Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, MI 48109, USA
| | - John R Prensner
- Chad Carr Pediatric Brain Tumor Center, University of Michigan Medical School, Ann Arbor, MI 48109, USA
- Department of Pediatrics, Division of Pediatric Hematology/Oncology, University of Michigan Medical School, Ann Arbor, MI 48109, USA
- Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, MI 48109, USA
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2
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Hernández G, Vazquez-Pianzola P. eIF4E as a molecular wildcard in metazoans RNA metabolism. Biol Rev Camb Philos Soc 2023; 98:2284-2306. [PMID: 37553111 DOI: 10.1111/brv.13005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2023] [Revised: 07/01/2023] [Accepted: 07/25/2023] [Indexed: 08/10/2023]
Abstract
The evolutionary origin of eukaryotes spurred the transition from prokaryotic-like translation to a more sophisticated, eukaryotic translation. During this process, successive gene duplication of a single, primordial eIF4E gene encoding the mRNA cap-binding protein eukaryotic translation initiation factor 4E (eIF4E) gave rise to a plethora of paralog genes across eukaryotes that underwent further functional diversification in RNA metabolism. The ability to take different roles is due to eIF4E promiscuity in binding many partner proteins, rendering eIF4E a highly versatile and multifunctional player that functions as a molecular wildcard. Thus, in metazoans, eIF4E paralogs are involved in various processes, including messenger RNA (mRNA) processing, export, translation, storage, and decay. Moreover, some paralogs display differential expression in tissues and developmental stages and show variable biochemical properties. In this review, we discuss recent advances shedding light on the functional diversification of eIF4E in metazoans. We emphasise humans and two phylogenetically distant species which have become paradigms for studies on development, namely the fruit fly Drosophila melanogaster and the roundworm Caenorhabditis elegans.
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Affiliation(s)
- Greco Hernández
- mRNA and Cancer Laboratory, Unit of Biomedical Research on Cancer, National Institute of Cancer (Instituto Nacional de Cancerología, INCan), 22 San Fernando Ave., Tlalpan, Mexico City, 14080, Mexico
| | - Paula Vazquez-Pianzola
- Institute of Cell Biology, University of Bern, Baltzerstrasse 4, Berne, 3012, Switzerland
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3
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Zhigailov AV, Nizkorodova AS, Sharipov KO, Polimbetova NS, Iskakov BK. Glyphosate treatment mediates the accumulation of small discrete 5'- and 3'-terminal fragments of 18S rRNA in plant cells. Vavilovskii Zhurnal Genet Selektsii 2023; 27:93-98. [PMID: 37063515 PMCID: PMC10090119 DOI: 10.18699/vjgb-23-13] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2022] [Revised: 08/31/2022] [Accepted: 09/01/2022] [Indexed: 04/18/2023] Open
Abstract
Under many kinds of stress, eukaryotic cells rapidly decrease the overall translation level of the majority of mRNAs. However, some molecular mechanisms of protein synthesis inhibition like phosphorylation of eukaryotic elongation factor 2 (eEF2), which are known to be functional in animals and yeast, are not implemented in plants. We suggest that there is an alternative mechanism for the inhibition of protein synthesis in plant cells and possibly, in other eukaryotes, which is based on the discrete fragmentation of 18S rRNA molecules within small ribosomal subunits. We identified four stress-induced small RNAs, which are 5'- and 3'-terminal fragments of 18S rRNA. In the present work, we studied the induction of 18S rRNA discrete fragmentation and phosphorylation of the α-subunit of eukaryotic initiation factor 2 (eIF2α) in germinated wheat embryos in the presence of glyphosate, which imitates the condition of amino acid starvation. Using northern and western blotting, we have shown that stress-induced 18S rRNA fragments started to accumulate in wheat embryos at glyphosate concentrations that did not evoke eIF2α phosphorylation. It was also found that cleavage of 18S rRNA near the 5'-terminus began much earlier than eIF2α phosphorylation, which became noticeable only at higher concentration (500 μM) of glyphosate. This result suggests that discrete fragmentation of 18S rRNA may constitute a regulatory mechanism of mRNA translation in response to stress and may occur in plant cells in parallel with and independently of eIF2α phosphorylation. The identified small 5'- and 3'-terminal fragments of 18S rRNA that accumulate during various stresses may serve as stress resistance markers in the breeding of economically important plant crops.
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Affiliation(s)
- A V Zhigailov
- M.A. Aitkhozhin Institute of Molecular Biology and Biochemistry of the Ministry of Science and Higher Education of the Republic of Kazakhstan, Almaty, Kazakhstan
| | - A S Nizkorodova
- M.A. Aitkhozhin Institute of Molecular Biology and Biochemistry of the Ministry of Science and Higher Education of the Republic of Kazakhstan, Almaty, Kazakhstan
| | - K O Sharipov
- M.A. Aitkhozhin Institute of Molecular Biology and Biochemistry of the Ministry of Science and Higher Education of the Republic of Kazakhstan, Almaty, Kazakhstan
| | - N S Polimbetova
- M.A. Aitkhozhin Institute of Molecular Biology and Biochemistry of the Ministry of Science and Higher Education of the Republic of Kazakhstan, Almaty, Kazakhstan
| | - B K Iskakov
- M.A. Aitkhozhin Institute of Molecular Biology and Biochemistry of the Ministry of Science and Higher Education of the Republic of Kazakhstan, Almaty, Kazakhstan
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4
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Son S, Park SR. Plant translational reprogramming for stress resilience. FRONTIERS IN PLANT SCIENCE 2023; 14:1151587. [PMID: 36909402 PMCID: PMC9998923 DOI: 10.3389/fpls.2023.1151587] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/26/2023] [Accepted: 02/14/2023] [Indexed: 06/18/2023]
Abstract
Organisms regulate gene expression to produce essential proteins for numerous biological processes, from growth and development to stress responses. Transcription and translation are the major processes of gene expression. Plants evolved various transcription factors and transcriptome reprogramming mechanisms to dramatically modulate transcription in response to environmental cues. However, even the genome-wide modulation of a gene's transcripts will not have a meaningful effect if the transcripts are not properly biosynthesized into proteins. Therefore, protein translation must also be carefully controlled. Biotic and abiotic stresses threaten global crop production, and these stresses are seriously deteriorating due to climate change. Several studies have demonstrated improved plant resistance to various stresses through modulation of protein translation regulation, which requires a deep understanding of translational control in response to environmental stresses. Here, we highlight the translation mechanisms modulated by biotic, hypoxia, heat, and drought stresses, which are becoming more serious due to climate change. This review provides a strategy to improve stress tolerance in crops by modulating translational regulation.
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5
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Sadic M, Schneider WM, Katsara O, Medina GN, Fisher A, Mogulothu A, Yu Y, Gu M, de los Santos T, Schneider RJ, Dittmann M. DDX60 selectively reduces translation off viral type II internal ribosome entry sites. EMBO Rep 2022; 23:e55218. [PMID: 36256515 PMCID: PMC9724679 DOI: 10.15252/embr.202255218] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2022] [Revised: 09/07/2022] [Accepted: 09/15/2022] [Indexed: 11/05/2022] Open
Abstract
Co-opting host cell protein synthesis is a hallmark of many virus infections. In response, certain host defense proteins limit mRNA translation globally, albeit at the cost of the host cell's own protein synthesis. Here, we describe an interferon-stimulated helicase, DDX60, that decreases translation from viral internal ribosome entry sites (IRESs). DDX60 acts selectively on type II IRESs of encephalomyocarditis virus (EMCV) and foot and mouth disease virus (FMDV), but not by other IRES types or by 5' cap. Correspondingly, DDX60 reduces EMCV and FMDV (type II IRES) replication, but not that of poliovirus or bovine enterovirus 1 (BEV-1; type I IRES). Furthermore, replacing the IRES of poliovirus with a type II IRES is sufficient for DDX60 to inhibit viral replication. Finally, DDX60 selectively modulates the amount of translating ribosomes on viral and in vitro transcribed type II IRES mRNAs, but not 5' capped mRNA. Our study identifies a novel facet in the repertoire of interferon-stimulated effector genes, the selective downregulation of translation from viral type II IRES elements.
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Affiliation(s)
| | | | | | - Gisselle N Medina
- Plum Island Animal Disease Center, ARSUSDAGreenportNYUSA,National Bio and Agro‐Defense Facility (NBAF), ARSUSDAManhattanKSUSA
| | | | - Aishwarya Mogulothu
- Plum Island Animal Disease Center, ARSUSDAGreenportNYUSA,Department of Pathobiology and Veterinary ScienceUniversity of ConnecticutStorrsCTUSA
| | - Yingpu Yu
- The Rockefeller UniversityNew YorkNYUSA
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6
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Tomar S, Subba A, Bala M, Singh AK, Pareek A, Singla-Pareek SL. Genetic Conservation of CBS Domain Containing Protein Family in Oryza Species and Their Association with Abiotic Stress Responses. Int J Mol Sci 2022; 23:ijms23031687. [PMID: 35163610 PMCID: PMC8836131 DOI: 10.3390/ijms23031687] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2021] [Revised: 01/01/2022] [Accepted: 01/04/2022] [Indexed: 01/27/2023] Open
Abstract
Crop Wild Relatives (CWRs) form a comprehensive gene pool that can answer the queries related to plant domestication, speciation, and ecological adaptation. The genus ‘Oryza’ comprises about 27 species, of which two are cultivated, while the remaining are wild. Here, we have attempted to understand the conservation and diversification of the genes encoding Cystathionine β-synthase (CBS) domain-containing proteins (CDCPs) in domesticated and CWRs of rice. Few members of CDCPs were previously identified to be stress-responsive and associated with multiple stress tolerance in rice. Through genome-wide analysis of eleven rice genomes, we identified a total of 36 genes encoding CDCPs in O. longistaminata, 38 in O. glaberrima, 39 each in O. rufipogon, O. glumaepatula, O. brachyantha, O. punctata, and O. sativa subsp. japonica, 40 each in O. barthii and O. meridionalis, 41 in O. nivara, and 42 in O. sativa subsp. indica. Gene duplication analysis as well as non-synonymous and synonymous substitutions in the duplicated gene pairs indicated that this family is shaped majorly by the negative or purifying selection pressure through the long-term evolution process. We identified the presence of two additional hetero-domains, namely TerCH and CoatomerE (specifically in O. sativa subsp. indica), which were not reported previously in plant CDCPs. The in silico expression analysis revealed some of the members to be responsive to various abiotic stresses. Furthermore, the qRT-PCR based analysis identified some members to be highly inducive specifically in salt-tolerant genotype in response to salinity. The cis-regulatory element analysis predicted the presence of numerous stress as well as a few phytohormone-responsive elements in their promoter region. The data presented in this study would be helpful in the characterization of these CDCPs from rice, particularly in relation to abiotic stress tolerance.
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Affiliation(s)
- Surabhi Tomar
- Plant Stress Biology Group, International Centre for Genetic Engineering and Biotechnology, New Delhi 110067, India; (S.T.); (A.S.)
| | - Ashish Subba
- Plant Stress Biology Group, International Centre for Genetic Engineering and Biotechnology, New Delhi 110067, India; (S.T.); (A.S.)
| | - Meenu Bala
- School of Genetic Engineering, ICAR-Indian Institute of Agricultural Biotechnology, Ranchi 834010, India; (M.B.); (A.K.S.)
| | - Anil Kumar Singh
- School of Genetic Engineering, ICAR-Indian Institute of Agricultural Biotechnology, Ranchi 834010, India; (M.B.); (A.K.S.)
- ICAR-National Institute for Plant Biotechnology, LBS Centre, Pusa Campus, New Delhi 110012, India
| | - Ashwani Pareek
- Stress Physiology and Molecular Biology Laboratory, School of Life Sciences, Jawaharlal Nehru University, New Delhi 110067, India;
- National Agri-Food Biotechnology Institute, Mohali 140306, India
| | - Sneh Lata Singla-Pareek
- Plant Stress Biology Group, International Centre for Genetic Engineering and Biotechnology, New Delhi 110067, India; (S.T.); (A.S.)
- Correspondence:
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7
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Francis N, Laishram RS. Transgenesis of mammalian PABP reveals mRNA polyadenylation as a general stress response mechanism in bacteria. iScience 2021; 24:103119. [PMID: 34646982 PMCID: PMC8496165 DOI: 10.1016/j.isci.2021.103119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2021] [Revised: 04/23/2021] [Accepted: 09/09/2021] [Indexed: 12/01/2022] Open
Abstract
In eukaryotes, mRNA 3′-polyadenylation triggers poly(A) binding protein (PABP) recruitment and stabilization. In a stark contrast, polyadenylation marks mRNAs for degradation in bacteria. To study this difference, we trans-express the mammalian nuclear PABPN1 chromosomally and extra-chromosomally in Escherichia coli. Expression of PABPN1 but not the mutant PABPN1 stabilizes polyadenylated mRNAs and improves their half-lives. In the presence of PABPN1, 3′-exonuclease PNPase is not detected on PA-tailed mRNAs compromising the degradation. We show that PABPN1 trans-expression phenocopies pcnB (that encodes poly(A) polymerase, PAPI) mutation and regulates plasmid copy number. Genome-wide RNA-seq analysis shows a general up-regulation of polyadenylated mRNAs on PABPN1 expression, the largest subset of which are those involved in general stress response. However, major global stress regulators are unaffected on PABPN1 expression. Concomitantly, PABPN1 expression or pcnB mutation imparts cellular tolerance to multiple stresses. This study establishes mRNA 3′-polyadenylation as a general stress response mechanism in E. coli. Trans expression of mammalian PABPN1 stabilizes polyadenyated mRNAs in E. coli PABPN1 expression phenocopies pcnB mutation and regulates plasmid copy number 3′-polyadenylation acts as a general stress response mechanism in bacteria This study indicates an evolutionary significance of PABP in mRNA metabolism
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Affiliation(s)
- Nimmy Francis
- Cardiovascular and Diabetes Biology Group, Rajiv Gandhi Centre for Biotechnology, Thycaud Post, Poojappura, Trivandrum 695014, India.,Manipal Academy of Higher Education, Manipal 576104, India
| | - Rakesh S Laishram
- Cardiovascular and Diabetes Biology Group, Rajiv Gandhi Centre for Biotechnology, Thycaud Post, Poojappura, Trivandrum 695014, India
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8
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Reprogramming translation for gene therapy. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2021; 182:439-476. [PMID: 34175050 DOI: 10.1016/bs.pmbts.2021.01.028] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Translational control plays a fundamental role in the regulation of gene expression in eukaryotes. Modulating translational efficiency allows the cell to fine-tune the expression of genes, spatially control protein localization, and trigger fast responses to environmental stresses. Translational regulation involves mechanisms acting on multiple steps of the protein synthesis pathway: initiation, elongation, and termination. Many cis-acting elements present in the 5' UTR of transcripts can influence translation at the initiation step. Among them, the Kozak sequence impacts translational efficiency by regulating the recognition of the start codon; upstream open reading frames (uORFs) are associated with inhibition of translation of the downstream protein; internal ribosomal entry sites (IRESs) can promote cap-independent translation. CRISPR-Cas technology is a revolutionary gene-editing tool that has also been applied to the regulation of gene expression. In this chapter, we focus on the genome editing approaches developed to modulate the translational efficiency with the aim to find novel therapeutic approaches, in particular acting on the cis-elements, that regulate the initiation of protein synthesis.
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Hernández G, García A, Sonenberg N, Lasko P. Unorthodox Mechanisms to Initiate Translation Open Novel Paths for Gene Expression. J Mol Biol 2020; 432:166702. [PMID: 33166539 DOI: 10.1016/j.jmb.2020.10.035] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2020] [Revised: 10/14/2020] [Accepted: 10/19/2020] [Indexed: 12/24/2022]
Abstract
Translation in eukaryotes is dependent on the activity of translation initiation factor (eIF) 4G family of proteins, a scaffold protein that, during the initiation step, coordinates the activity of other eIFs to recruit the 40S ribosomal subunit to the mRNA. Three decades of research on protein synthesis and its regulation has provided a wealth of evidence supporting the crucial role of cap-dependent translation initiation, which involves eIF4G. However, the recent discovery of a surprising variety of alternative mechanisms to initiate translation in the absence of eIF4G has stirred the orthodox view of how protein synthesis is performed. These mechanisms involve novel interactions among known eIFs, or between known eIFs and other proteins not previously linked to translation. Thus, a new picture is emerging in which the unorthodox translation initiation complexes contribute to the diversity of mechanisms that regulate gene expression in eukaryotes.
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Affiliation(s)
- Greco Hernández
- Translation and Cancer Laboratory, Unit of Biomedical Research on Cancer, National Institute of Cancer (Instituto Nacional de Cancerología, INCan), 22 San Fernando Ave., Tlalpan, 14080 Mexico City, Mexico.
| | - Alejandra García
- Translation and Cancer Laboratory, Unit of Biomedical Research on Cancer, National Institute of Cancer (Instituto Nacional de Cancerología, INCan), 22 San Fernando Ave., Tlalpan, 14080 Mexico City, Mexico
| | - Nahum Sonenberg
- Department of Biochemistry and Goodman Cancer Centre, McGill University, Montreal, Quebec H3A 1A3, Canada
| | - Paul Lasko
- Department of Biology, McGill University, Montreal, Québec, Canada; Department of Human Genetics, Radboud University Medical Center, Nijmegen, Netherlands
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10
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CMTR1-Catalyzed 2'-O-Ribose Methylation Controls Neuronal Development by Regulating Camk2α Expression Independent of RIG-I Signaling. Cell Rep 2020; 33:108269. [PMID: 33086056 PMCID: PMC7574844 DOI: 10.1016/j.celrep.2020.108269] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2020] [Revised: 08/10/2020] [Accepted: 09/23/2020] [Indexed: 12/14/2022] Open
Abstract
Eukaryotic mRNAs are 5′ end capped with a 7-methylguanosine, which is important for processing and translation of mRNAs. Cap methyltransferase 1 (CMTR1) catalyzes 2′-O-ribose methylation of the first transcribed nucleotide (N1 2′-O-Me) to mask mRNAs from innate immune surveillance by retinoic-acid-inducible gene-I (RIG-I). Nevertheless, whether this modification regulates gene expression for neuronal functions remains unexplored. Here, we find that knockdown of CMTR1 impairs dendrite development independent of secretory cytokines and RIG-I signaling. Using transcriptomic analyses, we identify altered gene expression related to dendrite morphogenesis instead of RIG-I-activated interferon signaling, such as decreased calcium/calmodulin-dependent protein kinase 2α (Camk2α). In line with these molecular changes, dendritic complexity in CMTR1-insufficient neurons is rescued by ectopic expression of CaMK2α but not by inactivation of RIG-I signaling. We further generate brain-specific CMTR1-knockout mice to validate these findings in vivo. Our study reveals the indispensable role of CMTR1-catalyzed N1 2′-O-Me in gene regulation for brain development. Every mRNA molecule in neurons is N1 2′-O methylated by CMTR1 CMTR1 is essential for neuromorphogenesis and brain development CMTR1 deficiency does not activate RIG-I and interferon signaling CMTR1 promotes Camk2α expression to support dendrite development
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Zhigailov AV, Alexandrova AM, Nizkorodova AS, Stanbekova GE, Kryldakov RV, Karpova OV, Polimbetova NS, Halford NG, Iskakov BK. Evidence That Phosphorylation of the α-Subunit of eIF2 Does Not Essentially Inhibit mRNA Translation in Wheat Germ Cell-Free System. FRONTIERS IN PLANT SCIENCE 2020; 11:936. [PMID: 32655610 PMCID: PMC7324750 DOI: 10.3389/fpls.2020.00936] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/07/2020] [Accepted: 06/09/2020] [Indexed: 05/30/2023]
Abstract
A mechanism based on reversible phosphorylation of the α-subunit of eukaryotic initiation factor 2 (eIF2α) has been confirmed as an important regulatory pathway for the inhibition of protein synthesis in mammalian and yeast cells, while plants constitute the significant exception. We studied the induction of TaeIF2α phosphorylation in germinated wheat (Triticum aestivum) embryos subjected to different adverse conditions. Data confirmed that formation of TaeIF2(αP) was not a general response, as no phosphorylation was observed under salt, oxidative, or heat stress. Nevertheless, treatment by salicylic acid, UV-light, cold shock and histidinol did induce phosphorylation of TaeIF2α of wheat as has been established previously for AteIF2α in Arabidopsis (Arabidopsis thaliana). The influence of TaeIF2α phosphorylation on translation of reporter mRNA with different 5'-untranslated regions (5'UTRs) was studied in wheat germ cell-free system (WG-CFS), in which TaeIF2α was first phosphorylated either by heterologous recombinant human protein kinase, HsPKR (activated by double-stranded (ds)RNA), or by endogenous protein kinase TaGCN2 (activated by histidinol). Pretreatment of WG-CFS with HsPKR in the presence of dsRNA or with histidinol resulted in intense phosphorylation of TaeIF2α; however, the translation levels of all tested mRNAs decreased by only 10-15% and remained relatively high. In addition, factor OceIF2 from rabbit (Oryctolagus cuniculus) bound GDP much more strongly than the homologous factor TaeIF2 from wheat germ. Furthermore, factor OceIF2B was able to stimulate guanine nucleotide exchange (GDP→GTP) on OceIF2 but had no effect on a similar exchange on TaeIF2. These results suggest that the mechanism of stress response via eIF2α phosphorylation is not identical in all eukaryotes, and further research is required to find and study in detail new plant-specific mechanisms that may inhibit overall protein synthesis in plants under stress.
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Affiliation(s)
- Andrey V. Zhigailov
- M.A. Aitkhozhin Institute of Molecular Biology and Biochemistry, Science Committee, Ministry of Education and Science, Almaty, Kazakhstan
| | - Alena M. Alexandrova
- M.A. Aitkhozhin Institute of Molecular Biology and Biochemistry, Science Committee, Ministry of Education and Science, Almaty, Kazakhstan
| | - Anna S. Nizkorodova
- M.A. Aitkhozhin Institute of Molecular Biology and Biochemistry, Science Committee, Ministry of Education and Science, Almaty, Kazakhstan
| | - Gulshan E. Stanbekova
- M.A. Aitkhozhin Institute of Molecular Biology and Biochemistry, Science Committee, Ministry of Education and Science, Almaty, Kazakhstan
| | - Ruslan V. Kryldakov
- M.A. Aitkhozhin Institute of Molecular Biology and Biochemistry, Science Committee, Ministry of Education and Science, Almaty, Kazakhstan
- Institute of Plant Biology and Biotechnology, Science Committee, Ministry of Education and Science, Almaty, Kazakhstan
| | - Oxana V. Karpova
- M.A. Aitkhozhin Institute of Molecular Biology and Biochemistry, Science Committee, Ministry of Education and Science, Almaty, Kazakhstan
| | - Nailya S. Polimbetova
- M.A. Aitkhozhin Institute of Molecular Biology and Biochemistry, Science Committee, Ministry of Education and Science, Almaty, Kazakhstan
| | - Nigel G. Halford
- Plant Sciences Department, Rothamsted Research, Harpenden, United Kingdom
| | - Bulat K. Iskakov
- M.A. Aitkhozhin Institute of Molecular Biology and Biochemistry, Science Committee, Ministry of Education and Science, Almaty, Kazakhstan
- Institute of Plant Biology and Biotechnology, Science Committee, Ministry of Education and Science, Almaty, Kazakhstan
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12
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Zhang F, Pirooznia M, Xu H. Mitochondria regulate intestinal stem cell proliferation and epithelial homeostasis through FOXO. Mol Biol Cell 2020; 31:1538-1549. [PMID: 32374658 PMCID: PMC7359575 DOI: 10.1091/mbc.e19-10-0560] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
A metabolic transition from glycolysis to oxidative phosphorylation is often associated with differentiation of many types of stem cells. However, the link between mitochondrial respiration and stem cells' behavior is not fully understood. We genetically disrupted electron transport chain (ETC) complexes in the intestinal stem cells (ISCs) of Drosophila. We found that ISCs carrying impaired ETC proliferated much more slowly than normal and produced very few enteroblasts, which failed to further differentiate into enterocytes. One of the main impediments to ISC proliferation and lineage specification appeared to be abnormally elevated forkhead box O (FOXO) signaling in the ETC-deficient ISCs, as genetically suppressing the signaling pathway partially restored the number of enterocytes. Contrary to common belief, reactive oxygen species (ROS) accumulation did not appear to mediate the ETC mutant phenotype. Our results demonstrate that mitochondrial respiration is essential for Drosophila ISC proliferation and lineage specification in vivo and acts at least partially by repressing endogenous FOXO signaling.
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Affiliation(s)
- Fan Zhang
- National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892
| | - Mehdi Pirooznia
- National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892
| | - Hong Xu
- National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892
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13
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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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14
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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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15
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Hernández G, Osnaya VG, Pérez-Martínez X. Conservation and Variability of the AUG Initiation Codon Context in Eukaryotes. Trends Biochem Sci 2019; 44:1009-1021. [PMID: 31353284 DOI: 10.1016/j.tibs.2019.07.001] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2018] [Revised: 06/22/2019] [Accepted: 07/02/2019] [Indexed: 01/30/2023]
Abstract
Selection of the translation initiation site (TIS) is a crucial step during translation. In the 1980s Marylin Kozak performed key studies on vertebrate mRNAs to characterize the optimal TIS consensus sequence, the Kozak motif. Within this motif, conservation of nucleotides in crucial positions, namely a purine at -3 and a G at +4 (where the A of the AUG is numbered +1), is essential for TIS recognition. Ever since its characterization the Kozak motif has been regarded as the optimal sequence to initiate translation in all eukaryotes. We revisit here published in silico data on TIS consensus sequences, as well as experimental studies from diverse eukaryotic lineages, and propose that, while the -3A/G position is universally conserved, the remaining variability of the consensus sequences enables their classification as optimal, strong, and moderate TIS sequences.
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Affiliation(s)
- Greco Hernández
- Translation and Cancer Laboratory, Unit of Biomedical Research on Cancer, National Institute of Cancer (Instituto Nacional de Cancerología, INCan), 22 San Fernando Avenue, Tlalpan, 14080 Mexico City, Mexico.
| | - Vincent G Osnaya
- Translation and Cancer Laboratory, Unit of Biomedical Research on Cancer, National Institute of Cancer (Instituto Nacional de Cancerología, INCan), 22 San Fernando Avenue, Tlalpan, 14080 Mexico City, Mexico
| | - Xochitl Pérez-Martínez
- Department of Molecular Genetics, Cell Physiology Institute (Instituto de Fisiología Celular), Universidad Nacional Autónoma de México (UNAM), 04510 Mexico City, Mexico
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16
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Leppek K, Das R, Barna M. Functional 5' UTR mRNA structures in eukaryotic translation regulation and how to find them. Nat Rev Mol Cell Biol 2018; 19:158-174. [PMID: 29165424 PMCID: PMC5820134 DOI: 10.1038/nrm.2017.103] [Citation(s) in RCA: 465] [Impact Index Per Article: 77.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
RNA molecules can fold into intricate shapes that can provide an additional layer of control of gene expression beyond that of their sequence. In this Review, we discuss the current mechanistic understanding of structures in 5' untranslated regions (UTRs) of eukaryotic mRNAs and the emerging methodologies used to explore them. These structures may regulate cap-dependent translation initiation through helicase-mediated remodelling of RNA structures and higher-order RNA interactions, as well as cap-independent translation initiation through internal ribosome entry sites (IRESs), mRNA modifications and other specialized translation pathways. We discuss known 5' UTR RNA structures and how new structure probing technologies coupled with prospective validation, particularly compensatory mutagenesis, are likely to identify classes of structured RNA elements that shape post-transcriptional control of gene expression and the development of multicellular organisms.
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Affiliation(s)
- Kathrin Leppek
- Department of Developmental Biology, Stanford University, Stanford, California 94305, USA
- Department of Genetics, Stanford University, Stanford, California 94305, USA
| | - Rhiju Das
- Departments of Biochemistry and Physics, Stanford University, Stanford, California 94305, USA
| | - Maria Barna
- Department of Developmental Biology, Stanford University, Stanford, California 94305, USA
- Department of Genetics, Stanford University, Stanford, California 94305, USA
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17
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Sesma A, Castresana C, Castellano MM. Regulation of Translation by TOR, eIF4E and eIF2α in Plants: Current Knowledge, Challenges and Future Perspectives. FRONTIERS IN PLANT SCIENCE 2017; 8:644. [PMID: 28491073 PMCID: PMC5405063 DOI: 10.3389/fpls.2017.00644] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2017] [Accepted: 04/10/2017] [Indexed: 05/06/2023]
Abstract
An important step in eukaryotic gene expression is the synthesis of proteins from mRNA, a process classically divided into three stages, initiation, elongation, and termination. Translation is a precisely regulated and conserved process in eukaryotes. The presence of plant-specific translation initiation factors and the lack of well-known translational regulatory pathways in this kingdom nonetheless indicate how a globally conserved process can diversify among organisms. The control of protein translation is a central aspect of plant development and adaptation to environmental stress, but the mechanisms are still poorly understood. Here we discuss current knowledge of the principal mechanisms that regulate translation initiation in plants, with special attention to the singularities of this eukaryotic kingdom. In addition, we highlight the major recent breakthroughs in the field and the main challenges to address in the coming years.
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Affiliation(s)
- Ane Sesma
- Centro de Biotecnología y Genómica de Plantas, Universidad Politécnica de Madrid – Instituto Nacional de Investigación y Tecnología Agraria y AlimentariaMadrid, Spain
- Departamento Biotecnología y Biología Vegetal, Universidad Politécnica de MadridMadrid, Spain
| | - Carmen Castresana
- Centro Nacional de Biotecnología – Consejo Superior de Investigaciones Científicas (CSIC)Madrid, Spain
| | - M. Mar Castellano
- Centro de Biotecnología y Genómica de Plantas, Universidad Politécnica de Madrid – Instituto Nacional de Investigación y Tecnología Agraria y AlimentariaMadrid, Spain
- *Correspondence: M. Mar Castellano,
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18
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Zuberek J, Kuchta K, Hernández G, Sonenberg N, Ginalski K. Diverse cap-binding properties of Drosophila eIF4E isoforms. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2016; 1864:1292-303. [PMID: 27374989 DOI: 10.1016/j.bbapap.2016.06.015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 06/07/2016] [Accepted: 06/28/2016] [Indexed: 10/21/2022]
Abstract
The majority of eukaryotic mRNAs are translated in a cap-dependent manner, which requires recognition of the mRNA 5' cap by eIF4E protein. Multiple eIF4E family members have been identified in most eukaryotic organisms. Drosophila melanogaster (Dm) has eight eIF4E related proteins; seven of them belong to Class I and one to Class II. Their biological roles with the exception of Dm eIF4E-1, Dm eIF4E-3 and Dm 4EHP, remain unknown. Here, we compare the molecular basis of Dm eIF4E's interactions with cap and eIF4G peptide by using homology modelling and fluorescence binding assays with various cap analogues. We found that despite the presence of conserved key residues responsible for cap recognition, the differences in binding different cap analogues among Class I Dm eIF4E isoforms are up to 14-fold. The highest affinity for cap analogues was observed for Dm eIF4E-3. We suggest that Dm eIF4E-3 and Dm eIF4E-5 bind the second nucleoside of the cap in an unusual manner via stacking interactions with a histidine or a phenylalanine residue, respectively. Moreover, the analysis of ternary complexes of eIF4G peptide-eIF4E-cap analogue showed cooperativity between eIF4G and cap binding only for Dm eIF4E-4, which exhibits the lowest affinity for cap analogues among all Dm eIF4Es.
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Affiliation(s)
- Joanna Zuberek
- Division of Biophysics, Institute of Experimental Physics, Faculty of Physics, University of Warsaw, Warsaw 02-089, Poland.
| | - Krzysztof Kuchta
- Laboratory of Bioinformatics and Systems Biology, Centre of New Technologies, University of Warsaw, Warsaw 02-097, Poland; College of Inter-Faculty Individual Studies in Mathematics and Natural Sciences, University of Warsaw, Warsaw 02-089, Poland.
| | - Greco Hernández
- Division of Basic Research, National Institute of Cancer (INCan), Tlalpan, Mexico City 14080, Mexico.
| | - Nahum Sonenberg
- Department of Biochemistry and Goodman Cancer Research Centre, McGill University, Montreal, QC H3A 1A3, Canada.
| | - Krzysztof Ginalski
- Laboratory of Bioinformatics and Systems Biology, Centre of New Technologies, University of Warsaw, Warsaw 02-097, Poland.
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Moura DMN, Reis CRS, Xavier CC, da Costa Lima TD, Lima RP, Carrington M, de Melo Neto OP. Two related trypanosomatid eIF4G homologues have functional differences compatible with distinct roles during translation initiation. RNA Biol 2015; 12:305-19. [PMID: 25826663 DOI: 10.1080/15476286.2015.1017233] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
Abstract
In higher eukaryotes, eIF4A, eIF4E and eIF4G homologues interact to enable mRNA recruitment to the ribosome. eIF4G acts as a scaffold for these interactions and also interacts with other proteins of the translational machinery. Trypanosomatid protozoa have multiple homologues of eIF4E and eIF4G and the precise function of each remains unclear. Here, 2 previously described eIF4G homologues, EIF4G3 and EIF4G4, were further investigated. In vitro, both homologues bound EIF4AI, but with different interaction properties. Binding to distinct eIF4Es was also confirmed; EIF4G3 bound EIF4E4 while EIF4G4 bound EIF4E3, both these interactions required similar binding motifs. EIF4G3, but not EIF4G4, interacted with PABP1, a poly-A binding protein homolog. Work in vivo with Trypanosoma brucei showed that both EIF4G3 and EIF4G4 are cytoplasmic and essential for viability. Depletion of EIF4G3 caused a rapid reduction in total translation while EIF4G4 depletion led to changes in morphology but no substantial inhibition of translation. Site-directed mutagenesis was used to disrupt interactions of the eIF4Gs with either eIF4E or eIF4A, causing different levels of growth inhibition. Overall the results show that only EIF4G3, with its cap binding partner EIF4E4, plays a major role in translational initiation.
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Affiliation(s)
- Danielle M N Moura
- a Centro de Pesquisas Aggeu Magalhães; Fundação Oswaldo Cruz ; Campus UFPE; Recife , PE , Brazil
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20
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de Melo Neto OP, da Costa Lima TDC, Xavier CC, Nascimento LM, Romão TP, Assis LA, Pereira MMC, Reis CRS, Papadopoulou B. The unique Leishmania EIF4E4 N-terminus is a target for multiple phosphorylation events and participates in critical interactions required for translation initiation. RNA Biol 2015; 12:1209-21. [PMID: 26338184 DOI: 10.1080/15476286.2015.1086865] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
The eukaryotic initiation factor 4E (eIF4E) recognizes the mRNA cap structure and, together with eIF4G and eIF4A, form the eIF4F complex that regulates translation initiation in eukaryotes. In trypanosomatids, 2 eIF4E homologues (EIF4E3 and EIF4E4) have been shown to be part of eIF4F-like complexes with presumed roles in translation initiation. Both proteins possess unique N-terminal extensions, which can be targeted for phosphorylation. Here, we provide novel insights on the Leishmania infantum EIF4E4 function and regulation. We show that EIF4E4 is constitutively expressed throughout the parasite development but is preferentially phosphorylated in exponentially grown promastigote and amastigote life stages, hence correlating with high levels of translation. Phosphorylation targets multiple serine-proline or threonine-proline residues within the N-terminal extension of EIF4E4 but does not require binding to the EIF4E4's partner, EIF4G3, or to the cap structure. We also report that EIF4E4 interacts with PABP1 through 3 conserved boxes at the EIF4E4 N-terminus and that this interaction is a prerequisite for efficient EIF4E4 phosphorylation. EIF4E4 is essential for Leishmania growth and an EIF4E4 null mutant was only obtained in the presence of an ectopically provided wild type gene. Complementation for the loss of EIF4E4 with several EIF4E4 mutant proteins affecting either phosphorylation or binding to mRNA or to EIF4E4 protein partners revealed that, in contrast to other eukaryotes, only the EIF4E4-PABP1 interaction but neither the binding to EIF4G3 nor phosphorylation is essential for translation. These studies also demonstrated that the lack of both EIF4E4 phosphorylation and EIF4G3 binding leads to a non-functional protein. Altogether, these findings further highlight the unique features of the translation initiation process in trypanosomatid protozoa.
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Affiliation(s)
- Osvaldo P de Melo Neto
- a Departamento de Microbiologia ; Centro de Pesquisas Aggeu Magalhães-FIOCRUZ ; Recife , PE , Brazil
| | - Tamara D C da Costa Lima
- a Departamento de Microbiologia ; Centro de Pesquisas Aggeu Magalhães-FIOCRUZ ; Recife , PE , Brazil
| | - Camila C Xavier
- a Departamento de Microbiologia ; Centro de Pesquisas Aggeu Magalhães-FIOCRUZ ; Recife , PE , Brazil
| | - Larissa M Nascimento
- a Departamento de Microbiologia ; Centro de Pesquisas Aggeu Magalhães-FIOCRUZ ; Recife , PE , Brazil.,b CHU de Quebec Research Center and Department of Microbiology ; Infectious Disease and Immunology; Laval University ; Quebec, QC , Canada
| | - Tatiany P Romão
- a Departamento de Microbiologia ; Centro de Pesquisas Aggeu Magalhães-FIOCRUZ ; Recife , PE , Brazil
| | - Ludmila A Assis
- a Departamento de Microbiologia ; Centro de Pesquisas Aggeu Magalhães-FIOCRUZ ; Recife , PE , Brazil
| | - Mariana M C Pereira
- a Departamento de Microbiologia ; Centro de Pesquisas Aggeu Magalhães-FIOCRUZ ; Recife , PE , Brazil
| | - Christian R S Reis
- a Departamento de Microbiologia ; Centro de Pesquisas Aggeu Magalhães-FIOCRUZ ; Recife , PE , Brazil
| | - Barbara Papadopoulou
- b CHU de Quebec Research Center and Department of Microbiology ; Infectious Disease and Immunology; Laval University ; Quebec, QC , Canada
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21
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Browning KS, Bailey-Serres J. Mechanism of cytoplasmic mRNA translation. THE ARABIDOPSIS BOOK 2015; 13:e0176. [PMID: 26019692 PMCID: PMC4441251 DOI: 10.1199/tab.0176] [Citation(s) in RCA: 144] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Protein synthesis is a fundamental process in gene expression that depends upon the abundance and accessibility of the mRNA transcript as well as the activity of many protein and RNA-protein complexes. Here we focus on the intricate mechanics of mRNA translation in the cytoplasm of higher plants. This chapter includes an inventory of the plant translational apparatus and a detailed review of the translational processes of initiation, elongation, and termination. The majority of mechanistic studies of cytoplasmic translation have been carried out in yeast and mammalian systems. The factors and mechanisms of translation are for the most part conserved across eukaryotes; however, some distinctions are known to exist in plants. A comprehensive understanding of the complex translational apparatus and its regulation in plants is warranted, as the modulation of protein production is critical to development, environmental plasticity and biomass yield in diverse ecosystems and agricultural settings.
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Affiliation(s)
- Karen S. Browning
- Department of Molecular Biosciences and Institute for Cell and Molecular Biology, University of Texas at Austin, Austin TX 78712-0165
- Both authors contributed equally to this work
| | - Julia Bailey-Serres
- Department of Botany and Plant Sciences and Center for Plant Cell Biology, University of California, Riverside, CA, 92521 USA
- Both authors contributed equally to this work
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22
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Hajjawi OS. Ribonucleic acid (RNA) biosynthesis in human cancer. Cancer Cell Int 2015; 15:22. [PMID: 25717284 PMCID: PMC4339644 DOI: 10.1186/s12935-015-0167-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2014] [Accepted: 01/20/2015] [Indexed: 12/28/2022] Open
Abstract
In many respects, the most remarkable chemical substances within the genome of eukaryotic cells are remarkable proteins which are the critical structural and functional units of living cells. The specifications for everything that goes in the cell are natural digital-to-digital decoding process in an archive sequence by deoxyribonucleic acid (DNA) and an articulate construction by ribonucleic acid (RNA). The products of DNA transcription are long polymers of ribonucleotides rather than deoxyribonucleotides and are termed ribonucleic acids. Certain deoxyribonucleotide sequences, or genes, give rise to transfer RNA (tRNA) and other ribosomal RNA (rRNA) when transcribed. The ribonucleotide sequences fold extensively and rRNA is associated with specific proteins to yield the essential cell components, ribosomes. Transcription of other special sequences yields messenger RNAs (mRNAs) that contain ribonucleotide sequences that will be ultimately translated into new types of amino acid sequences of functional cellular protein molecules. This switch to a different variety of cellular molecular sequences is complex, but each sequence of the three ribonucleotides specifies the insertion of one particular amino acid into the polypeptide chain under production. Whilst mRNA is considered the vehicle by which genetic information is transmitted from the genome and allocated in the appropriate cytoplasmic sites for translation into protein via cap-dependent mechanism, the actual translation depends also on the presence of other so-called household and luxury protein molecules. Recent evidence suggests RNA species are required at initiation, because treatment of cells with antibiotics or drugs that inhibit RNA synthesis cause a decrease in protein synthesis. The rRNA is necessary as a structural constituent of the ribosomes upon which translation takes place, whereas tRNA is necessary as an adaptor in amino acid activation and elongation protein chains to ribosomes. In this article, we review malignant tumor, with stem like properties, and recent technical advances into the phenomenon of micro-particles and micro-vesicles containing cell-free nucleic acids that circulate plasma. New areas of research have been opened into screening tumor telomerase progression, prognosis of aptamers targeting cell surface, monitoring the efficacy of anticancer therapies, oncogenic transformation of host cell, and RNA polymerases role in the cell cycle progression and differentiation.
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Affiliation(s)
- Omar S Hajjawi
- Department of Biology, Arab American University, P. O. Box 240, Jenin, Israeli Occupied Territories of Palestine
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23
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Expression of human Hemojuvelin (HJV) is tightly regulated by two upstream open reading frames in HJV mRNA that respond to iron overload in hepatic cells. Mol Cell Biol 2015; 35:1376-89. [PMID: 25666510 DOI: 10.1128/mcb.01462-14] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
The gene encoding human hemojuvelin (HJV) is one of the genes that, when mutated, can cause juvenile hemochromatosis, an early-onset inherited disorder associated with iron overload. The 5' untranslated region of the human HJV mRNA has two upstream open reading frames (uORFs), with 28 and 19 codons formed by two upstream AUGs (uAUGs) sharing the same in-frame stop codon. Here we show that these uORFs decrease the translational efficiency of the downstream main ORF in HeLa and HepG2 cells. Indeed, ribosomal access to the main AUG is conditioned by the strong uAUG context, which results in the first uORF being translated most frequently. The reach of the main ORF is then achieved by ribosomes that resume scanning after uORF translation. Furthermore, the amino acid sequences of the uORF-encoded peptides also reinforce the translational repression of the main ORF. Interestingly, when iron levels increase, translational repression is relieved specifically in hepatic cells. The upregulation of protein levels occurs along with phosphorylation of the eukaryotic initiation factor 2α. Nevertheless, our results support a model in which the increasing recognition of the main AUG is mediated by a tissue-specific factor that promotes uORF bypass. These results support a tight HJV translational regulation involved in iron homeostasis.
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24
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Barbosa C, Romão L. Translation of the human erythropoietin transcript is regulated by an upstream open reading frame in response to hypoxia. RNA (NEW YORK, N.Y.) 2014; 20:594-608. [PMID: 24647661 PMCID: PMC3988562 DOI: 10.1261/rna.040915.113] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2013] [Accepted: 01/10/2014] [Indexed: 05/22/2023]
Abstract
Erythropoietin (EPO) is a key mediator hormone for hypoxic induction of erythropoiesis that also plays important nonhematopoietic functions. It has been shown that EPO gene expression regulation occurs at different levels, including transcription and mRNA stabilization. In this report, we show that expression of EPO is also regulated at the translational level by an upstream open reading frame (uORF) of 14 codons. As judged by comparisons of protein and mRNA levels, the uORF acts as a cis-acting element that represses translation of the main EPO ORF in unstressed HEK293, HepG2, and HeLa cells. However, in response to hypoxia, this repression is significantly released, specifically in HeLa cells, through a mechanism that involves processive scanning of ribosomes from the 5' end of the EPO transcript and enhanced ribosome bypass of the uORF. In addition, we demonstrate that in HeLa cells, hypoxia induces the phosphorylation of eukaryotic translation initiation factor 2α (eIF2α) concomitantly with a significant increase of EPO protein synthesis. These findings provide a framework for understanding that production of high levels of EPO induced by hypoxia also involves regulation at the translational level.
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25
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Estevan J, Maréna A, Callot C, Lacombe S, Moretti A, Caranta C, Gallois JL. Specific requirement for translation initiation factor 4E or its isoform drives plant host susceptibility to Tobacco etch virus. BMC PLANT BIOLOGY 2014; 14:67. [PMID: 24645730 PMCID: PMC3999954 DOI: 10.1186/1471-2229-14-67] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2014] [Accepted: 03/12/2014] [Indexed: 05/02/2023]
Abstract
BACKGROUND In plants, eIF4E translation initiation factors and their eIFiso4E isoforms are essential susceptibility factors for many RNA viruses, including potyviruses. Mutations altering these factors are a major source of resistance to the viruses. The eIF4E allelic series is associated with specific resistance spectra in crops such as Capsicum annum. Genetic evidence shows that potyviruses have a specific requirement for a given 4E isoform that depends on the host plant. For example, Tobacco etch virus (TEV) uses eIF4E1 to infect Capsicum annuum but uses eIFiso4E to infect Arabidopsis thaliana. Here, we investigated how TEV exploits different translation initiation factor isoforms to infect these two plant species. RESULTS A complementation system was set up in Arabidopsis to test the restoration of systemic infection by TEV. Using this system, Arabidopsis susceptibility to TEV was complemented with a susceptible pepper eIF4E1 allele but not with a resistant allele. Therefore, in Arabidopsis, TEV can use the pepper eIF4E1 instead of the endogenous eIFiso4E isoform so is able to switch between translation initiation factor 4E isoform to infect the same host. Moreover, we show that overexpressing the pepper eIF4E1 alleles is sufficient to make Arabidopsis susceptible to an otherwise incompatible TEV strain. Lastly, we show that the resistant eIF4E1 allele is similarly overcome by a resistance-breaking TEV strain as in pepper, confirming that this Arabidopsis TEV-susceptibility complementation system is allele-specific. CONCLUSION We report here a complementation system in Arabidopsis that makes it possible to assess the role of pepper pvr2-eIF4E alleles in susceptibility to TEV. Heterologous complementation experiments showed that the idiosyncratic properties of the 4E and iso4E proteins create a major checkpoint for viral infection of different hosts. This system could be used to screen natural or induced eIF4E alleles to find and study alleles of interest for plant breeding.
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Affiliation(s)
- Joan Estevan
- INRA-UR1052, Genetics and Breeding of Fruits and Vegetables, Dom. St Maurice, CS 60094, Montfavet Cedex F-84143, France
| | - Aramata Maréna
- INRA-UR1052, Genetics and Breeding of Fruits and Vegetables, Dom. St Maurice, CS 60094, Montfavet Cedex F-84143, France
| | - Caroline Callot
- INRA-UR1052, Genetics and Breeding of Fruits and Vegetables, Dom. St Maurice, CS 60094, Montfavet Cedex F-84143, France
| | - Séverine Lacombe
- INRA-UR1052, Genetics and Breeding of Fruits and Vegetables, Dom. St Maurice, CS 60094, Montfavet Cedex F-84143, France
| | - André Moretti
- INRA-UR1052, Genetics and Breeding of Fruits and Vegetables, Dom. St Maurice, CS 60094, Montfavet Cedex F-84143, France
| | - Carole Caranta
- INRA-UR1052, Genetics and Breeding of Fruits and Vegetables, Dom. St Maurice, CS 60094, Montfavet Cedex F-84143, France
| | - Jean-Luc Gallois
- INRA-UR1052, Genetics and Breeding of Fruits and Vegetables, Dom. St Maurice, CS 60094, Montfavet Cedex F-84143, France
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26
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Callot C, Gallois JL. Pyramiding resistances based on translation initiation factors in Arabidopsis is impaired by male gametophyte lethality. PLANT SIGNALING & BEHAVIOR 2014; 9:e27940. [PMID: 24492391 PMCID: PMC4091535 DOI: 10.4161/psb.27940] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2014] [Accepted: 01/21/2014] [Indexed: 05/20/2023]
Abstract
In eukaryotes, eIF4E translation initiation factors are essential proteins encoded by a small multigene family. In plants, they are a major source of host plant resistance to potyviruses that require specific 4E factors to infect cells. Combining mutations in different eIF4E genes could be a way of broadening the spectrum of plant resistance to viruses. We attempted to combine null mutations affecting the two main Arabidopsis thaliana 4E factors eIF4E1 and eIFiso4E but discovered that this combination is lethal. Transmission through the male gametophyte is completely abolished in the eif4e1 eifiso4e double mutant. This shows that eIF4E1 and eIFiso4E are essential for male gametophyte development and act redundantly. These results may have implications for eIF4E-based pyramiding strategies to improve crop resistance.
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Garrocho-Villegas V, Aguilar C R, Sánchez de Jiménez E. Insights into the TOR-S6K signaling pathway in maize (Zea mays L.). pathway activation by effector-receptor interaction. Biochemistry 2013; 52:9129-40. [PMID: 24358933 DOI: 10.1021/bi401474x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The primordial TOR pathway, known to control growth and cell proliferation, has still not been fully described for plants. Nevertheless, in maize, an insulin-like growth factor (ZmIGF) peptide has been reported to stimulate this pathway. This research provides further insight into the TOR pathway in maize, using a biochemical approach in cultures of fast-growing (FG) and slow-growing (SG) calli, as a model system. Our results revealed that addition of either ZmIGF or insulin to SG calli stimulated DNA synthesis and increased the growth rate through cell proliferation and increased the rate of ribosomal protein (RP) synthesis by the selective mobilization of RP mRNAs into polysomes. Furthermore, analysis of the phosphorylation status of the main TOR and S6K kinases from the TOR pathway revealed stimulation by ZmIGF or insulin, whereas rapamycin inhibited its activation. Remarkably, a putative maize insulin-like receptor was recognized by a human insulin receptor antibody, as demonstrated by immunoprecipitation from membrane protein extracts of maize callus. Furthermore, competition experiments between ZmIGF and insulin for the receptor site on maize protoplasts suggested structural recognition of the putative receptor by either effector. These data were confirmed by confocal immunolocalization within the cell membrane of callus cells. Taken together, these data indicate that cell growth and cell proliferation in maize depend on the activation of the TOR-S6K pathway through the interaction of an insulin-like growth factor and its receptor. This evidence suggests that higher plants as well as metazoans have conserved this biochemical pathway to regulate their growth, supporting the conclusion that it is a highly evolved conserved pathway.
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A comprehensive analysis of the importance of translation initiation factors for Haloferax volcanii applying deletion and conditional depletion mutants. PLoS One 2013; 8:e77188. [PMID: 24244275 PMCID: PMC3828320 DOI: 10.1371/journal.pone.0077188] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2012] [Accepted: 09/08/2013] [Indexed: 11/19/2022] Open
Abstract
Translation is an important step in gene expression. The initiation of translation is phylogenetically diverse, since currently five different initiation mechanisms are known. For bacteria the three initiation factors IF1 – IF3 are described in contrast to archaea and eukaryotes, which contain a considerably higher number of initiation factor genes. As eukaryotes and archaea use a non-overlapping set of initiation mechanisms, orthologous proteins of both domains do not necessarily fulfill the same function. The genome of Haloferax volcanii contains 14 annotated genes that encode (subunits of) initiation factors. To gain a comprehensive overview of the importance of these genes, it was attempted to construct single gene deletion mutants of all genes. In 9 cases single deletion mutants were successfully constructed, showing that the respective genes are not essential. In contrast, the genes encoding initiation factors aIF1, aIF2γ, aIF5A, aIF5B, and aIF6 were found to be essential. Factors aIF1A and aIF2β are encoded by two orthologous genes in H. volcanii. Attempts to generate double mutants failed in both cases, indicating that also these factors are essential. A translatome analysis of one of the single aIF2β deletion mutants revealed that the translational efficiency of the second ortholog was enhanced tenfold and thus the two proteins can replace one another. The phenotypes of the single deletion mutants also revealed that the two aIF1As and aIF2βs have redundant but not identical functions. Remarkably, the gene encoding aIF2α, a subunit of aIF2 involved in initiator tRNA binding, could be deleted. However, the mutant had a severe growth defect under all tested conditions. Conditional depletion mutants were generated for the five essential genes. The phenotypes of deletion mutants and conditional depletion mutants were compared to that of the wild-type under various conditions, and growth characteristics are discussed.
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McBride EG, Rubel EW, Wang Y. Afferent regulation of chicken auditory brainstem neurons: rapid changes in phosphorylation of elongation factor 2. J Comp Neurol 2013; 521:1165-83. [PMID: 22987813 DOI: 10.1002/cne.23227] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2012] [Revised: 08/27/2012] [Accepted: 09/07/2012] [Indexed: 12/21/2022]
Abstract
The relationships between protein synthesis and neuronal survival are poorly understood. In chicken nucleus magnocellularis (NM), significant alterations in overall protein synthesis precede neuronal death induced by deprivation of excitatory afferent activity. Previously we demonstrated an initial reduction in the overall rate of protein synthesis in all deprived NM neurons, followed by quick recovery (starting at 6 hours) in some, but not all, neurons. Neurons with recovered protein synthesis ultimately survive, whereas others become "ghost" cells (no detectable Nissl substance) at 12-24 hours and die within 48 hours. To explore the mechanisms underlying this differential influence of afferent input on protein synthesis and cell survival, the current study investigates the involvement of eukaryotic translation elongation factor 2 (eEF2), the phosphorylation of which reduces overall protein synthesis. Using immunocytochemistry for either total or phosphorylated eEF2 (p-eEF2), we found significant reductions in the level of phosphorylated, but not total, eEF2 in NM neurons as early as 0.5-1 hour following cochlea removal. Unexpectedly, neurons with low levels of p-eEF2 show reduced protein synthesis at 6 hours, indicated by a marker for active ribosomes. At 12 hours, all "ghost" cells exhibited little or no p-eEF2 staining, although not every neuron with a comparable low level of p-eEF2 was a "ghost" cell. These observations demonstrate that a reduced level of p-eEF2 is not responsible for immediate responses (including reduced overall protein synthesis) of a neuron to compromised afferent input but may impair the neuron's ability to initiate recovery signaling for survival and make the neuron more vulnerable to death.
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Affiliation(s)
- Ethan G McBride
- Virginia Merrill Bloedel Hearing Research Center, Department of Otolaryngology-Head and Neck Surgery, University of Washington School of Medicine, Seattle, Washington 98195, USA
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The eIF4E subunits of two distinct trypanosomatid eIF4F complexes are subjected to differential post-translational modifications associated to distinct growth phases in culture. Mol Biochem Parasitol 2013; 190:82-6. [DOI: 10.1016/j.molbiopara.2013.06.008] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2013] [Revised: 06/27/2013] [Accepted: 06/28/2013] [Indexed: 11/19/2022]
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Mextli is a novel eukaryotic translation initiation factor 4E-binding protein that promotes translation in Drosophila melanogaster. Mol Cell Biol 2013; 33:2854-64. [PMID: 23716590 DOI: 10.1128/mcb.01354-12] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Translation is a fundamental step in gene expression, and translational control is exerted in many developmental processes. Most eukaryotic mRNAs are translated by a cap-dependent mechanism, which requires recognition of the 5'-cap structure of the mRNA by eukaryotic translation initiation factor 4E (eIF4E). eIF4E activity is controlled by eIF4E-binding proteins (4E-BPs), which by competing with eIF4G for eIF4E binding act as translational repressors. Here, we report the discovery of Mextli (Mxt), a novel Drosophila melanogaster 4E-BP that in sharp contrast to other 4E-BPs, has a modular structure, binds RNA, eIF3, and several eIF4Es, and promotes translation. Mxt is expressed at high levels in ovarian germ line stem cells (GSCs) and early-stage cystocytes, as is eIF4E-1, and we demonstrate the two proteins interact in these cells. Phenotypic analysis of mxt mutants indicates a role for Mxt in germ line stem cell (GSC) maintenance and in early embryogenesis. Our results support the idea that Mxt, like eIF4G, coordinates the assembly of translation initiation complexes, rendering Mxt the first example of evolutionary convergence of eIF4G function.
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Verta JP, Landry CR, MacKay JJ. Are long-lived trees poised for evolutionary change? Single locus effects in the evolution of gene expression networks in spruce. Mol Ecol 2013; 22:2369-79. [DOI: 10.1111/mec.12189] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2012] [Accepted: 11/26/2012] [Indexed: 02/04/2023]
Affiliation(s)
- Jukka-Pekka Verta
- Département des Sciences du Bois et de la Forêt & Centre d’Étude de la Forêt; Université Laval; Québec QC Canada G1V 0A6
- Institut de Biologie Intégrative et des Systèmes; Université Laval; Québec QC Canada G1V 0A6
| | - Christian R. Landry
- Institut de Biologie Intégrative et des Systèmes; Université Laval; Québec QC Canada G1V 0A6
- Département de Biologie & PROTEO; Université Laval; Québec QC Canada G1V 0A6
| | - John J. MacKay
- Département des Sciences du Bois et de la Forêt & Centre d’Étude de la Forêt; Université Laval; Québec QC Canada G1V 0A6
- Institut de Biologie Intégrative et des Systèmes; Université Laval; Québec QC Canada G1V 0A6
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Hernández G, Han H, Gandin V, Fabian L, Ferreira T, Zuberek J, Sonenberg N, Brill JA, Lasko P. Eukaryotic initiation factor 4E-3 is essential for meiotic chromosome segregation, cytokinesis and male fertility in Drosophila. Development 2012; 139:3211-20. [PMID: 22833128 DOI: 10.1242/dev.073122] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Gene expression is translationally regulated during many cellular and developmental processes. Translation can be modulated by affecting the recruitment of mRNAs to the ribosome, which involves recognition of the 5' cap structure by the cap-binding protein eIF4E. Drosophila has several genes encoding eIF4E-related proteins, but the biological role of most of them remains unknown. Here, we report that Drosophila eIF4E-3 is required specifically during spermatogenesis. Males lacking eIF4E-3 are sterile, showing defects in meiotic chromosome segregation, cytokinesis, nuclear shaping and individualization. We show that eIF4E-3 physically interacts with both eIF4G and eIF4G-2, the latter being a factor crucial for spermatocyte meiosis. In eIF4E-3 mutant testes, many proteins are present at different levels than in wild type, suggesting widespread effects on translation. Our results imply that eIF4E-3 forms specific eIF4F complexes that are essential for spermatogenesis.
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Affiliation(s)
- Greco Hernández
- Department of Biology, McGill University, 3649 Promenade Sir William Osler, Montréal, Québec, H3G 0B1, Canada
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Gai Z, Kitagawa Y, Tanaka Y, Shimizu N, Komoda K, Tanaka I, Yao M. The binding mechanism of eIF2β with its partner proteins, eIF5 and eIF2Bε. Biochem Biophys Res Commun 2012; 423:515-9. [PMID: 22683627 DOI: 10.1016/j.bbrc.2012.05.155] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2012] [Accepted: 05/28/2012] [Indexed: 12/16/2022]
Abstract
The eukaryotic translation initiation factor eIF2 delivers Met-tRNAiMet to the ribosomal small subunit in GTP-bound form associated with eIF1, eIF1A, eIF3 and eIF5, and dissociates together with eIF5 as eIF5-eIF2-GDP complex from the ribosomal small subunit after formation of start codon-anticodon base pairing between Met-tRNAiMet and mRNA. The inactive form eIF2-GDP is then exchanged for the active form eIF2-GTP by eIF2B for further initiation cycle. Previous studies showed that the C-terminal domains of eIF5 (eIF5-CTD) and eIF2Bε (eIF2Bε-CTD) have a common eIF2β-binding site for interacting with an N-terminal region of eIF2β (eIF2β-NTD). Here we have reconstructed the complexes of (eIF5-CTD)-(eIF2β-NTD) and (eIF2Bε-CTD)-(eIF2β-NTD) in vitro, and investigated binding mechanism by circular dichroism spectroscopy and small angle X-ray scattering in solution. The results showed the conformation of eIF2β-NTD was changed when bound to partner proteins, whereas the structures of eIF5-CTD and eIF2Bε-CTD were similar in both isolated and complex states. We propose that eIF2β-NTD works as an intrinsically disordered domain which is disorder in the isolated state, but folds into a definite structure when bound to its partner proteins. Such flexibility of eIF2β-NTD is expected to be responsible for its binding capability.
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Affiliation(s)
- Zuoqi Gai
- Graduate School of Life Science, Faculty of Advanced Life Science, Hokkaido University, Sapporo 060-0810, Japan
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Tettweiler G, Kowanda M, Lasko P, Sonenberg N, Hernández G. The Distribution of eIF4E-Family Members across Insecta. Comp Funct Genomics 2012; 2012:960420. [PMID: 22745595 PMCID: PMC3382400 DOI: 10.1155/2012/960420] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2011] [Accepted: 03/14/2012] [Indexed: 11/20/2022] Open
Abstract
Insects are part of the earliest faunas that invaded terrestrial environments and are the first organisms that evolved controlled flight. Nowadays, insects are the most diverse animal group on the planet and comprise the majority of extant animal species described. Moreover, they have a huge impact in the biosphere as well as in all aspects of human life and economy; therefore understanding all aspects of insect biology is of great importance. In insects, as in all cells, translation is a fundamental process for gene expression. However, translation in insects has been mostly studied only in the model organism Drosophila melanogaster. We used all publicly available genomic sequences to investigate in insects the distribution of the genes encoding the cap-binding protein eIF4E, a protein that plays a crucial role in eukaryotic translation. We found that there is a diversity of multiple ortholog genes encoding eIF4E isoforms within the genus Drosophila. In striking contrast, insects outside this genus contain only a single eIF4E gene, related to D. melanogaster eIF4E-1. We also found that all insect species here analyzed contain only one Class II gene, termed 4E-HP. We discuss the possible evolutionary causes originating the multiplicity of eIF4E genes within the genus Drosophila.
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Affiliation(s)
- Gritta Tettweiler
- Department of Biology, McGill University, 1205 Dr. Penfield, Montreal, QC, Canada H3A 1B1
- Department of Biochemistry and Goodman Cancer Research Center, McGill University, Montreal, QC, Canada H3A 1A3
| | - Michelle Kowanda
- Department of Biology, McGill University, 1205 Dr. Penfield, Montreal, QC, Canada H3A 1B1
| | - Paul Lasko
- Department of Biology, McGill University, 1205 Dr. Penfield, Montreal, QC, Canada H3A 1B1
| | - Nahum Sonenberg
- Department of Biochemistry and Goodman Cancer Research Center, McGill University, Montreal, QC, Canada H3A 1A3
| | - Greco Hernández
- Division of Basic Research, National Institute for Cancer (INCan), Avenida San Fernando No. 22, Tlalpan, 14080 Mexico City, DF, Mexico
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Conservation of the RNA Transport Machineries and Their Coupling to Translation Control across Eukaryotes. Comp Funct Genomics 2012; 2012:287852. [PMID: 22666086 PMCID: PMC3361156 DOI: 10.1155/2012/287852] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2011] [Accepted: 02/09/2012] [Indexed: 01/03/2023] Open
Abstract
Restriction of proteins to discrete subcellular regions is a common mechanism to establish cellular asymmetries and depends on a coordinated program of mRNA localization and translation control. Many processes from the budding of a yeast to the establishment of metazoan embryonic axes and the migration of human neurons, depend on this type of cell polarization. How factors controlling transport and translation assemble to regulate at the same time the movement and translation of transported mRNAs, and whether these mechanisms are conserved across kingdoms is not yet entirely understood. In this review we will focus on some of the best characterized examples of mRNA transport machineries, the "yeast locasome" as an example of RNA transport and translation control in unicellular eukaryotes, and on the Drosophila Bic-D/Egl/Dyn RNA localization machinery as an example of RNA transport in higher eukaryotes. This focus is motivated by the relatively advanced knowledge about the proteins that connect the localizing mRNAs to the transport motors and the many well studied proteins involved in translational control of specific transcripts that are moved by these machineries. We will also discuss whether the core of these RNA transport machineries and factors regulating mRNA localization and translation are conserved across eukaryotes.
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Hernández G, Proud CG, Preiss T, Parsyan A. On the Diversification of the Translation Apparatus across Eukaryotes. Comp Funct Genomics 2012; 2012:256848. [PMID: 22666084 PMCID: PMC3359775 DOI: 10.1155/2012/256848] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2011] [Accepted: 03/07/2012] [Indexed: 11/21/2022] Open
Abstract
Diversity is one of the most remarkable features of living organisms. Current assessments of eukaryote biodiversity reaches 1.5 million species, but the true figure could be several times that number. Diversity is ingrained in all stages and echelons of life, namely, the occupancy of ecological niches, behavioral patterns, body plans and organismal complexity, as well as metabolic needs and genetics. In this review, we will discuss that diversity also exists in a key biochemical process, translation, across eukaryotes. Translation is a fundamental process for all forms of life, and the basic components and mechanisms of translation in eukaryotes have been largely established upon the study of traditional, so-called model organisms. By using modern genome-wide, high-throughput technologies, recent studies of many nonmodel eukaryotes have unveiled a surprising diversity in the configuration of the translation apparatus across eukaryotes, showing that this apparatus is far from being evolutionarily static. For some of the components of this machinery, functional differences between different species have also been found. The recent research reviewed in this article highlights the molecular and functional diversification the translational machinery has undergone during eukaryotic evolution. A better understanding of all aspects of organismal diversity is key to a more profound knowledge of life.
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Affiliation(s)
- Greco Hernández
- Division of Basic Research, National Institute for Cancer (INCan), Avenida San Fernando No. 22, Col. Sección XVI, Tlalpan, 14080 Mexico City, Mexico
| | - Christopher G. Proud
- Centre for Biological Sciences, University of Southampton, Life Sciences Building (B85), Southampton SO17 1BJ, UK
| | - Thomas Preiss
- Genome Biology Department, The John Curtin School of Medical Research, The Australian National University, Building 131, Garran Road, Acton, Canberra, ACT 0200, Australia
| | - Armen Parsyan
- Goodman Cancer Centre and Department of Biochemistry, Faculty of Medicine, McGill University, 1160 Pine Avenue West, Montreal, QC, Canada H3A 1A3
- Division of General Surgery, Department of Surgery, Faculty of Medicine, McGill University Health Centre, Royal Victoria Hospital, 687 Pine Avenue West, Montreal, QC, Canada H3A 1A1
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Dephosphorylation of eIF2α is essential for protein synthesis increase and cell cycle progression after sea urchin fertilization. Dev Biol 2012; 365:303-9. [DOI: 10.1016/j.ydbio.2012.03.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2011] [Revised: 02/15/2012] [Accepted: 03/02/2012] [Indexed: 11/21/2022]
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Muench DG, Zhang C, Dahodwala M. Control of cytoplasmic translation in plants. WILEY INTERDISCIPLINARY REVIEWS-RNA 2012; 3:178-94. [DOI: 10.1002/wrna.1104] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Kruse S, Zhong S, Bodi Z, Button J, Alcocer MJC, Hayes CJ, Fray R. A novel synthesis and detection method for cap-associated adenosine modifications in mouse mRNA. Sci Rep 2011; 1:126. [PMID: 22355643 PMCID: PMC3216607 DOI: 10.1038/srep00126] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2011] [Accepted: 10/07/2011] [Indexed: 11/17/2022] Open
Abstract
A method is described for the detection of certain nucleotide modifications adjacent to the 5' 7-methyl guanosine cap of mRNAs from individual genes. The method quantitatively measures the relative abundance of 2'-O-methyl and N6,2'-O-dimethyladenosine, two of the most common modifications. In order to identify and quantitatify the amounts of N6,2'-O-dimethyladenosine, a novel method for the synthesis of modified adenosine phosphoramidites was developed. This method is a one step synthesis and the product can directly be used for the production of N6,2'-O-dimethyladenosine containing RNA oligonucleotides. The nature of the cap-adjacent nucleotides were shown to be characteristic for mRNAs from individual genes transcribed in liver and testis.
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Affiliation(s)
- Susanne Kruse
- School of Chemistry, The University of Nottingham, University Park, Nottingham, NG7 2RD, UK
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Jiménez-López S, Mancera-Martínez E, Donayre-Torres A, Rangel C, Uribe L, March S, Jiménez-Sánchez G, Sánchez de Jiménez E. Expression profile of maize (Zea mays L.) embryonic axes during germination: translational regulation of ribosomal protein mRNAs. PLANT & CELL PHYSIOLOGY 2011; 52:1719-33. [PMID: 21880676 DOI: 10.1093/pcp/pcr114] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Seed germination is a critical developmental period for plant propagation. Information regarding gene expression within this important period is relevant for understanding the main biochemical processes required for successful germination, particularly in maize, one of the most important cereals in the world. The present research focuses on the global microarray analysis of differential gene expression between quiescent and germinated maize embryo stages. This analysis revealed that a large number of mRNAs stored in the quiescent embryonic axes (QEAs) were differentially regulated during germination in the 24 h germinated embryonic axes (GEAs). These genes belong to 14 different functional categories and most of them correspond to metabolic processes, followed by transport, transcription and translation. Interestingly, the expression of mRNAs encoding ribosomal proteins [(r)-proteins], required for new ribosome formation during this fast-growing period, remains mostly unchanged throughout the germination process, suggesting that these genes are not regulated at the transcriptional level during this developmental period. To investigate this issue further, comparative microarray analyses on polysomal mRNAs from growth-stimulated and non-stimulated GEAs were performed. The results revealed that (r)-protein mRNAs accumulate to high levels in polysomes of the growth-stimulated tissues, indicating a translational control mechanism to account for the rapid (r)-protein synthesis observed within this period. Bioinformatic analysis of (r)-protein mRNAs showed that 5' TOP (tract of pyrimidines)-like sequences are present only in the 5'-untranslated region set of up-regulated (r)-protein mRNAs. This overall approach to the germination process allows an in-depth view of molecular changes, enabling a broader understanding of the regulatory mechanisms that occur during this process.
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Affiliation(s)
- Sara Jiménez-López
- Biochemistry Department, Faculty of Chemistry, Universidad Nacional Autónoma de Mexico (UNAM), Ciudad Universitaria, 04510 Mexico, D.F. México
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Santiveri CM, Mirassou Y, Rico-Lastres P, Martínez-Lumbreras S, Pérez-Cañadillas JM. Pub1p C-terminal RRM domain interacts with Tif4631p through a conserved region neighbouring the Pab1p binding site. PLoS One 2011; 6:e24481. [PMID: 21931728 PMCID: PMC3169606 DOI: 10.1371/journal.pone.0024481] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2011] [Accepted: 08/11/2011] [Indexed: 11/18/2022] Open
Abstract
Pub1p, a highly abundant poly(A)+ mRNA binding protein in Saccharomyces cerevisiae, influences the stability and translational control of many cellular transcripts, particularly under some types of environmental stresses. We have studied the structure, RNA and protein recognition modes of different Pub1p constructs by NMR spectroscopy. The structure of the C-terminal RRM domain (RRM3) shows a non-canonical N-terminal helix that packs against the canonical RRM fold in an original fashion. This structural trait is conserved in Pub1p metazoan homologues, the TIA-1 family, defining a new class of RRM-type domains that we propose to name TRRM (TIA-1 C-terminal domain-like RRM). Pub1p TRRM and the N-terminal RRM1-RRM2 tandem bind RNA with high selectivity for U-rich sequences, with TRRM showing additional preference for UA-rich ones. RNA-mediated chemical shift changes map to β-sheet and protein loops in the three RRMs. Additionally, NMR titration and biochemical in vitro cross-linking experiments determined that Pub1p TRRM interacts specifically with the N-terminal region (1-402) of yeast eIF4G1 (Tif4631p), very likely through the conserved Box1, a short sequence motif neighbouring the Pab1p binding site in Tif4631p. The interaction involves conserved residues of Pub1p TRRM, which define a protein interface that mirrors the Pab1p-Tif4631p binding mode. Neither protein nor RNA recognition involves the novel N-terminal helix, whose functional role remains unclear. By integrating these new results with the current knowledge about Pub1p, we proposed different mechanisms of Pub1p recruitment to the mRNPs and Pub1p-mediated mRNA stabilization in which the Pub1p/Tif4631p interaction would play an important role.
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Affiliation(s)
- Clara M. Santiveri
- Department of Biological Physical Chemistry, Instituto de Química-Física “Rocasolano”, CSIC, Madrid, Spain
| | - Yasmina Mirassou
- Department of Biological Physical Chemistry, Instituto de Química-Física “Rocasolano”, CSIC, Madrid, Spain
| | - Palma Rico-Lastres
- Department of Biological Physical Chemistry, Instituto de Química-Física “Rocasolano”, CSIC, Madrid, Spain
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Ribosome binding to a 5' translational enhancer is altered in the presence of the 3' untranslated region in cap-independent translation of turnip crinkle virus. J Virol 2011; 85:4638-53. [PMID: 21389125 DOI: 10.1128/jvi.00005-11] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Plus-strand RNA viruses without 5' caps require noncanonical mechanisms for ribosome recruitment. A translational enhancer in the 3' untranslated region (UTR) of Turnip crinkle virus (TCV) contains an internal T-shaped structure (TSS) that binds to 60S ribosomal subunits. We now report that the 63-nucleotide (nt) 5' UTR of TCV contains a 19-nt pyrimidine-rich element near the initiation codon that supports translation of an internal open reading frame (ORF) independent of upstream 5' UTR sequences. Addition of 80S ribosomes to the 5' UTR reduced the flexibility of the polypyrimidine residues and generated a toeprint consistent with binding to this region. Binding of salt-washed 40S ribosomal subunits was reduced 6-fold when the pyrimidine-rich sequence was mutated. 40S subunit binding generated the same toeprint as 80S ribosomes but also additional ones near the 5' end. Generation of out-of-frame AUGs upstream of the polypyrimidine region reduced translation, which suggests that 5'-terminal entry of 40S subunits is followed by scanning and that the polypyrimidine region is needed for an alternative function that requires ribosome binding. No evidence for RNA-RNA interactions between 5' and 3' sequences was found, suggesting that TCV utilizes an alternative means for circularizing its genome. Combining 5' and 3' UTR fragments in vitro had no discernible effect on the structures of the RNAs. In contrast, when 80S ribosomes were added to both fragments, structural changes were found in the 5' UTR polypyrimidine tract that were not evident when ribosomes interacted with the individual fragments. This suggests that ribosomes can promote an interaction between the 5' and 3' UTRs of TCV.
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Malys N, McCarthy JEG. Translation initiation: variations in the mechanism can be anticipated. Cell Mol Life Sci 2011; 68:991-1003. [PMID: 21076851 PMCID: PMC11115079 DOI: 10.1007/s00018-010-0588-z] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2010] [Revised: 10/25/2010] [Accepted: 10/28/2010] [Indexed: 01/05/2023]
Abstract
Translation initiation is a critical step in protein synthesis. Previously, two major mechanisms of initiation were considered as essential: prokaryotic, based on SD interaction; and eukaryotic, requiring cap structure and ribosomal scanning. Although discovered decades ago, cap-independent translation has recently been acknowledged as a widely spread mechanism in viruses, which may take place in some cellular mRNA translations. Moreover, it has become evident that translation can be initiated on the leaderless mRNA in all three domains of life. New findings demonstrate that other distinguishable types of initiation exist, including SD-independent in Bacteria and Archaea, and various modifications of 5' end-dependent and internal initiation mechanisms in Eukarya. Since translation initiation has developed through the loss, acquisition, and modification of functional elements, all of which have been elevated by competition with viral translation in a large number of organisms of different complexity, more variation in initiation mechanisms can be anticipated.
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Affiliation(s)
- Naglis Malys
- Manchester Centre for Integrative Systems Biology, Faculty of Life Sciences, Manchester Interdisciplinary Biocentre, The University of Manchester, UK.
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