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Blázquez MA. Polyamines: Their Role in Plant Development and Stress. ANNUAL REVIEW OF PLANT BIOLOGY 2024; 75:95-117. [PMID: 38382905 DOI: 10.1146/annurev-arplant-070623-110056] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/23/2024]
Abstract
This review focuses on the intricate relationship between plant polyamines and the genetic circuits and signaling pathways that regulate various developmental programs and the defense responses of plants when faced with biotic and abiotic aggressions. Particular emphasis is placed on genetic evidence supporting the involvement of polyamines in specific processes, such as the pivotal role of thermospermine in regulating xylem cell differentiation and the significant contribution of polyamine metabolism in enhancing plant resilience to drought. Based on the numerous studies describing effects of the manipulation of plant polyamine levels, two conceptually different mechanisms for polyamine activity are discussed: direct participation of polyamines in translational regulation and the indirect production of hydrogen peroxide as a defensive mechanism against pathogens. By describing the multifaceted functions of polyamines, this review underscores the profound significance of these compounds in enabling plants to adapt and thrive in challenging environments.
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Affiliation(s)
- Miguel A Blázquez
- Instituto de Biología Molecular y Celular de Plantas, Consejo Superior de Investigaciones Científicas-Universitat Politècnica de València, Valencia, Spain;
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2
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Zhang R, Zhang W, Wang C, Wen CK. Arabidopsis Fhit-like tumor suppressor resumes early terminated constitutive triple response1-10 mRNA translation. PLANT PHYSIOLOGY 2024; 195:2073-2093. [PMID: 38563472 DOI: 10.1093/plphys/kiae192] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2023] [Revised: 02/09/2024] [Accepted: 02/14/2024] [Indexed: 04/04/2024]
Abstract
The Arabidopsis (Arabidopsis thaliana) constitutive triple response1-10 (ctr1-10) mutant produces a reduced level of CTR1 protein and exhibits a weak ctr1 mutant phenotype. Sequence analysis revealed highly active translation of the upstream open reading frame (uORF) at the extended 5'-UTR of the ctr1-10 mRNA, resulting from T-DNA insertion. Enhancer screening for ctr1-10 isolated the fragile histidine triad-1 (fhit-1) mutation. The fhit-1 ctr1-10 mutant phenotypically resembled strong ctr1 mutants and barely produced CTR1, and the fhit-1 mutation reduced the translation efficiency of ctr1-10 but not that of CTR1 mRNA. The human (Homo sapiens) Fhit that involves tumorigenesis and genome instability has the in vitro dinucleotide 5',5'″-P1, P3-triphosphate hydrolase activity, and expression of the human HsFHIT or the hydrolase-defective HsFHITH96N transgene reversed the fhit-1 ctr1-10 mutant phenotype and restored CTR1 levels. Genetic editing that in situ disrupts individual upstream ATG codons proximal to the ctr1-10 mORF elevated CTR1 levels in ctr1-10 plants independent of FHIT. EUKARYOTIC INITIATION FACTOR3G (eIF3G), which is involved in translation and reinitiation, interacted with FHIT, and both were associated with the polysome. We propose that FHIT resumes early terminated ctr1-10 mORF translation in the face of active and complex uORF translation. Our study unveils a niche that may lead to investigations on the molecular mechanism of Fhit-like proteins in translation reinitiation. The biological significance of FHIT-regulated translation is discussed.
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Affiliation(s)
- Ranran Zhang
- National Key Laboratory of Plant Molecular Genetics, CAS Center for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai 200032, China
| | - Wei Zhang
- National Key Laboratory of Plant Molecular Genetics, CAS Center for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai 200032, China
| | - Chenrunshu Wang
- National Key Laboratory of Plant Molecular Genetics, CAS Center for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai 200032, China
| | - Chi-Kuang Wen
- National Key Laboratory of Plant Molecular Genetics, CAS Center for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai 200032, China
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Aoyama H, Arae T, Yamashita Y, Toyoda A, Naito S, Sotta N, Chiba Y. Impact of translational regulation on diel expression revealed by time-series ribosome profiling in Arabidopsis. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2024; 118:1889-1906. [PMID: 38494830 DOI: 10.1111/tpj.16716] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/18/2023] [Revised: 02/19/2024] [Accepted: 02/28/2024] [Indexed: 03/19/2024]
Abstract
Plants have developed the ability to adjust to the day/night cycle through the expression of diel genes, which allow them to effectively respond to environmental changes and optimise their growth and development. Diel oscillations also have substantial implications in many physiological processes, including photosynthesis, floral development, and environmental stress responses. The expression of diel genes is regulated by a combination of the circadian clock and responses to environmental cues, such as light and temperature. A great deal of information is available on the transcriptional regulation of diel gene expression. However, the extent to which translational regulation is involved in controlling diel changes in expression is not yet clear. To investigate the impact of translational regulation on diel expression, we conducted Ribo-seq and RNA-seq analyses on a time-series sample of Arabidopsis shoots cultivated under a 12 h light/dark cycle. Our results showed that translational regulation is involved in about 71% of the genes exhibiting diel changes in mRNA abundance or translational activity, including clock genes, many of which are subject to both translational and transcriptional control. They also revealed that the diel expression of glycosylation and ion-transporter-related genes is mainly established through translational regulation. The expression of several diel genes likely subject to translational regulation through upstream open-reading frames was also determined.
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Affiliation(s)
- Haruka Aoyama
- Graduate School of Life Science, Hokkaido University, Sapporo, 060-0810, Japan
| | - Toshihiro Arae
- Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, 277-8562, Japan
| | - Yui Yamashita
- Graduate School of Agriculture, Hokkaido University, Sapporo, 060-8589, Japan
| | - Atsushi Toyoda
- Advanced Genomics Center, National Institute of Genetics, Mishima, 411-8540, Japan
| | - Satoshi Naito
- Graduate School of Agriculture, Hokkaido University, Sapporo, 060-8589, Japan
| | - Naoyuki Sotta
- Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, 113-8657, Japan
| | - Yukako Chiba
- Graduate School of Life Science, Hokkaido University, Sapporo, 060-0810, Japan
- Faculty of Science, Hokkaido University, Sapporo, 060-0810, Japan
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4
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Wu HYL, Jen J, Hsu PY. What, where, and how: Regulation of translation and the translational landscape in plants. THE PLANT CELL 2024; 36:1540-1564. [PMID: 37437121 PMCID: PMC11062462 DOI: 10.1093/plcell/koad197] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2023] [Revised: 06/14/2023] [Accepted: 06/15/2023] [Indexed: 07/14/2023]
Abstract
Translation is a crucial step in gene expression and plays a vital role in regulating various aspects of plant development and environmental responses. It is a dynamic and complex program that involves interactions between mRNAs, transfer RNAs, and the ribosome machinery through both cis- and trans-regulation while integrating internal and external signals. Translational control can act in a global (transcriptome-wide) or mRNA-specific manner. Recent advances in genome-wide techniques, particularly ribosome profiling and proteomics, have led to numerous exciting discoveries in both global and mRNA-specific translation. In this review, we aim to provide a "primer" that introduces readers to this fascinating yet complex cellular process and provide a big picture of how essential components connect within the network. We begin with an overview of mRNA translation, followed by a discussion of the experimental approaches and recent findings in the field, focusing on unannotated translation events and translational control through cis-regulatory elements on mRNAs and trans-acting factors, as well as signaling networks through 3 conserved translational regulators TOR, SnRK1, and GCN2. Finally, we briefly touch on the spatial regulation of mRNAs in translational control. Here, we focus on cytosolic mRNAs; translation in organelles and viruses is not covered in this review.
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Affiliation(s)
- Hsin-Yen Larry Wu
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824, USA
| | - Joey Jen
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824, USA
| | - Polly Yingshan Hsu
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824, USA
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Khan D, Fox PL. Host-like RNA Elements Regulate Virus Translation. Viruses 2024; 16:468. [PMID: 38543832 PMCID: PMC10976276 DOI: 10.3390/v16030468] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2024] [Revised: 03/14/2024] [Accepted: 03/17/2024] [Indexed: 04/01/2024] Open
Abstract
Viruses are obligate, intracellular parasites that co-opt host cell machineries for propagation. Critical among these machineries are those that translate RNA into protein and their mechanisms of control. Most regulatory mechanisms effectuate their activity by targeting sequence or structural features at the RNA termini, i.e., at the 5' or 3' ends, including the untranslated regions (UTRs). Translation of most eukaryotic mRNAs is initiated by 5' cap-dependent scanning. In contrast, many viruses initiate translation at internal RNA regions at internal ribosome entry sites (IRESs). Eukaryotic mRNAs often contain upstream open reading frames (uORFs) that permit condition-dependent control of downstream major ORFs. To offset genome compression and increase coding capacity, some viruses take advantage of out-of-frame overlapping uORFs (oORFs). Lacking the essential machinery of protein synthesis, for example, ribosomes and other translation factors, all viruses utilize the host apparatus to generate virus protein. In addition, some viruses exhibit RNA elements that bind host regulatory factors that are not essential components of the translation machinery. SARS-CoV-2 is a paradigm example of a virus taking advantage of multiple features of eukaryotic host translation control: the virus mimics the established human GAIT regulatory element and co-opts four host aminoacyl tRNA synthetases to form a stimulatory binding complex. Utilizing discontinuous transcription, the elements are present and identical in all SARS-CoV-2 subgenomic RNAs (and the genomic RNA). Thus, the virus exhibits a post-transcriptional regulon that improves upon analogous eukaryotic regulons, in which a family of functionally related mRNA targets contain elements that are structurally similar but lacking sequence identity. This "thrifty" virus strategy can be exploited against the virus since targeting the element can suppress the expression of all subgenomic RNAs as well as the genomic RNA. Other 3' end viral elements include 3'-cap-independent translation elements (3'-CITEs) and 3'-tRNA-like structures. Elucidation of virus translation control elements, their binding proteins, and their mechanisms can lead to novel therapeutic approaches to reduce virus replication and pathogenicity.
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Affiliation(s)
- Debjit Khan
- Department of Cardiovascular and Metabolic Sciences, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195, USA
| | - Paul L. Fox
- Department of Cardiovascular and Metabolic Sciences, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195, USA
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Liu Q, Peng X, Shen M, Qian Q, Xing J, Li C, Gregory R. Ribo-uORF: a comprehensive data resource of upstream open reading frames (uORFs) based on ribosome profiling. Nucleic Acids Res 2023; 51:D248-D261. [PMID: 36440758 PMCID: PMC9825487 DOI: 10.1093/nar/gkac1094] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2022] [Revised: 10/27/2022] [Accepted: 11/22/2022] [Indexed: 11/29/2022] Open
Abstract
Upstream open reading frames (uORFs) are typically defined as translation sites located within the 5' untranslated region upstream of the main protein coding sequence (CDS) of messenger RNAs (mRNAs). Although uORFs are prevalent in eukaryotic mRNAs and modulate the translation of downstream CDSs, a comprehensive resource for uORFs is currently lacking. We developed Ribo-uORF (http://rnainformatics.org.cn/RiboUORF) to serve as a comprehensive functional resource for uORF analysis based on ribosome profiling (Ribo-seq) data. Ribo-uORF currently supports six species: human, mouse, rat, zebrafish, fruit fly, and worm. Ribo-uORF includes 501 554 actively translated uORFs and 107 914 upstream translation initiation sites (uTIS), which were identified from 1495 Ribo-seq and 77 quantitative translation initiation sequencing (QTI-seq) datasets, respectively. We also developed mRNAbrowse to visualize items such as uORFs, cis-regulatory elements, genetic variations, eQTLs, GWAS-based associations, RNA modifications, and RNA editing. Ribo-uORF provides a very intuitive web interface for conveniently browsing, searching, and visualizing uORF data. Finally, uORFscan and UTR5var were developed in Ribo-uORF to precisely identify uORFs and analyze the influence of genetic mutations on uORFs using user-uploaded datasets. Ribo-uORF should greatly facilitate studies of uORFs and their roles in mRNA translation and posttranscriptional control of gene expression.
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Affiliation(s)
- Qi Liu
- Rice Research Institute, Guangdong Academy of Agricultural Sciences, Guangzhou 510640, China
- Guangdong Key Laboratory of New Technology in Rice Breeding, Guangzhou 510640, China
- Guangdong Rice Engineering Laboratory, Guangzhou 510640, China
- Key Laboratory of Genetics and Breeding of High Quality Rice in Southern China (Co-construction by Ministry and Province), Guangzhou 510640, China
| | - Xin Peng
- Rice Research Institute, Guangdong Academy of Agricultural Sciences, Guangzhou 510640, China
- Guangdong Key Laboratory of New Technology in Rice Breeding, Guangzhou 510640, China
- Guangdong Rice Engineering Laboratory, Guangzhou 510640, China
- Key Laboratory of Genetics and Breeding of High Quality Rice in Southern China (Co-construction by Ministry and Province), Guangzhou 510640, China
| | - Mengyuan Shen
- Rice Research Institute, Guangdong Academy of Agricultural Sciences, Guangzhou 510640, China
- Guangdong Key Laboratory of New Technology in Rice Breeding, Guangzhou 510640, China
- Guangdong Rice Engineering Laboratory, Guangzhou 510640, China
- Key Laboratory of Genetics and Breeding of High Quality Rice in Southern China (Co-construction by Ministry and Province), Guangzhou 510640, China
| | - Qian Qian
- Rice Research Institute, Guangdong Academy of Agricultural Sciences, Guangzhou 510640, China
- Guangdong Key Laboratory of New Technology in Rice Breeding, Guangzhou 510640, China
- Guangdong Rice Engineering Laboratory, Guangzhou 510640, China
- Key Laboratory of Genetics and Breeding of High Quality Rice in Southern China (Co-construction by Ministry and Province), Guangzhou 510640, China
| | - Junlian Xing
- Rice Research Institute, Guangdong Academy of Agricultural Sciences, Guangzhou 510640, China
- Guangdong Key Laboratory of New Technology in Rice Breeding, Guangzhou 510640, China
- Guangdong Rice Engineering Laboratory, Guangzhou 510640, China
- Key Laboratory of Genetics and Breeding of High Quality Rice in Southern China (Co-construction by Ministry and Province), Guangzhou 510640, China
| | - Chen Li
- Rice Research Institute, Guangdong Academy of Agricultural Sciences, Guangzhou 510640, China
- Guangdong Key Laboratory of New Technology in Rice Breeding, Guangzhou 510640, China
- Guangdong Rice Engineering Laboratory, Guangzhou 510640, China
- Key Laboratory of Genetics and Breeding of High Quality Rice in Southern China (Co-construction by Ministry and Province), Guangzhou 510640, China
| | - Richard I Gregory
- Stem Cell Program, Division of Hematology/Oncology, Boston Children's Hospital, Boston, MA 02115, USA
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA
- Department of Pediatrics, Harvard Medical School, Boston, MA 02115, USA
- Harvard Initiative for RNA Medicine, Boston, MA 02115, USA
- Harvard Stem Cell Institute, Cambridge, MA 02138, USA
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7
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Hiragori Y, Takahashi H, Karino T, Kaido A, Hayashi N, Sasaki S, Nakao K, Motomura T, Yamashita Y, Naito S, Onouchi H. Genome-wide identification of Arabidopsis non-AUG-initiated upstream ORFs with evolutionarily conserved regulatory sequences that control protein expression levels. PLANT MOLECULAR BIOLOGY 2023; 111:37-55. [PMID: 36044152 DOI: 10.1007/s11103-022-01309-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2022] [Accepted: 08/11/2022] [Indexed: 06/15/2023]
Abstract
This study identified four novel regulatory non-AUG-initiated upstream ORFs (uORFs) with evolutionarily conserved sequences in Arabidopsis and elucidated the mechanism by which a non-AUG-initiated uORF promotes main ORF translation. Upstream open reading frames (uORFs) are short ORFs found in the 5'-untranslated regions (5'-UTRs) of eukaryotic transcripts and can influence the translation of protein-coding main ORFs (mORFs). Recent genome-wide ribosome profiling studies have revealed that hundreds or thousands of uORFs initiate translation at non-AUG start codons. However, the physiological significance of these non-AUG uORFs has so far been demonstrated for only a few of them. In this study, to identify physiologically important regulatory non-AUG uORFs in Arabidopsis, we took an approach that combined bioinformatics and experimental analysis. Since physiologically important non-AUG uORFs are likely to be conserved across species, we first searched the Arabidopsis genome for non-AUG-initiated uORFs with evolutionarily conserved sequences. Then, we examined the effects of the conserved non-AUG uORFs on the expression of the downstream mORFs using transient expression assays. As a result, three inhibitory and one promotive non-AUG uORFs were identified. Among the inhibitory non-AUG uORFs, two exerted repressive effects on mORF expression in an amino acid sequence-dependent manner. These two non-AUG uORFs are likely to encode regulatory peptides that cause ribosome stalling, thereby enhancing their repressive effects. In contrast, one of the identified regulatory non-AUG uORFs promoted mORF expression by alleviating the inhibitory effect of a downstream AUG-initiated uORF. These findings provide insights into the mechanisms that enable non-AUG uORFs to play regulatory roles despite their low translation initiation efficiencies.
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Affiliation(s)
- Yuta Hiragori
- Graduate School of Agriculture, Hokkaido University, Sapporo, 060-8589, Japan
| | - Hiro Takahashi
- Graduate School of Medical Sciences, Kanazawa University, Kanazawa, 920-1192, Japan
- Graduate School of Horticulture, Chiba University, Matsudo, 271-8510, Japan
| | - Taihei Karino
- Graduate School of Agriculture, Hokkaido University, Sapporo, 060-8589, Japan
| | - Atsushi Kaido
- Graduate School of Agriculture, Hokkaido University, Sapporo, 060-8589, Japan
| | - Noriya Hayashi
- Graduate School of Agriculture, Hokkaido University, Sapporo, 060-8589, Japan
| | - Shun Sasaki
- Graduate School of Agriculture, Hokkaido University, Sapporo, 060-8589, Japan
| | - Kodai Nakao
- Graduate School of Agriculture, Hokkaido University, Sapporo, 060-8589, Japan
| | - Taichiro Motomura
- Graduate School of Medical Sciences, Kanazawa University, Kanazawa, 920-1192, Japan
| | - Yui Yamashita
- Graduate School of Agriculture, Hokkaido University, Sapporo, 060-8589, Japan
- Research Faculty of Agriculture, Hokkaido University, Sapporo, 060-8589, Japan
| | - Satoshi Naito
- Research Faculty of Agriculture, Hokkaido University, Sapporo, 060-8589, Japan
- Graduate School of Life Science, Hokkaido University, Sapporo, 060-0810, Japan
| | - Hitoshi Onouchi
- Graduate School of Agriculture, Hokkaido University, Sapporo, 060-8589, Japan.
- Research Faculty of Agriculture, Hokkaido University, Sapporo, 060-8589, Japan.
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8
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Guo R, Yu X, Gregory BD. The identification of conserved sequence features of co-translationally decayed mRNAs and upstream open reading frames in angiosperm transcriptomes. PLANT DIRECT 2023; 7:e479. [PMID: 36643787 PMCID: PMC9831718 DOI: 10.1002/pld3.479] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/08/2022] [Revised: 12/19/2022] [Accepted: 12/20/2022] [Indexed: 06/17/2023]
Abstract
RNA turnover is essential in maintaining messenger RNA (mRNA) homeostasis during various developmental stages and stress responses. Co-translational mRNA decay (CTRD), a process in which mRNAs are degraded while still associated with translating ribosomes, has recently been discovered to function in yeast and three angiosperm transcriptomes. However, it is still unclear how prevalent CTRD across the plant lineage. Moreover, the sequence features of co-translationally decayed mRNAs have not been well-studied. Here, utilizing a collection of publicly available degradome sequencing datasets for another seven angiosperm transcriptomes, we have confirmed that CTRD is functioning in at least 10 angiosperms and likely throughout the plant lineage. Additionally, we have identified sequence features shared by the co-translationally decayed mRNAs in these species, implying a possible conserved triggering mechanism for this pathway. Given that degradome sequencing datasets can also be used to identify actively translating upstream open reading frames (uORFs), which are quite understudied in plants, we have identified numerous actively translating uORFs in the same 10 angiosperms. These findings reveal that actively translating uORFs are prevalent in plant transcriptomes, some of which are conserved across this lineage. We have also observed conserved sequence features in the regions flanking these uORFs' stop codons that might contribute to ribosome stalling at these sequences. Finally, we discovered that there were very few overlaps between the mRNAs harboring actively translating uORFs and those sorted into the co-translational decay pathway in the majority of the studied angiosperms, suggesting that these two processes might be nearly mutually exclusive in those species. In total, our findings provide the identification of CTRD and actively translating uORFs across a broad collection of plants and provide novel insights into the important sequence features associated with these collections of mRNAs and regulatory elements, respectively.
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Affiliation(s)
- Rong Guo
- Department of BiologyUniversity of PennsylvaniaPhiladelphiaPennsylvaniaUSA
| | - Xiang Yu
- Department of BiologyUniversity of PennsylvaniaPhiladelphiaPennsylvaniaUSA
- Present address:
School of Life Sciences and BiotechnologyShanghai Jiao Tong UniversityShanghaiChina
| | - Brian D. Gregory
- Department of BiologyUniversity of PennsylvaniaPhiladelphiaPennsylvaniaUSA
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Dong Y, Ryabova LA. Do plants drive translation reinitiation to dodge nonsense-mediated decay? JOURNAL OF EXPERIMENTAL BOTANY 2023; 74:7-11. [PMID: 36563104 PMCID: PMC9786829 DOI: 10.1093/jxb/erac444] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/05/2022] [Accepted: 11/08/2022] [Indexed: 06/17/2023]
Abstract
This article comments on: Cymerman MA, Saul H, Farhi R, Vexler K, Gottlieb D, Berezin I, Shaul O. 2023. Plant transcripts with long or structured upstream open reading frames in the NDL2 5ʹ UTR can escape nonsense-mediated mRNA decay in a reinitiation-independent manner. Journal of Experimental Botany 74, 91–103.
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Affiliation(s)
- Yihan Dong
- Institut de biologie moléculaire des plantes UPR2357 du CNRS, Université de Strasbourg, Strasbourg, France
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10
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Cymerman MA, Saul H, Farhi R, Vexler K, Gottlieb D, Berezin I, Shaul O. Plant transcripts with long or structured upstream open reading frames in the NDL2 5' UTR can escape nonsense-mediated mRNA decay in a reinitiation-independent manner. JOURNAL OF EXPERIMENTAL BOTANY 2023; 74:91-103. [PMID: 36169317 DOI: 10.1093/jxb/erac385] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2022] [Accepted: 09/26/2022] [Indexed: 06/16/2023]
Abstract
Many eukaryotic transcripts contain upstream open reading frames (uORFs). Translated uORFs can inhibit the translation of main ORFs by imposing the need for reinitiation of translation. Translated uORFs can also lead to transcript degradation by the nonsense-mediated mRNA decay (NMD) pathway. In mammalian cells, translated uORFs were shown to target their transcripts to NMD if the uORFs were long (>23-32 amino acids), structured, or inhibit reinitiation. Reinitiation was shown to rescue uORF-containing mammalian transcripts from NMD. Much less is known about the significance of the length, structure, and reinitiation efficiency of translated uORFs for NMD targeting in plants. Although high-throughput studies suggested that uORFs do not globally reduce plant transcript abundance, it was not clear whether this was due to NMD-escape-permitting parameters of uORF recognition, length, structure, or reinitiation efficiency. We expressed in Arabidopsis reporter genes that included NDL2 5' untranslated region and various uORFs with modulation of the above parameters. We found that transcripts can escape NMD in plants even when they include efficiently translated uORFs up to 70 amino acids long, or structured uORFs, in the absence of reinitiation. These data highlight an apparent difference between the rules that govern the exposure of uORF-containing transcripts to NMD in mammalian and plant cells.
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Affiliation(s)
- Miryam A Cymerman
- The Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 5290002, Israel
| | - Helen Saul
- The Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 5290002, Israel
| | - Ronit Farhi
- The Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 5290002, Israel
| | - Karina Vexler
- The Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 5290002, Israel
| | - Dror Gottlieb
- The Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 5290002, Israel
| | - Irina Berezin
- The Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 5290002, Israel
| | - Orit Shaul
- The Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 5290002, Israel
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Kurihara Y, Makita Y, Kawauchi M, Kageyama A, Kuriyama T, Matsui M. Intergenic splicing-stimulated transcriptional readthrough is suppressed by nonsense-mediated mRNA decay in Arabidopsis. Commun Biol 2022; 5:1390. [PMID: 36539571 PMCID: PMC9768141 DOI: 10.1038/s42003-022-04348-y] [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: 06/09/2022] [Accepted: 12/05/2022] [Indexed: 12/24/2022] Open
Abstract
Recent emerging evidence has shown that readthrough transcripts (RTs), including polycistronic mRNAs, are also transcribed in eukaryotes. However, the post-transcriptional regulation for these remains to be elucidated. Here, we identify 271 polycistronic RT-producing loci in Arabidopsis. Increased accumulation of RTs is detected in the nonsense-mediated mRNA decay (NMD)-deficient mutants compared with wild type, and the second open reading frames (ORFs) of bicistronic mRNAs are rarely translated in contrast to the first ORFs. Intergenic splicing (IS) events which occur between first and second genes are seen in 158 RTs. Splicing inhibition assays suggest that IS eliminates the chance of transcription termination at the polyadenylation sites of the first gene and promotes accumulation of RTs. These results indicate that RTs arise from genes whose transcription termination is relatively weak or attenuated by IS, but NMD selectively degrades them. Ultimately, this report presents a eukaryotic strategy for RNA metabolism.
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Affiliation(s)
- Yukio Kurihara
- grid.509461.f0000 0004 1757 8255Synthetic Genomics Research Group, RIKEN Center for Sustainable Resource Science, Suehiro-cho 1-7-22, Tsurumi-ku, Yokohama, Kanagawa 230-0045 Japan ,grid.26999.3d0000 0001 2151 536XDepartment of Life Sciences, Graduate School of Arts and Sciences, University of Tokyo, Komaba 3-8-1, Meguro-ku, Tokyo 153-8902 Japan
| | - Yuko Makita
- grid.509461.f0000 0004 1757 8255Synthetic Genomics Research Group, RIKEN Center for Sustainable Resource Science, Suehiro-cho 1-7-22, Tsurumi-ku, Yokohama, Kanagawa 230-0045 Japan ,grid.444244.60000 0004 0628 9167Faculty of Engineering, Maebashi Institute of Technology, Kamisadori 460-1, Maebashi, Gunma 371-0816 Japan
| | - Masaharu Kawauchi
- grid.509461.f0000 0004 1757 8255Synthetic Genomics Research Group, RIKEN Center for Sustainable Resource Science, Suehiro-cho 1-7-22, Tsurumi-ku, Yokohama, Kanagawa 230-0045 Japan
| | - Ami Kageyama
- grid.509461.f0000 0004 1757 8255Synthetic Genomics Research Group, RIKEN Center for Sustainable Resource Science, Suehiro-cho 1-7-22, Tsurumi-ku, Yokohama, Kanagawa 230-0045 Japan ,grid.268441.d0000 0001 1033 6139Graduate School of Nanobioscience, Department of Life and Environmental System Science, Yokohama City University, Yokohama, Kanagawa 236-0027 Japan
| | - Tomoko Kuriyama
- grid.509461.f0000 0004 1757 8255Synthetic Genomics Research Group, RIKEN Center for Sustainable Resource Science, Suehiro-cho 1-7-22, Tsurumi-ku, Yokohama, Kanagawa 230-0045 Japan
| | - Minami Matsui
- grid.509461.f0000 0004 1757 8255Synthetic Genomics Research Group, RIKEN Center for Sustainable Resource Science, Suehiro-cho 1-7-22, Tsurumi-ku, Yokohama, Kanagawa 230-0045 Japan ,grid.268441.d0000 0001 1033 6139Graduate School of Nanobioscience, Department of Life and Environmental System Science, Yokohama City University, Yokohama, Kanagawa 236-0027 Japan
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12
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Bottorff TA, Park H, Geballe AP, Subramaniam AR. Translational buffering by ribosome stalling in upstream open reading frames. PLoS Genet 2022; 18:e1010460. [PMID: 36315596 PMCID: PMC9648851 DOI: 10.1371/journal.pgen.1010460] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2022] [Revised: 11/10/2022] [Accepted: 10/04/2022] [Indexed: 11/05/2022] Open
Abstract
Upstream open reading frames (uORFs) are present in over half of all human mRNAs. uORFs can potently regulate the translation of downstream open reading frames through several mechanisms: siphoning away scanning ribosomes, regulating re-initiation, and allowing interactions between scanning and elongating ribosomes. However, the consequences of these different mechanisms for the regulation of protein expression remain incompletely understood. Here, we performed systematic measurements on the uORF-containing 5' UTR of the cytomegaloviral UL4 mRNA to test alternative models of uORF-mediated regulation in human cells. We find that a terminal diproline-dependent elongating ribosome stall in the UL4 uORF prevents decreases in main ORF protein expression when ribosome loading onto the mRNA is reduced. This uORF-mediated buffering is insensitive to the location of the ribosome stall along the uORF. Computational kinetic modeling based on our measurements suggests that scanning ribosomes dissociate rather than queue when they collide with stalled elongating ribosomes within the UL4 uORF. We identify several human uORFs that repress main ORF protein expression via a similar terminal diproline motif. We propose that ribosome stalls in uORFs provide a general mechanism for buffering against reductions in main ORF translation during stress and developmental transitions.
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Affiliation(s)
- Ty A. Bottorff
- Basic Sciences Division and Computational Biology Program of the Public Health Sciences Division, Fred Hutchinson Cancer Center, Seattle, Washington, United States of America
- Biological Physics, Structure and Design Graduate Program, University of Washington, Seattle, Washington, United States of America
| | - Heungwon Park
- Basic Sciences Division and Computational Biology Program of the Public Health Sciences Division, Fred Hutchinson Cancer Center, Seattle, Washington, United States of America
| | - Adam P. Geballe
- Human Biology and Clinical Research Divisions, Fred Hutchinson Cancer Center, Seattle, Washington, United States of America
| | - Arvind Rasi Subramaniam
- Basic Sciences Division and Computational Biology Program of the Public Health Sciences Division, Fred Hutchinson Cancer Center, Seattle, Washington, United States of America
- Biological Physics, Structure and Design Graduate Program, University of Washington, Seattle, Washington, United States of America
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13
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Causier B, Hopes T, McKay M, Paling Z, Davies B. Plants utilise ancient conserved peptide upstream open reading frames in stress-responsive translational regulation. PLANT, CELL & ENVIRONMENT 2022; 45:1229-1241. [PMID: 35128674 PMCID: PMC9305500 DOI: 10.1111/pce.14277] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2021] [Revised: 11/30/2021] [Accepted: 12/01/2021] [Indexed: 05/08/2023]
Abstract
The regulation of protein synthesis plays an important role in the growth and development of all organisms. Upstream open reading frames (uORFs) are commonly found in eukaryotic messenger RNA transcripts and typically attenuate the translation of associated downstream main ORFs (mORFs). Conserved peptide uORFs (CPuORFs) are a rare subset of uORFs, some of which have been shown to conditionally regulate translation by ribosome stalling. Here, we show that Arabidopsis CPuORF19, CPuORF46 and CPuORF47, which are ancient in origin, regulate translation of any downstream ORF, in response to the agriculturally significant environmental signals, heat stress and water limitation. Consequently, these CPuORFs represent a versatile toolkit for inducible gene expression with broad applications. Finally, we note that different classes of CPuORFs may operate during distinct phases of translation, which has implications for the bioengineering of these regulatory factors.
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Affiliation(s)
- Barry Causier
- Faculty of Biological Sciences, Centre for Plant SciencesUniversity of LeedsLeedsUK
| | - Tayah Hopes
- Faculty of Biological Sciences, Centre for Plant SciencesUniversity of LeedsLeedsUK
- Faculty of Biological Sciences, School of Molecular and Cellular BiologyUniversity of LeedsLeedsUK
| | - Mary McKay
- Faculty of Biological Sciences, Centre for Plant SciencesUniversity of LeedsLeedsUK
| | - Zachary Paling
- Faculty of Biological Sciences, Centre for Plant SciencesUniversity of LeedsLeedsUK
| | - Brendan Davies
- Faculty of Biological Sciences, Centre for Plant SciencesUniversity of LeedsLeedsUK
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14
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Translational and post-translational regulation of polyamine metabolic enzymes in plants. J Biotechnol 2021; 344:1-10. [PMID: 34915092 DOI: 10.1016/j.jbiotec.2021.12.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2021] [Revised: 09/19/2021] [Accepted: 12/03/2021] [Indexed: 10/19/2022]
Abstract
Polyamines are small organic and basic polycations that perform essential regulatory functions in all living organisms. Fluctuations in polyamine content have been observed to occur during growth, development and under stress conditions, implying that polyamines play pivotal roles in diverse cellular and physiological processes. To achieve polyamine homeostasis, the entire metabolic pathway is subjected to a fine-tuned regulation of its biosynthetic and catabolic genes and enzymes. In this review, we describe and discuss the most important mechanisms implicated in the translational and post-translational regulation of polyamine metabolic enzymes in plants. At the translational level, we emphasize the role of polyamines in the modulation of upstream open reading frame (uORF) activities that control the translation of polyamine biosynthetic and catabolic mRNAs. At the post-translational level, different aspects of the regulation of polyamine metabolic proteins are depicted, such as the proteolytic activation of enzyme precursors, the importance of dimerization in protein stability as well as in protein intracellular localization.
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15
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Alghoul F, Laure S, Eriani G, Martin F. Translation inhibitory elements from Hoxa3 and Hoxa11 mRNAs use uORFs for translation inhibition. eLife 2021; 10:e66369. [PMID: 34076576 PMCID: PMC8172242 DOI: 10.7554/elife.66369] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2021] [Accepted: 05/20/2021] [Indexed: 01/20/2023] Open
Abstract
During embryogenesis, Hox mRNA translation is tightly regulated by a sophisticated molecular mechanism that combines two RNA regulons located in their 5'UTR. First, an internal ribosome entry site (IRES) enables cap-independent translation. The second regulon is a translation inhibitory element or TIE, which ensures concomitant cap-dependent translation inhibition. In this study, we deciphered the molecular mechanisms of mouse Hoxa3 and Hoxa11 TIEs. Both TIEs possess an upstream open reading frame (uORF) that is critical to inhibit cap-dependent translation. However, the molecular mechanisms used are different. In Hoxa3 TIE, we identify an uORF which inhibits cap-dependent translation and we show the requirement of the non-canonical initiation factor eIF2D for this process. The mode of action of Hoxa11 TIE is different, it also contains an uORF but it is a minimal uORF formed by an uAUG followed immediately by a stop codon, namely a 'start-stop'. The 'start-stop' sequence is species-specific and in mice, is located upstream of a highly stable stem loop structure which stalls the 80S ribosome and thereby inhibits cap-dependent translation of Hoxa11 main ORF.
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Affiliation(s)
- Fatima Alghoul
- Institut de Biologie Moléculaire et Cellulaire, “Architecture et Réactivité de l’ARN” CNRS UPR9002, Université de StrasbourgStrasbourgFrance
| | - Schaeffer Laure
- Institut de Biologie Moléculaire et Cellulaire, “Architecture et Réactivité de l’ARN” CNRS UPR9002, Université de StrasbourgStrasbourgFrance
| | - Gilbert Eriani
- Institut de Biologie Moléculaire et Cellulaire, “Architecture et Réactivité de l’ARN” CNRS UPR9002, Université de StrasbourgStrasbourgFrance
| | - Franck Martin
- Institut de Biologie Moléculaire et Cellulaire, “Architecture et Réactivité de l’ARN” CNRS UPR9002, Université de StrasbourgStrasbourgFrance
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16
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Sotta N, Chiba Y, Miwa K, Takamatsu S, Tanaka M, Yamashita Y, Naito S, Fujiwara T. Global analysis of boron-induced ribosome stalling reveals its effects on translation termination and unique regulation by AUG-stops in Arabidopsis shoots. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2021; 106:1455-1467. [PMID: 33772920 DOI: 10.1111/tpj.15248] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2020] [Revised: 03/05/2021] [Accepted: 03/12/2021] [Indexed: 06/12/2023]
Abstract
We previously reported that ribosome stalling at AUG-stop sequences in the 5'-untranslated region plays a critical role in regulating the expression of Arabidopsis thaliana NIP5;1, which encodes a boron uptake transporter, in response to boron conditions in media. This ribosome stalling is triggered specifically by boric acid, but the mechanisms are unknown. Although upstream open reading frames (uORFs) are known in many cases to regulate translation through peptides encoded by the uORF, AUG-stop stalling does not involve any peptide synthesis. The unique feature of AUG-stops - that termination follows immediately after initiation - suggests a possible effect of boron on the translational process itself. However, the generality of AUG-stop-mediated translational regulation and the effect of boron on translation at the genome scale are not clear. Here, we conducted a ribosome profiling analysis to reveal the genome-wide regulation of translation in response to boron conditions in A. thaliana shoots. We identified hundreds of translationally regulated genes that function in various biological processes. Under high-boron conditions, transcripts with reduced translation efficiency were rich in uORFs, highlighting the importance of uORF-mediated translational regulation. We found 673 uORFs that had more frequent ribosome association. Moreover, transcripts that were translationally downregulated under high-boron conditions were rich in minimum uORFs (AUG-stops), suggesting that AUG-stops play a global role in the boron response. Metagene analysis revealed that boron increased the ribosome occupancy of stop codons, indicating that this element is involved in global translational termination processes.
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Affiliation(s)
- Naoyuki Sotta
- Graduate School of Agricultural and Life Science, University of Tokyo, Tokyo, 113-8657, Japan
- School of Biosciences, Cardiff University, Cardiff, CF10 3AX, UK
| | - Yukako Chiba
- Faculty of Science, Hokkaido University, Sapporo, 060-0810, Japan
- Graduate School of Life Science, Hokkaido University, Sapporo, 060-0810, Japan
| | - Kyoko Miwa
- Graduate School of Environmental Science, Hokkaido University, Sapporo, 060-0810, Japan
| | - Seidai Takamatsu
- Graduate School of Life Science, Hokkaido University, Sapporo, 060-0810, Japan
| | - Mayuki Tanaka
- Graduate School of Agricultural and Life Science, University of Tokyo, Tokyo, 113-8657, Japan
| | - Yui Yamashita
- Graduate School of Agriculture, Hokkaido University, Sapporo, 060-8589, Japan
| | - Satoshi Naito
- Graduate School of Life Science, Hokkaido University, Sapporo, 060-0810, Japan
- Graduate School of Agriculture, Hokkaido University, Sapporo, 060-8589, Japan
| | - Toru Fujiwara
- Graduate School of Agricultural and Life Science, University of Tokyo, Tokyo, 113-8657, Japan
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17
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Urquidi-Camacho RA, Lokdarshi A, von Arnim AG. Translational gene regulation in plants: A green new deal. WILEY INTERDISCIPLINARY REVIEWS. RNA 2020; 11:e1597. [PMID: 32367681 PMCID: PMC9258721 DOI: 10.1002/wrna.1597] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/06/2020] [Revised: 03/31/2020] [Accepted: 04/01/2020] [Indexed: 01/09/2023]
Abstract
The molecular machinery for protein synthesis is profoundly similar between plants and other eukaryotes. Mechanisms of translational gene regulation are embedded into the broader network of RNA-level processes including RNA quality control and RNA turnover. However, over eons of their separate history, plants acquired new components, dropped others, and generally evolved an alternate way of making the parts list of protein synthesis work. Research over the past 5 years has unveiled how plants utilize translational control to defend themselves against viruses, regulate translation in response to metabolites, and reversibly adjust translation to a wide variety of environmental parameters. Moreover, during seed and pollen development plants make use of RNA granules and other translational controls to underpin developmental transitions between quiescent and metabolically active stages. The economics of resource allocation over the daily light-dark cycle also include controls over cellular protein synthesis. Important new insights into translational control on cytosolic ribosomes continue to emerge from studies of translational control mechanisms in viruses. Finally, sketches of coherent signaling pathways that connect external stimuli with a translational response are emerging, anchored in part around TOR and GCN2 kinase signaling networks. These again reveal some mechanisms that are familiar and others that are different from other eukaryotes, motivating deeper studies on translational control in plants. This article is categorized under: Translation > Translation Regulation RNA Structure and Dynamics > Influence of RNA Structure in Biological Systems RNA Interactions with Proteins and Other Molecules > Protein-RNA Interactions: Functional Implications.
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Affiliation(s)
- Ricardo A. Urquidi-Camacho
- UT-ORNL Graduate School of Genome Science and Technology, The University of Tennessee, Knoxville, TN 37996
| | - Ansul Lokdarshi
- Department of Biochemistry & Cellular and Molecular Biology, University of Tennessee, Knoxville, TN 37996
| | - Albrecht G von Arnim
- Department of Biochemistry & Cellular and Molecular Biology and UT-ORNL Graduate School of Genome Science and Technology, University of Tennessee, Knoxville, TN 37996
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18
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Li YR, Liu MJ. Prevalence of alternative AUG and non-AUG translation initiators and their regulatory effects across plants. Genome Res 2020; 30:1418-1433. [PMID: 32973042 PMCID: PMC7605272 DOI: 10.1101/gr.261834.120] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2020] [Accepted: 08/19/2020] [Indexed: 12/11/2022]
Abstract
Translation initiation is a key step determining protein synthesis. Studies have uncovered a number of alternative translation initiation sites (TISs) in mammalian mRNAs and showed their roles in reshaping the proteome. However, the extent to which alternative TISs affect gene expression across plants remains largely unclear. Here, by profiling initiating ribosome positions, we globally identified in vivo TISs in tomato and Arabidopsis and found thousands of genes with more than one TIS. Of the identified TISs, >19% and >20% were located at unannotated AUG and non-AUG sites, respectively. CUG and ACG were the most frequently observed codons at non-AUG TISs, a phenomenon also found in mammals. In addition, although alternative TISs were usually found in both orthologous genes, the TIS sequences were not conserved, suggesting the conservation of alternative initiation mechanisms but flexibility in using TISs. Unlike upstream AUG TISs, the presence of upstream non-AUG TISs was not correlated with the translational repression of main open reading frames, a pattern observed across plants. Also, the generation of proteins with diverse N-terminal regions through the use of alternative TISs contributes to differential subcellular localization, as mutating alternative TISs resulted in the loss of organelle localization. Our findings uncovered the hidden coding potential of plant genomes and, importantly, the constraint and flexibility of translational initiation mechanisms in the regulation of gene expression across plant species.
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Affiliation(s)
- Ya-Ru Li
- Biotechnology Center in Southern Taiwan, Academia Sinica, Tainan 741, Taiwan
| | - Ming-Jung Liu
- Biotechnology Center in Southern Taiwan, Academia Sinica, Tainan 741, Taiwan.,Agricultural Biotechnology Research Center, Academia Sinica, Taipei 115, Taiwan
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19
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Dever TE, Ivanov IP, Sachs MS. Conserved Upstream Open Reading Frame Nascent Peptides That Control Translation. Annu Rev Genet 2020; 54:237-264. [PMID: 32870728 DOI: 10.1146/annurev-genet-112618-043822] [Citation(s) in RCA: 37] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Cells utilize transcriptional and posttranscriptional mechanisms to alter gene expression in response to environmental cues. Gene-specific controls, including changing the translation of specific messenger RNAs (mRNAs), provide a rapid means to respond precisely to different conditions. Upstream open reading frames (uORFs) are known to control the translation of mRNAs. Recent studies in bacteria and eukaryotes have revealed the functions of evolutionarily conserved uORF-encoded peptides. Some of these uORF-encoded nascent peptides enable responses to specific metabolites to modulate the translation of their mRNAs by stalling ribosomes and through ribosome stalling may also modulate the level of their mRNAs. In this review, we highlight several examples of conserved uORF nascent peptides that stall ribosomes to regulate gene expression in response to specific metabolites in bacteria, fungi, mammals, and plants.
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Affiliation(s)
- Thomas E Dever
- Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA; ,
| | - Ivaylo P Ivanov
- Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA; ,
| | - Matthew S Sachs
- Department of Biology, Texas A&M University, College Station, Texas 77843, USA;
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20
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uORFs: Important Cis-Regulatory Elements in Plants. Int J Mol Sci 2020; 21:ijms21176238. [PMID: 32872304 PMCID: PMC7503886 DOI: 10.3390/ijms21176238] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2020] [Revised: 08/20/2020] [Accepted: 08/22/2020] [Indexed: 11/17/2022] Open
Abstract
Gene expression is regulated at many levels, including mRNA transcription, translation, and post-translational modification. Compared with transcriptional regulation, mRNA translational control is a more critical step in gene expression and allows for more rapid changes of encoded protein concentrations in cells. Translation is highly regulated by complex interactions between cis-acting elements and trans-acting factors. Initiation is not only the first phase of translation, but also the core of translational regulation, because it limits the rate of protein synthesis. As potent cis-regulatory elements in eukaryotic mRNAs, upstream open reading frames (uORFs) generally inhibit the translation initiation of downstream major ORFs (mORFs) through ribosome stalling. During the past few years, with the development of RNA-seq and ribosome profiling, functional uORFs have been identified and characterized in many organisms. Here, we review uORF identification, uORF classification, and uORF-mediated translation initiation. More importantly, we summarize the translational regulation of uORFs in plant metabolic pathways, morphogenesis, disease resistance, and nutrient absorption, which open up an avenue for precisely modulating the plant growth and development, as well as environmental adaption. Additionally, we also discuss prospective applications of uORFs in plant breeding.
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21
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uORF Shuffling Fine-Tunes Gene Expression at a Deep Level of the Process. PLANTS 2020; 9:plants9050608. [PMID: 32403214 PMCID: PMC7284334 DOI: 10.3390/plants9050608] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/08/2020] [Revised: 05/06/2020] [Accepted: 05/08/2020] [Indexed: 01/01/2023]
Abstract
Upstream open reading frames (uORFs) are present in the 5’ leader sequences (or 5’ untranslated regions) upstream of the protein-coding main ORFs (mORFs) in eukaryotic polycistronic mRNA. It is well known that a uORF negatively affects translation of the mORF. Emerging ribosome profiling approaches have revealed that uORFs themselves, as well as downstream mORFs, can be translated. However, it has also been revealed that plants can fine-tune gene expression by modulating uORF-mediated regulation in some situations. This article reviews several proposed mechanisms that enable genes to escape from uORF-mediated negative regulation and gives insight into the application of uORF-mediated regulation for precisely controlling gene expression.
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22
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Takahashi H, Hayashi N, Hiragori Y, Sasaki S, Motomura T, Yamashita Y, Naito S, Takahashi A, Fuse K, Satou K, Endo T, Kojima S, Onouchi H. Comprehensive genome-wide identification of angiosperm upstream ORFs with peptide sequences conserved in various taxonomic ranges using a novel pipeline, ESUCA. BMC Genomics 2020; 21:260. [PMID: 32228449 PMCID: PMC7106846 DOI: 10.1186/s12864-020-6662-5] [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: 07/23/2019] [Accepted: 03/10/2020] [Indexed: 12/27/2022] Open
Abstract
Background Upstream open reading frames (uORFs) in the 5′-untranslated regions (5′-UTRs) of certain eukaryotic mRNAs encode evolutionarily conserved functional peptides, such as cis-acting regulatory peptides that control translation of downstream main ORFs (mORFs). For genome-wide searches for uORFs with conserved peptide sequences (CPuORFs), comparative genomic studies have been conducted, in which uORF sequences were compared between selected species. To increase chances of identifying CPuORFs, we previously developed an approach in which uORF sequences were compared using BLAST between Arabidopsis and any other plant species with available transcript sequence databases. If this approach is applied to multiple plant species belonging to phylogenetically distant clades, it is expected to further comprehensively identify CPuORFs conserved in various plant lineages, including those conserved among relatively small taxonomic groups. Results To efficiently compare uORF sequences among many species and efficiently identify CPuORFs conserved in various taxonomic lineages, we developed a novel pipeline, ESUCA. We applied ESUCA to the genomes of five angiosperm species, which belong to phylogenetically distant clades, and selected CPuORFs conserved among at least three different orders. Through these analyses, we identified 89 novel CPuORF families. As expected, ESUCA analysis of each of the five angiosperm genomes identified many CPuORFs that were not identified from ESUCA analyses of the other four species. However, unexpectedly, these CPuORFs include those conserved across wide taxonomic ranges, indicating that the approach used here is useful not only for comprehensive identification of narrowly conserved CPuORFs but also for that of widely conserved CPuORFs. Examination of the effects of 11 selected CPuORFs on mORF translation revealed that CPuORFs conserved only in relatively narrow taxonomic ranges can have sequence-dependent regulatory effects, suggesting that most of the identified CPuORFs are conserved because of functional constraints of their encoded peptides. Conclusions This study demonstrates that ESUCA is capable of efficiently identifying CPuORFs likely to be conserved because of the functional importance of their encoded peptides. Furthermore, our data show that the approach in which uORF sequences from multiple species are compared with those of many other species, using ESUCA, is highly effective in comprehensively identifying CPuORFs conserved in various taxonomic ranges.
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Affiliation(s)
- Hiro Takahashi
- Graduate School of Medical Sciences, Kanazawa University, Kanazawa, 920-1192, Japan. .,Graduate School of Horticulture, Chiba University, Matsudo, 271-8510, Japan.
| | - Noriya Hayashi
- Graduate School of Agriculture, Hokkaido University, Sapporo, 060-8589, Japan
| | - Yuta Hiragori
- Graduate School of Agriculture, Hokkaido University, Sapporo, 060-8589, Japan
| | - Shun Sasaki
- Graduate School of Agriculture, Hokkaido University, Sapporo, 060-8589, Japan
| | - Taichiro Motomura
- Graduate School of Medical Sciences, Kanazawa University, Kanazawa, 920-1192, Japan
| | - Yui Yamashita
- Graduate School of Agriculture, Hokkaido University, Sapporo, 060-8589, Japan
| | - Satoshi Naito
- Graduate School of Agriculture, Hokkaido University, Sapporo, 060-8589, Japan.,Graduate School of Life Science, Hokkaido University, Sapporo, 060-0810, Japan
| | - Anna Takahashi
- Faculty of Information Technologies and Control, Belarusian State University of Informatics and Radio Electronics, 220013, Minsk, Belarus
| | - Kazuyuki Fuse
- New Business Development Office, Churitsu Electric Corporation, Toyoake, 470-1112, Japan
| | - Kenji Satou
- Faculty of Biological Science and Technology, Institute of Science and Engineering, Kanazawa University, Kanazawa, 920-1192, Japan
| | - Toshinori Endo
- Graduate School of Information Science and Technology, Hokkaido University, Sapporo, 060-0814, Japan
| | - Shoko Kojima
- Graduate School of Bioscience and Biotechnology, Chubu University, Kasugai, 487-8501, Japan
| | - Hitoshi Onouchi
- Graduate School of Agriculture, Hokkaido University, Sapporo, 060-8589, Japan.
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23
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Takamatsu S, Ohashi Y, Onoue N, Tajima Y, Imamichi T, Yonezawa S, Morimoto K, Onouchi H, Yamashita Y, Naito S. Reverse genetics-based biochemical studies of the ribosomal exit tunnel constriction region in eukaryotic ribosome stalling: spatial allocation of the regulatory nascent peptide at the constriction. Nucleic Acids Res 2020; 48:1985-1999. [PMID: 31875230 PMCID: PMC7038982 DOI: 10.1093/nar/gkz1190] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2019] [Revised: 12/09/2019] [Accepted: 12/12/2019] [Indexed: 11/12/2022] Open
Abstract
A number of regulatory nascent peptides have been shown to regulate gene expression by causing programmed ribosome stalling during translation. Nascent peptide emerges from the ribosome through the exit tunnel, and one-third of the way along which β-loop structures of ribosomal proteins uL4 and uL22 protrude into the tunnel to form the constriction region. Structural studies have shown interactions between nascent peptides and the exit tunnel components including the constriction region. In eukaryotes, however, there is a lack of genetic studies for the involvement of the constriction region in ribosome stalling. Here, we established transgenic Arabidopsis lines that carry mutations in the β-loop structure of uL4. Translation analyses using a cell-free translation system derived from the transgenic Arabidopsis carrying the mutant ribosome showed that the uL4 mutations reduced the ribosome stalling of four eukaryotic stalling systems, including those for which stalled structures have been solved. Our data, which showed differential effects of the uL4 mutations depending on the stalling systems, explained the spatial allocations of the nascent peptides at the constriction that were deduced by structural studies. Conversely, our data may predict allocation of the nascent peptide at the constriction of stalling systems for which structural studies are not done.
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Affiliation(s)
- Seidai Takamatsu
- Division of Life Science, Graduate School of Life Science, Hokkaido University, Sapporo 060-0810, Japan
| | - Yubun Ohashi
- Frontiers in Biosciences, Graduate School of Agriculture, Hokkaido University, Sapporo 060-8589, Japan
| | - Noriyuki Onoue
- Division of Life Science, Graduate School of Life Science, Hokkaido University, Sapporo 060-0810, Japan
| | - Yoko Tajima
- Department of Applied Bioscience, Faculty of Agriculture, Hokkaido University, Sapporo 060-8589, Japan
| | - Tomoya Imamichi
- Division of Life Science, Graduate School of Life Science, Hokkaido University, Sapporo 060-0810, Japan
| | - Shinya Yonezawa
- Division of Life Science, Graduate School of Life Science, Hokkaido University, Sapporo 060-0810, Japan
| | - Kyoko Morimoto
- Department of Applied Bioscience, Faculty of Agriculture, Hokkaido University, Sapporo 060-8589, Japan
| | - Hitoshi Onouchi
- Frontiers in Biosciences, Graduate School of Agriculture, Hokkaido University, Sapporo 060-8589, Japan.,Department of Applied Bioscience, Faculty of Agriculture, Hokkaido University, Sapporo 060-8589, Japan.,Research Group of Applied Bioscience, Research Faculty of Agriculture, Hokkaido University, Sapporo 060-8589, Japan
| | - Yui Yamashita
- Frontiers in Biosciences, Graduate School of Agriculture, Hokkaido University, Sapporo 060-8589, Japan.,Department of Applied Bioscience, Faculty of Agriculture, Hokkaido University, Sapporo 060-8589, Japan.,Research Group of Applied Bioscience, Research Faculty of Agriculture, Hokkaido University, Sapporo 060-8589, Japan
| | - Satoshi Naito
- Division of Life Science, Graduate School of Life Science, Hokkaido University, Sapporo 060-0810, Japan.,Department of Applied Bioscience, Faculty of Agriculture, Hokkaido University, Sapporo 060-8589, Japan.,Research Group of Applied Bioscience, Research Faculty of Agriculture, Hokkaido University, Sapporo 060-8589, Japan
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24
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Function and Evolution of Upstream ORFs in Eukaryotes. Trends Biochem Sci 2019; 44:782-794. [PMID: 31003826 DOI: 10.1016/j.tibs.2019.03.002] [Citation(s) in RCA: 78] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2019] [Revised: 03/08/2019] [Accepted: 03/19/2019] [Indexed: 12/18/2022]
Abstract
There is growing interest in the role of translational regulation in cellular homeostasis during organismal development. Translation initiation is the rate-limiting step in mRNA translation and is central to translational regulation. Upstream open reading frames (uORFs) are regulatory elements that are prevalent in eukaryotic mRNAs. uORFs modulate the translation initiation rate of downstream coding sequences (CDSs) by sequestering ribosomes. Over the past several years, genome-wide studies have revealed the widespread regulatory functions of uORFs in different species in different biological contexts. Here, we review the current understanding of uORF-mediated translational regulation from the perspective of functional and evolutionary genomics and address remaining gaps that deserve further study.
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25
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van der Horst S, Snel B, Hanson J, Smeekens S. Novel pipeline identifies new upstream ORFs and non-AUG initiating main ORFs with conserved amino acid sequences in the 5' leader of mRNAs in Arabidopsis thaliana. RNA (NEW YORK, N.Y.) 2019; 25:292-304. [PMID: 30567971 PMCID: PMC6380273 DOI: 10.1261/rna.067983.118] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2018] [Accepted: 12/10/2018] [Indexed: 05/10/2023]
Abstract
Eukaryotic mRNAs contain a 5' leader sequence preceding the main open reading frame (mORF) and, depending on the species, 20%-50% of eukaryotic mRNAs harbor an upstream ORF (uORF) in the 5' leader. An unknown fraction of these uORFs encode sequence conserved peptides (conserved peptide uORFs, CPuORFs). Experimentally validated CPuORFs demonstrated to regulate the translation of downstream mORFs often do so in a metabolite concentration-dependent manner. Previous research has shown that most CPuORFs possess a start codon context suboptimal for translation initiation, which turns out to be favorable for translational regulation. The suboptimal initiation context may even include non-AUG start codons, which makes CPuORFs hard to predict. For this reason, we developed a novel pipeline to identify CPuORFs unbiased of start codon using well-annotated sequence data from 31 eudicot plant species and rice. Our new pipeline was able to identify 29 novel Arabidopsis thaliana (Arabidopsis) CPuORFs, conserved across a wide variety of eudicot species of which 15 do not initiate with an AUG start codon. In addition to CPuORFs, the pipeline was able to find 14 conserved coding regions directly upstream and in frame with the mORF, which likely initiate translation on a non-AUG start codon. Altogether, our pipeline identified highly conserved coding regions in the 5' leaders of Arabidopsis transcripts, including in genes with proven functional importance such as LHY, a key regulator of the circadian clock, and the RAPTOR1 subunit of the target of rapamycin (TOR) kinase.
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Affiliation(s)
- Sjors van der Horst
- Molecular Plant Physiology, Institute of Environmental Biology, Utrecht University, 3584 CH, Utrecht, The Netherlands
| | - Berend Snel
- Theoretical Biology and Bioinformatics, Department of Biology, Utrecht University, 3584 CH, Utrecht, The Netherlands
| | - Johannes Hanson
- Molecular Plant Physiology, Institute of Environmental Biology, Utrecht University, 3584 CH, Utrecht, The Netherlands
- Umeå Plant Science Center, Department of Plant Physiology, Umeå University, SE-901 87 Umeå, Sweden
| | - Sjef Smeekens
- Molecular Plant Physiology, Institute of Environmental Biology, Utrecht University, 3584 CH, Utrecht, The Netherlands
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26
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Shedding some blue light on alternative promoter usage in plants. Proc Natl Acad Sci U S A 2018; 115:7654-7656. [PMID: 29970421 DOI: 10.1073/pnas.1809312115] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
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27
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Transcripts from downstream alternative transcription start sites evade uORF-mediated inhibition of gene expression in Arabidopsis. Proc Natl Acad Sci U S A 2018; 115:7831-7836. [PMID: 29915080 PMCID: PMC6064979 DOI: 10.1073/pnas.1804971115] [Citation(s) in RCA: 62] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
The upstream ORFs (uORFs) in the 5′UTRs of mRNA often function as repressors of main ORF translation or triggers of nonsense-mediated mRNA decay. In this study, we report on transcription start site (TSS) selection when etiolated Arabidopsis seedlings are exposed to blue light, and reveal that transcription from uORF-avoiding TSSs is induced throughout the genome. It is possible that transcripts arising from TSSs downstream of uORFs evade uORF-mediated inhibition of gene expression. Thus, uORF-avoiding transcription starts are an important mechanism of gene expression regulation during a plant’s response to environmental changes. Plants adapt to alterations in light conditions by controlling their gene expression profiles. Expression of light-inducible genes is transcriptionally induced by transcription factors such as HY5. However, few detailed analyses have been carried out on the control of transcription start sites (TSSs). Of the various wavelengths of light, it is blue light (BL) that regulates physiological responses such as hypocotyl elongation and flowering time. To understand how gene expression is controlled not only by transcript abundance but also by TSS selection, we examined genome-wide TSS profiles in Arabidopsis seedlings after exposure to BL irradiation following initial growth in the dark. Thousands of genes use multiple TSSs, and some transcripts have upstream ORFs (uORFs) that take precedence over the main ORF (mORF) encoding proteins. The uORFs often function as translation inhibitors of the mORF or as triggers of nonsense-mediated mRNA decay (NMD). Transcription from TSSs located downstream of the uORFs in 220 genes is enhanced by BL exposure. This type of regulation is found in HY5 and HYH, major regulators of light-dependent gene expression. Translation efficiencies of the genes showing enhanced usage of these TSSs increased upon BL exposure. We also show that transcripts from TSSs upstream of uORFs in 45 of the 220 genes, including HY5, accumulated in a mutant of NMD. These results suggest that BL controls gene expression not only by enhancing transcriptions but also by choosing the TSS, and transcripts from downstream TSSs evade uORF-mediated inhibition to ensure high expression of light-regulated genes.
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28
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Srivastava AK, Lu Y, Zinta G, Lang Z, Zhu JK. UTR-Dependent Control of Gene Expression in Plants. TRENDS IN PLANT SCIENCE 2018; 23:248-259. [PMID: 29223924 PMCID: PMC5828884 DOI: 10.1016/j.tplants.2017.11.003] [Citation(s) in RCA: 115] [Impact Index Per Article: 19.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2017] [Revised: 10/25/2017] [Accepted: 11/06/2017] [Indexed: 05/22/2023]
Abstract
Throughout their lives, plants sense many developmental and environmental stimuli, and activation of optimal responses against these stimuli requires extensive transcriptional reprogramming. To facilitate this activation, plant mRNA contains untranslated regions (UTRs) that significantly increase the coding capacity of the genome by producing multiple mRNA variants from the same gene. In this review we compare UTRs of arabidopsis (Arabidopsis thaliana) and rice (Oryza sativum) at the genome scale to highlight their complexity in crop plants. We discuss different modes of UTR-based regulation with emphasis on genes that regulate multiple plant processes, including flowering, stress responses, and nutrient homeostasis. We demonstrate functional specificity in genes with variable UTR length and propose future research directions.
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Affiliation(s)
- Ashish Kumar Srivastava
- Shanghai Center for Plant Stress Biology and Center of Excellence for Molecular Plant Sciences, Chinese Academy of Sciences, Shanghai, China; Permanent address: Nuclear Agriculture and Biotechnology Division, Bhabha Atomic Research Centre, Mumbai 400085, India.
| | - Yuming Lu
- Shanghai Center for Plant Stress Biology and Center of Excellence for Molecular Plant Sciences, Chinese Academy of Sciences, Shanghai, China
| | - Gaurav Zinta
- Shanghai Center for Plant Stress Biology and Center of Excellence for Molecular Plant Sciences, Chinese Academy of Sciences, Shanghai, China
| | - Zhaobo Lang
- Shanghai Center for Plant Stress Biology and Center of Excellence for Molecular Plant Sciences, Chinese Academy of Sciences, Shanghai, China
| | - Jian-Kang Zhu
- Shanghai Center for Plant Stress Biology and Center of Excellence for Molecular Plant Sciences, Chinese Academy of Sciences, Shanghai, China; Department of Horticulture and Landscape Architecture, Purdue University, West Lafayette, IN, USA.
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29
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Ohbayashi I, Sugiyama M. Plant Nucleolar Stress Response, a New Face in the NAC-Dependent Cellular Stress Responses. FRONTIERS IN PLANT SCIENCE 2018; 8:2247. [PMID: 29375613 PMCID: PMC5767325 DOI: 10.3389/fpls.2017.02247] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2017] [Accepted: 12/21/2017] [Indexed: 05/24/2023]
Abstract
The nucleolus is the most prominent nuclear domain, where the core processes of ribosome biogenesis occur vigorously. All these processes are finely orchestrated by many nucleolar factors to build precisely ribosome particles. In animal cells, perturbations of ribosome biogenesis, mostly accompanied by structural disorders of the nucleolus, cause a kind of cellular stress to induce cell cycle arrest, senescence, or apoptosis, which is called nucleolar stress response. The best-characterized pathway of this stress response involves p53 and MDM2 as key players. p53 is a crucial transcription factor that functions in response to not only nucleolar stress but also other cellular stresses such as DNA damage stress. These cellular stresses release p53 from the inhibition by MDM2, an E3 ubiquitin ligase targeting p53, in various ways, which leads to p53-dependent activation of a set of genes. In plants, genetic impairments of ribosome biogenesis factors or ribosome components have been shown to cause characteristic phenotypes, including a narrow and pointed leaf shape, implying a common signaling pathway connecting ribosomal perturbations and certain aspects of growth and development. Unlike animals, however, plants have neither p53 nor MDM2 family proteins. Then the question arises whether plant cells have a nucleolar stress response pathway. In recent years, it has been reported that several members of the plant-specific transcription factor family NAC play critical roles in the pathways responsive to various cellular stresses. In this mini review, we outline the plant cellular stress response pathways involving NAC transcription factors with reference to the p53-MDM2-dependent pathways of animal cells, and discuss the possible involvement of a plant-unique, NAC-mediated pathway in the nucleolar stress response in plants.
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Affiliation(s)
- Iwai Ohbayashi
- FAFU-UCR Joint Center and Fujian Provincial Key Laboratory of Haixia Applied Plant Systems Biology, Haixia Institute of Science and Technology, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Munetaka Sugiyama
- Botanical Gardens, Graduate School of Science, The University of Tokyo, Tokyo, Japan
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30
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Hayashi N, Sasaki S, Takahashi H, Yamashita Y, Naito S, Onouchi H. Identification of Arabidopsis thaliana upstream open reading frames encoding peptide sequences that cause ribosomal arrest. Nucleic Acids Res 2017. [PMID: 28637336 PMCID: PMC5587730 DOI: 10.1093/nar/gkx528] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Specific sequences of certain nascent peptides cause programmed ribosomal arrest during mRNA translation to control gene expression. In eukaryotes, most known regulatory arrest peptides are encoded by upstream open reading frames (uORFs) present in the 5′-untranslated region of mRNAs. However, to date, a limited number of eukaryotic uORFs encoding arrest peptides have been reported. Here, we searched for arrest peptide-encoding uORFs among Arabidopsis thaliana uORFs with evolutionarily conserved peptide sequences. Analysis of in vitro translation products of 22 conserved uORFs identified three novel uORFs causing ribosomal arrest in a peptide sequence-dependent manner. Stop codon-scanning mutagenesis, in which the effect of changing the uORF stop codon position on the ribosomal arrest was examined, and toeprint analysis revealed that two of the three uORFs cause ribosomal arrest during translation elongation, whereas the other one causes ribosomal arrest during translation termination. Transient expression assays showed that the newly identified arrest-causing uORFs exerted a strong sequence-dependent repressive effect on the expression of the downstream reporter gene in A. thaliana protoplasts. These results suggest that the peptide sequences of the three uORFs identified in this study cause ribosomal arrest in the uORFs, thereby repressing the expression of proteins encoded by the main ORFs.
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Affiliation(s)
- Noriya Hayashi
- Graduate School of Agriculture, Hokkaido University, Sapporo 060-8589, Japan
| | - Shun Sasaki
- Graduate School of Agriculture, Hokkaido University, Sapporo 060-8589, Japan
| | - Hiro Takahashi
- Graduate School of Horticulture, Chiba University, Chiba 263-8522, Japan
| | - Yui Yamashita
- Graduate School of Agriculture, Hokkaido University, Sapporo 060-8589, Japan
| | - Satoshi Naito
- Graduate School of Agriculture, Hokkaido University, Sapporo 060-8589, Japan.,Graduate School of Life Science, Hokkaido University, Sapporo 060-0810, Japan
| | - Hitoshi Onouchi
- Graduate School of Agriculture, Hokkaido University, Sapporo 060-8589, Japan
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31
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Abstract
A large body of evidence indicates that genome annotation pipelines have biased our view of coding sequences because they generally undersample small proteins and peptides. The recent development of genome-wide translation profiling reveals the prevalence of small/short open reading frames (smORFs or sORFs), which are scattered over all classes of transcripts, including both mRNAs and presumptive long noncoding RNAs. Proteomic approaches further confirm an unexpected variety of smORF-encoded peptides (SEPs), representing an overlooked reservoir of bioactive molecules. Indeed, functional studies in a broad range of species from yeast to humans demonstrate that SEPs can harbor key activities for the control of development, differentiation, and physiology. Here we summarize recent advances in the discovery and functional characterization of smORF/SEPs and discuss why these small players can no longer be ignored with regard to genome function.
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Affiliation(s)
- Serge Plaza
- Laboratoire de Recherches en Sciences Végétales, Université de Toulouse, Université Paul Sabatier, 31326 Castanet Tolosan, France; .,CNRS, UMR5546, Laboratoire de Recherches en Sciences Végétales, 31326 Castanet Tolosan, France
| | - Gerben Menschaert
- Department of Mathematical Modeling, Statistics and Bioinformatics, University of Ghent, 9000 Gent, Belgium
| | - François Payre
- Centre de Biologie du Développement, Centre de Biologie Intégrative, Université de Toulouse, CNRS, Université Paul Sabatier, 31062 Toulouse, France;
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32
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Merchante C, Stepanova AN, Alonso JM. Translation regulation in plants: an interesting past, an exciting present and a promising future. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2017; 90:628-653. [PMID: 28244193 DOI: 10.1111/tpj.13520] [Citation(s) in RCA: 108] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/29/2016] [Revised: 02/17/2017] [Accepted: 02/21/2017] [Indexed: 05/19/2023]
Abstract
Changes in gene expression are at the core of most biological processes, from cell differentiation to organ development, including the adaptation of the whole organism to the ever-changing environment. Although the central role of transcriptional regulation is solidly established and the general mechanisms involved in this type of regulation are relatively well understood, it is clear that regulation at a translational level also plays an essential role in modulating gene expression. Despite the large number of examples illustrating the critical role played by translational regulation in determining the expression levels of a gene, our understanding of the molecular mechanisms behind such types of regulation has been slow to emerge. With the recent development of high-throughput approaches to map and quantify different critical parameters affecting translation, such as RNA structure, protein-RNA interactions and ribosome occupancy at the genome level, a renewed enthusiasm toward studying translation regulation is warranted. The use of these new powerful technologies in well-established and uncharacterized translation-dependent processes holds the promise to decipher the likely complex and diverse, but also fascinating, mechanisms behind the regulation of translation.
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Affiliation(s)
- Catharina Merchante
- Departamento de Biologia Molecular y Bioquimica, Universidad de Malaga-Instituto de Hortofruticultura Subtropical y Mediterranea, IHSM-UMA-CSIC, Malaga, Andalucía, Spain
| | - Anna N Stepanova
- Department of Plant and Microbial Biology, Genetics Graduate Program, North Carolina State University, Raleigh, NC, 27607, USA
| | - Jose M Alonso
- Department of Plant and Microbial Biology, Genetics Graduate Program, North Carolina State University, Raleigh, NC, 27607, USA
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33
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Yamashita Y, Takamatsu S, Glasbrenner M, Becker T, Naito S, Beckmann R. Sucrose sensing through nascent peptide-meditated ribosome stalling at the stop codon of Arabidopsis bZIP11 uORF2. FEBS Lett 2017; 591:1266-1277. [PMID: 28369795 DOI: 10.1002/1873-3468.12634] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2017] [Revised: 03/14/2017] [Accepted: 03/21/2017] [Indexed: 11/10/2022]
Abstract
Arabidopsis bZIP11 is a transcription factor that modulates amino acid metabolism under high-sucrose conditions. Expression of bZIP11 is downregulated in a sucrose-dependent manner during translation. Previous in vivo studies have identified the second upstream open reading frame (uORF2) as an essential regulatory element for the sucrose-dependent translational repression of bZIP11. However, it remains unclear how uORF2 represses bZIP11 expression under high-sucrose conditions. Through biochemical experiments using cell-free translation systems, we report on sucrose-mediated ribosome stalling at the stop codon of uORF2. The C-terminal 10 amino acids (29-SFSVxFLxxLYYV-41) of uORF2 are important for ribosome stalling. Our results demonstrate that uORF2 encodes a regulatory nascent peptide that functions to sense intracellular sucrose abundance. This is the first biochemical identification of the intracellular sucrose sensor.
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Affiliation(s)
- Yui Yamashita
- Gene Center, Department of Biochemistry and Center for integrated Protein Science Munich (CiPSM), Ludwig-Maximilians-Universität München, Germany
| | - Seidai Takamatsu
- Graduate School of Life Science, Hokkaido University, Sapporo, Japan
| | - Michael Glasbrenner
- Gene Center, Department of Biochemistry and Center for integrated Protein Science Munich (CiPSM), Ludwig-Maximilians-Universität München, Germany
| | - Thomas Becker
- Gene Center, Department of Biochemistry and Center for integrated Protein Science Munich (CiPSM), Ludwig-Maximilians-Universität München, Germany
| | - Satoshi Naito
- Graduate School of Life Science, Hokkaido University, Sapporo, Japan.,Graduate School of Agriculture, Hokkaido University, Sapporo, Japan
| | - Roland Beckmann
- Gene Center, Department of Biochemistry and Center for integrated Protein Science Munich (CiPSM), Ludwig-Maximilians-Universität München, Germany
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34
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Guerrero-González MDLL, Ortega-Amaro MA, Juárez-Montiel M, Jiménez-Bremont JF. Arabidopsis Polyamine oxidase-2 uORF is required for downstream translational regulation. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2016; 108:381-390. [PMID: 27526386 DOI: 10.1016/j.plaphy.2016.08.006] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2016] [Revised: 08/04/2016] [Accepted: 08/04/2016] [Indexed: 05/10/2023]
Abstract
In eukaryotic mRNAs, small upstream open reading frames (uORFs) located in the 5'-untranslated region control the translation of the downstream main ORF. Polyamine oxidase (PAO) enzymes catalyze the oxidation of higher polyamines such as spermidine and spermine, and therefore contribute to the maintenance of intracellular polyamine content and to the regulation of physiological processes through their catabolic products. Recently, we reported that the Arabidopsis thaliana Polyamine Oxidase 2 (AtPAO2) is post-transcriptionally regulated by its 5'-UTR region through an uORF. In the present study, we analyzed whether the translation of the uORF is needed for the translational repression of the main ORF, and whether the inactivation of the uORF had an effect on the translational control mediated by polyamines. To this aim, we generated diverse single mutations in the uORF sequence; these mutant 5'-UTRs were fused to the GUS reporter gene, and tested in onion monolayer cells and A. thaliana transgenic seedlings. Removal of the start codon or introduction of a premature stop codon in the AtPAO2 uORF sequence abolished the negative regulation of the GUS expression exerted by the wild-type AtPAO2 uORF. An artificial uORF (32 amino acids in length) generated by the addition of a single nucleotide in AtPAO2 uORF proved to be less repressive than the wild-type uORF. Thus, our findings suggest that translation of the AtPAO2 uORF is necessary for the translational repression of the main ORF.
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Affiliation(s)
| | - María Azucena Ortega-Amaro
- Instituto Potosino de Investigación Científica y Tecnológica AC, División de Biología Molecular, San Luis Potosí, Mexico
| | - Margarita Juárez-Montiel
- Instituto Potosino de Investigación Científica y Tecnológica AC, División de Biología Molecular, San Luis Potosí, Mexico
| | - Juan Francisco Jiménez-Bremont
- Instituto Potosino de Investigación Científica y Tecnológica AC, División de Biología Molecular, San Luis Potosí, Mexico.
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35
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Hellens RP, Brown CM, Chisnall MAW, Waterhouse PM, Macknight RC. The Emerging World of Small ORFs. TRENDS IN PLANT SCIENCE 2016; 21:317-328. [PMID: 26684391 DOI: 10.1016/j.tplants.2015.11.005] [Citation(s) in RCA: 72] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2015] [Revised: 10/23/2015] [Accepted: 11/05/2015] [Indexed: 05/10/2023]
Abstract
Small open reading frames (sORFs) are an often overlooked feature of plant genomes. Initially found in plant viral RNAs and considered an interesting curiosity, an increasing number of these sORFs have been shown to encode functional peptides or play a regulatory role. The recent discovery that many of these sORFs initiate with start codons other than AUG, together with the identification of functional small peptides encoded in supposedly noncoding primary miRNA transcripts (pri-miRs), has drastically increased the number of potentially functional sORFs within the genome. Here we review how advances in technology, notably ribosome profiling (RP) assays, are complementing bioinformatics and proteogenomic methods to provide powerful ways to identify these elusive features of plant genomes, and highlight the regulatory roles sORFs can play.
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Affiliation(s)
- Roger P Hellens
- Centre for Tropical Crops and Biocommodities, Queensland University of Technology, GPO Box 2434, Brisbane, QLD 4001, Australia
| | - Chris M Brown
- Department of Biochemistry, University of Otago, PO Box 56, Dunedin 9054, New Zealand
| | - Matthew A W Chisnall
- Department of Biochemistry, University of Otago, PO Box 56, Dunedin 9054, New Zealand
| | - Peter M Waterhouse
- Centre for Tropical Crops and Biocommodities, Queensland University of Technology, GPO Box 2434, Brisbane, QLD 4001, Australia
| | - Richard C Macknight
- Department of Biochemistry, University of Otago, PO Box 56, Dunedin 9054, New Zealand; New Zealand Institute for Plant and Food Research Ltd.
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36
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Lei L, Shi J, Chen J, Zhang M, Sun S, Xie S, Li X, Zeng B, Peng L, Hauck A, Zhao H, Song W, Fan Z, Lai J. Ribosome profiling reveals dynamic translational landscape in maize seedlings under drought stress. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2015; 84:1206-18. [PMID: 26568274 DOI: 10.1111/tpj.13073] [Citation(s) in RCA: 115] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/11/2015] [Revised: 10/30/2015] [Accepted: 11/09/2015] [Indexed: 05/19/2023]
Abstract
Plants can respond to environmental changes with various mechanisms occurred at transcriptional and translational levels. Thus far, there have been relatively extensive understandings of stress responses of plants on transcriptional level, while little information is known about that on translational level. To uncover the landscape of translation in plants in response to drought stress, we performed the recently developed ribosome profiling assay with maize seedlings growing under normal and drought conditions. Comparative analysis of the ribosome profiling data and the RNA-seq data showed that the fold changes of gene expression at transcriptional level were moderately correlated with that of translational level globally (R(2) = 0.69). However, less than half of the responsive genes were shared by transcription and translation under drought condition, suggesting that drought stress can introduce transcriptional and translational responses independently. We found that the translational efficiencies of 931 genes were changed significantly in response to drought stress. Further analysis revealed that the translational efficiencies of genes were highly influenced by their sequence features including GC content, length of coding sequences and normalized minimal free energy. In addition, we detected potential translation of 3063 upstream open reading frames (uORFs) on 2558 genes and these uORFs may affect the translational efficiency of downstream main open reading frames (ORFs). Our study indicates that plant can respond to drought stress with highly dynamic translational mechanism, that acting synergistically with that of transcription.
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Affiliation(s)
- Lei Lei
- State Key Laboratory of Agrobiotechnology and National Maize Improvement Center, Department of Plant Genetics and Breeding, China Agricultural University, Beijing, 100193, China
- State Key Laboratory of Agrobiotechnology and Department of Plant Pathology, China Agricultural University, Beijing, 100193, China
| | - Junpeng Shi
- State Key Laboratory of Agrobiotechnology and National Maize Improvement Center, Department of Plant Genetics and Breeding, China Agricultural University, Beijing, 100193, China
| | - Jian Chen
- State Key Laboratory of Agrobiotechnology and National Maize Improvement Center, Department of Plant Genetics and Breeding, China Agricultural University, Beijing, 100193, China
| | - Mei Zhang
- State Key Laboratory of Agrobiotechnology and National Maize Improvement Center, Department of Plant Genetics and Breeding, China Agricultural University, Beijing, 100193, China
| | - Silong Sun
- State Key Laboratory of Agrobiotechnology and National Maize Improvement Center, Department of Plant Genetics and Breeding, China Agricultural University, Beijing, 100193, China
| | - Shaojun Xie
- State Key Laboratory of Agrobiotechnology and National Maize Improvement Center, Department of Plant Genetics and Breeding, China Agricultural University, Beijing, 100193, China
| | - Xiaojie Li
- State Key Laboratory of Agrobiotechnology and National Maize Improvement Center, Department of Plant Genetics and Breeding, China Agricultural University, Beijing, 100193, China
| | - Biao Zeng
- State Key Laboratory of Agrobiotechnology and National Maize Improvement Center, Department of Plant Genetics and Breeding, China Agricultural University, Beijing, 100193, China
| | - Lizeng Peng
- State Key Laboratory of Agrobiotechnology and National Maize Improvement Center, Department of Plant Genetics and Breeding, China Agricultural University, Beijing, 100193, China
| | - Andrew Hauck
- State Key Laboratory of Agrobiotechnology and National Maize Improvement Center, Department of Plant Genetics and Breeding, China Agricultural University, Beijing, 100193, China
| | - Haiming Zhao
- State Key Laboratory of Agrobiotechnology and National Maize Improvement Center, Department of Plant Genetics and Breeding, China Agricultural University, Beijing, 100193, China
| | - Weibin Song
- State Key Laboratory of Agrobiotechnology and National Maize Improvement Center, Department of Plant Genetics and Breeding, China Agricultural University, Beijing, 100193, China
| | - Zaifeng Fan
- State Key Laboratory of Agrobiotechnology and Department of Plant Pathology, China Agricultural University, Beijing, 100193, China
| | - Jinsheng Lai
- State Key Laboratory of Agrobiotechnology and National Maize Improvement Center, Department of Plant Genetics and Breeding, China Agricultural University, Beijing, 100193, China
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Shaul O. Unique Aspects of Plant Nonsense-Mediated mRNA Decay. TRENDS IN PLANT SCIENCE 2015; 20:767-779. [PMID: 26442679 DOI: 10.1016/j.tplants.2015.08.011] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/25/2015] [Revised: 08/17/2015] [Accepted: 08/20/2015] [Indexed: 05/20/2023]
Abstract
Nonsense-mediated mRNA Decay (NMD) is a eukaryotic quality-control mechanism that governs the stability of both aberrant and normal transcripts. Although plant and mammalian NMD share great similarity, they differ in certain mechanistic and regulatory aspects. Whereas SMG6 (from Caenorhabditis elegans 'suppressor with morphogenetic effect on genitalia')-catalyzed endonucleolytic cleavage is a prominent step in mammalian NMD, plant NMD targets are degraded by an SMG7-induced exonucleolytic pathway. Both mammalian and plant NMD are downregulated by stress, thereby enhancing the expression of defense response genes. However, the target genes and processes affected differ. Several plant and mammalian NMD factors are regulated by negative feedback-loops. However, while the loop regulating UPF3 (up-frameshift 3) expression in not vital for mammalian NMD, the sensitivity of UPF3 to NMD is crucial for the overall regulation of plant NMD.
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Affiliation(s)
- Orit Shaul
- The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 5290002, Israel.
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Ebina I, Takemoto-Tsutsumi M, Watanabe S, Koyama H, Endo Y, Kimata K, Igarashi T, Murakami K, Kudo R, Ohsumi A, Noh AL, Takahashi H, Naito S, Onouchi H. Identification of novel Arabidopsis thaliana upstream open reading frames that control expression of the main coding sequences in a peptide sequence-dependent manner. Nucleic Acids Res 2015; 43:1562-76. [PMID: 25618853 PMCID: PMC4330380 DOI: 10.1093/nar/gkv018] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Upstream open reading frames (uORFs) are often found in the 5'-leader regions of eukaryotic mRNAs and can negatively modulate the translational efficiency of the downstream main ORF. Although the effects of most uORFs are thought to be independent of their encoded peptide sequences, certain uORFs control translation of the main ORF in a peptide sequence-dependent manner. For genome-wide identification of such peptide sequence-dependent regulatory uORFs, exhaustive searches for uORFs with conserved amino acid sequences have been conducted using bioinformatic analyses. However, whether the conserved uORFs identified by these bioinformatic approaches encode regulatory peptides has not been experimentally determined. Here we analyzed 16 recently identified Arabidopsis thaliana conserved uORFs for the effects of their amino acid sequences on the expression of the main ORF using a transient expression assay. We identified five novel uORFs that repress main ORF expression in a peptide sequence-dependent manner. Mutational analysis revealed that, in four of them, the C-terminal region of the uORF-encoded peptide is critical for the repression of main ORF expression. Intriguingly, we also identified one exceptional sequence-dependent regulatory uORF, in which the stop codon position is not conserved and the C-terminal region is not important for the repression of main ORF expression.
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Affiliation(s)
- Isao Ebina
- Graduate School of Life Science, Hokkaido University, Sapporo 060-0810, Japan
| | | | - Shun Watanabe
- Graduate School of Life Science, Hokkaido University, Sapporo 060-0810, Japan
| | - Hiroaki Koyama
- Graduate School of Agriculture, Hokkaido University, Sapporo 060-8589, Japan
| | - Yayoi Endo
- Faculty of Agriculture, Hokkaido University, Sapporo 060-8589, Japan
| | - Kaori Kimata
- Graduate School of Agriculture, Hokkaido University, Sapporo 060-8589, Japan
| | - Takuya Igarashi
- Graduate School of Agriculture, Hokkaido University, Sapporo 060-8589, Japan
| | - Karin Murakami
- Graduate School of Agriculture, Hokkaido University, Sapporo 060-8589, Japan
| | - Rin Kudo
- Graduate School of Agriculture, Hokkaido University, Sapporo 060-8589, Japan
| | - Arisa Ohsumi
- Graduate School of Agriculture, Hokkaido University, Sapporo 060-8589, Japan
| | - Abdul Latif Noh
- Graduate School of Agriculture, Hokkaido University, Sapporo 060-8589, Japan
| | - Hiro Takahashi
- Graduate School of Horticulture, Chiba University, Matsudo 271-8510, Japan
| | - Satoshi Naito
- Graduate School of Life Science, Hokkaido University, Sapporo 060-0810, Japan Graduate School of Agriculture, Hokkaido University, Sapporo 060-8589, Japan
| | - Hitoshi Onouchi
- Graduate School of Agriculture, Hokkaido University, Sapporo 060-8589, Japan
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Celik A, Kervestin S, Jacobson A. NMD: At the crossroads between translation termination and ribosome recycling. Biochimie 2014; 114:2-9. [PMID: 25446649 DOI: 10.1016/j.biochi.2014.10.027] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2014] [Accepted: 10/27/2014] [Indexed: 10/24/2022]
Abstract
Nonsense-mediated mRNA decay (NMD) is one of three regulatory mechanisms that monitor the cytoplasm for aberrant mRNAs. NMD is usually triggered by premature translation termination codons that arise from mutations, transcription errors, or inefficient splicing, but which also occur in transcripts with alternately spliced isoforms or upstream open reading frames, or in the context of long 3'-UTRs. This surveillance pathway requires detection of the nonsense codon by the eukaryotic release factors (eRF1 and eRF3) and the activities of the Upf proteins, but the exact mechanism by which a nonsense codon is recognized as premature, and the individual roles of the Upf proteins, are poorly understood. In this review, we highlight important differences between premature and normal termination. Based on our current understanding of normal termination and ribosome recycling, we propose a similar mechanism for premature termination events that includes a role for the Upf proteins. In this model, the Upf proteins not only target the mRNA and nascent peptide for degradation, but also assume the role of recycling factors and rescue a ribosome stalled at a premature nonsense codon. The ATPase and helicase activities of Upf1, with the help of Upf2 and Upf3, are thus thought to be the catalytic force in ribosome subunit dissociation and ribosome recycling at an otherwise poorly dissociable termination event. While this model is somewhat speculative, it provides a unified vision for current data and a direction for future research.
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Affiliation(s)
- Alper Celik
- Department of Microbiology and Physiological Systems, University of Massachusetts Medical School, 368 Plantation Street, Worcester, MA 01655-0122, USA
| | - Stephanie Kervestin
- CNRS FRE3630 Associated with Université Diderot, Sorbonne Paris Cité, Institut de Biologie Physico-Chimique, 75005 Paris, France
| | - Allan Jacobson
- Department of Microbiology and Physiological Systems, University of Massachusetts Medical School, 368 Plantation Street, Worcester, MA 01655-0122, USA.
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