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Bhattacharya A, Renault TT, Innis CA. The ribosome as a small-molecule sensor. Curr Opin Microbiol 2024; 77:102418. [PMID: 38159358 DOI: 10.1016/j.mib.2023.102418] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2023] [Revised: 12/04/2023] [Accepted: 12/05/2023] [Indexed: 01/03/2024]
Abstract
Sensing small molecules is crucial for microorganisms to adapt their genetic programs to changes in their environment. Arrest peptides encoded by short regulatory open reading frames program the ribosomes that translate them to undergo translational arrest in response to specific metabolites. Ribosome stalling in turn controls the expression of downstream genes on the same messenger RNA by translational or transcriptional means. In this review, we present our current understanding of the mechanisms by which ribosomes translating arrest peptides sense different metabolites, such as antibiotics or amino acids, to control gene expression.
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Affiliation(s)
- Arunima Bhattacharya
- Univ. Bordeaux, Centre National de la Recherche Scientifique, Institut National de la Santé et de la Recherche Médicale, ARNA, UMR 5320, U1212, Institut Européen de Chimie et Biologie, F-33600 Pessac, France
| | - Thibaud T Renault
- Univ. Bordeaux, Centre National de la Recherche Scientifique, Institut National de la Santé et de la Recherche Médicale, ARNA, UMR 5320, U1212, Institut Européen de Chimie et Biologie, F-33600 Pessac, France
| | - C Axel Innis
- Univ. Bordeaux, Centre National de la Recherche Scientifique, Institut National de la Santé et de la Recherche Médicale, ARNA, UMR 5320, U1212, Institut Européen de Chimie et Biologie, F-33600 Pessac, France.
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2
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Chen YH, Lu J, Yang X, Huang LC, Zhang CQ, Liu QQ, Li QF. Gene editing of non-coding regulatory DNA and its application in crop improvement. JOURNAL OF EXPERIMENTAL BOTANY 2023; 74:6158-6175. [PMID: 37549968 DOI: 10.1093/jxb/erad313] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/23/2023] [Accepted: 08/04/2023] [Indexed: 08/09/2023]
Abstract
The development of the clustered regularly interspaced short palindromic repeats/CRISPR-associated protein (CRISPR/Cas) system has provided precise and efficient strategies to edit target genes and generate transgene-free crops. Significant progress has been made in the editing of protein-coding genes; however, studies on the editing of non-coding DNA with regulatory roles lags far behind. Non-coding regulatory DNAs, including those which can be transcribed into long non-coding RNAs (lncRNAs), and miRNAs, together with cis-regulatory elements (CREs), play crucial roles in regulating plant growth and development. Therefore, the combination of CRISPR/Cas technology and non-coding regulatory DNA has great potential to generate novel alleles that affect various agronomic traits of crops, thus providing valuable genetic resources for crop breeding. Herein, we review recent advances in the roles of non-coding regulatory DNA, attempts to edit non-coding regulatory DNA for crop improvement, and potential application of novel editing tools in modulating non-coding regulatory DNA. Finally, the existing problems, possible solutions, and future applications of gene editing of non-coding regulatory DNA in modern crop breeding practice are also discussed.
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Affiliation(s)
- Yu-Hao Chen
- Jiangsu Key Laboratory of Crop Genomics and Molecular Breeding/Key Laboratory of Plant Functional Genomics of the Ministry of Education, College of Agriculture, Yangzhou University, Yangzhou 225009, Jiangsu, China
| | - Jun Lu
- Jiangsu Key Laboratory of Crop Genomics and Molecular Breeding/Key Laboratory of Plant Functional Genomics of the Ministry of Education, College of Agriculture, Yangzhou University, Yangzhou 225009, Jiangsu, China
| | - Xia Yang
- Jiangsu Key Laboratory of Crop Genomics and Molecular Breeding/Key Laboratory of Plant Functional Genomics of the Ministry of Education, College of Agriculture, Yangzhou University, Yangzhou 225009, Jiangsu, China
| | - Li-Chun Huang
- Jiangsu Key Laboratory of Crop Genomics and Molecular Breeding/Key Laboratory of Plant Functional Genomics of the Ministry of Education, College of Agriculture, Yangzhou University, Yangzhou 225009, Jiangsu, China
| | - Chang-Quan Zhang
- Jiangsu Key Laboratory of Crop Genomics and Molecular Breeding/Key Laboratory of Plant Functional Genomics of the Ministry of Education, College of Agriculture, Yangzhou University, Yangzhou 225009, Jiangsu, China
| | - Qiao-Quan Liu
- Jiangsu Key Laboratory of Crop Genomics and Molecular Breeding/Key Laboratory of Plant Functional Genomics of the Ministry of Education, College of Agriculture, Yangzhou University, Yangzhou 225009, Jiangsu, China
- Co-Innovation Center for Modern Production Technology of Grain Crops of Jiangsu Province, Yangzhou University, Yangzhou 225009, Jiangsu, China
| | - Qian-Feng Li
- Jiangsu Key Laboratory of Crop Genomics and Molecular Breeding/Key Laboratory of Plant Functional Genomics of the Ministry of Education, College of Agriculture, Yangzhou University, Yangzhou 225009, Jiangsu, China
- Co-Innovation Center for Modern Production Technology of Grain Crops of Jiangsu Province, Yangzhou University, Yangzhou 225009, Jiangsu, China
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3
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Höpfler M, Hegde RS. Control of mRNA fate by its encoded nascent polypeptide. Mol Cell 2023; 83:2840-2855. [PMID: 37595554 PMCID: PMC10501990 DOI: 10.1016/j.molcel.2023.07.014] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2023] [Revised: 07/03/2023] [Accepted: 07/11/2023] [Indexed: 08/20/2023]
Abstract
Cells tightly regulate mRNA processing, localization, and stability to ensure accurate gene expression in diverse cellular states and conditions. Most of these regulatory steps have traditionally been thought to occur before translation by the action of RNA-binding proteins. Several recent discoveries highlight multiple co-translational mechanisms that modulate mRNA translation, localization, processing, and stability. These mechanisms operate by recognition of the nascent protein, which is necessarily coupled to its encoding mRNA during translation. Hence, the distinctive sequence or structure of a particular nascent chain can recruit recognition factors with privileged access to the corresponding mRNA in an otherwise crowded cellular environment. Here, we draw on both well-established and recent examples to provide a conceptual framework for how cells exploit nascent protein recognition to direct mRNA fate. These mechanisms allow cells to dynamically and specifically regulate their transcriptomes in response to changes in cellular states to maintain protein homeostasis.
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4
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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: 46] [Impact Index Per Article: 11.5] [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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5
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Renz PF, Valdivia-Francia F, Sendoel A. Some like it translated: small ORFs in the 5'UTR. Exp Cell Res 2020; 396:112229. [PMID: 32818479 DOI: 10.1016/j.yexcr.2020.112229] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2020] [Revised: 07/28/2020] [Accepted: 08/07/2020] [Indexed: 01/06/2023]
Abstract
The 5' untranslated region (5'UTR) is critical in determining post-transcriptional control, which is partly mediated by short upstream open reading frames (uORFs) present in half of mammalian transcripts. uORFs are generally considered to provide functionally important repression of the main-ORF by engaging initiating ribosomes, but under specific environmental conditions such as cellular stress, uORFs can become essential to activate the translation of the main coding sequence. In addition, a growing number of uORF-encoded bioactive microproteins have been described, which have the potential to significantly increase cellular protein diversity. Here we review the diverse cellular contexts in which uORFs play a critical role and discuss the molecular mechanisms underlying their function and regulation. The progress over the last decades in dissecting uORF function suggests that the 5'UTR remains an exciting frontier towards understanding how the cellular proteome is shaped in health and disease.
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Affiliation(s)
- Peter F Renz
- Institute for Regenerative Medicine (IREM), University of Zurich, Wagistrasse 12, CH-8952 Schlieren, Switzerland
| | - Fabiola Valdivia-Francia
- Institute for Regenerative Medicine (IREM), University of Zurich, Wagistrasse 12, CH-8952 Schlieren, Switzerland; Life Science Zurich Graduate School, Molecular Life Science Program, University of Zurich/ ETH Zurich, Switzerland
| | - Ataman Sendoel
- Institute for Regenerative Medicine (IREM), University of Zurich, Wagistrasse 12, CH-8952 Schlieren, Switzerland.
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6
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Lin Y, May GE, Kready H, Nazzaro L, Mao M, Spealman P, Creeger Y, McManus CJ. Impacts of uORF codon identity and position on translation regulation. Nucleic Acids Res 2019; 47:9358-9367. [PMID: 31392980 PMCID: PMC6755093 DOI: 10.1093/nar/gkz681] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2019] [Revised: 07/15/2019] [Accepted: 07/25/2019] [Indexed: 01/03/2023] Open
Abstract
Translation regulation plays an important role in eukaryotic gene expression. Upstream open reading frames (uORFs) are potent regulatory elements located in 5′ mRNA transcript leaders. Translation of uORFs usually inhibit the translation of downstream main open reading frames, but some enhance expression. While a minority of uORFs encode conserved functional peptides, the coding regions of most uORFs are not conserved. Thus, the importance of uORF coding sequences on their regulatory functions remains largely unknown. We investigated the impact of an uORF coding region on gene regulation by assaying the functions of thousands of variants in the yeast YAP1 uORF. Varying uORF codons resulted in a wide range of functions, including repressing and enhancing expression of the downstream ORF. The presence of rare codons resulted in the most inhibitory YAP1 uORF variants. Inhibitory functions of such uORFs were abrogated by overexpression of complementary tRNA. Finally, regression analysis of our results indicated that both codon identity and position impact uORF function. Our results support a model in which a uORF coding sequence impacts its regulatory functions by altering the speed of uORF translation.
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Affiliation(s)
- Yizhu Lin
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, PA 15213, USA.,Department of Cell and Tissue Biology, University of California, San Francisco, CA 94143, USA
| | - Gemma E May
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, PA 15213, USA
| | - Hunter Kready
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, PA 15213, USA
| | - Lauren Nazzaro
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, PA 15213, USA
| | - Mao Mao
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, PA 15213, USA.,Roche Sequencing Solutions, Santa Clara, CA 95050, USA
| | - Pieter Spealman
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, PA 15213, USA.,Center for Genomics and Systems Biology, New York University, New York, NY 10003, USA
| | - Yehuda Creeger
- Molecular Biosensor and Imaging Center, Carnegie Mellon University, Pittsburgh, PA 15213, USA
| | - C Joel McManus
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, PA 15213, USA.,Computational Biology Department, Carnegie Mellon University, Pittsburgh, PA 15213, USA
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7
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Seip B, Sacheau G, Dupuy D, Innis CA. Ribosomal stalling landscapes revealed by high-throughput inverse toeprinting of mRNA libraries. Life Sci Alliance 2018; 1:e201800148. [PMID: 30456383 PMCID: PMC6238534 DOI: 10.26508/lsa.201800148] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2018] [Revised: 09/25/2018] [Accepted: 09/27/2018] [Indexed: 11/24/2022] Open
Abstract
High-throughput inverse toeprinting identifies peptide-encoding transcripts that induce ribosome stalling and allows the systematic analysis of sequence-dependent translational events. Although it is known that the amino acid sequence of a nascent polypeptide can impact its rate of translation, dedicated tools to systematically investigate this process are lacking. Here, we present high-throughput inverse toeprinting, a method to identify peptide-encoding transcripts that induce ribosomal stalling in vitro. Unlike ribosome profiling, inverse toeprinting protects the entire coding region upstream of a stalled ribosome, making it possible to work with random or focused transcript libraries that efficiently sample the sequence space. We used inverse toeprinting to characterize the stalling landscapes of free and drug-bound Escherichia coli ribosomes, obtaining a comprehensive list of arrest motifs that were validated in vivo, along with a quantitative measure of their pause strength. Thanks to the modest sequencing depth and small amounts of material required, inverse toeprinting provides a highly scalable and versatile tool to study sequence-dependent translational processes.
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Affiliation(s)
- Britta Seip
- Institut Européen de Chimie et Biologie, Université de Bordeaux, Institut National de la Santé et de la Recherche Médicale and Centre National de la Recherche Scientifique, Pessac, France
| | - Guénaël Sacheau
- Institut Européen de Chimie et Biologie, Université de Bordeaux, Institut National de la Santé et de la Recherche Médicale and Centre National de la Recherche Scientifique, Pessac, France
| | - Denis Dupuy
- Institut Européen de Chimie et Biologie, Université de Bordeaux, Institut National de la Santé et de la Recherche Médicale and Centre National de la Recherche Scientifique, Pessac, France
| | - C Axel Innis
- Institut Européen de Chimie et Biologie, Université de Bordeaux, Institut National de la Santé et de la Recherche Médicale and Centre National de la Recherche Scientifique, Pessac, France
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8
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Li S, Breaker RR. Identification of 15 candidate structured noncoding RNA motifs in fungi by comparative genomics. BMC Genomics 2017; 18:785. [PMID: 29029611 PMCID: PMC5640933 DOI: 10.1186/s12864-017-4171-y] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2017] [Accepted: 10/05/2017] [Indexed: 12/28/2022] Open
Abstract
BACKGROUND With the development of rapid and inexpensive DNA sequencing, the genome sequences of more than 100 fungal species have been made available. This dataset provides an excellent resource for comparative genomics analyses, which can be used to discover genetic elements, including noncoding RNAs (ncRNAs). Bioinformatics tools similar to those used to uncover novel ncRNAs in bacteria, likewise, should be useful for searching fungal genomic sequences, and the relative ease of genetic experiments with some model fungal species could facilitate experimental validation studies. RESULTS We have adapted a bioinformatics pipeline for discovering bacterial ncRNAs to systematically analyze many fungal genomes. This comparative genomics pipeline integrates information on conserved RNA sequence and structural features with alternative splicing information to reveal fungal RNA motifs that are candidate regulatory domains, or that might have other possible functions. A total of 15 prominent classes of structured ncRNA candidates were identified, including variant HDV self-cleaving ribozyme representatives, atypical snoRNA candidates, and possible structured antisense RNA motifs. Candidate regulatory motifs were also found associated with genes for ribosomal proteins, S-adenosylmethionine decarboxylase (SDC), amidase, and HexA protein involved in Woronin body formation. We experimentally confirm that the variant HDV ribozymes undergo rapid self-cleavage, and we demonstrate that the SDC RNA motif reduces the expression of SAM decarboxylase by translational repression. Furthermore, we provide evidence that several other motifs discovered in this study are likely to be functional ncRNA elements. CONCLUSIONS Systematic screening of fungal genomes using a computational discovery pipeline has revealed the existence of a variety of novel structured ncRNAs. Genome contexts and similarities to known ncRNA motifs provide strong evidence for the biological and biochemical functions of some newly found ncRNA motifs. Although initial examinations of several motifs provide evidence for their likely functions, other motifs will require more in-depth analysis to reveal their functions.
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Affiliation(s)
- Sanshu Li
- Institute of Genomics, School of Biomedical Sciences, Huaqiao University, 668 Jimei Road, Xiamen, 361021 China
- Howard Hughes Medical Institute, Yale University, Box 208103, New Haven, CT 06520-8103 USA
| | - Ronald R. Breaker
- Howard Hughes Medical Institute, Yale University, Box 208103, New Haven, CT 06520-8103 USA
- Department of Molecular, Cellular and Developmental Biology, Yale University, Box 208103, New Haven, CT 06520-8103 USA
- Department of Molecular Biophysics and Biochemistry, Yale University, Box 208103, New Haven, CT 06520-8103 USA
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9
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Translation regulation via nascent polypeptide-mediated ribosome stalling. Curr Opin Struct Biol 2016; 37:123-33. [DOI: 10.1016/j.sbi.2016.01.008] [Citation(s) in RCA: 110] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2015] [Revised: 01/08/2016] [Accepted: 01/12/2016] [Indexed: 11/23/2022]
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10
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Kumar M, Srinivas V, Patankar S. Upstream AUGs and upstream ORFs can regulate the downstream ORF in Plasmodium falciparum. Malar J 2015; 14:512. [PMID: 26692187 PMCID: PMC4687322 DOI: 10.1186/s12936-015-1040-5] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2015] [Accepted: 12/08/2015] [Indexed: 11/10/2022] Open
Abstract
Background Upstream open reading frames (uORFs) and upstream AUGs (uAUGs) can regulate the translation of downstream ORFs. The AT rich genome of Plasmodium falciparum, due to the higher AT content of start and stop codons, has the potential to give rise to a large number of uORFs and uAUGs that may affect expression of their flanking ORFs. Methods A bioinformatics approach was used to detect uATGs associated with different genes in the parasite. To study the effect of some of these uAUGs on the expression of the downstream ORF, promoters and 5′ leaders containing uAUGs and uORFs were cloned upstream of a luciferase reporter gene. Luciferase assays were carried out in transient transfection experiments to assess the effects of uAUGs and mutations on reporter expression. Results The average number of uATGs and uORFs seen in P. falciparum coding sequences (CDS) is expectedly high compared to other less biased genomes. Certain genes, including the var gene family contain the maximum number of uATGs and uORFs in the parasite. They possess ~5 times more uORFs and ~4.5 times more uAUGs within 100 bases upstream of the start codons than other CDS of the parasite. A 60 bp upstream region containing three ORFs and five ATGs from var gene PF3D7_0400100 and a gene of unknown function (PF3D7_0517100) when cloned upstream of the luciferase start codon, driven by the hsp86 promoter, resulted in loss of luciferase activity. This was restored when all the ATGs present in the −60 bp were mutated to TTGs. Point mutations in the ATGs showed that even one AUG was sufficient to repress the luciferase gene. Conclusions Overall, this work indicates that the P. falciparum genome has a large number of uATGs and uORFs that can repress the expression of flanking ORFs. The role of AUGs in translation initiation suggests that this repression is mediated by preventing the translation initiation complex from reaching the main AUG of the downstream ORF. How the P. falciparum ribosome is able to bypass these uAUGs and uORFs for highly expressed genes remains a question for future research. Electronic supplementary material The online version of this article (doi:10.1186/s12936-015-1040-5) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Mayank Kumar
- Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Powai, Mumbai, 400076, India.
| | - Vivek Srinivas
- Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Powai, Mumbai, 400076, India.
| | - Swati Patankar
- Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Powai, Mumbai, 400076, India.
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11
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Abstract
Each peptide bond of a protein is generated at the peptidyl transferase center (PTC) of the ribosome and then moves through the exit tunnel, which accommodates ever-changing segments of ≈ 40 amino acids of newly translated polypeptide. A class of proteins, called ribosome arrest peptides, contains specific sequences of amino acids (arrest sequences) that interact with distinct components of the PTC-exit tunnel region of the ribosome and arrest their own translation continuation, often in a manner regulated by environmental cues. Thus, the ribosome that has translated an arrest sequence is inactivated for peptidyl transfer, translocation, or termination. The stalled ribosome then changes the configuration or localization of mRNA, resulting in specific biological outputs, including regulation of the target gene expression and downstream events of mRNA/polypeptide maturation or localization. Living organisms thus seem to have integrated potentially harmful arrest sequences into elaborate regulatory mechanisms to express genetic information in productive directions.
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Affiliation(s)
- Koreaki Ito
- Faculty of Life Sciences, Kyoto Sangyo University, Motoyama, Kamigamo, Kita-Ku, Kyoto 603-8555, Japan.
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12
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Dual short upstream open reading frames control translation of a herpesviral polycistronic mRNA. PLoS Pathog 2013; 9:e1003156. [PMID: 23382684 PMCID: PMC3561293 DOI: 10.1371/journal.ppat.1003156] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2012] [Accepted: 12/11/2012] [Indexed: 12/21/2022] Open
Abstract
The Kaposi's sarcoma-associated herpesvirus (KSHV) protein kinase, encoded by ORF36, functions to phosphorylate cellular and viral targets important in the KSHV lifecycle and to activate the anti-viral prodrug ganciclovir. Unlike the vast majority of mapped KSHV genes, no viral transcript has been identified with ORF36 positioned as the 5′-proximal gene. Here we report that ORF36 is robustly translated as a downstream cistron from the ORF35–37 polycistronic transcript in a cap-dependent manner. We identified two short, upstream open reading frames (uORFs) within the 5′ UTR of the polycistronic mRNA. While both uORFs function as negative regulators of ORF35, unexpectedly, the second allows for the translation of the downstream ORF36 gene by a termination-reinitiation mechanism. Positional conservation of uORFs within a number of related viruses suggests that this may be a common γ-herpesviral adaptation of a host translational regulatory mechanism. Kaposi's sarcoma-associated herpesvirus (KSHV) is the etiologic agent of multicentric Castleman's disease, primary effusion lymphoma and Kaposi's sarcoma. KSHV expresses a number of transcripts with the potential to generate multiple proteins, yet relies on the cellular translation machinery that is primed to synthesize only one protein per mRNA. Here we report that the viral transcript encompassing ORF35–37 is able to direct synthesis of two proteins and that the translational switch is regulated by two short upstream open reading frames (uORFs) in the native 5′ untranslated region. uORFs are elements commonly found upstream of mammalian genes that function to interfere with unrestrained ribosomal scanning and thus repress translation of the major ORF. The sequence of the viral uORF appears unimportant, and instead functions to position the translation machinery in a location that favors translation of the downstream major ORF, via a reinitiation mechanism. Thus, KSHV uses a host strategy generally reserved to repress translation to instead allow for the expression of an internal gene.
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Rayson S, Ashworth M, de Torres Zabala M, Grant M, Davies B. The salicylic acid dependent and independent effects of NMD in plants. PLANT SIGNALING & BEHAVIOR 2012; 7:1434-7. [PMID: 22990450 PMCID: PMC3548866 DOI: 10.4161/psb.21960] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
In eukaryotes, nonsense-mediated mRNA decay (NMD) targets aberrant and selected non-aberrant mRNAs for destruction. A recent screen for mRNAs showing increased abundance in Arabidopsis NMD-deficient mutants revealed that most are associated with the salicylic acid (SA)-mediated defense pathway. mRNAs with conserved peptide upstream open reading frames (CpuORFs or CuORFs) are hugely overrepresented among the smaller class of NMD-regulated transcripts not associated with SA. Here we show that the common phenotypes observed in Arabidopsis NMD mutants are SA-dependent, whereas the upregulation of CpuORF-containing transcripts in NMD mutants is independent of SA. We speculate that CpuORFs could allow the conditional targeting of mRNAs for destruction using the NMD pathway.
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Affiliation(s)
- Samantha Rayson
- Centre for Plant Sciences; Faculty of Biological Sciences; University of Leeds; Leeds, UK
| | - Mary Ashworth
- Centre for Plant Sciences; Faculty of Biological Sciences; University of Leeds; Leeds, UK
| | - Marta de Torres Zabala
- Biosciences; College of Life and Environmental Sciences; Geoffrey Pope; University of Exeter; Exeter, UK
| | - Murray Grant
- Biosciences; College of Life and Environmental Sciences; Geoffrey Pope; University of Exeter; Exeter, UK
| | - Brendan Davies
- Centre for Plant Sciences; Faculty of Biological Sciences; University of Leeds; Leeds, UK
- Correspondence to: Brendan Davies,
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14
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The arginine attenuator peptide interferes with the ribosome peptidyl transferase center. Mol Cell Biol 2012; 32:2396-406. [PMID: 22508989 DOI: 10.1128/mcb.00136-12] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The fungal arginine attenuator peptide (AAP) is encoded by a regulatory upstream open reading frame (uORF). The AAP acts as a nascent peptide within the ribosome tunnel to stall translation in response to arginine (Arg). The effect of AAP and Arg on ribosome peptidyl transferase center (PTC) function was analyzed in Neurospora crassa and wheat germ translation extracts using the transfer of nascent AAP to puromycin as an assay. In the presence of a high concentration of Arg, the wild-type AAP inhibited PTC function, but a mutated AAP that lacked stalling activity did not. While AAP of wild-type length was most efficient at stalling ribosomes, based on primer extension inhibition (toeprint) assays and reporter synthesis assays, a window of inhibitory function spanning four residues was observed at the AAP's C terminus. The data indicate that inhibition of PTC function by the AAP in response to Arg is the basis for the AAP's function of stalling ribosomes at the uORF termination codon. Arg could interfere with PTC function by inhibiting peptidyltransferase activity and/or by restricting PTC A-site accessibility. The mode of PTC inhibition appears unusual because neither specific amino acids nor a specific nascent peptide chain length was required for AAP to inhibit PTC function.
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15
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Thalor SK, Berberich T, Lee SS, Yang SH, Zhu X, Imai R, Takahashi Y, Kusano T. Deregulation of sucrose-controlled translation of a bZIP-type transcription factor results in sucrose accumulation in leaves. PLoS One 2012; 7:e33111. [PMID: 22457737 PMCID: PMC3310857 DOI: 10.1371/journal.pone.0033111] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2011] [Accepted: 02/09/2012] [Indexed: 12/22/2022] Open
Abstract
Sucrose is known to repress the translation of Arabidopsis thaliana AtbZIP11 transcript which encodes a protein belonging to the group of S (S - stands for small) basic region-leucine zipper (bZIP)-type transcription factor. This repression is called sucrose-induced repression of translation (SIRT). It is mediated through the sucrose-controlled upstream open reading frame (SC-uORF) found in the AtbZIP11 transcript. The SIRT is reported for 4 other genes belonging to the group of S bZIP in Arabidopsis. Tobacco tbz17 is phylogenetically closely related to AtbZIP11 and carries a putative SC-uORF in its 5′-leader region. Here we demonstrate that tbz17 exhibits SIRT mediated by its SC-uORF in a manner similar to genes belonging to the S bZIP group of the Arabidopsis genus. Furthermore, constitutive transgenic expression of tbz17 lacking its 5′-leader region containing the SC-uORF leads to production of tobacco plants with thicker leaves composed of enlarged cells with 3–4 times higher sucrose content compared to wild type plants. Our finding provides a novel strategy to generate plants with high sucrose content.
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Affiliation(s)
- Sunil Kumar Thalor
- Graduate School of Life Sciences, Tohoku University, Aoba, Sendai, Miyagi, Japan
| | - Thomas Berberich
- Graduate School of Life Sciences, Tohoku University, Aoba, Sendai, Miyagi, Japan
- Biodiversity and Climate Research Center (BiK-F), BioCampus-Westend, Frankfurt, Germany
| | - Sung Shin Lee
- Graduate School of Life Sciences, Tohoku University, Aoba, Sendai, Miyagi, Japan
| | - Seung Hwan Yang
- Division of Bioscience and Bioinformatics, College of Natural Science, Myongji University Science Campus, Namdong, Cheoin-Gu, Yongin, Gyeonggi, Korea
| | - XuJun Zhu
- Graduate School of Life Sciences, Tohoku University, Aoba, Sendai, Miyagi, Japan
| | - Ryozo Imai
- Crop Cold Research Team, National Agricultural Research Center for Hokkaido Region, Toyohira-ku, Sapporo, Japan
| | - Yoshihiro Takahashi
- Graduate School of Life Sciences, Tohoku University, Aoba, Sendai, Miyagi, Japan
| | - Tomonobu Kusano
- Graduate School of Life Sciences, Tohoku University, Aoba, Sendai, Miyagi, Japan
- * E-mail:
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16
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Role of antibiotic ligand in nascent peptide-dependent ribosome stalling. Proc Natl Acad Sci U S A 2011; 108:10496-501. [PMID: 21670252 DOI: 10.1073/pnas.1103474108] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Specific nascent peptides in the ribosome exit tunnel can elicit translation arrest. Such ribosome stalling is used for regulation of expression of some bacterial and eukaryotic genes. The stalling is sensitive to additional cellular cues, most commonly the binding of specific small-molecular-weight cofactors to the ribosome. The role of cofactors in programmed translation arrest is unknown. By analyzing nascent peptide- and antibiotic-dependent ribosome stalling that controls inducible expression of antibiotic resistance genes in bacteria, we have found that the antibiotic is directly recognized as a part of the translation modulating signal. Even minute structural alterations preclude it from assisting in ribosome stalling, indicating the importance of precise molecular interactions of the drug with the ribosome. One of the sensors that monitor the structure of the antibiotic is the 23S rRNA residue C2610, whose mutation reduces the efficiency of nascent peptide- and antibiotic-dependent ribosome stalling. These findings establish a new paradigm of the role of the cofactor in programmed translation arrest in which a small molecule is recognized along with specific nascent peptide sequences as a composite structure that provokes arrest of translation. A similar mechanism could be used by the ribosome to sense a variety of cellular metabolites.
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17
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Spevak CC, Ivanov IP, Sachs MS. Sequence requirements for ribosome stalling by the arginine attenuator peptide. J Biol Chem 2010; 285:40933-42. [PMID: 20884617 DOI: 10.1074/jbc.m110.164152] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The 5' regions of eukaryotic mRNAs often contain upstream open reading frames (uORFs). The Neurospora crassa arg-2 uORF encodes the 24-residue arginine attenuator peptide (AAP). This regulatory uORF-encoded peptide, which is evolutionarily conserved in fungal transcripts specifying an arginine biosynthetic enzyme, functions as a nascent peptide within the ribosomal tunnel and negatively regulates gene expression. The nascent AAP causes ribosomes to stall at the uORF stop codon in response to arginine, thus, blocking ribosomes from reaching the ARG-2 initiation codon. Here scanning mutagenesis with alanine and proline was performed to systematically determine which AAP residues were important for conferring regulation. Changing many of the most highly conserved residues (Asp-12, Tyr-13, Lys-14, and Trp-19) abolished regulatory function. The minimal functional domain of the AAP was determined by positioning AAP sequences internally within a large polypeptide. Pulse-chase analyses revealed that residues 9-20 of the AAP composed the minimal domain that was sufficient to confer regulatory function. An extensive analysis of predicted fungal AAPs revealed that the minimal functional domain of the N. crassa AAP corresponded closely to the region that was most highly conserved among the fungi. We also observed that the tripeptide RGD could function similarly to arginine in triggering AAP-mediated ribosome stalling. These studies provide a better understanding of the elements required for a nascent peptide and a small regulatory molecule to control translational processes.
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Affiliation(s)
- Christina C Spevak
- Department of Neurobiology, The Scripps Research Institute, La Jolla, California 92037, USA
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18
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Zhang Y, Zhao T, Li W, Vore M. The 5'-untranslated region of multidrug resistance associated protein 2 (MRP2; ABCC2) regulates downstream open reading frame expression through translational regulation. Mol Pharmacol 2009; 77:237-46. [PMID: 19890061 DOI: 10.1124/mol.109.058982] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
MRP2 (ABCC2), a member of the ATP binding cassette superfamily of efflux transporters that mediates the apical efflux of organic anions from hepatocytes, enterocytes, and renal epithelial cells, is postulated to undergo post-transcriptional regulation. The MRP2 5'-untranslated region (5'UTR) contains seven upstream start codons and six upstream open reading frames (uORFs). Ribonuclease protection assays in human liver, placenta, kidney, small intestine, and HepG2 cells identified multiple MRP2 transcription initiation sites. We investigated MRP2 5'UTRs [-247 (-247 to -1), -204 (-204 to -1), or -99 (-99 to -1)] for their effects on regulation of gene expression with the use of transient gene expression in HepG2 cells and in vitro translation assays. In HepG2 cells transfected with SV40-MRP2-5'UTR-Luciferase cassettes, luciferase activities of constructs -247 and -204 were significantly lower than that of -99. Disruption of the uORFs at -105 and -74 nucleotides by mutation of ATGs to AAG enhanced luciferase activity significantly without affecting luciferase mRNA expression. The translation efficiencies of T7-5'UTR-Luciferase cassettes determined in vitro were consistent with transfected HepG2 cells and showed that inhibition of translation by the -105 uORF occurred only in the cis configuration and not in the trans configuration and that inhibition of translation by the -105 uORF was independent of the encoded peptide sequence. Characterization of an MRP2 polymorphism, -24C>T, in the MRP2 5'UTR, demonstrated no effect on mRNA expression or downstream ORF translation. These data indicate for the first time that the 5'UTR of MRP2 mRNA transcripts and the uORF at -105 markedly influence MRP2 translation.
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Affiliation(s)
- Yuanyuan Zhang
- University of Kentucky, College of Medicine, Lexington, KY 40536, USA
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19
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Hood HM, Neafsey DE, Galagan J, Sachs MS. Evolutionary roles of upstream open reading frames in mediating gene regulation in fungi. Annu Rev Microbiol 2009; 63:385-409. [PMID: 19514854 DOI: 10.1146/annurev.micro.62.081307.162835] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Upstream open reading frames (uORFs) are frequently present in the 5'-leader regions of fungal mRNAs. They can affect translation by controlling the ability of ribosomes that scan from the mRNA 5' end to reach the downstream genic reading frame. The translation of uORFs can also affect mRNA stability. For several genes, including Saccharomyces cerevisiae GCN4, S. cerevisiae CPA1, and Neurospora crassa arg-2, regulation by uORFs controls expression in response to specific physiological signals. The roles of many uORFs that are identified by genome-level approaches, as have been initiated for Saccharomyces, Aspergillus, and Cryptococcus species, remain to be determined. Some uORFs may have regulatory roles, while others may exist to insulate the genic reading frame from the negative impacts of upstream translation start sites in the mRNA 5' leader.
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Affiliation(s)
- Heather M Hood
- Department of Science and Engineering, Oregon Health & Science University, Beaverton, Oregon 97006, USA
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20
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Rahmani F, Hummel M, Schuurmans J, Wiese-Klinkenberg A, Smeekens S, Hanson J. Sucrose control of translation mediated by an upstream open reading frame-encoded peptide. PLANT PHYSIOLOGY 2009; 150:1356-67. [PMID: 19403731 PMCID: PMC2705056 DOI: 10.1104/pp.109.136036] [Citation(s) in RCA: 121] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/25/2009] [Accepted: 04/26/2009] [Indexed: 05/18/2023]
Abstract
Regulation of gene expression through translational control is common in many organisms. The Arabidopsis (Arabidopsis thaliana) transcription factor bZIP11 is translational repressed in response to sucrose (Suc), resulting in Suc-regulated changes in amino acid metabolism. The 5' leader of the bZIP11 mRNA harbors several upstream open reading frames (uORFs), of which the second uORF is well conserved among bZIP11 homologous genes. The uORF2 element encodes a Suc control peptide (SC-peptide) of 28 residues that is sufficient for imposing Suc-induced repression of translation (SIRT) on a heterologous mRNA. Detailed analysis of the SC-peptide suggests that it functions as an attenuator peptide. Results suggest that the SC-peptide inhibits bZIP11 translation in response to high Suc levels by stalling the ribosome on the mRNA. The conserved noncanonical AUG contexts of bZIP11 uORFs allow inefficient translational initiation of the uORF, resulting in translation initiation of the scanning ribosome at the AUG codon of the bZIP11 main ORF. The results presented show that Suc-dependent signaling mediates differential translation of mRNAs containing SC-peptides encoding uORFs.
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Affiliation(s)
- Fatemeh Rahmani
- Molecular Plant Physiology, Utrecht University, 3584 CH Utrecht, The Netherlands
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21
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An upstream open reading frame controls translation of var2csa, a gene implicated in placental malaria. PLoS Pathog 2009; 5:e1000256. [PMID: 19119419 PMCID: PMC2603286 DOI: 10.1371/journal.ppat.1000256] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2008] [Accepted: 12/05/2008] [Indexed: 01/06/2023] Open
Abstract
Malaria, caused by the parasite Plasmodium falciparum, is responsible for substantial morbidity, mortality and economic losses in tropical regions of the world. Pregnant women are exceptionally vulnerable to severe consequences of the infection, due to the specific adhesion of parasite-infected erythrocytes in the placenta. This adhesion is mediated by a unique variant of PfEMP1, a parasite encoded, hyper-variable antigen placed on the surface of infected cells. This variant, called VAR2CSA, binds to chondroitin sulfate A on syncytiotrophoblasts in the intervillous space of placentas. VAR2CSA appears to only be expressed in the presence of a placenta, suggesting that its expression is actively repressed in men, children or non-pregnant women; however, the mechanism of repression is not understood. Using cultured parasite lines and reporter gene constructs, we show that the gene encoding VAR2CSA contains a small upstream open reading frame that acts to repress translation of the resulting mRNA, revealing a novel form of gene regulation in malaria parasites. The mechanism underlying this translational repression is reversible, allowing high levels of protein translation upon selection, thus potentially enabling parasites to upregulate expression of this variant antigen in the presence of the appropriate host tissue. Infection by the protozoan parasite Plasmodium falciparum results in the most severe form of human malaria and is responsible for significant morbidity and mortality in the developing world. This disease can be particularly severe in pregnant women due to the specific adhesion of parasite-infected red blood cells within the placenta. Expression of a single gene called var2csa has been linked to targeting of the placenta, and thus this gene represents a key element in the virulence of P. falciparum infections. It was previously shown that var2csa is predominantly expressed by parasites in pregnant women, suggesting that parasites might have the ability to down regulate this gene when no placenta is available. Here we describe an upstream open reading frame (uORF)–mediated mechanism used by parasites to repress translation of var2csa mRNA, thus providing a mechanism for controlling gene expression at the level of protein translation. This mechanism has not previously been observed in malaria parasites, and may represent a form of regulation used to control expression of other genes within the genome.
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22
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Elleuche S, Pöggeler S. A cyanase is transcriptionally regulated by arginine and involved in cyanate decomposition in Sordaria macrospora. Fungal Genet Biol 2008; 45:1458-69. [PMID: 18796334 DOI: 10.1016/j.fgb.2008.08.005] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2008] [Revised: 08/04/2008] [Accepted: 08/15/2008] [Indexed: 10/21/2022]
Abstract
Cyanase degrades toxic cyanate to NH3 and CO2 in a bicarbonate-dependent reaction. High concentrations of cyanate are fairly toxic to organisms. Here, we characterize a eukaryotic cyanase for the first time. We have isolated the cyn1 gene encoding a cyanase from the filamentous ascomycete Sordaria macrospora and functionally characterized the cyn1 product after heterologous expression in Escherichia coli. Site-directed mutagenesis confirmed a predicted catalytic centre of three conserved amino-acids. A Deltacyn1 knockout in S. macrospora was totally devoid of cyanase activity and showed an increased sensitivity to exogenously supplied cyanate in an arginine-depleted medium, defects in ascospore germination, but no other obvious morphological phenotype. By means of real-time PCR we have demonstrated that the transcriptional level of cyn1 is markedly elevated in the presence of cyanate and down-regulated by addition of arginine. The putative functions of cyanase in fungi are discussed.
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Affiliation(s)
- Skander Elleuche
- Institute of Microbiology and Genetics, Department of Genetics of Eukaryotic Microorganisms, Georg-August University, Grisebachstr. 8, D-37077 Göttingen, Germany
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23
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Tran MK, Schultz CJ, Baumann U. Conserved upstream open reading frames in higher plants. BMC Genomics 2008; 9:361. [PMID: 18667093 PMCID: PMC2527020 DOI: 10.1186/1471-2164-9-361] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2008] [Accepted: 07/31/2008] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Upstream open reading frames (uORFs) can down-regulate the translation of the main open reading frame (mORF) through two broad mechanisms: ribosomal stalling and reducing reinitiation efficiency. In distantly related plants, such as rice and Arabidopsis, it has been found that conserved uORFs are rare in these transcriptomes with approximately 100 loci. It is unclear how prevalent conserved uORFs are in closely related plants. RESULTS We used a homology-based approach to identify conserved uORFs in five cereals (monocots) that could potentially regulate translation. Our approach used a modified reciprocal best hit method to identify putative orthologous sequences that were then analysed by a comparative R-nomics program called uORFSCAN to find conserved uORFs. CONCLUSION This research identified new genes that may be controlled at the level of translation by conserved uORFs. We report that conserved uORFs are rare (<150 loci contain them) in cereal transcriptomes, are generally short (less than 100 nt), highly conserved (50% median amino acid sequence similarity), position independent in their 5'-UTRs, and their start codon context and the usage of rare codons for translation does not appear to be important.
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Affiliation(s)
- Michael K Tran
- Australian Centre for Plant Functional Genomics PMB 1 Glen Osmond SA 5064, Australia.
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24
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Hood HM, Spevak CC, Sachs MS. Evolutionary changes in the fungal carbamoyl-phosphate synthetase small subunit gene and its associated upstream open reading frame. Fungal Genet Biol 2006; 44:93-104. [PMID: 16979358 DOI: 10.1016/j.fgb.2006.07.009] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2006] [Revised: 07/11/2006] [Accepted: 07/19/2006] [Indexed: 11/28/2022]
Abstract
The Neurospora crassa arg-2 and the Saccharomyces cerevisiae ortholog CPA1 encode the arginine-specific carbamoyl-phosphate synthetase (CPS-A) small subunit. Arginine decreases synthesis of this subunit through the action of a 5' upstream open reading frame in the mRNA that encodes a cis-regulatory element, the arginine attenuator peptide (AAP), which stalls ribosomes in response to arginine. We performed a comparative analysis of the genomic structure and predicted peptide sequence of the AAP and CPS-A small subunit across many fungi. Differences at the genomic level included variation in intron number and position within the AAP and CPS-A coding regions and differences in known regulatory motifs. Although differences exist in AAP sequence, there were three absolutely conserved amino acid residues in the predicted peptide, including an aspartic acid crucial for arginine-dependent regulation of arg-2 and CPA1. A diverged Basidiomycete AAP was shown to retain function as an Arg-specific negative regulator of translation.
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Affiliation(s)
- Heather M Hood
- Department of Environmental and Biomolecular Systems, Oregon Health & Science University, Beaverton, OR 97006-8921, USA
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25
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Imai A, Hanzawa Y, Komura M, Yamamoto KT, Komeda Y, Takahashi T. The dwarf phenotype of the Arabidopsis acl5 mutant is suppressed by a mutation in an upstream ORF of a bHLH gene. Development 2006; 133:3575-85. [PMID: 16936072 DOI: 10.1242/dev.02535] [Citation(s) in RCA: 119] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Loss-of-function mutants of the Arabidopsis thaliana ACAULIS 5(ACL5) gene, which encodes spermine synthase, exhibit a severe dwarf phenotype. To elucidate the ACL5-mediated regulatory pathways of stem internode elongation, we isolated four suppressor of acaulis(sac) mutants that reverse the acl5 dwarf phenotype. Because these mutants do not rescue the dwarfism of known phytohormone-related mutants, the SAC genes appear to act specifically on the ACL5 pathways. We identify the gene responsible for the dominant sac51-d mutant, which almost completely suppresses the acl5phenotype. sac51-d disrupts a short upstream open reading frame(uORF) of SAC51, which encodes a bHLH-type transcription factor. Our results indicate that premature termination of the uORF in sac51-dresults in an increase in its own transcript level, probably as a result of an increased translation of the main ORF. We suggest a model in which ACL5 plays a role in the translational activation of SAC51,which may lead to the expression of a subset of genes required for stem elongation.
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Affiliation(s)
- Akihiro Imai
- Division of Bioscience, Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan
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26
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de Las Mercedes Dana M, Pintor-Toro JA. Post-transcriptional control of a glucoamylase gene from Trichoderma harzianum under stress conditions. Mol Microbiol 2005; 57:250-60. [PMID: 15948964 DOI: 10.1111/j.1365-2958.2005.04682.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We have examined the regulation of Trichoderma harzianum glucoamylase gene (Gla66) in response to different growth conditions. Transcription of the Gla66 gene is initiated from two different sites, yielding two transcripts of 2.1 kb and 2.6 kb respectively. The 2.1 kb mRNA (ST) encodes for an extracellular glucoamylase of 66 kDa. This protein shows the domains conserved in other fungal glucoamylases: a signal peptide responsible for protein secretion and a catalytic domain, both joined by a linker region. The longest transcript (LT) is untranslated, it contains an unusually extended 5'-untranslated region and is transcribed under stress and growth limiting conditions. The translational control of LT could be defined by the presence of four upstream open reading frames (uORFs) in its 5'-leader sequence. The analysis of these uORFs in a yeast heterologous system shows that two of these uORFs prevent the Gla66 translation under unfavourable growth conditions, when the LT transcript is accumulated.
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27
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Lai LB, Tausta SL, Nelson TM. Differential regulation of transcripts encoding cytosolic NADP-malic enzyme in C3 and C4 Flaveria species. PLANT PHYSIOLOGY 2002; 128:140-9. [PMID: 11788759 PMCID: PMC148956] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Received: 05/17/2001] [Revised: 07/10/2001] [Accepted: 09/25/2001] [Indexed: 05/23/2023]
Abstract
A cytosolic NADP-malic enzyme (CYTME) has been described previously in several plants, all C3 species. CYTME is distinct from the chloroplastic NADP-malic enzyme (CHLME) that is highly active in C4 species. We show that at least one CytMe gene is present in all Flaveria spp., including C3, C4, and C3-C4 intermediate types. Based on the CytMe expression patterns in Flaveria pringlei (C3) and Flaveria trinervia (C4), we suggest CYTME has several distinct roles, including the supplying of NADPH for cytosolic metabolism, the supporting of wound response or repair, and the balancing of cellular pH in illuminated leaves. These three roles are likely correlated with CytMe mRNAs of apparent sizes 2.0, 2.2, and 2.4 kb, respectively, which differ in the length of the 5' untranslated regions. Various regulatory mechanisms involving RNA processing and translational efficiency are discussed.
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MESH Headings
- Adaptation, Physiological
- Asteraceae/enzymology
- Asteraceae/genetics
- Base Sequence
- Blotting, Northern
- Chloroplasts/enzymology
- Cloning, Molecular
- Cytosol/enzymology
- DNA, Complementary/chemistry
- DNA, Complementary/genetics
- Gene Expression Regulation, Enzymologic/radiation effects
- Gene Expression Regulation, Plant/radiation effects
- Light
- Malate Dehydrogenase/genetics
- Malate Dehydrogenase/metabolism
- Molecular Sequence Data
- Multigene Family
- Photosynthesis/genetics
- Plant Leaves/enzymology
- Plant Leaves/genetics
- Plant Leaves/growth & development
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Sequence Alignment
- Sequence Analysis, DNA
- Sequence Homology, Nucleic Acid
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Affiliation(s)
- Lien B Lai
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, Connecticut 06520-8104, USA
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28
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Lai LB, Tausta SL, Nelson TM. Differential regulation of transcripts encoding cytosolic NADP-malic enzyme in C3 and C4 Flaveria species. PLANT PHYSIOLOGY 2002; 128:140-149. [PMID: 11788759 DOI: 10.1104/pp.010449] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
A cytosolic NADP-malic enzyme (CYTME) has been described previously in several plants, all C3 species. CYTME is distinct from the chloroplastic NADP-malic enzyme (CHLME) that is highly active in C4 species. We show that at least one CytMe gene is present in all Flaveria spp., including C3, C4, and C3-C4 intermediate types. Based on the CytMe expression patterns in Flaveria pringlei (C3) and Flaveria trinervia (C4), we suggest CYTME has several distinct roles, including the supplying of NADPH for cytosolic metabolism, the supporting of wound response or repair, and the balancing of cellular pH in illuminated leaves. These three roles are likely correlated with CytMe mRNAs of apparent sizes 2.0, 2.2, and 2.4 kb, respectively, which differ in the length of the 5' untranslated regions. Various regulatory mechanisms involving RNA processing and translational efficiency are discussed.
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MESH Headings
- Adaptation, Physiological
- Asteraceae/enzymology
- Asteraceae/genetics
- Base Sequence
- Blotting, Northern
- Chloroplasts/enzymology
- Cloning, Molecular
- Cytosol/enzymology
- DNA, Complementary/chemistry
- DNA, Complementary/genetics
- Gene Expression Regulation, Enzymologic/radiation effects
- Gene Expression Regulation, Plant/radiation effects
- Light
- Malate Dehydrogenase/genetics
- Malate Dehydrogenase/metabolism
- Molecular Sequence Data
- Multigene Family
- Photosynthesis/genetics
- Plant Leaves/enzymology
- Plant Leaves/genetics
- Plant Leaves/growth & development
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Sequence Alignment
- Sequence Analysis, DNA
- Sequence Homology, Nucleic Acid
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Affiliation(s)
- Lien B Lai
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, Connecticut 06520-8104, USA
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29
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Gaba A, Wang Z, Krishnamoorthy T, Hinnebusch AG, Sachs MS. Physical evidence for distinct mechanisms of translational control by upstream open reading frames. EMBO J 2001; 20:6453-63. [PMID: 11707416 PMCID: PMC125715 DOI: 10.1093/emboj/20.22.6453] [Citation(s) in RCA: 108] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The Saccharomyces cerevisiae GCN4 mRNA 5'-leader contains four upstream open reading frames (uORFs) and the CPA1 leader contains a single uORF. To determine how these uORFs control translation, we examined mRNAs containing these leaders in cell-free translation extracts to determine where ribosomes were loaded first and where they were loaded during steady-state translation. Ribosomes predominantly loaded first at GCN4 uORF1. Following its translation, but not the translation of uORF4, they efficiently reinitiated protein synthesis at Gcn4p. Adding purified eIF2 increased reinitiation at uORFs 3 or 4 and reduced reinitiation at Gcn4p. This indicates that eIF2 affects the site of reinitiation following translation of GCN4 uORF1 in vitro. In contrast, for mRNA containing the CPA1 uORF, ribosomes reached the downstream start codon by scanning past the uORF. Addition of arginine caused ribosomes that had synthesized the uORF polypeptide to stall at its termination codon, reducing loading at the downstream start codon, apparently by blocking scanning ribosomes, and not by affecting reinitiation. The GCN4 and CPA1 uORFs thus control translation in fundamentally different ways.
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Affiliation(s)
- Anthony Gaba
- Department of Biochemistry and Molecular Biology, OGI School of Science and Engineering, Oregon Health and Science University, 20 000 NW Walker Road, Beaverton, OR 97006-8921, National Institute of Child Health and Human Development, Laboratory of Eukaryotic Gene Regulation, Bethesda, MD 20892-2716 and Department of Molecular Microbiology and Immunology, School of Medicine, Oregon Health and Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97201-3098, USA Present address: Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, CA 94720-3204, USA Present address: Wistar Institute, 3601 Spruce Street, Philadelphia, PA 19104, USA Corresponding author e-mail:
| | - Zhong Wang
- Department of Biochemistry and Molecular Biology, OGI School of Science and Engineering, Oregon Health and Science University, 20 000 NW Walker Road, Beaverton, OR 97006-8921, National Institute of Child Health and Human Development, Laboratory of Eukaryotic Gene Regulation, Bethesda, MD 20892-2716 and Department of Molecular Microbiology and Immunology, School of Medicine, Oregon Health and Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97201-3098, USA Present address: Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, CA 94720-3204, USA Present address: Wistar Institute, 3601 Spruce Street, Philadelphia, PA 19104, USA Corresponding author e-mail:
| | - Thanuja Krishnamoorthy
- Department of Biochemistry and Molecular Biology, OGI School of Science and Engineering, Oregon Health and Science University, 20 000 NW Walker Road, Beaverton, OR 97006-8921, National Institute of Child Health and Human Development, Laboratory of Eukaryotic Gene Regulation, Bethesda, MD 20892-2716 and Department of Molecular Microbiology and Immunology, School of Medicine, Oregon Health and Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97201-3098, USA Present address: Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, CA 94720-3204, USA Present address: Wistar Institute, 3601 Spruce Street, Philadelphia, PA 19104, USA Corresponding author e-mail:
| | - Alan G. Hinnebusch
- Department of Biochemistry and Molecular Biology, OGI School of Science and Engineering, Oregon Health and Science University, 20 000 NW Walker Road, Beaverton, OR 97006-8921, National Institute of Child Health and Human Development, Laboratory of Eukaryotic Gene Regulation, Bethesda, MD 20892-2716 and Department of Molecular Microbiology and Immunology, School of Medicine, Oregon Health and Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97201-3098, USA Present address: Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, CA 94720-3204, USA Present address: Wistar Institute, 3601 Spruce Street, Philadelphia, PA 19104, USA Corresponding author e-mail:
| | - Matthew S. Sachs
- Department of Biochemistry and Molecular Biology, OGI School of Science and Engineering, Oregon Health and Science University, 20 000 NW Walker Road, Beaverton, OR 97006-8921, National Institute of Child Health and Human Development, Laboratory of Eukaryotic Gene Regulation, Bethesda, MD 20892-2716 and Department of Molecular Microbiology and Immunology, School of Medicine, Oregon Health and Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97201-3098, USA Present address: Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, CA 94720-3204, USA Present address: Wistar Institute, 3601 Spruce Street, Philadelphia, PA 19104, USA Corresponding author e-mail:
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Jousse C, Bruhat A, Carraro V, Urano F, Ferrara M, Ron D, Fafournoux P. Inhibition of CHOP translation by a peptide encoded by an open reading frame localized in the chop 5'UTR. Nucleic Acids Res 2001; 29:4341-51. [PMID: 11691921 PMCID: PMC60176 DOI: 10.1093/nar/29.21.4341] [Citation(s) in RCA: 112] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Chop is a ubiquitously expressed mammalian gene encoding a small nuclear protein related to the CCAAT/enhancer-binding protein (C/EBP) family of transcription factors. CHOP protein plays an important role in various cellular processes such as growth, differentiation and programmed cell death. CHOP expression is strongly increased in response to a large variety of stresses including perturbation of the endoplasmic reticulum function, DNA damage and nutrient deprivation. Multiple mechanisms including transcriptional and post-transcriptional controls are involved in the regulation of CHOP expression. We show here that the 5'UTR of the Chop transcript plays an important role in controlling the synthesis of CHOP protein. In particular, the 5'UTR contains a conserved uORF which encodes a 31 amino acid peptide that inhibits the expression of the downstream ORF. Mutational analysis of the 5' leader region and peptide coding sequences suggests that the peptide itself inhibits expression of the downstream ORF. Such results suggest a role for uORF in limiting ribosomal access to downstream initiation sites. With respect to the importance of CHOP protein in the regulation of cellular functions, the mechanisms that regulate its basal level are of considerable interest.
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Affiliation(s)
- C Jousse
- UR 238 - Unité de Nutrition Cellulaire et Moléculaire, INRA de Theix, 63122 Saint Genès Champanelle, France
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31
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Punt PJ, Seiboth B, Weenink XO, van Zeijl C, Lenders M, Konetschny C, Ram AF, Montijn R, Kubicek CP, van den Hondel CA. Identification and characterization of a family of secretion-related small GTPase-encoding genes from the filamentous fungus Aspergillus niger: a putative SEC4 homologue is not essential for growth. Mol Microbiol 2001; 41:513-25. [PMID: 11489135 DOI: 10.1046/j.1365-2958.2001.02541.x] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
DNA fragments containing genetic information for five secretion-related small GTPases of Aspergillus niger (srgA-E) were isolated and identified as members of different Rab/Ypt subfamilies. This isolation and the search for similar sequences in fungal genomic and EST databases showed that, in contrast to Saccharomyces cerevisiae, filamentous fungi also possess homologues of mammalian Rab2 GTPases. Multiple transcripts with unusually long 5' and 3' untranslated regions were found for all srg genes. Their level of expression was independent of the type of carbon source used for growth. Although the transcripts of srgA and srgB were abundant to the same extent throughout the cultivation, that of the other genes peaked during the early growth phase and then declined. Two genes, srgA and srgB, were characterized further. The protein encoded by srgA exhibited relatively low identity (58%) to its closest S. cerevisiae homologue SEC4, whereas the protein encoded by srgB showed 73% identity with S. cerevisiae YPT1. In contrast to other SEC4 homologues, srgA was unable to complement an S. cerevisiae sec4 mutant, and its disruption was not lethal in A. niger. SrgA mutants displayed a twofold increase in their hyphal diameter, unusual apical branching and strongly reduced protein secretion during growth on glucose.
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Affiliation(s)
- P J Punt
- Department of Applied Microbiology and Gene Technology, TNO Voeding, PO Box 360, 3700 AJ Zeist, The Netherlands.
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Schier N, Liese R, Fischer R. A Pcl-like cyclin of Aspergillus nidulans is transcriptionally activated by developmental regulators and is involved in sporulation. Mol Cell Biol 2001; 21:4075-88. [PMID: 11359914 PMCID: PMC87069 DOI: 10.1128/mcb.21.12.4075-4088.2001] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The filamentous fungus Aspergillus nidulans reproduces asexually through the formation of spores on a multicellular aerial structure, called a conidiophore. A key regulator of asexual development is the TFIIIA-type zinc finger containing transcriptional activator Bristle (BRLA). Besides BRLA, the transcription factor ABAA, which is located downstream of BRLA in the developmental regulation cascade, is necessary to direct later gene expression during sporulation. We isolated a new developmental mutant and identified a leaky brlA mutation and the mutated Saccharomyces cerevisiae cyclin homologue pclA, both contributing to the developmental phenotype of the mutant. pclA was found to be 10-fold transcriptionally upregulated during conidiation, and a pclA deletion strain was reduced three- to fivefold in production of conidia. Expression of pclA was strongly induced by ectopic expression of brlA or abaA under conidiation-suppressing conditions, indicating a direct role for brlA and abaA in pclA regulation. PCLA is homologous to yeast Pcl cyclins, which interact with the Pho85 cyclin-dependent kinase. Although interaction with a PSTAIRE kinase was shown in vivo, PCLA function during sporulation was independent of the A. nidulans Pho85 homologue PHOA. Besides the developmental regulation, pclA expression was cell cycle dependent with peak transcript levels in S phase. Our findings suggest a role for PCLA in mediating cell cycle events during late stages of sporulation.
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Affiliation(s)
- N Schier
- Laboratorium für Mikrobiologie, Philipps-Universität Marburg and Max-Planck-Institut für Terrestrische Mikrobiologie, D-35043 Marburg, Germany
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33
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Affiliation(s)
- D R Morris
- Departments of Biochemistry, University of Washington, Seattle, USA.
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34
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Fang P, Wang Z, Sachs MS. Evolutionarily Conserved Features of the Arginine Attenuator Peptide Provide the Necessary Requirements for Its Function in Translational Regulation. J Biol Chem 2000. [DOI: 10.1016/s0021-9258(19)61434-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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35
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Goldstein LA, Chen WT. Identification of an alternatively spliced seprase mRNA that encodes a novel intracellular isoform. J Biol Chem 2000; 275:2554-9. [PMID: 10644713 DOI: 10.1074/jbc.275.4.2554] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Seprase is a homodimeric 170-kDa integral membrane gelatinase that is related to the ectoenzyme dipeptidyl peptidase IV. We have identified an alternatively spliced seprase messenger from the human melanoma cell line LOX that encodes a novel truncated isoform, seprase-s. The splice variant mRNA is generated by an out-of-frame deletion of a 1223-base pair exonic region that encodes part of the cytoplasmic tail, transmembrane, and the membrane proximal-central regions of the extracellular domain (Val(5) through Ser(412)) of the seprase 97-kDa subunit (seprase-l). The seprase-s mRNA has an elongated 5' leader (548 nucleotides) that harbors at least two upstream open reading frames that inhibit seprase-s expression from a downstream major open reading frame. Deletion mutagenesis of the wild type splice variant cDNA confirms that initiation of the seprase-s coding sequence begins with an ATG codon that corresponds to Met(522) of seprase-l. The seprase-s open reading frame encodes a 239-amino acid polypeptide with an M(r) approximately 27,000 that precisely overlaps the carboxyl-terminal catalytic region of seprase-l.
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Affiliation(s)
- L A Goldstein
- Department of Medicine, Division of Medical Oncology, State University of New York, Stony Brook, New York 11794-8160, USA
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36
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Wang Z, Gaba A, Sachs MS. A highly conserved mechanism of regulated ribosome stalling mediated by fungal arginine attenuator peptides that appears independent of the charging status of arginyl-tRNAs. J Biol Chem 1999; 274:37565-74. [PMID: 10608810 DOI: 10.1074/jbc.274.53.37565] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The Arg attenuator peptide (AAP) is an evolutionarily conserved peptide involved in Arg-specific negative translational control. It is encoded as an upstream open reading frame (uORF) in fungal mRNAs specifying the small subunit of Arg-specific carbamoyl phosphate synthetase. We examined the functions of the Saccharomyces cerevisiae CPA1 and Neurospora crassa arg-2 AAPs using translation extracts from S. cerevisiae, N. crassa, and wheat germ. Synthetic RNA containing AAP and firefly luciferase (LUC) sequences were used to program translation; analyses of LUC activity indicated that the AAPs conferred Arg-specific negative regulation in each system. The AAPs functioned either as uORFs or fused in-frame at the N terminus of LUC. Mutant AAPs lacking function in vivo did not function in vitro. Therefore, trans-acting factors conferring AAP-mediated regulation are in both fungal and plant systems. Analyses of ribosome stalling in the fungal extracts by primer extension inhibition (toeprint) assays showed that these AAPs acted similarly to stall ribosomes in the region immediately distal to the AAP coding region in response to Arg. The regulatory effect increased as the Arg concentration increased; all of the arginyl-tRNAs examined appeared maximally charged at low Arg concentrations. Therefore, AAP-mediated Arg-specific regulation appeared independent of the charging status of arginyl-tRNA.
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Affiliation(s)
- Z Wang
- Department of Biochemistry, Oregon Graduate Institute of Science and Technology, Beaverton, Oregon 97006-8921, USA
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37
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Alderete JP, Jarrahian S, Geballe AP. Translational effects of mutations and polymorphisms in a repressive upstream open reading frame of the human cytomegalovirus UL4 gene. J Virol 1999; 73:8330-7. [PMID: 10482583 PMCID: PMC112850 DOI: 10.1128/jvi.73.10.8330-8337.1999] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The human cytomegalovirus (HCMV) gpUL4 mRNA contains a 22-codon upstream open reading frame (uORF2), the peptide product of which represses downstream translation by blocking translation termination at its own stop codon and by causing ribosomes to stall on the mRNA. A distinctive feature of this unusual mechanism is its strict dependence on the uORF2 peptide sequence. To delineate sequence elements that function in the inhibitory mechanism, deletions and missense mutations affecting the previously uncharacterized amino-terminal region of uORF2 were analyzed in transient-transfection and infection assays. These experiments identified multiple codons in this region that are necessary for inhibition of downstream translation by uORF2 and, in conjunction with previous results, demonstrated that amino acids dispersed throughout the uORF2 peptide participate in the repressive mechanism. In contrast to the highly conserved carboxy terminus, the amino-terminal portion of the uORF2 peptide is polymorphic. A survey of uORF2 sequences in HCMV clinical isolates revealed that although most have uORF2 sequences that are predicted to retain the uORF2 inhibitory activity, approximately 15% contain polymorphisms at codons that are essential for full inhibition by uORF2. Consistent with predictions based on analyses of engineered mutations, two viral isolates with uORF2 sequences that do not inhibit downstream translation in transfection assays expressed much more gpUL4 protein but similar levels of UL4 mRNA compared to the levels produced by the prototypic laboratory strain HCMV (Towne) and another clinical isolate with an inhibitory variant uORF2. These results demonstrate that uORF2 is polymorphic in sequence and repressive activity and suggest that the uORF2 regulatory mechanism, although prevalent among natural HCMV isolates, is not absolutely essential for viral replication.
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Affiliation(s)
- J P Alderete
- Divisions of Human Biology and Clinical Research, Fred Hutchinson Cancer Research Center, Seattle, Washington 98109, USA
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38
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Child SJ, Miller MK, Geballe AP. Translational control by an upstream open reading frame in the HER-2/neu transcript. J Biol Chem 1999; 274:24335-41. [PMID: 10446211 DOI: 10.1074/jbc.274.34.24335] [Citation(s) in RCA: 89] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Overexpression of the HER-2 (neu, erbB-2) receptor results in cellular transformation and is associated with a variety of human cancers. Multiple mechanisms, including gene amplification and transcriptional, post-transcriptional, and translational controls contribute to the regulation of HER-2 expression. One of the components of these regulatory mechanisms is a short upstream open reading frame (uORF) in the HER-2 mRNA that represses downstream translation in a variety of cell types. Here we explore the mechanism by which this uORF exerts its inhibitory effect. As judged by comparisons of protein and mRNA abundance and by polysomal distribution analyses, the uORF represses translation of the HER-2 cistron or of a heterologous reporter gene. Despite its conservation among mammalian species, the peptide sequence of the uORF is not required for this inhibitory effect. Rather, the majority of ribosomes that load on the HER-2 mRNA most likely translate the uORF and are then unable to reinitiate at the downstream AUG codon, in part due to the short intercistronic spacing. A minority of ribosomes gain access to the HER-2 initiation codon either by leaky scanning past the upstream AUG codon or by reinitiating after having translated the uORF despite the short intercistronic region. These results suggest that the HER-2 uORF controls synthesis of this oncoprotein by limiting ribosomal access to downstream initiation sites.
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Affiliation(s)
- S J Child
- Divisions of Human Biology and Clinical Research, C2-023, Fred Hutchinson Cancer Research Center, Seattle, Washington 98109, USA
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39
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Vilela C, Ramirez CV, Linz B, Rodrigues-Pousada C, McCarthy JE. Post-termination ribosome interactions with the 5'UTR modulate yeast mRNA stability. EMBO J 1999; 18:3139-52. [PMID: 10357825 PMCID: PMC1171395 DOI: 10.1093/emboj/18.11.3139] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
A novel form of post-transcriptional control is described. The 5' untranslated region (5'UTR) of the Saccharomyces cerevisiae gene encoding the AP1-like transcription factor Yap2 contains two upstream open reading frames (uORF1 and uORF2). The YAP2-type of uORF functions as a cis-acting element that attenuates gene expression at the level of mRNA turnover via termination-dependent decay. Release of post-termination ribosomes from the YAP2 5'UTR causes accelerated decay which is largely independent of the termination modulator gene UPF1. Both of the YAP2 uORFs contribute to the destabilization effect. A G/C-rich stop codon context, which seems to promote ribosome release, allows an uORF to act as a transferable 5'UTR-destabilizing element. Moreover, termination-dependent destabilization is potentiated by stable secondary structure 3' of the uORF stop codon. The potentiation of uORF-mediated destabilization is eliminated if the secondary structure is located further downstream of the uORF, and is also influenced by a modulatory mechanism involving eIF2. Destabilization is therefore linked to the kinetics of acquisition of reinitiation-competence by post-termination ribosomes in the 5'UTR. Our data explain the destabilizing properties of YAP2-type uORFs and also support a more general model for the mode of action of other known uORFs, such as those in the GCN4 mRNA.
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MESH Headings
- 5' Untranslated Regions/chemistry
- 5' Untranslated Regions/genetics
- 5' Untranslated Regions/metabolism
- Base Sequence
- Codon, Initiator/genetics
- Codon, Terminator/genetics
- DNA-Binding Proteins/genetics
- Eukaryotic Initiation Factor-2/genetics
- Eukaryotic Initiation Factor-2/physiology
- Fungal Proteins/genetics
- Gene Expression Regulation, Fungal
- Genes, Fungal/genetics
- Genes, Fungal/physiology
- Half-Life
- Models, Genetic
- Mutation
- Nucleic Acid Conformation
- Open Reading Frames/genetics
- Protein Biosynthesis/genetics
- Protein Kinases/genetics
- RNA Helicases/genetics
- RNA Helicases/metabolism
- RNA, Fungal/chemistry
- RNA, Fungal/genetics
- RNA, Fungal/metabolism
- RNA, Messenger/chemistry
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Ribosomes/metabolism
- Ribosomes/physiology
- Saccharomyces cerevisiae/genetics
- Saccharomyces cerevisiae/metabolism
- Saccharomyces cerevisiae Proteins
- Transcription Factors/genetics
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Affiliation(s)
- C Vilela
- Post-transcriptional Control Group, Department of Biomolecular Sciences, University of Manchester Institute of Science and Technology (UMIST), PO Box 88, Manchester M60 1QD, UK
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40
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Child SJ, Miller MK, Geballe AP. Cell type-dependent and -independent control of HER-2/neu translation. Int J Biochem Cell Biol 1999; 31:201-13. [PMID: 10216954 DOI: 10.1016/s1357-2725(98)00068-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
Abstract
Overexpression of the HER-2 oncogene occurs in a variety of human tumors, including 25-30% of breast carcinomas, and has been associated with an adverse prognosis. Amplification of the HER-2 gene is frequently detected in tumors, but by itself may not fully account for HER-2 overexpression since transcriptional and post-transcriptional mechanisms also regulate HER-2 protein synthesis. Our studies reveal that the efficiency of HER-2 translation differs between primary and transformed cells. In primary human fibroblasts and human mammary epithelial cells, the HER-2 mRNA is associated with monosome and small polysome fractions. In contrast, in BT474 and MCF-7 human breast cancer cell lines and in COS-7 cells the mRNA co-sedimented with larger polysomes, indicating that it is more efficiently translated in these transformed cells. Northern analysis revealed no detectable mRNA size difference, and nuclease S1 protection and sequence analyses showed no differences between the HER-2 transcript leader in primary cells compared to transformed human cells. The transcript leader in all cell types contains a short upstream open reading frame that is also conserved in other mammalian species. Transient transfection assays revealed that the HER-2 transcript leader repressed downstream translation approximately five-fold in both primary and transformed cells and mutation of the upstream initiation codon alleviated most of the inhibitory effect. These results indicate that HER2 expression is translationally controlled both by a short upstream open reading frame that represses HER-2 translation in a cell type-independent manner, and by a distinct cell type-dependent mechanism that increases translational efficiency of HER-2 in transformed cells.
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Affiliation(s)
- S J Child
- Division of Molecular Medicine, Fred Hutchinson Cancer Research Center, Seattle, WA 98109-1024, USA
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41
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Mize GJ, Ruan H, Low JJ, Morris DR. The inhibitory upstream open reading frame from mammalian S-adenosylmethionine decarboxylase mRNA has a strict sequence specificity in critical positions. J Biol Chem 1998; 273:32500-5. [PMID: 9829983 DOI: 10.1074/jbc.273.49.32500] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The upstream open reading frame (uORF) in the 5' leader of the mammalian mRNA encoding S-adenosylmethionine decarboxylase (AdoMetDC) serves as a negative regulatory element by suppressing translation of the associated downstream cistron. Certain changes in the amino acid sequence of the hexapeptide (sequence MAGDIS) encoded by the uORF destroy suppressive activity, implying specific interaction with a cellular target. In this paper, we examine the extent of alterations that can be tolerated in this uORF. The mammalian AdoMetDC uORF inhibits downstream translation when placed into the 5' leader of a yeast mRNA with characteristics resembling those in mammalian cells, suggesting that the encoded peptide has a similar target across species. Using yeast for the initial screen, we tested the specificity of the critical three codons at the 3' end of the uORF by saturation mutagenesis. Altered uORFs selected from the primary yeast screen were then retested in mammalian cells. The requirements at codons 4 and 5 were quite stringent; only aspartic acid at codon 4 yielded a fully suppressive peptide, and only valine could substitute productively for isoleucine at codon 5. The specificity at codon 6 was much looser, with many substitutions retaining suppressive activity in both yeast and mammalian cells.
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Affiliation(s)
- G J Mize
- Department of Biochemistry, University of Washington, Seattle, Washington 98195-7350, USA
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42
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Abstract
Studies of the budding yeast Saccharomyces cerevisiae have greatly advanced our understanding of the posttranscriptional steps of eukaryotic gene expression. Given the wide range of experimental tools applicable to S. cerevisiae and the recent determination of its complete genomic sequence, many of the key challenges of the posttranscriptional control field can be tackled particularly effectively by using this organism. This article reviews the current knowledge of the cellular components and mechanisms related to translation and mRNA decay, with the emphasis on the molecular basis for rate control and gene regulation. Recent progress in characterizing translation factors and their protein-protein and RNA-protein interactions has been rapid. Against the background of a growing body of structural information, the review discusses the thermodynamic and kinetic principles that govern the translation process. As in prokaryotic systems, translational initiation is a key point of control. Modulation of the activities of translational initiation factors imposes global regulation in the cell, while structural features of particular 5' untranslated regions, such as upstream open reading frames and effector binding sites, allow for gene-specific regulation. Recent data have revealed many new details of the molecular mechanisms involved while providing insight into the functional overlaps and molecular networking that are apparently a key feature of evolving cellular systems. An overall picture of the mechanisms governing mRNA decay has only very recently begun to develop. The latest work has revealed new information about the mRNA decay pathways, the components of the mRNA degradation machinery, and the way in which these might relate to the translation apparatus. Overall, major challenges still to be addressed include the task of relating principles of posttranscriptional control to cellular compartmentalization and polysome structure and the role of molecular channelling in these highly complex expression systems.
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Affiliation(s)
- J E McCarthy
- Posttranscriptional Control Group, Department of Biomolecular Sciences, University of Manchester Institute of Science and Technology (UMIST), Manchester M60 1QD, United Kingdom.
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43
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Wang Z, Fang P, Sachs MS. The evolutionarily conserved eukaryotic arginine attenuator peptide regulates the movement of ribosomes that have translated it. Mol Cell Biol 1998; 18:7528-36. [PMID: 9819438 PMCID: PMC109333 DOI: 10.1128/mcb.18.12.7528] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/1998] [Accepted: 08/28/1998] [Indexed: 11/20/2022] Open
Abstract
Translation of the upstream open reading frame (uORF) in the 5' leader segment of the Neurospora crassa arg-2 mRNA causes reduced initiation at a downstream start codon when arginine is plentiful. Previous examination of this translational attenuation mechanism using a primer-extension inhibition (toeprint) assay in a homologous N. crassa cell-free translation system showed that arginine causes ribosomes to stall at the uORF termination codon. This stalling apparently regulates translation by preventing trailing scanning ribosomes from reaching the downstream start codon. Here we provide evidence that neither the distance between the uORF stop codon and the downstream initiation codon nor the nature of the stop codon used to terminate translation of the uORF-encoded arginine attenuator peptide (AAP) is important for regulation. Furthermore, translation of the AAP coding region regulates synthesis of the firefly luciferase polypeptide when it is fused directly at the N terminus of that polypeptide. In this case, the elongating ribosome stalls in response to Arg soon after it translates the AAP coding region. Regulation by this eukaryotic leader peptide thus appears to be exerted through a novel mechanism of cis-acting translational control.
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Affiliation(s)
- Z Wang
- Department of Biochemistry and Molecular Biology, Oregon Graduate Institute of Science & Technology, Portland, Oregon 97291-1000, USA
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44
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Wang L, Wessler SR. Inefficient reinitiation is responsible for upstream open reading frame-mediated translational repression of the maize R gene. THE PLANT CELL 1998; 10:1733-46. [PMID: 9761799 PMCID: PMC143946 DOI: 10.1105/tpc.10.10.1733] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Maize R genes encode a small family of transcriptional activators of several structural genes in the anthocyanin biosynthetic pathway. The 5' leader region of most R genes contains a 38-codon upstream open reading frame (uORF) that previously was shown to be responsible for the repression of downstream gene expression in a transient transformation assay. In this study, we report that the 5' leader also can repress translation of the downstream luciferase gene both in the rabbit reticulocyte translation system and in transgenic rice plants. The ability to visualize the uORF peptide after in vitro translation permits quantification of both products of dicistronic mRNAs. Similarly, the construction of transgenic rice plants expressing wild-type and mutant constructs permits the quantification and correlation of steady state mRNA levels and reporter gene activities. Using these assays, we demonstrate directly that translation of the uORF is required for repression, that increasing translation of the uORF peptide decreases downstream gene expression, and that repression is unaffected by either subtle or gross changes in the uORF peptide. Rather, we find that ribosomes that translate the uORF reinitiate inefficiently and that the intercistronic sequence downstream of the uORF mediates this effect.
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Affiliation(s)
- L Wang
- Departments of Botany and Genetics, University of Georgia, Athens, Georgia 30602, USA
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45
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Affiliation(s)
- M S Sachs
- Department of Biochemistry and Molecular Biology, Oregon Graduate Institute of Science and Technology, Portland 97291-1000, USA.
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46
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Baek JM, Kenerley CM. The arg2 gene of Trichoderma virens: cloning and development of a homologous transformation system. Fungal Genet Biol 1998; 23:34-44. [PMID: 9501476 DOI: 10.1006/fgbi.1997.1025] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The arg2 gene which encodes the small subunit of carbamoyl phosphate synthetase for Trichoderma virens has been cloned and used to develop a homologous transformation system. A genomic clone containing the arg2 gene was isolated from a cosmid library of T. virens based on complementation of an arginine auxotrophic mutant of this fungus. The predicted amino acid sequence of the arg2 gene shows 56-82% identity with homologous polypeptides from other fungi. It also contains an upstream open reading frame which encodes 24 amino acids. As is observed with other gene sequences encoding this polypeptide in filamentous fungi, the N-terminus of the predicted polypeptide showed characteristic features of a mitochondrial signal sequence. The arg2 gene was used for genetic transformation of T. virens in frequencies of up to 370 transformants/microgram of DNA. Heat-shock treatment of T. virens protoplasts increased the transformation frequency by fivefold, but more than 85% of the transformants were abortive. Both single-copy, homologous integration events and ectopic, non-homologous integration events were detected by Southern analyses of genomic DNA from transformed strains.
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Affiliation(s)
- J M Baek
- Department of Plant Pathology and Microbiology, Texas A&M University, College Station 77843, USA
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Wu J, Miller BL. Aspergillus asexual reproduction and sexual reproduction are differentially affected by transcriptional and translational mechanisms regulating stunted gene expression. Mol Cell Biol 1997; 17:6191-201. [PMID: 9315680 PMCID: PMC232470 DOI: 10.1128/mcb.17.10.6191] [Citation(s) in RCA: 84] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The Stunted protein (StuAp) is a member of a family of transcription factors that regulate fungal development and cell cycle progression. Regulated stuA gene expression is required for correct cell pattern formation during asexual reproduction (conidiation) and for initiation of the sexual reproductive cycle in Aspergillus nidulans. Transcriptional initiation from two different promoters yields overlapping mRNAs (stuA alpha and stuAbeta) that upon translation yield the same protein. Here we show that multiple regulatory mechanisms interact to control (i) developmental competence-dependent expression of both transcripts and (ii) induction-dependent expression of stuA alpha, but not stuAbeta, by the conidiation-specific Bristle (BrlAp) transcriptional activator. Quantitative levels of both mRNAs are further modulated by (i) an activator(s) located at a far-upstream upstream activation sequence, (ii) feedback regulation by StuAp, and (iii) positive translational regulation that requires the peptide product of a micro-open reading frame unique to the stuA alpha mRNA 5' untranslated region. Gradients in stuA alpha expression were most important for correct cell and tissue type development. Threshold requirements were as follows: metula-phialide differentiation < ascosporogenesis < cleistothecial shell-Hülle cell differentiation. Altered stuA expression affected conidiophore morphology and conidial yields quantitatively but did not alter the temporal development of cell types or conidiophore density. By contrast, the sexual cycle showed both temporal delay and quantitative reduction in the number of cleistothecial initials but normal morphogenesis of tissue types.
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Affiliation(s)
- J Wu
- Department of Microbiology, Molecular Biology and Biochemistry, University of Idaho, Moscow 83844, USA
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48
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Wang Z, Sachs MS. Ribosome stalling is responsible for arginine-specific translational attenuation in Neurospora crassa. Mol Cell Biol 1997; 17:4904-13. [PMID: 9271370 PMCID: PMC232343 DOI: 10.1128/mcb.17.9.4904] [Citation(s) in RCA: 102] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The Neurospora crassa arg-2 upstream open reading frame (uORF) plays a role in negative arginine-specific translational regulation. Primer extension inhibition analyses of arg-2 uORF-containing RNA translated in a cell-free system in which arginine-specific regulation was retained revealed "toeprints" corresponding to ribosomes positioned at the uORF initiation and termination codons and at the downstream initiation codon. At high arginine concentrations, the toeprint signal corresponding to ribosomes at the uORF termination codon rapidly increased; a new, broad toeprint that represents additional ribosomes stalled on the uORF appeared 21 to 30 nucleotides upstream of this site; and the toeprint signal corresponding to ribosomes at the downstream initiation codon decreased. These data suggest that arginine increases ribosomal stalling and thereby decreases translation from the downstream initiation codon.
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Affiliation(s)
- Z Wang
- Department of Biochemistry and Molecular Biology, Oregon Graduate Institute of Science & Technology, Portland 97291-1000, USA
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Sachs MS, Selker EU, Lin B, Roberts CJ, Luo Z, Vaught-Alexander D, Margolin BS. Expression of herpes virus thymidine kinase in Neurospora crassa. Nucleic Acids Res 1997; 25:2389-95. [PMID: 9171090 PMCID: PMC146768 DOI: 10.1093/nar/25.12.2389] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The expression of thymidine kinase in fungi, which normally lack this enzyme, will greatly aid the study of DNA metabolism and provide useful drug-sensitive phenotypes. The herpes simplex virus type-1 thymidine kinase gene ( tk ) was expressed in Neurospora crassa. tk was expressed as a fusion to N.crassa arg-2 regulatory sequences and as a hygromycin phosphotransferase-thymidine kinase fusion gene under the control of cytomegalovirus and SV40 sequences. Only strains containing tk showed thymidine kinase enzyme activity. In strains containing the arg-2 - tk gene, both the level of enzyme activity and the level of mRNA were reduced by growth in arginine medium, consistent with control through arg-2 regulatory sequences. Expression of thymidine kinase in N.crassa facilitated radioactive labeling of replicating DNA following addition of [3H]thymidine or [14C]thymidine to the growth medium. Thymidine labeling of DNA enabled demonstration that hydroxyurea can be used to block replication and synchronize the N.crassa mitotic cycle. Strains expressing thymidine kinase were also more sensitive than strains lacking thymidine kinase to anticancer and antiviral nucleoside drugs that are activated by thymidine kinase, including 5-fluoro-2'-deoxyuridine, 1-(2-deoxy-2-fluoro-beta-D-arabinofuranosyl)-5-iodouridine and trifluorothymidine. Finally, expression of thymidine kinase in N. crassa enabled incorporation of bromodeoxyuridine into DNA at levels sufficient to separate newly replicated DNA from old DNA using equilibrium centrifugation.
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Affiliation(s)
- M S Sachs
- Department of Biochemistry and Molecular Biology, Oregon Graduate Institute of Science and Technology, PO Box 91000, Portland, OR 97291-1000, USA.
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Liu Y, Garceau NY, Loros JJ, Dunlap JC. Thermally regulated translational control of FRQ mediates aspects of temperature responses in the neurospora circadian clock. Cell 1997; 89:477-86. [PMID: 9150147 DOI: 10.1016/s0092-8674(00)80228-7] [Citation(s) in RCA: 210] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Two forms of FRQ, a central component of the Neurospora circadian clock, arise through alternative in-frame initiation of translation. Either form alone suffices for a functional clock at some temperatures, but both are always necessary for robust rhythmicity. Temperature regulates the ratio of FRQ forms by favoring different initiation codons at different temperatures; when either initiation codon is eliminated, the temperature range permissive for rhythmicity is demonstrably reduced. This temperature-influenced choice of translation-initiation site represents a novel adaptive mechanism that extends the physiological temperature range over which clocks function. Additionally, a temperature-dependent threshold level of FRQ is required to establish the feedback loop comprising the oscillator. These data may explain how temperature limits permissive for rhythmicity are established, thus providing a molecular understanding for a basic characteristic of circadian clocks.
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Affiliation(s)
- Y Liu
- Department of Biochemistry, Dartmouth Medical School, Hanover, New Hampshire 03755-3844, USA
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