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Zhang X, Liang X, He S, Tian H, Liu W, Jia Y, Zhang L, Zhang W, Kuang H, Chen J. Seed color in lettuce is determined by the LsTT2, LsCHS, and Ls2OGD genes from the flavonoid biosynthesis pathway. TAG. THEORETICAL AND APPLIED GENETICS. THEORETISCHE UND ANGEWANDTE GENETIK 2023; 136:241. [PMID: 37930450 DOI: 10.1007/s00122-023-04491-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2023] [Accepted: 10/20/2023] [Indexed: 11/07/2023]
Abstract
KEY MESSAGE The mutated LsTT2 and Ls2OGD genes are responsible for white seeds and yellow seeds in lettuce, respectively. Three LsCHS genes are involved in the biosynthesis of flavonoid in seed coats. Lettuce seeds have several different colors, including black, yellow, and white. The genetic mechanisms underlying color variations of lettuce seeds remain unknown. We used genome-wide association studies (GWAS) and map-based cloning approaches to clone genes controlling the color of lettuce seeds. LsTT2, which encodes an R2R3-MYB transcription factor and is homologous to the TT2 gene in Arabidopsis, was shown to be the causal gene for the variation of black and white seeds in lettuce. A point mutation leads to the lack of stop codon in the LsTT2 transcript, resulting in white seeds. Knockout of the LsTT2 gene converted black seeds to white seeds. The locus controlling yellow seeds was mapped to Chromosome 2. Knockout of two 2-oxoglutarate-dependent dioxygenases (2OGD) genes from the candidate region converted black seeds to yellow seeds, suggesting that these two 2OGD proteins catalyze the conversion of yellow metabolites to black metabolites. We also showed that three LsCHS genes from the candidate region are associated with flavonoid biosynthesis in seeds. Knockout mutants of the three LsCHS genes decreased color intensity. This study provides new insights into the regulation of flavonoid biosynthesis in plants.
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Affiliation(s)
- Xiaoyan Zhang
- National Key Laboratory for Germplasm Innovation and Utilization for Fruit and Vegetable Horticultural Crops, College of Horticulture and Forestry Sciences, Huazhong Agricultural University, Wuhan, 430070, People's Republic of China
| | - Xiaoli Liang
- National Key Laboratory for Germplasm Innovation and Utilization for Fruit and Vegetable Horticultural Crops, College of Horticulture and Forestry Sciences, Huazhong Agricultural University, Wuhan, 430070, People's Republic of China
| | - Shuping He
- National Key Laboratory for Germplasm Innovation and Utilization for Fruit and Vegetable Horticultural Crops, College of Horticulture and Forestry Sciences, Huazhong Agricultural University, Wuhan, 430070, People's Republic of China
| | - Hao Tian
- National Key Laboratory for Germplasm Innovation and Utilization for Fruit and Vegetable Horticultural Crops, College of Horticulture and Forestry Sciences, Huazhong Agricultural University, Wuhan, 430070, People's Republic of China
| | - Wenye Liu
- National Key Laboratory for Germplasm Innovation and Utilization for Fruit and Vegetable Horticultural Crops, College of Horticulture and Forestry Sciences, Huazhong Agricultural University, Wuhan, 430070, People's Republic of China
| | - Yue Jia
- National Key Laboratory for Germplasm Innovation and Utilization for Fruit and Vegetable Horticultural Crops, College of Horticulture and Forestry Sciences, Huazhong Agricultural University, Wuhan, 430070, People's Republic of China
| | - Lei Zhang
- Jiangsu Key Laboratory of Phylogenomics and Comparative Genomics, School of Life Sciences, Jiangsu Normal University, Xuzhou, 221116, Jiangsu Province, People's Republic of China
| | - Weiyi Zhang
- National Key Laboratory for Germplasm Innovation and Utilization for Fruit and Vegetable Horticultural Crops, College of Horticulture and Forestry Sciences, Huazhong Agricultural University, Wuhan, 430070, People's Republic of China
| | - Hanhui Kuang
- National Key Laboratory for Germplasm Innovation and Utilization for Fruit and Vegetable Horticultural Crops, College of Horticulture and Forestry Sciences, Huazhong Agricultural University, Wuhan, 430070, People's Republic of China
| | - Jiongjiong Chen
- National Key Laboratory for Germplasm Innovation and Utilization for Fruit and Vegetable Horticultural Crops, College of Horticulture and Forestry Sciences, Huazhong Agricultural University, Wuhan, 430070, People's Republic of China.
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2
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Morra R, Pratama F, Butterfield T, Tomazetto G, Young K, Lopez R, Dixon N. arfA antisense RNA regulates MscL excretory activity. Life Sci Alliance 2023; 6:e202301954. [PMID: 37012050 PMCID: PMC10070815 DOI: 10.26508/lsa.202301954] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2023] [Revised: 03/20/2023] [Accepted: 03/20/2023] [Indexed: 04/05/2023] Open
Abstract
Excretion of cytoplasmic protein (ECP) is a commonly observed phenomenon in bacteria, and this partial extracellular localisation of the intracellular proteome has been implicated in a variety of stress response mechanisms. In response to hypoosmotic shock and ribosome stalling in Escherichia coli, ECP is dependent upon the presence of the large-conductance mechanosensitive channel and the alternative ribosome-rescue factor A gene products. However, it is not known if a mechanistic link exists between the corresponding genes and the respective stress response pathways. Here, we report that the corresponding mscL and arfA genes are commonly co-located on the genomes of Gammaproteobacteria and display overlap in their respective 3' UTR and 3' CDS. We show this unusual genomic arrangement permits an antisense RNA-mediated regulatory control between mscL and arfA, and this modulates MscL excretory activity in E. coli These findings highlight a mechanistic link between osmotic, translational stress responses and ECP in E. coli, further elucidating the previously unknown regulatory function of arfA sRNA.
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Affiliation(s)
- Rosa Morra
- Department of Chemistry, Manchester Institute of Biotechnology, The University of Manchester, Manchester, UK
| | - Fenryco Pratama
- Department of Chemistry, Manchester Institute of Biotechnology, The University of Manchester, Manchester, UK
- Institut Teknologi Bandung, Bandung, Indonesia
| | - Thomas Butterfield
- Department of Chemistry, Manchester Institute of Biotechnology, The University of Manchester, Manchester, UK
| | - Geizecler Tomazetto
- Department of Chemistry, Manchester Institute of Biotechnology, The University of Manchester, Manchester, UK
| | - Kate Young
- Department of Chemistry, Manchester Institute of Biotechnology, The University of Manchester, Manchester, UK
| | - Ruth Lopez
- Department of Chemistry, Manchester Institute of Biotechnology, The University of Manchester, Manchester, UK
| | - Neil Dixon
- Department of Chemistry, Manchester Institute of Biotechnology, The University of Manchester, Manchester, UK
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3
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Moreno S, Muriel-Millán LF, Rodríguez-Martínez K, Ortíz-Vasco C, Bedoya-Pérez LP, Espín G. The ribosome rescue pathways SsrA-SmpB, ArfA, and ArfB mediate tolerance to heat and antibiotic stresses in Azotobacter vinelandii. FEMS Microbiol Lett 2022; 369:6824435. [PMID: 36368695 DOI: 10.1093/femsle/fnac104] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2022] [Revised: 08/29/2022] [Accepted: 10/31/2022] [Indexed: 11/13/2022] Open
Abstract
Bacteria have a mechanism to rescue stalled ribosomes known as trans-translation consisting of SsrA, a transfer-messenger RNA (tmRNA), and the small protein SmpB. Other alternative rescue mechanisms mediated by ArfA and ArfB proteins are present only in some species. Ribosome rescue mechanisms also play a role in tolerance to antibiotics and various stresses such as heat. This study shows that the genome of the soil bacterium A. vinelandii harbours genes encoding for tmRNA, SmpB, two paralogs of ArfA (arfA1 and arfA2), and ArfB. A number of mutant strains carrying mutations in the ssrA, arfA1, arfA2, and arfB genes were constructed and tested for their growth and susceptibility to heat and the antibiotic tetracycline. We found that the inactivation of both ssrA and one or the two arfA genes was detrimental to growth and caused a higher susceptibility to heat and to the antibiotic tetracycline. Interestingly, the arfB mutant strain was unable to grow after 2 h of incubation at 45°C. Inactivation of arfB in the ssrA-arfA1-arfA2 strain caused a lethal phenotype since the quadruple mutant could not be isolated. Taken together, our data suggest that both arfA1 and arfA2, as well as arfB, are functional as back up mechanisms, and that the ArfB pathway has an essential role that confers A. vinelandii resistance to high temperatures.
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Affiliation(s)
- Soledad Moreno
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Av. Universidad 2001, Col. Chamilpa, Cuernavaca, Morelos 62210, México
| | - Luis Felipe Muriel-Millán
- Departamento de Biología Molecular y Biotecnología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, 04510 Ciudad Universitaria, CDMX, México
| | - Karen Rodríguez-Martínez
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Av. Universidad 2001, Col. Chamilpa, Cuernavaca, Morelos 62210, México
| | - Cristian Ortíz-Vasco
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Av. Universidad 2001, Col. Chamilpa, Cuernavaca, Morelos 62210, México
| | - Leidy Patricia Bedoya-Pérez
- Programa de Biología Sintética, Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, Av. Universidad 2001, Col. Chamilpa, Cuernavaca, Morelos 62210, México
| | - Guadalupe Espín
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Av. Universidad 2001, Col. Chamilpa, Cuernavaca, Morelos 62210, México
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4
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Wu Y, Tang M, Wang Z, Yang Y, Li Z, Liang S, Yin P, Qi H. Efficient In Vitro Full-Sense-Codons Protein Synthesis. Adv Biol (Weinh) 2022; 6:e2200023. [PMID: 35676219 DOI: 10.1002/adbi.202200023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2022] [Revised: 04/14/2022] [Indexed: 01/28/2023]
Abstract
Termination of translation is essential but hinders applications of genetic code engineering, e.g., unnatural amino acids incorporation and codon randomization mediated saturation mutagenesis. Here, for the first time, it is demonstrated that E. coli Pth and ArfB together play an efficient translation termination without codon preference in the absence of class-I release factors. By degradation of the targeted protein, both essential and alternative termination types of machinery are completely removed to disable codon-dependent termination in cell extract. Moreover, a total of 153 engineered tRNAs are screened for efficient all stop-codons decoding to construct a codon-dependent termination defect in vitro protein synthesis with all 64 sense-codons, iPSSC. Finally, this full sense genetic code achieves significant improvement in the incorporation of distinct unnatural amino acids at up to 12 positions and synthesis of protein encoding consecutive NNN codons. By decoding all information in nucleotides to amino acids, iPSSC may hold great potential in building artificial protein synthesis beyond the cell.
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Affiliation(s)
- Yang Wu
- School of Chemical Engineering and Technology, Tianjin University, Tianjin, China.,Key Laboratory of Systems Bioengineering of Ministry of Education, Tianjin University, Tianjin, China.,College of Life Sciences, Hebei Agricultural University, Baoding, Hebei, China
| | - Mengtong Tang
- School of Chemical Engineering and Technology, Tianjin University, Tianjin, China.,Key Laboratory of Systems Bioengineering of Ministry of Education, Tianjin University, Tianjin, China
| | - Zhaoguan Wang
- School of Chemical Engineering and Technology, Tianjin University, Tianjin, China.,Key Laboratory of Systems Bioengineering of Ministry of Education, Tianjin University, Tianjin, China
| | - Youhui Yang
- School of Chemical Engineering and Technology, Tianjin University, Tianjin, China.,Key Laboratory of Systems Bioengineering of Ministry of Education, Tianjin University, Tianjin, China
| | - Zhong Li
- School of Chemical Engineering and Technology, Tianjin University, Tianjin, China.,Key Laboratory of Systems Bioengineering of Ministry of Education, Tianjin University, Tianjin, China
| | - Shurui Liang
- School of Chemical Engineering and Technology, Tianjin University, Tianjin, China.,Key Laboratory of Systems Bioengineering of Ministry of Education, Tianjin University, Tianjin, China
| | - Peng Yin
- School of Chemical Engineering and Technology, Tianjin University, Tianjin, China.,Key Laboratory of Systems Bioengineering of Ministry of Education, Tianjin University, Tianjin, China
| | - Hao Qi
- School of Chemical Engineering and Technology, Tianjin University, Tianjin, China.,Key Laboratory of Systems Bioengineering of Ministry of Education, Tianjin University, Tianjin, China.,Zhejiang Institute of Tianjin University, Shaoxing, Zhejiang, China
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5
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Zarechenskaia AS, Sergiev PV, Osterman IA. Quality Control Mechanisms in Bacterial Translation. Acta Naturae 2021; 13:32-44. [PMID: 34377554 PMCID: PMC8327144 DOI: 10.32607/actanaturae.11401] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2021] [Accepted: 05/15/2021] [Indexed: 12/24/2022] Open
Abstract
Ribosome stalling during translation significantly reduces cell viability, because cells have to spend resources on the synthesis of new ribosomes. Therefore, all bacteria have developed various mechanisms of ribosome rescue. Usually, the release of ribosomes is preceded by hydrolysis of the tRNA-peptide bond, but, in some cases, the ribosome can continue translation thanks to the activity of certain factors. This review describes the mechanisms of ribosome rescue thanks to trans-translation and the activity of the ArfA, ArfB, BrfA, ArfT, HflX, and RqcP/H factors, as well as continuation of translation via the action of EF-P, EF-4, and EttA. Despite the ability of some systems to duplicate each other, most of them have their unique functional role, related to the quality control of bacterial translation in certain abnormalities caused by mutations, stress cultivation conditions, or antibiotics.
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Affiliation(s)
- A. S. Zarechenskaia
- Lomonosov Moscow State University, Faculty of Bioengineering and Bioinformatics and Belozersky Institute of Physico-Chemical Biology, Moscow, 119992 Russia
| | - P. V. Sergiev
- Center of Life Sciences, Skolkovo Institute of Science and Technology, Skolkovo, 143028 Russia
- Lomonosov Moscow State University, Institute of functional genomics, Moscow, 119992 Russia
- Lomonosov Moscow State University, Department of Chemistry, Moscow, 119992 Russia
| | - I. A. Osterman
- Center of Life Sciences, Skolkovo Institute of Science and Technology, Skolkovo, 143028 Russia
- Lomonosov Moscow State University, Department of Chemistry, Moscow, 119992 Russia
- Sirius University of Science and Technology, Genetics and Life Sciences Research Center, Sochi, 354340 Russia
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6
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Müller C, Crowe-McAuliffe C, Wilson DN. Ribosome Rescue Pathways in Bacteria. Front Microbiol 2021; 12:652980. [PMID: 33815344 PMCID: PMC8012679 DOI: 10.3389/fmicb.2021.652980] [Citation(s) in RCA: 32] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2021] [Accepted: 02/23/2021] [Indexed: 12/18/2022] Open
Abstract
Ribosomes that become stalled on truncated or damaged mRNAs during protein synthesis must be rescued for the cell to survive. Bacteria have evolved a diverse array of rescue pathways to remove the stalled ribosomes from the aberrant mRNA and return them to the free pool of actively translating ribosomes. In addition, some of these pathways target the damaged mRNA and the incomplete nascent polypeptide chain for degradation. This review highlights the recent developments in our mechanistic understanding of bacterial ribosomal rescue systems, including drop-off, trans-translation mediated by transfer-messenger RNA and small protein B, ribosome rescue by the alternative rescue factors ArfA and ArfB, as well as Bacillus ribosome rescue factor A, an additional rescue system found in some Gram-positive bacteria, such as Bacillus subtilis. Finally, we discuss the recent findings of ribosome-associated quality control in particular bacterial lineages mediated by RqcH and RqcP. The importance of rescue pathways for bacterial survival suggests they may represent novel targets for the development of new antimicrobial agents against multi-drug resistant pathogenic bacteria.
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Affiliation(s)
| | | | - Daniel N. Wilson
- Institute for Biochemistry and Molecular Biology, University of Hamburg, Hamburg, Germany
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7
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Inada T. Quality controls induced by aberrant translation. Nucleic Acids Res 2020; 48:1084-1096. [PMID: 31950154 PMCID: PMC7026593 DOI: 10.1093/nar/gkz1201] [Citation(s) in RCA: 58] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2019] [Revised: 12/01/2019] [Accepted: 12/18/2019] [Indexed: 12/31/2022] Open
Abstract
During protein synthesis, translating ribosomes encounter many challenges imposed by various types of defective mRNAs that can lead to reduced cellular fitness and, in some cases, even threaten cell viability. Aberrant translation leads to activation of one of several quality control pathways depending on the nature of the problem. These pathways promote the degradation of the problematic mRNA as well as the incomplete translation product, the nascent polypeptide chain. Many of these quality control systems feature critical roles for specialized regulatory factors that work in concert with conventional factors. This review focuses on the mechanisms used by these quality control pathways to recognize aberrant ribosome stalling and discusses the conservation of these systems.
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Affiliation(s)
- Toshifumi Inada
- Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai 980-8578, Japan
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8
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Release factor-dependent ribosome rescue by BrfA in the Gram-positive bacterium Bacillus subtilis. Nat Commun 2019; 10:5397. [PMID: 31776341 PMCID: PMC6881298 DOI: 10.1038/s41467-019-13408-7] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2019] [Accepted: 11/07/2019] [Indexed: 12/14/2022] Open
Abstract
Rescue of the ribosomes from dead-end translation complexes, such as those on truncated (non-stop) mRNA, is essential for the cell. Whereas bacteria use trans-translation for ribosome rescue, some Gram-negative species possess alternative and release factor (RF)-dependent rescue factors, which enable an RF to catalyze stop-codon-independent polypeptide release. We now discover that the Gram-positive Bacillus subtilis has an evolutionarily distinct ribosome rescue factor named BrfA. Genetic analysis shows that B. subtilis requires the function of either trans-translation or BrfA for growth, even in the absence of proteotoxic stresses. Biochemical and cryo-electron microscopy (cryo-EM) characterization demonstrates that BrfA binds to non-stop stalled ribosomes, recruits homologous RF2, but not RF1, and induces its transition into an open active conformation. Although BrfA is distinct from E. coli ArfA, they use convergent strategies in terms of mode of action and expression regulation, indicating that many bacteria may have evolved as yet unidentified ribosome rescue systems. In bacteria, the conserved trans-translation system serves as the primary pathway of ribosome rescue, but many species can also use alternative rescue pathways. Here the authors report that in B. subtilis, the rescue factor BrfA binds to non-stop stalled ribosomes, recruits RF2 but not RF1, and induces transition of the ribosome into an open active conformation.
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9
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Ma NJ, Hemez CF, Barber KW, Rinehart J, Isaacs FJ. Organisms with alternative genetic codes resolve unassigned codons via mistranslation and ribosomal rescue. eLife 2018; 7:34878. [PMID: 30375330 PMCID: PMC6207430 DOI: 10.7554/elife.34878] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2018] [Accepted: 08/26/2018] [Indexed: 11/13/2022] Open
Abstract
Organisms possessing genetic codes with unassigned codons raise the question of how cellular machinery resolves such codons and how this could impact horizontal gene transfer. Here, we use a genomically recoded Escherichia coli to examine how organisms address translation at unassigned UAG codons, which obstruct propagation of UAG-containing viruses and plasmids. Using mass spectrometry, we show that recoded organisms resolve translation at unassigned UAG codons via near-cognate suppression, dramatic frameshifting from at least −3 to +19 nucleotides, and rescue by ssrA-encoded tmRNA, ArfA, and ArfB. We then demonstrate that deleting tmRNA restores expression of UAG-ending proteins and propagation of UAG-containing viruses and plasmids in the recoded strain, indicating that tmRNA rescue and nascent peptide degradation is the cause of impaired virus and plasmid propagation. The ubiquity of tmRNA homologs suggests that genomic recoding is a promising path for impairing horizontal gene transfer and conferring genetic isolation in diverse organisms. Usually, DNA passes from parent to offspring, vertically down the generations. But not always. In some cases, it can move directly from one organism to another by a process called horizontal gene transfer. In bacteria, this happens when DNA segments pass through a bacterium’s cell wall, which can then be picked up by another bacterium. Because the vast majority of organisms share the same genetic code, the bacteria can read this DNA with ease, as it is in the same biological language. Horizontal gene transfer helps bacteria adapt and evolve to their surroundings, letting them swap and share genetic information that could be useful. The process also poses a threat to human health because the DNA that bacteria share can help spread antibiotic resistance. However, some organisms use an alternative genetic code, which obstructs horizontal gene transfer. They cannot read the DNA transmitted to them, because it is in a different ‘biological language’. The mechanism of how this language barrier works has been poorly understood until now. Ma, Hemez, Barber et al. investigated this using Escherichia coli bacteria with an artificially alternated genetic code. In this E. coli, one of the three-letter DNA ‘words’ in the sequence is a blank – it does not exist in the bacterium’s biological language. This three-letter DNA word normally corresponds to a particular protein building block. Using a technique called mass spectrometry, Ma et al. analyzed the proteins this E. coli forms. The results showed that it has several strategies to deal with DNA transmitted horizontally into the bacterium. One method is destroying the proteins that are half-created from the DNA, using molecules called tmRNAs. These are part of a rescue system that intervenes when protein translation stalls on the blank word. The tmRNAs help to add a tag to half-formed proteins, marking them for destruction. This mechanism creates a ‘genetic firewall’ that prevents horizontal gene transfer. In organisms engineered to work from an altered genetic code, this helps to isolate them from outside interference. The findings could have applications in creating engineered bacteria that are safer for use in fields such as medicine and biofuel production.
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Affiliation(s)
- Natalie Jing Ma
- Department of Molecular, Cellular & Developmental Biology, Yale University, New Haven, United States.,Systems Biology Institute, Yale University, West Haven, United States
| | - Colin F Hemez
- Systems Biology Institute, Yale University, West Haven, United States.,Department of Biomedical Engineering, Yale University, New Haven, United States
| | - Karl W Barber
- Systems Biology Institute, Yale University, West Haven, United States.,Department of Cellular & Molecular Physiology, Yale University School of Medicine, New Haven, United States
| | - Jesse Rinehart
- Systems Biology Institute, Yale University, West Haven, United States.,Department of Cellular & Molecular Physiology, Yale University School of Medicine, New Haven, United States
| | - Farren J Isaacs
- Department of Molecular, Cellular & Developmental Biology, Yale University, New Haven, United States.,Systems Biology Institute, Yale University, West Haven, United States
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10
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Abstract
The apparent mislocalization or excretion of cytoplasmic proteins is a commonly observed phenomenon in both bacteria and eukaryotes. However, reports on the mechanistic basis and the cellular function of this so-called “nonclassical protein secretion” are limited. Here we report that protein overexpression in recombinant cells and antibiotic-induced translation stress in wild-type Escherichia coli cells both lead to excretion of cytoplasmic protein (ECP). Condition-specific metabolomic and proteomic analyses, combined with genetic knockouts, indicate a role for both the large mechanosensitive channel (MscL) and the alternative ribosome rescue factor A (ArfA) in ECP. Collectively, the findings indicate that MscL-dependent protein excretion is positively regulated in response to both osmotic stress and arfA-mediated translational stress. Protein translocation is an essential feature of cellular organisms. Bacteria, like all single-cell organisms, interact with their environment by translocation of proteins across their cell membranes via dedicated secretion pathways. Proteins destined for secretion are directed toward the secretion pathways by the presence of specific signal peptides. This study demonstrates that under conditions of both osmotic stress and translation stress, E. coli cells undergo an excretion phenomenon whereby signal peptide-less proteins are translocated across both the inner and outer cell membranes into the extracellular environment. Confirming the presence of alternative translocation/excretion pathways and understanding their function and regulation are thus important for fundamental microbiology and biotechnology.
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11
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Liu P, Huang D, Hu X, Tang Y, Ma X, Yan R, Han Q, Guo J, Zhang Y, Sun Q, Liu Z. Targeting Inhibition of SmpB by Peptide Aptamer Attenuates the Virulence to Protect Zebrafish against Aeromonas veronii Infection. Front Microbiol 2017; 8:1766. [PMID: 28955325 PMCID: PMC5601406 DOI: 10.3389/fmicb.2017.01766] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2017] [Accepted: 08/31/2017] [Indexed: 11/21/2022] Open
Abstract
Aeromonas veronii is an important pathogen of aquatic animals, wherein Small protein B (SmpB) is required for pathogenesis by functioning as both a component in stalled-ribosome rescue and a transcription factor in upregulation of virulence gene bvgS expression. Here a specific peptide aptamer PA-1 was selected from peptide aptamer library by bacterial two-hybrid system employing pBT-SmpB as bait. The binding affinity between SmpB and PA-1 was evaluated using enzyme-linked immunosorbent assay. The key amino acids of SmpB that interact with PA-1 were identified. After PA-1 was introduced into A. veronii, the engineered strain designated as A. veronii (pN-PA-1) was more sensitive and grew slower under salt stress in comparison with wild type, as the disruption of SmpB by PA-1 resulted in significant transcription reductions of virulence-related genes. Consistent with these observations, A. veronii (pN-PA-1) was severely attenuated in model organism zebrafish, and vaccination of zebrafish with A. veronii (pN-PA-1) induced a strong antibody response. The vaccinated zebrafish were well protected against subsequent lethal challenges with virulent parental strain. Collectively, we propose that targeting inhibition of SmpB by peptide aptamer PA-1 possesses the desired qualities for a live attenuated vaccine against pathogenic A. veronii.
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Affiliation(s)
- Peng Liu
- Hainan Key Laboratory for Sustainable Utilization of Tropical Bioresources, College of Biological Sciences, Hainan UniversityHaikou, China
| | - Dongyi Huang
- Hainan Key Laboratory for Sustainable Utilization of Tropical Bioresources, College of Biological Sciences, Hainan UniversityHaikou, China
| | - Xinwen Hu
- Hainan Key Laboratory for Sustainable Utilization of Tropical Bioresources, College of Biological Sciences, Hainan UniversityHaikou, China
| | - Yanqiong Tang
- Hainan Key Laboratory for Sustainable Utilization of Tropical Bioresources, College of Biological Sciences, Hainan UniversityHaikou, China
| | - Xiang Ma
- Hainan Key Laboratory for Sustainable Utilization of Tropical Bioresources, College of Biological Sciences, Hainan UniversityHaikou, China
| | - Rihui Yan
- Hainan Key Laboratory for Sustainable Utilization of Tropical Bioresources, College of Biological Sciences, Hainan UniversityHaikou, China
| | - Qian Han
- Hainan Key Laboratory for Sustainable Utilization of Tropical Bioresources, College of Biological Sciences, Hainan UniversityHaikou, China
| | - Jianchun Guo
- Institute of Tropical Bioscience and Biotechnology, Chinese Academy of Tropical Agricultural SciencesHaikou, China
| | - Yueling Zhang
- Department of Biology, College of Science, Shantou UniversityShantou, China
| | - Qun Sun
- Department of Biotechnology, College of Life Sciences, Sichuan UniversityChengdu, China
| | - Zhu Liu
- Hainan Key Laboratory for Sustainable Utilization of Tropical Bioresources, College of Biological Sciences, Hainan UniversityHaikou, China
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12
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Huter P, Müller C, Arenz S, Beckert B, Wilson DN. Structural Basis for Ribosome Rescue in Bacteria. Trends Biochem Sci 2017. [PMID: 28629612 DOI: 10.1016/j.tibs.2017.05.009] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
Ribosomes that translate mRNAs lacking stop codons become stalled at the 3' end of the mRNA. Recycling of these stalled ribosomes is essential for cell viability. In bacteria three ribosome rescue systems have been identified so far, with the most ubiquitous and best characterized being the trans-translation system mediated by transfer-messenger RNA (tmRNA) and small protein B (SmpB). The two additional rescue systems present in some bacteria employ alternative rescue factor (Arf) A and release factor (RF) 2 or ArfB. Recent structures have revealed how ArfA mediates ribosome rescue by recruiting the canonical termination factor RF2 to ribosomes stalled on truncated mRNAs. This now provides us with the opportunity to compare and contrast the available structures of all three bacterial ribosome rescue systems.
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Affiliation(s)
- Paul Huter
- Gene Center, Department of Biochemistry and Center for Integrated Protein Science Munich (CiPSM), Feodor-Lynenstr. 25, 81377 München, Germany
| | - Claudia Müller
- Gene Center, Department of Biochemistry and Center for Integrated Protein Science Munich (CiPSM), Feodor-Lynenstr. 25, 81377 München, Germany
| | - Stefan Arenz
- Gene Center, Department of Biochemistry and Center for Integrated Protein Science Munich (CiPSM), Feodor-Lynenstr. 25, 81377 München, Germany
| | - Bertrand Beckert
- Gene Center, Department of Biochemistry and Center for Integrated Protein Science Munich (CiPSM), Feodor-Lynenstr. 25, 81377 München, Germany; Institute for Biochemistry and Molecular Biology, University of Hamburg, Martin-Luther-King-Platz 6, 20146 Hamburg, Germany
| | - Daniel N Wilson
- Gene Center, Department of Biochemistry and Center for Integrated Protein Science Munich (CiPSM), Feodor-Lynenstr. 25, 81377 München, Germany; Institute for Biochemistry and Molecular Biology, University of Hamburg, Martin-Luther-King-Platz 6, 20146 Hamburg, Germany.
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13
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El Houmami N, Seligmann H. Evolution of Nucleotide Punctuation Marks: From Structural to Linear Signals. Front Genet 2017; 8:36. [PMID: 28396681 PMCID: PMC5366352 DOI: 10.3389/fgene.2017.00036] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2016] [Accepted: 03/13/2017] [Indexed: 01/13/2023] Open
Abstract
We present an evolutionary hypothesis assuming that signals marking nucleotide synthesis (DNA replication and RNA transcription) evolved from multi- to unidimensional structures, and were carried over from transcription to translation. This evolutionary scenario presumes that signals combining secondary and primary nucleotide structures are evolutionary transitions. Mitochondrial replication initiation fits this scenario. Some observations reported in the literature corroborate that several signals for nucleotide synthesis function in translation, and vice versa. (a) Polymerase-induced frameshift mutations occur preferentially at translational termination signals (nucleotide deletion is interpreted as termination of nucleotide polymerization, paralleling the role of stop codons in translation). (b) Stem-loop hairpin presence/absence modulates codon-amino acid assignments, showing that translational signals sometimes combine primary and secondary nucleotide structures (here codon and stem-loop). (c) Homopolymer nucleotide triplets (AAA, CCC, GGG, TTT) cause transcriptional and ribosomal frameshifts. Here we find in recently described human mitochondrial RNAs that systematically lack mono-, dinucleotides after each trinucleotide (delRNAs) that delRNA triplets include 2x more homopolymers than mitogenome regions not covered by delRNA. Further analyses of delRNAs show that the natural circular code X (a little-known group of 20 translational signals enabling ribosomal frame retrieval consisting of 20 codons {AAC, AAT, ACC, ATC, ATT, CAG, CTC, CTG, GAA, GAC, GAG, GAT, GCC, GGC, GGT, GTA, GTC, GTT, TAC, TTC} universally overrepresented in coding versus other frames of gene sequences), regulates frameshift in transcription and translation. This dual transcription and translation role confirms for X the hypothesis that translational signals were carried over from transcriptional signals.
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Affiliation(s)
- Nawal El Houmami
- URMITE, Aix Marseille Université UM63, CNRS 7278, IRD 198, INSERM 1095, IHU - Méditerranée Infection Marseille, France
| | - Hervé Seligmann
- URMITE, Aix Marseille Université UM63, CNRS 7278, IRD 198, INSERM 1095, IHU - Méditerranée Infection Marseille, France
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14
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Demo G, Svidritskiy E, Madireddy R, Diaz-Avalos R, Grant T, Grigorieff N, Sousa D, Korostelev AA. Mechanism of ribosome rescue by ArfA and RF2. eLife 2017; 6. [PMID: 28300532 PMCID: PMC5378476 DOI: 10.7554/elife.23687] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2016] [Accepted: 03/14/2017] [Indexed: 11/13/2022] Open
Abstract
ArfA rescues ribosomes stalled on truncated mRNAs by recruiting release factor RF2, which normally binds stop codons to catalyze peptide release. We report two 3.2 Å resolution cryo-EM structures – determined from a single sample – of the 70S ribosome with ArfA•RF2 in the A site. In both states, the ArfA C-terminus occupies the mRNA tunnel downstream of the A site. One state contains a compact inactive RF2 conformation. Ordering of the ArfA N-terminus in the second state rearranges RF2 into an extended conformation that docks the catalytic GGQ motif into the peptidyl-transferase center. Our work thus reveals the structural dynamics of ribosome rescue. The structures demonstrate how ArfA ‘senses’ the vacant mRNA tunnel and activates RF2 to mediate peptide release without a stop codon, allowing stalled ribosomes to be recycled. DOI:http://dx.doi.org/10.7554/eLife.23687.001
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Affiliation(s)
- Gabriel Demo
- RNA Therapeutics Institute, University of Massachusetts Medical School, Worcester, United States
| | - Egor Svidritskiy
- RNA Therapeutics Institute, University of Massachusetts Medical School, Worcester, United States
| | - Rohini Madireddy
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, United States
| | - Ruben Diaz-Avalos
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, United States
| | - Timothy Grant
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, United States
| | - Nikolaus Grigorieff
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, United States
| | - Duncan Sousa
- Department of Biological Science, Florida State University, Tallahassee, United States
| | - Andrei A Korostelev
- RNA Therapeutics Institute, University of Massachusetts Medical School, Worcester, United States.,Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, United States
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15
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Zeng F, Chen Y, Remis J, Shekhar M, Phillips JC, Tajkhorshid E, Jin H. Structural basis of co-translational quality control by ArfA and RF2 bound to ribosome. Nature 2017; 541:554-557. [PMID: 28077875 DOI: 10.1038/nature21053] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2016] [Accepted: 12/14/2016] [Indexed: 01/26/2023]
Abstract
Quality control mechanisms intervene appropriately when defective translation events occur, in order to preserve the integrity of protein synthesis. Rescue of ribosomes translating on messenger RNAs that lack stop codons is one of the co-translational quality control pathways. In many bacteria, ArfA recognizes stalled ribosomes and recruits the release factor RF2, which catalyses the termination of protein synthesis. Although an induced-fit mechanism of nonstop mRNA surveillance mediated by ArfA and RF2 has been reported, the molecular interaction between ArfA and RF2 in the ribosome that is responsible for the mechanism is unknown. Here we report an electron cryo-microscopy structure of ArfA and RF2 in complex with the 70S ribosome bound to a nonstop mRNA. The structure, which is consistent with our kinetic and biochemical data, reveals the molecular interactions that enable ArfA to specifically recruit RF2, not RF1, into the ribosome and to enable RF2 to release the truncated protein product in this co-translational quality control pathway. The positively charged C-terminal domain of ArfA anchors in the mRNA entry channel of the ribosome. Furthermore, binding of ArfA and RF2 induces conformational changes in the ribosomal decoding centre that are similar to those seen in other protein-involved decoding processes. Specific interactions between residues in the N-terminal domain of ArfA and RF2 help RF2 to adopt a catalytically competent conformation for peptide release. Our findings provide a framework for understanding recognition of the translational state of the ribosome by new proteins, and expand our knowledge of the decoding potential of the ribosome.
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Affiliation(s)
- Fuxing Zeng
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
| | - Yanbo Chen
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
| | - Jonathan Remis
- Department of Molecular Biosciences, Northwestern University, Evanston, Illinois 60208-3500, USA
| | - Mrinal Shekhar
- Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.,Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
| | - James C Phillips
- Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
| | - Emad Tajkhorshid
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.,Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.,Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
| | - Hong Jin
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.,Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
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16
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Brito L, Wilton J, Ferrándiz MJ, Gómez-Sanz A, de la Campa AG, Amblar M. Absence of tmRNA Has a Protective Effect against Fluoroquinolones in Streptococcus pneumoniae. Front Microbiol 2017; 7:2164. [PMID: 28119681 PMCID: PMC5222879 DOI: 10.3389/fmicb.2016.02164] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2016] [Accepted: 12/23/2016] [Indexed: 11/13/2022] Open
Abstract
The transfer messenger RNA (tmRNA), encoded by the ssrA gene, is a small non-coding RNA involved in trans-translation that contributes to the recycling of ribosomes stalled on aberrant mRNAs. In most bacteria, its inactivation has been related to a decreased ability to respond to and recover from a variety of stress conditions. In this report, we investigated the role of tmRNA in stress adaptation in the human pathogen Streptococcus pneumoniae. We constructed a tmRNA deletion mutant and analyzed its response to several lethal stresses. The ΔssrA strain grew slower than the wild type, indicating that, although not essential, tmRNA is important for normal pneumococcal growth. Moreover, deletion of tmRNA increased susceptibility to UV irradiation, to exogenous hydrogen peroxide and to antibiotics that inhibit protein synthesis and transcription. However, the ΔssrA strain was more resistant to fluoroquinolones, showing twofold higher MIC values and up to 1000-fold higher survival rates than the wild type. Deletion of SmpB, the other partner in trans-translation, also reduced survival to levofloxacin in a similar extent. Accumulation of intracellular reactive oxygen species associated to moxifloxacin and levofloxacin treatment was also highly reduced (∼100-fold). Nevertheless, the ΔssrA strain showed higher intracellular accumulation of ethidium bromide and levofloxacin than the wild type, suggesting that tmRNA deficiency protects pneumococcal cells from fluoroquinolone-mediated killing. In fact, analysis of chromosome integrity revealed that deletion of tmRNA prevented the fragmentation of the chromosome associated to levofloxacin treatment. Moreover, such protective effect appears to relay mainly on inhibition of protein synthesis, since a similar effect was observed with antibiotics that inhibit that process. The emergence and spread of drug-resistant pneumococci is a matter of concern and these results contribute to a better comprehension of the mechanisms underlying fluoroquinolones action.
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Affiliation(s)
- Liliana Brito
- Unidad de Patología Molecular del Neumococo, Centro Nacional de Microbiología, Instituto de Salud Carlos III Madrid, Spain
| | - Joana Wilton
- Unidad de Patología Molecular del Neumococo, Centro Nacional de Microbiología, Instituto de Salud Carlos III Madrid, Spain
| | - María J Ferrándiz
- Unidad de Genética Bacteriana, Centro Nacional de Microbiología, Instituto de Salud Carlos III Madrid, Spain
| | - Alicia Gómez-Sanz
- Unidad de Patología Molecular del Neumococo, Centro Nacional de Microbiología, Instituto de Salud Carlos III Madrid, Spain
| | - Adela G de la Campa
- Unidad de Genética Bacteriana, Centro Nacional de Microbiología, Instituto de Salud Carlos IIIMadrid, Spain; Presidencia, Consejo Superior de Investigaciones CientíficasMadrid, Spain
| | - Mónica Amblar
- Unidad de Patología Molecular del Neumococo, Centro Nacional de Microbiología, Instituto de Salud Carlos III Madrid, Spain
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17
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James NR, Brown A, Gordiyenko Y, Ramakrishnan V. Translational termination without a stop codon. Science 2016; 354:1437-1440. [PMID: 27934701 PMCID: PMC5351859 DOI: 10.1126/science.aai9127] [Citation(s) in RCA: 59] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2016] [Accepted: 11/17/2016] [Indexed: 11/02/2022]
Abstract
Ribosomes stall when they encounter the end of messenger RNA (mRNA) without an in-frame stop codon. In bacteria, these "nonstop" complexes can be rescued by alternative ribosome-rescue factor A (ArfA). We used electron cryomicroscopy to determine structures of ArfA bound to the ribosome with 3'-truncated mRNA, at resolutions ranging from 3.0 to 3.4 angstroms. ArfA binds within the ribosomal mRNA channel and substitutes for the absent stop codon in the A site by specifically recruiting release factor 2 (RF2), initially in a compact preaccommodated state. A similar conformation of RF2 may occur on stop codons, suggesting a general mechanism for release-factor-mediated translational termination in which a conformational switch leads to peptide release only when the appropriate signal is present in the A site.
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Affiliation(s)
- Nathan R James
- Medical Research Council (MRC) Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge, CB2 0QH, UK
| | - Alan Brown
- Medical Research Council (MRC) Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge, CB2 0QH, UK
| | - Yuliya Gordiyenko
- Medical Research Council (MRC) Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge, CB2 0QH, UK
| | - V Ramakrishnan
- Medical Research Council (MRC) Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge, CB2 0QH, UK.
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18
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Huter P, Müller C, Beckert B, Arenz S, Berninghausen O, Beckmann R, Wilson DN. Structural basis for ArfA-RF2-mediated translation termination on mRNAs lacking stop codons. Nature 2016; 541:546-549. [PMID: 27906161 DOI: 10.1038/nature20821] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2016] [Accepted: 11/25/2016] [Indexed: 11/09/2022]
Abstract
In bacteria, ribosomes stalled on truncated mRNAs that lack a stop codon are rescued by the transfer-messenger RNA (tmRNA), alternative rescue factor A (ArfA) or ArfB systems. Although tmRNA-ribosome and ArfB-ribosome structures have been determined, how ArfA recognizes the presence of truncated mRNAs and recruits the canonical termination release factor RF2 to rescue the stalled ribosomes is unclear. Here we present a cryo-electron microscopy reconstruction of the Escherichia coli 70S ribosome stalled on a truncated mRNA in the presence of ArfA and RF2. The structure shows that the C terminus of ArfA binds within the mRNA entry channel on the small ribosomal subunit, and explains how ArfA distinguishes between ribosomes that bear truncated or full-length mRNAs. The N terminus of ArfA establishes several interactions with the decoding domain of RF2, and this finding illustrates how ArfA recruits RF2 to the stalled ribosome. Furthermore, ArfA is shown to stabilize a unique conformation of the switch loop of RF2, which mimics the canonical translation termination state by directing the catalytically important GGQ motif within domain 3 of RF2 towards the peptidyl-transferase centre of the ribosome. Thus, our structure reveals not only how ArfA recruits RF2 to the ribosome but also how it promotes an active conformation of RF2 to enable translation termination in the absence of a stop codon.
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Affiliation(s)
- Paul Huter
- Gene Center, Department of Biochemistry and Center for integrated Protein Science Munich (CiPSM), Ludwig-Maximilians-Universität München, Feodor-Lynen-Strasse 25, 81377 Munich, Germany
| | - Claudia Müller
- Gene Center, Department of Biochemistry and Center for integrated Protein Science Munich (CiPSM), Ludwig-Maximilians-Universität München, Feodor-Lynen-Strasse 25, 81377 Munich, Germany
| | - Bertrand Beckert
- Gene Center, Department of Biochemistry and Center for integrated Protein Science Munich (CiPSM), Ludwig-Maximilians-Universität München, Feodor-Lynen-Strasse 25, 81377 Munich, Germany.,Institute for Biochemistry and Molecular Biology, University of Hamburg, Martin-Luther-King-Pl. 6, 20146 Hamburg, Germany
| | - Stefan Arenz
- Gene Center, Department of Biochemistry and Center for integrated Protein Science Munich (CiPSM), Ludwig-Maximilians-Universität München, Feodor-Lynen-Strasse 25, 81377 Munich, Germany
| | - Otto Berninghausen
- Gene Center, Department of Biochemistry and Center for integrated Protein Science Munich (CiPSM), Ludwig-Maximilians-Universität München, Feodor-Lynen-Strasse 25, 81377 Munich, Germany
| | - Roland Beckmann
- Gene Center, Department of Biochemistry and Center for integrated Protein Science Munich (CiPSM), Ludwig-Maximilians-Universität München, Feodor-Lynen-Strasse 25, 81377 Munich, Germany
| | - Daniel N Wilson
- Gene Center, Department of Biochemistry and Center for integrated Protein Science Munich (CiPSM), Ludwig-Maximilians-Universität München, Feodor-Lynen-Strasse 25, 81377 Munich, Germany.,Institute for Biochemistry and Molecular Biology, University of Hamburg, Martin-Luther-King-Pl. 6, 20146 Hamburg, Germany
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19
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Mechanistic insights into the alternative translation termination by ArfA and RF2. Nature 2016; 541:550-553. [PMID: 27906160 DOI: 10.1038/nature20822] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2016] [Accepted: 11/25/2016] [Indexed: 01/07/2023]
Abstract
During cellular translation of messenger RNAs by ribosomes, the translation apparatus sometimes pauses or stalls at the elongation and termination steps. With the exception of programmed stalling, which is usually used by cells for regulatory purposes, ribosomes stalled on mRNAs need to be terminated and recycled to maintain adequate translation capacity. Much ribosome stalling originates in aberrant mRNAs that lack a stop codon. Transcriptional errors, misprocessing of primary transcripts, and undesired mRNA cleavage all contribute to the formation of non-stop mRNAs. Ribosomes stalled at the 3' end of non-stop mRNAs do not undergo normal termination owing to the lack of specific stop-codon recognition by canonical peptide release factors at the A-site decoding centre. In bacteria, the transfer-messenger RNA (tmRNA)-SmpB-mediated trans-translation rescue system reroutes stalled ribosomes to the normal elongation cycle and translation termination. Two additional rescue systems, ArfA-RF2 (refs 13, 14, 15, 16) and ArfB (formerly known as YaeJ), are also present in many bacterial species, but their mechanisms are not fully understood. Here, using cryo-electron microscopy, we characterize the structure of the Escherichia coli 70S ribosome bound with ArfA, the release factor RF2, a short non-stop mRNA and a cognate P-site tRNA. The C-terminal loop of ArfA occupies the mRNA entry channel on the 30S subunit, whereas its N terminus is sandwiched between the decoding centre and the switch loop of RF2, leading to marked conformational changes in both the decoding centre and RF2. Despite the distinct conformation of RF2, its conserved catalytic GGQ motif is precisely positioned next to the CCA-end of the P-site tRNA. These data illustrate a stop-codon surrogate mechanism for ArfA in facilitating the termination of non-stop ribosomal complexes by RF2.
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20
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Zeng F, Jin H. Peptide release promoted by methylated RF2 and ArfA in nonstop translation is achieved by an induced-fit mechanism. RNA (NEW YORK, N.Y.) 2016; 22:49-60. [PMID: 26554029 PMCID: PMC4691834 DOI: 10.1261/rna.053082.115] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2015] [Accepted: 10/01/2015] [Indexed: 05/27/2023]
Abstract
Here we report that the specificity of peptide release in the ribosome on a nonstop mRNA by ArfA and RF2 is achieved by an induced-fit mechanism. Using RF2 that is methylated on the glutamine of its GGQ motif (RF2(m)), we show that methylation substantially increases the rate of ArfA/RF2-catalyzed peptide release on a nonstop mRNA that does not occupy the ribosomal A site, but has only a modest effect on k(cat) by the same proteins on longer nonstop mRNAs occupying the A site of the mRNA channel in the ribosome. Our data suggest that enhancement in the kcat of peptide release by ArfA and RF2 under the cognate decoding condition is the result of favorable conformational changes in the nonstop complex. We demonstrate a shared mechanism between canonical and nonstop termination, supported by similarities in the kinetic mechanisms in antibiotic inhibition and methylation-correlated enhancement in the rate of peptide release. Despite these similarities, our data suggest that nonstop termination differs from canonical pathway in the downstream event of recycling.
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Affiliation(s)
- Fuxing Zeng
- Department of Biochemistry, Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
| | - Hong Jin
- Department of Biochemistry, Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
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21
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22
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23
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Abstract
La synthèse des protéines, également appelée traduction, est assurée dans chaque cellule par des machines moléculaires très sophistiquées : les ribosomes. Compte tenu de l’immense quantité de données biologiques à traiter, il arrive régulièrement que ces machines se bloquent et mettent en péril la survie de la cellule. Chez les bactéries, le principal processus de sauvetage des ribosomes bloqués est la trans-traduction. Il est assuré par un acide ribonucléique (ARN) hybride, l’ARN transfert-messager (ARNtm), associé à une petite protéine basique, SmpB (small protein B). Plusieurs autres systèmes de contrôle qualité ont récemment été mis en évidence, révélant un réseau de maintien de la survie cellulaire très sophistiqué. Cette machinerie du contrôle qualité de la synthèse protéique est une cible très prometteuse pour le développement de futurs antibiotiques.
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24
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Abstract
Bacterial ribosomes frequently translate to the 3′ end of an mRNA without terminating at a stop codon. Almost all bacteria use the transfer-messenger RNA (tmRNA)-based trans-translation pathway to release these “nonstop” ribosomes and maintain protein synthesis capacity. trans-translation is essential in some species, but in others, such as Caulobacter crescentus, trans-translation can be inactivated. To determine why trans-translation is dispensable in C. crescentus, a Tn-seq screen was used to identify genes that specifically alter growth in cells lacking ssrA, the gene encoding tmRNA. One of these genes, CC1214, was essential in ΔssrA cells. Purified CC1214 protein could release nonstop ribosomes in vitro. CC1214 is a homolog of the Escherichia coli ArfB protein, and using the CC1214 sequence, ArfB homologs were identified in the majority of bacterial phyla. Most species in which ssrA has been deleted contain an ArfB homolog, suggesting that release of nonstop ribosomes may be essential in most or all bacteria. Genes that are conserved across large phylogenetic distances are expected to confer a selective advantage. The genes required for trans-translation, ssrA and smpB, have been found in >99% of sequenced bacterial genomes, suggesting that they are broadly important. However, these genes can be deleted in some species without loss of viability. The identification and characterization of C. crescentus ArfB reveals why trans-translation is not essential in C. crescentus and suggests that many other bacteria are likely to use ArfB to survive when trans-translation is compromised.
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25
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Kurita D, Chadani Y, Muto A, Abo T, Himeno H. ArfA recognizes the lack of mRNA in the mRNA channel after RF2 binding for ribosome rescue. Nucleic Acids Res 2014; 42:13339-52. [PMID: 25355516 PMCID: PMC4245945 DOI: 10.1093/nar/gku1069] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Although trans-translation mediated by tmRNA-SmpB has long been known as the sole system to relieve bacterial stalled ribosomes, ArfA has recently been identified as an alternative factor for ribosome rescue in Escherichia coli. This process requires hydrolysis of nascent peptidyl-tRNA by RF2, which usually acts as a stop codon-specific peptide release factor. It poses a fascinating question of how ArfA and RF2 recognize and rescue the stalled ribosome. Here, we mapped the location of ArfA in the stalled ribosome by directed hydroxyl radical probing. It revealed an ArfA-binding site around the neck region of the 30S subunit in which the N- and C-terminal regions of ArfA are close to the decoding center and the mRNA entry channel, respectively. ArfA and RF2 sequentially enter the ribosome stalled in either the middle or 3′ end of mRNA, whereas RF2 induces a productive conformational change of ArfA only when ribosome is stalled at the 3′ end of mRNA. On the basis of these results, we propose that ArfA functions as the sensor to recognize the target ribosome after RF2 binding.
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Affiliation(s)
- Daisuke Kurita
- Department of Biochemistry and Molecular Biology, Faculty of Agriculture and Life Science, Hirosaki University, Hirosaki 036-8561, Japan
| | - Yuhei Chadani
- Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan
| | - Akira Muto
- Department of Biochemistry and Molecular Biology, Faculty of Agriculture and Life Science, Hirosaki University, Hirosaki 036-8561, Japan
| | - Tatsuhiko Abo
- Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan Department of Biology, Faculty of Science, Okayama University, Okayama 700-8530, Japan
| | - Hyouta Himeno
- Department of Biochemistry and Molecular Biology, Faculty of Agriculture and Life Science, Hirosaki University, Hirosaki 036-8561, Japan
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26
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Starosta AL, Lassak J, Jung K, Wilson DN. The bacterial translation stress response. FEMS Microbiol Rev 2014; 38:1172-201. [PMID: 25135187 DOI: 10.1111/1574-6976.12083] [Citation(s) in RCA: 134] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2014] [Revised: 07/18/2014] [Accepted: 08/07/2014] [Indexed: 11/30/2022] Open
Abstract
Throughout their life, bacteria need to sense and respond to environmental stress. Thus, such stress responses can require dramatic cellular reprogramming, both at the transcriptional as well as the translational level. This review focuses on the protein factors that interact with the bacterial translational apparatus to respond to and cope with different types of environmental stress. For example, the stringent factor RelA interacts with the ribosome to generate ppGpp under nutrient deprivation, whereas a variety of factors have been identified that bind to the ribosome under unfavorable growth conditions to shut-down (RelE, pY, RMF, HPF and EttA) or re-program (MazF, EF4 and BipA) translation. Additional factors have been identified that rescue ribosomes stalled due to stress-induced mRNA truncation (tmRNA, ArfA, ArfB), translation of unfavorable protein sequences (EF-P), heat shock-induced subunit dissociation (Hsp15), or antibiotic inhibition (TetM, FusB). Understanding the mechanism of how the bacterial cell responds to stress will not only provide fundamental insight into translation regulation, but will also be an important step to identifying new targets for the development of novel antimicrobial agents.
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Affiliation(s)
- Agata L Starosta
- Gene Center, Department for Biochemistry, Ludwig-Maximilians-Universität München, Munich, Germany; Center for integrated Protein Science Munich (CiPSM), Ludwig-Maximilians-Universität München, Munich, Germany
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27
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Stunnenberg HG, Hubner NC. Genomics meets proteomics: identifying the culprits in disease. Hum Genet 2014; 133:689-700. [PMID: 24135908 PMCID: PMC4021166 DOI: 10.1007/s00439-013-1376-2] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2013] [Accepted: 10/01/2013] [Indexed: 12/20/2022]
Abstract
Genome-wide association studies (GWAS) revealed genomic risk loci that potentially have an impact on disease and phenotypic traits. This extensive resource holds great promise in providing novel directions for personalized medicine, including disease risk prediction, prevention and targeted medication. One of the major challenges that researchers face on the path between the initial identification of an association and precision treatment of patients is the comprehension of the biological mechanisms that underlie these associations. Currently, the focus to solve these questions lies on the integrative analysis of system-wide data on global genome variation, gene expression, transcription factor binding, epigenetic profiles and chromatin conformation. The generation of this data mainly relies on next-generation sequencing. However, due to multiple recent developments, mass spectrometry-based proteomics now offers additional, by the GWAS field so far hardly recognized possibilities for the identification of functional genome variants and, in particular, for the identification and characterization of (differentially) bound protein complexes as well as physiological target genes. In this review, we introduce these proteomics advances and suggest how they might be integrated in post-GWAS workflows. We argue that the combination of highly complementary techniques is powerful and can provide an unbiased, detailed picture of GWAS loci and their mechanistic involvement in disease.
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Affiliation(s)
- Hendrik G. Stunnenberg
- Department of Molecular Biology, Faculty of Science, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen, 6525 GA Nijmegen, The Netherlands
| | - Nina C. Hubner
- Department of Molecular Biology, Faculty of Science, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen, 6525 GA Nijmegen, The Netherlands
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Shimizu Y. Biochemical aspects of bacterial strategies for handling the incomplete translation processes. Front Microbiol 2014; 5:170. [PMID: 24782856 PMCID: PMC3989591 DOI: 10.3389/fmicb.2014.00170] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2013] [Accepted: 03/28/2014] [Indexed: 11/13/2022] Open
Abstract
During protein synthesis in cells, translating ribosomes may encounter abnormal situations that lead to retention of immature peptidyl-tRNA on the ribosome due to failure of suitable termination processes. Bacterial cells handle such situations by employing three systems that rescue the stalled translation machinery. The transfer messenger RNA/small protein B (tmRNA/SmpB) system, also called the trans-translation system, rescues stalled ribosomes by initiating template switching from the incomplete mRNA to the short open reading frame of tmRNA, leading to the production of a protein containing a C-terminal tag that renders it susceptible to proteolysis. The ArfA/RF2 and ArfB systems rescue stalled ribosomes directly by hydrolyzing the immature peptidyl-tRNA remaining on the ribosome. Here, the biochemical aspects of these systems, as clarified by recent studies, are reviewed.
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Affiliation(s)
- Yoshihiro Shimizu
- Laboratory for Cell-Free Protein Synthesis, Quantitative Biology Center - RIKEN Kobe, Hyogo, Japan
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Abstract
Problems during gene expression can result in a ribosome that has translated to the 3' end of an mRNA without terminating at a stop codon, forming a nonstop translation complex. The nonstop translation complex contains a ribosome with the mRNA and peptidyl-tRNA engaged, but because there is no codon in the A site, the ribosome cannot elongate or terminate the nascent chain. Recent work has illuminated the importance of resolving these nonstop complexes in bacteria. Transfer-messenger RNA (tmRNA)-SmpB specifically recognizes and resolves nonstop translation complexes in a reaction known as trans-translation. trans-Translation releases the ribosome and promotes degradation of the incomplete nascent polypeptide and problematic mRNA. tmRNA and SmpB have been found in all bacteria and are essential in some species. However, other bacteria can live without trans-translation because they have one of the alternative release factors, ArfA or ArfB. ArfA recruits RF2 to nonstop translation complexes to promote hydrolysis of the peptidyl-tRNAs. ArfB recognizes nonstop translation complexes in a manner similar to tmRNA-SmpB recognition and directly hydrolyzes the peptidyl-tRNAs to release the stalled ribosomes. Genetic studies indicate that most or all species require at least one mechanism to resolve nonstop translation complexes. Consistent with such a requirement, small molecules that inhibit resolution of nonstop translation complexes have broad-spectrum antibacterial activity. These results suggest that resolving nonstop translation complexes is a matter of life or death for bacteria.
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Kogure H, Handa Y, Nagata M, Kanai N, Güntert P, Kubota K, Nameki N. Identification of residues required for stalled-ribosome rescue in the codon-independent release factor YaeJ. Nucleic Acids Res 2013; 42:3152-63. [PMID: 24322300 PMCID: PMC3950681 DOI: 10.1093/nar/gkt1280] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The YaeJ protein is a codon-independent release factor with peptidyl-tRNA hydrolysis (PTH) activity, and functions as a stalled-ribosome rescue factor in Escherichia coli. To identify residues required for YaeJ function, we performed mutational analysis for in vitro PTH activity towards rescue of ribosomes stalled on a non-stop mRNA, and for ribosome-binding efficiency. We focused on residues conserved among bacterial YaeJ proteins. Additionally, we determined the solution structure of the GGQ domain of YaeJ from E. coli using nuclear magnetic resonance spectroscopy. YaeJ and a human homolog, ICT1, had similar levels of PTH activity, despite various differences in sequence and structure. While no YaeJ-specific residues important for PTH activity occur in the structured GGQ domain, Arg118, Leu119, Lys122, Lys129 and Arg132 in the following C-terminal extension were required for PTH activity. All of these residues are completely conserved among bacteria. The equivalent residues were also found in the C-terminal extension of ICT1, allowing an appropriate sequence alignment between YaeJ and ICT1 proteins from various species. Single amino acid substitutions for each of these residues significantly decreased ribosome-binding efficiency. These biochemical findings provide clues to understanding how YaeJ enters the A-site of stalled ribosomes.
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Affiliation(s)
- Hiroyuki Kogure
- Division of Molecular Science, Faculty of Science and Technology, Gunma University, 1-5-1 Tenjin-cho, Kiryu, Gunma 376-8515, Japan, Institute of Biophysical Chemistry, Center for Biomolecular Magnetic Resonance, and Frankfurt Institute for Advanced Studies, Goethe University, Frankfurt am Main, Germany and Graduate School of Science and Engineering, Tokyo Metropolitan University, 1-1 Minami-ohsawa, Hachioji, Tokyo 192-0397, Japan
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The transfer-messenger RNA-small protein B system plays a role in avian pathogenic Escherichia coli pathogenicity. J Bacteriol 2013; 195:5064-71. [PMID: 24013628 DOI: 10.1128/jb.00628-13] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Extraintestinal pathogenic Escherichia coli (ExPEC) is capable of colonizing outside of the intestinal tract and evolving into a systemic infection. Avian pathogenic E. coli (APEC) is a member of the ExPEC group and causes avian colibacillosis. Transfer-mRNA-small protein B (tmRNA-SmpB)-mediated trans-translation is a bacterial translational control system that directs the modification and degradation of proteins, the biosynthesis of which has stalled or has been interrupted, facilitating the rescue of ribosomes stalled at the 3' ends of defective mRNAs that lack a stop codon. We found that disruption of one, or both, of the smpB or ssrA genes significantly decreased the virulence of the APEC strain E058, as assessed by chicken infection assays. Furthermore, the mutants were obviously attenuated in colonization and persistence assays. The results of quantitative real-time reverse transcription-PCR analysis indicated that the transcription levels of the transcriptional regulation gene rfaH and the virulence genes kpsM, chuA, and iss were significantly decreased compared to those of the wild-type strain. Macrophage infection assays showed that the mutant strains reduced the replication and/or survival ability in the macrophage HD11 cell line compared to that of the parent strain, E058. However, no significant differences were observed in ingestion by macrophages and in chicken serum resistance between the mutant and the wild-type strains. These data indicate that the tmRNA-SmpB system is important in the pathogenesis of APEC O2 strain E058.
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Giudice E, Gillet R. The task force that rescues stalled ribosomes in bacteria. Trends Biochem Sci 2013; 38:403-11. [PMID: 23820510 DOI: 10.1016/j.tibs.2013.06.002] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2013] [Revised: 05/28/2013] [Accepted: 06/03/2013] [Indexed: 11/29/2022]
Abstract
In bacteria, the main quality control mechanism for rescuing ribosomes that have arrested during translation is trans-translation, performed by transfer-mRNA (tmRNA) associated with small protein B (SmpB). Intriguingly, this very elegant mechanism is not always necessary to maintain cell viability, suggesting the existence of alternatives. Other rescue systems have recently been discovered, revealing a far more complicated story than expected. These include the alternative ribosome rescue factors ArfA and ArfB, the elongation factors EF4 and EF-P, the peptidyl-tRNA hydrolase Pth, and several protein synthesis factors. These discoveries make it possible to describe a large network of factors dedicated to ribosome rescue, thus ensuring cell survival during stresses that induce ribosome stalling.
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Affiliation(s)
- Emmanuel Giudice
- Translation and Folding Team, Université de Rennes 1, UMR CNRS 6290 IGDR, Campus de Beaulieu 35042 Rennes cedex, France
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Small molecule inhibitors of trans-translation have broad-spectrum antibiotic activity. Proc Natl Acad Sci U S A 2013; 110:10282-7. [PMID: 23733947 DOI: 10.1073/pnas.1302816110] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The trans-translation pathway for protein tagging and ribosome release plays a critical role for viability and virulence in a wide range of pathogens but is not found in animals. To explore the use of trans-translation as a target for antibiotic development, a high-throughput screen and secondary screening assays were used to identify small molecule inhibitors of the pathway. Compounds that inhibited protein tagging and proteolysis of tagged proteins were recovered from the screen. One of the most active compounds, KKL-35, inhibited the trans-translation tagging reaction with an IC50 = 0.9 µM. KKL-35 and other compounds identified in the screen exhibited broad-spectrum antibiotic activity, validating trans-translation as a target for drug development. This unique target could play a key role in combating strains of pathogenic bacteria that are resistant to existing antibiotics.
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Abstract
Nonstop mRNAs pose a challenge for bacteria, because translation cannot terminate efficiently without a stop codon. The trans-translation pathway resolves nonstop translation complexes by removing the nonstop mRNA, the incomplete protein, and the stalled ribosome. P1 co-transduction experiments demonstrated that tmRNA, a key component of the trans-translation pathway, is essential for viability in Shigella flexneri. tmRNA was previously shown to be dispensable in the closely related species Escherichia coli, because E. coli contains a backup system for trans-translation mediated by the alternative release factor ArfA. Genome sequence analysis showed that S. flexneri does not have a gene encoding ArfA. E. coli ArfA could suppress the requirement for tmRNA in S. flexneri, indicating that tmRNA is essential in S. flexneri because there is no functional backup system. These data suggest that resolution of nonstop translation complexes is required for most bacteria.
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Affiliation(s)
- Nitya S. Ramadoss
- Pennsylvania State University, Department of Biochemistry & Molecular Biology, University Park, Pennsylvania, United States of America
| | - Xin Zhou
- Pennsylvania State University, Department of Biochemistry & Molecular Biology, University Park, Pennsylvania, United States of America
| | - Kenneth C. Keiler
- Pennsylvania State University, Department of Biochemistry & Molecular Biology, University Park, Pennsylvania, United States of America
- * E-mail:
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