1
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Villa TG, Abril AG, Sánchez-Pérez A. Mastering the control of the Rho transcription factor for biotechnological applications. Appl Microbiol Biotechnol 2021; 105:4053-4071. [PMID: 33963893 DOI: 10.1007/s00253-021-11326-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2021] [Revised: 04/22/2021] [Accepted: 04/27/2021] [Indexed: 12/25/2022]
Abstract
The present review represents an update on the fundamental role played by the Rho factor, which facilitates the process of Rho-dependent transcription termination in the prokaryotic world; it also provides a summary of relevant mutations in the Rho factor and the insights they provide into the functions carried out by this protein. Furthermore, a section is dedicated to the putative future use of Rho (the 'taming' of Rho) to facilitate biotechnological processes and adapt them to different technological contexts. Novel bacterial strains can be designed, containing mutations in the rho gene, that are better suited for different biotechnological applications. This process can obtain novel microbial strains that are adapted to lower temperatures of fermentation, shorter production times, exhibit better nutrient utilization, or display other traits that are beneficial in productive Biotechnology. Additional important issues reviewed here include epistasis, the design of TATA boxes, the role of small RNAs, and the manipulation of clathrin-mediated endocytosis, by some pathogenic bacteria, to invade eukaryotic cells. KEY POINTS: • It is postulated that controlling the action of the prokaryotic Rho factor could generate major biotechnological improvements, such as an increase in bacterial productivity or a reduction of the microbial-specific growth rate. • The review also evaluates the putative impact of epistatic mechanisms on Biotechnology, both as possible responsible for unexpected failures in gene cloning and more important for the genesis of new strains for biotechnological applications • The use of clathrin-coated vesicles by intracellular bacterial microorganisms is included too and proposed as a putative delivery mechanism, for drugs and vaccines.
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Affiliation(s)
- Tomás G Villa
- Department of Microbiology and Parasitology, Faculty of Pharmacy, University of Santiago de Compostela, La Coruña, 15706, Santiago de Compostela, Spain.
| | - Ana G Abril
- Department of Microbiology and Parasitology, Faculty of Pharmacy, University of Santiago de Compostela, La Coruña, 15706, Santiago de Compostela, Spain.
| | - Angeles Sánchez-Pérez
- Sydney School of Veterinary Science, Faculty of Science, University of Sydney, Sydney, NSW, 2006, Australia.
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2
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Dever TE, Ivanov IP, Sachs MS. Conserved Upstream Open Reading Frame Nascent Peptides That Control Translation. Annu Rev Genet 2020; 54:237-264. [PMID: 32870728 DOI: 10.1146/annurev-genet-112618-043822] [Citation(s) in RCA: 37] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Cells utilize transcriptional and posttranscriptional mechanisms to alter gene expression in response to environmental cues. Gene-specific controls, including changing the translation of specific messenger RNAs (mRNAs), provide a rapid means to respond precisely to different conditions. Upstream open reading frames (uORFs) are known to control the translation of mRNAs. Recent studies in bacteria and eukaryotes have revealed the functions of evolutionarily conserved uORF-encoded peptides. Some of these uORF-encoded nascent peptides enable responses to specific metabolites to modulate the translation of their mRNAs by stalling ribosomes and through ribosome stalling may also modulate the level of their mRNAs. In this review, we highlight several examples of conserved uORF nascent peptides that stall ribosomes to regulate gene expression in response to specific metabolites in bacteria, fungi, mammals, and plants.
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Affiliation(s)
- Thomas E Dever
- Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA; ,
| | - Ivaylo P Ivanov
- Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA; ,
| | - Matthew S Sachs
- Department of Biology, Texas A&M University, College Station, Texas 77843, USA;
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3
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Emmanuel JS, Sengupta A, Gordon ER, Noble JT, Cruz-Vera LR. The regulatory TnaC nascent peptide preferentially inhibits release factor 2-mediated hydrolysis of peptidyl-tRNA. J Biol Chem 2019; 294:19224-19235. [PMID: 31712310 DOI: 10.1074/jbc.ra119.011313] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2019] [Revised: 11/01/2019] [Indexed: 01/29/2023] Open
Abstract
The tnaC regulatory gene from the tna operon of Escherichia coli controls the transcription of its own operon through an attenuation mechanism relying on the accumulation of arrested ribosomes during inhibition of its own translation termination. This free l-Trp-dependent mechanism of inhibition of translation termination remains unclear. Here, we analyzed the inhibitory effects of l-Trp on the function of two known E. coli translation termination factors, RF1 and RF2. Using a series of reporter genes, we found that the in vivo l-Trp sensitivity of tnaC gene expression is influenced by the identity of its stop codon, with the UGA stop codon producing higher expression efficiency of the tnaA-lacZ gene construct than the UAG stop codon. In vitro TnaC-peptidyl-tRNA accumulation and toe-printing assays confirmed that in the presence of l-Trp, the UGA stop codon generates higher accumulation of both TnaC-peptidyl-tRNA and arrested ribosomes than does the UAG stop codon. RF-mediated hydrolysis assays corroborated that l-Trp blocks RF2 function more than that of RF1. Mutational analyses disclosed that amino acids substitutions at the 246 and 256 residue positions surrounding the RF2-GGQ functional motif reduce l-Trp-dependent expression of the tnaC(UGA) tnaA-lacZ construct and the ability of l-Trp to inhibit RF2-mediated cleavage of the TnaC-peptidyl-tRNA. Altogether, our results indicate that l-Trp preferentially blocks RF2 activity during translation termination of the tnaC gene. This inhibition depends on the identities of amino acid residues surrounding the RF2-GGQ functional motif.
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Affiliation(s)
| | - Arnab Sengupta
- University of Alabama in Huntsville, Huntsville, Alabama 35899
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4
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Darkoh C, Plants-Paris K, Bishoff D, DuPont HL. Clostridium difficile Modulates the Gut Microbiota by Inducing the Production of Indole, an Interkingdom Signaling and Antimicrobial Molecule. mSystems 2019; 4:e00346-18. [PMID: 30944877 PMCID: PMC6426650 DOI: 10.1128/msystems.00346-18] [Citation(s) in RCA: 54] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2018] [Accepted: 02/27/2019] [Indexed: 02/07/2023] Open
Abstract
Clostridium (Clostridioides) difficile infection (CDI) is associated with dysbiosis. C. difficile has a characteristic propensity to persist and recur 1 to 4 weeks after treatment, but the mechanism is unknown. We hypothesized that C. difficile may persist by manipulating the intestinal microenvironment, thereby hampering gut microbiota reconstitution following antibiotic-mediated dysbiosis. By screening stools from CDI patients for unique markers, a metabolite identified to be indole by mass spectrometry and Fourier transform infrared spectroscopy was identified. The average fecal indole concentration detected in CDI patients (n = 216; mean, 1,684.0 ± 84.4 µM) was significantly higher than in stools of patients with non-C. difficile diarrhea (n = 204; mean, 762.8 ± 53.8 µM). Certain intestinal bacteria, but not C. difficile, produce indole, a potent antimicrobial antioxidant. Remarkably, C. difficile induced other indole-producing gut microbes to produce increasing amounts of indole. Furthermore, a C. difficile accessory gene regulator 1 quorum sensing system mutant cannot induce indole, but complementation of the mutant strain with the wild-type gene restored its ability to induce indole production. Indole tolerance assays indicated that the amount of indole required to inhibit growth of most gut-protective bacteria was within the range detected in the CDI stools. We think that a high indole level limits the growth of beneficial indole-sensitive bacteria in the colon and alters colonization resistance and this might allow C. difficile to proliferate and persist. Together, these results reveal a unique mechanism of C. difficile persistence and provide insight into complex interactions and chemical warfare among the gut microbiota. IMPORTANCE Clostridium difficile infection is the leading cause of hospital-acquired and antibiotic-associated diarrhea worldwide. C. difficile flourishes in the colon after the diversity of the beneficial and protective gut microbiota have been altered by antibiotic therapy. C. difficile tends to persist, as does dysbiosis, encouraging recurrence a few days to weeks after treatment, and this further complicates treatment options. Here, we show that C. difficile might persist by manipulating the indigenous microbiota to produce indole, a bioactive molecule that inhibits the growth and reconstitution of the protective gut microbiota during infection. This discovery may explain a unique strategy C. difficile uses to control other bacteria in the colon and provide insight into the complex interactions and chemical warfare among the gut microbiota.
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Affiliation(s)
- Charles Darkoh
- University of Texas Health Science Center, School of Public Health, Department of Epidemiology, Human Genetics, and Environmental Sciences, Center For Infectious Diseases, Houston, Texas, USA
- Microbiology and Infectious Diseases Program, UTHealth Graduate School of Biomedical Sciences, University of Texas MD Anderson Cancer Center, Houston, Texas, USA
| | - Kimberly Plants-Paris
- University of Texas Health Science Center, School of Public Health, Department of Epidemiology, Human Genetics, and Environmental Sciences, Center For Infectious Diseases, Houston, Texas, USA
| | - Dayna Bishoff
- University of Texas Health Science Center, School of Public Health, Department of Epidemiology, Human Genetics, and Environmental Sciences, Center For Infectious Diseases, Houston, Texas, USA
| | - Herbert L. DuPont
- University of Texas Health Science Center, School of Public Health, Department of Epidemiology, Human Genetics, and Environmental Sciences, Center For Infectious Diseases, Houston, Texas, USA
- Microbiology and Infectious Diseases Program, UTHealth Graduate School of Biomedical Sciences, University of Texas MD Anderson Cancer Center, Houston, Texas, USA
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5
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Bastet L, Turcotte P, Wade JT, Lafontaine DA. Maestro of regulation: Riboswitches orchestrate gene expression at the levels of translation, transcription and mRNA decay. RNA Biol 2018. [PMID: 29537923 DOI: 10.1080/15476286.2018.1451721] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Riboswitches are RNA regulators that control gene expression by modulating their structure in response to metabolite binding. The study of mechanisms by which riboswitches modulate gene expression is crucial to understand how riboswitches are involved in maintaining cellular homeostasis. Previous reports indicate that riboswitches can control gene expression at the level of translation, transcription or mRNA decay. However, there are very few described examples where riboswitches regulate multiple steps in gene expression. Recent studies of a translation-regulating, TPP-dependent riboswitch have revealed that ligand binding is also involved in the control of mRNA levels. In this model, TPP binding to the riboswitch leads to the inhibition of translation, which in turn allows for Rho-dependent transcription termination. Thus, mRNA levels are indirectly controlled through ribosome occupancy. This is in contrast to other riboswitches that directly control mRNA levels by modulating the access of regulatory sequences involved in either Rho-dependent transcription termination or RNase E cleavage activity. Together, these findings indicate that riboswitches modulate both translation initiation and mRNA levels using multiple strategies that direct the outcome of gene expression.
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Affiliation(s)
- Laurène Bastet
- a Laboratorio de Regulación Génica Bacteriana. Instituto de Agrobiotecnología , CSIC- UPNA. Avda. Pamplona 123 , Mutilva , Navarra
| | - Pierre Turcotte
- b Department of Biology , Faculty of Science, RNA Group, Université de Sherbrooke , Sherbrooke , Québec , Canada
| | - Joseph T Wade
- c Wadsworth Center , New York State Department of Health , Albany , NY , USA.,d Department of Biomedical Sciences , University at Albany , Albany , NY , USA
| | - Daniel A Lafontaine
- b Department of Biology , Faculty of Science, RNA Group, Université de Sherbrooke , Sherbrooke , Québec , Canada
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6
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Chu HY, Sprouffske K, Wagner A. The role of recombination in evolutionary adaptation of Escherichia coli to a novel nutrient. J Evol Biol 2017; 30:1692-1711. [PMID: 28612351 DOI: 10.1111/jeb.13132] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2017] [Revised: 05/11/2017] [Accepted: 06/05/2017] [Indexed: 12/11/2022]
Abstract
The benefits and detriments of recombination for adaptive evolution have been studied both theoretically and experimentally, with conflicting predictions and observations. Most pertinent experiments examine recombination's effects in an unchanging environment and do not study its genomewide effects. Here, we evolved six replicate populations of either highly recombining R+ or lowly recombining R- E. coli strains in a changing environment, by introducing the novel nutrients L-arabinose or indole into the environment. The experiment's ancestral strains are not viable on these nutrients, but 130 generations of adaptive evolution were sufficient to render them viable. Recombination conferred a more pronounced advantage to populations adapting to indole. To study the genomic changes associated with this advantage, we sequenced the genomes of 384 clones isolated from selected replicates at the end of the experiment. These genomes harbour complex changes that range from point mutations to large-scale DNA amplifications. Among several candidate adaptive mutations, those in the tryptophanase regulator tnaC stand out, because the tna operon in which it resides has a known role in indole metabolism. One of the highly recombining populations also shows a significant excess of large-scale segmental DNA amplifications that include the tna operon. This lineage also shows a unique and potentially adaptive combination of point mutations and DNA amplifications that may have originated independently from one another, to be joined later by recombination. Our data illustrate that the advantages of recombination for adaptive evolution strongly depend on the environment and that they can be associated with complex genomic changes.
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Affiliation(s)
- H-Y Chu
- Department of Evolutionary Biology and Environmental Studies, University of Zurich, Zurich, Switzerland
| | - K Sprouffske
- Department of Evolutionary Biology and Environmental Studies, University of Zurich, Zurich, Switzerland
| | - A Wagner
- Department of Evolutionary Biology and Environmental Studies, University of Zurich, Zurich, Switzerland.,The Swiss Institute of Bioinformatics, Quartier Sorge, Batiment Genopode, Lausanne, Switzerland.,The Santa Fe Institute, Santa Fe, NM, USA
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7
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Abstract
This review considers the pathways for the degradation of amino acids and a few related compounds (agmatine, putrescine, ornithine, and aminobutyrate), along with their functions and regulation. Nitrogen limitation and an acidic environment are two physiological cues that regulate expression of several amino acid catabolic genes. The review considers Escherichia coli, Salmonella enterica serovar Typhimurium, and Klebsiella species. The latter is included because the pathways in Klebsiella species have often been thoroughly characterized and also because of interesting differences in pathway regulation. These organisms can essentially degrade all the protein amino acids, except for the three branched-chain amino acids. E. coli, Salmonella enterica serovar Typhimurium, and Klebsiella aerogenes can assimilate nitrogen from D- and L-alanine, arginine, asparagine, aspartate, glutamate, glutamine, glycine, proline, and D- and L-serine. There are species differences in the utilization of agmatine, citrulline, cysteine, histidine, the aromatic amino acids, and polyamines (putrescine and spermidine). Regardless of the pathway of glutamate synthesis, nitrogen source catabolism must generate ammonia for glutamine synthesis. Loss of glutamate synthase (glutamineoxoglutarate amidotransferase, or GOGAT) prevents utilization of many organic nitrogen sources. Mutations that create or increase a requirement for ammonia also prevent utilization of most organic nitrogen sources.
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8
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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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9
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In vivo dynamics of intracistronic transcriptional polarity. J Mol Biol 2008; 385:733-47. [PMID: 19059415 DOI: 10.1016/j.jmb.2008.11.020] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2008] [Revised: 11/09/2008] [Accepted: 11/12/2008] [Indexed: 11/24/2022]
Abstract
Transcriptional polarity occurs in Escherichia coli when cryptic Rho-dependent transcription terminators become activated as a consequence of reduced translation. Increased spacing between RNA polymerase and the leading ribosome allows the transcription termination factor Rho to bind to mRNA, migrate to the RNA polymerase, and induce termination. Transcriptional polarity results in decreased synthesis of inefficiently translated mRNAs and, therefore, in decreased expression not only of downstream genes in the same operon (intercistronic polarity) but also of the cistron in which termination occurs (intracistronic polarity). To quantitatively measure the effect of different levels of translation on intracistronic transcription termination, the polarity-prone lacZ reporter gene was fused to a range of mutated ribosome binding sites, repressed to different degrees by local RNA structure. The results show that polarity gradually increases with decreasing frequency of translational initiation, as expected. Closer analysis, with the help of a newly developed kinetic model, reveals that efficient intracistronic termination requires very low translational initiation frequencies. This finding is unexpected because Rho is a relatively small protein that binds rapidly to its RNA target, but it appears to be true also for other examples of transcriptional polarity reported in the literature. The conclusion must be that polarity is more complex than just an increased exposure of the Rho binding site as the spacing between the polymerase and the leading ribosome becomes larger. Biological consequences and possible mechanisms are discussed.
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10
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11
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Cruz-Vera LR, Rajagopal S, Squires C, Yanofsky C. Features of ribosome-peptidyl-tRNA interactions essential for tryptophan induction of tna operon expression. Mol Cell 2005; 19:333-43. [PMID: 16061180 DOI: 10.1016/j.molcel.2005.06.013] [Citation(s) in RCA: 121] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2005] [Revised: 05/31/2005] [Accepted: 06/20/2005] [Indexed: 11/17/2022]
Abstract
Certain nascent peptide sequences, when within the ribosomal exit tunnel, can inhibit translation termination and/or peptide elongation. The 24 residue leader peptidyl-tRNA of the tna operon of E. coli, TnaC-tRNA(Pro), in the presence of excess tryptophan, resists cleavage at the tnaC stop codon. TnaC residue Trp12 is crucial for this inhibition. The approximate location of Trp12 in the exit tunnel was determined by crosslinking Lys11 of TnaC-tRNA(Pro) to nucleotide A750 of 23S rRNA. Methylation of nucleotide A788 of 23S rRNA was reduced by the presence of Trp12 in TnaC-tRNA(Pro), implying A788 displacement. Inserting an adenylate at position 751, or introducing the change U2609C in 23S rRNA or the change K90H or K90W in ribosomal protein L22, virtually eliminated tryptophan induction. These modified and mutated regions are mostly located near the putative site occupied by Trp12 of TnaC-tRNA(Pro). These findings identify features of the ribosomal exit tunnel essential for tna operon induction.
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MESH Headings
- Biotinylation
- Cross-Linking Reagents/chemistry
- Escherichia coli/genetics
- Escherichia coli/metabolism
- Escherichia coli Proteins/analysis
- Escherichia coli Proteins/chemistry
- Escherichia coli Proteins/genetics
- Escherichia coli Proteins/metabolism
- Gene Expression/genetics
- Gene Expression Regulation, Bacterial/genetics
- Genotype
- Lac Operon/genetics
- Macromolecular Substances/chemistry
- Macromolecular Substances/isolation & purification
- Macromolecular Substances/metabolism
- Models, Molecular
- Mutation/genetics
- Operon/genetics
- Peptide Termination Factors/analysis
- Peptide Termination Factors/metabolism
- Photoaffinity Labels/chemistry
- Plasmids/genetics
- Protein Biosynthesis/genetics
- RNA, Messenger/metabolism
- RNA, Ribosomal, 23S/chemistry
- RNA, Ribosomal, 23S/genetics
- RNA, Transfer, Amino Acyl/genetics
- RNA, Transfer, Amino Acyl/metabolism
- RNA, Transfer, Pro/genetics
- RNA-Binding Proteins/genetics
- Ribosomal Proteins/genetics
- Ribosomes/metabolism
- Tryptophan/genetics
- Tryptophan/metabolism
- Tryptophanase/genetics
- Uridine/metabolism
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12
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Polissi A, De Laurentis W, Zangrossi S, Briani F, Longhi V, Pesole G, Dehò G. Changes in Escherichia coli transcriptome during acclimatization at low temperature. Res Microbiol 2003; 154:573-80. [PMID: 14527658 DOI: 10.1016/s0923-2508(03)00167-0] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Upon cold shock Escherichia coli transiently stops growing and adapts to the new temperature (acclimatization phase). The major physiological effects of cold temperature are a decrease in membrane fluidity and the stabilization of secondary structures of RNA and DNA, which may affect the efficiencies of translation, transcription, and replication. Specific proteins are transiently induced in the acclimatization phase. mRNA stabilization and increased translatability play a major role in this phenomenon. Polynucleotide phosphorylase (PNPase) is one of the cold-induced proteins and is essential for E. coli growth at low temperatures. We investigated the global changes in mRNA abundance during cold adaptation both in wild type E. coli MG1655 and in a PNPase-deficient mutant. We observed a twofold or greater variation in the relative mRNA abundance of 20 genes upon cold shock, notably the cold-inducible subset of csp genes and genes not previously associated with cold shock response, among these, the extracytoplasmic stress response regulators rpoE and rseA, and eight genes with unknown function. Interestingly, we found that PNPase both negatively and positively modulated the transcript abundance of some of these genes, thus suggesting a complex role of PNPase in controlling cold adaptation.
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MESH Headings
- Adaptation, Physiological
- Cold Temperature
- Escherichia coli/genetics
- Escherichia coli/physiology
- Escherichia coli Proteins/genetics
- Gene Expression Profiling
- Gene Expression Regulation, Bacterial
- Genes, Bacterial
- Heat-Shock Proteins/genetics
- Membrane Proteins/genetics
- Mutation
- Nucleic Acid Hybridization/methods
- Polyribonucleotide Nucleotidyltransferase/genetics
- RNA, Bacterial/genetics
- RNA, Bacterial/isolation & purification
- RNA, Bacterial/metabolism
- RNA, Messenger/genetics
- RNA, Messenger/isolation & purification
- RNA, Messenger/metabolism
- Sigma Factor/genetics
- Transcription Factors/genetics
- Transcription, Genetic
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13
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Vilela C, McCarthy JEG. Regulation of fungal gene expression via short open reading frames in the mRNA 5'untranslated region. Mol Microbiol 2003; 49:859-67. [PMID: 12890013 DOI: 10.1046/j.1365-2958.2003.03622.x] [Citation(s) in RCA: 113] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
We review how the expression of fungal mRNAs can be controlled by ribosome interactions with short upstream open reading frames (uORFs) within the 5'untranslated region. The efficiency of uAUG recognition modulates the impact of a uORF but steps during and after translation of the uORF also influence uORF function. The post-termination behaviour of ribosomes, therefore, plays a major role in determining the expression level of these main ORFs. Translation of a uORF can produce a cis-acting peptide that causes effector molecule-dependent stalling of the ribosomes at the end of the uORF. In other cases it is the length or position, or other features of the uORF, rather than the peptide it encodes, that determine the efficiency with which ribosomes reinitiate translation downstream of it. Whether the form of the ribosome that resumes scanning after termination is the 40S subunit alone or the entire 80S ribosome is not known. Translation of the uORF can also control gene expression by affecting the stability of the mRNA. Finally, trans-acting factors may participate in the regulatory mechanisms. Future work will need not only to provide more information on the mechanisms underlying the known cases of uORF-mediated control but also to define the full complement of uORF-containing mRNAs in at least one fungal organism.
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Affiliation(s)
- Cristina Vilela
- Posttranscriptional Control Group, Department of Biomolecular Sciences, UMIST, PO Box 88, Manchester M60 1QD, UK
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14
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Sunohara T, Abo T, Inada T, Aiba H. The C-terminal amino acid sequence of nascent peptide is a major determinant of SsrA tagging at all three stop codons. RNA (NEW YORK, N.Y.) 2002; 8:1416-27. [PMID: 12458795 PMCID: PMC1370348 DOI: 10.1017/s1355838202020198] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Recent studies on endogenous SsrA-tagged proteins have revealed that the tagging could occur at a position corresponding to the normal termination codon. During the study of SsrA-mediated Lacl tagging (Abo et al., EMBO J, 2000 19:3762-3769), we found that a variant Lacl (Lacl deltaC1) lacking the last C-terminal amino acid residue is efficiently tagged in a stop codon-dependent manner. SsrA tagging of Lacl deltaC1 occurred efficiently without Lacl binding to the lac operators at any one of three stop codons. The C-terminal (R)LESG peptide of Lacl deltaC1 was shown to trigger the SsrA tagging of an unrelated protein (CRP) when fused to its C terminus. Mass spectrometry analysis of the purified fusion proteins revealed that SsrA tagging occurs at a position corresponding to the termination codon. The alteration of the amino acid sequence but not the nucleotide sequence of the C-terminal portion eliminated the tagging. We also showed that the tagging-provoking sequences cause an efficient translational readthrough at UGA but not UAA codons. In addition, we found that C-terminal dipeptides known to induce an efficient translation readthrough could cause an efficient tagging at stop codons. We conclude that the amino acid sequence of nascent polypeptide prior to stop codons is a major determinant for the SsrA tagging at all three stop codons.
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Affiliation(s)
- Takafumi Sunohara
- Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa, Nagoya 464-8602, Japan
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15
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Abstract
Interactions between the antiterminator NusB and boxA elements in the nut sites are necessary to ensure lambda N-mediated processive antitermination. Similarly, in the bacterial cell, interactions between NusB and boxA elements help RNA polymerase to counteract polarity during transcription of rrn operons. We analyzed the effects of NusB on intragenic termination at the level of two tandem terminators located in the hisG cistron, GTTE1 and GTTE2. Unexpectedly, we found that NusB enhances transcription termination at the sub-optimal Rho site GTTE1. Moreover, site-directed mutagenesis of a boxA homolog located within GTTE1 and the masking of this element by translating ribosomes demonstrated that the recruitment of NusB in the termination complex is mediated by a boxA element. The mutated boxA also abolishes the formation of a NusB-dependent complex on GTTE1 RNA. On the whole, results provide evidence that interactions between NusB and boxA can enhance Rho-dependent termination.
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Affiliation(s)
- M S Carlomagno
- Dipartimento di Biologie e Patologia Cellulare e Molecolare L. Califano, Università degli Studi di Napoli Federico II, Italy.
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16
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Abstract
Translational bypassing joins the information found within two disparate open reading frames into a single polypeptide chain. The underlying mechanism centers on the decoding properties of peptidyl-transfer RNA (tRNA) and involves three stages: take-off, scanning, and landing. In take-off, the peptidyl-tRNA/messenger RNA (mRNA) complex in the P site of the ribosome dissociates, and the mRNA begins to move through the ribosome. In scanning, the peptidyl-tRNA probes the mRNA sliding through the decoding center. In landing, the peptidyl-tRNA re-pairs with a codon with which it can form a stable interaction. Although few examples of genes are known that rely on translational bypassing to couple open reading frames, ribosomes appear to have an innate capacity for bypassing. This suggests that the strategy of translational bypassing may be more common than presently appreciated. The best characterized example of this phenomenon is T4 gene 60, in which a complex set of signals stimulates bypassing of 50 nucleotides between the two open reading frames. In this review, we focus on the bypassing mechanism of gene 60 in terms of take-off, scanning, and landing.
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MESH Headings
- Amino Acid Sequence
- Base Sequence
- Genes, Bacterial
- Models, Biological
- Models, Molecular
- Molecular Sequence Data
- Open Reading Frames
- Peptide Chain Termination, Translational
- Protein Biosynthesis
- Protein Sorting Signals/genetics
- RNA, Bacterial/genetics
- RNA, Bacterial/metabolism
- RNA, Ribosomal, 16S/genetics
- RNA, Ribosomal, 16S/metabolism
- RNA, Ribosomal, 23S/genetics
- RNA, Ribosomal, 23S/metabolism
- RNA, Transfer, Amino Acyl/genetics
- RNA, Transfer, Amino Acyl/metabolism
- Ribosomal Proteins/genetics
- Ribosomal Proteins/metabolism
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Affiliation(s)
- A J Herr
- Department of Human Genetics, The University of Utah, Salt Lake City, Utah 84112-5330, USA.
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17
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Gong F, Yanofsky C. Reproducing tna operon regulation in vitro in an S-30 system. Tryptophan induction inhibits cleavage of TnaC peptidyl-tRNA. J Biol Chem 2001; 276:1974-83. [PMID: 11050101 DOI: 10.1074/jbc.m008892200] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Expression of the tryptophanase (tna) operon of Escherichia coli is regulated by catabolite repression and tryptophan-induced transcription antitermination. Catabolite repression regulates transcription initiation, whereas excess tryptophan induces antitermination at Rho factor-dependent termination sites in the leader region of the operon. Synthesis of the leader peptide, TnaC, is essential for antitermination. BoxA and rut sites in the immediate vicinity of the tnaC stop codon are required for termination. In this paper we use an in vitro S-30 cell-free system to analyze the features of tna operon regulation. We show that transcription initiation is cyclic AMP (cAMP)-dependent and is not influenced by tryptophan. Continuation of transcription beyond the leader region requires the presence of inducing levels of tryptophan and synthesis of the TnaC leader peptide. Using a tnaA'-'trpE fusion, we demonstrate that induction results in a 15-20-fold increase in synthesis of the tryptophan-free TnaA-TrpE fusion protein. Replacing Trp codon 12 of tnaC by an Arg codon, or changing the tnaC start codon to a stop codon, eliminates induction. Addition of bicyclomycin, a specific inhibitor of Rho factor action, substantially increases basal level expression. Analyses of tna mRNA synthesis in vitro demonstrate that, in the absence of inducer transcription is terminated and the terminated transcripts are degraded. In the presence of inducer, antitermination increases the synthesis of the read-through transcript. TnaC synthesis is observed in the cell-free system. However, in the presence of tryptophan, a peptidyl-tRNA also appears, TnaC-tRNA(Pro). Our findings suggest that inducer acts by preventing cleavage of TnaC peptidyl-tRNA. The ribosome associated with this newly synthesized peptidyl-tRNA presumably stalls at the tnaC stop codon, blocking Rho's access to the BoxA and rut sites, thereby preventing termination. 1-Methyltryptophan also is an effective inducer in vitro. This tryptophan analog is not incorporated into TnaC.
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Affiliation(s)
- F Gong
- Department of Biological Sciences, Stanford University, Stanford, California 94305, USA
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18
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Affiliation(s)
- D R Morris
- Departments of Biochemistry, University of Washington, Seattle, USA.
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19
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Konan KV, Yanofsky C. Rho-dependent transcription termination in the tna operon of Escherichia coli: roles of the boxA sequence and the rut site. J Bacteriol 2000; 182:3981-8. [PMID: 10869076 PMCID: PMC94583 DOI: 10.1128/jb.182.14.3981-3988.2000] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Expression of the tryptophanase (tna) operon of Escherichia coli is regulated by catabolite repression and by tryptophan-induced transcription antitermination. Tryptophan induction prevents Rho-dependent transcription termination in the leader region of the operon. Induction requires translation of a 24-residue leader peptide-coding region, tnaC, containing a single, crucial Trp codon. Studies with a lacZ reporter construct lacking the tnaC-tnaA spacer region suggest that, in the presence of excess tryptophan, the TnaC leader peptide acts in cis on the ribosome translating tnaC to inhibit its release. The stalled ribosome is thought to block Rho's access to the transcript. In this paper we examine the roles of the boxA sequence and the rut site in Rho-dependent termination. Deleting six nucleotides (CGC CCT) of boxA or introducing specific point mutations in boxA results in high-level constitutive expression. Some constitutive changes introduced in boxA do not change the TnaC peptide sequence. We confirm that deletion of the rut site results in constitutive expression. We also demonstrate that, in each constitutive construct, replacement of the tnaC start codon by a UAG stop codon reduces expression significantly, suggesting that constitutive expression requires translation of the tnaC coding sequence. Addition of bicyclomycin, an inhibitor of Rho, to these UAG constructs increases expression, demonstrating that reduced expression is due to Rho action. Combining a boxA point mutation with rut site deletion results in constitutive expression comparable to that of a maximally induced operon. These results support the hypothesis that in the presence of tryptophan the ribosome translating tnaC blocks Rho's access to the boxA and rut sites, thereby preventing transcription termination.
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Affiliation(s)
- K V Konan
- Department of Biological Sciences, Stanford University, CA 94305-5020, USA
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20
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Abstract
Transcription termination is a dynamic process and is subject to control at a number of levels. New information about the molecular mechanisms of transcription elongation and termination, as well as new insights into protein-RNA interactions, are providing a framework for increased understanding of the molecular details of transcription termination control.
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Affiliation(s)
- T M Henkin
- Department of Microbiology, The Ohio State University, Columbus, OH 43210, USA.
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21
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Affiliation(s)
- C Yanofsky
- Department of Biological Sciences, Stanford University, Stanford, California 94305, USA.
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22
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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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