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Kohl MP, Chane-Woon-Ming B, Bahena-Ceron R, Jaramillo-Ponce J, Antoine L, Herrgott L, Romby P, Marzi S. Ribosome Profiling Methods Adapted to the Study of RNA-Dependent Translation Regulation in Staphylococcus aureus. Methods Mol Biol 2024; 2741:73-100. [PMID: 38217649 DOI: 10.1007/978-1-0716-3565-0_5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2024]
Abstract
Noncoding RNAs, including regulatory RNAs (sRNAs), are instrumental in regulating gene expression in pathogenic bacteria, allowing them to adapt to various stresses encountered in their host environments. Staphylococcus aureus is a well-studied model for RNA-mediated regulation of virulence and pathogenicity, with sRNAs playing significant roles in shaping S. aureus interactions with human and animal hosts. By modulating the translation and/or stability of target mRNAs, sRNAs regulate the synthesis of virulence factors and regulatory proteins required for pathogenesis. Moreover, perturbation of the levels of RNA modifications in two other classes of noncoding RNAs, rRNAs, and tRNAs, has been proposed to contribute to stress adaptation. However, the study of how these various factors affect translation regulation has often been restricted to specific genes, using in vivo reporters and/or in vitro translation systems. Genome-wide sequencing approaches offer novel perspectives for studying RNA-dependent regulation. In particular, ribosome profiling methods provide a powerful resource for characterizing the overall landscape of translational regulation, contributing to a better understanding of S. aureus physiopathology. Here, we describe protocols that we have adapted to perform ribosome profiling in S. aureus.
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Affiliation(s)
- Maximilian P Kohl
- Architecture et Réactivité de l'ARN, CNRS 9002, Université de Strasbourg, Strasbourg, France
| | | | - Roberto Bahena-Ceron
- Architecture et Réactivité de l'ARN, CNRS 9002, Université de Strasbourg, Strasbourg, France
| | - Jose Jaramillo-Ponce
- Architecture et Réactivité de l'ARN, CNRS 9002, Université de Strasbourg, Strasbourg, France
| | - Laura Antoine
- Architecture et Réactivité de l'ARN, CNRS 9002, Université de Strasbourg, Strasbourg, France
| | - Lucas Herrgott
- Architecture et Réactivité de l'ARN, CNRS 9002, Université de Strasbourg, Strasbourg, France
| | - Pascale Romby
- Architecture et Réactivité de l'ARN, CNRS 9002, Université de Strasbourg, Strasbourg, France
| | - Stefano Marzi
- Architecture et Réactivité de l'ARN, CNRS 9002, Université de Strasbourg, Strasbourg, France.
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Antoine L, Bahena-Ceron R, Devi Bunwaree H, Gobry M, Loegler V, Romby P, Marzi S. RNA Modifications in Pathogenic Bacteria: Impact on Host Adaptation and Virulence. Genes (Basel) 2021; 12:1125. [PMID: 34440299 PMCID: PMC8394870 DOI: 10.3390/genes12081125] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2021] [Revised: 07/16/2021] [Accepted: 07/19/2021] [Indexed: 12/19/2022] Open
Abstract
RNA modifications are involved in numerous biological processes and are present in all RNA classes. These modifications can be constitutive or modulated in response to adaptive processes. RNA modifications play multiple functions since they can impact RNA base-pairings, recognition by proteins, decoding, as well as RNA structure and stability. However, their roles in stress, environmental adaptation and during infections caused by pathogenic bacteria have just started to be appreciated. With the development of modern technologies in mass spectrometry and deep sequencing, recent examples of modifications regulating host-pathogen interactions have been demonstrated. They show how RNA modifications can regulate immune responses, antibiotic resistance, expression of virulence genes, and bacterial persistence. Here, we illustrate some of these findings, and highlight the strategies used to characterize RNA modifications, and their potential for new therapeutic applications.
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Affiliation(s)
| | | | | | | | | | | | - Stefano Marzi
- Université de Strasbourg, CNRS, Architecture et Réactivité de l’ARN, UPR 9002, F-67000 Strasbourg, France; (L.A.); (R.B.-C.); (H.D.B.); (M.G.); (V.L.); (P.R.)
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Masters TL, Wachter J, Hill SA. Loop structures in the 5' untranslated region and antisense RNA mediate pilE gene expression in Neisseria gonorrhoeae. MICROBIOLOGY (READING, ENGLAND) 2016; 162:2005-2016. [PMID: 27590250 DOI: 10.1099/mic.0.000369] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Regulation of the Neisseria gonorrhoeae pilE gene is ill-defined. In this study, post-transcriptional effects on expression were assessed. In silico analysis predicts the formation of three putative stable stem-loop structures with favourable free energies within the 5' untranslated region of the pilE message. Using quantitative reverse transcriptase PCR analyses, we show that each loop structure forms, with introduced destabilizing stem-loop mutations diminishing loop stability. Utilizing a series of pilE translational fusions, deletion of either loop 1 or loop 2 caused a significant reduction of pilE mRNA resulting in reduced expression of the reporter gene. Consequently, the formation of the loops apparently protects the pilE transcript from degradation. Putative loop 3 contains the pilE ribosomal binding site. Consequently, its formation may influence translation. Analysis of a small RNA transcriptome revealed an antisense RNA being produced upstream of the pilE promoter that is predicted to hybridize across the 5' untranslated region loops. Insertional mutants were created where the antisense RNA is not transcribed. In these mutants, pilE transcript levels are greatly diminished, with any residual message apparently not being translated. Complementation of these insertion mutants in trans with the antisense RNA gene facilitates pilE translation yielding a pilus + phenotype. Overall, this study demonstrates a complex relationship between loop-dependent transcript protection and antisense RNA in modulating pilE expression levels.
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Affiliation(s)
- Thao L Masters
- Department of Biological Sciences, Northern Illinois University, DeKalb, IL 60115, USA
| | - Jenny Wachter
- Department of Biological Sciences, Northern Illinois University, DeKalb, IL 60115, USA
| | - Stuart A Hill
- Department of Biological Sciences, Northern Illinois University, DeKalb, IL 60115, USA
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Duval M, Simonetti A, Caldelari I, Marzi S. Multiple ways to regulate translation initiation in bacteria: Mechanisms, regulatory circuits, dynamics. Biochimie 2015; 114:18-29. [PMID: 25792421 DOI: 10.1016/j.biochi.2015.03.007] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2014] [Accepted: 03/08/2015] [Indexed: 11/15/2022]
Abstract
To adapt their metabolism rapidly and constantly in response to environmental variations, bacteria often target the translation initiation process, during which the ribosome assembles on the mRNA. Here, we review different mechanisms of regulation mediated by cis-acting elements, sRNAs and proteins, showing, when possible, their intimate connection with the translational apparatus. Indeed the ribosome itself could play a direct role in several regulatory mechanisms. Different features of the regulatory signals (sequences, structures and their positions on the mRNA) are contributing to the large variety of regulatory mechanisms. Ribosome heterogeneity, variation of individual cells responses and the spatial and temporal organization of the translation process add more layers of complexity. This hampers to define manageable set of rules for bacterial translation initiation control.
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Affiliation(s)
- Mélodie Duval
- Architecture et Réactivité de l'ARN, Université de Strasbourg, IBMC-CNRS, F-67084 Strasbourg, France
| | - Angelita Simonetti
- Architecture et Réactivité de l'ARN, Université de Strasbourg, IBMC-CNRS, F-67084 Strasbourg, France
| | - Isabelle Caldelari
- Architecture et Réactivité de l'ARN, Université de Strasbourg, IBMC-CNRS, F-67084 Strasbourg, France
| | - Stefano Marzi
- Architecture et Réactivité de l'ARN, Université de Strasbourg, IBMC-CNRS, F-67084 Strasbourg, France
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Furusawa H, Tsuyuki Y, Takahashi S, Okahata Y. In situ monitoring of structural changes during formation of 30S translation initiation complex by energy dissipation measurement using 27-MHz quartz-crystal microbalance. Anal Chem 2014; 86:5406-15. [PMID: 24794712 DOI: 10.1021/ac500487b] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Ribosome is a bionanomachine that facilitates an orderly translation process during protein synthesis in living cells. Real-time monitoring of conformational changes in ribosomal subunits in aqueous solution is important to understand the regulatory mechanism of protein synthesis, because conformational changes in ribosome in E. coli have been predicted to operate the switch from translation initiation to an elongation process during translation. We performed an energy dissipation measurement by using a quartz-crystal microbalance-admittance (QCM-A) technique for in situ monitoring of conformational changes in pre-30S translation initiation complex in response to the binding of fMet-tRNA(fMet) in aqueous solution. The addition of fMet-tRNA(fMet) caused changes in the physical property (increased dehydration and elasticity) in 30S ribosomal subunit in the presence of mRNA and IF2/guanosine 5'-triphosphate (GTP) on the QCM plate. Furthermore, two sequential changes triggered by the addition of fMet-tRNA(fMet) were observed in 30S ribosomal subunit bound to mRNA in the presence of IF2/GTP and IF3. These observations suggest that the structural changes in 30S ribosomal subunit caused by the binding of fMet-tRNA(fMet) with IF2/GTP in the presence of IF3 could act as a switch to regulate the orderly processing in the construction of translation initiation complex, because the structural distinction can be a guidepost in the process for the relevant biomolecules.
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Affiliation(s)
- Hiroyuki Furusawa
- Innovative Flex Course for Frontier Organic Material Systems (iFront), Yamagata University , 4-3-16 Jonan, Yonezawa, Yamagata 992-8510, Japan
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Role for cis-acting RNA sequences in the temperature-dependent expression of the multiadhesive lig proteins in Leptospira interrogans. J Bacteriol 2013; 195:5092-101. [PMID: 24013626 DOI: 10.1128/jb.00663-13] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
The spirochete Leptospira interrogans causes a systemic infection that provokes a febrile illness. The putative lipoproteins LigA and LigB promote adhesion of Leptospira to host proteins, interfere with coagulation, and capture complement regulators. In this study, we demonstrate that the expression level of the LigA and LigB proteins was substantially higher when L. interrogans proliferated at 37°C instead of the standard culture temperature of 30°C. The RNA comprising the 175-nucleotide 5' untranslated region (UTR) and first six lig codons, whose sequence is identical in ligA and ligB, is predicted to fold into two distinct stem-loop structures separated by a single-stranded region. The ribosome-binding site is partially sequestered in double-stranded RNA within the second structure. Toeprint analysis revealed that in vitro formation of a 30S-tRNA(fMet)-mRNA ternary complex was inhibited unless a 5' deletion mutation disrupted the second stem-loop structure. To determine whether the lig sequence could mediate temperature-regulated gene expression in vivo, the 5' UTR and the first six codons were inserted between the Escherichia coli l-arabinose promoter and bgaB (β-galactosidase from Bacillus stearothermophilus) to create a translational fusion. The lig fragment successfully conferred thermoregulation upon the β-galactosidase reporter in E. coli. The second stem-loop structure was sufficient to confer thermoregulation on the reporter, while sequences further upstream in the 5' UTR slightly diminished expression at each temperature tested. Finally, the expression level of β-galactosidase was significantly higher when point mutations predicted to disrupt base pairs in the second structure were introduced into the stem. Compensatory mutations that maintained base pairing of the stem without restoring the wild-type sequence reinstated the inhibitory effect of the 5' UTR on expression. These results indicate that ligA and ligB expression is limited by double-stranded RNA that occludes the ribosome-binding site. At elevated temperatures, the ribosome-binding site is exposed to promote translation initiation.
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Shasmal M, Sengupta J. Structural diversity in bacterial ribosomes: mycobacterial 70S ribosome structure reveals novel features. PLoS One 2012; 7:e31742. [PMID: 22384065 PMCID: PMC3286452 DOI: 10.1371/journal.pone.0031742] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2011] [Accepted: 01/12/2012] [Indexed: 12/25/2022] Open
Abstract
Here we present analysis of a 3D cryo-EM map of the 70S ribosome from Mycobacterium smegmatis, a saprophytic cousin of the etiological agent of tuberculosis in humans, Mycobacterium tuberculosis. In comparison with the 3D structures of other prokaryotic ribosomes, the density map of the M. smegmatis 70S ribosome reveals unique structural features and their relative orientations in the ribosome. Dramatic changes in the periphery due to additional rRNA segments and extra domains of some of the peripheral ribosomal proteins like S3, S5, S16, L17, L25, are evident. One of the most notable features appears in the large subunit near L1 stalk as a long helical structure next to helix 54 of the 23S rRNA. The sharp upper end of this structure is located in the vicinity of the mRNA exit channel. Although the M. smegmatis 70S ribosome possesses conserved core structure of bacterial ribosome, the new structural features, unveiled in this study, demonstrates diversity in the 3D architecture of bacterial ribosomes. We postulate that the prominent helical structure related to the 23S rRNA actively participates in the mechanisms of translation in mycobacteria.
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Affiliation(s)
| | - Jayati Sengupta
- Structural Biology and Bio-Informatics Division, Indian Institute of Chemical Biology (Council of Scientific and Industrial Research), Jadavpur, Kolkata, West Bengal, India
- * E-mail:
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8
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Abstract
Techniques to manipulate cellular gene expression such that amino acid analogs not encoded by the genetic code are incorporated into a polypeptide chain have recently gained increasing interest. The so-called noncanonical amino acids often have unusual properties that can be translated into target proteins by reprogrammed ribosomal protein synthesis. Residue-specific substitution of a specific canonical amino acid by its analogs provokes global effects in the resulting protein congeners that include improved stability or catalytic activity, reduced redox sensitivity, as well as altered spectral properties. Thus, the approach holds great promise for the engineering of synthetic proteins.This contribution describes a protocol for the incorporation of a noncanonical amino acid into a target protein expressed in an appropriate amino acid auxotrophic E. coli strain.
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9
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Smith DP, Kitner JB, Norbeck AD, Clauss TR, Lipton MS, Schwalbach MS, Steindler L, Nicora CD, Smith RD, Giovannoni SJ. Transcriptional and translational regulatory responses to iron limitation in the globally distributed marine bacterium Candidatus pelagibacter ubique. PLoS One 2010; 5:e10487. [PMID: 20463970 PMCID: PMC2864753 DOI: 10.1371/journal.pone.0010487] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2010] [Accepted: 04/11/2010] [Indexed: 11/19/2022] Open
Abstract
Iron is recognized as an important micronutrient that limits microbial plankton productivity over vast regions of the oceans. We investigated the gene expression responses of Candidatus Pelagibacter ubique cultures to iron limitation in natural seawater media supplemented with a siderophore to chelate iron. Microarray data indicated transcription of the periplasmic iron binding protein sfuC increased by 16-fold, and iron transporter subunits, iron-sulfur center assembly genes, and the putative ferroxidase rubrerythrin transcripts increased to a lesser extent. Quantitative peptide mass spectrometry revealed that sfuC protein abundance increased 27-fold, despite an average decrease of 59% across the global proteome. Thus, we propose sfuC as a marker gene for indicating iron limitation in marine metatranscriptomic and metaproteomic ecological surveys. The marked proteome reduction was not directly correlated to changes in the transcriptome, implicating post-transcriptional regulatory mechanisms as modulators of protein expression. Two RNA-binding proteins, CspE and CspL, correlated well with iron availability, suggesting that they may contribute to the observed differences between the transcriptome and proteome. We propose a model in which the RNA-binding activity of CspE and CspL selectively enables protein synthesis of the iron acquisition protein SfuC during transient growth-limiting episodes of iron scarcity.
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Affiliation(s)
- Daniel P. Smith
- Molecular and Cellular Biology Program, Oregon State University, Corvallis, Oregon, United States of America
| | - Joshua B. Kitner
- Department of Microbiology, Oregon State University, Corvallis, Oregon, United States of America
| | - Angela D. Norbeck
- Biological and Computational Sciences Division, Pacific Northwest National Laboratory, Richland, Washington, United States of America
| | - Therese R. Clauss
- Biological and Computational Sciences Division, Pacific Northwest National Laboratory, Richland, Washington, United States of America
| | - Mary S. Lipton
- Biological and Computational Sciences Division, Pacific Northwest National Laboratory, Richland, Washington, United States of America
| | - Michael S. Schwalbach
- Department of Microbiology, Oregon State University, Corvallis, Oregon, United States of America
| | - Laura Steindler
- Department of Microbiology, Oregon State University, Corvallis, Oregon, United States of America
| | - Carrie D. Nicora
- Biological and Computational Sciences Division, Pacific Northwest National Laboratory, Richland, Washington, United States of America
| | - Richard D. Smith
- Biological and Computational Sciences Division, Pacific Northwest National Laboratory, Richland, Washington, United States of America
| | - Stephen J. Giovannoni
- Department of Microbiology, Oregon State University, Corvallis, Oregon, United States of America
- * E-mail:
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Lioliou E, Romilly C, Romby P, Fechter P. RNA-mediated regulation in bacteria: from natural to artificial systems. N Biotechnol 2010; 27:222-35. [PMID: 20211281 DOI: 10.1016/j.nbt.2010.03.002] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Bacteria use various means of RNA-mediated gene regulation. Regulatory RNAs include mRNA leaders that affect expression in cis or in trans, non-coding RNAs that trap regulatory proteins or interact with one or multiple target mRNAs, and RNAs that protect the bacteria against foreign and invasive DNA. The aim of this review is to outline the basic principles of bacterial RNA-mediated regulation, with a special focus on both cis-acting regulatory regions of mRNAs and antisense RNAs (asRNAs), and to give a brief overview of selected examples of RNA-based technology that have paved the way for biotechnological applications.
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Affiliation(s)
- Efthimia Lioliou
- Architecture et Réactivité de l'ARN, Université de Strasbourg, CNRS, IBMC, 15 rue René Descartes, Strasbourg cedex, France
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11
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Geissmann T, Chevalier C, Cros MJ, Boisset S, Fechter P, Noirot C, Schrenzel J, François P, Vandenesch F, Gaspin C, Romby P. A search for small noncoding RNAs in Staphylococcus aureus reveals a conserved sequence motif for regulation. Nucleic Acids Res 2010; 37:7239-57. [PMID: 19786493 PMCID: PMC2790875 DOI: 10.1093/nar/gkp668] [Citation(s) in RCA: 169] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Bioinformatic analysis of the intergenic regions of Staphylococcus aureus predicted multiple regulatory regions. From this analysis, we characterized 11 novel noncoding RNAs (RsaA-K) that are expressed in several S. aureus strains under different experimental conditions. Many of them accumulate in the late-exponential phase of growth. All ncRNAs are stable and their expression is Hfq-independent. The transcription of several of them is regulated by the alternative sigma B factor (RsaA, D and F) while the expression of RsaE is agrA-dependent. Six of these ncRNAs are specific to S. aureus, four are conserved in other Staphylococci, and RsaE is also present in Bacillaceae. Transcriptomic and proteomic analysis indicated that RsaE regulates the synthesis of proteins involved in various metabolic pathways. Phylogenetic analysis combined with RNA structure probing, searches for RsaE-mRNA base pairing, and toeprinting assays indicate that a conserved and unpaired UCCC sequence motif of RsaE binds to target mRNAs and prevents the formation of the ribosomal initiation complex. This study unexpectedly shows that most of the novel ncRNAs carry the conserved C-rich motif, suggesting that they are members of a class of ncRNAs that target mRNAs by a shared mechanism.
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Affiliation(s)
- Thomas Geissmann
- Architecture et Réactivité de l'ARN, Université de Strasbourg, CNRS, IBMC, 15 rue René Descartes, F-67084 Strasbourg, France
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12
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Wahid AM, Coventry VK, Conn GL. The PKR-binding domain of adenovirus VA RNAI exists as a mixture of two functionally non-equivalent structures. Nucleic Acids Res 2009; 37:5830-7. [PMID: 19635730 PMCID: PMC2761268 DOI: 10.1093/nar/gkp595] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
VA RNAI is a non-coding adenoviral transcript that counteracts the host cell anti-viral defenses such as immune responses mediated via PKR. We investigated potential alternate secondary structure conformations within the PKR-binding domain of VA RNAI using site-directed mutagenesis, RNA UV-melting analysis and enzymatic RNA secondary structure probing. The latter data clearly indicated that the wild-type VA RNAI apical stem can adopt two different conformations and that it exists as a mixed population of these two structures. In contrast, in two sequence variants we designed to eliminate one of the possible structures, while leaving the other intact, each formed a unique secondary structure. This clarification of the apical stem pairing also suggests a small alteration to the apical stem–loop secondary structure. The relative ability of the two apical stem conformations to bind PKR and inhibit kinase activity was measured by isothermal titration calorimetry and PKR autophosphorylation inhibition assay. We found that the two sequence variants displayed markedly different activities, with one being a significantly poorer binder and inhibitor of PKR. Whether the presence of the VA RNAI conformation with reduced PKR inhibitory activity is directly beneficial to the virus in the cell for some other function requires further investigation.
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Affiliation(s)
- Ahmed M Wahid
- Manchester Interdisciplinary Biocentre, Faculty of Life Sciences, University of Manchester, 131 Princess Street, Manchester, M1 7DN
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13
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Ribosomal initiation complexes probed by toeprinting and effect of trans-acting translational regulators in bacteria. Methods Mol Biol 2009; 540:247-63. [PMID: 19381565 DOI: 10.1007/978-1-59745-558-9_18] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/09/2023]
Abstract
Toeprinting was developed to study the formation of ribosomal initiation complexes in bacteria. This approach, based on the inhibition of reverse transcriptase elongation, was used to monitor the effect of ribosomal components and translational factors on the formation of the active ribosomal initiation complex. Moreover, this method offers an easy way to study in vitro how mRNA conformational changes alter ribosome binding at the initiation site. These changes can be induced either by environmental cues (temperature, ion concentration), or by the binding of metabolites, regulatory proteins, and trans-acting RNAs. An experimental guide is given to follow the different steps of the formation of ribosomal initiation complexes in Escherichia coli and Staphylococcus aureus, and to monitor the mechanism of action of several regulators on translation initiation in vitro. Protocols to prepare the ribosome and the subunits are also given for Thermus thermophilus, Staphylococcus aureus, and Escherichia coli.
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Dreyfus M. Killer and protective ribosomes. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2009; 85:423-66. [PMID: 19215779 DOI: 10.1016/s0079-6603(08)00811-8] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
In prokaryotes, translation influences mRNA decay. The breakdown of most Escherichia coli mRNAs is initiated by RNase E, a 5'-dependent endonuclease. Some mRNAs are protected by ribosomes even if these are located far upstream of cleavage sites ("protection at a distance"), whereas others require direct shielding of these sites. I argue that these situations reflect different modes of interaction of RNase E with mRNAs. Protection at a distance is most impressive in Bacilli, where ribosomes can protect kilobases of unstable downstream sequences. I propose that this protection reflects the role in mRNA decay of RNase J1, a 5'-->3' exonuclease with no E. coli equivalent. Finally, recent years have shown that besides their protective role, ribosomes can also cleave their mRNA under circumstances that cause ribosome stalling. The endonuclease associated with this "killing" activity, which has a eukaryotic counterpart ("no-go decay"), is not characterized; it may be borne by the distressed ribosome itself.
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15
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Levine E, Hwa T. Small RNAs establish gene expression thresholds. Curr Opin Microbiol 2008; 11:574-9. [PMID: 18935980 DOI: 10.1016/j.mib.2008.09.016] [Citation(s) in RCA: 92] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2008] [Revised: 09/24/2008] [Accepted: 09/24/2008] [Indexed: 02/01/2023]
Abstract
The central role of small RNAs in regulating bacterial gene expression has been elucidated in the past years. Typically, small RNAs act via specific basepairing with target mRNAs, leading to modulation of translation initiation and mRNA stability. Quantitative studies suggest that small RNA regulation is characterized by unique features, which allow it to complement regulation at the transcriptional level. In particular, small RNAs are shown to establish a threshold for the expression of their target, providing safety mechanism against random fluctuations and transient signals. The threshold level is set by the transcription rate of the small RNA and can thus be modulated dynamically to reflect changing environmental conditions.
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Affiliation(s)
- Erel Levine
- Center for Theoretical Biological Physics and Department of Physics, University of California at San Diego, La Jolla, CA 92093, United States.
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