1
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Bonar CD, Han J, Wang R, Panchapakesan SSS, Unrau PJ. E. coli 6S RNA complexed to RNA polymerase maintains product RNA synthesis at low cellular ATP levels by initiation with noncanonical initiator nucleotides. RNA (NEW YORK, N.Y.) 2022; 28:1643-1658. [PMID: 36198425 PMCID: PMC9670815 DOI: 10.1261/rna.079356.122] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2022] [Accepted: 09/21/2022] [Indexed: 06/16/2023]
Abstract
The E. coli 6S RNA is an RNA polymerase (RNAP) inhibitor that competes with σ70-dependent DNA promoters for binding to RNAP holoenzyme (RNAP:σ70). The 6S RNA when bound is then used as a template to synthesize a short product RNA (pRNA; usually 13-nt-long). This pRNA changes the 6S RNA structure, triggering the 6S RNA:pRNA complex to release and allowing DNA-dependent housekeeping gene expression to resume. In high nutrient conditions, 6S RNA turnover is extremely rapid but becomes very slow in low nutrient environments. This leads to a large accumulation of inhibited RNAP:σ70 in stationary phase. As pRNA initiates synthesis with ATP, we and others have proposed that the 6S RNA release rate strongly depends on ATP levels as a proxy for sensing the cellular metabolic state. By purifying endogenous 6S RNA:pRNA complexes using RNA Mango and using reverse transcriptase to generate pRNA-cDNA chimeras, we demonstrate that 6S RNA:pRNA formation can be simultaneous with 6S RNA 5' maturation. More importantly, we find a dramatic accumulation of capped pRNAs during stationary phase. This indicates that ATP levels in stationary phase are low enough for noncanonical initiator nucleotides (NCINs) such as NAD+ and NADH to initiate pRNA synthesis. In vitro, mutation of the conserved 6S RNA template sequence immediately upstream of the pRNA transcriptional start site can increase or decrease the pRNA capping efficiency, suggesting that evolution has tuned the biological 6S RNA sequence for an optimal capping rate. NCIN-initiated pRNA synthesis may therefore be essential for cell viability in low nutrient conditions.
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Affiliation(s)
- Christopher D Bonar
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, B.C. V5A 1S6, Canada
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, USA
| | - Jonathan Han
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, B.C. V5A 1S6, Canada
- Faculty of Medicine, University of British Columbia, Vancouver, B.C. V6T 1Z3, Canada
| | - Robert Wang
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, B.C. V5A 1S6, Canada
- Cheriton School of Computer Science, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
| | - Shanker Shyam Sundhar Panchapakesan
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, B.C. V5A 1S6, Canada
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, Connecticut 06520-8103, USA
| | - Peter J Unrau
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, B.C. V5A 1S6, Canada
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2
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Vaňková Hausnerová V, Marvalová O, Šiková M, Shoman M, Havelková J, Kambová M, Janoušková M, Kumar D, Halada P, Schwarz M, Krásný L, Hnilicová J, Pánek J. Ms1 RNA Interacts With the RNA Polymerase Core in Streptomyces coelicolor and Was Identified in Majority of Actinobacteria Using a Linguistic Gene Synteny Search. Front Microbiol 2022; 13:848536. [PMID: 35633709 PMCID: PMC9130861 DOI: 10.3389/fmicb.2022.848536] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2022] [Accepted: 02/22/2022] [Indexed: 11/15/2022] Open
Abstract
Bacteria employ small non-coding RNAs (sRNAs) to regulate gene expression. Ms1 is an sRNA that binds to the RNA polymerase (RNAP) core and affects the intracellular level of this essential enzyme. Ms1 is structurally related to 6S RNA that binds to a different form of RNAP, the holoenzyme bearing the primary sigma factor. 6S RNAs are widespread in the bacterial kingdom except for the industrially and medicinally important Actinobacteria. While Ms1 RNA was identified in Mycobacterium, it is not clear whether Ms1 RNA is present also in other Actinobacteria species. Here, using a computational search based on secondary structure similarities combined with a linguistic gene synteny approach, we identified Ms1 RNA in Streptomyces. In S. coelicolor, Ms1 RNA overlaps with the previously annotated scr3559 sRNA with an unknown function. We experimentally confirmed that Ms1 RNA/scr3559 associates with the RNAP core without the primary sigma factor HrdB in vivo. Subsequently, we applied the computational approach to other Actinobacteria and identified Ms1 RNA candidates in 824 Actinobacteria species, revealing Ms1 RNA as a widespread class of RNAP binding sRNAs, and demonstrating the ability of our multifactorial computational approach to identify weakly conserved sRNAs in evolutionarily distant genomes.
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Affiliation(s)
- Viola Vaňková Hausnerová
- Laboratory of Microbial Genetics and Gene Expression, Institute of Microbiology of the Czech Academy of Sciences, Prague, Czechia
| | - Olga Marvalová
- Laboratory of Microbial Genetics and Gene Expression, Institute of Microbiology of the Czech Academy of Sciences, Prague, Czechia
| | - Michaela Šiková
- Laboratory of Microbial Genetics and Gene Expression, Institute of Microbiology of the Czech Academy of Sciences, Prague, Czechia
| | - Mahmoud Shoman
- Laboratory of Microbial Genetics and Gene Expression, Institute of Microbiology of the Czech Academy of Sciences, Prague, Czechia
| | - Jarmila Havelková
- Laboratory of Microbial Genetics and Gene Expression, Institute of Microbiology of the Czech Academy of Sciences, Prague, Czechia
| | - Milada Kambová
- Laboratory of Microbial Genetics and Gene Expression, Institute of Microbiology of the Czech Academy of Sciences, Prague, Czechia
| | - Martina Janoušková
- Laboratory of Microbial Genetics and Gene Expression, Institute of Microbiology of the Czech Academy of Sciences, Prague, Czechia
| | - Dilip Kumar
- Laboratory of Microbial Genetics and Gene Expression, Institute of Microbiology of the Czech Academy of Sciences, Prague, Czechia
| | - Petr Halada
- Laboratory of Structural Biology and Cell Signaling, Institute of Microbiology of the Czech Academy of Sciences, Vestec, Czechia
| | - Marek Schwarz
- Laboratory of Bioinformatics, Institute of Microbiology of the Czech Academy of Sciences, Prague, Czechia
| | - Libor Krásný
- Laboratory of Microbial Genetics and Gene Expression, Institute of Microbiology of the Czech Academy of Sciences, Prague, Czechia
| | - Jarmila Hnilicová
- Laboratory of Microbial Genetics and Gene Expression, Institute of Microbiology of the Czech Academy of Sciences, Prague, Czechia
| | - Josef Pánek
- Laboratory of Bioinformatics, Institute of Microbiology of the Czech Academy of Sciences, Prague, Czechia
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3
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Structural and Functional Insight into the Mechanism of Bacillus subtilis 6S-1 RNA Release from RNA Polymerase. Noncoding RNA 2022; 8:ncrna8010020. [PMID: 35202093 PMCID: PMC8876501 DOI: 10.3390/ncrna8010020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2021] [Revised: 02/03/2022] [Accepted: 02/07/2022] [Indexed: 11/29/2022] Open
Abstract
Here we investigated the refolding of Bacillus subtilis 6S-1 RNA and its release from σA-RNA polymerase (σA-RNAP) in vitro using truncated and mutated 6S-1 RNA variants. Truncated 6S-1 RNAs, only consisting of the central bubble (CB) flanked by two short helical arms, can still traverse the mechanistic 6S RNA cycle in vitro despite ~10-fold reduced σA-RNAP affinity. This indicates that the RNA’s extended helical arms including the ‘−35′-like region are not required for basic 6S-1 RNA functionality. The role of the ‘central bubble collapse helix’ (CBCH) in pRNA-induced refolding and release of 6S-1 RNA from σA-RNAP was studied by stabilizing mutations. This also revealed base identities in the 5’-part of the CB (5’-CB), upstream of the pRNA transcription start site (nt 40), that impact ground state binding of 6S-1 RNA to σA-RNAP. Stabilization of the CBCH by the C44/45 double mutation shifted the pRNA length pattern to shorter pRNAs and, combined with a weakened P2 helix, resulted in more effective release from RNAP. We conclude that formation of the CBCH supports pRNA-induced 6S-1 RNA refolding and release. Our mutational analysis also unveiled that formation of a second short hairpin in the 3′-CB is detrimental to 6S-1 RNA release. Furthermore, an LNA mimic of a pRNA as short as 6 nt, when annealed to 6S-1 RNA, retarded the RNA’s gel mobility and interfered with σA-RNAP binding. This effect incrementally increased with pLNA 7- and 8-mers, suggesting that restricted conformational flexibility introduced into the 5’-CB by base pairing with pRNAs prevents 6S-1 RNA from adopting an elongated shape. Accordingly, atomic force microscopy of free 6S-1 RNA versus 6S-1:pLNA 8- and 14-mer complexes revealed that 6S-1:pRNA hybrid structures, on average, adopt a more compact structure than 6S-1 RNA alone. Overall, our findings also illustrate that the wild-type 6S-1 RNA sequence and structure ensures an optimal balance of the different functional aspects involved in the mechanistic cycle of 6S-1 RNA.
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4
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Wassarman KM. 6S RNA, a Global Regulator of Transcription. Microbiol Spectr 2018; 6:10.1128/microbiolspec.RWR-0019-2018. [PMID: 29916345 PMCID: PMC6013841 DOI: 10.1128/microbiolspec.rwr-0019-2018] [Citation(s) in RCA: 51] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2018] [Indexed: 01/06/2023] Open
Abstract
6S RNA is a small RNA regulator of RNA polymerase (RNAP) that is present broadly throughout the bacterial kingdom. Initial functional studies in Escherichia coli revealed that 6S RNA forms a complex with RNAP resulting in regulation of transcription, and cells lacking 6S RNA have altered survival phenotypes. The last decade has focused on deepening the understanding of several aspects of 6S RNA activity, including (i) addressing questions of how broadly conserved 6S RNAs are in diverse organisms through continued identification and initial characterization of divergent 6S RNAs; (ii) the nature of the 6S RNA-RNAP interaction through examination of variant proteins and mutant RNAs, cross-linking approaches, and ultimately a cryo-electron microscopic structure; (iii) the physiological consequences of 6S RNA function through identification of the 6S RNA regulon and promoter features that determine 6S RNA sensitivity; and (iv) the mechanism and cellular impact of 6S RNA-directed synthesis of product RNAs (i.e., pRNA synthesis). Much has been learned about this unusual RNA, its mechanism of action, and how it is regulated; yet much still remains to be investigated, especially regarding potential differences in behavior of 6S RNAs in diverse bacteria.
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Affiliation(s)
- Karen M Wassarman
- Department of Bacteriology, University of Wisconsin-Madison, Madison, WI 53562
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5
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Chen J, Wassarman KM, Feng S, Leon K, Feklistov A, Winkelman JT, Li Z, Walz T, Campbell EA, Darst SA. 6S RNA Mimics B-Form DNA to Regulate Escherichia coli RNA Polymerase. Mol Cell 2017; 68:388-397.e6. [PMID: 28988932 DOI: 10.1016/j.molcel.2017.09.006] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2017] [Revised: 08/11/2017] [Accepted: 09/05/2017] [Indexed: 01/25/2023]
Abstract
Noncoding RNAs (ncRNAs) regulate gene expression in all organisms. Bacterial 6S RNAs globally regulate transcription by binding RNA polymerase (RNAP) holoenzyme and competing with promoter DNA. Escherichia coli (Eco) 6S RNA interacts specifically with the housekeeping σ70-holoenzyme (Eσ70) and plays a key role in the transcriptional reprogramming upon shifts between exponential and stationary phase. Inhibition is relieved upon 6S RNA-templated RNA synthesis. We report here the 3.8 Å resolution structure of a complex between 6S RNA and Eσ70 determined by single-particle cryo-electron microscopy and validation of the structure using footprinting and crosslinking approaches. Duplex RNA segments have A-form C3' endo sugar puckers but widened major groove widths, giving the RNA an overall architecture that mimics B-form promoter DNA. Our results help explain the specificity of Eco 6S RNA for Eσ70 and show how an ncRNA can mimic B-form DNA to directly regulate transcription by the DNA-dependent RNAP.
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Affiliation(s)
- James Chen
- Laboratory of Molecular Biophysics, The Rockefeller University, New York, NY 10065, USA
| | - Karen M Wassarman
- Department of Bacteriology, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Shili Feng
- Laboratory of Molecular Biophysics, The Rockefeller University, New York, NY 10065, USA
| | - Katherine Leon
- Laboratory of Molecular Biophysics, The Rockefeller University, New York, NY 10065, USA
| | - Andrey Feklistov
- Laboratory of Molecular Biophysics, The Rockefeller University, New York, NY 10065, USA
| | - Jared T Winkelman
- Department of Bacteriology, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Zongli Li
- Howard Hughes Medical Institute, Chevy Chase, MD 20815, USA; Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA
| | - Thomas Walz
- Laboratory of Molecular Electron Microscopy, The Rockefeller University, New York, NY 10065, USA
| | - Elizabeth A Campbell
- Laboratory of Molecular Biophysics, The Rockefeller University, New York, NY 10065, USA.
| | - Seth A Darst
- Laboratory of Molecular Biophysics, The Rockefeller University, New York, NY 10065, USA.
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6
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Fadouloglou VE, Lin HTV, Tria G, Hernández H, Robinson CV, Svergun DI, Luisi BF. Maturation of 6S regulatory RNA to a highly elongated structure. FEBS J 2015; 282:4548-64. [PMID: 26367381 PMCID: PMC7610929 DOI: 10.1111/febs.13516] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2015] [Revised: 09/04/2015] [Accepted: 09/10/2015] [Indexed: 12/11/2022]
Abstract
As bacterial populations leave the exponential growth phase and enter the stationary phase, their patterns of gene expression undergo marked changes. A key effector of this change is 6S RNA, which is a highly conserved regulatory RNA that impedes the transcription of genes associated with exponential growth by forming an inactivating ternary complex with RNA polymerase and sigma factor σ(70) (σ(70)-RNAP). In Escherichia coli, the endoribonuclease RNase E generates 6S RNA by specific cleavage of a precursor that is nearly twice the size of the 58 kDa mature form. We have explored recognition of the precursor by RNase E, and observed that processing is inhibited under conditions of excess substrate. This finding supports a largely distributive mechanism, meaning that each round of catalysis results in enzyme dissociation and re-binding to the substrate. We show that the precursor molecule and the mature 6S share a structural core dominated by an A-type helix, indicating that processing is not accompanied by extensive refolding. Both precursor and mature forms of 6S have a highly stable secondary structure, adopt an elongated shape, and show the potential to form dimers under specific conditions; nonetheless, 6S has a high structural plasticity that probably enables it to be structurally adapted upon binding to its cognate protein partners. Analysis of the 6S-σ(70)-RNAP complex by native mass spectrometry reveals a stable association with a stoichiometry of 1:1:1. A theoretical 3D model of mature 6S is presented, which is consistent with the experimental data and supports a previously proposed structure with a small stem-loop inside the central bubble.
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Affiliation(s)
- Vasiliki E Fadouloglou
- Department of Biochemistry, University of Cambridge, UK
- Department of Molecular Biology & Genetics, Democritus University of Thrace, Alexandroupolis, Greece
| | | | - Giancarlo Tria
- European Molecular Biology Laboratory, Hamburg Outstation, European Molecular Biology Laboratory/Deutsches Elektronen Synchrotron, Hamburg, Germany
| | | | | | - Dmitri I Svergun
- European Molecular Biology Laboratory, Hamburg Outstation, European Molecular Biology Laboratory/Deutsches Elektronen Synchrotron, Hamburg, Germany
| | - Ben F Luisi
- Department of Biochemistry, University of Cambridge, UK
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7
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Burenina OY, Elkina DA, Hartmann RK, Oretskaya TS, Kubareva EA. Small noncoding 6S RNAs of bacteria. BIOCHEMISTRY (MOSCOW) 2015; 80:1429-46. [DOI: 10.1134/s0006297915110048] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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8
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Köhler K, Duchardt-Ferner E, Lechner M, Damm K, Hoch PG, Salas M, Hartmann RK. Structural and mechanistic characterization of 6S RNA from the hyperthermophilic bacterium Aquifex aeolicus. Biochimie 2015; 117:72-86. [PMID: 25771336 DOI: 10.1016/j.biochi.2015.03.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2014] [Accepted: 03/03/2015] [Indexed: 01/26/2023]
Abstract
Bacterial 6S RNAs competitively inhibit binding of RNA polymerase (RNAP) holoenzymes to DNA promoters, thereby globally regulating transcription. RNAP uses 6S RNA itself as a template to synthesize short transcripts, termed pRNAs (product RNAs). Longer pRNAs (approx. ≥ 10 nt) rearrange the 6S RNA structure and thereby disrupt the 6S RNA:RNAP complex, which enables the enzyme to resume transcription at DNA promoters. We studied 6S RNA of the hyperthermophilic bacterium Aquifex aeolicus, representing the thermodynamically most stable 6S RNA known so far. Applying structure probing and NMR, we show that the RNA adopts the canonical rod-shaped 6S RNA architecture with little structure formation in the central bulge (CB) even at moderate temperatures (≤37 °C). 6S RNA:pRNA complex formation triggers an internal structure rearrangement of 6S RNA, i.e. formation of a so-called central bulge collapse (CBC) helix. The persistence of several characteristic NMR imino proton resonances upon pRNA annealing demonstrates that defined helical segments on both sides of the CB are retained in the pRNA-bound state, thus representing a basic framework of the RNA's architecture. RNA-seq analyses revealed pRNA synthesis from 6S RNA in A. aeolicus, identifying 9 to ∼17-mers as the major length species. A. aeolicus 6S RNA can also serve as a template for in vitro pRNA synthesis by RNAP from the mesophile Bacillus subtilis. Binding of a synthetic pRNA to A. aeolicus 6S RNA blocks formation of 6S RNA:RNAP complexes. Our findings indicate that A. aeolicus 6S RNA function in its hyperthermophilic host is mechanistically identical to that of other bacterial 6S RNAs. The use of artificial pRNA variants, designed to disrupt helix P2 from the 3'-CB instead of the 5'-CB but preventing formation of the CBC helix, indicated that the mechanism of pRNA-induced RNAP release has been evolutionarily optimized for transcriptional pRNA initiation in the 5'-CB.
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MESH Headings
- Bacteria/genetics
- Bacteria/metabolism
- Base Sequence
- DNA, Bacterial/genetics
- DNA, Bacterial/metabolism
- DNA-Directed RNA Polymerases/metabolism
- Gene Expression Regulation, Bacterial
- Hot Temperature
- Magnetic Resonance Spectroscopy
- Models, Molecular
- Molecular Sequence Data
- Nucleic Acid Conformation
- Protein Binding
- RNA Stability
- RNA, Bacterial/chemistry
- RNA, Bacterial/genetics
- RNA, Bacterial/metabolism
- RNA, Untranslated/chemistry
- RNA, Untranslated/genetics
- RNA, Untranslated/metabolism
- Sequence Analysis, RNA
- Substrate Specificity
- Transcription, Genetic
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Affiliation(s)
- Karen Köhler
- Philipps-Universität Marburg, Fachbereich Pharmazie, Institut für Pharmazeutische Chemie, Marbacher Weg 6, D-35037 Marburg, Germany.
| | - Elke Duchardt-Ferner
- Goethe-Universität Frankfurt am Main, Institut für Molekulare Biowissenschaften, Max-von-Laue-Straße 9, D-60438 Frankfurt am Main, Germany; Zentrum für biomagnetische Resonanzspektroskopie (BMRZ), Goethe-Universität Frankfurt am Main, Max-von-Laue-Str. 9, D-60438 Frankfurt am Main, Germany.
| | - Marcus Lechner
- Philipps-Universität Marburg, Fachbereich Pharmazie, Institut für Pharmazeutische Chemie, Marbacher Weg 6, D-35037 Marburg, Germany.
| | - Katrin Damm
- Philipps-Universität Marburg, Fachbereich Pharmazie, Institut für Pharmazeutische Chemie, Marbacher Weg 6, D-35037 Marburg, Germany.
| | - Philipp G Hoch
- Philipps-Universität Marburg, Fachbereich Pharmazie, Institut für Pharmazeutische Chemie, Marbacher Weg 6, D-35037 Marburg, Germany.
| | - Margarita Salas
- Centro de Biología Molecular "Severo Ochoa" (CSIC-UAM), Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain.
| | - Roland K Hartmann
- Philipps-Universität Marburg, Fachbereich Pharmazie, Institut für Pharmazeutische Chemie, Marbacher Weg 6, D-35037 Marburg, Germany.
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9
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Hnilicová J, Jirát Matějčková J, Šiková M, Pospíšil J, Halada P, Pánek J, Krásný L. Ms1, a novel sRNA interacting with the RNA polymerase core in mycobacteria. Nucleic Acids Res 2014; 42:11763-76. [PMID: 25217589 PMCID: PMC4191392 DOI: 10.1093/nar/gku793] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2014] [Revised: 08/19/2014] [Accepted: 08/20/2014] [Indexed: 11/12/2022] Open
Abstract
Small RNAs (sRNAs) are molecules essential for a number of regulatory processes in the bacterial cell. Here we characterize Ms1, a sRNA that is highly expressed in Mycobacterium smegmatis during stationary phase of growth. By glycerol gradient ultracentrifugation, RNA binding assay, and RNA co-immunoprecipitation, we show that Ms1 interacts with the RNA polymerase (RNAP) core that is free of the primary sigma factor (σA) or any other σ factor. This contrasts with the situation in most other species where it is 6S RNA that interacts with RNAP and this interaction requires the presence of σA. The difference in the interaction of the two types of sRNAs (Ms1 or 6S RNA) with RNAP possibly reflects the difference in the composition of the transcriptional machinery between mycobacteria and other species. Unlike Escherichia coli, stationary phase M. smegmatis cells contain relatively few RNAP molecules in complex with σA. Thus, Ms1 represents a novel type of small RNAs interacting with RNAP.
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Affiliation(s)
- Jarmila Hnilicová
- Department of Molecular Genetics of Bacteria, Institute of Microbiology, Academy of Sciences of the Czech Republic, Prague 142 20, Czech Republic
| | - Jitka Jirát Matějčková
- Department of Molecular Genetics of Bacteria, Institute of Microbiology, Academy of Sciences of the Czech Republic, Prague 142 20, Czech Republic
| | - Michaela Šiková
- Department of Molecular Genetics of Bacteria, Institute of Microbiology, Academy of Sciences of the Czech Republic, Prague 142 20, Czech Republic
| | - Jiří Pospíšil
- Department of Molecular Genetics of Bacteria, Institute of Microbiology, Academy of Sciences of the Czech Republic, Prague 142 20, Czech Republic
| | - Petr Halada
- Department of Molecular Structure Characterization, Institute of Microbiology, Academy of Sciences of the Czech Republic, Prague 142 20, Czech Republic
| | - Josef Pánek
- Department of Bioinformatics, Institute of Microbiology, Academy of Sciences of the Czech Republic, Prague 142 20, Czech Republic
| | - Libor Krásný
- Department of Molecular Genetics of Bacteria, Institute of Microbiology, Academy of Sciences of the Czech Republic, Prague 142 20, Czech Republic
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10
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Cavanagh AT, Wassarman KM. 6S RNA, a Global Regulator of Transcription inEscherichia coli,Bacillus subtilis, and Beyond. Annu Rev Microbiol 2014; 68:45-60. [DOI: 10.1146/annurev-micro-092611-150135] [Citation(s) in RCA: 82] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Amy T. Cavanagh
- Department of Bacteriology, University of Wisconsin–Madison, Madison, Wisconsin 53706;
| | - Karen M. Wassarman
- Department of Bacteriology, University of Wisconsin–Madison, Madison, Wisconsin 53706;
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11
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Oviedo Ovando M, Shephard L, Unrau PJ. In vitro characterization of 6S RNA release-defective mutants uncovers features of pRNA-dependent release from RNA polymerase in E. coli. RNA (NEW YORK, N.Y.) 2014; 20:670-80. [PMID: 24681966 PMCID: PMC3988568 DOI: 10.1261/rna.036343.112] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
6S RNA is a noncoding RNA that inhibits bacterial transcription by sequestering RNA polymerase holoenzyme (Eσ(70)) in low-nutrient conditions. This transcriptional block can be relieved by the synthesis of a short product RNA (pRNA) using the 6S RNA as a template. Here, we selected a range of 6S RNA release-defective mutants from a high diversity in vitro pool. Studying the release-defective variant R9-33 uncovered complex interactions between three regions of the 6S RNA. As expected, mutating the transcriptional start site (TSS) slowed and partially inhibited release. Surprisingly, additional mutations near the TSS were found that rescued this effect. Likewise, three mutations in the top strand of the large open bubble (LOB) could considerably slow release but were rescued by the addition of upstream mutations found between a highly conserved "-35" motif and the LOB. Combining the three top strand LOB mutations with mutations near the TSS, however, was particularly effective at preventing release, and this effect could be further enhanced by inclusion of the upstream mutations. Overexpressing R9-33 and a series of milder release-defective mutants in Escherichia coli resulted in a delayed entry into exponential phase together with a decrease in cell survival that correlated well with the severity of the in vitro phenotypes. The complex crosstalk observed between distinct regions of the 6S RNA supports a scrunching type model of 6S RNA release, where at least three regions of the 6S RNA must interact with Eσ(70) in a cooperative manner so as to ensure effective pRNA-dependent release.
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12
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Steuten B, Hoch PG, Damm K, Schneider S, Köhler K, Wagner R, Hartmann RK. Regulation of transcription by 6S RNAs: insights from the Escherichia coli and Bacillus subtilis model systems. RNA Biol 2014; 11:508-21. [PMID: 24786589 DOI: 10.4161/rna.28827] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Whereas, the majority of bacterial non-coding RNAs and functional RNA elements regulate post-transcriptional processes, either by interacting with other RNAs via base-pairing or through binding of small ligands (riboswitches), 6S RNAs affect transcription itself by binding to the housekeeping holoenzyme of RNA polymerase (RNAP). Remarkably, 6S RNAs serve as RNA templates for bacterial RNAP, giving rise to the de novo synthesis of short transcripts, termed pRNAs (product RNAs). Hence, 6S RNAs prompt the enzyme to act as an RNA-dependent RNA polymerase (RdRP). Synthesis of pRNAs exceeding a certain length limit (~13 nt) persistently rearrange the 6S RNA structure, which in turn, disrupts the 6S RNA:RNAP complex. This pRNA synthesis-mediated "reanimation" of sequestered RNAP molecules represents the conceivably fastest mechanism for resuming transcription in cells that enter a new exponential growth phase. The many different 6S RNAs found in a wide variety of bacteria do not share strong sequence homology but have in common a conserved rod-shaped structure with a large internal loop, termed the central bulge; this architecture mediates specific binding to the active site of RNAP. In this article, we summarize the overall state of knowledge as well as very recent findings on the structure, function, and physiological effects of 6S RNA examples from the two model organisms, Escherichia coli and Bacillus subtilis. Comparison of the presently known properties of 6S RNAs in the two organisms highlights common principles as well as diverse features.
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Affiliation(s)
- Benedikt Steuten
- Heinrich-Heine-Universität Düsseldorf; Institut für Physikalische Biologie Universitätsstr; Düsseldorf, Germany
| | | | - Katrin Damm
- Philipps-Universität Marburg; Marburg, Germany
| | - Sabine Schneider
- Heinrich-Heine-Universität Düsseldorf; Institut für Physikalische Biologie Universitätsstr; Düsseldorf, Germany
| | | | - Rolf Wagner
- Heinrich-Heine-Universität Düsseldorf; Institut für Physikalische Biologie Universitätsstr; Düsseldorf, Germany
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13
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Steuten B, Schneider S, Wagner R. 6S RNA: recent answers--future questions. Mol Microbiol 2014; 91:641-8. [PMID: 24308327 DOI: 10.1111/mmi.12484] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/04/2013] [Indexed: 01/31/2023]
Abstract
6S RNA is a non-coding RNA, found in almost all phylogenetic branches of bacteria. Through its conserved secondary structure, resembling open DNA promoters, it binds to RNA polymerase and interferes with transcription at many promoters. That way, it functions as transcriptional regulator facilitating adaptation to stationary phase conditions. Strikingly, 6S RNA acts as template for the synthesis of small RNAs (pRNA), which trigger the disintegration of the inhibitory RNA polymerase-6S RNA complex releasing 6S RNA-dependent repression. The regulatory implications of 6S RNAs vary among different bacterial species depending on the lifestyle and specific growth conditions that they have to face. The influence of 6S RNA can be seen on many different processes including stationary growth, sporulation, light adaptation or intracellular growth of pathogenic bacteria. Recent structural and functional studies have yielded details of the interaction between E. coli 6S RNA and RNA polymerase. Genome-wide transcriptome analyses provided insight into the functional diversity of 6S RNAs. Moreover, the mechanism and physiological consequences of pRNA synthesis have been explored in several systems. A major function of 6S RNA as a guardian regulating the economic use of cellular resources under limiting conditions and stress emerges as a common perception from numerous recent studies.
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Affiliation(s)
- Benedikt Steuten
- Molecular Biology of Bacteria, Heinrich-Heine-University Düsseldorf, Universitätsstr. 1, D-40225, Düsseldorf, Germany
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14
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Mapping the Spatial Neighborhood of the Regulatory 6S RNA Bound to Escherichia coli RNA Polymerase Holoenzyme. J Mol Biol 2013; 425:3649-61. [DOI: 10.1016/j.jmb.2013.07.008] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2013] [Revised: 06/28/2013] [Accepted: 07/04/2013] [Indexed: 11/15/2022]
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15
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Lee JY, Park H, Bak G, Kim KS, Lee Y. Regulation of transcription from two ssrS promoters in 6S RNA biogenesis. Mol Cells 2013; 36:227-34. [PMID: 23864284 PMCID: PMC3887979 DOI: 10.1007/s10059-013-0082-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2013] [Revised: 06/24/2013] [Accepted: 06/24/2013] [Indexed: 10/26/2022] Open
Abstract
ssrS-encoded 6S RNA is an abundant noncoding RNA that binds σ(70)-RNA polymerase and regulates expression at a subset of promoters in Escherichia coli. It is transcribed from two tandem promoters, ssrS P1 and ssrS P2. Regulation of transcription from two ssrS promoters in 6S RNA biogenesis was examined. Both P1 and P2 were growth phase-dependently regulated. Depletion of 6S RNA had no effect on growth-phase-dependent transcription from either promoter, whereas overexpression of 6S RNA increased P1 transcription and decreased P2 transcription, suggesting that transcription from P1 and P2 is subject to feedback activation and feedback inhibition, respectively. This feedback regulation disappeared in Δfis strains, supporting involvement of Fis in this process. The differential feedback regulation may provide a means for maintaining appropriate cellular concentrations of 6S RNA.
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Affiliation(s)
- Ji Young Lee
- Department of Chemistry, Korea Advanced Institute of Science and Technology, Daejeon 305-701, Korea
| | - Hongmarn Park
- Department of Chemistry, Korea Advanced Institute of Science and Technology, Daejeon 305-701, Korea
| | - Geunu Bak
- Department of Chemistry, Korea Advanced Institute of Science and Technology, Daejeon 305-701, Korea
| | | | - Younghoon Lee
- Department of Chemistry, Korea Advanced Institute of Science and Technology, Daejeon 305-701, Korea
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16
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Abstract
Besides canonical double-strand DNA promoters, multisubunit RNAPs (RNA polymerases) recognize a number of specific single-strand DNA and RNA templates, resulting in synthesis of various types of RNA transcripts. The general recognition principles and the mechanisms of transcription initiation on these templates are not fully understood. To investigate further the molecular mechanisms underlying the transcription of single-strand templates by bacterial RNAP, we selected high-affinity single-strand DNA aptamers that are specifically bound by RNAP holoenzyme, and characterized a novel class of aptamer-based transcription templates. The aptamer templates have a hairpin structure that mimics the upstream part of the open promoter bubble with accordingly placed specific promoter elements. The affinity of the RNAP holoenzyme to such DNA structures probably underlies its promoter-melting activity. Depending on the template structure, the aptamer templates can direct synthesis of productive RNA transcripts or effectively trap RNAP in the process of abortive synthesis, involving DNA scrunching, and competitively inhibit promoter recognition. The aptamer templates provide a novel tool for structure-function studies of transcription initiation by bacterial RNAP and its inhibition.
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Cabrera-Ostertag IJ, Cavanagh AT, Wassarman KM. Initiating nucleotide identity determines efficiency of RNA synthesis from 6S RNA templates in Bacillus subtilis but not Escherichia coli. Nucleic Acids Res 2013; 41:7501-11. [PMID: 23761441 PMCID: PMC3753640 DOI: 10.1093/nar/gkt517] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The 6S RNA is a non-coding small RNA that binds within the active site of housekeeping forms of RNA polymerases (e.g. Eσ70 in Escherichia coli, EσA in Bacillus subtilis) and regulates transcription. Efficient release of RNA polymerase from 6S RNA regulation during outgrowth from stationary phase is dependent on use of 6S RNA as a template to generate a product RNA (pRNA). Interestingly, B. subtilis has two 6S RNAs, 6S-1 and 6S-2, but only 6S-1 RNA appears to be used efficiently as a template for pRNA synthesis during outgrowth. Here, we demonstrate that the identity of the initiating nucleotide is particularly important for the B. subtilis RNA polymerase to use RNA templates. Specifically, initiation with guanosine triphosphate (GTP) is required for efficient pRNA synthesis, providing mechanistic insight into why 6S-2 RNA does not support robust pRNA synthesis as it initiates with adenosine triphosphate (ATP). Intriguingly, E. coli RNA polymerase does not have a strong preference for initiating nucleotide identity. These observations highlight an important difference in biochemical properties of B. subtilis and E. coli RNA polymerases, specifically in their ability to use RNA templates efficiently, which also may reflect the differences in GTP and ATP metabolism in these two organisms.
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18
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Panchapakesan SSS, Unrau PJ. E. coli 6S RNA release from RNA polymerase requires σ70 ejection by scrunching and is orchestrated by a conserved RNA hairpin. RNA (NEW YORK, N.Y.) 2012; 18:2251-9. [PMID: 23118417 PMCID: PMC3504675 DOI: 10.1261/rna.034785.112] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
The 6S RNA in Escherichia coli suppresses housekeeping transcription by binding to RNA polymerase holoenzyme (core polymerase + σ⁷⁰) under low nutrient conditions and rescues σ⁷⁰-dependent transcription in high nutrient conditions by the synthesis of a short product RNA (pRNA) using itself as a template. Here we characterize a kinetic intermediate that arises during 6S RNA release. This state, consisting of 6S RNA and core polymerase, is related to the formation of a top-strand "release" hairpin that is conserved across the γ-proteobacteria. Deliberately slowing the intrinsic 6S RNA release rate by nucleotide feeding experiments reveals that σ⁷⁰ ejection occurs abruptly once a pRNA length of 9 nucleotides (nt) is reached. After σ⁷⁰ ejection, an additional 4 nt of pRNA synthesis is required before the 6S:pRNA complex is finally released from core polymerase. Changing the E. coli 6S RNA sequence to preclude formation of the release hairpin dramatically slows the speed of 6S RNA release but, surprisingly, does not alter the abruptness of σ⁷⁰ ejection. Rather, the pRNA size required to trigger σ⁷⁰ release increases from 9 nt to 14 nt. That a precise pRNA length is required to trigger σ⁷⁰ release either with or without a hairpin implicates an intrinsic "scrunching"-type release mechanism. We speculate that the release hairpin serves two primary functions in the γ-proteobacteria: First, its formation strips single-stranded "-10" 6S RNA interactions away from σ⁷⁰. Second, the formation of the hairpin accumulates RNA into a region of the polymerase complex previously associated with DNA scrunching, further destabilizing the 6S:pRNA:polymerase complex.
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Affiliation(s)
- Shanker Shyam S Panchapakesan
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada
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19
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Beckmann BM, Hoch PG, Marz M, Willkomm DK, Salas M, Hartmann RK. A pRNA-induced structural rearrangement triggers 6S-1 RNA release from RNA polymerase in Bacillus subtilis. EMBO J 2012; 31:1727-38. [PMID: 22333917 DOI: 10.1038/emboj.2012.23] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2011] [Accepted: 01/18/2012] [Indexed: 11/09/2022] Open
Abstract
Bacillus subtilis 6S-1 RNA binds to the housekeeping RNA polymerase (σ(A)-RNAP) and directs transcription of short 'product' RNAs (pRNAs). Here, we demonstrate that once newly synthesized pRNAs form a sufficiently stable duplex with 6S-1 RNA, a structural rearrangement is induced in cis, which involves base-pairing between sequences in the 5'-portion of the central bulge and nucleotides that become available as a result of pRNA invasion. The rearrangement decreases 6S-1 RNA affinity for σ(A)-RNAP. Among the pRNA length variants synthesized by σ(A)-RNAP (up to ∼14 nt), only the longer ones, such as 12-14-mers, form a duplex with 6S-1 RNA that is sufficiently long-lived to induce the rearrangement. Yet, an LNA (locked nucleic acid) 8-mer can induce the same rearrangement due to conferring increased duplex stability. We propose that an interplay of rate constants for polymerization (k(pol)), for pRNA:6S-1 RNA hybrid duplex dissociation (k(off)) and for the rearrangement (k(conf)) determines whether pRNAs dissociate or rearrange 6S-1 structure to trigger 6S-1 RNA release from σ(A)-RNAP. A bioinformatic screen suggests that essentially all bacterial 6S RNAs have the potential to undergo a pRNA-induced structural rearrangement.
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Affiliation(s)
- Benedikt M Beckmann
- Institut für Pharmazeutische Chemie, Philipps Universität Marburg, Marburg, Germany
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Cavanagh AT, Sperger JM, Wassarman KM. Regulation of 6S RNA by pRNA synthesis is required for efficient recovery from stationary phase in E. coli and B. subtilis. Nucleic Acids Res 2011; 40:2234-46. [PMID: 22102588 PMCID: PMC3299989 DOI: 10.1093/nar/gkr1003] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
6S RNAs function through interaction with housekeeping forms of RNA polymerase holoenzyme (Eσ70 in Escherichia coli, EσA in Bacillus subtilis). Escherichia coli 6S RNA accumulates to high levels during stationary phase, and has been shown to be released from Eσ70 during exit from stationary phase by a process in which 6S RNA serves as a template for Eσ70 to generate product RNAs (pRNAs). Here, we demonstrate that not only does pRNA synthesis occur, but it is an important mechanism for regulation of 6S RNA function that is required for cells to exit stationary phase efficiently in both E. coli and B. subtilis. Bacillus subtilis has two 6S RNAs, 6S-1 and 6S-2. Intriguingly, 6S-2 RNA does not direct pRNA synthesis under physiological conditions and its non-release from EσA prevents efficient outgrowth in cells lacking 6S-1 RNA. The behavioral differences in the two B. subtilis RNAs clearly demonstrate that they act independently, revealing a higher than anticipated diversity in 6S RNA function globally. Overexpression of a pRNA-synthesis-defective 6S RNA in E. coli leads to decreased cell viability, suggesting pRNA synthesis-mediated regulation of 6S RNA function is important at other times of growth as well.
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Affiliation(s)
- Amy T Cavanagh
- Department of Bacteriology, University of Wisconsin-Madison, Madison, WI 53706, USA
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