151
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Quantitative characterization of gene regulation by Rho dependent transcription termination. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2015; 1849:940-54. [DOI: 10.1016/j.bbagrm.2015.05.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2014] [Revised: 04/03/2015] [Accepted: 05/07/2015] [Indexed: 11/23/2022]
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152
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Bakshi S, Choi H, Weisshaar JC. The spatial biology of transcription and translation in rapidly growing Escherichia coli. Front Microbiol 2015; 6:636. [PMID: 26191045 PMCID: PMC4488752 DOI: 10.3389/fmicb.2015.00636] [Citation(s) in RCA: 75] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2015] [Accepted: 06/12/2015] [Indexed: 11/21/2022] Open
Abstract
Single-molecule fluorescence provides high resolution spatial distributions of ribosomes and RNA polymerase (RNAP) in live, rapidly growing Escherichia coli. Ribosomes are more strongly segregated from the nucleoids (chromosomal DNA) than previous widefield fluorescence studies suggested. While most transcription may be co-translational, the evidence indicates that most translation occurs on free mRNA copies that have diffused from the nucleoids to a ribosome-rich region. Analysis of time-resolved images of the nucleoid spatial distribution after treatment with the transcription-halting drug rifampicin and the translation-halting drug chloramphenicol shows that both drugs cause nucleoid contraction on the 0–3 min timescale. This is consistent with the transertion hypothesis. We suggest that the longer-term (20–30 min) nucleoid expansion after Rif treatment arises from conversion of 70S-polysomes to 30S and 50S subunits, which readily penetrate the nucleoids. Monte Carlo simulations of a polymer bead model built to mimic the chromosomal DNA and ribosomes (either 70S-polysomes or 30S and 50S subunits) explain spatial segregation or mixing of ribosomes and nucleoids in terms of excluded volume and entropic effects alone. A comprehensive model of the transcription-translation-transertion system incorporates this new information about the spatial organization of the E. coli cytoplasm. We propose that transertion, which radially expands the nucleoids, is essential for recycling of 30S and 50S subunits from ribosome-rich regions back into the nucleoids. There they initiate co-transcriptional translation, which is an important mechanism for maintaining RNAP forward progress and protecting the nascent mRNA chain. Segregation of 70S-polysomes from the nucleoid may facilitate rapid growth by shortening the search time for ribosomes to find free mRNA concentrated outside the nucleoid and the search time for RNAP concentrated within the nucleoid to find transcription initiation sites.
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Affiliation(s)
- Somenath Bakshi
- Department of Chemistry and Molecular Biophysics Program, University of Wisconsin-Madison, Madison WI, USA
| | - Heejun Choi
- Department of Chemistry and Molecular Biophysics Program, University of Wisconsin-Madison, Madison WI, USA
| | - James C Weisshaar
- Department of Chemistry and Molecular Biophysics Program, University of Wisconsin-Madison, Madison WI, USA
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153
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Abstract
Bacteria lack subcellular compartments and harbor a single RNA polymerase that synthesizes both structural and protein-coding RNAs, which are cotranscriptionally processed by distinct pathways. Nascent rRNAs fold into elaborate secondary structures and associate with ribosomal proteins, whereas nascent mRNAs are translated by ribosomes. During elongation, nucleic acid signals and regulatory proteins modulate concurrent RNA-processing events, instruct RNA polymerase where to pause and terminate transcription, or act as roadblocks to the moving enzyme. Communications among complexes that carry out transcription, translation, repair, and other cellular processes ensure timely execution of the gene expression program and survival under conditions of stress. This network is maintained by auxiliary proteins that act as bridges between RNA polymerase, ribosome, and repair enzymes, blurring boundaries between separate information-processing steps and making assignments of unique regulatory functions meaningless. Understanding the regulation of transcript elongation thus requires genome-wide approaches, which confirm known and reveal new regulatory connections.
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Affiliation(s)
| | - Irina Artsimovitch
- Department of Microbiology and Center for RNA Biology, The Ohio State University, Columbus, Ohio 43210;
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154
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Castro-Roa D, Zenkin N. Methodology for the analysis of transcription and translation in transcription-coupled-to-translation systems in vitro. Methods 2015; 86:51-9. [PMID: 26080048 DOI: 10.1016/j.ymeth.2015.05.029] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2015] [Revised: 05/26/2015] [Accepted: 05/29/2015] [Indexed: 11/27/2022] Open
Abstract
The various properties of RNA polymerase (RNAP) complexes with nucleic acids during different stages of transcription involve various types of regulation and different cross-talk with other cellular entities and with fellow RNAP molecules. The interactions of transcriptional apparatus with the translational machinery have been focused mainly in terms of outcomes of gene expression, whereas the study of the physical interaction of the ribosome and the RNAP remains obscure partly due to the lack of a system that allows such observations. In this article we will describe the methodology needed to set up a pure, transcription-coupled-to-translation system in which the translocation of the ribosome can be performed in a step-wise manner towards RNAP allowing investigation of the interactions between the two machineries at colliding and non-colliding distances. In the same time RNAP can be put in various types of states, such as paused, roadblocked, backtracked, etc. The experimental system thus allows studying the effects of the ribosome on different aspects of transcription elongation and the effects by RNAP on translation.
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Affiliation(s)
- Daniel Castro-Roa
- Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, Newcastle University, Baddiley-Clark Building, Richardson Road, Newcastle upon Tyne NE2 4AX, UK.
| | - Nikolay Zenkin
- Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, Newcastle University, Baddiley-Clark Building, Richardson Road, Newcastle upon Tyne NE2 4AX, UK
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155
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Two-level inhibition of galK expression by Spot 42: Degradation of mRNA mK2 and enhanced transcription termination before the galK gene. Proc Natl Acad Sci U S A 2015; 112:7581-6. [PMID: 26045496 DOI: 10.1073/pnas.1424683112] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The Escherichia coli gal operon has the structure Pgal-galE-galT-galK-galM. During early log growth, a gradient in gene expression, named type 2 polarity, is established, as follows: galE > galT > galK > galM. However, during late-log growth, type 1 polarity is established in which galK is greater than galT, as follows: galE > galK > galT > galM. We found that type 2 polarity occurs as a result of the down-regulation of galK, which is caused by two different molecular mechanisms: Spot 42-mediated degradation of the galK-specific mRNA, mK2, and Spot 42-mediated Rho-dependent transcription termination at the end of galT. Because the concentration of Spot 42 drops during the transition period of the polarity type switch, these results demonstrate that type 1 polarity is the result of alleviation of Spot 42-mediated galK down-regulation. Because the Spot 42-binding site overlaps with a putative Rho-binding site, a molecular mechanism is proposed to explain how Spot 42, possibly with Hfq, enhances Rho-mediated transcription termination at the end of galT.
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156
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Drögemüller J, Strauß M, Schweimer K, Wöhrl BM, Knauer SH, Rösch P. Exploring RNA polymerase regulation by NMR spectroscopy. Sci Rep 2015; 5:10825. [PMID: 26043358 PMCID: PMC4650657 DOI: 10.1038/srep10825] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2015] [Accepted: 04/22/2015] [Indexed: 11/16/2022] Open
Abstract
RNA synthesis is a central process in all organisms, with RNA polymerase (RNAP) as the key enzyme. Multisubunit RNAPs are evolutionary related and are tightly regulated by a multitude of transcription factors. Although Escherichia coli RNAP has been studied extensively, only little information is available about its dynamics and transient interactions. This information, however, are crucial for the complete understanding of transcription regulation in atomic detail. To study RNAP by NMR spectroscopy we developed a highly efficient procedure for the assembly of active RNAP from separately expressed subunits that allows specific labeling of the individual constituents. We recorded [1H,13C] correlation spectra of isoleucine, leucine, and valine methyl groups of complete RNAP and the separately labeled β’ subunit within reconstituted RNAP. We further produced all RNAP subunits individually, established experiments to determine which RNAP subunit a certain regulator binds to, and identified the β subunit to bind NusE.
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Affiliation(s)
- Johanna Drögemüller
- Lehrstuhl Biopolymere und Forschungszentrum für Bio-Makromoleküle, Universität Bayreuth, Universitätsstraße 30, 95447 Bayreuth, Germany
| | - Martin Strauß
- 1] [2] Lehrstuhl Biopolymere und Forschungszentrum für Bio-Makromoleküle, Universität Bayreuth, Universitätsstraße 30, 95447 Bayreuth, Germany
| | - Kristian Schweimer
- Lehrstuhl Biopolymere und Forschungszentrum für Bio-Makromoleküle, Universität Bayreuth, Universitätsstraße 30, 95447 Bayreuth, Germany
| | - Birgitta M Wöhrl
- Lehrstuhl Biopolymere und Forschungszentrum für Bio-Makromoleküle, Universität Bayreuth, Universitätsstraße 30, 95447 Bayreuth, Germany
| | - Stefan H Knauer
- Lehrstuhl Biopolymere und Forschungszentrum für Bio-Makromoleküle, Universität Bayreuth, Universitätsstraße 30, 95447 Bayreuth, Germany
| | - Paul Rösch
- Lehrstuhl Biopolymere und Forschungszentrum für Bio-Makromoleküle, Universität Bayreuth, Universitätsstraße 30, 95447 Bayreuth, Germany
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157
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Leskinen K, Li CM, Varjosalo M, Li Z, Skurnik M. Expression of the Yersinia enterocolitica O:3 LPS O-antigen and outer core gene clusters is RfaH-dependent. Microbiology (Reading) 2015; 161:1282-94. [DOI: 10.1099/mic.0.000076] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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158
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Washburn RS, Gottesman ME. Regulation of transcription elongation and termination. Biomolecules 2015; 5:1063-78. [PMID: 26035374 PMCID: PMC4496710 DOI: 10.3390/biom5021063] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2015] [Revised: 05/20/2015] [Accepted: 05/21/2015] [Indexed: 11/16/2022] Open
Abstract
This article will review our current understanding of transcription elongation and termination in E. coli. We discuss why transcription elongation complexes pause at certain template sites and how auxiliary host and phage transcription factors affect elongation and termination. The connection between translation and transcription elongation is described. Finally we present an overview indicating where progress has been made and where it has not.
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Affiliation(s)
- Robert S Washburn
- Department of Microbiology and Immunology, Columbia University Medical Center, New York, NY 10032, USA.
| | - Max E Gottesman
- Department of Microbiology and Immunology, Columbia University Medical Center, New York, NY 10032, USA.
- Department of Biochemistry and Molecular Biophysics, Columbia University Medical Center, New York, NY 10032, USA.
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159
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Rifampicin-resistance, rpoB polymorphism and RNA polymerase genetic engineering. J Biotechnol 2015; 202:60-77. [DOI: 10.1016/j.jbiotec.2014.11.024] [Citation(s) in RCA: 65] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2014] [Revised: 11/22/2014] [Accepted: 11/26/2014] [Indexed: 01/22/2023]
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160
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Casjens SR, Hendrix RW. Bacteriophage lambda: Early pioneer and still relevant. Virology 2015; 479-480:310-30. [PMID: 25742714 PMCID: PMC4424060 DOI: 10.1016/j.virol.2015.02.010] [Citation(s) in RCA: 182] [Impact Index Per Article: 20.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2014] [Revised: 01/13/2015] [Accepted: 02/05/2015] [Indexed: 12/14/2022]
Abstract
Molecular genetic research on bacteriophage lambda carried out during its golden age from the mid-1950s to mid-1980s was critically important in the attainment of our current understanding of the sophisticated and complex mechanisms by which the expression of genes is controlled, of DNA virus assembly and of the molecular nature of lysogeny. The development of molecular cloning techniques, ironically instigated largely by phage lambda researchers, allowed many phage workers to switch their efforts to other biological systems. Nonetheless, since that time the ongoing study of lambda and its relatives has continued to give important new insights. In this review we give some relevant early history and describe recent developments in understanding the molecular biology of lambda's life cycle.
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Affiliation(s)
- Sherwood R Casjens
- Division of Microbiology and Immunology, Pathology Department, University of Utah School of Medicine, Emma Eccles Jones Medical Research Building, 15 North Medical Drive East, Salt Lake City, UT 84112, USA; Biology Department, University of Utah, Salt Lake City, UT 84112, USA.
| | - Roger W Hendrix
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA
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161
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Strauß M, Schweimer K, Burmann BM, Richter A, Güttler S, Wöhrl BM, Rösch P. The two domains ofMycobacterium tuberculosisNusG protein are dynamically independent. J Biomol Struct Dyn 2015; 34:352-61. [DOI: 10.1080/07391102.2015.1031700] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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162
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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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163
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NandyMazumdar M, Artsimovitch I. Ubiquitous transcription factors display structural plasticity and diverse functions: NusG proteins - Shifting shapes and paradigms. Bioessays 2015; 37:324-34. [PMID: 25640595 DOI: 10.1002/bies.201400177] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Numerous accessory factors modulate RNA polymerase response to regulatory signals and cellular cues and establish communications with co-transcriptional RNA processing. Transcription regulators are astonishingly diverse, with similar mechanisms arising via convergent evolution. NusG/Spt5 elongation factors comprise the only universally conserved and ancient family of regulators. They bind to the conserved clamp helices domain of RNA polymerase, which also interacts with non-homologous initiation factors in all domains of life, and reach across the DNA channel to form processivity clamps that enable uninterrupted RNA chain synthesis. In addition to this ubiquitous function, NusG homologs exert diverse, and sometimes opposite, effects on gene expression by competing with each other and other regulators for binding to the clamp helices and by recruiting auxiliary factors that facilitate termination, antitermination, splicing, translation, etc. This surprisingly diverse range of activities and the underlying unprecedented structural changes make studies of these "transformer" proteins both challenging and rewarding.
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Affiliation(s)
- Monali NandyMazumdar
- Department of Microbiology and The Center for RNA Biology, The Ohio State University, Columbus, OH, USA
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164
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Castro-Roa D, Zenkin N. Methods for the assembly and analysis of in vitro transcription-coupled-to-translation systems. Methods Mol Biol 2015; 1276:81-99. [PMID: 25665559 DOI: 10.1007/978-1-4939-2392-2_5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
RNA polymerase is a complex machinery, which is further embedded in interactions with other cellular components that interplay with either the transcribed DNA (DNA polymerases, topoisomerases, etc.) or the nascent RNA (RNA processing enzymes, ribosomes, etc.). In prokaryotes, coupling of transcription and translation is thought to play many regulatory roles but the mechanistic understanding of their interactions has been hindered by the lack of a defined experimental system. Here, we describe a pure transcription-coupled-to-translation system in which control of the ribosome has been achieved through its stepwise translocation towards RNA polymerase. This system can be used to study the effects of concurrent translation on RNA chain elongation and to elucidate the interface between the two macromolecular complexes.
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Affiliation(s)
- Daniel Castro-Roa
- Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, Newcastle University, Baddiley-Clark Building, Richardson Road, Newcastle Upon Tyne, NE2 4AX, UK,
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165
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Kalyani BS, Kunamneni R, Wal M, Ranjan A, Sen R. A NusG paralogue from Mycobacterium tuberculosis, Rv0639, has evolved to interact with ribosomal protein S10 (Rv0700) but not to function as a transcription elongation–termination factor. Microbiology (Reading) 2015; 161:67-83. [DOI: 10.1099/mic.0.083709-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Affiliation(s)
- B. Sudha Kalyani
- Laboratory of Transcription, Center for DNA Fingerprinting and Diagnostics, Nampally, Hyderabad-500 001, India
| | - Radhika Kunamneni
- Laboratory of Transcription, Center for DNA Fingerprinting and Diagnostics, Nampally, Hyderabad-500 001, India
| | - Megha Wal
- Laboratory of Transcription, Center for DNA Fingerprinting and Diagnostics, Nampally, Hyderabad-500 001, India
| | - Amitabh Ranjan
- Laboratory of Transcription, Center for DNA Fingerprinting and Diagnostics, Nampally, Hyderabad-500 001, India
| | - Ranjan Sen
- Laboratory of Transcription, Center for DNA Fingerprinting and Diagnostics, Nampally, Hyderabad-500 001, India
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166
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Kurata T, Nakanishi S, Hashimoto M, Taoka M, Yamazaki Y, Isobe T, Kato JI. Novel essential gene Involved in 16S rRNA processing in Escherichia coli. J Mol Biol 2014; 427:955-965. [PMID: 25545592 DOI: 10.1016/j.jmb.2014.12.013] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2014] [Revised: 12/15/2014] [Accepted: 12/16/2014] [Indexed: 12/21/2022]
Abstract
Biogenesis of ribosomes is a complex process mediated by many factors. While its transcription proceeds, ribosomal RNA (rRNA) folds itself into a characteristic three-dimensional structure through interaction with ribosomal proteins, during which its ends are processed. Here, we show that the essential protein YqgF, a RuvC family protein with an RNase-H-like motif, is involved in the processing of pre-16S rRNA during ribosome maturation. Indeed, pre-16S rRNA accumulated in cells of a temperature-sensitive yqgF mutant (yqgF(ts)) cultured at a non-permissive temperature. In addition, purified YqgF was shown to process the 5' end of pre-16S rRNA within 70S ribosomes in vitro. Mass spectrometry analysis of the total proteins in the yqgF(ts) mutant cells showed that the expression of genes containing multiple Shine-Dalgarno-like sequences was observed to be lower than in wild type. These results are interpreted to indicate that YqgF is involved in a novel enzymic activity necessary for the processing of pre-16S rRNA, thereby affecting elongation of translation.
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Affiliation(s)
- Tatsuaki Kurata
- Department of Biological Sciences, Graduate Schools of Science and Engineering, Tokyo Metropolitan University, Tokyo 192-0397, Japan
| | - Shinobu Nakanishi
- Department of Biological Sciences, Graduate Schools of Science and Engineering, Tokyo Metropolitan University, Tokyo 192-0397, Japan
| | - Masayuki Hashimoto
- Institute of Molecular Medicine, Medical College, National Cheng-Kung University, Tainan City 704, Taiwan; Infectious Disease and Signal Transduction Center, Medical College, National Cheng-Kung University, Tainan City 704, Taiwan
| | - Masato Taoka
- Department of Chemistry, Graduate Schools of Science and Engineering, Tokyo Metropolitan University, Tokyo 192-0397, Japan
| | - Yukiko Yamazaki
- Genetic Informatics Laboratory, Genetic Strains Research Center, National Institute of Genetics, Shizuoka 411-8540, Japan
| | - Toshiaki Isobe
- Department of Chemistry, Graduate Schools of Science and Engineering, Tokyo Metropolitan University, Tokyo 192-0397, Japan
| | - Jun-Ichi Kato
- Department of Biological Sciences, Graduate Schools of Science and Engineering, Tokyo Metropolitan University, Tokyo 192-0397, Japan.
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167
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The place of RNA in the origin and early evolution of the genetic machinery. Life (Basel) 2014; 4:1050-91. [PMID: 25532530 PMCID: PMC4284482 DOI: 10.3390/life4041050] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2014] [Revised: 12/02/2014] [Accepted: 12/09/2014] [Indexed: 11/17/2022] Open
Abstract
The extant genetic machinery revolves around three interrelated polymers: RNA, DNA and proteins. Two evolutionary views approach this vital connection from opposite perspectives. The RNA World theory posits that life began in a cold prebiotic broth of monomers with the de novo emergence of replicating RNA as functionally self-contained polymer and that subsequent evolution is characterized by RNA → DNA memory takeover and ribozyme → enzyme catalyst takeover. The FeS World theory posits that life began as an autotrophic metabolism in hot volcanic-hydrothermal fluids and evolved with organic products turning into ligands for transition metal catalysts thereby eliciting feedback and feed-forward effects. In this latter context it is posited that the three polymers of the genetic machinery essentially coevolved from monomers through oligomers to polymers, operating functionally first as ligands for ligand-accelerated transition metal catalysis with later addition of base stacking and base pairing, whereby the functional dichotomy between hereditary DNA with stability on geologic time scales and transient, catalytic RNA with stability on metabolic time scales existed since the dawn of the genetic machinery. Both approaches are assessed comparatively for chemical soundness.
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168
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Epshtein V. UvrD helicase: an old dog with a new trick: how one step backward leads to many steps forward. Bioessays 2014; 37:12-9. [PMID: 25345862 DOI: 10.1002/bies.201400106] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Transcription-coupled repair (TCR) is a phenomenon that exists in a wide variety of organisms from bacteria to humans. This mechanism allows cells to repair the actively transcribed DNA strand much faster than the non-transcribed one. At the sites of bulky DNA damage RNA polymerase stalls, initiating recruitment of the repair machinery. It is a commonly accepted paradigm that bacterial cells utilize a sole coupling factor, called Mfd to initiate TCR. According to that model, Mfd removes transcription complexes stalled at the lesion site and simultaneously recruits repair machinery. However, this model was recently put in doubt by various discrepancies between the proposed universal role of Mfd in the TCR and its biochemical and phenotypical properties. Here, I present a second pathway of bacterial TCR recently discovered in my laboratory, which does not involve Mfd but implicates a common repair factor, UvrD, in a central position in the process.
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Affiliation(s)
- Vitaliy Epshtein
- Department of Biochemistry, New York University, Langhorn Medical Center, New York, NY, USA
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169
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Burmann BM, Rösch P. The role of E. coli Nus-factors in transcription regulation and transcription:translation coupling: From structure to mechanism. Transcription 2014; 2:130-134. [PMID: 21922055 DOI: 10.4161/trns.2.3.15671] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2011] [Revised: 03/31/2011] [Accepted: 03/31/2011] [Indexed: 11/19/2022] Open
Abstract
Bacterial transcription mediated by RNA polymerase (RNAP) is a highly regulated process and RNAP action is modulated during the different phases of initiation, elongation and termination by proteins such as the Escherichia coli Nus transcription-factors. Here we discuss the structural interplay and the mechanistic role of the Nus-factors that are directly involved in the processivity of elongation, transcription:translation coupling and termination, as well as the varying effects of these proteins on transcription under the influence of additional signals.
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Affiliation(s)
- Björn M Burmann
- Lehrstuhl Biopolymere und Forschungszentrum für Bio-Makromoleküle; Universität Bayreuth; Bayreuth, Germany
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170
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Yam H, Abdul Rahim A, Mohamad S, Mahadi NM, Abdul Manaf U, Shu-Chien AC, Najimudin N. The multiple roles of hypothetical gene BPSS1356 in Burkholderia pseudomallei. PLoS One 2014; 9:e99218. [PMID: 24927285 PMCID: PMC4057154 DOI: 10.1371/journal.pone.0099218] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2014] [Accepted: 05/12/2014] [Indexed: 11/26/2022] Open
Abstract
Burkholderia pseudomallei is an opportunistic pathogen and the causative agent of melioidosis. It is able to adapt to harsh environments and can live intracellularly in its infected hosts. In this study, identification of transcriptional factors that associate with the β' subunit (RpoC) of RNA polymerase was performed. The N-terminal region of this subunit is known to trigger promoter melting when associated with a sigma factor. A pull-down assay using histidine-tagged B. pseudomallei RpoC N-terminal region as bait showed that a hypothetical protein BPSS1356 was one of the proteins bound. This hypothetical protein is conserved in all B. pseudomallei strains and present only in the Burkholderia genus. A BPSS1356 deletion mutant was generated to investigate its biological function. The mutant strain exhibited reduced biofilm formation and a lower cell density during the stationary phase of growth in LB medium. Electron microscopic analysis revealed that the ΔBPSS1356 mutant cells had a shrunken cytoplasm indicative of cell plasmolysis and a rougher surface when compared to the wild type. An RNA microarray result showed that a total of 63 genes were transcriptionally affected by the BPSS1356 deletion with fold change values of higher than 4. The expression of a group of genes encoding membrane located transporters was concurrently down-regulated in ΔBPSS1356 mutant. Amongst the affected genes, the putative ion transportation genes were the most severely suppressed. Deprivation of BPSS1356 also down-regulated the transcriptions of genes for the arginine deiminase system, glycerol metabolism, type III secretion system cluster 2, cytochrome bd oxidase and arsenic resistance. It is therefore obvious that BPSS1356 plays a multiple regulatory roles on many genes.
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Affiliation(s)
- Hokchai Yam
- School of Biological Sciences, Universiti Sains Malaysia, Minden, Pulau Pinang, Malaysia
| | - Ainihayati Abdul Rahim
- School of Biological Sciences, Universiti Sains Malaysia, Minden, Pulau Pinang, Malaysia
- Faculty of Agro Based Industry, Universiti Malaysia Kelantan, Jeli, Kelantan, Malaysia
| | - Suriani Mohamad
- School of Pharmaceutical Sciences, Universiti Sains Malaysia, Minden, Pulau Pinang, Malaysia
| | - Nor Muhammad Mahadi
- Comparative Genomics and Genetics Research Centre, Malaysia Genome Institute, Kajang, Selangor, Malaysia
| | - Uyub Abdul Manaf
- School of Biological Sciences, Universiti Sains Malaysia, Minden, Pulau Pinang, Malaysia
| | | | - Nazalan Najimudin
- School of Biological Sciences, Universiti Sains Malaysia, Minden, Pulau Pinang, Malaysia
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171
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DksA guards elongating RNA polymerase against ribosome-stalling-induced arrest. Mol Cell 2014; 53:766-78. [PMID: 24606919 DOI: 10.1016/j.molcel.2014.02.005] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2013] [Revised: 12/20/2013] [Accepted: 01/28/2014] [Indexed: 11/23/2022]
Abstract
In bacteria, translation-transcription coupling inhibits RNA polymerase (RNAP) stalling. We present evidence suggesting that, upon amino acid starvation, inactive ribosomes promote rather than inhibit RNAP stalling. We developed an algorithm to evaluate genome-wide polymerase progression independently of local noise and used it to reveal that the transcription factor DksA inhibits promoter-proximal pausing and increases RNAP elongation when uncoupled from translation by depletion of charged tRNAs. DksA has minimal effect on RNAP elongation in vitro and on untranslated RNAs in vivo. In these cases, transcripts can form RNA structures that prevent backtracking. Thus, the effect of DksA on transcript elongation may occur primarily upon ribosome slowing/stalling or at promoter-proximal locations that limit the potential for RNA structure. We propose that inactive ribosomes prevent formation of backtrack-blocking mRNA structures and that, in this circumstance, DksA acts as a transcription elongation factor in vivo.
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172
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Mycobacterial RNA polymerase requires a U-tract at intrinsic terminators and is aided by NusG at suboptimal terminators. mBio 2014; 5:e00931. [PMID: 24713321 PMCID: PMC3993855 DOI: 10.1128/mbio.00931-14] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Intrinsic terminators, which encode GC-rich RNA hairpins followed immediately by a 7-to-9-nucleotide (nt) U-rich “U-tract,” play principal roles of punctuating and regulating transcription in most bacteria. However, canonical intrinsic terminators with strong U-tracts are underrepresented in some bacterial lineages, notably mycobacteria, leading to proposals that their RNA polymerases stop at noncanonical intrinsic terminators encoding various RNA structures lacking U-tracts. We generated recombinant forms of mycobacterial RNA polymerase and its major elongation factors NusA and NusG to characterize mycobacterial intrinsic termination. Using in vitro transcription assays devoid of possible mycobacterial contaminants, we established that mycobacterial RNA polymerase terminates more efficiently than Escherichia coli RNA polymerase at canonical terminators with imperfect U-tracts but does not terminate at putative terminators lacking U-tracts even in the presence of mycobacterial NusA and NusG. However, mycobacterial NusG exhibits a novel termination-stimulating activity that may allow intrinsic terminators with suboptimal U-tracts to function efficiently. Bacteria rely on transcription termination to define and regulate units of gene expression. In most bacteria, precise termination and much regulation by attenuation are accomplished by intrinsic terminators that encode GC-rich hairpins and U-tracts necessary to disrupt stable transcription elongation complexes. Thus, the apparent dearth of canonical intrinsic terminators with recognizable U-tracts in mycobacteria is of significant interest both because noncanonical intrinsic terminators could reveal novel routes to destabilize transcription complexes and because accurate understanding of termination is crucial for strategies to combat mycobacterial diseases and for computational bioinformatics generally. Our finding that mycobacterial RNA polymerase requires U-tracts for intrinsic termination, which can be aided by NusG, will guide future study of mycobacterial transcription and aid improvement of predictive algorithms to annotate bacterial genome sequences.
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173
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Yakhnin AV, Babitzke P. NusG/Spt5: are there common functions of this ubiquitous transcription elongation factor? Curr Opin Microbiol 2014; 18:68-71. [PMID: 24632072 DOI: 10.1016/j.mib.2014.02.005] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2013] [Revised: 02/06/2014] [Accepted: 02/13/2014] [Indexed: 11/18/2022]
Abstract
NusG/Spt5 is a transcription elongation factor that assists in DNA-templated RNA synthesis by cellular RNA polymerases (RNAP). The modular domain composition of NusG/Spt5 and the way it binds to RNAP are conserved in all three domains of life. NusG/Spt5 closes RNAP around the DNA binding channel, thereby increasing transcription processivity. Recruitment of additional factors to elongating RNAP may be another conserved function of this ubiquitous protein. Eukaryotic Spt5 couples RNA processing and chromatin modification to transcription elongation, whereas bacterial NusG participates in a wide variety of processes, including RNAP pausing and Rho-dependent termination. Elongating RNAP forms a transcriptional bubble in which ∼12bp of the two DNA strands are locally separated. Within this transcription bubble the growing 3'-end of nascent RNA forms an 8-9bp long hybrid with the template DNA strand. Because of their location in the transcriptional bubble, NusG and its paralog RfaH recognize specific sequences in the nontemplate DNA strand and regulate transcription elongation in response to these signals.
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Affiliation(s)
- Alexander V Yakhnin
- Department of Biochemistry and Molecular Biology, Center for RNA Molecular Biology, Pennsylvania State University, University Park, PA 16802, USA
| | - Paul Babitzke
- Department of Biochemistry and Molecular Biology, Center for RNA Molecular Biology, Pennsylvania State University, University Park, PA 16802, USA.
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174
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Chai Q, Singh B, Peisker K, Metzendorf N, Ge X, Dasgupta S, Sanyal S. Organization of ribosomes and nucleoids in Escherichia coli cells during growth and in quiescence. J Biol Chem 2014; 289:11342-11352. [PMID: 24599955 DOI: 10.1074/jbc.m114.557348] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We have examined the distribution of ribosomes and nucleoids in live Escherichia coli cells under conditions of growth, division, and in quiescence. In exponentially growing cells translating ribosomes are interspersed among and around the nucleoid lobes, appearing as alternative bands under a fluorescence microscope. In contrast, inactive ribosomes either in stationary phase or after treatment with translation inhibitors such as chloramphenicol, tetracycline, and streptomycin gather predominantly at the cell poles and boundaries with concomitant compaction of the nucleoid. However, under all conditions, spatial segregation of the ribosomes and the nucleoids is well maintained. In dividing cells, ribosomes accumulate on both sides of the FtsZ ring at the mid cell. However, the distribution of the ribosomes among the new daughter cells is often unequal. Both the shape of the nucleoid and the pattern of ribosome distribution are also modified when the cells are exposed to rifampicin (transcription inhibitor), nalidixic acid (gyrase inhibitor), or A22 (MreB-cytoskeleton disruptor). Thus we conclude that the intracellular organization of the ribosomes and the nucleoids in bacteria are dynamic and critically dependent on cellular growth processes (replication, transcription, and translation) as well as on the integrity of the MreB cytoskeleton.
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Affiliation(s)
- Qian Chai
- Department of Cell and Molecular Biology, Uppsala University, Box-596, BMC, 75124, Uppsala, Sweden
| | - Bhupender Singh
- Department of Cell and Molecular Biology, Uppsala University, Box-596, BMC, 75124, Uppsala, Sweden
| | - Kristin Peisker
- Department of Cell and Molecular Biology, Uppsala University, Box-596, BMC, 75124, Uppsala, Sweden
| | - Nicole Metzendorf
- Department of Cell and Molecular Biology, Uppsala University, Box-596, BMC, 75124, Uppsala, Sweden
| | - Xueliang Ge
- Department of Cell and Molecular Biology, Uppsala University, Box-596, BMC, 75124, Uppsala, Sweden
| | - Santanu Dasgupta
- Department of Cell and Molecular Biology, Uppsala University, Box-596, BMC, 75124, Uppsala, Sweden
| | - Suparna Sanyal
- Department of Cell and Molecular Biology, Uppsala University, Box-596, BMC, 75124, Uppsala, Sweden.
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175
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Tomar SK, Artsimovitch I. NusG-Spt5 proteins-Universal tools for transcription modification and communication. Chem Rev 2013; 113:8604-19. [PMID: 23638618 PMCID: PMC4259564 DOI: 10.1021/cr400064k] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Sushil Kumar Tomar
- Department of Microbiology and The Center for RNA Biology, The Ohio State University , Columbus, Ohio 43210, United States
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176
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Genome-wide effects of selenium and translational uncoupling on transcription in the termite gut symbiont Treponema primitia. mBio 2013; 4:e00869-13. [PMID: 24222491 PMCID: PMC3892789 DOI: 10.1128/mbio.00869-13] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
When prokaryotic cells acquire mutations, encounter translation-inhibiting substances, or experience adverse environmental conditions that limit their ability to synthesize proteins, transcription can become uncoupled from translation. Such uncoupling is known to suppress transcription of protein-encoding genes in bacteria. Here we show that the trace element selenium controls transcription of the gene for the selenocysteine-utilizing enzyme formate dehydrogenase (fdhFSec) through a translation-coupled mechanism in the termite gut symbiont Treponema primitia, a member of the bacterial phylum Spirochaetes. We also evaluated changes in genome-wide transcriptional patterns caused by selenium limitation and by generally uncoupling translation from transcription via antibiotic-mediated inhibition of protein synthesis. We observed that inhibiting protein synthesis in T. primitia influences transcriptional patterns in unexpected ways. In addition to suppressing transcription of certain genes, the expected consequence of inhibiting protein synthesis, we found numerous examples in which transcription of genes and operons is truncated far downstream from putative promoters, is unchanged, or is even stimulated overall. These results indicate that gene regulation in bacteria allows for specific post-initiation transcriptional responses during periods of limited protein synthesis, which may depend both on translational coupling and on unclassified intrinsic elements of protein-encoding genes. A large body of literature demonstrates that the coupling of transcription and translation is a general and essential method by which bacteria regulate gene expression levels. However, the potential role of noncanonical amino acids in regulating transcriptional output via translational control remains, for the most part, undefined. Furthermore, the genome-wide transcriptional state in response to translational decoupling is not well quantified. The results presented here suggest that the noncanonical amino acid selenocysteine is able to tune transcription of an important metabolic gene via translational coupling. Furthermore, a genome-wide analysis reveals that transcriptional decoupling produces a wide-ranging effect and that this effect is not uniform. These results exemplify how growth conditions that impact translational processivity can rapidly feed back on transcriptional productivity of prespecified groups of genes, providing bacteria with an efficient response to environmental changes.
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177
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Affiliation(s)
- Finn Werner
- RNAP Laboratory, Institute for Structural and Molecular Biology, Division of Biosciences, University College London , Darwin Building, Gower Street, London WC1E 6BT, U.K
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178
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Transcription termination controls prophage maintenance in Escherichia coli genomes. Proc Natl Acad Sci U S A 2013; 110:14414-9. [PMID: 23940369 DOI: 10.1073/pnas.1303400110] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Prophages represent a large fraction of prokaryotic genomes and often provide new functions to their hosts, in particular virulence and fitness. How prokaryotic cells maintain such gene providers is central for understanding bacterial genome evolution by horizontal transfer. Prophage excision occurs through site-specific recombination mediated by a prophage-encoded integrase. In addition, a recombination directionality factor (or excisionase) directs the reaction toward excision and prevents the phage genome from being reintegrated. In this work, we describe the role of the transcription termination factor Rho in prophage maintenance through control of the synthesis of transcripts that mediate recombination directionality factor expression and, thus, excisive recombination. We show that Rho inhibition by bicyclomycin allows for the expression of prophage genes that lead to excisive recombination. Thus, besides its role in the silencing of horizontally acquired genes, Rho also maintains lysogeny of defective and functional prophages.
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179
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Archaeology of RNA polymerase: factor swapping during the transcription cycle. Biochem Soc Trans 2013; 41:362-7. [PMID: 23356312 DOI: 10.1042/bst20120274] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
All RNAPs (RNA polymerases) repeatedly make use of their DNA template by progressing through the transcription cycle multiple times. During transcription initiation and elongation, distinct sets of transcription factors associate with multisubunit RNAPs and modulate their nucleic-acid-binding and catalytic properties. Between the initiation and elongation phases of the cycle, the factors have to be exchanged by a largely unknown mechanism. We have shown that the binding sites for initiation and elongation factors are overlapping and that the binding of the factors to RNAP is mutually exclusive. This ensures an efficient exchange or 'swapping' of factors and could furthermore assist RNAP during promoter escape, enabling robust transcription. A similar mechanism applies to the bacterial RNAP system. The elongation factors are evolutionarily conserved between the bacterial (NusG) and archaeo-eukaryotic (Spt5) systems; however, the initiation factors [σ and TBP (TATA-box-binding protein)/TF (transcription factor) B respectively] are not. Therefore we propose that this factor-swapping mechanism, operating in all three domains of life, is the outcome of convergent evolution.
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180
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Gowrishankar J, Leela JK, Anupama K. R-loops in bacterial transcription: their causes and consequences. Transcription 2013; 4:153-7. [PMID: 23756343 PMCID: PMC3977913 DOI: 10.4161/trns.25101] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Nascent untranslated transcripts in bacteria are prone to generating RNA-DNA hybrids (R-loops); Rho-dependent transcription termination acts to reduce their prevalence. Here we discuss the mechanisms of R-loop formation and growth inhibition in bacteria.
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Affiliation(s)
- J Gowrishankar
- Laboratory of Bacterial Genetics; Centre for DNA Fingerprinting and Diagnostics; Hyderabad, India
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181
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Abstract
Cyclin-dependent kinases (CDKs) play a central role in governing eukaryotic cell division. It is becoming clear that the transcription cycle of RNA polymerase II (RNAP II) is also regulated by CDKs; in metazoans, the cell cycle and transcriptional CDK networks even share an upstream activating kinase, which is itself a CDK. From recent chemical-genetic analyses we know that CDKs and their substrates control events both early in transcription (the transition from initiation to elongation) and late (3' end formation and transcription termination). Moreover, mutual dependence on CDK activity might couple the "beginning" and "end" of the cycle, to ensure the fidelity of mRNA maturation and the efficient recycling of RNAP II from sites of termination to the transcription start site (TSS). As is the case for CDKs involved in cell cycle regulation, different transcriptional CDKs act in defined sequence on multiple substrates. These phosphorylations are likely to influence gene expression by several mechanisms, including direct, allosteric effects on the transcription machinery, co-transcriptional recruitment of proteins needed for mRNA-capping, splicing and 3' end maturation, dependent on multisite phosphorylation of the RNAP II C-terminal domain (CTD) and, perhaps, direct regulation of RNA-processing or histone-modifying machinery. Here we review these recent advances, and preview the emerging challenges for transcription-cycle research.
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Affiliation(s)
- Miriam Sansó
- Department of Structural and Chemical Biology; Icahn School of Medicine at Mount Sinai; New York, NY USA
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182
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The Escherichia coli translation-associated heat shock protein YbeY is involved in rRNA transcription antitermination. PLoS One 2013; 8:e62297. [PMID: 23638028 PMCID: PMC3639268 DOI: 10.1371/journal.pone.0062297] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2012] [Accepted: 03/19/2013] [Indexed: 11/29/2022] Open
Abstract
A new group of translation-associated heat shock genes has been recently identified. One of these novel genes is ybeY which is highly conserved in bacteria. In Escherichia coli the YbeY protein is important for efficient translation at all temperatures and is essential at high temperatures. Deletion mutants of ybeY are defective in protein translation, due to impaired 30 S ribosomal subunits. Here we provide evidence which tie YbeY to the transcription antitermination process. Thus, in ybeY deletion mutants transcription is significantly inhibited when the “nut like” sequences required for transcriptional antitermination are present, while if these sequences are removed transcription is not affected by the mutation.
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183
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Boudvillain M, Figueroa-Bossi N, Bossi L. Terminator still moving forward: expanding roles for Rho factor. Curr Opin Microbiol 2013; 16:118-24. [DOI: 10.1016/j.mib.2012.12.003] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2012] [Revised: 12/28/2012] [Accepted: 12/29/2012] [Indexed: 12/29/2022]
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184
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McGary K, Nudler E. RNA polymerase and the ribosome: the close relationship. Curr Opin Microbiol 2013; 16:112-7. [PMID: 23433801 DOI: 10.1016/j.mib.2013.01.010] [Citation(s) in RCA: 91] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2012] [Revised: 01/18/2013] [Accepted: 01/23/2013] [Indexed: 01/17/2023]
Abstract
In bacteria transcription and translation are linked in time and space. When coupled to RNA polymerase (RNAP), the translating ribosome ensures transcriptional processivity by preventing RNAP backtracking. Recent advances in the field have characterized important linker proteins that bridge the gap between transcription and translation: In particular, the NusE(S10):NusG complex and the NusG homolog, RfaH. The direct link between the moving ribosome and RNAP provides a basis for maintaining genomic integrity while enabling efficient transcription and timely translation of various genes within the bacterial cell.
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Affiliation(s)
- Katelyn McGary
- Department of Biochemistry, New York University School of Medicine, New York, NY 10016, USA
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185
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Drögemüller J, Stegmann CM, Mandal A, Steiner T, Burmann BM, Gottesman ME, Wöhrl BM, Rösch P, Wahl MC, Schweimer K. An autoinhibited state in the structure of Thermotoga maritima NusG. Structure 2013; 21:365-75. [PMID: 23415559 DOI: 10.1016/j.str.2012.12.015] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2012] [Revised: 11/19/2012] [Accepted: 12/21/2012] [Indexed: 01/05/2023]
Abstract
NusG is a conserved regulatory protein interacting with RNA polymerase (RNAP) and other proteins to form multicomponent complexes that modulate transcription. The crystal structure of Thermotoga maritima NusG (TmNusG) shows a three-domain architecture, comprising well-conserved amino-terminal (NTD) and carboxy-terminal (CTD) domains with an additional, species-specific domain inserted into the NTD. NTD and CTD directly contact each other, occluding a surface of the NTD for binding to RNAP and a surface on the CTD interacting either with transcription termination factor Rho or transcription antitermination factor NusE. NMR spectroscopy confirmed the intramolecular NTD-CTD interaction up to the optimal growth temperature of Thermotoga maritima. The domain interaction involves a dynamic equilibrium between open and closed states and contributes significantly to the overall fold stability of the protein. Wild-type TmNusG and deletion variants could not replace endogenous Escherichia coli NusG, suggesting that the NTD-CTD interaction of TmNusG represents an autoinhibited state.
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Affiliation(s)
- Johanna Drögemüller
- Lehrstuhl Biopolymere und Forschungszentrum für Biomakromoleküle, Universität Bayreuth, Universitätsstrasse 30, Bayreuth, Germany
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186
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Cellular organization of the transfer of genetic information. Curr Opin Microbiol 2013; 16:171-6. [PMID: 23395479 DOI: 10.1016/j.mib.2013.01.007] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2012] [Revised: 01/15/2013] [Accepted: 01/16/2013] [Indexed: 11/22/2022]
Abstract
Each step involved in the transfer of genetic information is spatially regulated in eukaryotic cells, as transcription, translation and mRNA degradation mostly occur in distinct functional compartments (e.g., nucleus, cytoplasm and P-bodies). At first glance in bacteria, these processes seem to take place in the same compartment - the cytoplasm - because of the conspicuous absence of membrane-enclosed organelles. However, it is becoming increasingly evident that mRNA-related processes are also spatially organized inside bacterial cells, and that this organization affects cellular function. The aims of this review are to summarize the current knowledge about this organization and to consider the mechanisms and forces shaping the cell interior. The field stands at an exciting point where new technologies are making long-standing questions amenable to experimentation.
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187
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De Lay N, Schu DJ, Gottesman S. Bacterial small RNA-based negative regulation: Hfq and its accomplices. J Biol Chem 2013; 288:7996-8003. [PMID: 23362267 DOI: 10.1074/jbc.r112.441386] [Citation(s) in RCA: 202] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A large group of bacterial small regulatory RNAs (sRNAs) use the Hfq chaperone to mediate pairing with and regulation of mRNAs. Recent findings help to clarify how Hfq acts and highlight the role of the endonuclease RNase E and its associated proteins (the degradosome) in negative regulation by these sRNAs. sRNAs frequently uncouple transcription and translation by blocking ribosome access to the mRNA, allowing other proteins access to the mRNA. As more examples of sRNA-mediated regulation are studied, more variations on how Hfq, RNase E, and other proteins collaborate to bring about sRNA-based regulation are being found.
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Affiliation(s)
- Nicholas De Lay
- Laboratory of Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892
| | - Daniel J Schu
- Laboratory of Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892
| | - Susan Gottesman
- Laboratory of Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892.
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188
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Peters JM, Mooney RA, Grass JA, Jessen ED, Tran F, Landick R. Rho and NusG suppress pervasive antisense transcription in Escherichia coli. Genes Dev 2013. [PMID: 23207917 DOI: 10.1101/gad.196741.112] [Citation(s) in RCA: 188] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Despite the prevalence of antisense transcripts in bacterial transcriptomes, little is known about how their synthesis is controlled. We report that a major function of the Escherichia coli termination factor Rho and its cofactor, NusG, is suppression of ubiquitous antisense transcription genome-wide. Rho binds C-rich unstructured nascent RNA (high C/G ratio) prior to its ATP-dependent dissociation of transcription complexes. NusG is required for efficient termination at minority subsets (~20%) of both antisense and sense Rho-dependent terminators with lower C/G ratio sequences. In contrast, a widely studied nusA deletion proposed to compromise Rho-dependent termination had no effect on antisense or sense Rho-dependent terminators in vivo. Global colocalization of the histone-like nucleoid-structuring protein (H-NS) with Rho-dependent terminators and genetic interactions between hns and rho suggest that H-NS aids Rho in suppression of antisense transcription. The combined actions of Rho, NusG, and H-NS appear to be analogous to the Sen1-Nrd1-Nab3 and nucleosome systems that suppress antisense transcription in eukaryotes.
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Affiliation(s)
- Jason M Peters
- Department of Biochemistry, University of Wisconsin, Madison, WI 53706, USA
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189
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Regulation of internal promoters in a zinc-responsive operon is influenced by transcription from upstream promoters. J Bacteriol 2013; 195:1285-93. [PMID: 23316045 DOI: 10.1128/jb.01488-12] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In the cyanobacterium Anabaena sp. strain PCC 7120 (also known as Nostoc sp. strain PCC 7120), a zinc-responsive operon (all4725-all4721) has been described, which contains 4 distinct promoters. The two most upstream ones bind Zur with high affinity, whereas the other two do not or do so with a very low affinity. In this paper, a detailed characterization of the four promoters is presented, showing that all four were induced by metal depletion, and they were constitutively derepressed in a zur mutant, despite the two downstream promoters not being direct targets for this regulator. Crucially, induction by metal depletion of the two downstream promoters was abrogated when transcription initiated at the upstream promoters was interrupted by a polar insertion midway in the operon. In contrast, insertion of a nitrogen-responsive promoter at a roughly similar position provoked the two downstream promoters to adopt a regulatory pattern mimicking that of the inserted promoter. Thus, regulation of the two downstream promoters is apparently influenced by transcription from promoters upstream. Evidence is presented indicating that the activity of the two downstream promoters is kept basal in Anabaena by repression. A regulatory model compatible with these results is proposed, where promoters controlled by repression in bacterial operons may be subjected to a hierarchical regulation depending on their position in the operon. According to this model, internal promoters may respond to stimuli governing the activity of promoters upstream by an indirect regulation and to specific stimuli by a direct regulation.
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190
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Rho-dependent transcription termination is essential to prevent excessive genome-wide R-loops in Escherichia coli. Proc Natl Acad Sci U S A 2012; 110:258-63. [PMID: 23251031 DOI: 10.1073/pnas.1213123110] [Citation(s) in RCA: 91] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Two pathways of transcription termination, factor-independent and -dependent, exist in bacteria. The latter pathway operates on nascent transcripts that are not simultaneously translated and requires factors Rho, NusG, and NusA, each of which is essential for viability of WT Escherichia coli. NusG and NusA are also involved in antitermination of transcription at the ribosomal RNA operons, as well as in regulating the rates of transcription elongation of all genes. We have used a bisulfite-sensitivity assay to demonstrate genome-wide increase in the occurrence of RNA-DNA hybrids (R-loops), including from antisense and read-through transcripts, in a nusG missense mutant defective for Rho-dependent termination. Lethality associated with complete deficiency of Rho and NusG (but not NusA) was rescued by ectopic expression of an R-loop-helicase UvsW, especially so on defined growth media. Our results suggest that factor-dependent transcription termination subserves a surveillance function to prevent translation-uncoupled transcription from generating R-loops, which would block replication fork progression and therefore be lethal, and that NusA performs additional essential functions as well in E. coli. Prevention of R-loop-mediated transcription-replication conflicts by cotranscriptional protein engagement of nascent RNA is emerging as a unifying theme among both prokaryotes and eukaryotes.
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191
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Affiliation(s)
- Stefan H. Knauer
- Lehrstuhl Biopolymere und Forschungszentrum für Bio-Makromoleküle; Universität Bayreuth; Bayreuth, Germany
| | - Irina Artsimovitch
- Department of Microbiology and The Center for RNA Biology; The Ohio State University; Columbus, OH USA
| | - Paul Rösch
- Lehrstuhl Biopolymere und Forschungszentrum für Bio-Makromoleküle; Universität Bayreuth; Bayreuth, Germany
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192
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Abstract
The textbook view that a primary sequence determines the unique fold of a given protein has been challenged by identification of proteins with variant structures, such as prions. Our recent studies revealed that the transcription factor RfaH simultaneously changes its topology and function. RfaH is a two-domain protein whose N-terminal domain binds to transcribing RNA polymerase, stimulating its processivity. The α-helical C-terminal domain masks the RNA polymerase-binding site of the N-terminal domain, preventing unwarranted recruitment to genes lacking a specific DNA sequence. Upon binding to its DNA target, RfaH domains dissociate, and the C-terminal domain refolds into a β-barrel. This dramatic transformation allows binding to the ribosomal protein S10 and subsequent recruitment of a ribosome, coupling transcription and translation. We define RfaH as first example of "transformer proteins", in which two alternative structural states have distinct cellular functions and hypothesize that transformer proteins may be widespread in nature.
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Affiliation(s)
- Stefan H Knauer
- Lehrstuhl Biopolymere und Forschungszentrum für Bio-Makromoleküle, Universität Bayreuth, Bayreuth, Germany.
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193
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Bossi L, Schwartz A, Guillemardet B, Boudvillain M, Figueroa-Bossi N. A role for Rho-dependent polarity in gene regulation by a noncoding small RNA. Genes Dev 2012; 26:1864-73. [PMID: 22895254 DOI: 10.1101/gad.195412.112] [Citation(s) in RCA: 98] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Gene regulation by bacterial trans-encoded small RNAs (sRNAs) is generally regarded as a post-transcriptional process bearing exclusively on the translation and/or the stability of target messenger RNA (mRNA). The work presented here revealed the existence of a transcriptional component in the regulation of a bicistronic operon-the chiPQ locus-by the ChiX sRNA in Salmonella. By studying the mechanism by which ChiX, upon pairing near the 5' end of the transcript, represses the distal gene in the operon, we discovered that the action of the sRNA induces Rho-dependent transcription termination within the chiP cistron. Apparently, by inhibiting chiP mRNA translation cotranscriptionally, ChiX uncouples translation from transcription, causing the nascent mRNA to become susceptible to Rho action. A Rho utilization (rut) site was identified in vivo through mutational analysis, and the termination pattern was characterized in vitro with a purified system. Remarkably, Rho activity at this site was found to be completely dependent on the function of the NusG protein both in vivo and in vitro. The recognition that trans-encoded sRNA act cotranscriptionally unveils a hitherto neglected aspect of sRNA function in bacteria.
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194
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Ribeiro AS, Häkkinen A, Lloyd-Price J. Effects of gene length on the dynamics of gene expression. Comput Biol Chem 2012; 41:1-9. [PMID: 23142668 DOI: 10.1016/j.compbiolchem.2012.10.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2012] [Revised: 10/11/2012] [Accepted: 10/11/2012] [Indexed: 01/06/2023]
Abstract
In Escherichia coli, the nucleotide length of a gene is bound to affect its expression dynamics. From simulations of a stochastic model of gene expression at the nucleotide and codon levels we show that, within realistic parameter values, the nucleotide length affects RNA and protein mean levels, as well as the expected transient time for RNA and protein numbers to change, following a signal. Fluctuations in RNA and protein numbers are found to be minimized for a small range of lengths, which matches the means of the distributions of lengths found in E. coli of both essential and non-essential genes. The variance of the length distribution for essential genes is found to be smaller than for non-essential genes, implying that these distributions are far from random. Finally, gene lengths are shown to affect the kinetics of a genetic switch, namely, the correlation between temporal proteins numbers, the stability of the two noisy attractors of the switch, and how biased is the choice of noisy attractor. The stability increases with gene length due to increased 'memory' about the previous states of the switch. We argue that, by affecting the dynamics of gene expression and of genetic circuits, gene lengths are subject to selection.
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Affiliation(s)
- Andre S Ribeiro
- Laboratory of Biosystem Dynamics, Computational Systems Biology Research Group, Department of Signal Processing, Tampere University of Technology, PO Box 553, 33101 Tampere, Finland.
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195
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Abstract
Transcription antiterminator RfaH alternates between closed (inactive) and open (activated) conformation. In this issue of Cell, Burmann et al. show that opening is accompanied by dramatic all-α to all-β refolding of its C-terminal domain. Each of the folds has a distinct function: all-α-fold acts as a specificity determinant, directing RfaH to a small subset of operons, whereas the all-β-fold recruits ribosome, thereby coupling RfaH-stimulated transcription to translation.
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Affiliation(s)
- Vladimir Svetlov
- Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, NY 10016, USA
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196
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Burmann BM, Knauer SH, Sevostyanova A, Schweimer K, Mooney RA, Landick R, Artsimovitch I, Rösch P. An α helix to β barrel domain switch transforms the transcription factor RfaH into a translation factor. Cell 2012; 150:291-303. [PMID: 22817892 DOI: 10.1016/j.cell.2012.05.042] [Citation(s) in RCA: 162] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2011] [Revised: 03/28/2012] [Accepted: 05/07/2012] [Indexed: 12/24/2022]
Abstract
NusG homologs regulate transcription and coupled processes in all living organisms. The Escherichia coli (E. coli) two-domain paralogs NusG and RfaH have conformationally identical N-terminal domains (NTDs) but dramatically different carboxy-terminal domains (CTDs), a β barrel in NusG and an α hairpin in RfaH. Both NTDs interact with elongating RNA polymerase (RNAP) to reduce pausing. In NusG, NTD and CTD are completely independent, and NusG-CTD interacts with termination factor Rho or ribosomal protein S10. In contrast, RfaH-CTD makes extensive contacts with RfaH-NTD to mask an RNAP-binding site therein. Upon RfaH interaction with its DNA target, the operon polarity suppressor (ops) DNA, RfaH-CTD is released, allowing RfaH-NTD to bind to RNAP. Here, we show that the released RfaH-CTD completely refolds from an all-α to an all-β conformation identical to that of NusG-CTD. As a consequence, RfaH-CTD binding to S10 is enabled and translation of RfaH-controlled operons is strongly potentiated. PAPERFLICK:
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Affiliation(s)
- Björn M Burmann
- Lehrstuhl Biopolymere und Forschungszentrum für Bio-Makromoleküle, Universität Bayreuth, Universitätsstraße 30, 95447 Bayreuth, Germany
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197
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Muteeb G, Dey D, Mishra S, Sen R. A multipronged strategy of an anti-terminator protein to overcome Rho-dependent transcription termination. Nucleic Acids Res 2012; 40:11213-28. [PMID: 23024214 PMCID: PMC3526286 DOI: 10.1093/nar/gks872] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
One of the important role of Rho-dependent transcription termination in bacteria is to prevent gene expressions from the bacteriophage DNA. The transcription anti-termination systems of the lambdoid phages have been designed to overcome this Rho action. The anti-terminator protein N has three interacting regions, which interact with the mRNA, with the NusA and with the RNA polymerase. Here, we show that N uses all these interaction modules to overcome the Rho action. N and Rho co-occupy their overlapping binding sites on the nascent RNA (the nutR/tR1 site), and this configuration slows down the rate of ATP hydrolysis and the rate of RNA release by Rho from the elongation complex. N-RNA polymerase interaction is not too important for this Rho inactivation process near/at the nutR site. This interaction becomes essential when the elongation complex moves away from the nutR site. From the unusual NusA-dependence property of a Rho mutant E134K, a suppressor of N, we deduced that the N-NusA complex in the anti-termination machinery reduces the efficiency of Rho by removing NusA from the termination pathway. We propose that NusA-remodelling is also one of the mechanisms used by N to overcome the termination signals.
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Affiliation(s)
- Ghazala Muteeb
- Laboratory of Transcription, Center for DNA Fingerprinting and Diagnostics, Tuljaguda Complex, 4-1-714 Mozamjahi Road, Nampally, Hyderabad 500 001, India
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198
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Hartzog GA, Fu J. The Spt4-Spt5 complex: a multi-faceted regulator of transcription elongation. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2012; 1829:105-15. [PMID: 22982195 DOI: 10.1016/j.bbagrm.2012.08.007] [Citation(s) in RCA: 88] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/27/2012] [Revised: 08/21/2012] [Accepted: 08/29/2012] [Indexed: 10/27/2022]
Abstract
In all domains of life, elongating RNA polymerases require the assistance of accessory factors to maintain their processivity and regulate their rate. Among these elongation factors, the Spt5/NusG factors stand out. Members of this protein family appear to be the only transcription accessory proteins that are universally conserved across all domains of life. In archaea and eukaryotes, Spt5 associates with a second protein, Spt4. In addition to regulating elongation, the eukaryotic Spt4-Spt5 complex appears to couple chromatin modification states and RNA processing to transcription elongation. This review discusses the experimental bases for our current understanding of Spt4-Spt5 function and recent studies that are beginning to elucidate the structure of Spt4-Spt5/RNA polymerase complexes and mechanism of Spt4-Spt5 action. This article is part of a Special Issue entitled: RNA polymerase II Transcript Elongation.
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Affiliation(s)
- Grant A Hartzog
- Department of MCD Biology, University of California, Santa Cruz, CA 95064, USA.
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199
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Dahan N, Choder M. The eukaryotic transcriptional machinery regulates mRNA translation and decay in the cytoplasm. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2012; 1829:169-73. [PMID: 22982191 DOI: 10.1016/j.bbagrm.2012.08.004] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/01/2012] [Revised: 07/28/2012] [Accepted: 08/29/2012] [Indexed: 11/29/2022]
Abstract
In eukaryotes, nuclear mRNA synthesis is physically separated from its cytoplasmic translation and degradation. Recent unexpected findings have revealed that, despite this separation, the transcriptional machinery can remotely control the cytoplasmic stages. Key to this coupling is the capacity of the transcriptional machinery to "imprint" the transcript with factors that escort it to the cytoplasm and regulate its localization, translation and decay. Some of these factors are known transcriptional regulators that also function in mRNA decay and are hence named "synthegradases". Imprinting can be carried out and/or regulated by RNA polymerase II or by promoter cis- and trans-acting elements. This article is part of a Special Issue entitled: RNA polymerase II Transcript Elongation.
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Affiliation(s)
- Nili Dahan
- Department of Molecular Microbiology, Technion-Israel Institute of Technology, Haifa, Israel
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200
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Abstract
RNA polymerase is a ratchet machine that oscillates between productive and backtracked states at numerous DNA positions. Since its first description 15 years ago, backtracking--the reversible sliding of RNA polymerase along DNA and RNA--has been implicated in many critical processes in bacteria and eukaryotes, including the control of transcription elongation, pausing, termination, fidelity, and genome instability.
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