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Saecker RM, Mueller AU, Malone B, Chen J, Budell WC, Dandey VP, Maruthi K, Mendez JH, Molina N, Eng ET, Yen LY, Potter CS, Carragher B, Darst SA. Early intermediates in bacterial RNA polymerase promoter melting visualized by time-resolved cryo-electron microscopy. Nat Struct Mol Biol 2024:10.1038/s41594-024-01349-9. [PMID: 38951624 DOI: 10.1038/s41594-024-01349-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2023] [Accepted: 06/06/2024] [Indexed: 07/03/2024]
Abstract
During formation of the transcription-competent open complex (RPo) by bacterial RNA polymerases (RNAPs), transient intermediates pile up before overcoming a rate-limiting step. Structural descriptions of these interconversions in real time are unavailable. To address this gap, here we use time-resolved cryogenic electron microscopy (cryo-EM) to capture four intermediates populated 120 ms or 500 ms after mixing Escherichia coli σ70-RNAP and the λPR promoter. Cryo-EM snapshots revealed that the upstream edge of the transcription bubble unpairs rapidly, followed by stepwise insertion of two conserved nontemplate strand (nt-strand) bases into RNAP pockets. As the nt-strand 'read-out' extends, the RNAP clamp closes, expelling an inhibitory σ70 domain from the active-site cleft. The template strand is fully unpaired by 120 ms but remains dynamic, indicating that yet unknown conformational changes complete RPo formation in subsequent steps. Given that these events likely describe DNA opening at many bacterial promoters, this study provides insights into how DNA sequence regulates steps of RPo formation.
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Affiliation(s)
- Ruth M Saecker
- Laboratory of Molecular Biophysics, The Rockefeller University, New York, NY, USA
| | - Andreas U Mueller
- Laboratory of Molecular Biophysics, The Rockefeller University, New York, NY, USA
| | - Brandon Malone
- Laboratory of Molecular Biophysics, The Rockefeller University, New York, NY, USA
- Memorial Sloan Kettering Cancer Center, Sloan Kettering Institute, New York, NY, USA
| | - James Chen
- Laboratory of Molecular Biophysics, The Rockefeller University, New York, NY, USA
- Laboratory of Host-Pathogen Biology, The Rockefeller University, New York, NY, USA
| | - William C Budell
- The National Resource for Automated Molecular Microscopy, Simons Electron Microscopy Center, New York Structural Biology Center, New York, NY, USA
| | - Venkata P Dandey
- The National Resource for Automated Molecular Microscopy, Simons Electron Microscopy Center, New York Structural Biology Center, New York, NY, USA
- National Institute of Environmental Health Sciences, Durham, NC, USA
| | - Kashyap Maruthi
- The National Resource for Automated Molecular Microscopy, Simons Electron Microscopy Center, New York Structural Biology Center, New York, NY, USA
| | - Joshua H Mendez
- The National Resource for Automated Molecular Microscopy, Simons Electron Microscopy Center, New York Structural Biology Center, New York, NY, USA
| | - Nina Molina
- Laboratory of Molecular Biophysics, The Rockefeller University, New York, NY, USA
| | - Edward T Eng
- The National Resource for Automated Molecular Microscopy, Simons Electron Microscopy Center, New York Structural Biology Center, New York, NY, USA
| | - Laura Y Yen
- The National Resource for Automated Molecular Microscopy, Simons Electron Microscopy Center, New York Structural Biology Center, New York, NY, USA
| | - Clinton S Potter
- The National Resource for Automated Molecular Microscopy, Simons Electron Microscopy Center, New York Structural Biology Center, New York, NY, USA
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY, USA
- Chan Zuckerberg Imaging Institute, San Francisco, CA, USA
| | - Bridget Carragher
- The National Resource for Automated Molecular Microscopy, Simons Electron Microscopy Center, New York Structural Biology Center, New York, NY, USA
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY, USA
- Chan Zuckerberg Imaging Institute, San Francisco, CA, USA
| | - Seth A Darst
- Laboratory of Molecular Biophysics, The Rockefeller University, New York, NY, USA.
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2
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Saecker RM, Mueller AU, Malone B, Chen J, Budell WC, Dandey VP, Maruthi K, Mendez JH, Molina N, Eng ET, Yen LY, Potter CS, Carragher B, Darst SA. Early intermediates in bacterial RNA polymerase promoter melting visualized by time-resolved cryo-electron microscopy. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.03.13.584744. [PMID: 38559232 PMCID: PMC10979975 DOI: 10.1101/2024.03.13.584744] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/04/2024]
Abstract
During formation of the transcription-competent open complex (RPo) by bacterial RNA polymerases (RNAP), transient intermediates pile up before overcoming a rate-limiting step. Structural descriptions of these interconversions in real time are unavailable. To address this gap, time-resolved cryo-electron microscopy (cryo-EM) was used to capture four intermediates populated 120 or 500 milliseconds (ms) after mixing Escherichia coli σ70-RNAP and the λPR promoter. Cryo-EM snapshots revealed the upstream edge of the transcription bubble unpairs rapidly, followed by stepwise insertion of two conserved nontemplate strand (nt-strand) bases into RNAP pockets. As nt-strand "read-out" extends, the RNAP clamp closes, expelling an inhibitory σ70 domain from the active-site cleft. The template strand is fully unpaired by 120 ms but remains dynamic, indicating yet unknown conformational changes load it in subsequent steps. Because these events likely describe DNA opening at many bacterial promoters, this study provides needed insights into how DNA sequence regulates steps of RPo formation.
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Affiliation(s)
- Ruth M. Saecker
- Laboratory of Molecular Biophysics, The Rockefeller University, New York, NY 10065 USA
| | - Andreas U. Mueller
- Laboratory of Molecular Biophysics, The Rockefeller University, New York, NY 10065 USA
| | - Brandon Malone
- Laboratory of Molecular Biophysics, The Rockefeller University, New York, NY 10065 USA
| | - James Chen
- Laboratory of Molecular Biophysics, The Rockefeller University, New York, NY 10065 USA
| | - William C. Budell
- The National Resource for Automated Molecular Microscopy, Simons Electron Microscopy Center, New York Structural Biology Center, New York, NY USA
| | - Venkata P. Dandey
- The National Resource for Automated Molecular Microscopy, Simons Electron Microscopy Center, New York Structural Biology Center, New York, NY USA
| | - Kashyap Maruthi
- The National Resource for Automated Molecular Microscopy, Simons Electron Microscopy Center, New York Structural Biology Center, New York, NY USA
| | - Joshua H. Mendez
- The National Resource for Automated Molecular Microscopy, Simons Electron Microscopy Center, New York Structural Biology Center, New York, NY USA
| | - Nina Molina
- Laboratory of Molecular Biophysics, The Rockefeller University, New York, NY 10065 USA
| | - Edward T. Eng
- The National Resource for Automated Molecular Microscopy, Simons Electron Microscopy Center, New York Structural Biology Center, New York, NY USA
| | - Laura Y. Yen
- The National Resource for Automated Molecular Microscopy, Simons Electron Microscopy Center, New York Structural Biology Center, New York, NY USA
| | - Clinton S. Potter
- The National Resource for Automated Molecular Microscopy, Simons Electron Microscopy Center, New York Structural Biology Center, New York, NY USA
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY USA
| | - Bridget Carragher
- The National Resource for Automated Molecular Microscopy, Simons Electron Microscopy Center, New York Structural Biology Center, New York, NY USA
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY USA
| | - Seth A. Darst
- Laboratory of Molecular Biophysics, The Rockefeller University, New York, NY 10065 USA
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3
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Abstract
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We
explore the process of base-flipping for four central bases,
adenine, guanine, cytosine, and thymine, in a deoxyribonucleic acid
(DNA) duplex using the energy landscape perspective. NMR imino-proton
exchange and fluorescence correlation spectroscopy studies have been
used in previous experiments to obtain lifetimes for bases in paired
and extrahelical states. However, the difference of almost 4 orders
of magnitude in the base-flipping rates obtained by the two methods
implies that they are exploring different pathways and possibly different
open states. Our results support the previous suggestion that minor
groove opening may be favored by distortions in the DNA backbone and
reveal links between sequence effects and the direction of opening,
i.e., whether the base flips toward the major or the minor groove
side. In particular, base flipping along the minor groove pathway
was found to align toward the 5′ side of the backbone. We find
that bases align toward the 3′ side of the backbone when flipping
along the major groove pathway. However, in some cases for cytosine
and thymine, the base flipping along the major groove pathway also
aligns toward the 5′ side. The sequence effect may be caused
by the polar interactions between the flipping-base and its neighboring
bases on either of the strands. For guanine flipping toward the minor
groove side, we find that the equilibrium constant for opening is
large compared to flipping via the major groove. We find that the
estimated rates of base opening, and hence the lifetimes of the closed
state, obtained for thymine flipping through small and large angles
along the major groove differ by 6 orders of magnitude, whereas for
thymine flipping through small angles along the minor groove and large
angles along the major groove, the rates differ by 3 orders of magnitude.
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Affiliation(s)
- Nicy
- Yusuf Hamied Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, U.K
| | - Debayan Chakraborty
- Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712, United States
| | - David J. Wales
- Yusuf Hamied Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, U.K
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4
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Shaheen C, Hastie C, Metera K, Scott S, Zhang Z, Chen S, Gu G, Weber L, Munsky B, Kouzine F, Levens D, Benham C, Leslie S. Non-equilibrium structural dynamics of supercoiled DNA plasmids exhibits asymmetrical relaxation. Nucleic Acids Res 2022; 50:2754-2764. [PMID: 35188541 PMCID: PMC8934633 DOI: 10.1093/nar/gkac101] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2021] [Revised: 01/28/2022] [Accepted: 02/04/2022] [Indexed: 12/12/2022] Open
Abstract
Many cellular processes occur out of equilibrium. This includes site-specific unwinding in supercoiled DNA, which may play an important role in gene regulation. Here, we use the Convex Lens-induced Confinement (CLiC) single-molecule microscopy platform to study these processes with high-throughput and without artificial constraints on molecular structures or interactions. We use two model DNA plasmid systems, pFLIP-FUSE and pUC19, to study the dynamics of supercoiling-induced secondary structural transitions after perturbations away from equilibrium. We find that structural transitions can be slow, leading to long-lived structural states whose kinetics depend on the duration and direction of perturbation. Our findings highlight the importance of out-of-equilibrium studies when characterizing the complex structural dynamics of DNA and understanding the mechanisms of gene regulation.
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Affiliation(s)
- Cynthia Shaheen
- Department of Physics, McGill University, Montreal, QC H3A 2T8, Canada
- Michael Smith Laboratories, University of British Columbia, BC V6T 1Z4, Canada
- Department of Physics and Astronomy, University of British Columbia, BC V6T 1Z1, Canada
| | - Cameron Hastie
- Department of Physics, McGill University, Montreal, QC H3A 2T8, Canada
- Michael Smith Laboratories, University of British Columbia, BC V6T 1Z4, Canada
- Department of Physics and Astronomy, University of British Columbia, BC V6T 1Z1, Canada
| | - Kimberly Metera
- Department of Physics, McGill University, Montreal, QC H3A 2T8, Canada
| | - Shane Scott
- Department of Physics, McGill University, Montreal, QC H3A 2T8, Canada
- Institute of Materials Science, Kiel University, 24142 Kiel, Germany
| | - Zhi Zhang
- Department of Physics, McGill University, Montreal, QC H3A 2T8, Canada
| | - Sitong Chen
- Department of Physics, McGill University, Montreal, QC H3A 2T8, Canada
| | - Gracia Gu
- Department of Physics, McGill University, Montreal, QC H3A 2T8, Canada
| | - Lisa Weber
- Department of Chemical and Biological Engineering and School of Biomedical Engineering, Colorado State University, Fort Collins, CO 80523, USA
| | - Brian Munsky
- Department of Chemical and Biological Engineering and School of Biomedical Engineering, Colorado State University, Fort Collins, CO 80523, USA
| | - Fedor Kouzine
- Center for Cancer Research, National Cancer Institute, Bethesda, MD 20892, USA
| | - David Levens
- Center for Cancer Research, National Cancer Institute, Bethesda, MD 20892, USA
| | - Craig Benham
- Genome Center, University of California Davis, Davis, CA 95616, USA
| | - Sabrina Leslie
- Department of Physics, McGill University, Montreal, QC H3A 2T8, Canada
- Michael Smith Laboratories, University of British Columbia, BC V6T 1Z4, Canada
- Department of Physics and Astronomy, University of British Columbia, BC V6T 1Z1, Canada
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5
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Yakushevich LV, Krasnobaeva LA. Ideas and methods of nonlinear mathematics and theoretical physics in DNA science: the McLaughlin-Scott equation and its application to study the DNA open state dynamics. Biophys Rev 2021; 13:315-338. [PMID: 34178171 PMCID: PMC8214655 DOI: 10.1007/s12551-021-00801-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2021] [Accepted: 04/22/2021] [Indexed: 12/11/2022] Open
Abstract
The review is devoted to a new and rapidly developing area related to the application of ideas and methods of nonlinear mathematics and theoretical physics to study the internal dynamics of DNA and, in particular, the behavior of the open states of DNA. There are two main competing approaches to this research. The first approach is based on the molecular dynamics method, which takes into account the motions of all structural elements of the DNA molecule and all interactions between them. The second approach is based on prior selection of the main (dominant) motions and their mathematical description using a small number of model equations. This review describes the results of the study of the open states of DNA performed within the framework of the second approach using the McLaughlin-Scott equation. We present the results obtained both in the case of homogeneous sequences: poly (A), poly (T), poly (G) and poly (C), and in the inhomogeneous case when the McLaughlin-Scott equation has been used for studying the dynamics of open states activated in the promoters A1, A2 and A3 of the bacteriophage T7 genome, in the genes IFNA17, ADRB2, NOS1 and IL-5, in the pBR322 and pTTQ18 plasmids. Particular attention is paid to the results concerning the effect of various external fields on the behavior of open states. In the concluding part of the review, new possibilities and prospects for the development of the considered approach and especially of the McLaughlin-Scott equation are discussed. SUPPLEMENTARY INFORMATION The online version contains supplementary material available at 10.1007/s12551-021-00801-0.
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Affiliation(s)
- Ludmila V. Yakushevich
- Institute of Cell Biophysics, Russian Academy of Sciences, Pushchino, Moscow Region, Russia
| | - Larisa A. Krasnobaeva
- Siberian State Medical University, Tomsk, Russia
- Tomsk State University, Tomsk, Russia
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6
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Newman SL, Will WR, Libby SJ, Fang FC. The curli regulator CsgD mediates stationary phase counter-silencing of csgBA in Salmonella Typhimurium. Mol Microbiol 2018; 108:101-114. [PMID: 29388265 DOI: 10.1111/mmi.13919] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2016] [Revised: 01/26/2018] [Accepted: 01/26/2018] [Indexed: 12/23/2022]
Abstract
Integration of horizontally acquired genes into transcriptional networks is essential for the regulated expression of virulence in bacterial pathogens. In Salmonella enterica, expression of such genes is repressed by the nucleoid-associated protein H-NS, which recognizes and binds to AT-rich DNA. H-NS-mediated silencing must be countered by other DNA-binding proteins to allow expression under appropriate conditions. Some genes that can be transcribed by RNA polymerase (RNAP) associated with the alternative sigma factor σS or the housekeeping sigma factor σ70 in vitro appear to be preferentially transcribed by σS in the presence of H-NS, suggesting that σS may act as a counter-silencer. To determine whether σS directly counters H-NS-mediated silencing and whether co-regulation by H-NS accounts for the σS selectivity of certain promoters, we examined the csgBA operon, which is required for curli fimbriae expression and is known to be regulated by both H-NS and σS . Using genetics and in vitro biochemical analyses, we found that σS is not directly required for csgBA transcription, but rather up-regulates csgBA via an indirect upstream mechanism. Instead, the biofilm master regulator CsgD directly counter-silences the csgBA promoter by altering the DNA-protein complex structure to disrupt H-NS-mediated silencing in addition to directing the binding of RNAP.
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Affiliation(s)
- S L Newman
- Molecular and Cellular Biology Program, University of Washington, Seattle, WA, USA.,Department of Laboratory Medicine, University of Washington, Seattle, WA, USA
| | - W R Will
- Department of Microbiology, University of Washington, Seattle WA, USA
| | - S J Libby
- Department of Microbiology, University of Washington, Seattle WA, USA
| | - F C Fang
- Department of Laboratory Medicine, University of Washington, Seattle, WA, USA.,Department of Microbiology, University of Washington, Seattle WA, USA
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7
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Liu Y, Freeman A, Déclais AC, Gartner A, Lilley DMJ. Biochemical and Structural Properties of Fungal Holliday Junction-Resolving Enzymes. Methods Enzymol 2018; 600:543-568. [PMID: 29458774 DOI: 10.1016/bs.mie.2017.11.021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Four-way Holliday junctions in DNA are the central intermediates of genetic recombination and must be processed into regular duplex species. One mechanism for achieving this is called resolution, brought about by structure-selective nucleases. GEN1 is an important junction-resolving enzyme in eukaryotic cells, a member of the FEN1/EXO1 superfamily of nucleases. While human GEN1 is difficult to work with because of aggregation, orthologs from thermophilic fungi have been identified using bioinformatics and have proved to have excellent properties. Here, the expression and purification of this enzyme from Chaetomium thermophilum is described, together with the means of investigating its biochemical properties. The enzyme is quite similar to junction-resolving enzymes from lower organisms, binding to junctions in dimeric form, introducing symmetrical bilateral cleavages, the second of which is accelerated to promote productive resolution. Crystallization of C. thermophilum GEN1 is described, and the structure of a DNA-product complex. Juxtaposition of complexes in the crystal lattice suggests how the structure of a dimeric enzyme with an intact junction is organized.
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Affiliation(s)
- Yijin Liu
- Cancer Research UK Nucleic Acid Structure Research Group, The University of Dundee, Dundee, United Kingdom
| | - Alasdair Freeman
- Cancer Research UK Nucleic Acid Structure Research Group, The University of Dundee, Dundee, United Kingdom
| | - Anne-Cécile Déclais
- Cancer Research UK Nucleic Acid Structure Research Group, The University of Dundee, Dundee, United Kingdom
| | - Anton Gartner
- Cancer Research UK Nucleic Acid Structure Research Group, The University of Dundee, Dundee, United Kingdom
| | - David M J Lilley
- Cancer Research UK Nucleic Acid Structure Research Group, The University of Dundee, Dundee, United Kingdom.
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8
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Hook-Barnard IG, Hinton DM. Transcription Initiation by Mix and Match Elements: Flexibility for Polymerase Binding to Bacterial Promoters. GENE REGULATION AND SYSTEMS BIOLOGY 2017. [DOI: 10.1177/117762500700100020] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Bacterial RNA polymerase is composed of a core of subunits (β β′, α1, α2, ω), which have RNA synthesizing activity, and a specificity factor (σ), which identifies the start of transcription by recognizing and binding to sequence elements within promoter DNA. Four core promoter consensus sequences, the –10 element, the extended –10 (TGn) element, the –35 element, and the UP elements, have been known for many years; the importance of a nontemplate G at position -5 has been recognized more recently. However, the functions of these elements are not the same. The AT-rich UP elements, the –35 elements (–35TTGACA–30), and the extended –10 (15TGn–13) are recognized as double-stranded binding elements, whereas the –5 nontemplate G is recognized in the context of single-stranded DNA at the transcription bubble. Furthermore, the –10 element (–12TATAAT–7) is recognized as both double-stranded DNA for the T:A bp at position –12 and as nontemplate, single-stranded DNA from positions –11 to –7. The single-stranded sequences at positions –11 to –7 as well as the –5 contribute to later steps in transcription initiation that involve isomerization of polymerase and separation of the promoter DNA around the transcription start site. Recent work has demonstrated that the double-stranded elements may be used in various combinations to yield an effective promoter. Thus, while some minimal number of contacts is required for promoter function, polymerase allows the elements to be mixed and matched. Interestingly, which particular elements are used does not appear to fundamentally alter the transcription bubble generated in the stable complex. In this review, we discuss the multiple steps involved in forming a transcriptionally competent polymerase/promoter complex, and we examine what is known about polymerase recognition of core promoter elements. We suggest that considering promoter elements according to their involvement in early (polymerase binding) or later (polymerase isomerization) steps in transcription initiation rather than simply from their match to conventional promoter consensus sequences is a more instructive form of promoter classification.
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Affiliation(s)
- India G. Hook-Barnard
- Gene Expression and Regulation Section, Laboratory of Molecular and Cellular Biology, National Institute of Diabetes Digestive and Kidney Diseases, National Institutes of Health, Bldg. 8 Room 2A-13, Bethesda, MD 20892-0830
| | - Deborah M. Hinton
- Gene Expression and Regulation Section, Laboratory of Molecular and Cellular Biology, National Institute of Diabetes Digestive and Kidney Diseases, National Institutes of Health, Bldg. 8 Room 2A-13, Bethesda, MD 20892-0830
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9
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Fouqueau T, Blombach F, Werner F. Evolutionary Origins of Two-Barrel RNA Polymerases and Site-Specific Transcription Initiation. Annu Rev Microbiol 2017; 71:331-348. [PMID: 28657884 DOI: 10.1146/annurev-micro-091014-104145] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Evolution-related multisubunit RNA polymerases (RNAPs) carry out RNA synthesis in all domains life. Although their catalytic cores and fundamental mechanisms of transcription elongation are conserved, the initiation stage of the transcription cycle differs substantially in bacteria, archaea, and eukaryotes in terms of the requirements for accessory factors and details of the molecular mechanisms. This review focuses on recent insights into the evolution of the transcription apparatus with regard to (a) the surprisingly pervasive double-Ψ β-barrel active-site configuration among different nucleic acid polymerase families, (b) the origin and phylogenetic distribution of TBP, TFB, and TFE transcription factors, and
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Affiliation(s)
- Thomas Fouqueau
- Institute of Structural and Molecular Biology, Division of Biosciences, University College London, London WC1E 6BT, United Kingdom; ,
| | - Fabian Blombach
- Institute of Structural and Molecular Biology, Division of Biosciences, University College London, London WC1E 6BT, United Kingdom; ,
| | - Finn Werner
- Institute of Structural and Molecular Biology, Division of Biosciences, University College London, London WC1E 6BT, United Kingdom; ,
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10
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Mechanism of transcription initiation and promoter escape by E. coli RNA polymerase. Proc Natl Acad Sci U S A 2017; 114:E3032-E3040. [PMID: 28348246 DOI: 10.1073/pnas.1618675114] [Citation(s) in RCA: 53] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
To investigate roles of the discriminator and open complex (OC) lifetime in transcription initiation by Escherichia coli RNA polymerase (RNAP; α2ββ'ωσ70), we compare productive and abortive initiation rates, short RNA distributions, and OC lifetime for the λPR and T7A1 promoters and variants with exchanged discriminators, all with the same transcribed region. The discriminator determines the OC lifetime of these promoters. Permanganate reactivity of thymines reveals that strand backbones in open regions of long-lived λPR-discriminator OCs are much more tightly held than for shorter-lived T7A1-discriminator OCs. Initiation from these OCs exhibits two kinetic phases and at least two subpopulations of ternary complexes. Long RNA synthesis (constrained to be single round) occurs only in the initial phase (<10 s), at similar rates for all promoters. Less than half of OCs synthesize a full-length RNA; the majority stall after synthesizing a short RNA. Most abortive cycling occurs in the slower phase (>10 s), when stalled complexes release their short RNA and make another without escaping. In both kinetic phases, significant amounts of 8-nt and 10-nt transcripts are produced by longer-lived, λPR-discriminator OCs, whereas no RNA longer than 7 nt is produced by shorter-lived T7A1-discriminator OCs. These observations and the lack of abortive RNA in initiation from short-lived ribosomal promoter OCs are well described by a quantitative model in which ∼1.0 kcal/mol of scrunching free energy is generated per translocation step of RNA synthesis to overcome OC stability and drive escape. The different length-distributions of abortive RNAs released from OCs with different lifetimes likely play regulatory roles.
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11
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Molecular Mechanisms of Transcription Initiation-Structure, Function, and Evolution of TFE/TFIIE-Like Factors and Open Complex Formation. J Mol Biol 2016; 428:2592-2606. [PMID: 27107643 DOI: 10.1016/j.jmb.2016.04.016] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2016] [Revised: 04/06/2016] [Accepted: 04/12/2016] [Indexed: 11/24/2022]
Abstract
Transcription initiation requires that the promoter DNA is melted and the template strand is loaded into the active site of the RNA polymerase (RNAP), forming the open complex (OC). The archaeal initiation factor TFE and its eukaryotic counterpart TFIIE facilitate this process. Recent structural and biophysical studies have revealed the position of TFE/TFIIE within the pre-initiation complex (PIC) and illuminated its role in OC formation. TFE operates via allosteric and direct mechanisms. Firstly, it interacts with the RNAP and induces the opening of the flexible RNAP clamp domain, concomitant with DNA melting and template loading. Secondly, TFE binds physically to single-stranded DNA in the transcription bubble of the OC and increases its stability. The identification of the β-subunit of archaeal TFE enabled us to reconstruct the evolutionary history of TFE/TFIIE-like factors, which is characterised by winged helix (WH) domain expansion in eukaryotes and loss of metal centres including iron-sulfur clusters and Zinc ribbons. OC formation is an important target for the regulation of transcription in all domains of life. We propose that TFE and the bacterial general transcription factor CarD, although structurally and evolutionary unrelated, show interesting parallels in their mechanism to enhance OC formation. We argue that OC formation is used as a way to regulate transcription in all domains of life, and these regulatory mechanisms coevolved with the basal transcription machinery.
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12
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Sreenivasan R, Heitkamp S, Chhabra M, Saecker R, Lingeman E, Poulos M, McCaslin D, Capp MW, Artsimovitch I, Record MT. Fluorescence Resonance Energy Transfer Characterization of DNA Wrapping in Closed and Open Escherichia coli RNA Polymerase-λP(R) Promoter Complexes. Biochemistry 2016; 55:2174-86. [PMID: 26998673 DOI: 10.1021/acs.biochem.6b00125] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Initial recognition of promoter DNA by RNA polymerase (RNAP) is proposed to trigger a series of conformational changes beginning with bending and wrapping of the 40-50 bp of DNA immediately upstream of the -35 region. Kinetic studies demonstrated that the presence of upstream DNA facilitates bending and entry of the downstream duplex (to +20) into the active site cleft to form an advanced closed complex (CC), prior to melting of ∼13 bp (-11 to +2), including the transcription start site (+1). Atomic force microscopy and footprinting revealed that the stable open complex (OC) is also highly wrapped (-60 to +20). To test the proposed bent-wrapped model of duplex DNA in an advanced RNAP-λP(R) CC and compare wrapping in the CC and OC, we use fluorescence resonance energy transfer (FRET) between cyanine dyes at far-upstream (-100) and downstream (+14) positions of promoter DNA. Similarly large intrinsic FRET efficiencies are observed for the CC (0.30 ± 0.07) and the OC (0.32 ± 0.11) for both probe orientations. Fluorescence enhancements at +14 are observed in the single-dye-labeled CC and OC. These results demonstrate that upstream DNA is extensively wrapped and the start site region is bent into the cleft in the advanced CC, reducing the distance between positions -100 and +14 on promoter DNA from >300 to <100 Å. The proximity of upstream DNA to the downstream cleft in the advanced CC is consistent with the proposed mechanism for facilitation of OC formation by upstream DNA.
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Affiliation(s)
- Raashi Sreenivasan
- Biophysics Program, ‡Department of Biochemistry, and §Department of Chemistry, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States.,Department of Microbiology and ⊥Center for RNA Biology, The Ohio State University , Columbus, Ohio 43210, United States
| | - Sara Heitkamp
- Biophysics Program, ‡Department of Biochemistry, and §Department of Chemistry, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States.,Department of Microbiology and ⊥Center for RNA Biology, The Ohio State University , Columbus, Ohio 43210, United States
| | - Munish Chhabra
- Biophysics Program, ‡Department of Biochemistry, and §Department of Chemistry, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States.,Department of Microbiology and ⊥Center for RNA Biology, The Ohio State University , Columbus, Ohio 43210, United States
| | - Ruth Saecker
- Biophysics Program, ‡Department of Biochemistry, and §Department of Chemistry, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States.,Department of Microbiology and ⊥Center for RNA Biology, The Ohio State University , Columbus, Ohio 43210, United States
| | - Emily Lingeman
- Biophysics Program, ‡Department of Biochemistry, and §Department of Chemistry, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States.,Department of Microbiology and ⊥Center for RNA Biology, The Ohio State University , Columbus, Ohio 43210, United States
| | - Mikaela Poulos
- Biophysics Program, ‡Department of Biochemistry, and §Department of Chemistry, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States.,Department of Microbiology and ⊥Center for RNA Biology, The Ohio State University , Columbus, Ohio 43210, United States
| | - Darrell McCaslin
- Biophysics Program, ‡Department of Biochemistry, and §Department of Chemistry, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States.,Department of Microbiology and ⊥Center for RNA Biology, The Ohio State University , Columbus, Ohio 43210, United States
| | - Michael W Capp
- Biophysics Program, ‡Department of Biochemistry, and §Department of Chemistry, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States.,Department of Microbiology and ⊥Center for RNA Biology, The Ohio State University , Columbus, Ohio 43210, United States
| | - Irina Artsimovitch
- Biophysics Program, ‡Department of Biochemistry, and §Department of Chemistry, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States.,Department of Microbiology and ⊥Center for RNA Biology, The Ohio State University , Columbus, Ohio 43210, United States
| | - M Thomas Record
- Biophysics Program, ‡Department of Biochemistry, and §Department of Chemistry, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States.,Department of Microbiology and ⊥Center for RNA Biology, The Ohio State University , Columbus, Ohio 43210, United States
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13
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Karpen ME, deHaseth PL. Base flipping in open complex formation at bacterial promoters. Biomolecules 2015; 5:668-78. [PMID: 25927327 PMCID: PMC4496690 DOI: 10.3390/biom5020668] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2015] [Revised: 03/16/2015] [Accepted: 04/14/2015] [Indexed: 12/18/2022] Open
Abstract
In the process of transcription initiation, the bacterial RNA polymerase binds double-stranded (ds) promoter DNA and subsequently effects strand separation of 12 to 14 base pairs (bp), including the start site of transcription, to form the so-called "open complex" (also referred to as RP(o)). This complex is competent to initiate RNA synthesis. Here we will review the role of σ70 and its homologs in the strand separation process, and evidence that strand separation is initiated at the -11A (the A of the non-template strand that is 11 bp upstream from the transcription start site) of the promoter. By using the fluorescent adenine analog, 2-aminopurine, it was demonstrated that the -11A on the non-template strand flips out of the DNA helix and into a hydrophobic pocket where it stacks with tyrosine 430 of σ70. Open complexes are remarkably stable, even though in vivo, and under most experimental conditions in vitro, dsDNA is much more stable than its strand-separated form. Subsequent structural studies of other researchers have confirmed that in the open complex the -11A has flipped into a hydrophobic pocket of σ70. It was also revealed that RPo was stabilized by three additional bases of the non-template strand being flipped out of the helix and into hydrophobic pockets, further preventing re-annealing of the two complementary DNA strands.
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Affiliation(s)
- Mary E Karpen
- Department of Chemistry, Grand Valley State University, 1 Campus Drive, 312 Padnos Hall, Allendale, MI 49401, USA.
| | - Pieter L deHaseth
- Center for RNA Molecular Biology, Case Western Reserve University, 2109 Adelbert Road, Cleveland, OH 44106, USA.
- Department of Biochemistry, Case Western Reserve University, 2109 Adelbert Road, Cleveland, OH 44106, USA.
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14
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Gyssels E, Carrette LLG, Vercruysse E, Stevens K, Madder A. Triplex crosslinking through furan oxidation requires perturbation of the structured triple-helix. Chembiochem 2015; 16:651-8. [PMID: 25630588 DOI: 10.1002/cbic.201402602] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2014] [Indexed: 01/08/2023]
Abstract
Short oligonucleotides can selectively recognize duplexes by binding in the major groove thereby forming triplexes. Based on the success of our recently developed strategy for furan-based crosslinking in DNA duplexes, we here investigated for the first time the use of the furan-oxidation crosslink methodology for the covalent locking of triplex structures by an interstrand crosslink. It was shown that in a triplex context, although crosslinking yields are surprisingly low (to nonexistent) when targeting fully complementary duplexes, selective crosslinking can be achieved towards mismatched duplex sites at the interface of triplex to duplex structures. We show the promising potential of furan-containing probes for the selective detection of single-stranded regions within nucleic acids containing a variety of structural motifs.
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Affiliation(s)
- Ellen Gyssels
- Organic and Biomimetic Chemistry Research Group, Department of Organic and Macromolecular Chemistry, Ghent University, Krijgslaan 281, S4, 9000 Gent (Belgium)
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15
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Beloglazova N, Kuznedelov K, Flick R, Datsenko KA, Brown G, Popovic A, Lemak S, Semenova E, Severinov K, Yakunin AF. CRISPR RNA binding and DNA target recognition by purified Cascade complexes from Escherichia coli. Nucleic Acids Res 2015; 43:530-43. [PMID: 25488810 PMCID: PMC4288178 DOI: 10.1093/nar/gku1285] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2014] [Revised: 11/22/2014] [Accepted: 11/24/2014] [Indexed: 12/26/2022] Open
Abstract
Clustered regularly interspaced short palindromic repeats (CRISPRs) and their associated Cas proteins comprise a prokaryotic RNA-guided adaptive immune system that interferes with mobile genetic elements, such as plasmids and phages. The type I-E CRISPR interference complex Cascade from Escherichia coli is composed of five different Cas proteins and a 61-nt-long guide RNA (crRNA). crRNAs contain a unique 32-nt spacer flanked by a repeat-derived 5' handle (8 nt) and a 3' handle (21 nt). The spacer part of crRNA directs Cascade to DNA targets. Here, we show that the E. coli Cascade can be expressed and purified from cells lacking crRNAs and loaded in vitro with synthetic crRNAs, which direct it to targets complementary to crRNA spacer. The deletion of even one nucleotide from the crRNA 5' handle disrupted its binding to Cascade and target DNA recognition. In contrast, crRNA variants with just a single nucleotide downstream of the spacer part bound Cascade and the resulting ribonucleotide complex containing a 41-nt-long crRNA specifically recognized DNA targets. Thus, the E. coli Cascade-crRNA system exhibits significant flexibility suggesting that this complex can be engineered for applications in genome editing and opening the way for incorporation of site-specific labels in crRNA.
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Affiliation(s)
- Natalia Beloglazova
- Department of Chemical Engineering and Applied Chemistry, University of Toronto, Toronto, Ontario, M5S 3E5, Canada
| | - Konstantin Kuznedelov
- Waksman Institute of Microbiology, Rutgers, the State University of New Jersey, Piscataway, NJ 08854, USA
| | - Robert Flick
- Department of Chemical Engineering and Applied Chemistry, University of Toronto, Toronto, Ontario, M5S 3E5, Canada
| | - Kirill A Datsenko
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, USA
| | - Greg Brown
- Department of Chemical Engineering and Applied Chemistry, University of Toronto, Toronto, Ontario, M5S 3E5, Canada
| | - Ana Popovic
- Department of Chemical Engineering and Applied Chemistry, University of Toronto, Toronto, Ontario, M5S 3E5, Canada
| | - Sofia Lemak
- Department of Chemical Engineering and Applied Chemistry, University of Toronto, Toronto, Ontario, M5S 3E5, Canada
| | - Ekaterina Semenova
- Waksman Institute of Microbiology, Rutgers, the State University of New Jersey, Piscataway, NJ 08854, USA
| | - Konstantin Severinov
- Waksman Institute of Microbiology, Rutgers, the State University of New Jersey, Piscataway, NJ 08854, USA Institute of Molecular Genetics, Russian Academy of Sciences, Moscow 123182, Russia
| | - Alexander F Yakunin
- Department of Chemical Engineering and Applied Chemistry, University of Toronto, Toronto, Ontario, M5S 3E5, Canada
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16
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Differential role of base pairs on gal promoters strength. J Mol Biol 2014; 427:792-806. [PMID: 25543084 DOI: 10.1016/j.jmb.2014.12.010] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2014] [Revised: 12/16/2014] [Accepted: 12/18/2015] [Indexed: 11/23/2022]
Abstract
Sequence alignments of promoters in prokaryotes postulated that the frequency of occurrence of a base pair at a given position of promoter elements reflects its contribution to intrinsic promoter strength. We directly assessed the contribution of the four base pairs in each position in the intrinsic promoter strength by keeping the context constant in Escherichia coli cAMP-CRP (cAMP receptor protein) regulated gal promoters by in vitro transcription assays. First, we show that base pair frequency within known consensus elements correlates well with promoter strength. Second, we observe some substitutions upstream of the ex-10 TG motif that are important for promoter function. Although the galP1 and P2 promoters overlap, only three positions where substitutions inactivated both promoters were found. We propose that RNA polymerase binds to the -12T base pair as part of double-stranded DNA while opening base pairs from -11A to +3 to form the single-stranded transcription bubble DNA during isomerization. The cAMP-CRP complex rescued some deleterious substitutions in the promoter region. The base pair roles and their flexibilities reported here for E. coli gal promoters may help construction of synthetic promoters in gene circuitry experiments in which overlapping promoters with differential controls may be warranted.
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17
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Evolutionary expansion of a regulatory network by counter-silencing. Nat Commun 2014; 5:5270. [PMID: 25348042 PMCID: PMC4215172 DOI: 10.1038/ncomms6270] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2014] [Accepted: 09/15/2014] [Indexed: 11/09/2022] Open
Abstract
Horizontal gene transfer plays a major role in bacterial evolution. Successful acquisition of new genes requires their incorporation into existing regulatory networks. This study compares the regulation of conserved genes in the PhoPQ regulon of Salmonella enterica serovar Typhimurium with that of PhoPQ-regulated horizontally-acquired genes, which are silenced by the histone-like protein H-NS. We demonstrate that PhoP up-regulates conserved and horizontally-acquired genes by distinct mechanisms. Conserved genes are regulated by classical PhoP-mediated activation and are invariant in promoter architecture, whereas horizontally-acquired genes exhibit variable promoter architecture and are regulated by PhoP-mediated counter-silencing. Biochemical analyses show that a horizontally-acquired promoter adopts different structures in the silenced and counter-silenced states, implicating the remodeling of the H-NS nucleoprotein filament and the subsequent restoration of open complex formation as the central mechanism of counter-silencing. Our results indicate that counter-silencing is favored in the regulatory integration of newly-acquired genes because it is able to accommodate multiple promoter architectures.
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18
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DNA looping-dependent autorepression of LEE1 P1 promoters by Ler in enteropathogenic Escherichia coli (EPEC). Proc Natl Acad Sci U S A 2014; 111:E2586-95. [PMID: 24920590 DOI: 10.1073/pnas.1322033111] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Ler, a homolog of H-NS in enteropathogenic Escherichia coli (EPEC), plays a critical role in the expression of virulence genes encoded by the pathogenic island, locus of enterocyte effacement (LEE). Although Ler acts as an antisilencer of multiple LEE operons by alleviating H-NS-mediated silencing, it represses its own expression from two LEE1 P1 promoters, P1A and P1B, that are separated by 10 bp. Various in vitro biochemical methods were used in this study to elucidate the mechanism underlying transcription repression by Ler. Ler acts through two AATT motifs, centered at position -111.5 on the coding strand and at +65.5 on the noncoding strand, by simultaneously repressing P1A and P1B through DNA-looping. DNA-looping was visualized using atomic force microscopy. It is intriguing that an antisilencing protein represses transcription, not by steric exclusion of RNA polymerase, but by DNA-looping. We propose that the DNA-looping prevents further processing of open promoter complex (RPO) at these promoters during transcription initiation.
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19
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Jin DJ, Cagliero C, Zhou YN. Role of RNA polymerase and transcription in the organization of the bacterial nucleoid. Chem Rev 2013; 113:8662-82. [PMID: 23941620 PMCID: PMC3830623 DOI: 10.1021/cr4001429] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- Ding Jun Jin
- Transcription Control Section, Gene Regulation and Chromosome Biology Laboratory National Cancer Institute, NIH, P.O. Box B, Frederick, MD 21702
| | - Cedric Cagliero
- Transcription Control Section, Gene Regulation and Chromosome Biology Laboratory National Cancer Institute, NIH, P.O. Box B, Frederick, MD 21702
| | - Yan Ning Zhou
- Transcription Control Section, Gene Regulation and Chromosome Biology Laboratory National Cancer Institute, NIH, P.O. Box B, Frederick, MD 21702
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20
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Cagliero C, Jin DJ. Dissociation and re-association of RNA polymerase with DNA during osmotic stress response in Escherichia coli. Nucleic Acids Res 2013; 41:315-26. [PMID: 23093594 PMCID: PMC3592413 DOI: 10.1093/nar/gks988] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2012] [Revised: 09/26/2012] [Accepted: 09/27/2012] [Indexed: 11/12/2022] Open
Abstract
The thermodynamic association of RNA polymerase (RNAP) with DNA is sensitive to salt concentration in vitro. Paradoxically, previous studies of changes in osmolarity during steady-state cell growth found no dependence between the association of RNAP to DNA and K(+) concentration in Escherichia coli. We reevaluated this issue by following the interaction of RNAP and genomic DNA in time-course experiments during the hyper-osmotic response. Our results show that the interaction is temporally controlled by the same physical chemistry principle in the cell as in vitro. RNAP rapidly dissociates from the genome during the initial response when the cytoplasmic K(+) accumulates transiently, and concurrently the nucleoid becomes hyper-condensed. The freed RNAP re-associates with the genome during a subsequent osmoadaptation phase when organic osmoprotectants accumulate as K(+) levels decrease. RNAP first surrounds the hyper-condensed nucleoid forming a sphere of RNAP before it progressively moves in to the center of the nucleoid. Our findings reinterpret the dynamic protein-DNA interactions during osmotic stress response. We discuss the implications of the dissociation/association of RNAP for osmotic protection and nucleoid structure.
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Affiliation(s)
| | - Ding Jun Jin
- Transcription control section, Gene Regulation and Chromosome Biology Laboratory, Frederick National Laboratory for Cancer Research, National Cancer Institute, National Institutes of Health, Frederick, MD, USA
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21
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Drennan A, Kraemer M, Capp M, Gries T, Ruff E, Sheppard C, Wigneshweraraj S, Artsimovitch I, Record MT. Key roles of the downstream mobile jaw of Escherichia coli RNA polymerase in transcription initiation. Biochemistry 2012; 51:9447-59. [PMID: 23116321 PMCID: PMC3517728 DOI: 10.1021/bi301260u] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Differences in kinetics of transcription initiation by RNA polymerase (RNAP) at different promoters tailor the pattern of gene expression to cellular needs. After initial binding, large conformational changes occur in promoter DNA and RNAP to form initiation-capable complexes. To understand the mechanism and regulation of transcription initiation, the nature and sequence of these conformational changes must be determined. Escherichia coli RNAP uses binding free energy to unwind and separate 13 base pairs of λP(R) promoter DNA to form the unstable open intermediate I(2), which rapidly converts to much more stable open complexes (I(3), RP(o)). Conversion of I(2) to RP(o) involves folding/assembly of several mobile RNAP domains on downstream duplex DNA. Here, we investigate effects of a 42-residue deletion in the mobile β' jaw (ΔJAW) and truncation of promoter DNA beyond +12 (DT+12) on the steps of initiation. We find that in stable ΔJAW open complexes the downstream boundary of hydroxyl radical protection shortens by 5-10 base pairs, as compared to wild-type (WT) complexes. Dissociation kinetics of open complexes formed with ΔJAW RNAP and/or DT+12 DNA resemble those deduced for the structurally uncharacterized intermediate I(3). Overall rate constants (k(a)) for promoter binding and DNA opening by ΔJAW RNAP are much smaller than for WT RNAP. Values of k(a) for WT RNAP with DT+12 and full-length λP(R) are similar, though contributions of binding and isomerization steps differ. Hence, the jaw plays major roles both early and late in RP(o) formation, while downstream DNA functions primarily as the assembly platform after DNA opening.
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Affiliation(s)
- Amanda Drennan
- Department of Biochemistry, The University of Wisconsin-Madison, Madison, WI 53706
| | - Mark Kraemer
- Department of Biochemistry, The University of Wisconsin-Madison, Madison, WI 53706
| | - Michael Capp
- Department of Biochemistry, The University of Wisconsin-Madison, Madison, WI 53706
| | - Theodore Gries
- Department of Biochemistry, The University of Wisconsin-Madison, Madison, WI 53706
| | - Emily Ruff
- Department of Chemistry, The University of Wisconsin-Madison, Madison, WI 53706
| | - Carol Sheppard
- Department of Microbiology and Centre for Molecular Microbiology and Infection, Imperial College, London, SW7 2AZ
| | - Sivaramesh Wigneshweraraj
- Department of Microbiology and Centre for Molecular Microbiology and Infection, Imperial College, London, SW7 2AZ
| | - Irina Artsimovitch
- Department of Microbiology and Center for RNA Biology, The Ohio State University, Columbus, OH 43210
| | - M. Thomas Record
- Department of Biochemistry, The University of Wisconsin-Madison, Madison, WI 53706
- Department of Chemistry, The University of Wisconsin-Madison, Madison, WI 53706
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22
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Shin M, Lagda AC, Lee JW, Bhat A, Rhee JH, Kim JS, Takeyasu K, Choy HE. Gene silencing by H-NS from distal DNA site. Mol Microbiol 2012; 86:707-19. [PMID: 22924981 DOI: 10.1111/mmi.12012] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/20/2012] [Indexed: 11/29/2022]
Abstract
In the modern concept of gene regulation, 'DNA looping' is the most common underlying mechanism in the interaction between RNA polymerase (RNAP) and transcription factors acting at a distance. This study demonstrates an additional mechanism by which DNA-bound proteins communicate with each other, by analysing the bacterial histone-like nucleoid-structuring protein (H-NS), a general transcriptional silencer. The LEE5 promoter (LEE5p) of enteropathogenic Escherichia coli was used as a model system to investigate the mechanism of H-NS-mediated transcription repression. We found that H-NS represses LEE5p by binding to a cluster of A tracks upstream of -114, followed by spreading to a site at the promoter through the oligomerization of H-NS molecules. At the promoter, the H-NS makes a specific contact with the carboxy terminal domain of the α subunit of RNAP, which prevents the processing of RNAP-promoter complexes into initiation-competent open promoter complexes, thereby regulating LEE5p from distance.
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Affiliation(s)
- Minsang Shin
- Center for Host Defense against Enteropathogenic Bacteria Infection, Kwangju, 501-746, South Korea
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23
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Gaballa A, MacLellan S, Helmann JD. Transcription activation by the siderophore sensor Btr is mediated by ligand-dependent stimulation of promoter clearance. Nucleic Acids Res 2011; 40:3585-95. [PMID: 22210890 PMCID: PMC3333878 DOI: 10.1093/nar/gkr1280] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Bacterial transcription factors often function as DNA-binding proteins that selectively activate or repress promoters, although the biochemical mechanisms vary. In most well-understood examples, activators function by either increasing the affinity of RNA polymerase (RNAP) for the target promoter, or by increasing the isomerization of the initial closed complex to the open complex. We report that Bacillus subtilis Btr, a member of the AraC family of activators, functions principally as a ligand-dependent activator of promoter clearance. In the presence of its co-activator, the siderophore bacillibactin (BB), the Btr:BB complex enhances productive transcription, while having only modest effects on either RNAP promoter association or the production of abortive transcripts. Btr binds to two direct repeat sequences adjacent to the −35 region; recognition of the downstream motif is most important for establishing a productive interaction between the Btr:BB complex and RNAP. The resulting Btr:BB dependent increase in transcription enables the production of the ferric-BB importer to be activated by the presence of its cognate substrate.
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Affiliation(s)
- Ahmed Gaballa
- Department of Microbiology, Cornell University, Ithaca, NY 14853-8101, USA
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24
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Effects of substitutions at position 180 in the Escherichia coli RNA polymerase σ 70 subunit. J Biosci 2011; 36:43-54. [PMID: 21451247 DOI: 10.1007/s12038-011-9007-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
In order to investigate the role of His180 residue, located in the non-conserved region of the σ 70 subunit of Escherichia coli RNA polymerase, two mutant variants of the protein with substitutions for either alanine or glutamic acid were constructed and purified using the IMPACT system. The ability of mutant σ 70 subunits to interact with core RNA polymerase was investigated using native gel-electrophoresis. The properties of the corresponding reconstituted holoenzymes, as provided by gel shift analysis of their complexes with single- and double-stranded promoter-like DNA and by in vitro transcription experiments, allowed one to deduce that His180 influences several steps of transcription initiation, including core binding, promoter DNA recognition and open complex formation.
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25
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Mekler V, Minakhin L, Severinov K. A critical role of downstream RNA polymerase-promoter interactions in the formation of initiation complex. J Biol Chem 2011; 286:22600-8. [PMID: 21525530 DOI: 10.1074/jbc.m111.247080] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Nucleation of promoter melting in bacteria is coupled with RNA polymerase (RNAP) binding to a conserved -10 promoter element located at the upstream edge of the transcription bubble. The mechanism of downstream propagation of the transcription bubble to include the transcription start site is unclear. Here we introduce new model downstream fork junction promoter fragments that specifically bind RNAP and mimic the downstream segment of promoter complexes. We demonstrate that RNAP binding to downstream fork junctions is coupled with DNA melting around the transcription start point. Consequently, certain downstream fork junction probes can serve as transcription templates. Using a protein beacon fluorescent method, we identify structural determinants of affinity and transcription activity of RNAP-downstream fork junction complexes. Measurements of RNAP interaction with double-stranded promoter fragments reveal that the strength of RNAP interactions with downstream DNA plays a critical role in promoter opening and that the length of the downstream duplex must exceed a critical length for efficient formation of transcription competent open promoter complex.
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Affiliation(s)
- Vladimir Mekler
- Waksman Institute of Microbiology, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854, USA
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26
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Chen Q, Decker KB, Boucher PE, Hinton D, Stibitz S. Novel architectural features of Bordetella pertussis fimbrial subunit promoters and their activation by the global virulence regulator BvgA. Mol Microbiol 2011; 77:1326-40. [PMID: 20662776 DOI: 10.1111/j.1365-2958.2010.07293.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A prominent feature of the promoters of Bordetella pertussis fimbrial subunit genes fim2, fim3 and fimX is the presence of a 'C-stretch', a monotonic run of C residues. The C-stretch renders these genes capable of phase variation, through spontaneous variations in its length. For each of these we determined the length of the C-stretch that gave maximal transcriptional activity, and found that the three optimized promoters align perfectly, with identical distances between conserved upstream sequences and the downstream -10 elements and transcriptional start sites. We also demonstrated, for Pfim3, that the conserved sequence corresponds to BvgA binding sites. The more upstream of the two binding sites is predicted to be high affinity, by comparison to a functionally derived consensus BvgA-binding sequence. The other binding site is a fairly poor match to this consensus, with 10 of 14 bp belonging to the C-stretch. Interestingly, the centre of this downstream site of BvgA binding coincides exactly with the centre of the expected typical location of a -35 sequence. However, the lack of a recognizable -35 element (CCCCCC versus TTGACA), and the occupation of this site by BvgA∼P suggest that activation of the fim promoters involves unusual interactions among BvgA, RNA polymerase and promoter DNA.
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Affiliation(s)
- Qing Chen
- Division of Bacterial, Parasitic, and Allergenic Products, Center for Biologics Evaluation and Research, FDA, Bethesda, MD 20892, USA.
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27
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Licht A, Freede P, Brantl S. Transcriptional repressor CopR acts by inhibiting RNA polymerase binding. MICROBIOLOGY-SGM 2011; 157:1000-1008. [PMID: 21252280 DOI: 10.1099/mic.0.047209-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
CopR is a transcriptional repressor encoded by the broad-host-range streptococcal plasmid pIP501, which also replicates in Bacillus subtilis. It acts in concert with the antisense RNA, RNAIII, to control pIP501 replication. CopR represses transcription of the essential repR mRNA about 10- to 20-fold. In previous work, DNA binding and dimerization constants were determined and the motifs responsible localized. The C terminus of CopR was shown to be required for stability. Furthermore, SELEX of the copR operator revealed that in vivo evolution was for maximal binding affinity. Here, we elucidate the repression mechanism of CopR. Competition assays showed that CopR-operator complexes are 18-fold less stable than RNA polymerase (RNAP)-pII complexes. DNase I footprinting revealed that the binding sites for CopR and RNAP overlap. Gel-shift assays demonstrated that CopR and B. subtilis RNAP cannot bind simultaneously, but compete for binding at promoter pII. Due to its higher intracellular concentration CopR inhibits RNAP binding. Additionally, KMnO(4) footprinting experiments indicated that prevention of open complex formation at pII does not further contribute to the repression effect of CopR.
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Affiliation(s)
- Andreas Licht
- Friedrich-Schiller-Universität Jena, Biologisch-Pharmazeutische Fakultät, AG Bakteriengenetik, Philosophenweg 12, Jena D-07743, Germany
| | - Peggy Freede
- Friedrich-Schiller-Universität Jena, Biologisch-Pharmazeutische Fakultät, AG Bakteriengenetik, Philosophenweg 12, Jena D-07743, Germany
| | - Sabine Brantl
- Friedrich-Schiller-Universität Jena, Biologisch-Pharmazeutische Fakultät, AG Bakteriengenetik, Philosophenweg 12, Jena D-07743, Germany
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28
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Hinton DM. Transcriptional control in the prereplicative phase of T4 development. Virol J 2010; 7:289. [PMID: 21029433 PMCID: PMC2988021 DOI: 10.1186/1743-422x-7-289] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2010] [Accepted: 10/28/2010] [Indexed: 12/18/2022] Open
Abstract
Control of transcription is crucial for correct gene expression and orderly development. For many years, bacteriophage T4 has provided a simple model system to investigate mechanisms that regulate this process. Development of T4 requires the transcription of early, middle and late RNAs. Because T4 does not encode its own RNA polymerase, it must redirect the polymerase of its host, E. coli, to the correct class of genes at the correct time. T4 accomplishes this through the action of phage-encoded factors. Here I review recent studies investigating the transcription of T4 prereplicative genes, which are expressed as early and middle transcripts. Early RNAs are generated immediately after infection from T4 promoters that contain excellent recognition sequences for host polymerase. Consequently, the early promoters compete extremely well with host promoters for the available polymerase. T4 early promoter activity is further enhanced by the action of the T4 Alt protein, a component of the phage head that is injected into E. coli along with the phage DNA. Alt modifies Arg265 on one of the two α subunits of RNA polymerase. Although work with host promoters predicts that this modification should decrease promoter activity, transcription from some T4 early promoters increases when RNA polymerase is modified by Alt. Transcription of T4 middle genes begins about 1 minute after infection and proceeds by two pathways: 1) extension of early transcripts into downstream middle genes and 2) activation of T4 middle promoters through a process called sigma appropriation. In this activation, the T4 co-activator AsiA binds to Region 4 of σ⁷⁰, the specificity subunit of RNA polymerase. This binding dramatically remodels this portion of σ⁷⁰, which then allows the T4 activator MotA to also interact with σ⁷⁰. In addition, AsiA restructuring of σ⁷⁰ prevents Region 4 from forming its normal contacts with the -35 region of promoter DNA, which in turn allows MotA to interact with its DNA binding site, a MotA box, centered at the -30 region of middle promoter DNA. T4 sigma appropriation reveals how a specific domain within RNA polymerase can be remolded and then exploited to alter promoter specificity.
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Affiliation(s)
- Deborah M Hinton
- Laboratory of Molecular and Cellular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Building 8, Room 2A-13, Bethesda, MD 20892-0830, USA.
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Manso I, García JL, Galán B. Escherichia coli mhpR gene expression is regulated by catabolite repression mediated by the cAMP-CRP complex. MICROBIOLOGY-SGM 2010; 157:593-600. [PMID: 20966094 DOI: 10.1099/mic.0.043620-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The expression of the mhp genes involved in the degradation of the aromatic compound 3-(3-hydroxyphenyl)propionic acid (3HPP) in Escherichia coli is dependent on the MhpR transcriptional activator at the Pa promoter. This catabolic promoter is also subject to catabolic repression in the presence of glucose mediated by the cAMP-CRP complex. The Pr promoter drives the MhpR-independent expression of the regulatory gene. In vivo and in vitro experiments have shown that transcription from the Pr promoter is downregulated by the addition of glucose and this catabolic repression is also mediated by the cAMP-CRP complex. The activation role of the cAMP-CRP regulatory system was further investigated by DNase I footprinting assays, which showed that the cAMP-CRP complex binds to the Pr promoter sequence, protecting a region centred at position -40.5, which allowed the classification of Pr as a class II CRP-dependent promoter. Open complex formation at the Pr promoter is observed only when RNA polymerase and cAMP-CRP are present. Finally, by in vitro transcription assays we have demonstrated the absolute requirement of the cAMP-CRP complex for the activation of the Pr promoter.
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Affiliation(s)
- I Manso
- Departamento de Biología Medioambiental, Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas (CSIC), Ramiro de Maeztu 9, 28040 Madrid, Spain
| | - J L García
- Departamento de Biología Medioambiental, Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas (CSIC), Ramiro de Maeztu 9, 28040 Madrid, Spain
| | - B Galán
- Departamento de Biología Medioambiental, Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas (CSIC), Ramiro de Maeztu 9, 28040 Madrid, Spain
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Wang G, Zhao J, Vasquez KM. Methods to determine DNA structural alterations and genetic instability. Methods 2009; 48:54-62. [PMID: 19245837 PMCID: PMC2693251 DOI: 10.1016/j.ymeth.2009.02.012] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2008] [Accepted: 02/15/2009] [Indexed: 11/16/2022] Open
Abstract
Chromosomal DNA is a dynamic structure that can adopt a variety of non-canonical (i.e., non-B) conformations. In this regard, at least 10 different forms of non-B DNA conformations have been identified; many of them have been found to be mutagenic, and associated with human disease development. Despite the importance of non-B DNA structures in genetic instability and DNA metabolic processes, mechanisms by which instability occurs remain largely undefined. The purpose of this review is to summarize current methodologies that are used to address questions in the field of non-B DNA structure-induced genetic instability. Advantages and disadvantages of each method will be discussed. A focused effort to further elucidate the mechanisms of non-B DNA-induced genetic instability will lead to a better understanding of how these structure-forming sequences contribute to the development of human disease.
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Affiliation(s)
- Guliang Wang
- Department of Carcinogenesis, University of Texas M.D. Anderson Cancer Center, Science Park-Research Division, 1808 Park Road 1-C, Smithville, TX 78957
| | - Junhua Zhao
- Department of Carcinogenesis, University of Texas M.D. Anderson Cancer Center, Science Park-Research Division, 1808 Park Road 1-C, Smithville, TX 78957
| | - Karen M. Vasquez
- Department of Carcinogenesis, University of Texas M.D. Anderson Cancer Center, Science Park-Research Division, 1808 Park Road 1-C, Smithville, TX 78957
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32
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Busby S, Kolb A, Buc H. Where it all Begins: An Overview of Promoter Recognition and Open Complex Formation. RNA POLYMERASES AS MOLECULAR MOTORS 2009. [DOI: 10.1039/9781847559982-00013] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Affiliation(s)
- Stephen Busby
- School of Biosciences, University of Birmingham Birmingham B15 2TT United Kingdom
| | - Annie Kolb
- Institut Pasteur, Molecular Genetics Unit and CNRS URA 2172 25 rue du Dr. Roux 75724 Paris Cedex 15 France
| | - Henri Buc
- CIS Institut Pasteur75724Paris Cedex 15France
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33
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Gilmour DS, Fan R. Detecting transcriptionally engaged RNA polymerase in eukaryotic cells with permanganate genomic footprinting. Methods 2009; 48:368-74. [PMID: 19272453 DOI: 10.1016/j.ymeth.2009.02.020] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2008] [Revised: 02/23/2009] [Accepted: 02/25/2009] [Indexed: 11/27/2022] Open
Abstract
Analysis of the distribution of RNA polymerase II on the genomes of Drosophila and human cells using in vivo protein-DNA crosslinking reveals that RNA polymerase II (Pol II) is concentrated at the 5'-ends of thousands of genes. This appears to be irrespective of transcription levels. Hence, a potential regulatory step in the transcription of many genes occurs after Pol II has associated with the promoter. The protein-DNA crosslinking technique widely used to monitor Pol II and other proteins on chromosomes in vivo, however, does not reveal if Pol II is transcriptionally engaged on DNA. Genomic footprinting with potassium permanganate provides one method for detecting transcriptionally engaged Pol II. Using this approach, we have determined that the Pol II associated with the promoters of many genes has initiated transcription but paused in the region 20-50 nucleotides from the start. Here we describe the application of this method in Drosophila and human cells. The method should prove useful in assessing if promoter bound Pol II has engaged in transcription and for investigating the establishment and regulation of transcriptionally engaged Pol II.
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Affiliation(s)
- David S Gilmour
- Center for Eukaryotic Gene Regulation, Department of Biochemistry and Molecular Biology, The Pennsylvania State University, 208 Althouse, University Park, PA 16802, United States.
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34
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Gralla JD, Huo YX. Remodeling and activation of Escherichia coli RNA polymerase by osmolytes. Biochemistry 2009; 47:13189-96. [PMID: 19053283 DOI: 10.1021/bi801075x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The ability of bacteria to survive environmental stresses and colonize the gastrointestinal tract depends on adaptation to high osmolarity. The adaptation involves global reprogramming of gene expression, including inhibition of bulk sigma70 RNA polymerase transcription and activation of bulk sigma38 transcription. The activating signal transduction pathways that originate with osmolytes remain to be established. Experiments here confirm that accumulation of a simple signaling molecule, glutamate, can reprogram RNA polymerase in vitro without the need for specific protein receptors. During osmotic activation, glutamate appears to act as a Hofmeister series osmolyte to facilitate promoter escape. Escape is accompanied by a remodeling of the key interaction between the sigma38 stress protein and the beta-flap of the bacterial core RNA polymerase. This activation event contrasts with the established mechanism of inhibition in which glutamate, by virtue of its electrostatic properties, helps to inhibit binding to ribosomal promoters after osmotic shock. Overall, Escherichia coli survival in natural hosts and reservoirs is expected to rely on the accumulation of simple ions that trigger changes in protein conformation that lead to global changes in transcription.
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Affiliation(s)
- Jay D Gralla
- Department of Chemistry and Biochemistry and Molecular Biology Institute, University of California, Box 951569, Los Angeles, California 90095, USA.
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35
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The promoter spacer influences transcription initiation via sigma70 region 1.1 of Escherichia coli RNA polymerase. Proc Natl Acad Sci U S A 2009; 106:737-42. [PMID: 19139410 DOI: 10.1073/pnas.0808133106] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Transcription initiation is a dynamic process in which RNA polymerase (RNAP) and promoter DNA act as partners, changing in response to one another, to produce a polymerase/promoter open complex (RPo) competent for transcription. In Escherichia coli RNAP, region 1.1, the N-terminal 100 residues of sigma(70), is thought to occupy the channel that will hold the DNA downstream of the transcription start site; thus, region 1.1 must move from this channel as RPo is formed. Previous work has also shown that region 1.1 can modulate RPo formation depending on the promoter. For some promoters region 1.1 stimulates the formation of open complexes; at the P(minor) promoter, region 1.1 inhibits this formation. We demonstrate here that the AT-rich P(minor) spacer sequence, rather than promoter recognition elements or downstream DNA, determines the effect of region 1.1 on promoter activity. Using a P(minor) derivative that contains good sigma(70)-dependent DNA elements, we find that the presence of a more GC-rich spacer or a spacer with the complement of the P(minor) sequence results in a promoter that is no longer inhibited by region 1.1. Furthermore, the presence of the P(minor) spacer, the GC-rich spacer, or the complement spacer results in different mobilities of promoter DNA during gel electrophoresis, suggesting that the spacer regions impart differing conformations or curvatures to the DNA. We speculate that the spacer can influence the trajectory or flexibility of DNA as it enters the RNAP channel and that region 1.1 acts as a "gatekeeper" to monitor channel entry.
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Abstract
Transcription factors interact at promoters to modulate the transcription of genes. This chapter describes three in vitro methods that can be used to monitor their activity: transcript assays, abortive initiation assays, and potassium permanganate footprinting. These techniques have been developed using bacterial systems, and can be used to study the kinetics of transcription initiation, and hence to unravel regulatory mechanisms.
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Affiliation(s)
- Douglas Browning
- School of Biosciences, The University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK
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Abstract
Enterotoxigenic Escherichia coli is a major cause of acute diarrheal illness worldwide and is responsible for high infant and child mortality rates in developing nations. Two types of enterotoxins, one heat labile and the other heat stable, are known to cause diarrhea. The expression of soluble heat-labile toxin is subject to catabolite (glucose) activation, and three binding sites for cAMP receptor protein (CRP or CAP) were identified upstream and within the toxin promoter by DNase I footprinting. One CRP operator is centered at -31.5, thus encompassing the promoter's -35 hexamer. Potassium permanganate footprinting revealed that the occupancy of this operator prevents RNA polymerase from forming an open complex in vitro. However, the operator centered at -31.5 is not sufficient for full repression in vivo because the deletion of the other two CRP binding sites partially relieved the CRP-dependent repression of the heat-labile toxin promoter. In contrast to heat-labile toxin, CRP positively regulates the expression of heat-stable toxin. Thus, the conditions for the optimal expression of one enterotoxin limit the expression of the other. Since glucose inhibits the activity of CRP by suppressing the pathogen's synthesis of cyclic AMP (cAMP), the concentration of glucose in the lumen of the small intestine may determine which enterotoxin is maximally expressed. In addition, our results suggest that the host may also modulate enterotoxin expression because cells intoxicated with heat-labile toxin overproduce and release cAMP.
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38
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England P, Westblade LF, Karimova G, Robbe-Saule V, Norel F, Kolb A. Binding of the unorthodox transcription activator, Crl, to the components of the transcription machinery. J Biol Chem 2008; 283:33455-64. [PMID: 18818199 PMCID: PMC2586269 DOI: 10.1074/jbc.m807380200] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2008] [Indexed: 11/06/2022] Open
Abstract
The small regulatory protein Crl binds to sigmaS, the RNA polymerase stationary phase sigma factor. Crl facilitates the formation of the sigmaS-associated holoenzyme (EsigmaS) and thereby activates sigmaS-dependent genes. Using a real time surface plasmon resonance biosensor, we characterized in greater detail the specificity and mode of action of Crl. Crl specifically forms a 1:1 complex with sigmaS, which results in an increase of the association rate of sigmaS to core RNA polymerase without any effect on the dissociation rate of EsigmaS. Crl is also able to associate with preformed EsigmaS with a higher affinity than with sigmaS alone. Furthermore, even at saturating sigmaS concentrations, Crl significantly increases EsigmaS association with the katN promoter and the productive isomerization of the EsigmaS-katN complex, supporting a direct role of Crl in transcription initiation. Finally, we show that Crl does not bind to sigma70 itself but is able at high concentrations to form a weak and transient 1:1 complex with both core RNA polymerase and the sigma70-associated holoenzyme, leaving open the possibility that Crl might also exert a side regulatory role in the transcriptional activity of additional non-sigmaS holoenzymes.
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Affiliation(s)
- Patrick England
- Institut Pasteur, Plate-forme de Biophysique des Macromolécules et de leurs Interactions, Paris, France.
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39
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Huo YX, Rosenthal AZ, Gralla JD. General stress response signalling: unwrapping transcription complexes by DNA relaxation via the sigma38 C-terminal domain. Mol Microbiol 2008; 70:369-78. [PMID: 18761624 DOI: 10.1111/j.1365-2958.2008.06412.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Escherichia coli responds to stress by a combination of specific and general transcription signalling pathways. The general pathways typically require the master stress regulator sigma38 (rpoS). Here we show that the signalling from multiple stresses that relax DNA is processed by a non-conserved eight-amino-acid tail of the sigma 38 C-terminal domain. By contrast, responses to two stresses that accumulate potassium glutamate do not rely on this short tail, but still require the overall C-terminal domain. In vitro transcription and footprinting studies suggest that multiple stresses can target a poised RNA polymerase and activate it by unwrapping DNA from a nucleosome-like state, allowing the RNA polymerase to escape into productive mode. This transition can be accomplished by either the DNA relaxation or potassium glutamate accumulation that characterizes many stresses.
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Affiliation(s)
- Yi-Xin Huo
- Department of Chemistry and Biochemistry and the Molecular Biology Institute, University of California, PO Box 951569, Los Angeles, CA 90095, USA
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40
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Williams H, Jayaraman PS, Gaston K. DNA wrapping and distortion by an oligomeric homeodomain protein. J Mol Biol 2008; 383:10-23. [PMID: 18755198 DOI: 10.1016/j.jmb.2008.08.004] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2008] [Revised: 07/04/2008] [Accepted: 08/01/2008] [Indexed: 12/29/2022]
Abstract
Many transcription factors alter DNA or chromatin structure. Changes in chromatin structure are often brought about by the recruitment of chromatin-binding proteins, chromatin-modifying proteins, or other transcription co-activator or co-repressor proteins. However, some transcription factors form oligomeric assemblies that may themselves induce changes in DNA conformation and chromatin structure. The proline-rich homeodomain (PRH/Hex) protein is a transcription factor that regulates cell differentiation and cell proliferation, and has multiple roles in embryonic development. Earlier, we showed that PRH can repress transcription by multiple mechanisms, including the recruitment of co-repressor proteins belonging to the TLE family of chromatin-binding proteins. Our in vivo crosslinking studies have shown that PRH forms oligomeric complexes in cells and a variety of biophysical techniques suggest that the protein forms octamers. However, as yet we have little knowledge of the role played by PRH oligomerisation in the regulation of promoter activity or of the architecture of promoters that are regulated directly by PRH in cells. Here, we compare the binding of PRH and the isolated PRH homeodomain to DNA fragments with single and multiple PRH sites, using gel retardation assays and DNase I and chemical footprinting. We show that the PRH oligomer binds to multiple sites within the human Goosecoid promoter with high affinity and that the binding of PRH brings about DNA distortion. We suggest that PRH octamers wrap DNA in order to bring about transcriptional repression.
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Affiliation(s)
- Hannah Williams
- Department of Biochemistry, School of Medical Sciences, University of Bristol, Bristol, UK
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41
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Lewis DEA, Komissarova N, Le P, Kashlev M, Adhya S. DNA sequences in gal operon override transcription elongation blocks. J Mol Biol 2008; 382:843-58. [PMID: 18691599 DOI: 10.1016/j.jmb.2008.07.060] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2008] [Revised: 06/12/2008] [Accepted: 07/23/2008] [Indexed: 12/01/2022]
Abstract
The DNA loop that represses transcription from galactose (gal) promoters is infrequently formed in stationary-phase cells because the concentration of the loop architectural protein HU is significantly low at that state, resulting in expression of the operon in the absence of the gal inducer D-galactose. Unexpectedly, transcription from the gal promoters under these conditions overrides physical block because of the presence of the Gal repressor bound to an internal operator (O(I)) located downstream of the promoters. We have shown here that although a stretch of pyrimidine residues (UUCU) in the RNA:DNA hybrid located immediately upstream of O(I) weakens the RNA:DNA hybrid and favors RNA polymerase (RNAP) pausing and backtracking, a stretch of purines (GAGAG) in the RNA present immediately upstream of the pause sequence in the hybrid acts as an antipause element by stabilizing the RNA:DNA duplex and preventing backtracking. This facilitates forward translocation of RNAP, including overriding of the DNA-bound Gal repressor barrier at O(I). When the GAGAG sequence is separated from the pyrimidine sequence by a 5-bp DNA insertion, RNAP backtracking is favored from a weak hybrid to a more stable hybrid. RNAP backtracking is sensitive to Gre factors, D-galactose, and antisense oligonucleotides. The ability of a native DNA sequence to override transcription elongation blocks in the gal operon uncovers a previously unknown way of regulating gal metabolism in Escherichia coli. It also explains the synthesis of gal enzymes in the absence of inducer for biosynthetic reactions.
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Affiliation(s)
- Dale E A Lewis
- Laboratory of Molecular Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892-4264, USA.
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42
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Hatoum A, Roberts J. Prevalence of RNA polymerase stalling at Escherichia coli promoters after open complex formation. Mol Microbiol 2008; 68:17-28. [PMID: 18333883 DOI: 10.1111/j.1365-2958.2008.06138.x] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
RNA polymerase (RNAP) trapped in intermediate stages of promoter escape, as well as RNAP paused at promoter-proximal sigma(70)-dependent pause sites, gives rise to stable, transcriptionally engaged stalled complexes that can limit promoter function and present potential sites for transcription regulation. To investigate the prevalence of such intermediates, we screened 118 Escherichia coli candidate promoters for RNAP stalling at or near the promoter, using in vivo KMnO(4) mapping of RNAP on chromosomal DNA. Of 34 active promoters, the seven preceding lacZ, tnaA, cspA, cspD, rplK, rpsA and rpsU harboured stalled RNAP in vivo; this finding suggests that RNAP stalling after initiation is widespread in E. coli. Consistent with the characteristics of both abortive and promoter-proximal sigma(70)-dependent paused complexes, RNAP trapping at most of the newly identified stall sites was eliminated by the rpoDL402Fsigma(70) mutational alteration and by site mutations, and was enhanced by GreA deficiency. In addition to promoter-proximal RNAP trapping, we observed transcription-dependent DNA modifications spanning the tnaA and cspA leader regions up to 100 bp downstream of the transcription start site.
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Affiliation(s)
- Asma Hatoum
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
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43
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MacLellan SR, Wecke T, Helmann JD. A previously unidentified sigma factor and two accessory proteins regulate oxalate decarboxylase expression in Bacillus subtilis. Mol Microbiol 2008; 69:954-67. [PMID: 18573182 DOI: 10.1111/j.1365-2958.2008.06331.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
We have investigated the function of a cell envelope stress-inducible gene, yvrI, which encodes a 22.5 kDa protein that includes a predicted sigma(70) region 4 domain, but lacks an apparent region 2 domain. YvrI interacts with RNA polymerase and overexpression of YvrI results in induction of OxdC, an oxalate decarboxylase maximally expressed under low-pH conditions. We have used microarray-based analyses to define the YvrI regulon. YvrI is required for the transcription of three operons (oxdC-yvrL, yvrJ and yvrI-yvrHa) each of which is preceded by a highly similar promoter sequence. Activation of these promoters requires both YvrI and the product of the second gene in the yvrI-yvrHa operon, YvrHa. YvrI and YvrHa together allow recognition of the oxdC promoter, stimulate DNA melting and activate transcription by core RNA polymerase. Together, these results suggest that YvrI is a previously unrecognized sigma factor in Bacillus subtilis and that the 9.5 kDa YvrHa protein acts as a required co-activator of transcription. A yvrL deletion results in the upregulation of YvrI activity suggesting that YvrL is a negative regulator of YvrI-dependent transcription, possibly functioning as an anti-sigma factor.
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Affiliation(s)
- Shawn R MacLellan
- Department of Microbiology, Cornell University, Ithaca, NY 14853, USA
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44
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Roles of effectors in XylS-dependent transcription activation: intramolecular domain derepression and DNA binding. J Bacteriol 2008; 190:3118-28. [PMID: 18296514 DOI: 10.1128/jb.01784-07] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
XylS, an AraC family protein, activates transcription from the benzoate degradation pathway Pm promoter in the presence of a substrate effector such as 3-methylbenzoate (3MB). We developed a procedure to obtain XylS-enriched preparations which proved suitable to analyze its activation mechanism. XylS showed specific 3MB-independent binding to its target operator, which became strictly 3MB dependent in a dimerization-defective mutant. We demonstrated that the N-terminal domain of the protein can make linker-independent interactions with the C-terminal domain and inhibit its capacity to bind DNA. Interactions are hampered in the presence of 3MB effector. We propose two independent roles for 3MB in XylS activation: in addition to its known influence favoring protein dimerization, the effector is able to modify XylS conformation to trigger N-terminal domain intramolecular derepression. We also show that activation by XylS involves RNA polymerase recruitment to the Pm promoter as demonstrated by chromatin immunoprecipitation assays. RNA polymerase switching in Pm transcription was reproduced in in vitro transcription assays. All sigma(32)-, sigma(38)-, and sigma(70)-dependent RNA polymerases were able to carry out Pm transcription in a rigorous XylS-dependent manner, as demonstrated by the formation of open complexes only in the presence of the regulator.
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45
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Abstract
Over the last two decades, a large amount of data on initiation of transcription by bacterial RNA polymerase (RNAP) has been obtained. However, a question of how the open complex is formed still remains open, and several qualitative hypotheses for opening of DNA by RNAP have been proposed. To provide a theoretical framework needed to analyze the assembled experimental data, we here develop the first quantitative model of the open complex formation by bacterial RNAP. We first show that a simple hypothesis (which might follow from recent bioinformatic and experimental results), by which promoter DNA is melted in one step through thermal fluctuations, is inconsistent with experimental data. We next consider a more complex two-step view of the open complex formation. According to this hypothesis, the transcription bubble is formed in the -10 region, and consequently extends to the transcription start site. We derive how the open complex formation rate depends on DNA duplex melting energy and on interaction energies of RNAP with promoter DNA in the closed and open complex. This relationship provides an explicit connection between transcription initiation rate and physical properties of the promoter sequence and promoter-RNAP interactions. We compare our model with both biochemical measurements and genomics data and report a very good agreement with the experiments, with no free parameters used in model testing. This agreement therefore strongly supports both the quantitative model that we propose and the qualitative hypothesis on which the model is based. From a practical point, our results allow efficient estimation of promoter kinetic parameters, as well as engineering of promoter sequences with the desired kinetic properties.
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46
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Tchernaenko V, Halvorson HR, Kashlev M, Lutter LC. DNA bubble formation in transcription initiation. Biochemistry 2008; 47:1871-84. [PMID: 18205393 DOI: 10.1021/bi701289g] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The properties of the DNA bubble in the transcription open complex have been characterized by topological analysis of DNA circles containing the lac UV5 promoter or the PR promoter from bacteriophage lambda. Topological analysis is particularly well suited to this purpose since it quantifies the changes in DNA duplex geometry caused by bubble formation as well as by superhelical DNA wrapping. The duplex unwinding that results from bubble formation is detected as a reduction in topological linking number of the DNA circle, and the precision of this measurement has been enhanced in the current study through the use of 8 or 10 promoter copies per circle. Several lines of evidence indicate that the linking number change induced by open complex formation is essentially all due to bubble generation, with very little derived from superhelical wrapping. Accordingly, the linking number change of -1.17 measured for the lac UV5 promoter indicates that the size of the lac UV5 bubble is about 12.3 base pairs, while the change of -0.98 measured for the lambda PR promoter indicates that the lambda PR bubble is 10.3 base pairs. It was also found that the presence or absence of magnesium ion had little effect on the value of the linking number change, a result that resolves the uncertainty associated with use of chemical probes to study the effect of magnesium on bubble size. Finally, the magnitude of linking number change increases progressively when the 3' end of a transcript is extended to +2 and +3 in an abortive initiation complex. This indicates that the transcription bubble expands at its leading edge in the abortive complex, results that confirm and extend the proposal of a DNA "scrunching" mechanism at the onset of transcription. These results are relevant to several models for the structure of DNA in the functional open complex in solution, and provide an important complement to the structural information available from recent crystal structures.
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Affiliation(s)
- Vladimir Tchernaenko
- Molecular Biology Section, Bone and Joint Center, Henry Ford Hospital, Detroit, Michigan 48202, USA
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47
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Rosenthal AZ, Kim Y, Gralla JD. Poising of Escherichia coli RNA polymerase and its release from the sigma 38 C-terminal tail for osmY transcription. J Mol Biol 2008; 376:938-49. [PMID: 18201723 DOI: 10.1016/j.jmb.2007.12.037] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2007] [Revised: 12/14/2007] [Accepted: 12/17/2007] [Indexed: 10/22/2022]
Abstract
Bacteria must adapt their transcription to overcome the osmotic stress associated with the gastrointestinal tract of their host. This requires the sigma 38 (rpoS) form of RNA polymerase. Here, chromatin immunoprecipitation experiments show that activation is associated with a poise-and-release mechanism in vivo. A C-terminal tail unique among sigma factors is shown to be required for in vivo recruitment of RNA polymerase to the promoter region prior to osmotic shock. C-terminal domain tail-dependent transcription in vivo can be mimicked by using the intracellular signaling molecule potassium glutamate in vitro. Following signaling, the barrier to elongation into the gene body is overcome and RNA polymerase is released to produce osmY mRNA.
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Affiliation(s)
- Adam Z Rosenthal
- Department of Chemistry and Biochemistry and the Molecular Biology Institute, University of California, Los Angeles, CA 90095, USA
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Sclavi B, Beatty CM, Thach DS, Fredericks CE, Buckle M, Wolfe AJ. The multiple roles of CRP at the complex acs promoter depend on activation region 2 and IHF. Mol Microbiol 2007; 65:425-40. [PMID: 17630973 DOI: 10.1111/j.1365-2958.2007.05797.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
acs encodes a high-affinity enzyme that permits survival during carbon starvation. As befits a survival gene, its transcription is subject to complex regulation. Previously, we reported that cAMP receptor protein (CRP) activates acs transcription by binding tandem DNA sites located upstream of the major acsP2 promoter and that the nucleoid protein IHF (integration host factor) binds three specific sites located just upstream. In vivo, the sequence that includes these IHF sites exerts a positive effect on CRP-dependent transcription, while a construct containing only the most proximal site exhibits reduced transcription compared with the full-length promoter or with a construct lacking all three IHF sites. Here, we defined the minimal system required for this IHF-dependent inhibition, showing it requires the promoter-distal CRP site and an amino acid residue located within activation region 2 (AR2), a surface determinant of CRP that interacts with RNA polymerase (RNAP). Surprisingly, for a Class III promoter, disruption of AR2 caused significant changes in the activity and structure of both the full-length promoter and the construct with the single proximal IHF site. We propose that AR2, together with IHF, mediates formation of a multi-protein complex, in which RNAP is stabilized in an open complex that remains poised on the promoter ready to respond rapidly to environmental changes.
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Affiliation(s)
- Bianca Sclavi
- LBPA, UMR8113, CNRS/Ecole Normale Supérieure de Cachan, 94230 Cachan, France
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Mazzitelli CL, Brodbelt JS. Probing ligand binding to duplex DNA using KMnO4 reactions and electrospray ionization tandem mass spectrometry. Anal Chem 2007; 79:4636-47. [PMID: 17508717 PMCID: PMC2531255 DOI: 10.1021/ac070145p] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
An electrospray ionization tandem mass spectrometry (ESI-MS/MS) strategy employing the thymine-selective KMnO4 oxidation reaction to detect conformational changes and ligand binding sites in noncovalent DNA/drug complexes is reported. ESI-MS/MS is used to detect specific mass shifts of the DNA ions that are associated with the oxidation of thymines. This KMnO4 oxidation/ESI-MS/MS approach is an alternative to conventional gel-based oxidation methods and affords excellent sensitivity while eliminating the reliance on radiolabeled DNA. Comparison of single-strand versus duplex DNA indicates that the duplexes exhibit a significant resistance to the reaction, thus confirming that the oxidation process is favored for unwound or single-strand regions of DNA. DNA complexes containing different drugs including echinomycin, actinomycin-D, ethidium bromide, Hoechst 33342, and cis-C1 were subjected to the oxidation reaction. Echinomycin, a ligand with a bisintercalative binding mode, was found to induce the greatest KMnO4 reactivity, while Hoechst 33342, a minor groove binder, caused no increase in the oxidation of DNA. The oxidation of echinomycin/DNA complexes containing duplexes with different sequences and lengths was also assessed. Duplexes with thymines closer to the terminal ends of the duplex demonstrated a greater increase in the degree of oxidation than those with thymines in the middle of the sequence. Collisional activated dissociation (CAD) and infrared multiphoton dissociation (IRMPD) experiments were used to determine the site of oxidation based on oligonucleotide fragmentation patterns.
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Affiliation(s)
- Carolyn L Mazzitelli
- Department of Chemistry and Biochemistry, 1 University Station A5300, University of Texas at Austin, Austin, Texas 78712, USA
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Wright JG, Natan MJ, MacDonnel FM, Ralston DM, O'Halloran TV. Mercury(II)-Thiolate Chemistry and the Mechanism of the Heavy Metal Biosensor MerR. PROGRESS IN INORGANIC CHEMISTRY 2007. [DOI: 10.1002/9780470166390.ch6] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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