1
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Hien EDM, Chauvier A, St-Pierre P, Lafontaine DA. Structural Characterization of the Cotranscriptional Folding of the Thiamin Pyrophosphate Sensing thiC Riboswitch in Escherichia coli. Biochemistry 2024. [PMID: 38864595 DOI: 10.1021/acs.biochem.3c00665] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2024]
Abstract
Riboswitches are RNA-regulating elements that mostly rely on structural changes to modulate gene expression at various levels. Recent studies have revealed that riboswitches may control several regulatory mechanisms cotranscriptionally, i.e., during the transcription elongation of the riboswitch or early in the coding region of the regulated gene. Here, we study the structure of the nascent thiamin pyrophosphate (TPP)-sensing thiC riboswitch in Escherichia coli by using biochemical and enzymatic conventional probing approaches. Our chemical (in-line and lead probing) and enzymatic (nucleases S1, A, T1, and RNase H) probing data provide a comprehensive model of how TPP binding modulates the structure of the thiC riboswitch. Furthermore, by using transcriptional roadblocks along the riboswitch sequence, we find that a certain portion of nascent RNA is needed to sense TPP that coincides with the formation of the P5 stem loop. Together, our data suggest that conventional techniques may readily be used to study cotranscriptional folding of nascent RNAs.
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Affiliation(s)
- Elsa D M Hien
- Department of Biology, Faculty of Science, RNA Group, Université de Sherbrooke, Sherbrooke, Quebec J1K 2R1, Canada
| | - Adrien Chauvier
- Department of Biology, Faculty of Science, RNA Group, Université de Sherbrooke, Sherbrooke, Quebec J1K 2R1, Canada
| | - Patrick St-Pierre
- Department of Biology, Faculty of Science, RNA Group, Université de Sherbrooke, Sherbrooke, Quebec J1K 2R1, Canada
| | - Daniel A Lafontaine
- Department of Biology, Faculty of Science, RNA Group, Université de Sherbrooke, Sherbrooke, Quebec J1K 2R1, Canada
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2
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Qian J, Cartee A, Xu W, Yan Y, Wang B, Artsimovitch I, Dunlap D, Finzi L. Reciprocating RNA Polymerase batters through roadblocks. Nat Commun 2024; 15:3193. [PMID: 38609371 PMCID: PMC11014978 DOI: 10.1038/s41467-024-47531-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2023] [Accepted: 04/04/2024] [Indexed: 04/14/2024] Open
Abstract
RNA polymerases must transit through protein roadblocks to produce full-length transcripts. Here we report real-time measurements of Escherichia coli RNA polymerase passing through different barriers. As intuitively expected, assisting forces facilitated, and opposing forces hindered, RNA polymerase passage through lac repressor protein bound to natural binding sites. Force-dependent differences were significant at magnitudes as low as 0.2 pN and were abolished in the presence of the transcript cleavage factor GreA, which rescues backtracked RNA polymerase. In stark contrast, opposing forces promoted passage when the rate of RNA polymerase backtracking was comparable to, or faster than the rate of dissociation of the roadblock, particularly in the presence of GreA. Our experiments and simulations indicate that RNA polymerase may transit after roadblocks dissociate, or undergo cycles of backtracking, recovery, and ramming into roadblocks to pass through. We propose that such reciprocating motion also enables RNA polymerase to break protein-DNA contacts that hold RNA polymerase back during promoter escape and RNA chain elongation. This may facilitate productive transcription in vivo.
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Affiliation(s)
- Jin Qian
- Physics Department, Emory University, Atlanta, GA, USA
| | | | - Wenxuan Xu
- Physics Department, Emory University, Atlanta, GA, USA
| | - Yan Yan
- Physics Department, Emory University, Atlanta, GA, USA
| | - Bing Wang
- The Center for RNA Biology and Department of Microbiology, The Ohio State University, Columbus, OH, USA
| | - Irina Artsimovitch
- The Center for RNA Biology and Department of Microbiology, The Ohio State University, Columbus, OH, USA
| | - David Dunlap
- Physics Department, Emory University, Atlanta, GA, USA
| | - Laura Finzi
- Physics Department, Emory University, Atlanta, GA, USA.
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3
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Hao N, Donnelly AJ, Dodd IB, Shearwin KE. When push comes to shove - RNA polymerase and DNA-bound protein roadblocks. Biophys Rev 2023; 15:355-366. [PMID: 37396453 PMCID: PMC10310618 DOI: 10.1007/s12551-023-01064-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2023] [Accepted: 05/21/2023] [Indexed: 07/04/2023] Open
Abstract
In recent years, transcriptional roadblocking has emerged as a crucial regulatory mechanism in gene expression, whereby other DNA-bound obstacles can block the progression of transcribing RNA polymerase (RNAP), leading to RNAP pausing and ultimately dissociation from the DNA template. In this review, we discuss the mechanisms by which transcriptional roadblocks can impede RNAP progression, as well as how RNAP can overcome these obstacles to continue transcription. We examine different DNA-binding proteins involved in transcriptional roadblocking and their biophysical properties that determine their effectiveness in blocking RNAP progression. The catalytically dead CRISPR-Cas (dCas) protein is used as an example of an engineered programmable roadblock, and the current literature in understanding the polarity of dCas roadblocking is also discussed. Finally, we delve into a stochastic model of transcriptional roadblocking and highlight the importance of transcription factor binding kinetics and its resistance to dislodgement by an elongating RNAP in determining the strength of a roadblock.
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Affiliation(s)
- Nan Hao
- Department of Molecular and Biomedical Science, School of Biological Sciences, The University of Adelaide, Adelaide, SA 5005 Australia
| | - Alana J. Donnelly
- Department of Molecular and Biomedical Science, School of Biological Sciences, The University of Adelaide, Adelaide, SA 5005 Australia
| | - Ian B. Dodd
- Department of Molecular and Biomedical Science, School of Biological Sciences, The University of Adelaide, Adelaide, SA 5005 Australia
| | - Keith E. Shearwin
- Department of Molecular and Biomedical Science, School of Biological Sciences, The University of Adelaide, Adelaide, SA 5005 Australia
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4
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Site-specific photolabile roadblocks for the study of transcription elongation in biologically complex systems. Commun Biol 2022; 5:457. [PMID: 35552496 PMCID: PMC9098449 DOI: 10.1038/s42003-022-03382-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2021] [Accepted: 04/20/2022] [Indexed: 12/14/2022] Open
Abstract
Transcriptional pausing is crucial for the timely expression of genetic information. Biochemical methods quantify the half-life of paused RNA polymerase (RNAP) by monitoring restarting complexes across time. However, this approach may produce apparent half-lives that are longer than true pause escape rates in biological contexts where multiple consecutive pause sites are present. We show here that the 6-nitropiperonyloxymethyl (NPOM) photolabile group provides an approach to monitor transcriptional pausing in biological systems containing multiple pause sites. We validate our approach using the well-studied his pause and show that an upstream RNA sequence modulates the pause half-life. NPOM was also used to study a transcriptional region within the Escherichia coli thiC riboswitch containing multiple consecutive pause sites. We find that an RNA hairpin structure located upstream to the region affects the half-life of the 5′ most proximal pause site—but not of the 3′ pause site—in contrast to results obtained using conventional approaches not preventing asynchronous transcription. Our results show that NPOM is a powerful tool to study transcription elongation dynamics within biologically complex systems. Transcriptional pausing can be achieved by 6-nitropiperonyloxymethyl modification, which can halt RNAP without causing backtracking and be efficiently removed by short illumination with a moderately intense UV light.
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5
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Xu W, Yan Y, Artsimovitch I, Dunlap D, Finzi L. Positive supercoiling favors transcription elongation through lac repressor-mediated DNA loops. Nucleic Acids Res 2022; 50:2826-2835. [PMID: 35188572 PMCID: PMC8934669 DOI: 10.1093/nar/gkac093] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2021] [Revised: 12/22/2021] [Accepted: 02/20/2022] [Indexed: 11/30/2022] Open
Abstract
Some proteins, like the lac repressor (LacI), mediate long-range loops that alter DNA topology and create torsional barriers. During transcription, RNA polymerase generates supercoiling that may facilitate passage through such barriers. We monitored E. coli RNA polymerase progress along templates in conditions that prevented, or favored, 400 bp LacI-mediated DNA looping. Tethered particle motion measurements revealed that RNA polymerase paused longer at unlooped LacI obstacles or those barring entry to a loop than those barring exit from the loop. Enhanced dissociation of a LacI roadblock by the positive supercoiling generated ahead of a transcribing RNA polymerase within a torsion-constrained DNA loop may be responsible for this reduction in pause time. In support of this idea, RNA polymerase transcribed 6-fold more slowly through looped DNA and paused at LacI obstacles for 66% less time on positively supercoiled compared to relaxed templates, especially under increased tension (torque). Positive supercoiling propagating ahead of polymerase facilitated elongation along topologically complex, protein-coated templates.
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Affiliation(s)
- Wenxuan Xu
- Physics Department, Emory University, Atlanta, GA, USA
| | - Yan Yan
- Physics Department, Emory University, Atlanta, GA, USA
| | | | - David Dunlap
- Physics Department, Emory University, Atlanta, GA, USA
| | - Laura Finzi
- Physics Department, Emory University, Atlanta, GA, USA
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6
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Abstract
Cotranscriptional folding is a fundamental step in RNA biogenesis and the basis for many RNA-mediated gene regulation systems. Understanding how RNA folds as it is synthesized requires experimental methods that can systematically identify intermediate RNA structures that form during transcription. Cotranscriptional RNA chemical probing experiments achieve this by applying high-throughput RNA structure probing to an in vitro transcribed array of cotranscriptionally folded intermediate transcripts. In this chapter, we present guidelines and procedures for integrating single-round in vitro transcription using E. coli RNA polymerase with high-throughput RNA chemical probing workflows. We provide an overview of key concepts including DNA template design, transcription roadblocking strategies, single-round in vitro transcription with E. coli RNA polymerase, and RNA chemical probing and describe procedures for DNA template preparation, cotranscriptional RNA chemical probing, RNA purification, and 3' adapter ligation. The end result of these procedures is a purified RNA library that can be prepared for Illumina sequencing using established high-throughput RNA structure probing library construction strategies.
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Affiliation(s)
- Courtney E Szyjka
- Department of Biological Sciences, The University at Buffalo, Buffalo, NY, USA
| | - Eric J Strobel
- Department of Biological Sciences, The University at Buffalo, Buffalo, NY, USA.
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7
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Thompson MK, Nocedal I, Culviner PH, Zhang T, Gozzi KR, Laub MT. Escherichia coli SymE is a DNA-binding protein that can condense the nucleoid. Mol Microbiol 2021; 117:851-870. [PMID: 34964191 DOI: 10.1111/mmi.14877] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2021] [Revised: 12/23/2021] [Accepted: 12/23/2021] [Indexed: 11/28/2022]
Abstract
Type I toxin-antitoxin (TA) systems typically consist of a protein toxin that imbeds in the inner membrane where it can oligomerize and form pores that change membrane permeability, and an RNA antitoxin that interacts directly with toxin mRNA to inhibit its translation. In Escherichia coli, symE/symR is annotated as a type I TA system with a non-canonical toxin. SymE was initially suggested to be an endoribonuclease, but has predicted structural similarity to DNA binding proteins. To better understand SymE function, we used RNA-seq to examine cells ectopically producing it. Although SymE drives major changes in gene expression, we do not find strong evidence of endoribonucleolytic activity. Instead, our biochemical and cell biological studies indicate that SymE binds DNA. We demonstrate that the toxicity of symE overexpression likely stems from its ability to drive severe nucleoid condensation, which disrupts DNA and RNA synthesis and leads to DNA damage, similar to the effects of overproducing the nucleoid-associated protein H-NS. Collectively, our results suggest that SymE represents a new class of nucleoid-associated proteins that is widely distributed in bacteria.
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Affiliation(s)
- Mary K Thompson
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Isabel Nocedal
- Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Peter H Culviner
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Tong Zhang
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Kevin R Gozzi
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Michael T Laub
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA.,Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
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8
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Sakono M, Hayakawa R. Repressor-Like On-Off Regulation of Protein Expression by the DNA-Binding Transcription Activator-Like Effector in T7 Promoter-Based Cell-Free Protein Synthesis. Chembiochem 2020; 22:888-893. [PMID: 33085169 DOI: 10.1002/cbic.202000591] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2020] [Revised: 10/21/2020] [Indexed: 01/24/2023]
Abstract
The aim of this study was to develop a transcription activator-like effector (TALE)-based technology to regulate protein synthesis in cell-free systems. We attempted to regulate the T7 promoter system, which has no natural mechanism of expression control, and sought to arbitrarily induce protein expression through the formation and dissociation of TALE and target DNA complexes. Protein synthesis was performed in a cell-free system in the presence of TALE, which recognized and bound to a sequence upstream of the T7 promoter, and protein expression was suppressed by approximately 80 % compared to in the absence of TALE. This suggests that masking part of the promoter region strongly suppresses protein synthesis. Additionally, competitive inhibition of TALE binding to the target DNA template led to protein synthesis levels that were equivalent to the levels in the absence of TALE. Our results demonstrate that DNA recognition by TALE can regulate the expression of the T7 promoter system.
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Affiliation(s)
- Masafumi Sakono
- Department of Applied Chemistry Graduate School of Science and Engineering, University of Toyama, 3190 Gofuku, Toyama, 930-8555, Japan
| | - Ryoto Hayakawa
- Department of Applied Chemistry Graduate School of Science and Engineering, University of Toyama, 3190 Gofuku, Toyama, 930-8555, Japan
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9
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Strobel EJ, Lis JT, Lucks JB. Chemical roadblocking of DNA transcription for nascent RNA display. J Biol Chem 2020; 295:6401-6412. [PMID: 32209658 DOI: 10.1074/jbc.ra120.012641] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2020] [Revised: 03/20/2020] [Indexed: 11/06/2022] Open
Abstract
Site-specific arrest of RNA polymerases (RNAPs) is fundamental to several technologies that assess RNA structure and function. Current in vitro transcription "roadblocking" approaches inhibit transcription elongation by blocking RNAP with a protein bound to the DNA template. One limitation of protein-mediated transcription roadblocking is that it requires inclusion of a protein factor extrinsic to the minimal in vitro transcription reaction. In this work, we developed a chemical approach for halting transcription by Escherichia coli RNAP. We first established a sequence-independent method for site-specific incorporation of chemical lesions into dsDNA templates by sequential PCR and translesion synthesis. We then show that interrupting the transcribed DNA strand with an internal desthiobiotin-triethylene glycol modification or 1,N6-etheno-2'-deoxyadenosine base efficiently and stably halts Escherichia coli RNAP transcription. By encoding an intrinsic stall site within the template DNA, our chemical transcription roadblocking approach enables display of nascent RNA molecules from RNAP in a minimal in vitro transcription reaction.
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Affiliation(s)
- Eric J Strobel
- Department of Chemical and Biological Engineering, Northwestern University, Evanston, Illinois 60208 .,Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York 14850
| | - John T Lis
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York 14850
| | - Julius B Lucks
- Department of Chemical and Biological Engineering, Northwestern University, Evanston, Illinois 60208.,Center for Synthetic Biology, Northwestern University, Evanston, Illinois 60208
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10
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Widom JR, Rai V, Rohlman CE, Walter NG. Versatile transcription control based on reversible dCas9 binding. RNA (NEW YORK, N.Y.) 2019; 25:1457-1469. [PMID: 31320398 PMCID: PMC6795147 DOI: 10.1261/rna.071613.119] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/30/2019] [Accepted: 07/15/2019] [Indexed: 06/10/2023]
Abstract
The ability to control transcription in a time-dependent manner in vitro promises numerous applications in molecular biology and nanotechnology. Here we demonstrate an approach that enables precise, independent control over the production of multiple RNA transcripts in vitro using single guide RNA (sgRNA)-directed transcription blockades by catalytically dead Streptococcus pyogenes CRISPR-Cas9 enzyme (dCas9). We show that when bound to a DNA template, the dCas9:sgRNA complex forms a robust blockade to transcription by RNA polymerases (RNAPs) from bacteriophages SP6, T3, and T7 (>99.5% efficiency), and a partial blockade to transcription by Escherichia coli RNAP (∼70% efficiency). We find that all three bacteriophage RNAPs dissociate from the DNA template upon encountering the dCas9 blockade, while E. coli RNAP stays bound for at least the 90-min duration of our experiments. The blockade maintains >95% efficiency when four mismatches are introduced into the 5' end of the sgRNA target sequence. Notably, when using such a mismatched blockade, production of specific RNA species can be activated on demand by addition of a double-stranded competitor DNA perfectly matching the sgRNA. This strategy enables the independent production of multiple RNA species in a temporally controlled fashion from the same DNA template, demonstrating a new approach for transcription control.
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Affiliation(s)
- Julia R Widom
- Single Molecule Analysis Group, Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA
- Center for RNA Biomedicine, University of Michigan, Ann Arbor, Michigan 48109, USA
| | - Victoria Rai
- Single Molecule Analysis Group, Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA
- Center for RNA Biomedicine, University of Michigan, Ann Arbor, Michigan 48109, USA
- Biophysics Program and Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA
| | | | - Nils G Walter
- Single Molecule Analysis Group, Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA
- Center for RNA Biomedicine, University of Michigan, Ann Arbor, Michigan 48109, USA
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11
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Shen BA, Landick R. Transcription of Bacterial Chromatin. J Mol Biol 2019; 431:4040-4066. [PMID: 31153903 PMCID: PMC7248592 DOI: 10.1016/j.jmb.2019.05.041] [Citation(s) in RCA: 40] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2019] [Revised: 05/22/2019] [Accepted: 05/23/2019] [Indexed: 12/12/2022]
Abstract
Decades of research have probed the interplay between chromatin (genomic DNA associated with proteins and RNAs) and transcription by RNA polymerase (RNAP) in all domains of life. In bacteria, chromatin is compacted into a membrane-free region known as the nucleoid that changes shape and composition depending on the bacterial state. Transcription plays a key role in both shaping the nucleoid and organizing it into domains. At the same time, chromatin impacts transcription by at least five distinct mechanisms: (i) occlusion of RNAP binding; (ii) roadblocking RNAP progression; (iii) constraining DNA topology; (iv) RNA-mediated interactions; and (v) macromolecular demixing and heterogeneity, which may generate phase-separated condensates. These mechanisms are not mutually exclusive and, in combination, mediate gene regulation. Here, we review the current understanding of these mechanisms with a focus on gene silencing by H-NS, transcription coordination by HU, and potential phase separation by Dps. The myriad questions about transcription of bacterial chromatin are increasingly answerable due to methodological advances, enabling a needed paradigm shift in the field of bacterial transcription to focus on regulation of genes in their native state. We can anticipate answers that will define how bacterial chromatin helps coordinate and dynamically regulate gene expression in changing environments.
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Affiliation(s)
- Beth A Shen
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706, United States
| | - Robert Landick
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706, United States; Department of Bacteriology, University of Wisconsin-Madison, Madison, WI 53706, United States.
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12
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Ragheb M, Merrikh H. The enigmatic role of Mfd in replication-transcription conflicts in bacteria. DNA Repair (Amst) 2019; 81:102659. [PMID: 31311770 PMCID: PMC6892258 DOI: 10.1016/j.dnarep.2019.102659] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Conflicts between replication and transcription can have life-threatening consequences. RNA polymerase (RNAP) is the major impediment to replication progression, and its efficient removal from DNA should mitigate the consequences of collisions with replication. Cells have various proteins that can resolve conflicts by removing stalled (or actively translocating) RNAP from DNA. It would therefore seem logical that RNAP-associated factors, such as the bacterial DNA translocase Mfd, would minimize the effects of conflicts. Despite seemingly conclusive statements in most textbooks, the role of Mfd in conflicts remains an enigma. In this review, we will discuss the different physical states of RNAP during transcription, and how each distinct state can influence conflict severity and potentially trigger the involvement of Mfd. We propose models to explain the contradictory conclusions from published studies on the potential role of Mfd in resolving conflicts.
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Affiliation(s)
- Mark Ragheb
- Molecular and Cellular Biology Graduate Program and Medical Scientist Training Program, University of Washington, Seattle, WA, USA
| | - Houra Merrikh
- Department of Biochemistry, Vanderbilt University, Nashville, TN, 37205, USA; Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, TN, 37232, USA.
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13
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Roberts JW. Mechanisms of Bacterial Transcription Termination. J Mol Biol 2019; 431:4030-4039. [PMID: 30978344 DOI: 10.1016/j.jmb.2019.04.003] [Citation(s) in RCA: 80] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2019] [Revised: 03/28/2019] [Accepted: 04/02/2019] [Indexed: 01/28/2023]
Abstract
Bacterial transcription termination, described mostly for Escherichia coli, occurs in three recognized ways: intrinsic termination, an activity only of the core RNAP enzyme and transcript sequences that encode an RNA hairpin and terminal uridine-rich segment; termination by the enzyme Rho, an ATP-dependent RNA translocase that releases RNA by forcing uncharacterized structural changes in the elongating complex; and Mfd-dependent termination, the activity of an ATP-dependent DNA translocase that is thought to dissociate the elongation complex by exerting torque on a stalled RNAP. Intrinsic termination can be described in terms of the nucleic acid movements in the process, whereas the enzymatic mechanisms have been illuminated importantly by definitive structural and biochemical analysis of their activity.
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Affiliation(s)
- Jeffrey W Roberts
- Department of Molecular Biology and Genetics, Biotechnology Building, Cornell University, Ithaca, NY 14853, USA.
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14
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Kang JY, Mooney RA, Nedialkov Y, Saba J, Mishanina TV, Artsimovitch I, Landick R, Darst SA. Structural Basis for Transcript Elongation Control by NusG Family Universal Regulators. Cell 2018; 173:1650-1662.e14. [PMID: 29887376 PMCID: PMC6003885 DOI: 10.1016/j.cell.2018.05.017] [Citation(s) in RCA: 105] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2018] [Revised: 04/09/2018] [Accepted: 05/08/2018] [Indexed: 10/14/2022]
Abstract
NusG/RfaH/Spt5 transcription elongation factors are the only transcription regulators conserved across all life. Bacterial NusG regulates RNA polymerase (RNAP) elongation complexes (ECs) across most genes, enhancing elongation by suppressing RNAP backtracking and coordinating ρ-dependent termination and translation. The NusG paralog RfaH engages the EC only at operon polarity suppressor (ops) sites and suppresses both backtrack and hairpin-stabilized pausing. We used single-particle cryoelectron microscopy (cryo-EM) to determine structures of ECs at ops with NusG or RfaH. Both factors chaperone base-pairing of the upstream duplex DNA to suppress backtracking, explaining stimulation of elongation genome-wide. The RfaH-opsEC structure reveals how RfaH confers operon specificity through specific recognition of an ops hairpin in the single-stranded nontemplate DNA and tighter binding to the EC to exclude NusG. Tight EC binding by RfaH sterically blocks the swiveled RNAP conformation necessary for hairpin-stabilized pausing. The universal conservation of NusG/RfaH/Spt5 suggests that the molecular mechanisms uncovered here are widespread.
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Affiliation(s)
- Jin Young Kang
- The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA
| | - Rachel Anne Mooney
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Yuri Nedialkov
- Department of Microbiology, The Ohio State University, Columbus, OH 43210, USA; The Center for RNA Biology, The Ohio State University, Columbus, OH 43210, USA
| | - Jason Saba
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Tatiana V Mishanina
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Irina Artsimovitch
- Department of Microbiology, The Ohio State University, Columbus, OH 43210, USA; The Center for RNA Biology, The Ohio State University, Columbus, OH 43210, USA
| | - Robert Landick
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706, USA; Department of Bacteriology, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Seth A Darst
- The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA.
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15
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Inuzuka S, Kakizawa H, Nishimura KI, Naito T, Miyazaki K, Furuta H, Matsumura S, Ikawa Y. Recognition of cyclic-di-GMP by a riboswitch conducts translational repression through masking the ribosome-binding site distant from the aptamer domain. Genes Cells 2018; 23:435-447. [PMID: 29693296 DOI: 10.1111/gtc.12586] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2017] [Accepted: 03/18/2018] [Indexed: 12/31/2022]
Abstract
The riboswitch is a class of RNA-based gene regulatory machinery that is dependent on recognition of its target ligand by RNA tertiary structures. Ligand recognition is achieved by the aptamer domain, and ligand-dependent structural changes of the expression platform then usually mediate termination of transcription or translational initiation. Ligand-dependent structural changes of the aptamer domain and expression platform have been reported for several riboswitches with short (<40 nucleotides) expression platforms. In this study, we characterized structural changes of the Vc2 c-di-GMP riboswitch that represses translation of downstream open reading frames in a ligand-dependent manner. The Vc2 riboswitch has a long (97 nucleotides) expression platform, but its structure and function are largely unknown. Through mutational analysis and chemical probing, we identified its secondary structures that are possibly responsible for switch-OFF and switch-ON states of translational initiation.
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Affiliation(s)
- Saki Inuzuka
- Department of Chemistry, Graduate School of Science and Engineering, University of Toyama, Toyama, Japan
| | - Hitoshi Kakizawa
- Department of Chemistry, Graduate School of Science and Engineering, University of Toyama, Toyama, Japan
| | - Kei-Ichiro Nishimura
- Department of Chemistry and Biochemistry, Graduate School of Engineering, Kyushu University, Fukuoka, Japan
| | - Takuto Naito
- Department of Chemistry, Graduate School of Science and Engineering, University of Toyama, Toyama, Japan
| | - Katsushi Miyazaki
- Department of Chemistry, Graduate School of Science and Engineering, University of Toyama, Toyama, Japan
| | - Hiroyuki Furuta
- Department of Chemistry and Biochemistry, Graduate School of Engineering, Kyushu University, Fukuoka, Japan
| | - Shigeyoshi Matsumura
- Department of Chemistry, Graduate School of Science and Engineering, University of Toyama, Toyama, Japan
| | - Yoshiya Ikawa
- Department of Chemistry, Graduate School of Science and Engineering, University of Toyama, Toyama, Japan
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16
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Strobel EJ, Watters KE, Nedialkov Y, Artsimovitch I, Lucks JB. Distributed biotin-streptavidin transcription roadblocks for mapping cotranscriptional RNA folding. Nucleic Acids Res 2017; 45:e109. [PMID: 28398514 PMCID: PMC5499547 DOI: 10.1093/nar/gkx233] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2017] [Accepted: 04/02/2017] [Indexed: 01/24/2023] Open
Abstract
RNA folding during transcription directs an order of folding that can determine RNA structure and function. However, the experimental study of cotranscriptional RNA folding has been limited by the lack of easily approachable methods that can interrogate nascent RNA structure at nucleotide resolution. To address this, we previously developed cotranscriptional selective 2΄-hydroxyl acylation analyzed by primer extension sequencing (SHAPE-Seq) to simultaneously probe all intermediate RNA transcripts during transcription by stalling elongation complexes at catalytically dead EcoRIE111Q roadblocks. While effective, the distribution of elongation complexes using EcoRIE111Q requires laborious PCR using many different oligonucleotides for each sequence analyzed. Here, we improve the broad applicability of cotranscriptional SHAPE-Seq by developing a sequence-independent biotin-streptavidin (SAv) roadblocking strategy that simplifies the preparation of roadblocking DNA templates. We first determine the properties of biotin-SAv roadblocks. We then show that randomly distributed biotin-SAv roadblocks can be used in cotranscriptional SHAPE-Seq experiments to identify the same RNA structural transitions related to a riboswitch decision-making process that we previously identified using EcoRIE111Q. Lastly, we find that EcoRIE111Q maps nascent RNA structure to specific transcript lengths more precisely than biotin-SAv and propose guidelines to leverage the complementary strengths of each transcription roadblock in cotranscriptional SHAPE-Seq.
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Affiliation(s)
- Eric J. Strobel
- Department of Chemical and Biological Engineering, Northwestern University, Evanston, IL 60201, USA
| | - Kyle E. Watters
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA
| | - Yuri Nedialkov
- Department of Microbiology, The Ohio State University, Columbus, OH 43210, USA
- The Center for RNA Biology, The Ohio State University, Columbus, OH 43210, USA
| | - Irina Artsimovitch
- Department of Microbiology, The Ohio State University, Columbus, OH 43210, USA
- The Center for RNA Biology, The Ohio State University, Columbus, OH 43210, USA
| | - Julius B. Lucks
- Department of Chemical and Biological Engineering, Northwestern University, Evanston, IL 60201, USA
- To whom correspondence should be addressed. Tel: +1 847 467 2943; Fax: +1 847 491 3728;
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17
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Identification of a Residue (Glu60) in TRAP Required for Inducing Efficient Transcription Termination at the trp Attenuator Independent of Binding Tryptophan and RNA. J Bacteriol 2017; 199:JB.00710-16. [PMID: 28069823 DOI: 10.1128/jb.00710-16] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2016] [Accepted: 12/31/2016] [Indexed: 11/20/2022] Open
Abstract
Transcription of the tryptophan (trp) operon in Bacillus subtilis is regulated by an attenuation mechanism. Attenuation is controlled by the trpRNA-binding attenuation protein (TRAP). TRAP binds to a site in the 5' leader region of the nascent trp transcript in response to the presence of excess intracellular tryptophan. This binding induces transcription termination upstream of the structural genes of the operon. In prior attenuation models, the role of TRAP was only to alter the secondary structure of the leader region RNA so as to promote formation of the trp attenuator, which was presumed to function as an intrinsic terminator. However, formation of the attenuator alone has been shown to be insufficient to induce efficient termination, indicating that TRAP plays an additional role in this process. To further examine the function of TRAP, we performed a genetic selection for mutant TRAPs that bind tryptophan and RNA but show diminished termination at the trp attenuator. Five such TRAP mutants were obtained. Four of these have substitutions at Glu60, three of which are Lys (E60K) substitutions and the fourth of which is a Val (E60V) substitution. The fifth mutant obtained contains a substitution at Ile63, which is on the same β-strand of TRAP as Glu60. Purified E60K TRAP binds tryptophan and RNA with properties similar to those of the wild type but is defective at inducing termination at the trp attenuator in vitroIMPORTANCE Prior models for attenuation control of the B. subtilis trp operon suggested that the only role for TRAP is to bind to the leader region RNA and alter its folding to induce formation of an intrinsic terminator. However, several recent studies suggested that TRAP plays an additional role in the termination mechanism. We hypothesized that this function could involve residues in TRAP other than those required to bind tryptophan and RNA. Here we obtained TRAP mutants with alterations at Glu60 that are deficient at inducing termination in the leader region while maintaining tryptophan and RNA binding properties similar to those of the WT protein. These studies provide additional evidence that TRAP-mediated transcription termination at the trp attenuator is neither intrinsic nor Rho dependent.
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De Paepe B, Peters G, Coussement P, Maertens J, De Mey M. Tailor-made transcriptional biosensors for optimizing microbial cell factories. J Ind Microbiol Biotechnol 2016; 44:623-645. [PMID: 27837353 DOI: 10.1007/s10295-016-1862-3] [Citation(s) in RCA: 65] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2016] [Accepted: 10/30/2016] [Indexed: 12/24/2022]
Abstract
Monitoring cellular behavior and eventually properly adapting cellular processes is key to handle the enormous complexity of today's metabolic engineering questions. Hence, transcriptional biosensors bear the potential to augment and accelerate current metabolic engineering strategies, catalyzing vital advances in industrial biotechnology. The development of such transcriptional biosensors typically starts with exploring nature's richness. Hence, in a first part, the transcriptional biosensor architecture and the various modi operandi are briefly discussed, as well as experimental and computational methods and relevant ontologies to search for natural transcription factors and their corresponding binding sites. In the second part of this review, various engineering approaches are reviewed to tune the main characteristics of these (natural) transcriptional biosensors, i.e., the response curve and ligand specificity, in view of specific industrial biotechnology applications, which is illustrated using success stories of transcriptional biosensor engineering.
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Affiliation(s)
- Brecht De Paepe
- Department of Biochemical and Microbial Technology, Ghent University, Coupure Links 653, 9000, Ghent, Belgium
| | - Gert Peters
- Department of Biochemical and Microbial Technology, Ghent University, Coupure Links 653, 9000, Ghent, Belgium
| | - Pieter Coussement
- Department of Biochemical and Microbial Technology, Ghent University, Coupure Links 653, 9000, Ghent, Belgium
| | - Jo Maertens
- Department of Biochemical and Microbial Technology, Ghent University, Coupure Links 653, 9000, Ghent, Belgium
| | - Marjan De Mey
- Department of Biochemical and Microbial Technology, Ghent University, Coupure Links 653, 9000, Ghent, Belgium.
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19
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Watters KE, Strobel EJ, Yu AM, Lis JT, Lucks JB. Cotranscriptional folding of a riboswitch at nucleotide resolution. Nat Struct Mol Biol 2016; 23:1124-1131. [PMID: 27798597 PMCID: PMC5497173 DOI: 10.1038/nsmb.3316] [Citation(s) in RCA: 110] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2016] [Accepted: 10/05/2016] [Indexed: 12/19/2022]
Abstract
RNAs can begin to fold immediately after emerging from RNA polymerase during transcription. Interactions between nascent RNAs and ligands during cotranscriptional folding can direct the formation of alternative RNA structures, a feature exploited by non-coding RNAs called riboswitches to make gene regulatory decisions. Despite their importance, cotranscriptional folding pathways have yet to be uncovered with sufficient resolution to reveal how cotranscriptional folding governs RNA structure and function. To access cotranscriptional folding at nucleotide resolution, we extend selective 2’-hydroxyl acylation analyzed by primer extension sequencing (SHAPE-Seq) to measure structural information of nascent RNAs during transcription. With cotranscriptional SHAPE-Seq, we determine how the B. cereus crcB fluoride riboswitch cotranscriptional folding pathway undergoes a ligand-dependent bifurcation that delays or promotes terminator formation via a series of coordinated structural transitions. Our results directly link cotranscriptional RNA folding to a genetic decision and establish a framework for cotranscriptional analysis of RNA structure at nucleotide resolution.
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Affiliation(s)
- Kyle E Watters
- Robert F. Smith School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York, USA
| | - Eric J Strobel
- Robert F. Smith School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York, USA
| | - Angela M Yu
- Robert F. Smith School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York, USA.,Tri-Institutional Training Program in Computational Biology and Medicine at Cornell University, Ithaca, New York, USA; Weill Cornell Medical College, New York, New York, USA; and Memorial Sloan-Kettering Cancer Center, New York, New York, USA.,Computational Biology Program, Memorial Sloan-Kettering Cancer Center, New York, New York, USA
| | - John T Lis
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York, USA
| | - Julius B Lucks
- Robert F. Smith School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York, USA.,Department of Chemical and Biological Engineering, Northwestern University, Evanston, Illinois, USA
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20
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Chander M, Lee A, Vallery TK, Thandar M, Jiang Y, Hsu LM. Mechanisms of Very Long Abortive Transcript Release during Promoter Escape. Biochemistry 2015; 54:7393-408. [PMID: 26610896 DOI: 10.1021/acs.biochem.5b00712] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A phage T5 N25 promoter variant, DG203, undergoes the escape transition at the +16 to +19 positions after transcription initiation. By specifically examining the abortive activity of the initial transcribing complex at position +19 (ITC19), we observe the production of both GreB-sensitive and GreB-resistant VLAT19. This suggests that ITC19, which is perched on the brink of escape, is highly unstable and can achieve stabilization through either backtracking or forward translocation. Of the forward-tracked fraction, only a small percentage escapes normally (followed by stepwise elongation) to produce full-length RNA; the rest presumably hypertranslocates to release GreB-resistant VLATs. VLAT formation is dependent not only on consensus -35/-10 promoters with 17 bp spacing but also on sequence characteristics of the spacer DNA. Analysis of DG203 promoter variants containing different spacer sequences reveals that AT-rich spacers intrinsically elevate the level of VLAT formation. The AT-rich spacer of DG203 joined to the -10 box presents an UP element sequence capable of interacting with the polymerase α subunit C-terminal domain (αCTD) during the escape transition, which in turn enhances VLAT release. Utilization of the spacer/-10 region UP element by αCTD subunits requires a 10-15 bp hypertranslocation. We document the physical occurrence of hyper forward translocation using ExoIII footprinting analysis.
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Affiliation(s)
- Monica Chander
- Biology Department, Bryn Mawr College , Bryn Mawr, Pennsylvania 19010, United States
| | - Ahri Lee
- Program in Biochemistry, Mount Holyoke College , South Hadley, Massachusetts 01075, United States
| | - Tenaya K Vallery
- Program in Biochemistry, Mount Holyoke College , South Hadley, Massachusetts 01075, United States
| | - Mya Thandar
- Program in Biochemistry, Mount Holyoke College , South Hadley, Massachusetts 01075, United States
| | - Yunnan Jiang
- Program in Biochemistry, Mount Holyoke College , South Hadley, Massachusetts 01075, United States
| | - Lilian M Hsu
- Program in Biochemistry, Mount Holyoke College , South Hadley, Massachusetts 01075, United States
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21
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Functions that Protect Escherichia coli from Tightly Bound DNA-Protein Complexes Created by Mutant EcoRII Methyltransferase. PLoS One 2015; 10:e0128092. [PMID: 25993347 PMCID: PMC4437897 DOI: 10.1371/journal.pone.0128092] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2014] [Accepted: 04/23/2015] [Indexed: 11/19/2022] Open
Abstract
Expression of mutant EcoRII methyltransferase protein (M.EcoRII-C186A) in Escherichia coli leads to tightly bound DNA-protein complexes (TBCs), located sporadically on the chromosome rather than in tandem arrays. The mechanisms behind the lethality induced by such sporadic TBCs are not well studied, nor is it clear whether very tight binding but non-covalent complexes are processed in the same way as covalent DNA-protein crosslinks (DPCs). Using 2D gel electrophoresis, we found that TBCs induced by M.EcoRII-C186A block replication forks in vivo. Specific bubble molecules were detected as spots on the 2D gel, only when M.EcoRII-C186A was induced, and a mutation that eliminates a specific EcoRII methylation site led to disappearance of the corresponding spot. We also performed a candidate gene screen for mutants that are hypersensitive to TBCs induced by M.EcoRII-C186A. We found several gene products necessary for protection against these TBCs that are known to also protect against DPCs induced with wild-type M.EcoRII (after 5-azacytidine incorporation): RecA, RecBC, RecG, RuvABC, UvrD, FtsK, XerCD and SsrA (tmRNA). In contrast, the RecFOR pathway and Rep helicase are needed for protection against TBCs but not DPCs induced by M.EcoRII. We propose that stalled fork processing by RecFOR and RecA promotes release of tightly bound (but non-covalent) blocking proteins, perhaps by licensing Rep helicase-driven dissociation of the blocking M.EcoRII-C186A. Our studies also argued against the involvement of several proteins that might be expected to protect against TBCs. We took the opportunity to directly compare the sensitivity of all tested mutants to two quinolone antibiotics, which target bacterial type II topoisomerases and induce a unique form of DPC. We uncovered rep, ftsK and xerCD as novel quinolone hypersensitive mutants, and also obtained evidence against the involvement of a number of functions that might be expected to protect against quinolones.
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22
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Krasich R, Wu SY, Kuo HK, Kreuzer KN. Functions that protect Escherichia coli from DNA-protein crosslinks. DNA Repair (Amst) 2015; 28:48-59. [PMID: 25731940 DOI: 10.1016/j.dnarep.2015.01.016] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2014] [Revised: 01/27/2015] [Accepted: 01/30/2015] [Indexed: 10/24/2022]
Abstract
Pathways for tolerating and repairing DNA-protein crosslinks (DPCs) are poorly defined. We used transposon mutagenesis and candidate gene approaches to identify DPC-hypersensitive Escherichia coli mutants. DPCs were induced by azacytidine (aza-C) treatment in cells overexpressing cytosine methyltransferase; hypersensitivity was verified to depend on methyltransferase expression. We isolated hypersensitive mutants that were uncovered in previous studies (recA, recBC, recG, and uvrD), hypersensitive mutants that apparently activate phage Mu Gam expression, and novel hypersensitive mutants in genes involved in DNA metabolism, cell division, and tRNA modification (dinG, ftsK, xerD, dnaJ, hflC, miaA, mnmE, mnmG, and ssrA). Inactivation of SbcCD, which can cleave DNA at protein-DNA complexes, did not cause hypersensitivity. We previously showed that tmRNA pathway defects cause aza-C hypersensitivity, implying that DPCs block coupled transcription/translation complexes. Here, we show that mutants in tRNA modification functions miaA, mnmE and mnmG cause defects in aza-C-induced tmRNA tagging, explaining their hypersensitivity. In order for tmRNA to access a stalled ribosome, the mRNA must be cleaved or released from RNA polymerase. Mutational inactivation of functions involved in mRNA processing and RNA polymerase elongation/release (RNase II, RNaseD, RNase PH, RNase LS, Rep, HepA, GreA, GreB) did not cause aza-C hypersensitivity; the mechanism of tmRNA access remains unclear.
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Affiliation(s)
- Rachel Krasich
- Department of Biochemistry, Duke University Medical Center, Durham NC 27710, United States
| | - Sunny Yang Wu
- Department of Biochemistry, Duke University Medical Center, Durham NC 27710, United States
| | - H Kenny Kuo
- Department of Biochemistry, Duke University Medical Center, Durham NC 27710, United States
| | - Kenneth N Kreuzer
- Department of Biochemistry, Duke University Medical Center, Durham NC 27710, United States.
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23
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Colin J, Candelli T, Porrua O, Boulay J, Zhu C, Lacroute F, Steinmetz LM, Libri D. Roadblock termination by reb1p restricts cryptic and readthrough transcription. Mol Cell 2015; 56:667-80. [PMID: 25479637 DOI: 10.1016/j.molcel.2014.10.026] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2014] [Revised: 06/09/2014] [Accepted: 10/29/2014] [Indexed: 02/09/2023]
Abstract
Widely transcribed compact genomes must cope with the major challenge of frequent overlapping or concurrent transcription events. Efficient and timely transcription termination is crucial to control pervasive transcription and prevent transcriptional interference. In yeast, transcription termination of RNA polymerase II (RNAPII) occurs via two possible pathways that both require recognition of termination signals on nascent RNA by specific factors. We describe here an additional mechanism of transcription termination for RNAPII and demonstrate its biological significance. We show that the transcriptional activator Reb1p bound to DNA is a roadblock for RNAPII, which pauses and is ubiquitinated, thus triggering termination. Reb1p-dependent termination generates a class of cryptic transcripts that are degraded in the nucleus by the exosome. We also observed transcriptional interference between neighboring genes in the absence of Reb1p. This work demonstrates the importance of roadblock termination for controlling pervasive transcription and preventing transcription through gene regulatory regions.
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Affiliation(s)
- Jessie Colin
- Centre de Génétique Moléculaire, CNRS UPR3404, 91190 Gif sur Yvette, France
| | - Tito Candelli
- Centre de Génétique Moléculaire, CNRS UPR3404, 91190 Gif sur Yvette, France
| | - Odil Porrua
- Centre de Génétique Moléculaire, CNRS UPR3404, 91190 Gif sur Yvette, France
| | - Jocelyne Boulay
- Centre de Génétique Moléculaire, CNRS UPR3404, 91190 Gif sur Yvette, France
| | - Chenchen Zhu
- European Molecular Biology Laboratory (EMBL), Genome Biology Unit, 69117 Heidelberg, Germany
| | - François Lacroute
- Centre de Génétique Moléculaire, CNRS UPR3404, 91190 Gif sur Yvette, France
| | - Lars M Steinmetz
- European Molecular Biology Laboratory (EMBL), Genome Biology Unit, 69117 Heidelberg, Germany; Department of Genetics, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Domenico Libri
- Centre de Génétique Moléculaire, CNRS UPR3404, 91190 Gif sur Yvette, France.
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24
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Kotlajich MV, Hron DR, Boudreau BA, Sun Z, Lyubchenko YL, Landick R. Bridged filaments of histone-like nucleoid structuring protein pause RNA polymerase and aid termination in bacteria. eLife 2015; 4. [PMID: 25594903 PMCID: PMC4337669 DOI: 10.7554/elife.04970] [Citation(s) in RCA: 98] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2014] [Accepted: 01/15/2015] [Indexed: 11/13/2022] Open
Abstract
Bacterial H-NS forms nucleoprotein filaments that spread on DNA and bridge distant DNA sites. H-NS filaments co-localize with sites of Rho-dependent termination in Escherichia coli, but their direct effects on transcriptional pausing and termination are untested. In this study, we report that bridged H-NS filaments strongly increase pausing by E. coli RNA polymerase at a subset of pause sites with high potential for backtracking. Bridged but not linear H-NS filaments promoted Rho-dependent termination by increasing pause dwell times and the kinetic window for Rho action. By observing single H-NS filaments and elongating RNA polymerase molecules using atomic force microscopy, we established that bridged filaments surround paused complexes. Our results favor a model in which H-NS-constrained changes in DNA supercoiling driven by transcription promote pausing at backtracking-susceptible sites. Our findings provide a mechanistic rationale for H-NS stimulation of Rho-dependent termination in horizontally transferred genes and during pervasive antisense and noncoding transcription in bacteria.
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Affiliation(s)
- Matthew V Kotlajich
- Department of Biochemistry, University of Wisconsin-Madison, Madison, United States
| | - Daniel R Hron
- Department of Biochemistry, University of Wisconsin-Madison, Madison, United States
| | - Beth A Boudreau
- Department of Biochemistry, University of Wisconsin-Madison, Madison, United States
| | - Zhiqiang Sun
- Department of Pharmaceutical Sciences, University of Nebraska Medical Center, Omaha, United States
| | - Yuri L Lyubchenko
- Department of Pharmaceutical Sciences, University of Nebraska Medical Center, Omaha, United States
| | - Robert Landick
- Department of Biochemistry, University of Wisconsin-Madison, Madison, United States
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25
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Rydenfelt M, Garcia HG, Cox RS, Phillips R. The influence of promoter architectures and regulatory motifs on gene expression in Escherichia coli. PLoS One 2014; 9:e114347. [PMID: 25549361 PMCID: PMC4280137 DOI: 10.1371/journal.pone.0114347] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2014] [Accepted: 11/02/2014] [Indexed: 12/31/2022] Open
Abstract
The ability to regulate gene expression is of central importance for the adaptability of living organisms to changes in their external and internal environment. At the transcriptional level, binding of transcription factors (TFs) in the promoter region can modulate the transcription rate, hence making TFs central players in gene regulation. For some model organisms, information about the locations and identities of discovered TF binding sites have been collected in continually updated databases, such as RegulonDB for the well-studied case of E. coli. In order to reveal the general principles behind the binding-site arrangement and function of these regulatory architectures we propose a random promoter architecture model that preserves the overall abundance of binding sites to identify overrepresented binding site configurations. This model is analogous to the random network model used in the study of genetic network motifs, where regulatory motifs are identified through their overrepresentation with respect to a “randomly connected” genetic network. Using our model we identify TF pairs which coregulate operons in an overrepresented fashion, or individual TFs which act at multiple binding sites per promoter by, for example, cooperative binding, DNA looping, or through multiple binding domains. We furthermore explore the relationship between promoter architecture and gene expression, using three different genome-wide protein copy number censuses. Perhaps surprisingly, we find no systematic correlation between the number of activator and repressor binding sites regulating a gene and the level of gene expression. A position-weight-matrix model used to estimate the binding affinity of RNA polymerase (RNAP) to the promoters of activated and repressed genes suggests that this lack of correlation might in part be due to differences in basal transcription levels, with repressed genes having a higher basal activity level. This quantitative catalogue relating promoter architecture and function provides a first step towards genome-wide predictive models of regulatory function.
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Affiliation(s)
- Mattias Rydenfelt
- Department of Physics, California Institute of Technology, Pasadena, CA, United States of America
- Integrative Research Institute for the Life Sciences and Institute for Theoretical Biology, Humboldt University, Berlin, Germany
| | - Hernan G. Garcia
- Joseph-Henry Laboratories of Physics, Princeton University, Princeton, NJ, United States of America
| | - Robert Sidney Cox
- Department of Chemical Science and Engineering, Kobe University, Kobe, Japan
| | - Rob Phillips
- Department of Applied Physics, California Institute of Technology, Pasadena, CA, United States of America
- Division of Biology, California Institute of Technology, Pasadena, CA, United States of America
- * E-mail:
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26
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Hao N, Krishna S, Ahlgren-Berg A, Cutts EE, Shearwin KE, Dodd IB. Road rules for traffic on DNA-systematic analysis of transcriptional roadblocking in vivo. Nucleic Acids Res 2014; 42:8861-72. [PMID: 25034688 PMCID: PMC4132739 DOI: 10.1093/nar/gku627] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Genomic DNA is bound by many proteins that could potentially impede elongation of RNA polymerase (RNAP), but the factors determining the magnitude of transcriptional roadblocking in vivo are poorly understood. Through systematic experiments and modeling, we analyse how roadblocking by the lac repressor (LacI) in Escherichia coli cells is controlled by promoter firing rate, the concentration and affinity of the roadblocker protein, the transcription-coupled repair protein Mfd, and promoter–roadblock spacing. Increased readthrough of the roadblock at higher RNAP fluxes requires active dislodgement of LacI by multiple RNAPs. However, this RNAP cooperation effect occurs only for strong promoters because roadblock-paused RNAP is quickly terminated by Mfd. The results are most consistent with a single RNAP also sometimes dislodging LacI, though we cannot exclude the possibility that a single RNAP reads through by waiting for spontaneous LacI dissociation. Reducing the occupancy of the roadblock site by increasing the LacI off-rate (weakening the operator) increased dislodgement strongly, giving a stronger effect on readthrough than decreasing the LacI on-rate (decreasing LacI concentration). Thus, protein binding kinetics can be tuned to maintain site occupation while reducing detrimental roadblocking.
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Affiliation(s)
- Nan Hao
- School of Molecular and Biomedical Sciences (Biochemistry), The University of Adelaide, Adelaide, SA 5005, Australia
| | - Sandeep Krishna
- Simons Centre for the Study of Living Machines, National Centre for Biological Sciences, Bangalore 560065, India
| | - Alexandra Ahlgren-Berg
- School of Molecular and Biomedical Sciences (Biochemistry), The University of Adelaide, Adelaide, SA 5005, Australia
| | - Erin E Cutts
- School of Molecular and Biomedical Sciences (Biochemistry), The University of Adelaide, Adelaide, SA 5005, Australia
| | - Keith E Shearwin
- School of Molecular and Biomedical Sciences (Biochemistry), The University of Adelaide, Adelaide, SA 5005, Australia
| | - Ian B Dodd
- School of Molecular and Biomedical Sciences (Biochemistry), The University of Adelaide, Adelaide, SA 5005, Australia
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27
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Sharma S, Gollnick P. Modulating TRAP-mediated transcription termination by AT during transcription of the leader region of the Bacillus subtilis trp operon. Nucleic Acids Res 2014; 42:5543-55. [PMID: 24682818 PMCID: PMC4027176 DOI: 10.1093/nar/gku211] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
An 11-subunit protein called trpRNA binding Attenuation Protein (TRAP) controls attenuation of the tryptophan biosynthetic (trpEDCFBA) operon in Bacillus subtilis. Tryptophan-activated TRAP binds to 11 (G/U)AG repeats in the 5′ leader region of trp mRNAs, and downregulates expression of the operon by promoting transcription termination prior to the structural genes. Anti-TRAP (AT) is an antagonist that binds to tryptophan-activated TRAP and prevents TRAP from binding to RNA, thereby upregulating expression of the trp genes. AT forms trimers, and multiple trimers bind to a TRAP 11mer. It is not known how many trimers must bind to TRAP in order to interfere with RNA binding. Studies of isolated TRAP and AT showed that AT can prevent TRAP from binding to the trp leader RNA but cannot dissociate a pre-formed TRAP-RNA complex. Here, we show that AT can prevent TRAP-mediated termination of transcription by inducing dissociation of TRAP from the nascent RNA when it has bound to fewer than all 11 (G/U)AG repeats. The 5′-most region of the TRAP binding site in the nascent transcript is most susceptible to dissociation from TRAP. We also show that one AT trimer bound to TRAP 11mer reduces the affinity of TRAP for RNA and eliminates TRAP-mediated transcription termination in vitro.
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Affiliation(s)
- Shraddha Sharma
- Department of Biological Sciences, University at Buffalo, The State University of New York, Buffalo, NY 14260, USA
| | - Paul Gollnick
- Department of Biological Sciences, University at Buffalo, The State University of New York, Buffalo, NY 14260, USA
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28
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Politz MC, Copeland MF, Pfleger BF. Artificial repressors for controlling gene expression in bacteria. Chem Commun (Camb) 2012; 49:4325-7. [PMID: 23230569 DOI: 10.1039/c2cc37107c] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Transcriptional repression is a common approach to control gene expression in synthetic biology applications. Here, an engineered DNA binding protein based upon a transcription activator-like effector (TALE) scaffold was shown to outperform LacI in blocking transcription from a promoter and to repress expression of a downstream gene in an operon.
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Affiliation(s)
- Mark C Politz
- University of Wisconsin-Madison, Department of Chemical and Biological Engineering, 3629 Engineering Hall, 1415 Engineering Dr Madison, WI, 53706, USA
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29
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Garcia HG, Sanchez A, Boedicker JQ, Osborne M, Gelles J, Kondev J, Phillips R. Operator sequence alters gene expression independently of transcription factor occupancy in bacteria. Cell Rep 2012; 2:150-61. [PMID: 22840405 DOI: 10.1016/j.celrep.2012.06.004] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2012] [Revised: 05/14/2012] [Accepted: 06/06/2012] [Indexed: 11/17/2022] Open
Abstract
A canonical quantitative view of transcriptional regulation holds that the only role of operator sequence is to set the probability of transcription factor binding, with operator occupancy determining the level of gene expression. In this work, we test this idea by characterizing repression in vivo and the binding of RNA polymerase in vitro in experiments where operators of various sequences were placed either upstream or downstream from the promoter in Escherichia coli. Surprisingly, we find that operators with a weaker binding affinity can yield higher repression levels than stronger operators. Repressor bound to upstream operators modulates promoter escape, and the magnitude of this modulation is not correlated with the repressor-operator binding affinity. This suggests that operator sequences may modulate transcription by altering the nature of the interaction of the bound transcription factor with the transcriptional machinery, implying a new layer of sequence dependence that must be confronted in the quantitative understanding of gene expression.
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Affiliation(s)
- Hernan G Garcia
- Department of Physics, California Institute of Technology, Pasadena, CA 91125, USA
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30
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Tate J, Gollnick P. Role of forward translocation in nucleoside triphosphate phosphohydrolase I (NPH I)-mediated transcription termination of vaccinia virus early genes. J Biol Chem 2011; 286:44764-75. [PMID: 22069335 PMCID: PMC3247973 DOI: 10.1074/jbc.m111.263822] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2011] [Revised: 10/28/2011] [Indexed: 01/04/2023] Open
Abstract
Termination of transcription of vaccinia virus early genes requires the virion form of the viral RNA polymerase (RNAP), a termination signal (UUUUUNU) in the nascent RNA, vaccinia termination factor, nucleoside triphosphate phosphohydrolase I (NPH I), and ATP. NPH I uses ATP hydrolysis to mediate transcript release, and in vitro, ATPase activity requires single-stranded DNA. NPH I shows sequence similarity with the DEXH-box family of proteins, which includes an Escherichia coli ATP-dependent motor protein, Mfd. Mfd releases transcripts and rescues arrested transcription complexes by moving the transcription elongation complex downstream on the DNA template in the absence of transcription elongation. This mechanism is known as forward translocation. In this study, we demonstrate that NPH I also uses forward translocation to catalyze transcript release from viral RNAP. Moreover, we show that NPH I-mediated release can occur at a stalled RNAP in the absence of vaccinia termination factor and U(5)NU when transcription elongation is prevented.
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Affiliation(s)
- Jessica Tate
- From the Department of Biological Sciences, University at Buffalo, Buffalo, New York 14226
| | - Paul Gollnick
- From the Department of Biological Sciences, University at Buffalo, Buffalo, New York 14226
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31
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Novel transcript truncating function of Rap1p revealed by synthetic codon-optimized Ty1 retrotransposon. Genetics 2011; 190:523-35. [PMID: 22135353 DOI: 10.1534/genetics.111.136648] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Extensive mutagenesis via massive recoding of retrotransposon Ty1 produced a synthetic codon-optimized retrotransposon (CO-Ty1). CO-Ty1 is defective for retrotransposition, suggesting a sequence capable of down-regulating retrotransposition. We mapped this sequence to a critical ~20-bp region within CO-Ty1 reverse transcriptase (RT) and confirmed that it reduced Ty1 transposition, protein, and RNA levels. Repression was not Ty1 specific; when introduced immediately downstream of the green fluorescent protein (GFP) stop codon, GFP expression was similarly reduced. Rap1p mediated this down-regulation, as shown by mutagenesis and chromatin immunoprecipitation. A regular threefold drop is observed in different contexts, suggesting utility for synthetic circuits. A large reduction of RNAP II occupancy on the CO-Ty1 construct was observed 3' to the identified Rap1p site and a novel 3' truncated RNA species was observed. We propose a novel mechanism of transcriptional regulation by Rap1p whereby it serves as a transcriptional roadblock when bound to transcription unit sequences.
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32
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Proshkin SA, Mironov AS. Regulation of bacterial transcription elongation. Mol Biol 2011. [DOI: 10.1134/s0026893311020154] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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33
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Potter KD, Merlino NM, Jacobs T, Gollnick P. TRAP binding to the Bacillus subtilis trp leader region RNA causes efficient transcription termination at a weak intrinsic terminator. Nucleic Acids Res 2010; 39:2092-102. [PMID: 21097886 PMCID: PMC3064811 DOI: 10.1093/nar/gkq965] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
The Bacillus subtilis trpEDCFBA operon is regulated by a transcription attenuation mechanism controlled by the trp RNA-binding attenuation protein (TRAP). TRAP binds to 11 (G/U)AG repeats in the trp leader transcript and prevents formation of an antiterminator, which allows formation of an intrinsic terminator (attenuator). Previously, formation of the attenuator RNA structure was believed to be solely responsible for signaling RNA polymerase (RNAP) to halt transcription. However, base substitutions that prevent formation of the antiterminator, and thus allow the attenuator structure to form constitutively, do not result in efficient transcription termination. The observation that the attenuator requires the presence of TRAP bound to the nascent RNA to cause efficient transcription termination suggests TRAP has an additional role in causing termination at the attenuator. We show that the trp attenuator is a weak intrinsic terminator due to low GC content of the hairpin stem and interruptions in the U-stretch following the hairpin. We also provide evidence that termination at the trp attenuator requires forward translocation of RNA polymerase and that TRAP binding to the nascent transcript can induce this activity.
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Affiliation(s)
- Kristine D Potter
- Department of Biological Sciences, University at Buffalo, the State University of New York, Buffalo, New York 14260, USA
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34
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Kuo HK, Krasich R, Bhagwat AS, Kreuzer KN. Importance of the tmRNA system for cell survival when transcription is blocked by DNA-protein cross-links. Mol Microbiol 2010; 78:686-700. [PMID: 20807197 DOI: 10.1111/j.1365-2958.2010.07355.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Anticancer drug 5-azacytidine (aza-C) induces DNA-protein cross-links (DPCs) between cytosine methyltransferase and DNA as the drug inhibits methylation. We found that mutants defective in the tmRNA translational quality control system are hypersensitive to aza-C. Hypersensitivity requires expression of active methyltransferase, indicating the importance of DPC formation. Furthermore, the tmRNA pathway is activated upon aza-C treatment in cells expressing methyltransferase, resulting in increased levels of SsrA tagged proteins. These results argue that the tmRNA pathway clears stalled ribosome-mRNA complexes generated after transcriptional blockage by aza-C-induced DPCs. In support, an ssrA mutant is also hypersensitive to streptolydigin, which blocks RNA polymerase elongation by a different mechanism. The tmRNA pathway is thought to act only on ribosomes containing a 3' RNA end near the A site, and the known pathway for releasing RNA 3' ends from a blocked polymerase involves Mfd helicase. However, an mfd knockout mutant is not hypersensitive to either aza-C-induced DPC formation or streptolydigin, indicating that Mfd is not involved. Transcription termination factor Rho is also likely not involved, because the Rho-specific inhibitor bicyclomycin failed to show synergism with either aza-C or streptolydigin. Based on these findings, we discuss models for how E. coli processes transcription/translation complexes blocked at DPCs.
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Affiliation(s)
- H Kenny Kuo
- Department of Biochemistry, Duke University Medical Center, Durham, NC 27710, USA
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35
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Hedglin M, O’Brien PJ. Hopping enables a DNA repair glycosylase to search both strands and bypass a bound protein. ACS Chem Biol 2010; 5:427-36. [PMID: 20201599 DOI: 10.1021/cb1000185] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Spontaneous DNA damage occurs throughout the genome, requiring that DNA repair enzymes search each nucleotide every cell cycle. This search is postulated to be more efficient if the enzyme can diffuse along the DNA, but our understanding of this process is incomplete. A key distinction between mechanisms of diffusion is whether the protein maintains continuous contact (sliding) or whether it undergoes microscopic dissociation (hopping). We describe a simple chemical assay to detect the ability of a DNA modifying enzyme to hop and have applied it to human alkyladenine DNA glycosylase (AAG), a monomeric enzyme that initiates repair of alkylated and deaminated purine bases. Our results indicate that AAG uses hopping to effectively search both strands of a DNA duplex in a single binding encounter. This raised the possibility that AAG might be capable of circumnavigating blocks such as tightly bound proteins. We tested this hypothesis by binding an EcoRI endonuclease dimer between two sites of DNA damage and measuring the ability of AAG to act at both damaged sites in a single binding encounter. Remarkably, AAG bypasses this roadblock in approximately 50% of the binding events. We infer that AAG makes significant excursions from the surface of the DNA, allowing reorientation between strands and the bypass of a bound protein. This has important biological implications for the search for DNA damage because eukaryotic DNA is replete with proteins and only transiently accessible.
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Affiliation(s)
| | - Patrick J. O’Brien
- Chemical Biology Program
- Department of Biological Chemistry, University of Michigan, Ann Arbor, Michigan 48109-5606
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36
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Kireeva M, Kashlev M, Burton ZF. Translocation by multi-subunit RNA polymerases. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2010; 1799:389-401. [PMID: 20097318 DOI: 10.1016/j.bbagrm.2010.01.007] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/28/2009] [Revised: 01/14/2010] [Accepted: 01/14/2010] [Indexed: 11/30/2022]
Abstract
DNA template and RNA/DNA hybrid movement through RNA polymerase (RNAP) is referred to as "translocation". Because nucleic acid movement is coupled to NTP loading, pyrophosphate release, and conformational changes, the precise ordering of events during bond addition is consequential. Moreover, based on several lines of experimental evidence, translocation, pyrophosphate release or an associated conformational change may determine the transcription elongation rate. In this review we discuss various models of translocation, the data supporting the hypothesis that translocation rate determines transcription elongation rate and also data that may be inconsistent with this point of view. A model of the nucleotide addition cycle accommodating available experimental data is proposed. On the basis of this model, the molecular mechanisms regulating translocation and potential routes for NTP entry are discussed.
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Affiliation(s)
- Maria Kireeva
- National Cancer Institute-Frederick, Frederick, MD 21702-1201, USA
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37
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Green NJ, Grundy FJ, Henkin TM. The T box mechanism: tRNA as a regulatory molecule. FEBS Lett 2009; 584:318-24. [PMID: 19932103 DOI: 10.1016/j.febslet.2009.11.056] [Citation(s) in RCA: 110] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2009] [Revised: 11/13/2009] [Accepted: 11/16/2009] [Indexed: 11/18/2022]
Abstract
The T box mechanism is widely used in Gram-positive bacteria to regulate expression of aminoacyl-tRNA synthetase genes and genes involved in amino acid biosynthesis and uptake. Binding of a specific uncharged tRNA to a riboswitch element in the nascent transcript causes a structural change in the transcript that promotes expression of the downstream coding sequence. In most cases, this occurs by stabilization of an antiterminator element that competes with formation of a terminator helix. Specific tRNA recognition by the nascent transcript results in increased expression of genes important for tRNA aminoacylation in response to decreased pools of charged tRNA.
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Affiliation(s)
- Nicholas J Green
- Department of Microbiology, Center for RNA Biology, The Ohio State University, Columbus, OH 43210, USA
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38
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Stepanova EV, Shevelev AB, Borukhov SI, Severinov KV. Mechanisms of action of RNA polymerase-binding transcription factors that do not bind to DNA. Biophysics (Nagoya-shi) 2009. [DOI: 10.1134/s0006350909050017] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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39
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Ma N, McAllister WT. In a head-on collision, two RNA polymerases approaching one another on the same DNA may pass by one another. J Mol Biol 2009; 391:808-12. [PMID: 19576223 DOI: 10.1016/j.jmb.2009.06.060] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2009] [Revised: 06/16/2009] [Accepted: 06/23/2009] [Indexed: 11/28/2022]
Abstract
Using a template that contains promoters for T3 and T7 RNA polymerases (RNAPs) in opposing orientations, and His-tagged derivatives of these RNAPs that allow immobilization on solid matrices, we have determined that a T7 elongation complex (EC) may be advanced past a halted T3 EC, and that after the collision the halted T3 EC may resume transcription. Since RNAPs moving in opposite directions use two different strands of the DNA as their templates, it seems likely that they manage to pass by one other by temporarily releasing their nontemplate strand while maintaining association with their template strand.
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Affiliation(s)
- Na Ma
- Department of Microbiology and Immunology, SUNY Downstate Medical Center, Brooklyn, NY 11203, USA
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40
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Stuchinskaya T, Mitchenall LA, Schoeffler AJ, Corbett KD, Berger JM, Bates AD, Maxwell A. How do type II topoisomerases use ATP hydrolysis to simplify DNA topology beyond equilibrium? Investigating the relaxation reaction of nonsupercoiling type II topoisomerases. J Mol Biol 2008; 385:1397-408. [PMID: 19094994 DOI: 10.1016/j.jmb.2008.11.056] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2008] [Revised: 11/19/2008] [Accepted: 11/23/2008] [Indexed: 11/16/2022]
Abstract
DNA topoisomerases control the topology of DNA (e.g., the level of supercoiling) in all cells. Type IIA topoisomerases are ATP-dependent enzymes that have been shown to simplify the topology of their DNA substrates to a level beyond that expected at equilibrium (i.e., more relaxed than the product of relaxation by ATP-independent enzymes, such as type I topoisomerases, or a lower-than-equilibrium level of catenation). The mechanism of this effect is currently unknown, although several models have been suggested. We have analyzed the DNA relaxation reactions of type II topoisomerases to further explore this phenomenon. We find that all type IIA topoisomerases tested exhibit the effect to a similar degree and that it is not dependent on the supercoil-sensing C-terminal domains of the enzymes. As recently reported, the type IIB topoisomerase, topoisomerase VI (which is only distantly related to type IIA enzymes), does not exhibit topology simplification. We find that topology simplification is not significantly dependent on circle size in the range approximately 2-9 kbp and is not altered by reducing the free energy available from ATP hydrolysis by varying the ADP:ATP ratio. A direct test of one model (DNA tracking; i.e., sliding of a protein clamp along DNA to trap supercoils) suggests that this is unlikely to be the explanation for the effect. We conclude that geometric selection of DNA segments by the enzymes is likely to be a primary source of the effect, but that it is possible that other kinetic factors contribute. We also speculate whether topology simplification might simply be an evolutionary relic, with no adaptive significance.
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Affiliation(s)
- Tanya Stuchinskaya
- Department of Biological Chemistry, John Innes Centre, Colney, Norwich, UK
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41
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Conant CR, Goodarzi JP, Weitzel SE, von Hippel PH. The antitermination activity of bacteriophage lambda N protein is controlled by the kinetics of an RNA-looping-facilitated interaction with the transcription complex. J Mol Biol 2008; 384:87-108. [PMID: 18922547 PMCID: PMC2590625 DOI: 10.1016/j.jmb.2008.05.014] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2007] [Revised: 05/07/2008] [Accepted: 05/08/2008] [Indexed: 10/22/2022]
Abstract
Protein N of bacteriophage lambda activates the lytic phase of phage development in infected Escherichia coli cells by suppressing the activity of transcriptional terminators that prevent the synthesis of essential phage proteins. N binds tightly to the boxB RNA hairpin located near the 5' end of the nascent pL and pR transcripts and induces an antitermination response in the RNA polymerase (RNAP) of elongation complexes located at terminators far downstream. Here we test an RNA looping model for this N-dependent "action at a distance" by cleaving the nascent transcript between boxB and RNAP during transcript elongation. Cleavage decreases antitermination, showing that an intact RNA transcript is required to stabilize the interaction of boxB-bound N with RNAP during transcription. In contrast, an antitermination complex that also contains Nus factors retains N-dependent activity after transcript cleavage, suggesting that these host factors further stabilize the N-RNAP interaction. Thus, the binding of N alone to RNAP is controlled by an RNA looping equilibrium, but after formation of the initial RNA loop and in the presence of Nus factors the system no longer equilibrates on the transcription time scale, meaning that the "range" of antitermination activity along the template in the full antitermination system is kinetically controlled by the dissociation rate of the stabilized N-RNAP complex. Theoretical calculations of nucleic acid end-to-end contact probabilities are used to estimate the local concentrations of boxB-bound N at elongation complexes poised at terminators, and are combined with N activity measurements at various boxB-to-terminator distances to obtain an intrinsic affinity (K(d)) of approximately 2 x 10(-5) M for the N-RNAP interaction. This RNA looping approach is extended to include the effects of N binding at nonspecific RNA sites on the transcript and the implications for transcription control in other regulatory systems are discussed.
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Affiliation(s)
| | - Jim P. Goodarzi
- Institute of Molecular Biology and Department of Chemistry, University of Oregon, Eugene, OR 97403
| | - Steven E. Weitzel
- Institute of Molecular Biology and Department of Chemistry, University of Oregon, Eugene, OR 97403
| | - Peter H. von Hippel
- Institute of Molecular Biology and Department of Chemistry, University of Oregon, Eugene, OR 97403
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42
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Dimitri A, Burns JA, Broyde S, Scicchitano DA. Transcription elongation past O6-methylguanine by human RNA polymerase II and bacteriophage T7 RNA polymerase. Nucleic Acids Res 2008; 36:6459-71. [PMID: 18854351 PMCID: PMC2582612 DOI: 10.1093/nar/gkn657] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
O6-Methylguanine (O6-meG) is a major mutagenic, carcinogenic and cytotoxic DNA adduct produced by various endogenous and exogenous methylating agents. We report the results of transcription past a site-specifically modified O6-meG DNA template by bacteriophage T7 RNA polymerase and human RNA polymerase II. These data show that O6-meG partially blocks T7 RNA polymerase and human RNA polymerase II elongation. In both cases, the sequences of the truncated transcripts indicate that both polymerases stop precisely at the damaged site without nucleotide incorporation opposite the lesion, while extensive misincorporation of uracil is observed in the full-length RNA. For both polymerases, computer models suggest that bypass occurs only when O6-meG adopts an anti conformation around its glycosidic bond, with the methyl group in the proximal orientation; in contrast, blockage requires the methyl group to adopt a distal conformation. Furthermore, the selection of cytosine and uracil partners opposite O6-meG is rationalized with modeled hydrogen-bonding patterns that agree with experimentally observed O6-meG:C and O6-meG:U pairing schemes. Thus, in vitro, O6-meG contributes substantially to transcriptional mutagenesis. In addition, the partial blockage of RNA polymerase II suggests that transcription-coupled DNA repair could play an auxiliary role in the clearance of this lesion.
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Affiliation(s)
- Alexandra Dimitri
- Department of Biology, New York University, 1009 Silver Center, 100 Washington Square East, New York, NY 10003, USA
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43
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Dynamical analysis on gene activity in the presence of repressors and an interfering promoter. Biophys J 2008; 95:4228-40. [PMID: 18658208 DOI: 10.1529/biophysj.108.132894] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Transcription is regulated through interplay among transcription factors, an RNA polymerase (RNAP), and a promoter. Even for a simple repressive transcription factor that disturbs promoter activity at initial binding of RNAP, its repression level is not determined solely by the dissociation constant of transcription factor but is sensitive to timescales of processes in RNAP. We first analyze the promoter activity under strong repression by a slow binding repressor, in which case transcription events occur in bursts, followed by long quiescent periods while a repressor binds to the operator; the number of transcription events, bursting, and quiescent times are estimated by reaction rates. We then examine interference effect from an opposing promoter, using the correlation function of initiation events for a single promoter. The interference is shown to de-repress the promoter because RNAPs from the opposing promoter most likely encounter the repressor and remove it in case of strong repression. This de-repression mechanism should be especially prominent for the promoters that facilitate fast formation of open complex with the repressor whose binding rate is slower than approximately 1/s. Finally, we discuss possibility of this mechanism for high activity of promoter PR in the hyp-mutant of lambda-phage.
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44
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DNA looping can enhance lysogenic CI transcription in phage lambda. Proc Natl Acad Sci U S A 2008; 105:5827-32. [PMID: 18391225 DOI: 10.1073/pnas.0705570105] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The lysogenic state of bacteriophage lambda is maintained by CI repressor, which negatively regulates two promoters to block lytic gene expression. Expression of CI is itself controlled by positive and negative feedback as CI binds to O(R) to regulate the P(RM) promoter. In addition to direct interactions with operator DNA, CI tetramers bound at O(L) and O(R) can come together to form an octamer, looping the DNA that lies between them and allowing O(L) to assist with negative regulation of P(RM). We used a fluorescent reporter protein to measure the CI concentration for a set of constructs that differ in their ability to assume various forms of the looped structure. Based on the observed steady-state fluorescence for these constructs, the presence of O(L) increases P(RM) activation unless both operators can be fully occupied. By calculating the probabilities for the underlying operator configurations present in each construct, two different models for the mechanism of enhanced activation allow us to predict that when the DNA is looped, P(RM) activation can be 2- to 4-fold higher than is possible for unlooped DNA. Based on our results, transcriptional regulation for lambda's lysogenic/lytic switch includes both activation and repression due to DNA looping.
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45
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Shankar S, Hatoum A, Roberts JW. A transcription antiterminator constructs a NusA-dependent shield to the emerging transcript. Mol Cell 2007; 27:914-27. [PMID: 17889665 PMCID: PMC2075354 DOI: 10.1016/j.molcel.2007.07.025] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2007] [Revised: 06/15/2007] [Accepted: 07/24/2007] [Indexed: 10/22/2022]
Abstract
The universal bacterial transcription elongation factor NusA mediates elongation activities of RNA polymerase. By itself, NusA induces transcription pausing and facilitates intrinsic termination, but NusA also is a cofactor of antiterminators that antagonize pausing and prevent termination. We show that NusA is required for lambda-related phage 82 antiterminator Q(82) to construct a stable complex in which RNA-based termination mechanisms have restricted access to the emerging transcript; this result suggests a locale for both Q(82) and NusA near the beta flap domain of RNA polymerase. Furthermore, as NusA is not required for the antipausing activity of Q(82) in vitro, we distinguish two distinct activities of antiterminators, namely antipausing and RNA occlusion, and discuss their roles in Q(82) function.
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Affiliation(s)
- Smita Shankar
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
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46
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Degnan PH, Michalowski CB, Babić AC, Cordes MHJ, Little JW. Conservation and diversity in the immunity regions of wild phages with the immunity specificity of phage lambda. Mol Microbiol 2007; 64:232-44. [PMID: 17376085 DOI: 10.1111/j.1365-2958.2007.05650.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
The gene regulatory circuitry of phage lambda is among the best-understood circuits. Much of the circuitry centres around the immunity region, which includes genes for two repressors, CI and Cro, and their cis-acting sites. Related phages, termed lambdoid phages, have different immunity regions, but similar regulatory circuitry and genome organization to that of lambda, and show a mosaic organization, arising by recombination between lambdoid phages. We sequenced the immunity regions of several wild phages with the immunity specificity of lambda, both to determine whether natural variation exists in regulation, and to analyse conservation and variability in a region rich in well-studied regulatory elements. CI, Cro and their cis-acting sites are almost identical to those in lambda, implying that regulatory mechanisms controlled by the immunity region are conserved. A segment adjacent to one of the operator regions is also conserved, and may be a novel regulatory element. In most isolates, different alleles of two regulatory proteins (N and CII) flank the immunity region; possibly the lysis-lysogeny decision is more variable among isolates. Extensive mosaicism was observed for several elements flanking the immunity region. Very short sequence elements or microhomologies were also identified. Our findings suggest mechanisms by which fine-scale mosaicism arises.
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Affiliation(s)
- Patrick H Degnan
- Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ 85721, USA
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47
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Bondarenko VA, Steele LM, Ujvári A, Gaykalova DA, Kulaeva OI, Polikanov YS, Luse DS, Studitsky VM. Nucleosomes can form a polar barrier to transcript elongation by RNA polymerase II. Mol Cell 2006; 24:469-79. [PMID: 17081995 DOI: 10.1016/j.molcel.2006.09.009] [Citation(s) in RCA: 208] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2006] [Revised: 07/05/2006] [Accepted: 09/20/2006] [Indexed: 11/25/2022]
Abstract
Nucleosomes uniquely positioned on high-affinity DNA sequences present a polar barrier to transcription by human and yeast RNA polymerase II (Pol II). In one transcriptional orientation, these nucleosomes provide a strong, factor- and salt-insensitive barrier at the entry into the H3/H4 tetramer that can be recapitulated without H2A/H2B dimers. The same nucleosomes transcribed in the opposite orientation form a weaker, more diffuse barrier that is largely relieved by higher salt, TFIIS, or FACT. Barrier properties are therefore dictated by both the local nucleosome structure (influenced by the strength of the histone-DNA interactions) and the location of the high-affinity DNA region within the nucleosome. Pol II transcribes DNA sequences at the entry into the tetramer much less efficiently than the same sequences located distal to the nucleosome dyad. Thus, entry into the tetramer by Pol II facilitates further transcription, perhaps due to partial unfolding of the tetramer from DNA.
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Affiliation(s)
- Vladimir A Bondarenko
- Department of Pharmacology, University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, 675 Hoes Lane, Room 405, Piscataway, New Jersey 08854, USA
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Sastry SS, Spielmann HP, Hearst JE. Psoralens and their application to the study of some molecular biological processes. ADVANCES IN ENZYMOLOGY AND RELATED AREAS OF MOLECULAR BIOLOGY 2006; 66:85-148. [PMID: 8430517 DOI: 10.1002/9780470123126.ch3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Affiliation(s)
- S S Sastry
- Department of Chemistry, University of California, Lawrence Berkeley Laboratory, Berkeley
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Liu GL, Yin Y, Kunchakarra S, Mukherjee B, Gerion D, Jett SD, Bear DG, Gray JW, Alivisatos AP, Lee LP, Chen FF. A nanoplasmonic molecular ruler for measuring nuclease activity and DNA footprinting. NATURE NANOTECHNOLOGY 2006; 1:47-52. [PMID: 18654141 DOI: 10.1038/nnano.2006.51] [Citation(s) in RCA: 180] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/18/2006] [Accepted: 08/29/2006] [Indexed: 05/26/2023]
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Crampton N, Bonass WA, Kirkham J, Rivetti C, Thomson NH. Collision events between RNA polymerases in convergent transcription studied by atomic force microscopy. Nucleic Acids Res 2006; 34:5416-25. [PMID: 17012275 PMCID: PMC1636470 DOI: 10.1093/nar/gkl668] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2006] [Revised: 07/14/2006] [Accepted: 08/30/2006] [Indexed: 12/01/2022] Open
Abstract
Atomic force microscopy (AFM) has been used to image, at single molecule resolution, transcription events by Escherichia coli RNA polymerase (RNAP) on a linear DNA template with two convergently aligned lambda(pr) promoters. For the first time experimentally, the outcome of collision events during convergent transcription by two identical RNAP has been studied. Measurement of the positions of the RNAP on the DNA, allows distinction of open promoter complexes (OPCs) and elongating complexes (EC) and collided complexes (CC). This discontinuous time-course enables subsequent analysis of collision events where both RNAP remain bound on the DNA. After collision, the elongating RNAP has caused the other (usually stalled) RNAP to back-track along the template. The final positions of the two RNAP indicate that these are collisions between an EC and a stalled EC (SEC) or OPC (previously referred to as sitting-ducks). Interestingly, the distances between the two RNAP show that they are not always at closest approach after 'collision' has caused their arrest.
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Affiliation(s)
- Neal Crampton
- Department of Oral Biology, University of LeedsLeeds LS2 9LU, UK
- Institute of Molecular Biophysics, School of Physics and Astronomy, University of LeedsLeeds LS2 9JT, UK
| | | | - Jennifer Kirkham
- Department of Oral Biology, University of LeedsLeeds LS2 9LU, UK
| | - Claudio Rivetti
- Department of Biochemistry and Molecular Biology, University of Parma43100 Parma, Italy
| | - Neil H. Thomson
- Department of Oral Biology, University of LeedsLeeds LS2 9LU, UK
- Institute of Molecular Biophysics, School of Physics and Astronomy, University of LeedsLeeds LS2 9JT, UK
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