1
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Hong Y, Ye F, Qian J, Gao X, Inman JT, Wang MD. Optical torque calculations and measurements for DNA torsional studies. Biophys J 2024:S0006-3495(24)00444-2. [PMID: 38961622 DOI: 10.1016/j.bpj.2024.07.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2023] [Revised: 05/20/2024] [Accepted: 07/01/2024] [Indexed: 07/05/2024] Open
Abstract
The angular optical trap (AOT) is a powerful instrument for measuring the torsional and rotational properties of a biological molecule. Thus far, AOT studies of DNA torsional mechanics have been carried out using a high numerical aperture oil-immersion objective, which permits strong trapping but inevitably introduces spherical aberrations due to the glass-aqueous interface. However, the impact of these aberrations on torque measurements is not fully understood experimentally, partly due to a lack of theoretical guidance. Here, we present a numerical platform based on the finite element method to calculate forces and torques on a trapped quartz cylinder. We have also developed a new experimental method to accurately determine the shift in the trapping position due to the spherical aberrations by using a DNA molecule as a distance ruler. We found that the calculated and measured focal shift ratios are in good agreement. We further determined how the angular trap stiffness depends on the trap height and the cylinder displacement from the trap center and found full agreement between predictions and measurements. As a further verification of the methodology, we showed that DNA torsional properties, which are intrinsic to DNA, could be determined robustly under different trap heights and cylinder displacements. Thus, this work has laid both a theoretical and experimental framework that can be readily extended to investigate the trapping forces and torques exerted on particles with arbitrary shapes and optical properties.
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Affiliation(s)
- Yifeng Hong
- Department of Electrical and Computer Engineering, Cornell University, Ithaca, New York
| | - Fan Ye
- Howard Hughes Medical Institute, Cornell University, Ithaca, New York; Department of Physics & LASSP, Cornell University, Ithaca, New York
| | - Jin Qian
- Department of Physics & LASSP, Cornell University, Ithaca, New York
| | - Xiang Gao
- Howard Hughes Medical Institute, Cornell University, Ithaca, New York; Department of Physics & LASSP, Cornell University, Ithaca, New York
| | - James T Inman
- Howard Hughes Medical Institute, Cornell University, Ithaca, New York; Department of Physics & LASSP, Cornell University, Ithaca, New York
| | - Michelle D Wang
- Howard Hughes Medical Institute, Cornell University, Ithaca, New York; Department of Physics & LASSP, Cornell University, Ithaca, New York.
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2
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Hustmyer CM, Landick R. Bacterial chromatin proteins, transcription, and DNA topology: Inseparable partners in the control of gene expression. Mol Microbiol 2024; 122:81-112. [PMID: 38847475 PMCID: PMC11260248 DOI: 10.1111/mmi.15283] [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: 01/11/2024] [Revised: 05/10/2024] [Accepted: 05/13/2024] [Indexed: 06/15/2024]
Abstract
DNA in bacterial chromosomes is organized into higher-order structures by DNA-binding proteins called nucleoid-associated proteins (NAPs) or bacterial chromatin proteins (BCPs). BCPs often bind to or near DNA loci transcribed by RNA polymerase (RNAP) and can either increase or decrease gene expression. To understand the mechanisms by which BCPs alter transcription, one must consider both steric effects and the topological forces that arise when DNA deviates from its fully relaxed double-helical structure. Transcribing RNAP creates DNA negative (-) supercoils upstream and positive (+) supercoils downstream whenever RNAP and DNA are unable to rotate freely. This (-) and (+) supercoiling generates topological forces that resist forward translocation of DNA through RNAP unless the supercoiling is constrained by BCPs or relieved by topoisomerases. BCPs also may enhance topological stress and overall can either inhibit or aid transcription. Here, we review current understanding of how RNAP, BCPs, and DNA topology interplay to control gene expression.
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Affiliation(s)
| | - Robert Landick
- Department of Biochemistry, University of Wisconsin-Madison
- Department of Bacteriology, University of Wisconsin-Madison
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3
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Hong Y, Ye F, Qian J, Gao X, Inman JT, Wang MD. Optical Torque Calculations and Measurements for DNA Torsional Studies. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.05.29.596477. [PMID: 38853956 PMCID: PMC11160753 DOI: 10.1101/2024.05.29.596477] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2024]
Abstract
The angular optical trap (AOT) is a powerful instrument for measuring the torsional and rotational properties of a biological molecule. Thus far, AOT studies of DNA torsional mechanics have been carried out using a high numerical aperture oil-immersion objective, which permits strong trapping, but inevitably introduces spherical aberrations due to the glass-aqueous interface. However, the impact of these aberrations on torque measurements is not fully understood experimentally, partly due to a lack of theoretical guidance. Here, we present a numerical platform based on the finite element method to calculate forces and torques on a trapped quartz cylinder. We have also developed a new experimental method to accurately determine the shift in the trapping position due to the spherical aberrations by using a DNA molecule as a distance ruler. We found that the calculated and measured focal shift ratios are in good agreement. We further determined how the angular trap stiffness depends on the trap height and the cylinder displacement from the trap center and found full agreement between predictions and measurements. As further verification of the methodology, we showed that DNA torsional properties, which are intrinsic to DNA, could be determined robustly under different trap heights and cylinder displacements. Thus, this work has laid both a theoretical and experimental framework that can be readily extended to investigate the trapping forces and torques exerted on particles with arbitrary shapes and optical properties. SIGNIFICANCE We developed a simulation platform based on the finite element method for force and torque calculation for particles in an angular optical trap (AOT), with considerations of tightly focused Gaussian beam, spherical aberrations, and optically anisotropic particles. Experimental measurements of focal shift ratio, force, and torque under multiple conditions were in good agreement with predictions from the simulations. We also demonstrated that intrinsic DNA torsional properties can be robustly measured under different AOT measurement conditions, strongly validating our simulations and calibrations. Our platform can facilitate trapping particle design for single-molecule assays using the AOT.
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4
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Fukute J, Maki K, Adachi T. The nucleolar shell provides anchoring sites for DNA untwisting. Commun Biol 2024; 7:83. [PMID: 38263258 PMCID: PMC10805735 DOI: 10.1038/s42003-023-05750-w] [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: 08/18/2023] [Accepted: 12/28/2023] [Indexed: 01/25/2024] Open
Abstract
DNA underwinding (untwisting) is a crucial step in transcriptional activation. DNA underwinding occurs between the site where torque is generated by RNA polymerase (RNAP) and the site where the axial rotation of DNA is constrained. However, what constrains DNA axial rotation in the nucleus is yet unknown. Here, we show that the anchorage to the nuclear protein condensates constrains DNA axial rotation for DNA underwinding in the nucleolus. In situ super-resolution imaging of underwound DNA reveal that underwound DNA accumulates in the nucleolus, a nuclear condensate with a core-shell structure. Specifically, underwound DNA is distributed in the nucleolar core owing to RNA polymerase I (RNAPI) activities. Furthermore, underwound DNA in the core decreases when nucleolar shell components are prevented from binding to their recognition structure, G-quadruplex (G4). Taken together, these results suggest that the nucleolar shell provides anchoring sites that constrain DNA axial rotation for RNAPI-driven DNA underwinding in the core. Our findings will contribute to understanding how nuclear protein condensates make up constraints for the site-specific regulation of DNA underwinding and transcription.
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Affiliation(s)
- Jumpei Fukute
- Laboratory of Cellular and Molecular Biomechanics, Department of Mammalian Regulatory Network, Graduate School of Biostudies, Kyoto University, Sakyo, Kyoto, Japan
- Laboratory of Biomechanics, Institute for Life and Medical Sciences, Kyoto University, Sakyo, Kyoto, Japan
| | - Koichiro Maki
- Laboratory of Cellular and Molecular Biomechanics, Department of Mammalian Regulatory Network, Graduate School of Biostudies, Kyoto University, Sakyo, Kyoto, Japan.
- Laboratory of Biomechanics, Institute for Life and Medical Sciences, Kyoto University, Sakyo, Kyoto, Japan.
- Department of Micro Engineering, Graduate School of Engineering, Kyoto University, Sakyo, Kyoto, Japan.
- Department of Medicine and Medical Science, Graduate School of Medicine, Kyoto University, Sakyo, Kyoto, Japan.
| | - Taiji Adachi
- Laboratory of Cellular and Molecular Biomechanics, Department of Mammalian Regulatory Network, Graduate School of Biostudies, Kyoto University, Sakyo, Kyoto, Japan
- Laboratory of Biomechanics, Institute for Life and Medical Sciences, Kyoto University, Sakyo, Kyoto, Japan
- Department of Micro Engineering, Graduate School of Engineering, Kyoto University, Sakyo, Kyoto, Japan
- Department of Medicine and Medical Science, Graduate School of Medicine, Kyoto University, Sakyo, Kyoto, Japan
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5
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Zou Z, Liang J, Jia Q, Bai D, Xie W, Wu W, Tan C, Ma J. A versatile and high-throughput flow-cell system combined with fluorescence imaging for simultaneous single-molecule force measurement and visualization. NANOSCALE 2023; 15:17443-17454. [PMID: 37859523 DOI: 10.1039/d3nr03214k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/21/2023]
Abstract
A flow-cell offers many advantages for single-molecule studies. But, its merit as a quantitative single-molecule tool has long been underestimated. In this work, we developed a gas-pumped fully calibrated flow-cell system combined with fluorescence imaging for simultaneous single-molecule force measurement and visualization. Such a flow-cell system has considered the hydrodynamic drags on biomolecules and hence can apply and measure force up to more than 100 pN in sub-pN precision with an ultra-high force stability (force drift <0.01 pN in 10 minutes) and tuning accuracy (∼0.04 pN). Meanwhile, it also allows acquiring force signals and fluorescence images at the same time, parallelly tracking hundreds of protein motors in real time as well as monitoring the conformational changes of biomolecules under a well-controlled force, as demonstrated by a series of single-molecule experiments in this work, including the studies of DNA overstretching dynamics, transcription under force and DNA folding/unfolding dynamics. Interesting findings, such as the very tight association of single-stranded binding (SSB) proteins with ssDNA and the reversed transcription, have also been made. These results together lay down an essential foundation for a flow-cell to be used as a versatile, quantitative and high-throughput tool for single-molecule manipulation and visualization.
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Affiliation(s)
- Zhenyu Zou
- School of Physics, Sun Yat-sen University, Guangzhou 510275, P.R. China.
- State Key Laboratory of Optoelectronic Materials and Technologies, Sun Yat-sen University, Guangzhou 510275, P.R. China
| | - Jialun Liang
- School of Physics, Sun Yat-sen University, Guangzhou 510275, P.R. China.
- State Key Laboratory of Optoelectronic Materials and Technologies, Sun Yat-sen University, Guangzhou 510275, P.R. China
| | - Qian Jia
- MOE Key Laboratory of Gene Function and Regulation, State Key Laboratory for Biocontrol, School of Life Sciences, Sun Yat-Sen University, Guangzhou, Guangdong, 510006, P.R. China
| | - Di Bai
- School of Life Sciences, State Key Laboratory of Crop Stress Adaptation and Improvement, Henan University, Kaifeng 475001, P.R. China
| | - Wei Xie
- MOE Key Laboratory of Gene Function and Regulation, State Key Laboratory for Biocontrol, School of Life Sciences, Sun Yat-Sen University, Guangzhou, Guangdong, 510006, P.R. China
| | - Wenqiang Wu
- School of Life Sciences, State Key Laboratory of Crop Stress Adaptation and Improvement, Henan University, Kaifeng 475001, P.R. China
| | - Chuang Tan
- School of Physics, Sun Yat-sen University, Guangzhou 510275, P.R. China.
- State Key Laboratory of Optoelectronic Materials and Technologies, Sun Yat-sen University, Guangzhou 510275, P.R. China
| | - Jie Ma
- School of Physics, Sun Yat-sen University, Guangzhou 510275, P.R. China.
- State Key Laboratory of Optoelectronic Materials and Technologies, Sun Yat-sen University, Guangzhou 510275, P.R. China
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6
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Junier I, Ghobadpour E, Espeli O, Everaers R. DNA supercoiling in bacteria: state of play and challenges from a viewpoint of physics based modeling. Front Microbiol 2023; 14:1192831. [PMID: 37965550 PMCID: PMC10642903 DOI: 10.3389/fmicb.2023.1192831] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2023] [Accepted: 09/25/2023] [Indexed: 11/16/2023] Open
Abstract
DNA supercoiling is central to many fundamental processes of living organisms. Its average level along the chromosome and over time reflects the dynamic equilibrium of opposite activities of topoisomerases, which are required to relax mechanical stresses that are inevitably produced during DNA replication and gene transcription. Supercoiling affects all scales of the spatio-temporal organization of bacterial DNA, from the base pair to the large scale chromosome conformation. Highlighted in vitro and in vivo in the 1960s and 1970s, respectively, the first physical models were proposed concomitantly in order to predict the deformation properties of the double helix. About fifteen years later, polymer physics models demonstrated on larger scales the plectonemic nature and the tree-like organization of supercoiled DNA. Since then, many works have tried to establish a better understanding of the multiple structuring and physiological properties of bacterial DNA in thermodynamic equilibrium and far from equilibrium. The purpose of this essay is to address upcoming challenges by thoroughly exploring the relevance, predictive capacity, and limitations of current physical models, with a specific focus on structural properties beyond the scale of the double helix. We discuss more particularly the problem of DNA conformations, the interplay between DNA supercoiling with gene transcription and DNA replication, its role on nucleoid formation and, finally, the problem of scaling up models. Our primary objective is to foster increased collaboration between physicists and biologists. To achieve this, we have reduced the respective jargon to a minimum and we provide some explanatory background material for the two communities.
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Affiliation(s)
- Ivan Junier
- CNRS, UMR 5525, VetAgro Sup, Grenoble INP, TIMC, Université Grenoble Alpes, Grenoble, France
| | - Elham Ghobadpour
- CNRS, UMR 5525, VetAgro Sup, Grenoble INP, TIMC, Université Grenoble Alpes, Grenoble, France
- École Normale Supérieure (ENS) de Lyon, CNRS, Laboratoire de Physique and Centre Blaise Pascal de l'ENS de Lyon, Lyon, France
| | - Olivier Espeli
- Center for Interdisciplinary Research in Biology (CIRB), Collège de France, CNRS, INSERM, Université PSL, Paris, France
| | - Ralf Everaers
- École Normale Supérieure (ENS) de Lyon, CNRS, Laboratoire de Physique and Centre Blaise Pascal de l'ENS de Lyon, Lyon, France
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7
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Lee J, Wu M, Inman JT, Singh G, Park SH, Lee JH, Fulbright RM, Hong Y, Jeong J, Berger JM, Wang MD. Chromatinization modulates topoisomerase II processivity. Nat Commun 2023; 14:6844. [PMID: 37891161 PMCID: PMC10611788 DOI: 10.1038/s41467-023-42600-z] [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: 02/12/2023] [Accepted: 10/17/2023] [Indexed: 10/29/2023] Open
Abstract
Type IIA topoisomerases are essential DNA processing enzymes that must robustly and reliably relax DNA torsional stress. While cellular processes constantly create varying torsional stress, how this variation impacts type IIA topoisomerase function remains obscure. Using multiple single-molecule approaches, we examined the torsional dependence of eukaryotic topoisomerase II (topo II) activity on naked DNA and chromatin. We observed that topo II is ~50-fold more processive on buckled DNA than previously estimated. We further discovered that topo II relaxes supercoiled DNA prior to plectoneme formation, but with processivity reduced by ~100-fold. This relaxation decreases with diminishing torsion, consistent with topo II capturing transient DNA loops. Topo II retains high processivity on buckled chromatin (~10,000 turns) and becomes highly processive even on chromatin under low torsional stress (~1000 turns), consistent with chromatin's predisposition to readily form DNA crossings. This work establishes that chromatin is a major stimulant of topo II function.
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Affiliation(s)
- Jaeyoon Lee
- Physics Department & LASSP, Cornell University, Ithaca, NY, 14853, USA
| | - Meiling Wu
- Physics Department & LASSP, Cornell University, Ithaca, NY, 14853, USA
- Howard Hughes Medical Institute, Cornell University, Ithaca, NY, 14853, USA
| | - James T Inman
- Physics Department & LASSP, Cornell University, Ithaca, NY, 14853, USA
- Howard Hughes Medical Institute, Cornell University, Ithaca, NY, 14853, USA
| | - Gundeep Singh
- Biophysics Program, Cornell University, Ithaca, NY, 14853, USA
| | - Seong Ha Park
- Biophysics Program, Cornell University, Ithaca, NY, 14853, USA
| | - Joyce H Lee
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA
| | | | - Yifeng Hong
- Department of Electrical and Computer Engineering, Cornell University, Ithaca, NY, 14853, USA
| | - Joshua Jeong
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA
| | - James M Berger
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA
| | - Michelle D Wang
- Physics Department & LASSP, Cornell University, Ithaca, NY, 14853, USA.
- Howard Hughes Medical Institute, Cornell University, Ithaca, NY, 14853, USA.
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8
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Boulas I, Bruno L, Rimsky S, Espeli O, Junier I, Rivoire O. Assessing in vivo the impact of gene context on transcription through DNA supercoiling. Nucleic Acids Res 2023; 51:9509-9521. [PMID: 37667073 PMCID: PMC10570042 DOI: 10.1093/nar/gkad688] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2022] [Revised: 07/24/2023] [Accepted: 08/09/2023] [Indexed: 09/06/2023] Open
Abstract
Gene context can have significant impact on gene expression but is currently not integrated in quantitative models of gene regulation despite known biophysical principles and quantitative in vitro measurements. Conceptually, the simplest gene context consists of a single gene framed by two topological barriers, known as the twin transcriptional-loop model, which illustrates the interplay between transcription and DNA supercoiling. In vivo, DNA supercoiling is additionally modulated by topoisomerases, whose modus operandi remains to be quantified. Here, we bridge the gap between theory and in vivo properties by realizing in Escherichia coli the twin transcriptional-loop model and by measuring how gene expression varies with promoters and distances to the topological barriers. We find that gene expression depends on the distance to the upstream barrier but not to the downstream barrier, with a promoter-dependent intensity. We rationalize these findings with a first-principle biophysical model of DNA transcription. Our results are explained if TopoI and gyrase both act specifically, respectively upstream and downstream of the gene, with antagonistic effects of TopoI, which can repress initiation while facilitating elongation. Altogether, our work sets the foundations for a systematic and quantitative description of the impact of gene context on gene regulation.
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Affiliation(s)
- Ihab Boulas
- Center for Interdisciplinary Research in Biology (CIRB), Collège de France, CNRS, INSERM, Université PSL, Paris, France
| | - Lisa Bruno
- Center for Interdisciplinary Research in Biology (CIRB), Collège de France, CNRS, INSERM, Université PSL, Paris, France
| | - Sylvie Rimsky
- Center for Interdisciplinary Research in Biology (CIRB), Collège de France, CNRS, INSERM, Université PSL, Paris, France
| | - Olivier Espeli
- Center for Interdisciplinary Research in Biology (CIRB), Collège de France, CNRS, INSERM, Université PSL, Paris, France
| | - Ivan Junier
- Univ. Grenoble Alpes, CNRS, UMR 5525, VetAgro Sup, Grenoble INP, TIMC, 38000 Grenoble, France
| | - Olivier Rivoire
- Center for Interdisciplinary Research in Biology (CIRB), Collège de France, CNRS, INSERM, Université PSL, Paris, France
- Gulliver, ESPCI, CNRS, Université PSL, Paris, France
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9
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Hall PM, Inman JT, Fulbright RM, Le TT, Brewer JJ, Lambert G, Darst SA, Wang MD. Polarity of the CRISPR roadblock to transcription. Nat Struct Mol Biol 2022; 29:1217-1227. [PMID: 36471058 PMCID: PMC9758054 DOI: 10.1038/s41594-022-00864-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Accepted: 10/12/2022] [Indexed: 12/12/2022]
Abstract
CRISPR (clustered regularly interspaced short palindromic repeats) utility relies on a stable Cas effector complex binding to its target site. However, a Cas complex bound to DNA may be removed by motor proteins carrying out host processes and the mechanism governing this removal remains unclear. Intriguingly, during CRISPR interference, RNA polymerase (RNAP) progression is only fully blocked by a bound endonuclease-deficient Cas (dCas) from the protospacer adjacent motif (PAM)-proximal side. By mapping dCas-DNA interactions at high resolution, we discovered that the collapse of the dCas R-loop allows Escherichia coli RNAP read-through from the PAM-distal side for both Sp-dCas9 and As-dCas12a. This finding is not unique to RNAP and holds for the Mfd translocase. This mechanistic understanding allowed us to modulate the dCas R-loop stability by modifying the guide RNAs. This work highlights the importance of the R-loop in dCas-binding stability and provides valuable mechanistic insights for broad applications of CRISPR technology.
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Affiliation(s)
- Porter M Hall
- Biophysics Program, Cornell University, Ithaca, NY, USA
| | - James T Inman
- Department of Physics, Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, NY, USA
- Howard Hughes Medical Institute, Cornell University, Ithaca, NY, USA
| | - Robert M Fulbright
- Department of Physics, Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, NY, USA
| | - Tung T Le
- Department of Physics, Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, NY, USA
- Howard Hughes Medical Institute, Cornell University, Ithaca, NY, USA
| | - Joshua J Brewer
- Laboratory of Molecular Biophysics, Rockefeller University, New York, NY, USA
| | - Guillaume Lambert
- Department of Applied and Engineering Physics, Cornell University, Ithaca, NY, USA
| | - Seth A Darst
- Laboratory of Molecular Biophysics, Rockefeller University, New York, NY, USA
| | - Michelle D Wang
- Department of Physics, Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, NY, USA.
- Howard Hughes Medical Institute, Cornell University, Ithaca, NY, USA.
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10
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Zhao YL, Lin W, Jitapunkul K, Zhao R, Zhang RQ, Van Hove MA. Surface-Mounted Dipolar Molecular Rotors Driven by External Electric Field, As Revealed by Torque Analyses. ACS OMEGA 2022; 7:35159-35169. [PMID: 36211039 PMCID: PMC9535713 DOI: 10.1021/acsomega.2c04128] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/01/2022] [Accepted: 07/18/2022] [Indexed: 06/16/2023]
Abstract
Driven by a high-speed rotating electric field (E-field), molecular motors with polar groups may perform a unidirectional, repetitive, and GHz frequency rotation and thus offer potential applications as nanostirrers. To drive the unidirectional rotation of molecular motors, it is crucial to consider factors of internal charge flow, thermal noise, molecular flexibility, and so forth before selecting an appropriate frequency of a rotating E-field. Herein, we studied two surface-mounted dipolar rotors of a "caltrop-like" molecule and a "sandwich" molecule by using quantum-mechanical computations in combination with torque analyses. We find that the rotational trend as indicated by the magnitude and the direction of torque vectors can sensitively change with the lag angle (α) between the dipolar arm and the E-field. The atomic charges timely flow within the molecule as the E-field rotates, so the lag angle α must be kept in particular intervals to maintain the rotor's unidirectional rotation. The thermal effect can substantially slow down the rotation of the dipolar rotor in the E-field. The flexible dipolar arm shows a more rigid geometry in the E-field with higher rotation speed. Our work would be useful for designing E-driven molecular rotors and for guiding their practical applications in future.
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Affiliation(s)
- Yan-Ling Zhao
- Department
of Physics, City University of Hong Kong, Hong Kong SAR 999077, China
- Shenzhen
Research Institute, City University of Hong
Kong, Shenzhen 518057, China
| | - Wanxing Lin
- Department
of Physics, City University of Hong Kong, Hong Kong SAR 999077, China
| | - Kulpavee Jitapunkul
- Department
of Physics, City University of Hong Kong, Hong Kong SAR 999077, China
| | - Rundong Zhao
- School
of Physics, Beihang University, Beijing 100191, China
- Shenzhen
JL Computational Science and Applied Research Institute, Shenzhen 518129, China
| | - Rui-Qin Zhang
- Department
of Physics, City University of Hong Kong, Hong Kong SAR 999077, China
- Shenzhen
JL Computational Science and Applied Research Institute, Shenzhen 518129, China
| | - Michel A. Van Hove
- Institute
of Computational and Theoretical Studies & Department of Physics, Hong Kong Baptist University, Hong Kong SAR 999077, China
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11
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Geng Y, Bohrer CH, Yehya N, Hendrix H, Shachaf L, Liu J, Xiao J, Roberts E. A spatially resolved stochastic model reveals the role of supercoiling in transcription regulation. PLoS Comput Biol 2022; 18:e1009788. [PMID: 36121892 PMCID: PMC9522292 DOI: 10.1371/journal.pcbi.1009788] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2021] [Revised: 09/29/2022] [Accepted: 08/12/2022] [Indexed: 11/18/2022] Open
Abstract
In Escherichia coli, translocation of RNA polymerase (RNAP) during transcription introduces supercoiling to DNA, which influences the initiation and elongation behaviors of RNAP. To quantify the role of supercoiling in transcription regulation, we developed a spatially resolved supercoiling model of transcription. The integrated model describes how RNAP activity feeds back with the local DNA supercoiling and how this mechanochemical feedback controls transcription, subject to topoisomerase activities and stochastic topological domain formation. This model establishes that transcription-induced supercoiling mediates the cooperation of co-transcribing RNAP molecules in highly expressed genes, and this cooperation is achieved under moderate supercoiling diffusion and high topoisomerase unbinding rates. It predicts that a topological domain could serve as a transcription regulator, generating substantial transcriptional noise. It also shows the relative orientation of two closely arranged genes plays an important role in regulating their transcription. The model provides a quantitative platform for investigating how genome organization impacts transcription.
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Affiliation(s)
- Yuncong Geng
- Department of Biomedical Engineering, Johns Hopkins School of Medicine, Baltimore, Maryland, United States of America
- * E-mail:
| | - Christopher Herrick Bohrer
- Department of Biophysics, Johns Hopkins University, Baltimore, Maryland, United States of America
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins School of Medicine, Baltimore, Maryland, United States of America
| | - Nicolás Yehya
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins School of Medicine, Baltimore, Maryland, United States of America
| | - Hunter Hendrix
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins School of Medicine, Baltimore, Maryland, United States of America
| | - Lior Shachaf
- Department of Biophysics, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Jian Liu
- Center for Cell Dynamics, Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Jie Xiao
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins School of Medicine, Baltimore, Maryland, United States of America
| | - Elijah Roberts
- Department of Biophysics, Johns Hopkins University, Baltimore, Maryland, United States of America
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12
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Joyeux M. Models of topological barriers and molecular motors of bacterial DNA. MOLECULAR SIMULATION 2022. [DOI: 10.1080/08927022.2022.2120626] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
Affiliation(s)
- Marc Joyeux
- Laboratoire Interdisciplinaire de Physique, CNRS and Université Grenoble Alpes, Grenoble, France
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13
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Marshall CJ, Qayyum MZ, Walker JE, Murakami KS, Santangelo TJ. The structure and activities of the archaeal transcription termination factor Eta detail vulnerabilities of the transcription elongation complex. Proc Natl Acad Sci U S A 2022; 119:e2207581119. [PMID: 35917344 PMCID: PMC9371683 DOI: 10.1073/pnas.2207581119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2022] [Accepted: 06/22/2022] [Indexed: 02/04/2023] Open
Abstract
Transcription must be properly regulated to ensure dynamic gene expression underlying growth, development, and response to environmental cues. Regulation is imposed throughout the transcription cycle, and while many efforts have detailed the regulation of transcription initiation and early elongation, the termination phase of transcription also plays critical roles in regulating gene expression. Transcription termination can be driven by only a few proteins in each domain of life. Detailing the mechanism(s) employed provides insight into the vulnerabilities of transcription elongation complexes (TECs) that permit regulated termination to control expression of many genes and operons. Here, we describe the biochemical activities and crystal structure of the superfamily 2 helicase Eta, one of two known factors capable of disrupting archaeal transcription elongation complexes. Eta retains a twin-translocase core domain common to all superfamily 2 helicases and a well-conserved C terminus wherein individual amino acid substitutions can critically abrogate termination activities. Eta variants that perturb ATPase, helicase, single-stranded DNA and double-stranded DNA translocase and termination activities identify key regions of the C terminus of Eta that, when combined with modeling Eta-TEC interactions, provide a structural model of Eta-mediated termination guided in part by structures of Mfd and the bacterial TEC. The susceptibility of TECs to disruption by termination factors that target the upstream surface of RNA polymerase and potentially drive termination through forward translocation and allosteric mechanisms that favor opening of the clamp to release the encapsulated nucleic acids emerges as a common feature of transcription termination mechanisms.
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Affiliation(s)
- Craig J. Marshall
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80523
| | - M. Zuhaib Qayyum
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA 16802
| | - Julie E. Walker
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80523
| | - Katsuhiko S. Murakami
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA 16802
| | - Thomas J. Santangelo
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80523
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14
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Portman JR, Qayyum MZ, Murakami KS, Strick TR. On the stability of stalled RNA polymerase and its removal by RapA. Nucleic Acids Res 2022; 50:7396-7405. [PMID: 35819188 PMCID: PMC9303389 DOI: 10.1093/nar/gkac558] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2022] [Revised: 06/10/2022] [Accepted: 07/07/2022] [Indexed: 11/23/2022] Open
Abstract
Stalling of the transcription elongation complex formed by DNA, RNA polymerase (RNAP) and RNA presents a serious obstacle to concurrent processes due to the extremely high stability of the DNA-bound polymerase. RapA, known to remove RNAP from DNA in an ATP-dependent fashion, was identified over 50 years ago as an abundant binding partner of RNAP; however, its mechanism of action remains unknown. Here, we use single-molecule magnetic trapping assays to characterize RapA activity and begin to specify its mechanism of action. We first show that stalled RNAP resides on DNA for times on the order of 106 seconds and that increasing positive torque on the DNA reduces this lifetime. Using stalled RNAP as a substrate we show that the RapA protein stimulates dissociation of stalled RNAP from positively supercoiled DNA but not negatively supercoiled DNA. We observe that RapA-dependent RNAP dissociation is torque-sensitive, is inhibited by GreB and depends on RNA length. We propose that stalled RNAP is dislodged from DNA by RapA via backtracking in a supercoiling- and torque-dependent manner, suggesting that RapA’s activity on transcribing RNAP in vivo is responsible for resolving conflicts between converging polymerase molecular motors.
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Affiliation(s)
- James R Portman
- Institut de Biologie de l'Ecole Normale Supérieure, PSL Université, INSERM, CNRS, Paris 75005, France.,Horizons 2020 Innovative Training Network, DNAREPAIRMAN, Paris 75005, France
| | - M Zuhaib Qayyum
- Department of Biochemistry and Molecular Biology, The Center for RNA Molecular Biology, The Center for Structural Biology, Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Katsuhiko S Murakami
- Department of Biochemistry and Molecular Biology, The Center for RNA Molecular Biology, The Center for Structural Biology, Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Terence R Strick
- Institut de Biologie de l'Ecole Normale Supérieure, PSL Université, INSERM, CNRS, Paris 75005, France.,Horizons 2020 Innovative Training Network, DNAREPAIRMAN, Paris 75005, France.,Equipe Labellisée de la Ligue Nationale Contre le Cancer, Paris 75013, France
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15
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Ye F, Inman JT, Hong Y, Hall PM, Wang MD. Resonator nanophotonic standing-wave array trap for single-molecule manipulation and measurement. Nat Commun 2022; 13:77. [PMID: 35013276 PMCID: PMC8748738 DOI: 10.1038/s41467-021-27709-3] [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: 07/24/2021] [Accepted: 12/03/2021] [Indexed: 11/29/2022] Open
Abstract
Nanophotonic tweezers represent emerging platforms with significant potential for parallel manipulation and measurements of single biological molecules on-chip. However, trapping force generation represents a substantial obstacle for their broader utility. Here, we present a resonator nanophotonic standing-wave array trap (resonator-nSWAT) that demonstrates significant force enhancement. This platform integrates a critically-coupled resonator design to the nSWAT and incorporates a novel trap reset scheme. The nSWAT can now perform standard single-molecule experiments, including stretching DNA molecules to measure their force-extension relations, unzipping DNA molecules, and disrupting and mapping protein-DNA interactions. These experiments have realized trapping forces on the order of 20 pN while demonstrating base-pair resolution with measurements performed on multiple molecules in parallel. Thus, the resonator-nSWAT platform now meets the benchmarks of a table-top precision optical trapping instrument in terms of force generation and resolution. This represents the first demonstration of a nanophotonic platform for such single-molecule experiments. Applications of nanophotonic tweezers have been limited by the low trapping force. Here, the authors present enhanced force generation in a nanophotonic standing-wave array trap by integrating a critically-coupled resonator design and demonstrate common single-molecule experiments.
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Affiliation(s)
- Fan Ye
- Howard Hughes Medical Institute, Ithaca, NY, 14853, USA.,Department of Physics & LASSP, Ithaca, NY, 14853, USA
| | - James T Inman
- Howard Hughes Medical Institute, Ithaca, NY, 14853, USA.,Department of Physics & LASSP, Ithaca, NY, 14853, USA
| | - Yifeng Hong
- Department of Electrical and Computer Engineering, Ithaca, NY, 14853, USA
| | | | - Michelle D Wang
- Howard Hughes Medical Institute, Ithaca, NY, 14853, USA. .,Department of Physics & LASSP, Ithaca, NY, 14853, USA.
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16
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Gao X, Inman JT, Wang MD. Angular Optical Trapping to Directly Measure DNA Torsional Mechanics. Methods Mol Biol 2022; 2478:37-73. [PMID: 36063318 DOI: 10.1007/978-1-0716-2229-2_4] [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] [Indexed: 04/14/2023]
Abstract
Angular optical trapping (AOT) is a powerful technique that permits direct angular manipulation of a trapped particle with simultaneous measurement of torque and rotation, while also retaining the capabilities of position and force detection. This technique provides unique approaches to investigate the torsional properties of nucleic acids and DNA-protein complexes, as well as impacts of torsional stress on fundamental biological processes, such as transcription and replication. Here we describe the principle, construction, and calibration of the AOT in detail and provide a guide to the performance of single-molecule torque measurements on DNA molecules. We include the constant-force method and, notably, a new constant-extension method that enables measurement of the twist persistence length of both extended DNA, under an extremely low force, and plectonemic DNA. This chapter can assist in the implementation and application of this technique for general researchers in the single-molecule field.
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Affiliation(s)
- Xiang Gao
- Howard Hughes Medical Institute, Cornell University, Ithaca, NY, USA
- Laboratory of Atomic and Solid State Physics (LASSP), Department of Physics, Cornell University, Ithaca, NY, USA
| | - James T Inman
- Howard Hughes Medical Institute, Cornell University, Ithaca, NY, USA
- Laboratory of Atomic and Solid State Physics (LASSP), Department of Physics, Cornell University, Ithaca, NY, USA
| | - Michelle D Wang
- Howard Hughes Medical Institute, Cornell University, Ithaca, NY, USA.
- Laboratory of Atomic and Solid State Physics (LASSP), Department of Physics, Cornell University, Ithaca, NY, USA.
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17
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Chatterjee P, Goldenfeld N, Kim S. DNA Supercoiling Drives a Transition between Collective Modes of Gene Synthesis. PHYSICAL REVIEW LETTERS 2021; 127:218101. [PMID: 34860091 PMCID: PMC9034659 DOI: 10.1103/physrevlett.127.218101] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/19/2021] [Accepted: 10/18/2021] [Indexed: 05/20/2023]
Abstract
Transcription of genes can be affected by both biochemical and mechanical factors. Recent experiments suggested that the mechanical stress associated with transcription-induced DNA supercoiling is responsible for the transition from cooperative to antagonistic group dynamics of RNA polymerases (RNAPs) upon promoter repression. To underpin the mechanism behind this drastic transition, we developed a continuum deterministic model for transcription under torsion. In our model, the speed of an RNAP is affected by the local DNA supercoiling, as well as two global factors: (i) the number of RNAPs on the gene affecting the torsional stress experienced by individual RNAPs and (ii) transcription factors blocking the diffusion of DNA supercoils. Our minimal model can successfully reproduce the experimental findings and helps elucidate the interplay of mechanical and biological factors in the collective dynamics of molecular machines involved in gene expression.
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18
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Papadopoulos D, Solvie D, Baluapuri A, Endres T, Ha SA, Herold S, Kalb J, Giansanti C, Schülein-Völk C, Ade CP, Schneider C, Gaballa A, Vos S, Fischer U, Dobbelstein M, Wolf E, Eilers M. MYCN recruits the nuclear exosome complex to RNA polymerase II to prevent transcription-replication conflicts. Mol Cell 2021; 82:159-176.e12. [PMID: 34847357 DOI: 10.1016/j.molcel.2021.11.002] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2021] [Revised: 08/17/2021] [Accepted: 11/02/2021] [Indexed: 01/05/2023]
Abstract
The MYCN oncoprotein drives the development of numerous neuroendocrine and pediatric tumors. Here we show that MYCN interacts with the nuclear RNA exosome, a 3'-5' exoribonuclease complex, and recruits the exosome to its target genes. In the absence of the exosome, MYCN-directed elongation by RNA polymerase II (RNAPII) is slow and non-productive on a large group of cell-cycle-regulated genes. During the S phase of MYCN-driven tumor cells, the exosome is required to prevent the accumulation of stalled replication forks and of double-strand breaks close to the transcription start sites. Upon depletion of the exosome, activation of ATM causes recruitment of BRCA1, which stabilizes nuclear mRNA decapping complexes, leading to MYCN-dependent transcription termination. Disruption of mRNA decapping in turn activates ATR, indicating transcription-replication conflicts. We propose that exosome recruitment by MYCN maintains productive transcription elongation during S phase and prevents transcription-replication conflicts to maintain the rapid proliferation of neuroendocrine tumor cells.
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Affiliation(s)
- Dimitrios Papadopoulos
- Theodor Boveri Institute, Department of Biochemistry and Molecular Biology, Biocenter, University of Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Daniel Solvie
- Theodor Boveri Institute, Department of Biochemistry and Molecular Biology, Biocenter, University of Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Apoorva Baluapuri
- Cancer Systems Biology Group, Department of Biochemistry and Molecular Biology, Biocenter, University of Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Theresa Endres
- Theodor Boveri Institute, Department of Biochemistry and Molecular Biology, Biocenter, University of Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Stefanie Anh Ha
- Theodor Boveri Institute, Department of Biochemistry and Molecular Biology, Biocenter, University of Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Steffi Herold
- Theodor Boveri Institute, Department of Biochemistry and Molecular Biology, Biocenter, University of Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Jacqueline Kalb
- Theodor Boveri Institute, Department of Biochemistry and Molecular Biology, Biocenter, University of Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Celeste Giansanti
- Institute of Molecular Oncology, Center of Molecular Biosciences, University of Göttingen, Justus von Liebig Weg 11, 37077 Göttingen, Germany
| | - Christina Schülein-Völk
- Core Unit High-Content Microscopy, Biocenter, University of Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Carsten Patrick Ade
- Theodor Boveri Institute, Department of Biochemistry and Molecular Biology, Biocenter, University of Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Cornelius Schneider
- Department of Biochemistry, Biocenter, University of Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Abdallah Gaballa
- Theodor Boveri Institute, Department of Biochemistry and Molecular Biology, Biocenter, University of Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Seychelle Vos
- Department of Biology, Massachusetts Institute of Technology, 31 Ames Street, Cambridge, MA 02142, USA
| | - Utz Fischer
- Department of Biochemistry, Biocenter, University of Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Matthias Dobbelstein
- Institute of Molecular Oncology, Center of Molecular Biosciences, University of Göttingen, Justus von Liebig Weg 11, 37077 Göttingen, Germany
| | - Elmar Wolf
- Cancer Systems Biology Group, Department of Biochemistry and Molecular Biology, Biocenter, University of Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Martin Eilers
- Theodor Boveri Institute, Department of Biochemistry and Molecular Biology, Biocenter, University of Würzburg, Am Hubland, 97074 Würzburg, Germany.
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19
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Abstract
Cellular life depends on transcription of DNA by RNA polymerase to express genetic information. RNA polymerase has evolved not just to read information from DNA and write it to RNA but also to sense and process information from the cellular and extracellular environments. Much of this information processing occurs during transcript elongation, when transcriptional pausing enables regulatory decisions. Transcriptional pauses halt RNA polymerase in response to DNA and RNA sequences and structures at locations and times that help coordinate interactions with small molecules and transcription factors important for regulation. Four classes of transcriptional pause signals are now evident after decades of study: elemental pauses, backtrack pauses, hairpin-stabilized pauses, and regulator-stabilized pauses. In this review, I describe current understanding of the molecular mechanisms of these four classes of pause signals, remaining questions about how RNA polymerase responds to pause signals, and the many exciting directions now open to understand pausing and the regulation of transcript elongation on a genome-wide scale. Expected final online publication date for the Annual Review of Microbiology, Volume 75 is October 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
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Affiliation(s)
- Robert Landick
- Department of Biochemistry and Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA;
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20
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Gao X, Hong Y, Ye F, Inman JT, Wang MD. Torsional Stiffness of Extended and Plectonemic DNA. PHYSICAL REVIEW LETTERS 2021; 127:028101. [PMID: 34296898 PMCID: PMC9007542 DOI: 10.1103/physrevlett.127.028101] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Accepted: 04/15/2021] [Indexed: 06/13/2023]
Abstract
DNA torsional elastic properties play a crucial role in DNA structure, topology, and the regulation of motor protein progression. However, direct measurements of these parameters are experimentally challenging. Here, we present a constant-extension method integrated into an angular optical trap to directly measure torque during DNA supercoiling. We measured the twist persistence length of extended DNA to be 22 nm under an extremely low force (∼0.02 pN) and the twist persistence length of plectonemic DNA to be 24 nm. In addition, we implemented a rigorous data analysis scheme that bridged our measurements with existing theoretical models of DNA torsional behavior. This comprehensive set of torsional parameters demonstrates that at least 20% of DNA supercoiling is partitioned into twist for both extended DNA and plectonemic DNA. This work provides a new experimental methodology, as well as an analytical and interpretational framework, which will enable, expand, and enhance future studies of DNA torsional properties.
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Affiliation(s)
- Xiang Gao
- Howard Hughes Medical Institute, Cornell University, Ithaca, NY 14853, USA
- Department of Physics & LASSP, Cornell University, Ithaca, NY 14853, USA
| | - Yifeng Hong
- Department of Electrical and Computer Engineering, Cornell University, Ithaca, NY 14853, USA
| | - Fan Ye
- Howard Hughes Medical Institute, Cornell University, Ithaca, NY 14853, USA
- Department of Physics & LASSP, Cornell University, Ithaca, NY 14853, USA
| | - James T. Inman
- Howard Hughes Medical Institute, Cornell University, Ithaca, NY 14853, USA
- Department of Physics & LASSP, Cornell University, Ithaca, NY 14853, USA
| | - Michelle D. Wang
- Howard Hughes Medical Institute, Cornell University, Ithaca, NY 14853, USA
- Department of Physics & LASSP, Cornell University, Ithaca, NY 14853, USA
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21
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Liu W, Zhong Z, Ma J. Simple way to correct the drift in surface-coupled optical tweezers using the laser reflection pattern. OPTICS EXPRESS 2021; 29:18769-18780. [PMID: 34154126 DOI: 10.1364/oe.423759] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2021] [Accepted: 05/18/2021] [Indexed: 06/13/2023]
Abstract
The surface-coupled optical tweezers are widely used to resolve small units of motion in biology. However, such motions could readily be interfered by the drift between the trap and surface. We present a simple and low-cost method to correct the drift both actively and passively based on video tracking the distance between the laser reflection pattern and the reference bead. As a result, we achieved sub-nanometer resolution and stability for the stuck bead over a broad range of averaging time (0.002-100 s) as demonstrated by the Allan deviation analysis. The sub-nanometer resolution was further manifested with step measurement. Finally, in double-stranded DNA and DNA hairpin stretching experiments, an extension resolution of 1-2 nm with the stability over 120 s has been demonstrated under a constant force. This work thus provides an easy way to bring the benefit of nanometer resolution and long-term stability to the surface-coupled optical tweezers.
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22
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Abstract
R-loops are nucleic acid hybrids which form when an RNA invades duplex DNA to pair with its template sequence. Although they are implicated in a growing number of gene regulatory processes, their mechanistic origins remain unclear. We here report real-time observations of cotranscriptional R-loop formation at single-molecule resolution and propose a mechanism for their formation. We show that the bacterial Mfd protein can simultaneously interact with both elongating RNA polymerase and upstream DNA, tethering the two together and partitioning the DNA into distinct supercoiled domains. A highly negatively supercoiled domain forms in between Mfd and RNA polymerase, and compensatory positive supercoiling appears in front of the RNA polymerase and behind Mfd. The nascent RNA invades the negatively supercoiled domain and forms a stable R-loop that can drive mutagenesis. This mechanism theoretically enables any protein that simultaneously binds an actively translocating RNA polymerase and upstream DNA to stimulate R-loop formation.
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23
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Bustamante CJ, Chemla YR, Liu S, Wang MD. Optical tweezers in single-molecule biophysics. NATURE REVIEWS. METHODS PRIMERS 2021; 1:25. [PMID: 34849486 PMCID: PMC8629167 DOI: 10.1038/s43586-021-00021-6] [Citation(s) in RCA: 112] [Impact Index Per Article: 37.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 02/12/2021] [Indexed: 12/15/2022]
Abstract
Optical tweezers have become the method of choice in single-molecule manipulation studies. In this Primer, we first review the physical principles of optical tweezers and the characteristics that make them a powerful tool to investigate single molecules. We then introduce the modifications of the method to extend the measurement of forces and displacements to torques and angles, and to develop optical tweezers with single-molecule fluorescence detection capabilities. We discuss force and torque calibration of these instruments, their various modes of operation and most common experimental geometries. We describe the type of data obtained in each experimental design and their analyses. This description is followed by a survey of applications of these methods to the studies of protein-nucleic acid interactions, protein/RNA folding and molecular motors. We also discuss data reproducibility, the factors that lead to the data variability among different laboratories and the need to develop field standards. We cover the current limitations of the methods and possible ways to optimize instrument operation, data extraction and analysis, before suggesting likely areas of future growth.
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Affiliation(s)
- Carlos J. Bustamante
- Department of Molecular and Cell Biology, University of California, Berkeley, CA, USA
- Department of Physics, University of California, Berkeley, CA, USA
- Department of Chemistry, University of California, Berkeley, CA, USA
- Kavli Energy NanoScience Institute, University of California, Berkeley, CA, USA
- Howard Hughes Medical Institute, University of California, Berkeley, CA, USA
| | - Yann R. Chemla
- Department of Physics, Center for the Physics of Living Cells, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Shixin Liu
- Laboratory of Nanoscale Biophysics and Biochemistry, The Rockefeller University, New York, NY, USA
| | - Michelle D. Wang
- Department of Physics, Laboratory of Atomic and Solid State Physics, Howard Hughes Medical Institute, Cornell University, Ithaca, NY, USA
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24
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Birnie A, Dekker C. Genome-in-a-Box: Building a Chromosome from the Bottom Up. ACS NANO 2021; 15:111-124. [PMID: 33347266 PMCID: PMC7844827 DOI: 10.1021/acsnano.0c07397] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2020] [Accepted: 12/16/2020] [Indexed: 05/24/2023]
Abstract
Chromosome structure and dynamics are essential for life, as the way that our genomes are spatially organized within cells is crucial for gene expression, differentiation, and genome transfer to daughter cells. There is a wide variety of methods available to study chromosomes, ranging from live-cell studies to single-molecule biophysics, which we briefly review. While these technologies have yielded a wealth of data, such studies still leave a significant gap between top-down experiments on live cells and bottom-up in vitro single-molecule studies of DNA-protein interactions. Here, we introduce "genome-in-a-box" (GenBox) as an alternative in vitro approach to build and study chromosomes, which bridges this gap. The concept is to assemble a chromosome from the bottom up by taking deproteinated genome-sized DNA isolated from live cells and subsequently add purified DNA-organizing elements, followed by encapsulation in cell-sized containers using microfluidics. Grounded in the rationale of synthetic cell research, the approach would enable to experimentally study emergent effects at the global genome level that arise from the collective action of local DNA-structuring elements. We review the various DNA-structuring elements present in nature, from nucleoid-associated proteins and SMC complexes to phase separation and macromolecular crowders. Finally, we discuss how GenBox can contribute to several open questions on chromosome structure and dynamics.
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Affiliation(s)
- Anthony Birnie
- Department of Bionanoscience, Kavli
Institute of Nanoscience Delft, Delft University
of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Cees Dekker
- Department of Bionanoscience, Kavli
Institute of Nanoscience Delft, Delft University
of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
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25
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Le TT, Gao X, Park SH, Lee J, Inman JT, Lee JH, Killian JL, Badman RP, Berger JM, Wang MD. Synergistic Coordination of Chromatin Torsional Mechanics and Topoisomerase Activity. Cell 2020; 179:619-631.e15. [PMID: 31626768 PMCID: PMC6899335 DOI: 10.1016/j.cell.2019.09.034] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2019] [Revised: 06/16/2019] [Accepted: 09/24/2019] [Indexed: 12/23/2022]
Abstract
DNA replication in eukaryotes generates DNA supercoiling, which may intertwine (braid) daughter chromatin fibers to form precatenanes, posing topological challenges during chromosome segregation. The mechanisms that limit precatenane formation remain unclear. By making direct torque measurements, we demonstrate that the intrinsic mechanical properties of chromatin play a fundamental role in dictating precatenane formation and regulating chromatin topology. Whereas a single chromatin fiber is torsionally soft, a braided fiber is torsionally stiff, indicating that supercoiling on chromatin substrates is preferentially directed in front of the fork during replication. We further show that topoisomerase II relaxation displays a strong preference for a single chromatin fiber over a braided fiber. These results suggest a synergistic coordination-the mechanical properties of chromatin inherently suppress precatenane formation during replication elongation by driving DNA supercoiling ahead of the fork, where supercoiling is more efficiently removed by topoisomerase II. VIDEO ABSTRACT.
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Affiliation(s)
- Tung T Le
- Howard Hughes Medical Institute, Cornell University, Ithaca, NY 14853, USA; Physics Department & LASSP, Cornell University, Ithaca, NY 14853, USA
| | - Xiang Gao
- Howard Hughes Medical Institute, Cornell University, Ithaca, NY 14853, USA; Physics Department & LASSP, Cornell University, Ithaca, NY 14853, USA
| | - Seong Ha Park
- Biophysics Program, Cornell University, Ithaca, NY 14853, USA
| | - Jaeyoon Lee
- Physics Department & LASSP, Cornell University, Ithaca, NY 14853, USA
| | - James T Inman
- Howard Hughes Medical Institute, Cornell University, Ithaca, NY 14853, USA; Physics Department & LASSP, Cornell University, Ithaca, NY 14853, USA
| | - Joyce H Lee
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Jessica L Killian
- Howard Hughes Medical Institute, Cornell University, Ithaca, NY 14853, USA; Physics Department & LASSP, Cornell University, Ithaca, NY 14853, USA
| | - Ryan P Badman
- Physics Department & LASSP, Cornell University, Ithaca, NY 14853, USA
| | - James M Berger
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Michelle D Wang
- Howard Hughes Medical Institute, Cornell University, Ithaca, NY 14853, USA; Physics Department & LASSP, Cornell University, Ithaca, NY 14853, USA.
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26
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Type II DNA Topoisomerases Cause Spontaneous Double-Strand Breaks in Genomic DNA. Genes (Basel) 2019; 10:genes10110868. [PMID: 31671674 PMCID: PMC6895833 DOI: 10.3390/genes10110868] [Citation(s) in RCA: 46] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2019] [Revised: 10/22/2019] [Accepted: 10/26/2019] [Indexed: 12/31/2022] Open
Abstract
Type II DNA topoisomerase enzymes (TOP2) catalyze topological changes by strand passage reactions. They involve passing one intact double stranded DNA duplex through a transient enzyme-bridged break in another (gated helix) followed by ligation of the break by TOP2. A TOP2 poison, etoposide blocks TOP2 catalysis at the ligation step of the enzyme-bridged break, increasing the number of stable TOP2 cleavage complexes (TOP2ccs). Remarkably, such pathological TOP2ccs are formed during the normal cell cycle as well as in postmitotic cells. Thus, this ‘abortive catalysis’ can be a major source of spontaneously arising DNA double-strand breaks (DSBs). TOP2-mediated DSBs are also formed upon stimulation with physiological concentrations of androgens and estrogens. The frequent occurrence of TOP2-mediated DSBs was previously not appreciated because they are efficiently repaired. This repair is performed in collaboration with BRCA1, BRCA2, MRE11 nuclease, and tyrosyl-DNA phosphodiesterase 2 (TDP2) with nonhomologous end joining (NHEJ) factors. This review first discusses spontaneously arising DSBs caused by the abortive catalysis of TOP2 and then summarizes proteins involved in repairing stalled TOP2ccs and discusses the genotoxicity of the sex hormones.
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Mohapatra S, Lin CT, Feng XA, Basu A, Ha T. Single-Molecule Analysis and Engineering of DNA Motors. Chem Rev 2019; 120:36-78. [DOI: 10.1021/acs.chemrev.9b00361] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
| | | | | | | | - Taekjip Ha
- Howard Hughes Medical Institute, Baltimore, Maryland 21205, United States
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28
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Artsimovitch I. RNA synthesis is a team effort. Nat Microbiol 2019; 4:1776-1777. [PMID: 31649357 DOI: 10.1038/s41564-019-0600-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Irina Artsimovitch
- Department of Microbiology and Center for RNA Biology, The Ohio State University, Columbus, OH, USA.
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29
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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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Badman RP, Ye F, Caravan W, Wang MD. High Trap Stiffness Microcylinders for Nanophotonic Trapping. ACS APPLIED MATERIALS & INTERFACES 2019; 11:25074-25080. [PMID: 31274286 PMCID: PMC6946062 DOI: 10.1021/acsami.9b10041] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Nanophotonic waveguides have enabled on-chip optical trap arrays for high-throughput manipulation and measurements. However, the realization of the full potential of these devices requires trapping enhancement for applications that need large trapping force. Here, we demonstrate a solution via fabrication of high refractive index cylindrical trapping particles. Using two different fabrication processes, a cleaving method and a novel lift-off method, we produced cylindrical silicon nitride (Si3N4) particles and characterized their trapping properties using the recently developed nanophotonic standing-wave array trap (nSWAT) platform. Relative to conventionally used polystyrene microspheres, the fabricated Si3N4 microcylinders attain an approximately 3- to 6-fold trap stiffness enhancement. Furthermore, both fabrication processes permit tunable microcylinder geometry, and the lift-off method also results in ultrasmooth surface termination of the ends of the microcylinders. These combined features make the Si3N4 microcylinders uniquely suited for a broad range of high-throughput, high-force, nanophotonic waveguide-based optical trapping applications.
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Affiliation(s)
- Ryan P. Badman
- Department of Physics - LASSP, Cornell University, Ithaca, New York 14853
| | - Fan Ye
- Department of Physics - LASSP, Cornell University, Ithaca, New York 14853
- Howard Hughes Medical Institute, Cornell University, Ithaca, New York 14853
| | - Wagma Caravan
- Department of Physics - LASSP, Cornell University, Ithaca, New York 14853
- Current address: Department of Chemistry, Adelphi University, Garden City, NY 11530
| | - Michelle D. Wang
- Department of Physics - LASSP, Cornell University, Ithaca, New York 14853
- Howard Hughes Medical Institute, Cornell University, Ithaca, New York 14853
- corresponding author:
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31
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Belogurov GA, Artsimovitch I. The Mechanisms of Substrate Selection, Catalysis, and Translocation by the Elongating RNA Polymerase. J Mol Biol 2019; 431:3975-4006. [PMID: 31153902 DOI: 10.1016/j.jmb.2019.05.042] [Citation(s) in RCA: 43] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2019] [Revised: 05/24/2019] [Accepted: 05/24/2019] [Indexed: 11/15/2022]
Abstract
Multi-subunit DNA-dependent RNA polymerases synthesize all classes of cellular RNAs, ranging from short regulatory transcripts to gigantic messenger RNAs. RNA polymerase has to make each RNA product in just one try, even if it takes millions of successive nucleotide addition steps. During each step, RNA polymerase selects a correct substrate, adds it to a growing chain, and moves one nucleotide forward before repeating the cycle. However, RNA synthesis is anything but monotonous: RNA polymerase frequently pauses upon encountering mechanical, chemical and torsional barriers, sometimes stepping back and cleaving off nucleotides from the growing RNA chain. A picture in which these intermittent dynamics enable processive, accurate, and controllable RNA synthesis is emerging from complementary structural, biochemical, computational, and single-molecule studies. Here, we summarize our current understanding of the mechanism and regulation of the on-pathway transcription elongation. We review the details of substrate selection, catalysis, proofreading, and translocation, focusing on rate-limiting steps, structural elements that modulate them, and accessory proteins that appear to control RNA polymerase translocation.
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Affiliation(s)
| | - Irina Artsimovitch
- Department of Microbiology and The Center for RNA Biology, The Ohio State University, Columbus, OH, USA.
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Ha S, Tang Y, van Oene MM, Janissen R, Dries RM, Solano B, Adam AJL, Dekker NH. Single-Crystal Rutile TiO 2 Nanocylinders are Highly Effective Transducers of Optical Force and Torque. ACS PHOTONICS 2019; 6:1255-1265. [PMID: 31119185 PMCID: PMC6524961 DOI: 10.1021/acsphotonics.9b00220] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/06/2019] [Indexed: 05/05/2023]
Abstract
Optical trapping of (sub)micron-sized particles is broadly employed in nanoscience and engineering. The materials commonly employed for these particles, however, have physical properties that limit the transfer of linear or angular momentum (or both). This reduces the magnitude of forces and torques, and the spatiotemporal resolution, achievable in linear and angular traps. Here, we overcome these limitations through the use of single-crystal rutile TiO2, which has an exceptionally large optical birefringence, a high index of refraction, good chemical stability, and is amenable to geometric control at the nanoscale. We show that rutile TiO2 nanocylinders form powerful joint force and torque transducers in aqueous environments by using only moderate laser powers to apply nN·nm torques at kHz rotational frequencies to tightly trapped particles. In doing so, we demonstrate how rutile TiO2 nanocylinders outperform other materials and offer unprecedented opportunities to expand the control of optical force and torque at the nanoscale.
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Affiliation(s)
- Seungkyu Ha
- Department
of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Ying Tang
- Optics
Research Group, Department of Imaging Physics, Delft University of Technology, van der Waalsweg 8, 2628 CH Delft, The Netherlands
| | - Maarten M. van Oene
- Department
of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Richard Janissen
- Department
of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Roland M. Dries
- Department
of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Belen Solano
- Department
of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Aurèle J. L. Adam
- Optics
Research Group, Department of Imaging Physics, Delft University of Technology, van der Waalsweg 8, 2628 CH Delft, The Netherlands
- E-mail:
| | - Nynke H. Dekker
- Department
of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, van der Maasweg 9, 2629 HZ Delft, The Netherlands
- E-mail:
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