1
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Dong R, Yi N, Jiang D. Advances in single molecule arrays (SIMOA) for ultra-sensitive detection of biomolecules. Talanta 2024; 270:125529. [PMID: 38091745 DOI: 10.1016/j.talanta.2023.125529] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2023] [Revised: 11/25/2023] [Accepted: 12/05/2023] [Indexed: 01/27/2024]
Abstract
In the contemporary era of scientific and medical advancements, the accurate and ultra-sensitive detection of proteins, nucleic acids and metabolites plays a pivotal role in disease diagnosis and treatment monitoring. Single-molecule detection technologies play a great role in achieving this goal. In recent years, digital detection methods based on single molecule arrays (SIMOA) have brought groundbreaking contributions to the field of single-molecule detection. By confining the target molecules to femtoliter-sized containers, the SIMOA technology achieves detection sensitivity of attomolar. This review delves into the historical evolution and fundamentals of SIMOA technology, summarizes various approaches to optimize its performance, and describes the applications of SIMOA for the ultrasensitive detection of biomarkers for diseases such as cancer, COVID-19, and neurological disorders, as well as in DNA detection. Currently, some SIMOA technologies have been realized for high-throughput and multiplexed detection. It is believed that SIMOA technology will play a significant role in medical monitoring and disease prevention in the future.
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Affiliation(s)
- Renkai Dong
- State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210023, China
| | - Ning Yi
- State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210023, China
| | - Dechen Jiang
- State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210023, China.
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2
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Arseniev A, Panfilov M, Pobegalov G, Potyseva A, Pavlinova P, Yakunina M, Lee J, Borukhov S, Severinov K, Khodorkovskii M. Single-molecule studies reveal the off-pathway elemental pause state as a target of streptolydigin inhibition of RNA polymerase and its dramatic enhancement by Gre factors. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.06.05.542125. [PMID: 37333075 PMCID: PMC10274647 DOI: 10.1101/2023.06.05.542125] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/20/2023]
Abstract
Antibiotic streptolydigin (Stl) inhibits bacterial transcription by blocking the trigger loop folding in the active center of RNA polymerase (RNAP), which is essential for catalysis. We use acoustic force spectroscopy to characterize the dynamics of transcription elongation in ternary elongation complexes of RNAP (ECs) in the presence of Stl at a single-molecule level. We found that Stl induces long-lived stochastic pauses while the instantaneous velocity of transcription between the pauses is unaffected. Stl enhances the short-lived pauses associated with an off-pathway elemental paused state of the RNAP nucleotide addition cycle. Unexpectedly, we found that transcript cleavage factors GreA and GreB, which were thought to be Stl competitors, do not alleviate the streptolydigin-induced pausing; instead, they synergistically increase transcription inhibition by Stl. This is the first known instance of a transcriptional factor enhancing antibiotic activity. We propose a structural model of the EC-Gre-Stl complex that explains the observed Stl activities and provides insight into possible cooperative action of secondary channel factors and other antibiotics binding at the Stl-pocket. These results offer a new strategy for high-throughput screening for prospective antibacterial agents.
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Affiliation(s)
- Anatolii Arseniev
- Peter the Great St. Petersburg Polytechnic University, Saint Petersburg, Russia
- Institute of Molecular Genetics, Russian Academy of Sciences, Moscow, Russian Federation
| | - Mikhail Panfilov
- Peter the Great St. Petersburg Polytechnic University, Saint Petersburg, Russia
| | - Georgii Pobegalov
- Peter the Great St. Petersburg Polytechnic University, Saint Petersburg, Russia
| | - Alina Potyseva
- Peter the Great St. Petersburg Polytechnic University, Saint Petersburg, Russia
| | - Polina Pavlinova
- Peter the Great St. Petersburg Polytechnic University, Saint Petersburg, Russia
| | - Maria Yakunina
- Peter the Great St. Petersburg Polytechnic University, Saint Petersburg, Russia
| | - Jookyung Lee
- Department of Cell Biology and Neuroscience, Rowan University School of Osteopathic Medicine, Stratford, NJ 08084-1489, USA
| | - Sergei Borukhov
- Department of Cell Biology and Neuroscience, Rowan University School of Osteopathic Medicine, Stratford, NJ 08084-1489, USA
| | - Konstantin Severinov
- Institute of Gene Biology, Russian Academy of Sciences, Moscow, Russia
- Waksman Institute of Microbiology, Rutgers, The State University of New Jersey, Piscataway, NJ, United States
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3
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Wang L, Watters JW, Ju X, Lu G, Liu S. Head-on and co-directional RNA polymerase collisions orchestrate bidirectional transcription termination. Mol Cell 2023; 83:1153-1164.e4. [PMID: 36917983 PMCID: PMC10081963 DOI: 10.1016/j.molcel.2023.02.017] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2022] [Revised: 01/03/2023] [Accepted: 02/15/2023] [Indexed: 03/14/2023]
Abstract
Genomic DNA is a crowded track where motor proteins frequently collide. It remains underexplored whether these collisions carry physiological function. In this work, we develop a single-molecule assay to visualize the trafficking of individual E. coli RNA polymerases (RNAPs) on DNA. Based on transcriptomic data, we hypothesize that RNAP collisions drive bidirectional transcription termination of convergent gene pairs. Single-molecule results show that the head-on collision between two converging RNAPs is necessary to prevent transcriptional readthrough but insufficient to release the RNAPs from the DNA. Remarkably, co-directional collision of a trailing RNAP into the head-on collided complex dramatically increases the termination efficiency. Furthermore, stem-loop structures formed in the nascent RNA are required for collisions to occur at well-defined positions between convergent genes. These findings suggest that physical collisions between RNAPs furnish a mechanism for transcription termination and that programmed genomic conflicts can be exploited to co-regulate the expression of multiple genes.
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Affiliation(s)
- Ling Wang
- Laboratory of Nanoscale Biophysics and Biochemistry, The Rockefeller University, New York, NY, USA.
| | - John W Watters
- Laboratory of Nanoscale Biophysics and Biochemistry, The Rockefeller University, New York, NY, USA
| | - Xiangwu Ju
- Laboratory of Nanoscale Biophysics and Biochemistry, The Rockefeller University, New York, NY, USA
| | - Genzhe Lu
- Laboratory of Nanoscale Biophysics and Biochemistry, The Rockefeller University, New York, NY, USA
| | - Shixin Liu
- Laboratory of Nanoscale Biophysics and Biochemistry, The Rockefeller University, New York, NY, USA.
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4
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Fan H. Single‐molecule tethered particle motion to study
protein‐DNA
interaction. J CHIN CHEM SOC-TAIP 2023. [DOI: 10.1002/jccs.202300051] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/31/2023]
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5
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Song E, Hwang S, Munasingha PR, Seo YS, Kang J, Kang C, Hohng S. Transcriptional pause extension benefits the stand-by rather than catch-up Rho-dependent termination. Nucleic Acids Res 2023; 51:2778-2789. [PMID: 36762473 PMCID: PMC10085680 DOI: 10.1093/nar/gkad051] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2022] [Revised: 12/30/2022] [Accepted: 01/19/2023] [Indexed: 02/11/2023] Open
Abstract
Transcriptional pause is essential for all types of termination. In this single-molecule study on bacterial Rho factor-dependent terminators, we confirm that the three Rho-dependent termination routes operate compatibly together in a single terminator, and discover that their termination efficiencies depend on the terminational pauses in unexpected ways. Evidently, the most abundant route is that Rho binds nascent RNA first and catches up with paused RNA polymerase (RNAP) and this catch-up Rho mediates simultaneous releases of transcript RNA and template DNA from RNAP. The fastest route is that the catch-up Rho effects RNA-only release and leads to 1D recycling of RNAP on DNA. The slowest route is that the RNAP-prebound stand-by Rho facilitates only the simultaneous rather than sequential releases. Among the three routes, only the stand-by Rho's termination efficiency positively correlates with pause duration, contrary to a long-standing speculation, invariably in the absence or presence of NusA/NusG factors, competitor RNAs or a crowding agent. Accordingly, the essential terminational pause does not need to be long for the catch-up Rho's terminations, and long pauses benefit only the stand-by Rho's terminations. Furthermore, the Rho-dependent termination of mgtA and ribB riboswitches is controlled mainly by modulation of the stand-by rather than catch-up termination.
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Affiliation(s)
- Eunho Song
- Department of Physics and Astronomy, and Institute of Applied Physics, Seoul National University, Seoul 08826, Republic of Korea
| | - Seungha Hwang
- Department of Chemistry, Korea Advanced Institute of Science and Technology, Daejeon 34141, Republic of Korea
| | - Palinda Ruvan Munasingha
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Daejeon 34141, Republic of Korea
| | - Yeon-Soo Seo
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Daejeon 34141, Republic of Korea
| | - Jin Young Kang
- Correspondence may also be addressed to Jin Young Kang. Tel: +82 42 350 2831;
| | - Changwon Kang
- Correspondence may also be addressed to Changwon Kang. Tel: +82 42 350 2610;
| | - Sungchul Hohng
- To whom correspondence should be addressed. Tel: +82 2 880 6593;
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6
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Landgraf T, Völklein AE, Fürtig B, Schwalbe H. The cotranscriptional folding landscape for two cyclic di-nucleotide-sensing riboswitches with highly homologous aptamer domains acting either as ON- or OFF-switches. Nucleic Acids Res 2022; 50:6639-6655. [PMID: 35736222 PMCID: PMC9262584 DOI: 10.1093/nar/gkac514] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2022] [Revised: 05/03/2022] [Accepted: 06/07/2022] [Indexed: 12/24/2022] Open
Abstract
Riboswitches are gene regulatory elements located in untranslated mRNA regions. They bind inducer molecules with high affinity and specificity. Cyclic-di-nucleotide-sensing riboswitches are major regulators of genes for the environment, membranes and motility (GEMM) of bacteria. Up to now, structural probing assays or crystal structures have provided insight into the interaction between cyclic-di-nucleotides and their corresponding riboswitches. ITC analysis, NMR analysis and computational modeling allowed us to gain a detailed understanding of the gene regulation mechanisms for the Cd1 (Clostridium difficile) and for the pilM (Geobacter metallireducens) riboswitches and their respective di-nucleotides c-di-GMP and c-GAMP. Binding capability showed a 25 nucleotide (nt) long window for pilM and a 61 nt window for Cd1. Within this window, binding affinities ranged from 35 μM to 0.25 μM spanning two orders of magnitude for Cd1 and pilM showing a strong dependence on competing riboswitch folds. Experimental results were incorporated into a Markov simulation to further our understanding of the transcriptional folding pathways of riboswitches. Our model showed the ability to predict riboswitch gene regulation and its dependence on transcription speed, pausing and ligand concentration.
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Affiliation(s)
| | | | - Boris Fürtig
- Correspondence may also be addressed to Boris Fürtig.
| | - Harald Schwalbe
- To whom correspondence should be addressed. Tel: +49 69 798 29737; Fax: +49 69 798 29515;
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7
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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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8
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Yeou S, Lee NK. Single-Molecule Methods for Investigating the Double-Stranded DNA Bendability. Mol Cells 2022; 45:33-40. [PMID: 34470919 PMCID: PMC8819492 DOI: 10.14348/molcells.2021.0182] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2021] [Revised: 07/19/2021] [Accepted: 07/20/2021] [Indexed: 11/27/2022] Open
Abstract
The various DNA-protein interactions associated with the expression of genetic information involve double-stranded DNA (dsDNA) bending. Due to the importance of the formation of the dsDNA bending structure, dsDNA bending properties have long been investigated in the biophysics field. Conventionally, DNA bendability is characterized by innate averaging data from bulk experiments. The advent of single-molecule methods, such as atomic force microscopy, optical and magnetic tweezers, tethered particle motion, and single-molecule fluorescence resonance energy transfer measurement, has provided valuable tools to investigate not only the static structures but also the dynamic properties of bent dsDNA. Here, we reviewed the single-molecule methods that have been used for investigating dsDNA bendability and new findings related to dsDNA bending. Single-molecule approaches are promising tools for revealing the unknown properties of dsDNA related to its bending, particularly in cells.
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Affiliation(s)
- Sanghun Yeou
- Department of Physics, Pohang University of Science and Technology, Pohang 37673, Korea
| | - Nam Ki Lee
- Department of Chemistry, Seoul National University, Seoul 08826, Korea
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9
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Isolation of synchronized E. coli elongation complexes for solid-phase and solution-based in vitro transcription assays. Methods Enzymol 2022; 675:159-192. [DOI: 10.1016/bs.mie.2022.07.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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10
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van Dongen JE, Spoelstra LR, Berendsen JTW, Loessberg-Zahl JT, Eijkel JCT, Segerink LI. A Multiplexable Plasmonic Hairpin-DNA Sensor Based On Target-specific Tether Dynamics. ACS Sens 2021; 6:4297-4303. [PMID: 34851614 PMCID: PMC8715532 DOI: 10.1021/acssensors.1c02097] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
![]()
The need for measurements
of multiple biomarkers simultaneously
at subnanomolar concentrations asks for the development of new sensors
with high sensitivity, specificity, precision, and accuracy. Currently,
multiplexed sensing in single molecule sensors increases the complexity
of the system in terms of reagents and sample read-out. In this letter,
we propose a novel approach to multiplex hairpin-based single-DNA
molecule sensors, which overcomes the limitations of the present approaches
for multiplexing. By target-dependent ssDNA hairpin design, we can
create DNA tethers that have distinct tether dynamics upon target
binding. Our numerical model shows that by changing the stem length
of the ssDNA hairpin, significantly different dynamic tether behavior
will be observed. By exploiting the distance-dependent coupling of
AuNPs to gold films, we can probe this dynamic behavior along the z-axis using a simple laser equipped microscope.
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Affiliation(s)
- Jeanne Elisabeth van Dongen
- BIOS Lab on a Chip Group, MESA+ & TechMed Institutes, Max Planck Center for Complex Fluid Dynamics, University of Twente, P.O. Box 217 7500 AE Enschede, The Netherlands
| | - Laurens Rudi Spoelstra
- BIOS Lab on a Chip Group, MESA+ & TechMed Institutes, Max Planck Center for Complex Fluid Dynamics, University of Twente, P.O. Box 217 7500 AE Enschede, The Netherlands
| | - Johanna Theodora Wilhelmina Berendsen
- BIOS Lab on a Chip Group, MESA+ & TechMed Institutes, Max Planck Center for Complex Fluid Dynamics, University of Twente, P.O. Box 217 7500 AE Enschede, The Netherlands
| | - Joshua Taylor Loessberg-Zahl
- BIOS Lab on a Chip Group, MESA+ & TechMed Institutes, Max Planck Center for Complex Fluid Dynamics, University of Twente, P.O. Box 217 7500 AE Enschede, The Netherlands
| | - Jan Cornelis Titus Eijkel
- BIOS Lab on a Chip Group, MESA+ & TechMed Institutes, Max Planck Center for Complex Fluid Dynamics, University of Twente, P.O. Box 217 7500 AE Enschede, The Netherlands
| | - Loes Irene Segerink
- BIOS Lab on a Chip Group, MESA+ & TechMed Institutes, Max Planck Center for Complex Fluid Dynamics, University of Twente, P.O. Box 217 7500 AE Enschede, The Netherlands
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11
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Wilson H, Wang Q. Joint Detection of Change Points in Multichannel Single-Molecule Measurements. J Phys Chem B 2021; 125:13425-13435. [PMID: 34870418 DOI: 10.1021/acs.jpcb.1c08869] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Recent developments in single-molecule measurement technology have expanded the capability to measure multiple parameters. These emergent modalities provide more holistic observations of complex biomolecular processes and call for new analysis methods to detect state changes in multichannel data. Here we develop an algorithm called MULLR (MUlti-channel Log-Likelihood Ratio test) to jointly identify change points in multichannel single-molecule measurements. MULLR is an extension of the popular single-channel implementation for change point detection based on a binary segmentation and log-likelihood ratio test framework. We validate the algorithm on simulated data and characterize the power of detection and false positive rate. We show that MULLR can identify change points in experimental multichannel data and naturally works with different noise statistics and time resolutions across channels. Further, we quantify the benefit of MULLR compared to single-channel analysis. We envision that the MULLR algorithm will be useful to a range of multiparameter single-molecule measurements.
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Affiliation(s)
- Hugh Wilson
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, New Jersey 08540, United States
| | - Quan Wang
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, New Jersey 08540, United States
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12
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Wang Y, Jiang B, Wang Y, Wei W, Niu B, Chen H, Wang H. Imaging the Heterogeneous Localization of a Single Molecule. Anal Chem 2021; 93:12464-12471. [PMID: 34459585 DOI: 10.1021/acs.analchem.1c02787] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Single-molecule localization allows determining the underlying biological and biochemical processes and promotes the development of super-resolution imaging techniques. Here, we present an optical technique of tracking the motion of a single nanoparticle linked to a substrate via a biomolecule tether to reveal the localization of single biomolecules and the transient states of single nanoparticle switching between specific binding pairs. The affinities, steric hindrance, and conformational variation of a single-molecule binding pair uncover the dynamic details and intrinsic mechanism of binding processes with high specificity and accuracy (a few nanometers). The application of tracking motions of single soft liposomes on different modified surfaces was further demonstrated, which revealed the characteristic behavior related to surface chemistry. Our results show that the trajectory of nanoscale liposomes loaded with small-drug molecules is linked to the compositional inhomogeneity, which provides a route for thorough comprehension of the fundamental biotechnological process.
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Affiliation(s)
- Yi Wang
- State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China
| | - Bo Jiang
- State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China
| | - Yan Wang
- Biodesign Center for Bioelectronics and Biosensors, and School of Electrical, Energy, and Computer Engineering, Arizona State University, Tempe, Arizona 85287, United States
| | - Wei Wei
- State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China
| | - Ben Niu
- State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China
| | - Hongyuan Chen
- State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China
| | - Hui Wang
- State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China
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13
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Lee CY, Myong S. Probing steps in DNA transcription using single-molecule methods. J Biol Chem 2021; 297:101086. [PMID: 34403697 PMCID: PMC8441165 DOI: 10.1016/j.jbc.2021.101086] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2021] [Revised: 08/12/2021] [Accepted: 08/13/2021] [Indexed: 11/22/2022] Open
Abstract
Transcriptional regulation is one of the key steps in determining gene expression. Diverse single-molecule techniques have been applied to characterize the stepwise progression of transcription, yielding complementary results. These techniques include, but are not limited to, fluorescence-based microscopy with single or multiple colors, force measuring and manipulating microscopy using magnetic field or light, and atomic force microscopy. Here, we summarize and evaluate these current methodologies in studying and resolving individual steps in the transcription reaction, which encompasses RNA polymerase binding, initiation, elongation, mRNA production, and termination. We also describe the advantages and disadvantages of each method for studying transcription.
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Affiliation(s)
- Chun-Ying Lee
- Department of Biophysics, Johns Hopkins University, Baltimore, Maryland, USA
| | - Sua Myong
- Department of Biophysics, Johns Hopkins University, Baltimore, Maryland, USA; Physics Frontier Center (Center for Physics of Living Cells), University of Illinois, Urbana, Illinois, USA.
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14
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Meng X, Kukura P, Faez S. Sensing force and charge at the nanoscale with a single-molecule tether. NANOSCALE 2021; 13:12687-12696. [PMID: 34477619 PMCID: PMC8319944 DOI: 10.1039/d1nr01970h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/29/2021] [Accepted: 07/04/2021] [Indexed: 06/13/2023]
Abstract
Measuring the electrophoretic mobility of molecules is a powerful experimental approach for investigating biomolecular processes. A frequent challenge in the context of single-particle measurements is throughput, limiting the obtainable statistics. Here, we present a molecular force sensor and charge detector based on parallelised imaging and tracking of tethered double-stranded DNA functionalised with charged nanoparticles interacting with an externally applied electric field. Tracking the position of the tethered particle with simultaneous nanometre precision and microsecond temporal resolution allows us to detect and quantify the electrophoretic force down to the sub-piconewton scale. Furthermore, we demonstrate that this approach is suitable for detecting changes to the particle charge state, as induced by the addition of charged biomolecules or changes to pH. Our approach provides an alternative route to studying structural and charge dynamics at the single molecule level.
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Affiliation(s)
- Xuanhui Meng
- Physical and Theoretical Chemistry Laboratory, University of OxfordSouth Parks RoadOX1 3QZ OxfordUK
| | - Philipp Kukura
- Physical and Theoretical Chemistry Laboratory, University of OxfordSouth Parks RoadOX1 3QZ OxfordUK
| | - Sanli Faez
- Nanophotonics, Debye Institute for Nanomaterials Research, Utrecht UniversityNLThe Netherlands
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15
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Qian J, Xu W, Dunlap D, Finzi L. Single-molecule insights into torsion and roadblocks in bacterial transcript elongation. Transcription 2021; 12:219-231. [PMID: 34719335 PMCID: PMC8632135 DOI: 10.1080/21541264.2021.1997315] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2021] [Revised: 10/18/2021] [Accepted: 10/20/2021] [Indexed: 12/12/2022] Open
Abstract
During transcription, RNA polymerase (RNAP) translocates along the helical template DNA while maintaining high transcriptional fidelity. However, all genomes are dynamically twisted, writhed, and decorated by bound proteins and motor enzymes. In prokaryotes, proteins bound to DNA, specifically or not, frequently compact DNA into conformations that may silence genes by obstructing RNAP. Collision of RNAPs with these architectural proteins, may result in RNAP stalling and/or displacement of the protein roadblock. It is important to understand how rapidly transcribing RNAPs operate under different levels of supercoiling or in the presence of roadblocks. Given the broad range of asynchronous dynamics exhibited by transcriptional complexes, single-molecule assays, such as atomic force microscopy, fluorescence detection, optical and magnetic tweezers, etc. are well suited for detecting and quantifying activity with adequate spatial and temporal resolution. Here, we summarize current understanding of the effects of torsion and roadblocks on prokaryotic transcription, with a focus on single-molecule assays that provide real-time detection and readout.
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Affiliation(s)
- Jin Qian
- Emory University, Atlanta, GA, USA
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16
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Bianco PR, Lu Y. Single-molecule insight into stalled replication fork rescue in Escherichia coli. Nucleic Acids Res 2021; 49:4220-4238. [PMID: 33744948 PMCID: PMC8096234 DOI: 10.1093/nar/gkab142] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2020] [Revised: 02/15/2021] [Accepted: 02/22/2021] [Indexed: 01/05/2023] Open
Abstract
DNA replication forks stall at least once per cell cycle in Escherichia coli. DNA replication must be restarted if the cell is to survive. Restart is a multi-step process requiring the sequential action of several proteins whose actions are dictated by the nature of the impediment to fork progression. When fork progress is impeded, the sequential actions of SSB, RecG and the RuvABC complex are required for rescue. In contrast, when a template discontinuity results in the forked DNA breaking apart, the actions of the RecBCD pathway enzymes are required to resurrect the fork so that replication can resume. In this review, we focus primarily on the significant insight gained from single-molecule studies of individual proteins, protein complexes, and also, partially reconstituted regression and RecBCD pathways. This insight is related to the bulk-phase biochemical data to provide a comprehensive review of each protein or protein complex as it relates to stalled DNA replication fork rescue.
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Affiliation(s)
- Piero R Bianco
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Nebraska Medical Center, Omaha, NE 68198-6025, USA
| | - Yue Lu
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Nebraska Medical Center, Omaha, NE 68198-6025, USA
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17
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Visser EWA, Miladinovic J, Milstein JN. An Ultrastable and Dense Single-Molecule Click Platform for Sensing Protein-Deoxyribonucleic Acid Interactions. SMALL METHODS 2021; 5:e2001180. [PMID: 34928085 DOI: 10.1002/smtd.202001180] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/26/2020] [Revised: 01/29/2021] [Indexed: 06/14/2023]
Abstract
An ultrastable, highly dense single-molecule assay ideal for observing protein-DNA interactions is demonstrated. Stable click tethered particle motion leverages next generation click-chemistry to achieve an ultrahigh density of surface tethered reporter particles, and has low non-specific interactions, is stable at elevated temperatures to at least 45 °C, and is compatible with Mg2+ , an important ionic component of many regulatory protein-DNA interactions. Prepared samples remain stable, with little degradation, for >6 months in physiological buffers. These improvements enable the authors to study previously inaccessible sequence and temperature-dependent effects on DNA binding by the bacterial protein, histone-like nucleoid-structuring protein, a global transcriptional regulator found in Escherichia coli. This greatly improved assay can directly be translated to accelerate existing tethered particle-based, single-molecule biosensing applications.
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Affiliation(s)
- Emiel W A Visser
- Department of Chemical and Physical Sciences, University of Toronto Mississauga, Mississauga, ON L5L 1C6, Canada
- Eindhoven University of Technology, Eindhoven, 5612 AZ, The Netherlands
| | - Jovana Miladinovic
- Department of Chemical and Physical Sciences, University of Toronto Mississauga, Mississauga, ON L5L 1C6, Canada
| | - Joshua N Milstein
- Department of Chemical and Physical Sciences, University of Toronto Mississauga, Mississauga, ON L5L 1C6, Canada
- Department of Physics, University of Toronto, Toronto, ON M5S 1A1, Canada
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18
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Lin YY, Li MH, Chang YC, Fu PY, Ohniwa RL, Li HW, Lin JJ. Dynamic DNA Shortening by Telomere-Binding Protein Cdc13. J Am Chem Soc 2021; 143:5815-5825. [PMID: 33831300 DOI: 10.1021/jacs.1c00820] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Telomeres are essential for chromosome maintenance. Cdc13 is a single-stranded telomeric DNA binding protein that caps telomeres and regulates telomerase function in yeast. Although specific binding of Cdc13 to telomeric DNA is critical for telomere protection, the detail mechanism how Cdc13-DNA complex protects telomere is unclear. Using two single-molecule methods, tethered particle motion and atomic force microscopy, we demonstrate that specific binding of Cdc13 on single-stranded telomeric DNA shortens duplex DNA into distinct states differed by ∼70-80 base pairs. DNA shortening by Cdc13 is dynamic and independent of duplex DNA sequences or length. Significantly, we found that Pif1 helicase is incapable of removing Cdc13 from the shortened DNA-Cdc13 complex, suggesting that Cdc13 forms structurally stable complex by shortening of the bound DNA. Together our data identified shortening of DNA by Cdc13 and provided an indication for efficient protection of telomere ends by the shortened DNA-Cdc13 complex.
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Affiliation(s)
- Yi-Yun Lin
- Institute of Biochemistry and Molecular Biology, National Taiwan University, Taipei City 10617, Taiwan
| | - Min-Hsuan Li
- Institute of Biochemistry and Molecular Biology, National Taiwan University, Taipei City 10617, Taiwan
| | - Yen-Chan Chang
- Department of Chemistry, National Taiwan University, Taipei City 10617, Taiwan
| | - Peng-Yu Fu
- Institute of Biochemistry and Molecular Biology, National Taiwan University, Taipei City 10617, Taiwan
| | - Ryosuke L Ohniwa
- Faculty of Medicine, University of Tsukuba, Ibaraki 305-8577, Japan.,Center for Biotechnology, National Taiwan University, Taipei City 10617, Taiwan
| | - Hung-Wen Li
- Department of Chemistry, National Taiwan University, Taipei City 10617, Taiwan
| | - Jing-Jer Lin
- Institute of Biochemistry and Molecular Biology, National Taiwan University, Taipei City 10617, Taiwan.,Institute of Biopharmaceutical Sciences, National Yang-Ming University, Taipei City 112, Taiwan
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19
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20
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Single-cell measurement of plasmid copy number and promoter activity. Nat Commun 2021; 12:1475. [PMID: 33674569 PMCID: PMC7935883 DOI: 10.1038/s41467-021-21734-y] [Citation(s) in RCA: 36] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2020] [Accepted: 02/08/2021] [Indexed: 01/31/2023] Open
Abstract
Accurate measurements of promoter activities are crucial for predictably building genetic systems. Here we report a method to simultaneously count plasmid DNA, RNA transcripts, and protein expression in single living bacteria. From these data, the activity of a promoter in units of RNAP/s can be inferred. This work facilitates the reporting of promoters in absolute units, the variability in their activity across a population, and their quantitative toll on cellular resources, all of which provide critical insights for cellular engineering.
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21
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Akama K, Noji H. Multiparameter single-particle motion analysis for homogeneous digital immunoassay. Analyst 2021; 146:1303-1310. [DOI: 10.1039/d0an02056g] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Digital homogeneous non-enzymatic immunosorbent assay (digital Ho-Non ELISA) is a new class of digital immunoassay. In this paper, we developed a multiparameter single-particle motion analysis method for a highly sensitive digital Ho-Non ELISA.
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Affiliation(s)
- Kenji Akama
- Department of Applied Chemistry
- Graduate School of Engineering
- The University of Tokyo
- Tokyo 113-8656
- Japan
| | - Hiroyuki Noji
- Department of Applied Chemistry
- Graduate School of Engineering
- The University of Tokyo
- Tokyo 113-8656
- Japan
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22
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Armstrong RE, Horáček M, Zijlstra P. Plasmonic Assemblies for Real-Time Single-Molecule Biosensing. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2020; 16:e2003934. [PMID: 33258287 DOI: 10.1002/smll.202003934] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2020] [Revised: 10/09/2020] [Indexed: 05/11/2023]
Abstract
Their tunable optical properties and versatile surface functionalization have sparked applications of plasmonic assemblies in the fields of biosensing, nonlinear optics, and photonics. Particularly, in the field of biosensing, rapid advances have occurred in the use of plasmonic assemblies for real-time single-molecule sensing. Compared to individual particles, the use of assemblies as sensors provides stronger signals, more control over the optical properties, and access to a broader range of timescales. In the past years, they have been used to directly reveal single-molecule interactions, mechanical properties, and conformational dynamics. This review summarizes the development of real-time single-molecule sensors built around plasmonic assemblies. First, a brief overview of their optical properties is given, and then recent applications are described. The current challenges in the field and suggestions to overcome those challenges are discussed in detail. Their stability, specificity, and sensitivity as sensors provide a complementary approach to other single-molecule techniques like force spectroscopy and single-molecule fluorescence. In future applications, the impact in real-time sensing on ultralong timescales (hours) and ultrashort timescales (sub-millisecond), time windows that are difficult to access using other techniques, is particularly foreseen.
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Affiliation(s)
- Rachel E Armstrong
- Department of Applied Physics & Institute for Complex Molecular Systems, Eindhoven University of Technology, Postbus 513, Eindhoven, MB, 5600, the Netherlands
| | - Matěj Horáček
- Department of Applied Physics & Institute for Complex Molecular Systems, Eindhoven University of Technology, Postbus 513, Eindhoven, MB, 5600, the Netherlands
| | - Peter Zijlstra
- Department of Applied Physics & Institute for Complex Molecular Systems, Eindhoven University of Technology, Postbus 513, Eindhoven, MB, 5600, the Netherlands
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23
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Ukogu OA, Smith AD, Devenica LM, Bediako H, McMillan RB, Ma Y, Balaji A, Schwab RD, Anwar S, Dasgupta M, Carter AR. Protamine loops DNA in multiple steps. Nucleic Acids Res 2020; 48:6108-6119. [PMID: 32392345 PMCID: PMC7293030 DOI: 10.1093/nar/gkaa365] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2019] [Revised: 04/12/2020] [Accepted: 04/27/2020] [Indexed: 11/13/2022] Open
Abstract
Protamine proteins dramatically condense DNA in sperm to almost crystalline packing levels. Here, we measure the first step in the in vitro pathway, the folding of DNA into a single loop. Current models for DNA loop formation are one-step, all-or-nothing models with a looped state and an unlooped state. However, when we use a Tethered Particle Motion (TPM) assay to measure the dynamic, real-time looping of DNA by protamine, we observe the presence of multiple folded states that are long-lived (∼100 s) and reversible. In addition, we measure folding on DNA molecules that are too short to form loops. This suggests that protamine is using a multi-step process to loop the DNA rather than a one-step process. To visualize the DNA structures, we used an Atomic Force Microscopy (AFM) assay. We see that some folded DNA molecules are loops with a ∼10-nm radius and some of the folded molecules are partial loops—c-shapes or s-shapes—that have a radius of curvature of ∼10 nm. Further analysis of these structures suggest that protamine is bending the DNA to achieve this curvature rather than increasing the flexibility of the DNA. We therefore conclude that protamine loops DNA in multiple steps, bending it into a loop.
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Affiliation(s)
- Obinna A Ukogu
- Department of Physics, Amherst College, Amherst, MA 01002, USA
| | - Adam D Smith
- Department of Physics, Amherst College, Amherst, MA 01002, USA
| | - Luka M Devenica
- Department of Physics, Amherst College, Amherst, MA 01002, USA
| | - Hilary Bediako
- Department of Physics, Amherst College, Amherst, MA 01002, USA
| | - Ryan B McMillan
- Department of Physics, Amherst College, Amherst, MA 01002, USA
| | - Yuxing Ma
- Department of Physics, Amherst College, Amherst, MA 01002, USA
| | - Ashwin Balaji
- Department of Physics, Amherst College, Amherst, MA 01002, USA
| | - Robert D Schwab
- Department of Physics, Amherst College, Amherst, MA 01002, USA
| | - Shahzad Anwar
- Department of Physics, Amherst College, Amherst, MA 01002, USA
| | | | - Ashley R Carter
- Department of Physics, Amherst College, Amherst, MA 01002, USA
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24
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Hirokawa S, Chure G, Belliveau NM, Lovely GA, Anaya M, Schatz DG, Baltimore D, Phillips R. Sequence-dependent dynamics of synthetic and endogenous RSSs in V(D)J recombination. Nucleic Acids Res 2020; 48:6726-6739. [PMID: 32449932 PMCID: PMC7337519 DOI: 10.1093/nar/gkaa418] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2020] [Revised: 04/20/2020] [Accepted: 05/07/2020] [Indexed: 12/25/2022] Open
Abstract
Developing lymphocytes of jawed vertebrates cleave and combine distinct gene segments to assemble antigen-receptor genes. This process called V(D)J recombination that involves the RAG recombinase binding and cutting recombination signal sequences (RSSs) composed of conserved heptamer and nonamer sequences flanking less well-conserved 12- or 23-bp spacers. Little quantitative information is known about the contributions of individual RSS positions over the course of the RAG-RSS interaction. We employ a single-molecule method known as tethered particle motion to track the formation, lifetime and cleavage of individual RAG-12RSS-23RSS paired complexes (PCs) for numerous synthetic and endogenous 12RSSs. We reveal that single-bp changes, including in the 12RSS spacer, can significantly and selectively alter PC formation or the probability of RAG-mediated cleavage in the PC. We find that some rarely used endogenous gene segments can be mapped directly to poor RAG binding on their adjacent 12RSSs. Finally, we find that while abrogating RSS nicking with Ca2+ leads to substantially shorter PC lifetimes, analysis of the complete lifetime distributions of any 12RSS even on this reduced system reveals that the process of exiting the PC involves unidentified molecular details whose involvement in RAG-RSS dynamics are crucial to quantitatively capture kinetics in V(D)J recombination.
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Affiliation(s)
- Soichi Hirokawa
- Department of Applied Physics, California Institute of Technology, Pasadena, CA 91125, USA
| | - Griffin Chure
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Nathan M Belliveau
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Geoffrey A Lovely
- National Institute on Aging, National Institutes of Health, Baltimore, MD 21224, USA
| | - Michael Anaya
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - David G Schatz
- Department of Immunobiology, Yale University School of Medicine, New Haven, CT 06520, USA
| | - David Baltimore
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Rob Phillips
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
- Department of Physics, California Institute of Technology, Pasadena, CA 91125, USA
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25
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Farka Z, Mickert MJ, Pastucha M, Mikušová Z, Skládal P, Gorris HH. Fortschritte in der optischen Einzelmoleküldetektion: Auf dem Weg zu höchstempfindlichen Bioaffinitätsassays. Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.201913924] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Zdeněk Farka
- CEITEC – Central European Institute of TechnologyMasaryk University 625 00 Brno Czech Republic
| | - Matthias J. Mickert
- Institut für Analytische Chemie, Chemo- und BiosensorikUniversität Regensburg Universitätsstraße 31 93040 Regensburg Deutschland
| | - Matěj Pastucha
- CEITEC – Central European Institute of TechnologyMasaryk University 625 00 Brno Czech Republic
- Department of BiochemistryFaculty of ScienceMasaryk University 625 00 Brno Czech Republic
| | - Zuzana Mikušová
- CEITEC – Central European Institute of TechnologyMasaryk University 625 00 Brno Czech Republic
- Department of BiochemistryFaculty of ScienceMasaryk University 625 00 Brno Czech Republic
| | - Petr Skládal
- CEITEC – Central European Institute of TechnologyMasaryk University 625 00 Brno Czech Republic
- Department of BiochemistryFaculty of ScienceMasaryk University 625 00 Brno Czech Republic
| | - Hans H. Gorris
- Institut für Analytische Chemie, Chemo- und BiosensorikUniversität Regensburg Universitätsstraße 31 93040 Regensburg Deutschland
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26
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Farka Z, Mickert MJ, Pastucha M, Mikušová Z, Skládal P, Gorris HH. Advances in Optical Single-Molecule Detection: En Route to Supersensitive Bioaffinity Assays. Angew Chem Int Ed Engl 2020; 59:10746-10773. [PMID: 31869502 PMCID: PMC7318240 DOI: 10.1002/anie.201913924] [Citation(s) in RCA: 68] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2019] [Revised: 12/20/2019] [Indexed: 12/11/2022]
Abstract
The ability to detect low concentrations of analytes and in particular low-abundance biomarkers is of fundamental importance, e.g., for early-stage disease diagnosis. The prospect of reaching the ultimate limit of detection has driven the development of single-molecule bioaffinity assays. While many review articles have highlighted the potentials of single-molecule technologies for analytical and diagnostic applications, these technologies are not as widespread in real-world applications as one should expect. This Review provides a theoretical background on single-molecule-or better digital-assays to critically assess their potential compared to traditional analog assays. Selected examples from the literature include bioaffinity assays for the detection of biomolecules such as proteins, nucleic acids, and viruses. The structure of the Review highlights the versatility of optical single-molecule labeling techniques, including enzymatic amplification, molecular labels, and innovative nanomaterials.
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Affiliation(s)
- Zdeněk Farka
- CEITEC – Central European Institute of TechnologyMasaryk University625 00BrnoCzech Republic
| | - Matthias J. Mickert
- Institute of Analytical Chemistry, Chemo- and BiosensorsUniversity of RegensburgUniversitätsstraße 3193040RegensburgGermany
| | - Matěj Pastucha
- CEITEC – Central European Institute of TechnologyMasaryk University625 00BrnoCzech Republic
- Department of BiochemistryFaculty of ScienceMasaryk University625 00BrnoCzech Republic
| | - Zuzana Mikušová
- CEITEC – Central European Institute of TechnologyMasaryk University625 00BrnoCzech Republic
- Department of BiochemistryFaculty of ScienceMasaryk University625 00BrnoCzech Republic
| | - Petr Skládal
- CEITEC – Central European Institute of TechnologyMasaryk University625 00BrnoCzech Republic
- Department of BiochemistryFaculty of ScienceMasaryk University625 00BrnoCzech Republic
| | - Hans H. Gorris
- Institute of Analytical Chemistry, Chemo- and BiosensorsUniversity of RegensburgUniversitätsstraße 3193040RegensburgGermany
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27
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Akama K, Iwanaga N, Yamawaki K, Okuda M, Jain K, Ueno H, Soga N, Minagawa Y, Noji H. Wash- and Amplification-Free Digital Immunoassay Based on Single-Particle Motion Analysis. ACS NANO 2019; 13:13116-13126. [PMID: 31675215 DOI: 10.1021/acsnano.9b05917] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Digital enzyme-linked immunosorbent assay (ELISA) is a powerful analytical method for highly sensitive protein biomarker detection. The current protocol of digital ELISA requires multiple washing steps and signal amplification using an enzyme, which could be the potential drawback in in vitro diagnosis. In this study, we propose a digital immunoassay method, which we call "Digital HoNon-ELISA" (digital homogeneous non-enzymatic immunosorbent assay) for highly sensitive detection without washing and signal amplification. Target antigen molecules react with antibody-coated magnetic nanoparticles, which are then magnetically pulled into femtoliter-sized reactors. The antigens on the particles are captured by antibodies anchored on the bottom surface of the reactor via molecular tethers. Magnetic force enhances the efficiency of particle encapsulation in the reactors. Subsequent physical compartmentalization of the particles enhances the binding efficiency of antigen-carrying particles to the antibodies. The tethered particles show characteristic Brownian motion within a limited space by the molecular tethering, which is distinct from free diffusion or nonspecific binding of antigen-free particles. The number of tethered particles directly correlates with the concentration of the target antigen. Digital HoNon-ELISA was used with a prostate-specific antigen to achieve a detection of 0.093 pg/mL, which is over 9.0-fold the sensitivity of commercialized highly sensitive ELISA (0.84 pg/mL) and comparable to digital ELISA (0.055 pg/mL). This digital immunoassay strategy has sensitivity similar to digital ELISA with simplicity similar to homogeneous assay. Such similarity allows for potential application in rapid and simple digital diagnostic tests without the need for washing and enzymatic amplification.
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Affiliation(s)
- Kenji Akama
- Department of Applied Chemistry, Graduate School of Engineering , The University of Tokyo , 7-3-1 Hongo , Bunkyo-ku, Tokyo 113-8656 , Japan
- Central Research Laboratories , Sysmex Corporation , 4-4-4 Takatsukadai , Nishi-ku, Kobe 651-2271 , Japan
| | - Niina Iwanaga
- Central Research Laboratories , Sysmex Corporation , 4-4-4 Takatsukadai , Nishi-ku, Kobe 651-2271 , Japan
| | - Koya Yamawaki
- Central Research Laboratories , Sysmex Corporation , 4-4-4 Takatsukadai , Nishi-ku, Kobe 651-2271 , Japan
| | - Masaki Okuda
- Central Research Laboratories , Sysmex Corporation , 4-4-4 Takatsukadai , Nishi-ku, Kobe 651-2271 , Japan
| | - Krupali Jain
- Central Research Laboratories , Sysmex Corporation , 4-4-4 Takatsukadai , Nishi-ku, Kobe 651-2271 , Japan
| | - Hiroshi Ueno
- Department of Applied Chemistry, Graduate School of Engineering , The University of Tokyo , 7-3-1 Hongo , Bunkyo-ku, Tokyo 113-8656 , Japan
| | - Naoki Soga
- Department of Applied Chemistry, Graduate School of Engineering , The University of Tokyo , 7-3-1 Hongo , Bunkyo-ku, Tokyo 113-8656 , Japan
| | - Yoshihiro Minagawa
- Department of Applied Chemistry, Graduate School of Engineering , The University of Tokyo , 7-3-1 Hongo , Bunkyo-ku, Tokyo 113-8656 , Japan
| | - Hiroyuki Noji
- Department of Applied Chemistry, Graduate School of Engineering , The University of Tokyo , 7-3-1 Hongo , Bunkyo-ku, Tokyo 113-8656 , Japan
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28
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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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29
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Statistical physics and mesoscopic modeling to interpret tethered particle motion experiments. Methods 2019; 169:57-68. [PMID: 31302177 DOI: 10.1016/j.ymeth.2019.07.006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2019] [Revised: 06/11/2019] [Accepted: 07/07/2019] [Indexed: 11/22/2022] Open
Abstract
Tethered particle motion experiments are versatile single-molecule techniques enabling one to address in vitro the molecular properties of DNA and its interactions with various partners involved in genetic regulations. These techniques provide raw data such as the tracked particle amplitude of movement, from which relevant information about DNA conformations or states must be recovered. Solving this inverse problem appeals to specific theoretical tools that have been designed in the two last decades, together with the data pre-processing procedures that ought to be implemented to avoid biases inherent to these experimental techniques. These statistical tools and models are reviewed in this paper.
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30
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Parallelized DNA tethered bead measurements to scrutinize DNA mechanical structure. Methods 2019; 169:46-56. [PMID: 31351926 DOI: 10.1016/j.ymeth.2019.07.020] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2019] [Revised: 07/01/2019] [Accepted: 07/22/2019] [Indexed: 01/05/2023] Open
Abstract
Tethering beads to DNA offers a panel of single molecule techniques for the refined analysis of the conformational dynamics of DNA and the elucidation of the mechanisms of enzyme activity. Recent developments include the massive parallelization of these techniques achieved by the fabrication of dedicated nanoarrays by soft nanolithography. We focus here on two of these techniques: the Tethered Particle motion and Magnetic Tweezers allowing analysis of the behavior of individual DNA molecules in the absence of force and under the application of a force and/or a torque, respectively. We introduce the experimental protocols for the parallelization and discuss the benefits already gained, and to come, for these single molecule investigations.
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31
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Mickolajczyk KJ, Cook ASI, Jevtha JP, Fricks J, Hancock WO. Insights into Kinesin-1 Stepping from Simulations and Tracking of Gold Nanoparticle-Labeled Motors. Biophys J 2019; 117:331-345. [PMID: 31301807 DOI: 10.1016/j.bpj.2019.06.010] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2018] [Revised: 06/04/2019] [Accepted: 06/10/2019] [Indexed: 02/02/2023] Open
Abstract
High-resolution tracking of gold nanoparticle-labeled proteins has emerged as a powerful technique for measuring the structural kinetics of processive enzymes and other biomacromolecules. These techniques use point spread function (PSF) fitting methods borrowed from single-molecule fluorescence imaging to determine molecular positions below the diffraction limit. However, compared to fluorescence, gold nanoparticle tracking experiments are performed at significantly higher frame rates and utilize much larger probes. In the current work, we use Brownian dynamics simulations of nanoparticle-labeled proteins to investigate the regimes in which the fundamental assumptions of PSF fitting hold and where they begin to break down. We find that because gold nanoparticles undergo tethered diffusion around their anchor point, PSF fitting cannot be extended to arbitrarily fast frame rates. Instead, camera exposure times that allow the nanoparticle to fully populate its stationary positional distribution achieve a spatial averaging that increases fitting precision. We furthermore find that changes in the rotational freedom of the tagged protein can lead to artifactual translations in the fitted particle position. Finally, we apply these lessons to dissect a standing controversy in the kinesin field over the structure of a dimer in the ATP waiting state. Combining new experiments with simulations, we determine that the rear kinesin head in the ATP waiting state is unbound but not displaced from its previous microtubule binding site and that apparent differences in separately published reports were simply due to differences in the gold nanoparticle attachment position. Our results highlight the importance of gold conjugation decisions and imaging parameters to high-resolution tracking results and will serve as a useful guide for the design of future gold nanoparticle tracking experiments.
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Affiliation(s)
- Keith J Mickolajczyk
- Department of Biomedical Engineering; Intercollege Graduate Degree Program in Bioengineering
| | - Annan S I Cook
- Department of Biomedical Engineering; Department of Physics, Pennsylvania State University, University Park, Pennsylvania
| | | | - John Fricks
- School of Mathematical and Statistical Sciences, Arizona State University, Tempe, Arizona
| | - William O Hancock
- Department of Biomedical Engineering; Intercollege Graduate Degree Program in Bioengineering.
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32
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Kramm K, Endesfelder U, Grohmann D. A Single-Molecule View of Archaeal Transcription. J Mol Biol 2019; 431:4116-4131. [PMID: 31207238 DOI: 10.1016/j.jmb.2019.06.009] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2019] [Revised: 05/27/2019] [Accepted: 06/06/2019] [Indexed: 01/03/2023]
Abstract
The discovery of the archaeal domain of life is tightly connected to an in-depth analysis of the prokaryotic RNA world. In addition to Carl Woese's approach to use the sequence of the 16S rRNA gene as phylogenetic marker, the finding of Karl Stetter and Wolfram Zillig that archaeal RNA polymerases (RNAPs) were nothing like the bacterial RNAP but are more complex enzymes that resemble the eukaryotic RNAPII was one of the key findings supporting the idea that archaea constitute the third major branch on the tree of life. This breakthrough in transcriptional research 40years ago paved the way for in-depth studies of the transcription machinery in archaea. However, although the archaeal RNAP and the basal transcription factors that fine-tune the activity of the RNAP during the transcription cycle are long known, we still lack information concerning the architecture and dynamics of archaeal transcription complexes. In this context, single-molecule measurements were instrumental as they provided crucial insights into the process of transcription initiation, the architecture of the initiation complex and the dynamics of mobile elements of the RNAP. In this review, we discuss single-molecule approaches suitable to examine molecular mechanisms of transcription and highlight findings that shaped our understanding of the archaeal transcription apparatus. We furthermore explore the possibilities and challenges of next-generation single-molecule techniques, for example, super-resolution microscopy and single-molecule tracking, and ask whether these approaches will ultimately allow us to investigate archaeal transcription in vivo.
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Affiliation(s)
- Kevin Kramm
- Institute of Biochemistry, Genetics and Microbiology, University of Regensburg, Universitätsstraße 31, 93053 Regensburg, Germany
| | - Ulrike Endesfelder
- Department of Systems and Synthetic Microbiology, Max Planck Institute for Terrestrial Microbiology and LOEWE Center for Synthetic Microbiology (SYNMIKRO), Karl-von-Frisch-Str. 16, 35043 Marburg, Germany
| | - Dina Grohmann
- Institute of Biochemistry, Genetics and Microbiology, University of Regensburg, Universitätsstraße 31, 93053 Regensburg, Germany.
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Probing Mitotic CENP-E Kinesin with the Tethered Cargo Motion Assay and Laser Tweezers. Biophys J 2019; 114:2640-2652. [PMID: 29874614 DOI: 10.1016/j.bpj.2018.04.017] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2017] [Revised: 03/22/2018] [Accepted: 04/10/2018] [Indexed: 12/18/2022] Open
Abstract
Coiled-coil stalks of various kinesins differ significantly in predicted length and structure; this is an adaption that helps these motors carry out their specialized functions. However, little is known about the dynamic stalk configuration in moving motors. To gain insight into the conformational properties of the transporting motors, we developed a theoretical model to predict Brownian motion of a microbead tethered to the tail of a single, freely walking molecule. This approach, which we call the tethered cargo motion (TCM) assay, provides an accurate measure of the mechanical properties of motor-cargo tethering, verified using kinesin-1 conjugated to a microbead via DNA links in vitro. Applying the TCM assay to the mitotic kinesin CENP-E unexpectedly revealed that when walking along a microtubule track, this highly elongated molecule with a contour length of 230 nm formed a 20-nm-long tether. The stalk of a walking CENP-E could not be extended fully by application of sideways force with optical tweezers (up to 4 pN), implying that CENP-E carries its cargo in a compact configuration. Assisting force applied along the microtubule track accelerates CENP-E walking, but this increase does not depend on the presence of the CENP-E stalk. Our results suggest that the unusually large stalk of CENP-E has little role in regulating its function as a transporter. The adjustable stalk configuration may represent a regulatory mechanism for controlling the physical reach between kinetochore-bound CENP-E and spindle microtubules, or it may assist localizing various kinetochore regulators in the immediate vicinity of the kinetochore-embedded microtubule ends. The TCM assay and underlying theoretical framework will provide a general guide for determining the dynamic configurations of various molecular motors moving along their tracks, freely or under force.
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Henneman B, Heinsman J, Battjes J, Dame RT. Quantitation of DNA-Binding Affinity Using Tethered Particle Motion. Methods Mol Biol 2019; 1837:257-275. [PMID: 30109615 DOI: 10.1007/978-1-4939-8675-0_14] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
The binding constant is an important characteristic of a DNA-binding protein. A large number of methods exist to measure the binding constant, but many of those methods have intrinsic flaws that influence the outcome of the characterization. Tethered Particle Motion (TPM) is a simple, cheap, and high-throughput single-molecule method that can be used to reliably measure binding constants of proteins binding to DNA, provided that they distort DNA. In TPM, the motion of a bead tethered to a surface by DNA is tracked using light microscopy. A protein binding to the DNA will alter bead motion. This makes it possible to measure binding properties. We use the bacterial protein Integration Host Factor (IHF) as an example to show how specific binding to DNA can be measured. Moreover, we show a new intuitive quantitative approach to displaying data obtained via TPM.
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Affiliation(s)
- Bram Henneman
- Leiden Institute of Chemistry, Leiden University, Leiden, The Netherlands
| | - Joost Heinsman
- Leiden Institute of Physics, Leiden University, Leiden, The Netherlands
| | - Julius Battjes
- Leiden Institute of Chemistry, Leiden University, Leiden, The Netherlands
| | - Remus T Dame
- Leiden Institute of Chemistry and Centre for Microbial Cell Biology, Leiden University, Leiden, The Netherlands.
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35
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Duss O, Stepanyuk GA, Grot A, O'Leary SE, Puglisi JD, Williamson JR. Real-time assembly of ribonucleoprotein complexes on nascent RNA transcripts. Nat Commun 2018; 9:5087. [PMID: 30504830 PMCID: PMC6269517 DOI: 10.1038/s41467-018-07423-3] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2018] [Accepted: 10/26/2018] [Indexed: 12/22/2022] Open
Abstract
Cellular protein-RNA complexes assemble on nascent transcripts, but methods to observe transcription and protein binding in real time and at physiological concentrations are not available. Here, we report a single-molecule approach based on zero-mode waveguides that simultaneously tracks transcription progress and the binding of ribosomal protein S15 to nascent RNA transcripts during early ribosome biogenesis. We observe stable binding of S15 to single RNAs immediately after transcription for the majority of the transcripts at 35 °C but for less than half at 20 °C. The remaining transcripts exhibit either rapid and transient binding or are unable to bind S15, likely due to RNA misfolding. Our work establishes the foundation for studying transcription and its coupled co-transcriptional processes, including RNA folding, ligand binding, and enzymatic activity such as in coupling of transcription to splicing, ribosome assembly or translation. The early steps of ribosome assembly occur co-transcriptionally on the nascent ribosomal RNA. Here the authors demonstrate an approach that allows simultaneous monitoring of transcription and ribosomal protein assembly at the single-molecule level in real time.
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Affiliation(s)
- Olivier Duss
- Department of Integrative Structural and Computational Biology, Department of Chemistry, and The Skaggs Institute for Chemical Biology, The Scripps Research Institute, La Jolla, CA, 92037, USA.,Department of Structural Biology, Stanford University School of Medicine, CA, 94305, California, USA
| | - Galina A Stepanyuk
- Department of Integrative Structural and Computational Biology, Department of Chemistry, and The Skaggs Institute for Chemical Biology, The Scripps Research Institute, La Jolla, CA, 92037, USA
| | - Annette Grot
- Department of Research and Development, Pacific Biosciences Inc, Menlo Park, CA, 94025, USA
| | - Seán E O'Leary
- Department of Structural Biology, Stanford University School of Medicine, CA, 94305, California, USA.,Department of Biochemistry, University of California, Riverside, CA, 92521, USA
| | - Joseph D Puglisi
- Department of Structural Biology, Stanford University School of Medicine, CA, 94305, California, USA.
| | - James R Williamson
- Department of Integrative Structural and Computational Biology, Department of Chemistry, and The Skaggs Institute for Chemical Biology, The Scripps Research Institute, La Jolla, CA, 92037, USA.
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36
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Jung HS, Cho KJ, Seol Y, Takagi Y, Dittmore A, Roche PA, Neuman KC. Polydopamine encapsulation of fluorescent nanodiamonds for biomedical applications. ADVANCED FUNCTIONAL MATERIALS 2018; 28:1801252. [PMID: 30686957 PMCID: PMC6342502 DOI: 10.1002/adfm.201801252] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2018] [Indexed: 05/13/2023]
Abstract
Fluorescent nanodiamonds (FNDs) are promising bio-imaging probes compared with other fluorescent nanomaterials such as quantum dots, dye-doped nanoparticles, and metallic nanoclusters, due to their remarkable optical properties and excellent biocompatibility. Nevertheless, they are prone to aggregation in physiological salt solutions, and modifying their surface to conjugate biologically active agents remains challenging. Here, inspired by the adhesive protein of marine mussels, we demonstrate encapsulation of FNDs within a polydopamine (PDA) shell. These PDA surfaces are readily modified via Michael addition or Schiff base reactions with molecules presenting thiol or nitrogen derivatives. We describe modification of PDA shells by thiol terminated poly(ethylene glycol) (PEG-SH) molecules to enhance colloidal stability and biocompatibility of FNDs. We demonstrate their use as fluorescent probes for cell imaging; we find that PEGylated FNDs are taken up by HeLa cells and mouse bone marrow-derived dendritic cells and exhibit reduced nonspecific membrane adhesion. Furthermore, we demonstrate functionalization with biotin-PEG-SH and perform long-term high-resolution single-molecule fluorescence based tracking measurements of FNDs tethered via streptavidin to individual biotinylated DNA molecules. Our robust polydopamine encapsulation and functionalization strategy presents a facile route to develop FNDs as multifunctional labels, drug delivery vehicles, and targeting agents for biomedical applications.
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Affiliation(s)
- Hak-Sung Jung
- Laboratory of Single Molecule Biophysics, NHLBI, NIH, Bethesda, MD 20892, USA
| | - Kyung-Jin Cho
- Experimental Immunology Branch, NCI, NIH, Bethesda, MD 20892, USA
| | - Yeonee Seol
- Laboratory of Single Molecule Biophysics, NHLBI, NIH, Bethesda, MD 20892, USA
| | - Yasuharu Takagi
- Laboratory of Single Molecule Biophysics, NHLBI, NIH, Bethesda, MD 20892, USA
| | - Andrew Dittmore
- Laboratory of Single Molecule Biophysics, NHLBI, NIH, Bethesda, MD 20892, USA
| | - Paul A Roche
- Experimental Immunology Branch, NCI, NIH, Bethesda, MD 20892, USA
| | - Keir C Neuman
- Laboratory of Single Molecule Biophysics, NHLBI, NIH, Bethesda, MD 20892, USA
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37
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Tethered multifluorophore motion reveals equilibrium transition kinetics of single DNA double helices. Proc Natl Acad Sci U S A 2018; 115:E7512-E7521. [PMID: 30037988 PMCID: PMC6094131 DOI: 10.1073/pnas.1800585115] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Understanding cellular functions and dysfunctions often begins with quantifying the interactions between the binding partners involved in the processes. Learning about the kinetics of the interactions is of particular importance to understand the dynamics of cellular processes. We created a tethered multifluorophore motion assay using DNA origami that enables over 1-hour-long recordings of the statistical binding and unbinding of single pairs of biomolecules directly in equilibrium. The experimental concept is simple and the data interpretation is very direct, which makes the system easy to use for a wide variety of researchers. Due to the modularity and addressability of the DNA origami-based assay, our system may be readily adapted to study various other molecular interactions. We describe a tethered multifluorophore motion assay based on DNA origami for revealing bimolecular reaction kinetics on the single-molecule level. Molecular binding partners may be placed at user-defined positions and in user-defined stoichiometry; and binding states are read out by tracking the motion of quickly diffusing fluorescent reporter units. Multiple dyes per reporter unit enable singe-particle observation for more than 1 hour. We applied the system to study in equilibrium reversible hybridization and dissociation of complementary DNA single strands as a function of tether length, cation concentration, and sequence. We observed up to hundreds of hybridization and dissociation events per single reactant pair and could produce cumulative statistics with tens of thousands of binding and unbinding events. Because the binding partners per particle do not exchange, we could also detect subtle heterogeneity from molecule to molecule, which enabled separating data reflecting the actual target strand pair binding kinetics from falsifying influences stemming from chemically truncated oligonucleotides. Our data reflected that mainly DNA strand hybridization, but not strand dissociation, is affected by cation concentration, in agreement with previous results from different assays. We studied 8-bp-long DNA duplexes with virtually identical thermodynamic stability, but different sequences, and observed strongly differing hybridization kinetics. Complementary full-atom molecular-dynamics simulations indicated two opposing sequence-dependent phenomena: helical templating in purine-rich single strands and secondary structures. These two effects can increase or decrease, respectively, the fraction of strand collisions leading to successful nucleation events for duplex formation.
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38
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Visser EWA, Yan J, van IJzendoorn LJ, Prins MWJ. Continuous biomarker monitoring by particle mobility sensing with single molecule resolution. Nat Commun 2018; 9:2541. [PMID: 29959314 PMCID: PMC6026194 DOI: 10.1038/s41467-018-04802-8] [Citation(s) in RCA: 54] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2018] [Accepted: 05/16/2018] [Indexed: 12/21/2022] Open
Abstract
Healthcare is in demand of technologies for real-time sensing in order to continuously guard the state of patients. Here we present biomarker-monitoring based on the sensing of particle mobility, a concept wherein particles are coupled to a substrate via a flexible molecular tether, with both the particles and substrate provided with affinity molecules for effectuating specific and reversible interactions. Single-molecular binding and unbinding events modulate the Brownian particle motion and the state changes are recorded using optical scattering microscopy. The technology is demonstrated with DNA and protein as model biomarkers, in buffer and in blood plasma, showing sensitivity to picomolar and nanomolar concentrations. The sensing principle is direct and self-contained, without consuming or producing any reactants. With its basis in reversible interactions and single-molecule resolution, we envisage that the presented technology will enable biosensors for continuous biomarker monitoring with high sensitivity, specificity, and accuracy.
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Affiliation(s)
- Emiel W A Visser
- Department of Applied Physics, Eindhoven University of Technology, 5600 MB, Eindhoven, The Netherlands
- Institute for Complex Molecular Systems (ICMS), Eindhoven University of Technology, 5600 MB, Eindhoven, Netherlands
| | - Junhong Yan
- Institute for Complex Molecular Systems (ICMS), Eindhoven University of Technology, 5600 MB, Eindhoven, Netherlands
- Department of Biomedical Engineering, Eindhoven University of Technology, 5600 MB, Eindhoven, Netherlands
| | - Leo J van IJzendoorn
- Department of Applied Physics, Eindhoven University of Technology, 5600 MB, Eindhoven, The Netherlands
- Institute for Complex Molecular Systems (ICMS), Eindhoven University of Technology, 5600 MB, Eindhoven, Netherlands
| | - Menno W J Prins
- Department of Applied Physics, Eindhoven University of Technology, 5600 MB, Eindhoven, The Netherlands.
- Institute for Complex Molecular Systems (ICMS), Eindhoven University of Technology, 5600 MB, Eindhoven, Netherlands.
- Department of Biomedical Engineering, Eindhoven University of Technology, 5600 MB, Eindhoven, Netherlands.
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39
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Helicase promotes replication re-initiation from an RNA transcript. Nat Commun 2018; 9:2306. [PMID: 29899338 PMCID: PMC5997990 DOI: 10.1038/s41467-018-04702-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2017] [Accepted: 04/30/2018] [Indexed: 11/12/2022] Open
Abstract
To ensure accurate DNA replication, a replisome must effectively overcome numerous obstacles on its DNA substrate. After encountering an obstacle, a progressing replisome often aborts DNA synthesis but continues to unwind. However, little is known about how DNA synthesis is resumed downstream of an obstacle. Here, we examine the consequences of a non-replicating replisome collision with a co-directional RNA polymerase (RNAP). Using single-molecule and ensemble methods, we find that T7 helicase interacts strongly with a non-replicating T7 DNA polymerase (DNAP) at a replication fork. As the helicase advances, the associated DNAP also moves forward. The presence of the DNAP increases both helicase’s processivity and unwinding rate. We show that such a DNAP, together with its helicase, is indeed able to actively disrupt a stalled transcription elongation complex, and then initiates replication using the RNA transcript as a primer. These observations exhibit T7 helicase’s novel role in replication re-initiation. During DNA replication, replicative helicases play an essential role for DNA unwinding to occur. Here the authors find that bacteriophage T7 helicase is also involved in replication re-initiation by interacting with a non-replicating DNAP and increasing unwinding rate.
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40
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Fan HF, Ma CH, Jayaram M. Single-Molecule Tethered Particle Motion: Stepwise Analyses of Site-Specific DNA Recombination. MICROMACHINES 2018; 9:E216. [PMID: 30424148 PMCID: PMC6187709 DOI: 10.3390/mi9050216] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/15/2018] [Revised: 04/25/2018] [Accepted: 04/28/2018] [Indexed: 12/17/2022]
Abstract
Tethered particle motion/microscopy (TPM) is a biophysical tool used to analyze changes in the effective length of a polymer, tethered at one end, under changing conditions. The tether length is measured indirectly by recording the Brownian motion amplitude of a bead attached to the other end. In the biological realm, DNA, whose interactions with proteins are often accompanied by apparent or real changes in length, has almost exclusively been the subject of TPM studies. TPM has been employed to study DNA bending, looping and wrapping, DNA compaction, high-order DNA⁻protein assembly, and protein translocation along DNA. Our TPM analyses have focused on tyrosine and serine site-specific recombinases. Their pre-chemical interactions with DNA cause reversible changes in DNA length, detectable by TPM. The chemical steps of recombination, depending on the substrate and the type of recombinase, may result in a permanent length change. Single molecule TPM time traces provide thermodynamic and kinetic information on each step of the recombination pathway. They reveal how mechanistically related recombinases may differ in their early commitment to recombination, reversibility of individual steps, and in the rate-limiting step of the reaction. They shed light on the pre-chemical roles of catalytic residues, and on the mechanisms by which accessory proteins regulate recombination directionality.
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Affiliation(s)
- Hsiu-Fang Fan
- Biophotonics and Molecular Imaging Center, Department of Life Sciences and Institute of Genome Sciences, National Yang-Ming University, Taipei 112, Taiwan.
- Institute of Cellular and Organismic Biology, Academia Sinica, Taipei 115, Taiwan.
| | - Chien-Hui Ma
- Department of Molecular Biosciences, University of Texas at Austin, Austin, TX 78712, USA.
| | - Makkuni Jayaram
- Department of Molecular Biosciences, University of Texas at Austin, Austin, TX 78712, USA.
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41
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Nir G, Chetrit E, Vivante A, Garini Y, Berkovich R. The role of near-wall drag effects in the dynamics of tethered DNA under shear flow. SOFT MATTER 2018; 14:2219-2226. [PMID: 29451293 DOI: 10.1039/c7sm01328k] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We utilized single-molecule tethered particle motion (TPM) tracking, optimized for studying the behavior of short (0.922 μm) dsDNA molecules under shear flow conditions, in the proximity of a wall (surface). These experiments track the individual trajectories through a gold nanobead (40 nm in radius), attached to the loose end of the DNA molecules. Under such circumstances, local interactions with the wall become more pronounced, manifested through hydrodynamic interactions. To elucidate the mechanical mechanism that affects the statistics of the molecular trajectories of the tethered molecules, we estimate the resting diffusion coefficient of our system. Using this value and our measured data, we calculate the orthogonal distance of the extended DNA molecules from the surface. This calculation considers the hydrodynamic drag effect that emerges from the proximity of the molecule to the surface, using the Faxén correction factors. Our finding enables the construction of a scenario according to which the tension along the chain builds up with the applied shear force, driving the loose end of the DNA molecule away from the wall. With the extension from the wall, the characteristic times of the system decrease by three orders of magnitude, while the drag coefficients decay to a plateau value that indicates that the molecule still experiences hydrodynamic effects due to its proximity to the wall.
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Affiliation(s)
- Guy Nir
- Dep. of Genetics, Harvard Medical School, Boston, MA 02115, USA. and Department of Physics and Institute of Nanotechnology, Bar Ilan University, Ramat Gan 52900, Israel
| | - Einat Chetrit
- Department of Chemical-Engineering, Ben-Gurion University of the Negev, Beer Sheva 84105, Israel.
| | - Anat Vivante
- Department of Physics and Institute of Nanotechnology, Bar Ilan University, Ramat Gan 52900, Israel
| | - Yuval Garini
- Department of Physics and Institute of Nanotechnology, Bar Ilan University, Ramat Gan 52900, Israel
| | - Ronen Berkovich
- Department of Chemical-Engineering, Ben-Gurion University of the Negev, Beer Sheva 84105, Israel. and The Ilze Katz Institute for Nanoscience and Technology, Ben-Gurion University of the Negev, Beer Sheva 84105, Israel
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42
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Kovari DT, Yan Y, Finzi L, Dunlap D. Tethered Particle Motion: An Easy Technique for Probing DNA Topology and Interactions with Transcription Factors. Methods Mol Biol 2018; 1665:317-340. [PMID: 28940077 DOI: 10.1007/978-1-4939-7271-5_17] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Tethered Particle Motion (TPM) is a versatile in vitro technique for monitoring the conformations a linear macromolecule, such as DNA, can exhibit. The technique involves monitoring the diffusive motion of a particle anchored to a fixed point via the macromolecule of interest, which acts as a tether. In this chapter, we provide an overview of TPM, review the fundamental principles that determine the accuracy with which effective tether lengths can be used to distinguish different tether conformations, present software tools that assist in capturing and analyzing TPM data, and provide a protocol which uses TPM to characterize lac repressor-induced DNA looping. Critical to any TPM assay is the understanding of the timescale over which the diffusive motion of the particle must be observed to accurately distinguish tether conformations. Approximating the tether as a Hookean spring, we show how to estimate the diffusion timescale and discuss how it relates to the confidence with which tether conformations can be distinguished. Applying those estimates to a lac repressor titration assay, we describe how to perform a TPM experiment. We also provide graphically driven software which can be used to speed up data collection and analysis. Lastly, we detail how TPM data from the titration assay can be used to calculate relevant molecular descriptors such as the J factor for DNA looping and lac repressor-operator dissociation constants. While the included protocol is geared toward studying DNA looping, the technique, fundamental principles, and analytical methods are more general and can be adapted to a wide variety of molecular systems.
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Affiliation(s)
- Daniel T Kovari
- Department of Physics, Emory University, 400 Dowman Dr, Atlanta, GA, 30322, USA
| | - Yan Yan
- Department of Physics, Emory University, 400 Dowman Dr, Atlanta, GA, 30322, USA
| | - Laura Finzi
- Department of Physics, Emory University, 400 Dowman Dr, Atlanta, GA, 30322, USA
| | - David Dunlap
- Department of Physics, Emory University, 400 Dowman Dr, Atlanta, GA, 30322, USA.
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43
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Le TT, Yang Y, Tan C, Suhanovsky MM, Fulbright RM, Inman JT, Li M, Lee J, Perelman S, Roberts JW, Deaconescu AM, Wang MD. Mfd Dynamically Regulates Transcription via a Release and Catch-Up Mechanism. Cell 2017; 172:344-357.e15. [PMID: 29224782 DOI: 10.1016/j.cell.2017.11.017] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2017] [Revised: 09/21/2017] [Accepted: 11/09/2017] [Indexed: 11/25/2022]
Abstract
The bacterial Mfd ATPase is increasingly recognized as a general transcription factor that participates in the resolution of transcription conflicts with other processes/roadblocks. This function stems from Mfd's ability to preferentially act on stalled RNA polymerases (RNAPs). However, the mechanism underlying this preference and the subsequent coordination between Mfd and RNAP have remained elusive. Here, using a novel real-time translocase assay, we unexpectedly discovered that Mfd translocates autonomously on DNA. The speed and processivity of Mfd dictate a "release and catch-up" mechanism to efficiently patrol DNA for frequently stalled RNAPs. Furthermore, we showed that Mfd prevents RNAP backtracking or rescues a severely backtracked RNAP, allowing RNAP to overcome stronger obstacles. However, if an obstacle's resistance is excessive, Mfd dissociates the RNAP, clearing the DNA for other processes. These findings demonstrate a remarkably delicate coordination between Mfd and RNAP, allowing efficient targeting and recycling of Mfd and expedient conflict resolution.
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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
| | - Yi Yang
- Howard Hughes Medical Institute, Cornell University, Ithaca, NY 14853, USA; Physics Department & LASSP, Cornell University, Ithaca, NY 14853, USA
| | - Chuang Tan
- Howard Hughes Medical Institute, Cornell University, Ithaca, NY 14853, USA; Physics Department & LASSP, Cornell University, Ithaca, NY 14853, USA
| | - Margaret M Suhanovsky
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, RI 02903, USA
| | | | - James T Inman
- Howard Hughes Medical Institute, Cornell University, Ithaca, NY 14853, USA; Physics Department & LASSP, Cornell University, Ithaca, NY 14853, USA
| | - Ming Li
- Department of Chemistry, Cornell University, Ithaca, NY 14853, USA
| | - Jaeyoon Lee
- Physics Department & LASSP, Cornell University, Ithaca, NY 14853, USA
| | - Sarah Perelman
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, RI 02903, USA
| | - Jeffrey W Roberts
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
| | - Alexandra M Deaconescu
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, RI 02903, 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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44
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Merkus KE, Prins MWJ, Storm C. Single-Bond Association Kinetics Determined by Tethered Particle Motion: Concept and Simulations. Biophys J 2017; 111:1612-1620. [PMID: 27760349 DOI: 10.1016/j.bpj.2016.08.045] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2016] [Revised: 07/20/2016] [Accepted: 08/01/2016] [Indexed: 11/30/2022] Open
Abstract
Tethered particle motion (TPM), the motion of a micro- or nanoparticle tethered to a substrate by a macromolecule, is a system that has proven to be extremely useful for its ability to reveal physical features of the tether, because the thermal motion of the bound particle reports sensitively on parameters like the length, the rigidity, or the folding state of its tether. In this article, we survey the applicability of TPM to probe the kinetics of single secondary bonds, bonds that form and break between the tethered particle and a substrate due, for instance, to receptor/ligand pairs on particle and substrate. Much like the tether itself affects the motion pattern, so do the presence and absence of such secondary connections. Keeping the tether properties constant, we demonstrate how raw positional TPM data may be parsed to generate detailed insights into the association and dissociation kinetics of single secondary bonds. We do this using coarse-grained molecular dynamics simulations specifically developed to treat the motion of particles close to interfaces.
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Affiliation(s)
- Koen E Merkus
- Department of Applied Physics, Eindhoven University of Technology, Eindhoven, the Netherlands
| | - Menno W J Prins
- Department of Applied Physics, Eindhoven University of Technology, Eindhoven, the Netherlands; Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, the Netherlands; Institute for Complex Molecular Systems, Eindhoven University of Technology, Eindhoven, the Netherlands.
| | - Cornelis Storm
- Department of Applied Physics, Eindhoven University of Technology, Eindhoven, the Netherlands; Institute for Complex Molecular Systems, Eindhoven University of Technology, Eindhoven, the Netherlands
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45
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Stracy M, Kapanidis AN. Single-molecule and super-resolution imaging of transcription in living bacteria. Methods 2017; 120:103-114. [PMID: 28414097 PMCID: PMC5670121 DOI: 10.1016/j.ymeth.2017.04.001] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2017] [Revised: 03/21/2017] [Accepted: 04/05/2017] [Indexed: 12/20/2022] Open
Abstract
In vivo single-molecule and super-resolution techniques are transforming our ability to study transcription as it takes place in its native environment in living cells. This review will detail the methods for imaging single molecules in cells, and the data-analysis tools which can be used to extract quantitative information on the spatial organization, mobility, and kinetics of the transcription machinery from these experiments. Furthermore, we will highlight studies which have applied these techniques to shed new light on bacterial transcription.
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Affiliation(s)
- Mathew Stracy
- Biological Physics Research Group, Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, United Kingdom.
| | - Achillefs N Kapanidis
- Biological Physics Research Group, Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, United Kingdom.
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46
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Vörös Z, Yan Y, Kovari DT, Finzi L, Dunlap D. Proteins mediating DNA loops effectively block transcription. Protein Sci 2017; 26:1427-1438. [PMID: 28295806 PMCID: PMC5477534 DOI: 10.1002/pro.3156] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2016] [Revised: 03/07/2017] [Accepted: 03/08/2017] [Indexed: 12/17/2022]
Abstract
Loops are ubiquitous topological elements formed when proteins simultaneously bind to two noncontiguous DNA sites. While a loop‐mediating protein may regulate initiation at a promoter, the presence of the protein at the other site may be an obstacle for RNA polymerases (RNAP) transcribing a different gene. To test whether a DNA loop alters the extent to which a protein blocks transcription, the lac repressor (LacI) was used. The outcome of in vitro transcription along templates containing two LacI operators separated by 400 bp in the presence of LacI concentrations that produced both looped and unlooped molecules was visualized with scanning force microscopy (SFM). An analysis of transcription elongation complexes, moving for 60 s at an average of 10 nt/s on unlooped DNA templates, revealed that they more often surpassed LacI bound to the lower affinity O2 operator than to the highest affinity Os operator. However, this difference was abrogated in looped DNA molecules where LacI became a strong roadblock independently of the affinity of the operator. Recordings of transcription elongation complexes, using magnetic tweezers, confirmed that they halted for several minutes upon encountering a LacI bound to a single operator. The average pause lifetime is compatible with RNAP waiting for LacI dissociation, however, the LacI open conformation visualized in the SFM images also suggests that LacI could straddle RNAP to let it pass. Independently of the mechanism by which RNAP bypasses the LacI roadblock, the data indicate that an obstacle with looped topology more effectively interferes with transcription.
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Affiliation(s)
- Zsuzsanna Vörös
- Department of Physics, Emory University, Atlanta, Georgia, 30322
| | - Yan Yan
- Department of Physics, Emory University, Atlanta, Georgia, 30322
| | - Daniel T Kovari
- Department of Physics, Emory University, Atlanta, Georgia, 30322
| | - Laura Finzi
- Department of Physics, Emory University, Atlanta, Georgia, 30322
| | - David Dunlap
- Department of Physics, Emory University, Atlanta, Georgia, 30322
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47
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Metelev M, Arseniev A, Bushin LB, Kuznedelov K, Artamonova TO, Kondratenko R, Khodorkovskii M, Seyedsayamdost MR, Severinov K. Acinetodin and Klebsidin, RNA Polymerase Targeting Lasso Peptides Produced by Human Isolates of Acinetobacter gyllenbergii and Klebsiella pneumoniae. ACS Chem Biol 2017; 12:814-824. [PMID: 28106375 DOI: 10.1021/acschembio.6b01154] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
We report the bioinformatic prediction and structural validation of two lasso peptides, acinetodin and klebsidin, encoded by the genomes of several human-associated strains of Acinetobacter and Klebsiella. Computation of the three-dimensional structures of these peptides using NMR NOESY constraints verifies that they contain a lasso motif. Despite the lack of sequence similarity to each other or to microcin J25, a prototypical lasso peptide and transcription inhibitor from Escherichia coli, acinetodin and klebsidin also inhibit transcript elongation by the E. coli RNA polymerase by binding to a common site. Yet, unlike microcin J25, acinetodin and klebsidin are unable to permeate wild type E. coli cells and inhibit their growth. We show that the E. coli cells become sensitive to klebsidin when expressing the outer membrane receptor FhuA homologue from Klebsiella pneumoniae. It thus appears that specificity to a common target, the RNA polymerase secondary channel, can be attained by a surprisingly diverse set of primary sequences folded into a common threaded-lasso fold. In contrast, transport into cells containing sensitive targets appears to be much more specific and must be the major determinant of the narrow range of bioactivity of known lasso peptides.
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Affiliation(s)
- Mikhail Metelev
- Peter the Great St.Petersburg Polytechnic University, St. Petersburg, 195251, Russia
- Institute
of Antimicrobial Chemotherapy, Smolensk State Medical Academy, Smolensk, 214018, Russia
| | - Anatolii Arseniev
- Peter the Great St.Petersburg Polytechnic University, St. Petersburg, 195251, Russia
| | - Leah B. Bushin
- Departments
of Chemistry and Molecular Biology, Princeton University, Princeton, New Jersey 08544, United States
| | - Konstantin Kuznedelov
- Waksman Institute of Microbiology, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854, United States
| | - Tatiana O. Artamonova
- Peter the Great St.Petersburg Polytechnic University, St. Petersburg, 195251, Russia
| | - Ruslan Kondratenko
- Peter the Great St.Petersburg Polytechnic University, St. Petersburg, 195251, Russia
| | - Mikhail Khodorkovskii
- Peter the Great St.Petersburg Polytechnic University, St. Petersburg, 195251, Russia
| | - Mohammad R. Seyedsayamdost
- Departments
of Chemistry and Molecular Biology, Princeton University, Princeton, New Jersey 08544, United States
| | - Konstantin Severinov
- Peter the Great St.Petersburg Polytechnic University, St. Petersburg, 195251, Russia
- Waksman Institute of Microbiology, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854, United States
- Skolkovo Institute of Science and Technology, Skolkovo, 143025, Russia
- Institute of Molecular Genetics, Russian Academy of Sciences, Moscow, 123142, Russia
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48
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Abstract
During transcriptional elongation, RNA polymerases (RNAP) employ a stepping mechanism to translocate along the DNA template while synthesizing RNA. Optical trapping assays permit the progress of single molecules of RNA polymerase to be monitored in real time, at resolutions down to the level of individual base pairs. Additionally, optical trapping assays permit the application of exquisitely controlled, external forces on RNAP. Responses to such forces can reveal details of the load-dependent kinetics of transcriptional elongation and pausing. Traditionally, the bacterial form of RNAP from E. coli has served as a model for the study of transcriptional elongation using optical traps. However, it is now feasible to perform optical trapping experiments using the eukaryotic polymerase, RNAPII, as well. In this report, we describe the methods to perform optical trapping transcriptional elongation assays with both prokaryotic RNAP and eukaryotic RNAPII. We provide detailed instructions on how to reconstitute transcription elongation complexes, derivatize beads used in the assays, and perform optical trapping measurements.
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49
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Ucuncuoglu S, Schneider DA, Weeks ER, Dunlap D, Finzi L. Multiplexed, Tethered Particle Microscopy for Studies of DNA-Enzyme Dynamics. Methods Enzymol 2016; 582:415-435. [PMID: 28062044 DOI: 10.1016/bs.mie.2016.08.008] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
DNA is the carrier of genetic information and, as such, is at the center of most essential cellular processes. To regulate its physiological function, specific proteins and motor enzymes constantly change conformational states with well-controlled dynamics. Twenty-five years ago, Schafer, Gelles, Sheetz, and Landick employed the tethered particle motion (TPM) technique for the first time to study transcription by RNA polymerase at the single-molecule level. TPM has since then remained one of the simplest, most affordable, and yet incisive single-molecule techniques available. It is an in vitro technique which allows investigation of DNA-protein interactions that change the effective length of a DNA tether. In this chapter, we will describe a recent strategy to multiplex TPM which substantially increases the throughput of TPM experiments, as well as a simulation to estimate the time resolution of experiments, such as transcriptional elongation assays, in which lengthy time averaging of the signal is impossible due to continual change of the DNA tether length. These improvements allow efficient study of several DNA-protein systems, including transcriptionally active DNA-RNA polymerase I complexes and DNA-gyrase complexes.
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Affiliation(s)
| | - D A Schneider
- University of Alabama at Birmingham, Birmingham, AL, United States
| | - E R Weeks
- Emory University, Atlanta, GA, United States
| | - D Dunlap
- Emory University, Atlanta, GA, United States
| | - L Finzi
- Emory University, Atlanta, GA, United States.
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50
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Abstract
The production of a single mRNA is the result of many sequential steps, from docking of transcription factors to polymerase initiation, elongation, splicing, and, finally, termination. Much of our knowledge about the fundamentals of RNA synthesis and processing come from ensemble in vitro biochemical measurements. Single-molecule approaches are very much in this same reductionist tradition but offer exquisite sensitivity in space and time along with the ability to observe heterogeneous behavior and actually manipulate macromolecules. These techniques can also be applied in vivo, allowing one to address questions in living cells that were previously restricted to reconstituted systems. In this review, we examine the unique insights that single-molecule techniques have yielded on the mechanisms of gene expression.
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Affiliation(s)
- Huimin Chen
- Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Daniel R Larson
- Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
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