1
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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: 10] [Impact Index Per Article: 10.0] [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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2
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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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3
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Stochastic models coupling gene expression and partitioning in cell division in Escherichia coli. Biosystems 2020; 193-194:104154. [PMID: 32353481 DOI: 10.1016/j.biosystems.2020.104154] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2019] [Revised: 04/03/2020] [Accepted: 04/16/2020] [Indexed: 12/18/2022]
Abstract
Regulation of future RNA and protein numbers is a key process by which cells continuously best fit the environment. In bacteria, RNA and proteins exist in small numbers and their regulatory processes are stochastic. Consequently, there is cell-to-cell variability in these numbers, even between sister cells. Traditionally, the two most studied sources of this variability are gene expression and RNA and protein degradation, with evidence suggesting that the latter is subject to little regulation, when compared to the former. However, time-lapse microscopy and single molecule fluorescent tagging have produced evidence that cell division can also be a significant source of variability due to asymmetries in the partitioning of RNA and proteins. Relevantly, the impact of this noise differs from noise in production and degradation since, unlike these, it is not continuous. Rather, it occurs at specific time points, at which moment it can introduce major fluctuations. Several models have now been proposed that integrate noise from cell division, in addition to noise in gene expression, to mimic the dynamics of RNA and protein numbers of cell lineages. This is expected to be particularly relevant in genetic circuits, where significant fluctuations in one component protein, at specific time moments, are expected to perturb near-equilibrium states of the circuits, which can have long-lasting consequences. Here we review stochastic models coupling these processes in Escherichia coli, from single genes to small circuits.
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4
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Häkkinen A, Oliveira SMD, Neeli-Venkata R, Ribeiro AS. Transcription closed and open complex formation coordinate expression of genes with a shared promoter region. J R Soc Interface 2019; 16:20190507. [PMID: 31822223 DOI: 10.1098/rsif.2019.0507] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Many genes are spaced closely, allowing coordination without explicit control through shared regulatory elements and molecular interactions. We study the dynamics of a stochastic model of a gene-pair in a head-to-head configuration, sharing promoter elements, which accounts for the rate-limiting steps in transcription initiation. We find that only in specific regions of the parameter space of the rate-limiting steps is orderly coexpression exhibited, suggesting that successful cooperation between closely spaced genes requires the coevolution of compatible rate-limiting step configuration. The model predictions are validated using in vivo single-cell, single-RNA measurements of the dynamics of pairs of genes sharing promoter elements. Our results suggest that, in E. coli, the kinetics of the rate-limiting steps in active transcription can play a central role in shaping the dynamics of gene-pairs sharing promoter elements.
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Affiliation(s)
- Antti Häkkinen
- BioMediTech Institute and Department of Signal Processing, Tampere University of Technology, PO Box 553 33101, Tampere, Finland
| | - Samuel M D Oliveira
- BioMediTech Institute and Department of Signal Processing, Tampere University of Technology, PO Box 553 33101, Tampere, Finland
| | - Ramakanth Neeli-Venkata
- BioMediTech Institute and Department of Signal Processing, Tampere University of Technology, PO Box 553 33101, Tampere, Finland
| | - Andre S Ribeiro
- BioMediTech Institute and Department of Signal Processing, Tampere University of Technology, PO Box 553 33101, Tampere, Finland
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5
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Swiecicki JM, Santana JT, Imperiali B. A Strategic Approach for Fluorescence Imaging of Membrane Proteins in a Native-like Environment. Cell Chem Biol 2019; 27:245-251.e3. [PMID: 31831268 DOI: 10.1016/j.chembiol.2019.11.008] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2019] [Revised: 09/22/2019] [Accepted: 11/14/2019] [Indexed: 01/06/2023]
Abstract
Biological membranes are complex barriers in which membrane proteins and thousands of lipidic species participate in structural and functional interactions. Developing a strategic approach that allows uniform labeling of membrane proteins while maintaining a lipidic environment that retains functional interactions is highly desirable for in vitro fluorescence studies. Herein, we focus on complementing current methods by integrating the powerful processes of unnatural amino acid mutagenesis, bioorthogonal labeling, and the detergent-free membrane protein solubilization based on the amphiphilic styrene-maleic acid (SMA) polymer. Importantly, the SMA polymer preserves a thermodynamically stable shell of phospholipids. The approach that we present is both rapid and generalizable providing a population of uniquely labeled membrane proteins in lipid nanoparticles for quantitative fluorescence-based studies.
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Affiliation(s)
- Jean-Marie Swiecicki
- Department of Biology, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
| | - Jordan Tyler Santana
- Department of Biology, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA; Department of Physics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
| | - Barbara Imperiali
- Department of Biology, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA; Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA.
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6
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Yang S, Kim S, Kim DK, Jeon An H, Bae Son J, Hedén Gynnå A, Ki Lee N. Transcription and translation contribute to gene locus relocation to the nucleoid periphery in E. coli. Nat Commun 2019; 10:5131. [PMID: 31719538 PMCID: PMC6851099 DOI: 10.1038/s41467-019-13152-y] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2019] [Accepted: 10/21/2019] [Indexed: 11/23/2022] Open
Abstract
Transcription by RNA polymerase (RNAP) is coupled with translation in bacteria. Here, we observe the dynamics of transcription and subcellular localization of a specific gene locus (encoding a non-membrane protein) in living E. coli cells at subdiffraction-limit resolution. The movement of the gene locus to the nucleoid periphery correlates with transcription, driven by either E. coli RNAP or T7 RNAP, and the effect is potentiated by translation.
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Affiliation(s)
- Sora Yang
- Department of Chemistry, Seoul National University, Seoul, 08826, Korea
| | - Seunghyeon Kim
- Department of Physics, Pohang University of Science and Technology, Pohang, 37673, Korea
| | - Dong-Kyun Kim
- School of Interdisciplinary Bioscience and Bioengineering, Pohang University of Science and Technology, Pohang, 37673, Korea
| | - Hyeong Jeon An
- Department of Physics, Pohang University of Science and Technology, Pohang, 37673, Korea
| | - Jung Bae Son
- Department of Chemistry, Seoul National University, Seoul, 08826, Korea
| | - Arvid Hedén Gynnå
- Department of Cell and Molecular Biology, Uppsala University, 75236, Uppsala, Sweden
| | - Nam Ki Lee
- Department of Chemistry, Seoul National University, Seoul, 08826, Korea.
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7
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Effect of heparin and heparan sulphate on open promoter complex formation for a simple tandem gene model using ex situ atomic force microscopy. Methods 2017; 120:91-102. [DOI: 10.1016/j.ymeth.2017.04.010] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2017] [Revised: 04/10/2017] [Accepted: 04/14/2017] [Indexed: 11/23/2022] Open
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8
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Effects of σ factor competition are promoter initiation kinetics dependent. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2016; 1859:1281-8. [DOI: 10.1016/j.bbagrm.2016.07.011] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/03/2016] [Revised: 07/05/2016] [Accepted: 07/07/2016] [Indexed: 01/29/2023]
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9
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Lloyd-Price J, Startceva S, Kandavalli V, Chandraseelan JG, Goncalves N, Oliveira SMD, Häkkinen A, Ribeiro AS. Dissecting the stochastic transcription initiation process in live Escherichia coli. DNA Res 2016; 23:203-14. [PMID: 27026687 PMCID: PMC4909308 DOI: 10.1093/dnares/dsw009] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2015] [Accepted: 02/11/2016] [Indexed: 02/01/2023] Open
Abstract
We investigate the hypothesis that, in Escherichia coli, while the concentration of RNA polymerases differs in different growth conditions, the fraction of RNA polymerases free for transcription remains approximately constant within a certain range of these conditions. After establishing this, we apply a standard model-fitting procedure to fully characterize the in vivo kinetics of the rate-limiting steps in transcription initiation of the Plac/ara-1 promoter from distributions of intervals between transcription events in cells with different RNA polymerase concentrations. We find that, under full induction, the closed complex lasts ∼788 s while subsequent steps last ∼193 s, on average. We then establish that the closed complex formation usually occurs multiple times prior to each successful initiation event. Furthermore, the promoter intermittently switches to an inactive state that, on average, lasts ∼87 s. This is shown to arise from the intermittent repression of the promoter by LacI. The methods employed here should be of use to resolve the rate-limiting steps governing the in vivo dynamics of initiation of prokaryotic promoters, similar to established steady-state assays to resolve the in vitro dynamics.
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Affiliation(s)
- Jason Lloyd-Price
- Laboratory of Biosystem Dynamics, Department of Signal Processing, Tampere University of Technology, PO Box 553, Office TC336, 33101 Tampere, Finland
| | - Sofia Startceva
- Laboratory of Biosystem Dynamics, Department of Signal Processing, Tampere University of Technology, PO Box 553, Office TC336, 33101 Tampere, Finland
| | - Vinodh Kandavalli
- Laboratory of Biosystem Dynamics, Department of Signal Processing, Tampere University of Technology, PO Box 553, Office TC336, 33101 Tampere, Finland
| | - Jerome G Chandraseelan
- Laboratory of Biosystem Dynamics, Department of Signal Processing, Tampere University of Technology, PO Box 553, Office TC336, 33101 Tampere, Finland
| | - Nadia Goncalves
- Laboratory of Biosystem Dynamics, Department of Signal Processing, Tampere University of Technology, PO Box 553, Office TC336, 33101 Tampere, Finland
| | - Samuel M D Oliveira
- Laboratory of Biosystem Dynamics, Department of Signal Processing, Tampere University of Technology, PO Box 553, Office TC336, 33101 Tampere, Finland
| | - Antti Häkkinen
- Laboratory of Biosystem Dynamics, Department of Signal Processing, Tampere University of Technology, PO Box 553, Office TC336, 33101 Tampere, Finland
| | - Andre S Ribeiro
- Laboratory of Biosystem Dynamics, Department of Signal Processing, Tampere University of Technology, PO Box 553, Office TC336, 33101 Tampere, Finland
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10
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Vvedenskaya IO, Zhang Y, Goldman SR, Valenti A, Visone V, Taylor DM, Ebright RH, Nickels BE. Massively Systematic Transcript End Readout, "MASTER": Transcription Start Site Selection, Transcriptional Slippage, and Transcript Yields. Mol Cell 2015; 60:953-65. [PMID: 26626484 DOI: 10.1016/j.molcel.2015.10.029] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2015] [Revised: 08/14/2015] [Accepted: 10/14/2015] [Indexed: 11/24/2022]
Abstract
We report the development of a next-generation sequencing-based technology that entails construction of a DNA library comprising up to at least 4(7) (∼ 16,000) barcoded sequences, production of RNA transcripts, and analysis of transcript ends and transcript yields (massively systematic transcript end readout, "MASTER"). Using MASTER, we define full inventories of transcription start sites ("TSSomes") of Escherichia coli RNA polymerase for initiation at a consensus core promoter in vitro and in vivo; we define the TSS-region DNA sequence determinants for TSS selection, reiterative initiation ("slippage synthesis"), and transcript yield; and we define effects of DNA topology and NTP concentration. The results reveal that slippage synthesis occurs from the majority of TSS-region DNA sequences and that TSS-region DNA sequences have profound, up to 100-fold, effects on transcript yield. The results further reveal that TSSomes depend on DNA topology, consistent with the proposal that TSS selection involves transcription-bubble expansion ("scrunching") and transcription-bubble contraction ("anti-scrunching").
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Affiliation(s)
- Irina O Vvedenskaya
- Department of Genetics, Rutgers University, Piscataway, NJ 08854, USA; Waksman Institute, Rutgers University, Piscataway, NJ 08854, USA
| | - Yuanchao Zhang
- Department of Genetics, Rutgers University, Piscataway, NJ 08854, USA; Department of Biomedical and Health Informatics, The Children's Hospital of Philadelphia, Philadelphia, PA 19041, USA
| | - Seth R Goldman
- Department of Genetics, Rutgers University, Piscataway, NJ 08854, USA; Waksman Institute, Rutgers University, Piscataway, NJ 08854, USA
| | - Anna Valenti
- Institute of Biosciences and Bioresources, National Research Council of Italy, Via P. Castellino 111, Naples 80131, Italy
| | - Valeria Visone
- Institute of Biosciences and Bioresources, National Research Council of Italy, Via P. Castellino 111, Naples 80131, Italy
| | - Deanne M Taylor
- Department of Genetics, Rutgers University, Piscataway, NJ 08854, USA; Department of Biomedical and Health Informatics, The Children's Hospital of Philadelphia, Philadelphia, PA 19041, USA; Department of Pediatrics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, 19104, USA; Department of Obstetrics, Gynecology and Reproductive Sciences, Rutgers Robert Wood Johnson Medical School, New Brunswick, NJ 08901, USA
| | - Richard H Ebright
- Waksman Institute, Rutgers University, Piscataway, NJ 08854, USA; Department of Chemistry and Chemical Biology, Rutgers University, Piscataway, NJ 08854, USA
| | - Bryce E Nickels
- Department of Genetics, Rutgers University, Piscataway, NJ 08854, USA; Waksman Institute, Rutgers University, Piscataway, NJ 08854, USA.
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11
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Friedman LJ, Gelles J. Multi-wavelength single-molecule fluorescence analysis of transcription mechanisms. Methods 2015; 86:27-36. [PMID: 26032816 DOI: 10.1016/j.ymeth.2015.05.026] [Citation(s) in RCA: 79] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2015] [Revised: 05/14/2015] [Accepted: 05/15/2015] [Indexed: 01/22/2023] Open
Abstract
Multi-wavelength single molecule fluorescence microscopy is a valuable tool for clarifying transcription mechanisms, which involve multiple components and intermediates. Here we describe methods for the analysis and interpretation of such single molecule data. The methods described include those for image alignment, drift correction, spot discrimination, as well as robust methods for analyzing single-molecule binding and dissociation kinetics that account for non-specific binding and photobleaching. Finally, we give an example of the use of the resulting data to extract the kinetic mechanism of promoter binding by a bacterial RNA polymerase holoenzyme.
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Affiliation(s)
- Larry J Friedman
- Department of Biochemistry, Brandeis University, Waltham, MA 02454, United States.
| | - Jeff Gelles
- Department of Biochemistry, Brandeis University, Waltham, MA 02454, United States.
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12
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Juette MF, Terry DS, Wasserman MR, Zhou Z, Altman RB, Zheng Q, Blanchard SC. The bright future of single-molecule fluorescence imaging. Curr Opin Chem Biol 2014; 20:103-11. [PMID: 24956235 DOI: 10.1016/j.cbpa.2014.05.010] [Citation(s) in RCA: 99] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2014] [Accepted: 05/09/2014] [Indexed: 11/13/2022]
Abstract
Single-molecule Förster resonance energy transfer (smFRET) is an essential and maturing tool to probe biomolecular interactions and conformational dynamics in vitro and, increasingly, in living cells. Multi-color smFRET enables the correlation of multiple such events and the precise dissection of their order and timing. However, the requirements for good spectral separation, high time resolution, and extended observation times place extraordinary demands on the fluorescent labels used in such experiments. Together with advanced experimental designs and data analysis, the development of long-lasting, non-fluctuating fluorophores is therefore proving key to progress in the field. Recently developed strategies for obtaining ultra-stable organic fluorophores spanning the visible spectrum are underway that will enable multi-color smFRET studies to deliver on their promise of previously unachievable biological insights.
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Affiliation(s)
- Manuel F Juette
- Department of Physiology and Biophysics, Weill Medical College of Cornell University, 1300 York Avenue, New York, NY 10065, United States
| | - Daniel S Terry
- Department of Physiology and Biophysics, Weill Medical College of Cornell University, 1300 York Avenue, New York, NY 10065, United States
| | - Michael R Wasserman
- Department of Physiology and Biophysics, Weill Medical College of Cornell University, 1300 York Avenue, New York, NY 10065, United States
| | - Zhou Zhou
- Department of Physiology and Biophysics, Weill Medical College of Cornell University, 1300 York Avenue, New York, NY 10065, United States
| | - Roger B Altman
- Department of Physiology and Biophysics, Weill Medical College of Cornell University, 1300 York Avenue, New York, NY 10065, United States
| | - Qinsi Zheng
- Department of Physiology and Biophysics, Weill Medical College of Cornell University, 1300 York Avenue, New York, NY 10065, United States; Tri-Institutional Training Program in Chemical Biology, Weill Medical College of Cornell University, 1300 York Avenue, New York, NY 10065, United States
| | - Scott C Blanchard
- Department of Physiology and Biophysics, Weill Medical College of Cornell University, 1300 York Avenue, New York, NY 10065, United States; Tri-Institutional Training Program in Chemical Biology, Weill Medical College of Cornell University, 1300 York Avenue, New York, NY 10065, United States.
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13
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Robison AD, Finkelstein IJ. High-throughput single-molecule studies of protein-DNA interactions. FEBS Lett 2014; 588:3539-46. [PMID: 24859086 DOI: 10.1016/j.febslet.2014.05.021] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2014] [Revised: 05/11/2014] [Accepted: 05/12/2014] [Indexed: 10/25/2022]
Abstract
Fluorescence and force-based single-molecule studies of protein-nucleic acid interactions continue to shed critical insights into many aspects of DNA and RNA processing. As single-molecule assays are inherently low-throughput, obtaining statistically relevant datasets remains a major challenge. Additionally, most fluorescence-based single-molecule particle-tracking assays are limited to observing fluorescent proteins that are in the low-nanomolar range, as spurious background signals predominate at higher fluorophore concentrations. These technical limitations have traditionally limited the types of questions that could be addressed via single-molecule methods. In this review, we describe new approaches for high-throughput and high-concentration single-molecule biochemical studies. We conclude with a discussion of outstanding challenges for the single-molecule biologist and how these challenges can be tackled to further approach the biochemical complexity of the cell.
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Affiliation(s)
- Aaron D Robison
- Department of Molecular Biosciences, The University of Texas at Austin, Austin, TX 78712, United States
| | - Ilya J Finkelstein
- Department of Molecular Biosciences, The University of Texas at Austin, Austin, TX 78712, United States; Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, TX 78712, United States; Center for Systems and Synthetic Biology, The University of Texas at Austin, Austin, TX 78712, United States.
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14
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Shimamoto N. Nanobiology of RNA polymerase: biological consequence of inhomogeneity in reactant. Chem Rev 2013; 113:8400-22. [PMID: 24074222 DOI: 10.1021/cr400006b] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Affiliation(s)
- Nobuo Shimamoto
- Faculty of Life Sciences, Kyoto Sangyo University , Kamigamo-Motoyama, Kita-Ku, Kyoto, 603-8555 Japan
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15
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Abstract
Transcription initiation is a key event in the regulation of gene expression. RNA polymerase (RNAP), the central enzyme of transcription, is able to efficiently locate promoters in the genome, carry out promoter opening, and initiate RNA synthesis. All the substeps of transcription initiation are subject to complex cellular regulation. Understanding the molecular details of each step in the promoter-opening pathway is essential for a complete mechanistic and quantitative picture of gene expression. In this minireview, primarily using bacterial RNAP as an example, I briefly summarize some of the key recent advances in our understanding of the mechanisms of promoter search and promoter opening.
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Affiliation(s)
- Andrey Feklistov
- Laboratory of Molecular Biophysics, The Rockefeller University, New York, New York 10065, USA.
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16
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RNA polymerase approaches its promoter without long-range sliding along DNA. Proc Natl Acad Sci U S A 2013; 110:9740-5. [PMID: 23720315 DOI: 10.1073/pnas.1300221110] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Sequence-specific DNA binding proteins must quickly bind target sequences, despite the enormously larger amount of nontarget DNA present in cells. RNA polymerases (or associated general transcription factors) are hypothesized to reach promoter sequences by facilitated diffusion (FD). In FD, a protein first binds to nontarget DNA and then reaches the target by a 1D sliding search. We tested whether Escherichia coli σ(54)RNA polymerase reaches a promoter by FD using the colocalization single-molecule spectroscopy (CoSMoS) multiwavelength fluorescence microscopy technique. Experiments directly compared the rates of initial polymerase binding to and dissociation from promoter and nonpromoter DNAs measured in the same sample under identical conditions. Binding to a nonpromoter DNA was much slower than binding to a promoter-containing DNA of the same length, indicating that the detected nonspecific binding events are not on the pathway to promoter binding. Truncating one of the DNA segments flanking the promoter to a length as short as 7 bp or lengthening it to ~3,000 bp did not alter the promoter-specific binding rate. These results exclude FD over distances corresponding to the length of the promoter or longer from playing any significant role in accelerating promoter search. Instead, the data support a direct binding mechanism, in which σ(54)RNA polymerase reaches the local vicinity of promoters by 3D diffusion through solution, and suggest that binding may be accelerated by atypical structural or dynamic features of promoter DNA. Direct binding explains how polymerase can quickly reach a promoter, despite occupancy of promoter-flanking DNA by bound proteins that would impede FD.
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17
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Eom T, Zhang C, Wang H, Lay K, Fak J, Noebels JL, Darnell RB. NOVA-dependent regulation of cryptic NMD exons controls synaptic protein levels after seizure. eLife 2013; 2:e00178. [PMID: 23359859 PMCID: PMC3552424 DOI: 10.7554/elife.00178] [Citation(s) in RCA: 81] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2012] [Accepted: 11/29/2012] [Indexed: 12/13/2022] Open
Abstract
The neuronal RNA binding protein NOVA regulates splicing, shuttles to the cytoplasm, and co-localizes with target transcripts in dendrites, suggesting links between splicing and local translation. Here we identified >200 transcripts showing NOVA-dependent changes in abundance, but, surprisingly, HITS-CLIP revealed NOVA binds these RNAs in introns rather than 3′ UTRs. This led us to discover NOVA-regulated splicing of cryptic exons within these introns. These exons triggered nonsense mediated decay (NMD), as UPF1 and protein synthesis were required for NOVA's effect on RNA levels. Their regulation was dynamic and physiologically relevant. The NMD exons were regulated by seizures, which also induced changes in Nova subcellular localization and mediated large changes in synaptic proteins, including proteins implicated in familial epilepsy. Moreover, Nova haploinsufficient mice had spontaneous epilepsy. The data reveal a hidden means of dynamic RNA regulation linking electrical activity to splicing and protein output, and of mediating homeostatic excitation/inhibition balance in neurons. DOI:http://dx.doi.org/10.7554/eLife.00178.001 After the DNA in a gene has been transcribed into messenger RNA, portions of the mRNA called introns are removed, and the remaining stretches of mRNA, which are known as exons, are spliced together. Within eukaryotic cells, a process known as alternative splicing allows a single gene to encode for multiple protein variants by ensuring that some exons are included in the final, modified mRNA, while other exons are excluded. This modified mRNA is then translated into proteins. Eukaryotic cells also contain proteins that bind to RNA to regulate alternative splicing. These RNA-binding proteins are often found in both the cytoplasm and nucleus of cells, and their involvement in splicing may be linked to other processes in the cell such as mRNA localization and translation. It has also become clear over the past two decades that certain types of RNA-binding proteins, including NOVA proteins, are only found in neurons, and that these proteins have been best characterized as alternative splicing regulators. Recent work has also suggested that they also have important roles in regulating neuronal activity and development, and that their actions in neuronal nuclei and cytoplasm might be coordinated. Now Eom et al. use the predictive power of a high throughput sequencing and crosslinking method termed HITS-CLIP to show that NOVA proteins can indirectly regulate cytoplasmic mRNA levels by regulating the process of alternative splicing in the nucleus to produce ‘cryptic’ exons in the brains of mice. The presence of these exons in the mRNA leads to the production of premature termination codons in the cytoplasm. These codons trigger a process called nonsense-mediated decay that involves identifying mRNA transcripts that contain nonsense mutations, and then degrading them. These cryptic exons were seen in mice missing the NOVA proteins, where they are expressed in abnormally high levels; in normal mice, these exons have not been seen before, hence they were termed ‘cryptic’. Eom et al. also show that these cryptic exons are physiologically relevant by inducing epileptic seizures in mice. Following the seizures, they find that the NOVA proteins up-regulate and down-regulate the levels of different cryptic exons, leading to changes in the levels of the proteins encoded by these mRNAs, including proteins that inhibit further seizures. Overall the results indicate that, by controlling the production of various proteins in neurons, these previously unknown cryptic exons have important roles in the workings of the brain. DOI:http://dx.doi.org/10.7554/eLife.00178.002
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Affiliation(s)
- Taesun Eom
- Laboratory of Molecular Neuro-Oncology , Rockefeller University , New York , United States
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Ohta Y, Nishiyama A, Wada Y, Ruan Y, Kodama T, Tsuboi T, Tokihiro T, Ihara S. Path-preference cellular-automaton model for traffic flow through transit points and its application to the transcription process in human cells. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2012; 86:021918. [PMID: 23005796 DOI: 10.1103/physreve.86.021918] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2011] [Revised: 06/17/2012] [Indexed: 06/01/2023]
Abstract
We all use path routing everyday as we take shortcuts to avoid traffic jams, or by using faster traffic means. Previous models of traffic flow of RNA polymerase II (RNAPII) during transcription, however, were restricted to one dimension along the DNA template. Here we report the modeling and application of traffic flow in transcription that allows preferential paths of different dimensions only restricted to visit some transit points, as previously introduced between the 5' and 3' end of the gene. According to its position, an RNAPII protein molecule prefers paths obeying two types of time-evolution rules. One is an asymmetric simple exclusion process (ASEP) along DNA, and the other is a three-dimensional jump between transit points in DNA where RNAPIIs are staying. Simulations based on our model, and comparison experimental results, reveal how RNAPII molecules are distributed at the DNA-loop-formation-related protein binding sites as well as CTCF insulator proteins (or exons). As time passes after the stimulation, the RNAPII density at these sites becomes higher. Apparent far-distance jumps in one dimension are realized by short-range three-dimensional jumps between DNA loops. We confirm the above conjecture by applying our model calculation to the SAMD4A gene by comparing the experimental results. Our probabilistic model provides possible scenarios for assembling RNAPII molecules into transcription factories, where RNAPII and related proteins cooperatively transcribe DNA.
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Affiliation(s)
- Yoshihiro Ohta
- Research Center for Advanced Science and Technology, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8904, Japan
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Dynamics of lesion processing by bacterial nucleotide excision repair proteins. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2012; 110:1-24. [PMID: 22749140 DOI: 10.1016/b978-0-12-387665-2.00001-8] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Single-molecule approaches permit an unrivalled view of how complex systems operate and have recently been used to understand DNA-protein interactions. These tools have enabled advances in a particularly challenging problem, the search for damaged sites on DNA. DNA repair proteins are present at the level of just a few hundred copies in bacterial cells to just a few thousand in human cells, and they scan the entire genome in search of their specific substrates. How do these proteins achieve this herculean task when their targets may differ from undamaged DNA by only a single hydrogen bond? Here we examine, using single-molecule approaches, how the prokaryotic nucleotide excision repair system balances the necessity for speed against specificity. We discuss issues at a theoretical, biological, and technical level and finally pose questions for future research.
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