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Fijen C, Drogalis Beckham L, Terino D, Li Y, Ramsden DA, Wood RD, Doublié S, Rothenberg E. Sequential requirements for distinct Polθ domains during theta-mediated end joining. Mol Cell 2024; 84:1460-1474.e6. [PMID: 38640894 PMCID: PMC11031631 DOI: 10.1016/j.molcel.2024.03.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2023] [Revised: 01/10/2024] [Accepted: 03/12/2024] [Indexed: 04/21/2024]
Abstract
DNA polymerase θ (Polθ) plays a central role in a DNA double-strand break repair pathway termed theta-mediated end joining (TMEJ). TMEJ functions by pairing short-sequence "microhomologies" (MHs) in single-stranded DNA at each end of a break and subsequently initiating DNA synthesis. It is not known how the Polθ helicase domain (HD) and polymerase domain (PD) operate to bring together MHs and facilitate repair. To resolve these transient processes in real time, we utilized in vitro single-molecule FRET approaches and biochemical analyses. We find that the Polθ-HD mediates the initial capture of two ssDNA strands, bringing them in close proximity. The Polθ-PD binds and stabilizes pre-annealed MHs to form a synaptic complex (SC) and initiate repair synthesis. Individual synthesis reactions show that Polθ is inherently non-processive, accounting for complex mutational patterns during TMEJ. Binding of Polθ-PD to stem-loop-forming sequences can substantially limit synapsis, depending on the available dNTPs and sequence context.
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Affiliation(s)
- Carel Fijen
- Department of Biochemistry and Molecular Pharmacology, NYU Grossman School of Medicine, New York, NY 10016, USA.
| | - Lea Drogalis Beckham
- Department of Microbiology and Molecular Genetics, University of Vermont, Burlington, VT 05405, USA
| | - Dante Terino
- Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Yuzhen Li
- Department of Epigenetics and Molecular Carcinogenesis, University of Texas MD Anderson Cancer Center, Houston, TX 77230, USA
| | - Dale A Ramsden
- Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Richard D Wood
- Department of Epigenetics and Molecular Carcinogenesis, University of Texas MD Anderson Cancer Center, Houston, TX 77230, USA
| | - Sylvie Doublié
- Department of Microbiology and Molecular Genetics, University of Vermont, Burlington, VT 05405, USA
| | - Eli Rothenberg
- Department of Biochemistry and Molecular Pharmacology, NYU Grossman School of Medicine, New York, NY 10016, USA.
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2
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Buchel G, Nayak AR, Herbine K, Sarfallah A, Sokolova VO, Zamudio-Ochoa A, Temiakov D. Structural basis for DNA proofreading. Nat Commun 2023; 14:8501. [PMID: 38151585 PMCID: PMC10752894 DOI: 10.1038/s41467-023-44198-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2023] [Accepted: 12/04/2023] [Indexed: 12/29/2023] Open
Abstract
DNA polymerase (DNAP) can correct errors in DNA during replication by proofreading, a process critical for cell viability. However, the mechanism by which an erroneously incorporated base translocates from the polymerase to the exonuclease site and the corrected DNA terminus returns has remained elusive. Here, we present an ensemble of nine high-resolution structures representing human mitochondrial DNA polymerase Gamma, Polγ, captured during consecutive proofreading steps. The structures reveal key events, including mismatched base recognition, its dissociation from the polymerase site, forward translocation of DNAP, alterations in DNA trajectory, repositioning and refolding of elements for primer separation, DNAP backtracking, and displacement of the mismatched base into the exonuclease site. Altogether, our findings suggest a conserved 'bolt-action' mechanism of proofreading based on iterative cycles of DNAP translocation without dissociation from the DNA, facilitating primer transfer between catalytic sites. Functional assays and mutagenesis corroborate this mechanism, connecting pathogenic mutations to crucial structural elements in proofreading steps.
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Affiliation(s)
- Gina Buchel
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, 1020 Locust St, Philadelphia, PA, 19107, USA
| | - Ashok R Nayak
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, 1020 Locust St, Philadelphia, PA, 19107, USA
| | - Karl Herbine
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, 1020 Locust St, Philadelphia, PA, 19107, USA
| | - Azadeh Sarfallah
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, 1020 Locust St, Philadelphia, PA, 19107, USA
| | - Viktoriia O Sokolova
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, 1020 Locust St, Philadelphia, PA, 19107, USA
| | - Angelica Zamudio-Ochoa
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, 1020 Locust St, Philadelphia, PA, 19107, USA
| | - Dmitry Temiakov
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, 1020 Locust St, Philadelphia, PA, 19107, USA.
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3
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Liu T, Khanal S, Hertslet GD, Lamichhane R. Single-molecule analysis reveals that a glucagon-bound extracellular domain of the glucagon receptor is dynamic. J Biol Chem 2023; 299:105160. [PMID: 37586587 PMCID: PMC10514447 DOI: 10.1016/j.jbc.2023.105160] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2023] [Revised: 08/07/2023] [Accepted: 08/10/2023] [Indexed: 08/18/2023] Open
Abstract
Dynamic information is vital to understanding the activation mechanism of G protein-coupled receptors (GPCRs). Despite the availability of high-resolution structures of different conformational states, the dynamics of those states at the molecular level are poorly understood. Here, we used total internal reflection fluorescence microscopy to study the extracellular domain (ECD) of the glucagon receptor (GCGR), a class B family GPCR that controls glucose homeostasis. Single-molecule fluorescence resonance energy transfer was used to observe the ECD dynamics of GCGR molecules expressed and purified from mammalian cells. We observed that for apo-GCGR, the ECD is dynamic and spent time predominantly in a closed conformation. In the presence of glucagon, the ECD is wide open and also shows more dynamic behavior than apo-GCGR, a finding that was not previously reported. These results suggest that both apo-GCGR and glucagon-bound GCGRs show reversible opening and closing of the ECD with respect to the seven-transmembrane (7TM) domain. This work demonstrates a molecular approach to visualizing the dynamics of the GCGR ECD and provides a foundation for understanding the conformational changes underlying GPCR activation, which is critical in the development of new therapeutics.
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Affiliation(s)
- Ting Liu
- Department of Biochemistry & Cellular and Molecular Biology, College of Arts & Sciences, University of Tennessee, Knoxville, Tennessee, USA
| | - Susmita Khanal
- Department of Biochemistry & Cellular and Molecular Biology, College of Arts & Sciences, University of Tennessee, Knoxville, Tennessee, USA
| | - Gillian D Hertslet
- Department of Biochemistry & Cellular and Molecular Biology, College of Arts & Sciences, University of Tennessee, Knoxville, Tennessee, USA
| | - Rajan Lamichhane
- Department of Biochemistry & Cellular and Molecular Biology, College of Arts & Sciences, University of Tennessee, Knoxville, Tennessee, USA.
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4
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Park J, Herrmann GK, Mitchell PG, Sherman MB, Yin YW. Polγ coordinates DNA synthesis and proofreading to ensure mitochondrial genome integrity. Nat Struct Mol Biol 2023; 30:812-823. [PMID: 37202477 PMCID: PMC10920075 DOI: 10.1038/s41594-023-00980-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2022] [Accepted: 03/28/2023] [Indexed: 05/20/2023]
Abstract
Accurate replication of mitochondrial DNA (mtDNA) by DNA polymerase γ (Polγ) is essential for maintaining cellular energy supplies, metabolism, and cell cycle control. To illustrate the structural mechanism for Polγ coordinating polymerase (pol) and exonuclease (exo) activities to ensure rapid and accurate DNA synthesis, we determined four cryo-EM structures of Polγ captured after accurate or erroneous incorporation to a resolution of 2.4-3.0 Å. The structures show that Polγ employs a dual-checkpoint mechanism to sense nucleotide misincorporation and initiate proofreading. The transition from replication to error editing is accompanied by increased dynamics in both DNA and enzyme, in which the polymerase relaxes its processivity and the primer-template DNA unwinds, rotates, and backtracks to shuttle the mismatch-containing primer terminus 32 Å to the exo site for editing. Our structural and functional studies also provide a foundation for analyses of Polγ mutation-induced human diseases and aging.
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Affiliation(s)
- Joon Park
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX, USA
- Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, Galveston, TX, USA
| | - Geoffrey K Herrmann
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX, USA
- Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, Galveston, TX, USA
| | - Patrick G Mitchell
- Division of CryoEM and Bioimaging, Stanford Synchrotron Radiation Lightsource, Stanford Linear Accelerator Center National Accelerator Laboratory, Stanford University, Menlo Park, CA, USA
| | - Michael B Sherman
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX, USA
- Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, Galveston, TX, USA
| | - Y Whitney Yin
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX, USA.
- Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, Galveston, TX, USA.
- Department of Pharmacology and Toxicology, University of Texas Medical Branch, Galveston, TX, USA.
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5
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Dangerfield T, Johnson KA. Substrate Specificity and Kinetics of RNA Hydrolysis by SARS-CoV-2 NSP10/14 Exonuclease. ACS BIO & MED CHEM AU 2022; 2:600-606. [PMID: 36570070 PMCID: PMC9718090 DOI: 10.1021/acsbiomedchemau.2c00046] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/13/2022] [Revised: 09/09/2022] [Accepted: 09/09/2022] [Indexed: 11/18/2022]
Abstract
Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), the virus that causes COVID-19, continues to evolve resistance to vaccines and existing antiviral therapies at an alarming rate, increasing the need for new direct-acting antiviral drugs. Despite significant advances in our fundamental understanding of the kinetics and mechanism of viral RNA replication, there are still open questions regarding how the proofreading exonuclease (NSP10/NSP14 complex) contributes to replication fidelity and resistance to nucleoside analogs. Through single turnover kinetic analysis, we show that the preferred substrate for the exonuclease is double-stranded RNA without any mismatches. Double-stranded RNA containing a 3'-terminal remdesivir was hydrolyzed at a rate similar to a correctly base-paired cognate nucleotide. Surprisingly, single-stranded RNA or duplex RNA containing a 3'-terminal mismatch was hydrolyzed at rates 125- and 45-fold slower, respectively, compared to the correctly base-paired double-stranded RNA. These results define the substrate specificity and rate of removal of remdesivir for the exonuclease and outline rigorous kinetic assays that could help in finding next-generation exonuclease inhibitors or nucleoside analogs that are able to evade excision. These results also raise important questions about the role of the polymerase/exonuclease complex in proofreading during viral replication. Addressing these questions through rigorous kinetic analysis will facilitate the search for desperately needed antiviral drugs to combat COVID-19.
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6
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Kinetics of DNA strand transfer between polymerase and proofreading exonuclease active sites regulates error correction during high-fidelity replication. J Biol Chem 2022; 299:102744. [PMID: 36436560 PMCID: PMC9800556 DOI: 10.1016/j.jbc.2022.102744] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2022] [Revised: 11/18/2022] [Accepted: 11/20/2022] [Indexed: 11/25/2022] Open
Abstract
We show that T7 DNA polymerase (pol) and exonuclease (exo) domains contribute to selective error correction during DNA replication by regulating bidirectional strand transfer between the two active sites. To explore the kinetic basis for selective removal of mismatches, we used a fluorescent cytosine analog (1,3-diaza-2-oxophenoxazine) to monitor the kinetics of DNA transfer between the exo and pol sites. We globally fit stopped-flow fluorescence and base excision kinetic data and compared results obtained with ssDNA versus duplex DNA to resolve how DNA transfer governs exo specificity. We performed parallel studies using hydrolysis-resistant phosphorothioate oligonucleotides to monitor DNA transfer to the exo site without hydrolysis. ssDNA binds to the exo site at the diffusion limit (109 M-1 s-1, Kd = 40 nM) followed by fast hydrolysis of the 3'-terminal nucleotide (>5000 s-1). Analysis using duplex DNA with a 3'-terminal mismatch or a buried mismatch exposed a unique intermediate state between pol and exo active sites and revealed that transfer via the intermediate to the exo site is stimulated by free nucleoside triphosphates. Transfer from the exo site back to the pol site after cleavage is fast and efficient. We propose a model to explain why buried mismatches are removed faster than single 3'-terminal mismatches and thereby provide an additional opportunity for error correction. Our data provide the first comprehensive model to explain how DNA transfer from pol to exo active sites and back again after base excision allow efficient selective mismatch removal during DNA replication to improve fidelity by more than 1000-fold.
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7
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Millar DP. Conformational Dynamics of DNA Polymerases Revealed at the Single-Molecule Level. Front Mol Biosci 2022; 9:826593. [PMID: 35281261 PMCID: PMC8913937 DOI: 10.3389/fmolb.2022.826593] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Accepted: 01/20/2022] [Indexed: 12/25/2022] Open
Abstract
DNA polymerases are intrinsically dynamic macromolecular machines. The purpose of this review is to describe the single-molecule Förster resonance energy transfer (smFRET) methods that are used to probe the conformational dynamics of DNA polymerases, focusing on E. coli DNA polymerase I. The studies reviewed here reveal the conformational dynamics underpinning the nucleotide selection, proofreading and 5′ nuclease activities of Pol I. Moreover, the mechanisms revealed for Pol I are likely employed across the DNA polymerase family. smFRET methods have also been used to examine other aspects of DNA polymerase activity.
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8
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Evans GW, Craggs T, Kapanidis AN. The Rate-limiting Step of DNA Synthesis by DNA Polymerase Occurs in the Fingers-closed Conformation. J Mol Biol 2022; 434:167410. [PMID: 34929202 PMCID: PMC8783057 DOI: 10.1016/j.jmb.2021.167410] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Revised: 11/22/2021] [Accepted: 12/12/2021] [Indexed: 12/03/2022]
Abstract
DNA polymerases maintain genomic integrity by copying DNA with high fidelity, part of which relies on the polymerase fingers opening-closing transition, a series of conformational changes during the DNA synthesis reaction cycle. Fingers opening and closing has been challenging to study, mainly due to the need to synchronise molecular ensembles. We previously studied fingers opening-closing on single polymerase-DNA complexes using single-molecule FRET; however, our work was limited to pre-chemistry reaction steps. Here, we advance our analysis to extensible substrates, and observe DNA polymerase (Pol) conformational changes across the entire DNA polymerisation reaction in real-time, gaining direct access to an elusive post-chemistry step rate-limiting for DNA synthesis. Our results showed that Pol adopts the fingers-closed conformation during polymerisation, and that the post-chemistry rate-limiting step occurs in the fingers-closed conformation. We found that fingers-opening in the Pol-DNA binary complex in the absence of polymerisation is slow (∼5.3 s-1), and comparable to the rate of fingers-opening after polymerisation (3.4 s-1); this indicates that the fingers-opening step itself could be largely responsible for the slow post-chemistry step, with the residual rate potentially accounted for by pyrophosphase release. We also observed that DNA chain-termination of the 3' end of the primer increases substantially the rate of fingers-opening in the Pol-DNA binary complex (5.3 → 29 s-1), demonstrating that the 3'-OH residue is important for the kinetics of fingers conformational changes. Our observations offer mechanistic insight and tools to offer mechanistic insight for all nucleic acid polymerases.
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Affiliation(s)
- Geraint W Evans
- Department of Physics and Biological Physics Research Group, Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom. https://twitter.com/geraintwe
| | - Timothy Craggs
- Department of Physics and Biological Physics Research Group, Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom; Sheffield Institute for Nucleic Acids, Department of Chemistry, University of Sheffield, Brook Hill, Sheffield S3 7HF, United Kingdom. https://twitter.com/Craggs_Lab
| | - Achillefs N Kapanidis
- Department of Physics and Biological Physics Research Group, Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom.
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9
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Carvajal-Maldonado D, Drogalis Beckham L, Wood RD, Doublié S. When DNA Polymerases Multitask: Functions Beyond Nucleotidyl Transfer. Front Mol Biosci 2022; 8:815845. [PMID: 35071329 PMCID: PMC8782244 DOI: 10.3389/fmolb.2021.815845] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2021] [Accepted: 12/13/2021] [Indexed: 11/13/2022] Open
Abstract
DNA polymerases catalyze nucleotidyl transfer, the central reaction in synthesis of DNA polynucleotide chains. They function not only in DNA replication, but also in diverse aspects of DNA repair and recombination. Some DNA polymerases can perform translesion DNA synthesis, facilitating damage tolerance and leading to mutagenesis. In addition to these functions, many DNA polymerases conduct biochemically distinct reactions. This review presents examples of DNA polymerases that carry out nuclease (3'-5' exonuclease, 5' nuclease, or end-trimming nuclease) or lyase (5' dRP lyase) extracurricular activities. The discussion underscores how DNA polymerases have a remarkable ability to manipulate DNA strands, sometimes involving relatively large intramolecular movement.
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Affiliation(s)
- Denisse Carvajal-Maldonado
- Department of Epigenetics and Molecular Carcinogenesis, The University of Texas MD Anderson Center, Houston, TX, United States
| | - Lea Drogalis Beckham
- Department of Microbiology and Molecular Genetics, University of Vermont, Burlington, VT, United States
| | - Richard D Wood
- Department of Epigenetics and Molecular Carcinogenesis, The University of Texas MD Anderson Center, Houston, TX, United States
| | - Sylvie Doublié
- Department of Microbiology and Molecular Genetics, University of Vermont, Burlington, VT, United States
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10
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Li QS, Shu YG, Ou-Yang ZC, Li M. Kinetic assays of DNA polymerase fidelity: A theoretical perspective beyond Michaelis-Menten kinetics. Phys Rev E 2021; 104:014408. [PMID: 34412358 DOI: 10.1103/physreve.104.014408] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2020] [Accepted: 06/23/2021] [Indexed: 11/07/2022]
Abstract
The high fidelity of DNA polymerase (DNAP) is critical for the faithful replication of DNA. There are several quantitative approaches to measure DNAP fidelity. Directly counting the error frequency in the replication products gives the true fidelity but it turns out very hard to implement in practice. Two biochemical kinetic approaches, the steady-state assay and the transient-state assay, were then suggested and widely adopted. In these assays, the error frequency is indirectly estimated by using kinetic theories combined with the measured apparent kinetic rates. However, whether it is equivalent to the true fidelity has never been clarified theoretically, and in particular there are different strategies using these assays to quantify the proofreading efficiency of DNAP but often lead to inconsistent results. In this paper, we make a comprehensive examination on the theoretical foundation of the two kinetic assays, based on the theory of DNAP fidelity recently proposed by us. Our studies show that while the conventional kinetic assays are generally valid to quantify the discrimination efficiency of DNAP, they are valid to quantify the proofreading efficiency of DNAP only when the kinetic parameters satisfy some constraints which will be given explicitly in this paper. These results may inspire more carefully-designed experiments to quantify DNAP fidelity.
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Affiliation(s)
- Qiu-Shi Li
- School of Physical Science, University of Chinese Academy of Sciences, No. 19(A) Yuquan Road, Shijingshan District, Beijing 101400, People's Republic of China
| | - Yao-Gen Shu
- Wenzhou Institute, University of Chinese Academy of Sciences, No 1, Jinlian Road, Longwan District, Wenzhou, Zhejiang 325000, People's Republic of China
| | - Zhong-Can Ou-Yang
- Institute of Theoretical Physics, Chinese Academy of Sciences, Zhong Guan Cun East Street 55, P. O. Box 2735, Beijing 100190, People's Republic of China
| | - Ming Li
- School of Physical Science, University of Chinese Academy of Sciences, No. 19(A) Yuquan Road, Shijingshan District, Beijing 101400, People's Republic of China
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11
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Bocanegra R, Ismael Plaza GA, Pulido CR, Ibarra B. DNA replication machinery: Insights from in vitro single-molecule approaches. Comput Struct Biotechnol J 2021; 19:2057-2069. [PMID: 33995902 PMCID: PMC8085672 DOI: 10.1016/j.csbj.2021.04.013] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2021] [Revised: 04/03/2021] [Accepted: 04/03/2021] [Indexed: 11/16/2022] Open
Abstract
The replisome is the multiprotein molecular machinery that replicates DNA. The replisome components work in precise coordination to unwind the double helix of the DNA and replicate the two strands simultaneously. The study of DNA replication using in vitro single-molecule approaches provides a novel quantitative understanding of the dynamics and mechanical principles that govern the operation of the replisome and its components. ‘Classical’ ensemble-averaging methods cannot obtain this information. Here we describe the main findings obtained with in vitro single-molecule methods on the performance of individual replisome components and reconstituted prokaryotic and eukaryotic replisomes. The emerging picture from these studies is that of stochastic, versatile and highly dynamic replisome machinery in which transient protein-protein and protein-DNA associations are responsible for robust DNA replication.
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Affiliation(s)
- Rebeca Bocanegra
- IMDEA Nanociencia, Faraday 9, Campus Cantoblanco, 28049 Madrid, Spain
| | - G A Ismael Plaza
- IMDEA Nanociencia, Faraday 9, Campus Cantoblanco, 28049 Madrid, Spain
| | - Carlos R Pulido
- IMDEA Nanociencia, Faraday 9, Campus Cantoblanco, 28049 Madrid, Spain
| | - Borja Ibarra
- IMDEA Nanociencia, Faraday 9, Campus Cantoblanco, 28049 Madrid, Spain
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12
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Pauszek RF, Lamichhane R, Rajkarnikar Singh A, Millar DP. Single-molecule view of coordination in a multi-functional DNA polymerase. eLife 2021; 10:e62046. [PMID: 33704066 PMCID: PMC7952088 DOI: 10.7554/elife.62046] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2020] [Accepted: 12/28/2020] [Indexed: 01/01/2023] Open
Abstract
Replication and repair of genomic DNA requires the actions of multiple enzymatic functions that must be coordinated in order to ensure efficient and accurate product formation. Here, we have used single-molecule FRET microscopy to investigate the physical basis of functional coordination in DNA polymerase I (Pol I) from Escherichia coli, a key enzyme involved in lagging-strand replication and base excision repair. Pol I contains active sites for template-directed DNA polymerization and 5' flap processing in separate domains. We show that a DNA substrate can spontaneously transfer between polymerase and 5' nuclease domains during a single encounter with Pol I. Additionally, we show that the flexibly tethered 5' nuclease domain adopts different positions within Pol I-DNA complexes, depending on the nature of the DNA substrate. Our results reveal the structural dynamics that underlie functional coordination in Pol I and are likely relevant to other multi-functional DNA polymerases.
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Affiliation(s)
- Raymond F Pauszek
- Department of Integrative Structural and Computational Biology, The Scripps Research InstituteLa JollaUnited States
| | - Rajan Lamichhane
- Department of Integrative Structural and Computational Biology, The Scripps Research InstituteLa JollaUnited States
| | - Arishma Rajkarnikar Singh
- Department of Integrative Structural and Computational Biology, The Scripps Research InstituteLa JollaUnited States
| | - David P Millar
- Department of Integrative Structural and Computational Biology, The Scripps Research InstituteLa JollaUnited States
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13
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Mukherjee P, Chandra Singh P. Experimental insight into enzyme catalysis and dynamics: A review on applications of state of art spectroscopic methods. ADVANCES IN PROTEIN CHEMISTRY AND STRUCTURAL BIOLOGY 2021; 122:33-62. [PMID: 32951815 DOI: 10.1016/bs.apcsb.2020.06.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Enzymes are dynamic in nature and understanding their activity depends on exploring their overall structural fluctuation as well as transformation at the active site in free state as well as turnover conditions. In this chapter, the application of several different spectroscopy techniques viz. single molecule spectroscopy, ultrafast spectroscopy and Raman spectroscopy in the context of enzyme dynamics and catalysis are discussed. The importance of such studies are significant in the understanding of new discoveries of drugs, cure for some lethal diseases, gene modification as well as in industrial applications.
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Affiliation(s)
- Puspal Mukherjee
- School of Chemical Sciences, Indian Association for the Cultivation of Science, Kolkata, West Bengal, India
| | - Prashant Chandra Singh
- School of Chemical Sciences, Indian Association for the Cultivation of Science, Kolkata, West Bengal, India
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14
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Singh A, Pandey M, Nandakumar D, Raney KD, Yin YW, Patel SS. Excessive excision of correct nucleotides during DNA synthesis explained by replication hurdles. EMBO J 2020; 39:e103367. [PMID: 32037587 PMCID: PMC7073461 DOI: 10.15252/embj.2019103367] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2019] [Revised: 12/23/2019] [Accepted: 01/07/2020] [Indexed: 11/25/2022] Open
Abstract
The proofreading exonuclease activity of replicative DNA polymerase excises misincorporated nucleotides during DNA synthesis, but these events are rare. Therefore, we were surprised to find that T7 replisome excised nearly 7% of correctly incorporated nucleotides during leading and lagging strand syntheses. Similar observations with two other DNA polymerases establish its generality. We show that excessive excision of correctly incorporated nucleotides is not due to events such as processive degradation of nascent DNA or spontaneous partitioning of primer‐end to the exonuclease site as a “cost of proofreading”. Instead, we show that replication hurdles, including secondary structures in template, slowed helicase, or uncoupled helicase–polymerase, increase DNA reannealing and polymerase backtracking, and generate frayed primer‐ends that are shuttled to the exonuclease site and excised efficiently. Our studies indicate that active‐site shuttling occurs at a high frequency, and we propose that it serves as a proofreading mechanism to protect primer‐ends from mutagenic extensions.
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Affiliation(s)
- Anupam Singh
- Department of Biochemistry and Molecular Biology, Robert Wood Johnson Medical School, Rutgers University, Piscataway, NJ, USA
| | - Manjula Pandey
- Department of Biochemistry and Molecular Biology, Robert Wood Johnson Medical School, Rutgers University, Piscataway, NJ, USA
| | - Divya Nandakumar
- Department of Biochemistry and Molecular Biology, Robert Wood Johnson Medical School, Rutgers University, Piscataway, NJ, USA
| | - Kevin D Raney
- Department of Biochemistry and Molecular Biology, The University of Arkansas for Medical Sciences, Little Rock, AR, USA
| | - Y Whitney Yin
- Department of Pharmacology and Toxicology, Sealy Center for Structural Biology, University of Texas Medical Branch, Galveston, TX, USA
| | - Smita S Patel
- Department of Biochemistry and Molecular Biology, Robert Wood Johnson Medical School, Rutgers University, Piscataway, NJ, USA
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15
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Lamichhane R, Liu JJ, White KL, Katritch V, Stevens RC, Wüthrich K, Millar DP. Biased Signaling of the G-Protein-Coupled Receptor β 2AR Is Governed by Conformational Exchange Kinetics. Structure 2020; 28:371-377.e3. [PMID: 31978323 DOI: 10.1016/j.str.2020.01.001] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2019] [Revised: 10/11/2019] [Accepted: 01/03/2020] [Indexed: 01/14/2023]
Abstract
G-protein-coupled receptors (GPCRs) mediate a wide range of human physiological functions by transducing extracellular ligand binding events into intracellular responses. GPCRs can activate parallel, independent signaling pathways mediated by G proteins or β-arrestins. Whereas "balanced" agonists activate both pathways equally, "biased" agonists dominantly activate one pathway, which is of interest for designing GPCR-targeting drugs because it may mitigate undesirable side effects. Previous studies demonstrated that β-arrestin activation is associated with transmembrane helix VII (TM VII) of GPCRs. Here, single-molecule fluorescence spectroscopy with the β2-adrenergic receptor (β2AR) in the ligand-free state showed that TM VII spontaneously fluctuates between one inactive and one active-like conformation. The presence of the β-arrestin-biased agonist isoetharine prolongs the dwell time of TM VII in the active-like conformation compared with the balanced agonist formoterol, suggesting that ligands can induce signaling bias by modulating the kinetics of receptor conformational exchange.
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Affiliation(s)
- Rajan Lamichhane
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Jeffrey J Liu
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Kate L White
- Departments of Biological Sciences and Chemistry, Bridge Institute, USC Michelson Center for Convergent Bioscience, University of Southern California, Childs Way, MC3502, Los Angeles, CA 90089, USA
| | - Vsevolod Katritch
- Departments of Biological Sciences and Chemistry, Bridge Institute, USC Michelson Center for Convergent Bioscience, University of Southern California, Childs Way, MC3502, Los Angeles, CA 90089, USA
| | - Raymond C Stevens
- Departments of Biological Sciences and Chemistry, Bridge Institute, USC Michelson Center for Convergent Bioscience, University of Southern California, Childs Way, MC3502, Los Angeles, CA 90089, USA
| | - Kurt Wüthrich
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA; Skaggs Institute of Chemical Biology, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - David P Millar
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA.
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16
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Sowers ML, Anderson APP, Wrabl JO, Yin YW. Networked Communication between Polymerase and Exonuclease Active Sites in Human Mitochondrial DNA Polymerase. J Am Chem Soc 2019; 141:10821-10829. [PMID: 31251605 PMCID: PMC7119269 DOI: 10.1021/jacs.9b04655] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
High fidelity human mitochondrial DNA polymerase (Pol γ) contains two active sites, a DNA polymerization site (pol) and a 3'-5' exonuclease site (exo) for proofreading. Although separated by 35 Å, coordination between the pol and exo sites is crucial to high fidelity replication. The biophysical mechanisms for this coordination are not completely understood. To understand the communication between the two active sites, we used a statistical-mechanical model of the protein ensemble to calculate the energetic landscape and local stability. We compared a series of structures of Pol γ, complexed with primer/template DNA, and either a nucleotide substrate or a series of nucleotide analogues, which are differentially incorporated and excised by pol and exo activity. Despite the nucleotide or its analogues being bound in the pol, Pol γ residue stability varied across the protein, particularly in the exo domain. This suggests that substrate presence in the pol can be "sensed" in the exo domain. Consistent with this hypothesis, in silico mutations made in one active site mutually perturbed the energetics of the other. To identify specific regions of the polymerase that contributed to this communication, we constructed an allosteric network connectivity map that further demonstrates specific pol-exo cooperativity. Thus, a cooperative network underlies energetic connectivity. We propose that Pol γ and other dual-function polymerases exploit an energetic coupling network that facilitates domain-domain communication to enhance discrimination between correct and incorrect nucleotides.
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Affiliation(s)
- Mark L. Sowers
- MD-PhD Combined Degree Program, University of Texas Medical Branch, Galveston, Texas 77555, United States
- Department of Pharmacology and Toxicology, University of Texas Medical Branch, Galveston, Texas 77555, United States
| | - Andrew P. P. Anderson
- Department of Pharmacology and Toxicology, University of Texas Medical Branch, Galveston, Texas 77555, United States
- Program of Quantitative and Computational Biosciences, Baylor College of Medicine, Houston, Texas 71115, United States
| | - James O. Wrabl
- Department of Biology, Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, United States
| | - Y. Whitney Yin
- Department of Pharmacology and Toxicology, University of Texas Medical Branch, Galveston, Texas 77555, United States
- Sealy Center for Structural Biology, University of Texas Medical Branch, Galveston, Texas 77555, United States
- Program of Quantitative and Computational Biosciences, Baylor College of Medicine, Houston, Texas 71115, United States
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17
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Gahlon HL, Walker AR, Cisneros GA, Lamers MH, Rueda DS. Reduced structural flexibility for an exonuclease deficient DNA polymerase III mutant. Phys Chem Chem Phys 2018; 20:26892-26902. [PMID: 30345999 PMCID: PMC6278910 DOI: 10.1039/c8cp04112a] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
DNA synthesis, carried out by DNA polymerases, requires balancing speed and accuracy for faithful replication of the genome. High fidelity DNA polymerases contain a 3'-5' exonuclease domain that can remove misincorporated nucleotides on the 3' end of the primer strand, a process called proofreading. The E. coli replicative polymerase, DNA polymerase III, has spatially separated (∼55 Å apart) polymerase and exonuclease subunits. Here, we report on the dynamics of E. coli DNA polymerase III proofreading in the presence of its processivity factor, the β2-sliding clamp, at varying base pair termini using single-molecule FRET. We find that the binding kinetics do not depend on the base identity at the termini, indicating a tolerance for DNA mismatches. Further, our single-molecule data and MD simulations show two previously unobserved features: (1) DNA Polymerase III is a highly dynamic protein that adopts multiple conformational states while bound to DNA with matched or mismatched ends, and (2) an exonuclease-deficient DNA polymerase III has reduced conformational flexibility. Overall, our single-molecule experiments provide high time-resolution insight into a mechanism that ensures high fidelity DNA replication to maintain genome integrity.
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Affiliation(s)
- Hailey L Gahlon
- Department of Medicine, Molecular Virology, Imperial College London, Du Cane Road, London W12 0NN, UK.
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18
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Christian TV, Konigsberg WH. Single-molecule FRET reveals proofreading complexes in the large fragment of Bacillus stearothermophilus DNA polymerase I. AIMS BIOPHYSICS 2018; 5:144-154. [PMID: 29888335 PMCID: PMC5990039 DOI: 10.3934/biophy.2018.2.144] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
There is increasing interest in the use of DNA polymerases (DNA pols) in next-generation sequencing strategies. These methodologies typically rely on members of the A and B family of DNA polymerases that are classified as high-fidelity DNA polymerases. These enzymes possess the ability to selectively incorporate the correct nucleotide opposite a templating base with an error frequency of only 1 in 106 insertion events. How they achieve this remarkable fidelity has been the subject of numerous investigations, yet the mechanism by which these enzymes achieve this level of accuracy remains elusive. Several smFRET assays were designed to monitor the conformational changes associated with the nucleotide selection mechanism(s) employed by DNA pols. smFRET has also been used to monitor the movement of DNA pols along a DNA substrate as well as to observe the formation of proof-reading complexes. One member among this class of enzymes, the large fragment of Bacillus stearothermophilus DNA polymerase I (Bst pol I LF), contains both 5'→3' polymerase and 3'→5' exonuclease domains, but reportedly lacks exonuclease activity. We have designed a smFRET assay showing that Bst pol I LF forms proofreading complexes. The formation of proofreading complexes at the single molecule level is strongly influenced by the presence of the 3' hydroxyl at the primer-terminus of the DNA substrate. Our assays also identify an additional state, observed in the presence of a mismatched primer-template terminus, that may be involved in the transfer of the primer-terminus from the polymerase to the exonuclease active site.
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Affiliation(s)
- Thomas V Christian
- Konigsberg Laboratory, Yale University, 333 Cedar Street, New Haven, CT 06520, USA
| | - William H Konigsberg
- Konigsberg Laboratory, Yale University, 333 Cedar Street, New Haven, CT 06520, USA
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19
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Fidelity of DNA replication-a matter of proofreading. Curr Genet 2018; 64:985-996. [PMID: 29500597 PMCID: PMC6153641 DOI: 10.1007/s00294-018-0820-1] [Citation(s) in RCA: 82] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2018] [Revised: 02/27/2018] [Accepted: 02/28/2018] [Indexed: 01/29/2023]
Abstract
DNA that is transmitted to daughter cells must be accurately duplicated to maintain genetic integrity and to promote genetic continuity. A major function of replicative DNA polymerases is to replicate DNA with the very high accuracy. The fidelity of DNA replication relies on nucleotide selectivity of replicative DNA polymerase, exonucleolytic proofreading, and postreplicative DNA mismatch repair (MMR). Proofreading activity that assists most of the replicative polymerases is responsible for removal of incorrectly incorporated nucleotides from the primer terminus before further primer extension. It is estimated that proofreading improves the fidelity by a 2–3 orders of magnitude. The primer with the incorrect terminal nucleotide has to be moved to exonuclease active site, and after removal of the wrong nucleotide must be transferred back to polymerase active site. The mechanism that allows the transfer of the primer between pol and exo site is not well understood. While defects in MMR are well known to be linked with increased cancer incidence only recently, the replicative polymerases that have alterations in the exonuclease domain have been associated with some sporadic and hereditary human cancers. In this review, we would like to emphasize the importance of proofreading (3′-5′ exonuclease activity) in the fidelity of DNA replication and to highlight what is known about switching from polymerase to exonuclease active site.
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20
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Hammond JA, Zhou L, Lamichhane R, Chu HY, Millar DP, Gerace L, Williamson JR. A Survey of DDX21 Activity During Rev/RRE Complex Formation. J Mol Biol 2018; 430:537-553. [PMID: 28705764 PMCID: PMC5762417 DOI: 10.1016/j.jmb.2017.06.023] [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] [Received: 05/18/2017] [Revised: 06/26/2017] [Accepted: 06/27/2017] [Indexed: 01/17/2023]
Abstract
HIV-1 requires a specialized nuclear export pathway to transport unspliced and partially spliced viral transcripts to the cytoplasm. Central to this pathway is the viral protein Rev, which binds to the Rev response element in stem IIB located on unspliced viral transcripts and subsequently oligomerizes in a cooperative manner. Previous work identified a number of cellular DEAD-box helicases as in vivo binding partners of Rev, and siRNA experiments indicated a functional role for many in the HIV replication cycle. Two DEAD-box proteins, DDX1 and DDX3, had previously been shown to play a role in HIV pathogenesis. In this study, another protein identified in that screen, DDX21, is tested for protein and RNA binding and subsequent enzymatic activities in the context of the Rev/RRE pathway. We found that DDX21 can bind to the RRE with high affinity, and this binding stimulates ATPase activity with an enzymatic efficiency similar to DDX1. Furthermore, DDX21 is both an ATP-dependent and ATP-independent helicase, and both ATPase and ATP-dependent helicase activities are inhibited by Rev in a dose-dependent manner, although ATP-independent helicase activity is not. A conserved binding interaction between DDX protein's DEAD domain and Rev was identified, with Rev's nuclear diffusion inhibitory signal motif playing a significant role in binding. Finally, DDX21 was shown to enhance Rev binding to the RRE in a manner similar to that previously described for DDX1, although DDX3 does not. These data indicate that DDX1 and DDX21 have similar biochemical activities with regard to the Rev/RRE system, while DDX3 differs.
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Affiliation(s)
- John A Hammond
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Li Zhou
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Rajan Lamichhane
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Hui-Yi Chu
- Department of Molecular Medicine, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - David P Millar
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Larry Gerace
- Department of Molecular Medicine, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - James R Williamson
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, CA 92037, USA.
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21
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Park J, Jergic S, Jeon Y, Cho WK, Lee R, Dixon NE, Lee JB. Dynamics of Proofreading by the E. coli Pol III Replicase. Cell Chem Biol 2017; 25:57-66.e4. [PMID: 29104063 DOI: 10.1016/j.chembiol.2017.09.008] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2017] [Revised: 08/09/2017] [Accepted: 09/27/2017] [Indexed: 02/05/2023]
Abstract
The αɛθ core of Escherichia coli DNA polymerase III (Pol III) associates with the β2 sliding clamp to processively synthesize DNA and remove misincorporated nucleotides. The α subunit is the polymerase while ɛ is the 3' to 5' proofreading exonuclease. In contrast to the polymerase activity of Pol III, dynamic features of proofreading are poorly understood. We used single-molecule assays to determine the excision rate and processivity of the β2-associated Pol III core, and observed that both properties are enhanced by mutational strengthening of the interaction between ɛ and β2. Thus, the ɛ-β2 contact is maintained in both the synthesis and proofreading modes. Remarkably, single-molecule real-time fluorescence imaging revealed the dynamics of transfer of primer-template DNA between the polymerase and proofreading sites, showing that it does not involve breaking of the physical interaction between ɛ and β2.
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Affiliation(s)
- Jonghyun Park
- Department of Physics, Pohang University of Science & Technology (POSTECH), Pohang 37673, Korea
| | - Slobodan Jergic
- Centre for Medical and Molecular Bioscience, University of Wollongong & Illawarra Health and Medical Research Institute, Wollongong, NSW 2522, Australia
| | - Yongmoon Jeon
- Department of Physics, Pohang University of Science & Technology (POSTECH), Pohang 37673, Korea
| | - Won-Ki Cho
- Department of Physics, Pohang University of Science & Technology (POSTECH), Pohang 37673, Korea
| | - Ryanggeun Lee
- Department of Physics, Pohang University of Science & Technology (POSTECH), Pohang 37673, Korea
| | - Nicholas E Dixon
- Centre for Medical and Molecular Bioscience, University of Wollongong & Illawarra Health and Medical Research Institute, Wollongong, NSW 2522, Australia.
| | - Jong-Bong Lee
- Department of Physics, Pohang University of Science & Technology (POSTECH), Pohang 37673, Korea; School of Interdisciplinary Bioscience and Bioengineering, POSTECH, Pohang 37673, Korea.
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22
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Mass-spectrometry analysis of modifications at DNA termini induced by DNA polymerases. Sci Rep 2017; 7:6674. [PMID: 28751641 PMCID: PMC5532294 DOI: 10.1038/s41598-017-06136-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2017] [Accepted: 06/01/2017] [Indexed: 12/27/2022] Open
Abstract
Non-natural nucleotide substrates are widely used in the enzymatic synthesis of modified DNA. The terminal activity of polymerases in the presence of modified nucleotides is an important, but poorly characterized, aspect of enzymatic DNA synthesis. Here, we studied different types of polymerase activity at sequence ends using extendable and non-extendable synthetic models in the presence of the Cy5-dUTP analog Y. In primer extension reactions with selected exonuclease-deficient polymerases, nucleotide Y appeared to be a preferential substrate for non-templated 3'-tailing, as determined by MALDI mass-spectrometry and gel-electrophoresis. This result was further confirmed by the 3'-tailing of a non-extendable hairpin oligonucleotide model. Additionally, DNA polymerases induce an exchange of the 3' terminal thymidine for a non-natural nucleotide via pyrophosphorolysis in the presence of inorganic pyrophosphate. In primer extension reactions, the proofreading polymerases Vent, Pfu, and Phusion did not support the synthesis of Y-modified primer strand. Nevertheless, Pfu and Phusion polymerases were shown to initiate terminal nucleotide exchange at the template. Unlike non-proofreading polymerases, these two enzymes recruit 3'-5' exonuclease functions to cleave the 3' terminal thymidine in the absence of pyrophosphate.
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23
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Hammond JA, Lamichhane R, Millar DP, Williamson JR. A DEAD-Box Helicase Mediates an RNA Structural Transition in the HIV-1 Rev Response Element. J Mol Biol 2017; 429:697-714. [PMID: 28153748 PMCID: PMC5510989 DOI: 10.1016/j.jmb.2017.01.018] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2016] [Revised: 01/04/2017] [Accepted: 01/21/2017] [Indexed: 01/17/2023]
Abstract
Nuclear export of partially spliced or unspliced HIV-1 RNA transcripts requires binding of the viral protein regulator of expression of virion (Rev) to the Rev response element (RRE) and subsequent oligomerization in a cooperative manner. Cellular DEAD-box helicase DEAD-box protein 1 (DDX1) plays a role in HIV replication, interacting with and affecting Rev-containing HIV transcripts in vivo, interacting directly with the RRE and Rev in vitro, and promoting Rev oligomerization in vitro. Binding of DDX1 results in enhancement of Rev oligomerization on the RRE that is correlated with an RNA structural change within the RRE that persists even after dissociation of DDX1. Furthermore, this structural transition is likely located within the three-way junction of stem II of the RRE that is responsible for initial Rev binding. This discovery of the stem II structural transition leads to a model wherein DDX1 can act as an RNA chaperone, folding stem IIB into a proper Rev binding conformation.
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Affiliation(s)
- John A Hammond
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Rajan Lamichhane
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - David P Millar
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - James R Williamson
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, CA 92037, USA.
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24
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Song YS, Shu YG, Zhou X, Ou-Yang ZC, Li M. Proofreading of DNA polymerase: a new kinetic model with higher-order terminal effects. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:025101. [PMID: 27842005 DOI: 10.1088/0953-8984/29/2/025101] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The fidelity of DNA replication by DNA polymerase (DNAP) has long been an important issue in biology. While numerous experiments have revealed details of the molecular structure and working mechanism of DNAP which consists of both a polymerase site and an exonuclease (proofreading) site, there were quite a few theoretical studies on the fidelity issue. The first model which explicitly considered both sites was proposed in the 1970s and the basic idea was widely accepted by later models. However, all these models did not systematically investigate the dominant factor on DNAP fidelity, i.e. the higher-order terminal effects through which the polymerization pathway and the proofreading pathway coordinate to achieve high fidelity. In this paper, we propose a new and comprehensive kinetic model of DNAP based on some recent experimental observations, which includes previous models as special cases. We present a rigorous and unified treatment of the corresponding steady-state kinetic equations of any-order terminal effects, and derive analytical expressions for fidelity in terms of kinetic parameters under bio-relevant conditions. These expressions offer new insights on how the higher-order terminal effects contribute substantially to the fidelity in an order-by-order way, and also show that the polymerization-and-proofreading mechanism is dominated only by very few key parameters. We then apply these results to calculate the fidelity of some real DNAPs, which are in good agreements with previous intuitive estimates given by experimentalists.
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Affiliation(s)
- Yong-Shun Song
- School of Physical Sciences, University of Chinese Academy of Sciences, No 19A Yuquan Road, Beijing 100049, People's Republic of China
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25
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Lamichhane R, Mukherjee S, Smolin N, Pauszek RF, Bradley M, Sastri J, Robia SL, Millar D, Campbell EM. Dynamic conformational changes in the rhesus TRIM5α dimer dictate the potency of HIV-1 restriction. Virology 2016; 500:161-168. [PMID: 27821283 DOI: 10.1016/j.virol.2016.10.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2016] [Revised: 10/01/2016] [Accepted: 10/05/2016] [Indexed: 11/26/2022]
Abstract
The TRIM5α protein from rhesus macaques (rhTRIM5α) mediates a potent inhibition of HIV-1 infection via a mechanism that involves the abortive disassembly of the viral core. We have demonstrated that alpha-helical elements within the Linker 2 (L2) region, which lies between the SPRY domain and the Coiled-Coil domain, influence the potency of restriction. Here, we utilize single-molecule FRET analysis to reveal that the L2 region of the TRIM5α dimer undergoes dynamic conformational changes, which results in the displacement of L2 regions by 25 angstroms relative to each other. Analysis of restriction enhancing or abrogating mutations in the L2 region reveal that restriction defective mutants are unable to undergo dynamic conformational changes and do not assume compact, alpha-helical conformations in the L2 region. These data suggest a model in which conformational changes in the L2 region mediate displacement of CA bound SPRY domains to induce the destabilization of assembled capsid during restriction.
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Affiliation(s)
- Rajan Lamichhane
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, CA, USA
| | - Santanu Mukherjee
- Department of Microbiology and Immunology, Stritch School of Medicine, Loyola University Chicago, Chicago, IL, USA
| | - Nikolai Smolin
- Department of Cell and Molecular Physiology, Stritch School of Medicine, Loyola University Chicago, Chicago, IL, USA
| | - Raymond F Pauszek
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, CA, USA
| | - Margret Bradley
- Department of Microbiology and Immunology, Stritch School of Medicine, Loyola University Chicago, Chicago, IL, USA
| | - Jaya Sastri
- Viral Mutation Section, HIV Dynamics and Replication Program, National Cancer Institute at Frederick, Frederick, MD, USA
| | - Seth L Robia
- Department of Cell and Molecular Physiology, Stritch School of Medicine, Loyola University Chicago, Chicago, IL, USA
| | - David Millar
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, CA, USA
| | - Edward M Campbell
- Department of Microbiology and Immunology, Stritch School of Medicine, Loyola University Chicago, Chicago, IL, USA
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26
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Hartmann S, Weidlich D, Klostermeier D. Single-Molecule Confocal FRET Microscopy to Dissect Conformational Changes in the Catalytic Cycle of DNA Topoisomerases. Methods Enzymol 2016; 581:317-351. [PMID: 27793284 DOI: 10.1016/bs.mie.2016.08.013] [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: 01/04/2023]
Abstract
Molecular machines undergo large-scale conformational changes during their catalytic cycles that are linked to their biological functions. DNA topoisomerases are molecular machines that interconvert different DNA topoisomers and resolve torsional stress that is introduced during cellular processes that involve local DNA unwinding. DNA gyrase catalyzes the introduction of negative supercoils into DNA in an ATP-dependent reaction. During its catalytic cycle, gyrase undergoes large-scale conformational changes that drive the supercoiling reaction. These conformational changes can be followed by single-molecule Förster resonance energy transfer (FRET). Here, we use DNA gyrase from Bacillus subtilis as an illustrative example to present strategies for the investigation of conformational dynamics of multisubunit complexes. We provide a brief introduction into single-molecule FRET and confocal microscopy, with a focus on practical considerations in sample preparation and data analysis. Different strategies in the preparation of donor-acceptor-labeled molecules suitable for single-molecule FRET experiments are outlined. The insight into the mechanism of DNA supercoiling by gyrase gained from single-molecule FRET experiment is summarized. The general strategies described here can also be applied to investigate conformational changes and their link to biological function of other multisubunit molecular machines.
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Affiliation(s)
- S Hartmann
- Institute for Physical Chemistry, University of Muenster, Muenster, Germany
| | - D Weidlich
- Institute for Physical Chemistry, University of Muenster, Muenster, Germany
| | - D Klostermeier
- Institute for Physical Chemistry, University of Muenster, Muenster, Germany.
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27
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Raper AT, Gadkari VV, Maxwell BA, Suo Z. Single-Molecule Investigation of Response to Oxidative DNA Damage by a Y-Family DNA Polymerase. Biochemistry 2016; 55:2187-96. [PMID: 27002236 DOI: 10.1021/acs.biochem.6b00166] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Y-family DNA polymerases are known to bypass DNA lesions in vitro and in vivo and rescue stalled DNA replication machinery. Dpo4, a well-characterized model Y-family DNA polymerase, is known to catalyze translesion synthesis across a variety of DNA lesions including 8-oxo-7,8-dihydro-2'-deoxyguanine (8-oxo-dG). Our previous X-ray crystallographic, stopped-flow Förster resonance energy transfer (FRET), and computational simulation studies have revealed that Dpo4 samples a variety of global conformations as it recognizes and binds DNA. Here we employed single-molecule FRET (smFRET) techniques to investigate the kinetics and conformational dynamics of Dpo4 when it encountered 8-oxo-dG, a major oxidative lesion with high mutagenic potential. Our smFRET data indicated that Dpo4 bound the DNA substrate in multiple conformations, as suggested by three observed FRET states. An incoming correct or incorrect nucleotide affected the distribution and stability of these states with the correct nucleotide completely shifting the equilibrium toward a catalytically competent complex. Furthermore, the presence of the 8-oxo-dG lesion in the DNA stabilized both the binary and ternary complexes of Dpo4. Thus, our smFRET analysis provided a basis for the enhanced efficiency which Dpo4 is known to exhibit when replicating across from 8-oxo-dG.
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Affiliation(s)
- Austin T Raper
- Department of Chemistry and Biochemistry, †Ohio State Biochemistry Program and ‡Ohio State Biophysics Program, The Ohio State University , Columbus, Ohio 43210, United States
| | - Varun V Gadkari
- Department of Chemistry and Biochemistry, †Ohio State Biochemistry Program and ‡Ohio State Biophysics Program, The Ohio State University , Columbus, Ohio 43210, United States
| | - Brian A Maxwell
- Department of Chemistry and Biochemistry, †Ohio State Biochemistry Program and ‡Ohio State Biophysics Program, The Ohio State University , Columbus, Ohio 43210, United States
| | - Zucai Suo
- Department of Chemistry and Biochemistry, †Ohio State Biochemistry Program and ‡Ohio State Biophysics Program, The Ohio State University , Columbus, Ohio 43210, United States
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28
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Single-molecule view of basal activity and activation mechanisms of the G protein-coupled receptor β2AR. Proc Natl Acad Sci U S A 2015; 112:14254-9. [PMID: 26578769 DOI: 10.1073/pnas.1519626112] [Citation(s) in RCA: 82] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Binding of extracellular ligands to G protein-coupled receptors (GPCRs) initiates transmembrane signaling by inducing conformational changes on the cytoplasmic receptor surface. Knowledge of this process provides a platform for the development of GPCR-targeting drugs. Here, using a site-specific Cy3 fluorescence probe in the human β2-adrenergic receptor (β2AR), we observed that individual receptor molecules in the native-like environment of phospholipid nanodiscs undergo spontaneous transitions between two distinct conformational states. These states are assigned to inactive and active-like receptor conformations. Individual receptor molecules in the apo form repeatedly sample both conformations, with a bias toward the inactive conformation. Experiments in the presence of drug ligands show that binding of the full agonist formoterol shifts the conformational distribution in favor of the active-like conformation, whereas binding of the inverse agonist ICI-118,551 favors the inactive conformation. Analysis of single-molecule dwell-time distributions for each state reveals that formoterol increases the frequency of activation transitions, while also reducing the frequency of deactivation events. In contrast, the inverse agonist increases the frequency of deactivation transitions. Our observations account for the high level of basal activity of this receptor and provide insights that help to rationalize, on the molecular level, the widely documented variability of the pharmacological efficacies among GPCR-targeting drugs.
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29
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Pugliese KM, Gul OT, Choi Y, Olsen TJ, Sims PC, Collins PG, Weiss GA. Processive Incorporation of Deoxynucleoside Triphosphate Analogs by Single-Molecule DNA Polymerase I (Klenow Fragment) Nanocircuits. J Am Chem Soc 2015; 137:9587-94. [PMID: 26147714 DOI: 10.1021/jacs.5b02074] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
DNA polymerases exhibit a surprising tolerance for analogs of deoxyribonucleoside triphosphates (dNTPs), despite the enzymes' highly evolved mechanisms for the specific recognition and discrimination of native dNTPs. Here, individual DNA polymerase I Klenow fragment (KF) molecules were tethered to a single-walled carbon nanotube field-effect transistor (SWCNT-FET) to investigate accommodation of dNTP analogs with single-molecule resolution. Each base incorporation accompanied a change in current with its duration defined by τclosed. Under Vmax conditions, the average time of τclosed was similar for all analog and native dNTPs (0.2 to 0.4 ms), indicating no kinetic impact on this step due to analog structure. Accordingly, the average rates of dNTP analog incorporation were largely determined by durations with no change in current defined by τopen, which includes molecular recognition of the incoming dNTP. All α-thio-dNTPs were incorporated more slowly, at 40 to 65% of the rate for the corresponding native dNTPs. During polymerization with 6-Cl-2APTP, 2-thio-dTTP, or 2-thio-dCTP, the nanocircuit uncovered an alternative conformation represented by positive current excursions that does not occur with native dNTPs. A model consistent with these results invokes rotations by the enzyme's O-helix; this motion can test the stability of nascent base pairs using nonhydrophilic interactions and is allosterically coupled to charged residues near the site of SWCNT attachment. This model with two opposing O-helix motions differs from the previous report in which all current excursions were solely attributed to global enzyme closure and covalent-bond formation. The results suggest the enzyme applies a dynamic stability-checking mechanism for each nascent base pair.
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Affiliation(s)
- Kaitlin M Pugliese
- Departments of †Chemistry, §Physics and Astronomy, and ⊥Molecular Biology and Biochemistry, University of California, Irvine, California 92697, United States
| | - O Tolga Gul
- Departments of †Chemistry, §Physics and Astronomy, and ⊥Molecular Biology and Biochemistry, University of California, Irvine, California 92697, United States
| | - Yongki Choi
- Departments of †Chemistry, §Physics and Astronomy, and ⊥Molecular Biology and Biochemistry, University of California, Irvine, California 92697, United States
| | - Tivoli J Olsen
- Departments of †Chemistry, §Physics and Astronomy, and ⊥Molecular Biology and Biochemistry, University of California, Irvine, California 92697, United States
| | - Patrick C Sims
- Departments of †Chemistry, §Physics and Astronomy, and ⊥Molecular Biology and Biochemistry, University of California, Irvine, California 92697, United States
| | - Philip G Collins
- Departments of †Chemistry, §Physics and Astronomy, and ⊥Molecular Biology and Biochemistry, University of California, Irvine, California 92697, United States
| | - Gregory A Weiss
- Departments of †Chemistry, §Physics and Astronomy, and ⊥Molecular Biology and Biochemistry, University of California, Irvine, California 92697, United States
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30
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Evans GW, Hohlbein J, Craggs T, Aigrain L, Kapanidis AN. Real-time single-molecule studies of the motions of DNA polymerase fingers illuminate DNA synthesis mechanisms. Nucleic Acids Res 2015; 43:5998-6008. [PMID: 26013816 PMCID: PMC4499156 DOI: 10.1093/nar/gkv547] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2015] [Accepted: 05/13/2015] [Indexed: 12/30/2022] Open
Abstract
DNA polymerases maintain genomic integrity by copying DNA with high fidelity. A conformational change important for fidelity is the motion of the polymerase fingers subdomain from an open to a closed conformation upon binding of a complementary nucleotide. We previously employed intra-protein single-molecule FRET on diffusing molecules to observe fingers conformations in polymerase-DNA complexes. Here, we used the same FRET ruler on surface-immobilized complexes to observe fingers-opening and closing of individual polymerase molecules in real time. Our results revealed the presence of intrinsic dynamics in the binary complex, characterized by slow fingers-closing and fast fingers-opening. When binary complexes were incubated with increasing concentrations of complementary nucleotide, the fingers-closing rate increased, strongly supporting an induced-fit model for nucleotide recognition. Meanwhile, the opening rate in ternary complexes with complementary nucleotide was 6 s(-1), much slower than either fingers closing or the rate-limiting step in the forward direction; this rate balance ensures that, after nucleotide binding and fingers-closing, nucleotide incorporation is overwhelmingly likely to occur. Our results for ternary complexes with a non-complementary dNTP confirmed the presence of a state corresponding to partially closed fingers and suggested a radically different rate balance regarding fingers transitions, which allows polymerase to achieve high fidelity.
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Affiliation(s)
- Geraint W Evans
- Department of Physics and Biological Physics Research Group, Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom
| | - Johannes Hohlbein
- Department of Physics and Biological Physics Research Group, Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom
| | - Timothy Craggs
- Department of Physics and Biological Physics Research Group, Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom
| | - Louise Aigrain
- Department of Physics and Biological Physics Research Group, Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom
| | - Achillefs N Kapanidis
- Department of Physics and Biological Physics Research Group, Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom
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31
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Morin JA, Cao FJ, Lázaro JM, Arias-Gonzalez JR, Valpuesta JM, Carrascosa JL, Salas M, Ibarra B. Mechano-chemical kinetics of DNA replication: identification of the translocation step of a replicative DNA polymerase. Nucleic Acids Res 2015; 43:3643-52. [PMID: 25800740 PMCID: PMC4402526 DOI: 10.1093/nar/gkv204] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2014] [Revised: 02/14/2015] [Accepted: 02/27/2015] [Indexed: 11/25/2022] Open
Abstract
During DNA replication replicative polymerases move in discrete mechanical steps along the DNA template. To address how the chemical cycle is coupled to mechanical motion of the enzyme, here we use optical tweezers to study the translocation mechanism of individual bacteriophage Phi29 DNA polymerases during processive DNA replication. We determine the main kinetic parameters of the nucleotide incorporation cycle and their dependence on external load and nucleotide (dNTP) concentration. The data is inconsistent with power stroke models for translocation, instead supports a loose-coupling mechanism between chemical catalysis and mechanical translocation during DNA replication. According to this mechanism the DNA polymerase works by alternating between a dNTP/PPi-free state, which diffuses thermally between pre- and post-translocated states, and a dNTP/PPi-bound state where dNTP binding stabilizes the post-translocated state. We show how this thermal ratchet mechanism is used by the polymerase to generate work against large opposing loads (∼50 pN).
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Affiliation(s)
- José A Morin
- Instituto Madrileño de Estudios Avanzados en Nanociencia, IMDEA Nanociencia, 28049 Madrid, Spain
| | - Francisco J Cao
- Departamento Física Atómica, Molecular y Nuclear, Universidad Complutense, 28040 Madrid, Spain
| | - José M Lázaro
- Centro de Biología Molecular 'Severo Ochoa' (CSIC-UAM), Universidad Autónoma, Cantoblanco, 28049 Madrid, Spain
| | - J Ricardo Arias-Gonzalez
- Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA Nanociencia) & CNB-CSIC-IMDEA Nanociencia Associated Unit 'Unidad de Nanobiotecnología', 28049 Madrid, Spain
| | - José M Valpuesta
- Centro Nacional de Biotecnología (CNB-CSIC), 28049 Madrid, Spain
| | - José L Carrascosa
- Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA Nanociencia) & CNB-CSIC-IMDEA Nanociencia Associated Unit 'Unidad de Nanobiotecnología', 28049 Madrid, Spain Centro Nacional de Biotecnología (CNB-CSIC), 28049 Madrid, Spain
| | - Margarita Salas
- Centro de Biología Molecular 'Severo Ochoa' (CSIC-UAM), Universidad Autónoma, Cantoblanco, 28049 Madrid, Spain
| | - Borja Ibarra
- Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA Nanociencia) & CNB-CSIC-IMDEA Nanociencia Associated Unit 'Unidad de Nanobiotecnología', 28049 Madrid, Spain
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32
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Vashishtha AK, Kuchta RD. Polymerase and exonuclease activities in herpes simplex virus type 1 DNA polymerase are not highly coordinated. Biochemistry 2015; 54:240-9. [PMID: 25517265 PMCID: PMC4303300 DOI: 10.1021/bi500840v] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
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The
herpes polymerase–processivity factor complex consists
of the catalytic UL30 subunit containing both polymerase and proofreading
exonuclease activities and the UL42 subunit that acts as a processivity
factor. Curiously, the highly active exonuclease has minimal impact
on the accumulation of mismatches generated by the polymerase activity.
We utilized a series of oligonucleotides of defined sequence to define
the interactions between the polymerase and exonuclease active sites.
Exonuclease activity requires unwinding of two nucleotides of the
duplex primer–template. Surprisingly, even though the exonuclease
rate is much higher than the rate of DNA dissociation, the exonuclease
degrades both single- and double-stranded DNA in a nonprocessive manner.
Efficient proofreading of incorrect nucleotides incorporated by the
polymerase would seem to require efficient translocation of DNA between
the exonuclease and polymerase active sites. However, we found that translocation of
DNA from the exonuclease to polymerase active site is remarkably inefficient.
Consistent with inefficient translocation, the DNA binding sites for
the exonuclease and polymerase active sites appear to be largely independent,
such that the two activities appear noncoordinated. Finally, the presence
or absence of UL42 did not impact the coordination of the polymerase
and exonuclease activities. In addition to providing fundamental insights
into how the polymerase and exonuclease function together, these activities
provide a rationale for understanding why the exonuclease minimally
impacts accumulation of mismatches by the purified polymerase and
raise the question of how these two activities function together in
vivo.
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Affiliation(s)
- Ashwani Kumar Vashishtha
- Department of Chemistry and Biochemistry, University of Colorado , Boulder, Colorado 80309-0215, United States
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33
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Lieberman KR, Dahl JM, Wang H. Kinetic mechanism at the branchpoint between the DNA synthesis and editing pathways in individual DNA polymerase complexes. J Am Chem Soc 2014; 136:7117-31. [PMID: 24761828 PMCID: PMC4046759 DOI: 10.1021/ja5026408] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Exonucleolytic editing of incorrectly incorporated nucleotides by replicative DNA polymerases (DNAPs) plays an essential role in the fidelity of DNA replication. Editing requires that the primer strand of the DNA substrate be transferred between the DNAP polymerase and exonuclease sites, separated by a distance that is typically on the order of ~30 Å. Dynamic transitions between functional states can be quantified with single-nucleotide spatial precision and submillisecond temporal resolution from ionic current time traces recorded when individual DNAP complexes are held atop a nanoscale pore in an electric field. In this study, we have exploited this capability to determine the kinetic relationship between the translocation step and primer strand transfer between the polymerase and exonuclease sites in complexes formed between the replicative DNAP from bacteriophage Φ29 and DNA. We demonstrate that the pathway for primer strand transfer from the polymerase to exonuclease site initiates prior to the translocation step, while complexes are in the pre-translocation state. We developed a mathematical method to determine simultaneously the forward and reverse translocation rates and the rates of primer strand transfer in both directions between the polymerase and the exonuclease sites, and we have applied it to determine these rates for Φ29 DNAP complexes formed with a DNA substrate bearing a fully complementary primer-template duplex. This work provides a framework that will be extended to determine the kinetic mechanisms by which incorporation of noncomplementary nucleotides promotes primer strand transfer from the polymerase site to the exonuclease site.
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Affiliation(s)
- Kate R Lieberman
- Department of Biomolecular Engineering, ‡Department of Applied Mathematics and Statistics, Baskin School of Engineering, University of California , Santa Cruz, California 95064, United States
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34
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Maxwell BA, Suo Z. Recent insight into the kinetic mechanisms and conformational dynamics of Y-Family DNA polymerases. Biochemistry 2014; 53:2804-14. [PMID: 24716482 PMCID: PMC4018064 DOI: 10.1021/bi5000405] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
![]()
The
kinetic mechanisms by which DNA polymerases catalyze DNA replication
and repair have long been areas of active research. Recently discovered
Y-family DNA polymerases catalyze the bypass of damaged DNA bases
that would otherwise block replicative DNA polymerases and stall replication
forks. Unlike DNA polymerases from the five other families, the Y-family
DNA polymerases have flexible, solvent-accessible active sites that
are able to tolerate various types of damaged template bases and allow
for efficient lesion bypass. Their promiscuous active sites, however,
also lead to fidelities that are much lower than those observed for
other DNA polymerases and give rise to interesting mechanistic properties.
Additionally, the Y-family DNA polymerases have several other unique
structural features and undergo a set of conformational changes during
substrate binding and catalysis different from those observed for
replicative DNA polymerases. In recent years, pre-steady-state kinetic
methods have been extensively employed to reveal a wealth of information
about the catalytic properties of these fascinating noncanonical DNA
polymerases. Here, we review many of the recent findings on the kinetic
mechanisms of DNA polymerization with undamaged and damaged DNA substrates
by the Y-family DNA polymerases, and the conformational dynamics employed
by these error-prone enzymes during catalysis.
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Affiliation(s)
- Brian A Maxwell
- Ohio State Biophysics Program and ‡Department of Chemistry and Biochemistry, The Ohio State University , Columbus, Ohio 43210, United States
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35
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Farooq S, Fijen C, Hohlbein J. Studying DNA-protein interactions with single-molecule Förster resonance energy transfer. PROTOPLASMA 2014; 251:317-32. [PMID: 24374460 DOI: 10.1007/s00709-013-0596-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/06/2013] [Accepted: 12/09/2013] [Indexed: 05/21/2023]
Abstract
Single-molecule Förster resonance energy transfer (smFRET) has emerged as a powerful tool for elucidating biological structure and mechanisms on the molecular level. Here, we focus on applications of smFRET to study interactions between DNA and enzymes such as DNA and RNA polymerases. SmFRET, used as a nanoscopic ruler, allows for the detection and precise characterisation of dynamic and rarely occurring events, which are otherwise averaged out in ensemble-based experiments. In this review, we will highlight some recent developments that provide new means of studying complex biological systems either by combining smFRET with force-based techniques or by using data obtained from smFRET experiments as constrains for computer-aided modelling.
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Affiliation(s)
- Shazia Farooq
- Laboratory of Biophysics, Wageningen UR, Wageningen, The Netherlands
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