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Islam F, Mishra PP. Molecular Insight into the Structural Dynamics of Holliday Junctions Modulated by Integration Host Factor. J Phys Chem B 2024; 128:5642-5657. [PMID: 38812070 DOI: 10.1021/acs.jpcb.4c02997] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/31/2024]
Abstract
The integration host factor (IHF) in Escherichia coli is a nucleoid-associated protein with multifaceted roles that encompass DNA packaging, viral DNA integration, and recombination. IHF binds to double-stranded DNA featuring a 13-base pair (bp) consensus sequence with high affinity, causing a substantial bend of approximately 160° upon binding. Although wild-type IHF (WtIHF) is principally involved in DNA bending to facilitate foreign DNA integration into the host genome, its engineered counterpart, single-chain IHF (ScIHF), was specifically designed for genetic engineering and biotechnological applications. Our study delves into the interactions of both IHF variants with Holliday junctions (HJs), pivotal intermediates in DNA repair, and homologous recombination. HJs are dynamic structures capable of adopting open or stacked conformations, with the open conformation facilitating processes such as branch migration and strand exchange. Using microscale thermophoresis, we quantitatively assessed the binding of IHF to four-way DNA junctions that harbor specific binding sequences H' and H1. Our findings demonstrate that both IHF variants exhibit a strong affinity for HJs, signifying a structure-based recognition mechanism. Circular dichroism (CD) experiments unveiled the impact of the protein on the junction's conformation. Furthermore, single-molecule Förster resonance energy transfer (smFRET) confirmed the influence of IHF on the junction's dynamicity. Intriguingly, our results revealed that WtIHF and ScIHF binding shifts the population toward the open conformation of the junction and stabilizes it in that state. In summary, our findings underscore the robust affinity of the IHF for HJs and its capacity to stabilize the open conformation of these junctions.
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Affiliation(s)
- Farhana Islam
- Single Molecule Biophysics Lab, Chemical Sciences Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700064, India
- Homi Bhabha National Institute, Mumbai 400094, India
| | - Padmaja Prasad Mishra
- Single Molecule Biophysics Lab, Chemical Sciences Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700064, India
- Homi Bhabha National Institute, Mumbai 400094, India
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2
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Safar M, Saurabh A, Sarkar B, Fazel M, Ishii K, Tahara T, Sgouralis I, Pressé S. Single-photon smFRET. III. Application to pulsed illumination. BIOPHYSICAL REPORTS 2022; 2:100088. [PMID: 36530182 PMCID: PMC9747580 DOI: 10.1016/j.bpr.2022.100088] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/21/2022] [Accepted: 11/21/2022] [Indexed: 06/17/2023]
Abstract
Förster resonance energy transfer (FRET) using pulsed illumination has been pivotal in leveraging lifetime information in FRET analysis. However, there remain major challenges in quantitative single-photon, single-molecule FRET (smFRET) data analysis under pulsed illumination including 1) simultaneously deducing kinetics and number of system states; 2) providing uncertainties over estimates, particularly uncertainty over the number of system states; and 3) taking into account detector noise sources such as cross talk and the instrument response function contributing to uncertainty; in addition to 4) other experimental noise sources such as background. Here, we implement the Bayesian nonparametric framework described in the first companion article that addresses all aforementioned issues in smFRET data analysis specialized for the case of pulsed illumination. Furthermore, we apply our method to both synthetic as well as experimental data acquired using Holliday junctions.
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Affiliation(s)
- Matthew Safar
- Center for Biological Physics, Arizona State University, Tempe, Arizona
- Department of Mathematics and Statistical Science, Arizona State University, Tempe, Arizona
| | - Ayush Saurabh
- Center for Biological Physics, Arizona State University, Tempe, Arizona
- Department of Physics, Arizona State University, Tempe, Arizona
| | - Bidyut Sarkar
- Molecular Spectroscopy Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama, Japan
- Ultrafast Spectroscopy Research Team, RIKEN Center for Advanced Photonics (RAP), 2-1 Hirosawa, Wako, Saitama, Japan
| | - Mohamadreza Fazel
- Center for Biological Physics, Arizona State University, Tempe, Arizona
- Department of Physics, Arizona State University, Tempe, Arizona
| | - Kunihiko Ishii
- Molecular Spectroscopy Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama, Japan
- Ultrafast Spectroscopy Research Team, RIKEN Center for Advanced Photonics (RAP), 2-1 Hirosawa, Wako, Saitama, Japan
| | - Tahei Tahara
- Molecular Spectroscopy Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama, Japan
- Ultrafast Spectroscopy Research Team, RIKEN Center for Advanced Photonics (RAP), 2-1 Hirosawa, Wako, Saitama, Japan
| | - Ioannis Sgouralis
- Department of Mathematics, University of Tennessee Knoxville, Knoxville, Tennessee
| | - Steve Pressé
- Center for Biological Physics, Arizona State University, Tempe, Arizona
- Department of Physics, Arizona State University, Tempe, Arizona
- School of Molecular Sciences, Arizona State University, Phoenix, Arizona
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3
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Mahmoud R, Dhakal S. Single-Molecule Analysis of DNA Branch Migration under Biomimetic Environments. J Phys Chem B 2022; 126:7252-7261. [DOI: 10.1021/acs.jpcb.2c03153] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Roaa Mahmoud
- Department of Chemistry, Virginia Commonwealth University, 1001 West Main Street, Richmond, Virginia 23284, United States
| | - Soma Dhakal
- Department of Chemistry, Virginia Commonwealth University, 1001 West Main Street, Richmond, Virginia 23284, United States
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4
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Bianco PR. OB-fold Families of Genome Guardians: A Universal Theme Constructed From the Small β-barrel Building Block. Front Mol Biosci 2022; 9:784451. [PMID: 35223988 PMCID: PMC8881015 DOI: 10.3389/fmolb.2022.784451] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Accepted: 01/19/2022] [Indexed: 11/13/2022] Open
Abstract
The maintenance of genome stability requires the coordinated actions of multiple proteins and protein complexes, that are collectively known as genome guardians. Within this broadly defined family is a subset of proteins that contain oligonucleotide/oligosaccharide-binding folds (OB-fold). While OB-folds are widely associated with binding to single-stranded DNA this view is no longer an accurate depiction of how these domains are utilized. Instead, the core of the OB-fold is modified and adapted to facilitate binding to a variety of DNA substrates (both single- and double-stranded), phospholipids, and proteins, as well as enabling catalytic function to a multi-subunit complex. The flexibility accompanied by distinctive oligomerization states and quaternary structures enables OB-fold genome guardians to maintain the integrity of the genome via a myriad of complex and dynamic, protein-protein; protein-DNA, and protein-lipid interactions in both prokaryotes and eukaryotes.
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Affiliation(s)
- Piero R. Bianco
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Nebraska Medical Center, Omaha, NE, United States
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5
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Gándara C, Torres R, Carrasco B, Ayora S, Alonso JC. DisA Restrains the Processing and Cleavage of Reversed Replication Forks by the RuvAB-RecU Resolvasome. Int J Mol Sci 2021; 22:11323. [PMID: 34768753 PMCID: PMC8583203 DOI: 10.3390/ijms222111323] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Revised: 10/04/2021] [Accepted: 10/16/2021] [Indexed: 11/17/2022] Open
Abstract
DNA lesions that impede fork progression cause replisome stalling and threaten genome stability. Bacillus subtilis RecA, at a lesion-containing gap, interacts with and facilitates DisA pausing at these branched intermediates. Paused DisA suppresses its synthesis of the essential c-di-AMP messenger. The RuvAB-RecU resolvasome branch migrates and resolves formed Holliday junctions (HJ). We show that DisA prevents DNA degradation. DisA, which interacts with RuvB, binds branched structures, and reduces the RuvAB DNA-dependent ATPase activity. DisA pre-bound to HJ DNA limits RuvAB and RecU activities, but such inhibition does not occur if the RuvAB- or RecU-HJ DNA complexes are pre-formed. RuvAB or RecU pre-bound to HJ DNA strongly inhibits DisA-mediated synthesis of c-di-AMP, and indirectly blocks cell proliferation. We propose that DisA limits RuvAB-mediated fork remodeling and RecU-mediated HJ cleavage to provide time for damage removal and replication restart in order to preserve genome integrity.
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Affiliation(s)
| | | | | | - Silvia Ayora
- Department of Microbial Biotechnology, Centro Nacional de Biotecnología, CNB-CSIC, 3 Darwin St, 28049 Madrid, Spain; (C.G.); (R.T.); (B.C.)
| | - Juan C. Alonso
- Department of Microbial Biotechnology, Centro Nacional de Biotecnología, CNB-CSIC, 3 Darwin St, 28049 Madrid, Spain; (C.G.); (R.T.); (B.C.)
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6
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Bandyopadhyay D, Mishra PP. Decoding the Structural Dynamics and Conformational Alternations of DNA Secondary Structures by Single-Molecule FRET Microspectroscopy. Front Mol Biosci 2021; 8:725541. [PMID: 34540899 PMCID: PMC8446445 DOI: 10.3389/fmolb.2021.725541] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2021] [Accepted: 07/30/2021] [Indexed: 12/02/2022] Open
Abstract
In addition to the canonical double helix form, DNA is known to be extrapolated into several other secondary structural patterns involving themselves in inter- and intramolecular type hydrogen bonding. The secondary structures of nucleic acids go through several stages of multiple, complex, and interconvertible heterogeneous conformations. The journey of DNA through these conformers has significant importance and has been monitored thoroughly to establish qualitative and quantitative information about the transition between the unfolded, folded, misfolded, and partially folded states. During this structural interconversion, there always exist specific populations of intermediates, which are short-lived or sometimes even do not accumulate within a heterogeneous population and are challenging to characterize using conventional ensemble techniques. The single-molecule FRET(sm-FRET) microspectroscopic method has the advantages to overcome these limitations and monitors biological phenomena transpiring at a measurable high rate and balanced stochastically over time. Thus, tracing the time trajectory of a particular molecule enables direct measurement of the rate constant of each transition step, including the intermediates that are hidden in the ensemble level due to their low concentrations. This review is focused on the advantages of the employment of single-molecule Forster's resonance energy transfer (sm-FRET), which is worthwhile to access the dynamic architecture and structural transition of various secondary structures that DNA adopts, without letting the donor of one molecule to cross-talk with the acceptor of any other. We have emphasized the studies performed to explore the states of folding and unfolding of several nucleic acid secondary structures, for example, the DNA hairpin, Holliday junction, G-quadruplex, and i-motif.
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Affiliation(s)
- Debolina Bandyopadhyay
- Single-Molecule Biophysics Lab, Chemical Sciences Division, Saha Institute of Nuclear Physics, Kolkata, India
- HBNI, Mumbai, India
| | - Padmaja P. Mishra
- Single-Molecule Biophysics Lab, Chemical Sciences Division, Saha Institute of Nuclear Physics, Kolkata, India
- HBNI, Mumbai, India
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7
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Bianco PR, Lu Y. Single-molecule insight into stalled replication fork rescue in Escherichia coli. Nucleic Acids Res 2021; 49:4220-4238. [PMID: 33744948 PMCID: PMC8096234 DOI: 10.1093/nar/gkab142] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2020] [Revised: 02/15/2021] [Accepted: 02/22/2021] [Indexed: 01/05/2023] Open
Abstract
DNA replication forks stall at least once per cell cycle in Escherichia coli. DNA replication must be restarted if the cell is to survive. Restart is a multi-step process requiring the sequential action of several proteins whose actions are dictated by the nature of the impediment to fork progression. When fork progress is impeded, the sequential actions of SSB, RecG and the RuvABC complex are required for rescue. In contrast, when a template discontinuity results in the forked DNA breaking apart, the actions of the RecBCD pathway enzymes are required to resurrect the fork so that replication can resume. In this review, we focus primarily on the significant insight gained from single-molecule studies of individual proteins, protein complexes, and also, partially reconstituted regression and RecBCD pathways. This insight is related to the bulk-phase biochemical data to provide a comprehensive review of each protein or protein complex as it relates to stalled DNA replication fork rescue.
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Affiliation(s)
- Piero R Bianco
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Nebraska Medical Center, Omaha, NE 68198-6025, USA
| | - Yue Lu
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Nebraska Medical Center, Omaha, NE 68198-6025, USA
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8
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Ramakrishnan S, Subramaniam S, Kielar C, Grundmeier G, Stewart AF, Keller A. Protein-Assisted Room-Temperature Assembly of Rigid, Immobile Holliday Junctions and Hierarchical DNA Nanostructures. Molecules 2020; 25:molecules25215099. [PMID: 33153073 PMCID: PMC7663122 DOI: 10.3390/molecules25215099] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2020] [Revised: 10/28/2020] [Accepted: 10/30/2020] [Indexed: 12/30/2022] Open
Abstract
Immobile Holliday junctions represent not only the most fundamental building block of structural DNA nanotechnology but are also of tremendous importance for the in vitro investigation of genetic recombination and epigenetics. Here, we present a detailed study on the room-temperature assembly of immobile Holliday junctions with the help of the single-strand annealing protein Redβ. Individual DNA single strands are initially coated with protein monomers and subsequently hybridized to form a rigid blunt-ended four-arm junction. We investigate the efficiency of this approach for different DNA/protein ratios, as well as for different DNA sequence lengths. Furthermore, we also evaluate the potential of Redβ to anneal sticky-end modified Holliday junctions into hierarchical assemblies. We demonstrate the Redβ-mediated annealing of Holliday junction dimers, multimers, and extended networks several microns in size. While these hybrid DNA–protein nanostructures may find applications in the crystallization of DNA–protein complexes, our work shows the great potential of Redβ to aid in the synthesis of functional DNA nanostructures under mild reaction conditions.
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Affiliation(s)
- Saminathan Ramakrishnan
- Technical and Macromolecular Chemistry, Paderborn University, Warburger Str. 100, 33098 Paderborn, Germany; (S.R.); (C.K.); (G.G.)
- Structural Biophysics Laboratory, Center for Cancer Research, National Cancer Institute, Frederick, MD 21702, USA
| | - Sivaraman Subramaniam
- Biotechnology Center, Department of Genomics, Technische Universität Dresden, Tatzberg 47-51, 01307 Dresden, Germany; (S.S.); (A.F.S.)
- Cluster of Excellence Physics of Life, Technische Universität Dresden, 01062 Dresden, Germany
| | - Charlotte Kielar
- Technical and Macromolecular Chemistry, Paderborn University, Warburger Str. 100, 33098 Paderborn, Germany; (S.R.); (C.K.); (G.G.)
| | - Guido Grundmeier
- Technical and Macromolecular Chemistry, Paderborn University, Warburger Str. 100, 33098 Paderborn, Germany; (S.R.); (C.K.); (G.G.)
| | - A. Francis Stewart
- Biotechnology Center, Department of Genomics, Technische Universität Dresden, Tatzberg 47-51, 01307 Dresden, Germany; (S.S.); (A.F.S.)
- Cluster of Excellence Physics of Life, Technische Universität Dresden, 01062 Dresden, Germany
| | - Adrian Keller
- Technical and Macromolecular Chemistry, Paderborn University, Warburger Str. 100, 33098 Paderborn, Germany; (S.R.); (C.K.); (G.G.)
- Correspondence:
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9
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Single-molecule fluorescence-based analysis of protein conformation, interaction, and oligomerization in cellular systems. Biophys Rev 2017; 10:317-326. [PMID: 29243093 PMCID: PMC5899725 DOI: 10.1007/s12551-017-0366-3] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2017] [Accepted: 11/19/2017] [Indexed: 12/23/2022] Open
Abstract
Single-molecule imaging (SMI) of proteins in operation has a history of intensive investigations over 20 years and is now widely used in various fields of biology and biotechnology. We review the recent advances in SMI of fluorescently-tagged proteins in structural biology, focusing on technical applicability of SMI to the measurements in living cells. Basic technologies and recent applications of SMI in structural biology are introduced. Distinct from other methods in structural biology, SMI directly observes single molecules and single-molecule events one-by-one, thus, explicitly analyzing the distribution of protein structures and the history of protein dynamics. It also allows one to detect single events of protein interaction. One unique feature of SMI is that it is applicable in complicated and heterogeneous environments, including living cells. The numbers, location, movements, interaction, oligomerization, and conformation of single-protein molecules have been determined using SMI in cellular systems.
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10
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Srinivas N, Parkin J, Seelig G, Winfree E, Soloveichik D. Enzyme-free nucleic acid dynamical systems. Science 2017; 358:358/6369/eaal2052. [DOI: 10.1126/science.aal2052] [Citation(s) in RCA: 189] [Impact Index Per Article: 27.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2016] [Accepted: 10/25/2017] [Indexed: 01/10/2023]
Abstract
Chemistries exhibiting complex dynamics—from inorganic oscillators to gene regulatory networks—have been long known but either cannot be reprogrammed at will or rely on the sophisticated enzyme chemistry underlying the central dogma. Can simpler molecular mechanisms, designed from scratch, exhibit the same range of behaviors? Abstract chemical reaction networks have been proposed as a programming language for complex dynamics, along with their systematic implementation using short synthetic DNA molecules. We developed this technology for dynamical systems by identifying critical design principles and codifying them into a compiler automating the design process. Using this approach, we built an oscillator containing only DNA components, establishing that Watson-Crick base-pairing interactions alone suffice for complex chemical dynamics and that autonomous molecular systems can be designed via molecular programming languages.
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11
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Cannon BL, Kellis DL, Patten LK, Davis PH, Lee J, Graugnard E, Yurke B, Knowlton WB. Coherent Exciton Delocalization in a Two-State DNA-Templated Dye Aggregate System. J Phys Chem A 2017; 121:6905-6916. [PMID: 28813152 DOI: 10.1021/acs.jpca.7b04344] [Citation(s) in RCA: 56] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Coherent exciton delocalization in dye aggregate systems gives rise to a variety of intriguing optical phenomena, including J- and H-aggregate behavior and Davydov splitting. Systems that exhibit coherent exciton delocalization at room temperature are of interest for the development of artificial light-harvesting devices, colorimetric detection schemes, and quantum computers. Here, we report on a simple dye system templated by DNA that exhibits tunable optical properties. At low salt and DNA concentrations, a DNA duplex with two internally functionalized Cy5 dyes (i.e., dimer) persists and displays predominantly J-aggregate behavior. Increasing the salt and/or DNA concentrations was found to promote coupling between two of the DNA duplexes via branch migration, thus forming a four-armed junction (i.e., tetramer) with H-aggregate behavior. This H-tetramer aggregate exhibits a surprisingly large Davydov splitting in its absorbance spectrum that produces a visible color change of the solution from cyan to violet and gives clear evidence of coherent exciton delocalization.
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Affiliation(s)
- Brittany L Cannon
- Micron School of Materials Science & Engineering, ‡Department of Chemistry & Biochemistry, and §Department of Electrical & Computer Engineering, Boise State University , Boise, Idaho 83725, United States
| | - Donald L Kellis
- Micron School of Materials Science & Engineering, ‡Department of Chemistry & Biochemistry, and §Department of Electrical & Computer Engineering, Boise State University , Boise, Idaho 83725, United States
| | - Lance K Patten
- Micron School of Materials Science & Engineering, ‡Department of Chemistry & Biochemistry, and §Department of Electrical & Computer Engineering, Boise State University , Boise, Idaho 83725, United States
| | - Paul H Davis
- Micron School of Materials Science & Engineering, ‡Department of Chemistry & Biochemistry, and §Department of Electrical & Computer Engineering, Boise State University , Boise, Idaho 83725, United States
| | - Jeunghoon Lee
- Micron School of Materials Science & Engineering, ‡Department of Chemistry & Biochemistry, and §Department of Electrical & Computer Engineering, Boise State University , Boise, Idaho 83725, United States
| | - Elton Graugnard
- Micron School of Materials Science & Engineering, ‡Department of Chemistry & Biochemistry, and §Department of Electrical & Computer Engineering, Boise State University , Boise, Idaho 83725, United States
| | - Bernard Yurke
- Micron School of Materials Science & Engineering, ‡Department of Chemistry & Biochemistry, and §Department of Electrical & Computer Engineering, Boise State University , Boise, Idaho 83725, United States
| | - William B Knowlton
- Micron School of Materials Science & Engineering, ‡Department of Chemistry & Biochemistry, and §Department of Electrical & Computer Engineering, Boise State University , Boise, Idaho 83725, United States
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12
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Moiseeva ED, Bazhulina NP, Gursky YG, Grokhovsky SL, Surovaya AN, Gursky GV. Targeting Holliday junctions by origin DNA-binding protein of herpes simplex virus type 1. J Biomol Struct Dyn 2016; 35:704-723. [PMID: 26987269 DOI: 10.1080/07391102.2016.1161561] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
In the present paper, the interactions of the origin binding protein (OBP) of herpes simplex virus type 1 (HSV1) with synthetic four-way Holliday junctions (HJs) were studied using electrophoresis mobility shift assay and the FRET method and compared with the interactions of the protein with duplex and single-stranded DNAs. It has been found that OBP exhibits a strong preference for binding to four-way and three-way DNA junctions and possesses much lower affinities to duplex and single-stranded DNAs. The protein forms three types of complexes with HJs. It forms complexes I and II which are reminiscent of the tetramer and octamer complexes with four-way junction of HJ-specific protein RuvA of Escherichia coli. The binding approaches saturation level when two OBP dimers are bound per junction. In the presence of Mg2+ ions (≥2 mM) OBP also interacts with HJ in the stacked arm form (complex III). In the presence of 5 mM ATP and 10 mM Mg2+ ions OBP catalyzes processing of the HJ in which one of the annealed oligonucleotides has a 3'-terminal tail containing 20 unpaired thymine residues. The observed preference of OBP for binding to the four-way DNA junctions provides a basis for suggestion that OBP induces large DNA structural changes upon binding to Box I and Box II sites in OriS. These changes involve the bending and partial melting of the DNA at A+T-rich spacer and also include the formation of HJ containing Box I and Box II inverted repeats and flanking DNA sequences.
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Affiliation(s)
- E D Moiseeva
- a Engelhardt Institute of Molecular Biology , Russian Academy of Sciences , ul. Vavilova 32, 119991 Moscow , Russia
| | - N P Bazhulina
- a Engelhardt Institute of Molecular Biology , Russian Academy of Sciences , ul. Vavilova 32, 119991 Moscow , Russia
| | - Y G Gursky
- b Russian Cardiology Research-and-Production Complex , 3ya Cherepkovskaya ul. 15a, 121552 Moscow , Russia
| | - S L Grokhovsky
- a Engelhardt Institute of Molecular Biology , Russian Academy of Sciences , ul. Vavilova 32, 119991 Moscow , Russia
| | - A N Surovaya
- a Engelhardt Institute of Molecular Biology , Russian Academy of Sciences , ul. Vavilova 32, 119991 Moscow , Russia
| | - G V Gursky
- a Engelhardt Institute of Molecular Biology , Russian Academy of Sciences , ul. Vavilova 32, 119991 Moscow , Russia
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13
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Holliday Junction Thermodynamics and Structure: Coarse-Grained Simulations and Experiments. Sci Rep 2016; 6:22863. [PMID: 26971574 PMCID: PMC4789735 DOI: 10.1038/srep22863] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2015] [Accepted: 02/22/2016] [Indexed: 02/08/2023] Open
Abstract
Holliday junctions play a central role in genetic recombination, DNA repair and other cellular processes. We combine simulations and experiments to evaluate the ability of the 3SPN.2 model, a coarse-grained representation designed to mimic B-DNA, to predict the properties of DNA Holliday junctions. The model reproduces many experimentally determined aspects of junction structure and stability, including the temperature dependence of melting on salt concentration, the bias between open and stacked conformations, the relative populations of conformers at high salt concentration, and the inter-duplex angle (IDA) between arms. We also obtain a close correspondence between the junction structure evaluated by all-atom and coarse-grained simulations. We predict that, for salt concentrations at physiological and higher levels, the populations of the stacked conformers are independent of salt concentration, and directly observe proposed tetrahedral intermediate sub-states implicated in conformational transitions. Our findings demonstrate that the 3SPN.2 model captures junction properties that are inaccessible to all-atom studies, opening the possibility to simulate complex aspects of junction behavior.
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14
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Okamoto K, Sako Y. State transition analysis of spontaneous branch migration of the Holliday junction by photon-based single-molecule fluorescence resonance energy transfer. Biophys Chem 2016; 209:21-7. [DOI: 10.1016/j.bpc.2015.11.004] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2015] [Revised: 11/27/2015] [Accepted: 11/28/2015] [Indexed: 11/17/2022]
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15
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Brème C, Heslot F. Mapping of single-base differences between two DNA strands in a single molecule using holliday junction nanomechanics. PLoS One 2013; 8:e55154. [PMID: 23393565 PMCID: PMC3564857 DOI: 10.1371/journal.pone.0055154] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2012] [Accepted: 12/20/2012] [Indexed: 11/19/2022] Open
Abstract
OBJECTIVE The aim of this work is to demonstrate a novel single-molecule DNA sequence comparison assay that is purely based on DNA mechanics. METHODS A molecular construct that contained the two homologous but non-identical DNA sequences that were to be compared was prepared such that a four-way (Holliday) junction could be formed by the formation of heteroduplexes through the inter-recombination of the strands. Magnetic tweezers were used to manipulate the force and the winding applied to this construct for inducing both the formation and the migration of a Holliday junction. The end-to-end distance of the construct was measured as a function of the winding and was used to monitor the behavior of the Holliday junction in different regions of the intra-molecular recombination. MAIN RESULTS In the appropriate buffer, the magnet rotation induces the migration of the Holliday junction in the regions where there is no sequence difference between the recombining sequences. In contrast, even a single-base difference between the recombining sequences leads to a long-lasting blockage of the migration in the same buffer; this effect was obtained when the junction was positioned near this locus (the site of the single-base difference) and forced toward the formation of heteroduplexes that comprise the locus. The migration blockages were detected through the identification of the formation of plectonemes. The detection of the presence of sequence differences and their respective mappings were obtained from the series of blockages that were detected. SIGNIFICANCE This work presents a novel single-molecule sequence comparison assay that is based on the use of a Holliday junction as an ultra-sensitive nanomechanism; the mismatches act as blocking grains of sand in the Holliday "DNA gearbox". This approach will potentially have future applications in biotechnology.
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Affiliation(s)
- Camille Brème
- Laboratoire Pierre Aigrain, Unité Mixte de Recherche 8551 de l’Ecole Normale Supérieure, Paris, France
- Laboratoire Pierre Aigrain, Université Pierre et Marie Curie - Paris 6, Paris, France
- Laboratoire Pierre Aigrain, Université Paris Diderot - Paris 7, Paris, France
| | - François Heslot
- Laboratoire Pierre Aigrain, Unité Mixte de Recherche 8551 de l’Ecole Normale Supérieure, Paris, France
- Laboratoire Pierre Aigrain, Université Pierre et Marie Curie - Paris 6, Paris, France
- Laboratoire Pierre Aigrain, Université Paris Diderot - Paris 7, Paris, France
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16
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Forth S, Deufel C, Patel SS, Wang MD. Direct measurements of torque during Holliday junction migration. Biophys J 2011; 101:L5-7. [PMID: 21767475 DOI: 10.1016/j.bpj.2011.05.066] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2011] [Revised: 04/25/2011] [Accepted: 05/03/2011] [Indexed: 11/25/2022] Open
Abstract
DNA experiences torsional stress resulting from the activities of motor enzymes and bound proteins. The mechanisms by which this torsional stress is dissipated to maintain DNA structural integrity are not fully known. Here, we show that a Holliday junction can limit torsion by coupling rotation to translocation and torque to force. The torque required to mechanically migrate through individual junctions was found to be an order of magnitude smaller than that required to melt DNA. We also directly show that substantially more torque was required to migrate through even a single-base sequence heterology, which has important implications for the activity of junction-migrating enzymes.
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17
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Vitoc CI, Mukerji I. HU binding to a DNA four-way junction probed by Förster resonance energy transfer. Biochemistry 2011; 50:1432-41. [PMID: 21230005 PMCID: PMC4724199 DOI: 10.1021/bi1007589] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The Escherichia coli protein HU is a non-sequence-specific DNA-binding protein that interacts with DNA primarily through electrostatic interactions. In addition to nonspecific binding to linear DNA, HU has been shown to bind with nanomolar affinity to discontinuous DNA substrates, such as repair and recombination intermediates. This work specifically examines the HU-four-way junction (4WJ) interaction using fluorescence spectroscopic methods. The conformation of the junction in the presence of different counterions was investigated by Förster resonance energy transfer (FRET) measurements, which revealed an ion-type conformational dependence, where Na(+) yields the most stacked conformation followed by K(+) and Mg(2+). HU binding induces a greater degree of stacking in the Na(+)-stabilized and Mg(2+)-stabilized junctions but not the K(+)-stabilized junction, which is attributed to differences in the size of the ionic radii and potential differences in ion binding sites. Interestingly, junction conformation modulates binding affinity, where HU exhibits the lowest affinity for the Mg(2+)-stabilized form (24 μM(-1)), which is the least stacked conformation. Protein binding to a mixed population of open and stacked forms of the junction leads to nearly complete formation of a protein-stabilized stacked-X junction. These results strongly support a model in which HU binds to and stabilizes the stacked-X conformation.
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Affiliation(s)
- Codruta Iulia Vitoc
- Molecular Biology and Biochemistry Department, Molecular Biophysics Program, Wesleyan University, Middletown, Connecticut 06459-0175
| | - Ishita Mukerji
- Molecular Biology and Biochemistry Department, Molecular Biophysics Program, Wesleyan University, Middletown, Connecticut 06459-0175
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18
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Palets D, Lushnikov AY, Karymov MA, Lyubchenko YL. Effect of single-strand break on branch migration and folding dynamics of Holliday junctions. Biophys J 2010; 99:1916-24. [PMID: 20858437 PMCID: PMC2941029 DOI: 10.1016/j.bpj.2010.07.011] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2010] [Revised: 06/29/2010] [Accepted: 07/13/2010] [Indexed: 10/19/2022] Open
Abstract
The Holliday junction (HJ), or four-way junction, is a central intermediate state of DNA for homologous genetic recombination and other genetic processes such as replication and repair. Branch migration is the process by which the exchange of homologous DNA regions occurs, and it can be spontaneous or driven by proteins. Unfolding of the HJ is required for branch migration. Our previous single-molecule fluorescence studies led to a model according to which branch migration is a stepwise process consisting of consecutive migration and folding steps. Folding of the HJ in one of the folded conformations terminates the branch migration phase. At the same time, in the unfolded state HJ rapidly migrates over entire homology region of the HJ in one hop. This process can be affected by irregularities in the DNA double helical structure, so mismatches almost terminate a spontaneous branch migration. Single-stranded breaks or nicks are the most ubiquitous defects in the DNA helix; however, to date, their effect on the HJ branch migration has not been studied. In addition, although nicked HJs are specific substrates for a number of enzymes involved in DNA recombination and repair, the role of this substrate specificity remains unclear. Our main goal in this work was to study the effect of nicks on the efficiency of HJ branch migration and the dynamics of the HJ. To accomplish this goal, we applied two single-molecule methods: atomic force microscopy and fluorescence resonance energy transfer. The atomic force microscopy data show that the nick does not prevent branch migration, but it does decrease the probability that the HJ will pass the DNA lesion. The single-molecule fluorescence resonance energy transfer approaches were instrumental in detailing the effects of nicks. These studies reveal a dramatic change of the HJ dynamics. The nick changes the structure and conformational dynamics of the junctions, leading to conformations with geometries that are different from those for the intact HJ. On the basis of these data, we propose a model of branch migration in which the propensity of the junction to unfold decreases the lifetimes of folded states, thereby increasing the frequency of junction fluctuations between the folded states.
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Affiliation(s)
| | | | | | - Yuri L. Lyubchenko
- Department of Pharmaceutical Sciences, University of Nebraska Medical Center, Omaha, Nebraska
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19
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A polymerase-site-jumping model for strand transfer during DNA synthesis by reverse transcriptase. Virus Res 2009; 144:65-73. [PMID: 19427048 DOI: 10.1016/j.virusres.2009.03.022] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2009] [Revised: 03/27/2009] [Accepted: 03/28/2009] [Indexed: 11/23/2022]
Abstract
During reverse transcription, besides the obligatory strand transfers associated with replication at the ends of the viral genome, multiple strand transfers often occur associated with replication within internal regions. Here, based on previous structural and biochemical studies, a model is proposed for processive DNA synthesis along a single template mediated by reverse transcriptase and, based on this model, the mechanism of inter- or intramolecular strand transfers during minus DNA synthesis is presented. A strand-transfer event involves two steps, with the first one being the annealing of the nascent DNA with acceptor RNA at the upstream position of the reverse transcriptase while the second one being the jumping of the polymerase active site to the acceptor. Using the model, the promotion of strand transfer by pausing and high frequent deletions induced by strand transfers can be well explained. We present analytical studies of the efficiency of single strand-transfer event and of the efficiency of multiple-strand-transfer events, with which the high negative interference can be well explained. The dependence of strand-transfer efficiency on the ratio between polymerase and RNase H rates, the role of the polymerase-dependent and polymerase-independent cleavages in strand transfers and the efficiency of nonhomologous strand transfer are analytically studied. The theoretical results are in agreement with the available experimental data. Moreover, some predicted results of the dependence of negative interference on the ratio of polymerase over RNase H rates are presented.
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20
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Karymov MA, Chinnaraj M, Bogdanov A, Srinivasan AR, Zheng G, Olson WK, Lyubchenko YL. Structure, dynamics, and branch migration of a DNA Holliday junction: a single-molecule fluorescence and modeling study. Biophys J 2008; 95:4372-83. [PMID: 18658216 PMCID: PMC2567953 DOI: 10.1529/biophysj.108.135103] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2008] [Accepted: 07/18/2008] [Indexed: 11/18/2022] Open
Abstract
The Holliday junction (HJ) is a central intermediate of various genetic processes, including homologous and site-specific DNA recombination and DNA replication. Elucidating the structure and dynamics of HJs provides the basis for understanding the molecular mechanisms of these genetic processes. Our previous single-molecule fluorescence studies led to a model according to which branch migration is a stepwise process consisting of consecutive migration and folding steps. These data led us to the conclusion that one hop can be more than 1 basepair (bp); moreover, we hypothesized that continuous runs over the entire sequence homology (5 bp) can occur. Direct measurements of the dependence of the fluorescence resonance energy transfer (FRET) value on the donor-acceptor (D-A) distance are required to justify this model and are the major goal of this article. To accomplish this goal, we performed single-molecule FRET experiments with a set of six immobile HJ molecules with varying numbers of bps between fluorescent dyes placed on opposite arms. The designs were made in such a way that the distances between the donor and acceptor were equal to the distances between the dyes formed upon 1-bp migration hops of a HJ having 10-bp homology. Using these designs, we confirmed our previous hypothesis that the migration of the junction can be measured with bp accuracy. Moreover, the FRET values determined for each acceptor-donor separation corresponded very well to the values for the steps on the FRET time trajectories, suggesting that each step corresponds to the migration of the branch at a defined depth. We used the dependence of the FRET value on the D-A distance to measure directly the size for each step on the FRET time trajectories. These data showed that one hop is not necessarily 1 bp. The junction is able to migrate over several bps, detected as one hop and confirming our model. The D-A distances extracted from the FRET properties of the immobile junctions formed the basis for modeling the HJ structures. The composite data fit a partially opened, side-by-side model with adjacent double-helical arms slightly kinked at the four-way junction and the junction as a whole adopting a global X-shaped form that mimics the coaxially stacked-X structure implicated in previous solution studies.
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Affiliation(s)
- Mikhail A Karymov
- Department of Pharmaceutical Sciences, University of Nebraska Medical Center, 986025 Nebraska Medical Center, Omaha, Nebraska 68198-6025, USA
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21
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Karymov MA, Bogdanov A, Lyubchenko YL. Single molecule fluorescence analysis of branch migration of holliday junctions: effect of DNA sequence. Biophys J 2008; 95:1239-47. [PMID: 18424495 PMCID: PMC2479582 DOI: 10.1529/biophysj.107.127522] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2007] [Accepted: 03/25/2008] [Indexed: 11/18/2022] Open
Abstract
The Holliday junction is a central intermediate in various genetic processes including homologous, site-specific recombination and DNA replication. Recent single molecule FRET experiments led to the model for branch migration as a stepwise stochastic process in which the branch migration hop is terminated by the folding of the junction. In this article, we studied the effect of the sequence on Holliday junction dynamics and branch migration process. We show that a GC pair placed at the border of the homologous region almost prevents the migration into this position. At the same time, insertion of a GC pair into the middle of the AT tract does not show this effect, however when the junction folds at this position, it resides at this position much longer time in comparison to the folding at AT pairs. Two contiguous GC pairs do not block migration as well and generally manifest the same effect as one GC pair--the junction when it folds resides at these positions for a relatively long time. The same elevated residence time was obtained for the design with the homology region that consists of only GC pairs. These data suggest a model for branch migration in which the sequence modulates the overall stochastic process of the junction dynamics and branch migration by the variability of the time that the junction dwells before making a migration hop.
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Affiliation(s)
- Mikhail A Karymov
- Department of Pharmaceutical Sciences, University of Nebraska Medical Center, Nebraska Medical Center, Omaha, Nebraska 68198-6025, USA
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22
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Yeast Rad5 protein required for postreplication repair has a DNA helicase activity specific for replication fork regression. Mol Cell 2008; 28:167-75. [PMID: 17936713 PMCID: PMC2034406 DOI: 10.1016/j.molcel.2007.07.030] [Citation(s) in RCA: 227] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2007] [Revised: 06/22/2007] [Accepted: 07/30/2007] [Indexed: 11/24/2022]
Abstract
Lesions in the template DNA strand block the progression of the replication fork. In the yeast Saccharomyces cerevisiae, replication through DNA lesions is mediated by different Rad6-Rad18-dependent means, which include translesion synthesis and a Rad5-dependent postreplicational repair pathway that repairs the discontinuities that form in the DNA synthesized from damaged templates. Although translesion synthesis is well characterized, little is known about the mechanisms that modulate Rad5-dependent postreplicational repair. Here we show that yeast Rad5 has a DNA helicase activity that is specialized for replication fork regression. On model replication fork structures, Rad5 concertedly unwinds and anneals the nascent and the parental strands without exposing extended single-stranded regions. These observations provide insight into the mechanism of postreplicational repair in which Rad5 action promotes template switching for error-free damage bypass.
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23
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Karymov M, Daniel D, Sankey OF, Lyubchenko YL. Holliday junction dynamics and branch migration: single-molecule analysis. Proc Natl Acad Sci U S A 2005; 102:8186-91. [PMID: 15917329 PMCID: PMC1140338 DOI: 10.1073/pnas.0407210102] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The Holliday junction (HJ) is a central intermediate in various genetic processes including homologous and site-specific recombination and DNA replication. Branch migration allows the exchange between homologous DNA regions, but the detailed mechanism for this key step of DNA recombination is unidentified. Here, we report direct real-time detection of branch migration in individual molecules. Using appropriately designed HJ constructs we were able to follow junction branch migration at the single-molecule level. Branch migration is detected as a stepwise random process with the overall kinetics dependent on Mg2+ concentration. We developed a theoretical approach to analyze the mechanism of HJ branch migration. The data show steps in which the junction flips between conformations favorable to branch migration and conformations unfavorable to it. In the favorable conformation (the extended HJ geometry), the branch can migrate over several base pairs detected, usually as a single large step. Mg2+ cations stabilize folded conformations and stall branch migration for a period considerably longer than the hopping step. The conformational flip and the variable base pair hopping step provide insights into the regulatory mechanism of genetic processes involving HJs.
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Affiliation(s)
- Mikhail Karymov
- School of Life Sciences, and Department of Chemistry and Biochemistry, Arizona State University, Tempe, AZ 85287, USA
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24
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Hays FA, Teegarden A, Jones ZJR, Harms M, Raup D, Watson J, Cavaliere E, Ho PS. How sequence defines structure: a crystallographic map of DNA structure and conformation. Proc Natl Acad Sci U S A 2005; 102:7157-62. [PMID: 15870206 PMCID: PMC1129101 DOI: 10.1073/pnas.0409455102] [Citation(s) in RCA: 111] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The fundamental question of how sequence defines conformation is explicitly answered if the structures of all possible sequences of a macromolecule are determined. We present here a crystallographic screen of all permutations of the inverted repeat DNA sequence d(CCnnnN6N7N8GG), where N6, N7, and N8 are any of the four naturally occurring nucleotides. At this point, 63 of the 64 possible permutations have been crystallized from a defined set of solutions. When combined with previous work, we have assembled a data set of 37 single-crystal structures from 29 of the sequences in this motif, representing three structural classes of DNA (B-DNA, A-DNA, and four-stranded Holliday junctions). This data set includes a unique set of amphimorphic sequence, those that crystallize in two different conformations and serve to bridge the three structural phases. We have thus constructed a map of DNA structures that can be walked through in single nucleotide steps. Finally, the resulting data set allows us to dissect in detail the stabilization of and conformational variations within structural classes and identify significant conformational deviations within a particular structural class that result from sequence rather than crystal or crystallization effects.
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Affiliation(s)
- Franklin A Hays
- Department of Biochemistry and Biophysics, Oregon State University, Agricultural and Life Sciences Building 2011, Corvallis, OR 97331-7305, USA
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25
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McKinney SA, Freeman ADJ, Lilley DMJ, Ha T. Observing spontaneous branch migration of Holliday junctions one step at a time. Proc Natl Acad Sci U S A 2005; 102:5715-20. [PMID: 15824311 PMCID: PMC556122 DOI: 10.1073/pnas.0409328102] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Genetic recombination occurs between homologous DNA molecules via a four-way (Holliday) junction intermediate. This ancient and ubiquitous process is important for the repair of double-stranded breaks, the restart of stalled replication forks, and the creation of genetic diversity. Once formed, the four-way junction alone can undergo the stepwise exchange of base pairs known as spontaneous branch migration. Conventional ensemble assays, useful for finding average migration rates over long sequences, have been unable to examine the affect of sequence and structure on the migration process. Here, we present a single-molecule spontaneous branch migration assay with single-base pair resolution in a study of individual DNA junctions that can undergo one step of migration. Junctions exhibit markedly different dynamics of exchange between stacking conformers depending on the point of strand exchange, allowing the moment at which branch migration occurs to be detected. The free energy landscape of spontaneous branch migration is found to be highly nonuniform and governed by two types of sequence-dependent barriers, with unmediated local migration being up to 10 times more rapid than the previously deduced average rate.
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Affiliation(s)
- Sean A McKinney
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
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26
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27
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Joo C, McKinney SA, Lilley DMJ, Ha T. Exploring rare conformational species and ionic effects in DNA Holliday junctions using single-molecule spectroscopy. J Mol Biol 2004; 341:739-51. [PMID: 15288783 DOI: 10.1016/j.jmb.2004.06.024] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2004] [Revised: 05/24/2004] [Accepted: 06/07/2004] [Indexed: 11/28/2022]
Abstract
The four-way DNA (Holliday) junction is an essential intermediate in DNA recombination, and its dynamic characteristics are likely to be important in its cellular processing. In our previous study we observed transitions between two antiparallel stacked conformations using a single-molecule fluorescence approach. The magnesium concentration-dependent rates of transitions between stacking conformers suggested that an unstacked open structure, which is stable in the absence of metal ions, is an intermediate. Here, we sought to detect possible rare species such as open and parallel conformations and further characterized ionic effects. The hypothesized open intermediate cannot be resolved directly due to the limited time resolution and sensitivity, but our study suggests that the open form is achieved very frequently, hundreds of times per second under physiologically relevant conditions. Therefore despite being a minority species, its frequent formation raises the probability that it could become stabilized by protein binding. By contrast, we cannot detect even a transient existence of the junctions in a parallel form, and the probability of such forms with a lifetime greater than 5 ms is less than 0.01%. Stacking conformer transitions are observable in the presence of sodium or hexammine cobalt (III) ions as well as magnesium ions, but the transition rates are higher for lower valence ions at the same concentrations. This further supports the notion that electrostatic stabilization of the stacked structures dictates the interconversion rates between different structural forms.
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Affiliation(s)
- Chirlmin Joo
- Physics Department, University of Illinois, Urbana-Champaign, Urbana, IL 61801, USA
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28
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Dawid A, Croquette V, Grigoriev M, Heslot F. Single-molecule study of RuvAB-mediated Holliday-junction migration. Proc Natl Acad Sci U S A 2004; 101:11611-6. [PMID: 15292508 PMCID: PMC511028 DOI: 10.1073/pnas.0404369101] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Branch migration of Holliday junctions is an important step of genetic recombination and DNA repair. In Escherichia coli, this process is driven by the RuvAB complex acting as a molecular motor. Using magnetic tweezers, we studied the RuvAB-directed migration of individual Holliday junctions formed between two approximately 6-kb DNA molecules of identical sequence, and we measured the migration rate at 37 degrees C and 1 mM ATP. We directly demonstrate that RuvAB is a highly processive DNA motor protein that is able to drive continuous and unidirectional branch migration of Holliday junctions at a well defined average speed over several kilobases through homologous sequences. We observed directional inversions of the migration at the DNA molecule boundaries leading to forth-and-back migration of the branch point and allowing us to measure the migration rate in the presence of negative or positive loads. The average migration rate at zero load was found to be approximately 43 bp/sec. Furthermore, the load dependence of the migration rate is small, within the force range of -3.4 pN (hindering force) to +3.4 pN (assisting force).
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Affiliation(s)
- A Dawid
- Laboratoire Pierre Aigrain, Unité Mixte de Recherche 8551, Ecole Normale Supérieure, 24 Rue Lhomond, 75005 Paris, France
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29
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Lushnikov AY, Bogdanov A, Lyubchenko YL. DNA recombination: holliday junctions dynamics and branch migration. J Biol Chem 2003; 278:43130-4. [PMID: 12949070 DOI: 10.1074/jbc.m308228200] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Holliday junctions are critical intermediates for homologous, site-specific recombination, DNA repair, and replication. A wealth of structural information is available for immobile four-way junctions, but the controversy on the mechanism of branch migration of Holliday junctions remains unsolved. Two models for the mechanism of branch migration were suggested. According to the early model of Alberts-Meselson-Sigal (Sigal, N., and Alberts, B. (1972) J. Mol. Biol. 71, 789-793 and Meselson, M. (1972) J. Mol. Biol. 71, 795-798), exchanging DNA strands around the junction remain parallel during branch migration. Kinetic studies of branch migration (Panyutin, I. G., and Hsieh, P. (1994) Proc. Natl. Acad. Sci. U. S. A. 91, 2021-2025) suggest an alternative model in which the junction adopts an extended conformation. We tested these models using a Holliday junction undergoing branch migration and time-lapse atomic force microscopy, an imaging technique capable of imaging DNA dynamics. The single molecule atomic force microscopy experiments performed in the presence and in the absence of divalent cations show that mobile Holliday junctions adopt an unfolded conformation during branch migration that is retained despite a broad range of motion in the arms of the junction. This conformation of the junction remains unchanged until strand separation. The data obtained support the model for branch migration having the extended conformation of the Holliday junction.
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30
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Hays FA, Watson J, Ho PS. Caution! DNA crossing: crystal structures of Holliday junctions. J Biol Chem 2003; 278:49663-6. [PMID: 14563836 DOI: 10.1074/jbc.r300033200] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Affiliation(s)
- Franklin A Hays
- Department of Biochemistry and Biophysics, Oregon State University, Corvallis, Oregon 97331-7305, USA
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31
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Ahn JS, Whitby MC. The role of the SAP motif in promoting Holliday junction binding and resolution by SpCCE1. J Biol Chem 2003; 278:29121-9. [PMID: 12748193 DOI: 10.1074/jbc.m302314200] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Holliday junctions are four-way branched DNA structures that are formed during recombination and by replication fork regression. Their processing depends on helicases that catalyze junction branch migration, and endonucleases that resolve the junction into nicked linear DNAs. Here we have investigated the role of a DNA binding motif called SAP in binding and resolving Holliday junctions by the fission yeast mitochondrial resolvase SpCCE1. Mutation or partial/complete deletion of the SAP motif dramatically impairs the ability of SpCCE1 to resolve Holliday junctions in a heterologous in vivo system. These mutant proteins retain the ability to recognize the junction structure and to distort it upon binding. However, once formed the mutant protein-junction complexes are relatively unstable and dissociate much faster than wild-type complexes. We show that binding stability is necessary for efficient junction resolution, and that this may be due in part to a requirement for maintaining the junction in an open conformation so that it can branch migrate to cleavable sites.
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Affiliation(s)
- Jong Sook Ahn
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, United Kingdom
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32
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Li G, Tolstonog GV, Sabasch M, Traub P. Type III intermediate filament proteins interact with four-way junction DNA and facilitate its cleavage by the junction-resolving enzyme T7 endonuclease I. DNA Cell Biol 2003; 22:261-91. [PMID: 12823903 DOI: 10.1089/104454903321908656] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The isolation from proliferating mouse and human embryo fibroblasts of SDS-stable crosslinkage products of vimentin with DNA fragments containing inverted repeats capable of cruciform formation under superhelical stress and the competitive effect of a synthetic Holliday junction on the binding of cytoplasmic intermediate filament (cIF) proteins to supercoiled DNA prompted a detailed investigation of the proteins' capacity to associate with four-way junction DNA and to influence its processing by junction-resolving endonucleases. Electrophoretic mobility shift analysis of reaction products obtained from vimentin and Holliday junctions under varying ionic conditions revealed efficient complex formation of the filament protein not only with the unstacked, square-planar configuration of the junctions but also with their coaxially stacked X-conformation. Glial fibrillary acidic protein (GFAP) was less efficient and desmin virtually inactive in complex formation. Electron microscopy showed binding of vimentin tetramers or octamers almost exclusively to the branchpoint of the Holliday junctions under physiological ionic conditions. Even at several hundredfold molar excess, sequence-related single- and double-stranded DNAs were unable to chase Holliday junctions from their complexes with vimentin. Vimentin also stimulated bacteriophage T7 endonuclease I in introducing single-strand cuts diametrically across the branchpoint and thus in the resolution of the Holliday junctions. This effect is very likely due to vimentin-induced structural distortion of the branchpoint, as suggested by the results of hydroxyl radical footprinting of Holliday junctions in the absence and the presence of vimentin. Moreover, vimentin, and to a lesser extent GFAP and desmin, interacted with the cruciform structures of inverted repeats inserted into a supercoiled vector plasmid, thereby changing their configuration via branch migration and sensibilizing them to processing by T7 endonuclease I. This refers to both plasmid relaxation caused by unilateral scission and, particularly, linearization via bilateral scission at primary and cIF protein-induced secondary cruciform branchpoints that were identified by T7 endonuclease I footprinting. cIF proteins share these activities with a variety of other architectural proteins interacting with and structurally modulating four-way DNA junctions. In view of the known and hypothetical functions of four-way DNA junctions and associated protein factors in DNA metabolism, cIF proteins as complementary nuclear matrix proteins may play important roles in such nuclear matrix-associated processes as DNA replication, recombination, repair, and transcription, with special emphasis on both the preservation and evolution of the genome.
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Affiliation(s)
- Guohong Li
- Max-Planck-Institut für Zellbiologie, Rosenhof, 68526 Ladenburg, Germany
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33
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Eichman BF, Ortiz-Lombardía M, Aymamí J, Coll M, Ho PS. The inherent properties of DNA four-way junctions: comparing the crystal structures of holliday junctions. J Mol Biol 2002; 320:1037-51. [PMID: 12126623 PMCID: PMC4537162 DOI: 10.1016/s0022-2836(02)00540-5] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Holliday junctions are four-stranded DNA complexes that are formed during recombination and related DNA repair events. Much work has focused on the overall structure and properties of four-way junctions in solution, but we are just now beginning to understand these complexes at the atomic level. The crystal structures of two all-DNA Holliday junctions have been determined recently from the sequences d(CCGGGACCGG) and d(CCGGTACCGG). A detailed comparison of the two structures helps to distinguish distortions of the DNA conformation that are inherent to the cross-overs of the junctions in this crystal system from those that are consequences of the mismatched dG.dA base-pair in the d(CCGGGACCGG) structure. This analysis shows that the junction itself perturbs the sequence-dependent conformational features of the B-DNA duplexes and the associated patterns of hydration in the major and minor grooves only minimally. This supports the idea that a DNA four-way junction can be assembled at relatively low energetic cost. Both structures show a concerted rotation of the adjacent duplex arms relative to B-DNA, and this is discussed in terms of the conserved interactions between the duplexes at the junctions and further down the helical arms. The interactions distant from the strand cross-overs of the junction appear to be significant in defining its macroscopic properties, including the angle relating the stacked duplexes across the junction.
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Affiliation(s)
- Brandt F. Eichman
- Department of Biochemistry and Biophysics, ALS 2011, Oregon State University, Corvallis, OR 97331-7305, USA
| | - Miguel Ortiz-Lombardía
- Instìtut Pasteur, Unité de, Biochimie Structurale, 25, rue, du Dr. Roux, 75724 Paris, Cedex 15, France
| | - Joan Aymamí
- Institut de Biologia Molecular, de Barcelona, C.S.I.C., Jordi Girona 18, E-08034, Barcelona, Spain
- Department d’Enginyeria, Quimica, Universitat, Politècnica de Catalunya, Diagonal 647, 08028 Barcelona, Spain
| | - Miquel Coll
- Institut de Biologia Molecular, de Barcelona, C.S.I.C., Jordi Girona 18, E-08034, Barcelona, Spain
- Corresponding authors: ;
| | - Pui Shing Ho
- Department of Biochemistry and Biophysics, ALS 2011, Oregon State University, Corvallis, OR 97331-7305, USA
- Corresponding authors: ;
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Iwaasa M, Umeda S, Ohsato T, Takamatsu C, Fukuoh A, Iwasaki H, Shinagawa H, Hamasaki N, Kang D. 1-Methyl-4-phenylpyridinium ion, a toxin that can cause parkinsonism, alters branched structures of DNA. J Neurochem 2002; 82:30-7. [PMID: 12091462 DOI: 10.1046/j.1471-4159.2002.00996.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
During replication, human mitochondrial DNA (mtDNA) takes on a triple-stranded structure known as a D-loop, which is implicated in replication and transcription. 1-Methyl-4-phenylpyridinium ion (MPP+), a toxin inducing parkinsonism, inhibits mtDNA replication, possibly by resolving the D-loops. For initiation of mtDNA replication, mitochondria are thought to have another triple-stranded structure, an R-loop. The R-loop, which is resolved by a bacterial junction-specific helicase, RecG, is also resolved by MPP+. Because mitochondrial D-loops are likewise resolved by RecG, the D- and R-loops may share a similar branched structure. MPP+ resolves cruciform DNA in supercoiled DNA. MPP+ converts a stacked conformation to an extended conformation in a synthetic Holliday junction. This conversion is reversed by 1 mM Mg(2+), as is the resolution of the D-loops or cruciform DNA. These observations suggest that the junction structure of mitochondrial D- and R-loops is affected by MPP+.
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Affiliation(s)
- Mitsutoshi Iwaasa
- Department of Neurosurgery, Fukuoka University Faculty of Medicine, Fukuoka, Japan
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35
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Fogg JM, Kvaratskhelia M, White MF, Lilley DM. Distortion of DNA junctions imposed by the binding of resolving enzymes: a fluorescence study. J Mol Biol 2001; 313:751-64. [PMID: 11697901 DOI: 10.1006/jmbi.2001.5081] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Junction-resolving enzymes are nucleases that are specific for the structure of the four-way DNA junction. The binding of RuvC of Escherichia coli and Hjc of Sulfolobus solfataricus can be followed by an increase in the fluorescence anisotropy of Cy3 terminally attached to one of the helical arms of a four-way junction. By contrast, there was no change in fluorescein anisotropy with the binding of single dimers of these proteins. Fluorescence resonance energy transfer has therefore been used between fluorescein and Cy3 fluorophores attached to the ends of helical arms to analyse the global structure of the junction on protein binding. The results indicate that both enzymes induce a marked change in the global DNA conformation on the binding of a single dimer. The structure of the protein-junction complexes is independent of the presence or absence of divalent metal ions, unlike that of the protein-free junction. The structures of the RuvC and Hjc complexes are different, but both represent a significant opening of the structure compared to the stacked X-structure of the protein-free junction in the presence of magnesium ions. This protein-induced opening is likely to be important in the function of these enzymes.
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Affiliation(s)
- J M Fogg
- CRC Nucleic Acid Structure Research Group, Department of Biochemistry, MSI/WTB Complex, The University of Dundee, Dundee, DD1 5EH, UK
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36
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Abstract
Junction-resolving enzymes are ubiquitous nucleases that are important for DNA repair and recombination and act on DNA molecules containing branch points, especially four-way junctions. They show a pronounced selectivity for the structure of the DNA substrate but, despite its importance, the structural selectivity is not well understood. This poses an intriguing challenge in molecular recognition on a relatively large scale.
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Affiliation(s)
- D M Lilley
- CRC Nucleic Acid Structure Research Group, Department of Biochemistry, University of Dundee, Dundee DD1 5EH, UK.
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38
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Metzler DE, Metzler CM, Sauke DJ. The Nucleic Acids. Biochemistry 2001. [DOI: 10.1016/b978-012492543-4/50008-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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39
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Nowakowski J, Shim PJ, Stout CD, Joyce GF. Alternative conformations of a nucleic acid four-way junction. J Mol Biol 2000; 300:93-102. [PMID: 10864501 DOI: 10.1006/jmbi.2000.3826] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
A crystal structure of a 108 nucleotide RNA-DNA complex containing a four-way junction was solved at 3.1 A resolution. The structure of the junction differs substantially from the "stacked-X" conformation observed previously, due to a 135 degrees rotation of the branches. Comparison of the two conformers provides insight into the factors contributing to the flexibility of four-way junctions. The stacked-X conformation maximizes base-stacking but causes unfavorable repulsion between phosphate groups, whereas the 135 degrees -rotated "crossed" conformation minimizes electrostatic clashes at the expense of reduced base-stacking. Despite the large rotation of the branches, both junction structures exhibit an antiparallel arrangement of the continuous strands and opposite polarity of the crossover strands.
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Affiliation(s)
- J Nowakowski
- Department of Chemistry and The Skaggs Institute for Chemical Biology, The Scripps Research Institute, 10550 N. Torrey Pines Road, La Jolla, CA, 92037, USA
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40
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Abstract
Mismatches, and the proteins that repair them, play multiple roles during meiosis from generating the diversity upon which selection acts to preventing the intermingling of diverged populations and species. The mechanisms by which the mismatch repair proteins accomplish these many roles include gene conversion, reciprocal crossing over, mismatch repair-induced recombination and anti-recombination. This review focuses on recent studies, predominantly in Saccharomyces cerevisiae, that have advanced our understanding of the details of mismatch repair complexes and how they apply to the diverse roles these proteins play in meiosis. These studies have also revealed unexpected and novel functions for some of the mismatch repair proteins.
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Affiliation(s)
- R H Borts
- Genome Stability Group, Department of Biochemistry, University of Oxford, South Parks Road, OX1 3QU, Oxford, UK.
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41
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Déclais AC, Lilley DM. Extensive central disruption of a four-way junction on binding CCE1 resolving enzyme. J Mol Biol 2000; 296:421-33. [PMID: 10669598 DOI: 10.1006/jmbi.1999.3479] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Junction-resolving enzymes are nucleases that are selective for the structure of the four-way DNA junction that is important in genetic recombination. They exhibit selectivity for the structure of the junction, but they also manipulate the structure. Local disruption of DNA structure around the centre of the junction by CCE1 of Saccharomyces cerevisiae has been investigated using 2-aminopurine fluorescence. On binding CCE1, 2-aminopurine bases located at the point of strand exchange exhibit a large increase in fluorescence intensity (up to 39-fold enhancement), consistent with complete unstacking. This was observed for all positions around the centre of the junction, both 5' and 3' to the point of strand exchange. Thymine bases complementary to the modified adenine bases adjacent to the junction centre were strongly reactive to potassium permanganate. The results indicate that binding of CCE1 results in a complete unpairing of the four central base-pairs of the junction, with a lesser disruption of the next base-pairs.
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Affiliation(s)
- A C Déclais
- Department of Biochemistry, CRC Nucleic Acid Structure Research Group, Dundee, DD1 4HN, UK
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42
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Namsaraev EA, Berg P. Rad51 uses one mechanism to drive DNA strand exchange in both directions. J Biol Chem 2000; 275:3970-6. [PMID: 10660552 DOI: 10.1074/jbc.275.6.3970] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The Rad51 protein of Saccharomyces cerevisiae, like its bacterial counterpart RecA, promotes strand exchange between circular single-stranded DNA (ssDNA) and linear double-stranded DNA (dsDNA) in vitro. However, the two proteins differ in the requirement for initiating joint molecules and in the polarity of branch migration. Whereas RecA initiates joint molecules from any type of ends on the dsDNA and branch migration proceeds exclusively in the 5'- to 3'-direction with respect to the single strand DNA substrate, initiation mediated by Rad51 requires a complementary 3' or 5' overhanging end of the linear dsDNA and branch migration proceeds in either direction. Here we report that the rates of Rad51-mediated branch migration in either the 5'- to 3'- or 3'- to 5'-directions are affected to the same extent by temperature and MgCl(2). Furthermore, branch migration in both directions is equally impeded by insertions of non-homologous sequences in the dsDNA, inserts of 6 base pairs or more being completely inhibitory. We have also found that the preference of strand exchange in the 5'- to 3'-direction does not change if RPA is replaced by Escherichia coli SSB or T4 gene 32 proteins, suggesting that the preference for the direction of strand exchange is intrinsic to Rad51. Based on these results, we conclude that Rad51-promoted branch migration in either direction occurs fundamentally by the same mechanism, quite probably by stabilizing successively formed heteroduplex base pair.
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Affiliation(s)
- E A Namsaraev
- Department of Biochemistry, Beckman Center for Molecular and Genetic Medicine, Stanford University School of Medicine, Stanford, California 94305-4525, USA
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43
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Kvaratskhelia M, George SJ, Cooper A, White MF. Quantitation of metal ion and DNA junction binding to the Holliday junction endonuclease Cce1. Biochemistry 1999; 38:16613-9. [PMID: 10600123 DOI: 10.1021/bi9921788] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Cce1 is a magnesium-dependent Holliday junction endonuclease involved in the resolution of recombining mitochondrial DNA in Saccharomyces cerevisiae. Cce1 binds four-way DNA junctions as a dimer, opening the junction into an extended, 4-fold symmetric structure, and resolves junctions by the introduction of paired nicks in opposing strands at the point of strand exchange. In the present study, we have examined the interactions of wild-type Cce1 with a noncleavable four-way DNA junction and metal ions (Mg(2+) and Mn(2+)) using isothermal titration calorimetry, EPR, and gel electrophoresis techniques. Mg(2+) or Mn(2+) ions bind to Cce1 in the absence of DNA junctions with a stoichiometry of two metal ions per Cce1 monomer. Cce1 binds to four-way junctions with a stoichiometry of two Cce1 dimers per junction molecule in the presence of EDTA, and one dimer of Cce1 per junction in 15 mM magnesium. The presence of 15 mM Mg(2+) dramatically reduces the affinity of Cce1 for four-way DNA junctions, by about 900-fold. This allows an estimation of DeltaG degrees for stacking of four-way DNA junction 7 of -4.1 kcal/mol, consistent with the estimate of -3.3 to -4.5 kcal/mol calculated from branch migration and NMR experiments [Overmars and Altona (1997) J. Mol. Biol. 273, 519-524; Panyutin et al. (1995) EMBO J. 14, 1819-1826]. The striking effect of magnesium ions on the affinity of Cce1 binding to the four-way junction is predicted to be a general one for proteins that unfold the stacked X-structure of the Holliday junction on binding.
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Abstract
Branch-migration is a fundamental step in the process of DNA recombination that determines the location, and extent, of the exchange between the recombining duplexes. Four-way Holliday junctions assembled in vitro can migrate spontaneously in an uncatalysed reaction that mimics some of the aspects involved in branch-migration. Here, we have analysed the effects of a d(GA.TC)22 and a d(CA.TG)30 sequence on the rate of spontaneous branch-migration. Under most of the experimental conditions assayed, no significant effect was observed. However, the d(GA.TC)22 sequence induces a very strong arrest when branch-migration is performed at low pH, under conditions where the repeated sequence is forming an intramolecular [C(+)T(GA.TC)] triplex. A similar arrest is observed when the recombining duplexes contain intermolecular triplexes arising from the annealing of a d(GA.TC)22 duplex and a d(TC)22 oligonucleotide, indicating that the formation of triplex DNA constitutes a strong barrier for the progression of the Holliday junction. These results are discussed in the context of the possible contribution of triplex DNA to DNA recombination.
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Affiliation(s)
- A Benet
- Centre d'Investigació i Desenvolupament, Institut de Biologia Molecular de Barcelona, CSIC, Jordi Girona Salgado 18-26, Barcelona, 08034, Spain
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45
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Kuzminov A. Recombinational repair of DNA damage in Escherichia coli and bacteriophage lambda. Microbiol Mol Biol Rev 1999; 63:751-813, table of contents. [PMID: 10585965 PMCID: PMC98976 DOI: 10.1128/mmbr.63.4.751-813.1999] [Citation(s) in RCA: 718] [Impact Index Per Article: 28.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Although homologous recombination and DNA repair phenomena in bacteria were initially extensively studied without regard to any relationship between the two, it is now appreciated that DNA repair and homologous recombination are related through DNA replication. In Escherichia coli, two-strand DNA damage, generated mostly during replication on a template DNA containing one-strand damage, is repaired by recombination with a homologous intact duplex, usually the sister chromosome. The two major types of two-strand DNA lesions are channeled into two distinct pathways of recombinational repair: daughter-strand gaps are closed by the RecF pathway, while disintegrated replication forks are reestablished by the RecBCD pathway. The phage lambda recombination system is simpler in that its major reaction is to link two double-stranded DNA ends by using overlapping homologous sequences. The remarkable progress in understanding the mechanisms of recombinational repair in E. coli over the last decade is due to the in vitro characterization of the activities of individual recombination proteins. Putting our knowledge about recombinational repair in the broader context of DNA replication will guide future experimentation.
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Affiliation(s)
- A Kuzminov
- Institute of Molecular Biology, University of Oregon, Eugene, Oregon 97403, USA.
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46
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Abstract
The double D-loop DNA hybrid contains four DNA strands following hybridization of two RecA protein coated complementary single-stranded DNA probes with a homologous region of a double-stranded DNA target. A remarkable feature of the double D-loop DNA hybrids is their kinetic stabilities at internal sites within linear DNA targets after removal of RecA protein from hybrids. We report here that heterologous DNA inserts in one or both probe strands affect the kinetic stability of protein-free double D-loop hybrids. DNA heterologies normally distort DNA-DNA hybrids and consequently accelerate hybrid dissociation. In contrast, heterologous DNA inserts impede dissociation of double D-loops, especially when the insert sequences interact with each other by DNA base pairing. We propose a mechanism for this kinetic stabilization by heterologous DNA inserts based on the hypothesis that the main pathway of dissociation of double D-loop DNA hybrids is a DNA branch migration process involving the rotation of both probe-target duplexes in the hybrids. Heterologous DNA inserts constrain rotation of probe-target duplexes and consequently impede hybrid dissociation. Potential applications of the stabilized double D-loops for gene targeting are discussed.
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47
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Affiliation(s)
- S C West
- Imperial Cancer Research Fund, Clare Hall Laboratories, South Mimms, Herts, United Kingdom
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48
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Abstract
The Holliday junction is a central intermediate in the process of genetic recombination. The position of its branch-point can relocate through an isomerization known as branch migration. This migration occurs because the branch-point is flanked by homologous symmetry. All attempts at modeling the kinetics of branch migration have relied on the assumption that branch migration minima are sequence-independent. We have tested that assumption here, using a competition assay based on symmetric immobile branched junctions; these are junctions that cannot undergo branch migration, despite the fact that they are flanked by homology. The assay used is predicated on the non-association of strands displaced in the assay; we have tested this assumption, and have performed our experiments under conditions where we know that it is true. We have measured the free energy of relocating a branched junction from a fixed non-homologous sequence to all possible dimeric symmetric sequences. We find that the assumption of sequence-independence is often valid, but that it is not universally true. We find that the flanking sequences can have a marked effect on the free energy measured, both for extensions of symmetry and for reversals of flanking nucleotides. We have varied the temperature in our experiments, and have derived both enthalpies and entropies for the different sequences. The entropies are largely unfavorable, whereas the enthalpies are largely favorable; regardless of the signs of these quantities, we see that this is another system where enthalpy-entropy compensation is operative.
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Affiliation(s)
- W Sun
- Department of Chemistry, New York University, New York, NY 10003, USA
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49
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Zerbib D, Mézard C, George H, West SC. Coordinated actions of RuvABC in Holliday junction processing. J Mol Biol 1998; 281:621-30. [PMID: 9710535 DOI: 10.1006/jmbi.1998.1959] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The RuvA, RuvB and RuvC proteins of Escherichia coli process Holliday junctions during genetic recombination and DNA repair. Biochemical studies have shown that RuvA and RuvB promote branch migration whereas RuvC resolves junctions by endonucleolytic cleavage. Here we show that RuvAB stimulate Holliday junction resolution by RuvC. Elevated RuvC activity was dependent upon RuvAB-mediated ATP-hydrolysis. These results show that the three Ruv proteins work in a coordinated manner to promote Holliday junction resolution, and account for the resolvase-defective phenotype exhibited by ruvA, ruvB or ruvC mutant strains.
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Affiliation(s)
- D Zerbib
- Clare Hall Laboratories, Imperial Cancer Research Fund, South Mimms, Herts, EN6 3LD, UK
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50
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Whitby MC, Lloyd RG. Targeting Holliday junctions by the RecG branch migration protein of Escherichia coli. J Biol Chem 1998; 273:19729-39. [PMID: 9677403 DOI: 10.1074/jbc.273.31.19729] [Citation(s) in RCA: 76] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The RecG protein of Escherichia coli is a junction-specific DNA helicase that drives branch migration of Holliday intermediates in genetic recombination and DNA repair. The reaction was investigated using synthetic X-junctions. RecG dissociates X-junctions to flayed duplex products, although DNA unwinding of the heterologous arms is limited to </=30 base pairs. Junction unwinding requires Mg2+ and the hydrolysis of ATP. X-junction DNA stimulates the ATPase activity of RecG. ATPase activity is also stimulated by linear duplex DNA, although to a lesser extent than by X-DNA, but not by linear single-stranded DNA. In situ 1,10-phenanthroline-copper footprinting shows that RecG binds to the strand cross-over point at the center of the X-junction. Substrate recognition by RecG was investigated using DNAs that represented the various component parts of an X-junction. The minimal DNA structure that RecG forms a stable complex with is a flayed duplex, suggesting that this is the critical feature for junction recognition by RecG. Junction binding and unwinding also depend critically on the concentration of free Mg2+, excess free cation dramatically inhibiting both processes. These inhibitory effects are not mediated specifically by Mg2+; e.g. both Ca2+ and hexamminecobalt(III) chloride also inhibit X-junction binding and unwinding by RecG. The relative abilities of these cations to inhibit RecG-junction binding is correlated with their respective abilities to stack X-junction DNA. From this we conclude that RecG is unable to bind or binds very poorly to fully stacked X-junctions.
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Affiliation(s)
- M C Whitby
- Microbiology Unit, Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, United Kingdom.
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