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Niekamp S, Marr SK, Oei TA, Subramanian R, Kingston RE. Modularity of PRC1 composition and chromatin interaction define condensate properties. Mol Cell 2024; 84:1651-1666.e12. [PMID: 38521066 PMCID: PMC11234260 DOI: 10.1016/j.molcel.2024.03.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2023] [Revised: 01/04/2024] [Accepted: 02/29/2024] [Indexed: 03/25/2024]
Abstract
Polycomb repressive complexes (PRCs) play a key role in gene repression and are indispensable for proper development. Canonical PRC1 forms condensates in vitro and in cells that are proposed to contribute to the maintenance of repression. However, how chromatin and the various subunits of PRC1 contribute to condensation is largely unexplored. Using a reconstitution approach and single-molecule imaging, we demonstrate that nucleosomal arrays and PRC1 act synergistically, reducing the critical concentration required for condensation by more than 20-fold. We find that the exact combination of PHC and CBX subunits determines condensate initiation, morphology, stability, and dynamics. Particularly, PHC2's polymerization activity influences condensate dynamics by promoting the formation of distinct domains that adhere to each other but do not coalesce. Live-cell imaging confirms CBX's role in condensate initiation and highlights PHC's importance for condensate stability. We propose that PRC1 composition can modulate condensate properties, providing crucial regulatory flexibility across developmental stages.
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Affiliation(s)
- Stefan Niekamp
- Department of Molecular Biology, Massachusetts General Hospital Research Institute, Massachusetts General Hospital, Boston, MA 02114, USA; Department of Genetics, Harvard Medical School, Boston, MA 02115, USA
| | - Sharon K Marr
- Department of Molecular Biology, Massachusetts General Hospital Research Institute, Massachusetts General Hospital, Boston, MA 02114, USA; Department of Genetics, Harvard Medical School, Boston, MA 02115, USA
| | - Theresa A Oei
- Department of Molecular Biology, Massachusetts General Hospital Research Institute, Massachusetts General Hospital, Boston, MA 02114, USA; Department of Genetics, Harvard Medical School, Boston, MA 02115, USA; Department of Chemical Biology, Harvard University, Cambridge, MA 02138, USA
| | - Radhika Subramanian
- Department of Molecular Biology, Massachusetts General Hospital Research Institute, Massachusetts General Hospital, Boston, MA 02114, USA; Department of Genetics, Harvard Medical School, Boston, MA 02115, USA.
| | - Robert E Kingston
- Department of Molecular Biology, Massachusetts General Hospital Research Institute, Massachusetts General Hospital, Boston, MA 02114, USA; Department of Genetics, Harvard Medical School, Boston, MA 02115, USA.
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2
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Niekamp S, Marr SK, Oei TA, Subramanian R, Kingston RE. Modularity of PRC1 Composition and Chromatin Interaction define Condensate Properties. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.10.26.564217. [PMID: 37961190 PMCID: PMC10634914 DOI: 10.1101/2023.10.26.564217] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2023]
Abstract
Polycomb repressive complexes (PRC) play a key role in gene repression and are indispensable for proper development. Canonical PRC1 forms condensates in vitro and in cells and the ability of PRC1 to form condensates has been proposed to contribute to maintenance of repression. However, how chromatin and the various subunits of PRC1 contribute to condensation is largely unexplored. Using single-molecule imaging, we demonstrate that nucleosomal arrays and PRC1 act synergistically, reducing the critical concentration required for condensation by more than 20-fold. By reconstituting and imaging PRC1 with various subunit compositions, we find that the exact combination of PHC and CBX subunits determine the initiation, morphology, stability, and dynamics of condensates. In particular, the polymerization activity of PHC2 strongly influences condensate dynamics to promote formation of structures with distinct domains that adhere to each other but do not coalesce. Using live cell imaging, we confirmed that CBX properties are critical for condensate initiation and that PHC polymerization is important to maintain stable condensates. Together, we propose that PRC1 can fine-tune the degree and type of condensation by altering its composition which might offer important flexibility of regulatory function during different stages of development.
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3
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Ding J, Li X, Shen J, Zhao Y, Zhong S, Lai L, Niu H, Qi Z. ssDNA accessibility of Rad51 is regulated by orchestrating multiple RPA dynamics. Nat Commun 2023; 14:3864. [PMID: 37391417 PMCID: PMC10313831 DOI: 10.1038/s41467-023-39579-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2022] [Accepted: 06/20/2023] [Indexed: 07/02/2023] Open
Abstract
The eukaryotic single-stranded DNA (ssDNA)-binding protein Replication Protein A (RPA) plays a crucial role in various DNA metabolic pathways, including DNA replication and repair, by dynamically associating with ssDNA. While the binding of a single RPA molecule to ssDNA has been thoroughly studied, the accessibility of ssDNA is largely governed by the bimolecular behavior of RPA, the biophysical nature of which remains unclear. In this study, we develop a three-step low-complexity ssDNA Curtains method, which, when combined with biochemical assays and a Markov chain model in non-equilibrium physics, allow us to decipher the dynamics of multiple RPA binding to long ssDNA. Interestingly, our results suggest that Rad52, the mediator protein, can modulate the ssDNA accessibility of Rad51, which is nucleated on RPA coated ssDNA through dynamic ssDNA exposure between neighboring RPA molecules. We find that this process is controlled by the shifting between the protection mode and action mode of RPA ssDNA binding, where tighter RPA spacing and lower ssDNA accessibility are favored under RPA protection mode, which can be facilitated by the Rfa2 WH domain and inhibited by Rad52 RPA interaction.
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Affiliation(s)
- Jiawei Ding
- Center for Quantitative Biology, Peking-Tsinghua Center for Life Sciences, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China
| | - Xiangting Li
- Department of Computational Medicine, University of California, Los Angeles, CA, USA
| | - Jiangchuan Shen
- Department of Molecular and Cellular Biochemistry, Indiana University, Bloomington, IN, USA
| | - Yiling Zhao
- Center for Quantitative Biology, Peking-Tsinghua Center for Life Sciences, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China
- Institute of Systems Biomedicine, School of Basic Medical Sciences, Peking University Health Science Center, Beijing, China
| | - Shuchen Zhong
- BNLMS, College of Chemistry and Molecular Engineering, Peking University, Beijing, China
| | - Luhua Lai
- Center for Quantitative Biology, Peking-Tsinghua Center for Life Sciences, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China
- BNLMS, College of Chemistry and Molecular Engineering, Peking University, Beijing, China
| | - Hengyao Niu
- Department of Molecular and Cellular Biochemistry, Indiana University, Bloomington, IN, USA.
| | - Zhi Qi
- Center for Quantitative Biology, Peking-Tsinghua Center for Life Sciences, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China.
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4
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Zhou R, Tian K, Huang J, Duan W, Fu H, Feng Y, Wang H, Jiang Y, Li Y, Wang R, Hu J, Ma H, Qi Z, Ji X. CTCF DNA binding domain undergoes dynamic and selective protein–protein interactions. iScience 2022; 25:105011. [PMID: 36117989 PMCID: PMC9474293 DOI: 10.1016/j.isci.2022.105011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2022] [Revised: 05/13/2022] [Accepted: 08/19/2022] [Indexed: 11/24/2022] Open
Abstract
CTCF is a predominant insulator protein required for three-dimensional chromatin organization. However, the roles of its insulation of enhancers in a 3D nuclear organization have not been fully explained. Here, we found that the CTCF DNA-binding domain (DBD) forms dynamic self-interacting clusters. Strikingly, CTCF DBD clusters were found to incorporate other insulator proteins but are not coenriched with transcriptional activators in the nucleus. This property is not observed in other domains of CTCF or the DBDs of other transcription factors. Moreover, endogenous CTCF shows a phenotype consistent with the DBD by forming small protein clusters and interacting with CTCF motif arrays that have fewer transcriptional activators bound. Our results reveal an interesting phenomenon in which CTCF DBD interacts with insulator proteins and selectively localizes to nuclear positions with lower concentrations of transcriptional activators, providing insights into the insulation function of CTCF. The CTCF DNA-binding domain forms protein clusters in vivo and in vitro CTCF DBD clusters colocalize with insulator proteins but not with activators Arginine residues of CTCF DBD are frequently mutated in cancers Multiple transcription factor DBDs form protein clusters
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5
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Rad54 and Rdh54 prevent Srs2-mediated disruption of Rad51 presynaptic filaments. Proc Natl Acad Sci U S A 2022; 119:2113871119. [PMID: 35042797 PMCID: PMC8795549 DOI: 10.1073/pnas.2113871119] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/29/2021] [Indexed: 11/18/2022] Open
Abstract
Homologous DNA recombination is an essential pathway necessary for the repair of double-stranded DNA breaks. Defects in this pathway are associated with hereditary breast cancer, ovarian cancer, and cancer-prone syndromes. Although essential, too much recombination is also bad and can lead to genetic mutations. Thus, cells have evolved “antirecombinase” enzymes that can actively dismantle recombination intermediates to prevent excessive recombination. However, our current understanding of how antirecombinases are themselves regulated remains very limited. Here, we study the antirecombinase Srs2 and its regulation by the recombination accessory factors Rad54 and Rdh54. Our data suggest that Rad54 and Rdh54 act synergistically to function as key regulators of Srs2, thus serving as “licensing factors” that enable timely progression of DNA repair. Srs2 is a superfamily 1 (SF1) helicase that participates in several pathways necessary for the repair of damaged DNA. Srs2 regulates formation of early homologous recombination (HR) intermediates by actively removing the recombinase Rad51 from single-stranded DNA (ssDNA). It is not known whether and how Srs2 itself is down-regulated to allow for timely HR progression. Rad54 and Rdh54 are two closely related superfamily 2 (SF2) motor proteins that promote the formation of Rad51-dependent recombination intermediates. Rad54 and Rdh54 bind tightly to Rad51-ssDNA and act downstream of Srs2, suggesting that they may affect the ability of Srs2 to dismantle Rad51 filaments. Here, we used DNA curtains to determine whether Rad54 and Rdh54 alter the ability of Srs2 to disrupt Rad51 filaments. We show that Rad54 and Rdh54 act synergistically to greatly restrict the antirecombinase activity of Srs2. Our findings suggest that Srs2 may be accorded only a limited time window to act and that Rad54 and Rdh54 fulfill a role of prorecombinogenic licensing factors.
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6
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Chanou A, Hamperl S. Single-Molecule Techniques to Study Chromatin. Front Cell Dev Biol 2021; 9:699771. [PMID: 34291054 PMCID: PMC8287188 DOI: 10.3389/fcell.2021.699771] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2021] [Accepted: 05/26/2021] [Indexed: 12/14/2022] Open
Abstract
Besides the basic organization in nucleosome core particles (NCPs), eukaryotic chromatin is further packed through interactions with numerous protein complexes including transcription factors, chromatin remodeling and modifying enzymes. This nucleoprotein complex provides the template for many important biological processes, such as DNA replication, transcription, and DNA repair. Thus, to understand the molecular basis of these DNA transactions, it is critical to define individual changes of the chromatin structure at precise genomic regions where these machineries assemble and drive biological reactions. Single-molecule approaches provide the only possible solution to overcome the heterogenous nature of chromatin and monitor the behavior of individual chromatin transactions in real-time. In this review, we will give an overview of currently available single-molecule methods to obtain mechanistic insights into nucleosome positioning, histone modifications and DNA replication and transcription analysis-previously unattainable with population-based assays.
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Affiliation(s)
| | - Stephan Hamperl
- Chromosome Dynamics and Genome Stability, Institute of Epigenetics and Stem Cells, Helmholtz Zentrum München, Munich, Germany
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7
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Fairlamb MS, Whitaker AM, Bain FE, Spies M, Freudenthal BD. Construction of a Three-Color Prism-Based TIRF Microscope to Study the Interactions and Dynamics of Macromolecules. BIOLOGY 2021; 10:biology10070571. [PMID: 34201434 PMCID: PMC8301196 DOI: 10.3390/biology10070571] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/11/2021] [Revised: 06/08/2021] [Accepted: 06/15/2021] [Indexed: 02/05/2023]
Abstract
Simple Summary Prism-based single-molecule total internal reflection fluorescence (prismTIRF) microscopes are excellent tools for studying macromolecular dynamics and interactions. Here, we provide an easy-to-follow guide for the design, assembly, and operation of a three-color prismTIRF microscope using commercially available components with the hope of assisting those who aim to implement TIRF imaging techniques in their laboratory. Abstract Single-molecule total internal reflection fluorescence (TIRF) microscopy allows for the real-time visualization of macromolecular dynamics and complex assembly. Prism-based TIRF microscopes (prismTIRF) are relatively simple to operate and can be easily modulated to fit the needs of a wide variety of experimental applications. While building a prismTIRF microscope without expert assistance can pose a significant challenge, the components needed to build a prismTIRF microscope are relatively affordable and, with some guidance, the assembly can be completed by a determined novice. Here, we provide an easy-to-follow guide for the design, assembly, and operation of a three-color prismTIRF microscope which can be utilized for the study of macromolecular complexes, including the multi-component protein–DNA complexes responsible for DNA repair, replication, and transcription. Our hope is that this article can assist laboratories that aspire to implement single-molecule TIRF techniques, and consequently expand the application of this technology.
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Affiliation(s)
- Max S. Fairlamb
- Department of Biochemistry and Molecular Biology and Department of Cancer Biology, University of Kansas Medical Center, Kansas City, KS 66160, USA; (M.S.F.); (A.M.W.)
| | - Amy M. Whitaker
- Department of Biochemistry and Molecular Biology and Department of Cancer Biology, University of Kansas Medical Center, Kansas City, KS 66160, USA; (M.S.F.); (A.M.W.)
| | - Fletcher E. Bain
- Department of Biochemistry and Molecular Biology, University of Iowa Carver College of Medicine, 51 Newton Road, Iowa City, IA 52242, USA; (F.E.B.); (M.S.)
| | - Maria Spies
- Department of Biochemistry and Molecular Biology, University of Iowa Carver College of Medicine, 51 Newton Road, Iowa City, IA 52242, USA; (F.E.B.); (M.S.)
| | - Bret D. Freudenthal
- Department of Biochemistry and Molecular Biology and Department of Cancer Biology, University of Kansas Medical Center, Kansas City, KS 66160, USA; (M.S.F.); (A.M.W.)
- Correspondence:
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8
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Adolph MB, Mohamed TM, Balakrishnan S, Xue C, Morati F, Modesti M, Greene EC, Chazin WJ, Cortez D. RADX controls RAD51 filament dynamics to regulate replication fork stability. Mol Cell 2021; 81:1074-1083.e5. [PMID: 33453169 PMCID: PMC7935748 DOI: 10.1016/j.molcel.2020.12.036] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2020] [Revised: 11/02/2020] [Accepted: 12/21/2020] [Indexed: 01/10/2023]
Abstract
The RAD51 recombinase forms nucleoprotein filaments to promote double-strand break repair, replication fork reversal, and fork stabilization. The stability of these filaments is highly regulated, as both too little and too much RAD51 activity can cause genome instability. RADX is a single-strand DNA (ssDNA) binding protein that regulates DNA replication. Here, we define its mechanism of action. We find that RADX inhibits RAD51 strand exchange and D-loop formation activities. RADX directly and selectively interacts with ATP-bound RAD51, stimulates ATP hydrolysis, and destabilizes RAD51 nucleofilaments. The RADX interaction with RAD51, in addition to its ssDNA binding capability, is required to maintain replication fork elongation rates and fork stability. Furthermore, BRCA2 can overcome the RADX-dependent RAD51 inhibition. Thus, RADX functions in opposition to BRCA2 in regulating RAD51 nucleofilament stability to ensure the right level of RAD51 function during DNA replication.
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Affiliation(s)
- Madison B Adolph
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Taha M Mohamed
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Swati Balakrishnan
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN, USA; Center for Structural Biology, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Chaoyou Xue
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY USA
| | - Florian Morati
- Cancer Research Center of Marseille, CNRS UMR7258, Inserm U1068, Institut Paoli-Calmettes, Aix-Marseille Université U105, Marseille, France
| | - Mauro Modesti
- Cancer Research Center of Marseille, CNRS UMR7258, Inserm U1068, Institut Paoli-Calmettes, Aix-Marseille Université U105, Marseille, France
| | - Eric C Greene
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY USA
| | - Walter J Chazin
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN, USA; Center for Structural Biology, Vanderbilt University School of Medicine, Nashville, TN, USA.
| | - David Cortez
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN, USA.
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9
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Crickard JB, Kwon Y, Sung P, Greene EC. Rad54 and Rdh54 occupy spatially and functionally distinct sites within the Rad51-ssDNA presynaptic complex. EMBO J 2020; 39:e105705. [PMID: 32790929 PMCID: PMC7560196 DOI: 10.15252/embj.2020105705] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2020] [Revised: 07/13/2020] [Accepted: 07/29/2020] [Indexed: 12/21/2022] Open
Abstract
Rad54 and Rdh54 are closely related ATP-dependent motor proteins that participate in homologous recombination (HR). During HR, these enzymes functionally interact with the Rad51 presynaptic complex (PSC). Despite their importance, we know little about how they are organized within the PSC, or how their organization affects PSC function. Here, we use single-molecule optical microscopy and genetic analysis of chimeric protein constructs to evaluate the binding distributions of Rad54 and Rdh54 within the PSC. We find that Rad54 and Rdh54 have distinct binding sites within the PSC, which allow these proteins to act cooperatively as DNA sequences are aligned during homology search. Our data also reveal that Rad54 must bind to a specific location within the PSC, whereas Rdh54 retains its function in the repair of MMS-induced DNA damage even when recruited to the incorrect location. These findings support a model in which the relative binding sites of Rad54 and Rdh54 help to define their functions during mitotic HR.
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Affiliation(s)
- J Brooks Crickard
- Department of Biochemistry & Molecular BiophysicsColumbia UniversityNew YorkNYUSA
| | - Youngho Kwon
- Department of Biochemistry and Structural BiologyUniversity of Texas Health Science Center at San AntonioSan AntonioTXUSA
| | - Patrick Sung
- Department of Biochemistry and Structural BiologyUniversity of Texas Health Science Center at San AntonioSan AntonioTXUSA
| | - Eric C Greene
- Department of Biochemistry & Molecular BiophysicsColumbia UniversityNew YorkNYUSA
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10
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Homologous Recombination under the Single-Molecule Fluorescence Microscope. Int J Mol Sci 2019; 20:ijms20236102. [PMID: 31816946 PMCID: PMC6929127 DOI: 10.3390/ijms20236102] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Revised: 11/26/2019] [Accepted: 11/30/2019] [Indexed: 11/16/2022] Open
Abstract
Homologous recombination (HR) is a complex biological process and is central to meiosis and for repair of DNA double-strand breaks. Although the HR process has been the subject of intensive study for more than three decades, the complex protein–protein and protein–DNA interactions during HR present a significant challenge for determining the molecular mechanism(s) of the process. This knowledge gap is largely because of the dynamic interactions between HR proteins and DNA which is difficult to capture by routine biochemical or structural biology methods. In recent years, single-molecule fluorescence microscopy has been a popular method in the field of HR to visualize these complex and dynamic interactions at high spatiotemporal resolution, revealing mechanistic insights of the process. In this review, we describe recent efforts that employ single-molecule fluorescence microscopy to investigate protein–protein and protein–DNA interactions operating on three key DNA-substrates: single-stranded DNA (ssDNA), double-stranded DNA (dsDNA), and four-way DNA called Holliday junction (HJ). We also outline the technological advances and several key insights revealed by these studies in terms of protein assembly on these DNA substrates and highlight the foreseeable promise of single-molecule fluorescence microscopy in advancing our understanding of homologous recombination.
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11
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Steinfeld JB, Beláň O, Kwon Y, Terakawa T, Al-Zain A, Smith MJ, Crickard JB, Qi Z, Zhao W, Rothstein R, Symington LS, Sung P, Boulton SJ, Greene EC. Defining the influence of Rad51 and Dmc1 lineage-specific amino acids on genetic recombination. Genes Dev 2019; 33:1191-1207. [PMID: 31371435 PMCID: PMC6719624 DOI: 10.1101/gad.328062.119] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2019] [Accepted: 07/01/2019] [Indexed: 02/06/2023]
Abstract
The vast majority of eukaryotes possess two DNA recombinases: Rad51, which is ubiquitously expressed, and Dmc1, which is meiosis-specific. The evolutionary origins of this two-recombinase system remain poorly understood. Interestingly, Dmc1 can stabilize mismatch-containing base triplets, whereas Rad51 cannot. Here, we demonstrate that this difference can be attributed to three amino acids conserved only within the Dmc1 lineage of the Rad51/RecA family. Chimeric Rad51 mutants harboring Dmc1-specific amino acids gain the ability to stabilize heteroduplex DNA joints with mismatch-containing base triplets, whereas Dmc1 mutants with Rad51-specific amino acids lose this ability. Remarkably, RAD-51 from Caenorhabditis elegans, an organism without Dmc1, has acquired "Dmc1-like" amino acids. Chimeric C. elegans RAD-51 harboring "canonical" Rad51 amino acids gives rise to toxic recombination intermediates, which must be actively dismantled to permit normal meiotic progression. We propose that Dmc1 lineage-specific amino acids involved in the stabilization of heteroduplex DNA joints with mismatch-containing base triplets may contribute to normal meiotic recombination.
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Affiliation(s)
- Justin B Steinfeld
- Department of Biochemistry and Molecular Biophysics, Columbia University Irving Medical Center, New York, New York 10032, USA
| | - Ondrej Beláň
- DSB Repair Metabolism Laboratory, The Francis Crick Institute, London NW1 1AT, United Kingdom
| | - Youngho Kwon
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center at San Antonio, San Antonio, Texas 78229, USA
| | - Tsuyoshi Terakawa
- Department of Biochemistry and Molecular Biophysics, Columbia University Irving Medical Center, New York, New York 10032, USA
| | - Amr Al-Zain
- Department of Microbiology and Immunology, Columbia University Irving Medical Center, New York, New York 10032, USA
| | - Michael J Smith
- Department of Genetics and Development, Columbia University Irving Medical Center, New York, New York 10032, USA
| | - J Brooks Crickard
- Department of Biochemistry and Molecular Biophysics, Columbia University Irving Medical Center, New York, New York 10032, USA
| | - Zhi Qi
- Center for Quantitative Biology, Peking University-Tsinghua University Joint Center for Life Sciences, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871, China
| | - Weixing Zhao
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center at San Antonio, San Antonio, Texas 78229, USA
| | - Rodney Rothstein
- Department of Genetics and Development, Columbia University Irving Medical Center, New York, New York 10032, USA
| | - Lorraine S Symington
- Department of Microbiology and Immunology, Columbia University Irving Medical Center, New York, New York 10032, USA
| | - Patrick Sung
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center at San Antonio, San Antonio, Texas 78229, USA
| | - Simon J Boulton
- DSB Repair Metabolism Laboratory, The Francis Crick Institute, London NW1 1AT, United Kingdom
| | - Eric C Greene
- Department of Biochemistry and Molecular Biophysics, Columbia University Irving Medical Center, New York, New York 10032, USA
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12
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Zhou H, Song Z, Zhong S, Zuo L, Qi Z, Qu L, Lai L. Mechanism of DNA‐Induced Phase Separation for Transcriptional Repressor VRN1. Angew Chem Int Ed Engl 2019; 58:4858-4862. [DOI: 10.1002/anie.201810373] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2018] [Indexed: 02/02/2023]
Affiliation(s)
- Huabin Zhou
- BNLMSState Key Laboratory for Structural Chemistry of Unstable and Stable Species, Peking-Tsinghua Center for Life Sciences, College of Chemistry and Molecular EngineeringPeking University Beijing 100871 P. R. China
- Center for Quantitative Biology, Peking-Tsinghua Center for Life Sciences, Academy for Advanced Interdisciplinary StudiesPeking University Beijing 100871 P. R. China
| | - Zihan Song
- State Key Laboratory for Protein and Plant Gene ResearchPeking-Tsinghua Center for Life Sciences, College of Life SciencesPeking University Beijing 100871 P. R. China
| | - Sheng Zhong
- State Key Laboratory for Protein and Plant Gene ResearchPeking-Tsinghua Center for Life Sciences, College of Life SciencesPeking University Beijing 100871 P. R. China
| | - Linyu Zuo
- Center for Quantitative Biology, Peking-Tsinghua Center for Life Sciences, Academy for Advanced Interdisciplinary StudiesPeking University Beijing 100871 P. R. China
| | - Zhi Qi
- Center for Quantitative Biology, Peking-Tsinghua Center for Life Sciences, Academy for Advanced Interdisciplinary StudiesPeking University Beijing 100871 P. R. China
| | - Li‐Jia Qu
- State Key Laboratory for Protein and Plant Gene ResearchPeking-Tsinghua Center for Life Sciences, College of Life SciencesPeking University Beijing 100871 P. R. China
- National Plant Gene Research Center Beijing 100101 P. R. China
| | - Luhua Lai
- BNLMSState Key Laboratory for Structural Chemistry of Unstable and Stable Species, Peking-Tsinghua Center for Life Sciences, College of Chemistry and Molecular EngineeringPeking University Beijing 100871 P. R. China
- Center for Quantitative Biology, Peking-Tsinghua Center for Life Sciences, Academy for Advanced Interdisciplinary StudiesPeking University Beijing 100871 P. R. China
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13
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Zhou H, Song Z, Zhong S, Zuo L, Qi Z, Qu L, Lai L. Mechanism of DNA‐Induced Phase Separation for Transcriptional Repressor VRN1. Angew Chem Int Ed Engl 2019. [DOI: 10.1002/ange.201810373] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Huabin Zhou
- BNLMSState Key Laboratory for Structural Chemistry of Unstable and Stable Species, Peking-Tsinghua Center for Life Sciences, College of Chemistry and Molecular EngineeringPeking University Beijing 100871 P. R. China
- Center for Quantitative Biology, Peking-Tsinghua Center for Life Sciences, Academy for Advanced Interdisciplinary StudiesPeking University Beijing 100871 P. R. China
| | - Zihan Song
- State Key Laboratory for Protein and Plant Gene ResearchPeking-Tsinghua Center for Life Sciences, College of Life SciencesPeking University Beijing 100871 P. R. China
| | - Sheng Zhong
- State Key Laboratory for Protein and Plant Gene ResearchPeking-Tsinghua Center for Life Sciences, College of Life SciencesPeking University Beijing 100871 P. R. China
| | - Linyu Zuo
- Center for Quantitative Biology, Peking-Tsinghua Center for Life Sciences, Academy for Advanced Interdisciplinary StudiesPeking University Beijing 100871 P. R. China
| | - Zhi Qi
- Center for Quantitative Biology, Peking-Tsinghua Center for Life Sciences, Academy for Advanced Interdisciplinary StudiesPeking University Beijing 100871 P. R. China
| | - Li‐Jia Qu
- State Key Laboratory for Protein and Plant Gene ResearchPeking-Tsinghua Center for Life Sciences, College of Life SciencesPeking University Beijing 100871 P. R. China
- National Plant Gene Research Center Beijing 100101 P. R. China
| | - Luhua Lai
- BNLMSState Key Laboratory for Structural Chemistry of Unstable and Stable Species, Peking-Tsinghua Center for Life Sciences, College of Chemistry and Molecular EngineeringPeking University Beijing 100871 P. R. China
- Center for Quantitative Biology, Peking-Tsinghua Center for Life Sciences, Academy for Advanced Interdisciplinary StudiesPeking University Beijing 100871 P. R. China
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14
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Crickard JB, Kwon Y, Sung P, Greene EC. Dynamic interactions of the homologous pairing 2 (Hop2)-meiotic nuclear divisions 1 (Mnd1) protein complex with meiotic presynaptic filaments in budding yeast. J Biol Chem 2019; 294:490-501. [PMID: 30420424 PMCID: PMC6333877 DOI: 10.1074/jbc.ra118.006146] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2018] [Revised: 11/02/2018] [Indexed: 12/19/2022] Open
Abstract
Homologous recombination (HR) is a universally conserved DNA repair pathway that can result in the exchange of genetic material. In eukaryotes, HR has evolved into an essential step in meiosis. During meiosis many eukaryotes utilize a two-recombinase pathway. This system consists of Rad51 and the meiosis-specific recombinase Dmc1. Both recombinases have distinct activities during meiotic HR, despite being highly similar in sequence and having closely related biochemical activities, raising the question of how these two proteins can perform separate functions. A likely explanation for their differential regulation involves the meiosis-specific recombination proteins Hop2 and Mnd1, which are part of a highly conserved eukaryotic protein complex that participates in HR, albeit through poorly understood mechanisms. To better understand how Hop2-Mnd1 functions during HR, here we used DNA curtains in conjunction with single-molecule imaging to measure and quantify the binding of the Hop2-Mnd1 complex from Saccharomyces cerevisiae to recombination intermediates comprising Rad51- and Dmc1-ssDNA in real time. We found that yeast Hop2-Mnd1 bound rapidly to Dmc1-ssDNA filaments with high affinity and remained bound for ∼1.3 min before dissociating. We also observed that this binding interaction was highly specific for Dmc1 and found no evidence for an association of Hop2-Mnd1 with Rad51-ssDNA or RPA-ssDNA. Our findings provide new quantitative insights into the binding dynamics of Hop2-Mnd1 with the meiotic presynaptic complex. On the basis of these findings, we propose a model in which recombinase specificities for meiotic accessory proteins enhance separation of the recombinases' functions during meiotic HR.
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Affiliation(s)
- J Brooks Crickard
- From the Department of Biochemistry and Molecular Biophysics, Columbia University, New York, New York 10032
| | - Youngho Kwon
- the Department of Molecular Biophysics and Biochemistry, Yale University School of Medicine, New Haven, Connecticut 06520, and
- the Department of Biochemistry and Structural Biology, University of Texas Health San Antonio, San Antonio, Texas 78229
| | - Patrick Sung
- the Department of Molecular Biophysics and Biochemistry, Yale University School of Medicine, New Haven, Connecticut 06520, and
- the Department of Biochemistry and Structural Biology, University of Texas Health San Antonio, San Antonio, Texas 78229
| | - Eric C Greene
- From the Department of Biochemistry and Molecular Biophysics, Columbia University, New York, New York 10032,
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15
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Abstract
Meiosis is the basis for sexual reproduction and is marked by the sequential reduction of chromosome number during successive cell cycles, resulting in four haploid gametes. A central component of the meiotic program is the formation and repair of programmed double strand breaks. Recombination-driven repair of these meiotic breaks differs from recombination during mitosis in that meiotic breaks are preferentially repaired using the homologous chromosomes in a process known as homolog bias. Homolog bias allows for physical interactions between homologous chromosomes that are required for proper chromosome segregation, and the formation of crossover products ensuring genetic diversity in progeny. An important aspect of meiosis in the differential regulation of the two eukaryotic RecA homologs, Rad51 and Dmc1. In this review we will discuss the relationship between biological programs designed to regulate recombinase function.
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Affiliation(s)
- J Brooks Crickard
- a Department of Biochemistry & Molecular Biophysics , Columbia University , New York , NY , USA
| | - Eric C Greene
- a Department of Biochemistry & Molecular Biophysics , Columbia University , New York , NY , USA
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16
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Crickard JB, Kaniecki K, Kwon Y, Sung P, Lisby M, Greene EC. Regulation of Hed1 and Rad54 binding during maturation of the meiosis-specific presynaptic complex. EMBO J 2018; 37:embj.201798728. [PMID: 29444896 DOI: 10.15252/embj.201798728] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2017] [Revised: 01/03/2018] [Accepted: 01/23/2018] [Indexed: 12/31/2022] Open
Abstract
Most eukaryotes have two Rad51/RecA family recombinases, Rad51, which promotes recombination during mitotic double-strand break (DSB) repair, and the meiosis-specific recombinase Dmc1. During meiosis, the strand exchange activity of Rad51 is downregulated through interactions with the meiosis-specific protein Hed1, which helps ensure that strand exchange is driven by Dmc1 instead of Rad51. Hed1 acts by preventing Rad51 from interacting with Rad54, a cofactor required for promoting strand exchange during homologous recombination. However, we have a poor quantitative understanding of the regulatory interplay between these proteins. Here, we use real-time single-molecule imaging to probe how the Hed1- and Rad54-mediated regulatory network contributes to the identity of mitotic and meiotic presynaptic complexes. Based on our findings, we define a model in which kinetic competition between Hed1 and Rad54 helps define the functional identity of the presynaptic complex as cells undergo the transition from mitotic to meiotic repair.
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Affiliation(s)
- J Brooks Crickard
- Department of Biochemistry & Molecular Biophysics, Columbia University, New York, NY, USA
| | - Kyle Kaniecki
- Department of Genetics and Development, Columbia University, New York, NY, USA
| | - YoungHo Kwon
- Department of Molecular Biophysics and Biochemistry, Yale University School of Medicine, New Haven, CT, USA
| | - Patrick Sung
- Department of Molecular Biophysics and Biochemistry, Yale University School of Medicine, New Haven, CT, USA
| | - Michael Lisby
- Department of Biology, University of Copenhagen, Copenhagen N, Denmark
| | - Eric C Greene
- Department of Biochemistry & Molecular Biophysics, Columbia University, New York, NY, USA
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17
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De Tullio L, Kaniecki K, Greene EC. Single-Stranded DNA Curtains for Studying the Srs2 Helicase Using Total Internal Reflection Fluorescence Microscopy. Methods Enzymol 2018; 600:407-437. [PMID: 29458768 DOI: 10.1016/bs.mie.2017.12.004] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Helicases are crucial participants in many types of DNA repair reactions, including homologous recombination. The properties of these enzymes can be assayed by traditional bulk biochemical analysis; however, these types of assays cannot directly access some types of information. In particular, bulk biochemical assays cannot readily access information that may be obscured in population averages. Single-molecule assays offer the potential advantage of being able to visualize the molecules in question in real time, thus providing direct access to questions relating to translocation velocity, processivity, and insights into how helicases may behave on different types of substrates. Here, we describe the use of single-stranded DNA (ssDNA) curtains as an assay for directly viewing the behavior of the Saccharomyces cerevisiae Srs2 helicase on single molecules of ssDNA. When used with total internal reflection fluorescence microscopy, these methods can be used to track the binding and movements of individual helicase complexes, and allow new insights into helicase behaviors at the single-molecule level.
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18
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Xue H, Bei Y, Zhan Z, Chen X, Xu X, Fu YV. Utilizing Biotinylated Proteins Expressed in Yeast to Visualize DNA-Protein Interactions at the Single-Molecule Level. Front Microbiol 2017; 8:2062. [PMID: 29123507 PMCID: PMC5662892 DOI: 10.3389/fmicb.2017.02062] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2017] [Accepted: 10/09/2017] [Indexed: 11/30/2022] Open
Abstract
Much of our knowledge in conventional biochemistry has derived from bulk assays. However, many stochastic processes and transient intermediates are hidden when averaged over the ensemble. The powerful technique of single-molecule fluorescence microscopy has made great contributions to the understanding of life processes that are inaccessible when using traditional approaches. In single-molecule studies, quantum dots (Qdots) have several unique advantages over other fluorescent probes, such as high brightness, extremely high photostability, and large Stokes shift, thus allowing long-time observation and improved signal-to-noise ratios. So far, however, there is no convenient way to label proteins purified from budding yeast with Qdots. Based on BirA-Avi and biotin-streptavidin systems, we have established a simple method to acquire a Qdot-labeled protein and visualize its interaction with DNA using total internal reflection fluorescence microscopy. For proof-of-concept, we chose replication protein A (RPA) and origin recognition complex (ORC) as the proteins of interest. Proteins were purified from budding yeast with high biotinylation efficiency and rapidly labeled with streptavidin-coated Qdots. Interactions between proteins and DNA were observed successfully at the single-molecule level.
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Affiliation(s)
- Huijun Xue
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
- Savaid Medical School, University of Chinese Academy of Sciences, Beijing, China
| | - Yuanyuan Bei
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
- Savaid Medical School, University of Chinese Academy of Sciences, Beijing, China
| | - Zhengyan Zhan
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
| | - Xiuqiang Chen
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
- Savaid Medical School, University of Chinese Academy of Sciences, Beijing, China
| | - Xin Xu
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
| | - Yu V. Fu
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
- Savaid Medical School, University of Chinese Academy of Sciences, Beijing, China
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19
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The more the merrier: high-throughput single-molecule techniques. Biochem Soc Trans 2017; 45:759-769. [PMID: 28620037 DOI: 10.1042/bst20160137] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2016] [Revised: 03/26/2017] [Accepted: 03/28/2017] [Indexed: 12/24/2022]
Abstract
The single-molecule approach seeks to understand molecular mechanisms by observing biomolecular processes at the level of individual molecules. These methods have led to a developing understanding that for many processes, a diversity of behaviours will be observed, representing a multitude of pathways. This realisation necessitates that an adequate number of observations are recorded to fully characterise this diversity. The requirement for large numbers of observations to adequately sample distributions, subpopulations, and rare events presents a significant challenge for single-molecule techniques, which by their nature do not typically provide very high throughput. This review will discuss many developing techniques which address this issue by combining nanolithographic approaches, such as zero-mode waveguides and DNA curtains, with single-molecule fluorescence microscopy, and by drastically increasing throughput of force-based approaches such as magnetic tweezers and laminar-flow techniques. These methods not only allow the collection of large volumes of single-molecule data in single experiments, but have also made improvements to ease-of-use, accessibility, and automation of data analysis.
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20
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Lee JY, Steinfeld JB, Qi Z, Kwon Y, Sung P, Greene EC. Sequence imperfections and base triplet recognition by the Rad51/RecA family of recombinases. J Biol Chem 2017; 292:11125-11135. [PMID: 28476890 DOI: 10.1074/jbc.m117.787614] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2017] [Revised: 04/27/2017] [Indexed: 11/06/2022] Open
Abstract
Homologous recombination plays key roles in double-strand break repair, rescue, and repair of stalled replication forks and meiosis. The broadly conserved Rad51/RecA family of recombinases catalyzes the DNA strand invasion reaction that takes place during homologous recombination. We have established single-stranded (ss)DNA curtain assays for measuring individual base triplet steps during the early stages of strand invasion. Here, we examined how base triplet stepping by RecA, Rad51, and Dmc1 is affected by DNA sequence imperfections, such as single and multiple mismatches, abasic sites, and single nucleotide insertions. Our work reveals features of base triplet stepping that are conserved among these three phylogenetic lineages of the Rad51/RecA family and also reveals lineage-specific behaviors reflecting properties that are unique to each recombinase. These findings suggest that Dmc1 is tolerant of single mismatches, multiple mismatches, and even abasic sites, whereas RecA and Rad51 are not. Interestingly, the presence of single nucleotide insertion abolishes recognition of an adjacent base triplet by all three recombinases. On the basis of these findings, we describe models for how sequence imperfections may affect base triplet recognition by Rad51/RecA family members, and we discuss how these models and our results may relate to the different biological roles of RecA, Rad51, and Dmc1.
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Affiliation(s)
- Ja Yil Lee
- From the Department of Biochemistry and Molecular Biophysics, Columbia University, New York, New York 10032 and
| | - Justin B Steinfeld
- From the Department of Biochemistry and Molecular Biophysics, Columbia University, New York, New York 10032 and
| | - Zhi Qi
- From the Department of Biochemistry and Molecular Biophysics, Columbia University, New York, New York 10032 and
| | - YoungHo Kwon
- the Department of Molecular Biophysics and Biochemistry, Yale University School of Medicine, New Haven, Connecticut 06510
| | - Patrick Sung
- the Department of Molecular Biophysics and Biochemistry, Yale University School of Medicine, New Haven, Connecticut 06510
| | - Eric C Greene
- From the Department of Biochemistry and Molecular Biophysics, Columbia University, New York, New York 10032 and
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21
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Lewis JH, Jamiolkowski RM, Woody MS, Ostap EM, Goldman YE. Deconvolution of Camera Instrument Response Functions. Biophys J 2017; 112:1214-1220. [PMID: 28355548 DOI: 10.1016/j.bpj.2017.02.014] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2016] [Revised: 02/05/2017] [Accepted: 02/07/2017] [Indexed: 02/03/2023] Open
Abstract
Temporal sequences of fluorescence intensities in single-molecule experiments are often obtained from stacks of camera images. The dwell times of different macromolecular structural or functional states, correlated with characteristic fluorescence intensities, are extracted from the images and combined into dwell time distributions that are fitted by kinetic functions to extract corresponding rate constants. The frame rate of the camera limits the time resolution of the experiment and thus the fastest rate processes that can be reliably detected and quantified. However, including the influence of discrete sampling (framing) on the detected time series in the fitted model enables rate processes near to the frame rate to be reliably estimated. This influence, similar to the instrument response function in other types of instruments, such as pulsed emission decay fluorometers, is easily incorporated into the fitted model. The same concept applies to any temporal data that is low-pass filtered or decimated to improve signal to noise ratio.
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Affiliation(s)
- John H Lewis
- Department of Physiology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania
| | - Ryan M Jamiolkowski
- Department of Physiology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania; Pennsylvania Muscle Institute, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania
| | - Michael S Woody
- Department of Physiology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania; Pennsylvania Muscle Institute, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania
| | - E Michael Ostap
- Department of Physiology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania; Pennsylvania Muscle Institute, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania
| | - Yale E Goldman
- Department of Physiology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania; Pennsylvania Muscle Institute, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania.
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22
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Annealing of Complementary DNA Sequences During Double-Strand Break Repair in Drosophila Is Mediated by the Ortholog of SMARCAL1. Genetics 2017; 206:467-480. [PMID: 28258182 DOI: 10.1534/genetics.117.200238] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2017] [Accepted: 02/22/2017] [Indexed: 12/18/2022] Open
Abstract
DNA double-strand breaks (DSBs) pose a serious threat to genomic integrity. If unrepaired, they can lead to chromosome fragmentation and cell death. If repaired incorrectly, they can cause mutations and chromosome rearrangements. DSBs are repaired using end-joining or homology-directed repair strategies, with the predominant form of homology-directed repair being synthesis-dependent strand annealing (SDSA). SDSA is the first defense against genomic rearrangements and information loss during DSB repair, making it a vital component of cell health and an attractive target for chemotherapeutic development. SDSA has also been proposed to be the primary mechanism for integration of large insertions during genome editing with CRISPR/Cas9. Despite the central role for SDSA in genome stability, little is known about the defining step: annealing. We hypothesized that annealing during SDSA is performed by the annealing helicase SMARCAL1, which can anneal RPA-coated single DNA strands during replication-associated DNA damage repair. We used unique genetic tools in Drosophila melanogaster to test whether the fly ortholog of SMARCAL1, Marcal1, mediates annealing during SDSA. Repair that requires annealing is significantly reduced in Marcal1 null mutants in both synthesis-dependent and synthesis-independent (single-strand annealing) assays. Elimination of the ATP-binding activity of Marcal1 also reduced annealing-dependent repair, suggesting that the annealing activity requires translocation along DNA. Unlike the null mutant, however, the ATP-binding defect mutant showed reduced end joining, shedding light on the interaction between SDSA and end-joining pathways.
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23
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Pavankumar TL, Exell JC, Kowalczykowski SC. Direct Fluorescent Imaging of Translocation and Unwinding by Individual DNA Helicases. Methods Enzymol 2016; 581:1-32. [PMID: 27793277 DOI: 10.1016/bs.mie.2016.09.010] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
The unique translocation and DNA unwinding properties of DNA helicases can be concealed by the stochastic behavior of enzyme molecules within the necessarily large populations used in ensemble experiments. With recent technological advances, the direct visualization of helicases acting on individual DNA molecules has contributed significantly to the current understanding of their mechanisms of action and biological functions. The combination of single-molecule techniques that enable both manipulation of individual protein or DNA molecules and visualization of their actions has made it possible to literally see novel and unique biochemical characteristics that were previously masked. Here, we describe the execution and use of single-molecule fluorescence imaging techniques, focusing on methods that include optical trapping in conjunction with epifluorescent imaging, and also surface immobilization in conjunction with total internal reflection fluorescence visualization. Combined with microchannel flow cells and microfluidic control, these methods allow individual fluorescently labeled protein and DNA molecules to be imaged and tracked, affording measurement of DNA unwinding and translocation at single-molecule resolution.
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Affiliation(s)
| | - J C Exell
- University of California, Davis, CA, United States
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24
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Lee JY, Qi Z, Greene EC. ATP hydrolysis Promotes Duplex DNA Release by the RecA Presynaptic Complex. J Biol Chem 2016; 291:22218-22230. [PMID: 27587394 DOI: 10.1074/jbc.m116.740563] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2016] [Indexed: 01/13/2023] Open
Abstract
Homologous recombination is an important DNA repair pathway that plays key roles in maintaining genome stability. Escherichia coli RecA is an ATP-dependent DNA-binding protein that catalyzes the DNA strand exchange reactions in homologous recombination. RecA assembles into long helical filaments on single-stranded DNA, and these presynaptic complexes are responsible for locating and pairing with a homologous duplex DNA. Recent single molecule studies have provided new insights into RecA behavior, but the potential influence of ATP in the reactions remains poorly understood. Here we examine how ATP influences the ability of the RecA presynaptic complex to interact with homologous dsDNA. We demonstrate that over short time regimes, RecA presynaptic complexes sample heterologous dsDNA similarly in the presence of either ATP or ATPγS, suggesting that initial interactions do not depend on ATP hydrolysis. In addition, RecA stabilizes pairing intermediates in three-base steps, and stepping energetics is seemingly unaltered in the presence of ATP. However, the overall dissociation rate of these paired intermediates with ATP is ∼4-fold higher than with ATPγS. These experiments suggest that ATP plays an unanticipated role in promoting the turnover of captured duplex DNA intermediates as RecA attempts to align homologous sequences during the early stages of recombination.
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Affiliation(s)
- Ja Yil Lee
- From the Department of Biochemistry & Molecular Biophysics, Columbia University, New York, New York 10032 and
| | - Zhi Qi
- the Center of Quantitative Biology & Center of Life Sciences, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, 100871 China
| | - Eric C Greene
- From the Department of Biochemistry & Molecular Biophysics, Columbia University, New York, New York 10032 and
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