1
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Shibata T, Ikawa S, Iwasaki W, Sasanuma H, Masai H, Hirota K. Homology recognition without double-stranded DNA-strand separation in D-loop formation by RecA. Nucleic Acids Res 2024; 52:2565-2577. [PMID: 38214227 PMCID: PMC10954442 DOI: 10.1093/nar/gkad1260] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2023] [Revised: 12/15/2023] [Accepted: 12/30/2023] [Indexed: 01/13/2024] Open
Abstract
RecA protein and RecA/Rad51 orthologues are required for homologous recombination and DNA repair in all living creatures. RecA/Rad51 catalyzes formation of the D-loop, an obligatory recombination intermediate, through an ATP-dependent reaction consisting of two phases: homology recognition between double-stranded (ds)DNA and single-stranded (ss)DNA to form a hybrid-duplex core of 6-8 base pairs and subsequent hybrid-duplex/D-loop processing. How dsDNA recognizes homologous ssDNA is controversial. The aromatic residue at the tip of the β-hairpin loop (L2) was shown to stabilize dsDNA-strand separation. We tested a model in which dsDNA strands were separated by the aromatic residue before homology recognition and found that the aromatic residue was not essential to homology recognition, but was required for D-loop processing. Contrary to the model, we found that the double helix was not unwound even a single turn during search for sequence homology, but rather was unwound only after the homologous sequence was recognized. These results suggest that dsDNA recognizes its homologous ssDNA before strand separation. The search for homologous sequence with homologous ssDNA without dsDNA-strand separation does not generate stress within the dsDNA; this would be an advantage for dsDNA to express homology-dependent functions in vivo and also in vitro.
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Affiliation(s)
- Takehiko Shibata
- Department of Chemistry, Graduate School of Science, Tokyo Metropolitan University, 1-1 Minami Ohsawa, Hachioji, Tokyo 192-0397, Japan
- Genome Dynamics Project, Department of Basic Medical Sciences, Tokyo Metropolitan Institute of Medical Science, 2-1-6 Kamikitazawa, Setagaya-ku, Tokyo 156-8506, Japan
- Cellular & Molecular Biology Laboratory, RIKEN, Wako-shi, Saitama 351-0198, Japan
| | - Shukuko Ikawa
- Cellular & Molecular Biology Laboratory, RIKEN, Wako-shi, Saitama 351-0198, Japan
| | - Wakana Iwasaki
- Laboratory for Translation Structural Biology, RIKEN Center for Biosystems Dynamics Research, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan
| | - Hiroyuki Sasanuma
- Genome Dynamics Project, Department of Basic Medical Sciences, Tokyo Metropolitan Institute of Medical Science, 2-1-6 Kamikitazawa, Setagaya-ku, Tokyo 156-8506, Japan
| | - Hisao Masai
- Genome Dynamics Project, Department of Basic Medical Sciences, Tokyo Metropolitan Institute of Medical Science, 2-1-6 Kamikitazawa, Setagaya-ku, Tokyo 156-8506, Japan
| | - Kouji Hirota
- Department of Chemistry, Graduate School of Science, Tokyo Metropolitan University, 1-1 Minami Ohsawa, Hachioji, Tokyo 192-0397, Japan
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2
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Nautiyal A, Thakur M. Prokaryotic DNA Crossroads: Holliday Junction Formation and Resolution. ACS OMEGA 2024; 9:12515-12538. [PMID: 38524412 PMCID: PMC10956419 DOI: 10.1021/acsomega.3c09866] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/10/2023] [Revised: 02/04/2024] [Accepted: 02/09/2024] [Indexed: 03/26/2024]
Abstract
Cells are continually exposed to a multitude of internal and external stressors, which give rise to various types of DNA damage. To protect the integrity of their genetic material, cells are equipped with a repertoire of repair proteins that engage in various repair mechanisms, facilitated by intricate networks of protein-protein and protein-DNA interactions. Among these networks is the homologous recombination (HR) system, a molecular repair mechanism conserved in all three domains of life. On one hand, HR ensures high-fidelity, template-dependent DNA repair, while on the other hand, it results in the generation of combinatorial genetic variations through allelic exchange. Despite substantial progress in understanding this pathway in bacteria, yeast, and humans, several critical questions remain unanswered, including the molecular processes leading to the exchange of DNA segments, the coordination of protein binding, conformational switching during branch migration, and the resolution of Holliday Junctions (HJs). This Review delves into our current understanding of the HR pathway in bacteria, shedding light on the roles played by various proteins or their complexes at different stages of HR. In the first part of this Review, we provide a brief overview of the end resection processes and the strand-exchange reaction, offering a concise depiction of the mechanisms that culminate in the formation of HJs. In the latter half, we expound upon the alternative methods of branch migration and HJ resolution more comprehensively and holistically, considering the historical research timelines. Finally, when we consolidate our knowledge about HR within the broader context of genome replication and the emergence of resistant species, it becomes evident that the HR pathway is indispensable for the survival of bacteria in diverse ecological niches.
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Affiliation(s)
- Astha Nautiyal
- Department
of Biochemistry, Indian Institute of Science, Bangalore 560012, India
| | - Manoj Thakur
- Sri
Venkateswara College, Benito Juarez Road, University of Delhi, New Delhi 110021, India
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3
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Deveryshetty J, Chadda R, Mattice JR, Karunakaran S, Rau MJ, Basore K, Pokhrel N, Englander N, Fitzpatrick JAJ, Bothner B, Antony E. Yeast Rad52 is a homodecamer and possesses BRCA2-like bipartite Rad51 binding modes. Nat Commun 2023; 14:6215. [PMID: 37798272 PMCID: PMC10556141 DOI: 10.1038/s41467-023-41993-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2023] [Accepted: 09/25/2023] [Indexed: 10/07/2023] Open
Abstract
Homologous recombination (HR) is an essential double-stranded DNA break repair pathway. In HR, Rad52 facilitates the formation of Rad51 nucleoprotein filaments on RPA-coated ssDNA. Here, we decipher how Rad52 functions using single-particle cryo-electron microscopy and biophysical approaches. We report that Rad52 is a homodecameric ring and each subunit possesses an ordered N-terminal and disordered C-terminal half. An intrinsic structural asymmetry is observed where a few of the C-terminal halves interact with the ordered ring. We describe two conserved charged patches in the C-terminal half that harbor Rad51 and RPA interacting motifs. Interactions between these patches regulate ssDNA binding. Surprisingly, Rad51 interacts with Rad52 at two different bindings sites: one within the positive patch in the disordered C-terminus and the other in the ordered ring. We propose that these features drive Rad51 nucleation onto a single position on the DNA to promote formation of uniform pre-synaptic Rad51 filaments in HR.
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Affiliation(s)
- Jaigeeth Deveryshetty
- Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, MO, USA
| | - Rahul Chadda
- Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, MO, USA
| | - Jenna R Mattice
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, MT, USA
| | - Simrithaa Karunakaran
- Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, MO, USA
| | - Michael J Rau
- Center for Cellular Imaging, Washington University in St. Louis School of Medicine, St. Louis, MO, USA
| | - Katherine Basore
- Center for Cellular Imaging, Washington University in St. Louis School of Medicine, St. Louis, MO, USA
| | - Nilisha Pokhrel
- Department of Biological Sciences, Marquette University, Milwaukee, WI, USA
- Aera Therapeutics, Boston, MA, USA
| | - Noah Englander
- Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, MO, USA
| | - James A J Fitzpatrick
- Center for Cellular Imaging, Washington University in St. Louis School of Medicine, St. Louis, MO, USA
| | - Brian Bothner
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, MT, USA
| | - Edwin Antony
- Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, MO, USA.
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4
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Deveryshetty J, Chadda R, Mattice J, Karunakaran S, Rau MJ, Basore K, Pokhrel N, Englander N, Fitzpatrick JA, Bothner B, Antony E. Homodecameric Rad52 promotes single-position Rad51 nucleation in homologous recombination. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.02.05.527205. [PMID: 36778491 PMCID: PMC9915710 DOI: 10.1101/2023.02.05.527205] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Homologous recombination (HR) is a pathway for the accurate repair of double-stranded DNA breaks. These breaks are resected to yield single-stranded DNA (ssDNA) that are coated by Replication Protein A (RPA). Saccharomyces cerevisiae Rad52 is a mediator protein that promotes HR by facilitating formation of Rad51 nucleoprotein filaments on RPA-coated ssDNA. Canonically, Rad52 has been described to function by displacing RPA to promote Rad51 binding. However, in vitro, Rad51 readily forms a filament by displacing RPA in the absence of Rad52. Yet, in vivo, Rad52 is essential for HR. Here, we resolve how Rad52 functions as a mediator using single-particle cryo-electron microscopy and biophysical approaches. We show that Rad52 functions as a homodecamer and catalyzes single-position nucleation of Rad51. The N-terminal half of Rad52 is a well-ordered ring, while the C-terminal half is disordered. An intrinsic asymmetry within Rad52 is observed, where one or a few of the C-terminal halves interact with the ordered N-terminal ring. Within the C-terminal half, we identify two conserved charged patches that harbor the Rad51 and RPA interacting motifs. Interactions between these two charged patches regulate a ssDNA binding. These features drive Rad51 binding to a single position on the Rad52 decameric ring. We propose a Rad52 catalyzed single-position nucleation model for the formation of pre-synaptic Rad51 filaments in HR.
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Affiliation(s)
- Jaigeeth Deveryshetty
- Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, MO
| | - Rahul Chadda
- Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, MO
| | - Jenna Mattice
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, MT
| | - Simrithaa Karunakaran
- Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, MO
| | - Michael J. Rau
- Center for Cellular Imaging, Washington University in St. Louis School of Medicine, St. Louis, MO
| | - Katherine Basore
- Center for Cellular Imaging, Washington University in St. Louis School of Medicine, St. Louis, MO
| | - Nilisha Pokhrel
- Department of Biological Sciences, Marquette University, Milwaukee, WI (Present address: Aera Therapeutics, Boston, MA, USA)
| | - Noah Englander
- Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, MO
| | - James A.J. Fitzpatrick
- Center for Cellular Imaging, Washington University in St. Louis School of Medicine, St. Louis, MO
| | - Brian Bothner
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, MT
| | - Edwin Antony
- Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, MO
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5
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Yu F, Zhang D, Zhao C, Zhao Q, Jiang G, Wang H. Flanking strand separation activity of RecA nucleoprotein filaments in DNA strand exchange reactions. Nucleic Acids Res 2023; 51:2270-2283. [PMID: 36807462 PMCID: PMC10018334 DOI: 10.1093/nar/gkad078] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2022] [Revised: 01/20/2023] [Accepted: 01/28/2023] [Indexed: 02/22/2023] Open
Abstract
The recombinase RecA/Rad51 ATPase family proteins catalyze paramount DNA strand exchange reactions that are critically involved in maintaining genome integrity. However, it remains unclear how DNA strand exchange proceeds when encountering RecA-free defects in recombinase nucleoprotein filaments. Herein, by designing a series of unique substrates (e.g. truncated or conjugated incoming single-stranded DNA, and extended donor double-stranded DNA) and developing a two-color alternating excitation-modified single-molecule real-time fluorescence imaging assay, we resolve the two key steps (donor strand separation and new base-pair formation) that are usually inseparable during the reaction, revealing a novel long-range flanking strand separation activity of synaptic RecA nucleoprotein filaments. We further evaluate the kinetics and free energetics of strand exchange reactions mediated by various substrates, and elucidate the mechanism of flanking strand separation. Based on these findings, we propose a potential fundamental molecular model involved in flanking strand separation, which provides new insights into strand exchange mechanism and homologous recombination.
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Affiliation(s)
- Fangzhi Yu
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
| | - Dapeng Zhang
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
- School of Environment, Hangzhou Institute for Advanced Study, UCAS, Hangzhou 310024, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Chubin Zhao
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
- School of Environment, Hangzhou Institute for Advanced Study, UCAS, Hangzhou 310024, China
| | - Qiang Zhao
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
- School of Environment, Hangzhou Institute for Advanced Study, UCAS, Hangzhou 310024, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Guibin Jiang
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
- School of Environment, Hangzhou Institute for Advanced Study, UCAS, Hangzhou 310024, China
- School of Environment and Health, Jianghan University, Wuhan 430056, China
- University of Chinese Academy of Sciences, Beijing 100049, China
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6
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Korkmazhan E, Dunn AR. The membrane-actin linker ezrin acts as a sliding anchor. SCIENCE ADVANCES 2022; 8:eabo2779. [PMID: 35930643 PMCID: PMC9355349 DOI: 10.1126/sciadv.abo2779] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
Protein linkages to filamentous (F)-actin provide the cell membrane with mechanical stability and support intricate membrane architectures. However, the actin cytoskeleton is highly dynamic and undergoes rapid changes in shape during cell motility and other processes. The molecular mechanisms that generate a mechanically robust yet fluid connection between the membrane and actin cytoskeleton remain poorly understood. Here, we adapted a single-molecule optical trap assay to examine how the prototypical membrane-actin linker ezrin acts to anchor F-actin to the cell membrane. We find that ezrin forms a complex that slides along F-actin over micrometer distances while resisting detachment by forces oriented perpendicular to the filament axis. The ubiquity of ezrin and analogous proteins suggests that sliding anchors such as ezrin may constitute an important but overlooked element in the construction of the actin cytoskeleton.
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Affiliation(s)
- Elgin Korkmazhan
- Department of Chemical Engineering, Stanford University, Stanford, CA 94305 USA
- Graduate Program in Biophysics, Stanford University, Stanford, CA 94305 USA
| | - Alexander R. Dunn
- Department of Chemical Engineering, Stanford University, Stanford, CA 94305 USA
- Corresponding author.
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7
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Chevigny N, Weber-Lotfi F, Le Blevenec A, Nadiras C, Fertet A, Bichara M, Erhardt M, Dietrich A, Raynaud C, Gualberto JM. RADA-dependent branch migration has a predominant role in plant mitochondria and its defect leads to mtDNA instability and cell cycle arrest. PLoS Genet 2022; 18:e1010202. [PMID: 35550632 PMCID: PMC9129000 DOI: 10.1371/journal.pgen.1010202] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2022] [Revised: 05/24/2022] [Accepted: 04/14/2022] [Indexed: 12/21/2022] Open
Abstract
Mitochondria of flowering plants have large genomes whose structure and segregation are modulated by recombination activities. The post-synaptic late steps of mitochondrial DNA (mtDNA) recombination are still poorly characterized. Here we show that RADA, a plant ortholog of bacterial RadA/Sms, is an organellar protein that drives the major branch-migration pathway of plant mitochondria. While RadA/Sms is dispensable in bacteria, RADA-deficient Arabidopsis plants are severely impacted in their development and fertility, correlating with increased mtDNA recombination across intermediate-size repeats and accumulation of recombination-generated mitochondrial subgenomes. The radA mutation is epistatic to recG1 that affects the additional branch migration activity. In contrast, the double mutation radA recA3 is lethal, underlining the importance of an alternative RECA3-dependent pathway. The physical interaction of RADA with RECA2 but not with RECA3 further indicated that RADA is required for the processing of recombination intermediates in the RECA2-depedent recombination pathway of plant mitochondria. Although RADA is dually targeted to mitochondria and chloroplasts we found little to no effects of the radA mutation on the stability of the plastidial genome. Finally, we found that the deficient maintenance of the mtDNA in radA apparently triggers a retrograde signal that activates nuclear genes repressing cell cycle progression. In flowering plants, the mitochondrial genome is very large and dynamic, and its stability influences plant fitness and development. Rearrangements by recombination drive its very rapid evolution and can lead to valuable agronomic traits such as cytoplasmic sterility, used by breeders for the production of hybrid seeds. Here we describe RADA, a DNA helicase essential for the stability of the mitochondrial DNA in Arabidopsis. We demonstrate that RADA has branch migrating activity, accelerating the processing of recombination intermediates. radA mutants are severely affected in development and fertility. They display mitochondrial genome instability that results in uncoordinated replication of subgenomes created by recombination. Furthermore, we found that an important component of the growth defects of radA mutants is apparently a cellular response triggered by the sensing of damages to the mitochondrial genome, resulting in the activation of genes that suppress the progression of the cell cycle. Our results underline the importance of better understanding the plant mitochondrial recombination pathways and their cross-talk with nuclear gene expression.
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Affiliation(s)
- Nicolas Chevigny
- Institut de Biologie Moléculaire des Plantes, CNRS, Université de Strasbourg, Strasbourg, France
| | - Frédérique Weber-Lotfi
- Institut de Biologie Moléculaire des Plantes, CNRS, Université de Strasbourg, Strasbourg, France
| | - Anaïs Le Blevenec
- Institut de Biologie Moléculaire des Plantes, CNRS, Université de Strasbourg, Strasbourg, France
| | - Cédric Nadiras
- Institut de Biologie Moléculaire des Plantes, CNRS, Université de Strasbourg, Strasbourg, France
| | - Arnaud Fertet
- Institut de Biologie Moléculaire des Plantes, CNRS, Université de Strasbourg, Strasbourg, France
| | - Marc Bichara
- Biotechnologie et Signalisation Cellulaire, CNRS, Université de Strasbourg, Illkirch-Graffenstaden, France
| | - Mathieu Erhardt
- Institut de Biologie Moléculaire des Plantes, CNRS, Université de Strasbourg, Strasbourg, France
| | - André Dietrich
- Institut de Biologie Moléculaire des Plantes, CNRS, Université de Strasbourg, Strasbourg, France
| | - Cécile Raynaud
- Université Paris-Saclay, CNRS, INRAE, Univ Evry, Institute of Plant Sciences Paris-Saclay (IPS2), Orsay, France
- Université de Paris, CNRS, INRAE, Institute of Plant Sciences Paris-Saclay (IPS2), Orsay, France
| | - José M. Gualberto
- Institut de Biologie Moléculaire des Plantes, CNRS, Université de Strasbourg, Strasbourg, France
- * E-mail:
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8
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Xu J, Zhao L, Peng S, Chu H, Liang R, Tian M, Connell PP, Li G, Chen C, Wang HW. Mechanisms of distinctive mismatch tolerance between Rad51 and Dmc1 in homologous recombination. Nucleic Acids Res 2021; 49:13135-13149. [PMID: 34871438 PMCID: PMC8682777 DOI: 10.1093/nar/gkab1141] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2021] [Revised: 11/01/2021] [Accepted: 11/27/2021] [Indexed: 12/03/2022] Open
Abstract
Homologous recombination (HR) is a primary DNA double-strand breaks (DSBs) repair mechanism. The recombinases Rad51 and Dmc1 are highly conserved in the RecA family; Rad51 is mainly responsible for DNA repair in somatic cells during mitosis while Dmc1 only works during meiosis in germ cells. This spatiotemporal difference is probably due to their distinctive mismatch tolerance during HR: Rad51 does not permit HR in the presence of mismatches, whereas Dmc1 can tolerate certain mismatches. Here, the cryo-EM structures of Rad51-DNA and Dmc1-DNA complexes revealed that the major conformational differences between these two proteins are located in their Loop2 regions, which contain invading single-stranded DNA (ssDNA) binding residues and double-stranded DNA (dsDNA) complementary strand binding residues, stabilizing ssDNA and dsDNA in presynaptic and postsynaptic complexes, respectively. By combining molecular dynamic simulation and single-molecule FRET assays, we identified that V273 and D274 in the Loop2 region of human RAD51 (hRAD51), corresponding to P274 and G275 of human DMC1 (hDMC1), are the key residues regulating mismatch tolerance during strand exchange in HR. This HR accuracy control mechanism provides mechanistic insights into the specific roles of Rad51 and Dmc1 in DNA double-strand break repair and may shed light on the regulatory mechanism of genetic recombination in mitosis and meiosis.
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Affiliation(s)
- Jingfei Xu
- Ministry of Education Key Laboratory of Protein Sciences, Tsinghua-Peking Joint Center for Life Sciences, Beijing Advanced Innovation Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing, 100084, China
- School of Life Sciences, Beijing Normal University, Beijing, 100875, China
| | - Lingyun Zhao
- Ministry of Education Key Laboratory of Protein Sciences, Tsinghua-Peking Joint Center for Life Sciences, Beijing Advanced Innovation Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing, 100084, China
- Imaging and Characterization Core Lab, King Abdullah University of Science and Technology (KAUST), Thuwal, 23955-6900, Saudi Arabia
| | - Sijia Peng
- Beijing Advanced Innovation Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing, 100084, China
| | - Huiying Chu
- Laboratory of Molecular Modeling and Design, State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Science, 457 Zhongshan Road, Dalian, 116023, China
| | - Rui Liang
- Ministry of Education Key Laboratory of Protein Sciences, Tsinghua-Peking Joint Center for Life Sciences, Beijing Advanced Innovation Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing, 100084, China
| | - Meng Tian
- Ministry of Education Key Laboratory of Protein Sciences, Tsinghua-Peking Joint Center for Life Sciences, Beijing Advanced Innovation Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing, 100084, China
| | - Philip P Connell
- Department of Radiation and Cellular Oncology, University of Chicago, Chicago, IL 60615, USA
| | - Guohui Li
- Laboratory of Molecular Modeling and Design, State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Science, 457 Zhongshan Road, Dalian, 116023, China
| | - Chunlai Chen
- Beijing Advanced Innovation Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing, 100084, China
| | - Hong-Wei Wang
- Ministry of Education Key Laboratory of Protein Sciences, Tsinghua-Peking Joint Center for Life Sciences, Beijing Advanced Innovation Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing, 100084, China
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9
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Kong M, Greene EC. Mechanistic Insights From Single-Molecule Studies of Repair of Double Strand Breaks. Front Cell Dev Biol 2021; 9:745311. [PMID: 34869333 PMCID: PMC8636147 DOI: 10.3389/fcell.2021.745311] [Citation(s) in RCA: 6] [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: 07/21/2021] [Accepted: 10/28/2021] [Indexed: 01/01/2023] Open
Abstract
DNA double strand breaks (DSBs) are among some of the most deleterious forms of DNA damage. Left unrepaired, they are detrimental to genome stability, leading to high risk of cancer. Two major mechanisms are responsible for the repair of DSBs, homologous recombination (HR) and nonhomologous end joining (NHEJ). The complex nature of both pathways, involving a myriad of protein factors functioning in a highly coordinated manner at distinct stages of repair, lend themselves to detailed mechanistic studies using the latest single-molecule techniques. In avoiding ensemble averaging effects inherent to traditional biochemical or genetic methods, single-molecule studies have painted an increasingly detailed picture for every step of the DSB repair processes.
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Affiliation(s)
| | - Eric C. Greene
- Department of Biochemistry and Molecular Biophysics, Columbia University Irving Medical Center, New York, NY, United States
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10
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Yang XW, Liu J. Observing Protein One-Dimensional Sliding: Methodology and Biological Significance. Biomolecules 2021; 11:biom11111618. [PMID: 34827616 PMCID: PMC8615959 DOI: 10.3390/biom11111618] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2021] [Revised: 10/15/2021] [Accepted: 10/16/2021] [Indexed: 11/28/2022] Open
Abstract
One-dimensional (1D) sliding of DNA-binding proteins has been observed by numerous kinetic studies. It appears that many of these sliding events play important roles in a wide range of biological processes. However, one challenge is to determine the physiological relevance of these motions in the context of the protein’s biological function. Here, we discuss methods of measuring protein 1D sliding by highlighting the single-molecule approaches that are capable of visualizing particle movement in real time. We also present recent findings that show how protein sliding contributes to function.
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11
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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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12
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Lee AJ, Endo M, Hobbs JK, Davies AG, Wälti C. Micro-homology intermediates: RecA's transient sampling revealed at the single molecule level. Nucleic Acids Res 2021; 49:1426-1435. [PMID: 33476368 PMCID: PMC7897476 DOI: 10.1093/nar/gkaa1258] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2020] [Revised: 12/12/2020] [Accepted: 01/07/2021] [Indexed: 01/21/2023] Open
Abstract
Recombinase A (RecA) is central to homologous recombination. However, despite significant advances, the mechanism with which RecA is able to orchestrate a search for homology remains elusive. DNA nanostructure-augmented high-speed AFM offers the spatial and temporal resolutions required to study the RecA recombination mechanism directly and at the single molecule level. We present the direct in situ observation of RecA-orchestrated alignment of homologous DNA strands to form a stable recombination product within a supporting DNA nanostructure. We show the existence of subtle and short-lived states in the interaction landscape, which suggests that RecA transiently samples micro-homology at the single RecA monomer-level throughout the search for sequence alignment. These transient interactions form the early steps in the search for sequence homology, prior to the formation of stable pairings at >8 nucleotide seeds. The removal of sequence micro-homology results in the loss of the associated transient sampling at that location.
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Affiliation(s)
- Andrew J Lee
- Bioelectronics, The Pollard Institute, School of Electronic and Electrical Engineering, University of Leeds, Woodhouse lane, Leeds LS2 9JT, UK
| | - Masayuki Endo
- Institute for Integrated Cell-Material Sciences, Kyoto University, Yoshida-ushinomiyacho, Sakyo-ku, Kyoto 606-8501, Japan
| | - Jamie K Hobbs
- Department of Physics and Astronomy, University of Sheffield, Houndsfield Road, Sheffield S3 7RH, UK
| | - A Giles Davies
- Bioelectronics, The Pollard Institute, School of Electronic and Electrical Engineering, University of Leeds, Woodhouse lane, Leeds LS2 9JT, UK
| | - Christoph Wälti
- Bioelectronics, The Pollard Institute, School of Electronic and Electrical Engineering, University of Leeds, Woodhouse lane, Leeds LS2 9JT, UK
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13
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Effects of individual base-pairs on in vivo target search and destruction kinetics of bacterial small RNA. Nat Commun 2021; 12:874. [PMID: 33558533 PMCID: PMC7870926 DOI: 10.1038/s41467-021-21144-0] [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: 09/16/2020] [Accepted: 01/11/2021] [Indexed: 01/30/2023] Open
Abstract
Base-pairing interactions mediate many intermolecular target recognition events. Even a single base-pair mismatch can cause a substantial difference in activity but how such changes influence the target search kinetics in vivo is unknown. Here, we use high-throughput sequencing and quantitative super-resolution imaging to probe the mutants of bacterial small RNA, SgrS, and their regulation of ptsG mRNA target. Mutations that disrupt binding of a chaperone protein, Hfq, and are distal to the mRNA annealing region still decrease the rate of target association, kon, and increase the dissociation rate, koff, showing that Hfq directly facilitates sRNA-mRNA annealing in vivo. Single base-pair mismatches in the annealing region reduce kon by 24-31% and increase koff by 14-25%, extending the time it takes to find and destroy the target by about a third. The effects of disrupting contiguous base-pairing are much more modest than that expected from thermodynamics, suggesting that Hfq buffers base-pair disruptions.
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14
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Shibata T, Iwasaki W, Hirota K. The intrinsic ability of double-stranded DNA to carry out D-loop and R-loop formation. Comput Struct Biotechnol J 2020; 18:3350-3360. [PMID: 33294131 PMCID: PMC7677664 DOI: 10.1016/j.csbj.2020.10.025] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2020] [Revised: 10/22/2020] [Accepted: 10/25/2020] [Indexed: 12/03/2022] Open
Abstract
Double-stranded (ds)DNA, not dsRNA, has an ability to form a homologous complex with single-stranded (ss)DNA or ssRNA of homologous sequence. D-loops and homologous triplexes are homologous complexes formed with ssDNA by RecA/Rad51-family homologous-pairing proteins, and are a key intermediate of homologous (genetic/DNA) recombination. R-loop formation independent of transcription (R-loop formation in trans) was recently found to play roles in gene regulation and development of mammals and plants. In addition, the crRNA-Cas effector complex in CRISPR-Cas systems also relies on R-loop formation to recognize specific target. In homologous complex formation, ssDNA/ssRNA finds a homologous sequence in dsDNA by Watson-Crick base-pairing. crRNA-Cas effector complexes appear to actively melt dsDNA to make its bases available for annealing to crRNA. On the other hand, in D-loop formation and homologous-triplex formation, it is likely that dsDNA recognizes the homologous sequence before the melting of its double helix by using its intrinsic molecular function depending on CH2 at the 2'-position of the deoxyribose, and that the major role of RecA is the extension of ssDNA and the holding dsDNA at a position suitable for homology search. This intrinsic dsDNA function would also play a role in R-loop formation. The dependency of homologous-complex formation on 2'-CH2 of the deoxyribose would explain the absence of homologous complex formation by dsRNA, and dsDNA as sole genome molecule in all cellular organisms.
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Affiliation(s)
- Takehiko Shibata
- Department of Chemistry, Graduate School of Science, Tokyo Metropolitan University, Hachioji, Tokyo, Japan
| | - Wakana Iwasaki
- Laboratory for Translation Structural Biology, RIKEN Center for Biosystems Dynamics Research, Tsurumi, Yokohama, Japan
| | - Kouji Hirota
- Department of Chemistry, Graduate School of Science, Tokyo Metropolitan University, Hachioji, Tokyo, Japan
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15
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You S, Lee HG, Kim K, Yoo J. Improved Parameterization of Protein-DNA Interactions for Molecular Dynamics Simulations of PCNA Diffusion on DNA. J Chem Theory Comput 2020; 16:4006-4013. [PMID: 32543861 DOI: 10.1021/acs.jctc.0c00241] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
As the field of molecular dynamics simulation utilizing the force fields is moving toward more complex systems, the accuracy of intermolecular interactions has become a central issue of the field. Here, we quantitatively evaluate the accuracy of the protein-DNA interactions in AMBER and CHARMM force fields by comparing experimental and simulated diffusion coefficients of proliferating cell nuclear antigen. We find that both force fields underestimate diffusion coefficients by at least an order of magnitude because the interactions between basic amino acids and DNA phosphate groups are too attractive. Then, we propose Lennard-Jones parameters optimized using the experimental osmotic pressure data of model chemicals, by using which one can reproduce the experimental diffusion coefficients. Newly optimized parameters will have a broad impact on general protein-DNA interactions.
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Affiliation(s)
- Seonju You
- Department of Chemistry, Pohang University of Science and Technology, Pohang 37673, Republic of Korea
| | - Hong-Guen Lee
- Division of Advanced Materials Science, Pohang University of Science and Technology, Pohang 37673, Republic of Korea.,Center for Self-Assembly and Complexity, Institute for Basic Science, Pohang 37673, Republic of Korea
| | - Kimoon Kim
- Department of Chemistry, Pohang University of Science and Technology, Pohang 37673, Republic of Korea.,Center for Self-Assembly and Complexity, Institute for Basic Science, Pohang 37673, Republic of Korea
| | - Jejoong Yoo
- Center for Self-Assembly and Complexity, Institute for Basic Science, Pohang 37673, Republic of Korea.,Department of Physics, Sungkyunkwan University, Suwon 16419, Republic of Korea
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16
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Crickard JB, Moevus CJ, Kwon Y, Sung P, Greene EC. Rad54 Drives ATP Hydrolysis-Dependent DNA Sequence Alignment during Homologous Recombination. Cell 2020; 181:1380-1394.e18. [PMID: 32502392 DOI: 10.1016/j.cell.2020.04.056] [Citation(s) in RCA: 61] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2019] [Revised: 03/07/2020] [Accepted: 04/29/2020] [Indexed: 12/30/2022]
Abstract
Homologous recombination (HR) helps maintain genome integrity, and HR defects give rise to disease, especially cancer. During HR, damaged DNA must be aligned with an undamaged template through a process referred to as the homology search. Despite decades of study, key aspects of this search remain undefined. Here, we use single-molecule imaging to demonstrate that Rad54, a conserved Snf2-like protein found in all eukaryotes, switches the search from the diffusion-based pathways characteristic of the basal HR machinery to an active process in which DNA sequences are aligned via an ATP-dependent molecular motor-driven mechanism. We further demonstrate that Rad54 disrupts the donor template strands, enabling the search to take place within a migrating DNA bubble-like structure that is bound by replication protein A (RPA). Our results reveal that Rad54, working together with RPA, fundamentally alters how DNA sequences are aligned during HR.
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Affiliation(s)
- J Brooks Crickard
- Department of Biochemistry & Molecular Biophysics, Columbia University, New York, NY 10032, USA
| | - Corentin J Moevus
- Department of Biochemistry & Molecular Biophysics, Columbia University, New York, NY 10032, USA
| | - Youngho Kwon
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA
| | - Patrick Sung
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA
| | - Eric C Greene
- Department of Biochemistry & Molecular Biophysics, Columbia University, New York, NY 10032, USA.
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17
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Chevigny N, Schatz-Daas D, Lotfi F, Gualberto JM. DNA Repair and the Stability of the Plant Mitochondrial Genome. Int J Mol Sci 2020; 21:E328. [PMID: 31947741 PMCID: PMC6981420 DOI: 10.3390/ijms21010328] [Citation(s) in RCA: 65] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2019] [Revised: 12/27/2019] [Accepted: 01/01/2020] [Indexed: 12/13/2022] Open
Abstract
The mitochondrion stands at the center of cell energy metabolism. It contains its own genome, the mtDNA, that is a relic of its prokaryotic symbiotic ancestor. In plants, the mitochondrial genetic information influences important agronomic traits including fertility, plant vigor, chloroplast function, and cross-compatibility. Plant mtDNA has remarkable characteristics: It is much larger than the mtDNA of other eukaryotes and evolves very rapidly in structure. This is because of recombination activities that generate alternative mtDNA configurations, an important reservoir of genetic diversity that promotes rapid mtDNA evolution. On the other hand, the high incidence of ectopic recombination leads to mtDNA instability and the expression of gene chimeras, with potential deleterious effects. In contrast to the structural plasticity of the genome, in most plant species the mtDNA coding sequences evolve very slowly, even if the organization of the genome is highly variable. Repair mechanisms are probably responsible for such low mutation rates, in particular repair by homologous recombination. Herein we review some of the characteristics of plant organellar genomes and of the repair pathways found in plant mitochondria. We further discuss how homologous recombination is involved in the evolution of the plant mtDNA.
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Affiliation(s)
| | | | | | - José Manuel Gualberto
- Institut de biologie moléculaire des plantes, CNRS, Université de Strasbourg, 67081 Strasbourg, France; (N.C.); (D.S.-D.); (F.L.)
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18
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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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19
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Lin YH, Chu CC, Fan HF, Wang PY, Cox MM, Li HW. A 5'-to-3' strand exchange polarity is intrinsic to RecA nucleoprotein filaments in the absence of ATP hydrolysis. Nucleic Acids Res 2019; 47:5126-5140. [PMID: 30916331 PMCID: PMC6547424 DOI: 10.1093/nar/gkz189] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2018] [Revised: 03/08/2019] [Accepted: 03/11/2019] [Indexed: 01/13/2023] Open
Abstract
RecA is essential to recombinational DNA repair in which RecA filaments mediate the homologous DNA pairing and strand exchange. Both RecA filament assembly and the subsequent DNA strand exchange are directional. Here, we demonstrate that the polarity of DNA strand exchange is embedded within RecA filaments even in the absence of ATP hydrolysis, at least over short DNA segments. Using single-molecule tethered particle motion, we show that successful strand exchange in the presence of ATP proceeds with a 5′-to-3′ polarity, as demonstrated previously. RecA filaments prepared with ATPγS also exhibit a 5′-to-3′ progress of strand exchange, suggesting that the polarity is not determined by RecA disassembly and/or ATP hydrolysis. RecAΔC17 mutants, lacking a C-terminal autoregulatory flap, also promote strand exchange in a 5′-to-3′ polarity in ATPγS, a polarity that is largely lost with this RecA variant when ATP is hydrolyzed. We propose that there is an inherent strand exchange polarity mediated by the structure of the RecA filament groove, associated by conformation changes propagated in a polar manner as DNA is progressively exchanged. ATP hydrolysis is coupled to polar strand exchange over longer distances, and its contribution to the polarity requires an intact RecA C-terminus.
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Affiliation(s)
- Yu-Hsuan Lin
- Department of Chemistry, National Taiwan University, 10617, Taiwan
| | - Chia-Chieh Chu
- Department of Chemistry, National Taiwan University, 10617, Taiwan
| | - Hsiu-Fang Fan
- Department of Life Sciences and Institute of Genome Sciences, National Yang-Ming University, 11221 Taiwan
| | - Pang-Yen Wang
- Department of Chemistry, National Taiwan University, 10617, Taiwan
| | - Michael M Cox
- Department of Biochemistry, University of Wisconsin, Madison, 53706, USA
| | - Hung-Wen Li
- Department of Chemistry, National Taiwan University, 10617, Taiwan
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20
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Brieba LG. Structure-Function Analysis Reveals the Singularity of Plant Mitochondrial DNA Replication Components: A Mosaic and Redundant System. PLANTS 2019; 8:plants8120533. [PMID: 31766564 PMCID: PMC6963530 DOI: 10.3390/plants8120533] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/18/2019] [Revised: 11/18/2019] [Accepted: 11/19/2019] [Indexed: 02/06/2023]
Abstract
Plants are sessile organisms, and their DNA is particularly exposed to damaging agents. The integrity of plant mitochondrial and plastid genomes is necessary for cell survival. During evolution, plants have evolved mechanisms to replicate their mitochondrial genomes while minimizing the effects of DNA damaging agents. The recombinogenic character of plant mitochondrial DNA, absence of defined origins of replication, and its linear structure suggest that mitochondrial DNA replication is achieved by a recombination-dependent replication mechanism. Here, I review the mitochondrial proteins possibly involved in mitochondrial DNA replication from a structural point of view. A revision of these proteins supports the idea that mitochondrial DNA replication could be replicated by several processes. The analysis indicates that DNA replication in plant mitochondria could be achieved by a recombination-dependent replication mechanism, but also by a replisome in which primers are synthesized by three different enzymes: Mitochondrial RNA polymerase, Primase-Helicase, and Primase-Polymerase. The recombination-dependent replication model and primers synthesized by the Primase-Polymerase may be responsible for the presence of genomic rearrangements in plant mitochondria.
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Affiliation(s)
- Luis Gabriel Brieba
- Laboratorio Nacional de Genómica para la Biodiversidad, Centro de Investigación y de Estudios Avanzados del IPN, Apartado Postal 629, Irapuato, Guanajuato C.P. 36821, Mexico
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21
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Mohapatra S, Lin CT, Feng XA, Basu A, Ha T. Single-Molecule Analysis and Engineering of DNA Motors. Chem Rev 2019; 120:36-78. [DOI: 10.1021/acs.chemrev.9b00361] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
| | | | | | | | - Taekjip Ha
- Howard Hughes Medical Institute, Baltimore, Maryland 21205, United States
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22
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Cui TJ, Klein M, Hegge JW, Chandradoss SD, van der Oost J, Depken M, Joo C. Argonaute bypasses cellular obstacles without hindrance during target search. Nat Commun 2019; 10:4390. [PMID: 31558728 PMCID: PMC6763497 DOI: 10.1038/s41467-019-12415-y] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2019] [Accepted: 09/09/2019] [Indexed: 12/13/2022] Open
Abstract
Argonaute (Ago) proteins are key players in both gene regulation (eukaryotes) and host defense (prokaryotes). Acting on single-stranded nucleic-acid substrates, Ago relies on base pairing between a small nucleic-acid guide and its complementary target sequences for specificity. To efficiently scan nucleic-acid chains for targets, Ago diffuses laterally along the substrate and must bypass secondary structures as well as protein barriers. Using single-molecule FRET in conjunction with kinetic modelling, we reveal that target scanning is mediated through loose protein-nucleic acid interactions, allowing Ago to slide short distances over secondary structures, as well as to bypass protein barriers via intersegmental transfer. Our combined single-molecule experiment and kinetic modelling approach may serve as a platform to dissect search processes and study the effect of sequence on search kinetics for other nucleic acid-guided proteins.
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Affiliation(s)
- Tao Ju Cui
- Kavli Institute of Nanoscience and Department of Bionanoscience, Delft University of Technology, Delft, The Netherlands
| | - Misha Klein
- Kavli Institute of Nanoscience and Department of Bionanoscience, Delft University of Technology, Delft, The Netherlands
| | - Jorrit W Hegge
- Laboratory of Microbiology, Department of Agrotechnology and Food Sciences, Wageningen University, Wageningen, The Netherlands
| | - Stanley D Chandradoss
- Kavli Institute of Nanoscience and Department of Bionanoscience, Delft University of Technology, Delft, The Netherlands.,Oxford NanoImaging, Oxford, UK
| | - John van der Oost
- Laboratory of Microbiology, Department of Agrotechnology and Food Sciences, Wageningen University, Wageningen, The Netherlands
| | - Martin Depken
- Kavli Institute of Nanoscience and Department of Bionanoscience, Delft University of Technology, Delft, The Netherlands.
| | - Chirlmin Joo
- Kavli Institute of Nanoscience and Department of Bionanoscience, Delft University of Technology, Delft, The Netherlands.
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23
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RecA kinetically selects homologous DNA by testing a five- or six-nucleotide matching sequence and deforming the second DNA. Q Rev Biophys 2019; 51:e11. [PMID: 30912492 DOI: 10.1017/s0033583518000094] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
RecA family proteins pair two DNAs with the same sequence to promote strand exchange during homologous recombination. To understand how RecA proteins search for and recognize homology, we sought to determine the length of homologous sequence that permits RecA to start its reaction. Specifically, we analyzed the effect of sequence heterogeneity on the association rate of homologous DNA with RecA/single-stranded DNA complex. We assumed that the reaction can start with equal likelihood at any point in the DNA, and that sequence heterogeneity abolishes some possible initiation sites. This analysis revealed that the effective recognition size is five or six nucleotides, larger than the three nucleotides recognized by a RecA monomer. Because the first DNA is elongated 1.5-fold by intercalation of amino acid residues of RecA every three bases, the second bound DNA must be elongated to pair with the first. Because this length is similar to estimates based on the strand-exchange reaction or DNA pair formation, the homology test is likely to occur primarily at the association step. The energetic difference due to the absence of hydrogen bonding is too small to discriminate single-nucleotide heterogeneity over a five- or six-nucleotide sequence. The selection is very likely to be made kinetically, and probably involves some structural factor other than Watson-Crick hydrogen bonding. It would be valuable to determine whether this is also the case for other biological reactions involving DNA base complementarity, such as replication, transcription, and translation.
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24
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Cui TJ, Joo C. Facilitated diffusion of Argonaute-mediated target search. RNA Biol 2019; 16:1093-1107. [PMID: 31068066 PMCID: PMC6693542 DOI: 10.1080/15476286.2019.1616353] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2018] [Revised: 04/29/2019] [Accepted: 05/01/2019] [Indexed: 10/26/2022] Open
Abstract
Argonaute (Ago) proteins are of key importance in many cellular processes. In eukaryotes, Ago can induce translational repression followed by deadenylation and degradation of mRNA molecules through base pairing of microRNAs (miRNAs) with a complementary target on a mRNA sequence. In bacteria, Ago eliminates foreign DNA through base pairing of siDNA (small interfering DNA) with a target on a DNA sequence. Effective targeting activities of Ago require fast recognition of the cognate target sequence among numerous off-target sites. Other target search proteins such as transcription factors (TFs) are known to rely on facilitated diffusion for this goal, but it is undetermined to what extent these small nucleic acid-guided proteins utilize this mechanism. Here, we review recent single-molecule studies on Ago target search. We discuss the consequences of the recent findings on the search mechanism. Furthermore, we discuss the open standing research questions that need to be addressed for a complete picture of facilitated target search by small nucleic acids.
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Affiliation(s)
- Tao Ju Cui
- Kavli Institute of Nanoscience and Department of Bionanoscience, Delft University of Technology, Delft, The Netherlands
| | - Chirlmin Joo
- Kavli Institute of Nanoscience and Department of Bionanoscience, Delft University of Technology, Delft, The Netherlands
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25
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Globyte V, Lee SH, Bae T, Kim JS, Joo C. CRISPR/Cas9 searches for a protospacer adjacent motif by lateral diffusion. EMBO J 2018; 38:embj.201899466. [PMID: 30573670 DOI: 10.15252/embj.201899466] [Citation(s) in RCA: 58] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2018] [Revised: 11/09/2018] [Accepted: 11/15/2018] [Indexed: 12/27/2022] Open
Abstract
The Streptococcus pyogenes CRISPR/Cas9 (SpCas9) nuclease has been widely applied in genetic engineering. Despite its importance in genome editing, aspects of the precise molecular mechanism of Cas9 activity remain ambiguous. In particular, because of the lack of a method with high spatio-temporal resolution, transient interactions between Cas9 and DNA could not be reliably investigated. It therefore remains controversial how Cas9 searches for protospacer adjacent motif (PAM) sequences. We have developed single-molecule Förster resonance energy transfer (smFRET) assays to monitor transient interactions of Cas9 and DNA in real time. Our study shows that Cas9 interacts with the PAM sequence weakly, yet probing neighboring sequences via facilitated diffusion. This dynamic mode of interactions leads to translocation of Cas9 to another PAM nearby and consequently an on-target sequence. We propose a model in which lateral diffusion competes with three-dimensional diffusion and thus is involved in PAM finding and consequently on-target binding. Our results imply that the neighboring sequences can be very important when choosing a target in genetic engineering applications.
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Affiliation(s)
- Viktorija Globyte
- Department of BioNanoScience, Kavli Institute of Nanoscience, Delft University of Technology, Delft, The Netherlands
| | - Seung Hwan Lee
- Department of BioNanoScience, Kavli Institute of Nanoscience, Delft University of Technology, Delft, The Netherlands.,Center for Genome Engineering, Institute for Basic Science, Seoul, Korea
| | - Taegeun Bae
- Center for Genome Engineering, Institute for Basic Science, Seoul, Korea
| | - Jin-Soo Kim
- Center for Genome Engineering, Institute for Basic Science, Seoul, Korea .,Department of Chemistry, Seoul National University, Seoul, Korea
| | - Chirlmin Joo
- Department of BioNanoScience, Kavli Institute of Nanoscience, Delft University of Technology, Delft, The Netherlands
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26
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Shinohara T, Arai N, Iikura Y, Kasagi M, Masuda-Ozawa T, Yamaguchi Y, Suzuki-Nagata K, Shibata T, Mikawa T. Nonfilament-forming RecA dimer catalyzes homologous joint formation. Nucleic Acids Res 2018; 46:10855-10869. [PMID: 30285153 PMCID: PMC6237804 DOI: 10.1093/nar/gky877] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2018] [Accepted: 09/19/2018] [Indexed: 01/18/2023] Open
Abstract
Homologous recombination is essential to genome maintenance, and also to genome diversification. In virtually all organisms, homologous recombination depends on the RecA/Rad51-family recombinases, which catalyze ATP-dependent formation of homologous joints—critical intermediates in homologous recombination. RecA/Rad51 binds first to single-stranded (ss) DNA at a damaged site to form a spiral nucleoprotein filament, after which double-stranded (ds) DNA interacts with the filament to search for sequence homology and to form consecutive base pairs with ssDNA (‘pairing’). How sequence homology is recognized and what exact role filament formation plays remain unknown. We addressed the question of whether filament formation is a prerequisite for homologous joint formation. To this end we constructed a nonpolymerizing (np) head-to-tail-fused RecA dimer (npRecA dimer) and an npRecA monomer. The npRecA dimer bound to ssDNA, but did not form continuous filaments upon binding to DNA; it formed beads-on-string structures exclusively. Although its efficiency was lower, the npRecA dimer catalyzed the formation of D-loops (a type of homologous joint), whereas the npRecA monomer was completely defective. Thus, filament formation contributes to efficiency, but is not essential to sequence-homology recognition and pairing, for which a head-to-tail dimer form of RecA protomer is required and sufficient.
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Affiliation(s)
- Takeshi Shinohara
- Cellular & Molecular Biology Laboratory, RIKEN, 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan
- RIKEN Center for Sustainable Resource Science, 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan
- Department of Supramolecular Biology, Graduate School of Nanobiosciences, Yokohama City University, 1-7-29 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan
| | - Naoto Arai
- Department of Applied Biological Science, Nihon University College of Bioresource Sciences, 1866 Kameino, Fujisawa-shi, Kanagawa 252-0880, Japan
| | - Yukari Iikura
- Cellular & Molecular Biology Laboratory, RIKEN, 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan
- RIKEN Center for Sustainable Resource Science, 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan
| | - Motochika Kasagi
- Cellular & Molecular Biology Laboratory, RIKEN, 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan
- Department of Supramolecular Biology, Graduate School of Nanobiosciences, Yokohama City University, 1-7-29 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan
| | - Tokiha Masuda-Ozawa
- Cellular & Molecular Biology Laboratory, RIKEN, 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan
- Department of Supramolecular Biology, Graduate School of Nanobiosciences, Yokohama City University, 1-7-29 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan
| | - Yuuki Yamaguchi
- Cellular & Molecular Biology Laboratory, RIKEN, 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan
- Department of Supramolecular Biology, Graduate School of Nanobiosciences, Yokohama City University, 1-7-29 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan
| | - Kayo Suzuki-Nagata
- RIKEN Quantitative Biology Center, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan
| | - Takehiko Shibata
- Cellular & Molecular Biology Laboratory, RIKEN, 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan
- RIKEN Center for Sustainable Resource Science, 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan
- Department of Supramolecular Biology, Graduate School of Nanobiosciences, Yokohama City University, 1-7-29 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan
- Department of Chemistry, Graduate School of Science, Tokyo Metropolitan University, Minami-Osawa 1-1, Hachioji-shi, Tokyo 192-0397, Japan
- To whom correspondence should be addressed. Takehiko Shibata. Tel: +81 3 3950 2534; . Correspondence may also be addressed to Tsutomu Mikawa. Tel: +81 45 633 8013;
| | - Tsutomu Mikawa
- Cellular & Molecular Biology Laboratory, RIKEN, 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan
- Department of Supramolecular Biology, Graduate School of Nanobiosciences, Yokohama City University, 1-7-29 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan
- RIKEN Quantitative Biology Center, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan
- RIKEN Center for Biosystems Dynamics Research, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan
- To whom correspondence should be addressed. Takehiko Shibata. Tel: +81 3 3950 2534; . Correspondence may also be addressed to Tsutomu Mikawa. Tel: +81 45 633 8013;
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Manikandan K, Prasad D, Srivastava A, Singh N, Dabeer S, Krishnan A, Muniyappa K, Sinha KM. The second messenger cyclic di-AMP negatively regulates the expression of Mycobacterium smegmatis recA and attenuates DNA strand exchange through binding to the C-terminal motif of mycobacterial RecA proteins. Mol Microbiol 2018; 109:600-614. [PMID: 29873124 DOI: 10.1111/mmi.13991] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/18/2018] [Indexed: 12/26/2022]
Abstract
Cyclic di-GMP and cyclic di-AMP are second messengers produced by a wide variety of bacteria. They influence bacterial cell survival, biofilm formation, virulence and bacteria-host interactions. However, many of their cellular targets and biological effects are yet to be determined. A chemical proteomics approach revealed that Mycobacterium smegmatis RecA (MsRecA) possesses a high-affinity cyclic di-AMP binding activity. We further demonstrate that both cyclic di-AMP and cyclic di-GMP bind specifically to the C-terminal motif of MsRecA and Mycobacterium tuberculosis RecA (MtRecA). Escherichia coli RecA (EcRecA) was devoid of cyclic di-AMP binding but have cyclic di-GMP binding activity. Notably, cyclic di-AMP attenuates the DNA strand exchange promoted by MsRecA as well as MtRecA through the disassembly of RecA nucleoprotein filaments. However, the structure and DNA strand exchange activity of EcRecA nucleoprotein filaments remain largely unaffected. Furthermore, M. smegmatis ΔdisA cells were found to have undetectable RecA levels due to the translational repression of recA mRNA. Consequently, the ΔdisA mutant exhibited enhanced sensitivity to DNA-damaging agents. Altogether, this study points out the importance of sequence diversity among recA genes, the role(s) of cyclic di-AMP and reveals a new mode of negative regulation of recA gene expression, DNA repair and homologous recombination in mycobacteria.
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Affiliation(s)
- Kasi Manikandan
- Institute of Molecular Medicine, 254 Okhla Industrial Estate, Phase 3, New Delh, India
| | - Deepika Prasad
- Department of Biochemistry, Indian Institute of Science, Bangalore, India
| | - Ankita Srivastava
- Institute of Molecular Medicine, 254 Okhla Industrial Estate, Phase 3, New Delh, India
| | - Nirpendra Singh
- Central Instrument Facility, University of Delhi South Campus, New Delhi, India
| | - Sadaf Dabeer
- Institute of Molecular Medicine, 254 Okhla Industrial Estate, Phase 3, New Delh, India
| | - Anuja Krishnan
- Institute of Molecular Medicine, 254 Okhla Industrial Estate, Phase 3, New Delh, India
| | - K Muniyappa
- Department of Biochemistry, Indian Institute of Science, Bangalore, India
| | - Krishna Murari Sinha
- Institute of Molecular Medicine, 254 Okhla Industrial Estate, Phase 3, New Delh, India
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28
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SUN LL, SU YY, GAO YJ, Li W, LYU H, LI B, LI D. Progresses of Single Molecular Fluorescence Resonance Energy Transfer in Studying Biomacromolecule Dynamic Process. CHINESE JOURNAL OF ANALYTICAL CHEMISTRY 2018. [DOI: 10.1016/s1872-2040(18)61088-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
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Abstract
Most everyday processes in life involve a necessity for an entity to locate its target. On a cellular level, many proteins have to find their target to perform their function. From gene-expression regulation to DNA repair to host defense, numerous nucleic acid-interacting proteins use distinct target search mechanisms. Several proteins achieve that with the help of short RNA strands known as guides. This review focuses on single-molecule advances studying the target search and recognition mechanism of Argonaute and CRISPR (clustered regularly interspaced short palindromic repeats) systems. We discuss different steps involved in search and recognition, from the initial complex prearrangement into the target-search competent state to the final proofreading steps. We focus on target search mechanisms that range from weak interactions, to one- and three-dimensional diffusion, to conformational proofreading. We compare the mechanisms of Argonaute and CRISPR with a well-studied target search system, RecA.
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Affiliation(s)
- Viktorija Globyte
- Kavli Institute of Nanoscience and Department of Bionanoscience, Delft University of Technology, 2629 HZ Delft, The Netherlands; , ,
| | - Sung Hyun Kim
- Kavli Institute of Nanoscience and Department of Bionanoscience, Delft University of Technology, 2629 HZ Delft, The Netherlands; , ,
- School of Biological Sciences, Seoul National University, Seoul 08826, Republic of Korea
| | - Chirlmin Joo
- Kavli Institute of Nanoscience and Department of Bionanoscience, Delft University of Technology, 2629 HZ Delft, The Netherlands; , ,
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30
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Braslavsky I, Stavans J. Application of Algebraic Topology to Homologous Recombination of DNA. iScience 2018; 4:64-67. [PMID: 30240753 PMCID: PMC6146625 DOI: 10.1016/j.isci.2018.05.008] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2018] [Revised: 04/30/2018] [Accepted: 05/11/2018] [Indexed: 11/23/2022] Open
Abstract
Brouwer's fixed point theorem, a fundamental theorem in algebraic topology proved more than a hundred years ago, states that given any continuous map from a closed, simply connected set into itself, there is a point that is mapped unto itself. Here we point out the connection between a one-dimensional application of Brouwer's fixed point theorem and a mechanism proposed to explain how extension of single-stranded DNA substrates by recombinases of the RecA superfamily facilitates significantly the search for homologous sequences on long chromosomes. RecA family recombinases stretch their DNA substrates by 1.5 Stretching facilitates the search for homologous genomic targets during recombination This facilitating mechanism derives from a foundational theorem of Algebraic Topology
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Affiliation(s)
- Ido Braslavsky
- The Institute of Biochemistry, Food Science and Nutrition, Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, P.O. Box 12, Rehovot 7610001, Israel.
| | - Joel Stavans
- Department of Physics of Complex Systems, Weizmann Institute of Science, Rehovot 7610001, Israel.
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31
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Abstract
The repair of chromosomal double-strand breaks (DSBs) by homologous recombination is essential to maintain genome integrity. The key step in DSB repair is the RecA/Rad51-mediated process to match sequences at the broken end to homologous donor sequences that can be used as a template to repair the lesion. Here, in reviewing research about DSB repair, I consider the many factors that appear to play important roles in the successful search for homology by several homologous recombination mechanisms. See also the video abstract here: https://youtu.be/vm7-X5uIzS8.
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Affiliation(s)
- James E Haber
- Department of Biology and Rosenstiel Basic Medical Sciences Research Center, Brandeis University, Waltham, MA 02454-9110, USA
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32
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Lee AJ, Endo M, Hobbs JK, Wälti C. Direct Single-Molecule Observation of Mode and Geometry of RecA-Mediated Homology Search. ACS NANO 2018; 12:272-278. [PMID: 29202219 DOI: 10.1021/acsnano.7b06208] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Genomic integrity, when compromised by accrued DNA lesions, is maintained through efficient repair via homologous recombination. For this process the ubiquitous recombinase A (RecA), and its homologues such as the human Rad51, are of central importance, able to align and exchange homologous sequences within single-stranded and double-stranded DNA in order to swap out defective regions. Here, we directly observe the widely debated mechanism of RecA homology searching at a single-molecule level using high-speed atomic force microscopy (HS-AFM) in combination with tailored DNA origami frames to present the reaction targets in a way suitable for AFM-imaging. We show that RecA nucleoprotein filaments move along DNA substrates via short-distance facilitated diffusions, or slides, interspersed with longer-distance random moves, or hops. Importantly, from the specific interaction geometry, we find that the double-stranded substrate DNA resides in the secondary DNA binding-site within the RecA nucleoprotein filament helical groove during the homology search. This work demonstrates that tailored DNA origami, in conjunction with HS-AFM, can be employed to reveal directly conformational and geometrical information on dynamic protein-DNA interactions which was previously inaccessible at an individual single-molecule level.
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Affiliation(s)
- Andrew J Lee
- Bioelectronics, The Pollard Institute, School of Electronic and Electrical Engineering, University of Leeds , Woodhouse Lane, Leeds LS2 9JT, United Kingdom
| | - Masayuki Endo
- Institute for Integrated Cell-Material Sciences, Kyoto University , Yoshida-ushinomiyacho, Sakyo-ku, Kyoto 606-8501, Japan
| | - Jamie K Hobbs
- Department of Physics and Astronomy, University of Sheffield , Houndsfield Road, Sheffield S3 7RH, United Kingdom
| | - Christoph Wälti
- Bioelectronics, The Pollard Institute, School of Electronic and Electrical Engineering, University of Leeds , Woodhouse Lane, Leeds LS2 9JT, United Kingdom
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33
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Gothe HJ, Minneker V, Roukos V. Dynamics of Double-Strand Breaks: Implications for the Formation of Chromosome Translocations. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2018; 1044:27-38. [PMID: 29956289 DOI: 10.1007/978-981-13-0593-1_3] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Illegitimate joining of chromosome breaks can lead to the formation of chromosome translocations, a catastrophic type of genome rearrangements that often plays key roles in tumorigenesis. Emerging evidence suggests that the mobility of broken DNA loci can be an important determinant in partner search and clustering of individual breaks, events that can influence translocation frequency. We summarize here the recent literature on the mechanisms that regulate chromatin movement, focusing on studies exploring the motion properties of double-strand breaks in the context of chromatin, the functional consequences for DNA repair, and the formation of chromosome fusions.
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Lee AJ, Sharma R, Hobbs JK, Wälti C. Cooperative RecA clustering: the key to efficient homology searching. Nucleic Acids Res 2017; 45:11743-11751. [PMID: 28977583 PMCID: PMC5714135 DOI: 10.1093/nar/gkx769] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2017] [Accepted: 08/25/2017] [Indexed: 01/17/2023] Open
Abstract
The mechanism by which pre-synaptic RecA nucleoprotein filaments efficiently locate sequence homology across genomic DNA remains unclear. Here, using atomic force microscopy, we directly investigate the intermediates of the RecA-mediated homologous recombination process and find it to be highly cooperative, involving multiple phases. Initially, the process is dominated by a rapid ‘association’ phase, where multiple filaments interact on the same dsDNA simultaneously. This cooperative nature is reconciled by the observation of localized dense clusters of pre-synaptic filaments interacting with the observed dsDNA molecules. This confinement of reactive species within the vicinity of the dsDNA, is likely to play an important role in ensuring that a high interaction rate between the nucleoprotein filaments and the dsDNA can be achieved. This is followed by a slower ‘resolution’ phase, where the synaptic joints either locate sequence homology and progress to a post-synaptic joint, or dissociate from the dsDNA. Surprisingly, the number of simultaneous synaptic joints decreases rapidly after saturation of the dsDNA population, suggesting a reduction in interaction activity of the RecA filaments. We find that the time-scale of this decay is in line with the time-scale of the dispersion of the RecA filament clusters, further emphasising the important role this cooperative phenomena may play in the RecA-facilitated homology search.
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Affiliation(s)
- Andrew J Lee
- Bioelectronics Group, School of Electronic & Electrical Engineering, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT, UK.,Department of Physics and Astronomy, University of Sheffield, Hounsfield Road, Sheffield, S3 7RH, UK
| | - Rajan Sharma
- Bioelectronics Group, School of Electronic & Electrical Engineering, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT, UK
| | - Jamie K Hobbs
- Department of Physics and Astronomy, University of Sheffield, Hounsfield Road, Sheffield, S3 7RH, UK.,The Krebs Institute, University of Sheffield, Sheffield, S10 2TN, UK
| | - Christoph Wälti
- Bioelectronics Group, School of Electronic & Electrical Engineering, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT, UK
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35
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Abstract
Genetic recombination occurs in all organisms and is vital for genome stability. Indeed, in humans, aberrant recombination can lead to diseases such as cancer. Our understanding of homologous recombination is built upon more than a century of scientific inquiry, but achieving a more complete picture using ensemble biochemical and genetic approaches is hampered by population heterogeneity and transient recombination intermediates. Recent advances in single-molecule and super-resolution microscopy methods help to overcome these limitations and have led to new and refined insights into recombination mechanisms, including a detailed understanding of DNA helicase function and synaptonemal complex structure. The ability to view cellular processes at single-molecule resolution promises to transform our understanding of recombination and related processes.
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36
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High homology is not required at the site of strand invasion during recombinational double-strand break repair in mammalian chromosomes. DNA Repair (Amst) 2017; 60:1-8. [PMID: 29055804 DOI: 10.1016/j.dnarep.2017.10.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2017] [Revised: 09/22/2017] [Accepted: 10/11/2017] [Indexed: 12/23/2022]
Abstract
We investigated the impact of sequence divergence on DNA double-strand break (DSB) repair occurring via recombination in cultured thymidine kinase deficient mouse fibroblasts. We stably transfected cells with a DNA construct harboring a herpes thymidine kinase (tk) gene (the "recipient") rendered nonfunctional by insertion of an oligonucleotide containing the recognition site for endonuclease I-SceI. The construct also contained a closely linked truncated "donor" tk sequence. The donor could potentially restore function to the recipient gene via recombination provoked by induction of a DSB at the I-SceI site in the recipient. Repair events were recoverable by selection for tk-positive clones. The donor contained 33 mismatches relative to the recipient. The mismatches were clustered, forming a localized segment of DNA sequence displaying about 20% divergence relative to the recipient, and the mismatched segment was surrounded by regions of high homology. When the donor was aligned with the recipient, the DSB site in the recipient aligned opposite the mismatched segment, allowing us to potentially capture recombinational repair events initiating between diverged sequences. Previous work demonstrated that mammalian cells effectively avoid recombination between 20% diverged sequences. In the current study we asked whether flanking regions of high homology would enable genetic exchange between highly diverged sequences or, instead, would rejection of exchange between diverged sequences remain unchanged. We found that by surrounding mismatches with high homology, suppression of recombination between diverged sequences was overcome. Strikingly, we recovered a high frequency of gene conversion tracts positioned entirely within the mismatched sequences. We infer that such events were enabled by homologous pairing interactions between sequences surrounding the site of strand invasion. Our results suggest a search for high homology prior to recombination that is not mediated by an invading DNA terminus.
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37
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Structural Foundations of RNA Silencing by Argonaute. J Mol Biol 2017; 429:2619-2639. [PMID: 28757069 DOI: 10.1016/j.jmb.2017.07.018] [Citation(s) in RCA: 90] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2017] [Revised: 07/24/2017] [Accepted: 07/25/2017] [Indexed: 12/19/2022]
Abstract
Nearly every cell in the human body contains a set of programmable gene-silencing proteins named Argonaute. Argonaute proteins mediate gene regulation by small RNAs and thereby contribute to cellular homeostasis during diverse physiological process, such as stem cell maintenance, fertilization, and heart development. Over the last decade, remarkable progress has been made toward understanding Argonaute proteins, small RNAs, and their roles in eukaryotic biology. Here, we review current understanding of Argonaute proteins from a structural prospective and discuss unanswered questions surrounding this fascinating class of enzymes.
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38
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Kochugaeva MP, Shvets AA, Kolomeisky AB. On the Mechanism of Homology Search by RecA Protein Filaments. Biophys J 2017; 112:859-867. [PMID: 28297645 DOI: 10.1016/j.bpj.2017.01.018] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2016] [Revised: 01/20/2017] [Accepted: 01/24/2017] [Indexed: 10/20/2022] Open
Abstract
Genetic stability is a key factor in maintaining, survival, and reproduction of biological cells. It relies on many processes, but one of the most important is a homologous recombination, in which the repair of breaks in double-stranded DNA molecules is taking place with a help of several specific proteins. In bacteria, this task is accomplished by RecA proteins that are active as nucleoprotein filaments formed on single-stranded segments of DNA. A critical step in the homologous recombination is a search for a corresponding homologous region on DNA, which is called a homology search. Recent single-molecule experiments clarified some aspects of this process, but its molecular mechanisms remain not well understood. We developed a quantitative theoretical approach to analyze the homology search. It is based on a discrete-state stochastic model that takes into account the most relevant physical-chemical processes in the system. Using a method of first-passage processes, a full dynamic description of the homology search is presented. It is found that the search dynamics depends on the degree of extension of DNA molecules and on the size of RecA nucleoprotein filaments, in agreement with experimental single-molecule measurements of DNA pairing by RecA proteins. Our theoretical calculations, supported by extensive Monte Carlo computer simulations, provide a molecular description of the mechanisms of the homology search.
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Affiliation(s)
- Maria P Kochugaeva
- Department of Chemistry, Rice University, Houston, Texas; Center for Theoretical Biological Physics, Rice University, Houston, Texas
| | - Alexey A Shvets
- Department of Chemistry, Rice University, Houston, Texas; Center for Theoretical Biological Physics, Rice University, Houston, Texas
| | - Anatoly B Kolomeisky
- Department of Chemistry, Rice University, Houston, Texas; Center for Theoretical Biological Physics, Rice University, Houston, Texas.
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39
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Abstract
The exchange of DNA strands between broken and intact molecules lies at the heart of fundamental cellular processes ranging from repairing DNA damage by homologous recombination to generation of genetic diversity during sexual reproduction. New work by Lee and colleagues utilizes the DNA curtain method, an elegant single-molecule technique, to demonstrate common and idiosyncratic features in the DNA strand exchange mechanisms of three RecA-family recombinases, bacterial RecA, and eukaryotic Rad51 and Dmc1 proteins.
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Affiliation(s)
- Maria Spies
- From the Department of Biochemistry, Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242
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40
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Uranga LA, Reyes ED, Patidar PL, Redman LN, Lusetti SL. The cohesin-like RecN protein stimulates RecA-mediated recombinational repair of DNA double-strand breaks. Nat Commun 2017; 8:15282. [PMID: 28513583 PMCID: PMC5442325 DOI: 10.1038/ncomms15282] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2016] [Accepted: 03/15/2017] [Indexed: 12/12/2022] Open
Abstract
RecN is a cohesin-like protein involved in DNA double-strand break repair in bacteria. The RecA recombinase functions to mediate repair via homologous DNA strand invasion to form D-loops. Here we provide evidence that the RecN protein stimulates the DNA strand invasion step of RecA-mediated recombinational DNA repair. The intermolecular DNA tethering activity of RecN protein described previously cannot fully explain this novel activity since stimulation of RecA function is species-specific and requires RecN ATP hydrolysis. Further, DNA-bound RecA protein increases the rate of ATP hydrolysis catalysed by RecN during the DNA pairing reaction. DNA-dependent RecN ATPase kinetics are affected by RecA protein in a manner suggesting a specific order of protein-DNA assembly, with RecN acting after RecA binds DNA. We present a model for RecN function that includes presynaptic stimulation of the bacterial repair pathway perhaps by contributing to the RecA homology search before ternary complex formation.
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Affiliation(s)
- Lee A. Uranga
- Department of Chemistry and Biochemistry, New Mexico State University, P.O. Box 30001, MSC 3C, Las Cruces, New Mexico 88003, USA
| | - Emigdio D. Reyes
- Department of Chemistry and Biochemistry, New Mexico State University, P.O. Box 30001, MSC 3C, Las Cruces, New Mexico 88003, USA
| | - Praveen L. Patidar
- Department of Chemistry and Biochemistry, New Mexico State University, P.O. Box 30001, MSC 3C, Las Cruces, New Mexico 88003, USA
| | - Lindsay N. Redman
- Department of Chemistry and Biochemistry, New Mexico State University, P.O. Box 30001, MSC 3C, Las Cruces, New Mexico 88003, USA
| | - Shelley L. Lusetti
- Department of Chemistry and Biochemistry, New Mexico State University, P.O. Box 30001, MSC 3C, Las Cruces, New Mexico 88003, USA
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41
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Anand R, Beach A, Li K, Haber J. Rad51-mediated double-strand break repair and mismatch correction of divergent substrates. Nature 2017; 544:377-380. [PMID: 28405019 PMCID: PMC5544500 DOI: 10.1038/nature22046] [Citation(s) in RCA: 93] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2016] [Accepted: 03/06/2017] [Indexed: 01/14/2023]
Abstract
The Rad51 (also known as RecA) family of recombinases executes the critical step in homologous recombination: the search for homologous DNA to serve as a template during the repair of DNA double-strand breaks (DSBs). Although budding yeast Rad51 has been extensively characterized in vitro, the stringency of its search and sensitivity to mismatched sequences in vivo remain poorly defined. Here, in Saccharomyces cerevisiae, we analysed Rad51-dependent break-induced replication in which the invading DSB end and its donor template share a 108-base-pair homology region and the donor carries different densities of single-base-pair mismatches. With every eighth base pair mismatched, repair was about 14% of that of completely homologous sequences. With every sixth base pair mismatched, repair was still more than 5%. Thus, completing break-induced replication in vivo overcomes the apparent requirement for at least 6-8 consecutive paired bases that has been inferred from in vitro studies. When recombination occurs without a protruding nonhomologous 3' tail, the mismatch repair protein Msh2 does not discourage homeologous recombination. However, when the DSB end contains a 3' protruding nonhomologous tail, Msh2 promotes the rejection of mismatched substrates. Mismatch correction of strand invasion heteroduplex DNA is strongly polar, favouring correction close to the DSB end. Nearly all mismatch correction depends on the proofreading activity of DNA polymerase-δ, although the repair proteins Msh2, Mlh1 and Exo1 influence the extent of correction.
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Affiliation(s)
| | - Annette Beach
- Rosenstiel Basic Medical Sciences Research Center and Department of Biology, Brandeis University, Waltham, Massachusetts 02254-9110
| | - Kevin Li
- Rosenstiel Basic Medical Sciences Research Center and Department of Biology, Brandeis University, Waltham, Massachusetts 02254-9110
| | - James Haber
- Rosenstiel Basic Medical Sciences Research Center and Department of Biology, Brandeis University, Waltham, Massachusetts 02254-9110
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42
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Abstract
Ubiquitous conserved processes that repair DNA damage are essential for the maintenance and propagation of genomes over generations. Then again, inaccuracies in DNA transactions and failures to remove mutagenic lesions cause heritable genome changes. Building on decades of research using genetics and biochemistry, unprecedented quantitative insight into DNA repair mechanisms has come from the new-found ability to measure single proteins in vitro and inside individual living cells. This has brought together biologists, chemists, engineers, physicists, and mathematicians to solve long-standing questions about the way in which repair enzymes search for DNA lesions and form protein complexes that act in DNA repair pathways. Furthermore, unexpected discoveries have resulted from capabilities to resolve molecular heterogeneity and cell subpopulations, provoking new questions about the role of stochastic processes in DNA repair and mutagenesis. These studies are leading to new technologies that will find widespread use in basic research, biotechnology, and medicine.
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Affiliation(s)
- Stephan Uphoff
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom; ,
| | - David J Sherratt
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom; ,
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43
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Enhancement of RecA-mediated self-assembly in DNA nanostructures through basepair mismatches and single-strand nicks. Sci Rep 2017; 7:41081. [PMID: 28112216 PMCID: PMC5253629 DOI: 10.1038/srep41081] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2016] [Accepted: 12/14/2016] [Indexed: 12/16/2022] Open
Abstract
The use of DNA as a structural material for nanometre-scale construction has grown extensively over the last decades. The development of more advanced DNA-based materials would benefit from a modular approach enabling the direct assembly of additional elements onto nanostructures after fabrication. RecA-based nucleoprotein filaments encapsulating short ssDNA have been demonstrated as a tool for highly efficient and fully programmable post-hoc patterning of duplex DNA scaffold. However, the underlying assembly process is not fully understood, in particular when patterning complex DNA topologies. Here, we report the effect of basepair-mismatched regions and single-strand nicks in the double-stranded DNA scaffold on the yield of RecA-based assembly. Significant increases in assembly yield are observed upon the introduction of unpaired basepairs directly adjacent to the assembly region. However, when the unpaired regions were introduced further from the assembly site the assembly yield initially decreased as the length of the unpaired region was increased. These results suggest that an unpaired region acts as a kinetic trap for RecA-based nucleoprotein filaments, impeding the assembly mechanism. Conversely, when the unpaired region is located directly adjacent to the assembly site, it leads to an increase in efficiency of RecA patterning owing to increased breathing of the assembly site.
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44
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Probing Nature's Nanomachines One Molecule at a Time. Biophys J 2016; 110:1004-7. [PMID: 26958873 DOI: 10.1016/j.bpj.2016.02.009] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2015] [Accepted: 01/15/2016] [Indexed: 11/20/2022] Open
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45
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Chai R, Zhang C, Tian F, Li H, Yang Q, Song A, Qiu L. Recombination function and recombination kinetics of Escherichia coli single-stranded DNA-binding protein. Sci Bull (Beijing) 2016. [DOI: 10.1007/s11434-016-1160-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Singh D, Sternberg SH, Fei J, Doudna JA, Ha T. Real-time observation of DNA recognition and rejection by the RNA-guided endonuclease Cas9. Nat Commun 2016; 7:12778. [PMID: 27624851 PMCID: PMC5027287 DOI: 10.1038/ncomms12778] [Citation(s) in RCA: 168] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2016] [Accepted: 08/01/2016] [Indexed: 12/16/2022] Open
Abstract
Binding specificity of Cas9-guide RNA complexes to DNA is important for genome-engineering applications; however, how mismatches influence target recognition/rejection kinetics is not well understood. Here we used single-molecule FRET to probe real-time interactions between Cas9-RNA and DNA targets. The bimolecular association rate is only weakly dependent on sequence; however, the dissociation rate greatly increases from <0.006 s(-1) to >2 s(-1) upon introduction of mismatches proximal to protospacer-adjacent motif (PAM), demonstrating that mismatches encountered early during heteroduplex formation induce rapid rejection of off-target DNA. In contrast, PAM-distal mismatches up to 11 base pairs in length, which prevent DNA cleavage, still allow formation of a stable complex (dissociation rate <0.006 s(-1)), suggesting that extremely slow rejection could sequester Cas9-RNA, increasing the Cas9 expression level necessary for genome-editing, thereby aggravating off-target effects. We also observed at least two different bound FRET states that may represent distinct steps in target search and proofreading.
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Affiliation(s)
- Digvijay Singh
- Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
| | - Samuel H. Sternberg
- Department of Chemistry, University of California, Berkeley, California 94720, USA
| | - Jingyi Fei
- Department of Physics and Center for the Physics of Living Cells, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
- Howard Hughes Medical Institute, Baltimore, Maryland 21205, USA
| | - Jennifer A. Doudna
- Department of Chemistry, University of California, Berkeley, California 94720, USA
- Department of Molecular and Cell Biology, University of California, Berkeley, California 94720, USA
- Howard Hughes Medical Institute, Berkeley, California 94720, USA
- Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
- Innovative Genomics Initiative, University of California, Berkeley, California 94720, USA
| | - Taekjip Ha
- Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
- Department of Physics and Center for the Physics of Living Cells, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
- Howard Hughes Medical Institute, Baltimore, Maryland 21205, USA
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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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48
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Abstract
The repair of DNA by homologous recombination is an essential, efficient, and high-fidelity process that mends DNA lesions formed during cellular metabolism; these lesions include double-stranded DNA breaks, daughter-strand gaps, and DNA cross-links. Genetic defects in the homologous recombination pathway undermine genomic integrity and cause the accumulation of gross chromosomal abnormalities-including rearrangements, deletions, and aneuploidy-that contribute to cancer formation. Recombination proceeds through the formation of joint DNA molecules-homologously paired but metastable DNA intermediates that are processed by several alternative subpathways-making recombination a versatile and robust mechanism to repair damaged chromosomes. Modern biophysical methods make it possible to visualize, probe, and manipulate the individual molecules participating in the intermediate steps of recombination, revealing new details about the mechanics of genetic recombination. We review and discuss the individual stages of homologous recombination, focusing on common pathways in bacteria, yeast, and humans, and place particular emphasis on the molecular mechanisms illuminated by single-molecule methods.
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Affiliation(s)
- Jason C Bell
- Department of Microbiology and Molecular Genetics, and Department of Molecular and Cellular Biology, University of California, Davis, California 95616;
| | - Stephen C Kowalczykowski
- Department of Microbiology and Molecular Genetics, and Department of Molecular and Cellular Biology, University of California, Davis, California 95616;
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49
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Bell JC, Kowalczykowski SC. RecA: Regulation and Mechanism of a Molecular Search Engine. Trends Biochem Sci 2016; 41:491-507. [PMID: 27156117 PMCID: PMC4892382 DOI: 10.1016/j.tibs.2016.04.002] [Citation(s) in RCA: 137] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2016] [Revised: 04/04/2016] [Accepted: 04/05/2016] [Indexed: 11/19/2022]
Abstract
Homologous recombination maintains genomic integrity by repairing broken chromosomes. The broken chromosome is partially resected to produce single-stranded DNA (ssDNA) that is used to search for homologous double-stranded DNA (dsDNA). This homology driven 'search and rescue' is catalyzed by a class of DNA strand exchange proteins that are defined in relation to Escherichia coli RecA, which forms a filament on ssDNA. Here, we review the regulation of RecA filament assembly and the mechanism by which RecA quickly and efficiently searches for and identifies a unique homologous sequence among a vast excess of heterologous DNA. Given that RecA is the prototypic DNA strand exchange protein, its behavior affords insight into the actions of eukaryotic RAD51 orthologs and their regulators, BRCA2 and other tumor suppressors.
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Affiliation(s)
- Jason C Bell
- Department of Microbiology and Molecular Genetics and Department of Molecular and Cellular Biology, University of California, Davis, CA 95616, USA
| | - Stephen C Kowalczykowski
- Department of Microbiology and Molecular Genetics and Department of Molecular and Cellular Biology, University of California, Davis, CA 95616, USA.
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50
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Klein M, Chandradoss SD, Depken M, Joo C. Why Argonaute is needed to make microRNA target search fast and reliable. Semin Cell Dev Biol 2016; 65:20-28. [PMID: 27235676 DOI: 10.1016/j.semcdb.2016.05.017] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2016] [Revised: 05/19/2016] [Accepted: 05/21/2016] [Indexed: 10/21/2022]
Abstract
MicroRNA (miRNA) interferes with the translation of cognate messenger RNA (mRNA) by finding, preferentially binding, and marking it for degradation. To facilitate the search process, Argonaute (Ago) proteins come together with miRNA, forming a dynamic search complex. In this review we use the language of free-energy landscapes to discuss recent single-molecule and high-resolution structural data in the light of theoretical work appropriated from the study of transcription-factor search. We suggest that experimentally observed internal states of the Ago-miRNA search complex may have the explicit biological function of speeding up search while maintaining specificity.
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Affiliation(s)
- Misha Klein
- Kavli Institute of NanoScience and Department of BioNanoScience, Delft University of Technology, Delft, 2629HZ, The Netherlands
| | - Stanley D Chandradoss
- Kavli Institute of NanoScience and Department of BioNanoScience, Delft University of Technology, Delft, 2629HZ, The Netherlands
| | - Martin Depken
- Kavli Institute of NanoScience and Department of BioNanoScience, Delft University of Technology, Delft, 2629HZ, The Netherlands.
| | - Chirlmin Joo
- Kavli Institute of NanoScience and Department of BioNanoScience, Delft University of Technology, Delft, 2629HZ, The Netherlands.
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