1
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Zhang D, Xu S, Luo Z, Lin Z. MOC1 cleaves Holliday junctions through a cooperative nick and counter-nick mechanism mediated by metal ions. Nat Commun 2024; 15:5140. [PMID: 38886375 PMCID: PMC11183143 DOI: 10.1038/s41467-024-49490-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2023] [Accepted: 06/06/2024] [Indexed: 06/20/2024] Open
Abstract
Holliday junction resolution is a crucial process in homologous recombination and DNA double-strand break repair. Complete Holliday junction resolution requires two stepwise incisions across the center of the junction, but the precise mechanism of metal ion-catalyzed Holliday junction cleavage remains elusive. Here, we perform a metal ion-triggered catalysis in crystals to investigate the mechanism of Holliday junction cleavage by MOC1. We capture the structures of MOC1 in complex with a nicked Holliday junction at various catalytic states, including the ground state, the one-metal ion binding state, and the two-metal ion binding state. Moreover, we also identify a third metal ion that may aid in the nucleophilic attack on the scissile phosphate. Further structural and biochemical analyses reveal a metal ion-mediated allosteric regulation between the two active sites, contributing to the enhancement of the second strand cleavage following the first strand cleavage, as well as the precise symmetric cleavage across the Holliday junction. Our work provides insights into the mechanism of metal ion-catalyzed Holliday junction resolution by MOC1, with implications for understanding how cells preserve genome integrity during the Holliday junction resolution phase.
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Affiliation(s)
- Danping Zhang
- College of Chemistry, Fuzhou University, Fuzhou, 350108, China
| | - Shenjie Xu
- MOE Key Laboratory of Geriatric Diseases and Immunology, Institute of Molecular Enzymology, School of Biology and Basic Medical Sciences, Suzhou Medical College, Soochow University, Suzhou, 215123, China
| | - Zhipu Luo
- MOE Key Laboratory of Geriatric Diseases and Immunology, Institute of Molecular Enzymology, School of Biology and Basic Medical Sciences, Suzhou Medical College, Soochow University, Suzhou, 215123, China.
| | - Zhonghui Lin
- College of Chemistry, Fuzhou University, Fuzhou, 350108, China.
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2
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Li L, Guo B, Dai L, Liu C, Lin Z. Ebselen and TPI-1, as RecG helicase inhibitors, potently enhance the susceptibility of Pseudomonas aeruginosa to DNA damage agents. Biochem Pharmacol 2024; 222:116051. [PMID: 38354956 DOI: 10.1016/j.bcp.2024.116051] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2023] [Revised: 02/08/2024] [Accepted: 02/08/2024] [Indexed: 02/16/2024]
Abstract
Holliday junction (HJ) is a four-way structured DNA intermediate in processes of homologous recombination and DNA double-stranded break (DSB) repair. In bacteria, HJs are processed via either the RuvABC or RecG-dependent pathways. In addition, RecG also plays a critical role in the reactivation of stalled replication forks, making it an attractive target for antibacterial drug development. Here, we conducted a high-throughput screening targeting the RecG helicase from a common opportunistic pathogen Pseudomonas aeruginosa (Pa). From a library containing 7920 compounds, we identified Ebselen and TPI-1 (2',5'-Dichloro-[1,1'-biphenyl]-2,5-dione) as two potent PaRecG inhibitors, with IC50 values of 0.31 ± 0.02 μM and 1.16 ± 0.06 μM, respectively. Further biochemical analyses suggested that both Ebselen and TPI-1 inhibited the ATPase activity of PaRecG, and hindered its binding to HJ DNA with high selectivity. These compounds, when combined with our previously reported RuvAB inhibitors, resulted in more severe DNA repair defects than the individual treatment, and potently enhanced the susceptibility of P. aeruginosa to the DNA damage agents. This work reports novel small molecule inhibitors of RecG, offering valuable chemical tools for advancing our understanding of RecG's function and mechanism. Additionally, these inhibitors might be further developed as promising antibacterial agents in the fight against P. aeruginosa infections.
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Affiliation(s)
- Longheng Li
- College of Chemistry, Fuzhou University, Fuzhou 350108, China
| | - Binbin Guo
- College of Chemistry, Fuzhou University, Fuzhou 350108, China
| | - Lin Dai
- College of Chemistry, Fuzhou University, Fuzhou 350108, China
| | - Chun Liu
- College of Biological Science and Engineering, Fuzhou University, Fuzhou 350108, China.
| | - Zhonghui Lin
- College of Chemistry, Fuzhou University, Fuzhou 350108, China.
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3
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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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4
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Dai L, Lu L, Zhang X, Wu J, Li J, Lin Z. Identification of small-molecule inhibitors of the DNA repair proteins RuvAB from Pseudomonas aeruginosa. Bioorg Med Chem 2022; 73:117022. [PMID: 36155320 DOI: 10.1016/j.bmc.2022.117022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2022] [Revised: 09/13/2022] [Accepted: 09/14/2022] [Indexed: 11/18/2022]
Abstract
The Holliday junction (HJ) branch migrator RuvAB complex plays a fundamental role during homologous recombination and DNA damage repair, and therefore, is an attractive target for the treatment of bacterial pathogens. Pseudomonas aeruginosa (P. aeruginosa, Pa) is one of the most common clinical opportunistic bacterial pathogens, which can cause a series of life-threatening acute or chronic infections. Here, we performed a high throughput small-molecule screening targeting PaRuvAB using the FRET-based HJ branch migration assay. We identified that corilagin, bardoxolone methyl (BM) and 10-(6'-plastoquinonyl) decyltriphenylphosphonium (SKQ1) could efficiently inhibit the branch migration activity of PaRuvAB, with IC50 values of 0.40 ± 0.04 μM, 0.38 ± 0.05 μM and 4.64 ± 0.27 μM, respectively. Further biochemical and molecular docking analyses demonstrated that corilagin directly bound to PaRuvB at the ATPase domain, and thus prevented ATP hydrolysis. In contrast, BM and SKQ1 acted through blocking the interactions between PaRuvA and HJ DNA. Finally, these compounds were shown to increase the susceptibility of P. aeruginosa to UV-C irradiation. Our work, for the first time, reports the small-molecule inhibitors of RuvA and RuvB from any species, providing valuable chemical tools to dissect the functional role of each individual protein in vivo.
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Affiliation(s)
- Lin Dai
- College of Chemistry, Fuzhou University, Fuzhou 350108, China
| | - Lian Lu
- College of Chemistry, Fuzhou University, Fuzhou 350108, China
| | - Xu Zhang
- College of Chemistry, Fuzhou University, Fuzhou 350108, China
| | - Juhong Wu
- College of Chemistry, Fuzhou University, Fuzhou 350108, China
| | - Jinyu Li
- College of Chemistry, Fuzhou University, Fuzhou 350108, China
| | - Zhonghui Lin
- College of Chemistry, Fuzhou University, Fuzhou 350108, China.
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5
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Versoza CJ, Howell AA, Aftab T, Blanco M, Brar A, Chaffee E, Howell N, Leach W, Lobatos J, Luca M, Maddineni M, Mirji R, Mitra C, Strasser M, Munig S, Patel Z, So M, Sy M, Weiss S, Pfeifer SP. Comparative Genomics of Closely-Related Gordonia Cluster DR Bacteriophages. Viruses 2022; 14:v14081647. [PMID: 36016269 PMCID: PMC9413003 DOI: 10.3390/v14081647] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2022] [Revised: 07/16/2022] [Accepted: 07/25/2022] [Indexed: 12/10/2022] Open
Abstract
Bacteriophages infecting bacteria of the genus Gordonia have increasingly gained interest in the scientific community for their diverse applications in agriculture, biotechnology, and medicine, ranging from biocontrol agents in wastewater management to the treatment of opportunistic pathogens in pulmonary disease patients. However, due to the time and costs associated with experimental isolation and cultivation, host ranges for many bacteriophages remain poorly characterized, hindering a more efficient usage of bacteriophages in these areas. Here, we perform a series of computational genomic inferences to predict the putative host ranges of all Gordonia cluster DR bacteriophages known to date. Our analyses suggest that BiggityBass (as well as several of its close relatives) is likely able to infect host bacteria from a wide range of genera—from Gordonia to Nocardia to Rhodococcus, making it a suitable candidate for future phage therapy and wastewater treatment strategies.
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Affiliation(s)
- Cyril J. Versoza
- Center for Evolution and Medicine, School of Life Sciences, Arizona State University, Tempe, AZ 85281, USA;
| | - Abigail A. Howell
- Biodesign Institute, School of Life Sciences, Arizona State University, Tempe, AZ 85281, USA;
| | - Tanya Aftab
- School of Life Sciences, Arizona State University, Tempe, AZ 85281, USA; (T.A.); (M.B.); (A.B.); (E.C.); (N.H.); (J.L.); (M.L.); (R.M.); (C.M.); (M.S.); (S.M.); (Z.P.); (M.S.); (M.S.); (S.W.)
| | - Madison Blanco
- School of Life Sciences, Arizona State University, Tempe, AZ 85281, USA; (T.A.); (M.B.); (A.B.); (E.C.); (N.H.); (J.L.); (M.L.); (R.M.); (C.M.); (M.S.); (S.M.); (Z.P.); (M.S.); (M.S.); (S.W.)
| | - Akarshi Brar
- School of Life Sciences, Arizona State University, Tempe, AZ 85281, USA; (T.A.); (M.B.); (A.B.); (E.C.); (N.H.); (J.L.); (M.L.); (R.M.); (C.M.); (M.S.); (S.M.); (Z.P.); (M.S.); (M.S.); (S.W.)
| | - Elaine Chaffee
- School of Life Sciences, Arizona State University, Tempe, AZ 85281, USA; (T.A.); (M.B.); (A.B.); (E.C.); (N.H.); (J.L.); (M.L.); (R.M.); (C.M.); (M.S.); (S.M.); (Z.P.); (M.S.); (M.S.); (S.W.)
| | - Nicholas Howell
- School of Life Sciences, Arizona State University, Tempe, AZ 85281, USA; (T.A.); (M.B.); (A.B.); (E.C.); (N.H.); (J.L.); (M.L.); (R.M.); (C.M.); (M.S.); (S.M.); (Z.P.); (M.S.); (M.S.); (S.W.)
- School of Mathematical and Statistical Sciences, Arizona State University, Tempe, AZ 85281, USA;
| | - Willow Leach
- School of Mathematical and Statistical Sciences, Arizona State University, Tempe, AZ 85281, USA;
| | - Jackelyn Lobatos
- School of Life Sciences, Arizona State University, Tempe, AZ 85281, USA; (T.A.); (M.B.); (A.B.); (E.C.); (N.H.); (J.L.); (M.L.); (R.M.); (C.M.); (M.S.); (S.M.); (Z.P.); (M.S.); (M.S.); (S.W.)
| | - Michael Luca
- School of Life Sciences, Arizona State University, Tempe, AZ 85281, USA; (T.A.); (M.B.); (A.B.); (E.C.); (N.H.); (J.L.); (M.L.); (R.M.); (C.M.); (M.S.); (S.M.); (Z.P.); (M.S.); (M.S.); (S.W.)
- School of Molecular Sciences, Arizona State University, Tempe, AZ 85281, USA;
| | - Meghna Maddineni
- School of Molecular Sciences, Arizona State University, Tempe, AZ 85281, USA;
| | - Ruchira Mirji
- School of Life Sciences, Arizona State University, Tempe, AZ 85281, USA; (T.A.); (M.B.); (A.B.); (E.C.); (N.H.); (J.L.); (M.L.); (R.M.); (C.M.); (M.S.); (S.M.); (Z.P.); (M.S.); (M.S.); (S.W.)
| | - Corinne Mitra
- School of Life Sciences, Arizona State University, Tempe, AZ 85281, USA; (T.A.); (M.B.); (A.B.); (E.C.); (N.H.); (J.L.); (M.L.); (R.M.); (C.M.); (M.S.); (S.M.); (Z.P.); (M.S.); (M.S.); (S.W.)
| | - Maria Strasser
- School of Life Sciences, Arizona State University, Tempe, AZ 85281, USA; (T.A.); (M.B.); (A.B.); (E.C.); (N.H.); (J.L.); (M.L.); (R.M.); (C.M.); (M.S.); (S.M.); (Z.P.); (M.S.); (M.S.); (S.W.)
| | - Saige Munig
- School of Life Sciences, Arizona State University, Tempe, AZ 85281, USA; (T.A.); (M.B.); (A.B.); (E.C.); (N.H.); (J.L.); (M.L.); (R.M.); (C.M.); (M.S.); (S.M.); (Z.P.); (M.S.); (M.S.); (S.W.)
| | - Zeel Patel
- School of Life Sciences, Arizona State University, Tempe, AZ 85281, USA; (T.A.); (M.B.); (A.B.); (E.C.); (N.H.); (J.L.); (M.L.); (R.M.); (C.M.); (M.S.); (S.M.); (Z.P.); (M.S.); (M.S.); (S.W.)
| | - Minerva So
- School of Life Sciences, Arizona State University, Tempe, AZ 85281, USA; (T.A.); (M.B.); (A.B.); (E.C.); (N.H.); (J.L.); (M.L.); (R.M.); (C.M.); (M.S.); (S.M.); (Z.P.); (M.S.); (M.S.); (S.W.)
| | - Makena Sy
- School of Life Sciences, Arizona State University, Tempe, AZ 85281, USA; (T.A.); (M.B.); (A.B.); (E.C.); (N.H.); (J.L.); (M.L.); (R.M.); (C.M.); (M.S.); (S.M.); (Z.P.); (M.S.); (M.S.); (S.W.)
| | - Sarah Weiss
- School of Life Sciences, Arizona State University, Tempe, AZ 85281, USA; (T.A.); (M.B.); (A.B.); (E.C.); (N.H.); (J.L.); (M.L.); (R.M.); (C.M.); (M.S.); (S.M.); (Z.P.); (M.S.); (M.S.); (S.W.)
| | - Susanne P. Pfeifer
- Center for Evolution and Medicine, School of Life Sciences, Arizona State University, Tempe, AZ 85281, USA;
- Correspondence:
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6
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Thakur M, Mohan D, Singh AK, Agarwal A, Gopal B, Muniyappa K. Novel insights into ATP-Stimulated Cleavage of branched DNA and RNA Substrates through Structure-Guided Studies of the Holliday Junction Resolvase RuvX. J Mol Biol 2021; 433:167014. [PMID: 33933468 DOI: 10.1016/j.jmb.2021.167014] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2021] [Revised: 04/05/2021] [Accepted: 04/23/2021] [Indexed: 11/18/2022]
Abstract
Much of our understanding of the homologous recombination (HR) machinery hinges on studies using Escherichia coli as a model organism. Interestingly enough, studies on the HR machinery in different bacterial species casts doubt on the universality of the E. coli paradigm. The human pathogen Mycobacterium tuberculosis encodes two Holliday junction (HJ)-resolvase paralogues, namely RuvC and RuvX; however, insights into their structural features and functional relevance is still limited. Here, we report on structure-guided functional studies of the M. tuberculosis RuvX HJ resolvase (MtRuvX). The crystalline MtRuvX is a dimer in the asymmetric unit, and each monomer has a RNAse H fold vis-à-vis RuvC-like nucleases. Interestingly, MtRuvX also contains some unique features, including the residues essential for ATP binding/coordination of Mg2+ ions. Indeed, MtRuvX exhibited an intrinsic, robust ATPase activity, which was further accentuated by DNA cofactors. Structure-guided substitutions of single residues at the ATP binding/Mg2+coordination sites while markedly attenuating the ATPase activity completely abrogated HJ cleavage, indicating an unanticipated relationship between ATP hydrolysis and DNA cleavage. However, the affinity of ATPase-deficient mutants for the HJ was not impaired. Contrary to RuvC, MtRuvX exhibits relaxed substrate specificity, cleaving a variety of branched DNA/RNA substrates. Notably, ATP hydrolysis plays a regulatory role, rendering MtRuvX from a canonical HJ resolvase to a DNA/RNA non-sequence specific endonuclease, indicating a link between HJ resolvase and nucleic acid metabolism. These findings provide novel insights into the structure and dual-functional activities of MtRuvX, and suggest that it may play an important role in DNA/RNA metabolism.
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Affiliation(s)
- Manoj Thakur
- Department of Biochemistry, Indian Institute of Science, Bangalore 560 012, India
| | - Disha Mohan
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore 560 012, India
| | - Ankur Kumar Singh
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore 560 012, India
| | - Ankit Agarwal
- Department of Biochemistry, Indian Institute of Science, Bangalore 560 012, India
| | | | - Kalappa Muniyappa
- Department of Biochemistry, Indian Institute of Science, Bangalore 560 012, India.
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7
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Pérez-Arnaiz P, Dattani A, Smith V, Allers T. Haloferax volcanii-a model archaeon for studying DNA replication and repair. Open Biol 2020; 10:200293. [PMID: 33259746 PMCID: PMC7776575 DOI: 10.1098/rsob.200293] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2020] [Accepted: 11/09/2020] [Indexed: 12/16/2022] Open
Abstract
The tree of life shows the relationship between all organisms based on their common ancestry. Until 1977, it comprised two major branches: prokaryotes and eukaryotes. Work by Carl Woese and other microbiologists led to the recategorization of prokaryotes and the proposal of three primary domains: Eukarya, Bacteria and Archaea. Microbiological, genetic and biochemical techniques were then needed to study the third domain of life. Haloferax volcanii, a halophilic species belonging to the phylum Euryarchaeota, has provided many useful tools to study Archaea, including easy culturing methods, genetic manipulation and phenotypic screening. This review will focus on DNA replication and DNA repair pathways in H. volcanii, how this work has advanced our knowledge of archaeal cellular biology, and how it may deepen our understanding of bacterial and eukaryotic processes.
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Affiliation(s)
| | | | | | - Thorsten Allers
- School of Life Sciences, University of Nottingham, Queen's Medical Centre, Nottingham, UK
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8
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Zettl T, Shi X, Bonilla S, Sedlak SM, Lipfert J, Herschlag D. The structural ensemble of a Holliday junction determined by X-ray scattering interference. Nucleic Acids Res 2020; 48:8090-8098. [PMID: 32597986 PMCID: PMC7641307 DOI: 10.1093/nar/gkaa509] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2019] [Revised: 05/31/2020] [Accepted: 06/26/2020] [Indexed: 11/14/2022] Open
Abstract
The DNA four-way (Holliday) junction is the central intermediate of genetic recombination, yet key aspects of its conformational and thermodynamic properties remain unclear. While multiple experimental approaches have been used to characterize the canonical X-shape conformers under specific ionic conditions, the complete conformational ensemble of this motif, especially at low ionic conditions, remains largely undetermined. In line with previous studies, our single-molecule Förster resonance energy transfer (smFRET) measurements of junction dynamics revealed transitions between two states under high salt conditions, but smFRET could not determine whether there are fast and unresolvable transitions between distinct conformations or a broad ensemble of related states under low and intermediate salt conditions. We therefore used an emerging technique, X-ray scattering interferometry (XSI), to directly probe the conformational ensemble of the Holliday junction across a wide range of ionic conditions. Our results demonstrated that the four-way junction adopts an out-of-plane geometry under low ionic conditions and revealed a conformational state at intermediate ionic conditions previously undetected by other methods. Our results provide critical information to build toward a full description of the conformational landscape of the Holliday junction and underscore the utility of XSI for probing conformational ensembles under a wide range of solution conditions.
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Affiliation(s)
- Thomas Zettl
- Department of Physics, Nanosystems Initiative Munich, and Center for Nanoscience, LMU Munich, 80799 Munich, Germany
- Department of Biochemistry, Stanford University, Stanford, CA 94305, USA
| | - Xuesong Shi
- Department of Biochemistry, Stanford University, Stanford, CA 94305, USA
| | - Steve Bonilla
- Department of Biochemistry, Stanford University, Stanford, CA 94305, USA
- Department of Chemical Engineering, Stanford University, Stanford, CA 94305, USA
| | - Steffen M Sedlak
- Department of Physics, Nanosystems Initiative Munich, and Center for Nanoscience, LMU Munich, 80799 Munich, Germany
| | - Jan Lipfert
- Department of Physics, Nanosystems Initiative Munich, and Center for Nanoscience, LMU Munich, 80799 Munich, Germany
| | - Daniel Herschlag
- Department of Biochemistry, Stanford University, Stanford, CA 94305, USA
- Department of Chemical Engineering, Stanford University, Stanford, CA 94305, USA
- Department of Chemistry, Stanford University, Stanford, CA 94305, USA
- Stanford ChEM-H, Stanford University, Stanford, CA 94305, USA
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9
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Structural basis of sequence-specific Holliday junction cleavage by MOC1. Nat Chem Biol 2019; 15:1241-1248. [PMID: 31611704 DOI: 10.1038/s41589-019-0377-4] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2019] [Accepted: 09/02/2019] [Indexed: 02/04/2023]
Abstract
The Holliday junction (HJ) is a key intermediate during homologous recombination and DNA double-strand break repair. Timely HJ resolution by resolvases is critical for maintaining genome stability. The mechanisms underlying sequence-specific substrate recognition and cleavage by resolvases remain elusive. The monokaryotic chloroplast 1 protein (MOC1) specifically cleaves four-way DNA junctions in a sequence-specific manner. Here, we report the crystal structures of MOC1 from Zea mays, alone or bound to HJ DNA. MOC1 uses a unique β-hairpin to embrace the DNA junction. A base-recognition motif specifically interacts with the junction center, inducing base flipping and pseudobase-pair formation at the strand-exchanging points. Structures of MOC1 bound to HJ and different metal ions support a two-metal ion catalysis mechanism. Further molecular dynamics simulations and biochemical analyses reveal a communication between specific substrate recognition and metal ion-dependent catalysis. Our study thus provides a mechanism for how a resolvase turns substrate specificity into catalytic efficiency.
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10
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Zhou R, Yang O, Déclais AC, Jin H, Gwon GH, Freeman ADJ, Cho Y, Lilley DMJ, Ha T. Junction resolving enzymes use multivalency to keep the Holliday junction dynamic. Nat Chem Biol 2019; 15:269-275. [PMID: 30664685 PMCID: PMC6377835 DOI: 10.1038/s41589-018-0209-y] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2017] [Accepted: 11/30/2018] [Indexed: 11/21/2022]
Abstract
Holliday junction (HJ) resolution by resolving enzymes is essential for chromosome segregation and recombination-mediated DNA repair. HJs undergo two types of structural dynamics that determine the outcome of recombination: conformer exchange between two isoforms and branch migration. However, it is unknown how the preferred branch point and conformer are achieved between enzyme binding and HJ resolution given the extensive binding interactions seen in static crystal structures. Single-molecule fluorescence resonance energy transfer analysis of resolving enzymes from bacteriophages (T7 endonuclease I), bacteria (RuvC), fungi (GEN1) and humans (hMus81-Eme1) showed that both types of HJ dynamics still occur after enzyme binding. These dimeric enzymes use their multivalent interactions to achieve this, going through a partially dissociated intermediate in which the HJ undergoes nearly unencumbered dynamics. This evolutionarily conserved property of HJ resolving enzymes provides previously unappreciated insight on how junction resolution, conformer exchange and branch migration may be coordinated.
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Affiliation(s)
- Ruobo Zhou
- Department of Physics and Center for the Physics of Living Cells, University of Illinois at Urbana-Champaign, Champaign, IL, USA.
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, USA.
| | - Olivia Yang
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins University, Baltimore, MD, USA
| | - Anne-Cécile Déclais
- Cancer Research UK Nucleic Acid Structure Research Group, School of Life Sciences, The University of Dundee, Dundee, UK
| | - Hyeonseok Jin
- Department of Life Science, Pohang University of Science and Technology, Pohang, South Korea
| | - Gwang Hyeon Gwon
- Department of Life Science, Pohang University of Science and Technology, Pohang, South Korea
| | - Alasdair D J Freeman
- Cancer Research UK Nucleic Acid Structure Research Group, School of Life Sciences, The University of Dundee, Dundee, UK
| | - Yunje Cho
- Department of Life Science, Pohang University of Science and Technology, Pohang, South Korea
| | - David M J Lilley
- Cancer Research UK Nucleic Acid Structure Research Group, School of Life Sciences, The University of Dundee, Dundee, UK
| | - Taekjip Ha
- Department of Physics and Center for the Physics of Living Cells, University of Illinois at Urbana-Champaign, Champaign, IL, USA.
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins University, Baltimore, MD, USA.
- Howard Hughes Medical Institute, Baltimore, MD, USA.
- Department of Biophysics, Johns Hopkins University, Baltimore, MD, USA.
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD, USA.
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11
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Sobhy MA, Bralić A, Raducanu VS, Takahashi M, Tehseen M, Rashid F, Zaher MS, Hamdan SM. Resolution of the Holliday junction recombination intermediate by human GEN1 at the single-molecule level. Nucleic Acids Res 2019; 47:1935-1949. [PMID: 30590761 PMCID: PMC6393306 DOI: 10.1093/nar/gky1280] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2018] [Revised: 11/19/2018] [Accepted: 12/13/2018] [Indexed: 01/18/2023] Open
Abstract
Human GEN1 is a cytosolic homologous recombination protein that resolves persisting four-way Holliday junctions (HJ) after the dissolution of the nuclear membrane. GEN1 dimerization has been suggested to play key role in the resolution of the HJ, but the kinetic details of its reaction remained elusive. Here, single-molecule FRET shows how human GEN1 binds the HJ and always ensures its resolution within the lifetime of the GEN1-HJ complex. GEN1 monomer generally follows the isomer bias of the HJ in its initial binding and subsequently distorts it for catalysis. GEN1 monomer remains tightly bound with no apparent dissociation until GEN1 dimer is formed and the HJ is fully resolved. Fast on- and slow off-rates of GEN1 dimer and its increased affinity to the singly-cleaved HJ enforce the forward reaction. Furthermore, GEN1 monomer binds singly-cleaved HJ tighter than intact HJ providing a fail-safe mechanism if GEN1 dimer or one of its monomers dissociates after the first cleavage. The tight binding of GEN1 monomer to intact- and singly-cleaved HJ empowers it as the last resort to process HJs that escape the primary mechanisms.
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Affiliation(s)
- Mohamed A Sobhy
- Laboratory of DNA Replication and Recombination, Biological and Environmental Sciences and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
| | - Amer Bralić
- Laboratory of DNA Replication and Recombination, Biological and Environmental Sciences and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
| | - Vlad-Stefan Raducanu
- Laboratory of DNA Replication and Recombination, Biological and Environmental Sciences and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
| | - Masateru Takahashi
- Laboratory of DNA Replication and Recombination, Biological and Environmental Sciences and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
| | - Muhammad Tehseen
- Laboratory of DNA Replication and Recombination, Biological and Environmental Sciences and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
| | - Fahad Rashid
- Laboratory of DNA Replication and Recombination, Biological and Environmental Sciences and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
| | - Manal S Zaher
- Laboratory of DNA Replication and Recombination, Biological and Environmental Sciences and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
| | - Samir M Hamdan
- Laboratory of DNA Replication and Recombination, Biological and Environmental Sciences and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
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12
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Abstract
Since the first demonstration that CRISPR-Cas systems provide bacteria and archaea with adaptive immunity against phages and plasmids, numerous studies have yielded key insights into the molecular mechanisms governing how these systems attack and degrade foreign DNA. However, the molecular mechanisms underlying the adaptation stage, in which new immunological memory is formed, have until recently represented a major unresolved question. In this Progress article, we discuss recent discoveries that have shown both how foreign DNA is identified by the CRISPR-Cas adaptation machinery and the molecular basis for its integration into the chromosome to form an immunological memory. Furthermore, we describe the roles of each of the specific CRISPR-Cas components that are involved in memory formation, and consider current models for their evolutionary origin.
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13
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Wyatt HDM, Sarbajna S, Matos J, West SC. Coordinated actions of SLX1-SLX4 and MUS81-EME1 for Holliday junction resolution in human cells. Mol Cell 2013; 52:234-47. [PMID: 24076221 DOI: 10.1016/j.molcel.2013.08.035] [Citation(s) in RCA: 223] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2013] [Revised: 07/18/2013] [Accepted: 08/14/2013] [Indexed: 10/26/2022]
Abstract
Holliday junctions (HJs) are four-way DNA intermediates that form during homologous recombination, and their efficient resolution is essential for chromosome segregation. Here, we show that three structure-selective endonucleases, namely SLX1-SLX4, MUS81-EME1, and GEN1, define two pathways of HJ resolution in human cells. One pathway is mediated by GEN1, whereas SLX1-SLX4 and MUS81-EME1 provide a second and genetically distinct pathway (SLX-MUS). Cells depleted for SLX-MUS or GEN1 pathway proteins exhibit severe defects in chromosome segregation and reduced survival. In response to CDK-mediated phosphorylation, SLX1-SLX4 and MUS81-EME1 associate at the G2/M transition to form a stable SLX-MUS holoenzyme, which can be reconstituted in vitro. Biochemical studies show that SLX-MUS is a HJ resolvase that coordinates the active sites of two distinct endonucleases during HJ resolution. This cleavage reaction is more efficient and orchestrated than that mediated by SLX1-SLX4 alone, which exhibits a potent nickase activity that acts promiscuously upon DNA secondary structures.
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Affiliation(s)
- Haley D M Wyatt
- London Research Institute, Cancer Research UK, Clare Hall Laboratories, South Mimms, Herts EN6 3LD, UK
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14
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Schwartz EK, Wright WD, Ehmsen KT, Evans JE, Stahlberg H, Heyer WD. Mus81-Mms4 functions as a single heterodimer to cleave nicked intermediates in recombinational DNA repair. Mol Cell Biol 2012; 32:3065-80. [PMID: 22645308 PMCID: PMC3434506 DOI: 10.1128/mcb.00547-12] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2012] [Accepted: 05/18/2012] [Indexed: 11/20/2022] Open
Abstract
The formation of crossovers is a fundamental genetic process. The XPF-family endonuclease Mus81-Mms4 (Eme1) contributes significantly to crossing over in eukaryotes. A key question is whether Mus81-Mms4 can process Holliday junctions that contain four uninterrupted strands. Holliday junction cleavage requires the coordination of two active sites, necessitating the assembly of two Mus81-Mms4 heterodimers. Contrary to this expectation, we show that Saccharomyces cerevisiae Mus81-Mms4 exists as a single heterodimer both in solution and when bound to DNA substrates in vitro. Consistently, immunoprecipitation experiments demonstrate that Mus81-Mms4 does not multimerize in vivo. Moreover, chromatin-bound Mus81-Mms4 does not detectably form higher-order multimers. We show that Cdc5 kinase activates Mus81-Mms4 nuclease activity on 3' flaps and Holliday junctions in vitro but that activation does not induce a preference for Holliday junctions and does not induce multimerization of the Mus81-Mms4 heterodimer. These data support a model in which Mus81-Mms4 cleaves nicked recombination intermediates such as displacement loops (D-loops), nicked Holliday junctions, or 3' flaps but not intact Holliday junctions with four uninterrupted strands. We infer that Mus81-dependent crossing over occurs in a noncanonical manner that does not involve the coordinated cleavage of classic Holliday junctions.
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Affiliation(s)
| | | | | | - James E. Evans
- Department of Molecular and Cellular Biology, University of California, Davis, Davis, California, USA
| | - Henning Stahlberg
- Center for Cellular Imaging and Nano Analytics, University Basel, Basel, Switzerland
| | - Wolf-Dietrich Heyer
- Department of Microbiology
- Department of Molecular and Cellular Biology, University of California, Davis, Davis, California, USA
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15
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Wheatley E, Pieniazek S, Mukerji I, Beveridge D. Molecular dynamics of a DNA Holliday junction: the inverted repeat sequence d(CCGGTACCGG)₄. Biophys J 2012; 102:552-60. [PMID: 22325278 PMCID: PMC3274787 DOI: 10.1016/j.bpj.2011.11.4023] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2011] [Revised: 11/08/2011] [Accepted: 11/10/2011] [Indexed: 12/01/2022] Open
Abstract
All-atom molecular dynamics (MD) computer simulations have been applied successfully to duplex DNA structures in solution for some years and found to give close accord with observed results. However, the MD force fields have generally not been parameterized against unusual DNA structures, and their use to obtain dynamical models for this class of systems needs to be independently validated. The four-way junction (4WJ), or Holliday junction, is a dynamic DNA structure involved in central cellular processes of homologous replication and double strand break repair. Two conformations are observed in solution: a planar open-X form (OPN) with a mobile center and four duplex arms, and an immobile stacked-X (STX) form with two continuous strands and two crossover strands, stabilized by high salt conditions. To characterize the accuracy of MD modeling on 4WJ, we report a set of explicit solvent MD simulations of ∼100 ns on the repeat sequence d(CCGGTACCGG)(4) starting from the STX structure (PDB code 1dcw), and an OPN structure built for the same sequence. All 4WJ MD simulations converged to a stable STX structure in close accord with the crystal structure. Our MD beginning in the OPN form converts to the STX form spontaneously at both high and low salt conditions, providing a model for the conformational transition. Thus, these simulations provide a successful account of the dynamical structure of the STX form of d(CCGGTACCGG)(4) in solution, and provide new, to our knowledge, information on the conformational stability of the junction and distribution of counterions in the junction interior.
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Affiliation(s)
| | | | - Ishita Mukerji
- Department of Molecular Biology and Biochemistry, and Molecular Biophysics Program, Wesleyan University, Middletown, Connecticut
| | - D.L. Beveridge
- Department of Chemistry, Wesleyan University, Middletown, Connecticut
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16
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Vitoc CI, Mukerji I. HU binding to a DNA four-way junction probed by Förster resonance energy transfer. Biochemistry 2011; 50:1432-41. [PMID: 21230005 PMCID: PMC4724199 DOI: 10.1021/bi1007589] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The Escherichia coli protein HU is a non-sequence-specific DNA-binding protein that interacts with DNA primarily through electrostatic interactions. In addition to nonspecific binding to linear DNA, HU has been shown to bind with nanomolar affinity to discontinuous DNA substrates, such as repair and recombination intermediates. This work specifically examines the HU-four-way junction (4WJ) interaction using fluorescence spectroscopic methods. The conformation of the junction in the presence of different counterions was investigated by Förster resonance energy transfer (FRET) measurements, which revealed an ion-type conformational dependence, where Na(+) yields the most stacked conformation followed by K(+) and Mg(2+). HU binding induces a greater degree of stacking in the Na(+)-stabilized and Mg(2+)-stabilized junctions but not the K(+)-stabilized junction, which is attributed to differences in the size of the ionic radii and potential differences in ion binding sites. Interestingly, junction conformation modulates binding affinity, where HU exhibits the lowest affinity for the Mg(2+)-stabilized form (24 μM(-1)), which is the least stacked conformation. Protein binding to a mixed population of open and stacked forms of the junction leads to nearly complete formation of a protein-stabilized stacked-X junction. These results strongly support a model in which HU binds to and stabilizes the stacked-X conformation.
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Affiliation(s)
- Codruta Iulia Vitoc
- Molecular Biology and Biochemistry Department, Molecular Biophysics Program, Wesleyan University, Middletown, Connecticut 06459-0175
| | - Ishita Mukerji
- Molecular Biology and Biochemistry Department, Molecular Biophysics Program, Wesleyan University, Middletown, Connecticut 06459-0175
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17
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Turnbull C, Hines S, Renwick A, Hughes D, Pernet D, Elliott A, Seal S, Warren-Perry M, Gareth Evans D, Eccles D, Stratton MR, Rahman N. Mutation and association analysis of GEN1 in breast cancer susceptibility. Breast Cancer Res Treat 2010; 124:283-8. [PMID: 20512659 PMCID: PMC3632835 DOI: 10.1007/s10549-010-0949-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2010] [Accepted: 05/11/2010] [Indexed: 10/19/2022]
Abstract
GEN1 was recently identified as a key Holliday junction resolvase involved in homologous recombination. Somatic truncating GEN1 mutations have been reported in two breast cancers. Together these data led to the proposition that GEN1 is a breast cancer predisposition gene. In this article we have formally investigated this hypothesis. We performed full-gene mutational analysis of GEN1 in 176 BRCA1/2-negative familial breast cancer samples and 159 controls. We genotyped six SNPs tagging the 30 common variants in the transcribed region of GEN1 in 3,750 breast cancer cases and 4,907 controls. Mutation analysis revealed one truncating variant, c.2515_2519delAAGTT, which was present in 4% of cases and 4% of controls. We identified control individuals homozygous for the deletion, demonstrating that the last 69 amino acids of GEN1 are dispensable for its function. We identified 17 other variants, but their frequency did not significantly differ between cases and controls. Analysis of 3,750 breast cancer cases and 4,907 controls demonstrated no evidence of significant association with breast cancer for six SNPs tagging the 30 common GEN1 variants. These data indicate that although it also plays a key role in double-strand DNA break repair, GEN1 does not make an appreciable contribution to breast cancer susceptibility by acting as a high- or intermediate-penetrance breast cancer predisposition gene like BRCA1, BRCA2, CHEK2, ATM, BRIP1 and PALB2 and that common GEN1 variants do not act as low-penetrance susceptibility alleles analogous to SNPs in FGFR2. Furthermore, our analyses demonstrate the importance of undertaking appropriate genetic investigations, typically full gene screening in cases and controls together with large-scale case-control association analyses, to evaluate the contribution of genes to cancer susceptibility.
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Affiliation(s)
- Clare Turnbull
- Section of Cancer Genetics, the Institute of Cancer Research, 15 Cotswold Road, Sutton, Surrey SM2 5NG, UK
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18
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Abstract
Four-way DNA (Holliday) junctions are resolved into duplex species by the action of the junction-resolving enzymes, nucleases selective for the structure of helical branchpoints. These have been isolated from bacteria and their phages, archaea, yeasts and mammals, including humans. They are all dimeric proteins that bind with high selectivity to DNA junctions and generate bilateral cleavage within the lifetime of the DNA-protein complex. Recent success in obtaining X-ray crystal structures of resolving enzymes bound to DNA junctions has revealed how the structural selectivity of these enzymes is achieved.
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19
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Rescue of bacteriophage T7 DNA polymerase of low processivity by suppressor mutations affecting gene 3 endonuclease. J Virol 2009; 83:8418-27. [PMID: 19535436 DOI: 10.1128/jvi.00855-09] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The DNA polymerase encoded by gene 5 (gp5) of bacteriophage T7 has low processivity, dissociating after the incorporation of a few nucleotides. Upon binding to its processivity factor, Escherichia coli thioredoxin (Trx), the processivity is increased to approximately 800 nucleotides per binding event. Several interactions between gp5/Trx and DNA are required for processive DNA synthesis. A basic region in T7 DNA polymerase (residues K587, K589, R590, and R591) is located in proximity to the 5' overhang of the template strand. Replacement of these residues with asparagines results in a threefold reduction of the polymerization activity on primed M13 single-stranded DNA. The altered gp5/Trx exhibits a 10-fold reduction in its ability to support growth of T7 phage lacking gene 5. However, T7 phages that grow at a similar rate provided with either wild-type or altered polymerase emerge. Most of the suppressor phages contain genetic changes in or around the coding region for gene 3, an endonuclease. Altered gene 3 proteins derived from suppressor strains show reduced catalytic activity and are inefficient in complementing growth of T7 phage lacking gene 3. Results from this study reveal that defects in processivity of DNA polymerase can be suppressed by reducing endonuclease activity.
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20
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Identification of Holliday junction resolvases from humans and yeast. Nature 2008; 456:357-61. [PMID: 19020614 DOI: 10.1038/nature07470] [Citation(s) in RCA: 290] [Impact Index Per Article: 18.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2008] [Accepted: 09/26/2008] [Indexed: 11/09/2022]
Abstract
Four-way DNA intermediates, also known as Holliday junctions, are formed during homologous recombination and DNA repair, and their resolution is necessary for proper chromosome segregation. Here we identify nucleases from Saccharomyces cerevisiae and human cells that promote Holliday junction resolution, in a manner analogous to that shown by the Escherichia coli Holliday junction resolvase RuvC. The human Holliday junction resolvase, GEN1, and its yeast orthologue, Yen1, were independently identified using two distinct experimental approaches: GEN1 was identified by mass spectrometry following extensive fractionation of HeLa cell-free extracts, whereas Yen1 was detected by screening a yeast gene fusion library for nucleases capable of Holliday junction resolution. The eukaryotic Holliday junction resolvases represent a new subclass of the Rad2/XPG family of nucleases. Recombinant GEN1 and Yen1 resolve Holliday junctions by the introduction of symmetrically related cuts across the junction point, to produce nicked duplex products in which the nicks can be readily ligated.
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21
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Abstract
Rad54, a key protein of homologous recombination, physically interacts with a DNA structure-specific endonuclease, Mus81-Eme1. Genetic data indicate that Mus81-Eme1 and Rad54 might function together in the repair of damaged DNA. In vitro, Rad54 promotes branch migration of Holliday junctions, whereas the Mus81-Eme1 complex resolves DNA junctions by endonucleolytic cleavage. Here, we show that human Rad54 stimulates Mus81-Eme1 endonuclease activity on various Holliday junction-like intermediates. This stimulation is the product of specific interactions between the human Rad54 (hRad54) and Mus81 proteins, considering that Saccharomyces cerevisiae Rad54 protein does not stimulate human Mus81-Eme1 endonuclease activity. Stimulation of Mus81-Eme1 cleavage activity depends on formation of specific Rad54 complexes on DNA substrates occurring in the presence of ATP and, to a smaller extent, of other nucleotide cofactors. Thus, our results demonstrate a functional link between the branch migration activity of hRad54 and the structure-specific endonuclease activity of hMus81-Eme1, suggesting that the Rad54 and Mus81-Eme1 proteins may cooperate in the processing of Holliday junction-like intermediates during homologous recombination or DNA repair.
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22
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Cleavage mechanism of human Mus81-Eme1 acting on Holliday-junction structures. Proc Natl Acad Sci U S A 2008; 105:3757-62. [PMID: 18310322 DOI: 10.1073/pnas.0710291105] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Recombination-mediated repair plays a central role in maintaining genomic integrity during DNA replication. The human Mus81-Eme1 endonuclease is involved in recombination repair, but the exact structures it acts on in vivo are not known. Using kinetic and enzymatic analysis of highly purified recombinant enzyme, we find that Mus81-Eme1 catalyzes coordinate bilateral cleavage of model Holliday-junction structures. Using a self-limiting, cruciform-containing substrate, we demonstrate that bilateral cleavage occurs sequentially within the lifetime of the enzyme-substrate complex. Coordinate bilateral cleavage is promoted by the highly cooperative nature of the enzyme and results in symmetrical cleavage of a cruciform structure, thus, Mus81-Eme1 can ensure coordinate, bilateral cleavage of Holliday junction-like structures.
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23
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Biertümpfel C, Yang W, Suck D. Crystal structure of T4 endonuclease VII resolving a Holliday junction. Nature 2007; 449:616-20. [PMID: 17873859 DOI: 10.1038/nature06152] [Citation(s) in RCA: 103] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2007] [Accepted: 08/07/2007] [Indexed: 11/08/2022]
Abstract
Holliday proposed a four-way DNA junction as an intermediate in homologous recombination, and such Holliday junctions have since been identified as a central component in DNA recombination and repair. Phage T4 endonuclease VII (endo VII) was the first enzyme shown to resolve Holliday junctions into duplex DNAs by introducing symmetrical nicks in equivalent strands. Several Holliday junction resolvases have since been characterized, but an atomic structure of a resolvase complex with a Holliday junction remained elusive. Here we report the crystal structure of an inactive T4 endo VII(N62D) complexed with an immobile four-way junction with alternating arm lengths of 10 and 14 base pairs. The junction is a hybrid of the conventional square-planar and stacked-X conformation. Endo VII protrudes into the junction point from the minor groove side, opening it to a 14 A x 32 A parallelogram. This interaction interrupts the coaxial stacking, yet every base pair surrounding the junction remains intact. Additional interactions involve the positively charged protein and DNA phosphate backbones. Each scissile phosphate that is two base pairs from the crossover interacts with a Mg2+ ion in the active site. The similar overall shape and surface charge potential of the Holliday junction resolvases endo VII, RuvC, Ydc2, Hjc and RecU, despite having different folds, active site composition and DNA sequence preference, suggest a conserved binding mode for Holliday junctions.
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Affiliation(s)
- Christian Biertümpfel
- National Institute of Diabetes and Digestive and Kidney Diseases, Laboratory of Molecular Biology, 9000 Rockville Pike, Bethesda, Maryland 20892, USA
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24
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Hadden JM, Déclais AC, Carr SB, Lilley DMJ, Phillips SEV. The structural basis of Holliday junction resolution by T7 endonuclease I. Nature 2007; 449:621-4. [PMID: 17873858 DOI: 10.1038/nature06158] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2007] [Accepted: 08/07/2007] [Indexed: 11/09/2022]
Abstract
The four-way (Holliday) DNA junction is the central intermediate in homologous recombination, a ubiquitous process that is important in DNA repair and generation of genetic diversity. The penultimate stage of recombination requires resolution of the DNA junction into nicked-duplex species by the action of a junction-resolving enzyme, examples of which have been identified in a wide variety of organisms. These enzymes are nucleases that are highly selective for the structure of branched DNA. The mechanism of this selectivity has, however, been unclear in the absence of structural data. Here we present the crystal structure of the junction-resolving enzyme phage T7 endonuclease I in complex with a synthetic four-way DNA junction. Although the enzyme is structure-selective, significant induced fit occurs in the interaction, with changes in the structure of both the protein and the junction. The dimeric enzyme presents two binding channels that contact the backbones of the junction's helical arms over seven nucleotides. These interactions effectively measure the relative orientations and positions of the arms of the junction, thereby ensuring that binding is selective for branched DNA that can achieve this geometry.
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Affiliation(s)
- Jonathan M Hadden
- Astbury Centre for Structural Molecular Biology, Institute of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, UK
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25
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Losch FO, Bredenbeck A, Hollstein VM, Walden P, Wrede P. Evidence for a large double-cruciform DNA structure on the X chromosome of human and chimpanzee. Hum Genet 2007; 122:337-43. [PMID: 17638018 DOI: 10.1007/s00439-007-0405-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2007] [Accepted: 07/09/2007] [Indexed: 01/05/2023]
Abstract
The human X chromosome consists of a high number of large inverted repeat (IR) DNA sequences which fulfill all requirements for formation of cruciform DNA structures. Such alternative DNA structures are suggested to have a great impact in altering the chromatin architecture and function. Our comprehensive analysis of the corresponding orthologous nucleotide sequences of an IR sequence from Homo sapiens and Pan troglodytes revealed that most of the nucleotide differences between the two species are symmetrical to the apex of the IR, and that the spacer region of the orthologous IRs are in reverse orientation. We provide evidence that this IR forms a large non-B DNA structure containing two Holliday junctions, allowing intrastrand nucleotide pairing of the arms and interstrand pairing of the spacer region of the IR. This structure would extrude into a large double-cruciform DNA structure providing the molecular basis of translocation events and regulation of gene expression.
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MESH Headings
- Animals
- Antigens, Neoplasm/genetics
- Base Sequence
- Chromosomes, Human, X/chemistry
- Chromosomes, Human, X/genetics
- DNA/chemistry
- DNA/genetics
- DNA, Cruciform/chemistry
- DNA, Cruciform/genetics
- Humans
- Models, Molecular
- Nucleic Acid Conformation
- Pan troglodytes/genetics
- Phylogeny
- Repetitive Sequences, Nucleic Acid
- Sequence Homology, Nucleic Acid
- Species Specificity
- X Chromosome/chemistry
- X Chromosome/genetics
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Affiliation(s)
- Florian O Losch
- Clinical Research Group Tumor Immunology, Department of Dermatology, Charité - Universitätsmedizin Berlin, 10098 Berlin, Germany.
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26
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Gaskell LJ, Osman F, Gilbert RJC, Whitby MC. Mus81 cleavage of Holliday junctions: a failsafe for processing meiotic recombination intermediates? EMBO J 2007; 26:1891-901. [PMID: 17363897 PMCID: PMC1847671 DOI: 10.1038/sj.emboj.7601645] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2006] [Accepted: 02/19/2007] [Indexed: 11/09/2022] Open
Abstract
The Holliday junction (HJ) is a central intermediate of homologous recombination. Its cleavage is critical for the formation of crossover recombinants during meiosis, which in turn helps to establish chiasmata and promote genetic diversity. Enzymes that cleave HJs, called HJ resolvases, have been identified in all domains of life except eukaryotic nuclei. Controversially, the Mus81-Eme1 endonuclease has been proposed to be an example of a eukaryotic nuclear resolvase. However, hitherto little or no HJ cleavage has been detected in recombinant preparations of Mus81-Eme1. Here, we report the purification of active forms of recombinant Schizosaccharomyces pombe Mus81-Eme1 and Saccharomyces cerevisiae Mus81-Mms4, which display robust HJ cleavage in vitro, which, in the case of Mus81-Eme1, is as good as the archetypal HJ resolvase RuvC in single turnover kinetic analysis. We also present genetic evidence that suggests that this activity might be utilised as a back-up to Mus81-Eme1's main activity of cleaving nicked HJs during meiosis in S. pombe.
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Affiliation(s)
| | - Fekret Osman
- Department of Biochemistry, University of Oxford, Oxford, UK
| | - Robert J C Gilbert
- Division of Structural Biology, Henry Wellcome Building for Genomic Medicine, Oxford, UK
| | - Matthew C Whitby
- Department of Biochemistry, University of Oxford, Oxford, UK
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford, Oxfordshire, OX1 3QU, UK. Tel.: +44 1865 275192; Fax: +44 1865 275297; E-mail:
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27
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Abstract
The crystal structure of the four-stranded DNA Holliday junction has now been determined in the presence and absence of junction binding proteins, with the extended open-X form of the junction seen in all protein complexes, but the more compact stacked-X structure observed in free DNA. The structures of the stacked-X junction were crystallized because of an unexpected sequence dependence on the stability of this structure. Inverted repeat sequences that contain the general motif NCC or ANC favor formation of stacked-X junctions, with the junction cross-over occurring between the first two positions of the trinucleotides. This review focuses on the sequence dependent structure of the stacked-X junction and how it may play a role in structural recognition by a class of dimeric junction resolving enzymes that themselves show no direct sequence recognition.
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Affiliation(s)
- Patricia A. Khuu
- Department of Biochemistry and Biophysics, Oregon State University, Corvallis, OR, 97331-7305, USA
| | - Andrea Regier Voth
- Department of Biochemistry and Biophysics, Oregon State University, Corvallis, OR, 97331-7305, USA
| | | | - P. Shing Ho
- Department of Biochemistry and Biophysics, Oregon State University, Corvallis, OR, 97331-7305, USA
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28
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Wijeratne AJ, Chen C, Zhang W, Timofejeva L, Ma H. The Arabidopsis thaliana PARTING DANCERS gene encoding a novel protein is required for normal meiotic homologous recombination. Mol Biol Cell 2006; 17:1331-43. [PMID: 16394097 PMCID: PMC1382321 DOI: 10.1091/mbc.e05-09-0902] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Recent studies of meiotic recombination in the budding yeast and the model plant Arabidopsis thaliana indicate that meiotic crossovers (COs) occur through two genetic pathways: the interference-sensitive pathway and the interference-insensitive pathway. However, few genes have been identified in either pathway. Here, we describe the identification of the PARTING DANCERS (PTD) gene, as a gene with an elevated expression level in meiocytes. Analysis of two independently generated transferred DNA insertional lines in PTD showed that the mutants had reduced fertility. Further cytological analysis of male meiosis in the ptd mutants revealed defects in meiosis, including reduced formation of chiasmata, the cytological appearance of COs. The residual chiasmata in the mutants were distributed randomly, indicating that the ptd mutants are defective for CO formation in the interference-sensitive pathway. In addition, transmission electron microscopic analysis of the mutants detected no obvious abnormality of synaptonemal complexes and apparently normal late recombination nodules at the pachytene stage, suggesting that the mutant's defects in bivalent formation were postsynaptic. Comparison to other genes with limited sequence similarity raises the possibility that PTD may present a previously unknown function conserved in divergent eukaryotic organisms.
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Affiliation(s)
- Asela J Wijeratne
- Intercollege Graduate Program in Plant Physiology, The Pennsylvania State University, University Park, PA 16802, USA
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29
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Parker JL, White MF. The endonuclease Hje catalyses rapid, multiple turnover resolution of Holliday junctions. J Mol Biol 2005; 350:1-6. [PMID: 15921693 DOI: 10.1016/j.jmb.2005.04.056] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2005] [Revised: 04/20/2005] [Accepted: 04/26/2005] [Indexed: 10/25/2022]
Abstract
Holliday junction-resolving enzymes are ubiquitous, structure-specific endonucleases that resolve four-way DNA junctions by the introduction of paired nicks in opposing strands, and are required for homologous recombination, double-strand break repair, recombination-dependent restart of stalled or collapsed DNA replication forks, and phage DNA processing. Here, we present the first steady-state kinetic characterisation of a junction-resolving enzyme; the Hje endonuclease from Sulfolobus solfataricus. We demonstrate that substrate turnover by Hje is sequence-independent and limited largely by the rate of cleavage of the phosphodiester bonds of the bound Holliday junction substrate, rather than substrate association or product dissociation. Reaction rates under multiple turnover conditions compare favourably with type II restriction enzymes. These properties, coupled with a high level of specificity for four-way junctions over all other DNA substrates, make Hje a suitable enzyme for applications requiring the detection and cleavage of Holliday junctions in vitro.
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Affiliation(s)
- Joanne L Parker
- Centre for Biomolecular Sciences, University of St Andrews, North Haugh, St Andrews, Fife KY16 9ST, UK
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30
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McKinney SA, Freeman ADJ, Lilley DMJ, Ha T. Observing spontaneous branch migration of Holliday junctions one step at a time. Proc Natl Acad Sci U S A 2005; 102:5715-20. [PMID: 15824311 PMCID: PMC556122 DOI: 10.1073/pnas.0409328102] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Genetic recombination occurs between homologous DNA molecules via a four-way (Holliday) junction intermediate. This ancient and ubiquitous process is important for the repair of double-stranded breaks, the restart of stalled replication forks, and the creation of genetic diversity. Once formed, the four-way junction alone can undergo the stepwise exchange of base pairs known as spontaneous branch migration. Conventional ensemble assays, useful for finding average migration rates over long sequences, have been unable to examine the affect of sequence and structure on the migration process. Here, we present a single-molecule spontaneous branch migration assay with single-base pair resolution in a study of individual DNA junctions that can undergo one step of migration. Junctions exhibit markedly different dynamics of exchange between stacking conformers depending on the point of strand exchange, allowing the moment at which branch migration occurs to be detected. The free energy landscape of spontaneous branch migration is found to be highly nonuniform and governed by two types of sequence-dependent barriers, with unmediated local migration being up to 10 times more rapid than the previously deduced average rate.
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Affiliation(s)
- Sean A McKinney
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
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31
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Curtis FA, Reed P, Sharples GJ. Evolution of a phage RuvC endonuclease for resolution of both Holliday and branched DNA junctions. Mol Microbiol 2004; 55:1332-45. [PMID: 15720544 DOI: 10.1111/j.1365-2958.2004.04476.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Resolution of Holliday junction recombination intermediates in most Gram-negative bacteria is accomplished by the RuvC endonuclease acting in concert with the RuvAB branch migration machinery. Gram-positive species, however, lack RuvC, with the exception of distantly related orthologues from bacteriophages infecting Lactococci and Streptococci. We have purified one of these proteins, 67RuvC, from Lactococcus lactis phage bIL67 and demonstrated that it functions as a Holliday structure resolvase. Differences in the sequence selectivity of resolution between 67RuvC and Escherichia coli RuvC were noted, although both enzymes prefer to cleave 3' of thymidine residues. However, unlike its cellular counterpart, 67RuvC readily binds and cleaves a variety of branched DNA substrates in addition to Holliday junctions. Plasmids expressing 67RuvC induce chromosomal breaks, probably as a consequence of replication fork cleavage, and cannot be recovered from recombination-defective E. coli strains. Despite these deleterious effects, 67RuvC constructs suppress the UV light sensitivity of ruvA, ruvAB and ruvABC mutant strains confirming that the phage protein mediates Holliday junction resolution in vivo. The characterization of 67RuvC offers a unique insight into how a Holliday junction-specific resolvase can evolve into a debranching endonuclease tailored to the requirements of phage recombination.
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Affiliation(s)
- Fiona A Curtis
- Centre for Infectious Diseases, Wolfson Research Institute, University of Durham, Queen's Campus, Stockton-on-Tees TS17 6BH, UK
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32
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McPherson JP, Lemmers B, Chahwan R, Pamidi A, Migon E, Matysiak-Zablocki E, Moynahan ME, Essers J, Hanada K, Poonepalli A, Sanchez-Sweatman O, Khokha R, Kanaar R, Jasin M, Hande MP, Hakem R. Involvement of mammalian Mus81 in genome integrity and tumor suppression. Science 2004; 304:1822-6. [PMID: 15205536 DOI: 10.1126/science.1094557] [Citation(s) in RCA: 150] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Mus81-Eme1 endonuclease has been implicated in the rescue of stalled replication forks and the resolution of meiotic recombination intermediates in yeast. We used gene targeting to study the physiological requirements of Mus81 in mammals. Mus81-/- mice are viable and fertile, which indicates that mammalian Mus81 is not essential for recombination processes associated with meiosis. Mus81-deficient mice and cells were hypersensitive to the DNA cross-linking agent mitomycin C but not to gamma-irradiation. Remarkably, both homozygous Mus81-/- and heterozygous Mus81+/- mice exhibited a similar susceptibility to spontaneous chromosomal damage and a profound and equivalent predisposition to lymphomas and other cancers. These studies demonstrate a critical role for the proper biallelic expression of the mammalian Mus81 in the maintenance of genomic integrity and tumor suppression.
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Affiliation(s)
- John Peter McPherson
- Ontario Cancer Institute, 620 University Avenue, Suite 706, Toronto, Ontario, Canada M5G 2C1
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Abstract
Werner syndrome (WS) is one of three heritable human genetic instability/cancer predisposition syndromes that result from mutations in a member of the gene family encoding human RecQ helicases. Cellular defects are a prominent part of the WS phenotype. Here we review recent work to identify in vivo functions of the WS protein and discuss how loss of function leads to cellular defects. These new results provide clues to the origin of cell lineage-specific defects in WS patients and suggest a broader role for Werner protein function in determining disease risk in the general population.
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Affiliation(s)
- Raymond J Monnat
- Department of Pathology, University of Washington, Seattle, WA 98195, USA.
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Ayora S, Carrasco B, Doncel-Perez E, Doncel E, Lurz R, Alonso JC. Bacillus subtilis RecU protein cleaves Holliday junctions and anneals single-stranded DNA. Proc Natl Acad Sci U S A 2003; 101:452-7. [PMID: 14701911 PMCID: PMC327168 DOI: 10.1073/pnas.2533829100] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Bacillus subtilis RecU protein is involved in homologous recombination, DNA repair, and chromosome segregation. Purified RecU binds preferentially to three- and four-strand junctions when compared to single-stranded DNA (ssDNA) and double-stranded DNA (dsDNA) ( approximately 10- and approximately 40-fold lower efficiency, respectively). RecU cleaves mobile four-way junctions but fails to cleave a linear dsDNA with a putative cognate site, a finding consistent with a similar genetic defect observed for genes classified within the epsilon epistatic group (namely ruvA, recD, and recU). In the presence of Mg(2+), RecU also anneals a circular ssDNA and a homologous linear dsDNA with a ssDNA tail and a linear ssDNA and a homologous supercoiled dsDNA substrate. These results suggest that RecU, which cleaves recombination intermediates with high specificity, might also help in their assembly.
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Affiliation(s)
- Silvia Ayora
- Department of Microbial Biotechnology, Centro Nacional de Biotecnología-Consejo Superior de Investigaciones Científicas, Campus Universidad Autónoma de Madrid, 28049 Madrid, Spain
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35
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Blais V, Gao H, Elwell CA, Boddy MN, Gaillard PHL, Russell P, McGowan CH. RNA interference inhibition of Mus81 reduces mitotic recombination in human cells. Mol Biol Cell 2003; 15:552-62. [PMID: 14617801 PMCID: PMC329235 DOI: 10.1091/mbc.e03-08-0580] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Mus81 is a highly conserved endonuclease with homology to the XPF subunit of the XPF-ERCC1 complex. In yeast Mus81 associates with a second subunit, Eme1 or Mms4, which is essential for endonuclease activity in vitro and for in vivo function. Human Mus81 binds to a homolog of fission yeast Eme1 in vitro and in vivo. We show that recombinant Mus81-Eme1 cleaves replication forks, 3' flap substrates, and Holliday junctions in vitro. By use of differentially tagged versions of Mus81 and Eme1, we find that Mus81 associates with Mus81 and that Eme1 associates with Eme1. Thus, complexes containing two or more Mus81-Eme1 units could function to coordinate substrate cleavage in vivo. Down-regulation of Mus81 by RNA interference reduces mitotic recombination in human somatic cells. The recombination defect is rescued by expression of a bacterial Holliday junction resolvase. These data provide direct evidence for a role of Mus81-Eme1 in mitotic recombination in higher eukaryotes and support the hypothesis that Mus81-Eme1 resolves Holliday junctions in vivo.
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Affiliation(s)
- Veronique Blais
- Department of Molecular Biology, The Scripps Research Institute, La Jolla, California 92037, USA
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36
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Hays FA, Watson J, Ho PS. Caution! DNA crossing: crystal structures of Holliday junctions. J Biol Chem 2003; 278:49663-6. [PMID: 14563836 DOI: 10.1074/jbc.r300033200] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Affiliation(s)
- Franklin A Hays
- Department of Biochemistry and Biophysics, Oregon State University, Corvallis, Oregon 97331-7305, USA
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37
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Hays FA, Vargason JM, Ho PS. Effect of sequence on the conformation of DNA holliday junctions. Biochemistry 2003; 42:9586-97. [PMID: 12911300 DOI: 10.1021/bi0346603] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Structures of the DNA sequences d(CCGGCGCCGG) and d(CCAGTACbr(5)UGG) are presented here as four-way Holliday junctions in their compact stacked-X forms, with antiparallel alignment of the DNA strands. Thus, the ACC-trinucleotide motif, previously identified as important for stabilizing the junction, is now extended to PuCPy, where Pu is either an adenine or guanine, and Py is either a cytosine, 5-methylcytosine, or 5-bromouracil but not thymine nucleotide. We see that both sequence and base substituents affect the geometry of the junction in terms of the interduplex angle as well as the previously defined conformational variables, J(roll) (the rotation of the stacked duplexes about their respective helical axis) and J(slide) (the translational displacement of the stacked duplexes along their respective helical axis). The structures of the GCC and parent ACC containing junctions fall into a distinct conformational class that is relatively undistorted in terms of J(slide) and J(roll), with interduplex angles of 40-43 degrees. The substituted ACbr(5)U structure, however, is more akin to that of the distorted methylated ACm(5)C containing junction, with J(slide) (>or=2.3 A) and a similar J(roll) (164 degrees) opening the major groove-side of the junction, but shows a reduced interduplex angle. In contrast, the analogous d(CCAGTACTGG) sequence has to date been crystallized only as resolved B-DNA duplexes. This suggests that there is an electronic effect of substituents at the pyrimidine Py position on the stability of four-stranded junctions. The single-crystal structures presented here, therefore, show how sequence affects the detailed geometry, and subsequently, the associated stability and conformational dynamics of the Holliday junction.
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Affiliation(s)
- Franklin A Hays
- Department of Biochemistry and Biophysics, ALS 2011, Oregon State University, Corvallis, Oregon 97331, USA
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38
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Ahn JS, Whitby MC. The role of the SAP motif in promoting Holliday junction binding and resolution by SpCCE1. J Biol Chem 2003; 278:29121-9. [PMID: 12748193 DOI: 10.1074/jbc.m302314200] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Holliday junctions are four-way branched DNA structures that are formed during recombination and by replication fork regression. Their processing depends on helicases that catalyze junction branch migration, and endonucleases that resolve the junction into nicked linear DNAs. Here we have investigated the role of a DNA binding motif called SAP in binding and resolving Holliday junctions by the fission yeast mitochondrial resolvase SpCCE1. Mutation or partial/complete deletion of the SAP motif dramatically impairs the ability of SpCCE1 to resolve Holliday junctions in a heterologous in vivo system. These mutant proteins retain the ability to recognize the junction structure and to distort it upon binding. However, once formed the mutant protein-junction complexes are relatively unstable and dissociate much faster than wild-type complexes. We show that binding stability is necessary for efficient junction resolution, and that this may be due in part to a requirement for maintaining the junction in an open conformation so that it can branch migrate to cleavable sites.
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Affiliation(s)
- Jong Sook Ahn
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, United Kingdom
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39
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Sasnauskas G, Halford SE, Siksnys V. How the BfiI restriction enzyme uses one active site to cut two DNA strands. Proc Natl Acad Sci U S A 2003; 100:6410-5. [PMID: 12750473 PMCID: PMC164460 DOI: 10.1073/pnas.1131003100] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Unlike other restriction enzymes, BfiI functions without metal ions. It recognizes an asymmetric DNA sequence, 5'-ACTGGG-3', and cuts top and bottom strands at fixed positions downstream of this sequence. Many restriction enzymes are dimers of identical subunits, with one active site for each DNA strand. Others, like FokI, dimerize transiently during catalysis. BfiI is also a dimer but it has only one active site, at the dimer interface. We show here that BfiI remains a dimer as it makes double-strand breaks in DNA and that its single active site acts sequentially, first on the bottom and then the top strand. Hence, after cutting the bottom strand, a rearrangement of either the protein and/or the DNA in the BfiI-DNA complex must switch the active site to the top strand. Low pH values selectively block top-strand cleavage, converting BfiI into a nicking enzyme that cleaves only the bottom strand. The switch to the top strand may depend on the ionization of the cleaved 5' phosphate in the bottom strand. BfiI thus uses a mechanism for making double-strand breaks that is novel among restriction enzymes.
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40
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Saintigny Y, Makienko K, Swanson C, Emond MJ, Monnat RJ. Homologous recombination resolution defect in werner syndrome. Mol Cell Biol 2002; 22:6971-8. [PMID: 12242278 PMCID: PMC139822 DOI: 10.1128/mcb.22.20.6971-6978.2002] [Citation(s) in RCA: 209] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2002] [Revised: 07/05/2002] [Accepted: 07/12/2002] [Indexed: 11/20/2022] Open
Abstract
Werner syndrome (WRN) is an uncommon autosomal recessive disease whose phenotype includes features of premature aging, genetic instability, and an elevated risk of cancer. We used three different experimental strategies to show that WRN cellular phenotypes of limited cell division potential, DNA damage hypersensitivity, and defective homologous recombination (HR) are interrelated. WRN cell survival and the generation of viable mitotic recombinant progeny could be rescued by expressing wild-type WRN protein or by expressing the bacterial resolvase protein RusA. The dependence of WRN cellular phenotypes on RAD51-dependent HR pathways was demonstrated by using a dominant-negative RAD51 protein to suppress mitotic recombination in WRN and control cells: the suppression of RAD51-dependent recombination led to significantly improved survival of WRN cells following DNA damage. These results define a physiological role for the WRN RecQ helicase protein in RAD51-dependent HR and identify a mechanistic link between defective recombination resolution and limited cell division potential, DNA damage hypersensitivity, and genetic instability in human somatic cells.
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Affiliation(s)
- Yannick Saintigny
- Departments of Pathology. Biostatistics. Genome Sciences, University of Washington, Seattle, Washington 98195-7705, USA
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41
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Kvaratskhelia M, Wardleworth BN, Bond CS, Fogg JM, Lilley DMJ, White MF. Holliday junction resolution is modulated by archaeal chromatin components in vitro. J Biol Chem 2002; 277:2992-6. [PMID: 11709558 DOI: 10.1074/jbc.m109496200] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The Holliday junction-resolving enzyme Hjc is conserved in the archaea and probably plays a role analogous to that of Escherichia coli RuvC in the pathway of homologous recombination. Hjc specifically recognizes four-way DNA junctions, cleaving them without sequence preference to generate recombinant DNA duplex products. Hjc imposes an X-shaped global conformation on the bound DNA junction and distorts base stacking around the point of cleavage, three nucleotides 3' of the junction center. We show that Hjc is autoinhibitory under single turnover assay conditions and that this can be relieved by the addition of either competitor duplex DNA or the architectural double-stranded DNA-binding protein Sso7d (i.e. by approximating in vivo conditions more closely). Using a combination of isothermal titration calorimetry and fluorescent resonance energy transfer, we demonstrate that multiple Hjc dimers can bind to each synthetic four-way junction and provide evidence for significant distortion of the junction structure at high protein:DNA ratios. Analysis of crystal packing interactions in the crystal structure of Hjc suggests a molecular basis for this autoinhibition. The wider implications of these findings for the quantitative study of DNA-protein interactions is discussed.
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Affiliation(s)
- Mamuka Kvaratskhelia
- Centre for Biomolecular Science, University of Saint Andrews, North Haugh, Saint Andrews, KY16 9ST, United Kingdom
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42
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New Year's resolution. Nat Rev Mol Cell Biol 2002. [DOI: 10.1038/nrm706] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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