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Liu C, Hauk G, Yan Q, Berger JM. Structure of Escherichia coli exonuclease VII. Proc Natl Acad Sci U S A 2024; 121:e2319644121. [PMID: 38271335 PMCID: PMC10835039 DOI: 10.1073/pnas.2319644121] [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: 11/08/2023] [Accepted: 12/15/2023] [Indexed: 01/27/2024] Open
Abstract
Exonuclease VII (ExoVII) is a ubiquitous bacterial nuclease. Encoded by the xseA and xseB genes, ExoVII participates in multiple nucleic acid-dependent pathways including the processing of multicopy single-stranded DNA and the repair of covalent DNA-protein crosslinks (DPCs). Although many biochemical properties of ExoVII have been defined, little is known about its structure/function relationships. Here, we use cryoelectron microscopy (cryoEM) to determine that Escherichia coli ExoVII comprises a highly elongated XseA4·XseB24 holo-complex. Each XseA subunit dimerizes through a central extended α-helical segment decorated by six XseB subunits and a C-terminal, domain-swapped β-barrel element; two XseA2·XseB12 subcomplexes further associate using N-terminal OB (oligonucleotide/oligosaccharide-binding) folds and catalytic domains to form a spindle-shaped, catenated octaicosamer. The catalytic domains of XseA, which adopt a nuclease fold related to 3-dehydroquinate dehydratases, are sequestered in the center of the complex and accessible only through large pores formed between XseA tetramers. The architectural organization of ExoVII, combined with biochemical studies, indicate that substrate selectivity is controlled by steric access to its nuclease elements and that tetramer dissociation results from substrate DNA binding. Despite a lack of sequence and fold homology, the physical organization of ExoVII is reminiscent of Mre11·Rad50/SbcCD ATP (adenosine triphosphate)-dependent nucleases used in the repair of double-stranded DNA breaks, including those formed by DPCs through aberrant topoisomerase activity, suggesting that there may have been convergent evolutionary pressure to contend with such damage events.
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Affiliation(s)
- Chuan Liu
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - Glenn Hauk
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - Qianyun Yan
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - James M Berger
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD 21205
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2
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The Biochemical Mechanism of Fork Regression in Prokaryotes and Eukaryotes—A Single Molecule Comparison. Int J Mol Sci 2022; 23:ijms23158613. [PMID: 35955746 PMCID: PMC9368896 DOI: 10.3390/ijms23158613] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2022] [Revised: 07/29/2022] [Accepted: 08/02/2022] [Indexed: 02/04/2023] Open
Abstract
The rescue of stalled DNA replication forks is essential for cell viability. Impeded but still intact forks can be rescued by atypical DNA helicases in a reaction known as fork regression. This reaction has been studied at the single-molecule level using the Escherichia coli DNA helicase RecG and, separately, using the eukaryotic SMARCAL1 enzyme. Both nanomachines possess the necessary activities to regress forks: they simultaneously couple DNA unwinding to duplex rewinding and the displacement of bound proteins. Furthermore, they can regress a fork into a Holliday junction structure, the central intermediate of many fork regression models. However, there are key differences between these two enzymes. RecG is monomeric and unidirectional, catalyzing an efficient and processive fork regression reaction and, in the process, generating a significant amount of force that is used to displace the tightly-bound E. coli SSB protein. In contrast, the inefficient SMARCAL1 is not unidirectional, displays limited processivity, and likely uses fork rewinding to facilitate RPA displacement. Like many other eukaryotic enzymes, SMARCAL1 may require additional factors and/or post-translational modifications to enhance its catalytic activity, whereas RecG can drive fork regression on its own.
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Thompson MK, Nocedal I, Culviner PH, Zhang T, Gozzi KR, Laub MT. Escherichia coli SymE is a DNA-binding protein that can condense the nucleoid. Mol Microbiol 2021; 117:851-870. [PMID: 34964191 DOI: 10.1111/mmi.14877] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2021] [Revised: 12/23/2021] [Accepted: 12/23/2021] [Indexed: 11/28/2022]
Abstract
Type I toxin-antitoxin (TA) systems typically consist of a protein toxin that imbeds in the inner membrane where it can oligomerize and form pores that change membrane permeability, and an RNA antitoxin that interacts directly with toxin mRNA to inhibit its translation. In Escherichia coli, symE/symR is annotated as a type I TA system with a non-canonical toxin. SymE was initially suggested to be an endoribonuclease, but has predicted structural similarity to DNA binding proteins. To better understand SymE function, we used RNA-seq to examine cells ectopically producing it. Although SymE drives major changes in gene expression, we do not find strong evidence of endoribonucleolytic activity. Instead, our biochemical and cell biological studies indicate that SymE binds DNA. We demonstrate that the toxicity of symE overexpression likely stems from its ability to drive severe nucleoid condensation, which disrupts DNA and RNA synthesis and leads to DNA damage, similar to the effects of overproducing the nucleoid-associated protein H-NS. Collectively, our results suggest that SymE represents a new class of nucleoid-associated proteins that is widely distributed in bacteria.
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Affiliation(s)
- Mary K Thompson
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Isabel Nocedal
- Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Peter H Culviner
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Tong Zhang
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Kevin R Gozzi
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Michael T Laub
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA.,Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
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Mandal RK, Jiang T, Kwon YM. Genetic Determinants in Salmonella enterica Serotype Typhimurium Required for Overcoming In Vitro Stressors in the Mimicking Host Environment. Microbiol Spectr 2021; 9:e0015521. [PMID: 34878334 PMCID: PMC8653844 DOI: 10.1128/spectrum.00155-21] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Accepted: 10/29/2021] [Indexed: 11/20/2022] Open
Abstract
Salmonella enterica serotype Typhimurium, a nontyphoidal Salmonella (NTS), results in a range of enteric diseases, representing a major disease burden worldwide. There is still a significant portion of Salmonella genes whose mechanistic basis to overcome host innate defense mechanisms largely remains unknown. Here, we have applied transposon insertion sequencing (Tn-seq) method to unveil the genetic factors required for the growth or survival of S. Typhimurium under various host stressors simulated in vitro. A highly saturating Tn5 library of S. Typhimurium 14028s was subjected to selection during growth in the presence of short-chain fatty acid (100 mM propionate), osmotic stress (3% NaCl), or oxidative stress (1 mM H2O2) or survival in extreme acidic pH (30 min in pH 3) or starvation (12 days in 1× phosphate-buffered saline [PBS]). We have identified a total of 339 conditionally essential genes (CEGs) required to overcome at least one of these conditions mimicking host insults. Interestingly, all eight genes encoding FoF1-ATP synthase subunit proteins were required for fitness in all five stresses. Intriguingly, a total of 88 genes in Salmonella pathogenicity islands (SPI), including SPI-1, SPI-2, SPI-3, SPI-5, SPI-6, and SPI-11, are also required for fitness under the in vitro conditions. Additionally, by comparative analysis of the genes identified in this study and the genes previously shown to be required for in vivo fitness, we identified novel genes (marBCT, envF, barA, hscA, rfaQ, rfbI, and the genes encoding putative proteins STM14_1138, STM14_3334, STM14_4825, and STM_5184) that have compelling potential for the development of vaccines and antibacterial drugs to curb Salmonella infection. IMPORTANCE Salmonella enterica serotype Typhimurium is a major human bacterial pathogen that enters the food chain through meat animals asymptomatically carrying this pathogen. Despite the rich genome sequence data, a significant portion of Salmonella genes remain to be characterized for their potential contributions to virulence. In this study, we used transposon insertion sequencing (Tn-seq) to elucidate the genetic factors required for growth or survival under various host stressors, including short-chain fatty acids, osmotic stress, oxidative stress, extreme acid, and starvation. Among the total of 339 conditionally essential genes (CEGs) that are required under at least one of these five stress conditions were 221 previously known virulence genes required for in vivo fitness during infection in at least one of four animal species, including mice, chickens, pigs, and cattle. This comprehensive map of virulence phenotype-genotype in S. Typhimurium provides a roadmap for further interrogation of the biological functions encoded by the genome of this important human pathogen to survive in hostile host environments.
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Affiliation(s)
- Rabindra K. Mandal
- Center of Excellence for Poultry Science, University of Arkansas System Division of Agriculture, Fayetteville, Arkansas, USA
| | - Tieshan Jiang
- Center of Excellence for Poultry Science, University of Arkansas System Division of Agriculture, Fayetteville, Arkansas, USA
| | - Young Min Kwon
- Center of Excellence for Poultry Science, University of Arkansas System Division of Agriculture, Fayetteville, Arkansas, USA
- Cell and Molecular Biology Program, University of Arkansas, Fayetteville, Arkansas, USA
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Yi X, Khey J, Kazlauskas RJ, Travisano M. Plasmid hypermutation using a targeted artificial DNA replisome. SCIENCE ADVANCES 2021; 7:7/29/eabg8712. [PMID: 34272238 PMCID: PMC8284885 DOI: 10.1126/sciadv.abg8712] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Accepted: 06/02/2021] [Indexed: 06/13/2023]
Abstract
Extensive exploration of a protein's sequence space for improved or new molecular functions requires in vivo evolution with large populations. But disentangling the evolution of a target protein from the rest of the proteome is challenging. Here, we designed a protein complex of a targeted artificial DNA replisome (TADR) that operates in live cells to processively replicate one strand of a plasmid with errors. It enhanced mutation rates of the target plasmid up to 2.3 × 105-fold with only a 78-fold increase in off-target mutagenesis. It was used to evolve itself to increase error rate and increase the efficiency of an efflux pump while simultaneously expanding the substrate repertoire. TADR enables multiple simultaneous substitutions to discover functions inaccessible by accumulating single substitutions, affording potential for solving hard problems in molecular evolution and developing biologic drugs and industrial catalysts.
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Affiliation(s)
- Xiao Yi
- BioTechnology Institute, University of Minnesota, Minneapolis, MN, USA.
| | - Joleen Khey
- Department of Plant and Microbial Biology, University of Minnesota, Minneapolis, MN, USA
| | - Romas J Kazlauskas
- BioTechnology Institute, University of Minnesota, Minneapolis, MN, USA.
- Department of Biochemistry Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN, USA
| | - Michael Travisano
- BioTechnology Institute, University of Minnesota, Minneapolis, MN, USA.
- Department of Ecology Evolution and Behavior, University of Minnesota, Minneapolis, MN, USA
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Bianco PR, Lu Y. Single-molecule insight into stalled replication fork rescue in Escherichia coli. Nucleic Acids Res 2021; 49:4220-4238. [PMID: 33744948 PMCID: PMC8096234 DOI: 10.1093/nar/gkab142] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2020] [Revised: 02/15/2021] [Accepted: 02/22/2021] [Indexed: 01/05/2023] Open
Abstract
DNA replication forks stall at least once per cell cycle in Escherichia coli. DNA replication must be restarted if the cell is to survive. Restart is a multi-step process requiring the sequential action of several proteins whose actions are dictated by the nature of the impediment to fork progression. When fork progress is impeded, the sequential actions of SSB, RecG and the RuvABC complex are required for rescue. In contrast, when a template discontinuity results in the forked DNA breaking apart, the actions of the RecBCD pathway enzymes are required to resurrect the fork so that replication can resume. In this review, we focus primarily on the significant insight gained from single-molecule studies of individual proteins, protein complexes, and also, partially reconstituted regression and RecBCD pathways. This insight is related to the bulk-phase biochemical data to provide a comprehensive review of each protein or protein complex as it relates to stalled DNA replication fork rescue.
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Affiliation(s)
- Piero R Bianco
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Nebraska Medical Center, Omaha, NE 68198-6025, USA
| | - Yue Lu
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Nebraska Medical Center, Omaha, NE 68198-6025, USA
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Huang SYN, Michaels SA, Mitchell BB, Majdalani N, Vanden Broeck A, Canela A, Tse-Dinh YC, Lamour V, Pommier Y. Exonuclease VII repairs quinolone-induced damage by resolving DNA gyrase cleavage complexes. SCIENCE ADVANCES 2021; 7:7/10/eabe0384. [PMID: 33658195 PMCID: PMC7929499 DOI: 10.1126/sciadv.abe0384] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/06/2020] [Accepted: 01/19/2021] [Indexed: 05/25/2023]
Abstract
The widely used quinolone antibiotics act by trapping prokaryotic type IIA topoisomerases, resulting in irreversible topoisomerase cleavage complexes (TOPcc). Whereas the excision repair pathways of TOPcc in eukaryotes have been extensively studied, it is not known whether equivalent repair pathways for prokaryotic TOPcc exist. By combining genetic, biochemical, and molecular biology approaches, we demonstrate that exonuclease VII (ExoVII) excises quinolone-induced trapped DNA gyrase, an essential prokaryotic type IIA topoisomerase. We show that ExoVII repairs trapped type IIA TOPcc and that ExoVII displays tyrosyl nuclease activity for the tyrosyl-DNA linkage on the 5'-DNA overhangs corresponding to trapped type IIA TOPcc. ExoVII-deficient bacteria fail to remove trapped DNA gyrase, consistent with their hypersensitivity to quinolones. We also identify an ExoVII inhibitor that synergizes with the antimicrobial activity of quinolones, including in quinolone-resistant bacterial strains, further demonstrating the functional importance of ExoVII for the repair of type IIA TOPcc.
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Affiliation(s)
- Shar-Yin N Huang
- Laboratory of Molecular Pharmacology, Developmental Therapeutics Branch, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, MD 20892, USA.
| | - Stephanie A Michaels
- Laboratory of Molecular Pharmacology, Developmental Therapeutics Branch, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, MD 20892, USA
| | - Brianna B Mitchell
- Laboratory of Molecular Pharmacology, Developmental Therapeutics Branch, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, MD 20892, USA
| | - Nadim Majdalani
- Laboratory of Molecular Biology, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, MD 20892, USA
| | - Arnaud Vanden Broeck
- Integrated Structural Biology Department, IGBMC, UMR7104 CNRS, U1258 Inserm, University of Strasbourg, Illkirch 67404, France
| | - Andres Canela
- The Hakubi Center for Advanced Research, Radiation Biology Center, Graduate School of Biostudies, Kyoto University, Yoshida-Konoe-cho, Sakyo-ku, Kyoto 606-8501, Japan
| | - Yuk-Ching Tse-Dinh
- Department of Chemistry and Biochemistry, Biomolecular Sciences Institute, Florida International University, Miami, FL 33199, USA
| | - Valerie Lamour
- Integrated Structural Biology Department, IGBMC, UMR7104 CNRS, U1258 Inserm, University of Strasbourg, Illkirch 67404, France
| | - Yves Pommier
- Laboratory of Molecular Pharmacology, Developmental Therapeutics Branch, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, MD 20892, USA.
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Bush NG, Diez-Santos I, Abbott LR, Maxwell A. Quinolones: Mechanism, Lethality and Their Contributions to Antibiotic Resistance. Molecules 2020; 25:E5662. [PMID: 33271787 PMCID: PMC7730664 DOI: 10.3390/molecules25235662] [Citation(s) in RCA: 116] [Impact Index Per Article: 29.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2020] [Revised: 11/27/2020] [Accepted: 11/28/2020] [Indexed: 12/05/2022] Open
Abstract
Fluoroquinolones (FQs) are arguably among the most successful antibiotics of recent times. They have enjoyed over 30 years of clinical usage and become essential tools in the armoury of clinical treatments. FQs target the bacterial enzymes DNA gyrase and DNA topoisomerase IV, where they stabilise a covalent enzyme-DNA complex in which the DNA is cleaved in both strands. This leads to cell death and turns out to be a very effective way of killing bacteria. However, resistance to FQs is increasingly problematic, and alternative compounds are urgently needed. Here, we review the mechanisms of action of FQs and discuss the potential pathways leading to cell death. We also discuss quinolone resistance and how quinolone treatment can lead to resistance to non-quinolone antibiotics.
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Affiliation(s)
| | | | | | - Anthony Maxwell
- Department of Biological Chemistry, John Innes Centre, Norwich Research Park, Norwich NR4 7UH, UK; (N.G.B.); (I.D.-S.); (L.R.A.)
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9
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Bianco PR. DNA Helicase-SSB Interactions Critical to the Regression and Restart of Stalled DNA Replication forks in Escherichia coli. Genes (Basel) 2020; 11:E471. [PMID: 32357475 PMCID: PMC7290993 DOI: 10.3390/genes11050471] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2020] [Revised: 04/21/2020] [Accepted: 04/23/2020] [Indexed: 01/25/2023] Open
Abstract
In Escherichia coli, DNA replication forks stall on average once per cell cycle. When this occurs, replisome components disengage from the DNA, exposing an intact, or nearly intact fork. Consequently, the fork structure must be regressed away from the initial impediment so that repair can occur. Regression is catalyzed by the powerful, monomeric DNA helicase, RecG. During this reaction, the enzyme couples unwinding of fork arms to rewinding of duplex DNA resulting in the formation of a Holliday junction. RecG works against large opposing forces enabling it to clear the fork of bound proteins. Following subsequent processing of the extruded junction, the PriA helicase mediates reloading of the replicative helicase DnaB leading to the resumption of DNA replication. The single-strand binding protein (SSB) plays a key role in mediating PriA and RecG functions at forks. It binds to each enzyme via linker/OB-fold interactions and controls helicase-fork loading sites in a substrate-dependent manner that involves helicase remodeling. Finally, it is displaced by RecG during fork regression. The intimate and dynamic SSB-helicase interactions play key roles in ensuring fork regression and DNA replication restart.
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Affiliation(s)
- Piero R Bianco
- Center for Single Molecule Biophysics, University at Buffalo, SUNY, Buffalo, NY 14221, USA
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Lim CSQ, Ha KP, Clarke RS, Gavin LA, Cook DT, Hutton JA, Sutherell CL, Edwards AM, Evans LE, Tate EW, Lanyon-Hogg T. Identification of a potent small-molecule inhibitor of bacterial DNA repair that potentiates quinolone antibiotic activity in methicillin-resistant Staphylococcus aureus. Bioorg Med Chem 2019; 27:114962. [PMID: 31307763 PMCID: PMC6892255 DOI: 10.1016/j.bmc.2019.06.025] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2019] [Revised: 06/12/2019] [Accepted: 06/13/2019] [Indexed: 11/03/2022]
Abstract
The global emergence of antibiotic resistance is one of the most serious challenges facing modern medicine. There is an urgent need for validation of new drug targets and the development of small molecules with novel mechanisms of action. We therefore sought to inhibit bacterial DNA repair mediated by the AddAB/RecBCD protein complexes as a means to sensitize bacteria to DNA damage caused by the host immune system or quinolone antibiotics. A rational, hypothesis-driven compound optimization identified IMP-1700 as a cell-active, nanomolar potency compound. IMP-1700 sensitized multidrug-resistant Staphylococcus aureus to the fluoroquinolone antibiotic ciprofloxacin, where resistance results from a point mutation in the fluoroquinolone target, DNA gyrase. Cellular reporter assays indicated IMP-1700 inhibited the bacterial SOS-response to DNA damage, and compound-functionalized Sepharose successfully pulled-down the AddAB repair complex. This work provides validation of bacterial DNA repair as a novel therapeutic target and delivers IMP-1700 as a tool molecule and starting point for therapeutic development to address the pressing challenge of antibiotic resistance.
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Affiliation(s)
- Carine S Q Lim
- Department of Chemistry, Molecular Sciences Research Hub, Imperial College London, London W12 0BZ, UK
| | - Kam Pou Ha
- MRC Centre for Molecular Bacteriology and Infection, Department of Medicine, Imperial College London, London SW7 2AZ, UK
| | - Rebecca S Clarke
- MRC Centre for Molecular Bacteriology and Infection, Department of Medicine, Imperial College London, London SW7 2AZ, UK
| | - Leigh-Anne Gavin
- Department of Chemistry, Molecular Sciences Research Hub, Imperial College London, London W12 0BZ, UK
| | - Declan T Cook
- Department of Chemistry, Molecular Sciences Research Hub, Imperial College London, London W12 0BZ, UK
| | - Jennie A Hutton
- Department of Chemistry, Molecular Sciences Research Hub, Imperial College London, London W12 0BZ, UK
| | - Charlotte L Sutherell
- Department of Chemistry, Molecular Sciences Research Hub, Imperial College London, London W12 0BZ, UK
| | - Andrew M Edwards
- MRC Centre for Molecular Bacteriology and Infection, Department of Medicine, Imperial College London, London SW7 2AZ, UK
| | - Lindsay E Evans
- Department of Chemistry, Molecular Sciences Research Hub, Imperial College London, London W12 0BZ, UK; MRC Centre for Molecular Bacteriology and Infection, Department of Medicine, Imperial College London, London SW7 2AZ, UK.
| | - Edward W Tate
- Department of Chemistry, Molecular Sciences Research Hub, Imperial College London, London W12 0BZ, UK.
| | - Thomas Lanyon-Hogg
- Department of Chemistry, Molecular Sciences Research Hub, Imperial College London, London W12 0BZ, UK.
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Wilkinson M, Troman LA, Wan Nur Ismah WAK, Chaban Y, Avison MB, Dillingham MS, Wigley DB. Structural basis for the inhibition of RecBCD by Gam and its synergistic antibacterial effect with quinolones. eLife 2016; 5:e22963. [PMID: 28009252 PMCID: PMC5218532 DOI: 10.7554/elife.22963] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2016] [Accepted: 12/22/2016] [Indexed: 12/11/2022] Open
Abstract
Our previous paper (Wilkinson et al, 2016) used high-resolution cryo-electron microscopy to solve the structure of the Escherichia coli RecBCD complex, which acts in both the repair of double-stranded DNA breaks and the degradation of bacteriophage DNA. To counteract the latter activity, bacteriophage λ encodes a small protein inhibitor called Gam that binds to RecBCD and inactivates the complex. Here, we show that Gam inhibits RecBCD by competing at the DNA-binding site. The interaction surface is extensive and involves molecular mimicry of the DNA substrate. We also show that expression of Gam in E. coli or Klebsiella pneumoniae increases sensitivity to fluoroquinolones; antibacterials that kill cells by inhibiting topoisomerases and inducing double-stranded DNA breaks. Furthermore, fluoroquinolone-resistance in K. pneumoniae clinical isolates is reversed by expression of Gam. Together, our data explain the synthetic lethality observed between topoisomerase-induced DNA breaks and the RecBCD gene products, suggesting a new co-antibacterial strategy.
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Affiliation(s)
- Martin Wilkinson
- Department of Medicine, Section of Structural Biology, Imperial College London, London, United Kingdom
| | - Luca A Troman
- School of Biochemistry, University of Bristol, Bristol, United Kingdom
| | - Wan AK Wan Nur Ismah
- School of Cellular and Molecular Medicine, University of Bristol, Bristol, United Kingdom
| | - Yuriy Chaban
- Department of Medicine, Section of Structural Biology, Imperial College London, London, United Kingdom
| | - Matthew B Avison
- School of Cellular and Molecular Medicine, University of Bristol, Bristol, United Kingdom
| | - Mark S Dillingham
- School of Biochemistry, University of Bristol, Bristol, United Kingdom
| | - Dale B Wigley
- Department of Medicine, Section of Structural Biology, Imperial College London, London, United Kingdom
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