1
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Kijewski ACR, Witsø IL, Sundaram AYM, Brynildsrud OB, Pettersen K, Anonsen EB, Anonsen JH, Aspholm ME. Transcriptomic and proteomic analysis of the virulence inducing effect of ciprofloxacin on enterohemorrhagic Escherichia coli. PLoS One 2024; 19:e0298746. [PMID: 38787890 PMCID: PMC11125564 DOI: 10.1371/journal.pone.0298746] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2023] [Accepted: 01/29/2024] [Indexed: 05/26/2024] Open
Abstract
Enterohemorrhagic E. coli (EHEC) is considered to be the most dangerous pathotype of E. coli, as it causes severe conditions such as hemorrhagic colitis (HC) and hemolytic uremic syndrome (HUS). Antibiotic treatment of EHEC infections is generally not recommended since it may promote the production of the Shiga toxin (Stx) and lead to worsened symptoms. This study explores how exposure to the fluoroquinolone ciprofloxacin reorganizes the transcriptome and proteome of EHEC O157:H7 strain EDL933, with special emphasis on virulence-associated factors. As expected, exposure to ciprofloxacin caused an extensive upregulation of SOS-response- and Stx-phage proteins, including Stx. A range of other virulence-associated factors were also upregulated, including many genes encoded by the LEE-pathogenicity island, the enterohemolysin gene (ehxA), as well as several genes and proteins involved in LPS production. However, a large proportion of the genes and proteins (17 and 8%, respectively) whose expression was upregulated upon ciprofloxacin exposure (17 and 8%, respectively) are not functionally assigned. This indicates a knowledge gap in our understanding of mechanisms involved in EHECs response to antibiotic-induced stress. Altogether, the results contribute to better understanding of how exposure to ciprofloxacin influences the virulome of EHEC and generates a knowledge base for further studies on how EHEC responds to antibiotic-induced stress. A deeper understanding on how EHEC responds to antibiotics will facilitate development of novel and safer treatments for EHEC infections.
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Affiliation(s)
| | - Ingun Lund Witsø
- Faculty of Veterinary Medicine, Unit for Food Safety, Norwegian University of Life Sciences, Oslo, Norway
| | - Arvind Y. M. Sundaram
- Department of Medical Genetics, Norwegian Sequencing Centre, Oslo University Hospital, Oslo, Norway
| | | | | | | | - Jan Haug Anonsen
- Department of Biosciences IBV, Mass Spectrometry and Proteomics Unit, University of Oslo, Oslo, Norway
- Norwegian Research Centre AS, Stavanger, Norway
| | - Marina Elisabeth Aspholm
- Faculty of Veterinary Medicine, Unit for Food Safety, Norwegian University of Life Sciences, Oslo, Norway
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2
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Nautiyal A, Thakur M. Prokaryotic DNA Crossroads: Holliday Junction Formation and Resolution. ACS OMEGA 2024; 9:12515-12538. [PMID: 38524412 PMCID: PMC10956419 DOI: 10.1021/acsomega.3c09866] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/10/2023] [Revised: 02/04/2024] [Accepted: 02/09/2024] [Indexed: 03/26/2024]
Abstract
Cells are continually exposed to a multitude of internal and external stressors, which give rise to various types of DNA damage. To protect the integrity of their genetic material, cells are equipped with a repertoire of repair proteins that engage in various repair mechanisms, facilitated by intricate networks of protein-protein and protein-DNA interactions. Among these networks is the homologous recombination (HR) system, a molecular repair mechanism conserved in all three domains of life. On one hand, HR ensures high-fidelity, template-dependent DNA repair, while on the other hand, it results in the generation of combinatorial genetic variations through allelic exchange. Despite substantial progress in understanding this pathway in bacteria, yeast, and humans, several critical questions remain unanswered, including the molecular processes leading to the exchange of DNA segments, the coordination of protein binding, conformational switching during branch migration, and the resolution of Holliday Junctions (HJs). This Review delves into our current understanding of the HR pathway in bacteria, shedding light on the roles played by various proteins or their complexes at different stages of HR. In the first part of this Review, we provide a brief overview of the end resection processes and the strand-exchange reaction, offering a concise depiction of the mechanisms that culminate in the formation of HJs. In the latter half, we expound upon the alternative methods of branch migration and HJ resolution more comprehensively and holistically, considering the historical research timelines. Finally, when we consolidate our knowledge about HR within the broader context of genome replication and the emergence of resistant species, it becomes evident that the HR pathway is indispensable for the survival of bacteria in diverse ecological niches.
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Affiliation(s)
- Astha Nautiyal
- Department
of Biochemistry, Indian Institute of Science, Bangalore 560012, India
| | - Manoj Thakur
- Sri
Venkateswara College, Benito Juarez Road, University of Delhi, New Delhi 110021, India
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3
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Albisetti A, Hälg S, Zoltner M, Mäser P, Wiedemar N. Suramin action in African trypanosomes involves a RuvB-like DNA helicase. Int J Parasitol Drugs Drug Resist 2023; 23:44-53. [PMID: 37757728 PMCID: PMC10520940 DOI: 10.1016/j.ijpddr.2023.09.003] [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: 08/04/2023] [Revised: 09/15/2023] [Accepted: 09/19/2023] [Indexed: 09/29/2023]
Abstract
Suramin is one of the oldest drugs in use today. It is still the treatment of choice for the hemolymphatic stage of African sleeping sickness caused by Trypanosoma brucei rhodesiense, and it is also used for surra in camels caused by Trypanosoma evansi. Yet despite one hundred years of use, suramin's mode of action is not fully understood. Suramin is a polypharmacological molecule that inhibits diverse proteins. Here we demonstrate that a DNA helicase of the pontin/ruvB-like 1 family, termed T. brucei RuvBL1, is involved in suramin resistance in African trypanosomes. Bloodstream-form T. b. rhodesiense under long-term selection for suramin resistance acquired a homozygous point mutation, isoleucine-312 to valine, close to the ATP binding site of T. brucei RuvBL1. The introduction of this missense mutation, by reverse genetics, into drug-sensitive trypanosomes significantly decreased their sensitivity to suramin. Intriguingly, the corresponding residue of T. evansi RuvBL1 was found mutated in a suramin-resistant field isolate, in that case to a leucine. RuvBL1 (Tb927.4.1270) is predicted to build a heterohexameric complex with RuvBL2 (Tb927.4.2000). RNAi-mediated silencing of gene expression of either T. brucei RuvBL1 or RuvBL2 caused cell death within 72 h. At 36 h after induction of RNAi, bloodstream-form trypanosomes exhibited a cytokinesis defect resulting in the accumulation of cells with two nuclei and two or more kinetoplasts. Taken together, these data indicate that RuvBL1 DNA helicase is involved in suramin action in African trypanosomes.
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Affiliation(s)
- Anna Albisetti
- Swiss Tropical and Public Health Institute, Kreuzstrasse 2, 4123, Allschwil, Switzerland; University of Basel, Petersplatz 1, 4001, Basel, Switzerland
| | - Silvan Hälg
- Swiss Tropical and Public Health Institute, Kreuzstrasse 2, 4123, Allschwil, Switzerland; University of Basel, Petersplatz 1, 4001, Basel, Switzerland
| | - Martin Zoltner
- Department of Parasitology, Faculty of Science, Charles University in Prague, Biocev, Vestec, Czech Republic
| | - Pascal Mäser
- Swiss Tropical and Public Health Institute, Kreuzstrasse 2, 4123, Allschwil, Switzerland; University of Basel, Petersplatz 1, 4001, Basel, Switzerland
| | - Natalie Wiedemar
- Swiss Tropical and Public Health Institute, Kreuzstrasse 2, 4123, Allschwil, Switzerland; University of Basel, Petersplatz 1, 4001, Basel, Switzerland.
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4
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Monteith W, Pascoe B, Mourkas E, Clark J, Hakim M, Hitchings MD, McCarthy N, Yahara K, Asakura H, Sheppard SK. Contrasting genes conferring short- and long-term biofilm adaptation in Listeria. Microb Genom 2023; 9:001114. [PMID: 37850975 PMCID: PMC10634452 DOI: 10.1099/mgen.0.001114] [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: 06/22/2023] [Accepted: 09/28/2023] [Indexed: 10/19/2023] Open
Abstract
Listeria monocytogenes is an opportunistic food-borne bacterium that is capable of infecting humans with high rates of hospitalization and mortality. Natural populations are genotypically and phenotypically variable, with some lineages being responsible for most human infections. The success of L. monocytogenes is linked to its capacity to persist on food and in the environment. Biofilms are an important feature that allow these bacteria to persist and infect humans, so understanding the genetic basis of biofilm formation is key to understanding transmission. We sought to investigate the biofilm-forming ability of L. monocytogenes by identifying genetic variation that underlies biofilm formation in natural populations using genome-wide association studies (GWAS). Changes in gene expression of specific strains during biofilm formation were then investigated using RNA sequencing (RNA-seq). Genetic variation associated with enhanced biofilm formation was identified in 273 genes by GWAS and differential expression in 220 genes by RNA-seq. Statistical analyses show that the number of overlapping genes flagged by either type of experiment is less than expected by random sampling. This novel finding is consistent with an evolutionary scenario where rapid adaptation is driven by variation in gene expression of pioneer genes, and this is followed by slower adaptation driven by nucleotide changes within the core genome.
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Affiliation(s)
- William Monteith
- Department of Biology, University of Oxford, Oxford, UK
- Department of Biology, University of Bath, Claverton Down, Bath, UK
| | - Ben Pascoe
- Department of Biology, University of Oxford, Oxford, UK
- Big Data Institute, University of Oxford, Oxford, UK
| | | | - Jack Clark
- Department of Genetics, University of Leicester, University Road, Leicester, UK
| | - Maliha Hakim
- Cancer Research UK Cambridge Institute, University of Cambridge, Li Ka Shing Centre, Robinson Way, Cambridge, UK
| | - Matthew D. Hitchings
- Swasnsea University Medical School, Swansea University, Singleton Campus, Swansea, UK
| | - Noel McCarthy
- School of Medicine, Trinity College Dublin, Dublin, Ireland
| | - Koji Yahara
- Antimicrobial Resistance Research Center, National Institute of Infectious Diseases, Tokyo, Japan
| | - Hiroshi Asakura
- Division of Biomedical Food Research, National Institute of Health Sciences, Tonomachi 3-25-26, Kawasaki-ku, Kawasaki, Kanagawa 210-9501, Japan
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5
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Cox MM, Goodman MF, Keck JL, van Oijen A, Lovett ST, Robinson A. Generation and Repair of Postreplication Gaps in Escherichia coli. Microbiol Mol Biol Rev 2023; 87:e0007822. [PMID: 37212693 PMCID: PMC10304936 DOI: 10.1128/mmbr.00078-22] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/23/2023] Open
Abstract
When replication forks encounter template lesions, one result is lesion skipping, where the stalled DNA polymerase transiently stalls, disengages, and then reinitiates downstream to leave the lesion behind in a postreplication gap. Despite considerable attention in the 6 decades since postreplication gaps were discovered, the mechanisms by which postreplication gaps are generated and repaired remain highly enigmatic. This review focuses on postreplication gap generation and repair in the bacterium Escherichia coli. New information to address the frequency and mechanism of gap generation and new mechanisms for their resolution are described. There are a few instances where the formation of postreplication gaps appears to be programmed into particular genomic locations, where they are triggered by novel genomic elements.
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Affiliation(s)
- Michael M. Cox
- Department of Biochemistry, University of Wisconsin—Madison, Madison, Wisconsin, USA
| | - Myron F. Goodman
- Department of Biological Sciences, University of Southern California, University Park, Los Angeles, California, USA
- Department of Chemistry, University of Southern California, University Park, Los Angeles, California, USA
| | - James L. Keck
- Department of Biological Chemistry, University of Wisconsin—Madison School of Medicine, Madison, Wisconsin, USA
| | - Antoine van Oijen
- Molecular Horizons, University of Wollongong, Wollongong, New South Wales, Australia
- School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, New South Wales, Australia
| | - Susan T. Lovett
- Department of Biology, Brandeis University, Waltham, Massachusetts, USA
| | - Andrew Robinson
- Molecular Horizons, University of Wollongong, Wollongong, New South Wales, Australia
- School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, New South Wales, Australia
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6
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Mahmoud R, Dhakal S. Single-Molecule Analysis of DNA Branch Migration under Biomimetic Environments. J Phys Chem B 2022; 126:7252-7261. [DOI: 10.1021/acs.jpcb.2c03153] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Roaa Mahmoud
- Department of Chemistry, Virginia Commonwealth University, 1001 West Main Street, Richmond, Virginia 23284, United States
| | - Soma Dhakal
- Department of Chemistry, Virginia Commonwealth University, 1001 West Main Street, Richmond, Virginia 23284, United States
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7
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Wald J, Fahrenkamp D, Goessweiner-Mohr N, Lugmayr W, Ciccarelli L, Vesper O, Marlovits TC. Mechanism of AAA+ ATPase-mediated RuvAB-Holliday junction branch migration. Nature 2022; 609:630-639. [PMID: 36002576 PMCID: PMC9477746 DOI: 10.1038/s41586-022-05121-1] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2021] [Accepted: 07/18/2022] [Indexed: 12/12/2022]
Abstract
The Holliday junction is a key intermediate formed during DNA recombination across all kingdoms of life1. In bacteria, the Holliday junction is processed by two homo-hexameric AAA+ ATPase RuvB motors, which assemble together with the RuvA-Holliday junction complex to energize the strand-exchange reaction2. Despite its importance for chromosome maintenance, the structure and mechanism by which this complex facilitates branch migration are unknown. Here, using time-resolved cryo-electron microscopy, we obtained structures of the ATP-hydrolysing RuvAB complex in seven distinct conformational states, captured during assembly and processing of a Holliday junction. Five structures together resolve the complete nucleotide cycle and reveal the spatiotemporal relationship between ATP hydrolysis, nucleotide exchange and context-specific conformational changes in RuvB. Coordinated motions in a converter formed by DNA-disengaged RuvB subunits stimulate hydrolysis and nucleotide exchange. Immobilization of the converter enables RuvB to convert the ATP-contained energy into a lever motion, which generates the pulling force driving the branch migration. We show that RuvB motors rotate together with the DNA substrate, which, together with a progressing nucleotide cycle, forms the mechanistic basis for DNA recombination by continuous branch migration. Together, our data decipher the molecular principles of homologous recombination by the RuvAB complex, elucidate discrete and sequential transition-state intermediates for chemo-mechanical coupling of hexameric AAA+ motors and provide a blueprint for the design of state-specific compounds targeting AAA+ motors.
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Affiliation(s)
- Jiri Wald
- Institute of Structural and Systems Biology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
- Centre for Structural Systems Biology, Hamburg, Germany.
- Deutsches Elektronen Synchrotron (DESY), Hamburg, Germany.
- Institute of Molecular Biotechnology GmbH (IMBA), Austrian Academy of Sciences, Vienna, Austria.
- Research Institute of Molecular Pathology (IMP), Vienna, Austria.
| | - Dirk Fahrenkamp
- Institute of Structural and Systems Biology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
- Centre for Structural Systems Biology, Hamburg, Germany.
- Deutsches Elektronen Synchrotron (DESY), Hamburg, Germany.
| | - Nikolaus Goessweiner-Mohr
- Institute of Structural and Systems Biology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
- Centre for Structural Systems Biology, Hamburg, Germany
- Deutsches Elektronen Synchrotron (DESY), Hamburg, Germany
- Institute of Molecular Biotechnology GmbH (IMBA), Austrian Academy of Sciences, Vienna, Austria
- Research Institute of Molecular Pathology (IMP), Vienna, Austria
- Institute of Biophysics, Johannes Kepler University (JKU), Linz, Austria
| | - Wolfgang Lugmayr
- Institute of Structural and Systems Biology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
- Centre for Structural Systems Biology, Hamburg, Germany
- Deutsches Elektronen Synchrotron (DESY), Hamburg, Germany
- Institute of Molecular Biotechnology GmbH (IMBA), Austrian Academy of Sciences, Vienna, Austria
- Research Institute of Molecular Pathology (IMP), Vienna, Austria
| | - Luciano Ciccarelli
- Institute of Structural and Systems Biology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
- Centre for Structural Systems Biology, Hamburg, Germany
- Institute of Molecular Biotechnology GmbH (IMBA), Austrian Academy of Sciences, Vienna, Austria
- Research Institute of Molecular Pathology (IMP), Vienna, Austria
- GlaxoSmithKline Vaccines, Siena, Italy
| | - Oliver Vesper
- Institute of Structural and Systems Biology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
- Centre for Structural Systems Biology, Hamburg, Germany
- Deutsches Elektronen Synchrotron (DESY), Hamburg, Germany
- Institute of Molecular Biotechnology GmbH (IMBA), Austrian Academy of Sciences, Vienna, Austria
- Research Institute of Molecular Pathology (IMP), Vienna, Austria
| | - Thomas C Marlovits
- Institute of Structural and Systems Biology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
- Centre for Structural Systems Biology, Hamburg, Germany.
- Deutsches Elektronen Synchrotron (DESY), Hamburg, Germany.
- Institute of Molecular Biotechnology GmbH (IMBA), Austrian Academy of Sciences, Vienna, Austria.
- Research Institute of Molecular Pathology (IMP), Vienna, Austria.
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8
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Bianco PR. OB-fold Families of Genome Guardians: A Universal Theme Constructed From the Small β-barrel Building Block. Front Mol Biosci 2022; 9:784451. [PMID: 35223988 PMCID: PMC8881015 DOI: 10.3389/fmolb.2022.784451] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Accepted: 01/19/2022] [Indexed: 11/13/2022] Open
Abstract
The maintenance of genome stability requires the coordinated actions of multiple proteins and protein complexes, that are collectively known as genome guardians. Within this broadly defined family is a subset of proteins that contain oligonucleotide/oligosaccharide-binding folds (OB-fold). While OB-folds are widely associated with binding to single-stranded DNA this view is no longer an accurate depiction of how these domains are utilized. Instead, the core of the OB-fold is modified and adapted to facilitate binding to a variety of DNA substrates (both single- and double-stranded), phospholipids, and proteins, as well as enabling catalytic function to a multi-subunit complex. The flexibility accompanied by distinctive oligomerization states and quaternary structures enables OB-fold genome guardians to maintain the integrity of the genome via a myriad of complex and dynamic, protein-protein; protein-DNA, and protein-lipid interactions in both prokaryotes and eukaryotes.
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Affiliation(s)
- Piero R. Bianco
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Nebraska Medical Center, Omaha, NE, United States
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9
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Lemma AS, Soto-Echevarria N, Brynildsen MP. Fluoroquinolone Persistence in Escherichia coli Requires DNA Repair despite Differing between Starving Populations. Microorganisms 2022; 10:286. [PMID: 35208744 PMCID: PMC8877308 DOI: 10.3390/microorganisms10020286] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2021] [Revised: 01/19/2022] [Accepted: 01/20/2022] [Indexed: 12/04/2022] Open
Abstract
When faced with nutritional deprivation, bacteria undergo a range of metabolic, regulatory, and biosynthetic changes. Those adjustments, which can be specific or independent of the missing nutrient, often alter bacterial tolerance to antibiotics. Here, using fluoroquinolones, we quantified Escherichia coli persister levels in cultures experiencing starvation from a lack of carbon (C), nitrogen (N), phosphorous (P), or magnesium (Mg2+). Interestingly, persister levels varied significantly based on the type of starvation as well as fluoroquinolone used with N-starved populations exhibiting the highest persistence to levofloxacin, and P-starved populations exhibiting the highest persistence to moxifloxacin. However, regardless of the type of starvation or fluoroquinolone used, DNA repair was required by persisters, with ∆recA and ∆recB uniformly exhibiting the lowest persistence of the mutants assayed. These results suggest that while the type of starvation and fluoroquinolone will modulate the level of persistence, the importance of homologous recombination is consistently observed, which provides further support for efforts to target homologous recombination for anti-persister purposes.
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Affiliation(s)
- Annabel S. Lemma
- Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ 08544, USA;
| | | | - Mark P. Brynildsen
- Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ 08544, USA;
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA;
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10
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Fuji N, Pichichero M, Ehrlich RL, Mell JC, Ehrlich GD, Kaur R. Transition of Serotype 35B Pneumococci From Commensal to Prevalent Virulent Strain in Children. Front Cell Infect Microbiol 2021; 11:744742. [PMID: 34765566 PMCID: PMC8577857 DOI: 10.3389/fcimb.2021.744742] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2021] [Accepted: 09/13/2021] [Indexed: 11/13/2022] Open
Abstract
In our community-based prospective cohort study in young children, we observed a significant increase in pneumococcal serotype 35B nasopharyngeal (NP) commensal colonization during the 2011–2014 timeframe, but these strains were not associated with disease. Beginning in 2015 and continuing through to the present, the serotype 35B virulence changed, and it became the dominant bacteria isolated and associated with pneumococcal acute otitis-media (AOM) in our cohort. We performed comparative analyses of 250 35B isolates obtained from 140 children collected between 2006 and 2019. Changes in prevalence, clonal-complex composition, and antibiotic resistance were analyzed. Seventy-two (29%) of 35B isolates underwent whole-genome sequencing to investigate genomic changes associated with the shift in virulence that resulted in increased rates of 35B-associated AOM disease. 35B strains that were commensals and AOM disease-causing were mainly associated with sequence type (ST) 558. Antibiotic concentrations of β-lactams and ofloxacin necessary to inhibit growth of 35B strains rose significantly (2006–2019) (p<0.005). However, only isolates from the 35B/ST558 showed significant increases in MIC50 of penicillin and ofloxacin between the years 2006–2014 and 2015–2019 (p=0.007 and p<0.0001). One hundred thirty-eight SNPs located in 34 different genes were significantly associated with post-2015 strains. SNPs were found in nrdG (metal binding, 10%); metP and metN (ABC transporter, 9%); corA (Mg2+ transporter, 6%); priA (DNA replication, 5%); and on the enzymic gene ldcB (LD-carboxypeptidase, 3%). Pneumococcal serotype 35B strains was a common NP commensal during 2010–2014. In 2015, a shift in increasing number of AOM cases occurred in young children caused by 35B, that was associated with changes in genetic composition and antibiotic susceptibility.
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Affiliation(s)
- Naoko Fuji
- Center for Infectious Diseases and Immunology, Rochester General Hospital Research Institute, Rochester, NY, United States
| | - Michael Pichichero
- Center for Infectious Diseases and Immunology, Rochester General Hospital Research Institute, Rochester, NY, United States
| | - Rachel L Ehrlich
- Department of Microbiology and Immunology, Drexel University College of Medicine, and Center for Genomic Sciences, Institute of Molecular Medicine and Infectious Disease, Philadelphia, PA, United States
| | - Joshua Chang Mell
- Department of Microbiology and Immunology, Drexel University College of Medicine, and Center for Genomic Sciences, Institute of Molecular Medicine and Infectious Disease, Philadelphia, PA, United States
| | - Garth D Ehrlich
- Department of Microbiology and Immunology, Drexel University College of Medicine, and Center for Genomic Sciences, Institute of Molecular Medicine and Infectious Disease, Philadelphia, PA, United States.,Department of Otolaryngology-Head and Neck Surgery, Drexel University College of Medicine, Philadelphia, PA, United States
| | - Ravinder Kaur
- Center for Infectious Diseases and Immunology, Rochester General Hospital Research Institute, Rochester, NY, United States
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11
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Gándara C, Torres R, Carrasco B, Ayora S, Alonso JC. DisA Restrains the Processing and Cleavage of Reversed Replication Forks by the RuvAB-RecU Resolvasome. Int J Mol Sci 2021; 22:11323. [PMID: 34768753 PMCID: PMC8583203 DOI: 10.3390/ijms222111323] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Revised: 10/04/2021] [Accepted: 10/16/2021] [Indexed: 11/17/2022] Open
Abstract
DNA lesions that impede fork progression cause replisome stalling and threaten genome stability. Bacillus subtilis RecA, at a lesion-containing gap, interacts with and facilitates DisA pausing at these branched intermediates. Paused DisA suppresses its synthesis of the essential c-di-AMP messenger. The RuvAB-RecU resolvasome branch migrates and resolves formed Holliday junctions (HJ). We show that DisA prevents DNA degradation. DisA, which interacts with RuvB, binds branched structures, and reduces the RuvAB DNA-dependent ATPase activity. DisA pre-bound to HJ DNA limits RuvAB and RecU activities, but such inhibition does not occur if the RuvAB- or RecU-HJ DNA complexes are pre-formed. RuvAB or RecU pre-bound to HJ DNA strongly inhibits DisA-mediated synthesis of c-di-AMP, and indirectly blocks cell proliferation. We propose that DisA limits RuvAB-mediated fork remodeling and RecU-mediated HJ cleavage to provide time for damage removal and replication restart in order to preserve genome integrity.
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Affiliation(s)
| | | | | | - Silvia Ayora
- Department of Microbial Biotechnology, Centro Nacional de Biotecnología, CNB-CSIC, 3 Darwin St, 28049 Madrid, Spain; (C.G.); (R.T.); (B.C.)
| | - Juan C. Alonso
- Department of Microbial Biotechnology, Centro Nacional de Biotecnología, CNB-CSIC, 3 Darwin St, 28049 Madrid, Spain; (C.G.); (R.T.); (B.C.)
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12
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Direct unfolding of RuvA-HJ complex at the single-molecule level. Biophys J 2021; 120:1894-1902. [PMID: 33737156 DOI: 10.1016/j.bpj.2021.03.006] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2020] [Revised: 03/03/2021] [Accepted: 03/09/2021] [Indexed: 11/20/2022] Open
Abstract
The repair of double-stranded DNA breaks via homologous recombination involves a four-way cross-strand intermediate known as Holliday junction (HJ), which is recognized, processed, and resolved by a specific set of proteins. RuvA, a prokaryotic HJ-binding protein, is known to stabilize the square-planar conformation of the HJ, which is otherwise a short-lived intermediate. Despite much progress being made regarding the molecular mechanism of RuvA-HJ interactions, the mechanochemical aspect of this protein-HJ complex is yet to be investigated. Here, we employed an optical-tweezers-based, single-molecule manipulation assay to detect the formation of RuvA-HJ complex and determined its mechanical and thermodynamic properties in a manner that would be impossible with traditional ensemble techniques. We found that the binding of RuvA increases the unfolding force (Funfold) of the HJ by ∼2-fold. Compared with the ΔGunfold of the HJ alone (54 ± 13 kcal/mol), the increased free energy of the RuvA-HJ complex (101 ± 20 kcal/mol) demonstrates that the RuvA protein stabilizes HJs. Interestingly, the protein remains bound to the mechanically melted HJ, facilitating its refolding at an unusually high force when the stretched DNA molecule is relaxed. These results suggest that the RuvA protein not only stabilizes the HJs but also induces refolding of the HJs. The single-molecule platform that we employed here for studying the RuvA-HJ interaction is broadly applicable to study other HJ-binding proteins involved in the critical DNA repair process.
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13
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Hu Y, He Y, Lin Z. Biochemical and structural characterization of the Holliday junction resolvase RuvC from Pseudomonas aeruginosa. Biochem Biophys Res Commun 2020; 525:265-271. [PMID: 32085896 DOI: 10.1016/j.bbrc.2020.02.062] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2020] [Accepted: 02/09/2020] [Indexed: 11/19/2022]
Abstract
The Holliday junction, a four-way DNA structure, is an important intermediate of homologous recombination. Proper Holliday junction resolution is critical to complete the recombination process. In most bacterial cells, the Holliday junction cleavage is mainly performed by a specific endonuclease RuvC. Here, we describe the biochemical properties and the crystal structure of RuvC from an opportunistic pathogen, Pseudomonas aeruginosa (PaRuvC). PaRuvC specifically binds to the Holliday junction DNA and preferentially cleaves it at the consensus 5'-TTC-3'. PaRuvC uses Mg2+ as the preferred divalent metal cofactor for Holliday junction cleavage and its optimum pH is 8.0-9.0. Elevated temperatures (37-60 °C) boost the catalytic activity, but temperatures higher than 53 °C reduce the protein stability. The crystal structure of PaRuvC determined at 2.4 Å and mutagenesis analysis reveal key residues involved in the dimer formation, substrate binding and catalysis. Our results are expected to provide useful information to combat antibiotic resistance of Pseudomonas aeruginosa by targeting its homologous recombination system.
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Affiliation(s)
- Yi Hu
- College of Chemistry, Fuzhou University, Fuzhou, 350108, China
| | - Yuhua He
- College of Chemistry, Fuzhou University, Fuzhou, 350108, China
| | - Zhonghui Lin
- College of Chemistry, Fuzhou University, Fuzhou, 350108, China.
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14
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Weaver GM, Mettrick KA, Corocher TA, Graham A, Grainge I. Replication fork collapse at a protein-DNA roadblock leads to fork reversal, promoted by the RecQ helicase. Mol Microbiol 2018; 111:455-472. [PMID: 30466158 DOI: 10.1111/mmi.14166] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/09/2018] [Indexed: 11/27/2022]
Abstract
Proteins that bind DNA are the cause of the majority of impediments to replication fork progression and can lead to subsequent collapse of the replication fork. Failure to deal with fork collapse efficiently leads to mutation or cell death. Several models have been proposed for how a cell processes a stalled or collapsed replication fork; eukaryotes and bacteria are not dissimilar in terms of the general pathways undertaken to deal with these events. This study shows that replication fork regression, the combination of replication fork reversal leading to formation of a Holliday Junction along with exonuclease digestion, is the preferred pathway for dealing with a collapsed fork in Escherichia coli. Direct endo-nuclease activity at the replication fork was not observed. The protein that had the greatest effect on these fork processing events was the RecQ helicase, while RecG and RuvABC, which have previously been implicated in this process, were found to play a lesser role. Eukaryotic RecQ homologues, BLM and WRN, have also been implicated in processing events following replication fork collapse and may reflect a conserved mechanism. Finally, the SOS response was not induced by the protein-DNA roadblock under these conditions, so did not affect fork processing.
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Affiliation(s)
- Georgia M Weaver
- School of Environmental and Life Sciences, University of Newcastle, Callaghan, Australia
| | - Karla A Mettrick
- School of Environmental and Life Sciences, University of Newcastle, Callaghan, Australia
| | - Tayla-Ann Corocher
- School of Environmental and Life Sciences, University of Newcastle, Callaghan, Australia
| | - Adam Graham
- School of Environmental and Life Sciences, University of Newcastle, Callaghan, Australia
| | - Ian Grainge
- School of Environmental and Life Sciences, University of Newcastle, Callaghan, Australia
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15
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Gibbs DR, Dhakal S. Single-Molecule Imaging Reveals Conformational Manipulation of Holliday Junction DNA by the Junction Processing Protein RuvA. Biochemistry 2018; 57:3616-3624. [PMID: 29767969 DOI: 10.1021/acs.biochem.8b00404] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Interactions between DNA and motor proteins regulate nearly all biological functions of DNA such as gene expression, DNA replication and repair, and transcription. During the late stages of homologous recombination (HR), the Escherichia coli recombination machinery, RuvABC, resolves the four-way DNA motifs called Holliday junctions (HJs) that are formed during exchange of nucleotide sequences between two homologous duplex DNA. Although the formation of the RuvA-HJ complex is known to be the first critical step in the RuvABC pathway, the mechanism for the binding interaction between RuvA and HJ has remained elusive. Here, using single-molecule fluorescence resonance energy transfer (smFRET) and ensemble analyses, we show that RuvA stably binds to the HJ, halting its conformational dynamics. Our FRET experiments in different ionic environments created by Mg2+ and Na+ ions suggest that RuvA binds to the HJ via electrostatic interaction. Further, while recent studies have indicated that the HR process can be modulated for therapeutic applications by selective targeting of the HJ by chemotherapeutic drugs, we investigated the effect of drug-modified HJ on binding. Using cisplatin as a proof-of-concept drug, we show that RuvA binds to the cisplatin-modified HJ as efficiently as to the unmodified HJ, demonstrating that RuvA accommodates for the cisplatin-introduced charges and/or topological changes on the HJ.
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Affiliation(s)
- Dalton R Gibbs
- Department of Chemistry , Virginia Commonwealth University , 1001 West Main Street , Richmond , Virginia 23284 , United States
| | - Soma Dhakal
- Department of Chemistry , Virginia Commonwealth University , 1001 West Main Street , Richmond , Virginia 23284 , United States
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16
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Inano S, Sato K, Katsuki Y, Kobayashi W, Tanaka H, Nakajima K, Nakada S, Miyoshi H, Knies K, Takaori-Kondo A, Schindler D, Ishiai M, Kurumizaka H, Takata M. RFWD3-Mediated Ubiquitination Promotes Timely Removal of Both RPA and RAD51 from DNA Damage Sites to Facilitate Homologous Recombination. Mol Cell 2017; 66:622-634.e8. [PMID: 28575658 DOI: 10.1016/j.molcel.2017.04.022] [Citation(s) in RCA: 104] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2016] [Revised: 01/28/2017] [Accepted: 04/26/2017] [Indexed: 12/12/2022]
Abstract
RFWD3 is a recently identified Fanconi anemia protein FANCW whose E3 ligase activity toward RPA is essential in homologous recombination (HR) repair. However, how RPA ubiquitination promotes HR remained unknown. Here, we identified RAD51, the central HR protein, as another target of RFWD3. We show that RFWD3 polyubiquitinates both RPA and RAD51 in vitro and in vivo. Phosphorylation by ATR and ATM kinases is required for this activity in vivo. RFWD3 inhibits persistent mitomycin C (MMC)-induced RAD51 and RPA foci by promoting VCP/p97-mediated protein dynamics and subsequent degradation. Furthermore, MMC-induced chromatin loading of MCM8 and RAD54 is defective in cells with inactivated RFWD3 or expressing a ubiquitination-deficient mutant RAD51. Collectively, our data reveal a mechanism that facilitates timely removal of RPA and RAD51 from DNA damage sites, which is crucial for progression to the late-phase HR and suppression of the FA phenotype.
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Affiliation(s)
- Shojiro Inano
- Laboratory of DNA Damage Signaling, Department of Late Effects Studies, Radiation Biology Center, Kyoto University, Kyoto 606-8501, Japan; Department of Hematology and Oncology, Graduate School of Medicine, Kyoto University, Kyoto 606-8507, Japan
| | - Koichi Sato
- Laboratory of Structural Biology, Graduate School of Advanced Science and Engineering, Waseda University, Tokyo 169-8050, Japan
| | - Yoko Katsuki
- Laboratory of DNA Damage Signaling, Department of Late Effects Studies, Radiation Biology Center, Kyoto University, Kyoto 606-8501, Japan
| | - Wataru Kobayashi
- Laboratory of Structural Biology, Graduate School of Advanced Science and Engineering, Waseda University, Tokyo 169-8050, Japan
| | - Hiroki Tanaka
- Laboratory of Structural Biology, Graduate School of Advanced Science and Engineering, Waseda University, Tokyo 169-8050, Japan
| | - Kazuhiro Nakajima
- Department of Bioregulation and Cellular Response, Graduate School of Medicine, Osaka University, Osaka 565-0871, Japan
| | - Shinichiro Nakada
- Department of Bioregulation and Cellular Response, Graduate School of Medicine, Osaka University, Osaka 565-0871, Japan; Institute for Advanced Co-Creation Studies, Osaka University, Osaka 565-0871, Japan
| | - Hiroyuki Miyoshi
- Department of Physiology, Keio University School of Medicine, Tokyo 160-8582, Japan
| | - Kerstin Knies
- Department of Human Genetics, Biozentrum, University of Wurzburg, 97074 Wurzburg, Germany
| | - Akifumi Takaori-Kondo
- Department of Hematology and Oncology, Graduate School of Medicine, Kyoto University, Kyoto 606-8507, Japan
| | - Detlev Schindler
- Department of Human Genetics, Biozentrum, University of Wurzburg, 97074 Wurzburg, Germany
| | - Masamichi Ishiai
- Laboratory of DNA Damage Signaling, Department of Late Effects Studies, Radiation Biology Center, Kyoto University, Kyoto 606-8501, Japan
| | - Hitoshi Kurumizaka
- Laboratory of Structural Biology, Graduate School of Advanced Science and Engineering, Waseda University, Tokyo 169-8050, Japan
| | - Minoru Takata
- Laboratory of DNA Damage Signaling, Department of Late Effects Studies, Radiation Biology Center, Kyoto University, Kyoto 606-8501, Japan.
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17
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TRF2 binds branched DNA to safeguard telomere integrity. Nat Struct Mol Biol 2017; 24:734-742. [PMID: 28805810 DOI: 10.1038/nsmb.3451] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2017] [Accepted: 07/11/2017] [Indexed: 12/16/2022]
Abstract
Although t-loops protect telomeres, they are at risk of cleavage by Holliday junction (HJ) resolvases if branch migration converts the three-way t-loop junction into four-way HJs. T-loop cleavage is repressed by the TRF2 basic domain, which binds three- and four-way junctions and protects HJs in vitro. By replacing the basic domain with bacterial-protein domains binding three- and four-way junctions, we demonstrated the in vivo relevance of branched-DNA binding. Branched-DNA binding also repressed PARP1, presumably by masking the PARP1 site in the t-loop junction. Although PARP1 recruits HJ resolvases and promotes t-loop cleavage, PARP1 activation alone did not result in t-loop cleavage, thus suggesting that the basic domain also prevents formation of HJs. Concordantly, removal of HJs by BLM helicase mitigated t-loop cleavage in response to loss of the basic domain. We propose that TRF2 masks and stabilizes the t-loop three-way junction, thereby protecting telomeres from detrimental deletions and PARP1 activation.
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18
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Iwasa T, Han YW, Hiramatsu R, Yokota H, Nakao K, Yokokawa R, Ono T, Harada Y. Synergistic effect of ATP for RuvA-RuvB-Holliday junction DNA complex formation. Sci Rep 2015; 5:18177. [PMID: 26658024 PMCID: PMC4677358 DOI: 10.1038/srep18177] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2015] [Accepted: 11/13/2015] [Indexed: 11/25/2022] Open
Abstract
The Escherichia coli RuvB hexameric ring motor proteins, together with RuvAs, promote branch migration of Holliday junction DNA. Zero mode waveguides (ZMWs) constitute of nanosized holes and enable the visualization of a single fluorescent molecule under micromolar order of the molecules, which is applicable to characterize the formation of RuvA–RuvB–Holliday junction DNA complex. In this study, we used ZMWs and counted the number of RuvBs binding to RuvA–Holliday junction DNA complex. Our data demonstrated that different nucleotide analogs increased the amount of Cy5-RuvBs binding to RuvA–Holliday junction DNA complex in the following order: no nucleotide, ADP, ATPγS, and mixture of ADP and ATPγS. These results suggest that not only ATP binding to RuvB but also ATP hydrolysis by RuvB facilitates a stable RuvA–RuvB–Holliday junction DNA complex formation.
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Affiliation(s)
- Takuma Iwasa
- Institute for Integrated Cell-Materials Science (WPI-iCeMS), Kyoto University, Sakyo, Kyoto 606-8501, Japan.,Graduate School of Biostudies, Kyoto University, Sakyo, Kyoto 606-8501, Japan
| | - Yong-Woon Han
- Institute for Integrated Cell-Materials Science (WPI-iCeMS), Kyoto University, Sakyo, Kyoto 606-8501, Japan.,CREST, Japan Science and Technology Corporation (JST), Sanbancho, Chiyoda, Tokyo 102-0075, Japan
| | - Ryo Hiramatsu
- Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan
| | - Hiroaki Yokota
- Institute for Integrated Cell-Materials Science (WPI-iCeMS), Kyoto University, Sakyo, Kyoto 606-8501, Japan
| | - Kimiko Nakao
- Institute for Integrated Cell-Materials Science (WPI-iCeMS), Kyoto University, Sakyo, Kyoto 606-8501, Japan
| | - Ryuji Yokokawa
- Department of Micro Engineering, Graduate School of Technology, Kyoto University, Sakyo, Kyoto 606-8501, Japan
| | - Teruo Ono
- Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan
| | - Yoshie Harada
- Institute for Integrated Cell-Materials Science (WPI-iCeMS), Kyoto University, Sakyo, Kyoto 606-8501, Japan.,Graduate School of Biostudies, Kyoto University, Sakyo, Kyoto 606-8501, Japan.,CREST, Japan Science and Technology Corporation (JST), Sanbancho, Chiyoda, Tokyo 102-0075, Japan
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19
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Kowalczykowski SC. An Overview of the Molecular Mechanisms of Recombinational DNA Repair. Cold Spring Harb Perspect Biol 2015; 7:a016410. [PMID: 26525148 PMCID: PMC4632670 DOI: 10.1101/cshperspect.a016410] [Citation(s) in RCA: 320] [Impact Index Per Article: 35.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Recombinational DNA repair is a universal aspect of DNA metabolism and is essential for genomic integrity. It is a template-directed process that uses a second chromosomal copy (sister, daughter, or homolog) to ensure proper repair of broken chromosomes. The key steps of recombination are conserved from phage through human, and an overview of those steps is provided in this review. The first step is resection by helicases and nucleases to produce single-stranded DNA (ssDNA) that defines the homologous locus. The ssDNA is a scaffold for assembly of the RecA/RAD51 filament, which promotes the homology search. On finding homology, the nucleoprotein filament catalyzes exchange of DNA strands to form a joint molecule. Recombination is controlled by regulating the fate of both RecA/RAD51 filaments and DNA pairing intermediates. Finally, intermediates that mature into Holliday structures are disjoined by either nucleolytic resolution or topological dissolution.
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Affiliation(s)
- Stephen C Kowalczykowski
- Department of Microbiology & Molecular Genetics and Department of Molecular and Cellular Biology, University of California, Davis, Davis, California 95616
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20
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Abstract
Four-way DNA intermediates, called Holliday junctions (HJs), can form during meiotic and mitotic recombination, and their removal is crucial for chromosome segregation. A group of ubiquitous and highly specialized structure-selective endonucleases catalyze the cleavage of HJs into two disconnected DNA duplexes in a reaction called HJ resolution. These enzymes, called HJ resolvases, have been identified in bacteria and their bacteriophages, archaea, and eukaryotes. In this review, we discuss fundamental aspects of the HJ structure and their interaction with junction-resolving enzymes. This is followed by a brief discussion of the eubacterial RuvABC enzymes, which provide the paradigm for HJ resolvases in other organisms. Finally, we review the biochemical and structural properties of some well-characterized resolvases from archaea, bacteriophage, and eukaryotes.
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Affiliation(s)
- Haley D M Wyatt
- London Research Institute, Cancer Research UK, Clare Hall Laboratories, South Mimms, Herts EN6 3LD, United Kingdom
| | - Stephen C West
- London Research Institute, Cancer Research UK, Clare Hall Laboratories, South Mimms, Herts EN6 3LD, United Kingdom
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21
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Ahmad M, Tuteja R. Plasmodium falciparum RuvB2 translocates in 5′–3′ direction, relocalizes during schizont stage and its enzymatic activities are up regulated by RuvB3 of the same complex. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2013; 1834:2795-811. [DOI: 10.1016/j.bbapap.2013.10.010] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/11/2013] [Revised: 10/14/2013] [Accepted: 10/16/2013] [Indexed: 11/27/2022]
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22
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Tolerance of Escherichia coli to fluoroquinolone antibiotics depends on specific components of the SOS response pathway. Genetics 2013; 195:1265-76. [PMID: 24077306 DOI: 10.1534/genetics.113.152306] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Bacteria exposed to bactericidal fluoroquinolone (FQ) antibiotics can survive without becoming genetically resistant. Survival of these phenotypically resistant cells, commonly called "persisters," depends on the SOS gene network. We have examined mutants in all known SOS-regulated genes to identify functions essential for tolerance in Escherichia coli. The absence of DinG and UvrD helicases and the Holliday junction processing enzymes RuvA and RuvB leads to a decrease in survival. Analysis of the respective mutants indicates that, in addition to repair of double-strand breaks, tolerance depends on the repair of collapsed replication forks and stalled transcription complexes. Mutation in recF results in increased survival, which identifies RecAF recombination as a poisoning mechanism not previously linked to FQ lethality. DinG acts upstream of SOS promoting its induction, whereas RuvAB participates in repair only. UvrD directly promotes all repair processes initiated by FQ-induced damage and prevents RecAF-dependent misrepair, making it one of the crucial SOS functions required for tolerance.
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23
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Abd Wahab S, Choi M, Bianco PR. Characterization of the ATPase activity of RecG and RuvAB proteins on model fork structures reveals insight into stalled DNA replication fork repair. J Biol Chem 2013; 288:26397-409. [PMID: 23893472 DOI: 10.1074/jbc.m113.500223] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
RecG and RuvAB are proposed to act at stalled DNA replication forks to facilitate replication restart. To clarify the roles of these proteins in fork regression, we used a coupled spectrophotometric ATPase assay to determine how these helicases act on two groups of model fork substrates: the first group mimics nascent stalled forks, whereas the second mimics regressed fork structures. The results show that RecG is active on the substrates in group 1, whereas these are poor substrates for RuvAB. In addition, in the presence of group 1 forks, the single-stranded DNA-binding protein (SSB) enhances the activity of RecG and enables it to compete with excess RuvA. In contrast, SSB inhibits the activity of RuvAB on these substrates. Results also show that the preferred regressed fork substrate for RuvAB is a Holliday junction, not a forked DNA. The active form of the enzyme on the Holliday junction contains a single RuvA tetramer. In contrast, although the enzyme is active on a regressed fork structure, RuvB loading by a single RuvA tetramer is impaired, and full activity requires the cooperative binding of two forked DNA substrate molecules. Collectively, the data support a model where RecG is responsible for stalled DNA replication fork regression. SSB ensures that if the nascent fork has single-stranded DNA character RuvAB is inhibited, whereas the activity of RecG is preferentially enhanced. Only once the fork has been regressed and the DNA is relaxed can RuvAB bind to a RecG-extruded Holliday junction.
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24
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Osakabe A, Tachiwana H, Takaku M, Hori T, Obuse C, Kimura H, Fukagawa T, Kurumizaka H. Vertebrate Spt2 is a novel nucleolar histone chaperone that assists in ribosomal DNA transcription. J Cell Sci 2013; 126:1323-32. [PMID: 23378026 DOI: 10.1242/jcs.112623] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In eukaryotes, transcription occurs in the chromatin context with the assistance of histone-binding proteins, such as chromatin/nucleosome remodeling factors and histone chaperones. However, it is unclear how each remodeling factor or histone chaperone functions in transcription. Here, we identify a novel histone-binding protein, Spt2, in higher eukaryotes. Recombinant human Spt2 binds to histones and DNA, and promotes nucleosome assembly in vitro. Spt2 accumulates in nucleoli and interacts with RNA polymerase I in chicken DT40 cells, suggesting its involvement in ribosomal RNA transcription. Consistently, Spt2-deficient chicken DT40 cells are sensitive to RNA polymerase I inhibitors and exhibit decreased transcription activity, as shown by a transcription run-on assay. Domain analyses of Spt2 revealed that the C-terminal region, containing the region homologous to yeast Spt2, is responsible for histone binding, while the central region is essential for nucleolar localization and DNA binding. Based on these results, we conclude that vertebrate Spt2 is a novel histone chaperone with a separate DNA-binding domain that facilitates ribosomal DNA transcription through chromatin remodeling during transcription.
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Affiliation(s)
- Akihisa Osakabe
- Laboratory of Structural Biology, Graduate School of Advanced Science and Engineering, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo 162-8480, Japan
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25
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Chen L, Shi K, Yin Z, Aihara H. Structural asymmetry in the Thermus thermophilus RuvC dimer suggests a basis for sequential strand cleavages during Holliday junction resolution. Nucleic Acids Res 2013; 41:648-56. [PMID: 23118486 PMCID: PMC3592405 DOI: 10.1093/nar/gks1015] [Citation(s) in RCA: 26] [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: 06/05/2012] [Revised: 09/27/2012] [Accepted: 10/02/2012] [Indexed: 01/06/2023] Open
Abstract
Holliday junction (HJ) resolvases are structure-specific endonucleases that cleave four-way DNA junctions (HJs) generated during DNA recombination and repair. Bacterial RuvC, a prototypical HJ resolvase, functions as homodimer and nicks DNA strands precisely across the junction point. To gain insights into the mechanisms underlying symmetrical strand cleavages by RuvC, we performed crystallographic and biochemical analyses of RuvC from Thermus thermophilus (T.th. RuvC). The crystal structure of T.th. RuvC shows an overall protein fold similar to that of Escherichia coli RuvC, but T.th. RuvC has a more tightly associated dimer interface possibly reflecting its thermostability. The binding mode of a HJ-DNA substrate can be inferred from the shape/charge complementarity between the T.th. RuvC dimer and HJ-DNA, as well as positions of sulfate ions bound on the protein surface. Unexpectedly, the structure of T.th. RuvC homodimer refined at 1.28 Å resolution shows distinct asymmetry near the dimer interface, in the region harboring catalytically important aromatic residues. The observation suggests that the T.th. RuvC homodimer interconverts between two asymmetric conformations, with alternating subunits switched on for DNA strand cleavage. This model provides a structural basis for the 'nick-counter-nick' mechanism in HJ resolution, a mode of HJ processing shared by prokaryotic and eukaryotic HJ resolvases.
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Affiliation(s)
| | | | | | - Hideki Aihara
- Department of Biochemistry, Molecular biology and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA
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26
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Ahmad M, Tuteja R. Plasmodium falciparum RuvB proteins: Emerging importance and expectations beyond cell cycle progression. Commun Integr Biol 2012; 5:350-61. [PMID: 23060959 PMCID: PMC3460840 DOI: 10.4161/cib.20005] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The urgent requirement of next generation antimalarials has been of recent interest due to the emergence of drug-resistant parasite. The genome-wide analysis of Plasmodium falciparum helicases revealed three RuvB proteins. Due to the presence of helicase motif I and II in PfRuvBs, there is a high probability that they contain ATPase and possibly helicase activity. The Plasmodium database has homologs of several key proteins that interact with RuvBs and are most likely involved in the cell cycle progression, chromatin remodeling, and other cellular activities. Phylogenetically PfRuvBs are closely related to Saccharomyces cerevisiae RuvB, which is essential for cell cycle progression and survival of yeast. Thus PfRuvBs can serve as potential drug target if they show an essential role in the survival of parasite.
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Affiliation(s)
- Moaz Ahmad
- Malaria Group; International Centre for Genetic Engineering and Biotechnology; New Delhi, India
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27
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Vink C, Rudenko G, Seifert HS. Microbial antigenic variation mediated by homologous DNA recombination. FEMS Microbiol Rev 2012; 36:917-948. [PMID: 22212019 PMCID: PMC3334452 DOI: 10.1111/j.1574-6976.2011.00321.x] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2011] [Revised: 12/12/2011] [Accepted: 12/13/2011] [Indexed: 11/27/2022] Open
Abstract
Pathogenic microorganisms employ numerous molecular strategies in order to delay or circumvent recognition by the immune system of their host. One of the most widely used strategies of immune evasion is antigenic variation, in which immunogenic molecules expressed on the surface of a microorganism are continuously modified. As a consequence, the host is forced to constantly adapt its humoral immune response against this pathogen. An antigenic change thus provides the microorganism with an opportunity to persist and/or replicate within the host (population) for an extended period of time or to effectively infect a previously infected host. In most cases, antigenic variation is caused by genetic processes that lead to the modification of the amino acid sequence of a particular antigen or to alterations in the expression of biosynthesis genes that induce changes in the expression of a variant antigen. Here, we will review antigenic variation systems that rely on homologous DNA recombination and that are found in a wide range of cellular, human pathogens, including bacteria (such as Neisseria spp., Borrelia spp., Treponema pallidum, and Mycoplasma spp.), fungi (such as Pneumocystis carinii) and parasites (such as the African trypanosome Trypanosoma brucei). Specifically, the various DNA recombination-based antigenic variation systems will be discussed with a focus on the employed mechanisms of recombination, the DNA substrates, and the enzymatic machinery involved.
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Affiliation(s)
- Cornelis Vink
- Department of Pediatrics, Erasmus MC, Rotterdam, The Netherlands
| | - Gloria Rudenko
- Division of Cell and Molecular Biology, Imperial College-South Kensington, London, UK
| | - H. Steven Seifert
- Department of Microbiology-Immunology, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA
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28
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Sato K, Toda K, Ishiai M, Takata M, Kurumizaka H. DNA robustly stimulates FANCD2 monoubiquitylation in the complex with FANCI. Nucleic Acids Res 2012; 40:4553-61. [PMID: 22287633 PMCID: PMC3378891 DOI: 10.1093/nar/gks053] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
FANCI and FANCD2 form a complex, and play essential roles in the repair of interstrand DNA crosslinks (ICLs) by the Fanconi anemia (FA) pathway. FANCD2 is monoubiquitylated by the FA core complex, composed of 10 FA proteins including FANCL as the catalytic E3 subunit. FANCD2 monoubiquitylation can be reconstituted with purified minimal components, such as FANCI, E1, UBE2T (E2) and FANCL (E3) in vitro; however, its efficiency is quite low as compared to the in vivo monoubiquitylation of FANCD2. In this study, we found that various forms of DNA, such as single-stranded, double-stranded and branched DNA, robustly stimulated the FANCD2 monoubiquitylation in vitro up to a level comparable to its in vivo monoubiquitylation. This stimulation of the FANCD2 monoubiquitylation strictly required FANCI, suggesting that FANCD2 monoubiquitylation may occur in the FANCI–FANCD2 complex. A FANCI mutant that was defective in DNA binding was also significantly defective in FANCD2 monoubiquitylation in vitro. In the presence of 5′ flapped DNA, a DNA substrate mimicking the arrested replication fork, about 70% of the input FANCD2 was monoubiquitylated, while less than 1% FANCD2 monoubiquitylation was observed in the absence of the DNA. Therefore, DNA may be the unidentified factor required for proper FANCD2 monoubiquitylation.
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Affiliation(s)
- Koichi Sato
- Laboratory of Structural Biology, Graduate School of Advanced Science and Engineering, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo 162-8480, Japan
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Khanduja JS, Muniyappa K. Functional analysis of DNA replication fork reversal catalyzed by Mycobacterium tuberculosis RuvAB proteins. J Biol Chem 2012; 287:1345-60. [PMID: 22094465 PMCID: PMC3256873 DOI: 10.1074/jbc.m111.304741] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2011] [Revised: 11/14/2011] [Indexed: 11/06/2022] Open
Abstract
Initially discovered in Escherichia coli, RuvAB proteins are ubiquitous in bacteria and play a dual role as molecular motor proteins responsible for branch migration of the Holliday junction(s) and reversal of stalled replication forks. Despite mounting genetic evidence for a crucial role of RuvA and RuvB proteins in reversal of stalled replication forks, the mechanistic aspects of this process are still not fully understood. Here, we elucidate the ability of Mycobacterium tuberculosis RuvAB (MtRuvAB) complex to catalyze the reversal of replication forks using a range of DNA replication fork substrates. Our studies show that MtRuvAB, unlike E. coli RuvAB, is able to drive replication fork reversal via the formation of Holliday junction intermediates, suggesting that RuvAB-catalyzed fork reversal involves concerted unwinding and annealing of nascent leading and lagging strands. We also demonstrate the reversal of replication forks carrying hemi-replicated DNA, indicating that MtRuvAB complex-catalyzed fork reversal is independent of symmetry at the fork junction. The fork reversal reaction catalyzed by MtRuvAB is coupled to ATP hydrolysis, is processive, and culminates in the formation of an extended reverse DNA arm. Notably, we found that sequence heterology failed to impede the fork reversal activity of MtRuvAB. We discuss the implications of these results in the context of recognition and processing of varied types of replication fork structures by RuvAB proteins.
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Affiliation(s)
- Jasbeer Singh Khanduja
- From the Department of Biochemistry, Indian Institute of Science, Bangalore 560012, India
| | - K. Muniyappa
- From the Department of Biochemistry, Indian Institute of Science, Bangalore 560012, India
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Kang YH, Munashingha PR, Lee CH, Nguyen TA, Seo YS. Biochemical studies of the Saccharomyces cerevisiae Mph1 helicase on junction-containing DNA structures. Nucleic Acids Res 2011; 40:2089-106. [PMID: 22090425 PMCID: PMC3300029 DOI: 10.1093/nar/gkr983] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
Abstract
Saccharomyces cerevisiae Mph1 is a 3–5′ DNA helicase, required for the maintenance of genome integrity. In order to understand the ATPase/helicase role of Mph1 in genome stability, we characterized its helicase activity with a variety of DNA substrates, focusing on its action on junction structures containing three or four DNA strands. Consistent with its 3′ to 5′ directionality, Mph1 displaced 3′-flap substrates in double-fixed or equilibrating flap substrates. Surprisingly, Mph1 displaced the 5′-flap strand more efficiently than the 3′ flap strand from double-flap substrates, which is not expected for a 3–5′ DNA helicase. For this to occur, Mph1 required a threshold size (>5 nt) of 5′ single-stranded DNA flap. Based on the unique substrate requirements of Mph1 defined in this study, we propose that the helicase/ATPase activity of Mph1 play roles in converting multiple-stranded DNA structures into structures cleavable by processing enzymes such as Fen1. We also found that the helicase activity of Mph1 was used to cause structural alterations required for restoration of replication forks stalled due to damaged template. The helicase properties of Mph1 reported here could explain how it resolves D-loop structure, and are in keeping with a model proposed for the error-free damage avoidance pathway.
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Affiliation(s)
- Young-Hoon Kang
- Department of Biological Sciences, Center for DNA Replication and Genome Instability, Korea Advanced Institute of Science and Technology, Daejeon, 305-701, Korea
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31
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Functional characterization of the RuvB homologs from Mycoplasma pneumoniae and Mycoplasma genitalium. J Bacteriol 2011; 193:6425-35. [PMID: 21949077 DOI: 10.1128/jb.06003-11] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Homologous recombination between repeated DNA elements in the genomes of Mycoplasma species has been hypothesized to be a crucial causal factor in sequence variation of antigenic proteins at the bacterial surface. To investigate this notion, studies were initiated to identify and characterize the proteins that form part of the homologous DNA recombination machinery in Mycoplasma pneumoniae as well as Mycoplasma genitalium. Among the most likely participants of this machinery are homologs of the Holliday junction migration motor protein RuvB. In both M. pneumoniae and M. genitalium, genes have been identified that have the capacity to encode RuvB homologs (MPN536 and MG359, respectively). Here, the characteristics of the MPN536- and MG359-encoded proteins (the RuvB proteins from M. pneumoniae strain FH [RuvB(FH)] and M. genitalium [RuvB(Mge)], respectively) are described. Both RuvB(FH) and RuvB(Mge) were found to have ATPase activity and to bind DNA. In addition, both proteins displayed divalent cation- and ATP-dependent DNA helicase activity on partially double-stranded DNA substrates. The helicase activity of RuvB(Mge), however, was significantly lower than that of RuvB(FH). Interestingly, we found RuvB(FH) to be expressed exclusively by subtype 2 strains of M. pneumoniae. In strains belonging to the other major subtype (subtype 1), a version of the protein is expressed (the RuvB protein from M. pneumoniae strain M129 [RuvB(M129)]) that differs from RuvB(FH) in a single amino acid residue (at position 140). In contrast to RuvB(FH), RuvB(M129) displayed only marginal levels of DNA-unwinding activity. These results demonstrate that M. pneumoniae strains (as well as closely related Mycoplasma spp.) can differ significantly in the function of components of their DNA recombination and repair machinery.
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Brázda V, Laister RC, Jagelská EB, Arrowsmith C. Cruciform structures are a common DNA feature important for regulating biological processes. BMC Mol Biol 2011; 12:33. [PMID: 21816114 PMCID: PMC3176155 DOI: 10.1186/1471-2199-12-33] [Citation(s) in RCA: 177] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2011] [Accepted: 08/05/2011] [Indexed: 04/10/2023] Open
Abstract
DNA cruciforms play an important role in the regulation of natural processes involving DNA. These structures are formed by inverted repeats, and their stability is enhanced by DNA supercoiling. Cruciform structures are fundamentally important for a wide range of biological processes, including replication, regulation of gene expression, nucleosome structure and recombination. They also have been implicated in the evolution and development of diseases including cancer, Werner's syndrome and others. Cruciform structures are targets for many architectural and regulatory proteins, such as histones H1 and H5, topoisomerase IIβ, HMG proteins, HU, p53, the proto-oncogene protein DEK and others. A number of DNA-binding proteins, such as the HMGB-box family members, Rad54, BRCA1 protein, as well as PARP-1 polymerase, possess weak sequence specific DNA binding yet bind preferentially to cruciform structures. Some of these proteins are, in fact, capable of inducing the formation of cruciform structures upon DNA binding. In this article, we review the protein families that are involved in interacting with and regulating cruciform structures, including (a) the junction-resolving enzymes, (b) DNA repair proteins and transcription factors, (c) proteins involved in replication and (d) chromatin-associated proteins. The prevalence of cruciform structures and their roles in protein interactions, epigenetic regulation and the maintenance of cell homeostasis are also discussed.
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Affiliation(s)
- Václav Brázda
- Institute of Biophysics, Academy of Sciences of the Czech Republic, v,v,i,, Královopolská 135, Brno, 612 65, Czech Republic.
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Abstract
Deinococcus radiodurans is a robust bacterium best known for its capacity to repair massive DNA damage efficiently and accurately. It is extremely resistant to many DNA-damaging agents, including ionizing radiation and UV radiation (100 to 295 nm), desiccation, and mitomycin C, which induce oxidative damage not only to DNA but also to all cellular macromolecules via the production of reactive oxygen species. The extreme resilience of D. radiodurans to oxidative stress is imparted synergistically by an efficient protection of proteins against oxidative stress and an efficient DNA repair mechanism, enhanced by functional redundancies in both systems. D. radiodurans assets for the prevention of and recovery from oxidative stress are extensively reviewed here. Radiation- and desiccation-resistant bacteria such as D. radiodurans have substantially lower protein oxidation levels than do sensitive bacteria but have similar yields of DNA double-strand breaks. These findings challenge the concept of DNA as the primary target of radiation toxicity while advancing protein damage, and the protection of proteins against oxidative damage, as a new paradigm of radiation toxicity and survival. The protection of DNA repair and other proteins against oxidative damage is imparted by enzymatic and nonenzymatic antioxidant defense systems dominated by divalent manganese complexes. Given that oxidative stress caused by the accumulation of reactive oxygen species is associated with aging and cancer, a comprehensive outlook on D. radiodurans strategies of combating oxidative stress may open new avenues for antiaging and anticancer treatments. The study of the antioxidation protection in D. radiodurans is therefore of considerable potential interest for medicine and public health.
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Gilbreath JJ, Cody WL, Merrell DS, Hendrixson DR. Change is good: variations in common biological mechanisms in the epsilonproteobacterial genera Campylobacter and Helicobacter. Microbiol Mol Biol Rev 2011; 75:84-132. [PMID: 21372321 PMCID: PMC3063351 DOI: 10.1128/mmbr.00035-10] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Microbial evolution and subsequent species diversification enable bacterial organisms to perform common biological processes by a variety of means. The epsilonproteobacteria are a diverse class of prokaryotes that thrive in diverse habitats. Many of these environmental niches are labeled as extreme, whereas other niches include various sites within human, animal, and insect hosts. Some epsilonproteobacteria, such as Campylobacter jejuni and Helicobacter pylori, are common pathogens of humans that inhabit specific regions of the gastrointestinal tract. As such, the biological processes of pathogenic Campylobacter and Helicobacter spp. are often modeled after those of common enteric pathogens such as Salmonella spp. and Escherichia coli. While many exquisite biological mechanisms involving biochemical processes, genetic regulatory pathways, and pathogenesis of disease have been elucidated from studies of Salmonella spp. and E. coli, these paradigms often do not apply to the same processes in the epsilonproteobacteria. Instead, these bacteria often display extensive variation in common biological mechanisms relative to those of other prototypical bacteria. In this review, five biological processes of commonly studied model bacterial species are compared to those of the epsilonproteobacteria C. jejuni and H. pylori. Distinct differences in the processes of flagellar biosynthesis, DNA uptake and recombination, iron homeostasis, interaction with epithelial cells, and protein glycosylation are highlighted. Collectively, these studies support a broader view of the vast repertoire of biological mechanisms employed by bacteria and suggest that future studies of the epsilonproteobacteria will continue to provide novel and interesting information regarding prokaryotic cellular biology.
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Affiliation(s)
- Jeremy J. Gilbreath
- Department of Microbiology and Immunology, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814, Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, Texas 75390
| | - William L. Cody
- Department of Microbiology and Immunology, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814, Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, Texas 75390
| | - D. Scott Merrell
- Department of Microbiology and Immunology, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814, Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, Texas 75390
| | - David R. Hendrixson
- Department of Microbiology and Immunology, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814, Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, Texas 75390
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35
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Ishida H. Branch migration of Holliday junction in RuvA tetramer complex studied by umbrella sampling simulation using a path-search algorithm. J Comput Chem 2010; 31:2317-29. [PMID: 20575014 DOI: 10.1002/jcc.21525] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Branch migration of the Holliday junction takes place at the center of the RuvA tetramer. To elucidate how branch migration occurs, umbrella sampling simulations were performed for complexes of the RuvA tetramer and Holliday junction DNA. Although conventional umbrella sampling simulations set sampling points a priori, the umbrella sampling simulation in this study set the sampling points one by one in order to search for a realistic path of the branch migration during the simulations. Starting from the X-ray structure of the complex, in which the hydrogen bonds between two base-pairs were unformed, the hydrogen bonds between the next base-pairs of the shrinking stems were observed to start to disconnect. At the intermediate stage, three or four of the eight unpaired bases interacted closely with the acidic pins from RuvA. During the final stage, these bases moved away from the pins and formed the hydrogen bonds of the new base-pairs of the growing stems. The free-energy profile along this reaction path showed that the intermediate stage was a meta-stable state between two free-energy barriers of about 10 to 15 kcal/mol. These results imply that the pins play an important role in stabilizing the interactions between the pins and the unpaired base-pairs.
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Affiliation(s)
- Hisashi Ishida
- Quantum Beam Science Directorate, Japan Atomic Energy Agency, 8-1-7 Umemidai, Kizugawa-shi, Kyoto 619-0215, Japan.
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36
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Abstract
DNA and RNA helicases are organized into six superfamilies of enzymes on the basis of sequence alignments, biochemical data, and available crystal structures. DNA helicases, members of which are found in each of the superfamilies, are an essential group of motor proteins that unwind DNA duplexes into their component single strands in a process that is coupled to the hydrolysis of nucleoside 5'-triphosphates. The purpose of this DNA unwinding is to provide nascent, single-stranded DNA (ssDNA) for the processes of DNA repair, replication, and recombination. Not surprisingly, DNA helicases share common biochemical properties that include the binding of single- and double-stranded DNA, nucleoside 5'-triphosphate binding and hydrolysis, and nucleoside 5'-triphosphate hydrolysis-coupled, polar unwinding of duplex DNA. These enzymes participate in every aspect of DNA metabolism due to the requirement for transient separation of small regions of the duplex genome into its component strands so that replication, recombination, and repair can occur. In Escherichia coli, there are currently twelve DNA helicases that perform a variety of tasks ranging from simple strand separation at the replication fork to more sophisticated processes in DNA repair and genetic recombination. In this chapter, the superfamily classification, role(s) in DNA metabolism, effects of mutations, biochemical analysis, oligomeric nature, and interacting partner proteins of each of the twelve DNA helicases are discussed.
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Horikoshi N, Morozumi Y, Takaku M, Takizawa Y, Kurumizaka H. Holliday junction-binding activity of human SPF45. Genes Cells 2010; 15:373-83. [PMID: 20236180 DOI: 10.1111/j.1365-2443.2010.01383.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
SPF45 is considered to be a bifunctional protein that functions in splicing and DNA repair. A previous genetic study reported that Drosophila SPF45 participates in the DNA-repair pathway with a RAD51-family protein, RAD201, suggesting that SPF45 may function in DNA repair by the homologous-recombination pathway. To study the function of SPF45 in homologous recombination, we purified human SPF45 and found that it preferentially binds to the Holliday junction, which is a key DNA intermediate in the homologous-recombination pathway. Deletion analyses revealed that the RNA recognition motif, which is located in the C-terminal region of human SPF45, is not involved in DNA binding. On the other hand, alanine-scanning mutagenesis identified the N-terminal lysine residues, which may be involved in Holliday junction binding by human SPF45. We also found that human SPF45 significantly binds to a RAD51 paralog, RAD51B, although it also binds to RAD51 and DMC1 with lower affinity. These biochemical results support the idea that human SPF45 functions in DNA repair by homologous recombination.
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Affiliation(s)
- Naoki Horikoshi
- Laboratory of Structural Biology, Graduate School of Advanced Science and Engineering, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo 162-8480, Japan
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Lin T, Gao L, Edmondson DG, Jacobs MB, Philipp MT, Norris SJ. Central role of the Holliday junction helicase RuvAB in vlsE recombination and infectivity of Borrelia burgdorferi. PLoS Pathog 2009; 5:e1000679. [PMID: 19997622 PMCID: PMC2780311 DOI: 10.1371/journal.ppat.1000679] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2009] [Accepted: 11/04/2009] [Indexed: 01/11/2023] Open
Abstract
Antigenic variation plays a vital role in the pathogenesis of many infectious bacteria and protozoa including Borrelia burgdorferi, the causative agent of Lyme disease. VlsE, a 35 kDa surface-exposed lipoprotein, undergoes antigenic variation during B. burgdorferi infection of mammalian hosts, and is believed to be a critical mechanism by which the spirochetes evade immune clearance. Random, segmental recombination between the expressed vlsE gene and adjacent vls silent cassettes generates a large number of different VlsE variants within the infected host. Although the occurrence and importance of vlsE sequence variation is well established, little is known about the biological mechanism of vlsE recombination. To identify factors important in antigenic variation and vlsE recombination, we screened transposon mutants of genes known to be involved in DNA recombination and repair for their effects on infectivity and vlsE recombination. Several mutants, including those in BB0023 (ruvA), BB0022 (ruvB), BB0797 (mutS), and BB0098 (mutS-II), showed reduced infectivity in immunocompetent C3H/HeN mice. Mutants in ruvA and ruvB exhibited greatly reduced rates of vlsE recombination in C3H/HeN mice, as determined by restriction fragment polymorphism (RFLP) screening and DNA sequence analysis. In severe combined immunodeficiency (C3H/scid) mice, the ruvA mutant retained full infectivity; however, all recovered clones retained the ‘parental’ vlsE sequence, consistent with low rates of vlsE recombination. These results suggest that the reduced infectivity of ruvA and ruvB mutants is the result of ineffective vlsE recombination and underscores the important role that vlsE recombination plays in immune evasion. Based on functional studies in other organisms, the RuvAB complex of B. burgdorferi may promote branch migration of Holliday junctions during vlsE recombination. Our findings are consistent with those in the accompanying article by Dresser et al., and together these studies provide the first examples of trans-acting factors involved in vlsE recombination. Lyme disease is the most prevalent tick-borne infection in North America and Eurasia. It is caused by the bacterium Borrelia burgdorferi and is transmitted to humans via the bite of infected ticks. These spirochetes can cause both acute and chronic infection and inflammation of the skin, joints, heart, and central nervous system. The persistence of infection despite the presence of an active immune response is dependent upon antigenic variation of VlsE, a 35 kDa surface-exposed lipoprotein. A large number of different VlsE variants are present in the host simultaneously and are generated by recombination of the vlsE gene with adjacent vls silent cassettes. To try to identify factors important in vlsE recombination and immune evasion, we selected mutants in genes involved in DNA recombination and repair and screened them for infectivity and vlsE recombination. Mutants in genes encoding RuvA and RuvB (which act together to promote the exchange of strands between two different DNA molecules) had reduced infectivity and greatly diminished vlsE recombination. In immunodeficient mice, ruvA mutants retained full infectivity, and no vlsE recombination was detected. Our findings reinforce the importance of vlsE variation in immune evasion and persistent infection.
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Affiliation(s)
- Tao Lin
- Department of Pathology and Laboratory Medicine, Medical School, University of Texas Health Science Center at Houston, Houston, Texas, United States of America
| | - Lihui Gao
- Department of Pathology and Laboratory Medicine, Medical School, University of Texas Health Science Center at Houston, Houston, Texas, United States of America
| | - Diane G. Edmondson
- Department of Pathology and Laboratory Medicine, Medical School, University of Texas Health Science Center at Houston, Houston, Texas, United States of America
| | - Mary B. Jacobs
- Division of Bacteriology and Parasitology, Tulane National Primate Research Center, Tulane University Health Sciences Center, Covington, Louisiana, United States of America
| | - Mario T. Philipp
- Division of Bacteriology and Parasitology, Tulane National Primate Research Center, Tulane University Health Sciences Center, Covington, Louisiana, United States of America
| | - Steven J. Norris
- Department of Pathology and Laboratory Medicine, Medical School, University of Texas Health Science Center at Houston, Houston, Texas, United States of America
- Department of Microbiology and Molecular Genetics, Medical School, University of Texas Health Science Center at Houston, Houston, Texas, United States of America
- * E-mail:
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Khanduja JS, Tripathi P, Muniyappa K. Mycobacterium tuberculosis RuvA induces two distinct types of structural distortions between the homologous and heterologous Holliday junctions. Biochemistry 2009; 48:27-40. [PMID: 19072585 DOI: 10.1021/bi8016526] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A central step in the process of homologous genetic recombination is the strand exchange between two homologous DNA molecules, leading to the formation of the Holliday junction intermediate. Several lines of evidence, both in vitro and in vivo, suggest a concerted role for the Escherichia coli RuvABC protein complex in the process of branch migration and the resolution of the Holliday junctions. A number of investigations have examined the role of RuvA protein in branch migration of the Holliday junction in conjunction with its natural cellular partner, RuvB. However, it remains unclear whether the RuvABC protein complex or its individual subunits function differently in the context of DNA repair and homologous recombination. In this study, we have specifically investigated the function of RuvA protein using Holliday junctions containing either homologous or heterologous arms. Our data show that Mycobacterium tuberculosis ruvA complements E. coli DeltaruvA mutants for survival to genotoxic stress caused by different DNA-damaging agents, and the purified RuvA protein binds HJ in preference to any other substrates. Strikingly, our analysis revealed two distinct types of structural distortions caused by M. tuberculosis RuvA between the homologous and heterologous Holliday junctions. We interpret these data as evidence that local distortion of base pairing in the arms of homologous Holliday junctions by RuvA might augment branch migration catalyzed by RuvB. The biological significance of two modes of structural distortion caused by M. tuberculosis RuvA and the implications for its role in DNA repair and homologous recombination are discussed.
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40
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Buss JA, Kimura Y, Bianco PR. RecG interacts directly with SSB: implications for stalled replication fork regression. Nucleic Acids Res 2008; 36:7029-42. [PMID: 18986999 PMCID: PMC2602778 DOI: 10.1093/nar/gkn795] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
RecG and RuvAB are proposed to act at stalled DNA replication forks to facilitate replication restart. To define the roles of these proteins in fork regression, we used a combination of assays to determine whether RecG, RuvAB or both are capable of acting at a stalled fork. The results show that RecG binds to the C-terminus of single-stranded DNA binding protein (SSB) forming a stoichiometric complex of 2 RecG monomers per SSB tetramer. This binding occurs in solution and to SSB protein bound to single stranded DNA (ssDNA). The result of this binding is stabilization of the interaction of RecG with ssDNA. In contrast, RuvAB does not bind to SSB. Side-by-side analysis of the catalytic efficiency of the ATPase activity of each enzyme revealed that (-)scDNA and ssDNA are potent stimulators of the ATPase activity of RecG but not for RuvAB, whereas relaxed circular DNA is a poor cofactor for RecG but an excellent one for RuvAB. Collectively, these data suggest that the timing of repair protein access to the DNA at stalled forks is determined by the nature of the DNA available at the fork. We propose that RecG acts first, with RuvAB acting either after RecG or in a separate pathway following protein-independent fork regression.
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Affiliation(s)
- Jackson A Buss
- Department of Microbiology and Immunology, Center for Single Molecule Biophysics, University at Buffalo, Buffalo, NY 14214, USA
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41
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Cañas C, Carrasco B, Ayora S, Alonso JC. The RecU Holliday junction resolvase acts at early stages of homologous recombination. Nucleic Acids Res 2008; 36:5242-9. [PMID: 18684995 PMCID: PMC2532717 DOI: 10.1093/nar/gkn500] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Homologous recombination is essential for DNA repair and generation of genetic diversity in all organisms. It occurs through a series of presynaptic steps where the substrate is presented to the recombinase (RecA in bacteria). Then, the recombinase nucleoprotein filament mediates synapsis by first promoting the formation of a D-loop and later of a Holliday junction (HJ) that is subsequently cleaved by the HJ resolvase. The coordination of the synaptic step with the late resolution step is poorly understood. Bacillus subtilis RecU catalyzes resolution of HJs, and biochemical evidence suggests that it might modulate RecA. We report here the isolation and characterization of two mutants of RecU (recU56 and recU71), which promote resolution of HJs, but do not promote RecA modulation. In vitro, the RecU mutant proteins (RecUK56A or RecUR71A) bind and cleave HJs and interact with RuvB. RecU interacts with RecA and inhibits its single-stranded DNA-dependent dATP hydrolysis, but RecUK56A and RecUR71A do not exert a negative effect on the RecA dATPase and fail to interact with it. Both activities are important in vivo since RecU mutants impaired only in RecA interaction are as sensitive to DNA damaging agents as a deletion mutant.
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Affiliation(s)
- Cristina Cañas
- Departmento de Biotecnología Microbiana, Centro Nacional de Biotecnología, CSIC, C/Darwin 3, Campus Universidad Autónoma de Madrid, 28049 Madrid, Spain
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Abstract
SUMMARY The AAA+ superfamily is a large and functionally diverse superfamily of NTPases that are characterized by a conserved nucleotide-binding and catalytic module, the AAA+ module. Members are involved in an astonishing range of different cellular processes, attaining this functional diversity through additions of structural motifs and modifications to the core AAA+ module.
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Affiliation(s)
- Jamie Snider
- Department of Biochemistry, University of Toronto, Medical Sciences Building, 1 King's College Circle, Toronto, Ontario M5S 1A8, Canada
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43
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Fujiwara Y, Mayanagi K, Morikawa K. Functional significance of octameric RuvA for a branch migration complex from Thermus thermophilus. Biochem Biophys Res Commun 2007; 366:426-31. [PMID: 18068124 DOI: 10.1016/j.bbrc.2007.11.149] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2007] [Accepted: 11/26/2007] [Indexed: 11/25/2022]
Abstract
The RuvAB complex promotes migration of Holliday junction at the late stage of homologous recombination. The RuvA tetramer specifically recognizes Holliday junction to form two types of complexes. A single tetramer is bound to the open configuration of the junction DNA in complex I, while the octameric RuvA core structure sandwiches the same junction in complex II. The hexameric RuvB rings, symmetrically bound to both sides of RuvA on Holliday junction, pump out DNA duplexes, depending upon ATP hydrolysis. We investigated functional differences between the wild-type RuvA from Thermus thermophilus and mutants impaired the ability of complex II formation. These mutant RuvA, exclusively forming complex I, reduced activities of branch migration and ATP hydrolysis, suggesting that the octameric RuvA is essential for efficient branch migration. Together with our recent electron microscopic analysis, this finding provides important insights into functional roles of complex II in the coordinated branch migration mechanism.
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Affiliation(s)
- Yoshie Fujiwara
- Graduate School of Engineering Science, Osaka University, 1-3, Machikaneyama, Toyonaka, Osaka 560-8531, Japan
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A YY1-INO80 complex regulates genomic stability through homologous recombination-based repair. Nat Struct Mol Biol 2007; 14:1165-72. [PMID: 18026119 DOI: 10.1038/nsmb1332] [Citation(s) in RCA: 160] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2007] [Accepted: 10/08/2007] [Indexed: 01/14/2023]
Abstract
DNA damage repair is crucial for the maintenance of genome integrity and cancer suppression. We found that loss of the mouse transcription factor YY1 resulted in polyploidy and chromatid aberrations, which are signatures of defects in homologous recombination. Further biochemical analyses identified a YY1 complex comprising components of the evolutionarily conserved INO80 chromatin-remodeling complex. Notably, RNA interference-mediated knockdown of YY1 and INO80 increased cellular sensitivity toward DNA-damaging agents. Functional assays revealed that both YY1 and INO80 are essential in homologous recombination-based DNA repair (HRR), which was further supported by the finding that YY1 preferentially bound a recombination-intermediate structure in vitro. Collectively, these observations reveal a link between YY1 and INO80 and roles for both in HRR, providing new insight into mechanisms that control the cellular response to genotoxic stress.
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Model for RuvAB-mediated branch migration of Holliday junctions. J Theor Biol 2007; 249:566-73. [PMID: 17919660 DOI: 10.1016/j.jtbi.2007.08.026] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2007] [Revised: 08/27/2007] [Accepted: 08/27/2007] [Indexed: 11/21/2022]
Abstract
During RuvAB-mediated Holliday-junction migration two opposite arms of double-stranded DNA (dsDNA) are driven to translocate unidirectional by two respective ring-like hexameric RuvB proteins. However, how the RuvB protein, powered by ATP hydrolysis, drives unidirectional translocation of dsDNA is not clear. Here a model is presented for this mechanochemical-coupling mechanism. In the model, the unidirectional translocation is resulted from both the ATP hydrolysis-induced rotation (power stroke) of the RuvB subunits and the passage of the strong DNA binding from the previous to next RuvB subunits during the sequential ATPase activities around the ring. Using the model, the relationship between the power-stroke size, the step size of DNA translocation and the ratio of the rotational rate of DNA over that of RuvB relative to RuvA is predicted.
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Han YW, Tani T, Hayashi M, Hishida T, Iwasaki H, Shinagawa H, Harada Y. Direct observation of DNA rotation during branch migration of Holliday junction DNA by Escherichia coli RuvA-RuvB protein complex. Proc Natl Acad Sci U S A 2006; 103:11544-8. [PMID: 16864792 PMCID: PMC1544206 DOI: 10.1073/pnas.0600753103] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The Escherichia coli RuvA-RuvB complex promotes branch migration of Holliday junction DNA, which is the central intermediate of homologous recombination. Like many DNA motor proteins, it is suggested that RuvA-RuvB promotes branch migration by driving helical rotation of the DNA. To clarify the RuvA-RuvB-mediated branch migration mechanism in more detail, we observed DNA rotation during Holliday junction branch migration by attaching a bead to one end of cruciform DNA that was fixed to a glass surface at the opposite end. Bead rotation was observed when RuvA, RuvB, and ATP were added to the solution. We measured the rotational rates of the beads caused by RuvA-RuvB-mediated branch migration at various ATP concentrations. The data provided a K(m) value of 65 microM and a V(max) value of 1.6 revolutions per second, which corresponds to 8.3 bp per second. This real-time observation of the DNA rotation not only allows us to measure the kinetics of the RuvA-RuvB-mediated branch migration, but also opens the possibility of elucidating the branch migration mechanism in detail.
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Affiliation(s)
- Yong-Woon Han
- Tokyo Metropolitan Institute of Medical Science, Bunkyo-ku, Tokyo 113-8613, Japan
| | - Tomomi Tani
- Tokyo Metropolitan Institute of Medical Science, Bunkyo-ku, Tokyo 113-8613, Japan
| | - Masahito Hayashi
- Tokyo Metropolitan Institute of Medical Science, Bunkyo-ku, Tokyo 113-8613, Japan
| | - Takashi Hishida
- Research Institute for Microbial Diseases, Osaka University, Suita, Osaka 565-0871, Japan
| | - Hiroshi Iwasaki
- Graduate School of Integrated Science, Yokohama City University, Tsurumi-ku, Yokohama 230-0045, Japan
| | - Hideo Shinagawa
- Research Institute for Microbial Diseases, Osaka University, Suita, Osaka 565-0871, Japan
- Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Agency (JST), Honcho, Kawaguchi, Saitama 332-0012, Japan; and
- BioAcademia, Inc., Saito-Asagi, Ibaraki, Osaka 567-0085, Japan
| | - Yoshie Harada
- Tokyo Metropolitan Institute of Medical Science, Bunkyo-ku, Tokyo 113-8613, Japan
- Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Agency (JST), Honcho, Kawaguchi, Saitama 332-0012, Japan; and
- To whom correspondence should be addressed. E-mail:
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Enomoto R, Kinebuchi T, Sato M, Yagi H, Kurumizaka H, Yokoyama S. Stimulation of DNA strand exchange by the human TBPIP/Hop2-Mnd1 complex. J Biol Chem 2006; 281:5575-81. [PMID: 16407260 DOI: 10.1074/jbc.m506506200] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
In Saccharomyces cerevisiae, the Hop2 protein forms a complex with the Mnd1 protein and is required for the alignment of homologous chromosomes during meiosis, probably through extensive homology matching between them. The Rad51 and Dmc1 proteins, the eukaryotic RecA orthologs, promote strand exchange and may function in the extensive matching of homology within paired DNA molecules. In the present study, we purified the human TBPIP/Hop2-Mnd1 complex and found that it significantly stimulates the Dmc1- and Rad51-mediated strand exchange. The human Hop2-Mnd1 complex preferentially binds to a three-stranded DNA branch, which mimics the strand-exchange intermediate. These findings are consistent with genetic data, which showed that the Hop2 and Mnd1 proteins are required for homology matching between homologous chromosomes. Therefore, the human TBPIP/Hop2-Mnd1 complex may ensure proper pairing between homologous chromosomes through its stimulation of strand exchange during meiosis.
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Affiliation(s)
- Rima Enomoto
- RIKEN Genomic Sciences Center, 1-7-22 Suehiro-cho, Tsurumi, Yokohama 230-0045, Japan
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Ohnishi T, Hishida T, Harada Y, Iwasaki H, Shinagawa H. Structure-function analysis of the three domains of RuvB DNA motor protein. J Biol Chem 2005; 280:30504-10. [PMID: 15972826 DOI: 10.1074/jbc.m502400200] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
RuvB protein forms two hexameric rings that bind to the RuvA tetramer at DNA Holliday junctions. The RuvAB complex utilizes the energy of ATP hydrolysis to promote branch migration of Holliday junctions. The crystal structure of RuvB from Thermus thermophilus (Tth) HB8 showed that each RuvB monomer has three domains (N, M, and C). This study is a structure-function analysis of the three domains of RuvB. The results show that domain N is involved in RuvA-RuvB and RuvB-RuvB subunit interactions, domains N and M are required for ATP hydrolysis and ATP binding-induced hexamer formation, and domain C plays an essential role in DNA binding. The side chain of Arg-318 is essential for DNA binding and may directly interact with DNA. The data also provide evidence that coordinated ATP-dependent interactions between domains N, M, and C play an essential role during formation of the RuvAB Holliday junction ternary complex.
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Affiliation(s)
- Takayuki Ohnishi
- Department of Molecular Microbiology, Research Institute for Microbial Diseases, Osaka University, Suita, Osaka 565-0871, Japan
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Abstract
In 1964, the geneticist Robin Holliday proposed a mechanism of DNA-strand exchange that attempted to explain gene-conversion events that occur during meiosis in fungi. His proposal marked the birthday of the now famous cross-stranded DNA structure, or Holliday junction. To understand the importance of the Holliday model we must look back in the history of science beyond the last 40 years, to a time when theories of heredity were being proposed by Gregor Johann Mendel.
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Affiliation(s)
- Yilun Liu
- Cancer Research UK, London Research Institute, Clare Hall Laboratories, South Mimms, Hertfordshire EN6 3LD, UK
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Mashimo K, Nagata Y, Kawata M, Iwasaki H, Yamamoto K. Role of the RuvAB protein in avoiding spontaneous formation of deletion mutations in the Escherichia coli K-12 endogenous tonB gene. Biochem Biophys Res Commun 2004; 323:197-203. [PMID: 15351721 DOI: 10.1016/j.bbrc.2004.08.078] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2004] [Indexed: 11/17/2022]
Abstract
The endogenous tonB gene of Escherichia coli was used as a target for spontaneous deletion mutations which were isolated from ruvAB-, recG-, and ruvC- cells. The rates of tonB mutation were essentially the same in ruv+, ruvAB-, recG-, and ruvC- cells. We analyzed tonB mutants by sequencing. In the ruv+, recG-, and ruvC- strains, the spectra were different from those obtained from the ruvAB- cells, where deletions dominated followed by IS insertions, base substitutions, and frameshifts, in that order. We then analyzed the tonB-trp large deletion, due to simultaneous mutations of the trp operon, and found that the frequency in ruvAB- was higher than those in ruv+, recG-, and ruvC- cells. To characterize deletion formation further, we analyzed all the tonB mutants from one colicin plate. Seven deletions were identified at five sites from the 45 tonB mutants of ruv+ cells and 24 deletions at 11 sites from the 43 tonB mutants of ruvAB- cells. Thus, the ruvAB- strain is a deletion mutator. We discuss the role of RuvAB in avoiding deletions.
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Affiliation(s)
- Kazumi Mashimo
- Department of Biomolecular Sciences, Graduate School of Life Sciences, Tohoku University, Sendai 980-8577, Japan
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