1
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Straube H, Straube J, Rinne J, Fischer L, Niehaus M, Witte CP, Herde M. An inosine triphosphate pyrophosphatase safeguards plant nucleic acids from aberrant purine nucleotides. THE NEW PHYTOLOGIST 2023; 237:1759-1775. [PMID: 36464781 DOI: 10.1111/nph.18656] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/20/2022] [Accepted: 11/22/2022] [Indexed: 06/17/2023]
Abstract
In plants, inosine is enzymatically introduced in some tRNAs, but not in other RNAs or DNA. Nonetheless, our data show that RNA and DNA from Arabidopsis thaliana contain (deoxy)inosine, probably derived from nonenzymatic adenosine deamination in nucleic acids and usage of (deoxy)inosine triphosphate (dITP and ITP) during nucleic acid synthesis. We combined biochemical approaches, LC-MS, as well as RNA-Seq to characterize a plant INOSINE TRIPHOSPHATE PYROPHOSPHATASE (ITPA) from A. thaliana, which is conserved in many organisms, and investigated the sources of deaminated purine nucleotides in plants. Inosine triphosphate pyrophosphatase dephosphorylates deaminated nucleoside di- and triphosphates to the respective monophosphates. ITPA loss-of-function causes inosine di- and triphosphate accumulation in vivo and an elevated inosine and deoxyinosine content in RNA and DNA, respectively, as well as salicylic acid (SA) accumulation, early senescence, and upregulation of transcripts associated with immunity and senescence. Cadmium-induced oxidative stress and biochemical inhibition of the INOSINE MONOPHOSPHATE DEHYDROGENASE leads to more IDP and ITP in the wild-type (WT), and this effect is enhanced in itpa mutants, suggesting that ITP originates from ATP deamination and IMP phosphorylation. Inosine triphosphate pyrophosphatase is part of a molecular protection system in plants, preventing the accumulation of (d)ITP and its usage for nucleic acid synthesis.
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Affiliation(s)
- Henryk Straube
- Department of Molecular Nutrition and Biochemistry of Plants, Leibniz Universität Hannover, Hannover, 30419, Germany
| | - Jannis Straube
- Department of Molecular Plant Breeding, Leibniz Universität Hannover, Hannover, 30419, Germany
| | - Jannis Rinne
- Department of Molecular Nutrition and Biochemistry of Plants, Leibniz Universität Hannover, Hannover, 30419, Germany
| | - Lisa Fischer
- Department of Molecular Nutrition and Biochemistry of Plants, Leibniz Universität Hannover, Hannover, 30419, Germany
| | - Markus Niehaus
- Department of Molecular Nutrition and Biochemistry of Plants, Leibniz Universität Hannover, Hannover, 30419, Germany
| | - Claus-Peter Witte
- Department of Molecular Nutrition and Biochemistry of Plants, Leibniz Universität Hannover, Hannover, 30419, Germany
| | - Marco Herde
- Department of Molecular Nutrition and Biochemistry of Plants, Leibniz Universität Hannover, Hannover, 30419, Germany
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2
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Rao TVP, Kuzminov A. Robust linear DNA degradation supports replication-initiation-defective mutants in Escherichia coli. G3 (BETHESDA, MD.) 2022; 12:jkac228. [PMID: 36165702 PMCID: PMC9635670 DOI: 10.1093/g3journal/jkac228] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/13/2022] [Accepted: 08/22/2022] [Indexed: 06/16/2023]
Abstract
RecBCD helicase/nuclease supports replication fork progress via recombinational repair or linear DNA degradation, explaining recBC mutant synthetic lethality with replication elongation defects. Since replication initiation defects leave chromosomes without replication forks, these should be insensitive to the recBCD status. Surprisingly, we found that both Escherichia coli dnaA46(Ts) and dnaC2(Ts) initiation mutants at semi-permissive temperatures are also recBC-colethal. Interestingly, dnaA46 recBC lethality suppressors suggest underinitiation as the problem, while dnaC2 recBC suppressors signal overintiation. Using genetic and physical approaches, we studied the dnaA46 recBC synthetic lethality, for the possibility that RecBCD participates in replication initiation. Overproduced DnaA46 mutant protein interferes with growth of dnaA+ cells, while the residual viability of the dnaA46 recBC mutant depends on the auxiliary replicative helicase Rep, suggesting replication fork inhibition by the DnaA46 mutant protein. The dnaA46 mutant depends on linear DNA degradation by RecBCD, rather than on recombinational repair. At the same time, the dnaA46 defect also interacts with Holliday junction-moving defects, suggesting reversal of inhibited forks. However, in contrast to all known recBC-colethals, which fragment their chromosomes, the dnaA46 recBC mutant develops no chromosome fragmentation, indicating that its inhibited replication forks are stable. Physical measurements confirm replication inhibition in the dnaA46 mutant shifted to semi-permissive temperatures, both at the level of elongation and initiation, while RecBCD gradually restores elongation and then initiation. We propose that RecBCD-catalyzed resetting of inhibited replication forks allows replication to displace the "sticky" DnaA46(Ts) protein from the chromosomal DNA, mustering enough DnaA for new initiations.
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Affiliation(s)
| | - Andrei Kuzminov
- Corresponding author: Department of Microbiology, University of Illinois at Urbana-Champaign, B103 C&LSL, 601 South Goodwin Avenue, Urbana, IL 61801-3709, USA.
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3
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Kozmin SG, Rogozin IB, Moore EA, Abney M, Schaaper RM, Pavlov YI. Comment on "A commensal strain of Staphylococcus epidermidis protects against skin neoplasia" by Nakatsuji et al. SCIENCE ADVANCES 2019; 5:eaaw3915. [PMID: 31535021 PMCID: PMC6739109 DOI: 10.1126/sciadv.aaw3915] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/15/2018] [Accepted: 08/15/2019] [Indexed: 06/10/2023]
Abstract
A recent article in Science Advances described the striking discovery that the commensal Staphylococcus epidermidis strain MO34 displays antimicrobial and antitumor activities by producing a small molecule, identified as the nucleobase analog 6-N-hydroxylaminopurine (6-HAP). However, in contradiction to the literature, the authors claimed that 6-HAP is nonmutagenic and proposed that the toxic effect of 6-HAP results from its ability to inhibit, in its base form, DNA synthesis. To resolve the discrepancy, we proved by genetic experiments with bacteria and yeast that extracts of MO34 do contain a mutagenic compound whose effects are identical to chemically synthesized 6-HAP. The MO34 extract induced the same mutation spectrum as authentic 6-HAP. Notably, the toxic and mutagenic effects of both synthetic and MO34-derived 6-HAP depended on conversion to the corresponding nucleotide. The nucleobase 6-HAP does not inhibit DNA synthesis in vitro, and we conclude that 6-HAP exerts its biological activity when incorporated into DNA.
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Affiliation(s)
- Stanislav G. Kozmin
- National Institute of Environmental Health Sciences, Research Triangle Park, NC, USA
| | - Igor B. Rogozin
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD, USA
| | - Elizabeth A. Moore
- Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, NE, USA
| | - Mariah Abney
- Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, NE, USA
- University of Nebraska at Omaha, Omaha, NE, USA
| | - Roel M. Schaaper
- National Institute of Environmental Health Sciences, Research Triangle Park, NC, USA
| | - Youri I. Pavlov
- Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, NE, USA
- Departments of Microbiology and Pathology, Biochemistry and Molecular Biology, Genetics, Cell Biology and Anatomy, University of Nebraska Medical Center, Omaha, NE, USA
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4
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Tomlinson KR, Pablo‐Rodriguez JL, Bunawan H, Nanyiti S, Green P, Miller J, Alicai T, Seal SE, Bailey AM, Foster GD. Cassava brown streak virus Ham1 protein hydrolyses mutagenic nucleotides and is a necrosis determinant. MOLECULAR PLANT PATHOLOGY 2019; 20:1080-1092. [PMID: 31154674 PMCID: PMC6640186 DOI: 10.1111/mpp.12813] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
Cassava brown streak disease (CBSD) is a leading cause of cassava losses in East and Central Africa, and is currently having a severe impact on food security. The disease is caused by two viruses within the Potyviridae family: Cassava brown streak virus (CBSV) and Ugandan cassava brown streak virus (UCBSV), which both encode atypical Ham1 proteins with highly conserved inosine triphosphate (ITP) pyrophosphohydrolase (ITPase) domains. ITPase proteins are widely encoded by plant, animal, and archaea. They selectively hydrolyse mutagenic nucleotide triphosphates to prevent their incorporation into nucleic acid and thereby function to reduce mutation rates. It has previously been hypothesized that U/CBSVs encode Ham1 proteins with ITPase activity to reduce viral mutation rates during infection. In this study, we investigate the potential roles of U/CBSV Ham1 proteins. We show that both CBSV and UCBSV Ham1 proteins have ITPase activities through in vitro enzyme assays. Deep-sequencing experiments found no evidence of the U/CBSV Ham1 proteins providing mutagenic protection during infections of Nicotiana hosts. Manipulations of the CBSV_Tanza infectious clone were performed, including a Ham1 deletion, ITPase point mutations, and UCBSV Ham1 chimera. Unlike severely necrotic wild-type CBSV_Tanza infections, infections of Nicotiana benthamiana with the manipulated CBSV infectious clones do not develop necrosis, indicating that that the CBSV Ham1 is a necrosis determinant. We propose that the presence of U/CBSV Ham1 proteins with highly conserved ITPase motifs indicates that they serve highly selectable functions during infections of cassava and may represent a euphorbia host adaptation that could be targeted in antiviral strategies.
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Affiliation(s)
- Katie R. Tomlinson
- School of Biological SciencesUniversity of BristolLife Sciences Building, 24 Tyndall Avenue BristolBS8 1TQUK
| | - José Luis Pablo‐Rodriguez
- School of Biological SciencesUniversity of BristolLife Sciences Building, 24 Tyndall Avenue BristolBS8 1TQUK
- CINVESTAVCampus IrapuatoMexico
| | - Hamidun Bunawan
- School of Biological SciencesUniversity of BristolLife Sciences Building, 24 Tyndall Avenue BristolBS8 1TQUK
- Institute of Systems Biology (INBIOSIS)Universiti Kebangsaan Malaysia, UKMBangi43600Selangor Darul EhsanMalaysia
| | - Sarah Nanyiti
- School of Biological SciencesUniversity of BristolLife Sciences Building, 24 Tyndall Avenue BristolBS8 1TQUK
- National Crops Resources Research Institute (NaCRRI)P.O. Box 7084KampalaUganda
| | - Patrick Green
- School of Biological SciencesUniversity of BristolLife Sciences Building, 24 Tyndall Avenue BristolBS8 1TQUK
| | - Josie Miller
- School of Biological SciencesUniversity of BristolLife Sciences Building, 24 Tyndall Avenue BristolBS8 1TQUK
| | - Titus Alicai
- National Crops Resources Research Institute (NaCRRI)P.O. Box 7084KampalaUganda
| | - Susan E. Seal
- Natural Resources InstituteChatham Maritime, KentME4 4TBUK
| | - Andy M. Bailey
- School of Biological SciencesUniversity of BristolLife Sciences Building, 24 Tyndall Avenue BristolBS8 1TQUK
| | - Gary D. Foster
- School of Biological SciencesUniversity of BristolLife Sciences Building, 24 Tyndall Avenue BristolBS8 1TQUK
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5
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Cronan GE, Kouzminova EA, Kuzminov A. Near-continuously synthesized leading strands in Escherichia coli are broken by ribonucleotide excision. Proc Natl Acad Sci U S A 2019; 116:1251-1260. [PMID: 30617079 PMCID: PMC6347710 DOI: 10.1073/pnas.1814512116] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
In vitro, purified replisomes drive model replication forks to synthesize continuous leading strands, even without ligase, supporting the semidiscontinuous model of DNA replication. However, nascent replication intermediates isolated from ligase-deficient Escherichia coli comprise only short (on average 1.2-kb) Okazaki fragments. It was long suspected that cells replicate their chromosomal DNA by the semidiscontinuous mode observed in vitro but that, in vivo, the nascent leading strand was artifactually fragmented postsynthesis by excision repair. Here, using high-resolution separation of pulse-labeled replication intermediates coupled with strand-specific hybridization, we show that excision-proficient E. coli generates leading-strand intermediates >10-fold longer than lagging-strand Okazaki fragments. Inactivation of DNA-repair activities, including ribonucleotide excision, further increased nascent leading-strand size to ∼80 kb, while lagging-strand Okazaki fragments remained unaffected. We conclude that in vivo, repriming occurs ∼70× less frequently on the leading versus lagging strands, and that DNA replication in E. coli is effectively semidiscontinuous.
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Affiliation(s)
- Glen E Cronan
- Department of Microbiology, University of Illinois at Urbana-Champaign, Urbana, IL 61801
| | - Elena A Kouzminova
- Department of Microbiology, University of Illinois at Urbana-Champaign, Urbana, IL 61801
| | - Andrei Kuzminov
- Department of Microbiology, University of Illinois at Urbana-Champaign, Urbana, IL 61801
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6
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Klein HL, Bačinskaja G, Che J, Cheblal A, Elango R, Epshtein A, Fitzgerald DM, Gómez-González B, Khan SR, Kumar S, Leland BA, Marie L, Mei Q, Miné-Hattab J, Piotrowska A, Polleys EJ, Putnam CD, Radchenko EA, Saada AA, Sakofsky CJ, Shim EY, Stracy M, Xia J, Yan Z, Yin Y, Aguilera A, Argueso JL, Freudenreich CH, Gasser SM, Gordenin DA, Haber JE, Ira G, Jinks-Robertson S, King MC, Kolodner RD, Kuzminov A, Lambert SAE, Lee SE, Miller KM, Mirkin SM, Petes TD, Rosenberg SM, Rothstein R, Symington LS, Zawadzki P, Kim N, Lisby M, Malkova A. Guidelines for DNA recombination and repair studies: Cellular assays of DNA repair pathways. MICROBIAL CELL (GRAZ, AUSTRIA) 2019; 6:1-64. [PMID: 30652105 PMCID: PMC6334234 DOI: 10.15698/mic2019.01.664] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/24/2018] [Revised: 08/29/2018] [Accepted: 09/14/2018] [Indexed: 12/29/2022]
Abstract
Understanding the plasticity of genomes has been greatly aided by assays for recombination, repair and mutagenesis. These assays have been developed in microbial systems that provide the advantages of genetic and molecular reporters that can readily be manipulated. Cellular assays comprise genetic, molecular, and cytological reporters. The assays are powerful tools but each comes with its particular advantages and limitations. Here the most commonly used assays are reviewed, discussed, and presented as the guidelines for future studies.
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Affiliation(s)
- Hannah L. Klein
- Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, NY, USA
| | - Giedrė Bačinskaja
- Department of Biology, University of Copenhagen, DK-2200 Copenhagen N, Denmark
| | - Jun Che
- Department of Radiation Oncology, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX, USA
| | - Anais Cheblal
- Friedrich Miescher Institute for Biomedical Research (FMI), 4058 Basel, Switzerland
| | - Rajula Elango
- Department of Biology, University of Iowa, Iowa City, IA, USA
| | - Anastasiya Epshtein
- Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, NY, USA
| | - Devon M. Fitzgerald
- Dan L Duncan Comprehensive Cancer Center, Baylor College of Medicine, Houston, TX, USA
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
- Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, TX, USA
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, TX, USA
| | - Belén Gómez-González
- Centro Andaluz de BIología Molecular y Medicina Regenerativa-CABIMER, Universidad de Sevilla, Seville, Spain
| | - Sharik R. Khan
- Department of Microbiology, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Sandeep Kumar
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
| | | | - Léa Marie
- Department of Microbiology and Immunology, Columbia University Medical Center, New York, NY, USA
| | - Qian Mei
- Systems, Synthetic and Physical Biology Graduate Program, Rice University, Houston, TX, USA
| | - Judith Miné-Hattab
- Institut Curie, PSL Research University, CNRS, UMR3664, F-75005 Paris, France
- Sorbonne Université, Institut Curie, CNRS, UMR3664, F-75005 Paris, France
| | - Alicja Piotrowska
- NanoBioMedical Centre, Faculty of Physics, Adam Mickiewicz University, Umultowska 85, 61-614 Poznan, Poland
| | | | - Christopher D. Putnam
- Ludwig Institute for Cancer Research, University of California School of Medicine, San Diego, La Jolla, CA, USA
- Department of Medicine, University of California School of Medicine, San Diego, La Jolla, CA, USA
| | | | - Anissia Ait Saada
- Institut Curie, PSL Research University, CNRS, UMR3348 F-91405, Orsay, France
- University Paris Sud, Paris-Saclay University, CNRS, UMR3348, F-91405, Orsay, France
| | - Cynthia J. Sakofsky
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, Durham, NC, USA
| | - Eun Yong Shim
- Department of Radiation Oncology, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX, USA
| | - Mathew Stracy
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU, UK
| | - Jun Xia
- Dan L Duncan Comprehensive Cancer Center, Baylor College of Medicine, Houston, TX, USA
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
- Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, TX, USA
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, TX, USA
| | - Zhenxin Yan
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
| | - Yi Yin
- Department of Molecular Genetics and Microbiology and University Program in Genetics and Genomics, Duke University Medical Center, Durham, NC USA
| | - Andrés Aguilera
- Centro Andaluz de BIología Molecular y Medicina Regenerativa-CABIMER, Universidad de Sevilla, Seville, Spain
| | - Juan Lucas Argueso
- Department of Environmental and Radiological Health Sciences, Colorado State University, Fort Collins, CO, USA
| | - Catherine H. Freudenreich
- Department of Biology, Tufts University, Medford, MA USA
- Program in Genetics, Tufts University, Boston, MA, USA
| | - Susan M. Gasser
- Friedrich Miescher Institute for Biomedical Research (FMI), 4058 Basel, Switzerland
| | - Dmitry A. Gordenin
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, Durham, NC, USA
| | - James E. Haber
- Department of Biology and Rosenstiel Basic Medical Sciences Research Center Brandeis University, Waltham, MA, USA
| | - Grzegorz Ira
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
| | - Sue Jinks-Robertson
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC USA
| | | | - Richard D. Kolodner
- Ludwig Institute for Cancer Research, University of California School of Medicine, San Diego, La Jolla, CA, USA
- Department of Cellular and Molecular Medicine, University of California School of Medicine, San Diego, La Jolla, CA, USA
- Moores-UCSD Cancer Center, University of California School of Medicine, San Diego, La Jolla, CA, USA
- Institute of Genomic Medicine, University of California School of Medicine, San Diego, La Jolla, CA, USA
| | - Andrei Kuzminov
- Department of Microbiology, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Sarah AE Lambert
- Institut Curie, PSL Research University, CNRS, UMR3348 F-91405, Orsay, France
- University Paris Sud, Paris-Saclay University, CNRS, UMR3348, F-91405, Orsay, France
| | - Sang Eun Lee
- Department of Radiation Oncology, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX, USA
| | - Kyle M. Miller
- Dan L Duncan Comprehensive Cancer Center, Baylor College of Medicine, Houston, TX, USA
- Department of Molecular Biosciences, University of Texas at Austin, Austin, TX, USA
| | | | - Thomas D. Petes
- Department of Molecular Genetics and Microbiology and University Program in Genetics and Genomics, Duke University Medical Center, Durham, NC USA
| | - Susan M. Rosenberg
- Dan L Duncan Comprehensive Cancer Center, Baylor College of Medicine, Houston, TX, USA
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
- Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, TX, USA
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, TX, USA
- Systems, Synthetic and Physical Biology Graduate Program, Rice University, Houston, TX, USA
| | - Rodney Rothstein
- Department of Genetics & Development, Columbia University Irving Medical Center, New York, NY, USA
| | - Lorraine S. Symington
- Department of Microbiology and Immunology, Columbia University Medical Center, New York, NY, USA
| | - Pawel Zawadzki
- NanoBioMedical Centre, Faculty of Physics, Adam Mickiewicz University, Umultowska 85, 61-614 Poznan, Poland
| | - Nayun Kim
- Department of Microbiology and Molecular Genetics, The University of Texas Health Science Center at Houston, Houston, TX, USA
| | - Michael Lisby
- Department of Biology, University of Copenhagen, DK-2200 Copenhagen N, Denmark
| | - Anna Malkova
- Department of Biology, University of Iowa, Iowa City, IA, USA
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7
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Campos M, Govers SK, Irnov I, Dobihal GS, Cornet F, Jacobs-Wagner C. Genomewide phenotypic analysis of growth, cell morphogenesis, and cell cycle events in Escherichia coli. Mol Syst Biol 2018; 14:e7573. [PMID: 29941428 PMCID: PMC6018989 DOI: 10.15252/msb.20177573] [Citation(s) in RCA: 50] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Cell size, cell growth, and cell cycle events are necessarily intertwined to achieve robust bacterial replication. Yet, a comprehensive and integrated view of these fundamental processes is lacking. Here, we describe an image‐based quantitative screen of the single‐gene knockout collection of Escherichia coli and identify many new genes involved in cell morphogenesis, population growth, nucleoid (bulk chromosome) dynamics, and cell division. Functional analyses, together with high‐dimensional classification, unveil new associations of morphological and cell cycle phenotypes with specific functions and pathways. Additionally, correlation analysis across ~4,000 genetic perturbations shows that growth rate is surprisingly not predictive of cell size. Growth rate was also uncorrelated with the relative timings of nucleoid separation and cell constriction. Rather, our analysis identifies scaling relationships between cell size and nucleoid size and between nucleoid size and the relative timings of nucleoid separation and cell division. These connections suggest that the nucleoid links cell morphogenesis to the cell cycle.
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Affiliation(s)
- Manuel Campos
- Microbial Sciences Institute, Yale University, West Haven, CT, USA.,Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT, USA.,Howard Hughes Medical Institute, Yale University, New Haven, CT, USA.,Laboratoire de Microbiologie et Génétique Moléculaires (LMGM; UMR5100), Centre de Biologie Intégrative (CBI), Centre National de la Recherche Scientifique (CNRS), Université de Toulouse, UPS, Toulouse, France
| | - Sander K Govers
- Microbial Sciences Institute, Yale University, West Haven, CT, USA.,Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT, USA
| | - Irnov Irnov
- Microbial Sciences Institute, Yale University, West Haven, CT, USA.,Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT, USA
| | - Genevieve S Dobihal
- Microbial Sciences Institute, Yale University, West Haven, CT, USA.,Howard Hughes Medical Institute, Yale University, New Haven, CT, USA
| | - François Cornet
- Laboratoire de Microbiologie et Génétique Moléculaires (LMGM; UMR5100), Centre de Biologie Intégrative (CBI), Centre National de la Recherche Scientifique (CNRS), Université de Toulouse, UPS, Toulouse, France
| | - Christine Jacobs-Wagner
- Microbial Sciences Institute, Yale University, West Haven, CT, USA .,Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT, USA.,Howard Hughes Medical Institute, Yale University, New Haven, CT, USA.,Department of Microbial Pathogenesis, Yale School of Medicine, New Haven, CT, USA
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8
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Abstract
In all organisms, replication impairments are an important source of genome rearrangements, mainly because of the formation of double-stranded DNA (dsDNA) ends at inactivated replication forks. Three reactions for the formation of dsDNA ends at replication forks were originally described for Escherichia coli and became seminal models for all organisms: the encounter of replication forks with preexisting single-stranded DNA (ssDNA) interruptions, replication fork reversal, and head-to-tail collisions of successive replication rounds. Here, we first review the experimental evidence that now allows us to know when, where, and how these three different reactions occur in E. coli. Next, we recall our recent studies showing that in wild-type E. coli, spontaneous replication fork breakage occurs in 18% of cells at each generation. We propose that it results from the replication of preexisting nicks or gaps, since it does not involve replication fork reversal or head-to-tail fork collisions. In the recB mutant, deficient for double-strand break (DSB) repair, fork breakage triggers DSBs in the chromosome terminus during cell division, a reaction that is heritable for several generations. Finally, we recapitulate several observations suggesting that restart from intact inactivated replication forks and restart from recombination intermediates require different sets of enzymatic activities. The finding that 18% of cells suffer replication fork breakage suggests that DNA remains intact at most inactivated forks. Similarly, only 18% of cells need the helicase loader for replication restart, which leads us to speculate that the replicative helicase remains on DNA at intact inactivated replication forks and is reactivated by the replication restart proteins.
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9
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Ji D, Stepchenkova EI, Cui J, Menezes MR, Pavlov YI, Kool ET. Measuring deaminated nucleotide surveillance enzyme ITPA activity with an ATP-releasing nucleotide chimera. Nucleic Acids Res 2017; 45:11515-11524. [PMID: 29036687 PMCID: PMC5714213 DOI: 10.1093/nar/gkx774] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2017] [Accepted: 08/23/2017] [Indexed: 01/24/2023] Open
Abstract
Nucleotide quality surveillance enzymes play important roles in human health, by detecting damaged molecules in the nucleotide pool and deactivating them before they are incorporated into chromosomal DNA or adversely affect metabolism. In particular, deamination of adenine moiety in (deoxy)nucleoside triphosphates, resulting in formation of (d)ITP, can be deleterious, leading to DNA damage, mutagenesis and other harmful cellular effects. The 21.5 kDa human enzyme that mitigates this damage by conversion of (d)ITP to monophosphate, ITPA, has been proposed as a possible therapeutic and diagnostic target for multiple diseases. Measuring the activity of this enzyme is useful both in basic research and in clinical applications involving this pathway, but current methods are nonselective and are not applicable to measurement of the enzyme from cells or tissues. Here, we describe the design and synthesis of an ITPA-specific chimeric dinucleotide (DIAL) that replaces the pyrophosphate leaving group of the native substrate with adenosine triphosphate, enabling sensitive detection via luciferase luminescence signaling. The probe is shown to function sensitively and selectively to quantify enzyme activity in vitro, and can be used to measure the activity of ITPA in bacterial, yeast and human cell lysates.
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Affiliation(s)
- Debin Ji
- Department of Chemistry, Stanford University, Stanford, CA 94305, USA
| | - Elena I Stepchenkova
- The Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, NE 68198, USA.,Department of Genetics and Biotechnology, Saint-Petersburg State University, St Petersburg, 199034, Russia.,Saint-Petersburg Branch of Vavilov Institute of General Genetics, RAS, St Petersburg, 199034, Russia
| | - Jian Cui
- The Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, NE 68198, USA
| | - Miriam R Menezes
- Department of Neurosurgery, University of Texas Health Science Center, Houston, TX 77030, USA
| | - Youri I Pavlov
- The Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, NE 68198, USA.,Departments of Biochemistry and Molecular Biology; Microbiology and Pathology; Genetics Cell Biology and Anatomy; University of Nebraska Medical Center, Omaha, NE 61818, USA
| | - Eric T Kool
- Department of Chemistry, Stanford University, Stanford, CA 94305, USA
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10
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Kouzminova EA, Kadyrov FF, Kuzminov A. RNase HII Saves rnhA Mutant Escherichia coli from R-Loop-Associated Chromosomal Fragmentation. J Mol Biol 2017; 429:2873-2894. [PMID: 28821455 DOI: 10.1016/j.jmb.2017.08.004] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2017] [Revised: 08/09/2017] [Accepted: 08/10/2017] [Indexed: 01/02/2023]
Abstract
The rnhAB mutant Escherichia coli, deficient in two RNase H enzymes that remove both R-loops and incorporated ribonucleotides (rNs) from DNA, grow slowly, suggesting accumulation of rN-containing DNA lesions (R-lesions). We report that the rnhAB mutants have reduced viability, form filaments with abnormal nucleoids, induce SOS, and fragment their chromosome, revealing replication and/or segregation stress. R-loops are known to interfere with replication forks, and sensitivity of the double rnhAB mutants to translation inhibition points to R-loops as precursors for R-lesions. However, the strict specificity of bacterial RNase HII for RNA-DNA junctions indicates that R-lesions have rNs integrated into DNA. Indeed, instead of relieving problems of rnhAB mutants, transient inhibition of replication from oriC kills them, suggesting that oriC-initiated replication removes R-loops instead of compounding them to R-lesions. Yet, replication from an R-loop-initiating plasmid origin kills the double rnhAB mutant, revealing generation of R-lesions by R-loop-primed DNA synthesis. These R-lesions could be R-tracts, contiguous runs of ≥4 RNA nucleotides within DNA strand and the only common substrate between the two bacterial RNase H enzymes. However, a plasmid relaxation test failed to detect R-tracts in DNA of the rnhAB mutants, although it readily detected R-patches (runs of 1-3 rNs). Instead, we detected R-gaps, single-strand gaps containing rNs, in the chromosomal DNA of the rnhAB mutant. Therefore, we propose that RNase H-deficient mutants convert some R-loops into R-tracts, which progress into R-gaps and then to double-strand breaks-explaining why R-tracts do not accumulate in RNase H-deficient cells, while double-strand breaks do.
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Affiliation(s)
- Elena A Kouzminova
- Department of Microbiology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Farid F Kadyrov
- Department of Microbiology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Andrei Kuzminov
- Department of Microbiology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
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11
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Suppressors of dGTP Starvation in Escherichia coli. J Bacteriol 2017; 199:JB.00142-17. [PMID: 28373271 DOI: 10.1128/jb.00142-17] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2017] [Accepted: 03/23/2017] [Indexed: 11/20/2022] Open
Abstract
dGTP starvation, a newly discovered phenomenon in which Escherichia coli cells are starved specifically for the DNA precursor dGTP, leads to impaired growth and, ultimately, cell death. Phenomenologically, it represents an example of nutritionally induced unbalanced growth: cell mass amplifies normally as dictated by the nutritional status of the medium, but DNA content growth is specifically impaired. The other known example of such a condition, thymineless death (TLD), involves starvation for the DNA precursor dTTP, which has been found to have important chemotherapeutic applications. Experimentally, dGTP starvation is induced by depriving an E. coligpt optA1 strain of its required purine source, hypoxanthine. In our studies of this phenomenon, we noted the emergence of a relatively high frequency of suppressor mutants that proved resistant to the treatment. To study such suppressors, we used next-generation sequencing on a collection of independently obtained mutants. A significant fraction was found to carry a defect in the PurR transcriptional repressor, controlling de novo purine biosynthesis, or in its downstream purEK operon. Thus, upregulation of de novo purine biosynthesis appears to be a major mode of overcoming the lethal effects of dGTP starvation. In addition, another large fraction of the suppressors contained a large tandem duplication of a 250- to 300-kb genomic region that included the purEK operon as well as the acrAB-encoded multidrug efflux system. Thus, the suppressive effects of the duplications could potentially involve beneficial effects of a number of genes/operons within the amplified regions.IMPORTANCE Concentrations of the four precursors for DNA synthesis (2'-deoxynucleoside-5'-triphosphates [dNTPs]) are critical for both the speed of DNA replication and its accuracy. Previously, we investigated consequences of dGTP starvation, where the DNA precursor dGTP was specifically reduced to a low level. Under this condition, E. coli cells continued cell growth but eventually developed a DNA replication defect, leading to cell death due to formation of unresolvable DNA structures. Nevertheless, dGTP-starved cultures eventually resumed growth due to the appearance of resistant mutants. Here, we used whole-genome DNA sequencing to identify the responsible suppressor mutations. We show that the majority of suppressors can circumvent death by upregulating purine de novo biosynthesis, leading to restoration of dGTP to acceptable levels.
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12
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Potentiation of hydrogen peroxide toxicity: From catalase inhibition to stable DNA-iron complexes. MUTATION RESEARCH-REVIEWS IN MUTATION RESEARCH 2016; 773:274-281. [PMID: 28927535 DOI: 10.1016/j.mrrev.2016.08.006] [Citation(s) in RCA: 70] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 04/22/2016] [Accepted: 08/29/2016] [Indexed: 12/15/2022]
Abstract
Hydrogen peroxide (H2O2) is unique among general toxins, because it is stable in abiotic environments at ambient temperature and neutral pH, yet rapidly kills any type of cells by producing highly-reactive hydroxyl radicals. This life-specific reactivity follows the distribution of soluble iron, Fe(II) (which combines with H2O2 to form the famous Fenton's reagent),Fe(II) is concentrated inside cells, but is virtually absent outside them. Because of the immediate danger of H2O2, all cells have powerful H2O2 scavengers, the equally famous catalases, which enable cells to survive thousand-fold higher concentrations of H2O2 and, in combination with adequate movement of H2O2 across membranes, make the killing H2O2 concentrations virtually impractical to generate in vivo. And yet, low concentrations of H2O2 are somehow used as an efficient biological weapon. Here we review several examples of how cells potentiate H2O2 toxicity with other chemicals. At first, these potentiators were thought to simply inhibit catalases, but recent findings with cyanide suggest that potentiators mostly promote the other side of Fenton's reaction, recruiting iron from cell depots into stable DNA-iron complexes that, in the presence of elevated H2O2, efficiently break duplex DNA, pulverizing the chromosome. This multifaceted potentiation of H2O2 toxicity results in robust and efficient killing.
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13
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Mahaseth T, Kuzminov A. Cyanide enhances hydrogen peroxide toxicity by recruiting endogenous iron to trigger catastrophic chromosomal fragmentation. Mol Microbiol 2015; 96:349-67. [PMID: 25598241 DOI: 10.1111/mmi.12938] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/15/2015] [Indexed: 11/28/2022]
Abstract
Hydrogen peroxide (HP) or cyanide (CN) are bacteriostatic at low-millimolar concentrations for growing Escherichia coli, whereas CN + HP mixture is strongly bactericidal. We show that this synergistic toxicity is associated with catastrophic chromosomal fragmentation. Since CN alone does not kill at any concentration, while HP alone kills at 20 mM, CN must potentiate HP poisoning. The CN + HP killing is blocked by iron chelators, suggesting Fenton's reaction. Indeed, we show that CN enhances plasmid DNA relaxation due to Fenton's reaction in vitro. However, mutants with elevated iron or HP pools are not acutely sensitive to HP-alone treatment, suggesting that, in addition, in vivo CN recruits iron from intracellular depots. We found that part of the CN-recruited iron pool is managed by ferritin and Dps: ferritin releases iron on cue from CN, while Dps sequesters it, quelling Fenton's reaction. We propose that disrupting intracellular iron trafficking is a common strategy employed by the immune system to kill microbes.
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Affiliation(s)
- Tulip Mahaseth
- Department of Microbiology, University of Illinois at Urbana-Champaign, Urbana, IL, 61801-3709, USA
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14
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Cheng Z, Tan G, Wang W, Su X, Landry AP, Lu J, Ding H. Iron and zinc binding activity of Escherichia coli topoisomerase I homolog YrdD. Biometals 2014; 27:229-36. [PMID: 24469504 DOI: 10.1007/s10534-013-9698-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2013] [Accepted: 12/27/2013] [Indexed: 11/26/2022]
Abstract
YrdD, a homolog of the C-terminal zinc-binding region of Escherichia coli topoisomerase I, is highly conserved among proteobacteria and enterobacteria. However, the function of YrdD remains elusive. Here we report that YrdD purified from E. coli cells grown in LB media contains both zinc and iron. Supplement of exogenous zinc in the medium abolishes the iron binding of YrdD in E. coli cells, indicating that iron and zinc may compete for the same metal binding sites in the protein. While the zinc-bound YrdD is able to bind single-stranded (ss) DNA and protect ssDNA from the DNase I digestion in vitro, the iron-bound YrdD has very little or no binding activity for ssDNA, suggesting that the zinc-bound YrdD may have an important role in DNA repair by interacting with ssDNA in cells.
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Affiliation(s)
- Zishuo Cheng
- Department of Biological Sciences, Louisiana State University, 202 Life Sciences Building, Baton Rouge, LA, 70803, USA
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15
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Simone PD, Pavlov YI, Borgstahl GEO. ITPA (inosine triphosphate pyrophosphatase): from surveillance of nucleotide pools to human disease and pharmacogenetics. Mutat Res 2013; 753:131-146. [PMID: 23969025 DOI: 10.1016/j.mrrev.2013.08.001] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2013] [Revised: 07/31/2013] [Accepted: 08/02/2013] [Indexed: 01/08/2023]
Abstract
Cellular nucleotide pools are often contaminated by base analog nucleotides which interfere with a plethora of biological reactions, from DNA and RNA synthesis to cellular signaling. An evolutionarily conserved inosine triphosphate pyrophosphatase (ITPA) removes the non-canonical purine (d)NTPs inosine triphosphate and xanthosine triphosphate by hydrolyzing them into their monophosphate form and pyrophosphate. Mutations in the ITPA orthologs in model organisms lead to genetic instability and, in mice, to severe developmental anomalies. In humans there is genetic polymorphism in ITPA. One allele leads to a proline to threonine substitution at amino acid 32 and causes varying degrees of ITPA deficiency in tissues and plays a role in patients' response to drugs. Structural analysis of this mutant protein reveals that the protein is destabilized by the formation of a cavity in its hydrophobic core. The Pro32Thr allele is thought to cause the observed dominant negative effect because the resulting active enzyme monomer targets both homo- and heterodimers to degradation.
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Affiliation(s)
- Peter D Simone
- The Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, NE 68198, USA
| | - Youri I Pavlov
- The Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, NE 68198, USA; Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, USA; Department of Pathology and Microbiology, University of Nebraska Medical Center, USA; Department of Genetics, St-Petersburg University, St-Petersburg, 199034, Russia
| | - Gloria E O Borgstahl
- The Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, NE 68198, USA; Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, USA; Department of Pharmaceutical Sciences, University of Nebraska Medical Center, USA.
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16
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Couvé S, Ishchenko AA, Fedorova OS, Ramanculov EM, Laval J, Saparbaev M. Direct DNA Lesion Reversal and Excision Repair in Escherichia coli. EcoSal Plus 2013; 5. [PMID: 26442931 DOI: 10.1128/ecosalplus.7.2.4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2012] [Indexed: 06/05/2023]
Abstract
Cellular DNA is constantly challenged by various endogenous and exogenous genotoxic factors that inevitably lead to DNA damage: structural and chemical modifications of primary DNA sequence. These DNA lesions are either cytotoxic, because they block DNA replication and transcription, or mutagenic due to the miscoding nature of the DNA modifications, or both, and are believed to contribute to cell lethality and mutagenesis. Studies on DNA repair in Escherichia coli spearheaded formulation of principal strategies to counteract DNA damage and mutagenesis, such as: direct lesion reversal, DNA excision repair, mismatch and recombinational repair and genotoxic stress signalling pathways. These DNA repair pathways are universal among cellular organisms. Mechanistic principles used for each repair strategies are fundamentally different. Direct lesion reversal removes DNA damage without need for excision and de novo DNA synthesis, whereas DNA excision repair that includes pathways such as base excision, nucleotide excision, alternative excision and mismatch repair, proceeds through phosphodiester bond breakage, de novo DNA synthesis and ligation. Cell signalling systems, such as adaptive and oxidative stress responses, although not DNA repair pathways per se, are nevertheless essential to counteract DNA damage and mutagenesis. The present review focuses on the nature of DNA damage, direct lesion reversal, DNA excision repair pathways and adaptive and oxidative stress responses in E. coli.
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17
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Waisertreiger ISR, Liston VG, Menezes MR, Kim HM, Lobachev KS, Stepchenkova EI, Tahirov TH, Rogozin IB, Pavlov YI. Modulation of mutagenesis in eukaryotes by DNA replication fork dynamics and quality of nucleotide pools. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2012; 53:699-724. [PMID: 23055184 PMCID: PMC3893020 DOI: 10.1002/em.21735] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2012] [Revised: 08/13/2012] [Accepted: 08/15/2012] [Indexed: 06/01/2023]
Abstract
The rate of mutations in eukaryotes depends on a plethora of factors and is not immediately derived from the fidelity of DNA polymerases (Pols). Replication of chromosomes containing the anti-parallel strands of duplex DNA occurs through the copying of leading and lagging strand templates by a trio of Pols α, δ and ϵ, with the assistance of Pol ζ and Y-family Pols at difficult DNA template structures or sites of DNA damage. The parameters of the synthesis at a given location are dictated by the quality and quantity of nucleotides in the pools, replication fork architecture, transcription status, regulation of Pol switches, and structure of chromatin. The result of these transactions is a subject of survey and editing by DNA repair.
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Affiliation(s)
- Irina S.-R. Waisertreiger
- Eppley Institute for Research in Cancer and Allied Diseases, ESH 7009, 986805 Nebraska Medical Center, Omaha, NE 68198-6805, U.S.A
| | - Victoria G. Liston
- Eppley Institute for Research in Cancer and Allied Diseases, ESH 7009, 986805 Nebraska Medical Center, Omaha, NE 68198-6805, U.S.A
| | - Miriam R. Menezes
- Eppley Institute for Research in Cancer and Allied Diseases, ESH 7009, 986805 Nebraska Medical Center, Omaha, NE 68198-6805, U.S.A
| | - Hyun-Min Kim
- School of Biology and Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA 30332, U.S.A
| | - Kirill S. Lobachev
- School of Biology and Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA 30332, U.S.A
| | - Elena I. Stepchenkova
- Eppley Institute for Research in Cancer and Allied Diseases, ESH 7009, 986805 Nebraska Medical Center, Omaha, NE 68198-6805, U.S.A
- Saint Petersburg Branch of Vavilov Institute of General Genetics, Universitetskaya emb. 7/9, St Petersburg, 199034, Russia
- Department of Genetics, Saint Petersburg University, Universitetskaya emb. 7/9, St Petersburg, 199034, Russia
| | - Tahir H. Tahirov
- Eppley Institute for Research in Cancer and Allied Diseases, ESH 7009, 986805 Nebraska Medical Center, Omaha, NE 68198-6805, U.S.A
| | - Igor B. Rogozin
- National Center for Biotechnology Information NLM, National Institutes of Health, Bethesda, MD 20894, U.S.A
- Institute of Cytology and Genetics, 630090 Novosibirsk, Russia
| | - Youri. I. Pavlov
- Eppley Institute for Research in Cancer and Allied Diseases, ESH 7009, 986805 Nebraska Medical Center, Omaha, NE 68198-6805, U.S.A
- Department of Genetics, Saint Petersburg University, Universitetskaya emb. 7/9, St Petersburg, 199034, Russia
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18
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Menezes MR, Waisertreiger ISR, Lopez-Bertoni H, Luo X, Pavlov YI. Pivotal role of inosine triphosphate pyrophosphatase in maintaining genome stability and the prevention of apoptosis in human cells. PLoS One 2012; 7:e32313. [PMID: 22384212 PMCID: PMC3288088 DOI: 10.1371/journal.pone.0032313] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2011] [Accepted: 01/25/2012] [Indexed: 12/22/2022] Open
Abstract
Pure nucleotide precursor pools are a prerequisite for high-fidelity DNA replication and the suppression of mutagenesis and carcinogenesis. ITPases are nucleoside triphosphate pyrophosphatases that clean the precursor pools of the non-canonical triphosphates of inosine and xanthine. The precise role of the human ITPase, encoded by the ITPA gene, is not clearly defined. ITPA is clinically important because a widespread polymorphism, 94C>A, leads to null ITPase activity in erythrocytes and is associated with an adverse reaction to thiopurine drugs. We studied the cellular function of ITPA in HeLa cells using the purine analog 6-N hydroxylaminopurine (HAP), whose triphosphate is also a substrate for ITPA. In this study, we demonstrate that ITPA knockdown sensitizes HeLa cells to HAP-induced DNA breaks and apoptosis. The HAP-induced DNA damage and cytotoxicity observed in ITPA knockdown cells are rescued by an overexpression of the yeast ITPase encoded by the HAM1 gene. We further show that ITPA knockdown results in elevated mutagenesis in response to HAP treatment. Our studies reveal the significance of ITPA in preventing base analog-induced apoptosis, DNA damage and mutagenesis in human cells. This implies that individuals with defective ITPase are predisposed to genome damage by impurities in nucleotide pools, which is drastically augmented by therapy with purine analogs. They are also at an elevated risk for degenerative diseases and cancer.
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Affiliation(s)
| | | | | | | | - Youri I. Pavlov
- Eppley Institute for Research in Cancer and Allied Diseases, Nebraska Medical Center, Omaha, Nebraska, United States of America
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19
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Khan SR, Kuzminov A. Replication forks stalled at ultraviolet lesions are rescued via RecA and RuvABC protein-catalyzed disintegration in Escherichia coli. J Biol Chem 2012; 287:6250-65. [PMID: 22194615 PMCID: PMC3307332 DOI: 10.1074/jbc.m111.322990] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2011] [Revised: 12/09/2011] [Indexed: 11/06/2022] Open
Abstract
Ultraviolet (UV) irradiation is not known to induce chromosomal fragmentation in sublethal doses, and yet UV irradiation causes genetic instability and cancer, suggesting that chromosomes are fragmented. Here we show that UV irradiation induces fragmentation in sublethal doses, but the broken chromosomes are repaired or degraded by RecBCD; therefore, to observe full fragmentation, RecBCD enzyme needs to be inactivated. Using quantitative pulsed field gel electrophoresis and sensitive DNA synthesis measurements, we investigated the mechanisms of UV radiation-induced chromosomal fragmentation in recBC mutants, comparing five existing models of DNA damage-induced fragmentation. We found that fragmentation depends on active DNA synthesis before, but not after, UV irradiation. At low UV irradiation doses, fragmentation does not need excision repair or daughter strand gap repair. Fragmentation absolutely depends on both RecA-catalyzed homologous strand exchange and RuvABC-catalyzed Holliday junction resolution. Thus, chromosomes fragment when replication forks stall at UV lesions and regress, generating Holliday junctions. Remarkably, cells specifically utilize fork breakage to rescue stalled replication and avoid lethality.
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Affiliation(s)
- Sharik R. Khan
- From the Department of Microbiology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801
| | - Andrei Kuzminov
- From the Department of Microbiology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801
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20
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Sakumi K, Abolhassani N, Behmanesh M, Iyama T, Tsuchimoto D, Nakabeppu Y. ITPA protein, an enzyme that eliminates deaminated purine nucleoside triphosphates in cells. Mutat Res 2010; 703:43-50. [PMID: 20601097 DOI: 10.1016/j.mrgentox.2010.06.009] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2010] [Accepted: 06/13/2010] [Indexed: 12/14/2022]
Abstract
Inosine triphosphate pyrophosphatase (ITPA protein) (EC 3.6.1.19) hydrolyzes deaminated purine nucleoside triphosphates, such as ITP and dITP, to their corresponding purine nucleoside monophosphate and pyrophosphate. In mammals, this enzyme is encoded by the Itpa gene. Using the Itpa gene-disrupted mouse as a model, we have elucidated the biological significance of the ITPA protein and its substrates, ITP and dITP. Itpa(-/-) mice exhibited peri- or post-natal lethality dependent on the genetic background. The heart of the Itpa(-/-) mouse was found to be structurally and functionally abnormal. Significantly higher levels of deoxyinosine and inosine were detected in nuclear DNA and RNA prepared from Itpa(-/-) embryos compared to wild type embryos. In addition, an accumulation of ITP was observed in the erythrocytes of Itpa(-/-) mice. We found that Itpa(-/-) primary mouse embryonic fibroblasts (MEFs), which have no detectable ability to generate IMP from ITP in whole cell extracts, exhibited a prolonged population-doubling time, increased chromosome abnormalities and accumulation of single-strand breaks in their nuclear DNA, in comparison to primary MEFs prepared from wild type embryos. These results revealed that (1) ITP and dITP are spontaneously produced in vivo and (2) accumulation of ITP and dITP is responsible for the harmful effects observed in the Itpa(-/-) mouse. In addition to its effect as the precursor nucleotide for RNA transcription, ITP has the potential to influence the activity of ATP/GTP-binding proteins. The biological significance of ITP and dITP in the nucleotide pool remains to be elucidated.
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Affiliation(s)
- Kunihiko Sakumi
- Division of Neurofunctional Genomics, Department of Immunobiology and Neuroscience, Medical Institute of Bioregulation, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan.
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21
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Waisertreiger ISR, Menezes MR, Randazzo J, Pavlov YI. Elevated Levels of DNA Strand Breaks Induced by a Base Analog in the Human Cell Line with the P32T ITPA Variant. J Nucleic Acids 2010; 2010. [PMID: 20936128 PMCID: PMC2948936 DOI: 10.4061/2010/872180] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2010] [Accepted: 07/11/2010] [Indexed: 12/29/2022] Open
Abstract
Base analogs are powerful antimetabolites and dangerous mutagens generated endogenously by oxidative stress, inflammation, and aberrant nucleotide biosynthesis. Human inosine triphosphate pyrophosphatase (ITPA) hydrolyzes triphosphates of noncanonical purine bases (i.e., ITP, dITP, XTP, dXTP, or their mimic: 6-hydroxyaminopurine (HAP) deoxynucleoside triphosphate) and thus regulates nucleotide pools and protects cells from DNA damage. We demonstrate that the model purine base analog HAP induces DNA breaks in human cells and leads to elevation of levels of ITPA. A human polymorphic allele of the ITPA, 94C->A encodes for the enzyme with a P32T amino-acid change and leads to accumulation of nonhydrolyzed ITP. The polymorphism has been associated with adverse reaction to purine base-analog drugs. The level of both spontaneous and HAP-induced DNA breaks is elevated in the cell line with the ITPA P32T variant. The results suggested that human ITPA plays a pivotal role in the protection of DNA from noncanonical purine base analogs.
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Affiliation(s)
- Irina S-R Waisertreiger
- Eppley Institute for Research in Cancer, University of Nebraska Medical Center, Omaha, NE 68198-6805, USA
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