1
|
Vanderwaeren L, Dok R, Voordeckers K, Nuyts S, Verstrepen KJ. Saccharomyces cerevisiae as a Model System for Eukaryotic Cell Biology, from Cell Cycle Control to DNA Damage Response. Int J Mol Sci 2022; 23:11665. [PMID: 36232965 PMCID: PMC9570374 DOI: 10.3390/ijms231911665] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2022] [Revised: 09/26/2022] [Accepted: 09/28/2022] [Indexed: 11/08/2022] Open
Abstract
The yeast Saccharomyces cerevisiae has been used for bread making and beer brewing for thousands of years. In addition, its ease of manipulation, well-annotated genome, expansive molecular toolbox, and its strong conservation of basic eukaryotic biology also make it a prime model for eukaryotic cell biology and genetics. In this review, we discuss the characteristics that made yeast such an extensively used model organism and specifically focus on the DNA damage response pathway as a prime example of how research in S. cerevisiae helped elucidate a highly conserved biological process. In addition, we also highlight differences in the DNA damage response of S. cerevisiae and humans and discuss the challenges of using S. cerevisiae as a model system.
Collapse
Affiliation(s)
- Laura Vanderwaeren
- Laboratory of Experimental Radiotherapy, Department of Oncology, KU Leuven, 3000 Leuven, Belgium
- Laboratory of Genetics and Genomics, Centre for Microbial and Plant Genetics, Department M2S, KU Leuven, 3001 Leuven, Belgium
- Laboratory for Systems Biology, VIB-KU Leuven Center for Microbiology, 3001 Leuven, Belgium
| | - Rüveyda Dok
- Laboratory of Experimental Radiotherapy, Department of Oncology, KU Leuven, 3000 Leuven, Belgium
| | - Karin Voordeckers
- Laboratory of Genetics and Genomics, Centre for Microbial and Plant Genetics, Department M2S, KU Leuven, 3001 Leuven, Belgium
- Laboratory for Systems Biology, VIB-KU Leuven Center for Microbiology, 3001 Leuven, Belgium
| | - Sandra Nuyts
- Laboratory of Experimental Radiotherapy, Department of Oncology, KU Leuven, 3000 Leuven, Belgium
- Department of Radiation Oncology, Leuven Cancer Institute, University Hospitals Leuven, 3000 Leuven, Belgium
| | - Kevin J. Verstrepen
- Laboratory of Genetics and Genomics, Centre for Microbial and Plant Genetics, Department M2S, KU Leuven, 3001 Leuven, Belgium
- Laboratory for Systems Biology, VIB-KU Leuven Center for Microbiology, 3001 Leuven, Belgium
| |
Collapse
|
2
|
Jin SG, Meng Y, Johnson J, Szabó PE, Pfeifer GP. Concordance of hydrogen peroxide-induced 8-oxo-guanine patterns with two cancer mutation signatures of upper GI tract tumors. SCIENCE ADVANCES 2022; 8:eabn3815. [PMID: 35658030 PMCID: PMC9166614 DOI: 10.1126/sciadv.abn3815] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/22/2021] [Accepted: 04/15/2022] [Indexed: 05/22/2023]
Abstract
Oxidative DNA damage has been linked to inflammation, cancer, and aging. Here, we have mapped two types of oxidative DNA damage, oxidized guanines produced by hydrogen peroxide and oxidized thymines created by potassium permanganate, at a single-base resolution. 8-Oxo-guanine occurs strictly dependent on the G/C sequence context and shows a pronounced peak at transcription start sites (TSSs). We determined the trinucleotide sequence pattern of guanine oxidation. This pattern shows high similarity to the cancer-associated single-base substitution signatures SBS18 and SBS36. SBS36 is found in colorectal cancers that carry mutations in MUTYH, encoding a repair enzyme that operates on 8-oxo-guanine mispairs. SBS18 is common in inflammation-associated upper gastrointestinal tract tumors including esophageal and gastric adenocarcinomas. Oxidized thymines induced by permanganate occur with a distinct dinucleotide specificity, 5'T-A/C, and are depleted at the TSS. Our data suggest that two cancer mutational signatures, SBS18 and SBS36, are caused by reactive oxygen species.
Collapse
Affiliation(s)
- Seung-Gi Jin
- Department of Epigenetics, Van Andel Institute, Grand Rapids, MI 49503, USA
| | - Yingying Meng
- Department of Epigenetics, Van Andel Institute, Grand Rapids, MI 49503, USA
| | - Jennifer Johnson
- Department of Epigenetics, Van Andel Institute, Grand Rapids, MI 49503, USA
| | - Piroska E. Szabó
- Department of Epigenetics, Van Andel Institute, Grand Rapids, MI 49503, USA
| | | |
Collapse
|
3
|
|
4
|
Wallace SS. Molecular radiobiology and the origins of the base excision repair pathway: an historical perspective. Int J Radiat Biol 2021; 99:891-902. [DOI: 10.1080/09553002.2021.1908639] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- Susan S. Wallace
- Department of Microbiology and Molecular Genetics, University of Vermont, Burlington, VT, USA
| |
Collapse
|
5
|
Usher J, Chaudhari Y, Attah V, Ho HL, Haynes K. Functional Characterization of a Novel Oxidative Stress Protection Protein in the Pathogenic Yeast Candida glabrata. Front Genet 2020; 11:530915. [PMID: 33101372 PMCID: PMC7545072 DOI: 10.3389/fgene.2020.530915] [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: 01/30/2020] [Accepted: 08/27/2020] [Indexed: 11/25/2022] Open
Abstract
Candida species are important pathogens of humans and the fourth most commonly isolated pathogen from nosocomial blood stream infections. Although Candida albicans is the principle causative agent of invasive candidosis, the incidence of Candida glabrata infections has rapidly grown. The reason for this increase is not fully understood, but it is clear that the species has a higher innate tolerance to commonly administered azole antifungals, in addition to being highly tolerant to stresses especially oxidative stress. Taking the approach that using the model organism, Saccharomyces cerevisiae, with its intrinsic sensitivity to oxidative stress, we hypothesized that by expressing mediators of stress resistance from C. glabrata in S. cerevisiae, it would result in induced resistance. To test this we transformed, en-masse, the C. glabrata ORFeome library into S. cerevisiae. This resulted in 1,500 stress resistant colonies and the recovered plasmids of 118 ORFs. Sequencing of these plasmids revealed a total of 16 different C. glabrata ORFs. The recovery of genes encoding known stress protectant proteins such as GPD1, GPD2 and TRX3 was predicted and validated the integrity of the screen. Through this screen we identified a C. glabrata unique ORF that confers oxidative stress resistance. We set to characterise this gene herein, examining expression in oxidative stress sensitive strains, comet assays to measure DNA damage and synthetic genetic array analysis to identify genetic interaction maps in the presence and absence of oxidative stress.
Collapse
Affiliation(s)
- Jane Usher
- Medical Research Council Centre for Medical Mycology, University of Exeter, Exeter, United Kingdom
- School of Biosciences, University of Exeter, Exeter, United Kingdom
| | - Yogesh Chaudhari
- School of Biosciences, University of Exeter, Exeter, United Kingdom
- Hawkesbury Institute for the Environment, Western Sydney University, Penrith, NSW, Australia
| | - Victoria Attah
- School of Biosciences, University of Exeter, Exeter, United Kingdom
| | - Hsueh-lui Ho
- School of Biosciences, University of Exeter, Exeter, United Kingdom
| | - Ken Haynes
- School of Biosciences, University of Exeter, Exeter, United Kingdom
| |
Collapse
|
6
|
Lindahl PA. A comprehensive mechanistic model of iron metabolism in Saccharomyces cerevisiae. Metallomics 2019; 11:1779-1799. [PMID: 31531508 DOI: 10.1039/c9mt00199a] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The ironome of budding yeast (circa 2019) consists of approximately 139 proteins and 5 nonproteinaceous species. These proteins were grouped according to location in the cell, type of iron center(s), and cellular function. The resulting 27 groups were used, along with an additional 13 nonprotein components, to develop a mesoscale mechanistic model that describes the import, trafficking, metallation, and regulation of iron within growing yeast cells. The model was designed to be simultaneously mutually autocatalytic and mutually autoinhibitory - a property called autocatinhibitory that should be most realistic for simulating cellular biochemical processes. The model was assessed at the systems' level. General conclusions are presented, including a new perspective on understanding regulatory mechanisms in cellular systems. Some unsettled issues are described. This model, once fully developed, has the potential to mimic the phenotype (at a coarse-grain level) of all iron-related genetic mutations in this simple and well-studied eukaryote.
Collapse
Affiliation(s)
- Paul A Lindahl
- Departments of Chemistry and of Biochemistry and Biophysics, Texas A&M University, College Station, TX 77843-3255, USA.
| |
Collapse
|
7
|
Puig S, Ramos-Alonso L, Romero AM, Martínez-Pastor MT. The elemental role of iron in DNA synthesis and repair. Metallomics 2018; 9:1483-1500. [PMID: 28879348 DOI: 10.1039/c7mt00116a] [Citation(s) in RCA: 180] [Impact Index Per Article: 30.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Iron is an essential redox element that functions as a cofactor in many metabolic pathways. Critical enzymes in DNA metabolism, including multiple DNA repair enzymes (helicases, nucleases, glycosylases, demethylases) and ribonucleotide reductase, use iron as an indispensable cofactor to function. Recent striking results have revealed that the catalytic subunit of DNA polymerases also contains conserved cysteine-rich motifs that bind iron-sulfur (Fe/S) clusters that are essential for the formation of stable and active complexes. In line with this, mitochondrial and cytoplasmic defects in Fe/S cluster biogenesis and insertion into the nuclear iron-requiring enzymes involved in DNA synthesis and repair lead to DNA damage and genome instability. Recent studies have shown that yeast cells possess multi-layered mechanisms that regulate the ribonucleotide reductase function in response to fluctuations in iron bioavailability to maintain optimal deoxyribonucleotide concentrations. Finally, a fascinating DNA charge transport model indicates how the redox active Fe/S centers present in DNA repair machinery components are critical for detecting and repairing DNA mismatches along the genome by long-range charge transfers through double-stranded DNA. These unexpected connections between iron and DNA replication and repair have to be considered to properly understand cancer, aging and other DNA-related diseases.
Collapse
Affiliation(s)
- Sergi Puig
- Departamento de Biotecnología, Instituto de Agroquímica y Tecnología de Alimentos (IATA), Consejo Superior de Investigaciones Científicas (CSIC), Ave. Agustín Escardino 7, 46980, Paterna, Valencia, Spain.
| | | | | | | |
Collapse
|
8
|
Boiteux S, Coste F, Castaing B. Repair of 8-oxo-7,8-dihydroguanine in prokaryotic and eukaryotic cells: Properties and biological roles of the Fpg and OGG1 DNA N-glycosylases. Free Radic Biol Med 2017; 107:179-201. [PMID: 27903453 DOI: 10.1016/j.freeradbiomed.2016.11.042] [Citation(s) in RCA: 104] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/05/2016] [Revised: 11/22/2016] [Accepted: 11/25/2016] [Indexed: 01/23/2023]
Abstract
Oxidatively damaged DNA results from the attack of sugar and base moieties by reactive oxygen species (ROS), which are formed as byproducts of normal cell metabolism and during exposure to endogenous or exogenous chemical or physical agents. Guanine, having the lowest redox potential, is the DNA base the most susceptible to oxidation, yielding products such as 8-oxo-7,8-dihydroguanine (8-oxoG) and 2-6-diamino-4-hydroxy-5-formamidopyrimidine (FapyG). In DNA, 8-oxoG was shown to be mutagenic yielding GC to TA transversions upon incorporation of dAMP opposite this lesion by replicative DNA polymerases. In prokaryotic and eukaryotic cells, 8-oxoG is primarily repaired by the base excision repair pathway (BER) initiated by a DNA N-glycosylase, Fpg and OGG1, respectively. In Escherichia coli, Fpg cooperates with MutY and MutT to prevent 8-oxoG-induced mutations, the "GO-repair system". In Saccharomyces cerevisiae, OGG1 cooperates with nucleotide excision repair (NER), mismatch repair (MMR), post-replication repair (PRR) and DNA polymerase η to prevent mutagenesis. Human and mouse cells mobilize all these pathways using OGG1, MUTYH (MutY-homolog also known as MYH), MTH1 (MutT-homolog also known as NUDT1), NER, MMR, NEILs and DNA polymerases η and λ, to prevent 8-oxoG-induced mutations. In fact, mice deficient in both OGG1 and MUTYH develop cancer in different organs at adult age, which points to the critical impact of 8-oxoG repair on genetic stability in mammals. In this review, we will focus on Fpg and OGG1 proteins, their biochemical and structural properties as well as their biological roles. Other DNA N-glycosylases able to release 8-oxoG from damaged DNA in various organisms will be discussed. Finally, we will report on the role of OGG1 in human disease and the possible use of 8-oxoG DNA N-glycosylases as therapeutic targets.
Collapse
Affiliation(s)
- Serge Boiteux
- Centre de Biophysique Moléculaire, CNRS, UPR4301, rue Charles Sadron, 45072 Orléans, France.
| | - Franck Coste
- Centre de Biophysique Moléculaire, CNRS, UPR4301, rue Charles Sadron, 45072 Orléans, France
| | - Bertrand Castaing
- Centre de Biophysique Moléculaire, CNRS, UPR4301, rue Charles Sadron, 45072 Orléans, France.
| |
Collapse
|
9
|
Repair of oxidatively induced DNA damage by DNA glycosylases: Mechanisms of action, substrate specificities and excision kinetics. MUTATION RESEARCH-REVIEWS IN MUTATION RESEARCH 2017; 771:99-127. [PMID: 28342455 DOI: 10.1016/j.mrrev.2017.02.001] [Citation(s) in RCA: 63] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2016] [Indexed: 02/07/2023]
Abstract
Endogenous and exogenous reactive species cause oxidatively induced DNA damage in living organisms by a variety of mechanisms. As a result, a plethora of mutagenic and/or cytotoxic products are formed in cellular DNA. This type of DNA damage is repaired by base excision repair, although nucleotide excision repair also plays a limited role. DNA glycosylases remove modified DNA bases from DNA by hydrolyzing the glycosidic bond leaving behind an apurinic/apyrimidinic (AP) site. Some of them also possess an accompanying AP-lyase activity that cleaves the sugar-phosphate chain of DNA. Since the first discovery of a DNA glycosylase, many studies have elucidated the mechanisms of action, substrate specificities and excision kinetics of these enzymes present in all living organisms. For this purpose, most studies used single- or double-stranded oligodeoxynucleotides with a single DNA lesion embedded at a defined position. High-molecular weight DNA with multiple base lesions has been used in other studies with the advantage of the simultaneous investigation of many DNA base lesions as substrates. Differences between the substrate specificities and excision kinetics of DNA glycosylases have been found when these two different substrates were used. Some DNA glycosylases possess varying substrate specificities for either purine-derived lesions or pyrimidine-derived lesions, whereas others exhibit cross-activity for both types of lesions. Laboratory animals with knockouts of the genes of DNA glycosylases have also been used to provide unequivocal evidence for the substrates, which had previously been found in in vitro studies, to be the actual substrates in vivo as well. On the basis of the knowledge gained from the past studies, efforts are being made to discover small molecule inhibitors of DNA glycosylases that may be used as potential drugs in cancer therapy.
Collapse
|
10
|
Suzuki H, Sakabe T, Hirose Y, Eki T. Development and evaluation of yeast-based GFP and luciferase reporter assays for chemical-induced genotoxicity and oxidative damage. Appl Microbiol Biotechnol 2016; 101:659-671. [PMID: 27766356 DOI: 10.1007/s00253-016-7911-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2016] [Revised: 09/21/2016] [Accepted: 09/28/2016] [Indexed: 11/30/2022]
Abstract
We aimed to develop the bioassays for genotixicity and/or oxidative damage using the recombinant yeast. A genotoxicity assay was developed using recombinant Saccharomyces cerevisiae strain BY4741 with a green fluorescent protein (GFP) reporter plasmid, driven by the DNA damage-responsive RNR3 promoter. Enhanced fluorescence induction was observed in DNA repair-deficient strains treated with methyl methanesulfonate, but not with hydrogen peroxide. A GFP reporter yeast strain driven by the oxidative stress-responsive TRX2 promoter was newly developed to assess oxidative damage, but fluorescence was poorly induced by oxidants. In place of GFP, yeast strains with luciferase gene reporter plasmids (luc2 and luc2CP, encoding stable and unstable luciferase, respectively) were prepared. Transient induction of luciferase activity was clearly detected only in a TRX2 promoter-driven luc2CP reporter strain within 90 min of oxidant exposure. However, luciferase was strongly induced by hydroxyurea in the RNR3 promoter-driven luc2 and GFP reporter strains over 8 h after the exposure, suggesting that the RNR3 promoter is continuously upregulated by DNA damage, whereas the TRX2 promoter is transiently activated by oxidative agents. Luciferase activity levels were also increased in a TRX2-promoter-driven luc2CP reporter strain treated with tert-butyl hydroperoxide and menadione and weakly induced with diamide and diethyl maleate. Weakly enhanced luciferase activity induction was detected in the sod1Δ, sod2Δ, and rad27Δ strains treated with hydrogen peroxide compared with that in the wild-type strain. In conclusion, tests using GFP and stable luciferase reporters are useful for genotoxicity, and oxidative damage can be clearly detected by assay with an unstable luciferase reporter.
Collapse
Affiliation(s)
- Hajime Suzuki
- Molecular Genetics Laboratory, Division of Bioscience and Biotechnology, Department of Environmental and Life Sciences, Toyohashi University of Technology, 1-1 Hibarigaoka, Tempaku-cho, Toyohashi, Aichi, 441-8580, Japan
| | - Takahiro Sakabe
- Molecular Genetics Laboratory, Division of Bioscience and Biotechnology, Department of Environmental and Life Sciences, Toyohashi University of Technology, 1-1 Hibarigaoka, Tempaku-cho, Toyohashi, Aichi, 441-8580, Japan
| | - Yuu Hirose
- Molecular Genetics Laboratory, Division of Bioscience and Biotechnology, Department of Environmental and Life Sciences, Toyohashi University of Technology, 1-1 Hibarigaoka, Tempaku-cho, Toyohashi, Aichi, 441-8580, Japan.,The Electronics-Inspired Interdisciplinary Research Institute (EIIRIS), Toyohashi University of Technology, 1-1 Hibarigaoka, Tempaku-cho, Toyohashi, Aichi, 441-8580, Japan
| | - Toshihiko Eki
- Molecular Genetics Laboratory, Division of Bioscience and Biotechnology, Department of Environmental and Life Sciences, Toyohashi University of Technology, 1-1 Hibarigaoka, Tempaku-cho, Toyohashi, Aichi, 441-8580, Japan.
| |
Collapse
|
11
|
Bauer NC, Corbett AH, Doetsch PW. The current state of eukaryotic DNA base damage and repair. Nucleic Acids Res 2015; 43:10083-101. [PMID: 26519467 PMCID: PMC4666366 DOI: 10.1093/nar/gkv1136] [Citation(s) in RCA: 104] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2015] [Accepted: 10/16/2015] [Indexed: 12/15/2022] Open
Abstract
DNA damage is a natural hazard of life. The most common DNA lesions are base, sugar, and single-strand break damage resulting from oxidation, alkylation, deamination, and spontaneous hydrolysis. If left unrepaired, such lesions can become fixed in the genome as permanent mutations. Thus, evolution has led to the creation of several highly conserved, partially redundant pathways to repair or mitigate the effects of DNA base damage. The biochemical mechanisms of these pathways have been well characterized and the impact of this work was recently highlighted by the selection of Tomas Lindahl, Aziz Sancar and Paul Modrich as the recipients of the 2015 Nobel Prize in Chemistry for their seminal work in defining DNA repair pathways. However, how these repair pathways are regulated and interconnected is still being elucidated. This review focuses on the classical base excision repair and strand incision pathways in eukaryotes, considering both Saccharomyces cerevisiae and humans, and extends to some important questions and challenges facing the field of DNA base damage repair.
Collapse
Affiliation(s)
- Nicholas C Bauer
- Department of Biochemistry, Emory University School of Medicine, Atlanta, GA 30322, USA Graduate Program in Biochemistry, Cell, and Developmental Biology, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Anita H Corbett
- Department of Biochemistry, Emory University School of Medicine, Atlanta, GA 30322, USA Winship Cancer Institute, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Paul W Doetsch
- Department of Biochemistry, Emory University School of Medicine, Atlanta, GA 30322, USA Winship Cancer Institute, Emory University School of Medicine, Atlanta, GA 30322, USA Department of Radiation Oncology, Emory University School of Medicine, Atlanta, GA 30322, USA Department of Hematology and Medical Oncology, Emory University School of Medicine, Atlanta, GA 30322, USA
| |
Collapse
|
12
|
Oxidatively induced DNA damage and its repair in cancer. MUTATION RESEARCH-REVIEWS IN MUTATION RESEARCH 2014; 763:212-45. [PMID: 25795122 DOI: 10.1016/j.mrrev.2014.11.002] [Citation(s) in RCA: 179] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/14/2014] [Revised: 11/03/2014] [Accepted: 11/04/2014] [Indexed: 12/28/2022]
Abstract
Oxidatively induced DNA damage is caused in living organisms by endogenous and exogenous reactive species. DNA lesions resulting from this type of damage are mutagenic and cytotoxic and, if not repaired, can cause genetic instability that may lead to disease processes including carcinogenesis. Living organisms possess DNA repair mechanisms that include a variety of pathways to repair multiple DNA lesions. Mutations and polymorphisms also occur in DNA repair genes adversely affecting DNA repair systems. Cancer tissues overexpress DNA repair proteins and thus develop greater DNA repair capacity than normal tissues. Increased DNA repair in tumors that removes DNA lesions before they become toxic is a major mechanism for development of resistance to therapy, affecting patient survival. Accumulated evidence suggests that DNA repair capacity may be a predictive biomarker for patient response to therapy. Thus, knowledge of DNA protein expressions in normal and cancerous tissues may help predict and guide development of treatments and yield the best therapeutic response. DNA repair proteins constitute targets for inhibitors to overcome the resistance of tumors to therapy. Inhibitors of DNA repair for combination therapy or as single agents for monotherapy may help selectively kill tumors, potentially leading to personalized therapy. Numerous inhibitors have been developed and are being tested in clinical trials. The efficacy of some inhibitors in therapy has been demonstrated in patients. Further development of inhibitors of DNA repair proteins is globally underway to help eradicate cancer.
Collapse
|
13
|
Christov PP, Son KJ, Rizzo CJ. Synthesis and characterization of oligonucleotides containing a nitrogen mustard formamidopyrimidine monoadduct of deoxyguanosine. Chem Res Toxicol 2014; 27:1610-8. [PMID: 25136769 PMCID: PMC4164228 DOI: 10.1021/tx5002354] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
![]()
N5-Substituted formamidopyrimidine
adducts have been observed from the reaction of dGuo or DNA with aziridine
containing electrophiles, including nitrogen mustards. However, the
role of substituted Fapy-dGuo adducts in the biological response to
nitrogen mustards and related species has not been extensively explored.
We have developed chemistry for the site-specific synthesis of oligonucleotides
containing an N5-nitrogen mustard Fapy-dGuo
using the phosphoramidite approach. The lesion was found to be a good
substrate for Escherichia coli endonuclease
IV and formamidopyrimidine glycosylase.
Collapse
Affiliation(s)
- Plamen P Christov
- Departments of Chemistry and Biochemistry, Center in Molecular Toxicology, and Vanderbilt-Ingram Cancer Center, Vanderbilt University , Nashville, Tennessee 37235, United States
| | | | | |
Collapse
|
14
|
Schroeder EA, Shadel GS. Crosstalk between mitochondrial stress signals regulates yeast chronological lifespan. Mech Ageing Dev 2013; 135:41-9. [PMID: 24373996 DOI: 10.1016/j.mad.2013.12.002] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2013] [Revised: 12/04/2013] [Accepted: 12/16/2013] [Indexed: 01/09/2023]
Abstract
Mitochondrial DNA (mtDNA) exists in multiple copies per cell and is essential for oxidative phosphorylation. Depleted or mutated mtDNA promotes numerous human diseases and may contribute to aging. Reduced TORC1 signaling in the budding yeast, Saccharomyces cerevisiae, extends chronological lifespan (CLS) in part by generating a mitochondrial ROS (mtROS) signal that epigenetically alters nuclear gene expression. To address the potential requirement for mtDNA maintenance in this response, we analyzed strains lacking the mitochondrial base-excision repair enzyme Ntg1p. Extension of CLS by mtROS signaling and reduced TORC1 activity, but not caloric restriction, was abrogated in ntg1Δ strains that exhibited mtDNA depletion without defects in respiration. The DNA damage response (DDR) kinase Rad53p, which transduces pro-longevity mtROS signals, is also activated in ntg1Δ strains. Restoring mtDNA copy number alleviated Rad53p activation and re-established CLS extension following mtROS signaling, indicating that Rad53p senses mtDNA depletion directly. Finally, DDR kinases regulate nucleus-mitochondria localization dynamics of Ntg1p. From these results, we conclude that the DDR pathway senses and may regulate Ntg1p-dependent mtDNA stability. Furthermore, Rad53p senses multiple mitochondrial stresses in a hierarchical manner to elicit specific physiological outcomes, exemplified by mtDNA depletion overriding the ability of Rad53p to transduce an adaptive mtROS longevity signal.
Collapse
Affiliation(s)
- Elizabeth A Schroeder
- Department of Pathology, Yale University School of Medicine, New Haven, CT 06520, United States; Department of Genetics, Yale University School of Medicine, New Haven, CT 06520, United States
| | - Gerald S Shadel
- Department of Pathology, Yale University School of Medicine, New Haven, CT 06520, United States; Department of Genetics, Yale University School of Medicine, New Haven, CT 06520, United States.
| |
Collapse
|
15
|
The contribution of Nth and Nei DNA glycosylases to mutagenesis in Mycobacterium smegmatis. DNA Repair (Amst) 2013; 13:32-41. [PMID: 24342191 DOI: 10.1016/j.dnarep.2013.11.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2013] [Revised: 11/21/2013] [Accepted: 11/26/2013] [Indexed: 11/20/2022]
Abstract
The increased prevalence of drug resistant strains of Mycobacterium tuberculosis (Mtb) indicates that significant mutagenesis occurs during tuberculosis disease in humans. DNA damage by host-derived reactive oxygen/nitrogen species is hypothesized to be critical for the mutagenic process in Mtb thus, highlighting an important role for DNA repair enzymes in maintenance of genome fidelity. Formamidopyrimidine (Fpg/MutM/Fapy) and EndonucleaseVIII (Nei) constitute the Fpg/Nei family of DNA glycosylases and together with EndonucleaseIII (Nth) are central to the base excision repair pathway in bacteria. In this study we assess the contribution of Nei and Nth DNA repair enzymes in Mycobacterium smegmatis (Msm), which retains a single nth homologue and duplications of the Fpg (fpg1 and fpg2) and Nei (nei1 and nei2) homologues. Using an Escherichia coli nth deletion mutant, we confirm the functionality of the mycobacterial nth gene in the base excision repair pathway. Msm mutants lacking nei1, nei2 and nth individually or in combination did not display aberrant growth in broth culture. Deletion of nth individually results in increased UV-induced mutagenesis and combinatorial deletion with the nei homologues results in reduced survival under oxidative stress conditions and an increase in spontaneous mutagenesis to rifampicin. Deletion of nth together with the fpg homolgues did not result in any growth/survival defects or changes in mutation rate. Furthermore, no differential emergence of the common rifampicin resistance conferring genotypes were noted. Collectively, these data confirm a role for Nth in base excision repair in mycobacteria and further highlight a novel interplay between the Nth and Nei homologues in spontaneous mutagenesis.
Collapse
|
16
|
Abstract
DNA repair mechanisms are critical for maintaining the integrity of genomic DNA, and their loss is associated with cancer predisposition syndromes. Studies in Saccharomyces cerevisiae have played a central role in elucidating the highly conserved mechanisms that promote eukaryotic genome stability. This review will focus on repair mechanisms that involve excision of a single strand from duplex DNA with the intact, complementary strand serving as a template to fill the resulting gap. These mechanisms are of two general types: those that remove damage from DNA and those that repair errors made during DNA synthesis. The major DNA-damage repair pathways are base excision repair and nucleotide excision repair, which, in the most simple terms, are distinguished by the extent of single-strand DNA removed together with the lesion. Mistakes made by DNA polymerases are corrected by the mismatch repair pathway, which also corrects mismatches generated when single strands of non-identical duplexes are exchanged during homologous recombination. In addition to the true repair pathways, the postreplication repair pathway allows lesions or structural aberrations that block replicative DNA polymerases to be tolerated. There are two bypass mechanisms: an error-free mechanism that involves a switch to an undamaged template for synthesis past the lesion and an error-prone mechanism that utilizes specialized translesion synthesis DNA polymerases to directly synthesize DNA across the lesion. A high level of functional redundancy exists among the pathways that deal with lesions, which minimizes the detrimental effects of endogenous and exogenous DNA damage.
Collapse
|
17
|
Gaytán BD, Loguinov AV, De La Rosa VY, Lerot JM, Vulpe CD. Functional genomics indicates yeast requires Golgi/ER transport, chromatin remodeling, and DNA repair for low dose DMSO tolerance. Front Genet 2013; 4:154. [PMID: 23964287 PMCID: PMC3741465 DOI: 10.3389/fgene.2013.00154] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2013] [Accepted: 07/24/2013] [Indexed: 11/13/2022] Open
Abstract
Dimethyl sulfoxide (DMSO) is frequently utilized as a solvent in toxicological and pharmaceutical investigations. It is therefore important to establish the cellular and molecular targets of DMSO in order to differentiate its intrinsic effects from those elicited by a compound of interest. We performed a genome-wide functional screen in Saccharomyces cerevisiae to identify deletion mutants exhibiting sensitivity to 1% DMSO, a concentration standard to yeast chemical profiling studies. We report that mutants defective in Golgi/ER transport are sensitive to DMSO, including those lacking components of the conserved oligomeric Golgi (COG) complex. Moreover, strains deleted for members of the SWR1 histone exchange complex are hypersensitive to DMSO, with additional chromatin remodeling mutants displaying a range of growth defects. We also identify DNA repair genes important for DMSO tolerance. Finally, we demonstrate that overexpression of histone H2A.Z, which replaces chromatin-associated histone H2A in a SWR1-catalyzed reaction, confers resistance to DMSO. Many yeast genes described in this study have homologs in more complex organisms, and the data provided is applicable to future investigations into the cellular and molecular mechanisms of DMSO toxicity.
Collapse
Affiliation(s)
- Brandon D Gaytán
- Department of Nutritional Science and Toxicology, University of California Berkeley, CA, USA
| | | | | | | | | |
Collapse
|
18
|
Aljuhani N, Michail K, Karapetyan Z, Siraki AG. The effect of bicarbonate on menadione-induced redox cycling and cytotoxicity: potential involvement of the carbonate radical. Can J Physiol Pharmacol 2013; 91:783-90. [PMID: 24144048 DOI: 10.1139/cjpp-2012-0254] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
We have investigated the effect of NaHCO3 on menadione redox cycling and cytotoxicity. A cell-free system utilized menadione and ascorbic acid to catalyze a redox cycle, and we utilized murine hepatoma (Hepa 1c1c7) cells for in vitro experiments. Experiments were performed using low (2 mmol/L) and physiological (25 mmol/L) levels of NaHCO3 in buffer equilibrated to physiological pH. Using oximetry, ascorbic acid oxidation, and ascorbyl radical detection, we found that menadione redox cycling was enhanced by NaHCO3. Furthermore, Hepa 1c1c7 cells treated with menadione demonstrated cytotoxicity that was significantly increased with physiological concentrations of NaHCO3 in the media, compared with low levels of NaHCO3. Interestingly, the inhibition of superoxide dismutase (SOD) with 2 different metal chelators was associated with a protective effect against menadione cytotoxicity. Using isolated protein, we found a significant increase in protein carbonyls with menadione-ascorbate-SOD with physiological NaHCO3 levels; low NaHCO3 or SOD-free reactions produced lower levels of protein carbonyls. In conclusion, these findings suggest that the hydrogen peroxide generated by menadione redox cycling together with NaHCO3-CO2 are potential substrates for SOD peroxidase activity that can lead to carbonate-radical-enhanced cytotoxicity. These findings demonstrate the importance of NaHCO3 in menadione redox cycling and cytotoxicity.
Collapse
Affiliation(s)
- Naif Aljuhani
- a University of Alberta, Faculty of Pharmacy and Pharmaceutical Sciences, Edmonton, AB T6G 2E1, Canada
| | | | | | | |
Collapse
|
19
|
Dzierzbicki P, Kaniak-Golik A, Malc E, Mieczkowski P, Ciesla Z. The generation of oxidative stress-induced rearrangements in Saccharomyces cerevisiae mtDNA is dependent on the Nuc1 (EndoG/ExoG) nuclease and is enhanced by inactivation of the MRX complex. Mutat Res 2012; 740:21-33. [PMID: 23276591 DOI: 10.1016/j.mrfmmm.2012.12.004] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2012] [Revised: 12/10/2012] [Accepted: 12/20/2012] [Indexed: 12/17/2022]
Abstract
Oxidative stress is known to enhance the frequency of two major types of alterations in the mitochondrial genome of Saccharomyces cerevisiae: point mutations and large deletions resulting in the generation of respiration-deficient petite rhō mutants. We investigated the effect of antimycin A, a well-known agent inducing oxidative stress, on the stability of mtDNA. We show that antimycin enhances exclusively the generation of respiration-deficient petite mutants and this is accompanied by a significant increase in the level of reactive oxygen species (ROS) and in a marked drop of cellular ATP. Whole mitochondrial genome sequencing revealed that mtDNAs of antimycin-induced petite mutants are deleted for most of the wild-type sequence and usually contain one of the active origins of mtDNA replication: ori1, ori2 ori3 or ori5. We show that the frequency of antimycin-induced rhō mutants is significantly elevated in mutants deleted either for the RAD50 or XRS2 gene, both encoding the components of the MRX complex, which is known to be involved in the repair of double strand breaks (DSBs) in DNA. Furthermore, enhanced frequency of rhō mutants in cultures of antimycin-treated cells lacking Rad50 was further increased by the simultaneous absence of the Ogg1 glycosylase, an important enzyme functioning in mtBER. We demonstrate also that rad50Δ and xrs2Δ deletion mutants display a considerable reduction in the frequency of allelic mitochondrial recombination, suggesting that it is the deficiency in homologous recombination which is responsible for enhanced rearrangements of mtDNA in antimycin-treated cells of these mutants. Finally, we show that the generation of large-scale mtDNA deletions induced by antimycin is markedly decreased in a nuc1Δ mutant lacking the activity of the Nuc1 nuclease, an ortholog of the mammalian mitochondrial nucleases EndoG and ExoG. This result indicates that the nuclease plays an important role in processing of oxidative stress-induced lesions in the mitochondrial genome.
Collapse
Affiliation(s)
- Piotr Dzierzbicki
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, Poland
| | | | | | | | | |
Collapse
|
20
|
Dolinnaya NG, Kubareva EA, Romanova EA, Trikin RM, Oretskaya TS. Thymidine glycol: the effect on DNA molecular structure and enzymatic processing. Biochimie 2012; 95:134-47. [PMID: 23000318 DOI: 10.1016/j.biochi.2012.09.008] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2012] [Accepted: 09/12/2012] [Indexed: 12/18/2022]
Abstract
Thymine glycol (Tg) in DNA is a biologically active oxidative damage caused by ionizing radiation or oxidative stress. Due to chirality of C5 and C6 atoms, Tg exists as a mixture of two pairs of cis and trans diastereomers: 5R cis-trans pair (5R,6S; 5R,6R) and 5S cis-trans pair (5S,6R; 5S,6S). Of all the modified pyrimidine lesions that have been studied to date, only thymine glycol represents a strong block to high-fidelity DNA polymerases in vitro and is lethal in vivo. Here we describe the preparation of thymine glycol-containing oligonucleotides and the influence of the oxidized residue on the structure of DNA in different sequence contexts, thymine glycol being paired with either adenine or guanine. The effect of thymine glycol on biochemical processing of DNA, such as biosynthesis, transcription and repair in vitro and in vivo, is also reviewed. Special attention is paid to stereochemistry and 5R cis-trans epimerization of Tg, and their relation to the structure of DNA double helix and enzyme-mediated DNA processing. Described here are the comparative structure and properties of other forms of pyrimidine base oxidation, as well as the role of Tg in tandem lesions.
Collapse
Affiliation(s)
- Nina G Dolinnaya
- Department of Chemistry and Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 1 Leninskie Gory, 119991 Moscow, Russia
| | | | | | | | | |
Collapse
|
21
|
Ihemere UE, Narayanan NN, Sayre RT. Iron Biofortification and Homeostasis in Transgenic Cassava Roots Expressing the Algal Iron Assimilatory Gene, FEA1. FRONTIERS IN PLANT SCIENCE 2012; 3:171. [PMID: 22993514 PMCID: PMC3440605 DOI: 10.3389/fpls.2012.00171] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2011] [Accepted: 07/11/2012] [Indexed: 05/20/2023]
Abstract
We have engineered the tropical root crop cassava (Manihot esculenta) to express the Chlamydomonas reinhardtii iron assimilatory gene, FEA1, in its storage roots with the objective of enhancing the root nutritional qualities. Iron levels in mature cassava storage roots were increased from 10 to 36 ppm in the highest iron accumulating transgenic lines. These iron levels are sufficient to meet the minimum daily requirement for iron in a 500 g meal. Significantly, the expression of the FEA1 gene in storage roots did not alter iron levels in leaves. Transgenic plants also had normal levels of zinc in leaves and roots consistent with the specific uptake of ferrous iron mediated by the FEA1 protein. Relative to wild-type plants, fibrous roots of FEA1 expressing plants had reduced Fe (III) chelate reductase activity consistent with the more efficient uptake of iron in the transgenic plants. We also show that multiple cassava genes involved in iron homeostasis have altered tissue-specific patterns of expression in leaves, stems, and roots of transgenic plants consistent with increased iron sink strength in transgenic roots. These results are discussed in terms of strategies for the iron biofortification of plants.
Collapse
|
22
|
Swartzlander DB, Bauer NC, Corbett AH, Doetsch PW. Regulation of base excision repair in eukaryotes by dynamic localization strategies. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2012; 110:93-121. [PMID: 22749144 DOI: 10.1016/b978-0-12-387665-2.00005-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
This chapter discusses base excision repair (BER) and the known mechanisms defined thus far regulating BER in eukaryotes. Unlike the situation with nucleotide excision repair and double-strand break repair, little is known about how BER is regulated to allow for efficient and accurate repair of many types of DNA base damage in both nuclear and mitochondrial genomes. Regulation of BER has been proposed to occur at multiple, different levels including transcription, posttranslational modification, protein-protein interactions, and protein localization; however, none of these regulatory mechanisms characterized thus far affect a large spectrum of BER proteins. This chapter discusses a recently discovered mode of BER regulation defined in budding yeast cells that involves mobilization of DNA repair proteins to DNA-containing organelles in response to genotoxic stress.
Collapse
Affiliation(s)
- Daniel B Swartzlander
- Department of Biochemistry, Emory University School of Medicine, Atlanta, Georgia, USA
| | | | | | | |
Collapse
|
23
|
Narayanan NN, Ihemere U, Chiu WT, Siritunga D, Rajamani S, Singh S, Oda S, Sayre RT. The Iron Assimilatory Protein, FEA1, from Chlamydomonas reinhardtii Facilitates Iron-Specific Metal Uptake in Yeast and Plants. FRONTIERS IN PLANT SCIENCE 2011; 2:67. [PMID: 22639604 PMCID: PMC3355668 DOI: 10.3389/fpls.2011.00067] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2011] [Accepted: 10/05/2011] [Indexed: 05/08/2023]
Abstract
We demonstrate that the unique green algal iron assimilatory protein, FEA1, is able to complement the Arabidopsis iron-transporter mutant, irt1, as well as enhance iron accumulation in FEA1 expressing wild-type plants. Expression of the FEA1 protein reduced iron-deficient growth phenotypes when plants were grown under iron limiting conditions and enhanced iron accumulation up to fivefold relative to wild-type plants when grown in iron sufficient media. Using yeast iron-uptake mutants, we demonstrate that the FEA1 protein specifically facilitates the uptake of the ferrous form of iron. Significantly, the FEA1 protein does not increase sensitivity to toxic concentrations of competing, non-ferrous metals nor facilitate their (cadmium) accumulation. These results indicate that the FEA1 protein is iron specific consistent with the observation the FEA1 protein is overexpressed in cadmium stressed algae presumably to facilitate iron uptake. We propose that the FEA1 iron assimilatory protein has ideal characteristics for the iron biofortification of crops and/or for facilitated iron uptake in plants when they are grown in low iron, high pH soils, or soils that may be contaminated with heavy metals.
Collapse
Affiliation(s)
| | - Uzoma Ihemere
- Donald Danforth Plant Science CenterSt. Louis, MO, USA
| | - Wai Ting Chiu
- Department of Plant Cellular and Molecular Biology, The Ohio State UniversityColumbus, OH, USA
| | - Dimuth Siritunga
- Department of Biology, University of Puerto RicoMayaguez, PR, USA
| | - Sathish Rajamani
- Department of Plant Cellular and Molecular Biology, The Ohio State UniversityColumbus, OH, USA
| | - Sareena Singh
- Department of Plant Cellular and Molecular Biology, The Ohio State UniversityColumbus, OH, USA
| | - Saharu Oda
- Department of Plant Cellular and Molecular Biology, The Ohio State UniversityColumbus, OH, USA
| | | |
Collapse
|
24
|
Stolc V, Shmygelska A, Griko Y. Adaptation of organisms by resonance of RNA transcription with the cellular redox cycle. PLoS One 2011; 6:e25270. [PMID: 21980411 PMCID: PMC3182209 DOI: 10.1371/journal.pone.0025270] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2010] [Accepted: 08/30/2011] [Indexed: 01/26/2023] Open
Abstract
Sequence variation in organisms differs across the genome and the majority of mutations are caused by oxidation, yet its origin is not fully understood. It has also been shown that the reduction-oxidation reaction cycle is the fundamental biochemical cycle that coordinates the timing of all biochemical processes in the cell, including energy production, DNA replication, and RNA transcription. We show that the temporal resonance of transcriptome biosynthesis with the oscillating binary state of the reduction-oxidation reaction cycle serves as a basis for non-random sequence variation at specific genome-wide coordinates that change faster than by accumulation of chance mutations. This work demonstrates evidence for a universal, persistent and iterative feedback mechanism between the environment and heredity, whereby acquired variation between cell divisions can outweigh inherited variation.
Collapse
Affiliation(s)
- Viktor Stolc
- NASA Ames Research Center, Moffett Field, California, United States of America.
| | | | | |
Collapse
|
25
|
Ling F, Mikawa T, Shibata T. Enlightenment of yeast mitochondrial homoplasmy: diversified roles of gene conversion. Genes (Basel) 2011; 2:169-90. [PMID: 24710143 PMCID: PMC3924846 DOI: 10.3390/genes2010169] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2011] [Revised: 01/18/2011] [Accepted: 01/25/2011] [Indexed: 11/29/2022] Open
Abstract
Mitochondria have their own genomic DNA. Unlike the nuclear genome, each cell contains hundreds to thousands of copies of mitochondrial DNA (mtDNA). The copies of mtDNA tend to have heterogeneous sequences, due to the high frequency of mutagenesis, but are quickly homogenized within a cell ("homoplasmy") during vegetative cell growth or through a few sexual generations. Heteroplasmy is strongly associated with mitochondrial diseases, diabetes and aging. Recent studies revealed that the yeast cell has the machinery to homogenize mtDNA, using a common DNA processing pathway with gene conversion; i.e., both genetic events are initiated by a double-stranded break, which is processed into 3' single-stranded tails. One of the tails is base-paired with the complementary sequence of the recipient double-stranded DNA to form a D-loop (homologous pairing), in which repair DNA synthesis is initiated to restore the sequence lost by the breakage. Gene conversion generates sequence diversity, depending on the divergence between the donor and recipient sequences, especially when it occurs among a number of copies of a DNA sequence family with some sequence variations, such as in immunoglobulin diversification in chicken. MtDNA can be regarded as a sequence family, in which the members tend to be diversified by a high frequency of spontaneous mutagenesis. Thus, it would be interesting to determine why and how double-stranded breakage and D-loop formation induce sequence homogenization in mitochondria and sequence diversification in nuclear DNA. We will review the mechanisms and roles of mtDNA homoplasmy, in contrast to nuclear gene conversion, which diversifies gene and genome sequences, to provide clues toward understanding how the common DNA processing pathway results in such divergent outcomes.
Collapse
Affiliation(s)
- Feng Ling
- Chemical Genetics Laboratory, RIKEN Advanced Science Institute/2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan.
| | - Tsutomu Mikawa
- Biometal Science Laboratory, RIKEN SPring-8 Center/Mikazuki cho, Hyogo 679-5148 Japan.
| | - Takehiko Shibata
- Division of Molecular and Cellular Physiology, Department of Supramolecular Biology, Graduate School of Nanobiosciences, Yokohama City University/1-7-29 Suehiro cho, Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan.
| |
Collapse
|
26
|
Rellán-Álvarez R, El-Jendoubi H, Wohlgemuth G, Abadía A, Fiehn O, Abadía J, Álvarez-Fernández A. Metabolite profile changes in xylem sap and leaf extracts of strategy I plants in response to iron deficiency and resupply. FRONTIERS IN PLANT SCIENCE 2011; 2:66. [PMID: 22645546 PMCID: PMC3355808 DOI: 10.3389/fpls.2011.00066] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2011] [Accepted: 10/04/2011] [Indexed: 05/04/2023]
Abstract
The metabolite profile changes induced by Fe deficiency in leaves and xylem sap of several Strategy I plant species have been characterized. We have confirmed that Fe deficiency causes consistent changes both in the xylem sap and leaf metabolite profiles. The main changes in the xylem sap metabolite profile in response to Fe deficiency include consistent decreases in amino acids, N-related metabolites and carbohydrates, and increases in TCA cycle metabolites. In tomato, Fe resupply causes a transitory flush of xylem sap carboxylates, but within 1 day the metabolite profile of the xylem sap from Fe-deficient plants becomes similar to that of Fe-sufficient controls. The main changes in the metabolite profile of leaf extracts in response to Fe deficiency include consistent increases in amino acids and N-related metabolites, carbohydrates and TCA cycle metabolites. In leaves, selected pairs of amino acids and TCA cycle metabolites show high correlations, with the sign depending of the Fe status. These data suggest that in low photosynthesis, C-starved Fe-deficient plants anaplerotic reactions involving amino acids can be crucial for short-term survival.
Collapse
Affiliation(s)
- Rubén Rellán-Álvarez
- Group of Plant Stress Physiology, Department of Plant Nutrition, Aula Dei Experimental StationZaragoza, Spain
| | - Hamdi El-Jendoubi
- Group of Plant Stress Physiology, Department of Plant Nutrition, Aula Dei Experimental StationZaragoza, Spain
| | - Gert Wohlgemuth
- Metabolomics Fiehn Lab, Genome Center, University of California DavisCA, USA
| | - Anunciación Abadía
- Group of Plant Stress Physiology, Department of Plant Nutrition, Aula Dei Experimental StationZaragoza, Spain
| | - Oliver Fiehn
- Metabolomics Fiehn Lab, Genome Center, University of California DavisCA, USA
| | - Javier Abadía
- Group of Plant Stress Physiology, Department of Plant Nutrition, Aula Dei Experimental StationZaragoza, Spain
- *Correspondence: Javier Abadía, Group of Plant Stress Physiology, Department of Plant Nutrition, Aula Dei Experimental Station, P.O. Box 13034, Zaragoza E-50080, Spain. e-mail:
| | - Ana Álvarez-Fernández
- Group of Plant Stress Physiology, Department of Plant Nutrition, Aula Dei Experimental StationZaragoza, Spain
| |
Collapse
|
27
|
DNA repair defects sensitize cells to anticodon nuclease yeast killer toxins. Mol Genet Genomics 2010; 285:185-95. [PMID: 21188417 DOI: 10.1007/s00438-010-0597-5] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2010] [Accepted: 12/11/2010] [Indexed: 12/21/2022]
Abstract
Killer toxins from Kluyveromyces lactis (zymocin) and Pichia acaciae (PaT) were found to disable translation in target cells by virtue of anticodon nuclease (ACNase) activities on tRNA(Glu) and tRNA(Gln), respectively. Surprisingly, however, ACNase exposure does not only impair translation, but also affects genome integrity and concomitantly DNA damage occurs. Previously, it was shown that homologous recombination protects cells from ACNase toxicity. Here, we have analyzed whether other DNA repair pathways are functional in conferring ACNase resistance as well. In addition to HR, base excision repair (BER) and postreplication repair (PRR) promote clear resistance to either, PaT and zymocin. Comparative toxin sensitivity analysis of BER mutants revealed that its ACNase protective function is due to the endonucleases acting on apurinic (AP) sites, whereas none of the known DNA glycosylases is involved. Because PaT and zymocin require the presence of the ELP3/TRM9-dependent wobble uridine modification 5-methoxy-carbonyl-methyl (mcm(5)) for tRNA cleavage, we analyzed toxin response in DNA repair mutants additionally lacking such tRNA modifications. ACNase resistance caused by elp3 or trm9 mutations was found to rescue hypersensitivity of DNA repair defects, consistent with DNA damage to occur as a consequence of tRNA cleavage. The obtained genetic evidence promises to reveal new aspects into the mechanism linking translational fidelity and genome surveillance.
Collapse
|
28
|
Olsen I, Balasingham SV, Davidsen T, Debebe E, Rødland EA, van Soolingen D, Kremer K, Alseth I, Tønjum T. Characterization of the major formamidopyrimidine-DNA glycosylase homolog in Mycobacterium tuberculosis and its linkage to variable tandem repeats. ACTA ACUST UNITED AC 2009; 56:151-61. [PMID: 19496823 PMCID: PMC2734929 DOI: 10.1111/j.1574-695x.2009.00562.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The ability to repair DNA damage is likely to play an important role in the survival of facultative intracellular parasites because they are exposed to high levels of reactive oxygen species and nitrogen intermediates inside phagocytes. Correcting oxidative damage in purines and pyrimidines is the primary function of the enzymes formamidopyrimidine (faPy)–DNA glycosylase (Fpg) and endonuclease VIII (Nei) of the base excision repair pathway, respectively. Four gene homologs, belonging to the fpg/nei family, have been identified in Mycobacterium tuberculosis H37Rv. The recombinant protein encoded by M. tuberculosis Rv2924c, termed Mtb-Fpg1, was overexpressed, purified and biochemically characterized. The enzyme removed faPy and 5-hydroxycytosine lesions, as well as 8-oxo-7,8-dihydroguanine (8oxoG) opposite to C, T and G. Mtb-Fpg1 thus exhibited substrate specificities typical for Fpg enzymes. Although Mtb-fpg1 showed nearly complete nucleotide sequence conservation in 32 M. tuberculosis isolates, the region upstream of Mtb-fpg1 in these strains contained tandem repeat motifs of variable length. A relationship between repeat length and Mtb-fpg1 expression level was demonstrated in M. tuberculosis strains, indicating that an increased length of the tandem repeats positively influenced the expression levels of Mtb-fpg1. This is the first example of such a tandem repeat region of variable length being linked to the expression level of a bacterial gene.
Collapse
Affiliation(s)
- Ingrid Olsen
- Centre for Molecular Biology and Neuroscience, Institute of Microbiology, University of Oslo, Oslo University Hospital (Rikshospitalet), Oslo, Norway
| | | | | | | | | | | | | | | | | |
Collapse
|
29
|
Forsbring M, Vik ES, Dalhus B, Karlsen TH, Bergquist A, Schrumpf E, Bjørås M, Boberg KM, Alseth I. Catalytically impaired hMYH and NEIL1 mutant proteins identified in patients with primary sclerosing cholangitis and cholangiocarcinoma. Carcinogenesis 2009; 30:1147-54. [PMID: 19443904 PMCID: PMC2704287 DOI: 10.1093/carcin/bgp118] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The human hMYH and NEIL1 genes encode DNA glycosylases involved in repair of oxidative base damage and mutations in these genes are associated with certain cancers. Primary sclerosing cholangitis (PSC), a chronic cholestatic liver disease characterized by inflammatory destruction of the biliary tree, is often complicated by the development of cholangiocarcinoma (CCA). Here, we aimed to investigate the influence of genetic variations in the hMYH and NEIL1 genes on risk of CCA in PSC patients. The hMYH and NEIL1 gene loci in addition to the DNA repair genes hOGG1, NTHL1 and NUDT1 were analyzed in 66 PSC patients (37 with CCA and 29 without cancer) by complete genomic sequencing of exons and adjacent intronic regions. Several single-nucleotide polymorphisms and mutations were identified and severe impairment of protein function was observed for three non-synonymous variants. The NEIL1 G83D mutant was dysfunctional for the major oxidation products 7,8-dihydro-8-oxoguanine (8oxoG), thymine glycol and dihydrothymine in duplex DNA, and the ability to perform δ-elimination at abasic sites was significantly reduced. The hMYH R260Q mutant had severe defect in adenine DNA glycosylase activity, whereas hMYH H434D could excise adenines from A:8oxoG pairs but not from A:G mispairs. We found no overall associations between the 18 identified variants and susceptibility to CCA in PSC patients; however, the impaired variants may be of significance for carcinogenesis in general. Our findings demonstrate the importance of complete resequencing of selected candidate genes in order to identify rare genetic variants and their possible contribution to individual susceptibility to cancer development.
Collapse
Affiliation(s)
- Monika Forsbring
- Institute of Medical Microbiology, Rikshospitalet University Hospital HF and Centre for Molecular Biology and Neuroscience, University of Oslo, Oslo, Norway
| | | | | | | | | | | | | | | | | |
Collapse
|
30
|
Kaniak A, Dzierzbicki P, Rogowska AT, Malc E, Fikus M, Ciesla Z. Msh1p counteracts oxidative lesion-induced instability of mtDNA and stimulates mitochondrial recombination in Saccharomyces cerevisiae. DNA Repair (Amst) 2009; 8:318-29. [DOI: 10.1016/j.dnarep.2008.11.004] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2008] [Revised: 11/02/2008] [Accepted: 11/05/2008] [Indexed: 01/01/2023]
|
31
|
Tibballs KL, Ambur OH, Alfsnes K, Homberset H, Frye SA, Davidsen T, Tønjum T. Characterization of the meningococcal DNA glycosylase Fpg involved in base excision repair. BMC Microbiol 2009; 9:7. [PMID: 19134198 PMCID: PMC2628661 DOI: 10.1186/1471-2180-9-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2008] [Accepted: 01/09/2009] [Indexed: 11/10/2022] Open
Abstract
Background Neisseria meningitidis, the causative agent of meningococcal disease, is exposed to high levels of reactive oxygen species inside its exclusive human host. The DNA glycosylase Fpg of the base excision repair pathway (BER) is a central player in the correction of oxidative DNA damage. This study aimed at characterizing the meningococcal Fpg and its role in DNA repair. Results The deduced N. meningitidis Fpg amino acid sequence was highly homologous to other Fpg orthologues, with particularly high conservation of functional domains. As for most N. meningitidis DNA repair genes, the fpg gene contained a DNA uptake sequence mediating efficient transformation of DNA. The recombinant N. meningitidis Fpg protein was over-expressed, purified to homogeneity and assessed for enzymatic activity. N. meningitidis Fpg was found to remove 2,6-diamino-4-hydroxy-5-formamidopyrimidine (faPy) lesions and 7,8-dihydro-8-oxo-2'-deoxyguanosine (8oxoG) opposite of C, T and G and to a lesser extent opposite of A. Moreover, the N. meningitidis fpg single mutant was only slightly affected in terms of an increase in the frequency of phase variation as compared to a mismatch repair mutant. Conclusion Collectively, these findings show that meningococcal Fpg functions are similar to those of prototype Fpg orthologues in other bacterial species.
Collapse
Affiliation(s)
- Katrina L Tibballs
- Centre for Molecular Biology and Neuroscience and Institute of Microbiology, University of Oslo, Rikshospitalet, NO-0027 Oslo, Norway.
| | | | | | | | | | | | | |
Collapse
|
32
|
Hori A, Yoshida M, Shibata T, Ling F. Reactive oxygen species regulate DNA copy number in isolated yeast mitochondria by triggering recombination-mediated replication. Nucleic Acids Res 2008; 37:749-61. [PMID: 19074198 PMCID: PMC2647299 DOI: 10.1093/nar/gkn993] [Citation(s) in RCA: 102] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Mitochondrial DNA (mtDNA) encodes proteins that are essential for cellular ATP production. Reactive oxygen species (ROS) are respiratory byproducts that damage mtDNA and other cellular components. In Saccharomyces cerevisiae, the oxidized base excision-repair enzyme Ntg1 introduces a double-stranded break (DSB) at the mtDNA replication origin ori5; this DSB initiates the rolling-circle mtDNA replication mediated by the homologous DNA pairing protein Mhr1. Thus, ROS may play a role in the regulation of mtDNA copy number. Here, we show that the treatment of isolated mitochondria with low concentrations of hydrogen peroxide increased mtDNA copy number in an Ntg1- and Mhr1-dependent manner. This treatment elevated the DSB levels at ori5 of hypersuppressive [rho–] mtDNA only if Ntg1 was active. In vitro Ntg1-treatment of hypersuppressive [rho–] mtDNA extracted from hydrogen peroxide-treated mitochondria revealed increased oxidative modifications at ori5 loci. We also observed that purified Ntg1 created breaks in single-stranded DNA harboring oxidized bases, and that ori5 loci have single-stranded character. Furthermore, chronic low levels of hydrogen peroxide increased in vivo mtDNA copy number. We therefore propose that ROS act as a regulator of mtDNA copy number, acting through the Mhr1-dependent initiation of rolling-circle replication promoted by Ntg1-induced DSB in the single-stranded regions at ori5.
Collapse
Affiliation(s)
- Akiko Hori
- Chemical Genetics Laboratory, RIKEN Advanced Science Institute, Hirosawa 2-1, Wako-shi, Saitama 351-0198, Japan
| | | | | | | |
Collapse
|
33
|
Excision of the oxidatively formed 5-hydroxyhydantoin and 5-hydroxy-5-methylhydantoin pyrimidine lesions by Escherichia coli and Saccharomyces cerevisiae DNA N-glycosylases. Biochim Biophys Acta Gen Subj 2008; 1790:16-24. [PMID: 18983898 DOI: 10.1016/j.bbagen.2008.10.001] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2008] [Revised: 09/25/2008] [Accepted: 10/01/2008] [Indexed: 11/23/2022]
Abstract
BACKGROUND (5R) and (5S) diastereomers of 1-[2-deoxy-beta-D-erythro-pentofuranosyl]-5-hydroxyhydantoin (5-OH-dHyd) and 1-[2-deoxy-beta-D-erythro-pentofuranosyl]-5-hydroxy-5-methylhydantoin (5-OH-5-Me-dHyd) are major oxidation products of 2'-deoxycytidine and thymidine respectively. If not repaired, when present in cellular DNA, these base lesions may be processed by DNA polymerases that induce mutagenic and cell lethality processes. METHODS Synthetic oligonucleotides that contained a unique 5-hydroxyhydantoin (5-OH-Hyd) or 5-hydroxy-5-methylhydantoin (5-OH-5-Me-Hyd) nucleobase were used as probes for repair studies involving several E. coli, yeast and human purified DNA N-glycosylases. Enzymatic reaction mixtures were analyzed by denaturing polyacrylamide gel electrophoresis after radiolabeling of DNA oligomers or by MALDI-TOF mass spectrometry measurements. RESULTS In vitro DNA excision experiments carried out with endo III, endo VIII, Fpg, Ntg1 and Ntg2, show that both base lesions are substrates for these DNA N-glycosylases. The yeast and human Ogg1 proteins (yOgg1 and hOgg1 respectively) and E. coli AlkA were unable to cleave the N-glycosidic bond of the 5-OH-Hyd and 5-OH-5-Me-Hyd lesions. Comparison of the kcat/Km ratio reveals that 8-oxo-7,8-dihydroguanine is only a slightly better substrate than 5-OH-Hyd and 5-OH-5-Me-Hyd. The kinetic results obtained with endo III indicate that 5-OH-Hyd and 5-OH-5-Me-Hyd are much better substrates than 5-hydroxycytosine, a well known oxidized pyrimidine substrate for this DNA N-glycosylase. CONCLUSIONS The present study supports a biological relevance of the base excision repair processes toward the hydantoin lesions, while the removal by the Fpg and endo III proteins are effected at better or comparable rates to that of the removal of 8-oxoGua and 5-OH-Cyt, two established cellular substrates. GENERAL SIGNIFICANCE The study provides new insights into the substrate specificity of DNA N-glycosylases involved in the base excision repair of oxidized bases, together with complementary information on the biological role of hydantoin type lesions.
Collapse
|
34
|
Baute J, Depicker A. Base excision repair and its role in maintaining genome stability. Crit Rev Biochem Mol Biol 2008; 43:239-76. [PMID: 18756381 DOI: 10.1080/10409230802309905] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
For all living organisms, genome stability is important, but is also under constant threat because various environmental and endogenous damaging agents can modify the structural properties of DNA bases. As a defense, organisms have developed different DNA repair pathways. Base excision repair (BER) is the predominant pathway for coping with a broad range of small lesions resulting from oxidation, alkylation, and deamination, which modify individual bases without large effect on the double helix structure. As, in mammalian cells, this damage is estimated to account daily for 10(4) events per cell, the need for BER pathways is unquestionable. The damage-specific removal is carried out by a considerable group of enzymes, designated as DNA glycosylases. Each DNA glycosylase has its unique specificity and many of them are ubiquitous in microorganisms, mammals, and plants. Here, we review the importance of the BER pathway and we focus on the different roles of DNA glycosylases in various organisms.
Collapse
Affiliation(s)
- Joke Baute
- Department of Plant Systems Biology, Flanders Institute for Biotechnology, Gent, Belgium
| | | |
Collapse
|
35
|
Krishnamurthy N, Haraguchi K, Greenberg MM, David SS. Efficient removal of formamidopyrimidines by 8-oxoguanine glycosylases. Biochemistry 2007; 47:1043-50. [PMID: 18154319 DOI: 10.1021/bi701619u] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Under conditions of oxidative stress, the formamidopyrimidine lesions (FapyG and FapyA) are formed in competition with the corresponding 8-oxopurines (OG and OA) from a common intermediate. In order to reveal features of the repair of these lesions, and the potential contribution of repair in mitigating or exacerbating the mutagenic properties of Fapy lesions, their excision by three glycosylases, Fpg, hOGG1 and Ntg1, was examined in various base pair contexts under single-turnover conditions. FapyG was removed at least as efficiently as OG by all three glycosylases. In addition, the rates of removal of FapyG by Fpg and hOGG1 were influenced by their base pair partner, with preference for removal when base paired with the correct Watson-Crick partner C. With the FapyA lesion, Fpg and Ntg1 catalyze its removal more readily than OG opposite all four natural bases. In contrast, the removal of FapyA by hOGG1 was not as robust as FapyG or OG, and was only significant when the lesion was paired with C. The discrimination by the various glycosylases with respect to the opposing base was highly dependent on the identity of the lesion. OG induced the greatest selectivity against its removal when part of a promutagenic base pair. The superb activity of the various OG glycosylases toward removal of FapyG and FapyA in vitro suggests that these enzymes may act upon these oxidized lesions in vivo. The differences in the activity of the various glycosylases for removal of FapyG and FapyA compared to OG in nonmutagenic versus promutagenic base pair contexts may serve to alter the mutagenic profiles of these lesions in vivo.
Collapse
Affiliation(s)
- Nirmala Krishnamurthy
- Department of Chemistry, University of Utah, 315 South, 1400 East, Salt Lake City, Utah 84112, USA
| | | | | | | |
Collapse
|
36
|
Yoshitani A, Yoshida M, Ling F. A novel cis-acting element required for DNA damage-inducible expression of yeast DIN7. Biochem Biophys Res Commun 2007; 365:183-8. [PMID: 17988640 DOI: 10.1016/j.bbrc.2007.10.177] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2007] [Accepted: 10/26/2007] [Indexed: 10/22/2022]
Abstract
Din7 is a DNA damage-inducible mitochondrial nuclease that modulates the stability of mitochondrial DNA (mtDNA) in Saccharomyces cerevisiae. How DIN7 gene expression is regulated, however, has remained largely unclear. Using promoter sequence alignment, we found a highly conserved 19-bp sequence in the promoter regions of DIN7 and NTG1, which encodes an oxidative stress-inducible base-excision-repair enzyme. Deletion of the 19-bp sequence markedly reduced the hydroxyurea (HU)-enhanced DIN7 promoter activity. In addition, nuclear fractions prepared from HU-treated cells were used in in vitro band shift assays to reveal the presence of currently unidentified trans-acting factor(s) that preferentially bound to the 19-bp region. These results suggest that the 19-bp sequence is a novel cis-acting element that is required for the regulation of DIN7 expression in response to HU-induced DNA damage.
Collapse
Affiliation(s)
- Ayako Yoshitani
- Chemical Genetics Laboratory, RIKEN Discovery Research Institute, Hirosawa 2-1, Wako-shi, Saitama 351-0198, Japan
| | | | | |
Collapse
|
37
|
Jaruga P, Jabil R, McCullough AK, Rodriguez H, Dizdaroglu M, Lloyd RS. Chlorella Virus Pyrimidine Dimer Glycosylase Excises Ultraviolet Radiation- and Hydroxyl Radical-induced Products 4,6-Diamino-5-formamidopyrimidine and 2,6-Diamino-4-hydroxy-5-formamidopyrimidine from DNA¶. Photochem Photobiol 2007. [DOI: 10.1562/0031-8655(2002)0750085cvpdge2.0.co2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
|
38
|
Ling F, Hori A, Shibata T. DNA recombination-initiation plays a role in the extremely biased inheritance of yeast [rho-] mitochondrial DNA that contains the replication origin ori5. Mol Cell Biol 2006; 27:1133-45. [PMID: 17116696 PMCID: PMC1800698 DOI: 10.1128/mcb.00770-06] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Hypersuppressiveness, as observed in Saccharomyces cerevisiae, is an extremely biased inheritance of a small mitochondrial DNA (mtDNA) fragment that contains a replication origin (HS [rho(-)] mtDNA). Our previous studies showed that concatemers (linear head-to-tail multimers) are obligatory intermediates for mtDNA partitioning and are primarily formed by rolling-circle replication mediated by Mhr1, a protein required for homologous mtDNA recombination. In this study, we found that Mhr1 is required for the hypersuppressiveness of HS [ori5] [rho(-)] mtDNA harboring ori5, one of the replication origins of normal ([rho(+)]) mtDNA. In addition, we detected an Ntg1-stimulated double-strand break at the ori5 locus. Purified Ntg1, a base excision repair enzyme, introduced a double-stranded break by itself into HS [ori5] [rho(-)] mtDNA at ori5 isolated from yeast cells. Both hypersuppressiveness and concatemer formation of HS [ori5] [rho(-)] mtDNA are simultaneously suppressed by the ntg1 null mutation. These results support a model in which, like homologous recombination, rolling-circle HS [ori5] [rho(-)] mtDNA replication is initiated by double-stranded breakage in ori5, followed by Mhr1-mediated homologous pairing of the processed nascent DNA ends with circular mtDNA. The hypersuppressiveness of HS [ori5] [rho(-)] mtDNA depends on a replication advantage furnished by the higher density of ori5 sequences and on a segregation advantage furnished by the higher genome copy number on transmitted concatemers.
Collapse
Affiliation(s)
- Feng Ling
- RIKEN Discovery Research Institute, Hirosawa 2-1, Wako-shi, Saitama 351-0198, Japan
| | | | | |
Collapse
|
39
|
Hazra TK, Das A, Das S, Choudhury S, Kow YW, Roy R. Oxidative DNA damage repair in mammalian cells: a new perspective. DNA Repair (Amst) 2006; 6:470-80. [PMID: 17116430 PMCID: PMC2702509 DOI: 10.1016/j.dnarep.2006.10.011] [Citation(s) in RCA: 208] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Oxidatively induced DNA lesions have been implicated in the etiology of many diseases (including cancer) and in aging. Repair of oxidatively damaged bases in all organisms occurs primarily via the DNA base excision repair (BER) pathway, initiated with their excision by DNA glycosylases. Only two mammalian DNA glycosylases, OGG1 and NTH1 of E. coli Nth family, were previously characterized, which excise majority of the oxidatively damaged base lesions. We recently discovered and characterized two human orthologs of E. coli Nei, the prototype of the second family of oxidized base-specific glycosylases and named them NEIL (Nei-like)-1 and 2. NEILs are distinct from NTH1 and OGG1 in structural features and reaction mechanism but act on many of the same substrates. Nth-type DNA glycosylases after base excision, cleave the DNA strand at the resulting AP-site to produce a 3'-alphabeta unsaturated aldehyde whereas Nei-type enzymes produce 3'-phosphate terminus. E. coli APEs efficiently remove both types of termini in addition to cleaving AP sites to generate 3'-OH, the primer terminus for subsequent DNA repair synthesis. In contrast, the mammalian APE, APE1, which has an essential role in NTH1/OGG1-initiated BER, has negligible 3'-phosphatase activity and is dispensable for NEIL-initiated BER. Polynucleotide kinase (PNK), present in mammalian cells but not in E. coli, removes the 3' phosphate, and is involved in NEIL-initiated BER. NEILs show a unique preference for excising lesions from a DNA bubble, while most DNA glycosylases, including OGG1 and NTH1, are active only with duplex DNA. The dichotomy in the preference of NEILs and NTH1/OGG1 for bubble versus duplex DNA substrates suggests that NEILs function preferentially in repair of base lesions during replication and/or transcription and hence play a unique role in maintaining the functional integrity of mammalian genomes.
Collapse
Affiliation(s)
- Tapas K Hazra
- Sealy Center for Molecular Science and Department of Biochemistry and Molecular Biology, 6.136 Medical Research Building, Route 1079, University of Texas Medical Branch, Galveston, TX 77555, USA.
| | | | | | | | | | | |
Collapse
|
40
|
Phadnis N, Mehta R, Meednu N, Sia EA. Ntg1p, the base excision repair protein, generates mutagenic intermediates in yeast mitochondrial DNA. DNA Repair (Amst) 2006; 5:829-39. [PMID: 16730479 DOI: 10.1016/j.dnarep.2006.04.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2006] [Revised: 04/12/2006] [Accepted: 04/13/2006] [Indexed: 11/25/2022]
Abstract
Mitochondrial DNA is predicted to be highly prone to oxidative damage due to its proximity to free radicals generated by oxidative phosphorylation. Base excision repair (BER) is the primary repair pathway responsible for repairing oxidative damage in nuclear and mitochondrial genomes. In yeast mitochondria, three N-glycosylases have been identified so far, Ntg1p, Ogg1p and Ung1p. Ntg1p, a broad specificity N-glycosylase, takes part in catalyzing the first step of BER that involves the removal of the damaged base. In this study, we examined the role of Ntg1p in maintaining yeast mitochondrial genome integrity. Using genetic reporters and assays to assess mitochondrial mutations, we found that loss of Ntg1p suppresses mitochondrial point mutation rates, frameshifts and recombination rates. We also observed a suppression of respiration loss in the ntg1-Delta cells in response to ultraviolet light exposure implying an overlap between BER and UV-induced damage in the yeast mitochondrial compartment. Over-expression of the BER AP endonuclease, Apn1p, did not significantly affect the mitochondrial mutation rate in the presence of Ntg1p, whereas Apn1p over-expression in an ntg1-Delta background increased the frequency of mitochondrial mutations. In addition, loss of Apn1p also suppressed mitochondrial point mutations. Our work suggests that both Ntg1p and Apn1p generate mutagenic intermediates in the yeast mitochondrial genome.
Collapse
Affiliation(s)
- Naina Phadnis
- Department of Biology, University of Rochester, NY 14627-0211, USA
| | | | | | | |
Collapse
|
41
|
Berti PJ, McCann JAB. Toward a detailed understanding of base excision repair enzymes: transition state and mechanistic analyses of N-glycoside hydrolysis and N-glycoside transfer. Chem Rev 2006; 106:506-55. [PMID: 16464017 DOI: 10.1021/cr040461t] [Citation(s) in RCA: 211] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Affiliation(s)
- Paul J Berti
- Department of Chemistry, McMaster University, Hamilton, Ontario, Canada.
| | | |
Collapse
|
42
|
Letavayová L, Marková E, Hermanská K, Vlcková V, Vlasáková D, Chovanec M, Brozmanová J. Relative contribution of homologous recombination and non-homologous end-joining to DNA double-strand break repair after oxidative stress in Saccharomyces cerevisiae. DNA Repair (Amst) 2006; 5:602-10. [PMID: 16515894 DOI: 10.1016/j.dnarep.2006.01.004] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2005] [Revised: 01/17/2006] [Accepted: 01/23/2006] [Indexed: 01/01/2023]
Abstract
Oxidative damage to DNA seems to be an important factor in developing many human diseases including cancer. It involves base and sugar damage, base-free sites, DNA-protein cross-links and DNA single-strand (SSB) and double-strand (DSB) breaks. Oxidative DSB can be formed in various ways such as their direct induction by the drug or their generation either through attempted and aborted repair of primary DNA lesions or through DNA replication-dependent conversion of SSB. In general, two main pathways are responsible for repairing DSB, homologous recombination (HR) and non-homologous end-joining (NHEJ), with both of them being potential candidates for the repair of oxidative DSB. We have examined relative contribution of HR and NHEJ to cellular response after oxidative stress in Saccharomyces cerevisiae. Therefore, cell survival, mutagenesis and DSB induction and repair in the rad52, yku70 and rad52 yku70 mutants after hydrogen peroxide (H(2)O(2)), menadione (MD) or bleomycin (BLM) exposure were compared to those obtained for the corresponding wild type. We show that MD exposure does not lead to observable DSB induction in yeast, suggesting that the toxic effects of this agent are mediated by other types of DNA damage. Although H(2)O(2) treatment generates some DSB, their yield is relatively low and hence DSB may only partially be responsible for toxicity of H(2)O(2), particularly at high doses of the agent. On the other hand, the basis of the BLM toxicity resides primarily in DSB induction. Both HR and NHEJ act on BLM-induced DSB, although their relative participation in the process is not equal. Based on our results we suggest that the complexity and/or the quality of the BLM-induced DSB might represent an obstacle for the NHEJ pathway.
Collapse
Affiliation(s)
- Lucia Letavayová
- Laboratory of Molecular Genetics, Cancer Research Institute, Slovak Academy of Sciences, Vlárska 7, 833 91 Bratislava, Slovak Republic
| | | | | | | | | | | | | |
Collapse
|
43
|
Ranneberg-Nilsen T, Bjørås M, Luna L, Slettebakk R, Dale HA, Seeberg E, Rollag H. Human cytomegalovirus infection modulates DNA base excision repair in fibroblast cells. Virology 2006; 348:389-97. [PMID: 16476462 DOI: 10.1016/j.virol.2006.01.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2005] [Revised: 09/26/2005] [Accepted: 01/03/2006] [Indexed: 10/25/2022]
Abstract
Regulation of DNA repair mechanisms during the viral replication cycle may have consequences for the virus with regards to genomic variability, adaptation, and replication of viral DNA. We have studied the activities and expression patterns of key enzymes involved in the first two steps of base excision repair (BER) of DNA in primary fibroblasts infected by human cytomegalovirus (HCMV). Infected cells were very proficient for removal of uracil and 5' hydrolysis of AP sites (AP endonuclease activity) as compared to the mock-infected cells, suggesting a direct role in generating free ends at uracil lesions in DNA for initiation of viral replication. Furthermore, the capacity to initiate repair of alkylated and oxidized base lesions were reduced in HCMV-infected cells, indicating increased mutation frequencies that could promote genetic variability. We hypothesize that modulation of BER activities may play an important role in HCMV pathogenesis to ensure efficient replication and genomic variation of viral DNA.
Collapse
Affiliation(s)
- Toril Ranneberg-Nilsen
- Department of Virology, Institute of Microbiology, University of Oslo, Rikshospitalet, Norway.
| | | | | | | | | | | | | |
Collapse
|
44
|
Watanabe T, Blaisdell JO, Wallace SS, Bond JP. Engineering functional changes in Escherichia coli endonuclease III based on phylogenetic and structural analyses. J Biol Chem 2005; 280:34378-84. [PMID: 16096281 DOI: 10.1074/jbc.m504916200] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Escherichia coli endonuclease III (EcoNth) plays an important cellular role by removing premutagenic pyrimidine damages produced by reactive oxygen species. EcoNth is a bifunctional enzyme that has DNA glycosylase and apurinic/apyrimidinic lyase activities. Using a phylogeny of natural sequences, we selected to study EcoNth serine 39, aspartate 44, and arginine 184, which are presumed to be in the vicinity of the damaged base in the glycosylase-substrate complex. These three amino acids are highly conserved among Nth orthologs, although not among homologous glycosylases, such as MutY, that have different base specificities and no lyase activity. To examine the role of these amino acids in catalysis, we constructed three mutants of EcoNth, in which Ser39 was replaced with leucine (S39L), Asp44 was replaced with valine (D44V), and Arg184 was replaced with alanine (R184A), which are the corresponding residues in EcoMutY. We showed that EcoNth S39L does not have significant glycosylase activity for oxidized pyrimidines, although it maintained AP lyase activity. In contrast, EcoNth D44V retained glycosylase activity against oxidized pyrimidines, but the apparent rate constant for the lyase activity of EcoNth D44V was significantly lower than that of EcoNth, indicating that Asp44 in EcoNth is required for beta-elimination. Finally, EcoNth R184A maintained lyase activity but exhibited glycosylase specificity different from that of EcoNth. The functional consequences of each of these three substitutions can be rationalized in the context of high resolution protein structures. Thus phylogeny-based scanning mutagenesis has allowed us to identify novel roles for amino acids in the substrate binding pocket of EcoNth in base recognition and/or catalysis.
Collapse
Affiliation(s)
- Takashi Watanabe
- Department of Microbiology and Molecular Genetics, The University of Vermont, Burlington, Vermont 05405, USA
| | | | | | | |
Collapse
|
45
|
Dizdaroglu M. Base-excision repair of oxidative DNA damage by DNA glycosylases. Mutat Res 2005; 591:45-59. [PMID: 16054172 DOI: 10.1016/j.mrfmmm.2005.01.033] [Citation(s) in RCA: 147] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2004] [Revised: 12/28/2004] [Accepted: 01/12/2005] [Indexed: 10/25/2022]
Abstract
Oxidative damage to DNA caused by free radicals and other oxidants generate base and sugar damage, strand breaks, clustered sites, tandem lesions and DNA-protein cross-links. Oxidative DNA damage is mainly repaired by base-excision repair in living cells with the involvement of DNA glycosylases in the first step and other enzymes in subsequent steps. DNA glycosylases remove modified bases from DNA, generating an apurinic/apyrimidinic (AP) site. Some of these enzymes that remove oxidatively modified DNA bases also possess AP-lyase activity to cleave DNA at AP sites. DNA glycosylases possess varying substrate specificities, and some of them exhibit cross-activity for removal of both pyrimidine- and purine-derived lesions. Most studies on substrate specificities and excision kinetics of DNA glycosylases were performed using oligonucleotides with a single modified base incorporated at a specific position. Other studies used high-molecular weight DNA containing multiple pyrimidine- and purine-derived lesions. In this case, substrate specificities and excision kinetics were found to be different from those observed with oligonucleotides. This paper reviews substrate specificities and excision kinetics of DNA glycosylases for removal of pyrimidine- and purine-derived lesions in high-molecular weight DNA.
Collapse
Affiliation(s)
- Miral Dizdaroglu
- Chemical Science and Technology Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899-8311, USA.
| |
Collapse
|
46
|
Davidsen T, Bjørås M, Seeberg EC, Tønjum T. Antimutator role of DNA glycosylase MutY in pathogenic Neisseria species. J Bacteriol 2005; 187:2801-9. [PMID: 15805527 PMCID: PMC1070393 DOI: 10.1128/jb.187.8.2801-2809.2005] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Genome alterations due to horizontal gene transfer and stress constantly generate strain on the gene pool of Neisseria meningitidis, the causative agent of meningococcal (MC) disease. The DNA glycosylase MutY of the base excision repair pathway is involved in the protection against oxidative stress. MC MutY expressed in Escherichia coli exhibited base excision activity towards DNA substrates containing A:7,8-dihydro-8-oxo-2'-deoxyguanosine and A:C mismatches. Expression in E. coli fully suppressed the elevated spontaneous mutation rate found in the E. coli mutY mutant. An assessment of MutY activity in lysates of neisserial wild-type and mutY mutant strains showed that both MC and gonococcal (GC) MutY is expressed and active in vivo. Strikingly, MC and GC mutY mutants exhibited 60- to 140-fold and 20-fold increases in mutation rates, respectively, compared to the wild-type strains. Moreover, the differences in transitions and transversions in rpoB conferring rifampin resistance observed with the wild type and mutants demonstrated that the neisserial MutY enzyme works in preventing GC-->AT transversions. These findings are important in the context of models linking mutator phenotypes of disease isolates to microbial fitness.
Collapse
Affiliation(s)
- T Davidsen
- Centre for Molecular Biology and Neuroscience and Institute of Microbiology, University of Oslo, Rikshospitalet, N-0027 Oslo, Norway
| | | | | | | |
Collapse
|
47
|
|
48
|
Michán C, Monje-Casas F, Pueyo C. Transcript copy number of genes for DNA repair and translesion synthesis in yeast: contribution of transcription rate and mRNA stability to the steady-state level of each mRNA along with growth in glucose-fermentative medium. DNA Repair (Amst) 2005; 4:469-78. [PMID: 15725627 DOI: 10.1016/j.dnarep.2004.12.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2004] [Revised: 12/02/2004] [Accepted: 12/06/2004] [Indexed: 11/24/2022]
Abstract
We quantitated the copy number of mRNAs (NTG1, NTG2, OGG1, APN1, APN2, MSH2, MSH6, REV3, RAD30) encoding different DNA repair enzymes and translesion-synthesis polymerases in yeast. Quantitations reported examine how the steady-state number of each transcript is modulated in association with the growth in glucose-fermentative medium, and evaluate the respective contribution of the rate of mRNA degradation and transcription initiation to the specific mRNA level profile of each gene. Each transcript displayed a unique growth-related profile, therefore altering the relative abundance of mRNAs coding for proteins with similar functions, as cells proceed from exponential to stationary phase. Nonetheless, as general trend, they exhibited maximal levels when cells proliferate rapidly and minimal values when cells cease proliferation. We found that previous calculations on the stability of the investigated mRNAs might be biased, in particular regarding those that respond to heat shock stress. Overall, the mRNAs experienced drastic increments in their stabilities in response to gradual depletion of essential nutrients in the culture. However, differences among the mRNA stability profiles suggest a dynamic modulation rather than a passive process. As general rule, the investigated genes were much more frequently transcribed during the fermentative growth than later during the diauxic arrest and the stationary phase, this finding conciliating low steady-state levels with increased mRNA stabilities. Interestingly, while the rate at which each gene is transcribed appeared as the only determinant of the number of mRNA copies at the exponential growth, later, when cell growth is arrested, the rate of mRNA degradation becomes also a key factor for gene expression. In short, our results raise the question of how important the respective contribution of transcription and mRNA stability mechanisms is for the steady-state profile of a given transcript, and how this contribution may change in response to nutrient-availability.
Collapse
Affiliation(s)
- Carmen Michán
- Departamento de Bioquímica y Biología Molecular, Campus de Rabanales, edificio Severo Ochoa, planta 2a, Carretera Madrid-Cádiz Km 396-a, Universidad de Córdoba, 14071-Córdoba, Spain
| | | | | |
Collapse
|
49
|
Dzierzbicki P, Koprowski P, Fikus MU, Malc E, Ciesla Z. Repair of oxidative damage in mitochondrial DNA of Saccharomyces cerevisiae: involvement of the MSH1-dependent pathway. DNA Repair (Amst) 2004; 3:403-11. [PMID: 15010316 DOI: 10.1016/j.dnarep.2003.12.005] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2003] [Revised: 12/18/2003] [Accepted: 12/22/2003] [Indexed: 10/26/2022]
Abstract
Mitochondrial DNA (mtDNA) is located close to the respiratory chain, a major source of reactive oxygen species (ROS). This proximity makes mtDNA more vulnerable than nuclear DNA to damage by ROS. Therefore, the efficient repair of oxidative lesions in mtDNA is essential for maintaining the stability of the mitochondrial genome. A series of genetic and biochemical studies has indicated that eukaryotic cells, including the model organism Saccharomyces cerevisiae, use several alternative strategies to prevent mutagenesis induced by endogenous oxidative damage to nuclear DNA. However, apart from base excision repair (BER), no other pathways involved in the repair of oxidative damage in mtDNA have been identified. In this study, we have examined mitochondrial mutagenesis in S. cerevisiae cells which lack the activity of the Ogg1 glycosylase, an enzyme playing a crucial role in the removal of 8-oxoG, the most abundant oxidative lesion of DNA. We show that the overall frequency of the mitochondrial oligomycin-resistant (Olir) mutants is increased in the ogg1 strain by about one order of magnitude compared to that of the wild-type strain. Noteworthy, in the mitochondrial oli1 gene, G:C to T:A transversions are generated approximately 50-fold more frequently in the ogg1 mutant relative to the wild-type strain. We also demonstrate that the increased frequency of Olir mutants in the ogg1 strain is markedly reduced by the presence of plasmids encoding Msh1p, a homologue of the bacterial mismatch protein MutS, which specifically functions in mitochondria. This suppression of the mitochondrial mutator phenotype of the ogg1 strain seems to be specific, since overexpression of the mutant allele msh1-R813W failed to exert this effect. Finally, we also show that the increased frequency of Olir mutants arising in an msh1/MSH1 heterozygote grown in glucose-containing medium is further enhanced if the cells are cultivated in glycerol-containing medium, i.e. under conditions when the respiratory chain is fully active. Taken together, these results strongly suggest that MSH1-dependent repair represents a significant back-up to mtBER in the repair of oxidative damage in mtDNA.
Collapse
Affiliation(s)
- Piotr Dzierzbicki
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawinskiego 5A, 02-106 Warsaw, Poland
| | | | | | | | | |
Collapse
|
50
|
Brozmanová J, Vlcková V, Chovanec M. How heterologously expressed Escherichia coli genes contribute to understanding DNA repair processes in Saccharomyces cerevisiae. Curr Genet 2004; 46:317-30. [PMID: 15614491 DOI: 10.1007/s00294-004-0536-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2004] [Revised: 09/13/2004] [Accepted: 09/18/2004] [Indexed: 10/26/2022]
Abstract
DNA-damaging agents constantly challenge cellular DNA; and efficient DNA repair is therefore essential to maintain genome stability and cell viability. Several DNA repair mechanisms have evolved and these have been shown to be highly conserved from bacteria to man. DNA repair studies were originally initiated in very simple organisms such as Escherichia coli and Saccharomyces cerevisiae, bacteria being the best understood organism to date. As a consequence, bacterial DNA repair genes encoding proteins with well characterized functions have been transferred into higher organisms in order to increase repair capacity, or to complement repair defects, in heterologous cells. While indicating the contribution of these repair functions to protection against the genotoxic effects of DNA-damaging agents, heterologous expression studies also highlighted the role of the DNA lesions that are substrates for such processes. In addition, bacterial DNA repair-like functions could be identified in higher organisms using this approach. We heterologously expressed three well characterized E. coli repair genes in S. cerevisiae cells of different genetic backgrounds: (1) the ada gene encoding O(6)-methylguanine DNA-methyltransferase, a protein involved in the repair of alkylation damage to DNA, (2) the recA gene encoding the main recombinase in E. coli and (3) the nth gene, the product of which (endonuclease III) is responsible for the repair of oxidative base damage. Here, we summarize our results and indicate the possible implications they have for a better understanding of particular DNA repair processes in S. cerevisiae.
Collapse
Affiliation(s)
- Jela Brozmanová
- Laboratory of Molecular Genetics, Cancer Research Institute, Vlárska 7, 83391 Bratislava, Slovak Republic.
| | | | | |
Collapse
|