1
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Gohil D, Sarker AH, Roy R. Base Excision Repair: Mechanisms and Impact in Biology, Disease, and Medicine. Int J Mol Sci 2023; 24:14186. [PMID: 37762489 PMCID: PMC10531636 DOI: 10.3390/ijms241814186] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2023] [Revised: 09/12/2023] [Accepted: 09/14/2023] [Indexed: 09/29/2023] Open
Abstract
Base excision repair (BER) corrects forms of oxidative, deamination, alkylation, and abasic single-base damage that appear to have minimal effects on the helix. Since its discovery in 1974, the field has grown in several facets: mechanisms, biology and physiology, understanding deficiencies and human disease, and using BER genes as potential inhibitory targets to develop therapeutics. Within its segregation of short nucleotide (SN-) and long patch (LP-), there are currently six known global mechanisms, with emerging work in transcription- and replication-associated BER. Knockouts (KOs) of BER genes in mouse models showed that single glycosylase knockout had minimal phenotypic impact, but the effects were clearly seen in double knockouts. However, KOs of downstream enzymes showed critical impact on the health and survival of mice. BER gene deficiency contributes to cancer, inflammation, aging, and neurodegenerative disorders. Medicinal targets are being developed for single or combinatorial therapies, but only PARP and APE1 have yet to reach the clinical stage.
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Affiliation(s)
- Dhara Gohil
- Department of Oncology, Lombardi Comprehensive Cancer Center, Georgetown University, Washington, DC 20057, USA;
| | - Altaf H. Sarker
- Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA;
| | - Rabindra Roy
- Department of Oncology, Lombardi Comprehensive Cancer Center, Georgetown University, Washington, DC 20057, USA;
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2
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Pan L, Xue Y, Wang K, Zheng X, Boldogh I. Detection of Oxidatively Modified Base Lesion(s) in Defined DNA Sequences by FLARE Quantitative PCR. Methods Mol Biol 2023; 2701:115-134. [PMID: 37574478 DOI: 10.1007/978-1-0716-3373-1_7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/15/2023]
Abstract
Assessment of DNA base and strand damage can be determined using a quantitative PCR assay that is based on the concept that damage blocks the progression of a thermostable polymerase thus resulting in decreased amplification. However, some of the mutagenic DNA base lesions cause little or no distortion in Watson-Crick base pairing. One of the most abundant such lesion is 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxo(d)Gua), although it affects the thermodynamic stability of the DNA, duplex 8-oxo(d)Gua does not inhibit DNA synthesis or arrest most of DNA or RNA polymerases during replication and transcription. When unrepaired, it is a pre-mutagenic base as it pairs with adenine in anti-syn conformation. Recent studies considered 8-oxo(d)Gua as an epigenetic-like mark and along with 8-oxoguanine DNA glycosylase1 (OGG1) and apurinic/apyrimidinic endonuclease1 (APE1) has roles in gene expression via nucleating transcription factor's promoter occupancy. Here, we introduce its identification through fragment length analysis with repair enzyme (FLARE)-coupled quantitative (q)-PCR. One of the strengths of the assay is that 8-oxo(d)Gua can be identified within short stretches of nuclear and mitochondrial DNA in ng quantities. Bellow we describe the benefits and limits of using FLARE qPCR to assess DNA damage in mammalian cells and provide a detailed protocol of the assay.
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Affiliation(s)
- Lang Pan
- Departments of Microbiology and Immunology, School of Medicine, University of Texas Medical Branch at Galveston, Galveston, TX, USA
| | - Yaoyao Xue
- Departments of Microbiology and Immunology, School of Medicine, University of Texas Medical Branch at Galveston, Galveston, TX, USA
| | - Ke Wang
- Departments of Microbiology and Immunology, School of Medicine, University of Texas Medical Branch at Galveston, Galveston, TX, USA
| | - Xu Zheng
- Departments of Microbiology and Immunology, School of Medicine, University of Texas Medical Branch at Galveston, Galveston, TX, USA
| | - Istvan Boldogh
- Departments of Microbiology and Immunology, School of Medicine, University of Texas Medical Branch at Galveston, Galveston, TX, USA.
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3
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Ljungman M. Transcription and genome integrity. DNA Repair (Amst) 2022; 118:103373. [PMID: 35914488 DOI: 10.1016/j.dnarep.2022.103373] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2022] [Revised: 07/16/2022] [Accepted: 07/17/2022] [Indexed: 11/03/2022]
Abstract
Transcription can cause genome instability by promoting R-loop formation but also act as a mutation-suppressing machinery by sensing of DNA lesions leading to the activation of DNA damage signaling and transcription-coupled repair. Recovery of RNA synthesis following the resolution of repair of transcription-blocking lesions is critical to avoid apoptosis and several new factors involved in this process have recently been identified. Some DNA repair proteins are recruited to initiating RNA polymerases and this may expediate the recruitment of other factors that participate in the repair of transcription-blocking DNA lesions. Recent studies have shown that transcription of protein-coding genes does not always give rise to spliced transcripts, opening the possibility that cells may use the transcription machinery in a splicing-uncoupled manner for other purposes including surveillance of the transcribed genome.
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Affiliation(s)
- Mats Ljungman
- Departments of Radiation Oncology and Environmental Health Sciences, Rogel Cancer Center and Center for RNA Biomedicine, University of Michigan, Ann Arbor, MI, USA.
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4
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Agapov A, Olina A, Kulbachinskiy A. OUP accepted manuscript. Nucleic Acids Res 2022; 50:3018-3041. [PMID: 35323981 PMCID: PMC8989532 DOI: 10.1093/nar/gkac174] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2021] [Revised: 02/26/2022] [Accepted: 03/03/2022] [Indexed: 11/14/2022] Open
Abstract
Cellular DNA is continuously transcribed into RNA by multisubunit RNA polymerases (RNAPs). The continuity of transcription can be disrupted by DNA lesions that arise from the activities of cellular enzymes, reactions with endogenous and exogenous chemicals or irradiation. Here, we review available data on translesion RNA synthesis by multisubunit RNAPs from various domains of life, define common principles and variations in DNA damage sensing by RNAP, and consider existing controversies in the field of translesion transcription. Depending on the type of DNA lesion, it may be correctly bypassed by RNAP, or lead to transcriptional mutagenesis, or result in transcription stalling. Various lesions can affect the loading of the templating base into the active site of RNAP, or interfere with nucleotide binding and incorporation into RNA, or impair RNAP translocation. Stalled RNAP acts as a sensor of DNA damage during transcription-coupled repair. The outcome of DNA lesion recognition by RNAP depends on the interplay between multiple transcription and repair factors, which can stimulate RNAP bypass or increase RNAP stalling, and plays the central role in maintaining the DNA integrity. Unveiling the mechanisms of translesion transcription in various systems is thus instrumental for understanding molecular pathways underlying gene regulation and genome stability.
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Affiliation(s)
- Aleksei Agapov
- Correspondence may also be addressed to Aleksei Agapov. Tel: +7 499 196 0015; Fax: +7 499 196 0015;
| | - Anna Olina
- Institute of Molecular Genetics, National Research Center “Kurchatov Institute” Moscow 123182, Russia
| | - Andrey Kulbachinskiy
- To whom correspondence should be addressed. Tel: +7 499 196 0015; Fax: +7 499 196 0015;
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5
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Bordin DL, Lirussi L, Nilsen H. Cellular response to endogenous DNA damage: DNA base modifications in gene expression regulation. DNA Repair (Amst) 2021; 99:103051. [PMID: 33540225 DOI: 10.1016/j.dnarep.2021.103051] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2020] [Revised: 01/15/2021] [Accepted: 01/18/2021] [Indexed: 12/19/2022]
Abstract
The integrity of the genetic information is continuously challenged by numerous genotoxic insults, most frequently in the form of oxidation, alkylation or deamination of the bases that result in DNA damage. These damages compromise the fidelity of the replication, and interfere with the progression and function of the transcription machineries. The DNA damage response (DDR) comprises a series of strategies to deal with DNA damage, including transient transcriptional inhibition, activation of DNA repair pathways and chromatin remodeling. Coordinated control of transcription and DNA repair is required to safeguardi cellular functions and identities. Here, we address the cellular responses to endogenous DNA damage, with a particular focus on the role of DNA glycosylases and the Base Excision Repair (BER) pathway, in conjunction with the DDR factors, in responding to DNA damage during the transcription process. We will also discuss functions of newly identified epigenetic and regulatory marks, such as 5-hydroxymethylcytosine and its oxidative products and 8-oxoguanine, that were previously considered only as DNA damages. In light of these resultsthe classical perception of DNA damage as detrimental for cellular processes are changing. and a picture emerges whereDNA glycosylases act as dynamic regulators of transcription, placing them at the intersection of DNA repair and gene expression modulation.
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Affiliation(s)
- Diana L Bordin
- Department of Clinical Molecular Biology, University of Oslo, 0318, Oslo, Norway; Department of Clinical Molecular Biology (EpiGen), Akershus University Hospital, 1478, Lørenskog, Norway
| | - Lisa Lirussi
- Department of Clinical Molecular Biology, University of Oslo, 0318, Oslo, Norway; Department of Clinical Molecular Biology (EpiGen), Akershus University Hospital, 1478, Lørenskog, Norway
| | - Hilde Nilsen
- Department of Clinical Molecular Biology, University of Oslo, 0318, Oslo, Norway; Department of Clinical Molecular Biology (EpiGen), Akershus University Hospital, 1478, Lørenskog, Norway.
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6
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Vessoni AT, Guerra CCC, Kajitani GS, Nascimento LLS, Garcia CCM. Cockayne Syndrome: The many challenges and approaches to understand a multifaceted disease. Genet Mol Biol 2020; 43:e20190085. [PMID: 32453336 PMCID: PMC7250278 DOI: 10.1590/1678-4685-gmb-2019-0085] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2019] [Accepted: 01/15/2020] [Indexed: 01/04/2023] Open
Abstract
The striking and complex phenotype of Cockayne syndrome (CS) patients combines progeria-like features with developmental deficits. Since the establishment of the in vitro culture of skin fibroblasts derived from patients with CS in the 1970s, significant progress has been made in the understanding of the genetic alterations associated with the disease and their impact on molecular, cellular, and organismal functions. In this review, we provide a historic perspective on the research into CS by revisiting seminal papers in this field. We highlighted the great contributions of several researchers in the last decades, ranging from the cloning and characterization of CS genes to the molecular dissection of their roles in DNA repair, transcription, redox processes and metabolism control. We also provide a detailed description of all pathological mutations in genes ERCC6 and ERCC8 reported to date and their impact on CS-related proteins. Finally, we review the contributions (and limitations) of many genetic animal models to the study of CS and how cutting-edge technologies, such as cell reprogramming and state-of-the-art genome editing, are helping us to address unanswered questions.
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Affiliation(s)
| | - Camila Chaves Coelho Guerra
- Universidade Federal de Ouro Preto, Instituto de Ciências Exatas e
Biológicas, Núcleo de Pesquisa em Ciências Biológicas & Departamento de Ciências
Biológicas, Ouro Preto, MG, Brazil
| | - Gustavo Satoru Kajitani
- Universidade Federal de Ouro Preto, Instituto de Ciências Exatas e
Biológicas, Núcleo de Pesquisa em Ciências Biológicas & Departamento de Ciências
Biológicas, Ouro Preto, MG, Brazil
- Universidade de São Paulo, Instituto de Ciências Biomédicas,
Departamento de Microbiologia, São Paulo,SP, Brazil
| | - Livia Luz Souza Nascimento
- Universidade de São Paulo, Instituto de Ciências Biomédicas,
Departamento de Microbiologia, São Paulo,SP, Brazil
| | - Camila Carrião Machado Garcia
- Universidade Federal de Ouro Preto, Instituto de Ciências Exatas e
Biológicas, Núcleo de Pesquisa em Ciências Biológicas & Departamento de Ciências
Biológicas, Ouro Preto, MG, Brazil
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7
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Role of Mfd and GreA in Bacillus subtilis Base Excision Repair-Dependent Stationary-Phase Mutagenesis. J Bacteriol 2020; 202:JB.00807-19. [PMID: 32041798 DOI: 10.1128/jb.00807-19] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2020] [Accepted: 02/05/2020] [Indexed: 12/15/2022] Open
Abstract
We report that the absence of an oxidized guanine (GO) system or the apurinic/apyrimidinic (AP) endonucleases Nfo, ExoA, and Nth promoted stress-associated mutagenesis (SAM) in Bacillus subtilis YB955 (hisC952 metB5 leuC427). Moreover, MutY-promoted SAM was Mfd dependent, suggesting that transcriptional transactions over nonbulky DNA lesions promoted error-prone repair. Here, we inquired whether Mfd and GreA, which control transcription-coupled repair and transcription fidelity, influence the mutagenic events occurring in nutritionally stressed B. subtilis YB955 cells deficient in the GO or AP endonuclease repair proteins. To this end, mfd and greA were disabled in genetic backgrounds defective in the GO and AP endonuclease repair proteins, and the strains were tested for growth-associated and stress-associated mutagenesis. The results revealed that disruption of mfd or greA abrogated the production of stress-associated amino acid revertants in the GO and nfo exoA nth strains, respectively. These results suggest that in nutritionally stressed B. subtilis cells, spontaneous nonbulky DNA lesions are processed in an error-prone manner with the participation of Mfd and GreA. In support of this notion, stationary-phase ΔytkD ΔmutM ΔmutY (referred to here as ΔGO) and Δnfo ΔexoA Δnth (referred to here as ΔAP) cells accumulated 8-oxoguanine (8-OxoG) lesions, which increased significantly following Mfd disruption. In contrast, during exponential growth, disruption of mfd or greA increased the production of His+, Met+, or Leu+ prototrophs in both DNA repair-deficient strains. Thus, in addition to unveiling a role for GreA in mutagenesis, our results suggest that Mfd and GreA promote or prevent mutagenic events driven by spontaneous genetic lesions during the life cycle of B. subtilis IMPORTANCE In this paper, we report that spontaneous genetic lesions of an oxidative nature in growing and nutritionally stressed B. subtilis strain YB955 (hisC952 metB5 leuC427) cells drive Mfd- and GreA-dependent repair transactions. However, whereas Mfd and GreA elicit faithful repair events during growth to maintain genome fidelity, under starving conditions, both factors promote error-prone repair to produce genetic diversity, allowing B. subtilis to escape from growth-limiting conditions.
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8
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Raetz AG, Banda DM, Ma X, Xu G, Rajavel AN, McKibbin PL, Lebrilla CB, David SS. The DNA repair enzyme MUTYH potentiates cytotoxicity of the alkylating agent MNNG by interacting with abasic sites. J Biol Chem 2020; 295:3692-3707. [PMID: 32001618 DOI: 10.1074/jbc.ra119.010497] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2019] [Revised: 01/22/2020] [Indexed: 11/06/2022] Open
Abstract
Higher expression of the human DNA repair enzyme MUTYH has previously been shown to be strongly associated with reduced survival in a panel of 24 human lymphoblastoid cell lines exposed to the alkylating agent N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). The molecular mechanism of MUTYH-enhanced MNNG cytotoxicity is unclear, because MUTYH has a well-established role in the repair of oxidative DNA lesions. Here, we show in mouse embryonic fibroblasts (MEFs) that this MNNG-dependent phenotype does not involve oxidative DNA damage and occurs independently of both O6-methyl guanine adduct cytotoxicity and MUTYH-dependent glycosylase activity. We found that blocking of abasic (AP) sites abolishes higher survival of Mutyh-deficient (Mutyh -/-) MEFs, but this blockade had no additive cytotoxicity in WT MEFs, suggesting the cytotoxicity is due to MUTYH interactions with MNNG-induced AP sites. We found that recombinant mouse MUTYH tightly binds AP sites opposite all four canonical undamaged bases and stimulated apurinic/apyrimidinic endonuclease 1 (APE1)-mediated DNA incision. Consistent with these observations, we found that stable expression of WT, but not catalytically-inactive MUTYH, enhances MNNG cytotoxicity in Mutyh -/- MEFs and that MUTYH expression enhances MNNG-induced genomic strand breaks. Taken together, these results suggest that MUTYH enhances the rapid accumulation of AP-site intermediates by interacting with APE1, implicating MUTYH as a factor that modulates the delicate process of base-excision repair independently of its glycosylase activity.
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Affiliation(s)
- Alan G Raetz
- Department of Chemistry, University of California, Davis, California 95616
| | - Douglas M Banda
- Department of Chemistry, University of California, Davis, California 95616
| | - Xiaoyan Ma
- Department of Chemistry, University of California, Davis, California 95616
| | - Gege Xu
- Department of Chemistry, University of California, Davis, California 95616
| | - Anisha N Rajavel
- Department of Chemistry, University of California, Davis, California 95616
| | - Paige L McKibbin
- Department of Chemistry, University of California, Davis, California 95616
| | - Carlito B Lebrilla
- Department of Chemistry, University of California, Davis, California 95616
| | - Sheila S David
- Department of Chemistry, University of California, Davis, California 95616.
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9
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Fleming AM, Burrows CJ. Interplay of Guanine Oxidation and G-Quadruplex Folding in Gene Promoters. J Am Chem Soc 2020; 142:1115-1136. [PMID: 31880930 PMCID: PMC6988379 DOI: 10.1021/jacs.9b11050] [Citation(s) in RCA: 88] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Living in an oxygen atmosphere demands an ability to thrive in the presence of reactive oxygen species (ROS). Aerobic organisms have successfully found solutions to the oxidative threats imposed by ROS by evolving an elaborate detoxification system, upregulating ROS during inflammation, and utilizing ROS as messenger molecules. In this Perspective, recent studies are discussed that demonstrate ROS as signaling molecules for gene regulation by combining two emergent properties of the guanine (G) heterocycle in DNA, namely, oxidation sensitivity and a propensity for G-quadruplex (G4) folding, both of which depend upon sequence context. In human gene promoters, this results from an elevated 5'-GG-3' dinucleotide frequency and GC enrichment near transcription start sites. Oxidation of DNA by ROS drives conversion of G to 8-oxo-7,8-dihydroguanine (OG) to mark target promoters for base excision repair initiated by OG-glycosylase I (OGG1). Sequence-dependent mechanisms for gene activation are available to OGG1 to induce transcription. Either OGG1 releases OG to yield an abasic site driving formation of a non-canonical fold, such as a G4, to be displayed to apurinic/apyrimidinic 1 (APE1) and stalling on the fold to recruit activating factors, or OGG1 binds OG and facilitates activator protein recruitment. The mechanisms described drive induction of stress response, DNA repair, or estrogen-induced genes, and these pathways are novel potential anticancer targets for therapeutic intervention. Chemical concepts provide a framework to discuss the regulatory or possible epigenetic potential of the OG modification in DNA, in which DNA "damage" and non-canonical folds collaborate to turn on or off gene expression. The next steps for scientific discovery in this growing field are discussed.
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Affiliation(s)
- Aaron M. Fleming
- 315 South 1400 East, Dept. of Chemistry, University of Utah, Salt Lake City, UT 84112-0850, USA
| | - Cynthia J. Burrows
- 315 South 1400 East, Dept. of Chemistry, University of Utah, Salt Lake City, UT 84112-0850, USA
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10
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Giorgio M, Dellino GI, Gambino V, Roda N, Pelicci PG. On the epigenetic role of guanosine oxidation. Redox Biol 2020; 29:101398. [PMID: 31926624 PMCID: PMC6926346 DOI: 10.1016/j.redox.2019.101398] [Citation(s) in RCA: 44] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2019] [Revised: 11/23/2019] [Accepted: 12/02/2019] [Indexed: 01/14/2023] Open
Abstract
Chemical modifications of DNA and RNA regulate genome functions or trigger mutagenesis resulting in aging or cancer. Oxidations of macromolecules, including DNA, are common reactions in biological systems and often part of regulatory circuits rather than accidental events. DNA alterations are particularly relevant since the unique role of nuclear and mitochondrial genome is coding enduring and inheritable information. Therefore, an alteration in DNA may represent a relevant problem given its transmission to daughter cells. At the same time, the regulation of gene expression allows cells to continuously adapt to the environmental changes that occur throughout the life of the organism to ultimately maintain cellular homeostasis. Here we review the multiple ways that lead to DNA oxidation and the regulation of mechanisms activated by cells to repair this damage. Moreover, we present the recent evidence suggesting that DNA damage caused by physiological metabolism acts as epigenetic signal for regulation of gene expression. In particular, the predisposition of guanine to oxidation might reflect an adaptation to improve the genome plasticity to redox changes.
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Affiliation(s)
- Marco Giorgio
- Department of Experimental Oncology, European Institute of Oncology-IRCCS, Via Adamello 16, 20139, Milano, Italy; Department of Biomedical Sciences, University of Padova, Via Ugo Bassi 58/B, 35131, Padova, Italy.
| | - Gaetano Ivan Dellino
- Department of Experimental Oncology, European Institute of Oncology-IRCCS, Via Adamello 16, 20139, Milano, Italy; Department of Oncology and Hemato-Oncology, University of Milan, Milan, Italy
| | - Valentina Gambino
- Department of Experimental Oncology, European Institute of Oncology-IRCCS, Via Adamello 16, 20139, Milano, Italy
| | - Niccolo' Roda
- Department of Experimental Oncology, European Institute of Oncology-IRCCS, Via Adamello 16, 20139, Milano, Italy
| | - Pier Giuseppe Pelicci
- Department of Experimental Oncology, European Institute of Oncology-IRCCS, Via Adamello 16, 20139, Milano, Italy; Department of Oncology and Hemato-Oncology, University of Milan, Milan, Italy
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11
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The in vivo and in vitro roles of Trypanosoma cruzi Rad51 in the repair of DNA double strand breaks and oxidative lesions. PLoS Negl Trop Dis 2018; 12:e0006875. [PMID: 30422982 PMCID: PMC6258567 DOI: 10.1371/journal.pntd.0006875] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2017] [Revised: 11/27/2018] [Accepted: 09/26/2018] [Indexed: 11/22/2022] Open
Abstract
In Trypanosoma cruzi, the etiologic agent of Chagas disease, Rad51 (TcRad51) is a central enzyme for homologous recombination. Here we describe the different roles of TcRad51 in DNA repair. Epimastigotes of T. cruzi overexpressing TcRAD51 presented abundant TcRad51-labeled foci before gamma irradiation treatment, and a faster growth recovery when compared to single-knockout epimastigotes for RAD51. Overexpression of RAD51 also promoted increased resistance against hydrogen peroxide treatment, while the single-knockout epimastigotes for RAD51 exhibited increased sensitivity to this oxidant agent, which indicates a role for this gene in the repair of DNA oxidative lesions. In contrast, TcRad51 was not involved in the repair of crosslink lesions promoted by UV light and cisplatin treatment. Also, RAD51 single-knockout epimastigotes showed a similar growth rate to that exhibited by wild-type ones after treatment with hydroxyurea, but an increased sensitivity to methyl methane sulfonate. Besides its role in epimastigotes, TcRad51 is also important during mammalian infection, as shown by increased detection of T. cruzi cells overexpressing RAD51, and decreased detection of single-knockout cells for RAD51, in both fibroblasts and macrophages infected with amastigotes. Besides that, RAD51-overexpressing parasites infecting mice also presented increased infectivity and higher resistance against benznidazole. We thus show that TcRad51 is involved in the repair of DNA double strands breaks and oxidative lesions in two different T. cruzi developmental stages, possibly playing an important role in the infectivity of this parasite. Trypanosoma cruzi is the causative agent of Chagas disease, a tropical neglected illness that affects 6 million people worldwide, mostly in Latin America. Our research group focuses on the elucidation of DNA repair and metabolism of T. cruzi, and on the possible implications of those mechanisms in both parasite genetic diversity and Chagas disease development. In this work, we investigated the involvement of homologous recombination in the oxidation-induced damage response, and in DNA repair, in T. cruzi cells after gamma radiation exposure. We also examined whether TcRad51 –a key protein for homologous recombination–could be an important factor for T. cruzi’s infectivity. We generated genetically-modified T. cruzi cells for RAD51 and studied the in vitro and in vivo infectivity of these mutant cells. Our results indicate that TcRad51 is a key protein involved in the repair of oxidative and DNA double-strand breaks lesions in two crucial developmental forms of T. cruzi.
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12
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Fleming AM, Zhu J, Ding Y, Burrows CJ. 8-Oxo-7,8-dihydroguanine in the Context of a Gene Promoter G-Quadruplex Is an On-Off Switch for Transcription. ACS Chem Biol 2017; 12:2417-2426. [PMID: 28829124 PMCID: PMC5604463 DOI: 10.1021/acschembio.7b00636] [Citation(s) in RCA: 70] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
![]()
Interplay
between DNA repair of the oxidatively modified base 8-oxo-7,8-dihydroguanine
(OG) and transcriptional activation has been documented in mammalian
genes. Previously, we synthesized OG into the VEGF potential G-quadruplex sequence (PQS) in the coding strand of a
luciferase promoter to identify that base excision repair (BER) unmasked
the G-quadruplex (G4) fold for gene activation. In the present work,
OG was site-specifically synthesized into a luciferase reporter plasmid
to follow the time-dependent expression in mammalian cells when OG
in the VEGF PQS context was located in the coding
vs template strands of the luciferase promoter. Removal of OG from
the coding strand by OG glycosylase-1 (OGG1)-mediated BER upregulated
transcription. When OG was in the template strand in the VEGF PQS context, transcription was downregulated by a BER-independent
process. The time course changes in transcription show that repair
in the template strand was more efficient than repair in the coding
strand. Promoters were synthesized with an OG:A base pair that requires
repair on both strands to yield a canonical G:C base pair. By monitoring
the up/down luciferase expression, we followed the timing of repair
of an OG:A base pair occurring on both strands in mammalian cells
in which one lesion resides in a G-quadruplex loop and one in a potential
i-motif. Depending on the strand in which OG resides, coding vs template,
this modification is an up/downregulator of transcription that couples
DNA repair with transcriptional regulation.
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Affiliation(s)
- Aaron M. Fleming
- Department of Chemistry, University of Utah, Salt Lake City, Utah 84112-0850, United States
| | - Judy Zhu
- Department of Chemistry, University of Utah, Salt Lake City, Utah 84112-0850, United States
| | - Yun Ding
- Department of Chemistry, University of Utah, Salt Lake City, Utah 84112-0850, United States
| | - Cynthia J. Burrows
- Department of Chemistry, University of Utah, Salt Lake City, Utah 84112-0850, United States
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13
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Reid-Bayliss KS, Loeb LA. Accurate RNA consensus sequencing for high-fidelity detection of transcriptional mutagenesis-induced epimutations. Proc Natl Acad Sci U S A 2017; 114:9415-9420. [PMID: 28798064 PMCID: PMC5584456 DOI: 10.1073/pnas.1709166114] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Transcriptional mutagenesis (TM) due to misincorporation during RNA transcription can result in mutant RNAs, or epimutations, that generate proteins with altered properties. TM has long been hypothesized to play a role in aging, cancer, and viral and bacterial evolution. However, inadequate methodologies have limited progress in elucidating a causal association. We present a high-throughput, highly accurate RNA sequencing method to measure epimutations with single-molecule sensitivity. Accurate RNA consensus sequencing (ARC-seq) uniquely combines RNA barcoding and generation of multiple cDNA copies per RNA molecule to eliminate errors introduced during cDNA synthesis, PCR, and sequencing. The stringency of ARC-seq can be scaled to accommodate the quality of input RNAs. We apply ARC-seq to directly assess transcriptome-wide epimutations resulting from RNA polymerase mutants and oxidative stress.
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Affiliation(s)
- Kate S Reid-Bayliss
- Department of Pathology, University of Washington School of Medicine, Seattle, WA 98195
| | - Lawrence A Loeb
- Department of Pathology, University of Washington School of Medicine, Seattle, WA 98195;
- Department of Biochemistry, University of Washington School of Medicine, Seattle, WA 98195
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14
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Kolbanovskiy M, Chowdhury MA, Nadkarni A, Broyde S, Geacintov NE, Scicchitano DA, Shafirovich V. The Nonbulky DNA Lesions Spiroiminodihydantoin and 5-Guanidinohydantoin Significantly Block Human RNA Polymerase II Elongation in Vitro. Biochemistry 2017; 56:3008-3018. [PMID: 28514164 DOI: 10.1021/acs.biochem.7b00295] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The most common, oxidatively generated lesion in cellular DNA is 8-oxo-7,8-dihydroguanine, which can be oxidized further to yield highly mutagenic spiroiminodihydantoin (Sp) and 5-guanidinohydantoin (Gh) in DNA. In human cell-free extracts, both lesions can be excised by base excision repair and global genomic nucleotide excision repair. However, it is not known if these lesions can be removed by transcription-coupled DNA repair (TCR), a pathway that clears lesions from DNA that impede RNA synthesis. To determine if Sp or Gh impedes transcription, which could make each a viable substrate for TCR, either an Sp or a Gh lesion was positioned on the transcribed strand of DNA under the control of a promoter that supports transcription by human RNA polymerase II. These constructs were incubated in HeLa nuclear extracts that contained active RNA polymerase II, and the resulting transcripts were resolved by denaturing polyacrylamide gel electrophoresis. The structurally rigid Sp strongly blocks transcription elongation, permitting 1.6 ± 0.5% nominal lesion bypass. In contrast, the conformationally flexible Gh poses less of a block to human RNAPII, allowing 9 ± 2% bypass. Furthermore, fractional lesion bypass for Sp and Gh is minimally affected by glycosylase activity found in the HeLa nuclear extract. These data specifically suggest that both Sp and Gh may well be susceptible to TCR because each poses a significant block to human RNA polymerase II progression. A more general principle is also proposed: Conformational flexibility may be an important structural feature of DNA lesions that enhances their transcriptional bypass.
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Affiliation(s)
- Marina Kolbanovskiy
- Department of Chemistry, New York University , 100 Washington Square East, New York, New York 10003-5180, United States
| | - Moinuddin A Chowdhury
- Department of Biology, New York University , 100 Washington Square East, New York, New York 10003-5180, United States
| | - Aditi Nadkarni
- Department of Biology, New York University , 100 Washington Square East, New York, New York 10003-5180, United States
| | - Suse Broyde
- Department of Biology, New York University , 100 Washington Square East, New York, New York 10003-5180, United States
| | - Nicholas E Geacintov
- Department of Chemistry, New York University , 100 Washington Square East, New York, New York 10003-5180, United States
| | - David A Scicchitano
- Department of Biology, New York University , 100 Washington Square East, New York, New York 10003-5180, United States.,Division of Science, New York University Abu Dhabi , P.O. Box 129188, Abu Dhabi, United Arab Emirates
| | - Vladimir Shafirovich
- Department of Chemistry, New York University , 100 Washington Square East, New York, New York 10003-5180, United States
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15
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Allgayer J, Kitsera N, Bartelt S, Epe B, Khobta A. Widespread transcriptional gene inactivation initiated by a repair intermediate of 8-oxoguanine. Nucleic Acids Res 2016; 44:7267-80. [PMID: 27220469 PMCID: PMC5009734 DOI: 10.1093/nar/gkw473] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2015] [Accepted: 05/12/2016] [Indexed: 12/18/2022] Open
Abstract
DNA damage can significantly modulate expression of the affected genes either by direct structural interference with transcription components or as a collateral outcome of cellular repair attempts. Thus, DNA glycosylases of the base excision repair (BER) pathway have been implicated in negative transcriptional response to several spontaneously generated DNA base modifications, including a common oxidative DNA base modification 8-oxoguanine (8-oxoG). Here, we report that single 8-oxoG situated in the non-transcribed DNA strand of a reporter gene has a pronounced negative effect on transcription, driven by promoters of various strength and with different structural properties, including viral, human, and artificial promoters. We further show that the magnitude of the negative effect on the gene expression correlates with excision of the modified base by OGG1 in all promoter constructs tested. Moreover, by using expression vectors with nuclease resistant backbone modifications, we demonstrate that OGG1 does not catalyse DNA strand cleavage in vivo. Rather, cleavage of the phosphate bond 5′ to 8-oxodG (catalysed by APE1) is essential and universally required for the onset of transcriptional silencing, regardless of the promoter structure. Hence, induction of transcriptional silencing emerges as a ubiquitous mode of biological response to 8-oxoG in DNA.
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Affiliation(s)
- Julia Allgayer
- Institute of Pharmacy and Biochemistry, Johannes Gutenberg University of Mainz, Mainz 55128, Germany
| | - Nataliya Kitsera
- Institute of Pharmacy and Biochemistry, Johannes Gutenberg University of Mainz, Mainz 55128, Germany Institute of Toxicology, University Medical Center Mainz, Mainz 55131, Germany
| | - Solveig Bartelt
- Institute of Pharmacy and Biochemistry, Johannes Gutenberg University of Mainz, Mainz 55128, Germany
| | - Bernd Epe
- Institute of Pharmacy and Biochemistry, Johannes Gutenberg University of Mainz, Mainz 55128, Germany
| | - Andriy Khobta
- Institute of Pharmacy and Biochemistry, Johannes Gutenberg University of Mainz, Mainz 55128, Germany Institute of Toxicology, University Medical Center Mainz, Mainz 55131, Germany
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16
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Grin I, Ishchenko AA. An interplay of the base excision repair and mismatch repair pathways in active DNA demethylation. Nucleic Acids Res 2016; 44:3713-27. [PMID: 26843430 PMCID: PMC4856981 DOI: 10.1093/nar/gkw059] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2015] [Accepted: 01/22/2016] [Indexed: 01/02/2023] Open
Abstract
Active DNA demethylation (ADDM) in mammals occurs via hydroxylation of 5-methylcytosine (5mC) by TET and/or deamination by AID/APOBEC family enzymes. The resulting 5mC derivatives are removed through the base excision repair (BER) pathway. At present, it is unclear how the cell manages to eliminate closely spaced 5mC residues whilst avoiding generation of toxic BER intermediates and whether alternative DNA repair pathways participate in ADDM. It has been shown that non-canonical DNA mismatch repair (ncMMR) can remove both alkylated and oxidized nucleotides from DNA. Here, a phagemid DNA containing oxidative base lesions and methylated sites are used to examine the involvement of various DNA repair pathways in ADDM in murine and human cell-free extracts. We demonstrate that, in addition to short-patch BER, 5-hydroxymethyluracil and uracil mispaired with guanine can be processed by ncMMR and long-patch BER with concomitant removal of distant 5mC residues. Furthermore, the presence of multiple mispairs in the same MMR nick/mismatch recognition region together with BER-mediated nick formation promotes proficient ncMMR resulting in the reactivation of an epigenetically silenced reporter gene in murine cells. These findings suggest cooperation between BER and ncMMR in the removal of multiple mismatches that might occur in mammalian cells during ADDM.
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Affiliation(s)
- Inga Grin
- Laboratoire «Stabilité Génétique et Oncogenèse» CNRS, UMR 8200, Univ. Paris-Sud, Université Paris-Saclay, Equipe Labellisée Ligue Contre le Cancer, F-94805 Villejuif, France Gustave Roussy Cancer Campus, F-94805 Villejuif, France SB RAS Institute of Chemical Biology and Fundamental Medicine, 8 Lavrentieva Avenue, Novosibirsk 630090, Russia Department of Natural Sciences, Novosibirsk State University, 2 Pirogova Street, Novosibirsk 630090, Russia
| | - Alexander A Ishchenko
- Laboratoire «Stabilité Génétique et Oncogenèse» CNRS, UMR 8200, Univ. Paris-Sud, Université Paris-Saclay, Equipe Labellisée Ligue Contre le Cancer, F-94805 Villejuif, France Gustave Roussy Cancer Campus, F-94805 Villejuif, France
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17
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Spivak G, Hanawalt PC. Photosensitive human syndromes. Mutat Res 2015; 776:24-30. [PMID: 26255937 PMCID: PMC4531261 DOI: 10.1016/j.mrfmmm.2014.11.003] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2014] [Revised: 10/17/2014] [Accepted: 11/06/2014] [Indexed: 02/06/2023]
Abstract
Photosensitivity in humans can result from defects in repair of light-induced DNA lesions, from photoactivation of chemicals (including certain medications) with sunlight to produce toxic mediators, and by immune reactions to sunlight exposures. Deficiencies in DNA repair and the processing of damaged DNA during replication and transcription may result in mutations and genomic instability. We will review current understanding of photosensitivity to short wavelength ultraviolet light (UV) due to genetic defects in particular DNA repair pathways; deficiencies in some are characterized by an extremely high incidence of cancer in sun-exposed tissues, while in others no cancers have been reported.
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Affiliation(s)
- Graciela Spivak
- Department of Biology, Stanford University, Stanford, CA 94305, USA.
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18
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Yasui M, Kanemaru Y, Kamoshita N, Suzuki T, Arakawa T, Honma M. Tracing the fates of site-specifically introduced DNA adducts in the human genome. DNA Repair (Amst) 2014; 15:11-20. [DOI: 10.1016/j.dnarep.2014.01.003] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2013] [Revised: 01/09/2014] [Accepted: 01/15/2014] [Indexed: 12/25/2022]
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19
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Aamann MD, Hvitby C, Popuri V, Muftuoglu M, Lemminger L, Skeby CK, Keijzers G, Ahn B, Bjørås M, Bohr VA, Stevnsner T. Cockayne Syndrome group B protein stimulates NEIL2 DNA glycosylase activity. Mech Ageing Dev 2014; 135:1-14. [PMID: 24406253 DOI: 10.1016/j.mad.2013.12.008] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2013] [Revised: 12/13/2013] [Accepted: 12/18/2013] [Indexed: 10/25/2022]
Abstract
Cockayne Syndrome is a segmental premature aging syndrome, which can be caused by loss of function of the CSB protein. CSB is essential for genome maintenance and has numerous interaction partners with established roles in different DNA repair pathways including transcription coupled nucleotide excision repair and base excision repair. Here, we describe a new interaction partner for CSB, the DNA glycosylase NEIL2. Using both cell extracts and recombinant proteins, CSB and NEIL2 were found to physically interact independently of DNA. We further found that CSB is able to stimulate NEIL2 glycosylase activity on a 5-hydroxyl uracil lesion in a DNA bubble structure substrate in vitro. A novel 4,6-diamino-5-formamidopyrimidine (FapyA) specific incision activity of NEIL2 was also stimulated by CSB. To further elucidate the biological role of the interaction, immunofluorescence studies were performed, showing an increase in cytoplasmic CSB and NEIL2 co-localization after oxidative stress. Additionally, stalling of the progression of the transcription bubble with α-amanitin resulted in increased co-localization of CSB and NEIL2. Finally, CSB knockdown resulted in reduced incision of 8-hydroxyguanine in a DNA bubble structure using whole cell extracts. Taken together, our data supports a biological role for CSB and NEIL2 in transcription associated base excision repair.
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Affiliation(s)
- Maria D Aamann
- Danish Center for Molecular Gerontology and Danish Aging Research Center, Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark
| | - Christina Hvitby
- Danish Center for Molecular Gerontology and Danish Aging Research Center, Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark
| | - Venkateswarlu Popuri
- Laboratory of Molecular Gerontology, National Institute on Aging, National Institutes of Health, Baltimore, MD, USA
| | - Meltem Muftuoglu
- Center for Healthy Aging, University of Copenhagen, Copenhagen, Denmark
| | - Lasse Lemminger
- Danish Center for Molecular Gerontology and Danish Aging Research Center, Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark
| | - Cecilie K Skeby
- Danish Center for Molecular Gerontology and Danish Aging Research Center, Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark
| | - Guido Keijzers
- Danish Center for Molecular Gerontology and Danish Aging Research Center, Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark; Center for Healthy Aging, University of Copenhagen, Copenhagen, Denmark
| | - Byungchan Ahn
- Danish Center for Molecular Gerontology and Danish Aging Research Center, Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark; University of Ulsan, Republic of Korea
| | - Magnar Bjørås
- Laboratory for Molecular Biology, Center for Molecular Biology and Neuroscience, Oslo University Hospital, Oslo, Norway
| | - Vilhelm A Bohr
- Laboratory of Molecular Gerontology, National Institute on Aging, National Institutes of Health, Baltimore, MD, USA
| | - Tinna Stevnsner
- Danish Center for Molecular Gerontology and Danish Aging Research Center, Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark.
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20
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Wells PG, Miller-Pinsler L, Shapiro AM. Impact of Oxidative Stress on Development. OXIDATIVE STRESS IN APPLIED BASIC RESEARCH AND CLINICAL PRACTICE 2014. [DOI: 10.1007/978-1-4939-1405-0_1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
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21
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Ondovcik SL, Preston TJ, McCallum GP, Wells PG. Expression of human oxoguanine glycosylase 1 or formamidopyrimidine glycosylase in human embryonic kidney 293 cells exacerbates methylmercury toxicity in vitro. Toxicol Appl Pharmacol 2013; 271:41-8. [DOI: 10.1016/j.taap.2013.04.008] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2013] [Revised: 03/19/2013] [Accepted: 04/01/2013] [Indexed: 10/26/2022]
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22
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Leach DM, Zacal NJ, Rainbow AJ. Host cell reactivation of gene expression for an adenovirus-encoded reporter gene reflects the repair of UVC-induced cyclobutane pyrimidine dimers and methylene blue plus visible light-induced 8-oxoguanine. Mutagenesis 2013; 28:507-13. [PMID: 23793457 DOI: 10.1093/mutage/get027] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Previously, we have reported the use of a recombinant adenovirus (Ad)-based host cell reactivation (HCR) assay to examine nucleotide excision repair (NER) of UVC-induced DNA lesions in several mammalian cell types. The recombinant non-replicating Ad expresses the Escherichia coli β-galactosidase (β-gal) reporter gene under control of the cytomegalovirus immediate-early enhancer region. We have also used methylene blue plus visible light (MB + VL) to induce the major oxidative lesion 7,8-dihydro-8-oxoguanine (8-oxoG) in the recombinant Ad-encoded reporter gene in order to study base excision repair (BER). The reported variability regarding 8-oxoG's potential to block transcription by RNA polymerase II and data demonstrating that a number of factors play a role in transcriptional bypass of the lesion led us to examine the repair of 8-oxoG in the Ad reporter and its relationship to HCR for expression of the reporter gene. We have used Southern blotting to examine removal of UVC- and MB + VL-induced DNA damage by loss of endonuclease-sensitive sites from the Ad-encoded β-gal reporter gene in human and rodent cells. We show that repair of MB + VL-induced 8-oxoG via BER and UVC-induced cyclobutane pyrimidine dimers (CPDs) via NER is substantially greater in human SV40-transformed GM637F skin fibroblasts compared to hamster CHO-AA8 cells. We also show that HCR for expression of the MB + VL-damaged and the UVC-damaged reporter gene is substantially greater in human SV40-transformed GM637F skin fibroblasts compared to hamster CHO-AA8 cells. The difference between the human and rodent cells in the removal of both 8-oxoG and CPDs from the damaged reporter gene was comparable to the difference in HCR for expression of the damaged reporter gene. These results suggest that the major factor for HCR of the MB + VL-treated reporter gene in mammalian cells is DNA repair in the Ad rather than lesion bypass.
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Affiliation(s)
- Derrik M Leach
- Department of Biology, McMaster University, 1280 Main Street West, Hamilton, Ontario L8S 4K1, Canada
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23
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Guo J, Hanawalt PC, Spivak G. Comet-FISH with strand-specific probes reveals transcription-coupled repair of 8-oxoGuanine in human cells. Nucleic Acids Res 2013; 41:7700-12. [PMID: 23775797 PMCID: PMC3763531 DOI: 10.1093/nar/gkt524] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Oxidized bases in DNA have been implicated in cancer, aging and neurodegenerative disease. We have developed an approach combining single-cell gel electrophoresis (comet) with fluorescence in situ hybridization (FISH) that enables the comparative quantification of low, physiologically relevant levels of DNA lesions in the respective strands of defined nucleotide sequences and in the genome overall. We have synthesized single-stranded probes targeting the termini of DNA segments of interest using a polymerase chain reaction-based method. These probes facilitate detection of damage at the single-molecule level, as the lesions are converted to DNA strand breaks by lesion-specific endonucleases or glycosylases. To validate our method, we have documented transcription-coupled repair of cyclobutane pyrimidine dimers in the ataxia telangiectasia-mutated (ATM) gene in human fibroblasts irradiated with 254 nm ultraviolet at 0.1 J/m2, a dose ∼100-fold lower than those typically used. The high specificity and sensitivity of our approach revealed that 7,8-dihydro-8-oxoguanine (8-oxoG) at an incidence of approximately three lesions per megabase is preferentially repaired in the transcribed strand of the ATM gene. We have also demonstrated that the hOGG1, XPA, CSB and UVSSA proteins, as well as actively elongating RNA polymerase II, are required for this process, suggesting cross-talk between DNA repair pathways.
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Affiliation(s)
- Jia Guo
- Department of Biology, Stanford University, 371 Serra Mall, Stanford, CA 94305-5020, USA
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24
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Abedin Z, Louis-Juste M, Stangl M, Field J. The role of base excision repair genes OGG1, APN1 and APN2 in benzo[a]pyrene-7,8-dione induced p53 mutagenesis. Mutat Res 2013; 750:121-8. [PMID: 23117049 PMCID: PMC3931135 DOI: 10.1016/j.mrgentox.2012.10.003] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2012] [Revised: 10/17/2012] [Accepted: 10/18/2012] [Indexed: 12/17/2022]
Abstract
Lung cancer is primarily caused by exposure to tobacco smoke. Tobacco smoke contains numerous carcinogens, including polycyclic aromatic hydrocarbons (PAH). The most common PAH studied is benzo[a]pyrene (B[a]P). B[a]P is metabolically activated through multiple routes, one of which is catalyzed by aldo-keto reductase (AKR) to B[a]P-7,8-dione (BPQ). BPQ undergoes a futile redox cycle in the presence of NADPH to generate reactive oxygen species (ROS). ROS, in turn, damages DNA. Studies with a yeast p53 mutagenesis system found that the generation of ROS by PAH o-quinones may contribute to lung carcinogenesis because of similarities between the patterns (types of mutations) and spectra (location of mutations) and those seen in lung cancer. The patterns were dominated by G to T transversions, and the spectra in the experimental system have mutations at lung cancer hotspots. To address repair mechanisms that are responsible for BPQ induced damage we observed the effect of mutating two DNA repair genes OGG1 and APE1 (APN1 in yeast) and tested them in a yeast reporter system for p53 mutagenesis. There was an increase in both the mutant frequency and the number of G:C/T:A transversions in p53 treated with BPQ in ogg1 yeast but not in apn1 yeast. Knocking out APN2 increased mutagenesis in the apn1 cells. In addition, we did not find a strand bias on p53 treated with BPQ in ogg1 yeast. These studies suggest that Ogg1 is involved in repairing the oxidative damage caused by BPQ, Apn1 and Apn2 have redundant functions and that the stand bias seen in lung cancer may not be due to impaired repair of oxidative lesions.
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Affiliation(s)
- Zahidur Abedin
- Department of Pharmacology, Centers for Excellence in Environmental Toxicology and Cancer Pharmacology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6084, USA
| | - Melissa Louis-Juste
- Department of Pharmacology, Centers for Excellence in Environmental Toxicology and Cancer Pharmacology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6084, USA
| | - Melissa Stangl
- Department of Pharmacology, Centers for Excellence in Environmental Toxicology and Cancer Pharmacology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6084, USA
| | - Jeffrey Field
- Department of Pharmacology, Centers for Excellence in Environmental Toxicology and Cancer Pharmacology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6084, USA
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25
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Ondovcik SL, Tamblyn L, McPherson JP, Wells PG. Oxoguanine glycosylase 1 (OGG1) protects cells from DNA double-strand break damage following methylmercury (MeHg) exposure. Toxicol Sci 2012; 128:272-83. [PMID: 22523232 DOI: 10.1093/toxsci/kfs138] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Methylmercury (MeHg) is a potent neurotoxin, teratogen, and probable carcinogen, but the underlying mechanisms of its actions remain unclear. Although MeHg causes several types of DNA damage, the toxicological consequences of this macromolecular damage are unknown. MeHg enhances oxidative stress, which can cause various oxidative DNA lesions that are primarily repaired by oxoguanine glycosylase 1 (OGG1). Herein, we compared the response of wild-type and OGG1 null (Ogg1(-/-)) murine embryonic fibroblasts to environmentally relevant, low micromolar concentrations of MeHg by measuring clonogenic efficiency, cell cycle arrest, DNA double-strand breaks (DSBs), and activation of the DNA damage response pathway.Ogg1(-/-) cells exhibited greater sensitivity to MeHg than wild-type controls, as measured by the clonogenic assay, and showed a greater propensity for MeHg-initiated apoptosis. Both wild-type and Ogg1(-/-) cells underwent cell cycle arrest when exposed to micromolar concentrations of MeHg; however, the extent of DSBs was exacerbated in Ogg1(-/-) cells compared with that in wild-type controls. Pretreatment with the antioxidative enzyme catalase reduced levels of DSBs in both wild-type and Ogg1(-/-) cells but failed to block MeHg-initiated apoptosis at micromolar concentrations. Our findings implicate reactive oxygen species mediated DNA damage in the mechanism of MeHg toxicity; and demonstrate for the first time that impaired DNA repair capacity enhances cellular sensitivity to MeHg. Accordingly, the genotoxic properties of MeHg may contribute to its neurotoxic and teratogenic effects, and an individual's response to oxidative stress and DNA damage may constitute an important determinant of risk.
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Affiliation(s)
- Stephanie L Ondovcik
- Department of Pharmaceutical Sciences, University of Toronto, Toronto, Ontario, Canada
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26
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Sung RJ, Zhang M, Qi Y, Verdine GL. Sequence-dependent structural variation in DNA undergoing intrahelical inspection by the DNA glycosylase MutM. J Biol Chem 2012; 287:18044-54. [PMID: 22465958 DOI: 10.1074/jbc.m111.313635] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
MutM, a bacterial DNA-glycosylase, plays a critical role in maintaining genome integrity by catalyzing glycosidic bond cleavage of 8-oxoguanine (oxoG) lesions to initiate base excision DNA repair. The task faced by MutM of locating rare oxoG residues embedded in an overwhelming excess of undamaged bases is especially challenging given the close structural similarity between oxoG and its normal progenitor, guanine (G). MutM actively interrogates the DNA to detect the presence of an intrahelical, fully base-paired oxoG, whereupon the enzyme promotes extrusion of the target nucleobase from the DNA duplex and insertion into the extrahelical active site. Recent structural studies have begun to provide the first glimpse into the protein-DNA interactions that enable MutM to distinguish an intrahelical oxoG from G; however, these initial studies left open the important question of how MutM can recognize oxoG residues embedded in 16 different neighboring sequence contexts (considering only the 5'- and 3'-neighboring base pairs). In this study we set out to understand the manner and extent to which intrahelical lesion recognition varies as a function of the 5'-neighbor. Here we report a comprehensive, systematic structural analysis of the effect of the 5'-neighboring base pair on recognition of an intrahelical oxoG lesion. These structures reveal that MutM imposes the same extrusion-prone ("extrudogenic") backbone conformation on the oxoG lesion irrespective of its 5'-neighbor while leaving the rest of the DNA relatively free to adjust to the particular demands of individual sequences.
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Affiliation(s)
- Rou-Jia Sung
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts 02138, USA
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27
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Generation of reporter plasmids containing defined base modifications in the DNA strand of choice. Anal Biochem 2012; 425:47-53. [PMID: 22406247 DOI: 10.1016/j.ab.2012.03.001] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2012] [Revised: 02/28/2012] [Accepted: 03/01/2012] [Indexed: 02/07/2023]
Abstract
Physiological effects of DNA bases other than A, G, C, and T as well as ways of removal of such bases from genomes are studied intensely. Methods for targeted insertion of modified bases into DNA, therefore, are highly demanded in the fields of DNA repair and epigenetics. This article describes efficient procedures for incorporation of modified DNA bases into a plasmid-borne enhanced green fluorescent protein (EGFP) gene. The procedure exploits excision of a stretch of 18 nt from either the transcribed or nontranscribed DNA strand with the help of the sequence-specific nicking endonucleases Nb.Bpu10I and Nt.Bpu10I. The excised single-stranded oligonucleotide is then swapped for a synthetic DNA strand containing a desired base modification. Base modifications that form Watson-Crick-type base pairs were efficiently incorporated into plasmid DNA by a straightforward strand exchange, which was achieved by local melting in the presence of large excesses of the synthetic oligonucleotides and reannealing followed by ligation. Base modifications that cause significant distortions of the normal DNA structure, such as thymine glycol and uracil mispaired with guanine, failed to produce high yields of direct strand exchange but could still be incorporated very efficiently when the excised fragment was depleted in an intermediate step.
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28
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Agnez-Lima LF, Melo JTA, Silva AE, Oliveira AHS, Timoteo ARS, Lima-Bessa KM, Martinez GR, Medeiros MHG, Di Mascio P, Galhardo RS, Menck CFM. DNA damage by singlet oxygen and cellular protective mechanisms. MUTATION RESEARCH-REVIEWS IN MUTATION RESEARCH 2012; 751:15-28. [PMID: 22266568 DOI: 10.1016/j.mrrev.2011.12.005] [Citation(s) in RCA: 126] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2011] [Revised: 12/14/2011] [Accepted: 12/21/2011] [Indexed: 12/23/2022]
Abstract
Reactive oxygen species, as singlet oxygen ((1)O(2)) and hydrogen peroxide, are continuously generated by aerobic organisms, and react actively with biomolecules. At excessive amounts, (1)O(2) induces oxidative stress and shows carcinogenic and toxic effects due to oxidation of lipids, proteins and nucleic acids. Singlet oxygen is able to react with DNA molecule and may induce G to T transversions due to 8-oxodG generation. The nucleotide excision repair, base excision repair and mismatch repair have been implicated in the correction of DNA lesions induced by (1)O(2) both in prokaryotic and in eukaryotic cells. (1)O(2) is also able to induce the expression of genes involved with the cellular responses to oxidative stress, such as NF-κB, c-fos and c-jun, and genes involved with tissue damage and inflammation, as ICAM-1, interleukins 1 and 6. The studies outlined in this review reinforce the idea that (1)O(2) is one of the more dangerous reactive oxygen species to the cells, and deserves our attention.
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Affiliation(s)
- Lucymara F Agnez-Lima
- Departamento de Biologia Celular e Genética, Centro de Biociências, Universidade Federal do Rio Grande do Norte, Natal, RN, Brazil
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Age-related neuronal degeneration: complementary roles of nucleotide excision repair and transcription-coupled repair in preventing neuropathology. PLoS Genet 2011; 7:e1002405. [PMID: 22174697 PMCID: PMC3234220 DOI: 10.1371/journal.pgen.1002405] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2011] [Accepted: 10/17/2011] [Indexed: 12/11/2022] Open
Abstract
Neuronal degeneration is a hallmark of many DNA repair syndromes. Yet, how DNA damage causes neuronal degeneration and whether defects in different repair systems affect the brain differently is largely unknown. Here, we performed a systematic detailed analysis of neurodegenerative changes in mouse models deficient in nucleotide excision repair (NER) and transcription-coupled repair (TCR), two partially overlapping DNA repair systems that remove helix-distorting and transcription-blocking lesions, respectively, and that are associated with the UV-sensitive syndromes xeroderma pigmentosum (XP) and Cockayne syndrome (CS). TCR–deficient Csa−/− and Csb−/− CS mice showed activated microglia cells surrounding oligodendrocytes in regions with myelinated axons throughout the nervous system. This white matter microglia activation was not observed in NER–deficient Xpa−/− and Xpc−/− XP mice, but also occurred in XpdXPCS mice carrying a point mutation (G602D) in the Xpd gene that is associated with a combined XPCS disorder and causes a partial NER and TCR defect. The white matter abnormalities in TCR–deficient mice are compatible with focal dysmyelination in CS patients. Both TCR–deficient and NER–deficient mice showed no evidence for neuronal degeneration apart from p53 activation in sporadic (Csa−/−, Csb−/−) or highly sporadic (Xpa−/−, Xpc−/−) neurons and astrocytes. To examine to what extent overlap occurs between both repair systems, we generated TCR–deficient mice with selective inactivation of NER in postnatal neurons. These mice develop dramatic age-related cumulative neuronal loss indicating DNA damage substrate overlap and synergism between TCR and NER pathways in neurons, and they uncover the occurrence of spontaneous DNA injury that may trigger neuronal degeneration. We propose that, while Csa−/− and Csb−/− TCR–deficient mice represent powerful animal models to study the mechanisms underlying myelin abnormalities in CS, neuron-specific inactivation of NER in TCR–deficient mice represents a valuable model for the role of NER in neuronal maintenance and survival. Metabolism produces reactive oxygen species that damage our DNA and other cellular components, and as such it contributes to the aging process, including neuronal degeneration. Accordingly, genetic disorders associated with impaired DNA damage repair are frequently associated with premature onset of aging pathology in a variety of tissues, including the brain. This is well-illustrated by the progeroid DNA repair syndromes xeroderma pigmentosum (XP) and Cockayne syndrome (CS), in which patients suffer from defects in nucleotide excision repair (NER) and transcription-coupled repair (TCR), two partially overlapping DNA repair systems that remove helix-distorting and transcription-blocking lesions, respectively. We have used a panel of XP and CS mice (including conditional double-mutant animals) to systematically investigate the impact of NER and TCR defects on neuronal degeneration. We have shown that, whereas a TCR defect causes white matter pathology, a NER defect can result in age related cumulative loss of neurons. These findings well match the neuropathology observed in CS and XP patients, underscoring the impact of spontaneous DNA damage in the onset of neuronal aging. Therefore, the XP and CS mouse models serve as valuable tools to delineate intervention strategies that combat age-associated pathology of the brain.
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Reis AMC, Mills WK, Ramachandran I, Friedberg EC, Thompson D, Queimado L. Targeted detection of in vivo endogenous DNA base damage reveals preferential base excision repair in the transcribed strand. Nucleic Acids Res 2011; 40:206-19. [PMID: 21911361 PMCID: PMC3245927 DOI: 10.1093/nar/gkr704] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Endogenous DNA damage is removed mainly via base excision repair (BER), however, whether there is preferential strand repair of endogenous DNA damage is still under intense debate. We developed a highly sensitive primer-anchored DNA damage detection assay (PADDA) to map and quantify in vivo endogenous DNA damage. Using PADDA, we documented significantly higher levels of endogenous damage in Saccharomyces cerevisiae cells in stationary phase than in exponential phase. We also documented that yeast BER-defective cells have significantly higher levels of endogenous DNA damage than isogenic wild-type cells at any phase of growth. PADDA provided detailed fingerprint analysis at the single-nucleotide level, documenting for the first time that persistent endogenous nucleotide damage in CAN1 co-localizes with previously reported spontaneous CAN1 mutations. To quickly and reliably quantify endogenous strand-specific DNA damage in the constitutively expressed CAN1 gene, we used PADDA on a real-time PCR setting. We demonstrate that wild-type cells repair endogenous damage preferentially on the CAN1 transcribed strand. In contrast, yeast BER-defective cells accumulate endogenous damage preferentially on the CAN1 transcribed strand. These data provide the first direct evidence for preferential strand repair of endogenous DNA damage and documents the major role of BER in this process.
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Affiliation(s)
- António M C Reis
- Department of Dermatology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA
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31
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Javeri A, Lyons JG, Huang XX, Halliday GM. Downregulation of Cockayne syndrome B protein reduces human 8-oxoguanine DNA glycosylase-1 expression and repair of UV radiation-induced 8-oxo-7,8-dihydro-2'-deoxyguanine. Cancer Sci 2011; 102:1651-8. [PMID: 21668583 PMCID: PMC11159239 DOI: 10.1111/j.1349-7006.2011.02005.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Human 8-oxoguanine DNA glycosylase-1 (hOGG1) is the key DNA repair enzyme responsible for initiating repair of UV radiation-induced 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxo-dG). Previously we have shown that basal cells in human epidermis are particularly sensitive to UVA-mediated DNA damage probably due to low expression of hOGG1. Here we investigate some aspects of the regulatory role of Cockayne syndrome B (CSB) on hOGG1 expression and function. Cockayne syndrome B and hOGG1 genes were knocked down by miRNA technology in the HaCaT human keratinocyte cell line. Loss of the CSB gene decreased hOGG1 mRNA, and loss of hOGG1 increased CSB, indicating that they influence each other's expression. Protein levels were assessed in cells grown into engineered human skin using immunohistochemistry. This confirmed that CSB knockdown with miRNA reduced hOGG1 protein levels, but hOGG1 knockdown did not influence expression of CSB protein. Using comet assay we found that both hOGG1 and CSB knockdown reduced repair of both UVA- and UVB-induced 8-oxo-dG, consistent with CSB downregulation of hOGG1 mRNA and protein. In contrast, CSB but not hOGG1 knockdown reduced repair of UVB- and UVA-induced cyclobutane pyrimidine dimer photolesions. In engineered human skin, repair of UVA-induced 8-oxo-dG was inhibited by both hOGG1 and CSB knockdown, confirming the functional role of both proteins in cells with 3-D cellular contacts. These findings directly indicate that hOGG1 and CSB influence each other's expression. CSB is required for maintaining hOGG1 enzyme levels and function. Cockayne syndrome B could therefore be required for 8-oxo-dG repair due to its regulatory effect on hOGG1 expression. Cockayne syndrome B but not hOGG1 is also required for efficient repair of cyclobutane pyrimidine dimers. Cockayne syndrome B regulation of DNA repair could contribute to the effect of UVA in causing mutations that lead to skin cancer in humans.
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Affiliation(s)
- Arash Javeri
- Discipline of Dermatology, Bosch Institute, Dermatology Research Laboratory, University of Sydney, Sydney, New South Wales, Australia
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32
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The role of XPC: implications in cancer and oxidative DNA damage. Mutat Res 2011; 728:107-17. [PMID: 21763452 DOI: 10.1016/j.mrrev.2011.07.001] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2011] [Revised: 06/30/2011] [Accepted: 07/01/2011] [Indexed: 01/14/2023]
Abstract
The accumulation of DNA damage is a slow but hazardous phenomenon that may lead to cell death, accelerated aging features and cancer. One of the most versatile and important defense mechanisms against the accumulation of DNA damage is nucleotide excision repair (NER), in which the Xeroderma pigmentosum group C (XPC) protein plays a prominent role. NER can be divided into global genome repair (GG-NER) and transcription coupled repair (TC-NER). XPC is a key factor in GG-NER where it functions in DNA damage recognition and after which the repair machinery is recruited to eliminate the DNA damage. Defective XPC functioning has been shown to result in a cancer prone phenotype, in human as well as in mice. Mutation accumulation in XPC deficient mice is accelerated and increased, resulting in an increased tumor incidence. More recently XPC has also been linked to functions outside of NER since XPC deficient mice show a divergent tumor spectrum compared to other NER deficient mouse models. Multiple in vivo and in vitro experiments indicate that XPC appears to be involved in the initiation of several DNA damage-induced cellular responses. XPC seems to function in the removal of oxidative DNA damage, redox homeostasis and cell cycle control. We hypothesize that this combination of increased oxidative DNA damage sensitivity, disturbed redox homeostasis together with inefficient cell cycle control mechanisms are causes of the observed increased cancer susceptibility in oxygen exposed tissues. Such a phenotype is absent in other NER-deficient mice, including Xpa.
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Kitsera N, Stathis D, Lühnsdorf B, Müller H, Carell T, Epe B, Khobta A. 8-Oxo-7,8-dihydroguanine in DNA does not constitute a barrier to transcription, but is converted into transcription-blocking damage by OGG1. Nucleic Acids Res 2011; 39:5926-34. [PMID: 21441539 PMCID: PMC3152326 DOI: 10.1093/nar/gkr163] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
The common DNA base modification 8-oxo-7,8-dihydroguanine (8-oxo-G) affects the efficiency and fidelity of transcription. We constructed plasmid substrates carrying single 8-oxo-G residues, specifically positioned in the transcribed or the non-transcribed DNA strands, to investigate their effects on the expression of an EGFP reporter gene and to explore the role of base excision repair in the mechanism of transcription inhibition. We report that 8-oxo-G does not directly block transcription in cells, since a single 8-oxo-G in the transcribed DNA strand did not reduce the EGFP expression levels in repair-deficient (OGG1-null) mouse embryonic fibroblast cell lines. Rather, inhibition of transcription by 8-oxo-G fully depends on 8-oxoguanine DNA glycosylase (OGG1) and, at the same time, does not require the localization of the lesion in the transcribed DNA strand. We propose that the interruption of transcription is induced by base excision repair intermediates and, therefore, could be a common consequence of various DNA base modifications. Concordantly, the non-blocking DNA modification uracil was also found to inhibit transcription, but in an OGG1-independent manner.
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Affiliation(s)
- Nataliya Kitsera
- Institute of Pharmacy and Biochemistry, Johannes Gutenberg University of Mainz, Staudingerweg 5, 55128 Mainz, Germany
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34
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McCallum GP, Wong AW, Wells PG. Cockayne syndrome B protects against methamphetamine-enhanced oxidative DNA damage in murine fetal brain and postnatal neurodevelopmental deficits. Antioxid Redox Signal 2011; 14:747-56. [PMID: 20673160 PMCID: PMC3116650 DOI: 10.1089/ars.2009.2946] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Methamphetamine (METH) increases the oxidative DNA lesion 8-oxoguanine (8-oxoG) in fetal mouse brain, and causes postnatal motor coordination deficits after in utero exposure. Like oxoguanine glycosylase 1 (OGG1), the Cockayne syndrome B (CSB) protein is involved in the repair of oxidatively damaged DNA, although its function is unclear. Here we used CSB-deficient Csb(m/m) knockout mice to investigate the developmental role of DNA oxidation and CSB in METH-initiated neurodevelopmental deficits. METH (40 mg/kg intraperitoneally) administration to pregnant Csb females on gestational day 17 increased 8-oxoG levels in Csb(m/m) fetal brains (p < 0.05). CSB modulated 8-oxoG levels independent of OGG1 activity, as 8-oxoG incision activity in fetal nuclear extracts was identical in Csb(m/m) and Csb(+/+)mice. This CSB effect was evident despite 7.1-fold higher OGG1 activity in Csb(+/+) mice compared to outbred CD-1 mice. Female Csb(m/m) offspring exposed in utero to METH exhibited motor coordination deficits postnatally (p < 0.05). In utero METH exposure did not cause dopaminergic nerve terminal degeneration, in contrast to adult exposures. This is the first evidence that CSB protects the fetus from xenobiotic-enhanced DNA oxidation and postnatal functional deficits, suggesting that oxidatively damaged DNA is developmentally pathogenic, and that fetal CSB activity may modulate the risk of reactive oxygen species-mediated adverse developmental outcomes.
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Affiliation(s)
- Gordon P McCallum
- Faculty of Pharmacy, University of Toronto, 144 College Street, Toronto, Ontario, Canada
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35
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Abstract
The majority of human cells do not multiply continuously but are quiescent or slow-replicating and devote a large part of their energy to transcription. When DNA damage in the transcribed strand of an active gene is bypassed by a RNA polymerase, they can miscode at the damaged site and produce mutant transcripts. This process is known as transcriptional mutagenesis and, as discussed in this Perspective, could lead to the production of mutant proteins and might therefore be important in tumour development.
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Affiliation(s)
- Damien Brégeon
- Université Paris Sud-11, Institut de Génétique et Microbiologie, CNRS UMR 8621, Bât 400, F-91405 Orsay Cedex, France, Tel : +33 1 69 15 35 61, Fax : +33 1 69 15 46 29,
| | - Paul W. Doetsch
- Departments of Biochemistry and Radiation Oncology, Winship Cancer Institute, Emory University School of Medicine, 1510 Clifton Rd NE, Atlanta, Georgia 30322, USA, Tel : +1 (404) 727-0409, Fax : +1 (404) 727-2618,
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36
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Leach DM, Rainbow AJ. Early host cell reactivation of an oxidatively damaged adenovirus-encoded reporter gene requires the Cockayne syndrome proteins CSA and CSB. Mutagenesis 2011; 26:315-21. [PMID: 21059811 PMCID: PMC3044198 DOI: 10.1093/mutage/geq096] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2010] [Revised: 08/22/2010] [Accepted: 09/20/2010] [Indexed: 11/14/2022] Open
Abstract
Reduced host cell reactivation (HCR) of a reporter gene containing 8-oxoguanine (8-oxoG) lesions in Cockayne syndrome (CS) fibroblasts has previously been attributed to increased 8-oxoG-mediated inhibition of transcription resulting from a deficiency in repair. This interpretation has been challenged by a report suggesting reduced expression from an 8-oxoG containing reporter gene occurs in all cells by a mechanism involving gene inactivation by 8-oxoG DNA glycosylase and this inactivation is strongly enhanced in the absence of the CS group B (CSB) protein. The observation of reduced gene expression in the absence of CSB protein led to speculation that decreased HCR in CS cells results from enhanced gene inactivation rather than reduced gene reactivation. Using an adenovirus-based β-galactosidase (β-gal) reporter gene assay, we have examined the effect of methylene blue plus visible light (MB + VL)-induced 8-oxoG lesions on the time course of gene expression in normal and CSA and CSB mutant human SV40-transformed fibroblasts, repair proficient and CSB mutant Chinese hamster ovary (CHO) cells and normal mouse embryo fibroblasts. We demonstrate that MB + VL treatment of the reporter leads to reduced expression of the damaged β-gal reporter relative to control at early time points following infection in all cells, consistent with in vivo inhibition of RNA polII-mediated transcription. In addition, we have demonstrated HCR of reporter gene expression occurs in all cell types examined. A significant reduction in the rate of gene reactivation in human SV40-transformed cells lacking functional CSA or CSB compared to normal cells was found. Similarly, a significant reduction in the rate of reactivation in CHO cells lacking functional CSB (CHO-UV61) was observed compared to the wild-type parental counterpart (CHO-AA8). The data presented demonstrate that expression of an oxidatively damaged reporter gene is reactivated over time and that CSA and CSB are required for normal reactivation.
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Affiliation(s)
| | - Andrew J. Rainbow
- Department of Biology, McMaster University, 1280 Main Street West, Hamilton, Ontario L8S 4K1, Canada
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Clauson CL, Saxowsky TT, Doetsch PW. Dynamic flexibility of DNA repair pathways in growth arrested Escherichia coli. DNA Repair (Amst) 2010; 9:842-7. [PMID: 20462807 PMCID: PMC2893249 DOI: 10.1016/j.dnarep.2010.04.004] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2010] [Accepted: 04/06/2010] [Indexed: 01/17/2023]
Abstract
The DNA of all organisms is constantly damaged by exogenous and endogenous agents. Base excision repair (BER) is important for the removal of several non-bulky lesions from the DNA, however not much is known about the contributions of other DNA repair pathways to the processing of non-bulky lesions. Here we utilized a luciferase reporter system to assess the contributions of transcription-coupled repair (TCR), BER and nucleotide excision repair (NER) to the repair of two non-bulky lesions, 8-oxoguanine (8OG) and uracil (U), in vivo under non-growth conditions. We demonstrate that both TCR and NER are utilized by Escherichia coli to repair 8OG and U. Additionally, the relative level of recognition of these lesions by BER and NER suggests that TCR can utilize components of either pathway for lesion removal, depending upon their availability. These findings indicate a dynamic flexibility of DNA repair pathways in the removal of non-bulky DNA lesions in prokaryotes, and reveal their respective contributions to the repair of 8OG and U in vivo.
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Affiliation(s)
- Cheryl L. Clauson
- Department of Biochemistry, Emory University School of Medicine, 1510 Clifton Rd. NE, Atlanta, GA 30322 U.S.A
- Graduate Program in Genetics and Molecular Biology
| | - Tina T. Saxowsky
- Department of Biochemistry, Emory University School of Medicine, 1510 Clifton Rd. NE, Atlanta, GA 30322 U.S.A
| | - Paul W. Doetsch
- Department of Biochemistry, Emory University School of Medicine, 1510 Clifton Rd. NE, Atlanta, GA 30322 U.S.A
- Division of Cancer Biology, Department of Radiation Oncology, Department of Hematology and Medical Oncology and Winship Cancer Institute, Emory University School of Medicine
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38
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Evans MD, Saparbaev M, Cooke MS. DNA repair and the origins of urinary oxidized 2'-deoxyribonucleosides. Mutagenesis 2010; 25:433-42. [PMID: 20522520 DOI: 10.1093/mutage/geq031] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Monitoring oxidative stress in vivo is made easier by the ability to use samples obtained non-invasively, such as urine. The analysis of DNA oxidation, by measurement of oxidized 2'-deoxyribonucleosides in urine, particularly 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG), has been reported extensively in the literature in many situations relating to various pathologies, populations and environmental exposures. Understanding the origins of urinary 8-oxodG, other than it simply being a marker of DNA oxidation or its synthetic precursors, is important to being able to effectively interpret differences in baseline urinary 8-oxodG levels between subject groups and changes in excretion. Diet and cell turnover play negligible roles in contributing to urinary 8-oxodG levels, leaving DNA repair as a primary source of this lesion. However, which repair processes contribute, and to what extent, to urinary 8-oxodG is still open to question. The most rational source would be the activity of selected members of the Nudix hydrolase family of enzymes, sanitizing the deoxyribonucleotide pool via the degradation of 8-oxo-7,8-dihydro-2'-deoxyguanosine-5'-triphosphate and 8-oxo-7,8-dihydro-2'-deoxyguanosine-5'-diphosphate, yielding mononucleotide products that can then be dephosphorylated to 8-oxodG and excreted. However, nucleotide excision repair (NER), transcription-coupled repair, nucleotide incision repair (NIR), mismatch repair and various exonuclease activities, such as proofreading function associated with DNA polymerases, can all feasibly generate initial products that could yield 8-oxodG after further metabolism. A recent study implying that a significant proportion of genomic 8-oxodG exists in the context of tandem lesions, refractory to repair by glycosylases, suggests the roles of NER and/or NIR remain to be further examined and defined as a source of 8-oxodG. 8-OxodG has been the primary focus of investigation, but other oxidized 2'-deoxyribonucleosides have been detected in urine, 2'-deoxythymidine glycol and 5-hydroxymethyl-2'-deoxyuridine; the origins of these compounds in urine, however, are presently even more speculative than for 8-oxodG.
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Affiliation(s)
- Mark D Evans
- Radiation and Oxidative Stress Section, Department of Cancer Studies and Molecular Medicine, University of Leicester, Leicester LE1 7RH, UK.
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Khobta A, Anderhub S, Kitsera N, Epe B. Gene silencing induced by oxidative DNA base damage: association with local decrease of histone H4 acetylation in the promoter region. Nucleic Acids Res 2010; 38:4285-95. [PMID: 20338881 PMCID: PMC2910050 DOI: 10.1093/nar/gkq170] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Oxidized DNA bases, particularly 7,8-dihydro-8-oxoguanine (8-oxoG), are endogenously generated in cells, being a cause of carcinogenic mutations and possibly interfering with gene expression. We found that expression of an oxidatively damaged plasmid DNA is impaired after delivery into human host cells not only due to decreased retention in the transfected cells, but also due to selective silencing of the damaged reporter gene. To test whether the gene silencing was associated with a specific change of the chromatin structure, we determined the levels of histone modifications related to transcriptional activation (acetylated histones H3 and H4) or repression (methylated K9 and K27 of the histone H3, and histone H1) in the promoter region and in the downstream transcribed DNA. Acetylation of histone H4 was found to be specifically decreased by 25% in the proximal promoter region of the damaged gene, while minor quantitative changes in other tested chromatin components could not be proven as significant. Treatment with an inhibitor of histone deacetylases, trichostatin A, partially restored expression of the damaged DNA, suggesting a causal connection between the changes of histone acetylation and persistent gene repression. Based on these findings, we propose that silencing of the oxidatively damaged DNA may occur in a chromatin-mediated mechanism.
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Affiliation(s)
- Andriy Khobta
- Johannes Gutenberg University of Mainz, Institute of Pharmacy, Staudingerweg 5, 55128 Mainz, Germany.
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40
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Hartwig A. The role of DNA repair in benzene-induced carcinogenesis. Chem Biol Interact 2010; 184:269-72. [PMID: 20056111 DOI: 10.1016/j.cbi.2009.12.029] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2009] [Revised: 12/17/2009] [Accepted: 12/22/2009] [Indexed: 01/27/2023]
Abstract
Benzene is a well-known human carcinogen, but the ultimate mode of action is still not known. Several reactive metabolites have been identified, including benzene oxide, phenol, hydrochinone, catechol and benzoquinones, generating different types of DNA lesions. Furthermore, the latter three metabolites may lead to the formation of reactive oxygen species (ROS) due to redox cycling, which give rise to oxidative DNA lesions and altered signaling pathways. Also, the inhibition of DNA topoisomerase II may result in DNA double strand breaks. Even though the exact contribution of the respective metabolites to benzene-induced carcinogenicity is not yet resolved, the major DNA repair pathways such as base excision repair (BER), nucleotide excision repair (NER) and double strand break (DSB) repair are involved in the removal of benzene-induced DNA lesions. The observed target organ specificity may result from increased adduct formation, but also from poor repair in bone marrow progenitor cells. While especially excision repair pathways are predominantly error-free and thus protective, DSB repair is largely error prone and may contribute to benzene-induced genomic instability.
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Affiliation(s)
- Andrea Hartwig
- Fachgebiet Lebensmittelchemie und Toxikologie, Institut für Lebensmitteltechnologie und Lebensmittelchemie, Technische Universität Berlin, Gustav-Meyer-Allee 25, 13355 Berlin, Germany.
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41
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Hamann I, Schwerdtle T, Hartwig A. Establishment of a non-radioactive cleavage assay to assess the DNA repair capacity towards oxidatively damaged DNA in subcellular and cellular systems and the impact of copper. Mutat Res 2009; 669:122-130. [PMID: 19505484 DOI: 10.1016/j.mrfmmm.2009.05.011] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2009] [Revised: 05/19/2009] [Accepted: 05/27/2009] [Indexed: 05/27/2023]
Abstract
Oxidative stress is involved in many diseases, and the search for appropriate biomarkers is one major focus in molecular epidemiology. 8-Oxoguanine (8-oxoG), a potentially mutagenic DNA lesion, is considered to be a sensitive biomarker for oxidative stress. Another approach consists in assessing the repair capacity towards 8-oxoG, mediated predominantly by the human 8-oxoguanine DNA glycosylase 1 (hOGG1). With respect to the latter, during the last few years so-called cleavage assays have been described, investigating the incision of (32)P-labelled and 8-oxoG damaged oligonucleotides by cell extracts. Within the present study, a sensitive non-radioactive test system based on a Cy5-labelled oligonucleotide has been established. Sources of incision activity are isolated proteins or extracts prepared from cultured cells and peripheral blood mononuclear cells (PBMC). After comparing different oligonucleotide structures, a hairpin-like structure was selected which was not degraded by cell extracts. Applying this test system the impact of copper on the activity of isolated hOGG1 and on hOGG activity in A549 cells was examined, showing a distinct inhibition of the isolated protein at low copper concentration as compared to a modest inhibition of hOGG activity in cells at beginning cytotoxic concentrations. For investigating PBMC, all reaction conditions, including the amounts of oligonucleotide and cell extract as well as the reaction time have been optimized. The incision activities of PBMC protein extracts obtained from different donors have been investigated, and inter-individual differences have been observed. In summary, the established method is as sensitive and even faster than the radioactive technique, and additionally, offers the advantage of reduced costs and low health risk.
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Affiliation(s)
- Ingrit Hamann
- Fachgebiet Lebensmittelchemie und Toxikologie, Institut für Lebensmitteltechnologie und Lebensmittelchemie, Technische Universität Berlin, Berlin, Germany
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Wells PG, McCallum GP, Chen CS, Henderson JT, Lee CJJ, Perstin J, Preston TJ, Wiley MJ, Wong AW. Oxidative stress in developmental origins of disease: teratogenesis, neurodevelopmental deficits, and cancer. Toxicol Sci 2009; 108:4-18. [PMID: 19126598 DOI: 10.1093/toxsci/kfn263] [Citation(s) in RCA: 304] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
In the developing embryo and fetus, endogenous or xenobiotic-enhanced formation of reactive oxygen species (ROS) like hydroxyl radicals may adversely alter development by oxidatively damaging cellular lipids, proteins and DNA, and/or by altering signal transduction. The postnatal consequences may include an array of birth defects (teratogenesis), postnatal functional deficits, and diseases. In animal models, the adverse developmental consequences of in utero exposure to agents like thalidomide, methamphetamine, phenytoin, benzo[a]pyrene, and ionizing radiation can be modulated by altering pathways that control the embryonic ROS balance, including enzymes that bioactivate endogenous substrates and xenobiotics to free radical intermediates, antioxidative enzymes that detoxify ROS, and enzymes that repair oxidative DNA damage. ROS-mediated signaling via Ras, nuclear factor kappa B and related transducers also may contribute to altered development. Embryopathies can be reduced by free radical spin trapping agents and antioxidants, and enhanced by glutathione depletion. Further modulatory approaches to evaluate such mechanisms in vivo and/or in embryo culture have included the use of knockout mice, transgenic knock-ins and mutant deficient mice with altered enzyme activities, as well as antisense oligonucleotides, protein therapy with antioxidative enzymes, dietary depletion of essential cofactors and chemical enzyme inhibitors. In a few cases, measures anticipated to be protective have conversely enhanced the risk of adverse developmental outcomes, indicating the complexity of development and need for caution in testing therapeutic strategies in humans. A better understanding of the developmental effects of ROS may provide insights for risk assessment and the reduction of adverse postnatal consequences.
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Affiliation(s)
- Peter G Wells
- Faculty of Pharmacy, University of Toronto, Toronto, Ontario, Canada.
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A set of vectors for introduction of antibiotic resistance genes by in vitro Cre-mediated recombination. BMC Res Notes 2008; 1:135. [PMID: 19105832 PMCID: PMC2654900 DOI: 10.1186/1756-0500-1-135] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2008] [Accepted: 12/23/2008] [Indexed: 11/10/2022] Open
Abstract
Background Introduction of new antibiotic resistance genes in the plasmids of interest is a frequent task in molecular cloning practice. Classical approaches involving digestion with restriction endonucleases and ligation are time-consuming. Findings We have created a set of insertion vectors (pINS) carrying genes that provide resistance to various antibiotics (puromycin, blasticidin and G418) and containing a loxP site. Each vector (pINS-Puro, pINS-Blast or pINS-Neo) contains either a chloramphenicol or a kanamycin resistance gene and is unable to replicate in most E. coli strains as it contains a conditional R6Kγ replication origin. Introduction of the antibiotic resistance genes into the vector of interest is achieved by Cre-mediated recombination between the replication-incompetent pINS and a replication-competent target vector. The recombination mix is then transformed into E. coli and selected by the resistance marker (kanamycin or chloramphenicol) present in pINS, which allows to recover the recombinant plasmids with 100% efficiency. Conclusion Here we propose a simple strategy that allows to introduce various antibiotic-resistance genes into any plasmid containing a replication origin, an ampicillin resistance gene and a loxP site.
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Khobta A, Kitsera N, Speckmann B, Epe B. 8-Oxoguanine DNA glycosylase (Ogg1) causes a transcriptional inactivation of damaged DNA in the absence of functional Cockayne syndrome B (Csb) protein. DNA Repair (Amst) 2008; 8:309-17. [PMID: 19061977 DOI: 10.1016/j.dnarep.2008.11.006] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2008] [Revised: 11/03/2008] [Accepted: 11/05/2008] [Indexed: 10/21/2022]
Abstract
We have analysed the effect of oxidative guanine lesions on the expression of a transfected reporter gene in mouse embryonic fibroblasts deficient in Cockayne syndrome B protein (Csb) and/or the 8-oxoguanine DNA glycosylase (Ogg1). We used a highly sensitive flow cytometry-based approach and quantitative real-time PCR to measure the changes in gene expression caused by the presence of oxidised guanine residues generated by photosensitisation in the vector DNA. In wild-type cells, small numbers (one or three) of oxidised guanines did not affect gene expression at short times after transfections, whereas progressive reduction of the transgene expression was observed at later time points. Although Ogg1 has a major contribution to the repair of oxidised guanine bases, its absence did not have a strong effect on the gene expression. In contrast, the lack of functional Csb protein caused a pronounced inactivation of the damaged reporter gene. Most strikingly, an additional Ogg1 deficiency significantly attenuated this effect. The results indicate that the processing of oxidative guanine modifications by Ogg1 can mediate host cell inactivation rather than reactivation of the damaged genes and that this effect is strongly enhanced in the absence of Csb.
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Affiliation(s)
- Andriy Khobta
- Johannes Gutenberg University of Mainz, Institute of Pharmacy, Mainz, Germany.
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Transcription-coupled DNA repair: two decades of progress and surprises. Nat Rev Mol Cell Biol 2008; 9:958-70. [PMID: 19023283 DOI: 10.1038/nrm2549] [Citation(s) in RCA: 765] [Impact Index Per Article: 47.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Expressed genes are scanned by translocating RNA polymerases, which sensitively detect DNA damage and initiate transcription-coupled repair (TCR), a subpathway of nucleotide excision repair that removes lesions from the template DNA strands of actively transcribed genes. Human hereditary diseases that present a deficiency only in TCR are characterized by sunlight sensitivity without enhanced skin cancer. Although multiple gene products are implicated in TCR, we still lack an understanding of the precise signals that can trigger this pathway. Futile cycles of TCR at naturally occurring non-canonical DNA structures might contribute to genomic instability and genetic disease.
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8-Oxoguanine-mediated transcriptional mutagenesis causes Ras activation in mammalian cells. Proc Natl Acad Sci U S A 2008; 105:18877-82. [PMID: 19020090 DOI: 10.1073/pnas.0806464105] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
8-Oxoguanine (8OG) is efficiently bypassed by RNA polymerases in vitro and in bacterial cells in vivo, leading to mutant transcripts by directing incorporation of an incorrect nucleotide during transcription. Such transcriptional mutagenesis (TM) may produce a pool of mutant proteins. In contrast, transcription-coupled repair safeguards against DNA damage, contingent upon the ability of lesions to arrest elongating RNA polymerase. In mammalian cells, the Cockayne syndrome B protein (Csb) mediates transcription-coupled repair, and its involvement in the repair of 8OG is controversial. The DNA glycosylase Ogg1 initiates base excision repair of 8OG, but its influence on TM is unknown. We have developed a mammalian system for TM in congenic mouse embryonic fibroblasts (MEFs), either WT or deficient in Ogg1 (ogg(-/-)), Csb (csb(-/-)), or both. This system uses expression of the Ras oncogene in which an 8OG replaces guanine in codon 61. Repair of 8OG restores the WT sequence; however, bypass and misinsertion opposite this lesion during transcription leads to a constitutively active mutant Ras protein and activation of downstream signaling events, including increased phosphorylation of ERK kinase. Upon transfection of MEFs with replication-incompetent 8OG constructs, we observed a marked increase in phospho-ERK in ogg(-/-) and csb(-/-)ogg(-/-) cells at 6 h, indicating persistence of the lesion and the occurrence of TM. This effect is absent in WT and csb(-/-) cells, suggesting rapid repair. These studies provide evidence that 8OG causes TM in mammalian cells, leading to a phenotypic change with important implications for the role of TM in tumorigenesis.
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Oxoguanine glycosylase 1 protects against methamphetamine-enhanced fetal brain oxidative DNA damage and neurodevelopmental deficits. J Neurosci 2008; 28:9047-54. [PMID: 18768699 DOI: 10.1523/jneurosci.2557-08.2008] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
In utero methamphetamine (METH) exposure enhances the oxidative DNA lesion 7,8-dihydro-8-oxoguanine (8-oxoG) in CD-1 fetal mouse brain, and causes long-term postnatal motor coordination deficits. Herein we used oxoguanine glycosylase 1 (ogg1) knock-out mice to determine the pathogenic roles of 8-oxoG and OGG1, which repairs 8-oxoG, in METH-initiated neurodevelopmental anomalies. Administration of METH (20 or 40 mg/kg) on gestational day 17 to pregnant +/- OGG1-deficient females caused a drug dose- and gene dose-dependent increase in 8-oxoG levels in OGG1-deficient fetal brains (p < 0.05). Female ogg1 knock-out offspring exposed in utero to high-dose METH exhibited gene dose-dependent enhanced motor coordination deficits for at least 12 weeks postnatally (p < 0.05). Contrary to METH-treated adult mice, METH-exposed CD-1 fetal brains did not exhibit altered apoptosis or DNA synthesis, and OGG1-deficient offspring exposed in utero to METH did not exhibit postnatal dopaminergic nerve terminal degeneration, suggesting different mechanisms. Enhanced 8-oxoG repair activity in fetal relative to adult organs suggests an important developmental protective role of OGG1 against in utero genotoxic stress. These observations provide the most direct evidence to date that 8-oxoG constitutes an embryopathic molecular lesion, and that functional fetal DNA repair protects against METH teratogenicity.
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Stevnsner T, Muftuoglu M, Aamann MD, Bohr VA. The role of Cockayne Syndrome group B (CSB) protein in base excision repair and aging. Mech Ageing Dev 2008; 129:441-8. [PMID: 18541289 DOI: 10.1016/j.mad.2008.04.009] [Citation(s) in RCA: 106] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2008] [Revised: 04/17/2008] [Accepted: 04/22/2008] [Indexed: 11/19/2022]
Abstract
Cockayne Syndrome (CS) is a rare human genetic disorder characterized by progressive multisystem degeneration and segmental premature aging. The CS complementation group B (CSB) protein is engaged in transcription coupled and global nucleotide excision repair, base excision repair and general transcription. However, the precise molecular function of the CSB protein is still unclear. In the current review we discuss the involvement of CSB in some of these processes, with focus on the role of CSB in repair of oxidative damage, as deficiencies in the repair of these lesions may be an important aspect of the premature aging phenotype of CS.
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Affiliation(s)
- Tinna Stevnsner
- Danish Centre for Molecular Gerontology, Department of Molecular Biology, University of Aarhus, C.F. Møllers Allé, Aarhus C, Denmark.
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Abstract
The recent decade has engendered a convergence of the otherwise distinct fields of DNA replication, recombination, and repair, as we are learning how these essential transactions can operate in coordination to achieve genomic stability and to ensure cellular viability. In the next decade, we can anticipate a functional understanding of the roles of posttranslational protein modifications in the regulation and prioritizing of pathways for genomic maintenance. The fundamental knowledge gained should lead to more effective clinical intervention in human disease.
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Affiliation(s)
- Philip C Hanawalt
- Department of Biological Sciences, Stanford University, Stanford, CA 94305, USA.
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