1
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Zhang S, Coffing SL, Gunther WC, Homiski ML, Spellman RA, Van P, Schuler M. Assessing the genotoxicity of N-nitrosodiethylamine with three in vivo endpoints in male Big Blue® transgenic and wild-type C57BL/6N mice. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2024. [PMID: 39012003 DOI: 10.1002/em.22615] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/09/2024] [Revised: 06/11/2024] [Accepted: 06/14/2024] [Indexed: 07/17/2024]
Abstract
The detection of N-nitrosamines in drug products has raised global regulatory interest in recent years due to the carcinogenic potential of some nitrosamines in animals and a need to identify a testing strategy has emerged. Ideally, methods used would allow for the use of quantitative analysis of dose-response data from in vivo genotoxicity assays to determine a compound-specific acceptable intake for novel nitrosamines without sufficient carcinogenicity data. In a previous study we compared the dose-response relationships of N-nitrosodiethylamine (NDEA) in three in vivo genotoxicity endpoints in rats. Here we report a comparison of NDEA's genotoxicity profile in mice. Big Blue® mice were administered NDEA at doses of 0.001, 0.01, 0.1, 1 and 3 mg/kg/day by oral gavage for 28 days followed by 3 days of expression. Statistically significant increases in the NDEA induced mutations were detected by both the transgenic rodent mutation assay (TGR) using the cII endpoint and by duplex sequencing in the liver but not bone marrow of mice. In addition, administration of NDEA for two consecutive days in male C57BL/6N mice caused elevated DNA damage levels in the liver as measured by % tail DNA in comet assay. The benchmark dose (BMD) analysis shows a BMDL50 of 0.03, 0.04 and 0.72 mg/kg/day for TGR, duplex sequencing and comet endpoints, respectively. Overall, this study demonstrated a similar genotoxicity profile of NDEA between mice and rats and provides a reference that can be used to compare the potential potency of other novel nitrosamines for the induction of gene mutations.
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Affiliation(s)
- Shaofei Zhang
- Pfizer Research, Development, and Medical, Groton, Connecticut, USA
| | | | | | | | | | - Phu Van
- TwinStrand Biosciences, Inc., Seattle, Washington, USA
| | - Maik Schuler
- Pfizer Research, Development, and Medical, Groton, Connecticut, USA
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2
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Chen T. Unveiling the significance of inducible nitric oxide synthase: Its impact on cancer progression and clinical implications. Cancer Lett 2024; 592:216931. [PMID: 38701892 DOI: 10.1016/j.canlet.2024.216931] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2024] [Revised: 04/14/2024] [Accepted: 04/29/2024] [Indexed: 05/05/2024]
Abstract
The intricate role of inducible nitric oxide synthase (iNOS) in cancer pathophysiology has garnered significant attention, highlighting the complex interplay between tumorigenesis, immune response, and cellular metabolism. As an enzyme responsible for producing nitric oxide (NO) in response to inflammatory stimuli. iNOS is implicated in various aspects of cancer development, including DNA damage, angiogenesis, and evasion of apoptosis. This review synthesizes the current findings from both preclinical and clinical studies on iNOS across different cancer types, reflecting the variability depending on cellular context and tumor microenvironment. We explore the molecular mechanisms by which iNOS modulates cancer cell growth, survival, and metastasis, emphasizing its impact on immune surveillance and response to treatment. Additionally, the potential of targeting iNOS as a therapeutic strategy in cancer treatment is examined. By integrating insights from recent advances, this review aims to elucidate the significant role of iNOS in cancer and pave the way for novel diagnostic and therapeutic approaches.
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Affiliation(s)
- Tong Chen
- Division of Medical Oncology, Department of Internal Medicine, The Ohio State University College of Medicine, Columbus, OH, 43210, USA; The Ohio State University Comprehensive Cancer Center, Columbus, OH, 43210, USA.
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3
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Seo JE, Le Y, Revollo J, Miranda-Colon J, Xu H, McKinzie P, Mei N, Chen T, Heflich RH, Zhou T, Robison T, Bonzo JA, Guo X. Evaluating the mutagenicity of N-nitrosodimethylamine in 2D and 3D HepaRG cell cultures using error-corrected next generation sequencing. Arch Toxicol 2024; 98:1919-1935. [PMID: 38584193 PMCID: PMC11106104 DOI: 10.1007/s00204-024-03731-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2023] [Accepted: 03/07/2024] [Indexed: 04/09/2024]
Abstract
Human liver-derived metabolically competent HepaRG cells have been successfully employed in both two-dimensional (2D) and 3D spheroid formats for performing the comet assay and micronucleus (MN) assay. In the present study, we have investigated expanding the genotoxicity endpoints evaluated in HepaRG cells by detecting mutagenesis using two error-corrected next generation sequencing (ecNGS) technologies, Duplex Sequencing (DS) and High-Fidelity (HiFi) Sequencing. Both HepaRG 2D cells and 3D spheroids were exposed for 72 h to N-nitrosodimethylamine (NDMA), followed by an additional incubation for the fixation of induced mutations. NDMA-induced DNA damage, chromosomal damage, and mutagenesis were determined using the comet assay, MN assay, and ecNGS, respectively. The 72-h treatment with NDMA resulted in concentration-dependent increases in cytotoxicity, DNA damage, MN formation, and mutation frequency in both 2D and 3D cultures, with greater responses observed in the 3D spheroids compared to 2D cells. The mutational spectrum analysis showed that NDMA induced predominantly A:T → G:C transitions, along with a lower frequency of G:C → A:T transitions, and exhibited a different trinucleotide signature relative to the negative control. These results demonstrate that the HepaRG 2D cells and 3D spheroid models can be used for mutagenesis assessment using both DS and HiFi Sequencing, with the caveat that severe cytotoxic concentrations should be avoided when conducting DS. With further validation, the HepaRG 2D/3D system may become a powerful human-based metabolically competent platform for genotoxicity testing.
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Affiliation(s)
- Ji-Eun Seo
- Division of Genetic and Molecular Toxicology, National Center for Toxicological Research, U.S. Food and Drug Administration, Jefferson, AR, 72079, USA
| | - Yuan Le
- Division of Genetic and Molecular Toxicology, National Center for Toxicological Research, U.S. Food and Drug Administration, Jefferson, AR, 72079, USA
| | - Javier Revollo
- Division of Genetic and Molecular Toxicology, National Center for Toxicological Research, U.S. Food and Drug Administration, Jefferson, AR, 72079, USA
| | - Jaime Miranda-Colon
- Division of Genetic and Molecular Toxicology, National Center for Toxicological Research, U.S. Food and Drug Administration, Jefferson, AR, 72079, USA
| | - Hannah Xu
- Division of Genetic and Molecular Toxicology, National Center for Toxicological Research, U.S. Food and Drug Administration, Jefferson, AR, 72079, USA
| | - Page McKinzie
- Division of Genetic and Molecular Toxicology, National Center for Toxicological Research, U.S. Food and Drug Administration, Jefferson, AR, 72079, USA
| | - Nan Mei
- Division of Genetic and Molecular Toxicology, National Center for Toxicological Research, U.S. Food and Drug Administration, Jefferson, AR, 72079, USA
| | - Tao Chen
- Division of Genetic and Molecular Toxicology, National Center for Toxicological Research, U.S. Food and Drug Administration, Jefferson, AR, 72079, USA
| | - Robert H Heflich
- Division of Genetic and Molecular Toxicology, National Center for Toxicological Research, U.S. Food and Drug Administration, Jefferson, AR, 72079, USA
| | - Tong Zhou
- Center for Veterinary Medicine, U.S. Food and Drug Administration, Rockville, MD, 20855, USA
| | - Timothy Robison
- Center for Drug Evaluation and Research, U.S. Food and Drug Administration, Silver Spring, MD, 20993, USA
| | - Jessica A Bonzo
- Center for Drug Evaluation and Research, U.S. Food and Drug Administration, Silver Spring, MD, 20993, USA
| | - Xiaoqing Guo
- Division of Genetic and Molecular Toxicology, National Center for Toxicological Research, U.S. Food and Drug Administration, Jefferson, AR, 72079, USA.
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4
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Lafranconi M, Anderson J, Budinsky R, Corey L, Forsberg N, Klapacz J, LeBaron MJ. An integrated assessment of the 1,4-dioxane cancer mode of action and threshold response in rodents. Regul Toxicol Pharmacol 2023:105428. [PMID: 37277058 DOI: 10.1016/j.yrtph.2023.105428] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2023] [Revised: 05/19/2023] [Accepted: 06/02/2023] [Indexed: 06/07/2023]
Abstract
1,4-Dioxane is an environmental contaminant that has been shown to cause cancer in rodents after chronic high dose exposures. We reviewed and integrated information from recently published studies to update our understanding of the cancer mode of action of 1,4-dioxane. Tumor development in rodents from exposure to high doses of 1,4-dioxane is preceded by pre-neoplastic events including increased hepatic genomic signaling activity related to mitogenesis, elevation of Cyp2E1 activity and oxidative stress leading to genotoxicity and cytotoxicity. These events are followed by regenerative repair and proliferation and eventual development of tumors. Importantly, these events occur at doses that exceed the metabolic clearance of absorbed 1,4-dioxane in rats and mice resulting in elevated systemic levels of parent 1,4-dioxane. Consistent with previous reviews, we found no evidence of direct mutagenicity from exposure to 1,4-dioxane. We also found no evidence of CAR/PXR, AhR or PPARα activation resulting from exposure to 1,4-dioxane. This integrated assessment supports a cancer mode of action that is dependent on exceeding the metabolic clearance of absorbed 1,4-dioxane, direct mitogenesis, elevation of Cyp2E1 activity and oxidative stress leading to genotoxicity and cytotoxicity followed by sustained proliferation driven by regenerative repair and progression of heritable lesions to tumor development.
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5
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Fahrer J, Christmann M. DNA Alkylation Damage by Nitrosamines and Relevant DNA Repair Pathways. Int J Mol Sci 2023; 24:ijms24054684. [PMID: 36902118 PMCID: PMC10003415 DOI: 10.3390/ijms24054684] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2023] [Revised: 02/17/2023] [Accepted: 02/24/2023] [Indexed: 03/04/2023] Open
Abstract
Nitrosamines occur widespread in food, drinking water, cosmetics, as well as tobacco smoke and can arise endogenously. More recently, nitrosamines have been detected as impurities in various drugs. This is of particular concern as nitrosamines are alkylating agents that are genotoxic and carcinogenic. We first summarize the current knowledge on the different sources and chemical nature of alkylating agents with a focus on relevant nitrosamines. Subsequently, we present the major DNA alkylation adducts induced by nitrosamines upon their metabolic activation by CYP450 monooxygenases. We then describe the DNA repair pathways engaged by the various DNA alkylation adducts, which include base excision repair, direct damage reversal by MGMT and ALKBH, as well as nucleotide excision repair. Their roles in the protection against the genotoxic and carcinogenic effects of nitrosamines are highlighted. Finally, we address DNA translesion synthesis as a DNA damage tolerance mechanism relevant to DNA alkylation adducts.
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Affiliation(s)
- Jörg Fahrer
- Division of Food Chemistry and Toxicology, Department of Chemistry, RPTU Kaiserslautern-Landau, Erwin-Schrödinger Strasse 52, D-67663 Kaiserslautern, Germany
- Correspondence: (J.F.); (M.C.); Tel.: +496312052974 (J.F.); Tel: +496131179066 (M.C.)
| | - Markus Christmann
- Department of Toxicology, University Medical Center Mainz, Obere Zahlbacher Strasse 67, D-55131 Mainz, Germany
- Correspondence: (J.F.); (M.C.); Tel.: +496312052974 (J.F.); Tel: +496131179066 (M.C.)
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6
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Xu K, Yao Y, Liu H, Yang M, Yuan L, Du X, Yang Y, Qin L, Wang W, Zhou K, Wu X, Liu C. ITGB4 deficiency induces DNA damage by downregulating HDAC1 in airway epithelial cells under stress stimulation. Pediatr Allergy Immunol 2022; 33:e13871. [PMID: 36282138 DOI: 10.1111/pai.13871] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/05/2022] [Revised: 10/01/2022] [Accepted: 10/04/2022] [Indexed: 11/06/2022]
Abstract
BACKGROUND DNA damage in airway epithelia under exogenous disruptors can trigger various pulmonary diseases. Integrin beta 4 (ITGB4) is a structural adhesion molecule, which is indicated to regulate the process of DNA damage in airway epithelia for its unique long cytoplasmic domain subunit. METHODS The expression level of ITGB4 and the degree of DNA damage were observed in the house dust mite (HDM)-stressed model and ozone-challenged model, respectively. Besides, ITGB4 conditional knockout mice and ITGB4-deficient airway epithelial cells were constructed to observe the influence of ITGB4 deficiency on DNA damage. Furthermore, the influence of ITGB4 deficiency on HDAC1 expression in airway epithelia was determined under stress stimulation. Finally, corresponding intervention strategies were carried out to verify the involvement of the ITGB4-mediated HDAC1 pathway in DNA damage of airway epithelial cells. RESULTS HDM stress and ozone challenge reduced the expression of ITGB4, which is accompanied by the increased expression of 8-oxoG and γ-H2AX both in vivo and in vitro. Moreover, ITGB4 deficiency in airway epithelia aggravates the degree of DNA damage under HDM stimulation and ozone stress, respectively. Furthermore, ITGB4 deficiency downregulated the expression of HDAC1 during DNA damage, and restoring HDAC1 can reverse the enhanced DNA damage in airway epithelial cells after exogenous stress. CONCLUSIONS This study confirmed the involvement of ITGB4 in the regulation of DNA damage through mediating HDAC1 in airway epithelial cells under exogenous stress. These results supply some useful insights into the mechanism of DNA damage in airway epithelial cells, which would provide possible targets for early prediction and intervention of pulmonary diseases.
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Affiliation(s)
- Kun Xu
- School of Medicine, Hunan Normal University, Changsha, China
| | - Ye Yao
- Department of Respiratory Medicine, National Clinical Research Center for Respiratory Diseases, Xiangya Hospital, Central South University, Changsha, China.,Department of Physiology, School of Basic Medicine Science, Central South University, Changsha, China.,Basic and Clinical Research Laboratory of Major Respiratory Diseases, Central South University, Changsha, China
| | - Huijun Liu
- Department of Physiology, School of Basic Medicine Science, Central South University, Changsha, China.,Basic and Clinical Research Laboratory of Major Respiratory Diseases, Central South University, Changsha, China
| | - Ming Yang
- Centre for Asthma and Respiratory Disease, School of Biomedical Sciences and Pharmacy, Faculty of Health and Medicine, University of Newcastle and Hunter Medical Research Institute, Callaghan, New South Wales, Australia
| | - Lin Yuan
- Department of Physiology, School of Basic Medicine Science, Central South University, Changsha, China.,Basic and Clinical Research Laboratory of Major Respiratory Diseases, Central South University, Changsha, China
| | - Xizi Du
- Department of Physiology, School of Basic Medicine Science, Central South University, Changsha, China.,Basic and Clinical Research Laboratory of Major Respiratory Diseases, Central South University, Changsha, China
| | - Yu Yang
- Department of Physiology, School of Basic Medicine Science, Central South University, Changsha, China.,Basic and Clinical Research Laboratory of Major Respiratory Diseases, Central South University, Changsha, China
| | - Ling Qin
- Department of Respiratory Medicine, National Clinical Research Center for Respiratory Diseases, Xiangya Hospital, Central South University, Changsha, China.,Basic and Clinical Research Laboratory of Major Respiratory Diseases, Central South University, Changsha, China
| | - Weijie Wang
- Department of Physiology, School of Basic Medicine Science, Central South University, Changsha, China.,Basic and Clinical Research Laboratory of Major Respiratory Diseases, Central South University, Changsha, China
| | - Kai Zhou
- Department of Physiology, School of Basic Medicine Science, Central South University, Changsha, China.,Basic and Clinical Research Laboratory of Major Respiratory Diseases, Central South University, Changsha, China
| | - Xinyu Wu
- Department of Physiology, School of Basic Medicine Science, Central South University, Changsha, China.,Basic and Clinical Research Laboratory of Major Respiratory Diseases, Central South University, Changsha, China
| | - Chi Liu
- Department of Respiratory Medicine, National Clinical Research Center for Respiratory Diseases, Xiangya Hospital, Central South University, Changsha, China.,Department of Physiology, School of Basic Medicine Science, Central South University, Changsha, China.,Basic and Clinical Research Laboratory of Major Respiratory Diseases, Central South University, Changsha, China
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7
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Koirala RP, Pokhrel R, Baral P, Tiwari PB, Chapagain PP, Adhikari NP. Structural insights into the repair mechanism of AGT for methyl-induced DNA damage. Biol Chem 2021; 402:1203-1211. [PMID: 34192828 DOI: 10.1515/hsz-2021-0198] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2021] [Accepted: 05/29/2021] [Indexed: 02/06/2023]
Abstract
Methylation induced DNA base-pairing damage is one of the major causes of cancer. O6-alkylguanine-DNA alkyltransferase (AGT) is considered a demethylation agent of the methylated DNA. Structural investigations with thermodynamic properties of the AGT-DNA complex are still lacking. In this report, we modeled two catalytic states of AGT-DNA interactions and an AGT-DNA covalent complex and explored structural features using molecular dynamics (MD) simulations. We utilized the umbrella sampling method to investigate the changes in the free energy of the interactions in two different AGT-DNA catalytic states, one with methylated GUA in DNA and the other with methylated CYS145 in AGT. These non-covalent complexes represent the pre- and post-repair complexes. Therefore, our study encompasses the process of recognition, complex formation, and separation of the AGT and the damaged (methylated) DNA base. We believe that the use of parameters for the amino acid and nucleotide modifications and for the protein-DNA covalent bond will allow investigations of the DNA repair mechanism as well as the exploration of cancer therapeutics targeting the AGT-DNA complexes at various functional states as well as explorations via stabilization of the complex.
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Affiliation(s)
| | - Rudramani Pokhrel
- Department of Physics, Florida International University, Miami, FL, USA
| | - Prabin Baral
- Department of Physics, Florida International University, Miami, FL, USA
| | | | - Prem P Chapagain
- Department of Physics, Florida International University, Miami, FL, USA.,Biomolecular Sciences Institute, Florida International University, Miami, FL, USA
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8
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Soll JM, Brickner JR, Mudge MC, Mosammaparast N. RNA ligase-like domain in activating signal cointegrator 1 complex subunit 1 (ASCC1) regulates ASCC complex function during alkylation damage. J Biol Chem 2018; 293:13524-13533. [PMID: 29997253 DOI: 10.1074/jbc.ra117.000114] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2017] [Revised: 07/03/2018] [Indexed: 02/05/2023] Open
Abstract
Multiple DNA damage response (DDR) pathways have evolved to sense the presence of damage and recruit the proper repair factors. We recently reported a signaling pathway induced upon alkylation damage to recruit the AlkB homolog 3, α-ketoglutarate-dependent dioxygenase (ALKBH3)-activating signal cointegrator 1 complex subunit 3 (ASCC3) dealkylase-helicase repair complex. As in other DDR pathways, the recruitment of these repair factors is mediated through a ubiquitin-dependent mechanism. However, the machinery that coordinates the proper assembly of this repair complex and controls its recruitment is still poorly defined. Here, we demonstrate that the ASCC1 accessory subunit is important for the regulation of ASCC complex function. ASCC1 interacts with the ASCC complex through the ASCC3 helicase subunit. We find that ASCC1 is present at nuclear speckle foci prior to damage, but leaves the foci in response to alkylation. Strikingly, ASCC1 loss significantly increases ASCC3 foci formation during alkylation damage, yet most of these foci lack ASCC2. These results suggest that ASCC1 coordinates the proper recruitment of the ASCC complex during alkylation, a function that appears to depend on a putative RNA-binding motif near the ASCC1 C terminus. Consistent with its role in alkylation damage signaling and repair, ASCC1 knockout through a CRISPR/Cas9 approach results in alkylation damage sensitivity in a manner epistatic with ASCC3. Together, our results identify a critical regulator of the ALKBH3-ASCC alkylation damage signaling pathway and suggest a potential role for RNA-interacting domains in the alkylation damage response.
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Affiliation(s)
- Jennifer M Soll
- From the Department of Pathology and Immunology, Division of Laboratory and Genomic Medicine, Washington University in St. Louis, St. Louis, Missouri 63110
| | - Joshua R Brickner
- From the Department of Pathology and Immunology, Division of Laboratory and Genomic Medicine, Washington University in St. Louis, St. Louis, Missouri 63110
| | - Miranda C Mudge
- From the Department of Pathology and Immunology, Division of Laboratory and Genomic Medicine, Washington University in St. Louis, St. Louis, Missouri 63110
| | - Nima Mosammaparast
- From the Department of Pathology and Immunology, Division of Laboratory and Genomic Medicine, Washington University in St. Louis, St. Louis, Missouri 63110
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9
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Sacre L, O'Flaherty DK, Archambault P, Copp W, Peslherbe GH, Muchall HM, Wilds CJ. O 4 -Alkylated-2-Deoxyuridine Repair by O 6 -Alkylguanine DNA Alkyltransferase is Augmented by a C5-Fluorine Modification. Chembiochem 2018; 19:575-582. [PMID: 29243336 DOI: 10.1002/cbic.201700660] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2017] [Indexed: 11/10/2022]
Abstract
Oligonucleotides containing various adducts, including ethyl, benzyl, 4-hydroxybutyl and 7-hydroxyheptyl groups, at the O4 atom of 5-fluoro-O4 -alkyl-2'-deoxyuridine were prepared by solid-phase synthesis. UV thermal denaturation studies demonstrated that these modifications destabilised the duplex by approximately 10 °C, relative to the control containing 5-fluoro-2'-deoxyuridine. Circular dichroism spectroscopy revealed that these modified duplexes all adopted a B-form DNA structure. O6 -Alkylguanine DNA alkyltransferase (AGT) from humans (hAGT) was most efficient at repair of the 5-fluoro-O4 -benzyl-2'-deoxyuridine adduct, whereas the thymidine analogue was refractory to repair. The Escherichia coli AGT variant (OGT) was also efficient at removing O4 -ethyl and benzyl adducts of 5-fluoro-2-deoxyuridine. Computational assessment of N1-methyl analogues of the O4 -alkylated nucleobases revealed that the C5-fluorine modification had an influence on reducing the electron density of the O4 -Cα bond, relative to thymine (C5-methyl) and uracil (C5-hydrogen). These results reveal the positive influence of the C5-fluorine atom on the repair of larger O4 -alkyl adducts to expand knowledge of the range of substrates able to be repaired by AGT.
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Affiliation(s)
- Lauralicia Sacre
- Department of Chemistry and Biochemistry and, Centre for Research in Molecular Modeling (CERMM), Concordia University, 7141 Sherbrooke St. West, Montréal, Québec, H4B 1R6, Canada
| | - Derek K O'Flaherty
- Department of Chemistry and Biochemistry and, Centre for Research in Molecular Modeling (CERMM), Concordia University, 7141 Sherbrooke St. West, Montréal, Québec, H4B 1R6, Canada.,Present address: Howard Hughes Medical Institute, Department of Molecular Biology and, Center for Computational and Integrative Biology, Massachusetts General Hospital, 185 Cambridge Street, Boston, MA, 02114, USA
| | - Philippe Archambault
- Department of Chemistry and Biochemistry and, Centre for Research in Molecular Modeling (CERMM), Concordia University, 7141 Sherbrooke St. West, Montréal, Québec, H4B 1R6, Canada
| | - William Copp
- Department of Chemistry and Biochemistry and, Centre for Research in Molecular Modeling (CERMM), Concordia University, 7141 Sherbrooke St. West, Montréal, Québec, H4B 1R6, Canada
| | - Gilles H Peslherbe
- Department of Chemistry and Biochemistry and, Centre for Research in Molecular Modeling (CERMM), Concordia University, 7141 Sherbrooke St. West, Montréal, Québec, H4B 1R6, Canada
| | - Heidi M Muchall
- Department of Chemistry and Biochemistry and, Centre for Research in Molecular Modeling (CERMM), Concordia University, 7141 Sherbrooke St. West, Montréal, Québec, H4B 1R6, Canada
| | - Christopher J Wilds
- Department of Chemistry and Biochemistry and, Centre for Research in Molecular Modeling (CERMM), Concordia University, 7141 Sherbrooke St. West, Montréal, Québec, H4B 1R6, Canada
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10
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Salam T, Premila Devi S, Duncan Lyngdoh RH. Molecular criteria for mutagenesis by DNA methylation: Some computational elucidations. Mutat Res 2018; 807:10-20. [PMID: 29220701 DOI: 10.1016/j.mrfmmm.2017.10.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2017] [Revised: 10/05/2017] [Accepted: 10/25/2017] [Indexed: 06/07/2023]
Abstract
Alkylating agents and N-nitroso compounds are well-known mutagens and carcinogens which act by alkylating DNA at the nucleobase moieties. Criteria for mutagenicity through DNA alkylation include (a) absence of the Watson-Crick (N1-guanine and N3-thymine) protons, (b) rotation of the alkyl group away from the H-bonding zone, (c) configuration of the alkylated base pair close to the Watson-Crick type. This computational study brings together these three molecular criteria for the first time. Three methylated DNA bases-N7-methylguanine, O6-methylguanine and O4-methylthymine-are studied using computational chemical methods. Watson-Crick proton loss is predicted more feasible for the mutagenic O6-methylguanine and O4-methylthymine than for the non-mutagenic N7-methylguanine in agreement with the observed trend for pKa values. Attainment of a conformer conducive to mutagenesis is more feasible for O6-methylguanine than for O4-methylthymine, though the latter is more mutagenic. These methylated bases yield 9 H-bonded pairs with normal DNA bases. At biological pH, O6-methylguanine and O4-methylthymine would yield stable mutagenic pairs having Watson-Crick type configuration by H-bonded pairing with thymine and guanine respectively, while N7-methylguanine would yield a non-mutagenic pair with cytosine. The three criteria thus well differentiate the non-mutagenic N7-methylguanine from the mutagenic O6-methylguanine and O4-methylthymine in good accord with experimental observations.
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Affiliation(s)
- Tejeshwori Salam
- Department of Chemistry, North-Eastern Hill University, Shillong 793022, India
| | - S Premila Devi
- Department of Chemistry, North-Eastern Hill University, Shillong 793022, India
| | - R H Duncan Lyngdoh
- Department of Chemistry, North-Eastern Hill University, Shillong 793022, India.
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11
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Saki M, Prakash A. DNA damage related crosstalk between the nucleus and mitochondria. Free Radic Biol Med 2017; 107:216-227. [PMID: 27915046 PMCID: PMC5449269 DOI: 10.1016/j.freeradbiomed.2016.11.050] [Citation(s) in RCA: 101] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/08/2016] [Revised: 10/25/2016] [Accepted: 11/29/2016] [Indexed: 12/18/2022]
Abstract
The electron transport chain is the primary pathway by which a cell generates energy in the form of ATP. Byproducts of this process produce reactive oxygen species that can cause damage to mitochondrial DNA. If not properly repaired, the accumulation of DNA damage can lead to mitochondrial dysfunction linked to several human disorders including neurodegenerative diseases and cancer. Mitochondria are able to combat oxidative DNA damage via repair mechanisms that are analogous to those found in the nucleus. Of the repair pathways currently reported in the mitochondria, the base excision repair pathway is the most comprehensively described. Proteins that are involved with the maintenance of mtDNA are encoded by nuclear genes and translocate to the mitochondria making signaling between the nucleus and mitochondria imperative. In this review, we discuss the current understanding of mitochondrial DNA repair mechanisms and also highlight the sensors and signaling pathways that mediate crosstalk between the nucleus and mitochondria in the event of mitochondrial stress.
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Affiliation(s)
- Mohammad Saki
- Mitchell Cancer Institute, The University of South Alabama, 1660 Springhill Avenue, Mobile, AL 36604, United States
| | - Aishwarya Prakash
- Mitchell Cancer Institute, The University of South Alabama, 1660 Springhill Avenue, Mobile, AL 36604, United States.
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12
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Chatterjee N, Walker GC. Mechanisms of DNA damage, repair, and mutagenesis. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2017; 58:235-263. [PMID: 28485537 PMCID: PMC5474181 DOI: 10.1002/em.22087] [Citation(s) in RCA: 997] [Impact Index Per Article: 142.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2016] [Accepted: 03/16/2017] [Indexed: 05/08/2023]
Abstract
Living organisms are continuously exposed to a myriad of DNA damaging agents that can impact health and modulate disease-states. However, robust DNA repair and damage-bypass mechanisms faithfully protect the DNA by either removing or tolerating the damage to ensure an overall survival. Deviations in this fine-tuning are known to destabilize cellular metabolic homeostasis, as exemplified in diverse cancers where disruption or deregulation of DNA repair pathways results in genome instability. Because routinely used biological, physical and chemical agents impact human health, testing their genotoxicity and regulating their use have become important. In this introductory review, we will delineate mechanisms of DNA damage and the counteracting repair/tolerance pathways to provide insights into the molecular basis of genotoxicity in cells that lays the foundation for subsequent articles in this issue. Environ. Mol. Mutagen. 58:235-263, 2017. © 2017 Wiley Periodicals, Inc.
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Marsoner T, Schmidt OP, Triemer T, Luedtke NW. DNA-Targeted Inhibition of MGMT. Chembiochem 2017; 18:894-898. [PMID: 28177192 DOI: 10.1002/cbic.201600652] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2016] [Indexed: 12/17/2022]
Abstract
The cationic porphyrin 5,10,15,20-tetrakis (diisopropyl-guanidine)-21H,23H-porphine (DIGPor) selectively binds to DNA containing O6 -methylguanine (O6 -MeG) and inhibits the DNA repair enzyme O6 -methylguanine-DNA methyltransferase (MGMT). The O6 -MeG selectivity and MGMT inhibitory activity of DIGPor were improved by incorporating ZnII into the porphyrin. The resulting metal complex (Zn-DIGPor) potentiated the activity of the DNA-alkylating drug temozolomide in an MGMT-expressing cell line. To the best of our knowledge, this is the first example of DNA-targeted MGMT inhibition.
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Affiliation(s)
- Theodor Marsoner
- Department of Chemistry, University of Zürich, Winterthurerstrasse 190, 8057, Zürich, Switzerland
| | - Olivia P Schmidt
- Department of Chemistry, University of Zürich, Winterthurerstrasse 190, 8057, Zürich, Switzerland
| | - Therese Triemer
- Department of Chemistry, University of Zürich, Winterthurerstrasse 190, 8057, Zürich, Switzerland
| | - Nathan W Luedtke
- Department of Chemistry, University of Zürich, Winterthurerstrasse 190, 8057, Zürich, Switzerland
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14
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Matsuda S, Matsuda R, Matsuda Y, Yanagisawa SY, Ikura M, Ikura T, Matsuda T. An Easy-to-use Genotoxicity Assay Using EGFP-MDC1-expressing Human Cells. Genes Environ 2014. [DOI: 10.3123/jemsge.2014.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
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15
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McManus FP, Khaira A, Noronha AM, Wilds CJ. Preparation of covalently linked complexes between DNA and O(6)-alkylguanine-DNA alkyltransferase using interstrand cross-linked DNA. Bioconjug Chem 2013; 24:224-33. [PMID: 23347328 DOI: 10.1021/bc300553u] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
O(6)-alkylguanine-DNA alkyltransferases (AGT) are responsible for the removal of alkylation at both the O(6) atom of guanine and O(4) atom of thymine. AGT homologues show vast substrate differences with respect to the size of the adduct and which alkylated atoms they can restore. The human AGT (hAGT) has poor capabilities for removal of methylation at the O(4) atom of thymidine, which is not the case in most homologues. No structural data are available to explain this poor hAGT repair. We prepared and characterized O(6)G-butylene-O(4)T (XLGT4) and O(6)G-heptylene-O(4)T (XLGT7) interstrand cross-linked (ICL) DNA as probes for hAGT and the Escherichia coli homologues, OGT and Ada-C, for the formation of DNA-AGT covalent complexes. XLGT7 reacted only with hAGT and did so with a cross-linking efficiency of 25%, while XLGT4 was inert to all AGT tested. The hAGT mediated repair of XLGT7 occurred slowly, on the order of hours as opposed to the repair of O(6)-methyl-2'-deoxyguanosine which requires seconds. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis of the repair reaction revealed the formation of a covalent complex with an observed migration in accordance with a DNA-AGT complex. The identity of this covalent complex, as determined by mass spectrometry, was composed of a heptamethylene bridge between the O(4) atom of thymidine (in an 11-mer DNA strand) to residue Cys145 of hAGT. This procedure can be applied to produce well-defined covalent complexes between AGT with DNA.
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Affiliation(s)
- Francis P McManus
- Department of Chemistry and Biochemistry, Concordia University, 7141 Sherbrooke St. West, Montréal, QC, Canada H4B 1R6
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Andersen N, Wang J, Wang P, Jiang Y, Wang Y. In-vitro replication studies on O(2)-methylthymidine and O(4)-methylthymidine. Chem Res Toxicol 2012; 25:2523-31. [PMID: 23113558 PMCID: PMC3502631 DOI: 10.1021/tx300325q] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
O(2)- and O(4)-methylthymidine (O(2)-MdT and O(4)-MdT) can be induced in tissues of laboratory animals exposed with N-methyl-N-nitrosourea, a known carcinogen. These two O-methylated DNA adducts have been shown to be poorly repaired and may contribute to the mutations arising from exposure to DNA methylating agents. Here, in vitro replication studies with duplex DNA substrates containing site-specifically incorporated O(2)-MdT and O(4)-MdT showed that both lesions blocked DNA synthesis mediated by three different DNA polymerases, including the exonuclease-free Klenow fragment of Escherichia coli DNA polymerase I (Kf(-)), human DNA polymerase κ (pol κ), and Saccharomyces cerevisiae DNA polymerase η (pol η). Results from steady-state kinetic measurements and LC-MS/MS analysis of primer extension products revealed that Kf(-) and pol η preferentially incorporated the correct nucleotide (dAMP) opposite O(2)-MdT, while O(4)-MdT primarily directed dGMP misincorporation. While steady-state kinetic experiments showed that pol κ-mediated nucleotide insertion opposite O(2)-MdT and O(4)-MdT is highly promiscuous, LC-MS/MS analysis of primer extension products demonstrated that pol κ favorably incorporated the incorrect dGMP opposite both lesions. Our results underscored the limitation of the steady-state kinetic assay in determining how DNA lesions compromise DNA replication in vitro. In addition, the results from our study revealed that, if left unrepaired, O-methylated thymidine lesions may constitute important sources of nucleobase substitutions emanating from exposure to alkylating agents.
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Affiliation(s)
- Nisana Andersen
- Department of Chemistry, University of California, Riverside, California 92521-0403
| | - Jianshuang Wang
- Department of Chemistry, University of California, Riverside, California 92521-0403
| | - Pengcheng Wang
- Environmental Toxicology Graduate Program, University of California, Riverside, California 92521-0403
| | - Yong Jiang
- Environmental Toxicology Graduate Program, University of California, Riverside, California 92521-0403
| | - Yinsheng Wang
- Department of Chemistry, University of California, Riverside, California 92521-0403
- Environmental Toxicology Graduate Program, University of California, Riverside, California 92521-0403
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Zaïr ZM, Jenkins GJ, Doak SH, Singh R, Brown K, Johnson GE. N-Methylpurine DNA Glycosylase Plays a Pivotal Role in the Threshold Response of Ethyl Methanesulfonate–Induced Chromosome Damage. Toxicol Sci 2010; 119:346-58. [DOI: 10.1093/toxsci/kfq341] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
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18
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Luo F, Ye H, Hamoudi R, Dong G, Zhang W, Patek CE, Poulogiannis G, Arends MJ. K-ras exon 4A has a tumour suppressor effect on carcinogen-induced murine colonic adenoma formation. J Pathol 2010; 220:542-50. [PMID: 20087880 DOI: 10.1002/path.2672] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
K-ras encodes two isoforms, K-ras 4A and 4B, that are jointly affected by K-ras activating mutations, which are prevalent in colorectal cancer (CRC). CRC shows alterations in the expressed K-ras 4A : 4B isoform ratio in favour of K-ras 4B, in tumours both with and without K-ras mutations. The present study evaluated whether K-ras 4A expression can suppress colonic adenoma development in the absence of its oncogenic allele. Mice with homozygous targeted deletions of K-ras exon 4A (K-ras(tmDelta4A/tmDelta4A)) that can express the K-ras 4B isoform only, along with heterozygous K-ras(tmDelta4A/+) and wild-type mice, were given ten weekly 1,2-dimethylhydrazine (DMH) treatments to induce colonic adenomas. There was a significant increase in both the number and the size of colonic adenomas in DMH-treated K-ras(tmDelta4A/tmDelta4A) mice, with reduced survival, compared with heterozygous and wild-type mice. No K-ras mutations were found in any of the 30 tumours tested from the three groups. Lack of expression of K-ras 4A transcripts was confirmed, whereas the relative expression levels of K-ras 4B transcripts were significantly increased in the adenomas of K-ras(tmDelta4A/tmDelta4A) mice compared with K-ras(tmDelta4A/+) and wild-type mice. Immunohistochemical studies showed that adenomas of K-ras(tmDelta4A/tmDelta4A) mice had significantly increased cell proliferation and significantly decreased apoptosis with evidence of activation of MapKinase and Akt pathways, with increased phospho-Erk1/2 and both phospho-Akt-Thr308 and phospho-Akt-Ser473 immunostaining, compared with adenomas from K-ras(tmDelta4A/+) and wild-type mice. In conclusion, following DMH treatment, K-ras exon 4A deletion promoted increased number and size of colonic adenomas showing increased K-ras 4B expression, increased proliferation, decreased apoptosis, and activation of MapKinase and Akt pathways, in the absence of K-ras mutations. Therefore, K-ras 4A expression had a tumour suppressor effect on carcinogen-induced murine colonic adenoma formation, explaining the selective advantage of the altered K-ras 4A : 4B isoform ratio found in human colorectal cancer.
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Affiliation(s)
- Feijun Luo
- Department of Pathology, University of Cambridge, Addenbrooke's Hospital, Hills Road, Cambridge, CB2 2QQ, UK
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Shrivastav N, Li D, Essigmann JM. Chemical biology of mutagenesis and DNA repair: cellular responses to DNA alkylation. Carcinogenesis 2009; 31:59-70. [PMID: 19875697 DOI: 10.1093/carcin/bgp262] [Citation(s) in RCA: 207] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The reaction of DNA-damaging agents with the genome results in a plethora of lesions, commonly referred to as adducts. Adducts may cause DNA to mutate, they may represent the chemical precursors of lethal events and they can disrupt expression of genes. Determination of which adduct is responsible for each of these biological endpoints is difficult, but this task has been accomplished for some carcinogenic DNA-damaging agents. Here, we describe the respective contributions of specific DNA lesions to the biological effects of low molecular weight alkylating agents.
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Affiliation(s)
- Nidhi Shrivastav
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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20
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Dalhus B, Laerdahl JK, Backe PH, Bjørås M. DNA base repair--recognition and initiation of catalysis. FEMS Microbiol Rev 2009; 33:1044-78. [PMID: 19659577 DOI: 10.1111/j.1574-6976.2009.00188.x] [Citation(s) in RCA: 108] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Endogenous DNA damage induced by hydrolysis, reactive oxygen species and alkylation modifies DNA bases and the structure of the DNA duplex. Numerous mechanisms have evolved to protect cells from these deleterious effects. Base excision repair is the major pathway for removing base lesions. However, several mechanisms of direct base damage reversal, involving enzymes such as transferases, photolyases and oxidative demethylases, are specialized to remove certain types of photoproducts and alkylated bases. Mismatch excision repair corrects for misincorporation of bases by replicative DNA polymerases. The determination of the 3D structure and visualization of DNA repair proteins and their interactions with damaged DNA have considerably aided our understanding of the molecular basis for DNA base lesion repair and genome stability. Here, we review the structural biochemistry of base lesion recognition and initiation of one-step direct reversal (DR) of damage as well as the multistep pathways of base excision repair (BER), nucleotide incision repair (NIR) and mismatch repair (MMR).
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Affiliation(s)
- Bjørn Dalhus
- Centre for Molecular Biology and Neuroscience (CMBN), Rikshospitalet University Hospital, Oslo, Norway
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21
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Feitsma H, Akay A, Cuppen E. Alkylation damage causes MMR-dependent chromosomal instability in vertebrate embryos. Nucleic Acids Res 2008; 36:4047-56. [PMID: 18522974 PMCID: PMC2475609 DOI: 10.1093/nar/gkn341] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
SN1-type alkylating agents, like N-methyl-N-nitrosourea (MNU) and N-ethyl-N-nitrosourea (ENU), are potent mutagens. Exposure to alkylating agents gives rise to O6-alkylguanine, a modified base that is recognized by DNA mismatch repair (MMR) proteins but is not repairable, resulting in replication fork stalling and cell death. We used a somatic mutation detection assay to study the in vivo effects of alkylation damage on lethality and mutation frequency in developing zebrafish embryos. Consistent with the damage-sensing role of the MMR system, mutant embryos lacking the MMR enzyme MSH6 displayed lower lethality than wild-type embryos after exposure to ENU and MNU. In line with this, alkylation-induced somatic mutation frequencies were found to be higher in wild-type embryos than in the msh6 loss-of-function mutants. These mutations were found to be chromosomal aberrations that may be caused by chromosomal breaks that arise from stalled replication forks. As these chromosomal breaks arise at replication, they are not expected to be repaired by non-homologous end joining. Indeed, Ku70 loss-of-function mutants were found to be equally sensitive to ENU as wild-type embryos. Taken together, our results suggest that in vivo alkylation damage results in chromosomal instability and cell death due to aberrantly processed MMR-induced stalled replication forks.
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Affiliation(s)
| | | | - Edwin Cuppen
- *To whom correspondence should be addressed. +31 30 2121969+31 30 2516554
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22
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Feitsma H, de Bruijn E, van de Belt J, Nijman IJ, Cuppen E. Mismatch repair deficiency does not enhance ENU mutagenesis in the zebrafish germ line. Mutagenesis 2008; 23:325-9. [PMID: 18469325 DOI: 10.1093/mutage/gen019] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
S(N)1-type alkylating agents such as N-ethyl-N-nitrosourea (ENU) are very potent mutagens. They act by transferring their alkyl group to DNA bases, which, upon mispairing during replication, can cause single base pair mutations in the next replication cycle. As DNA mismatch repair (MMR) proteins are involved in the recognition of alkylation damage, we hypothesized that ENU-induced mutation rates could be increased in a MMR-deficient background, which would be beneficial for mutagenesis approaches. We applied a standard ENU mutagenesis protocol to adult zebrafish deficient in the MMR gene msh6 and heterozygous controls to study the effect of MMR on ENU-induced DNA damage. Dose-dependent lethality was found to be similar for homozygous and heterozygous mutants, indicating that there is no difference in ENU resistance. Mutation discovery by high-throughput dideoxy resequencing of genomic targets in outcrossed progeny of the mutagenized fish did also not reveal any differences in germ line mutation frequency. These results may indicate that the maximum mutation load for zebrafish has been reached with the currently used, highly optimized ENU mutagenesis protocol. Alternatively, the MMR system in the zebrafish germ line may be saturated very rapidly, thereby having a limited effect on high-dose ENU mutagenesis.
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Affiliation(s)
- Harma Feitsma
- Hubrecht Institute and Cancer Genomics Center, 3584 CT Utrecht, The Netherlands
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23
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NCX 4040, an NO-donating acetylsalicylic acid derivative: efficacy and mechanisms of action in cancer cells. Nitric Oxide 2008; 19:225-36. [PMID: 18472019 DOI: 10.1016/j.niox.2008.04.007] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2008] [Revised: 04/14/2008] [Accepted: 04/14/2008] [Indexed: 12/12/2022]
Abstract
Non-steroidal anti-inflammatory drugs (NSAIDs) have repeatedly shown to be effective in tumor prevention, but important side-effects limit their wide clinical use. Nitric oxide-releasing derivatives (NO-NSAIDs) are a promising class of compounds synthesized by combining a classic NSAID molecule with an NO-releasing moiety to counteract side-effects. These new chemical entities exhibit a significantly higher activity and much lower toxicity with respect to the parental drug. In the present paper, we report the results obtained from in in vitro experimental systems aimed to evaluate the activity and mechanisms of action of the novel NO-releasing aspirin derivative, NCX 4040. The in vitro studies were carried out on a panel of human colon (LoVo, LoVo Dx, WiDr, LRWZ), bladder (HT1376, MCR), and pancreatic (Capan-2, MIA PaCa-2, T3M4) cancer cell lines. With regard to colon cancer, NCX 4040 activity was also investigated in vitro in combination with drugs currently used in clinical practice and was validated in vivo on tumor-bearing mice xenografted with the aforementioned colon cancer cell lines. The in vitro studies showed a high cytotoxic activity of NCX 4040 in all tumor histotypes and demonstrated the pivotal role of the NO component in drug activity. It was also observed that NCX 4040 exerts a pro-apoptotic activity via a mitochondria-dependent pathway. Moreover, the in vivo studies on xenografted mice further confirmed the antitumor efficacy and low toxicity of NCX 4040 in colon cancer and highlighted its role as sensitizing agent of oxaliplatin cytotoxicity.
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Nilsson R. De minimus non curat lex--virtual thresholds for cancer initiation by tobacco specific nitrosamines--prospects for harm reduction by smokeless tobacco. Int J Occup Med Environ Health 2006; 19:6-35. [PMID: 16881596 DOI: 10.2478/v10001-006-0004-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Whereas the impact of tobacco specific nitrosamines in smokers is obscured by the presence of numerous other carcinogens and promoters, for smokeless tobacco virtually all the carcinogenic potential is associated with 4-(nitrosomethylamino)-1-(3-pyridyl)-1-butanone (NNK) and N'-nitrosonornicotine (NNN). In some countries exposure to smokeless tobacco with extremely high nitrosamine concentrations have been found to induce cancers in the head-neck region, whereas three recent large epidemiological studies failed to detect any such risk with respect to Swedish low-nitrosamine snuff. This review deals with quantitative aspects of DNA adduct formation from NNN and NNK in relation to the background levels ubiquitously found in healthy humans without known exposures to either tobacco or alkylating agents. The lack of significant increases of pro-mutagenic O6-methylations and DNA pyridyloxobutylations seen in smokers, as well as the negative outcome of the Swedish epidemiological studies, can be expected on basis of extrapolation of the dose response relationships found in rodents to actual exposures to NNK and NNN in Swedish snuff or from smoking. Sweden has the lowest prevalence of male smokers and smoking related diseases in the Western World, which has been ascribed to the fact that more than 20% of the grown up male population uses snuff. Smokeless tobacco represents an inexpensive and effective alternative to nicotine delivering products like nicotine patch, spray or gum. Considering that all other tobacco products are freely marketed, the ban on low-nitrosamine snuff in all countries in EU except Sweden is difficult to defend on either medical or ethical grounds.
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Affiliation(s)
- Robert Nilsson
- Department of Toxicology and Carcinogenesis, Nofer Institute of Occupational Medicine, Lódź, Poland.
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25
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Affiliation(s)
- Yukiko Mishina
- Department of Chemistry, The University of Chicago, 5735 South Ellis Avenue, Chicago, Illinois 60637
| | - Erica M. Duguid
- Department of Chemistry, The University of Chicago, 5735 South Ellis Avenue, Chicago, Illinois 60637
| | - Chuan He
- Department of Chemistry, The University of Chicago, 5735 South Ellis Avenue, Chicago, Illinois 60637
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26
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Duguid EM, Rice PA, He C. The structure of the human AGT protein bound to DNA and its implications for damage detection. J Mol Biol 2005; 350:657-66. [PMID: 15964013 DOI: 10.1016/j.jmb.2005.05.028] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2005] [Revised: 05/04/2005] [Accepted: 05/14/2005] [Indexed: 11/23/2022]
Abstract
O6-Alklyguanine-DNA alkyltransferase (AGT) is an important DNA repair protein that protects cells from mutagenesis and toxicity arising from alkylating agents. We present an X-ray crystal structure of the wild-type human protein (hAGT) bound to double-stranded DNA with a chemically modified cytosine base. The protein binds at two different sites: one at the modified base, and the other across a sticky-ended DNA junction. The protein molecule that binds the modified cytosine base flips the base and recognizes it in its active site. The one that binds ends of neighboring DNA molecules partially flips an overhanging thymine base. This base is not inserted into the active-site pocket of the protein. These two different hAGT/DNA interactions observed in the structure suggest that hAGT may not detect DNA lesions by searching for the adduct itself, but rather for weakened and/or distorted base-pairs caused by base damage in the duplex DNA. We propose that hAGT imposes a strain on the DNA duplex and searches for DNA regions where the native structure is destabilized. The structure provides implications for pyrimidine recognition, improved inhibitor design, and a possible protein/protein interaction patch on hAGT.
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Affiliation(s)
- Erica M Duguid
- Department of Chemistry, 5735 South Ellis Avenue, The University of Chicago, Chicago, IL 60637, USA
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27
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Hickman MJ, Samson LD. Apoptotic signaling in response to a single type of DNA lesion, O(6)-methylguanine. Mol Cell 2004; 14:105-16. [PMID: 15068807 DOI: 10.1016/s1097-2765(04)00162-5] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2003] [Revised: 02/16/2004] [Accepted: 02/23/2004] [Indexed: 11/30/2022]
Abstract
Until now, it has been difficult to establish exactly how a specific DNA lesion signals apoptosis because each DNA damaging agent produces a collection of distinct DNA lesions and produces damage in RNA, protein, and lipids. We have developed a system in human cells that focuses on the response to a single type of DNA lesion, namely O(6)-methylguanine (O(6)MeG). We dissect the signaling pathways involved in O(6)MeG-induced apoptosis, a response dependent on the MutSalpha heterodimer that is normally involved in DNA mismatch repair. O(6)MeG triggers robust activation of caspases associated with both death receptor- and mitochondrial-mediated apoptosis. Despite this, O(6)MeG/MutSalpha-triggered apoptosis is only partly dependent on caspase activation; moreover, it is mediated solely by mitochondrial signaling and not at all by death receptor signaling. Finally, while Bcl-2 and Bcl-x(L), negative regulators of mitochondrial-regulated apoptosis, could effectively block O(6)MeG/MutSalpha-dependent apoptosis, they were unable to prevent the cells from ultimately dying.
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Affiliation(s)
- Mark J Hickman
- Department of Biological Engineering and Center for Environmental Health Sciences, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
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28
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Duguid EM, Mishina Y, He C. How Do DNA Repair Proteins Locate Potential Base Lesions? A Chemical Crosslinking Method to Investigate O6-Alkylguanine-DNA Alkyltransferases. ACTA ACUST UNITED AC 2003; 10:827-35. [PMID: 14522053 DOI: 10.1016/j.chembiol.2003.08.007] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
O(6)-alkylguanine-DNA alkyltransferases directly reverse the alkylation on the O(6) position of guanine in DNA. This group of proteins has been proposed to repair the damaged base in an extrahelical manner; however, the detailed mechanism is not understood. Here we applied a chemical disulfide crosslinking method to probe the damage-searching mechanism of two O(6)-alkylguanine-DNA alkyltransferases, the Escherichia coli C-Ada and the human AGT. Crosslinking reactions with different efficiency occur between the reactive Cys residues of both proteins and a modified cytosine bearing a thiol tether in various DNA probes. Our results indicate that it is not necessary for these proteins to actively flip out every base to find damage. Instead they can locate potential lesions by simply capturing a lesioned base that is transiently extrahelical or sensing the unstable nature of a damaged base pair.
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Affiliation(s)
- Erica M Duguid
- Department of Chemistry, University of Chicago, 5735 South Ellis Avenue, Chicago, IL 60637, USA
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29
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Rajnakova A, Moochhala S, Goh PM, Ngoi S. Expression of nitric oxide synthase, cyclooxygenase, and p53 in different stages of human gastric cancer. Cancer Lett 2001; 172:177-85. [PMID: 11566494 DOI: 10.1016/s0304-3835(01)00645-0] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The present study evaluated the significance of nitric oxide synthase (NOS), cyclooxygenase (COX) expression and p53 status in 55 patients with gastric adenocarcinoma and relationship of these molecular markers to tumor characteristics and metastatic potential. Immunohistochemical technique was used to identify the cellular location and distribution of the enzymes in the specific cells of gastric tumors. In gastric cancer tissue, the expression of inducible enzymes, iNOS and COX-2, increased significantly with increasing tumor stage (P=0.015, P=0.001, respectively), size (P=0.025, P=0.001, respectively) and the presence of metastases (P=0.002, P=0.015, respectively). The expression of constitutive enzymes, ecNOS and COX-1, followed the opposite pattern. COX-1 was significantly reduced in advanced gastric tumors (P=0.007) and tumors larger than 5 cm (P=0.007). Reduced expression of ecNOS was also observed in advanced gastric tumors; however, this did not reach statistical significance. 53% of gastric tumors showed accumulation of p53. This was significantly higher in advanced tumors (P=0.004), larger than 5 cm (P=0.015) with metastases (P<0.001). Gastric tumors positive for accumulation of p53 had significantly stronger expression of iNOS (P=0.018) and COX-2 (P=0.01) enzymes than tumors negative for this nucleophosphoprotein. We conclude, that tumor-associated nitric oxide production, as well as COX-2 overexpression, may promote gastric cancer progression by providing a selective growth advantage to tumor cells with non-functioning p53.
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Affiliation(s)
- A Rajnakova
- Department of Medicine, National University of Singapore, 5 Lower Kent Ridge Road, 119074, Singapore, Singapore.
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30
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Takagi M, Kai Y, Imanaka T. Methylguanine methyltransferase from Thermococcus kodakaraensis KOD1. Methods Enzymol 2001; 334:239-48. [PMID: 11398466 DOI: 10.1016/s0076-6879(01)34472-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/20/2023]
Affiliation(s)
- M Takagi
- Department of Biotechnology, Osaka University Graduate School of Engineering, Osaka 565-0871, Japan
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31
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Walter RB, Sung HM, Intano GW, Walter CA. Characterization of O(6)-methylguanine-DNA-methyltransferase (O(6)-MGMT) activity in Xiphophorus fishes. Mutat Res 2001; 493:11-22. [PMID: 11516711 DOI: 10.1016/s1383-5718(01)00169-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
We utilized a custom-synthesized double-strand oligonucleotide containing a single O(6)-methylguanine (O(6)-MG) residue within a restriction endonuclease recognition site to determine O(6)-methylguanine-DNA-methyltransferase (O(6)-MGMT) activity in various tissue extracts prepared from Xiphophorus fish. The results suggest Xiphophorus fish O(6)-MGMT activity has many of the same characteristics as Escherichia coli and mammalian O(6)-MGMT's including rapid reaction kinetics consistent with stoichiometric removal of methyl groups, but exhibits a temperature optimum of 23 degrees C. Results from protein extract activity assays indicate O(6)-MGMT activity patterns among four Xiphophorus tissues followed the order: brain> or =testes>gill> or =liver. In mammals, O(6)-MGMT activity is high in liver, while activity in brain is minimal (i.e. approximately 9% of liver); however, we report that in the Xiphophorus fishes examined, brain tissue extracts exhibited much higher (approximately six-fold) O(6)-MGMT activity levels than liver. Comparison of O(6)-MGMT activity between Xiphophorus species employed in tumor induction experiments did not indicate significant differences in ability to clear the pre-mutagenic O(6)-MG from the oligonucleotide substrate.
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Affiliation(s)
- R B Walter
- Department of Chemistry and Biochemistry, Southwest Texas State University, 419 Centennial Hall, 601 University Drive, San Marcos, TX 78666, USA.
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32
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Kanugula S, Pegg AE. Novel DNA repair alkyltransferase from Caenorhabditis elegans. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2001; 38:235-243. [PMID: 11746760 DOI: 10.1002/em.1077] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
O6-alkylguanine DNA-alkyltransferase (AGT) is a widely distributed DNA repair protein that protects living organisms from endogenous and exogenous alkylation damage to DNA at the O6-position of guanine. The search of the C. elegans genome database for an AGT protein revealed the presence of a protein (cAGT-2) with some similarity to known AGTs in addition to the easily recognized cAGT-1 protein. The predicted protein sequence of cAGT-2 contains the amino acid sequence -ProCysHisPro- at the presumed active site of the protein, whereas all other known AGTs have -ProCysHisArg-. A truncated version of the cAGT-2 protein was expressed in E. coli. This purified recombinant protein was able to repair O6-methylguanine and O4-methylthymine adducts in DNA in vitro and also reacted with the bulky benzyl adduct in O6-benzylguanine. This fragment of cAGT-2 (104 amino acids) is the smallest protein possessing AGT activity yet described. The full-length cAGT-2 protein (274 amino acids) totally lacks the N-terminal domain present in all other known AGTs but has a long C-terminal extension that has significant homology to histone 1C. Expression of cAGT-2 in an E. coli strain lacking endogenous AGT activity provided modest but statistically significant resistance to the toxicity of N-methyl-N'-nitro-N-nitrosoguanidine, confirming that cAGT-2 is an alkyltransferase.
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Affiliation(s)
- S Kanugula
- Department of Cellular and Molecular Physiology, Pennsylvania State University College of Medicine, The Milton S. Hershey Medical Center, Hershey, Pennsylvania 17033-0850, USA
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33
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Frosina G. Overexpression of enzymes that repair endogenous damage to DNA. EUROPEAN JOURNAL OF BIOCHEMISTRY 2000; 267:2135-49. [PMID: 10759836 DOI: 10.1046/j.1432-1327.2000.01266.x] [Citation(s) in RCA: 82] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
A significant contribution to human mutagenesis and carcinogenesis may come from DNA damage of endogenous, rather than exogenous, origin. Efficient repair mechanisms have evolved to cope with this. The main repair pathway involved in repair of endogenous damage is DNA base excision repair. In addition, an important contribution is given by O6-alkylguanine DNA alkyltranferase, that repairs specifically the miscoding base O6-alkylguanine. In recent years, several attempts have been carried out to enhance the efficiency of repair of endogenous damage by overexpressing in mammalian cells single enzymatic activities. In some cases (e.g. O6-alkylguanine DNA alkyltransferase or yeast AP endonuclease) this approach has been successful in improving cellular protection from endogenous and exogenous mutagens, while overexpression of other enzymatic activities (e.g. alkyl N-purine glycosylase or DNA polymerase beta) were detrimental and even produced a genome instability phenotype. The reasons for these different outcomes are analyzed and alternative enzymatic activities whose overexpression may improve the efficiency of repair of endogenous damage in human cells are proposed.
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Affiliation(s)
- G Frosina
- DNA Repair Unit, Mutagenesis laboratory, Istituto Nazionale Ricerca Cancro, Genova, Italy.
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Abstract
The role of nitric oxide (NO) in tumorigenesis is multifactorial. NO can participate in the complicated process of carcinogenesis by mediating DNA damage in early phases of tumorigenesis, as well as support tumor progression through the induction of angiogenesis and suppression of the immune response. This paper addresses the effects of NO on transcriptional regulation following DNA damage and cyclooxygenase expression in the multistep process of tumorigenesis.
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Affiliation(s)
- S Moochhala
- Applied Physiology Branch, Defence Medical Research Institute, National University of Singapore, Singapore.
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35
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Hickman MJ, Samson LD. Role of DNA mismatch repair and p53 in signaling induction of apoptosis by alkylating agents. Proc Natl Acad Sci U S A 1999; 96:10764-9. [PMID: 10485900 PMCID: PMC17957 DOI: 10.1073/pnas.96.19.10764] [Citation(s) in RCA: 219] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
All cells are unavoidably exposed to chemicals that can alkylate DNA to form genotoxic damage. Among the various DNA lesions formed, O(6)-alkylguanine lesions can be highly cytotoxic, and we recently demonstrated that O(6)-methylguanine (O(6)MeG) and O(6)-chloroethylguanine (O(6)CEG) specifically initiate apoptosis in hamster cells. Here we show, in both hamster and human cells, that the MutSalpha branch of the DNA mismatch repair pathway (but not the MutSbeta branch) is absolutely required for signaling the initiation of apoptosis in response to O(6)MeGs and is partially required for signaling apoptosis in response to O(6)CEGs. Further, O(6)MeG lesions signal the stabilization of the p53 tumor suppressor, and such signaling is also MutSalpha-dependent. Despite this, MutSalpha-dependent apoptosis can be executed in a p53-independent manner. DNA mismatch repair status did not influence the response of cells to other inducers of p53 and apoptosis. Thus, it appears that mismatch repair status, rather than p53 status, is a strong indicator of the susceptibility of cells to alkylation-induced apoptosis. This experimental system will allow dissection of the signal transduction events that couple a specific type of DNA base lesion with the final outcome of apoptotic cell death.
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Affiliation(s)
- M J Hickman
- Department of Cancer Cell Biology, Toxicology Division, Harvard School of Public Health, 665 Huntington Avenue, Boston, MA 02115, USA
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36
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Kooistra R, Zonneveld JB, Watson AJ, Margison GP, Lohman PH, Pastink A. Identification and characterisation of the Drosophila melanogaster O6-alkylguanine-DNA alkyltransferase cDNA. Nucleic Acids Res 1999; 27:1795-801. [PMID: 10101186 PMCID: PMC148386 DOI: 10.1093/nar/27.8.1795] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The protein O 6-alkylguanine-DNA alkyltransferase(alkyltransferase) is involved in the repair of O 6-alkylguanine and O 4-alkylthymine in DNA and plays an important role in most organisms in attenuating the cytotoxic and mutagenic effects of certain classes of alkylating agents. A genomic clone encompassing the Drosophila melanogaster alkyltransferase gene ( DmAGT ) was identified on the basis of sequence homology with corresponding genes in Saccharomyces cerevisiae and man. The DmAGT gene is located at position 84A on the third chromosome. The nucleotide sequence of DmAGT cDNA revealed an open reading frame encoding 194 amino acids. The MNNG-hypersensitive phenotype of alkyltransferase-deficient bacteria was rescued by expression of the DmAGT cDNA. Furthermore, alkyltransferase activity was identified in crude extracts of Escherichia coli harbouring DmAGT cDNA and this activity was inhibited by preincubation of the extract with an oligonucleotide containing a single O6-methylguanine lesion. Similar to E.coli Ogt and yeast alkyltransferase but in contrast to the human alkyltransferase, the Drosophila alkyltransferase is resistant to inactivation by O 6-benzylguanine. In an E.coli lac Z reversion assay, expression of DmAGT efficiently suppressed MNNG-induced G:C-->A:T as well as A:T-->G:C transition mutations in vivo. These results demonstrate the presence of an alkyltransferase specific for the repair of O 6-methylguanine and O 4-methylthymine in Drosophila.
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Affiliation(s)
- R Kooistra
- MGC Department of Radiation Genetics and Chemical Mutagenesis, Leiden University Medical Centre, Wassenaarseweg 72, 2333 AL Leiden, The Netherlands
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37
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Paalman SR, Sung C, Clarke ND. Specificity of DNA repair methyltransferases determined by competitive inactivation with oligonucleotide substrates: evidence that Escherichia coli Ada repairs O6-methylguanine and O4-methylthymine with similar efficiency. Biochemistry 1997; 36:11118-24. [PMID: 9287154 DOI: 10.1021/bi970740t] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
DNA repair methyltransferases (MTases) are stoichiometric acceptor molecules that are irreversibly inactivated in the course of removing a methyl group from O6-methylguanine (meG)-DNA or O4-methylthymine (meT)-DNA. A new assay has been developed to determine the relative efficiency of repair of meG and meT. The assay is based on the deprotection of methylated restriction sites in synthetic oligonucleotides and can be used to measure meG repair or meT repair directly. More importantly, relative repair efficiencies can be measured in competition experiments, using each of the methylated oligomers in turn as an inhibitor of repair for the other. Relative repair rates are determined by numerical solution of the coupled rate equations that describe this competition to the experimental data. We find that the human MTase repairs meT about 35-fold less well than meG, qualitatively similar to earlier studies. Contrary to previous reports, however, we find that Escherichia coli Ada repairs meG and meT with nearly equal efficiency. This finding, in conjunction with other recent reports, may indicate that low meT repair is a relatively unusual characteristic of the human homolog.
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Affiliation(s)
- S R Paalman
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins School of Medicine, Baltimore, Maryland 21205, USA
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38
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Miyakawa H, Liu J, Noguchi O, Marumo F, Sato C. Effect of alcohol drinking on gene expression of hepatic O6-methylguanine DNA methyltransferase in chronic liver diseases. Alcohol Clin Exp Res 1997. [PMID: 8986226 DOI: 10.1111/j.1530-0277.1996.tb01796.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
O6-methylguanine DNA methyltransferase (MGMT) is a repair protein that transfers methyl groups from O6-methylguanine to a cysteine acceptor in its own molecule, and restores DNA to its undamaged state. If left unrepaired, O6-methylguanine can pair with either a thymine or a cytosine, causing a C-G to T-A transition, which is considered to be one of the molecular mechanisms of both mutagenesis and carcinogenesis. The expression of MGMT mRNA in liver tissue was quantitatively assessed by the competitive reverse transcription-polymerase chain reaction method in patients with chronic liver diseases with or without alcohol drinking. MGMT mRNA expression was 1.4 +/- 0.9 pg/micrograms RNA in control livers. Its expression in chronic hepatitis was 3.8 +/- 0.7 in alcoholics and 2.7 +/- 0.8 in nonalcoholics, which were not statistically different. MGMT mRNA expression in liver cirrhosis was significantly low, compared with that in chronic hepatitis, and 0.8 +/- 0.3 in alcoholics and 0.5 +/- 0.1 in nonalcoholics, which also were not significantly different. The present study shows that MGMT mRNA was not decreased in patients with chronic liver diseases with alcohol drinking, compared with those without alcohol drinking.
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Affiliation(s)
- H Miyakawa
- Department of Gastroenterology, Ohme City General Hospital, Tokyo, Japan
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Laval F, Wink DA, Laval J. A discussion of mechanisms of NO genotoxicity: implication of inhibition of DNA repair proteins. Rev Physiol Biochem Pharmacol 1997; 131:175-91. [PMID: 9204692 DOI: 10.1007/3-540-61992-5_8] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Affiliation(s)
- F Laval
- U347 INSERM, Rue du Général Leclerc, Le Kremlin-Bicêtre, France
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40
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Miyakawa H, Liu J, Noguchi O, Marumo F, Sato C. Effect of Alcohol Drinking on Gene Expression of Hepatic O6-Methylguanine DNA Methyltransferase in Chronic Liver Diseases. Alcohol Clin Exp Res 1996. [DOI: 10.1111/j.1530-0277.1996.tb01161.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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41
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Abstract
Our genetic information is constantly challenged by exposure to endogenous and exogenous DNA-damaging agents, by DNA polymerase errors, and thereby inherent instability of the DNA molecule itself. The integrity of our genetic information is maintained by numerous DNA repair pathways, and the importance of these pathways is underscored by their remarkable structural and functional conservation across the evolutionary spectrum. Because of the highly conserved nature of DNA repair, the enzymes involved in this crucial function are often able to function in heterologous cells; as an example, the E. coli Ada DNA repair methyltransferase functions efficiently in yeast, in cultured rodent and human cells, in transgenic mice, and in ex vivo-modified mouse bone marrow cells. The heterologous expression of DNA repair functions has not only been used as a powerful cloning strategy, but also for the exploration of the biological and biochemical features of numerous enzymes involved in DNA repair pathways. In this review we highlight examples where the expression of DNA repair enzymes in heterologous cells was used to address fundamental questions about DNA repair processes in many different organisms.
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Affiliation(s)
- A Memisoglu
- Harvard School of Public Health, Boston, MA 02115, USA
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42
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Iwakuma T, Shiraishi A, Fukuhara M, Kawate H, Sekiguchi M. Organization and expression of the mouse gene for DNA repair methyltransferase. DNA Cell Biol 1996; 15:863-72. [PMID: 8892758 DOI: 10.1089/dna.1996.15.863] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
06-Methylguanine-DNA methyltransferase (MGMT) is present in various organisms, from bacteria to human cells, and plays an important role in preventing mutations caused by alkylating substances. To understand better the regulatory mechanism involved in the expression of the gene and to construct a mouse model to investigate roles of the enzyme in carcinogenesis, the genomic sequence for mouse methyltransferase was isolated and characterized. The gene consists of 5 exons and spans over 180 kb, whereas mRNA for the enzyme was less than 1 kb. The promoter region for the gene is GC-rich, contains many Sp1 recognition sequences and lacks typical TATA and CCAAT boxes. Primer extension and S1 mapping revealed the existence of multiple transcription initiation sites, among which a major site was defined as +1. The putative promoter region was placed upstream of the chloramphenicol acetyltransferase (CAT) reporter gene and the construct was introduced into mouse NIH-3T3 cells. Deletion analyses revealed that a sequence from -262 to + 56 carries the basic promoter activity. In addition, an adjacent region, spanning from +56 to +95, carries an E2F-like element that greatly stimulates the frequency of transcription. Alteration of TTTTGGGGC to TTAACGGGC considerably reduced the activity.
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Affiliation(s)
- T Iwakuma
- Department of Biochemistry, Medical Institute of Bioregulation, Kyushu University, Fukuoka, Japan
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43
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Sekiguchi M, Nakabeppu Y, Sakumi K, Tuzuki T. DNA-repair methyltransferase as a molecular device for preventing mutation and cancer. J Cancer Res Clin Oncol 1996; 122:199-206. [PMID: 8601571 DOI: 10.1007/bf01209646] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Alkylation of DNA at the 0(6) position of guanine is regarded as one o f the most critical events leading to induction of mutations and cancers in organisms. Once 0(6)-methylguanine is formed, it can pair with thymine during DNA replication, the result being a conversion of the guanine.cytosine to an adenine.thymine pair in DNA, and such mutations are often found in tumors induced by alkylating agents. To counteract such effects, organisms possess a mechanism to repair 0(6)-methylguanine in DNA. An enzyme, 0(6)-methylguanine-DNA methyltransferase, is present in various organism, from bacteria to human cells, and appears to be responsible for preventing the occurrence of such mutations. The enzyme transfers methyl groups from 0(6)-methylguanine and other methylated moieties of the DNA to its own molecule, thereby repairing DNA lesions in a single-step reaction. To elucidate the role of methyltransferase in preventing cancers, animal models with altered levels of enzyme activity were generated. Transgenic mice carrying the foreign methyltransferase gene with functional promoters had higher levels of methyltransferase activity and showed a decreased susceptibility to N-nitroso compounds in regard to liver carcinogenesis. Mouse lines deficient in the methyltransferase gene, which were established by gene targeting, exhibited an extraordinarily high sensitivity to an alkylating carcinogen.
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Affiliation(s)
- M Sekiguchi
- Medical Institute of Bioregulation, Kyushu University, Fukuoka, Japan
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44
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Wink DA, Hanbauer I, Grisham MB, Laval F, Nims RW, Laval J, Cook J, Pacelli R, Liebmann J, Krishna M, Ford PC, Mitchell JB. Chemical biology of nitric oxide: regulation and protective and toxic mechanisms. CURRENT TOPICS IN CELLULAR REGULATION 1996; 34:159-87. [PMID: 8646847 DOI: 10.1016/s0070-2137(96)80006-9] [Citation(s) in RCA: 209] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Affiliation(s)
- D A Wink
- Chemistry Section, National Cancer Institute, Frederick Cancer Research and Development Center, MD 21702, USA
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45
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Pegg AE, Dolan ME, Moschel RC. Structure, function, and inhibition of O6-alkylguanine-DNA alkyltransferase. PROGRESS IN NUCLEIC ACID RESEARCH AND MOLECULAR BIOLOGY 1995; 51:167-223. [PMID: 7659775 DOI: 10.1016/s0079-6603(08)60879-x] [Citation(s) in RCA: 341] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- A E Pegg
- Department of Cellular and Molecular Physiology, Pennsylvania State University College of Medicine, Hershey 17033, USA
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