1
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Conlon S, Khuu C, Trasviña-Arenas CH, Xia T, Hamm ML, Raetz AG, David SS. Cellular Repair of Synthetic Analogs of Oxidative DNA Damage Reveals a Key Structure-Activity Relationship of the Cancer-Associated MUTYH DNA Repair Glycosylase. ACS CENTRAL SCIENCE 2024; 10:291-301. [PMID: 38435525 PMCID: PMC10906249 DOI: 10.1021/acscentsci.3c00784] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/28/2023] [Revised: 12/22/2023] [Accepted: 12/26/2023] [Indexed: 03/05/2024]
Abstract
The base excision repair glycosylase MUTYH prevents mutations associated with the oxidatively damaged base, 8-oxo-7,8-dihydroguanine (OG), by removing undamaged misincorporated adenines from OG:A mispairs. Defects in OG:A repair in individuals with inherited MUTYH variants are correlated with the colorectal cancer predisposition syndrome known as MUTYH-associated polyposis (MAP). Herein, we reveal key structural features of OG required for efficient repair by human MUTYH using structure-activity relationships (SAR). We developed a GFP-based plasmid reporter assay to define SAR with synthetically generated OG analogs in human cell lines. Cellular repair results were compared with kinetic parameters measured by adenine glycosylase assays in vitro. Our results show substrates lacking the 2-amino group of OG, such as 8OI:A (8OI = 8-oxoinosine), are not repaired in cells, despite being excellent substrates in in vitro adenine glycosylase assays, new evidence that the search and detection steps are critical factors in cellular MUTYH repair functionality. Surprisingly, modification of the O8/N7H of OG, which is the distinguishing feature of OG relative to G, was tolerated in both MUTYH-mediated cellular repair and in vitro adenine glycosylase activity. The lack of sensitivity to alterations at the O8/N7H in the SAR of MUTYH substrates is distinct from previous work with bacterial MutY, indicating that the human enzyme is much less stringent in its lesion verification. Our results imply that the human protein relies almost exclusively on detection of the unique major groove position of the 2-amino group of OG within OGsyn:Aanti mispairs to select contextually incorrect adenines for excision and thereby thwart mutagenesis. These results predict that MUTYH variants that exhibit deficiencies in OG:A detection will be severely compromised in a cellular setting. Moreover, the reliance of MUTYH on the interaction with the OG 2-amino group suggests that disrupting this interaction with small molecules may provide a strategy to develop potent and selective MUTYH inhibitors.
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Affiliation(s)
- Savannah
G. Conlon
- Department
of Chemistry, University of California,
Davis, One Shields Avenue, Davis, California 95616, United States
- Graduate
Program in Chemistry and Chemical Biology, University of California, Davis, One Shields Avenue, Davis, California 95616, United States
| | - Cindy Khuu
- Department
of Chemistry, University of California,
Davis, One Shields Avenue, Davis, California 95616, United States
- Biochemistry,
Molecular, Cellular and Developmental Biology Graduate Group, University of California, Davis, One Shields Avenue, Davis, California 95616, United States
| | - Carlos H. Trasviña-Arenas
- Department
of Chemistry, University of California,
Davis, One Shields Avenue, Davis, California 95616, United States
| | - Tian Xia
- Department
of Chemistry, University of California,
Davis, One Shields Avenue, Davis, California 95616, United States
- Graduate
Program in Chemistry and Chemical Biology, University of California, Davis, One Shields Avenue, Davis, California 95616, United States
| | - Michelle L. Hamm
- Department
of Chemistry, University of Richmond, 410 Westhampton Way, Richmond, Virginia 23173, United States
| | - Alan G. Raetz
- Department
of Chemistry, University of California,
Davis, One Shields Avenue, Davis, California 95616, United States
- Biochemistry,
Molecular, Cellular and Developmental Biology Graduate Group, University of California, Davis, One Shields Avenue, Davis, California 95616, United States
| | - Sheila S. David
- Department
of Chemistry, University of California,
Davis, One Shields Avenue, Davis, California 95616, United States
- Graduate
Program in Chemistry and Chemical Biology, University of California, Davis, One Shields Avenue, Davis, California 95616, United States
- Biochemistry,
Molecular, Cellular and Developmental Biology Graduate Group, University of California, Davis, One Shields Avenue, Davis, California 95616, United States
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2
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Li J, Hu Z, Liu D, Wang P. Mass spectrometry-based assays for assessing replicative bypass and repair of DNA alkylation in cells. RSC Adv 2023; 13:15490-15497. [PMID: 37223415 PMCID: PMC10201546 DOI: 10.1039/d2ra08340j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2022] [Accepted: 05/15/2023] [Indexed: 05/25/2023] Open
Abstract
Endogenous metabolism and environmental exposure can give rise to DNA alkylation, which can elicit deleterious biological consequences. In the search for reliable and quantitative analytical methods to elucidate the impact of DNA alkylation on the flow of genetic information, mass spectrometry (MS) has attracted increasing attention, owing to its unambiguous determination of molecular mass. The MS-based assays obviate conventional colony-picking methods and Sanger sequencing procedures, and retained the high sensitivity of postlabeling methods. With the help of the CRISPR/Cas9 gene editing method, MS-based assays showed high potential in studying individual functions of repair proteins and translesion synthesis (TLS) polymerases in DNA replication. In this mini-review, we have summarized the development of MS-based competitive and replicative adduct bypass (CRAB) assays and their recent applications in assessing the impact of alkylation on DNA replication. With further development of MS instruments for high resolving power and high throughput, these assays should be generally applicable and efficient in quantitative measurement of the biological consequences and repair of other DNA lesions.
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Affiliation(s)
- Jiaxian Li
- Institute of Surface Analysis and Chemical Biology, University of Jinan Jinan Shandong 250022 P. R. China
| | - Zhihai Hu
- Institute of Surface Analysis and Chemical Biology, University of Jinan Jinan Shandong 250022 P. R. China
| | - Dandan Liu
- Institute of Surface Analysis and Chemical Biology, University of Jinan Jinan Shandong 250022 P. R. China
| | - Pengcheng Wang
- Institute of Surface Analysis and Chemical Biology, University of Jinan Jinan Shandong 250022 P. R. China
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3
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Teng JY, Yang DP, Tang C, Fang HS, Sun HY, Xiang YN, Li XM, Yang F, Xia RX, Fan F, Liu J, Yu J, Hu JC, Li BS, Li H, Meng FL, Duan CW, Zhou BBS. Targeting DNA polymerase β elicits synthetic lethality with mismatch repair deficiency in acute lymphoblastic leukemia. Leukemia 2023:10.1038/s41375-023-01902-3. [PMID: 37095208 DOI: 10.1038/s41375-023-01902-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2022] [Revised: 03/26/2023] [Accepted: 04/12/2023] [Indexed: 04/26/2023]
Abstract
Mismatch repair (MMR) deficiency has been linked to thiopurine resistance and hypermutation in relapsed acute lymphoblastic leukemia (ALL). However, the repair mechanism of thiopurine-induced DNA damage in the absence of MMR remains unclear. Here, we provide evidence that DNA polymerase β (POLB) of base excision repair (BER) pathway plays a critical role in the survival and thiopurine resistance of MMR-deficient ALL cells. In these aggressive resistant ALL cells, POLB depletion and its inhibitor oleanolic acid (OA) treatment result in synthetic lethality with MMR deficiency through increased cellular apurinic/apyrimidinic (AP) sites, DNA strand breaks and apoptosis. POLB depletion increases thiopurine sensitivities of resistant cells, and OA synergizes with thiopurine to kill these cells in ALL cell lines, patient-derived xenograft (PDX) cells and xenograft mouse models. Our findings suggest BER and POLB's roles in the process of repairing thiopurine-induced DNA damage in MMR-deficient ALL cells, and implicate their potentials as therapeutic targets against aggressive ALL progression.
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Affiliation(s)
- Ji-Yuan Teng
- Key Laboratory of Pediatric Hematology and Oncology Ministry of Health, Pediatric Translational Medicine Institute, Shanghai Children's Medical Center, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Ding-Peng Yang
- Key Laboratory of Pediatric Hematology and Oncology Ministry of Health, Pediatric Translational Medicine Institute, Shanghai Children's Medical Center, School of Medicine, Shanghai Jiao Tong University, Shanghai, China.
| | - Chao Tang
- Key Laboratory of Pediatric Hematology and Oncology Ministry of Health, Pediatric Translational Medicine Institute, Shanghai Children's Medical Center, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Hou-Shun Fang
- Key Laboratory of Pediatric Hematology and Oncology Ministry of Health, Pediatric Translational Medicine Institute, Shanghai Children's Medical Center, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Hui-Ying Sun
- Key Laboratory of Pediatric Hematology and Oncology Ministry of Health, Pediatric Translational Medicine Institute, Shanghai Children's Medical Center, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Yue-Ning Xiang
- Shanghai Key Laboratory of Medical Epigenetics, International Co-laboratory of Medical Epigenetics and Metabolism, Institutes of Biomedical Sciences, Fudan University, Shanghai, China
| | - Xiao-Meng Li
- Key Laboratory of Pediatric Hematology and Oncology Ministry of Health, Pediatric Translational Medicine Institute, Shanghai Children's Medical Center, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Fan Yang
- Key Laboratory of Pediatric Hematology and Oncology Ministry of Health, Pediatric Translational Medicine Institute, Shanghai Children's Medical Center, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Rui-Xue Xia
- Key Laboratory of Pediatric Hematology and Oncology Ministry of Health, Pediatric Translational Medicine Institute, Shanghai Children's Medical Center, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Fu Fan
- Key Laboratory of Pediatric Hematology and Oncology Ministry of Health, Pediatric Translational Medicine Institute, Shanghai Children's Medical Center, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Jingjing Liu
- Department of Computational Biology, St Jude Children's Research Hospital, Memphis, TN, USA
| | - Jiyang Yu
- Department of Computational Biology, St Jude Children's Research Hospital, Memphis, TN, USA
| | - Jin-Chuan Hu
- Shanghai Key Laboratory of Medical Epigenetics, International Co-laboratory of Medical Epigenetics and Metabolism, Institutes of Biomedical Sciences, Fudan University, Shanghai, China
| | - Ben-Shang Li
- Key Laboratory of Pediatric Hematology and Oncology Ministry of Health, Pediatric Translational Medicine Institute, Shanghai Children's Medical Center, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Hui Li
- Key Laboratory of Pediatric Hematology and Oncology Ministry of Health, Pediatric Translational Medicine Institute, Shanghai Children's Medical Center, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Fei-Long Meng
- State Key Laboratory of Molecular Biology, Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, Shanghai, China
| | - Cai-Wen Duan
- Key Laboratory of Pediatric Hematology and Oncology Ministry of Health, Pediatric Translational Medicine Institute, Shanghai Children's Medical Center, School of Medicine, Shanghai Jiao Tong University, Shanghai, China.
| | - Bin-Bing S Zhou
- Key Laboratory of Pediatric Hematology and Oncology Ministry of Health, Pediatric Translational Medicine Institute, Shanghai Children's Medical Center, School of Medicine, Shanghai Jiao Tong University, Shanghai, China.
- Department of Pharmacology and Chemical Biology, School of Basic Medicine and Collaborative Innovation Center for Translational Medicine, School of Medicine, Shanghai Jiao Tong University, Shanghai, China.
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4
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Kobets T, Duan JD, Vock E, Deschl U, Williams GM. Evaluation of Pharmaceuticals for DNA Damage in the Chicken Egg Genotoxicity Assay (CEGA). Int J Toxicol 2022; 41:297-311. [PMID: 35658642 DOI: 10.1177/10915818221093583] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
DNA damage is an established initiating event in the mutagenicity and carcinogenicity of genotoxic chemicals. Accordingly, assessment of this endpoint is critical for chemicals which are being developed for use in humans. To assess the ability of the Chicken Egg Genotoxicity Assay (CEGA) to detect genotoxic pharmaceuticals, a set of 23 compounds with different pharmacological and reported genotoxic effects was tested for the potential to produce nuclear DNA adducts and strand breaks in the embryo-fetal livers using the 32P-nucleotide postlabeling (NPL) and comet assays, respectively. Due to high toxicity, two aneugens, colchicine and vinblastine, and an autophagy inhibitor, hydroxychloroquine, could not be evaluated. Out of the 20 remaining pharmaceuticals, 10 including estrogen modulators, diethylstilbestrol and tamoxifen, antineoplastics cyclophosphamide, etoposide, and mitomycin C, antifungal griseofulvin, local anesthetics lidocaine and prilocaine, and antihistamines diphenhydramine and doxylamine, yielded clear positive outcomes in at least one of the assays. The antihypertensive vasodilator hydralazine and antineoplastics streptozotocin and teniposide, produced only DNA strand breaks, which were not dose-dependent, and thus, the results with these 3 pharmaceuticals were considered equivocal. No DNA damage was detected for 7 compounds, including the purine antagonist 6-thioguanine, antipyretic analgesics acetaminophen and phenacetin, antibiotic ciprofloxacin, antilipidemic clofibrate, anti-inflammatory ibuprofen, and sedative phenobarbital. However, low solubility of these compounds limited dosages tested in CEGA. Overall, results in CEGA were largely in concordance with the outcomes in other systems in vitro and in vivo, indicating that CEGA provides reliable detection of DNA damaging activity of genotoxic compounds. Further evaluations with a broader set of compounds would support this conclusion.
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Affiliation(s)
- Tetyana Kobets
- Department of Pathology, Immunology and Microbiology, 8137New York Medical College, Valhalla, NY, USA
| | - Jian-Dong Duan
- Department of Pathology, Immunology and Microbiology, 8137New York Medical College, Valhalla, NY, USA
| | - Esther Vock
- Boehringer Ingelheim Pharma GmbH&Co. KG, Biberach an der Riss, Germany
| | - Ulrich Deschl
- Boehringer Ingelheim Pharma GmbH&Co. KG, Biberach an der Riss, Germany
| | - Gary M Williams
- Department of Pathology, Immunology and Microbiology, 8137New York Medical College, Valhalla, NY, USA
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5
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Du H, Wang P, Wu J, He X, Wang Y. The roles of polymerases ν and θ in replicative bypass of O6- and N2-alkyl-2'-deoxyguanosine lesions in human cells. J Biol Chem 2020; 295:4556-4562. [PMID: 32098870 PMCID: PMC7135994 DOI: 10.1074/jbc.ra120.012830] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2020] [Revised: 02/20/2020] [Indexed: 12/28/2022] Open
Abstract
Exogenous and endogenous chemicals can react with DNA to produce DNA lesions that may block DNA replication. Not much is known about the roles of polymerase (Pol) ν and Pol θ in translesion synthesis (TLS) in cells. Here we examined the functions of these two polymerases in bypassing major-groove O6-alkyl-2'-deoxyguanosine (O6-alkyl-dG) and minor-groove N2-alkyl-dG lesions in human cells, where the alkyl groups are ethyl, n-butyl (nBu), and, for O6-alkyl-dG, pyridyloxobutyl. We found that Pol ν and Pol θ promote TLS across major-groove O6-alkyl-dG lesions. O6-alkyl-dG lesions mainly induced G→A mutations that were modulated by the two TLS polymerases and the structures of the alkyl groups. Simultaneous ablation of Pol ν and Pol θ resulted in diminished mutation frequencies for all three O6-alkyl-dG lesions. Depletion of Pol ν alone reduced mutations only for O6-nBu-dG, and sole loss of Pol θ attenuated the mutation rates for O6-nBu-dG and O6-pyridyloxobutyl-dG. Replication across the two N2-alkyl-dG lesions was error-free, and Pol ν and Pol θ were dispensable for their replicative bypass. Together, our results provide critical knowledge about the involvement of Pol ν and Pol θ in bypassing alkylated guanine lesions in human cells.
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Affiliation(s)
- Hua Du
- Department of Chemistry, University of California, Riverside, California 92521-0403
| | - Pengcheng Wang
- Department of Chemistry, University of California, Riverside, California 92521-0403
| | - Jun Wu
- Department of Chemistry, University of California, Riverside, California 92521-0403
| | - Xiaomei He
- Department of Chemistry, University of California, Riverside, California 92521-0403
| | - Yinsheng Wang
- Department of Chemistry, University of California, Riverside, California 92521-0403
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6
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Bayoumy AB, Simsek M, Seinen ML, Mulder CJJ, Ansari A, Peters GJ, De Boer NK. The continuous rediscovery and the benefit-risk ratio of thioguanine, a comprehensive review. Expert Opin Drug Metab Toxicol 2020; 16:111-123. [PMID: 32090622 DOI: 10.1080/17425255.2020.1719996] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Introduction: In the 1950s, thioguanine (TG), a thiopurine-derivative together with azathioprine (AZA) and mercaptopurine (MP), were developed for the treatment of childhood leukemia. Over the years, the use of TG was also explored for other, mainly immune-mediated and inflammatory, diseases such as in the field of dermatology and rheumatology (e.g. psoriasis, systemic lupus erythematosus (SLE)) and gastroenterology and hepatology (e.g. inflammatory bowel diseases (IBD), autoimmune hepatitis).Areas covered: This review provides a comprehensive overview of all the clinical uses of TG and describes its mechanism of action, pharmacokinetic/pharmacodynamic features, and toxicity.Expert opinion: Thioguanine has shown beneficial clinical effects in hematological (particularly leukemia) and several immune-inflammatory diseases including psoriasis, SLE, polycythemia vera, Churg-Strauss syndrome, IBD, collagenous sprue, refractory celiac disease, and autoimmune hepatitis. Thioguanine is not effective in treating solid-cancers. At relatively low dosages, i.e. 0.2- 0.3mg/kg/day or 20 mg/day, TG has a favorable risk-benefit ratio and is a safe and effective drug in the long-term treatment of amongst other IBD patients. Thioguanine toxicity, especially myelotoxicity, and hepatotoxicity, including nodular regenerative hyperplasia (NRH) of the liver, is limited when dosed adequately. The occurrence of NRH appears dose-dependent and has been especially described during high dose TG above 40 mg/day.
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Affiliation(s)
- Ahmed B Bayoumy
- Amsterdam UMC, Department of Gastroenterology and Hepatology, VU University Medical Center, Amsterdam, Netherlands
| | - Melek Simsek
- Amsterdam UMC, Department of Gastroenterology and Hepatology, VU University Medical Center, AG&M Research Institute, Amsterdam, Netherlands
| | - Margien L Seinen
- Amsterdam UMC, Department of Gastroenterology and Hepatology, VU University Medical Center, Amsterdam, Netherlands
| | - Chris J J Mulder
- Amsterdam UMC, Department of Gastroenterology and Hepatology, VU University Medical Center, Amsterdam, Netherlands
| | - Azhar Ansari
- Department of Gastroenterology, Surrey and Sussex NHS, Easy Surrey Hospital, Surrey, UK
| | - Godefridus J Peters
- Amsterdam UMC, VU University Medical Center, Laboratory Medical Oncology, Cancer Center Amsterdam, Amsterdam, Netherlands.,Department of Biochemistry, Medical University of Gdansk, Gdansk, Poland
| | - Nanne K De Boer
- Amsterdam UMC, Department of Gastroenterology and Hepatology, VU University Medical Center, AG&M Research Institute, Amsterdam, Netherlands
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7
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Du H, Wang P, Li L, Wang Y. Repair and translesion synthesis of O6-alkylguanine DNA lesions in human cells. J Biol Chem 2019; 294:11144-11153. [PMID: 31167778 PMCID: PMC6643039 DOI: 10.1074/jbc.ra119.009054] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2019] [Revised: 05/31/2019] [Indexed: 12/15/2022] Open
Abstract
O6-alkyl-2'-deoxyguanosine (O6-alkyl-dG) lesions are among the most mutagenic and prevalent alkylated DNA lesions that are associated with cancer initiation and progression. In this study, using a shuttle vector-based strand-specific PCR-competitive replication and adduct bypass assay in conjunction with tandem MS for product identification, we systematically assessed the repair and replicative bypass of a series of O6-alkyl-dG lesions, with the alkyl group being a Me, Et, nPr, iPr, nBu, iBu, or sBu, in several human cell lines. We found that the extent of replication-blocking effects of these lesions is influenced by the size of the alkyl groups situated on the O6 position of the guanine base. We also noted involvement of distinct DNA repair pathways and translesion synthesis polymerases (Pols) in ameliorating the replication blockage effects elicited by the straight- and branched-chain O6-alkyl-dG lesions. We observed that O6-methylguanine DNA methyltransferase is effective in removing the smaller alkyl groups from the O6 position of guanine, whereas repair of the branched-chain lesions relied on nucleotide excision repair. Moreover, these lesions were highly mutagenic during cellular replication and exclusively directed G→A mutations; Pol η and Pol ζ participated in error-prone bypass of the straight-chain lesions, whereas Pol κ preferentially incorporated the correct dCMP opposite the branched-chain lesions. Together, these results uncover key cellular proteins involved in repair and translesion synthesis of O6-alkyl-dG lesions and provide a better understanding of the roles of these types of lesions in the etiology of human cancer.
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Affiliation(s)
- Hua Du
- Department of Chemistry, University of California, Riverside, California 92521-0403
| | - Pengcheng Wang
- Department of Chemistry, University of California, Riverside, California 92521-0403
| | - Lin Li
- Department of Chemistry, University of California, Riverside, California 92521-0403
| | - Yinsheng Wang
- Department of Chemistry, University of California, Riverside, California 92521-0403
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Biological Evaluation of DNA Biomarkers in a Chemically Defined and Site-Specific Manner. TOXICS 2019; 7:toxics7020036. [PMID: 31242562 PMCID: PMC6631660 DOI: 10.3390/toxics7020036] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/25/2019] [Revised: 06/13/2019] [Accepted: 06/14/2019] [Indexed: 02/06/2023]
Abstract
As described elsewhere in this Special Issue on biomarkers, much progress has been made in the detection of modified DNA within organisms at endogenous and exogenous levels of exposure to chemical species, including putative carcinogens and chemotherapeutic agents. Advances in the detection of damaged or unnatural bases have been able to provide correlations to support or refute hypotheses between the level of exposure to oxidative, alkylative, and other stresses, and the resulting DNA damage (lesion formation). However, such stresses can form a plethora of modified nucleobases, and it is therefore difficult to determine the individual contribution of a particular modification to alter a cell's genetic fate, as measured in the form of toxicity by stalled replication past the damage, by subsequent mutation, and by lesion repair. Chemical incorporation of a modification at a specific site within a vector (site-specific mutagenesis) has been a useful tool to deconvolute what types of damage quantified in biologically relevant systems may lead to toxicity and/or mutagenicity, thereby allowing researchers to focus on the most relevant biomarkers that may impact human health. Here, we will review a sampling of the DNA modifications that have been studied by shuttle vector techniques.
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9
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Du H, Wang P, Li L, Amato NJ, Wang Y. Cytotoxic and Mutagenic Properties of C1' and C3'-Epimeric Lesions of 2'-Deoxyribonucleosides in Human Cells. ACS Chem Biol 2019; 14:478-485. [PMID: 30768892 DOI: 10.1021/acschembio.8b01126] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Genomic integrity is constantly challenged by exposure to environmental and endogenous genotoxic agents. Reactive oxygen species (ROS) represent one of the most common types of DNA damaging agents. While ROS mainly induce single-nucleobase lesions, epimeric 2-deoxyribose lesions can also be induced upon hydrogen atom abstraction from the C1', C3', or C4' carbon and the subsequent incorrect chemical repair of the resulting carbon-centered radicals. Herein, we investigated the replicative bypass of the C1'- and C3'-epimeric lesions of the four 2'-deoxynucleosides in HEK293T human embryonic kidney epithelial cells. Our results revealed distinct bypass efficiencies and mutagenic properties of these two types of epimeric lesions. Replicative bypasses of all C1'-epimeric lesions except α-dA are mutagenic in HEK293T cells, and their mutagenic properties are further modulated by translesion synthesis (TLS) DNA polymerases. By contrast, none of the four C3'-epimeric lesions are mutagenic, and the replicative bypass of these lesions is not compromised upon depletion of polymerase η, ι, κ, or ζ. Together, our results provide important new knowledge about the cytotoxic and mutagenic properties of C1' and C3' epimeric lesions, and reveal the roles of TLS DNA polymerases in bypassing these lesions in human cells.
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Affiliation(s)
- Hua Du
- Department of Chemistry, University of California, Riverside, California 92521-0403, United States
| | - Pengcheng Wang
- Department of Chemistry, University of California, Riverside, California 92521-0403, United States
| | - Lin Li
- Department of Chemistry, University of California, Riverside, California 92521-0403, United States
| | - Nicholas J. Amato
- Department of Chemistry, University of California, Riverside, California 92521-0403, United States
| | - Yinsheng Wang
- Department of Chemistry, University of California, Riverside, California 92521-0403, United States
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10
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Fernández-Moreira V, Herrera RP, Gimeno MC. Anticancer properties of gold complexes with biologically relevant ligands. PURE APPL CHEM 2018. [DOI: 10.1515/pac-2018-0901] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Abstract
The present review highlights our findings in the field of antitumor gold complexes bearing biologically relevant molecules, such as DNA-bases, amino acids or peptide derivatives. The results show that very active complexes are achieved with this sort of ligands in several cancer cells. In these compounds the gold center is bonded to these biological molecules mainly through a sulfur atom belonging to a cysteine moiety or to a thionicotinic moiety as result of the functionalization of the biological compounds, and additionally phosphines or N-heterocyclic carbenes are present as ancillary ligands. These robust compounds are stable in the biological media and can be transported to their targets without previous deactivation. The presence of these scaffolds represents a good approach to obtain complexes with improved biologically activity, better transport and biodistribution to cancer cells. Thioredoxin reductase (TrxR) has been shown as the main target for these complexes and in some cases, DNA interactions has been also observed.
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Affiliation(s)
- Vanesa Fernández-Moreira
- Departamento de Química Inorgánica, Instituto de Síntesis Química y Catálisis Homogénea (ISQCH) , CSIC-Universidad de Zaragoza , C/Pedro Cerbuna, No. 12 , E-50009 Zaragoza , Spain
| | - Raquel P. Herrera
- Departamento de Química Orgánica, Laboratorio de Organocatálisis Asimétrica, Instituto de Síntesis Química y Catálisis Homogénea (ISQCH) , CSIC-Universidad de Zaragoza , C/Pedro Cerbuna, No. 12 , E-50009 Zaragoza , Spain
| | - M. Concepción Gimeno
- Departamento de Química Inorgánica, Instituto de Síntesis Química y Catálisis Homogénea (ISQCH) , CSIC-Universidad de Zaragoza , C/Pedro Cerbuna, No. 12 , E-50009 Zaragoza , Spain
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11
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Du H, Leng J, Wang P, Li L, Wang Y. Impact of tobacco-specific nitrosamine-derived DNA adducts on the efficiency and fidelity of DNA replication in human cells. J Biol Chem 2018; 293:11100-11108. [PMID: 29789427 PMCID: PMC6052226 DOI: 10.1074/jbc.ra118.003477] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2018] [Revised: 05/12/2018] [Indexed: 11/06/2022] Open
Abstract
The tobacco-derived nitrosamines 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and N'-nitrosonornicotine (NNN) are known human carcinogens. Following metabolic activation, NNK and NNN can induce a number of DNA lesions, including several 4-(3-pyridyl)-4-oxobut-1-yl (POB) adducts. However, it remains unclear to what extent these lesions affect the efficiency and accuracy of DNA replication and how their replicative bypass is influenced by translesion synthesis (TLS) DNA polymerases. In this study, we investigated the effects of three stable POB DNA adducts (O2-POB-dT, O4-POB-dT, and O6-POB-dG) on the efficiency and fidelity of DNA replication in HEK293T human cells. We found that, when situated in a double-stranded plasmid, O2-POB-dT and O4-POB-dT moderately blocked DNA replication and induced exclusively T→A (∼14.9%) and T→C (∼35.2%) mutations, respectively. On the other hand, O6-POB-dG slightly impeded DNA replication, and this lesion elicited primarily the G→A transition (∼75%) together with a low frequency of the G→T transversion (∼3%). By conducting replication studies in isogenic cells in which specific TLS DNA polymerases (Pols) were deleted by CRISPR-Cas9 genome editing, we observed that multiple TLS Pols, especially Pol η and Pol ζ, are involved in bypassing these lesions. Our findings reveal the cytotoxic and mutagenic properties of specific POB DNA adducts and unravel the roles of several TLS polymerases in the replicative bypass of these adducts in human cells. Together, these results provide important new knowledge about the biological consequences of POB adducts.
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Affiliation(s)
- Hua Du
- From the Department of Chemistry, University of California, Riverside, California 92521-0403
| | - Jiapeng Leng
- From the Department of Chemistry, University of California, Riverside, California 92521-0403
| | - Pengcheng Wang
- From the Department of Chemistry, University of California, Riverside, California 92521-0403
| | - Lin Li
- From the Department of Chemistry, University of California, Riverside, California 92521-0403
| | - Yinsheng Wang
- From the Department of Chemistry, University of California, Riverside, California 92521-0403
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12
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Moore EA, Xu YZ. The effect of S-substitution at the O6-guanine site on the structure and dynamics of a DNA oligomer containing a G:T mismatch. PLoS One 2017; 12:e0184801. [PMID: 28910418 PMCID: PMC5599020 DOI: 10.1371/journal.pone.0184801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2017] [Accepted: 08/31/2017] [Indexed: 11/21/2022] Open
Abstract
The effect of S-substitution on the O6 guanine site of a 13-mer DNA duplex containing a G:T mismatch is studied using molecular dynamics. The structure, dynamic evolution and hydration of the S-substituted duplex are compared with those of a normal duplex, a duplex with S-substitution on guanine, but no mismatch and a duplex with just a G:T mismatch. The S-substituted mismatch leads to cell death rather than repair. One suggestion is that the G:T mismatch recognition protein recognises the S-substituted mismatch (GS:T) as G:T. This leads to a cycle of futile repair ending in DNA breakage and cell death. We find that some structural features of the helix are similar for the duplex with the G:T mismatch and that with the S-substituted mismatch, but differ from the normal duplex, notably the helical twist. These differences arise from the change in the hydrogen-bonding pattern of the base pair. However a marked feature of the S-substituted G:T mismatch duplex is a very large opening. This showed considerable variability. It is suggested that this enlarged opening would lend support to an alternative model of cell death in which the mismatch protein attaches to thioguanine and activates downstream damage-response pathways. Attack on the sulphur by reactive oxygen species, also leading to cell death, would also be aided by the large, variable opening.
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Affiliation(s)
- Elaine Ann Moore
- School of Life, Health and Chemical Sciences, STEM Faculty, The Open University, Milton Keynes, Buckinghamshire, United Kingdom
- * E-mail:
| | - Yao-Zhong Xu
- School of Life, Health and Chemical Sciences, STEM Faculty, The Open University, Milton Keynes, Buckinghamshire, United Kingdom
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13
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Wu J, Li L, Wang P, You C, Williams NL, Wang Y. Translesion synthesis of O4-alkylthymidine lesions in human cells. Nucleic Acids Res 2016; 44:9256-9265. [PMID: 27466394 PMCID: PMC5100597 DOI: 10.1093/nar/gkw662] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2016] [Accepted: 07/13/2016] [Indexed: 12/18/2022] Open
Abstract
Environmental exposure, endogenous metabolism and cancer chemotherapy can give rise to alkylation of DNA, and the resulting alkylated thymidine (alkyldT) lesions were found to be poorly repaired and persistent in mammalian tissues. Unrepaired DNA lesions may compromise genomic integrity by inhibiting DNA replication and inducing mutations in these processes. In this study, we explored how eight O4-alkyldT lesions, with the alkyl group being a Me, Et, nPr, iPr, nBu, iBu, (R)-sBu and (S)-sBu, are recognized by DNA replication machinery in HEK293T human embryonic kidney cells. We found that the O4-alkyldT lesions are moderately blocking to DNA replication, with the bypass efficiencies ranging from 20 to 33% in HEK293T cells, and these lesions induced substantial frequencies T→C transition mutation. We also conducted the replication experiments in the isogenic cells where individual translesion synthesis (TLS) DNA polymerases were depleted by the CRISPR/Cas9 genome editing method. Our results showed that deficiency in Pol η or Pol ζ, but not Pol κ or Pol ι, led to pronounced drops in bypass efficiencies for all the O4-alkyldT lesions except O4-MedT. In addition, depletion of Pol ζ resulted in significant decreases in T→C mutation frequencies for all the O4-alkyldT lesions except O4-MedT and O4-nBudT. Thus, our study provided important new knowledge about the cytotoxic and mutagenic properties of the O4-alkyldT lesions and defined the roles of TLS polymerases in bypassing these lesions in human cells.
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Affiliation(s)
- Jun Wu
- Department of Chemistry, University of California, Riverside, CA 92521-0403, USA
| | - Lin Li
- Department of Chemistry, University of California, Riverside, CA 92521-0403, USA
| | - Pengcheng Wang
- Environmental Toxicology Graduate Program, University of California, Riverside, CA 92521-0403, USA
| | - Changjun You
- Department of Chemistry, University of California, Riverside, CA 92521-0403, USA
| | - Nicole L Williams
- Environmental Toxicology Graduate Program, University of California, Riverside, CA 92521-0403, USA
| | - Yinsheng Wang
- Department of Chemistry, University of California, Riverside, CA 92521-0403, USA .,Environmental Toxicology Graduate Program, University of California, Riverside, CA 92521-0403, USA
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14
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You C, Wang Y. Mass Spectrometry-Based Quantitative Strategies for Assessing the Biological Consequences and Repair of DNA Adducts. Acc Chem Res 2016; 49:205-13. [PMID: 26758048 DOI: 10.1021/acs.accounts.5b00437] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The genetic integrity of living organisms is constantly threatened by environmental and endogenous sources of DNA damaging agents that can induce a plethora of chemically modified DNA lesions. Unrepaired DNA lesions may elicit cytotoxic and mutagenic effects and contribute to the development of human diseases including cancer and neurodegeneration. Understanding the deleterious outcomes of DNA damage necessitates the investigation about the effects of DNA adducts on the efficiency and fidelity of DNA replication and transcription. Conventional methods for measuring lesion-induced replicative or transcriptional alterations often require time-consuming colony screening and DNA sequencing procedures. Recently, a series of mass spectrometry (MS)-based strategies have been developed in our laboratory as an efficient platform for qualitative and quantitative analyses of the changes in genetic information induced by DNA adducts during DNA replication and transcription. During the past few years, we have successfully used these MS-based methods for assessing the replicative or transcriptional blocking and miscoding properties of more than 30 distinct DNA adducts. When combined with genetic manipulation, these methods have also been successfully employed for revealing the roles of various DNA repair proteins or translesion synthesis DNA polymerases (Pols) in modulating the adverse effects of DNA lesions on transcription or replication in mammalian and bacterial cells. For instance, we found that Escherichia coli Pol IV and its mammalian ortholog (i.e., Pol κ) are required for error-free bypass of N(2)-(1-carboxyethyl)-2'-deoxyguanosine (N(2)-CEdG) in cells. We also found that the N(2)-CEdG lesions strongly inhibit DNA transcription and they are repaired by transcription-coupled nucleotide excision repair in mammalian cells. In this Account, we focus on the development of MS-based approaches for determining the effects of DNA adducts on DNA replication and transcription, where liquid chromatography-tandem mass spectrometry is employed for the identification, and sometimes quantification, of the progeny products arising from the replication or transcription of lesion-bearing DNA substrates in vitro and in mammalian cells. We also highlight their applications to lesion bypass, mutagenesis, and repair studies of three representative types of DNA lesions, that is, the methylglyoxal-induced N(2)-CEdG, oxidatively induced 8,5'-cyclopurine-2'-deoxynucleosides, and regioisomeric alkylated thymidine lesions. Specially, we discuss the similar and distinct effects of the minor-groove DNA lesions including N(2)-CEdG and O(2)-alkylated thymidine lesions, as well as the major-groove O(4)-alkylated thymidine lesions on DNA replication and transcription machinery. For example, we found that the addition of an alkyl group to the O(4) position of thymine may facilitate its preferential pairing with guanine and thus induce exclusively the misincorporation of guanine nucleotide opposite the lesion, whereas alkylation of thymine at the O(2) position may render the nucleobase unfavorable in pairing with any of the canonical nucleobases and thus exhibit promiscuous miscoding properties during DNA replication and transcription. The MS-based strategies described herein should be generally applicable for quantitative measurement of the biological consequences and repair of other DNA lesions in vitro and in cells.
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Affiliation(s)
- Changjun You
- Department
of Chemistry, University of California, Riverside, California 92521-0403, United States
| | - Yinsheng Wang
- Department
of Chemistry, University of California, Riverside, California 92521-0403, United States
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15
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Sabir N, Khan N, Völkner J, Widdascheck F, del Pino P, Witte G, Riedel M, Lisdat F, Konrad M, Parak WJ. Photo-electrochemical Bioanalysis of Guanosine Monophosphate Using Coupled Enzymatic Reactions at a CdS/ZnS Quantum Dot Electrode. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2015; 11:5844-5850. [PMID: 26395754 DOI: 10.1002/smll.201501883] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2015] [Revised: 08/10/2015] [Indexed: 06/05/2023]
Abstract
A photo-electrochemical sensor for the specific detection of guanosine monophosphate (GMP) is demonstrated, based on three enzymes combined in a coupled reaction assay. The first reaction involves the adenosine triphosphate (ATP)-dependent conversion of GMP to guanosine diphosphate (GDP) by guanylate kinase, which warrants substrate specificity. The reaction products ADP and GDPare co-substrates for the enzymatic conversion of phosphoenolpyruvate to pyruvate in a second reaction mediated by pyruvate kinase. Pyruvate in turn is the co-substrate for lactate dehydrogenase that generates lactate via oxidation of nicotinamide adenine dinucleotide (reduced form) NADH to NAD(+). This third enzymatic reaction is electrochemically detected. For this purpose a CdS/ZnS quantum dot (QD) electrode is illuminated and the photocurrent response under fixed potential conditions is evaluated. The sequential enzyme reactions are first evaluated in solution. Subsequently, a sensor for GMP is constructed using polyelectrolytes for enzyme immobilization.
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Affiliation(s)
- Nadeem Sabir
- Fachbereich Physik, Philipps-Universität Marburg, Renthof 5, D-35032, Marburg, Germany
| | - Nazimuddin Khan
- Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, D-37077, Göttingen, Germany
| | - Johannes Völkner
- Fachbereich Physik, Philipps-Universität Marburg, Renthof 5, D-35032, Marburg, Germany
| | - Felix Widdascheck
- Fachbereich Physik, Philipps-Universität Marburg, Renthof 5, D-35032, Marburg, Germany
| | - Pablo del Pino
- CIC biomaGUNE, Parque Tecnológico de San Sebastián, P° Miramón 182 - Ed. Empresarial C, 20009, San Sebastian, Spain
| | - Gregor Witte
- Fachbereich Physik, Philipps-Universität Marburg, Renthof 5, D-35032, Marburg, Germany
| | - Marc Riedel
- Biosystems Technology, Institute of Applied Life Sciences, Technical University Wildau, Hochschulring 1, D-15745, Wildau, Germany
| | - Fred Lisdat
- Biosystems Technology, Institute of Applied Life Sciences, Technical University Wildau, Hochschulring 1, D-15745, Wildau, Germany
| | - Manfred Konrad
- Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, D-37077, Göttingen, Germany
| | - Wolfgang J Parak
- Fachbereich Physik, Philipps-Universität Marburg, Renthof 5, D-35032, Marburg, Germany
- CIC biomaGUNE, Parque Tecnológico de San Sebastián, P° Miramón 182 - Ed. Empresarial C, 20009, San Sebastian, Spain
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16
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Liu S, Wang Y. Mass spectrometry for the assessment of the occurrence and biological consequences of DNA adducts. Chem Soc Rev 2015; 44:7829-54. [PMID: 26204249 PMCID: PMC4787602 DOI: 10.1039/c5cs00316d] [Citation(s) in RCA: 98] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Exogenous and endogenous sources of chemical species can react, directly or after metabolic activation, with DNA to yield DNA adducts. If not repaired, DNA adducts may compromise cellular functions by blocking DNA replication and/or inducing mutations. Unambiguous identification of the structures and accurate measurements of the levels of DNA adducts in cellular and tissue DNA constitute the first and important step towards understanding the biological consequences of these adducts. The advances in mass spectrometry (MS) instrumentation in the past 2-3 decades have rendered MS an important tool for structure elucidation, quantification, and revelation of the biological consequences of DNA adducts. In this review, we summarized the development of MS techniques on these fronts for DNA adduct analysis. We placed our emphasis of discussion on sample preparation, the combination of MS with gas chromatography- or liquid chromatography (LC)-based separation techniques for the quantitative measurement of DNA adducts, and the use of LC-MS along with molecular biology tools for understanding the human health consequences of DNA adducts. The applications of mass spectrometry-based DNA adduct analysis for predicting the therapeutic outcome of anti-cancer agents, for monitoring the human exposure to endogenous and environmental genotoxic agents, and for DNA repair studies were also discussed.
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Affiliation(s)
- Shuo Liu
- Environmental Toxicology Graduate Program, University of California, Riverside, California, USA
| | - Yinsheng Wang
- Environmental Toxicology Graduate Program, University of California, Riverside, California, USA and Department of Chemistry, University of California, Riverside, CA 92521-0403, USA.
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17
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Effects of Tet-mediated oxidation products of 5-methylcytosine on DNA transcription in vitro and in mammalian cells. Sci Rep 2014; 4:7052. [PMID: 25394478 PMCID: PMC4231326 DOI: 10.1038/srep07052] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2014] [Accepted: 10/24/2014] [Indexed: 12/21/2022] Open
Abstract
5-methylcytosine (5-mC) is a well-characterized epigenetic regulator in mammals. Recent studies showed that Ten-eleven translocation (Tet) proteins can catalyze the stepwise oxidation of 5-mC to produce 5-hydroxymethylcytosine (5-HmC), 5-formylcytosine (5-FoC) and 5-carboxylcytosine (5-CaC). The exciting discovery of these novel cytosine modifications has stimulated substantial research interests about their roles in epigenetic regulation. Here we systematically examined the effects of the oxidized 5-mC derivatives on the efficiency and fidelity of DNA transcription using a recently developed competitive transcription and adduct bypass assay. Our results showed that, when located on the transcribed strand, 5-FoC and 5-CaC exhibited marginal mutagenic and modest inhibitory effects on DNA transcription mediated by single-subunit T7 RNA polymerase or multi-subunit human RNA polymerase II in vitro and in human cells. 5-HmC displayed relatively milder blocking effects on transcription, and no mutant transcript could be detectable for 5-HmC in vitro or in cells. The lack of considerable mutagenic effects of the oxidized 5-mC derivatives on transcription was in agreement with their functions in epigenetic regulation. The modest blocking effects on transcription suggested that 5-FoC and 5-CaC may function in transcriptional regulation. These findings provided new evidence for the potential functional interplay between cytosine methylation status and transcription.
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18
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Facile enzymatic synthesis of base J-containing oligodeoxyribonucleotides and an analysis of the impact of base J on DNA replication in cells. PLoS One 2014; 9:e103335. [PMID: 25061973 PMCID: PMC4111573 DOI: 10.1371/journal.pone.0103335] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2014] [Accepted: 06/26/2014] [Indexed: 12/17/2022] Open
Abstract
We reported here the use of T4 bacteriophage β-glucosyltransferase (T4 β-GT) for the facile synthesis of base J-containing oligodeoxyribonucleotides (ODNs). We found that the enzyme could catalyze the glucosylation of 5-hydroxymethyl-2-deoxyuridine (5hmU) in both single- and double-stranded ODNs, though the latter reaction occurred only when 5hmU was mispaired with a guanine. In addition, base J blocked moderately DNA replication, but it did not induce mutations during replication in human cells.
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19
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Ji D, You C, Wang P, Wang Y. Effects of tet-induced oxidation products of 5-methylcytosine on DNA replication in mammalian cells. Chem Res Toxicol 2014; 27:1304-9. [PMID: 24979327 PMCID: PMC4216192 DOI: 10.1021/tx500169u] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
![]()
Recently 5-hydroxymethyl-2′-deoxycytidine
(5hmdC), 5-formyl-2′-deoxycytidine
(5fdC), and 5-carboxyl-2′-deoxycytidine (5cadC) were discovered
in mammalian DNA as oxidation products of 5-methyl-2′-deoxycytidine
(5mdC) induced by the ten-eleven translocation family of enzymes.
These oxidized derivatives of 5mdC may not only act as intermediates
of active cytosine demethylation in mammals but also serve as epigenetic
marks on their own. It remains unclear how 5hmdC, 5fdC, and 5cadC
affect DNA replication in mammalian cells. Here, we examined the effects
of the three modified nucleosides on the efficiency and accuracy of
DNA replication in HEK293T human kidney epithelial cells. Our results
demonstrated that a single, site-specifically incorporated 5fdC or
5cadC conferred modest drops, by approximately 30%, in replication
bypass efficiency without inducing detectable mutations in human cells,
whereas replicative bypass of 5hmdC is both accurate and efficient.
The lack of pronounced perturbation of these oxidized 5mdC derivatives
on DNA replication is consistent with their roles in epigenetic regulation
of gene expression.
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Affiliation(s)
- Debin Ji
- Department of Chemistry, University of California , Riverside, California 92521, United States
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20
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Hemphill J, Govan J, Uprety R, Tsang M, Deiters A. Site-specific promoter caging enables optochemical gene activation in cells and animals. J Am Chem Soc 2014; 136:7152-8. [PMID: 24802207 PMCID: PMC4333597 DOI: 10.1021/ja500327g] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
![]()
In
cell and molecular biology, double-stranded circular DNA constructs,
known as plasmids, are extensively used to express a gene of interest.
These gene expression systems rely on a specific promoter region to
drive the transcription of genes either constitutively (i.e., in a
continually “ON” state) or conditionally (i.e., in response
to a specific transcription initiator). However, controlling plasmid-based
expression with high spatial and temporal resolution in cellular environments
and in multicellular organisms remains challenging. To overcome this
limitation, we have site-specifically installed nucleobase-caging
groups within a plasmid promoter region to enable optochemical control
of transcription and, thus, gene expression, via photolysis of the
caging groups. Through the light-responsive modification of plasmid-based
gene expression systems, we have demonstrated optochemical activation
of an exogenous fluorescent reporter gene in both tissue culture and
a live animal model, as well as light-induced overexpression of an
endogenous signaling protein.
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Affiliation(s)
- James Hemphill
- Department of Chemistry, North Carolina State University , Raleigh, North Carolina 27695, United States
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21
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Strong inhibition of thioredoxin reductase by highly cytotoxic gold(I) complexes. DNA binding studies. J Inorg Biochem 2013; 130:32-7. [PMID: 24157605 DOI: 10.1016/j.jinorgbio.2013.09.019] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2013] [Revised: 09/30/2013] [Accepted: 09/30/2013] [Indexed: 12/11/2022]
Abstract
Biological properties of a series of aminophosphine-thiolate gold(I) complexes [Au(SR)(PPh2NHpy)] [Ph2PNHpy=2-(diphenylphosphinoamino)pyridine; HSR=2-mercaptopyridine (2-HSpy) (3), 2-mercaptonicotinic acid (2-H2-mna) (4), 2-thiouracil (2-HTU) (5) or 2-thiocytosine (2-HTC) (6)] and [Au(SR){PPh2NH(Htrz)}] [Ph2PNH(Htrz)=3-(diphenylphosphinoamino)-1,2,4-triazole]; HSR=2-mercaptopyridine (2-HSpy) (7), 2-thiocytosine (2-HTC) (8) or 6-thioguanine (6-HTG) (9) have been studied. Their antitumor properties have been tested in vitro against two tumor human cell lines, HeLa (derived from cervical cancer) and MCF-7 (derived from breast cancer), using a metabolic activity test (3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyl tetrazolium bromide, MTT). Some of them showed excellent cytotoxic activity. With the aim to obtain more information about the mechanisms of action of these derivatives, the interactions of complexes 3, 5, 7 and 9 with thioredoxin reductase in HeLa cells were studied. They showed a potent inhibition of thioredoxin reductase activity. In order to complete this study, interactions of the complexes with calf thymus (CT-) DNA and with different bacterial DNAs, namely the plasmid pEMBL9 and the promoter region of the furA (ferric uptake regulator A) gene from Anabaena sp. PCC 7120 were investigated. Although interactions of complexes with CT-DNA have been verified, none of them cause significant changes in its structure.
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22
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Zhang F, Fu L, Wang Y. 6-thioguanine induces mitochondrial dysfunction and oxidative DNA damage in acute lymphoblastic leukemia cells. Mol Cell Proteomics 2013; 12:3803-11. [PMID: 24043426 DOI: 10.1074/mcp.m113.029595] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Thiopurines are among the most successful chemotherapeutic agents used for treating various human diseases, including acute lymphoblastic leukemia and chronic inflammation. Although metabolic conversion and the subsequent incorporation of 6-thioguanine ((S)G) nucleotides into nucleic acids are considered important for allowing the thiopurine drugs to induce their cytotoxic effects, alternative mechanisms may also exist. We hypothesized that an unbiased analysis of (S)G-induced perturbation of the entire proteome might uncover novel mechanism(s) of action of the drug. We performed a quantitative assessment of global protein expression in control and (S)G-treated Jurkat T cells by employing stable isotope labeling by amino acids in cell culture and liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis. LC-MS/MS quantification results uncovered substantially decreased expression of a large number of proteins in the mitochondrial respiratory chain complex, and Ingenuity Pathway Analysis of the significantly altered proteins showed that (S)G treatment induced mitochondrial dysfunction. This was accompanied by diminished uptake of MitoTracker Deep Red and the elevated formation of oxidatively induced DNA lesions, including 8,5'-cyclo-2'-deoxyadenosine and 8,5'-cyclo-2'-deoxyguanosine. Together, our results suggested that (S)G may exert its cytotoxic effect by inducing mitochondrial dysfunction and reactive oxygen species formation in acute lymphoblastic leukemia cells.
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Affiliation(s)
- Fan Zhang
- Department of Chemistry, University of California, Riverside, California 92521-0403
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23
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Epigenetics and the developmental origins of inflammatory bowel diseases. CANADIAN JOURNAL OF GASTROENTEROLOGY = JOURNAL CANADIEN DE GASTROENTEROLOGIE 2013; 26:909-15. [PMID: 23248794 DOI: 10.1155/2012/526408] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The gut microbiota, the intestinal mucosa and the host immune system are among the large biological networks involved in the development of inflammatory bowel disease (IBD), which includes Crohn disease (CD) and ulcerative colitis (UC). Host genetics and environmental factors can significantly modulate the interactive relationships among these biological systems and influence predilection toward IBD. High monozygotic twin discordance rates and the rapid rise in the prevalence of IBD indicate that environmental influences may be as important or even more important in their pathogenesis than genetic susceptibility. However, the nature and timing of environmental factors critical for inducing IBD remain largely unknown. The molecular mechanisms and the key biological component(s) that may be affected by such factors are also in question. Epigenetic changes, such as DNA methylation (the methylation of cytosines followed by a guanine in CpG dinucleotides) can be modified by environmental influences during finite developmental periods and have been implicated in the pathogenesis of IBD. Mucosal DNA methylation can also react to changes in the commensal microbiota, underscoring the intercalating relationships among the large biological systems involved in gastrointestinal disorders. Therefore, transient environmental influences during specific periods of development may induce critical change(s) in an isolated or concomitant fashion within the intestinal biomic networks and lead to increased susceptibility to IBD. The present review focuses on the emerging paradigm shift considering IBD to originate from critical environmental effects during pre- and postnatal development.
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24
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Harris RA, Nagy-Szakal D, Pedersen N, Opekun A, Bronsky J, Munkholm P, Jespersgaard C, Andersen PS, Melegh B, Ferry G, Jess T, Kellermayer R. Genome-wide peripheral blood leukocyte DNA methylation microarrays identified a single association with inflammatory bowel diseases. Inflamm Bowel Dis 2012; 18:2334-41. [PMID: 22467598 PMCID: PMC3812910 DOI: 10.1002/ibd.22956] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/13/2012] [Accepted: 02/22/2012] [Indexed: 12/12/2022]
Abstract
BACKGROUND Crohn's disease (CD) and ulcerative colitis (UC) are common forms of inflammatory bowel disease (IBD). Monozygotic (MZ) twin discordance rates and epidemiologic data implicate that environmental changes and epigenetic factors may play a pathogenic role in IBD. DNA methylation (the methylation of cytosines within CpG dinucleotides) is an epigenetic modification, which can respond to environmental influences. We investigated whether DNA methylation might be connected with IBD in peripheral blood leukocyte (PBL) DNA by utilizing genome-wide microarrays. METHODS Two different high-throughput microarray-based methods for genome-wide DNA methylation analysis were employed. First, DNA isolated from MZ twin pairs concordant (CD: 4; UC: 3) and discordant (CD: 4; UC: 7) for IBD was interrogated by a custom-made methylation-specific amplification microarray (MSAM). Second, the recently developed Illumina Infinium HumanMethylation450 BeadChip arrays were used on 48 samples of PBL DNA from discordant MZ twin pairs (CD: 3; UC: 3) and treatment-naive pediatric cases of IBD (CD: 14; UC: 8), as well as controls (n = 14). The microarrays were validated with bisulfite pyrosequencing. RESULTS The MSAMs did not yield significant IBD associations. The Methylation BeadChip approach identified a single DNA methylation association of IBD at TEPP (testis, prostate and placenta-expressed protein) when DNA isolated selectively from peripheral blood mononuclear cells was analyzed (8.6% increase in methylation between CD and control, FDR = 0.0065). CONCLUSIONS Microarray interrogation of IBD-dependent DNA methylation from PBLs appears to have limited ability to detect significant disease associations. More detailed and/or selective approaches may be useful for the elucidation of connections between the DNA methylome and IBD in the future.
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Affiliation(s)
- R. Alan. Harris
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
| | - Dorottya Nagy-Szakal
- Department of Pediatrics, Section of Pediatric Gastroenterology, Baylor College of Medicine, Texas Children’s Hospital, Houston, TX, USA,USDA/ARS Children’s Nutrition Research Center, Houston, TX, USA
| | - Natalia Pedersen
- Gastroenterology Unit, Herlev University Hospital, Herlev, Denmark
| | - Antone Opekun
- Department of Pediatrics, Section of Pediatric Gastroenterology, Baylor College of Medicine, Texas Children’s Hospital, Houston, TX, USA,Department of Gasteonterology-TMC Digestive Disease Center, Baylor College of Medicine
| | - Jiri Bronsky
- Department of Pediatrics, Second Medical Faculty, Charles University and University Hospital Motol, Prague, Czech Republic
| | - Pia Munkholm
- Gastroenterology Unit, Herlev University Hospital, Herlev, Denmark
| | - Cathrine Jespersgaard
- Department of Clinical Biochemistry and Immunology, Statens Serum Institut, Copenhagen, Denmark
| | - Paal Skytt Andersen
- Department of Microbiological Surveillance and Research, Statens Serum Institut, Copenhagen, Denmark
| | - Bela Melegh
- Department of Medical Genetics, University of Pecs, Hungary
| | - George Ferry
- Department of Pediatrics, Section of Pediatric Gastroenterology, Baylor College of Medicine, Texas Children’s Hospital, Houston, TX, USA
| | - Tine Jess
- Department of Epidemiology Research, Statens Serum Institut, Copenhagen, Denmark
| | - Richard Kellermayer
- Department of Pediatrics, Section of Pediatric Gastroenterology, Baylor College of Medicine, Texas Children’s Hospital, Houston, TX, USA,USDA/ARS Children’s Nutrition Research Center, Houston, TX, USA
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25
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You C, Dai X, Yuan B, Wang Y. Effects of 6-thioguanine and S6-methylthioguanine on transcription in vitro and in human cells. J Biol Chem 2012; 287:40915-23. [PMID: 23076150 DOI: 10.1074/jbc.m112.418681] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Thiopurine drugs are extensively used as chemotherapeutic agents in clinical practice, even though there is concern about the risk of therapy-related cancers. It has been previously suggested that the cytotoxicity of thiopurine drugs involves their metabolic activation, the resultant generation of 6-thioguanine ((S)G) and S(6)-methylthioguanine (S(6)mG) in DNA, and the futile mismatch repair triggered by replication-induced (S)G:T and S(6)mG:T mispairs. Disruption of transcription is known to be one of the major consequences of DNA damage induced by many antiviral and antitumor agents; however, it remains undefined how (S)G and S(6)mG compromise the efficiency and fidelity of transcription. Using our recently developed competitive transcription and adduct bypass assay, herein we examined the impact of (S)G and S(6)mG on transcription in vitro and in human cells. Our results revealed that, when situated on the transcribed strand, S(6)mG exhibited both inhibitory and mutagenic effects during transcription mediated by single-subunit T7 RNA polymerase or multisubunit human RNA polymerase II in vitro and in human cells. Moreover, we found that the impact of S(6)mG on transcriptional efficiency and fidelity is modulated by the transcription-coupled nucleotide excision repair capacity. In contrast, (S)G did not considerably compromise the efficiency or fidelity of transcription, and it was a poor substrate for NER. We propose that S(6)mG might contribute, at least in part, to thiopurine-mediated cytotoxicity through inhibition of transcription and to potential therapy-related carcinogenesis via transcriptional mutagenesis.
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Affiliation(s)
- Changjun You
- Department of Chemistry, University of California, Riverside, California 92521-0403, USA
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26
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Hofmann U, Heinkele G, Angelberger S, Schaeffeler E, Lichtenberger C, Jaeger S, Reinisch W, Schwab M. Simultaneous quantification of eleven thiopurine nucleotides by liquid chromatography-tandem mass spectrometry. Anal Chem 2012; 84:1294-301. [PMID: 22220820 DOI: 10.1021/ac2031699] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The prodrugs azathioprine and 6-mercaptopurine, which are well-established anticancer and immunosuppressive agents, are extensively metabolized by activating and inactivating enzymes. Whereas the 6-thioguanine nucleotides (TGN) are currently being considered as major active metabolites, methylthioinosine nucleotides seem to contribute to the cytotoxic effect as well. Thiopurine-related adverse drug reactions and thiopurine failure are frequent. Thus, therapeutic monitoring of TGN and methylthioinosine derivatives has been suggested to improve thiopurine therapy, however with limited success. To elucidate systematically underlying molecular mechanisms as potential explanation for interindividual variability of thiopurine response, we developed a novel highly specific and sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for simultaneous quantitation of eleven mono-, di-, and triphosphates of thioguanosine, methylthioinosine, methylthioguanosine, and thioinosine. Using stable isotope-labeled analogues as internal standards obtained by chemical synthesis, an intra- and interassay variability below 8% and an accuracy of 92% to 107% were achieved in spiked quality control samples with known standards. All eleven metabolites could be determined in red blood cells from patients with inflammatory bowel diseases and long-term azathioprine therapy. Thus, our novel method opens a new avenue for the understanding of the thiopurine metabolism by quantitation of all important thiopurine nucleotide metabolites in one run.
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Affiliation(s)
- Ute Hofmann
- Dr Margarete Fischer-Bosch Institute of Clinical Pharmacology, Stuttgart, Germany
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27
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Hosni-Ahmed A, Barnes JD, Wan J, Jones TS. Thiopurine methyltransferase predicts the extent of cytotoxicty and DNA damage in astroglial cells after thioguanine exposure. PLoS One 2011; 6:e29163. [PMID: 22216194 PMCID: PMC3244435 DOI: 10.1371/journal.pone.0029163] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2011] [Accepted: 11/22/2011] [Indexed: 01/11/2023] Open
Abstract
Thiopurine methyltransferase (Tpmt) is the primary enzyme responsible for deactivating thiopurine drugs. Thiopurine drugs (i.e., thioguanine [TG], mercaptopurine, azathioprine) are commonly used for the treatment of cancer, organ transplant, and autoimmune disorders. Chronic thiopurine therapy has been linked to the development of brain cancer (most commonly astrocytomas), and Tpmt status has been associated with this risk. Therefore, we investigated whether the level of Tpmt protein activity could predict TG-associated cytotoxicity and DNA damage in astrocytic cells. We found that TG induced cytotoxicity in a dose-dependent manner in Tpmt+/+, Tpmt+/− and Tpmt−/− primary mouse astrocytes and that a low Tpmt phenotype predicted significantly higher sensitivity to TG than did a high Tpmt phenotype. We also found that TG exposure induced significantly more DNA damage in the form of single strand breaks (SSBs) and double strand breaks (DSBs) in primary astrocytes with low Tpmt versus high Tpmt. More interestingly, we found that Tpmt+/− astrocytes had the highest degree of cytotoxicity and genotoxicity (i.e., IC50, SSBs and DSBs) after TG exposure. We then used human glioma cell lines as model astroglial cells to represent high (T98) and low (A172) Tpmt expressers and found that A172 had the highest degree of cytoxicity and SSBs after TG exposure. When we over-expressed Tpmt in the A172 cell line, we found that TG IC50 was significantly higher and SSB's were significantly lower as compared to mock transfected cells. This study shows that low Tpmt can lead to greater sensitivity to thiopurine therapy in astroglial cells. When Tpmt deactivation at the germ-line is considered, this study also suggests that heterozygosity may be subject to the greatest genotoxic effects of thiopurine therapy.
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Affiliation(s)
- Amira Hosni-Ahmed
- Department of Pharmaceutical Sciences, University of Tennessee Health Science Center, Memphis, Tennessee, United States of America
- Department of Chemistry, College of Science, Fayoum University, Fayoum, Egypt
| | - Joseph D. Barnes
- Department of Clinical Pharmacy, University of Tennessee Health Science Center, Memphis, Tennessee, United States of America
| | - Jim Wan
- Division of Biostatistics and Epidemiology, University of Tennessee Health Science Center, Memphis, Tennessee, United States of America
| | - Terreia S. Jones
- Department of Clinical Pharmacy, University of Tennessee Health Science Center, Memphis, Tennessee, United States of America
- Department of Pharmaceutical Sciences, University of Tennessee Health Science Center, Memphis, Tennessee, United States of America
- Department of Neurosurgery, University of Tennessee Health Science Center, Memphis, Tennessee, United States of America
- * E-mail:
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28
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Yuan B, Wang J, Cao H, Sun R, Wang Y. High-throughput analysis of the mutagenic and cytotoxic properties of DNA lesions by next-generation sequencing. Nucleic Acids Res 2011; 39:5945-54. [PMID: 21470959 PMCID: PMC3152323 DOI: 10.1093/nar/gkr159] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Human cells are constantly exposed to environmental and endogenous agents which can induce damage to DNA. Understanding the implications of these DNA modifications in the etiology of human diseases requires the examination about how these DNA lesions block DNA replication and induce mutations in cells. All previously reported shuttle vector-based methods for investigating the cytotoxic and mutagenic properties of DNA lesions in cells have low-throughput, where plasmids containing individual lesions are transfected into cells one lesion at a time and the products from the replication of individual lesions are analyzed separately. The advent of next-generation sequencing (NGS) technology has facilitated investigators to design scientific approaches that were previously not technically feasible or affordable. In this study, we developed a new method employing NGS, together with shuttle vector technology, to have a multiplexed and quantitative assessment of how DNA lesions perturb the efficiency and accuracy of DNA replication in cells. By using this method, we examined the replication of four carboxymethylated DNA lesions and two oxidatively induced bulky DNA lesions including (5′S) diastereomers of 8,5′-cyclo-2′-deoxyguanosine (cyclo-dG) and 8,5′-cyclo-2′-deoxyadenosine (cyclo-dA) in five different strains of Escherichia coli cells. We further validated the results obtained from NGS using previously established methods. Taken together, the newly developed method provided a high-throughput and readily affordable method for assessing quantitatively how DNA lesions compromise the efficiency and fidelity of DNA replication in cells.
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Affiliation(s)
- Bifeng Yuan
- Department of Chemistry, University of California, Riverside, CA 92521-0403, USA
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29
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Yuan B, You C, Andersen N, Jiang Y, Moriya M, O'Connor TR, Wang Y. The roles of DNA polymerases κ and ι in the error-free bypass of N2-carboxyalkyl-2'-deoxyguanosine lesions in mammalian cells. J Biol Chem 2011; 286:17503-11. [PMID: 21454642 DOI: 10.1074/jbc.m111.232835] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
To counteract the deleterious effects of DNA damage, cells are equipped with specialized polymerases to bypass DNA lesions. Previous biochemical studies revealed that DinB family DNA polymerases, including Escherichia coli DNA polymerase IV and human DNA polymerase κ, efficiently incorporate the correct nucleotide opposite some N(2)-modified 2'-deoxyguanosine derivatives. Herein, we used shuttle vector technology and demonstrated that deficiency in Polk or Poli in mouse embryonic fibroblast (MEF) cells resulted in elevated frequencies of G→T and G→A mutations at N(2)-(1-carboxyethyl)-2'-deoxyguanosine (N(2)-CEdG) and N(2)-carboxymethyl-2'-deoxyguanosine (N(2)-CMdG) sites. Steady-state kinetic measurements revealed that human DNA polymerase ι preferentially inserts the correct nucleotide, dCMP, opposite N(2)-CEdG lesions. In contrast, no mutation was found after the N(2)-CEdG- and N(2)-CMdG-bearing plasmids were replicated in POLH-deficient human cells or Rev3-deficient MEF cells. Together, our results revealed that, in mammalian cells, both polymerases κ and ι are necessary for the error-free bypass of N(2)-CEdG and N(2)-CMdG. However, in the absence of polymerase κ or ι, other translesion synthesis polymerase(s) could incorporate nucleotide(s) opposite these lesions but would do so inaccurately.
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Affiliation(s)
- Bifeng Yuan
- From the Department of Chemistry, University of California, Riverside, California 92521, USA
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30
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Yuan B, Zhang J, Wang H, Xiong L, Cai Q, Wang T, Jacobsen S, Pradhan S, Wang Y. 6-Thioguanine reactivates epigenetically silenced genes in acute lymphoblastic leukemia cells by facilitating proteasome-mediated degradation of DNMT1. Cancer Res 2011; 71:1904-11. [PMID: 21239472 DOI: 10.1158/0008-5472.can-10-3430] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Thiopurines including 6-thioguanine ((S)G), 6-mercaptopurine, and azathioprine are effective anticancer agents with remarkable success in clinical practice, especially in effective treatment of acute lymphoblastic leukemia (ALL). (S)G is understood to act as a DNA hypomethylating agent in ALL cells, however, the underlying mechanism leading to global cytosine demethylation remains unclear. Here we report that (S)G treatment results in reactivation of epigenetically silenced genes in T leukemia cells. Bisulfite genomic sequencing revealed that (S)G treatment universally elicited demethylation in the promoters and/or first exons of the genes that were reactivated. (S)G treatment also attenuated the expression of histone lysine-specific demethylase 1 (LSD1), thereby stimulating lysine methylation of the DNA methylase DNMT1 and triggering its degradation via the ubiquitin-proteasomal pathway. Taken together, our findings reveal a previously uncharacterized but vital mechanistic link between (S)G treatment and DNA hypomethylation.
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Affiliation(s)
- Bifeng Yuan
- Department of Chemistry, University of California, Riverside, California 92521-0403, USA
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