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Wang J, Takyi NA, Hsiao YC, Tang Q, Chen YT, Liu CW, Ma J, Qi R, Bian K, Peng Z, Essigmann JM, Lu K, Wetmore SD, Li D. Stable Interstrand Cross-Links Generated from the Repair of 1, N6-Ethenoadenine in DNA by α-Ketoglutarate/Fe(II)-Dependent Dioxygenase ALKBH2. J Am Chem Soc 2024; 146:10381-10392. [PMID: 38573229 PMCID: PMC11060877 DOI: 10.1021/jacs.3c12890] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/05/2024]
Abstract
DNA cross-links severely challenge replication and transcription in cells, promoting senescence and cell death. In this paper, we report a novel type of DNA interstrand cross-link (ICL) produced as a side product during the attempted repair of 1,N6-ethenoadenine (εA) by human α-ketoglutarate/Fe(II)-dependent enzyme ALKBH2. This stable/nonreversible ICL was characterized by denaturing polyacrylamide gel electrophoresis analysis and quantified by high-resolution LC-MS in well-matched and mismatched DNA duplexes, yielding 5.7% as the highest level for cross-link formation. The binary lesion is proposed to be generated through covalent bond formation between the epoxide intermediate of εA repair and the exocyclic N6-amino group of adenine or the N4-amino group of cytosine residues in the complementary strand under physiological conditions. The cross-links occur in diverse sequence contexts, and molecular dynamics simulations rationalize the context specificity of cross-link formation. In addition, the cross-link generated from attempted εA repair was detected in cells by highly sensitive LC-MS techniques, giving biological relevance to the cross-link adducts. Overall, a combination of biochemical, computational, and mass spectrometric methods was used to discover and characterize this new type of stable cross-link both in vitro and in human cells, thereby uniquely demonstrating the existence of a potentially harmful ICL during DNA repair by human ALKBH2.
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Affiliation(s)
- Jie Wang
- Department of Biomedical and Pharmaceutical Sciences, College of Pharmacy, University of Rhode Island, Kingston, Rhode Island 02881, United States
| | - Nathania A Takyi
- Department of Chemistry and Biochemistry, University of Lethbridge, 4401 University Drive West, Lethbridge, Alberta T1K 3M4, Canada
| | - Yun-Chung Hsiao
- Department of Environmental Sciences and Engineering, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
| | - Qi Tang
- Department of Biomedical and Pharmaceutical Sciences, College of Pharmacy, University of Rhode Island, Kingston, Rhode Island 02881, United States
| | - Yi-Tzai Chen
- Department of Biomedical and Pharmaceutical Sciences, College of Pharmacy, University of Rhode Island, Kingston, Rhode Island 02881, United States
| | - Chih-Wei Liu
- Department of Environmental Sciences and Engineering, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
| | - Jian Ma
- Department of Biomedical and Pharmaceutical Sciences, College of Pharmacy, University of Rhode Island, Kingston, Rhode Island 02881, United States
| | - Rui Qi
- Department of Biomedical and Pharmaceutical Sciences, College of Pharmacy, University of Rhode Island, Kingston, Rhode Island 02881, United States
| | - Ke Bian
- Department of Biomedical and Pharmaceutical Sciences, College of Pharmacy, University of Rhode Island, Kingston, Rhode Island 02881, United States
| | - Zhiyuan Peng
- Department of Biomedical and Pharmaceutical Sciences, College of Pharmacy, University of Rhode Island, Kingston, Rhode Island 02881, United States
| | - John M Essigmann
- Departments of Biological Engineering, Chemistry, and Center for Environmental Health Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Kun Lu
- Department of Environmental Sciences and Engineering, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
| | - Stacey D Wetmore
- Department of Chemistry and Biochemistry, University of Lethbridge, 4401 University Drive West, Lethbridge, Alberta T1K 3M4, Canada
| | - Deyu Li
- Department of Biomedical and Pharmaceutical Sciences, College of Pharmacy, University of Rhode Island, Kingston, Rhode Island 02881, United States
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2
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Price NE, Gates KS. Novel Processes Associated with the Repair of Interstrand Cross-Links Derived from Abasic Sites in Duplex DNA: Roles for the Base Excision Repair Glycosylase NEIL3 and the SRAP Protein HMCES. Chem Res Toxicol 2024; 37:199-207. [PMID: 38198604 DOI: 10.1021/acs.chemrestox.3c00345] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2024]
Abstract
Recent studies have defined a novel pathway for the repair of interstrand cross-links derived from the reaction of an adenine residue with an apurinic/apyrimidinic (AP) site on the opposing strand of DNA (dA-AP ICL). Stalling of a replication fork at the dA-AP ICL triggers TRAIP-dependent ubiquitylation of the CMG helicase that recruits the base excision repair glycosylase NEIL3 to the lesion. NEIL3 unhooks the dA-AP ICL to regenerate the native adenine residue on one strand and an AP site on the other strand. Covalent capture of the abasic site by the SRAP protein HMCES protects against genomic instability that would result from cleavage of the abasic site in the context of single-stranded DNA at the replication fork. After repair synthesis moves the HMCES-AP adduct into the context of double-stranded DNA, the DNA-protein cross-link is resolved by a nonproteolytic mechanism involving dissociation of thiazolidine attachment. The AP site in duplex DNA is then repaired by the base excision repair pathway.
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Affiliation(s)
- Nathan E Price
- Department of Chemistry, University of Missouri, 125 Chemistry Building, Columbia, Missouri 65211, United States
| | - Kent S Gates
- Department of Chemistry, University of Missouri, 125 Chemistry Building, Columbia, Missouri 65211, United States
- Department of Biochemistry, University of Missouri, 125 Chemistry Building, Columbia, Missouri 65211, United States
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3
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Yin J, Gates KS, Wang Y. N-Methyl- N-nitrosourea Induced 3'-Glutathionylated DNA-Cleavage Products in Mammalian Cells. Anal Chem 2022; 94:15595-15603. [PMID: 36332130 PMCID: PMC9869666 DOI: 10.1021/acs.analchem.2c02003] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Apurinic/apyrimidinic (AP) sites, that is, abasic sites, are among the most frequently induced DNA lesions. Spontaneous or DNA glycosylase-mediated β-elimination of the 3'-phosphoryl group can lead to strand cleavages at AP sites to yield a highly reactive, electrophilic 3'-phospho-α,β-unsaturated aldehyde (3'-PUA) remnant. The latter can react with amine or thiol groups of biological small molecules, DNA, and proteins to yield various damaged 3'-end products. Considering its high intracellular concentration, glutathione (GSH) may conjugate with 3'-PUA to yield 3-glutathionyl-2,3-dideoxyribose (GS-ddR), which may constitute a significant, yet previously unrecognized endogenous lesion. Here, we developed a liquid chromatography tandem mass spectroscopy method, in combination with the use of a stable isotope-labeled internal standard, to quantify GS-ddR in genomic DNA of cultured human cells. Our results revealed the presence of GS-ddR in the DNA of untreated cells, and its level was augmented in cells upon exposure to an alkylating agent, N-methyl-N-nitrosourea (MNU). In addition, inhibition of AP endonuclease (APE1) led to an elevated level of GS-ddR in the DNA of MNU-treated cells. Together, we reported here, for the first time, the presence of appreciable levels of GS-ddR in cellular DNA, the induction of GS-ddR by a DNA alkylating agent, and the role of APE1 in modulating its level in human cells.
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Affiliation(s)
- Jiekai Yin
- Environmental Toxicology Graduate Program, University of California, Riverside, California 92521-0403, United States
| | - Kent S Gates
- Department of Chemistry, University of Missouri, Columbia, Missouri 65211, United States
- Department of Biochemistry, University of Missouri, Columbia, Missouri 65211, United States
| | - Yinsheng Wang
- Environmental Toxicology Graduate Program, University of California, Riverside, California 92521-0403, United States
- Department of Chemistry, University of California, Riverside, California 92521-0403, United States
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4
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Amin SM, Islam T, Price NE, Wallace A, Guo X, Gomina A, Heidari M, Johnson KM, Lewis CD, Yang Z, Gates KS. Effects of Local Sequence, Reaction Conditions, and Various Additives on the Formation and Stability of Interstrand Cross-Links Derived from the Reaction of an Abasic Site with an Adenine Residue in Duplex DNA. ACS OMEGA 2022; 7:36888-36901. [PMID: 36278095 PMCID: PMC9583646 DOI: 10.1021/acsomega.2c05736] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/04/2022] [Accepted: 09/28/2022] [Indexed: 06/16/2023]
Abstract
The experiments described here examined the effects of reaction conditions, various additives, and local sequence on the formation and stability interstrand cross-links (ICLs) derived from the reaction of an apurinic/apyrimidinic (AP) site with the exocyclic amino group of an adenine residue on the opposing strand in duplex DNA. Cross-link formation was observed in a range of different buffers, with faster formation rates observed at pH 5. Inclusion of the base excision repair enzyme alkyladenine DNA glycosylase (hAAG) which binds tightly to AP-containing duplexes decreased, but did not completely prevent, formation of the dA-AP ICL. Formation of the dA-AP ICL was not altered by the presence of the biological metal ion Mg2+ or the biological thiol, glutathione. Several organocatalysts of imine formation did not enhance the rate of dA-AP ICL formation. Duplex length did not have a large effect on dA-AP yield, so long as the melting temperature of the duplex was not significantly below the reaction temperature (the duplex must remain hybridized for efficient ICL formation). Formation of the dA-AP ICL was examined in over 40 different sequences that varied the neighboring and opposing bases at the cross-linking site. The results indicate that ICL formation can occur in a wide variety of sequence contexts under physiological conditions. Formation of the dA-AP ICL was strongly inhibited by the aldehyde-trapping agents methoxyamine and hydralazine, by NaBH3CN, by the intercalator ethidium bromide, and by the minor groove-binding agent netropsin. ICL formation was inhibited to some extent in bicarbonate and Tris buffers. The dA-AP ICL showed substantial inherent stability under a variety of conditions and was not a substrate for AP-processing enzymes APE1 or Endo IV. Finally, we characterized cross-link formation in a small (11 bp) stem-loop (hairpin) structure and in DNA-RNA hybrid duplexes.
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Affiliation(s)
- Saosan
Binth Md. Amin
- Department
of Chemistry, University of Missouri, Columbia, Missouri 65211, United States
| | - Tanhaul Islam
- Department
of Chemistry, University of Missouri, Columbia, Missouri 65211, United States
| | - Nathan E. Price
- Department
of Chemistry, University of Missouri, Columbia, Missouri 65211, United States
| | - Amanda Wallace
- Department
of Chemistry, University of Missouri, Columbia, Missouri 65211, United States
| | - Xu Guo
- Department
of Chemistry, University of Missouri, Columbia, Missouri 65211, United States
| | - Anuoluwapo Gomina
- Department
of Chemistry, University of Missouri, Columbia, Missouri 65211, United States
| | - Marjan Heidari
- Department
of Chemistry, University of Missouri, Columbia, Missouri 65211, United States
| | - Kevin M. Johnson
- Department
of Chemistry, University of Missouri, Columbia, Missouri 65211, United States
| | - Calvin D. Lewis
- Department
of Chemistry, University of Missouri, Columbia, Missouri 65211, United States
| | - Zhiyu Yang
- Department
of Chemistry, University of Missouri, Columbia, Missouri 65211, United States
| | - Kent S. Gates
- Department
of Chemistry, University of Missouri, Columbia, Missouri 65211, United States
- Department
of Biochemistry, University of Missouri, Columbia, Missouri 65211, United States
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Abstract
DNA damage by chemicals, radiation, or oxidative stress leads to a mutational spectrum, which is complex because it is determined in part by lesion structure, the DNA sequence context of the lesion, lesion repair kinetics, and the type of cells in which the lesion is replicated. Accumulation of mutations may give rise to genetic diseases such as cancer and therefore understanding the process underlying mutagenesis is of immense importance to preserve human health. Chemical or physical agents that cause cancer often leave their mutational fingerprints, which can be used to back-calculate the molecular events that led to disease. To make a clear link between DNA lesion structure and the mutations a given lesion induces, the field of single-lesion mutagenesis was developed. In the last three decades this area of research has seen much growth in several directions, which we attempt to describe in this Perspective.
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Affiliation(s)
- Ashis K Basu
- Department of Chemistry, The University of Connecticut Storrs, Storrs, Connecticut 06269, United States
| | - John M Essigmann
- Departments of Chemistry, Biological Engineering and Center for Environmental Health Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
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Huskova A, Landova B, Boura E, Silhan J. The rate of formation and stability of abasic site interstrand crosslinks in the DNA duplex. DNA Repair (Amst) 2022; 113:103300. [PMID: 35255312 DOI: 10.1016/j.dnarep.2022.103300] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2022] [Revised: 02/08/2022] [Accepted: 02/08/2022] [Indexed: 11/03/2022]
Abstract
DNA interstrand crosslinks (ICLs) strands pose an impenetrable barrier for DNA replication. Different ICLs are known to recruit distinct DNA repair pathways. NEIL3 glycosylase has been known to remove an abasic (Ap) site derived DNA crosslink (Ap-ICL). An Ap-ICL forms spontaneously from the Ap site with an adjacent adenine in the opposite strand. Lack of genetic models and a poor understanding of the fate of these lesions leads to many questions about the occurrence and the toxicity of Ap-ICL in cells. Here, we investigate the circumstances of Ap-ICL formation. With an array of different oligos, we have investigated the rates of formation, the yields, and the stability of Ap-ICL. Our findings point out how different bases in the vicinity of the Ap site change crosslink formation in vitro. We reveal that AT-rich rather than GC-rich regions in the surrounding Ap site lead to higher rates of Ap-ICL formation. Overall, our data reveal that Ap-ICL can be formed in virtually any DNA sequence context surrounding a hot spot of a 5'-Ap-dT pair, albeit with significantly different rates and yields. Based on Ap-ICL formation in vitro, we attempt to predict the number of Ap-ICLs in the cell.
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Affiliation(s)
- Andrea Huskova
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Flemingovo namesti 2, 166 10 Prague 6, Czech Republic
| | - Barbora Landova
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Flemingovo namesti 2, 166 10 Prague 6, Czech Republic
| | - Evzen Boura
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Flemingovo namesti 2, 166 10 Prague 6, Czech Republic
| | - Jan Silhan
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Flemingovo namesti 2, 166 10 Prague 6, Czech Republic.
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Xue L, Yu D, Wang L, Sun J, Song Y, Jia Y, Wu A, Zhang B, Mi W, Fan H, Sun H. Selective Antitumor Activity and Photocytotoxicity of Glutathione-Activated Abasic Site Trapping Agents. ACS Chem Biol 2022; 17:797-803. [PMID: 35297620 DOI: 10.1021/acschembio.2c00061] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Abasic (AP) sites are one of the most common DNA lesions in cells. Aldehyde-reactive alkoxyamines capture AP sites and block the activity of APE1, the enzyme responsible for initiating their repair. Blocking the APE1 repair of AP sites leads to cell death, and it is an actively investigated approach for treating cancer. However, unselective AP site capture in different cells produces side effects and limits the application of alkoxyamines in chemotherapy. Herein we take advantage of the higher glutathione (GSH) concentration in cancer cells over normal cells to develop GSH-inducible agents that selectively kill cancer cells. 2,4-Dinitrobenzenesulfonamide caged coumarin-based alkoxyamines 1 and 2 are selectively revealed by GSH to release SO2 and fluorescent coumarin-based alkoxyamines 3 and 4 that trap AP sites in cells. GSH-directed AP site trapping and SO2 release result in selective cytotoxicity (defined as IC50WI38/IC50H1299) against H1299 lung cancer cells over normal WI38 lung cells, ranging from 1.8 to 2.8 for 1 and 2. The alkylating agent methylmethanesulfonate (MMS) promotes the formation of AP sites in cells and enhances the cytotoxicity of agent 1 in a dose-dependent way. Moreover, the comet assay and γH2AX assay suggest that AP adducts form a highly toxic DNA interstrand cross-link (ICL) upon photolysis, leading to further cell death. DNA flow cytometric analysis showed that 1 promoted cell apoptosis in the early stage and induced G2/M phase cell-cycle arrest. The 2,4-dinitrobenzenesulfonamide-caged alkoxyamines exhibited selective antitumor activity and photocytotoxicity in cancer cells, illuminating their potential as GSH-directed chemotherapeutic agents.
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Affiliation(s)
- Li Xue
- Tianjin Key Laboratory on Technologies Enabling Development of Clinical Therapeutics and Diagnostics, Department of Chemical Biology, School of Pharmacy, Tianjin Medical University, Tianjin 300070, P. R. China
| | - Dehao Yu
- Tianjin Key Laboratory on Technologies Enabling Development of Clinical Therapeutics and Diagnostics, Department of Chemical Biology, School of Pharmacy, Tianjin Medical University, Tianjin 300070, P. R. China
| | - Lingling Wang
- Key Laboratory of Immune Microenvironment and Disease (Ministry of Education), Department of Immunology, School of Basic Medical Sciences, Tianjin Medical University, Tianjin 300070, P. R. China
| | - Jing Sun
- Tianjin Key Laboratory on Technologies Enabling Development of Clinical Therapeutics and Diagnostics, Department of Chemical Biology, School of Pharmacy, Tianjin Medical University, Tianjin 300070, P. R. China
| | - Ying Song
- Institute of Biomedical Research, Yunnan University, Kunming 650500, P. R. China
| | - Yuanyuan Jia
- Tianjin Key Laboratory on Technologies Enabling Development of Clinical Therapeutics and Diagnostics, Department of Chemical Biology, School of Pharmacy, Tianjin Medical University, Tianjin 300070, P. R. China
| | - Ang Wu
- Tianjin Key Laboratory on Technologies Enabling Development of Clinical Therapeutics and Diagnostics, Department of Chemical Biology, School of Pharmacy, Tianjin Medical University, Tianjin 300070, P. R. China
| | - Beibei Zhang
- Institute of Biomedical Research, Yunnan University, Kunming 650500, P. R. China
| | - Wenyi Mi
- Key Laboratory of Immune Microenvironment and Disease (Ministry of Education), Department of Immunology, School of Basic Medical Sciences, Tianjin Medical University, Tianjin 300070, P. R. China
- The Province and Ministry Co-sponsored Collaborative Innovation Center for Medical Epigenetics, School of Basic Medical Sciences, Tianjin Medical University, Tianjin 300070, P. R. China
| | - Heli Fan
- Tianjin Key Laboratory on Technologies Enabling Development of Clinical Therapeutics and Diagnostics, Department of Chemical Biology, School of Pharmacy, Tianjin Medical University, Tianjin 300070, P. R. China
| | - Huabing Sun
- Tianjin Key Laboratory on Technologies Enabling Development of Clinical Therapeutics and Diagnostics, Department of Chemical Biology, School of Pharmacy, Tianjin Medical University, Tianjin 300070, P. R. China
- The Province and Ministry Co-sponsored Collaborative Innovation Center for Medical Epigenetics, School of Basic Medical Sciences, Tianjin Medical University, Tianjin 300070, P. R. China
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Haldar T, Jha JS, Yang Z, Nel C, Housh K, Cassidy OJ, Gates KS. Unexpected Complexity in the Products Arising from NaOH-, Heat-, Amine-, and Glycosylase-Induced Strand Cleavage at an Abasic Site in DNA. Chem Res Toxicol 2022; 35:218-232. [PMID: 35129338 PMCID: PMC9482271 DOI: 10.1021/acs.chemrestox.1c00409] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Hydrolytic loss of nucleobases from the deoxyribose backbone of DNA is one of the most common unavoidable types of damage in synthetic and cellular DNA. The reaction generates abasic sites in DNA, and it is important to understand the properties of these lesions. The acidic nature of the α-protons of the ring-opened abasic aldehyde residue facilitates the β-elimination of the 3'-phosphoryl group. This reaction is expected to generate a DNA strand break with a phosphoryl group on the 5'-terminus and a trans-α,β-unsaturated aldehyde residue on the 3'-terminus; however, a handful of studies have identified noncanonical sugar remnants on the 3'-terminus, suggesting that the products arising from strand cleavage at apurinic/apyrimidinic sites in DNA may be more complex than commonly thought. We characterized the strand cleavage induced by the treatment of an abasic site-containing DNA oligonucleotide with heat, NaOH, piperidine, spermine, and the base excision repair glycosylases Fpg and Endo III. The results showed that under multiple conditions, cleavage at an abasic site in a DNA oligomer generated noncanonical sugar remnants including cis-α,β-unsaturated aldehyde, 2-deoxyribose, and 3-thio-2,3-dideoxyribose products on the 3'-terminus of the strand break.
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Affiliation(s)
- Tuhin Haldar
- University of Missouri, Department of Chemistry, 125 Chemistry Building, Columbia, MO 65211
| | - Jay S. Jha
- University of Missouri, Department of Chemistry, 125 Chemistry Building, Columbia, MO 65211
| | - Zhiyu Yang
- University of Missouri, Department of Chemistry, 125 Chemistry Building, Columbia, MO 65211
| | - Christopher Nel
- University of Missouri, Department of Chemistry, 125 Chemistry Building, Columbia, MO 65211
| | - Kurt Housh
- University of Missouri, Department of Chemistry, 125 Chemistry Building, Columbia, MO 65211
| | - Orla J. Cassidy
- University of Missouri, Department of Chemistry, 125 Chemistry Building, Columbia, MO 65211
| | - Kent S. Gates
- University of Missouri, Department of Chemistry, 125 Chemistry Building, Columbia, MO 65211,University of Missouri, Department of Biochemistry, Columbia, MO 65211,Address correspondence to Kent S. Gates – Departments of Chemistry and Biochemistry, 125 Chemistry Bldg. University of Missouri, Columbia, MO 65211, United States; ORCHID ID: 0000-0002-4218-7411; Phone: (573) 882-6763;
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Chan W, Jin L. DNA-Protein Cross-Links Formed by Reacting Lysine with Apurinic/Apyrimidinic Sites in DNA and Human Cells: Quantitative Analysis by Liquid Chromatography-Tandem Mass Spectrometry Coupled with Stable Isotope Dilution. Anal Chem 2021; 94:803-810. [PMID: 34971314 DOI: 10.1021/acs.analchem.1c03356] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Accumulating evidence suggests that DNA lesion-induced DNA-protein cross-links (DPCs) interrupt normal DNA metabolic processes, such as transcription, replication, and repair, resulting in profound biological consequences, including the development of many human diseases, such as cancers. Although apurinic/apyrimidinic (AP) sites are among the most predominant DNA lesions and are in close proximity to the histone proteins that they wrap around in the nucleosome, knowledge of the chemical structure or biological consequences of their associated DPCs is limited in part due to a lack of sensitive and selective analytical methods. We developed liquid chromatography-tandem mass spectrometry coupled with a stable isotope dilution method for rigorous quantitation of DPCs formed by reacting a DNA AP site with a lysine residue. In combination with chemical derivatization with fluorenylmethoxycarbonyl chloride to form a hydrophobic conjugate, the developed LC-MS/MS method allows sensitive detection of AP site-Lys cross-links down to sub-1 adduct per 106 nt. After validation using a synthetic AP site-lysine-cross-linked peptide and an oligodeoxyribonucleotide, the method was used to determine the concentration of AP site-lysine cross-links in hot acid-treated DNA and in human cells exposed to methyl methanesulfonate.
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Affiliation(s)
- Wan Chan
- Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong
| | - Long Jin
- Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong
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