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Li Y, Hecht SS. Metabolic Activation and DNA Interactions of Carcinogenic N-Nitrosamines to Which Humans Are Commonly Exposed. Int J Mol Sci 2022; 23:ijms23094559. [PMID: 35562949 PMCID: PMC9105260 DOI: 10.3390/ijms23094559] [Citation(s) in RCA: 45] [Impact Index Per Article: 22.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2022] [Revised: 04/15/2022] [Accepted: 04/18/2022] [Indexed: 02/04/2023] Open
Abstract
Carcinogenic N-nitrosamine contamination in certain drugs has recently caused great concern and the attention of regulatory agencies. These carcinogens-widely detectable in relatively low levels in food, water, cosmetics, and drugs-are well-established and powerful animal carcinogens. The electrophiles resulting from the cytochrome P450-mediated metabolism of N-nitrosamines can readily react with DNA and form covalent addition products (DNA adducts) that play a central role in carcinogenesis if not repaired. In this review, we aim to provide a comprehensive and updated review of progress on the metabolic activation and DNA interactions of 10 carcinogenic N-nitrosamines to which humans are commonly exposed. Certain DNA adducts such as O6-methylguanine with established miscoding properties play central roles in the cancer induction process, whereas others have been linked to the high incidence of certain types of cancers. We hope the data summarized here will help researchers gain a better understanding of the bioactivation and DNA interactions of these 10 carcinogenic N-nitrosamines and facilitate further research on their toxicologic and carcinogenic properties.
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Affiliation(s)
- Yupeng Li
- Masonic Cancer Center, University of Minnesota, Minneapolis, MN 55455, USA;
- Department of Medicinal Chemistry, College of Pharmacy, University of Minnesota, Minneapolis, MN 55455, USA
- Correspondence: ; Tel.: +1-612-624-8187
| | - Stephen S. Hecht
- Masonic Cancer Center, University of Minnesota, Minneapolis, MN 55455, USA;
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2
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Ghodke PP, Gonzalez-Vasquez G, Wang H, Johnson KM, Sedgeman CA, Guengerich FP. Enzymatic bypass of an N 6-deoxyadenosine DNA-ethylene dibromide-peptide cross-link by translesion DNA polymerases. J Biol Chem 2021; 296:100444. [PMID: 33617883 PMCID: PMC8024977 DOI: 10.1016/j.jbc.2021.100444] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2021] [Revised: 02/15/2021] [Accepted: 02/17/2021] [Indexed: 12/25/2022] Open
Abstract
Unrepaired DNA-protein cross-links, due to their bulky nature, can stall replication forks and result in genome instability. Large DNA-protein cross-links can be cleaved into DNA-peptide cross-links, but the extent to which these smaller fragments disrupt normal replication is not clear. Ethylene dibromide (1,2-dibromoethane) is a known carcinogen that can cross-link the repair protein O6-alkylguanine-DNA alkyltransferase (AGT) to the N6 position of deoxyadenosine (dA) in DNA, as well as four other positions in DNA. We investigated the effect of a 15-mer peptide from the active site of AGT, cross-linked to the N6 position of dA, on DNA replication by human translesion synthesis DNA polymerases (Pols) η, ⍳, and κ. The peptide-DNA cross-link was bypassed by the three polymerases at different rates. In steady-state kinetics, the specificity constant (kcat/Km) for incorporation of the correct nucleotide opposite to the adduct decreased by 220-fold with Pol κ, tenfold with pol η, and not at all with Pol ⍳. Pol η incorporated all four nucleotides across from the lesion, with the preference dT > dC > dA > dG, while Pol ⍳ and κ only incorporated the correct nucleotide. However, LC-MS/MS analysis of the primer-template extension product revealed error-free bypass of the cross-linked 15-mer peptide by Pol η. We conclude that a bulky 15-mer peptide cross-linked to the N6 position of dA can retard polymerization and cause miscoding but that overall fidelity is not compromised because only correct pairs are extended.
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Affiliation(s)
- Pratibha P Ghodke
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee, USA
| | | | - Hui Wang
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee, USA
| | - Kevin M Johnson
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee, USA
| | - Carl A Sedgeman
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee, USA
| | - F Peter Guengerich
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee, USA.
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3
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Mohsen MG, Ji D, Kool ET. Polymerase synthesis of four-base DNA from two stable dimeric nucleotides. Nucleic Acids Res 2019; 47:9495-9501. [PMID: 31504784 PMCID: PMC6765132 DOI: 10.1093/nar/gkz741] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2019] [Revised: 08/12/2019] [Accepted: 08/16/2019] [Indexed: 11/25/2022] Open
Abstract
We document the preparation and properties of dimerized pentaphosphate-bridged deoxynucleotides (dicaptides) that contain reactive components of two different nucleotides simultaneously. Importantly, dicaptides are found to be considerably more stable to hydrolysis than standard dNTPs. Steady-state kinetics studies show that the dimers exhibit reasonably good efficiency with the Klenow fragment of DNA polymerase I, and we identify thermostable enzymes that process them efficiently at high temperature. Experiments show that the dAp5dT dimer successfully acts as a combination of dATP and dTTP in primer extension reactions, and the dGp5dC dimer as a combination of dGTP and dCTP. The two dimers in combination promote successful 4-base primer extension. The final byproduct of the reaction, triphosphate, is shown to be less inhibitory to primer extension than pyrophosphate, the canonical byproduct. Finally, we document PCR amplification of DNA with two dimeric nucleotides, and show that the dimers can promote amplification under extended conditions when PCR with normal dNTPs fails. These dimeric nucleotides represent a novel and simple approach for increasing stability of nucleotides and avoiding inhibition from pyrophosphate.
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Affiliation(s)
- Michael G Mohsen
- Department of Chemistry, Stanford University, Stanford, CA 94305, USA
| | - Debin Ji
- Department of Chemistry, Stanford University, Stanford, CA 94305, USA
| | - Eric T Kool
- Department of Chemistry, Stanford University, Stanford, CA 94305, USA
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4
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Wu J, Wang P, Li L, Williams NL, Ji D, Zahurancik WJ, You C, Wang J, Suo Z, Wang Y. Replication studies of carboxymethylated DNA lesions in human cells. Nucleic Acids Res 2017; 45:7276-7284. [PMID: 28531304 PMCID: PMC5499590 DOI: 10.1093/nar/gkx442] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2016] [Accepted: 05/04/2017] [Indexed: 12/11/2022] Open
Abstract
Metabolic activation of some N-nitroso compounds (NOCs), an important class of DNA damaging agents, can induce the carboxymethylation of nucleobases in DNA. Very little was previously known about how the carboxymethylated DNA lesions perturb DNA replication in human cells. Here, we investigated the effects of five carboxymethylated DNA lesions, i.e. O6-CMdG, N6-CMdA, N4-CMdC, N3-CMdT and O4-CMdT on the efficiency and fidelity of DNA replication in HEK293T human embryonic kidney cells. We found that, while neither N6-CMdA nor N4-CMdC blocked DNA replication or induced mutations, N3-CMdT, O4-CMdT and O6-CMdG moderately blocked DNA replication and induced substantial frequencies of T→A (81%), T→C (68%) and G→A (6.4%) mutations, respectively. In addition, our results revealed that CRISPR-Cas9-mediated depletion of Pol η resulted in significant drops in bypass efficiencies of N4-CMdC and N3-CMdT. Diminution in bypass efficiencies was also observed for N6-CMdA and O6-CMdG upon depletion of Pol κ, and for O6-CMdG upon removal of Pol ζ. Together, our study provided molecular-level insights into the impacts of the carboxymethylated DNA lesions on DNA replication in human cells, revealed the roles of individual translesion synthesis DNA polymerases in bypassing these lesions, and suggested the contributions of O6-CMdG, N3-CMdT and O4-CMdT to the mutations found in p53 gene of human gastrointestinal cancers.
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Affiliation(s)
- Jun Wu
- Department of Chemistry, University of California, Riverside, CA 92521, USA
| | - Pengcheng Wang
- Environmental Toxicology Graduate Program, University of California, Riverside, CA 92521, USA
| | - Lin Li
- Department of Chemistry, University of California, Riverside, CA 92521, USA
| | - Nicole L Williams
- Environmental Toxicology Graduate Program, University of California, Riverside, CA 92521, USA
| | - Debin Ji
- Department of Chemistry, University of California, Riverside, CA 92521, USA
| | - Walter J Zahurancik
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA
| | - Changjun You
- Department of Chemistry, University of California, Riverside, CA 92521, USA
| | - Jianshuang Wang
- Department of Chemistry, University of California, Riverside, CA 92521, USA
| | - Zucai Suo
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA
| | - Yinsheng Wang
- Department of Chemistry, University of California, Riverside, CA 92521, USA.,Environmental Toxicology Graduate Program, University of California, Riverside, CA 92521, USA
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5
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Sedgeman CA, Su Y, Guengerich FP. Formation of S-[2-(N 6-Deoxyadenosinyl)ethyl]glutathione in DNA and Replication Past the Adduct by Translesion DNA Polymerases. Chem Res Toxicol 2017; 30:1188-1196. [PMID: 28395138 DOI: 10.1021/acs.chemrestox.7b00022] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
1,2-Dibromoethane (DBE, ethylene dibromide) is a potent carcinogen due at least in part to its DNA cross-linking effects. DBE cross-links glutathione (GSH) to DNA, notably to sites on 2'-deoxyadenosine and 2'-deoxyguanosine ( Cmarik , J. L. , et al. ( 1991 ) J. Biol. Chem. 267 , 6672 - 6679 ). Adduction at the N6 position of 2'-deoxyadenosine (dA) had not been detected, but this is a site for the linkage of O6-alkylguanine DNA alkyltransferase ( Chowdhury , G. , et al. ( 2013 ) Angew. Chem. Int. Ed. 52 , 12879 - 12882 ). We identified and quantified a new adduct, S-[2-(N6-deoxyadenosinyl)ethyl]GSH, in calf thymus DNA using LC-MS/MS. Replication studies were performed in duplex oligonucleotides containing this adduct with human DNA polymerases (hPols) η, ι, and κ, as well as with Sulfolobus solfataricus Dpo4, Escherichia coli polymerase I Klenow fragment, and bacteriophage T7 polymerase. hPols η and ι, Dpo4, and Klenow fragment were able to bypass the adduct with only slight impedance; hPol η and ι showed increased misincorporation opposite the adduct compared to that of unmodified 2'-deoxyadenosine. LC-MS/MS analysis of full-length primer extension products by hPol η confirmed the incorporation of dC opposite S-[2-(N6-deoxyadenosinyl)ethyl]GSH and also showed the production of a -1 frameshift. These results reveal the significance of N6-dA GSH-DBE adducts in blocking replication, as well as producing mutations, by human translesion synthesis DNA polymerases.
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Affiliation(s)
- Carl A Sedgeman
- Department of Biochemistry, Vanderbilt University School of Medicine , Nashville, Tennessee 37232-0146, United States
| | - Yan Su
- Department of Biochemistry, Vanderbilt University School of Medicine , Nashville, Tennessee 37232-0146, United States
| | - F Peter Guengerich
- Department of Biochemistry, Vanderbilt University School of Medicine , Nashville, Tennessee 37232-0146, United States
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6
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Gu S, Xue Q, Liu Q, Xiong M, Wang W, Zhang H. Error-Free Bypass of 7,8-dihydro-8-oxo-2'-deoxyguanosineby DNA Polymerase of Pseudomonas aeruginosa Phage PaP1. Genes (Basel) 2017; 8:genes8010018. [PMID: 28067844 PMCID: PMC5295013 DOI: 10.3390/genes8010018] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2016] [Revised: 12/26/2016] [Accepted: 12/30/2016] [Indexed: 12/16/2022] Open
Abstract
As one of the most common forms of oxidative DNA damage, 7,8-dihydro-8-oxo-2′-deoxyguanosine (8-oxoG) generally leads to G:C to T:A mutagenesis. To study DNA replication encountering 8-oxoG by the sole DNA polymerase (Gp90) of Pseudomonasaeruginosa phage PaP1, we performed steady-state and pre-steady-state kinetic analyses of nucleotide incorporation opposite 8-oxoG by Gp90 D234A that lacks exonuclease activities on ssDNA and dsDNA substrates. Gp90 D234A could bypass 8-oxoG in an error-free manner, preferentially incorporate dCTP opposite 8-oxoG, and yield similar misincorporation frequency to unmodified G. Gp90 D234A could extend beyond C:8-oxoG or A:8-oxoG base pairs with the same efficiency. dCTP incorporation opposite G and dCTP or dATP incorporation opposite 8-oxoG showed fast burst phases. The burst of incorporation efficiency (kpol/Kd,dNTP) is decreased as dCTP:G > dCTP:8-oxoG > dATP:8-oxoG. The presence of 8-oxoG in DNA does not affect its binding to Gp90 D234A in a binary complex but it does affect it in a ternary complex with dNTP and Mg2+, and dATP misincorporation opposite 8-oxoG further weakens the binding of Gp90 D234A to DNA. This study reveals Gp90 D234A can bypass 8-oxoG in an error-free manner, providing further understanding in DNA replication encountering oxidation lesion for P.aeruginosa phage PaP1.
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Affiliation(s)
- Shiling Gu
- College of Pharmacy and Bioengineering, Chongqing University of Technology, No. 29 Hongguang Street, Banan District, Chongqing 400054, China.
- Public Health Laboratory Sciences and Toxicology, West China School of Public Health, Sichuan University, No. 17 People's South Road, Chengdu 610041, China.
| | - Qizhen Xue
- Public Health Laboratory Sciences and Toxicology, West China School of Public Health, Sichuan University, No. 17 People's South Road, Chengdu 610041, China.
| | - Qin Liu
- College of Pharmacy and Bioengineering, Chongqing University of Technology, No. 29 Hongguang Street, Banan District, Chongqing 400054, China.
| | - Mei Xiong
- Public Health Laboratory Sciences and Toxicology, West China School of Public Health, Sichuan University, No. 17 People's South Road, Chengdu 610041, China.
| | - Wanneng Wang
- College of Pharmacy and Bioengineering, Chongqing University of Technology, No. 29 Hongguang Street, Banan District, Chongqing 400054, China.
| | - Huidong Zhang
- Public Health Laboratory Sciences and Toxicology, West China School of Public Health, Sichuan University, No. 17 People's South Road, Chengdu 610041, China.
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7
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Räz MH, Dexter HR, Millington CL, van Loon B, Williams DM, Sturla SJ. Bypass of Mutagenic O(6)-Carboxymethylguanine DNA Adducts by Human Y- and B-Family Polymerases. Chem Res Toxicol 2016; 29:1493-503. [PMID: 27404553 DOI: 10.1021/acs.chemrestox.6b00168] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The generation of chemical alkylating agents from nitrosation of glycine and bile acid conjugates in the gastrointestinal tract is hypothesized to initiate carcinogenesis. O(6)-carboxymethylguanine (O(6)-CMG) is a product of DNA alkylation derived from nitrosated glycine. Although the tendency of the structurally related adduct O(6)-methylguanine to code for the misincoporation of TTP during DNA replication is well-established, the impact of the presence of the O(6)-CMG adduct in a DNA template on the efficiency and fidelity of translesion DNA synthesis (TLS) by human DNA polymerases (Pols) has hitherto not been described. Herein, we characterize the ability of the four human TLS Pols η, ι, κ, and ζ and the replicative Pol δ to bypass O(6)-CMG in a prevalent mutational hot-spot for colon cancer. The results indicate that Pol η replicates past O(6)-CMG, incorporating dCMP or dAMP, whereas Pol κ incorporates dCMP only, and Pol ι incorporates primarily dTMP. Additionally, the subsequent extension step was carried out with high efficiency by TLS Pols η, κ, and ζ, while Pol ι was unable to extend from a terminal mismatch. These results provide a first basis of O(6)-CMG-promoted base misincorporation by Y- and B-family polymerases potentially leading to mutational signatures associated with colon cancer.
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Affiliation(s)
- Michael H Räz
- Department of Health Sciences and Technology, ETH Zürich , Schmelzbergstrasse 9, 8092 Zürich, Switzerland
| | - Hannah R Dexter
- Center for Chemical Biology, Department of Chemistry, Krebs Institute, University of Sheffield , Sheffield S3 7HF, United Kingdom
| | - Christopher L Millington
- Center for Chemical Biology, Department of Chemistry, Krebs Institute, University of Sheffield , Sheffield S3 7HF, United Kingdom
| | - Barbara van Loon
- Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology (NTNU) , Erling Skjalgssons gate 1, 7491 Trondheim, Norway
| | - David M Williams
- Center for Chemical Biology, Department of Chemistry, Krebs Institute, University of Sheffield , Sheffield S3 7HF, United Kingdom
| | - Shana J Sturla
- Department of Health Sciences and Technology, ETH Zürich , Schmelzbergstrasse 9, 8092 Zürich, Switzerland
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8
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You C, Wang P, Nay SL, Wang J, Dai X, O’Connor TR, Wang Y. Roles of Aag, Alkbh2, and Alkbh3 in the Repair of Carboxymethylated and Ethylated Thymidine Lesions. ACS Chem Biol 2016; 11:1332-8. [PMID: 26930515 DOI: 10.1021/acschembio.6b00085] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Environmental and endogenous genotoxic agents can result in a variety of alkylated and carboxymethylated DNA lesions, including N3-ethylthymidine (N3-EtdT), O(2)-EtdT, and O(4)-EtdT as well as N3-carboxymethylthymidine (N3-CMdT) and O(4)-CMdT. By using nonreplicative double-stranded vectors harboring a site-specifically incorporated DNA lesion, we assessed the potential roles of alkyladenine DNA glycosylase (Aag); alkylation repair protein B homologue 2 (Alkbh2); or Alkbh3 in modulating the effects of N3-EtdT, O(2)-EtdT, O(4)-EtdT, N3-CMdT, or O(4)-CMdT on DNA transcription in mammalian cells. We found that the depletion of Aag did not significantly change the transcriptional inhibitory or mutagenic properties of all five examined lesions, suggesting a negligible role of Aag in the repair of these DNA adducts in mammalian cells. In addition, our results revealed that N3-EtdT, but not other lesions, could be repaired by Alkbh2 and Alkbh3 in mammalian cells. Furthermore, we demonstrated the direct reversal of N3-EtdT by purified human Alkbh2 protein in vitro. These findings provided important new insights into the repair of the carboxymethylated and alkylated thymidine lesions in mammalian cells.
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Affiliation(s)
- Changjun You
- Department
of Chemistry, University of California, Riverside, California, United States
| | - Pengcheng Wang
- Environmental
Toxicology Graduate Program, University of California, Riverside, California, United States
| | - Stephanie L. Nay
- Department
of Cancer Biology, Beckman Research Institute, Duarte, California, United States
| | - Jianshuang Wang
- Department
of Chemistry, University of California, Riverside, California, United States
| | - Xiaoxia Dai
- Department
of Chemistry, University of California, Riverside, California, United States
| | - Timothy R. O’Connor
- Department
of Cancer Biology, Beckman Research Institute, Duarte, California, United States
| | - Yinsheng Wang
- Department
of Chemistry, University of California, Riverside, California, United States
- Environmental
Toxicology Graduate Program, University of California, Riverside, California, United States
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9
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O'Flaherty DK, Patra A, Su Y, Guengerich FP, Egli M, Wilds CJ. Lesion Orientation of O4-Alkylthymidine Influences Replication by Human DNA Polymerase η. Chem Sci 2016; 7:4896-4904. [PMID: 27574558 PMCID: PMC5001687 DOI: 10.1039/c6sc00666c] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Conformation of the α-carbon of O4-alkylthymidine was shown to exert an influence on human DNA polymerase η (hPol η) bypass. Crystal structures of hPol η·DNA·dNTP ternary complexes reveal a unique conformation adopted by O4-methylthymidine, where the nucleobase resides nestled at the active site ceiling where hydrogen-bonding with the incoming nucleotide is prevented.
DNA lesions that elude repair may undergo translesion synthesis catalyzed by Y-family DNA polymerases. O4-Alkylthymidines, persistent adducts that can result from carcinogenic agents, may be encountered by DNA polymerases. The influence of lesion orientation around the C4–O4 bond on processing by human DNA polymerase η (hPol η) was studied for oligonucleotides containing O4-methylthymidine (O4MedT), O4-ethylthymidine (O4EtdT), and analogs restricting the O4-methylene group in an anti-orientation. Primer extension assays revealed that the O4-alkyl orientation influences hPol η bypass. Crystal structures of hPol η·DNA·dNTP ternary complexes with O4MedT or O4EtdT in the template strand showed the nucleobase of the former lodged near the ceiling of the active site, with the syn-O4-methyl group engaged in extensive hydrophobic interactions. This unique arrangement for O4-methylthymidine with hPol η, inaccessible for the other analogs due to steric/conformational restriction, is consistent with differences observed for nucleotide incorporation and supports the concept that lesion conformation influences extension across DNA damage. Together, these results provide mechanistic insights on the mutagenicity of O4MedT and O4EtdT when acted upon by hPol η.
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Affiliation(s)
- D K O'Flaherty
- Department of Chemistry and Biochemistry, Concordia University, Montréal, Québec H4B1R6, Canada
| | - A Patra
- Department of Biochemistry, Vanderbilt Institute of Chemical Biology, and Center for Structural Biology, School of Medicine, Vanderbilt University, Nashville, Tennessee 37232, United States
| | - Y Su
- Department of Biochemistry, Vanderbilt Institute of Chemical Biology, and Center for Structural Biology, School of Medicine, Vanderbilt University, Nashville, Tennessee 37232, United States
| | - F P Guengerich
- Department of Biochemistry, Vanderbilt Institute of Chemical Biology, and Center for Structural Biology, School of Medicine, Vanderbilt University, Nashville, Tennessee 37232, United States
| | - M Egli
- Department of Biochemistry, Vanderbilt Institute of Chemical Biology, and Center for Structural Biology, School of Medicine, Vanderbilt University, Nashville, Tennessee 37232, United States
| | - C J Wilds
- Department of Chemistry and Biochemistry, Concordia University, Montréal, Québec H4B1R6, Canada
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10
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Kinetic analysis of bypass of O(6)- methylguanine by the catalytic core of yeast DNA polymerase eta. Arch Biochem Biophys 2016; 596:99-107. [PMID: 26976707 DOI: 10.1016/j.abb.2016.03.009] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2016] [Revised: 03/04/2016] [Accepted: 03/07/2016] [Indexed: 12/18/2022]
Abstract
Alkylating agents can form O(6)-methylguansine (O(6)-MeG). To study the intrinsic kinetic behaviors of bypassing O(6)-MeG, we used the catalytic core of yeast DNA polymerase η (Pol ηcore, residues 1-513), instead of the full-length Pol η, to study their elementary steps, eliminating the effects of the C-terminal C2H2 motif on dNTP incorporation. The misincorporation frequencies were 10(-4) for G and 0.055-0.446 for O(6)-MeG. O(6)-MeG does not affect the extension efficiency. Pol ηcore showed no fast burst phase for any incorporation opposite G or O(6)-MeG. Primer extension was greatly blocked by O(6)-MeG and about 67% dTTP, 31% dCTP and 2% dATP were incorporated opposite O(6)-MeG. This study provides further understanding of the mutation mechanism of alkylated lesion for yeast DNA polymerase η.
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11
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Kinetic analysis of bypass of 7,8-dihydro-8-oxo-2'-deoxyguanosine by the catalytic core of yeast DNA polymerase η. Biochimie 2015; 121:161-9. [PMID: 26700143 DOI: 10.1016/j.biochi.2015.12.009] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2015] [Accepted: 12/07/2015] [Indexed: 11/22/2022]
Abstract
Reactive oxygen species damage DNA bases to produce 7,8-dihydro-8-oxo-2'-deoxyguanosine (8-oxoG), which results in G:C to T:A transversions. To better understand mechanisms of dNTP incorporation opposite 8-oxoG, we performed pre-steady-state kinetic analysis of nucleotide incorporation using the catalytic core of yeast DNA polymerase η (Pol ηcore, residues 1-513) instead of full-length Pol η, eliminating potential effects of the C-terminal C2H2 sequence motif on dNTP incorporation. Kinetic analysis showed that Pol ηcore preferred to incorporate dCTP opposite 8-oxoG. A lack of a pre-steady-state kinetic burst for Pol ηcore suggested that dCTP incorporation is slower than the dissociation of the polymerase from DNA. The extension products beyond the 8-oxoG were determined by LC-MS/MS and showed that 57% of the products corresponded to the correct incorporation (C) and 43% corresponded to dATP misincorporation. More dATP was incorporated opposite 8-oxoG with a mixture of dNTPs than predicted using only a single dNTP. The kinetic analysis of 8-oxoG bypass by yeast DNA Pol ηcore provides further understanding of the mechanism of mutation at this oxidation lesion with yeast DNA polymerase η.
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12
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Yang J, Wang R, Liu B, Xue Q, Zhong M, Zeng H, Zhang H. Kinetic analysis of bypass of abasic site by the catalytic core of yeast DNA polymerase eta. Mutat Res 2015. [PMID: 26203649 DOI: 10.1016/j.mrfmmm.2015.07.001] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Abasic sites (Apurinic/apyrimidinic (AP) sites), produced ∼ 50,000 times/cell/day, are very blocking and miscoding. To better understand miscoding mechanisms of abasic site for yeast DNA polymerase η, pre-steady-state nucleotide incorporation and LC-MS/MS sequence analysis of extension product were studied using pol η(core) (catalytic core, residues 1-513), which can completely eliminate the potential effects of the C-terminal C2H2 motif of pol η on dNTP incorporation. The extension beyond the abasic site was very inefficient. Compared with incorporation of dCTP opposite G, the incorporation efficiencies opposite abasic site were greatly reduced according to the order of dGTP > dATP >> dCTP and dTTP. Pol η(core) showed no fast burst phase for any incorporation opposite G or abasic site, suggesting that the catalytic step is not faster than the dissociation of polymerase from DNA. LC-MS/MS sequence analysis of extension products showed that 53% products were dGTP misincorporation, 33% were dATP and 14% were -1 frameshift, indicating that Pol η(core) bypasses abasic site by a combined G-rule, A-rule and -1 frameshift deletions. Compared with full-length pol η, pol η(core) relatively reduced the efficiency of incorporation of dCTP opposite G, increased the efficiencies of dNTP incorporation opposite abasic site and the exclusive incorporation of dGTP opposite abasic site, but inhibited the extension beyond abasic site, and increased the priority in extension of A: abasic site relative to G: abasic site. This study provides further understanding in the mutation mechanism of abasic sites for yeast DNA polymerase η.
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Affiliation(s)
- Juntang Yang
- Institute of Toxicology, College of Preventive Medicine, Third Military Medical University, Chongqing, PR China
| | - Rong Wang
- Institute of Toxicology, College of Preventive Medicine, Third Military Medical University, Chongqing, PR China
| | - Binyan Liu
- Institute of Toxicology, College of Preventive Medicine, Third Military Medical University, Chongqing, PR China
| | - Qizhen Xue
- Institute of Toxicology, College of Preventive Medicine, Third Military Medical University, Chongqing, PR China
| | - Mengyu Zhong
- Institute of Toxicology, College of Preventive Medicine, Third Military Medical University, Chongqing, PR China
| | - Hao Zeng
- Institute of Toxicology, College of Preventive Medicine, Third Military Medical University, Chongqing, PR China
| | - Huidong Zhang
- Institute of Toxicology, College of Preventive Medicine, Third Military Medical University, Chongqing, PR China.
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You C, Wang J, Dai X, Wang Y. Transcriptional inhibition and mutagenesis induced by N-nitroso compound-derived carboxymethylated thymidine adducts in DNA. Nucleic Acids Res 2015; 43:1012-8. [PMID: 25572317 PMCID: PMC4333421 DOI: 10.1093/nar/gku1391] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
N-nitroso compounds represent a common type of environmental and endogenous DNA-damaging agents. After metabolic activation, many N-nitroso compounds are converted into a diazoacetate intermediate that can react with nucleobases to give carboxymethylated DNA adducts such as N3-carboxymethylthymidine (N3-CMdT) and O4-carboxymethylthymidine (O4-CMdT). In this study, we constructed non-replicative plasmids carrying a single N3-CMdT or O4-CMdT, site-specifically positioned in the transcribed strand, to investigate how these lesions compromise the flow of genetic information during transcription. Our results revealed that both N3-CMdT and O4-CMdT substantially inhibited DNA transcription mediated by T7 RNA polymerase or human RNA polymerase II in vitro and in human cells. In addition, we found that N3-CMdT and O4-CMdT were miscoding lesions and predominantly directed the misinsertion of uridine and guanosine, respectively. Our results also suggested that these carboxymethylated thymidine lesions may constitute efficient substrates for transcription-coupled nucleotide excision repair in human cells. These findings provided important new insights into the biological consequences of the carboxymethylated DNA lesions in living cells.
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Affiliation(s)
- Changjun You
- Department of Chemistry, University of California, Riverside, CA 92521-0403, USA
| | - Jianshuang Wang
- Department of Chemistry, University of California, Riverside, CA 92521-0403, USA
| | - Xiaoxia Dai
- Department of Chemistry, University of California, Riverside, CA 92521-0403, USA
| | - Yinsheng Wang
- Department of Chemistry, University of California, Riverside, CA 92521-0403, USA
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14
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Andersen N, Wang J, Wang P, Jiang Y, Wang Y. In-vitro replication studies on O(2)-methylthymidine and O(4)-methylthymidine. Chem Res Toxicol 2012; 25:2523-31. [PMID: 23113558 PMCID: PMC3502631 DOI: 10.1021/tx300325q] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
O(2)- and O(4)-methylthymidine (O(2)-MdT and O(4)-MdT) can be induced in tissues of laboratory animals exposed with N-methyl-N-nitrosourea, a known carcinogen. These two O-methylated DNA adducts have been shown to be poorly repaired and may contribute to the mutations arising from exposure to DNA methylating agents. Here, in vitro replication studies with duplex DNA substrates containing site-specifically incorporated O(2)-MdT and O(4)-MdT showed that both lesions blocked DNA synthesis mediated by three different DNA polymerases, including the exonuclease-free Klenow fragment of Escherichia coli DNA polymerase I (Kf(-)), human DNA polymerase κ (pol κ), and Saccharomyces cerevisiae DNA polymerase η (pol η). Results from steady-state kinetic measurements and LC-MS/MS analysis of primer extension products revealed that Kf(-) and pol η preferentially incorporated the correct nucleotide (dAMP) opposite O(2)-MdT, while O(4)-MdT primarily directed dGMP misincorporation. While steady-state kinetic experiments showed that pol κ-mediated nucleotide insertion opposite O(2)-MdT and O(4)-MdT is highly promiscuous, LC-MS/MS analysis of primer extension products demonstrated that pol κ favorably incorporated the incorrect dGMP opposite both lesions. Our results underscored the limitation of the steady-state kinetic assay in determining how DNA lesions compromise DNA replication in vitro. In addition, the results from our study revealed that, if left unrepaired, O-methylated thymidine lesions may constitute important sources of nucleobase substitutions emanating from exposure to alkylating agents.
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Affiliation(s)
- Nisana Andersen
- Department of Chemistry, University of California, Riverside, California 92521-0403
| | - Jianshuang Wang
- Department of Chemistry, University of California, Riverside, California 92521-0403
| | - Pengcheng Wang
- Environmental Toxicology Graduate Program, University of California, Riverside, California 92521-0403
| | - Yong Jiang
- Environmental Toxicology Graduate Program, University of California, Riverside, California 92521-0403
| | - Yinsheng Wang
- Department of Chemistry, University of California, Riverside, California 92521-0403
- Environmental Toxicology Graduate Program, University of California, Riverside, California 92521-0403
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