1
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Gutierrez R, Chan AYS, Lai SWT, Itoh S, Lee DH, Sun K, Battad A, Chen S, O'Connor TR, Shuck SC. Lack of mismatch repair enhances resistance to methylating agents for cells deficient in oxidative demethylation. J Biol Chem 2024; 300:107492. [PMID: 38925328 DOI: 10.1016/j.jbc.2024.107492] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2023] [Revised: 05/21/2024] [Accepted: 05/31/2024] [Indexed: 06/28/2024] Open
Abstract
The human alkylation B (AlkB) homologs, ALKBH2 and ALKBH3, respond to methylation damage to maintain genomic integrity and cellular viability. Both ALKBH2 and ALKBH3 are direct reversal repair enzymes that remove 1-methyladenine (1meA) and 3-methylcytosine (3meC) lesions commonly generated by alkylating chemotherapeutic agents. Thus, the existence of deficiencies in ALKBH proteins can be exploited in synergy with chemotherapy. In this study, we investigated possible interactions between ALKBH2 and ALKBH3 with other proteins that could alter damage response and discovered an interaction with the mismatch repair (MMR) system. To test whether the lack of active MMR impacts ALKBH2 and/or ALKBH3 response to methylating agents, we generated cells deficient in ALKBH2, ALKBH3, or both in addition to Mlh homolog 1 (MLH1), another MMR protein. We found that MLH1koALKBH3ko cells showed enhanced resistance toward SN1- and SN2-type methylating agents, whereas MLH1koALKBH2ko cells were only resistant to SN1-type methylating agents. Concomitant loss of ALKBH2 and ALKBH3 (ALKBH2ko3ko) rendered cells sensitive to SN1- and SN2-agents, but the additional loss of MLH1 enhanced resistance to both types of damage. We also showed that ALKBH2ko3ko cells have an ATR-dependent arrest at the G2/M checkpoint, increased apoptotic signaling, and replication fork stress in response to methylation. However, these responses were not observed with the loss of functional MLH1 in MLH1koALKBH2ko3ko cells. Finally, in MLH1koALKBH2ko3ko cells, we observed elevated mutant frequency in untreated and temozolomide treated cells. These results suggest that obtaining a more accurate prognosis of chemotherapeutic outcome requires information on the functionality of ALKBH2, ALKBH3, and MLH1.
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Affiliation(s)
- Roberto Gutierrez
- Department of Cancer Biology, Irell & Manella Graduate School of Biological Sciences, Beckman Research Institute at the City of Hope, Duarte, California, USA
| | - Annie Yin S Chan
- Department of Cancer Biology, Irell & Manella Graduate School of Biological Sciences, Beckman Research Institute at the City of Hope, Duarte, California, USA
| | - Seigmund Wai Tsuen Lai
- Department of Diabetes and Cancer Metabolism, Beckman Research Institute at the City of Hope, Duarte, California, USA
| | - Shunsuke Itoh
- Department of Cancer Biology, Irell & Manella Graduate School of Biological Sciences, Beckman Research Institute at the City of Hope, Duarte, California, USA
| | - Dong-Hyun Lee
- Department of Biological Sciences, College of Natural Sciences, Chonnam National University, Gwangju, South Korea
| | - Kelani Sun
- Department of Diabetes and Cancer Metabolism, Beckman Research Institute at the City of Hope, Duarte, California, USA
| | - Alana Battad
- Department of Diabetes and Cancer Metabolism, Beckman Research Institute at the City of Hope, Duarte, California, USA
| | - Shiuan Chen
- Department of Cancer Biology, Irell & Manella Graduate School of Biological Sciences, Beckman Research Institute at the City of Hope, Duarte, California, USA
| | - Timothy R O'Connor
- Department of Cancer Biology, Irell & Manella Graduate School of Biological Sciences, Beckman Research Institute at the City of Hope, Duarte, California, USA.
| | - Sarah C Shuck
- Department of Diabetes and Cancer Metabolism, Beckman Research Institute at the City of Hope, Duarte, California, USA.
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2
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Computational Insights in DNA Methylation: Catalytic and Mechanistic Elucidations for Forming 3-Methyl Cytosine. J CHEM-NY 2022. [DOI: 10.1155/2022/2673396] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Methylation at C5 position of cytosine (5 mC) is the most abundantly occurring methylation process at CpG island, which has been well known as an epigenetic modification linked to many human diseases. Recently, another methylation approach has been discovered to show that DNA methyltransferases (DNMTs) promote the addition of the methyl group at position 3 to yield 3 mC. The existence of 3 mC can cause severe damages to the DNA strand, such as blocking its replication, repair, and transcription, affecting its stability, and initiating a double-strand DNA break. To gain a deeper insight into the formation of 3 mC, we have performed density functional theory (DFT) modeling studies at different levels of theory to clearly map out the mechanistic details for this new methylation approach. Our computed results are in harmony with pertinent experimental observations and shed light on a crucial off-target activity of DNMTs.
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3
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Christov PP, Richie-Jannetta R, Kingsley PJ, Vemulapalli A, Kim K, Sulikowski GA, Rizzo CJ, Ketkar A, Eoff RL, Rouzer CA, Marnett LJ. Site-Specific Synthesis of Oligonucleotides Containing 6-Oxo-M 1dG, the Genomic Metabolite of M 1dG, and Liquid Chromatography-Tandem Mass Spectrometry Analysis of Its In Vitro Bypass by Human Polymerase ι. Chem Res Toxicol 2021; 34:2567-2578. [PMID: 34860508 PMCID: PMC10518890 DOI: 10.1021/acs.chemrestox.1c00334] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The lipid peroxidation product malondialdehyde and the DNA peroxidation product base-propenal react with dG to generate the exocyclic adduct, M1dG. This mutagenic lesion has been found in human genomic and mitochondrial DNA. M1dG in genomic DNA is enzymatically oxidized to 6-oxo-M1dG, a lesion of currently unknown mutagenic potential. Here, we report the synthesis of an oligonucleotide containing 6-oxo-M1dG and the results of extension experiments aimed at determining the effect of the 6-oxo-M1dG lesion on the activity of human polymerase iota (hPol ι). For this purpose, a liquid chromatography-tandem mass spectrometry (LC-MS/MS) assay was developed to obtain reliable quantitative data on the utilization of poorly incorporated nucleotides. Results demonstrate that hPol ι primarily incorporates deoxycytidine triphosphate (dCTP) and thymidine triphosphate (dTTP) across from 6-oxo-M1dG with approximately equal efficiency, whereas deoxyadenosine triphosphate (dATP) and deoxyguanosine triphosphate (dGTP) are poor substrates. Following the incorporation of a single nucleotide opposite the lesion, 6-oxo-M1dG blocks further replication by the enzyme.
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Affiliation(s)
- Plamen P. Christov
- Department of Chemistry, Vanderbilt University; Vanderbilt Institute of Chemical Biology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, United States
| | - Robyn Richie-Jannetta
- A. B. Hancock, Jr., Memorial Laboratory for Cancer Research, Departments of Biochemistry, and Pharmacology, Vanderbilt Institute of Chemical Biology, and Vanderbilt-Ingram Cancer Center, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, United States
| | - Philip J. Kingsley
- A. B. Hancock, Jr., Memorial Laboratory for Cancer Research, Departments of Biochemistry, and Pharmacology, Vanderbilt Institute of Chemical Biology, and Vanderbilt-Ingram Cancer Center, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, United States
| | - Anoop Vemulapalli
- A. B. Hancock, Jr., Memorial Laboratory for Cancer Research, Departments of Biochemistry, and Pharmacology, Vanderbilt Institute of Chemical Biology, and Vanderbilt-Ingram Cancer Center, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, United States
| | - Kwangho Kim
- Department of Chemistry, Vanderbilt University; Vanderbilt Institute of Chemical Biology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, United States
| | - Gary A. Sulikowski
- Department of Chemistry, Vanderbilt University; Vanderbilt Institute of Chemical Biology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, United States
| | - Carmelo J. Rizzo
- Departments of Chemistry and Biochemistry, Vanderbilt-Ingram Cancer Center, Vanderbilt University, Nashville, Tennessee 37235
| | - Amit Ketkar
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205, United States
| | - Robert L. Eoff
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205, United States
| | - Carol A. Rouzer
- A. B. Hancock, Jr., Memorial Laboratory for Cancer Research, Departments of Biochemistry, and Pharmacology, Vanderbilt Institute of Chemical Biology, and Vanderbilt-Ingram Cancer Center, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, United States
| | - Lawrence J. Marnett
- Department of Chemistry, Vanderbilt University; Vanderbilt Institute of Chemical Biology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, United States
- A. B. Hancock, Jr., Memorial Laboratory for Cancer Research, Departments of Biochemistry, and Pharmacology, Vanderbilt Institute of Chemical Biology, and Vanderbilt-Ingram Cancer Center, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, United States
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4
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Abstract
Mutation produces the raw material for adaptive evolution but also imposes a burden because most mutations are deleterious. The rate of mutation at a particular site is affected by a variety of factors. Methylation of cytosine in DNA at position C5 increases the rate of C→T mutations in bacteria and eukaryotes. Methylation at the N4 position, employed by some restriction-modification systems, is not known to increase the mutation rate. Here, I report that a Salmonella enterica Type III restriction-modification system that includes a cytosine-N4 methyltransferase causes an enormous increase in the rate of mutation of the methylated cytosines, which occur at the overlined C in the motif CACC̅GT. Mutations consist mainly of C→A transversions, the rate of which is increased ∼500-fold by the restriction-modification system. The rate of C→T transitions is also increased and somewhat exceeds that at C5-methylated cytosines in Dcm sites. Two other Salmonella N4 methyltransferases investigated do not have such dramatic effects, although in one case there is a modest increase in C→A mutations along with an increase in C→T mutations. The sensitivity of the C→A rate to orientation with respect to both DNA replication and transcription is higher at hypermutable sites than at other cytosines, suggesting a fundamental mechanistic difference between hypermutation and ordinary mutation.
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Joseph SA, Taglialatela A, Leuzzi G, Huang JW, Cuella-Martin R, Ciccia A. Time for remodeling: SNF2-family DNA translocases in replication fork metabolism and human disease. DNA Repair (Amst) 2020; 95:102943. [PMID: 32971328 DOI: 10.1016/j.dnarep.2020.102943] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2020] [Revised: 07/24/2020] [Accepted: 07/26/2020] [Indexed: 02/07/2023]
Abstract
Over the course of DNA replication, DNA lesions, transcriptional intermediates and protein-DNA complexes can impair the progression of replication forks, thus resulting in replication stress. Failure to maintain replication fork integrity in response to replication stress leads to genomic instability and predisposes to the development of cancer and other genetic disorders. Multiple DNA damage and repair pathways have evolved to allow completion of DNA replication following replication stress, thus preserving genomic integrity. One of the processes commonly induced in response to replication stress is fork reversal, which consists in the remodeling of stalled replication forks into four-way DNA junctions. In normal conditions, fork reversal slows down replication fork progression to ensure accurate repair of DNA lesions and facilitates replication fork restart once the DNA lesions have been removed. However, in certain pathological situations, such as the deficiency of DNA repair factors that protect regressed forks from nuclease-mediated degradation, fork reversal can cause genomic instability. In this review, we describe the complex molecular mechanisms regulating fork reversal, with a focus on the role of the SNF2-family fork remodelers SMARCAL1, ZRANB3 and HLTF, and highlight the implications of fork reversal for tumorigenesis and cancer therapy.
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Affiliation(s)
- Sarah A Joseph
- Department of Genetics and Development, Herbert Irving Comprehensive Cancer Center, Columbia University Irving Medical Center, New York, NY, USA
| | - Angelo Taglialatela
- Department of Genetics and Development, Herbert Irving Comprehensive Cancer Center, Columbia University Irving Medical Center, New York, NY, USA
| | - Giuseppe Leuzzi
- Department of Genetics and Development, Herbert Irving Comprehensive Cancer Center, Columbia University Irving Medical Center, New York, NY, USA
| | - Jen-Wei Huang
- Department of Genetics and Development, Herbert Irving Comprehensive Cancer Center, Columbia University Irving Medical Center, New York, NY, USA
| | - Raquel Cuella-Martin
- Department of Genetics and Development, Herbert Irving Comprehensive Cancer Center, Columbia University Irving Medical Center, New York, NY, USA
| | - Alberto Ciccia
- Department of Genetics and Development, Herbert Irving Comprehensive Cancer Center, Columbia University Irving Medical Center, New York, NY, USA.
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6
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Zhang H. Mechanisms of mutagenesis induced by DNA lesions: multiple factors affect mutations in translesion DNA synthesis. Crit Rev Biochem Mol Biol 2020; 55:219-251. [PMID: 32448001 DOI: 10.1080/10409238.2020.1768205] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Environmental mutagens lead to mutagenesis. However, the mechanisms are very complicated and not fully understood. Environmental mutagens produce various DNA lesions, including base-damaged or sugar-modified DNA lesions, as well as epigenetically modified DNA. DNA polymerases produce mutation spectra in translesion DNA synthesis (TLS) through misincorporation of incorrect nucleotides, frameshift deletions, blockage of DNA replication, imbalance of leading- and lagging-strand DNA synthesis, and genome instability. Motif or subunit in DNA polymerases further affects the mutations in TLS. Moreover, protein interactions and accessory proteins in DNA replisome also alter mutations in TLS, demonstrated by several representative DNA replisomes. Finally, in cells, multiple DNA polymerases or cellular proteins collaborate in TLS and reduce in vivo mutagenesis. Summaries and perspectives were listed. This review shows mechanisms of mutagenesis induced by DNA lesions and the effects of multiple factors on mutations in TLS in vitro and in vivo.
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Affiliation(s)
- Huidong Zhang
- Key Laboratory of Environment and Female Reproductive Health, West China School of Public Health and West China Fourth Hospital, Sichuan University, Chengdu, China
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7
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Seelinger M, Søgaard CK, Otterlei M. The Human RAD5 Homologs, HLTF and SHPRH, Have Separate Functions in DNA Damage Tolerance Dependent on The DNA Lesion Type. Biomolecules 2020; 10:biom10030463. [PMID: 32192191 PMCID: PMC7175315 DOI: 10.3390/biom10030463] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2020] [Revised: 03/13/2020] [Accepted: 03/14/2020] [Indexed: 12/18/2022] Open
Abstract
Helicase-like transcription factor (HLTF) and SNF2, histone-linker, PHD and RING finger domain-containing helicase (SHPRH), the two human homologs of yeast Rad5, are believed to have a vital role in DNA damage tolerance (DDT). Here we show that HLTF, SHPRH and HLTF/SHPRH knockout cell lines show different sensitivities towards UV-irradiation, methyl methanesulfonate (MMS), cisplatin and mitomycin C (MMC), which are drugs that induce different types of DNA lesions. In general, the HLTF/SHPRH double knockout cell line was less sensitive than the single knockouts in response to all drugs, and interestingly, especially to MMS and cisplatin. Using the SupF assay, we detected an increase in the mutation frequency in HLTF knockout cells both after UV- and MMS-induced DNA lesions, while we detected a decrease in mutation frequency over UV lesions in the HLTF/SHPRH double knockout cells. No change in the mutation frequency was detected in the HLTF/SHPRH double knockout cell line after MMS treatment, even though these cells were more resistant to MMS and grew faster than the other cell lines after treatment with DNA damaging agents. This phenotype could possibly be explained by a reduced activation of checkpoint kinase 2 (CHK2) and MCM2 (a component of the pre-replication complex) after MMS treatment in cells lacking SHPRH. Our data reveal both distinct and common roles of the human RAD5 homologs dependent on the nature of DNA lesions, and identified SHPRH as a regulator of CHK2, a central player in DNA damage response.
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8
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McIntyre J. Polymerase iota - an odd sibling among Y family polymerases. DNA Repair (Amst) 2019; 86:102753. [PMID: 31805501 DOI: 10.1016/j.dnarep.2019.102753] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2019] [Revised: 11/18/2019] [Accepted: 11/19/2019] [Indexed: 12/14/2022]
Abstract
It has been two decades since the discovery of the most mutagenic human DNA polymerase, polymerase iota (Polι). Since then, the biochemical activity of this translesion synthesis (TLS) enzyme has been extensively explored, mostly through in vitro experiments, with some insight into its cellular activity. Polι is one of four members of the Y-family of polymerases, which are the best characterized DNA damage-tolerant polymerases involved in TLS. Polι shares some common Y-family features, including low catalytic efficiency and processivity, high infidelity, the ability to bypass some DNA lesions, and a deficiency in 3'→5' exonucleolytic proofreading. However, Polι exhibits numerous properties unique among the Y-family enzymes. Polι has an unusual catalytic pocket structure and prefers Hoogsteen over Watson-Crick pairing, and its replication fidelity strongly depends on the template; further, it prefers Mn2+ ions rather than Mg2+ as catalytic activators. In addition to its polymerase activity, Polι possesses also 5'-deoxyribose phosphate (dRP) lyase activity, and its ability to participate in base excision repair has been shown. As a highly error-prone polymerase, its regulation is crucial and mostly involves posttranslational modifications and protein-protein interactions. The upregulation and downregulation of Polι are correlated with different types of cancer and suggestions regarding the possible function of this polymerase have emerged from studies of various cancer lines. Nonetheless, after twenty years of research, the biological function of Polι certainly remains unresolved.
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Affiliation(s)
- Justyna McIntyre
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, ul. Pawinskiego 5a, 02-106, Warsaw, Poland.
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9
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McIntyre J, Sobolewska A, Fedorowicz M, McLenigan MP, Macias M, Woodgate R, Sledziewska-Gojska E. DNA polymerase ι is acetylated in response to S N2 alkylating agents. Sci Rep 2019; 9:4789. [PMID: 30886224 PMCID: PMC6423139 DOI: 10.1038/s41598-019-41249-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2018] [Accepted: 03/04/2019] [Indexed: 02/07/2023] Open
Abstract
DNA polymerase iota (Polι) belongs to the Y-family of DNA polymerases that are involved in DNA damage tolerance through their role in translesion DNA synthesis. Like all other Y-family polymerases, Polι interacts with proliferating cell nuclear antigen (PCNA), Rev1, ubiquitin and ubiquitinated-PCNA and is also ubiquitinated itself. Here, we report that Polι also interacts with the p300 acetyltransferase and is acetylated. The primary acetylation site is K550, located in the Rev1-interacting region. However, K550 amino acid substitutions have no effect on Polι's ability to interact with Rev1. Interestingly, we find that acetylation of Polι significantly and specifically increases in response to SN2 alkylating agents and to a lower extent to SN1 alkylating and oxidative agents. As we have not observed acetylation of Polι's closest paralogue, DNA polymerase eta (Polη), with which Polι shares many functional similarities, we believe that this modification might exclusively regulate yet to be determined, and separate function(s) of Polι.
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Affiliation(s)
- Justyna McIntyre
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, ul. Pawinskiego 5a, 02-106, Warsaw, Poland.
| | - Aleksandra Sobolewska
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, ul. Pawinskiego 5a, 02-106, Warsaw, Poland
| | - Mikolaj Fedorowicz
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, ul. Pawinskiego 5a, 02-106, Warsaw, Poland
| | - Mary P McLenigan
- Laboratory of Genomic Integrity, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, 20892-3371, USA
| | - Matylda Macias
- Laboratory of Molecular and Cellular Neurobiology, International Institute of Molecular and Cell Biology, ul. Ks. Trojdena 4, 02-109, Warsaw, Poland
| | - Roger Woodgate
- Laboratory of Genomic Integrity, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, 20892-3371, USA
| | - Ewa Sledziewska-Gojska
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, ul. Pawinskiego 5a, 02-106, Warsaw, Poland
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10
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Evolutionary analysis indicates that DNA alkylation damage is a byproduct of cytosine DNA methyltransferase activity. Nat Genet 2018; 50:452-459. [PMID: 29459678 PMCID: PMC5865749 DOI: 10.1038/s41588-018-0061-8] [Citation(s) in RCA: 52] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2016] [Accepted: 01/16/2018] [Indexed: 01/31/2023]
Abstract
Methylation at the 5 position of cytosine in DNA (5meC) is a key epigenetic mark in eukaryotes. Once introduced, 5meC can be maintained through DNA replication by the activity of 'maintenance' DNA methyltransferases (DNMTs). Despite their ancient origin, DNA methylation pathways differ widely across animals, such that 5meC is either confined to transcribed genes or lost altogether in several lineages. We used comparative epigenomics to investigate the evolution of DNA methylation. Although the model nematode Caenorhabditis elegans lacks DNA methylation, more basal nematodes retain cytosine DNA methylation, which is targeted to repeat loci. We found that DNA methylation coevolved with the DNA alkylation repair enzyme ALKB2 across eukaryotes. In addition, we found that DNMTs introduced the toxic lesion 3-methylcytosine into DNA both in vitro and in vivo. Alkylation damage is therefore intrinsically associated with DNMT activity, and this may promote the loss of DNA methylation in many species.
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11
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Gutierrez R, Thompson Y, R. O’Connor T. DNA direct repair pathways in cancer. AIMS MEDICAL SCIENCE 2018. [DOI: 10.3934/medsci.2018.3.284] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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12
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Mentegari E, Crespan E, Bavagnoli L, Kissova M, Bertoletti F, Sabbioneda S, Imhof R, Sturla SJ, Nilforoushan A, Hübscher U, van Loon B, Maga G. Ribonucleotide incorporation by human DNA polymerase η impacts translesion synthesis and RNase H2 activity. Nucleic Acids Res 2017; 45:2600-2614. [PMID: 27994034 PMCID: PMC5389505 DOI: 10.1093/nar/gkw1275] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2016] [Accepted: 12/07/2016] [Indexed: 12/25/2022] Open
Abstract
Ribonucleotides (rNs) incorporated in the genome by DNA polymerases (Pols) are removed by RNase H2. Cytidine and guanosine preferentially accumulate over the other rNs. Here we show that human Pol η can incorporate cytidine monophosphate (rCMP) opposite guanine, 8-oxo-7,8-dihydroguanine, 8-methyl-2΄-deoxyguanosine and a cisplatin intrastrand guanine crosslink (cis-PtGG), while it cannot bypass a 3-methylcytidine or an abasic site with rNs as substrates. Pol η is also capable of synthesizing polyribonucleotide chains, and its activity is enhanced by its auxiliary factor DNA Pol δ interacting protein 2 (PolDIP2). Human RNase H2 removes cytidine and guanosine less efficiently than the other rNs and incorporation of rCMP opposite DNA lesions further reduces the efficiency of RNase H2. Experiments with XP-V cell extracts indicate Pol η as the major basis of rCMP incorporation opposite cis-PtGG. These results suggest that translesion synthesis by Pol η can contribute to the accumulation of rCMP in the genome, particularly opposite modified guanines.
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Affiliation(s)
- Elisa Mentegari
- DNA Enzymology & Molecular Virology and Cell Nucleus & DNA replication Units, Institute of Molecular Genetics IGM-CNR, via Abbiategrasso 207, I-27100 Pavia, Italy
| | - Emmanuele Crespan
- DNA Enzymology & Molecular Virology and Cell Nucleus & DNA replication Units, Institute of Molecular Genetics IGM-CNR, via Abbiategrasso 207, I-27100 Pavia, Italy
| | - Laura Bavagnoli
- DNA Enzymology & Molecular Virology and Cell Nucleus & DNA replication Units, Institute of Molecular Genetics IGM-CNR, via Abbiategrasso 207, I-27100 Pavia, Italy
| | - Miroslava Kissova
- DNA Enzymology & Molecular Virology and Cell Nucleus & DNA replication Units, Institute of Molecular Genetics IGM-CNR, via Abbiategrasso 207, I-27100 Pavia, Italy
| | - Federica Bertoletti
- DNA Enzymology & Molecular Virology and Cell Nucleus & DNA replication Units, Institute of Molecular Genetics IGM-CNR, via Abbiategrasso 207, I-27100 Pavia, Italy
| | - Simone Sabbioneda
- DNA Enzymology & Molecular Virology and Cell Nucleus & DNA replication Units, Institute of Molecular Genetics IGM-CNR, via Abbiategrasso 207, I-27100 Pavia, Italy
| | - Ralph Imhof
- Department of Molecular Mechanisms of Disease, University of Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland
| | - Shana J Sturla
- Department of Health Sciences and Technology, ETH Zurich, Schmelzbergstrasse 9, CH-8092 Zürich, Switzerland
| | - Arman Nilforoushan
- Department of Health Sciences and Technology, ETH Zurich, Schmelzbergstrasse 9, CH-8092 Zürich, Switzerland
| | - Ulrich Hübscher
- Department of Molecular Mechanisms of Disease, University of Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland
| | - Barbara van Loon
- Department of Molecular Mechanisms of Disease, University of Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland
| | - Giovanni Maga
- DNA Enzymology & Molecular Virology and Cell Nucleus & DNA replication Units, Institute of Molecular Genetics IGM-CNR, via Abbiategrasso 207, I-27100 Pavia, Italy
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13
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Ignatov A, Bondarenko K, Makarova A. Non-bulky Lesions in Human DNA: the Ways of Formation, Repair, and Replication. Acta Naturae 2017; 9:12-26. [PMID: 29104772 PMCID: PMC5662270] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2017] [Indexed: 11/06/2022] Open
Abstract
DNA damage is a major cause of replication interruption, mutations, and cell death. DNA damage is removed by several types of repair processes. The involvement of specialized DNA polymerases in replication provides an important mechanism that helps tolerate persistent DNA damage. Specialized DNA polymerases incorporate nucleotides opposite lesions with high efficiency but demonstrate low accuracy of DNA synthesis. In this review, we summarize the types and mechanisms of formation and repair of non-bulky DNA lesions, and we provide an overview of the role of specialized DNA polymerases in translesion DNA synthesis.
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Affiliation(s)
- A.V. Ignatov
- Institute of Molecular Genetics of Russian Academy of Sciences, Kurchatov sq. 2, Moscow, 123182 , Russia
- Department of Molecular Biology, Faculty of Biology, Moscow State University, Leninskie Gory 1, bldg. 12, Moscow, 119991, Russia
| | - K.A. Bondarenko
- Institute of Molecular Genetics of Russian Academy of Sciences, Kurchatov sq. 2, Moscow, 123182 , Russia
| | - A.V. Makarova
- Institute of Molecular Genetics of Russian Academy of Sciences, Kurchatov sq. 2, Moscow, 123182 , Russia
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14
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Kogaki T, Ohshio I, Kawaguchi M, Kimoto M, Kitae K, Hase H, Ueda Y, Jingushi K, Tsujikawa K. TP53 gene status is a critical determinant of phenotypes induced by ALKBH3 knockdown in non-small cell lung cancers. Biochem Biophys Res Commun 2017; 488:285-290. [DOI: 10.1016/j.bbrc.2017.05.024] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2017] [Accepted: 05/03/2017] [Indexed: 10/19/2022]
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15
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Anindya R. Non-heme dioxygenases in tumor hypoxia: They're all bound with the same fate. DNA Repair (Amst) 2016; 49:21-25. [PMID: 27964836 DOI: 10.1016/j.dnarep.2016.12.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2016] [Revised: 11/30/2016] [Accepted: 12/01/2016] [Indexed: 01/05/2023]
Abstract
Tumor tissues are known to harbor hypoxic areas. The hypoxic microenvironment promotes angiogenesis. Hypoxic tumor cells also manifest genome instability. DNA damage repair pathways, such as double-strand break repair, mismatch repair and base excision repair are known to be altered during hypoxia. This review is focused on the non-heme Fe(II) and 2-oxoglutarate-dependent dioxygenases which are involved in repair of DNA alkylation adducts. Activities of these DNA repair enzymes are completely oxygen-dependent and little information is available about inhibition of these enzymes during hypoxia. While impairment of function of non-heme dioxygenase during tumor hypoxia has been implicated in different studies, the possible outcomes with respect to mutagenesis and genomic instability are explored here.
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Affiliation(s)
- Roy Anindya
- Department of Biotechnology, Indian Institute of Technology Hyderabad, Kandi 502285, Hyderabad, Telangana, India.
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16
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Xu W, Kool D, O'Flaherty DK, Keating AM, Sacre L, Egli M, Noronha A, Wilds CJ, Zhao L. O 6-2'-Deoxyguanosine-butylene-O 6-2'-deoxyguanosine DNA Interstrand Cross-Links Are Replication-Blocking and Mutagenic DNA Lesions. Chem Res Toxicol 2016; 29:1872-1882. [PMID: 27768841 DOI: 10.1021/acs.chemrestox.6b00278] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
DNA interstrand cross-links (ICLs) are cytotoxic DNA lesions derived from reactions of DNA with a number of anti-cancer reagents as well as endogenous bifunctional electrophiles. Deciphering the DNA repair mechanisms of ICLs is important for understanding the toxicity of DNA cross-linking agents and for developing effective chemotherapies. Previous research has focused on ICLs cross-linked with the N7 and N2 atoms of guanine as well as those formed at the N6 atom of adenine; however, little is known about the mutagenicity of O6-dG-derived ICLs. Although less abundant, O6-alkylated guanine DNA lesions are chemically stable and highly mutagenic. Here, O6-2'-deoxyguanosine-butylene-O6-2'-deoxyguanosine (O6-dG-C4-O6-dG) is designed as a chemically stable ICL, which can be induced by the action of bifunctional alkylating agents. We investigate the DNA replication-blocking and mutagenic properties of O6-dG-C4-O6-dG ICLs during an important step in ICL repair, translesion DNA synthesis (TLS). The model replicative DNA polymerase (pol) Sulfolobus solfataricus P2 DNA polymerase B1 (Dpo1) is able to incorporate a correct nucleotide opposite the cross-linked template guanine of ICLs with low efficiency and fidelity but cannot extend beyond the ICLs. Translesion synthesis by human pol κ is completely inhibited by O6-dG-C4-O6-dG ICLs. Moderate bypass activities are observed for human pol η and S. solfataricus P2 DNA polymerase IV (Dpo4). Among the pols tested, pol η exhibits the highest bypass activity; however, 70% of the bypass products are mutagenic containing substitutions or deletions. The increase in the size of unhooked repair intermediates elevates the frequency of deletion mutation. Lastly, the importance of pol η in O6-dG-derived ICL bypass is demonstrated using whole cell extracts of Xeroderma pigmentosum variant patient cells and those complemented with pol η. Together, this study provides the first set of biochemical evidence for the mutagenicity of O6-dG-derived ICLs.
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Affiliation(s)
| | | | - Derek K O'Flaherty
- Department of Chemistry and Biochemistry, Concordia University , 7141 Sherbrooke Street West, Montréal, Québec H4B 1R6, Canada
| | | | - Lauralicia Sacre
- Department of Chemistry and Biochemistry, Concordia University , 7141 Sherbrooke Street West, Montréal, Québec H4B 1R6, Canada
| | - Martin Egli
- Department of Biochemistry, Vanderbilt University School of Medicine , Nashville, Tennessee 37232-0146, United States
| | - Anne Noronha
- Department of Chemistry and Biochemistry, Concordia University , 7141 Sherbrooke Street West, Montréal, Québec H4B 1R6, Canada
| | - Christopher J Wilds
- Department of Chemistry and Biochemistry, Concordia University , 7141 Sherbrooke Street West, Montréal, Québec H4B 1R6, Canada
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17
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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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18
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Pataillot-Meakin T, Pillay N, Beck S. 3-methylcytosine in cancer: an underappreciated methyl lesion? Epigenomics 2016; 8:451-4. [PMID: 27032436 DOI: 10.2217/epi.15.121] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Affiliation(s)
- Thomas Pataillot-Meakin
- Department of Cancer Biology, UCL Cancer Institute, 72 Huntley Street, London, WC1E 6DD, UK
- Department of Pathology, UCL Cancer Institute, 72 Huntley Street, London, WC1E 6DD, UK
| | - Nischalan Pillay
- Department of Pathology, UCL Cancer Institute, 72 Huntley Street, London, WC1E 6DD, UK
| | - Stephan Beck
- Department of Cancer Biology, UCL Cancer Institute, 72 Huntley Street, London, WC1E 6DD, UK
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19
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Crespan E, Furrer A, Rösinger M, Bertoletti F, Mentegari E, Chiapparini G, Imhof R, Ziegler N, Sturla SJ, Hübscher U, van Loon B, Maga G. Impact of ribonucleotide incorporation by DNA polymerases β and λ on oxidative base excision repair. Nat Commun 2016; 7:10805. [PMID: 26917111 PMCID: PMC4773436 DOI: 10.1038/ncomms10805] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2015] [Accepted: 01/22/2016] [Indexed: 12/17/2022] Open
Abstract
Oxidative stress is a very frequent source of DNA damage. Many cellular DNA polymerases (Pols) can incorporate ribonucleotides (rNMPs) during DNA synthesis. However, whether oxidative stress-triggered DNA repair synthesis contributes to genomic rNMPs incorporation is so far not fully understood. Human specialized Pols β and λ are the important enzymes involved in the oxidative stress tolerance, acting both in base excision repair and in translesion synthesis past the very frequent oxidative lesion 7,8-dihydro-8-oxoguanine (8-oxo-G). We found that Pol β, to a greater extent than Pol λ can incorporate rNMPs opposite normal bases or 8-oxo-G, and with a different fidelity. Further, the incorporation of rNMPs opposite 8-oxo-G delays repair by DNA glycosylases. Studies in Pol β- and λ-deficient cell extracts suggest that Pol β levels can greatly affect rNMP incorporation opposite oxidative DNA lesions. Oxidative stress is a common source of DNA damage and is repaired by the base excision repair machinery, including polymerase beta. Here the authors find that polymerase beta, and to a lesser extent lambda, can mistakenly incorporate ribonucleotides during synthesis.
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Affiliation(s)
- Emmanuele Crespan
- DNA Enzymology &Molecular Virology Unit, Institute of Molecular Genetics IGM-CNR, via Abbiategrasso 207, I-27100 Pavia, Italy
| | - Antonia Furrer
- Department of Molecular Mechanisms of Disease, University of Zürich, CH-8057 Zürich, Switzerland
| | - Marcel Rösinger
- Department of Molecular Mechanisms of Disease, University of Zürich, CH-8057 Zürich, Switzerland
| | - Federica Bertoletti
- DNA Enzymology &Molecular Virology Unit, Institute of Molecular Genetics IGM-CNR, via Abbiategrasso 207, I-27100 Pavia, Italy
| | - Elisa Mentegari
- DNA Enzymology &Molecular Virology Unit, Institute of Molecular Genetics IGM-CNR, via Abbiategrasso 207, I-27100 Pavia, Italy
| | - Giulia Chiapparini
- DNA Enzymology &Molecular Virology Unit, Institute of Molecular Genetics IGM-CNR, via Abbiategrasso 207, I-27100 Pavia, Italy
| | - Ralph Imhof
- Department of Molecular Mechanisms of Disease, University of Zürich, CH-8057 Zürich, Switzerland
| | - Nathalie Ziegler
- Department of Health Sciences and Technology, ETH Zurich, CH-8092 Zürich, Switzerland
| | - Shana J Sturla
- Department of Health Sciences and Technology, ETH Zurich, CH-8092 Zürich, Switzerland
| | - Ulrich Hübscher
- Department of Molecular Mechanisms of Disease, University of Zürich, CH-8057 Zürich, Switzerland
| | - Barbara van Loon
- Department of Molecular Mechanisms of Disease, University of Zürich, CH-8057 Zürich, Switzerland
| | - Giovanni Maga
- DNA Enzymology &Molecular Virology Unit, Institute of Molecular Genetics IGM-CNR, via Abbiategrasso 207, I-27100 Pavia, Italy
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20
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Fu D, Samson LD, Hübscher U, van Loon B. The interaction between ALKBH2 DNA repair enzyme and PCNA is direct, mediated by the hydrophobic pocket of PCNA and perturbed in naturally-occurring ALKBH2 variants. DNA Repair (Amst) 2015; 35:13-8. [PMID: 26408825 DOI: 10.1016/j.dnarep.2015.09.008] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Human AlkB homolog 2 (ALKBH2) is a DNA repair enzyme that catalyzes the direct reversal of DNA methylation damage through oxidative demethylation. While ALKBH2 colocalizes with proliferating cell nuclear antigen (PCNA) in DNA replication foci, it remains unknown whether these two proteins alone form a complex or require additional components for interaction. Here, we demonstrate that ALKBH2 can directly interact with PCNA independent from other cellular factors, and we identify the hydrophobic pocket of PCNA as the key domain mediating this interaction. Moreover, we find that PCNA association with ALKBH2 increases significantly during DNA replication, suggesting that ALKBH2 forms a cell-cycle dependent complex with PCNA. Intriguingly, we show that an ALKBH2 germline variant, as well as a variant found in cancer, display altered interaction with PCNA. Our studies reveal the ALKBH2 binding interface of PCNA and indicate that both germline and somatic ALKBH2 variants could have cellular effects on ALKBH2 function in DNA repair.
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Affiliation(s)
- Dragony Fu
- Institute of Veterinary Biochemistry and Molecular Biology, University of Zürich, Winterthurerstrasse 190, 8057 Zürich, Switzerland.
| | - Leona D Samson
- Department of Biological Engineering and Biology, Center for Environmental Health Sciences, David H. Koch Center for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Ullrich Hübscher
- Institute of Veterinary Biochemistry and Molecular Biology, University of Zürich, Winterthurerstrasse 190, 8057 Zürich, Switzerland
| | - Barbara van Loon
- Institute of Veterinary Biochemistry and Molecular Biology, University of Zürich, Winterthurerstrasse 190, 8057 Zürich, Switzerland.
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21
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Nilforoushan A, Furrer A, Wyss LA, van Loon B, Sturla SJ. Nucleotides with altered hydrogen bonding capacities impede human DNA polymerase η by reducing synthesis in the presence of the major cisplatin DNA adduct. J Am Chem Soc 2015; 137:4728-34. [PMID: 25786104 DOI: 10.1021/ja512547g] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Human DNA polymerase η (hPol η) contributes to anticancer drug resistance by catalyzing the replicative bypass of DNA adducts formed by the widely used chemotherapeutic agent cis-diamminedichloroplatinum (cisplatin). A chemical basis for overcoming bypass-associated resistance requires greater knowledge of how small molecules influence the hPol η-catalyzed bypass of DNA adducts. In this study, we demonstrated how synthetic nucleoside triphosphates act as hPol η substrates and characterized their influence on hPol η-mediated DNA synthesis over unmodified and platinated DNA. The single nucleotide incorporation efficiency of the altered nucleotides varied by more than 10-fold and the higher incorporation rates appeared to be attributable to the presence of an additional hydrogen bond between incoming dNTP and templating base. Finally, full-length DNA synthesis in the presence of increasing concentrations of synthetic nucleotides reduced the amount of DNA product independent of the template, representing the first example of hPol η inhibition in the presence of a platinated DNA template.
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Affiliation(s)
- Arman Nilforoushan
- §Department of Health Sciences and Technology, ETH Zürich, Schmelzbergstrasse 9, 8092 Zürich, Switzerland
| | - Antonia Furrer
- ‡Institute of Veterinary Biochemistry and Molecular Biology, University of Zurich, Wintherthurerstrasse 190, 8057 Zürich, Switzerland
| | - Laura A Wyss
- §Department of Health Sciences and Technology, ETH Zürich, Schmelzbergstrasse 9, 8092 Zürich, Switzerland
| | - Barbara van Loon
- ‡Institute of Veterinary Biochemistry and Molecular Biology, University of Zurich, Wintherthurerstrasse 190, 8057 Zürich, Switzerland
| | - Shana J Sturla
- §Department of Health Sciences and Technology, ETH Zürich, Schmelzbergstrasse 9, 8092 Zürich, Switzerland
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22
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Makarova AV, Ignatov A, Miropolskaya N, Kulbachinskiy A. Roles of the active site residues and metal cofactors in noncanonical base-pairing during catalysis by human DNA polymerase iota. DNA Repair (Amst) 2014; 22:67-76. [PMID: 25108837 DOI: 10.1016/j.dnarep.2014.07.006] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2014] [Revised: 07/12/2014] [Accepted: 07/14/2014] [Indexed: 12/15/2022]
Abstract
Human DNA polymerase iota (Pol ι) is a Y-family polymerase that can bypass various DNA lesions but possesses very low fidelity of DNA synthesis in vitro. Structural analysis of Pol ι revealed a narrow active site that promotes noncanonical base-pairing during catalysis. To better understand the structure-function relationships in the active site of Pol ι we investigated substitutions of individual amino acid residues in its fingers domain that contact either the templating or the incoming nucleotide. Two of the substitutions, Y39A and Q59A, significantly decreased the catalytic activity but improved the fidelity of Pol ι. Surprisingly, in the presence of Mn(2+) ions, the wild-type and mutant Pol ι variants efficiently incorporated nucleotides opposite template purines containing modifications that disrupted either Hoogsteen or Watson-Crick base-pairing, suggesting that Pol ι may use various types of interactions during nucleotide addition. In contrast, in Mg(2+) reactions, wild-type Pol ι was dependent on Hoogsteen base-pairing, the Y39A mutant was essentially inactive, and the Q59A mutant promoted Watson-Crick interactions with template purines. The results suggest that Pol ι utilizes distinct mechanisms of nucleotide incorporation depending on the metal cofactor and reveal important roles of specific residues from the fingers domain in base-pairing and catalysis.
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Affiliation(s)
- Alena V Makarova
- Institute of Molecular Genetics, Russian Academy of Sciences, Moscow 123182, Russia.
| | - Artem Ignatov
- Institute of Molecular Genetics, Russian Academy of Sciences, Moscow 123182, Russia
| | | | - Andrey Kulbachinskiy
- Institute of Molecular Genetics, Russian Academy of Sciences, Moscow 123182, Russia.
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