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Fang Q. The Versatile Attributes of MGMT: Its Repair Mechanism, Crosstalk with Other DNA Repair Pathways, and Its Role in Cancer. Cancers (Basel) 2024; 16:331. [PMID: 38254819 PMCID: PMC10814553 DOI: 10.3390/cancers16020331] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2023] [Revised: 01/09/2024] [Accepted: 01/10/2024] [Indexed: 01/24/2024] Open
Abstract
O6-methylguanine-DNA methyltransferase (MGMT or AGT) is a DNA repair protein with the capability to remove alkyl groups from O6-AlkylG adducts. Moreover, MGMT plays a crucial role in repairing DNA damage induced by methylating agents like temozolomide and chloroethylating agents such as carmustine, and thereby contributes to chemotherapeutic resistance when these agents are used. This review delves into the structural roles and repair mechanisms of MGMT, with emphasis on the potential structural and functional roles of the N-terminal domain of MGMT. It also explores the development of cancer therapeutic strategies that target MGMT. Finally, it discusses the intriguing crosstalk between MGMT and other DNA repair pathways.
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Affiliation(s)
- Qingming Fang
- Department of Biochemistry and Structural Biology, Greehey Children's Cancer Research Institute, University of Texas Health San Antonio, San Antonio, TX 78229, USA
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2
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Tessmer I, Margison GP. The DNA Alkyltransferase Family of DNA Repair Proteins: Common Mechanisms, Diverse Functions. Int J Mol Sci 2023; 25:463. [PMID: 38203633 PMCID: PMC10779285 DOI: 10.3390/ijms25010463] [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] [Received: 11/30/2023] [Revised: 12/22/2023] [Accepted: 12/27/2023] [Indexed: 01/12/2024] Open
Abstract
DNA alkyltransferase and alkyltransferase-like family proteins are responsible for the repair of highly mutagenic and cytotoxic O6-alkylguanine and O4-alkylthymine bases in DNA. Their mechanism involves binding to the damaged DNA and flipping the base out of the DNA helix into the active site pocket in the protein. Alkyltransferases then directly and irreversibly transfer the alkyl group from the base to the active site cysteine residue. In contrast, alkyltransferase-like proteins recruit nucleotide excision repair components for O6-alkylguanine elimination. One or more of these proteins are found in all kingdoms of life, and where this has been determined, their overall DNA repair mechanism is strictly conserved between organisms. Nevertheless, between species, subtle as well as more extensive differences that affect target lesion preferences and/or introduce additional protein functions have evolved. Examining these differences and their functional consequences is intricately entwined with understanding the details of their DNA repair mechanism(s) and their biological roles. In this review, we will present and discuss various aspects of the current status of knowledge on this intriguing protein family.
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Affiliation(s)
- Ingrid Tessmer
- Rudolf Virchow Center, University of Würzburg, Josef-Schneider-Strasse 2, 97080 Würzburg, Germany
| | - Geoffrey P. Margison
- School of Health Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester M13 9PL, UK;
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3
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Tessmer I. The roles of non-productive complexes of DNA repair proteins with DNA lesions. DNA Repair (Amst) 2023; 129:103542. [PMID: 37453245 DOI: 10.1016/j.dnarep.2023.103542] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2023] [Revised: 06/30/2023] [Accepted: 07/07/2023] [Indexed: 07/18/2023]
Abstract
A multitude of different types of lesions is continuously introduced into the DNA inside our cells, and their rapid and efficient repair is fundamentally important for the maintenance of genomic stability and cellular viability. This is achieved by a number of DNA repair systems that each involve different protein factors and employ versatile strategies to target different types of DNA lesions. Intriguingly, specialized DNA repair proteins have also evolved to form non-functional complexes with their target lesions. These proteins allow the marking of innocuous lesions to render them visible for DNA repair systems and can serve to directly recruit DNA repair cascades. Moreover, they also provide links between different DNA repair mechanisms or even between DNA lesions and transcription regulation. I will focus here in particular on recent findings from single molecule analyses on the alkyltransferase-like protein ATL, which is believed to initiate nucleotide excision repair (NER) of non-native NER target lesions, and the base excision repair (BER) enzyme hOGG1, which recruits the oncogene transcription factor Myc to gene promoters under oxidative stress.
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Affiliation(s)
- Ingrid Tessmer
- Rudolf Virchow Center, University of Würzburg, Josef Schneider Str. 2, 97080 Würzburg, Germany
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4
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Abstract
Bacteria are continuously exposed to numerous endogenous and exogenous DNA-damaging agents. To maintain genome integrity and ensure cell survival, bacteria have evolved several DNA repair pathways to correct different types of DNA damage and non-canonical bases, including strand breaks, nucleotide modifications, cross-links, mismatches and ribonucleotide incorporations. Recent advances in genome-wide screens, the availability of thousands of whole-genome sequences and advances in structural biology have enabled the rapid discovery and characterization of novel bacterial DNA repair pathways and new enzymatic activities. In this Review, we discuss recent advances in our understanding of base excision repair and nucleotide excision repair, and we discuss several new repair processes including the EndoMS mismatch correction pathway and the MrfAB excision repair system.
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Affiliation(s)
- Katherine J Wozniak
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI, USA
| | - Lyle A Simmons
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI, USA.
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5
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Alkyltransferase-like protein clusters scan DNA rapidly over long distances and recruit NER to alkyl-DNA lesions. Proc Natl Acad Sci U S A 2020; 117:9318-9328. [PMID: 32273391 DOI: 10.1073/pnas.1916860117] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Alkylation of guanine bases in DNA is detrimental to cells due to its high mutagenic and cytotoxic potential and is repaired by the alkyltransferase AGT. Additionally, alkyltransferase-like proteins (ATLs), which are structurally similar to AGTs, have been identified in many organisms. While ATLs are per se catalytically inactive, strong evidence has suggested that ATLs target alkyl lesions to the nucleotide excision repair system (NER). Using a combination of single-molecule and ensemble approaches, we show here recruitment of UvrA, the initiating enzyme of prokaryotic NER, to an alkyl lesion by ATL. We further characterize lesion recognition by ATL and directly visualize DNA lesion search by highly motile ATL and ATL-UvrA complexes on DNA at the molecular level. Based on the high similarity of ATLs and the DNA-interacting domain of AGTs, our results provide important insight in the lesion search mechanism, not only by ATL but also by AGT, thus opening opportunities for controlling the action of AGT for therapeutic benefit during chemotherapy.
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6
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Aunins TR, Eller KA, Courtney CM, Levy M, Goodman SM, Nagpal P, Chatterjee A. Isolating the Escherichia coli Transcriptomic Response to Superoxide Generation from Cadmium Chalcogenide Quantum Dots. ACS Biomater Sci Eng 2019; 5:4206-4218. [PMID: 33417778 DOI: 10.1021/acsbiomaterials.9b01087] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Nanomaterials have been extensively used in the biomedical field and have recently garnered attention as potential antimicrobial agents. Cadmium telluride quantum dots (QDs) with a bandgap of 2.4 eV (CdTe-2.4) were previously shown to inhibit multidrug-resistant clinical isolates of bacterial pathogens via light-activated superoxide generation. Here we investigate the transcriptomic response of Escherichia coli to phototherapeutic CdTe-2.4 QDs both with and without illumination, as well as in comparison with the non-superoxide-generating cadmium selenide QDs (CdSe-2.4) as a negative control. Our analysis sought to separate the transcriptomic response of E. coli to the generation of superoxide by the CdTe-2.4 QDs from the presence of cadmium chalcogenide nanoparticles alone. We used comparisons between illuminated CdTe-2.4 conditions and all others to establish the superoxide generation response and used comparisons between all QD conditions and the no treatment condition to establish the cadmium chalcogenide QD response. In our analysis of the gene expression experiments, we found eight genes to be consistently differentially expressed as a response to superoxide generation, and these genes demonstrate a consistent association with the DNA damage response and deactivation of iron-sulfur clusters. Each of these responses is characteristic of a bacterial superoxide response. We found 18 genes associated with the presence of cadmium chalcogenide QDs but not the generation of superoxide by CdTe-2.4, including several that implicated metabolism of amino acids in the E. coli response. To explore each of these gene sets further, we performed both gene knockout and amino acid supplementation experiments. We identified the importance of leucyl-tRNA downregulation as a cadmium chalcogenide QD response and reinforced the relationship between CdTe-2.4 stress and iron-sulfur clusters through examination of the gene tusA. This study demonstrates the transcriptomic response of E. coli to CdTe-2.4 and CdSe-2.4 QDs and parses the different effects of superoxide versus material effects on the bacteria. Our findings may provide useful information toward the development of QD-based antibacterial therapy in the future.
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7
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Nagel ZD, Beharry AA, Mazzucato P, Kitange GJ, Sarkaria JN, Kool ET, Samson LD. Fluorescent reporter assays provide direct, accurate, quantitative measurements of MGMT status in human cells. PLoS One 2019; 14:e0208341. [PMID: 30811507 PMCID: PMC6392231 DOI: 10.1371/journal.pone.0208341] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2018] [Accepted: 11/15/2018] [Indexed: 12/21/2022] Open
Abstract
The DNA repair protein O6-methylguanine DNA methyltransferase (MGMT) strongly influences the effectiveness of cancer treatment with chemotherapeutic alkylating agents, and MGMT status in cancer cells could potentially contribute to tailored therapies for individual patients. However, the promoter methylation and immunohistochemical assays presently used for measuring MGMT in clinical samples are indirect, cumbersome and sometimes do not accurately report MGMT activity. Here we directly compare the accuracy of 6 analytical methods, including two fluorescent reporter assays, against the in vitro MGMT activity assay that is considered the gold standard for measuring MGMT DNA repair capacity. We discuss the relative advantages of each method. Our data indicate that two recently developed fluorescence-based assays measure MGMT activity accurately and efficiently, and could provide a functional dimension to clinical efforts to identify patients who are likely to benefit from alkylating chemotherapy.
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Affiliation(s)
- Zachary D. Nagel
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
| | - Andrew A. Beharry
- Department of Chemistry, Stanford University, Stanford, California, United States of America
| | - Patrizia Mazzucato
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
| | - Gaspar J. Kitange
- Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota, United States of America
| | - Jann N. Sarkaria
- Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota, United States of America
| | - Eric T. Kool
- Department of Chemistry, Stanford University, Stanford, California, United States of America
| | - Leona D. Samson
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
- * E-mail:
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8
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A radioisotope-nondependent high-sensitivity method for measuring the activity of glioblastoma-related O6-methylguanine DNA methyltransferase. Anal Biochem 2015; 480:82-4. [DOI: 10.1016/j.ab.2014.08.012] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2014] [Revised: 08/11/2014] [Accepted: 08/16/2014] [Indexed: 11/18/2022]
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9
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Tomaszowski KH, Aasland D, Margison GP, Williams E, Pinder SI, Modesti M, Fuchs RP, Kaina B. The bacterial alkyltransferase-like (eATL) protein protects mammalian cells against methylating agent-induced toxicity. DNA Repair (Amst) 2015; 28:14-20. [PMID: 25703834 DOI: 10.1016/j.dnarep.2015.01.009] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2014] [Revised: 12/13/2014] [Accepted: 01/22/2015] [Indexed: 11/16/2022]
Abstract
In both pro- and eukaryotes, the mutagenic and toxic DNA adduct O(6)-methylguanine (O(6)MeG) is subject to repair by alkyltransferase proteins via methyl group transfer. In addition, in prokaryotes, there are proteins with sequence homology to alkyltransferases, collectively designated as alkyltransferase-like (ATL) proteins, which bind to O(6)-alkylguanine adducts and mediate resistance to alkylating agents. Whether such proteins might enable similar protection in higher eukaryotes is unknown. Here we expressed the ATL protein of Escherichia coli (eATL) in mammalian cells and addressed the question whether it is able to protect them against the cytotoxic effects of alkylating agents. The Chinese hamster cell line CHO-9, the nucleotide excision repair (NER) deficient derivative 43-3B and the DNA mismatch repair (MMR) impaired derivative Tk22-C1 were transfected with eATL cloned in an expression plasmid and the sensitivity to N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) was determined in reproductive survival, DNA double-strand break (DSB) and apoptosis assays. The results indicate that eATL expression is tolerated in mammalian cells and conferes protection against killing by MNNG in both wild-type and 43-3B cells, but not in the MMR-impaired cell line. The protection effect was dependent on the expression level of eATL and was completely ablated in cells co-expressing the human O(6)-methylguanine-DNA methyltransferase (MGMT). eATL did not protect against cytotoxicity induced by the chloroethylating agent lomustine, suggesting that O(6)-chloroethylguanine adducts are not target of eATL. To investigate the mechanism of protection, we determined O(6)MeG levels in DNA after MNNG treatment and found that eATL did not cause removal of the adduct. However, eATL expression resulted in a significantly lower level of DSBs in MNNG-treated cells, and this was concomitant with attenuation of G2 blockage and a lower level of apoptosis. The results suggest that eATL confers protection against methylating agents by masking O(6)MeG/thymine mispaired adducts, preventing them from becoming a substrate for mismatch repair-mediated DSB formation and cell death.
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Affiliation(s)
- Karl-Heinz Tomaszowski
- Department of Toxicology, University Medical Center, Obere Zahlbacher Strasse 67, D-55131 Mainz, Germany
| | - Dorthe Aasland
- Department of Toxicology, University Medical Center, Obere Zahlbacher Strasse 67, D-55131 Mainz, Germany
| | - Geoffrey P Margison
- Paterson Institute for Cancer Research, University of Manchester, Wilmslow Road, Manchester, M20 4BX Manchester, UK
| | - Emma Williams
- Paterson Institute for Cancer Research, University of Manchester, Wilmslow Road, Manchester, M20 4BX Manchester, UK
| | - Sarah I Pinder
- Paterson Institute for Cancer Research, University of Manchester, Wilmslow Road, Manchester, M20 4BX Manchester, UK
| | - Mauro Modesti
- Centre de Recherche en Cancérologie de Marseille, CNRS-UMR7258, Inserm-U1068, Institut Paoli-Calmettes, Université Aix-Marseille, France
| | - Robert P Fuchs
- Centre de Recherche en Cancérologie de Marseille, CNRS-UMR7258, Inserm-U1068, Institut Paoli-Calmettes, Université Aix-Marseille, France
| | - Bernd Kaina
- Department of Toxicology, University Medical Center, Obere Zahlbacher Strasse 67, D-55131 Mainz, Germany.
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10
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Couvé S, Ishchenko AA, Fedorova OS, Ramanculov EM, Laval J, Saparbaev M. Direct DNA Lesion Reversal and Excision Repair in Escherichia coli. EcoSal Plus 2013; 5. [PMID: 26442931 DOI: 10.1128/ecosalplus.7.2.4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2012] [Indexed: 06/05/2023]
Abstract
Cellular DNA is constantly challenged by various endogenous and exogenous genotoxic factors that inevitably lead to DNA damage: structural and chemical modifications of primary DNA sequence. These DNA lesions are either cytotoxic, because they block DNA replication and transcription, or mutagenic due to the miscoding nature of the DNA modifications, or both, and are believed to contribute to cell lethality and mutagenesis. Studies on DNA repair in Escherichia coli spearheaded formulation of principal strategies to counteract DNA damage and mutagenesis, such as: direct lesion reversal, DNA excision repair, mismatch and recombinational repair and genotoxic stress signalling pathways. These DNA repair pathways are universal among cellular organisms. Mechanistic principles used for each repair strategies are fundamentally different. Direct lesion reversal removes DNA damage without need for excision and de novo DNA synthesis, whereas DNA excision repair that includes pathways such as base excision, nucleotide excision, alternative excision and mismatch repair, proceeds through phosphodiester bond breakage, de novo DNA synthesis and ligation. Cell signalling systems, such as adaptive and oxidative stress responses, although not DNA repair pathways per se, are nevertheless essential to counteract DNA damage and mutagenesis. The present review focuses on the nature of DNA damage, direct lesion reversal, DNA excision repair pathways and adaptive and oxidative stress responses in E. coli.
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11
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Senthong P, Millington CL, Wilkinson OJ, Marriott AS, Watson AJ, Reamtong O, Eyers CE, Williams DM, Margison GP, Povey AC. The nitrosated bile acid DNA lesion O6-carboxymethylguanine is a substrate for the human DNA repair protein O6-methylguanine-DNA methyltransferase. Nucleic Acids Res 2013; 41:3047-55. [PMID: 23335782 PMCID: PMC3597670 DOI: 10.1093/nar/gks1476] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
Abstract
The consumption of red meat is a risk factor in human colorectal cancer (CRC). One hypothesis is that red meat facilitates the nitrosation of bile acid conjugates and amino acids, which rapidly convert to DNA-damaging carcinogens. Indeed, the toxic and mutagenic DNA adduct O6-carboxymethylguanine (O6-CMG) is frequently present in human DNA, increases in abundance in people with high levels of dietary red meat and may therefore be a causative factor in CRC. Previous reports suggested that O6-CMG is not a substrate for the human version of the DNA damage reversal protein O6-methylguanine-DNA methyltransferase (MGMT), which protects against the genotoxic effects of other O6-alkylguanine lesions by removing alkyl groups from the O6-position. We now show that synthetic oligodeoxyribonucleotides containing the known MGMT substrate O6-methylguanine (O6-MeG) or O6-CMG effectively inactivate MGMT in vitro (IC50 0.93 and 1.8 nM, respectively). Inactivation involves the removal of the O6-alkyl group and its transfer to the active-site cysteine residue of MGMT. O6-CMG is therefore an MGMT substrate, and hence MGMT is likely to be a protective factor in CRC under conditions where O6-CMG is a potential causative agent.
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Affiliation(s)
- Pattama Senthong
- Centre for Occupational and Environmental Health, Faculty of Medical & Human Sciences, University of Manchester, Manchester M13 9PL, UK
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12
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Abstract
Endogenous and exogenous factors constantly challenge cellular DNA, generating cytotoxic and/or mutagenic DNA adducts. As a result, organisms have evolved different mechanisms to defend against the deleterious effects of DNA damage. Among these diverse repair pathways, direct DNA-repair systems provide cells with simple yet efficient solutions to reverse covalent DNA adducts. In this review, we focus on recent advances in the field of direct DNA repair, namely, photolyase-, alkyltransferase-, and dioxygenase-mediated repair processes. We present specific examples to describe new findings of known enzymes and appealing discoveries of new proteins. At the end of this article, we also briefly discuss the influence of direct DNA repair on other fields of biology and its implication on the discovery of new biology.
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Affiliation(s)
- Chengqi Yi
- State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences, Peking University, Beijing 100871, China
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13
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Alkyltransferase-like protein (Atl1) distinguishes alkylated guanines for DNA repair using cation-π interactions. Proc Natl Acad Sci U S A 2012; 109:18755-60. [PMID: 23112169 DOI: 10.1073/pnas.1209451109] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Alkyltransferase-like (ATL) proteins in Schizosaccharomyces pombe (Atl1) and Thermus thermophilus (TTHA1564) protect against the adverse effects of DNA alkylation damage by flagging O(6)-alkylguanine lesions for nucleotide excision repair (NER). We show that both ATL proteins bind with high affinity to oligodeoxyribonucleotides containing O(6)-alkylguanines differing in size, polarity, and charge of the alkyl group. However, Atl1 shows a greater ability than TTHA1564 to distinguish between O(6)-alkylguanine and guanine and in an unprecedented mechanism uses Arg69 to probe the electrostatic potential surface of O(6)-alkylguanine, as determined using molecular mechanics calculations. An unexpected consequence of this feature is the recognition of 2,6-diaminopurine and 2-aminopurine, as confirmed in crystal structures of respective Atl1-DNA complexes. O(6)-Alkylguanine and guanine discrimination is diminished for Atl1 R69A and R69F mutants, and S. pombe R69A and R69F mutants are more sensitive toward alkylating agent toxicity, revealing the key role of Arg69 in identifying O(6)-alkylguanines critical for NER recognition.
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14
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Millington CL, Watson AJ, Marriott AS, Margison GP, Povey AC, Williams DM. Convenient and efficient syntheses of oligodeoxyribonucleotides containing O(6)-(carboxymethyl)guanine and O(6)-(4-oxo-4-(3-pyridyl)butyl)guanine. NUCLEOSIDES NUCLEOTIDES & NUCLEIC ACIDS 2012; 31:328-38. [PMID: 22444194 DOI: 10.1080/15257770.2012.656784] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
O(6)-(carboxymethyl)guanine (O(6)-CMG) and O(6)-(4-oxo-4-(3-pyridyl)butyl)guanine (O(6)-pobG) are toxic lesions formed in DNA following exposure to alkylating agents. O(6)-CMG results from exposure to nitrosated glycine or nitrosated bile acid conjugates and may be associated with diets rich in red meat. O(6)-pobG lesions are derived from alkylating agents found in tobacco smoke. Efficient syntheses of oligodeoxyribonucleotides (ODNs) containing O(6)-CMG and O(6)-pobG are described that involve nucleophilic displacement by the appropriate alcohol on a common synthetic ODN containing the reactive base 2-amino-6-methylsulfonylpurine. ODNs containing O(6)-pobG and O (6)-CMG were found to be good substrates for the S. pombe alkyltransferase-like protein Atl1.
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Affiliation(s)
- Christopher L Millington
- Centre for Chemical Biology, Department of Chemistry, Krebs Institute, University of Sheffield, Sheffield S3 7HF, UK
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15
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Latypov VF, Tubbs JL, Watson AJ, Marriott AS, McGown G, Thorncroft M, Wilkinson OJ, Senthong P, Butt A, Arvai AS, Millington CL, Povey AC, Williams DM, Santibanez-Koref MF, Tainer JA, Margison GP. Atl1 regulates choice between global genome and transcription-coupled repair of O(6)-alkylguanines. Mol Cell 2012; 47:50-60. [PMID: 22658721 DOI: 10.1016/j.molcel.2012.04.028] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2012] [Revised: 04/05/2012] [Accepted: 04/20/2012] [Indexed: 11/20/2022]
Abstract
Nucleotide excision repair (NER) has long been known to remove DNA lesions induced by chemical carcinogens, and the molecular mechanism has been partially elucidated. Here we demonstrate that in Schizosaccharomyces pombe a DNA recognition protein, alkyltransferase-like 1 (Atl1), can play a pivotal role in selecting a specific NER pathway, depending on the nature of the DNA modification. The relative ease of dissociation of Atl1 from DNA containing small O(6)-alkylguanines allows accurate completion of global genome repair (GGR), whereas strong Atl1 binding to bulky O(6)-alkylguanines blocks GGR, stalls the transcription machinery, and diverts the damage to transcription-coupled repair. Our findings redraw the initial stages of the NER process in those organisms that express an alkyltransferase-like gene and raise the question of whether or not O(6)-alkylguanine lesions that are poor substrates for the alkyltransferase proteins in higher eukaryotes might, by analogy, signal such lesions for repair by NER.
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Affiliation(s)
- Vitaly F Latypov
- Cancer Research UK Carcinogenesis Group, Paterson Institute for Cancer Research, University of Manchester, Manchester M20 4BX, UK
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16
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Morita R, Hishinuma H, Ohyama H, Mega R, Ohta T, Nakagawa N, Agari Y, Fukui K, Shinkai A, Kuramitsu S, Masui R. An alkyltransferase-like protein from Thermus thermophilus HB8 affects the regulation of gene expression in alkylation response. J Biochem 2011; 150:327-39. [PMID: 21531768 DOI: 10.1093/jb/mvr052] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Alkylation is a type of stress that is fatal to cells. However, cells have various responses to alkylation. Alkyltransferase-like (ATL) protein is a novel protein involved in the repair of alkylated DNA; however, its repair mechanism at the molecular level is unclear. DNA microarray analysis revealed that the upregulation of 71 genes because of treatment with an alkylating agent N-methyl-N'-nitro-N-nitrosoguanidine was related to the presence of TTHA1564, the ATL protein from Thermus thermophilus HB8. Affinity chromatography showed a direct interaction of purified TTHA1564 with purified RNA polymerase holoenzyme. The amino acid sequence of TTHA1564 is homologous to that of the C-terminal domain of Ada protein, which acts as a transcriptional activator. These results suggest that TTHA1564 might act as a transcriptional regulator. The results of DNA microarray analysis also implied that the alkylating agent induced oxidation stress in addition to alkylation stress.
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Affiliation(s)
- Rihito Morita
- Department of Biological Sciences, Graduate School of Science, Osaka University, 1-1 Machikaneyama-cho, Toyonaka, Osaka 560-0043, Japan
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17
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Pegg AE. Multifaceted roles of alkyltransferase and related proteins in DNA repair, DNA damage, resistance to chemotherapy, and research tools. Chem Res Toxicol 2011; 24:618-39. [PMID: 21466232 DOI: 10.1021/tx200031q] [Citation(s) in RCA: 155] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
O(6)-Alkylguanine-DNA alkyltransferase (AGT) is a widely distributed, unique DNA repair protein that acts as a single agent to directly remove alkyl groups located on the O(6)-position of guanine from DNA restoring the DNA in one step. The protein acts only once, and its alkylated form is degraded rapidly. It is a major factor in counteracting the mutagenic, carcinogenic, and cytotoxic effects of agents that form such adducts including N-nitroso-compounds and a number of cancer chemotherapeutics. This review describes the structure, function, and mechanism of action of AGTs and of a family of related alkyltransferase-like proteins, which do not act alone to repair O(6)-alkylguanines in DNA but link repair to other pathways. The paradoxical ability of AGTs to stimulate the DNA-damaging ability of dihaloalkanes and other bis-electrophiles via the formation of AGT-DNA cross-links is also described. Other important properties of AGTs include the ability to provide resistance to cancer therapeutic alkylating agents, and the availability of AGT inhibitors such as O(6)-benzylguanine that might overcome this resistance is discussed. Finally, the properties of fusion proteins in which AGT sequences are linked to other proteins are outlined. Such proteins occur naturally, and synthetic variants engineered to react specifically with derivatives of O(6)-benzylguanine are the basis of a valuable research technique for tagging proteins with specific reagents.
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Affiliation(s)
- Anthony E Pegg
- Department of Cellular and Molecular Physiology, Milton S. Hershey Medical Center, Pennsylvania State University College of Medicine , Pennsylvania 17033, United States.
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Onodera T, Morino K, Tokishita SI, Morita R, Masui R, Kuramitsu S, Ohta T. Role of alkyltransferase-like (ATL) protein in repair of methylated DNA lesions in Thermus thermophilus. Mutagenesis 2010; 26:303-8. [PMID: 21059809 DOI: 10.1093/mutage/geq093] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Thermus thermophilus is an extremely thermophilic eubacterium that grows optimally at 70-75°C. It does not have a gene encoding O(6)-alkylguanine-DNA alkyltransferase (AGT) for the repair of O(6)-methylguanine (O(6)-meG), but it has a homologous gene atl encoding alkyltransferase-like (ATL) proteins in which the cysteine residue in the active site of the PCHR motif conserved in AGT is replaced by alanine (i.e. lack of methyltransferase activity). To investigate the role of ATL protein in the repair of O(6)-meG, we isolated atl deletion mutants and measured specific G:C→A:T transition mutations induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) by a His(+) reversion system at the hisD3110 locus. MNNG caused an increased mutation frequency in the atl-deficient mutant but a significantly higher frequency increase in a uvrA mutant, which is deficient in nucleotide excision repair (NER), indicating that both ATL protein and NER played an important role in preventing G:C→A:T transitions. We observed no difference in MNNG sensitivity between the uvrA atl double mutant and the parent uvrA strain. Our results support a recently proposed repair model in which ATL protein acts as a sensor of O(6)-meG damage and recruits UvrA protein to repair the lesion via an NER system. In addition, the finding that the uvrA atl strain mutated with greater frequency than the single atl strain suggests that O(6)-meG is repaired by NER in the absence of ATL protein. We also discuss the possible association of a transcription-repair coupling factor in a transcription-coupled repair pathway and of MutS protein in a mismatch repair pathway with ATL/NER-mediated repair of O(6)-meG.
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Affiliation(s)
- Takefumi Onodera
- Department of Environmental Genomics, School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, 1432-1 Horinouchi, Hachioji, Tokyo 192-0392, Japan
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19
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Mazon G, Philippin G, Cadet J, Gasparutto D, Modesti M, Fuchs RP. Alkyltransferase-like protein (eATL) prevents mismatch repair-mediated toxicity induced by O6-alkylguanine adducts in Escherichia coli. Proc Natl Acad Sci U S A 2010; 107:18050-5. [PMID: 20921378 PMCID: PMC2964255 DOI: 10.1073/pnas.1008635107] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
O(6)-alkylG adducts are highly mutagenic due to their capacity to efficiently form O(6)-alkylG:T mispairs during replication, thus triggering G→A transitions. Mutagenesis is largely prevented by repair strategies such as reversal by alkyltransferases or excision by nucleotide excision repair (NER). Moreover, methyl-directed mismatch repair (MMR) is known to trigger sensitivity to methylating agents via a mechanism that involves recognition by MutS of the O(6)-mG:T replication intermediates. We wanted to investigate the mechanism by which MMR controls the genotoxicity of environmentally relevant O(6)-alkylG adducts formed by ethylene oxide and propylene oxide. Recently, the alkyltransferase-like gene ybaZ (eATL) was shown to enhance repair of these slightly larger O(6)-alkylG adducts by NER. We analyzed the toxicity and mutagenesis induced by these O(6)-alkylG adducts using single-adducted plasmid probes. We show that the eATL gene product prevents MMR-mediated attack of the O(6)-alkylG:T replication intermediate for the larger alkyl groups but not for methyl. In vivo data are compatible with the occurrence of repeated cycles of MMR attack of the O(6)-alkylG:T intermediate. In addition, in vitro, the eATL protein efficiently prevents binding of MutS to the O(6)-alkylG:T mispairs formed by the larger alkyl groups but not by methyl. In conclusion, eATL not only enhances the efficiency of repair of these larger adducts by NER, it also shields these adducts from MMR-mediated toxicity.
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Affiliation(s)
- Gerard Mazon
- Centre National de la Recherche Scientifique (CNRS), Unité Propre de Recherche 3081, Genome Instability and Carcinogenesis, Conventionné par l'Université d'Aix-Marseille 2, 13402 Marseille Cedex 20, France; and
| | - Gaëlle Philippin
- Centre National de la Recherche Scientifique (CNRS), Unité Propre de Recherche 3081, Genome Instability and Carcinogenesis, Conventionné par l'Université d'Aix-Marseille 2, 13402 Marseille Cedex 20, France; and
| | - Jean Cadet
- Institut Nanosciences et Cryogénie/Service de Chimie Inorganique et Biologique-Unité Mixte de Recherche E3 Commissariat à l'Énergie Atomique (CEA)-Université Joseph Fourier, Federation de Recherche en Evolution 3200 CEA-CNRS/CEA Grenoble, F-38054 Grenoble Cedex 9, France
| | - Didier Gasparutto
- Institut Nanosciences et Cryogénie/Service de Chimie Inorganique et Biologique-Unité Mixte de Recherche E3 Commissariat à l'Énergie Atomique (CEA)-Université Joseph Fourier, Federation de Recherche en Evolution 3200 CEA-CNRS/CEA Grenoble, F-38054 Grenoble Cedex 9, France
| | - Mauro Modesti
- Centre National de la Recherche Scientifique (CNRS), Unité Propre de Recherche 3081, Genome Instability and Carcinogenesis, Conventionné par l'Université d'Aix-Marseille 2, 13402 Marseille Cedex 20, France; and
| | - Robert P. Fuchs
- Centre National de la Recherche Scientifique (CNRS), Unité Propre de Recherche 3081, Genome Instability and Carcinogenesis, Conventionné par l'Université d'Aix-Marseille 2, 13402 Marseille Cedex 20, France; and
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20
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Morita R, Nakane S, Shimada A, Inoue M, Iino H, Wakamatsu T, Fukui K, Nakagawa N, Masui R, Kuramitsu S. Molecular mechanisms of the whole DNA repair system: a comparison of bacterial and eukaryotic systems. J Nucleic Acids 2010; 2010:179594. [PMID: 20981145 PMCID: PMC2957137 DOI: 10.4061/2010/179594] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2010] [Accepted: 07/27/2010] [Indexed: 11/20/2022] Open
Abstract
DNA is subjected to many endogenous and exogenous damages. All organisms have developed a complex network of DNA repair mechanisms. A variety of different DNA repair pathways have been reported: direct reversal, base excision repair, nucleotide excision repair, mismatch repair, and recombination repair pathways. Recent studies of the fundamental mechanisms for DNA repair processes have revealed a complexity beyond that initially expected, with inter- and intrapathway complementation as well as functional interactions between proteins involved in repair pathways. In this paper we give a broad overview of the whole DNA repair system and focus on the molecular basis of the repair machineries, particularly in Thermus thermophilus HB8.
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Affiliation(s)
- Rihito Morita
- Department of Biological Sciences, Graduate School of Science, Osaka University, 1-1 Machikaneyama-cho, Toyonaka, Osaka 560-0043, Japan
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21
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Alkyltransferase-like proteins: molecular switches between DNA repair pathways. Cell Mol Life Sci 2010; 67:3749-62. [PMID: 20502938 DOI: 10.1007/s00018-010-0405-8] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2010] [Revised: 05/04/2010] [Accepted: 05/10/2010] [Indexed: 01/08/2023]
Abstract
Alkyltransferase-like proteins (ATLs) play a role in the protection of cells from the biological effects of DNA alkylation damage. Although ATLs share functional motifs with the DNA repair protein and cancer chemotherapy target O⁶-alkylguanine-DNA alkyltransferase, they lack the reactive cysteine residue required for alkyltransferase activity, so its mechanism for cell protection was previously unknown. Here we review recent advances in unraveling the enigmatic cellular protection provided by ATLs against the deleterious effects of DNA alkylation damage. We discuss exciting new evidence that ATLs aid in the repair of DNA O⁶-alkylguanine lesions through a novel repair cross-talk between DNA-alkylation base damage responses and the DNA nucleotide excision repair pathway.
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22
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Aramini JM, Tubbs JL, Kanugula S, Rossi P, Ertekin A, Maglaqui M, Hamilton K, Ciccosanti CT, Jiang M, Xiao R, Soong TT, Rost B, Acton TB, Everett JK, Pegg AE, Tainer JA, Montelione GT. Structural basis of O6-alkylguanine recognition by a bacterial alkyltransferase-like DNA repair protein. J Biol Chem 2010; 285:13736-41. [PMID: 20212037 DOI: 10.1074/jbc.m109.093591] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Alkyltransferase-like proteins (ATLs) are a novel class of DNA repair proteins related to O(6)-alkylguanine-DNA alkyltransferases (AGTs) that tightly bind alkylated DNA and shunt the damaged DNA into the nucleotide excision repair pathway. Here, we present the first structure of a bacterial ATL, from Vibrio parahaemolyticus (vpAtl). We demonstrate that vpAtl adopts an AGT-like fold and that the protein is capable of tightly binding to O(6)-methylguanine-containing DNA and disrupting its repair by human AGT, a hallmark of ATLs. Mutation of highly conserved residues Tyr(23) and Arg(37) demonstrate their critical roles in a conserved mechanism of ATL binding to alkylated DNA. NMR relaxation data reveal a role for conformational plasticity in the guanine-lesion recognition cavity. Our results provide further evidence for the conserved role of ATLs in this primordial mechanism of DNA repair.
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Affiliation(s)
- James M Aramini
- Center for Advanced Biotechnology and Medicine, Department of Molecular Biology and Biochemistry, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854, USA.
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23
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Reißner T, Schorr S, Carell T. Once Overlooked, Now Made Visible: ATL Proteins and DNA Repair. Angew Chem Int Ed Engl 2009; 48:7293-5. [DOI: 10.1002/anie.200904042] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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24
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Reißner T, Schorr S, Carell T. Übersehenes sichtbar gemacht: ATL-Proteine und DNA-Reparatur. Angew Chem Int Ed Engl 2009. [DOI: 10.1002/ange.200904042] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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25
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Flipping of alkylated DNA damage bridges base and nucleotide excision repair. Nature 2009; 459:808-13. [PMID: 19516334 PMCID: PMC2729916 DOI: 10.1038/nature08076] [Citation(s) in RCA: 106] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2009] [Accepted: 04/17/2009] [Indexed: 01/01/2023]
Abstract
Alkyltransferase-like proteins (ATLs) share functional motifs with the cancer chemotherapy target O(6)-alkylguanine-DNA alkyltransferase (AGT) and paradoxically protect cells from the biological effects of DNA alkylation damage, despite lacking the reactive cysteine and alkyltransferase activity of AGT. Here we determine Schizosaccharomyces pombe ATL structures without and with damaged DNA containing the endogenous lesion O(6)-methylguanine or cigarette-smoke-derived O(6)-4-(3-pyridyl)-4-oxobutylguanine. These results reveal non-enzymatic DNA nucleotide flipping plus increased DNA distortion and binding pocket size compared to AGT. Our analysis of lesion-binding site conservation identifies new ATLs in sea anemone and ancestral archaea, indicating that ATL interactions are ancestral to present-day repair pathways in all domains of life. Genetic connections to mammalian XPG (also known as ERCC5) and ERCC1 in S. pombe homologues Rad13 and Swi10 and biochemical interactions with Escherichia coli UvrA and UvrC combined with structural results reveal that ATLs sculpt alkylated DNA to create a genetic and structural intersection of base damage processing with nucleotide excision repair.
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26
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Mazon G, Philippin G, Cadet J, Gasparutto D, Fuchs RP. The alkyltransferase-like ybaZ gene product enhances nucleotide excision repair of O(6)-alkylguanine adducts in E. coli. DNA Repair (Amst) 2009; 8:697-703. [PMID: 19269902 DOI: 10.1016/j.dnarep.2009.01.022] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2009] [Accepted: 01/29/2009] [Indexed: 11/16/2022]
Abstract
O(6)-methylguanine adducts are potent pre-mutagenic lesions owing to their high capacity to direct mis-insertion of thymine when bypassed by replicative DNA polymerases. The strong mutagenic potential of these adducts is prevented by alkyltransferases such as Ada and Ogt in Escherichia coli that transfer the methyl group to one of their cysteine residues. Alkyl residues larger than methyl are generally weak substrates for reversion by alkyltransferases. In this paper we have investigated the genotoxic potential of the O(6)-alkylguanine adducts formed by ethylene and propylene oxide using single-adducted plasmid probes. Our work shows that the ybaZ gene product, a member of the alkyltransferase-like protein family, strongly enhances the repair by nucleotide excision repair of the larger O(6)-alkylguanine adducts that are otherwise poor substrates for alkyltransferases. The YbaZ protein is shown to interact with UvrA. This factor may thus enhance the efficiency of nucleotide excision repair in a way similar to the Transcription-Repair Coupling factor Mfd, by recruiting the UvrA(2).UvrB complex to the adduct site via its interaction with UvrA.
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Affiliation(s)
- Gerard Mazon
- CNRS, UPR 3081, Genome Instability and Carcinogenesis, Conventionné par l'Université d'Aix-Marseille 2, 31, Chemin Joseph Aiguier, 13402 Marseille cedex 20, France
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27
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Morita R, Nakagawa N, Kuramitsu S, Masui R. An O6-methylguanine-DNA methyltransferase-like protein from Thermus thermophilus interacts with a nucleotide excision repair protein. J Biochem 2008; 144:267-77. [PMID: 18483064 DOI: 10.1093/jb/mvn065] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
The major damage to DNA caused by alkylating agents involves the formation of O6-methylguanine (O6-meG). Almost all species possess O6-methylguanine-DNA-methyltransferase (Ogt) to repair such damage. Ogt repairs O6-meG lesions in DNA by stoichiometric transfer of the methyl group to a cysteine residue in its active site (PCHR). Thermus thermophilus HB8 has an Ogt homologue, TTHA1564, but in this case an alanine residue replaces cysteine in the putative active site. To reveal the possible function of TTHA1564 in processing O6-meG-containing DNA, we characterized the biochemical properties of TTHA1564. No methyltransferase activity for synthetic O6-meG-containing DNA could be detected, indicating TTHA1564 is an alkyltransferase-like protein. Nevertheless, gel shift assays showed that TTHA1564 can bind to DNA containing O6-meG with higher affinity (9-fold) than normal (unmethylated) DNA. Experiments using a fluorescent oligonucleotide suggested that TTHA1564 recognizes O6-meG in DNA using the same mechanism as other Ogts. We then investigated whether TTHA1564 functions as a damage sensor. Pull-down assays identified 20 proteins, including a nucleotide excision repair protein UvrA, which interacts with TTHA1564. Interaction of TTHA1564 with UvrA was confirmed using a surface plasmon resonance assay. These results suggest the possible involvement of TTHA1564 in DNA repair pathways.
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Affiliation(s)
- Rihito Morita
- Department of Biological Sciences, Graduate School of Science, Osaka University, 1-1 Machikaneyama-cho, Toyonaka, Osaka 560-0043, Japan
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28
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A proteome chip approach reveals new DNA damage recognition activities in Escherichia coli. Nat Methods 2007; 5:69-74. [PMID: 18084297 DOI: 10.1038/nmeth1148] [Citation(s) in RCA: 98] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2007] [Accepted: 11/16/2007] [Indexed: 11/08/2022]
Abstract
Despite the fact that many genomes have been decoded, proteome chips comprising individually purified proteins have been reported only for budding yeast, mainly because of the complexity and difficulty of high-throughput protein purification. To facilitate proteomics studies in prokaryotes, we have developed a high-throughput protein purification protocol that allowed us to purify 4,256 proteins encoded by the Escherichia coli K12 strain within 10 h. The purified proteins were then spotted onto glass slides to create E. coli proteome chips. We used these chips to develop assays for identifying proteins involved in the recognition of potential base damage in DNA. By using a group of DNA probes, each containing a mismatched base pair or an abasic site, we found a small number of proteins that could recognize each type of probe with high affinity and specificity. We further evaluated two of these proteins, YbaZ and YbcN, by biochemical analyses. The assembly of libraries containing DNA probes with specific modifications and the availability of E. coli proteome chips have the potential to reveal important interactions between proteins and nucleic acids that are time-consuming and difficult to detect using other techniques.
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29
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Margison GP, Butt A, Pearson SJ, Wharton S, Watson AJ, Marriott A, Caetano CMPF, Hollins JJ, Rukazenkova N, Begum G, Santibáñez-Koref MF. Alkyltransferase-like proteins. DNA Repair (Amst) 2007; 6:1222-8. [PMID: 17500045 DOI: 10.1016/j.dnarep.2007.03.014] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Recent in silico analysis has revealed the presence of a group of proteins in pro and lower eukaryotes, but not in Man, that show extensive amino acid sequence similarity to known O(6)-alkylguanine-DNA alkyltransferases, but where the cysteine at the putative active site is replaced by another residue, usually tryptophan. Here we review recent work on these proteins, which we designate as alkyltransferase-like (ATL) proteins, and consider their mechanism of action and role in protecting the host organisms against the biological effects of O(6)-alkylating agents, and their evolution. ATL proteins from Escherichia coli (eAtl, transcribed from the ybaz open reading frame) and Schizosaccharomyces pombe (Atl1) are able to bind to a range of O(6)-alkylguanine residues in DNA and to reversibly inhibit the action of the human alkyltransferase (MGMT) upon these substrates. Isolated proteins were not able to remove the methyl group in O(6)-methylguanine-containing DNA or oligonucleotides, neither did they display glycosylase or endonuclease activity. S. pombe does not contain a functional alkyltransferase and atl1 inactivation sensitises this organism to a variety of alkylating agents, suggesting that Atl1 acts by binding to O(6)-alkylguanine lesions and signalling them for processing by other DNA repair pathways. Currently we cannot exclude the possibility that ATL proteins arose through independent mutation of the alkyltransferase gene in different organisms. However, analyses of the proteins from E. coli and S. pombe, are consistent with a common function.
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Affiliation(s)
- Geoffrey P Margison
- Cancer Research-UK Carcinogenesis Group, Paterson Institute for Cancer Research, University of Manchester, Manchester M20 4BX, United Kingdom.
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30
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Pearson SJ, Wharton S, Watson AJ, Begum G, Butt A, Glynn N, Williams DM, Shibata T, Santibáñez-Koref MF, Margison GP. A novel DNA damage recognition protein in Schizosaccharomyces pombe. Nucleic Acids Res 2006; 34:2347-54. [PMID: 16679453 PMCID: PMC1458281 DOI: 10.1093/nar/gkl270] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Toxic and mutagenic O6-alkylguanine adducts in DNA are repaired by O6-alkylguanine-DNA alkyltransferases (MGMT) by transfer of the alkyl group to a cysteine residue in the active site. Comparisons in silico of prokaryotes and lower eukaryotes reveal the presence of a group of proteins [alkyltransferase-like (ATL) proteins] showing amino acid sequence similarity to MGMT, but where the cysteine at the putative active site is replaced by tryptophan. To examine whether ATL proteins play a role in the biological effects of alkylating agents, we inactivated the gene, referred to as atl1+, in Schizosaccharomyces pombe, an organism that does not possess a functional MGMT homologue. The mutants are substantially more susceptible to the toxic effects of the methylating agents, N-methyl-N-nitrosourea, N-methyl-N′nitro-N-nitrosoguanidine and methyl methanesulfonate and longer chain alkylating agents including N-ethyl-N-nitrosourea, ethyl methanesulfonate, N-propyl-N-nitrosourea and N-butyl-N-nitrosourea. Purified Atl1 protein does not transfer methyl groups from O6-methylguanine in [3H]-methylated DNA but reversibly inhibits methyl transfer by human MGMT. Atl1 binds to short single-stranded oligonucleotides containing O6-methyl, -benzyl, -4-bromothenyl or -hydroxyethyl-guanine but does not remove the alkyl group or base and does not cleave the oligonucleotide in the region of the lesion. This suggests that Atl1 acts by binding to O6-alkylguanine lesions and signalling them for processing by other DNA repair pathways. This is the first report describing an activity that protects S.pombe against the toxic effects of O6-alkylguanine adducts and the biological function of a family of proteins that is widely found in prokaryotes and lower eukaryotes.
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Affiliation(s)
| | | | | | | | | | | | - David M. Williams
- Centre for Chemical Biology, Department of Chemistry, University of SheffieldUK
| | - Takayuki Shibata
- Centre for Chemical Biology, Department of Chemistry, University of SheffieldUK
| | | | - Geoffrey P. Margison
- To whom correspondence should be addressed. Tel: +44 161 446 3183; Fax: +44 161 446 8306;
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31
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Shibata T, Glynn N, McMurry TBH, McElhinney RS, Margison GP, Williams DM. Novel synthesis of O6-alkylguanine containing oligodeoxyribonucleotides as substrates for the human DNA repair protein, O6-methylguanine DNA methyltransferase (MGMT). Nucleic Acids Res 2006; 34:1884-91. [PMID: 16609128 PMCID: PMC1435717 DOI: 10.1093/nar/gkl117] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2005] [Revised: 01/10/2006] [Accepted: 03/12/2006] [Indexed: 11/14/2022] Open
Abstract
The human DNA repair protein O6-methylguanine DNA methyltransferase (MGMT) dealkylates mutagenic O6-alkylguanine lesions within DNA in an irreversible reaction which results in inactivation of the protein. MGMT also provides resistance of tumours to alkylating agents used in cancer chemotherapy and its inactivation is therefore of particular clinical importance. We describe a post-DNA synthesis strategy which exploits the novel, modified base 2-amino-6-methylsulfonylpurine and allows access for the first time to a wide variety of oligodeoxyribonucleotides (ODNs) containing O6-alkylguanines. One such ODN containing O6-(4-bromothenyl)guanine is the most potent inactivator described to date with an IC50 of 0.1 nM.
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Affiliation(s)
- Takayuki Shibata
- Department of Chemistry, Centre for Chemical Biology Richard Roberts Building, University of SheffieldSheffield, S3 7HF, UK
| | - Nicola Glynn
- Cancer Research-UK Carcinogenesis Group, Paterson Institute for Cancer ResearchManchester, M20 4BX, UK
| | | | | | - Geoffrey P. Margison
- Cancer Research-UK Carcinogenesis Group, Paterson Institute for Cancer ResearchManchester, M20 4BX, UK
| | - David M. Williams
- Department of Chemistry, Centre for Chemical Biology Richard Roberts Building, University of SheffieldSheffield, S3 7HF, UK
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