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Wang K, He Z, Jin G, Jin S, Du Y, Yuan S, Zhang J. Targeting DNA methyltransferases for cancer therapy. Bioorg Chem 2024; 151:107652. [PMID: 39024804 DOI: 10.1016/j.bioorg.2024.107652] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2024] [Revised: 06/29/2024] [Accepted: 07/14/2024] [Indexed: 07/20/2024]
Abstract
DNA methyltransferases (DNMTs) play a crucial role in genomic DNA methylation. In mammals, DNMTs regulate the dynamic patterns of DNA methylation in embryonic and adult cells. Abnormal functions of DNMTs are often indicative of cancers, including overall hypomethylation and partial hypermethylation of tumor suppressor genes (TSG), which accelerate the malignancy of tumors, worsen the condition of patients, and significantly exacerbate the difficulty of cancer treatment. Currently, nucleoside DNMT inhibitors such as Azacytidine and Decitabine have been approved by the FDA and EMA for the treatment of acute myeloid leukemia (AML), chronic myelomonocytic leukemia (CMML), and myelodysplastic syndrome (MDS). Therefore, targeting DNMTs is a very promising anti-tumor strategy. This review mainly summarizes the therapeutic effects of DNMT inhibitors on cancers. It aims to provide more possibilities for the treatment of cancers by discovering more DNMT inhibitors with high activity, high selectivity, and good drug-like properties in the future.
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Affiliation(s)
- Kaiyue Wang
- Pharmacy College, Henan University of Chinese Medicine, 450046 Zhengzhou, PR China
| | - Zhangxu He
- Pharmacy College, Henan University of Chinese Medicine, 450046 Zhengzhou, PR China.
| | - Gang Jin
- Pharmacy College, Henan University of Chinese Medicine, 450046 Zhengzhou, PR China
| | - Sasa Jin
- Pharmacy College, Henan University of Chinese Medicine, 450046 Zhengzhou, PR China
| | - Yuanbing Du
- Pharmacy College, Henan University of Chinese Medicine, 450046 Zhengzhou, PR China
| | - Shuo Yuan
- Children's Hospital Affiliated to Zhengzhou University, Henan Children's Hospital, Zhengzhou Children's Hospital, Zhengzhou 450018, PR China.
| | - Jingyu Zhang
- Pharmacy College, Henan University of Chinese Medicine, 450046 Zhengzhou, PR China.
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Horton JR, Pathuri S, Wong K, Ren R, Rueda L, Fosbenner DT, Heerding DA, McCabe MT, Pappalardi MB, Zhang X, King BW, Cheng X. Structural characterization of dicyanopyridine containing DNMT1-selective, non-nucleoside inhibitors. Structure 2022; 30:793-802.e5. [PMID: 35395178 PMCID: PMC9177618 DOI: 10.1016/j.str.2022.03.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2022] [Revised: 02/24/2022] [Accepted: 03/11/2022] [Indexed: 12/21/2022]
Abstract
DNMT1 maintains the parental DNA methylation pattern on newly replicated hemimethylated DNA. The failure of this maintenance process causes aberrant DNA methylation that affects transcription and contributes to the development and progression of cancers such as acute myeloid leukemia. Here, we structurally characterized a set of newly discovered DNMT1-selective, reversible, non-nucleoside inhibitors that bear a core 3,5-dicyanopyridine moiety, as exemplified by GSK3735967, to better understand their mechanism of inhibition. All of the dicyanopydridine-containing inhibitors examined intercalate into the hemimethylated DNA between two CpG base pairs through the DNA minor groove, resulting in conformational movement of the DNMT1 active-site loop. In addition, GSK3735967 introduces two new binding sites, where it interacts with and stabilizes the displaced DNMT1 active-site loop and it occupies an open aromatic cage in which trimethylated histone H4 lysine 20 is expected to bind. Our work represents a substantial step in generating potent, selective, and non-nucleoside inhibitors of DNMT1.
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Affiliation(s)
- John R Horton
- Department of Epigenetics and Molecular Carcinogenesis, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Sarath Pathuri
- Department of Epigenetics and Molecular Carcinogenesis, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Kristen Wong
- Cancer Epigenetics Research Unit, Oncology, GlaxoSmithKline, Collegeville, PA 19426, USA
| | - Ren Ren
- Department of Epigenetics and Molecular Carcinogenesis, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Lourdes Rueda
- Cancer Epigenetics Research Unit, Oncology, GlaxoSmithKline, Collegeville, PA 19426, USA
| | - David T Fosbenner
- Cancer Epigenetics Research Unit, Oncology, GlaxoSmithKline, Collegeville, PA 19426, USA
| | - Dirk A Heerding
- Cancer Epigenetics Research Unit, Oncology, GlaxoSmithKline, Collegeville, PA 19426, USA
| | - Michael T McCabe
- Cancer Epigenetics Research Unit, Oncology, GlaxoSmithKline, Collegeville, PA 19426, USA
| | - Melissa B Pappalardi
- Cancer Epigenetics Research Unit, Oncology, GlaxoSmithKline, Collegeville, PA 19426, USA
| | - Xing Zhang
- Department of Epigenetics and Molecular Carcinogenesis, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Bryan W King
- Cancer Epigenetics Research Unit, Oncology, GlaxoSmithKline, Collegeville, PA 19426, USA.
| | - Xiaodong Cheng
- Department of Epigenetics and Molecular Carcinogenesis, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA.
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Parker WB, Thottassery JV. 5-Aza-4'-thio-2'-deoxycytidine, a new orally bioavailable non-toxic "best-in-class" DNMT1 depleting agent in clinical development. J Pharmacol Exp Ther 2021; 379:211-222. [PMID: 34503994 DOI: 10.1124/jpet.121.000758] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2021] [Accepted: 09/01/2021] [Indexed: 11/22/2022] Open
Abstract
DNA methyltransferase 1 (DNMT1) is an enzyme that functions as a maintenance methyltransferase during DNA replication, and depletion of this enzyme from cells is considered to be a rational goal in DNA methylation dependent disorders. Two DNMT1 depleting agents aza-dCyd (5-aza-2'-deoxycytidine, decitabine) and aza-Cyd (5-aza-cytidine, azacitidine) are currently used for the treatment of myelodysplastic syndromes and acute myeloid leukemia, and have also been investigated for non-oncology indications such as sickle cell disease. However, these agents have several off-target activities leading to significant toxicities that limit dosing and duration of treatment. Development of more selective inhibitors of DNMT1 could therefore afford treatment for long durations at effective doses. We have discovered that 5-aza-4'-thio-2'-deoxycytidine (aza-T-dCyd) is as effective as aza-dCyd in depleting DNMT1 in mouse tumor models, but with markedly low toxicity. In this review we describe the preclinical studies that led to the development of aza-T-dCyd as a superior DNMT1 depleting agent with respect to aza-dCyd, and will describe its pharmacology, metabolism, and mechanism of action. In an effort to understand why aza-T-dCyd is a more selective DNMT1 depleting agent than aza-dCyd, we will also compare and contrast the activities of these two agents. Significance Statement Aza-T-dCyd is a potent DNMT1 depleting agent. Although similar in structure to decitabine (aza-dCyd) its metabolism and mechanism of action is different than that of aza-dCyd, resulting in less off target activity and less toxicity. The larger therapeutic index of aza-T-dCyd (DNMT1 depletion vs toxicity) in mice suggests that it would be a better clinical candidate to selectively deplete DNMT1 from target cells and determine whether or not depletion of DNMT1 is an effective target for various diseases.
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Nicorescu I, Dallinga GM, de Winther MP, Stroes ES, Bahjat M. Potential epigenetic therapeutics for atherosclerosis treatment. Atherosclerosis 2019; 281:189-197. [DOI: 10.1016/j.atherosclerosis.2018.10.006] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/27/2018] [Revised: 09/18/2018] [Accepted: 10/04/2018] [Indexed: 01/03/2023]
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Nucleosidic DNA demethylating epigenetic drugs – A comprehensive review from discovery to clinic. Pharmacol Ther 2018; 188:45-79. [DOI: 10.1016/j.pharmthera.2018.02.006] [Citation(s) in RCA: 68] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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Castillo-Aguilera O, Depreux P, Halby L, Arimondo PB, Goossens L. DNA Methylation Targeting: The DNMT/HMT Crosstalk Challenge. Biomolecules 2017; 7:biom7010003. [PMID: 28067760 PMCID: PMC5372715 DOI: 10.3390/biom7010003] [Citation(s) in RCA: 84] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2016] [Revised: 12/08/2016] [Accepted: 12/12/2016] [Indexed: 12/22/2022] Open
Abstract
Chromatin can adopt a decondensed state linked to gene transcription (euchromatin) and a condensed state linked to transcriptional repression (heterochromatin). These states are controlled by epigenetic modulators that are active on either the DNA or the histones and are tightly associated to each other. Methylation of both DNA and histones is involved in either the activation or silencing of genes and their crosstalk. Since DNA/histone methylation patterns are altered in cancers, molecules that target these modifications are interesting therapeutic tools. We present herein a vast panel of DNA methyltransferase inhibitors classified according to their mechanism, as well as selected histone methyltransferase inhibitors sharing a common mode of action.
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Affiliation(s)
- Omar Castillo-Aguilera
- Univ. Lille, ICPAL, EA 7365-GRITA-Groupe de Recherche sur les formes Injectables et les Technologies Associées, 3 rue du Pr. Laguesse, F-59000 Lille, France.
| | - Patrick Depreux
- Univ. Lille, ICPAL, EA 7365-GRITA-Groupe de Recherche sur les formes Injectables et les Technologies Associées, 3 rue du Pr. Laguesse, F-59000 Lille, France.
| | - Ludovic Halby
- FRE3600 Epigenetic Targeting of Cancer, CNRS, 31035 Toulouse, France.
| | - Paola B Arimondo
- FRE3600 Epigenetic Targeting of Cancer, CNRS, 31035 Toulouse, France.
- Churchill College, Cambridge CB3 0DS, UK.
| | - Laurence Goossens
- Univ. Lille, ICPAL, EA 7365-GRITA-Groupe de Recherche sur les formes Injectables et les Technologies Associées, 3 rue du Pr. Laguesse, F-59000 Lille, France.
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Singh S, Tanneeru K, Guruprasad L. Structure and dynamics of H. pylori 98-10 C5-cytosine specific DNA methyltransferase in complex with S-adenosyl-l-methionine and DNA. MOLECULAR BIOSYSTEMS 2016; 12:3111-23. [PMID: 27470658 DOI: 10.1039/c6mb00306k] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Helicobacter pylori is a Gram-negative bacterium that inhabits the human gastrointestinal tract, and some strains of this bacterium cause gastric ulcers and cancer. DNA methyltransferases (MTases) are promising drug targets for the treatment of cancer and other diseases that are also caused by epigenetic alternations of the genome. The C5-cytosine specific DNA methyltransferase from H. pylori (M. Hpy C5mC) catalyzes the transfer of the methyl group from the cofactor S-adenosyl-l-methionine (AdoMet) to the flipped cytosine of the substrate DNA. Herein we report the sequence analyses, 3-D structure modeling and molecular dynamics simulations of M. Hpy C5mC, when complexed with AdoMet as well as DNA. We analyzed the protein-DNA interactions prominently established by the flipped cytosine and the interactions between the protein and cofactor in the active site. We propose that the contacts made by cytosine O2 with Arg155 and Arg157, and the water-mediated interactions with cytosine N3 may be essential for the activity of methyl transfer as well as the deprotonation at the C5 position in our C5mC model. Specific recognition of DNA was mediated mainly by residues from Ser221-Arg229 and Ser243-Gln246 of the target recognition domain (TRD) and some residues of the loop Ser75-Lys83 from the large domain. These findings are further supported by alanine scanning mutagenesis studies. The results reported here explain the sequence, structure and binding features necessary for the recognition between the cofactor and the substrate by the key epigenetic enzyme, M. Hpy C5mC.
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Affiliation(s)
- Swati Singh
- School of Chemistry, University of Hyderabad, Hyderabad, 500046, India.
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Xu P, Hu G, Luo C, Liang Z. DNA methyltransferase inhibitors: an updated patent review (2012-2015). Expert Opin Ther Pat 2016; 26:1017-30. [PMID: 27376512 DOI: 10.1080/13543776.2016.1209488] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
INTRODUCTION DNA methyltransferases (DNMTs), important enzymes involved in epigenetic regulation of gene expression, represent promising targets in cancer therapy. DNMT inhibitors (DNMTi), which can modulate the aberrant DNA methylation pattern in a reversible way via inhibiting DNMT activity, have attracted significant attention in recent years. AREAS COVERED This review outlines the newly patented inhibitors targeting DNMTs, mainly incorporating small molecular inhibitors and oligonucleotide derivatives. The chemical structures, biological activity, and the encouraging clinical research in progress are delineated in detail. EXPERT OPINION Two drugs, azacitidine and decitabine, have evidently shown efficacy in hematologic malignancies, yet do not work well on solid tumors, have low specificity, substantial toxicity, and poor bioavailability. With the rapid advancement in systems biology, drug combinations, such as DNMTi, in conjugation with histone deacetylase inhibitors (HDACi) or immunotherapy, probably serve as an efficient way of implementing epigenetic therapy. Meanwhile, the resolved autoinhibitory structures of DNMTs afford a novel strategy for targeting the protein-protein interface involved in the autoinhi-bitory interactions. The molecular mechanism underlying the conformational transitions would also shed new light on the design of allosteric inhibitors. Both strategies would produce inhibitors with more selectivity compared to nucleotide derivatives.
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Affiliation(s)
- Pan Xu
- a Center for Systems Biology , Soochow University , Jiangsu , China.,b Shanghai Institute of Materia Medica, State Key Laboratory of Drug Research , Chinese Academy of Sciences , Shanghai , China
| | - Guang Hu
- a Center for Systems Biology , Soochow University , Jiangsu , China
| | - Cheng Luo
- b Shanghai Institute of Materia Medica, State Key Laboratory of Drug Research , Chinese Academy of Sciences , Shanghai , China
| | - Zhongjie Liang
- a Center for Systems Biology , Soochow University , Jiangsu , China
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Novel DNA methyltransferase-1 (DNMT1) depleting anticancer nucleosides, 4'-thio-2'-deoxycytidine and 5-aza-4'-thio-2'-deoxycytidine. Cancer Chemother Pharmacol 2014; 74:291-302. [PMID: 24908436 DOI: 10.1007/s00280-014-2503-z] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2013] [Accepted: 05/27/2014] [Indexed: 10/25/2022]
Abstract
PURPOSE Currently approved DNA hypomethylating nucleosides elicit their effects in part by depleting DNA methyltransferase I (DNMT1). However, their low response rates and adverse effects continue to drive the discovery of newer DNMT1 depleting agents. Herein, we identified two novel 2'-deoxycytidine (dCyd) analogs, 4'-thio-2'-deoxycytidine (T-dCyd) and 5-aza-4'-thio-2'-deoxycytidine (aza-T-dCyd) that potently deplete DNMT1 in both in vitro and in vivo models of cancer and concomitantly inhibit tumor growth. METHODS DNMT1 protein levels in in vitro and in vivo cancer models were determined by Western blotting and antitumor efficacy was evaluated using xenografts. Effects on CpG methylation were evaluated using methylation-specific PCR. T-dCyd metabolism was evaluated using radiolabeled substrate. RESULTS T-dCyd markedly depleted DNMT1 in CCRF-CEM and KG1a leukemia and NCI-H23 lung carcinoma cell lines, while it was ineffective in the HCT-116 colon or IGROV-1 ovarian tumor lines. On the other hand, aza-T-dCyd potently depleted DNMT1 in all of these lines indicating that dCyd analogs with minor structural dissimilarities induce different DNMT1 turnover mechanisms. Although T-dCyd was deaminated to 4'-thio-2'-deoxyuridine, very little was converted to 4'-thio-thymidine nucleotides, suggesting that inhibition of thymidylate synthase would be minimal with 4'-thio dCyd analogs. Both T-dCyd and aza-T-dCyd also depleted DNMT1 in human tumor xenografts and markedly reduced in vivo tumor growth. Interestingly, the selectivity index of aza-T-dCyd was at least tenfold greater than that of decitabine. CONCLUSIONS Collectively, these data show that 4'-thio modified dCyd analogs, such as T-dCyd or aza-T-dCyd, could be a new source of clinically effective DNMT1 depleting anticancer compounds with less toxicity.
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Advances in the development of nucleoside and nucleotide analogues for cancer and viral diseases. Nat Rev Drug Discov 2013; 12:447-64. [PMID: 23722347 DOI: 10.1038/nrd4010] [Citation(s) in RCA: 823] [Impact Index Per Article: 74.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Nucleoside analogues have been in clinical use for almost 50 years and have become cornerstones of treatment for patients with cancer or viral infections. The approval of several additional drugs over the past decade demonstrates that this family still possesses strong potential. Here, we review new nucleoside analogues and associated compounds that are currently in preclinical or clinical development for the treatment of cancer and viral infections, and that aim to provide increased response rates and reduced side effects. We also highlight the different approaches used in the development of these drugs and the potential of personalized therapy.
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Advances in the development of nucleoside and nucleotide analogues for cancer and viral diseases. NATURE REVIEWS. DRUG DISCOVERY 2013. [PMID: 23722347 DOI: 10.1038/nrd4010]] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Nucleoside analogues have been in clinical use for almost 50 years and have become cornerstones of treatment for patients with cancer or viral infections. The approval of several additional drugs over the past decade demonstrates that this family still possesses strong potential. Here, we review new nucleoside analogues and associated compounds that are currently in preclinical or clinical development for the treatment of cancer and viral infections, and that aim to provide increased response rates and reduced side effects. We also highlight the different approaches used in the development of these drugs and the potential of personalized therapy.
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Yang J, Lior-Hoffmann L, Wang S, Zhang Y, Broyde S. DNA cytosine methylation: structural and thermodynamic characterization of the epigenetic marking mechanism. Biochemistry 2013; 52:2828-38. [PMID: 23528166 DOI: 10.1021/bi400163k] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
DNA cytosine methyltransferases regulate the expression of the genome through the precise epigenetic marking of certain cytosines with a methyl group, and aberrant methylation is a hallmark of human diseases including cancer. Targeting these enzymes for drug design is currently a high priority. We have utilized ab initio quantum mechanical/molecular mechanical (QM/MM) molecular dynamics (MD) simulations to investigate extensively the reaction mechanism of the representative DNA methyltransferase HhaI (M.HhaI) from prokaryotes, whose overall mechanism is shared with the mammalian enzymes. We obtain for the first time full free energy profiles for the complete reaction, together with reaction dynamics in atomistic detail. Our results show an energetically preferred mechanism in which nucleophilic attack of cytosine C5 on the S-adenosyl-L-methionine (AdoMet) methyl group is concerted with formation of the Michael adduct between a conserved Cys in the active site with cytosine C6. Spontaneous and reversible proton transfer between a conserved Glu in the active site and cytosine N3 at the transition state was observed in our simulations, revealing the chemical participation of this Glu residue in the catalytic mechanism. Subsequently, the β-elimination of the C5 proton utilizes as base an OH(-) derived from a conserved crystal water that is part of a proton wire water channel, and this syn β-elimination reaction is the rate-limiting step. Design of novel cytosine methylation inhibitors would be advanced by our structural and thermodynamic characterization of the reaction mechanism.
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Affiliation(s)
- Jin Yang
- Department of Chemistry, New York University, New York, NY 10003, USA
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CpG underrepresentation and the bacterial CpG-specific DNA methyltransferase M.MpeI. Proc Natl Acad Sci U S A 2012; 110:105-10. [PMID: 23248272 DOI: 10.1073/pnas.1207986110] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Cytosine methylation promotes deamination. In eukaryotes, CpG methylation is thought to account for CpG underrepresentation. Whether scarcity of CpGs in prokaryotic genomes is diagnostic for methylation is not clear. Here, we report that Mycoplasms tend to be CpG depleted and to harbor a family of constitutively expressed or phase variable CpG-specific DNA methyltransferases. The very CpG poor Mycoplasma penetrans and its constitutively active CpG-specific methyltransferase M.MpeI were chosen for further characterization. Genome-wide sequencing of bisulfite-converted DNA indicated that M.MpeI methylated CpG target sites both in vivo and in vitro in a locus-nonselective manner. A crystal structure of M.MpeI with DNA at 2.15-Å resolution showed that the substrate base was flipped and that its place in the DNA stack was taken by a glutamine residue. A phenylalanine residue was intercalated into the "weak" CpG step of the nonsubstrate strand, indicating mechanistic similarities in the recognition of the short CpG target sequence by prokaryotic and eukaryotic DNA methyltransferases.
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Yoo J, Kim JH, Robertson KD, Medina-Franco JL. Molecular modeling of inhibitors of human DNA methyltransferase with a crystal structure: discovery of a novel DNMT1 inhibitor. ADVANCES IN PROTEIN CHEMISTRY AND STRUCTURAL BIOLOGY 2012; 87:219-47. [PMID: 22607757 PMCID: PMC3837394 DOI: 10.1016/b978-0-12-398312-1.00008-1] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
DNA methyltransferases (DNMTs) are promising epigenetic targets for the development of novel anticancer drugs and other diseases. Molecular modeling and experimental approaches are being used to identify and develop inhibitors of human DNMTs. Most of the computational efforts conducted so far with DNMT1 employ homology models of the enzyme. Recently, a crystallographic structure of the methyltransferase domain of human DNMT1 bound to unmethylated DNA was published. Following on our previous computational and experimental studies with DNMTs, we herein present molecular dynamics of the crystal structure of human DNMT1. Docking studies of established DNMT1 inhibitors with the crystal structure gave rise to a structure-based pharmacophore model that suggests key interactions of the inhibitors with the catalytic binding site. Results had a good agreement with the docking and pharmacophore models previously developed using a homology model of the catalytic domain of DNMT1. The docking protocol was able to distinguish active DNMT1 inhibitors from, for example, experimentally known inactive DNMT1 inhibitors. As part of our efforts to identify novel inhibitors of DNMT1, we conducted the experimental characterization of aurintricarboxylic acid (ATA) that in preliminary docking studies showed promising activity. ATA had a submicromolar inhibition (IC50 = 0.68 μM) against DNMT1. ATA was also evaluated for Dnmt3a inhibition showing an IC50 = 1.4 μM. This chapter illustrates the synergy from integrating molecular modeling and experimental methods to further advance the discovery of novel candidates for epigenetic therapies.
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Affiliation(s)
- Jakyung Yoo
- Torrey Pines Institute for Molecular Studies, Port St. Lucie, Florida, USA
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Yoo J, Medina-Franco JL. Homology modeling, docking and structure-based pharmacophore of inhibitors of DNA methyltransferase. J Comput Aided Mol Des 2011; 25:555-67. [DOI: 10.1007/s10822-011-9441-1] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2011] [Accepted: 05/30/2011] [Indexed: 11/28/2022]
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Medina-Franco JL, Caulfield T. Advances in the computational development of DNA methyltransferase inhibitors. Drug Discov Today 2011; 16:418-25. [DOI: 10.1016/j.drudis.2011.02.003] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2010] [Revised: 12/22/2010] [Accepted: 02/02/2011] [Indexed: 12/31/2022]
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Gerasimaitė R, Merkienė E, Klimašauskas S. Direct observation of cytosine flipping and covalent catalysis in a DNA methyltransferase. Nucleic Acids Res 2011; 39:3771-80. [PMID: 21245034 PMCID: PMC3089467 DOI: 10.1093/nar/gkq1329] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Methylation of the five position of cytosine in DNA plays important roles in epigenetic regulation in diverse organisms including humans. The transfer of methyl groups from the cofactor S-adenosyl-l-methionine is carried out by methyltransferase enzymes. Using the paradigm bacterial methyltransferase M.HhaI we demonstrate, in a chemically unperturbed system, the first direct real-time analysis of the key mechanistic events—the flipping of the target cytosine base and its covalent activation; these changes were followed by monitoring the hyperchromicity in the DNA and the loss of the cytosine chromophore in the target nucleotide, respectively. Combined with studies of M.HhaI variants containing redesigned tryptophan fluorophores, we find that the target base flipping and the closure of the mobile catalytic loop occur simultaneously, and the rate of this concerted motion inversely correlates with the stability of the target base pair. Subsequently, the covalent activation of the target cytosine is closely followed by but is not coincident with the methyl group transfer from the bound cofactor. These findings provide new insights into the temporal mechanism of this physiologically important reaction and pave the way to in-depth studies of other base-flipping systems.
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Affiliation(s)
- Rūta Gerasimaitė
- Department of Biological DNA Modification, Institute of Biotechnology, Vilnius University, LT-02241 Vilnius, Lithuania
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Medina-Franco JL, López-Vallejo F, Kuck D, Lyko F. Natural products as DNA methyltransferase inhibitors: a computer-aided discovery approach. Mol Divers 2010; 15:293-304. [PMID: 20697809 DOI: 10.1007/s11030-010-9262-5] [Citation(s) in RCA: 92] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2010] [Accepted: 07/20/2010] [Indexed: 01/25/2023]
Abstract
DNA methyltransferases (DNMTs) represent promising targets for the development of unique anticancer drugs. However, all DNMT inhibitors currently in clinical use are nonselective cytosine analogs with significant cytotoxic side-effects. Several natural products, covering diverse chemical classes, have indicated DNMT inhibitory activity, but these effects have yet to be systematically evaluated. In this study, we provide experimental data suggesting that two of the most prominent natural products associated with DNA methylation inhibition, (-)-epigallocathechin-3-gallate (EGCG) and curcumin, have little or no pharmacologically relevant inhibitory activity. We therefore conducted a virtual screen of a large database of natural products with a validated homology model of the catalytic domain of DNMT1. The virtual screening focused on a lead-like subset of the natural products docked with DNMT1, using three docking programs, following a multistep docking approach. Prior to docking, the lead-like subset was characterized in terms of chemical space coverage and scaffold content. Consensus hits with high predicted docking affinity for DNMT1 by all three docking programs were identified. One hit showed DNMT1 inhibitory activity in a previous study. The virtual screening hits were located within the biological-relevant chemical space of drugs, and represent potential unique DNMT inhibitors of natural origin. Validation of these virtual screening hits is warranted.
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Affiliation(s)
- Jose L Medina-Franco
- Torrey Pines Institute for Molecular Studies, 11350 SW Village Parkway, Port St. Lucie, FL 34987, USA.
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Homology modeling and molecular dynamics simulations of HgiDII methyltransferase in complex with DNA and S-adenosyl-methionine: catalytic mechanism and interactions with DNA. J Mol Model 2009; 16:1213-22. [PMID: 20033464 DOI: 10.1007/s00894-009-0632-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2009] [Accepted: 11/23/2009] [Indexed: 10/20/2022]
Abstract
M.HgiDII is a methyltransferase (MTase) from Herpetosiphon giganteus that recognizes the sequence GTCGAC. This enzyme belongs to a group of MTases that share a high degree of amino acid similarity, albeit none of them has been thoroughly characterized. To study the catalytic mechanism of M.HgiDII and its interactions with DNA, we performed molecular dynamics simulations with a homology model of M.HgiDII complexed with DNA and S-adenosyl-methionine. Our results indicate that M.HgiDII may not rely only on Glu119 to activate the cytosine ring, which is an early step in the catalysis of cytosine methylation; apparently, Arg160 and Arg162 may also participate in the activation by interacting with cytosine O2. Another residue from the catalytic site, Val118, also played a relevant role in the catalysis of M.HgiDII. Val118 interacted with the target cytosine and kept water molecules from accessing the region of the catalytic pocket where Cys79 interacts with cytosine, thus preventing water-mediated disruption of interactions in the catalytic site. Specific recognition of DNA was mediated mainly by amino acids of the target recognition domain, although some amino acids (loop 80-88) of the catalytic domain may also contribute to DNA recognition. These interactions involved direct contacts between M.HgiDII and DNA, as well as indirect contacts through water bridges. Additionally, analysis of sequence alignments with closely related MTases helped us to identify a motif in the TRD of M.HgiDII that may be relevant to specific DNA recognition.
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Kirsanova OV, Cherepanova NA, Gromova ES. Inhibition of C5-cytosine-DNA-methyltransferases. BIOCHEMISTRY (MOSCOW) 2009; 74:1175-86. [DOI: 10.1134/s0006297909110017] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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21
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Singh N, Dueñas-González A, Lyko F, Medina-Franco JL. Molecular modeling and molecular dynamics studies of hydralazine with human DNA methyltransferase 1. ChemMedChem 2009; 4:792-9. [PMID: 19322801 DOI: 10.1002/cmdc.200900017] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
DNA methyltransferases (DNMTs) are a family of enzymes that methylate DNA at the C5 position of cytosine residues, and their inhibition is a promising strategy for the treatment of various developmental and proliferative diseases, particularly cancers. In the present study, a binding model for hydralazine, with a validated homology model of human DNMT, was developed by the use of automated molecular docking and molecular dynamics simulations. The docking protocol was validated by predicting the binding mode of 2'-deoxycytidine, 5-azacytidine, and 5-aza-2'-deoxycytidine. The inhibitory activity of hydralazine toward DNMT may be rationalized at the molecular level by similar interactions within the binding pocket (e.g., by a similar pharmacophore) as established by substrate-like deoxycytidine analogues. These interactions involve a complex network of hydrogen bonds with arginine and glutamic acid residues that also play a major role in the mechanism of DNA methylation. Despite the different scaffolds of other non-nucleoside DNMT inhibitors such as procaine and procainamide, the current modeling work reveals that these drugs exhibit similar interactions within the DNMT1 binding site. These findings are valuable in guiding the rational design and virtual screening of novel DNMT inhibitors.
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Affiliation(s)
- Narender Singh
- Torrey Pines Institute for Molecular Studies, 11350 SW Village Parkway, Port St. Lucie, FL 34987, USA
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22
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van Bemmel DM, Brank AS, Eritja R, Marquez VE, Christman JK. DNA (Cytosine-C5) methyltransferase inhibition by oligodeoxyribonucleotides containing 2-(1H)-pyrimidinone (zebularine aglycon) at the enzymatic target site. Biochem Pharmacol 2009; 78:633-41. [PMID: 19467223 DOI: 10.1016/j.bcp.2009.05.017] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2009] [Revised: 05/15/2009] [Accepted: 05/15/2009] [Indexed: 11/16/2022]
Abstract
Aberrant cytosine methylation in promoter regions leads to gene silencing associated with cancer progression. A number of DNA methyltransferase inhibitors are known to reactivate silenced genes; including 5-azacytidine and 2-(1H)-pyrimidinone riboside (zebularine). Zebularine is a more stable, less cytotoxic inhibitor compared to 5-azacytidine. To determine the mechanistic basis for this difference, we carried out a detailed comparisons of the interaction between purified DNA methyltransferases and oligodeoxyribonucleotides (ODNs) containing either 5-azacytosine or 2-(1H)-pyrimidinone in place of the cytosine targeted for methylation. When incorporated into small ODNs, the rate of C5 DNA methyltransferase inhibition by both nucleosides is essentially identical. However, the stability and reversibility of the enzyme complex in the absence and presence of cofactor differs. 5-Azacytosine ODNs form complexes with C5 DNA methyltransferases that are irreversible when the 5-azacytosine ring is intact. ODNs containing 2-(1H)-pyrimidinone at the enzymatic target site are competitive inhibitors of both prokaryotic and mammalian DNA C5 methyltransferases. We determined that the ternary complexes between the enzymes, 2-(1H)-pyrimidinone inhibitor, and the cofactor S-adenosyl methionine are maintained through the formation of a reversible covalent interaction. The differing stability and reversibility of the covalent bonds may partially account for the observed differences in cytotoxicity between zebularine and 5-azacytidine inhibitors.
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Affiliation(s)
- Dana M van Bemmel
- Department of Biochemistry and Molecular Biology, Omaha, NE 68198-5870, USA.
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23
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Pederson K, Meints GA, Shajani Z, Miller PA, Drobny GP. Backbone dynamics in the DNA HhaI protein binding site. J Am Chem Soc 2008; 130:9072-9. [PMID: 18570423 DOI: 10.1021/ja801243d] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The dynamics of the phosphodiester backbone in the [5'-GCGC-3'] 2 moiety of the DNA oligomer [d(G 1A 2T 3A 4 G 5 C 6 G 7 C 8T 9A 10T 11C 12)] 2 are studied using deuterium solid-state NMR (SSNMR). SSNMR spectra obtained from DNAs nonstereospecifically deuterated on the 5' methylene group of nucleotides within the [5'-GCGC-3'] 2 moiety indicated that all of these positions are structurally flexible. Previous work has shown that methylation reduces the amplitude of motion in the phosphodiester backbone and furanose ring of the same DNA, and our observations indicate that methylation perturbs backbone dynamics through not only a loss of mobility but also a change of direction of motion. These NMR data indicate that the [5'-GCGC-3'] 2 moiety is dynamic, with the largest amplitude motions occurring nearest the methylation site. The change of orientation of this moiety in DNA upon methylation may make the molecule less amenable to binding to the HhaI endonuclease.
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Affiliation(s)
- Kari Pederson
- Department of Chemistry, University of Washington, Seattle, Washington 98195-1700, USA
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24
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Matsugami A, Ohyama T, Inada M, Inoue N, Minakawa N, Matsuda A, Katahira M. Unexpected A-form formation of 4'-thioDNA in solution, revealed by NMR, and the implications as to the mechanism of nuclease resistance. Nucleic Acids Res 2008; 36:1805-12. [PMID: 18252770 PMCID: PMC2330235 DOI: 10.1093/nar/gkn011] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Fully modified 4′-thioDNA, an oligonucleotide only comprising 2′-deoxy-4′-thionucleosides, exhibited resistance to an endonuclease, in addition to preferable hybridization with RNA. Therefore, 4′-thioDNA is promising for application as a functional oligonucleotide. Fully modified 4′-thioDNA was found to behave like an RNA molecule, but no details of its structure beyond the results of circular dichroism analysis are available. Here, we have determined the structure of fully modified 4′-thioDNA with the sequence of d(CGCGAATTCGCG) by NMR. Most sugars take on the C3′-endo conformation. The major groove is narrow and deep, while the minor groove is wide and shallow. Thus, fully modified 4′-thioDNA takes on the A-form characteristic of RNA, both locally and globally. The only structure reported for 4′-thioDNA showed that partially modified 4′-thioDNA that contained some 2′-deoxy-4′-thionucleosides took on the B-form in the crystalline form. We have determined the structure of 4′-thioDNA in solution for the first time, and demonstrated unexpected differences between the two structures. The origin of the formation of the A-form is discussed. The remarkable biochemical properties reported for fully modified 4′-thioDNA, including nuclease-resistance, are rationalized in the light of the elucidated structure.
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Affiliation(s)
- Akimasa Matsugami
- Supramolecular Biology, International Graduate School of Arts and Sciences, Yokohama City University, 1-7-29 Suehiro-cho, Tsurumi-ku, Yokohama 230-0045, Japan
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25
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Scott SA, Lakshimikuttysamma A, Sheridan DP, Sanche SE, Geyer CR, DeCoteau JF. Zebularine inhibits human acute myeloid leukemia cell growth in vitro in association with p15INK4B demethylation and reexpression. Exp Hematol 2007; 35:263-73. [PMID: 17258075 DOI: 10.1016/j.exphem.2006.10.005] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2006] [Revised: 09/30/2006] [Accepted: 10/05/2006] [Indexed: 12/20/2022]
Abstract
OBJECTIVE The p15INK4B tumor suppressor is frequently silenced by promoter hypermethylation in myelodysplastic syndrome and acute myeloid leukemia (AML). Clinically approved DNA methylation inhibitors, such as 5-aza-2'-deoxycytidine, can reverse p15INK4B promoter methylation, but widespread clinical use of these inhibitors is limited by their toxicity and instability in aqueous solution. The cytidine analog zebularine is a stable DNA methylation inhibitor that has minimal toxicity in vitro and in vivo. We evaluated zebularine effects on p15INK4B reactivation and cell growth in vitro to investigate a potential role for zebularine in treating myeloid malignancies. METHODS We examined the specific effects of zebularine on reexpression of transcriptionally silenced p15INK4B and its global effects on cell cycle and apoptosis in AML cell lines and primary patient samples. RESULTS Zebularine treatment of AML193, which has a densely methylated p15INK4B promoter, results in a dose-dependent increase in p15INK4B expression that correlates with CpG island promoter demethylation and enrichment of local histone acetylation. We observed enhanced p15INK4B induction following co-treatment with zebularine and the histone deacetylase inhibitor Trichostatin A. Zebularine inhibits cell proliferation, arrests cells at G(2)/M, and induces apoptosis at dosages that effectively demethylate the p15INK4B promoter. Zebularine treatment of KG-1 cells and AML patient blasts with hypermethylated p15INK4B promoters also reactivates p15INK4B reexpression and induces apoptosis. CONCLUSION Zebularine is an effective inhibitor of p15INK4B methylation and cell growth in human AML in vitro. Our results extend the spectrum of zebularine effects to nonepithelial malignancies and provide a strong rationale for evaluating its clinical utility in the treatment of myeloid malignancies.
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Affiliation(s)
- Stuart A Scott
- Department of Human Genetics, Mount Sinai School of Medicine, New York, NY., USA
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26
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Shieh FK, Reich NO. AdoMet-dependent Methyl-transfer: Glu119 Is Essential for DNA C5-Cytosine Methyltransferase M.HhaI. J Mol Biol 2007; 373:1157-68. [PMID: 17897676 DOI: 10.1016/j.jmb.2007.08.009] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2007] [Revised: 07/17/2007] [Accepted: 08/03/2007] [Indexed: 11/21/2022]
Abstract
The role of Glu119 in S-adenosyl-L-methionine-dependent DNA methyltransferase M.HhaI-catalyzed DNA methylation was studied. Glu119 belongs to the highly conserved Glu/Asn/Val motif found in all DNA C5-cytosine methyltransferases, and its importance for M.HhaI function remains untested. We show that formation of the covalent intermediate between Cys81 and the target cytosine requires Glu119, since conversion to Ala, Asp or Gln lowers the rate of methyl transfer 10(2)-10(6) fold. Further, unlike the wild-type M.HhaI, these mutants are not trapped by the substrate in which the target cytosine is replaced with the mechanism-based inhibitor 5-fluorocytosine. The DNA binding affinity for the Glu119Asp mutant is decreased 10(3)-fold. Thus, the ability of the enzyme to stabilize the extrahelical cytosine is coupled directly to tight DNA binding. The structures of the ternary protein/DNA/AdoHcy complexes for both the Glu119Ala and Glu119Gln mutants (2.70 A and 2.75 A, respectively) show that the flipped base is positioned nearly identically with that observed in the wild-type M.HhaI complex. A single water molecule in the Glu119Ala structure between Ala119 and the extrahelical cytosine N3 is lacking in the Glu119Gln and wild-type M.HhaI structures, and most likely accounts for this mutant's partial activity. Glu119 has essential roles in activating the target cytosine for nucleophilic attack and contributes to tight DNA binding.
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Affiliation(s)
- Fa-Kuen Shieh
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA 93106-9510, USA
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27
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Lin RK, Hsu CH, Wang YC. Mithramycin A inhibits DNA methyltransferase and metastasis potential of lung cancer cells. Anticancer Drugs 2007; 18:1157-64. [PMID: 17893516 DOI: 10.1097/cad.0b013e3282a215e9] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Abnormal CpG island hypermethylation of multiple tumor-suppressor genes (TSGs) can lead to the initiation and progression of human cancer. The cytosine of the CpG island on the promoter region is methylated by 5'-cytosine-methyltransferases (DNMTs). Pharmacologic inhibitors of CpG island methylation provide a rational approach to reactivate the TSGs in tumor cells and to restore the critical cellular pathways in cancer cells. Mithramycin A (MMA) is known to be a GC- and CG-rich DNA-binding agent. We sought to determine whether MMA could inhibit CpG island methylation and DNMT expression in lung cancer cells. We found that MMA reduced the CpG island methylation of antimetastasis TSGs, including SLIT2 and TIMP-3 genes, and was associated with the prevention of metastasis. When highly metastatic CL1-5 lung cancer cells were treated with low doses (10 nmol/l) of MMA for 14 days, they reexpressed mRNA levels for these genes. MMA also inhibited the invasion phenotypes of CL1-5 cells as indicated by its inhibition of cancer cell migration using wound-healing and transwell assays. Molecular docking of MMA onto the DNMT1 catalytic domain revealed that MMA might interact with the catalytic pocket of DNMT1. Western blots showed that DNMT1 protein levels were depleted after MMA. These data support the idea that MMA has demethylation and antimetastasis effects on lung cancer cells. This mechanism might be mediated by the interaction of MMA and DNMT1, leading to the depletion of the DNMT1 protein and the reversal of the metastasis phenotype in lung cancer cells.
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Affiliation(s)
- Ruo-Kai Lin
- Department of Life Sciences, National Taiwan Normal University, Taipei, Taiwan, ROC
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28
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Bruice TC. Computational approaches: reaction trajectories, structures, and atomic motions. Enzyme reactions and proficiency. Chem Rev 2007; 106:3119-39. [PMID: 16895321 DOI: 10.1021/cr050283j] [Citation(s) in RCA: 98] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Affiliation(s)
- Thomas C Bruice
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, California 93106-9510, USA.
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29
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Schubert HL, Blumenthal RM, Cheng X. 1 Protein Methyltransferases: Their Distribution Among the Five Structural Classes of AdoMet-Dependent Methyltransferases. Enzymes 2007; 24:3-28. [PMID: 26718035 DOI: 10.1016/s1874-6047(06)80003-x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
S-adenosyl-l-methionine (AdoMet) dependent methyltransferases (MTases) are involved in biosynthesis, signal transduction, protein repair, chromatin regulation, and gene silencing. Five different structural folds (designated I through V) have been described that bind AdoMet and catalyze methyltransfer to diverse substrates, although the great majority of known MTases have the Class I fold. Even within a particular MTase class the amino-acid sequence similarity can be as low as 10%. Thus, the structural and catalytic requirements for methyltransfer from AdoMet appear to be remarkably flexible. MTases that act on protein substrates have been found to date among three of the five structural classes (I, the classical fold; III, the corrin MTase fold; and V, the SET fold). "There are many paths to the top of the mountain, but the view is always the same."-Chinese proverb The Columbia World of Quotations, New York, Columbia University Press, 1996.
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Affiliation(s)
- Heidi L Schubert
- Department of Biochemistry University of Utah 15 North Medical DriveEast Salt Lake City, UT 84112, USA
| | - Robert M Blumenthal
- Department of Medical Microbiology and Immunology and Program in Bioinformatics and Proteomics/Genomics Medical University of Ohio 3000 Arlington Avenue Toledo, OH 43614, USA
| | - Xiaodong Cheng
- Department of Biochemistry Emory University School of Medicine 1510 Clifton Road Northeast Atlanta, GA 30322, USA
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30
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Shieh FK, Youngblood B, Reich NO. The role of Arg165 towards base flipping, base stabilization and catalysis in M.HhaI. J Mol Biol 2006; 362:516-27. [PMID: 16926025 DOI: 10.1016/j.jmb.2006.07.030] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2006] [Revised: 07/13/2006] [Accepted: 07/14/2006] [Indexed: 10/24/2022]
Abstract
Arg165 forms part of a previously identified base flipping motif in the bacterial DNA cytosine methyltransferase, M.HhaI. Replacement of Arg165 with Ala has no detectable effect on either DNA or AdoMet affinity, yet causes the base flipping and restacking transitions to be decreased approximately 16 and 190-fold respectively, thus confirming the importance of this motif. However, these kinetic changes cannot account for the mutant's observed 10(5)-fold decreased catalytic rate. The mutant enzyme/cognate DNA cocrystal structure (2.79 A resolution) shows the target cytosine to be positioned approximately 30 degrees into the major groove, which is consistent with a major groove pathway for nucleotide flipping. The pyrimidine-sugar chi angle is rotated to approximately +171 degrees, from a range of -95 degrees to -120 degrees in B DNA, and -77 degrees in the WT M.HhaI complex. Thus, Arg165 is important for maintaining the cytosine positioned for nucleophilic attack by Cys81. The cytosine sugar pucker is in the C2'-endo-C3'-exo (South conformation), in contrast to the previously reported C3'-endo (North conformation) described for the original 2.70 A resolution cocrystal structure of the WT M.HhaI/DNA complex. We determined a high resolution structure of the WT M.HhaI/DNA complex (1.96 A) to better determine the sugar pucker. This new structure is similar to the original, lower resolution WT M.HhaI complex, but shows that the sugar pucker is O4'-endo (East conformation), intermediate between the South and North conformers. In summary, Arg165 plays significant roles in base flipping, cytosine positioning, and catalysis. Furthermore, the previously proposed M.HhaI-mediated changes in sugar pucker may not be an important contributor to the base flipping mechanism. These results provide insights into the base flipping and catalytic mechanisms for bacterial and eukaryotic DNA methyltransferases.
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Affiliation(s)
- Fa-Kuen Shieh
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA 93106-9510, USA
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31
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Inoue N, Minakawa N, Matsuda A. Synthesis and properties of 4'-ThioDNA: unexpected RNA-like behavior of 4'-ThioDNA. Nucleic Acids Res 2006; 34:3476-83. [PMID: 16855286 PMCID: PMC1524900 DOI: 10.1093/nar/gkl491] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The synthesis and properties of fully modified 4′-thioDNAs, oligonucleotides consisting of 2′-deoxy-4′-thionucleosides, were examined. In addition to the known literature properties (preferable hybridization with RNA and resistance to endonuclease hydrolysis), we also observed higher resistance of 4′-thioDNA to 3′-exonuclease cleavage. Furthermore, we found that fully modified 4′-thioDNAs behaved like RNA molecules in their hybridization properties and structural aspect, at least in the case of the 4′-thioDNA duplex. This observation was confirmed by experiments using groove binders, in which a 4′-thioDNA duplex interacts with an RNA major groove binder, lividomycin A, but not with DNA groove binders, to give an increase in its thermal stability. Since a 4′-thioDNA duplex competitively inhibited the hydrolysis of an RNA duplex by RNase V1, it was not only the physical properties but also this biological data suggested that a 4′-thioDNA duplex has an RNA-like structure.
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Affiliation(s)
| | - Noriaki Minakawa
- Correspondence may also be addressed to Noriaki Minakawa. Tel: +81 11 706 3230; Fax: +81 11 706 4980;
| | - Akira Matsuda
- To whom correspondence should be addressed: Tel: +81 11 706 3228; Fax: +81 11 706 4980;
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32
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Zhang X, Bruice TC. The mechanism of M.HhaI DNA C5 cytosine methyltransferase enzyme: a quantum mechanics/molecular mechanics approach. Proc Natl Acad Sci U S A 2006; 103:6148-53. [PMID: 16606828 PMCID: PMC1458846 DOI: 10.1073/pnas.0601587103] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The mechanism of DNA cytosine-5-methylation catalyzed by the bacterial M.HhaI enzyme has been considered as a stepwise nucleophilic addition of Cys-81-S- to cytosine C6 followed by C5 nucleophilic replacement of the methyl of S-adenosyl-L-methionine to produce 5-methyl-6-Cys-81-S-5,6-dihydrocytosine. In this study, we show that the reaction is concerted from a series of energy calculations by using the quantum mechanical/molecular mechanical hybrid method. Deprotonation of 5-methyl-6-Cys-81-S-5,6-dihydrocytosine and expulsion of Cys-81-S- provides the product DNA 5-methylcytosine. A required base catalyst for this deprotonation is not available as a member of the active site structure. A water channel between the active site and bulk water allows entrance of solvent to the active site. Hydroxide at 10(-7) mole fraction (pH = 7) is shown to be sufficient for the required catalysis. We also show that Glu-119-CO2H can divert the reaction by protonating cytosine N3 when Cys-81-S- attacks cytosine, to form the 6-Cys-81-S-3-hydrocytosine. The reactants and 6-Cys-81-S-3-hydrocytosine product are in rapid equilibrium, and this explains the observed hydrogen exchange of cytosine with solvent.
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Affiliation(s)
- Xiaodong Zhang
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA 93106
| | - Thomas C. Bruice
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA 93106
- *To whom correspondence should be addressed. E-mail:
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33
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Luo J, Bruice TC. Low-frequency normal mode in DNA HhaI methyltransferase and motions of residues involved in the base flipping. Proc Natl Acad Sci U S A 2005; 102:16194-8. [PMID: 16236720 PMCID: PMC1283451 DOI: 10.1073/pnas.0507913102] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The results of normal-mode analyses are in accord with the proposal that a low-frequency motion of the HhaI methyltransferase enzyme is responsible for base flipping in bound DNA. The vectors of the low-frequency normal mode of residues Ser-85 and Ile-86 point directly to the phosphate and ribose moieties of the DNA backbone near the target base in position to rotate the dihedral angles and flip the base out of the DNA duplex. The vector of residue Gln-237 on the major groove is in the proper orientation to assist base separation. Our results favor the major groove pathway and the protein active process in base flipping.
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Affiliation(s)
- Jia Luo
- Department of Chemistry and Biology, University of California, Santa Barbara, CA 93106, USA
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34
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Kachalova GS, Artyukh RI, Lavrova NV, Ryazanova EM, Karyagina AS, Kubareva EA, Bartunik HD. Crystallization and preliminary crystallographic analysis of the (cytosine-5)-DNA methyltransferase NlaX from Neisseria lactamica. Acta Crystallogr Sect F Struct Biol Cryst Commun 2005; 61:852-4. [PMID: 16511177 PMCID: PMC1978117 DOI: 10.1107/s1744309105026709] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2005] [Accepted: 08/22/2005] [Indexed: 11/10/2022]
Abstract
Crystals of the (cytosine-5)-DNA methyltransferase NlaX from Neisseria lactamica (molecular weight 36.5 kDa) have been grown at 291 K using 2.5 M NaCl as precipitant. The crystals diffract to 3.0 A resolution at 100 K. The crystals belong to space group P321, with unit-cell parameters a = 121.98, b = 121.98, c = 56.71 A. There is one molecule in the asymmetric unit and the solvent content is estimated to be 62.1% by volume.
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Affiliation(s)
- Galina S Kachalova
- Max-Planck Unit for Structural Molecular Biology, Protein Dynamics Group, Hamburg 22607, Germany.
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35
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Haeberli P, Berger I, Pallan PS, Egli M. Syntheses of 4'-thioribonucleosides and thermodynamic stability and crystal structure of RNA oligomers with incorporated 4'-thiocytosine. Nucleic Acids Res 2005; 33:3965-75. [PMID: 16027443 PMCID: PMC1178003 DOI: 10.1093/nar/gki704] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
A facile synthetic route for the 4'-thioribonucleoside building block (4'S)N (N = U, C, A and G) with the ribose O4' replaced by sulfur is presented. Conversion of l-lyxose to 1,5-di-O-acetyl-2,3-di-O-benzoyl-4-thio-d-ribofuranose was achieved via an efficient four-step synthesis with high yield. Conversion of the thiosugar into the four ribonucleoside phosphoramidite building blocks was accomplished with additional four steps in each case. Incorporation of 4'-thiocytidines into oligoribonucleotides improved the thermal stability of the corresponding duplexes by approximately 1 degrees C per modification, irrespective of whether the strand contained a single modification or a consecutive stretch of (4'S)C residues. The gain in thermodynamic stability is comparable to that observed with oligoribonucleotides containing 2'-O-methylated residues. To establish potential conformational changes in RNA as a result of the 4'-thio modification and to better understand the origins of the observed stability changes, the crystal structure of the oligonucleotide 5'-r(CC(4'S)CCGGGG) was determined and analyzed using the previously solved structure of the native RNA octamer as a reference. The two 4'-thioriboses adopt conformations that are very similar to the C3'-endo pucker observed for the corresponding sugars in the native duplex. Subtle changes in the local geometry of the modified duplex are mostly due to the larger radius of sulfur compared to oxygen or appear to be lattice-induced. The significantly increased RNA affinity of 4'-thio-modified RNA relative to RNA, and the relatively minor conformational changes caused by the modification render this nucleic acid analog an interesting candidate for in vitro and in vivo applications, including use in RNA interference (RNAi), antisense, ribozyme, decoy and aptamer technologies.
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Affiliation(s)
| | - Imre Berger
- Institute for Molecular Biology and Biophysics, Swiss Federal Institute of TechnologyCH-8093 Zürich, Switzerland
| | - Pradeep S. Pallan
- Department of Biochemistry, Vanderbilt University, School of MedicineNashville, TN 37232, USA
| | - Martin Egli
- Department of Biochemistry, Vanderbilt University, School of MedicineNashville, TN 37232, USA
- To whom correspondence should be addressed. Tel: +1 615 343 8070; Fax: +1 615 322 7122;
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36
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Sharma V, Youngblood B, Reich N. Residues Distal from the Active Site that Alter Enzyme Function in M.HhaI DNA Cytosine Methyltransferase. J Biomol Struct Dyn 2005; 22:533-43. [PMID: 15702925 DOI: 10.1080/07391102.2005.10507023] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
Ten M.HhaI residues were replaced with alanine to probe the importance of distal protein elements to substrate/cofactor binding, methyl transfer, and product release. The substitutions, ranging from 6-20 A from the active site were evaluated by thermodynamic analysis, pre-steady and steady-state kinetics, to obtain Kd(AdoMet), Kd(DNA), kcat/Km(DNA), kcat, and kmethyltransfer values. For the wild-type M.HhaI, product release steps dominate catalytic turnover while the 4-fold faster internal microscopic constant kmethyltransfer presents an upper limit. The methyl transfer reaction has DeltaH and DeltaS values of 10.3 kcal/mol and -29.4 cal/(mol K), respectively, consistent with a compressed transition state similar to that observed in the gas phase. Although the ten mutants remained largely unperturbed in methyl transfer, long-range effects influencing substrate/cofactor binding and product release were observed. Positive enhancements were seen in Asp73Ala, which showed a 25-fold improvement in AdoMet affinity and in Val282Ala, which showed a 4-fold improvement in catalytic turnover. Based on an analysis of the positional probability within the C5-cytosine DNA methyltransferase family we propose that certain conserved distal residues may be important in mediating long-range effects.
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Affiliation(s)
- Vyas Sharma
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA 93106, USA
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37
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Estabrook RA, Luo J, Purdy MM, Sharma V, Weakliem P, Bruice TC, Reich NO. Statistical coevolution analysis and molecular dynamics: identification of amino acid pairs essential for catalysis. Proc Natl Acad Sci U S A 2005; 102:994-9. [PMID: 15657135 PMCID: PMC545822 DOI: 10.1073/pnas.0409128102] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Molecular dynamics (MD) simulations of HhaI DNA methyltransferase and statistical coupling analysis (SCA) data on the DNA cytosine methyltransferase family were combined to identify residues that are coupled by coevolution and motion. The highest ranking correlated pairs from the data matrix product (SCA.MD) are colocalized and form stabilizing interactions; the anticorrelated pairs are separated on average by 30 A and form a clear focal point centered near the active site. We suggest that these distal anti-correlated pairs are involved in mediating active-site compressions that may be important for catalysis. Mutants that disrupt the implicated interactions support the validity of our combined SCA.MD approach.
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Affiliation(s)
- R August Estabrook
- Department of Chemistry, University of California, Santa Barbara, CA 93106, USA
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38
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Merkienė E, Klimašauskas S. Probing a rate-limiting step by mutational perturbation of AdoMet binding in the HhaI methyltransferase. Nucleic Acids Res 2005; 33:307-15. [PMID: 15653631 PMCID: PMC546160 DOI: 10.1093/nar/gki175] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
DNA methylation plays important roles via regulation of numerous cellular mechanisms in diverse organisms, including humans. The paradigm bacterial methyltransferase (MTase) HhaI (M.HhaI) catalyzes the transfer of a methyl group from the cofactor S-adenosyl-l-methionine (AdoMet) onto the target cytosine in DNA, yielding 5-methylcytosine and S-adenosyl-l-homocysteine (AdoHcy). The turnover rate (kcat) of M.HhaI, and the other two cytosine-5 MTases examined, is limited by a step subsequent to methyl transfer; however, no such step has so far been identified. To elucidate the role of cofactor interactions during catalysis, eight mutants of Trp41, which is located in the cofactor binding pocket, were constructed and characterized. The mutants show full proficiency in DNA binding and base-flipping, and little variation is observed in the apparent methyl transfer rate kchem as determined by rapid-quench experiments using immobilized fluorescent-labeled DNA. However, the Trp41 replacements with short side chains substantially perturb cofactor binding (100-fold higher KDAdoMet and KMAdoMet) leading to a faster turnover of the enzyme (10-fold higher kcat). Our analysis indicates that the rate-limiting breakdown of a long-lived ternary product complex is initiated by the dissociation of AdoHcy or the opening of the catalytic loop in the enzyme.
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Affiliation(s)
| | - Saulius Klimašauskas
- To whom correspondence should be addressed. Tel: +370 5 260 2114; Fax: +370 5 260 2116;
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39
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Richardson F, Black C, Richardson K, Franks A, Wells E, Karimi S, Sennello G, Hart K, Meyer D, Emerson D, Brown E, LeRay J, Nilsson C, Tomkinson B, Bendele R. Incorporation of OSI-7836 into DNA of Calu-6 and H460 xenograft tumors. Cancer Chemother Pharmacol 2004; 55:213-21. [PMID: 15592840 DOI: 10.1007/s00280-004-0844-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2004] [Accepted: 04/09/2004] [Indexed: 10/26/2022]
Abstract
OSI-7836 (4'-thio-beta-D-arabinofuranosylcytosine) is a novel nucleoside analog in phase I clinical development for the treatment of cancer. As with other nucleoside analogs, the proposed mechanism of action involves phosphorylation to the triphosphate form followed by incorporation into cellular DNA, leading to cell death. This hypothesis has been examined by measuring and comparing the incorporation of ara-C, OSI-7836, and gemcitabine (dFdC) into DNA of cultured cells and by investigating the role of deoxycytidine kinase in OSI-7836 toxicity. We report here additional studies in which the role of cell cycling on OSI-7836 toxicity was investigated and incorporation of OSI-7836 into DNA of xenograft tumors measured. The role of the cell cycle was examined by comparing the toxicity of OSI-7836 in A549 NSCLC cells that were either in log phase growth or had reached confluence. A novel validated LC-MS/MS assay was developed to quantify the concentrations of OSI-7836 in DNA from Calu-6 and H460 human tumor xenografts in mice. Results showed that apoptosis induced by OSI-7836 was markedly greater in cycling cells than in confluent non-cycling cells despite only a modest increase in intracellular OSI-7836 triphosphate concentration. The LC-MS/MS assay developed to measure OSI-7836 incorporation into DNA had an on-column detection limit of 0.25 fmol, a quantification limit of 0.5 fmol, and a sensitivity of approximately 0.1 pmol OSI-7836/micromol dThy. Concentrations of OSI-7836 in splenic DNA (0.4 pmol OSI-7836/micromol dThy) averaged fivefold less than the average concentration in Calu-6 and H460 xenograft DNA (3.0 pmol OSI-7836/micromol dThy) following a 400 mg/kg dose of OSI-7836. Concentrations of OSI-7836 in Calu-6 tumor DNA isolated 24 h following a dose of 400, 1000, or 1600 mg OSI-7836/kg were approximately 1.3, 1 and 1.3 pmol OSI-7836/micromol dThy, respectively. Concentrations of OSI-7836 in DNA from H460 and Calu-6 xenografts did not appear to increase during repeated administration of 400 mg OSI-7836/kg on days 1, 4, 7, and 10. The majority of OSI-7836 in DNA from Calu-6 and H460 tumors of mice dosed with 1600 mg/kg was located at internal nucleotide linkages, similar to dFdC and ara-C. In conclusion, cell cycling studies supported the hypothesis that OSI-7836 cytotoxicity is dependent upon DNA synthesis. A validated LC-MS/MS assay was developed that could quantify OSI-7836 in DNA from tissues. The assay was used to show that OSI-7836 was incorporated in internal linkages in tumor DNA in a manner that was dose-independent at the doses tested and did not appear to accumulate during repeated dosing. The results suggest that if DNA incorporation is a toxic event, the relationships between administered dose, DNA incorporation, and toxicity are complex.
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Affiliation(s)
- Frank Richardson
- OSI Pharmaceuticals, Inc., 2860 Wilderness Place, Boulder, CO 80301, USA.
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40
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Daujotyte D, Serva S, Vilkaitis G, Merkiene E, Venclovas C, Klimasauskas S. HhaI DNA methyltransferase uses the protruding Gln237 for active flipping of its target cytosine. Structure 2004; 12:1047-55. [PMID: 15274924 DOI: 10.1016/j.str.2004.04.007] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2003] [Revised: 03/25/2004] [Accepted: 04/13/2004] [Indexed: 11/22/2022]
Abstract
Access to a nucleotide by its rotation out of the DNA helix (base flipping) is used by numerous DNA modification and repair enzymes. Despite extensive studies of the paradigm HhaI methyltransferase, initial events leading to base flipping remained elusive. Here we demonstrate that the replacement of the target C:G pair with the 2-aminopurine:T pair in the DNA or shortening of the side chain of Gln237 in the protein severely perturb base flipping, but retain specific DNA binding. Kinetic analyses and molecular modeling suggest that a steric interaction between the protruding side chain of Gln237 and the target cytosine in B-DNA reduces the energy barrier for flipping by 3 kcal/mol. Subsequent stabilization of an open state by further 4 kcal/mol is achieved through specific hydrogen bonding of the side chain to the orphan guanine. Gln237 thus plays a key role in actively opening the target C:G pair by a "push-and-bind" mechanism.
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Affiliation(s)
- Dalia Daujotyte
- Laboratory of Biological DNA Modification, Institute of Biotechnology, LT-02241 Vilnius, Lithuania
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41
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Miller DJ, Ouellette N, Evdokimova E, Savchenko A, Edwards A, Anderson WF. Crystal complexes of a predicted S-adenosylmethionine-dependent methyltransferase reveal a typical AdoMet binding domain and a substrate recognition domain. Protein Sci 2003; 12:1432-42. [PMID: 12824489 PMCID: PMC2323940 DOI: 10.1110/ps.0302403] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
S-adenosyl-L-methionine-dependent methyltransferases (MTs) are abundant, and highly conserved across phylogeny. These enzymes use the cofactor AdoMet to methylate a wide variety of molecular targets, thereby modulating important cellular and metabolic activities. Thermotoga maritima protein 0872 (TM0872) belongs to a large sequence family of predicted MTs, ranging phylogenetically from relatively simple bacteria to humans. The genes for many of the bacterial homologs are located within operons involved in cell wall synthesis and cell division. Despite preliminary biochemical studies in E. coli and B. subtilis, the substrate specificity of this group of more than 150 proteins is unknown. As part of the Midwest Center for Structural Genomics initiative (www.mcsg.anl.gov), we have determined the structure of TM0872 in complexes with AdoMet and with S-adenosyl-L-homocysteine (AdoHcy). As predicted, TM0872 has a typical MT domain, and binds endogenous AdoMet, or co-crystallized AdoHcy, in a manner consistent with other known MT structures. In addition, TM0872 has a second domain that is novel among MTs in both its location in the sequence and its structure. The second domain likely acts in substrate recognition and binding, and there is a potential substrate-binding cleft spanning the two domains. This long and narrow cleft is lined with positively charged residues which are located opposite the S(+)-CH(3) bond, suggesting that a negatively charged molecule might be targeted for catalysis. However, AdoMet and AdoHcy are both buried, and access to the methyl group would presumably require structural rearrangement. These TM0872 crystal structures offer the first structural glimpses at this phylogenetically conserved sequence family.
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Affiliation(s)
- Darcie J. Miller
- Department of Molecular Pharmacology and Biological Chemistry and
- Drug Discovery Program, Northwestern University Feinberg School of Medicine, Chicago, Illinois 60611, USA
| | - Nancy Ouellette
- C.H. Best Institute, University of Toronto, Toronto ON M5G 1L6, Canada
| | - Elena Evdokimova
- C.H. Best Institute, University of Toronto, Toronto ON M5G 1L6, Canada
| | - Alexei Savchenko
- C.H. Best Institute, University of Toronto, Toronto ON M5G 1L6, Canada
| | - Aled Edwards
- C.H. Best Institute, University of Toronto, Toronto ON M5G 1L6, Canada
| | - Wayne F. Anderson
- Department of Molecular Pharmacology and Biological Chemistry and
- Drug Discovery Program, Northwestern University Feinberg School of Medicine, Chicago, Illinois 60611, USA
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42
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Abstract
S-adenosyl-L-methionine (AdoMet) dependent methyltransferases (MTases) are involved in biosynthesis, signal transduction, protein repair, chromatin regulation and gene silencing. Five different structural folds (I-V) have been described that bind AdoMet and catalyze methyltransfer to diverse substrates, although the great majority of known MTases have the Class I fold. Even within a particular MTase class the amino-acid sequence similarity can be as low as 10%. Thus, the structural and catalytic requirements for methyltransfer from AdoMet appear to be remarkably flexible.
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Affiliation(s)
- Heidi L. Schubert
- Department of Biochemistry, University of Utah, Salt Lake City, UT 84132-201, USA
| | - Robert M. Blumenthal
- Department of Microbiology and Immunology and Program in Bioinformatics and Proteomics/Genomics, Medical College of Ohio, Toledo, OH 43614-806, USA
| | - Xiaodong Cheng
- Department of Biochemistry, Emory University School of Medicine Atlanta, GA 30322, USA
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43
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Lappalainen I, Vihinen M. Structural basis of ICF-causing mutations in the methyltransferase domain of DNMT3B. Protein Eng Des Sel 2002; 15:1005-14. [PMID: 12601140 DOI: 10.1093/protein/15.12.1005] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Mutations in the gene encoding for a de novo methyltransferase, DNMT3B, lead to an autosomal recessive Immunodeficiency, Centromeric instability and Facial anomalies (ICF) syndrome. To analyse the protein structure and consequences of ICF-causing mutations, we modelled the structure of the DNMT3B methyltransferase domain based on Haemophilus haemolyticus protein in complex with the cofactor AdoMet and the target DNA sequence. The structural model has a two-subdomain fold where the DNA-binding region is situated between the subdomains on a surface cleft having positive electrostatic potential. The smaller subdomains of the methyltransferases differ in length and sequences and therefore only the target recognition domain loop was modelled to show the location of an ICF-causing mutation. Based on the model, the DNMT3B recognizes the GC sequence and flips the cytosine from the double-stranded DNA to the catalytic pocket. The amino acids in the cofactor and target cytosine binding sites and also the electrostatic properties of the binding pockets are conserved. In addition, a registry of all known ICF-causing mutations, DNMT3Bbase, was constructed. The structural principles of the pathogenic mutations based on the modelled structure and the analysis of chi angle rotation changes of mutated side chains are discussed.
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Affiliation(s)
- Ilkka Lappalainen
- Institute of Medical Technology, FIN-33014 University of Tampere, Tampere, Finland
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44
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Keller JP, Smith PM, Benach J, Christendat D, deTitta GT, Hunt JF. The crystal structure of MT0146/CbiT suggests that the putative precorrin-8w decarboxylase is a methyltransferase. Structure 2002; 10:1475-87. [PMID: 12429089 DOI: 10.1016/s0969-2126(02)00876-6] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The CbiT and CbiE enzymes participate in the biosynthesis of vitamin B12. They are fused together in some organisms to form a protein called CobL, which catalyzes two methylations and one decarboxylation on a precorrin intermediate. Because CbiE has sequence homology to canonical precorrin methyltransferases, CbiT was hypothesized to catalyze the decarboxylation. We herein present the crystal structure of MT0146, the CbiT homolog from Methanobacterium thermoautotrophicum. The protein shows structural similarity to Rossmann-like S-adenosyl-methionine-dependent methyltransferases, and our 1.9 A cocrystal structure shows that it binds S-adenosyl-methionine in standard geometry near a binding pocket that could accommodate a precorrin substrate. Therefore, MT0146/CbiT probably functions as a precorrin methyltransferase and represents the first enzyme identified with this activity that does not have the canonical precorrin methyltransferase fold.
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Affiliation(s)
- Jacob P Keller
- Department of Biological Sciences, 702A Fairchild Center, MC2434, Columbia University, New York, NY 10027, USA
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45
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Abstract
DNA methyltransferases catalyze the transfer of a methyl group from S-adenosyl-L-methionine to cytosine or adenine bases in DNA. These enzymes challenge the Watson/Crick dogma in two instances: 1) They attach inheritable information to the DNA that is not encoded in the nucleotide sequence. This so-called epigenetic information has many important biological functions. In prokaryotes, DNA methylation is used to coordinate DNA replication and the cell cycle, to direct postreplicative mismatch repair, and to distinguish self and nonself DNA. In eukaryotes, DNA methylation contributes to the control of gene expression, the protection of the genome against selfish DNA, maintenance of genome integrity, parental imprinting, X-chromosome inactivation in mammals, and regulation of development. 2) The enzymatic mechanism of DNA methyltransferases is unusual, because these enzymes flip their target base out of the DNA helix and, thereby, locally disrupt the B-DNA helix. This review describes the biological functions of DNA methylation in bacteria, fungi, plants, and mammals. In addition, the structures and mechanisms of the DNA methyltransferases, which enable them to specifically recognize their DNA targets and to induce such large conformational changes of the DNA, are discussed.
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Affiliation(s)
- Albert Jeltsch
- Institut für Biochemie, FB 8, Justus-Liebig-Universität, Heinrich-Buff-Ring 58, 35392 Giessen, Germany.
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46
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Zhou L, Cheng X, Connolly B, Dickman M, Hurd P, Hornby D. Zebularine: a novel DNA methylation inhibitor that forms a covalent complex with DNA methyltransferases. J Mol Biol 2002; 321:591-9. [PMID: 12206775 PMCID: PMC2713825 DOI: 10.1016/s0022-2836(02)00676-9] [Citation(s) in RCA: 246] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Mechanism-based inhibitors of enzymes, which mimic reactive intermediates in the reaction pathway, have been deployed extensively in the analysis of metabolic pathways and as candidate drugs. The inhibition of cytosine-[C5]-specific DNA methyltransferases (C5 MTases) by oligodeoxynucleotides containing 5-azadeoxycytidine (AzadC) and 5-fluorodeoxycytidine (FdC) provides a well-documented example of mechanism-based inhibition of enzymes central to nucleic acid metabolism. Here, we describe the interaction between the C5 MTase from Haemophilus haemolyticus (M.HhaI) and an oligodeoxynucleotide duplex containing 2-H pyrimidinone, an analogue often referred to as zebularine and known to give rise to high-affinity complexes with MTases. X-ray crystallography has demonstrated the formation of a covalent bond between M.HhaI and the 2-H pyrimidinone-containing oligodeoxynucleotide. This observation enables a comparison between the mechanisms of action of 2-H pyrimidinone with other mechanism-based inhibitors such as FdC. This novel complex provides a molecular explanation for the mechanism of action of the anti-cancer drug zebularine.
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Affiliation(s)
- L. Zhou
- Department of Biochemistry, Emory University School of Medicine, 1510 Clifton Road, Atlanta, GA 30322, USA
| | - X. Cheng
- Department of Biochemistry, Emory University School of Medicine, 1510 Clifton Road, Atlanta, GA 30322, USA
| | - B.A. Connolly
- Department of Biochemistry and Genetics, University of Newcastle, Newcastle-upon-Tyne NE2, 4HH, UK
| | - M.J. Dickman
- Krebs Institute, Department of Molecular Biology and Biotechnology, University of Sheffield, P.O. Box 594, First Court, Western Bank, Sheffield, S10 2TN, UK
| | - P.J. Hurd
- Wellcome/CRC Institute of Cancer and Developmental Biology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QR, UK
| | - D.P. Hornby
- Krebs Institute, Department of Molecular Biology and Biotechnology, University of Sheffield, P.O. Box 594, First Court, Western Bank, Sheffield, S10 2TN, UK
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47
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Sankpal UT, Rao DN. Mutational analysis of conserved residues in HhaI DNA methyltransferase. Nucleic Acids Res 2002; 30:2628-38. [PMID: 12060679 PMCID: PMC117292 DOI: 10.1093/nar/gkf380] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
HhaI DNA methyltransferase belongs to the C5-cytosine methyltransferase family, which is characterized by the presence of a set of highly conserved amino acids and motifs present in an invariant order. HhaI DNA methyltransferase has been subjected to a lot of biochemical and crystallographic studies. A number of issues, especially the role of the conserved amino acids in the methyltransferase activity, have not been addressed. Using sequence comparison and structural data, a structure-guided mutagenesis approach was undertaken, to assess the role of conserved amino acids in catalysis. Site-directed mutagenesis was performed on amino acids involved in cofactor S-adenosyl-L-methionine (AdoMet) binding (Phe18, Trp41, Asp60 and Leu100). Characterization of these mutants, by in vitro /in vivo restriction assays and DNA/AdoMet binding studies, indicated that most of the residues present in the AdoMet-binding pocket were not absolutely essential. This study implies plasticity in the recognition of cofactor by HhaI DNA methyltransferase.
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Affiliation(s)
- Umesh T Sankpal
- Department of Biochemistry, Indian Institute of Science, Bangalore 560012, India
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48
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Abstract
DNA methyltransferases catalyze the transfer of a methyl group from S-adenosyl-L-methionine to cytosine or adenine bases in DNA. These enzymes challenge the Watson/Crick dogma in two instances: 1) They attach inheritable information to the DNA that is not encoded in the nucleotide sequence. This so-called epigenetic information has many important biological functions. In prokaryotes, DNA methylation is used to coordinate DNA replication and the cell cycle, to direct postreplicative mismatch repair, and to distinguish self and nonself DNA. In eukaryotes, DNA methylation contributes to the control of gene expression, the protection of the genome against selfish DNA, maintenance of genome integrity, parental imprinting, X-chromosome inactivation in mammals, and regulation of development. 2) The enzymatic mechanism of DNA methyltransferases is unusual, because these enzymes flip their target base out of the DNA helix and, thereby, locally disrupt the B-DNA helix. This review describes the biological functions of DNA methylation in bacteria, fungi, plants, and mammals. In addition, the structures and mechanisms of the DNA methyltransferases, which enable them to specifically recognize their DNA targets and to induce such large conformational changes of the DNA, are discussed.
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Affiliation(s)
- Albert Jeltsch
- Institut für Biochemie, FB 8, Justus-Liebig-Universität, Heinrich-Buff-Ring 58, 35392 Giessen, Germany.
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49
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Morávek Z, Neidle S, Schneider B. Protein and drug interactions in the minor groove of DNA. Nucleic Acids Res 2002; 30:1182-91. [PMID: 11861910 PMCID: PMC101234 DOI: 10.1093/nar/30.5.1182] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Interactions between proteins, drugs, water and B-DNA minor groove have been analyzed in crystal structures of 60 protein-DNA and 14 drug-DNA complexes. It was found that only purine N3, pyrimidine O2, guanine N2 and deoxyribose O4' are involved in the interactions, and that contacts to N3 and O2 are most frequent and more polar than contacts to O4'. Many protein contacts are mediated by water, possibly to increase the DNA effective surface. Fewer water-mediated contacts are observed in drug complexes. The distributions of ligands around N3 are significantly more compact than around O2, and distributions of water molecules are the most compact. Distributions around O4' are more diffuse than for the base atoms but most distributions still have just one binding site. Ligands bind to N3 and O2 atoms in analogous positions, and simultaneous binding to N3 and N2 in guanines is extremely rare. Contacts with two consecutive nucleotides are much more frequent than base-sugar contacts within one nucleotide. The probable reason for this is the large energy of deformation of hydrogen bonds for the one nucleotide motif. Contacts of Arg, the most frequent amino acid ligand, are stereochemically indistinguishable from the binding of the remaining amino acids except asparagine (Asn) and phenylalanine (Phe). Asn and Phe bind in distinct ways, mostly to a deformed DNA, as in the complexes of TATA-box binding proteins. DNA deformation concentrates on dinucleotide regions with a distinct deformation of the delta and epsilon backbone torsion angles for the Asn and delta, epsilon, zeta and chi for the Phe-contacted regions.
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Affiliation(s)
- Zdenek Morávek
- Faculty of Mathematics and Physics, Charles University, Ke Karlovu 5, Prague, Czech Republic
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50
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Cheng X, Roberts RJ. AdoMet-dependent methylation, DNA methyltransferases and base flipping. Nucleic Acids Res 2001; 29:3784-95. [PMID: 11557810 PMCID: PMC55914 DOI: 10.1093/nar/29.18.3784] [Citation(s) in RCA: 358] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Twenty AdoMet-dependent methyltransferases (MTases) have been characterized structurally by X-ray crystallography and NMR. These include seven DNA MTases, five RNA MTases, four protein MTases and four small molecule MTases acting on the carbon, oxygen or nitrogen atoms of their substrates. The MTases share a common core structure of a mixed seven-stranded beta-sheet (6 downward arrow 7 upward arrow 5 downward arrow 4 downward arrow 1 downward arrow 2 downward arrow 3 downward arrow) referred to as an 'AdoMet-dependent MTase fold', with the exception of a protein arginine MTase which contains a compact consensus fold lacking the antiparallel hairpin strands (6 downward arrow 7 upward arrow). The consensus fold is useful to identify hypothetical MTases during structural proteomics efforts on unannotated proteins. The same core structure works for very different classes of MTase including those that act on substrates differing in size from small molecules (catechol or glycine) to macromolecules (DNA, RNA and protein). DNA MTases use a 'base flipping' mechanism to deliver a specific base within a DNA molecule into a typically concave catalytic pocket. Base flipping involves rotation of backbone bonds in double-stranded DNA to expose an out-of-stack nucleotide, which can then be a substrate for an enzyme-catalyzed chemical reaction. The phenomenon is fully established for DNA MTases and for DNA base excision repair enzymes, and is likely to prove general for enzymes that require access to unpaired, mismatched or damaged nucleotides within base-paired regions in DNA and RNA. Several newly discovered MTase families in eukaryotes (DNA 5mC MTases and protein arginine and lysine MTases) offer new challenges in the MTase field.
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Affiliation(s)
- X Cheng
- Emory University School of Medicine, Department of Biochemistry, 1510 Clifton Road, Atlanta, GA 30322, USA.
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