1
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Pederson K, Meints GA, Drobny GP. Base Dynamics in the HhaI Protein Binding Site. J Phys Chem B 2023; 127:7266-7275. [PMID: 37561575 PMCID: PMC10461302 DOI: 10.1021/acs.jpcb.3c03687] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2023] [Revised: 07/18/2023] [Indexed: 08/12/2023]
Abstract
Protein-DNA interactions play an important role in numerous biological functions within the living cell. In many of these interactions, the DNA helix is significantly distorted upon protein-DNA complex formation. The HhaI restriction-modification system is one such system, where the methylation target is flipped out of the helix when bound to the methyltransferase. However, the base flipping mechanism is not well understood. The dynamics of the binding site of the HhaI methyltransferase and endonuclease (underlined) within the DNA oligomer [d(G1A2T3A4G5C6G7C8T9A10T11C12)]2 are studied using deuterium solid-state NMR (SSNMR). SSNMR spectra obtained from DNAs deuterated on the base of nucleotides within and flanking the [5'-GCGC-3']2 sequence indicate that all of these positions are structurally flexible. Previously, conformational flexibility within the phosphodiester backbone and furanose ring within the target sequence has been observed and hypothesized to play a role in the distortion mechanism. However, whether that distortion was occurring through an active or passive mechanism remained unclear. These NMR data demonstrate that although the [5'-GCGC-3']2 sequence is dynamic, the target cytosine is not passively flipping out of the double-helix on the millisecond-picosecond time scale. Additionally, although previous studies have shown that both the furanose ring and phosphodiester backbone experience a change in dynamics upon methylation, which may play a role in recognition and cleavage by the endonuclease, our observations here indicate that methylation has no effect on the dynamics of the base itself.
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Affiliation(s)
- Kari Pederson
- Department
of Chemistry & Biochemistry, California
State University at Dominguez Hills, Carson, California 90747, United States
| | - Gary A. Meints
- Department
of Chemistry, Missouri State University, Springfield, Missouri 65897, United States
| | - Gary P. Drobny
- Department
of Chemistry, University of Washington, Seattle, Washington 98195-1700, United
States
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2
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Zhang Z, Wang G, Li Y, Lei D, Xiang J, Ouyang L, Wang Y, Yang J. Recent progress in DNA methyltransferase inhibitors as anticancer agents. Front Pharmacol 2022; 13:1072651. [PMID: 37077808 PMCID: PMC10107375 DOI: 10.3389/fphar.2022.1072651] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2022] [Accepted: 11/28/2022] [Indexed: 12/23/2022] Open
Abstract
DNA methylation mediated by DNA methyltransferase is an important epigenetic process that regulates gene expression in mammals, which plays a key role in silencing certain genes, such as tumor suppressor genes, in cancer, and it has become a promising therapeutic target for cancer treatment. Similar to other epigenetic targets, DNA methyltransferase can also be modulated by chemical agents. Four agents have already been approved to treat hematological cancers. In order to promote the development of a DNA methyltransferase inhibitor as an anti-tumor agent, in the current review, we discuss the relationship between DNA methylation and tumor, the anti-tumor mechanism, the research progress and pharmacological properties of DNA methyltransferase inhibitors, and the future research trend of DNA methyltransferase inhibitors.
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Affiliation(s)
- Zhixiong Zhang
- State Key Laboratory of Biotherapy and Cancer Center, National Clinical Research Center for Geriatrics, Innovation Center of Nursing Research, West China Hospital, and Collaborative Innovation Center of Biotherapy, Sichuan University, Chengdu, China
- Targeted Tracer Research and Development Laboratory, Institute of Respiratory Health, Frontiers Science Center for Disease-related Molecular Network, West China Hospital, Sichuan University, Chengdu, China
| | - Guan Wang
- State Key Laboratory of Biotherapy and Cancer Center, National Clinical Research Center for Geriatrics, Innovation Center of Nursing Research, West China Hospital, and Collaborative Innovation Center of Biotherapy, Sichuan University, Chengdu, China
| | - Yuyan Li
- State Key Laboratory of Biotherapy and Cancer Center, National Clinical Research Center for Geriatrics, Innovation Center of Nursing Research, West China Hospital, and Collaborative Innovation Center of Biotherapy, Sichuan University, Chengdu, China
- Targeted Tracer Research and Development Laboratory, Institute of Respiratory Health, Frontiers Science Center for Disease-related Molecular Network, West China Hospital, Sichuan University, Chengdu, China
| | - Dongsheng Lei
- School of Physical Science and Technology, Electron Microscopy Center of Lanzhou University, Lanzhou University, Lanzhou, China
| | - Jin Xiang
- State Key Laboratory of Biotherapy and Cancer Center, National Clinical Research Center for Geriatrics, Innovation Center of Nursing Research, West China Hospital, and Collaborative Innovation Center of Biotherapy, Sichuan University, Chengdu, China
| | - Liang Ouyang
- State Key Laboratory of Biotherapy and Cancer Center, National Clinical Research Center for Geriatrics, Innovation Center of Nursing Research, West China Hospital, and Collaborative Innovation Center of Biotherapy, Sichuan University, Chengdu, China
- Science and Technology Department, National Clinical Research Center for Geriatrics, West China Hospital, Sichuan University, Chengdu, China
| | - Yanyan Wang
- State Key Laboratory of Biotherapy and Cancer Center, National Clinical Research Center for Geriatrics, Innovation Center of Nursing Research, West China Hospital, and Collaborative Innovation Center of Biotherapy, Sichuan University, Chengdu, China
- Science and Technology Department, National Clinical Research Center for Geriatrics, West China Hospital, Sichuan University, Chengdu, China
- *Correspondence: Yanyan Wang, ; Jinliang Yang,
| | - Jinliang Yang
- State Key Laboratory of Biotherapy and Cancer Center, National Clinical Research Center for Geriatrics, Innovation Center of Nursing Research, West China Hospital, and Collaborative Innovation Center of Biotherapy, Sichuan University, Chengdu, China
- *Correspondence: Yanyan Wang, ; Jinliang Yang,
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3
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DNMT3B and TET1 mediated DNA methylation of LATS1 regulates BC progression via hippo signaling pathway. Pathol Res Pract 2022; 240:154231. [DOI: 10.1016/j.prp.2022.154231] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/24/2022] [Revised: 11/08/2022] [Accepted: 11/16/2022] [Indexed: 11/19/2022]
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4
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Prasad Y, Kumar R, Chaudhary AK, Dhanaraju R, Majumdar S, Rao DN. Kinetic and catalytic properties of M.HpyAXVII, a phase-variable DNA methyltransferase from Helicobacter pylori. J Biol Chem 2018; 294:1019-1034. [PMID: 30478171 DOI: 10.1074/jbc.ra118.003769] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2018] [Revised: 11/10/2018] [Indexed: 01/26/2023] Open
Abstract
The bacterium Helicobacter pylori is one of the most common infectious agents found in the human stomach. H. pylori has an unusually large number of DNA methyltransferases (MTases), prompting speculation that they may be involved in the cancerization of epithelial cells. The mod-4a/4b locus, consisting of the hp1369 and hp1370 ORFs, encodes for a truncated and inactive MTase in H. pylori strain 26695. However, slipped-strand synthesis within the phase-variable polyguanine tract in hp1369 results in expression of an active HP1369-1370 fusion N 6-adenine methyltransferase, designated M.HpyAXVII. Sequence analysis of the mod-4a/4b locus across 74 H. pylori strain genomes has provided insights into the regulation of M.HpyAXVII expression. To better understand the role of M.HpyAXVII in the H. pylori biology, here we cloned and overexpressed the hp1369-70 fusion construct in Escherichia coli BL21(DE3) cells. Results from size-exclusion chromatography and multi-angle light scattering (MALS) analyses suggested that M.HpyAXVII exists as a dimer in solution. Kinetic studies, including product and substrate inhibition analyses, initial velocity dependence between substrates, and isotope partitioning, suggested that M.HpyAXVII catalyzes DNA methylation in an ordered Bi Bi mechanism in which the AdoMet binding precedes DNA binding and AdoMet's methyl group is then transferred to an adenine within the DNA recognition sequence. Altering the highly conserved catalytic motif (DPP(Y/F)) as well as the AdoMet-binding motif (FXGXG) by site-directed mutagenesis abolished the catalytic activity of M.HpyAXVII. These results provide insights into the enzyme kinetic mechanism of M.HpyAXVII. We propose that AdoMet binding conformationally "primes" the enzyme for DNA binding.
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Affiliation(s)
- Yedu Prasad
- From the Department of Biochemistry, Indian Institute of Science, Bangalore-560012, Karnataka, India and
| | - Ritesh Kumar
- From the Department of Biochemistry, Indian Institute of Science, Bangalore-560012, Karnataka, India and
| | - Awanish Kumar Chaudhary
- From the Department of Biochemistry, Indian Institute of Science, Bangalore-560012, Karnataka, India and
| | - Rajkumar Dhanaraju
- From the Department of Biochemistry, Indian Institute of Science, Bangalore-560012, Karnataka, India and
| | - Soneya Majumdar
- Biological Sciences and Bioengineering, Indian Institute of Technology, Kanpur-208016, Uttar Pradesh, India
| | - Desirazu N Rao
- From the Department of Biochemistry, Indian Institute of Science, Bangalore-560012, Karnataka, India and
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5
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Liang Z, Hu J, Yan W, Jiang H, Hu G, Luo C. Deciphering the role of dimer interface in intrinsic dynamics and allosteric pathways underlying the functional transformation of DNMT3A. Biochim Biophys Acta Gen Subj 2018; 1862:1667-1679. [DOI: 10.1016/j.bbagen.2018.04.015] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2017] [Revised: 04/03/2018] [Accepted: 04/13/2018] [Indexed: 01/06/2023]
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6
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Singh S, Guruprasad L. N6-Adenosine DNA Methyltransferase from H. pylori 98-10 Strain in Complex with DNA and AdoMet: Structural Insights from in Silico Studies. J Phys Chem B 2017; 121:365-378. [PMID: 28054779 DOI: 10.1021/acs.jpcb.6b08433] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Helicobacter pylori is a primitive Gram-negative bacterium that resides in the acidic environment of 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 N6-adenine-specific DNA MTase from H. pylori (M. Hpy N6mA) catalyzes the transfer of a methyl group from the cofactor S-adenosyl-l-methionine (AdoMet) to the flipped adenine of the substrate DNA. In this work, we report the sequence analyses, three-dimensional structure modeling, and molecular dynamics simulations of M. Hpy N6mA, when complexed with AdoMet as well as DNA. We analyzed the protein-DNA interactions prominently established by the flipped cytosine and the interactions between protein cofactors in the active site. The comparable orientation of AdoMet in both systems confirms that AdoMet is in a catalytically competent orientation in the bimolecular system that is retained upon DNA binding in the termolecular system of M. Hpy N6mA. In both systems, AdoMet is stabilized in the binding pocket by hydrogen bonding (Thr84, Glu99, Asp122, and Phe123) as well as van der Waals (Ile100, Phe160, Arg104, and Cys76) interactions. We propose that the contacts made by flipped adenine DA6 with Asn138 (N6 and N1 atom of DA6) and Pro139 (N6) and π-stacking interactions with Phe141 and Phe219 play an important role in the methylation mechanism at the N6 position in our N6mA model. Specific recognition of DNA is mediated by residues 143-155, 183-189, 212-220, 280-293, and 308-325. These findings are further supported by alanine scanning mutagenesis studies. The conserved residues in distantly related sequences of the small domain are important in DNA binding. Results reported here elucidate the sequence, structure, and binding features necessary for the recognition between cofactor AdoMet and substrate DNA by the vital epigenetic enzyme, M. Hpy N6mA.
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Affiliation(s)
- Swati Singh
- School of Chemistry, University of Hyderabad , Hyderabad 500046, India
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7
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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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8
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Qiao MX, Li C, Zhang AQ, Hou LL, Yang J, Hu HG. Regulation of DEK expression by AP-2α and methylation level of DEK promoter in hepatocellular carcinoma. Oncol Rep 2016; 36:2382-90. [PMID: 27499261 DOI: 10.3892/or.2016.4984] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2016] [Accepted: 06/23/2016] [Indexed: 11/06/2022] Open
Abstract
DEK is overexpressed in multiple invasive tumors. However, the transcriptional regulatory mechanism of DEK remains unclear. In the present study, progressive-type truncation assay indicated that CpG2-2 (-167 bp/+35 bp) was the DEK core promoter, whose methylation inhibited DEK expression. Bisulfite genomic sequencing analysis indicated that the methylation levels of the DEK promoter in normal hepatic cells and tissues were higher than those in hepatocellular carcinoma (HCC) cells. TFSEARCH result revealed transcription factor binding sites in CpG2-2. Among the sites, the AP-2α binding site showed the most significant methylation difference; hence, AP-2α is a key transcription factor that regulates DEK expression. Point or deletion mutation of the AP-2α binding site significantly reduced the promoter activity. Chromatin immunoprecipitation assay demonstrated the binding of AP-2α to the core promoter. Furthermore, knock down of endogenous AP-2α downregulated DEK expression, whereas overexpression of AP-2α upregulated DEK expression. Thus, AP-2α is an important transcription factor of DEK expression, which is correlated with the methylation level of the DEK core promoter in HCC.
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Affiliation(s)
- Ming-Xu Qiao
- College of Life Sciences and Bioengineering, School of Science, Beijing Jiaotong University, Beijing 100044, P.R. China
| | - Chun Li
- College of Life Sciences and Bioengineering, School of Science, Beijing Jiaotong University, Beijing 100044, P.R. China
| | - Ai-Qun Zhang
- Institute of Hepatobiliary Surgery, PLA General Hospital, Beijing 100853, P.R. China
| | - Ling-Ling Hou
- College of Life Sciences and Bioengineering, School of Science, Beijing Jiaotong University, Beijing 100044, P.R. China
| | - Juan Yang
- College of Life Sciences and Bioengineering, School of Science, Beijing Jiaotong University, Beijing 100044, P.R. China
| | - Hong-Gang Hu
- College of Life Sciences and Bioengineering, School of Science, Beijing Jiaotong University, Beijing 100044, P.R. China
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9
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Abstract
The review is withdrawn as it was abandoned and has not been updated since its last edition in 2008. A new team of authors resumed the work on the review, and so far, a major update to the protocol is published. The review is expected to be finalised towards the end of 2016. The editorial group responsible for this previously published document have withdrawn it from publication.
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Affiliation(s)
- Andrea Rambaldi
- Copenhagen Trial Unit, Centre for Clinical Intervention Research, Department 3344, Rigshospitalet, Copenhagen University HospitalCochrane Hepato‐Biliary GroupBlegdamsvej 9CopenhagenDenmarkDK‐2100
| | - Christian Gluud
- Copenhagen Trial Unit, Centre for Clinical Intervention Research, Department 7812, Rigshospitalet, Copenhagen University HospitalThe Cochrane Hepato‐Biliary GroupBlegdamsvej 9CopenhagenDenmarkDK‐2100
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10
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Xie FW, Peng YH, Wang WW, Chen X, Chen X, Li J, Yu ZY, Ouyang XN. Influence of UGT1A1 gene methylation level in colorectal cancer cells on the sensitivity of the chemotherapy drug CPT-11. Biomed Pharmacother 2014; 68:825-31. [PMID: 25260839 DOI: 10.1016/j.biopha.2014.08.012] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2014] [Accepted: 08/06/2014] [Indexed: 11/18/2022] Open
Abstract
OBJECTIVE To study the influence of the methylation level of UGT1A1 gene related to CPT-11 metabolic enzymes in colorectal cancer cells on the sensitivity of chemotherapy drugs. METHODS Test the changes in sensitivity of seven colorectal cancer cell strains that have been/not been subject to DAC treatment to CPT-11, analyze its correlation with CES2, UGT1A1 and GUSB mRNA expression according to IC50; screen the effective interference sequence of UGT1A1 siRNA, test the changes in cytotoxicity of CPT-11 after UGT1A1 siRNA is transfected, select RK0 cells and make them transfected with the chemosynthetic UGT1A1 siRNA after their UGT1A1 expression is restored with or without demethylation treatment. RESULTS The sensitivity of different colorectal cancer cell strains to CPT-11 showed difference (P<0.05), UGT1A1 expression in colorectal cell lines had a negative correlation with the IC50 (r=0.790648, P<0.05), the interference efficiency of the screened UGT1A1 siRNA was up to 78%. The IC50 value of siRNA decreased by nearly one time after transfected with HT-29 (P<0.01); which of methylated RK0 cells of UGT1A1 gene increased instead after the demethylation treatment. However, the IC50 value of the demethylation treatment group increased compared with the non-demethylation treatment group after UGT1A1 siRNA was transfected. CONCLUSIONS The cytotoxicity of CPT-11 to colorectal cancer cells has a negative correlation with UGT1A1 expression, and positive correlation with CES2 and GUSB. The specific silencing UGT1A1 gene of siRNA could significantly increase the sensitivity of CPT-11 to the chemotherapy of colorectal cancer cells. UGT1A1 methylation was an important factor affecting the chemosensitivity of CPT-11.
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Affiliation(s)
- Fang-Wei Xie
- Department of Medicine Oncology, Fuzhou General Hospital of Nanjing Military Command, Fuzhou, Fujian, China; Fuzhou Dongfang Hospital affiliated to Medical College of Xiamen University, China; Fuzhou General Hospital of Nanjing Military Command Affiliated to Fujian University of Traditional Chinese Medicine, China; Fuzhou General Hospital of Nanjing Military Command Affiliated to Fujian Medical University, China
| | - Yong-Hai Peng
- Department of Medicine Oncology, Fuzhou General Hospital of Nanjing Military Command, Fuzhou, Fujian, China
| | - Wen-Wu Wang
- Department of Medicine Oncology, Fuzhou General Hospital of Nanjing Military Command, Fuzhou, Fujian, China
| | - Xi Chen
- Department of Medicine Oncology, Fuzhou General Hospital of Nanjing Military Command, Fuzhou, Fujian, China
| | - Xiong Chen
- Department of Medicine Oncology, Fuzhou General Hospital of Nanjing Military Command, Fuzhou, Fujian, China
| | - Jie Li
- Department of Medicine Oncology, Fuzhou General Hospital of Nanjing Military Command, Fuzhou, Fujian, China
| | - Zong-Yang Yu
- Department of Medicine Oncology, Fuzhou General Hospital of Nanjing Military Command, Fuzhou, Fujian, China
| | - Xue-Nong Ouyang
- Department of Medicine Oncology, Fuzhou General Hospital of Nanjing Military Command, Fuzhou, Fujian, China; Fuzhou Dongfang Hospital affiliated to Medical College of Xiamen University, China; Fuzhou General Hospital of Nanjing Military Command Affiliated to Fujian University of Traditional Chinese Medicine, China; Fuzhou General Hospital of Nanjing Military Command Affiliated to Fujian Medical University, China.
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11
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Xu F, Zhang M, Wu Q, Lin X. Novel l-amino acid ester prodrugs of azacitidine: Design, enzymatic synthesis and the investigation of release behavior. ACTA ACUST UNITED AC 2014. [DOI: 10.1016/j.molcatb.2014.03.018] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
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12
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Ke HP, Jiang HL, Lv YS, Huang YZ, Liu RR, Chen XL, Du ZF, Luo YQ, Xu CM, Fan QH, Zhang XN. KRT9 gene mutation as a reliable indicator in the prenatal molecular diagnosis of epidermolytic palmoplantar keratoderma. Gene 2014; 546:124-8. [PMID: 24862219 DOI: 10.1016/j.gene.2014.05.048] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2013] [Revised: 04/23/2014] [Accepted: 05/22/2014] [Indexed: 11/18/2022]
Abstract
Epidermolytic palmoplantar keratoderma (EPPK) is the most frequent form of such keratodermas. It is inherited in an autosomal dominant pattern and is clinically characterized by diffuse yellowish thickening of the skin on the palms and soles with erythematous borders during the first weeks or months after birth. EPPK is generally caused by mutations of the KRT9 gene. More than 26 KRT9 gene mutations responsible for EPPK have been described (Human Intermediate Filament Database, www.interfil.org), and many of these variants are located within the highly-conserved coil 1A region of the α-helical rod domain of keratin 9. Unfortunately, there is no satisfactory treatment for EPPK. Thus, prenatal molecular diagnosis or pre-pregnancy diagnosis is crucial and benefits those affected who seek healthy descendants. In the present study, we performed amniotic fluid-DNA-based prenatal testing for three at-risk pregnant EPPK women from three unrelated southern Chinese families who carried the KRT9 missense mutations p.Arg163Trp and p.Arg163Gln, and successfully helped two families to bear normal daughters. We suggest that before the successful application of preimplantation genetic diagnosis (PGD), and noninvasive prenatal diagnosis of EPPK that analyzes fetal cells or cell-free DNA in maternal blood, prenatal genetic diagnosis by amniocentesis or chorionic villus sampling (CVS) offers a quite acceptable option for EPPK couples-at-risk to avoid the birth of affected offspring, especially in low- and middle-income countries.
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Affiliation(s)
- Hai-Ping Ke
- Department of Biology, Ningbo College of Health Sciences, Ningbo, Zhejiang Province 315100, China; Department of Cell Biology and Medical Genetics, Research Center of Molecular Medicine, National Education Base for Basic Medical Sciences, Institute of Cell Biology, Zhejiang University School of Medicine, Hangzhou, Zhejiang Province 310058, China
| | - Hu-Ling Jiang
- Department of Cell Biology and Medical Genetics, Research Center of Molecular Medicine, National Education Base for Basic Medical Sciences, Institute of Cell Biology, Zhejiang University School of Medicine, Hangzhou, Zhejiang Province 310058, China
| | - Ya-Su Lv
- Department of Cell Biology and Medical Genetics, Research Center of Molecular Medicine, National Education Base for Basic Medical Sciences, Institute of Cell Biology, Zhejiang University School of Medicine, Hangzhou, Zhejiang Province 310058, China
| | - Yi-Zhou Huang
- Department of Cell Biology and Medical Genetics, Research Center of Molecular Medicine, National Education Base for Basic Medical Sciences, Institute of Cell Biology, Zhejiang University School of Medicine, Hangzhou, Zhejiang Province 310058, China
| | - Rong-Rong Liu
- Department of Cell Biology and Medical Genetics, Research Center of Molecular Medicine, National Education Base for Basic Medical Sciences, Institute of Cell Biology, Zhejiang University School of Medicine, Hangzhou, Zhejiang Province 310058, China
| | - Xiao-Ling Chen
- Department of Cell Biology and Medical Genetics, Research Center of Molecular Medicine, National Education Base for Basic Medical Sciences, Institute of Cell Biology, Zhejiang University School of Medicine, Hangzhou, Zhejiang Province 310058, China
| | - Zhen-Fang Du
- Department of Cell Biology and Medical Genetics, Research Center of Molecular Medicine, National Education Base for Basic Medical Sciences, Institute of Cell Biology, Zhejiang University School of Medicine, Hangzhou, Zhejiang Province 310058, China
| | - Yu-Qin Luo
- Key Laboratory of Reproductive Genetics (Zhejiang), Ministry of Education, and Centre of Reproductive Medicine, Women's Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang Province 310006, China
| | - Chen-Ming Xu
- Key Laboratory of Reproductive Genetics (Zhejiang), Ministry of Education, and Centre of Reproductive Medicine, Women's Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang Province 310006, China
| | - Qi-Hui Fan
- Department of Gynaecology and Obstetrics, Ningbo Women and Children's Hospital, Ningbo, Zhejiang Province 315012, China
| | - Xian-Ning Zhang
- Department of Cell Biology and Medical Genetics, Research Center of Molecular Medicine, National Education Base for Basic Medical Sciences, Institute of Cell Biology, Zhejiang University School of Medicine, Hangzhou, Zhejiang Province 310058, China.
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13
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Vujjini SK, Varanasi G, Arevelli S, Kandala SC, Tirumalaraju SR, Bandichhor R, Kagga M, Cherukupally P. An Improved and Scalable Process for the Synthesis of 5-Azacytidine: An Antineoplastic Drug. Org Process Res Dev 2013. [DOI: 10.1021/op300192e] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Satish Kumar Vujjini
- API-Research and Development,
Integrated Product Development, Innovation Plaza, Dr. Reddy’s Laboratories Ltd., Bachupally, Qutubullapur,
R R Dist-500072, AP, India
| | - Ganesh Varanasi
- API-Research and Development,
Integrated Product Development, Innovation Plaza, Dr. Reddy’s Laboratories Ltd., Bachupally, Qutubullapur,
R R Dist-500072, AP, India
| | - Srinivas Arevelli
- API-Research and Development,
Integrated Product Development, Innovation Plaza, Dr. Reddy’s Laboratories Ltd., Bachupally, Qutubullapur,
R R Dist-500072, AP, India
| | - Sreenatha Charyulu Kandala
- API-Research and Development,
Integrated Product Development, Innovation Plaza, Dr. Reddy’s Laboratories Ltd., Bachupally, Qutubullapur,
R R Dist-500072, AP, India
| | - Satyanarayana Raju Tirumalaraju
- API-Research and Development,
Integrated Product Development, Innovation Plaza, Dr. Reddy’s Laboratories Ltd., Bachupally, Qutubullapur,
R R Dist-500072, AP, India
| | - Rakeshwar Bandichhor
- API-Research and Development,
Integrated Product Development, Innovation Plaza, Dr. Reddy’s Laboratories Ltd., Bachupally, Qutubullapur,
R R Dist-500072, AP, India
| | - Mukkanti Kagga
- Department of Chemistry, Institute
of Science and Technology, J.N.T University, Kukatpally, Hyderabad, India
| | - Praveen Cherukupally
- API-Research and Development,
Integrated Product Development, Innovation Plaza, Dr. Reddy’s Laboratories Ltd., Bachupally, Qutubullapur,
R R Dist-500072, AP, India
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14
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Malygin EG, Hattman S. DNA methyltransferases: mechanistic models derived from kinetic analysis. Crit Rev Biochem Mol Biol 2012; 47:97-193. [PMID: 22260147 DOI: 10.3109/10409238.2011.620942] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The sequence-specific transfer of methyl groups from donor S-adenosyl-L-methionine (AdoMet) to certain positions of DNA-adenine or -cytosine residues by DNA methyltransferases (MTases) is a major form of epigenetic modification. It is virtually ubiquitous, except for some notable exceptions. Site-specific methylation can be regarded as a means to increase DNA information capacity and is involved in a large spectrum of biological processes. The importance of these functions necessitates a deeper understanding of the enzymatic mechanism(s) of DNA methylation. DNA MTases fall into one of two general classes; viz. amino-MTases and [C5-cytosine]-MTases. Amino-MTases, common in prokaryotes and lower eukaryotes, catalyze methylation of the exocyclic amino group of adenine ([N6-adenine]-MTase) or cytosine ([N4-cytosine]-MTase). In contrast, [C5-cytosine]-MTases methylate the cyclic carbon-5 atom of cytosine. Characteristics of DNA MTases are highly variable, differing in their affinity to their substrates or reaction products, their kinetic parameters, or other characteristics (order of substrate binding, rate limiting step in the overall reaction). It is not possible to present a unifying account of the published kinetic analyses of DNA methylation because different authors have used different substrate DNAs and/or reaction conditions. Nevertheless, it would be useful to describe those kinetic data and the mechanistic models that have been derived from them. Thus, this review considers in turn studies carried out with the most consistently and extensively investigated [N6-adenine]-, [N4-cytosine]- and [C5-cytosine]-DNA MTases.
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Affiliation(s)
- Ernst G Malygin
- Institute of Molecular Biology, State Research Center of Virology and Biotechnology Vector, Novosibirsk, Russia
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Madhusoodanan UK, Rao DN. Diversity of DNA methyltransferases that recognize asymmetric target sequences. Crit Rev Biochem Mol Biol 2010; 45:125-45. [PMID: 20184512 DOI: 10.3109/10409231003628007] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
DNA methyltransferases (MTases) are a group of enzymes that catalyze the methyl group transfer from S-adenosyl-L-methionine in a sequence-specific manner. Orthodox Type II DNA MTases usually recognize palindromic DNA sequences and add a methyl group to the target base (either adenine or cytosine) on both strands. However, there are a number of MTases that recognize asymmetric target sequences and differ in their subunit organization. In a bacterial cell, after each round of replication, the substrate for any MTase is hemimethylated DNA, and it therefore needs only a single methylation event to restore the fully methylated state. This is in consistent with the fact that most of the DNA MTases studied exist as monomers in solution. Multiple lines of evidence suggest that some DNA MTases function as dimers. Further, functional analysis of many restriction-modification systems showed the presence of more than one or fused MTase genes. It was proposed that presence of two MTases responsible for the recognition and methylation of asymmetric sequences would protect the nascent strands generated during DNA replication from cognate restriction endonuclease. In this review, MTases recognizing asymmetric sequences have been grouped into different subgroups based on their unique properties. Detailed characterization of these unusual MTases would help in better understanding of their specific biological roles and mechanisms of action. The rapid progress made by the genome sequencing of bacteria and archaea may accelerate the identification and study of species- and strain-specific MTases of host-adapted bacteria and their roles in pathogenic mechanisms.
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16
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Neisseria gonorrhoeae FA1090 carries genes encoding two classes of Vsr endonucleases. J Bacteriol 2010; 192:3951-60. [PMID: 20511499 DOI: 10.1128/jb.00098-10] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
A very short patch repair system prevents mutations resulting from deamination of 5-methylcytosine to thymine. The Vsr endonuclease is the key enzyme of this system, providing sequence specificity. We identified two genes encoding Vsr endonucleases V.NgoAXIII and V.NgoAXIV from Neisseria gonorrhoeae FA1090 based on DNA sequence similarity to genes encoding Vsr endonucleases from other bacteria. After expression of the gonococcal genes in Escherichia coli, the proteins were biochemically characterized and the endonucleolytic activities and specificities of V.NgoAXIII and V.NgoAXIV were determined. V.NgoAXIII was found to be multispecific and to recognize T:G mismatches in every nucleotide context tested, whereas V.NgoAXIV recognized T:G mismatches in the following sequences: GTGG, CTGG, GTGC, ATGC, and CTGC. Alanine mutagenesis of conserved residues showed that Asp50 and His68 of V.NgoAXIII and Asp51 and His69 of V.NgoAXIV are essential for hydrolytic activity. Glu25, His64, and Asp97 of V.NgoAXIV and Glu24, Asp63, and Asp97 of V.NgoAXIII are important but not crucial for the activity of V.NgoAXIII and V.NgoAXIV. However, Glu24 and Asp63 are also important for the specificity of V.NgoAXIII. On the basis of our results concerning features of Vsr endonucleases expressed by N. gonorrhoeae FA1090, we postulate that at least two types of Vsr endonucleases can be distinguished.
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17
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Kumar R, Mukhopadhyay AK, Rao DN. Characterization of an N6 adenine methyltransferase from Helicobacter pylori strain 26695 which methylates adjacent adenines on the same strand. FEBS J 2010; 277:1666-83. [PMID: 20180846 DOI: 10.1111/j.1742-4658.2010.07593.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Genomic sequences of Helicobacter pylori strains 26695, J99, HPAGI and G27 have revealed an abundance of restriction and modification genes. hp0050, which encodes an N(6) adenine DNA methyltransferase, was cloned, overexpressed and purified to near homogeneity. It recognizes the sequence 5'-GRRG-3' (where R is A or G) and, most intriguingly, methylates both adenines when R is A (5'-GAAG-3'). Kinetic analysis suggests a nonprocessive (repeated-hit) mechanism of methylation in which HP0050 methyltransferase methylates one adenine at a time in the sequence 5'-GAAG-3'. This is the first report of an N(6) adenine DNA methyltransferase that methylates two adjacent residues on the same strand. Interestingly, HP0050 homologs from two clinical strains of H. pylori (PG227 and 128) methylate only 5'-GAGG-3' compared with 5'-GRRG-3' in strain 26695. HP0050 methyltransferase is highly conserved as it is present in more than 90% of H. pylori strains. Inactivation of hp0050 in strain PG227 resulted in poor growth, suggesting its role in the biology of H. pylori. Collectively, these findings provide impetus for exploring the role(s) of this conserved DNA methyltransferase in the cellular processes of H. pylori.
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Affiliation(s)
- Ritesh Kumar
- Department of Biochemistry, Indian Institute of Science, Bangalore, India
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18
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Morita R, Ishikawa H, Nakagawa N, Kuramitsu S, Masui R. Crystal structure of a putative DNA methylase TTHA0409 from Thermus thermophilus HB8. Proteins 2008; 73:259-64. [DOI: 10.1002/prot.22158] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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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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20
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Meints GA, Miller PA, Pederson K, Shajani Z, Drobny G. Solid-state nuclear magnetic resonance spectroscopy studies of furanose ring dynamics in the DNA HhaI binding site. J Am Chem Soc 2008; 130:7305-14. [PMID: 18489097 DOI: 10.1021/ja075775n] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The dynamics of the furanose rings in the GCGC 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 by using deuterium solid-state NMR (SSNMR). SSNMR spectra obtained from DNAs selectively deuterated on the furanose rings of nucleotides within the 5'-GCGC-3' moiety indicated that all of these positions are structurally flexible. The furanose ring within the deoxycytidine that is the methylation target displays the largest-amplitude structural changes according to the observed deuterium NMR line shapes, whereas the furanose rings of nucleotides more remote from the methylation site have less-mobile furanose rings (i.e., with puckering amplitudes < 0.3 A). Previous work has shown that methylation reduces the amplitude of motion in the phosphodiester backbone of the same DNA, and our observations indicate that methylation perturbs backbone dynamics through the furanose ring. These NMR data indicate that the 5'-GCGC-3' is dynamic, with the largest-amplitude motions occurring nearest the methylation site. The inherent flexibility of this moiety in DNA makes the molecule more amenable to the large-amplitude structural rearrangements that must occur when the DNA binds to the HhaI methyltransferase.
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Affiliation(s)
- Gary A Meints
- Department of Chemistry, Missouri State University, Springfield, Missouri 65897, and Department of Chemistry, University of Washington, Seattle, Washington 98195-1700, USA
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21
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Lafon-Hughes L, Di Tomaso MV, Méndez-Acuña L, Martínez-López W. Chromatin-remodelling mechanisms in cancer. Mutat Res 2008; 658:191-214. [PMID: 18403253 DOI: 10.1016/j.mrrev.2008.01.008] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2007] [Revised: 01/29/2008] [Accepted: 01/29/2008] [Indexed: 02/06/2023]
Abstract
Chromatin-remodelling mechanisms include DNA methylation, histone-tail acetylation, poly-ADP-ribosylation, and ATP-dependent chromatin-remodelling processes. Some epigenetic modifications among others have been observed in cancer cells, namely (1) local DNA hypermethylation and global hypomethylation, (2) alteration in histone acetylation/deacetylation balance, (3) increased or decreased poly-ADP-ribosylation, and (4) failures in ATP-dependent chromatin-remodelling mechanisms. Moreover, these alterations can influence the response to classical anti-tumour treatments. Drugs targeting epigenetic alterations are under development. Currently, DNA methylation and histone deacetylase inhibitors are in use in cancer therapy, and poly-ADP-ribosylation inhibitors are undergoing clinical trials. Epigenetic therapy is gaining in importance in pharmacology as a new tool to improve anti-cancer therapies.
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Affiliation(s)
- Laura Lafon-Hughes
- Genetic Toxicology Department, Instituto de Investigaciones Biológicas Clemente Estable, Montevideo, Uruguay
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Zhuge J, Cederbaum AI. Depletion of S-adenosyl-l-methionine with cycloleucine potentiates cytochrome P450 2E1 toxicity in primary rat hepatocytes. Arch Biochem Biophys 2007; 466:177-85. [PMID: 17640612 PMCID: PMC2040067 DOI: 10.1016/j.abb.2007.06.007] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2007] [Accepted: 06/12/2007] [Indexed: 12/13/2022]
Abstract
S-Adenosyl-l-methionine (SAM) is the principal biological methyl donor. Methionine adenosyltransferase (MAT) catalyzes the only reaction that generates SAM. Hepatocytes were treated with cycloleucine, an inhibitor of MAT, to evaluate whether hepatocytes enriched in cytochrome P450 2E1 (CYP2E1) were more sensitive to a decline in SAM. Cycloleucine decreased SAM and glutathione (GSH) levels and induced cytotoxicity in hepatocytes from pyrazole-treated rats (with an increased content of CYP2E1) to a greater extent as compared to hepatocytes from saline-treated rats. Apoptosis caused by cycloleucine in pyrazole hepatocytes appeared earlier and was more pronounced than control hepatocytes and could be prevented by incubation with SAM, glutathione reduced ethyl ester and antioxidants. The cytotoxicity was prevented by treating rats with chlormethiazole, a specific inhibitor of CYP2E1. Cycloleucine induced greater production of reactive oxygen species (ROS) in pyrazole hepatocytes than in control hepatocytes, and treatment with SAM, Trolox, and chlormethiazole lowered ROS formation. In conclusion, lowering of hepatic SAM levels produced greater toxicity and apoptosis in hepatocytes enriched in CYP2E1. This is due to elevated ROS production by CYP2E1 coupled to lower levels of hepatoprotective SAM and GSH. We speculate that such interactions e.g. induction of CYP2E1, decline in SAM and GSH may contribute to alcohol liver toxicity.
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Affiliation(s)
- Jian Zhuge
- Department of Pharmacology and Systems Therapeutics, Mount Sinai School of Medicine, New York, NY 10029, USA
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23
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Nikitin D, Mokrishcheva M, Solonin A. 6His-Eco29kI methyltransferase methylation site and kinetic mechanism characterization. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2007; 1774:1014-9. [PMID: 17604705 DOI: 10.1016/j.bbapap.2007.05.014] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/07/2007] [Revised: 05/29/2007] [Accepted: 05/29/2007] [Indexed: 11/28/2022]
Abstract
A new type II 6His-Eco29kI DNA methyltransferase was tested for methylation site (CC(Me)GCGG) and catalytic reaction optimal conditions. With high substrate concentrations, an inhibitory effect of DNA, but not AdoMet, on its activity was observed. Isotope partitioning and substrate preincubation assays showed that the enzyme-AdoMet complex is catalytically active. Considering effect of different concentrations of DNA and AdoMet on initial velocity, ping-pong mechanisms were ruled out. According to data obtained, the enzyme appears to work by preferred ordered bi-bi mechanism with AdoMet as leading substrate.
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Affiliation(s)
- Dmitri Nikitin
- Institute of Biochemistry and Physiology of Microorganisms, Russian Academy of Sciences, Prospekt Nauki 5, Pushchino, Moscow Region 142290, Russia.
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Bheemanaik S, Reddy Y, Rao D. Structure, function and mechanism of exocyclic DNA methyltransferases. Biochem J 2006; 399:177-90. [PMID: 16987108 PMCID: PMC1609917 DOI: 10.1042/bj20060854] [Citation(s) in RCA: 104] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
DNA MTases (methyltransferases) catalyse the transfer of methyl groups to DNA from AdoMet (S-adenosyl-L-methionine) producing AdoHcy (S-adenosyl-L-homocysteine) and methylated DNA. The C5 and N4 positions of cytosine and N6 position of adenine are the target sites for methylation. All three methylation patterns are found in prokaryotes, whereas cytosine at the C5 position is the only methylation reaction that is known to occur in eukaryotes. In general, MTases are two-domain proteins comprising one large and one small domain with the DNA-binding cleft located at the domain interface. The striking feature of all the structurally characterized DNA MTases is that they share a common core structure referred to as an 'AdoMet-dependent MTase fold'. DNA methylation has been reported to be essential for bacterial virulence, and it has been suggested that DNA adenine MTases (Dams) could be potential targets for both vaccines and antimicrobials. Drugs that block Dam could slow down bacterial growth and therefore drug-design initiatives could result in a whole new generation of antibiotics. The transfer of larger chemical entities in a MTase-catalysed reaction has been reported and this represents an interesting challenge for bio-organic chemists. In general, amino MTases could therefore be used as delivery systems for fluorescent or other reporter groups on to DNA. This is one of the potential applications of DNA MTases towards developing non-radioactive DNA probes and these could have interesting applications in molecular biology. Being nucleotide-sequence-specific, DNA MTases provide excellent model systems for studies on protein-DNA interactions. The focus of this review is on the chemistry, enzymology and structural aspects of exocyclic amino MTases.
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Affiliation(s)
| | - Yeturu V. R. Reddy
- Department of Biochemistry, Indian Institute of Science, Bangalore 560 012, India
| | - Desirazu N. Rao
- Department of Biochemistry, Indian Institute of Science, Bangalore 560 012, India
- To whom correspondence should be addressed (email )
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Bheemanaik S, Bujnicki JM, Nagaraja V, Rao DN. Functional analysis of amino acid residues at the dimerisation interface of KpnI DNA methyltransferase. Biol Chem 2006; 387:515-23. [PMID: 16740122 DOI: 10.1515/bc.2006.067] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
KpnI DNA-(N6-adenine) methyltransferase (M.KpnI) recognises the sequence 5'-GGTACC-3' and transfers the methyl group from S-adenosyl-L-methionine (AdoMet) to the N6 position of the adenine residue in each strand. Earlier studies have shown that M.KpnI exists as a dimer in solution, unlike most other MTases. To address the importance of dimerisation for enzyme function, a three-dimensional model of M.KpnI was obtained based on protein fold-recognition analysis, using the crystal structures of M.RsrI and M.MboIIA as templates. Residues I146, I161 and Y167, the side chains of which are present in the putative dimerisation interface in the model, were targeted for site-directed mutagenesis. Methylation and in vitro restriction assays showed that the mutant MTases are catalytically inactive. Mutation at the I146 position resulted in complete disruption of the dimer. The replacement of I146 led to drastically reduced DNA and cofactor binding. Substitution of I161 resulted in weakening of the interaction between monomers, leading to both monomeric and dimeric species. Steady-state fluorescence measurements showed that the wild-type KpnI MTase induces structural distortion in bound DNA, while the mutant MTases do not. The results establish that monomeric MTase is catalytically inactive and that dimerisation is an essential event for M.KpnI to catalyse the methyl transfer reaction.
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Priyakumar UD, MacKerell AD. Computational approaches for investigating base flipping in oligonucleotides. Chem Rev 2006; 106:489-505. [PMID: 16464016 DOI: 10.1021/cr040475z] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- U Deva Priyakumar
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, 21201, USA
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Abstract
BACKGROUND Alcohol is a major cause of liver disease and disrupts methionine and oxidative balances. S-adenosyl-L-methionine (SAMe) acts as a methyl donor for methylation reactions and participates in the synthesis of glutathione, the main cellular antioxidant. Randomised clinical trials have addressed the question whether SAMe may benefit patients with alcoholic liver diseases. OBJECTIVES To evaluate the beneficial and harmful effects of SAMe for patients with alcoholic liver diseases. SEARCH STRATEGY We searched The Cochrane Hepato-Biliary Group Controlled Trials Register (May 2005), The Cochrane Central Register of Controlled Trials in The Cochrane Library (Issue 2, 2005), MEDLINE (1950 to May 2005), EMBASE (1980 to May 2005), and Science Citation Index Expanded (searched May 2005). SELECTION CRITERIA We included randomised clinical trials studying patients with alcoholic liver diseases. Interventions encompassed per oral or parenteral administration of SAMe at any dose versus placebo or no intervention. DATA COLLECTION AND ANALYSIS We performed all analyses according to the intention-to-treat method using RevMan Analyses provided by the Cochrane Collaboration. We evaluated the methodological quality of the randomised clinical trials by quality components. MAIN RESULTS We identified nine randomised clinical trials including a heterogeneous sample of 434 patients with alcoholic liver diseases. The methodological quality regarding randomisation was generally low, but 8 out of 9 trials were placebo controlled. Only one trial including 123 patients with alcoholic cirrhosis used adequate methodology and reported clearly on all-cause mortality and liver transplantation. We found no significant effects of SAMe on all-cause mortality (relative risks (RR) 0.62, 95% confidence interval (CI) 0.30 to 1.26), liver-related mortality (RR 0.68, 95% CI 0.31 to 1.48), all-cause mortality or liver transplantation (RR 0.55; 95% CI 0.27 to 1.09), or complications (RR 1.35, 95% CI 0.84 to 2.16), but the analysis is based mostly on one trial only. SAMe was not significantly associated with non-serious adverse events (RR 4.92; 95% CI 0.59 to 40.89) and no serious adverse events were reported. AUTHORS' CONCLUSIONS We could not find evidence supporting or refuting the use of SAMe for patients with alcoholic liver diseases. We need more long-term, high-quality randomised trials on SAMe for these patients before SAMe may be recommended for clinical practice.
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Affiliation(s)
- A Rambaldi
- Ospedale San Paolo, Divisione di Medicina Generale, Via Terracina, Napoli, Campania, Italy, 80100.
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Zhao CH, Zhang N, Bu XM, Li Y, Zhang HP. Multiple genes methylation detection in gastric cancer. Shijie Huaren Xiaohua Zazhi 2006; 14:1004-1007. [DOI: 10.11569/wcjd.v14.i10.1004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
AIM: To determine methylation state of p16, hMLH1, E-cadherin and RUNX3 and explore the role of these genes concurrent methylation in gastric cancer.
METHODS: DNA in gastric cancer, cancer-adjacent tissues and normal gastric mucosa was extracted by saturated NaCl method. Methylation state of these genes was detected by methylation-specific polymerase chain reaction (MSP).
RESULTS: Methylation of E-cadherin and RUNX3 was found in 38.9% and 16.7% normal gastric mucosa respectively. Methylation of p16 and hMLH1 was not present in any normal gastric mucosa. The methylation rate of p16, hMLH1, E-cadherin and RUNX3 is 8.3%, 4.2%, 54.2% and 29.2% in cancer-adjacent tissues and 33.3%, 20.8%, 70.8% and 54.2% in gastric cancer respectively. Two or more than two genes concurrent methylation was found in 66.7% gastric cancer, significantly higher than that in cancer-adjacent tissues(37.5%, χ2 = 4.09, P < 0.05)and that in normal gastric mucosa (5.6%, χ2 = 15.94, P < 0.01). And the rate in cancer-adjacent was higher than that in normal gastric mucosa(χ2 = 4.16, P < 0.05). In 5 gastric cancer cases ,methylation of these genes was not found at all.
CONCLUSION: Multiple genes concurrent methylation is an early event in gastric cancer. It suggests that multiple genes concurrent methylation plays an important role in some gastric cancers.
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Marks P, McGeehan J, Kneale G. A novel strategy for the expression and purification of the DNA methyltransferase, M.AhdI. Protein Expr Purif 2005; 37:236-42. [PMID: 15294304 DOI: 10.1016/j.pep.2004.06.008] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2004] [Revised: 06/03/2004] [Indexed: 11/20/2022]
Abstract
Biochemical and structural studies of the methylase from the type 1 1/2 R-M system AhdI require the ability to purify this multi-subunit enzyme in significant quantities in a soluble and active form. Several Escherichia coli expression systems were tested for their ability to produce the intact methylase but this could not be achieved in a simple co-expression system. Expression experiments were optimised to produce high yields of soluble M and S subunits as individual proteins. Temperature and conditions of induction proved to be the most useful factors and although purification of the S subunit was successful, an efficient strategy for the M subunit remained elusive. A novel strategy was developed in which individual subunits are expressed separately and the bacterial cells mixed before lysis. This method produced a high yield of the multi-subunit methylase when purified to homogeneity by means of heparin and size-exclusion chromatography. It was found to be essential, however, to remove tightly bound DNA by ammonium sulphate precipitation in 1 M NaCl. The intact methylase can now be consistently produced, avoiding the use of fusion proteins. The purified enzyme is stable over long time periods, unlike the individual subunits. This method may be of general application where the expression of multi-subunit proteins, or indeed their individual components, is problematic.
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Affiliation(s)
- Phil Marks
- Biophysics Laboratories, Institute of Biomedical and Biomolecular Sciences, University of Portsmouth, Portsmouth POI 2DT, UK
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Zaleski P, Piekarowicz A. Characterization of a dam mutant of Haemophilus influenzae Rd. Microbiology (Reading) 2004; 150:3773-3781. [PMID: 15528663 DOI: 10.1099/mic.0.27225-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The gene encoding Dam methyltransferase ofHaemophilus influenzaewas mutagenized by the insertion of a chloramphenicol-resistance cassette into the middle of the Dam coding sequence. This mutant construct was introduced into theH. influenzaechromosome by transformation and selection for CamRtransformants. The authors have shown that several phenotypic properties, resistance to antibiotics, dyes and detergent as well as efficiency of transformation, depend on the Dam methylation state of the DNA. Although the major role of the methyl-directed mismatch repair (MMR) system is to repair postreplicative errors, it seems that inH. influenzaeits effect is more apparent in repairing DNA damage caused by oxidative compounds. In thedammutant treated with hydrogen peroxide, MMR is not targeted to newly replicated DNA strands and therefore mismatches are converted into single- and double-strand DNA breaks. This is shown by the increased peroxide sensitivity of thedammutant and the finding that the sensitivity can be suppressed by amutHmutation inactivating MMR. In thedammutant treated with nitrofurazone the resulting damage is not converted into DNA breaks but the high sensitivity is also suppressed by amutHmutation.
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Affiliation(s)
- Piotr Zaleski
- Institute of Microbiology, University of Warsaw, Miecznikowa 1, 02-096 Warsaw, Poland
| | - Andrzej Piekarowicz
- Institute of Microbiology, University of Warsaw, Miecznikowa 1, 02-096 Warsaw, Poland
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31
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Slovinská L, Elbertová A, Misúrová E. Transmission of genome damage from irradiated male rats to their progeny. Mutat Res 2004; 559:29-37. [PMID: 15066571 DOI: 10.1016/j.mrgentox.2003.12.005] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2003] [Revised: 12/10/2003] [Accepted: 12/12/2003] [Indexed: 11/21/2022]
Abstract
The effect of gamma-radiation (3Gy) on slowly proliferating liver tissue of male rats and their progeny was investigated with respect to induction and duration of latent damage. The irradiation caused latent cytogenetic damage in the liver in irradiated males of the F(0) generation, which manifested itself in different ways during proliferation of hepatocytes induced by partial hepatectomy: a reduced proliferating activity, a higher frequency of chromosomal aberrations and a higher proportion of cells with apoptotic DNA fragments were observed, compared with non-irradiated rats. In the progeny of irradiated males (F(1) and F(2) generation), the latent genome damage manifested itself during regeneration of the liver after partial hepatectomy by similar, but less pronounced changes compared with those seen in irradiated males of the parental generation. This finding gave evidence of the transfer of part of the radiation-induced genome damage from parents to their offspring. Irradiation of F(1) and F(2) progeny of irradiated males (their total radiation load being 3 + 3 and 3 + 0 + 3 Gy, respectively) caused less change as irradiation of progeny of non-irradiated control males (their total radiation load being 0 + 3 and 0 + 0 + 3 Gy, respectively).
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Affiliation(s)
- Lucia Slovinská
- Department of Cellular and Molecular Biology, Faculty of Sciences, P.J. Safárik University, Moyzesova 11, 041 54 Kosice, Slovak Republic.
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Bist P, Rao DN. Identification and mutational analysis of Mg2+ binding site in EcoP15I DNA methyltransferase: involvement in target base eversion. J Biol Chem 2003; 278:41837-48. [PMID: 12917398 DOI: 10.1074/jbc.m307053200] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
EcoP15I DNA methyltransferase catalyzes the transfer of the methyl group of S-adenosyl-l-methionine to the N6 position of the second adenine within the double-stranded DNA sequence 5'-CAGCAG-3'. To achieve catalysis, the enzyme requires a magnesium ion. Binding of magnesium to the enzyme induces significant conformational changes as monitored by circular dichroism spectroscopy. EcoP15I DNA methyltransferase was rapidly inactivated by micromolar concentrations of ferrous sulfate in the presence of ascorbate at pH 8.0. The inactivated enzyme was cleaved into two fragments with molecular masses of 36 and 35 kDa. Using this affinity cleavage assay, we have located the magnesium binding-like motif to amino acids 355-377 of EcoP15I DNA methyltransferase. Sequence homology comparisons between EcoP15I DNA methyltransferase and other restriction endonucleases allowed us to identify a PD(X)n(D/E)XK-like sequence as the putative magnesium ion binding site. Point mutations generated in this region were analyzed for their role in methyltransferase activity, metal coordination, and substrate binding. Although the mutant methyltransferases bind DNA and S-adenosyl-l-methionine as well as the wild-type enzyme does, they are inactive primarily because of their inability to flip the target base. Collectively, these data are consistent with the fact that acidic amino acid residues of the region 355-377 in EcoP15I DNA methyltransferase are important for the critical positioning of magnesium ions for catalysis. This is the first example of metal-dependent function of a DNA methyltransferase. These findings provide impetus for exploring the role(s) of metal ions in the structure and function of DNA methyltransferases.
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Affiliation(s)
- Pradeep Bist
- Department of Biochemistry, Indian Institute of Science, Bangalore 560 012, India
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Malygin EG, Zinoviev VV, Evdokimov AA, Lindstrom WM, Reich NO, Hattman S. DNA (cytosine-N4-)- and -(adenine-N6-)-methyltransferases have different kinetic mechanisms but the same reaction route. A comparison of M.BamHI and T4 Dam. J Biol Chem 2003; 278:15713-9. [PMID: 12598537 DOI: 10.1074/jbc.m213213200] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We studied the kinetics of methyl group transfer by the BamHI DNA-(cytosine-N(4)-)-methyltransferase (MTase) from Bacillus amyloliquefaciens to a 20-mer oligodeoxynucleotide duplex containing the palindromic recognition site GGATCC. Under steady state conditions the BamHI MTase displayed a simple kinetic behavior toward the 20-mer duplex. There was no apparent substrate inhibition at concentrations much higher than the K(m) for either DNA (100-fold higher) or S-adenosyl-l-methionine (AdoMet) (20-fold higher); this indicates that dead-end complexes did not form in the course of the methylation reaction. The DNA methylation rate was analyzed as a function of both substrate and product concentrations. It was found to exhibit product inhibition patterns consistent with a steady state random bi-bi mechanism in which the dominant order of substrate binding and product release (methylated DNA, DNA(Me), and S-adenosyl-l-homocysteine, AdoHcy) was Ado-Met DNA DNA(Me) AdoHcy. The M.BamHI kinetic scheme was compared with that for the T4 Dam (adenine-N(6)-)-MTase. The two differed with respect to an effector action of substrates and in the rate-limiting step of the reaction (product inhibition patterns are the same for the both MTases). From this we conclude that the common chemical step in the methylation reaction, methyl transfer from AdoMet to a free exocyclic amino group, is not sufficient to dictate a common kinetic scheme even though both MTases follow the same reaction route.
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Affiliation(s)
- Ernst G Malygin
- Institute of Molecular Biology, State Research Center of Virology and Biotechnology "Vector," Koltsovo, Novosibirsk Region, 630559 Russia
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Bheemanaik S, Chandrashekaran S, Nagaraja V, Rao DN. Kinetic and catalytic properties of dimeric KpnI DNA methyltransferase. J Biol Chem 2003; 278:7863-74. [PMID: 12506109 DOI: 10.1074/jbc.m211458200] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
KpnI DNA-(N(6)-adenine)-methyltransferase (KpnI MTase) is a member of a restriction-modification (R-M) system in Klebsiella pneumoniae and recognizes the sequence 5'-GGTACC-3'. It modifies the recognition sequence by transferring the methyl group from S-adenosyl-l-methionine (AdoMet) to the N(6) position of adenine residue. KpnI MTase occurs as a dimer in solution as shown by gel filtration and chemical cross-linking analysis. The nonlinear dependence of methylation activity on enzyme concentration indicates that the functionally active form of the enzyme is also a dimer. Product inhibition studies with KpnI MTase showed that S-adenosyl-l-homocysteine is a competitive inhibitor with respect to AdoMet and noncompetitive inhibitor with respect to DNA. The methylated DNA showed noncompetitive inhibition with respect to both DNA and AdoMet. A reduction in the rate of methylation was observed at high concentrations of duplex DNA. The kinetic analysis where AdoMet binds first followed by DNA, supports an ordered bi bi mechanism. After methyl transfer, methylated DNA dissociates followed by S-adenosyl-l-homocysteine. Isotope-partitioning analysis showed that KpnI MTase-AdoMet complex is catalytically active.
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Swaminathan CP, Sankpal UT, Rao DN, Surolia A. Water-assisted dual mode cofactor recognition by HhaI DNA methyltransferase. J Biol Chem 2002; 277:4042-9. [PMID: 11729191 DOI: 10.1074/jbc.m109237200] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Energetically competent binary recognition of the cofactor S-adenosyl-L-methionine (AdoMet) and the product S-adenosyl-L-homocysteine (AdoHcy) by the DNA (cytosine C-5) methyltransferase (M.HhaI) is demonstrated herein. Titration calorimetry reveals a dual mode, involving a primary dominant exothermic reaction followed by a weaker endothermic one, for the recognition of AdoMet and AdoHcy by M.HhaI. Conservation of the bimodal recognition in W41I and W41Y mutants of M.HhaI excludes the cation-pi interaction between the methylsulfonium group of AdoMet and the pi face of the Trp(41) indole ring from a role in its origin. Small magnitude of temperature-independent heat capacity changes upon AdoMet or AdoHcy binding by M.HhaI preclude appreciable conformational alterations in the reacting species. Coupled osmotic-calorimetric analyses of AdoMet and AdoHcy binding by M.HhaI indicate that a net uptake of nearly eight and 10 water molecules, respectively, assists their primary recognition. A change in water activity at constant temperature and pH is sufficient to engender and conserve enthalpy-entropy compensation, consistent with a true osmotic effect. The results implicate solvent reorganization in providing the major contribution to the origin of this isoequilibrium phenomenon in AdoMet and AdoHcy recognition by M.HhaI. The observations provide unequivocal evidence for the binding of AdoMet as well as AdoHcy to M.HhaI in solution state. Isotope partitioning analysis and preincubation studies favor a random mechanism for M.HhaI-catalyzed reaction. Taken together, the results clearly resolve the issue of cofactor recognition by free M.HhaI, specifically in the absence of DNA, leading to the formation of an energetically and catalytically competent binary complex.
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Affiliation(s)
- Chittoor P Swaminathan
- Molecular Biophysics Unit and Department of Biochemistry, Indian Institute of Science, Bangalore 560 012, India
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Evdokimov AA, Zinoviev VV, Malygin EG, Schlagman SL, Hattman S. Bacteriophage T4 Dam DNA-[N6-adenine]methyltransferase. Kinetic evidence for a catalytically essential conformational change in the ternary complex. J Biol Chem 2002; 277:279-86. [PMID: 11687585 DOI: 10.1074/jbc.m108864200] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We carried out a steady state kinetic analysis of the bacteriophage T4 DNA-[N6-adenine]methyltransferase (T4 Dam) mediated methyl group transfer reaction from S-adenosyl-l-methionine (AdoMet) to Ade in the palindromic recognition sequence, GATC, of a 20-mer oligonucleotide duplex. Product inhibition patterns were consistent with a steady state-ordered bi-bi mechanism in which the order of substrate binding and product (methylated DNA, DNA(Me) and S-adenosyl-l-homocysteine, AdoHcy) release was AdoMet downward arrow DNA downward arrow DNA(Me) upward arrow AdoHcy upward arrow. A strong reduction in the rate of methylation was observed at high concentrations of the substrate 20-mer DNA duplex. In contrast, increasing substrate AdoMet concentration led to stimulation in the reaction rate with no evidence of saturation. We propose the following model. Free T4 Dam (initially in conformational form E) randomly interacts with substrates AdoMet and DNA to form a ternary T4 Dam-AdoMet-DNA complex in which T4 Dam has isomerized to conformational state F, which is specifically adapted for catalysis. After the chemical step of methyl group transfer from AdoMet to DNA, product DNA(Me) dissociates relatively rapidly (k(off) = 1.7 x s(-1)) from the complex. In contrast, dissociation of product AdoHcy proceeds relatively slowly (k(off) = 0.018 x s(-1)), indicating that its release is the rate-limiting step, consistent with kcat = 0.015 x s(-1). After AdoHcy release, the enzyme remains in the F conformational form and is able to preferentially bind AdoMet (unlike form E, which randomly binds AdoMet and DNA), and the AdoMet-F binary complex then binds DNA to start another methylation cycle. We also propose an alternative pathway in which the release of AdoHcy is coordinated with the binding of AdoMet in a single concerted event, while T4 Dam remains in the isomerized form F. The resulting AdoMet-F binary complex then binds DNA, and another methylation reaction ensues. This route is preferred at high AdoMet concentrations.
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Affiliation(s)
- Alexey A Evdokimov
- Institute of Molecular Biology, State Research Center of Virology and Biotechnology Vector, Novosibirsk 630559, Russia
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Meints GA, Drobny GP. Dynamic impact of methylation at the M. Hhai target site: a solid-state deuterium NMR study. Biochemistry 2001; 40:12436-43. [PMID: 11591165 DOI: 10.1021/bi0102555] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Base methylation plays an important role in numerous biological functions of DNA, from inhibition of cleavage by endonucleases to inhibition of transcription factor binding. Studies of nucleic acid structure have shown little differences in unmethylated DNAs and the identical sequence containing methylated analogues. We have investigated changes in the local dynamics of DNA upon substitution of a methylated cytosine analogue for cytosine using solid-state deuterium NMR. In particular, we have observed changes in the local dynamics at the target site of the M. HhaI restriction system. These studies observe changes in the amplitudes of the local backbone dynamics at the actual target site of the HhaI methyltransferase. This conclusion is another indication that the significant result of base methylation is to perturb the local dynamics, and therefore the local conformational flexibility, of the DNA helix, inhibiting or restricting the protein's ability to manipulate the DNA helix in order to perform its chemical alterations.
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Affiliation(s)
- G A Meints
- Department of Chemistry, University of Washington, Seattle, 98195, USA
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Abstract
When Chlamydomonas reinhardtii cells mate, a zygotic maturation program is activated, part of which leads to destruction of chloroplast DNA (cpDNA) from the mating type minus (mt-) parent, and, therefore, to uniparental inheritance of mating type plus (mt+) cpDNA. A long-standing model that explains the selective destruction of mt(-) cpDNA in zygotes invokes a methylation-restriction system. We tested this model by using the potent methylation inhibitor 5-aza-2'-deoxycytidine (5adc) to hypomethylate parental cpDNA and found that the pattern of cpDNA inheritance is altered by 5adc in a manner that is consistent with the model. Surprisingly, however, hypomethylated mt+ cpDNA is not destroyed in zygotes as the methylation-restriction model predicts it should be. Destruction of mt- cpDNA is also unaffected when the parental mt+ cpDNA is hypomethylated. Instead, loss of methylation affects the relative rates of replication of residual mt- cpDNA and mt+ cpDNA in germinating zygotes. The mode of action for 5adc on cpDNA replication in germinating zygotes may be via hypomethylation of mt+ cpDNA, but is also consistent with its action as a DNA-damaging agent. Interestingly, 5adc causes reduced cpDNA replication only in germinating zygotes, not in vegetatively grown cells, indicating that cpDNA replication is qualitatively different in these two stages of the life cycle. Our results demonstrate that methylation is not necessary for protection of the mt+ cpDNA in early zygotes and uncover a novel stage of the Chlamydomonas life cycle when replication of cpDNA is highly susceptible to perturbation. Our data support a model in which differential cpDNA replication in germinating zygotes is used as a mechanism to selectively amplify intact and properly methylated cpDNA molecules.
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Affiliation(s)
- J G Umen
- Department of Biology, Washington University, St. Louis, MO 63130, USA
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Zheng W, Scheibner KA, Ho AK, Cole PA. Mechanistic studies on the alkyltransferase activity of serotonin N-acetyltransferase. CHEMISTRY & BIOLOGY 2001; 8:379-89. [PMID: 11325593 DOI: 10.1016/s1074-5521(01)00020-5] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
BACKGROUND Serotonin N-acetyltransferase (arylalkylamine N-acetyltransferase, AANAT) catalyzes the first, rate-limiting step in the biosynthesis of the circadian hormone melatonin (5-methoxy-N-acetyltryptamine) from serotonin. Our recent discovery that, in addition to catalyzing the acetyl transfer from acetyl-coenzyme A (acetyl-CoASH) to serotonin, AANAT is also a robust catalyst for the alkyl transfer reaction between CoASH and N-bromoacetyltryptamine has not only opened up a new way to develop cell-permeable AANAT acetyltransferase inhibitors that are valuable in vivo tools in helping elucidate melatonin's (patho)physiological roles, but has also raised a question - how does AANAT accelerate the alkyl transfer reaction? In this study, mechanistic aspects of the AANAT-catalyzed alkyl transfer reaction were explored by employing CoASH and a series of N-haloacetyltryptamines that were also evaluated for their AANAT acetyltransferase inhibitory activities. RESULTS Investigation of various N-haloacetyltryptamine analogs showed a similar leaving group effect on the enzymatic and non-enzymatic reaction rates. Steady-state kinetic analyses demonstrated that AANAT alkyltransferase obeys a sequential, ternary complex mechanism, with random substrate binding. Rate versus pH profiles revealed the catalytic importance of an ionizable group with pK(a) of approximately 7. All those N-haloacetyltryptamines that serve as substrates of AANAT alkyltransferase are also potent (low micromolar) in vitro inhibitors against AANAT acetyltransferase activity. In particular, N-chloroacetyltryptamine was also shown to be a potent inhibitor of intracellular melatonin production in a pineal cell culture assay. CONCLUSIONS This is the first detailed investigation of the alkyltransferase activity associated with an acetyltransferase. Our results indicate that AANAT does not accelerate the alkyl transfer reaction by simple approximation effect as previously proposed for the similar alkyl transfer reaction catalyzed by other acyltransferases. This study has general implications for developing novel inhibitors by taking advantage of the promiscuous alkyltransferase activity associated with several acyltransferases.
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Affiliation(s)
- W Zheng
- Department of Pharmacology and Molecular Sciences, The Johns Hopkins University School of Medicine, Baltimore MD 21205, USA
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Abstract
BACKGROUND Alcohol is a major cause of liver disease in the Western world today. S-adenosyl-L-methionine (SAMe) acts as a methyl donor for all known biological methylation reactions and participates in the synthesis of glutathione, the main cellular anti-oxidant. Randomised clinical trials have addressed the question whether SAMe has any efficacy in patients with alcoholic liver diseases. OBJECTIVES The objectives were to assess the efficacy of SAMe on mortality, clinical symptoms, complications, liver biochemistry, and liver histology in patients with alcoholic liver diseases. Adverse events were also analysed. SEARCH STRATEGY The Cochrane Hepato-Biliary Group Controlled Trials Register, The Cochrane Library, MEDLINE, EMBASE, and full text searches were combined. SELECTION CRITERIA Randomised clinical trials studying patients with alcoholic liver diseases were included. Interventions encompassed peroral or parenteral administration of SAMe at any dose versus placebo or no intervention. The trials could be double blind, single blind, or unblinded. The trials could be unpublished or published as an article, an abstract, or a letter, and no language limitations were applied. DATA COLLECTION AND ANALYSIS All analyses were performed according to the intention-to-treat method. The statistical package (RevMan and MetaView) provided by the Cochrane Collaboration was used. The methodological quality of the randomised clinical trials was evaluated by components of quality and the Jadad-score. MAIN RESULTS Eight placebo-controlled randomised clinical trials including a heterogeneous sample of 330 patients with alcoholic liver disease were identified. Only one trial including 123 patients with alcoholic cirrhosis used adequate methodology and reported clearly on mortality and liver transplantation. It demonstrated no significant effects of SAMe on mortality (Peto odds ratio (OR) 0.53, 95% confidence interval (CI) 0.22 to 1.29), liver related mortality (OR 0.63, 95% CI 0.25 to 1.58), mortality or liver transplantation (OR 0.47; 95% CI 0.20 to 1.09), or patients without complications (OR 0.63, 95% CI 0.30 to 1.31). SAMe was not significantly associated with adverse events (OR 3.95, 95% CI 0.77 to 20.24). REVIEWER'S CONCLUSIONS This systematic review could not demonstrate any significant effect of SAMe on mortality, liver related mortality, mortality or liver transplantation, and liver complications of patients with alcoholic liver disease. SAMe should not be used for alcoholic liver disease outside randomised clinical trials.
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Affiliation(s)
- A Rambaldi
- Copenhagen Trial Unit, Centre for Clinical Intervention Research, Copenhagen University Hospital, H:S Rigshopitalet, Blegdamsvej 9, Copenhagen, Denmark, DK-2100.
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Sharath AN, Weinhold E, Bhagwat AS. Reviving a dead enzyme: cytosine deaminations promoted by an inactive DNA methyltransferase and an S-adenosylmethionine analogue. Biochemistry 2000; 39:14611-6. [PMID: 11087417 DOI: 10.1021/bi001610e] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The enzymes that transfer a methyl group to C5 of cytosine within specific sequences (C5 Mtases) deaminate the target cytosine to uracil if the methyl donor S-adenosylmethionine (SAM) is omitted from the reaction. Recently, it was shown that cytosine deamination caused by C5 Mtases M.HpaII, M.SssI and M.MspI is enhanced in the presence of several analogues of SAM, and a mechanism for this analogue-promoted deamination was proposed. According to this mechanism, the analogues protonate C5 of the target cytosine, creating a dihydrocytosine intermediate that is susceptible to deamination. We show here that one of these analogues, 5'-aminoadenosine (AA), enhances cytosine deamination by the Mtase M. EcoRII, but it does so without enhancing protonation of C5. Further, we show that uracil is an intermediate in the mutational pathway and propose an alternate mechanism for the analogue-promoted deamination. The new mechanism involves a facilitated water attack at C4 but does not require attack at C6 by the enzyme. The latter feature of the mechanism was tested by using M.EcoRII mutants defective in the nucleophilic attack at C6 in the deamination assay. We find that although these proteins are defective in methyl transfer and cytosine deamination, they cause cytosine deaminations in the presence of AA in the reaction. Our results point to a possible connection between the catalytic mechanism of C5 Mtases and of enzymes that transfer methyl groups to N(4) of cytosine. Further, they provide an unusual example where a coenzyme activates an otherwise "dead" enzyme to perform catalysis by a new reaction pathway.
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Affiliation(s)
- A N Sharath
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202, USA
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Cooper MT, Porter TD. Mutagenicity of nitrosamines in methyltransferase-deficient strains of Salmonella typhimurium coexpressing human cytochrome P450 2E1 and reductase. Mutat Res 2000; 454:45-52. [PMID: 11035158 DOI: 10.1016/s0027-5107(00)00099-3] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Although dialkylnitrosamines are environmentally significant carcinogens, the use of short-term bioassays to assess the mutagenic potential of these compounds is problematic. The Ames test, a mutagenicity assay based on the reversion of Salmonella typhimurium histidine auxotrophs, is the most widely used bioassay in genetic toxicology, but the traditional Ames tester strains are largely insensitive to dialkylnitrosamine mutagenicity. We have constructed two mutagenicity tester strains that co-express full-length human cytochrome P450 2E1 and P450 reductase in S. typhimurium lacking ogt and ada methyltransferases (YG7104ER, ogt- and YG7108ER, ogt-, ada-). These new strains are susceptible to dialkylnitrosamine mutagenicity in the absence of an exogenous metabolic activating system (S9 fraction). Mutagenicity is dependent upon the coexpression of P450 2E1 with P450 reductase and is similar to or greater than that obtained with the parental strains in the presence of S9 fraction from ethanol-induced rat liver. These strains were also sensitive to nitrosamines with longer alkyl side chains including diethylnitrosamine, dipropylnitrosamine and dibutylnitrosamine. Mutagenicity decreased with alkyl chain length, consistent with the stringency of the ada-encoded enzyme for methyl and ethyl DNA adducts. These new strains may prove useful in the evaluation of nitrosamine contamination of food and environmental samples.
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Affiliation(s)
- M T Cooper
- Graduate Center for Toxicology, University of Kentucky, Lexington, KY 40536-0305, USA
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Gaubert G, Mathé C, Imbach J, Eriksson S, Vincenzetti S, Salvatori D, Vita A, Maury G. Unnatural enantiomers of 5-azacytidine analogues: syntheses and enzymatic properties. Eur J Med Chem 2000; 35:1011-9. [PMID: 11137229 DOI: 10.1016/s0223-5234(00)01184-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Although 2'-deoxy-beta-D-5-azacytidine (Decitabine) and beta-D-5-azacytidine display potent antileukemic properties, their therapeutic use is hampered by their sensitivity to nucleophiles and to deamination catalysed by cytidine deaminase. As shown earlier [Shafiee M., Griffon J.-F., Gosselin G., Cambi A., Vincenzetti S., Vita A., Erikson S., Imbach J.-L., Maury G., Biochem. Pharmacol. 56 (1998) 1237-1242], beta-L-enantiomers of cytidine derivatives are resistant to cytidine deaminase. We thus synthesized several 5-azacytosine beta-L-nucleoside analogues to evaluate their enzymatic and biological properties. 2'-Deoxy-beta-L-5-azacytidine (L-Decitabine), beta-L-5-azacytidine, 1-(beta-L-xylo-furanosyl)5-azacytosine, and 1-(2-deoxy-beta-L-threo-pentofuranosyl)5-azacytosine were stereospecifically prepared starting from L-ribose and L-xylose. D- and L-enantiomers of 2'-deoxy-beta-5-azacytidine were weak substrates of human recombinant deoxycytidine kinase (dCK) compared to beta-D-deoxycytidine, whereas both enantiomers of beta-5-azacytidine or the L-xylo-analogues were not substrates of the enzyme. As expected, none of the presently reported derivatives of beta-L-5-azacytidine was a substrate of human recombinant cytidine deaminase (CDA). The prepared compounds were tested for their activity against HIV and HBV and they did not show any significant activity or cytotoxicity. In the case of L-Decitabine, this suggests that the enantioselectivities of concerned enzymes other than dCK and CDA might not be favourable.
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Affiliation(s)
- G Gaubert
- UMR 5625 du CNRS, Département de Chimie, Université Montpellier II, Place Bataillon, 34095 5, Montpellier Cedex, France
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Gowher H, Jeltsch A. Molecular enzymology of the EcoRV DNA-(Adenine-N (6))-methyltransferase: kinetics of DNA binding and bending, kinetic mechanism and linear diffusion of the enzyme on DNA. J Mol Biol 2000; 303:93-110. [PMID: 11021972 DOI: 10.1006/jmbi.2000.4127] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The EcoRV DNA-(adenine-N(6))-methyltransferase recognizes GATATC sequences and modifies the first adenine residue within this site. We show here, that the enzyme binds to the DNA and the cofactor S-adenosylmethionine (AdoMet) in an ordered bi-bi fashion, with AdoMet being bound first. M.EcoRV binds DNA in a non-specific manner and the enzyme searches for its recognition site by linear diffusion with a range of approximately 1800 bp. During linear diffusion the enzyme continuously scans the DNA for the presence of recognition sites. Upon specific M.EcoRV-DNA complex formation a strong increase in the fluorescence of an oligonucleotide containing a 2-aminopurine base analogue at the GAT-2AP-TC position is observed which, most likely, is correlated with DNA bending. In contrast to the GAT-2AP-TC substrate, a G-2AP-TATC substrate in which the target base is replaced by 2-aminopurine does not show an increase in fluorescence upon M.EcoRV binding, demonstrating that 2-aminopurine is not a general tool to detect base flipping. Stopped-flow experiments show that DNA bending is a fast process with rate constants >10 s(-1). In the presence of cofactor, the specific complex adopts a second conformation, in which the target sequence is more tightly contacted by the enzyme. M.EcoRV exists in an open and in a closed state that are in slow equilibrium. Closing the open state is a slow process (rate constant approximately 0.7 min(-1)) that limits the rate of DNA methylation under single turnover conditions. Product release requires opening of the closed complex which is very slow (rate constant approximately 0.05-0.1 min(-1)) and limits the rate of DNA methylation under multiple turnover conditions. M.EcoRV methylates DNA sequences containing more than one recognition sites in a distributive manner. Since the dissociation rate from non-specific DNA does not depend on the length of the DNA fragment, DNA dissociation does not preferentially occur at the ends of the DNA.
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Affiliation(s)
- H Gowher
- Institut für Biochemie, Fachbereich 8, Giessen, 35392, Germany
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Rugge M, Shiao YH, Busatto G, Cassaro M, Strobbe C, Russo VM, Leo G, Parenti AR, Scapinello A, Arslan P, Egarter-Vigl E. The p53 gene in patients under the age of 40 with gastric cancer: mutation rates are low but are associated with a cardiac location. Mol Pathol 2000; 53:207-10. [PMID: 11040944 PMCID: PMC1186971 DOI: 10.1136/mp.53.4.207] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
BACKGROUND Determining both the frequency and the spectrum of p53 gene mutation in young patients with gastric cancer might provide clues to the host related genetic mechanism(s) in gastric carcinogenesis. PATIENTS AND METHODS p53 mutations were assessed (by means of polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP), followed by DNA sequencing) in a cohort of 105 consecutive Italian patients in whom gastric cancer was ascertained before the age of 41. RESULTS A low prevalence of p53 mutations (eight of 105) was observed, with no significant difference between intestinal (three of 31; 10%) and diffuse (five of 74; 7%) phenotypes. A significantly higher prevalence of p53 mutations was associated with the cardiac location (odds ratio, 7.09; confidence interval, 1.56 to 32.11). In all but one case, p53 mutations were associated with a stage higher than I. All eight mutations were located at CpG sites, where G : C to A : T transitions have been associated with frequent methylation at the C5 position of cytosine. CONCLUSIONS These findings show that, unlike what has been consistently demonstrated in the general population, p53 mutations are uncommon in gastric cancer occurring in young patients, and in such patients, p53 alterations are significantly associated with the cardiac location.
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Affiliation(s)
- M Rugge
- Department of Oncology and Surgical Sciences, University of Padova, ULSS15-Regione Veneto, Italy.
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Friedrich T, Fatemi M, Gowhar H, Leismann O, Jeltsch A. Specificity of DNA binding and methylation by the M.FokI DNA methyltransferase. BIOCHIMICA ET BIOPHYSICA ACTA 2000; 1480:145-59. [PMID: 11004560 DOI: 10.1016/s0167-4838(00)00065-0] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The M.FokI adenine-N(6) DNA methyltransferase recognizes the asymmetric DNA sequence GGATG/CATCC. It consists of two domains each containing all motifs characteristic for adenine-N(6) DNA methyltransferases. We have studied the specificity of DNA-methylation by both domains using 27 hemimethylated oligonucleotide substrates containing recognition sites which differ in one or two base pairs from GGATG or CATCC. The N-terminal domain of M.FokI interacts very specifically with GGATG-sequences, because only one of the altered sites is modified. In contrast, the C-terminal domain shows lower specificity. It prefers CATCC-sequences but only two of the 12 star sites (i.e. sites that differ in 1 bp from the recognition site) are not accepted and some star sites are modified with rates reduced only 2-3-fold. In addition, GGATGC- and CGATGC-sites are modified which differ at two positions from CATCC. DNA binding experiments show that the N-terminal domain preferentially binds to hemimethylated GGATG/C(m)ATCC sequences whereas the C-terminal domain binds to DNA with higher affinity but without specificity. Protein-protein interaction assays show that both domains of M.FokI are in contact with each other. However, several DNA-binding experiments demonstrate that DNA-binding of both domains is mutually exclusive in full-length M.FokI and both domains do not functionally influence each other. The implications of these results on the molecular evolution of type IIS restriction/modification systems are discussed.
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Affiliation(s)
- T Friedrich
- Institut für Biochemie, Fachbereich 8, Heinrich-Buff-Ring 58, 35392, Giessen, Germany
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Reddy YV, Rao DN. Binding of EcoP15I DNA methyltransferase to DNA reveals a large structural distortion within the recognition sequence. J Mol Biol 2000; 298:597-610. [PMID: 10788323 DOI: 10.1006/jmbi.2000.3673] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
EcoP15I DNA methyltransferase, a member of the type III restriction-modification system, binds to the sequence 5'-CAGCAG-3' transferring a methyl group from S-adenosyl-l-methionine to the second adenine base. We have investigated protein-DNA interactions in the methylase-DNA complex by three methods. Determination of equilibrium dissociation constants indicated that the enzyme had higher affinity for DNA containing mismatches at the target base within the recognition sequence. Potassium permanganate footprinting studies revealed that there was a hyper-reactive permanganate cleavage site coincident with adenine that is the target base for methylation. More importantly, to detect DNA conformational alterations within the enzyme-DNA complexes, we have used a fluorescence-based assay. When EcoP15I DNA methyltransferase bound to DNA containing 2-aminopurine substitutions within the cognate sequence, an eight to tenfold fluorescent enhancement resulting from enzymatic flipping of the target adenine base was observed. Furthermore, fluorescence spectroscopy analysis showed that the changes attributable to structural distortion were specific for only the bases within the recognition sequence. More importantly, we observed that both the adenine bases in the recognition site appear to be structurally distorted to the same extent. While the target adenine base is probably flipped out of the DNA duplex, our results also suggest that fluorescent enhancements could be derived from protein-DNA interactions other than base flipping. Taken together, our results support the proposed base flipping mechanism for adenine methyltransferases.
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Affiliation(s)
- Y V Reddy
- Department of Biochemistry, Indian Institute of Science, Bangalore, 560012, India
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Geahigan KB, Meints GA, Hatcher ME, Orban J, Drobny GP. The dynamic impact of CpG methylation in DNA. Biochemistry 2000; 39:4939-46. [PMID: 10769153 DOI: 10.1021/bi9917636] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Solid-state deuterium NMR is used to investigate perturbations of the local, internal dynamics in the EcoRI restriction binding site, -GAATTC- induced by cytidine methylation. Methylation of the cytidine base in this sequence is known to suppress hydrolysis by the EcoRI restriction enzyme. Previous solid-state deuterium NMR studies have detected large amplitude motions of the phosphate-sugar backbone at the AT-CG junction of the unmethylated DNA sequence. This study shows that methylation of the cytidine base in a CpG dinucleotide reduces the amplitudes of motions of the phosphate-sugar backbone. These observations suggest a direct link between suppression of the amplitudes of localized, internal motions of the sugar-phosphate backbone of the DNA and inhibition of restriction enzyme cleavage.
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Affiliation(s)
- K B Geahigan
- Department of Chemistry, University of Washington, Seattle, WA 98195, USA
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Rao DN, Saha S, Krishnamurthy V. ATP-dependent restriction enzymes. PROGRESS IN NUCLEIC ACID RESEARCH AND MOLECULAR BIOLOGY 2000; 64:1-63. [PMID: 10697406 DOI: 10.1016/s0079-6603(00)64001-1] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/15/2023]
Abstract
The phenomenon of restriction and modification (R-M) was first observed in the course of studies on bacteriophages in the early 1950s. It was only in the 1960s that work of Arber and colleagues provided a molecular explanation for the host specificity. DNA restriction and modification enzymes are responsible for the host-specific barriers to interstrain and interspecies transfer of genetic information that have been observed in a variety of bacterial cell types. R-M systems comprise an endonuclease and a methyltransferase activity. They serve to protect bacterial cells against bacteriophage infection, because incoming foreign DNA is specifically cleaved by the restriction enzyme if it contains the recognition sequence of the endonuclease. The DNA is protected from cleavage by a specific methylation within the recognition sequence, which is introduced by the methyltransferase. Classic R-M systems are now divided into three types on the basis of enzyme complexity, cofactor requirements, and position of DNA cleavage, although new systems are being discovered that do not fit readily into this classification. This review concentrates on multisubunit, multifunctional ATP-dependent restriction enzymes. A growing number of these enzymes are being subjected to biochemical and genetic studies that, when combined with ongoing structural analyses, promise to provide detailed models for mechanisms of DNA recognition and catalysis. It is now clear that DNA cleavage by these enzymes involves highly unusual modes of interaction between the enzymes and their substrates. These unique features of mechanism pose exciting questions and in addition have led to the suggestion that these enzymes may have biological functions beyond that of restriction and modification. The purpose of this review is to describe the exciting developments in our understanding of how the ATP-dependent restriction enzymes recognize specific DNA sequences and cleave or modify DNA.
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Affiliation(s)
- D N Rao
- Department of Biochemistry, Indian Institute of Science, Bangalore, India
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Roth M, Jeltsch A. Biotin-avidin microplate assay for the quantitative analysis of enzymatic methylation of DNA by DNA methyltransferases. Biol Chem 2000; 381:269-72. [PMID: 10782999 DOI: 10.1515/bc.2000.035] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
An assay is described to measure methylation of biotinylated oligonucleotide substrates by DNA methyltransferases using [methyl-3H]-AdoMet. After the methylation reaction the oligonucleotides are immobilized on an avidin-coated microplate. The incorporation of [3H] into the DNA is quenched by addition of unlabeled AdoMet to the binding buffer. Unreacted AdoMet and enzyme are removed by washing. To release the radioactivity incorporated into the DNA, the wells are incubated with a non-specific endonuclease and the radioactivity determined by liquid scintillation counting. As an example, we have studied methylation of DNA by the EcoRV DNA methyltransferase. The reaction progress curves measured with this assay are linear with respect to time. Methylation rates linearly increase with enzyme concentration. The rates are comparable to results obtained with the same enzyme using a different assay. The biotin-avidin assay is inexpensive, convenient, quantitative, fast and well suited to process many samples in parallel. The accuracy of the assay is high, allowing to reproduce results within +/- 10%. The assay is very sensitive as demonstrated by the detection of incorporation of 0.8 fmol methyl groups into the DNA. Under the experimental conditions, this corresponds to methylation of only 0.03% of all target sites of the substrate. Using this assay, the DNA methylation activity of some M.EcoRV variants could be detected that was not visible by other in vitro methylation assays.
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Affiliation(s)
- M Roth
- Institut für Biochemie, Justus-Liebig-Universität, Giessen, Germany
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