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Liu S, Su J, Xie X, Huang R, Li H, Luo R, Li J, Liu X, He J, Huang Y, Wu P. Detection of methyltransferase activity and inhibitor screening based on rGO-mediated silver enhancement signal amplification strategy. Anal Biochem 2023:115207. [PMID: 37290576 DOI: 10.1016/j.ab.2023.115207] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2023] [Revised: 05/20/2023] [Accepted: 06/04/2023] [Indexed: 06/10/2023]
Abstract
DNA methylation refers to the chemical modification process of obtaining a methyl group by the covalent bonding of a specific base in DNA sequence with S-adenosyl methionine (SAM) as a methyl donor under the catalysis of methyltransferase (MTase), which is related to the occurrence of multiple diseases. Therefore, the detection of MTase activity is of great significance for disease diagnosis and drug screening. Because reduced graphene oxide (rGO) has a unique planar structure and remarkable catalytic performance, it is not clear whether rGO can rapidly catalyze silver deposition as an effective way of signal amplification. However, in this study, we were pleasantly surprised to find that using H2O2 as a reducing agent, rGO can rapidly catalyze silver deposition, and its catalytic efficiency of silver deposition is significantly better than that of GO. Therefore, based on further verifying the mechanism of catalytic properties of rGO, we constructed a novel electrochemical biosensor (rGO/silver biosensor) for the detection of dam MTase activity, which has high selectivity and sensitivity to MTase in the range of 0.1 U/mL to 10.0 U/mL, and the detection limit is as low as 0.07 U/mL. Besides, this study also used Gentamicin and 5-Fluorouracil as inhibitor models, confirming that the biosensor has a good application prospect in the high-throughput screening of dam MTase inhibitors.
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Affiliation(s)
- Shuyan Liu
- Center for Medical Genetics & Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan, 410008, China; State Key Laboratory of Targeting Oncology, National Center for International Research of Biotargeting Theranostics, Guangxi Key Laboratory of Biotargeting Theranostics, Collaborative Innovation Center for Targeting Tumor Diagnosis and Therapy, Guangxi Medical University, Nanning, Guangxi, 530021, China
| | - Jing Su
- State Key Laboratory of Targeting Oncology, National Center for International Research of Biotargeting Theranostics, Guangxi Key Laboratory of Biotargeting Theranostics, Collaborative Innovation Center for Targeting Tumor Diagnosis and Therapy, Guangxi Medical University, Nanning, Guangxi, 530021, China; College of Chemistry & Chemical Engineering, Jiangxi Science & Technology Normal University, Nanchang, 330013, China
| | - Xixiang Xie
- State Key Laboratory of Targeting Oncology, National Center for International Research of Biotargeting Theranostics, Guangxi Key Laboratory of Biotargeting Theranostics, Collaborative Innovation Center for Targeting Tumor Diagnosis and Therapy, Guangxi Medical University, Nanning, Guangxi, 530021, China
| | - Rongping Huang
- State Key Laboratory of Targeting Oncology, National Center for International Research of Biotargeting Theranostics, Guangxi Key Laboratory of Biotargeting Theranostics, Collaborative Innovation Center for Targeting Tumor Diagnosis and Therapy, Guangxi Medical University, Nanning, Guangxi, 530021, China
| | - Haiping Li
- State Key Laboratory of Targeting Oncology, National Center for International Research of Biotargeting Theranostics, Guangxi Key Laboratory of Biotargeting Theranostics, Collaborative Innovation Center for Targeting Tumor Diagnosis and Therapy, Guangxi Medical University, Nanning, Guangxi, 530021, China
| | - Ruiyu Luo
- State Key Laboratory of Targeting Oncology, National Center for International Research of Biotargeting Theranostics, Guangxi Key Laboratory of Biotargeting Theranostics, Collaborative Innovation Center for Targeting Tumor Diagnosis and Therapy, Guangxi Medical University, Nanning, Guangxi, 530021, China
| | - Jinghua Li
- State Key Laboratory of Targeting Oncology, National Center for International Research of Biotargeting Theranostics, Guangxi Key Laboratory of Biotargeting Theranostics, Collaborative Innovation Center for Targeting Tumor Diagnosis and Therapy, Guangxi Medical University, Nanning, Guangxi, 530021, China
| | - Xiyu Liu
- State Key Laboratory of Targeting Oncology, National Center for International Research of Biotargeting Theranostics, Guangxi Key Laboratory of Biotargeting Theranostics, Collaborative Innovation Center for Targeting Tumor Diagnosis and Therapy, Guangxi Medical University, Nanning, Guangxi, 530021, China
| | - Jian He
- State Key Laboratory of Targeting Oncology, National Center for International Research of Biotargeting Theranostics, Guangxi Key Laboratory of Biotargeting Theranostics, Collaborative Innovation Center for Targeting Tumor Diagnosis and Therapy, Guangxi Medical University, Nanning, Guangxi, 530021, China.
| | - Yong Huang
- State Key Laboratory of Targeting Oncology, National Center for International Research of Biotargeting Theranostics, Guangxi Key Laboratory of Biotargeting Theranostics, Collaborative Innovation Center for Targeting Tumor Diagnosis and Therapy, Guangxi Medical University, Nanning, Guangxi, 530021, China.
| | - Pan Wu
- State Key Laboratory of Targeting Oncology, National Center for International Research of Biotargeting Theranostics, Guangxi Key Laboratory of Biotargeting Theranostics, Collaborative Innovation Center for Targeting Tumor Diagnosis and Therapy, Guangxi Medical University, Nanning, Guangxi, 530021, China.
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2
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Zhou J, Deng Y, Iyamu ID, Horton JR, Yu D, Hajian T, Vedadi M, Rotili D, Mai A, Blumenthal RM, Zhang X, Huang R, Cheng X. Comparative Study of Adenosine Analogs as Inhibitors of Protein Arginine Methyltransferases and a Clostridioides difficile-Specific DNA Adenine Methyltransferase. ACS Chem Biol 2023; 18:734-745. [PMID: 37082867 PMCID: PMC10127221 DOI: 10.1021/acschembio.3c00035] [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: 01/17/2023] [Accepted: 02/07/2023] [Indexed: 02/25/2023]
Abstract
S-Adenosyl-l-methionine (SAM) analogs are adaptable tools for studying and therapeutically inhibiting SAM-dependent methyltransferases (MTases). Some MTases play significant roles in host-pathogen interactions, one of which is Clostridioides difficile-specific DNA adenine MTase (CamA). CamA is needed for efficient sporulation and alters persistence in the colon. To discover potent and selective CamA inhibitors, we explored modifications of the solvent-exposed edge of the SAM adenosine moiety. Starting from the two parental compounds (6e and 7), we designed an adenosine analog (11a) carrying a 3-phenylpropyl moiety at the adenine N6-amino group, and a 3-(cyclohexylmethyl guanidine)-ethyl moiety at the sulfur atom off the ribose ring. Compound 11a (IC50 = 0.15 μM) is 10× and 5× more potent against CamA than 6e and 7, respectively. The structure of the CamA-DNA-inhibitor complex revealed that 11a adopts a U-shaped conformation, with the two branches folded toward each other, and the aliphatic and aromatic rings at the two ends interacting with one another. 11a occupies the entire hydrophobic surface (apparently unique to CamA) next to the adenosine binding site. Our work presents a hybrid knowledge-based and fragment-based approach to generating CamA inhibitors that would be chemical agents to examine the mechanism(s) of action and therapeutic potentials of CamA in C. difficile infection.
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Affiliation(s)
- Jujun Zhou
- Department
of Epigenetics and Molecular Carcinogenesis, University of Texas MD Anderson Cancer Center, Houston, Texas 77030, United States
| | - Youchao Deng
- Department
of Medicinal Chemistry and Molecular Pharmacology, Institute for Drug
Discovery, Center for Cancer Research, Purdue
University, West Lafayette, Indiana 47907, United States
| | - Iredia D. Iyamu
- Department
of Medicinal Chemistry and Molecular Pharmacology, Institute for Drug
Discovery, Center for Cancer Research, Purdue
University, West Lafayette, Indiana 47907, United States
| | - John R. Horton
- Department
of Epigenetics and Molecular Carcinogenesis, University of Texas MD Anderson Cancer Center, Houston, Texas 77030, United States
| | - Dan Yu
- Department
of Epigenetics and Molecular Carcinogenesis, University of Texas MD Anderson Cancer Center, Houston, Texas 77030, United States
| | - Taraneh Hajian
- Drug
Discovery Program, Ontario Institute for
Cancer Research, Toronto, ON M5G 0A3, Canada
| | - Masoud Vedadi
- Department
of Pharmacology and Toxicology, University
of Toronto, Toronto, ON M5S 1A8, Canada
- Drug
Discovery Program, Ontario Institute for
Cancer Research, Toronto, ON M5G 0A3, Canada
| | - Dante Rotili
- Department
of Drug Chemistry and Technologies, Sapienza
University of Rome, P.le A. Moro 5, 00185 Rome, Italy
| | - Antonello Mai
- Department
of Drug Chemistry and Technologies, Sapienza
University of Rome, P.le A. Moro 5, 00185 Rome, Italy
- Pasteur Institute,
Cenci-Bolognetti Foundation, Sapienza University
of Rome, P.le A. Moro 5, 00185 Rome, Italy
| | - Robert M. Blumenthal
- Department
of Medical Microbiology and Immunology and Program in Bioinformatics, The University of Toledo College of Medicine and Life
Sciences, Toledo, Ohio 43614, United States
| | - Xing Zhang
- Department
of Epigenetics and Molecular Carcinogenesis, University of Texas MD Anderson Cancer Center, Houston, Texas 77030, United States
| | - Rong Huang
- Department
of Medicinal Chemistry and Molecular Pharmacology, Institute for Drug
Discovery, Center for Cancer Research, Purdue
University, West Lafayette, Indiana 47907, United States
| | - Xiaodong Cheng
- Department
of Epigenetics and Molecular Carcinogenesis, University of Texas MD Anderson Cancer Center, Houston, Texas 77030, United States
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3
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Zhou J, Horton JR, Yu D, Ren R, Blumenthal RM, Zhang X, Cheng X. Repurposing epigenetic inhibitors to target the Clostridioides difficile-specific DNA adenine methyltransferase and sporulation regulator CamA. Epigenetics 2021; 17:970-981. [PMID: 34523387 PMCID: PMC9487755 DOI: 10.1080/15592294.2021.1976910] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Epigenetically targeted therapeutic development, particularly for SAM-dependent methylations of DNA, mRNA and histones has been proceeding rapidly for cancer treatments over the past few years. However, this approach has barely begun to be exploited for developing new antibiotics, despite an overwhelming global need to counter antimicrobial resistance. Here, we explore whether SAM analogues, some of which are in (pre)clinical studies as inhibitors of human epigenetic enzymes, can also inhibit Clostridioides difficile-specific DNA adenine methyltransferase (CamA), a sporulation regulator present in all C. difficile genomes sequenced to date, but found in almost no other bacteria. We found that SGC0946 (an inhibitor of DOT1L), JNJ-64619178 (an inhibitor of PRMT5) and SGC8158 (an inhibitor of PRMT7) inhibit CamA enzymatic activity in vitro at low micromolar concentrations. Structural investigation of the ternary complexes of CamA-DNA in the presence of SGC0946 or SGC8158 revealed conformational rearrangements of the N-terminal arm, with no apparent disturbance of the active site. This N-terminal arm and its modulation of exchanges between SAM (the methyl donor) and SAH (the reaction product) during catalysis of methyl transfer are, to date, unique to CamA. Our work presents a substantial first step in generating potent and selective inhibitors of CamA that would serve in the near term as chemical probes to investigate the cellular mechanism(s) of CamA in controlling spore formation and colonization, and eventually as therapeutic antivirulence agents useful in treating C. difficile infection.
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Affiliation(s)
- Jujun Zhou
- Department of Epigenetics and Molecular Carcinogenesis, University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - John R Horton
- Department of Epigenetics and Molecular Carcinogenesis, University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Dan Yu
- Department of Epigenetics and Molecular Carcinogenesis, University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Ren Ren
- Department of Epigenetics and Molecular Carcinogenesis, University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Robert M Blumenthal
- Department of Medical Microbiology and Immunology, and Program in Bioinformatics, The University of Toledo College of Medicine and Life Sciences, Toledo, OH USA
| | - Xing Zhang
- Department of Epigenetics and Molecular Carcinogenesis, University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Xiaodong Cheng
- Department of Epigenetics and Molecular Carcinogenesis, University of Texas MD Anderson Cancer Center, Houston, TX, USA
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Czernecki D, Bonhomme F, Kaminski PA, Delarue M. Characterization of a triad of genes in cyanophage S-2L sufficient to replace adenine by 2-aminoadenine in bacterial DNA. Nat Commun 2021; 12:4710. [PMID: 34354070 PMCID: PMC8342488 DOI: 10.1038/s41467-021-25064-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Accepted: 07/21/2021] [Indexed: 11/09/2022] Open
Abstract
Cyanophage S-2L is known to profoundly alter the biophysical properties of its DNA by replacing all adenines (A) with 2-aminoadenines (Z), which still pair with thymines but with a triple hydrogen bond. It was recently demonstrated that a homologue of adenylosuccinate synthetase (PurZ) and a dATP triphosphohydrolase (DatZ) are two important pieces of the metabolism of 2-aminoadenine, participating in the synthesis of ZTGC-DNA. Here, we determine that S-2L PurZ can use either dATP or ATP as a source of energy, thereby also depleting the pool of nucleotides in dATP. Furthermore, we identify a conserved gene (mazZ) located between purZ and datZ genes in S-2L and related phage genomes. We show that it encodes a (d)GTP-specific diphosphohydrolase, thereby providing the substrate of PurZ in the 2-aminoadenine synthesis pathway. High-resolution crystal structures of S-2L PurZ and MazZ with their respective substrates provide a rationale for their specificities. The Z-cluster made of these three genes - datZ, mazZ and purZ - was expressed in E. coli, resulting in a successful incorporation of 2-aminoadenine in the bacterial chromosomal and plasmidic DNA. This work opens the possibility to study synthetic organisms containing ZTGC-DNA.
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Affiliation(s)
- Dariusz Czernecki
- Unit of Architecture and Dynamics of Biological Macromolecules, CNRS UMR 3528, 25-28 rue du Docteur Roux, Institut Pasteur, Paris, France
- Sorbonne Université, Collège Doctoral, ED 515, Paris, France
| | - Frédéric Bonhomme
- Unit of Epigenetic Chemical Biology, CNRS UMR 3523, 25-28 rue du Docteur Roux, Institut Pasteur, Paris, France
| | - Pierre-Alexandre Kaminski
- Unit of Biology of Pathogenic Gram-Positive Bacteria, CNRS UMR 2001, 25-28 rue du Docteur Roux, Institut Pasteur, Paris, France
| | - Marc Delarue
- Unit of Architecture and Dynamics of Biological Macromolecules, CNRS UMR 3528, 25-28 rue du Docteur Roux, Institut Pasteur, Paris, France.
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Zhou J, Horton JR, Blumenthal RM, Zhang X, Cheng X. Clostridioides difficile specific DNA adenine methyltransferase CamA squeezes and flips adenine out of DNA helix. Nat Commun 2021; 12:3436. [PMID: 34103525 PMCID: PMC8187626 DOI: 10.1038/s41467-021-23693-w] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2021] [Accepted: 05/13/2021] [Indexed: 12/13/2022] Open
Abstract
Clostridioides difficile infections are an urgent medical problem. The newly discovered C. difficile adenine methyltransferase A (CamA) is specified by all C. difficile genomes sequenced to date (>300), but is rare among other bacteria. CamA is an orphan methyltransferase, unassociated with a restriction endonuclease. CamA-mediated methylation at CAAAAA is required for normal sporulation, biofilm formation, and intestinal colonization by C. difficile. We characterized CamA kinetic parameters, and determined its structure bound to DNA containing the recognition sequence. CamA contains an N-terminal domain for catalyzing methyl transfer, and a C-terminal DNA recognition domain. Major and minor groove DNA contacts in the recognition site involve base-specific hydrogen bonds, van der Waals contacts and the Watson-Crick pairing of a rearranged A:T base pair. These provide sufficient sequence discrimination to ensure high specificity. Finally, the surprisingly weak binding of the methyl donor S-adenosyl-L-methionine (SAM) might provide avenues for inhibiting CamA activity using SAM analogs.
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Affiliation(s)
- Jujun Zhou
- Department of Epigenetics and Molecular Carcinogenesis, University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - John R Horton
- Department of Epigenetics and Molecular Carcinogenesis, University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Robert M Blumenthal
- Department of Medical Microbiology and Immunology, and Program in Bioinformatics, The University of Toledo College of Medicine and Life Sciences, Toledo, OH, USA
| | - Xing Zhang
- Department of Epigenetics and Molecular Carcinogenesis, University of Texas MD Anderson Cancer Center, Houston, TX, USA.
| | - Xiaodong Cheng
- Department of Epigenetics and Molecular Carcinogenesis, University of Texas MD Anderson Cancer Center, Houston, TX, USA.
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Zhou J, Zhang X, Xiong E, Yu P, Li X, Chen J. SDR-recycling signal amplification for highly sensitive methyltransferase activity assay. J Electroanal Chem (Lausanne) 2016. [DOI: 10.1016/j.jelechem.2016.06.019] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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7
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Liu W, Lai H, Huang R, Zhao C, Wang Y, Weng X, Zhou X. DNA methyltransferase activity detection based on fluorescent silver nanocluster hairpin-shaped DNA probe with 5’-C-rich/G-rich-3’ tails. Biosens Bioelectron 2015; 68:736-740. [DOI: 10.1016/j.bios.2015.02.005] [Citation(s) in RCA: 59] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2014] [Revised: 01/25/2015] [Accepted: 02/05/2015] [Indexed: 12/31/2022]
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8
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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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9
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Terrazas M, Eritja R. Synthesis and properties of small interfering RNA duplexes carrying 5-ethyluridine residues. Mol Divers 2010; 15:677-86. [PMID: 21080069 DOI: 10.1007/s11030-010-9290-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2010] [Accepted: 10/22/2010] [Indexed: 11/30/2022]
Abstract
Oligoribonucleotides carrying 5-ethyluridine units were prepared using solid-phase phosphoramidite chemistry. The introduction of the tert-butyldimethylsilyl group at the 2'-OH position proceeded in good yield and very high 2'-regioselectivity. RNA duplexes carrying 5-ethyluridine either at the sense or the guide strands display RNAi activity comparable to or slightly better than that of unmodified RNA duplexes. Gene suppression experiments using luciferase targets in SH-SY5Y cells show that the ethyl group is generally well accepted at all positions although a small decrease in RNA interference activity is observed when one 5-ethylU residue is incorporated in the 3' overhangs.
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Affiliation(s)
- Montserrat Terrazas
- Institute for Research in Biomedicine (IRB Barcelona), Institute for Advanced Chemistry of Catalonia (IQAC-CSIC), Networking Center on Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN), Baldiri i Reixac 10, 08028 Barcelona, Spain
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10
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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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Humeny A, Beck C, Becker CM, Jeltsch A. Detection and analysis of enzymatic DNA methylation of oligonucleotide substrates by matrix-assisted laser desorption ionization time-of-flight mass spectrometry. Anal Biochem 2003; 313:160-6. [PMID: 12576072 DOI: 10.1016/s0003-2697(02)00568-7] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF) mass spectrometry was employed to analyze DNA methylation carried out by the Escherichia coli dam DNA methyltransferase using oligonucleotide substrates with molecular masses of 5000-10,000 Da per strand. The mass spectrometry assay offers several advantages: (i) it directly shows the methylation as the increase in the mass of the substrate DNA, (ii) it is nonradioactive, (iii) it is quantitative, and (iv) it can be automated for high-throughput applications. Since unmethylated and methylated DNA are detected, the ratio of methylation can be determined directly and accurately. Furthermore, the assay allows detection individually of the methylation of several substrates in competition, offering an ideal setup to analyze the specificity of DNA interacting with enzymes. We could not identify methylation at any noncanonical site, indicating that the dam MTase is a very specific enzyme. Finally, MALDI-TOF mass spectrometry permitted assessment of the number of methyl groups incorporated into each DNA strand, thereby, allowing study of mechanistic details such as the processivity of the methylation reaction. We provide evidence that the dam MTase modifies DNA in a processive reaction, confirming earlier findings.
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Affiliation(s)
- Andreas Humeny
- Institut für Biochemie, Emil-Fischer-Zentrum, Friedrich-Alexander Universität Erlangen-Nürnberg, Fahrstrasse 17, 91054 Erlangen, Germany
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12
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Urig S, Gowher H, Hermann A, Beck C, Fatemi M, Humeny A, Jeltsch A. The Escherichia coli dam DNA methyltransferase modifies DNA in a highly processive reaction. J Mol Biol 2002; 319:1085-96. [PMID: 12079349 DOI: 10.1016/s0022-2836(02)00371-6] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The Escherichia coli dam adenine-N6 methyltransferase modifies DNA at GATC sequences. It is involved in post-replicative mismatch repair, control of DNA replication and gene regulation. We show that E. coli dam acts as a functional monomer and methylates only one strand of the DNA in each binding event. The preferred way of ternary complex assembly is that the enzyme first binds to DNA and then to S-adenosylmethionine. The enzyme methylates an oligonucleotide containing two dam sites and a 879 bp PCR product with four sites in a fully processive reaction. On lambda-DNA comprising 48,502 bp and 116 dam sites, E. coli dam scans 3000 dam sites per binding event in a random walk, that on average leads to a processive methylation of 55 sites. Processive methylation of DNA considerably accelerates DNA methylation. The highly processive mechanism of E. coli dam could explain why small amounts of E. coli dam are able to maintain the methylation state of dam sites during DNA replication. Furthermore, our data support the general rule that solitary DNA methyltransferase modify DNA processively whereas methyltransferases belonging to a restriction-modification system show a distributive mechanism, because processive methylation of DNA would interfere with the biological function of restriction-modification systems.
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Affiliation(s)
- Sabine Urig
- Institut für Biochemie, Fachbereich Biologie, Justus-Liebig-Universität, Heinrich-Buff-Ring 58, 35392 Giessen, Germany
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13
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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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Zinoviev VV, Evdokimov AA, Gorbunov YA, Malygin EG, Kossykh VG, Hattman S. Phage T4 DNA [N6-adenine] methyltransferase: kinetic studies using oligonucleotides containing native or modified recognition sites. Biol Chem 1998; 379:481-8. [PMID: 9628341 DOI: 10.1515/bchm.1998.379.4-5.481] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The DNA-[N6-adenine] methyltransferase of T4 phage (T4 Dam MTase) catalyzes methyl group transfer from S-adenosyl-L-methionine (AdoMet) to the N6-position of adenine in the palindromic sequence, GATC. We have investigated the effect of eliminating different structural components of the recognition site on the ability of a substrate to be bound and methylated by T4 Dam. For this purpose, steady state binding (by gel shift assays) and kinetic parameters of methylation (using the methyl donor, [3H-CH3]-AdoMet, at 25 degrees C) were studied using various synthetic duplex oligonucleotides containing some defect in the DNA-target site; e.g., the absence of an internucleotide phosphate or a nucleotide(s) within the recognition site, or a single stranded region. The salient results are summarized as follows: (1) Addition of T4 Dam to a complete reaction mixture (with a 20-mer duplex as substrate) resulted in a 'burst' of 3H-methylated product, followed by a constant rate of product formation that reflected establishment of steady-state conditions. This suggests that the rate-limiting step is release of product methylated DNA from the enzyme [and not the transfer of the methyl group]. (2) A number of the defects in duplex structure had only a weak influence on the binding and Km values, but strongly reduced the kcat. At the same time, several poorly bound duplexes retained good substrate characteristics, especially duplexes having uninterrupted GAT-sequences in both strands. Whereas having only one half of the recognition site element intact was sufficient for stable complex formation, the catalytic turnover process had a strict requirement for an uninterrupted GAT-sequence on both strands. (3) There was no correlation between Km and binding capability; the apparent Kd for some duplexes was 5-70 times higher than Km. This indicates that the T4 Dam methylation reaction can not be explained by a simple Michaelian scheme.
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Affiliation(s)
- V V Zinoviev
- Institute of Molecular Biology, State Research Center Vector, Novosibirsk, Russia
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Jeltsch A, Friedrich T, Roth M. Kinetics of methylation and binding of DNA by the EcoRV adenine-N6 methyltransferase. J Mol Biol 1998; 275:747-58. [PMID: 9480766 DOI: 10.1006/jmbi.1997.1492] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The EcoRV DNA methyltransferase (M.EcoRV) specifically methylates the first adenine within its recognition sequence GATATC. Methylation rates of DNA by this enzyme are strongly influenced by the length of oligonucleotide substrates employed. If substrates >20 bp compared to a 12mer substrate, the kcat/Km increases 100-fold, although the enzyme does not contact more than 12 base-pairs on the DNA. Single-turnover rates are higher than kcat values. M.EcoRV binding to DNA is fast but dissociation from the DNA is slow, demonstrating that the multiple-turnover rate is limited by the rate of product release. The kinetics of DNA binding by M.EcoRV are not in accordance with the thermodynamics binding constant, suggesting that the M.EcoRV-DNA complex is involved in a slow conformational change. The salt dependence of DNA binding is different for non-specific substrates (d ln(KAss)/d ln(cNaCl) = - 2, indicative of electrostatic interactions) and specific substrates (d ln(KAss)/d ln(cNaCl) = + 1, indicative of hydrophobic interactions). This result demonstrates that the M.EcoRV-DNA complex has a different conformation in both binding modes. M.EcoRV does not discriminate between hemimethylated and unmethylated substrates. Using the 20mer we have analyzed the temperature and pH dependence of the single-turnover rate constant of M.EcoRV-DNA methylation by M.EcoRV has an activation energy of 40 kJ/mol and its rate increases with increasing pH. The pH dependence reveals the presence of an ionizable residue with a pKa of 7.9, which must be unprotonated for catalysis. The rates of DNA methylation remain unchanged if an abasic site is introduced instead of the thymidine residue that is base-paired to the target adenine, demonstrating that flipping out the target adenine cannot contribute to the rate-limiting step of the enzymatic reaction.
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Affiliation(s)
- A Jeltsch
- Institut für Biochemie, Fachbereich Biologie, Justus-Liebig Universität, Heinrich-Buff Ring 58, Giessen, 35392, Germany
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Thielking V, Dubois S, Eritja R, Guschlbauer W. Dam methyltransferase from Escherichia coli: kinetic studies using modified DNA oligomers: nonmethylated substrates. Biol Chem 1997; 378:407-15. [PMID: 9191027 DOI: 10.1515/bchm.1997.378.5.407] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Steady-state kinetics of the N6-adenine Dam methyltransferase have been measured using as substrates non-self-complementary tetradecanucleotide duplexes that contain the GATC target sequence. Modifications in the GATC target sequence of one or both of the strands included substitution of guanine by hypoxanthine, thymine by uracil or 5-ethyl-uracil and adenine by diamino-purine (2-amino-adenine). Thermodynamic parameters for the 14-mer duplexes were also determined. DNA methylation of duplexes containing single dl for dG substitution of the Dam recognition site was little perturbed compared with the canonical substrate. Replacement of dG residues by dl in both strands resulted in a decrease of the specificity constant. Substitution in both strands appears to be cumulative. Substitution of the methyl-accepting adenine residues by 2-amino-adenine resulted in surprisingly little perturbation. Dam methyltransferase is rather tolerant to different substitutions. The results show much less spread than those for the analogous hemimethylated substrates studied previously (Marzabal et al., 1995). The absence of the methylation marker appears to be deleterious to the specificity of the transition state of the active complex, while the binding of the DNA substrate to the enzyme appears to be mostly determined by the thermodynamic stability of the DNA duplex.
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Affiliation(s)
- V Thielking
- CEA/Saclay, Service de Biochimie et Génétique Moléculaire, Gif-sur-Yvette, France
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Sawai H, Seki J, Ozaki H. Comparative studies of duplex and triplex formation of 2'-5' and 3'-5' linked oligoribonucleotides. J Biomol Struct Dyn 1996; 13:1043-51. [PMID: 8832387 DOI: 10.1080/07391102.1996.10508919] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
We have studied double and triple helix formation between 2'-5' or 3'-5' linked oligoriboadenylates and oligoribouridylates with chain length 7 or 10 by CD spectrometry. The complex formation depends on the type of linkage of oligoribonucleotides, chain length, concentration and molar ratio of the strands, temperature and the cationic concentration. Mixture of any linkage isomers of oligo(rA) and oligo(rU) in 1:1 molar ratio form duplex at 0.1 M NaCl. The duplex stability largely depends on the type of the linkages and is in the following order, [3'-5'] oligo(rA)-[3'-5'] oligo(rU) > [2'-5'] oligo(rA)-[3'-5'] oligo(rU) > [3'-5'] oligo(rA)-[2'-5'] oligo(rU) > [2'-5'] oligo(rA)-[2'-5'] oligo(rU). The higher cationic concentrations, 0.5 M MgCl2, stabilize the complex and either duplex or triplex is formed depending on the input strand ratio and the type of linkage. Thermodynamic parameters, DH and DS, for the complex formation between linkage isomers of oligo(rA) and oligo(rU) showed a linear relationship indicating an enthalpy-entropy compensation phenomena. The duplex and triplex composed of [2'-5'] oligo(rA) and [2'-5'] oligo(rU) exhibit different CD spectra compared to those of any others containing 3'-5' linkage, suggesting that the fully 2'-5' duplex and triplex may possess a unique conformation. We describe prebiological significance of the linkage isomers of RNA and selection of the 3'-5' linkage against 2'-5 linkage.
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Affiliation(s)
- H Sawai
- Department of Chemistry, Gunma University, Japan
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