1
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Wang WJ, Wang T, Zhao Y, Li BN, Chen DZ. Theoretical Insights into N-Glycoside Bond Cleavage of 5-Carboxycytosine by Thymine DNA Glycosylase: A QM/MM Study. J Phys Chem B 2024; 128:4621-4630. [PMID: 38697651 DOI: 10.1021/acs.jpcb.4c00221] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/05/2024]
Abstract
Thymine DNA glycosylase (TDG)-mediated excision of 5-formylcytosine and 5-carboxylcytosine (5-caC) is a critical step in active DNA demethylation. Herein, we employed a combined quantum mechanics/molecular mechanics approach to investigate the reaction mechanism of TDG-catalyzed N-glycosidic bond cleavage of 5-caC. The calculated results show that TDG-catalyzed 5-caC excision follows a concerted (SN2) mechanism in which glycosidic bond dissociation is coupled with nucleophile attack. Protonation of the 5-caC anion contributes to the cleavage of the N-glycoside bond, in which the N3-protonated zwitterion and imino tautomers are more favorable than carboxyl-protonated amino tautomers. This is consistent with the experimental data. Furthermore, our results reveal that the configuration rearrangement process of the protonated 5-caC would lower the stability of the N-glycoside bond and substantially reduce the barrier height for the subsequent C1'-N1 bond cleavage. This should be attributed to the smaller electrostatic repulsion between the leaving base and the negative phosphate group as a result of the structural rearrangement.
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Affiliation(s)
- Wen-Juan Wang
- College of Chemistry, Chemical Engineering and Materials Science, Collaborative Innovation Center of Functionalized Probes for Chemical Imaging in Universities of Shandong, Key Laboratory of Molecular and Nano Probes, Ministry of Education, Shandong Provincial Key Laboratory of Clean Production of Fine Chemicals, Shandong Normal University, Jinan 250014, P. R. China
| | - Tian Wang
- College of Chemistry, Chemical Engineering and Materials Science, Collaborative Innovation Center of Functionalized Probes for Chemical Imaging in Universities of Shandong, Key Laboratory of Molecular and Nano Probes, Ministry of Education, Shandong Provincial Key Laboratory of Clean Production of Fine Chemicals, Shandong Normal University, Jinan 250014, P. R. China
| | - Ying Zhao
- College of Chemistry, Chemical Engineering and Materials Science, Collaborative Innovation Center of Functionalized Probes for Chemical Imaging in Universities of Shandong, Key Laboratory of Molecular and Nano Probes, Ministry of Education, Shandong Provincial Key Laboratory of Clean Production of Fine Chemicals, Shandong Normal University, Jinan 250014, P. R. China
| | - Bi-Na Li
- College of Chemistry, Chemical Engineering and Materials Science, Collaborative Innovation Center of Functionalized Probes for Chemical Imaging in Universities of Shandong, Key Laboratory of Molecular and Nano Probes, Ministry of Education, Shandong Provincial Key Laboratory of Clean Production of Fine Chemicals, Shandong Normal University, Jinan 250014, P. R. China
| | - De-Zhan Chen
- College of Chemistry, Chemical Engineering and Materials Science, Collaborative Innovation Center of Functionalized Probes for Chemical Imaging in Universities of Shandong, Key Laboratory of Molecular and Nano Probes, Ministry of Education, Shandong Provincial Key Laboratory of Clean Production of Fine Chemicals, Shandong Normal University, Jinan 250014, P. R. China
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2
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Li NN, Lun DX, Gong N, Meng G, Du XY, Wang H, Bao X, Li XY, Song JW, Hu K, Li L, Li SY, Liu W, Zhu W, Zhang Y, Li J, Yao T, Mou L, Han X, Hao F, Hu Y, Liu L, Zhu H, Wu Y, Liu B. Targeting the chromatin structural changes of antitumor immunity. J Pharm Anal 2024; 14:100905. [PMID: 38665224 PMCID: PMC11043877 DOI: 10.1016/j.jpha.2023.11.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2023] [Revised: 09/28/2023] [Accepted: 11/21/2023] [Indexed: 04/28/2024] Open
Abstract
Epigenomic imbalance drives abnormal transcriptional processes, promoting the onset and progression of cancer. Although defective gene regulation generally affects carcinogenesis and tumor suppression networks, tumor immunogenicity and immune cells involved in antitumor responses may also be affected by epigenomic changes, which may have significant implications for the development and application of epigenetic therapy, cancer immunotherapy, and their combinations. Herein, we focus on the impact of epigenetic regulation on tumor immune cell function and the role of key abnormal epigenetic processes, DNA methylation, histone post-translational modification, and chromatin structure in tumor immunogenicity, and introduce these epigenetic research methods. We emphasize the value of small-molecule inhibitors of epigenetic modulators in enhancing antitumor immune responses and discuss the challenges of developing treatment plans that combine epigenetic therapy and immunotherapy through the complex interaction between cancer epigenetics and cancer immunology.
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Affiliation(s)
- Nian-nian Li
- Weifang People's Hospital, Weifang, Shandong, 261000, China
- School of Life Sciences, Nankai University, Tianjin, 300071, China
| | - Deng-xing Lun
- Weifang People's Hospital, Weifang, Shandong, 261000, China
| | - Ningning Gong
- Weifang Traditional Chinese Medicine Hospital, Weifang, Shandong, 261000, China
| | - Gang Meng
- Shaanxi Key Laboratory of Sericulture, Ankang University, Ankang, Shaanxi, 725000, China
| | - Xin-ying Du
- Weifang People's Hospital, Weifang, Shandong, 261000, China
| | - He Wang
- Weifang People's Hospital, Weifang, Shandong, 261000, China
| | - Xiangxiang Bao
- Weifang People's Hospital, Weifang, Shandong, 261000, China
| | - Xin-yang Li
- Guizhou Education University, Guiyang, 550018, China
| | - Ji-wu Song
- Weifang People's Hospital, Weifang, Shandong, 261000, China
| | - Kewei Hu
- Weifang Traditional Chinese Medicine Hospital, Weifang, Shandong, 261000, China
| | - Lala Li
- Guizhou Normal University, Guiyang, 550025, China
| | - Si-ying Li
- Weifang People's Hospital, Weifang, Shandong, 261000, China
| | - Wenbo Liu
- Weifang People's Hospital, Weifang, Shandong, 261000, China
| | - Wanping Zhu
- Weifang People's Hospital, Weifang, Shandong, 261000, China
| | - Yunlong Zhang
- School of Medical Imaging, Weifang Medical University, Weifang, Shandong, 261053, China
| | - Jikai Li
- Department of Bone and Soft Tissue Oncology, Tianjin Hospital, Tianjin, 300299, China
| | - Ting Yao
- School of Life Sciences, Nankai University, Tianjin, 300071, China
- Teda Institute of Biological Sciences & Biotechnology, Nankai University, Tianjin, 300457, China
| | - Leming Mou
- Weifang People's Hospital, Weifang, Shandong, 261000, China
| | - Xiaoqing Han
- Weifang People's Hospital, Weifang, Shandong, 261000, China
| | - Furong Hao
- Weifang People's Hospital, Weifang, Shandong, 261000, China
| | - Yongcheng Hu
- Weifang People's Hospital, Weifang, Shandong, 261000, China
| | - Lin Liu
- School of Life Sciences, Nankai University, Tianjin, 300071, China
| | - Hongguang Zhu
- Weifang People's Hospital, Weifang, Shandong, 261000, China
| | - Yuyun Wu
- Xinqiao Hospital of Army Military Medical University, Chongqing, 400038, China
| | - Bin Liu
- Weifang People's Hospital, Weifang, Shandong, 261000, China
- School of Life Sciences, Nankai University, Tianjin, 300071, China
- Teda Institute of Biological Sciences & Biotechnology, Nankai University, Tianjin, 300457, China
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3
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Demir M, Russelburg LP, Lin WJ, Trasviña-Arenas C, Huang B, Yuen P, Horvath M, David S. Structural snapshots of base excision by the cancer-associated variant MutY N146S reveal a retaining mechanism. Nucleic Acids Res 2023; 51:1034-1049. [PMID: 36631987 PMCID: PMC9943663 DOI: 10.1093/nar/gkac1246] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2022] [Revised: 11/18/2022] [Accepted: 12/16/2022] [Indexed: 01/13/2023] Open
Abstract
DNA glycosylase MutY plays a critical role in suppression of mutations resulted from oxidative damage, as highlighted by cancer-association of the human enzyme. MutY requires a highly conserved catalytic Asp residue for excision of adenines misinserted opposite 8-oxo-7,8-dihydroguanine (OG). A nearby Asn residue hydrogen bonds to the catalytic Asp in structures of MutY and its mutation to Ser is an inherited variant in human MUTYH associated with colorectal cancer. We captured structural snapshots of N146S Geobacillus stearothermophilus MutY bound to DNA containing a substrate, a transition state analog and enzyme-catalyzed abasic site products to provide insight into the base excision mechanism of MutY and the role of Asn. Surprisingly, despite the ability of N146S to excise adenine and purine (P) in vitro, albeit at slow rates, N146S-OG:P complex showed a calcium coordinated to the purine base altering its conformation to inhibit hydrolysis. We obtained crystal structures of N146S Gs MutY bound to its abasic site product by removing the calcium from crystals of N146S-OG:P complex to initiate catalysis in crystallo or by crystallization in the absence of calcium. The product structures of N146S feature enzyme-generated β-anomer abasic sites that support a retaining mechanism for MutY-catalyzed base excision.
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Affiliation(s)
- Merve Demir
- Department of Chemistry, University of California, Davis, CA 95616, USA
| | - L Peyton Russelburg
- School of Biological Sciences, University of Utah, Salt Lake City, UT 84112, USA
| | - Wen-Jen Lin
- Department of Chemistry, University of California, Davis, CA 95616, USA
| | | | - Beili Huang
- Department of Chemistry, University of California, Davis, CA 95616, USA
| | - Philip K Yuen
- Department of Chemistry, University of California, Davis, CA 95616, USA
| | - Martin P Horvath
- School of Biological Sciences, University of Utah, Salt Lake City, UT 84112, USA
| | - Sheila S David
- Department of Chemistry, University of California, Davis, CA 95616, USA
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4
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Pidugu LS, Servius HW, Sevdalis SE, Cook ME, Varney KM, Pozharski E, Drohat AC. Characterizing inhibitors of human AP endonuclease 1. PLoS One 2023; 18:e0280526. [PMID: 36652434 PMCID: PMC9847973 DOI: 10.1371/journal.pone.0280526] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2022] [Accepted: 12/30/2022] [Indexed: 01/19/2023] Open
Abstract
AP endonuclease 1 (APE1) processes DNA lesions including apurinic/apyrimidinic sites and 3´-blocking groups, mediating base excision repair and single strand break repair. Much effort has focused on developing specific inhibitors of APE1, which could have important applications in basic research and potentially lead to clinical anticancer agents. We used structural, biophysical, and biochemical methods to characterize several reported inhibitors, including 7-nitroindole-2-carboxylic acid (CRT0044876), given its small size, reported potency, and widespread use for studying APE1. Intriguingly, NMR chemical shift perturbation (CSP) experiments show that CRT0044876 and three similar indole-2-carboxylic acids bind a pocket distal from the APE1 active site. A crystal structure confirms these findings and defines the pose for 5-nitroindole-2-carboxylic acid. However, dynamic light scattering experiments show the indole compounds form colloidal aggregates that could bind (sequester) APE1, causing nonspecific inhibition. Endonuclease assays show the compounds lack significant APE1 inhibition under conditions (detergent) that disrupt aggregation. Thus, binding of the indole-2-carboxylic acids at the remote pocket does not inhibit APE1 repair activity. Myricetin also forms aggregates and lacks APE1 inhibition under aggregate-disrupting conditions. Two other reported compounds (MLS000552981, MLS000419194) inhibit APE1 in vitro with low micromolar IC50 and do not appear to aggregate in this concentration range. However, NMR CSP experiments indicate the compounds do not bind specifically to apo- or Mg2+-bound APE1, pointing to a non-specific mode of inhibition, possibly DNA binding. Our results highlight methods for rigorous interrogation of putative APE1 inhibitors and should facilitate future efforts to discover compounds that specifically inhibit this important repair enzyme.
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Affiliation(s)
- Lakshmi S. Pidugu
- Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, Maryland, United States of America
| | - Hardler W. Servius
- Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, Maryland, United States of America
| | - Spiridon E. Sevdalis
- Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, Maryland, United States of America
| | - Mary E. Cook
- Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, Maryland, United States of America
| | - Kristen M. Varney
- Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, Maryland, United States of America
| | - Edwin Pozharski
- Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, Maryland, United States of America
- Center for Biomolecular Therapeutics, Institute for Bioscience and Biotechnology Research, Rockville, Maryland, United States of America
- * E-mail: (EP); (ACD)
| | - Alexander C. Drohat
- Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, Maryland, United States of America
- * E-mail: (EP); (ACD)
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5
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Zhang Q, Zhang X, Ma F, Zhang CY. Advances in quantum dot-based biosensors for DNA-modifying enzymes assay. Coord Chem Rev 2022. [DOI: 10.1016/j.ccr.2022.214674] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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6
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Wang L, Song K, Yu J, Da LT. Computational investigations on target-site searching and recognition mechanisms by thymine DNA glycosylase during DNA repair process. Acta Biochim Biophys Sin (Shanghai) 2022; 54:796-806. [PMID: 35593467 PMCID: PMC9828053 DOI: 10.3724/abbs.2022050] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
DNA glycosylase, as one member of DNA repair machineries, plays an essential role in correcting mismatched/damaged DNA nucleotides by cleaving the N-glycosidic bond between the sugar and target nucleobase through the base excision repair (BER) pathways. Efficient corrections of these DNA lesions are critical for maintaining genome integrity and preventing premature aging and cancers. The target-site searching/recognition mechanisms and the subsequent conformational dynamics of DNA glycosylase, however, remain challenging to be characterized using experimental techniques. In this review, we summarize our recent studies of sequential structural changes of thymine DNA glycosylase (TDG) during the DNA repair process, achieved mostly by molecular dynamics (MD) simulations. Computational simulations allow us to reveal atomic-level structural dynamics of TDG as it approaches the target-site, and pinpoint the key structural elements responsible for regulating the translocation of TDG along DNA. Subsequently, upon locating the lesions, TDG adopts a base-flipping mechanism to extrude the mispaired nucleobase into the enzyme active-site. The constructed kinetic network model elucidates six metastable states during the base-extrusion process and suggests an active role of TDG in flipping the intrahelical nucleobase. Finally, the molecular mechanism of product release dynamics after catalysis is also summarized. Taken together, we highlight to what extent the computational simulations advance our knowledge and understanding of the molecular mechanism underlying the conformational dynamics of TDG, as well as the limitations of current theoretical work.
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Affiliation(s)
- Lingyan Wang
- Key Laboratory of Systems Biomedicine (Ministry of Education)Shanghai Center for Systems BiomedicineShanghai Jiao Tong UniversityShanghai200240China
| | - Kaiyuan Song
- Key Laboratory of Systems Biomedicine (Ministry of Education)Shanghai Center for Systems BiomedicineShanghai Jiao Tong UniversityShanghai200240China
| | - Jin Yu
- Department of Physics and AstronomyDepartment of ChemistryNSF-Simons Center for Multiscale Cell Fate ResearchUniversity of CaliforniaIrvineCA92697USA
| | - Lin-Tai Da
- Key Laboratory of Systems Biomedicine (Ministry of Education)Shanghai Center for Systems BiomedicineShanghai Jiao Tong UniversityShanghai200240China,Correspondence address. Tel: +86-21-34207348; E-mail:
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7
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Zhang Q, Liu F, Chen W, Miao H, Liang H, Liao Z, Zhang Z, Zhang B. The role of RNA m 5C modification in cancer metastasis. Int J Biol Sci 2021; 17:3369-3380. [PMID: 34512153 PMCID: PMC8416729 DOI: 10.7150/ijbs.61439] [Citation(s) in RCA: 68] [Impact Index Per Article: 22.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2021] [Accepted: 07/19/2021] [Indexed: 12/26/2022] Open
Abstract
Epigenetic modification plays a crucial regulatory role in the biological processes of eukaryotic cells. The recent characterization of DNA and RNA methylation is still ongoing. Tumor metastasis has long been an unconquerable feature in the fight against cancer. As an inevitable component of the epigenetic regulatory network, 5-methylcytosine is associated with multifarious cellular processes and systemic diseases, including cell migration and cancer metastasis. Recently, gratifying progress has been achieved in determining the molecular interactions between m5C writers (DNMTs and NSUNs), demethylases (TETs), readers (YTHDF2, ALYREF and YBX1) and RNAs. However, the underlying mechanism of RNA m5C methylation in cell mobility and metastasis remains unclear. The functions of m5C writers and readers are believed to regulate gene expression at the post-transcription level and are involved in cellular metabolism and movement. In this review, we emphatically summarize the recent updates on m5C components and related regulatory networks. The content will be focused on writers and readers of the RNA m5C modification and potential mechanisms in diseases. We will discuss relevant upstream and downstream interacting molecules and their associations with cell migration and metastasis.
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Affiliation(s)
- Qiaofeng Zhang
- Hepatic Surgery Center, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430030, China.,Hubei Province for the Clinical Medicine Research Center of Hepatic Surgery, Wuhan, Hubei 430030, China.,Hubei key laboratory of Hepato-Pancreato-Biliary Diseases, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430030, China
| | - Furong Liu
- Hepatic Surgery Center, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430030, China.,Hubei Province for the Clinical Medicine Research Center of Hepatic Surgery, Wuhan, Hubei 430030, China.,Hubei key laboratory of Hepato-Pancreato-Biliary Diseases, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430030, China
| | - Wei Chen
- Hepatic Surgery Center, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430030, China.,Hubei Province for the Clinical Medicine Research Center of Hepatic Surgery, Wuhan, Hubei 430030, China.,Hubei key laboratory of Hepato-Pancreato-Biliary Diseases, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430030, China
| | - Hongrui Miao
- Hepatic Surgery Center, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430030, China.,Hubei Province for the Clinical Medicine Research Center of Hepatic Surgery, Wuhan, Hubei 430030, China.,Hubei key laboratory of Hepato-Pancreato-Biliary Diseases, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430030, China
| | - Huifang Liang
- Hepatic Surgery Center, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430030, China.,Hubei Province for the Clinical Medicine Research Center of Hepatic Surgery, Wuhan, Hubei 430030, China.,Hubei key laboratory of Hepato-Pancreato-Biliary Diseases, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430030, China
| | - Zhibin Liao
- Hepatic Surgery Center, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430030, China.,Hubei Province for the Clinical Medicine Research Center of Hepatic Surgery, Wuhan, Hubei 430030, China.,Hubei key laboratory of Hepato-Pancreato-Biliary Diseases, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430030, China
| | - Zhanguo Zhang
- Hepatic Surgery Center, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430030, China.,Hubei Province for the Clinical Medicine Research Center of Hepatic Surgery, Wuhan, Hubei 430030, China.,Hubei key laboratory of Hepato-Pancreato-Biliary Diseases, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430030, China
| | - Bixiang Zhang
- Hepatic Surgery Center, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430030, China.,Hubei Province for the Clinical Medicine Research Center of Hepatic Surgery, Wuhan, Hubei 430030, China.,Hubei key laboratory of Hepato-Pancreato-Biliary Diseases, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430030, China
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8
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Pidugu LS, Bright H, Lin WJ, Majumdar C, Van Ostrand RP, David SS, Pozharski E, Drohat AC. Structural Insights into the Mechanism of Base Excision by MBD4. J Mol Biol 2021; 433:167097. [PMID: 34107280 PMCID: PMC8286355 DOI: 10.1016/j.jmb.2021.167097] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Revised: 05/24/2021] [Accepted: 06/01/2021] [Indexed: 11/28/2022]
Abstract
DNA glycosylases remove damaged or modified nucleobases by cleaving the N-glycosyl bond and the correct nucleotide is restored through subsequent base excision repair. In addition to excising threatening lesions, DNA glycosylases contribute to epigenetic regulation by mediating DNA demethylation and perform other important functions. However, the catalytic mechanism remains poorly defined for many glycosylases, including MBD4 (methyl-CpG binding domain IV), a member of the helix-hairpin-helix (HhH) superfamily. MBD4 excises thymine from G·T mispairs, suppressing mutations caused by deamination of 5-methylcytosine, and it removes uracil and modified uracils (e.g., 5-hydroxymethyluracil) mispaired with guanine. To investigate the mechanism of MBD4 we solved high-resolution structures of enzyme-DNA complexes at three stages of catalysis. Using a non-cleavable substrate analog, 2'-deoxy-pseudouridine, we determined the first structure of an enzyme-substrate complex for wild-type MBD4, which confirms interactions that mediate lesion recognition and suggests that a catalytic Asp, highly conserved in HhH enzymes, binds the putative nucleophilic water molecule and stabilizes the transition state. Observation that mutating the Asp (to Gly) reduces activity by 2700-fold indicates an important role in catalysis, but probably not one as the nucleophile in a double-displacement reaction, as previously suggested. Consistent with direct-displacement hydrolysis, a structure of the enzyme-product complex indicates a reaction leading to inversion of configuration. A structure with DNA containing 1-azadeoxyribose models a potential oxacarbenium-ion intermediate and suggests the Asp could facilitate migration of the electrophile towards the nucleophilic water. Finally, the structures provide detailed snapshots of the HhH motif, informing how these ubiquitous metal-binding elements mediate DNA binding.
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Affiliation(s)
- Lakshmi S Pidugu
- Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Hilary Bright
- Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Wen-Jen Lin
- Department of Chemistry, University of California Davis, Davis, CA 95616, USA
| | - Chandrima Majumdar
- Department of Chemistry, University of California Davis, Davis, CA 95616, USA
| | | | - Sheila S David
- Department of Chemistry, University of California Davis, Davis, CA 95616, USA
| | - Edwin Pozharski
- Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, MD 21201, USA; Center for Biomolecular Therapeutics, Institute for Bioscience and Biotechnology Research, Rockville, MD 20850, USA.
| | - Alexander C Drohat
- Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, MD 21201, USA.
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9
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Krajewski AE, Lee JK. Gas-Phase Experimental and Computational Studies of 5-Halouracils: Intrinsic Properties and Biological Implications. J Org Chem 2021; 86:6361-6370. [PMID: 33891415 DOI: 10.1021/acs.joc.1c00183] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The gas-phase acidity and proton affinity (PA) of 5-halouracils (5-fluorouracil, 5-chlorouracil, 5-bromouracil, and 5-iodouracil) have been examined using both theoretical and experimental methods. This work represents a comprehensive study of the thermochemical properties of these nucleobases. Other than 5-fluorouracil acidity, the intrinsic acidity and PA of these halouracils have not been heretofore measured; these new experimental data provide a benchmark for the computational values. Furthermore, we examine these 5-halouracils in the context of the enzyme thymine DNA glycosylase (TDG), which is an enzyme that protects the genome by cleaving these substrates from DNA. Our gas-phase results are compared and contrasted to TDG excision rates to afford insights into the TDG mechanism.
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Affiliation(s)
- Allison E Krajewski
- Department of Chemistry and Chemical Biology Rutgers, The State University of New Jersey, New Brunswick, New Jersey 08901, USA
| | - Jeehiun K Lee
- Department of Chemistry and Chemical Biology Rutgers, The State University of New Jersey, New Brunswick, New Jersey 08901, USA
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10
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Reading Targeted DNA Damage in the Active Demethylation Pathway: Role of Accessory Domains of Eukaryotic AP Endonucleases and Thymine-DNA Glycosylases. J Mol Biol 2020:S0022-2836(19)30720-X. [DOI: 10.1016/j.jmb.2019.12.020] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2019] [Revised: 11/24/2019] [Accepted: 12/05/2019] [Indexed: 01/07/2023]
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11
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Pidugu LS, Dai Q, Malik SS, Pozharski E, Drohat AC. Excision of 5-Carboxylcytosine by Thymine DNA Glycosylase. J Am Chem Soc 2019; 141:18851-18861. [PMID: 31693361 DOI: 10.1021/jacs.9b10376] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
5-Methylcytosine (mC) is an epigenetic mark that is written by methyltransferases, erased through passive and active mechanisms, and impacts transcription, development, diseases including cancer, and aging. Active DNA demethylation involves TET-mediated stepwise oxidation of mC to 5-hydroxymethylcytosine, 5-formylcytosine (fC), or 5-carboxylcytosine (caC), excision of fC or caC by thymine DNA glycosylase (TDG), and subsequent base excision repair. Many elements of this essential process are poorly defined, including TDG excision of caC. To address this problem, we solved high-resolution structures of human TDG bound to DNA with cadC (5-carboxyl-2'-deoxycytidine) flipped into its active site. The structures unveil detailed enzyme-substrate interactions that mediate recognition and removal of caC, many involving water molecules. Importantly, two water molecules contact a carboxylate oxygen of caC and are poised to facilitate acid-catalyzed caC excision. Moreover, a substrate-dependent conformational change in TDG modulates the hydrogen bond interactions for one of these waters, enabling productive interaction with caC. An Asn residue (N191) that is critical for caC excision is found to contact N3 and N4 of caC, suggesting a mechanism for acid-catalyzed base excision that features an N3-protonated form of caC but would be ineffective for C, mC, or hmC. We also investigated another Asn residue (N140) that is catalytically essential and strictly conserved in the TDG-MUG enzyme family. A structure of N140A-TDG bound to cadC DNA provides the first high-resolution insight into how enzyme-substrate interactions, including water molecules, are impacted by depleting the conserved Asn, informing its role in binding and addition of the nucleophilic water molecule.
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Affiliation(s)
- Lakshmi S Pidugu
- Department of Biochemistry and Molecular Biology , University of Maryland School of Medicine , Baltimore , Maryland 21201 , United States
| | - Qing Dai
- Department of Chemistry , The University of Chicago , Chicago , Illinois 60637 , United States
| | - Shuja S Malik
- Department of Biochemistry and Molecular Biology , University of Maryland School of Medicine , Baltimore , Maryland 21201 , United States
| | - Edwin Pozharski
- Department of Biochemistry and Molecular Biology , University of Maryland School of Medicine , Baltimore , Maryland 21201 , United States.,Center for Biomolecular Therapeutics , Institute for Bioscience and Biotechnology Research , Rockville , Maryland 20850 , United States
| | - Alexander C Drohat
- Department of Biochemistry and Molecular Biology , University of Maryland School of Medicine , Baltimore , Maryland 21201 , United States
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12
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Coey CT, Drohat AC. Defining the impact of sumoylation on substrate binding and catalysis by thymine DNA glycosylase. Nucleic Acids Res 2019; 46:5159-5170. [PMID: 29660017 PMCID: PMC6007377 DOI: 10.1093/nar/gky278] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2018] [Accepted: 04/04/2018] [Indexed: 01/22/2023] Open
Abstract
Thymine DNA glycosylase (TDG) excises thymine from mutagenic G·T mispairs generated by deamination of 5-methylcytosine (mC) and it removes two mC derivatives, 5−formylcytosine (fC) and 5−carboxylcytosine (caC), in a multistep pathway for DNA demethylation. TDG is modified by small ubiquitin-like modifier (SUMO) proteins, but the impact of sumoylation on TDG activity is poorly defined and the functions of TDG sumoylation remain unclear. We determined the effect of TDG sumoylation, by SUMO-1 or SUMO-2, on substrate binding and catalytic parameters. Single turnover experiments reveal that sumoylation dramatically impairs TDG base-excision activity, such that G·T activity is reduced by ≥45-fold and fC and caC are excised slowly, with a reaction half-life of ≥9 min (37°C). Fluorescence anisotropy studies reveal that unmodified TDG binds tightly to G·fC and G·caC substrates, with dissociation constants in the low nanomolar range. While sumoylation of TDG weakens substrate binding, the residual affinity is substantial and is comparable to that of biochemically-characterized readers of fC and caC. Our findings raise the possibility that sumoylation enables TDG to function, at least transiently, as reader of fC and caC. Notably, sumoylation could potentially facilitate TDG recruitment of other proteins, including transcription factors or epigenetic regulators, to these sites in DNA.
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Affiliation(s)
- Christopher T Coey
- Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Alexander C Drohat
- Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, MD 21201, USA.,Molecular and Structural Biology Program, University of Maryland Marlene and Stewart Greenebaum Comprehensive Cancer Center, Baltimore, MD 21201, USA
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13
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Da LT, Yu J. Base-flipping dynamics from an intrahelical to an extrahelical state exerted by thymine DNA glycosylase during DNA repair process. Nucleic Acids Res 2019; 46:5410-5425. [PMID: 29762710 PMCID: PMC6009601 DOI: 10.1093/nar/gky386] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2018] [Accepted: 04/30/2018] [Indexed: 12/17/2022] Open
Abstract
Thymine DNA glycosylase (TDG) is a DNA repair enzyme that excises a variety of mismatched or damaged nucleotides (nts), e.g. dU, dT, 5fC and 5caC. TDG is shown to play essential roles in maintaining genome integrity and correctly programming epigenetic modifications through DNA demethylation. After locating the lesions, TDG employs a base-flipping strategy to recognize the damaged nucleobases, whereby the interrogated nt is extruded from the DNA helical stack and binds into the TDG active site. The dynamic mechanism of the base-flipping process at an atomistic resolution, however, remains elusive. Here, we employ the Markov State Model (MSM) constructed from extensive all-atom molecular dynamics (MD) simulations to reveal the complete base-flipping process for a G.T mispair at a tens of microsecond timescale. Our studies identify critical intermediates of the mispaired dT during its extrusion process and reveal the key TDG residues involved in the inter-state transitions. Notably, we find an active role of TDG in promoting the intrahelical nt eversion, sculpturing the DNA backbone, and penetrating into the DNA minor groove. Three additional TDG substrates, namely dU, 5fC, and 5caC, are further tested to evaluate the substituent effects of various chemical modifications of the pyrimidine ring on base-flipping dynamics.
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Affiliation(s)
- Lin-Tai Da
- Key Laboratory of Systems Biomedicine (Ministry of Education), Shanghai Center for Systems Biomedicine, Shanghai JiaoTong University, 800 Dongchuan Road, Shanghai 200240, China
| | - Jin Yu
- Beijing Computational Science Research Center, Beijing 100193, China
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14
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Da LT, Shi Y, Ning G, Yu J. Dynamics of the excised base release in thymine DNA glycosylase during DNA repair process. Nucleic Acids Res 2019; 46:568-581. [PMID: 29253232 PMCID: PMC5778594 DOI: 10.1093/nar/gkx1261] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2017] [Accepted: 12/06/2017] [Indexed: 01/09/2023] Open
Abstract
Thymine DNA glycosylase (TDG) initiates base excision repair by cleaving the N-glycosidic bond between the sugar and target base. After catalysis, the release of excised base is a requisite step to terminate the catalytic cycle and liberate the TDG for the following enzymatic reactions. However, an atomistic-level understanding of the dynamics of the product release process in TDG remains unknown. Here, by employing molecular dynamics simulations combined with the Markov State Model, we reveal the dynamics of the thymine release after the excision at microseconds timescale and all-atom resolution. We identify several key metastable states of the thymine and its dominant releasing pathway. Notably, after replacing the TDG residue Gly142 with tyrosine, the thymine release is delayed compared to the wild-type (wt) TDG, as supported by our potential of mean force (PMF) calculations. These findings warrant further experimental tests to potentially trap the excised base in the active site of TDG after the catalysis, which had been unsuccessful by previous attempts. Finally, we extended our studies to other TDG products, including the uracil, 5hmU, 5fC and 5caC bases in order to compare the product release for different targeting bases in the TDG–DNA complex.
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Affiliation(s)
- Lin-Tai Da
- Key Laboratory of Systems Biomedicine (Ministry of Education), Shanghai Center for Systems Biomedicine, Shanghai JiaoTong University, 800 Dongchuan Road, Shanghai 200240, China
| | - Yi Shi
- Key Laboratory of Systems Biomedicine (Ministry of Education), Shanghai Center for Systems Biomedicine, Shanghai JiaoTong University, 800 Dongchuan Road, Shanghai 200240, China
| | - Guodong Ning
- Technical Center of Erlianhot Entry-exit Inspection and Quarantine Bureau, 1266 Qianjin North Road, Erlianhot, Inner Mongolia, China
| | - Jin Yu
- Beijing Computational Science Research Center, Beijing 100193, China
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15
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Naydenova E, Dietschreit JCB, Ochsenfeld C. Reaction Mechanism for the N-Glycosidic Bond Cleavage of 5-Formylcytosine by Thymine DNA Glycosylase. J Phys Chem B 2019; 123:4173-4179. [PMID: 31042033 DOI: 10.1021/acs.jpcb.8b11706] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Thymine DNA glycosylase (TDG) initiates the base excision repair mechanism for the deamination and oxidation products of cytosine and 5-methylcytosine. This enzyme has a key role in epigenetic regulation, and its catalytic inactivation results in, e.g., mice embryo lethality. Here, we employ molecular dynamics simulations and quantum mechanics/molecular mechanics calculations to investigate the reaction mechanism of the TDG-catalyzed N-glycosidic bond hydrolysis of the modified base 5-formylcytosine. Our results reveal a reaction pathway, which in its first step features a reorganization of the substrate that lowers the barrier height for the subsequent C1'-N1 bond dissociation. The suggested mechanism is consistent with the experimental data, as it is not acid-catalyzed and proceeds through an oxocarbenium-like transition state. It also provides insights into the catalytic roles of the Thr197 and Asn140 residues.
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Affiliation(s)
- Eli Naydenova
- Chair of Theoretical Chemistry, Department of Chemistry , University of Munich (LMU) , Butenandtstr. 7 , D-81377 Munich , Germany.,Center for Integrated Protein Science Munich (CIPSM) at the Department of Chemistry , University of Munich (LMU) , Butenandtstr. 5-13 , D-81377 Munich , Germany
| | - Johannes C B Dietschreit
- Chair of Theoretical Chemistry, Department of Chemistry , University of Munich (LMU) , Butenandtstr. 7 , D-81377 Munich , Germany.,Center for Integrated Protein Science Munich (CIPSM) at the Department of Chemistry , University of Munich (LMU) , Butenandtstr. 5-13 , D-81377 Munich , Germany
| | - Christian Ochsenfeld
- Chair of Theoretical Chemistry, Department of Chemistry , University of Munich (LMU) , Butenandtstr. 7 , D-81377 Munich , Germany.,Center for Integrated Protein Science Munich (CIPSM) at the Department of Chemistry , University of Munich (LMU) , Butenandtstr. 5-13 , D-81377 Munich , Germany
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16
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Dow BJ, Malik SS, Drohat AC. Defining the Role of Nucleotide Flipping in Enzyme Specificity Using 19F NMR. J Am Chem Soc 2019; 141:4952-4962. [PMID: 30841696 DOI: 10.1021/jacs.9b00146] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
A broad range of proteins employ nucleotide flipping to recognize specific sites in nucleic acids, including DNA glycosylases, which remove modified nucleobases to initiate base excision repair. Deamination, a pervasive mode of damage, typically generates lesions that are recognized by glycosylases as being foreign to DNA. However, deamination of 5-methylcytosine (mC) generates thymine, a canonical DNA base, presenting a challenge for damage recognition. Nevertheless, repair of mC deamination is important because the resulting G·T mispairs cause C → T transition mutations, and mC is abundant in all three domains of life. Countering this threat are three types of glycosylases that excise thymine from G·T mispairs, including thymine DNA glycosylase (TDG). These enzymes must minimize excision of thymine that is not generated by mC deamination, in A·T pairs and in polymerase-generated G·T mispairs. TDG preferentially removes thymine from DNA contexts in which cytosine methylation is prevalent, including CG and one non-CG site. This remarkable context specificity could be attained through modulation of nucleotide flipping, a reversible step that precedes base excision. We tested this idea using fluorine NMR and DNA containing 2'-fluoro-substituted nucleotides. We find that dT nucleotide flipping depends on DNA context and is efficient only in contexts known to feature cytosine methylation. We also show that a conserved Ala residue limits thymine excision by hindering nucleotide flipping. A linear free energy correlation reveals that TDG attains context specificity for thymine excision through modulation of nucleotide flipping. Our results provide a framework for characterizing nucleotide flipping in nucleic acids using 19F NMR.
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Affiliation(s)
- Blaine J Dow
- Department of Biochemistry and Molecular Biology , University of Maryland School of Medicine , Baltimore , Maryland 21201 , United States
| | - Shuja S Malik
- Department of Biochemistry and Molecular Biology , University of Maryland School of Medicine , Baltimore , Maryland 21201 , United States
| | - Alexander C Drohat
- Department of Biochemistry and Molecular Biology , University of Maryland School of Medicine , Baltimore , Maryland 21201 , United States
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17
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Hardwick JS, Lane AN, Brown T. Epigenetic Modifications of Cytosine: Biophysical Properties, Regulation, and Function in Mammalian DNA. Bioessays 2018; 40. [DOI: 10.1002/bies.201700199] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2017] [Revised: 12/13/2017] [Indexed: 12/21/2022]
Affiliation(s)
- Jack S. Hardwick
- Chemistry Research Laboratory; Department of Chemistry; University of Oxford; 12 Mansfield Road Oxford OX1 3TA UK
| | - Andrew N. Lane
- Department of Toxicology and Cancer Biology; University of Kentucky; 789 S. Limestone St. Lexington KY 40536 USA
| | - Tom Brown
- Chemistry Research Laboratory; Department of Chemistry; University of Oxford; 12 Mansfield Road Oxford OX1 3TA UK
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18
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Abstract
In mammals, DNA methylation in the form of 5-methylcytosine (5mC) can be actively reversed to unmodified cytosine (C) through TET dioxygenase-mediated oxidation of 5mC to 5-hydroxymethylcytosine (5hmC), 5-formylcytosine (5fC) and 5-carboxylcytosine (5caC), followed by replication-dependent dilution or thymine DNA glycosylase (TDG)-dependent base excision repair. In the past few years, biochemical and structural studies have revealed mechanistic insights into how TET and TDG mediate active DNA demethylation. Additionally, many regulatory mechanisms of this process have been identified. Technological advances in mapping and tracing the oxidized forms of 5mC allow further dissection of their functions. Furthermore, the biological functions of active DNA demethylation in various biological contexts have also been revealed. In this Review, we summarize the recent advances and highlight key unanswered questions.
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19
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Coey CT, Drohat AC. Kinetic Methods for Studying DNA Glycosylases Functioning in Base Excision Repair. Methods Enzymol 2017; 592:357-376. [PMID: 28668127 DOI: 10.1016/bs.mie.2017.03.016] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
Base excision repair (BER) is a conserved and ubiquitous pathway that is initiated by DNA glycosylases, which recognize and remove damaged or mismatched nucleobases, setting the stage for restoration of the correct DNA sequence by follow-on BER enzymes. DNA glycosylases employ a nucleotide-flipping step prior to cleavage of the N-glycosyl bond, and most exhibit slow release of the abasic DNA product and/or strong product inhibition. As such, studying the catalytic mechanism of these enzymes requires care in the design, execution, and interpretation of single- and multiple-turnover kinetics experiments, which is the topic of this chapter.
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Affiliation(s)
| | - Alexander C Drohat
- University of Maryland School of Medicine, Baltimore, MD, United States; Marlene and Stewart Greenebaum Cancer Center, University of Maryland School of Medicine, Baltimore, MD, United States.
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20
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SMUG2 DNA glycosylase from Pedobacter heparinus as a new subfamily of the UDG superfamily. Biochem J 2017; 474:923-938. [PMID: 28049757 DOI: 10.1042/bcj20160934] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2016] [Revised: 12/11/2016] [Accepted: 01/03/2017] [Indexed: 11/17/2022]
Abstract
Base deamination is a common type of DNA damage that occurs in all organisms. DNA repair mechanisms are essential to maintain genome integrity, in which the base excision repair (BER) pathway plays a major role in the removal of base damage. In the BER pathway, the uracil DNA glycosylase superfamily is responsible for excising the deaminated bases from DNA and generates apurinic/apyrimidinic (AP) sites. Using bioinformatics tools, we identified a family 3 SMUG1-like DNA glycoyslase from Pedobacter heparinus (named Phe SMUG2), which displays catalytic activities towards DNA containing uracil or hypoxanthine/xanthine. Phylogenetic analyses show that SMUG2 enzymes are closely related to family 3 SMUG1s but belong to a distinct branch of the family. The high-resolution crystal structure of the apoenzyme reveals that the general fold of Phe SMUG2 resembles SMUG1s, yet with several distinct local structural differences. Mutational studies, coupled with structural modeling, identified several important amino acid residues for glycosylase activity. Substitution of G65 with a tyrosine results in loss of all glycosylase activity. The crystal structure of the G65Y mutant suggests a potential misalignment at the active site due to the mutation. The relationship between the new subfamily and other families in the UDG superfamily is discussed. The present study provides new mechanistic insight into the molecular mechanism of the UDG superfamily.
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21
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Zanello P. The competition between chemistry and biology in assembling iron–sulfur derivatives. Molecular structures and electrochemistry. Part V. {[Fe4S4](SCysγ)4} proteins. Coord Chem Rev 2017. [DOI: 10.1016/j.ccr.2016.10.003] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
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22
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Sulfolobus acidocaldarius UDG Can Remove dU from the RNA Backbone: Insight into the Specific Recognition of Uracil Linked with Deoxyribose. Genes (Basel) 2017; 8:genes8010038. [PMID: 28106786 PMCID: PMC5295032 DOI: 10.3390/genes8010038] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2016] [Revised: 01/01/2017] [Accepted: 01/11/2017] [Indexed: 12/12/2022] Open
Abstract
Sulfolobus acidocaldarius encodes family 4 and 5 uracil-DNA glycosylase (UDG). Two recombinant S. acidocaldarius UDGs (SacUDG) were prepared and biochemically characterized using oligonucleotides carrying a deaminated base. Both SacUDGs can remove deoxyuracil (dU) base from both double-stranded DNA and single-stranded DNA. Interestingly, they can remove U linked with deoxyribose from single-stranded RNA backbone, suggesting that the riboses on the backbone have less effect on the recognition of dU and hydrolysis of the C-N glycosidic bond. However, the removal of rU from DNA backbone is inefficient, suggesting strong steric hindrance comes from the 2′ hydroxyl of ribose linked to uracil. Both SacUDGs cannot remove 2,2′-anhydro uridine, hypoxanthine, and 7-deazaxanthine from single-stranded DNA and single-stranded DNA. Compared with the family 2 MUG, other family UDGs have an extra N-terminal structure consisting of about 50 residues. Removal of the 46 N-terminal residues of family 5 SacUDG resulted in only a 40% decrease in activity, indicating that the [4Fe-4S] cluster and truncated secondary structure are not the key elements in hydrolyzing the glycosidic bond. Combining our biochemical and structural results with those of other groups, we discussed the UDGs’ catalytic mechanism and the possible repair reactions of deaminated bases in prokaryotes.
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23
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Wang LJ, Wang ZY, Zhang Q, Tang B, Zhang CY. Cyclic enzymatic repairing-mediated dual-signal amplification for real-time monitoring of thymine DNA glycosylase. Chem Commun (Camb) 2017; 53:3878-3881. [DOI: 10.1039/c7cc00946a] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
We develop a new fluorescence method for real-time monitoring of thymine DNA glycosylase activity through cyclic enzymatic repairing-mediated dual-signal amplification.
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Affiliation(s)
- Li-Juan Wang
- College of Chemistry
- Chemical Engineering and Materials Science
- Collaborative Innovation Center of Functionalized Probes for Chemical Imaging in Universities of Shandong
- Key Laboratory of Molecular and Nano Probes
- Ministry of Education
| | - Zi-Yue Wang
- College of Chemistry
- Chemical Engineering and Materials Science
- Collaborative Innovation Center of Functionalized Probes for Chemical Imaging in Universities of Shandong
- Key Laboratory of Molecular and Nano Probes
- Ministry of Education
| | | | - Bo Tang
- College of Chemistry
- Chemical Engineering and Materials Science
- Collaborative Innovation Center of Functionalized Probes for Chemical Imaging in Universities of Shandong
- Key Laboratory of Molecular and Nano Probes
- Ministry of Education
| | - Chun-Yang Zhang
- College of Chemistry
- Chemical Engineering and Materials Science
- Collaborative Innovation Center of Functionalized Probes for Chemical Imaging in Universities of Shandong
- Key Laboratory of Molecular and Nano Probes
- Ministry of Education
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24
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Lin S, Kang TS, Lu L, Wang W, Ma DL, Leung CH. A G-quadruplex-selective luminescent probe with an anchor tail for the switch-on detection of thymine DNA glycosylase activity. Biosens Bioelectron 2016; 86:849-857. [DOI: 10.1016/j.bios.2016.07.082] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2016] [Revised: 07/23/2016] [Accepted: 07/23/2016] [Indexed: 11/25/2022]
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25
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Pidugu LS, Flowers JW, Coey CT, Pozharski E, Greenberg MM, Drohat AC. Structural Basis for Excision of 5-Formylcytosine by Thymine DNA Glycosylase. Biochemistry 2016; 55:6205-6208. [PMID: 27805810 DOI: 10.1021/acs.biochem.6b00982] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Thymine DNA glycosylase (TDG) is a base excision repair enzyme with key functions in epigenetic regulation. Performing a critical step in a pathway for active DNA demethylation, TDG removes 5-formylcytosine and 5-carboxylcytosine, oxidized derivatives of 5-methylcytosine that are generated by TET (ten-eleven translocation) enzymes. We determined a crystal structure of TDG bound to DNA with a noncleavable (2'-fluoroarabino) analogue of 5-formyldeoxycytidine flipped into its active site, revealing how it recognizes and hydrolytically excises fC. Together with previous structural and biochemical findings, the results illustrate how TDG employs an adaptable active site to excise a broad variety of nucleobases from DNA.
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Affiliation(s)
- Lakshmi S Pidugu
- Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine , Baltimore, Maryland 21201, United States
| | - Joshua W Flowers
- Department of Chemistry, Johns Hopkins University , 3400 North Charles Street, Baltimore, Maryland 21218, United States
| | - Christopher T Coey
- Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine , Baltimore, Maryland 21201, United States
| | - Edwin Pozharski
- Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine , Baltimore, Maryland 21201, United States.,Center for Biomolecular Therapeutics, Institute for Bioscience and Biotechnology Research , Rockville, Maryland 20850, United States
| | - Marc M Greenberg
- Department of Chemistry, Johns Hopkins University , 3400 North Charles Street, Baltimore, Maryland 21218, United States
| | - Alexander C Drohat
- Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine , Baltimore, Maryland 21201, United States
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26
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Coey CT, Malik SS, Pidugu LS, Varney KM, Pozharski E, Drohat AC. Structural basis of damage recognition by thymine DNA glycosylase: Key roles for N-terminal residues. Nucleic Acids Res 2016; 44:10248-10258. [PMID: 27580719 PMCID: PMC5137436 DOI: 10.1093/nar/gkw768] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2016] [Revised: 08/20/2016] [Accepted: 08/22/2016] [Indexed: 11/13/2022] Open
Abstract
Thymine DNA Glycosylase (TDG) is a base excision repair enzyme functioning in DNA repair and epigenetic regulation. TDG removes thymine from mutagenic G·T mispairs arising from deamination of 5-methylcytosine (mC), and it processes other deamination-derived lesions including uracil (U). Essential for DNA demethylation, TDG excises 5-formylcytosine and 5-carboxylcytosine, derivatives of mC generated by Tet (ten-eleven translocation) enzymes. Here, we report structural and functional studies of TDG82-308, a new construct containing 29 more N-terminal residues than TDG111-308, the construct used for previous structures of DNA-bound TDG. Crystal structures and NMR experiments demonstrate that most of these N-terminal residues are disordered, for substrate- or product-bound TDG82-308 Nevertheless, G·T substrate affinity and glycosylase activity of TDG82-308 greatly exceeds that of TDG111-308 and is equivalent to full-length TDG. We report the first high-resolution structures of TDG in an enzyme-substrate complex, for G·U bound to TDG82-308 (1.54 Å) and TDG111-308 (1.71 Å), revealing new enzyme-substrate contacts, direct and water-mediated. We also report a structure of the TDG82-308 product complex (1.70 Å). TDG82-308 forms unique enzyme-DNA interactions, supporting its value for structure-function studies. The results advance understanding of how TDG recognizes and removes modified bases from DNA, particularly those resulting from deamination.
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Affiliation(s)
- Christopher T Coey
- Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Shuja S Malik
- Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Lakshmi S Pidugu
- Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Kristen M Varney
- Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, MD 21201, USA.,University of Maryland Marlene and Stewart Greenebaum Cancer Center, Baltimore, MD 21201, USA.,Center for Biomolecular Therapeutics, Institute for Bioscience and Biotechnology Research, Rockville, MD 20850, USA
| | - Edwin Pozharski
- Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, MD 21201, USA .,University of Maryland Marlene and Stewart Greenebaum Cancer Center, Baltimore, MD 21201, USA.,Center for Biomolecular Therapeutics, Institute for Bioscience and Biotechnology Research, Rockville, MD 20850, USA
| | - Alexander C Drohat
- Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, MD 21201, USA .,University of Maryland Marlene and Stewart Greenebaum Cancer Center, Baltimore, MD 21201, USA
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27
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Drohat AC, Coey CT. Role of Base Excision "Repair" Enzymes in Erasing Epigenetic Marks from DNA. Chem Rev 2016; 116:12711-12729. [PMID: 27501078 DOI: 10.1021/acs.chemrev.6b00191] [Citation(s) in RCA: 76] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Base excision repair (BER) is one of several DNA repair pathways found in all three domains of life. BER counters the mutagenic and cytotoxic effects of damage that occurs continuously to the nitrogenous bases in DNA, and its critical role in maintaining genomic integrity is well established. However, BER also performs essential functions in processes other than DNA repair, where it acts on naturally modified bases in DNA. A prominent example is the central role of BER in mediating active DNA demethylation, a multistep process that erases the epigenetic mark 5-methylcytosine (5mC), and derivatives thereof, converting them back to cytosine. Herein, we review recent advances in the understanding of how BER mediates this critical component of epigenetic regulation in plants and animals.
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Affiliation(s)
- Alexander C Drohat
- Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine , Baltimore, Maryland 21201, United States
| | - Christopher T Coey
- Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine , Baltimore, Maryland 21201, United States
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28
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McLaughlin D, Coey CT, Yang WC, Drohat AC, Matunis MJ. Characterizing Requirements for Small Ubiquitin-like Modifier (SUMO) Modification and Binding on Base Excision Repair Activity of Thymine-DNA Glycosylase in Vivo. J Biol Chem 2016; 291:9014-24. [PMID: 26917720 DOI: 10.1074/jbc.m115.706325] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2015] [Indexed: 12/12/2022] Open
Abstract
Thymine-DNA glycosylase (TDG) plays critical roles in DNA base excision repair and DNA demethylation. It has been proposed, based on structural studies and in vitro biochemistry, that sumoylation is required for efficient TDG enzymatic turnover following base excision. However, whether sumoylation is required for TDG activity in vivo has not previously been tested. We have developed an in vivo assay for TDG activity that takes advantage of its recently discovered role in DNA demethylation and selective recognition and repair of 5-carboxylcytosine. Using this assay, we investigated the role of sumoylation in regulating TDG activity through the use of TDG mutants defective for sumoylation and Small Ubiquitin-like Modifier (SUMO) binding and by altering TDG sumoylation through SUMO and SUMO protease overexpression experiments. Our findings indicate that sumoylation and SUMO binding are not essential for TDG-mediated excision and repair of 5-carboxylcytosine bases. Moreover, in vitro assays revealed that apurinic/apyrimidinic nuclease 1 provides nearly maximum stimulation of TDG processing of G·caC substrates. Thus, under our assay conditions, apurinic/apyrimidinic nuclease 1-mediated stimulation or other mechanisms sufficiently alleviate TDG product inhibition and promote its enzymatic turnover in vivo.
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Affiliation(s)
- Dylan McLaughlin
- From the Department of Biochemistry and Molecular Biology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland 21205 and
| | - Christopher T Coey
- the Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, Maryland 21201
| | - Wei-Chih Yang
- From the Department of Biochemistry and Molecular Biology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland 21205 and
| | - Alexander C Drohat
- the Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, Maryland 21201
| | - Michael J Matunis
- From the Department of Biochemistry and Molecular Biology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland 21205 and
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