1
|
Villiger L, Joung J, Koblan L, Weissman J, Abudayyeh OO, Gootenberg JS. CRISPR technologies for genome, epigenome and transcriptome editing. Nat Rev Mol Cell Biol 2024; 25:464-487. [PMID: 38308006 DOI: 10.1038/s41580-023-00697-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/18/2023] [Indexed: 02/04/2024]
Abstract
Our ability to edit genomes lags behind our capacity to sequence them, but the growing understanding of CRISPR biology and its application to genome, epigenome and transcriptome engineering is narrowing this gap. In this Review, we discuss recent developments of various CRISPR-based systems that can transiently or permanently modify the genome and the transcriptome. The discovery of further CRISPR enzymes and systems through functional metagenomics has meaningfully broadened the applicability of CRISPR-based editing. Engineered Cas variants offer diverse capabilities such as base editing, prime editing, gene insertion and gene regulation, thereby providing a panoply of tools for the scientific community. We highlight the strengths and weaknesses of current CRISPR tools, considering their efficiency, precision, specificity, reliance on cellular DNA repair mechanisms and their applications in both fundamental biology and therapeutics. Finally, we discuss ongoing clinical trials that illustrate the potential impact of CRISPR systems on human health.
Collapse
Affiliation(s)
- Lukas Villiger
- McGovern Institute for Brain Research, Massachusetts Institute of Technology Cambridge, Cambridge, MA, USA
| | - Julia Joung
- Whitehead Institute for Biomedical Research, Cambridge, MA, USA
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Luke Koblan
- Whitehead Institute for Biomedical Research, Cambridge, MA, USA
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Jonathan Weissman
- Whitehead Institute for Biomedical Research, Cambridge, MA, USA
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, USA
- Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, MA, USA
- David H. Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Omar O Abudayyeh
- McGovern Institute for Brain Research, Massachusetts Institute of Technology Cambridge, Cambridge, MA, USA.
| | - Jonathan S Gootenberg
- McGovern Institute for Brain Research, Massachusetts Institute of Technology Cambridge, Cambridge, MA, USA.
| |
Collapse
|
2
|
Zhang Q, Hu J, Li DL, Qiu JG, Jiang BH, Zhang CY. Construction of single-molecule counting-based biosensors for DNA-modifying enzymes: A review. Anal Chim Acta 2024; 1298:342395. [PMID: 38462345 DOI: 10.1016/j.aca.2024.342395] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2023] [Revised: 02/18/2024] [Accepted: 02/19/2024] [Indexed: 03/12/2024]
Abstract
DNA-modifying enzymes act as critical regulators in a wide range of genetic functions (e.g., DNA damage & repair, DNA replication), and their aberrant expression may interfere with regular genetic functions and induce various malignant diseases including cancers. DNA-modifying enzymes have emerged as the potential biomarkers in early diagnosis of diseases and new therapeutic targets in genomic research. Consequently, the development of highly specific and sensitive biosensors for the detection of DNA-modifying enzymes is of great importance for basic biomedical research, disease diagnosis, and drug discovery. Single-molecule fluorescence detection has been widely implemented in the field of molecular diagnosis due to its simplicity, high sensitivity, visualization capability, and low sample consumption. In this paper, we summarize the recent advances in single-molecule counting-based biosensors for DNA-modifying enzyme (i.e, alkaline phosphatase, DNA methyltransferase, DNA glycosylase, flap endonuclease 1, and telomerase) assays in the past four years (2019 - 2023). We highlight the principles and applications of these biosensors, and give new insight into the future challenges and perspectives in the development of single-molecule counting-based biosensors.
Collapse
Affiliation(s)
- Qian Zhang
- Translational Medicine Center, The First Affiliated Hospital of Zhengzhou University, The Academy of Medical Sciences, Zhengzhou University, Zhengzhou, 450052, Henan, China; College of Chemistry, Chemical Engineering and Materials Science, Shandong Normal University, Jinan, 250014, China
| | - Juan Hu
- School of Chemistry and Chemical Engineering, Southeast University, Nanjing, 211189, China
| | - Dong-Ling Li
- School of Chemistry and Chemical Engineering, Southeast University, Nanjing, 211189, China
| | - Jian-Ge Qiu
- Translational Medicine Center, The First Affiliated Hospital of Zhengzhou University, The Academy of Medical Sciences, Zhengzhou University, Zhengzhou, 450052, Henan, China
| | - Bing-Hua Jiang
- Translational Medicine Center, The First Affiliated Hospital of Zhengzhou University, The Academy of Medical Sciences, Zhengzhou University, Zhengzhou, 450052, Henan, China.
| | - Chun-Yang Zhang
- School of Chemistry and Chemical Engineering, Southeast University, Nanjing, 211189, China.
| |
Collapse
|
3
|
Chen L, Hong M, Luan C, Gao H, Ru G, Guo X, Zhang D, Zhang S, Li C, Wu J, Randolph PB, Sousa AA, Qu C, Zhu Y, Guan Y, Wang L, Liu M, Feng B, Song G, Liu DR, Li D. Adenine transversion editors enable precise, efficient A•T-to-C•G base editing in mammalian cells and embryos. Nat Biotechnol 2024; 42:638-650. [PMID: 37322276 DOI: 10.1038/s41587-023-01821-9] [Citation(s) in RCA: 38] [Impact Index Per Article: 38.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2023] [Accepted: 05/08/2023] [Indexed: 06/17/2023]
Abstract
Base editors have substantial promise in basic research and as therapeutic agents for the correction of pathogenic mutations. The development of adenine transversion editors has posed a particular challenge. Here we report a class of base editors that enable efficient adenine transversion, including precise A•T-to-C•G editing. We found that a fusion of mouse alkyladenine DNA glycosylase (mAAG) with nickase Cas9 and deaminase TadA-8e catalyzed adenosine transversion in specific sequence contexts. Laboratory evolution of mAAG significantly increased A-to-C/T conversion efficiency up to 73% and expanded the targeting scope. Further engineering yielded adenine-to-cytosine base editors (ACBEs), including a high-accuracy ACBE-Q variant, that precisely install A-to-C transversions with minimal Cas9-independent off-targeting effects. ACBEs mediated high-efficiency installation or correction of five pathogenic mutations in mouse embryos and human cell lines. Founder mice showed 44-56% average A-to-C edits and allelic frequencies of up to 100%. Adenosine transversion editors substantially expand the capabilities and possible applications of base editing technology.
Collapse
Affiliation(s)
- Liang Chen
- Shanghai Frontiers Science Center of Genome Editing and Cell Therapy, Shanghai Key Laboratory of Regulatory Biology, Institute of Biomedical Sciences and School of Life Sciences, East China Normal University, Shanghai, China
| | - Mengjia Hong
- Shanghai Frontiers Science Center of Genome Editing and Cell Therapy, Shanghai Key Laboratory of Regulatory Biology, Institute of Biomedical Sciences and School of Life Sciences, East China Normal University, Shanghai, China
| | - Changming Luan
- Shanghai Frontiers Science Center of Genome Editing and Cell Therapy, Shanghai Key Laboratory of Regulatory Biology, Institute of Biomedical Sciences and School of Life Sciences, East China Normal University, Shanghai, China
| | - Hongyi Gao
- Shanghai Frontiers Science Center of Genome Editing and Cell Therapy, Shanghai Key Laboratory of Regulatory Biology, Institute of Biomedical Sciences and School of Life Sciences, East China Normal University, Shanghai, China
| | - Gaomeng Ru
- Shanghai Frontiers Science Center of Genome Editing and Cell Therapy, Shanghai Key Laboratory of Regulatory Biology, Institute of Biomedical Sciences and School of Life Sciences, East China Normal University, Shanghai, China
| | - Xinyuan Guo
- Shanghai Frontiers Science Center of Genome Editing and Cell Therapy, Shanghai Key Laboratory of Regulatory Biology, Institute of Biomedical Sciences and School of Life Sciences, East China Normal University, Shanghai, China
| | - Dujuan Zhang
- Shanghai Frontiers Science Center of Genome Editing and Cell Therapy, Shanghai Key Laboratory of Regulatory Biology, Institute of Biomedical Sciences and School of Life Sciences, East China Normal University, Shanghai, China
| | - Shun Zhang
- Shanghai Frontiers Science Center of Genome Editing and Cell Therapy, Shanghai Key Laboratory of Regulatory Biology, Institute of Biomedical Sciences and School of Life Sciences, East China Normal University, Shanghai, China
| | - Changwei Li
- Department of Orthopedics, Shanghai Key Laboratory for Prevention and Treatment of Bone and Joint Diseases with Integrated Chinese-Western Medicine, Shanghai Institute of Traumatology and Orthopedics, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China
| | - Jun Wu
- Shanghai Frontiers Science Center of Genome Editing and Cell Therapy, Shanghai Key Laboratory of Regulatory Biology, Institute of Biomedical Sciences and School of Life Sciences, East China Normal University, Shanghai, China
| | - Peyton B Randolph
- Merkin Institute of Transformative Technologies in Healthcare, Broad Institute of MIT and Harvard, Cambridge, MA, USA
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, USA
- Howard Hughes Medical Institute, Cambridge, MA, USA
| | - Alexander A Sousa
- Merkin Institute of Transformative Technologies in Healthcare, Broad Institute of MIT and Harvard, Cambridge, MA, USA
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, USA
- Howard Hughes Medical Institute, Cambridge, MA, USA
| | - Chao Qu
- Shanghai Frontiers Science Center of Genome Editing and Cell Therapy, Shanghai Key Laboratory of Regulatory Biology, Institute of Biomedical Sciences and School of Life Sciences, East China Normal University, Shanghai, China
| | - Yifan Zhu
- Shanghai Frontiers Science Center of Genome Editing and Cell Therapy, Shanghai Key Laboratory of Regulatory Biology, Institute of Biomedical Sciences and School of Life Sciences, East China Normal University, Shanghai, China
| | - Yuting Guan
- Shanghai Frontiers Science Center of Genome Editing and Cell Therapy, Shanghai Key Laboratory of Regulatory Biology, Institute of Biomedical Sciences and School of Life Sciences, East China Normal University, Shanghai, China
| | - Liren Wang
- Shanghai Frontiers Science Center of Genome Editing and Cell Therapy, Shanghai Key Laboratory of Regulatory Biology, Institute of Biomedical Sciences and School of Life Sciences, East China Normal University, Shanghai, China
| | - Mingyao Liu
- Shanghai Frontiers Science Center of Genome Editing and Cell Therapy, Shanghai Key Laboratory of Regulatory Biology, Institute of Biomedical Sciences and School of Life Sciences, East China Normal University, Shanghai, China
- BRL Medicine, Inc., Shanghai, China
| | - Bo Feng
- School of Biomedical Sciences, Faculty of Medicine, Chinese University of Hong Kong, Hong Kong, China
| | - Gaojie Song
- Shanghai Frontiers Science Center of Genome Editing and Cell Therapy, Shanghai Key Laboratory of Regulatory Biology, Institute of Biomedical Sciences and School of Life Sciences, East China Normal University, Shanghai, China
| | - David R Liu
- Merkin Institute of Transformative Technologies in Healthcare, Broad Institute of MIT and Harvard, Cambridge, MA, USA
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, USA
- Howard Hughes Medical Institute, Cambridge, MA, USA
| | - Dali Li
- Shanghai Frontiers Science Center of Genome Editing and Cell Therapy, Shanghai Key Laboratory of Regulatory Biology, Institute of Biomedical Sciences and School of Life Sciences, East China Normal University, Shanghai, China.
| |
Collapse
|
4
|
Liu B, Qi Y, Wang X, Gao X, Yao Y, Zhang L. Investigation of the Flipping Dynamics of 1, N6-Ethenoadenine in Alkyladenine DNA Glycosylase. J Phys Chem B 2024; 128:1606-1617. [PMID: 38331753 DOI: 10.1021/acs.jpcb.3c06853] [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: 02/10/2024]
Abstract
Alkyladenine DNA glycosylase (AAG) is an essential enzyme responsible for maintaining genome integrity by repairing several DNA lesions damaged by alkylation or deamination. Understanding how it can recognize and excise the lesions thus lays the foundation for therapeutic treatment against lesion-associated diseases or cancers. However, the molecular details of how the lesion can be distinguished from the matched base by AAG and how it enters the cleavage site, ready for excision, are not fully elucidated. In this study, we have revealed the molecular details of the flipping dynamics of 1, N6-ethenoadenine (εA) not only in the form of free double-stranded DNA (dsDNA) but also in the form of the AAG-dsDNA complex. Our MD simulations and PMF calculations have shown that the flipping of εA and dA is thermodynamically disfavored in the free dsDNA, even though εA has a lower flipping energy barrier than dA. By sharp contrast, the flipping of εA is thermodynamically favored in AAG with an obvious free energy drop, while dA is equally stabilized before and after the flipping. Moreover, a comparison of the PMFs in the forms of free dsDNA and the AAG-dsDNA complex has pinpointed the role of AAG in discriminating εA against dA and facilitating the flipping of εA. Besides, the flipping process is simulated along the major and minor grooves, and our results have additionally demonstrated that the flipping is not directional in the free dsDNA while flipping along the major groove is kinetically more favorable than the minor groove in the AAG-dsDNA complex. Overall, our study has offered molecular insights into the flipping dynamics of εA and revealed its discrimination mechanism by AAG, which is expected to guide further enzyme engineering for therapeutic applications.
Collapse
Affiliation(s)
- Bin Liu
- State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yanping Qi
- State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Xiaowei Wang
- Department of Chemical and Biological Engineering and Department of Mathematics, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon 999077, Hong Kong
| | - Xin Gao
- Computational Bioscience Research Center, King Abdullah University of Science and Technology (KAUST), Thuwal 23955, Saudi Arabia
- Computer, Electrical and Mathematical Sciences and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal 23955, Saudi Arabia
| | - Yuan Yao
- Department of Chemical and Biological Engineering and Department of Mathematics, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon 999077, Hong Kong
| | - Lu Zhang
- State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002, China
- University of Chinese Academy of Sciences, Beijing 100049, China
- Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, Fuzhou, Fujian 361005, China
| |
Collapse
|
5
|
Tong H, Liu N, Wei Y, Zhou Y, Li Y, Wu D, Jin M, Cui S, Li H, Li G, Zhou J, Yuan Y, Zhang H, Shi L, Yao X, Yang H. Programmable deaminase-free base editors for G-to-Y conversion by engineered glycosylase. Natl Sci Rev 2023; 10:nwad143. [PMID: 37404457 PMCID: PMC10317176 DOI: 10.1093/nsr/nwad143] [Citation(s) in RCA: 19] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2023] [Revised: 05/13/2023] [Accepted: 05/13/2023] [Indexed: 07/06/2023] Open
Abstract
Current DNA base editors contain nuclease and DNA deaminase that enables deamination of cytosine (C) or adenine (A), but no method for guanine (G) or thymine (T) editing is available at present. Here we developed a deaminase-free glycosylase-based guanine base editor (gGBE) with G editing ability, by fusing Cas9 nickase with engineered N-methylpurine DNA glycosylase protein (MPG). By several rounds of MPG mutagenesis via unbiased and rational screening using an intron-split EGFP reporter, we demonstrated that gGBE with engineered MPG could increase G editing efficiency by more than 1500 fold. Furthermore, this gGBE exhibited high base editing efficiency (up to 81.2%) and high G-to-T or G-to-C (i.e. G-to-Y) conversion ratio (up to 0.95) in both cultured human cells and mouse embryos. Thus, we have provided a proof-of-concept of a new base editing approach by endowing the engineered DNA glycosylase the capability to selectively excise a new type of substrate.
Collapse
Affiliation(s)
| | | | | | | | | | | | - Ming Jin
- Department of Neurology and Institute of Neurology of First Affiliated Hospital, Institute of Neuroscience, and Fujian Key Laboratory of Molecular Neurology, Fujian Medical University, Fuzhou 350004, China
| | - Shuna Cui
- HuidaGene Therapeutics Co., Ltd., Shanghai 200131, China
| | - Hengbin Li
- HuidaGene Therapeutics Co., Ltd., Shanghai 200131, China
| | - Guoling Li
- HuidaGene Therapeutics Co., Ltd., Shanghai 200131, China
| | - Jingxing Zhou
- HuidaGene Therapeutics Co., Ltd., Shanghai 200131, China
| | - Yuan Yuan
- HuidaGene Therapeutics Co., Ltd., Shanghai 200131, China
| | - Hainan Zhang
- HuidaGene Therapeutics Co., Ltd., Shanghai 200131, China
| | - Linyu Shi
- HuidaGene Therapeutics Co., Ltd., Shanghai 200131, China
| | - Xuan Yao
- HuidaGene Therapeutics Co., Ltd., Shanghai 200131, China
| | | |
Collapse
|
6
|
Zheng L, Tsai B, Gao N. Structural and mechanistic insights into the DNA glycosylase AAG-mediated base excision in nucleosome. Cell Discov 2023; 9:62. [PMID: 37339965 DOI: 10.1038/s41421-023-00560-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2022] [Accepted: 05/06/2023] [Indexed: 06/22/2023] Open
Abstract
The engagement of a DNA glycosylase with a damaged DNA base marks the initiation of base excision repair. Nucleosome-based packaging of eukaryotic genome obstructs DNA accessibility, and how DNA glycosylases locate the substrate site on nucleosomes is currently unclear. Here, we report cryo-electron microscopy structures of nucleosomes bearing a deoxyinosine (DI) in various geometric positions and structures of them in complex with the DNA glycosylase AAG. The apo nucleosome structures show that the presence of a DI alone perturbs nucleosomal DNA globally, leading to a general weakening of the interface between DNA and the histone core and greater flexibility for the exit/entry of the nucleosomal DNA. AAG makes use of this nucleosomal plasticity and imposes further local deformation of the DNA through formation of the stable enzyme-substrate complex. Mechanistically, local distortion augmentation, translation/rotational register shift and partial opening of the nucleosome are employed by AAG to cope with substrate sites in fully exposed, occluded and completely buried positions, respectively. Our findings reveal the molecular basis for the DI-induced modification on the structural dynamics of the nucleosome and elucidate how the DNA glycosylase AAG accesses damaged sites on the nucleosome with different solution accessibility.
Collapse
Affiliation(s)
- Lvqin Zheng
- State Key Laboratory of Membrane Biology, Peking-Tsinghua Center for Life Sciences, School of Life Sciences, Peking University, Beijing, China
- Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China
| | - Bin Tsai
- State Key Laboratory of Membrane Biology, Peking-Tsinghua Center for Life Sciences, School of Life Sciences, Peking University, Beijing, China
| | - Ning Gao
- State Key Laboratory of Membrane Biology, Peking-Tsinghua Center for Life Sciences, School of Life Sciences, Peking University, Beijing, China.
| |
Collapse
|
7
|
Abstract
DNA-editing enzymes perform chemical reactions on DNA nucleobases. These reactions can change the genetic identity of the modified base or modulate gene expression. Interest in DNA-editing enzymes has burgeoned in recent years due to the advent of clustered regularly interspaced short palindromic repeat-associated (CRISPR-Cas) systems, which can be used to direct their DNA-editing activity to specific genomic loci of interest. In this review, we showcase DNA-editing enzymes that have been repurposed or redesigned and developed into programmable base editors. These include deaminases, glycosylases, methyltransferases, and demethylases. We highlight the astounding degree to which these enzymes have been redesigned, evolved, and refined and present these collective engineering efforts as a paragon for future efforts to repurpose and engineer other families of enzymes. Collectively, base editors derived from these DNA-editing enzymes facilitate programmable point mutation introduction and gene expression modulation by targeted chemical modification of nucleobases.
Collapse
Affiliation(s)
- Kartik L Rallapalli
- Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California, USA;
| | - Alexis C Komor
- Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California, USA;
| |
Collapse
|
8
|
Nikkel DJ, Wetmore SD. Distinctive Formation of a DNA-Protein Cross-Link during the Repair of DNA Oxidative Damage: Insights into Human Disease from MD Simulations and QM/MM Calculations. J Am Chem Soc 2023. [PMID: 37285289 DOI: 10.1021/jacs.3c01773] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Reactive oxygen species damage DNA and result in health issues. The major damage product, 8-oxo-7,8-dihydroguanine (8oG), is repaired by human adenine DNA glycosylase homologue (MUTYH). Although MUTYH misfunction is associated with a genetic disorder called MUTYH-associated polyposis (MAP) and MUTYH is a potential target for cancer drugs, the catalytic mechanism required to develop disease treatments is debated in the literature. This study uses molecular dynamics simulations and quantum mechanics/molecular mechanics techniques initiated from DNA-protein complexes that represent different stages of the repair pathway to map the catalytic mechanism of the wild-type MUTYH bacterial homologue (MutY). This multipronged computational approach characterizes a DNA-protein cross-linking mechanism that is consistent with all previous experimental data and is a distinct pathway across the broad class of monofunctional glycosylase repair enzymes. In addition to clarifying how the cross-link is formed, accommodated by the enzyme, and hydrolyzed for product release, our calculations rationalize why cross-link formation is favored over immediate glycosidic bond hydrolysis, the accepted mechanism for all other monofunctional DNA glycosylases to date. Calculations on the Y126F mutant MutY highlight critical roles for active site residues throughout the reaction, while investigation of the N146S mutant rationalizes the connection between the analogous N224S MUTYH mutation and MAP. In addition to furthering our knowledge of the chemistry associated with a devastating disorder, the structural information gained about the distinctive MutY mechanism compared to other repair enzymes represents an important step for the development of specific and potent small-molecule inhibitors as cancer therapeutics.
Collapse
Affiliation(s)
- Dylan J Nikkel
- Department of Chemistry and Biochemistry, University of Lethbridge, 4401 University Drive West, Lethbridge, Alberta T1K 3M4, Canada
| | - Stacey D Wetmore
- Department of Chemistry and Biochemistry, University of Lethbridge, 4401 University Drive West, Lethbridge, Alberta T1K 3M4, Canada
| |
Collapse
|
9
|
Song YQ, Li GD, Niu D, Chen F, Jing S, Wai Wong VK, Wang W, Leung CH. A robust luminescent assay for screening alkyladenine DNA glycosylase inhibitors to overcome DNA repair and temozolomide drug resistance. J Pharm Anal 2023; 13:514-522. [PMID: 37305785 PMCID: PMC10257196 DOI: 10.1016/j.jpha.2023.04.010] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2023] [Revised: 03/22/2023] [Accepted: 04/15/2023] [Indexed: 06/13/2023] Open
Abstract
Temozolomide (TMZ) is an anticancer agent used to treat glioblastoma, typically following radiation therapy and/or surgical resection. However, despite its effectiveness, at least 50% of patients do not respond to TMZ, which is associated with repair and/or tolerance of TMZ-induced DNA lesions. Studies have demonstrated that alkyladenine DNA glycosylase (AAG), an enzyme that triggers the base excision repair (BER) pathway by excising TMZ-induced N3-methyladenine (3meA) and N7-methylguanine lesions, is overexpressed in glioblastoma tissues compared to normal tissues. Therefore, it is essential to develop a rapid and efficient screening method for AAG inhibitors to overcome TMZ resistance in glioblastomas. Herein, we report a robust time-resolved photoluminescence platform for identifying AAG inhibitors with improved sensitivity compared to conventional steady-state spectroscopic methods. As a proof-of-concept, this assay was used to screen 1440 food and drug administration-approved drugs against AAG, resulting in the repurposing of sunitinib as a potential AAG inhibitor. Sunitinib restored glioblastoma (GBM) cancer cell sensitivity to TMZ, inhibited GBM cell proliferation and stem cell characteristics, and induced GBM cell cycle arrest. Overall, this strategy offers a new method for the rapid identification of small-molecule inhibitors of BER enzyme activities that can prevent false negatives due to a fluorescent background.
Collapse
Affiliation(s)
- Ying-Qi Song
- State Key Laboratory of Quality Research in Chinese Medicine, Institute of Chinese Medical Sciences, University of Macau, Macao, 999078, China
| | - Guo-Dong Li
- State Key Laboratory of Quality Research in Chinese Medicine, Institute of Chinese Medical Sciences, University of Macau, Macao, 999078, China
| | - Dou Niu
- State Key Laboratory of Quality Research in Chinese Medicine, Institute of Chinese Medical Sciences, University of Macau, Macao, 999078, China
| | - Feng Chen
- State Key Laboratory of Quality Research in Chinese Medicine, Institute of Chinese Medical Sciences, University of Macau, Macao, 999078, China
| | - Shaozhen Jing
- Institute of Medical Research, Northwestern Polytechnical University, Xi'an, 710072, China
| | - Vincent Kam Wai Wong
- Dr. Neher's Biophysics Laboratory for Innovative Drug Discovery, State Key Laboratory of Quality Research in Chinese Medicine, Macau University of Science and Technology, Macao, 999078, China
| | - Wanhe Wang
- Institute of Medical Research, Northwestern Polytechnical University, Xi'an, 710072, China
| | - Chung-Hang Leung
- State Key Laboratory of Quality Research in Chinese Medicine, Institute of Chinese Medical Sciences, University of Macau, Macao, 999078, China
- Department of Biomedical Sciences, Faculty of Health Sciences, University of Macau, Macao, 999078, China
| |
Collapse
|
10
|
Zhou L, Yao S. Recent advances in therapeutic CRISPR-Cas9 genome editing: mechanisms and applications. MOLECULAR BIOMEDICINE 2023; 4:10. [PMID: 37027099 PMCID: PMC10080534 DOI: 10.1186/s43556-023-00115-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2022] [Accepted: 01/04/2023] [Indexed: 04/08/2023] Open
Abstract
Recently, clustered regularly interspaced palindromic repeats (CRISPR)-Cas9 derived editing tools had significantly improved our ability to make desired changes in the genome. Wild-type Cas9 protein recognizes the target genomic loci and induced local double strand breaks (DSBs) in the guidance of small RNA molecule. In mammalian cells, the DSBs are mainly repaired by endogenous non-homologous end joining (NHEJ) pathway, which is error prone and results in the formation of indels. The indels can be harnessed to interrupt gene coding sequences or regulation elements. The DSBs can also be fixed by homology directed repair (HDR) pathway to introduce desired changes, such as base substitution and fragment insertion, when proper donor templates are provided, albeit in a less efficient manner. Besides making DSBs, Cas9 protein can be mutated to serve as a DNA binding platform to recruit functional modulators to the target loci, performing local transcriptional regulation, epigenetic remolding, base editing or prime editing. These Cas9 derived editing tools, especially base editors and prime editors, can introduce precise changes into the target loci at a single-base resolution and in an efficient and irreversible manner. Such features make these editing tools very promising for therapeutic applications. This review focuses on the evolution and mechanisms of CRISPR-Cas9 derived editing tools and their applications in the field of gene therapy.
Collapse
Affiliation(s)
- Lifang Zhou
- Laboratory of Biotherapy, National Key Laboratory of Biotherapy, Cancer Center, West China Hospital, Sichuan University, Renmin Nanlu 17, Chengdu, 610041, Sichuan, China
| | - Shaohua Yao
- Laboratory of Biotherapy, National Key Laboratory of Biotherapy, Cancer Center, West China Hospital, Sichuan University, Renmin Nanlu 17, Chengdu, 610041, Sichuan, China.
| |
Collapse
|
11
|
Liu C, Jiang H, Li Y, Xue B, Yao YY, Yang ZZ. Development of a QM/MM(ABEEM) method combined with a polarizable force field to investigate the excision reaction mechanism of damaged thymine. Phys Chem Chem Phys 2023; 25:3432-3448. [PMID: 36637033 DOI: 10.1039/d2cp05873a] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
This paper focuses on the development of a quantum mechanics/molecular mechanics method using the ABEEM polarizable force field (QM/MM(ABEEM) method) to investigate the excision reaction mechanism of damaged thymine. This method does not simply combine the QM method with the polarizable force field. A valence electronegativity piecewise function with the distance between atoms as a variable is introduced to describe the atomic partial charges, and changes greatly during the reaction process. At the same time, the charge transfer effect is treated using the condition of local charge conservation. Compared with the traditional QM/MM method, the QM/MM(ABEEM) method can more accurately simulate the polarization effect and charge transfer effect in the reaction process. Focusing on the controversial problems of the excision of damaged bases, six reaction pathways were designed for monofunctional and difunctional deglycosylation of neutral bases and protonated bases. The results show that the QM/MM(ABEEM) method accurately simulates the polarization effect, charge transfer effect, activation energy and other properties of the reaction process. The process in which the active residue Asp activates the nucleophile H2O to attack the protonated base is the preferred path. The average activation energy and free activation energy of the protonated base are 7.00-14.00 kcal mol-1 lower than that of the neutral base. The study in this paper is helpful to understand the mechanism of repair enzymes in repairing bases.
Collapse
Affiliation(s)
- Cui Liu
- School of Chemistry and Chemical Engineering, Liaoning Normal University, Dalian, 116029, People's Republic of China.
| | - He Jiang
- School of Chemistry and Chemical Engineering, Liaoning Normal University, Dalian, 116029, People's Republic of China.
| | - Yue Li
- School of Chemistry and Chemical Engineering, Liaoning Normal University, Dalian, 116029, People's Republic of China.
| | - Bing Xue
- School of Chemistry and Chemical Engineering, Liaoning Normal University, Dalian, 116029, People's Republic of China.
| | - Yu-Ying Yao
- School of Chemistry and Chemical Engineering, Liaoning Normal University, Dalian, 116029, People's Republic of China.
| | - Zhong-Zhi Yang
- School of Chemistry and Chemical Engineering, Liaoning Normal University, Dalian, 116029, People's Republic of China.
| |
Collapse
|
12
|
Jang S, Kumar N, Schaich MA, Zhong Z, van Loon B, Watkins S, Van Houten B. Cooperative interaction between AAG and UV-DDB in the removal of modified bases. Nucleic Acids Res 2022; 50:12856-12871. [PMID: 36511855 PMCID: PMC9825174 DOI: 10.1093/nar/gkac1145] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2022] [Revised: 11/05/2022] [Accepted: 11/16/2022] [Indexed: 12/15/2022] Open
Abstract
UV-DDB is a DNA damage recognition protein recently discovered to participate in the removal of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxoG) by stimulating multiple steps of base excision repair (BER). In this study, we examined whether UV-DDB has a wider role in BER besides oxidized bases and found it has specificity for two known DNA substrates of alkyladenine glycosylase (AAG)/N-methylpurine DNA glycosylase (MPG): 1, N6-ethenoadenine (ϵA) and hypoxanthine. Gel mobility shift assays show that UV-DDB recognizes these two lesions 4-5 times better than non-damaged DNA. Biochemical studies indicated that UV-DDB stimulated AAG activity on both substrates by 4- to 5-fold. Native gels indicated UV-DDB forms a transient complex with AAG to help facilitate release of AAG from the abasic site product. Single molecule experiments confirmed the interaction and showed that UV-DDB can act to displace AAG from abasic sites. Cells when treated with methyl methanesulfonate resulted in foci containing AAG and UV-DDB that developed over the course of several hours after treatment. While colocalization did not reach 100%, foci containing AAG and UV-DDB reached a maximum at three hours post treatment. Together these data indicate that UV-DDB plays an important role in facilitating the repair of AAG substrates.
Collapse
Affiliation(s)
- Sunbok Jang
- Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, PA 15261, USA
- UPMC Hillman Cancer Center, PA 15213, USA
- College of Pharmacy and Graduate School of Pharmaceutical Sciences, Ewha Womans University, Seoul 03760, South Korea
| | - Namrata Kumar
- UPMC Hillman Cancer Center, PA 15213, USA
- Molecular Genetics and Developmental Biology Graduate Program, University of Pittsburgh School of Medicine, PA 15261, USA
| | - Mathew A Schaich
- Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, PA 15261, USA
- UPMC Hillman Cancer Center, PA 15213, USA
| | - Zhou Zhong
- Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, PA 15261, USA
- UPMC Hillman Cancer Center, PA 15213, USA
| | - Barbara van Loon
- Department of Clinical and Molecular Medicine, Faculty of Medicine and Health Sciences, Norwegian University of Science and Technology (NTNU), 7491, Trondheim, Norway
| | - Simon C Watkins
- Center for Biologic Imaging, University of Pittsburgh, PA 15261, USA
| | - Bennett Van Houten
- Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, PA 15261, USA
- UPMC Hillman Cancer Center, PA 15213, USA
| |
Collapse
|
13
|
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]
|
14
|
Conformational Dynamics of Human ALKBH2 Dioxygenase in the Course of DNA Repair as Revealed by Stopped-Flow Fluorescence Spectroscopy. Molecules 2022; 27:molecules27154960. [PMID: 35956910 PMCID: PMC9370705 DOI: 10.3390/molecules27154960] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2022] [Revised: 07/28/2022] [Accepted: 08/01/2022] [Indexed: 11/30/2022] Open
Abstract
Elucidation of physicochemical mechanisms of enzymatic processes is one of the main tasks of modern biology. High efficiency and selectivity of enzymatic catalysis are mostly ensured by conformational dynamics of enzymes and substrates. Here, we applied a stopped-flow kinetic analysis based on fluorescent spectroscopy to investigate mechanisms of conformational transformations during the removal of alkylated bases from DNA by ALKBH2, a human homolog of Escherichia coli AlkB dioxygenase. This enzyme protects genomic DNA against various alkyl lesions through a sophisticated catalytic mechanism supported by a cofactor (Fe(II)), a cosubstrate (2-oxoglutarate), and O2. We present here a comparative study of conformational dynamics in complexes of the ALKBH2 protein with double-stranded DNA substrates containing N1-methyladenine, N3-methylcytosine, or 1,N6-ethenoadenine. By means of fluorescent labels of different types, simultaneous detection of conformational transitions in the protein globule and DNA substrate molecule was performed. Fitting of the kinetic curves by a nonlinear-regression method yielded a molecular mechanism and rate constants of its individual steps. The results shed light on overall conformational dynamics of ALKBH2 and damaged DNA during the catalytic cycle.
Collapse
|
15
|
Wang L, Xi K, Zhu L, Da LT. DNA Deformation Exerted by Regulatory DNA-Binding Motifs in Human Alkyladenine DNA Glycosylase Promotes Base Flipping. J Chem Inf Model 2022; 62:3213-3226. [PMID: 35708296 DOI: 10.1021/acs.jcim.2c00091] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Human alkyladenine DNA glycosylase (AAG) is a key enzyme that corrects a broad range of alkylated and deaminated nucleobases to maintain genomic integrity. When encountering the lesions, AAG adopts a base-flipping strategy to extrude the target base from the DNA duplex to its active site, thereby cleaving the glycosidic bond. Despite its functional importance, the detailed mechanism of such base extrusion and how AAG distinguishes the lesions from an excess of normal bases both remain elusive. Here, through the Markov state model constructed on extensive all-atom molecular dynamics simulations, we find that the alkylated nucleobase (N3-methyladenine, 3MeA) everts through the DNA major groove. Two key AAG motifs, the intercalation and E131-N146 motifs, play active roles in bending/pressing the DNA backbone and widening the DNA minor groove during 3MeA eversion. In particular, the intercalated residue Y162 is involved in buckling the target site at the early stage of 3MeA eversion. Our traveling-salesman based automated path searching algorithm further revealed that a non-target normal adenine tends to be trapped in an exo site near the active site, which however barely exists for a target base 3MeA. Collectively, these results suggest that the Markov state model combined with traveling-salesman based automated path searching acts as a promising approach for studying complex conformational changes of biomolecules and dissecting the elaborate mechanism of target recognition by this unique enzyme.
Collapse
Affiliation(s)
- Lingyan Wang
- Key Laboratory of Systems Biomedicine (Ministry of Education), Shanghai Center for Systems Biomedicine, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, China
| | - Kun Xi
- Warshel Institute for Computational Biology, School of Life and Health Sciences, The Chinese University of Hong Kong (Shenzhen), Shenzhen, Guangdong 518172, P. R. China
| | - Lizhe Zhu
- Warshel Institute for Computational Biology, School of Life and Health Sciences, The Chinese University of Hong Kong (Shenzhen), Shenzhen, Guangdong 518172, P. R. China
| | - Lin-Tai Da
- Key Laboratory of Systems Biomedicine (Ministry of Education), Shanghai Center for Systems Biomedicine, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, China
| |
Collapse
|
16
|
Tang S, Stokasimov E, Cui Y, Pellman D. Breakage of cytoplasmic chromosomes by pathological DNA base excision repair. Nature 2022; 606:930-936. [PMID: 35477155 PMCID: PMC10680091 DOI: 10.1038/s41586-022-04767-1] [Citation(s) in RCA: 40] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2021] [Accepted: 04/15/2022] [Indexed: 12/31/2022]
Abstract
Chromothripsis is a catastrophic mutational process that promotes tumorigenesis and causes congenital disease1-4. Chromothripsis originates from aberrations of nuclei called micronuclei or chromosome bridges5-8. These structures are associated with fragile nuclear envelopes that spontaneously rupture9,10, leading to DNA damage when chromatin is exposed to the interphase cytoplasm. Here we identify a mechanism explaining a major fraction of this DNA damage. Micronuclei accumulate large amounts of RNA-DNA hybrids, which are edited by adenine deaminases acting on RNA (ADAR enzymes) to generate deoxyinosine. Deoxyinosine is then converted into abasic sites by a DNA base excision repair (BER) glycosylase, N-methyl-purine DNA glycosylase11,12 (MPG). These abasic sites are cleaved by the BER endonuclease, apurinic/apyrimidinic endonuclease12 (APE1), creating single-stranded DNA nicks that can be converted to DNA double strand breaks by DNA replication or when closely spaced nicks occur on opposite strands13,14. This model predicts that MPG should be able to remove the deoxyinosine base from the DNA strand of RNA-DNA hybrids, which we demonstrate using purified proteins and oligonucleotide substrates. These findings identify a mechanism for fragmentation of micronuclear chromosomes, an important step in generating chromothripsis. Rather than breaking any normal chromosome, we propose that the eukaryotic cytoplasm only damages chromosomes with pre-existing defects such as the DNA base abnormality described here.
Collapse
Affiliation(s)
- Shangming Tang
- Howard Hughes Medical Institute, Chevy Chase, MD, USA
- Department of Pediatric Oncology, Dana-Farber Cancer Institute, Boston, MA, USA
- Department of Cell Biology, Blavatnik Institute, Harvard Medical School, Boston, MA, USA
| | - Ema Stokasimov
- Howard Hughes Medical Institute, Chevy Chase, MD, USA
- Department of Pediatric Oncology, Dana-Farber Cancer Institute, Boston, MA, USA
- Department of Cell Biology, Blavatnik Institute, Harvard Medical School, Boston, MA, USA
| | - Yuxiang Cui
- Department of Chemistry, University of California, Riverside, Riverside, CA, USA
| | - David Pellman
- Howard Hughes Medical Institute, Chevy Chase, MD, USA.
- Department of Pediatric Oncology, Dana-Farber Cancer Institute, Boston, MA, USA.
- Department of Cell Biology, Blavatnik Institute, Harvard Medical School, Boston, MA, USA.
| |
Collapse
|
17
|
Chen S, Liu Z, Yu H, Lai L, Li Z. Efficient multi-nucleotide deletions using deaminase-Cas9 fusions in human cells. J Genet Genomics 2022; 49:927-933. [DOI: 10.1016/j.jgg.2022.03.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2021] [Revised: 03/06/2022] [Accepted: 03/22/2022] [Indexed: 11/16/2022]
|
18
|
Off-target effects of base editors: what we know and how we can reduce it. Curr Genet 2021; 68:39-48. [PMID: 34515826 DOI: 10.1007/s00294-021-01211-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2021] [Revised: 08/23/2021] [Accepted: 08/31/2021] [Indexed: 10/20/2022]
Abstract
The recently discovered CRISPR-Cas9 modification, base editors (BEs), is considered as one of the most promising tools for correcting disease-causing mutations in humans, since it allows point substitutions to be edited without generating double-stranded DNA breaks, and, therefore, with a significant decrease in non-specific activity. Until recently, this method was considered the safest, but at the same time, it is quite effective. However, recent studies of non-specific activity of BEs revealed that some of them lead to the formation of a huge number of off-targets in both DNA and RNA, occurring due to the nature of the Cas9-fused proteins used. In this review article, we have considered and combined data from numerous studies about the most commonly used and more described in detail APOBEC-based BEs and Target-AID version of CBE, as well as ABE7 and ABE8 with their basic modifications into TadA to improve BEs' specificity. In our opinion, modern advances in molecular genetics make it possible to dramatically reduce the off-target activity of base editors due to introducing mutations into the domains of deaminases or inhibition of Cas9 by anti-CRISPR proteins, which returns BEs to the leading position in genome editing technologies.
Collapse
|
19
|
DNA repair glycosylase hNEIL1 triages damaged bases via competing interaction modes. Nat Commun 2021; 12:4108. [PMID: 34226550 PMCID: PMC8257757 DOI: 10.1038/s41467-021-24431-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2020] [Accepted: 06/14/2021] [Indexed: 12/31/2022] Open
Abstract
DNA glycosylases must distinguish the sparse damaged sites from the vast expanse of normal DNA bases. However, our understanding of the nature of nucleobase interrogation is still limited. Here, we show that hNEIL1 (human endonuclease VIII-like 1) captures base lesions via two competing states of interaction: an activated state that commits catalysis and base excision repair, and a quarantine state that temporarily separates and protects the flipped base via auto-inhibition. The relative dominance of the two states depends on key residues of hNEIL1 and chemical properties (e.g. aromaticity and hydrophilicity) of flipped bases. Such a DNA repair mechanism allows hNEIL1 to recognize a broad spectrum of DNA damage while keeps potential gratuitous repair in check. We further reveal the molecular basis of hNEIL1 activity regulation mediated by post-transcriptional modifications and provide an example of how exquisite structural dynamics serves for orchestrated enzyme functions. hNEIL1 (human endonuclease VIII-like 1) is a broadly specific DNA glycosylase for base excision repair. Here, the authors show that hNEIL1 can assume activated or triage conformations: the structural basis for the mechanism that enables broad specificity and reduces futile repair of normal bases.
Collapse
|
20
|
Insights into the substrate discrimination mechanisms of methyl-CpG-binding domain 4. Biochem J 2021; 478:1985-1997. [PMID: 33960375 DOI: 10.1042/bcj20210017] [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: 01/15/2021] [Revised: 05/05/2021] [Accepted: 05/07/2021] [Indexed: 11/17/2022]
Abstract
G:T mismatches, the major mispairs generated during DNA metabolism, are repaired in part by mismatch-specific DNA glycosylases such as methyl-CpG-binding domain 4 (MBD4) and thymine DNA glycosylase (TDG). Mismatch-specific DNA glycosylases must discriminate the mismatches against million-fold excess correct base pairs. MBD4 efficiently removes thymine opposite guanine but not opposite adenine. Previous studies have revealed that the substrate thymine is flipped out and enters the catalytic site of the enzyme, while the estranged guanine is stabilized by Arg468 of MBD4. To gain further insights into the mismatch discrimination mechanism of MBD4, we assessed the glycosylase activity of MBD4 toward various base pairs. In addition, we determined a crystal structure of MBD4 bound to T:O6-methylguanine-containing DNA, which suggests the O6 and N2 of purine and the O4 of pyrimidine are required to be a substrate for MBD4. To understand the role of the Arg468 finger in catalysis, we evaluated the glycosylase activity of MBD4 mutants, which revealed the guanidinium moiety of Arg468 may play an important role in catalysis. D560N/R468K MBD4 bound to T:G mismatched DNA shows that the side chain amine moiety of the Lys stabilizes the flipped-out thymine by a water-mediated phosphate pinching, while the backbone carbonyl oxygen of the Lys engages in hydrogen bonds with N2 of the estranged guanine. Comparison of various DNA glycosylase structures implies the guanidinium and amine moieties of Arg and Lys, respectively, may involve in discriminating between substrate mismatches and nonsubstrate base pairs.
Collapse
|
21
|
Westwood MN, Ljunggren KD, Boyd B, Becker J, Dwyer TJ, Meints GA. Single-Base Lesions and Mismatches Alter the Backbone Conformational Dynamics in DNA. Biochemistry 2021; 60:873-885. [PMID: 33689312 DOI: 10.1021/acs.biochem.0c00784] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
DNA damage has been implicated in numerous human diseases, particularly cancer, and the aging process. Single-base lesions and mismatches in DNA can be cytotoxic or mutagenic and are recognized by a DNA glycosylase during the process of base excision repair. Altered local dynamics and conformational properties in damaged DNAs have previously been suggested to assist in recognition and specificity. Herein, we use solution nuclear magnetic resonance to quantify changes in BI-BII backbone conformational dynamics due to the presence of single-base lesions in DNA, including uracil, dihydrouracil, 1,N6-ethenoadenine, and T:G mismatches. Stepwise changes to the %BII and ΔG of the BI-BII dynamic equilibrium compared to those of unmodified sequences were observed. Additionally, the equilibrium skews toward endothermicity for the phosphates nearest the lesion/mismatched base pair. Finally, the phosphates with the greatest alterations correlate with those most relevant to the repair of enzyme binding. All of these results suggest local conformational rearrangement of the DNA backbone may play a role in lesion recognition by repair enzymes.
Collapse
Affiliation(s)
- M N Westwood
- Department of Chemistry, Missouri State University, 901 South National Avenue, Springfield, Missouri 65897, United States
| | - K D Ljunggren
- Department of Chemistry, Missouri State University, 901 South National Avenue, Springfield, Missouri 65897, United States
| | - Benjamin Boyd
- Department of Chemistry, Missouri State University, 901 South National Avenue, Springfield, Missouri 65897, United States
| | - Jaclyn Becker
- Department of Chemistry, Missouri State University, 901 South National Avenue, Springfield, Missouri 65897, United States
| | - Tammy J Dwyer
- Department of Chemistry and Biochemistry, University of San Diego, San Diego, California 92110, United States
| | - Gary A Meints
- Department of Chemistry, Missouri State University, 901 South National Avenue, Springfield, Missouri 65897, United States
| |
Collapse
|
22
|
Mondal M, Yang L, Cai Z, Patra P, Gao YQ. A perspective on the molecular simulation of DNA from structural and functional aspects. Chem Sci 2021; 12:5390-5409. [PMID: 34168783 PMCID: PMC8179617 DOI: 10.1039/d0sc05329e] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
As genetic material, DNA not only carries genetic information by sequence, but also affects biological functions ranging from base modification to replication, transcription and gene regulation through its structural and dynamic properties and variations. The motion and structural properties of DNA involved in related biological processes are also multi-scale, ranging from single base flipping to local DNA deformation, TF binding, G-quadruplex and i-motif formation, TAD establishment, compartmentalization and even chromosome territory formation, just to name a few. The sequence-dependent physical properties of DNA play vital role in all these events, and thus it is interesting to examine how simple sequence information affects DNA and the formation of the chromatin structure in these different hierarchical orders. Accordingly, molecular simulations can provide atomistic details of interactions and conformational dynamics involved in different biological processes of DNA, including those inaccessible by current experimental methods. In this perspective, which is mainly based on our recent studies, we provide a brief overview of the atomistic simulations on how the hierarchical structure and dynamics of DNA can be influenced by its sequences, base modifications, environmental factors and protein binding in the context of the protein-DNA interactions, gene regulation and structural organization of chromatin. We try to connect the DNA sequence, the hierarchical structures of DNA and gene regulation.
Collapse
Affiliation(s)
- Manas Mondal
- Institute of Systems and Physical Biology, Shenzhen Bay Laboratory 518055 Shenzhen China
| | - Lijiang Yang
- Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University 100871 Beijing China
| | - Zhicheng Cai
- Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University 100871 Beijing China.,Biomedical Pioneering Innovation Center, Peking University 100871 Beijing China
| | - Piya Patra
- Institute of Systems and Physical Biology, Shenzhen Bay Laboratory 518055 Shenzhen China .,Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University 100871 Beijing China
| | - Yi Qin Gao
- Institute of Systems and Physical Biology, Shenzhen Bay Laboratory 518055 Shenzhen China .,Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University 100871 Beijing China.,Biomedical Pioneering Innovation Center, Peking University 100871 Beijing China.,Beijing Advanced Innovation Center for Genomics, Peking University 100871 Beijing China
| |
Collapse
|
23
|
Kladova OA, Kuznetsov NA, Fedorova OS. Initial stages of DNA Base Excision Repair in Nucleosomes. Mol Biol 2021. [DOI: 10.1134/s0026893321020096] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
|
24
|
Catalytic mechanism of the mismatch-specific DNA glycosylase methyl-CpG-binding domain 4. Biochem J 2020; 477:1601-1612. [PMID: 32297632 DOI: 10.1042/bcj20200125] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2020] [Revised: 04/09/2020] [Accepted: 04/14/2020] [Indexed: 12/15/2022]
Abstract
Thymine:guanine base pairs are major promutagenic mismatches occurring in DNA metabolism. If left unrepaired, these mispairs can cause C to T transition mutations. In humans, T:G mismatches are repaired in part by mismatch-specific DNA glycosylases such as methyl-CpG-binding domain 4 (hMBD4) and thymine-DNA glycosylase. Unlike lesion-specific DNA glycosylases, T:G-mismatch-specific DNA glycosylases specifically recognize both bases of the mismatch and remove the thymine but only from mispairs with guanine. Despite the advances in biochemical and structural characterizations of hMBD4, the catalytic mechanism of hMBD4 remains elusive. Herein, we report two structures of hMBD4 processing T:G-mismatched DNA. A high-resolution crystal structure of Asp560Asn hMBD4-T:G complex suggests that hMBD4-mediated glycosidic bond cleavage occurs via a general base catalysis mechanism assisted by Asp560. A structure of wild-type hMBD4 encountering T:G-containing DNA shows the generation of an apurinic/apyrimidinic (AP) site bearing the C1'-(S)-OH. The inversion of the stereochemistry at the C1' of the AP-site indicates that a nucleophilic water molecule approaches from the back of the thymine substrate, suggesting a bimolecular displacement mechanism (SN2) for hMBD4-catalyzed thymine excision. The AP-site is stabilized by an extensive hydrogen bond network in the MBD4 catalytic site, highlighting the role of MBD4 in protecting the genotoxic AP-site.
Collapse
|
25
|
Abstract
Genomic DNA is chemically reactive and therefore susceptible to damage by many exogenous and endogenous sources. Lesions produced from these damaging events can have various mutagenic and genotoxic consequences. This Perspective follows the journey of one particular lesion, 1,N6-ethenoadenine (εA), from its formation to replication and repair, and its role in cancerous tissues and inflammatory diseases. εA is generated by the reaction of adenine (A) with vinyl chloride or lipid peroxidation products. We present the miscoding properties of εA with an emphasis on how bacterial and mammalian cells can process lesions differently, leading to varied mutational spectra. But with information from these assays, we can better understand how the miscoding properties of εA lead to biological consequences and how genomic stability can be maintained via DNA repair mechanisms. We discuss how base excision repair (BER) and direct reversal repair (DRR) can minimize the biological consequences of εA lesions. Kinetic parameters of glycosylases and AlkB family enzymes are described, along with a discussion of the relative contributions of the BER and DRR pathways in the repair of εA. Because eukaryotic DNA is packaged in chromatin, we also discuss the impact of this packaging on BER and DRR, specifically in regards to repair of εA. Studying DNA lesions like εA in this context, from origin to biological implications, can provide crucial information to better understand prevention of mutagenesis and cancer.
Collapse
Affiliation(s)
- Katelyn L Rioux
- Department of Chemistry, Brown University, Providence, Rhode Island 02912, United States
| | - Sarah Delaney
- Department of Chemistry, Brown University, Providence, Rhode Island 02912, United States
| |
Collapse
|
26
|
Kotandeniya D, Rogers MS, Fernandez J, Kanugula S, Hudson RHE, Rodriguez F, Lipscomb JD, Tretyakova N. 6-phenylpyrrolocytosine as a fluorescent probe to examine nucleotide flipping catalyzed by a DNA repair protein. Biopolymers 2020; 112:e23405. [PMID: 33098572 DOI: 10.1002/bip.23405] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2020] [Revised: 09/30/2020] [Accepted: 09/30/2020] [Indexed: 11/05/2022]
Abstract
Cellular exposure to tobacco-specific nitrosamines causes formation of promutagenic O6 -[4-oxo-4-(3-pyridyl)but-1-yl]guanine (O6 -POB-G) and O6 -methylguanine (O6 -Me-G) adducts in DNA. These adducts can be directly repaired by O6 -alkylguanine-DNA alkyltransferase (AGT). Repair begins by flipping the damaged base out of the DNA helix. AGT binding and base-flipping have been previously studied using pyrrolocytosine as a fluorescent probe paired to the O6 -alkylguanine lesion, but low fluorescence yield limited the resolution of steps in the repair process. Here, we utilize the highly fluorescent 6-phenylpyrrolo-2'-deoxycytidine (6-phenylpyrrolo-C) to investigate AGT-DNA interactions. Synthetic oligodeoxynucleotide duplexes containing O6 -POB-G and O6 -Me-G adducts were placed within the CpG sites of codons 158, 245, and 248 of the p53 tumor suppressor gene and base-paired to 6-phenylpyrrolo-C in the opposite strand. Neighboring cytosine was either unmethylated or methylated. Stopped-flow fluorescence measurements were performed by mixing the DNA duplexes with C145A or R128G AGT variants. We observe a rapid, two-step, nearly irreversible binding of AGT to DNA followed by two slower steps, one of which is base-flipping. Placing 5-methylcytosine immediately 5' to the alkylated guanosine causes a reduction in rate constant of nucleotide flipping. O6 -POB-G at codon 158 decreased the base flipping rate constant by 3.5-fold compared with O6 -Me-G at the same position. A similar effect was not observed at other codons.
Collapse
Affiliation(s)
- Delshanee Kotandeniya
- Department of Medicinal Chemistry and the Masonic Cancer Center, University of Minnesota, Minneapolis, Minnesota, USA
| | - Melanie S Rogers
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, Minnesota, USA
| | - Jenna Fernandez
- Department of Medicinal Chemistry and the Masonic Cancer Center, University of Minnesota, Minneapolis, Minnesota, USA
| | - Sreenivas Kanugula
- Department of Cellular and Molecular Physiology, Pennsylvania State University College of Medicine, Hershey, Pennsylvania, USA
| | - Robert H E Hudson
- Department of Chemistry, University of Western Ontario, London, Ontario, Canada
| | - Freddys Rodriguez
- Department of Medicinal Chemistry and the Masonic Cancer Center, University of Minnesota, Minneapolis, Minnesota, USA
| | - John D Lipscomb
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, Minnesota, USA
| | - Natalia Tretyakova
- Department of Medicinal Chemistry and the Masonic Cancer Center, University of Minnesota, Minneapolis, Minnesota, USA
| |
Collapse
|
27
|
Verma P, Tandon R, Yadav G, Gaur V. Structural Aspects of DNA Repair and Recombination in Crop Improvement. Front Genet 2020; 11:574549. [PMID: 33024442 PMCID: PMC7516265 DOI: 10.3389/fgene.2020.574549] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2020] [Accepted: 08/25/2020] [Indexed: 12/18/2022] Open
Abstract
The adverse effects of global climate change combined with an exponentially increasing human population have put substantial constraints on agriculture, accelerating efforts towards ensuring food security for a sustainable future. Conventional plant breeding and modern technologies have led to the creation of plants with better traits and higher productivity. Most crop improvement approaches (conventional breeding, genome modification, and gene editing) primarily rely on DNA repair and recombination (DRR). Studying plant DRR can provide insights into designing new strategies or improvising the present techniques for crop improvement. Even though plants have evolved specialized DRR mechanisms compared to other eukaryotes, most of our insights about plant-DRRs remain rooted in studies conducted in animals. DRR mechanisms in plants include direct repair, nucleotide excision repair (NER), base excision repair (BER), mismatch repair (MMR), non-homologous end joining (NHEJ) and homologous recombination (HR). Although each DRR pathway acts on specific DNA damage, there is crosstalk between these. Considering the importance of DRR pathways as a tool in crop improvement, this review focuses on a general description of each DRR pathway, emphasizing on the structural aspects of key DRR proteins. The review highlights the gaps in our understanding and the importance of studying plant DRR in the context of crop improvement.
Collapse
Affiliation(s)
- Prabha Verma
- National Institute of Plant Genome Research, New Delhi, India
| | - Reetika Tandon
- National Institute of Plant Genome Research, New Delhi, India
| | - Gitanjali Yadav
- National Institute of Plant Genome Research, New Delhi, India
| | - Vineet Gaur
- National Institute of Plant Genome Research, New Delhi, India
| |
Collapse
|
28
|
Kladova OA, Alekseeva IV, Saparbaev M, Fedorova OS, Kuznetsov NA. Modulation of the Apurinic/Apyrimidinic Endonuclease Activity of Human APE1 and of Its Natural Polymorphic Variants by Base Excision Repair Proteins. Int J Mol Sci 2020; 21:ijms21197147. [PMID: 32998246 PMCID: PMC7583023 DOI: 10.3390/ijms21197147] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2020] [Revised: 09/24/2020] [Accepted: 09/25/2020] [Indexed: 11/25/2022] Open
Abstract
Human apurinic/apyrimidinic endonuclease 1 (APE1) is known to be a critical player of the base excision repair (BER) pathway. In general, BER involves consecutive actions of DNA glycosylases, AP endonucleases, DNA polymerases, and DNA ligases. It is known that these proteins interact with APE1 either at upstream or downstream steps of BER. Therefore, we may propose that even a minor disturbance of protein–protein interactions on the DNA template reduces coordination and repair efficiency. Here, the ability of various human DNA repair enzymes (such as DNA glycosylases OGG1, UNG2, and AAG; DNA polymerase Polβ; or accessory proteins XRCC1 and PCNA) to influence the activity of wild-type (WT) APE1 and its seven natural polymorphic variants (R221C, N222H, R237A, G241R, M270T, R274Q, and P311S) was tested. Förster resonance energy transfer–based kinetic analysis of abasic site cleavage in a model DNA substrate was conducted to detect the effects of interacting proteins on the activity of WT APE1 and its single-nucleotide polymorphism (SNP) variants. The results revealed that WT APE1 activity was stimulated by almost all tested DNA repair proteins. For the SNP variants, the matters were more complicated. Analysis of two SNP variants, R237A and G241R, suggested that a positive charge in this area of the APE1 surface impairs the protein–protein interactions. In contrast, variant R221C (where the affected residue is located near the DNA-binding site) showed permanently lower activation relative to WT APE1, whereas neighboring SNP N222H did not cause a noticeable difference as compared to WT APE1. Buried substitution P311S had an inconsistent effect, whereas each substitution at the DNA-binding site, M270T and R274Q, resulted in the lowest stimulation by BER proteins. Protein–protein molecular docking was performed between repair proteins to identify amino acid residues involved in their interactions. The data uncovered differences in the effects of BER proteins on APE1, indicating an important role of protein–protein interactions in the coordination of the repair pathway.
Collapse
Affiliation(s)
- Olga A. Kladova
- Institute of Chemical Biology and Fundamental Medicine, Siberian Branch of Russian Academy of Sciences, Novosibirsk 630090, Russia; (O.A.K.); (I.V.A.)
| | - Irina V. Alekseeva
- Institute of Chemical Biology and Fundamental Medicine, Siberian Branch of Russian Academy of Sciences, Novosibirsk 630090, Russia; (O.A.K.); (I.V.A.)
| | - Murat Saparbaev
- Groupe «Mechanisms of DNA Repair and Carcinogenesis», Equipe Labellisée LIGUE 2016, CNRS UMR9019, Université Paris-Saclay, Gustave Roussy Cancer Campus, CEDEX, F-94805 Villejuif, France;
| | - Olga S. Fedorova
- Institute of Chemical Biology and Fundamental Medicine, Siberian Branch of Russian Academy of Sciences, Novosibirsk 630090, Russia; (O.A.K.); (I.V.A.)
- Department of Natural Sciences, Novosibirsk State University, Novosibirsk 630090, Russia
- Correspondence: (O.S.F.); (N.A.K.)
| | - Nikita A. Kuznetsov
- Institute of Chemical Biology and Fundamental Medicine, Siberian Branch of Russian Academy of Sciences, Novosibirsk 630090, Russia; (O.A.K.); (I.V.A.)
- Department of Natural Sciences, Novosibirsk State University, Novosibirsk 630090, Russia
- Correspondence: (O.S.F.); (N.A.K.)
| |
Collapse
|
29
|
Bangalore DM, Heil HS, Mehringer CF, Hirsch L, Hemmen K, Heinze KG, Tessmer I. Automated AFM analysis of DNA bending reveals initial lesion sensing strategies of DNA glycosylases. Sci Rep 2020; 10:15484. [PMID: 32968112 PMCID: PMC7511397 DOI: 10.1038/s41598-020-72102-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2020] [Accepted: 08/25/2020] [Indexed: 12/31/2022] Open
Abstract
Base excision repair is the dominant DNA repair pathway of chemical modifications such as deamination, oxidation, or alkylation of DNA bases, which endanger genome integrity due to their high mutagenic potential. Detection and excision of these base lesions is achieved by DNA glycosylases. To investigate the remarkably high efficiency in target site search and recognition by these enzymes, we applied single molecule atomic force microscopy (AFM) imaging to a range of glycosylases with structurally different target lesions. Using a novel, automated, unbiased, high-throughput analysis approach, we were able to resolve subtly different conformational states of these glycosylases during DNA lesion search. Our results lend support to a model of enhanced lesion search efficiency through initial lesion detection based on altered mechanical properties at lesions. Furthermore, its enhanced sensitivity and easy applicability also to other systems recommend our novel analysis tool for investigations of diverse, fundamental biological interactions.
Collapse
Affiliation(s)
- Disha M Bangalore
- Rudolf Virchow Center for Experimental Biomedicine, University of Würzburg, Josef-Schneider-Strasse 2, 97080, Würzburg, Germany
| | - Hannah S Heil
- Rudolf Virchow Center for Experimental Biomedicine, University of Würzburg, Josef-Schneider-Strasse 2, 97080, Würzburg, Germany
| | - Christian F Mehringer
- Rudolf Virchow Center for Experimental Biomedicine, University of Würzburg, Josef-Schneider-Strasse 2, 97080, Würzburg, Germany
| | - Lisa Hirsch
- Rudolf Virchow Center for Experimental Biomedicine, University of Würzburg, Josef-Schneider-Strasse 2, 97080, Würzburg, Germany
| | - Katherina Hemmen
- Rudolf Virchow Center for Experimental Biomedicine, University of Würzburg, Josef-Schneider-Strasse 2, 97080, Würzburg, Germany
| | - Katrin G Heinze
- Rudolf Virchow Center for Experimental Biomedicine, University of Würzburg, Josef-Schneider-Strasse 2, 97080, Würzburg, Germany.
| | - Ingrid Tessmer
- Rudolf Virchow Center for Experimental Biomedicine, University of Würzburg, Josef-Schneider-Strasse 2, 97080, Würzburg, Germany.
| |
Collapse
|
30
|
Pinthong N, Limudomporn P, Vasuvat J, Adisakwattana P, Rattaprasert P, Chavalitshewinkoon-Petmitr P. Molecular characterization of Plasmodium falciparum DNA-3-methyladenine glycosylase. Malar J 2020; 19:284. [PMID: 32762689 PMCID: PMC7409487 DOI: 10.1186/s12936-020-03355-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2020] [Accepted: 07/28/2020] [Indexed: 11/10/2022] Open
Abstract
Background The emergence of artemisinin-resistant malaria parasites highlights the need for novel drugs and their targets. Alkylation of purine bases can hinder DNA replication and if unresolved would eventually result in cell death. DNA-3-methyladenine glycosylase (MAG) is responsible for the repair of those alkylated bases. Plasmodium falciparum (Pf) MAG was characterized for its potential for development as an anti-malarial candidate. Methods Native PfMAG from crude extract of chloroquine- and pyrimethamine-resistant P. falciparum K1 strain was partially purified using three chromatographic procedures. From bio-informatics analysis, primers were designed for amplification, insertion into pBAD202/D-TOPO and heterologous expression in Escherichia coli of recombinant PfMAG. Functional and biochemical properties of the recombinant enzyme were characterized. Results PfMAG activity was most prominent in parasite schizont stages, with a specific activity of 147 U/mg (partially purified) protein. K1 PfMAG contained an insertion of AAT (coding for asparagine) compared to 3D7 strain and 16% similarity to the human enzyme. Recombinant PfMAG (74 kDa) was twice as large as the human enzyme, preferred double-stranded DNA substrate, and demonstrated glycosylase activity over a pH range of 4–9, optimal salt concentration of 100–200 mM NaCl but reduced activity at 250 mM NaCl, no requirement for divalent cations, which were inhibitory in a dose-dependent manner. Conclusion PfMAG activity increased with parasite development being highest in the schizont stages. K1 PfMAG contained an indel AAT (asparagine) not present in 3D7 strain and the recombinant enzyme was twice as large as the human enzyme. Recombinant PfMAG had a wide range of optimal pH activity, and was inhibited at high (250 mM) NaCl concentration as well as by divalent cations. The properties of PfMAG provide basic data that should be of assistance in developing anti-malarials against this potential parasite target.
Collapse
Affiliation(s)
- Nattapon Pinthong
- Department of Protozoology, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Paviga Limudomporn
- Department of Zoology, Faculty of Science, Kasetsart University, Bangkok, Thailand
| | - Jitlada Vasuvat
- Department of Protozoology, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Poom Adisakwattana
- Department of Helminthology, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Pongruj Rattaprasert
- Department of Protozoology, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | | |
Collapse
|
31
|
Arbab M, Shen MW, Mok B, Wilson C, Matuszek Ż, Cassa CA, Liu DR. Determinants of Base Editing Outcomes from Target Library Analysis and Machine Learning. Cell 2020; 182:463-480.e30. [PMID: 32533916 PMCID: PMC7384975 DOI: 10.1016/j.cell.2020.05.037] [Citation(s) in RCA: 148] [Impact Index Per Article: 37.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2019] [Revised: 04/09/2020] [Accepted: 05/19/2020] [Indexed: 12/26/2022]
Abstract
Although base editors are widely used to install targeted point mutations, the factors that determine base editing outcomes are not well understood. We characterized sequence-activity relationships of 11 cytosine and adenine base editors (CBEs and ABEs) on 38,538 genomically integrated targets in mammalian cells and used the resulting outcomes to train BE-Hive, a machine learning model that accurately predicts base editing genotypic outcomes (R ≈ 0.9) and efficiency (R ≈ 0.7). We corrected 3,388 disease-associated SNVs with ≥90% precision, including 675 alleles with bystander nucleotides that BE-Hive correctly predicted would not be edited. We discovered determinants of previously unpredictable C-to-G, or C-to-A editing and used these discoveries to correct coding sequences of 174 pathogenic transversion SNVs with ≥90% precision. Finally, we used insights from BE-Hive to engineer novel CBE variants that modulate editing outcomes. These discoveries illuminate base editing, enable editing at previously intractable targets, and provide new base editors with improved editing capabilities.
Collapse
Affiliation(s)
- Mandana Arbab
- Merkin Institute of Transformative Technologies in Healthcare, Broad Institute of Harvard and MIT, Cambridge, MA 02142, USA; Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138, USA; Howard Hughes Medical Institute, Harvard University, Cambridge, MA 02138, USA
| | - Max W Shen
- Merkin Institute of Transformative Technologies in Healthcare, Broad Institute of Harvard and MIT, Cambridge, MA 02142, USA; Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138, USA; Howard Hughes Medical Institute, Harvard University, Cambridge, MA 02138, USA; Computational and Systems Biology Program, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Beverly Mok
- Merkin Institute of Transformative Technologies in Healthcare, Broad Institute of Harvard and MIT, Cambridge, MA 02142, USA; Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138, USA; Howard Hughes Medical Institute, Harvard University, Cambridge, MA 02138, USA
| | - Christopher Wilson
- Merkin Institute of Transformative Technologies in Healthcare, Broad Institute of Harvard and MIT, Cambridge, MA 02142, USA; Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138, USA; Howard Hughes Medical Institute, Harvard University, Cambridge, MA 02138, USA
| | - Żaneta Matuszek
- Merkin Institute of Transformative Technologies in Healthcare, Broad Institute of Harvard and MIT, Cambridge, MA 02142, USA; Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138, USA; Howard Hughes Medical Institute, Harvard University, Cambridge, MA 02138, USA; Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA
| | - Christopher A Cassa
- Division of Genetics, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA; Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - David R Liu
- Merkin Institute of Transformative Technologies in Healthcare, Broad Institute of Harvard and MIT, Cambridge, MA 02142, USA; Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138, USA; Howard Hughes Medical Institute, Harvard University, Cambridge, MA 02138, USA.
| |
Collapse
|
32
|
Anzalone AV, Koblan LW, Liu DR. Genome editing with CRISPR-Cas nucleases, base editors, transposases and prime editors. Nat Biotechnol 2020; 38:824-844. [PMID: 32572269 DOI: 10.1038/s41587-020-0561-9] [Citation(s) in RCA: 1153] [Impact Index Per Article: 288.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2020] [Accepted: 05/15/2020] [Indexed: 12/14/2022]
Abstract
The development of new CRISPR-Cas genome editing tools continues to drive major advances in the life sciences. Four classes of CRISPR-Cas-derived genome editing agents-nucleases, base editors, transposases/recombinases and prime editors-are currently available for modifying genomes in experimental systems. Some of these agents have also moved rapidly into the clinic. Each tool comes with its own capabilities and limitations, and major efforts have broadened their editing capabilities, expanded their targeting scope and improved editing specificity. We analyze key considerations when choosing genome editing agents and identify opportunities for future improvements and applications in basic research and therapeutics.
Collapse
Affiliation(s)
- Andrew V Anzalone
- Merkin Institute of Transformative Technologies in Healthcare, Broad Institute of Harvard and MIT, Cambridge, MA, USA.,Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, USA.,Howard Hughes Medical Institute, Harvard University, Cambridge, MA, USA
| | - Luke W Koblan
- Merkin Institute of Transformative Technologies in Healthcare, Broad Institute of Harvard and MIT, Cambridge, MA, USA.,Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, USA.,Howard Hughes Medical Institute, Harvard University, Cambridge, MA, USA
| | - David R Liu
- Merkin Institute of Transformative Technologies in Healthcare, Broad Institute of Harvard and MIT, Cambridge, MA, USA. .,Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, USA. .,Howard Hughes Medical Institute, Harvard University, Cambridge, MA, USA.
| |
Collapse
|
33
|
An aza-nucleoside, fragment-like inhibitor of the DNA repair enzyme alkyladenine glycosylase (AAG). Bioorg Med Chem 2020; 28:115507. [PMID: 32327352 DOI: 10.1016/j.bmc.2020.115507] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2020] [Revised: 04/06/2020] [Accepted: 04/09/2020] [Indexed: 11/21/2022]
Abstract
The DNA repair enzyme AAG has been shown in mice to promote tissue necrosis in response to ischaemic reperfusion or treatment with alkylating agents. A chemical probe inhibitor is required for investigations of the biological mechanism causing this phenomenon and as a lead for drugs that are potentially protective against tissue damage from organ failure and transplantation, and alkylative chemotherapy. Herein, we describe the rationale behind the choice of arylmethylpyrrolidines as appropriate aza-nucleoside mimics for an inhibitor followed by their synthesis and the first use of a microplate-based assay for quantification of their inhibition of AAG. We finally report the discovery of an imidazol-4-ylmethylpyrrolidine as a fragment-sized, weak inhibitor of AAG.
Collapse
|
34
|
Kaur R, Nikkel DJ, Wetmore SD. Computational studies of DNA repair: Insights into the function of monofunctional DNA glycosylases in the base excision repair pathway. WIRES COMPUTATIONAL MOLECULAR SCIENCE 2020. [DOI: 10.1002/wcms.1471] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Affiliation(s)
- Rajwinder Kaur
- Department of Chemistry and Biochemistry University of Lethbridge Lethbridge Alberta Canada
| | - Dylan J. Nikkel
- Department of Chemistry and Biochemistry University of Lethbridge Lethbridge Alberta Canada
| | - Stacey D. Wetmore
- Department of Chemistry and Biochemistry University of Lethbridge Lethbridge Alberta Canada
| |
Collapse
|
35
|
Thelen AZ, O'Brien PJ. Recognition of 1, N2-ethenoguanine by alkyladenine DNA glycosylase is restricted by a conserved active-site residue. J Biol Chem 2020; 295:1685-1693. [PMID: 31882538 PMCID: PMC7008384 DOI: 10.1074/jbc.ra119.011459] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2019] [Revised: 12/19/2019] [Indexed: 12/30/2022] Open
Abstract
The adenine, cytosine, and guanine bases of DNA are susceptible to alkylation by the aldehyde products of lipid peroxidation and by the metabolic byproducts of vinyl chloride pollutants. The resulting adducts spontaneously cyclize to form harmful etheno lesions. Cells employ a variety of DNA repair pathways to protect themselves from these pro-mutagenic modifications. Human alkyladenine DNA glycosylase (AAG) is thought to initiate base excision repair of both 1,N6-ethenoadenine (ϵA) and 1,N2-ethenoguanine (ϵG). However, it is not clear how AAG might accommodate ϵG in an active site that is complementary to ϵA. This prompted a thorough investigation of AAG-catalyzed excision of ϵG from several relevant contexts. Using single-turnover and multiple-turnover kinetic analyses, we found that ϵG in its natural ϵG·C context is very poorly recognized relative to ϵA·T. Bulged and mispaired ϵG contexts, which can form during DNA replication, were similarly poor substrates for AAG. Furthermore, AAG could not recognize an ϵG site in competition with excess undamaged DNA sites. Guided by previous structural studies, we hypothesized that Asn-169, a conserved residue in the AAG active-site pocket, contributes to discrimination against ϵG. Consistent with this model, the N169S variant of AAG was 7-fold more active for excision of ϵG compared with the wildtype (WT) enzyme. Taken together, these findings suggest that ϵG is not a primary substrate of AAG, and that current models for etheno lesion repair in humans should be revised. We propose that other repair and tolerance mechanisms operate in the case of ϵG lesions.
Collapse
Affiliation(s)
- Adam Z Thelen
- Department of Biological Chemistry, University of Michigan, Ann Arbor, Michigan 48109-0600
| | - Patrick J O'Brien
- Department of Biological Chemistry, University of Michigan, Ann Arbor, Michigan 48109-0600.
| |
Collapse
|
36
|
Kladova OA, Kuznetsova AA, Barthes NPF, Michel BY, Burger A, Fedorova OS, Kuznetsov NA. New Fluorescent Analogs of Nucleotides Based on 3-Hydroxychromone for Recording Conformational Changes of DNA. RUSSIAN JOURNAL OF BIOORGANIC CHEMISTRY 2020. [DOI: 10.1134/s1068162019060220] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
|
37
|
Li CC, Liu WX, Hu J, Zhang CY. A single quantum dot-based nanosensor with multilayer of multiple acceptors for ultrasensitive detection of human alkyladenine DNA glycosylase. Chem Sci 2019; 10:8675-8684. [PMID: 31803442 PMCID: PMC6849492 DOI: 10.1039/c9sc02137j] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2019] [Accepted: 08/05/2019] [Indexed: 12/17/2022] Open
Abstract
Base excision repair (BER) is an important DNA repair pathway involved in the maintenance of genome stability. As the initiator of BER, DNA glycosylase can remove a damaged base from DNA through cleaving the N-glycosidic bond between the sugar moiety and the damaged base. Accurate quantification of DNA glycosylase is essential for the early diagnosis of various human diseases. However, conventional methods for DNA glycosylase assay usually suffer from poor sensitivity and complex probe design. Herein, we develop a single quantum dot-based nanosensor with multilayer of multiple acceptors for ultrasensitive detection of human alkyladenine DNA glycosylase (hAAG) using apurinic/apyrimidinic endonuclease 1 (APE1)-assisted cyclic cleavage-mediated signal amplification in combination with the DNA polymerase-assisted multiple cyanine 5 (Cy5)-mediated fluorescence resonance energy transfer (FRET). The presence of hAAG induces the cleavage of the hairpin substrate, generating a trigger. The resultant trigger can hybridize with a probe modified with an AP site, initiating the APE1-mediated cyclic cleavage to produce a large number of primers. The primers can subsequently initiate the polymerase-mediated signal amplification with a biotin-modified capture probe as the template, generating the biotin-/multiple Cy5-labeled double-stranded DNAs (dsDNAs). The resultant dsDNAs can assemble onto the QD surface to form the QD-dsDNA-Cy5 nanostructure, leading to efficient FRET from the QD to Cy5 under the excitation of 405 nm. In contrast to the typical QD-based FRET approaches, the assembly of multilayer of multiple Cy5 molecules onto a single QD significantly amplifies the FRET signal. We further verify the FRET model with one donor and multilayered acceptors theoretically and experimentally. This single QD-based nanosensor can sensitively detect hAAG with a detection limit of as low as 4.42 × 10-12 U μL-1. Moreover, it can detect hAAG even in a single cancer cell, and distinguish the cancer cells from the normal cells. Importantly, this single QD-based nanosensor can be used for the kinetic study and inhibition assay, and it may become a universal platform for the detection of other DNA repair enzymes by designing appropriate DNA substrates.
Collapse
Affiliation(s)
- Chen-Chen 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 , China . ; ; ; Tel: +86 0531-86186033
| | - Wan-Xin Liu
- 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 , China . ; ; ; Tel: +86 0531-86186033
| | - Juan Hu
- 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 , China . ; ; ; Tel: +86 0531-86186033
| | - 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 , Shandong Provincial Key Laboratory of Clean Production of Fine Chemicals , Shandong Normal University , Jinan 250014 , China . ; ; ; Tel: +86 0531-86186033
| |
Collapse
|
38
|
Michel M, Visnes T, Homan EJ, Seashore-Ludlow B, Hedenström M, Wiita E, Vallin K, Paulin CBJ, Zhang J, Wallner O, Scobie M, Schmidt A, Jenmalm-Jensen A, Warpman Berglund U, Helleday T. Computational and Experimental Druggability Assessment of Human DNA Glycosylases. ACS OMEGA 2019; 4:11642-11656. [PMID: 31460271 PMCID: PMC6682003 DOI: 10.1021/acsomega.9b00162] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/17/2019] [Accepted: 05/21/2019] [Indexed: 06/10/2023]
Abstract
Due to a polar or even charged binding interface, DNA-binding proteins are considered extraordinarily difficult targets for development of small-molecule ligands and only a handful of proteins have been targeted successfully to date. Recently, however, it has been shown that development of selective and efficient inhibitors of 8-oxoguanine DNA glycosylase is possible. Here, we describe the initial druggability assessment of DNA glycosylases in a computational setting and experimentally investigate several methods to target endonuclease VIII-like 1 (NEIL1) with small-molecule inhibitors. We find that DNA glycosylases exhibit good predicted druggability in both DNA-bound and -unbound states. Furthermore, we find catalytic sites to be highly flexible, allowing for a range of interactions and binding partners. One flexible catalytic site was rationalized for NEIL1 and further investigated experimentally using both a biochemical assay in the presence of DNA and a thermal shift assay in the absence of DNA.
Collapse
Affiliation(s)
- Maurice Michel
- Science
for Life Laboratory, Department of Oncology-Pathology, Karolinska Institutet, S-171 76 Stockholm, Sweden
| | - Torkild Visnes
- Science
for Life Laboratory, Department of Oncology-Pathology, Karolinska Institutet, S-171 76 Stockholm, Sweden
- Department
of Biotechnology and Nanomedicine, SINTEF
Industry, N-7465 Trondheim, Norway
| | - Evert J. Homan
- Science
for Life Laboratory, Department of Oncology-Pathology, Karolinska Institutet, S-171 76 Stockholm, Sweden
| | - Brinton Seashore-Ludlow
- Chemical
Biology Consortium Sweden, Science for Life Laboratory, Division of
Translational Medicine and Chemical Biology, Department of Medical
Biochemistry and Biophysics, Karolinska
Institutet, S-171 21 Stockholm, Sweden
| | | | - Elisée Wiita
- Science
for Life Laboratory, Department of Oncology-Pathology, Karolinska Institutet, S-171 76 Stockholm, Sweden
| | - Karl Vallin
- Science
for Life Laboratory, Department of Oncology-Pathology, Karolinska Institutet, S-171 76 Stockholm, Sweden
| | - Cynthia B. J. Paulin
- Science
for Life Laboratory, Department of Oncology-Pathology, Karolinska Institutet, S-171 76 Stockholm, Sweden
| | - Jiaxi Zhang
- Institute
of Organic Chemistry, Clausthal University
of Technology, Leibnizstrasse
6, D-38678 Clausthal-Zellerfeld, Germany
| | - Olov Wallner
- Science
for Life Laboratory, Department of Oncology-Pathology, Karolinska Institutet, S-171 76 Stockholm, Sweden
| | - Martin Scobie
- Science
for Life Laboratory, Department of Oncology-Pathology, Karolinska Institutet, S-171 76 Stockholm, Sweden
| | - Andreas Schmidt
- Institute
of Organic Chemistry, Clausthal University
of Technology, Leibnizstrasse
6, D-38678 Clausthal-Zellerfeld, Germany
| | - Annika Jenmalm-Jensen
- Chemical
Biology Consortium Sweden, Science for Life Laboratory, Division of
Translational Medicine and Chemical Biology, Department of Medical
Biochemistry and Biophysics, Karolinska
Institutet, S-171 21 Stockholm, Sweden
| | - Ulrika Warpman Berglund
- Science
for Life Laboratory, Department of Oncology-Pathology, Karolinska Institutet, S-171 76 Stockholm, Sweden
| | - Thomas Helleday
- Science
for Life Laboratory, Department of Oncology-Pathology, Karolinska Institutet, S-171 76 Stockholm, Sweden
- Sheffield
Cancer Centre, Department of Oncology and Metabolism, University of Sheffield, S10 2RX Sheffield, U.K.
| |
Collapse
|
39
|
Abstract
RNA-guided programmable nucleases from CRISPR systems generate precise breaks in DNA or RNA at specified positions. In cells, this activity can lead to changes in DNA sequence or RNA transcript abundance. Base editing is a newer genome-editing approach that uses components from CRISPR systems together with other enzymes to directly install point mutations into cellular DNA or RNA without making double-stranded DNA breaks. DNA base editors comprise a catalytically disabled nuclease fused to a nucleobase deaminase enzyme and, in some cases, a DNA glycosylase inhibitor. RNA base editors achieve analogous changes using components that target RNA. Base editors directly convert one base or base pair into another, enabling the efficient installation of point mutations in non-dividing cells without generating excess undesired editing by-products. In this Review, we summarize base-editing strategies to generate specific and precise point mutations in genomic DNA and RNA, highlight recent developments that expand the scope, specificity, precision and in vivo delivery of base editors and discuss limitations and future directions of base editing for research and therapeutic applications.
Collapse
Affiliation(s)
- Holly A Rees
- Merkin Institute of Transformative Technologies in Healthcare, Broad Institute of MIT and Harvard, Cambridge, MA, USA
- Howard Hughes Medical Institute, Harvard University, Cambridge, MA, USA
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, USA
| | - David R Liu
- Merkin Institute of Transformative Technologies in Healthcare, Broad Institute of MIT and Harvard, Cambridge, MA, USA.
- Howard Hughes Medical Institute, Harvard University, Cambridge, MA, USA.
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, USA.
| |
Collapse
|
40
|
Kingsland A, Maibaum L. DNA Base Pair Mismatches Induce Structural Changes and Alter the Free-Energy Landscape of Base Flip. J Phys Chem B 2018; 122:12251-12259. [DOI: 10.1021/acs.jpcb.8b06007] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Addie Kingsland
- Department of Chemistry, University of Washington, Seattle, Washington 98195, United States
| | - Lutz Maibaum
- Department of Chemistry, University of Washington, Seattle, Washington 98195, United States
| |
Collapse
|
41
|
Esadze A, Stivers JT. Facilitated Diffusion Mechanisms in DNA Base Excision Repair and Transcriptional Activation. Chem Rev 2018; 118:11298-11323. [PMID: 30379068 DOI: 10.1021/acs.chemrev.8b00513] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Preservation of the coding potential of the genome and highly regulated gene expression over the life span of a human are two fundamental requirements of life. These processes require the action of repair enzymes or transcription factors that efficiently recognize specific sites of DNA damage or transcriptional regulation within a restricted time frame of the cell cycle or metabolism. A failure of these systems to act results in accumulated mutations, metabolic dysfunction, and disease. Despite the multifactorial complexity of cellular DNA repair and transcriptional regulation, both processes share a fundamental physical requirement that the proteins must rapidly diffuse to their specific DNA-binding sites that are embedded within the context of a vastly greater number of nonspecific DNA-binding sites. Superimposed on the needle-in-the-haystack problem is the complex nature of the cellular environment, which contains such high concentrations of macromolecules that the time frame for diffusion is expected to be severely extended as compared to dilute solution. Here we critically review the mechanisms for how these proteins solve the needle-in-the-haystack problem and how the effects of cellular macromolecular crowding can enhance facilitated diffusion processes. We restrict the review to human proteins that use stochastic, thermally driven site-recognition mechanisms, and we specifically exclude systems involving energy cofactors or circular DNA clamps. Our scope includes ensemble and single-molecule studies of the past decade or so, with an emphasis on connecting experimental observations to biological function.
Collapse
Affiliation(s)
- Alexandre Esadze
- Department of Pharmacology and Molecular Sciences , Johns Hopkins University School of Medicine , 725 North Wolfe Street , WBSB 314, Baltimore , Maryland 21205 , United States
| | - James T Stivers
- Department of Pharmacology and Molecular Sciences , Johns Hopkins University School of Medicine , 725 North Wolfe Street , WBSB 314, Baltimore , Maryland 21205 , United States
| |
Collapse
|
42
|
Taylor EL, Kesavan PM, Wolfe AE, O'Brien PJ. Distinguishing Specific and Nonspecific Complexes of Alkyladenine DNA Glycosylase. Biochemistry 2018; 57:4440-4454. [PMID: 29940097 DOI: 10.1021/acs.biochem.8b00531] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Human alkyladenine DNA glycosylase (AAG) recognizes many alkylated and deaminated purine lesions and excises them to initiate the base excision DNA repair pathway. AAG employs facilitated diffusion to rapidly scan nonspecific sites and locate rare sites of damage. Nonspecific DNA binding interactions are critical to the efficiency of this search for damage, but little is known about the binding footprint or the affinity of AAG for nonspecific sites. We used biochemical and biophysical approaches to characterize the binding of AAG to both undamaged and damaged DNA. Although fluorescence anisotropy is routinely used to study DNA binding, we found unexpected complexities in the data for binding of AAG to DNA. Systematic comparison of different fluorescent labels and different lengths of DNA allowed binding models to be distinguished and demonstrated that AAG can bind with high affinity and high density to nonspecific DNA. Fluorescein-labeled DNA gave the most complex behavior but also showed the greatest potential to distinguish specific and nonspecific binding modes. We suggest a unified model that is expected to apply to many DNA binding proteins that exhibit affinity for nonspecific DNA. Although AAG strongly prefers to excise lesions from duplex DNA, nonspecific binding is comparable for single- and double-stranded nonspecific sites. The electrostatically driven binding of AAG to small DNA sites (∼5 nucleotides of single-stranded and ∼6 base pairs of duplex) facilitates the search for DNA damage in chromosomal DNA, which is bound by nucleosomes and other proteins.
Collapse
Affiliation(s)
- Erin L Taylor
- Department of Biological Chemistry , University of Michigan , Ann Arbor , Michigan 48109 , United States
| | - Preethi M Kesavan
- Department of Biological Chemistry , University of Michigan , Ann Arbor , Michigan 48109 , United States
| | - Abigail E Wolfe
- Department of Biological Chemistry , University of Michigan , Ann Arbor , Michigan 48109 , United States
| | - Patrick J O'Brien
- Department of Biological Chemistry , University of Michigan , Ann Arbor , Michigan 48109 , United States
| |
Collapse
|
43
|
Jayanth N, Ogirala N, Yadav A, Puranik M. Structural basis for substrate discrimination by E. colirepair enzyme, AlkB. RSC Adv 2018; 8:1281-1291. [PMID: 35540905 PMCID: PMC9076979 DOI: 10.1039/c7ra11333a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2017] [Accepted: 11/14/2017] [Indexed: 11/21/2022] Open
Abstract
Positive charge on methylated nucleotides is a prime criterion for substrate recognition byE. coliAlkB.
Collapse
Affiliation(s)
- Namrata Jayanth
- National Centre for Biological Sciences
- Tata Institute of Fundamental Research
- GKVK Campus
- Bangalore 560065
- India
| | - Nirmala Ogirala
- National Centre for Biological Sciences
- Tata Institute of Fundamental Research
- GKVK Campus
- Bangalore 560065
- India
| | - Anil Yadav
- Indian Institute of Science Education and Research (IISER)
- Pune
- India
| | - Mrinalini Puranik
- National Centre for Biological Sciences
- Tata Institute of Fundamental Research
- GKVK Campus
- Bangalore 560065
- India
| |
Collapse
|
44
|
Lenz SAP, Wetmore SD. QM/MM Study of the Reaction Catalyzed by Alkyladenine DNA Glycosylase: Examination of the Substrate Specificity of a DNA Repair Enzyme. J Phys Chem B 2017; 121:11096-11108. [PMID: 29148771 DOI: 10.1021/acs.jpcb.7b09646] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Human alkyladenine DNA glycosylase (AAG) functions as part of the base excision repair pathway to excise structurally diverse oxidized and alkylated DNA purines. Specifically, AAG uses a water molecule activated by a general base and a nonspecific active site lined with aromatic residues to cleave the N-glycosidic bond. Despite broad substrate specificity, AAG does not target the natural purines (adenine (A) and guanine (G)). Using the ONIOM(QM:MM) methodology, we provide fundamental atomic level details of AAG bound to DNA-containing a neutral substrate (hypoxanthine (Hx)), a nonsubstrate (G), or a cationic substrate (7-methylguanine (7MeG)) and probe changes in the reaction pathway that occur when AAG targets different nucleotides. We reveal that subtle differences in protein-DNA contacts upon binding different substrates within the flexible AAG active site can significantly affect the deglycosylation reaction. Notably, we predict that AAG excises Hx in a concerted mechanism that is facilitated through correct alignment of the (E125) general base due to hydrogen bonding with a neighboring aromatic amino acid (Y127). Hx departure is further stabilized by π-π interactions with aromatic amino acids and hydrogen bonds with active site water. Despite possessing a similar structure to Hx, G is not excised since the additional exocyclic amino group leads to misalignment of the general base due to disruption of the key E125-Y127 hydrogen bond, the catalytically unfavorable placement of water within the active site, and weakened π-contacts between aromatic amino acids and the nucleobase. In contrast, cationic 7MeG does not occupy the same position within the AAG active site as G due to steric clashes with the additional N7 methyl group, which results in the correct alignment of the general base and permits nucleobase excision as observed for neutral Hx. Overall, our structural data rationalizes the observed substrate specificity of AAG and contributes to our fundamental understanding of enzymes with flexible active sites and broad substrate specificities.
Collapse
Affiliation(s)
- Stefan A P Lenz
- Department of Chemistry and Biochemistry, University of Lethbridge , 4401 University Drive West, Lethbridge, Alberta T1K 3M4, Canada
| | - Stacey D Wetmore
- Department of Chemistry and Biochemistry, University of Lethbridge , 4401 University Drive West, Lethbridge, Alberta T1K 3M4, Canada
| |
Collapse
|
45
|
Gaudelli NM, Komor AC, Rees HA, Packer MS, Badran AH, Bryson DI, Liu DR. Programmable base editing of A•T to G•C in genomic DNA without DNA cleavage. Nature 2017. [PMID: 29160308 DOI: 10.1038/nature24644.] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The spontaneous deamination of cytosine is a major source of transitions from C•G to T•A base pairs, which account for half of known pathogenic point mutations in humans. The ability to efficiently convert targeted A•T base pairs to G•C could therefore advance the study and treatment of genetic diseases. The deamination of adenine yields inosine, which is treated as guanine by polymerases, but no enzymes are known to deaminate adenine in DNA. Here we describe adenine base editors (ABEs) that mediate the conversion of A•T to G•C in genomic DNA. We evolved a transfer RNA adenosine deaminase to operate on DNA when fused to a catalytically impaired CRISPR-Cas9 mutant. Extensive directed evolution and protein engineering resulted in seventh-generation ABEs that convert targeted A•T base pairs efficiently to G•C (approximately 50% efficiency in human cells) with high product purity (typically at least 99.9%) and low rates of indels (typically no more than 0.1%). ABEs introduce point mutations more efficiently and cleanly, and with less off-target genome modification, than a current Cas9 nuclease-based method, and can install disease-correcting or disease-suppressing mutations in human cells. Together with previous base editors, ABEs enable the direct, programmable introduction of all four transition mutations without double-stranded DNA cleavage.
Collapse
Affiliation(s)
- Nicole M Gaudelli
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, USA.,Howard Hughes Medical Institute, Harvard University, Cambridge, Massachusetts 02138, USA.,Broad Institute of MIT and Harvard, Cambridge, Massachusetts 02142, USA
| | - Alexis C Komor
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, USA.,Howard Hughes Medical Institute, Harvard University, Cambridge, Massachusetts 02138, USA.,Broad Institute of MIT and Harvard, Cambridge, Massachusetts 02142, USA
| | - Holly A Rees
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, USA.,Howard Hughes Medical Institute, Harvard University, Cambridge, Massachusetts 02138, USA.,Broad Institute of MIT and Harvard, Cambridge, Massachusetts 02142, USA
| | - Michael S Packer
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, USA.,Howard Hughes Medical Institute, Harvard University, Cambridge, Massachusetts 02138, USA.,Broad Institute of MIT and Harvard, Cambridge, Massachusetts 02142, USA
| | - Ahmed H Badran
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, USA.,Howard Hughes Medical Institute, Harvard University, Cambridge, Massachusetts 02138, USA.,Broad Institute of MIT and Harvard, Cambridge, Massachusetts 02142, USA
| | - David I Bryson
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, USA.,Howard Hughes Medical Institute, Harvard University, Cambridge, Massachusetts 02138, USA.,Broad Institute of MIT and Harvard, Cambridge, Massachusetts 02142, USA
| | - David R Liu
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, USA.,Howard Hughes Medical Institute, Harvard University, Cambridge, Massachusetts 02138, USA.,Broad Institute of MIT and Harvard, Cambridge, Massachusetts 02142, USA
| |
Collapse
|
46
|
Gaudelli NM, Komor AC, Rees HA, Packer MS, Badran AH, Bryson DI, Liu DR. Programmable base editing of A•T to G•C in genomic DNA without DNA cleavage. Nature 2017; 551:464-471. [PMID: 29160308 PMCID: PMC5726555 DOI: 10.1038/nature24644] [Citation(s) in RCA: 2402] [Impact Index Per Article: 343.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2017] [Accepted: 10/17/2017] [Indexed: 12/18/2022]
Abstract
The spontaneous deamination of cytosine is a major source of transitions from C•G to T•A base pairs, which account for half of known pathogenic point mutations in humans. The ability to efficiently convert targeted A•T base pairs to G•C could therefore advance the study and treatment of genetic diseases. The deamination of adenine yields inosine, which is treated as guanine by polymerases, but no enzymes are known to deaminate adenine in DNA. Here we describe adenine base editors (ABEs) that mediate the conversion of A•T to G•C in genomic DNA. We evolved a transfer RNA adenosine deaminase to operate on DNA when fused to a catalytically impaired CRISPR-Cas9 mutant. Extensive directed evolution and protein engineering resulted in seventh-generation ABEs that convert targeted A•T base pairs efficiently to G•C (approximately 50% efficiency in human cells) with high product purity (typically at least 99.9%) and low rates of indels (typically no more than 0.1%). ABEs introduce point mutations more efficiently and cleanly, and with less off-target genome modification, than a current Cas9 nuclease-based method, and can install disease-correcting or disease-suppressing mutations in human cells. Together with previous base editors, ABEs enable the direct, programmable introduction of all four transition mutations without double-stranded DNA cleavage.
Collapse
Affiliation(s)
- Nicole M. Gaudelli
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, 02138
- Howard Hughes Medical Institute, Harvard University, Cambridge, MA, 02138
- Broad Institute of MIT and Harvard, Cambridge, MA, 02141
| | - Alexis C. Komor
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, 02138
- Howard Hughes Medical Institute, Harvard University, Cambridge, MA, 02138
- Broad Institute of MIT and Harvard, Cambridge, MA, 02141
| | - Holly A. Rees
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, 02138
- Howard Hughes Medical Institute, Harvard University, Cambridge, MA, 02138
- Broad Institute of MIT and Harvard, Cambridge, MA, 02141
| | - Michael S. Packer
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, 02138
- Howard Hughes Medical Institute, Harvard University, Cambridge, MA, 02138
- Broad Institute of MIT and Harvard, Cambridge, MA, 02141
| | - Ahmed H. Badran
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, 02138
- Howard Hughes Medical Institute, Harvard University, Cambridge, MA, 02138
- Broad Institute of MIT and Harvard, Cambridge, MA, 02141
| | - David I. Bryson
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, 02138
- Howard Hughes Medical Institute, Harvard University, Cambridge, MA, 02138
- Broad Institute of MIT and Harvard, Cambridge, MA, 02141
| | - David R. Liu
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, 02138
- Howard Hughes Medical Institute, Harvard University, Cambridge, MA, 02138
- Broad Institute of MIT and Harvard, Cambridge, MA, 02141
| |
Collapse
|
47
|
Gaudelli NM, Komor AC, Rees HA, Packer MS, Badran AH, Bryson DI, Liu DR. Programmable base editing of A•T to G•C in genomic DNA without DNA cleavage. Nature 2017. [PMID: 29160308 DOI: 10.1038/nature24644.programmable] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/19/2023]
Abstract
The spontaneous deamination of cytosine is a major source of transitions from C•G to T•A base pairs, which account for half of known pathogenic point mutations in humans. The ability to efficiently convert targeted A•T base pairs to G•C could therefore advance the study and treatment of genetic diseases. The deamination of adenine yields inosine, which is treated as guanine by polymerases, but no enzymes are known to deaminate adenine in DNA. Here we describe adenine base editors (ABEs) that mediate the conversion of A•T to G•C in genomic DNA. We evolved a transfer RNA adenosine deaminase to operate on DNA when fused to a catalytically impaired CRISPR-Cas9 mutant. Extensive directed evolution and protein engineering resulted in seventh-generation ABEs that convert targeted A•T base pairs efficiently to G•C (approximately 50% efficiency in human cells) with high product purity (typically at least 99.9%) and low rates of indels (typically no more than 0.1%). ABEs introduce point mutations more efficiently and cleanly, and with less off-target genome modification, than a current Cas9 nuclease-based method, and can install disease-correcting or disease-suppressing mutations in human cells. Together with previous base editors, ABEs enable the direct, programmable introduction of all four transition mutations without double-stranded DNA cleavage.
Collapse
Affiliation(s)
- Nicole M Gaudelli
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, USA
- Howard Hughes Medical Institute, Harvard University, Cambridge, Massachusetts 02138, USA
- Broad Institute of MIT and Harvard, Cambridge, Massachusetts 02142, USA
| | - Alexis C Komor
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, USA
- Howard Hughes Medical Institute, Harvard University, Cambridge, Massachusetts 02138, USA
- Broad Institute of MIT and Harvard, Cambridge, Massachusetts 02142, USA
| | - Holly A Rees
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, USA
- Howard Hughes Medical Institute, Harvard University, Cambridge, Massachusetts 02138, USA
- Broad Institute of MIT and Harvard, Cambridge, Massachusetts 02142, USA
| | - Michael S Packer
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, USA
- Howard Hughes Medical Institute, Harvard University, Cambridge, Massachusetts 02138, USA
- Broad Institute of MIT and Harvard, Cambridge, Massachusetts 02142, USA
| | - Ahmed H Badran
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, USA
- Howard Hughes Medical Institute, Harvard University, Cambridge, Massachusetts 02138, USA
- Broad Institute of MIT and Harvard, Cambridge, Massachusetts 02142, USA
| | - David I Bryson
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, USA
- Howard Hughes Medical Institute, Harvard University, Cambridge, Massachusetts 02138, USA
- Broad Institute of MIT and Harvard, Cambridge, Massachusetts 02142, USA
| | - David R Liu
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, USA
- Howard Hughes Medical Institute, Harvard University, Cambridge, Massachusetts 02138, USA
- Broad Institute of MIT and Harvard, Cambridge, Massachusetts 02142, USA
| |
Collapse
|
48
|
Hendershot JM, O'Brien PJ. Search for DNA damage by human alkyladenine DNA glycosylase involves early intercalation by an aromatic residue. J Biol Chem 2017; 292:16070-16080. [PMID: 28747435 PMCID: PMC5625039 DOI: 10.1074/jbc.m117.782813] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2017] [Revised: 07/19/2017] [Indexed: 01/22/2023] Open
Abstract
DNA repair enzymes recognize and remove damaged bases that are embedded in the duplex. To gain access, most enzymes use nucleotide flipping, whereby the target nucleotide is rotated 180° into the active site. In human alkyladenine DNA glycosylase (AAG), the enzyme that initiates base excision repair of alkylated bases, the flipped-out nucleotide is stabilized by intercalation of the side chain of tyrosine 162 that replaces the lesion nucleobase. Previous kinetic studies provided evidence for the formation of a transient complex that precedes the stable flipped-out complex, but it is not clear how this complex differs from nonspecific complexes. We used site-directed mutagenesis and transient-kinetic approaches to investigate the timing of Tyr162 intercalation for AAG. The tryptophan substitution (Y162W) appeared to be conservative, because the mutant protein retained a highly favorable equilibrium constant for flipping the 1,N6-ethenoadenine (ϵA) lesion, and the rate of N-glycosidic bond cleavage was identical to that of the wild-type enzyme. We assigned the tryptophan fluorescence signal from Y162W by removing two native tryptophan residues (W270A/W284A). Stopped-flow experiments then demonstrated that the change in tryptophan fluorescence of the Y162W mutant is extremely rapid upon binding to either damaged or undamaged DNA, much faster than the lesion-recognition and nucleotide flipping steps that were independently determined by monitoring the ϵA fluorescence. These observations suggest that intercalation by this aromatic residue is one of the earliest steps in the search for DNA damage and that this interaction is important for the progression of AAG from nonspecific searching to specific-recognition complexes.
Collapse
Affiliation(s)
- Jenna M Hendershot
- From the Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan 48109-0600
| | - Patrick J O'Brien
- From the Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan 48109-0600
| |
Collapse
|
49
|
Talhaoui I, Matkarimov BT, Tchenio T, Zharkov DO, Saparbaev MK. Aberrant base excision repair pathway of oxidatively damaged DNA: Implications for degenerative diseases. Free Radic Biol Med 2017; 107:266-277. [PMID: 27890638 DOI: 10.1016/j.freeradbiomed.2016.11.040] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/30/2016] [Revised: 11/22/2016] [Accepted: 11/23/2016] [Indexed: 02/06/2023]
Abstract
In cellular organisms composition of DNA is constrained to only four nucleobases A, G, T and C, except for minor DNA base modifications such as methylation which serves for defence against foreign DNA or gene expression regulation. Interestingly, this severe evolutionary constraint among other things demands DNA repair systems to discriminate between regular and modified bases. DNA glycosylases specifically recognize and excise damaged bases among vast majority of regular bases in the base excision repair (BER) pathway. However, the mismatched base pairs in DNA can occur from a spontaneous conversion of 5-methylcytosine to thymine and DNA polymerase errors during replication. To counteract these mutagenic threats to genome stability, cells evolved special DNA repair systems that target the non-damaged DNA strand in a duplex to remove mismatched regular DNA bases. Mismatch-specific adenine- and thymine-DNA glycosylases (MutY/MUTYH and TDG/MBD4, respectively) initiated BER and mismatch repair (MMR) pathways can recognize and remove normal DNA bases in mismatched DNA duplexes. Importantly, in DNA repair deficient cells bacterial MutY, human TDG and mammalian MMR can act in the aberrant manner: MutY and TDG removes adenine and thymine opposite misincorporated 8-oxoguanine and damaged adenine, respectively, whereas MMR removes thymine opposite to O6-methylguanine. These unusual activities lead either to mutations or futile DNA repair, thus indicating that the DNA repair pathways which target non-damaged DNA strand can act in aberrant manner and introduce genome instability in the presence of unrepaired DNA lesions. Evidences accumulated showing that in addition to the accumulation of oxidatively damaged DNA in cells, the aberrant DNA repair can also contribute to cancer, brain disorders and premature senescence. For example, the aberrant BER and MMR pathways for oxidized guanine residues can lead to trinucleotide expansion that underlies Huntington's disease, a severe hereditary neurodegenerative syndrome. This review summarises the present knowledge about the aberrant DNA repair pathways for oxidized base modifications and their possible role in age-related diseases.
Collapse
Affiliation(s)
- Ibtissam Talhaoui
- Groupe «Réparation de l'ADN», Equipe Labellisée par la Ligue Nationale Contre le Cancer, CNRS UMR8200, Université Paris-Sud, Gustave Roussy Cancer Campus, F-94805 Villejuif Cedex, France
| | - Bakhyt T Matkarimov
- National laboratory Astana, Nazarbayev University, Astana 010000, Kazakhstan
| | - Thierry Tchenio
- LBPA, UMR8113 ENSC - CNRS, Ecole Normale Supérieure de Cachan, Cachan, France
| | - Dmitry O Zharkov
- SB RAS Institute of Chemical Biology and Fundamental Medicine, Novosibirsk 630090, Russia; Novosibirsk State University, Novosibirsk 630090, Russia
| | - Murat K Saparbaev
- Groupe «Réparation de l'ADN», Equipe Labellisée par la Ligue Nationale Contre le Cancer, CNRS UMR8200, Université Paris-Sud, Gustave Roussy Cancer Campus, F-94805 Villejuif Cedex, France.
| |
Collapse
|
50
|
Hendershot JM, O'Brien PJ. Transient Kinetic Methods for Mechanistic Characterization of DNA Binding and Nucleotide Flipping. Methods Enzymol 2017; 592:377-415. [PMID: 28668128 DOI: 10.1016/bs.mie.2017.04.003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Enzymes that modify nucleobases in double-stranded genomic DNA, either as part of a DNA repair pathway or as an epigenetic modifying pathway, adopt a multistep pathway to locate target sites and reconfigure the DNA to gain access. Work on several different enzymes has shown that in almost all cases base flipping, also known as nucleotide flipping, is a key feature of specific site recognition. In this chapter, we discuss some of the strategies that can be used to perform a kinetic characterization for DNA binding and nucleotide flipping. The resulting kinetic and thermodynamic framework provides a platform for understanding substrate specificity, mechanisms of inhibition, and the roles of important amino acids. We use a human DNA repair glycosylase called alkyladenine DNA glycosylase as a case study, because this is one of the best-characterized nucleotide-flipping enzymes. However, the approaches that are described can be readily adapted to study other enzymes, and future studies are needed to understand the mechanism of substrate recognition in each individual case. As more enzymes are characterized, we can hope to uncover which features of DNA searching and nucleotide flipping are fundamental features shared by many different families of DNA modifying enzymes, and which features are specific to a particular enzyme. Such an understanding provides reasonable models for less characterized enzymes that are important for epigenetic DNA modification and DNA repair pathways.
Collapse
Affiliation(s)
| | - Patrick J O'Brien
- University of Michigan Medical School, Ann Arbor, MI, United States.
| |
Collapse
|