1
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Alniss HY, Kemp BM, Holmes E, Hoffmann J, Ploch RM, Ramadan WS, Msallam YA, Al-Jubeh HM, Madkour MM, Celikkaya BC, Scott FJ, El-Awady R, Parkinson JA. Spectroscopic, biochemical and computational studies of bioactive DNA minor groove binders targeting 5'-WGWWCW-3' motif. Bioorg Chem 2024; 148:107414. [PMID: 38733748 DOI: 10.1016/j.bioorg.2024.107414] [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: 01/23/2024] [Revised: 04/18/2024] [Accepted: 04/27/2024] [Indexed: 05/13/2024]
Abstract
Spectroscopic, biochemical, and computational modelling studies have been used to assess the binding capability of a set of minor groove binding (MGB) ligands against the self-complementary DNA sequences 5'-d(CGCACTAGTGCG)-3' and 5'-d(CGCAGTACTGCG)-3'. The ligands were carefully designed to target the DNA response element, 5'-WGWWCW-3', the binding site for several nuclear receptors. Basic 1D 1H NMR spectra of the DNA samples prepared with three MGB ligands show subtle variations suggestive of how each ligand associates with the double helical structure of both DNA sequences. The variations among the investigated ligands were reflected in the line shape and intensity of 1D 1H and 31P-{1H} NMR spectra. Rapid visual inspection of these 1D NMR spectra proves to be beneficial in providing valuable insights on MGB binding molecules. The NMR results were consistent with the findings from both UV DNA denaturation and molecular modelling studies. Both the NMR spectroscopic and computational analyses indicate that the investigated ligands bind to the minor grooves as antiparallel side-by-side dimers in a head-to-tail fashion. Moreover, comparisons with results from biochemical studies offered valuable insights into the mechanism of action, and antitumor activity of MGBs in relation to their structures, essential pre-requisites for future optimization of MGBs as therapeutic agents.
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Affiliation(s)
- Hasan Y Alniss
- College of Pharmacy, Department of Medicinal Chemistry, University of Sharjah, Sharjah 27272, United Arab Emirates; Research Institute for Medical and Health Sciences, University of Sharjah, Sharjah 27272, United Arab Emirates.
| | - Bryony M Kemp
- Department of Pure and Applied Chemistry, University of Strathclyde, 295 Cathedral Street, Glasgow G1 1XL, Scotland, UK
| | - Elizabeth Holmes
- Department of Pure and Applied Chemistry, University of Strathclyde, 295 Cathedral Street, Glasgow G1 1XL, Scotland, UK
| | - Joanna Hoffmann
- Department of Pure and Applied Chemistry, University of Strathclyde, 295 Cathedral Street, Glasgow G1 1XL, Scotland, UK
| | - Rafal M Ploch
- Department of Pure and Applied Chemistry, University of Strathclyde, 295 Cathedral Street, Glasgow G1 1XL, Scotland, UK
| | - Wafaa S Ramadan
- Research Institute for Medical and Health Sciences, University of Sharjah, Sharjah 27272, United Arab Emirates
| | - Yousef A Msallam
- College of Pharmacy, Department of Medicinal Chemistry, University of Sharjah, Sharjah 27272, United Arab Emirates; Research Institute for Medical and Health Sciences, University of Sharjah, Sharjah 27272, United Arab Emirates
| | - Hadeel M Al-Jubeh
- Research Institute for Medical and Health Sciences, University of Sharjah, Sharjah 27272, United Arab Emirates
| | - Moustafa M Madkour
- College of Pharmacy, Department of Medicinal Chemistry, University of Sharjah, Sharjah 27272, United Arab Emirates; Research Institute for Medical and Health Sciences, University of Sharjah, Sharjah 27272, United Arab Emirates
| | - Bekir C Celikkaya
- Department of Pure and Applied Chemistry, University of Strathclyde, 295 Cathedral Street, Glasgow G1 1XL, Scotland, UK
| | - Fraser J Scott
- Department of Pure and Applied Chemistry, University of Strathclyde, 295 Cathedral Street, Glasgow G1 1XL, Scotland, UK
| | - Raafat El-Awady
- College of Pharmacy, Department of Medicinal Chemistry, University of Sharjah, Sharjah 27272, United Arab Emirates; Research Institute for Medical and Health Sciences, University of Sharjah, Sharjah 27272, United Arab Emirates
| | - John A Parkinson
- Department of Pure and Applied Chemistry, University of Strathclyde, 295 Cathedral Street, Glasgow G1 1XL, Scotland, UK.
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2
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Crisalli AM, Chen YT, Cai A, Li D, Cho BP. Conformation-dependent lesion bypass of bulky arylamine-dG adducts generated from 2-nitrofluorene in epigenetic sequence contexts. Nucleic Acids Res 2023; 51:12043-12053. [PMID: 37953358 PMCID: PMC10711442 DOI: 10.1093/nar/gkad1038] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2023] [Revised: 09/27/2023] [Accepted: 10/24/2023] [Indexed: 11/14/2023] Open
Abstract
Sequence context influences structural characteristics and repair of DNA adducts, but there is limited information on how epigenetic modulation affects conformational heterogeneity and bypass of DNA lesions. Lesions derived from the environmental pollutant 2-nitrofluorene have been extensively studied as chemical carcinogenesis models; they adopt a sequence-dependent mix of two significant conformers: major groove binding (B) and base-displaced stacked (S). We report a conformation-dependent bypass of the N-(2'-deoxyguanosin-8-yl)-7-fluoro-2-aminofluorene (dG-FAF) lesion in epigenetic sequence contexts (d[5'-CTTCTC#G*NCCTCATTC-3'], where C# is C or 5-methylcytosine (5mC), G* is G or G-FAF, and N is A, T, C or G). FAF-modified sequences with a 3' flanking pyrimidine were better bypassed when the 5' base was 5mC, whereas sequences with a 3' purine exhibited the opposite effect. The conformational basis behind these variations differed; for -CG*C- and -CG*T-, bypass appeared to be inversely correlated with population of the duplex-destabilizing S conformer. On the other hand, the connection between conformation and a decrease in bypass for flanking purines in the 5mC sequences relative to C was more complex. It could be related to the emergence of a disruptive non-S/B conformation. The present work provides novel conformational insight into how 5mC influences the bypass efficiency of bulky DNA damage.
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Affiliation(s)
- Alicia M Crisalli
- Department of Biomedical and Pharmaceutical Sciences, College of Pharmacy, University of Rhode Island, Kingston, RI 02881, USA
| | - Yi-Tzai Chen
- Department of Biomedical and Pharmaceutical Sciences, College of Pharmacy, University of Rhode Island, Kingston, RI 02881, USA
| | - Ang Cai
- Department of Biomedical and Pharmaceutical Sciences, College of Pharmacy, University of Rhode Island, Kingston, RI 02881, USA
| | - Deyu Li
- Department of Biomedical and Pharmaceutical Sciences, College of Pharmacy, University of Rhode Island, Kingston, RI 02881, USA
| | - Bongsup P Cho
- Department of Biomedical and Pharmaceutical Sciences, College of Pharmacy, University of Rhode Island, Kingston, RI 02881, USA
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3
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Ganguly S, Murugan NA, Ghosh D, Narayanaswamy N, Govindaraju T, Basu G. DNA Minor Groove-Induced cis- trans Isomerization of a Near-Infrared Fluorescent Probe. Biochemistry 2021; 60:2084-2097. [PMID: 34142803 DOI: 10.1021/acs.biochem.1c00281] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The discovery of small molecules that exhibit turn-on far-red or near-infrared (NIR) fluorescence upon DNA binding and understanding how they bind DNA are important for imaging and bioanalytical applications. Here we report the DNA-bound structure and the DNA binding mechanism of quinone cyanine dithiazole (QCy-DT), a recently reported AT-specific turn-on NIR fluorescent probe for double-stranded DNA. The nuclear magnetic resonance (NMR)-derived structure showed minor groove binding but no specific ligand-DNA interactions, consistent with an endothermic and entropy-driven binding mechanism deduced from isothermal titration calorimetry. Minor groove binding is typically fast because it minimally perturbs the DNA structure. However, QCy-DT exhibited unusually slow DNA binding. The cyanine-based probe is capable of cis-trans isomerization due to overlapping methine bridges, with 16 possible slowly interconverting cis/trans isomers. Using NMR, density functional theory, and free energy calculations, we show that the DNA-free and DNA-bound environments of QCy-DT prefer distinctly different isomers, indicating that the origin of the slow kinetics is a cis-trans isomerization and that the minor groove preferentially selects an otherwise unstable cis/trans isomer of QCy-DT. Flux analysis showed the conformational selection pathway to be the dominating DNA binding mechanism at low DNA concentrations, which switches to the induced fit pathway at high DNA concentrations. This report of cis/trans isomerization of a ligand, upon binding the DNA minor groove, expands the prevailing understanding of unique discriminatory powers of the minor groove and has an important bearing on using polymethine cyanine dyes to probe the kinetics of molecular interactions.
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Affiliation(s)
- Sudakshina Ganguly
- Department of Biophysics, Bose Institute, P-1/12 CIT Scheme VIIM, Kolkata 700054, West Bengal, India
| | - N Arul Murugan
- Division of Theoretical Chemistry and Biology, School of Biotechnology, KTH Royal Institute of Technology, S-106 91 Stockholm, Sweden
| | - Debasis Ghosh
- Bioorganic Chemistry Laboratory, New Chemistry Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur P.O., Bengaluru 560064, Karnataka, India
| | - Nagarjun Narayanaswamy
- Bioorganic Chemistry Laboratory, New Chemistry Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur P.O., Bengaluru 560064, Karnataka, India
| | - Thimmaiah Govindaraju
- Bioorganic Chemistry Laboratory, New Chemistry Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur P.O., Bengaluru 560064, Karnataka, India
| | - Gautam Basu
- Department of Biophysics, Bose Institute, P-1/12 CIT Scheme VIIM, Kolkata 700054, West Bengal, India
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4
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A New Generation of Minor-Groove-Binding-Heterocyclic Diamidines That Recognize G·C Base Pairs in an AT Sequence Context. Molecules 2019; 24:molecules24050946. [PMID: 30866557 PMCID: PMC6429135 DOI: 10.3390/molecules24050946] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2019] [Revised: 02/28/2019] [Accepted: 03/01/2019] [Indexed: 12/17/2022] Open
Abstract
We review the preparation of new compounds with good solution and cell uptake properties that can selectively recognize mixed A·T and G·C bp sequences of DNA. Our underlying aim is to show that these new compounds provide important new biotechnology reagents as well as a new class of therapeutic candidates with better properties and development potential than other currently available agents. In this review, entirely different ways to recognize mixed sequences of DNA by modifying AT selective heterocyclic cations are described. To selectively recognize a G·C base pair an H-bond acceptor must be incorporated with AT recognizing groups as with netropsin. We have used pyridine, azabenzimidazole and thiophene-N-methylbenzimidazole GC recognition units in modules crafted with both rational design and empirical optimization. These modules can selectively and strongly recognize a single G·C base pair in an AT sequence context. In some cases, a relatively simple change in substituents can convert a heterocyclic module from AT to GC recognition selectivity. Synthesis and DNA interaction results for initial example lead modules are described for single G·C base pair recognition compounds. The review concludes with a description of the initial efforts to prepare larger compounds to recognize sequences of DNA with more than one G·C base pairs. The challenges and initial successes are described along with future directions.
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5
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Spring-Connell AM, Evich M, Germann MW. NMR Structure Determination for Oligonucleotides. ACTA ACUST UNITED AC 2019; 72:7.28.1-7.28.39. [PMID: 29927124 DOI: 10.1002/cpnc.48] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
NMR spectroscopy is a versatile tool for determining the structure and dynamics of nucleic acids under solution conditions. In this unit, we provide an overview and detail of the experiments and methods used in our laboratory to determine the structure of oligonucleotides at natural abundance, thus limiting our approach to 1 H, 13 C, and 31 P NMR techniques. Isotopic labeling is heavily used in RNA NMR studies, however, labeling of DNA is still less common and, if modified nucleotides are investigated, is exceptionally expensive or not feasible. Each method described here is extensively documented and annotated with tips and observations to facilitate their application. Sections are devoted to sample preparation, NMR experiments and setup, resonance assignment, structure generation protocols, evaluation, tips that may be useful, and software sources. © 2018 by John Wiley & Sons, Inc.
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Affiliation(s)
| | - Marina Evich
- Department of Chemistry, Georgia State University, Atlanta, Georgia
| | - Markus W Germann
- Department of Chemistry, Georgia State University, Atlanta, Georgia.,Neuroscience Institute, Georgia State University, Atlanta, Georgia
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6
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Carter EK, Laughlin-Toth S, Dodd T, Wilson WD, Ivanov I. Small molecule binders recognize DNA microstructural variations via an induced fit mechanism. Phys Chem Chem Phys 2019; 21:1841-1851. [PMID: 30629058 PMCID: PMC6497476 DOI: 10.1039/c8cp05537h] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Regulation of gene-expression by specific targeting of protein-nucleic acid interactions has been a long-standing goal in medicinal chemistry. Transcription factors are considered "undruggable" because they lack binding sites well suited for binding small-molecules. In order to overcome this obstacle, we are interested in designing small molecules that bind to the corresponding promoter sequences and either prevent or modulate transcription factor association via an allosteric mechanism. To achieve this, we must design small molecules that are both sequence-specific and able to target G/C base pair sites. A thorough understanding of the relationship between binding affinity and the structural aspects of the small molecule-DNA complex would greatly aid in rational design of such compounds. Here we present a comprehensive analysis of sequence-specific DNA association of a synthetic minor groove binder using long timescale molecular dynamics. We show how binding selectivity arises from a combination of structural factors. Our results provide a framework for the rational design and optimization of synthetic small molecules in order to improve site-specific targeting of DNA for therapeutic uses in the design of selective DNA binders targeting transcription regulation.
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Affiliation(s)
- E. Kathleen Carter
- Department of Chemistry and Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, GA, USA. ;
| | - Sarah Laughlin-Toth
- Department of Chemistry and Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, GA, USA. ;
- Department of Pediatrics, Aflac Cancer and Blood Disorders Center, Emory University School of Medicine, Atlanta, GA, USA
| | - Thomas Dodd
- Department of Chemistry and Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, GA, USA. ;
| | - W. David Wilson
- Department of Chemistry and Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, GA, USA. ;
| | - Ivaylo Ivanov
- Department of Chemistry and Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, GA, USA. ;
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7
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Harika NK, Wilson WD. Bound Compound, Interfacial Water, and Phenyl Ring Rotation Dynamics of a Compound in the DNA Minor Groove. Biochemistry 2018; 57:5050-5057. [PMID: 30048590 DOI: 10.1021/acs.biochem.8b00647] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
DB2277, a heterocyclic diamidine, is a successful design for mixed base pair (bp) DNA sequence recognition. The compound has a central aza-benzimidazole group that forms two H-bonds with a GC bp that has flanking AT bps. The nuclear magnetic resonance structure of the DB2277-DNA complex with an AAGATA recognition site sequence was determined, and here we report extended molecular dynamics (MD) simulations of the structure. DB2277 has two terminal phenyl-amidine groups, one of which is directly linked to the DB2277 heterocyclic core and the other through a flexible -OCH2- group. The flexibly linked phenyl is too far from the minor groove floor to make direct H-bonds but is linked to an AT bp through water-mediated H-bonds. The flexibly linked phenyl-amidine with water-mediated H-bonds to the bases at the floor of the minor groove suggested that it might rotate in time spans accessible in MD. To test this idea, we conducted multimicrosecond MD simulations to determine if these phenyl rotations could be observed for a bound compound. In a 3 μs simulation, highly dynamic torsional motions were observed for the -OCH2-linked phenyl but not for the other phenyl. The dynamics periodically reached a level to allow 180° rotation of the phenyl while it was still bound in the minor groove. This is the first observation of rotation of a phenyl bound to DNA, and the results provide mechanistic details about how a rotation can occur as well as how mixed bp recognition can occur for monomer compounds bound to the minor groove.
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Affiliation(s)
- Narinder K Harika
- Department of Chemistry , Georgia State University , Atlanta , Georgia 30303-3083 , United States
| | - W David Wilson
- Department of Chemistry , Georgia State University , Atlanta , Georgia 30303-3083 , United States
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8
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Paul A, Kumar A, Nanjunda R, Farahat AA, Boykin DW, Wilson WD. Systematic synthetic and biophysical development of mixed sequence DNA binding agents. Org Biomol Chem 2018; 15:827-835. [PMID: 27995240 DOI: 10.1039/c6ob02390h] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
It is now well established that, although only about 5% of the human genome codes for protein, most of the DNA has some function, such as synthesis of specific, functional RNAs and/or control of gene expression. These functional sequences open immense possibilities in both biotechnology and therapeutics for the use of cell-permeable, small molecules that can bind mixed-base pair sequences of DNA for regulation of genomic functions. Unfortunately very few types of modules have been designed to recognize mixed DNA sequences and for progress in targeting specific genes, it is essential to have additional classes of compounds. Compounds that can be rationally designed from established modules and which can bind strongly to mixed base pair DNA sequences are especially attractive. Based on extensive experience in design of minor-groove agents for AT recognition, a small library of compounds with two AT specific binding modules, connected through linkers which can recognize the G·C base pairs, were prepared. The compound-DNA interactions were evaluated with a powerful array of biophysical methods and the results show that some pyridyl-linked compounds bind with the target sequence with sub-nanomolar KD, with very slow dissociation kinetics and 200 times selectivity over the related sequence without a G·C base pair. Interestingly, a set of compounds with AT module connected by different linkers shows cooperative dimer recognition of related sequences. This type of design approach can be expanded to additional modules for recognition of a wide variety of sequences.
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Affiliation(s)
- Ananya Paul
- Department of Chemistry and Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, GA 30303-3083, USA.
| | - Arvind Kumar
- Department of Chemistry and Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, GA 30303-3083, USA.
| | - Rupesh Nanjunda
- Department of Chemistry and Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, GA 30303-3083, USA. and Janssen Research and Development, 1400 McKean Rd, Spring House, PA 19477, USA
| | - Abdelbasset A Farahat
- Department of Chemistry and Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, GA 30303-3083, USA. and Department of Pharmaceutical Organic Chemistry, Faculty of Pharmacy, Mansoura University, Mansoura 35516, Egypt
| | - David W Boykin
- Department of Chemistry and Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, GA 30303-3083, USA.
| | - W David Wilson
- Department of Chemistry and Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, GA 30303-3083, USA.
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9
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Saha A, Kizaki S, Han JH, Yu Z, Sugiyama H. UVA irradiation of BrU-substituted DNA in the presence of Hoechst 33258. Bioorg Med Chem 2018; 26:37-40. [PMID: 29170027 DOI: 10.1016/j.bmc.2017.11.011] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2017] [Revised: 11/02/2017] [Accepted: 11/04/2017] [Indexed: 01/15/2023]
Abstract
Given that our knowledge of DNA repair is limited because of the complexity of the DNA system, a technique called UVA micro-irradiation has been developed that can be used to visualize the recruitment of DNA repair proteins at double-strand break (DSB) sites. Interestingly, Hoechst 33258 was used under micro-irradiation to sensitize 5-bromouracil (BrU)-labelled DNA, causing efficient DSBs. However, the molecular basis of DSB formation under UVA micro-irradiation remains unknown. Herein, we investigated the mechanism of DSB formation under UVA micro-irradiation conditions. Our results suggest that the generation of a uracil-5-yl radical through electron transfer from Hoechst 33258 to BrU caused DNA cleavage preferentially at self-complementary 5'-AABrUBrU-3' sequences to induce DSB. We also investigated the DNA cleavage in the context of the nucleosome to gain a better understanding of UVA micro-irradiation in a cell-like model. We found that DNA cleavage occurred in both core and linker DNA regions although its efficiency reduced in core DNA.
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Affiliation(s)
- Abhijit Saha
- Department of Science, Graduate School of Science, Kyoto University, Sakyo, Kyoto 606-8501, Japan
| | - Seiichiro Kizaki
- Department of Science, Graduate School of Science, Kyoto University, Sakyo, Kyoto 606-8501, Japan
| | - Ji Hoon Han
- Department of Science, Graduate School of Science, Kyoto University, Sakyo, Kyoto 606-8501, Japan
| | - Zutao Yu
- Department of Science, Graduate School of Science, Kyoto University, Sakyo, Kyoto 606-8501, Japan
| | - Hiroshi Sugiyama
- Department of Science, Graduate School of Science, Kyoto University, Sakyo, Kyoto 606-8501, Japan; Institute for Integrated Cell-Material Sciences (iCeMS), Kyoto University, Yoshida Ushinomiya-cho, Sakyo, Kyoto 606-8502, Japan.
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10
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Harika NK, Germann MW, Wilson WD. First Structure of a Designed Minor Groove Binding Heterocyclic Cation that Specifically Recognizes Mixed DNA Base Pair Sequences. Chemistry 2017; 23:17612-17620. [PMID: 29044822 PMCID: PMC6360951 DOI: 10.1002/chem.201704563] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2017] [Indexed: 12/24/2022]
Abstract
The high-resolution NMR structure of the first heterocyclic, non-amide, organic cation that strongly and selectively recognizes mixed AT/GC bp (bp=base pair) sequences of DNA in a 1:1 complex is described. Compound designs of this type provide essential methods for control of functional, non-genomic DNA sequences and have broad cell uptake capability, based on studies from animals to humans. The high-resolution structural studies described in this report are essential for understanding the molecular basis for the sequence-specific binding as well as for new ideas for additional compound designs for sequence-specific recognition. The molecular features, in this report, explain the mechanism of recognition of both A⋅T and G⋅C bps and are an interesting molecular recognition story. Examination of the experimental structure and the NMR restrained molecular dynamics model suggests that recognition of the G⋅C base pair involves two specific H-bonds. The structure illustrates a wealth of information on different DNA interactions and illustrates an interfacial water molecule that is a key component of the complex.
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Affiliation(s)
- Narinder K. Harika
- Department of Chemistry, Georgia State University, Atlanta, GA 30303-3083, USA
| | - Markus W. Germann
- Department of Chemistry, Georgia State University, Atlanta, GA 30303-3083, USA
| | - W. David Wilson
- Department of Chemistry, Georgia State University, Atlanta, GA 30303-3083, USA
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11
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Guo P, Paul A, Kumar A, Farahat AA, Kumar D, Wang S, Boykin DW, Wilson WD. The Thiophene "Sigma-Hole" as a Concept for Preorganized, Specific Recognition of G⋅C Base Pairs in the DNA Minor Groove. Chemistry 2016; 22:15404-15412. [PMID: 27624927 PMCID: PMC5214980 DOI: 10.1002/chem.201603422] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2016] [Indexed: 11/10/2022]
Abstract
In spite of its importance in cell function, targeting DNA is under-represented in the design of small molecules. A barrier to progress in this area is the lack of a variety of modules that recognize G⋅C base pairs (bp) in DNA sequences. To overcome this barrier, an entirely new design concept for modules that can bind to mixed G⋅C and A⋅T sequences of DNA is reported herein. Because of their successes in biological applications, minor-groove-binding heterocyclic cations were selected as the platform for design. Binding to A⋅T sequences requires hydrogen-bond donors whereas recognition of the G-NH2 requires an acceptor. The concept that we report herein uses pre-organized N-methylbenzimidazole (N-MeBI) thiophene modules for selective binding with mixed bp DNA sequences. The interaction between the thiophene sigma hole (positive electrostatic potential) and the electron-donor nitrogen of N-MeBI preorganizes the conformation for accepting an hydrogen bond from G-NH2 . The compound-DNA interactions were evaluated with a powerful array of biophysical methods and the results show that N-MeBI-thiophene monomer compounds can strongly and selectively recognize single G⋅C bp sequences. Replacing the thiophene with other moieties significantly reduces binding affinity and specificity, as predicted by the design concept. These results show that the use of molecular features, such as sigma-holes, can lead to new approaches for small molecules in biomolecular interactions.
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Affiliation(s)
- Pu Guo
- Department of Chemistry and Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, GA, 30303-3083, USA
| | - Ananya Paul
- Department of Chemistry and Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, GA, 30303-3083, USA
| | - Arvind Kumar
- Department of Chemistry and Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, GA, 30303-3083, USA
| | - Abdelbasset A Farahat
- Department of Chemistry and Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, GA, 30303-3083, USA
- Department of Pharmaceutical Organic Chemistry, Faculty of Pharmacy, Mansoura University, Mansoura, 35516, Egypt
| | - Dhiraj Kumar
- Department of Chemistry and Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, GA, 30303-3083, USA
| | - Siming Wang
- Department of Chemistry and Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, GA, 30303-3083, USA
| | - David W Boykin
- Department of Chemistry and Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, GA, 30303-3083, USA
| | - W David Wilson
- Department of Chemistry and Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, GA, 30303-3083, USA.
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12
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Abou-Elkhair RAI, Hassan AEA, Boykin DW, Wilson WD. Lithium Hexamethyldisilazane Transformation of Transiently Protected 4-Aza/Benzimidazole Nitriles to Amidines and their Dimethyl Sulfoxide Mediated Imidazole Ring Formation. Org Lett 2016; 18:4714-7. [PMID: 27607538 DOI: 10.1021/acs.orglett.6b02359] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Trimethylsilyl-transient protection successfully allowed the use of lithium hexamethyldisilazane to prepare benzimidazole (BI) and 4-azabenzimidazole (azaBI) amidines from nitriles in 58-88% yields. This strategy offers a much better choice to prepare BI/azaBI amidines than the lengthy, low-yielding Pinner reaction. Synthesis of aza/benzimidazole rings from aromatic diamines and aldehydes was affected in dimethyl sulfoxide in 10-15 min, while known procedures require long time and purification. These methods are important for the BI/azaBI-based drug industry and for developing specific DNA binders for expanded therapeutic applications.
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Affiliation(s)
- Reham A I Abou-Elkhair
- Department of Chemistry, Georgia State University , Atlanta, Georgia 30303, United States.,Applied Nucleic Acids Research Center & Chemistry Department, Faculty of Sciences, Zagazig University , Zagazig 44519, Egypt
| | - Abdalla E A Hassan
- Applied Nucleic Acids Research Center & Chemistry Department, Faculty of Sciences, Zagazig University , Zagazig 44519, Egypt
| | - David W Boykin
- Department of Chemistry, Georgia State University , Atlanta, Georgia 30303, United States
| | - W David Wilson
- Department of Chemistry, Georgia State University , Atlanta, Georgia 30303, United States
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