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Ogbonna E, Paul A, Farahat AA, Terrell JR, Mineva E, Ogbonna V, Boykin DW, Wilson WD. X-ray Structure Characterization of the Selective Recognition of AT Base Pair Sequences. ACS BIO & MED CHEM AU 2023; 3:335-348. [PMID: 37599788 PMCID: PMC10436263 DOI: 10.1021/acsbiomedchemau.3c00002] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2023] [Revised: 03/23/2023] [Accepted: 03/24/2023] [Indexed: 08/22/2023]
Abstract
The rational design of small molecules that target specific DNA sequences is a promising strategy to modulate gene expression. This report focuses on a diamidinobenzimidazole compound, whose selective binding to the minor groove of AT DNA sequences holds broad significance in the molecular recognition of AT-rich human promoter sequences. The objective of this study is to provide a more detailed and systematized understanding, at an atomic level, of the molecular recognition mechanism of different AT-specific sequences by a rationally designed minor groove binder. The specialized method of X-ray crystallography was utilized to investigate how the sequence-dependent recognition properties in general, A-tract, and alternating AT sequences affect the binding of diamidinobenzimidazole in the DNA minor groove. While general and A-tract AT sequences give a narrower minor groove, the alternating AT sequences intrinsically have a wider minor groove which typically constricts upon binding. A strong and direct hydrogen bond between the N-H of the benzimidazole and an H-bond acceptor atom in the minor groove is essential for DNA recognition in all sequences described. In addition, the diamidine compound specifically utilizes an interfacial water molecule for its DNA binding. DNA complexes of AATT and AAAAAA recognition sites show that the diamidine compound can bind in two possible orientations with a preference for water-assisted hydrogen bonding at either cationic end. The complex structures of AAATTT, ATAT, ATATAT, and AAAA are bound in a singular orientation. Analysis of the helical parameters shows a minor groove expansion of about 1 Å across all the nonalternating DNA complexes. The results from this systematic approach will convey a greater understanding of the specific recognition of a diverse array of AT-rich sequences by small molecules and more insight into the design of small molecules with enhanced specificity to AT and mixed DNA sequences.
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Affiliation(s)
- Edwin
N. Ogbonna
- Department
of Chemistry and Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, Georgia 30303-3083, United States
| | - Ananya Paul
- Department
of Chemistry and Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, Georgia 30303-3083, United States
| | - Abdelbasset A. Farahat
- Department
of Chemistry and Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, Georgia 30303-3083, United States
- Department
of Pharmaceutical Organic Chemistry, Faculty of Pharmacy, Mansoura University, Mansoura 35516, Egypt
- Master
of Pharmaceutical Sciences Program, California
North State University, 9700 W Taron Dr., Elk Grove, California 95757, United States
| | - J. Ross Terrell
- Department
of Chemistry and Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, Georgia 30303-3083, United States
| | - Ekaterina Mineva
- Department
of Chemistry and Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, Georgia 30303-3083, United States
| | - Victor Ogbonna
- Department
of Chemistry and Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, Georgia 30303-3083, United States
| | - David W Boykin
- Department
of Chemistry and Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, Georgia 30303-3083, United States
| | - W. David Wilson
- Department
of Chemistry and Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, Georgia 30303-3083, United States
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Paul A, Farahat AA, Boykin DW, Wilson WD. Thermodynamic Factors That Drive Sequence-Specific DNA Binding of Designed, Synthetic Minor Groove Binding Agents. Life (Basel) 2022; 12:life12050681. [PMID: 35629349 PMCID: PMC9147024 DOI: 10.3390/life12050681] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2022] [Revised: 04/29/2022] [Accepted: 04/29/2022] [Indexed: 11/16/2022] Open
Abstract
Ken Breslauer began studies on the thermodynamics of small cationic molecules binding in the DNA minor groove over 30 years ago, and the studies reported here are an extension of those ground-breaking reports. The goals of this report are to develop a detailed understanding of the binding thermodynamics of pyridine-based sequence-specific minor groove binders that have different terminal cationic groups. We apply biosensor-surface plasmon resonance and ITC methods to extend the understanding of minor groove binders in two directions: (i) by using designed, heterocyclic dicationic minor groove binders that can incorporate a G•C base pair (bp), with flanking AT base pairs, into their DNA recognition site, and bind to DNA sequences specifically; and (ii) by using a range of flanking AT sequences to better define molecular recognition of the minor groove. A G•C bp in the DNA recognition site causes a generally more negative binding enthalpy than with most previously used pure AT binding sites. The binding is enthalpy-driven at 25 °C and above. The flanking AT sequences also have a large effect on the binding energetics with the -AAAGTTT- site having the strongest affinity. As a result of these studies, we now have a much better understanding of the effects of the DNA sequence and compound structure on the molecular recognition and thermodynamics of minor groove complexes.
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Affiliation(s)
- Ananya Paul
- Department of Chemistry and Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, GA 30303, USA; (A.P.); (A.A.F.); (D.W.B.)
| | - Abdelbasset A. Farahat
- Department of Chemistry and Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, GA 30303, USA; (A.P.); (A.A.F.); (D.W.B.)
- 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, USA; (A.P.); (A.A.F.); (D.W.B.)
| | - W. David Wilson
- Department of Chemistry and Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, GA 30303, USA; (A.P.); (A.A.F.); (D.W.B.)
- Correspondence: ; Tel.: +1-404-413-5503; Fax: +1-404-413-5505
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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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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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Guo P, Farahat AA, Paul A, Harika NK, Boykin DW, Wilson WD. Compound Shape Effects in Minor Groove Binding Affinity and Specificity for Mixed Sequence DNA. J Am Chem Soc 2018; 140:14761-14769. [PMID: 30353731 PMCID: PMC6399738 DOI: 10.1021/jacs.8b08152] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
AT specific heterocyclic cations that bind in the DNA duplex minor groove have had major successes as cell and nuclear stains and as therapeutic agents which can effectively enter human cells. Expanding the DNA sequence recognition capability of the minor groove compounds could also expand their therapeutic targets and have an impact in many areas, such as modulation of transcription factor biological activity. Success in the design of mixed sequence binding compounds has been achieved with N-methylbenzimidazole ( N-MeBI) thiophenes which are preorganized to fit the shape of the DNA minor groove and H-bond to the -NH of G·C base pairs that project into the minor groove. Initial compounds bind strongly to a single G·C base pair in an AT context with a specificity ratio of 50 ( KD AT-GC/ KD AT) or less and this is somewhat low for biological use. We felt that modifications of compound shape could be used to probe local DNA microstructure in target mixed base pair sequences of DNA and potentially improve the compound binding selectivity. Modifications were made by increasing the size of the benzimidazole N-substituent, for example, by using N-isobutyl instead of N-Me, and by changing the molecular twist by introducing substitutions at specific positions on the aromatic core of the compounds. In both cases, we have been able to achieve a dramatic increase in binding specificity, including no detectible binding to pure AT sequences, without a significant loss in affinity to mixed base pair target sequences.
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Affiliation(s)
- Pu Guo
- Department of Chemistry and Center for Diagnostics and Therapeutics , Georgia State University , 50 Decatur Street South East , Atlanta , Georgia 30303 , United States
| | - Abdelbasset A Farahat
- Department of Chemistry and Center for Diagnostics and Therapeutics , Georgia State University , 50 Decatur Street South East , Atlanta , Georgia 30303 , United States
- Department of Pharmaceutical Organic Chemistry, Faculty of Pharmacy , Mansoura University , Mansoura 35516 , Egypt
| | - Ananya Paul
- Department of Chemistry and Center for Diagnostics and Therapeutics , Georgia State University , 50 Decatur Street South East , Atlanta , Georgia 30303 , United States
| | - Narinder K Harika
- Department of Chemistry and Center for Diagnostics and Therapeutics , Georgia State University , 50 Decatur Street South East , Atlanta , Georgia 30303 , United States
| | - David W Boykin
- Department of Chemistry and Center for Diagnostics and Therapeutics , Georgia State University , 50 Decatur Street South East , Atlanta , Georgia 30303 , United States
| | - W David Wilson
- Department of Chemistry and Center for Diagnostics and Therapeutics , Georgia State University , 50 Decatur Street South East , Atlanta , Georgia 30303 , United States
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