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Zhou W, Saran R, Ding J, Liu J. Two Completely Different Mechanisms for Highly Specific Na + Recognition by DNAzymes. Chembiochem 2017; 18:1828-1835. [PMID: 28658518 DOI: 10.1002/cbic.201700184] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2017] [Indexed: 02/06/2023]
Abstract
Our view of the interaction between Na+ and nucleic acids was changed by a few recently discovered Na+ -specific RNA-cleaving DNAzymes. In addition to nonspecific electrostatic interactions, highly specific recognition is also possible. Herein, two such DNAzymes, named EtNa and Ce13d, are compared to elucidate their mechanisms of Na+ binding. Mutation studies indicate that they have different sequence requirements. Phosphorothioate (PS) substitution at the scissile phosphate drops the activity of EtNa 140-fold, and it cannot be rescued by thiophilic Cd2+ or Mn2+ , whereas the activity of PS-modified Ce13d can be rescued. Na+ -dependent activity assays indicate that two Na+ ions bind cooperatively in EtNa, and each Na+ likely interacts with a nonbridging oxygen atom in the scissile phosphate, whereas Ce13d binds only one Na+ ion in a well-defined Na+ aptamer, and this Na+ ion does not directly interact with the scissile phosphate. Both DNAzymes display a normal pH-rate profile, with a single deprotonation reaction required for catalysis. For EtNa, Na+ fails to protect the conserved nucleotides from dimethyl sulfate attack, and no specific Na+ binding is detected by 2-aminopurine fluorescence, both of which are different from those observed for Ce13d. This work suggests that EtNa binds Na+ mainly through its scissile phosphate without significant involvement of the nucleotides in the enzyme strand, whereas Ce13d has a well-defined aptamer for Na+ binding. Therefore, DNA has at least two distinct ways to achieve highly selective Na+ binding.
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Affiliation(s)
- Wenhu Zhou
- Department of Chemistry and Waterloo Institute for Nanotechnology, University of Waterloo, 200 University Avenue West, Waterloo, Ontario, N2L 3G1, Canada.,Xiangya School of Pharmaceutical Sciences, Central South University, 172 Tongzipo Road, Changsha, Hunan, 410013, China
| | - Runjhun Saran
- Department of Chemistry and Waterloo Institute for Nanotechnology, University of Waterloo, 200 University Avenue West, Waterloo, Ontario, N2L 3G1, Canada
| | - Jinsong Ding
- Xiangya School of Pharmaceutical Sciences, Central South University, 172 Tongzipo Road, Changsha, Hunan, 410013, China
| | - Juewen Liu
- Department of Chemistry and Waterloo Institute for Nanotechnology, University of Waterloo, 200 University Avenue West, Waterloo, Ontario, N2L 3G1, Canada
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Affiliation(s)
- Wenhu Zhou
- Xiangya
School of Pharmaceutical Sciences, Central South University, Changsha, Hunan 410013, China
- Department
of Chemistry, Water Institute, and Waterloo Institute for Nanotechnology, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
| | - Runjhun Saran
- Department
of Chemistry, Water Institute, and Waterloo Institute for Nanotechnology, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
| | - Juewen Liu
- Department
of Chemistry, Water Institute, and Waterloo Institute for Nanotechnology, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
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Li W, Zhang Z, Zhou W, Liu J. Kinetic Discrimination of Metal Ions Using DNA for Highly Sensitive and Selective Cr 3+ Detection. ACS Sens 2017; 2:663-669. [PMID: 28723165 DOI: 10.1021/acssensors.7b00115] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Most metal sensors are designed for a strong binding affinity toward target metal ions, and the underlying principle relies on binding thermodynamics. The kinetic aspect of binding, however, was rarely explored for sensing. In this work, the binding kinetics of 19 common or toxic metal ions are compared based on a fluorescence quenching assay using DNA oligonucleotides as ligands. Among these metals, Cr3+ shows uniquely slow fluorescence quenching kinetics, and the quenched fluorescence cannot be recovered by EDTA or sulfide. Most other metals quenched fluorescence instantaneously and can be fully recovered by these metal chelators. Various factors such as DNA sequence and length, chelating agent, pH, and fluorophore type were studied to understand the binding mechanism, leading to a unique two-stage binding model for Cr3+. This system has a wide dynamic range of up to 50 μM Cr3+ and a low limit of detection of 80 nM. It is also useful for measuring Cr3+ in lake water. This work proposes a new metal sensor design by monitoring binding kinetics with Cr3+ being a primary example.
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Affiliation(s)
- Wang Li
- College of Food Science & Engineering, Central South University of Forestry & Technology, Changsha, Hunan 410004, China
- Department
of Chemistry, Water Institute and Waterloo Institute for Nanotechnology, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
| | - Zijie Zhang
- Department
of Chemistry, Water Institute and Waterloo Institute for Nanotechnology, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
| | - Wenhu Zhou
- Xiangya
School of Pharmaceutical Sciences, Central South University, Changsha, Hunan 410013, China
- Department
of Chemistry, Water Institute and Waterloo Institute for Nanotechnology, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
| | - Juewen Liu
- Department
of Chemistry, Water Institute and Waterloo Institute for Nanotechnology, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
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Chakravarthy M, Aung-Htut MT, Le BT, Veedu RN. Novel Chemically-modified DNAzyme targeting Integrin alpha-4 RNA transcript as a potential molecule to reduce inflammation in multiple sclerosis. Sci Rep 2017; 7:1613. [PMID: 28487530 PMCID: PMC5431638 DOI: 10.1038/s41598-017-01559-w] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2017] [Accepted: 03/28/2017] [Indexed: 11/19/2022] Open
Abstract
Integrin alpha-4 (ITGA4) is a validated therapeutic target for multiple sclerosis (MS) and Natalizumab, an antibody targeting ITGA4 is currently approved for treating MS. However, there are severe side effects related to this therapy. In this study, we report the development of a novel DNAzyme that can efficiently cleave the ITGA4 transcript. We designed a range of DNAzyme candidates across various exons of ITGA4. RNV143, a 30mer arm-loop-arm type DNAzyme efficiently cleaved 84% of the ITGA4 mRNA in human primary fibroblasts. RNV143 was then systematically modified by increasing the arm lengths on both sides of the DNAzymes by one, two and three nucleotides each, and incorporating chemical modifications such as inverted-dT, phosphorothioate backbone and LNA-nucleotides. Increasing the arm length of DNAzyme RNV143 did not improve the efficiency however, an inverted-dT modification provided the most resistance to 3′ → 5′ exonuclease compared to other modifications tested. Our results show that RNV143A could be a potential therapeutic nucleic acid drug molecule towards the treatment for MS.
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Affiliation(s)
- Madhuri Chakravarthy
- Centre for Comparative Genomics, Discovery Way, Murdoch University, Perth, WA, 6150, Australia.,Perron Institute for Neurological and Translational Science, Nedlands, WA, 6009, Australia
| | - May T Aung-Htut
- Centre for Comparative Genomics, Discovery Way, Murdoch University, Perth, WA, 6150, Australia.,Perron Institute for Neurological and Translational Science, Nedlands, WA, 6009, Australia
| | - Bao T Le
- Centre for Comparative Genomics, Discovery Way, Murdoch University, Perth, WA, 6150, Australia.,Perron Institute for Neurological and Translational Science, Nedlands, WA, 6009, Australia
| | - Rakesh N Veedu
- Centre for Comparative Genomics, Discovery Way, Murdoch University, Perth, WA, 6150, Australia. .,Perron Institute for Neurological and Translational Science, Nedlands, WA, 6009, Australia.
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Saran R, Kleinke K, Zhou W, Yu T, Liu J. A Silver-Specific DNAzyme with a New Silver Aptamer and Salt-Promoted Activity. Biochemistry 2017; 56:1955-1962. [PMID: 28345892 DOI: 10.1021/acs.biochem.6b01131] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Most RNA-cleaving DNAzymes require a metal ion to interact with the scissile phosphate for activity. Therefore, few unmodified DNAzymes work with thiophilic metals because of their low affinity for phosphate. Recently, an Ag+-specific Ag10c DNAzyme was reported via in vitro selection. Herein, Ag10c is characterized to rationalize the role of the strongly thiophilic Ag+. Systematic mutation studies indicate that Ag10c is a highly conserved DNAzyme and its Ag+ binding is unrelated to C-Ag+-C interaction. Its activity is enhanced by increasing Na+ concentrations in buffer. At the same metal concentration, activity decreases in the following order: Li+ > Na+ > K+. Ag10c binds one Na+ ion and two Ag+ ions for catalysis. The pH-rate profile has a slope of ∼1, indicating a single deprotonation step. Phosphorothioate substitution at the scissile phosphate suggests that Na+ interacts with the pro-Rp oxygen of the phosphate, and dimethyl sulfate footprinting indicates that the DNAzyme loop is a silver aptamer binding two Ag+ ions. Therefore, Ag+ exerts its function allosterically, while the scissile phosphate interacts with Na+, Li+, Na+, or Mg2+. This work suggests the possibility of isolating thiophilic metal aptamers based on DNAzyme selection, and it also demonstrates a new Ag+ aptamer.
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Affiliation(s)
- Runjhun Saran
- Department of Chemistry, Waterloo Institute for Nanotechnology, University of Waterloo , Waterloo, Ontario N2L 3G1, Canada
| | - Kimberly Kleinke
- Department of Chemistry, Waterloo Institute for Nanotechnology, University of Waterloo , Waterloo, Ontario N2L 3G1, Canada
| | - Wenhu Zhou
- Department of Chemistry, Waterloo Institute for Nanotechnology, University of Waterloo , Waterloo, Ontario N2L 3G1, Canada
| | - Tianmeng Yu
- Department of Chemistry, Waterloo Institute for Nanotechnology, University of Waterloo , Waterloo, Ontario N2L 3G1, Canada
| | - Juewen Liu
- Department of Chemistry, Waterloo Institute for Nanotechnology, University of Waterloo , Waterloo, Ontario N2L 3G1, Canada
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