1
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Fan H. Single‐molecule tethered particle motion to study
protein‐DNA
interaction. J CHIN CHEM SOC-TAIP 2023. [DOI: 10.1002/jccs.202300051] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/31/2023]
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2
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Single-exonuclease nanocircuits reveal the RNA degradation dynamics of PNPase and demonstrate potential for RNA sequencing. Nat Commun 2023; 14:552. [PMID: 36725855 PMCID: PMC9892577 DOI: 10.1038/s41467-023-36278-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2022] [Accepted: 01/23/2023] [Indexed: 02/03/2023] Open
Abstract
The degradation process of RNA is decisive in guaranteeing high-fidelity translation of genetic information in living organisms. However, visualizing the single-base degradation process in real time and deciphering the degradation mechanism at the single-enzyme level remain formidable challenges. Here, we present a reliable in-situ single-PNPase-molecule dynamic electrical detector based on silicon nanowire field-effect transistors with ultra-high temporal resolution. These devices are capable of realizing real-time and label-free monitoring of RNA analog degradation with single-base resolution, including RNA analog binding, single-nucleotide hydrolysis, and single-base movement. We discover a binding event of the enzyme (near the active site) with the nucleoside, offering a further understanding of the RNA degradation mechanism. Relying on systematic analyses of independent reads, approximately 80% accuracy in RNA nucleoside sequencing is achieved in a single testing process. This proof-of-concept sets up a Complementary Metal Oxide Semiconductor (CMOS)-compatible playground for the development of high-throughput detection technologies toward mechanistic exploration and single-molecule sequencing.
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3
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Jia X, Li Y, Wang T, Bi L, Guo L, Chen Z, Zhang X, Ye S, Chen J, Yang B, Sun B. Discrete RNA-DNA hybrid cleavage by the EXD2 exonuclease pinpoints two rate-limiting steps. EMBO J 2023; 42:e111703. [PMID: 36326837 PMCID: PMC9811613 DOI: 10.15252/embj.2022111703] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2022] [Revised: 10/17/2022] [Accepted: 10/17/2022] [Indexed: 11/06/2022] Open
Abstract
EXD2 is a recently identified exonuclease that cleaves RNA and DNA in double-stranded (ds) forms. It thus serves as a model system for investigating the similarities and discrepancies between exoribonuclease and exodeoxyribonuclease activities and for understanding the nucleic acid (NA) unwinding-degradation coordination of an exonuclease. Here, using a single-molecule fluorescence resonance energy transfer (smFRET) approach, we show that despite stable binding to both substrates, EXD2 barely cleaves dsDNA and yet displays both exoribonuclease and exodeoxyribonuclease activities toward RNA-DNA hybrids with a cleavage preference for RNA. Unexpectedly, EXD2-mediated hybrid cleavage proceeds in a discrete stepwise pattern, wherein a sudden 4-bp duplex unwinding increment and the subsequent dwell constitute a complete hydrolysis cycle. The relatively weak exodeoxyribonuclease activity of EXD2 partially originates from frequent hybrid rewinding. Importantly, kinetic analysis and comparison of the dwell times under varied conditions reveal two rate-limiting steps of hybrid unwinding and nucleotide excision. Overall, our findings help better understand the cellular functions of EXD2, and the cyclic coupling between duplex unwinding and exonucleolytic degradation may be generalizable to other exonucleases.
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Affiliation(s)
- Xinshuo Jia
- School of Life Science and TechnologyShanghaiTech UniversityShanghaiChina
| | - Yanan Li
- School of Life Science and TechnologyShanghaiTech UniversityShanghaiChina
| | - Teng Wang
- School of Life Science and TechnologyShanghaiTech UniversityShanghaiChina
| | - Lulu Bi
- School of Life Science and TechnologyShanghaiTech UniversityShanghaiChina
| | - Lijuan Guo
- School of Life Science and TechnologyShanghaiTech UniversityShanghaiChina
| | - Ziting Chen
- School of Life Science and TechnologyShanghaiTech UniversityShanghaiChina
| | - Xia Zhang
- School of Life Science and TechnologyShanghaiTech UniversityShanghaiChina
| | - Shasha Ye
- School of Life Science and TechnologyShanghaiTech UniversityShanghaiChina
- Present address:
ZJU‐Hangzhou Global Scientific and Technological Innovation CenterZhejiang UniversityHangzhouChina
| | - Jia Chen
- School of Life Science and TechnologyShanghaiTech UniversityShanghaiChina
| | - Bei Yang
- School of Life Science and TechnologyShanghaiTech UniversityShanghaiChina
- Shanghai Institute for Advanced Immunochemical StudiesShanghaiTech UniversityShanghaiChina
| | - Bo Sun
- School of Life Science and TechnologyShanghaiTech UniversityShanghaiChina
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4
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Improving the specificity of nucleic acid detection with endonuclease-actuated degradation. Commun Biol 2022; 5:290. [PMID: 35361863 PMCID: PMC8971390 DOI: 10.1038/s42003-022-03242-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2021] [Accepted: 03/07/2022] [Indexed: 11/08/2022] Open
Abstract
Nucleic acid detection is essential for numerous biomedical applications, but often requires complex protocols and/or suffers false-positive readouts. Here, we describe SENTINEL, an approach that combines isothermal amplification with a sequence-specific degradation method to detect nucleic acids with high sensitivity and sequence-specificity. Target single-stranded RNA or double-stranded DNA molecules are amplified by loop-mediated isothermal amplification (LAMP) and subsequently degraded by the combined action of lambda exonuclease and a sequence-specific DNA endonuclease (e.g., Cas9). By combining the sensitivity of LAMP with the precision of DNA endonucleases, the protocol achieves attomolar limits of detection while differentiating between sequences that differ by only one or two base pairs. The protocol requires less than an hour to complete using a 65 °C heat block and fluorometer, and detects SARS-CoV-2 virus particles in human saliva and nasopharyngeal swabs with high sensitivity.
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5
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Lee H, Cho H, Kim J, Lee S, Yoo J, Park D, Lee G. RNase H is an exo- and endoribonuclease with asymmetric directionality, depending on the binding mode to the structural variants of RNA:DNA hybrids. Nucleic Acids Res 2022; 50:1801-1814. [PMID: 34788459 PMCID: PMC8886854 DOI: 10.1093/nar/gkab1064] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2021] [Revised: 10/12/2021] [Accepted: 10/20/2021] [Indexed: 11/22/2022] Open
Abstract
RNase H is involved in fundamental cellular processes and is responsible for removing the short stretch of RNA from Okazaki fragments and the long stretch of RNA from R-loops. Defects in RNase H lead to embryo lethality in mice and Aicardi-Goutieres syndrome in humans, suggesting the importance of RNase H. To date, RNase H is known to be a non-sequence-specific endonuclease, but it is not known whether it performs other functions on the structural variants of RNA:DNA hybrids. Here, we used Escherichia coli RNase H as a model, and examined its catalytic mechanism and its substrate recognition modes, using single-molecule FRET. We discovered that RNase H acts as a processive exoribonuclease on the 3' DNA overhang side but as a distributive non-sequence-specific endonuclease on the 5' DNA overhang side of RNA:DNA hybrids or on blunt-ended hybrids. The high affinity of previously unidentified double-stranded (ds) and single-stranded (ss) DNA junctions flanking RNA:DNA hybrids may help RNase H find the hybrid substrates in long genomic DNA. Our study provides new insights into the multifunctionality of RNase H, elucidating unprecedented roles of junctions and ssDNA overhang on RNA:DNA hybrids.
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Affiliation(s)
- Hyunjee Lee
- School of Life Sciences, Gwangju Institute of Science and Technology, Gwangju 61005, Korea
- Single-Molecule Biology Laboratory, Gwangju Institute of Science and Technology, Gwangju 61005, Korea
- Cell Mechanobiology Laboratory, Gwangju Institute of Science and Technology, Gwangju 61005, Korea
| | - HyeokJin Cho
- School of Life Sciences, Gwangju Institute of Science and Technology, Gwangju 61005, Korea
- Single-Molecule Biology Laboratory, Gwangju Institute of Science and Technology, Gwangju 61005, Korea
- Cell Mechanobiology Laboratory, Gwangju Institute of Science and Technology, Gwangju 61005, Korea
| | - Jooyoung Kim
- School of Life Sciences, Gwangju Institute of Science and Technology, Gwangju 61005, Korea
| | - Sua Lee
- School of Life Sciences, Gwangju Institute of Science and Technology, Gwangju 61005, Korea
| | - Jungmin Yoo
- School of Life Sciences, Gwangju Institute of Science and Technology, Gwangju 61005, Korea
- Single-Molecule Biology Laboratory, Gwangju Institute of Science and Technology, Gwangju 61005, Korea
- Cell Mechanobiology Laboratory, Gwangju Institute of Science and Technology, Gwangju 61005, Korea
| | - Daeho Park
- School of Life Sciences, Gwangju Institute of Science and Technology, Gwangju 61005, Korea
- Cell Mechanobiology Laboratory, Gwangju Institute of Science and Technology, Gwangju 61005, Korea
| | - Gwangrog Lee
- School of Life Sciences, Gwangju Institute of Science and Technology, Gwangju 61005, Korea
- Single-Molecule Biology Laboratory, Gwangju Institute of Science and Technology, Gwangju 61005, Korea
- Cell Mechanobiology Laboratory, Gwangju Institute of Science and Technology, Gwangju 61005, Korea
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6
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Deshmukh AL, Caron MC, Mohiuddin M, Lanni S, Panigrahi GB, Khan M, Engchuan W, Shum N, Faruqui A, Wang P, Yuen RKC, Nakamori M, Nakatani K, Masson JY, Pearson CE. FAN1 exo- not endo-nuclease pausing on disease-associated slipped-DNA repeats: A mechanism of repeat instability. Cell Rep 2021; 37:110078. [PMID: 34879276 DOI: 10.1016/j.celrep.2021.110078] [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: 05/06/2021] [Revised: 07/02/2021] [Accepted: 11/09/2021] [Indexed: 12/19/2022] Open
Abstract
Ongoing inchworm-like CAG and CGG repeat expansions in brains, arising by aberrant processing of slipped DNAs, may drive Huntington's disease, fragile X syndrome, and autism. FAN1 nuclease modifies hyper-expansion rates by unknown means. We show that FAN1, through iterative cycles, binds, dimerizes, and cleaves slipped DNAs, yielding striking exo-nuclease pauses along slip-outs: 5'-C↓A↓GC↓A↓G-3' and 5'-C↓T↓G↓C↓T↓G-3'. CAG excision is slower than CTG and requires intra-strand A·A and T·T mismatches. Fully paired hairpins arrested excision, whereas disease-delaying CAA interruptions further slowed excision. Endo-nucleolytic cleavage is insensitive to slip-outs. Rare FAN1 variants are found in individuals with autism with CGG/CCG expansions, and CGG/CCG slip-outs show exo-nuclease pauses. The slip-out-specific ligand, naphthyridine-azaquinolone, which induces contractions of expanded repeats in vivo, requires FAN1 for its effect, and protects slip-outs from FAN1 exo-, but not endo-, nucleolytic digestion. FAN1's inchworm pausing of slip-out excision rates is well suited to modify inchworm expansion rates, which modify disease onset and progression.
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Affiliation(s)
- Amit Laxmikant Deshmukh
- Program of Genetics & Genome Biology, The Hospital for Sick Children, PGCRL, Toronto, Canada, 686 Bay Street, Toronto, ON M5G 0A4, Canada
| | - Marie-Christine Caron
- Genome Stability Laboratory, CHU de Québec Research Center, HDQ Pavilion, Oncology Division, Québec City, QC G1R 3S3, Canada; Department of Molecular Biology, Medical Biochemistry, and Pathology, Laval University Cancer Research Center, Québec City, QC G1R 3S3, Canada
| | - Mohiuddin Mohiuddin
- Program of Genetics & Genome Biology, The Hospital for Sick Children, PGCRL, Toronto, Canada, 686 Bay Street, Toronto, ON M5G 0A4, Canada
| | - Stella Lanni
- Program of Genetics & Genome Biology, The Hospital for Sick Children, PGCRL, Toronto, Canada, 686 Bay Street, Toronto, ON M5G 0A4, Canada
| | - Gagan B Panigrahi
- Program of Genetics & Genome Biology, The Hospital for Sick Children, PGCRL, Toronto, Canada, 686 Bay Street, Toronto, ON M5G 0A4, Canada
| | - Mahreen Khan
- Program of Genetics & Genome Biology, The Hospital for Sick Children, PGCRL, Toronto, Canada, 686 Bay Street, Toronto, ON M5G 0A4, Canada; Program of Molecular Genetics, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Worrawat Engchuan
- Program of Genetics & Genome Biology, The Hospital for Sick Children, PGCRL, Toronto, Canada, 686 Bay Street, Toronto, ON M5G 0A4, Canada
| | - Natalie Shum
- Program of Genetics & Genome Biology, The Hospital for Sick Children, PGCRL, Toronto, Canada, 686 Bay Street, Toronto, ON M5G 0A4, Canada; Program of Molecular Genetics, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Aisha Faruqui
- Program of Genetics & Genome Biology, The Hospital for Sick Children, PGCRL, Toronto, Canada, 686 Bay Street, Toronto, ON M5G 0A4, Canada; Program of Molecular Genetics, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Peixiang Wang
- Program of Genetics & Genome Biology, The Hospital for Sick Children, PGCRL, Toronto, Canada, 686 Bay Street, Toronto, ON M5G 0A4, Canada
| | - Ryan K C Yuen
- Program of Genetics & Genome Biology, The Hospital for Sick Children, PGCRL, Toronto, Canada, 686 Bay Street, Toronto, ON M5G 0A4, Canada; Program of Molecular Genetics, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Masayuki Nakamori
- Department of Neurology, Osaka University Graduate School of Medicine, Osaka 565-0871, Japan
| | - Kazuhiko Nakatani
- Department of Regulatory Bioorganic Chemistry, the Institute of Scientific and Industrial Research, Osaka University, Osaka 567-0047, Japan
| | - Jean-Yves Masson
- Genome Stability Laboratory, CHU de Québec Research Center, HDQ Pavilion, Oncology Division, Québec City, QC G1R 3S3, Canada; Department of Molecular Biology, Medical Biochemistry, and Pathology, Laval University Cancer Research Center, Québec City, QC G1R 3S3, Canada
| | - Christopher E Pearson
- Program of Genetics & Genome Biology, The Hospital for Sick Children, PGCRL, Toronto, Canada, 686 Bay Street, Toronto, ON M5G 0A4, Canada; Program of Molecular Genetics, University of Toronto, Toronto, ON M5S 1A8, Canada.
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7
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Yoo J, Lee D, Im H, Ji S, Oh S, Shin M, Park D, Lee G. The mechanism of gap creation by a multifunctional nuclease during base excision repair. SCIENCE ADVANCES 2021; 7:7/29/eabg0076. [PMID: 34261654 PMCID: PMC8279506 DOI: 10.1126/sciadv.abg0076] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/04/2020] [Accepted: 05/28/2021] [Indexed: 05/30/2023]
Abstract
During base excision repair, a transient single-stranded DNA (ssDNA) gap is produced at the apurinic/apyrimidinic (AP) site. Exonuclease III, capable of performing both AP endonuclease and exonuclease activity, are responsible for gap creation in bacteria. We used single-molecule fluorescence resonance energy transfer to examine the mechanism of gap creation. We found an AP site anchor-based mechanism by which the intrinsically distributive enzyme binds strongly to the AP site and becomes a processive enzyme, rapidly creating a gap and an associated transient ssDNA loop. The gap size is determined by the rigidity of the ssDNA loop and the duplex stability of the DNA and is limited to a few nucleotides to maintain genomic stability. When the 3' end is released from the AP endonuclease, polymerase I quickly initiates DNA synthesis and fills the gap. Our work provides previously unidentified insights into how a signal of DNA damage changes the enzymatic functions.
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Affiliation(s)
- Jungmin Yoo
- School of Life Sciences, Gwangju Institute of Science and Technology, Gwangju 61005, Korea
- Single-Molecule Biology Laboratory, Gwangju Institute of Science and Technology, Gwangju 61005, Korea
- Cell Mechanobiology Laboratory, Gwangju Institute of Science and Technology, Gwangju 61005, Korea
| | - Donghun Lee
- School of Life Sciences, Gwangju Institute of Science and Technology, Gwangju 61005, Korea
- Single-Molecule Biology Laboratory, Gwangju Institute of Science and Technology, Gwangju 61005, Korea
- Cell Mechanobiology Laboratory, Gwangju Institute of Science and Technology, Gwangju 61005, Korea
| | - Hyeryeon Im
- School of Life Sciences, Gwangju Institute of Science and Technology, Gwangju 61005, Korea
- Single-Molecule Biology Laboratory, Gwangju Institute of Science and Technology, Gwangju 61005, Korea
| | - Sangmi Ji
- School of Life Sciences, Gwangju Institute of Science and Technology, Gwangju 61005, Korea
- Single-Molecule Biology Laboratory, Gwangju Institute of Science and Technology, Gwangju 61005, Korea
| | - Sanghoon Oh
- Single-Molecule Biology Laboratory, Gwangju Institute of Science and Technology, Gwangju 61005, Korea
- Department of Biomedical Science and Engineering, Gwangju Institute of Science and Technology, Gwangju 61005, Korea
| | - Minsang Shin
- Department of Microbiology, School of Medicine, Kyungpook National University, 680 Gukchaebosang-Ro, Jung-gu, Daegu 41944, Korea
| | - Daeho Park
- School of Life Sciences, Gwangju Institute of Science and Technology, Gwangju 61005, Korea
- Cell Mechanobiology Laboratory, Gwangju Institute of Science and Technology, Gwangju 61005, Korea
| | - Gwangrog Lee
- School of Life Sciences, Gwangju Institute of Science and Technology, Gwangju 61005, Korea.
- Single-Molecule Biology Laboratory, Gwangju Institute of Science and Technology, Gwangju 61005, Korea
- Cell Mechanobiology Laboratory, Gwangju Institute of Science and Technology, Gwangju 61005, Korea
- Department of Biomedical Science and Engineering, Gwangju Institute of Science and Technology, Gwangju 61005, Korea
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8
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Brewster JL, Tolun G. Half a century of bacteriophage lambda recombinase: In vitro studies of lambda exonuclease and Red-beta annealase. IUBMB Life 2020; 72:1622-1633. [PMID: 32621393 PMCID: PMC7496540 DOI: 10.1002/iub.2343] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2019] [Revised: 06/10/2020] [Accepted: 06/10/2020] [Indexed: 01/03/2023]
Abstract
DNA recombination, replication, and repair are intrinsically interconnected processes. From viruses to humans, they are ubiquitous and essential to all life on Earth. Single‐strand annealing homologous DNA recombination is a major mechanism for the repair of double‐stranded DNA breaks. An exonuclease and an annealase work in tandem, forming a complex known as a two‐component recombinase. Redβ annealase and λ‐exonuclease from phage lambda form the archetypal two‐component recombinase complex. In this short review article, we highlight some of the in vitro studies that have led to our current understanding of the lambda recombinase system. We synthesize insights from more than half a century of research, summarizing the state of our current understanding. From this foundation, we identify the gaps in our knowledge and cast an eye forward to consider what the next 50 years of research may uncover.
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Affiliation(s)
- Jodi L Brewster
- Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Keiraville, New South Wales, Australia.,Illawarra Health and Medical Research Institute, Wollongong, New South Wales, Australia
| | - Gökhan Tolun
- Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Keiraville, New South Wales, Australia.,Illawarra Health and Medical Research Institute, Wollongong, New South Wales, Australia
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9
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You S, Lee HG, Kim K, Yoo J. Improved Parameterization of Protein-DNA Interactions for Molecular Dynamics Simulations of PCNA Diffusion on DNA. J Chem Theory Comput 2020; 16:4006-4013. [PMID: 32543861 DOI: 10.1021/acs.jctc.0c00241] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
As the field of molecular dynamics simulation utilizing the force fields is moving toward more complex systems, the accuracy of intermolecular interactions has become a central issue of the field. Here, we quantitatively evaluate the accuracy of the protein-DNA interactions in AMBER and CHARMM force fields by comparing experimental and simulated diffusion coefficients of proliferating cell nuclear antigen. We find that both force fields underestimate diffusion coefficients by at least an order of magnitude because the interactions between basic amino acids and DNA phosphate groups are too attractive. Then, we propose Lennard-Jones parameters optimized using the experimental osmotic pressure data of model chemicals, by using which one can reproduce the experimental diffusion coefficients. Newly optimized parameters will have a broad impact on general protein-DNA interactions.
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Affiliation(s)
- Seonju You
- Department of Chemistry, Pohang University of Science and Technology, Pohang 37673, Republic of Korea
| | - Hong-Guen Lee
- Division of Advanced Materials Science, Pohang University of Science and Technology, Pohang 37673, Republic of Korea.,Center for Self-Assembly and Complexity, Institute for Basic Science, Pohang 37673, Republic of Korea
| | - Kimoon Kim
- Department of Chemistry, Pohang University of Science and Technology, Pohang 37673, Republic of Korea.,Center for Self-Assembly and Complexity, Institute for Basic Science, Pohang 37673, Republic of Korea
| | - Jejoong Yoo
- Center for Self-Assembly and Complexity, Institute for Basic Science, Pohang 37673, Republic of Korea.,Department of Physics, Sungkyunkwan University, Suwon 16419, Republic of Korea
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10
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Fu S, Li N, Li J, Deng Y, Xu L, Yu C, Su X. Engineering high-robustness DNA molecular circuits by utilizing nucleases. NANOSCALE 2020; 12:6964-6970. [PMID: 32195488 DOI: 10.1039/c9nr09979d] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Toehold-mediated strand displacement (TMSD) as an important player in DNA nanotechnology has been widely utilized for engineering non-enzymatic molecular circuits. However, these circuits suffer from uncontrollable leakage and unsatisfactory response speed. We utilized site-specific and sequence-independent nucleases to engineer high- robustness DNA molecular circuits. First, we found that the kinetics of the APE1-catalyzed reaction is highly dependent on substrate stability, allowing for the elimination of asymptotic leakage of DNA split circuits. Second, we obtained strict substrate preference of λ exonuclease (λexo) by optimizing the reaction conditions. Robust single-layer and cascade gates with leak resistance were established by using λ exo. Owing to the remarkably fast kinetics of these nucleases, all the circuits yield a high speed of computation. Compared to TMSD-based approaches, nuclease-powered circuits render advanced features such as leakage resistance, hundreds of times higher speed, and simplified structures, representing a class of promising artificial molecule systems.
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Affiliation(s)
- Shengnan Fu
- College of Life Science and Technology, Beijing Advanced Innovation Center for Soft Matter Science and Engineering, Beijing University of Chemical Technology, Beijing 100029, China.
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11
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Mohapatra S, Lin CT, Feng XA, Basu A, Ha T. Single-Molecule Analysis and Engineering of DNA Motors. Chem Rev 2019; 120:36-78. [DOI: 10.1021/acs.chemrev.9b00361] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
| | | | | | | | - Taekjip Ha
- Howard Hughes Medical Institute, Baltimore, Maryland 21205, United States
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12
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Ding Y, Li X, Zhang X, Li F, Hou X, Wu P. Systematic Probing of the Sequence Selectivity of Exonuclease III with a Photosensitization Colorimetric Assay. ACS OMEGA 2019; 4:13382-13387. [PMID: 31460466 PMCID: PMC6705212 DOI: 10.1021/acsomega.9b01560] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/28/2019] [Accepted: 07/24/2019] [Indexed: 06/10/2023]
Abstract
Exonuclease III (Exo III) is an important enzymatic tool that is being widely used in molecular biology, biotechnology, and bioassay development. Exo III prefers to cleave double-stranded DNA (dsDNA) with blunt and recessed 3'-termini rather than their protruding counterpart. While it has been accepted that a short 3'-overhang (e.g., >4 nt) is necessary to protect a dsDNA from Exo III cleavage, critical roles of the length and sequence of this 3'-overhang remain unexplored. Herein, we develop a novel light-induced colorimetric assay allowing the systematic probe of the sequence selectivity of Exo III in a rapid and high-throughput manner. Our finding that Exo III is highly specific to 3'-overhang in terms of both length and sequence will be valuable for guiding the design of bioassays and DNA manipulating tools mediated by Exo III.
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Affiliation(s)
- Yu Ding
- Analytical
& Testing Center, College of Chemistry, Sichuan University, Chengdu 610064, China
| | - Xianming Li
- Analytical
& Testing Center, College of Chemistry, Sichuan University, Chengdu 610064, China
| | - Xinfeng Zhang
- College
of Materials and Chemistry & Chemical Engineering, Chengdu University of Technology, Chengdu 610059, China
| | - Feng Li
- Analytical
& Testing Center, College of Chemistry, Sichuan University, Chengdu 610064, China
- Department
of Chemistry, Center for Biotechnology, Brock University, St. Catharines, Ontario L2S 3A1, Canada
| | - Xiandeng Hou
- Analytical
& Testing Center, College of Chemistry, Sichuan University, Chengdu 610064, China
| | - Peng Wu
- Analytical
& Testing Center, College of Chemistry, Sichuan University, Chengdu 610064, China
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13
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Wu T, Yang Y, Chen W, Wang J, Yang Z, Wang S, Xiao X, Li M, Zhao M. Noncanonical substrate preference of lambda exonuclease for 5'-nonphosphate-ended dsDNA and a mismatch-induced acceleration effect on the enzymatic reaction. Nucleic Acids Res 2019; 46:3119-3129. [PMID: 29490081 PMCID: PMC5888420 DOI: 10.1093/nar/gky154] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2016] [Accepted: 02/19/2018] [Indexed: 01/01/2023] Open
Abstract
Lambda exonuclease (λ exo) plays an important role in the resection of DNA ends for DNA repair. Currently, it is also a widely used enzymatic tool in genetic engineering, DNA-binding protein mapping, nanopore sequencing and biosensing. Herein, we disclose two noncanonical properties of this enzyme and suggest a previously undescribed hydrophobic interaction model between λ exo and DNA substrates. We demonstrate that the length of the free portion of the substrate strand in the dsDNA plays an essential role in the initiation of digestion reactions by λ exo. A dsDNA with a 5' non-phosphorylated, two-nucleotide-protruding end can be digested by λ exo with very high efficiency. Moreover, we show that when a conjugated structure is covalently attached to an internal base of the dsDNA, the presence of a single mismatched base pair at the 5' side of the modified base may significantly accelerate the process of digestion by λ exo. A detailed comparison study revealed additional π-π stacking interactions between the attached label and the amino acid residues of the enzyme. These new findings not only broaden our knowledge of the enzyme but will also be very useful for research on DNA repair and in vitro processing of nucleic acids.
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Affiliation(s)
- Tongbo Wu
- Beijing National Laboratory for Molecular Sciences, MOE Key Laboratory of Bioorganic Chemistry and Molecular Engineering, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
| | - Yufei Yang
- Beijing National Laboratory for Molecular Sciences, MOE Key Laboratory of Bioorganic Chemistry and Molecular Engineering, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China.,Beijing NMR Center, Peking University, Beijing 100871, China
| | - Wei Chen
- Beijing National Laboratory for Molecular Sciences, MOE Key Laboratory of Bioorganic Chemistry and Molecular Engineering, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
| | - Jiayu Wang
- Beijing National Laboratory for Molecular Sciences, MOE Key Laboratory of Bioorganic Chemistry and Molecular Engineering, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
| | - Ziyu Yang
- Beijing National Laboratory for Molecular Sciences, MOE Key Laboratory of Bioorganic Chemistry and Molecular Engineering, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
| | - Shenlin Wang
- Beijing National Laboratory for Molecular Sciences, MOE Key Laboratory of Bioorganic Chemistry and Molecular Engineering, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China.,Beijing NMR Center, Peking University, Beijing 100871, China
| | - Xianjin Xiao
- Family Planning Research Institute/Center of Reproductive Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China
| | - Mengyuan Li
- Beijing National Laboratory for Molecular Sciences, MOE Key Laboratory of Bioorganic Chemistry and Molecular Engineering, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
| | - Meiping Zhao
- Beijing National Laboratory for Molecular Sciences, MOE Key Laboratory of Bioorganic Chemistry and Molecular Engineering, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
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14
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Highly Efficient and Reliable DNA Aptamer Selection Using the Partitioning Capabilities of ddPCR: The Hi-Fi SELEX Method. Methods Mol Biol 2019; 1768:531-554. [PMID: 29717463 DOI: 10.1007/978-1-4939-7778-9_30] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
In addition to its growing use in detecting and quantifying genes and larger genomic events, the partitioning used in digital PCR can serve as a powerful tool for high-fidelity amplification of synthetic combinatorial libraries of single-stranded DNA. Sequence-diverse libraries of this type are used as a basis for selecting tight-binding aptamers against a specific target. Here we provide a detailed description of the Hi-Fi SELEX protocol for rapid and efficient DNA aptamer selection. As part of that methodology, we describe how Hi-Fi SELEX gains advantages over other aptamer selection methods in part through the use of the massive partitioning capability of digital PCR.
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15
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Yu Y, Ma L, Li L, Deng Y, Xu L, Liu H, Xiao L, Su X. Digestion of Dynamic Substrate by Exonuclease Reveals High Single-Mismatch Selectivity. Anal Chem 2018; 90:13655-13662. [DOI: 10.1021/acs.analchem.8b03963] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Yingjie Yu
- College of Life Science and Technology, Beijing Advanced Innovation Center for Soft Matter Science and Engineering, Beijing University of Chemical Technology, Beijing 100029, China
- Department of Biomedical Engineering, Tufts University, Medford, Massachusetts 02155, United States
| | - Liang Ma
- Clinical laboratory, China-Japan Friendship Hospital, Beijing 100029, China
| | - Lidan Li
- College of Life Science and Technology, Beijing Advanced Innovation Center for Soft Matter Science and Engineering, Beijing University of Chemical Technology, Beijing 100029, China
| | - Yingnan Deng
- College of Life Science and Technology, Beijing Advanced Innovation Center for Soft Matter Science and Engineering, Beijing University of Chemical Technology, Beijing 100029, China
| | - Lida Xu
- College of Life Science and Technology, Beijing Advanced Innovation Center for Soft Matter Science and Engineering, Beijing University of Chemical Technology, Beijing 100029, China
| | - Hua Liu
- State Key Laboratory of Medicinal Chemical Biology, Tianjin Key Laboratory of Biosensing and Molecular Recognition, College of Chemistry, Nankai University, Tianjin, 300071, China
| | - Lehui Xiao
- State Key Laboratory of Medicinal Chemical Biology, Tianjin Key Laboratory of Biosensing and Molecular Recognition, College of Chemistry, Nankai University, Tianjin, 300071, China
| | - Xin Su
- College of Life Science and Technology, Beijing Advanced Innovation Center for Soft Matter Science and Engineering, Beijing University of Chemical Technology, Beijing 100029, China
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16
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Dynamic coordination of two-metal-ions orchestrates λ-exonuclease catalysis. Nat Commun 2018; 9:4404. [PMID: 30353000 PMCID: PMC6199318 DOI: 10.1038/s41467-018-06750-9] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2018] [Accepted: 09/22/2018] [Indexed: 11/08/2022] Open
Abstract
Metal ions at the active site of an enzyme act as cofactors, and their dynamic fluctuations can potentially influence enzyme activity. Here, we use λ-exonuclease as a model enzyme with two Mg2+ binding sites and probe activity at various concentrations of magnesium by single-molecule-FRET. We find that while MgA2+ and MgB2+ have similar binding constants, the dissociation rate of MgA2+ is two order of magnitude lower than that of MgB2+ due to a kinetic-barrier-difference. At physiological Mg2+ concentration, the MgB2+ ion near the 5'-terminal side of the scissile phosphate dissociates each-round of degradation, facilitating a series of DNA cleavages via fast product-release concomitant with enzyme-translocation. At a low magnesium concentration, occasional dissociation and slow re-coordination of MgA2+ result in pauses during processive degradation. Our study highlights the importance of metal-ion-coordination dynamics in correlation with the enzymatic reaction-steps, and offers insights into the origin of dynamic heterogeneity in enzymatic catalysis.
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17
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Li Z, Zhou X, Li L, Liu S, Wang C, Li L, Yu C, Su X. Probing DNA Hybridization Equilibrium by Cationic Conjugated Polymer for Highly Selective Detection and Imaging of Single-Nucleotide Mutation. Anal Chem 2018; 90:6804-6810. [PMID: 29766713 DOI: 10.1021/acs.analchem.8b00870] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Hybridization-based probes emerge as a promising tool for nucleic acid target detection and imaging. However, the single-nucleotide selectivity is still challenging because the specificity of hybridization reaction is typically low at room temperature. We disclose an effective and simple method for highly selective detection and in situ imaging of single-nucleotide mutation (SNM) by taking the advantages of the specific hybridization of short duplex and the signal amplifying effect of cationic conjugated polymer (CCP). Excellent discrimination of the nucleic acid strands only differing by single nucleotide was achieved enabling the sensitive detection of SNM at the abundance as low as 0.1%. Single-molecule fluorescence resonance energy transfer (smFRET) study reveals that the presence of CCP enhances the perfect matched duplex and the mismatched duplex to a different extent, which can be an explanation for the high single-nucleotide selectivity. Due to the simple design of the probe and the stable brightness of CCP, highly selective mRNA in situ imaging was achieved in fixed cells. Melanoma cell line A375 with BRAF V600E point mutation exhibits higher FRET efficiency than liver cancer cell line HegG2 that was not reported having the mutation at this point.
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Affiliation(s)
- Zehao Li
- College of Life Science and Technology , Beijing University of Chemical Technology , Beijing 100029 , China
| | - Xu Zhou
- College of Life Science and Technology , Beijing University of Chemical Technology , Beijing 100029 , China
| | - Lidan Li
- College of Life Science and Technology , Beijing University of Chemical Technology , Beijing 100029 , China
| | - Shue Liu
- Department of Gastroenterology , China-Japan Friendship Hospital , Beijing 100029 , China
| | - Congshan Wang
- College of Life Science and Technology , Beijing University of Chemical Technology , Beijing 100029 , China
| | - Lina Li
- College of Life Science and Technology , Beijing University of Chemical Technology , Beijing 100029 , China
| | - Changyuan Yu
- College of Life Science and Technology , Beijing University of Chemical Technology , Beijing 100029 , China
| | - Xin Su
- College of Life Science and Technology , Beijing University of Chemical Technology , Beijing 100029 , China
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18
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Loeff L, Brouns SJJ, Joo C. Repetitive DNA Reeling by the Cascade-Cas3 Complex in Nucleotide Unwinding Steps. Mol Cell 2018; 70:385-394.e3. [PMID: 29706536 DOI: 10.1016/j.molcel.2018.03.031] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2017] [Revised: 02/23/2018] [Accepted: 03/24/2018] [Indexed: 01/12/2023]
Abstract
CRISPR-Cas provides RNA-guided adaptive immunity against invading genetic elements. Interference in type I systems relies on the RNA-guided Cascade complex for target DNA recognition and the Cas3 helicase/nuclease protein for target degradation. Even though the biochemistry of CRISPR interference has been largely covered, the biophysics of DNA unwinding and coupling of the helicase and nuclease domains of Cas3 remains elusive. Here, we employed single-molecule Förster resonance energy transfer (FRET) to probe the helicase activity with high spatiotemporal resolution. We show that Cas3 remains tightly associated with the target-bound Cascade complex while reeling the DNA using a spring-loaded mechanism. This spring-loaded reeling occurs in distinct bursts of 3 bp, which underlie three successive 1-nt unwinding events. Reeling is highly repetitive, allowing Cas3 to repeatedly present its inefficient nuclease domain with single-strand DNA (ssDNA) substrate. Our study reveals that the discontinuous helicase properties of Cas3 and its tight interaction with Cascade ensure controlled degradation of target DNA only.
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Affiliation(s)
- Luuk Loeff
- Kavli Institute of Nanoscience and Department of Bionanoscience, Delft University of Technology, Delft 2629HZ, the Netherlands
| | - Stan J J Brouns
- Kavli Institute of Nanoscience and Department of Bionanoscience, Delft University of Technology, Delft 2629HZ, the Netherlands; Laboratory of Microbiology, Department of Agrotechnology and Food Sciences, Wageningen University, Wageningen 6708WE, the Netherlands.
| | - Chirlmin Joo
- Kavli Institute of Nanoscience and Department of Bionanoscience, Delft University of Technology, Delft 2629HZ, the Netherlands.
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19
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Zhou W, Ding J, Liu J. Splitting a DNAzyme enables a Na +-dependent FRET signal from the embedded aptamer. Org Biomol Chem 2018; 15:6959-6966. [PMID: 28792040 DOI: 10.1039/c7ob01709j] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Recently, a few Na+-specific RNA-cleaving DNAzymes have been reported, and a Na+ aptamer was identified from the NaA43 and Ce13d DNAzymes. These DNAzymes and the embedded aptamer have been used for Na+ detection. In this work, we studied the Na+-dependent folding of the Ce13d DNAzyme using fluorescence resonance energy transfer (FRET). When a FRET donor and an acceptor were respectively labeled at the ends of the DNAzyme, Na+ failed to induce an obvious end-to-end distance change, suggesting a rigid global structure. To relax this rigidity, the Ce13d DNAzyme was systematically split at various sites on both the enzyme and the substrate strands. The Na+ binding activity of the split structures was characterized by 2-aminopurine fluorescence, enzymatic activity, Tb3+-sensitized luminescence, and DMS footprinting. Among the various constructs, the only one that retained Na+ binding was the split at the cleavage site, and this construct was further labeled with two dyes near the split site. This FRET result showed Na+-dependent folding with a Kd of 26 mM Na+. This study provides important structural information related to Na+ binding to this new aptamer, which might also be useful for future work in biosensor design.
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Affiliation(s)
- Wenhu Zhou
- Xiangya School of Pharmaceutical Sciences, Central South University, Changsha, Hunan 410013, China
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20
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Kim DH, Kim DK, Zhou K, Park S, Kwon Y, Jeong MG, Lee NK, Ryu SH. Single particle tracking-based reaction progress kinetic analysis reveals a series of molecular mechanisms of cetuximab-induced EGFR processes in a single living cell. Chem Sci 2017; 8:4823-4832. [PMID: 28959404 PMCID: PMC5602156 DOI: 10.1039/c7sc01159h] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2017] [Accepted: 04/21/2017] [Indexed: 01/18/2023] Open
Abstract
Cellular processes occur through the orchestration of multi-step molecular reactions. Reaction progress kinetic analysis (RPKA) can provide the mechanistic details to elucidate the multi-step molecular reactions. However, current tools have limited ability to simultaneously monitor dynamic variations in multiple complex states at the single molecule level to apply RPKA in living cells. In this research, a single particle tracking-based reaction progress kinetic analysis (sptRPKA) was developed to simultaneously determine the kinetics of multiple states of protein complexes in the membrane of a single living cell. The subpopulation ratios of different states were quantitatively (and statistically) reliably extracted from the diffusion coefficient distribution rapidly acquired by single particle tracking at constant and high density over a long period of time using super-resolution microscopy. Using sptRPKA, a series of molecular mechanisms of epidermal growth factor receptor (EGFR) cellular processing induced by cetuximab were investigated. By comprehensively measuring the rate constants and cooperativity of the molecular reactions involving four EGFR complex states, a previously unknown intermediate state was identified that represents the rate limiting step responsible for the selectivity of cetuximab-induced EGFR endocytosis to cancer cells.
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Affiliation(s)
- Do-Hyeon Kim
- Department of Life Sciences , Pohang University of Science and Technology , Pohang , 790-784 , Republic of Korea .
| | - Dong-Kyun Kim
- School of Interdisciplinary Bioscience and Bioengineering , Pohang University of Science and Technology , Pohang , 790-784 , Republic of Korea
| | - Kai Zhou
- Department of Life Sciences , Pohang University of Science and Technology , Pohang , 790-784 , Republic of Korea .
| | - Soyeon Park
- Department of Life Sciences , Pohang University of Science and Technology , Pohang , 790-784 , Republic of Korea .
| | - Yonghoon Kwon
- Department of Life Sciences , Pohang University of Science and Technology , Pohang , 790-784 , Republic of Korea .
| | - Min Gyu Jeong
- Integrative Biosciences and Biotechnology , Pohang University of Science and Technology , Pohang , 790-784 , Republic of Korea
| | - Nam Ki Lee
- School of Interdisciplinary Bioscience and Bioengineering , Pohang University of Science and Technology , Pohang , 790-784 , Republic of Korea.,Department of Chemistry , Seoul National University , Seoul , 08826 , Republic of Korea .
| | - Sung Ho Ryu
- Department of Life Sciences , Pohang University of Science and Technology , Pohang , 790-784 , Republic of Korea . .,School of Interdisciplinary Bioscience and Bioengineering , Pohang University of Science and Technology , Pohang , 790-784 , Republic of Korea
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21
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Kamagata K, Murata A, Itoh Y, Takahashi S. Characterization of facilitated diffusion of tumor suppressor p53 along DNA using single-molecule fluorescence imaging. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY C-PHOTOCHEMISTRY REVIEWS 2017. [DOI: 10.1016/j.jphotochemrev.2017.01.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
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22
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Yu Y, Wu T, Johnson-Buck A, Li L, Su X. A two-layer assay for single-nucleotide variants utilizing strand displacement and selective digestion. Biosens Bioelectron 2016; 82:248-54. [PMID: 27100949 DOI: 10.1016/j.bios.2016.03.070] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2016] [Revised: 03/21/2016] [Accepted: 03/28/2016] [Indexed: 11/17/2022]
Abstract
Point mutations have emerged as prominent biomarkers for disease diagnosis, particularly in the case of cancer. Discovering single-nucleotide variants (SNVs) is also of great importance for the identification of single-nucleotide polymorphisms within the population. The competing requirements of thermodynamic stability and specificity in conventional nucleic acid hybridization probes make it challenging to achieve highly precise detection of point mutants. Here, we present a fluorescence-based assay for low-abundance mutation detection based on toehold-mediated strand displacement and nuclease-mediated strand digestion that enables highly precise detection of point mutations. We demonstrate that this combined assay provides 50-1000-fold discrimination (mean value: 255) between all possible single-nucleotide mutations and their corresponding wild-type sequence for a model DNA target. Using experiments and kinetic modeling, we investigate probe properties that obtain additive benefits from both strand displacement and nucleolytic digestion, thus providing guidance for the design of enzyme-mediated nucleic acid assays in the future.
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Affiliation(s)
- Yingjie Yu
- College of Life Science and Technology, Beijing University of Chemical Technology, Beijing 100029, China; Materials Science and Engineering, Stony Brook University, Stony Brook, NY 11790, USA
| | - Tongbo Wu
- Beijing National Laboratory for Molecular Sciences, MOE Key Laboratory of Bioorganic Chemistry and Molecular Engineering, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
| | | | - Lidan Li
- College of Life Science and Technology, Beijing University of Chemical Technology, Beijing 100029, China
| | - Xin Su
- College of Life Science and Technology, Beijing University of Chemical Technology, Beijing 100029, China.
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23
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Ouellet E, Foley JH, Conway EM, Haynes C. Hi-Fi SELEX: A High-Fidelity Digital-PCR Based Therapeutic Aptamer Discovery Platform. Biotechnol Bioeng 2016; 112:1506-22. [PMID: 25727321 DOI: 10.1002/bit.25581] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2015] [Accepted: 02/14/2015] [Indexed: 12/30/2022]
Abstract
Current technologies for aptamer discovery typically leverage the systematic evolution of ligands by exponential enrichment (SELEX) concept by recursively panning semi-combinatorial ssDNA or RNA libraries against a molecular target. The expectation is that this iterative selection process will be sufficiently stringent to identify a candidate pool of specific high-affinity aptamers. However, failure of this process to yield promising aptamers is common, due in part to (i) limitations in library designs, (ii) retention of non-specific aptamers during screening rounds, (iii) excessive accumulation of amplification artifacts, and (iv) the use of screening criteria (binding affinity) that does not reflect therapeutic activity. We report a new selection platform, High-Fidelity (Hi-Fi) SELEX, that introduces fixed-region blocking elements to safeguard the functional diversity of the library. The chemistry of the target-display surface and the composition of the equilibration solvent are engineered to strongly inhibit non-specific retention of aptamers. Partition efficiencies approaching 10(6) are thereby realized. Retained members are amplified in Hi-Fi SELEX by digital PCR in a manner that ensures both elimination of amplification artifacts and stoichiometric conversion of amplicons into the single-stranded library required for the next selection round. Improvements to aptamer selections are first demonstrated using human α-thrombin as the target. Three clinical targets (human factors IXa, X, and D) are then subjected to Hi-Fi SELEX. For each, rapid enrichment of ssDNA aptamers offering an order-nM mean equilibrium dissociation constant (Kd) is achieved within three selection rounds, as quantified by a new label-free qPCR assay reported here. Therapeutic candidates against factor D are identified.
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24
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Pan X, Smith CE, Zhang J, McCabe KA, Fu J, Bell CE. A Structure-Activity Analysis for Probing the Mechanism of Processive Double-Stranded DNA Digestion by λ Exonuclease Trimers. Biochemistry 2016; 54:6139-48. [PMID: 26361255 DOI: 10.1021/acs.biochem.5b00707] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
λ exonuclease (λexo) is an ATP-independent 5'-to-3' exonuclease that binds to double-stranded DNA (dsDNA) ends and processively digests the 5'-strand into mononucleotides. The crystal structure of λexo revealed that the enzyme forms a ring-shaped homotrimer with a central funnel-shaped channel for tracking along the DNA. On the basis of this structure, it was proposed that dsDNA enters the open end of the channel, the 5'-strand is digested at one of the three active sites, and the 3'-strand passes through the narrow end of the channel to emerge out the back. This model was largely confirmed by the structure of the λexo-DNA complex, which further revealed that the enzyme unwinds the DNA by 2 bp prior to cleavage, to thread the 5'-end of the DNA into the active site. On the basis of this structure, an "electrostatic ratchet" model was proposed, in which the enzyme uses a hydrophobic wedge to insert into the base pairs to unwind the DNA, a two-metal mechanism for nucleotide hydrolysis, a positively charged pocket to bind to the terminal 5'-phosphate generated after each round of cleavage, and an arginine residue (Arg-45) to bind to the minor groove of the downstream end of the DNA. To test this model, in this study we have determined the effects of 11 structure-based mutations in λexo on DNA binding and exonuclease activities in vitro, and on DNA recombination in vivo. The results are largely consistent with the model for the mechanism that was proposed on the basis of the structure and provide new insights into the roles of particular residues of the protein in promoting the reaction. In particular, a key role for Arg-45 in DNA binding is revealed.
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Affiliation(s)
| | | | | | | | - Jun Fu
- Shandong University-Helmholtz Institute of Biotechnology, State Key Laboratory of Microbial Technology, School of Life Science, Shandong University , Shanda Nanlu 27, 250100 Jinan, People's Republic of China
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25
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Yoo J, Lee G. Allosteric ring assembly and chemo-mechanical melting by the interaction between 5'-phosphate and λ exonuclease. Nucleic Acids Res 2015; 43:10861-9. [PMID: 26527731 PMCID: PMC4678818 DOI: 10.1093/nar/gkv1150] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2015] [Accepted: 10/19/2015] [Indexed: 11/13/2022] Open
Abstract
Phosphates along the DNA function as chemical energy frequently used by nucleases to drive their enzymatic reactions. Exonuclease functions as a machine that converts chemical energy of the phosphodiester-chain into mechanical work. However, the roles of phosphates during exonuclease activities are unknown. We employed λ exonuclease as a model system and investigated the roles of phosphates during degradation via single-molecule fluorescence resonance energy transfer (FRET). We found that 5′ phosphates, generated at each cleavage step of the reaction, chemo-mechanically facilitate the subsequent post-cleavage melting of the terminal base pairs. Degradation of DNA with a nick requires backtracking and thermal fraying at the cleavage site for re-initiation via the formation of a catalytically active complex. Unexpectedly, we discovered that a phosphate of a 5′ recessed DNA acts as a hotspot for an allosteric trimeric-ring assembly without passing through the central channel. Our study provides new insight into the versatile roles of phosphates during the processive enzymatic reaction.
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Affiliation(s)
- Jungmin Yoo
- School of life Sciences, Gwangju Institute of Science and Technology, Gwangju 500-712, Korea
| | - Gwangrog Lee
- School of life Sciences, Gwangju Institute of Science and Technology, Gwangju 500-712, Korea
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26
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Pan X, Yan J, Patel A, Wysocki VH, Bell CE. Mutant poisoning demonstrates a nonsequential mechanism for digestion of double-stranded DNA by λ exonuclease trimers. Biochemistry 2015; 54:942-51. [PMID: 25531139 DOI: 10.1021/bi501431w] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
λ Exonuclease (λexo) is a highly processive 5'-3' exonuclease that binds double-stranded DNA (dsDNA) ends and digests the 5'-strand into mononucleotides. The enzyme forms a toroidal homotrimer with a central tapered channel for tracking along the DNA. During catalysis, dsDNA enters the open end of the channel, and the 5'-strand is digested at one of the three active sites. It is currently not known if λexo uses a sequential mechanism, in which the DNA moves from one active site to the next around the trimer for each round of catalysis or a nonsequential mechanism, in which the DNA locks onto a single active site for multiple rounds. To understand how λexo uses its three active sites, we used a mutant poisoning approach, in which a 6xHis-tagged K131A inactive mutant of λexo was mixed with untagged wild type (WT) to form hybrid trimers. Nickel-spin pull-down analysis confirmed complete subunit exchange after 1 h at 37 °C. Exonuclease assays revealed an approximately linear decrease in activity with increasing fraction of mutant, as expected for a nonsequential mechanism. By fitting the observed rates of digestion to a simple mathematical model, the individual rates of the two hybrid species of trimer were determined. This analysis showed that trimers containing only one or two WT subunits contribute significantly to the observed activity, in further agreement with a nonsequential mechanism. Finally, purification of hybrid trimer mixtures by Ni-spin chromatography, to remove the contribution from fully WT trimers, also resulted in significant levels of activity, again consistent with a nonsequential mechanism.
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Affiliation(s)
- Xinlei Pan
- Ohio State Biochemistry Program, ‡Department of Molecular and Cellular Biochemistry, and §Department of Chemistry and Biochemistry, The Ohio State University , Columbus, Ohio 43210, United States
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27
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Oliver-Calixte NJ, Uba FI, Battle KN, Weerakoon-Ratnayake KM, Soper SA. Immobilization of lambda exonuclease onto polymer micropillar arrays for the solid-phase digestion of dsDNAs. Anal Chem 2014; 86:4447-54. [PMID: 24628008 PMCID: PMC4018173 DOI: 10.1021/ac5002965] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
![]()
The
process of immobilizing enzymes onto solid supports for bioreactions
has some compelling advantages compared to their solution-based counterpart
including the facile separation of enzyme from products, elimination
of enzyme autodigestion, and increased enzyme stability and activity.
We report the immobilization of λ-exonuclease onto poly(methylmethacrylate)
(PMMA) micropillars populated within a microfluidic device for the
on-chip digestion of double-stranded DNA. Enzyme immobilization was
successfully accomplished using 3-(3-dimethylaminopropyl) carbodiimide/N-hydroxysuccinimide (EDC/NHS) coupling to carboxylic acid
functionalized PMMA micropillars. Our results suggest that the efficiency
for the catalysis of dsDNA digestion using λ-exonuclease, including
its processivity and reaction rate, were higher when the enzyme was
attached to a solid support compared to the free solution digestion.
We obtained a clipping rate of 1.0 × 103 nucleotides
s–1 for the digestion of λ-DNA (48.5 kbp)
by λ-exonuclease. The kinetic behavior of the solid-phase reactor
could be described by a fractal Michaelis–Menten model with
a catalytic efficiency nearly 17% better than the homogeneous solution-phase
reaction. The results from this work will have important ramifications
in new single-molecule DNA sequencing strategies that employ free
mononucleotide identification.
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Affiliation(s)
- Nyoté J Oliver-Calixte
- Department of Chemistry, Louisiana State University , Baton Rouge, Louisiana 70803, United States
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28
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Abstract
A prerequisite for DNA replication is the unwinding of duplex DNA catalyzed by a replicative hexameric helicase. Despite a growing body of research, key elements of helicase mechanism remain under substantial debate. In particular, the number of DNA strands encircled by the helicase ring during unwinding and the ring orientation at the replication fork completely contrast in contemporary mechanistic models. Here we use single-molecule and ensemble assays to address these questions for the papillomavirus E1 helicase. We find that E1 unwinds DNA with a strand-exclusion mechanism, with the N-terminal side of the helicase ring facing the replication fork. We show that E1 generates strikingly heterogeneous unwinding patterns stemming from varying degrees of repetitive movements, which is modulated by the DNA-binding domain. Together, our studies reveal previously unrecognized dynamic facets of replicative helicase unwinding mechanisms.
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29
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Gracie K, Correa E, Mabbott S, Dougan JA, Graham D, Goodacre R, Faulds K. Simultaneous detection and quantification of three bacterial meningitis pathogens by SERS. Chem Sci 2014. [DOI: 10.1039/c3sc52875h] [Citation(s) in RCA: 118] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
We report the use of a SERS based DNA detection assay for the multiplexed, quantification of three bacterial meningitis pathogens.
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Affiliation(s)
- Kirsten Gracie
- Centre of Molecular Nanometrology
- WestCHEM
- Department of Pure and Applied Chemistry
- University of Strathclyde
- Glasgow, UK
| | - Elon Correa
- School of Chemistry and Manchester Institute of Biotechnology
- University of Manchester
- Manchester, UK
| | - Samuel Mabbott
- Centre of Molecular Nanometrology
- WestCHEM
- Department of Pure and Applied Chemistry
- University of Strathclyde
- Glasgow, UK
| | - Jennifer A. Dougan
- Centre of Molecular Nanometrology
- WestCHEM
- Department of Pure and Applied Chemistry
- University of Strathclyde
- Glasgow, UK
| | - Duncan Graham
- Centre of Molecular Nanometrology
- WestCHEM
- Department of Pure and Applied Chemistry
- University of Strathclyde
- Glasgow, UK
| | - Royston Goodacre
- School of Chemistry and Manchester Institute of Biotechnology
- University of Manchester
- Manchester, UK
| | - Karen Faulds
- Centre of Molecular Nanometrology
- WestCHEM
- Department of Pure and Applied Chemistry
- University of Strathclyde
- Glasgow, UK
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30
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Liu Y, Wang S, Zhang C, Su X, Huang S, Zhao M. Enhancing the Selectivity of Enzyme Detection by Using Tailor-Made Nanoparticles. Anal Chem 2013; 85:4853-7. [DOI: 10.1021/ac4007914] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Affiliation(s)
- Yibin Liu
- Beijing National
Laboratory for Molecular Sciences,
MOE Key Laboratory of Bioorganic Chemistry and Molecular Engineering,
College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, China
| | - Shanshan Wang
- Beijing National
Laboratory for Molecular Sciences,
MOE Key Laboratory of Bioorganic Chemistry and Molecular Engineering,
College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, China
| | - Chen Zhang
- Beijing National
Laboratory for Molecular Sciences,
MOE Key Laboratory of Bioorganic Chemistry and Molecular Engineering,
College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, China
| | - Xin Su
- Beijing National
Laboratory for Molecular Sciences,
MOE Key Laboratory of Bioorganic Chemistry and Molecular Engineering,
College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, China
| | - Shan Huang
- Beijing National
Laboratory for Molecular Sciences,
MOE Key Laboratory of Bioorganic Chemistry and Molecular Engineering,
College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, China
| | - Meiping Zhao
- Beijing National
Laboratory for Molecular Sciences,
MOE Key Laboratory of Bioorganic Chemistry and Molecular Engineering,
College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, China
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31
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Kim J, Seo MH, Lee S, Cho K, Yang A, Woo K, Kim HS, Park HS. Simple and efficient strategy for site-specific dual labeling of proteins for single-molecule fluorescence resonance energy transfer analysis. Anal Chem 2013; 85:1468-74. [PMID: 23276151 DOI: 10.1021/ac303089v] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Analysis of protein dynamics using single-molecule fluorescence resonance energy transfer (smFRET) is widely used to understand the structure and function of proteins. Nonetheless, site-specific labeling of proteins with a pair of donor and acceptor dyes still remains a challenge. Here we present a general and facile method for site-specific dual labeling of proteins by incorporating two different, readily available, unnatural amino acids (p-acetylphenylalanine and alkynyllysine) for smFRET. We used newly evolved alkynyllysine-specific aminoacyl-tRNA synthetase/tRNA(UCA) and p-acetylphenylalanyl-tRNA synthetase/tRNA(CUA). The utility of our approach was demonstrated by analyzing the conformational change of dual-labeled calmodulin using smFRET measurements. The present labeling approach is devoid of major limitations in conventional cysteine-based labeling. Therefore, our method will significantly increase the repertoire of proteins available for FRET study and expand our ability to explore more complicated molecular dynamics.
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Affiliation(s)
- Jihyo Kim
- Department of Chemistry, Korea Advanced Institute of Science and Technology, 291 Daehak-ro, Yuseong-gu, Daejeon 305-701, Korea
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32
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Na YR, Kim SY, Gaublomme JT, Shalek AK, Jorgolli M, Park H, Yang EG. Probing enzymatic activity inside living cells using a nanowire-cell "sandwich" assay. NANO LETTERS 2013; 13:153-8. [PMID: 23244056 PMCID: PMC3541459 DOI: 10.1021/nl3037068] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Developing a detailed understanding of enzyme function in the context of an intracellular signal transduction pathway requires minimally invasive methods for probing enzyme activity in situ. Here, we describe a new method for monitoring enzyme activity in living cells by sandwiching live cells between two vertical silicon nanowire (NW) arrays. Specifically, we use the first NW array to immobilize the cells and then present enzymatic substrates intracellularly via the second NW array by utilizing the NWs' ability to penetrate cellular membranes without affecting cells' viability or function. This strategy, when coupled with fluorescence microscopy and mass spectrometry, enables intracellular examination of protease, phosphatase, and protein kinase activities, demonstrating the assay's potential in uncovering the physiological roles of various enzymes.
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Affiliation(s)
- Yu-Ran Na
- Center for Theragnosis, Biomedical Research Institute, Korea Institute of Science and Technology, Hwarangno 14-gil 5, Seongbuk-gu, Seoul 136-791, South Korea
| | - So Yeon Kim
- Center for Theragnosis, Biomedical Research Institute, Korea Institute of Science and Technology, Hwarangno 14-gil 5, Seongbuk-gu, Seoul 136-791, South Korea
| | - Jellert T. Gaublomme
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, MA 02138, USA
| | - Alex K. Shalek
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, MA 02138, USA
| | - Marsela Jorgolli
- Department of Physics, Harvard University, 17 Oxford Street, Cambridge, MA 02138, USA
| | - Hongkun Park
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, MA 02138, USA
- Department of Physics, Harvard University, 17 Oxford Street, Cambridge, MA 02138, USA
| | - Eun Gyeong Yang
- Center for Theragnosis, Biomedical Research Institute, Korea Institute of Science and Technology, Hwarangno 14-gil 5, Seongbuk-gu, Seoul 136-791, South Korea
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33
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Lee G, Bratkowski MA, Ding F, Ke A, Ha T. Elastic coupling between RNA degradation and unwinding by an exoribonuclease. Science 2012; 336:1726-9. [PMID: 22745434 DOI: 10.1126/science.1216848] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Rrp44 (Dis3) is a key catalytic subunit of the yeast exosome complex and can processively digest structured RNA one nucleotide at a time in the 3' to 5' direction. Its motor function is powered by the energy released from the hydrolytic nuclease reaction instead of adenosine triphosphate hydrolysis as in conventional helicases. Single-molecule fluorescence analysis revealed that instead of unwinding RNA in single base pair steps, Rrp44 accumulates the energy released by multiple single nucleotide step hydrolysis reactions until about four base pairs are unwound in a burst. Kinetic analyses showed that RNA unwinding, not cleavage or strand release, determines the overall RNA degradation rate and that the unwinding step size is determined by the nonlinear elasticity of the Rrp44/RNA complex, but not by duplex stability.
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Affiliation(s)
- Gwangrog Lee
- Department of Physics, University of Illinois at Urbana-Champaign, 1110 West Green Street, Urbana, IL 61801, USA
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34
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Gandhi M, Evdokimova V, Nikiforov YE. Frequency of close positioning of chromosomal loci detected by FRET correlates with their participation in carcinogenic rearrangements in human cells. Genes Chromosomes Cancer 2012; 51:1037-44. [PMID: 22887574 DOI: 10.1002/gcc.21988] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2012] [Accepted: 07/01/2012] [Indexed: 11/05/2022] Open
Abstract
It has been well established that genes participating in oncogenic rearrangements are non-randomly positioned and frequently close to each other in human cell nuclei. However, the actual distance between these fusion partners has never been determined. The phenomenon of fluorescence resonance energy transfer (FRET) is observed when a donor fluorophore is close (<10 nm) to transfer some of it energy to an acceptor fluorophore. The aim of this study was to validate the use of FRET on directly labeled DNA molecules to assess the frequency of positioning at <10 nm distances between genes known to be involved in rearrangement and to correlate it with their probability to undergo rearrangement. In the validation experiments, the frequency of FRET-sensitized emission (SE) was found to be 93-96% between probes for the immediately adjacent chromosomal regions as compared to 0.1-0.2% between probes for the random loci located on large linear separation. Further, we found that the frequency of FRET-SE between four pairs of genes that form rearrangements in thyroid cancer was 5% for RET and CCDC6, 4% for RET and NCOA4, 2% for BRAF and AKAP9, and 2% for NTRK1 and TPR. Moreover, the frequency with which FRET was observed showed strong correlation (r = 0.9871) with the prevalence of respective rearrangements in thyroid cancer. Our findings demonstrate that FRET can be used as a technique to analyze proximity between specific DNA regions and that the frequency of gene positioning at distances allowing FRET correlates with their probability to undergo chromosomal rearrangements.
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Affiliation(s)
- Manoj Gandhi
- Department of Pathology, University of Pittsburgh, PA 15261, USA
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35
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Sengerová B, Allerston CK, Abu M, Lee SY, Hartley J, Kiakos K, Schofield CJ, Hartley JA, Gileadi O, McHugh PJ. Characterization of the human SNM1A and SNM1B/Apollo DNA repair exonucleases. J Biol Chem 2012; 287:26254-67. [PMID: 22692201 PMCID: PMC3406710 DOI: 10.1074/jbc.m112.367243] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Human SNM1A and SNM1B/Apollo have both been implicated in the repair of DNA interstrand cross-links (ICLs) by cellular studies, and SNM1B is also required for telomere protection. Here, we describe studies on the biochemical characterization of the SNM1A and SNM1B proteins. The results reveal some fundamental differences in the mechanisms of the two proteins. Both SNM1A and SNM1B digest double-stranded and single-stranded DNA with a 5'-to-3' directionality in a reaction that is stimulated by divalent cations, and both nucleases are inhibited by the zinc chelator o-phenanthroline. We find that SNM1A has greater affinity for single-stranded DNA over double-stranded DNA that is not observed with SNM1B. Although both proteins demonstrate a low level of processivity on low molecular weight DNA oligonucleotide substrates, when presented with high molecular weight DNA, SNM1A alone is rendered much more active, being capable of digesting kilobase-long stretches of DNA. Both proteins can digest past ICLs induced by the non-distorting minor groove cross-linking agent SJG-136, albeit with SNM1A showing a greater capacity to achieve this. This is consistent with the proposal that SNM1A and SNM1B might exhibit some redundancy in ICL repair. Together, our work establishes differences in the substrate selectivities of SNM1A and SNM1B that are likely to be relevant to their in vivo roles and which might be exploited in the development of selective inhibitors.
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Affiliation(s)
- Blanka Sengerová
- Department of Oncology, Weatherall Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, Oxford, UK
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36
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Lee G, Ha T. Single-Molecule Imaging: A Collagenase Pauses before Embarking on a Killing Spree. Curr Biol 2012; 22:R499-501. [DOI: 10.1016/j.cub.2012.04.037] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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37
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Quantitative fluorescence labeling of aldehyde-tagged proteins for single-molecule imaging. Nat Methods 2012; 9:499-503. [PMID: 22466795 PMCID: PMC3445270 DOI: 10.1038/nmeth.1954] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2011] [Accepted: 03/08/2012] [Indexed: 11/08/2022]
Abstract
A major hurdle for molecular mechanistic studies of many proteins is the lack of a general method for fluorescent labeling with high efficiency, specificity, and speed. By incorporating an aldehyde motif genetically into a protein and improving the labeling kinetics substantially under mild conditions, we achieved fast, site-specific labeling of a protein with ~100% efficiency while maintaining the biological function. We demonstrate that an aldehyde-tagged protein can be specifically labeled in cell extracts without protein purification and then can be used in single-molecule pull-down analysis. We further show the unique power of our method in a series of single-molecule studies on the transient interactions and switching between two quantitatively labeled DNA polymerases on their processivity factor.
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38
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Abstract
The advent of new technologies allowing the study of single biological molecules continues to have a major impact on studies of interacting systems as well as enzyme reactions. These approaches (fluorescence, optical, and magnetic tweezers), in combination with ensemble methods, have been particularly useful for mechanistic studies of protein-nucleic acid interactions and enzymes that function on nucleic acids. We review progress in the use of single-molecule methods to observe and perturb the activities of proteins and enzymes that function on flexible single-stranded DNA. These include single-stranded DNA binding proteins, recombinases (RecA/Rad51), and helicases/translocases that operate as motor proteins and play central roles in genome maintenance. We emphasize methods that have been used to detect and study the movement of these proteins (both ATP-dependent directional and random movement) along the single-stranded DNA and the mechanistic and functional information that can result from detailed analysis of such movement.
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Affiliation(s)
- Taekjip Ha
- Department of Physics and the Center for the Physics of Living Cells, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
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39
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Xiao X, Zhang C, Su X, Song C, Zhao M. A universal mismatch-directed signal amplification platform for ultra-selective and sensitive DNA detection under mild isothermal conditions. Chem Sci 2012. [DOI: 10.1039/c2sc20189e] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
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