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Abstract
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Telomeres are essential
chromosome end capping structures that
safeguard the genome from dangerous DNA processing events. DNA strand
invasion occurs during vital transactions at telomeres, including
telomere length maintenance by the alternative lengthening of telomeres
(ALT) pathway. During telomeric strand invasion, a single-stranded
guanine-rich (G-rich) DNA invades at a complementary duplex telomere
repeat sequence, forming a displacement loop (D-loop) in which the
displaced DNA consists of the same G-rich sequence as the invading
single-stranded DNA. Single-stranded G-rich telomeric DNA readily
folds into stable, compact, structures called G-quadruplexes (GQs)
in vitro and is anticipated to form within the context of a D-loop;
however, evidence supporting this hypothesis is lacking. Here, we
report a magnetic tweezers assay that permits the controlled formation
of telomeric D-loops (TDLs) within uninterrupted duplex human telomere
DNA molecules of physiologically relevant lengths. Our results are
consistent with a model wherein the displaced single-stranded DNA
of a TDL fold into a GQ. This study provides new insight into telomere
structure and establishes a framework for the development of novel
therapeutics designed to target GQs at telomeres in cancer cells.
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Affiliation(s)
- Terren R. Chang
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, 1156 High St, Santa Cruz, California 95064, United States
| | - Xi Long
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, 1156 High St, Santa Cruz, California 95064, United States
| | - Shankar Shastry
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, 1156 High St, Santa Cruz, California 95064, United States
- 10X Genomics, 6230 Stoneridge Mall Rd, Pleasanton, California 94588, United States
| | - Joseph W. Parks
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, 1156 High St, Santa Cruz, California 95064, United States
- Invitae, 1400 16th St, San Francisco, California 94103, United States
| | - Michael D. Stone
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, 1156 High St, Santa Cruz, California 95064, United States
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Abstract
Telomeres are specialized chromatin structures that protect chromosome ends from dangerous processing events. In most tissues, telomeres shorten with each round of cell division, placing a finite limit on cell growth. In rapidly dividing cells, including the majority of human cancers, cells bypass this growth limit through telomerase-catalyzed maintenance of telomere length. The dynamic properties of telomeres and telomerase render them difficult to study using ensemble biochemical and structural techniques. This review describes single-molecule approaches to studying how individual components of telomeres and telomerase contribute to function. Single-molecule methods provide a window into the complex nature of telomeres and telomerase by permitting researchers to directly visualize and manipulate the individual protein, DNA, and RNA molecules required for telomere function. The work reviewed in this article highlights how single-molecule techniques have been utilized to investigate the function of telomeres and telomerase.
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Affiliation(s)
- Joseph W Parks
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, California 95064; .,Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80303
| | - Michael D Stone
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, California 95064; .,Center for Molecular Biology of RNA, Santa Cruz, California 95064
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3
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Parks JW, Kappel K, Das R, Stone MD. Single-molecule FRET-Rosetta reveals RNA structural rearrangements during human telomerase catalysis. RNA 2017; 23:175-188. [PMID: 28096444 PMCID: PMC5238793 DOI: 10.1261/rna.058743.116] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/15/2016] [Accepted: 09/23/2016] [Indexed: 06/06/2023]
Abstract
Maintenance of telomeres by telomerase permits continuous proliferation of rapidly dividing cells, including the majority of human cancers. Despite its direct biomedical significance, the architecture of the human telomerase complex remains unknown. Generating homogeneous telomerase samples has presented a significant barrier to developing improved structural models. Here we pair single-molecule Förster resonance energy transfer (smFRET) measurements with Rosetta modeling to map the conformations of the essential telomerase RNA core domain within the active ribonucleoprotein. FRET-guided modeling places the essential pseudoknot fold distal to the active site on a protein surface comprising the C-terminal element, a domain that shares structural homology with canonical polymerase thumb domains. An independently solved medium-resolution structure of Tetrahymena telomerase provides a blind test of our modeling methodology and sheds light on the structural homology of this domain across diverse organisms. Our smFRET-Rosetta models reveal nanometer-scale rearrangements within the RNA core domain during catalysis. Taken together, our FRET data and pseudoatomic molecular models permit us to propose a possible mechanism for how RNA core domain rearrangement is coupled to template hybrid elongation.
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Affiliation(s)
- Joseph W Parks
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, California 95064, USA
- Center for Molecular Biology of RNA, University of California, Santa Cruz, California 95064, USA
| | - Kalli Kappel
- Biophysics Program, Stanford University, Stanford, California 94305, USA
| | - Rhiju Das
- Biophysics Program, Stanford University, Stanford, California 94305, USA
- Department of Biochemistry, Stanford University, Stanford, California 94305, USA
- Department of Physics, Stanford University, Stanford, California 94305, USA
| | - Michael D Stone
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, California 95064, USA
- Center for Molecular Biology of RNA, University of California, Santa Cruz, California 95064, USA
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Cai H, Stott MA, Ozcelik D, Parks JW, Hawkins AR, Schmidt H. On-chip wavelength multiplexed detection of cancer DNA biomarkers in blood. Biomicrofluidics 2016; 10:064116. [PMID: 28058082 PMCID: PMC5176344 DOI: 10.1063/1.4968033] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/22/2016] [Accepted: 11/06/2016] [Indexed: 05/03/2023]
Abstract
We have developed an optofluidic analysis system that processes biomolecular samples starting from whole blood and then analyzes and identifies multiple targets on a silicon-based molecular detection platform. We demonstrate blood filtration, sample extraction, target enrichment, and fluorescent labeling using programmable microfluidic circuits. We detect and identify multiple targets using a spectral multiplexing technique based on wavelength-dependent multi-spot excitation on an antiresonant reflecting optical waveguide chip. Specifically, we extract two types of melanoma biomarkers, mutated cell-free nucleic acids -BRAFV600E and NRAS, from whole blood. We detect and identify these two targets simultaneously using the spectral multiplexing approach with up to a 96% success rate. These results point the way toward a full front-to-back chip-based optofluidic compact system for high-performance analysis of complex biological samples.
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Affiliation(s)
- H Cai
- School of Engineering, University of California , Santa Cruz. 1156 High Street, Santa Cruz, California 95064, USA
| | - M A Stott
- Department of Electrical and Computer Engineering, Brigham Young University , 459 Clyde Building, Provo, Utah 84602, USA
| | - D Ozcelik
- School of Engineering, University of California , Santa Cruz. 1156 High Street, Santa Cruz, California 95064, USA
| | - J W Parks
- School of Engineering, University of California , Santa Cruz. 1156 High Street, Santa Cruz, California 95064, USA
| | - A R Hawkins
- Department of Electrical and Computer Engineering, Brigham Young University , 459 Clyde Building, Provo, Utah 84602, USA
| | - H Schmidt
- School of Engineering, University of California , Santa Cruz. 1156 High Street, Santa Cruz, California 95064, USA
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5
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Long X, Parks JW, Stone MD. Integrated magnetic tweezers and single-molecule FRET for investigating the mechanical properties of nucleic acid. Methods 2016; 105:16-25. [PMID: 27320203 DOI: 10.1016/j.ymeth.2016.06.009] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2016] [Revised: 06/09/2016] [Accepted: 06/13/2016] [Indexed: 02/02/2023] Open
Abstract
Many enzymes promote structural changes in their nucleic acid substrates via application of piconewton forces over nanometer length scales. Magnetic tweezers (MT) is a single molecule force spectroscopy method widely used for studying the energetics of such mechanical processes. MT permits stable application of a wide range of forces and torques over long time scales with nanometer spatial resolution. However, in any force spectroscopy experiment, the ability to monitor structural changes in nucleic acids with nanometer sensitivity requires the system of interest to be held under high degrees of tension to improve signal to noise. This limitation prohibits measurement of structural changes within nucleic acids under physiologically relevant conditions of low stretching forces. To overcome this challenge, researchers have integrated a spatially sensitive fluorescence spectroscopy method, single molecule-FRET, with MT to allow simultaneous observation and manipulation of nanoscale structural transitions over a wide range of forces. Here, we describe a method for using this hybrid instrument to analyze the mechanical properties of nucleic acids. We expect that this method for analysis of nucleic acid structure will be easily adapted for experiments aiming to interrogate the mechanical responses of other biological macromolecules.
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Affiliation(s)
- Xi Long
- Department of Chemistry and Biochemistry, University of California Santa Cruz, Santa Cruz, CA, USA
| | - Joseph W Parks
- Department of Chemistry and Biochemistry, University of California Santa Cruz, Santa Cruz, CA, USA
| | - Michael D Stone
- Department of Chemistry and Biochemistry, University of California Santa Cruz, Santa Cruz, CA, USA; Center for Molecular Biology of RNA, University of California Santa Cruz, Santa Cruz, CA, USA.
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Ozcelik D, Parks JW, Wall TA, Stott MA, Cai H, Parks JW, Hawkins AR, Schmidt H. Optofluidic wavelength division multiplexing for single-virus detection. Proc Natl Acad Sci U S A 2015. [PMID: 26438840 DOI: 10.1073/pnas.l511921112] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/23/2023] Open
Abstract
Optical waveguides simultaneously transport light at different colors, forming the basis of fiber-optic telecommunication networks that shuttle data in dozens of spectrally separated channels. Here, we reimagine this wavelength division multiplexing (WDM) paradigm in a novel context--the differentiated detection and identification of single influenza viruses on a chip. We use a single multimode interference (MMI) waveguide to create wavelength-dependent spot patterns across the entire visible spectrum and enable multiplexed single biomolecule detection on an optofluidic chip. Each target is identified by its time-dependent fluorescence signal without the need for spectral demultiplexing upon detection. We demonstrate detection of individual fluorescently labeled virus particles of three influenza A subtypes in two implementations: labeling of each virus using three different colors and two-color combinatorial labeling. By extending combinatorial multiplexing to three or more colors, MMI-based WDM provides the multiplexing power required for differentiated clinical tests and the growing field of personalized medicine.
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Affiliation(s)
- Damla Ozcelik
- Department of Electrical Engineering, University of California, Santa Cruz, CA 95064
| | - Joshua W Parks
- Department of Electrical Engineering, University of California, Santa Cruz, CA 95064
| | - Thomas A Wall
- Department of Electrical and Computer Engineering, Brigham Young University, Provo, UT 84602
| | - Matthew A Stott
- Department of Electrical and Computer Engineering, Brigham Young University, Provo, UT 84602
| | - Hong Cai
- Department of Electrical Engineering, University of California, Santa Cruz, CA 95064
| | - Joseph W Parks
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, CA 95064
| | - Aaron R Hawkins
- Department of Electrical and Computer Engineering, Brigham Young University, Provo, UT 84602
| | - Holger Schmidt
- Department of Electrical Engineering, University of California, Santa Cruz, CA 95064;
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Cai H, Parks JW, Wall TA, Stott MA, Stambaugh A, Alfson K, Griffiths A, Mathies RA, Carrion R, Patterson JL, Hawkins AR, Schmidt H. Optofluidic analysis system for amplification-free, direct detection of Ebola infection. Sci Rep 2015. [PMID: 26404403 DOI: 10.1038/srepl4494] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/23/2023] Open
Abstract
The massive outbreak of highly lethal Ebola hemorrhagic fever in West Africa illustrates the urgent need for diagnostic instruments that can identify and quantify infections rapidly, accurately, and with low complexity. Here, we report on-chip sample preparation, amplification-free detection and quantification of Ebola virus on clinical samples using hybrid optofluidic integration. Sample preparation and target preconcentration are implemented on a PDMS-based microfluidic chip (automaton), followed by single nucleic acid fluorescence detection in liquid-core optical waveguides on a silicon chip in under ten minutes. We demonstrate excellent specificity, a limit of detection of 0.2 pfu/mL and a dynamic range of thirteen orders of magnitude, far outperforming other amplification-free methods. This chip-scale approach and reduced complexity compared to gold standard RT-PCR methods is ideal for portable instruments that can provide immediate diagnosis and continued monitoring of infectious diseases at the point-of-care.
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Affiliation(s)
- H Cai
- School of Engineering, University of California Santa Cruz, 1156 High Street, Santa Cruz, CA 95064 USA
| | - J W Parks
- School of Engineering, University of California Santa Cruz, 1156 High Street, Santa Cruz, CA 95064 USA
| | - T A Wall
- ECEn Department, 459 Clyde Building, Brigham Young University, Provo, UT 84602 USA
| | - M A Stott
- ECEn Department, 459 Clyde Building, Brigham Young University, Provo, UT 84602 USA
| | - A Stambaugh
- School of Engineering, University of California Santa Cruz, 1156 High Street, Santa Cruz, CA 95064 USA
| | - K Alfson
- Department of Virology and Immunology, Texas Biomedical Research Institute, 7620 NW Loop 410, San Antonio, TX 78227 USA
| | - A Griffiths
- Department of Virology and Immunology, Texas Biomedical Research Institute, 7620 NW Loop 410, San Antonio, TX 78227 USA
| | - R A Mathies
- Department of Chemistry, University of California Berkeley, Berkeley, CA 94720 USA
| | - R Carrion
- Department of Virology and Immunology, Texas Biomedical Research Institute, 7620 NW Loop 410, San Antonio, TX 78227 USA
| | - J L Patterson
- Department of Virology and Immunology, Texas Biomedical Research Institute, 7620 NW Loop 410, San Antonio, TX 78227 USA
| | - A R Hawkins
- ECEn Department, 459 Clyde Building, Brigham Young University, Provo, UT 84602 USA
| | - H Schmidt
- School of Engineering, University of California Santa Cruz, 1156 High Street, Santa Cruz, CA 95064 USA
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Cai H, Parks JW, Wall TA, Stott MA, Stambaugh A, Alfson K, Griffiths A, Mathies RA, Carrion R, Patterson JL, Hawkins AR, Schmidt H. Optofluidic analysis system for amplification-free, direct detection of Ebola infection. Sci Rep 2015; 5:14494. [PMID: 26404403 PMCID: PMC4585921 DOI: 10.1038/srep14494] [Citation(s) in RCA: 90] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2015] [Accepted: 08/28/2015] [Indexed: 12/12/2022] Open
Abstract
The massive outbreak of highly lethal Ebola hemorrhagic fever in West Africa illustrates the urgent need for diagnostic instruments that can identify and quantify infections rapidly, accurately, and with low complexity. Here, we report on-chip sample preparation, amplification-free detection and quantification of Ebola virus on clinical samples using hybrid optofluidic integration. Sample preparation and target preconcentration are implemented on a PDMS-based microfluidic chip (automaton), followed by single nucleic acid fluorescence detection in liquid-core optical waveguides on a silicon chip in under ten minutes. We demonstrate excellent specificity, a limit of detection of 0.2 pfu/mL and a dynamic range of thirteen orders of magnitude, far outperforming other amplification-free methods. This chip-scale approach and reduced complexity compared to gold standard RT-PCR methods is ideal for portable instruments that can provide immediate diagnosis and continued monitoring of infectious diseases at the point-of-care.
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Affiliation(s)
- H Cai
- School of Engineering, University of California Santa Cruz, 1156 High Street, Santa Cruz, CA 95064 USA
| | - J W Parks
- School of Engineering, University of California Santa Cruz, 1156 High Street, Santa Cruz, CA 95064 USA
| | - T A Wall
- ECEn Department, 459 Clyde Building, Brigham Young University, Provo, UT 84602 USA
| | - M A Stott
- ECEn Department, 459 Clyde Building, Brigham Young University, Provo, UT 84602 USA
| | - A Stambaugh
- School of Engineering, University of California Santa Cruz, 1156 High Street, Santa Cruz, CA 95064 USA
| | - K Alfson
- Department of Virology and Immunology, Texas Biomedical Research Institute, 7620 NW Loop 410, San Antonio, TX 78227 USA
| | - A Griffiths
- Department of Virology and Immunology, Texas Biomedical Research Institute, 7620 NW Loop 410, San Antonio, TX 78227 USA
| | - R A Mathies
- Department of Chemistry, University of California Berkeley, Berkeley, CA 94720 USA
| | - R Carrion
- Department of Virology and Immunology, Texas Biomedical Research Institute, 7620 NW Loop 410, San Antonio, TX 78227 USA
| | - J L Patterson
- Department of Virology and Immunology, Texas Biomedical Research Institute, 7620 NW Loop 410, San Antonio, TX 78227 USA
| | - A R Hawkins
- ECEn Department, 459 Clyde Building, Brigham Young University, Provo, UT 84602 USA
| | - H Schmidt
- School of Engineering, University of California Santa Cruz, 1156 High Street, Santa Cruz, CA 95064 USA
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Akiyama BM, Parks JW, Stone MD. The telomerase essential N-terminal domain promotes DNA synthesis by stabilizing short RNA-DNA hybrids. Nucleic Acids Res 2015; 43:5537-49. [PMID: 25940626 PMCID: PMC4477650 DOI: 10.1093/nar/gkv406] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2014] [Accepted: 04/15/2015] [Indexed: 01/11/2023] Open
Abstract
Telomerase is an enzyme that adds repetitive DNA sequences to the ends of chromosomes and consists of two main subunits: the telomerase reverse transcriptase (TERT) protein and an associated telomerase RNA (TER). The telomerase essential N-terminal (TEN) domain is a conserved region of TERT proposed to mediate DNA substrate interactions. Here, we have employed single molecule telomerase binding assays to investigate the function of the TEN domain. Our results reveal telomeric DNA substrates bound to telomerase exhibit a dynamic equilibrium between two states: a docked conformation and an alternative conformation. The relative stabilities of the docked and alternative states correlate with the number of basepairs that can be formed between the DNA substrate and the RNA template, with more basepairing favoring the docked state. The docked state is further buttressed by the TEN domain and mutations within the TEN domain substantially alter the DNA substrate structural equilibrium. We propose a model in which the TEN domain stabilizes short RNA–DNA duplexes in the active site of the enzyme, promoting the docked state to augment telomerase processivity.
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Affiliation(s)
- Benjamin M Akiyama
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, CA 95064, USA Center for Molecular Biology of RNA, University of California, Santa Cruz, CA 95064, USA
| | - Joseph W Parks
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, CA 95064, USA Center for Molecular Biology of RNA, University of California, Santa Cruz, CA 95064, USA
| | - Michael D Stone
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, CA 95064, USA Center for Molecular Biology of RNA, University of California, Santa Cruz, CA 95064, USA
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10
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Parks JW, Olson MA, Kim J, Ozcelik D, Cai H, Carrion R, Patterson JL, Mathies RA, Hawkins AR, Schmidt H. Integration of programmable microfluidics and on-chip fluorescence detection for biosensing applications. Biomicrofluidics 2014; 8:054111. [PMID: 25584111 PMCID: PMC4290670 DOI: 10.1063/1.4897226] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2014] [Accepted: 09/24/2014] [Indexed: 05/05/2023]
Abstract
We describe the integration of an actively controlled programmable microfluidic sample processor with on-chip optical fluorescence detection to create a single, hybrid sensor system. An array of lifting gate microvalves (automaton) is fabricated with soft lithography, which is reconfigurably joined to a liquid-core, anti-resonant reflecting optical waveguide (ARROW) silicon chip fabricated with conventional microfabrication. In the automaton, various sample handling steps such as mixing, transporting, splitting, isolating, and storing are achieved rapidly and precisely to detect viral nucleic acid targets, while the optofluidic chip provides single particle detection sensitivity using integrated optics. Specifically, an assay for detection of viral nucleic acid targets is implemented. Labeled target nucleic acids are first captured and isolated on magnetic microbeads in the automaton, followed by optical detection of single beads on the ARROW chip. The combination of automated microfluidic sample preparation and highly sensitive optical detection opens possibilities for portable instruments for point-of-use analysis of minute, low concentration biological samples.
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Affiliation(s)
- J W Parks
- School of Engineering, University of California Santa Cruz , Santa Cruz, California 95064, USA
| | - M A Olson
- Department of Electrical and Computer Engineering, Brigham Young University , Provo, Utah 84602, USA
| | | | - D Ozcelik
- School of Engineering, University of California Santa Cruz , Santa Cruz, California 95064, USA
| | - H Cai
- School of Engineering, University of California Santa Cruz , Santa Cruz, California 95064, USA
| | - R Carrion
- Department of Virology and Immunology, Texas Biomedical Research Institute , 7620 NW Loop 410, San Antonio, Texas 78227, USA
| | - J L Patterson
- Department of Virology and Immunology, Texas Biomedical Research Institute , 7620 NW Loop 410, San Antonio, Texas 78227, USA
| | - R A Mathies
- Department of Chemistry, University of California Berkeley , Berkeley, California 94720, USA
| | - A R Hawkins
- Department of Electrical and Computer Engineering, Brigham Young University , Provo, Utah 84602, USA
| | - H Schmidt
- School of Engineering, University of California Santa Cruz , Santa Cruz, California 95064, USA
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Parks JW, Stone MD. Coordinated DNA dynamics during the human telomerase catalytic cycle. Nat Commun 2014; 5:4146. [PMID: 24923681 PMCID: PMC4107311 DOI: 10.1038/ncomms5146] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2013] [Accepted: 05/15/2014] [Indexed: 11/09/2022] Open
Abstract
The human telomerase reverse transcriptase (hTERT) utilizes a template within the integral RNA subunit (hTR) to direct extension of telomeres. Telomerase exhibits repeat addition processivity (RAP) and must therefore translocate the nascent DNA product into a new RNA:DNA hybrid register to prime each round of telomere repeat synthesis. Here we use single-molecule FRET and nuclease protection assays to monitor telomere DNA structure and dynamics during the telomerase catalytic cycle. DNA translocation during RAP proceeds through a previously uncharacterized kinetic sub-step during which the 3′-end of the DNA substrate base pairs downstream within the hTR template. The rate constant for DNA primer re-alignment reveals this step is not rate-limiting for RAP, suggesting a second slow conformational change repositions the RNA:DNA hybrid into the telomerase active site and drives the extrusion of the 5′-end of the DNA primer out of the enzyme complex.
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Affiliation(s)
- Joseph W Parks
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, California 95064, USA
| | - Michael D Stone
- 1] Department of Chemistry and Biochemistry, University of California, Santa Cruz, California 95064, USA [2] Center for Molecular Biology of RNA, University of California, 1156 High Street, Santa Cruz, California 95064, USA
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12
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Long X, Parks JW, Bagshaw CR, Stone MD. Mechanical Unfolding of Human Telomere G-Quadruplex DNA Probed by Integrated Fluorescence and Magnetic Tweezers Spectroscopy. Biophys J 2014. [DOI: 10.1016/j.bpj.2013.11.430] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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13
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Long X, Parks JW, Bagshaw CR, Stone MD. Mechanical unfolding of human telomere G-quadruplex DNA probed by integrated fluorescence and magnetic tweezers spectroscopy. Nucleic Acids Res 2013; 41:2746-55. [PMID: 23303789 PMCID: PMC3575832 DOI: 10.1093/nar/gks1341] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Single-molecule techniques facilitate analysis of mechanical transitions within nucleic acids and proteins. Here, we describe an integrated fluorescence and magnetic tweezers instrument that permits detection of nanometer-scale DNA structural rearrangements together with the application of a wide range of stretching forces to individual DNA molecules. We have analyzed the force-dependent equilibrium and rate constants for telomere DNA G-quadruplex (GQ) folding and unfolding, and have determined the location of the transition state barrier along the well-defined DNA-stretching reaction coordinate. Our results reveal the mechanical unfolding pathway of the telomere DNA GQ is characterized by a short distance (<1 nm) to the transition state for the unfolding reaction. This mechanical unfolding response reflects a critical contribution of long-range interactions to the global stability of the GQ fold, and suggests that telomere-associated proteins need only disrupt a few base pairs to destabilize GQ structures. Comparison of the GQ unfolded state with a single-stranded polyT DNA revealed the unfolded GQ exhibits a compacted non-native conformation reminiscent of the protein molten globule. We expect the capacity to interrogate macromolecular structural transitions with high spatial resolution under conditions of low forces will have broad application in analyses of nucleic acid and protein folding.
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Affiliation(s)
- Xi Long
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, Santa Cruz, CA 95064, USA
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Affiliation(s)
- J P Coxon
- Department of Urology, St George's Hospital, London, UK
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15
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Parks JW, Craig PJ, Neary BP, Ozburn G, Romani D. Biomonitoring in the mercury-contaminated Wabigoon-English-Winnipeg river (Canada) system: selecting the best available bioindicator. Appl Organomet Chem 1991. [DOI: 10.1002/aoc.590050606] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Parks JW, Curry C, Romani D, Russell DD. Young northern pike, yellow perch and crayfish as bioindicators in a mercury contaminated watercourse. Environ Monit Assess 1991; 16:39-73. [PMID: 24241775 DOI: 10.1007/bf00399593] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Young-of-the-year and yearling northern pike (Esox lucius), yearling yellow perch (Perca flavescens) and adult crayfish (Orconectes virilis) were collected in the mercury-contaminated Wabigoon/English/Winnipeg River System, Ontario, and analyzed for total mercury. Analysis of mercury concentrations in these organisms produced consistent geographical trends; i.e. mercury concentrations in biota downstream of Dryden > English River system > Winnipeg River system > control sites. In the Wabigoon River system the bioavailability of mercury increases with distance downstream of the historical point source. Mercury concentrations in the biota studied were highly correlated with mercury concentrations in fish species which are of sport and commercial interest. The locations where young fish obtain their bodyburdens are known typically within 100 m. The biota studied compare favourably with the criteria proposed by Phillips (1980) as prerequisites for biological indicators. The wide distribution of young pike, perch and crayfish in North America, Europe and Asia may enhance their appeal as biomonitors.
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Affiliation(s)
- J W Parks
- Ontario Ministry of the Environment, 435 James St. S., P7C 5G6, Thunder Bay, Ontario, Canada
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