1
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Centola M, Poppleton E, Ray S, Centola M, Welty R, Valero J, Walter NG, Šulc P, Famulok M. A rhythmically pulsing leaf-spring DNA-origami nanoengine that drives a passive follower. NATURE NANOTECHNOLOGY 2024; 19:226-236. [PMID: 37857824 PMCID: PMC10873200 DOI: 10.1038/s41565-023-01516-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/27/2023] [Accepted: 08/31/2023] [Indexed: 10/21/2023]
Abstract
Molecular engineering seeks to create functional entities for modular use in the bottom-up design of nanoassemblies that can perform complex tasks. Such systems require fuel-consuming nanomotors that can actively drive downstream passive followers. Most artificial molecular motors are driven by Brownian motion, in which, with few exceptions, the generated forces are non-directed and insufficient for efficient transfer to passive second-level components. Consequently, efficient chemical-fuel-driven nanoscale driver-follower systems have not yet been realized. Here we present a DNA nanomachine (70 nm × 70 nm × 12 nm) driven by the chemical energy of DNA-templated RNA-transcription-consuming nucleoside triphosphates as fuel to generate a rhythmic pulsating motion of two rigid DNA-origami arms. Furthermore, we demonstrate actuation control and the simple coupling of the active nanomachine with a passive follower, to which it then transmits its motion, forming a true driver-follower pair.
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Affiliation(s)
- Mathias Centola
- LIMES Program Unit Chemical Biology & Medicinal Chemistry, c/o Kekulé Institut für Organische Chemie und Biochemie, Universität Bonn, Bonn, Germany
- Max-Planck Institute for Neurobiology of Behaviour, Bonn, Germany
| | - Erik Poppleton
- School of Molecular Sciences and Center for Molecular Design and Biomimetics, The Biodesign Institute, Arizona State University, Tempe, AZ, USA
- Max-Planck-Institute for Medical Research, Heidelberg, Germany
| | - Sujay Ray
- Single Molecule Analysis Group, Department of Chemistry, Ann Arbor, MI, USA
| | | | - Robb Welty
- Single Molecule Analysis Group, Department of Chemistry, Ann Arbor, MI, USA
| | - Julián Valero
- LIMES Program Unit Chemical Biology & Medicinal Chemistry, c/o Kekulé Institut für Organische Chemie und Biochemie, Universität Bonn, Bonn, Germany
- Max-Planck Institute for Neurobiology of Behaviour, Bonn, Germany
- Interdisciplinary Nanoscience Center - INANO-MBG, iNANO-huset, Århus, Denmark
| | - Nils G Walter
- Single Molecule Analysis Group, Department of Chemistry, Ann Arbor, MI, USA.
| | - Petr Šulc
- LIMES Program Unit Chemical Biology & Medicinal Chemistry, c/o Kekulé Institut für Organische Chemie und Biochemie, Universität Bonn, Bonn, Germany.
- School of Molecular Sciences and Center for Molecular Design and Biomimetics, The Biodesign Institute, Arizona State University, Tempe, AZ, USA.
| | - Michael Famulok
- LIMES Program Unit Chemical Biology & Medicinal Chemistry, c/o Kekulé Institut für Organische Chemie und Biochemie, Universität Bonn, Bonn, Germany.
- Max-Planck Institute for Neurobiology of Behaviour, Bonn, Germany.
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2
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Hwang J, Palmer B, Myong S. Single-molecule observation of G-quadruplex and R-loop formation induced by transcription. Methods Enzymol 2024; 695:71-88. [PMID: 38521591 DOI: 10.1016/bs.mie.2024.01.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/25/2024]
Abstract
Potential G-quadruplex forming sequences (PQS) are enriched in cancer-related genes and immunoglobulin class-switch recombination. They are prevalent in the 5'UTR of transcriptionally active genes, thereby contributing to the regulation of gene expression. We and others previously demonstrated that the PQS located in the non-template strand leads to an R-loop formation followed by a G-quadruplex (G4) formation during transcription. These structural changes increase mRNA production. Here, we present how single-molecule technique was used to observe cotranscriptional G4 and R-loop formation and to examine the impact on transcription, particularly for the initiation and elongation stages.
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Affiliation(s)
- Jihee Hwang
- Program in Cellular and Molecular Medicine, Boston Children's Hospital and Harvard Medical School, Boston, MA, United States
| | - Bradleigh Palmer
- Program in Cellular Molecular Developmental Biology and Biophysics, Johns Hopkins University, Baltimore, MD, United States
| | - Sua Myong
- Program in Cellular and Molecular Medicine, Boston Children's Hospital and Harvard Medical School, Boston, MA, United States; Program in Cellular Molecular Developmental Biology and Biophysics, Johns Hopkins University, Baltimore, MD, United States.
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3
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Kuo HC, Prupes J, Chou CW, Finkelstein IJ. Massively parallel profiling of RNA-targeting CRISPR-Cas13d. Nat Commun 2024; 15:498. [PMID: 38216559 PMCID: PMC10786891 DOI: 10.1038/s41467-024-44738-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2023] [Accepted: 01/02/2024] [Indexed: 01/14/2024] Open
Abstract
CRISPR-Cas13d cleaves RNA and is used in vivo and for diagnostics. However, a systematic understanding of its RNA binding and cleavage specificity is lacking. Here, we describe an RNA Chip-Hybridized Association-Mapping Platform (RNA-CHAMP) for measuring the binding affinity for > 10,000 RNAs containing structural perturbations and other alterations relative to the CRISPR RNA (crRNA). Deep profiling of Cas13d reveals that it does not require a protospacer flanking sequence but is exquisitely sensitive to secondary structure within the target RNA. Cas13d binding is penalized by mismatches in the distal crRNA-target RNA region, while alterations in the proximal region inhibit nuclease activity. A biophysical model built from these data reveals that target recognition initiates in the distal end of the target RNA. Using this model, we design crRNAs that can differentiate between SARS-CoV-2 variants by modulating nuclease activation. This work describes the key determinants of RNA targeting by a type VI CRISPR enzyme.
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Affiliation(s)
- Hung-Che Kuo
- Department of Molecular Biosciences and Institute for Cellular and Molecular Biology, University of Texas at Austin, Austin, TX, 78712, USA.
| | - Joshua Prupes
- Department of Molecular Biosciences and Institute for Cellular and Molecular Biology, University of Texas at Austin, Austin, TX, 78712, USA
| | - Chia-Wei Chou
- Department of Molecular Biosciences and Institute for Cellular and Molecular Biology, University of Texas at Austin, Austin, TX, 78712, USA
| | - Ilya J Finkelstein
- Department of Molecular Biosciences and Institute for Cellular and Molecular Biology, University of Texas at Austin, Austin, TX, 78712, USA.
- Center for Systems and Synthetic Biology, University of Texas at Austin, Austin, TX, 78712, USA.
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4
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Ploetz E, Ambrose B, Barth A, Börner R, Erichson F, Kapanidis AN, Kim HD, Levitus M, Lohman TM, Mazumder A, Rueda DS, Steffen FD, Cordes T, Magennis SW, Lerner E. A new twist on PIFE: photoisomerisation-related fluorescence enhancement. Methods Appl Fluoresc 2023; 12:012001. [PMID: 37726007 PMCID: PMC10570931 DOI: 10.1088/2050-6120/acfb58] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2023] [Revised: 07/24/2023] [Accepted: 09/19/2023] [Indexed: 09/21/2023]
Abstract
PIFE was first used as an acronym for protein-induced fluorescence enhancement, which refers to the increase in fluorescence observed upon the interaction of a fluorophore, such as a cyanine, with a protein. This fluorescence enhancement is due to changes in the rate ofcis/transphotoisomerisation. It is clear now that this mechanism is generally applicable to interactions with any biomolecule. In this review, we propose that PIFE is thereby renamed according to its fundamental working principle as photoisomerisation-related fluorescence enhancement, keeping the PIFE acronym intact. We discuss the photochemistry of cyanine fluorophores, the mechanism of PIFE, its advantages and limitations, and recent approaches to turning PIFE into a quantitative assay. We provide an overview of its current applications to different biomolecules and discuss potential future uses, including the study of protein-protein interactions, protein-ligand interactions and conformational changes in biomolecules.
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Affiliation(s)
- Evelyn Ploetz
- Department of Chemistry and Center for NanoScience (CeNS), Ludwig-Maximilians-Universität München, Butenandtstr. 5-13, 81377 München, Germany
| | - Benjamin Ambrose
- Department of Infectious Disease, Faculty of Medicine, Imperial College London, London, W12 0HS, United Kingdom
- Single Molecule Imaging Group, MRC-London Institute of Medical Sciences, London, W12 0HS, United Kingdom
| | - Anders Barth
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Delft 2629 HZ, The Netherlands
| | - Richard Börner
- Laserinstitut Hochschule Mittweida, Mittweida University of Applied Sciences, Mittweida, Germany
| | - Felix Erichson
- Laserinstitut Hochschule Mittweida, Mittweida University of Applied Sciences, Mittweida, Germany
| | - Achillefs N Kapanidis
- Biological Physics Research Group, Department of Physics, University of Oxford, Oxford, United Kingdom
- Kavli Institute for Nanoscience Discovery, Dorothy Crowfoot Hodgkin Building, University of Oxford, Oxford, United Kingdom
| | - Harold D Kim
- School of Physics, Georgia Institute of Technology, 837 State Street, Atlanta, GA 30332, United States of America
| | - Marcia Levitus
- School of Molecular Sciences, Arizona State University, 551 E. University Drive, Tempe, AZ,85287, United States of America
| | - Timothy M Lohman
- Department of Biochemistry and Molecular Biophysics, Washington University in St. Louis School of Medicine, St. Louis, MO 63110, United States of America
| | - Abhishek Mazumder
- CSIR-Institute of Chemical Biology, 4, Raja S.C. Mullick Road, Jadavpur, Kolkata-700032, West Bengal, India
| | - David S Rueda
- Department of Infectious Disease, Faculty of Medicine, Imperial College London, London, W12 0HS, United Kingdom
- Single Molecule Imaging Group, MRC-London Institute of Medical Sciences, London, W12 0HS, United Kingdom
| | - Fabio D Steffen
- Department of Chemistry, University of Zurich, Zurich, Switzerland
| | - Thorben Cordes
- Physical and Synthetic Biology, Faculty of Biology, Großhadernerstr. 2-4, Ludwig-Maximilians-Universität München, 82152 Planegg-Martinsried, Germany
| | - Steven W Magennis
- School of Chemistry, University of Glasgow, Joseph Black Building, University Avenue, Glasgow, G12 8QQ, United Kingdom
| | - Eitan Lerner
- Department of Biological Chemistry, Alexander Silberman Institute of Life Sciences, Faculty of Mathematics & Science, Edmond J. Safra Campus, Hebrew University of Jerusalem; Jerusalem 9190401, Israel
- Center for Nanoscience and Nanotechnology, Hebrew University of Jerusalem; Jerusalem 9190401, Israel
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5
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Goovaerts Q, Shen J, De Wijngaert B, Basu U, Patel SS, Das K. Structures illustrate step-by-step mitochondrial transcription initiation. Nature 2023; 622:872-879. [PMID: 37821701 PMCID: PMC10600007 DOI: 10.1038/s41586-023-06643-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2022] [Accepted: 09/13/2023] [Indexed: 10/13/2023]
Abstract
Transcription initiation is a key regulatory step in gene expression during which RNA polymerase (RNAP) initiates RNA synthesis de novo, and the synthesized RNA at a specific length triggers the transition to the elongation phase. Mitochondria recruit a single-subunit RNAP and one or two auxiliary factors to initiate transcription. Previous studies have revealed the molecular architectures of yeast1 and human2 mitochondrial RNAP initiation complexes (ICs). Here we provide a comprehensive, stepwise mechanism of transcription initiation by solving high-resolution cryogenic electron microscopy (cryo-EM) structures of yeast mitochondrial RNAP and the transcription factor Mtf1 catalysing two- to eight-nucleotide RNA synthesis at single-nucleotide addition steps. The growing RNA-DNA is accommodated in the polymerase cleft by template scrunching and non-template reorganization, creating stressed intermediates. During early initiation, non-template strand scrunching and unscrunching destabilize the short two- and three-nucleotide RNAs, triggering abortive synthesis. Subsequently, the non-template reorganizes into a base-stacked staircase-like structure supporting processive five- to eight-nucleotide RNA synthesis. The expanded non-template staircase and highly scrunched template in IC8 destabilize the promoter interactions with Mtf1 to facilitate initiation bubble collapse and promoter escape for the transition from initiation to the elongation complex (EC). The series of transcription initiation steps, each guided by the interplay of multiple structural components, reveal a finely tuned mechanism for potential regulatory control.
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Affiliation(s)
- Quinten Goovaerts
- Laboratory of Virology and Chemotherapy, Rega Institute for Medical Research, KU Leuven, Leuven, Belgium
- Department of Microbiology, Immunology and Transplantation, KU Leuven, Leuven, Belgium
| | - Jiayu Shen
- Department of Biochemistry and Molecular Biology, Robert Wood Johnson Medical School, Rutgers University, Piscataway, NJ, USA
| | - Brent De Wijngaert
- Laboratory of Virology and Chemotherapy, Rega Institute for Medical Research, KU Leuven, Leuven, Belgium
- Department of Microbiology, Immunology and Transplantation, KU Leuven, Leuven, Belgium
| | - Urmimala Basu
- Department of Biochemistry and Molecular Biology, Robert Wood Johnson Medical School, Rutgers University, Piscataway, NJ, USA
| | - Smita S Patel
- Department of Biochemistry and Molecular Biology, Robert Wood Johnson Medical School, Rutgers University, Piscataway, NJ, USA.
| | - Kalyan Das
- Laboratory of Virology and Chemotherapy, Rega Institute for Medical Research, KU Leuven, Leuven, Belgium.
- Department of Microbiology, Immunology and Transplantation, KU Leuven, Leuven, Belgium.
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6
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Ploetz E, Ambrose B, Barth A, Börner R, Erichson F, Kapanidis AN, Kim HD, Levitus M, Lohman TM, Mazumder A, Rueda DS, Steffen FD, Cordes T, Magennis SW, Lerner E. A new twist on PIFE: photoisomerisation-related fluorescence enhancement. ARXIV 2023:arXiv:2302.12455v2. [PMID: 36866225 PMCID: PMC9980184] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 03/04/2023]
Abstract
PIFE was first used as an acronym for protein-induced fluorescence enhancement, which refers to the increase in fluorescence observed upon the interaction of a fluorophore, such as a cyanine, with a protein. This fluorescence enhancement is due to changes in the rate of cis/trans photoisomerisation. It is clear now that this mechanism is generally applicable to interactions with any biomolecule and, in this review, we propose that PIFE is thereby renamed according to its fundamental working principle as photoisomerisation-related fluorescence enhancement, keeping the PIFE acronym intact. We discuss the photochemistry of cyanine fluorophores, the mechanism of PIFE, its advantages and limitations, and recent approaches to turn PIFE into a quantitative assay. We provide an overview of its current applications to different biomolecules and discuss potential future uses, including the study of protein-protein interactions, protein-ligand interactions and conformational changes in biomolecules.
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Affiliation(s)
- Evelyn Ploetz
- Department of Chemistry and Center for NanoScience (CeNS), Ludwig-Maximilians-Universität München, Butenandtstr. 5-13, 81377 München, Germany
| | - Benjamin Ambrose
- Department of Infectious Disease, Faculty of Medicine, Imperial College London, London, W12 0HS, UK, Single Molecule Imaging Group, MRC-London Institute of Medical Sciences, London, W12 0HS, UK
| | - Anders Barth
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Delft 2629 HZ, The Netherlands
| | - Richard Börner
- Laserinstitut Hochschule Mittweida, Mittweida University of Applied Sciences, Mittweida, Germany
| | - Felix Erichson
- Laserinstitut Hochschule Mittweida, Mittweida University of Applied Sciences, Mittweida, Germany
| | - Achillefs N. Kapanidis
- Kavli Institute for Nanoscience Discovery, Department of Biological Physics, The University of Oxford, UK
| | - Harold D. Kim
- School of Physics, Georgia Institute of Technology, 837 State Street, Atlanta, GA 30332, USA
| | - Marcia Levitus
- School of Molecular Sciences, Arizona State University, 551 E. University Drive, Tempe, AZ, 85287, USA
| | - Timothy M. Lohman
- Department of Biochemistry and Molecular Biophysics, Washington University in St. Louis School of Medicine, St. Louis, MO 63110, USA
| | - Abhishek Mazumder
- Kavli Institute for Nanoscience Discovery, Department of Biological Physics, The University of Oxford, UK
| | - David S. Rueda
- Department of Infectious Disease, Faculty of Medicine, Imperial College London, London, W12 0HS, UK, Single Molecule Imaging Group, MRC-London Institute of Medical Sciences, London, W12 0HS, UK
| | - Fabio D. Steffen
- Department of Chemistry, University of Zurich, Zurich, Switzerland
| | - Thorben Cordes
- Physical and Synthetic Biology, Faculty of Biology, Ludwig-Maximilians-Universität München, Großhadernerstr, 2-4, 82152 Planegg-Martinsried, Germany
| | - Steven W. Magennis
- School of Chemistry, University of Glasgow, Joseph Black Building, University Avenue, Glasgow, G12 8QQ, UK
| | - Eitan Lerner
- Department of Biological Chemistry, Alexander Silberman Institute of Life Sciences, Faculty of Mathematics & Science, Edmond J. Safra Campus, Hebrew University of Jerusalem; Jerusalem 9190401, Israel, Center for Nanoscience and Nanotechnology, Hebrew University of Jerusalem; Jerusalem 9190401, Israel
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7
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Mazumder A, Ebright RH, Kapanidis AN. Transcription initiation at a consensus bacterial promoter proceeds via a 'bind-unwind-load-and-lock' mechanism. eLife 2021; 10:70090. [PMID: 34633286 PMCID: PMC8536254 DOI: 10.7554/elife.70090] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2021] [Accepted: 10/06/2021] [Indexed: 01/24/2023] Open
Abstract
Transcription initiation starts with unwinding of promoter DNA by RNA polymerase (RNAP) to form a catalytically competent RNAP-promoter complex (RPo). Despite extensive study, the mechanism of promoter unwinding has remained unclear, in part due to the transient nature of intermediates on path to RPo. Here, using single-molecule unwinding-induced fluorescence enhancement to monitor promoter unwinding, and single-molecule fluorescence resonance energy transfer to monitor RNAP clamp conformation, we analyse RPo formation at a consensus bacterial core promoter. We find that the RNAP clamp is closed during promoter binding, remains closed during promoter unwinding, and then closes further, locking the unwound DNA in the RNAP active-centre cleft. Our work defines a new, ‘bind-unwind-load-and-lock’, model for the series of conformational changes occurring during promoter unwinding at a consensus bacterial promoter and provides the tools needed to examine the process in other organisms and at other promoters.
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Affiliation(s)
- Abhishek Mazumder
- Biological Physics Research Group, Clarendon Laboratory, Department of Physics, University of Oxford, Oxford, United Kingdom
| | - Richard H Ebright
- Waksman Institute and Department of Chemistry, Rutgers University, Piscataway, United States
| | - Achillefs N Kapanidis
- Biological Physics Research Group, Clarendon Laboratory, Department of Physics, University of Oxford, Oxford, United Kingdom
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8
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Lee CY, Myong S. Probing steps in DNA transcription using single-molecule methods. J Biol Chem 2021; 297:101086. [PMID: 34403697 PMCID: PMC8441165 DOI: 10.1016/j.jbc.2021.101086] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2021] [Revised: 08/12/2021] [Accepted: 08/13/2021] [Indexed: 11/22/2022] Open
Abstract
Transcriptional regulation is one of the key steps in determining gene expression. Diverse single-molecule techniques have been applied to characterize the stepwise progression of transcription, yielding complementary results. These techniques include, but are not limited to, fluorescence-based microscopy with single or multiple colors, force measuring and manipulating microscopy using magnetic field or light, and atomic force microscopy. Here, we summarize and evaluate these current methodologies in studying and resolving individual steps in the transcription reaction, which encompasses RNA polymerase binding, initiation, elongation, mRNA production, and termination. We also describe the advantages and disadvantages of each method for studying transcription.
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Affiliation(s)
- Chun-Ying Lee
- Department of Biophysics, Johns Hopkins University, Baltimore, Maryland, USA
| | - Sua Myong
- Department of Biophysics, Johns Hopkins University, Baltimore, Maryland, USA; Physics Frontier Center (Center for Physics of Living Cells), University of Illinois, Urbana, Illinois, USA.
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9
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Temperature effects on RNA polymerase initiation kinetics reveal which open complex initiates and that bubble collapse is stepwise. Proc Natl Acad Sci U S A 2021; 118:2021941118. [PMID: 34290140 DOI: 10.1073/pnas.2021941118] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Transcription initiation is highly regulated by promoter sequence, transcription factors, and ligands. All known transcription inhibitors, an important class of antibiotics, act in initiation. To understand regulation and inhibition, the biophysical mechanisms of formation and stabilization of the "open" promoter complex (OC), of synthesis of a short RNA-DNA hybrid upon nucleotide addition, and of escape of RNA polymerase (RNAP) from the promoter must be understood. We previously found that RNAP forms three different OC with λPR promoter DNA. The 37 °C RNAP-λPR OC (RPO) is very stable. At lower temperatures, RPO is less stable and in equilibrium with an intermediate OC (I3). Here, we report step-by-step rapid quench-flow kinetic data for initiation and growth of the RNA-DNA hybrid at 25 and 37 °C that yield rate constants for each step of productive nucleotide addition. Analyzed together, with previously published data at 19 °C, our results reveal that I3 and not RPO is the productive initiation complex at all temperatures. From the strong variations of rate constants and activation energies and entropies for individual steps of hybrid extension, we deduce that contacts of RNAP with the bubble strands are disrupted stepwise as the hybrid grows and translocates. Stepwise disruption of RNAP-strand contacts is accompanied by stepwise bubble collapse, base stacking, and duplex formation, as the hybrid extends to a 9-mer prior to disruption of upstream DNA-RNAP contacts and escape of RNAP from the promoter.
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10
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Kapustina Ž, Jasponė A, Dubovskaja V, Mackevičius G, Lubys A. Enzymatic Synthesis of Chimeric DNA Oligonucleotides by in Vitro Transcription with dTTP, dCTP, dATP, and 2'-Fluoro Modified dGTP. ACS Synth Biol 2021; 10:1625-1632. [PMID: 34110794 DOI: 10.1021/acssynbio.1c00112] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Efficient ways to produce single-stranded DNA are of great interest for diverse applications in molecular biology and nanotechnology. In the present study, we selected T7 RNA polymerase mutants with reduced substrate specificity to employ an in vitro transcription reaction for the synthesis of chimeric DNA oligonucleotides, either individually or in pools. We performed in vitro evolution based on fluorescence-activated droplet sorting and identified mutations V783M, V783L, V689Q, and G555L as novel variants leading to relaxed substrate discrimination. Transcribed chimeric oligonucleotides were tested in PCR, and the quality of amplification products as well as fidelity of oligonucleotide synthesis were assessed by NGS. We concluded that enzymatically produced chimeric DNA transcripts contain significantly fewer deletions and insertions compared to chemically synthesized counterparts and can successfully serve as PCR primers, making the evolved enzymes superior for simple and cheap one-pot synthesis of multiple chimeric DNA oligonucleotides in parallel using a plethora of premixed templates.
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Affiliation(s)
- Žana Kapustina
- UAB Thermo Fisher Scientific Baltics, Research and Development, V. A. Graičiu̅no str. 8, Vilnius 02241, Lithuania
- Institute of Biosciences, Life Sciences Center, Vilnius University, Saulėtekio al. 7, Vilnius 10257, Lithuania
| | - Aistė Jasponė
- UAB Thermo Fisher Scientific Baltics, Research and Development, V. A. Graičiu̅no str. 8, Vilnius 02241, Lithuania
| | - Varvara Dubovskaja
- UAB Thermo Fisher Scientific Baltics, Research and Development, V. A. Graičiu̅no str. 8, Vilnius 02241, Lithuania
| | - Gytis Mackevičius
- UAB Thermo Fisher Scientific Baltics, Research and Development, V. A. Graičiu̅no str. 8, Vilnius 02241, Lithuania
| | - Arvydas Lubys
- UAB Thermo Fisher Scientific Baltics, Research and Development, V. A. Graičiu̅no str. 8, Vilnius 02241, Lithuania
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11
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De Wijngaert B, Sultana S, Singh A, Dharia C, Vanbuel H, Shen J, Vasilchuk D, Martinez SE, Kandiah E, Patel SS, Das K. Cryo-EM Structures Reveal Transcription Initiation Steps by Yeast Mitochondrial RNA Polymerase. Mol Cell 2020; 81:268-280.e5. [PMID: 33278362 DOI: 10.1016/j.molcel.2020.11.016] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2020] [Revised: 11/06/2020] [Accepted: 11/09/2020] [Indexed: 01/18/2023]
Abstract
Mitochondrial RNA polymerase (mtRNAP) is crucial in cellular energy production, yet understanding of mitochondrial DNA transcription initiation lags that of bacterial and nuclear DNA transcription. We report structures of two transcription initiation intermediate states of yeast mtRNAP that explain promoter melting, template alignment, DNA scrunching, abortive synthesis, and transition into elongation. In the partially melted initiation complex (PmIC), transcription factor MTF1 makes base-specific interactions with flipped non-template (NT) nucleotides "AAGT" at -4 to -1 positions of the DNA promoter. In the initiation complex (IC), the template in the expanded 7-mer bubble positions the RNA and NTP analog UTPαS, while NT scrunches into an NT loop. The scrunched NT loop is stabilized by the centrally positioned MTF1 C-tail. The IC and PmIC states coexist in solution, revealing a dynamic equilibrium between two functional states. Frequent scrunching/unscruching transitions and the imminent steric clashes of the inflating NT loop and growing RNA:DNA with the C-tail explain abortive synthesis and transition into elongation.
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Affiliation(s)
- Brent De Wijngaert
- Rega Institute for Medical Research, Department of Microbiology, Immunology and Transplantation, KU Leuven, 3000 Leuven, Belgium
| | - Shemaila Sultana
- Department of Biochemistry and Molecular Biology, Robert Wood Johnson Medical School, Rutgers University, Piscataway, NJ 08854, USA
| | - Anupam Singh
- Department of Biochemistry and Molecular Biology, Robert Wood Johnson Medical School, Rutgers University, Piscataway, NJ 08854, USA
| | - Chhaya Dharia
- Department of Biochemistry and Molecular Biology, Robert Wood Johnson Medical School, Rutgers University, Piscataway, NJ 08854, USA
| | - Hans Vanbuel
- Rega Institute for Medical Research, Department of Microbiology, Immunology and Transplantation, KU Leuven, 3000 Leuven, Belgium
| | - Jiayu Shen
- Department of Biochemistry and Molecular Biology, Robert Wood Johnson Medical School, Rutgers University, Piscataway, NJ 08854, USA
| | - Daniel Vasilchuk
- Department of Biochemistry and Molecular Biology, Robert Wood Johnson Medical School, Rutgers University, Piscataway, NJ 08854, USA
| | - Sergio E Martinez
- Rega Institute for Medical Research, Department of Microbiology, Immunology and Transplantation, KU Leuven, 3000 Leuven, Belgium
| | - Eaazhisai Kandiah
- European Synchrotron Radiation Facility, 71 Avenue des Martyrs, 38043 Grenoble, France
| | - Smita S Patel
- Department of Biochemistry and Molecular Biology, Robert Wood Johnson Medical School, Rutgers University, Piscataway, NJ 08854, USA.
| | - Kalyan Das
- Rega Institute for Medical Research, Department of Microbiology, Immunology and Transplantation, KU Leuven, 3000 Leuven, Belgium.
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12
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Passalacqua LFM, Dingilian AI, Lupták A. Single-pass transcription by T7 RNA polymerase. RNA (NEW YORK, N.Y.) 2020; 26:2062-2071. [PMID: 32958559 PMCID: PMC7668259 DOI: 10.1261/rna.076778.120] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/12/2020] [Accepted: 09/04/2020] [Indexed: 06/11/2023]
Abstract
RNA molecules can be conveniently synthesized in vitro by the T7 RNA polymerase (T7 RNAP). In some experiments, such as cotranscriptional biochemical analyses, continuous synthesis of RNA is not desired. Here, we propose a method for a single-pass transcription that yields a single transcript per template DNA molecule using the T7 RNAP system. We hypothesized that stalling the polymerase downstream from the promoter region and subsequent cleavage of the promoter by a restriction enzyme (to prevent promoter binding by another polymerase) would allow synchronized production of a single transcript per template. The single-pass transcription was verified in two different scenarios: a short self-cleaving ribozyme and a long mRNA. The results show that a controlled single-pass transcription using T7 RNAP allows precise measurement of cotranscriptional ribozyme activity, and this approach will facilitate the study of other kinetic events.
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Affiliation(s)
- Luiz F M Passalacqua
- Department of Pharmaceutical Sciences, University of California, Irvine, California 92697, USA
| | - Armine I Dingilian
- Department of Pharmaceutical Sciences, University of California, Irvine, California 92697, USA
| | - Andrej Lupták
- Department of Pharmaceutical Sciences, University of California, Irvine, California 92697, USA
- Department of Chemistry, University of California, Irvine, California 92697, USA
- Department of Molecular Biology and Biochemistry, University of California, Irvine, California 92697, USA
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13
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Liu Z, Liu H, Vera AM, Bernardi RC, Tinnefeld P, Nash MA. High force catch bond mechanism of bacterial adhesion in the human gut. Nat Commun 2020; 11:4321. [PMID: 32859904 PMCID: PMC7456326 DOI: 10.1038/s41467-020-18063-x] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2020] [Accepted: 08/04/2020] [Indexed: 12/28/2022] Open
Abstract
Bacterial colonization of the human intestine requires firm adhesion of bacteria to insoluble substrates under hydrodynamic flow. Here we report the molecular mechanism behind an ultrastable protein complex responsible for resisting shear forces and adhering bacteria to cellulose fibers in the human gut. Using single-molecule force spectroscopy (SMFS), single-molecule FRET (smFRET), and molecular dynamics (MD) simulations, we resolve two binding modes and three unbinding reaction pathways of a mechanically ultrastable R. champanellensis (Rc) Dockerin:Cohesin (Doc:Coh) complex. The complex assembles in two discrete binding modes with significantly different mechanical properties, with one breaking at ~500 pN and the other at ~200 pN at loading rates from 1-100 nN s-1. A neighboring X-module domain allosterically regulates the binding interaction and inhibits one of the low-force pathways at high loading rates, giving rise to a catch bonding mechanism that manifests under force ramp protocols. Multi-state Monte Carlo simulations show strong agreement with experimental results, validating the proposed kinetic scheme. These results explain mechanistically how gut microbes regulate cell adhesion strength at high shear stress through intricate molecular mechanisms including dual-binding modes, mechanical allostery and catch bonds.
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Affiliation(s)
- Zhaowei Liu
- Institute of Physical Chemistry, Department of Chemistry, University of Basel, 4058, Basel, Switzerland
- Department of Biosystems Science and Engineering, ETH Zurich, 4058, Basel, Switzerland
| | - Haipei Liu
- Institute of Physical Chemistry, Department of Chemistry, University of Basel, 4058, Basel, Switzerland
- Department of Biosystems Science and Engineering, ETH Zurich, 4058, Basel, Switzerland
| | - Andrés M Vera
- Faculty of Chemistry and Center for NanoScience, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Rafael C Bernardi
- NIH Center for Macromolecular Modeling and Bioinformatics, Theoretical and Computational Biophysics Group, Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, 61801, Urbana, IL, USA
- Department of Physics, Auburn University, 36849, Auburn, AL, USA
| | - Philip Tinnefeld
- Faculty of Chemistry and Center for NanoScience, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Michael A Nash
- Institute of Physical Chemistry, Department of Chemistry, University of Basel, 4058, Basel, Switzerland.
- Department of Biosystems Science and Engineering, ETH Zurich, 4058, Basel, Switzerland.
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14
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Sohn BK, Basu U, Lee SW, Cho H, Shen J, Deshpande A, Johnson LC, Das K, Patel SS, Kim H. The dynamic landscape of transcription initiation in yeast mitochondria. Nat Commun 2020; 11:4281. [PMID: 32855416 PMCID: PMC7452894 DOI: 10.1038/s41467-020-17793-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2019] [Accepted: 07/14/2020] [Indexed: 01/24/2023] Open
Abstract
Controlling efficiency and fidelity in the early stage of mitochondrial DNA transcription is crucial for regulating cellular energy metabolism. Conformational transitions of the transcription initiation complex must be central for such control, but how the conformational dynamics progress throughout transcription initiation remains unknown. Here, we use single-molecule fluorescence resonance energy transfer techniques to examine the conformational dynamics of the transcriptional system of yeast mitochondria with single-base resolution. We show that the yeast mitochondrial transcriptional complex dynamically transitions among closed, open, and scrunched states throughout the initiation stage. Then abruptly at position +8, the dynamic states of initiation make a sharp irreversible transition to an unbent conformation with associated promoter release. Remarkably, stalled initiation complexes remain in dynamic scrunching and unscrunching states without dissociating the RNA transcript, implying the existence of backtracking transitions with possible regulatory roles. The dynamic landscape of transcription initiation suggests a kinetically driven regulation of mitochondrial transcription.
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Affiliation(s)
- Byeong-Kwon Sohn
- School of Life Sciences, Ulsan National Institute of Science and Technology, Ulsan, Republic of Korea
| | - Urmimala Basu
- Department of Biochemistry and Molecular Biology, Rutgers University, Robert Wood Johnson Medical School, Piscataway, NJ, 08854, USA
| | - Seung-Won Lee
- School of Life Sciences, Ulsan National Institute of Science and Technology, Ulsan, Republic of Korea
| | - Hayoon Cho
- School of Life Sciences, Ulsan National Institute of Science and Technology, Ulsan, Republic of Korea
| | - Jiayu Shen
- Department of Biochemistry and Molecular Biology, Rutgers University, Robert Wood Johnson Medical School, Piscataway, NJ, 08854, USA
| | - Aishwarya Deshpande
- Department of Biochemistry and Molecular Biology, Rutgers University, Robert Wood Johnson Medical School, Piscataway, NJ, 08854, USA
| | - Laura C Johnson
- Department of Biochemistry and Molecular Biology, Rutgers University, Robert Wood Johnson Medical School, Piscataway, NJ, 08854, USA
| | - Kalyan Das
- Department of Microbiology, Immunology and Transplantation, Rega Institute for Medical Research, KU Leuven, 3000, Leuven, Belgium
| | - Smita S Patel
- Department of Biochemistry and Molecular Biology, Rutgers University, Robert Wood Johnson Medical School, Piscataway, NJ, 08854, USA.
| | - Hajin Kim
- School of Life Sciences, Ulsan National Institute of Science and Technology, Ulsan, Republic of Korea.
- Institute for Basic Science, Ulsan, Republic of Korea.
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15
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R-loop induced G-quadruplex in non-template promotes transcription by successive R-loop formation. Nat Commun 2020; 11:3392. [PMID: 32636376 PMCID: PMC7341879 DOI: 10.1038/s41467-020-17176-7] [Citation(s) in RCA: 40] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2019] [Accepted: 06/17/2020] [Indexed: 01/06/2023] Open
Abstract
G-quadruplex (G4) is a noncanonical secondary structure of DNA or RNA which can enhance or repress gene expression, yet the underlying molecular mechanism remains uncertain. Here we show that when positioned downstream of transcription start site, the orientation of potential G4 forming sequence (PQS), but not the sequence alters transcriptional output. Ensemble in vitro transcription assays indicate that PQS in the non-template increases mRNA production rate and yield. Using sequential single molecule detection stages, we demonstrate that while binding and initiation of T7 RNA polymerase is unchanged, the efficiency of elongation and the final mRNA output is higher when PQS is in the non-template. Strikingly, the enhanced elongation arises from the transcription-induced R-loop formation, which in turn generates G4 structure in the non-template. The G4 stabilized R-loop leads to increased transcription by a mechanism involving successive rounds of R-loop formation. G-quadruplex (G4) forming sequences are highly enriched in the human genome and function as important regulators of diverse range of biological processes. Here the authors show that while G4 structures on template strand block transcription, folding on the non-template strand enhances transcription by means of successive R-loop formation.
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16
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Yang S, Kim S, Kim DK, Jeon An H, Bae Son J, Hedén Gynnå A, Ki Lee N. Transcription and translation contribute to gene locus relocation to the nucleoid periphery in E. coli. Nat Commun 2019; 10:5131. [PMID: 31719538 PMCID: PMC6851099 DOI: 10.1038/s41467-019-13152-y] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2019] [Accepted: 10/21/2019] [Indexed: 11/23/2022] Open
Abstract
Transcription by RNA polymerase (RNAP) is coupled with translation in bacteria. Here, we observe the dynamics of transcription and subcellular localization of a specific gene locus (encoding a non-membrane protein) in living E. coli cells at subdiffraction-limit resolution. The movement of the gene locus to the nucleoid periphery correlates with transcription, driven by either E. coli RNAP or T7 RNAP, and the effect is potentiated by translation. Transcription and translation are coupled in bacteria. Here, the authors show that the movement of a gene locus to the nucleoid periphery correlates with transcription, and the effect is potentiated by translation.
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Affiliation(s)
- Sora Yang
- Department of Chemistry, Seoul National University, Seoul, 08826, Korea
| | - Seunghyeon Kim
- Department of Physics, Pohang University of Science and Technology, Pohang, 37673, Korea
| | - Dong-Kyun Kim
- School of Interdisciplinary Bioscience and Bioengineering, Pohang University of Science and Technology, Pohang, 37673, Korea
| | - Hyeong Jeon An
- Department of Physics, Pohang University of Science and Technology, Pohang, 37673, Korea
| | - Jung Bae Son
- Department of Chemistry, Seoul National University, Seoul, 08826, Korea
| | - Arvid Hedén Gynnå
- Department of Cell and Molecular Biology, Uppsala University, 75236, Uppsala, Sweden
| | - Nam Ki Lee
- Department of Chemistry, Seoul National University, Seoul, 08826, Korea.
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17
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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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18
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Kang J, Park SJ, Kim J, Sung J. Effects of Non‐Poisson Transcription Dynamics on Mean mRNA Number Dynamics in Living Cells. B KOREAN CHEM SOC 2019. [DOI: 10.1002/bkcs.11827] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Jingyu Kang
- Creative Research Initiative Center for Chemical Dynamics in Living CellsChung‐Ang University Seoul 06974 South Korea
- Department of ChemistryChung‐Ang University Seoul 06974 South Korea
| | - Seong Jun Park
- Creative Research Initiative Center for Chemical Dynamics in Living CellsChung‐Ang University Seoul 06974 South Korea
- Department of ChemistryChung‐Ang University Seoul 06974 South Korea
| | - Ji‐Hyun Kim
- Creative Research Initiative Center for Chemical Dynamics in Living CellsChung‐Ang University Seoul 06974 South Korea
| | - Jaeyoung Sung
- Creative Research Initiative Center for Chemical Dynamics in Living CellsChung‐Ang University Seoul 06974 South Korea
- Department of ChemistryChung‐Ang University Seoul 06974 South Korea
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19
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Gholamalipour Y, Karunanayake Mudiyanselage A, Martin CT. 3' end additions by T7 RNA polymerase are RNA self-templated, distributive and diverse in character-RNA-Seq analyses. Nucleic Acids Res 2019; 46:9253-9263. [PMID: 30219859 PMCID: PMC6182178 DOI: 10.1093/nar/gky796] [Citation(s) in RCA: 63] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2018] [Accepted: 08/23/2018] [Indexed: 11/13/2022] Open
Abstract
Synthetic RNA is widely used in basic science, nanotechnology and therapeutics research. The vast majority of this RNA is synthesized in vitro by T7 RNA polymerase or one of its close family members. However, the desired RNA is generally contaminated with products longer and shorter than the DNA-encoded product. To better understand these undesired byproducts and the processes that generate them, we analyze in vitro transcription reactions using RNA-Seq as a tool. The results unambiguously confirm that product RNA rebinds to the polymerase and self-primes (in cis) generation of a hairpin duplex, a process that favorably competes with promoter driven synthesis under high yield reaction conditions. While certain priming modes can be favored, the process is heterogeneous, both in initial priming and in the extent of priming, and already extended products can rebind for further extension, in a distributive process. Furthermore, addition of one or a few nucleotides, previously termed 'nontemplated addition,' also occurs via templated primer extension. At last, this work demonstrates the utility of RNA-Seq as a tool for in vitro mechanistic studies, providing information far beyond that provided by traditional gel electrophoresis.
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Affiliation(s)
- Yasaman Gholamalipour
- Department of Chemistry, University of Massachusetts Amherst, Amherst, MA 01003, USA
| | | | - Craig T Martin
- Department of Chemistry, University of Massachusetts Amherst, Amherst, MA 01003, USA
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20
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Baker MAB. ABA/ASB biophysics and medicine session 2018. Biophys Rev 2019; 11:273-274. [PMID: 31055759 DOI: 10.1007/s12551-019-00529-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2019] [Accepted: 04/24/2019] [Indexed: 01/21/2023] Open
Affiliation(s)
- Matthew A B Baker
- School of Biotechnology and Biomolecular Science, UNSW Sydney, Kensington, Australia.
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21
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Henderson KL, Evensen CE, Molzahn CM, Felth LC, Dyke S, Liao G, Shkel IA, Record MT. RNA Polymerase: Step-by-Step Kinetics and Mechanism of Transcription Initiation. Biochemistry 2019; 58:2339-2352. [PMID: 30950601 DOI: 10.1021/acs.biochem.9b00049] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
To determine the step-by-step kinetics and mechanism of transcription initiation and escape by E. coli RNA polymerase from the λPR promoter, we quantify the accumulation and decay of transient short RNA intermediates on the pathway to promoter escape and full-length (FL) RNA synthesis over a wide range of NTP concentrations by rapid-quench mixing and phosphorimager analysis of gel separations. Experiments are performed at 19 °C, where almost all short RNAs detected are intermediates in FL-RNA synthesis by productive complexes or end-products in nonproductive (stalled) initiation complexes and not from abortive initiation. Analysis of productive-initiation kinetic data yields composite second-order rate constants for all steps of NTP binding and hybrid extension up to the escape point (11-mer). The largest of these rate constants is for incorporation of UTP into the dinucleotide pppApU in a step which does not involve DNA opening or translocation. Subsequent steps, each of which begins with reversible translocation and DNA opening, are slower with rate constants that vary more than 10-fold, interpreted as effects of translocation stress on the translocation equilibrium constant. Rate constants for synthesis of 4- and 5-mer, 7-mer to 9-mer, and 11-mer are particularly small, indicating that RNAP-promoter interactions are disrupted in these steps. These reductions in rate constants are consistent with the previously determined ∼9 kcal cost of escape from λPR. Structural modeling and previous results indicate that the three groups of small rate constants correspond to sequential disruption of in-cleft, -10, and -35 interactions. Parallels to escape by T7 RNAP are discussed.
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Affiliation(s)
- Kate L Henderson
- Department of Biochemistry , University of Wisconsin-Madison , Madison , Wisconsin 53706 , United States
| | - Claire E Evensen
- Department of Biochemistry , University of Wisconsin-Madison , Madison , Wisconsin 53706 , United States
| | - Cristen M Molzahn
- Department of Biochemistry , University of Wisconsin-Madison , Madison , Wisconsin 53706 , United States
| | - Lindsey C Felth
- Department of Biochemistry , University of Wisconsin-Madison , Madison , Wisconsin 53706 , United States
| | - Sarah Dyke
- Department of Biochemistry , University of Wisconsin-Madison , Madison , Wisconsin 53706 , United States
| | - Guanyu Liao
- Department of Biochemistry , University of Wisconsin-Madison , Madison , Wisconsin 53706 , United States
| | - Irina A Shkel
- Department of Biochemistry , University of Wisconsin-Madison , Madison , Wisconsin 53706 , United States.,Department of Chemistry , University of Wisconsin-Madison , Madison , Wisconsin 53706 , United States
| | - M Thomas Record
- Department of Biochemistry , University of Wisconsin-Madison , Madison , Wisconsin 53706 , United States.,Department of Chemistry , University of Wisconsin-Madison , Madison , Wisconsin 53706 , United States
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