1
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Wang F, Holmes MJ, Hong HJ, Thaprawat P, Kannan G, Huynh MH, Schultz TL, Licon MH, Lourido S, Dong W, Brito Querido J, Sullivan WJ, O'Leary SE, Carruthers VB. Translation initiation factor eIF1.2 promotes Toxoplasma stage conversion by regulating levels of key differentiation factors. Nat Commun 2024; 15:4385. [PMID: 38782906 PMCID: PMC11116398 DOI: 10.1038/s41467-024-48685-4] [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: 11/16/2023] [Accepted: 05/07/2024] [Indexed: 05/25/2024] Open
Abstract
The parasite Toxoplasma gondii persists in its hosts by converting from replicating tachyzoites to latent bradyzoites housed in tissue cysts. The molecular mechanisms that mediate T. gondii differentiation remain poorly understood. Through a mutagenesis screen, we identified translation initiation factor eIF1.2 as a critical factor for T. gondii differentiation. A F97L mutation in eIF1.2 or the genetic ablation of eIF1.2 (∆eif1.2) markedly impeded bradyzoite cyst formation in vitro and in vivo. We demonstrated, at single-molecule level, that the eIF1.2 F97L mutation impacts the scanning process of the ribosome preinitiation complex on a model mRNA. RNA sequencing and ribosome profiling experiments unveiled that ∆eif1.2 parasites are defective in upregulating bradyzoite induction factors BFD1 and BFD2 during stress-induced differentiation. Forced expression of BFD1 or BFD2 significantly restored differentiation in ∆eif1.2 parasites. Together, our findings suggest that eIF1.2 functions by regulating the translation of key differentiation factors necessary to establish chronic toxoplasmosis.
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Affiliation(s)
- Fengrong Wang
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI, 48109, USA
| | - Michael J Holmes
- Department of Pharmacology & Toxicology, Indiana University School of Medicine, Indianapolis, IN, 46202, USA
| | - Hea Jin Hong
- Department of Biochemistry, University of California Riverside, Riverside, CA, 92521, USA
| | - Pariyamon Thaprawat
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI, 48109, USA
- Medical Scientist Training Program, University of Michigan Medical School, Ann Arbor, MI, 48109, USA
| | - Geetha Kannan
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI, 48109, USA
| | - My-Hang Huynh
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI, 48109, USA
| | - Tracey L Schultz
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI, 48109, USA
| | | | - Sebastian Lourido
- Whitehead Institute, Cambridge, MA, 02142, USA
- Biology Department, Massachusetts Institute of Technology, Cambridge, MA, 02142, USA
| | - Wenzhao Dong
- Department of Biological Chemistry, University of Michigan, Ann Arbor, MI, 48109, USA
- Life Sciences Institute, University of Michigan, Ann Arbor, MI, 48109, USA
- Center for RNA Biomedicine, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Jailson Brito Querido
- Department of Biological Chemistry, University of Michigan, Ann Arbor, MI, 48109, USA
- Life Sciences Institute, University of Michigan, Ann Arbor, MI, 48109, USA
- Center for RNA Biomedicine, University of Michigan, Ann Arbor, MI, 48109, USA
| | - William J Sullivan
- Department of Pharmacology & Toxicology, Indiana University School of Medicine, Indianapolis, IN, 46202, USA
- Department of Microbiology & Immunology, Indiana University School of Medicine, Indianapolis, IN, 46202, USA
| | - Seán E O'Leary
- Department of Biochemistry, University of California Riverside, Riverside, CA, 92521, USA
- Center for RNA Biology and Medicine, University of California Riverside, Riverside, CA, 92521, USA
| | - Vern B Carruthers
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI, 48109, USA.
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2
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Wang F, Holmes MJ, Hong HJ, Thaprawat P, Kannan G, Huynh MH, Schultz TL, Licon MH, Lourido S, Dong W, Querido JB, Sullivan WJ, O'Leary SE, Carruthers VB. Translation initiation factor eIF1.2 promotes Toxoplasma stage conversion by regulating levels of key differentiation factors. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.11.03.565545. [PMID: 37961607 PMCID: PMC10635126 DOI: 10.1101/2023.11.03.565545] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2023]
Abstract
The parasite Toxoplasma gondii persists in its hosts by converting from replicating tachyzoites to latent bradyzoites housed in tissue cysts. The molecular mechanisms that mediate T. gondii differentiation remain poorly understood. Through a mutagenesis screen, we identified translation initiation factor eIF1.2 as a critical factor for T. gondii differentiation. A F97L mutation in eIF1.2 or the genetic ablation of eIF1.2 (Δ eif1.2 ) markedly impeded bradyzoite cyst formation in vitro and in vivo . We demonstrated, at single-molecule level, that the eIF1.2 F97L mutation impacts the scanning process of the ribosome preinitiation complex on a model mRNA. RNA sequencing and ribosome profiling experiments unveiled that Δ eif1.2 parasites are defective in upregulating bradyzoite induction factors BFD1 and BFD2 during stress-induced differentiation. Forced expression of BFD1 or BFD2 significantly restored differentiation in Δ eif1.2 parasites. Together, our findings suggest that eIF1.2 functions by regulating the translation of key differentiation factors necessary to establish chronic toxoplasmosis.
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3
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Sengar A, Cervantes M, Bondalapati ST, Hess T, Kasson PM. Single-Virus Fusion Measurements Reveal Multiple Mechanistically Equivalent Pathways for SARS-CoV-2 Entry. J Virol 2023; 97:e0199222. [PMID: 37133381 DOI: 10.1128/jvi.01992-22] [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: 05/04/2023] Open
Abstract
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) binds to cell surface receptors and is activated for membrane fusion and cell entry via proteolytic cleavage. Phenomenological data have shown that SARS-CoV-2 can be activated for entry at either the cell surface or in endosomes, but the relative roles in different cell types and mechanisms of entry have been debated. Here, we used single-virus fusion experiments and exogenously controlled proteases to probe activation directly. We found that plasma membrane and an appropriate protease are sufficient to support SARS-CoV-2 pseudovirus fusion. Furthermore, fusion kinetics of SARS-CoV-2 pseudoviruses are indistinguishable no matter which of a broad range of proteases is used to activate the virus. This suggests that the fusion mechanism is insensitive to protease identity or even whether activation occurs before or after receptor binding. These data support a model for opportunistic fusion by SARS-CoV-2 in which the subcellular location of entry likely depends on the differential activity of airway, cellsurface, and endosomal proteases, but all support infection. Inhibition of any single host protease may thus reduce infection in some cells but may be less clinically robust. IMPORTANCE SARS-CoV-2 can use multiple pathways to infect cells, as demonstrated recently when new viral variants switched dominant infection pathways. Here, we used single-virus fusion experiments together with biochemical reconstitution to show that these multiple pathways coexist simultaneously and specifically that the virus can be activated by different proteases in different cellular compartments with mechanistically identical effects. The consequences of this are that the virus is evolutionarily plastic and that therapies targeting viral entry should address multiple pathways at once to achieve optimal clinical effects.
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Affiliation(s)
- Anjali Sengar
- Department of Molecular Physiology, Global Infectious Diseases Institute, University of Virginia, Charlottesville, Virginia, USA
- Department of Biomedical Engineering, Global Infectious Diseases Institute, University of Virginia, Charlottesville, Virginia, USA
| | - Marcos Cervantes
- Department of Molecular Physiology, Global Infectious Diseases Institute, University of Virginia, Charlottesville, Virginia, USA
- Department of Biomedical Engineering, Global Infectious Diseases Institute, University of Virginia, Charlottesville, Virginia, USA
| | - Sai T Bondalapati
- Department of Molecular Physiology, Global Infectious Diseases Institute, University of Virginia, Charlottesville, Virginia, USA
- Department of Biomedical Engineering, Global Infectious Diseases Institute, University of Virginia, Charlottesville, Virginia, USA
| | - Tobin Hess
- Department of Molecular Physiology, Global Infectious Diseases Institute, University of Virginia, Charlottesville, Virginia, USA
- Department of Biomedical Engineering, Global Infectious Diseases Institute, University of Virginia, Charlottesville, Virginia, USA
| | - Peter M Kasson
- Department of Molecular Physiology, Global Infectious Diseases Institute, University of Virginia, Charlottesville, Virginia, USA
- Department of Biomedical Engineering, Global Infectious Diseases Institute, University of Virginia, Charlottesville, Virginia, USA
- Department of Cell and Molecular Biology, Uppsala University, Uppsala, Sweden
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4
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Luo S, Zhang Z, Wang Z, Yang X, Chen X, Zhou T, Zhang J. Inferring transcriptional bursting kinetics from single-cell snapshot data using a generalized telegraph model. ROYAL SOCIETY OPEN SCIENCE 2023; 10:221057. [PMID: 37035293 PMCID: PMC10073913 DOI: 10.1098/rsos.221057] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/15/2022] [Accepted: 03/13/2023] [Indexed: 06/19/2023]
Abstract
Gene expression has inherent stochasticity resulting from transcription's burst manners. Single-cell snapshot data can be exploited to rigorously infer transcriptional burst kinetics, using mathematical models as blueprints. The classical telegraph model (CTM) has been widely used to explain transcriptional bursting with Markovian assumptions. However, growing evidence suggests that the gene-state dwell times are generally non-exponential, as gene-state switching is a multi-step process in organisms. Therefore, interpretable non-Markovian mathematical models and efficient statistical inference methods are urgently required in investigating transcriptional burst kinetics. We develop an interpretable and tractable model, the generalized telegraph model (GTM), to characterize transcriptional bursting that allows arbitrary dwell-time distributions, rather than exponential distributions, to be incorporated into the ON and OFF switching process. Based on the GTM, we propose an inference method for transcriptional bursting kinetics using an approximate Bayesian computation framework. This method demonstrates an efficient and scalable estimation of burst frequency and burst size on synthetic data. Further, the application of inference to genome-wide data from mouse embryonic fibroblasts reveals that GTM would estimate lower burst frequency and higher burst size than those estimated by CTM. In conclusion, the GTM and the corresponding inference method are effective tools to infer dynamic transcriptional bursting from static single-cell snapshot data.
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Affiliation(s)
- Songhao Luo
- Guangdong Province Key Laboratory of Computational Science, Sun Yat-sen University, Guangzhou, Guangdong Province 510275, People's Republic of China
- School of Mathematics, Sun Yat-sen University, Guangzhou, Guangdong Province 510275, People's Republic of China
| | - Zhenquan Zhang
- Guangdong Province Key Laboratory of Computational Science, Sun Yat-sen University, Guangzhou, Guangdong Province 510275, People's Republic of China
- School of Mathematics, Sun Yat-sen University, Guangzhou, Guangdong Province 510275, People's Republic of China
| | - Zihao Wang
- Guangdong Province Key Laboratory of Computational Science, Sun Yat-sen University, Guangzhou, Guangdong Province 510275, People's Republic of China
- School of Mathematics, Sun Yat-sen University, Guangzhou, Guangdong Province 510275, People's Republic of China
| | - Xiyan Yang
- School of Financial Mathematics and Statistics, Guangdong University of Finance, Guangzhou 510521, People's Republic of China
| | - Xiaoxuan Chen
- Guangdong Province Key Laboratory of Computational Science, Sun Yat-sen University, Guangzhou, Guangdong Province 510275, People's Republic of China
- School of Mathematics, Sun Yat-sen University, Guangzhou, Guangdong Province 510275, People's Republic of China
| | - Tianshou Zhou
- Guangdong Province Key Laboratory of Computational Science, Sun Yat-sen University, Guangzhou, Guangdong Province 510275, People's Republic of China
- School of Mathematics, Sun Yat-sen University, Guangzhou, Guangdong Province 510275, People's Republic of China
| | - Jiajun Zhang
- Guangdong Province Key Laboratory of Computational Science, Sun Yat-sen University, Guangzhou, Guangdong Province 510275, People's Republic of China
- School of Mathematics, Sun Yat-sen University, Guangzhou, Guangdong Province 510275, People's Republic of China
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5
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Singh D, Punia B, Chaudhury S. Theoretical Tools to Quantify Stochastic Fluctuations in Single-Molecule Catalysis by Enzymes and Nanoparticles. ACS OMEGA 2022; 7:47587-47600. [PMID: 36591158 PMCID: PMC9798497 DOI: 10.1021/acsomega.2c06316] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2022] [Accepted: 12/02/2022] [Indexed: 06/11/2023]
Abstract
Single-molecule microscopic techniques allow the counting of successive turnover events and the study of the time-dependent fluctuations of the catalytic activities of individual enzymes and different sites on a single heterogeneous nanocatalyst. It is important to establish theoretical methods to obtain the statistical measurements of such stochastic fluctuations that provide insight into the catalytic mechanism. In this review, we discuss a few theoretical frameworks for evaluating the first passage time distribution functions using a self-consistent pathway approach and chemical master equations, to establish a connection with experimental observables. The measurable probability distribution functions and their moments depend on the molecular details of the reaction and provide a way to quantify the molecular mechanisms of the reaction process. The statistical measurements of these fluctuations should provide insight into the enzymatic mechanism.
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Affiliation(s)
- Divya Singh
- School
of Chemistry, Tel Aviv University, Tel Aviv6997801, Israel
| | - Bhawakshi Punia
- Department
of Chemistry, Indian Institute of Science
Education and Research, Dr. Homi Bhabha Road, Pune411008, Maharashtra, India
| | - Srabanti Chaudhury
- Department
of Chemistry, Indian Institute of Science
Education and Research, Dr. Homi Bhabha Road, Pune411008, Maharashtra, India
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6
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Mannsverk S, Villamil Giraldo AM, Kasson PM. Influenza Virus Membrane Fusion Is Promoted by the Endosome-Resident Phospholipid Bis(monoacylglycero)phosphate. J Phys Chem B 2022; 126:10445-10451. [PMID: 36468619 PMCID: PMC9761668 DOI: 10.1021/acs.jpcb.2c06642] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The phospholipid bis(monoacylglycero)phosphate (BMP) is enriched in late endosomal and endolysosomal membranes and is believed to be involved in membrane deformation and generation of intralumenal vesicles within late endosomes. Previous studies have demonstrated that BMP promotes membrane fusion of several enveloped viruses, but a limited effect has been found on influenza virus. Here, we report the use of single-virus fusion assays to dissect BMP's effect on influenza virus fusion in greater depth. In agreement with prior reports, we found that hemifusion kinetics and efficiency were unaffected by the addition of 10-20 mol % BMP to the target membrane. However, using an assay for fusion pore formation and genome exposure, we found full fusion efficiency to be substantially enhanced by the addition of 10-20 mol % BMP to the target membrane, while the kinetics remained unaffected. By comparing BMP to other negatively charged phospholipids, we found the effect on fusion efficiency mainly attributable to headgroup charge, although we also hypothesize a role for BMP's unusual chemical structure. Our results suggest that BMP function as a permissive factor for a wider range of viruses than previously reported. We hypothesize that BMP may be a general cofactor for endosomal entry of enveloped viruses.
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Affiliation(s)
- Steinar Mannsverk
- Science
for Life Laboratory, Department of Cell and Molecular Biology, Uppsala University, Uppsala 75124, Sweden
| | - Ana M. Villamil Giraldo
- Science
for Life Laboratory, Department of Cell and Molecular Biology, Uppsala University, Uppsala 75124, Sweden
| | - Peter M. Kasson
- Science
for Life Laboratory, Department of Cell and Molecular Biology, Uppsala University, Uppsala 75124, Sweden,Departments
of Molecular Physiology and Biomedical Engineering, University of Virginia, Charlottesville, Virginia 22908, United States,
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7
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Zhong Y, Moghaddas Sani H, Paudel BP, Low JKK, Silva APG, Mueller S, Deshpande C, Panjikar S, Reid XJ, Bedward MJ, van Oijen AM, Mackay JP. The role of auxiliary domains in modulating CHD4 activity suggests mechanistic commonality between enzyme families. Nat Commun 2022; 13:7524. [PMID: 36473839 PMCID: PMC9726900 DOI: 10.1038/s41467-022-35002-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2022] [Accepted: 11/14/2022] [Indexed: 12/12/2022] Open
Abstract
CHD4 is an essential, widely conserved ATP-dependent translocase that is also a broad tumour dependency. In common with other SF2-family chromatin remodelling enzymes, it alters chromatin accessibility by repositioning histone octamers. Besides the helicase and adjacent tandem chromodomains and PHD domains, CHD4 features 1000 residues of N- and C-terminal sequence with unknown structure and function. We demonstrate that these regions regulate CHD4 activity through different mechanisms. An N-terminal intrinsically disordered region (IDR) promotes remodelling integrity in a manner that depends on the composition but not sequence of the IDR. The C-terminal region harbours an auto-inhibitory region that contacts the helicase domain. Auto-inhibition is relieved by a previously unrecognized C-terminal SANT-SLIDE domain split by ~150 residues of disordered sequence, most likely by binding of this domain to substrate DNA. Our data shed light on CHD4 regulation and reveal strong mechanistic commonality between CHD family members, as well as with ISWI-family remodellers.
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Affiliation(s)
- Yichen Zhong
- grid.1013.30000 0004 1936 834XSchool of Life and Environmental Sciences, University of Sydney, The University of Sydney, NSW 2006 Australia
| | - Hakimeh Moghaddas Sani
- grid.1013.30000 0004 1936 834XSchool of Life and Environmental Sciences, University of Sydney, The University of Sydney, NSW 2006 Australia
| | - Bishnu P. Paudel
- grid.1007.60000 0004 0486 528XMolecular Horizons, School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, NSW 2522 Australia ,grid.510958.0Illawarra Health and Medical Research Institute, Wollongong, NSW 2522 Australia
| | - Jason K. K. Low
- grid.1013.30000 0004 1936 834XSchool of Life and Environmental Sciences, University of Sydney, The University of Sydney, NSW 2006 Australia
| | - Ana P. G. Silva
- grid.1013.30000 0004 1936 834XSchool of Life and Environmental Sciences, University of Sydney, The University of Sydney, NSW 2006 Australia
| | - Stefan Mueller
- grid.1007.60000 0004 0486 528XMolecular Horizons, School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, NSW 2522 Australia ,grid.510958.0Illawarra Health and Medical Research Institute, Wollongong, NSW 2522 Australia
| | - Chandrika Deshpande
- grid.1013.30000 0004 1936 834XSchool of Life and Environmental Sciences, University of Sydney, The University of Sydney, NSW 2006 Australia
| | - Santosh Panjikar
- grid.248753.f0000 0004 0562 0567Australian Synchrotron, Clayton, VIC 3168 Australia ,grid.1002.30000 0004 1936 7857Department of Molecular Biology and Biochemistry, Monash University, Clayton, VIC 3800 Australia
| | - Xavier J. Reid
- grid.1013.30000 0004 1936 834XSchool of Life and Environmental Sciences, University of Sydney, The University of Sydney, NSW 2006 Australia
| | - Max J. Bedward
- grid.1013.30000 0004 1936 834XSchool of Life and Environmental Sciences, University of Sydney, The University of Sydney, NSW 2006 Australia
| | - Antoine M. van Oijen
- grid.1007.60000 0004 0486 528XMolecular Horizons, School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, NSW 2522 Australia ,grid.510958.0Illawarra Health and Medical Research Institute, Wollongong, NSW 2522 Australia
| | - Joel P. Mackay
- grid.1013.30000 0004 1936 834XSchool of Life and Environmental Sciences, University of Sydney, The University of Sydney, NSW 2006 Australia
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8
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Villamil Giraldo AM, Mannsverk S, Kasson PM. Measuring single-virus fusion kinetics using an assay for nucleic acid exposure. Biophys J 2022; 121:4467-4475. [PMID: 36330566 PMCID: PMC9748363 DOI: 10.1016/j.bpj.2022.11.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2022] [Revised: 09/26/2022] [Accepted: 10/31/2022] [Indexed: 11/11/2022] Open
Abstract
The kinetics by which individual enveloped viruses fuse with membranes provide an important window into viral-entry mechanisms. We have developed a real-time assay using fluorescent probes for single-virus genome exposure than can report on stages of viral entry including or subsequent to fusion pore formation and prior to viral genome trafficking. We accomplish this using oxazole yellow nucleic-acid-binding dyes, which can be encapsulated in the lumen of target membranes to permit specific detection of fusion events. Since increased fluorescence of the dye occurs only when it encounters viral genome via a fusion pore and binds, this assay excludes content leakage without fusion. Using this assay, we show that influenza virus fuses with liposomes of different sizes with indistinguishable kinetics by both testing liposomes extruded through pores of different radii and showing that the fusion kinetics of individual liposomes are uncorrelated with the size of the liposome. These results suggest that the starting curvature of such liposomes does not control the rate-limiting steps in influenza entry.
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Affiliation(s)
- Ana M Villamil Giraldo
- Science for Life Laboratory, Department of Cell and Molecular Biology, Uppsala University, Uppsala, Sweden
| | - Steinar Mannsverk
- Science for Life Laboratory, Department of Cell and Molecular Biology, Uppsala University, Uppsala, Sweden
| | - Peter M Kasson
- Science for Life Laboratory, Department of Cell and Molecular Biology, Uppsala University, Uppsala, Sweden; Departments of Molecular Physiology and Biomedical Engineering, University of Virginia, Charlottesville, Virginia.
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9
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Fu X, Kaur H, Rodgers ML, Montemayor EJ, Butcher SE, Hoskins AA. Identification of transient intermediates during spliceosome activation by single molecule fluorescence microscopy. Proc Natl Acad Sci U S A 2022; 119:e2206815119. [PMID: 36417433 PMCID: PMC9860250 DOI: 10.1073/pnas.2206815119] [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: 04/23/2022] [Accepted: 10/05/2022] [Indexed: 11/24/2022] Open
Abstract
Spliceosome activation is the process of creating the catalytic site for RNA splicing and occurs de novo on each intron following spliceosome assembly. Dozens of factors bind to or are released from the activating spliceosome including the Lsm2-8 heteroheptameric ring that binds the U6 small nuclear RNA 3'-end. Lsm2-8 must be released to permit active site stabilization by the Prp19-containing complex (NineTeen Complex, NTC); however, little is known about the temporal order of events and dynamic interactions that lead up to and follow Lsm2-8 release. We have used colocalization single molecule spectroscopy (CoSMoS) to visualize Lsm2-8 dynamics during activation of Saccharomyces cerevisiae spliceosomes in vitro. Lsm2-8 is recruited as a component of the tri-snRNP and is released after integration of the Prp19-containing complex (NTC). Despite Lsm2-8 and the NTC being mutually exclusive in existing cryo-EM structures of yeast B complex spliceosomes, we identify a transient intermediate containing both ([Formula: see text]) and provide a kinetic framework for its formation and transformation during activation. Prior to [Formula: see text] assembly, the NTC rapidly and reversibly samples the spliceosome suggesting a mechanism for preventing NTC sequestration by defective spliceosomes that fail to properly activate. In complementary ensemble assays, we show that a base-pairing-dependent ternary complex can form between Lsm2-8 and U2 and U6 helix II RNAs. We propose that this interaction may play a role in formation of transient spliceosome intermediates formed during activation.
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Affiliation(s)
- Xingyang Fu
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI53706
| | - Harpreet Kaur
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI53706
| | - Margaret L. Rodgers
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI53706
| | - Eric J. Montemayor
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI53706
| | - Samuel E. Butcher
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI53706
| | - Aaron A. Hoskins
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI53706
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI53706
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10
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Mueller SH, Fitschen LJ, Shirbini A, Hamdan SM, Spenkelink L, van Oijen A. Rapid single-molecule characterisation of enzymes involved in nucleic-acid metabolism. Nucleic Acids Res 2022; 51:e5. [PMID: 36321650 PMCID: PMC9841422 DOI: 10.1093/nar/gkac949] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2022] [Revised: 09/12/2022] [Accepted: 10/12/2022] [Indexed: 11/07/2022] Open
Abstract
The activity of enzymes is traditionally characterised through bulk-phase biochemical methods that only report on population averages. Single-molecule methods are advantageous in elucidating kinetic and population heterogeneity but are often complicated, time consuming, and lack statistical power. We present a highly-generalisable and high-throughput single-molecule assay to rapidly characterise proteins involved in DNA metabolism. The assay exclusively relies on changes in total fluorescence intensity of surface-immobilised DNA templates as a result of DNA synthesis, unwinding or digestion. Combined with an automated data-analysis pipeline, our method provides enzymatic activity data of thousands of molecules in less than an hour. We demonstrate our method by characterising three fundamentally different enzyme activities: digestion by the phage λ exonuclease, synthesis by the phage Phi29 polymerase, and unwinding by the E. coli UvrD helicase. We observe the previously unknown activity of the UvrD helicase to remove neutravidin bound to 5'-, but not 3'-ends of biotinylated DNA.
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Affiliation(s)
- Stefan H Mueller
- Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, New South Wales 2522, Australia,Illawarra Health & Medical Research Institute, Wollongong, New South Wales 2522, Australia
| | - Lucy J Fitschen
- Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, New South Wales 2522, Australia,Illawarra Health & Medical Research Institute, Wollongong, New South Wales 2522, Australia
| | - Afnan Shirbini
- Biological and Environmental Science and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Kingdom of Saudi Arabia
| | - Samir M Hamdan
- Biological and Environmental Science and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Kingdom of Saudi Arabia
| | - Lisanne M Spenkelink
- Correspondence may also be addressed to Lisanne M. Spenkelink. Tel: +61 2 4239 2371;
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11
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Single-molecule investigations of single-chain cellulose biosynthesis. Proc Natl Acad Sci U S A 2022; 119:e2122770119. [PMID: 36161928 PMCID: PMC9546554 DOI: 10.1073/pnas.2122770119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Cellulose biosynthesis in sessile bacterial colonies originates in the membrane-integrated bacterial cellulose synthase (Bcs) AB complex. We utilize optical tweezers to measure single-strand cellulose biosynthesis by BcsAB from Rhodobacter sphaeroides. Synthesis depends on uridine diphosphate glucose, Mg2+, and cyclic diguanosine monophosphate, with the last displaying a retention time of ∼80 min. Below a stall force of 12.7 pN, biosynthesis is relatively insensitive to force and proceeds at a rate of one glucose addition every 2.5 s at room temperature, increasing to two additions per second at 37°. At low forces, conformational hopping is observed. Single-strand cellulose stretching unveiled a persistence length of 6.2 nm, an axial stiffness of 40.7 pN, and an ability for complexes to maintain a tight grip, with forces nearing 100 pN. Stretching experiments exhibited hysteresis, suggesting that cellulose microstructure underpinning robust biofilms begins to form during synthesis. Cellohexaose spontaneously binds to nascent single cellulose strands, impacting polymer mechanical properties and increasing BcsAB activity.
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12
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Turvey MW, Gabriel KN, Lee W, Taulbee JJ, Kim JK, Chen S, Lau CJ, Kattan RE, Pham JT, Majumdar S, Garcia D, Weiss GA, Collins PG. Single-molecule Taq DNA polymerase dynamics. SCIENCE ADVANCES 2022; 8:eabl3522. [PMID: 35275726 PMCID: PMC8916733 DOI: 10.1126/sciadv.abl3522] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/08/2021] [Accepted: 01/21/2022] [Indexed: 06/14/2023]
Abstract
Taq DNA polymerase functions at elevated temperatures with fast conformational dynamics-regimes previously inaccessible to mechanistic, single-molecule studies. Here, single-walled carbon nanotube transistors recorded the motions of Taq molecules processing matched or mismatched template-deoxynucleotide triphosphate pairs from 22° to 85°C. By using four enzyme orientations, the whole-enzyme closures of nucleotide incorporations were distinguished from more rapid, 20-μs closures of Taq's fingers domain testing complementarity and orientation. On average, one transient closure was observed for every nucleotide binding event; even complementary substrate pairs averaged five transient closures between each catalytic incorporation at 72°C. The rate and duration of the transient closures and the catalytic events had almost no temperature dependence, leaving all of Taq's temperature sensitivity to its rate-determining open state.
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Affiliation(s)
- Mackenzie W. Turvey
- Department of Physics and Astronomy, University of California, Irvine, Irvine, CA 92697-4575, USA
| | - Kristin N. Gabriel
- Department of Molecular Biology and Biochemistry, University of California, Irvine, Irvine, CA 92697-3900, USA
| | - Wonbae Lee
- Department of Physics and Astronomy, University of California, Irvine, Irvine, CA 92697-4575, USA
| | - Jeffrey J. Taulbee
- Department of Physics and Astronomy, University of California, Irvine, Irvine, CA 92697-4575, USA
| | - Joshua K. Kim
- Department of Chemistry, University of California, Irvine, Irvine, CA 92697-2025, USA
| | - Silu Chen
- Department of Chemistry, University of California, Irvine, Irvine, CA 92697-2025, USA
| | - Calvin J. Lau
- Department of Physics and Astronomy, University of California, Irvine, Irvine, CA 92697-4575, USA
| | - Rebecca E. Kattan
- Department of Molecular Biology and Biochemistry, University of California, Irvine, Irvine, CA 92697-3900, USA
| | - Jenifer T. Pham
- Department of Chemistry, University of California, Irvine, Irvine, CA 92697-2025, USA
| | - Sudipta Majumdar
- Department of Chemistry, University of California, Irvine, Irvine, CA 92697-2025, USA
| | | | - Gregory A. Weiss
- Department of Molecular Biology and Biochemistry, University of California, Irvine, Irvine, CA 92697-3900, USA
- Department of Chemistry, University of California, Irvine, Irvine, CA 92697-2025, USA
- Department of Pharmaceutical Sciences, University of California, Irvine, Irvine, CA 92697-3958, USA
| | - Philip G. Collins
- Department of Physics and Astronomy, University of California, Irvine, Irvine, CA 92697-4575, USA
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13
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Mallimadugula UL, Galburt EA. Parallel path mechanisms lead to nonmonotonic force-velocity curves and an optimum load for molecular motor function. Phys Rev E 2022; 105:034405. [PMID: 35428051 DOI: 10.1103/physreve.105.034405] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2021] [Accepted: 02/15/2022] [Indexed: 06/14/2023]
Abstract
Molecular motors convert chemical potential energy into mechanical work and perform a great number of critical biological functions. Examples include the polymerization and manipulation of nucleic acids, the generation of cellular motility and contractility, the formation and maintenance of cell shape, and the transport of materials within cells. The mechanisms underlying these molecular machines are varied, but are almost always considered in the context of a single kinetic pathway that describes motor stepping. However, the multidimensional nature of protein energy landscapes suggests the possibility of multiple reaction pathways connecting two states. Here we investigate the properties of a hypothetical molecular motor able to utilize parallel translocation mechanisms. We explore motor velocity and force dependence as a function of the energy landscape of each path and reveal the potential for such a mechanism to result in negative differential conductance. More specifically, regimes exist where increasing opposing force leads to increased velocity and an optimum load for motor function. We explore how the presence of this optimum depends on the rates of the individual paths and show that the distribution of stepping times characterized by the randomness parameter may be used to test for parallel path mechanisms. Last, we caution that experimental data consisting solely of measurements of velocity as a function of ATP concentration and force cannot be used to eliminate the possibility of such a parallel path mechanism.
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Affiliation(s)
- Upasana L Mallimadugula
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, Saint Louis, Missouri 63108, USA
| | - Eric A Galburt
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, Saint Louis, Missouri 63108, USA
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14
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Sielaff H, Dienerowitz F, Dienerowitz M. Single-molecule FRET combined with electrokinetic trapping reveals real-time enzyme kinetics of individual F-ATP synthases. NANOSCALE 2022; 14:2327-2336. [PMID: 35084006 DOI: 10.1039/d1nr05754e] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Single-molecule Förster resonance energy transfer (smFRET) is a key technique to observe conformational changes in molecular motors and to access the details of single-molecule static and dynamic disorder during catalytic processes. However, studying freely diffusing molecules in solution is limited to a few tens of milliseconds, while surface attachment often bears the risk to restrict their natural motion. In this paper we combine smFRET and electrokinetic trapping (ABEL trap) to non-invasively hold single FOF1-ATP synthases for up to 3 s within the detection volume, thereby extending the observation time by a factor of 10 as compared to Brownian diffusion without surface attachment. In addition, we are able to monitor complete reaction cycles and to selectively trap active molecules based on their smFRET signal, thus speeding up the data acquisition process. We demonstrate the capability of our method to study the dynamics of single molecules by recording the ATP-hydrolysis driven rotation of individual FOF1-ATP synthase molecules over numerous reaction cycles and extract their kinetic rates. We argue that our method is not limited to motor proteins. Instead, it can be applied to monitor conformational changes with millisecond time resolution for a wide range of enzymes, thereby making it a versatile tool for studying protein dynamics.
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Affiliation(s)
- Hendrik Sielaff
- Department of Chemistry, Centre for BioImaging Sciences, National University of Singapore, 14 Science Drive 4, 117557 Singapore, Singapore
| | - Frank Dienerowitz
- Ernst-Abbe-Hochschule Jena, University of Applied Sciences, Carl-Zeiss-Promenade 2, 07745 Jena, Germany
| | - Maria Dienerowitz
- Single-Molecule Microscopy Group, Universitätsklinikum Jena, Nonnenplan 2-4, 07743 Jena, Germany.
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15
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Dietz J, Oelkers M, Hubrich R, Pérez-Lara A, Jahn R, Steinem C, Janshoff A. Forces, Kinetics, and Fusion Efficiency Altered by the Full-Length Synaptotagmin-1 -PI(4,5)P 2 Interaction in Constrained Geometries. NANO LETTERS 2022; 22:1449-1455. [PMID: 34855407 DOI: 10.1021/acs.nanolett.1c02491] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
A mechanism for full-length synaptotagmin-1 (syt-1) to interact with anionic bilayers and to promote fusion in the presence of SNAREs is proposed. Colloidal probe force spectroscopy in conjunction with tethered particle motion monitoring showed that in the absence of Ca2+ the binding of syt-1 to membranes depends on the presence and content of PI(4,5)P2. Addition of Ca2+ switches the interaction forces from weak to strong, eventually exceeding the cohesion of the C2A domain of syt-1 leading to partial unfolding of the protein. Fusion of single unilamellar vesicles equipped with syt-1 and synaptobrevin 2 with planar pore-spanning target membranes containing PS and PI(4,5)P2 shows an almost complete suppression of stalled intermediate fusion states and an accelerated fusion kinetics in the presence of Ca2+, which is further enhanced upon addition of ATP.
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Affiliation(s)
- Joern Dietz
- Institute for Physical Chemistry, Georg-August Universität, Tammannstr. 6, 37077 Göttingen, Germany
| | - Marieelen Oelkers
- Institute for Physical Chemistry, Georg-August Universität, Tammannstr. 6, 37077 Göttingen, Germany
| | - Raphael Hubrich
- Institute for Organic and Biomolecular Chemistry, Georg-August Universität, Tammannstr. 2, 37077 Göttingen, Germany
| | - Angel Pérez-Lara
- Department of Neurobiology, Max Planck Institute for Biophysical Chemistry, Am Faβberg 11, 37077 Göttingen, Germany
| | - Reinhard Jahn
- Department of Neurobiology, Max Planck Institute for Biophysical Chemistry, Am Faβberg 11, 37077 Göttingen, Germany
| | - Claudia Steinem
- Institute for Organic and Biomolecular Chemistry, Georg-August Universität, Tammannstr. 2, 37077 Göttingen, Germany
| | - Andreas Janshoff
- Institute for Physical Chemistry, Georg-August Universität, Tammannstr. 6, 37077 Göttingen, Germany
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16
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Nuclear export of the pre-60S ribosomal subunit through single nuclear pores observed in real time. Nat Commun 2021; 12:6211. [PMID: 34707094 PMCID: PMC8551241 DOI: 10.1038/s41467-021-26323-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2021] [Accepted: 09/02/2021] [Indexed: 11/08/2022] Open
Abstract
Ribosomal biogenesis has been studied by biochemical, genetic and electron microscopic approaches, but live cell data on the in vivo kinetics are still missing. Here we analyse the export kinetics of the large ribosomal subunit (pre-60S particle) through single NPCs in human cells. We established a stable cell line co-expressing Halo-tagged eIF6 and GFP-fused NTF2 to simultaneously label pre-60S particles and NPCs, respectively. By combining single molecule tracking and super resolution confocal microscopy we visualize the dynamics of single pre-60S particles during export through single NPCs. For export events, maximum particle accumulation is found in the centre of the pore, while unsuccessful export terminates within the nuclear basket. The export has a single rate limiting step and a duration of ∼24 milliseconds. Only about 1/3 of attempted export events are successful. Our results show that the mass flux through a single NPC can reach up to ~125 MDa·s-1 in vivo.
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17
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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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18
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All-or-none amyloid disassembly via chaperone-triggered fibril unzipping favors clearance of α-synuclein toxic species. Proc Natl Acad Sci U S A 2021; 118:2105548118. [PMID: 34462355 DOI: 10.1073/pnas.2105548118] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
α-synuclein aggregation is present in Parkinson's disease and other neuropathologies. Among the assemblies that populate the amyloid formation process, oligomers and short fibrils are the most cytotoxic. The human Hsc70-based disaggregase system can resolve α-synuclein fibrils, but its ability to target other toxic assemblies has not been studied. Here, we show that this chaperone system preferentially disaggregates toxic oligomers and short fibrils, while its activity against large, less toxic amyloids is severely impaired. Biochemical and kinetic characterization of the disassembly process reveals that this behavior is the result of an all-or-none abrupt solubilization of individual aggregates. High-speed atomic force microscopy explicitly shows that disassembly starts with the destabilization of the tips and rapidly progresses to completion through protofilament unzipping and depolymerization without accumulation of harmful oligomeric intermediates. Our data provide molecular insights into the selective processing of toxic amyloids, which is critical to identify potential therapeutic targets against increasingly prevalent neurodegenerative disorders.
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19
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Woo SO, Oh M, Alhalhooly L, Farmakes J, Rajapakse AJ, Yang Z, Collins PG, Choi Y. Different Single-Enzyme Conformational Dynamics upon Binding Hydrolyzable or Nonhydrolyzable Ligands. J Phys Chem B 2021; 125:5750-5756. [PMID: 34038124 DOI: 10.1021/acs.jpcb.1c01589] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Single-molecule measurements of protein dynamics help unveil the complex conformational changes and transitions that occur during ligand binding and catalytic processes. Using high-resolution single-molecule nanocircuit techniques, we have investigated differences in the conformational dynamics and transitions of lysozyme interacting with three ligands: peptidoglycan substrate, substrate-based chitin analogue, and indole derivative inhibitors. While processing peptidoglycan, lysozyme followed one of the two mechanistic pathways for the hydrolysis of the glycosidic bonds: a concerted mechanism inducing direct conformational changes from open to fully closed conformations or a nonconcerted mechanism involving transient pauses in intermediate conformations between the open and closed conformations. In the presence of either chitin or an indole inhibitor, lysozyme was unable to access the fully closed conformation where catalysis occurs. Instead, lysozymes' conformational closures terminated at slightly closed, "excited" conformations that were approximately one-quarter of the full hinge-bending range. With the indole inhibitor, lysozyme reached this excited conformation in a single step without any evidence of rate-liming intermediates, but the same conformational motions with chitin involved three hidden, intermediate processes and features similar to the nonconcerted peptidoglycan mechanism. The similarities suggest that these hidden processes involve attempts to accommodate imperfectly aligned polysaccharides in the active site. The results provide a detailed glimpse of the enzyme-ligand interplay at the crux of molecular recognition, enzyme specificity, and catalysis.
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Affiliation(s)
- Sung Oh Woo
- Department of Physics, North Dakota State University, Fargo, North Dakota 5810, United States
| | - Myungkeun Oh
- Materials and Nanotechnology Program, North Dakota State University, Fargo, North Dakota 58108, United States
| | - Lina Alhalhooly
- Department of Physics, North Dakota State University, Fargo, North Dakota 5810, United States
| | - Jasmin Farmakes
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108, United States
| | - Arith J Rajapakse
- Department of Physics and Astronomy, University of California, Irvine, California 92697, United States
| | - Zhongyu Yang
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108, United States
| | - Philip G Collins
- Department of Physics and Astronomy, University of California, Irvine, California 92697, United States
| | - Yongki Choi
- Department of Physics, North Dakota State University, Fargo, North Dakota 5810, United States.,Materials and Nanotechnology Program, North Dakota State University, Fargo, North Dakota 58108, United States
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20
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Bouvrais H, Chesneau L, Le Cunff Y, Fairbrass D, Soler N, Pastezeur S, Pécot T, Kervrann C, Pécréaux J. The coordination of spindle-positioning forces during the asymmetric division of the Caenorhabditis elegans zygote. EMBO Rep 2021; 22:e50770. [PMID: 33900015 DOI: 10.15252/embr.202050770] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2020] [Revised: 02/22/2021] [Accepted: 03/03/2021] [Indexed: 12/28/2022] Open
Abstract
In Caenorhabditis elegans zygote, astral microtubules generate forces essential to position the mitotic spindle, by pushing against and pulling from the cortex. Measuring microtubule dynamics there, we revealed the presence of two populations, corresponding to pulling and pushing events. It offers a unique opportunity to study, under physiological conditions, the variations of both spindle-positioning forces along space and time. We propose a threefold control of pulling force, by polarity, spindle position and mitotic progression. We showed that the sole anteroposterior asymmetry in dynein on-rate, encoding pulling force imbalance, is sufficient to cause posterior spindle displacement. The positional regulation, reflecting the number of microtubule contacts in the posterior-most region, reinforces this imbalance only in late anaphase. Furthermore, we exhibited the first direct proof that dynein processivity increases along mitosis. It reflects the temporal control of pulling forces, which strengthens at anaphase onset following mitotic progression and independently from chromatid separation. In contrast, the pushing force remains constant and symmetric and contributes to maintaining the spindle at the cell centre during metaphase.
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Affiliation(s)
| | | | - Yann Le Cunff
- CNRS, IGDR - UMR 6290, University of Rennes, Rennes, France
| | | | - Nina Soler
- CNRS, IGDR - UMR 6290, University of Rennes, Rennes, France
| | | | - Thierry Pécot
- INRIA, Centre Rennes - Bretagne Atlantique, Rennes, France
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21
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Bandey IN, Adolacion JRT, Romain G, Paniagua MM, An X, Saeedi A, Liadi I, You Z, Rajanayake RB, Hwu P, Singh H, Cooper LJ, Varadarajan N. Designed improvement to T-cell immunotherapy by multidimensional single cell profiling. J Immunother Cancer 2021; 9:e001877. [PMID: 33722906 PMCID: PMC7970283 DOI: 10.1136/jitc-2020-001877] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/19/2021] [Indexed: 11/30/2022] Open
Abstract
BACKGROUND Adoptive cell therapy based on the infusion of chimeric antigen receptor (CAR) T cells has shown remarkable efficacy for the treatment of hematologic malignancies. The primary mechanism of action of these infused T cells is the direct killing of tumor cells expressing the cognate antigen. However, understanding why only some T cells are capable of killing, and identifying mechanisms that can improve killing has remained elusive. METHODS To identify molecular and cellular mechanisms that can improve T-cell killing, we utilized integrated high-throughput single-cell functional profiling by microscopy, followed by robotic retrieval and transcriptional profiling. RESULTS With the aid of mathematical modeling we demonstrate that non-killer CAR T cells comprise a heterogeneous population that arise from failure in each of the discrete steps leading to the killing. Differential transcriptional single-cell profiling of killers and non-killers identified CD137 as an inducible costimulatory molecule upregulated on killer T cells. Our single-cell profiling results directly demonstrate that inducible CD137 is feature of killer (and serial killer) T cells and this marks a different subset compared with the CD107apos (degranulating) subset of CAR T cells. Ligation of the induced CD137 with CD137 ligand (CD137L) leads to younger CD19 CAR T cells with sustained killing and lower exhaustion. We genetically modified CAR T cells to co-express CD137L, in trans, and this lead to a profound improvement in anti-tumor efficacy in leukemia and refractory ovarian cancer models in mice. CONCLUSIONS Broadly, our results illustrate that while non-killer T cells are reflective of population heterogeneity, integrated single-cell profiling can enable identification of mechanisms that can enhance the function/proliferation of killer T cells leading to direct anti-tumor benefit.
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Affiliation(s)
- Irfan N Bandey
- Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas, USA
| | - Jay R T Adolacion
- Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas, USA
| | - Gabrielle Romain
- Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas, USA
| | | | - Xingyue An
- Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas, USA
| | - Arash Saeedi
- Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas, USA
| | - Ivan Liadi
- Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas, USA
| | - Zheng You
- Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas, USA
| | - Rasindu B Rajanayake
- Department of Biomedical Engineering, University of Houston, Houston, Texas, USA
| | - Patrick Hwu
- Department of of Melanoma Medical Oncology, Division of Cancer Medicine, The University of Texas MD Anderson Cancer Center, Houston, Texas, USA
| | - Harjeet Singh
- Divsion of Pediatrics, University of Texas MD Anderson Cancer Center, Houston, Texas, USA
| | - Laurence Jn Cooper
- Divsion of Pediatrics, University of Texas MD Anderson Cancer Center, Houston, Texas, USA
- Ziopharm Oncology, Houston, Texas, USA
| | - Navin Varadarajan
- Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas, USA
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22
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Dhatt S, Nandi M, Chaudhury P. Substrate inhibition versus product feedback inhibition: In the perspective of single molecule enzyme kinetics. INT J CHEM KINET 2021. [DOI: 10.1002/kin.21480] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
| | - Mintu Nandi
- Department of Chemistry University of Calcutta Kolkata India
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23
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Mandal S, Li Z, Chatterjee T, Khanna K, Montoya K, Dai L, Petersen C, Li L, Tewari M, Johnson-Buck A, Walter NG. Direct Kinetic Fingerprinting for High-Accuracy Single-Molecule Counting of Diverse Disease Biomarkers. Acc Chem Res 2021; 54:388-402. [PMID: 33382587 DOI: 10.1021/acs.accounts.0c00621] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Methods for detecting and quantifying disease biomarkers in biofluids with high specificity and sensitivity play a pivotal role in enabling clinical diagnostics, including point-of-care tests. The most widely used molecular biomarkers include proteins, nucleic acids, hormones, metabolites, and other small molecules. While numerous methods have been developed for analyzing biomarkers, most techniques are challenging to implement for clinical use due to insufficient analytical performance, high cost, and/or other practical shortcomings. For instance, the detection of cell-free nucleic acid (cfNA) biomarkers by digital PCR and next-generation sequencing (NGS) requires time-consuming nucleic acid extraction steps, often introduces enzymatic amplification bias, and can be costly when high specificity is required. While several amplification-free methods for detecting cfNAs have been reported, these techniques generally suffer from low specificity and sensitivity. Meanwhile, the quantification of protein biomarkers is generally performed using immunoassays such as enzyme-linked immunosorbent assay (ELISA); the analytical performance of these methods is often limited by the availability of antibodies with high affinity and specificity as well as the significant nonspecific binding of antibodies to assay surfaces. To address the drawbacks of existing biomarker detection methods and establish a universal diagnostics platform capable of detecting different types of analytes, we have developed an amplification-free approach, named single-molecule recognition through equilibrium Poisson sampling (SiMREPS), for the detection of diverse biomarkers with arbitrarily high specificity and single-molecule sensitivity. SiMREPS utilizes the transient, reversible binding of fluorescent detection probes to immobilized target molecules to generate kinetic fingerprints that are detected by single-molecule fluorescence microscopy. The analysis of these kinetic fingerprints enables nearly perfect discrimination between specific binding to target molecules and any nonspecific binding. Early proof-of-concept studies demonstrated the in vitro detection of miRNAs with a limit of detection (LOD) of approximately 1 fM and >500-fold selectivity for single-nucleotide polymorphisms. The SiMREPS approach was subsequently expanded to the detection of rare mutant DNA alleles from biofluids at mutant allele fractions of as low as 1 in 1 million, corresponding to a specificity of >99.99999%. Recently, SiMREPS was generalized to protein quantification using dynamically binding antibody probes, permitting LODs in the low-femtomolar to attomolar range. Finally, SiMREPS has been demonstrated to be suitable for the in situ detection of miRNAs in cultured cells, the quantification of small-molecule toxins and drugs, and the monitoring of telomerase activity at the single-molecule level. In this Account, we discuss the principles of SiMREPS for the highly specific and sensitive detection of molecular analytes, including considerations for assay design. We discuss the generality of SiMREPS for the detection of very disparate analytes and provide an overview of data processing methods, including the expansion of the dynamic range using super-resolution analysis and the improvement of performance using deep learning algorithms. Finally, we describe current challenges, opportunities, and future directions for the SiMREPS approach.
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24
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Mühlenbrock P, Sari M, Steinem C. In vitro single vesicle fusion assays based on pore-spanning membranes: merits and drawbacks. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2020; 50:239-252. [PMID: 33320298 PMCID: PMC8071798 DOI: 10.1007/s00249-020-01479-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/21/2020] [Revised: 11/06/2020] [Accepted: 11/09/2020] [Indexed: 12/22/2022]
Abstract
Neuronal fusion mediated by soluble N-ethylmaleimide-sensitive-factor attachment protein receptors (SNAREs) is a fundamental cellular process by which two initially distinct membranes merge resulting in one interconnected structure to release neurotransmitters into the presynaptic cleft. To get access to the different stages of the fusion process, several in vitro assays have been developed. In this review, we provide a short overview of the current in vitro single vesicle fusion assays. Among those assays, we developed a single vesicle assay based on pore-spanning membranes (PSMs) on micrometre-sized pores in silicon, which might overcome some of the drawbacks associated with the other membrane architectures used for investigating fusion processes. Prepared by spreading of giant unilamellar vesicles with reconstituted t-SNAREs, PSMs provide an alternative tool to supported lipid bilayers to measure single vesicle fusion events by means of fluorescence microscopy. Here, we discuss the diffusive behaviour of the reconstituted membrane components as well as that of the fusing synthetic vesicles with reconstituted synaptobrevin 2 (v-SNARE). We compare our results with those obtained if the synthetic vesicles are replaced by natural chromaffin granules under otherwise identical conditions. The fusion efficiency as well as the different fusion states observable in this assay by means of both lipid mixing and content release are illuminated.
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Affiliation(s)
- Peter Mühlenbrock
- Georg-August-Universität Göttingen, Institute of Organic and Biomolecular Chemistry, Tammannstr. 2, 37077, Göttingen, Germany
| | - Merve Sari
- Georg-August-Universität Göttingen, Institute of Organic and Biomolecular Chemistry, Tammannstr. 2, 37077, Göttingen, Germany
| | - Claudia Steinem
- Georg-August-Universität Göttingen, Institute of Organic and Biomolecular Chemistry, Tammannstr. 2, 37077, Göttingen, Germany. .,Max-Planck-Institute for Dynamics and Self Organization, Am Faßberg 17, 37077, Göttingen, Germany.
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25
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Villamil Giraldo AM, Kasson PM. Bilayer-Coated Nanoparticles Reveal How Influenza Viral Entry Depends on Membrane Deformability but Not Curvature. J Phys Chem Lett 2020; 11:7190-7196. [PMID: 32808796 DOI: 10.1021/acs.jpclett.0c01778] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Enveloped viruses infect cells via fusion between the viral envelope and a cellular membrane. This membrane fusion process is driven by viral proteins, but slow stochastic protein activation dominates the fusion kinetics, making it challenging to probe the role of membrane mechanics in viral entry directly. Furthermore, many changes to the interacting membranes alter the curvature, deformability, and spatial organization of membranes simultaneously. We have used bilayer-coated silica nanoparticles to restrict the deformability of lipid membranes in a controllable manner. The single-event kinetics for fusion of influenza virus to coated nanoparticles permits independent testing of how the membrane curvature and deformability control the free energy barriers to fusion. Varying the free energy of membrane deformation, but not membrane curvature, causes a corresponding response in the fusion kinetics and fusion protein stoichiometry. Thus, the main free energy barrier to lipid mixing by influenza virus is controlled by membrane deformability and not the initial membrane curvature.
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Affiliation(s)
- Ana M Villamil Giraldo
- Science for Life Laboratory, Department of Cell and Molecular Biology, Uppsala University, Uppsala 75124, Sweden
| | - Peter M Kasson
- Science for Life Laboratory, Department of Cell and Molecular Biology, Uppsala University, Uppsala 75124, Sweden
- Departments of Molecular Physiology and Biomedical Engineering, University of Virginia, Charlottesville, Virginia 22908, United States
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27
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Paudel BP, Moye AL, Abou Assi H, El-Khoury R, Cohen SB, Holien JK, Birrento ML, Samosorn S, Intharapichai K, Tomlinson CG, Teulade-Fichou MP, González C, Beck JL, Damha MJ, van Oijen AM, Bryan TM. A mechanism for the extension and unfolding of parallel telomeric G-quadruplexes by human telomerase at single-molecule resolution. eLife 2020; 9:56428. [PMID: 32723475 PMCID: PMC7426096 DOI: 10.7554/elife.56428] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2020] [Accepted: 07/28/2020] [Indexed: 02/07/2023] Open
Abstract
Telomeric G-quadruplexes (G4) were long believed to form a protective structure at telomeres, preventing their extension by the ribonucleoprotein telomerase. Contrary to this belief, we have previously demonstrated that parallel-stranded conformations of telomeric G4 can be extended by human and ciliate telomerase. However, a mechanistic understanding of the interaction of telomerase with structured DNA remained elusive. Here, we use single-molecule fluorescence resonance energy transfer (smFRET) microscopy and bulk-phase enzymology to propose a mechanism for the resolution and extension of parallel G4 by telomerase. Binding is initiated by the RNA template of telomerase interacting with the G-quadruplex; nucleotide addition then proceeds to the end of the RNA template. It is only through the large conformational change of translocation following synthesis that the G-quadruplex structure is completely unfolded to a linear product. Surprisingly, parallel G4 stabilization with either small molecule ligands or by chemical modification does not always inhibit G4 unfolding and extension by telomerase. These data reveal that telomerase is a parallel G-quadruplex resolvase.
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Affiliation(s)
- Bishnu P Paudel
- Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, Australia.,Illawara Health and Medical Research Institute, Wollongong, Australia
| | - Aaron Lavel Moye
- Children's Medical Research Institute, University of Sydney, Westmead, Australia
| | - Hala Abou Assi
- Department of Chemistry, McGill University, Montreal, Canada
| | | | - Scott B Cohen
- Children's Medical Research Institute, University of Sydney, Westmead, Australia
| | - Jessica K Holien
- School of Science, College of Science, Engineering and Health, RMIT University, Melbourne, Australia
| | - Monica L Birrento
- Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, Australia.,Illawara Health and Medical Research Institute, Wollongong, Australia
| | - Siritron Samosorn
- Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Srinakharinwirot University, Bangkok, Thailand
| | - Kamthorn Intharapichai
- Department of Biobased Materials Science, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto, Japan
| | | | - Marie-Paule Teulade-Fichou
- Institut Curie, PSL Research University, Orsay, France.,Université Paris Sud, Université Paris-Saclay, Orsay, France
| | - Carlos González
- Instituto de Química Física 'Rocasolano', CSIC, Madrid, Spain
| | - Jennifer L Beck
- Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, Australia.,Illawara Health and Medical Research Institute, Wollongong, Australia
| | - Masad J Damha
- Department of Chemistry, McGill University, Montreal, Canada
| | - Antoine M van Oijen
- Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, Australia.,Illawara Health and Medical Research Institute, Wollongong, Australia
| | - Tracy M Bryan
- Children's Medical Research Institute, University of Sydney, Westmead, Australia
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28
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Delaveris CS, Webster ER, Banik SM, Boxer SG, Bertozzi CR. Membrane-tethered mucin-like polypeptides sterically inhibit binding and slow fusion kinetics of influenza A virus. Proc Natl Acad Sci U S A 2020; 117:12643-12650. [PMID: 32457151 PMCID: PMC7293601 DOI: 10.1073/pnas.1921962117] [Citation(s) in RCA: 46] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
The mechanism(s) by which cell-tethered mucins modulate infection by influenza A viruses (IAVs) remain an open question. Mucins form both a protective barrier that can block virus binding and recruit IAVs to bind cells via the sialic acids of cell-tethered mucins. To elucidate the molecular role of mucins in flu pathogenesis, we constructed a synthetic glycocalyx to investigate membrane-tethered mucins in the context of IAV binding and fusion. We designed and synthesized lipid-tethered glycopolypeptide mimics of mucins and added them to lipid bilayers, allowing chemical control of length, glycosylation, and surface density of a model glycocalyx. We observed that the mucin mimics undergo a conformational change at high surface densities from a compact to an extended architecture. At high surface densities, asialo mucin mimics inhibited IAV binding to underlying glycolipid receptors, and this density correlated to the mucin mimic's conformational transition. Using a single virus fusion assay, we observed that while fusion of virions bound to vesicles coated with sialylated mucin mimics was possible, the kinetics of fusion was slowed in a mucin density-dependent manner. These data provide a molecular model for a protective mechanism by mucins in IAV infection, and therefore this synthetic glycocalyx provides a useful reductionist model for studying the complex interface of host-pathogen interactions.
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Affiliation(s)
| | | | - Steven M Banik
- Department of Chemistry, Stanford University, Stanford, CA 94305
| | - Steven G Boxer
- Department of Chemistry, Stanford University, Stanford, CA 94305;
| | - Carolyn R Bertozzi
- Department of Chemistry, Stanford University, Stanford, CA 94305;
- Howard Hughes Medical Institute, Stanford University, Stanford, CA 94305
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29
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Deng Y, Ma L, Han Q, Yu C, Johnson-Buck A, Su X. DNA-Templated Timer Probes for Multiplexed Sensing. NANO LETTERS 2020; 20:2688-2694. [PMID: 32119561 DOI: 10.1021/acs.nanolett.0c00313] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Simultaneous analysis based on encoded fluorophores suffers from potential crosstalk between fluorophores and the limited number of colors that can be practically resolved. Inspired by nontrivial temporal patterns in living organisms, we developed a DNA-templated probe by utilizing DNA polymerase (DNAP) for multiplexed detection of nucleic acids. These probes use differential delay times of signaling by a DNAP-mediated extension to distinguish different targets, which serve as the primers. Taking advantage of the high processivity and the controllable kinetics of DNAP, we find that multiplexed detection can be achieved in homogeneous solution using a single fluorophore. As a proof of concept, we developed assays for genomic DNA from four different bacteria. In addition, we designed and implemented probes to undergo a single oscillation in signal as an alternative way for multiplexing. We anticipate this approach will find broad applications not only in sensing but also in synthetic DNA nanosystems.
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Affiliation(s)
- Yingnan Deng
- College of Life Science and Technology, Beijing University of Chemical Technology, Beijing 100029, China
| | - Liang Ma
- Clinical Laboratory, China-Japan Friendship Hospital, Beijing 100029, China
| | - Qianqian Han
- 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
| | - Alexander Johnson-Buck
- Department of Internal Medicine, Division of Hematology/Oncology, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Xin Su
- College of Life Science and Technology, Beijing University of Chemical Technology, Beijing 100029, China
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30
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Zhong Y, Paudel BP, Ryan DP, Low JKK, Franck C, Patel K, Bedward MJ, Torrado M, Payne RJ, van Oijen AM, Mackay JP. CHD4 slides nucleosomes by decoupling entry- and exit-side DNA translocation. Nat Commun 2020; 11:1519. [PMID: 32251276 PMCID: PMC7090039 DOI: 10.1038/s41467-020-15183-2] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2019] [Accepted: 02/21/2020] [Indexed: 11/09/2022] Open
Abstract
Chromatin remodellers hydrolyse ATP to move nucleosomal DNA against histone octamers. The mechanism, however, is only partially resolved, and it is unclear if it is conserved among the four remodeller families. Here we use single-molecule assays to examine the mechanism of action of CHD4, which is part of the least well understood family. We demonstrate that the binding energy for CHD4-nucleosome complex formation-even in the absence of nucleotide-triggers significant conformational changes in DNA at the entry side, effectively priming the system for remodelling. During remodelling, flanking DNA enters the nucleosome in a continuous, gradual manner but exits in concerted 4-6 base-pair steps. This decoupling of entry- and exit-side translocation suggests that ATP-driven movement of entry-side DNA builds up strain inside the nucleosome that is subsequently released at the exit side by DNA expulsion. Based on our work and previous studies, we propose a mechanism for nucleosome sliding.
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Affiliation(s)
- Yichen Zhong
- School of Life and Environmental Sciences, University of Sydney, Sydney, NSW, 2006, Australia
| | - Bishnu P Paudel
- Molecular Horizons, School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, NSW, 2522, Australia.,Illawarra Health and Medical Research Institute, Wollongong, NSW, 2522, Australia
| | - Daniel P Ryan
- Department of Genome Sciences, The John Curtin School of Medical Research, The Australian National University, Canberra, ACT, 2601, Australia
| | - Jason K K Low
- School of Life and Environmental Sciences, University of Sydney, Sydney, NSW, 2006, Australia
| | - Charlotte Franck
- School of Life and Environmental Sciences, University of Sydney, Sydney, NSW, 2006, Australia.,School of Chemistry, The University of Sydney, Sydney, NSW, 2006, Australia
| | - Karishma Patel
- School of Life and Environmental Sciences, University of Sydney, Sydney, NSW, 2006, Australia
| | - Max J Bedward
- School of Life and Environmental Sciences, University of Sydney, Sydney, NSW, 2006, Australia
| | - Mario Torrado
- School of Life and Environmental Sciences, University of Sydney, Sydney, NSW, 2006, Australia
| | - Richard J Payne
- School of Chemistry, The University of Sydney, Sydney, NSW, 2006, Australia
| | - Antoine M van Oijen
- Molecular Horizons, School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, NSW, 2522, Australia. .,Illawarra Health and Medical Research Institute, Wollongong, NSW, 2522, Australia.
| | - Joel P Mackay
- School of Life and Environmental Sciences, University of Sydney, Sydney, NSW, 2006, Australia.
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31
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Blokhuis A, Nghe P, Peliti L, Lacoste D. The generality of transient compartmentalization and its associated error thresholds. J Theor Biol 2020; 487:110110. [PMID: 31837985 DOI: 10.1016/j.jtbi.2019.110110] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2019] [Revised: 12/03/2019] [Accepted: 12/05/2019] [Indexed: 01/20/2023]
Abstract
Can prelife proceed without cell division? A recently proposed mechanism suggests that transient compartmentalization could have preceded cell division in prebiotic scenarios. Here, we study transient compartmentalization dynamics in the presence of mutations and noise in replication, as both can be detrimental the survival of compartments. Our study comprises situations where compartments contain uncoupled autocatalytic reactions feeding on a common resource, and systems based on RNA molecules copied by replicases, following a recent experimental study. Using the theory of branching processes, we show analytically that two regimes are possible. In the diffusion-limited regime, replication is asynchronous which leads to a large variability in the composition of compartments. In contrast, in a replication-limited regime, the growth is synchronous and thus the compositional variability is low. Typically, simple autocatalysts are in the former regime, while polymeric replicators can access the latter. For deterministic growth dynamics, we introduce mutations that turn functional replicators into parasites. We derive the phase boundary separating coexistence or parasite dominance as a function of relative growth, inoculation size and mutation rate. We show that transient compartmentalization allows coexistence beyond the classical error threshold, above which the parasite dominates. Our findings invite to revisit major prebiotic transitions, notably the transitions towards cooperation, complex polymers and cell division.
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Affiliation(s)
- Alex Blokhuis
- Gulliver Laboratory, UMR CNRS 7083, PSL Research University, ESPCI, 10 rue Vauquelin, Paris F-75231, France; Laboratory of Biochemistry, PSL Research University, ESPCI, 10 rue Vauquelin, Paris F-75231, France.
| | - Philippe Nghe
- Laboratory of Biochemistry, PSL Research University, ESPCI, 10 rue Vauquelin, Paris F-75231, France
| | | | - David Lacoste
- Gulliver Laboratory, UMR CNRS 7083, PSL Research University, ESPCI, 10 rue Vauquelin, Paris F-75231, France
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32
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Chatterjee T, Li Z, Khanna K, Montoya K, Tewari M, Walter NG, Johnson-Buck A. Ultraspecific analyte detection by direct kinetic fingerprinting of single molecules. Trends Analyt Chem 2020; 123:115764. [PMID: 32863484 PMCID: PMC7451408 DOI: 10.1016/j.trac.2019.115764] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The detection and quantification of biomarkers have numerous applications in biological research and medicine. The most widely used methods to detect nucleic acids require amplification via the polymerase chain reaction (PCR). However, errors arising from the imperfect copying fidelity of DNA polymerases, limited specificity of primers, and heat-induced damage reduce the specificity of PCR-based methods, particularly for single-nucleotide variants. Furthermore, not all analytes can be amplified efficiently. While amplification-free methods avoid these pitfalls, the specificity of most such methods is strictly constrained by probe binding thermodynamics, which for example hampers detection of rare somatic mutations. In contrast, single-molecule recognition through equilibrium Poisson sampling (SiMREPS) provides ultraspecific detection with single-molecule and single-nucleotide sensitivity by monitoring the repetitive interactions of a fluorescent probe with surface-immobilized targets. In this review, we discuss SiMREPS in comparison with other analytical approaches, and describe its utility in quantifying a range of nucleic acids and other analytes.
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Affiliation(s)
- Tanmay Chatterjee
- Single Molecule Analysis Group, Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Zi Li
- Single Molecule Analysis Group, Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Kunal Khanna
- Single Molecule Analysis Group, Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Karen Montoya
- Single Molecule Analysis Group, Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Muneesh Tewari
- Department of Internal Medicine, Division of Hematology/Oncology, University of Michigan, Ann Arbor, Michigan 48109, United States
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan 48109, United States
- Center for RNA Biomedicine, University of Michigan, Ann Arbor, Michigan 48109, United States
- Center for Computational Medicine and Bioinformatics, University of Michigan, Ann Arbor, Michigan 48109, United States
- Biointerfaces Institute, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Nils G Walter
- Single Molecule Analysis Group, Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
- Center for RNA Biomedicine, University of Michigan, Ann Arbor, Michigan 48109, United States
- Center for Computational Medicine and Bioinformatics, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Alexander Johnson-Buck
- Single Molecule Analysis Group, Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
- Department of Internal Medicine, Division of Hematology/Oncology, University of Michigan, Ann Arbor, Michigan 48109, United States
- Center for RNA Biomedicine, University of Michigan, Ann Arbor, Michigan 48109, United States
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33
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34
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Lacy MM, Baddeley D, Berro J. Single-molecule turnover dynamics of actin and membrane coat proteins in clathrin-mediated endocytosis. eLife 2019; 8:52355. [PMID: 31855180 PMCID: PMC6977972 DOI: 10.7554/elife.52355] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2019] [Accepted: 12/18/2019] [Indexed: 12/22/2022] Open
Abstract
Actin dynamics generate forces to deform the membrane and overcome the cell’s high turgor pressure during clathrin-mediated endocytosis (CME) in yeast, but precise molecular details are still unresolved. Our previous models predicted that actin filaments of the endocytic meshwork continually polymerize and disassemble, turning over multiple times during an endocytic event, similar to other actin systems. We applied single-molecule speckle tracking in live fission yeast to directly measure molecular turnover within CME sites for the first time. In contrast with the overall ~20 s lifetimes of actin and actin-associated proteins in endocytic patches, we detected single-molecule residence times around 1 to 2 s, and similarly high turnover rates of membrane-associated proteins in CME. Furthermore, we find heterogeneous behaviors in many proteins’ motions. These results indicate that endocytic proteins turn over up to five times during the formation of an endocytic vesicle, and suggest revising quantitative models of force production.
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Affiliation(s)
- Michael M Lacy
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, United States.,Nanobiology Institute, Yale University, West Haven, United States.,Integrated Graduate Program in Physical and Engineering Biology, Yale University, New Haven, United States
| | - David Baddeley
- Nanobiology Institute, Yale University, West Haven, United States.,Department of Cell Biology, Yale University School of Medicine, New Haven, United States
| | - Julien Berro
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, United States.,Nanobiology Institute, Yale University, West Haven, United States.,Department of Cell Biology, Yale University School of Medicine, New Haven, United States
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35
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Lacy MM, Baddeley D, Berro J. Single-molecule turnover dynamics of actin and membrane coat proteins in clathrin-mediated endocytosis. eLife 2019; 8. [PMID: 31855180 DOI: 10.1101/617746] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2019] [Accepted: 12/18/2019] [Indexed: 05/20/2023] Open
Abstract
Actin dynamics generate forces to deform the membrane and overcome the cell's high turgor pressure during clathrin-mediated endocytosis (CME) in yeast, but precise molecular details are still unresolved. Our previous models predicted that actin filaments of the endocytic meshwork continually polymerize and disassemble, turning over multiple times during an endocytic event, similar to other actin systems. We applied single-molecule speckle tracking in live fission yeast to directly measure molecular turnover within CME sites for the first time. In contrast with the overall ~20 s lifetimes of actin and actin-associated proteins in endocytic patches, we detected single-molecule residence times around 1 to 2 s, and similarly high turnover rates of membrane-associated proteins in CME. Furthermore, we find heterogeneous behaviors in many proteins' motions. These results indicate that endocytic proteins turn over up to five times during the formation of an endocytic vesicle, and suggest revising quantitative models of force production.
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Affiliation(s)
- Michael M Lacy
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, United States
- Nanobiology Institute, Yale University, West Haven, United States
- Integrated Graduate Program in Physical and Engineering Biology, Yale University, New Haven, United States
| | - David Baddeley
- Nanobiology Institute, Yale University, West Haven, United States
- Department of Cell Biology, Yale University School of Medicine, New Haven, United States
| | - Julien Berro
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, United States
- Nanobiology Institute, Yale University, West Haven, United States
- Department of Cell Biology, Yale University School of Medicine, New Haven, United States
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36
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Cai S, Deng Y, Fu S, Li J, Yu C, Su X. Single-molecule dynamic DNA junctions for engineering robust molecular switches. Chem Sci 2019; 10:9922-9927. [PMID: 32110309 PMCID: PMC7006622 DOI: 10.1039/c9sc03389k] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2019] [Accepted: 10/04/2019] [Indexed: 12/23/2022] Open
Abstract
DNA molecular switches have emerged as a versatile and highly programmable toolbox and are extensively used in sensing, diagnosis, and therapeutics. Toehold mediated strand displacement serves as the core reaction for signal transduction and amplification. However, the severe leakage of this reaction limits the development of scalable and robust circuits. We engineered single-molecule dynamic DNA junctions for developing 'zero-leakage' molecular switches which are responsive to various inputs. Input binding enhances dynamic junctions' stability allowing for the transient binding of fluorescent probes as the output signal. Unlike the conventional intensity-based output, this molecular switch provides remarkably distinguishable kinetics-based outputs permitting ruling out leakage signals at the single-molecule level. The inputs are detected with significant sensitivity without using any amplification step. It is also revealed that the output signal is sensitive to the binding affinity of inputs and their recognition elements making the molecular switch a potential affinity meter. Considering these features, we anticipate that it would find broad applications in large-scale DNA circuits, responsive materials, and biomolecule interaction study.
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Affiliation(s)
- Shuang Cai
- College of Life Science and Technology , Beijing University of Chemical Technology , Beijing 100029 , China .
| | - Yingnan Deng
- College of Life Science and Technology , Beijing University of Chemical Technology , Beijing 100029 , China .
| | - Shengnan Fu
- College of Life Science and Technology , Beijing University of Chemical Technology , Beijing 100029 , China .
| | - Junjie 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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37
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LeBlanc SJ, Gauer JW, Hao P, Case BC, Hingorani MM, Weninger KR, Erie DA. Coordinated protein and DNA conformational changes govern mismatch repair initiation by MutS. Nucleic Acids Res 2019; 46:10782-10795. [PMID: 30272207 PMCID: PMC6237781 DOI: 10.1093/nar/gky865] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2018] [Accepted: 09/26/2018] [Indexed: 12/13/2022] Open
Abstract
MutS homologs identify base-pairing errors made in DNA during replication and initiate their repair. In the presence of adenosine triphosphate, MutS induces DNA bending upon mismatch recognition and subsequently undergoes conformational transitions that promote its interaction with MutL to signal repair. In the absence of MutL, these transitions lead to formation of a MutS mobile clamp that can move along the DNA. Previous single-molecule FRET (smFRET) studies characterized the dynamics of MutS DNA-binding domains during these transitions. Here, we use protein–DNA and DNA–DNA smFRET to monitor DNA conformational changes, and we use kinetic analyses to correlate DNA and protein conformational changes to one another and to the steps on the pathway to mobile clamp formation. The results reveal multiple sequential structural changes in both MutS and DNA, and they suggest that DNA dynamics play a critical role in the formation of the MutS mobile clamp. Taking these findings together with data from our previous studies, we propose a unified model of coordinated MutS and DNA conformational changes wherein initiation of mismatch repair is governed by a balance of DNA bending/unbending energetics and MutS conformational changes coupled to its nucleotide binding properties.
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Affiliation(s)
- Sharonda J LeBlanc
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.,Department of Physics, North Carolina State University, Raleigh, NC 27695, USA
| | - Jacob W Gauer
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Pengyu Hao
- Department of Physics, North Carolina State University, Raleigh, NC 27695, USA
| | - Brandon C Case
- Molecular Biology and Biochemistry Department, Wesleyan University, Middletown, CT 06459, USA
| | - Manju M Hingorani
- Molecular Biology and Biochemistry Department, Wesleyan University, Middletown, CT 06459, USA
| | - Keith R Weninger
- Department of Physics, North Carolina State University, Raleigh, NC 27695, USA
| | - Dorothy A Erie
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.,Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
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38
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Burnham DR, Kose HB, Hoyle RB, Yardimci H. The mechanism of DNA unwinding by the eukaryotic replicative helicase. Nat Commun 2019; 10:2159. [PMID: 31089141 PMCID: PMC6517413 DOI: 10.1038/s41467-019-09896-2] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2018] [Accepted: 04/05/2019] [Indexed: 12/18/2022] Open
Abstract
Accurate DNA replication is tightly regulated in eukaryotes to ensure genome stability during cell division and is performed by the multi-protein replisome. At the core an AAA+ hetero-hexameric complex, Mcm2-7, together with GINS and Cdc45 form the active replicative helicase Cdc45/Mcm2-7/GINS (CMG). It is not clear how this replicative ring helicase translocates on, and unwinds, DNA. We measure real-time dynamics of purified recombinant Drosophila melanogaster CMG unwinding DNA with single-molecule magnetic tweezers. Our data demonstrates that CMG exhibits a biased random walk, not the expected unidirectional motion. Through building a kinetic model we find CMG may enter up to three paused states rather than unwinding, and should these be prevented, in vivo fork rates would be recovered in vitro. We propose a mechanism in which CMG couples ATP hydrolysis to unwinding by acting as a lazy Brownian ratchet, thus providing quantitative understanding of the central process in eukaryotic DNA replication.
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Affiliation(s)
- Daniel R Burnham
- The Francis Crick Institute, 1 Midland Road, London, NW1 1AT, UK
| | - Hazal B Kose
- The Francis Crick Institute, 1 Midland Road, London, NW1 1AT, UK
| | - Rebecca B Hoyle
- School of Mathematical Sciences, University of Southampton, Southampton, SO17 1BJ, UK
| | - Hasan Yardimci
- The Francis Crick Institute, 1 Midland Road, London, NW1 1AT, UK.
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39
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Li L, Li N, Fu S, Deng Y, Yu C, Su X. Base excision repair-inspired DNA motor powered by intracellular apurinic/apyrimidinic endonuclease. NANOSCALE 2019; 11:1343-1350. [PMID: 30604811 DOI: 10.1039/c8nr07813k] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The transition of DNA nanomachines from test tubes to living cells would realize the ultimate goal of smart therapeutic dynamic DNA nanotechnology. The operation of DNA nanomachines in living cells remains challenging because it is difficult to utilize an endogenous driving force. Inspired by the base excision repair (BER) process, we demonstrate a 'burnt-bridge' DNA motor system powered by intracellular apurinic/apyrimidinic (AP) endonuclease APE1. The high specificity of APE1 to the AP site in double-stranded DNA permits directional and autonomous movement. The advanced single-molecule fluorescence technique was utilized to directly monitor the stepwise movement of the motor strand, confirming the excellent controllability and processivity of this system. The speed of this DNA motor relies highly on APE1 concentration, allowing discrimination by APE1 level against cancer cells and normal cells. Western blot was used to confirm APE1 expression level. Successful operation of the DNA motor in living cells demonstrates that an endogenous enzyme can operate the rationally designed DNA nanostructures in a programmable way, rather than digesting simple molecular probes. This is useful and practicable for broad application, such as for cellular diagnostic tools, gene regulators for DNA repair, and enzyme-mediated drug delivery.
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Affiliation(s)
- Lidan Li
- College of Life Science and Technology, Beijing University of Chemical Technology, Beijing 100029, China.
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40
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Piatt S, Price AC. Analyzing dwell times with the Generalized Method of Moments. PLoS One 2019; 14:e0197726. [PMID: 30620735 PMCID: PMC6324800 DOI: 10.1371/journal.pone.0197726] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2018] [Accepted: 12/24/2018] [Indexed: 11/18/2022] Open
Abstract
The Generalized Method of Moments (GMM) is a statistical method for the analysis of samples from random processes. First developed for the analysis of econometric data, the method is here formulated to extract hidden kinetic parameters from measurements of single molecule dwell times. Our method is based on the analysis of cumulants of the measured dwell times. We develop a general form of an objective function whose minimization can return estimates of decay parameters for any number of intermediates directly from the data. We test the performance of our technique using both simulated and experimental data. We also compare the performance of our method to nonlinear least-squares minimization (NL-LSQM), a commonly-used technique for analysis of single molecule dwell times. Our findings indicate that the GMM performs comparably to NL-LSQM over most of the parameter range we explore. It offers some benefits compared with NL-LSQM in that it does not require binning, exhibits slightly lower bias and variance with small sample sizes (N<20), and is somewhat superior in identifying fast decay times with these same low count data sets. Additionally, a comparison with the Classical Method of Moments (CMM) shows that the CMM can fail in many cases, whereas the GMM always returns estimates. Our results show that the GMM can be a useful tool and complements standard approaches to analysis of single molecule dwell times.
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Affiliation(s)
- Sadie Piatt
- Department of Chemistry and Physics, Emmanuel College, Boston, MA, United States of America
| | - Allen C. Price
- Department of Chemistry and Physics, Emmanuel College, Boston, MA, United States of America
- * E-mail:
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41
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Weng R, Lou S, Li L, Zhang Y, Qiu J, Su X, Qian Y, Walter NG. Single-Molecule Kinetic Fingerprinting for the Ultrasensitive Detection of Small Molecules with Aptasensors. Anal Chem 2019; 91:1424-1431. [PMID: 30562003 DOI: 10.1021/acs.analchem.8b04145] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Aptamers have emerged as promising molecular tools for small-molecule analyte sensing. However, the performance of such aptasensors is generally limited by leakage since it has been difficult to completely suppress signal in the absence of analyte, resulting in a compromise between sensitivity and specificity. Here, we describe a methodology for the ultrasensitive detection of analytes combining aptasensors with single-molecule kinetic fingerprinting. A short, fluorescently labeled DNA probe is utilized to detect the structural changes upon ligand binding to the designed hairpin-shaped aptasensor probe. The Poisson statistics of binding and dissociation events of the DNA probe to single surface-immobilized aptasensor molecules is monitored by total internal reflection fluorescence microscopy, permitting the high-accuracy discrimination of the ligand bound and ligand-free states, resulting in zero background. The programmable dynamics of the hairpin enables fine-tuning of the hybridization kinetics of the fluorescent probe, rendering the acquisition time sufficiently flexible to optimize discrimination. Remarkable detection limits are achieved for a diverse set of analytes when spiked into chicken meat extract: the nucleotide adenosine (0.3 pM), the insecticide acetamiprid (0.35 pM), and the dioxin-like toxin PCB-77 (0.72 pM), which is superior to recently reported aptasensors. Our generalizable method significantly improves the performance of aptasensors, with the potential to extend to other molecular biomarkers.
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Affiliation(s)
- Rui Weng
- Key Laboratory of Agro-food Safety and Quality of Ministry of Agriculture and Rural Affairs, Institute of Quality Standards and Testing Technology for Agro-Products , Chinese Academy of Agricultural Sciences , Beijing 100081 , China
| | - Shengting Lou
- Beijing Key Laboratory of Bioprocess, College of Life Science and Technology , Beijing University of Chemical Technology , Beijing 100029 , China
| | - Lidan Li
- Beijing Key Laboratory of Bioprocess, College of Life Science and Technology , Beijing University of Chemical Technology , Beijing 100029 , China
| | - Yi Zhang
- Beijing Key Laboratory of Bioprocess, College of Life Science and Technology , Beijing University of Chemical Technology , Beijing 100029 , China
| | - Jing Qiu
- Key Laboratory of Agro-food Safety and Quality of Ministry of Agriculture and Rural Affairs, Institute of Quality Standards and Testing Technology for Agro-Products , Chinese Academy of Agricultural Sciences , Beijing 100081 , China
| | - Xin Su
- Beijing Key Laboratory of Bioprocess, College of Life Science and Technology , Beijing University of Chemical Technology , Beijing 100029 , China
| | - Yongzhong Qian
- Key Laboratory of Agro-food Safety and Quality of Ministry of Agriculture and Rural Affairs, Institute of Quality Standards and Testing Technology for Agro-Products , Chinese Academy of Agricultural Sciences , Beijing 100081 , China
| | - Nils G Walter
- Single Molecule Analysis Group, Department of Chemistry , University of Michigan , Ann Arbor , Michigan 48109 , United States
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Nathan L, Daniel S. Single Virion Tracking Microscopy for the Study of Virus Entry Processes in Live Cells and Biomimetic Platforms. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1215:13-43. [PMID: 31317494 PMCID: PMC7122913 DOI: 10.1007/978-3-030-14741-9_2] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The most widely-used assays for studying viral entry, including infectivity, cofloatation, and cell-cell fusion assays, yield functional information but provide low resolution of individual entry steps. Structural characterization provides high-resolution conformational information, but on its own is unable to address the functional significance of these conformations. Single virion tracking microscopy techniques provide more detail on the intermediate entry steps than infection assays and more functional information than structural methods, bridging the gap between these methods. In addition, single virion approaches also provide dynamic information about the kinetics of entry processes. This chapter reviews single virion tracking techniques and describes how they can be applied to study specific virus entry steps. These techniques provide information complementary to traditional ensemble approaches. Single virion techniques may either probe virion behavior in live cells or in biomimetic platforms. Synthesizing information from ensemble, structural, and single virion techniques ultimately yields a more complete understanding of the viral entry process than can be achieved by any single method alone.
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Affiliation(s)
- Lakshmi Nathan
- Robert Frederick Smith School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, NY, USA.
| | - Susan Daniel
- Robert Frederick Smith School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, NY, USA.
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43
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Hubrich R, Park Y, Mey I, Jahn R, Steinem C. SNARE-Mediated Fusion of Single Chromaffin Granules with Pore-Spanning Membranes. Biophys J 2018; 116:308-318. [PMID: 30598283 DOI: 10.1016/j.bpj.2018.11.3138] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2018] [Revised: 11/15/2018] [Accepted: 11/29/2018] [Indexed: 01/09/2023] Open
Abstract
Pore-spanning membranes (PSMs) composed of supported membrane parts as well as freestanding membrane parts are shown to be very versatile to investigate SNARE-mediated fusion on the single-particle level. They provide a planar geometry readily accessible by confocal fluorescence microscopy, which enabled us for the first time, to our knowledge, to investigate the fusion of individual natural secretory granules (i.e., chromaffin granules (CGs)) on the single-particle level by two-color fluorescence microscopy in a time-resolved manner. The t-SNARE acceptor complex ΔN49 was reconstituted into PSMs containing 2 mol % 1,2-dipalmitoyl-sn-glycero-3-phosphatidylinositol-4,5-bisphosphate and Atto488-1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine, and CGs were fluorescently labeled with 2-((1E,3E)-5-((Z)-3,3-dimethyl-1-octadecylindolin-2-ylidene)penta-1,3-dien-1-yl)-3,3-dimethyl-1-octadecyl-3H-indol-1-ium perchlorate. We compared the dynamics of docked and hemifused CGs as well as their fusion efficacy and kinetics with the results obtained for synthetic synaptobrevin 2-doped vesicles fusing with PSMs of the same composition. Whereas the synthetic vesicles were fully immobile on supported PSMs, docked as well as hemifused CGs were mobile on both PSM parts, which suggests that this system resembles more closely the natural situation. The fusion process of CGs proceeded through three-dimensional post-lipid-mixing structures, which were readily resolved on the gold-covered pore rims of the PSMs and which are discussed in the context of intermediate states observed in live cells.
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Affiliation(s)
- Raphael Hubrich
- Institute of Organic and Biomolecular Chemistry, University of Göttingen, Göttingen, Germany
| | - Yongsoo Park
- Max-Planck Institute for Biophysical Chemistry, Göttingen, Germany; Department of Molecular Biology and Genetics, Koc University, Sarıyer, Istanbul, Turkey
| | - Ingo Mey
- Institute of Organic and Biomolecular Chemistry, University of Göttingen, Göttingen, Germany
| | - Reinhard Jahn
- Max-Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Claudia Steinem
- Institute of Organic and Biomolecular Chemistry, University of Göttingen, Göttingen, Germany; Max-Planck Institute for Dynamics and Self-Organization, Göttingen, Germany.
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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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45
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Conformational entropy of a single peptide controlled under force governs protease recognition and catalysis. Proc Natl Acad Sci U S A 2018; 115:11525-11530. [PMID: 30341218 DOI: 10.1073/pnas.1803872115] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
An immense repertoire of protein chemical modifications catalyzed by enzymes is available as proteomics data. Quantifying the impact of the conformational dynamics of the modified peptide remains challenging to understand the decisive kinetics and amino acid sequence specificity of these enzymatic reactions in vivo, because the target peptide must be disordered to accommodate the specific enzyme-binding site. Here, we were able to control the conformation of a single-molecule peptide chain by applying mechanical force to activate and monitor its specific cleavage by a model protease. We found that the conformational entropy impacts the reaction in two distinct ways. First, the flexibility and accessibility of the substrate peptide greatly increase upon mechanical unfolding. Second, the conformational sampling of the disordered peptide drives the specific recognition, revealing force-dependent reaction kinetics. These results support a mechanism of peptide recognition based on conformational selection from an ensemble that we were able to quantify with a torsional free-energy model. Our approach can be used to predict how entropy affects site-specific modifications of proteins and prompts conformational and mechanical selectivity.
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46
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Nord AL, Pols AF, Depken M, Pedaci F. Kinetic analysis methods applied to single motor protein trajectories. Phys Chem Chem Phys 2018; 20:18775-18781. [PMID: 29961801 DOI: 10.1039/c8cp03056a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Molecular motors convert chemical or electrical energy into mechanical displacement, either linear or rotary. Under ideal circumstances, single-molecule measurements can spatially and temporally resolve individual steps of the motor, revealing important properties of the underlying mechanochemical process. Unfortunately, steps are often hard to resolve, as they are masked by thermal noise. In such cases, details of the mechanochemistry can nonetheless be recovered by analyzing the fluctuations in the recorded traces. Here, we expand upon existing statistical analysis methods, providing two new avenues to extract the motor step size, the effective number of rate-limiting chemical states per translocation step, and the compliance of the link between the motor and the probe particle. We first demonstrate the power and limitations of these methods using simulated molecular motor trajectories, and we then apply these methods to experimental data of kinesin, the bacterial flagellar motor, and F1-ATPase.
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Affiliation(s)
- A L Nord
- CBS, Univ. Montpellier, CNRS, INSERM, Montpellier, France.
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Figliozzi P, Peterson CW, Rice SA, Scherer NF. Direct Visualization of Barrier Crossing Dynamics in a Driven Optical Matter System. ACS NANO 2018; 12:5168-5175. [PMID: 29694025 DOI: 10.1021/acsnano.8b02012] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
A major impediment to a more complete understanding of barrier crossing and other single-molecule processes is the inability to directly visualize the trajectories and dynamics of atoms and molecules in reactions. Rather, the kinetics are inferred from ensemble measurements or the position of a transducer ( e. g., an AFM cantilever) as a surrogate variable. Direct visualization is highly desirable. Here, we achieve the direct measurement of barrier crossing trajectories by using optical microscopy to observe position and orientation changes of pairs of Ag nanoparticles, i. e. passing events, in an optical ring trap. A two-step mechanism similar to a bimolecular exchange reaction or the Michaelis-Menten scheme is revealed by analysis that combines detailed knowledge of each trajectory, a statistically significant number of repetitions of the passing events, and the driving force dependence of the process. We find that while the total event rate increases with driving force, this increase is due to an increase in the rate of encounters. There is no drive force dependence on the rate of barrier crossing because the key motion for the process involves a random (thermal) radial fluctuation of one particle allowing the other to pass. This simple experiment can readily be extended to study more complex barrier crossing processes by replacing the spherical metal nanoparticles with anisotropic ones or by creating more intricate optical trapping potentials.
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Affiliation(s)
- Patrick Figliozzi
- Department of Chemistry and James Franck Institute , The University of Chicago , 929 E. 57th Street , Chicago , Illinois 60637 , United States
| | - Curtis W Peterson
- Department of Chemistry and James Franck Institute , The University of Chicago , 929 E. 57th Street , Chicago , Illinois 60637 , United States
| | - Stuart A Rice
- Department of Chemistry and James Franck Institute , The University of Chicago , 929 E. 57th Street , Chicago , Illinois 60637 , United States
| | - Norbert F Scherer
- Department of Chemistry and James Franck Institute , The University of Chicago , 929 E. 57th Street , Chicago , Illinois 60637 , United States
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48
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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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49
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Neagu IA, Olejarz J, Freeman M, Rosenbloom DI, Nowak MA, Hill AL. Life cycle synchronization is a viral drug resistance mechanism. PLoS Comput Biol 2018; 14:e1005947. [PMID: 29447150 PMCID: PMC5813899 DOI: 10.1371/journal.pcbi.1005947] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2017] [Accepted: 12/14/2017] [Indexed: 11/19/2022] Open
Abstract
Viral infections are one of the major causes of death worldwide, with HIV infection alone resulting in over 1.2 million casualties per year. Antiviral drugs are now being administered for a variety of viral infections, including HIV, hepatitis B and C, and influenza. These therapies target a specific phase of the virus's life cycle, yet their ultimate success depends on a variety of factors, such as adherence to a prescribed regimen and the emergence of viral drug resistance. The epidemiology and evolution of drug resistance have been extensively characterized, and it is generally assumed that drug resistance arises from mutations that alter the virus's susceptibility to the direct action of the drug. In this paper, we consider the possibility that a virus population can evolve towards synchronizing its life cycle with the pattern of drug therapy. The periodicity of the drug treatment could then allow for a virus strain whose life cycle length is a multiple of the dosing interval to replicate only when the concentration of the drug is lowest. This process, referred to as "drug tolerance by synchronization", could allow the virus population to maximize its overall fitness without having to alter drug binding or complete its life cycle in the drug's presence. We use mathematical models and stochastic simulations to show that life cycle synchronization can indeed be a mechanism of viral drug tolerance. We show that this effect is more likely to occur when the variability in both viral life cycle and drug dose timing are low. More generally, we find that in the presence of periodic drug levels, time-averaged calculations of viral fitness do not accurately predict drug levels needed to eradicate infection, even if there is no synchronization. We derive an analytical expression for viral fitness that is sufficient to explain the drug-pattern-dependent survival of strains with any life cycle length. We discuss the implications of these findings for clinically relevant antiviral strategies.
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Affiliation(s)
- Iulia A. Neagu
- Program for Evolutionary Dynamics, Department of Mathematics and Department of Organismic & Evolutionary Biology, Harvard University, Cambridge, Massachusetts, United States of America
- Department of Physics, Harvard University, Cambridge, Massachusetts, United States of America
| | - Jason Olejarz
- Program for Evolutionary Dynamics, Department of Mathematics and Department of Organismic & Evolutionary Biology, Harvard University, Cambridge, Massachusetts, United States of America
| | - Mark Freeman
- Program for Evolutionary Dynamics, Department of Mathematics and Department of Organismic & Evolutionary Biology, Harvard University, Cambridge, Massachusetts, United States of America
| | - Daniel I.S. Rosenbloom
- Department of Biomedical Informatics, Columbia University Medical Center, New York, New York, United States of America
| | - Martin A. Nowak
- Program for Evolutionary Dynamics, Department of Mathematics and Department of Organismic & Evolutionary Biology, Harvard University, Cambridge, Massachusetts, United States of America
| | - Alison L. Hill
- Program for Evolutionary Dynamics, Department of Mathematics and Department of Organismic & Evolutionary Biology, Harvard University, Cambridge, Massachusetts, United States of America
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50
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Hayne CK, Yumerefendi H, Cao L, Gauer JW, Lafferty MJ, Kuhlman B, Erie DA, Neher SB. We FRET so You Don't Have To: New Models of the Lipoprotein Lipase Dimer. Biochemistry 2018; 57:241-254. [PMID: 29303250 PMCID: PMC5860654 DOI: 10.1021/acs.biochem.7b01009] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Lipoprotein lipase (LPL) is a dimeric enzyme that is responsible for clearing triglyceride-rich lipoproteins from the blood. Although LPL plays a key role in cardiovascular health, an experimentally derived three-dimensional structure has not been determined. Such a structure would aid in understanding mutations in LPL that cause familial LPL deficiency in patients and help in the development of therapeutic strategies to target LPL. A major obstacle to structural studies of LPL is that LPL is an unstable protein that is difficult to produce in the quantities needed for nuclear magnetic resonance or crystallography. We present updated LPL structural models generated by combining disulfide mapping, computational modeling, and data derived from single-molecule Förster resonance energy transfer (smFRET). We pioneer the technique of smFRET for use with LPL by developing conditions for imaging active LPL and identifying positions in LPL for the attachment of fluorophores. Using this approach, we measure LPL-LPL intermolecular interactions to generate experimental constraints that inform new computational models of the LPL dimer structure. These models suggest that LPL may dimerize using an interface that is different from the dimerization interface suggested by crystal packing contacts seen in structures of pancreatic lipase.
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Affiliation(s)
- Cassandra K. Hayne
- Department of Biochemistry and Biophysics, University of North Carolina - Chapel Hill
| | - Hayretin Yumerefendi
- Department of Biochemistry and Biophysics, University of North Carolina - Chapel Hill
| | - Lin Cao
- Department of Biochemistry and Biophysics, University of North Carolina - Chapel Hill
| | - Jacob W. Gauer
- Department of Chemistry, University of North Carolina at Chapel Hill
| | - Michael J. Lafferty
- Department of Biochemistry and Biophysics, University of North Carolina - Chapel Hill
| | - Brian Kuhlman
- Department of Biochemistry and Biophysics, University of North Carolina - Chapel Hill
| | - Dorothy A. Erie
- Department of Chemistry, University of North Carolina at Chapel Hill
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill
| | - Saskia B. Neher
- Department of Biochemistry and Biophysics, University of North Carolina - Chapel Hill
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