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Feng XA, Yamadi M, Fu Y, Ness KM, Liu C, Ahmed I, Bowman GD, Johnson ME, Ha T, Wu C. GAGA zinc finger transcription factor searches chromatin by 1D-3D facilitated diffusion. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.07.14.549009. [PMID: 37502885 PMCID: PMC10369947 DOI: 10.1101/2023.07.14.549009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/29/2023]
Abstract
To elucidate how eukaryotic sequence-specific transcription factors (TFs) search for gene targets on chromatin, we used multi-color smFRET and single-particle imaging to track the diffusion of purified GAGA-Associated Factor (GAF) on DNA and nucleosomes. Monomeric GAF DNA-binding domain (DBD) bearing one zinc finger finds its cognate site by 1D or 3D diffusion on bare DNA and rapidly slides back-and-forth between naturally clustered motifs for seconds before escape. Multimeric, full-length GAF also finds clustered motifs on DNA by 1D-3D diffusion, but remains locked on target for longer periods. Nucleosome architecture effectively blocks GAF-DBD 1D-sliding into the histone core but favors retention of GAF-DBD when targeting solvent-exposed sites by 3D-diffusion. Despite the occlusive power of nucleosomes, 1D-3D facilitated diffusion enables GAF to effectively search for clustered cognate motifs in chromatin, providing a mechanism for navigation to nucleosome and nucleosome-free sites by a member of the largest TF family.
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Affiliation(s)
- Xinyu A Feng
- Department of Biology, Johns Hopkins University, Baltimore, Maryland, USA
- Department of Biophysics, Johns Hopkins University, Baltimore, Maryland, USA
| | - Maryam Yamadi
- Department of Biology, Johns Hopkins University, Baltimore, Maryland, USA
| | - Yiben Fu
- Department of Biophysics, Johns Hopkins University, Baltimore, Maryland, USA
| | - Kaitlin M Ness
- Department of Biology, Johns Hopkins University, Baltimore, Maryland, USA
| | - Celina Liu
- Department of Biology, Johns Hopkins University, Baltimore, Maryland, USA
| | - Ishtiyaq Ahmed
- Department of Biophysics, Johns Hopkins University, Baltimore, Maryland, USA
| | - Gregory D Bowman
- Department of Biophysics, Johns Hopkins University, Baltimore, Maryland, USA
| | - Margaret E Johnson
- Department of Biophysics, Johns Hopkins University, Baltimore, Maryland, USA
| | - Taekjip Ha
- Department of Biophysics, Johns Hopkins University, Baltimore, Maryland, USA
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
- Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, Massachusetts, United States
- Department of Pediatrics, Harvard Medical School, Boston, Massachusetts, USA
- Howard Hughes Medical Institute, Boston, Massachusetts, USA
| | - Carl Wu
- Department of Biology, Johns Hopkins University, Baltimore, Maryland, USA
- Department of Molecular Biology and Genetics, Johns Hopkins School of Medicine, Baltimore, Maryland, USA
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2
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Kim JM, Carcamo CC, Jazani S, Xie Z, Feng XA, Yamadi M, Poyton M, Holland KL, Grimm JB, Lavis LD, Ha T, Wu C. Dynamic 1D search and processive nucleosome translocations by RSC and ISW2 chromatin remodelers. eLife 2024; 12:RP91433. [PMID: 38497611 PMCID: PMC10948146 DOI: 10.7554/elife.91433] [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] [Indexed: 03/19/2024] Open
Abstract
Eukaryotic gene expression is linked to chromatin structure and nucleosome positioning by ATP-dependent chromatin remodelers that establish and maintain nucleosome-depleted regions (NDRs) near transcription start sites. Conserved yeast RSC and ISW2 remodelers exert antagonistic effects on nucleosomes flanking NDRs, but the temporal dynamics of remodeler search, engagement, and directional nucleosome mobilization for promoter accessibility are unknown. Using optical tweezers and two-color single-particle imaging, we investigated the Brownian diffusion of RSC and ISW2 on free DNA and sparse nucleosome arrays. RSC and ISW2 rapidly scan DNA by one-dimensional hopping and sliding, respectively, with dynamic collisions between remodelers followed by recoil or apparent co-diffusion. Static nucleosomes block remodeler diffusion resulting in remodeler recoil or sequestration. Remarkably, both RSC and ISW2 use ATP hydrolysis to translocate mono-nucleosomes processively at ~30 bp/s on extended linear DNA under tension. Processivity and opposing push-pull directionalities of nucleosome translocation shown by RSC and ISW2 shape the distinctive landscape of promoter chromatin.
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Affiliation(s)
- Jee Min Kim
- Department of Biology, Johns Hopkins UniversityBaltimoreUnited States
| | - Claudia C Carcamo
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of MedicineBaltimoreUnited States
| | - Sina Jazani
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of MedicineBaltimoreUnited States
| | - Zepei Xie
- Department of Biology, Johns Hopkins UniversityBaltimoreUnited States
| | - Xinyu A Feng
- Department of Biology, Johns Hopkins UniversityBaltimoreUnited States
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of MedicineBaltimoreUnited States
| | - Maryam Yamadi
- Department of Biology, Johns Hopkins UniversityBaltimoreUnited States
| | - Matthew Poyton
- Department of Biology, Johns Hopkins UniversityBaltimoreUnited States
| | - Katie L Holland
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Jonathan B Grimm
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Luke D Lavis
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Taekjip Ha
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of MedicineBaltimoreUnited States
- Howard Hughes Medical InstituteBostonUnited States
| | - Carl Wu
- Department of Biology, Johns Hopkins UniversityBaltimoreUnited States
- Department of Molecular Biology and Genetics, Johns Hopkins School of MedicineBaltimoreUnited States
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3
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Kim JM, Carcamo CC, Jazani S, Xie Z, Feng XA, Yamadi M, Poyton M, Holland KL, Grimm JB, Lavis LD, Ha T, Wu C. Dynamic 1D Search and Processive Nucleosome Translocations by RSC and ISW2 Chromatin Remodelers. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.06.13.544671. [PMID: 38293098 PMCID: PMC10827135 DOI: 10.1101/2023.06.13.544671] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2024]
Abstract
Eukaryotic gene expression is linked to chromatin structure and nucleosome positioning by ATP-dependent chromatin remodelers that establish and maintain nucleosome-depleted regions (NDRs) near transcription start-sites. Conserved yeast RSC and ISW2 remodelers exert antagonistic effects on nucleosomes flanking NDRs, but the temporal dynamics of remodeler search, engagement and directional nucleosome mobilization for promoter accessibility are unknown. Using optical tweezers and 2-color single-particle imaging, we investigated the Brownian diffusion of RSC and ISW2 on free DNA and sparse nucleosome arrays. RSC and ISW2 rapidly scan DNA by one-dimensional hopping and sliding respectively, with dynamic collisions between remodelers followed by recoil or apparent co-diffusion. Static nucleosomes block remodeler diffusion resulting in remodeler recoil or sequestration. Remarkably, both RSC and ISW2 use ATP hydrolysis to translocate mono-nucleosomes processively at ~30 bp/sec on extended linear DNA under tension. Processivity and opposing push-pull directionalities of nucleosome translocation shown by RSC and ISW2 shape the distinctive landscape of promoter chromatin.
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Affiliation(s)
- Jee Min Kim
- Department of Biology, Johns Hopkins University, Baltimore, MD 21218, USA
| | - Claudia C. Carcamo
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Sina Jazani
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Zepei Xie
- Department of Biology, Johns Hopkins University, Baltimore, MD 21218, USA
| | - Xinyu A. Feng
- Department of Biology, Johns Hopkins University, Baltimore, MD 21218, USA
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Maryam Yamadi
- Department of Biology, Johns Hopkins University, Baltimore, MD 21218, USA
| | - Matthew Poyton
- Department of Biology, Johns Hopkins University, Baltimore, MD 21218, USA
| | - Katie L. Holland
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, United States
| | - Jonathan B. Grimm
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, United States
| | - Luke D. Lavis
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, United States
| | - Taekjip Ha
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD, USA
- Howard Hughes Medical Institute, Boston, Massachusetts, USA
| | - Carl Wu
- Department of Biology, Johns Hopkins University, Baltimore, MD 21218, USA
- Department of Molecular Biology and Genetics, Johns Hopkins School of Medicine, Baltimore, MD 21287, USA
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4
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Al Masri C, Wan B, Yu J. Nonspecific vs. specific DNA binding free energetics of a transcription factor domain protein. Biophys J 2023; 122:4476-4487. [PMID: 37897044 PMCID: PMC10722393 DOI: 10.1016/j.bpj.2023.10.025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2023] [Revised: 07/06/2023] [Accepted: 10/20/2023] [Indexed: 10/29/2023] Open
Abstract
Transcription factor (TF) proteins regulate gene expression by binding to specific sites on the genome. In the facilitated diffusion model, an optimized search process is achieved by the TF alternating between 3D diffusion in the bulk and 1D diffusion along DNA. While undergoing 1D diffusion, the protein can switch from a search mode for fast diffusion along nonspecific DNA to a recognition mode for stable binding to specific DNA. It was recently noticed that, for a small TF domain protein, reorientations on DNA happen between the nonspecific and specific DNA binding. We here conducted all-atom molecular dynamics simulations with steering forces to reveal the protein-DNA binding free energetics, confirming that the search and recognition modes are distinguished primarily by protein orientations on the DNA. As the binding free energy difference between the specific and nonspecific DNA system slightly deviates from that being estimated directly from dissociation constants on 15-bp DNA constructs, we hypothesize that the discrepancy can come from DNA sequences flanking the 6-bp central binding sites that impact on the dissociation kinetics measurements. The hypothesis is supported by a simplified spherical protein-DNA model along with stochastic simulations and kinetic modeling.
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Affiliation(s)
- Carmen Al Masri
- Department of Physics and Astronomy, University of California, Irvine, California
| | - Biao Wan
- Wenzhou Institute, University of Chinese Academy of Sciences, Wenzhou, China
| | - Jin Yu
- Department of Physics and Astronomy, University of California, Irvine, California; Department of Physics and Astronomy, Department of Chemistry, NSF-Simons Center for Multiscale Cell Fate Research, University of California, Irvine, California.
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5
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Mersch K, Sokoloski J, Nguyen B, Galletto R, Lohman T. "Helicase" Activity promoted through dynamic interactions between a ssDNA translocase and a diffusing SSB protein. Proc Natl Acad Sci U S A 2023; 120:e2216777120. [PMID: 37011199 PMCID: PMC10104510 DOI: 10.1073/pnas.2216777120] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2022] [Accepted: 03/06/2023] [Indexed: 04/05/2023] Open
Abstract
Replication protein A (RPA) is a eukaryotic single-stranded (ss) DNA-binding (SSB) protein that is essential for all aspects of genome maintenance. RPA binds ssDNA with high affinity but can also diffuse along ssDNA. By itself, RPA is capable of transiently disrupting short regions of duplex DNA by diffusing from a ssDNA that flanks the duplex DNA. Using single-molecule total internal reflection fluorescence and optical trapping combined with fluorescence approaches, we show that S. cerevisiae Pif1 can use its ATP-dependent 5' to 3' translocase activity to chemomechanically push a single human RPA (hRPA) heterotrimer directionally along ssDNA at rates comparable to those of Pif1 translocation alone. We further show that using its translocation activity, Pif1 can push hRPA from a ssDNA loading site into a duplex DNA causing stable disruption of at least 9 bp of duplex DNA. These results highlight the dynamic nature of hRPA enabling it to be readily reorganized even when bound tightly to ssDNA and demonstrate a mechanism by which directional DNA unwinding can be achieved through the combined action of a ssDNA translocase that pushes an SSB protein. These results highlight the two basic requirements for any processive DNA helicase: transient DNA base pair melting (supplied by hRPA) and ATP-dependent directional ssDNA translocation (supplied by Pif1) and that these functions can be unlinked by using two separate proteins.
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Affiliation(s)
- Kacey N. Mersch
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO63110-1093
| | - Joshua E. Sokoloski
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO63110-1093
- Department of Chemistry, Salisbury University, Salisbury, MD21801
| | - Binh Nguyen
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO63110-1093
| | - Roberto Galletto
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO63110-1093
| | - Timothy M. Lohman
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO63110-1093
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6
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Hedgehog is relayed through dynamic heparan sulfate interactions to shape its gradient. Nat Commun 2023; 14:758. [PMID: 36765094 PMCID: PMC9918555 DOI: 10.1038/s41467-023-36450-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2022] [Accepted: 01/27/2023] [Indexed: 02/12/2023] Open
Abstract
Cellular differentiation is directly determined by concentration gradients of morphogens. As a central model for gradient formation during development, Hedgehog (Hh) morphogens spread away from their source to direct growth and pattern formation in Drosophila wing and eye discs. What is not known is how extracellular Hh spread is achieved and how it translates into precise gradients. Here we show that two separate binding areas located on opposite sides of the Hh molecule can interact directly and simultaneously with two heparan sulfate (HS) chains to temporarily cross-link the chains. Mutated Hh lacking one fully functional binding site still binds HS but shows reduced HS cross-linking. This, in turn, impairs Hhs ability to switch between both chains in vitro and results in striking Hh gradient hypomorphs in vivo. The speed and propensity of direct Hh switching between HS therefore shapes the Hh gradient, revealing a scalable design principle in morphogen-patterned tissues.
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7
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Lüking M, Elf J, Levy Y. Conformational Change of Transcription Factors from Search to Specific Binding: A lac Repressor Case Study. J Phys Chem B 2022; 126:9971-9984. [PMID: 36416228 PMCID: PMC9743208 DOI: 10.1021/acs.jpcb.2c05006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
In a process known as facilitated diffusion, DNA-binding proteins find their target sites by combining three-dimensional diffusion and one-dimensional scanning of the DNA. Following the trade-off between speed and stability, agile exploration of DNA requires loose binding, whereas, at the DNA target site, the searching protein needs to establish tight interactions with the DNA. To enable both efficient search and stable binding, DNA-binding proteins and DNA often switch conformations upon recognition. Here, we study the one-dimensional diffusion and DNA binding of the dimeric lac repressor (LacI), which was reported to adopt two different conformations when binding different conformations of DNA. Using coarse-grained molecular dynamic simulations, we studied the diffusion and the sequence-specific binding of these conformations of LacI, as well as their truncated or monomeric variants, with two DNA conformations: straight and bent. The simulations were compared to experimental observables. This study supports that linear diffusion along DNA combines tight rotation-coupled groove tracking and rotation-decoupled hopping, where the protein briefly dissociates and reassociates just a few base pairs away. Tight groove tracking is crucial for target-site recognition, while hopping speeds up the overall search process. We investigated the diffusion of different LacI conformations on DNA and show how the flexibility of LacI's hinge regions ensures agility on DNA as well as faithful groove tracking. If the hinge regions instead form α-helices at the protein-DNA interface, tight groove tracking is not possible. On the contrary, the helical hinge region is essential for tight binding to bent, specific DNA, for the formation of the specific complex. Based on our study of different encounter complexes, we argue that the conformational change in LacI and DNA bending are somewhat coupled. Our findings underline the importance of two distinct protein conformations for facilitated diffusion and specific binding, respectively.
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Affiliation(s)
- Malin Lüking
- Department
of Cell- and Molecular Biology-ICM, Uppsala
University, Uppsala, Uppsala County751 24, Sweden
| | - Johan Elf
- Department
of Cell- and Molecular Biology-ICM, Uppsala
University, Uppsala, Uppsala County751 24, Sweden
| | - Yaakov Levy
- Department
of Chemical and Structural Biology, Weizmann
Institute of Science, Rehovot, Central District76100, Israel,. Tel.: 972-8-9344587
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8
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Carcamo CC, Poyton MF, Ranjan A, Park G, Louder RK, Feng XA, Kim JM, Dzu T, Wu C, Ha T. ATP binding facilitates target search of SWR1 chromatin remodeler by promoting one-dimensional diffusion on DNA. eLife 2022; 11:e77352. [PMID: 35876491 PMCID: PMC9365391 DOI: 10.7554/elife.77352] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2022] [Accepted: 07/22/2022] [Indexed: 12/01/2022] Open
Abstract
One-dimensional (1D) target search is a well-characterized phenomenon for many DNA-binding proteins but is poorly understood for chromatin remodelers. Herein, we characterize the 1D scanning properties of SWR1, a conserved yeast chromatin remodeler that performs histone exchange on +1 nucleosomes adjacent to a nucleosome-depleted region (NDR) at gene promoters. We demonstrate that SWR1 has a kinetic binding preference for DNA of NDR length as opposed to gene-body linker length DNA. Using single and dual color single-particle tracking on DNA stretched with optical tweezers, we directly observe SWR1 diffusion on DNA. We found that various factors impact SWR1 scanning, including ATP which promotes diffusion through nucleotide binding rather than ATP hydrolysis. A DNA-binding subunit, Swc2, plays an important role in the overall diffusive behavior of the complex, as the subunit in isolation retains similar, although faster, scanning properties as the whole remodeler. ATP-bound SWR1 slides until it encounters a protein roadblock, of which we tested dCas9 and nucleosomes. The median diffusion coefficient, 0.024 μm2/s, in the regime of helical sliding, would mediate rapid encounter of NDR-flanking nucleosomes at length scales found in cellular chromatin.
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Affiliation(s)
- Claudia C Carcamo
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins UniversityBaltimoreUnited States
| | - Matthew F Poyton
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins UniversityBaltimoreUnited States
| | - Anand Ranjan
- Department of Biology, Johns Hopkins UniversityBaltimoreUnited States
| | - Giho Park
- Department of Biology, Johns Hopkins UniversityBaltimoreUnited States
| | - Robert K Louder
- Department of Biology, Johns Hopkins UniversityBaltimoreUnited States
| | - Xinyu A Feng
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins UniversityBaltimoreUnited States
| | - Jee Min Kim
- Department of Biology, Johns Hopkins UniversityBaltimoreUnited States
| | - Thuc Dzu
- Department of Biology, Johns Hopkins UniversityBaltimoreUnited States
| | - Carl Wu
- Department of Biology, Johns Hopkins UniversityBaltimoreUnited States
| | - Taekjip Ha
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins UniversityBaltimoreUnited States
- Howard Hughes Medical InstituteBaltimoreUnited States
- Johns Hopkins University, Department of Biomedical EngineeringBaltimoreUnited States
- Johns Hopkins University, Department of BiophysicsBaltimoreUnited States
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9
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Charman RJ, Kad NM. Single molecule iSCAT imaging reveals a fast, energy efficient search mode for the DNA repair protein UvrA. NANOSCALE 2022; 14:5174-5184. [PMID: 35311869 PMCID: PMC8969456 DOI: 10.1039/d1nr06913f] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Exposure to UV radiation results in numerous DNA lesions, which threaten genome integrity. The nucleotide excision DNA repair pathway detects and repairs a range of such UV-induced DNA lesions. In bacteria, initial damage detection and verification is carried out by two proteins: UvrA and UvrB. Despite decades of study, the process of how these proteins locate damage remains unclear. Here we use high-speed interferometric scattering (iSCAT) microscopy, in combination with a surface-bound-DNA assay, to investigate early damage detection by UvrA. We have discovered that UvrA interacts with DNA in two phases; a slow phase (∼1.3 s-1) that correlates with an ATP-consuming state previously identified, and a second, much faster search mode. These faster interactions persist for ∼130 ms and using ATP analogues we determine this phase does not require ATP consumption. Including this new fast-search state in a model of the DNA search process reveals that only with this state is it possible for basal levels of UvrA to explore 99% of the E. coli genome within a single division cycle. Altogether, this work uncovers the presence of a rapid, energy efficient search mechanism, which allows UvrA alone to search the entirety of the E. coli genome within a single division cycle.
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Affiliation(s)
- Robert J Charman
- School of Biological Sciences, Division of Natural Sciences, University of Kent, Canterbury CT2 7NH, UK.
| | - Neil M Kad
- School of Biological Sciences, Division of Natural Sciences, University of Kent, Canterbury CT2 7NH, UK.
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10
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Tan CJ, Basak R, Yadav I, van Kan JA, Arluison V, van der Maarel JRC. Mobility of Bacterial Protein Hfq on dsDNA: Role of C-Terminus-Mediated Transient Binding. J Phys Chem B 2022; 126:1477-1482. [PMID: 35166115 DOI: 10.1021/acs.jpcb.1c10234] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The mobility of protein is fundamental in the machinery of life. Here, we have investigated the effect of DNA binding in conjunction with DNA segmental fluctuation (internal motion) of the bacterial Hfq master regulator devoid of its amyloid C-terminus domain. Hfq is one of the most abundant nucleoid associated proteins that shape the bacterial chromosome and is involved in several aspects of nucleic acid metabolism. Fluorescence microscopy has been used to track a C-terminus domain lacking mutant form of Hfq on double-stranded DNA, which is stretched by confinement to a rectangular nanofluidic channel. The mobility of the mutant is strongly accelerated with respect to the wild-type variant. Furthermore, it shows a reverse dependence on the internal motion of DNA, in that slower motion results in slower protein diffusion. The results demonstrate the subtle role of DNA internal motion in controlling the mobility of a nucleoid associated protein, and, in particular, the importance of transient binding and moving DNA strands out of the way.
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Affiliation(s)
- Chuan Jie Tan
- Department of Physics, National University of Singapore, Singapore 117542, Singapore
| | - Rajib Basak
- Department of Physics, National University of Singapore, Singapore 117542, Singapore
| | - Indresh Yadav
- Department of Physics, National University of Singapore, Singapore 117542, Singapore
| | - Jeroen A van Kan
- Department of Physics, National University of Singapore, Singapore 117542, Singapore
| | - Véronique Arluison
- Université de Paris, UFR SDV, Paris 75006, France.,Laboratoire Léon Brillouin, CEA, CNRS, Université Paris Saclay, Gif-sur-Yvette 91191, France
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11
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Basak R, Yadav I, Arluison V, van Kan JA, van der Maarel JRC. Probing Amyloid-DNA Interaction with Nanofluidics. Methods Mol Biol 2022; 2538:305-317. [PMID: 35951308 DOI: 10.1007/978-1-0716-2529-3_20] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Nanofluidics is an emerging methodology to investigate single biomacromolecules without functionalization and/or attachment of the molecules to a substrate. In conjunction with fluorescence microscopy, it can be used to investigate structural and dynamical aspects of amyloid-DNA interaction. Here, we summarize the methodology for fabricating lab-on-chip devices in relatively cheap polymer resins and featuring quasi one-dimensional nanochannels with a cross-sectional diameter of tens to a few hundred nanometers. Site-specific staining of amyloid-forming protein Hfq with a fluorescence dye is also described. The methodology is illustrated with two application studies. The first study involves assembling bacterial amyloid proteins such as Hfq on double-stranded DNA and monitoring the folding and compaction of DNA in a condensed state. The second study is about the concerted motion of Hfq on DNA and how this is related to DNA's internal motion. Explicit details of procedures and workflows are given throughout.
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Affiliation(s)
- Rajib Basak
- Department of Physics, National University of Singapore, Singapore, Singapore
| | - Indresh Yadav
- Department of Physics, National University of Singapore, Singapore, Singapore
| | - Véronique Arluison
- Laboratoire Léon Brillouin LLB, CEA, CNRS UMR 12, Université Paris Saclay, CEA Saclay, Gif-sur-Yvette, France
- Université de Paris, Paris, France
| | - Jeroen A van Kan
- Department of Physics, National University of Singapore, Singapore, Singapore
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12
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Prototype Foamy Virus Integrase Displays Unique Biochemical Activities among Retroviral Integrases. Biomolecules 2021; 11:biom11121910. [PMID: 34944553 PMCID: PMC8699820 DOI: 10.3390/biom11121910] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2021] [Revised: 12/13/2021] [Accepted: 12/17/2021] [Indexed: 12/01/2022] Open
Abstract
Integrases of different retroviruses assemble as functional complexes with varying multimers of the protein. Retroviral integrases require a divalent metal cation to perform one-step transesterification catalysis. Tetrameric prototype foamy virus (PFV) intasomes assembled from purified integrase and viral DNA oligonucleotides were characterized for their activity in the presence of different cations. While most retroviral integrases are inactive in calcium, PFV intasomes appear to be uniquely capable of catalysis in calcium. The PFV intasomes also contrast with other retroviral integrases by displaying an inverse correlation of activity with increasing manganese beginning at relatively low concentrations. The intasomes were found to be significantly more active in the presence of chloride co-ions compared to acetate. While HIV-1 integrase appears to commit to a target DNA within 20 s, PFV intasomes do not commit to target DNA during their reaction lifetime. Together, these data highlight the unique biochemical activities of PFV integrase compared to other retroviral integrases.
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13
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Wang Z, Deng W. Dynamic transcription regulation at the single-molecule level. Dev Biol 2021; 482:67-81. [PMID: 34896367 DOI: 10.1016/j.ydbio.2021.11.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2021] [Revised: 11/14/2021] [Accepted: 11/15/2021] [Indexed: 02/07/2023]
Abstract
Cell fate changes during development, differentiation, and reprogramming are largely controlled at the transcription level. The DNA-binding transcription factors (TFs) often act in a combinatorial fashion to alter chromatin states and drive cell type-specific gene expression. Recent advances in fluorescent microscopy technologies have enabled direct visualization of biomolecules involved in the process of transcription and its regulatory events at the single-molecule level in living cells. Remarkably, imaging and tracking individual TF molecules at high temporal and spatial resolution revealed that they are highly dynamic in searching and binding cognate targets, rather than static and binding constantly. In combination with investigation using techniques from biochemistry, structure biology, genetics, and genomics, a more well-rounded view of transcription regulation is emerging. In this review, we briefly cover the technical aspects of live-cell single-molecule imaging and focus on the biological relevance and interpretation of the single-molecule dynamic features of transcription regulatory events observed in the native chromatin environment of living eukaryotic cells. We also discuss how these dynamic features might shed light on mechanistic understanding of transcription regulation.
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Affiliation(s)
- Zuhui Wang
- Biomedical Pioneering Innovation Center (BIOPIC), Peking University, Beijing, 100871, China; Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, 100871, China
| | - Wulan Deng
- Biomedical Pioneering Innovation Center (BIOPIC), Peking University, Beijing, 100871, China; Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, 100871, China; Beijing Advanced Innovation Center for Genomics (ICG), Peking University, Beijing, 100871, China; Peking-Tsinghua Center for Life Sciences (CLS), Peking University, Beijing, 100871, China; School of Life Sciences, Peking University, Beijing, 100871, China.
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14
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Kamagata K. Single-Molecule Microscopy Meets Molecular Dynamics Simulations for Characterizing the Molecular Action of Proteins on DNA and in Liquid Condensates. Front Mol Biosci 2021; 8:795367. [PMID: 34869607 PMCID: PMC8639857 DOI: 10.3389/fmolb.2021.795367] [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] [Received: 10/15/2021] [Accepted: 11/03/2021] [Indexed: 11/13/2022] Open
Abstract
DNA-binding proteins trigger various cellular functions and determine cellular fate. Before performing functions such as transcription, DNA repair, and DNA recombination, DNA-binding proteins need to search for and bind to their target sites in genomic DNA. Under evolutionary pressure, DNA-binding proteins have gained accurate and rapid target search and binding strategies that combine three-dimensional search in solution, one-dimensional sliding along DNA, hopping and jumping on DNA, and intersegmental transfer between two DNA molecules. These mechanisms can be achieved by the unique structural and dynamic properties of these proteins. Single-molecule fluorescence microscopy and molecular dynamics simulations have characterized the molecular actions of DNA-binding proteins in detail. Furthermore, these methodologies have begun to characterize liquid condensates induced by liquid-liquid phase separation, e.g., molecular principles of uptake and dynamics in droplets. This review discusses the molecular action of DNA-binding proteins on DNA and in liquid condensate based on the latest studies that mainly focused on the model protein p53.
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Affiliation(s)
- Kiyoto Kamagata
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai, Japan
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15
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Yang XW, Liu J. Observing Protein One-Dimensional Sliding: Methodology and Biological Significance. Biomolecules 2021; 11:1618. [PMID: 34827616 PMCID: PMC8615959 DOI: 10.3390/biom11111618] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2021] [Revised: 10/15/2021] [Accepted: 10/16/2021] [Indexed: 11/28/2022] Open
Abstract
One-dimensional (1D) sliding of DNA-binding proteins has been observed by numerous kinetic studies. It appears that many of these sliding events play important roles in a wide range of biological processes. However, one challenge is to determine the physiological relevance of these motions in the context of the protein's biological function. Here, we discuss methods of measuring protein 1D sliding by highlighting the single-molecule approaches that are capable of visualizing particle movement in real time. We also present recent findings that show how protein sliding contributes to function.
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Affiliation(s)
| | - Jiaquan Liu
- State Key Laboratory of Molecular Biology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Shanghai 200031, China;
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16
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Shurshalova GS, Scheidt HA, Fischer M, Huster D, Aganov AV, Klochkov VV. Interaction of the pitavastatin with model membranes. Biochem Biophys Rep 2021; 28:101143. [PMID: 34632116 PMCID: PMC8487990 DOI: 10.1016/j.bbrep.2021.101143] [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] [Received: 07/16/2021] [Revised: 09/07/2021] [Accepted: 09/21/2021] [Indexed: 11/27/2022] Open
Abstract
Pitavastatin is a statin drug that, by competitively inhibiting 3-hydroxy-3-methylglutaryl-coenzyme A reductase, can lower serum cholesterol levels of low-density lipoprotein (LDL) accompanied by side effects due to pleiotropic effects leading to statin intolerance. These effects can be explained by the lipophilicity of statins, which creates membrane affinity and causes statin localization in cellular membranes. In the current report, the interaction of pitavastatin with POPC model membranes and its influence on the membrane structure were investigated using H, H and P solid-state NMR spectroscopy. Our experiments show the average localization of pitavastatin at the lipid/water interface of the membrane, which is biased towards the hydrocarbon core in comparison to other statin molecules. The membrane binding of pitavastatin also introduced an isotropic component into the 31P NMR powder spectra, suggesting that some of the lamellar POPC molecules are converted into highly curved structures. Solid-state NMR spectroscopy shows pitavastatin effect on the bilayer •Pitavastatin lowers the POPC order parameters •Pitavastatin localize in the upper chain of the POPC bilayer •Isotropic membrane phases are observed in the presence of pitavastatin
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Affiliation(s)
- Guzel S Shurshalova
- Institute for Medical Physics and Biophysics, Leipzig University, Härtelstr. 16-18, D-04107 Leipzig, Germany.,Institute of Physics, Kazan (Volga Region) Federal University, 18 Kremlevskaya St., 420008 Kazan, Russian Federation
| | - Holger A Scheidt
- Institute for Medical Physics and Biophysics, Leipzig University, Härtelstr. 16-18, D-04107 Leipzig, Germany
| | - Markus Fischer
- Institute for Medical Physics and Biophysics, Leipzig University, Härtelstr. 16-18, D-04107 Leipzig, Germany
| | - Daniel Huster
- Institute for Medical Physics and Biophysics, Leipzig University, Härtelstr. 16-18, D-04107 Leipzig, Germany
| | - Albert V Aganov
- Institute of Physics, Kazan (Volga Region) Federal University, 18 Kremlevskaya St., 420008 Kazan, Russian Federation
| | - Vladimir V Klochkov
- Institute of Physics, Kazan (Volga Region) Federal University, 18 Kremlevskaya St., 420008 Kazan, Russian Federation
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17
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Yang M, Sun R, Deng P, Yang Y, Wang W, Liu JJG, Chen C. Nonspecific interactions between SpCas9 and dsDNA sites located downstream of the PAM mediate facilitated diffusion to accelerate target search. Chem Sci 2021; 12:12776-12784. [PMID: 34703564 PMCID: PMC8494019 DOI: 10.1039/d1sc02633j] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2021] [Accepted: 08/19/2021] [Indexed: 12/27/2022] Open
Abstract
RNA-guided Streptococcus pyogenes Cas9 (SpCas9) is a sequence-specific DNA endonuclease that works as one of the most powerful genetic editing tools. However, how Cas9 locates its target among huge amounts of dsDNAs remains elusive. Here, combining biochemical and single-molecule fluorescence assays, we revealed that Cas9 uses both three-dimensional and one-dimensional diffusion to find its target with high efficiency. We further observed surprising apparent asymmetric target search regions flanking PAM sites on dsDNA under physiological salt conditions, which accelerates the target search efficiency of Cas9 by ∼10-fold. Illustrated by a cryo-EM structure of the Cas9/sgRNA/dsDNA dimer, non-specific interactions between DNA ∼8 bp downstream of the PAM site and lysines within residues 1151–1156 of Cas9, especially lys1153, are the key elements to mediate the one-dimensional diffusion of Cas9 and cause asymmetric target search regions flanking the PAM. Disrupting these non-specific interactions, such as mutating these lysines to alanines, diminishes the contribution of one-dimensional diffusion and reduces the target search rate by several times. In addition, low ionic concentrations or mutations on PAM recognition residues that modulate interactions between Cas9 and dsDNA alter apparent asymmetric target search behaviors. Together, our results reveal a unique searching mechanism of Cas9 under physiological salt conditions, and provide important guidance for both in vitro and in vivo applications of Cas9. Nonspecific interactions between DNA ∼8 bp downstream of the PAM and lysines within residues 1151–1156 of Cas9 mediate one-dimensional diffusion and cause asymmetric target search regions flanking the PAM.![]()
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Affiliation(s)
- Mengyi Yang
- School of Life Sciences, Beijing Advanced Innovation Center for Structural Biology, Beijing Frontier Research Center for Biological Structure, Tsinghua University Beijing China .,Laboratory of Nutrition and Development, Key Laboratory of Major Diseases in Children, Ministry of Education, Beijing Pediatric Research Institutue, Beijing Children's Hospital, Capital Medical University, National Center for Children's Health Beijing 100045 China
| | - Ruirui Sun
- School of Life Sciences, Beijing Advanced Innovation Center for Structural Biology, Beijing Frontier Research Center for Biological Structure, Tsinghua University Beijing China
| | - Pujuan Deng
- School of Life Sciences, Tsinghua-Peking Joint Center for Life Sciences, Beijing Advanced Innovation Center for Structural Biology, Tsinghua University Beijing China
| | - Yuzhuo Yang
- School of Life Sciences, Beijing Advanced Innovation Center for Structural Biology, Beijing Frontier Research Center for Biological Structure, Tsinghua University Beijing China
| | - Wenjuan Wang
- School of Life Sciences, Technology Center for Protein Sciences, Tsinghua University Beijing China
| | - Jun-Jie Gogo Liu
- School of Life Sciences, Tsinghua-Peking Joint Center for Life Sciences, Beijing Advanced Innovation Center for Structural Biology, Tsinghua University Beijing China
| | - Chunlai Chen
- School of Life Sciences, Beijing Advanced Innovation Center for Structural Biology, Beijing Frontier Research Center for Biological Structure, Tsinghua University Beijing China
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18
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Kamagata K, Itoh Y, Tan C, Mano E, Wu Y, Mandali S, Takada S, Johnson RC. Testing mechanisms of DNA sliding by architectural DNA-binding proteins: dynamics of single wild-type and mutant protein molecules in vitro and in vivo. Nucleic Acids Res 2021; 49:8642-8664. [PMID: 34352099 PMCID: PMC8421229 DOI: 10.1093/nar/gkab658] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2021] [Revised: 07/10/2021] [Accepted: 07/22/2021] [Indexed: 01/06/2023] Open
Abstract
Architectural DNA-binding proteins (ADBPs) are abundant constituents of eukaryotic or bacterial chromosomes that bind DNA promiscuously and function in diverse DNA reactions. They generate large conformational changes in DNA upon binding yet can slide along DNA when searching for functional binding sites. Here we investigate the mechanism by which ADBPs diffuse on DNA by single-molecule analyses of mutant proteins rationally chosen to distinguish between rotation-coupled diffusion and DNA surface sliding after transient unbinding from the groove(s). The properties of yeast Nhp6A mutant proteins, combined with molecular dynamics simulations, suggest Nhp6A switches between two binding modes: a static state, in which the HMGB domain is bound within the minor groove with the DNA highly bent, and a mobile state, where the protein is traveling along the DNA surface by means of its flexible N-terminal basic arm. The behaviors of Fis mutants, a bacterial nucleoid-associated helix-turn-helix dimer, are best explained by mobile proteins unbinding from the major groove and diffusing along the DNA surface. Nhp6A, Fis, and bacterial HU are all near exclusively associated with the chromosome, as packaged within the bacterial nucleoid, and can be modeled by three diffusion modes where HU exhibits the fastest and Fis the slowest diffusion.
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Affiliation(s)
- Kiyoto Kamagata
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai 980-8577, Japan
| | - Yuji Itoh
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai 980-8577, Japan
| | - Cheng Tan
- Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| | - Eriko Mano
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai 980-8577, Japan
| | - Yining Wu
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai 980-8577, Japan
| | - Sridhar Mandali
- Department of Biological Chemistry, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1737, USA
| | - Shoji Takada
- Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| | - Reid C Johnson
- Department of Biological Chemistry, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1737, USA.,Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA 90095, USA
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19
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Moses ME, Lund PM, Bohr SSR, Iversen JF, Kæstel-Hansen J, Kallenbach AS, Iversen L, Christensen SM, Hatzakis NS. Single-Molecule Study of Thermomyces lanuginosus Lipase in a Detergency Application System Reveals Diffusion Pattern Remodeling by Surfactants and Calcium. ACS APPLIED MATERIALS & INTERFACES 2021; 13:33704-33712. [PMID: 34235926 DOI: 10.1021/acsami.1c08809] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Lipases comprise one of the major enzyme classes in biotechnology with applications within, e.g., baking, brewing, biocatalysis, and the detergent industry. Understanding the mechanisms of lipase function and regulation is therefore important to facilitate the optimization of their function by protein engineering. Advances in single-molecule studies in model systems have provided deep mechanistic insights on lipase function, such as the existence of functional states, their dependence on regulatory cues, and their correlation to activity. However, it is unclear how these observations translate to enzyme behavior in applied settings. Here, single-molecule tracking of individual Thermomyces lanuginosus lipase (TLL) enzymes in a detergency application system allowed real-time direct observation of spatiotemporal localization, and thus diffusional behavior, of TLL enzymes on a lard substrate. Parallelized imaging of thousands of individual enzymes allowed us to observe directly the existence and quantify the abundance and interconversion kinetics between three diffusional states that we recently provided evidence to correlate with function. We observe redistribution of the enzyme's diffusional pattern at the lipid-water interface as well as variations in binding efficiency in response to surfactants and calcium, demonstrating that detergency effectors can drive the sampling of lipase functional states. Our single-molecule results combined with ensemble activity assays and enzyme surface binding efficiency readouts allowed us to deconvolute how application conditions can significantly alter protein functional dynamics and/or surface binding, both of which underpin enzyme performance. We anticipate that our results will inspire further efforts to decipher and integrate the dynamic nature of lipases, and other enzymes, in the design of new biotechnological solutions.
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Affiliation(s)
- Matias E Moses
- Novozymes A/S, Biologiens Vej 2, DK-2800 Kgs. Lyngby, Denmark
- Department of Chemistry & Nano-science Center, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark
| | - Philip M Lund
- Novozymes A/S, Biologiens Vej 2, DK-2800 Kgs. Lyngby, Denmark
- Department of Chemistry & Nano-science Center, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark
| | - Søren S-R Bohr
- Department of Chemistry & Nano-science Center, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark
| | - Josephine F Iversen
- Department of Chemistry & Nano-science Center, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark
| | - Jacob Kæstel-Hansen
- Department of Chemistry & Nano-science Center, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark
| | - Amalie S Kallenbach
- Department of Chemistry & Nano-science Center, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark
| | - Lars Iversen
- Novozymes A/S, Biologiens Vej 2, DK-2800 Kgs. Lyngby, Denmark
| | | | - Nikos S Hatzakis
- Department of Chemistry & Nano-science Center, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark
- Novo Nordisk Foundation Centre for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3B, DK-2200 Copenhagen N, Denmark
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20
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Ahmadi A, Till K, Backe PH, Blicher P, Diekmann R, Schüttpelz M, Glette K, Tørresen J, Bjørås M, Rowe AD, Dalhus B. Non-flipping DNA glycosylase AlkD scans DNA without formation of a stable interrogation complex. Commun Biol 2021; 4:876. [PMID: 34267321 PMCID: PMC8282808 DOI: 10.1038/s42003-021-02400-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2020] [Accepted: 06/25/2021] [Indexed: 11/09/2022] Open
Abstract
The multi-step base excision repair (BER) pathway is initiated by a set of enzymes, known as DNA glycosylases, able to scan DNA and detect modified bases among a vast number of normal bases. While DNA glycosylases in the BER pathway generally bend the DNA and flip damaged bases into lesion specific pockets, the HEAT-like repeat DNA glycosylase AlkD detects and excises bases without sequestering the base from the DNA helix. We show by single-molecule tracking experiments that AlkD scans DNA without forming a stable interrogation complex. This contrasts with previously studied repair enzymes that need to flip bases into lesion-recognition pockets and form stable interrogation complexes. Moreover, we show by design of a loss-of-function mutant that the bimodality in scanning observed for the structural homologue AlkF is due to a key structural differentiator between AlkD and AlkF; a positively charged β-hairpin able to protrude into the major groove of DNA.
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Affiliation(s)
- Arash Ahmadi
- Department of Medical Biochemistry, Institute for Clinical Medicine, University of Oslo, Oslo, Norway
| | - Katharina Till
- FOM Institute AMOLF, Science Park 104, Amsterdam, The Netherlands.,Biomolecular Photonics, Department of Physics, University of Bielefeld, Bielefeld, Germany
| | - Paul Hoff Backe
- Department of Medical Biochemistry, Institute for Clinical Medicine, University of Oslo, Oslo, Norway.,Department of Microbiology, Oslo University Hospital HF, Rikshospitalet and University of Oslo, Oslo, Norway
| | - Pernille Blicher
- Department of Medical Biochemistry, Institute for Clinical Medicine, University of Oslo, Oslo, Norway
| | - Robin Diekmann
- Biomolecular Photonics, Department of Physics, University of Bielefeld, Bielefeld, Germany
| | - Mark Schüttpelz
- Biomolecular Photonics, Department of Physics, University of Bielefeld, Bielefeld, Germany
| | - Kyrre Glette
- Department of Informatics, University of Oslo, Oslo, Norway
| | - Jim Tørresen
- Department of Informatics, University of Oslo, Oslo, Norway
| | - Magnar Bjørås
- Department of Microbiology, Oslo University Hospital HF, Rikshospitalet and University of Oslo, Oslo, Norway.,Department of Clinical and Molecular Medicine, Faculty of Medicine and Health Sciences, Norwegian University of Science and Technology (NTNU), Trondheim, Norway
| | - Alexander D Rowe
- Department of Medical Biochemistry, Institute for Clinical Medicine, University of Oslo, Oslo, Norway.,Department of Newborn Screening, Division of Child and Adolescent Medicine, Oslo University Hospital, Oslo, Norway
| | - Bjørn Dalhus
- Department of Medical Biochemistry, Institute for Clinical Medicine, University of Oslo, Oslo, Norway. .,Department of Microbiology, Oslo University Hospital HF, Rikshospitalet and University of Oslo, Oslo, Norway.
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21
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Negri A, Werbowy O, Wons E, Dersch S, Hinrichs R, Graumann PL, Mruk I. Regulator-dependent temporal dynamics of a restriction-modification system's gene expression upon entering new host cells: single-cell and population studies. Nucleic Acids Res 2021; 49:3826-3840. [PMID: 33744971 PMCID: PMC8053105 DOI: 10.1093/nar/gkab183] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2020] [Revised: 03/02/2021] [Accepted: 03/04/2021] [Indexed: 01/05/2023] Open
Abstract
Restriction-modification (R-M) systems represent a first line of defense against invasive DNAs, such as bacteriophage DNAs, and are widespread among bacteria and archaea. By acquiring a Type II R-M system via horizontal gene transfer, the new hosts generally become more resistant to phage infection, through the action of a restriction endonuclease (REase), which cleaves DNA at or near specific sequences. A modification methyltransferase (MTase) serves to protect the host genome against its cognate REase activity. The production of R-M system components upon entering a new host cell must be finely tuned to confer protective methylation before the REase acts, to avoid host genome damage. Some type II R-M systems rely on a third component, the controller (C) protein, which is a transcription factor that regulates the production of REase and/or MTase. Previous studies have suggested C protein effects on the dynamics of expression of an R-M system during its establishment in a new host cell. Here, we directly examine these effects. By fluorescently labelling REase and MTase, we demonstrate that lack of a C protein reduces the delay of REase production, to the point of being simultaneous with, or even preceding, production of the MTase. Single molecule tracking suggests that a REase and a MTase employ different strategies for their target search within host cells, with the MTase spending much more time diffusing in proximity to the nucleoid than does the REase. This difference may partially ameliorate the toxic effects of premature REase expression.
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Affiliation(s)
- Alessandro Negri
- Department of Microbiology, Faculty of Biology, University of Gdansk, Wita Stwosza 59, Gdansk 80-308, Poland
| | - Olesia Werbowy
- Department of Microbiology, Faculty of Biology, University of Gdansk, Wita Stwosza 59, Gdansk 80-308, Poland
| | - Ewa Wons
- Department of Microbiology, Faculty of Biology, University of Gdansk, Wita Stwosza 59, Gdansk 80-308, Poland
| | - Simon Dersch
- SYNMIKRO, LOEWE Center for Synthetic Microbiology, Marburg, Germany.,Department of Chemistry, Philipps Universität Marburg, Hans-Meerwein-Strasse 6, 35032 Marburg, Germany
| | - Rebecca Hinrichs
- SYNMIKRO, LOEWE Center for Synthetic Microbiology, Marburg, Germany.,Department of Chemistry, Philipps Universität Marburg, Hans-Meerwein-Strasse 6, 35032 Marburg, Germany
| | - Peter L Graumann
- SYNMIKRO, LOEWE Center for Synthetic Microbiology, Marburg, Germany.,Department of Chemistry, Philipps Universität Marburg, Hans-Meerwein-Strasse 6, 35032 Marburg, Germany
| | - Iwona Mruk
- Department of Microbiology, Faculty of Biology, University of Gdansk, Wita Stwosza 59, Gdansk 80-308, Poland
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22
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Bigman LS, Greenblatt HM, Levy Y. What Are the Molecular Requirements for Protein Sliding along DNA? J Phys Chem B 2021; 125:3119-3131. [PMID: 33754737 PMCID: PMC8041311 DOI: 10.1021/acs.jpcb.1c00757] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
![]()
DNA-binding proteins rely on linear
diffusion along the longitudinal
DNA axis, supported by their nonspecific electrostatic affinity for
DNA, to search for their target recognition sites. One may therefore
expect that the ability to engage in linear diffusion along DNA is
universal to all DNA-binding proteins, with the detailed biophysical
characteristics of that diffusion differing between proteins depending
on their structures and functions. One key question is whether the
linear diffusion mechanism is defined by translation coupled with
rotation, a mechanism that is often termed sliding. We conduct coarse-grained
and atomistic molecular dynamics simulations to investigate the minimal
requirements for protein sliding along DNA. We show that coupling,
while widespread, is not universal. DNA-binding proteins that slide
along DNA transition to uncoupled translation–rotation (i.e.,
hopping) at higher salt concentrations. Furthermore, and consistently
with experimental reports, we find that the sliding mechanism is the
less dominant mechanism for some DNA-binding proteins, even at low
salt concentrations. In particular, the toroidal PCNA protein is shown
to follow the hopping rather than the sliding mechanism.
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Affiliation(s)
- Lavi S Bigman
- Department of Chemical and Structural Biology, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Harry M Greenblatt
- Department of Chemical and Structural Biology, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Yaakov Levy
- Department of Chemical and Structural Biology, Weizmann Institute of Science, Rehovot 76100, Israel
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23
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Martini L, Brameyer S, Hoyer E, Jung K, Gerland U. Dynamics of chromosomal target search by a membrane-integrated one-component receptor. PLoS Comput Biol 2021; 17:e1008680. [PMID: 33539417 PMCID: PMC7888679 DOI: 10.1371/journal.pcbi.1008680] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2020] [Revised: 02/17/2021] [Accepted: 01/07/2021] [Indexed: 12/03/2022] Open
Abstract
Membrane proteins account for about one third of the cellular proteome, but it is still unclear how dynamic they are and how they establish functional contacts with cytoplasmic interaction partners. Here, we consider a membrane-integrated one-component receptor that also acts as a transcriptional activator, and analyze how it kinetically locates its specific binding site on the genome. We focus on the case of CadC, the pH receptor of the acid stress response Cad system in E. coli. CadC is a prime example of a one-component signaling protein that directly binds to its cognate target site on the chromosome to regulate transcription. We combined fluorescence microscopy experiments, mathematical analysis, and kinetic Monte Carlo simulations to probe this target search process. Using fluorescently labeled CadC, we measured the time from activation of the receptor until successful binding to the DNA in single cells, exploiting that stable receptor-DNA complexes are visible as fluorescent spots. Our experimental data indicate that CadC is highly mobile in the membrane and finds its target by a 2D diffusion and capture mechanism. DNA mobility is constrained due to the overall chromosome organization, but a labeled DNA locus in the vicinity of the target site appears sufficiently mobile to randomly come close to the membrane. Relocation of the DNA target site to a distant position on the chromosome had almost no effect on the mean search time, which was between four and five minutes in either case. However, a mutant strain with two binding sites displayed a mean search time that was reduced by about a factor of two. This behavior is consistent with simulations of a coarse-grained lattice model for the coupled dynamics of DNA within a cell volume and proteins on its surface. The model also rationalizes the experimentally determined distribution of search times. Overall our findings reveal that DNA target search does not present a much bigger kinetic challenge for membrane-integrated proteins than for cytoplasmic proteins. More generally, diffusion and capture mechanisms may be sufficient for bacterial membrane proteins to establish functional contacts with cytoplasmic targets. Adaptation to changing environments is vital to bacteria and is enabled by sophisticated signal transduction systems. While signal transduction by two-component systems is well studied, the signal transduction of membrane-integrated one-component systems, where one protein performs both sensing and response regulation, are insufficiently understood. How can a membrane-integrated protein bind to specific sites on the genome to regulate transcription? Here, we study the kinetics of this process, which involves both protein diffusion within the membrane and conformational fluctuations of the genomic DNA. A well-suited model system for this question is CadC, the signaling protein of the E. coli Cad system involved in pH stress response. Fluorescently labeled CadC forms visible spots in single cells upon stable DNA-binding, marking the end of the protein-DNA search process. Moreover, the start of the search is triggered by a medium shift exposing cells to pH stress. We probe the underlying mechanism by varying the number and position of DNA target sites. We combine these experiments with mathematical analysis and kinetic Monte Carlo simulations of lattice models for the search process. Our results suggest that CadC diffusion in the membrane is pivotal for this search, while the DNA target site is just mobile enough to reach the membrane.
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Affiliation(s)
- Linda Martini
- Physics of Complex Biosystems, Technical University of Munich, Garching, Germany
| | - Sophie Brameyer
- Microbiology, Ludwig-Maximilians-University Munich, Martinsried, Germany
| | - Elisabeth Hoyer
- Microbiology, Ludwig-Maximilians-University Munich, Martinsried, Germany
| | - Kirsten Jung
- Microbiology, Ludwig-Maximilians-University Munich, Martinsried, Germany
- * E-mail: (KJ); (UG)
| | - Ulrich Gerland
- Physics of Complex Biosystems, Technical University of Munich, Garching, Germany
- * E-mail: (KJ); (UG)
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24
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Jana T, Brodsky S, Barkai N. Speed-Specificity Trade-Offs in the Transcription Factors Search for Their Genomic Binding Sites. Trends Genet 2021; 37:421-432. [PMID: 33414013 DOI: 10.1016/j.tig.2020.12.001] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2020] [Revised: 12/04/2020] [Accepted: 12/07/2020] [Indexed: 12/17/2022]
Abstract
Transcription factors (TFs) regulate gene expression by binding DNA sequences recognized by their DNA-binding domains (DBDs). DBD-recognized motifs are short and highly abundant in genomes. The ability of TFs to bind a specific subset of motif-containing sites, and to do so rapidly upon activation, is fundamental for gene expression in all eukaryotes. Despite extensive interest, our understanding of the TF-target search process is fragmented; although binding specificity and detection speed are two facets of this same process, trade-offs between them are rarely addressed. In this opinion article, we discuss potential speed-specificity trade-offs in the context of existing models. We further discuss the recently described 'distributed specificity' paradigm, suggesting that intrinsically disordered regions (IDRs) promote specificity while reducing the TF-target search time.
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Affiliation(s)
- Tamar Jana
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Sagie Brodsky
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Naama Barkai
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel.
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25
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D'Acunto M. Protein-DNA target search relies on quantum walk. Biosystems 2020; 201:104340. [PMID: 33387562 DOI: 10.1016/j.biosystems.2020.104340] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2020] [Revised: 12/21/2020] [Accepted: 12/21/2020] [Indexed: 01/25/2023]
Abstract
Protein-DNA interactions play a fundamental role in all life systems. A critical issue of such interactions is given by the strategy of protein search for specific targets on DNA. The mechanisms by which the protein are able to find relatively small cognate sequences, typically 15-20 base pairs (bps) for repressors, and 4-6 bps for restriction enzymes among the millions of bp of non-specific chromosomal DNA have hardly engaged researchers for decades. Recent experimental studies have generated new insights on the basic processes of protein-DNA interactions evidencing the underlying complex dynamic phenomena involved, which combine three-dimensional and one-dimensional motion along the DNA chain. It has been demonstrated that protein molecules have an extraordinary ability to find the target very quickly on the DNA chain, in some cases, with two orders of magnitude faster than the diffusion limit. This unique property of protein-DNA search mechanism is known as facilitated diffusion. Several theoretical mechanisms have been suggested to describe the origin of facilitated diffusion. However, none of such models currently has the ability to fully describe the protein search strategy. In this paper, we suggest that the ability of proteins to identify consensus sequences on DNA is based on the entanglement of π-π electrons between DNA nucleotides and protein amino acids. The π-π entanglement is based on Quantum Walk (QW), through Coin-position entanglement (CPE). First, the protein identifies a dimer belonging to the consensus sequence, and localize a π on such dimer, hence, the other π electron scans the DNA chain until the sequence is identified. Focusing on the example of recognition of consensus sequences of EcoRV or EcoRI, we will describe the quantum features of QW on protein-DNA complexes during the search strategy, such as walker quadratic spreading on a coherent superposition of different vertices and environment-supported long-time survival probability of the walker. We will employ both discrete- or continuous-time versions of QW. Biased and unbiased classical Random Walk (CRW) have been used for a long time to describe the Protein-DNA search strategy. QW, the quantum version of CRW, has been widely studied for its applications in quantum information applications. In our biological application, the walker (the protein) resides at a vertex in a graph (the DNA structural topology). Differently to CRW, where the walker moves randomly, the quantum walker can hop along the edges in the graph to reach other vertices entering coherently a superposition across different vertices spreading quadratically faster than CRW analogous evidencing the typical speed up features of the QW. When applied to a protein-DNA target search problem, QW gives the possibility to achieve the experimental diffusional motion of proteins over diffusion classical limits experienced along DNA chains exploiting quantum features such as CPE and long-time survival probability supported by the environment. In turn, we come to the conclusion that, under quantum picture, the protein search strategy does not distinguish between one-dimensional (1D) and three-dimensional (3D) cases.
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Affiliation(s)
- Mario D'Acunto
- CNR-IBF, Consiglio Nazionale delle Ricerche, Istituto di Biofisica, Via Moruzzi 1, 56124, Pisa, Italy.
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Graha Subekti DR, Kamagata K. The disordered DNA-binding domain of p53 is indispensable for forming an encounter complex to and jumping along DNA. Biochem Biophys Res Commun 2020; 534:21-26. [PMID: 33310183 DOI: 10.1016/j.bbrc.2020.12.006] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2020] [Accepted: 12/01/2020] [Indexed: 01/18/2023]
Abstract
The tumor suppressor p53 utilizes a facilitated diffusion mechanism to search for and bind to target DNA sequences. Sub-millisecond single-molecule fluorescence tracking demonstrated that p53 forms a short-lived encounter complex to DNA then converts to the long-lived complex that can move and jump along DNA during the target search. To reveal the role of each DNA-binding domain of p53 in these processes, we investigated two p53 mutants lacking either of two DNA-binding domains; structured core and disordered C-terminal domains, using sub-millisecond single-molecule fluorescence microscopy. We found that the C-terminal domain is required for the encounter complex formation and conversion to the long-lived complex. The long-lived complex is stabilized by the core domain as well as the C-terminal domain. Furthermore, only the C-terminal domain participates in the jump of p53 along DNA at a high salt concentration. We propose that the flexible C-terminal domain of p53 is twined around DNA, which can form the encounter complex, convert to the long-lived complex, and enable p53 to land on DNA after the jump.
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Affiliation(s)
- Dwiky Rendra Graha Subekti
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai, 980-8577, Japan; Department of Chemistry, Graduate School of Science, Tohoku University, Sendai, 980-8578, Japan
| | - Kiyoto Kamagata
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai, 980-8577, Japan; Department of Chemistry, Graduate School of Science, Tohoku University, Sendai, 980-8578, Japan.
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27
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Yadav I, Basak R, Yan P, van Kan JA, Arluison V, van der Maarel JRC. Role of Internal DNA Motion on the Mobility of a Nucleoid-Associated Protein. J Phys Chem Lett 2020; 11:8424-8429. [PMID: 32930601 DOI: 10.1021/acs.jpclett.0c02251] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Protein transport on DNA is at the core of the machinery of life. Here we investigated the influence of DNA internal motion on the mobility of Hfq, which is involved in several aspects of nucleic acid metabolism and is one of the nucleoid-associated proteins that shape the bacterial chromosome. Fluorescence microscopy was used to follow Hfq on double-stranded DNA that was stretched by confinement to a channel with a diameter of 125 nm. The protein mobility shows a strong dependence on the internal motion of DNA in that slower motion results in faster protein diffusion. A model of released diffusion is proposed that is based on three-dimensional diffusion through the interior of the DNA coil interspersed by periods in which the protein is immobilized in a bound state. We surmise that the coupling between DNA internal motion and protein mobility has important implications for DNA metabolism and protein-binding-related regulation of gene expression.
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Affiliation(s)
- Indresh Yadav
- Department of Physics, National University of Singapore, Singapore 117542
| | - Rajib Basak
- Department of Physics, National University of Singapore, Singapore 117542
| | - Peiyan Yan
- Department of Physics, National University of Singapore, Singapore 117542
| | - Jeroen A van Kan
- Department of Physics, National University of Singapore, Singapore 117542
| | - Véronique Arluison
- Université de Paris, UFR SDV, 75006 Paris, France
- Laboratoire Léon Brillouin, CEA, CNRS, Université Paris Saclay, 91191 Gif-sur-Yvette, France
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Target search and recognition mechanisms of glycosylase AlkD revealed by scanning FRET-FCS and Markov state models. Proc Natl Acad Sci U S A 2020; 117:21889-21895. [PMID: 32820079 PMCID: PMC7486748 DOI: 10.1073/pnas.2002971117] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
DNA glycosylase repairs DNA damage to maintain the genome integrity, and thus it is essential for the survival of all organisms. However, it remains a long-standing puzzle how glycosylase diffuses along the genomic DNA to locate the sparse and aberrant lesion sites efficiently and accurately in the genome containing numerous base pairs. Previously, only the high-speed–low-accuracy search mode has been characterized experimentally, while the low-speed–high-accuracy mode is undetectable. Here, we observed the low-speed mode of glycosylase AlkD translocating, and further dissected its molecular mechanisms. To achieve this, we developed an integrated platform by combining scanning FRET-FCS with Markov state model. We expect that this platform can be widely applied to investigate other glycosylases and DNA-binding proteins. DNA glycosylase is responsible for repairing DNA damage to maintain the genome stability and integrity. However, how glycosylase can efficiently and accurately recognize DNA lesions across the enormous DNA genome remains elusive. It has been hypothesized that glycosylase translocates along the DNA by alternating between a fast but low-accuracy diffusion mode and a slow but high-accuracy mode when searching for DNA lesions. However, the slow mode has not been successfully characterized due to the limitation in the spatial and temporal resolutions of current experimental techniques. Using a newly developed scanning fluorescence resonance energy transfer (FRET)–fluorescence correlation spectroscopy (FCS) platform, we were able to observe both slow and fast modes of glycosylase AlkD translocating on double-stranded DNA (dsDNA), reaching the temporal resolution of microsecond and spatial resolution of subnanometer. The underlying molecular mechanism of the slow mode was further elucidated by Markov state model built from extensive all-atom molecular dynamics simulations. We found that in the slow mode, AlkD follows an asymmetric diffusion pathway, i.e., rotation followed by translation. Furthermore, the essential role of Y27 in AlkD diffusion dynamics was identified both experimentally and computationally. Our results provided mechanistic insights on how conformational dynamics of AlkD–dsDNA complex coordinate different diffusion modes to accomplish the search for DNA lesions with high efficiency and accuracy. We anticipate that the mechanism adopted by AlkD to search for DNA lesions could be a general one utilized by other glycosylases and DNA binding proteins.
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29
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Transient binding and jumping dynamics of p53 along DNA revealed by sub-millisecond resolved single-molecule fluorescence tracking. Sci Rep 2020; 10:13697. [PMID: 32792545 PMCID: PMC7426816 DOI: 10.1038/s41598-020-70763-y] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2020] [Accepted: 08/04/2020] [Indexed: 12/14/2022] Open
Abstract
Characterization of the target search dynamics of DNA-binding proteins along DNA has been hampered by the time resolution of a standard single-molecule fluorescence microscopy. Here, we achieved the time resolution of 0.5 ms in the fluorescence microscopy measurements by optimizing the fluorescence excitation based on critical angle illumination and by utilizing the time delay integration mode of the electron-multiplying charge coupled device. We characterized the target search dynamics of the tumor suppressor p53 along nonspecific DNA at physiological salt concentrations. We identified a short-lived encounter intermediate before the formation of the long-lived p53–DNA complex. Both the jumps and the one-dimensional diffusion of p53 along DNA were accelerated at higher salt concentrations, suggesting the rotation-uncoupled movement of p53 along DNA grooves and conformational changes in the p53/DNA complex. This method can be used to clarify the unresolved dynamics of DNA-binding proteins previously hidden by time averaging.
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30
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Kamagata K, Itoh Y, Subekti DRG. How p53 Molecules Solve the Target DNA Search Problem: A Review. Int J Mol Sci 2020; 21:E1031. [PMID: 32033163 PMCID: PMC7037437 DOI: 10.3390/ijms21031031] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2019] [Revised: 01/11/2020] [Accepted: 01/31/2020] [Indexed: 12/14/2022] Open
Abstract
Interactions between DNA and DNA-binding proteins play an important role in many essential cellular processes. A key function of the DNA-binding protein p53 is to search for and bind to target sites incorporated in genomic DNA, which triggers transcriptional regulation. How do p53 molecules achieve "rapid" and "accurate" target search in living cells? The search dynamics of p53 were expected to include 3D diffusion in solution, 1D diffusion along DNA, and intersegmental transfer between two different DNA strands. Single-molecule fluorescence microscopy enabled the tracking of p53 molecules on DNA and the characterization of these dynamics quantitatively. Recent intensive single-molecule studies of p53 succeeded in revealing each of these search dynamics. Here, we review these studies and discuss the target search mechanisms of p53.
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Affiliation(s)
- Kiyoto Kamagata
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai 980-8577, Japan; (Y.I.); (D.R.G.S.)
- Department of Chemistry, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan
| | - Yuji Itoh
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai 980-8577, Japan; (Y.I.); (D.R.G.S.)
- Genome Dynamics Laboratory, National Institute of Genetics, Mishima, Shizuoka 411-8540, Japan
| | - Dwiky Rendra Graha Subekti
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai 980-8577, Japan; (Y.I.); (D.R.G.S.)
- Department of Chemistry, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan
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31
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Cheon NY, Kim HS, Yeo JE, Schärer OD, Lee JY. Single-molecule visualization reveals the damage search mechanism for the human NER protein XPC-RAD23B. Nucleic Acids Res 2019; 47:8337-8347. [PMID: 31372632 PMCID: PMC6895271 DOI: 10.1093/nar/gkz629] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2019] [Revised: 07/05/2019] [Accepted: 07/12/2019] [Indexed: 11/14/2022] Open
Abstract
DNA repair is critical for maintaining genomic integrity. Finding DNA lesions initiates the entire repair process. In human nucleotide excision repair (NER), XPC-RAD23B recognizes DNA lesions and recruits downstream factors. Although previous studies revealed the molecular features of damage identification by the yeast orthologs Rad4-Rad23, the dynamic mechanisms by which human XPC-RAD23B recognizes DNA defects have remained elusive. Here, we directly visualized the motion of XPC-RAD23B on undamaged and lesion-containing DNA using high-throughput single-molecule imaging. We observed three types of one-dimensional motion of XPC-RAD23B along DNA: diffusive, immobile and constrained. We found that consecutive AT-tracks led to increase in proteins with constrained motion. The diffusion coefficient dramatically increased according to ionic strength, suggesting that XPC-RAD23B diffuses along DNA via hopping, allowing XPC-RAD23B to bypass protein obstacles during the search for DNA damage. We also examined how XPC-RAD23B identifies cyclobutane pyrimidine dimers (CPDs) during diffusion. XPC-RAD23B makes futile attempts to bind to CPDs, consistent with low CPD recognition efficiency. Moreover, XPC-RAD23B binds CPDs in biphasic states, stable for lesion recognition and transient for lesion interrogation. Taken together, our results provide new insight into how XPC-RAD23B searches for DNA lesions in billions of base pairs in human genome.
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Affiliation(s)
- Na Young Cheon
- School of Life Sciences, Ulsan National Institute of Science and Technology, Ulsan 44919, Republic of Korea
| | - Hyun-Suk Kim
- Center for Genomic Integrity, Institute for Basic Science, Ulsan 44919, Republic of Korea
| | - Jung-Eun Yeo
- Center for Genomic Integrity, Institute for Basic Science, Ulsan 44919, Republic of Korea
| | - Orlando D Schärer
- School of Life Sciences, Ulsan National Institute of Science and Technology, Ulsan 44919, Republic of Korea.,Center for Genomic Integrity, Institute for Basic Science, Ulsan 44919, Republic of Korea
| | - Ja Yil Lee
- School of Life Sciences, Ulsan National Institute of Science and Technology, Ulsan 44919, Republic of Korea.,Center for Genomic Integrity, Institute for Basic Science, Ulsan 44919, Republic of Korea
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32
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Ahmadi A, Till K, Hafting Y, Schüttpelz M, Bjørås M, Glette K, Tørresen J, Rowe AD, Dalhus B. Additive manufacturing of laminar flow cells for single-molecule experiments. Sci Rep 2019; 9:16784. [PMID: 31727950 PMCID: PMC6856346 DOI: 10.1038/s41598-019-53151-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2019] [Accepted: 10/22/2019] [Indexed: 11/08/2022] Open
Abstract
A microfluidic laminar flow cell (LFC) forms an indispensable component in single-molecule experiments, enabling different substances to be delivered directly to the point under observation and thereby tightly controlling the biochemical environment immediately surrounding single molecules. Despite substantial progress in the production of such components, the process remains relatively inefficient, inaccurate and time-consuming. Here we address challenges and limitations in the routines, materials and the designs that have been commonly employed in the field, and introduce a new generation of LFCs designed for single-molecule experiments and assembled using additive manufacturing. We present single- and multi-channel, as well as reservoir-based LFCs produced by 3D printing to perform single-molecule experiments. Using these flow cells along with optical tweezers, we show compatibility with single-molecule experiments including the isolation and manipulation of single DNA molecules either attached to the surface of a coverslip or as freely movable DNA dumbbells, as well as direct observation of protein-DNA interactions. Using additive manufacturing to produce LFCs with versatility of design and ease of production allow experimentalists to optimize the flow cells to their biological experiments and provide considerable potential for performing multi-component single-molecule experiments.
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Affiliation(s)
- Arash Ahmadi
- Department of Medical Biochemistry, Institute for Clinical Medicine, University of Oslo, Oslo, Norway
| | - Katharina Till
- Biomolecular Photonics, Department of Physics, University of Bielefeld, Bielefeld, Germany
| | - Yngve Hafting
- Department of Informatics, University of Oslo, Oslo, Norway
| | - Mark Schüttpelz
- Biomolecular Photonics, Department of Physics, University of Bielefeld, Bielefeld, Germany
| | - Magnar Bjørås
- Department of Clinical and Molecular Medicine, Faculty of Medicine and Health Sciences, Norwegian University of Science and Technology (NTNU), Trondheim, Norway
- Department of Microbiology, Oslo University Hospital HF, Rikshospitalet and University of Oslo, Oslo, Norway
| | - Kyrre Glette
- Department of Informatics, University of Oslo, Oslo, Norway
| | - Jim Tørresen
- Department of Informatics, University of Oslo, Oslo, Norway
| | - Alexander D Rowe
- Department of Medical Biochemistry, Institute for Clinical Medicine, University of Oslo, Oslo, Norway.
- Department of Newborn Screening, Division of Child and Adolescent Medicine, Oslo University Hospital, Oslo, Norway.
| | - Bjørn Dalhus
- Department of Medical Biochemistry, Institute for Clinical Medicine, University of Oslo, Oslo, Norway.
- Department of Microbiology, Oslo University Hospital HF, Rikshospitalet and University of Oslo, Oslo, Norway.
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33
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Velmurugu Y, Vivas P, Connolly M, Kuznetsov SV, Rice PA, Ansari A. Two-step interrogation then recognition of DNA binding site by Integration Host Factor: an architectural DNA-bending protein. Nucleic Acids Res 2019; 46:1741-1755. [PMID: 29267885 PMCID: PMC5829579 DOI: 10.1093/nar/gkx1215] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2016] [Accepted: 12/08/2017] [Indexed: 12/23/2022] Open
Abstract
The dynamics and mechanism of how site-specific DNA-bending proteins initially interrogate potential binding sites prior to recognition have remained elusive for most systems. Here we present these dynamics for Integration Host factor (IHF), a nucleoid-associated architectural protein, using a μs-resolved T-jump approach. Our studies show two distinct DNA-bending steps during site recognition by IHF. While the faster (∼100 μs) step is unaffected by changes in DNA or protein sequence that alter affinity by >100-fold, the slower (1–10 ms) step is accelerated ∼5-fold when mismatches are introduced at DNA sites that are sharply kinked in the specific complex. The amplitudes of the fast phase increase when the specific complex is destabilized and decrease with increasing [salt], which increases specificity. Taken together, these results indicate that the fast phase is non-specific DNA bending while the slow phase, which responds only to changes in DNA flexibility at the kink sites, is specific DNA kinking during site recognition. Notably, the timescales for the fast phase overlap with one-dimensional diffusion times measured for several proteins on DNA, suggesting that these dynamics reflect partial DNA bending during interrogation of potential binding sites by IHF as it scans DNA.
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Affiliation(s)
- Yogambigai Velmurugu
- Department of Physics, University of Illinois at Chicago, Chicago, IL 60607, USA
| | - Paula Vivas
- Department of Physics, University of Illinois at Chicago, Chicago, IL 60607, USA
| | - Mitchell Connolly
- Department of Physics, University of Illinois at Chicago, Chicago, IL 60607, USA
| | - Serguei V Kuznetsov
- Department of Physics, University of Illinois at Chicago, Chicago, IL 60607, USA
| | - Phoebe A Rice
- Department of Biochemistry & Molecular Biology, University of Chicago, Chicago, IL 60637, USA
| | - Anjum Ansari
- Department of Physics, University of Illinois at Chicago, Chicago, IL 60607, USA.,Department of Bioengineering, University of Illinois at Chicago, Chicago, IL 60607, USA
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34
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Chakraborty S, Steinbach PJ, Paul D, Mu H, Broyde S, Min JH, Ansari A. Enhanced spontaneous DNA twisting/bending fluctuations unveiled by fluorescence lifetime distributions promote mismatch recognition by the Rad4 nucleotide excision repair complex. Nucleic Acids Res 2019; 46:1240-1255. [PMID: 29267981 PMCID: PMC5815138 DOI: 10.1093/nar/gkx1216] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2017] [Accepted: 12/12/2017] [Indexed: 12/15/2022] Open
Abstract
Rad4/XPC recognizes diverse DNA lesions including ultraviolet-photolesions and carcinogen-DNA adducts, initiating nucleotide excision repair. Studies have suggested that Rad4/XPC senses lesion-induced helix-destabilization to flip out nucleotides from damaged DNA sites. However, characterizing how DNA deformability and/or distortions impact recognition has been challenging. Here, using fluorescence lifetime measurements empowered by a maximum entropy algorithm, we mapped the conformational heterogeneities of artificially destabilized mismatched DNA substrates of varying Rad4-binding specificities. The conformational distributions, as probed by FRET between a cytosine-analog pair exquisitely sensitive to DNA twisting/bending, reveal a direct connection between intrinsic DNA deformability and Rad4 recognition. High-specificity CCC/CCC mismatch, free in solution, sampled a strikingly broad range of conformations from B-DNA-like to highly distorted conformations that resembled those observed with Rad4 bound; the extent of these distortions increased with bound Rad4 and with temperature. Conversely, the non-specific TAT/TAT mismatch had a homogeneous, B-DNA-like conformation. Molecular dynamics simulations also revealed a wide distribution of conformations for CCC/CCC, complementing experimental findings. We propose that intrinsic deformability promotes Rad4 damage recognition, perhaps by stalling a diffusing protein and/or facilitating ‘conformational capture’ of pre-distorted damaged sites. Surprisingly, even mismatched DNA specifically bound to Rad4 remains highly dynamic, a feature that may reflect the versatility of Rad4/XPC to recognize many structurally dissimilar lesions.
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Affiliation(s)
- Sagnik Chakraborty
- Department of Physics, University of Illinois at Chicago, Chicago, IL 60607, USA
| | - Peter J Steinbach
- Center for Molecular Modeling, Center for Information Technology, National Institutes of Health, Bethesda, MD 20892, USA
| | - Debamita Paul
- Department of Chemistry, University of Illinois at Chicago, Chicago, IL 60607, USA
| | - Hong Mu
- Department of Biology, New York University, New York, NY 10003, USA
| | - Suse Broyde
- Department of Biology, New York University, New York, NY 10003, USA
| | - Jung-Hyun Min
- Department of Chemistry, University of Illinois at Chicago, Chicago, IL 60607, USA
| | - Anjum Ansari
- Department of Physics, University of Illinois at Chicago, Chicago, IL 60607, USA.,Department of Bioengineering, University of Illinois at Chicago, Chicago, IL 60607, USA
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35
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Piatt SC, Loparo JJ, Price AC. The Role of Noncognate Sites in the 1D Search Mechanism of EcoRI. Biophys J 2019; 116:2367-2377. [PMID: 31113551 PMCID: PMC6588823 DOI: 10.1016/j.bpj.2019.04.035] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2018] [Revised: 04/18/2019] [Accepted: 04/29/2019] [Indexed: 02/02/2023] Open
Abstract
A one-dimensional (1D) search is an essential step in DNA target recognition. Theoretical studies have suggested that the sequence dependence of 1D diffusion can help resolve the competing demands of a fast search and high target affinity, a conflict known as the speed-selectivity paradox. The resolution requires that the diffusion energy landscape is correlated with the underlying specific binding energies. In this work, we report observations of a 1D search by quantum dot-labeled EcoRI. Our data supports the view that proteins search DNA via rotation-coupled sliding over a corrugated energy landscape. We observed that whereas EcoRI primarily slides along DNA at low salt concentrations, at higher concentrations, its diffusion is a combination of sliding and hopping. We also observed long-lived pauses at genomic star sites, which differ by a single nucleotide from the target sequence. To reconcile these observations with prior biochemical and structural data, we propose a model of search in which the protein slides over a sequence-independent energy landscape during fast search but rapidly interconverts with a "hemispecific" binding mode in which a half site is probed. This half site interaction stabilizes the transition to a fully specific mode of binding, which can then lead to target recognition.
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Affiliation(s)
- Sadie C Piatt
- Department of Chemistry and Physics, Emmanuel College, Boston, Massachusetts
| | - Joseph J Loparo
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts.
| | - Allen C Price
- Department of Chemistry and Physics, Emmanuel College, Boston, Massachusetts.
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36
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Sokolowski TR, Paijmans J, Bossen L, Miedema T, Wehrens M, Becker NB, Kaizu K, Takahashi K, Dogterom M, Ten Wolde PR. eGFRD in all dimensions. J Chem Phys 2019; 150:054108. [PMID: 30736681 DOI: 10.1063/1.5064867] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Biochemical reactions often occur at low copy numbers but at once in crowded and diverse environments. Space and stochasticity therefore play an essential role in biochemical networks. Spatial-stochastic simulations have become a prominent tool for understanding how stochasticity at the microscopic level influences the macroscopic behavior of such systems. While particle-based models guarantee the level of detail necessary to accurately describe the microscopic dynamics at very low copy numbers, the algorithms used to simulate them typically imply trade-offs between computational efficiency and biochemical accuracy. eGFRD (enhanced Green's Function Reaction Dynamics) is an exact algorithm that evades such trade-offs by partitioning the N-particle system into M ≤ N analytically tractable one- and two-particle systems; the analytical solutions (Green's functions) then are used to implement an event-driven particle-based scheme that allows particles to make large jumps in time and space while retaining access to their state variables at arbitrary simulation times. Here we present "eGFRD2," a new eGFRD version that implements the principle of eGFRD in all dimensions, thus enabling efficient particle-based simulation of biochemical reaction-diffusion processes in the 3D cytoplasm, on 2D planes representing membranes, and on 1D elongated cylinders representative of, e.g., cytoskeletal tracks or DNA; in 1D, it also incorporates convective motion used to model active transport. We find that, for low particle densities, eGFRD2 is up to 6 orders of magnitude faster than conventional Brownian dynamics. We exemplify the capabilities of eGFRD2 by simulating an idealized model of Pom1 gradient formation, which involves 3D diffusion, active transport on microtubules, and autophosphorylation on the membrane, confirming recent experimental and theoretical results on this system to hold under genuinely stochastic conditions.
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Affiliation(s)
| | - Joris Paijmans
- FOM Institute AMOLF, Science Park 104, 1098 XG Amsterdam, The Netherlands
| | - Laurens Bossen
- FOM Institute AMOLF, Science Park 104, 1098 XG Amsterdam, The Netherlands
| | - Thomas Miedema
- FOM Institute AMOLF, Science Park 104, 1098 XG Amsterdam, The Netherlands
| | - Martijn Wehrens
- FOM Institute AMOLF, Science Park 104, 1098 XG Amsterdam, The Netherlands
| | - Nils B Becker
- FOM Institute AMOLF, Science Park 104, 1098 XG Amsterdam, The Netherlands
| | - Kazunari Kaizu
- Center for Biosystems Dynamics Research (BDR), RIKEN, 6-2-3 Furuedai, Suita, Osaka 565-0874, Japan
| | - Koichi Takahashi
- Center for Biosystems Dynamics Research (BDR), RIKEN, 6-2-3 Furuedai, Suita, Osaka 565-0874, Japan
| | - Marileen Dogterom
- FOM Institute AMOLF, Science Park 104, 1098 XG Amsterdam, The Netherlands
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37
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Breaking the speed limit with multimode fast scanning of DNA by Endonuclease V. Nat Commun 2018; 9:5381. [PMID: 30568191 PMCID: PMC6300609 DOI: 10.1038/s41467-018-07797-4] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2018] [Accepted: 11/27/2018] [Indexed: 01/04/2023] Open
Abstract
In order to preserve genomic stability, cells rely on various repair pathways for removing DNA damage. The mechanisms how enzymes scan DNA and recognize their target sites are incompletely understood. Here, by using high-localization precision microscopy along with 133 Hz high sampling rate, we have recorded EndoV and OGG1 interacting with 12-kbp elongated λ-DNA in an optical trap. EndoV switches between three distinct scanning modes, each with a clear range of activation energy barriers. These results concur with average diffusion rate and occupancy of states determined by a hidden Markov model, allowing us to infer that EndoV confinement occurs when the intercalating wedge motif is involved in rigorous probing of the DNA, while highly mobile EndoV may disengage from a strictly 1D helical diffusion mode and hop along the DNA. This makes EndoV the first example of a monomeric, single-conformation and single-binding-site protein demonstrating the ability to switch between three scanning modes. How DNA repair proteins locate their target sites on DNA is still a matter of debate. Here the authors characterize by single-molecule fluorescence imaging the modes of scanning adopted by bacterial endonuclease V as it moves along linear DNA tracks.
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38
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Frederickx W, Rocha S, Fujita Y, Kennes K, De Keersmaecker H, De Feyter S, Uji-I H, Vanderlinden W. Orthogonal Probing of Single-Molecule Heterogeneity by Correlative Fluorescence and Force Microscopy. ACS NANO 2018; 12:168-177. [PMID: 29257876 DOI: 10.1021/acsnano.7b05405] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Correlative imaging by fluorescence and force microscopy is an emerging technology to acquire orthogonal information at the nanoscale. Whereas atomic force microscopy excels at resolving the envelope structure of nanoscale specimens, fluorescence microscopy can detect specific molecular labels, which enables the unambiguous recognition of molecules in a complex assembly. Whereas correlative imaging at the micrometer scale has been established, it remains challenging to push the technology to the single-molecule level. Here, we used an integrated setup to systematically evaluate the factors that influence the quality of correlative fluorescence and force microscopy. Optimized data processing to ensure accurate drift correction and high localization precision results in image registration accuracies of ∼25 nm on organic fluorophores, which represents a 2-fold improvement over the state of the art in correlative fluorescence and force microscopy. Furthermore, we could extend the Atto532 fluorophore bleaching time ∼2-fold, by chemical modification of the supporting mica surface. In turn, this enables probing the composition of macromolecular complexes by stepwise photobleaching with high confidence. We demonstrate the performance of our method by resolving the stoichiometry of molecular subpopulations in a heterogeneous EcoRV-DNA nucleoprotein ensemble.
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Affiliation(s)
- Wout Frederickx
- Department of Chemistry, Division of Molecular Imaging and Photonics, KU Leuven-University of Leuven , Celestijnenlaan 200F, B-3001, Leuven, Belgium
| | - Susana Rocha
- Department of Chemistry, Division of Molecular Imaging and Photonics, KU Leuven-University of Leuven , Celestijnenlaan 200F, B-3001, Leuven, Belgium
| | - Yasuhiko Fujita
- Department of Chemistry, Division of Molecular Imaging and Photonics, KU Leuven-University of Leuven , Celestijnenlaan 200F, B-3001, Leuven, Belgium
| | - Koen Kennes
- Department of Chemistry, Division of Molecular Imaging and Photonics, KU Leuven-University of Leuven , Celestijnenlaan 200F, B-3001, Leuven, Belgium
| | - Herlinde De Keersmaecker
- Department of Chemistry, Division of Molecular Imaging and Photonics, KU Leuven-University of Leuven , Celestijnenlaan 200F, B-3001, Leuven, Belgium
| | - Steven De Feyter
- Department of Chemistry, Division of Molecular Imaging and Photonics, KU Leuven-University of Leuven , Celestijnenlaan 200F, B-3001, Leuven, Belgium
| | - Hiroshi Uji-I
- Department of Chemistry, Division of Molecular Imaging and Photonics, KU Leuven-University of Leuven , Celestijnenlaan 200F, B-3001, Leuven, Belgium
- Research Institute for Electronic Science, Nanomaterials and Nanoscopy, Hokkaido University , Kita 10 Nishi 20, North Ward, Sapporo 001-0020, Japan
| | - Willem Vanderlinden
- Department of Chemistry, Division of Molecular Imaging and Photonics, KU Leuven-University of Leuven , Celestijnenlaan 200F, B-3001, Leuven, Belgium
- Department of Physics, Nanosystems Initiative Munich, and Center for NanoScience, LMU Munich , Amalienstrasse 54, 80799 Munich, Germany
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39
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Kamagata K, Mano E, Ouchi K, Kanbayashi S, Johnson RC. High Free-Energy Barrier of 1D Diffusion Along DNA by Architectural DNA-Binding Proteins. J Mol Biol 2018; 430:655-667. [PMID: 29307468 DOI: 10.1016/j.jmb.2018.01.001] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2017] [Revised: 12/13/2017] [Accepted: 01/02/2018] [Indexed: 01/25/2023]
Abstract
Architectural DNA-binding proteins function to regulate diverse DNA reactions and have the defining property of significantly changing DNA conformation. Although the 1D movement along DNA by other types of DNA-binding proteins has been visualized, the mobility of architectural DNA-binding proteins on DNA remains unknown. Here, we applied single-molecule fluorescence imaging on arrays of extended DNA molecules to probe the binding dynamics of three structurally distinct architectural DNA-binding proteins: Nhp6A, HU, and Fis. Each of these proteins was observed to move along DNA, and the salt concentration independence of the 1D diffusion implies sliding with continuous contact to DNA. Nhp6A and HU exhibit a single sliding mode, whereas Fis exhibits two sliding modes. Based on comparison of the diffusion coefficients and sizes of many DNA binding proteins, the architectural proteins are categorized into a new group distinguished by an unusually high free-energy barrier for 1D diffusion. The higher free-energy barrier for 1D diffusion by architectural proteins can be attributed to the large DNA conformational changes that accompany binding and impede rotation-coupled movement along the DNA grooves.
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Affiliation(s)
- Kiyoto Kamagata
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai 980-8577, Japan; Graduate School of Life Sciences, Tohoku University, Katahira 2-1-1, Aoba-ku, Aoba-ku, Sendai980-8577, Japan.
| | - Eriko Mano
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai 980-8577, Japan
| | - Kana Ouchi
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai 980-8577, Japan; Graduate School of Life Sciences, Tohoku University, Katahira 2-1-1, Aoba-ku, Aoba-ku, Sendai980-8577, Japan
| | - Saori Kanbayashi
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai 980-8577, Japan
| | - Reid C Johnson
- Department of Biological Chemistry, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA90095-1737, USA; Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA 90095, USA.
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40
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De Keersmaecker H, Frederickx W, Fujita Y, De Feyter S, Uji-I H, Rocha S, Vanderlinden W. Correlative Atomic Force and Single-Molecule Fluorescence Microscopy of Nucleoprotein Complexes. Methods Mol Biol 2018; 1814:339-359. [PMID: 29956242 DOI: 10.1007/978-1-4939-8591-3_20] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Correlative imaging by fluorescence and atomic force microscopy provides a versatile tool to extract orthogonal information on structurally heterogeneous biomolecular assemblies. In this chapter, we describe an integrated setup for correlative fluorescence and force microscopy. We present factors influencing data quality, as well as step-by-step protocols for sample preparation, data acquisition, and data processing that yield nanoscale topographic resolution, high image registration accuracy, and single-fluorophore sensitivity. We demonstrate the capabilities of the approach through simultaneous characterization of mesoscale geometry and composition in a multipart nucleoprotein complex.
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Affiliation(s)
- Herlinde De Keersmaecker
- Division of Molecular Imaging and Photonics, Department of Chemistry, KU Leuven-University of Leuven, Leuven, Belgium
| | - Wout Frederickx
- Division of Molecular Imaging and Photonics, Department of Chemistry, KU Leuven-University of Leuven, Leuven, Belgium
| | - Yasuhiko Fujita
- Division of Molecular Imaging and Photonics, Department of Chemistry, KU Leuven-University of Leuven, Leuven, Belgium
| | - Steven De Feyter
- Division of Molecular Imaging and Photonics, Department of Chemistry, KU Leuven-University of Leuven, Leuven, Belgium
| | - Hiroshi Uji-I
- Division of Molecular Imaging and Photonics, Department of Chemistry, KU Leuven-University of Leuven, Leuven, Belgium
- Research Institute for Electronic Science, Nanomaterials and Nanoscopy, Hokkaido University, Sapporo, Japan
| | - Susana Rocha
- Division of Molecular Imaging and Photonics, Department of Chemistry, KU Leuven-University of Leuven, Leuven, Belgium
| | - Willem Vanderlinden
- Division of Molecular Imaging and Photonics, Department of Chemistry, KU Leuven-University of Leuven, Leuven, Belgium.
- Department of Physics, Nanosystems Initiative Munich, and Center for NanoScience, LMU Munich, Munich, Germany.
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41
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Esadze A, Rodriguez G, Weiser BP, Cole PA, Stivers JT. Measurement of nanoscale DNA translocation by uracil DNA glycosylase in human cells. Nucleic Acids Res 2017; 45:12413-12424. [PMID: 29036472 PMCID: PMC5716149 DOI: 10.1093/nar/gkx848] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2017] [Accepted: 09/13/2017] [Indexed: 12/17/2022] Open
Abstract
DNA ‘sliding’ by human repair enzymes is considered to be important for DNA damage detection. Here, we transfected uracil-containing DNA duplexes into human cells and measured the probability that nuclear human uracil DNA glycosylase (hUNG2) excised two uracil lesions spaced 10–80 bp apart in a single encounter without escaping the micro-volume containing the target sites. The two-site transfer probabilities were 100% and 54% at a 10 and 40 bp spacing, but dropped to only 10% at 80 bp. Enzyme trapping experiments suggested that site transfers over 40 bp followed a DNA ‘hopping’ pathway in human cells, indicating that authentic sliding does not occur even over this short distance. The transfer probabilities were much greater than observed in aqueous buffers, but similar to in vitro measurements in the presence of polymer crowding agents. The findings reveal a new role for the crowded nuclear environment in facilitating DNA damage detection.
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Affiliation(s)
- Alexandre Esadze
- Department of Pharmacology and Molecular Sciences, The Johns Hopkins University School of Medicine, 725 North Wolfe Street, Baltimore, MD 21205-2185, USA
| | - Gaddiel Rodriguez
- Department of Pharmacology and Molecular Sciences, The Johns Hopkins University School of Medicine, 725 North Wolfe Street, Baltimore, MD 21205-2185, USA
| | - Brian P Weiser
- Department of Pharmacology and Molecular Sciences, The Johns Hopkins University School of Medicine, 725 North Wolfe Street, Baltimore, MD 21205-2185, USA
| | - Philip A Cole
- Department of Pharmacology and Molecular Sciences, The Johns Hopkins University School of Medicine, 725 North Wolfe Street, Baltimore, MD 21205-2185, USA
| | - James T Stivers
- Department of Pharmacology and Molecular Sciences, The Johns Hopkins University School of Medicine, 725 North Wolfe Street, Baltimore, MD 21205-2185, USA
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42
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Sahu D, Iwahara J. Discrete-State Kinetics Model for NMR-Based Analysis of Protein Translocation on DNA at Equilibrium. J Phys Chem B 2017; 121:9548-9556. [PMID: 28922916 DOI: 10.1021/acs.jpcb.7b07779] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
In the target DNA search process, sequence-specific DNA-binding proteins first nonspecifically bind to DNA and stochastically move from one site to another before reaching their targets. To rigorously assess how the translocation process influences NMR signals from proteins interacting with nonspecific DNA, we incorporated a discrete-state kinetic model for protein translocation on DNA into the McConnell equation. Using this equation, we simulated line shapes of NMR signals from proteins undergoing translocations on DNA through sliding, dissociation/reassociation, and intersegment transfer. Through this analysis, we validated an existing NMR approach for kinetic investigations of protein translocation on DNA, which utilizes NMR line shapes of two nonspecific DNA-protein complexes and their mixture. We found that, despite its use of simplistic two-state approximation neglecting the presence of many microscopic states, the previously proposed NMR approach provides accurate kinetic information on the intermolecular translocations of proteins between two DNA molecules. Interestingly, our results suggest that the same NMR approach can also provide qualitative information about the one-dimensional diffusion coefficient for proteins sliding on DNA.
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Affiliation(s)
- Debashish Sahu
- Department of Biochemistry and Molecular Biology, Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch , Galveston, Texas 77555-1068, United States
| | - Junji Iwahara
- Department of Biochemistry and Molecular Biology, Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch , Galveston, Texas 77555-1068, United States
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43
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Kostiuk G, Dikic J, Schwarz FW, Sasnauskas G, Seidel R, Siksnys V. The dynamics of the monomeric restriction endonuclease BcnI during its interaction with DNA. Nucleic Acids Res 2017; 45:5968-5979. [PMID: 28453854 PMCID: PMC5449598 DOI: 10.1093/nar/gkx294] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2016] [Accepted: 04/13/2017] [Indexed: 11/24/2022] Open
Abstract
Endonucleases that generate DNA double strand breaks often employ two independent subunits such that the active site from each subunit cuts either DNA strand. Restriction enzyme BcnI is a remarkable exception. It binds to the 5΄-CC/SGG-3΄ (where S = C or G, ‘/’ designates the cleavage position) target as a monomer forming an asymmetric complex, where a single catalytic center approaches the scissile phosphodiester bond in one of DNA strands. Bulk kinetic measurements have previously shown that the same BcnI molecule cuts both DNA strands at the target site without dissociation from the DNA. Here, we analyse the BcnI DNA binding and target recognition steps at the single molecule level. We find, using FRET, that BcnI adopts either ‘open’ or ‘closed’ conformation in solution. Next, we directly demonstrate that BcnI slides over long distances on DNA using 1D diffusion and show that sliding is accompanied by occasional jumping events, where the enzyme leaves the DNA and rebinds immediately at a distant site. Furthermore, we quantify the dynamics of the BcnI interactions with cognate and non-cognate DNA, and determine the preferred binding orientation of BcnI to the target site. These results provide new insights into the intricate dynamics of BcnI–DNA interactions.
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Affiliation(s)
- Georgij Kostiuk
- Institute of Biotechnology, Vilnius University, Sauletekio av. 7, LT-10257 Vilnius, Lithuania
| | - Jasmina Dikic
- Molecular Biophysics group, Institute for Experimental Physics I, Universität Leipzig, Linnéstr. 5, 04103 Leipzig, Germany
| | - Friedrich W Schwarz
- BCUBE, Technische Universitaet Dresden, Arnoldstrasse 18, 01307 Dresden, Germany
| | - Giedrius Sasnauskas
- Institute of Biotechnology, Vilnius University, Sauletekio av. 7, LT-10257 Vilnius, Lithuania
| | - Ralf Seidel
- Molecular Biophysics group, Institute for Experimental Physics I, Universität Leipzig, Linnéstr. 5, 04103 Leipzig, Germany
| | - Virginijus Siksnys
- Institute of Biotechnology, Vilnius University, Sauletekio av. 7, LT-10257 Vilnius, Lithuania
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44
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Murata A, Itoh Y, Mano E, Kanbayashi S, Igarashi C, Takahashi H, Takahashi S, Kamagata K. One-Dimensional Search Dynamics of Tumor Suppressor p53 Regulated by a Disordered C-Terminal Domain. Biophys J 2017; 112:2301-2314. [PMID: 28591603 DOI: 10.1016/j.bpj.2017.04.038] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2016] [Revised: 04/06/2017] [Accepted: 04/25/2017] [Indexed: 11/15/2022] Open
Abstract
Tumor suppressor p53 slides along DNA and finds its target sequence in drastically different and changing cellular conditions. To elucidate how p53 maintains efficient target search at different concentrations of divalent cations such as Ca2+ and Mg2+, we prepared two mutants of p53, each possessing one of its two DNA-binding domains, the CoreTet mutant having the structured core domain plus the tetramerization (Tet) domain, and the TetCT mutant having Tet plus the disordered C-terminal domain. We investigated their equilibrium and kinetic dissociation from DNA and search dynamics along DNA at various [Mg2+]. Although binding of CoreTet to DNA becomes markedly weaker at higher [Mg2+], binding of TetCT depends slightly on [Mg2+]. Single-molecule fluorescence measurements revealed that the one-dimensional diffusion of CoreTet along DNA consists of fast and slow search modes, the ratio of which depends strongly on [Mg2+]. In contrast, diffusion of TetCT consisted of only the fast mode. The disordered C-terminal domain can associate with DNA irrespective of [Mg2+], and can maintain an equilibrium balance of the two search modes and the p53 search distance. These results suggest that p53 modulates the quaternary structure of the complex between p53 and DNA under different [Mg2+] and that it maintains the target search along DNA.
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Affiliation(s)
- Agato Murata
- Institute of Multidisciplinary Research for Advanced Materials, Graduate School of Science, Tohoku University, Sendai, Miyagi, Japan; Department of Chemistry, Graduate School of Science, Tohoku University, Sendai, Miyagi, Japan
| | - Yuji Itoh
- Institute of Multidisciplinary Research for Advanced Materials, Graduate School of Science, Tohoku University, Sendai, Miyagi, Japan; Department of Chemistry, Graduate School of Science, Tohoku University, Sendai, Miyagi, Japan
| | - Eriko Mano
- Institute of Multidisciplinary Research for Advanced Materials, Graduate School of Science, Tohoku University, Sendai, Miyagi, Japan
| | - Saori Kanbayashi
- Institute of Multidisciplinary Research for Advanced Materials, Graduate School of Science, Tohoku University, Sendai, Miyagi, Japan
| | - Chihiro Igarashi
- Institute of Multidisciplinary Research for Advanced Materials, Graduate School of Science, Tohoku University, Sendai, Miyagi, Japan; Department of Chemistry, Graduate School of Science, Tohoku University, Sendai, Miyagi, Japan
| | - Hiroto Takahashi
- Institute of Multidisciplinary Research for Advanced Materials, Graduate School of Science, Tohoku University, Sendai, Miyagi, Japan
| | - Satoshi Takahashi
- Institute of Multidisciplinary Research for Advanced Materials, Graduate School of Science, Tohoku University, Sendai, Miyagi, Japan.
| | - Kiyoto Kamagata
- Institute of Multidisciplinary Research for Advanced Materials, Graduate School of Science, Tohoku University, Sendai, Miyagi, Japan.
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45
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Berezhkovskii AM, Dagdug L, Bezrukov SM. Bulk-mediated surface transport in the presence of bias. J Chem Phys 2017; 147:014103. [PMID: 28688439 PMCID: PMC5500123 DOI: 10.1063/1.4991730] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2017] [Accepted: 06/21/2017] [Indexed: 12/22/2022] Open
Abstract
Surface transport, when the particle is allowed to leave the surface, travel in the bulk for some time, and then return to the surface, is referred to as bulk-mediated surface transport. Recently, we proposed a formalism that significantly simplifies analysis of bulk-mediated surface diffusion [A. M. Berezhkovskii, L. Dagdug, and S. M. Bezrukov, J. Chem. Phys. 143, 084103 (2015)]. Here this formalism is extended to bulk-mediated surface transport in the presence of bias, i.e., when the particle has arbitrary drift velocities on the surface and in the bulk. A key advantage of our approach is that the transport problem reduces to that of a two-state problem of the particle transitions between the surface and the bulk. The latter can be solved with relative ease. The formalism is used to find the Laplace transforms of the first two moments of the particle displacement over the surface in time t at arbitrary values of the particle drift velocities and diffusivities on the surface and in the bulk. This allows us to analyze in detail the time dependence of the effective drift velocity of the particle on the surface, which can be highly nontrivial.
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Affiliation(s)
- Alexander M Berezhkovskii
- Section on Molecular Transport, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Leonardo Dagdug
- Section on Molecular Transport, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Sergey M Bezrukov
- Section on Molecular Transport, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA
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46
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Saito M, Terakawa T, Takada S. How one-dimensional diffusion of transcription factors are affected by obstacles: coarse-grained molecular dynamics study. MOLECULAR SIMULATION 2017. [DOI: 10.1080/08927022.2017.1334885] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Affiliation(s)
- Mami Saito
- Department of Biophysics, Division of Biological Sciences, Graduate School of Science, Kyoto University, Sakyo, Kyoto, Japan
| | - Tsuyoshi Terakawa
- Department of Biophysics, Division of Biological Sciences, Graduate School of Science, Kyoto University, Sakyo, Kyoto, Japan
- Department of Biochemistry and Molecular Biophysics, Columbia University Medical Center, New York, NY, USA
| | - Shoji Takada
- Department of Biophysics, Division of Biological Sciences, Graduate School of Science, Kyoto University, Sakyo, Kyoto, Japan
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47
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Kamagata K, Murata A, Itoh Y, Takahashi S. Characterization of facilitated diffusion of tumor suppressor p53 along DNA using single-molecule fluorescence imaging. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY C-PHOTOCHEMISTRY REVIEWS 2017. [DOI: 10.1016/j.jphotochemrev.2017.01.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
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48
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Martínez-García R, Calabrese JM, López C. Online games: a novel approach to explore how partial information influences human random searches. Sci Rep 2017; 7:40029. [PMID: 28059115 PMCID: PMC5216393 DOI: 10.1038/srep40029] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2016] [Accepted: 11/15/2016] [Indexed: 11/09/2022] Open
Abstract
Many natural processes rely on optimizing the success ratio of a search process. We use an experimental setup consisting of a simple online game in which players have to find a target hidden on a board, to investigate how the rounds are influenced by the detection of cues. We focus on the search duration and the statistics of the trajectories traced on the board. The experimental data are explained by a family of random-walk-based models and probabilistic analytical approximations. If no initial information is given to the players, the search is optimized for cues that cover an intermediate spatial scale. In addition, initial information about the extension of the cues results, in general, in faster searches. Finally, strategies used by informed players turn into non-stationary processes in which the length of e ach displacement evolves to show a well-defined characteristic scale that is not found in non-informed searches.
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Affiliation(s)
- Ricardo Martínez-García
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ 08544, USA
| | - Justin M. Calabrese
- Smithsonian Conservation Biology Institute, National Zoological Park, Front Royal, VA 22630, USA
- Department of Biology, University of Maryland, College Park, MD 20742, USA
| | - Cristóbal López
- IFISC, Instituto de Física Interdisciplinar y Sistemas Complejos (CSIC-UIB), E-07122 Palma de Mallorca, Spain
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49
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Ma Y, Chen Y, Yu W, Luo K. How nonspecifically DNA-binding proteins search for the target in crowded environments. J Chem Phys 2016; 144:125102. [PMID: 27036479 DOI: 10.1063/1.4944905] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
We investigate how a tracer particle searches a target located in DNA modeled by a stiff chain in crowded environments using theoretical analysis and Langevin dynamics simulations. First, we show that the three-dimensional (3D) diffusion coefficient of the tracer only depends on the density of crowders ϕ, while its one-dimensional (1D) diffusion coefficient is affected by not only ϕ but also the nonspecific binding energy ε. With increasing ϕ and ε, no obvious change in the average 3D diffusion time is observed, while the average 1D sliding time apparently increases. We propose theoretically that the 1D sliding of the tracer along the chain could be well captured by the Kramers' law of escaping rather than the Arrhenius law, which is verified directly by the simulations. Finally, the average search time increases monotonously with an increase in ϕ while it has a minimum as a function of ε, which could be understood from the different behaviors of the average number of search rounds with the increasing ϕ or ε. These results provide a deeper understanding of the role of facilitated diffusion in target search of proteins on DNA in vivo.
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Affiliation(s)
- Yiding Ma
- CAS Key Laboratory of Soft Matter Chemistry, Collaborative Innovation Center of Chemistry for Energy Materials, and Department of Polymer Science and Engineering, University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China
| | - Yuhao Chen
- CAS Key Laboratory of Soft Matter Chemistry, Collaborative Innovation Center of Chemistry for Energy Materials, and Department of Polymer Science and Engineering, University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China
| | - Wancheng Yu
- CAS Key Laboratory of Soft Matter Chemistry, Collaborative Innovation Center of Chemistry for Energy Materials, and Department of Polymer Science and Engineering, University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China
| | - Kaifu Luo
- CAS Key Laboratory of Soft Matter Chemistry, Collaborative Innovation Center of Chemistry for Energy Materials, and Department of Polymer Science and Engineering, University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China
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50
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Rad4 recognition-at-a-distance: Physical basis of conformation-specific anomalous diffusion of DNA repair proteins. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2016; 127:93-104. [PMID: 27939760 DOI: 10.1016/j.pbiomolbio.2016.12.004] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/08/2016] [Accepted: 12/06/2016] [Indexed: 11/20/2022]
Abstract
Since Robert Brown's first observations of random walks by pollen particles suspended in solution, the concept of diffusion has been subject to countless theoretical and experimental studies in diverse fields from finance and social sciences, to physics and biology. Diffusive transport of macromolecules in cells is intimately linked to essential cellular functions including nutrient uptake, signal transduction, gene expression, as well as DNA replication and repair. Advancement in experimental techniques has allowed precise measurements of these diffusion processes. Mathematical and physical descriptions and computer simulations have been applied to model complicated biological systems in which anomalous diffusion, in addition to simple Brownian motion, was observed. The purpose of this review is to provide an overview of the major physical models of anomalous diffusion and corresponding experimental evidence on the target search problem faced by DNA-binding proteins, with an emphasis on DNA repair proteins and the role of anomalous diffusion in DNA target recognition.
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