51
|
Bentivoglio A, Ancona M, Brackley CA, Gonnella G, Marenduzzo D. Non-equilibrium phase transition in a model for supercoiling-dependent DNA transcription. SOFT MATTER 2018; 14:3632-3639. [PMID: 29691522 DOI: 10.1039/c7sm02452e] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We study a variant of a recently proposed non-equilibrium stochastic model for supercoiling-dependent transcription in DNA. In the case of a circular DNA molecule with overall positive supercoiling, we find a non-equilibrium phase transition between an absorbing phase, where all genes are switched off due to the supercoiling, and an active phase with a non-zero transcription rate. Mean field theory predicts that the transition should be continuous at a critical value of the background supercoiling, and we focus our analysis on this case. Our simulations suggest that the switch between the transcribed and silent phases may actually be a fluctuation-induced discontinuous transition, where the jump in the transcription rate decreases with the number of genes in the system.
Collapse
Affiliation(s)
- A Bentivoglio
- SUPA, School of Physics and Astronomy, University of Edinburgh, Peter Guthrie Tait Road, Edinburgh EH9 3FD, UK.
| | | | | | | | | |
Collapse
|
52
|
Structure and Properties of DNA Molecules Over The Full Range of Biologically Relevant Supercoiling States. Sci Rep 2018; 8:6163. [PMID: 29670174 PMCID: PMC5906655 DOI: 10.1038/s41598-018-24499-5] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2017] [Accepted: 04/04/2018] [Indexed: 01/03/2023] Open
Abstract
Topology affects physical and biological properties of DNA and impacts fundamental cellular processes, such as gene expression, genome replication, chromosome structure and segregation. In all organisms DNA topology is carefully modulated and the supercoiling degree of defined genome regions may change according to physiological and environmental conditions. Elucidation of structural properties of DNA molecules with different topology may thus help to better understand genome functions. Whereas a number of structural studies have been published on highly negatively supercoiled DNA molecules, only preliminary observations of highly positively supercoiled are available, and a description of DNA structural properties over the full range of supercoiling degree is lacking. Atomic Force Microscopy (AFM) is a powerful tool to study DNA structure at single molecule level. We here report a comprehensive analysis by AFM of DNA plasmid molecules with defined supercoiling degree, covering the full spectrum of biologically relevant topologies, under different observation conditions. Our data, supported by statistical and biochemical analyses, revealed striking differences in the behavior of positive and negative plasmid molecules.
Collapse
|
53
|
Role of CTCF in DNA damage response. MUTATION RESEARCH-REVIEWS IN MUTATION RESEARCH 2018; 780:61-68. [PMID: 31395350 DOI: 10.1016/j.mrrev.2018.02.002] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/24/2017] [Accepted: 02/20/2018] [Indexed: 12/13/2022]
Abstract
CCCTC-binding factor (CTCF) is a highly conserved, ubiquitously expressed zinc finger protein. CTCF is a multifunctional protein, associated with a number of vital cellular processes such as transcriptional activation, repression, insulation, imprinting and genome organization. Emerging evidence indicates that CTCF is also involved in DNA damage response. In this review, we focus on the newly identified role of CTCF in facilitating DNA double-strand break repair. Due to the large number of cellular processes in which CTCF is involved, factors that functionally affect CTCF could have serious implications on genomic stability. It is becoming increasingly clear that exposure to environmental toxicants could have adverse effects on CTCF functions. Here we discuss the various ways that environmental toxicants could impact CTCF functions and the potential consequences on DNA damage response.
Collapse
|
54
|
Ouimette JF, Rougeulle C, Veitia RA. Three-dimensional genome architecture in health and disease. Clin Genet 2018; 95:189-198. [PMID: 29377081 DOI: 10.1111/cge.13219] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2017] [Revised: 01/15/2018] [Accepted: 01/23/2018] [Indexed: 11/29/2022]
Abstract
More than a decade of massive DNA sequencing efforts have generated a large body of genomic, transcriptomic and epigenomic information that has provided a more and more detailed view of the functional elements and transactions within the human genome. Considerable efforts have also focused on linking these elements with one another by mapping their interactions and by establishing 3-dimensional (3D) genomic landscapes in various cell and tissue types. In parallel, multiple studies have associated genomic deletions, duplications and other rearrangements with human pathologies. In this review, we explore recent progresses that have allowed connecting disease-causing alterations with perturbations of the 3D genome organization.
Collapse
Affiliation(s)
- J-F Ouimette
- Epigenetics and Cell Fate Center, UMR7216 CNRS, Université Paris Diderot, Paris, France.,Université Paris Diderot, Paris, France
| | - C Rougeulle
- Epigenetics and Cell Fate Center, UMR7216 CNRS, Université Paris Diderot, Paris, France.,Université Paris Diderot, Paris, France
| | - R A Veitia
- Université Paris Diderot, Paris, France.,Institut Jacques Monod, Paris, France
| |
Collapse
|
55
|
Chromosomal organization of transcription: in a nutshell. Curr Genet 2017; 64:555-565. [PMID: 29184972 DOI: 10.1007/s00294-017-0785-5] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2017] [Revised: 11/20/2017] [Accepted: 11/20/2017] [Indexed: 01/25/2023]
Abstract
Early studies of transcriptional regulation focused on individual gene promoters defined specific transcription factors as central agents of genetic control. However, recent genome-wide data propelled a different view by linking spatially organized gene expression patterns to chromosomal dynamics. Therefore, the major problem in contemporary molecular genetics concerned with transcriptional gene regulation is to establish a unifying model that reconciles these two views. This problem, situated at the interface of polymer physics and network theory, requires development of an integrative methodology. In this review, we discuss recent achievements in classical model organism E. coli and provide some novel insights gained from studies of a bacterial plant pathogen, D. dadantii. We consider DNA topology and the basal transcription machinery as key actors of regulation, in which activation of functionally relevant genes is coupled to and coordinated with the establishment of extended chromosomal domains of coherent transcription. We argue that the spatial organization of genome plays a fundamental role in its own regulation.
Collapse
|
56
|
Transformation of a Thermostable G-Quadruplex Structure into DNA Duplex Driven by Reverse Gyrase. Molecules 2017; 22:molecules22112021. [PMID: 29165328 PMCID: PMC6150213 DOI: 10.3390/molecules22112021] [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: 11/08/2017] [Revised: 11/14/2017] [Accepted: 11/17/2017] [Indexed: 11/27/2022] Open
Abstract
Reverse gyrase is a topoisomerase that can introduce positive supercoils to its substrate DNA. It is demonstrated in our studies that a highly thermal stable G-quadruplex structure in a mini-plasmid DNA was transformed into its duplex conformation after a treatment with reverse gyrase. The structural difference of the topoisomers were verified and analyzed by gel electrophoresis, atomic force microscopy examination, and endonuclease digestion assays. All evidence suggested that the overwinding structure of positive supercoil could provide a driven force to disintegrate G-quadruplex and reform duplex. The results of our studies could suggest that hyperthermophiles might use reverse gyrase to manipulate the disintegration of non-B DNA structures and safekeep their genomic information.
Collapse
|
57
|
Belotserkovskii BP, Soo Shin JH, Hanawalt PC. Strong transcription blockage mediated by R-loop formation within a G-rich homopurine-homopyrimidine sequence localized in the vicinity of the promoter. Nucleic Acids Res 2017; 45:6589-6599. [PMID: 28498974 PMCID: PMC5499740 DOI: 10.1093/nar/gkx403] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2017] [Accepted: 05/08/2017] [Indexed: 02/07/2023] Open
Abstract
Guanine-rich (G-rich) homopurine–homopyrimidine nucleotide sequences can block transcription with an efficiency that depends upon their orientation, composition and length, as well as the presence of negative supercoiling or breaks in the non-template DNA strand. We report that a G-rich sequence in the non-template strand reduces the yield of T7 RNA polymerase transcription by more than an order of magnitude when positioned close (9 bp) to the promoter, in comparison to that for a distal (∼250 bp) location of the same sequence. This transcription blockage is much less pronounced for a C-rich sequence, and is not significant for an A-rich sequence. Remarkably, the blockage is not pronounced if transcription is performed in the presence of RNase H, which specifically digests the RNA strands within RNA–DNA hybrids. The blockage also becomes less pronounced upon reduced RNA polymerase concentration. Based upon these observations and those from control experiments, we conclude that the blockage is primarily due to the formation of stable RNA–DNA hybrids (R-loops), which inhibit successive rounds of transcription. Our results could be relevant to transcription dynamics in vivo (e.g. transcription ‘bursting’) and may also have practical implications for the design of expression vectors.
Collapse
Affiliation(s)
| | - Jane Hae Soo Shin
- Department of Biology, Stanford University, Stanford, CA 94305-5020, USA
| | - Philip C Hanawalt
- Department of Biology, Stanford University, Stanford, CA 94305-5020, USA
| |
Collapse
|
58
|
Siebert JT, Kivel AN, Atkinson LP, Stevens TJ, Laue ED, Virnau P. Are There Knots in Chromosomes? Polymers (Basel) 2017; 9:polym9080317. [PMID: 30971010 PMCID: PMC6418659 DOI: 10.3390/polym9080317] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2017] [Revised: 07/24/2017] [Accepted: 07/25/2017] [Indexed: 02/02/2023] Open
Abstract
Recent developments have for the first time allowed the determination of three-dimensional structures of individual chromosomes and genomes in nuclei of single haploid mouse embryonic stem (ES) cells based on Hi⁻C chromosome conformation contact data. Although these first structures have a relatively low resolution, they provide the first experimental data that can be used to study chromosome and intact genome folding. Here we further analyze these structures and provide the first evidence that G1 phase chromosomes are knotted, consistent with the fact that plots of contact probability vs sequence separation show a power law dependence that is intermediate between that of a fractal globule and an equilibrium structure.
Collapse
Affiliation(s)
- Jonathan T Siebert
- Department of Physics, Johannes Gutenberg University Mainz, Staudinger Weg 9, 55128 Mainz, Germany.
| | - Alexey N Kivel
- Department of Physics, Johannes Gutenberg University Mainz, Staudinger Weg 9, 55128 Mainz, Germany.
| | - Liam P Atkinson
- Department of Biochemistry, University of Cambridge, 80 Tennis Court Road, Cambridge CB2 1GA, UK.
| | - Tim J Stevens
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge Biomedical Campus, Cambridge CB2 0QH, UK.
| | - Ernest D Laue
- Department of Biochemistry, University of Cambridge, 80 Tennis Court Road, Cambridge CB2 1GA, UK.
| | - Peter Virnau
- Department of Physics, Johannes Gutenberg University Mainz, Staudinger Weg 9, 55128 Mainz, Germany.
| |
Collapse
|
59
|
Gorle AK, Bottomley AL, Harry EJ, Collins JG, Keene FR, Woodward CE. DNA condensation in live E. coli provides evidence for transertion. MOLECULAR BIOSYSTEMS 2017; 13:677-680. [PMID: 28232991 DOI: 10.1039/c6mb00753h] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Condensation studies of chromosomal DNA in E. coli with a tetranuclear ruthenium complex are carried out and images obtained with wide-field fluorescence microscopy. Remarkably different condensate morphologies resulted, depending upon the treatment protocol. The occurrence of condensed nucleoid spirals in live bacteria provides evidence for the transertion hypothesis.
Collapse
Affiliation(s)
- Anil K Gorle
- School of Physical, Environmental and Mathematical Sciences, University of New South Wales, Australian Defence Force Academy, Canberra, ACT 2600, Australia.
| | - Amy L Bottomley
- The ithree institute, University of Technology Sydney, PO Box 123, Broadway, NSW 2007, Australia
| | - Elizabeth J Harry
- The ithree institute, University of Technology Sydney, PO Box 123, Broadway, NSW 2007, Australia
| | - J Grant Collins
- School of Physical, Environmental and Mathematical Sciences, University of New South Wales, Australian Defence Force Academy, Canberra, ACT 2600, Australia.
| | - F Richard Keene
- Centre for Biodiscovery & Molecular Development of Therapeutics, James Cook University, Townsville, QLD 4811, Australia and School of Physical Sciences, University of Adelaide, Adelaide, SA 5066, Australia.
| | - Clifford E Woodward
- School of Physical, Environmental and Mathematical Sciences, University of New South Wales, Australian Defence Force Academy, Canberra, ACT 2600, Australia.
| |
Collapse
|
60
|
Li D, Lv B, Wang Q, Liu Y, Zhuge Q. Direct observation of positive supercoils introduced by reverse gyrase through atomic force microscopy. Bioorg Med Chem Lett 2017; 27:4086-4090. [PMID: 28756025 DOI: 10.1016/j.bmcl.2017.07.044] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2017] [Revised: 07/13/2017] [Accepted: 07/14/2017] [Indexed: 11/18/2022]
Abstract
Reverse gyrase is a hyperthermophilic enzyme that can introduce positive supercoiling in substrate DNA. It is showed in our studies that positive DNA supercoils were induced in both pBR322 vector and an artificially synthesized mini-plasmid DNA by reverse gyrase. The left-handed structures adopted by positively supercoiled DNA molecules could be identified from their right-handed topoisomers through atomic force microscopic examination. Additional structural comparisons revealed that positively supercoiled DNA molecule AFM images exhibited increased contour lengths. Moreover, enzymatic assays showed that the positively supercoiled DNA could not be cleaved by T7 endonuclease. Together, this suggests that the overwound structure of positive supercoils could prevent genomic duplex DNA from randomly forming single-stranded DNA regions and intra-stranded secondary structures.
Collapse
Affiliation(s)
- Dawei Li
- Key Lab of Forest Genetics and Biotechnology, Nanjing Forestry University, 159 Longpan Road, Nanjing 210037, China.
| | - Bei Lv
- Jiangsu Key Laboratory for Biofunctional Molecules, College of Life Science and Chemistry, Jiangsu Second Normal University, Nanjing 210037, China
| | - Qiang Wang
- Key Lab of Forest Genetics and Biotechnology, Nanjing Forestry University, 159 Longpan Road, Nanjing 210037, China
| | - Yun Liu
- Key Lab of Forest Genetics and Biotechnology, Nanjing Forestry University, 159 Longpan Road, Nanjing 210037, China
| | - Qiang Zhuge
- Key Lab of Forest Genetics and Biotechnology, Nanjing Forestry University, 159 Longpan Road, Nanjing 210037, China
| |
Collapse
|
61
|
Humayun MZ, Zhang Z, Butcher AM, Moshayedi A, Saier MH. Hopping into a hot seat: Role of DNA structural features on IS5-mediated gene activation and inactivation under stress. PLoS One 2017; 12:e0180156. [PMID: 28666002 PMCID: PMC5493358 DOI: 10.1371/journal.pone.0180156] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2017] [Accepted: 06/09/2017] [Indexed: 11/30/2022] Open
Abstract
Insertion sequence elements (IS elements) are proposed to play major roles in shaping the genetic and phenotypic landscapes of prokaryotic cells. Recent evidence has raised the possibility that environmental stress conditions increase IS hopping into new sites, and often such hopping has the phenotypic effect of relieving the stress. Although stress-induced targeted mutations have been reported for a number of E. coli genes, the glpFK (glycerol utilization) and the cryptic bglGFB (β-glucoside utilization) systems are among the best characterized where the effects of IS insertion-mediated gene activation are well-characterized at the molecular level. In the glpFK system, starvation of cells incapable of utilizing glycerol leads to an IS5 insertion event that activates the glpFK operon, and enables glycerol utilization. In the case of the cryptic bglGFB operon, insertion of IS5 (and other IS elements) into a specific region in the bglG upstream sequence has the effect of activating the operon in both growing cells, and in starving cells. However, a major unanswered question in the glpFK system, the bgl system, as well as other examples, has been why the insertion events are promoted at specific locations, and how the specific stress condition (glycerol starvation for example) can be mechanistically linked to enhanced insertion at a specific locus. In this paper, we show that a specific DNA structural feature (superhelical stress-induced duplex destabilization, SIDD) is associated with "stress-induced" IS5 insertion in the glpFK, bglGFB, flhDC, fucAO and nfsB systems. We propose a speculative mechanistic model that links specific environmental conditions to the unmasking of an insertional hotspot in the glpFK system. We demonstrate that experimentally altering the predicted stability of a SIDD element in the nfsB gene significantly impacts IS5 insertion at its hotspot.
Collapse
Affiliation(s)
- M. Zafri Humayun
- Department of Microbiology, Biochemistry & Molecular Genetics, Rutgers—New Jersey Medical School, Newark, NJ, United States of America
| | - Zhongge Zhang
- Department of Molecular Biology, Division of Biological Sciences, University of California San Diego, La Jolla, CA, United States of America
| | - Anna M. Butcher
- Department of Molecular Biology, Division of Biological Sciences, University of California San Diego, La Jolla, CA, United States of America
| | - Aref Moshayedi
- Department of Molecular Biology, Division of Biological Sciences, University of California San Diego, La Jolla, CA, United States of America
| | - Milton H. Saier
- Department of Molecular Biology, Division of Biological Sciences, University of California San Diego, La Jolla, CA, United States of America
| |
Collapse
|
62
|
Reinhart M, Cardoso MC. A journey through the microscopic ages of DNA replication. PROTOPLASMA 2017; 254:1151-1162. [PMID: 27943022 PMCID: PMC5376393 DOI: 10.1007/s00709-016-1058-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/03/2016] [Accepted: 12/01/2016] [Indexed: 06/06/2023]
Abstract
Scientific discoveries and technological advancements are inseparable but not always take place in a coherent chronological manner. In the next, we will provide a seemingly unconnected and serendipitous series of scientific facts that, in the whole, converged to unveil DNA and its duplication. We will not cover here the many and fundamental contributions from microbial genetics and in vitro biochemistry. Rather, in this journey, we will emphasize the interplay between microscopy development culminating on super resolution fluorescence microscopy (i.e., nanoscopy) and digital image analysis and its impact on our understanding of DNA duplication. We will interlace the journey with landmark concepts and experiments that have brought the cellular DNA replication field to its present state.
Collapse
Affiliation(s)
- Marius Reinhart
- Cell Biology and Epigenetics, Department of Biology, Technische Universität Darmstadt, Schnittspahnstrasse 10, 64287, Darmstadt, Germany
| | - M Cristina Cardoso
- Cell Biology and Epigenetics, Department of Biology, Technische Universität Darmstadt, Schnittspahnstrasse 10, 64287, Darmstadt, Germany.
| |
Collapse
|
63
|
Lee DJO. Statistical mechanical model for a closed loop plectoneme with weak helix specific forces. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:145101. [PMID: 28251958 DOI: 10.1088/1361-648x/aa521c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We develop a statistical mechanical framework, based on a variational approximation, to describe closed loop plectonemes. This framework incorporates weak helix structure dependent forces into the determination of the free energy and average structure of a plectoneme. Notably, due to their chiral nature, helix structure dependent forces break the symmetry between left and right handed supercoiling. The theoretical approach, presented here, also provides a systematic way of enforcing the topological constraint of closed loop supercoiling in the variational approximation. At large plectoneme lengths, by considering correlation functions in an expansion in terms of the spatial mean twist density about its thermally averaged value, it can be argued that topological constraint may be approximated by replacing twist and writhe by their thermal averages. A Lagrange multiplier, containing the sum of average twist and writhe, can be added to the free energy to conveniently inforce this result. The average writhe can be calculated through the thermal average of the Gauss' integral in the variational approximation. Furthermore, this approach allows for a possible way to calculate finite size corrections due to the topological constraint. Using interaction energy terms from the mean-field Kornyshev-Leikin theory, for parameter values that correspond to weak helix dependent forces, we calculate the free energy, fluctuation magnitudes and mean geometric parameters for the plectoneme. We see a slight asymmetry, where interestingly, left handed supercoils have a looser structure than right handed ones, although with a lower free energy, unlike what the previous ground state calculations would suggest.
Collapse
Affiliation(s)
- Dominic J O' Lee
- Department of Chemistry, Imperial College London, SW7 2AZ, London, United Kingdom
| |
Collapse
|
64
|
Condensin, master organizer of the genome. Chromosome Res 2017; 25:61-76. [PMID: 28181049 DOI: 10.1007/s10577-017-9553-0] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2016] [Revised: 12/19/2016] [Accepted: 01/23/2017] [Indexed: 02/06/2023]
Abstract
A fundamental requirement in nature is for a cell to correctly package and divide its replicated genome. Condensin is a mechanical multisubunit complex critical to this process. Condensin uses ATP to power conformational changes in DNA to enable to correct DNA compaction, organization, and segregation of DNA from the simplest bacteria to humans. The highly conserved nature of the condensin complex and the structural similarities it shares with the related cohesin complex have provided important clues as to how it functions in cells. The fundamental requirement for condensin in mitosis and meiosis is well established, yet the precise mechanism of action is still an open question. Mutation or removal of condensin subunits across a range of species disrupts orderly chromosome condensation leading to errors in chromosome segregation and likely death of the cell. There are divergences in function across species for condensin. Once considered to function solely in mitosis and meiosis, an accumulating body of evidence suggests that condensin has key roles in also regulating the interphase genome. This review will examine how condensin organizes our genomes, explain where and how it binds the genome at a mechanical level, and highlight controversies and future directions as the complex continues to fascinate and baffle biologists.
Collapse
|
65
|
Affiliation(s)
- Giovanni Capranico
- Department
of Pharmacy and Biotechnology, University of Bologna, Via Belmeloro
8/2, 40126 Bologna, Italy
| | - Jessica Marinello
- Department
of Pharmacy and Biotechnology, University of Bologna, Via Belmeloro
8/2, 40126 Bologna, Italy
| | - Giovanni Chillemi
- SCAI
SuperComputing Applications and Innovation Department, Cineca, Via dei Tizii 6, 00185 Rome, Italy
| |
Collapse
|
66
|
Barutcu AR, Lian JB, Stein JL, Stein GS, Imbalzano AN. The connection between BRG1, CTCF and topoisomerases at TAD boundaries. Nucleus 2017; 8:150-155. [PMID: 28060558 PMCID: PMC5403164 DOI: 10.1080/19491034.2016.1276145] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
The eukaryotic genome is partitioned into topologically associating domains (TADs). Despite recent advances characterizing TADs and TAD boundaries, the organization of these structures is an important dimension of genome architecture and function that is not well understood. Recently, we demonstrated that knockdown of BRG1, an ATPase driving the chromatin remodeling activity of mammalian SWI/SNF enzymes, globally alters long-range genomic interactions and results in a reduction of TAD boundary strength. We provided evidence suggesting that this effect may be due to BRG1 affecting nucleosome occupancy around CTCF sites present at TAD boundaries. In this review, we elaborate on our findings and speculate that BRG1 may contribute to the regulation of the structural and functional properties of chromatin at TAD boundaries by affecting the function or the recruitment of CTCF and DNA topoisomerase complexes.
Collapse
Affiliation(s)
- A Rasim Barutcu
- a Department of Cell and Developmental Biology , University of Massachusetts Medical School , Worcester , MA , USA
| | - Jane B Lian
- b Department of Biochemistry , University of Vermont College of Medicine , Burlington , VT , USA
| | - Janet L Stein
- b Department of Biochemistry , University of Vermont College of Medicine , Burlington , VT , USA
| | - Gary S Stein
- b Department of Biochemistry , University of Vermont College of Medicine , Burlington , VT , USA
| | - Anthony N Imbalzano
- a Department of Cell and Developmental Biology , University of Massachusetts Medical School , Worcester , MA , USA
| |
Collapse
|
67
|
Takahashi S, Motooka S, Kawasaki S, Kurita H, Mizuno T, Matsuura SI, Hanaoka F, Mizuno A, Oshige M, Katsura S. Direct single-molecule observations of DNA unwinding by SV40 large tumor antigen under a negative DNA supercoil state. J Biomol Struct Dyn 2017; 36:32-44. [PMID: 27928933 DOI: 10.1080/07391102.2016.1269689] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
Superhelices, which are induced by the twisting and coiling of double-helical DNA in chromosomes, are thought to affect transcription, replication, and other DNA metabolic processes. In this study, we report the effects of negative supercoiling on the unwinding activity of simian virus 40 large tumor antigen (SV40 TAg) at a single-molecular level. The supercoiling density of linear DNA templates was controlled using magnetic tweezers and monitored using a fluorescent microscope in a flow cell. SV40 TAg-mediated DNA unwinding under relaxed and negative supercoil states was analyzed by the direct observation of both single- and double-stranded regions of single DNA molecules. Increased negative superhelicity stimulated SV40 TAg-mediated DNA unwinding more strongly than a relaxed state; furthermore, negative superhelicity was associated with an increased probability of SV40 TAg-mediated DNA unwinding. These results suggest that negative superhelicity helps to regulate the initiation of DNA replication.
Collapse
Affiliation(s)
- Shunsuke Takahashi
- a Department of Environmental Engineering Science, Graduate School of Science and Technology , Gunma University , Kiryu , Japan.,f Japan Society for the Promotion of Science
| | - Shinya Motooka
- a Department of Environmental Engineering Science, Graduate School of Science and Technology , Gunma University , Kiryu , Japan
| | - Shohei Kawasaki
- a Department of Environmental Engineering Science, Graduate School of Science and Technology , Gunma University , Kiryu , Japan
| | - Hirofumi Kurita
- b Department of Environmental and Life Sciences, Graduate School of Engineering , Toyohashi University of Technology , Toyohashi , Japan
| | - Takeshi Mizuno
- c Cellular Dynamics Laboratory , RIKEN, Wako , Saitama , Japan
| | - Shun-Ichi Matsuura
- d Research Institute for Chemical Process Technology , National Institute of Advanced Industrial Science and Technology (AIST) , Sendai , Japan
| | - Fumio Hanaoka
- e Faculty of Science, Institute for Biomolecular Science , Gakushuin University , Tokyo , Japan
| | - Akira Mizuno
- b Department of Environmental and Life Sciences, Graduate School of Engineering , Toyohashi University of Technology , Toyohashi , Japan
| | - Masahiko Oshige
- a Department of Environmental Engineering Science, Graduate School of Science and Technology , Gunma University , Kiryu , Japan
| | - Shinji Katsura
- a Department of Environmental Engineering Science, Graduate School of Science and Technology , Gunma University , Kiryu , Japan
| |
Collapse
|
68
|
Optical Torque Wrench Design and Calibration. Methods Mol Biol 2016; 1486:157-181. [PMID: 27844429 DOI: 10.1007/978-1-4939-6421-5_7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/14/2023]
Abstract
Expanding the capabilities of optical traps with angular control of the trapped particle has numerous potential applications in all fields where standard linear optical tweezers are employed. Here we describe in detail the construction, alignment, and calibration of the Optical Torque Wrench, a mode of function that can be added to linear optical tweezers to simultaneously apply and measure both force and torque on birefringent microscopic cylindrical particles. The interaction between the linear polarization of the laser and the birefringent cylinder creates an angular trap for the particle orientation, described by a periodic potential. As a consequence of the experimental control of the tilt of the periodic potential, the dynamical excitability of the system can be observed. Angular optical tweezers remain less widespread than their linear counterpart. We hope this technical guide can foster their development and new applications.
Collapse
|
69
|
Noy A, Sutthibutpong T, A Harris S. Protein/DNA interactions in complex DNA topologies: expect the unexpected. Biophys Rev 2016; 8:145-155. [PMID: 28035245 PMCID: PMC5153831 DOI: 10.1007/s12551-016-0241-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2016] [Accepted: 06/13/2016] [Indexed: 01/09/2023] Open
Abstract
DNA supercoiling results in compacted DNA structures that can bring distal sites into close proximity. It also changes the local structure of the DNA, which can in turn influence the way it is recognised by drugs, other nucleic acids and proteins. Here, we discuss how DNA supercoiling and the formation of complex DNA topologies can affect the thermodynamics of DNA recognition. We then speculate on the implications for transcriptional control and the three-dimensional organisation of the genetic material, using examples from our own simulations and from the literature. We introduce and discuss the concept of coupling between the multiple length-scales associated with hierarchical nuclear structural organisation through DNA supercoiling and topology.
Collapse
Affiliation(s)
- Agnes Noy
- Department of Physics, Biological Physical Sciences Institute, University of York, York, YO10 5DD UK
| | - Thana Sutthibutpong
- Theoretical and Computational Physics Group, Department of Physics, King Mongkut University of Technology Thonburi, 126 Pracha Uthit Road, Bang Mod, Thung Khru, Bangkok, Thailand 10140
| | - Sarah A Harris
- School of Physics and Astronomy, University of Leeds, 192 Woodhouse Lane, Leeds, UK LS2 9JT ; Astbury Centre for Structural and Molecular Biology, University of Leeds, 192 Woodhouse Lane, Leeds, UK LS2 9JT
| |
Collapse
|
70
|
The Coordinated Positive Regulation of Topoisomerase Genes Maintains Topological Homeostasis in Streptomyces coelicolor. J Bacteriol 2016; 198:3016-3028. [PMID: 27551021 PMCID: PMC5055605 DOI: 10.1128/jb.00530-16] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2016] [Accepted: 08/17/2016] [Indexed: 01/08/2023] Open
Abstract
Maintaining an optimal level of chromosomal supercoiling is critical for the progression of DNA replication and transcription. Moreover, changes in global supercoiling affect the expression of a large number of genes and play a fundamental role in adapting to stress. Topoisomerase I (TopA) and gyrase are key players in the regulation of bacterial chromosomal topology through their respective abilities to relax and compact DNA. Soil bacteria such as Streptomyces species, which grow as branched, multigenomic hyphae, are subject to environmental stresses that are associated with changes in chromosomal topology. The topological fluctuations modulate the transcriptional activity of a large number of genes and in Streptomyces are related to the production of antibiotics. To better understand the regulation of topological homeostasis in Streptomyces coelicolor, we investigated the interplay between the activities of the topoisomerase-encoding genes topA and gyrBA. We show that the expression of both genes is supercoiling sensitive. Remarkably, increased chromosomal supercoiling induces the topA promoter but only slightly influences gyrBA transcription, while DNA relaxation affects the topA promoter only marginally but strongly activates the gyrBA operon. Moreover, we showed that exposure to elevated temperatures induces rapid relaxation, which results in changes in the levels of both topoisomerases. We therefore propose a unique mechanism of S. coelicolor chromosomal topology maintenance based on the supercoiling-dependent stimulation, rather than repression, of the transcription of both topoisomerase genes. These findings provide important insight into the maintenance of topological homeostasis in an industrially important antibiotic producer. IMPORTANCE We describe the unique regulation of genes encoding two topoisomerases, topoisomerase I (TopA) and gyrase, in a model Streptomyces species. Our studies demonstrate the coordination of topoisomerase gene regulation, which is crucial for maintenance of topological homeostasis. Streptomyces species are producers of a plethora of biologically active secondary metabolites, including antibiotics, antitumor agents, and immunosuppressants. The significant regulatory factor controlling the secondary metabolism is the global chromosomal topology. Thus, the investigation of chromosomal topology homeostasis in Streptomyces strains is crucial for their use in industrial applications as producers of secondary metabolites.
Collapse
|
71
|
Roy A, Dutta A, Roy D, Ganguly P, Ghosh R, Kar RK, Bhunia A, Mukhopadhyay J, Chaudhuri S. Deciphering the role of the AT-rich interaction domain and the HMG-box domain of ARID-HMG proteins of Arabidopsis thaliana. PLANT MOLECULAR BIOLOGY 2016; 92:371-88. [PMID: 27503561 DOI: 10.1007/s11103-016-0519-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/11/2015] [Accepted: 07/28/2016] [Indexed: 05/22/2023]
Abstract
ARID-HMG DNA-binding proteins represent a novel group of HMG-box containing protein family where the AT-rich interaction domain (ARID) is fused with the HMG-box domain in a single polypeptide chain. ARID-HMG proteins are highly plant specific with homologs found both in flowering plants as well as in moss such as Physcomitrella. The expression of these proteins is ubiquitous in plant tissues and primarily localises in the cell nucleus. HMGB proteins are involved in several nuclear processes, but the role of ARID-HMG proteins in plants remains poorly explored. Here, we performed DNA-protein interaction studies with Arabidopsis ARID-HMG protein HMGB11 (At1g55650) to understand the functionality of this protein and its individual domains. DNA binding assays revealed that AtHMGB11 can bind double-stranded DNA with a weaker affinity (Kd = 475 ± 17.9 nM) compared to Arabidopsis HMGB1 protein (Kd = 39.8 ± 2.68 nM). AtHMGB11 also prefers AT-rich DNA as a substrate and shows structural bias for supercoiled DNA. Molecular docking of the DNA-AtHMGB11 complex indicated that the protein interacts with the DNA major groove, mainly through its ARID domain and the junction region connecting the ARID and the HMG-box domain. Also, predicted by the docking model, mutation of Lys(85) from the ARID domain and Arg(199) & Lys(202) from the junction region affects the DNA binding affinity of AtHMGB11. In addition, AtHMGB11 and its truncated form containing the HMG-box domain can not only promote DNA mini-circle formation but are also capable of inducing negative supercoils into relaxed plasmid DNA suggesting the involvement of this protein in several nuclear events. Overall, the study signifies that both the ARID and the HMG-box domain contribute to the optimal functioning of ARID-HMG protein in vivo.
Collapse
Affiliation(s)
- Adrita Roy
- Division of Plant Biology, Bose Institute, Kolkata, 700054, India
| | - Arkajyoti Dutta
- Department of Chemistry, Bose Institute, Kolkata, 700054, India
| | - Dipan Roy
- Division of Plant Biology, Bose Institute, Kolkata, 700054, India
| | - Payel Ganguly
- Division of Plant Biology, Bose Institute, Kolkata, 700054, India
| | - Ritesh Ghosh
- School of Biotechnology, Yeungnam University, Gyeongsan, 712-749, South Korea
| | - Rajiv K Kar
- Department of Biophysics, Bose Institute, Kolkata, 700054, India
| | - Anirban Bhunia
- Department of Biophysics, Bose Institute, Kolkata, 700054, India
| | | | - Shubho Chaudhuri
- Division of Plant Biology, Bose Institute, Kolkata, 700054, India.
| |
Collapse
|
72
|
Laptenko O, Tong DR, Manfredi J, Prives C. The Tail That Wags the Dog: How the Disordered C-Terminal Domain Controls the Transcriptional Activities of the p53 Tumor-Suppressor Protein. Trends Biochem Sci 2016; 41:1022-1034. [PMID: 27669647 DOI: 10.1016/j.tibs.2016.08.011] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2016] [Revised: 08/19/2016] [Accepted: 08/22/2016] [Indexed: 01/22/2023]
Abstract
The p53 tumor suppressor is a transcription factor (TF) that exerts antitumor functions through its ability to regulate the expression of multiple genes. Within the p53 protein resides a relatively short unstructured C-terminal domain (CTD) that remarkably participates in virtually every aspect of p53 performance as a TF. Because these aspects are often interdependent and it is not always possible to dissect them experimentally, there has been a great deal of controversy about the CTD. In this review we evaluate the significance and key features of this interesting region of p53 and its impact on the many aspects of p53 function in light of previous and more recent findings.
Collapse
Affiliation(s)
- Oleg Laptenko
- Department of Biological Sciences, Columbia University, New York, NY 10027, USA
| | - David R Tong
- Department of Biological Sciences, Columbia University, New York, NY 10027, USA
| | - James Manfredi
- Department of Oncological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Carol Prives
- Department of Biological Sciences, Columbia University, New York, NY 10027, USA.
| |
Collapse
|
73
|
Noy A, Sutthibutpong T, A Harris S. Protein/DNA interactions in complex DNA topologies: expect the unexpected. Biophys Rev 2016; 8:233-243. [PMID: 27738452 PMCID: PMC5039213 DOI: 10.1007/s12551-016-0208-8] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2016] [Accepted: 06/13/2016] [Indexed: 12/31/2022] Open
Abstract
DNA supercoiling results in compacted DNA structures that can bring distal sites into close proximity. It also changes the local structure of the DNA, which can in turn influence the way it is recognised by drugs, other nucleic acids and proteins. Here, we discuss how DNA supercoiling and the formation of complex DNA topologies can affect the thermodynamics of DNA recognition. We then speculate on the implications for transcriptional control and the three-dimensional organisation of the genetic material, using examples from our own simulations and from the literature. We introduce and discuss the concept of coupling between the multiple length-scales associated with hierarchical nuclear structural organisation through DNA supercoiling and topology.
Collapse
Affiliation(s)
- Agnes Noy
- Department of Physics, Biological Physical Sciences Institute, University of York, York, YO10 5DD UK
| | - Thana Sutthibutpong
- Theoretical and Computational Physics Group, Department of Physics, King Mongkut University of Technology Thonburi, 126 Pracha Uthit Road, Bang Mod, Thung Khru, Bangkok, Thailand 10140
| | - Sarah A Harris
- School of Physics and Astronomy, University of Leeds, 192 Woodhouse Lane, Leeds, UK LS2 9JT ; Astbury Centre for Structural and Molecular Biology, University of Leeds, 192 Woodhouse Lane, Leeds, UK LS2 9JT
| |
Collapse
|
74
|
Brackley CA, Johnson J, Bentivoglio A, Corless S, Gilbert N, Gonnella G, Marenduzzo D. Stochastic Model of Supercoiling-Dependent Transcription. PHYSICAL REVIEW LETTERS 2016; 117:018101. [PMID: 27419594 DOI: 10.1103/physrevlett.117.018101] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2014] [Indexed: 06/06/2023]
Abstract
We propose a stochastic model for gene transcription coupled to DNA supercoiling, where we incorporate the experimental observation that polymerases create supercoiling as they unwind the DNA helix and that these enzymes bind more favorably to regions where the genome is unwound. Within this model, we show that when the transcriptionally induced flux of supercoiling increases, there is a sharp crossover from a regime where torsional stresses relax quickly and gene transcription is random, to one where gene expression is highly correlated and tightly regulated by supercoiling. In the latter regime, the model displays transcriptional bursts, waves of supercoiling, and up regulation of divergent or bidirectional genes. It also predicts that topological enzymes which relax twist and writhe should provide a pathway to down regulate transcription.
Collapse
Affiliation(s)
- C A Brackley
- SUPA, School of Physics and Astronomy, University of Edinburgh, Peter Guthrie Tait Road, Edinburgh EH9 3FD, United Kingdom
| | - J Johnson
- SUPA, School of Physics and Astronomy, University of Edinburgh, Peter Guthrie Tait Road, Edinburgh EH9 3FD, United Kingdom
| | - A Bentivoglio
- Dipartimento di Fisica, Università di Bari and INFN, Sezione di Bari, 70126 Bari, Italy
| | - S Corless
- MRC Human Genetics Unit, Institute of Genetics and Molecular Medicine, The University of Edinburgh, Edinburgh EH4 2XU, United Kingdom
| | - N Gilbert
- MRC Human Genetics Unit, Institute of Genetics and Molecular Medicine, The University of Edinburgh, Edinburgh EH4 2XU, United Kingdom
| | - G Gonnella
- Dipartimento di Fisica, Università di Bari and INFN, Sezione di Bari, 70126 Bari, Italy
| | - D Marenduzzo
- SUPA, School of Physics and Astronomy, University of Edinburgh, Peter Guthrie Tait Road, Edinburgh EH9 3FD, United Kingdom
| |
Collapse
|
75
|
Brackley CA, Johnson J, Kelly S, Cook PR, Marenduzzo D. Simulated binding of transcription factors to active and inactive regions folds human chromosomes into loops, rosettes and topological domains. Nucleic Acids Res 2016; 44:3503-12. [PMID: 27060145 PMCID: PMC4856988 DOI: 10.1093/nar/gkw135] [Citation(s) in RCA: 110] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2015] [Revised: 02/22/2016] [Accepted: 02/24/2016] [Indexed: 01/12/2023] Open
Abstract
Biophysicists are modeling conformations of interphase chromosomes, often basing the strengths of interactions between segments distant on the genetic map on contact frequencies determined experimentally. Here, instead, we develop a fitting-free, minimal model: bivalent or multivalent red and green 'transcription factors' bind to cognate sites in strings of beads ('chromatin') to form molecular bridges stabilizing loops. In the absence of additional explicit forces, molecular dynamic simulations reveal that bound factors spontaneously cluster-red with red, green with green, but rarely red with green-to give structures reminiscent of transcription factories. Binding of just two transcription factors (or proteins) to active and inactive regions of human chromosomes yields rosettes, topological domains and contact maps much like those seen experimentally. This emergent 'bridging-induced attraction' proves to be a robust, simple and generic force able to organize interphase chromosomes at all scales.
Collapse
Affiliation(s)
- Chris A Brackley
- SUPA, School of Physics & Astronomy, University of Edinburgh, Peter Guthrie Tait Road, Edinburgh, EH9 3FD, UK
| | - James Johnson
- SUPA, School of Physics & Astronomy, University of Edinburgh, Peter Guthrie Tait Road, Edinburgh, EH9 3FD, UK
| | - Steven Kelly
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford OX1 3RB, UK
| | - Peter R Cook
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford, OX1 3RE, UK
| | - Davide Marenduzzo
- SUPA, School of Physics & Astronomy, University of Edinburgh, Peter Guthrie Tait Road, Edinburgh, EH9 3FD, UK
| |
Collapse
|
76
|
Bunch H. Role of genome guardian proteins in transcriptional elongation. FEBS Lett 2016; 590:1064-75. [PMID: 27010360 DOI: 10.1002/1873-3468.12152] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2016] [Revised: 03/18/2016] [Accepted: 03/21/2016] [Indexed: 12/17/2022]
Abstract
Maintaining genomic integrity is vital for cell survival and homeostasis. Mutations in critical genes in germ-line and somatic cells are often implicated with the onset or progression of diseases. DNA repair enzymes thus take important roles as guardians of the genome in the cell. Besides the known function to repair DNA damage, recent findings indicate that DNA repair enzymes regulate the transcription of protein-coding and noncoding RNA genes. In particular, a novel role of DNA damage response signaling has been identified in the regulation of transcriptional elongation. Topoisomerases-mediated DNA breaks appear important for the regulation. In this review, recent findings of these DNA break- and repair-associated enzymes in transcription and potential roles of transcriptional activation-coupled DNA breaks are discussed.
Collapse
Affiliation(s)
- Heeyoun Bunch
- Department of Genetics and Complex Diseases, Harvard School of Public Health, Boston, MA, USA
| |
Collapse
|
77
|
The Effect of Dimethyl Sulfoxide on Supercoiled DNA Relaxation Catalyzed by Type I Topoisomerases. BIOMED RESEARCH INTERNATIONAL 2015; 2015:320490. [PMID: 26682217 PMCID: PMC4670693 DOI: 10.1155/2015/320490] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/25/2015] [Revised: 10/26/2015] [Accepted: 11/01/2015] [Indexed: 11/30/2022]
Abstract
The effects of dimethyl sulfoxide (DMSO) on supercoiled plasmid DNA relaxation catalyzed by two typical type I topoisomerases were investigated in our studies. It is shown that DMSO in a low concentration (less than 20%, v/v) can induce a dose-related enhancement of the relaxation efficiency of Escherichia coli topoisomerase I (type IA). Conversely, obvious inhibitory effect on the activity of calf thymus topoisomerase I (type IB) was observed when the same concentration of DMSO is used. In addition, our studies demonstrate that 20% DMSO has an ability to reduce the inhibitory effect on EcTopo I, which was induced by double-stranded oligodeoxyribonucleotides while the same effect cannot be found in the case of CtTopo I. Moreover, our AFM examinations suggested that DMSO can change the conformation of negatively supercoiled plasmid by creating some locally loose regions in DNA molecules. Combining all the lines of evidence, we proposed that DMSO enhanced EcTopo I relaxation activity by (1) increasing the single-stranded DNA regions for the activities of EcTopo I in the early and middle stages of the reaction and (2) preventing the formation of double-stranded DNA-enzyme complex in the later stage, which can elevate the effective concentration of the topoisomerase in the reaction solution.
Collapse
|
78
|
Benabdallah NS, Bickmore WA. Regulatory Domains and Their Mechanisms. COLD SPRING HARBOR SYMPOSIA ON QUANTITATIVE BIOLOGY 2015; 80:45-51. [PMID: 26590168 DOI: 10.1101/sqb.2015.80.027268] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The concept of gene regulation is being refined as our understanding of the role of enhancer elements grows. Although described more than 30 years ago, the mechanisms through which these cis-regulating elements operate remain under debate. With the recognition that most of the human genetic variation contributing to common disease risk lies outside of genes and probably in enhancers, unraveling these mechanisms becomes ever more important. Originally, a popular view was to consider regulatory elements as an entry site for the transcription machinery that could scan the intervening chromatin until the cognate core promoter was located. Now, the most prominent model for distal enhancer-promoter interaction involves direct enhancer/promoter contacts with a looping out of intervening chromatin. However, a rising awareness of the importance of chromatin architecture and organization forces us to consider enhancer-promoter communication in light of the polymer folding properties of chromatin. Here, we discuss how three-dimensional chromatin folding, topological domains, and the constrained motion, plasticity, and accessibility of chromatin could offer a structural basis for regulatory domains that greatly enhances the probability of enhancer-promoter and transcription factor-promoter interactions and gene activation.
Collapse
Affiliation(s)
- Nezha S Benabdallah
- MRC Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh EH42XU, United Kingdom Edinburgh Super Resolution Imaging Consortium, Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh EH42XU, United Kingdom
| | - Wendy A Bickmore
- MRC Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh EH42XU, United Kingdom
| |
Collapse
|
79
|
Chokboribal J, Tachaboonyakiat W, Sangvanich P, Ruangpornvisuti V, Jettanacheawchankit S, Thunyakitpisal P. Deacetylation affects the physical properties and bioactivity of acemannan, an extracted polysaccharide from Aloe vera. Carbohydr Polym 2015; 133:556-66. [DOI: 10.1016/j.carbpol.2015.07.039] [Citation(s) in RCA: 91] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2015] [Revised: 06/27/2015] [Accepted: 07/11/2015] [Indexed: 11/30/2022]
|
80
|
Vlijm R, Lee M, Ordu O, Boltengagen A, Lusser A, Dekker NH, Dekker C. Comparing the Assembly and Handedness Dynamics of (H3.3-H4)2 Tetrasomes to Canonical Tetrasomes. PLoS One 2015; 10:e0141267. [PMID: 26506534 PMCID: PMC4623960 DOI: 10.1371/journal.pone.0141267] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2015] [Accepted: 10/05/2015] [Indexed: 01/18/2023] Open
Abstract
Eukaryotic nucleosomes consists of an (H3-H4)2 tetramer and two H2A-H2B dimers, around which 147 bp of DNA are wrapped in 1.7 left-handed helical turns. During chromatin assembly, the (H3-H4)2 tetramer binds first, forming a tetrasome that likely constitutes an important intermediate during ongoing transcription. We recently showed that (H3-H4)2 tetrasomes spontaneously switch between a left- and right-handed wrapped state of the DNA, a phenomenon that may serve to buffer changes in DNA torque induced by RNA polymerase in transcription. Within nucleosomes of actively transcribed genes, however, canonical H3 is progressively replaced by its variant H3.3. Consequently, one may ask if and how the DNA chirality dynamics of tetrasomes is altered by H3.3. Recent findings that H3.3-containing nucleosomes result in less stable and less condensed chromatin further underline the need to study the microscopic underpinnings of H3.3-containing tetrasomes and nucleosomes. Here we report real-time single-molecule studies of (H3.3-H4)2 tetrasome dynamics using Freely Orbiting Magnetic Tweezers and Electromagnetic Torque Tweezers. We find that the assembly of H3.3-containing tetrasomes and nucleosomes by the histone chaperone Nucleosome Assembly Protein 1 (NAP1) occurs in an identical manner to that of H3-containing tetrasomes and nucleosomes. Likewise, the flipping behavior of DNA handedness in tetrasomes is not impacted by the presence of H3.3. We also examine the effect of free NAP1, H3.3, and H4 in solution on flipping behavior and conclude that the probability for a tetrasome to occupy the left-handed state is only slightly enhanced by the presence of free protein. These data demonstrate that the incorporation of H3.3 does not alter the structural dynamics of tetrasomes, and hence that the preferred incorporation of this histone variant in transcriptionally active regions does not result from its enhanced ability to accommodate torsional stress, but rather may be linked to specific chaperone or remodeler requirements or communication with the nuclear environment.
Collapse
Affiliation(s)
- Rifka Vlijm
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Delft, The Netherlands
| | - Mina Lee
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Delft, The Netherlands
| | - Orkide Ordu
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Delft, The Netherlands
| | - Anastasiya Boltengagen
- Division of Molecular Biology, Biocenter, Innsbruck Medical University, Innsbruck, Austria
| | - Alexandra Lusser
- Division of Molecular Biology, Biocenter, Innsbruck Medical University, Innsbruck, Austria
| | - Nynke H. Dekker
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Delft, The Netherlands
- * E-mail: (NHD); (CD)
| | - Cees Dekker
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Delft, The Netherlands
- * E-mail: (NHD); (CD)
| |
Collapse
|
81
|
Lebeaupin T, Sellou H, Timinszky G, Huet S. Chromatin dynamics at DNA breaks: what, how and why? AIMS BIOPHYSICS 2015. [DOI: 10.3934/biophy.2015.4.458] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
|
82
|
Meyer S, Beslon G. Torsion-mediated interaction between adjacent genes. PLoS Comput Biol 2014; 10:e1003785. [PMID: 25188032 PMCID: PMC4154641 DOI: 10.1371/journal.pcbi.1003785] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2014] [Accepted: 06/26/2014] [Indexed: 11/17/2022] Open
Abstract
DNA torsional stress is generated by virtually all biomolecular processes involving the double helix, in particular transcription where a significant level of stress propagates over several kilobases. If another promoter is located in this range, this stress may strongly modify its opening properties, and hence facilitate or hinder its transcription. This mechanism implies that transcribed genes distant of a few kilobases are not independent, but coupled by torsional stress, an effect for which we propose the first quantitative and systematic model. In contrast to previously proposed mechanisms of transcriptional interference, the suggested coupling is not mediated by the transcription machineries, but results from the universal mechanical features of the double-helix. The model shows that the effect likely affects prokaryotes as well as eukaryotes, but with different consequences owing to their different basal levels of torsion. It also depends crucially on the relative orientation of the genes, enhancing the expression of eukaryotic divergent pairs while reducing that of prokaryotic convergent ones. To test the in vivo influence of the torsional coupling, we analyze the expression of isolated gene pairs in the Drosophila melanogaster genome. Their orientation and distance dependence is fully consistent with the model, suggesting that torsional gene coupling may constitute a widespread mechanism of (co)regulation in eukaryotes.
Collapse
Affiliation(s)
- Sam Meyer
- Université de Lyon, INSA Lyon, INRIA, LIRIS, CNRS UMR5205, Lyon, France
| | - Guillaume Beslon
- Université de Lyon, INSA Lyon, INRIA, LIRIS, CNRS UMR5205, Lyon, France
| |
Collapse
|
83
|
Corless S, Naughton C, Gilbert N. Profiling DNA supercoiling domains in vivo. GENOMICS DATA 2014; 2:264-7. [PMID: 26484106 PMCID: PMC4536041 DOI: 10.1016/j.gdata.2014.07.007] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/01/2014] [Accepted: 07/15/2014] [Indexed: 11/25/2022]
Abstract
Transitions in DNA structure have the capacity to regulate genes, but have been poorly characterised in eukaryotes due to a lack of appropriate techniques. One important example is DNA supercoiling, which can directly regulate transcription initiation, elongation and coordinated expression of neighbouring genes. DNA supercoiling is the over- or under-winding of the DNA double helix, which occurs as a consequence of polymerase activity and is modulated by topoisomerase activity [5]. To map the distribution of DNA supercoiling in nuclei, we developed biotinylated 4,5,8-trimethylpsoralen (bTMP) pull-down to preferentially enrich for under-wound DNA. Here we describe in detail the experimental design, quality controls and analyses associated with the study by Naughton et al. [13] that characterised for the first time the large-scale distribution of DNA supercoiling in human cells (GEO: GSE43488 and GSE43450GSE43488GSE43450).
Collapse
Affiliation(s)
- Samuel Corless
- Medical Research Council Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh, UK
| | - Catherine Naughton
- Medical Research Council Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh, UK
| | - Nick Gilbert
- Medical Research Council Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh, UK
| |
Collapse
|
84
|
Hirano T. Condensins and the evolution of torsion-mediated genome organization. Trends Cell Biol 2014; 24:727-33. [PMID: 25092191 DOI: 10.1016/j.tcb.2014.06.007] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2014] [Revised: 06/14/2014] [Accepted: 06/26/2014] [Indexed: 12/20/2022]
Abstract
At first glance, bacteria and eukaryotes appear to use different strategies to pack and organize their genomes. At the basal level, bacterial genome compaction relies on unconstrained, negative supercoils, whereas eukaryotic genomes are packaged into nucleosomes via constrained, negative supercoils. Here, I integrate the action of condensins, chromosome-packaging complexes conserved from bacteria to humans, into this picture, and discuss how torsional stress on DNA might have dual impacts on genome organization and function. A common theme is that organisms have evolved flexible and reversible strategies to pack their genomes while keeping them readily accessible to many activities such as gene expression.
Collapse
Affiliation(s)
- Tatsuya Hirano
- Chromosome Dynamics Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.
| |
Collapse
|
85
|
Fernández X, Díaz-Ingelmo O, Martínez-García B, Roca J. Chromatin regulates DNA torsional energy via topoisomerase II-mediated relaxation of positive supercoils. EMBO J 2014; 33:1492-501. [PMID: 24859967 DOI: 10.15252/embj.201488091] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Eukaryotic topoisomerases I (topo I) and II (topo II) relax the positive (+) and negative (-) DNA torsional stress (TS) generated ahead and behind the transcription machinery. It is unknown how this DNA relaxation activity is regulated and whether (+) and (-)TS are reduced at similar rates. Here, we used yeast circular minichromosomes to conduct the first comparative analysis of topo I and topo II activities in relaxing chromatin under (+) and (-)TS. We observed that, while topo I relaxed (+) and (-)TS with similar efficiency, topo II was more proficient and relaxed (+)TS more quickly than (-)TS. Accordingly, we found that the relaxation rate of (+)TS by endogenous topoisomerases largely surpassed that of (-)TS. We propose a model of how distinct conformations of chromatin under (+) and (-)TS may produce this unbalanced relaxation of DNA. We postulate that, while quick relaxation of (+)TS may facilitate the progression of RNA and DNA polymerases, slow relaxation of (-)TS may serve to favor DNA unwinding and other structural transitions at specific regions often required for genomic transactions.
Collapse
Affiliation(s)
- Xavier Fernández
- Instituto de Biología Molecular de Barcelona (IBMB), Consejo Superior de Investigaciones Científicas (CSIC), Barcelona, Spain
| | - Ofelia Díaz-Ingelmo
- Instituto de Biología Molecular de Barcelona (IBMB), Consejo Superior de Investigaciones Científicas (CSIC), Barcelona, Spain
| | - Belén Martínez-García
- Instituto de Biología Molecular de Barcelona (IBMB), Consejo Superior de Investigaciones Científicas (CSIC), Barcelona, Spain
| | - Joaquim Roca
- Instituto de Biología Molecular de Barcelona (IBMB), Consejo Superior de Investigaciones Científicas (CSIC), Barcelona, Spain
| |
Collapse
|
86
|
Brackley CA, Morozov AN, Marenduzzo D. Models for twistable elastic polymers in Brownian dynamics, and their implementation for LAMMPS. J Chem Phys 2014; 140:135103. [DOI: 10.1063/1.4870088] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
|