1
|
Becker NA, Peters JP, Lewis E, Daby CL, Clark K, Maher LJ. Engineered transcription activator-like effector dimer proteins confer DNA loop-dependent gene repression comparable to Lac repressor. Nucleic Acids Res 2024; 52:9996-10004. [PMID: 39077947 PMCID: PMC11381355 DOI: 10.1093/nar/gkae656] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2024] [Revised: 07/06/2024] [Accepted: 07/16/2024] [Indexed: 07/31/2024] Open
Abstract
Natural prokaryotic gene repression systems often exploit DNA looping to increase the local concentration of gene repressor proteins at a regulated promoter via contributions from repressor proteins bound at distant sites. Using principles from the Escherichia coli lac operon we design analogous repression systems based on target sequence-programmable Transcription Activator-Like Effector dimer (TALED) proteins. Such engineered switches may be valuable for synthetic biology and therapeutic applications. Previous TALEDs with inducible non-covalent dimerization showed detectable, but limited, DNA loop-based repression due to the repressor protein dimerization equilibrium. Here, we show robust DNA loop-dependent bacterial promoter repression by covalent TALEDs and verify that DNA looping dramatically enhances promoter repression in E. coli. We characterize repression using a thermodynamic model that quantitates this favorable contribution of DNA looping. This analysis unequivocally and quantitatively demonstrates that optimized TALED proteins can drive loop-dependent promoter repression in E. coli comparable to the natural LacI repressor system. This work elucidates key design principles that set the stage for wide application of TALED-dependent DNA loop-based repression of target genes.
Collapse
Affiliation(s)
- Nicole A Becker
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine and Science, Rochester, MN 55905, USA
| | - Justin P Peters
- Department of Chemistry and Biochemistry, University of Northern Iowa, Cedar Falls, IA 50614, USA
| | - Elizabeth Lewis
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine and Science, Rochester, MN 55905, USA
| | - Camden L Daby
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine and Science, Rochester, MN 55905, USA
| | - Karl Clark
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine and Science, Rochester, MN 55905, USA
- Department of Animal Science, Texas A&M University, College Station, TX 77843, USA
| | - L James Maher
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine and Science, Rochester, MN 55905, USA
| |
Collapse
|
2
|
Ghadirian N, Morgan RD, Horton NC. DNA Sequence Control of Enzyme Filamentation and Activation of the SgrAI Endonuclease. Biochemistry 2024; 63:326-338. [PMID: 38207281 DOI: 10.1021/acs.biochem.3c00313] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2024]
Abstract
Enzyme polymerization (also known as filamentation) has emerged as a new layer of enzyme regulation. SgrAI is a sequence-dependent DNA endonuclease that forms polymeric filaments with enhanced DNA cleavage activity as well as altered DNA sequence specificity. To better understand this unusual regulatory mechanism, full global kinetic modeling of the reaction pathway, including the enzyme filamentation steps, has been undertaken. Prior work with the primary DNA recognition sequence cleaved by SgrAI has shown how the kinetic rate constants of each reaction step are tuned to maximize activation and DNA cleavage while minimizing the extent of DNA cleavage to the host genome. In the current work, we expand on our prior study by now including DNA cleavage of a secondary recognition sequence, to understand how the sequence of the bound DNA modulates filamentation and activation of SgrAI. The work shows that an allosteric equilibrium between low and high activity states is modulated by the sequence of bound DNA, with primary sequences more prone to activation and filament formation, while SgrAI bound to secondary recognition sequences favor the low (and nonfilamenting) state by up to 40-fold. In addition, the degree of methylation of secondary sequences in the host organism, Streptomyces griseus, is now reported for the first time and shows that as predicted, these sequences are left unprotected from the SgrAI endonuclease making sequence specificity critical in this unusual filament-forming enzyme.
Collapse
Affiliation(s)
- Niloofar Ghadirian
- Department of Chemistry & Biochemistry, University of Arizona, Tucson, Arizona 85721, United States
| | - Richard D Morgan
- New England Biolabs, Inc., Ipswich, Massachusetts 01938, United States
| | - Nancy C Horton
- Department of Molecular and Cellular Biology, University of Arizona, Tucson, Arizona 85721, United States
| |
Collapse
|
3
|
Norris V, Kayser C, Muskhelishvili G, Konto-Ghiorghi Y. The roles of nucleoid-associated proteins and topoisomerases in chromosome structure, strand segregation, and the generation of phenotypic heterogeneity in bacteria. FEMS Microbiol Rev 2023; 47:fuac049. [PMID: 36549664 DOI: 10.1093/femsre/fuac049] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2022] [Revised: 12/06/2022] [Accepted: 12/21/2022] [Indexed: 12/24/2022] Open
Abstract
How to adapt to a changing environment is a fundamental, recurrent problem confronting cells. One solution is for cells to organize their constituents into a limited number of spatially extended, functionally relevant, macromolecular assemblies or hyperstructures, and then to segregate these hyperstructures asymmetrically into daughter cells. This asymmetric segregation becomes a particularly powerful way of generating a coherent phenotypic diversity when the segregation of certain hyperstructures is with only one of the parental DNA strands and when this pattern of segregation continues over successive generations. Candidate hyperstructures for such asymmetric segregation in prokaryotes include those containing the nucleoid-associated proteins (NAPs) and the topoisomerases. Another solution to the problem of creating a coherent phenotypic diversity is by creating a growth-environment-dependent gradient of supercoiling generated along the replication origin-to-terminus axis of the bacterial chromosome. This gradient is modulated by transcription, NAPs, and topoisomerases. Here, we focus primarily on two topoisomerases, TopoIV and DNA gyrase in Escherichia coli, on three of its NAPs (H-NS, HU, and IHF), and on the single-stranded binding protein, SSB. We propose that the combination of supercoiling-gradient-dependent and strand-segregation-dependent topoisomerase activities result in significant differences in the supercoiling of daughter chromosomes, and hence in the phenotypes of daughter cells.
Collapse
Affiliation(s)
- Vic Norris
- University of Rouen, Laboratory of Bacterial Communication and Anti-infection Strategies, EA 4312, 76821 Mont Saint Aignan, France
| | - Clara Kayser
- University of Rouen, Laboratory of Bacterial Communication and Anti-infection Strategies, EA 4312, 76821 Mont Saint Aignan, France
| | - Georgi Muskhelishvili
- Agricultural University of Georgia, School of Natural Sciences, 0159 Tbilisi, Georgia
| | - Yoan Konto-Ghiorghi
- University of Rouen, Laboratory of Bacterial Communication and Anti-infection Strategies, EA 4312, 76821 Mont Saint Aignan, France
| |
Collapse
|
4
|
Meijer WJJ, Boer DR, Ares S, Alfonso C, Rojo F, Luque-Ortega JR, Wu LJ. Multiple Layered Control of the Conjugation Process of the Bacillus subtilis Plasmid pLS20. Front Mol Biosci 2021; 8:648468. [PMID: 33816561 PMCID: PMC8014075 DOI: 10.3389/fmolb.2021.648468] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2020] [Accepted: 02/08/2021] [Indexed: 11/24/2022] Open
Abstract
Bacterial conjugation is the main horizontal gene transfer route responsible for the spread of antibiotic resistance, virulence and toxin genes. During conjugation, DNA is transferred from a donor to a recipient cell via a sophisticated channel connecting the two cells. Conjugation not only affects many different aspects of the plasmid and the host, ranging from the properties of the membrane and the cell surface of the donor, to other developmental processes such as competence, it probably also poses a burden on the donor cell due to the expression of the large number of genes involved in the conjugation process. Therefore, expression of the conjugation genes must be strictly controlled. Over the past decade, the regulation of the conjugation genes present on the conjugative Bacillus subtilis plasmid pLS20 has been studied using a variety of methods including genetic, biochemical, biophysical and structural approaches. This review focuses on the interplay between RcopLS20, RappLS20 and Phr*pLS20, the proteins that control the activity of the main conjugation promoter Pc located upstream of the conjugation operon. Proper expression of the conjugation genes requires the following two fundamental elements. First, conjugation is repressed by default and an intercellular quorum-signaling system is used to sense conditions favorable for conjugation. Second, different layers of regulation act together to repress the Pc promoter in a strict manner but allowing rapid activation. During conjugation, ssDNA is exported from the cell by a membrane-embedded DNA translocation machine. Another membrane-embedded DNA translocation machine imports ssDNA in competent cells. Evidences are reviewed indicating that conjugation and competence are probably mutually exclusive processes. Some of the questions that remain unanswered are discussed.
Collapse
Affiliation(s)
- Wilfried J J Meijer
- Laboratory 402, Centro de Biología Molecular "Severo Ochoa" (CSIC-UAM), Universidad Autónoma, Canto Blanco, Madrid, Spain
| | | | - Saúl Ares
- Laboratory 35, C. Grupo Interdisciplinar de Sistemas Complejos and Departamento de Biología de Sistemas, Centro Nacional de Biotecnología, CSIC, Madrid, Spain
| | - Carlos Alfonso
- Laboratory B08, Systems Biochemistry of Bacterial Division Lab, Centro de Investigaciones Biológicas Margarita Salas (CSIC), Madrid, Spain
| | - Fernando Rojo
- Laboratory 216, Department of Microbial Biotechnology, Centro Nacional de Biotecnología, CSIC, Madrid, Spain
| | - Juan R Luque-Ortega
- Laboratory S07, Molecular Interactions Facility, Centro de Investigaciones Biológicas Margarita Salas (CSIC), Madrid, Spain
| | - Ling Juan Wu
- Centre for Bacterial Cell Biology, Biosciences Institute, Newcastle University, Newcastle Upon Tyne, United Kingdom
| |
Collapse
|
5
|
Saran R, Wang Y, Li ITS. Mechanical Flexibility of DNA: A Quintessential Tool for DNA Nanotechnology. SENSORS (BASEL, SWITZERLAND) 2020; 20:E7019. [PMID: 33302459 PMCID: PMC7764255 DOI: 10.3390/s20247019] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/03/2020] [Revised: 12/04/2020] [Accepted: 12/04/2020] [Indexed: 02/06/2023]
Abstract
The mechanical properties of DNA have enabled it to be a structural and sensory element in many nanotechnology applications. While specific base-pairing interactions and secondary structure formation have been the most widely utilized mechanism in designing DNA nanodevices and biosensors, the intrinsic mechanical rigidity and flexibility are often overlooked. In this article, we will discuss the biochemical and biophysical origin of double-stranded DNA rigidity and how environmental and intrinsic factors such as salt, temperature, sequence, and small molecules influence it. We will then take a critical look at three areas of applications of DNA bending rigidity. First, we will discuss how DNA's bending rigidity has been utilized to create molecular springs that regulate the activities of biomolecules and cellular processes. Second, we will discuss how the nanomechanical response induced by DNA rigidity has been used to create conformational changes as sensors for molecular force, pH, metal ions, small molecules, and protein interactions. Lastly, we will discuss how DNA's rigidity enabled its application in creating DNA-based nanostructures from DNA origami to nanomachines.
Collapse
Affiliation(s)
- Runjhun Saran
- Department of Chemistry, Biochemistry and Molecular Biology, Irving K. Barber Faculty of Science, The University of British Columbia, Kelowna, BC V1V1V7, Canada;
| | - Yong Wang
- Department of Physics, Materials Science and Engineering Program, Cell and Molecular Biology Program, University of Arkansas, Fayetteville, AR 72701, USA;
| | - Isaac T. S. Li
- Department of Chemistry, Biochemistry and Molecular Biology, Irving K. Barber Faculty of Science, The University of British Columbia, Kelowna, BC V1V1V7, Canada;
| |
Collapse
|
6
|
Becker NA, Peters JP, Schwab TL, Phillips WJ, Wallace JP, Clark KJ, Maher LJ. Characterization of Gene Repression by Designed Transcription Activator-like Effector Dimer Proteins. Biophys J 2020; 119:2045-2054. [PMID: 33091377 PMCID: PMC7732741 DOI: 10.1016/j.bpj.2020.10.007] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2020] [Revised: 10/08/2020] [Accepted: 10/13/2020] [Indexed: 11/18/2022] Open
Abstract
Gene regulation by control of transcription initiation is a fundamental property of living cells. Much of our understanding of gene repression originated from studies of the Escherichia coli lac operon switch, in which DNA looping plays an essential role. To validate and generalize principles from lac for practical applications, we previously described artificial DNA looping driven by designed transcription activator-like effector dimer (TALED) proteins. Because TALE monomers bind the idealized symmetrical lac operator sequence in two orientations, our prior studies detected repression due to multiple DNA loops. We now quantitatively characterize gene repression in living E. coli by a collection of individual TALED loops with systematic loop length variation. Fitting of a thermodynamic model allows unequivocal demonstration of looping and comparison of the engineered TALED repression system with the natural lac repressor system.
Collapse
Affiliation(s)
- Nicole A Becker
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine and Science, Rochester, Minnesota
| | - Justin P Peters
- Department of Chemistry and Biochemistry, University of Northern Iowa, Cedar Falls, Iowa
| | - Tanya L Schwab
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine and Science, Rochester, Minnesota
| | - William J Phillips
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine and Science, Rochester, Minnesota
| | - Jordan P Wallace
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine and Science, Rochester, Minnesota
| | - Karl J Clark
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine and Science, Rochester, Minnesota
| | - L James Maher
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine and Science, Rochester, Minnesota.
| |
Collapse
|
7
|
Perinelli M, Guerrini R, Albanese V, Marchetti N, Bellotti D, Gentili S, Tegoni M, Remelli M. Cu(II) coordination to His-containing linear peptides and related branched ones: Equalities and diversities. J Inorg Biochem 2020; 205:110980. [PMID: 31931375 DOI: 10.1016/j.jinorgbio.2019.110980] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2019] [Revised: 12/13/2019] [Accepted: 12/24/2019] [Indexed: 01/20/2023]
Abstract
The two branched peptides (AAHAWG)4-PWT2 and (HAWG)4-PWT2 where synthesized by mounting linear peptides on a cyclam-based scaffold (PWT2), provided with four maleimide chains, through a thio-Michael reaction. The purpose of this study was primarily to verify if the two branched ligands had a Cu(II) coordination behavior reproducing that of the single-chain peptides, namely AAHAWG-NH2, which bears an Amino Terminal Cu(II)- and Ni(II)-Binding (ATCUN) Motif, and HAWG-NH2, which presents a His residue as the N-terminal amino acid, in a wide pH range. The study of Cu(II) binding was performed by potentiometric, spectroscopic (UV-vis absorption, CD, fluorescence) and ESI-MS techniques. ATCUN-type ligands ((AAHAWG)4-PWT2 and AAHAWG-NH2) were confirmed to bind one Cu(II) per peptide fragment at both pH 7.4 and pH 9.0, with a [NH2, 2N-, NIm] coordination mode. On the other hand, the ligand HAWG-NH2 forms a [CuL2]2+ species at neutral pH, while, at pH 9, the formation of 1:2 Cu(II):ligand adducts is prevented by amidic nitrogen deprotonation and coordination, to give rise solely to 1:1 species. Conversely, Cu(II) binding to (HAWG)4-PWT2 resulted in the formation of 1:2 copper:peptide chain also at pH 9: hence, through the latter branched peptide we obtained, at alkaline pH, the stabilization of a specific Cu(II) coordination mode which results unachievable using the corresponding single-chain peptide. This behavior could be explained in terms of high local peptide concentration on the basis of the speciation of the Cu(II)/single-chain peptide systems.
Collapse
Affiliation(s)
- Monica Perinelli
- Dipartimento di Scienze Chimiche, della Vita e della Sostenibilità Ambientale, Università di Parma, Parco Area delle Scienze 11/A, 43124 Parma, Italy
| | - Remo Guerrini
- Dipartimento di Scienze Chimiche e Farmaceutiche, Università di Ferrara, via Luigi Borsari 46, 44121 Ferrara, Italy
| | - Valentina Albanese
- Dipartimento di Scienze Chimiche e Farmaceutiche, Università di Ferrara, via Luigi Borsari 46, 44121 Ferrara, Italy
| | - Nicola Marchetti
- Dipartimento di Scienze Chimiche e Farmaceutiche, Università di Ferrara, via Luigi Borsari 46, 44121 Ferrara, Italy
| | - Denise Bellotti
- Dipartimento di Scienze Chimiche e Farmaceutiche, Università di Ferrara, via Luigi Borsari 46, 44121 Ferrara, Italy
| | - Silvia Gentili
- Dipartimento di Scienze Chimiche, della Vita e della Sostenibilità Ambientale, Università di Parma, Parco Area delle Scienze 11/A, 43124 Parma, Italy
| | - Matteo Tegoni
- Dipartimento di Scienze Chimiche, della Vita e della Sostenibilità Ambientale, Università di Parma, Parco Area delle Scienze 11/A, 43124 Parma, Italy.
| | - Maurizio Remelli
- Dipartimento di Scienze Chimiche e Farmaceutiche, Università di Ferrara, via Luigi Borsari 46, 44121 Ferrara, Italy.
| |
Collapse
|
8
|
Sharma J, Douglas T. Tuning the catalytic properties of P22 nanoreactors through compositional control. NANOSCALE 2020; 12:336-346. [PMID: 31825057 PMCID: PMC8859858 DOI: 10.1039/c9nr08348k] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Enzymes are biomacromolecular protein catalysts that are widely used in a plethora of industrial-scale applications due to their high selectivity, efficiency and ability to work under mild conditions. Many industrial processes require the immobilization of enzymes to enhance their performance and stability. Encapsulation of enzymes in protein cages provides an excellent immobilization platform to create nanoreactors with enhanced enzymatic stability and desired catalytic activities. Here we show that the catalytic activity of nanoreactors, derived from the bacteriophage P22 viral capsids, can be finely-tuned by controlling the packaging stoichiometry and packing density of encapsulated enzymes. The packaging stoichiometry of the enzyme alcohol dehydrogenase (AdhD) was controlled by co-encapsulating it with wild-type scaffold protein (wtSP) at different stoichiometric ratios using an in vitro assembly approach and the packing density was controlled by selectively removing wtSP from the assembled nanoreactors. An inverse relationship was observed between the catalytic activity (kcat) of AdhD enzyme and the concentration of co-encapsulated wtSP. Selective removal of the wtSP resulted in the similar activity of AdhD in all nanoreactors despite the difference in the volume occupied by enzymes inside nanoreactors, indicating that the AdhD enzymes do not experience self-crowding even under high molarity of confinement (Mconf) conditions. The approach demonstrated here not only allowed us to tailor the activity of encapsulated AdhD catalysts but also the overall functional output of nanoreactors (enzyme-VLP complex). The approach also allowed us to differentiate the effects of crowding and confinement on the functional properties of enzymes encapsulated in an enclosed system, which could pave the way for designing more efficient nanoreactors.
Collapse
Affiliation(s)
- Jhanvi Sharma
- Department of Chemistry, Indiana University, 800 E. Kirkwood Avenue, Bloomington, Indiana 47405, USA.
| | - Trevor Douglas
- Department of Chemistry, Indiana University, 800 E. Kirkwood Avenue, Bloomington, Indiana 47405, USA.
| |
Collapse
|
9
|
Richardson TT, Stevens D, Pelliciari S, Harran O, Sperlea T, Murray H. Identification of a basal system for unwinding a bacterial chromosome origin. EMBO J 2019; 38:e101649. [PMID: 31267560 PMCID: PMC6669920 DOI: 10.15252/embj.2019101649] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2019] [Revised: 06/06/2019] [Accepted: 06/07/2019] [Indexed: 01/03/2023] Open
Abstract
Genome duplication is essential for cell proliferation, and DNA synthesis is generally initiated by dedicated replication proteins at specific loci termed origins. In bacteria, the master initiator DnaA binds the chromosome origin (oriC) and unwinds the DNA duplex to permit helicase loading. However, despite decades of research it remained unclear how the information encoded within oriC guides DnaA-dependent strand separation. To address this fundamental question, we took a systematic genetic approach in vivo and identified the core set of essential sequence elements within the Bacillus subtilis chromosome origin unwinding region. Using this information, we then show in vitro that the minimal replication origin sequence elements are necessary and sufficient to promote the mechanical functions of DNA duplex unwinding by DnaA. Because the basal DNA unwinding system characterized here appears to be conserved throughout the bacterial domain, this discovery provides a framework for understanding oriC architecture, activity, regulation and diversity.
Collapse
Affiliation(s)
- Tomas T Richardson
- Centre for Bacterial Cell BiologyInstitute for Cell and Molecular BiosciencesNewcastle UniversityNewcastle Upon TyneUK
| | - Daniel Stevens
- Centre for Bacterial Cell BiologyInstitute for Cell and Molecular BiosciencesNewcastle UniversityNewcastle Upon TyneUK
| | - Simone Pelliciari
- Centre for Bacterial Cell BiologyInstitute for Cell and Molecular BiosciencesNewcastle UniversityNewcastle Upon TyneUK
| | - Omar Harran
- Centre for Bacterial Cell BiologyInstitute for Cell and Molecular BiosciencesNewcastle UniversityNewcastle Upon TyneUK
| | - Theodor Sperlea
- Chromosome Biology GroupLOEWE Center for Synthetic MicrobiologySYNMIKROPhilipps‐Universität MarburgMarburgGermany
| | - Heath Murray
- Centre for Bacterial Cell BiologyInstitute for Cell and Molecular BiosciencesNewcastle UniversityNewcastle Upon TyneUK
| |
Collapse
|
10
|
Jost D, Vaillant C. Epigenomics in 3D: importance of long-range spreading and specific interactions in epigenomic maintenance. Nucleic Acids Res 2019; 46:2252-2264. [PMID: 29365171 PMCID: PMC5861409 DOI: 10.1093/nar/gky009] [Citation(s) in RCA: 55] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2017] [Accepted: 01/11/2018] [Indexed: 02/05/2023] Open
Abstract
Recent progresses of genome-wide chromatin conformation capture techniques have shown that the genome is segmented into hierarchically organized spatial compartments. However, whether this non-random 3D organization only reflects or indeed contributes—and how—to the regulation of genome function remain to be elucidated. The observation in many species that 3D domains correlate strongly with the 1D epigenomic information along the genome suggests a dynamic coupling between chromatin organization and epigenetic regulation. Here, we posit that chromosome folding may contribute to the maintenance of a robust epigenomic identity via the formation of spatial compartments like topologically-associating domains. Using a novel theoretical framework, the living chromatin model, we show that 3D compartmentalization leads to the spatial colocalization of epigenome regulators, thus increasing their local concentration and enhancing their ability to spread an epigenomic signal at long-range. Interestingly, we find that the presence of 1D insulator elements, like CTCF, may contribute greatly to the stable maintenance of adjacent antagonistic epigenomic domains. We discuss the generic implications of our findings in the light of various biological contexts from yeast to human. Our approach provides a modular framework to improve our understanding and to investigate in details the coupling between the structure and function of chromatin.
Collapse
Affiliation(s)
- Daniel Jost
- Univ. Grenoble Alpes, CNRS, CHU Grenoble Alpes, Grenoble INP, TIMC-IMAG, 38000 Grenoble, France
- To whom correspondence should be addressed. Tel: +33 4 72 72 86 34; Fax: +33 4 72 72 89 50; . Correspondence may also be addressed to Daniel Jost. Tel: +33 4 56 52 00 69; Fax: +33 4 56 52 00 44;
| | - Cédric Vaillant
- Univ Lyon, ENS de Lyon, Univ Claude Bernard, CNRS, Laboratoire de Physique, 69007 Lyon, France
- To whom correspondence should be addressed. Tel: +33 4 72 72 86 34; Fax: +33 4 72 72 89 50; . Correspondence may also be addressed to Daniel Jost. Tel: +33 4 56 52 00 69; Fax: +33 4 56 52 00 44;
| |
Collapse
|
11
|
Does the Semiconservative Nature of DNA Replication Facilitate Coherent Phenotypic Diversity? J Bacteriol 2019; 201:JB.00119-19. [PMID: 30936370 DOI: 10.1128/jb.00119-19] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
It has been clear for over sixty years that the principal method whereby cells replicate and segregate their DNA is semiconservative. It is much less clear why it should be like this rather than, say, conservative. Recently, evidence has accumulated that supports the hypothesis that one of the functions of the cell cycle is to generate phenotypically different daughter cells, even in nondifferentiating bacteria such as Escherichia coli Evidence has also accumulated that the bacterial phenotype is determined by the functioning of extended assemblies of macromolecules termed hyperstructures. One class of these hyperstructures is attached dynamically to a DNA strand by the coupling of transcription and translation. Previously, we proposed in the strand segregation model that one set of hyperstructures accompanies one parental strand into one daughter cell while another set of hyperstructures accompanies the other parental strand into the other daughter cell. This epigenetic mechanism results in daughter cells having different phenotypes. Here, I propose that one of the reasons why semiconservative replication has been selected is because it allows the generation of a population containing cells with very different growth rates even in steady-state conditions.
Collapse
|
12
|
De Bruyn P, Hadži S, Vandervelde A, Konijnenberg A, Prolič-Kalinšek M, Sterckx YGJ, Sobott F, Lah J, Van Melderen L, Loris R. Thermodynamic Stability of the Transcription Regulator PaaR2 from Escherichia coli O157:H7. Biophys J 2019; 116:1420-1431. [PMID: 30979547 DOI: 10.1016/j.bpj.2019.03.015] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2018] [Revised: 02/26/2019] [Accepted: 03/19/2019] [Indexed: 11/25/2022] Open
Abstract
PaaR2 is a putative transcription regulator encoded by a three-component parDE-like toxin-antitoxin module from Escherichia coli O157:H7. Although this module's toxin, antitoxin, and toxin-antitoxin complex have been more thoroughly investigated, little remains known about its transcription regulator PaaR2. Using a wide range of biophysical techniques (circular dichroism spectroscopy, size-exclusion chromatography-multiangle laser light scattering, dynamic light scattering, small-angle x-ray scattering, and native mass spectrometry), we demonstrate that PaaR2 mainly consists of α-helices and displays a concentration-dependent octameric build-up in solution and that this octamer contains a global shape that is significantly nonspherical. Thermal unfolding of PaaR2 is reversible and displays several transitions, suggesting a complex unfolding mechanism. The unfolding data obtained from spectroscopic and calorimetric methods were combined into a unifying thermodynamic model, which suggests a five-state unfolding trajectory. Furthermore, the model allows the calculation of a stability phase diagram, which shows that, under physiological conditions, PaaR2 mainly exists as a dimer that can swiftly oligomerize into an octamer depending on local protein concentrations. These findings, based on a thorough biophysical and thermodynamic analysis of PaaR2, may provide important insights into biological function such as DNA binding and transcriptional regulation.
Collapse
Affiliation(s)
- Pieter De Bruyn
- Structural Biology Brussels, Department of Biotechnology, Vrije Universiteit Brussel, Brussels, Belgium; Center for Structural Biology, Vlaams Instituut voor Biotechnologie, Brussels, Belgium
| | - San Hadži
- Structural Biology Brussels, Department of Biotechnology, Vrije Universiteit Brussel, Brussels, Belgium; Center for Structural Biology, Vlaams Instituut voor Biotechnologie, Brussels, Belgium; Department of Physical Chemistry, Faculty of Chemistry and Chemical Technology, University of Ljubljana, Ljubljana, Slovenia
| | - Alexandra Vandervelde
- Structural Biology Brussels, Department of Biotechnology, Vrije Universiteit Brussel, Brussels, Belgium; Center for Structural Biology, Vlaams Instituut voor Biotechnologie, Brussels, Belgium
| | - Albert Konijnenberg
- Structural Biology Brussels, Department of Biotechnology, Vrije Universiteit Brussel, Brussels, Belgium; Center for Structural Biology, Vlaams Instituut voor Biotechnologie, Brussels, Belgium; Biomolecular and Analytical Mass Spectrometry Group, Department of Chemistry, University of Antwerp, Antwerpen, Belgium
| | - Maruša Prolič-Kalinšek
- Structural Biology Brussels, Department of Biotechnology, Vrije Universiteit Brussel, Brussels, Belgium; Center for Structural Biology, Vlaams Instituut voor Biotechnologie, Brussels, Belgium
| | - Yann G-J Sterckx
- Structural Biology Brussels, Department of Biotechnology, Vrije Universiteit Brussel, Brussels, Belgium; Center for Structural Biology, Vlaams Instituut voor Biotechnologie, Brussels, Belgium; Laboratory of Medical Biochemistry, University of Antwerp, Campus Drie Eiken, Wilrijk, Belgium
| | - Frank Sobott
- Biomolecular and Analytical Mass Spectrometry Group, Department of Chemistry, University of Antwerp, Antwerpen, Belgium; Astbury Centre for Structural Molecular Biology, Leeds, United Kingdom; School of Molecular and Cellular Biology, University of Leeds, Leeds, United Kingdom
| | - Jurij Lah
- Department of Physical Chemistry, Faculty of Chemistry and Chemical Technology, University of Ljubljana, Ljubljana, Slovenia
| | - Laurence Van Melderen
- Cellular and Molecular Microbiology, Faculté des Sciences, Université Libre de Bruxelles, Gosselies, Belgium
| | - Remy Loris
- Structural Biology Brussels, Department of Biotechnology, Vrije Universiteit Brussel, Brussels, Belgium; Center for Structural Biology, Vlaams Instituut voor Biotechnologie, Brussels, Belgium.
| |
Collapse
|
13
|
Becker NA, Schwab TL, Clark KJ, Maher LJ. Bacterial gene control by DNA looping using engineered dimeric transcription activator like effector (TALE) proteins. Nucleic Acids Res 2018; 46:2690-2696. [PMID: 29390154 PMCID: PMC5861415 DOI: 10.1093/nar/gky047] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2017] [Revised: 01/07/2018] [Accepted: 01/18/2018] [Indexed: 01/04/2023] Open
Abstract
Genetic switches must alternate between states whose probabilities are dependent on regulatory signals. Classical examples of transcriptional control in bacteria depend on repressive DNA loops anchored by proteins whose structures are sensitive to small molecule inducers or co-repressors. We are interested in exploiting these natural principles to engineer artificial switches for transcriptional control of bacterial genes. Here, we implement designed homodimeric DNA looping proteins ('Transcription Activator-Like Effector Dimers'; TALEDs) for this purpose in living bacteria. Using well-studied FKBP dimerization domains, we build switches that mimic regulatory characteristics of classical Escherichia coli lactose, galactose and tryptophan operon promoters, including induction or co-repression by small molecules. Engineered DNA looping using TALEDs is thus a new approach to tuning gene expression in bacteria. Similar principles may also be applicable for gene control in eukaryotes.
Collapse
Affiliation(s)
- Nicole A Becker
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine and Science, 200 First St. SW, Rochester, MN 55905, USA
| | - Tanya L Schwab
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine and Science, 200 First St. SW, Rochester, MN 55905, USA
| | - Karl J Clark
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine and Science, 200 First St. SW, Rochester, MN 55905, USA
| | - L. James Maher
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine and Science, 200 First St. SW, Rochester, MN 55905, USA
| |
Collapse
|
14
|
Zhao P, Wang W, Tian P. Development of cyclic AMP receptor protein-based artificial transcription factor for intensifying gene expression. Appl Microbiol Biotechnol 2018; 102:1673-1685. [DOI: 10.1007/s00253-018-8750-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2017] [Revised: 12/21/2017] [Accepted: 12/27/2017] [Indexed: 10/18/2022]
|
15
|
Tsai A, Muthusamy AK, Alves MR, Lavis LD, Singer RH, Stern DL, Crocker J. Nuclear microenvironments modulate transcription from low-affinity enhancers. eLife 2017; 6:28975. [PMID: 29095143 PMCID: PMC5695909 DOI: 10.7554/elife.28975] [Citation(s) in RCA: 92] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2017] [Accepted: 10/29/2017] [Indexed: 02/07/2023] Open
Abstract
Transcription factors bind low-affinity DNA sequences for only short durations. It is not clear how brief, low-affinity interactions can drive efficient transcription. Here, we report that the transcription factor Ultrabithorax (Ubx) utilizes low-affinity binding sites in the Drosophila melanogaster shavenbaby (svb) locus and related enhancers in nuclear microenvironments of high Ubx concentrations. Related enhancers colocalize to the same microenvironments independently of their chromosomal location, suggesting that microenvironments are highly differentiated transcription domains. Manipulating the affinity of svb enhancers revealed an inverse relationship between enhancer affinity and Ubx concentration required for transcriptional activation. The Ubx cofactor, Homothorax (Hth), was co-enriched with Ubx near enhancers that require Hth, even though Ubx and Hth did not co-localize throughout the nucleus. Thus, microenvironments of high local transcription factor and cofactor concentrations could help low-affinity sites overcome their kinetic inefficiency. Mechanisms that generate these microenvironments could be a general feature of eukaryotic transcriptional regulation.
Collapse
Affiliation(s)
- Albert Tsai
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, United States
| | - Anand K Muthusamy
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, United States
| | | | - Luke D Lavis
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, United States
| | - Robert H Singer
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, United States.,Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, United States
| | - David L Stern
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, United States
| | - Justin Crocker
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, United States.,European Molecular Biology Laboratory, Heidelberg, Germany
| |
Collapse
|
16
|
Bacterial pathogen gene regulation: a DNA-structure-centred view of a protein-dominated domain. Clin Sci (Lond) 2017; 130:1165-77. [PMID: 27252403 DOI: 10.1042/cs20160024] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2016] [Accepted: 04/15/2016] [Indexed: 02/03/2023]
Abstract
The mechanisms used by bacterial pathogens to regulate the expression of their genes, especially their virulence genes, have been the subject of intense investigation for several decades. Whole genome sequencing projects, together with more targeted studies, have identified hundreds of DNA-binding proteins that contribute to the patterns of gene expression observed during infection as well as providing important insights into the nature of the gene products whose expression is being controlled by these proteins. Themes that have emerged include the importance of horizontal gene transfer to the evolution of pathogens, the need to impose regulatory discipline upon these imported genes and the important roles played by factors normally associated with the organization of genome architecture as regulatory principles in the control of virulence gene expression. Among these architectural elements is the structure of DNA itself, its variable nature at a topological rather than just at a base-sequence level and its ability to play an active (as well as a passive) part in the gene regulation process.
Collapse
|
17
|
Marcus JI, Hassoun S, Nair NU. Computational prediction of functional abortive RNA in E. coli. Genomics 2017; 109:196-203. [PMID: 28347827 DOI: 10.1016/j.ygeno.2017.03.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2016] [Revised: 02/24/2017] [Accepted: 03/22/2017] [Indexed: 11/26/2022]
Abstract
Failure by RNA polymerase to break contacts with promoter DNA results in release of bound RNA and re-initiation of transcription. These abortive RNAs were assumed to be non-functional but have recently been shown to affect termination in bacteriophage T7. Little is known about the functional role of these RNA in other genetic models. Using a computational approach, we investigated whether abortive RNA could exert function in E. coli. Fragments generated from 3780 transcription units were used as query sequences within their respective transcription units to search for possible binding sites. Sites that fell within known regulatory features were then ranked based upon the free energy of hybridization to the abortive. We further hypothesize about mechanisms of regulatory action for a select number of likely matches. Future experimental validation of these putative abortive-mRNA pairs may confirm our findings and promote exploration of functional abortive RNAs (faRNAs) in natural and synthetic systems.
Collapse
Affiliation(s)
- Jeremy I Marcus
- Department of Computer Science, Tufts University, Medford, MA 02155, United States
| | - Soha Hassoun
- Department of Computer Science, Tufts University, Medford, MA 02155, United States; Department of Chemical and Biological Engineering, Tufts University, Medford, MA 02155, United States
| | - Nikhil U Nair
- Department of Chemical and Biological Engineering, Tufts University, Medford, MA 02155, United States.
| |
Collapse
|
18
|
Vörös Z, Yan Y, Kovari DT, Finzi L, Dunlap D. Proteins mediating DNA loops effectively block transcription. Protein Sci 2017; 26:1427-1438. [PMID: 28295806 PMCID: PMC5477534 DOI: 10.1002/pro.3156] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2016] [Revised: 03/07/2017] [Accepted: 03/08/2017] [Indexed: 12/17/2022]
Abstract
Loops are ubiquitous topological elements formed when proteins simultaneously bind to two noncontiguous DNA sites. While a loop‐mediating protein may regulate initiation at a promoter, the presence of the protein at the other site may be an obstacle for RNA polymerases (RNAP) transcribing a different gene. To test whether a DNA loop alters the extent to which a protein blocks transcription, the lac repressor (LacI) was used. The outcome of in vitro transcription along templates containing two LacI operators separated by 400 bp in the presence of LacI concentrations that produced both looped and unlooped molecules was visualized with scanning force microscopy (SFM). An analysis of transcription elongation complexes, moving for 60 s at an average of 10 nt/s on unlooped DNA templates, revealed that they more often surpassed LacI bound to the lower affinity O2 operator than to the highest affinity Os operator. However, this difference was abrogated in looped DNA molecules where LacI became a strong roadblock independently of the affinity of the operator. Recordings of transcription elongation complexes, using magnetic tweezers, confirmed that they halted for several minutes upon encountering a LacI bound to a single operator. The average pause lifetime is compatible with RNAP waiting for LacI dissociation, however, the LacI open conformation visualized in the SFM images also suggests that LacI could straddle RNAP to let it pass. Independently of the mechanism by which RNAP bypasses the LacI roadblock, the data indicate that an obstacle with looped topology more effectively interferes with transcription.
Collapse
Affiliation(s)
- Zsuzsanna Vörös
- Department of Physics, Emory University, Atlanta, Georgia, 30322
| | - Yan Yan
- Department of Physics, Emory University, Atlanta, Georgia, 30322
| | - Daniel T Kovari
- Department of Physics, Emory University, Atlanta, Georgia, 30322
| | - Laura Finzi
- Department of Physics, Emory University, Atlanta, Georgia, 30322
| | - David Dunlap
- Department of Physics, Emory University, Atlanta, Georgia, 30322
| |
Collapse
|
19
|
A model of dynamic stability of H3K9me3 heterochromatin to explain the resistance to reprogramming of differentiated cells. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2017; 1860:184-195. [DOI: 10.1016/j.bbagrm.2016.11.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2016] [Revised: 11/16/2016] [Accepted: 11/17/2016] [Indexed: 12/16/2022]
|
20
|
Haddad N, Jost D, Vaillant C. Perspectives: using polymer modeling to understand the formation and function of nuclear compartments. Chromosome Res 2017; 25:35-50. [PMID: 28091870 PMCID: PMC5346151 DOI: 10.1007/s10577-016-9548-2] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2016] [Revised: 12/18/2016] [Accepted: 12/21/2016] [Indexed: 12/20/2022]
Abstract
Compartmentalization is a ubiquitous feature of cellular function. In the nucleus, early observations revealed a non-random spatial organization of the genome with a large-scale segregation between transcriptionally active—euchromatin—and silenced—heterochromatin—parts of the genome. Recent advances in genome-wide mapping and imaging techniques have strikingly improved the resolution at which nuclear genome folding can be analyzed and have revealed a multiscale spatial compartmentalization with increasing evidences that such compartment may indeed result from and participate to genome function. Understanding the underlying mechanisms of genome folding and in particular the link to gene regulation requires a cross-disciplinary approach that combines the new high-resolution techniques with computational modeling of chromatin and chromosomes. In this perspective article, we first present how the copolymer theoretical framework can account for the genome compartmentalization. We then suggest, in a second part, that compartments may act as a “nanoreactor,” increasing the robustness of either activation or repression by enhancing the local concentration of regulators. We conclude with the need to develop a new framework, namely the “living chromatin” model that will allow to explicitly investigate the coupling between spatial compartmentalization and gene regulation.
Collapse
Affiliation(s)
- N Haddad
- CNRS, Laboratoire de Physique, University of Lyon, ENS de Lyon, University of Claude Bernard, 69007, Lyon, France
| | - D Jost
- University Grenoble-Alpes, CNRS, TIMC-IMAG lab, UMR 5525, Grenoble, France.
| | - C Vaillant
- CNRS, Laboratoire de Physique, University of Lyon, ENS de Lyon, University of Claude Bernard, 69007, Lyon, France.
| |
Collapse
|
21
|
Qian Z, Trostel A, Lewis DEA, Lee SJ, He X, Stringer AM, Wade JT, Schneider TD, Durfee T, Adhya S. Genome-Wide Transcriptional Regulation and Chromosome Structural Arrangement by GalR in E. coli. Front Mol Biosci 2016; 3:74. [PMID: 27900321 PMCID: PMC5110547 DOI: 10.3389/fmolb.2016.00074] [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: 08/12/2016] [Accepted: 10/26/2016] [Indexed: 11/13/2022] Open
Abstract
The regulatory protein, GalR, is known for controlling transcription of genes related to D-galactose metabolism in Escherichia coli. Here, using a combination of experimental and bioinformatic approaches, we identify novel GalR binding sites upstream of several genes whose function is not directly related to D-galactose metabolism. Moreover, we do not observe regulation of these genes by GalR under standard growth conditions. Thus, our data indicate a broader regulatory role for GalR, and suggest that regulation by GalR is modulated by other factors. Surprisingly, we detect regulation of 158 transcripts by GalR, with few regulated genes being associated with a nearby GalR binding site. Based on our earlier observation of long-range interactions between distally bound GalR dimers, we propose that GalR indirectly regulates the transcription of many genes by inducing large-scale restructuring of the chromosome.
Collapse
Affiliation(s)
- Zhong Qian
- Laboratory of Molecular Biology, National Institutes of Health, National Cancer Institute Bethesda, MD, USA
| | - Andrei Trostel
- Laboratory of Molecular Biology, National Institutes of Health, National Cancer Institute Bethesda, MD, USA
| | - Dale E A Lewis
- Laboratory of Molecular Biology, National Institutes of Health, National Cancer Institute Bethesda, MD, USA
| | - Sang Jun Lee
- Microbiomics and Immunity Research Center, Korea Research Institute of Bioscience and Biotechnology Daejeon, Korea
| | - Ximiao He
- Laboratory of Metabolism, National Institutes of Health, National Cancer Institute Bethesda, MD, USA
| | - Anne M Stringer
- Wadsworth Center, New York State Department of Health Albany, NY, USA
| | - Joseph T Wade
- Wadsworth Center, New York State Department of HealthAlbany, NY, USA; Department of Biomedical Sciences, School of Public Health, University of AlbanyAlbany, NY, USA
| | - Thomas D Schneider
- Gene Regulation and Chromosome Biology Laboratory, National Institutes of Health, National Cancer Institute, Center for Cancer Research Frederick, MD, USA
| | | | - Sankar Adhya
- Laboratory of Molecular Biology, National Institutes of Health, National Cancer Institute Bethesda, MD, USA
| |
Collapse
|
22
|
Roncarati D, Pelliciari S, Doniselli N, Maggi S, Vannini A, Valzania L, Mazzei L, Zambelli B, Rivetti C, Danielli A. Metal-responsive promoter DNA compaction by the ferric uptake regulator. Nat Commun 2016; 7:12593. [PMID: 27558202 PMCID: PMC5007355 DOI: 10.1038/ncomms12593] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2015] [Accepted: 07/13/2016] [Indexed: 01/09/2023] Open
Abstract
Short-range DNA looping has been proposed to affect promoter activity in many bacterial species and operator configurations, but only few examples have been experimentally investigated in molecular detail. Here we present evidence for a metal-responsive DNA condensation mechanism controlled by the Helicobacter pylori ferric uptake regulator (Fur), an orthologue of the widespread Fur family of prokaryotic metal-dependent regulators. H. pylori Fur represses the transcription of the essential arsRS acid acclimation operon through iron-responsive oligomerization and DNA compaction, encasing the arsR transcriptional start site in a repressive macromolecular complex. A second metal-dependent regulator NikR functions as nickel-dependent anti-repressor at this promoter, antagonizing the binding of Fur to the operator elements responsible for the DNA condensation. The results allow unifying H. pylori metal ion homeostasis and acid acclimation in a mechanistically coherent model, and demonstrate, for the first time, the existence of a selective metal-responsive DNA compaction mechanism controlling bacterial transcriptional regulation. The Fur protein regulates transcription of bacterial genes in response to metal ions. Here, the authors show that the Fur protein from Helicobacter pylori represses transcription by iron-responsive oligomerization and DNA compaction, encasing the transcriptional start site in a macromolecular complex.
Collapse
Affiliation(s)
- Davide Roncarati
- Department of Pharmacy and Biotechnology (FaBiT), University of Bologna, 40126 Bologna, Italy
| | - Simone Pelliciari
- Department of Pharmacy and Biotechnology (FaBiT), University of Bologna, 40126 Bologna, Italy
| | - Nicola Doniselli
- Department of Life Sciences, University of Parma, 43124 Parma, Italy
| | - Stefano Maggi
- Department of Life Sciences, University of Parma, 43124 Parma, Italy
| | - Andrea Vannini
- Department of Pharmacy and Biotechnology (FaBiT), University of Bologna, 40126 Bologna, Italy
| | - Luca Valzania
- Department of Pharmacy and Biotechnology (FaBiT), University of Bologna, 40126 Bologna, Italy
| | - Luca Mazzei
- Department of Pharmacy and Biotechnology (FaBiT), University of Bologna, 40126 Bologna, Italy
| | - Barbara Zambelli
- Department of Pharmacy and Biotechnology (FaBiT), University of Bologna, 40126 Bologna, Italy
| | - Claudio Rivetti
- Department of Life Sciences, University of Parma, 43124 Parma, Italy
| | - Alberto Danielli
- Department of Pharmacy and Biotechnology (FaBiT), University of Bologna, 40126 Bologna, Italy
| |
Collapse
|
23
|
Abstract
Several groups have generated programmable transcription factors based on the versatile Cas9 protein, yet their relative potency and effectiveness across various cell types and species remain unexplored. Here, we compare Cas9 activator systems and examine their ability to induce robust gene expression in several human, mouse, and fly cell lines. We also explore the potential for improved activation through the combination of the most potent activator systems and assess the role of cooperativity in maximizing gene expression.
Collapse
|
24
|
Gruet A, Dosnon M, Blocquel D, Brunel J, Gerlier D, Das RK, Bonetti D, Gianni S, Fuxreiter M, Longhi S, Bignon C. Fuzzy regions in an intrinsically disordered protein impair protein-protein interactions. FEBS J 2016; 283:576-94. [PMID: 26684000 DOI: 10.1111/febs.13631] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2015] [Revised: 11/22/2015] [Accepted: 12/15/2015] [Indexed: 12/13/2022]
Abstract
Despite the partial disorder-to-order transition that intrinsically disordered proteins often undergo upon binding to their partners, a considerable amount of residual disorder may be retained in the bound form, resulting in a fuzzy complex. Fuzzy regions flanking molecular recognition elements may enable partner fishing through non-specific, transient contacts, thereby facilitating binding, but may also disfavor binding through various mechanisms. So far, few computational or experimental studies have addressed the effect of fuzzy appendages on partner recognition by intrinsically disordered proteins. In order to shed light onto this issue, we used the interaction between the intrinsically disordered C-terminal domain of the measles virus (MeV) nucleoprotein (NTAIL ) and the X domain (XD) of the viral phosphoprotein as model system. After binding to XD, the N-terminal region of NTAIL remains conspicuously disordered, with α-helical folding taking place only within a short molecular recognition element. To study the effect of the N-terminal fuzzy region on NTAIL /XD binding, we generated N-terminal truncation variants of NTAIL , and assessed their binding abilities towards XD. The results revealed that binding increases with shortening of the N-terminal fuzzy region, with this also being observed with hsp70 (another MeV NTAIL binding partner), and for the homologous NTAIL /XD pairs from the Nipah and Hendra viruses. Finally, similar results were obtained when the MeV NTAIL fuzzy region was replaced with a highly dissimilar artificial disordered sequence, supporting a sequence-independent inhibitory effect of the fuzzy region.
Collapse
Affiliation(s)
- Antoine Gruet
- Aix-Marseille Université, Laboratoire Architecture et Fonction des Macromolécules Biologiques, UMR 7257, Marseille, France.,Centre National de la Recherche Scientifique, Laboratoire Architecture et Fonction des Macromolécules Biologiques, UMR 7257, Marseille, France
| | - Marion Dosnon
- Aix-Marseille Université, Laboratoire Architecture et Fonction des Macromolécules Biologiques, UMR 7257, Marseille, France.,Centre National de la Recherche Scientifique, Laboratoire Architecture et Fonction des Macromolécules Biologiques, UMR 7257, Marseille, France
| | - David Blocquel
- Aix-Marseille Université, Laboratoire Architecture et Fonction des Macromolécules Biologiques, UMR 7257, Marseille, France.,Centre National de la Recherche Scientifique, Laboratoire Architecture et Fonction des Macromolécules Biologiques, UMR 7257, Marseille, France
| | - Joanna Brunel
- Centre International de Recherche en Infectiologie, INSERM U1111, Centre National de la Recherche Scientifique, UMR 5308, Université Lyon 1, Lyon, France
| | - Denis Gerlier
- Centre International de Recherche en Infectiologie, INSERM U1111, Centre National de la Recherche Scientifique, UMR 5308, Université Lyon 1, Lyon, France
| | - Rahul K Das
- Department of Biomedical Engineering and Center for Biological Systems Engineering, Washington University in St Louis, MO, USA
| | - Daniela Bonetti
- Istituto Pasteur - Fondazione Cenci Bolognetti, Dipartimento di Scienze Biochimiche 'A. Rossi Fanelli' and Istituto di Biologia e Patologia Molecolari del Consiglio Nazionale delle Ricerche, Sapienza Università di Roma, Rome, Italy
| | - Stefano Gianni
- Istituto Pasteur - Fondazione Cenci Bolognetti, Dipartimento di Scienze Biochimiche 'A. Rossi Fanelli' and Istituto di Biologia e Patologia Molecolari del Consiglio Nazionale delle Ricerche, Sapienza Università di Roma, Rome, Italy.,Department of Chemistry, University of Cambridge, Cambridge, UK
| | - Monika Fuxreiter
- Hungarian Academy of Sciences, Momentum Laboratory of Protein Dynamics, Department of Biochemistry and Molecular Biology, University of Debrecen, Hungary
| | - Sonia Longhi
- Aix-Marseille Université, Laboratoire Architecture et Fonction des Macromolécules Biologiques, UMR 7257, Marseille, France.,Centre National de la Recherche Scientifique, Laboratoire Architecture et Fonction des Macromolécules Biologiques, UMR 7257, Marseille, France
| | - Christophe Bignon
- Aix-Marseille Université, Laboratoire Architecture et Fonction des Macromolécules Biologiques, UMR 7257, Marseille, France.,Centre National de la Recherche Scientifique, Laboratoire Architecture et Fonction des Macromolécules Biologiques, UMR 7257, Marseille, France
| |
Collapse
|
25
|
Ramachandran G, Singh PK, Luque-Ortega JR, Yuste L, Alfonso C, Rojo F, Wu LJ, Meijer WJJ. A complex genetic switch involving overlapping divergent promoters and DNA looping regulates expression of conjugation genes of a gram-positive plasmid. PLoS Genet 2014; 10:e1004733. [PMID: 25340403 PMCID: PMC4207663 DOI: 10.1371/journal.pgen.1004733] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2014] [Accepted: 09/03/2014] [Indexed: 11/22/2022] Open
Abstract
Plasmid conjugation plays a significant role in the dissemination of antibiotic resistance and pathogenicity determinants. Understanding how conjugation is regulated is important to gain insights into these features. Little is known about regulation of conjugation systems present on plasmids from Gram-positive bacteria. pLS20 is a native conjugative plasmid from the Gram-positive bacterium Bacillus subtilis. Recently the key players that repress and activate pLS20 conjugation have been identified. Here we studied in detail the molecular mechanism regulating the pLS20 conjugation genes using both in vivo and in vitro approaches. Our results show that conjugation is subject to the control of a complex genetic switch where at least three levels of regulation are integrated. The first of the three layers involves overlapping divergent promoters of different strengths regulating expression of the conjugation genes and the key transcriptional regulator RcoLS20. The second layer involves a triple function of RcoLS20 being a repressor of the main conjugation promoter and an activator and repressor of its own promoter at low and high concentrations, respectively. The third level of regulation concerns formation of a DNA loop mediated by simultaneous binding of tetrameric RcoLS20 to two operators, one of which overlaps with the divergent promoters. The combination of these three layers of regulation in the same switch allows the main conjugation promoter to be tightly repressed during conditions unfavorable to conjugation while maintaining the sensitivity to accurately switch on the conjugation genes when appropriate conditions occur. The implications of the regulatory switch and comparison with other genetic switches involving DNA looping are discussed. Plasmids are extrachromosomal, autonomously replicating units that are harbored by many bacteria. Many plasmids encode transfer function allowing them to be transferred into plasmid-free bacteria by a process named conjugation. Since many of them also carry antibiotic resistance genes, plasmid-mediated conjugation is a major mechanism in the dissemination of antibiotic resistance. In depth knowledge on the regulation of conjugation genes is a prerequisite to design measures interfering with the spread of antibiotic resistance. pLS20 is a conjugative plasmid of the soil bacterium Bacillus subtilis, which is also a gut commensal in animals and humans. Here we describe in detail the molecular mechanism by which the key transcriptional regulator tightly represses the conjugation genes during conditions unfavorable to conjugation without compromising the ability to switch on accurately the conjugation genes when appropriate. We found that conjugation is subject to the control of a unique genetic switch where at least three levels of regulation are integrated. The first level involves overlapping divergent promoters of different strengths. The second layer involves a triple function of the transcriptional regulator. And the third level of regulation concerns formation of a DNA loop mediated by the transcriptional regulator.
Collapse
Affiliation(s)
- Gayetri Ramachandran
- Centro de Biología Molecular “Severo Ochoa” (CSIC-UAM), Instituto de Biología Molecular “Eladio Viñuela” (CSIC), Universidad Autónoma, Canto Blanco, Madrid, Spain
| | - Praveen K. Singh
- Centro de Biología Molecular “Severo Ochoa” (CSIC-UAM), Instituto de Biología Molecular “Eladio Viñuela” (CSIC), Universidad Autónoma, Canto Blanco, Madrid, Spain
| | | | - Luis Yuste
- Centro Nacional de Biotecnología (CSIC), Canto Blanco, Madrid, Spain
| | - Carlos Alfonso
- Centro de Investigaciones Biológicas (CSIC), Madrid, Spain
| | - Fernando Rojo
- Centro Nacional de Biotecnología (CSIC), Canto Blanco, Madrid, Spain
| | - Ling J. Wu
- Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle Upon Tyne, United Kingdom
| | - Wilfried J. J. Meijer
- Centro de Biología Molecular “Severo Ochoa” (CSIC-UAM), Instituto de Biología Molecular “Eladio Viñuela” (CSIC), Universidad Autónoma, Canto Blanco, Madrid, Spain
- * E-mail:
| |
Collapse
|
26
|
Johnson S, van de Meent JW, Phillips R, Wiggins CH, Lindén M. Multiple LacI-mediated loops revealed by Bayesian statistics and tethered particle motion. Nucleic Acids Res 2014; 42:10265-77. [PMID: 25120267 PMCID: PMC4176382 DOI: 10.1093/nar/gku563] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
The bacterial transcription factor LacI loops DNA by binding to two separate locations on the DNA simultaneously. Despite being one of the best-studied model systems for transcriptional regulation, the number and conformations of loop structures accessible to LacI remain unclear, though the importance of multiple coexisting loops has been implicated in interactions between LacI and other cellular regulators of gene expression. To probe this issue, we have developed a new analysis method for tethered particle motion, a versatile and commonly used in vitro single-molecule technique. Our method, vbTPM, performs variational Bayesian inference in hidden Markov models. It learns the number of distinct states (i.e. DNA–protein conformations) directly from tethered particle motion data with better resolution than existing methods, while easily correcting for common experimental artifacts. Studying short (roughly 100 bp) LacI-mediated loops, we provide evidence for three distinct loop structures, more than previously reported in single-molecule studies. Moreover, our results confirm that changes in LacI conformation and DNA-binding topology both contribute to the repertoire of LacI-mediated loops formed in vitro, and provide qualitatively new input for models of looping and transcriptional regulation. We expect vbTPM to be broadly useful for probing complex protein–nucleic acid interactions.
Collapse
Affiliation(s)
- Stephanie Johnson
- Department of Biochemistry and Molecular Biophysics, California Institute of Technology, 1200 E. California Blvd., Pasadena, California 91125
| | - Jan-Willem van de Meent
- Department of Statistics, Columbia University, 1255 Amsterdam Avenue MC 4690, New York, New York 10027
| | - Rob Phillips
- Departments of Applied Physics and Biology, California Institute of Technology, 1200 E. California Blvd., Pasadena, California 91125
| | - Chris H Wiggins
- Department of Applied Physics and Applied Mathematics, Columbia University, 200 S.W. Mudd, 500 W. 120th St. MC 4701, New York, New York 10027
| | - Martin Lindén
- Center for Biomembrane Research, Department of Biochemistry and Biophysics, Stockholm University, Svante Arrhenius väg 16C, SE-106 91 Stockholm, Sweden Department of Cell and Molecular Biology, Uppsala University, Box 256, SE-751 05 Uppsala, Sweden
| |
Collapse
|
27
|
Becker NA, Greiner AM, Peters JP, Maher LJ. Bacterial promoter repression by DNA looping without protein-protein binding competition. Nucleic Acids Res 2014; 42:5495-504. [PMID: 24598256 PMCID: PMC4027209 DOI: 10.1093/nar/gku180] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
The Escherichia coli lactose operon provides a paradigm for understanding gene control by DNA looping where the lac repressor (LacI) protein competes with RNA polymerase for DNA binding. Not all promoter loops involve direct competition between repressor and RNA polymerase. This raises the possibility that positioning a promoter within a tightly constrained DNA loop is repressive per se, an idea that has previously only been considered in vitro. Here, we engineer living E. coli bacteria to measure repression due to promoter positioning within such a tightly constrained DNA loop in the absence of protein–protein binding competition. We show that promoters held within such DNA loops are repressed ∼100-fold, with up to an additional ∼10-fold repression (∼1000-fold total) dependent on topological positioning of the promoter on the inner or outer face of the DNA loop. Chromatin immunoprecipitation data suggest that repression involves inhibition of both RNA polymerase initiation and elongation. These in vivo results show that gene repression can result from tightly looping promoter DNA even in the absence of direct competition between repressor and RNA polymerase binding.
Collapse
Affiliation(s)
- Nicole A Becker
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, 200 First St. SW, Rochester, MN 55905, USA
| | - Alexander M Greiner
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, 200 First St. SW, Rochester, MN 55905, USA Luther College, Departments of Biology and Chemistry, Decorah, IA 52101, USA
| | - Justin P Peters
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, 200 First St. SW, Rochester, MN 55905, USA
| | - L James Maher
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, 200 First St. SW, Rochester, MN 55905, USA
| |
Collapse
|
28
|
Vilar JMG, Saiz L. Reliable prediction of complex phenotypes from a modular design in free energy space: an extensive exploration of the lac operon. ACS Synth Biol 2013; 2:576-86. [PMID: 23654358 DOI: 10.1021/sb400013w] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The basic methodology for designing, altering, and constructing biological systems is increasingly relying on well-established engineering principles to move forward from trial and error approaches to reliably predicting the system behavior from the properties of the components and their interactions. The inherent complexity of even the simplest biological systems, however, often precludes achieving such predictive power. A prototypical example is the lac operon, one of the best-characterized genetic systems, which still poses serious challenges for understanding the results of combining its parts into novel setups. The reason is the pervasive complex hierarchy of events involved in gene regulation that extend from specific protein-DNA interactions to the combinatorial assembly of nucleoprotein complexes. Here, we integrate such complexity into a few-parameter model to accurately predict gene expression from a few simple rules to connect the parts. The model accurately reproduces the observed transcriptional activity of the lac operon over a 10,000-fold range for 21 different operator setups, different repressor concentrations, and tetrameric and dimeric forms of the repressor. Incorporation of the calibrated model into more complex scenarios accurately captures the induction curves for key operator configurations and the temporal evolution of the β-galactosidase activity of cell populations.
Collapse
Affiliation(s)
- Jose M. G. Vilar
- Biophysics Unit (CSIC-UPV/EHU)
and Department of Biochemistry and Molecular Biology, University of the Basque Country, P.O. Box 644, 48080
Bilbao, Spain
- IKERBASQUE, Basque Foundation for Science, 48011 Bilbao, Spain
| | - Leonor Saiz
- Department of Biomedical Engineering, University of California, 451 E. Health Sciences Drive,
Davis, California 95616, United States
| |
Collapse
|
29
|
Abstract
Transcriptional regulation is at the heart of biological functions such as adaptation to a changing environment or to new carbon sources. One of the mechanisms which has been found to modulate transcription, either positively (activation) or negatively (repression), involves the formation of DNA loops. A DNA loop occurs when a protein or a complex of proteins simultaneously binds to two different sites on DNA with looping out of the intervening DNA. This simple mechanism is central to the regulation of several operons in the genome of the bacterium Escherichia coli, like the lac operon, one of the paradigms of genetic regulation. The aim of this review is to gather and discuss concepts and ideas from experimental biology and theoretical physics concerning DNA looping in genetic regulation. We first describe experimental techniques designed to show the formation of a DNA loop. We then present the benefits that can or could be derived from a mechanism involving DNA looping. Some of these are already experimentally proven, but others are theoretical predictions and merit experimental investigation. Then, we try to identify other genetic systems that could be regulated by a DNA looping mechanism in the genome of Escherichia coli. We found many operons that, according to our set of criteria, have a good chance to be regulated with a DNA loop. Finally, we discuss the proposition recently made by both biologists and physicists that this mechanism could also act at the genomic scale and play a crucial role in the spatial organization of genomes.
Collapse
|
30
|
Becker NA, Peters JP, Maher LJ, Lionberger TA. Mechanism of promoter repression by Lac repressor-DNA loops. Nucleic Acids Res 2012; 41:156-66. [PMID: 23143103 PMCID: PMC3592455 DOI: 10.1093/nar/gks1011] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The Escherichia coli lactose (lac) operon encodes the first genetic switch to be discovered, and lac remains a paradigm for studying negative and positive control of gene expression. Negative control is believed to involve competition of RNA polymerase and Lac repressor for overlapping binding sites. Contributions to the local Lac repressor concentration come from free repressor and repressor delivered to the operator from remote auxiliary operators by DNA looping. Long-standing questions persist concerning the actual role of DNA looping in the mechanism of promoter repression. Here, we use experiments in living bacteria to resolve four of these questions. We show that the distance dependence of repression enhancement is comparable for upstream and downstream auxiliary operators, confirming the hypothesis that repressor concentration increase is the principal mechanism of repression loops. We find that as few as four turns of DNA can be constrained in a stable loop by Lac repressor. We show that RNA polymerase is not trapped at repressed promoters. Finally, we show that constraining a promoter in a tight DNA loop is sufficient for repression even when promoter and operator do not overlap.
Collapse
Affiliation(s)
- Nicole A Becker
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, 200 First Street Southwest, Rochester, MN 55905, USA
| | | | | | | |
Collapse
|
31
|
Mayoral MJ, Rest C, Schellheimer J, Stepanenko V, Fernández G. Narcissistic versus social self-sorting of oligophenyleneethynylene derivatives: from isodesmic self-assembly to cooperative co-assembly. Chemistry 2012; 18:15607-11. [PMID: 23132726 DOI: 10.1002/chem.201202367] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2012] [Revised: 10/01/2012] [Indexed: 12/21/2022]
Abstract
Narcissistic versus social! The self-assembly of two structurally related oligophenyleneethynylene derivatives featuring polar or nonpolar peripheral chains is reported. Their remarkable narcissistic versus social self-sorting behaviour in aqueous media can be controlled by concentration and solvent changes.
Collapse
|
32
|
Waldminghaus T, Weigel C, Skarstad K. Replication fork movement and methylation govern SeqA binding to the Escherichia coli chromosome. Nucleic Acids Res 2012; 40:5465-76. [PMID: 22373925 PMCID: PMC3384311 DOI: 10.1093/nar/gks187] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
In Escherichia coli, the SeqA protein binds specifically to GATC sequences which are methylated on the A of the old strand but not on the new strand. Such hemimethylated DNA is produced by progression of the replication forks and lasts until Dam methyltransferase methylates the new strand. It is therefore believed that a region of hemimethylated DNA covered by SeqA follows the replication fork. We show that this is, indeed, the case by using global ChIP on Chip analysis of SeqA in cells synchronized regarding DNA replication. To assess hemimethylation, we developed the first genome-wide method for methylation analysis in bacteria. Since loss of the SeqA protein affects growth rate only during rapid growth when cells contain multiple replication forks, a comparison of rapid and slow growth was performed. In cells with six replication forks per chromosome, the two old forks were found to bind surprisingly little SeqA protein. Cell cycle analysis showed that loss of SeqA from the old forks did not occur at initiation of the new forks, but instead occurs at a time point coinciding with the end of SeqA-dependent origin sequestration. The finding suggests simultaneous origin de-sequestration and loss of SeqA from old replication forks.
Collapse
Affiliation(s)
- Torsten Waldminghaus
- Department of Cell Biology, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital and University of Oslo, 0310 Oslo, Norway
| | | | | |
Collapse
|
33
|
Kang J, Xu B, Yao Y, Lin W, Hennessy C, Fraser P, Feng J. A dynamical model reveals gene co-localizations in nucleus. PLoS Comput Biol 2011; 7:e1002094. [PMID: 21760760 PMCID: PMC3131386 DOI: 10.1371/journal.pcbi.1002094] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2010] [Accepted: 05/03/2011] [Indexed: 01/08/2023] Open
Abstract
Co-localization of networks of genes in the nucleus is thought to play an important role in determining gene expression patterns. Based upon experimental data, we built a dynamical model to test whether pure diffusion could account for the observed co-localization of genes within a defined subnuclear region. A simple standard Brownian motion model in two and three dimensions shows that preferential co-localization is possible for co-regulated genes without any direct interaction, and suggests the occurrence may be due to a limitation in the number of available transcription factors. Experimental data of chromatin movements demonstrates that fractional rather than standard Brownian motion is more appropriate to model gene mobilizations, and we tested our dynamical model against recent static experimental data, using a sub-diffusion process by which the genes tend to colocalize more easily. Moreover, in order to compare our model with recently obtained experimental data, we studied the association level between genes and factors, and presented data supporting the validation of this dynamic model. As further applications of our model, we applied it to test against more biological observations. We found that increasing transcription factor number, rather than factory number and nucleus size, might be the reason for decreasing gene co-localization. In the scenario of frequency- or amplitude-modulation of transcription factors, our model predicted that frequency-modulation may increase the co-localization between its targeted genes.
Collapse
Affiliation(s)
- Jing Kang
- Nuclear Dynamics Laboratory, The Babraham Institute, Cambridge, United Kingdom
- Centre for Scientific Computing, Warwick University, Coventry, United Kingdom
| | - Bing Xu
- Centre for Computational Systems Biology, Fudan University, Shanghai, People's Republic of China
| | - Ye Yao
- Centre for Computational Systems Biology, Fudan University, Shanghai, People's Republic of China
| | - Wei Lin
- Centre for Computational Systems Biology, Fudan University, Shanghai, People's Republic of China
| | - Conor Hennessy
- Nuclear Dynamics Laboratory, The Babraham Institute, Cambridge, United Kingdom
| | - Peter Fraser
- Nuclear Dynamics Laboratory, The Babraham Institute, Cambridge, United Kingdom
- * E-mail: (PF); (JF)
| | - Jianfeng Feng
- Centre for Scientific Computing, Warwick University, Coventry, United Kingdom
- Centre for Computational Systems Biology, Fudan University, Shanghai, People's Republic of China
- * E-mail: (PF); (JF)
| |
Collapse
|
34
|
Abstract
The double-helical DNA biopolymer is particularly resistant to bending and twisting deformations. This property has important implications for DNA folding in vitro and for the packaging and function of DNA in living cells. Among the outstanding questions in the field of DNA biophysics are the underlying origin of DNA stiffness and the mechanisms by which DNA stiffness is overcome within cells. Exploring these questions requires experimental methods to quantitatively measure DNA bending and twisting stiffness both in vitro and in vivo. Here, we discuss two classical approaches: T4 DNA ligase-mediated DNA cyclization kinetics and lac repressor-mediated DNA looping in Escherichia coli. We review the theoretical basis for these techniques and how each can be applied to quantitate biophysical parameters that describe the DNA polymer. We then show how we have modified these methods and applied them to quantitate how apparent DNA physical properties are altered in vitro and in vivo by sequence-nonspecific architectural DNA-binding proteins such as the E. coli HU protein and eukaryotic HMGB proteins.
Collapse
|
35
|
Braig D, Mircheva M, Sachelaru I, van der Sluis EO, Sturm L, Beckmann R, Koch HG. Signal sequence-independent SRP-SR complex formation at the membrane suggests an alternative targeting pathway within the SRP cycle. Mol Biol Cell 2011; 22:2309-23. [PMID: 21551068 PMCID: PMC3128533 DOI: 10.1091/mbc.e11-02-0152] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Our study reveals an alternative route in the SRP-dependent protein targeting pathway that includes a preassembled, membrane-bound SRP-SR complex. This alternative route is fully sufficient to maintain cell viability in the absence of a soluble SRP. Protein targeting by the signal recognition particle (SRP) and the bacterial SRP receptor FtsY requires a series of closely coordinated steps that monitor the presence of a substrate, the membrane, and a vacant translocon. Although the influence of substrate binding on FtsY-SRP complex formation is well documented, the contribution of the membrane is largely unknown. In the current study, we found that negatively charged phospholipids stimulate FtsY-SRP complex formation. Phospholipids act on a conserved positively charged amphipathic helix in FtsY and induce a conformational change that strongly enhances the FtsY-lipid interaction. This membrane-bound, signal sequence–independent FtsY-SRP complex is able to recruit RNCs to the membrane and to transfer them to the Sec translocon. Significantly, the same results were also observed with an artificial FtsY-SRP fusion protein, which was tethered to the membrane via a transmembrane domain. This indicates that substrate recognition by a soluble SRP is not essential for cotranslational targeting in Escherichia coli. Our findings reveal a remarkable flexibility of SRP-dependent protein targeting, as they indicate that substrate recognition can occur either in the cytosol via ribosome-bound SRP or at the membrane via a preassembled FtsY-SRP complex.
Collapse
Affiliation(s)
- David Braig
- Institut für Biochemie und Molekularbiologie, ZBMZ, 79104 Freiburg, Germany
| | | | | | | | | | | | | |
Collapse
|
36
|
Bomble YJ, Beckham GT, Matthews JF, Nimlos MR, Himmel ME, Crowley MF. Modeling the self-assembly of the cellulosome enzyme complex. J Biol Chem 2011; 286:5614-23. [PMID: 21098021 PMCID: PMC3037675 DOI: 10.1074/jbc.m110.186031] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2010] [Revised: 11/16/2010] [Indexed: 11/06/2022] Open
Abstract
Most bacteria use free enzymes to degrade plant cell walls in nature. However, some bacteria have adopted a different strategy wherein enzymes can either be free or tethered on a protein scaffold forming a complex called a cellulosome. The study of the structure and mechanism of these large macromolecular complexes is an active and ongoing research topic, with the goal of finding ways to improve biomass conversion using cellulosomes. Several mechanisms involved in cellulosome formation remain unknown, including how cellulosomal enzymes assemble on the scaffoldin and what governs the population of cellulosomes created during self-assembly. Here, we present a coarse-grained model to study the self-assembly of cellulosomes. The model captures most of the physical characteristics of three cellulosomal enzymes (Cel5B, CelS, and CbhA) and the scaffoldin (CipA) from Clostridium thermocellum. The protein structures are represented by beads connected by restraints to mimic the flexibility and shapes of these proteins. From a large simulation set, the assembly of cellulosomal enzyme complexes is shown to be dominated by their shape and modularity. The multimodular enzyme, CbhA, binds statistically more frequently to the scaffoldin than CelS or Cel5B. The enhanced binding is attributed to the flexible nature and multimodularity of this enzyme, providing a longer residence time around the scaffoldin. The characterization of the factors influencing the cellulosome assembly process may enable new strategies to create designers cellulosomes.
Collapse
Affiliation(s)
- Yannick J Bomble
- Biosciences Center, Colorado School of Mines, Golden, Colorado 80401, USA.
| | | | | | | | | | | |
Collapse
|
37
|
Bond LM, Peters JP, Becker NA, Kahn JD, Maher LJ. Gene repression by minimal lac loops in vivo. Nucleic Acids Res 2010; 38:8072-82. [PMID: 21149272 PMCID: PMC3001091 DOI: 10.1093/nar/gkq755] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2010] [Revised: 08/09/2010] [Accepted: 08/09/2010] [Indexed: 01/25/2023] Open
Abstract
The inflexibility of double-stranded DNA with respect to bending and twisting is well established in vitro. Understanding apparent DNA physical properties in vivo is a greater challenge. Here, we exploit repression looping with components of the Escherichia coli lac operon to monitor DNA flexibility in living cells. We create a minimal system for testing the shortest possible DNA repression loops that contain an E. coli promoter, and compare the results to prior experiments. Our data reveal that loop-independent repression occurs for certain tight operator/promoter spacings. When only loop-dependent repression is considered, fits to a thermodynamic model show that DNA twisting limits looping in vivo, although the apparent DNA twist flexibility is 2- to 4-fold higher than in vitro. In contrast, length-dependent resistance to DNA bending is not observed in these experiments, even for the shortest loops constraining <0.4 persistence lengths of DNA. As observed previously for other looping configurations, loss of the nucleoid protein heat unstable (HU) markedly disables DNA looping in vivo. Length-independent DNA bending energy may reflect the activities of architectural proteins and the structure of the DNA topological domain. We suggest that the shortest loops are formed in apical loops rather than along the DNA plectonemic superhelix.
Collapse
Affiliation(s)
- Laura M. Bond
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, 200 First St. SW, Rochester, MN 55905 and Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742-2021, USA
| | - Justin P. Peters
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, 200 First St. SW, Rochester, MN 55905 and Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742-2021, USA
| | - Nicole A. Becker
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, 200 First St. SW, Rochester, MN 55905 and Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742-2021, USA
| | - Jason D. Kahn
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, 200 First St. SW, Rochester, MN 55905 and Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742-2021, USA
| | - L. James Maher
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, 200 First St. SW, Rochester, MN 55905 and Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742-2021, USA
| |
Collapse
|
38
|
Abstract
It has been more than 50 years since the elucidation of the structure of double-helical DNA. Despite active research and progress in DNA biology and biochemistry, much remains to be learned in the field of DNA biophysics. Predicting the sequence-dependent curvature and flexibility of DNA is difficult. Applicability of the conventional worm-like chain polymer model of DNA has been challenged. The fundamental forces responsible for the remarkable resistance of DNA to bending and twisting remain controversial. The apparent 'softening' of DNA measured in vivo in the presence of kinking proteins and superhelical strain is incompletely understood. New methods and insights are being applied to these problems. This review places current work on DNA biophysics in historical context and illustrates the ongoing interplay between theory and experiment in this exciting field.
Collapse
|