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Melikishvili M, Fried MG, Fondufe-Mittendorf YN. Cooperative nucleic acid binding by Poly ADP-ribose polymerase 1. Sci Rep 2024; 14:7530. [PMID: 38553566 PMCID: PMC10980755 DOI: 10.1038/s41598-024-58076-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2023] [Accepted: 03/25/2024] [Indexed: 04/02/2024] Open
Abstract
Poly (ADP)-ribose polymerase 1 (PARP1) is an abundant nuclear protein well-known for its role in DNA repair yet also participates in DNA replication, transcription, and co-transcriptional splicing, where DNA is undamaged. Thus, binding to undamaged regions in DNA and RNA is likely a part of PARP1's normal repertoire. Here we describe analyses of PARP1 binding to two short single-stranded DNAs, a single-stranded RNA, and a double stranded DNA. The investigations involved comparing the wild-type (WT) full-length enzyme with mutants lacking the catalytic domain (∆CAT) or zinc fingers 1 and 2 (∆Zn1∆Zn2). All three protein types exhibited monomeric characteristics in solution and formed saturated 2:1 complexes with single-stranded T20 and U20 oligonucleotides. These complexes formed without accumulation of 1:1 intermediates, a pattern suggestive of positive binding cooperativity. The retention of binding activities by ∆CAT and ∆Zn1∆Zn2 enzymes suggests that neither the catalytic domain nor zinc fingers 1 and 2 are indispensable for cooperative binding. In contrast, when a double stranded 19mer DNA was tested, WT PARP1 formed a 4:1 complex while the ∆Zn1Zn2 mutant binding saturated at 1:1 stoichiometry. These deviations from the 2:1 pattern observed with T20 and U20 oligonucleotides show that PARP's binding mechanism can be influenced by the secondary structure of the nucleic acid. Our studies show that PARP1:nucleic acid interactions are strongly dependent on the nucleic acid type and properties, perhaps reflecting PARP1's ability to respond differently to different nucleic acid ligands in cells. These findings lay a platform for understanding how the functionally versatile PARP1 recognizes diverse oligonucleotides within the realms of chromatin and RNA biology.
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Affiliation(s)
- Manana Melikishvili
- Department of Epigenetics, Van Andel Institute, Grand Rapids, MI, 49503, USA
| | - Michael G Fried
- Center for Structural Biology, Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, KY, 40536, USA.
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2
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Villaluenga JPG, Brunete D, Cao-García FJ. Competitive ligand binding kinetics to linear polymers. Phys Rev E 2023; 107:024401. [PMID: 36932540 DOI: 10.1103/physreve.107.024401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2022] [Accepted: 01/10/2023] [Indexed: 02/04/2023]
Abstract
Different types of ligands compete in binding to polymers with different consequences for the physical and chemical properties of the resulting complex. Here, we derive a general kinetic model for the competitive binding kinetics of different types of ligands to a linear polymer, using the McGhee and von Hippel detailed binding-site counting procedure. The derived model allows the description of the competitive binding process in terms of the size of the ligand, binding, and release rates, and cooperativity parameters. We illustrate the implications of the general theory showing the equations for the competitive binding of two ligands. The size of the ligand, given by the number of monomers occluded, is shown to have a great impact on competitive binding. Ligands requiring a large available gap for binding are strongly inhibited by smaller ligands. Ligand size then has a leading role compared to binding affinity or cooperativity. For ligands that can bind in different modes (i.e., different number of monomers), this implies that they are more effective in covering or passivating the polymer in lower modes, if the different modes have similar binding energies.
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Affiliation(s)
- Juan P G Villaluenga
- Departamento de Estructura de la Materia, Física Térmica y Electrónica, Universidad Complutense de Madrid, Plaza de Ciencias, 1, 28040 Madrid, Spain
| | - David Brunete
- Departamento de Estructura de la Materia, Física Térmica y Electrónica, Universidad Complutense de Madrid, Plaza de Ciencias, 1, 28040 Madrid, Spain
| | - Francisco Javier Cao-García
- Departamento de Estructura de la Materia, Física Térmica y Electrónica, Universidad Complutense de Madrid, Plaza de Ciencias, 1, 28040 Madrid, Spain.,Instituto Madrileño de Estudios Avanzados en Nanociencia, IMDEA Nanociencia, Calle Faraday, 9, 28049 Madrid, Spain
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3
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Choi J, Kim R, Koh J. Quantitative Frameworks for Multivalent Macromolecular Interactions in Biological Linear Lattice Systems. Mol Cells 2022; 45:444-453. [PMID: 35754369 PMCID: PMC9260134 DOI: 10.14348/molcells.2022.0035] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2022] [Revised: 03/27/2022] [Accepted: 03/28/2022] [Indexed: 11/29/2022] Open
Abstract
Multivalent macromolecular interactions underlie dynamic regulation of diverse biological processes in ever-changing cellular states. These interactions often involve binding of multiple proteins to a linear lattice including intrinsically disordered proteins and the chromosomal DNA with many repeating recognition motifs. Quantitative understanding of such multivalent interactions on a linear lattice is crucial for exploring their unique regulatory potentials in the cellular processes. In this review, the distinctive molecular features of the linear lattice system are first discussed with a particular focus on the overlapping nature of potential protein binding sites within a lattice. Then, we introduce two general quantitative frameworks, combinatorial and conditional probability models, dealing with the overlap problem and relating the binding parameters to the experimentally measurable properties of the linear lattice-protein interactions. To this end, we present two specific examples where the quantitative models have been applied and further extended to provide biological insights into specific cellular processes. In the first case, the conditional probability model was extended to highlight the significant impact of nonspecific binding of transcription factors to the chromosomal DNA on gene-specific transcriptional activities. The second case presents the recently developed combinatorial models to unravel the complex organization of target protein binding sites within an intrinsically disordered region (IDR) of a nucleoporin. In particular, these models have suggested a unique function of IDRs as a molecular switch coupling distinct cellular processes. The quantitative models reviewed here are envisioned to further advance for dissection and functional studies of more complex systems including phase-separated biomolecular condensates.
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Affiliation(s)
- Jaejun Choi
- School of Biological Sciences, Seoul National University, Seoul 08826, Korea
| | - Ryeonghyeon Kim
- School of Biological Sciences, Seoul National University, Seoul 08826, Korea
| | - Junseock Koh
- School of Biological Sciences, Seoul National University, Seoul 08826, Korea
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4
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Villaluenga JP, Cao-García FJ. Cooperative kinetics of ligand binding to linear polymers. Comput Struct Biotechnol J 2022; 20:521-533. [PMID: 35495112 PMCID: PMC9019704 DOI: 10.1016/j.csbj.2021.12.043] [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: 09/30/2021] [Revised: 12/27/2021] [Accepted: 12/30/2021] [Indexed: 11/29/2022] Open
Abstract
Cooperative kinetic equation for large ligands binding to long polymers. Cooperativity in general affects binding and release rates. Appropriate counting of the available binding sites for a ligand to a linear polymer. Positive cooperativity increases polymer coverage by the ligand. Large ligand size reduces cooperativity effects.
Ligands change the chemical and mechanical properties of polymers. In particular, single strand binding protein (SSB) non-specifically bounds to single-stranded DNA (ssDNA), modifying the ssDNA stiffness and the DNA replication rate, as recently measured with single-molecule techniques. SSB is a large ligand presenting cooperativity in some of its binding modes. We aim to develop an accurate kinetic model for the cooperative binding kinetics of large ligands. Cooperativity accounts for the changes in the affinity of a ligand to the polymer due to the presence of another bound ligand. Large ligands, attaching to several binding sites, require a detailed counting of the available binding possibilities. This counting has been done by McGhee and von Hippel to obtain the equilibrium state of the ligands-polymer complex. The same procedure allows to obtain the kinetic equations for the cooperative binding of ligands to long polymers, for all ligand sizes. Here, we also derive approximate cooperative kinetic equations in the large ligand limit, at the leading and next-to-leading orders. We found cooperativity is negligible at the leading-order, and appears at the next-to-leading order. Positive cooperativity (increased affinity) can be originated by increased binding affinity or by decreased release affinity, implying different kinetics. Nevertheless, the equilibrium state is independent of the origin of cooperativity and only depends on the overall increase in affinity. Next-to-leading approximation is found to be accurate, particularly for small cooperativity. These results allow to understand and characterize relevant ligand binding processes, as the binding kinetics of SSB to ssDNA, which has been reported to affect the DNA replication rate for several SSB-polymerase pairs.
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Affiliation(s)
- Juan P.G. Villaluenga
- Departamento de Estructura de la Materia, Física Térmica y Electrónica, Universidad Complutense de Madrid, Plaza de Ciencias, 1, 28040 Madrid, Spain
- Corresponding author.
| | - Francisco Javier Cao-García
- Departamento de Estructura de la Materia, Física Térmica y Electrónica, Universidad Complutense de Madrid, Plaza de Ciencias, 1, 28040 Madrid, Spain
- Instituto Madrileño de Estudios Avanzados en Nanociencia, IMDEA Nanociencia, Calle Faraday, 9, 28049 Madrid, Spain
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5
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Boisvert O, Létourneau D, Delattre P, Tremblay C, Jolibois É, Montagne M, Lavigne P. Zinc Fingers 10 and 11 of Miz-1 undergo conformational exchange to achieve specific DNA binding. Structure 2021; 30:623-636.e5. [PMID: 34963061 DOI: 10.1016/j.str.2021.12.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2021] [Revised: 10/08/2021] [Accepted: 12/01/2021] [Indexed: 11/18/2022]
Abstract
Miz-1 (ZBTB17) is a poly-zinc finger BTB/POZ transcription factor with 12 consecutive C2H2 zinc fingers (ZFs) that binds transcriptional start sites (TSSs) to regulate the expression of genes involved in cell development and proliferation. As of now, it is not known which of the 12 consecutive ZFs are responsible for the recognition of the 24 base pair consensus sequence found at these TSSs. Evidence suggests ZFs 7-12 plays this role. We provide validation for this and describe the structural and dynamical characterization of unprecedented conformational exchange in the linker between ZFs 10 and 11. This conformational exchange uncouples ZFs 7-10 from 11 and 12 and promotes a scanning-recognition mechanism through which the two segments cooperate to bind two sub-sites at both ends of the consensus. We further show that this can result in the coiling of TSSs as part of Miz-1's mechanism of transcriptional transactivation.
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Affiliation(s)
- Olivier Boisvert
- Département de biochimie et de génomique fonctionnelle, Institut de Pharmacologie de Sherbrooke and PROTÉO, Faculté de médecine et des sciences de la santé, Université de Sherbrooke, 3001 12 Avenue N, Sherbrooke, Quebec J1H 5N4, Canada
| | - Danny Létourneau
- Département de biochimie et de génomique fonctionnelle, Institut de Pharmacologie de Sherbrooke and PROTÉO, Faculté de médecine et des sciences de la santé, Université de Sherbrooke, 3001 12 Avenue N, Sherbrooke, Quebec J1H 5N4, Canada
| | - Patrick Delattre
- Département de biochimie et de génomique fonctionnelle, Institut de Pharmacologie de Sherbrooke and PROTÉO, Faculté de médecine et des sciences de la santé, Université de Sherbrooke, 3001 12 Avenue N, Sherbrooke, Quebec J1H 5N4, Canada
| | - Cynthia Tremblay
- Département de biochimie et de génomique fonctionnelle, Institut de Pharmacologie de Sherbrooke and PROTÉO, Faculté de médecine et des sciences de la santé, Université de Sherbrooke, 3001 12 Avenue N, Sherbrooke, Quebec J1H 5N4, Canada
| | - Émilie Jolibois
- Département de biochimie et de génomique fonctionnelle, Institut de Pharmacologie de Sherbrooke and PROTÉO, Faculté de médecine et des sciences de la santé, Université de Sherbrooke, 3001 12 Avenue N, Sherbrooke, Quebec J1H 5N4, Canada
| | - Martin Montagne
- Département de biochimie et de génomique fonctionnelle, Institut de Pharmacologie de Sherbrooke and PROTÉO, Faculté de médecine et des sciences de la santé, Université de Sherbrooke, 3001 12 Avenue N, Sherbrooke, Quebec J1H 5N4, Canada
| | - Pierre Lavigne
- Département de biochimie et de génomique fonctionnelle, Institut de Pharmacologie de Sherbrooke and PROTÉO, Faculté de médecine et des sciences de la santé, Université de Sherbrooke, 3001 12 Avenue N, Sherbrooke, Quebec J1H 5N4, Canada.
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6
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Vo T, Albrecht AV, Wilson WD, Poon GMK. Quantifying length-dependent DNA end-binding by nucleoproteins. Biophys Chem 2019; 251:106177. [PMID: 31102748 DOI: 10.1016/j.bpc.2019.106177] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2019] [Revised: 04/26/2019] [Accepted: 04/27/2019] [Indexed: 01/23/2023]
Abstract
The ends of nucleic acids oligomers alter the statistics of interior nonspecific ligand binding and act as binding sites with altered properties. While the former aspect of "end effects" has received much theoretical attention in the literature, the physical nature of end-binding, and hence its potential impact on a wide range of studies with oligomers, remains poorly known. Here, we report for the first time end-binding to DNA using a model helix-turn-helix motif, the DNA-binding domain of ETV6, as a function of DNA sequence length. Spectral analysis of ETV6 intrinsic tryptophan fluorescence by singular value decomposition showed that end-binding to nonspecific fragments was negligible at >0.2 kbp and accumulated to 8% of total binding to 23-bp oligomers. The affinity for end-binding was insensitive to salt but tracked the affinity of interior binding, suggesting translocation from interior sites rather than free solution as its mechanism. As the presence of a cognate site in the 23-bp oligomer suppressed end-binding, neglect of end-binding to the short cognate DNA does not introduce significant error. However, the same applies to nonspecific DNA only if longer fragments (>0.2 kbp) are used.
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Affiliation(s)
- Tam Vo
- Department of Chemistry, Georgia State University, Atlanta, GA 30303, United States of America
| | - Amanda V Albrecht
- Department of Chemistry, Georgia State University, Atlanta, GA 30303, United States of America
| | - W David Wilson
- Department of Chemistry, Georgia State University, Atlanta, GA 30303, United States of America; Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, GA 30303, United States of America.
| | - Gregory M K Poon
- Department of Chemistry, Georgia State University, Atlanta, GA 30303, United States of America; Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, GA 30303, United States of America.
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7
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Shoute LCT, Loppnow GR. Characterization of the binding interactions between EvaGreen dye and dsDNA. Phys Chem Chem Phys 2018; 20:4772-4780. [PMID: 29380825 DOI: 10.1039/c7cp06058k] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Understanding the dsDNA·EG binding interaction is important because the EvaGreen (EG) dye is increasingly used in real-time quantitative polymerase chain reaction, high resolution melting analysis, and routine quantification of DNA. In this work, a binding isotherm for the interactions of EG with duplex DNA (poly-dA17·poly-dT17) has been determined from the absorption and fluorescence spectra of the EG and dsDNA·EG complex. The isotherm has a sigmoidal shape and can be modeled with the Hill equation, indicating positive cooperativity for the binding interaction. A Scatchard plot of the binding data yields a concave-down curve in agreement with the Hill analysis of the binding isotherm for a positive cooperative binding interaction. Analysis of the Scatchard plot with the modified McGhee and von Hippel model for a finite one-dimensional homogeneous lattice and nonspecific binding of ligands to duplex DNA yields the intrinsic binding constant, the number of lattice sites occluded by a bound ligand, and the cooperativity parameter of 3.6 × 105 M-1, 4.0, and 8.1, respectively. The occluded site size of 4 indicates that moieties of the EG intercalate into the adjacent base pairs of the duplex DNA with a gap of 1 intercalation site between EG binding sites, as expected for a bifunctional molecule. Interestingly, at high [EG]/[base pair], the intercalation is disrupted. A model is proposed based on the fluorescence spectrum where the formation of anti-parallel stacked chains of EGs bound externally to the duplex DNA occur at these high ratios.
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Affiliation(s)
- L C T Shoute
- Department of Chemistry, University of Alberta, Edmonton, AB T6G 2G2, Canada.
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8
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Connolly M, Arra A, Zvoda V, Steinbach PJ, Rice PA, Ansari A. Static Kinks or Flexible Hinges: Multiple Conformations of Bent DNA Bound to Integration Host Factor Revealed by Fluorescence Lifetime Measurements. J Phys Chem B 2018; 122:11519-11534. [DOI: 10.1021/acs.jpcb.8b07405] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Mitchell Connolly
- Department of Physics, University of Illinois at Chicago, Chicago, Illinois 60607, United States
| | - Aline Arra
- Department of Physics, University of Illinois at Chicago, Chicago, Illinois 60607, United States
| | - Viktoriya Zvoda
- Department of Physics, University of Illinois at Chicago, Chicago, Illinois 60607, United States
| | - Peter J. Steinbach
- Center for Molecular Modeling, Center for Information Technology, National Institutes of Health, Bethesda, Maryland 20892, United States
| | - Phoebe A. Rice
- Department of Biochemistry & Molecular Biology, University of Chicago, Chicago, Illinois 60637, United States
| | - Anjum Ansari
- Department of Physics, University of Illinois at Chicago, Chicago, Illinois 60607, United States
- Department of Bioengineering, University of Illinois at Chicago, Chicago, Illinois 60607, United States
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9
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Melikishvili M, Fried MG. Quaternary interactions and supercoiling modulate the cooperative DNA binding of AGT. Nucleic Acids Res 2017; 45:7226-7236. [PMID: 28575445 PMCID: PMC5737729 DOI: 10.1093/nar/gkx223] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2016] [Accepted: 05/25/2017] [Indexed: 01/11/2023] Open
Abstract
Human O6-alkylguanine-DNA alkyltransferase (AGT) repairs mutagenic O6-alkylguanine and O4-alkylthymine adducts in single-stranded and duplex DNAs. The search for these lesions, through a vast excess of competing, unmodified genomic DNA, is a mechanistic challenge that may limit the repair rate in vivo. Here, we examine influences of DNA secondary structure and twist on protein–protein interactions in cooperative AGT complexes formed on lesion-free DNAs that model the unmodified parts of the genome. We used a new approach to resolve nearest neighbor (nn) and long-range (lr) components from the ensemble-average cooperativity, ωave. We found that while nearest-neighbor contacts were significant, long-range interactions dominated cooperativity and this pattern held true whether the DNA was single-stranded or duplex. Experiments with single plasmid topoisomers showed that the average cooperativity was sensitive to DNA twist, and was strongest when the DNA was slightly underwound. This suggests that AGT proteins are optimally juxtaposed when the DNA is near its torsionally-relaxed state. Most striking was the decline of binding stoichiometry with linking number. As stoichiometry and affinity differences were not correlated, we interpret this as evidence that supercoiling occludes AGT binding sites. These features suggest that AGT's lesion-search distributes preferentially to sites containing torsionally-relaxed DNA, in vivo.
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Affiliation(s)
- Manana Melikishvili
- Center for Structural Biology, Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, KY 40536, USA
| | - Michael G Fried
- Center for Structural Biology, Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, KY 40536, USA
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10
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Vo T, Wang S, Poon GMK, Wilson WD. Electrostatic control of DNA intersegmental translocation by the ETS transcription factor ETV6. J Biol Chem 2017; 292:13187-13196. [PMID: 28592487 PMCID: PMC5555182 DOI: 10.1074/jbc.m117.792887] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2017] [Revised: 06/06/2017] [Indexed: 01/22/2023] Open
Abstract
To find their DNA target sites in complex solution environments containing excess heterogeneous DNA, sequence-specific DNA-binding proteins execute various translocation mechanisms known collectively as facilitated diffusion. For proteins harboring a single DNA contact surface, long-range translocation occurs by jumping between widely spaced DNA segments. We have configured biosensor-based surface plasmon resonance to directly measure the affinity and kinetics of this intersegmental jumping by the ETS-family transcription factor ETS variant 6 (ETV6). To isolate intersegmental target binding in a functionally defined manner, we pre-equilibrated ETV6 with excess salmon sperm DNA, a heterogeneous polymer, before exposing the nonspecifically bound protein to immobilized oligomeric DNA harboring a high-affinity ETV6 site. In this way, the mechanism of ETV6-target association could be toggled electrostatically through varying NaCl concentration in the bulk solution. Direct measurements of association and dissociation kinetics of the site-specific complex indicated that 1) freely diffusive binding by ETV6 proceeds through a nonspecific-like intermediate, 2) intersegmental jumping is rate-limited by dissociation from the nonspecific polymer, and 3) dissociation of the specific complex is independent of the history of complex formation. These results show that target searches by proteins with an ETS domain, such as ETV6, whose single DNA-binding domain cannot contact both source and destination sites simultaneously, are nonetheless strongly modulated by intersegmental jumping in heterogeneous site environments. Our findings establish biosensors as a general technique for directly and specifically measuring target site search by DNA-binding proteins via intersegmental translocation.
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Affiliation(s)
- Tam Vo
- From the Department of Chemistry and
| | - Shuo Wang
- From the Department of Chemistry and
| | - Gregory M K Poon
- From the Department of Chemistry and
- Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, Georgia 30303
| | - W David Wilson
- From the Department of Chemistry and
- Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, Georgia 30303
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11
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Hope CM, Rebay I, Reinitz J. DNA Occupancy of Polymerizing Transcription Factors: A Chemical Model of the ETS Family Factor Yan. Biophys J 2017; 112:180-192. [PMID: 28076810 DOI: 10.1016/j.bpj.2016.11.901] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2016] [Revised: 10/18/2016] [Accepted: 11/11/2016] [Indexed: 11/28/2022] Open
Abstract
Transcription factors use both protein-DNA and protein-protein interactions to assemble appropriate complexes to regulate gene expression. Although most transcription factors operate as monomers or dimers, a few, including the E26 transformation-specific family repressors Drosophila melanogaster Yan and its human homolog TEL/ETV6, can polymerize. Although polymerization is required for both the normal and oncogenic function of Yan and TEL/ETV6, the mechanisms by which it influences the recruitment, organization, and stability of transcriptional complexes remain poorly understood. Further, a quantitative description of the DNA occupancy of a polymerizing transcription factor is lacking, and such a description would have broader applications to the conceptually related area of polymerizing chromatin regulators. To expand the theoretical basis for understanding how the oligomeric state of a transcriptional regulator influences its chromatin occupancy and function, we leveraged the extensive biochemical characterization of E26 transformation-specific factors to develop a mathematical model of Yan occupancy at chemical equilibrium. We find that spreading condensation from a specific binding site can take place in a path-independent manner given reasonable values of the free energies of specific and non-specific DNA binding and protein-protein cooperativity. Our calculations show that polymerization confers upon a transcription factor the unique ability to extend occupancy across DNA regions far from specific binding sites. In contrast, dimerization promotes recruitment to clustered binding sites and maximizes discrimination between specific and non-specific sites. We speculate that the association with non-specific DNA afforded by polymerization may enable regulatory behaviors that are well-suited to transcriptional repressors but perhaps incompatible with precise activation.
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Affiliation(s)
- C Matthew Hope
- Department of Biochemistry and Molecular Biophysics, The University of Chicago, Chicago, Illinois
| | - Ilaria Rebay
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, Illinois; Ben May Department for Cancer Research, The University of Chicago, Chicago, Illinois.
| | - John Reinitz
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, Illinois; Department of Ecology and Evolution, The University of Chicago, Chicago, Illinois; Department of Statistics, The University of Chicago, Chicago, Illinois.
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12
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Nechipurenko YD, Guzaev AD, Khodykov MV, Stirmanov YV, Ivanov AA, Krylov AS, Zhuze AL. Analysis of calorimetric data for the binding of monomeric bis-benzimidazole, an analog of the Hoechst 33258 dye, to poly(dA) · poly(dT). Biophysics (Nagoya-shi) 2017. [DOI: 10.1134/s0006350917030137] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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13
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De S, Okon M, Graves BJ, McIntosh LP. Autoinhibition of ETV6 DNA Binding Is Established by the Stability of Its Inhibitory Helix. J Mol Biol 2016; 428:1515-30. [PMID: 26920109 PMCID: PMC5575937 DOI: 10.1016/j.jmb.2016.02.020] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2015] [Revised: 02/14/2016] [Accepted: 02/16/2016] [Indexed: 02/06/2023]
Abstract
The ETS transcriptional repressor ETV6 (or TEL) is autoinhibited by an α-helix that sterically blocks its DNA-binding ETS domain. The inhibitory helix is marginally stable and unfolds when ETV6 binds to either specific or non-specific DNA. Using NMR spectroscopy, we show that folding of the inhibitory helix requires a buried charge-dipole interaction with helix H1 of the ETS domain. This interaction also contributes directly to autoinhibition by precluding a highly conserved dipole-enhanced hydrogen bond between the phosphodiester backbone of bound DNA and the N terminus of helix H1. To probe further the thermodynamic basis of autoinhibition, ETV6 variants were generated with amino acid substitutions introduced along the solvent exposed surface of the inhibitory helix. These changes were designed to increase the intrinsic helical propensity of the inhibitory helix without perturbing its packing interactions with the ETS domain. NMR-monitored amide hydrogen exchange measurements confirmed that the stability of the folded inhibitory helix increases progressively with added helix-promoting substitutions. This also results in progressively reinforced autoinhibition and decreased DNA-binding affinity. Surprisingly, locking the inhibitory helix onto the ETS domain by a disulfide bridge severely impairs, but does not abolish DNA binding. Weak interactions still occur via an interface displaced from the canonical ETS domain DNA-binding surface. Collectively, these studies establish a direct thermodynamic linkage between inhibitory helix stability and ETV6 autoinhibition, and demonstrate that helix unfolding does not strictly precede DNA binding. Modulating inhibitory helix stability provides a potential route for the in vivo regulation of ETV6 activity.
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Affiliation(s)
- Soumya De
- Department of Biochemistry and Molecular Biology, Department of Chemistry, and Michael Smith Laboratories, University of British Columbia, Vancouver, BC V6T 1Z3, Canada
| | - Mark Okon
- Department of Biochemistry and Molecular Biology, Department of Chemistry, and Michael Smith Laboratories, University of British Columbia, Vancouver, BC V6T 1Z3, Canada
| | - Barbara J Graves
- Department of Oncological Sciences, School of Medicine, Huntsman Cancer Institute, University of Utah, Salt Lake City, UT 84112-5550, USA; Howard Hughes Medical Institute, Chevy Chase, MD 20815-6789, USA
| | - Lawrence P McIntosh
- Department of Biochemistry and Molecular Biology, Department of Chemistry, and Michael Smith Laboratories, University of British Columbia, Vancouver, BC V6T 1Z3, Canada.
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14
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Zhang X, Daaboul GG, Spuhler PS, Dröge P, Ünlü MS. Quantitative characterization of conformational-specific protein-DNA binding using a dual-spectral interferometric imaging biosensor. NANOSCALE 2016; 8:5587-5598. [PMID: 26890964 DOI: 10.1039/c5nr06785e] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
DNA-binding proteins play crucial roles in the maintenance and functions of the genome and yet, their specific binding mechanisms are not fully understood. Recently, it was discovered that DNA-binding proteins recognize specific binding sites to carry out their functions through an indirect readout mechanism by recognizing and capturing DNA conformational flexibility and deformation. High-throughput DNA microarray-based methods that provide large-scale protein-DNA binding information have shown effective and comprehensive analysis of protein-DNA binding affinities, but do not provide information of DNA conformational changes in specific protein-DNA complexes. Building on the high-throughput capability of DNA microarrays, we demonstrate a quantitative approach that simultaneously measures the amount of protein binding to DNA and nanometer-scale DNA conformational change induced by protein binding in a microarray format. Both measurements rely on spectral interferometry on a layered substrate using a single optical instrument in two distinct modalities. In the first modality, we quantitate the amount of binding of protein to surface-immobilized DNA in each DNA spot using a label-free spectral reflectivity technique that accurately measures the surface densities of protein and DNA accumulated on the substrate. In the second modality, for each DNA spot, we simultaneously measure DNA conformational change using a fluorescence vertical sectioning technique that determines average axial height of fluorophores tagged to specific nucleotides of the surface-immobilized DNA. The approach presented in this paper, when combined with current high-throughput DNA microarray-based technologies, has the potential to serve as a rapid and simple method for quantitative and large-scale characterization of conformational specific protein-DNA interactions.
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Affiliation(s)
- Xirui Zhang
- Department of Biomedical Engineering, Boston University, Boston, Massachusetts 02215, USA
| | - George G Daaboul
- Department of Biomedical Engineering, Boston University, Boston, Massachusetts 02215, USA and Department of Electrical and Computer Engineering, Boston University, Boston, Massachusetts 02215, USA.
| | - Philipp S Spuhler
- Department of Biomedical Engineering, Boston University, Boston, Massachusetts 02215, USA
| | - Peter Dröge
- School of Biological Sciences, Nanyang Technological University, Singapore 637551
| | - M Selim Ünlü
- Department of Biomedical Engineering, Boston University, Boston, Massachusetts 02215, USA and Department of Electrical and Computer Engineering, Boston University, Boston, Massachusetts 02215, USA.
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15
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Greive SJ, Fung HKH, Chechik M, Jenkins HT, Weitzel SE, Aguiar PM, Brentnall AS, Glousieau M, Gladyshev GV, Potts JR, Antson AA. DNA recognition for virus assembly through multiple sequence-independent interactions with a helix-turn-helix motif. Nucleic Acids Res 2015; 44:776-89. [PMID: 26673721 PMCID: PMC4737164 DOI: 10.1093/nar/gkv1467] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2015] [Accepted: 11/30/2015] [Indexed: 11/14/2022] Open
Abstract
The helix-turn-helix (HTH) motif features frequently in protein DNA-binding assemblies. Viral pac site-targeting small terminase proteins possess an unusual architecture in which the HTH motifs are displayed in a ring, distinct from the classical HTH dimer. Here we investigate how such a circular array of HTH motifs enables specific recognition of the viral genome for initiation of DNA packaging during virus assembly. We found, by surface plasmon resonance and analytical ultracentrifugation, that individual HTH motifs of the Bacillus phage SF6 small terminase bind the packaging regions of SF6 and related SPP1 genome weakly, with little local sequence specificity. Nuclear magnetic resonance chemical shift perturbation studies with an arbitrary single-site substrate suggest that the HTH motif contacts DNA similarly to how certain HTH proteins contact DNA non-specifically. Our observations support a model where specificity is generated through conformational selection of an intrinsically bent DNA segment by a ring of HTHs which bind weakly but cooperatively. Such a system would enable viral gene regulation and control of the viral life cycle, with a minimal genome, conferring a major evolutionary advantage for SPP1-like viruses.
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Affiliation(s)
- Sandra J Greive
- York Structural Biology Laboratory, Department of Chemistry, University of York, York YO10 5DD, UK
| | - Herman K H Fung
- York Structural Biology Laboratory, Department of Chemistry, University of York, York YO10 5DD, UK Department of Biology, University of York, York YO10 5DD, UK
| | - Maria Chechik
- York Structural Biology Laboratory, Department of Chemistry, University of York, York YO10 5DD, UK
| | - Huw T Jenkins
- York Structural Biology Laboratory, Department of Chemistry, University of York, York YO10 5DD, UK
| | - Stephen E Weitzel
- Institute of Molecular Biology, University of Oregon, Eugene, Oregon 97403, USA
| | - Pedro M Aguiar
- Department of Chemistry, University of York, York YO10 5DD, UK
| | | | - Matthieu Glousieau
- York Structural Biology Laboratory, Department of Chemistry, University of York, York YO10 5DD, UK
| | - Grigory V Gladyshev
- Department of Biochemistry, School of Biology, Moscow State University, Moscow 119234, Russian Federation
| | | | - Alfred A Antson
- York Structural Biology Laboratory, Department of Chemistry, University of York, York YO10 5DD, UK
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16
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Jayaraman B, Mavor D, Gross JD, Frankel AD. Thermodynamics of Rev-RNA interactions in HIV-1 Rev-RRE assembly. Biochemistry 2015; 54:6545-54. [PMID: 26422686 DOI: 10.1021/acs.biochem.5b00876] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
The HIV-1 protein Rev facilitates the nuclear export of intron-containing viral mRNAs by recognizing a structured RNA site, the Rev-response-element (RRE), contained in an intron. Rev assembles as a homo-oligomer on the RRE using its α-helical arginine-rich-motif (ARM) for RNA recognition. One unique feature of this assembly is the repeated use of the ARM from individual Rev subunits to contact distinct parts of the RRE in different binding modes. How the individual interactions differ and how they contribute toward forming a functional complex is poorly understood. Here we examine the thermodynamics of Rev-ARM peptide binding to two sites, RRE stem IIB, the high-affinity site that nucleates Rev assembly, and stem IA, a potential intermediate site during assembly, using NMR spectroscopy and isothermal titration calorimetry (ITC). NMR data indicate that the Rev-IIB complex forms a stable interface, whereas the Rev-IA interface is highly dynamic. ITC studies show that both interactions are enthalpy-driven, with binding to IIB being 20-30 fold tighter than to IA. Salt-dependent decreases in affinity were similar at both sites and predominantly enthalpic in nature, reflecting the roles of electrostatic interactions with arginines. However, the two interactions display strikingly different partitioning between enthalpy and entropy components, correlating well with the NMR observations. Our results illustrate how the variation in binding modes to different RRE target sites may influence the stability or order of Rev-RRE assembly and disassembly, and consequently its function.
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Affiliation(s)
- Bhargavi Jayaraman
- Department of Biochemistry and Biophysics and ‡Department of Pharmaceutical Chemistry, University of California , San Francisco, United States
| | - David Mavor
- Department of Biochemistry and Biophysics and ‡Department of Pharmaceutical Chemistry, University of California , San Francisco, United States
| | - John D Gross
- Department of Biochemistry and Biophysics and ‡Department of Pharmaceutical Chemistry, University of California , San Francisco, United States
| | - Alan D Frankel
- Department of Biochemistry and Biophysics and ‡Department of Pharmaceutical Chemistry, University of California , San Francisco, United States
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17
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Melikishvili M, Fried MG. Resolving the contributions of two cooperative mechanisms to the DNA binding of AGT. Biopolymers 2015; 103:509-16. [PMID: 26017689 PMCID: PMC5016775 DOI: 10.1002/bip.22684] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2015] [Revised: 05/16/2015] [Accepted: 05/17/2015] [Indexed: 11/25/2022]
Abstract
The O(6)-alkylguanine DNA alkyltransferase (AGT) is a DNA repair enzyme that binds DNA with moderate cooperativity. This cooperativity is important for its search for alkylated bases. A structural model of the cooperative complex of AGT with DNA predicts short-range interactions between nearest protein neighbors and long-range interactions between proteins separated in the array. DNA substrates ranging from 11bp to 30bp allowed us to use differences in binding stoichiometry to resolve short- and long-range protein contributions to the stability of AGT complexes. We found that the short-range component of ΔG°(coop) was nearly independent of DNA length and protein packing density. In contrast the long-range component oscillated with DNA length, with a period equal to the occluded binding site size (4bp). The amplitude of the long-range component decayed from ∼-4 kcal/mole of interaction to ∼-1.2 kcal/mol of interaction as the size of cooperative unit increased from 4 to 7 proteins, suggesting a mechanism to limit the size of cooperative clusters. These features allow us to make testable predictions about AGT distributions and interactions with chromatin structures in vivo.
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Affiliation(s)
- Manana Melikishvili
- Department of Molecular and Cellular Biochemistry, Center for Structural Biology, University of Kentucky, Lexington, KY, 40536
| | - Michael G Fried
- Department of Molecular and Cellular Biochemistry, Center for Structural Biology, University of Kentucky, Lexington, KY, 40536
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18
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Abstract
Analytical ultracentrifugation (AUC) is a powerful tool that can provide thermodynamic information on associating systems. Here, we discuss how to use the two fundamental AUC applications, sedimentation velocity (SV), and sedimentation equilibrium (SE), to study nonspecific protein-nucleic acid interactions, with a special emphasis on how to analyze the experimental data to extract thermodynamic information. We discuss three specific applications of this approach: (i) determination of nonspecific binding stoichiometry of E. coli integration host factor protein to dsDNA, (ii) characterization of nonspecific binding properties of Adenoviral IVa2 protein to dsDNA using SE-AUC, and (iii) analysis of the competition between specific and nonspecific DNA-binding interactions observed for E. coli integration host factor protein assembly on dsDNA. These approaches provide powerful tools that allow thermodynamic interrogation and thus a mechanistic understanding of how proteins bind nucleic acids by both specific and nonspecific interactions.
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19
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Macazo F, Karpel RL, White RJ. Monitoring cooperative binding using electrochemical DNA-based sensors. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:868-75. [PMID: 25517392 PMCID: PMC4303326 DOI: 10.1021/la504083c] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/15/2014] [Revised: 12/15/2014] [Indexed: 05/20/2023]
Abstract
Electrochemical DNA-based (E-DNA) sensors are utilized to detect a variety of targets including complementary DNA, small molecules, and proteins. These sensors typically employ surface-bound single-stranded oligonucleotides that are modified with a redox-active molecule on the distal 3' terminus. Target-induced flexibility changes of the DNA probe alter the efficiency of electron transfer between the redox active methylene blue and the electrode surface, allowing for quantitative detection of target concentration. While numerous studies have utilized the specific and sensitive abilities of E-DNA sensors to quantify target concentration, no studies to date have demonstrated the ability of this class of collision-based sensors to elucidate biochemical-binding mechanisms such as cooperativity. In this study, we demonstrate that E-DNA sensors fabricated with various lengths of surface-bound oligodeoxythymidylate [(dT)n] sensing probes are able to quantitatively distinguish between cooperative and noncooperative binding of a single-stranded DNA-binding protein. Specifically, we demonstrate that oligo(dT) E-DNA sensors are able to quantitatively detect nM levels (50 nM-4 μM) of gene 32 protein (g32p). Furthermore, the sensors exhibit signal that is able to distinguish between the cooperative binding of the full-length g32p and the noncooperative binding of the core domain (*III) fragment to single-stranded DNA. Finally, we demonstrate that this binding is both probe-length- and ionic-strength-dependent. This study illustrates a new quantitative property of this powerful class of biosensor and represents a rapid and simple methodology for understanding protein-DNA binding mechanisms.
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Affiliation(s)
- Florika
C. Macazo
- Department
of Chemistry and Biochemistry, University
of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore, Maryland 21250, United
States
| | - Richard L. Karpel
- Department
of Chemistry and Biochemistry, University
of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore, Maryland 21250, United
States
| | - Ryan J. White
- Department
of Chemistry and Biochemistry, University
of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore, Maryland 21250, United
States
- E-mail:
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20
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Sanyal SJ, Yang TC, Catalano CE. Integration host factor assembly at the cohesive end site of the bacteriophage lambda genome: implications for viral DNA packaging and bacterial gene regulation. Biochemistry 2014; 53:7459-70. [PMID: 25335823 PMCID: PMC4263431 DOI: 10.1021/bi501025s] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
![]()
Integration host factor (IHF) is
an Escherichia coli protein involved in (i) condensation
of the bacterial nucleoid and
(ii) regulation of a variety of cellular functions. In its regulatory
role, IHF binds to a specific sequence to introduce a strong bend
into the DNA; this provides a duplex architecture conducive to the
assembly of site-specific nucleoprotein complexes. Alternatively,
the protein can bind in a sequence-independent manner that weakly
bends and wraps the duplex to promote nucleoid formation. IHF is also
required for the development of several viruses, including bacteriophage
lambda, where it promotes site-specific assembly of a genome packaging
motor required for lytic development. Multiple IHF consensus sequences
have been identified within the packaging initiation site (cos), and we here interrogate IHF–cos binding interactions using complementary electrophoretic mobility
shift (EMS) and analytical ultracentrifugation (AUC) approaches. IHF
recognizes a single consensus sequence within cos (I1) to afford a strongly bent nucleoprotein complex.
In contrast, IHF binds weakly but with positive cooperativity to nonspecific
DNA to afford an ensemble of complexes with increasing masses and
levels of condensation. Global analysis of the EMS and AUC data provides
constrained thermodynamic binding constants and nearest neighbor cooperativity
factors for binding of IHF to I1 and to nonspecific
DNA substrates. At elevated IHF concentrations, the nucleoprotein
complexes undergo a transition from a condensed to an extended rodlike
conformation; specific binding of IHF to I1 imparts
a significant energy barrier to the transition. The results provide
insight into how IHF can assemble specific regulatory complexes in
the background of extensive nonspecific DNA condensation.
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Affiliation(s)
- Saurarshi J Sanyal
- Department of Medicinal Chemistry, School of Pharmacy, University of Washington , H-172 Health Sciences Building, Box 357610, Seattle, Washington 98195, United States
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21
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Yang TC, Maluf NK. Characterization of the non-specific DNA binding properties of the Adenoviral IVa2 protein. Biophys Chem 2014; 193-194:1-8. [PMID: 25038409 DOI: 10.1016/j.bpc.2014.06.005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2014] [Revised: 06/19/2014] [Accepted: 06/19/2014] [Indexed: 10/25/2022]
Abstract
Human Adenovirus (Ad) is a non-enveloped, icosahedral virus with a linear, double-stranded DNA genome. The Ad IVa2 protein is involved in multiple viral processes including viral late gene transcription and virus assembly. Previous studies have shown that IVa2 loads additional viral proteins onto conserved DNA elements within the Ad genome to regulate these viral processes. IVa2 also possesses strong non-specific DNA binding activity, and it is likely it uses this activity to recruit proteins to the conserved DNA elements. Here we have investigated the non-specific DNA binding activity of IVa2 using nitrocellulose/DEAE filter binding and sedimentation equilibrium techniques. We have analyzed our data using the McGhee and Von Hippel approach [1], and find that IVa2 binds with strong, positive nearest-neighbor cooperativity. In addition, we describe how to apply the McGhee and von Hippel approach to directly analyze sedimentation equilibrium data using non-linear least-squares methods. We discuss the implications of these results with respect to current virus assembly mechanisms.
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Affiliation(s)
- Teng-Chieh Yang
- University of Colorado Denver, School of Pharmacy, Dept. Pharm. Sciences, C238 12850 E. Montview Blvd., V20-4121, Aurora, CO 80045
| | - Nasib Karl Maluf
- University of Colorado Denver, School of Pharmacy, Dept. Pharm. Sciences, C238 12850 E. Montview Blvd., V20-4121, Aurora, CO 80045; Alliance Protein Laboratories, 6042 Cornerstone Ct West A, San Diego, CA 92121.
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22
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23
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De S, Chan ACK, Coyne HJ, Bhachech N, Hermsdorf U, Okon M, Murphy MEP, Graves BJ, McIntosh LP. Steric mechanism of auto-inhibitory regulation of specific and non-specific DNA binding by the ETS transcriptional repressor ETV6. J Mol Biol 2014; 426:1390-406. [PMID: 24333486 PMCID: PMC4278593 DOI: 10.1016/j.jmb.2013.11.031] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2013] [Revised: 11/05/2013] [Accepted: 11/09/2013] [Indexed: 11/29/2022]
Abstract
DNA binding by the ETS transcriptional repressor ETV6 (or TEL) is auto-inhibited ~50-fold due to an α-helix that sterically blocks its ETS domain binding interface. Using NMR spectroscopy, we demonstrate that this marginally stable helix is unfolded, and not displaced to a non-inhibitory position, when ETV6 is bound to DNA containing a consensus (5')GGAA(3') recognition site. Although significantly lower in affinity, binding to non-specific DNA is auto-inhibited ~5-fold and is also accompanied by helix unfolding. Based on NMR chemical shift perturbations, both specific and non-specific DNA are bound via the same canonical ETS domain interface. However, spectral perturbations are smaller for the non-specific complex, suggesting weaker and less well-defined interactions than in the specific complex. In parallel, the crystal structure of ETV6 bound to a specific DNA duplex was determined. The structure of this complex reveals that a non-conserved histidine residue in the ETS domain recognition helix helps establish the specificity of ETV6 for DNA-binding sites containing (5')GGAA(3')versus(5')GGAT(3'). These studies provide a unified steric mechanism for attenuating ETV6 binding to both specific and non-specific DNA and expand the repertoire of characterized auto-inhibitory strategies utilized to regulate ETS factors.
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Affiliation(s)
- Soumya De
- Department of Biochemistry and Molecular Biology, Department of Chemistry, and Michael Smith Laboratories, University of British Columbia, Vancouver, BC, Canada V6T 1Z3
| | - Anson C K Chan
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, BC, Canada V6T 1Z3
| | - H Jerome Coyne
- Department of Biochemistry and Molecular Biology, Department of Chemistry, and Michael Smith Laboratories, University of British Columbia, Vancouver, BC, Canada V6T 1Z3
| | - Niraja Bhachech
- Department of Oncological Sciences, University of Utah School of Medicine, and Huntsman Cancer Institute, University of Utah, Salt Lake City, UT 84112-5550, USA; Howard Hughes Medical Institute, Chevy Chase, MD 20815-6789, USA
| | - Ulrike Hermsdorf
- Department of Biochemistry and Molecular Biology, Department of Chemistry, and Michael Smith Laboratories, University of British Columbia, Vancouver, BC, Canada V6T 1Z3
| | - Mark Okon
- Department of Biochemistry and Molecular Biology, Department of Chemistry, and Michael Smith Laboratories, University of British Columbia, Vancouver, BC, Canada V6T 1Z3
| | - Michael E P Murphy
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, BC, Canada V6T 1Z3
| | - Barbara J Graves
- Department of Oncological Sciences, University of Utah School of Medicine, and Huntsman Cancer Institute, University of Utah, Salt Lake City, UT 84112-5550, USA; Howard Hughes Medical Institute, Chevy Chase, MD 20815-6789, USA
| | - Lawrence P McIntosh
- Department of Biochemistry and Molecular Biology, Department of Chemistry, and Michael Smith Laboratories, University of British Columbia, Vancouver, BC, Canada V6T 1Z3.
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24
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Chen PC, Hayashi MAF, Oliveira EB, Karpel RL. DNA-interactive properties of crotamine, a cell-penetrating polypeptide and a potential drug carrier. PLoS One 2012; 7:e48913. [PMID: 23145017 PMCID: PMC3493588 DOI: 10.1371/journal.pone.0048913] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2012] [Accepted: 10/08/2012] [Indexed: 01/17/2023] Open
Abstract
Crotamine, a 42-residue polypeptide derived from the venom of the South American rattlesnake Crotalus durissus terrificus, has been shown to be a cell-penetrating protein that targets chromosomes, carries plasmid DNA into cells, and shows specificity for actively proliferating cells. Given this potential role as a nucleic acid-delivery vector, we have studied in detail the binding of crotamine to single- and double-stranded DNAs of different lengths and base compositions over a range of ionic conditions. Agarose gel electrophoresis and ultraviolet spectrophotometry analysis indicate that complexes of crotamine with long-chain DNAs readily aggregate and precipitate at low ionic strength. This aggregation, which may be important for cellular uptake of DNA, becomes less likely with shorter chain length. 25-mer oligonucleotides do not show any evidence of such aggregation, permitting the determination of affinities and size via fluorescence quenching experiments. The polypeptide binds non-cooperatively to DNA, covering about 5 nucleotide residues when it binds to single (ss) or (ds) double stranded molecules. The affinities of the protein for ss- vs. ds-DNA are comparable, and inversely proportional to salt levels. Analysis of the dependence of affinity on [NaCl] indicates that there are a maximum of ∼3 ionic interactions between the protein and DNA, with some of the binding affinity attributable to non-ionic interactions. Inspection of the three-dimensional structure of the protein suggests that residues 31 to 35, Arg-Trp-Arg-Trp-Lys, could serve as a potential DNA-binding site. A hexapeptide containing this sequence displayed a lower DNA binding affinity and salt dependence as compared to the full-length protein, likely indicative of a more suitable 3D structure and the presence of accessory binding sites in the native crotamine. Taken together, the data presented here describing crotamine-DNA interactions may lend support to the design of more effective nucleic acid drug delivery vehicles which take advantage of crotamine as a carrier with specificity for actively proliferating cells.
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Affiliation(s)
- Pei-Chun Chen
- Department of Chemistry and Biochemistry, University of Maryland Baltimore County (UMBC), Baltimore, Maryland, United States of America
| | - Mirian A. F. Hayashi
- Departamento de Farmacologia, Universidade Federal de São Paulo (UNIFESP), São Paulo, São Paulo, Brazil
| | - Eduardo Brandt Oliveira
- Departamento de Bioquímica e Imunologia, Faculdade de Medicina, Universidade de São Paulo (USP), Ribeirão Preto, Brazil
| | - Richard L. Karpel
- Department of Chemistry and Biochemistry, University of Maryland Baltimore County (UMBC), Baltimore, Maryland, United States of America
- * E-mail:
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25
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Hieb AR, D'Arcy S, Kramer MA, White AE, Luger K. Fluorescence strategies for high-throughput quantification of protein interactions. Nucleic Acids Res 2011; 40:e33. [PMID: 22121211 PMCID: PMC3299996 DOI: 10.1093/nar/gkr1045] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Advances in high-throughput characterization of protein networks in vivo have resulted in large databases of unexplored protein interactions that occur during normal cell function. Their further characterization requires quantitative experimental strategies that are easy to implement in laboratories without specialized equipment. We have overcome many of the previous limitations to thermodynamic quantification of protein interactions, by developing a series of in-solution fluorescence-based strategies. These methods have high sensitivity, a broad dynamic range, and can be performed in a high-throughput manner. In three case studies we demonstrate how fluorescence (de)quenching and fluorescence resonance energy transfer can be used to quantitatively probe various high-affinity protein–DNA and protein–protein interactions. We applied these methods to describe the preference of linker histone H1 for nucleosomes over DNA, the ionic dependence of the DNA repair enzyme PARP1 in DNA binding, and the interaction between the histone chaperone Nap1 and the histone H2A–H2B heterodimer.
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Affiliation(s)
- Aaron R Hieb
- Howard Hughes Medical Institute and Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80523, USA
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26
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Lenormand H, Amar-Bacoup F, Vincent JC. pH effects on the hyaluronan hydrolysis catalysed by hyaluronidase in the presence of proteins. Part III. The electrostatic non-specific hyaluronan–hyaluronidase complex. Carbohydr Polym 2011. [DOI: 10.1016/j.carbpol.2011.06.044] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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27
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Bourassa P, Dubeau S, Maharvi GM, Fauq AH, Thomas TJ, Tajmir-Riahi HA. Locating the binding sites of anticancer tamoxifen and its metabolites 4-hydroxytamoxifen and endoxifen on bovine serum albumin. Eur J Med Chem 2011; 46:4344-53. [PMID: 21777996 DOI: 10.1016/j.ejmech.2011.07.005] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2011] [Revised: 06/21/2011] [Accepted: 07/02/2011] [Indexed: 10/18/2022]
Abstract
The breast anticancer drug tamoxifen and its metabolites bind serum albumins. We located the binding sites of tamoxifen, 4-hydroxytamoxifen and endoxifen on bovine serum albumin (BSA). FTIR, CD and fluorescence spectroscopic methods as well as molecular modeling were used to characterize the drug binding mode, binding constant and the effect of drug binding on BSA stability and conformation. Structural analysis showed that tamoxifen and its metabolites bind BSA via hydrophobic and hydrophilic interactions with overall binding constants of K(tam-BSA) = 1.96 (± 0.2)× 10(4)M(-1), K(4-hydroxytam-BSA) = 1.80 (± 0.4)× 10(4)M(-1) and K(endox-BSA) = 8.01 (± 0.8)× 10(3)M(-1). The number of bound drug molecules per protein is 1.7 (tamoxifen), 1.4 (4-hydroxitamoxifen) and 1.13 (endoxifen). The participation of several amino acid residues in drug-protein complexes is stabilized by extended hydrogen bonding network with the free binding energy of -13.47 (tamoxifen), -13.79 (4-hydroxtamoxifen) and -12.72 kcal/mol (endoxifen). The order of binding is 4-hydroxy-tamoxen>tamoxifen>endoxifen. BSA conformation was altered by a major reduction of α-helix from 63% (free BSA) to 41% with tamoxifen, to 39% with 4-hydroxytamoxifen, and to 47% with endoxifen. In addition, an increase in turn and random coil structures was found, suggesting partial protein unfolding. These results suggest that serum albumins might act as carrier proteins for tamoxifen and its metabolites in delivering them to target tissues.
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Affiliation(s)
- P Bourassa
- Département de Chimie-Biologie, Université du Québec à Trois-Rivières, CP 500, Trois-Rivières, Québec G9A 5H7, Canada
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28
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Teif VB, Rippe K. Calculating transcription factor binding maps for chromatin. Brief Bioinform 2011; 13:187-201. [PMID: 21737419 DOI: 10.1093/bib/bbr037] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Current high-throughput experiments already generate enough data for retrieving the DNA sequence-dependent binding affinities of transcription factors (TF) and other chromosomal proteins throughout the complete genome. However, the reverse task of calculating binding maps in a chromatin context for a given set of concentrations and TF affinities appears to be even more challenging and computationally demanding. The problem can be addressed by considering the DNA sequence as a one-dimensional lattice with units of one or more base pairs. To calculate protein occupancies in chromatin, one needs to consider the competition of TF and histone octamers for binding sites as well as the partial unwrapping of nucleosomal DNA. Here, we consider five different classes of algorithms to compute binding maps that include the binary variable, combinatorial, sequence generating function, transfer matrix and dynamic programming approaches. The calculation time of the binary variable algorithm scales exponentially with DNA length, which limits its use to the analysis of very small genomic regions. For regulatory regions with many overlapping binding sites, potentially applicable algorithms reduce either to the transfer matrix or dynamic programming approach. In addition to the recently proposed transfer matrix formalism for TF access to the nucleosomal organized DNA, we develop here a dynamic programming algorithm that accounts for this feature. In the absence of nucleosomes, dynamic programming outperforms the transfer matrix approach, but the latter is faster when nucleosome unwrapping has to be considered. Strategies are discussed that could further facilitate calculations to allow computing genome-wide TF binding maps.
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Affiliation(s)
- Vladimir B Teif
- BioQuant and German Cancer Research Center (DKFZ), Im Neuenheimer Feld 267, 69120 Heidelberg, Germany.
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29
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Binding of antitumor tamoxifen and its metabolites 4-hydroxytamoxifen and endoxifen to human serum albumin. Biochimie 2011; 93:1089-101. [DOI: 10.1016/j.biochi.2011.03.006] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2010] [Accepted: 03/12/2011] [Indexed: 11/17/2022]
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30
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Adams CA, Fried MG. Mutations that probe the cooperative assembly of O⁶-alkylguanine-DNA alkyltransferase complexes. Biochemistry 2011; 50:1590-8. [PMID: 21226457 DOI: 10.1021/bi101970d] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
O(6)-Alkylguanine-DNA alkyltransferase (AGT) repairs mutagenic O(6)-alkylguanine and O(4)-alkylthymine adducts present in DNA that has been exposed to alkylating agents. AGT binds DNA cooperatively, and models of cooperative complexes predict that residues 1-7 of one protein molecule and residues 163-169 of a neighboring protein are closely juxtaposed. To test these models, we used directed mutagenesis to substitute triplets of alanine for triplets of native residues across these two sequences. Six of eight designed mutants expressed AGT at detectable levels. All mutant AGTs that were expressed were folded compactly, bound DNA with stoichiometries equivalent to that of the wild-type protein, and were able to protect Escherichia coli to varying degrees from the potent alkylating agent N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). All mutations attenuated DNA binding cooperativity, but unexpectedly, they also reduced the affinity of AGT for DNA. This suggests that the protein-protein and protein-DNA interactions of AGT are strongly coupled. When normalized for differences in AGT expression, cells expressing mutants KDC(3-5)-AAA, DCE(4-6)-AAA, and KEW(165-167)-AAA were significantly more susceptible to MNNG than wild-type cells. This is the first evidence, to the best of our knowledge, of a role for residues at the protein-protein interface and, by implication, cooperative protein-protein interactions in the cell-protective mechanisms of AGT.
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Affiliation(s)
- Claire A Adams
- Center for Structural Biology, Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, Kentucky 40536, United States
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31
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Bernacchi S, Mercenne G, Tournaire C, Marquet R, Paillart JC. Importance of the proline-rich multimerization domain on the oligomerization and nucleic acid binding properties of HIV-1 Vif. Nucleic Acids Res 2010; 39:2404-15. [PMID: 21076154 PMCID: PMC3064812 DOI: 10.1093/nar/gkq979] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
The HIV-1 viral infectivity factor (Vif) is required for productive infection of non-permissive cells, including most natural HIV-1 targets, where it counteracts the antiviral activities of the cellular cytosine deaminases APOBEC-3G (A3G) and A3F. Vif is a multimeric protein and the conserved proline-rich domain 161PPLP164 regulating Vif oligomerization is crucial for its function and viral infectivity. Here, we expressed and purified wild-type Vif and a mutant protein in which alanines were substituted for the proline residues of the 161PPLP164 domain. Using dynamic light scattering, circular dichroism and fluorescence spectroscopy, we established the impact of these mutations on Vif oligomerization, secondary structure content and nucleic acids binding properties. In vitro, wild-type Vif formed oligomers of five to nine proteins, while Vif AALA formed dimers and/or trimers. Up to 40% of the unbound wild-type Vif protein appeared to be unfolded, but binding to the HIV-1 TAR apical loop promoted formation of β-sheets. Interestingly, alanine substitutions did not significantly affect the secondary structure of Vif, but they diminished its binding affinity and specificity for nucleic acids. Dynamic light scattering showed that Vif oligomerization, and interaction with folding-promoting nucleic acids, favor formation of high molecular mass complexes. These properties could be important for Vif functions involving RNAs.
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Affiliation(s)
- Serena Bernacchi
- Architecture et Réactivité de l'ARN, Université de Strasbourg, CNRS, Institut de Biologie Moléculaire et Cellulaire, 15 rue René Descartes, 67084 Strasbourg, France
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32
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Dubeau S, Bourassa P, Thomas TJ, Tajmir-Riahi HA. Biogenic and synthetic polyamines bind bovine serum albumin. Biomacromolecules 2010; 11:1507-15. [PMID: 20433143 DOI: 10.1021/bm100144v] [Citation(s) in RCA: 93] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Biogenic polyamines are found to modulate protein synthesis at different levels, while polyamine analogues have shown major antitumor activity in multiple experimental models, including breast cancer. The aim of this study was to examine the interaction of bovine serum albumin (BSA) with biogenic polyamines, spermine and spermidine, and polyamine analogues 3,7,11,15-tetrazaheptadecane x 4 HCl (BE-333) and 3,7,11,15,19-pentazahenicosane x 5 HCl (BE-3333) in aqueous solution at physiological conditions. FTIR, UV-visible, CD, and fluorescence spectroscopic methods were used to determine the polyamine binding mode and the effects of polyamine complexation on protein stability and secondary structure. Structural analysis showed that polyamines bind BSA via both hydrophilic and hydrophobic interactions. Stronger polyamine-protein complexes formed with biogenic than synthetic polyamines with overall binding constants of K(spm) = 3.56 (+/-0.5) x 10(5) M(-1), K(spmd) = 1.77 (+/-0.4) x 10(5) M(-1), K(BE-333) = 1.11 (+/-0.3) x 10(4) M(-1) and K(BE-3333) = 3.90 (+/-0.7) x 10(4) M(-1) that correlate with their positively charged amino group contents. Major alterations of protein conformation were observed with reduction of alpha-helix from 63% (free protein) to 55-33% and increase of turn 12% (free protein) to 28-16% and random coil from 6% (free protein) to 24-17% in the polyamine-BSA complexes, indicating a partial protein unfolding. These data suggest that serum albumins might act as polyamine carrier proteins in delivering polyamine analogues to target tissues.
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Affiliation(s)
- S Dubeau
- Département de Chimie-Biologie, Université du Québec à Trois-Rivières, C. P. 500, Trois-Rivières, Québec, G9A 5H7, Canada
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Teif VB, Rippe K. Statistical-mechanical lattice models for protein-DNA binding in chromatin. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2010; 22:414105. [PMID: 21386588 DOI: 10.1088/0953-8984/22/41/414105] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Statistical-mechanical lattice models for protein-DNA binding are well established as a method to describe complex ligand binding equilibria measured in vitro with purified DNA and protein components. Recently, a new field of applications has opened up for this approach since it has become possible to experimentally quantify genome-wide protein occupancies in relation to the DNA sequence. In particular, the organization of the eukaryotic genome by histone proteins into a nucleoprotein complex termed chromatin has been recognized as a key parameter that controls the access of transcription factors to the DNA sequence. New approaches have to be developed to derive statistical-mechanical lattice descriptions of chromatin-associated protein-DNA interactions. Here, we present the theoretical framework for lattice models of histone-DNA interactions in chromatin and investigate the (competitive) DNA binding of other chromosomal proteins and transcription factors. The results have a number of applications for quantitative models for the regulation of gene expression.
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Affiliation(s)
- Vladimir B Teif
- Research Group Genome Organization and Function, Deutsches Krebsforschungszentrum and BioQuant, Im Neuenheimer Feld 280, 69120 Heidelberg, Germany.
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Condensed DNA: condensing the concepts. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2010; 105:208-22. [PMID: 20638406 DOI: 10.1016/j.pbiomolbio.2010.07.002] [Citation(s) in RCA: 184] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2010] [Accepted: 07/11/2010] [Indexed: 01/09/2023]
Abstract
DNA is stored in vivo in a highly compact, so-called condensed phase, where gene regulatory processes are governed by the intricate interplay between different states of DNA compaction. These systems often have surprising properties, which one would not predict from classical concepts of dilute solutions. The mechanistic details of DNA packing are essential for its functioning, as revealed by the recent developments coming from biochemistry, electrostatics, statistical mechanics, and molecular and cell biology. Different aspects of condensed DNA behavior are linked to each other, but the links are often hidden in the bulk of experimental and theoretical details. Here we try to condense some of these concepts and provide interconnections between the different fields. After a brief description of main experimental features of DNA condensation inside viruses, bacteria, eukaryotes and the test tube, main theoretical approaches for the description of these systems are presented. We end up with an extended discussion of the role of DNA condensation in the context of gene regulation and mention potential applications of DNA condensation in gene therapy and biotechnology.
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35
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Lenormand H, Deschrevel B, Vincent JC. pH effects on the hyaluronan hydrolysis catalysed by hyaluronidase in the presence of proteins: Part I. Dual aspect of the pH-dependence. Matrix Biol 2009; 29:330-7. [PMID: 20043995 DOI: 10.1016/j.matbio.2009.12.007] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2009] [Revised: 11/09/2009] [Accepted: 12/17/2009] [Indexed: 10/20/2022]
Abstract
Hyaluronan (HA) hydrolysis catalysed by hyaluronidase (HAase) is strongly inhibited when performed at a low ratio of HAase to HA concentrations and at low ionic strength. This is because long HA chains can form non-active complexes with HAase. Bovine serum albumin (BSA) is able to compete with HAase to form electrostatic complexes with HA so freeing HAase which then recovers its catalytic activity. This BSA-dependence is characterised by two main domains separated by the optimal BSA concentration: below this concentration the HAase activity increases when the BSA concentration is increased, above this concentration the HAase activity decreases. This occurs provided that HA is negatively charged and BSA is positively charged, i.e. in a pH range from 3 to 5.25. The higher the pH value the higher the optimal BSA concentration. Other proteins can also modulate HAase activity. Lysozyme, which has a pI higher than that of BSA, is also able to compete with HAase to form electrostatic complexes with HA and liberate HAase. This occurs over a wider pH range that extends from 3 to 9. These results mean that HAase can form complexes with HA and recover its enzymatic activity at pH as high as 9, consistent with HAase having either a high pI value or positively charged patches on its surface at high pH. Finally, the pH-dependence of HAase activity, which results from the influence of pH on both the intrinsic HAase activity and the formation of complexes between HAase and HA, shows a maximum at pH 4 and a significant activity up to pH 9.
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Affiliation(s)
- Hélène Lenormand
- Laboratoire Polymères, Biopolymères, Surfaces, FRE 3101 CNRS - Université de Rouen, 76821 Mont-Saint-Aignan cedex, France
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36
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Abstract
The experiments described here demonstrate ways in which DNA length can be used as an experimental variable for the characterization of positively cooperative, sequence nonspecific DNA binding. Examples are drawn from recent studies of the interactions of O(6)-alkylguanine DNA alkyltransferase (AGT) with duplex DNAs (Melikishvili et al. (2008). Interactions of human O(6)-alkylguanine-DNA alkyltransferase (AGT) with short double-stranded DNAs. Biochemistry 47, 13754-13763). Oscillations in binding density and apparent binding site size (S(app)) are predicted by models in which a single cooperative assembly forms on each DNA molecule and in which enzyme molecules bind full-length binding sites, but not partial ones. These oscillations provide an accurate, DNA-length independent measure of the occluded binding site size (the length of DNA that one protein molecule occupies to the exclusion of others). In addition, length-dependent oscillations in association constant (K) and cooperativity (ω) reveal the degree to which substrate length can influence these parameters.
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37
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Mercenne G, Bernacchi S, Richer D, Bec G, Henriet S, Paillart JC, Marquet R. HIV-1 Vif binds to APOBEC3G mRNA and inhibits its translation. Nucleic Acids Res 2009; 38:633-46. [PMID: 19910370 PMCID: PMC2810999 DOI: 10.1093/nar/gkp1009] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
The HIV-1 viral infectivity factor (Vif) allows productive infection of non-permissive cells (including most natural HIV-1 targets) by counteracting the cellular cytosine deaminases APOBEC-3G (hA3G) and hA3F. The Vif-induced degradation of these restriction factors by the proteasome has been extensively studied, but little is known about the translational repression of hA3G and hA3F by Vif, which has also been proposed to participate in Vif function. Here, we studied Vif binding to hA3G mRNA and its role in translational repression. Filter binding assays and fluorescence titration curves revealed that Vif tightly binds to hA3G mRNA. Vif overall binding affinity was higher for the 3′UTR than for the 5′UTR, even though this region contained at least one high affinity Vif binding site (apparent Kd = 27 ± 6 nM). Several Vif binding sites were identified in 5′ and 3′UTRs using RNase footprinting. In vitro translation evidenced that Vif inhibited hA3G translation by two mechanisms: a main time-independent process requiring the 5′UTR and an additional time-dependent, UTR-independent process. Results using a Vif protein mutated in the multimerization domain suggested that the molecular mechanism of translational control is more complicated than a simple physical blockage of scanning ribosomes.
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Affiliation(s)
- Gaëlle Mercenne
- Architecture et Réactivité de l'ARN, Université de Strasbourg, CNRS, IBMC, 15 rue René Descartes, 67084, Strasbourg cedex, France
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38
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Analysis of cooperativity by isothermal titration calorimetry. Int J Mol Sci 2009; 10:3457-77. [PMID: 20111687 PMCID: PMC2812830 DOI: 10.3390/ijms10083457] [Citation(s) in RCA: 103] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2009] [Revised: 07/28/2009] [Accepted: 07/31/2009] [Indexed: 11/25/2022] Open
Abstract
Cooperative binding pervades Nature. This review discusses the use of isothermal titration calorimetry (ITC) in the identification and characterisation of cooperativity in biological interactions. ITC has broad scope in the analysis of cooperativity as it determines binding stiochiometries, affinities and thermodynamic parameters, including enthalpy and entropy in a single experiment. Examples from the literature are used to demonstrate the applicability of ITC in the characterisation of cooperative systems.
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39
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Adams CA, Melikishvili M, Rodgers DW, Rasimas JJ, Pegg AE, Fried MG. Topologies of complexes containing O6-alkylguanine-DNA alkyltransferase and DNA. J Mol Biol 2009; 389:248-63. [PMID: 19358853 DOI: 10.1016/j.jmb.2009.03.067] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2008] [Revised: 03/28/2009] [Accepted: 03/31/2009] [Indexed: 11/25/2022]
Abstract
The mutagenic and cytotoxic effects of many alkylating agents are reduced by O(6)-alkylguanine-DNA alkyltransferase (AGT). In humans, this protein not only protects the integrity of the genome, but also contributes to the resistance of tumors to DNA-alkylating chemotherapeutic agents. Here we describe and test models for cooperative multiprotein complexes of AGT with single-stranded and duplex DNAs that are based on in vitro binding data and the crystal structure of a 1:1 AGT-DNA complex. These models predict that cooperative assemblies contain a three-start helical array of proteins with dominant protein-protein interactions between the amino-terminal face of protein n and the carboxy-terminal face of protein n+3, and they predict that binding duplex DNA does not require large changes in B-form DNA geometry. Experimental tests using protein cross-linking analyzed by mass spectrometry, electrophoretic and analytical ultracentrifugation binding assays, and topological analyses with closed circular DNA show that the properties of multiprotein AGT-DNA complexes are consistent with these predictions.
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Affiliation(s)
- Claire A Adams
- Department of Molecular and Cellular Biochemistry and Center for Structural Biology, University of Kentucky, Lexington, KY 40536, USA
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40
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Melikishvili M, Rasimas JJ, Pegg AE, Fried MG. Interactions of human O(6)-alkylguanine-DNA alkyltransferase (AGT) with short double-stranded DNAs. Biochemistry 2009; 47:13754-63. [PMID: 19061338 DOI: 10.1021/bi801666c] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
O(6)-alkylguanine-DNA alkyltransferase (AGT) is a ubiquitous enzyme with an amino acid sequence that is conserved in Eubacteria, Archaea, and Eukarya. It repairs O(6)-alkylguanine and O(4)-alkylthymine adducts in single-stranded and duplex DNAs. In performing these functions, AGT must partition between adduct-containing sites and the large excess of adduct-free DNA distributed throughout the genome. Here, we characterize the binding of human AGT to linear double-stranded, adduct-free DNAs ranging in length from 11 bp to 2686 bp. Moderately cooperative binding (22.6 +/- 3.7 < or = omega < or = 145.0 +/- 37.0) results in an all-or-nothing association pattern on short templates. The apparent binding site size S(app) (mean = 4.39 +/- 0.02 bp) oscillates with increasing template length. Oscillations in cooperativity factor omega have the same frequency but are of opposite phase to S(app), with the result that the most stable protein-protein and protein-DNA interactions occur at the highest packing densities. The oscillation period (4.05 +/- 0.02 bp/protein) is nearly identical to the occluded binding site size obtained at the highest measured binding density (4 bp/protein) and is significantly smaller than the contour length ( approximately 8 bp) occupied in crystalline complexes. A model in which protein molecules overlap along the DNA contour is proposed to account for these features. High AGT densities resulting from cooperative binding may allow efficient search for lesions in the context of chromatin remodeling and DNA replication.
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Affiliation(s)
- Manana Melikishvili
- Department of Molecular and Cellular Biochemistry and Center for Structural Biology, University of Kentucky, Lexington, Kentucky 40536, USA
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41
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Levin MK, Hingorani MM, Holmes RM, Patel SS, Carson JH. Model-based global analysis of heterogeneous experimental data using gfit. Methods Mol Biol 2009; 500:335-359. [PMID: 19399438 PMCID: PMC2850822 DOI: 10.1007/978-1-59745-525-1_12] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Regression analysis is indispensible for quantitative understanding of biological systems and for developing accurate computational models. By applying regression analysis, one can validate models and quantify components of the system, including ones that cannot be observed directly. Global (simultaneous) analysis of all experimental data available for the system produces the most informative results. To quantify components of a complex system, the dataset needs to contain experiments of different types performed under a broad range of conditions. However, heterogeneity of such datasets complicates implementation of the global analysis. Computational models continuously evolve to include new knowledge and to account for novel experimental data, creating the demand for flexible and efficient analysis procedures. To address these problems, we have developed gfit software to globally analyze many types of experiments, to validate computational models, and to extract maximum information from the available experimental data.
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Affiliation(s)
- Mikhail K Levin
- Richard Berlin Center for Cell Analysis and Modeling, University of Connecticut Health Center, Farmington, 06030, USA
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42
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Lu P, Rha GB, Melikishvili M, Wu G, Adkins BC, Fried MG, Chi YI. Structural basis of natural promoter recognition by a unique nuclear receptor, HNF4alpha. Diabetes gene product. J Biol Chem 2008; 283:33685-97. [PMID: 18829458 DOI: 10.1074/jbc.m806213200] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
HNF4alpha (hepatocyte nuclear factor 4alpha) plays an essential role in the development and function of vertebrate organs, including hepatocytes and pancreatic beta-cells by regulating expression of multiple genes involved in organ development, nutrient transport, and diverse metabolic pathways. As such, HNF4alpha is a culprit gene product for a monogenic and dominantly inherited form of diabetes, known as maturity onset diabetes of the young (MODY). As a unique member of the nuclear receptor superfamily, HNF4alpha recognizes target genes containing two hexanucleotide direct repeat DNA-response elements separated by one base pair (DR1) by exclusively forming a cooperative homodimer. We describe here the 2.0 angstroms crystal structure of human HNF4alpha DNA binding domain in complex with a high affinity promoter element of another MODY gene, HNF1alpha, which reveals the molecular basis of unique target gene selection/recognition, DNA binding cooperativity, and dysfunction caused by diabetes-causing mutations. The predicted effects of MODY mutations have been tested by a set of biochemical and functional studies, which show that, in contrast to other MODY gene products, the subtle disruption of HNF4alpha molecular function can cause significant effects in afflicted MODY patients.
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Affiliation(s)
- Peng Lu
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, Kentucky 40536, USA
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43
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Wang M, Law M, Duhamel J, Chen P. Interaction of a self-assembling peptide with oligonucleotides: complexation and aggregation. Biophys J 2007; 93:2477-90. [PMID: 17545233 PMCID: PMC1965454 DOI: 10.1529/biophysj.106.102624] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2006] [Accepted: 05/17/2007] [Indexed: 11/18/2022] Open
Abstract
Molecular interaction of a self-assembling peptide, EAK16-II, to single- and double-stranded oligodeoxynucleotides (ODNs) was investigated under various solution conditions. The molecular events leading to EAK-ODN complexation and further aggregation were elucidated using a series of spectroscopic and microscopic methods. Despite the ability to self-assemble, EAK molecules bind to ODN molecules first upon mixing, resulting in EAK-ODN complexes. The complexes further associate to form EAK-ODN aggregates. A method based on UV-Vis absorption and centrifugation was developed to quantify the fraction of ODNs in the aggregates. The results were used to construct binding isotherms via a binding density function analysis. To compare the effects of different pH values and nucleotide types, the modified noncooperative McGhee and von Hippel model was used to extract binding parameters from the binding isotherms. The binding constant of EAK to ODNs was higher at pH 4 than at pH 7, and no binding was observed at pH 11, indicating that the interaction involved is primarily electrostatic in nature. EAK bound more strongly to single-stranded ODNs. The EAK-ODN aggregates were further visualized using atomic force microscopy; their size distribution as a function of EAK concentration was monitored by dynamic light scattering. The timescale for the EAK-ODN aggregation was on the order of minutes by fluorescence anisotropy and steady-state light scattering experiments. Fluorescence quenching experiments demonstrated that the ODNs in the aggregates were less accessible to the solvent, demonstrating a potential of oligonucleotide encapsulation by the self-assembling peptide.
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Affiliation(s)
- Mei Wang
- Department of Chemical Engineering, University of Waterloo, Waterloo, Ontario, Canada
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44
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Bernacchi S, Henriet S, Dumas P, Paillart JC, Marquet R. RNA and DNA binding properties of HIV-1 Vif protein: a fluorescence study. J Biol Chem 2007; 282:26361-8. [PMID: 17609216 DOI: 10.1074/jbc.m703122200] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The HIV-1 viral infectivity factor (Vif) is a small basic protein essential for viral fitness and pathogenicity. Some "non-permissive" cell lines cannot sustain replication of Vif(-) HIV-1 virions. In these cells, Vif counteracts the natural antiretroviral activity of the DNA-editing enzymes APOBEC3G/3F. Moreover, Vif is packaged into viral particles through a strong interaction with genomic RNA in viral nucleoprotein complexes. To gain insights into determinants of this binding process, we performed the first characterization of Vif/nucleic acid interactions using Vif intrinsic fluorescence. We determined the affinity of Vif for RNA fragments corresponding to various regions of the HIV-1 genome. Our results demonstrated preferential and moderately cooperative binding for RNAs corresponding to the 5'-untranslated region of HIV-1 (5'-untranslated region) and gag (cooperativity parameter omega approximately 65-80, and K(d) = 45-55 nM). In addition, fluorescence spectroscopy allowed us to point out the TAR apical loop and a short region in gag as primary strong affinity binding sites (K(d) = 9.5-14 nM). Interestingly, beside its RNA binding properties, the Vif protein can also bind the corresponding DNA oligonucleotides and their complementary counterparts with an affinity similar to the one observed for the RNA sequences, while other DNA sequences displayed reduced affinity. Taken together, our results suggest that Vif binding to RNA and DNA offers several non-exclusive ways to counteract APOBEC3G/3F factors, in addition to the well documented Vif-induced degradation by the proteasome and to the Vif-mediated repression of translation of these antiviral factors.
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MESH Headings
- 5' Untranslated Regions/genetics
- 5' Untranslated Regions/immunology
- 5' Untranslated Regions/metabolism
- APOBEC-3G Deaminase
- Binding Sites/physiology
- Cytidine Deaminase
- Cytosine Deaminase/immunology
- Cytosine Deaminase/metabolism
- DNA, Viral/genetics
- DNA, Viral/immunology
- DNA, Viral/metabolism
- DNA-Binding Proteins/genetics
- DNA-Binding Proteins/immunology
- DNA-Binding Proteins/metabolism
- Gene Products, gag/genetics
- Gene Products, gag/immunology
- Gene Products, gag/metabolism
- Gene Products, vif/genetics
- Gene Products, vif/immunology
- Gene Products, vif/metabolism
- Genome, Viral/physiology
- HIV Long Terminal Repeat/physiology
- HIV-1/genetics
- HIV-1/immunology
- HIV-1/metabolism
- HIV-1/pathogenicity
- Humans
- Immunity, Innate/physiology
- Nucleoside Deaminases/immunology
- Nucleoside Deaminases/metabolism
- Oligonucleotides/genetics
- Oligonucleotides/immunology
- Oligonucleotides/metabolism
- Protein Binding/physiology
- Protein Biosynthesis/physiology
- RNA, Viral/genetics
- RNA, Viral/immunology
- RNA, Viral/metabolism
- RNA-Binding Proteins/genetics
- RNA-Binding Proteins/immunology
- RNA-Binding Proteins/metabolism
- Repressor Proteins/genetics
- Repressor Proteins/immunology
- Repressor Proteins/metabolism
- vif Gene Products, Human Immunodeficiency Virus
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Affiliation(s)
- Serena Bernacchi
- Architecture et Réactivité de l'ARN, Université Louis Pasteur de Strasbourg, CNRS, IBMC, 15 Rue René Descartes, 67084 Strasbourg, France
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45
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Senear DF, Tretyachenko-Ladokhina V, Opel ML, Aeling KA, Wesley Hatfield G, Franklin LM, Darlington RC, Alexander Ross J. Pressure dissociation of integration host factor-DNA complexes reveals flexibility-dependent structural variation at the protein-DNA interface. Nucleic Acids Res 2007; 35:1761-72. [PMID: 17324943 PMCID: PMC1874591 DOI: 10.1093/nar/gkl1122] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
E. coli Integration host factor (IHF) condenses the bacterial nucleoid by wrapping DNA. Previously, we showed that DNA flexibility compensates for structural characteristics of the four consensus recognition elements associated with specific binding (Aeling et al., J. Biol. Chem. 281, 39236-39248, 2006). If elements are missing, high-affinity binding occurs only if DNA deformation energy is low. In contrast, if all elements are present, net binding energy is unaffected by deformation energy. We tested two hypotheses for this observation: in complexes containing all elements, (1) stiff DNA sequences are less bent upon binding IHF than flexible ones; or (2) DNA sequences with differing flexibility have interactions with IHF that compensate for unfavorable deformation energy. Time-resolved Förster resonance energy transfer (FRET) shows that global topologies are indistinguishable for three complexes with oligonucleotides of different flexibility. However, pressure perturbation shows that the volume change upon binding is smaller with increasing flexibility. We interpret these results in the context of Record and coworker's model for IHF binding (J. Mol. Biol. 310, 379-401, 2001). We propose that the volume changes reflect differences in hydration that arise from structural variation at IHF-DNA interfaces while the resulting energetic compensation maintains the same net binding energy.
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Affiliation(s)
- Donald F. Senear
- Department of Molecular Biology and Biochemistry, Department of Microbiology and Molecular Genetics, College of Medicine, Institute of Genomics and Bioinformatics, University of California, Irvine CA 92697 and Department of Chemistry, The University of Montana, Missoula, MT 59812, USA
- *To whom correspondence should be addressed: (949) 824-8014(949) 824-8551
| | - Vira Tretyachenko-Ladokhina
- Department of Molecular Biology and Biochemistry, Department of Microbiology and Molecular Genetics, College of Medicine, Institute of Genomics and Bioinformatics, University of California, Irvine CA 92697 and Department of Chemistry, The University of Montana, Missoula, MT 59812, USA
| | - Michael L. Opel
- Department of Molecular Biology and Biochemistry, Department of Microbiology and Molecular Genetics, College of Medicine, Institute of Genomics and Bioinformatics, University of California, Irvine CA 92697 and Department of Chemistry, The University of Montana, Missoula, MT 59812, USA
| | - Kimberly A. Aeling
- Department of Molecular Biology and Biochemistry, Department of Microbiology and Molecular Genetics, College of Medicine, Institute of Genomics and Bioinformatics, University of California, Irvine CA 92697 and Department of Chemistry, The University of Montana, Missoula, MT 59812, USA
| | - G. Wesley Hatfield
- Department of Molecular Biology and Biochemistry, Department of Microbiology and Molecular Genetics, College of Medicine, Institute of Genomics and Bioinformatics, University of California, Irvine CA 92697 and Department of Chemistry, The University of Montana, Missoula, MT 59812, USA
| | - Laurie M. Franklin
- Department of Molecular Biology and Biochemistry, Department of Microbiology and Molecular Genetics, College of Medicine, Institute of Genomics and Bioinformatics, University of California, Irvine CA 92697 and Department of Chemistry, The University of Montana, Missoula, MT 59812, USA
| | - Reuben C. Darlington
- Department of Molecular Biology and Biochemistry, Department of Microbiology and Molecular Genetics, College of Medicine, Institute of Genomics and Bioinformatics, University of California, Irvine CA 92697 and Department of Chemistry, The University of Montana, Missoula, MT 59812, USA
| | - J.B. Alexander Ross
- Department of Molecular Biology and Biochemistry, Department of Microbiology and Molecular Genetics, College of Medicine, Institute of Genomics and Bioinformatics, University of California, Irvine CA 92697 and Department of Chemistry, The University of Montana, Missoula, MT 59812, USA
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46
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Rasimas JJ, Kar SR, Pegg AE, Fried MG. Interactions of human O6-alkylguanine-DNA alkyltransferase (AGT) with short single-stranded DNAs. J Biol Chem 2007; 282:3357-66. [PMID: 17138560 PMCID: PMC1941669 DOI: 10.1074/jbc.m608876200] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The O6-alkylguanine-DNA alkyltransferase (AGT) repairs O6-alkylguanine and O4-alkylthymine adducts in single-stranded and duplex DNAs. Here we characterize the binding of AGT to single-stranded DNAs ranging in length from 5 to 78 nucleotides (nt). Binding is moderately cooperative (37.9 +/- 3.0
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Affiliation(s)
- Joseph J. Rasimas
- Department of Molecular Physiology, Penn State University
College of Medicine, Hershey, PA 17033 and
| | - Sambit R. Kar
- Department of Molecular Physiology, Penn State University
College of Medicine, Hershey, PA 17033 and
- Department of Molecular and Cellular Biochemistry and Center
for Structural Biology, University of Kentucky, Lexington, KY 40536
| | - Anthony E. Pegg
- Department of Molecular Physiology, Penn State University
College of Medicine, Hershey, PA 17033 and
| | - Michael G. Fried
- Department of Molecular and Cellular Biochemistry and Center
for Structural Biology, University of Kentucky, Lexington, KY 40536
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47
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Aeling KA, Opel ML, Steffen NR, Tretyachenko-Ladokhina V, Hatfield GW, Lathrop RH, Senear DF. Indirect recognition in sequence-specific DNA binding by Escherichia coli integration host factor: the role of DNA deformation energy. J Biol Chem 2006; 281:39236-48. [PMID: 17035240 DOI: 10.1074/jbc.m606363200] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Integration host factor (IHF) is a bacterial histone-like protein whose primary biological role is to condense the bacterial nucleoid and to constrain DNA supercoils. It does so by binding in a sequence-independent manner throughout the genome. However, unlike other structurally related bacterial histone-like proteins, IHF has evolved a sequence-dependent, high affinity DNA-binding motif. The high affinity binding sites are important for the regulation of a wide range of cellular processes. A remarkable feature of IHF is that it employs an indirect readout mechanism to bind and wrap DNA at both the nonspecific and high affinity (sequence-dependent) DNA sites. In this study we assessed the contributions of pre-formed and protein-induced DNA conformations to the energetics of IHF binding. Binding energies determined experimentally were compared with energies predicted for the IHF-induced deformation of the DNA helix (DNA deformation energy) in the IHF-DNA complex. Combinatorial sets of de novo DNA sequences were designed to systematically evaluate the influence of sequence-dependent structural characteristics of the conserved IHF recognition elements of the consensus DNA sequence. We show that IHF recognizes pre-formed conformational characteristics of the consensus DNA sequence at high affinity sites, whereas at all other sites relative affinity is determined by the deformational energy required for nearest-neighbor base pairs to adopt the DNA structure of the bound DNA-IHF complex.
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Affiliation(s)
- Kimberly A Aeling
- Institute for Genomics and Bioinformatics, Department of Microbiology and Molecular Genetics, School of Medicine, University of California 92697, USA
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48
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Flyvbjerg H, Keatch SA, Dryden DT. Strong physical constraints on sequence-specific target location by proteins on DNA molecules. Nucleic Acids Res 2006; 34:2550-7. [PMID: 16698961 PMCID: PMC3303175 DOI: 10.1093/nar/gkl271] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Sequence-specific binding to DNA in the presence of competing non-sequence-specific ligands is a problem faced by proteins in all organisms. It is akin to the problem of parking a truck at a loading bay by the side of a road in the presence of cars parked at random along the road. Cars even partially covering the loading bay prevent correct parking of the truck. Similarly on DNA, non-specific ligands interfere with the binding and function of sequence-specific proteins. We derive a formula for the probability that the loading bay is free from parked cars. The probability depends on the size of the loading bay and allows an estimation of the size of the footprint on the DNA of the sequence-specific protein by assaying protein binding or function in the presence of increasing concentrations of non-specific ligand. Assaying for function gives an 'activity footprint'; the minimum length of DNA required for function rather than the more commonly measured physical footprint. Assaying the complex type I restriction enzyme, EcoKI, gives an activity footprint of approximately 66 bp for ATP hydrolysis and 300 bp for the DNA cleavage function which is intimately linked with translocation of DNA by EcoKI. Furthermore, considering the coverage of chromosomal DNA by proteins in vivo, our theory shows that the search for a specific DNA sequence is very difficult; most sites are obscured by parked cars. This effectively rules out any significant role in target location for mechanisms invoking one-dimensional, linear diffusion along DNA.
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Affiliation(s)
- Henrik Flyvbjerg
- Risø National Laboratory, Biosystems Department and Danish Polymer Centre Building BIO-776, PO Box 49, Frederiksborgvej 399, DK-4000 Roskilde, Denmark
- Isaac Newton Institute for Mathematical Sciences 20 Clarkson Road, Cambridge, CB3 0EH, UK
| | - Steven A. Keatch
- School of Chemistry, The King's Buildings, The University of Edinburgh Edinburgh, EH9 3JJ, UK
| | - David T.F. Dryden
- School of Chemistry, The King's Buildings, The University of Edinburgh Edinburgh, EH9 3JJ, UK
- Isaac Newton Institute for Mathematical Sciences 20 Clarkson Road, Cambridge, CB3 0EH, UK
- To whom correspondence should be adressed. Tel: +0131 650 4735; Fax: +0131 650 6453;
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49
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Bashford JD. Salerno's model of DNA re-analysed: could breather solitons have biological significance? J Biol Phys 2006; 32:27-47. [PMID: 19669433 DOI: 10.1007/s10867-006-2719-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
We investigate the sequence-dependent behaviour of localised excitations in a toy, nonlinear model of DNA base-pair opening originally proposed by Salerno. Specifically we ask whether "breather" solitons could play a role in the facilitated location of promoters by RNA polymerase (RNAP). In an effective potential formalism, we find excellent correlation between potential minima and Escherichia coli promoter recognition sites in the T7 bacteriophage genome. Evidence for a similar relationship between phage promoters and downstream coding regions is found and alternative reasons for links between AT richness and transcriptionally-significant sites are discussed. Consideration of the soliton energy of translocation provides a novel dynamical picture of sliding: steep potential gradients correspond to deterministic motion, while "flat" regions, corresponding to homogeneous AT or GC content, are governed by random, thermal motion. Finally we demonstrate an interesting equivalence between planar, breather solitons and the helical motion of a sliding protein "particle" about a bent DNA axis.
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Affiliation(s)
- J D Bashford
- School of Mathematics and Physics, University of Tasmania, Hobart 7001, Tasmania, Australia.
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50
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Velázquez-Campoy A. Ligand binding to one-dimensional lattice-like macromolecules: analysis of the McGhee-von Hippel theory implemented in isothermal titration calorimetry. Anal Biochem 2005; 348:94-104. [PMID: 16289442 DOI: 10.1016/j.ab.2005.10.013] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2005] [Revised: 10/05/2005] [Accepted: 10/06/2005] [Indexed: 10/25/2022]
Abstract
The theory developed by McGhee and von Hippel for ligand binding to a one-dimensional lattice-like macromolecule provides a closed analytical form in the Scatchard representation. The application of such theory has been complicated by two facts: (1) it has been practically reduced to binding techniques, such as equilibrium dialysis, in which the partition between bound and free concentrations of all reactant species are directly accessible and experimentally determined, but infrequently applied to other binding techniques, such as calorimetry or spectroscopy, in which the direct observable is a magnitude proportional to the advance of the binding reaction monitored along the titration experiment, and (2) Scatchard analysis, developed as a quantitative graphical method, is currently outdated and used only qualitatively because of its weaknesses, limitations, and deficiencies. However, a general exact method for applying such theory to titration techniques in a correct and precise manner, without any limitation, can be delineated. In this article, the theory of cooperative ligand binding to linear lattice-like macromolecules has been implemented in isothermal titration calorimetry for the first time. This technique provides a complete thermodynamic characterization of ligand binding, but it has been barely used properly for this type of system. The description, the analysis of the formalism, and practical guidelines are presented, with considerations for experimental design and data analysis.
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Affiliation(s)
- Adrián Velázquez-Campoy
- Institute of Biocomputation and Complex Systems Physics (BIFI), Universidad de Zaragoza, Corona de Aragón 42, E-50009 Zaragoza, Spain.
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