1
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Patel R, Onyema A, Tang PK, Loverde SM. Conformational Dynamics of the Nucleosomal Histone H2B Tails Revealed by Molecular Dynamics Simulations. J Chem Inf Model 2024; 64:4709-4726. [PMID: 38865599 PMCID: PMC11200259 DOI: 10.1021/acs.jcim.4c00059] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2024] [Revised: 05/31/2024] [Accepted: 06/03/2024] [Indexed: 06/14/2024]
Abstract
Epigenetic modifications of histone N-terminal tails play a critical role in regulating the chromatin structure and biological processes such as transcription and DNA repair. One of the key post-translational modifications (PTMs) is the acetylation of lysine residues on histone tails. Epigenetic modifications are ubiquitous in the development of diseases, such as cancer and neurological disorders. Histone H2B tails are critical regulators of nucleosome dynamics, biological processes, and certain diseases. Here, we report all-atomistic molecular dynamics (MD) simulations of the nucleosome to demonstrate that acetylation of the histone tails changes their conformational space and interaction with DNA. We perform simulations of H2B tails, critical regulators of gene regulation, in both the lysine-acetylated (ACK) and unacetylated wild type (WT) states. To explore the effects of salt concentration, we use two different NaCl concentrations to perform simulations at microsecond time scales. Salt can modulate the effects of electrostatic interactions between the DNA phosphate backbone and histone tails. Upon acetylation, H2B tails shift their secondary structure helical propensity. The number of contacts between the DNA and the H2B tail decreases. We characterize the conformational dynamics of the H2B tails by principal component analysis (PCA). The ACK tails become more compact at increased salt concentrations, but conformations from the WT tails display the most contacts with DNA at both salt concentrations. Mainly, H2B acetylation may increase the DNA accessibility for regulatory proteins to bind, which can aid in gene regulation and NCP stability.
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Affiliation(s)
- Rutika Patel
- Ph.D.
Program in Biochemistry, The Graduate Center
of the City University of New York, New York, New York 10016, United States
- Department
of Chemistry, College of Staten Island, The City University of New York, 2800 Victory Boulevard, Staten Island, New
York, New York 10314, United States
| | - Augustine Onyema
- Ph.D.
Program in Biochemistry, The Graduate Center
of the City University of New York, New York, New York 10016, United States
- Department
of Chemistry, College of Staten Island, The City University of New York, 2800 Victory Boulevard, Staten Island, New
York, New York 10314, United States
| | - Phu K. Tang
- Ph.D.
Program in Biochemistry, The Graduate Center
of the City University of New York, New York, New York 10016, United States
- Department
of Chemistry, College of Staten Island, The City University of New York, 2800 Victory Boulevard, Staten Island, New
York, New York 10314, United States
| | - Sharon M. Loverde
- Ph.D.
Program in Biochemistry, The Graduate Center
of the City University of New York, New York, New York 10016, United States
- Department
of Chemistry, College of Staten Island, The City University of New York, 2800 Victory Boulevard, Staten Island, New
York, New York 10314, United States
- Ph.D.
Program in Chemistry, The Graduate Center
of the City University of New York, New York, New York 10016, United States
- Ph.D.
Program in Physics, The Graduate Center
of the City University of New York, New York, New York 10016, United States
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2
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Lebedenko OO, Salikov VA, Izmailov SA, Podkorytov IS, Skrynnikov NR. Using NMR diffusion data to validate MD models of disordered proteins: Test case of N-terminal tail of histone H4. Biophys J 2024; 123:80-100. [PMID: 37990496 PMCID: PMC10808029 DOI: 10.1016/j.bpj.2023.11.020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2023] [Revised: 10/28/2023] [Accepted: 11/17/2023] [Indexed: 11/23/2023] Open
Abstract
MD simulations can provide uniquely detailed models of intrinsically disordered proteins (IDPs). However, these models need careful experimental validation. The coefficient of translational diffusion Dtr, measurable by pulsed field gradient NMR, offers a potentially useful piece of experimental information related to the compactness of the IDP's conformational ensemble. Here, we investigate, both experimentally and via the MD modeling, the translational diffusion of a 25-residue N-terminal fragment from histone H4 (N-H4). We found that the predicted values of Dtr, as obtained from mean-square displacement of the peptide in the MD simulations, are largely determined by the viscosity of the MD water (which has been reinvestigated as a part of our study). Beyond that, our analysis of the diffusion data indicates that MD simulations of N-H4 in the TIP4P-Ew water give rise to an overly compact conformational ensemble for this peptide. In contrast, TIP4P-D and OPC simulations produce the ensembles that are consistent with the experimental Dtr result. These observations are supported by the analyses of the 15N spin relaxation rates. We also tested a number of empirical methods to predict Dtr based on IDP's coordinates extracted from the MD snapshots. In particular, we show that the popular approach involving the program HYDROPRO can produce misleading results. This happens because HYDROPRO is not intended to predict the diffusion properties of highly flexible biopolymers such as IDPs. Likewise, recent empirical schemes that exploit the relationship between the small-angle x-ray scattering-informed conformational ensembles of IDPs and the respective experimental Dtr values also prove to be problematic. In this sense, the first-principle calculations of Dtr from the MD simulations, such as demonstrated in this work, should provide a useful benchmark for future efforts in this area.
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Affiliation(s)
- Olga O Lebedenko
- Laboratory of Biomolecular NMR, St. Petersburg State University, St. Petersburg, Russia
| | - Vladislav A Salikov
- Laboratory of Biomolecular NMR, St. Petersburg State University, St. Petersburg, Russia
| | - Sergei A Izmailov
- Laboratory of Biomolecular NMR, St. Petersburg State University, St. Petersburg, Russia
| | - Ivan S Podkorytov
- Laboratory of Biomolecular NMR, St. Petersburg State University, St. Petersburg, Russia
| | - Nikolai R Skrynnikov
- Laboratory of Biomolecular NMR, St. Petersburg State University, St. Petersburg, Russia; Department of Chemistry, Purdue University, West Lafayette, Indiana.
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3
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Zhao H, Wu H, Guseman A, Abeykoon D, Camara CM, Dalal Y, Fushman D, Papoian GA. The role of cryptic ancestral symmetry in histone folding mechanisms across Eukarya and Archaea. PLoS Comput Biol 2024; 20:e1011721. [PMID: 38181064 PMCID: PMC10796010 DOI: 10.1371/journal.pcbi.1011721] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2023] [Revised: 01/18/2024] [Accepted: 11/28/2023] [Indexed: 01/07/2024] Open
Abstract
Histones compact and store DNA in both Eukarya and Archaea, forming heterodimers in Eukarya and homodimers in Archaea. Despite this, the folding mechanism of histones across species remains unclear. Our study addresses this gap by investigating 11 types of histone and histone-like proteins across humans, Drosophila, and Archaea through multiscale molecular dynamics (MD) simulations, complemented by NMR and circular dichroism experiments. We confirm and elaborate on the widely applied "folding upon binding" mechanism of histone dimeric proteins and report a new alternative conformation, namely, the inverted non-native dimer, which may be a thermodynamically metastable configuration. Protein sequence analysis indicated that the inverted conformation arises from the hidden ancestral head-tail sequence symmetry underlying all histone proteins, which is congruent with the previously proposed histone evolution hypotheses. Finally, to explore the potential formations of homodimers in Eukarya, we utilized MD-based AWSEM and AI-based AlphaFold-Multimer models to predict their structures and conducted extensive all-atom MD simulations to examine their respective structural stabilities. Our results suggest that eukaryotic histones may also form stable homodimers, whereas their disordered tails bring significant structural asymmetry and tip the balance towards the formation of commonly observed heterotypic dimers.
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Affiliation(s)
- Haiqing Zhao
- Biophysics Program, Institute for Physical Science and Technology, University of Maryland, College Park, Maryland, United States of America
- Laboratory of Receptor Biology and Gene Expression, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Hao Wu
- Biophysics Program, Institute for Physical Science and Technology, University of Maryland, College Park, Maryland, United States of America
| | - Alex Guseman
- Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland, United States of America
| | - Dulith Abeykoon
- Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland, United States of America
| | - Christina M. Camara
- Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland, United States of America
| | - Yamini Dalal
- Laboratory of Receptor Biology and Gene Expression, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - David Fushman
- Biophysics Program, Institute for Physical Science and Technology, University of Maryland, College Park, Maryland, United States of America
- Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland, United States of America
| | - Garegin A. Papoian
- Biophysics Program, Institute for Physical Science and Technology, University of Maryland, College Park, Maryland, United States of America
- Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland, United States of America
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4
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Sinha S, Pindi C, Ahsan M, Arantes PR, Palermo G. Machines on Genes through the Computational Microscope. J Chem Theory Comput 2023; 19:1945-1964. [PMID: 36947696 PMCID: PMC10104023 DOI: 10.1021/acs.jctc.2c01313] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/24/2023]
Abstract
Macromolecular machines acting on genes are at the core of life's fundamental processes, including DNA replication and repair, gene transcription and regulation, chromatin packaging, RNA splicing, and genome editing. Here, we report the increasing role of computational biophysics in characterizing the mechanisms of "machines on genes", focusing on innovative applications of computational methods and their integration with structural and biophysical experiments. We showcase how state-of-the-art computational methods, including classical and ab initio molecular dynamics to enhanced sampling techniques, and coarse-grained approaches are used for understanding and exploring gene machines for real-world applications. As this review unfolds, advanced computational methods describe the biophysical function that is unseen through experimental techniques, accomplishing the power of the "computational microscope", an expression coined by Klaus Schulten to highlight the extraordinary capability of computer simulations. Pushing the frontiers of computational biophysics toward a pragmatic representation of large multimegadalton biomolecular complexes is instrumental in bridging the gap between experimentally obtained macroscopic observables and the molecular principles playing at the microscopic level. This understanding will help harness molecular machines for medical, pharmaceutical, and biotechnological purposes.
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5
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Laghmach R, Malhotra I, Potoyan DA. Multiscale Modeling of Protein-RNA Condensation in and Out of Equilibrium. Methods Mol Biol 2023; 2563:117-133. [PMID: 36227470 PMCID: PMC11186142 DOI: 10.1007/978-1-0716-2663-4_5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
A vast number of intracellular membraneless bodies also known as biomolecular condensates form through a liquid-liquid phase separation (LLPS) of biomolecules. To date, phase separation has been identified as the main driving force for a membraneless organelles such as nucleoli, Cajal bodies, stress granules, and chromatin compartments. Recently, the protein-RNA condensation is receiving increased attention, because it is closely related to the biological function of cells such as transcription, translation, and RNA metabolism. Despite the multidisciplinary efforts put forth to study the biophysical properties of protein-RNA condensates, there are many fundamental unanswered questions regarding the mechanism of formation and regulation of protein-RNA condensates in eukaryotic cells. Major challenges in studying protein-RNA condensation stem from (i) the molecular heterogeneity and conformational flexibility of RNA and protein chains and (ii) the nonequilibrium nature of transcription and cellular environment. Computer simulations, bioinformatics, and mathematical models are uniquely positioned for shedding light on the microscopic nature of protein-RNA phase separation. To this end, there is an urgent need for innovative models with the right spatiotemporal resolution for confronting the experimental observables in a comprehensive and physics-based manner. In this chapter, we will summarize the currently emerging research efforts, which employ atomistic and coarse-grained molecular models and field theoretical models to understand equilibrium and nonequilibrium aspects of protein-RNA condensation.
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Affiliation(s)
- Rabia Laghmach
- Department of Chemistry, Iowa State University, Ames, IA, USA
| | - Isha Malhotra
- Department of Chemistry, Iowa State University, Ames, IA, USA
| | - Davit A Potoyan
- Department of Chemistry, Iowa State University, Ames, IA, USA.
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6
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Phosphorylation of Thr9 Affects the Folding Landscape of the N-Terminal Segment of Human AGT Enhancing Protein Aggregation of Disease-Causing Mutants. MOLECULES (BASEL, SWITZERLAND) 2022; 27:molecules27248762. [PMID: 36557898 PMCID: PMC9786777 DOI: 10.3390/molecules27248762] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/14/2022] [Revised: 12/07/2022] [Accepted: 12/08/2022] [Indexed: 12/14/2022]
Abstract
The mutations G170R and I244T are the most common disease cause in primary hyperoxaluria type I (PH1). These mutations cause the misfolding of the AGT protein in the minor allele AGT-LM that contains the P11L polymorphism, which may affect the folding of the N-terminal segment (NTT-AGT). The NTT-AGT is phosphorylated at T9, although the role of this event in PH1 is unknown. In this work, phosphorylation of T9 was mimicked by introducing the T9E mutation in the NTT-AGT peptide and the full-length protein. The NTT-AGT conformational landscape was studied by circular dichroism, NMR, and statistical mechanical methods. Functional and stability effects on the full-length AGT protein were characterized by spectroscopic methods. The T9E and P11L mutations together reshaped the conformational landscape of the isolated NTT-AGT peptide by stabilizing ordered conformations. In the context of the full-length AGT protein, the T9E mutation had no effect on the overall AGT function or conformation, but enhanced aggregation of the minor allele (LM) protein and synergized with the mutations G170R and I244T. Our findings indicate that phosphorylation of T9 may affect the conformation of the NTT-AGT and synergize with PH1-causing mutations to promote aggregation in a genotype-specific manner. Phosphorylation should be considered a novel regulatory mechanism in PH1 pathogenesis.
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7
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Weigle AT, Feng J, Shukla D. Thirty years of molecular dynamics simulations on posttranslational modifications of proteins. Phys Chem Chem Phys 2022; 24:26371-26397. [PMID: 36285789 PMCID: PMC9704509 DOI: 10.1039/d2cp02883b] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/06/2023]
Abstract
Posttranslational modifications (PTMs) are an integral component to how cells respond to perturbation. While experimental advances have enabled improved PTM identification capabilities, the same throughput for characterizing how structural changes caused by PTMs equate to altered physiological function has not been maintained. In this Perspective, we cover the history of computational modeling and molecular dynamics simulations which have characterized the structural implications of PTMs. We distinguish results from different molecular dynamics studies based upon the timescales simulated and analysis approaches used for PTM characterization. Lastly, we offer insights into how opportunities for modern research efforts on in silico PTM characterization may proceed given current state-of-the-art computing capabilities and methodological advancements.
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Affiliation(s)
- Austin T Weigle
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
| | - Jiangyan Feng
- Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
| | - Diwakar Shukla
- Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
- Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
- Department of Bioengineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
- Department of Plant Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
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8
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Generation of dynamic three-dimensional genome structure through phase separation of chromatin. Proc Natl Acad Sci U S A 2022; 119:e2109838119. [PMID: 35617433 PMCID: PMC9295772 DOI: 10.1073/pnas.2109838119] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Significance DNA functions in living cells are crucially affected by the three-dimensional genome structure and dynamics. We analyze the whole genome of human cells by developing a polymer model of interphase nuclei. The model reveals the essential importance of the unfolding process of chromosomes from the condensed mitotic state for describing the interphase nuclei; through the unfolding process, heterogeneous repulsive interactions among chromatin chains induce phase separation of chromatin, which quantitatively explains the experimentally observed various genomic data. We can use this model structure as a platform to analyze the relationship among genome structure, dynamics, and functions.
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9
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Prieto VA, Namitz KEW, Showalter SA. Transient Electrostatic Interactions between Fcp1 and Rap74 Bias the Conformational Ensemble of the Complex with Minimal Impact on Binding Affinity. J Phys Chem B 2021; 125:10917-10927. [PMID: 34550709 DOI: 10.1021/acs.jpcb.1c05131] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Intrinsically disordered protein (IDP) sequences often contain a high proportion of charged residues in conjunction with their high degree of hydrophilicity and solvation. For high net charge IDPs, long-range electrostatic interactions are thought to play a role in modulating the strength or kinetics of protein-protein interactions. In this work, we examined intramolecular interactions mediated by charged regions of a model IDP, the C-terminal tail of the phosphatase Fcp1. Specifically, this work focuses on intermolecular interactions between acidic and basic patches in the primary structure of Fcp1 and their contributions to binding its predominantly basic partner, the winged helix domain of Rap74. We observe both intramolecular and intermolecular interactions through paramagnetic relaxation enhancement (PRE) consistent with oppositely charged regions associating with one another, both in unbound Fcp1 and in the Fcp1-Rap74 complex. Formation of this complex is strongly driven by hydrophobic interactions in the minimal binding motif. Here, we test the hypothesis that charged residues in Fcp1 that flank the binding helix also contribute to the strength of binding. Charge inversion mutations in Fcp1 generally support this hypothesis, while PRE data suggest substitution of observed transient interactions in the unbound ensemble for similarly transient interactions with Rap74 in the complex.
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Affiliation(s)
- Victor A Prieto
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Kevin E W Namitz
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Scott A Showalter
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, United States.,Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
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10
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Röder K. Is the H4 histone tail intrinsically disordered or intrinsically multifunctional? Phys Chem Chem Phys 2021; 23:5134-5142. [PMID: 33624669 DOI: 10.1039/d0cp05405d] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The structural versatility of histone tails is one of the key elements in the organisation of chromatin, which allows for the compact storage of genomic information. However, this structural diversity also complicates experimental and computational studies. Here, the potential and free energy landscape for the isolated and bound H4 histone tail are explored. The landscapes exhibit a set of distinct structural ensembles separated by high energy barriers, with little difference between isolated and bound tails. This consistency is a desirable feature that facilitates the formation of transient interactions, which are required for the liquid-like chromatin organisation. The existence of multiple, distinct structures on a multifunnel energy landscape is likely to be associated with multifunctionality, i.e. a set of evolved, distinct functions. Contrasting it with previously reported results for other disordered peptides, this type of landscape may be associated with a conformational selection based binding mechanism. Given the similarity to other systems exhibiting similar multifunnel energy landscapes, the disorder in histone tails might be better described in context of multifunctionality.
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Affiliation(s)
- Konstantin Röder
- Yusuf Hamied Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK.
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11
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Mueterthies J, Potoyan DA. Solvent Exposure and Ionic Condensation Drive Fuzzy Dimerization of Disordered Heterochromatin Protein Sequence. Biomolecules 2021; 11:915. [PMID: 34203110 PMCID: PMC8234964 DOI: 10.3390/biom11060915] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2021] [Revised: 06/14/2021] [Accepted: 06/17/2021] [Indexed: 11/29/2022] Open
Abstract
Proteins with low complexity, disordered sequences are receiving increasing attention due to their central roles in the biogenesis and regulation of membraneless organelles. In eukaryotic organisms, a substantial fraction of disordered proteins reside in the nucleus, thereby facilitating the formation of nuclear bodies, nucleolus, and chromatin compartmentalization. The heterochromatin family of proteins (HP1) is an important player in driving the formation of gene silenced mesoscopic heterochromatin B compartments and pericentric regions. Recent experiments have shown that the HP1a sequence of Drosophila melanogaster can undergo liquid-liquid phase separation under both in vitro and in vivo conditions, induced by changes of the monovalent salt concentration. While the phase separation of HP1a is thought to be the mechanism underlying chromatin compartmentalization, the molecular level mechanistic picture of salt-driven phase separation of HP1a has remained poorly understood. The disordered hinge region of HP1a is seen as the driver of salt-induced condensation because of its charge enriched sequence and post-translational modifications. Here, we set out to decipher the mechanisms of salt-induced condensation of HP1a through a systematic study of salt-dependent conformations of single chains and fuzzy dimers of disordered HP1a hinge sequences. Using multiple independent all-atom simulations with and without enhanced sampling, we carry out detailed characterization of conformational ensembles of disordered HP1a chains under different ionic conditions using various polymeric and structural measures. We show that the mobile ion release, enhancement of local transient secondary structural elements, and side-chain exposure to solvent are robust trends that accompany fuzzy dimer formation. Furthermore, we find that salt-induced changes in the ensemble of conformations of HP1a disordered hinge sequence fine-tune the inter-chain vs. self-chain interactions in ways that favor fuzzy dimer formation under low salt conditions in the agreement with condensation trends seen in experiments.
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Affiliation(s)
| | - Davit A. Potoyan
- Department of Chemistry, Iowa State University, Ames, IA 50011, USA;
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12
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Huertas J, Schöler HR, Cojocaru V. Histone tails cooperate to control the breathing of genomic nucleosomes. PLoS Comput Biol 2021; 17:e1009013. [PMID: 34081696 PMCID: PMC8174689 DOI: 10.1371/journal.pcbi.1009013] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2020] [Accepted: 04/28/2021] [Indexed: 11/19/2022] Open
Abstract
Genomic DNA is packaged in chromatin, a dynamic fiber variable in size and compaction. In chromatin, repeating nucleosome units wrap 145–147 DNA basepairs around histone proteins. Genetic and epigenetic regulation of genes relies on structural transitions in chromatin which are driven by intra- and inter-nucleosome dynamics and modulated by chemical modifications of the unstructured terminal tails of histones. Here we demonstrate how the interplay between histone H3 and H2A tails control ample nucleosome breathing motions. We monitored large openings of two genomic nucleosomes, and only moderate breathing of an engineered nucleosome in atomistic molecular simulations amounting to 24 μs. Transitions between open and closed nucleosome conformations were mediated by the displacement and changes in compaction of the two histone tails. These motions involved changes in the DNA interaction profiles of clusters of epigenetic regulatory aminoacids in the tails. Removing the histone tails resulted in a large increase of the amplitude of nucleosome breathing but did not change the sequence dependent pattern of the motions. Histone tail modulated nucleosome breathing is a key mechanism of chromatin dynamics with important implications for epigenetic regulation. In the cell, the DNA is packed in chromatin. Chromatin is a highly dynamic fiber structure made of arrays of nucleosomes with different degrees of compaction. Each nucleosome has 145–147 basepairs of DNA wrapped around a protein octamer made of four unique histone proteins. Each histone is present twice and has a structured part and one or two disordered terminal tails. The regulation of gene expression in the cell and during cellular transitions depends on dynamic changes in chromatin structure. Chromatin dynamics are modulated by intra and inter nucleosome motions and by posttranslational chemical modifications of the histone tails. Here we reveal how histone tails control the intra nucleosome dynamics at atomic resolution. From extensive sampling of nucleosome dynamics in atomistic molecular simulations, we show that genomic nucleosomes breath more extensively than engineered ones and we describe how two histone tails cooperate to control nucleosome breathing through interactions between clusters of positively charged residues and the DNA. Nucleosome conformations with different degrees of opening are associated with different conformations, positions, and DNA interaction patterns of the tails. With this mechanism, we contribute to the understanding of chromatin dynamics at atomic resolution.
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Affiliation(s)
- Jan Huertas
- In Silico Biomolecular Structure and Dynamics Group, Hubrecht Institute, Utrecht, The Netherlands
- Department of Cellular and Developmental Biology, Max Planck Institute for Molecular Biomedicine, Münster, Germany
- Center for Multiscale Theory and Computation, Westfälische Wilhelms University, Münster, Germany
| | - Hans Robert Schöler
- Department of Cellular and Developmental Biology, Max Planck Institute for Molecular Biomedicine, Münster, Germany
- Medical Faculty, University of Münster, Münster, Germany
| | - Vlad Cojocaru
- In Silico Biomolecular Structure and Dynamics Group, Hubrecht Institute, Utrecht, The Netherlands
- Department of Cellular and Developmental Biology, Max Planck Institute for Molecular Biomedicine, Münster, Germany
- Center for Multiscale Theory and Computation, Westfälische Wilhelms University, Münster, Germany
- * E-mail: ,
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13
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Peng Y, Li S, Landsman D, Panchenko AR. Histone tails as signaling antennas of chromatin. Curr Opin Struct Biol 2021; 67:153-160. [PMID: 33279866 PMCID: PMC8096652 DOI: 10.1016/j.sbi.2020.10.018] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2020] [Revised: 10/07/2020] [Accepted: 10/18/2020] [Indexed: 12/19/2022]
Abstract
Histone tails, representing the N-terminal or C-terminal regions flanking the histone core, play essential roles in chromatin signaling networks. Intrinsic disorder of histone tails and their propensity for post-translational modifications allow them to serve as hubs in coordination of epigenetic processes within the nucleosomal context. Deposition of histone variants with distinct histone tail properties further enriches histone tails' repertoire in epigenetic signaling. Given the advances in experimental techniques and in silico modelling, we review the most recent data on histone tails' effects on nucleosome stability and dynamics, their function in regulating chromatin accessibility and folding. Finally, we discuss different molecular mechanisms to understand how histone tails are involved in nucleosome recognition by binding partners and formation of higher-order chromatin structures.
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Affiliation(s)
- Yunhui Peng
- National Center for Biotechnology Information, National Institutes of Health, Bethesda, MD, USA
| | - Shuxiang Li
- Department of Pathology and Molecular Medicine, School of Medicine, Queen's University, ON, Canada
| | - David Landsman
- National Center for Biotechnology Information, National Institutes of Health, Bethesda, MD, USA
| | - Anna R Panchenko
- Department of Pathology and Molecular Medicine, School of Medicine, Queen's University, ON, Canada.
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14
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Wu H, Dalal Y, Papoian GA. Binding Dynamics of Disordered Linker Histone H1 with a Nucleosomal Particle. J Mol Biol 2021; 433:166881. [PMID: 33617899 DOI: 10.1016/j.jmb.2021.166881] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2020] [Revised: 02/11/2021] [Accepted: 02/12/2021] [Indexed: 01/30/2023]
Abstract
Linker histone H1 is an essential regulatory protein for many critical biological processes, such as eukaryotic chromatin packaging and gene expression. Mis-regulation of H1s is commonly observed in tumor cells, where the balance between different H1 subtypes has been shown to alter the cancer phenotype. Consisting of a rigid globular domain and two highly charged terminal domains, H1 can bind to multiple sites on a nucleosomal particle to alter chromatin hierarchical condensation levels. In particular, the disordered H1 amino- and carboxyl-terminal domains (NTD/CTD) are believed to enhance this binding affinity, but their detailed dynamics and functions remain unclear. In this work, we used a coarse-grained computational model, AWSEM-DNA, to simulate the H1.0b-nucleosome complex, namely chromatosome. Our results demonstrate that H1 disordered domains restrict the dynamics and conformation of both globular H1 and linker DNA arms, resulting in a more compact and rigid chromatosome particle. Furthermore, we identified regions of H1 disordered domains that are tightly tethered to DNA near the entry-exit site. Overall, our study elucidates at near-atomic resolution the way the disordered linker histone H1 modulates nucleosome's structural preferences and conformational dynamics.
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Affiliation(s)
- Hao Wu
- Biophysics Program, Institute for Physical Science and Technology, University of Maryland, College Park, MD 20742, United States
| | - Yamini Dalal
- Laboratory of Receptor Biology and Gene Expression, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, United States.
| | - Garegin A Papoian
- Biophysics Program, Institute for Physical Science and Technology, University of Maryland, College Park, MD 20742, United States; Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742, United States.
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15
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Milorey B, Schweitzer-Stenner R, Andrews B, Schwalbe H, Urbanc B. Short peptides as predictors for the structure of polyarginine sequences in disordered proteins. Biophys J 2021; 120:662-676. [PMID: 33453267 PMCID: PMC7896027 DOI: 10.1016/j.bpj.2020.12.026] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2020] [Revised: 12/08/2020] [Accepted: 12/30/2020] [Indexed: 12/12/2022] Open
Abstract
Intrinsically disordered proteins and intrinsically disordered regions are frequently enriched in charged amino acids. Intrinsically disordered regions are regularly involved in important biological processes in which one or more charged residues is the driving force behind a protein-biomolecule interaction. Several lines of experimental and computational evidence suggest that polypeptides and proteins that carry high net charges have a high preference for extended conformations with average end-to-end distances exceeding expectations for self-avoiding random coils. Here, we show that charged arginine residues even in short glycine-capped model peptides (GRRG and GRRRG) significantly affect the conformational propensities of each other when compared with the intrinsic propensities of a mostly unperturbed arginine in the tripeptide GRG. A conformational analysis based on experimentally determined J-coupling constants from heteronuclear NMR spectroscopy and amide I' band profiles from vibrational spectroscopy reveals that nearest-neighbor interactions stabilize extended β-strand conformations at the expense of polyproline II and turn conformations. The results from molecular dynamics simulations with a CHARMM36m force field and TIP3P water reproduce our results only to a limited extent. The use of the Ramachandran distribution of the central residue of GRRRG in a calculation of end-to-end distances of polyarginines of different length yielded the expected power law behavior. The scaling coefficient of 0.66 suggests that such peptides would be more extended than predicted by a self-avoiding random walk. Our findings thus support in principle theoretical predictions.
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Affiliation(s)
- Bridget Milorey
- Department of Chemistry, Drexel University, Philadelphia, Pennsylvania
| | | | - Brian Andrews
- Department of Physics, Drexel University, Philadelphia, Pennsylvania
| | - Harald Schwalbe
- Institut für Organische Chemie und Chemische Biologie, Johann Wolfgang Goethe Universität, Frankfurt, Germany
| | - Brigita Urbanc
- Department of Physics, Drexel University, Philadelphia, Pennsylvania
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16
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Huertas J, Cojocaru V. Breaths, Twists, and Turns of Atomistic Nucleosomes. J Mol Biol 2020; 433:166744. [PMID: 33309853 DOI: 10.1016/j.jmb.2020.166744] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2020] [Revised: 12/02/2020] [Accepted: 12/02/2020] [Indexed: 02/07/2023]
Abstract
Gene regulation programs establish cellular identity and rely on dynamic changes in the structural packaging of genomic DNA. The DNA is packaged in chromatin, which is formed from arrays of nucleosomes displaying different degree of compaction and different lengths of inter-nucleosomal linker DNA. The nucleosome represents the repetitive unit of chromatin and is formed by wrapping 145-147 basepairs of DNA around an octamer of histone proteins. Each of the four histones is present twice and has a structured core and intrinsically disordered terminal tails. Chromatin dynamics are triggered by inter- and intra-nucleosome motions that are controlled by the DNA sequence, the interactions between the histone core and the DNA, and the conformations, positions, and DNA interactions of the histone tails. Understanding chromatin dynamics requires studying all these features at the highest possible resolution. For this, molecular dynamics simulations can be used as a powerful complement or alternative to experimental approaches, from which it is often very challenging to characterize the structural features and atomic interactions controlling nucleosome motions. Molecular dynamics simulations can be performed at different resolutions, by coarse graining the molecular system with varying levels of details. Here we review the successes and the remaining challenges of the application of atomic resolution simulations to study the structure and dynamics of nucleosomes and their complexes with interacting partners.
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Affiliation(s)
- Jan Huertas
- In Silico Biomolecular Structure and Dynamics Group, Hubrecht Institute, Utrecht, the Netherlands; Department of Cellular and Developmental Biology, Max Planck Institute for Molecular Biomedicine, Münster, Germany; Center for Multiscale Theory and Computation, Westfälische Wilhelms University, Münster, Germany
| | - Vlad Cojocaru
- In Silico Biomolecular Structure and Dynamics Group, Hubrecht Institute, Utrecht, the Netherlands; Department of Cellular and Developmental Biology, Max Planck Institute for Molecular Biomedicine, Münster, Germany; Center for Multiscale Theory and Computation, Westfälische Wilhelms University, Münster, Germany.
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17
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Shabane PS, Onufriev AV. Significant compaction of H4 histone tail upon charge neutralization by acetylation and its mimics, possible effects on chromatin structure. J Mol Biol 2020; 433:166683. [PMID: 33096105 DOI: 10.1016/j.jmb.2020.10.017] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2020] [Revised: 09/30/2020] [Accepted: 10/13/2020] [Indexed: 10/23/2022]
Abstract
The intrinsically disordered, positively charged H4 histone tail is important for chromatin structure and function. We have explored conformational ensembles of human H4 tail in solution, with varying levels of charge neutralization via acetylation or amino-acid substitutions such as K→Q. We have employed an explicit water model shown recently to be well suited for simulations of intrinsically disordered proteins. Upon progressive neutralization of the H4, its radius of gyration decreases linearly with the tail charge q, the trend is explained using a simple polymer model. While the wild type state (q=+8) is essentially a random coil, hyper-acetylated H4 (q=+3) is virtually as compact and stable as a globular protein of the same number of amino-acids. Conformational ensembles of acetylated H4 match the corresponding K→X substitutions only approximately: based on the ensemble similarity, we propose K→M as a possible alternative to the commonly used K→Q. Possible effects of the H4 tail compaction on chromatin structure are discussed within a qualitative model in which the chromatin is highly heterogeneous, easily inter-converting between various structural forms. We predict that upon progressive charge neutralization of the H4 tail, the least compact sub-states of chromatin de-condense first, followed by de-condensation of more compact structures, e.g. those that harbor a high fraction of stacked di-nucleosomes. The predicted hierarchy of DNA accessibility increase upon progressive acetylation of H4 might be utilized by the cell for selective DNA accessibility control.
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Affiliation(s)
| | - Alexey V Onufriev
- Departments of Computer Science, Virginia Tech, Blacksburg, VA 24060, United States; Department of Physics, Virginia Tech, Blacksburg, VA 24060, United States; Center for Soft Matter and Biological Physics, Virginia Tech, Blacksburg, VA 24061, USA.
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18
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Bendandi A, Patelli AS, Diaspro A, Rocchia W. The role of histone tails in nucleosome stability: An electrostatic perspective. Comput Struct Biotechnol J 2020; 18:2799-2809. [PMID: 33133421 PMCID: PMC7575852 DOI: 10.1016/j.csbj.2020.09.034] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2020] [Revised: 09/23/2020] [Accepted: 09/24/2020] [Indexed: 01/20/2023] Open
Abstract
We propose a methodology for the study of protein-DNA electrostatic interactions and apply it to clarify the effect of histone tails in nucleosomes. This method can be used to correlate electrostatic interactions to structural and functional features of protein-DNA systems, and can be combined with coarse-grained representations. In particular, we focus on the electrostatic field and resulting forces acting on the DNA. We investigate the electrostatic origins of effects such as different stages in DNA unwrapping, nucleosome destabilization upon histone tail truncation, and the role of specific arginines and lysines undergoing Post-Translational Modifications. We find that the positioning of the histone tails can oppose the attractive pull of the histone core, locally deform the DNA, and tune DNA unwrapping. Small conformational variations in the often overlooked H2A C-terminal tails had significant electrostatic repercussions near the DNA entry and exit sites. The H2A N-terminal tail exerts attractive electrostatic forces towards the histone core in positions where Polymerase II halts its progress. We validate our results with comparisons to previous experimental and computational observations.
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Affiliation(s)
- Artemi Bendandi
- DIFILAB, Department of Physics, University of Genoa, Via Dodecaneso 33, 16149 Genoa, Italy.,CHT Erzelli, Nanoscopy, Istituto Italiano di Tecnologia, Via Enrico Melen 83, 16152 Genoa, Italy
| | - Alessandro S Patelli
- LCVMM, Institute of Mathematics, Swiss Federal Institute of Technology (EPFL), CH-1015 Lausanne, Switzerland
| | - Alberto Diaspro
- DIFILAB, Department of Physics, University of Genoa, Via Dodecaneso 33, 16149 Genoa, Italy.,CHT Erzelli, Nanoscopy, Istituto Italiano di Tecnologia, Via Enrico Melen 83, 16152 Genoa, Italy
| | - Walter Rocchia
- Concept Lab, Istituto Italiano di Tecnologia, Via Enrico Melen 83, 16152 Genoa, Italy
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19
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Sridhar A, Orozco M, Collepardo-Guevara R. Protein disorder-to-order transition enhances the nucleosome-binding affinity of H1. Nucleic Acids Res 2020; 48:5318-5331. [PMID: 32356891 PMCID: PMC7261198 DOI: 10.1093/nar/gkaa285] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2020] [Revised: 04/02/2020] [Accepted: 04/14/2020] [Indexed: 12/18/2022] Open
Abstract
Intrinsically disordered proteins are crucial elements of chromatin heterogenous organization. While disorder in the histone tails enables a large variation of inter-nucleosome arrangements, disorder within the chromatin-binding proteins facilitates promiscuous binding to a wide range of different molecular targets, consistent with structural heterogeneity. Among the partially disordered chromatin-binding proteins, the H1 linker histone influences a myriad of chromatin characteristics including compaction, nucleosome spacing, transcription regulation, and the recruitment of other chromatin regulating proteins. Although it is now established that the long C-terminal domain (CTD) of H1 remains disordered upon nucleosome binding and that such disorder favours chromatin fluidity, the structural behaviour and thereby the role/function of the N-terminal domain (NTD) within chromatin is yet unresolved. On the basis of microsecond-long parallel-tempering metadynamics and temperature-replica exchange atomistic molecular dynamics simulations of different H1 NTD subtypes, we demonstrate that the NTD is completely unstructured in solution but undergoes an important disorder-to-order transition upon nucleosome binding: it forms a helix that enhances its DNA binding ability. Further, we show that the helical propensity of the H1 NTD is subtype-dependent and correlates with the experimentally observed binding affinity of H1 subtypes, suggesting an important functional implication of this disorder-to-order transition.
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Affiliation(s)
- Akshay Sridhar
- Maxwell Centre, Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, UK
| | - Modesto Orozco
- Institute for Research in Biomedicine, The Barcelona Institute of Science and Technology, Baldiri i Reixac, 19, 08028 Barcelona, Spain
- Department of Biochemistry and Biomedicine, University of Barcelona, Av. Diagonal 647. 08028 Barcelona, Spain
| | - Rosana Collepardo-Guevara
- Maxwell Centre, Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, UK
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK
- Department of Genetics, University of Cambridge, Cambridge CB2 3EH, UK
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20
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Moller J, de Pablo JJ. Bottom-Up Meets Top-Down: The Crossroads of Multiscale Chromatin Modeling. Biophys J 2020; 118:2057-2065. [PMID: 32320675 DOI: 10.1016/j.bpj.2020.03.014] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2019] [Revised: 03/04/2020] [Accepted: 03/20/2020] [Indexed: 01/19/2023] Open
Abstract
Chromatin can be viewed as a hierarchically structured fiber that regulates gene expression. It consists of a complex network of DNA and proteins whose characteristic dynamical modes facilitate compaction and rearrangement in the cell nucleus. These modes stem from chromatin's fundamental unit, the nucleosome, and their effects are propagated across length scales. Understanding the effects of nucleosome dynamics on the chromatin fiber, primarily through post-translational modifications that occur on the histones, is of central importance to epigenetics. Within the last decade, imaging and chromosome conformation capture techniques have revealed a number of structural and statistical features of the packaged chromatin fiber at a hitherto unavailable level of resolution. Such experiments have led to increased efforts to develop polymer models that aim to reproduce, explain, and predict the contact probability scaling and density heterogeneity. At nanometer scales, available models have focused on the role of the nucleosome and epigenetic marks on local chromatin structure. At micrometer scales, existing models have sought to explain scaling laws and density heterogeneity. Less work, however, has been done to reconcile these two approaches: bottom-up and top-down models of chromatin. In this perspective, we highlight the multiscale simulation models that are driving toward an understanding of chromatin structure and function, from the nanometer to the micron scale, and we highlight areas of opportunity and some of the prospects for new frameworks that bridge these two scales. Taken together, experimental and modeling advances over the last few years have established a robust platform for the study of chromatin fiber structure and dynamics, which will be of considerable use to the chromatin community in developing an understanding of the interplay between epigenomic regulation and molecular structure.
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Affiliation(s)
- Joshua Moller
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, Illinois
| | - Juan J de Pablo
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, Illinois; Material Science Division, Argonne National Laboratory, Lemont, Illinois.
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21
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Heterogeneous fluid-like movements of chromatin and their implications to transcription. Biophys Rev 2020; 12:461-468. [PMID: 32206982 DOI: 10.1007/s12551-020-00675-8] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2020] [Accepted: 03/02/2020] [Indexed: 01/10/2023] Open
Abstract
Eukaryotic chromatin is a complex of genome DNA and associated proteins, and its structure and dynamics play a crucial role in regulating DNA functions. Chromatin takes rather irregular structures in the nucleus and exhibits heterogeneous sub-diffusive movements as polymers fluctuating in a fluid state. Using genome-wide single-nucleosome tracking data, heterogeneity of movements was statistically analyzed, which categorized chromatin into two types: slow chromatin that moves under structurally constrained environments and fast chromatin that moves with less constraints. Interactions of chromatin to various protein factors determine the motional constraints. For example, loss of the cohesin complex that bundles the chromatin chains reduces the motional constraints and increases the population of fast chromatin. Another example is the transcriptional machinery. While it was previously thought that the transcriptional activity is associated with more open and dynamic chromatin structure, recent studies suggested a more nuanced role of transcription in chromatin dynamics: dynamic association/dissociation of active RNA polymerase II (RNAPII) and other transcription factors and Mediators (TF-Meds) transiently bridges transcriptionally active DNA regions, which forms a loose network of chromatin and constrains chromatin movement, enhancing the slow chromatin population. This new view on the dynamical effects of transcription urges a reflection on the traditional model of transcription factories and invites the more recent models of condensates/phase-separated liquid droplets of RNAPII, transcription factors, and Mediators. The combined procedure of genome-wide single-nucleosome tracking and its statistical analysis would unveil heterogeneity in the chromatin movement, which should provide a key to understanding the relations among chromatin dynamics, structure, and function.
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22
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Bendandi A, Dante S, Zia SR, Diaspro A, Rocchia W. Chromatin Compaction Multiscale Modeling: A Complex Synergy Between Theory, Simulation, and Experiment. Front Mol Biosci 2020; 7:15. [PMID: 32158765 PMCID: PMC7051991 DOI: 10.3389/fmolb.2020.00015] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2019] [Accepted: 01/27/2020] [Indexed: 12/24/2022] Open
Abstract
Understanding the mechanisms that trigger chromatin compaction, its patterns, and the factors they depend on, is a fundamental and still open question in Biology. Chromatin compacts and reinforces DNA and is a stable but dynamic structure, to make DNA accessible to proteins. In recent years, computational advances have provided larger amounts of data and have made large-scale simulations more viable. Experimental techniques for the extraction and reconstitution of chromatin fibers have improved, reinvigorating theoretical and experimental interest in the topic and stimulating debate on points previously considered as certainties regarding chromatin. A great assortment of approaches has emerged, from all-atom single-nucleosome or oligonucleosome simulations to various degrees of coarse graining, to polymer models, to fractal-like structures and purely topological models. Different fiber-start patterns have been studied in theory and experiment, as well as different linker DNA lengths. DNA is a highly charged macromolecule, making ionic and electrostatic interactions extremely important for chromatin topology and dynamics. Indeed, the repercussions of varying ionic concentration have been extensively examined at the computational level, using all-atom, coarse-grained, and continuum techniques. The presence of high-curvature AT-rich segments in DNA can cause conformational variations, attesting to the fact that the role of DNA is both structural and electrostatic. There have been some tentative attempts to describe the force fields governing chromatin conformational changes and the energy landscapes of these transitions, but the intricacy of the system has hampered reaching a consensus. The study of chromatin conformations is an intrinsically multiscale topic, influenced by a wide range of biological and physical interactions, spanning from the atomic to the chromosome level. Therefore, powerful modeling techniques and carefully planned experiments are required for an overview of the most relevant phenomena and interactions. The topic provides fertile ground for interdisciplinary studies featuring a synergy between theoretical and experimental scientists from different fields and the cross-validation of respective results, with a multi-scale perspective. Here, we summarize some of the most representative approaches, and focus on the importance of electrostatics and solvation, often overlooked aspects of chromatin modeling.
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Affiliation(s)
- Artemi Bendandi
- Physics Department, University of Genoa, Genoa, Italy
- Nanophysics & NIC@IIT, Istituto Italiano di Tecnologia, Genoa, Italy
| | - Silvia Dante
- Nanophysics & NIC@IIT, Istituto Italiano di Tecnologia, Genoa, Italy
| | - Syeda Rehana Zia
- Dr. Panjwani Center for Molecular Medicine and Drug Research, International Center for Chemical and Biological Sciences, University of Karachi, Karachi, Pakistan
| | - Alberto Diaspro
- Physics Department, University of Genoa, Genoa, Italy
- Nanophysics & NIC@IIT, Istituto Italiano di Tecnologia, Genoa, Italy
| | - Walter Rocchia
- Concept Lab, Istituto Italiano di Tecnologia, Genoa, Italy
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23
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Yeo JH, Lam YW, Fraser ST. Cellular dynamics of mammalian red blood cell production in the erythroblastic island niche. Biophys Rev 2019; 11:873-894. [PMID: 31418139 PMCID: PMC6874942 DOI: 10.1007/s12551-019-00579-2] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2019] [Accepted: 07/08/2019] [Indexed: 12/12/2022] Open
Abstract
Red blood cells, or erythrocytes, make up approximately a quarter of all cells in the human body with over 2 billion new erythrocytes made each day in a healthy adult human. This massive cellular production system is coupled with a set of cell biological processes unique to mammals, in particular, the elimination of all organelles, and the expulsion and destruction of the condensed erythroid nucleus. Erythrocytes from birds, reptiles, amphibians and fish possess nuclei, mitochondria and other organelles: erythrocytes from mammals lack all of these intracellular components. This review will focus on the dynamic changes that take place in developing erythroid cells that are interacting with specialized macrophages in multicellular clusters termed erythroblastic islands. Proerythroblasts enter the erythroblastic niche as large cells with active nuclei, mitochondria producing heme and energy, and attach to the central macrophage via a range of adhesion molecules. Proerythroblasts then mature into erythroblasts and, following enucleation, in reticulocytes. When reticulocytes exit the erythroblastic island, they are smaller cells, without nuclei and with few mitochondria, possess some polyribosomes and have a profoundly different surface molecule phenotype. Here, we will review, step-by-step, the biophysical mechanisms that regulate the remarkable process of erythropoiesis with a particular focus on the events taking place in the erythroblastic island niche. This is presented from the biological perspective to offer insight into the elements of red blood cell development in the erythroblastic island niche which could be further explored with biophysical modelling systems.
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Affiliation(s)
- Jia Hao Yeo
- Discipline of Anatomy and Histology, School of Medical Sciences, University of Sydney, Sydney, Australia.
- School of Chemistry, University of Sydney, Sydney, Australia.
- Discipline of Physiology, School of Medical Sciences, University of Sydney, Sydney, Australia.
| | - Yun Wah Lam
- Department of Chemistry, City University of Hong Kong, Kowloon Tong, Hong Kong
| | - Stuart T Fraser
- Discipline of Anatomy and Histology, School of Medical Sciences, University of Sydney, Sydney, Australia.
- Discipline of Physiology, School of Medical Sciences, University of Sydney, Sydney, Australia.
- Bosch Institute, School of Medical Sciences, University of Sydney, Sydney, Australia.
- University of Sydney Nano Institute, Sydney, Australia.
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24
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Kono H, Sakuraba S, Ishida H. Free energy profile for unwrapping outer superhelical turn of CENP-A nucleosome. Biophys Physicobiol 2019; 16:337-343. [PMID: 31984189 PMCID: PMC6975924 DOI: 10.2142/biophysico.16.0_337] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2019] [Accepted: 08/05/2019] [Indexed: 01/19/2023] Open
Abstract
Eukaryotic genome is packaged in a nucleus in the form of chromatin. The fundamental structural unit of the chromatin is the protein-DNA complex, nucleosome, where DNA of about 150 bp is wrapped around a histone core almost twice. In cellular processes such as gene expression, DNA repair and duplication, the nucleosomal DNA has to be unwrapped. Histone proteins have their variants, indicating there are a variety of constitutions of nucleosomes. These different constitutions are observed in different cellular processes. To investigate differences among nucleosomes, we calculated free energy profiles for unwrapping the outer superhelical turn of CENP-A nucleosome and compared them with those of the canonical nucleosome. The free energy profiles for CENP-A nucleosome suggest that CENP-A nucleosome is the most stable when 16 to 22 bps are unwrapped in total whereas the canonical nucleosome is the most stable when it is fully wrapped. This indicates that the flexible conformation of CENP-A nucleosome is ready to provide binding sites for the structural integrity of the centromere.
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Affiliation(s)
- Hidetoshi Kono
- Molecular Modelling and Simulation Group, Institute for Quantum Life Science (iQLS), National Institutes for Quantum and Radiological Science and Technology, Kizugawa, Kyoto 619-0215 Japan
| | - Shun Sakuraba
- Molecular Modelling and Simulation Group, Institute for Quantum Life Science (iQLS), National Institutes for Quantum and Radiological Science and Technology, Kizugawa, Kyoto 619-0215 Japan
| | - Hisashi Ishida
- Molecular Modelling and Simulation Group, Institute for Quantum Life Science (iQLS), National Institutes for Quantum and Radiological Science and Technology, Kizugawa, Kyoto 619-0215 Japan
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25
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Roche J, Potoyan DA. Disorder Mediated Oligomerization of DISC1 Proteins Revealed by Coarse-Grained Molecular Dynamics Simulations. J Phys Chem B 2019; 123:9567-9575. [PMID: 31614085 DOI: 10.1021/acs.jpcb.9b07467] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Disrupted-in-schizophrenia-1 (DISC1) is a scaffold protein of significant importance for neuro-development and a prominent candidate protein in the etiology of mental disorders. In this work, we investigate the role of conformational heterogeneity and local structural disorder in the oligomerization pathway of the full-length DISC1 and of two truncation variants. Through extensive coarse-grained molecular dynamics simulations with a predictive energy landscape-based model, we shed light on the interplay of local and global disorder which lead to different oligomerization pathways. We found that both global conformational heterogeneity and local structural disorder play an important role in shaping distinct oligomerization trends of DISC1. This study also sheds light on the differences in oligomerization pathways of the full-length protein compared to the truncated variants produced by a chromosomal translocation associated with schizophrenia. We report that oligomerization of full-length DISC1 sequence works in a nonadditive manner with respect to truncated fragments that do not mirror the conformational landscape or binding affinities of the full-length unit.
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Affiliation(s)
- Julien Roche
- Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology , Iowa State University , Ames , Iowa 50011 , United States
| | - Davit A Potoyan
- Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology , Iowa State University , Ames , Iowa 50011 , United States.,Department of Chemistry , Iowa State University , Ames , Iowa 50011 , United States.,Bioinformatics and Computational Biology Program , Iowa State University , Ames , Iowa 50011 , United States
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26
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Krajewski WA, Li J, Dou Y. Effects of histone H2B ubiquitylation on the nucleosome structure and dynamics. Nucleic Acids Res 2019; 46:7631-7642. [PMID: 29931239 PMCID: PMC6125632 DOI: 10.1093/nar/gky526] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2018] [Accepted: 05/25/2018] [Indexed: 01/01/2023] Open
Abstract
DNA in nucleosomes has restricted nucleosome dynamics and is refractory to DNA-templated processes. Histone post-translational modifications play important roles in regulating DNA accessibility in nucleosomes. Whereas most histone modifications function either by mitigating the electrostatic shielding of histone tails or by recruiting 'reader' proteins, we show that ubiquitylation of H2B K34, which is located in a tight space protected by two coils of DNA superhelix, is able to directly influence the canonical nucleosome conformation via steric hindrances by ubiquitin groups. H2B K34 ubiquitylation significantly enhances nucleosome dynamics and promotes generation of hexasomes both with symmetrically or asymmetrically modified nucleosomes. Our results indicate a direct mechanism by which a histone modification regulates the chromatin structural states.
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Affiliation(s)
- Wladyslaw A Krajewski
- N.K. Koltsov Institute of Developmental Biology, Russian Academy of Sciences, Vavilova Str. 26, Moscow, 119334, Russia.,Department of Pathology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Jiabin Li
- School of Life Sciences, University of Science and Technology of China, Hefei 230026, China
| | - Yali Dou
- Department of Pathology, University of Michigan, Ann Arbor, MI 48109, USA
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27
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Lv WL, Arnesano F, Carloni P, Natile G, Rossetti G. Effect of in vivo post-translational modifications of the HMGB1 protein upon binding to platinated DNA: a molecular simulation study. Nucleic Acids Res 2019; 46:11687-11697. [PMID: 30407547 PMCID: PMC6294504 DOI: 10.1093/nar/gky1082] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2018] [Accepted: 10/19/2018] [Indexed: 12/26/2022] Open
Abstract
Cisplatin is one of the most widely used anticancer drugs. Its efficiency is unfortunately severely hampered by resistance. The High Mobility Group Box (HMGB) proteins may sensitize tumor cells to cisplatin by specifically binding to platinated DNA (PtDNA) lesions. In vivo, the HMGB/PtDNA binding is regulated by multisite post-translational modifications (PTMs). The impact of PTMs on the HMGB/PtDNA complex at atomistic level is here investigated by enhanced sampling molecular simulations. The PTMs turn out to affect the structure of the complex, the mobility of several regions (including the platinated site), and the nature of the protein/PtDNA non-covalent interactions. Overall, the multisite PTMs increase significantly the apparent synchrony of all the contacts between the protein and PtDNA. Consequently, the hydrophobic anchoring of the side chain of F37 between the two cross-linked guanines at the platinated site-a key element of the complexes formation - is more stable than in the complex without PTM. These differences can account for the experimentally measured greater affinity for PtDNA of the protein isoforms with PTMs. The collective behavior of multisite PTMs, as revealed here by the synchrony of contacts, may have a general significance for the modulation of intermolecular recognitions occurring in vivo.
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Affiliation(s)
- Wenping Lyu Lv
- Computational Biomedicine, Institute for Advanced Simulation IAS-5 and Institute of Neuroscience and Medicine INM-9, Forschungszentrum Jülich, 52425 Jülich, Germany.,Faculty of Mathematics, Computer Science and Natural Sciences, RWTH-Aachen University, 52056 Aachen, Germany.,Computation-Based Science and Technology Research Center, Cyprus Institute, 2121 Aglantzia, Nicosia, Cyprus
| | - Fabio Arnesano
- Department of Chemistry, University of Bari "A. Moro", via Edoardo Orabona 4, 70125 Bari, Italy
| | - Paolo Carloni
- Computational Biomedicine, Institute for Advanced Simulation IAS-5 and Institute of Neuroscience and Medicine INM-9, Forschungszentrum Jülich, 52425 Jülich, Germany
| | - Giovanni Natile
- Department of Chemistry, University of Bari "A. Moro", via Edoardo Orabona 4, 70125 Bari, Italy
| | - Giulia Rossetti
- Computational Biomedicine, Institute for Advanced Simulation IAS-5 and Institute of Neuroscience and Medicine INM-9, Forschungszentrum Jülich, 52425 Jülich, Germany.,Department of Hematology, Oncology, Hemostaseology, and Stem Cell Transplantation, Faculty of Medicine, RWTH Aachen University, 52062 Aachen, Germany.,Jülich Supercomputing Centre (JSC), Forschungszentrum Jülich, 52425 Jülich, Germany
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28
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Onufriev AV, Schiessel H. The nucleosome: from structure to function through physics. Curr Opin Struct Biol 2019; 56:119-130. [DOI: 10.1016/j.sbi.2018.11.003] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2018] [Revised: 11/07/2018] [Accepted: 11/13/2018] [Indexed: 02/07/2023]
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29
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Parsons T, Zhang B. Critical role of histone tail entropy in nucleosome unwinding. J Chem Phys 2019; 150:185103. [PMID: 31091895 DOI: 10.1063/1.5085663] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The nucleosome is the fundamental packaging unit for the genome. It must remain tightly wound to ensure genome stability while simultaneously being flexible enough to keep the DNA molecule accessible for genome function. The set of physicochemical interactions responsible for the delicate balance between these naturally opposed processes have not been determined due to challenges in resolving partially unwound nucleosome configurations at atomic resolution. Using a near atomistic protein-DNA model and advanced sampling techniques, we calculate the free energy cost of nucleosome DNA unwinding. Our simulations identify a large energetic barrier that decouples the outer and the inner DNA unwinding into two separate processes, occurring on different time scales. This dynamical decoupling allows the exposure of outer DNA at a modest cost to ensure accessibility while keeping the inner DNA and the histone core intact to maintain stability. We also reveal that this energetic barrier arises from a delayed loss of contacts between disordered histone tails and the DNA and is, surprisingly, largely offset by an entropic contribution from these tails. Implications of this enthalpy entropy compensation for the regulation of nucleosome stability and genome function are discussed.
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Affiliation(s)
- Thomas Parsons
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139-4307, USA
| | - Bin Zhang
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139-4307, USA
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30
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Zhao H, Winogradoff D, Dalal Y, Papoian GA. The Oligomerization Landscape of Histones. Biophys J 2019; 116:1845-1855. [PMID: 31005236 DOI: 10.1016/j.bpj.2019.03.021] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2018] [Revised: 03/06/2019] [Accepted: 03/14/2019] [Indexed: 12/29/2022] Open
Abstract
In eukaryotes, DNA is packaged within nucleosomes. The DNA of each nucleosome is typically centered around an octameric histone protein core: one central tetramer plus two separate dimers. Studying the assembly mechanisms of histones is essential for understanding the dynamics of entire nucleosomes and higher-order DNA packaging. Here, we investigate canonical histone assembly and that of the centromere-specific histone variant, centromere protein A (CENP-A), using molecular dynamics simulations. We quantitatively characterize their thermodynamical and dynamical features, showing that two H3/H4 dimers form a structurally floppy, weakly bound complex, the latter exhibiting large instability around the central interface manifested via a swiveling motion of two halves. This finding is consistent with the recently observed DNA handedness flipping of the tetrasome. In contrast, the variant CENP-A encodes distinctive stability to its tetramer with a rigid but twisted interface compared to the crystal structure, implying diverse structural possibilities of the histone variant. Interestingly, the observed tetramer dynamics alter significantly and appear to reach a new balance when H2A/H2B dimers are present. Furthermore, we found that the preferred structure for the (CENP-A/H4)2 tetramer is incongruent with the octameric structure, explaining many of the unusual dynamical behaviors of the CENP-A nucleosome. In all, these data reveal key mechanistic insights and structural details for the assembly of canonical and variant histone tetramers and octamers, providing theoretical quantifications and physical interpretations for longstanding and recent experimental observations. Based on these findings, we propose different chaperone-assisted binding and nucleosome assembly mechanisms for the canonical and CENP-A histone oligomers.
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Affiliation(s)
- Haiqing Zhao
- Biophysics Program, Institute for Physical Science and Technology, University of Maryland, College Park, Maryland; Laboratory of Receptor Biology and Gene Expression, National Cancer Institute, National Institutes of Health, Bethesda, Maryland
| | - David Winogradoff
- Chemical Physics Program, Institute for Physical Science and Technology
| | - Yamini Dalal
- Laboratory of Receptor Biology and Gene Expression, National Cancer Institute, National Institutes of Health, Bethesda, Maryland.
| | - Garegin A Papoian
- Biophysics Program, Institute for Physical Science and Technology, University of Maryland, College Park, Maryland; Chemical Physics Program, Institute for Physical Science and Technology; Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland.
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31
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Shabane PS, Izadi S, Onufriev AV. General Purpose Water Model Can Improve Atomistic Simulations of Intrinsically Disordered Proteins. J Chem Theory Comput 2019; 15:2620-2634. [PMID: 30865832 DOI: 10.1021/acs.jctc.8b01123] [Citation(s) in RCA: 83] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Unconstrained atomistic simulations of intrinsically disordered proteins and peptides (IDP) remain a challenge: widely used, "general purpose" water models tend to favor overly compact structures relative to experiment. Here we have performed a total of 93 μs of unrestrained MD simulations to explore, in the context of IDPs, a recently developed "general-purpose" 4-point rigid water model OPC, which describes liquid state of water close to experiment. We demonstrate that OPC, together with a popular AMBER force field ff99SB, offers a noticeable improvement over TIP3P in producing more realistic structural ensembles of three common IDPs benchmarks: 55-residue apo N-terminal zinc-binding domain of HIV-1 integrase ("protein IN"), amyloid β-peptide (Aβ42) (residues 1-42), and 26-reside H4 histone tail. As a negative control, computed folding profile of a regular globular miniprotein (CLN025) in OPC water is in appreciably better agreement with experiment than that obtained in TIP3P, which tends to overstabilize the compact native state relative to the extended conformations. We employed Aβ42 peptide to investigate the possible influence of the solvent box size on simulation outcomes. We advocate a cautious approach for simulations of IDPs: we suggest that the solvent box size should be at least four times the radius of gyration of the random coil corresponding to the IDP. The computed free energy landscape of protein IN in OPC resembles a shallow "tub" - conformations with substantially different degrees of compactness that are within 2 kB T of each other. Conformations with very different secondary structure content coexist within 1 kB T of the global free energy minimum. States with higher free energy tend to have less secondary structure. Computed low helical content of the protein has virtually no correlation with its degree of compactness, which calls into question the possibility of using the helicity as a metric for assessing performance of water models for IDPs, when the helicity is low. Predicted radius of gyration ( R g) of H4 histone tail in OPC water falls in-between that of a typical globular protein and a fully denatured protein of the same size; the predicted R g is consistent with two independent predictions. In contrast, H4 tail in TIP3P water is as compact as the corresponding globular protein. The computed free energy landscape of H4 tail in OPC is relatively flat over a significant range of compactness, which, we argue, is consistent with its biological function as facilitator of internucleosome interactions.
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Affiliation(s)
| | - Saeed Izadi
- Early Stage Pharmaceutical Development , Genentech Inc. , South San Francisco , California 94080 , United States
| | - Alexey V Onufriev
- Department of Computer Science , Virginia Tech , Blacksburg , Virginia 24060 , United States.,Center for Soft Matter and Biological Physics , Virginia Tech , Blacksburg , Virginia 24061 , United States
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32
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Winogradoff D, Aksimentiev A. Molecular Mechanism of Spontaneous Nucleosome Unraveling. J Mol Biol 2019; 431:323-335. [PMID: 30468737 PMCID: PMC6331254 DOI: 10.1016/j.jmb.2018.11.013] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2018] [Revised: 10/26/2018] [Accepted: 11/12/2018] [Indexed: 11/18/2022]
Abstract
Meters of DNA wrap around histone proteins to form nucleosomes and fit inside the micron-diameter nucleus. For the genetic information encoded in the DNA to become available for transcription, replication, and repair, the DNA-histone assembly must be disrupted. Experiment has indicated that the outer stretches of nucleosomal DNA "breathe" by spontaneously detaching from and reattaching to the histone core. Here, we report direct observation of spontaneous DNA breathing in atomistic molecular dynamics simulations, detailing a microscopic mechanism of the DNA breathing process. According to our simulations, the outer stretches of nucleosomal DNA detach in discrete steps involving 5 or 10 base pairs, with the detachment process being orchestrated by the motion of several conserved histone residues. The inner stretches of nucleosomal DNA are found to be more stably associated with the histone core by more abundant nonspecific DNA-protein contacts, providing a microscopic interpretation of nucleosome unraveling experiments. The CG content of nucleosomal DNA is found to anticorrelate with the extent of unwrapping, supporting the possibility that AT-rich segments may signal the start of transcription by forming less stable nucleosomes.
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Affiliation(s)
- David Winogradoff
- Center for the Physics of Living Cells, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA; Department of Physics, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Aleksei Aksimentiev
- Center for the Physics of Living Cells, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA; Department of Physics, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA; Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
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33
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Bowerman S, Hickok RJ, Wereszczynski J. Unique Dynamics in Asymmetric macroH2A-H2A Hybrid Nucleosomes Result in Increased Complex Stability. J Phys Chem B 2019; 123:419-427. [PMID: 30557018 DOI: 10.1021/acs.jpcb.8b10668] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The fundamental unit of eukaryotic chromatin is the nucleosome core particle, a protein/DNA complex that binds ∼147 base pairs of DNA to a histone octamer. These histones-H3, H4, H2A, H2B-form the nucleosome core through a stacked interaction in which two H2A-H2B dimers flank the (H3-H4)2 tetramer. In vivo, genetic accessibility can be modulated by the substitution of canonical histones with variant proteins that contain the same structural motif but a different amino acid sequence, such as the transcriptional repression-associated macroH2A variant. Previously, Chakravarthy and Luger published a crystal study that showed that H2A substitution is not necessarily required of both H2A moieties, but that in vitro recombination of nucleosomes in the presence of both macroH2A and H2A histone folds results in a hybrid macroH2A-H2A nucleosome with one dimer of each type. Here, we present molecular dynamics simulations of this hybrid construct and compare the results to our previous study on homogeneous H2A- and macroH2A-containing nucleosomes. We find that the hybrid contains a unique set of dynamics that stabilize the interactions between protein constituents and create an altogether more stable nucleosome, both in terms of protein-DNA and protein-protein binding. While dimer-tetramer interactions are asymmetric, as the difference in moieties would suggest, we observe that it is the canonical dimer that is pulled further into the nucleosome core, resulting in more secure dimer-tetramer bonds and a more stable histone core, and we also find significantly more interaction between the dimer subunits. Together, these models provide evidence for hybrid H2A-macroH2A nucleosome formation being not only possible but actually energetically more favorable than a homogeneous construct, with dynamics that are unique from their homogeneous H2A or macroH2A nucleosome counterparts. These effects of hybrid substitution likely propagate into higher-order chromatin structures to hinder transcriptional activity.
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Affiliation(s)
- Samuel Bowerman
- Department of Physics and the Center for Molecular Study of Condensed Soft Matter, Illinois Institute of Technology , Chicago , Illinois 60616 , United States
| | - Robert J Hickok
- Department of Physics and the Center for Molecular Study of Condensed Soft Matter, Illinois Institute of Technology , Chicago , Illinois 60616 , United States
| | - Jeff Wereszczynski
- Department of Physics and the Center for Molecular Study of Condensed Soft Matter, Illinois Institute of Technology , Chicago , Illinois 60616 , United States
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34
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Wu H, Wolynes PG, Papoian GA. AWSEM-IDP: A Coarse-Grained Force Field for Intrinsically Disordered Proteins. J Phys Chem B 2018; 122:11115-11125. [PMID: 30091924 PMCID: PMC6713210 DOI: 10.1021/acs.jpcb.8b05791] [Citation(s) in RCA: 72] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The associative memory, water-mediated, structure and energy model (AWSEM) has been successfully used to study protein folding, binding, and aggregation problems. In this work, we introduce AWSEM-IDP, a new AWSEM branch for simulating intrinsically disordered proteins (IDPs), where the weights of the potentials determining secondary structure formation have been finely tuned, and a novel potential is introduced that helps to precisely control both the average extent of protein chain collapse and the chain's fluctuations in size. AWSEM-IDP can efficiently sample large conformational spaces, while retaining sufficient molecular accuracy to realistically model proteins. We applied this new model to two IDPs, demonstrating that AWSEM-IDP can reasonably well reproduce higher-resolution reference data, thus providing the foundation for a transferable IDP force field. Finally, we used thermodynamic perturbation theory to show that, in general, the conformational ensembles of IDPs are highly sensitive to fine-tuning of force field parameters.
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Affiliation(s)
- Hao Wu
- Biophysics Program, Institute for Physical Science and Technology, University of Maryland, College Park, Maryland 20742, United States
| | - Peter G. Wolynes
- Departments of Chemistry and Physics and Center for Theoretical Biological Physics, Rice University, Houston, Texas 77005, United States
| | - Garegin A. Papoian
- Biophysics Program, Institute for Physical Science and Technology, University of Maryland, College Park, Maryland 20742, United States
- Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742, United States
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35
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Chakraborty K, Kang M, Loverde SM. Molecular Mechanism for the Role of the H2A and H2B Histone Tails in Nucleosome Repositioning. J Phys Chem B 2018; 122:11827-11840. [DOI: 10.1021/acs.jpcb.8b07881] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Kaushik Chakraborty
- Department of Chemistry, College of Staten Island, The City University of New York, 2800 Victory Boulevard, Staten Island, New York 10314, United States
| | - Myungshim Kang
- Department of Chemistry, College of Staten Island, The City University of New York, 2800 Victory Boulevard, Staten Island, New York 10314, United States
| | - Sharon M. Loverde
- Department of Chemistry, College of Staten Island, The City University of New York, 2800 Victory Boulevard, Staten Island, New York 10314, United States
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36
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Kämpf K, Izmailov SA, Rabdano SO, Groves AT, Podkorytov IS, Skrynnikov NR. What Drives 15N Spin Relaxation in Disordered Proteins? Combined NMR/MD Study of the H4 Histone Tail. Biophys J 2018; 115:2348-2367. [PMID: 30527335 DOI: 10.1016/j.bpj.2018.11.017] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2018] [Revised: 11/07/2018] [Accepted: 11/12/2018] [Indexed: 12/26/2022] Open
Abstract
Backbone (15N) NMR relaxation is one of the main sources of information on dynamics of disordered proteins. Yet, we do not know very well what drives 15N relaxation in such systems, i.e., how different forms of motion contribute to the measurable relaxation rates. To address this problem, we have investigated, both experimentally and via molecular dynamics simulations, the dynamics of a 26-residue peptide imitating the N-terminal portion of the histone protein H4. One part of the peptide was found to be fully flexible, whereas the other part features some transient structure (a hairpin stabilized by hydrogen bonds). The following motional modes proved relevant for 15N relaxation. 1) Sub-picosecond librations attenuate relaxation rates according to S2 ∼0.85-0.90. 2) Axial peptide-plane fluctuations along a stretch of the peptide chain contribute to relaxation-active dynamics on a fast timescale (from tens to hundreds of picoseconds). 3) φ/ψ backbone jumps contribute to relaxation-active dynamics on both fast (from tens to hundreds of picoseconds) and slow (from hundreds of picoseconds to a nanosecond) timescales. The major contribution is from polyproline II (PPII) ↔ β transitions in the Ramachandran space; in the case of glycine residues, the major contribution is from PPII ↔ (β) ↔ rPPII transitions, in which rPPII is the mirror-image (right-handed) version of the PPII geometry, whereas β geometry plays the role of an intermediate state. 4) Reorientational motion of certain (sufficiently long-lived) elements of transient structure, i.e., rotational tumbling, contributes to slow relaxation-active dynamics on ∼1-ns timescale (however, it is difficult to isolate this contribution). In conclusion, recent advances in the area of force-field development have made it possible to obtain viable Molecular Dynamics models of protein disorder. After careful validation against the experimental relaxation data, these models can provide a valuable insight into mechanistic origins of spin relaxation in disordered peptides and proteins.
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Affiliation(s)
- Kerstin Kämpf
- Laboratory of Biomolecular NMR, St. Petersburg State University, St. Petersburg, Russia
| | - Sergei A Izmailov
- Laboratory of Biomolecular NMR, St. Petersburg State University, St. Petersburg, Russia
| | - Sevastyan O Rabdano
- Laboratory of Biomolecular NMR, St. Petersburg State University, St. Petersburg, Russia
| | - Adam T Groves
- Department of Chemistry, Purdue University, West Lafayette, Indiana
| | - Ivan S Podkorytov
- Laboratory of Biomolecular NMR, St. Petersburg State University, St. Petersburg, Russia
| | - Nikolai R Skrynnikov
- Laboratory of Biomolecular NMR, St. Petersburg State University, St. Petersburg, Russia; Department of Chemistry, Purdue University, West Lafayette, Indiana.
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37
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Zeng J, Huang Z. From Levinthal's Paradox to the Effects of Cell Environmental Perturbation on Protein Folding. Curr Med Chem 2018; 26:7537-7554. [PMID: 30332937 DOI: 10.2174/0929867325666181017160857] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2018] [Revised: 07/04/2018] [Accepted: 08/03/2018] [Indexed: 01/01/2023]
Abstract
BACKGROUND The rapidly increasing number of known protein sequences calls for more efficient methods to predict the Three-Dimensional (3D) structures of proteins, thus providing basic knowledge for rational drug design. Understanding the folding mechanism of proteins is valuable for predicting their 3D structures and for designing proteins with new functions and medicinal applications. Levinthal's paradox is that although the astronomical number of conformations possible even for proteins as small as 100 residues cannot be fully sampled, proteins in nature normally fold into the native state within timescales ranging from microseconds to hours. These conflicting results reveal that there are factors in organisms that can assist in protein folding. METHODS In this paper, we selected a crowded cell-like environment and temperature, and the top three Posttranslational Modifications (PTMs) as examples to show that Levinthal's paradox does not reflect the folding mechanism of proteins. We then revealed the effects of these factors on protein folding. RESULTS The results summarized in this review indicate that a crowded cell-like environment, temperature, and the top three PTMs reshape the Free Energy Landscapes (FELs) of proteins, thereby regulating the folding process. The balance between entropy and enthalpy is the key to understanding the effect of the crowded cell-like environment and PTMs on protein folding. In addition, the stability/flexibility of proteins is regulated by temperature. CONCLUSION This paper concludes that the cellular environment could directly intervene in protein folding. The long-term interactions of the cellular environment and sequence evolution may enable proteins to fold efficiently. Therefore, to correctly understand the folding mechanism of proteins, the effect of the cellular environment on protein folding should be considered.
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Affiliation(s)
- Juan Zeng
- Guangdong Provincial Key Laboratory of Medical Molecular Diagnostics, Dongguan Scientific Research Center, Guangdong Medical University, Dongguan, Guangdong 523808, China.,Laboratory of Computational Chemistry and Drug Design, Laboratory of Chemical Genomics, Peking University Shenzhen Graduate School, Shenzhen 518055, China
| | - Zunnan Huang
- Guangdong Provincial Key Laboratory of Medical Molecular Diagnostics, Dongguan Scientific Research Center, Guangdong Medical University, Dongguan, Guangdong 523808, China
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38
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Krajewski WA. Effects of DNA Superhelical Stress on the Stability of H2B-Ubiquitylated Nucleosomes. J Mol Biol 2018; 430:5002-5014. [PMID: 30267746 DOI: 10.1016/j.jmb.2018.09.014] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2018] [Revised: 08/27/2018] [Accepted: 09/21/2018] [Indexed: 01/31/2023]
Abstract
On the nucleosome level, histone posttranslational modifications function mainly as the regulatory signals; in addition, some posttranslational modifications can enhance nucleosome stochastic folding, which is restricted in "canonic" nucleosomes. Recently, it has been shown in vitro that symmetric or asymmetric nucleosome ubiquitylation at H2BK34 (and H2BK120, to a lesser extent) can destabilize one of the nucleosomal H2A-H2B dimers and promote nucleosome conversion to a hexasome particle [Krajewski et al. (2018). Nucleic Acids Res., 46, 7631-7642]. Such lability of H2Bub nucleosomes raises a question of whether they could accommodate transient changes in DNA torsional tensions, which are generated by virtually any process that manipulates DNA strands. Using positively or negatively supercoiled DNA minicircles and homogeneously-modified H2Bub histones, we have found that DNA topology could strongly and selectively affect nucleosome stability depending on its ubiquitylation state (here the term "nucleosome stability" means the nucleosome property to maintain its structural integrity and dynamics characteristic to "canonic" nucleosomes). The results point to a role for H2B ubiquitylation in amplifying or mitigating the effects of a DNA torque on the nucleosome stability and dynamics.
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Affiliation(s)
- Wladyslaw A Krajewski
- N.K. Koltsov Institute of Developmental Biology, Russian Academy of Sciences, Vavilova str. 26, Moscow 119334, Russia.
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39
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Watanabe S, Mishima Y, Shimizu M, Suetake I, Takada S. Interactions of HP1 Bound to H3K9me3 Dinucleosome by Molecular Simulations and Biochemical Assays. Biophys J 2018; 114:2336-2351. [PMID: 29685391 PMCID: PMC6129468 DOI: 10.1016/j.bpj.2018.03.025] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2017] [Revised: 02/27/2018] [Accepted: 03/26/2018] [Indexed: 01/01/2023] Open
Abstract
Heterochromatin protein 1 (HP1), associated with heterochromatin formation, recognizes an epigenetically repressive marker, trimethylated lysine 9 in histone H3 (H3K9me3), and generally contributes to long-term silencing. How HP1 induces heterochromatin is not fully understood. Recent experiments suggested that not one, but two nucleosomes provide a platform for this recognition. Integrating previous and new biochemical assays with computational modeling, we provide near-atomic structural models for HP1 binding to the dinucleosomes. We found that the dimeric HP1α tends to bind two H3K9me3s that are in adjacent nucleosomes, thus bridging two nucleosomes. We identified, to our knowledge, a novel DNA binding motif in the hinge region that is specific to HP1α and is essential for recognizing the H3K9me3 sites of two nucleosomes. An HP1 isoform, HP1γ, does not easily bridge two nucleosomes in extended conformations because of the absence of the above binding motif and its shorter hinge region. We propose a molecular mechanism for chromatin structural changes caused by HP1.
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Affiliation(s)
- Shuhei Watanabe
- Department of Biophysics, Graduate School of Science, Kyoto University, Kitashirakawa, Sakyo, Kyoto, Japan
| | - Yuichi Mishima
- Institute for Protein Research, Osaka University, Suita, Osaka, Japan
| | - Masahiro Shimizu
- Department of Biophysics, Graduate School of Science, Kyoto University, Kitashirakawa, Sakyo, Kyoto, Japan
| | - Isao Suetake
- Institute for Protein Research, Osaka University, Suita, Osaka, Japan; College of Nutrition, Koshien University, Takarazuka, Japan.
| | - Shoji Takada
- Department of Biophysics, Graduate School of Science, Kyoto University, Kitashirakawa, Sakyo, Kyoto, Japan.
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40
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Darling AL, Uversky VN. Intrinsic Disorder and Posttranslational Modifications: The Darker Side of the Biological Dark Matter. Front Genet 2018; 9:158. [PMID: 29780404 PMCID: PMC5945825 DOI: 10.3389/fgene.2018.00158] [Citation(s) in RCA: 154] [Impact Index Per Article: 25.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2018] [Accepted: 04/17/2018] [Indexed: 01/05/2023] Open
Abstract
Intrinsically disordered proteins (IDPs) and intrinsically disordered protein regions (IDPRs) are functional proteins and domains that devoid stable secondary and/or tertiary structure. IDPs/IDPRs are abundantly present in various proteomes, where they are involved in regulation, signaling, and control, thereby serving as crucial regulators of various cellular processes. Various mechanisms are utilized to tightly regulate and modulate biological functions, structural properties, cellular levels, and localization of these important controllers. Among these regulatory mechanisms are precisely controlled degradation and different posttranslational modifications (PTMs). Many normal cellular processes are associated with the presence of the right amounts of precisely activated IDPs at right places and in right time. However, wrecked regulation of IDPs/IDPRs might be associated with various human maladies, ranging from cancer and neurodegeneration to cardiovascular disease and diabetes. Pathogenic transformations of IDPs/IDPRs are often triggered by altered PTMs. This review considers some of the aspects of IDPs/IDPRs and their normal and aberrant regulation by PTMs.
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Affiliation(s)
- April L Darling
- Department of Molecular Medicine, USF Health Byrd Alzheimer's Institute, Morsani College of Medicine, University of South Florida, Tampa, FL, United States
| | - Vladimir N Uversky
- Department of Molecular Medicine, USF Health Byrd Alzheimer's Institute, Morsani College of Medicine, University of South Florida, Tampa, FL, United States.,Laboratory of New Methods in Biology, Institute for Biological Instrumentation, Russian Academy of Sciences, Pushchino, Russia
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41
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Kono H, Sakuraba S, Ishida H. Free energy profiles for unwrapping the outer superhelical turn of nucleosomal DNA. PLoS Comput Biol 2018; 14:e1006024. [PMID: 29505570 PMCID: PMC5854429 DOI: 10.1371/journal.pcbi.1006024] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2017] [Revised: 03/15/2018] [Accepted: 02/01/2018] [Indexed: 11/19/2022] Open
Abstract
The eukaryotic genome is packaged into a nucleus in the form of chromatin. The fundamental structural unit of chromatin is a protein-DNA complex, the nucleosome, where 146 or 147 base pairs of DNA wrap 1.75 times around a histone core. To function in cellular processes, however, nucleosomal DNA must be unwrapped. Although this unwrapping has been experimentally investigated, details of the process at an atomic level are not yet well understood. Here, we used molecular dynamics simulation with an enhanced sampling method to calculate the free energy profiles for unwrapping the outer superhelical turn of nucleosomal DNA. A free energy change of about 11.5 kcal/mol for the unwrapping agrees well with values obtained in single molecule experiments. This simulation revealed a variety of conformational states, indicating there are many potential paths to outer superhelicdal turn unwrapping, but the dominant path is likely asymmetric. At one end of the DNA, the first five bps unwrap, after which a second five bps unwrap at the same end with no increase in free energy. The unwrapping then starts at the other end of the DNA, where 10 bps are unwrapped. During further unwrapping of 15 bps, the unwrapping advances at one of the ends, after which the other end of the DNA unwraps to complete the unwrapping of the outer superhelical turn. These results provide insight into the construction, disruption, and repositioning of nucleosomes, which are continuously ongoing during cellular processes.
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Affiliation(s)
- Hidetoshi Kono
- Molecular Modeling and Simulation Group, Department of Quantum Beam Life Science, National Institutes for Quantum and Radiological Science and Technology, Umemidai, Kizugawa, Kyoto, Japan
- * E-mail:
| | - Shun Sakuraba
- Graduate School of Frontier Sciences, The University of Tokyo, Kashiwanoha, Kashiwa, Chiba, Japan
| | - Hisashi Ishida
- Molecular Modeling and Simulation Group, Department of Quantum Beam Life Science, National Institutes for Quantum and Radiological Science and Technology, Umemidai, Kizugawa, Kyoto, Japan
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42
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Chakraborty K, Loverde SM. Asymmetric breathing motions of nucleosomal DNA and the role of histone tails. J Chem Phys 2017; 147:065101. [DOI: 10.1063/1.4997573] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
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43
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Bui M, Pitman M, Nuccio A, Roque S, Donlin-Asp PG, Nita-Lazar A, Papoian GA, Dalal Y. Internal modifications in the CENP-A nucleosome modulate centromeric dynamics. Epigenetics Chromatin 2017; 10:17. [PMID: 28396698 PMCID: PMC5379712 DOI: 10.1186/s13072-017-0124-6] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2017] [Accepted: 03/23/2017] [Indexed: 12/21/2022] Open
Abstract
Background Posttranslational modifications of core histones are correlated with changes in transcriptional status, chromatin fiber folding, and nucleosome dynamics. However, within the centromere-specific histone H3 variant CENP-A, few modifications have been reported, and their functions remain largely unexplored. In this multidisciplinary report, we utilize in silico computational and in vivo approaches to dissect lysine 124 of human CENP-A, which was previously reported to be acetylated in advance of replication. Results Computational modeling demonstrates that acetylation of K124 causes tightening of the histone core and hinders accessibility to its C-terminus, which in turn diminishes CENP-C binding. Additionally, CENP-A K124ac/H4 K79ac containing nucleosomes are prone to DNA sliding. In vivo experiments using a CENP-A acetyl or unacetylatable mimic (K124Q and K124A, respectively) reveal alterations in CENP-C levels and a modest increase in mitotic errors. Furthermore, mutation of K124 results in alterations in centromeric replication timing. Purification of native CENP-A proteins followed by mass spectrometry analysis reveals that while CENP-A K124 is acetylated at G1/S, it switches to monomethylation during early S and mid-S phases. Finally, we provide evidence implicating the histone acetyltransferase (HAT) p300 in this cycle. Conclusions Taken together, our data suggest that cyclical modifications within the CENP-A nucleosome contribute to the binding of key kinetochore proteins, the integrity of mitosis, and centromeric replication. These data support the paradigm that modifications in histone variants can influence key biological processes. Electronic supplementary material The online version of this article (doi:10.1186/s13072-017-0124-6) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Minh Bui
- Chromatin Structure and Epigenetic Mechanisms Unit, Laboratory of Receptor Biology and Gene Expression, CCR, NCI, NIH, Bethesda, MD 20892 USA
| | - Mary Pitman
- Chromatin Structure and Epigenetic Mechanisms Unit, Laboratory of Receptor Biology and Gene Expression, CCR, NCI, NIH, Bethesda, MD 20892 USA.,Department of Biophysics, University of Maryland, College Park, MD USA
| | - Arthur Nuccio
- Cellular Networks Proteomics Unit, Laboratory of Systems Biology, NIAID, NIH, Bethesda, MD 20892 USA
| | - Serene Roque
- Chromatin Structure and Epigenetic Mechanisms Unit, Laboratory of Receptor Biology and Gene Expression, CCR, NCI, NIH, Bethesda, MD 20892 USA
| | - Paul Gregory Donlin-Asp
- Chromatin Structure and Epigenetic Mechanisms Unit, Laboratory of Receptor Biology and Gene Expression, CCR, NCI, NIH, Bethesda, MD 20892 USA.,Department of Cell Biology, Emory University, Atlanta, GA USA
| | - Aleksandra Nita-Lazar
- Cellular Networks Proteomics Unit, Laboratory of Systems Biology, NIAID, NIH, Bethesda, MD 20892 USA
| | - Garegin A Papoian
- Department of Biophysics, University of Maryland, College Park, MD USA
| | - Yamini Dalal
- Chromatin Structure and Epigenetic Mechanisms Unit, Laboratory of Receptor Biology and Gene Expression, CCR, NCI, NIH, Bethesda, MD 20892 USA
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44
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Fu I, Cai Y, Geacintov NE, Zhang Y, Broyde S. Nucleosome Histone Tail Conformation and Dynamics: Impacts of Lysine Acetylation and a Nearby Minor Groove Benzo[a]pyrene-Derived Lesion. Biochemistry 2017; 56:1963-1973. [PMID: 28304160 DOI: 10.1021/acs.biochem.6b01208] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Histone tails in nucleosomes play critical roles in regulation of many biological processes, including chromatin compaction, transcription, and DNA repair. Moreover, post-translational modifications, notably lysine acetylation, are crucial to these functions. While the tails have been intensively studied, how the structures and dynamics of tails are impacted by the presence of a nearby bulky DNA lesion is a frontier research area, and how these properties are impacted by tail lysine acetylation remains unexplored. To obtain molecular insight, we have utilized all atom 3 μs molecular dynamics simulations of nucleosome core particles (NCPs) to determine the impact of a nearby DNA lesion, 10S (+)-trans-anti-B[a]P-N2-dG-the major adduct derived from the procarcinogen benzo[a]pyrene-on H2B tail behavior in unacetylated and acetylated states. We similarly studied lesion-free NCPs to investigate the normal properties of the H2B tail in both states. In the lesion-free NCPs, charge neutralization upon lysine acetylation causes release of the tail from the DNA. When the lesion is present, it stably engulfs part of the nearby tail, impairing the interactions between DNA and tail. With the tail in an acetylated state, the lesion still interacts with part of it, although unstably. The lesion's partial entrapment of the tail should hinder the tail from interacting with other nucleosomes, and other proteins such as acetylases, deacetylases, and acetyl-lysine binding proteins, and thus disrupt critical tail-governed processes. Hence, the lesion would impede tail functions modulated by acetylation or deacetylation, causing aberrant chromatin structures and impaired biological transactions such as transcription and DNA repair.
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Affiliation(s)
| | | | | | - Yingkai Zhang
- NYU-ECNU Center for Computational Chemistry at NYU Shanghai , Shanghai 200062, China
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45
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Chen Q, Yang R, Korolev N, Liu CF, Nordenskiöld L. Regulation of Nucleosome Stacking and Chromatin Compaction by the Histone H4 N-Terminal Tail-H2A Acidic Patch Interaction. J Mol Biol 2017; 429:2075-2092. [PMID: 28322915 DOI: 10.1016/j.jmb.2017.03.016] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2016] [Revised: 03/13/2017] [Accepted: 03/13/2017] [Indexed: 01/15/2023]
Abstract
Chromatin folding and dynamics are critically dependent on nucleosome-nucleosome interactions with important contributions from internucleosome binding of the histone H4 N-terminal tail K16-R23 domain to the surface of the H2A/H2B dimer. The H4 Lys16 plays a pivotal role in this regard. Using in vitro reconstituted 12-mer nucleosome arrays, we have investigated the mechanism of the H4 N-terminal tail in maintaining nucleosome-nucleosome stacking and mediating intra- and inter-array chromatin compaction, with emphasis on the role of K16 and the positive charge region, R17-R23. Analytical ultracentrifugation sedimentation velocity experiments and precipitation assays were employed to analyze effects on chromatin folding and self-association, respectively. Effects on chromatin folding caused by various mutations and modifications at position K16 in the H4 histone were studied. Additionally, using charge-quenching mutations, we characterized the importance of the interaction of the residues within the H4 positive charge region R17-R23 with the H2A acidic patch of the adjacent nucleosome. Furthermore, crosslinking experiments were conducted to establish the proximity of the basic tail region to the acidic patch. Our data indicate that the positive charge and length of the side chain of H4 K16 are important for its access to the adjacent nucleosome in the process of nucleosome-nucleosome stacking and array folding. The location and orientation of the H4 R17-R23 domain on the H2A/H2B dimer surface of the neighboring nucleosome core particle (NCP) in the compacted chromatin fiber were established. The dominance of electrostatic interactions in maintaining intra-array interaction was demonstrated.
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Affiliation(s)
- Qinming Chen
- School of Biological Sciences, College of Science, Nanyang Technological University, 60, Nanyang Drive, 637551, Singapore
| | - Renliang Yang
- School of Biological Sciences, College of Science, Nanyang Technological University, 60, Nanyang Drive, 637551, Singapore
| | - Nikolay Korolev
- School of Biological Sciences, College of Science, Nanyang Technological University, 60, Nanyang Drive, 637551, Singapore
| | - Chuan Fa Liu
- School of Biological Sciences, College of Science, Nanyang Technological University, 60, Nanyang Drive, 637551, Singapore
| | - Lars Nordenskiöld
- School of Biological Sciences, College of Science, Nanyang Technological University, 60, Nanyang Drive, 637551, Singapore.
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46
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Zhang R, Erler J, Langowski J. Histone Acetylation Regulates Chromatin Accessibility: Role of H4K16 in Inter-nucleosome Interaction. Biophys J 2017; 112:450-459. [PMID: 27931745 PMCID: PMC5300776 DOI: 10.1016/j.bpj.2016.11.015] [Citation(s) in RCA: 92] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2016] [Revised: 09/30/2016] [Accepted: 11/14/2016] [Indexed: 12/17/2022] Open
Abstract
The N-terminal tail of histone H4 is an indispensable mediator for inter-nucleosome interaction, which is required for chromatin fiber condensation. H4K16 acetylation (H4K16Ac) activates gene transcription by influencing both chromatin structure and interplay with nonhistone proteins. To understand the influence of H4K16Ac on inter-nucleosome interaction, we performed a simulation study for the H4 tail in the context of two nucleosomes in neighboring unit cells in the crystal structure. The binding conformation of H4 tail with/without K16Ac was sampled by replica exchange with solute tempering, and the free energy landscape was explored by metadynamics. The results indicate two important features of H4K16: 1) it is the first button to anchor the H4 tail on the adjacent nucleosome; and 2) it is the only acetylation site interacting with the acidic patch. H4K16Ac disrupts the electrostatic interactions of K16, weakens H4 tail-acidic patch binding, and significantly increases H4 tail conformation diversity. Our study suggests that H4K16Ac directly reduces the inter-nucleosome interaction mediated by the H4 tail, which might further encourage the binding of nonhistone proteins on the acidic patch.
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Affiliation(s)
- Ruihan Zhang
- Division Biophysics of Macromolecules, German Cancer Research Center, Heidelberg, Germany
| | - Jochen Erler
- Division Biophysics of Macromolecules, German Cancer Research Center, Heidelberg, Germany
| | - Jörg Langowski
- Division Biophysics of Macromolecules, German Cancer Research Center, Heidelberg, Germany.
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47
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Chang L, Takada S. Histone acetylation dependent energy landscapes in tri-nucleosome revealed by residue-resolved molecular simulations. Sci Rep 2016; 6:34441. [PMID: 27698366 PMCID: PMC5048180 DOI: 10.1038/srep34441] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2016] [Accepted: 09/13/2016] [Indexed: 12/15/2022] Open
Abstract
Histone tail acetylation is a key epigenetic marker that tends to open chromatin folding and activate transcription. Despite intensive studies, precise roles of individual lysine acetylation in chromatin folding have only been poorly understood. Here, we revealed structural dynamics of tri-nucleosomes with several histone tail acetylation states and analyzed histone tail interactions with DNA by performing molecular simulations at an unprecedentedly high resolution. We found versatile acetylation-dependent landscapes of tri-nucleosome. The H4 and H2A tail acetylation reduced the contact between the first and third nucleosomes mediated by the histone tails. The H3 tail acetylation reduced its interaction with neighboring linker DNAs resulting in increase of the distance between consecutive nucleosomes. Notably, two copies of the same histone in a single nucleosome have markedly asymmetric interactions with DNAs, suggesting specific pattern of nucleosome docking albeit high inherent flexibility. Estimated transcription factor accessibility was significantly high for the H4 tail acetylated structures.
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Affiliation(s)
- Le Chang
- Department of Biophysics, Graduate School of Science, Kyoto University, Kitashirakawa, Sakyo 606-8502, Kyoto Japan
| | - Shoji Takada
- Department of Biophysics, Graduate School of Science, Kyoto University, Kitashirakawa, Sakyo 606-8502, Kyoto Japan
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48
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Zhang B, Zheng W, Papoian GA, Wolynes PG. Exploring the Free Energy Landscape of Nucleosomes. J Am Chem Soc 2016; 138:8126-33. [DOI: 10.1021/jacs.6b02893] [Citation(s) in RCA: 93] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Affiliation(s)
| | | | - Garegin A. Papoian
- Department
of Chemistry and Biochemistry and Institute for Physical Science and
Technology, University of Maryland, College Park, Maryland 20742, United States
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49
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Dans PD, Walther J, Gómez H, Orozco M. Multiscale simulation of DNA. Curr Opin Struct Biol 2016; 37:29-45. [DOI: 10.1016/j.sbi.2015.11.011] [Citation(s) in RCA: 99] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2015] [Revised: 11/23/2015] [Accepted: 11/25/2015] [Indexed: 01/05/2023]
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50
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Shearing of the CENP-A dimerization interface mediates plasticity in the octameric centromeric nucleosome. Sci Rep 2015; 5:17038. [PMID: 26602160 PMCID: PMC4658507 DOI: 10.1038/srep17038] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2015] [Accepted: 10/07/2015] [Indexed: 01/01/2023] Open
Abstract
The centromeric nucleosome is a key epigenetic determinant of centromere identity and function. Consequently, deciphering how CENP-A containing nucleosomes contribute structurally to centromere function is a fundamental question in chromosome biology. Here, we performed microsecond timescale all-atom molecular dynamics (MD) simulations of CENP-A and H3 nucleosomes, and report that the octameric CENP-A core particles and nucleosomes display different dynamics from their canonical H3-containing counterparts. The most significant motion observed is within key interactions at the heart of the CENP-A octameric core, wherein shearing of contacts within the CENP-A:CENP-A' dimerization interface results in a weaker four helix bundle, and an extrusion of 10-30 bp of DNA near the pseudo-dyad. Coupled to other local and global fluctuations, the CENP-A nucleosome occupies a more rugged free energy landscape than the canonical H3 nucleosome. Taken together, our data suggest that CENP-A encodes enhanced distortability to the octameric nucleosome, which may allow for enhanced flexing of the histone core in vivo.
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