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Li X, Chou T. Stochastic nucleosome disassembly mediated by remodelers and histone fragmentation. J Chem Phys 2023; 159:204107. [PMID: 38010331 PMCID: PMC10684310 DOI: 10.1063/5.0165136] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2023] [Accepted: 10/14/2023] [Indexed: 11/29/2023] Open
Abstract
We construct and analyze monomeric and multimeric models of the stochastic disassembly of a single nucleosome. Our monomeric model predicts the time needed for a number of histone-DNA contacts to spontaneously break, leading to dissociation of a non-fragmented histone from DNA. The dissociation process can be facilitated by DNA binding proteins or processing molecular motors that compete with histones for histone-DNA contact sites. Eigenvalue analysis of the corresponding master equation allows us to evaluate histone detachment times under both spontaneous detachment and protein-facilitated processes. We find that competitive DNA binding of remodeling proteins can significantly reduce the typical detachment time but only if these remodelers have DNA-binding affinities comparable to those of histone-DNA contact sites. In the presence of processive motors, the histone detachment rate is shown to be proportional to the product of the histone single-bond dissociation constant and the speed of motor protein procession. Our simple intact-histone model is then extended to allow for multimeric nucleosome kinetics that reveal additional pathways of disassembly. In addition to a dependence of complete disassembly times on subunit-DNA contact energies, we show how histone subunit concentrations in bulk solutions can mediate the disassembly process by rescuing partially disassembled nucleosomes. Moreover, our kinetic model predicts that remodeler binding can also bias certain pathways of nucleosome disassembly, with higher remodeler binding rates favoring intact-histone detachment.
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Affiliation(s)
- Xiangting Li
- Department of Computational Medicine, University of California, Los Angeles, California 90095-1766, USA
| | - Tom Chou
- Author to whom correspondence should be addressed:
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2
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Li X, Chou T. Stochastic nucleosome disassembly mediated by remodelers and histone fragmentation. ARXIV 2023:arXiv:2309.02736v1. [PMID: 37731652 PMCID: PMC10508821] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 09/22/2023]
Abstract
We construct and analyze monomeric and multimeric models of the stochastic disassembly of a single nucleosome. Our monomeric model predicts the time needed for a number of histone-DNA contacts to spontaneously break, leading to dissociation of a non-fragmented histone from DNA. The dissociation process can be facilitated by DNA binding proteins or processing molecular motors that compete with histones for histone-DNA contact sites. Eigenvalue analysis of the corresponding master equation allows us to evaluate histone detachment times under both spontaneous detachment and protein-facilitated processes. We find that competitive DNA binding of remodeling proteins can significantly reduce the typical detachment time but only if these remodelers have DNA-binding affinities comparable to those of histone-DNA contact sites. In the presence of processive motors, the histone detachment rate is shown to be proportional to the product of the histone single-bond dissociation constant and the speed of motor protein procession. Our simple intact-histone model is then extended to allow for multimeric nucleosome kinetics that reveal additional pathways of disassembly. In addition to a dependence of complete disassembly times on subunit-DNA contact energies, we show how histone subunit concentrations in bulk solution can mediate the disassembly process by rescuing partially disassembled nucleosomes. Moreover, our kinetic model predicts that remodeler binding can also bias certain pathways of nucleosome disassembly, with higher remodeler binding rates favoring intact-histone detachment.
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Affiliation(s)
- Xiangting Li
- Department of Computational Medicine, University of California, Los Angeles, CA 90095-1766 USA
| | - Tom Chou
- Department of Computational Medicine, University of California, Los Angeles, CA 90095-1766 USA
- Department of Mathematics, University of California, Los Angeles, CA 90095-1555 USA
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3
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Abstract
Nearly three-fourths of all eukaryotic DNA is occupied by nucleosomes, protein-DNA complexes comprising octameric histone core proteins and ∼150 base pairs of DNA. In addition to acting as a DNA compaction vehicle, the dynamics of nucleosomes regulate the DNA site accessibility for the nonhistone proteins, thereby controlling regulatory processes involved in determining the cell identity and cell fate. Here, we propose an analytical framework to analyze the role of nucleosome dynamics on the target search process of transcription factors through a simple discrete-state stochastic description of the search process. By considering the experimentally determined kinetic rates associated with protein and nucleosome dynamics as the only inputs, we estimate the target search time of a protein via first-passage probability calculations separately during nucleosome breathing and sliding dynamics. Although both the nucleosome dynamics permit transient access to the DNA sites that are otherwise occluded by the histone proteins, our result suggests substantial differences between the protein search mechanism on a nucleosome performing breathing and sliding dynamics. Furthermore, we identify the molecular factors that influence the search efficiency and demonstrate how these factors together portray a highly dynamic landscape of gene regulation. Our analytical results are validated using extensive Monte Carlo simulations.
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Affiliation(s)
- Sujeet Kumar Mishra
- School of Computational and Integrative Sciences, Jawaharlal Nehru University, New Delhi 110067, India
| | - Arnab Bhattacherjee
- School of Computational and Integrative Sciences, Jawaharlal Nehru University, New Delhi 110067, India
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Kumar Mishra S, Bhattacherjee A. Understanding the Target Search by Multiple Transcription Factors on Nucleosomal DNA. Chemphyschem 2023; 24:e202200644. [PMID: 36602094 DOI: 10.1002/cphc.202200644] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2022] [Revised: 01/04/2023] [Accepted: 01/05/2023] [Indexed: 01/06/2023]
Abstract
The association of multiple Transcription Factors (TFs) in the cis-regulatory region is imperative for developmental changes in eukaryotes. The underlying process is exceedingly complex, and it is not at all clear what orchestrates the overall search process by multiple TFs. In this study, by developing a theoretical model based on a discrete-state stochastic approach, we investigated the target search mechanism of multiple TFs on nucleosomal DNA. Experimental kinetic rate constants of different TFs are taken as input to estimate the Mean-First-Passage time to recognize the binding motifs by two TFs on a dynamic nucleosome model. The theory systematically analyzes when the TFs search their binding motifs hierarchically and when simultaneously by proceeding via the formation of a protein-protein complex. Our results, validated by extensive Monte Carlo simulations, elucidate the molecular basis of the complex target search phenomenon of multiple TFs on nucleosomal DNA.
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Affiliation(s)
- Sujeet Kumar Mishra
- School of Computational and Integrative Sciences, Jawaharlal Nehru University, New Delhi, India
| | - Arnab Bhattacherjee
- School of Computational and Integrative Sciences, Jawaharlal Nehru University, New Delhi, India
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Mondal A, Mishra SK, Bhattacherjee A. Nucleosome breathing facilitates cooperative binding of pluripotency factors Sox2 and Oct4 to DNA. Biophys J 2022; 121:4526-4542. [PMID: 36321206 PMCID: PMC9748375 DOI: 10.1016/j.bpj.2022.10.039] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2022] [Revised: 09/08/2022] [Accepted: 10/26/2022] [Indexed: 12/15/2022] Open
Abstract
Critical lineage commitment events are staged by multiple transcription factors (TFs) binding to their cognate motifs, often positioned at nucleosome-enriched regions of chromatin. The underlying mechanism remains elusive due to difficulty in disentangling the heterogeneity in chromatin states. Using a novel coarse-grained model and molecular dynamics simulations, here we probe the association of Sox2 and Oct4 proteins that show clustered binding at the entry-exit region of a nucleosome. The model captures the conformational heterogeneity of nucleosome breathing dynamics that features repeated wrap-unwrap transitions of a DNA segment from one end of the nucleosome. During the dynamics, DNA forms bulges that diffuse stochastically and may regulate the target search dynamics of a protein by nonspecifically interacting with it. The overall search kinetics of the TF pair follows a "dissociation-compensated-association" mechanism, where Oct4 binding is facilitated by the association of Sox2. The cooperativity stems from a change in entropy caused by an alteration in the nucleosome dynamics upon TF binding. The binding pattern is consistent with a live-cell single-particle tracking experiment, suggesting the mechanism observed for clustered binding of a TF pair, which is a hallmark of cis-regulatory elements, has broader implications in understanding gene regulation in a complex chromatin environment.
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Affiliation(s)
- Anupam Mondal
- School of Computational and Integrative Sciences, Jawaharlal Nehru University, New Delhi, India
| | - Sujeet Kumar Mishra
- School of Computational and Integrative Sciences, Jawaharlal Nehru University, New Delhi, India
| | - Arnab Bhattacherjee
- School of Computational and Integrative Sciences, Jawaharlal Nehru University, New Delhi, India.
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Zuiddam M, Shakiba B, Schiessel H. Multiplexing mechanical and translational cues on genes. Biophys J 2022; 121:4311-4324. [PMID: 36230003 PMCID: PMC9703045 DOI: 10.1016/j.bpj.2022.10.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2022] [Revised: 07/06/2022] [Accepted: 10/07/2022] [Indexed: 12/14/2022] Open
Abstract
The genetic code gives precise instructions on how to translate codons into amino acids. Due to the degeneracy of the genetic code-18 out of 20 amino acids are encoded for by more than one codon-more information can be stored in a basepair sequence. Indeed, various types of additional information have been discussed in the literature, e.g., the positioning of nucleosomes along eukaryotic genomes and the modulation of the translating efficiency in ribosomes to influence cotranslational protein folding. The purpose of this study is to show that it is indeed possible to carry more than one additional layer of information on top of a gene. In particular, we show how much translation efficiency and nucleosome positioning can be adjusted simultaneously without changing the encoded protein. We achieve this by mapping genes on weighted graphs that contain all synonymous genes, and then finding shortest paths through these graphs. This enables us, for example, to readjust the disrupted translational efficiency profile after a gene has been introduced from one organism (e.g., human) into another (e.g., yeast) without greatly changing the nucleosome landscape intrinsically encoded by the DNA molecule.
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Affiliation(s)
- Martijn Zuiddam
- Institute Lorentz for Theoretical Physics, Leiden University, Leiden, the Netherlands
| | - Bahareh Shakiba
- Institute Lorentz for Theoretical Physics, Leiden University, Leiden, the Netherlands
| | - Helmut Schiessel
- Cluster of Excellence Physics of Life, TU Dresden, Dresden, Germany.
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Konrad SF, Vanderlinden W, Lipfert J. Quantifying epigenetic modulation of nucleosome breathing by high-throughput AFM imaging. Biophys J 2022; 121:841-851. [PMID: 35065917 PMCID: PMC8943691 DOI: 10.1016/j.bpj.2022.01.014] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2021] [Revised: 11/30/2021] [Accepted: 01/19/2022] [Indexed: 11/30/2022] Open
Abstract
Nucleosomes are the basic units of chromatin and critical for storage and expression of eukaryotic genomes. Chromatin accessibility and gene readout are heavily regulated by epigenetic marks, in which post-translational modifications of histones play a key role. However, the mode of action and the structural implications at the single-molecule level of nucleosomes is still poorly understood. Here we apply a high-throughput atomic force microscopy imaging and analysis pipeline to investigate the conformational landscape of the nucleosome variants three additional methyl groups at lysine 36 of histone H3 (H3K36me3), phosphorylation of H3 histones at serine 10 (H3S10phos), and acetylation of H4 histones at lysines 5, 8, 12, and 16 (H4K5/8/12/16ac). Our data set of more than 25,000 nucleosomes reveals nucleosomal unwrapping steps corresponding to 5-bp DNA. We find that H3K36me3 nucleosomes unwrap significantly more than wild-type nucleosomes and additionally unwrap stochastically from both sides, similar to centromere protein A (CENP-A) nucleosomes and in contrast to the highly anticooperative unwrapping of wild-type nucleosomes. Nucleosomes with H3S10phos or H4K5/8/12/16ac modifications show unwrapping populations similar to wild-type nucleosomes and also retain the same level of anticooperativity. Our findings help to put the mode of action of these modifications into context. Although H3K36me3 likely acts partially by directly affecting nucleosome structure on the single-molecule level, H3S10phos and H4K5/8/12/16ac must predominantly act through higher-order processes. Our analysis pipeline is readily applicable to other nucleosome variants and will facilitate future high-resolution studies of the conformational landscape of nucleoprotein complexes.
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Affiliation(s)
- Sebastian F. Konrad
- Department of Physics and Center for NanoScience, LMU Munich, Munich, Germany
| | - Willem Vanderlinden
- Department of Physics and Center for NanoScience, LMU Munich, Munich, Germany
| | - Jan Lipfert
- Department of Physics and Center for NanoScience, LMU Munich, Munich, Germany.
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Mondal A, Mishra SK, Bhattacherjee A. Kinetic origin of nucleosome invasion by pioneer transcription factors. Biophys J 2021; 120:5219-5230. [PMID: 34757077 DOI: 10.1016/j.bpj.2021.10.039] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2020] [Revised: 05/14/2021] [Accepted: 10/27/2021] [Indexed: 01/25/2023] Open
Abstract
Recently, a cryo-electron microscopy study has captured different stages of nucleosome breathing dynamics that show partial unwrapping of DNA from histone core to permit transient access to the DNA sites by transcription factors. In practice, however, only a subset of transcription factors named pioneer factors can invade nucleosomes and bind to specific DNA sites to trigger essential DNA metabolic processes. We propose a discrete-state stochastic model that considers the interplay of nucleosome breathing and protein dynamics explicitly and estimate the mean time to search the target DNA sites. It is found that the molecular principle governing the search process on nucleosome is very different compared to that on naked DNA. The pioneer factors minimize their search times on nucleosomal DNA by compensating their nucleosome association rates by dissociation rates. A fine balance between the two presents a tradeoff between their nuclear mobility and error associated with the search process.
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Affiliation(s)
- Anupam Mondal
- School of Computational and Integrative Sciences, Jawaharlal Nehru University, New Delhi, India
| | - Sujeet Kumar Mishra
- School of Computational and Integrative Sciences, Jawaharlal Nehru University, New Delhi, India; Institute for Theoretical Physics, Heidelberg University, Heidelberg, Germany
| | - Arnab Bhattacherjee
- School of Computational and Integrative Sciences, Jawaharlal Nehru University, New Delhi, India.
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Dohnalová H, Lankaš F. Deciphering the mechanical properties of
B‐DNA
duplex. WIRES COMPUTATIONAL MOLECULAR SCIENCE 2021. [DOI: 10.1002/wcms.1575] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Hana Dohnalová
- Department of Informatics and Chemistry University of Chemistry and Technology Prague Praha 6 Czech Republic
| | - Filip Lankaš
- Department of Informatics and Chemistry University of Chemistry and Technology Prague Praha 6 Czech Republic
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Surprising Twists in Nucleosomal DNA with Implication for Higher-order Folding. J Mol Biol 2021; 433:167121. [PMID: 34192585 DOI: 10.1016/j.jmb.2021.167121] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2020] [Revised: 06/19/2021] [Accepted: 06/21/2021] [Indexed: 11/21/2022]
Abstract
While nucleosomes are dynamic entities that must undergo structural deformations to perform their functions, the general view from available high-resolution structures is a largely static one. Even though numerous examples of twist defects have been documented, the DNA wrapped around the histone core is generally thought to be overtwisted. Analysis of available high-resolution structures from the Protein Data Bank reveals a heterogeneous distribution of twist along the nucleosomal DNA, with clear patterns that are consistent with the literature, and a significant fraction of structures that are undertwisted. The subtle differences in nucleosomal DNA folding, which extend beyond twist, have implications for nucleosome disassembly and modeled higher-order structures. Simulations of oligonucleosome arrays built with undertwisted models behave very differently from those constructed from overtwisted models, in terms of compaction and inter-nucleosome contacts, introducing configurational changes equivalent to those associated with 2-3 base-pair changes in nucleosome spacing. Differences in the nucleosomal DNA pathway, which underlie the way that DNA enters and exits the nucleosome, give rise to different nucleosome-decorated minicircles and affect the topological mix of configurational states.
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Schlick T. Multiscale Genome Organization: Dazzling Subject and Inventive Methods. Biophys J 2020; 118:E1-E3. [PMID: 32305070 PMCID: PMC7161524 DOI: 10.1016/j.bpj.2020.04.007] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2020] [Accepted: 04/10/2020] [Indexed: 01/20/2023] Open
Affiliation(s)
- Tamar Schlick
- Department of Chemistry, Courant Institute of Mathematical Sciences, New York University, New York, New York.
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