1
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Carignano M, Kröger M, Almassalha LM, Agrawal V, Li WS, Pujadas-Liwag EM, Nap RJ, Backman V, Szleifer I. Local Volume Concentration, Packing Domains and Scaling Properties of Chromatin. ARXIV 2024:arXiv:2310.02257v3. [PMID: 38495560 PMCID: PMC10942481] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 03/19/2024]
Abstract
We propose the Self Returning Excluded Volume (SR-EV) model for the structure of chromatin based on stochastic rules and physical interactions. The SR-EV rules of return generate conformationally-defined domains observed by single cell imaging techniques. From nucleosome to chromosome scales, the model captures the overall chromatin organization as a corrugated system, with dense and dilute regions alternating in a manner that resembles the mixing of two disordered bi-continuous phases. This particular organizational topology is a consequence of the multiplicity of interactions and processes occurring in the nuclei, and mimicked by the proposed return rules. Single configuration properties and ensemble averages show a robust agreement between theoretical and experimental results including chromatin volume concentration, contact probability, packing domain identification and size characterization, and packing scaling behavior. Model and experimental results suggest that there is an inherent chromatin organization regardless of the cell character and resistant to an external forcing such as Rad21 degradation.
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Affiliation(s)
- Marcelo Carignano
- Department of Biomedical Engineering, Northwestern University, Evanston, IL 60208, USA
| | - Martin Kröger
- Magnetism and Interface Physics & Computational Polymer Physics, Department of Materials, ETH Zurich, CH-8093 Zurich, Switzerland
| | - Luay Matthew Almassalha
- Department of Gastroenterology and Hepatology, Northwestern Memorial Hospital, Chicago IL 60611, USA
| | - Vasundhara Agrawal
- Department of Biomedical Engineering, Northwestern University, Evanston, IL 60208, USA
| | - Wing Shun Li
- Applied Physics Program, Northwestern, University, Evanston, IL 60208, USA
| | | | - Rikkert J. Nap
- Department of Biomedical Engineering, Northwestern University, Evanston, IL 60208, USA
| | - Vadim Backman
- Department of Biomedical Engineering, Northwestern University, Evanston, IL 60208, USA
| | - Igal Szleifer
- Department of Biomedical Engineering, Northwestern University, Evanston, IL 60208, USA
- Department of Chemistry, Northwestern University, Evanston, IL 60208, USA
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2
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Li Z, Schlick T. Hi-BDiSCO: folding 3D mesoscale genome structures from Hi-C data using brownian dynamics. Nucleic Acids Res 2024; 52:583-599. [PMID: 38015443 PMCID: PMC10810283 DOI: 10.1093/nar/gkad1121] [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: 07/06/2023] [Revised: 10/12/2023] [Accepted: 11/22/2023] [Indexed: 11/29/2023] Open
Abstract
The structure and dynamics of the eukaryotic genome are intimately linked to gene regulation and transcriptional activity. Many chromosome conformation capture experiments like Hi-C have been developed to detect genome-wide contact frequencies and quantify loop/compartment structures for different cellular contexts and time-dependent processes. However, a full understanding of these events requires explicit descriptions of representative chromatin and chromosome configurations. With the exponentially growing amount of data from Hi-C experiments, many methods for deriving 3D structures from contact frequency data have been developed. Yet, most reconstruction methods use polymer models with low resolution to predict overall genome structure. Here we present a Brownian Dynamics (BD) approach termed Hi-BDiSCO for producing 3D genome structures from Hi-C and Micro-C data using our mesoscale-resolution chromatin model based on the Discrete Surface Charge Optimization (DiSCO) model. Our approach integrates reconstruction with chromatin simulations at nucleosome resolution with appropriate biophysical parameters. Following a description of our protocol, we present applications to the NXN, HOXC, HOXA and Fbn2 mouse genes ranging in size from 50 to 100 kb. Such nucleosome-resolution genome structures pave the way for pursuing many biomedical applications related to the epigenomic regulation of chromatin and control of human disease.
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Affiliation(s)
- Zilong Li
- Department of Chemistry, 100 Washington Square East, Silver Building, New York University, New York, NY 10003, USA
- Simons Center for Computational Physical Chemistry, 24 Waverly Place, Silver Building, New York University, New York, NY 10003, USA
| | - Tamar Schlick
- Department of Chemistry, 100 Washington Square East, Silver Building, New York University, New York, NY 10003, USA
- Courant Institute of Mathematical Sciences, New York University, 251 Mercer St., New York, NY 10012, USA
- New York University-East China Normal University Center for Computational Chemistry, New York University Shanghai, Shanghai 200122, China
- Simons Center for Computational Physical Chemistry, 24 Waverly Place, Silver Building, New York University, New York, NY 10003, USA
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3
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Portillo-Ledesma S, Chung S, Hoffman J, Schlick T. Regulation of chromatin architecture by transcription factor binding. eLife 2024; 12:RP91320. [PMID: 38241351 PMCID: PMC10945602 DOI: 10.7554/elife.91320] [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: 01/21/2024] Open
Abstract
Transcription factors (TF) bind to chromatin and regulate the expression of genes. The pair Myc:Max binds to E-box regulatory DNA elements throughout the genome to control the transcription of a large group of specific genes. We introduce an implicit modeling protocol for Myc:Max binding to mesoscale chromatin fibers at nucleosome resolution to determine TF effect on chromatin architecture and shed light into its mechanism of gene regulation. We first bind Myc:Max to different chromatin locations and show how it can direct fiber folding and formation of microdomains, and how this depends on the linker DNA length. Second, by simulating increasing concentrations of Myc:Max binding to fibers that differ in the DNA linker length, linker histone density, and acetylation levels, we assess the interplay between Myc:Max and other chromatin internal parameters. Third, we study the mechanism of gene silencing by Myc:Max binding to the Eed gene loci. Overall, our results show how chromatin architecture can be regulated by TF binding. The position of TF binding dictates the formation of microdomains that appear visible only at the ensemble level. At the same time, the level of linker histone and tail acetylation, or different linker DNA lengths, regulates the concentration-dependent effect of TF binding. Furthermore, we show how TF binding can repress gene expression by increasing fiber folding motifs that help compact and occlude the promoter region. Importantly, this effect can be reversed by increasing linker histone density. Overall, these results shed light on the epigenetic control of the genome dictated by TF binding.
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Affiliation(s)
- Stephanie Portillo-Ledesma
- Department of Chemistry, 100 Washington Square East, Silver Building, New York UniversityNew YorkUnited States
- Simons Center for Computational Physical Chemistry, 24 Waverly Place, Silver Building, New York UniversityNew YorkUnited States
| | - Suckwoo Chung
- Department of Chemistry, 100 Washington Square East, Silver Building, New York UniversityNew YorkUnited States
| | - Jill Hoffman
- Department of Chemistry, 100 Washington Square East, Silver Building, New York UniversityNew YorkUnited States
| | - Tamar Schlick
- Department of Chemistry, 100 Washington Square East, Silver Building, New York UniversityNew YorkUnited States
- Simons Center for Computational Physical Chemistry, 24 Waverly Place, Silver Building, New York UniversityNew YorkUnited States
- Courant Institute of Mathematical Sciences, New York UniversityNew YorkUnited States
- New York University-East China Normal University Center for Computational Chemistry, New York University ShanghaiShanghaiChina
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4
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Portillo-Ledesma S, Chung S, Hoffman J, Schlick T. Regulation of Chromatin Architecture by Transcription Factor Binding. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.09.26.559535. [PMID: 37808867 PMCID: PMC10557667 DOI: 10.1101/2023.09.26.559535] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/10/2023]
Abstract
Transcription factors (TF) bind to chromatin and regulate the expression of genes. The pair Myc:Max binds to E-box regulatory DNA elements throughout the genome, controlling transcription of a large group of specific genes. We introduce an implicit modeling protocol for Myc:Max binding to mesoscale chromatin fibers to determine TF effect on chromatin architecture and shed light on its mechanism of gene regulation. We first bind Myc:Max to different chromatin locations and show how it can direct fiber folding and formation of microdomains, and how this depends on the linker DNA length. Second, by simulating increasing concentrations of Myc:Max binding to fibers that differ in the DNA linker length, linker histone density, and acetylation levels, we assess the interplay between Myc:Max and other chromatin internal parameters. Third, we study the mechanism of gene silencing by Myc:Max binding to the Eed gene loci. Overall, our results show how chromatin architecture can be regulated by TF binding. The position of TF binding dictates the formation of microdomains that appear visible only at the ensemble level. On the other hand, the presence of linker histone, acetylations, or different linker DNA lengths regulates the concentration-dependent effect of TF binding. Furthermore, we show how TF binding can repress gene expression by increasing fiber folding motifs that help compact and occlude the promoter region. Importantly, this effect can be reversed by increasing linker histone density. Overall, these results shed light on the epigenetic control of the genome dictated by TF binding.
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Affiliation(s)
- Stephanie Portillo-Ledesma
- Department of Chemistry, 100 Washington Square East, Silver Building, New York University, New York, NY 10003 U.S.A
- Simons Center for Computational Physical Chemistry, 24 Waverly Place, Silver Building, New York University, New York, NY 10003 U.S.A
| | - Suckwoo Chung
- Department of Chemistry, 100 Washington Square East, Silver Building, New York University, New York, NY 10003 U.S.A
| | - Jill Hoffman
- Department of Chemistry, 100 Washington Square East, Silver Building, New York University, New York, NY 10003 U.S.A
| | - Tamar Schlick
- Department of Chemistry, 100 Washington Square East, Silver Building, New York University, New York, NY 10003 U.S.A
- Courant Institute of Mathematical Sciences, New York University, 251 Mercer St., New York, NY 10012 U.S.A
- New York University-East China Normal University Center for Computational Chemistry, New York University Shanghai, Shanghai 200122 China
- Simons Center for Computational Physical Chemistry, 24 Waverly Place, Silver Building, New York University, New York, NY 10003 U.S.A
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5
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Yu Y, Wang S, Wang Z, Gao R, Lee J. Arabidopsis thaliana: a powerful model organism to explore histone modifications and their upstream regulations. Epigenetics 2023; 18:2211362. [PMID: 37196184 DOI: 10.1080/15592294.2023.2211362] [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: 11/24/2022] [Revised: 04/07/2023] [Accepted: 04/28/2023] [Indexed: 05/19/2023] Open
Abstract
Histones are subjected to extensive covalent modifications that affect inter-nucleosomal interactions as well as alter chromatin structure and DNA accessibility. Through switching the corresponding histone modifications, the level of transcription and diverse downstream biological processes can be regulated. Although animal systems are widely used in studying histone modifications, the signalling processes that occur outside the nucleus prior to histone modifications have not been well understood due to the limitations including non viable mutants, partial lethality, and infertility of survivors. Here, we review the benefits of using Arabidopsis thaliana as the model organism to study histone modifications and their upstream regulations. Similarities among histones and key histone modifiers such as the Polycomb group (PcG) and Trithorax group (TrxG) in Drosophila, Human, and Arabidopsis are examined. Furthermore, prolonged cold-induced vernalization system has been well-studied and revealed the relationship between the controllable environment input (duration of vernalization), its chromatin modifications of FLOWERING LOCUS C (FLC), following gene expression, and the corresponding phenotypes. Such evidence suggests that research on Arabidopsis can bring insights into incomplete signalling pathways outside of the histone box, which can be achieved through viable reverse genetic screenings based on the phenotypes instead of direct monitoring of histone modifications among individual mutants. The potential upstream regulators in Arabidopsis can provide cues or directions for animal research based on the similarities between them.
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Affiliation(s)
- Yang Yu
- Division of Natural and Applied Sciences, Duke Kunshan University, Kunshan, Jiangsu, China
| | - Sihan Wang
- Division of Natural and Applied Sciences, Duke Kunshan University, Kunshan, Jiangsu, China
| | - Ziqin Wang
- Division of Natural and Applied Sciences, Duke Kunshan University, Kunshan, Jiangsu, China
| | - Renwei Gao
- Division of Natural and Applied Sciences, Duke Kunshan University, Kunshan, Jiangsu, China
| | - Joohyun Lee
- Division of Natural and Applied Sciences, Duke Kunshan University, Kunshan, Jiangsu, China
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6
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Carignano M, Kröger M, Almassalha L, Agrawal V, Li WS, Pujadas EM, Nap RJ, Backman V, Szleifer I. Local Volume Concentration, Packing Domains and Scaling Properties of Chromatin. RESEARCH SQUARE 2023:rs.3.rs-3399177. [PMID: 37886531 PMCID: PMC10602155 DOI: 10.21203/rs.3.rs-3399177/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/28/2023]
Abstract
We propose the Self Returning Excluded Volume (SR-EV) model for the structure of chromatin based on stochastic rules and physical interactions that is able to capture the observed behavior across imaging and sequencing based measures of chromatin organization. The SR-EV model takes the return rules of the Self Returning Random Walk, incorporates excluded volume interactions, chain connectivity and expands the length scales range from 10 nm to over 1 micron. The model is computationally fast and we created thousands of configurations that we grouped in twelve different ensembles according to the two main parameters of the model. The analysis of the configurations was done in a way completely analogous to the experimental treatments used to determine chromatin volume concentration, contact probability, packing domain identification and size characterization, and packing scaling behavior. We find a robust agreement between the theoretical and experimental results. The overall organization of the model chromatin is corrugated, with dense packing domains alternating with a very dilute regions in a manner that resembles the mixing of two disordered bi-continuous phases. The return rules combined with excluded volume interactions lead to the formation of packing domains. We observed a transition from a short scale regime to a long scale regime occurring at genomic separations of ~ 4 × 104 base pairs or ~ 100 nm in distance. The contact probability reflects this transition with a change in the scaling exponent from larger than -1 to approximately -1. The analysis of the pair correlation function reveals that chromatin organizes following a power law scaling with exponent D ∈ { 2 , 3 } in the transition region between the short and long distance regimes.
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Affiliation(s)
- Marcelo Carignano
- Department of Biomedical Engineering, Northwestern University, Evanston, IL 60208, USA
- These authors contributed equally: Marcelo Carignano. Martin Kröger and Luay Almassalha
| | - Martin Kröger
- Magnetism and Interface Physics & Computational Polymer Physics, Department of Materials, ETH Zurich, CH-8093 Zurich, Switzerland
- These authors contributed equally: Marcelo Carignano. Martin Kröger and Luay Almassalha
| | - Luay Almassalha
- Department of Gastroenterology and Hepatology, Northwestern Memorial Hospital, Chicago IL 60611, USA
- These authors contributed equally: Marcelo Carignano. Martin Kröger and Luay Almassalha
| | - Vasundhara Agrawal
- Department of Biomedical Engineering, Northwestern University, Evanston, IL 60208, USA
| | - Wing Shun Li
- Applied Physics Program, Northwestern University, Evanston, IL 60208, USA
| | - Emily M. Pujadas
- Department of Biomedical Engineering, Northwestern University, Evanston, IL 60208, USA
| | - Rikkert J. Nap
- Department of Biomedical Engineering, Northwestern University, Evanston, IL 60208, USA
| | - Vadim Backman
- Department of Biomedical Engineering, Northwestern University, Evanston, IL 60208, USA
| | - Igal Szleifer
- Department of Biomedical Engineering, Northwestern University, Evanston, IL 60208, USA
- Department of Chemistry, Northwestern University, Evanston, IL 60208, USA
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7
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Portillo-Ledesma S, Li Z, Schlick T. Genome modeling: From chromatin fibers to genes. Curr Opin Struct Biol 2023; 78:102506. [PMID: 36577295 PMCID: PMC9908845 DOI: 10.1016/j.sbi.2022.102506] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2022] [Revised: 11/01/2022] [Accepted: 11/06/2022] [Indexed: 12/27/2022]
Abstract
The intricacies of the 3D hierarchical organization of the genome have been approached by many creative modeling studies. The specific model/simulation technique combination defines and restricts the system and phenomena that can be investigated. We present the latest modeling developments and studies of the genome, involving models ranging from nucleosome systems and small polynucleosome arrays to chromatin fibers in the kb-range, chromosomes, and whole genomes, while emphasizing gene folding from first principles. Clever combinations allow the exploration of many interesting phenomena involved in gene regulation, such as nucleosome structure and dynamics, nucleosome-nucleosome stacking, polynucleosome array folding, protein regulation of chromatin architecture, mechanisms of gene folding, loop formation, compartmentalization, and structural transitions at the chromosome and genome levels. Gene-level modeling with full details on nucleosome positions, epigenetic factors, and protein binding, in particular, can in principle be scaled up to model chromosomes and cells to study fundamental biological regulation.
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Affiliation(s)
- Stephanie Portillo-Ledesma
- Department of Chemistry, New York University, 100 Washington Square East, Silver Building, New York, 10003, NY, USA
| | - Zilong Li
- Department of Chemistry, New York University, 100 Washington Square East, Silver Building, New York, 10003, NY, USA
| | - Tamar Schlick
- Department of Chemistry, New York University, 100 Washington Square East, Silver Building, New York, 10003, NY, USA; Courant Institute of Mathematical Sciences, New York University, 251 Mercer St., New York, 10012, NY, USA; New York University-East China Normal University Center for Computational Chemistry, New York University Shanghai, Room 340, Geography Building, 3663 North Zhongshan Road, Shanghai, 200122, China; Simons Center for Computational Physical Chemistry, 24 Waverly Place, Silver Building, New York University, New York, 10003, NY, USA.
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8
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Portillo-Ledesma S, Wagley M, Schlick T. Chromatin transitions triggered by LH density as epigenetic regulators of the genome. Nucleic Acids Res 2022; 50:10328-10342. [PMID: 36130289 PMCID: PMC9561278 DOI: 10.1093/nar/gkac757] [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: 05/31/2022] [Revised: 07/26/2022] [Accepted: 09/02/2022] [Indexed: 11/14/2022] Open
Abstract
Motivated by experiments connecting linker histone (LH) deficiency to lymphoma progression and retinal disorders, we study by mesoscale chromatin modeling how LH density (ρ) induces gradual, as well sudden, changes in chromatin architecture and how the process depends on DNA linker length, LH binding dynamics and binding mode, salt concentration, tail modifications, and combinations of ρ and linker DNA length. We show that ρ tightly regulates the overall shape and compaction of the fiber, triggering a transition from an irregular disordered state to a compact and ordered structure. Such a structural transition, resembling B to A compartment transition connected with lymphoma of B cells, appears to occur around ρ = 0.5. The associated mechanism is DNA stem formation by LH binding, which is optimal when the lengths of the DNA linker and LH C-terminal domain are similar. Chromatin internal and external parameters are key regulators, promoting or impeding the transition. The LH density thus emerges as a critical tunable variable in controlling cellular functions through structural transitions of the genome.
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Affiliation(s)
- Stephanie Portillo-Ledesma
- Department of Chemistry, New York University, 1001 Silver, 100 Washington Square East, New York, NY 10003, USA
| | - Meghna Wagley
- Department of Chemistry, New York University, 1001 Silver, 100 Washington Square East, New York, NY 10003, USA
| | - Tamar Schlick
- Department of Chemistry, New York University, 1001 Silver, 100 Washington Square East, New York, NY 10003, USA.,New York University-East China Normal University Center for Computational Chemistry at New York University Shanghai, Room 340, Geography Building, 3663 North Zhongshan Road, Shanghai 200062, China.,Courant Institute of Mathematical Sciences, New York University, 251 Mercer St, New York, NY 10012, USA.,Simons Center for Computational Physical Chemistry, 24 Waverly Place, Silver Building, New York University, New York, NY 10003 USA
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9
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Swygert SG, Lin D, Portillo-Ledesma S, Lin PY, Hunt DR, Kao CF, Schlick T, Noble WS, Tsukiyama T. Local chromatin fiber folding represses transcription and loop extrusion in quiescent cells. eLife 2021; 10:e72062. [PMID: 34734806 PMCID: PMC8598167 DOI: 10.7554/elife.72062] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2021] [Accepted: 11/03/2021] [Indexed: 12/16/2022] Open
Abstract
A longstanding hypothesis is that chromatin fiber folding mediated by interactions between nearby nucleosomes represses transcription. However, it has been difficult to determine the relationship between local chromatin fiber compaction and transcription in cells. Further, global changes in fiber diameters have not been observed, even between interphase and mitotic chromosomes. We show that an increase in the range of local inter-nucleosomal contacts in quiescent yeast drives the compaction of chromatin fibers genome-wide. Unlike actively dividing cells, inter-nucleosomal interactions in quiescent cells require a basic patch in the histone H4 tail. This quiescence-specific fiber folding globally represses transcription and inhibits chromatin loop extrusion by condensin. These results reveal that global changes in chromatin fiber compaction can occur during cell state transitions, and establish physiological roles for local chromatin fiber folding in regulating transcription and chromatin domain formation.
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Affiliation(s)
- Sarah G Swygert
- Basic Sciences Division, Fred Hutchinson Cancer Research CenterSeattleUnited States
| | - Dejun Lin
- Department of Genome Sciences, University of WashingtonSeattleUnited States
| | | | - Po-Yen Lin
- Institute of Cellular and Organismic Biology, Academia SinicaTaipeiTaiwan
| | - Dakota R Hunt
- Basic Sciences Division, Fred Hutchinson Cancer Research CenterSeattleUnited States
| | - Cheng-Fu Kao
- Institute of Cellular and Organismic Biology, Academia SinicaTaipeiTaiwan
| | - Tamar Schlick
- Department of Chemistry, New York UniversityNew YorkUnited States
- Courant Institute of Mathematical Sciences, New York UniversityNew YorkUnited States
- New York University-East China Normal University Center for Computational Chemistry at New York University ShanghaiShanghaiChina
| | - William S Noble
- Department of Genome Sciences, University of WashingtonSeattleUnited States
- Paul G. Allen School of Computer Science and Engineering, University of WashingtonSeattleUnited States
| | - Toshio Tsukiyama
- Basic Sciences Division, Fred Hutchinson Cancer Research CenterSeattleUnited States
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10
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Itoh Y, Woods EJ, Minami K, Maeshima K, Collepardo-Guevara R. Liquid-like chromatin in the cell: What can we learn from imaging and computational modeling? Curr Opin Struct Biol 2021; 71:123-135. [PMID: 34303931 DOI: 10.1016/j.sbi.2021.06.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2021] [Accepted: 06/08/2021] [Indexed: 12/23/2022]
Abstract
Chromatin in eukaryotic cells is a negatively charged long polymer consisting of DNA, histones, and various associated proteins. With its highly charged and heterogeneous nature, chromatin structure varies greatly depending on various factors (e.g. chemical modifications and protein enrichment) and the surrounding environment (e.g. cations): from a 10-nm fiber, a folded 30-nm fiber, to chromatin condensates/droplets. Recent advanced imaging has observed that chromatin exhibits a dynamic liquid-like behavior and undergoes structural variations within the cell. Current computational modeling has made it possible to reconstruct the liquid-like chromatin in the cell by dealing with a number of nucleosomes on multiscale levels and has become a powerful technique to inspect the molecular mechanisms giving rise to the observed behavior, which imaging methods cannot do on their own. Based on new findings from both imaging and modeling studies, we discuss the dynamic aspect of chromatin in living cells and its functional relevance.
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Affiliation(s)
- Yuji Itoh
- Genome Dynamics Laboratory, National Institute of Genetics, Mishima, Shizuoka 411-8540, Japan
| | - Esmae J Woods
- Maxwell Centre, Cavendish Laboratory, Department of Physics, University of Cambridge, J J Thomson Avenue, Cambridge CB3 0HE, UK
| | - Katsuhiko Minami
- Genome Dynamics Laboratory, National Institute of Genetics, Mishima, Shizuoka 411-8540, Japan; Department of Genetics, School of Life Science, Sokendai (Graduate University for Advanced Studies), Mishima, Shizuoka 411-8540, Japan
| | - Kazuhiro Maeshima
- Genome Dynamics Laboratory, National Institute of Genetics, Mishima, Shizuoka 411-8540, Japan; Department of Genetics, School of Life Science, Sokendai (Graduate University for Advanced Studies), Mishima, Shizuoka 411-8540, Japan.
| | - Rosana Collepardo-Guevara
- Maxwell Centre, Cavendish Laboratory, Department of Physics, University of Cambridge, J J 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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11
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DNA sequence-dependent positioning of the linker histone in a nucleosome: A single-pair FRET study. Biophys J 2021; 120:3747-3763. [PMID: 34293303 DOI: 10.1016/j.bpj.2021.07.012] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2021] [Revised: 06/25/2021] [Accepted: 07/13/2021] [Indexed: 01/01/2023] Open
Abstract
Linker histones (LHs) bind to nucleosomes with their globular domain (gH) positioned in either an on- or an off-dyad binding mode. Here, we study the effect of the linker DNA (L-DNA) sequence on the binding of a full-length LH, Xenopus laevis H1.0b, to a Widom 601 nucleosome core particle (NCP) flanked by two 40 bp long L-DNA arms, by single-pair FRET spectroscopy. We varied the sequence of the 11 bp of L-DNA adjoining the NCP on either side, making the sequence either A-tract, purely GC, or mixed with 64% AT. The labeled gH consistently exhibited higher FRET efficiency with the labeled L-DNA containing the A-tract than that with the pure-GC stretch, even when the stretches were swapped. However, it did not exhibit higher FRET efficiency with the L-DNA containing 64% AT-rich mixed DNA when compared to the pure-GC stretch. We explain our observations with a model that shows that the gH binds on dyad and that two arginines mediate recognition of the A-tract via its characteristically narrow minor groove. To investigate whether this on-dyad minor groove-based recognition was distinct from previously identified off-dyad major groove-based recognition, a nucleosome was designed with A-tracts on both the L-DNA arms. One A-tract was complementary to thymine and the other to deoxyuridine. The major groove of the thymine-tract was lined with methyl groups that were absent from the major groove of the deoxyuridine tract. The gH exhibited similar FRET for both these A-tracts, suggesting that it does not interact with the thymine methyl groups exposed on the major groove. Our observations thus complement previous studies that suggest that different LH isoforms may employ different ways of recognizing AT-rich DNA and A-tracts. This adaptability may enable the LH to universally compact scaffold-associated regions and constitutive heterochromatin, which are rich in such sequences.
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12
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Zhang C, Huang J. Interactions Between Nucleosomes: From Atomistic Simulation to Polymer Model. Front Mol Biosci 2021; 8:624679. [PMID: 33912585 PMCID: PMC8072053 DOI: 10.3389/fmolb.2021.624679] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2020] [Accepted: 02/09/2021] [Indexed: 11/23/2022] Open
Abstract
The organization of genomes in space and time dimension plays an important role in gene expression and regulation. Chromatin folding occurs in a dynamic, structured way that is subject to biophysical rules and biological processes. Nucleosomes are the basic unit of chromatin in living cells, and here we report on the effective interactions between two nucleosomes in physiological conditions using explicit-solvent all-atom simulations. Free energy landscapes derived from umbrella sampling simulations agree well with recent experimental and simulation results. Our simulations reveal the atomistic details of the interactions between nucleosomes in solution and can be used for constructing the coarse-grained model for chromatin in a bottom-up manner.
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Affiliation(s)
- Chengwei Zhang
- College of Life Sciences, Zhejiang University, Hangzhou, China
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, China
- Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, China
- Institute of Biology, Westlake Institute for Advanced Study, Hangzhou, China
| | - Jing Huang
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, China
- Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, China
- Institute of Biology, Westlake Institute for Advanced Study, Hangzhou, China
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13
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Gómez-García PA, Portillo-Ledesma S, Neguembor MV, Pesaresi M, Oweis W, Rohrlich T, Wieser S, Meshorer E, Schlick T, Cosma MP, Lakadamyali M. Mesoscale Modeling and Single-Nucleosome Tracking Reveal Remodeling of Clutch Folding and Dynamics in Stem Cell Differentiation. Cell Rep 2021; 34:108614. [PMID: 33440158 PMCID: PMC7842188 DOI: 10.1016/j.celrep.2020.108614] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2020] [Revised: 10/29/2020] [Accepted: 12/16/2020] [Indexed: 01/01/2023] Open
Abstract
Nucleosomes form heterogeneous groups in vivo, named clutches. Clutches are smaller and less dense in mouse embryonic stem cells (ESCs) compared to neural progenitor cells (NPCs). Using coarse-grained modeling of the pluripotency Pou5f1 gene, we show that the genome-wide clutch differences between ESCs and NPCs can be reproduced at a single gene locus. Larger clutch formation in NPCs is associated with changes in the compaction and internucleosome contact probability of the Pou5f1 fiber. Using single-molecule tracking (SMT), we further show that the core histone protein H2B is dynamic, and its local mobility relates to the structural features of the chromatin fiber. H2B is less stable and explores larger areas in ESCs compared to NPCs. The amount of linker histone H1 critically affects local H2B dynamics. Our results have important implications for how nucleosome organization and H2B dynamics contribute to regulate gene activity and cell identity.
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Affiliation(s)
- Pablo Aurelio Gómez-García
- Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology (BIST), 08003 Barcelona, Spain; Institute of Photonic Sciences (ICFO), The Barcelona Institute of Science and Technology (BIST), Castelldefels, 08860 Barcelona, Spain
| | - Stephanie Portillo-Ledesma
- Department of Chemistry, 1021 Silver Center, 100 Washington Square East, New York University, New York, NY 10003, USA
| | - Maria Victoria Neguembor
- Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology (BIST), 08003 Barcelona, Spain
| | - Martina Pesaresi
- Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology (BIST), 08003 Barcelona, Spain
| | - Walaa Oweis
- Department of Genetics, The Alexander Silberman Institute of Life Sciences, Faculty of Science, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, Jerusalem 91904, Israel
| | - Talia Rohrlich
- Department of Genetics, The Alexander Silberman Institute of Life Sciences, Faculty of Science, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, Jerusalem 91904, Israel
| | - Stefan Wieser
- Institute of Photonic Sciences (ICFO), The Barcelona Institute of Science and Technology (BIST), Castelldefels, 08860 Barcelona, Spain
| | - Eran Meshorer
- Department of Genetics, The Alexander Silberman Institute of Life Sciences, Faculty of Science, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, Jerusalem 91904, Israel; The Edmond and Lily Safra Center for Brain Sciences (ELSC), The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, Jerusalem 91904, Israel
| | - Tamar Schlick
- Department of Chemistry, 1021 Silver Center, 100 Washington Square East, New York University, New York, NY 10003, USA; Courant Institute of Mathematical Sciences, 251 Mercer Street, New York University, New York, NY 10012, USA; NYU-ECNU Center for Computational Chemistry at New York University Shanghai, 340 Geography Building, 3663 North Zhongshan Road, Shanghai 3663, China
| | - Maria Pia Cosma
- Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology (BIST), 08003 Barcelona, Spain; Universitat Pompeu Fabra (UPF), Dr Aiguader 88, 08003 Barcelona, Spain; Institució Catalana de Recerca i Estudis Avançats (ICREA), Pg. Lluís Companys 23, 08010 Barcelona, Spain; Bioland Laboratory, Guangzhou Regenerative Medicine and Health Guangdong Laboratory, Guangzhou 510005, China; CAS Key Laboratory of Regenerative Biology, Guangdong Provincial Key Laboratory of Stem Cell and Regenerative Medicine, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou 510530, China.
| | - Melike Lakadamyali
- Perelman School of Medicine, Department of Physiology, University of Pennsylvania, Clinical Research Building, 415 Curie Boulevard, Philadelphia, PA 19104, USA; Perelman School of Medicine, Department of Cell and Developmental Biology, University of Pennsylvania, Biomedical Research Building, 421 Curie Boulevard, Philadelphia, PA 19104, USA.
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14
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Portillo-Ledesma S, Tsao LH, Wagley M, Lakadamyali M, Cosma MP, Schlick T. Nucleosome Clutches are Regulated by Chromatin Internal Parameters. J Mol Biol 2020; 433:166701. [PMID: 33181171 DOI: 10.1016/j.jmb.2020.11.001] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2020] [Revised: 10/27/2020] [Accepted: 11/02/2020] [Indexed: 01/17/2023]
Abstract
Nucleosomes cluster together when chromatin folds in the cell to form heterogeneous groups termed "clutches". These structural units add another level of chromatin regulation, for example during cell differentiation. Yet, the mechanisms that regulate their size and compaction remain obscure. Here, using our chromatin mesoscale model, we dissect clutch patterns in fibers with different combinations of nucleosome positions, linker histone density, and acetylation levels to investigate their role in clutch regulation. First, we isolate the effect of each chromatin parameter by studying systems with regular nucleosome spacing; second, we design systems with naturally-occurring linker lengths that fold onto specific clutch patterns; third, we model gene-encoding fibers to understand how these combined factors contribute to gene structure. Our results show how these chromatin parameters act together to produce different-sized nucleosome clutches. The length of nucleosome free regions (NFRs) profoundly affects clutch size, while the length of linker DNA has a moderate effect. In general, higher linker histone densities produce larger clutches by a chromatin compaction mechanism, while higher acetylation levels produce smaller clutches by a chromatin unfolding mechanism. We also show that it is possible to design fibers with naturally-occurring DNA linkers and NFRs that fold onto specific clutch patterns. Finally, in gene-encoding systems, a complex combination of variables dictates a gene-specific clutch pattern. Together, these results shed light into the mechanisms that regulate nucleosome clutches and suggest a new epigenetic mechanism by which chromatin parameters regulate transcriptional activity via the three-dimensional folded state of the genome at a nucleosome level.
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Affiliation(s)
- Stephanie Portillo-Ledesma
- Department of Chemistry, New York University, 1021 Silver, 100 Washington Square East, New York, NY, 10003, USA
| | - Lucille H Tsao
- Department of Chemistry, New York University, 1021 Silver, 100 Washington Square East, New York, NY, 10003, USA
| | - Meghna Wagley
- Department of Chemistry, New York University, 1021 Silver, 100 Washington Square East, New York, NY, 10003, USA
| | - Melike Lakadamyali
- Perelman School of Medicine, Department of Physiology, University of Pennsylvania, Clinical Research Building, 415 Curie Boulevard, Philadelphia, PA 19104, USA; Perelman School of Medicine, Department of Cell and Developmental Biology, University of Pennsylvania, Clinical Research Building, 415 Curie Boulevard, Philadelphia, PA 19104, USA
| | - Maria Pia Cosma
- Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology (BIST), 08003 Barcelona, Spain; Universitat Pompeu Fabra (UPF), Dr Aiguader 88, 08003 Barcelona, Spain; Institució Catalana de Recerca i Estudis Avançats (ICREA), Pg. Lluís Companys 23, 08010 Barcelona, Spain; Bioland Laboratory, Guangzhou Regenerative Medicine and Health Guangdong Laboratory, Guangzhou 510005, China; CAS Key Laboratory of Regenerative Biology, Guangdong Provincial Key Laboratory of Stem Cell and Regenerative Medicine, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou 510530, China
| | - Tamar Schlick
- Department of Chemistry, New York University, 1021 Silver, 100 Washington Square East, New York, NY, 10003, USA; New York University-East China Normal University Center for Computational Chemistry at New York University Shanghai, Room 340, Geography Building, 3663 North Zhongshan Road, Shanghai, 200062, China; Courant Institute of Mathematical Sciences, New York University, 251 Mercer St, New York, NY, 10012, USA.
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15
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Peng J, Yuan C, Hua X, Zhang Z. Molecular mechanism of histone variant H2A.B on stability and assembly of nucleosome and chromatin structures. Epigenetics Chromatin 2020; 13:28. [PMID: 32664941 PMCID: PMC7362417 DOI: 10.1186/s13072-020-00351-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2019] [Accepted: 07/09/2020] [Indexed: 01/23/2023] Open
Abstract
BACKGROUND H2A.B, the most divergent histone variant of H2A, can significantly modulate nucleosome and chromatin structures. However, the related structural details and the underlying mechanism remain elusive to date. In this work, we built atomic models of the H2A.B-containing nucleosome core particle (NCP), chromatosome, and chromatin fiber. Multiscale modeling including all-atom molecular dynamics and coarse-grained simulations were then carried out for these systems. RESULTS It is found that sequence differences at the C-terminal tail, the docking domain, and the L2 loop, between H2A.B and H2A are directly responsible for the DNA unwrapping in the H2A.B NCP, whereas the N-terminus of H2A.B may somewhat compensate for the aforementioned unwrapping effect. The assembly of the H2A.B NCP is more difficult than that of the H2A NCP. H2A.B may also modulate the interactions of H1 with both the NCP and the linker DNA and could further affect the higher-order structure of the chromatin fiber. CONCLUSIONS The results agree with the experimental results and may shed new light on the biological function of H2A.B. Multiscale modeling may be a valuable tool for investigating structure and dynamics of the nucleosome and the chromatin induced by various histone variants.
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Affiliation(s)
- Junhui Peng
- MOE Key Laboratory for Membraneless Organelles & Cellular Dynamics, National Science Center for Physical Sciences at Microscale, School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, 230026, People's Republic of China.,Laboratory of Evolutionary Genetics and Genomics, The Rockefeller University, New York, NY, 10065, USA
| | - Chuang Yuan
- MOE Key Laboratory for Membraneless Organelles & Cellular Dynamics, National Science Center for Physical Sciences at Microscale, School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, 230026, People's Republic of China
| | - Xinfan Hua
- MOE Key Laboratory for Membraneless Organelles & Cellular Dynamics, National Science Center for Physical Sciences at Microscale, School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, 230026, People's Republic of China
| | - Zhiyong Zhang
- MOE Key Laboratory for Membraneless Organelles & Cellular Dynamics, National Science Center for Physical Sciences at Microscale, School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, 230026, People's Republic of China.
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16
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Myers CG, Olins DE, Olins AL, Schlick T. Mesoscale Modeling of Nucleosome-Binding Antibody PL2-6: Mono- versus Bivalent Chromatin Complexes. Biophys J 2020; 118:2066-2076. [PMID: 31668748 PMCID: PMC7202932 DOI: 10.1016/j.bpj.2019.08.019] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2019] [Revised: 07/25/2019] [Accepted: 08/15/2019] [Indexed: 12/28/2022] Open
Abstract
Interactions of chromatin with bivalent immunoglobin nucleosome-binding antibodies and their monovalent (papain-derived) antigen-binding fragment analogs are useful probes for examining chromatin conformational states. To help interpret antibody-chromatin interactions and explore how antibodies might compete for interactions with chromatin components, we incorporate coarse-grained PL2-6 antibody modeling into our mesoscale chromatin model. We analyze interactions and fiber structures for the antibody-chromatin complexes in open and condensed chromatin, with and without H1 linker histone (LH). Despite minimal and transient interactions at physiological salt, we capture significant differences in antibody-chromatin complex configurations in open fibers, with more intense interactions between the bivalent antibody and chromatin compared to monovalent antigen-binding fragments. For these open chromatin fiber morphologies, antibody binding to histone tails is increased and compaction is greater for bivalent compared to monovalent and antibody-free systems. Differences between monovalent and bivalent binding result from antibody competition with internal chromatin fiber components (nucleosome core and linker DNA) for histone tail (H3, H4, H2A, H2B) interactions. This antibody competition for tail contacts reduces tail-core and tail-linker interactions and increases tail-antibody interactions. Such internal structural changes in open fibers resemble mechanisms of LH condensation, driven by charge screening and entropy changes. For condensed fibers at physiological salt, the three systems are much more similar overall, but some subtle tail interaction differences can be noted. Adding LH results in less-dramatic changes for all systems, except that the bivalent complex at physiological salt shows cooperative effects between LH and the antibodies in condensing chromatin fibers. Such dynamic interactions that depend on the internal structure and complex-stabilizing interactions within the chromatin fiber have implications for gene regulation and other chromatin complexes such as with LH, remodeling proteins, and small molecular chaperones that bind and modulate chromatin structure.
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Affiliation(s)
| | - Donald E Olins
- Department of Pharmaceutical Sciences, College of Pharmacy, University of New England, Portland, Maine
| | - Ada L Olins
- Department of Pharmaceutical Sciences, College of Pharmacy, University of New England, Portland, Maine
| | - Tamar Schlick
- Department of Chemistry, New York University, New York, New York; Courant Institute of Mathematical Sciences, New York University, New York, New York; New York University-East China Normal University Center for Computational Chemistry at New York University Shanghai, Shanghai, China.
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17
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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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18
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Emergence of chromatin hierarchical loops from protein disorder and nucleosome asymmetry. Proc Natl Acad Sci U S A 2020; 117:7216-7224. [PMID: 32165536 DOI: 10.1073/pnas.1910044117] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Protein flexibility and disorder is emerging as a crucial modulator of chromatin structure. Histone tail disorder enables transient binding of different molecules to the nucleosomes, thereby promoting heterogeneous and dynamic internucleosome interactions and making possible recruitment of a wide-range of regulatory and remodeling proteins. On the basis of extensive multiscale modeling we reveal the importance of linker histone H1 protein disorder for chromatin hierarchical looping. Our multiscale approach bridges microsecond-long bias-exchange metadynamics molecular dynamics simulations of atomistic 211-bp nucleosomes with coarse-grained Monte Carlo simulations of 100-nucleosome systems. We show that the long C-terminal domain (CTD) of H1-a ubiquitous nucleosome-binding protein-remains disordered when bound to the nucleosome. Notably, such CTD disorder leads to an asymmetric and dynamical nucleosome conformation that promotes chromatin structural flexibility and establishes long-range hierarchical loops. Furthermore, the degree of condensation and flexibility of H1 can be fine-tuned, explaining chromosomal differences of interphase versus metaphase states that correspond to partial and hyperphosphorylated H1, respectively. This important role of H1 protein disorder in large-scale chromatin organization has a wide range of biological implications.
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19
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Öztürk MA, De M, Cojocaru V, Wade RC. Chromatosome Structure and Dynamics from Molecular Simulations. Annu Rev Phys Chem 2020; 71:101-119. [PMID: 32017651 DOI: 10.1146/annurev-physchem-071119-040043] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Chromatosomes are fundamental units of chromatin structure that are formed when a linker histone protein binds to a nucleosome. The positioning of the linker histone on the nucleosome influences the packing of chromatin. Recent simulations and experiments have shown that chromatosomes adopt an ensemble of structures that differ in the geometry of the linker histone-nucleosome interaction. In this article we review the application of Brownian, Monte Carlo, and molecular dynamics simulations to predict the structure of linker histone-nucleosome complexes, to study the binding mechanisms involved, and to predict how this binding affects chromatin fiber structure. These simulations have revealed the sensitivityof the chromatosome structure to variations in DNA and linker histone sequence, as well as to posttranslational modifications, thereby explaining the structural variability observed in experiments. We propose that a concerted application of experimental and computational approaches will reveal the determinants of chromatosome structural variability and how it impacts chromatin packing.
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Affiliation(s)
- Mehmet Ali Öztürk
- Centre for Biological Signalling Studies (BIOSS) and Centre for Integrative Biological Signalling Studies (CIBSS), University of Freiburg, 79104 Freiburg, Germany;
| | - Madhura De
- Molecular and Cellular Modeling Group, Heidelberg Institute for Theoretical Studies (HITS), 69118 Heidelberg, Germany; .,Department of Biophysics of Macromolecules, German Cancer Research Center (DKFZ), 69120 Heidelberg, Germany; .,Faculty of Biosciences, Heidelberg University, 69120 Heidelberg, Germany
| | - Vlad Cojocaru
- In Silico Biomolecular Structure and Dynamics, Hubrecht Institute, 3584 CT Utrecht, The Netherlands; .,Computational Structural Biology Group, Max Planck Institute for Molecular Biomedicine, 48149 Muenster, Germany
| | - Rebecca C Wade
- Molecular and Cellular Modeling Group, Heidelberg Institute for Theoretical Studies (HITS), 69118 Heidelberg, Germany; .,Faculty of Biosciences, Heidelberg University, 69120 Heidelberg, Germany.,Center for Molecular Biology (ZMBH), DKFZ-ZMBH Alliance, Heidelberg University, 69120 Heidelberg, Germany.,Interdisciplinary Center for Scientific Computing (IWR), 69120 Heidelberg, Germany
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20
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Perišić O, Portillo-Ledesma S, Schlick T. Sensitive effect of linker histone binding mode and subtype on chromatin condensation. Nucleic Acids Res 2019; 47:4948-4957. [PMID: 30968131 PMCID: PMC6547455 DOI: 10.1093/nar/gkz234] [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: 01/08/2019] [Revised: 03/19/2019] [Accepted: 03/22/2019] [Indexed: 12/14/2022] Open
Abstract
The complex role of linker histone (LH) on chromatin compaction regulation has been highlighted by recent discoveries of the effect of LH binding variability and isoforms on genome structure and function. Here we examine the effect of two LH variants and variable binding modes on the structure of chromatin fibers. Our mesoscale modeling considers oligonucleosomes with H1C and H1E, bound in three different on and off-dyad modes, and spanning different LH densities (0.5–1.6 per nucleosome), over a wide range of physiologically relevant nucleosome repeat lengths (NRLs). Our studies reveal an LH-variant and binding-mode dependent heterogeneous ensemble of fiber structures with variable packing ratios, sedimentation coefficients, and persistence lengths. For maximal compaction, besides dominantly interacting with parental DNA, LHs must have strong interactions with nonparental DNA and promote tail/nonparental core interactions. An off-dyad binding of H1E enables both; others compromise compaction for bendability. We also find that an increase of LH density beyond 1 is best accommodated in chromatosomes with one on-dyad and one off-dyad LH. We suggest that variable LH binding modes and concentrations are advantageous, allowing tunable levels of chromatin condensation and DNA accessibility/interactions. Thus, LHs add another level of epigenetic regulation of chromatin.
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Affiliation(s)
- Ognjen Perišić
- Department of Chemistry, New York University, 1001 Silver, 100 Washington Square East, New York, NY 10003, USA
| | - Stephanie Portillo-Ledesma
- Department of Chemistry, New York University, 1001 Silver, 100 Washington Square East, New York, NY 10003, USA
| | - Tamar Schlick
- Department of Chemistry, New York University, 1001 Silver, 100 Washington Square East, New York, NY 10003, USA.,Courant Institute of Mathematical Sciences, New York University, 251 Mercer Street, New York, NY 10012, USA.,New York University ECNU - Center for Computational Chemistry at NYU Shanghai, 3663 North Zhongshan Road, Shanghai, 200062, China
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21
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Portillo-Ledesma S, Schlick T. Bridging chromatin structure and function over a range of experimental spatial and temporal scales by molecular modeling. WILEY INTERDISCIPLINARY REVIEWS-COMPUTATIONAL MOLECULAR SCIENCE 2019; 10. [PMID: 34046090 DOI: 10.1002/wcms.1434] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Chromatin structure, dynamics, and function are being intensely investigated by a variety of methods, including microscopy, X-ray diffraction, nuclear magnetic resonance, biochemical crosslinking, chromosome conformation capture, and computation. A range of experimental techniques combined with modeling is clearly valuable to help interpret experimental data and, importantly, generate configurations and mechanisms related to the 3D organization and function of the genome. Contact maps, in particular, as obtained by a variety of chromosome conformation capture methods, are of increasing interest due to their implications on genome structure and regulation on many levels. In this perspective, using seven examples from our group's studies, we illustrate how molecular modeling can help interpret such experimental data. Specifically, we show how computed contact maps related to experimental systems can be used to explain structures of nucleosomes, chromatin higher-order folding, domain segregation mechanisms, gene organization, and the effect on chromatin structure of external and internal fiber parameters, such as nucleosome positioning, presence of nucleosome free regions, histone posttranslational modifications, and linker histone binding. We argue that such computations on multiple spatial and temporal scales will be increasingly important for the integration of genomic, epigenomic, and biophysical data on chromatin structure and related cellular processes.
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Affiliation(s)
- Stephanie Portillo-Ledesma
- Department of Chemistry, New York University, 1001 Silver, 100 Washington Square East, New York, New York, 10003, USA
| | - Tamar Schlick
- Department of Chemistry, New York University, 1001 Silver, 100 Washington Square East, New York, New York, 10003, USA.,Courant Institute of Mathematical Sciences, New York University, 251 Mercer St, New York, New York, 10012, USA.,New York University-East China Normal University Center for Computational Chemistry at New York University Shanghai, Room 340, Geography Building, 3663 North Zhongshan Road, Shanghai, 200062, China
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22
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Lequieu J, Córdoba A, Moller J, de Pablo JJ. 1CPN: A coarse-grained multi-scale model of chromatin. J Chem Phys 2019; 150:215102. [PMID: 31176328 DOI: 10.1063/1.5092976] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
A central question in epigenetics is how histone modifications influence the 3D structure of eukaryotic genomes and, ultimately, how this 3D structure is manifested in gene expression. The wide range of length scales that influence the 3D genome structure presents important challenges; epigenetic modifications to histones occur on scales of angstroms, yet the resulting effects of these modifications on genome structure can span micrometers. There is a scarcity of computational tools capable of providing a mechanistic picture of how molecular information from individual histones is propagated up to large regions of the genome. In this work, a new molecular model of chromatin is presented that provides such a picture. This new model, referred to as 1CPN, is structured around a rigorous multiscale approach, whereby free energies from an established and extensively validated model of the nucleosome are mapped onto a reduced coarse-grained topology. As such, 1CPN incorporates detailed physics from the nucleosome, such as histone modifications and DNA sequence, while maintaining the computational efficiency that is required to permit kilobase-scale simulations of genomic DNA. The 1CPN model reproduces the free energies and dynamics of both single nucleosomes and short chromatin fibers, and it is shown to be compatible with recently developed models of the linker histone. It is applied here to examine the effects of the linker DNA on the free energies of chromatin assembly and to demonstrate that these free energies are strongly dependent on the linker DNA length, pitch, and even DNA sequence. The 1CPN model is implemented in the LAMMPS simulation package and is distributed freely for public use.
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Affiliation(s)
- Joshua Lequieu
- Institute for Molecular Engineering, University of Chicago, Chicago, Illinois 60637, USA
| | - Andrés Córdoba
- Institute for Molecular Engineering, University of Chicago, Chicago, Illinois 60637, USA
| | - Joshua Moller
- Institute for Molecular Engineering, University of Chicago, Chicago, Illinois 60637, USA
| | - Juan J de Pablo
- Institute for Molecular Engineering, University of Chicago, Chicago, Illinois 60637, USA
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23
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Sanbonmatsu KY. Large-scale simulations of nucleoprotein complexes: ribosomes, nucleosomes, chromatin, chromosomes and CRISPR. Curr Opin Struct Biol 2019; 55:104-113. [PMID: 31125796 DOI: 10.1016/j.sbi.2019.03.004] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2019] [Accepted: 03/01/2019] [Indexed: 12/11/2022]
Abstract
Recent advances in biotechnology such as Hi-C, CRISPR/Cas9 and ribosome display have placed nucleoprotein complexes at center stage. Understanding the structural dynamics of these complexes aids in optimizing protocols and interpreting data for these new technologies. The integration of simulation and experiment has helped advance mechanistic understanding of these systems. Coarse-grained simulations, reduced-description models, and explicit solvent molecular dynamics simulations yield useful complementary perspectives on nucleoprotein complex structural dynamics. When combined with Hi-C, cryo-EM, and single molecule measurements, these simulations integrate disparate forms of experimental data into a coherent mechanism.
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24
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Mesoscale modeling reveals formation of an epigenetically driven HOXC gene hub. Proc Natl Acad Sci U S A 2019; 116:4955-4962. [PMID: 30718394 DOI: 10.1073/pnas.1816424116] [Citation(s) in RCA: 43] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Gene expression is orchestrated at the structural level by nucleosome positioning, histone tail acetylation, and linker histone (LH) binding. Here, we integrate available data on nucleosome positioning, nucleosome-free regions (NFRs), acetylation islands, and LH binding sites to "fold" in silico the 55-kb HOXC gene cluster and investigate the role of each feature on the gene's folding. The gene cluster spontaneously forms a dynamic connection hub, characterized by hierarchical loops which accommodate multiple contacts simultaneously and decrease the average distance between promoters by ∼100 nm. Contact probability matrices exhibit "stripes" near promoter regions, a feature associated with transcriptional regulation. Interestingly, while LH proteins alone decrease long-range contacts and acetylation alone increases transient contacts, combined LH and acetylation produce long-range contacts. Thus, our work emphasizes how chromatin architecture is coordinated strongly by epigenetic factors and opens the way for nucleosome resolution models incorporating epigenetic modifications to understand and predict gene activity.
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25
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Öztürk MA, Cojocaru V, Wade RC. Toward an Ensemble View of Chromatosome Structure: A Paradigm Shift from One to Many. Structure 2018; 26:1050-1057. [PMID: 29937356 DOI: 10.1016/j.str.2018.05.009] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2018] [Revised: 03/31/2018] [Accepted: 05/15/2018] [Indexed: 11/29/2022]
Abstract
There is renewed interest in linker histone (LH)-nucleosome binding and how LHs influence eukaryotic DNA compaction. For a long time, the goal was to uncover "the structure of the chromatosome," but recent studies of LH-nucleosome complexes have revealed an ensemble of structures. Notably, the reconstituted LH-nucleosome complexes used in experiments rarely correspond to the sequence combinations present in organisms. For a full understanding of the determinants of the distribution of the chromatosome structural ensemble, studies must include a complete description of the sequences and experimental conditions used, and be designed to enable systematic evaluation of sequence and environmental effects.
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Affiliation(s)
- Mehmet Ali Öztürk
- Molecular and Cellular Modeling Group, Heidelberg Institute for Theoretical Studies (HITS), 69118 Heidelberg, Germany; The Hartmut Hoffmann-Berling International Graduate School of Molecular and Cellular Biology (HBIGS), Heidelberg University, 69120 Heidelberg, Germany
| | - Vlad Cojocaru
- Computational Structural Biology Laboratory, Department of Cellular and Developmental Biology, Max Planck Institute for Molecular Biomedicine, 48149 Münster, Germany; Center for Multiscale Theory and Computation, Westfälische Wilhelms University, 48149 Münster, Germany
| | - Rebecca C Wade
- Molecular and Cellular Modeling Group, Heidelberg Institute for Theoretical Studies (HITS), 69118 Heidelberg, Germany; Center for Molecular Biology (ZMBH), DKFZ-ZMBH Alliance, Heidelberg University, 69120 Heidelberg, Germany; Interdisciplinary Center for Scientific Computing (IWR), 69120 Heidelberg, Germany.
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26
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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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27
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Öztürk MA, Cojocaru V, Wade RC. Dependence of Chromatosome Structure on Linker Histone Sequence and Posttranslational Modification. Biophys J 2018; 114:2363-2375. [PMID: 29759374 PMCID: PMC6129471 DOI: 10.1016/j.bpj.2018.04.034] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2018] [Revised: 03/18/2018] [Accepted: 04/09/2018] [Indexed: 12/20/2022] Open
Abstract
Linker histone (LH) proteins play a key role in higher-order structuring of chromatin for the packing of DNA in eukaryotic cells and in the regulation of genomic function. The common fruit fly (Drosophila melanogaster) has a single somatic isoform of the LH (H1). It is thus a useful model organism for investigating the effects of the LH on nucleosome compaction and the structure of the chromatosome, the complex formed by binding of an LH to a nucleosome. The structural and mechanistic details of how LH proteins bind to nucleosomes are debated. Here, we apply Brownian dynamics simulations to compare the nucleosome binding of the globular domain of D. melanogaster H1 (gH1) and the corresponding chicken (Gallus gallus) LH isoform, gH5, to identify residues in the LH that critically affect the structure of the chromatosome. Moreover, we investigate the effects of posttranslational modifications on the gH1 binding mode. We find that certain single-point mutations and posttranslational modifications of the LH proteins can significantly affect chromatosome structure. These findings indicate that even subtle differences in LH sequence can significantly shift the chromatosome structural ensemble and thus have implications for chromatin structure and transcriptional regulation.
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Affiliation(s)
- Mehmet Ali Öztürk
- Molecular and Cellular Modeling Group, Heidelberg Institute for Theoretical Studies (HITS), Heidelberg, Germany; The Hartmut Hoffmann-Berling International Graduate School of Molecular and Cellular Biology, Heidelberg University, Heidelberg, Germany
| | - Vlad Cojocaru
- Computational Structural Biology Laboratory, 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
| | - Rebecca C Wade
- Molecular and Cellular Modeling Group, Heidelberg Institute for Theoretical Studies (HITS), Heidelberg, Germany; Center for Molecular Biology (ZMBH), DKFZ-ZMBH Alliance, Heidelberg University, Heidelberg, Germany; Interdisciplinary Center for Scientific Computing (IWR), Heidelberg, Germany.
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28
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Bascom GD, Schlick T. Chromatin Fiber Folding Directed by Cooperative Histone Tail Acetylation and Linker Histone Binding. Biophys J 2018; 114:2376-2385. [PMID: 29655483 DOI: 10.1016/j.bpj.2018.03.008] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2018] [Revised: 03/05/2018] [Accepted: 03/12/2018] [Indexed: 12/01/2022] Open
Abstract
In eukaryotic chromatin, islands of histone tail acetylation are found near transcription start sites and enhancers, whereas linker histones (LHs) are localized in intergenic regions with wild-type (WT) histone tails. However, the structural mechanisms by which acetylation, in combination with LH binding, modulates chromatin compaction and hence transcription regulation are unknown. To explore the folding propensity by which these features may govern gene expression, we analyze 20 kb fibers that contain regularly spaced acetylation islands of two sizes (2 or 5 kb) with various LH levels by mesoscale modeling. Specifically, we investigate the effect of acetylating each histone tail (H3, H4, H2A, and H2B) individually, in combination (H3 and H4, or all tails), and adding LH to WT regions. We find that fibers with acetylated H4 tails lose local contacts (<1 kb) and fibers with all tails acetylated have decreased long-range contacts in those regions. Tail interaction plots show that this opening of the fiber is driven by the loss of tail-tail interactions in favor of tail-parent core interactions and/or increase in free tails. When adding LH to WT regions, the fibers undergo hierarchical looping, enriching long-range contacts between WT and acetylated domains. For reference, adding LH to the entire fiber results in local condensation and loss of overall long-range contacts. These findings highlight the cooperation between histone tail acetylation and regulatory proteins like LH in directing folding and structural heterogeneity of chromatin fibers. The results advance our understanding of chromatin contact domains, which represent a pivotal part of the cell cycle, diseased states, and differentiation states in eukaryotic cells.
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Affiliation(s)
- Gavin D Bascom
- Department of Chemistry, New York University, New York, New York
| | - Tamar Schlick
- Department of Chemistry, New York University, New York, New York; Courant Institute of Mathematical Sciences, New York, New York; New York University-East China Normal University Center for Computational Chemistry at New York University Shanghai, Shanghai, China.
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29
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Perišić O, Schlick T. Dependence of the Linker Histone and Chromatin Condensation on the Nucleosome Environment. J Phys Chem B 2017; 121:7823-7832. [PMID: 28732449 DOI: 10.1021/acs.jpcb.7b04917] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The linker histone (LH), an auxiliary protein that can bind to chromatin and interact with the linker DNA to form stem motifs, is a key element of chromatin compaction. By affecting the chromatin condensation level, it also plays an active role in gene expression. However, the presence and variable concentration of LH in chromatin fibers with different DNA linker lengths indicate that its folding and condensation are highly adaptable and dependent on the immediate nucleosome environment. Recent experimental studies revealed that the behavior of LH in mononucleosomes markedly differs from that in small nucleosome arrays, but the associated mechanism is unknown. Here we report a structural analysis of the behavior of LH in mononucleosomes and oligonucleosomes (2-6 nucleosomes) using mesoscale chromatin simulations. We show that the adapted stem configuration heavily depends on the strength of electrostatic interactions between LH and its parental DNA linkers, and that those interactions tend to be asymmetric in small oligonucleosome systems. Namely, LH in oligonucleosomes dominantly interacts with one DNA linker only, as opposed to mononucleosomes where LH has similar interactions with both linkers and forms a highly stable nucleosome stem. Although we show that the LH condensation depends sensitively on the electrostatic interactions with entering and exiting DNA linkers, other interactions, especially by nonparental cores and nonparental linkers, modulate the structural condensation by softening LH and thus making oligonucleosomes more flexible, in comparison to to mono- and dinucleosomes. We also find that the overall LH/chromatin interactions sensitively depend on the linker length because the linker length determines the maximal nucleosome stem length. For mononucleosomes with DNA linkers shorter than LH, LH condenses fully, while for DNA linkers comparable or longer than LH, the LH extension in mononucleosomes strongly follows the length of DNA linkers, unhampered by neighboring linker histones. Thus, LH is more condensed for mononucleosomes with short linkers, compared to oligonucleosomes, and its orientation is variable and highly environment-dependent. More generally, the work underscores the agility of LH whose folding dynamics critically controls genomic packaging and gene expression.
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Affiliation(s)
- Ognjen Perišić
- Big Blue Genomics , Vojvode Brane 32, 11000 Belgrade, Serbia
| | - Tamar Schlick
- Department of Chemistry, New York University , 1001 Silver, 100 Washington Square East, New York, New York 10003, United States.,Courant Institute of Mathematical Sciences, New York University , 251 Mercer Street, New York, New York 10012, United States
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30
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Bascom GD, Kim T, Schlick T. Kilobase Pair Chromatin Fiber Contacts Promoted by Living-System-Like DNA Linker Length Distributions and Nucleosome Depletion. J Phys Chem B 2017; 121:3882-3894. [PMID: 28299939 DOI: 10.1021/acs.jpcb.7b00998] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Nucleosome placement, or DNA linker length patterns, are believed to yield specific spatial features in chromatin fibers, but details are unknown. Here we examine by mesoscale modeling how kilobase (kb) range contacts and fiber looping depend on linker lengths ranging from 18 to 45 bp, with values modeled after living systems, including nucleosome free regions (NFRs) and gene encoding segments. We also compare artificial constructs with alternating versus randomly distributed linker lengths in the range of 18-72 bp. We show that nonuniform distributions with NFRs enhance flexibility and encourage kb-range contacts. NFRs between neighboring gene segments diminish short-range contacts between flanking nucleosomes, while enhancing kb-range contacts via hierarchical looping. We also demonstrate that variances in linker lengths enhance such contacts. In particular, moderate sized variations in fiber linker lengths (∼27 bp) encourage long-range contacts in randomly distributed linker length fibers. Our work underscores the importance of linker length patterns, alongside bound proteins, in biological regulation. Contacts formed by kb-range chromatin folding are crucial to gene activity. Because we find that special linker length distributions in living systems promote kb contacts, our work suggests ways to manipulate these patterns for regulation of gene activity.
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Affiliation(s)
- Gavin D Bascom
- Department of Chemistry, New York University , 100 Washington Square E, New York, New York 10003, United States
| | - Taejin Kim
- Department of Chemistry, New York University , 100 Washington Square E, New York, New York 10003, United States
| | - Tamar Schlick
- Department of Chemistry, New York University , 100 Washington Square E, New York, New York 10003, United States.,Courant Institute of Mathematical Sciences, New York University , 251 Mercer St, New York, New York 10012, United States.,New York University-East China Normal University Center for Computational Chemistry at New York University Shanghai , Room 340, Geography Building, North Zhongshan Road, 3663 Shanghai, China
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31
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Gilbert N, Marenduzzo D. Genome organization: experiments and modeling. Chromosome Res 2017; 25:1-4. [PMID: 28155082 PMCID: PMC5346143 DOI: 10.1007/s10577-017-9551-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2017] [Accepted: 01/11/2017] [Indexed: 11/29/2022]
Affiliation(s)
- Nick Gilbert
- MRC Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Crewe Rd, Edinburgh, EH4 2XR, UK.
| | - Davide Marenduzzo
- SUPA, School of Physics & Astronomy, University of Edinburgh, Peter Guthrie Tait Road, Edinburgh, EH9 3FD, UK.
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32
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Bascom G, Schlick T. Linking Chromatin Fibers to Gene Folding by Hierarchical Looping. Biophys J 2017; 112:434-445. [PMID: 28153411 DOI: 10.1016/j.bpj.2017.01.003] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2016] [Revised: 01/05/2017] [Accepted: 01/06/2017] [Indexed: 12/16/2022] Open
Abstract
While much is known about DNA structure on the basepair level, this scale represents only a fraction of the structural levels involved in folding the genomic material. With recent advances in experimental and theoretical techniques, a variety of structures have been observed on the fiber, gene, and chromosome levels of genome organization. Here we view chromatin architecture from nucleosomes and fibers to genes and chromosomes, highlighting the rich structural diversity and fiber fluidity emerging from both experimental and theoretical techniques. In this context, we discuss our recently proposed folding mechanism, which we call "hierarchical looping", similar to rope flaking used in mountain climbing, where 10-nm zigzag chromatin fibers are compacted laterally into self-associating loops which then stack and fold in space. We propose that hierarchical looping may act as a bridge between fibers and genes as well as provide a mechanism to relate key features of interphase and metaphase chromosome architecture to genome structural changes. This motif emerged by analysis of ultrastructural internucleosome contact data by electron microscopy-assisted nucleosome interaction capture cross-linking experiments, in combination with mesoscale modeling. We suggest that while the local folding of chromatin can be regulated at the fiber level by adjustment of internal factors such as linker-histone binding affinities, linker DNA lengths, and divalent ion levels, hierarchical looping on the gene level can additionally be controlled by posttranslational modifications and external factors such as polycomb group proteins. From a combination of 3C data and mesoscale modeling, we suggest that hierarchical looping could also play a role in epigenetic gene silencing, as stacked loops may occlude access to transcription start sites. With advances in crystallography, single-molecule in vitro biochemistry, in vivo imaging techniques, and genome-wide contact data experiments, various modeling approaches are allowing for previously unavailable structural interpretation of these data at multiple spatial and temporal scales. An unprecedented level of productivity and opportunity is on the horizon for the chromatin structure field.
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Affiliation(s)
- Gavin Bascom
- Department of Chemistry, New York University, New York, New York
| | - Tamar Schlick
- Department of Chemistry, New York University, New York, New York; Courant Institute of Mathematical Sciences, New York University, New York, New York; New York University-East China Normal University Center for Computational Chemistry at New York University Shanghai, Shanghai, China.
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33
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Abstract
Eukaryotic genomes are packaged in chromatin. The higher-order organization of nucleosome core particles is controlled by the association of the intervening linker DNA with either the linker histone H1 or high mobility group box (HMGB) proteins. While H1 is thought to stabilize the nucleosome by preventing DNA unwrapping, the DNA bending imposed by HMGB may propagate to the nucleosome to destabilize chromatin. For metazoan H1, chromatin compaction requires its lysine-rich C-terminal domain, a domain that is buried between globular domains in the previously characterized yeast Saccharomyces cerevisiae linker histone Hho1p. Here, we discuss the functions of S. cerevisiae HMO1, an HMGB family protein unique in containing a terminal lysine-rich domain and in stabilizing genomic DNA. On ribosomal DNA (rDNA) and genes encoding ribosomal proteins, HMO1 appears to exert its role primarily by stabilizing nucleosome-free regions or "fragile" nucleosomes. During replication, HMO1 likewise appears to ensure low nucleosome density at DNA junctions associated with the DNA damage response or the need for topoisomerases to resolve catenanes. Notably, HMO1 shares with the mammalian linker histone H1 the ability to stabilize chromatin, as evidenced by the absence of HMO1 creating a more dynamic chromatin environment that is more sensitive to nuclease digestion and in which chromatin-remodeling events associated with DNA double-strand break repair occur faster; such chromatin stabilization requires the lysine-rich extension of HMO1. Thus, HMO1 appears to have evolved a unique linker histone-like function involving the ability to stabilize both conventional nucleosome arrays as well as DNA regions characterized by low nucleosome density or the presence of noncanonical nucleosomes.
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34
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Öztürk MA, Pachov GV, Wade RC, Cojocaru V. Conformational selection and dynamic adaptation upon linker histone binding to the nucleosome. Nucleic Acids Res 2016; 44:6599-613. [PMID: 27270081 PMCID: PMC5001602 DOI: 10.1093/nar/gkw514] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2016] [Revised: 05/06/2016] [Accepted: 05/30/2016] [Indexed: 01/25/2023] Open
Abstract
Linker histones are essential for DNA compaction in chromatin. They bind to nucleosomes in a 1:1 ratio forming chromatosomes. Alternative configurations have been proposed in which the globular domain of the linker histone H5 (gH5) is positioned either on- or off-dyad between the nucleosomal and linker DNAs. However, the dynamic pathways of chromatosome assembly remain elusive. Here, we studied the conformational plasticity of gH5 in unbound and off-dyad nucleosome-bound forms with classical and accelerated molecular dynamics simulations. We find that the unbound gH5 converts between open and closed conformations, preferring the closed form. However, the open gH5 contributes to a more rigid chromatosome and restricts the motion of the nearby linker DNA through hydrophobic interactions with thymidines. Moreover, the closed gH5 opens and reorients in accelerated simulations of the chromatosome. Brownian dynamics simulations of chromatosome assembly, accounting for a range of amplitudes of nucleosome opening and different nucleosome DNA sequences, support the existence of both on- and off-dyad binding modes of gH5 and reveal alternative, sequence and conformation-dependent chromatosome configurations. Taken together, these findings suggest that the conformational dynamics of linker histones and nucleosomes facilitate alternative chromatosome configurations through an interplay between induced fit and conformational selection.
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Affiliation(s)
- Mehmet Ali Öztürk
- Molecular and Cellular Modeling Group, Heidelberg Institute for Theoretical Studies (HITS), Heidelberg 69118, Germany The Hartmut Hoffmann-Berling International Graduate School of Molecular and Cellular Biology (HBIGS), Heidelberg University, Heidelberg 69120, Germany
| | - Georgi V Pachov
- Molecular and Cellular Modeling Group, Heidelberg Institute for Theoretical Studies (HITS), Heidelberg 69118, Germany
| | - Rebecca C Wade
- Molecular and Cellular Modeling Group, Heidelberg Institute for Theoretical Studies (HITS), Heidelberg 69118, Germany Center for Molecular Biology (ZMBH), DKFZ-ZMBH Alliance, Heidelberg University, Heidelberg 69120, Germany Interdisciplinary Center for Scientific Computing (IWR), Heidelberg 69120, Germany
| | - Vlad Cojocaru
- Computational Structural Biology Laboratory, Department of Cellular and Developmental Biology, Max Planck Institute for Molecular Biomedicine, Münster 48149, Germany Center for Multiscale Theory and Computation, Westfälische Wilhelms University, Münster 48149, Germany
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35
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Fang H, Wei S, Lee TH, Hayes JJ. Chromatin structure-dependent conformations of the H1 CTD. Nucleic Acids Res 2016; 44:9131-9141. [PMID: 27365050 PMCID: PMC5100576 DOI: 10.1093/nar/gkw586] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2016] [Accepted: 06/20/2016] [Indexed: 12/17/2022] Open
Abstract
Linker histones are an integral component of chromatin but how these proteins promote assembly of chromatin fibers and higher order structures and regulate gene expression remains an open question. Using Förster resonance energy transfer (FRET) approaches we find that association of a linker histone with oligonucleosomal arrays induces condensation of the intrinsically disordered H1 CTD in a manner consistent with adoption of a defined fold or ensemble of folds in the bound state. However, H1 CTD structure when bound to nucleosomes in arrays is distinct from that induced upon H1 association with mononucleosomes or bare double stranded DNA. Moreover, the H1 CTD becomes more condensed upon condensation of extended nucleosome arrays to the contacting zig-zag form found in moderate salts, but does not detectably change during folding to fully compacted chromatin fibers. We provide evidence that linker DNA conformation is a key determinant of H1 CTD structure and that constraints imposed by neighboring nucleosomes cause linker DNAs to adopt distinct trajectories in oligonucleosomes compared to H1-bound mononucleosomes. Finally, inter-molecular FRET between H1s within fully condensed nucleosome arrays suggests a regular spatial arrangement for the H1 CTD within the 30 nm chromatin fiber.
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Affiliation(s)
- He Fang
- Department of Biochemistry and Biophysics, University of Rochester Medical Center, Rochester, NY 14642, USA
| | - Sijie Wei
- Department of Chemistry, The Pennsylvania State University, University Park, PA 16802, USA
| | - Tae-Hee Lee
- Department of Chemistry, The Pennsylvania State University, University Park, PA 16802, USA
| | - Jeffrey J Hayes
- Department of Biochemistry and Biophysics, University of Rochester Medical Center, Rochester, NY 14642, USA
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36
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Cutter AR, Hayes JJ. Linker histones: novel insights into structure-specific recognition of the nucleosome. Biochem Cell Biol 2016; 95:171-178. [PMID: 28177778 DOI: 10.1139/bcb-2016-0097] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Linker histones (H1s) are a primary component of metazoan chromatin, fulfilling numerous functions, both in vitro and in vivo, including stabilizing the wrapping of DNA around the nucleosome, promoting folding and assembly of higher order chromatin structures, influencing nucleosome spacing on DNA, and regulating specific gene expression. However, many molecular details of how H1 binds to nucleosomes and recognizes unique structural features on the nucleosome surface remain undefined. Numerous, confounding studies are complicated not only by experimental limitations, but the use of different linker histone isoforms and nucleosome constructions. This review summarizes the decades of research that has resulted in several models of H1 association with nucleosomes, with a focus on recent advances that suggest multiple modes of H1 interaction in chromatin, while highlighting the remaining questions.
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Affiliation(s)
- Amber R Cutter
- Department of Biochemistry & Biophysics, University of Rochester Medical Center, Rochester, NY 14642, USA.,Department of Biochemistry & Biophysics, University of Rochester Medical Center, Rochester, NY 14642, USA
| | - Jeffrey J Hayes
- Department of Biochemistry & Biophysics, University of Rochester Medical Center, Rochester, NY 14642, USA.,Department of Biochemistry & Biophysics, University of Rochester Medical Center, Rochester, NY 14642, USA
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37
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38
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Bascom GD, Sanbonmatsu KY, Schlick T. Mesoscale Modeling Reveals Hierarchical Looping of Chromatin Fibers Near Gene Regulatory Elements. J Phys Chem B 2016; 120:8642-53. [PMID: 27218881 DOI: 10.1021/acs.jpcb.6b03197] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
While it is well-recognized that chromatin loops play an important role in gene regulation, structural details regarding higher order chromatin loops are only emerging. Here we present a systematic study of restrained chromatin loops ranging from 25 to 427 nucleosomes (fibers of 5-80 Kb DNA in length), mimicking gene elements studied by 3C contact data. We find that hierarchical looping represents a stable configuration that can effectively bring distant regions of the GATA-4 gene together, satisfying connections reported by 3C experiments. Additionally, we find that restrained chromatin fibers larger than 100 nucleosomes (∼20Kb) form closed plectonemes, whereas fibers shorter than 100 nucleosomes form simple hairpin loops. By studying the dependence of loop structures on internal parameters, we show that loop features are sensitive to linker histone concentration, loop length, divalent ions, and DNA linker length. Specifically, increasing loop length, linker histone concentration, and divalent ion concentration are associated with increased persistence length (or decreased bending), while varying DNA linker length in a manner similar to experimentally observed "nucleosome free regions" (found near transcription start sites) disrupts intertwining and leads to loop opening and increased persistence length in linker histone depleted (-LH) fibers. Chromatin fiber structure sensitivity to these parameters, all of which vary throughout the cell cycle, tissue type, and species, suggests that caution is warranted when using uniform polymer models to fit chromatin conformation capture genome-wide data. Furthermore, the folding geometry we observe near the transcription initiation site of the GATA-4 gene suggests that hierarchical looping provides a structural mechanism for gene inhibition, and offers tunable parameters for design of gene regulation elements.
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Affiliation(s)
- Gavin D Bascom
- Department of Chemistry, New York University , 100 Washington Square East, New York, New York 10003, United States
| | - Karissa Y Sanbonmatsu
- Theoretical Biology and Biophysics Group, Theoretical Division, Los Alamos National Laboratory , Bikini Atoll Road, SM 30, Los Alamos, New Mexico 87545, United States
| | - Tamar Schlick
- Department of Chemistry, New York University , 100 Washington Square East, New York, New York 10003, United States.,Courant Institute of Mathematical Sciences, New York University , 251 Mercer Street, New York, New York 10012, United States
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39
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Luque A, Ozer G, Schlick T. Correlation among DNA Linker Length, Linker Histone Concentration, and Histone Tails in Chromatin. Biophys J 2016; 110:2309-2319. [PMID: 27276249 PMCID: PMC4906253 DOI: 10.1016/j.bpj.2016.04.024] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2015] [Revised: 04/12/2016] [Accepted: 04/19/2016] [Indexed: 01/08/2023] Open
Abstract
Eukaryotic cells condense their genetic material in the nucleus in the form of chromatin, a macromolecular complex made of DNA and multiple proteins. The structure of chromatin is intimately connected to the regulation of all eukaryotic organisms, from amoebas to humans, but its organization remains largely unknown. The nucleosome repeat length (NRL) and the concentration of linker histones (ρLH) are two structural parameters that vary among cell types and cell cycles; the NRL is the number of DNA basepairs wound around each nucleosome core plus the number of basepairs linking successive nucleosomes. Recent studies have found a linear empirical relationship between the variation of these two properties for different cells, but its underlying mechanism remains elusive. Here we apply our established mesoscale chromatin model to explore the mechanisms responsible for this relationship, by investigating chromatin fibers as a function of NRL and ρLH combinations. We find that a threshold of linker histone concentration triggers the compaction of chromatin into well-formed 30-nm fibers; this critical value increases linearly with NRL, except for long NRLs, where the fibers remain disorganized. Remarkably, the interaction patterns between core histone tails and chromatin elements are highly sensitive to the NRL and ρLH combination, suggesting a molecular mechanism that could have a key role in regulating the structural state of the fibers in the cell. An estimate of the minimized work and volume associated with storage of chromatin fibers in the nucleus further suggests factors that could spontaneously regulate the NRL as a function of linker histone concentration. Both the tail interaction map and DNA packing considerations support the empirical NRL/ρLH relationship and offer a framework to interpret experiments for different chromatin conditions in the cell.
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Affiliation(s)
- Antoni Luque
- Department of Mathematics and Statistics, Viral Information Institute and Computational Science Research Center, San Diego State University, San Diego, California
| | - Gungor Ozer
- Department of Chemistry, New York University, New York, New York
| | - Tamar Schlick
- Department of Chemistry, New York University, New York, New York; Courant Institute of Mathematical Sciences, New York University, New York, New York; New York University-East China Normal University Center for Computational Chemistry at New York University Shanghai, Shanghai, China.
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40
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Roque A, Ponte I, Suau P. Post-translational modifications of the intrinsically disordered terminal domains of histone H1: effects on secondary structure and chromatin dynamics. Chromosoma 2016; 126:83-91. [DOI: 10.1007/s00412-016-0591-8] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2016] [Revised: 04/05/2016] [Accepted: 04/07/2016] [Indexed: 01/14/2023]
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41
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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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42
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Hierarchical looping of zigzag nucleosome chains in metaphase chromosomes. Proc Natl Acad Sci U S A 2016; 113:1238-43. [PMID: 26787893 DOI: 10.1073/pnas.1518280113] [Citation(s) in RCA: 96] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The architecture of higher-order chromatin in eukaryotic cell nuclei is largely unknown. Here, we use electron microscopy-assisted nucleosome interaction capture (EMANIC) cross-linking experiments in combination with mesoscale chromatin modeling of 96-nucleosome arrays to investigate the internal organization of condensed chromatin in interphase cell nuclei and metaphase chromosomes at nucleosomal resolution. The combined data suggest a novel hierarchical looping model for chromatin higher-order folding, similar to rope flaking used in mountain climbing and rappelling. Not only does such packing help to avoid tangling and self-crossing, it also facilitates rope unraveling. Hierarchical looping is characterized by an increased frequency of higher-order internucleosome contacts for metaphase chromosomes compared with chromatin fibers in vitro and interphase chromatin, with preservation of a dominant two-start zigzag organization associated with the 30-nm fiber. Moreover, the strong dependence of looping on linker histone concentration suggests a hierarchical self-association mechanism of relaxed nucleosome zigzag chains rather than longitudinal compaction as seen in 30-nm fibers. Specifically, concentrations lower than one linker histone per nucleosome promote self-associations and formation of these looped networks of zigzag fibers. The combined experimental and modeling evidence for condensed metaphase chromatin as hierarchical loops and bundles of relaxed zigzag nucleosomal chains rather than randomly coiled threads or straight and stiff helical fibers reconciles aspects of other models for higher-order chromatin structure; it constitutes not only an efficient storage form for the genomic material, consistent with other genome-wide chromosome conformation studies that emphasize looping, but also a convenient organization for local DNA unraveling and genome access.
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43
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HERBOMEL G, GRICHINE A, FERTIN A, DELON A, VOURC'H C, SOUCHIER C, USSON Y. Wavelet transform analysis of chromatin texture changes during heat shock. J Microsc 2015; 262:295-305. [DOI: 10.1111/jmi.12363] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2014] [Accepted: 11/17/2015] [Indexed: 11/29/2022]
Affiliation(s)
- G. HERBOMEL
- INSERM, IAB, University Grenoble Alpes; Grenoble France
| | - A. GRICHINE
- INSERM, IAB, University Grenoble Alpes; Grenoble France
| | - A FERTIN
- CNRS, TIMC-IMAG, University Grenoble Alpes; Grenoble France
| | - A. DELON
- CNRS, LIPHY, University Grenoble Alpes; Grenoble France
| | - C. VOURC'H
- INSERM, IAB, University Grenoble Alpes; Grenoble France
| | - C. SOUCHIER
- INSERM, IAB, University Grenoble Alpes; Grenoble France
| | - Y. USSON
- CNRS, TIMC-IMAG, University Grenoble Alpes; Grenoble France
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Pan C, Fan Y. Role of H1 linker histones in mammalian development and stem cell differentiation. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2015; 1859:496-509. [PMID: 26689747 DOI: 10.1016/j.bbagrm.2015.12.002] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/09/2015] [Revised: 12/09/2015] [Accepted: 12/09/2015] [Indexed: 12/19/2022]
Abstract
H1 linker histones are key chromatin architectural proteins facilitating the formation of higher order chromatin structures. The H1 family constitutes the most heterogeneous group of histone proteins, with eleven non-allelic H1 variants in mammals. H1 variants differ in their biochemical properties and exhibit significant sequence divergence from one another, yet most of them are highly conserved during evolution from mouse to human. H1 variants are differentially regulated during development and their cellular compositions undergo dramatic changes in embryogenesis, gametogenesis, tissue maturation and cellular differentiation. As a group, H1 histones are essential for mouse development and proper stem cell differentiation. Here we summarize our current knowledge on the expression and functions of H1 variants in mammalian development and stem cell differentiation. Their diversity, sequence conservation, complex expression and distinct functions suggest that H1s mediate chromatin reprogramming and contribute to the large variations and complexity of chromatin structure and gene expression in the mammalian genome.
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Affiliation(s)
- Chenyi Pan
- School of Biology, Georgia Institute of Technology, Atlanta, GA 30332, USA; The Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA 30332, USA
| | - Yuhong Fan
- School of Biology, Georgia Institute of Technology, Atlanta, GA 30332, USA; The Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA 30332, USA.
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45
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Crane-Robinson C. Linker histones: History and current perspectives. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2015; 1859:431-5. [PMID: 26459501 DOI: 10.1016/j.bbagrm.2015.10.008] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2015] [Revised: 10/07/2015] [Accepted: 10/08/2015] [Indexed: 12/11/2022]
Abstract
Although the overall structure of the fifth histone (linker histone, H1) is understood, its location on the nucleosome is only partially defined. Whilst it is clear that H1 helps condense the chromatin fibre, precisely how this is achieved remains to be determined. H1 is not a general gene repressor in that although it must be displaced from transcription start sites for activity to occur, there is only partial loss along the body of genes. How the deposition and removal of H1 occurs in particular need of further study. Linker histones are highly abundant nuclear proteins about which we know too little.
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Affiliation(s)
- C Crane-Robinson
- Biophysics Laboratories, School of Biology, University of Portsmouth, PO1 2DT, UK
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46
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Roque A, Ponte I, Suau P. Interplay between histone H1 structure and function. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2015; 1859:444-54. [PMID: 26415976 DOI: 10.1016/j.bbagrm.2015.09.009] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2015] [Revised: 09/21/2015] [Accepted: 09/22/2015] [Indexed: 01/10/2023]
Abstract
H1 linker histones are involved both in the maintenance of higher-order chromatin structure and in gene regulation. Histone H1 exists in multiple isoforms, is evolutionarily variable and undergoes a large variety of post-translational modifications. We review recent progress in the understanding of the folding and structure of histone H1 domains with an emphasis on the interactions with DNA. The importance of intrinsic disorder and hydrophobic interactions in the folding and function of the carboxy-terminal domain (CTD) is discussed. The induction of a molten globule-state in the CTD by macromolecular crowding is also considered. The effects of phosphorylation by cyclin-dependent kinases on the structure of the CTD, as well as on chromatin condensation and oligomerization, are described. We also address the extranuclear functions of histone H1, including the interaction with the β-amyloid peptide.
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Affiliation(s)
- Alicia Roque
- Departamento de Bioquímica y Biología Molecular, Facultad de Biociencias, Universidad Autónoma de Barcelona, Spain
| | - Inma Ponte
- Departamento de Bioquímica y Biología Molecular, Facultad de Biociencias, Universidad Autónoma de Barcelona, Spain
| | - Pedro Suau
- Departamento de Bioquímica y Biología Molecular, Facultad de Biociencias, Universidad Autónoma de Barcelona, Spain.
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47
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Collepardo-Guevara R, Portella G, Vendruscolo M, Frenkel D, Schlick T, Orozco M. Chromatin Unfolding by Epigenetic Modifications Explained by Dramatic Impairment of Internucleosome Interactions: A Multiscale Computational Study. J Am Chem Soc 2015; 137:10205-15. [PMID: 26192632 PMCID: PMC6251407 DOI: 10.1021/jacs.5b04086] [Citation(s) in RCA: 107] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Histone tails and their epigenetic modifications play crucial roles in gene expression regulation by altering the architecture of chromatin. However, the structural mechanisms by which histone tails influence the interconversion between active and inactive chromatin remain unknown. Given the technical challenges in obtaining detailed experimental characterizations of the structure of chromatin, multiscale computations offer a promising alternative to model the effect of histone tails on chromatin folding. Here we combine multimicrosecond atomistic molecular dynamics simulations of dinucleosomes and histone tails in explicit solvent and ions, performed with three different state-of-the-art force fields and validated by experimental NMR measurements, with coarse-grained Monte Carlo simulations of 24-nucleosome arrays to describe the conformational landscape of histone tails, their roles in chromatin compaction, and the impact of lysine acetylation, a widespread epigenetic change, on both. We find that while the wild-type tails are highly flexible and disordered, the dramatic increase of secondary-structure order by lysine acetylation unfolds chromatin by decreasing tail availability for crucial fiber-compacting internucleosome interactions. This molecular level description of the effect of histone tails and their charge modifications on chromatin folding explains the sequence sensitivity and underscores the delicate connection between local and global structural and functional effects. Our approach also opens new avenues for multiscale processes of biomolecular complexes.
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Affiliation(s)
- Rosana Collepardo-Guevara
- Chemistry Department, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW UK
- Joint BSC-CRG-IRB Pro-gramme on Computational Biology. Institute for Research in Biomedicine. Baldiri i Reixac 19. 08028, Barcelona, Spain
| | - Guillem Portella
- Chemistry Department, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW UK
- Joint BSC-CRG-IRB Pro-gramme on Computational Biology. Institute for Research in Biomedicine. Baldiri i Reixac 19. 08028, Barcelona, Spain
| | - Michele Vendruscolo
- Chemistry Department, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW UK
| | - Daan Frenkel
- Chemistry Department, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW UK
| | - Tamar Schlick
- Department of Chemistry, New York University, 100 Washington Square East, New York, NY 10003, USA
- Courant Institute of Mathematical Sciences, New York University, 251 Mercer Street, New York, NY 10012, USA
| | - Modesto Orozco
- Joint BSC-CRG-IRB Pro-gramme on Computational Biology. Institute for Research in Biomedicine. Baldiri i Reixac 19. 08028, Barcelona, Spain
- Departament de Bioquímica i Biologia Molecular. Facultat de Biologia. Universitat de Barcelona. Avgda Diagonal 643, 08028, Barcelona, Spain
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Ozer G, Luque A, Schlick T. The chromatin fiber: multiscale problems and approaches. Curr Opin Struct Biol 2015; 31:124-39. [PMID: 26057099 DOI: 10.1016/j.sbi.2015.04.002] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2014] [Revised: 04/08/2015] [Accepted: 04/09/2015] [Indexed: 12/20/2022]
Abstract
The structure of chromatin, affected by many factors from DNA linker lengths to posttranslational modifications, is crucial to the regulation of eukaryotic cells. Combined experimental and computational methods have led to new insights into its structural and dynamical features, from interactions due to the flexible core histone tails or linker histones to the physical mechanism driving the formation of chromosomal domains. Here we present a perspective of recent advances in chromatin modeling techniques at the atomic, mesoscopic, and chromosomal scales with a view toward developing multiscale computational strategies to integrate such findings. Innovative modeling methods that connect molecular to chromosomal scales are crucial for interpreting experiments and eventually deciphering the complex dynamic organization and function of chromatin in the cell.
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Affiliation(s)
- Gungor Ozer
- Department of Chemistry, 100 Washington Square East, New York University, New York, NY 10003, USA
| | - Antoni Luque
- Department of Chemistry, 100 Washington Square East, New York University, New York, NY 10003, USA; Current address: Department of Mathematics & Statistics and Viral Information Institute, San Diego State University, 5500 Campanile Drive, San Diego, CA 92182-7720, USA
| | - Tamar Schlick
- Department of Chemistry, 100 Washington Square East, New York University, New York, NY 10003, USA; Courant Institute of Mathematical Sciences, New York University, 251 Mercer Street, New York, NY 10012, USA; NYU-ECNU Center for Computational Chemistry at NYU Shanghai, 3663 Zhongshan Road North, Shanghai 200062, China.
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Interaction of chromatin with a histone H1 containing swapped N- and C-terminal domains. Biosci Rep 2015; 35:BSR20150087. [PMID: 26182371 PMCID: PMC4613717 DOI: 10.1042/bsr20150087] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2015] [Accepted: 04/27/2015] [Indexed: 12/12/2022] Open
Abstract
The present study was to understand whether the globular or C-terminal linker histone domain is more important for its binding to chromatin. Using histone H1, with swapped domain orientation,
we found that both domains are equally important for nucleosome binding. Although the details of the structural involvement of histone H1 in the organization of the nucleosome are quite well understood, the sequential events involved in the recognition of its binding site are not as well known. We have used a recombinant human histone H1 (H1.1) in which the N- and C-terminal domains (NTD/CTD) have been swapped and we have reconstituted it on to a 208-bp nucleosome. We have shown that the swapped version of the protein is still able to bind to nucleosomes through its structurally folded wing helix domain (WHD); however, analytical ultracentrifuge analysis demonstrates its ability to properly fold the chromatin fibre is impaired. Furthermore, FRAP analysis shows that the highly dynamic binding association of histone H1 with the chromatin fibre is altered, with a severely decreased half time of residence. All of this suggests that proper binding of histone H1 to chromatin is determined by the simultaneous and synergistic binding of its WHD–CTD to the nucleosome.
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50
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Lopez R, Sarg B, Lindner H, Bartolomé S, Ponte I, Suau P, Roque A. Linker histone partial phosphorylation: effects on secondary structure and chromatin condensation. Nucleic Acids Res 2015; 43:4463-76. [PMID: 25870416 PMCID: PMC4482070 DOI: 10.1093/nar/gkv304] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2014] [Accepted: 03/27/2015] [Indexed: 11/29/2022] Open
Abstract
Linker histones are involved in chromatin higher-order structure and gene regulation. We have successfully achieved partial phosphorylation of linker histones in chicken erythrocyte soluble chromatin with CDK2, as indicated by HPCE, MALDI-TOF and Tandem MS. We have studied the effects of linker histone partial phosphorylation on secondary structure and chromatin condensation. Infrared spectroscopy analysis showed a gradual increase of β-structure in the phosphorylated samples, concomitant to a decrease in α-helix/turns, with increasing linker histone phosphorylation. This conformational change could act as the first step in the phosphorylation-induced effects on chromatin condensation. A decrease of the sedimentation rate through sucrose gradients of the phosphorylated samples was observed, indicating a global relaxation of the 30-nm fiber following linker histone phosphorylation. Analysis of specific genes, combining nuclease digestion and qPCR, showed that phosphorylated samples were more accessible than unphosphorylated samples, suggesting local chromatin relaxation. Chromatin aggregation was induced by MgCl2 and analyzed by dynamic light scattering (DLS). Phosphorylated chromatin had lower percentages in volume of aggregated molecules and the aggregates had smaller hydrodynamic diameter than unphosphorylated chromatin, indicating that linker histone phosphorylation impaired chromatin aggregation. These findings provide new insights into the effects of linker histone phosphorylation in chromatin condensation.
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Affiliation(s)
- Rita Lopez
- Departamento de Bioquímica y Biología Molecular, Facultad de Biociencias, Universidad Autónoma de Barcelona, 08193, Bellaterra, Barcelona, Spain
| | - Bettina Sarg
- Division of Clinical Biochemistry, Biocenter, Innsbruck Medical University, A-6020, Innsbruck, Austria
| | - Herbert Lindner
- Division of Clinical Biochemistry, Biocenter, Innsbruck Medical University, A-6020, Innsbruck, Austria
| | - Salvador Bartolomé
- Laboratorio de Luminiscencia y Espectroscopia de Biomoléculas, Universidad Autónoma de Barcelona, 08193, Bellaterra, Barcelona, Spain
| | - Inma Ponte
- Departamento de Bioquímica y Biología Molecular, Facultad de Biociencias, Universidad Autónoma de Barcelona, 08193, Bellaterra, Barcelona, Spain
| | - Pedro Suau
- Departamento de Bioquímica y Biología Molecular, Facultad de Biociencias, Universidad Autónoma de Barcelona, 08193, Bellaterra, Barcelona, Spain
| | - Alicia Roque
- Departamento de Bioquímica y Biología Molecular, Facultad de Biociencias, Universidad Autónoma de Barcelona, 08193, Bellaterra, Barcelona, Spain
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