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Clerkin AB, Pagane N, West DW, Spakowitz AJ, Risca VI. Determining mesoscale chromatin structure parameters from spatially correlated cleavage data using a coarse-grained oligonucleosome model. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.07.28.605011. [PMID: 39131347 PMCID: PMC11312488 DOI: 10.1101/2024.07.28.605011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 08/13/2024]
Abstract
The three-dimensional structure of chromatin has emerged as an important feature of eukaryotic gene regulation. Recent technological advances in DNA sequencing-based assays have revealed locus- and chromatin state-specific structural patterns at the length scale of a few nucleosomes (~1 kb). However, interpreting these data sets remains challenging. Radiation-induced correlated cleavage of chromatin (RICC-seq) is one such chromatin structure assay that maps DNA-DNA-contacts at base pair resolution by sequencing single-stranded DNA fragments released from irradiated cells. Here, we develop a flexible modeling and simulation framework to enable the interpretation of RICC-seq data in terms of oligonucleosome structure ensembles. Nucleosomes are modeled as rigid bodies with excluded volume and adjustable DNA wrapping, connected by linker DNA modeled as a worm-like chain. We validate the model's parameters against cryo-electron microscopy and sedimentation data. Our results show that RICC-seq is sensitive to nucleosome spacing, nucleosomal DNA wrapping, and the strength of inter-nucleosome interactions. We show that nucleosome repeat lengths consistent with orthogonal assays can be extracted from experimental RICC-seq data using a 1D convolutional neural net trained on RICC-seq signal predicted from simulated ensembles. We thus provide a suite of analysis tools that add quantitative structural interpretability to RICC-seq experiments.
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Affiliation(s)
- Ariana Brenner Clerkin
- Laboratory of Genome Architecture and Dynamics, The Rockefeller University, New York, NY
- Tri-Institutional PhD Program in Computational Biology and Medicine, Cornell University, New York, NY
| | - Nicole Pagane
- Present affiliation: Computational and Systems Biology PhD Program, Massachusetts Institute of Technology, Cambridge, MA
| | - Devany W. West
- Laboratory of Genome Architecture and Dynamics, The Rockefeller University, New York, NY
| | | | - Viviana I. Risca
- Laboratory of Genome Architecture and Dynamics, The Rockefeller University, New York, NY
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2
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Kaur U, Muñoz EN, Narlikar GJ. Hexasomal particles: consequence or also consequential? Curr Opin Genet Dev 2024; 85:102163. [PMID: 38412564 DOI: 10.1016/j.gde.2024.102163] [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: 09/21/2023] [Revised: 12/07/2023] [Accepted: 01/29/2024] [Indexed: 02/29/2024]
Abstract
It is long known that an RNA polymerase transcribing through a nucleosome can generate subnucleosomal particles called hexasomes. These particles lack an H2A-H2B dimer, breaking the symmetry of a nucleosome and revealing new interfaces. Whether hexasomes are simply a consequence of RNA polymerase action or they also have a regulatory impact remains an open question. Recent biochemical and structural studies of RNA polymerases and chromatin remodelers with hexasomes motivated us to revisit this question. Here, we build on previous models to discuss how formation of hexasomes can allow sophisticated regulation of transcription and also significantly impact chromatin folding. We anticipate that further cellular and biochemical analysis of these subnucleosomal particles will uncover additional regulatory roles.
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Affiliation(s)
- Upneet Kaur
- Department of Biochemistry and Biophysics, University of California, San Francisco, CA 94158, USA; Biophysics Graduate Program, University of California, San Francisco, CA 94158, USA
| | - Elise N Muñoz
- Department of Biochemistry and Biophysics, University of California, San Francisco, CA 94158, USA; Tetrad Graduate Program, University of California, San Francisco, CA 94158, USA
| | - Geeta J Narlikar
- Department of Biochemistry and Biophysics, University of California, San Francisco, CA 94158, USA.
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3
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Jentink N, Purnell C, Kable B, Swulius MT, Grigoryev SA. Cryoelectron tomography reveals the multiplex anatomy of condensed native chromatin and its unfolding by histone citrullination. Mol Cell 2023; 83:3236-3252.e7. [PMID: 37683647 PMCID: PMC10566567 DOI: 10.1016/j.molcel.2023.08.017] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2022] [Revised: 05/31/2023] [Accepted: 08/16/2023] [Indexed: 09/10/2023]
Abstract
Nucleosome chains fold and self-associate to form higher-order structures whose internal organization is unknown. Here, cryoelectron tomography (cryo-ET) of native human chromatin reveals intrinsic folding motifs such as (1) non-uniform nucleosome stacking, (2) intermittent parallel and perpendicular orientations of adjacent nucleosome planes, and (3) a regressive nucleosome chain path, which deviates from the direct zigzag topology seen in reconstituted nucleosomal arrays. By examining the self-associated structures, we observed prominent nucleosome stacking in cis and anti-parallel nucleosome interactions, which are consistent with partial nucleosome interdigitation in trans. Histone citrullination strongly inhibits nucleosome stacking and self-association with a modest effect on chromatin folding, whereas the reconstituted arrays undergo a dramatic unfolding into open zigzag chains induced by histone citrullination. This study sheds light on the internal structure of compact chromatin nanoparticles and suggests a mechanism for how epigenetic changes in chromatin folding are retained across both open and condensed forms.
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Affiliation(s)
- Nathan Jentink
- Penn State University College of Medicine, Department of Biochemistry & Molecular Biology, H171, Milton S. Hershey Medical Center, P.O. Box 850, 500 University Drive, Hershey, PA 17033, USA
| | - Carson Purnell
- Penn State University College of Medicine, Department of Biochemistry & Molecular Biology, H171, Milton S. Hershey Medical Center, P.O. Box 850, 500 University Drive, Hershey, PA 17033, USA
| | - Brianna Kable
- Penn State University College of Medicine, Department of Biochemistry & Molecular Biology, H171, Milton S. Hershey Medical Center, P.O. Box 850, 500 University Drive, Hershey, PA 17033, USA
| | - Matthew T Swulius
- Penn State University College of Medicine, Department of Biochemistry & Molecular Biology, H171, Milton S. Hershey Medical Center, P.O. Box 850, 500 University Drive, Hershey, PA 17033, USA.
| | - Sergei A Grigoryev
- Penn State University College of Medicine, Department of Biochemistry & Molecular Biology, H171, Milton S. Hershey Medical Center, P.O. Box 850, 500 University Drive, Hershey, PA 17033, USA.
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4
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Kadam S, Kumari K, Manivannan V, Dutta S, Mitra MK, Padinhateeri R. Predicting scale-dependent chromatin polymer properties from systematic coarse-graining. Nat Commun 2023; 14:4108. [PMID: 37433821 PMCID: PMC10336007 DOI: 10.1038/s41467-023-39907-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2022] [Accepted: 06/30/2023] [Indexed: 07/13/2023] Open
Abstract
Simulating chromatin is crucial for predicting genome organization and dynamics. Although coarse-grained bead-spring polymer models are commonly used to describe chromatin, the relevant bead dimensions, elastic properties, and the nature of inter-bead potentials are unknown. Using nucleosome-resolution contact probability (Micro-C) data, we systematically coarse-grain chromatin and predict quantities essential for polymer representation of chromatin. We compute size distributions of chromatin beads for different coarse-graining scales, quantify fluctuations and distributions of bond lengths between neighboring regions, and derive effective spring constant values. Unlike the prevalent notion, our findings argue that coarse-grained chromatin beads must be considered as soft particles that can overlap, and we derive an effective inter-bead soft potential and quantify an overlap parameter. We also compute angle distributions giving insights into intrinsic folding and local bendability of chromatin. While the nucleosome-linker DNA bond angle naturally emerges from our work, we show two populations of local structural states. The bead sizes, bond lengths, and bond angles show different mean behavior at Topologically Associating Domain (TAD) boundaries and TAD interiors. We integrate our findings into a coarse-grained polymer model and provide quantitative estimates of all model parameters, which can serve as a foundational basis for all future coarse-grained chromatin simulations.
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Affiliation(s)
- Sangram Kadam
- Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Mumbai, 400076, India.
| | - Kiran Kumari
- Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Mumbai, 400076, India
| | - Vinoth Manivannan
- Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Mumbai, 400076, India
| | - Shuvadip Dutta
- Department of Physics, Indian Institute of Technology Bombay, Mumbai, 400076, India
| | - Mithun K Mitra
- Department of Physics, Indian Institute of Technology Bombay, Mumbai, 400076, India
| | - Ranjith Padinhateeri
- Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Mumbai, 400076, India.
- Sunita Sanghi Centre of Aging and Neurodegenerative Diseases, Indian Institute of Technology Bombay, Mumbai, 400076, India.
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5
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Smrt ST, Gonzalez Salguero N, Thomas JK, Zandian M, Poirier MG, Jaroniec CP. Histone H3 core domain in chromatin with different DNA linker lengths studied by 1H-Detected solid-state NMR spectroscopy. Front Mol Biosci 2023; 9:1106588. [PMID: 36660422 PMCID: PMC9846530 DOI: 10.3389/fmolb.2022.1106588] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2022] [Accepted: 12/20/2022] [Indexed: 01/06/2023] Open
Abstract
Chromatin, a dynamic protein-DNA complex that regulates eukaryotic genome accessibility and essential functions, is composed of nucleosomes connected by linker DNA with each nucleosome consisting of DNA wrapped around an octamer of histones H2A, H2B, H3 and H4. Magic angle spinning solid-state nuclear magnetic resonance (NMR) spectroscopy can yield unique insights into histone structure and dynamics in condensed nucleosomes and nucleosome arrays representative of chromatin at physiological concentrations. Recently we used J-coupling-based solid-state NMR methods to investigate with residue-specific resolution the conformational dynamics of histone H3 N-terminal tails in 16-mer nucleosome arrays containing 15, 30 or 60 bp DNA linkers. Here, we probe the H3 core domain in the 16-mer arrays as a function of DNA linker length via dipolar coupling-based 1H-detected solid-state NMR techniques. Specifically, we established nearly complete assignments of backbone chemical shifts for H3 core residues in arrays with 15-60 bp DNA linkers reconstituted with 2H,13C,15N-labeled H3. Overall, these chemical shifts were similar irrespective of the DNA linker length indicating no major changes in H3 core conformation. Notably, however, multiple residues at the H3-nucleosomal DNA interface in arrays with 15 bp DNA linkers exhibited relatively pronounced differences in chemical shifts and line broadening compared to arrays with 30 and 60 bp linkers. These findings are consistent with increased heterogeneity in nucleosome packing and structural strain within arrays containing short DNA linkers that likely leads to side-chains of these interfacial residues experiencing alternate conformations or shifts in their rotamer populations relative to arrays with the longer DNA linkers.
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Affiliation(s)
- Sean T. Smrt
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH, United States
| | - Nicole Gonzalez Salguero
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH, United States
| | - Justin K. Thomas
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH, United States
| | - Mohamad Zandian
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH, United States
| | - Michael G. Poirier
- Department of Physics, The Ohio State University, Columbus, OH, United States
| | - Christopher P. Jaroniec
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH, United States,*Correspondence: Christopher P. Jaroniec,
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6
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DNA Sequence-Dependent Properties of Nucleosome Positioning in Regions of Distinct Chromatin States in Mouse Embryonic Stem Cells. Int J Mol Sci 2022; 23:ijms232214488. [PMID: 36430966 PMCID: PMC9693356 DOI: 10.3390/ijms232214488] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2022] [Revised: 11/18/2022] [Accepted: 11/19/2022] [Indexed: 11/23/2022] Open
Abstract
Chromatin architecture is orchestrated, and plays crucial roles during the developmental process by regulating gene expression. In embryonic stem cells (ESCs), three types of chromatin states, including active, repressive and poised states, were previously identified and characterized with specific chromatin modification marks and different transcription activity, but it is largely unknown how nucleosomes are organized in these chromatin states. In this study, by using a DNA deformation energy model, we investigated the sequence-dependent nucleosome organization within the chromatin states in mouse ESCs. The results revealed that: (1) compared with poised genes, active genes are characterized with a higher level of nucleosome occupancy around their transcription start sites (TSS) and transcription termination sites (TTS), and both types of genes do not have a nucleosome-depleted region at their TTS, contrasting with the MNase-seq based result; (2) based on our previous DNA bending energy model, we developed an improved model capable of predicting both rotational positioning and nucleosome occupancy determined by a chemical mapping approach; (3) DNA bending-energy-based analyses demonstrated that the fragile nucleosomes positioned at both gene ends could be explained largely by enhanced rotational positioning signals encoded in DNA, but nucleosome phasing around the TSS of active genes was not determined by sequence preference; (4) the nucleosome occupancy landscape around the binding sites of some developmentally important transcription factors known to bind with different chromatin contexts, was also successfully predicted; (5) the difference of nucleosome occupancy around the TSS between CpG-rich and CpG-poor promoters was partly captured by our sequence-dependent model. Taken together, by developing an improved deformation-energy-based model, we revealed some sequence-dependent properties of the nucleosome arrangements in regions of distinct chromatin states in mouse ESCs.
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7
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Patra SK, Szyf M. Epigenetic perspectives of COVID-19: Virus infection to disease progression and therapeutic control. Biochim Biophys Acta Mol Basis Dis 2022; 1868:166527. [PMID: 36002132 PMCID: PMC9393109 DOI: 10.1016/j.bbadis.2022.166527] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2022] [Revised: 08/05/2022] [Accepted: 08/18/2022] [Indexed: 11/20/2022]
Abstract
COVID-19 has caused numerous deaths as well as imposed social isolation and upheaval world-wide. Although, the genome and the composition of the virus, the entry process and replication mechanisms are well investigated from by several laboratories across the world, there are many unknown remaining questions. For example, what are the functions of membrane lipids during entry, packaging and exit of virus particles? Also, the metabolic aspects of the infected tissue cells are poorly understood. In the course of virus replication and formation of virus particles within the host cell, the enhanced metabolic activities of the host is directly proportional to viral loads. The epigenetic landscape of the host cells is also altered, particularly the expression/repression of genes associated with cellular metabolism as well as cellular processes that are antagonistic to the virus. Metabolic pathways are enzyme driven processes and the expression profile and mechanism of regulations of the respective genes encoding those enzymes during the course of pathogen invasion might be highly informative on the course of the disease. Recently, the metabolic profile of the patients' sera have been analysed from few patients. In view of this, and to gain further insights into the roles that epigenetic mechanisms might play in this scenario in regulation of metabolic pathways during the progression of COVID-19 are discussed and summarised in this contribution for ensuring best therapy.
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Affiliation(s)
- Samir Kumar Patra
- Epigenetics and Cancer Research Laboratory, Biochemistry and Molecular Biology Group, Department of Life Science, National Institute of Technology, Rourkela 769008, Odisha, India.
| | - Moshe Szyf
- Department of Pharmacology & Therapeutics, McIntyre Medical Sciences Building, McGill University, Montreal, QC H3G 1Y6, Canada
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8
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Katava M, Shi G, Thirumalai D. Chromatin dynamics controls epigenetic domain formation. Biophys J 2022; 121:2895-2905. [PMID: 35799447 PMCID: PMC9388564 DOI: 10.1016/j.bpj.2022.07.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2021] [Revised: 04/17/2022] [Accepted: 06/30/2022] [Indexed: 11/28/2022] Open
Abstract
In multicellular organisms, nucleosomes carry epigenetic information that defines distinct patterns of gene expression, which are inherited over multiple generations. The enhanced capacity for information storage arises by nucleosome modifications, which are triggered by enzymes. Modified nucleosomes can transfer the mark to others that are in proximity by a positive-feedback (modification begets modification) mechanism. We created a generic polymer model, referred to as 3DSpreader, in which each bead, representing a nucleosome, stochastically switches between unmodified (U) and modified (M) states depending on the states of the neighbors. Modification begins at a specific nucleation site (NS) that is permanently in the M state, and could spread to other loci that is dictated by chromatin dynamics. Transfer of marks among the non-nucleation loci occurs stochastically as chromatin evolves in time. If the spreading rate is slower than the chromatin relaxation rate, which is biologically pertinent, then finite-sized domains form, driven by contacts between nucleosomes through a three-dimensional looping mechanism. Surprisingly, simulations based on the 3DSpreader model result in finite bounded domains that arise without the need for any boundary elements. Maintenance of spatially and temporally stable domains requires the presence of the NS, whose removal eliminates finite-sized modified domains. The theoretical predictions are in excellent agreement with experimental data for H3K9me3 spreading in mouse embryonic stem cells.
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Affiliation(s)
- Marina Katava
- Laboratoire de Biochimie Théorique, CNRS, Université de Paris, Paris, France
| | - Guang Shi
- Department of Chemistry, The University of Texas, Austin, Texas
| | - D Thirumalai
- Department of Chemistry, The University of Texas, Austin, Texas.
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9
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Musselman CA, Kutateladze TG. Visualizing Conformational Ensembles of the Nucleosome by NMR. ACS Chem Biol 2022; 17:495-502. [PMID: 35196453 DOI: 10.1021/acschembio.1c00954] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The formation of chromatin not only compacts the eukaryotic genome into the nucleus but also provides a mechanism for the regulation of all DNA templated processes. Spatial and temporal modulation of the chromatin structure is critical in such regulation and involves fine-tuned functioning of the basic subunit of chromatin, the nucleosome. It has become apparent that the nucleosome is an inherently dynamic system, but characterization of these dynamics at the atomic level has remained challenging. NMR spectroscopy is a powerful tool for investigating the conformational ensemble and dynamics of proteins and protein complexes, and recent advances have made the study of large systems possible. Here, we review recent studies which utilize NMR spectroscopy to uncover the atomic level conformation and dynamics of the nucleosome and provide a better understanding of the importance of these dynamics in key regulatory events.
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Affiliation(s)
- Catherine A. Musselman
- Department of Biochemistry and Molecular Genetics, University of Colorado Anschutz Medical Campus, Aurora, Colorado 80045, United States
| | - Tatiana G. Kutateladze
- Department of Pharmacology, University of Colorado School of Medicine, Aurora, Colorado 80045, United States
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10
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Arimura Y, Shih RM, Froom R, Funabiki H. Structural features of nucleosomes in interphase and metaphase chromosomes. Mol Cell 2021; 81:4377-4397.e12. [PMID: 34478647 PMCID: PMC8571072 DOI: 10.1016/j.molcel.2021.08.010] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Revised: 08/05/2021] [Accepted: 08/06/2021] [Indexed: 12/17/2022]
Abstract
Structural heterogeneity of nucleosomes in functional chromosomes is unknown. Here, we devise the template-, reference- and selection-free (TRSF) cryo-EM pipeline to simultaneously reconstruct cryo-EM structures of protein complexes from interphase or metaphase chromosomes. The reconstructed interphase and metaphase nucleosome structures are on average indistinguishable from canonical nucleosome structures, despite DNA sequence heterogeneity, cell-cycle-specific posttranslational modifications, and interacting proteins. Nucleosome structures determined by a decoy-classifying method and structure variability analyses reveal the nucleosome structural variations in linker DNA, histone tails, and nucleosome core particle configurations, suggesting that the opening of linker DNA, which is correlated with H2A C-terminal tail positioning, is suppressed in chromosomes. High-resolution (3.4-3.5 Å) nucleosome structures indicate DNA-sequence-independent stabilization of superhelical locations ±0-1 and ±3.5-4.5. The linker histone H1.8 preferentially binds to metaphase chromatin, from which chromatosome cryo-EM structures with H1.8 at the on-dyad position are reconstituted. This study presents the structural characteristics of nucleosomes in chromosomes.
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Affiliation(s)
- Yasuhiro Arimura
- Laboratory of Chromosome and Cell Biology, The Rockefeller University, New York, NY 10065, USA.
| | - Rochelle M Shih
- Laboratory of Chromosome and Cell Biology, The Rockefeller University, New York, NY 10065, USA
| | - Ruby Froom
- Laboratory of Molecular Biophysics, The Rockefeller University, New York, NY 10065, USA
| | - Hironori Funabiki
- Laboratory of Chromosome and Cell Biology, The Rockefeller University, New York, NY 10065, USA.
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11
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Behrends M, Engmann O. Loop Interrupted: Dysfunctional Chromatin Relations in Neurological Diseases. Front Genet 2021; 12:732033. [PMID: 34422024 PMCID: PMC8376151 DOI: 10.3389/fgene.2021.732033] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2021] [Accepted: 07/20/2021] [Indexed: 12/19/2022] Open
Abstract
The majority of genetic variants for psychiatric disorders have been found within non-coding genomic regions. Physical interactions of gene promoters with distant regulatory elements carrying risk alleles may explain how the latter affect gene expression. Recently, whole genome maps of long-range chromosomal contacts from human postmortem brains have been integrated with gene sequence and chromatin accessibility data to decipher disease-specific alterations in chromatin architecture. Cell culture and rodent models provide a causal link between chromatin conformation, long-range chromosomal contacts, gene expression, and disease phenotype. Here, we give an overview of the techniques used to study chromatin contacts and their limitations in brain research. We present evidence for three-dimensional genome changes in physiological brain function and assess how its disturbance contributes to psychiatric disorders. Lastly, we discuss remaining questions and future research directions with a focus on clinical applications.
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Affiliation(s)
- Marthe Behrends
- Faculty of Medicine, Friedrich Schiller Universität, Jena, Thüringen, Germany
| | - Olivia Engmann
- Jena University Hospital, Institute for Human Genetics, Thüringen, Germany
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12
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Zandian M, Salguero NG, Shannon MD, Purusottam RN, Theint T, Poirier MG, Jaroniec CP. Conformational Dynamics of Histone H3 Tails in Chromatin. J Phys Chem Lett 2021; 12:6174-6181. [PMID: 34184895 PMCID: PMC8788308 DOI: 10.1021/acs.jpclett.1c01187] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Chromatin is a supramolecular DNA-protein complex that compacts eukaryotic genomes and regulates their accessibility and functions. Dynamically disordered histone H3 N-terminal tails are among key chromatin regulatory components. Here, we used high-resolution-magic-angle-spinning NMR measurements of backbone amide 15N spin relaxation rates to investigate, with residue-specific detail, the dynamics and interactions of H3 tails in recombinant 13C,15N-enriched nucleosome arrays containing 15, 30, or 60 bp linker DNA between the nucleosome repeats. These measurements were compared to analogous data available for mononucleosomes devoid of linker DNA or containing two 20 bp DNA overhangs. The H3 tail dynamics in nucleosome arrays were found to be considerably attenuated compared with nucleosomes with or without linker DNA due to transient electrostatic interactions with the linker DNA segments and the structured chromatin environment. Remarkably, however, the H3 tail dynamics were not modulated by the specific linker DNA length within the 15-60 bp range investigated here.
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Affiliation(s)
- Mohamad Zandian
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210
| | | | - Matthew D. Shannon
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210
| | - Rudra N. Purusottam
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210
| | - Theint Theint
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210
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13
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Parmar JJ, Padinhateeri R. Nucleosome positioning and chromatin organization. Curr Opin Struct Biol 2020; 64:111-118. [PMID: 32731156 DOI: 10.1016/j.sbi.2020.06.021] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2020] [Revised: 05/31/2020] [Accepted: 06/23/2020] [Indexed: 11/24/2022]
Abstract
In our cells, DNA is folded and packed with the help of many proteins into chromatin whose basic unit is a nucleosome-DNA wrapped around octamer of histone proteins. The chain of nucleosomes is further folded and arranged into many layers and has a dynamic organization. How does the complex chromatin organization emerge from interactions among DNA, histones, and non-histone proteins have been a question of great interest. Here we review recent literature that investigated how nucleosome positioning and nucleosome-mediated interactions drive chromatin organization. Unlike our earlier understanding, chromatin is organized into 3D domains of various sizes having irregularly organized nucleosomes. These domains emerge due to heterogeneous nucleosome positioning and diverse inter-nucleosome interactions that vary in space and time.
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Affiliation(s)
- Jyotsana J Parmar
- Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Mumbai 400 076, India
| | - Ranjith Padinhateeri
- Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Mumbai 400 076, India.
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14
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Intercalation of small molecules into DNA in chromatin is primarily controlled by superhelical constraint. PLoS One 2019; 14:e0224936. [PMID: 31747397 PMCID: PMC6867626 DOI: 10.1371/journal.pone.0224936] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2019] [Accepted: 09/30/2019] [Indexed: 12/22/2022] Open
Abstract
The restricted access of regulatory factors to their binding sites on DNA wrapped around the nucleosomes is generally interpreted in terms of molecular shielding exerted by nucleosomal structure and internucleosomal interactions. Binding of proteins to DNA often includes intercalation of hydrophobic amino acids into the DNA. To assess the role of constrained superhelicity in limiting these interactions, we studied the binding of small molecule intercalators to chromatin in close to native conditions by laser scanning cytometry. We demonstrate that the nucleosome-constrained superhelical configuration of DNA is the main barrier to intercalation. As a result, intercalating compounds are virtually excluded from the nucleosome-occupied regions of the chromatin. Binding of intercalators to extranucleosomal regions is limited to a smaller degree, in line with the existence of net supercoiling in the regions comprising linker and nucleosome free DNA. Its relaxation by inducing as few as a single nick per ~50 kb increases intercalation in the entire chromatin loop, demonstrating the possibility for long-distance effects of regulatory potential.
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15
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Bajpai G, Padinhateeri R. Irregular Chromatin: Packing Density, Fiber Width, and Occurrence of Heterogeneous Clusters. Biophys J 2019; 118:207-218. [PMID: 31810656 DOI: 10.1016/j.bpj.2019.11.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2019] [Revised: 10/12/2019] [Accepted: 11/05/2019] [Indexed: 12/12/2022] Open
Abstract
How chromatin is folded on the length scale of a gene is an open question. Recent experiments have suggested that, in vivo, chromatin is folded in an irregular manner and not as an ordered fiber with a width of 30 nm that is expected from theories of higher order packaging. Using computational methods, we examine how the interplay between DNA-bending nonhistone proteins, histone tails, intrachromatin electrostatic, and other interactions decide the nature of the packaging of chromatin. We show that although the DNA-bending nonhistone proteins make the chromatin irregular, they may not alter the packing density and size of the fiber. We find that the length of the interacting region and intrachromatin electrostatic interactions influence the packing density, clustering of nucleosomes, and the width of the chromatin fiber. Our results suggest that the heterogeneity in the interaction pattern will play an important role in deciding the nature of the packaging of chromatin.
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Affiliation(s)
- Gaurav Bajpai
- Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Mumbai, India
| | - Ranjith Padinhateeri
- Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Mumbai, India.
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16
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Lee TH. Physical Chemistry of Epigenetics: Single-Molecule Investigations. J Phys Chem B 2019; 123:8351-8362. [PMID: 31404497 PMCID: PMC6790939 DOI: 10.1021/acs.jpcb.9b06214] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2019] [Revised: 08/03/2019] [Indexed: 02/06/2023]
Abstract
The nucleosome is the fundamental building block of the eukaryotic genome, composed of an ∼147 base-pair DNA fragment wrapping around an octameric histone protein core. DNA and histone proteins are targets of enzymatic chemical modifications that serve as signals for gene regulation. These modifications are often referred to as epigenetic modifications that govern gene activities without altering the DNA sequence. Although the term epigenetics initially required inheritability, it now frequently includes noninherited histone modifications associated with gene regulation. Important epigenetic modifications for healthy cell growth and proliferation include DNA methylation, histone acetylation, methylation, phosphorylation, ubiquitination, and SUMOylation (SUMO = Small Ubiquitin-like Modifier). Our research focuses on the biophysical roles of these modifications in altering the structure and structural dynamics of the nucleosome and their implications in gene regulation mechanisms. As the changes are subtle and complex, we employ various single-molecule fluorescence approaches for their investigations. Our investigations revealed that these modifications induce changes in the structure and structural dynamics of the nucleosome and their thermodynamic and kinetic stabilities. We also suggested the implications of these changes in gene regulation mechanisms that are the foci of our current and future research.
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Affiliation(s)
- Tae-Hee Lee
- Department of Chemistry, The
Pennsylvania State University, University Park 16803, Pennsylvania, United States
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17
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Ohyama T. New Aspects of Magnesium Function: A Key Regulator in Nucleosome Self-Assembly, Chromatin Folding and Phase Separation. Int J Mol Sci 2019; 20:ijms20174232. [PMID: 31470631 PMCID: PMC6747271 DOI: 10.3390/ijms20174232] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2019] [Revised: 08/21/2019] [Accepted: 08/26/2019] [Indexed: 02/07/2023] Open
Abstract
Metal cations are associated with many biological processes. The effects of these cations on nucleic acids and chromatin were extensively studied in the early stages of nucleic acid and chromatin research. The results revealed that some monovalent and divalent metal cations, including Mg2+, profoundly affect the conformations and stabilities of nucleic acids, the folding of chromatin fibers, and the extent of chromosome condensation. Apart from these effects, there have only been a few reports on the functions of these cations. In 2007 and 2013, however, Mg2+-implicated novel phenomena were found: Mg2+ facilitates or enables both self-assembly of identical double-stranded (ds) DNA molecules and self-assembly of identical nucleosomes in vitro. These phenomena may be deeply implicated in the heterochromatin domain formation and chromatin-based phase separation. Furthermore, a recent study showed that elevation of the intranuclear Mg2+ concentration causes unusual differentiation of mouse ES (embryonic stem) cells. All of these phenomena seem to be closely related to one another. Mg2+ seems to be a key regulator of chromatin dynamics and chromatin-based biological processes.
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Affiliation(s)
- Takashi Ohyama
- Department of Biology, Faculty of Education and Integrated Arts and Sciences, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo 162-8480, Japan.
- Major in Integrative Bioscience and Biomedical Engineering, Graduate School of Science and Engineering, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo 162-8480, Japan.
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18
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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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19
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Unraveling the multiplex folding of nucleosome chains in higher order chromatin. Essays Biochem 2019; 63:109-121. [PMID: 31015386 DOI: 10.1042/ebc20180066] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2018] [Revised: 02/25/2019] [Accepted: 03/01/2019] [Indexed: 12/19/2022]
Abstract
The DNA of eukaryotic chromatin and chromosomes is repeatedly supercoiled around histone octamers forming 'beads-on-a-string' chains of nucleosomes. The extent of nucleosome chain folding and DNA accessibility vary between different functional and epigenetic states of nuclear chromatin and change dramatically upon cell differentiation, but the molecular mechanisms that direct 3D folding of the nucleosome chain in vivo are still enigmatic. Recent advances in cell imaging and chromosome capture techniques have radically challenged the established paradigm of regular and hierarchical chromatin fibers by highlighting irregular chromatin organization and the importance of the nuclear skeletal structures hoisting the nucleosome chains. Here, we argue that, by analyzing individual structural elements of the nucleosome chain - nucleosome spacing, linker DNA conformations, internucleosomal interactions, and nucleosome chain flexibility - and integrating these elements in multiplex 3D structural models, we can predict the features of the multiplex chromatin folding assemblies underlying distinct developmental and epigenetic states in living cells. Furthermore, partial disassembly of the nuclear structures suspending chromatin fibers may reveal the intrinsic mechanisms of nucleosome chain folding. These mechanisms and structures are expected to provide molecular cues to modify chromatin structure and functions related to developmental and disease processes.
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20
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Bass MV, Nikitina T, Norouzi D, Zhurkin VB, Grigoryev SA. Nucleosome spacing periodically modulates nucleosome chain folding and DNA topology in circular nucleosome arrays. J Biol Chem 2019; 294:4233-4246. [PMID: 30630950 DOI: 10.1074/jbc.ra118.006412] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2018] [Revised: 01/04/2019] [Indexed: 01/09/2023] Open
Abstract
The length of linker DNA that separates nucleosomes is highly variable, but its mechanistic role in modulating chromatin structure and functions remains unknown. Here, we established an experimental system using circular arrays of positioned nucleosomes to investigate whether variations in nucleosome linker length could affect nucleosome folding, self-association, and interactions. We conducted EM, DNA topology, native electrophoretic assays, and Mg2+-dependent self-association assays to study intrinsic folding of linear and circular nucleosome arrays with linker DNA length of 36 bp and 41 bp (3.5 turns and 4 turns of DNA double helix, respectively). These experiments revealed that potential artifacts arising from open DNA ends and full DNA relaxation in the linear arrays do not significantly affect overall chromatin compaction and self-association. We observed that the 0.5 DNA helical turn difference between the two DNA linker lengths significantly affects DNA topology and nucleosome interactions. In particular, the 41-bp linkers promoted interactions between any two nucleosome beads separated by one bead as expected for a zigzag fiber, whereas the 36-bp linkers promoted interactions between two nucleosome beads separated by two other beads and also reduced negative superhelicity. Monte Carlo simulations accurately reproduce periodic modulations of chromatin compaction, DNA topology, and internucleosomal interactions with a 10-bp periodicity. We propose that the nucleosome spacing and associated chromatin structure modulations may play an important role in formation of different chromatin epigenetic states, thus suggesting implications for how chromatin accessibility to DNA-binding factors and the RNA transcription machinery is regulated.
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Affiliation(s)
- Mikhail V Bass
- From the Department of Biochemistry and Molecular Biology, Penn State University College of Medicine, Hershey, Pennsylvania 17033.,Biological Faculty, Department of Molecular Biology, Lomonosov Moscow State University, 119192 Moscow, Russia, and
| | - Tatiana Nikitina
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892
| | - Davood Norouzi
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892
| | - Victor B Zhurkin
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892
| | - Sergei A Grigoryev
- From the Department of Biochemistry and Molecular Biology, Penn State University College of Medicine, Hershey, Pennsylvania 17033,
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