1
|
Lizana L, Schwartz YB. The scales, mechanisms, and dynamics of the genome architecture. SCIENCE ADVANCES 2024; 10:eadm8167. [PMID: 38598632 PMCID: PMC11006219 DOI: 10.1126/sciadv.adm8167] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/07/2023] [Accepted: 03/06/2024] [Indexed: 04/12/2024]
Abstract
Even when split into several chromosomes, DNA molecules that make up our genome are too long to fit into the cell nuclei unless massively folded. Such folding must accommodate the need for timely access to selected parts of the genome by transcription factors, RNA polymerases, and DNA replication machinery. Here, we review our current understanding of the genome folding inside the interphase nuclei. We consider the resulting genome architecture at three scales with a particular focus on the intermediate (meso) scale and summarize the insights gained from recent experimental observations and diverse computational models.
Collapse
Affiliation(s)
- Ludvig Lizana
- Integrated Science Lab, Department of Physics, Umeå University, Umeå, Sweden
| | | |
Collapse
|
2
|
Becker PB. Cell-free genomics: transcription factor interactions in reconstituted naïve embryonic chromatin. Biochem Soc Trans 2024; 52:423-429. [PMID: 38329186 DOI: 10.1042/bst20230878] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2023] [Revised: 01/26/2024] [Accepted: 01/30/2024] [Indexed: 02/09/2024]
Abstract
Extracts from Drosophila preblastoderm embryos (DREX) form the basis of a powerful in vitro chromatin reconstitution system that assembles entire genomes into complex chromatin with physiological nucleosome spacing and polymer condensation. As the zygotic genome has not yet been activated in preblastoderm embryos, the reconstitution extract lacks endogenous transcription factors (TFs) and the RNA polymerase machinery. At the same time, it contains high levels of ATP-dependent nucleosome sliding enzymes that render the reconstituted chromatin dynamic. The naïve chromatin can be used to determine the intrinsic DNA binding properties of exogenous, usually recombinant TFs (or DNA binding proteins in general) in a complex chromatin context. Recent applications of the system include the description of cooperation and competition of Drosophila pioneer TFs for composite binding sites, and the characterization of nucleosome interactions of mammalian pioneer TFs in the heterologous system.
Collapse
Affiliation(s)
- Peter B Becker
- Biomedical Center, Molecular Biology Division, Faculty of Medicine, LMU, Munich, Germany
| |
Collapse
|
3
|
Eggers N, Gkountromichos F, Krause S, Campos-Sparr A, Becker P. Physical interaction between MSL2 and CLAMP assures direct cooperativity and prevents competition at composite binding sites. Nucleic Acids Res 2023; 51:9039-9054. [PMID: 37602401 PMCID: PMC10516644 DOI: 10.1093/nar/gkad680] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2023] [Revised: 07/13/2023] [Accepted: 08/09/2023] [Indexed: 08/22/2023] Open
Abstract
MSL2, the DNA-binding subunit of the Drosophila dosage compensation complex, cooperates with the ubiquitous protein CLAMP to bind MSL recognition elements (MREs) on the X chromosome. We explore the nature of the cooperative binding to these GA-rich, composite sequence elements in reconstituted naïve embryonic chromatin. We found that the cooperativity requires physical interaction between both proteins. Remarkably, disruption of this interaction does not lead to indirect, nucleosome-mediated cooperativity as expected, but to competition. The protein interaction apparently not only increases the affinity for composite binding sites, but also locks both proteins in a defined dimeric state that prevents competition. High Affinity Sites of MSL2 on the X chromosome contain variable numbers of MREs. We find that the cooperation between MSL2/CLAMP is not influenced by MRE clustering or arrangement, but happens largely at the level of individual MREs. The sites where MSL2/CLAMP bind strongly in vitro locate to all chromosomes and show little overlap to an expanded set of X-chromosomal MSL2 in vivo binding sites generated by CUT&RUN. Apparently, the intrinsic MSL2/CLAMP cooperativity is limited to a small selection of potential sites in vivo. This restriction must be due to components missing in our reconstitution, such as roX2 lncRNA.
Collapse
Affiliation(s)
- Nikolas Eggers
- Biomedical Center, Molecular Biology Division, LMU, Munich, Germany
| | | | - Silke Krause
- Biomedical Center, Molecular Biology Division, LMU, Munich, Germany
| | | | - Peter B Becker
- Biomedical Center, Molecular Biology Division, LMU, Munich, Germany
| |
Collapse
|
4
|
Mansisidor AR, Risca VI. Chromatin accessibility: methods, mechanisms, and biological insights. Nucleus 2022; 13:236-276. [PMID: 36404679 PMCID: PMC9683059 DOI: 10.1080/19491034.2022.2143106] [Citation(s) in RCA: 21] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2022] [Revised: 10/23/2022] [Accepted: 10/30/2022] [Indexed: 11/22/2022] Open
Abstract
Access to DNA is a prerequisite to the execution of essential cellular processes that include transcription, replication, chromosomal segregation, and DNA repair. How the proteins that regulate these processes function in the context of chromatin and its dynamic architectures is an intensive field of study. Over the past decade, genome-wide assays and new imaging approaches have enabled a greater understanding of how access to the genome is regulated by nucleosomes and associated proteins. Additional mechanisms that may control DNA accessibility in vivo include chromatin compaction and phase separation - processes that are beginning to be understood. Here, we review the ongoing development of accessibility measurements, we summarize the different molecular and structural mechanisms that shape the accessibility landscape, and we detail the many important biological functions that are linked to chromatin accessibility.
Collapse
Affiliation(s)
- Andrés R. Mansisidor
- 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
| |
Collapse
|
5
|
Chen S, Rosin LF, Pegoraro G, Moshkovich N, Murphy PJ, Yu G, Lei EP. NURF301 contributes to gypsy chromatin insulator-mediated nuclear organization. Nucleic Acids Res 2022; 50:7906-7924. [PMID: 35819192 PMCID: PMC9371915 DOI: 10.1093/nar/gkac600] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2022] [Revised: 06/26/2022] [Accepted: 06/29/2022] [Indexed: 11/14/2022] Open
Abstract
Chromatin insulators are DNA-protein complexes that can prevent the spread of repressive chromatin and block communication between enhancers and promoters to regulate gene expression. In Drosophila, the gypsy chromatin insulator complex consists of three core proteins: CP190, Su(Hw), and Mod(mdg4)67.2. These factors concentrate at nuclear foci termed insulator bodies, and changes in insulator body localization have been observed in mutants defective for insulator function. Here, we identified NURF301/E(bx), a nucleosome remodeling factor, as a novel regulator of gypsy insulator body localization through a high-throughput RNAi imaging screen. NURF301 promotes gypsy-dependent insulator barrier activity and physically interacts with gypsy insulator proteins. Using ChIP-seq, we found that NURF301 co-localizes with insulator proteins genome-wide, and NURF301 promotes chromatin association of Su(Hw) and CP190 at gypsy insulator binding sites. These effects correlate with NURF301-dependent nucleosome repositioning. At the same time, CP190 and Su(Hw) both facilitate recruitment of NURF301 to chromatin. Finally, Oligopaint FISH combined with immunofluorescence revealed that NURF301 promotes 3D contact between insulator bodies and gypsy insulator DNA binding sites, and NURF301 is required for proper nuclear positioning of gypsy binding sites. Our data provide new insights into how a nucleosome remodeling factor and insulator proteins cooperatively contribute to nuclear organization.
Collapse
Affiliation(s)
- Shue Chen
- Nuclear Organization and Gene Expression Section, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, USA.,Laboratory of Biochemistry and Genetics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, USA
| | - Leah F Rosin
- Nuclear Organization and Gene Expression Section, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, USA.,Laboratory of Biochemistry and Genetics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, USA
| | - Gianluca Pegoraro
- High-Throughput Imaging Facility (HiTIF), Laboratory of Receptor Biology and Gene Expression, Center for Cancer Research, National Cancer Institute, Bethesda, MD, USA
| | - Nellie Moshkovich
- Nuclear Organization and Gene Expression Section, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, USA.,Laboratory of Cellular and Developmental Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, USA
| | - Patrick J Murphy
- Nuclear Organization and Gene Expression Section, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, USA.,Laboratory of Cellular and Developmental Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, USA
| | - Guoyun Yu
- Nuclear Organization and Gene Expression Section, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, USA.,Laboratory of Cellular and Developmental Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, USA
| | - Elissa P Lei
- Nuclear Organization and Gene Expression Section, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, USA.,Laboratory of Biochemistry and Genetics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, USA
| |
Collapse
|
6
|
Wiles ET, Mumford CC, McNaught KJ, Tanizawa H, Selker EU. The ACF chromatin-remodeling complex is essential for Polycomb repression. eLife 2022; 11:e77595. [PMID: 35257662 PMCID: PMC9038196 DOI: 10.7554/elife.77595] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2022] [Accepted: 03/03/2022] [Indexed: 11/13/2022] Open
Abstract
Establishing and maintaining appropriate gene repression is critical for the health and development of multicellular organisms. Histone H3 lysine 27 (H3K27) methylation is a chromatin modification associated with repressed facultative heterochromatin, but the mechanism of this repression remains unclear. We used a forward genetic approach to identify genes involved in transcriptional silencing of H3K27-methylated chromatin in the filamentous fungus Neurospora crassa. We found that the N. crassa homologs of ISWI (NCU03875) and ACF1 (NCU00164) are required for repression of a subset of H3K27-methylated genes and that they form an ACF chromatin-remodeling complex. This ACF complex interacts with chromatin throughout the genome, yet association with facultative heterochromatin is specifically promoted by the H3K27 methyltransferase, SET-7. H3K27-methylated genes that are upregulated when iswi or acf1 are deleted show a downstream shift of the +1 nucleosome, suggesting that proper nucleosome positioning is critical for repression of facultative heterochromatin. Our findings support a direct role of the ACF complex in Polycomb repression.
Collapse
Affiliation(s)
- Elizabeth T Wiles
- Institute of Molecular Biology, University of OregonEugeneUnited States
| | - Colleen C Mumford
- Institute of Molecular Biology, University of OregonEugeneUnited States
| | - Kevin J McNaught
- Institute of Molecular Biology, University of OregonEugeneUnited States
| | - Hideki Tanizawa
- Institute of Molecular Biology, University of OregonEugeneUnited States
| | - Eric U Selker
- Institute of Molecular Biology, University of OregonEugeneUnited States
| |
Collapse
|
7
|
Karl LA, Peritore M, Galanti L, Pfander B. DNA Double Strand Break Repair and Its Control by Nucleosome Remodeling. Front Genet 2022; 12:821543. [PMID: 35096025 PMCID: PMC8790285 DOI: 10.3389/fgene.2021.821543] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2021] [Accepted: 12/23/2021] [Indexed: 12/12/2022] Open
Abstract
DNA double strand breaks (DSBs) are repaired in eukaryotes by one of several cellular mechanisms. The decision-making process controlling DSB repair takes place at the step of DNA end resection, the nucleolytic processing of DNA ends, which generates single-stranded DNA overhangs. Dependent on the length of the overhang, a corresponding DSB repair mechanism is engaged. Interestingly, nucleosomes-the fundamental unit of chromatin-influence the activity of resection nucleases and nucleosome remodelers have emerged as key regulators of DSB repair. Nucleosome remodelers share a common enzymatic mechanism, but for global genome organization specific remodelers have been shown to exert distinct activities. Specifically, different remodelers have been found to slide and evict, position or edit nucleosomes. It is an open question whether the same remodelers exert the same function also in the context of DSBs. Here, we will review recent advances in our understanding of nucleosome remodelers at DSBs: to what extent nucleosome sliding, eviction, positioning and editing can be observed at DSBs and how these activities affect the DSB repair decision.
Collapse
Affiliation(s)
- Leonhard Andreas Karl
- Resarch Group DNA Replication and Genome Integrity, Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Martina Peritore
- Resarch Group DNA Replication and Genome Integrity, Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Lorenzo Galanti
- Resarch Group DNA Replication and Genome Integrity, Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Boris Pfander
- Resarch Group DNA Replication and Genome Integrity, Max Planck Institute of Biochemistry, Martinsried, Germany
| |
Collapse
|
8
|
Eggers N, Becker PB. Cell-free genomics reveal intrinsic, cooperative and competitive determinants of chromatin interactions. Nucleic Acids Res 2021; 49:7602-7617. [PMID: 34181732 PMCID: PMC8287947 DOI: 10.1093/nar/gkab558] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2021] [Revised: 06/08/2021] [Accepted: 06/21/2021] [Indexed: 11/13/2022] Open
Abstract
Metazoan transcription factors distinguish their response elements from a large excess of similar sequences. We explored underlying principles of DNA shape read-out and factor cooperativity in chromatin using a unique experimental system. We reconstituted chromatin on Drosophila genomes in extracts of preblastoderm embryos, mimicking the naïve state of the zygotic genome prior to developmental transcription activation. We then compared the intrinsic binding specificities of three recombinant transcription factors, alone and in combination, with GA-rich recognition sequences genome-wide. For MSL2, all functional elements reside on the X chromosome, allowing to distinguish physiological elements from non-functional 'decoy' sites. The physiological binding profile of MSL2 is approximated through interaction with other factors: cooperativity with CLAMP and competition with GAF, which sculpts the profile by occluding non-functional sites. An extended DNA shape signature is differentially read out in chromatin. Our results reveal novel aspects of target selection in a complex chromatin environment.
Collapse
Affiliation(s)
- Nikolas Eggers
- Biomedical Center, Molecular Biology Division, Ludwig-Maximilians-Universität, 82152 Planegg, Germany
| | - Peter B Becker
- Biomedical Center, Molecular Biology Division, Ludwig-Maximilians-Universität, 82152 Planegg, Germany
| |
Collapse
|
9
|
Oberbeckmann E, Niebauer V, Watanabe S, Farnung L, Moldt M, Schmid A, Cramer P, Peterson CL, Eustermann S, Hopfner KP, Korber P. Ruler elements in chromatin remodelers set nucleosome array spacing and phasing. Nat Commun 2021; 12:3232. [PMID: 34050140 PMCID: PMC8163753 DOI: 10.1038/s41467-021-23015-0] [Citation(s) in RCA: 32] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2020] [Accepted: 03/13/2021] [Indexed: 01/09/2023] Open
Abstract
Arrays of regularly spaced nucleosomes dominate chromatin and are often phased by alignment to reference sites like active promoters. How the distances between nucleosomes (spacing), and between phasing sites and nucleosomes are determined remains unclear, and specifically, how ATP-dependent chromatin remodelers impact these features. Here, we used genome-wide reconstitution to probe how Saccharomyces cerevisiae ATP-dependent remodelers generate phased arrays of regularly spaced nucleosomes. We find that remodelers bear a functional element named the 'ruler' that determines spacing and phasing in a remodeler-specific way. We use structure-based mutagenesis to identify and tune the ruler element residing in the Nhp10 and Arp8 modules of the INO80 remodeler complex. Generally, we propose that a remodeler ruler regulates nucleosome sliding direction bias in response to (epi)genetic information. This finally conceptualizes how remodeler-mediated nucleosome dynamics determine stable steady-state nucleosome positioning relative to other nucleosomes, DNA bound factors, DNA ends and DNA sequence elements.
Collapse
Affiliation(s)
- Elisa Oberbeckmann
- Division of Molecular Biology, Biomedical Center (BMC), Faculty of Medicine, LMU Munich, Martinsried, Germany
- Department of Molecular Biology, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Vanessa Niebauer
- Gene Center, Ludwig-Maximilians-Universität München, Munich, Germany
- Department of Biochemistry, Faculty of Chemistry and Pharmacy, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Shinya Watanabe
- Program of Molecular Medicine, University of Massachusetts, Worcester, MA, USA
| | - Lucas Farnung
- Department of Molecular Biology, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
- Department of Cell Biology, Blavatnik Institute, Harvard Medical School, Boston, USA
| | - Manuela Moldt
- Gene Center, Ludwig-Maximilians-Universität München, Munich, Germany
- Department of Biochemistry, Faculty of Chemistry and Pharmacy, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Andrea Schmid
- Division of Molecular Biology, Biomedical Center (BMC), Faculty of Medicine, LMU Munich, Martinsried, Germany
| | - Patrick Cramer
- Department of Molecular Biology, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Craig L Peterson
- Program of Molecular Medicine, University of Massachusetts, Worcester, MA, USA
| | - Sebastian Eustermann
- Gene Center, Ludwig-Maximilians-Universität München, Munich, Germany.
- Department of Biochemistry, Faculty of Chemistry and Pharmacy, Ludwig-Maximilians-Universität München, Munich, Germany.
- European Molecular Biology Laboratory (EMBL), Structural and Computational Biology Unit, Heidelberg, Germany.
| | - Karl-Peter Hopfner
- Gene Center, Ludwig-Maximilians-Universität München, Munich, Germany.
- Department of Biochemistry, Faculty of Chemistry and Pharmacy, Ludwig-Maximilians-Universität München, Munich, Germany.
| | - Philipp Korber
- Division of Molecular Biology, Biomedical Center (BMC), Faculty of Medicine, LMU Munich, Martinsried, Germany.
| |
Collapse
|
10
|
Cole L, Kurscheid S, Nekrasov M, Domaschenz R, Vera DL, Dennis JH, Tremethick DJ. Multiple roles of H2A.Z in regulating promoter chromatin architecture in human cells. Nat Commun 2021; 12:2524. [PMID: 33953180 PMCID: PMC8100287 DOI: 10.1038/s41467-021-22688-x] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2020] [Accepted: 03/25/2021] [Indexed: 01/02/2023] Open
Abstract
Chromatin accessibility of a promoter is fundamental in regulating transcriptional activity. The histone variant H2A.Z has been shown to contribute to this regulation, but its role has remained poorly understood. Here, we prepare high-depth maps of the position and accessibility of H2A.Z-containing nucleosomes for all human Pol II promoters in epithelial, mesenchymal and isogenic cancer cell lines. We find that, in contrast to the prevailing model, many different types of active and inactive promoter structures are observed that differ in their nucleosome organization and sensitivity to MNase digestion. Key aspects of an active chromatin structure include positioned H2A.Z MNase resistant nucleosomes upstream or downstream of the TSS, and a MNase sensitive nucleosome at the TSS. Furthermore, the loss of H2A.Z leads to a dramatic increase in the accessibility of transcription factor binding sites. Collectively, these results suggest that H2A.Z has multiple and distinct roles in regulating gene expression dependent upon its location in a promoter.
Collapse
Affiliation(s)
- Lauren Cole
- College of Arts and Sciences, Department of Biological Sciences, Florida State University, Tallahassee, FL, USA
| | - Sebastian Kurscheid
- The John Curtin School of Medical Research, The Australian National University, Canberra, Australia
| | - Maxim Nekrasov
- The John Curtin School of Medical Research, The Australian National University, Canberra, Australia
| | - Renae Domaschenz
- The John Curtin School of Medical Research, The Australian National University, Canberra, Australia
| | - Daniel L Vera
- College of Arts and Sciences, Department of Biological Sciences, Florida State University, Tallahassee, FL, USA
- Department of Genetics, Blavatnik Institute, Paul F. Glenn Center for Biology of Aging Research, Harvard Medical School, Boston, MA, USA
| | - Jonathan H Dennis
- College of Arts and Sciences, Department of Biological Sciences, Florida State University, Tallahassee, FL, USA.
| | - David J Tremethick
- The John Curtin School of Medical Research, The Australian National University, Canberra, Australia.
| |
Collapse
|
11
|
Donovan DA, Crandall JG, Truong VN, Vaaler AL, Bailey TB, Dinwiddie D, Banks OGB, McKnight LE, McKnight JN. Basis of specificity for a conserved and promiscuous chromatin remodeling protein. eLife 2021; 10:e64061. [PMID: 33576335 PMCID: PMC7968928 DOI: 10.7554/elife.64061] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2020] [Accepted: 02/11/2021] [Indexed: 12/11/2022] Open
Abstract
Eukaryotic genomes are organized dynamically through the repositioning of nucleosomes. Isw2 is an enzyme that has been previously defined as a genome-wide, nonspecific nucleosome spacing factor. Here, we show that Isw2 instead acts as an obligately targeted nucleosome remodeler in vivo through physical interactions with sequence-specific factors. We demonstrate that Isw2-recruiting factors use small and previously uncharacterized epitopes, which direct Isw2 activity through highly conserved acidic residues in the Isw2 accessory protein Itc1. This interaction orients Isw2 on target nucleosomes, allowing for precise nucleosome positioning at targeted loci. Finally, we show that these critical acidic residues have been lost in the Drosophila lineage, potentially explaining the inconsistently characterized function of Isw2-like proteins. Altogether, these data suggest an 'interacting barrier model,' where Isw2 interacts with a sequence-specific factor to accurately and reproducibly position a single, targeted nucleosome to define the precise border of phased chromatin arrays.
Collapse
Affiliation(s)
- Drake A Donovan
- Institute of Molecular Biology, University of OregonEugeneUnited States
| | | | - Vi N Truong
- Institute of Molecular Biology, University of OregonEugeneUnited States
| | - Abigail L Vaaler
- Institute of Molecular Biology, University of OregonEugeneUnited States
| | - Thomas B Bailey
- Institute of Molecular Biology, University of OregonEugeneUnited States
| | - Devin Dinwiddie
- Institute of Molecular Biology, University of OregonEugeneUnited States
| | - Orion GB Banks
- Institute of Molecular Biology, University of OregonEugeneUnited States
| | - Laura E McKnight
- Institute of Molecular Biology, University of OregonEugeneUnited States
| | - Jeffrey N McKnight
- Institute of Molecular Biology, University of OregonEugeneUnited States
- Phil and Penny Knight Campus for Accelerating Scientific Impact, University of OregonEugeneUnited States
| |
Collapse
|
12
|
Nucleosome Positioning and Spacing: From Mechanism to Function. J Mol Biol 2021; 433:166847. [PMID: 33539878 DOI: 10.1016/j.jmb.2021.166847] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2020] [Revised: 01/16/2021] [Accepted: 01/22/2021] [Indexed: 02/08/2023]
Abstract
Eukaryotes associate their genomes with histone proteins, forming nucleosome particles. Nucleosomes regulate and protect the genetic information. They often assemble into evenly spaced arrays of nucleosomes. These regular nucleosome arrays cover significant portions of the genome, in particular over genes. The presence of these evenly spaced nucleosome arrays is highly conserved throughout the entire eukaryotic domain. Here, we review the mechanisms behind the establishment of this primary structure of chromatin with special emphasis on the biogenesis of evenly spaced nucleosome arrays. We highlight the roles that transcription, nucleosome remodelers, DNA sequence, and histone density play towards the formation of evenly spaced nucleosome arrays and summarize our current understanding of their cellular functions. We end with key unanswered questions that remain to be explored to obtain an in-depth understanding of the biogenesis and function of the nucleosome landscape.
Collapse
|
13
|
Papin C, Le Gras S, Ibrahim A, Salem H, Karimi MM, Stoll I, Ugrinova I, Schröder M, Fontaine-Pelletier E, Omran Z, Bronner C, Dimitrov S, Hamiche A. CpG Islands Shape the Epigenome Landscape. J Mol Biol 2020; 433:166659. [PMID: 33010306 DOI: 10.1016/j.jmb.2020.09.018] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2020] [Revised: 09/22/2020] [Accepted: 09/22/2020] [Indexed: 02/07/2023]
Abstract
Epigenetic modifications and nucleosome positioning play an important role in modulating gene expression. However, how the patterns of epigenetic modifications and nucleosome positioning are established around promoters is not well understood. Here, we have addressed these questions in a series of genome-wide experiments coupled to a novel bioinformatic analysis approach. Our data reveal a clear correlation between CpG density, promoter activity and accumulation of active or repressive histone marks. CGI boundaries define the chromatin promoter regions that will be epigenetically modified. CpG-rich promoters are targeted by histone modifications and histone variants, while CpG-poor promoters are regulated by DNA methylation. CGIs boundaries, but not transcriptional activity, are essential determinants of H2A.Z positioning in vicinity of the promoters, suggesting that the presence of H2A.Z is not related to transcriptional control. Accordingly, H2A.Z depletion has no impact on gene expression of arrested mouse embryonic fibroblasts. Therefore, the underlying DNA sequence, the promoter CpG density and, to a lesser extent, transcriptional activity, are key factors implicated in promoter chromatin architecture.
Collapse
Affiliation(s)
- Christophe Papin
- Institut de Génétique et Biologie Moléculaire et Cellulaire (IGBMC), UdS, CNRS, INSERM, Equipe labellisée Ligue contre le Cancer, 1 rue Laurent Fries, B.P. 10142,67404 Illkirch Cedex, France.
| | - Stéphanie Le Gras
- Institut de Génétique et Biologie Moléculaire et Cellulaire (IGBMC), UdS, CNRS, INSERM, Equipe labellisée Ligue contre le Cancer, 1 rue Laurent Fries, B.P. 10142,67404 Illkirch Cedex, France
| | - Abdulkhaleg Ibrahim
- Institut de Génétique et Biologie Moléculaire et Cellulaire (IGBMC), UdS, CNRS, INSERM, Equipe labellisée Ligue contre le Cancer, 1 rue Laurent Fries, B.P. 10142,67404 Illkirch Cedex, France; Biotechnology Research Center (BTRC), Tripoli, Libya
| | - Hatem Salem
- Institut de Génétique et Biologie Moléculaire et Cellulaire (IGBMC), UdS, CNRS, INSERM, Equipe labellisée Ligue contre le Cancer, 1 rue Laurent Fries, B.P. 10142,67404 Illkirch Cedex, France; Biotechnology Research Center (BTRC), Tripoli, Libya
| | - Mohammad Mahdi Karimi
- Comprehensive Cancer Centre, School of Cancer & Pharmaceutical Sciences, Faculty of Life Sciences & Medicine, King's College London, Denmark Hill, London, UK
| | - Isabelle Stoll
- Institut de Génétique et Biologie Moléculaire et Cellulaire (IGBMC), UdS, CNRS, INSERM, Equipe labellisée Ligue contre le Cancer, 1 rue Laurent Fries, B.P. 10142,67404 Illkirch Cedex, France
| | - Iva Ugrinova
- Roumen Tsanev Institute of Molecular Biology, Bulgarian Academy of Sciences, Sofia, Bulgaria
| | - Maria Schröder
- Roumen Tsanev Institute of Molecular Biology, Bulgarian Academy of Sciences, Sofia, Bulgaria
| | - Emeline Fontaine-Pelletier
- Institute for Advanced Biosciences, Inserm U 1209, CNRS UMR 5309, Université Grenoble Alpes, 38000 Grenoble, France
| | - Ziad Omran
- Umm AlQura University, Faculty of Pharmacy, Saudi Arabia
| | - Christian Bronner
- Institut de Génétique et Biologie Moléculaire et Cellulaire (IGBMC), UdS, CNRS, INSERM, Equipe labellisée Ligue contre le Cancer, 1 rue Laurent Fries, B.P. 10142,67404 Illkirch Cedex, France
| | - Stefan Dimitrov
- Roumen Tsanev Institute of Molecular Biology, Bulgarian Academy of Sciences, Sofia, Bulgaria; Institute for Advanced Biosciences, Inserm U 1209, CNRS UMR 5309, Université Grenoble Alpes, 38000 Grenoble, France.
| | - Ali Hamiche
- Institut de Génétique et Biologie Moléculaire et Cellulaire (IGBMC), UdS, CNRS, INSERM, Equipe labellisée Ligue contre le Cancer, 1 rue Laurent Fries, B.P. 10142,67404 Illkirch Cedex, France.
| |
Collapse
|
14
|
Scacchetti A, Becker PB. Loss of nucleosome remodelers CHRAC/ACF does not sensitize early Drosophila embryos to X-rays. MICROPUBLICATION BIOLOGY 2020; 2020:10.17912/micropub.biology.000287. [PMID: 32760884 PMCID: PMC7396160 DOI: 10.17912/micropub.biology.000287] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Alessandro Scacchetti
- Molecular Biology Division, Biomedical Center, Ludwig-Maximilians-University, Munich, Germany
| | - Peter B. Becker
- Molecular Biology Division, Biomedical Center, Ludwig-Maximilians-University, Munich, Germany,
Correspondence to: Peter B. Becker ()
| |
Collapse
|
15
|
Stergachis AB, Debo BM, Haugen E, Churchman LS, Stamatoyannopoulos JA. Single-molecule regulatory architectures captured by chromatin fiber sequencing. Science 2020; 368:1449-1454. [PMID: 32587015 DOI: 10.1126/science.aaz1646] [Citation(s) in RCA: 83] [Impact Index Per Article: 20.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2019] [Revised: 01/12/2020] [Accepted: 04/24/2020] [Indexed: 12/14/2022]
Abstract
Gene regulation is chiefly determined at the level of individual linear chromatin molecules, yet our current understanding of cis-regulatory architectures derives from fragmented sampling of large numbers of disparate molecules. We developed an approach for precisely stenciling the structure of individual chromatin fibers onto their composite DNA templates using nonspecific DNA N6-adenine methyltransferases. Single-molecule long-read sequencing of chromatin stencils enabled nucleotide-resolution readout of the primary architecture of multikilobase chromatin fibers (Fiber-seq). Fiber-seq exposed widespread plasticity in the linear organization of individual chromatin fibers and illuminated principles guiding regulatory DNA actuation, the coordinated actuation of neighboring regulatory elements, single-molecule nucleosome positioning, and single-molecule transcription factor occupancy. Our approach and results open new vistas on the primary architecture of gene regulation.
Collapse
Affiliation(s)
- Andrew B Stergachis
- Division of Genetics, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA.
| | - Brian M Debo
- Division of Genetics, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA.,Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, MA, USA
| | - Eric Haugen
- Altius Institute for Biomedical Sciences, Seattle, WA, USA
| | - L Stirling Churchman
- Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, MA, USA
| | - John A Stamatoyannopoulos
- Altius Institute for Biomedical Sciences, Seattle, WA, USA. .,Departments of Genome Sciences and Medicine, University of Washington, Seattle, WA, USA
| |
Collapse
|
16
|
Beads on a string-nucleosome array arrangements and folding of the chromatin fiber. Nat Struct Mol Biol 2020; 27:109-118. [PMID: 32042149 DOI: 10.1038/s41594-019-0368-x] [Citation(s) in RCA: 60] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2019] [Accepted: 12/20/2019] [Indexed: 12/21/2022]
Abstract
Understanding how the genome is structurally organized as chromatin is essential for understanding its function. Here, we review recent developments that allowed the readdressing of old questions regarding the primary level of chromatin structure, the arrangement of nucleosomes along the DNA and the folding of the nucleosome fiber in nuclear space. In contrast to earlier views of nucleosome arrays as uniformly regular and folded, recent findings reveal heterogeneous array organization and diverse modes of folding. Local structure variations reflect a continuum of functional states characterized by differences in post-translational histone modifications, associated chromatin-interacting proteins and nucleosome-remodeling enzymes.
Collapse
|
17
|
Q-Nuc: a bioinformatics pipeline for the quantitative analysis of nucleosomal profiles. Interdiscip Sci 2019; 12:69-81. [PMID: 31845186 DOI: 10.1007/s12539-019-00354-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2019] [Revised: 10/20/2019] [Accepted: 11/22/2019] [Indexed: 12/26/2022]
Abstract
Nucleosomal profiling is an effective method to determine the positioning and occupancy of nucleosomes, which is essential to understand their roles in genomic processes. However, the positional randomness across the genome and its relationship with nucleosome occupancy remains poorly understood. Here we present a computational method that segments the profile into nucleosomal domains and quantifies their randomness and relative occupancy level. Applying this method to published data, we find on average ~ 3-fold differences in the degree of positional randomness between regions typically considered "well-ordered", as well as an unexpected predominance of only two types of domains of positional randomness in yeast cells. Further, we find that occupancy levels between domains actually differ maximally by ~ 2-3-fold in both cells, which has not been described before. We also developed a procedure by which one can estimate the sequencing depth that is required to identify nucleosomal positions even when regional positional randomness is high. Overall, we have developed a pipeline to quantitatively characterize domain-level features of nucleosome randomness and occupancy genome-wide, enabling the identification of otherwise unknown features in nucleosomal organization.
Collapse
|
18
|
Harpprecht L, Baldi S, Schauer T, Schmidt A, Bange T, Robles MS, Kremmer E, Imhof A, Becker PB. A Drosophila cell-free system that senses DNA breaks and triggers phosphorylation signalling. Nucleic Acids Res 2019; 47:7444-7459. [PMID: 31147711 PMCID: PMC6698661 DOI: 10.1093/nar/gkz473] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2019] [Revised: 05/13/2019] [Accepted: 05/16/2019] [Indexed: 11/23/2022] Open
Abstract
Preblastoderm Drosophila embryo development is characterized by fast cycles of nuclear divisions. Extracts from these embryos can be used to reconstitute complex chromatin with high efficiency. We now discovered that this chromatin assembly system contains activities that recognize unprotected DNA ends and signal DNA damage through phosphorylation. DNA ends are initially bound by Ku and MRN complexes. Within minutes, the phosphorylation of H2A.V (homologous to γH2A.X) initiates from DNA breaks and spreads over tens of thousands DNA base pairs. The γH2A.V phosphorylation remains tightly associated with the damaged DNA and does not spread to undamaged DNA in the same reaction. This first observation of long-range γH2A.X spreading along damaged chromatin in an in vitro system provides a unique opportunity for mechanistic dissection. Upon further incubation, DNA ends are rendered single-stranded and bound by the RPA complex. Phosphoproteome analyses reveal damage-dependent phosphorylation of numerous DNA-end-associated proteins including Ku70, RPA2, CHRAC16, the exonuclease Rrp1 and the telomer capping complex. Phosphorylation of spindle assembly checkpoint components and of microtubule-associated proteins required for centrosome integrity suggests this cell-free system recapitulates processes involved in the regulated elimination of fatally damaged syncytial nuclei.
Collapse
Affiliation(s)
- Lisa Harpprecht
- Molecular Biology Division, Biomedical Center, LMU Munich, 82152 Planegg-Martinsried, Germany
| | - Sandro Baldi
- Molecular Biology Division, Biomedical Center, LMU Munich, 82152 Planegg-Martinsried, Germany
- Center for Integrated Protein Science Munich, LMU Munich, 81377 Munich, Germany
| | - Tamas Schauer
- Molecular Biology Division, Biomedical Center, LMU Munich, 82152 Planegg-Martinsried, Germany
- Bioinformatics Unit, Biomedical Center, LMU Munich, 82152 Planegg-Martinsried, Germany
| | - Andreas Schmidt
- Molecular Biology Division, Biomedical Center, LMU Munich, 82152 Planegg-Martinsried, Germany
- Protein Analysis Unit, Biomedical Center, LMU Munich, 82152 Planegg-Martinsried, Germany
| | - Tanja Bange
- Institute of Medical Psychology, LMU Munich, 80336 Munich, Germany
| | - Maria S Robles
- Institute of Medical Psychology, LMU Munich, 80336 Munich, Germany
| | - Elisabeth Kremmer
- Institute of Molecular Immunology, German Research Center for Environmental Health, 81377 Munich, Germany
| | - Axel Imhof
- Molecular Biology Division, Biomedical Center, LMU Munich, 82152 Planegg-Martinsried, Germany
- Center for Integrated Protein Science Munich, LMU Munich, 81377 Munich, Germany
- Protein Analysis Unit, Biomedical Center, LMU Munich, 82152 Planegg-Martinsried, Germany
| | - Peter B Becker
- Molecular Biology Division, Biomedical Center, LMU Munich, 82152 Planegg-Martinsried, Germany
- Center for Integrated Protein Science Munich, LMU Munich, 81377 Munich, Germany
- To whom correspondence should be addressed. Tel: +49 89 2180 75427; Fax: +49 89 2180 75425;
| |
Collapse
|
19
|
Owens N, Papadopoulou T, Festuccia N, Tachtsidi A, Gonzalez I, Dubois A, Vandormael-Pournin S, Nora EP, Bruneau BG, Cohen-Tannoudji M, Navarro P. CTCF confers local nucleosome resiliency after DNA replication and during mitosis. eLife 2019; 8:e47898. [PMID: 31599722 PMCID: PMC6844645 DOI: 10.7554/elife.47898] [Citation(s) in RCA: 46] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2019] [Accepted: 10/09/2019] [Indexed: 12/20/2022] Open
Abstract
The access of Transcription Factors (TFs) to their cognate DNA binding motifs requires a precise control over nucleosome positioning. This is especially important following DNA replication and during mitosis, both resulting in profound changes in nucleosome organization over TF binding regions. Using mouse Embryonic Stem (ES) cells, we show that the TF CTCF displaces nucleosomes from its binding site and locally organizes large and phased nucleosomal arrays, not only in interphase steady-state but also immediately after replication and during mitosis. Correlative analyses suggest this is associated with fast gene reactivation following replication and mitosis. While regions bound by other TFs (Oct4/Sox2), display major rearrangement, the post-replication and mitotic nucleosome positioning activity of CTCF is not unique: Esrrb binding regions are also characterized by persistent nucleosome positioning. Therefore, selected TFs such as CTCF and Esrrb act as resilient TFs governing the inheritance of nucleosome positioning at regulatory regions throughout the cell-cycle.
Collapse
Affiliation(s)
- Nick Owens
- Epigenomics, Proliferation, and the Identity of Cells, Department of Developmental and Stem Cell BiologyInstitut Pasteur, CNRS UMR3738ParisFrance
- Equipe Labellisée LIGUE Contre le CancerParisFrance
| | - Thaleia Papadopoulou
- Epigenomics, Proliferation, and the Identity of Cells, Department of Developmental and Stem Cell BiologyInstitut Pasteur, CNRS UMR3738ParisFrance
- Equipe Labellisée LIGUE Contre le CancerParisFrance
| | - Nicola Festuccia
- Epigenomics, Proliferation, and the Identity of Cells, Department of Developmental and Stem Cell BiologyInstitut Pasteur, CNRS UMR3738ParisFrance
- Equipe Labellisée LIGUE Contre le CancerParisFrance
| | - Alexandra Tachtsidi
- Epigenomics, Proliferation, and the Identity of Cells, Department of Developmental and Stem Cell BiologyInstitut Pasteur, CNRS UMR3738ParisFrance
- Equipe Labellisée LIGUE Contre le CancerParisFrance
- Sorbonne Université, Collège DoctoralParisFrance
| | - Inma Gonzalez
- Epigenomics, Proliferation, and the Identity of Cells, Department of Developmental and Stem Cell BiologyInstitut Pasteur, CNRS UMR3738ParisFrance
- Equipe Labellisée LIGUE Contre le CancerParisFrance
| | - Agnes Dubois
- Epigenomics, Proliferation, and the Identity of Cells, Department of Developmental and Stem Cell BiologyInstitut Pasteur, CNRS UMR3738ParisFrance
- Equipe Labellisée LIGUE Contre le CancerParisFrance
| | - Sandrine Vandormael-Pournin
- Epigenomics, Proliferation, and the Identity of Cells, Department of Developmental and Stem Cell BiologyInstitut Pasteur, CNRS UMR3738ParisFrance
- Early Mammalian Development and Stem Cell Biology, Department of Developmental and Stem Cell BiologyInstitut Pasteur, CNRS UMR 3738ParisFrance
| | - Elphège P Nora
- Gladstone InstitutesSan FranciscoUnited States
- Cardiovascular Research InstituteUniversity of California, San FranciscoSan FranciscoUnited States
| | - Benoit G Bruneau
- Gladstone InstitutesSan FranciscoUnited States
- Cardiovascular Research InstituteUniversity of California, San FranciscoSan FranciscoUnited States
- Department of PediatricsUniversity of California, San FranciscoSan FranciscoUnited States
| | - Michel Cohen-Tannoudji
- Epigenomics, Proliferation, and the Identity of Cells, Department of Developmental and Stem Cell BiologyInstitut Pasteur, CNRS UMR3738ParisFrance
- Early Mammalian Development and Stem Cell Biology, Department of Developmental and Stem Cell BiologyInstitut Pasteur, CNRS UMR 3738ParisFrance
| | - Pablo Navarro
- Epigenomics, Proliferation, and the Identity of Cells, Department of Developmental and Stem Cell BiologyInstitut Pasteur, CNRS UMR3738ParisFrance
- Equipe Labellisée LIGUE Contre le CancerParisFrance
| |
Collapse
|
20
|
Nucleosome positioning and spacing: from genome-wide maps to single arrays. Essays Biochem 2019; 63:5-14. [PMID: 31015380 DOI: 10.1042/ebc20180058] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2018] [Revised: 02/07/2019] [Accepted: 02/11/2019] [Indexed: 01/07/2023]
Abstract
The positioning of nucleosomes relative to DNA and their neighboring nucleosomes represents a fundamental layer of chromatin organization. Changes in nucleosome positioning and spacing affect the accessibility of DNA to regulatory factors and the formation of higher order chromatin structures. Sequencing of mononucleosomal fragments allowed mapping nucleosome positions on a genome-wide level in many organisms. This revealed that successions of evenly spaced and well-positioned nucleosomes-so called phased nucleosome arrays-occur at the 5' end of many active genes and in the vicinity of transcription factor and other protein binding sites. Phased arrays arise from the interplay of barrier elements on the DNA, which position adjacent nucleosomes, and the nucleosome spacing activity of ATP-dependent chromatin remodelers. A shortcoming of classic mononucleosomal mapping experiments is that they only reveal nucleosome spacing and array regularity at select sites in the genome with well-positioned nucleosomes. However, new technological approaches elucidate nucleosome array structure throughout the genome and with single-cell resolution. In the future, it will be interesting to see whether changes in nucleosome array regularity and spacing contribute to the formation of higher order chromatin structures and the spatial organization of the genome in vivo.
Collapse
|
21
|
Zhao H, Winogradoff D, Dalal Y, Papoian GA. The Oligomerization Landscape of Histones. Biophys J 2019; 116:1845-1855. [PMID: 31005236 DOI: 10.1016/j.bpj.2019.03.021] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2018] [Revised: 03/06/2019] [Accepted: 03/14/2019] [Indexed: 12/29/2022] Open
Abstract
In eukaryotes, DNA is packaged within nucleosomes. The DNA of each nucleosome is typically centered around an octameric histone protein core: one central tetramer plus two separate dimers. Studying the assembly mechanisms of histones is essential for understanding the dynamics of entire nucleosomes and higher-order DNA packaging. Here, we investigate canonical histone assembly and that of the centromere-specific histone variant, centromere protein A (CENP-A), using molecular dynamics simulations. We quantitatively characterize their thermodynamical and dynamical features, showing that two H3/H4 dimers form a structurally floppy, weakly bound complex, the latter exhibiting large instability around the central interface manifested via a swiveling motion of two halves. This finding is consistent with the recently observed DNA handedness flipping of the tetrasome. In contrast, the variant CENP-A encodes distinctive stability to its tetramer with a rigid but twisted interface compared to the crystal structure, implying diverse structural possibilities of the histone variant. Interestingly, the observed tetramer dynamics alter significantly and appear to reach a new balance when H2A/H2B dimers are present. Furthermore, we found that the preferred structure for the (CENP-A/H4)2 tetramer is incongruent with the octameric structure, explaining many of the unusual dynamical behaviors of the CENP-A nucleosome. In all, these data reveal key mechanistic insights and structural details for the assembly of canonical and variant histone tetramers and octamers, providing theoretical quantifications and physical interpretations for longstanding and recent experimental observations. Based on these findings, we propose different chaperone-assisted binding and nucleosome assembly mechanisms for the canonical and CENP-A histone oligomers.
Collapse
Affiliation(s)
- Haiqing Zhao
- Biophysics Program, Institute for Physical Science and Technology, University of Maryland, College Park, Maryland; Laboratory of Receptor Biology and Gene Expression, National Cancer Institute, National Institutes of Health, Bethesda, Maryland
| | - David Winogradoff
- Chemical Physics Program, Institute for Physical Science and Technology
| | - Yamini Dalal
- Laboratory of Receptor Biology and Gene Expression, National Cancer Institute, National Institutes of Health, Bethesda, Maryland.
| | - Garegin A Papoian
- Biophysics Program, Institute for Physical Science and Technology, University of Maryland, College Park, Maryland; Chemical Physics Program, Institute for Physical Science and Technology; Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland.
| |
Collapse
|
22
|
Gilbert N. Biophysical regulation of local chromatin structure. Curr Opin Genet Dev 2019; 55:66-75. [DOI: 10.1016/j.gde.2019.06.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2019] [Revised: 05/31/2019] [Accepted: 06/02/2019] [Indexed: 10/26/2022]
|