DOCSLIB.ORG

Studies of Nucleosome Structure

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Studies of Nucleosome Structure Downloaded from symposium.cshlp.org on November 30, 2015 - Published by Cold Spring Harbor Laboratory Press Studies of Nucleosome Structure T.J. RICHMOND, T. RECHSTEINER, AND K. LUGER Institut fur Molekularbiologie und Biophysik, ETH-Honggerberg, CH-8093 Zurich, Switzerland The nucleosome is the universal protein/DNA ele- terminal regions in the core particle can be identified. ment repeated throughout the chromatin of eukaryotic For example, the entry point for the histone H4 amino- cells (Kornberg 1977; McGhee and Felsenfeld 1980). terminal "tail" and perhaps the tail itself can be recog- Presumably as a consequence of its fundamental role in nized. The H2A carboxy-terminal and the H3 amino- the organization of DNA in a compact unit, it has also terminal tails appear to form domains adjacent to the been found to take part in gene regulation (see, e.g., termini of the DNA superhelix. The positions of the Pederson et al. 1986; van Holde 1988; Grunstein 1990; histone protein/DNA cross-links are highly consistent Wolffe 1991; Kornberg and Lorch 1992). A major with the new electron density assignments, objective of our laboratory has been to obtain structur- To obtain greater structural detail for the nucleo- al information at high resolution for the nucleosome, its some, crystals of a nucleosome core particle containing higher-order structure, and its interactions with other DNA with a single sequence were prepared and found nuclear factors. Previously, the structure of the nucleo- to diffract to approximately 3.5 ,~ resolution (Rich- some core particle was solved by X-ray crystallography mond et al. 1988). To aid the selection of heavy-atom at 7 A_ resolution using the method of multiple iso- derivatives for structure determination and to permit morphous replacement (Richmond et al. 1984). This mutagenic analysis of particle stability and assembly, X-ray structure confirmed the size and shape of the, we have prepared and crystallized core particles that particle deduced earlier from several lines of infor- contain all the histones as recombinant proteins. The mation (Finch et al. 1979), showing that the "146"-bp higher-resolution structure should allow accurate DNA is arranged in 1.8 superhelical turns around the identification of the DNA path and location of many of histone octamer in a disk-like structure 57 A in height the side chains of the histone proteins. Finally, a along the superhelix axis and approximately 110 A, in nucleosome particle that contains 179 bp of DNA and diameter. The DNA was seen to be bent tightly at the globular domain of histone H1 is being character- several positions along its superhelical path. The shape ized and has been crystallized. and dimensions of the histone octamer within the nucleosome core particle were observed to match those Preparation of Nucleosome Core Particle Crystals measured from the octamer structure at 20 A, resolution determined by image reconstruction from electron mi- Nucleosome core particles can be obtained by lysis of crographs made from ordered aggregates under high- cell nuclei and partial digestion of the exposed chro- salt conditions (Klug et al. 1980). Even at low res- matin with micrococcal nuclease. The particles contain olution, the DNA superhelix was seen to follow a approximately 147 -+ 2 base pairs of DNA, representing helical ramp formed by the histone proteins. Regions of the natural abundance of DNA sequences (i.e., con- the histone octamer were assigned to the four pairs of taining mixed sequences), and two copies of each of the histones, H3, H4, H2A, and H2B, first in the 20 A, four core histones, H2A, H2B, H3, and H4, for a resolution structure, and then in the 7 A, X-ray struc- roughly equal mass of protein and DNA (Finch et al, ture, based on the DMS method of protein/DNA 1977). These particles of 206 kD yield crystals that cross-linking (Mirzabekov et al. 1978; Shick et al. diffract anisotropically to 3.5-7 A~ resolution and have 1980). Although many internal features of the histones resulted in a structure at 7 A, resolution (Finch et al. were seen, their assignment to individual histones could 1979; Richmond et al. 1984; Rhodes et al. 1989). be made only rather crudely, since the polypeptide To improve the X-ray diffraction from nucleosome chain could not be identified by recognition of indi- core particle crystals, the mixed sequence DNA was vidual amino acid side chains. replaced with a 146-bp DNA fragment of unique se- In light of the reinterpretation of the histone octamer quence (Richmond et al. 1988). The sequence selected crystal structure (Arents et al, 1991), it is now possible was from the 5S RNA gene of Lytechinus variegatus to assign the location of the histone proteins in the and contains the distal 25 bp of the transcription factor nucleosome core particle structure more accurately. IIIA (TFIIIA) binding site (Simpson and Stafford The location of essentially all the c~-helical regions 1983). After insertion of this fragment in multiple identified from the histone octamer crystals can be copies in a plasmid, amplification in bacteria, restric- located in the nucleosome core particle X-ray structure. tion enzyme excision, and high-performance liquid Although some rearrangement of structural elements is chromatography (HPLC) purification, core particles apparent, the entry or exit points of most of the histone were reconstituted in high yields using histone octamer Cold Spring Harbor Symposia on Quantltatwe Btology, Volume LVIII. 91993 Cold Spring Harbor Laboratory Press 0-87969-065-8/93 $5.00 265 Downloaded from symposium.cshlp.org on November 30, 2015 - Published by Cold Spring Harbor Laboratory Press 266 RICHMOND, RECHSTEINER, AND LUGER from chicken erythrocytes. Crystals of these particles measuring along several turns of an c~ helix. Since the diffract anisotropically, beyond 3 A in the best direc- molecular (also crystallographic) twofold axis in the tion and to 3.5-4 A in the poorest direction. Compared histone octamer is along the horizontal in Figure 3c, it to the mixed sequence crystals which have one particle must also be close to horizontal in Figure 5. Given the in the crystallographic asymmetric unit (asu), these lack of perfect mirror symmetry about a horizontal line defined sequence crystals have two particles for 412 kD for the outline of the whole octamer in Figure 3, the per asu. twofold axis must be somewhat out of the plane of the More recently, totally recombinant nucleosome core projection. It cannot lie very far out, however, since it particles have been produced using histone genes from must be perpendicular to the molecular superhelix axis, Xenopus laevis (Old et al. 1982) expressed in bacteria and the view in Figure 5, as noted by the authors, is (Studier et al. 1990; K. Luger et al., in prep.). Various approximately down the superhelix axis. By including a mutant histones have been prepared, and nucleosome second transparent copy of the Figure 5 ribbon diagram core particle crystals containing them have been grown. inverted about a horizontal axis in the previous Fragments of defined sequence DNA longer than the superposition, both ribbon diagrams can be translated 146 bp have also been made and reconstituted with the as required to fit the surface projections of the "pseu- do" space-filling model shown in Figure 3c. The core histones into particles which crystallize. In addi- twofold axis position determined in this manner relat- tion, the globular domain of histone H1 (Hlg), the ing the half octamers in the ribbon diagrams falls on the outer or linker histone protein, from X. laevis has also most obvious location for the twofold axis in the surface been expressed in bacteria. Hlg has been used to representation. assemble and crystallize a nucleosome containing all The tetrakismercurimethane compound (TAMM) five histone proteins and 179 bp of DNA (T. Rech- used to make the single heavy-atom derivative for the steiner and T.J. Richmond, in prep.). hsHO structure determination is most probably bound to the histone H3 Cys-ll0 residues, the only cysteine Assignment of the Histone Proteins in the Nucleosome groups in the molecule. Using coordinates for the Core Particle at 7 TAMM multi-heavy-atom group given by Arents et al. (1991), which apparently corresponds to a single mer- The electron density map of the histone octamer cury atom because of chemical decomposition (see crystals obtained at high salt concentrations has been Burlingame et al. 1985), the site is approximately 1 recalculated (Arents et al. 1991) and found to be away from the molecular dyad axis and adjacent to the substantially different from the map originally deter- carboxyl terminus of the H3 long helix. According to mined (Burlingame et al. 1985). The distribution of the the secondary structure assignments reported in Figure polypeptide chains is substantially altered from the 2 of Arents et al. (1991), H3 Cys-110 is located in the previous interpretation. The original histone octamer carboxy-terminal turn of this long a helix. This site structure had maximal dimensions of 110 A, • 65-70 provides a common structural marker very near the A, which have been reduced to 60 A, x 65 A in the molecular symmetry axis in both the hsHO and msNCP republished structure. These dimensions compare well histone octamer structures. with those for the 20 A resolution histone octamer In the presentation of the hsHS and msNCP histone structure reported as 56 A x 70 ~, (Klug et al. 1980). octamer structures, the views given in Figure 5 of The most recent structure of the "high salt'" histone Arents et al. (1991) and in all figures of Richmond et octamer (hsHO) using data to 3.1 A resolution war- al. (1984), respectively, are views approximately down rants comparison to the histone octamer structure the molecular superhelix axis.
Load more

Recommended publications
  • Datasheet for Histone H2B Human, Recombinant (M2505; Lot 0031404)
    Supplied in: 20 mM Sodium Phosphate (pH 7.0), Quality Control Assays: Ionization-Time of Flight Mass Spectrometry). The Histone H2B 300 mM NaCl and 1 mM EDTA. SDS-PAGE: 0.5 µg, 1.0 µg, 2.0 µg, 5.0 µg, average mass calculated from primary sequence Human, Recombinant 10.0 µg Histone H2B Human, Recombinant were is 13788.97 Da. This confirms the protein identity Note: The protein concentration (1 mg/ml, 73 µM) loaded on a 10–20% Tris-Glycine SDS-PAGE gel as well as the absence of any modifications of the is calculated using the molar extinction coefficient and stained with Coomassie Blue. The calculated histone. 1-800-632-7799 for Histone H2B (6400) and its absorbance at molecular weight is 13788.97 Da. Its apparent [email protected] 280 nm (3,4). 1.0 A units = 2.2 mg/ml N-terminal Protein Sequencing: Protein identity 280 molecular weight on 10–20% Tris-Glycine SDS- www.neb.com was confirmed using Edman Degradation to PAGE gel is ~17 kDa. M2505S 003140416041 Synonyms: Histone H2B/q, Histone H2B.1, sequence the intact protein. Histone H2B-GL105 Mass Spectrometry: The mass of purified Histone H2B Human, Recombinant is 13788.5 Da Protease Assay: After incubation of 10 µg of M2505S B r kDa 1 2 3 4 5 6 7 as determined by ESI-TOF MS (Electrospray Histone H2B Human, Recombinant with a standard 250 4.0 mixture of proteins for 2 hours at 37°C, no 100 µg 1.0 mg/ml Lot: 0031404 150 13788.5 100 proteolytic activity could be detected by SDS- RECOMBINANT Store at –20°C Exp: 4/16 80 PAGE.
    [Show full text]
  • H2A Ubiquitylated Mononucleosomes Next-Generation Substrates for Deubiquitylation Enzyme (DUB) Assays
    H2A Ubiquitylated Mononucleosomes Next-Generation Substrates for Deubiquitylation Enzyme (DUB) Assays Next-Generation DUB Assay Substrates are here. Get results that matter. • Enabling access to DUB targets that require nucleosome substrates in vitro • Proper substrates for DUB inhibitor development • Unmatched quality control for results you can trust Histone monoubiquitylation (ub1) acts as a critical signaling center that regulates cascades of downstream epigenetic enzymes to modify gene transcription. The physiological substrate for chromatin-targeting DUBs is the nucleosome (Nuc), the basic repeating unit of chromatin (comprised of histone proteins wrapped by DNA). Current high-throughput screening (HTS) DUB assays use unnatural modified or diubiquitin conjugates as substrates, which poorly mimic endogenous targets in vivo. In collaboration with Boston Biochem, EpiCypher is delivering ubiquitylated nucleosome substrates for drug screening and chromatin biology research. FIGURE 1 Ub Ub Schematic representation of mononucleosoms assembled from recombinant human histones Ub expressed in E. coli (two each of histones H2A, H2B, H3 and H4). H2A H2A Approximately 50% of the nucleosomes are monoubiquitylated on histone H2A lysine 118, while the other 50% are monoubiquitylated on both histone H2A lysine 118 and histone H2A lysine 119 (multi-mono- ubiquitylated). Next Generation Deubiquitylation Enzyme (DUB) Assay Substrates EpiCypher has developed recombinant mononucleosomes carrying monoubiquitylation on H2A. These ubiquitylated nucleosomes are generated enzymatically using the RING1B/BMI1 ubiquitin ligase complex. The resulting product is highly pure (>95% of nucleosomes are ubiquitylated) and consists of nucleosomes monoubiquitylated at H2A lysine 118/119 (Figure 1; the physiological target of RING1B/BMI1 in vivo). FIGURE 2 Deubiquitylation Assay Data: Mononucleosomes H2A Ubiquityl, Recombinant Human, Biotinylated (1 μg) were employed in a deubiquitylation (DUB) assay using no enzyme (Lane 1), USP5 (Lane 2) or USP16 (Lane 3) and run on an SDS PAGE gel.
    [Show full text]
  • FACT Is Recruited to the +1 Nucleosome of Transcribed Genes and Spreads in a Chd1-Dependent Manner
    bioRxiv preprint doi: https://doi.org/10.1101/2020.08.20.259960; this version posted August 21, 2020. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY-NC-ND 4.0 International license. FACT is recruited to the +1 nucleosome of transcribed genes and spreads in a Chd1-dependent manner Célia Jeronimo1, Andrew Angel2, Christian Poitras1, Pierre Collin1, Jane Mellor2 and François Robert1,3,4* 1 Institut de recherches cliniques de Montréal, 110 Avenue des Pins Ouest, Montréal, QC H2W 1R7, Canada. 2Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU, UK. 3 Département de Médecine, Faculté de Médecine, Université de Montréal, 2900 Boul. Édouard- Montpetit, Montréal, QC H3T 1J4, Canada. 4 Lead Contact *Correspondence: [email protected] The histone chaperone FACT occupies transcribed regions where it plays prominent roles in maintaining chromatin integrity and preserving epigenetic information. How it is targeted to transcribed regions, however, remains unclear. Proposed models for how FACT finds its way to transcriptionally active chromatin include docking on the RNA polymerase II (RNAPII) C-terminal domain (CTD), recruitment by elongation factors, recognition of modified histone tails and binding partially disassembled nucleosomes. Here, we systematically tested these and other scenarios in Saccharomyces cerevisiae and found that FACT binds transcribed chromatin, not RNAPII. Through a combination of experimental and mathematical modeling evidence, we propose that FACT recognizes the +1 nucleosome, as it is partially unwrapped by the engaging RNAPII, and spreads to downstream nucleosomes aided by the chromatin remodeler Chd1.
    [Show full text]
  • Topography of the Histone Octamer Surface: Repeating Structural Motifs Utilized in the Docking of Nucleosomal
    Proc. Natl. Acad. Sci. USA Vol. 90, pp. 10489-10493, November 1993 Biochemistry Topography of the histone octamer surface: Repeating structural motifs utilized in the docking of nucleosomal DNA (histone fold/helix-strand-helix motif/parallel fi bridge/binary DNA binding sites/nucleosome) GINA ARENTS* AND EVANGELOS N. MOUDRIANAKIS*t *Department of Biology, The Johns Hopkins University, Baltimore, MD 21218; and tDepartment of Biology, University of Athens, Athens, Greece Communicated by Christian B. Anfinsen, August 5, 1993 ABSTRACT The histone octamer core of the nucleosome is interactions. The model offers strong predictive criteria for a protein superhelix offour spirally arrayed histone dimers. The structural and genetic biology. cylindrical face of this superhelix is marked by intradimer and interdimer pseudodyad axes, which derive from the nature ofthe METHODS histone fold. The histone fold appears as the result of a tandem, parallel duplication of the "helix-strand-helix" motif. This The determination of the structure of the histone octamer at motif, by its occurrence in the four dimers, gives rise torepetitive 3.1 A has been described (3). The overall shape and volume structural elements-i.e., the "parallel 13 bridges" and the of this tripartite structure is in agreement with the results of "paired ends of helix I" motifs. A preponderance of positive three independent studies based on differing methodolo- charges on the surface of the octamer appears as a left-handed gies-i.e., x-ray diffraction, neutron diffraction, and electron spiral situated at the expected path of the DNA. We have microscopic image reconstruction (4-6). Furthermore, the matched a subset of DNA pseudodyads with the octamer identification of the histone fold, a tertiary structure motif of pseudodyads and thus have built a model of the nucleosome.
    [Show full text]
  • Watanabe S, Resch M, Lilyestrom W, Clark N
    NIH Public Access Author Manuscript Biochim Biophys Acta. Author manuscript; available in PMC 2010 November 1. NIH-PA Author ManuscriptPublished NIH-PA Author Manuscript in final edited NIH-PA Author Manuscript form as: Biochim Biophys Acta. 2010 ; 1799(5-6): 480±486. doi:10.1016/j.bbagrm.2010.01.009. Structural characterization of H3K56Q nucleosomes and nucleosomal arrays Shinya Watanabe1,*, Michael Resch2,*, Wayne Lilyestrom2, Nicholas Clark2, Jeffrey C. Hansen2, Craig Peterson1, and Karolin Luger2,3 1 Program in Molecular Medicine, University of Massachusetts Medical School, 373 Plantation St.; Worcester, Massachusetts 01605 2 Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80523-1870 3 Howard Hughes Medical Institute Abstract The posttranslational modification of histones is a key mechanism for the modulation of DNA accessibility. Acetylated lysine 56 in histone H3 is associated with nucleosome assembly during replication and DNA repair, and is thus likely to predominate in regions of chromatin containing nucleosome free regions. Here we show by x-ray crystallography that mutation of H3 lysine 56 to glutamine (to mimic acetylation) or glutamate (to cause a charge reversal) has no detectable effects on the structure of the nucleosome. At the level of higher order chromatin structure, the K to Q substitution has no effect on the folding of model nucleosomal arrays in cis, regardless of the degree of nucleosome density. In contrast, defects in array-array interactions in trans (‘oligomerization’) are selectively observed for mutant H3 lysine 56 arrays that contain nucleosome free regions. Our data suggests that H3K56 acetylation is one of the molecular mechanisms employed to keep chromatin with nucleosome free regions accessible to the DNA replication and repair machinery.
    [Show full text]
  • DNA Condensation and Packaging
    DNA condensation and packaging October 13, 2009 Professor Wilma K. Olson Viral DNA - chain molecules in confined spaces Viruses come in all shapes and sizes Clockwise: Human immuno deficiency virus (HIV); Aeromonas virus 31, Influenza virus, Orf virus, Herpes simplex virus (HSV), Small pox virus Image from U Wisconsin Microbial World website: http://bioinfo.bact.wisc.edu DNA packaging pathway of T3 and T7 bacteriophages • In vivo pathway - solid arrows Fang et al. (2008) “Visualization of bacteriophage T3 capsids with DNA incompletely packaged in vivo.” J. Mol. Biol. 384, 1384-1399 Cryo EM images of T3 capsids with 10.6 kbp packaged DNA • Labels mark particles representative of different types of capsids • Arrows point to tails on capsids Fang et al. (2008) “Visualization of bacteriophage T3 capsids with DNA incompletely packaged in vivo.”” J. Mol. Biol. 384, 1384-1399 Cryo EM images of representative particles • (b) 10.6 kbp DNA • (c) 22 kbp DNA • (d) bacteriophage T3 Fang et al. (2008) “Visualization of bacteriophage T3 capsids with DNA incompletely packaged in vivo.” J. Mol. Biol. 384, 1384-1399 3D icosohedral reconstructions of cryo-EM-imaged particles Threefold surface views and central cross sections • (b) 10.6 kbp DNA • (c) 22 kbp DNA • (d) bacteriophage T3 Fang et al. (2008) “Visualization of bacteriophage T3 capsids with DNA incompletely packaged in vivo.” J. Mol. Biol. 384, 1384-1399 Top-down views of λ phage DNA toroids captured in cryo-EM micrographs Note the circumferential winding of DNA found in collapsed toroidal particles produced in the presence of multi-valent cations. Hud & Vilfan (2005) “Toroidal DNA condensates: unraveling the fine structure and the role of nucleation in determining size.” Ann.
    [Show full text]
  • Investigating the Epigenetic Mechanisms of Trophoblast Giant Cells
    Biology ︱ Assistant Professor Koji Hayakawa NUCLEOSOME STRUCTURE OF TROPHOBLAST GIANT CELL (TGC) Diploid TSC Polyploid TGC H2A H2B H2AX/ Investigating the H2AZ epigenetic mechanisms Entry into DNA Endocycle H3 H4 H3.3 of trophoblast giant cells TGCs possess a loose chromatin structure owing to alterations in the histone composition of the nucleosomes, which involves the replacement of canonical histones with histone variants such as H2AX, H2AZ, and H3.3 during differentiation. Trophoblast giant cells (TGCs) ucleosome is a large molecule in the placenta of rodents, are a unique days, and that certain histone variants Many polyploid cells identified in plants are found in the placental in the cell which is primarily cell type that replicate their DNA until were associated with differentiated walls of rodents and play a Nmade up of DNA and proteins. the cell contains thousands of copies, cells. Overall, there was much less and animals appear to have a secretory role in maintaining pregnancy. The major protein in nucleosome is unlike most cells which normally contain variation in TGCs compared to the In contrast to most cell types called a histone, around which DNA two sets of chromosomes (diploid cells). undifferentiated, diploid cells. They or nutritive function. which contain two copies of wraps. These proteins are classified into The reasons for this condition are not found the histone profile to be very from undifferentiated cells showed distinct concentrations of salt buffer to disrupt each chromosome (diploid), canonical histones and non-canonical clear. However, it has been suggested similar in differentiated TSCs at day six bands when digested, demonstrating that DNA-protein bonds.
    [Show full text]
  • A Mutation in Histone H2B Represents a New Class of Oncogenic Driver
    Author Manuscript Published OnlineFirst on July 23, 2019; DOI: 10.1158/2159-8290.CD-19-0393 Author manuscripts have been peer reviewed and accepted for publication but have not yet been edited. A Mutation in Histone H2B Represents A New Class Of Oncogenic Driver Richard L. Bennett1, Aditya Bele1, Eliza C. Small2, Christine M. Will2, Behnam Nabet3, Jon A. Oyer2, Xiaoxiao Huang1,9, Rajarshi P. Ghosh4, Adrian T. Grzybowski5, Tao Yu6, Qiao Zhang7, Alberto Riva8, Tanmay P. Lele7, George C. Schatz9, Neil L. Kelleher9 Alexander J. Ruthenburg5, Jan Liphardt4 and Jonathan D. Licht1 * 1 Division of Hematology/Oncology, University of Florida Health Cancer Center, Gainesville, FL 2 Division of Hematology/Oncology, Northwestern University 3 Department of Cancer Biology, Dana Farber Cancer Institute and Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School 4 Department of Bioengineering, Stanford University 5 Department of Molecular Genetics and Cell Biology, The University of Chicago 6 Department of Chemistry, Tennessee Technological University 7 Department of Chemical Engineering, University of Florida 8 Bioinformatics Core, Interdisciplinary Center for Biotechnology Research, University of Florida 9 Department of Chemistry, Northwestern University, Evanston IL 60208 Running title: Histone mutations in cancer *Corresponding Author: Jonathan D. Licht, MD The University of Florida Health Cancer Center Cancer and Genetics Research Complex, Suite 145 2033 Mowry Road Gainesville, FL 32610 352-273-8143 [email protected] Disclosures: The authors have no conflicts of interest to declare Downloaded from cancerdiscovery.aacrjournals.org on September 27, 2021. © 2019 American Association for Cancer Research. Author Manuscript Published OnlineFirst on July 23, 2019; DOI: 10.1158/2159-8290.CD-19-0393 Author manuscripts have been peer reviewed and accepted for publication but have not yet been edited.
    [Show full text]
  • Condensed DNA: Condensing the Concepts
    Progress in Biophysics and Molecular Biology 105 (2011) 208e222 Contents lists available at ScienceDirect Progress in Biophysics and Molecular Biology journal homepage: www.elsevier.com/locate/pbiomolbio Review Condensed DNA: Condensing the concepts Vladimir B. Teif a,b,*, Klemen Bohinc c,d a BioQuant and German Cancer Research Center, Im Neuenheimer Feld 267, 69120 Heidelberg, Germany b Institute of Bioorganic Chemistry, Belarus National Academy of Sciences, Kuprevich 5/2, 220141, Minsk, Belarus c Faculty of Health Sciences, Zdravstvena pot 5, 1000 Ljubljana, Slovenia d Faculty of Electrical Engineering, University of Ljubljana, Trzaska 25, 1000 Ljubljana, Slovenia article info abstract Article history: DNA is stored in vivo in a highly compact, so-called condensed phase, where gene regulatory processes Available online 16 July 2010 are governed by the intricate interplay between different states of DNA compaction. These systems often have surprising properties, which one would not predict from classical concepts of dilute solutions. The Keywords: mechanistic details of DNA packing are essential for its functioning, as revealed by the recent devel- DNA condensation opments coming from biochemistry, electrostatics, statistical mechanics, and molecular and cell biology. Ligand binding Different aspects of condensed DNA behavior are linked to each other, but the links are often hidden in Counterion correlations the bulk of experimental and theoretical details. Here we try to condense some of these concepts and Macromolecular crowding fi Chromatin provide interconnections between the different elds. After a brief description of main experimental Gene regulation features of DNA condensation inside viruses, bacteria, eukaryotes and the test tube, main theoretical approaches for the description of these systems are presented.
    [Show full text]
  • Chromatin Structure
    Chromatin Structure Dr. Carol S. Newlon [email protected] ICPH E250P DNA Packaging Is a Formidable Challenge • Single DNA molecule in human chromosome ca. 5 cm long • Diploid genome contains ca. 2 meters of DNA • Nucleus of human cell ca. 5 µm in diameter • Human metaphase chromosome ca. 2.5 µm in length • 10,000 to 20,000 packaging ratio required Overview of DNA Packaging Packaging in Interphase Nucleus Chromatin Composition • Complex of DNA and histones in 1:1 mass ratio • Histones are small basic proteins – highly conserved during evolution – abundance of positively charged aa’s (lysine and arginine) bind negatively charged DNA • Four core histones: H2A, H2B, H3, H4 in 1:1:1:1 ratio • Linker histone: H1 in variable ratio Chromatin Fibers 11-nm fiber 30-nm fiber • beads = nucleosomes • physiological ionic • compaction = 2.5X strength (0.15 M KCl) • low ionic strength buffer • compaction = 42X • H1 not required • H1 required Micrococcal Nuclease Digestion of Chromatin Stochiometry of Histones and DNA • 146 bp DNA ca. 100 kDa • 8 histones ca 108 kDa • mass ratio of DNA:protein 1:1 Structure of Core Nucleosome 1.65 left handed turns of DNA around histone octamer Histone Structure Assembly of a Histone Octamer Nucleosomes Are Dynamic Chromatin Remodeling Large complexes of ≥ 10 proteins Use energy of ATP hydrolysis to partially disrupt histone-DNA contacts Catalyze nucleosome sliding or nucleosome removal 30-nm Chromatin Fiber Structure ?? Models for H1 and Core Histone Tails in Formation of 30-nm Fiber Histone Tails Covalent Modifications
    [Show full text]
  • Nucleosome Loss Leads to Global Transcriptional Up-Regulation and Genomic Instability During Yeast Aging
    Downloaded from genesdev.cshlp.org on September 25, 2021 - Published by Cold Spring Harbor Laboratory Press Nucleosome loss leads to global transcriptional up-regulation and genomic instability during yeast aging Zheng Hu,1,6 Kaifu Chen,2,3,6 Zheng Xia,2,3 Myrriah Chavez,1,4 Sangita Pal,1,5 Ja-Hwan Seol,1 Chin-Chuan Chen,1 Wei Li,2,7,8 and Jessica K. Tyler1,7,8 1Department of Biochemistry and Molecular Biology, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030, USA; 2Dan L. Duncan Cancer Center, 3Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, Texas 77030, USA; 4Molecular Biology Graduate Program, University of Colorado School of Medicine, Denver, Colorado 80010, USA; 5Genes and Development Graduate Program, The University of Texas Graduate School of Biomedical Sciences, Houston, Texas 77030, USA All eukaryotic cells divide a finite number of times, although the mechanistic basis of this replicative aging remains unclear. Replicative aging is accompanied by a reduction in histone protein levels, and this is a cause of aging in budding yeast. Here we show that nucleosome occupancy decreased by 50% across the whole genome during replicative aging using spike-in controlled micrococcal nuclease digestion followed by sequencing. Furthermore, nucleosomes became less well positioned or moved to sequences predicted to better accommodate histone octamers. The loss of histones during aging led to transcriptional induction of all yeast genes. Genes that are normally repressed by promoter nucleosomes were most induced, accompanied by preferential nucleosome loss from their promoters. We also found elevated levels of DNA strand breaks, mitochondrial DNA transfer to the nuclear genome, large-scale chromosomal alterations, translocations, and retrotransposition during aging.
    [Show full text]
  • Nucleosome Eviction and Activated Transcription Require P300 Acetylation of Histone H3 Lysine 14
    Nucleosome eviction and activated transcription require p300 acetylation of histone H3 lysine 14 Whitney R. Luebben1, Neelam Sharma1, and Jennifer K. Nyborg2 Department of Biochemistry and Molecular Biology, Campus Box 1870, Colorado State University, Fort Collins, CO 80523 Edited by Mark T. Groudine, Fred Hutchinson Cancer Research Center, Seattle, WA, and approved September 9, 2010 (received for review July 6, 2010) Histone posttranslational modifications and chromatin dynamics include H4 acetylation-dependent relaxation of the chromatin are inextricably linked to eukaryotic gene expression. Among fiber and recruitment of ATP-dependent chromatin-remodeling the many modifications that have been characterized, histone tail complexes via acetyl-lysine binding bromodomains (12–17). acetylation is most strongly correlated with transcriptional activa- However, the mechanism by which histone tail acetylation elicits tion. In Metazoa, promoters of transcriptionally active genes are chromatin reconfiguration and coupled transcriptional activation generally devoid of physically repressive nucleosomes, consistent is unknown (6). with the contemporaneous binding of the large RNA polymerase II In recent years, numerous high profile mapping studies of transcription machinery. The histone acetyltransferase p300 is also nucleosomes and their modifications identified nucleosome-free detected at active gene promoters, flanked by regions of histone regions (NFRs) at the promoters of transcriptionally active genes hyperacetylation. Although the correlation
    [Show full text]