scholarly journals Higher-order structure of human mitotic chromosomes.

1977 ◽  
Vol 74 (4) ◽  
pp. 1595-1599 ◽  
Author(s):  
A. L. Bak ◽  
J. Zeuthen ◽  
F. H. Crick
Keyword(s):  
Higher Order ◽  
Order Structure ◽  
Mitotic Chromosomes

scholarly journals The Forkhead Transcription Factor FoxI1 Remains Bound to Condensed Mitotic Chromosomes and Stably Remodels Chromatin Structure

2006 ◽  
Vol 26 (1) ◽  
pp. 155-168 ◽  
Author(s):  
Jizhou Yan ◽  
Lisha Xu ◽  
Gregory Crawford ◽  
Zenfeng Wang ◽  
Shawn M. Burgess
Keyword(s):  
Chromatin Structure ◽  
Fluorescent Protein ◽  
Living Cells ◽  
Dnase I ◽  
Higher Order ◽  
Micrococcal Nuclease ◽  
Stable Cell Line ◽  
Order Structure ◽  
Dna Fragments ◽  
Mitotic Chromosomes

ABSTRACT All forkhead (Fox) proteins contain a highly conserved DNA binding domain whose structure is remarkably similar to the winged-helix structures of histones H1 and H5. Little is known about Fox protein binding in the context of higher-order chromatin structure in living cells. We created a stable cell line expressing FoxI1-green fluorescent protein (GFP) or FoxI1-V5 fusion proteins under control of the reverse tetracycline-controlled transactivator doxycycline inducible system and found that unlike most transcription factors, FoxI1 remains bound to the condensed chromosomes during mitosis. To isolate DNA fragments directly bound by the FoxI1 protein within living cells, we performed chromatin immunoprecipitation assays (ChIPs) with antibodies to either enhanced GFP or the V5 epitope and subcloned the FoxI1-enriched DNA fragments. Sequence analyses indicated that 88% (106/121) of ChIP sequences contain the consensus binding sites for all Fox proteins. Testing ChIP sequences with a quantitative DNase I hypersensitivity assay showed that FoxI1 created stable DNase I sensitivity changes in condensed chromosomes. The majority of ChIP targets and random targets increased in resistance to DNase I in FoxI1-expressing cells, but a small number of targets became more accessible to DNase I. Consistently, the accessibility of micrococcal nuclease to chromatin was generally inhibited. Micrococcal nuclease partial digestion generated a ladder in which all oligonucleosomes were slightly longer than those observed with the controls. On the basis of these findings, we propose that FoxI1 is capable of remodeling chromatin higher-order structure and can stably create site-specific changes in chromatin to either stably create or remove DNase I hypersensitive sites.

scholarly journals Three-dimensional localization of CENP-A suggests a complex higher order structure of centromeric chromatin

2008 ◽  
Vol 183 (7) ◽  
pp. 1193-1202 ◽  
Author(s):  
Owen J. Marshall ◽  
Alan T. Marshall ◽  
K.H. Andy Choo
Keyword(s):  
Chromatin Immunoprecipitation ◽  
Protein A ◽  
Three Dimensional ◽  
Higher Order ◽  
Order Structure ◽  
Mitotic Chromosomes ◽  
Centromeric Chromatin ◽  
Centromere Protein A ◽  
Transmission Electron ◽  
Histone H3 Variant

The histone H3 variant centromere protein A (CENP-A) is central to centromere formation throughout eukaryotes. A long-standing question in centromere biology has been the organization of CENP-A at the centromere and its implications for the structure of centromeric chromatin. In this study, we describe the three-dimensional localization of CENP-A at the inner kinetochore plate through serial-section transmission electron microscopy of human mitotic chromosomes. At the kinetochores of normal centromeres and at a neocentromere, CENP-A occupies a compact domain at the inner kinetochore plate, stretching across two thirds of the length of the constriction but encompassing only one third of the constriction width and height. Within this domain, evidence of substructure is apparent. Combined with previous chromatin immunoprecipitation results (Saffery, R., H. Sumer, S. Hassan, L.H. Wong, J.M. Craig, K. Todokoro, M. Anderson, A. Stafford, and K.H.A. Choo. 2003. Mol. Cell. 12:509–516; Chueh, A.C., L.H. Wong, N. Wong, and K.H.A. Choo. 2005. Hum. Mol. Genet. 14:85–93), our data suggest that centromeric chromatin is arranged in a coiled 30-nm fiber that is itself coiled or folded to form a higher order structure.

Higher order structure of mitotic chromosomes

1978 ◽  
Vol 283 (997) ◽  
pp. 415-416 ◽  
Keyword(s):  
Human Fibroblasts ◽  
Higher Order ◽  
Order Structure ◽  
Mitotic Chromosomes ◽  
Cylindrical Structure

From observations on the partial disintegration of mitotic chromosomes isolated from human fibroblasts we propose that human mitotic chromatids are characterized by a rather simple organization based on the folding and coiling of a long, regular, hollow cylindrical structure the unit fibre , with a diameter of about 400 nm (Bak, Zeuthen & Crick 1977). This structure is postulated to consist of a super-solenoid formed by the coiling of the 30 nm solenoid (itself formed by coiling of the string of nucleosomes).

Molecular features of heterochromatin condensation

1993 ◽  
Vol 51 ◽  
pp. 72-73
Author(s):  
B.A. Hamkalo ◽  
K. Lundgren ◽  
M.H. Parseghian ◽  
M.Z. Radic ◽  
M. Saghbini
Keyword(s):  
Protein Interactions ◽  
Chromatin Condensation ◽  
Higher Order ◽  
Centromeric Heterochromatin ◽  
Order Structure ◽  
Sequence Motif ◽  
Dna Curvature ◽  
Mitotic Chromosomes ◽  
Metaphase Chromosomes ◽  
Molecular Features

Eukaryotic chromosomes are nonuniformly condensed in both interphase and metaphase. This difference is most apparent in mitotic chromosomes in which centromeric heterochromatin is distinguishable from euchromatic arms because of a higher degree of condensation. This difference prevails in interphase and has led to the designation of this type of heterochromatin as “constitutive”. Differences in condensation presumably are a consequence of differential stability of higher order chromatin structure. Since higher order structure is likely to be due to distinctive DNA-protein and protein-protein interactions, our goal is to identify components of such interactions as a first step in understanding the molecular basis for differential chromatin condensation.Analysis of the structure of the mouse major centromeric satellite DNA revealed the presence of stable DNA curvature which could be reversed if certain small ligands which recognize a sequence motif common to this highly repeated DNA were bound to the DNA. In addition, growth of cells in the presence of these ligands prevented complete condensation of centromere regions of metaphase chromosomes (Fig.1).

Macrocycles of Higher Ortho-Phenylenes: Assembly and Folding

2019 ◽  
Author(s):  
Zacharias Kinney ◽  
Viraj Kirinda ◽  
Scott Hartley
Keyword(s):  
Chemical Shift ◽  
Higher Order ◽  
Order Structure ◽  
Complex Geometries ◽  
Spatial Relationships ◽  
Predominant Species ◽  
Bite Angle ◽  
Direct Assembly

<p>Higher-order structure in abiotic foldamer systems represents an important but largely unrealized goal. As one approach to this challenge, covalent assembly can be used to assemble macrocycles with foldamer subunits in well-defined spatial relationships. Such systems have previously been shown to exhibit self-sorting, new folding motifs, and dynamic stereoisomerism, yet there remain important questions about the interplay between folding and macrocyclization and the effect of structural confinement on folding behavior. Here, we explore the dynamic covalent assembly of extended <i>ortho</i>-phenylenes (hexamer and decamer) with rod-shaped linkers. Characteristic <sup>1</sup>H chemical shift differences between cyclic and acyclic systems can be compared with computational conformer libraries to determine the folding states of the macrocycles. We show that the bite angle provides a measure of the fit of an <i>o</i>-phenylene conformer within a shape-persistent macrocycle, affecting both assembly and ultimate folding behavior. For the <i>o</i>-phenylene hexamer, the bite angle and conformer stability work synergistically to direct assembly toward triangular [3+3] macrocycles of well-folded oligomers. For the decamer, the energetic accessibility of conformers with small bite angles allows [2+2] macrocycles to be formed as the predominant species. In these systems, the <i>o</i>-phenylenes are forced into unusual folding states, preferentially adopting a backbone geometry with distinct helical blocks of opposite handedness. The results show that simple geometric restrictions can be used to direct foldamers toward increasingly complex geometries.</p>

Macrocycles of Higher ortho-Phenylenes: Assembly and Folding

2019 ◽  
Author(s):  
Zacharias Kinney ◽  
Viraj Kirinda ◽  
Scott Hartley
Keyword(s):  
Chemical Shift ◽  
Higher Order ◽  
Order Structure ◽  
Complex Geometries ◽  
Spatial Relationships ◽  
Predominant Species ◽  
Bite Angle ◽  
Direct Assembly

<p>Higher-order structure in abiotic foldamer systems represents an important but largely unrealized goal. As one approach to this challenge, covalent assembly can be used to assemble macrocycles with foldamer subunits in well-defined spatial relationships. Such systems have previously been shown to exhibit self-sorting, new folding motifs, and dynamic stereoisomerism, yet there remain important questions about the interplay between folding and macrocyclization and the effect of structural confinement on folding behavior. Here, we explore the dynamic covalent assembly of extended <i>ortho</i>-phenylenes (hexamer and decamer) with rod-shaped linkers. Characteristic <sup>1</sup>H chemical shift differences between cyclic and acyclic systems can be compared with computational conformer libraries to determine the folding states of the macrocycles. We show that the bite angle provides a measure of the fit of an <i>o</i>-phenylene conformer within a shape-persistent macrocycle, affecting both assembly and ultimate folding behavior. For the <i>o</i>-phenylene hexamer, the bite angle and conformer stability work synergistically to direct assembly toward triangular [3+3] macrocycles of well-folded oligomers. For the decamer, the energetic accessibility of conformers with small bite angles allows [2+2] macrocycles to be formed as the predominant species. In these systems, the <i>o</i>-phenylenes are forced into unusual folding states, preferentially adopting a backbone geometry with distinct helical blocks of opposite handedness. The results show that simple geometric restrictions can be used to direct foldamers toward increasingly complex geometries.</p>

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