Supranucleosomal organization of chromatin

Azorı́n, Fernando; Pérez-Grau, L.; Subirana, Juan A.

doi:10.1007/bf00294969

Cited by 24 publications

(1 citation statement)

References 21 publications

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“…Data suggesting the existence of a superstructure for the nucleofilament has already been reported in the case of calf thymus chromatin (29,30) but had been interpreted differently. Electron microscopy studies of the nucleofilament in low salt conditions, whether showing the zig-zag appearance or not (21,22,31), are compatible with the existence of a superstructure with an outer diameter of the order of 30nm. The regions in the electron micrographs showing the so-called "Onm" nucleofilament can easily be due to preparative artifacts.…”

Section: Resultsmentioning

confidence: 80%

Chromatin superstructure: synchrotron radiation X-ray scattering study on solutions and gels

Pérez-Grau¹,

Bordas²,

Koch³

1984

Nucl Acids Res

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X-ray small angle scattering patterns of solutions and gels of native chicken erythrocyte chromatin and chromatin depleted of H5 histones have been measured under several ionic conditions using synchrotron radiation. Features of the patterns are interpreted as resulting from a superstructure with an outer diameter of about 300A which is already present in uncondensed nucleofilaments. This superstructure which is shown to be maintained by the H5 histones also explains the rapid condensation of the nucleofilaments in higher ionic strengths.

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Section: Resultsmentioning

confidence: 80%

Chromatin superstructure: synchrotron radiation X-ray scattering study on solutions and gels

Pérez-Grau¹,

Bordas²,

Koch³

1984

Nucl Acids Res

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Differential scattering of circularly polarized light by chromatin modeled as a helical array of dielectric ellipsoids within the born approximation

1985

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SynopsisTheoretical predictions within the Born approximation of the expected differential light scattering of circularly polarized light (CIDS) were made for the 300-A chromatin fiber, modeled as a helical array of dielectric ellipsoids. Computed CIDS values were strongly dependent on the exact geometry of the solenoid model, depending particularly on parameters related to the chiral nature of the fiber and the orientation of the nucleosomes within the helix, in contrast to the values of the total light scattering, which mainJy probed size and shape.. In particular, both a superbead model and a strict linear 110-A nucleosome filament would be predicted as giving rise to zero CIDS (in disagreement with the finite values observed). At the same time, helical models in which the normal vectors to the nucleosome faces were exactly parallel to the helical axis also yielded zero CIDS. Confirming earlier'expectations, CIDS values were significantly less dependent on helical length than total light scattering. Finally, comparison of these calculated results from those extrapolated from available experimental data indicates that predicted CIDS values, based on currently accepted models of solenoid structure, are within an order of magnitude of those experimentally observed. Together, these results indicate the potential of differential light scattering measurements as a probe of chromatin higher-order structure, complementary to existing scattering measurements.

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Ultrastructural organization of heterochromatin within sea urchin sperm nuclei

Aboukarsh

Kunkle

1985

Gamete Research

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Chromatin within swollen or lysed isolated sperm nuclei of the sea urchin, Strongylocentrotus purpuratus, was examined by electron microscopy. Spread preparations of lysed sperm nuclei demonstrated dense aggregates of nondispersed material and beaded filaments radiating from these aggregates. These beaded fibers are similar in size and appearance to the “beads‐on‐a‐string” seen as characteristic of chromatin spreads from numerous interphase nuclei. The beads are nucleosomes that have an average diameter of 130 Å. The interconnecting string is 40 Å indiameter and corresponds to the spacer DNA. In thin sections of swollen nuclei the sperm chromatin appears to be composed of 400 Å superbeads that are closely apposed to form 400 Å fibers. As the chromatin disperses, the superbeads are seen to be attached to one another by chromatin fibers of 110 Å diameter. In thin sections, the 400 Å superbeads appear to disperse directly into the 110 Å fibers with no intervening structures. This work demonstrates that the heterochromatin in Strongylocentrotus purpuratus sperm nuclei is composed of nucleosomes that form 100 Å filaments that are compacted into 400 Å superbeads. The superbeads coalesce to give the morphological appearance of 400 Å fibers.

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Supranucleosomal organization of chromatin

Cited by 24 publications

References 21 publications

Chromatin superstructure: synchrotron radiation X-ray scattering study on solutions and gels

Chromatin superstructure: synchrotron radiation X-ray scattering study on solutions and gels

Differential scattering of circularly polarized light by chromatin modeled as a helical array of dielectric ellipsoids within the born approximation

Ultrastructural organization of heterochromatin within sea urchin sperm nuclei

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