title: Supercoiling of 30-nm chromatin fibers around a nuclear axis in human retinal pigment cell nuclei: electron microscope evidence for a chromatin macrostructure.
abstract: Nucleosomes and higher-order chromatin structures have been identified in the range of resolution of 10-30 nm. No information is available on higher configurations that involve chromatin arrangements at the nuclear level. Thin sections of human retinal pigment cell nuclei reveal an orderly array of 30-nm chromatin fibers on the inner nuclear surface. The observations can be three-dimensionally explained by a coiled or a serially circular arrangement of fibers around a central axis of the nucleus. The axial chromatin orientation shows no apparent relationship to the epithelial cell polarity nor to the irregular shape of the nuclei. The described configuration, which is compatible with a chromatin structure of third order, represents the first example of chromatin architecture coherently organized at the nuclear level.
mesh_terms: D002467:Cell Nucleus / Q000648:ultrastructure*; D002843:Chromatin / Q000648:ultrastructure*; D006801:Humans; D066298:In Vitro Techniques; D010857:Pigment Epithelium of Eye / Q000166:cytology* / Q000648:ultrastructure
chemical_list: D002843:Chromatin