title: Chromosomes without a 30-nm chromatin fiber.
abstract: How is a long strand of genomic DNA packaged into a mitotic chromosome or nucleus? The nucleosome fiber (beads-on-a-string), in which DNA is wrapped around core histones, has long been assumed to be folded into a 30-nm chromatin fiber, and a further helically folded larger fiber. However, when frozen hydrated human mitotic cells were observed using cryoelectron microscopy, no higher-order structures that included 30-nm chromatin fibers were found. To investigate the bulk structure of mitotic chromosomes further, we performed small-angle X-ray scattering (SAXS), which can detect periodic structures in noncrystalline materials in solution. The results were striking: no structural feature larger than 11 nm was detected, even at a chromosome-diameter scale (~1 μm). We also found a similar scattering pattern in interphase nuclei of HeLa cells in the range up to ~275 nm. Our findings suggest a common structural feature in interphase and mitotic chromatins: compact and irregular folding of nucleosome fibers occurs without a 30-nm chromatin structure.
authors: XFEL Division; Japan Synchrotron Radiation Research Institute, Sayo-cho, Japan.
authors: Yasumasa
authors: Y
authors: Joti
authors: Takaaki
authors: T
authors: Hikima
authors: Yoshinori
authors: Y
authors: Nishino
authors: Fukumi
authors: F
authors: Kamada
authors: Saera
authors: S
authors: Hihara
authors: Hideaki
authors: H
authors: Takata
authors: Tetsuya
authors: T
authors: Ishikawa
authors: Kazuhiro
authors: K
authors: Maeshima
mesh_terms: D002467:Cell Nucleus / Q000378:metabolism; D002843:Chromatin / Q000737:chemistry* / Q000378:metabolism; D022004:Chromosome Structures / Q000737:chemistry* / Q000378:metabolism; D006367:HeLa Cells; D006657:Histones / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D007399:Interphase; D008938:Mitosis; D009707:Nucleosomes / Q000737:chemistry / Q000378:metabolism; D053838:Scattering, Small Angle; D014961:X-Ray Diffraction
chemical_list: D002843:Chromatin; D006657:Histones; D009707:Nucleosomes