title: Human mitotic chromosomes consist predominantly of irregularly folded nucleosome fibres without a 30-nm chromatin structure.
abstract: How a long strand of genomic DNA is compacted into a mitotic chromosome remains one of the basic questions in biology. The nucleosome fibre, in which DNA is wrapped around core histones, has long been assumed to be folded into a 30-nm chromatin fibre and further hierarchical regular structures to form mitotic chromosomes, although the actual existence of these regular structures is controversial. Here, we show that human mitotic HeLa chromosomes are mainly composed of irregularly folded nucleosome fibres rather than 30-nm chromatin fibres. Our comprehensive and quantitative study using cryo-electron microscopy and synchrotron X-ray scattering resolved the long-standing contradictions regarding the existence of 30-nm chromatin structures and detected no regular structure >11 nm. Our finding suggests that the mitotic chromosome consists of irregularly arranged nucleosome fibres, with a fractal nature, which permits a more dynamic and flexible genome organization than would be allowed by static regular structures.
authors.affiliation: RIKEN SPring-8 Center, Hyogo, Japan.
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Nishino
authors.forename: Mikhail
authors.initials: M
authors.lastname: Eltsov
authors.forename: Yasumasa
authors.initials: Y
authors.lastname: Joti
authors.forename: Kazuki
authors.initials: K
authors.lastname: Ito
authors.forename: Hideaki
authors.initials: H
authors.lastname: Takata
authors.forename: Yukio
authors.initials: Y
authors.lastname: Takahashi
authors.forename: Saera
authors.initials: S
authors.lastname: Hihara
authors.forename: Achilleas S
authors.initials: AS
authors.lastname: Frangakis
authors.forename: Naoko
authors.initials: N
authors.lastname: Imamoto
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Ishikawa
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Maeshima
mesh_terms: D002843:Chromatin / Q000737:chemistry / Q000648:ultrastructure; D002877:Chromosomes, Human / Q000737:chemistry* / Q000648:ultrastructure; D020285:Cryoelectron Microscopy; D006367:HeLa Cells; D006801:Humans; D008938:Mitosis; D009707:Nucleosomes / Q000737:chemistry* / Q000648:ultrastructure; D017510:Protein Folding; D053838:Scattering, Small Angle; D014961:X-Ray Diffraction
chemical_list: D002843:Chromatin; D009707:Nucleosomes