title: The proto-chromatosome: A fundamental subunit of chromatin?
abstract: Eukaryotic DNA is packaged into regularly spaced nucleosomes, resembling beads on a string. Each bead contains ∼147 bp wrapped around a core histone octamer. Linker histone (H1) binds to the linker DNA to drive chromatin folding. Micrococcal nuclease (MNase) digestion studies reveal 2 mono-nucleosomal intermediates: the core particle (∼147 bp) and the chromatosome (∼160 bp; a core particle with additional DNA protected by H1). We have recently developed an improved method for mapping nucleosomes, using exonuclease III to remove residual linker (MNase-Exo-seq). (1) We discovered 2 new intermediate particles corresponding to core particles with ∼7 bp of linker protruding from one side (∼154 bp) or both sides (∼161 bp), which are formed in the absence of H1. We propose that these "proto-chromatosomes" are stabilized by core histone-DNA contacts in the linker, ∼7 bp from the nucleosome boundaries. These contacts may determine the topography of the H1 binding site.
authors.affiliation: a Division of Developmental Biology, Eunice Kennedy Shriver National Institute for Child Health and Human Development, National Institutes of Health , Bethesda , MD , USA.
authors.forename: Josefina
authors.initials: J
authors.lastname: Ocampo
authors.affiliation: b Thomas H. Gosnell School of Life Sciences, Rochester Institute of Technology , Rochester , NY , USA.
authors.forename: Feng
authors.initials: F
authors.lastname: Cui
authors.affiliation: c National Cancer Institute, National Institutes of Health , Bethesda , MD , USA.
authors.forename: Victor B
authors.initials: VB
authors.lastname: Zhurkin
authors.affiliation: a Division of Developmental Biology, Eunice Kennedy Shriver National Institute for Child Health and Human Development, National Institutes of Health , Bethesda , MD , USA.
authors.forename: David J
authors.initials: DJ
authors.lastname: Clark
mesh_terms: D002843:Chromatin / Q000235:genetics* / Q000378:metabolism*; D004247:DNA / Q000235:genetics / Q000378:metabolism; D006657:Histones / Q000378:metabolism; D008836:Micrococcal Nuclease / Q000378:metabolism; D009707:Nucleosomes / Q000378:metabolism
chemical_list: D002843:Chromatin; D006657:Histones; D009707:Nucleosomes; D004247:DNA; D008836:Micrococcal Nuclease
keywords: MNase-Exo-seq; Mnase-seq; chromatin folding; chromatosome; linker histone; nucleosome; nucleosome mapping; proto-chromatosome