title: Visualization of nucleosomal substructure in native chromatin by atomic force microscopy.
abstract: Intact rDNA minichromosomes from Tetrahymena thermophila were isolated as native chromatin and imaged by atomic force microscopy (AFM). AFM measurements of condensed rDNA chromatin were consistent with a 30 nm fiber that frequently (87% of molecules observed) contained stretches of nucleosome cores arranged in a zig-zag conformation. Examination of rDNA chromatin in a dispersed conformation by tapping mode AFM in low humidity resulted in high resolution images of partially dissociated nucleosome cores and associated linker DNA. A majority of these nucleosome cores contained six to eight smaller particles with dimensions consistent with those of individual histones. Many of the nucleosome cores showed a striking resemblance to the wedge (35%), axial (15%), and front (6%) views of the nucleosome histone octamer modeled by Arents et al. [Arents, G., Burlingame, R. W., Wang, B.-C., Love, W.E., & Moudrianakis, E. N. (1991) Proc. Natl. Acad. Sci. U.S.A. 88, 10148-10152]. This direct visualization of histone subunits and nucleosomal substructure in native chromatin illustrates the potential use of AFM to localize individual proteins in condensed cellular chromatin.
authors.affiliation: Department of Zoology and Genetics, Iowa State University, Ames 50011, USA.
authors.forename: L D
authors.initials: LD
authors.lastname: Martin
authors.forename: J P
authors.initials: JP
authors.lastname: Vesenka
authors.forename: E
authors.initials: E
authors.lastname: Henderson
authors.forename: D L
authors.initials: DL
authors.lastname: Dobbs
mesh_terms: D000818:Animals; D002843:Chromatin / Q000648:ultrastructure*; D016054:DNA, Protozoan / Q000648:ultrastructure; D018625:Microscopy, Atomic Force; D009707:Nucleosomes / Q000648:ultrastructure*; D016808:Tetrahymena thermophila / Q000235:genetics / Q000648:ultrastructure
chemical_list: D002843:Chromatin; D016054:DNA, Protozoan; D009707:Nucleosomes