title: Selective association between nucleosomes with identical DNA sequences.
abstract: Self-assembly is the autonomous organization of constituents into higher order structures or assemblages and is a fundamental mechanism in biological systems. There has been an unfounded idea that self-assembly may be used in the sensing and pairing of homologous chromosomes or chromatin, including meiotic chromosome pairing, polytene chromosome formation in Diptera and transvection. Recent studies proved that double-stranded DNA molecules have a sequence-sensing property and can self-assemble, which may play a role in the above phenomena. However, to explain these processes in terms of self-assembly, it first must be proved that nucleosomes retain a DNA sequence-sensing property and can self-assemble. Here, using atomic force microscopy (AFM)-based analyses and a quantitative interaction assay, we show that nucleosomes with identical DNA sequences preferentially associate with each other in the presence of Mg(2+) ions. Using Xenopus borealis 5S rDNA nucleosome-positioning sequence and 601 and 603 sequences, homomeric or heteromeric octa- or tetranucleosomes were reconstituted in vitro and induced to form weak intracondensates by MgCl(2). AFM clearly showed that DNA sequence-based selective association occurs between nucleosomes with identical DNA sequences. Selective association was also detected between mononucleosomes. We propose that nucleosome self-assembly and DNA self-assembly constitute the mechanism underlying sensing and pairing of homologous chromosomes or chromatin.
authors.affiliation: Department of Biology, Faculty of Education and Integrated Arts and Sciences, Waseda University, 2-2, Tokyo 162-8480, Japan.
authors.forename: Jun-ichi
authors.initials: J
authors.lastname: Nishikawa
authors.forename: Takashi
authors.initials: T
authors.lastname: Ohyama
mesh_terms: D000818:Animals; D001483:Base Sequence; D042002:Chromatin Assembly and Disassembly; D004247:DNA / Q000737:chemistry*; D018625:Microscopy, Atomic Force; D009707:Nucleosomes / Q000737:chemistry* / Q000378:metabolism / Q000648:ultrastructure; D012689:Sequence Homology, Nucleic Acid; D014981:Xenopus
chemical_list: D009707:Nucleosomes; D004247:DNA