title: Telomeric repeats act as nucleosome-disfavouring sequences in vivo.
abstract: Telomeric DNAs consist of tandem repeats of G-clusters such as TTAGGG and TG1-3, which are the human and yeast repeat sequences, respectively. In the yeast Saccharomyces cerevisiae, the telomeric repeats are non-nucleosomal, whereas in humans, they are organized in tightly packaged nucleosomes. However, previous in vitro studies revealed that the binding affinities of human and yeast telomeric repeat sequences to histone octamers in vitro were similar, which is apparently inconsistent with the differences in the human and yeast telomeric chromatin structures. To further investigate the relationship between telomeric sequences and chromatin structure, we examined the effect of telomeric repeats on the formation of positioned nucleosomes in vivo by indirect end-label mapping, primer extension mapping and nucleosome repeat analyses, using a defined minichromosome in yeast cells. We found that the human and yeast telomeric repeat sequences both disfavour nucleosome assembly and alter nucleosome positioning in the yeast minichromosome. We further demonstrated that the G-clusters in the telomeric repeats are required for the nucleosome-disfavouring properties. Thus, our results suggest that this inherent structural feature of the telomeric repeat sequences is involved in the functional dynamics of the telomeric chromatin structure.
authors.affiliation: Laboratory of Structural Biology, Graduate School of Advanced Science and Engineering/RISE, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo 162-8640, Japan, Program in Chemistry and Life Science, School of Science and Engineering, Department of Chemistry, Graduate School of Science and Engineering, Meisei University, 2-1-1 Hodokubo, Hino, Tokyo 191-8506, Japan and Graduate School of Medical Life Science, Yokohama City University, 1-7-29 Suehiro-cho, Tsurumi-ku, Yokohama 230-0045, Japan.
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Ichikawa
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Morohashi
authors.forename: Yoshifumi
authors.initials: Y
authors.lastname: Nishimura
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Kurumizaka
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Shimizu
mesh_terms: D006801:Humans; D008836:Micrococcal Nuclease; D009707:Nucleosomes / Q000378:metabolism*; D012091:Repetitive Sequences, Nucleic Acid; D012441:Saccharomyces cerevisiae / Q000235:genetics; D016615:Telomere / Q000737:chemistry* / Q000378:metabolism
chemical_list: D009707:Nucleosomes; D008836:Micrococcal Nuclease