title: Subnuclear relocalization and silencing of a chromosomal region by an ectopic ribosomal DNA repeat.
abstract: Our research addresses the relationship between subnuclear localization and gene expression in fission yeast. We observed the relocalization of a heterochromatic region, the mating-type region, from its natural location at the spindle-pole body to the immediate vicinity of the nucleolus. Relocalization occurred in response to a DNA rearrangement replacing a boundary element (IR-R) with a ribosomal DNA repeat (rDNA-R). Gene expression was strongly silenced in the relocalized mating-type region through mechanisms that differ from those operating in wild type. Also different from the wild-type situation, programmed recombination events failed to take place in the rDNA-R mutant. Increased silencing and perinucleolar localization depended on Reb1, a DNA-binding protein with cognate sites in the rDNA. Reb1 was recently shown to mediate long-range interchromosomal interactions in the nucleus through dimerization, providing a mechanism for the observed relocalization. Replacing the full rDNA repeat with Reb1-binding sites, and using mutants lacking the histone H3K9 methyltransferase Clr4, indicated that the relocalized region was silenced redundantly by heterochromatin and another mechanism, plausibly antisense transcription, achieving a high degree of repression in the rDNA-R strain.
authors.affiliation: Department of Biology, University of Copenhagen, DK-2200 Copenhagen, Denmark.
authors.forename: Tadas
authors.initials: T
authors.lastname: Jakociunas
authors.forename: Marie
authors.initials: M
authors.lastname: Domange Jordö
authors.forename: Mazhoura
authors.initials: M
authors.lastname: Aït Mebarek
authors.forename: Camilla Marie
authors.initials: CM
authors.lastname: Bünner
authors.forename: Janne
authors.initials: J
authors.lastname: Verhein-Hansen
authors.forename: Lene B
authors.initials: LB
authors.lastname: Oddershede
authors.forename: Geneviève
authors.initials: G
authors.lastname: Thon
mesh_terms: D001665:Binding Sites / Q000235:genetics; D004275:DNA, Ribosomal / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D020868:Gene Silencing; D006570:Heterochromatin / Q000502:physiology*; D042581:Intranuclear Space / Q000378:metabolism*; D060885:Multiplex Polymerase Chain Reaction; D012091:Repetitive Sequences, Nucleic Acid / Q000235:genetics; D012568:Schizosaccharomyces / Q000235:genetics / Q000378:metabolism*; D029702:Schizosaccharomyces pombe Proteins / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: D004275:DNA, Ribosomal; D004268:DNA-Binding Proteins; D006570:Heterochromatin; D029702:Schizosaccharomyces pombe Proteins; D014157:Transcription Factors; C512907:reb1 protein, S pombe
keywords: antisense transcription; boundary elements; chromatin; gene silencing; nuclear organization