title: Functional separation of the requirements for establishment and maintenance of centromeric heterochromatin.
abstract: The establishment and maintenance of centromeric heterochromatin in fission yeast require the RITS complex. Comprised of centromeric siRNAs, the chromodomain protein Chp1, Argonaute (Ago1), and Tas3, RITS couples the cellular RNAi pathway with assembly of constitutive heterochromatin. However, the mechanisms governing RITS-dependent establishment versus maintenance of centromeric heterochromatin remain unresolved. Here, we report that a mutant Tas3 protein that cannot bind Ago1 supports the maintenance of centromeric heterochromatin but cannot mediate efficient de novo establishment from cells transiently depleted for the histone H3 lysine 9 methyltransferase Clr4. In contrast, centromeric heterochromatin efficiently assembles in mutant cells transiently depleted for dicer. This mutant therefore allows ordering of the events leading to establishment of centromeric heterochromatin and places lysine 9 methylation of histone H3 upstream of dicer function.
authors.affiliation: Department of Biochemistry, St. Jude Children's Research Hospital, 332 N. Lauderdale, Memphis, TN 38105, USA. janet.partridge@stjude.org <janet.partridge@stjude.org>
authors.forename: Janet F
authors.initials: JF
authors.lastname: Partridge
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: DeBeauchamp
authors.forename: Aaron M
authors.initials: AM
authors.lastname: Kosinski
authors.forename: Dagny L
authors.initials: DL
authors.lastname: Ulrich
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Hadler
authors.forename: Victoria J P
authors.initials: VJ
authors.lastname: Noffsinger
mesh_terms: D060565:Argonaute Proteins; D002455:Cell Division; D002503:Centromere / Q000235:genetics*; D017931:DNA Primers; D006570:Heterochromatin / Q000235:genetics*; D020411:Oligonucleotide Array Sequence Analysis; D016133:Polymerase Chain Reaction; D012331:RNA, Fungal / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics; D016601:RNA-Binding Proteins; D012568:Schizosaccharomyces / Q000166:cytology / Q000235:genetics*; D029702:Schizosaccharomyces pombe Proteins / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic
chemical_list: C481643:Ago1 protein, S pombe; D060565:Argonaute Proteins; D017931:DNA Primers; D006570:Heterochromatin; D012331:RNA, Fungal; D034741:RNA, Small Interfering; D016601:RNA-Binding Proteins; D029702:Schizosaccharomyces pombe Proteins