title: Chp1-Tas3 interaction is required to recruit RITS to fission yeast centromeres and for maintenance of centromeric heterochromatin.
abstract: The maintenance of centromeric heterochromatin in fission yeast relies on the RNA interference-dependent complexes RITS (RNA-induced transcriptional silencing complex) and RDRC (RNA-directed RNA polymerase complex), which cooperate in a positive feedback loop to recruit high levels of histone H3 K9 methyltransferase activity to centromeres and to promote the assembly and maintenance of centromeric heterochromatin. However, it is unclear how these complexes are targeted to chromatin. RITS comprises Chp1, which binds K9-methylated histone H3; Ago1, which binds short interfering (siRNAs); the adaptor protein Tas3, which links Ago1 to Chp1; and centromeric siRNAs. We have generated mutants in RITS to determine the contribution of the two potential chromatin-targeting proteins Chp1 and Ago1 to the centromeric recruitment of RITS. Mutations in Tas3 that disrupt Ago1 binding are permissive for RITS recruitment and maintain centromeric heterochromatin, but the role of Tas3's interaction with Chp1 is unknown. Here, we define the Chp1 interaction domain of Tas3. A strain expressing a tas3 mutant that cannot bind Chp1 (Tas3(Delta)(10-24)) failed to maintain centromeric heterochromatin, with a loss of centromeric siRNAs, a failure to recruit RITS and RDRC to centromeres, and high levels of chromosome loss. These findings suggest a pivotal role for Chp1 and its association with Tas3 for the recruitment of RITS, RDRC, and histone H3 K9 methyltransferase activity to centromeres.
authors.affiliation: Mailstop 340, Department of Biochemistry, St. Jude Children's Research Hospital, 332 N. Lauderdale, Memphis, TN 38105, USA.
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Debeauchamp
authors.forename: Arian
authors.initials: A
authors.lastname: Moses
authors.forename: Victoria J P
authors.initials: VJ
authors.lastname: Noffsinger
authors.forename: Dagny L
authors.initials: DL
authors.lastname: Ulrich
authors.forename: Godwin
authors.initials: G
authors.lastname: Job
authors.forename: Aaron M
authors.initials: AM
authors.lastname: Kosinski
authors.forename: Janet F
authors.initials: JF
authors.lastname: Partridge
mesh_terms: D060565:Argonaute Proteins; D002352:Carrier Proteins / Q000235:genetics / Q000502:physiology*; D018797:Cell Cycle Proteins / Q000235:genetics / Q000502:physiology*; D002503:Centromere / Q000648:ultrastructure*; D015825:Chromosomes, Fungal / Q000648:ultrastructure*; D049770:Genes, Mating Type, Fungal / Q000235:genetics; D042822:Genomic Instability; D006570:Heterochromatin / Q000378:metabolism / Q000648:ultrastructure*; D000076983:Histone Methyltransferases; D011495:Histone-Lysine N-Methyltransferase / Q000378:metabolism; D046912:Multiprotein Complexes / Q000378:metabolism; D025941:Protein Interaction Mapping; D011496:Protein Methyltransferases; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D012331:RNA, Fungal / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D016601:RNA-Binding Proteins; D012568:Schizosaccharomyces / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D029702:Schizosaccharomyces pombe Proteins / Q000235:genetics / Q000502:physiology*; D016615:Telomere / Q000648:ultrastructure; D014158:Transcription, Genetic
chemical_list: C481643:Ago1 protein, S pombe; D060565:Argonaute Proteins; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; C115018:Chp1 protein, S pombe; D006570:Heterochromatin; D046912:Multiprotein Complexes; D012331:RNA, Fungal; D034741:RNA, Small Interfering; D016601:RNA-Binding Proteins; D029702:Schizosaccharomyces pombe Proteins; C499720:Tas3 protein, S pombe; D000076983:Histone Methyltransferases; D011496:Protein Methyltransferases; D011495:Histone-Lysine N-Methyltransferase