title: Two RNAi complexes, RITS and RDRC, physically interact and localize to noncoding centromeric RNAs.
abstract: RNAi-mediated heterochromatin assembly in fission yeast requires the RNA-induced transcriptional silencing (RITS) complex and a putative RNA-directed RNA polymerase (Rdp1). Here we show that Rdp1 is associated with two conserved proteins, Hrr1, an RNA helicase, and Cid12, a member of the polyA polymerase family, in a complex that has RNA-directed RNA polymerase activity (RDRC, RNA-directed RNA polymerase complex). RDRC physically interacts with RITS in a manner that requires the Dicer ribonuclease (Dcr1) and the Clr4 histone methyltransferase. Moreover, both complexes are localized to the nucleus and associate with noncoding centromeric RNAs in a Dcr1-dependent manner. In cells lacking Rdp1, Hrr1, or Cid12, RITS complexes are devoid of siRNAs and fail to localize to centromeric DNA repeats to initiate heterochromatin assembly. These findings reveal a physical and functional link between Rdp1 and RITS and suggest that noncoding RNAs provide a platform for siRNA-dependent localization of RNAi complexes to specific chromosome regions.
authors.affiliation: Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA.
authors.forename: Mohammad R
authors.initials: MR
authors.lastname: Motamedi
authors.forename: André
authors.initials: A
authors.lastname: Verdel
authors.forename: Serafin U
authors.initials: SU
authors.lastname: Colmenares
authors.forename: Scott A
authors.initials: SA
authors.lastname: Gerber
authors.forename: Steven P
authors.initials: SP
authors.lastname: Gygi
authors.forename: Danesh
authors.initials: D
authors.lastname: Moazed
mesh_terms: D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism*; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D002467:Cell Nucleus / Q000235:genetics / Q000378:metabolism; D002503:Centromere / Q000235:genetics / Q000378:metabolism*; D006570:Heterochromatin / Q000235:genetics / Q000378:metabolism*; D011495:Histone-Lysine N-Methyltransferase; D008780:Methyltransferases / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D020365:RNA Helicases / Q000235:genetics / Q000378:metabolism; D012331:RNA, Fungal / Q000235:genetics / Q000378:metabolism; D022661:RNA, Untranslated / Q000235:genetics / Q000378:metabolism; D034743:RNA-Induced Silencing Complex / Q000235:genetics / Q000378:metabolism*; D043244:Ribonuclease III / Q000235:genetics / Q000378:metabolism; D012568:Schizosaccharomyces / Q000235:genetics / Q000378:metabolism; D029702:Schizosaccharomyces pombe Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D018797:Cell Cycle Proteins; D006570:Heterochromatin; D012331:RNA, Fungal; D022661:RNA, Untranslated; D034743:RNA-Induced Silencing Complex; D029702:Schizosaccharomyces pombe Proteins; D008780:Methyltransferases; D011495:Histone-Lysine N-Methyltransferase; C112744:clr4 protein, S pombe; D043244:Ribonuclease III; D000251:Adenosine Triphosphatases; C416926:Rdp1 protein, S pombe; D020365:RNA Helicases