Two RNAi complexes, RITS and RDRC, physically interact and localize to noncoding centromeric RNAs.
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.
Mesh Terms:
Adenosine Triphosphatases, Cell Cycle Proteins, Cell Nucleus, Centromere, Heterochromatin, Methyltransferases, Protein Binding, RNA Helicases, RNA, Fungal, RNA, Untranslated, RNA-Induced Silencing Complex, Ribonuclease III, Schizosaccharomyces, Schizosaccharomyces pombe Proteins
Adenosine Triphosphatases, Cell Cycle Proteins, Cell Nucleus, Centromere, Heterochromatin, Methyltransferases, Protein Binding, RNA Helicases, RNA, Fungal, RNA, Untranslated, RNA-Induced Silencing Complex, Ribonuclease III, Schizosaccharomyces, Schizosaccharomyces pombe Proteins
Cell
Date: Dec. 17, 2004
PubMed ID: 15607976
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