title: RNA-interference-directed chromatin modification coupled to RNA polymerase II transcription.
abstract: RNA interference (RNAi) acts on long double-stranded RNAs (dsRNAs) in a variety of eukaryotes to generate small interfering RNAs that target homologous messenger RNA, resulting in their destruction. This process is widely used to 'knock-down' the expression of genes of interest to explore phenotypes. In plants, fission yeast, ciliates, flies and mammalian cells, short interfering RNAs (siRNAs) also induce DNA or chromatin modifications at the homologous genomic locus, which can result in transcriptional silencing or sequence elimination. siRNAs may direct DNA or chromatin modification by siRNA-DNA interactions at the homologous locus. Alternatively, they may act by interactions between siRNA and nascent transcript. Here we show that in fission yeast (Schizosaccharomyces pombe), chromatin modifications are only directed by RNAi if the homologous DNA sequences are transcribed. Furthermore, transcription by exogenous T7 polymerase is not sufficient. Ago1, a component of the RNAi effector RISC/RITS complex, associates with target transcripts and RNA polymerase II. Truncation of the regulatory carboxy-terminal domain (CTD) of RNA pol II disrupts transcriptional silencing, indicating that, like other RNA processing events, RNAi-directed chromatin modification is coupled to transcription.
authors.affiliation: Wellcome Trust Centre for Cell Biology, Institute of Cell and Molecular Biology, King's Buildings, University of Edinburgh, Edinburgh EH9 3JR, UK.
authors.forename: Vera
authors.initials: V
authors.lastname: Schramke
authors.forename: Daniel M
authors.initials: DM
authors.lastname: Sheedy
authors.forename: Ahmet M
authors.initials: AM
authors.lastname: Denli
authors.forename: Carolina
authors.initials: C
authors.lastname: Bonila
authors.forename: Karl
authors.initials: K
authors.lastname: Ekwall
authors.forename: Gregory J
authors.initials: GJ
authors.lastname: Hannon
authors.forename: Robin C
authors.initials: RC
authors.lastname: Allshire
mesh_terms: D060565:Argonaute Proteins; D002503:Centromere / Q000235:genetics / Q000378:metabolism; D002843:Chromatin / Q000235:genetics* / Q000378:metabolism*; D042002:Chromatin Assembly and Disassembly; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism; D015966:Gene Expression Regulation, Fungal; D011485:Protein Binding; D034622:RNA Interference; D012319:RNA Polymerase II / Q000737:chemistry / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D016601:RNA-Binding Proteins; D012260:Ribonucleases / Q000378:metabolism; D012568:Schizosaccharomyces / Q000201:enzymology / Q000235:genetics*; D029702:Schizosaccharomyces pombe Proteins / Q000378:metabolism; D014158:Transcription, Genetic; D014764:Viral Proteins / Q000378:metabolism
chemical_list: C481643:Ago1 protein, S pombe; D060565:Argonaute Proteins; D002843:Chromatin; D034741:RNA, Small Interfering; D016601:RNA-Binding Proteins; D029702:Schizosaccharomyces pombe Proteins; D014764:Viral Proteins; D012319:RNA Polymerase II; C062210:bacteriophage T7 RNA polymerase; D012321:DNA-Directed RNA Polymerases; D012260:Ribonucleases