title: Splicing factor Spf30 assists exosome-mediated gene silencing in fission yeast.
abstract: Heterochromatin assembly in fission yeast relies on the processing of cognate noncoding RNAs by both the RNA interference and the exosome degradation pathways. Recent evidence indicates that splicing factors facilitate the cotranscriptional processing of centromeric transcripts into small interfering RNAs (siRNAs). In contrast, how the exosome contributes to heterochromatin assembly and whether it also relies upon splicing factors were unknown. We provide here evidence that fission yeast Spf30 is a splicing factor involved in the exosome pathway of heterochromatin silencing. Spf30 and Dis3, the main exosome RNase, colocalize at centromeric heterochromatin and euchromatic genes. At the centromeres, Dis3 helps recruiting Spf30, whose deficiency phenocopies the dis3-54 mutant: heterochromatin is impaired, as evidenced by reduced silencing and the accumulation of polyadenylated centromeric transcripts, but the production of siRNAs appears to be unaffected. Consistent with a direct role, Spf30 binds centromeric transcripts and locates at the centromeres in an RNA-dependent manner. We propose that Spf30, bound to nascent centromeric transcripts, perhaps with other splicing factors, assists their processing by the exosome. Splicing factor intercession may thus be a common feature of gene silencing pathways.
authors.affiliation: CNRS, Institut de Biochimie et Génétique Cellulaires, UMR 5095, Bordeaux F-33077, France. pascal.bernard@ens-lyon.fr
authors.forename: Pascal
authors.initials: P
authors.lastname: Bernard
authors.forename: Julie
authors.initials: J
authors.lastname: Drogat
authors.forename: Sonia
authors.initials: S
authors.lastname: Dheur
authors.forename: Sylvie
authors.initials: S
authors.lastname: Genier
authors.forename: Jean-Paul
authors.initials: JP
authors.lastname: Javerzat
mesh_terms: D001483:Base Sequence; D002503:Centromere / Q000235:genetics / Q000378:metabolism; D017931:DNA Primers / Q000235:genetics; D005095:Exoribonucleases / Q000235:genetics / Q000378:metabolism; D063326:Exosome Multienzyme Ribonuclease Complex; D055354:Exosomes / Q000235:genetics / Q000378:metabolism; D020868:Gene Silencing; D005800:Genes, Fungal; D006570:Heterochromatin / Q000235:genetics / Q000378:metabolism; D006801:Humans; D012326:RNA Splicing; D016601:RNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism*; D012568:Schizosaccharomyces / Q000235:genetics* / Q000378:metabolism*; D029702:Schizosaccharomyces pombe Proteins / Q000235:genetics* / Q000378:metabolism*; D013045:Species Specificity
chemical_list: D017931:DNA Primers; D006570:Heterochromatin; D016601:RNA-Binding Proteins; D029702:Schizosaccharomyces pombe Proteins; D005095:Exoribonucleases; D063326:Exosome Multienzyme Ribonuclease Complex; C542284:dis3 protein, S pombe