RITS acts in cis to promote RNA interference-mediated transcriptional and post-transcriptional silencing.
RNA interference is a conserved mechanism by which double-stranded RNA is processed into short interfering RNAs (siRNAs) that can trigger both post-transcriptional and transcriptional gene silencing. In fission yeast, the RNA-induced initiation of transcriptional gene silencing (RITS) complex contains Dicer-generated siRNAs and is required for heterochromatic silencing. Here we show that RITS components, including Argonaute protein, bind to all known heterochromatic loci. At the mating-type region, RITS is recruited to the centromere-homologous repeat cenH in a Dicer-dependent manner, whereas the spreading of RITS across the entire 20-kb silenced domain, as well as its subsequent maintenance, requires heterochromatin machinery including Swi6 and occurs even in the absence of Dicer. Furthermore, our analyses suggest that RNA interference machinery operates in cis as a stable component of heterochromatic domains with RITS tethered to silenced loci by methylation of histone H3 at Lys9. This tethering promotes the processing of transcripts and generation of additional siRNAs for heterochromatin maintenance.
Laboratory of Molecular Cell Biology, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.
Ken-ichi
K
Noma
Tomoyasu
T
Sugiyama
Hugh
H
Cam
Andre
A
Verdel
Martin
M
Zofall
Songtao
S
Jia
Danesh
D
Moazed
Shiv I S
SI
Grewal
D000818:Animals; D002868:Chromosomal Proteins, Non-Histone / Q000235:genetics; D015825:Chromosomes, Fungal; D019175:DNA Methylation; D058851:GPI-Linked Proteins; D020868:Gene Silencing; D006570:Heterochromatin; D008957:Models, Genetic; D034622:RNA Interference; D034741:RNA, Small Interfering; D018124:Receptors, Tumor Necrosis Factor / Q000235:genetics; D053320:Receptors, Tumor Necrosis Factor, Member 10c; D012568:Schizosaccharomyces / Q000235:genetics*; D029702:Schizosaccharomyces pombe Proteins / Q000235:genetics; D053319:Tumor Necrosis Factor Decoy Receptors
C493641:CenH protein, S pombe; D002868:Chromosomal Proteins, Non-Histone; D058851:GPI-Linked Proteins; D006570:Heterochromatin; D034741:RNA, Small Interfering; D018124:Receptors, Tumor Necrosis Factor; D053320:Receptors, Tumor Necrosis Factor, Member 10c; D029702:Schizosaccharomyces pombe Proteins; C108661:TNFRSF10C protein, human; D053319:Tumor Necrosis Factor Decoy Receptors