Project description:We tested whether we could increase the population of Rdp1-independent primary siRNAs in fission yeast by overexpressing the Dcr1 ribonuclease. We found that in addition to generation of centromeric siRNAs, which was expected, Dcr1 overexpression also resulted in generation of genome-wide primary siRNAs, mapping to many open reading frames.
Project description:In the fission yeast Schizosaccharomyces pombe, the RNA interference (RNAi) pathway is required to generate small interfering RNAs (siRNAs) that mediate heterochromatic silencing of centromeric repeats. Here we demonstrate that RNAi also functions to repress genomic elements other than constitutive heterochromatin. Using DamID (DNA adenine methyltransferase identification) we show that Dcr1 and Rdp1 physically associate with some euchromatic genes, non-coding RNA (ncRNA) genes, and retrotransposon long terminal repeats (LTRs), and that this association is independent of the Clr4 histone methyltransferase. Physical association of RNAi with chromatin is sufficient to trigger a silencing response but not to assemble heterochromatin. The mode of silencing at the newly identified RNAi targets is consistent with a co-transcriptional gene silencing model as proposed earlier and functions with trace amounts of siRNAs. We anticipate that similar mechanisms could also be operational in other eukaryotes.
Project description:We tested whether we could increase the population of Rdp1-independent primary siRNAs in fission yeast by overexpressing the Dcr1 ribonuclease. We found that in addition to generation of centromeric siRNAs, which was expected, Dcr1 overexpression also resulted in generation of genome-wide primary siRNAs, mapping to many open reading frames. sequencing of 20-30nt sRNAs from total RNA
Project description:We provide evidence of the generation of Rdp1-mediated secondary siRNAs in vivo in fission yeast. Secondly, we show that the presence of Ago1-associated siRNAs does not guarantee robust silencing.