RNAi mediates post-transcriptional repression of gene expression in fission yeast Schizosaccharomyces pombe [Affymetrix]

RNA interference (RNAi) is a gene silencing mechanism conserved from fungi to mammals. Small interfering RNAs are products and mediators of the RNAi pathway and act as specificity factors in recruiting effector complexes. The Schizosaccharomyces pombe genome encodes one of each of the core RNAi proteins, Dicer, Argonaute and RNA-dependent RNA polymerase (dcr1, ago1, rdp1). Even though the function of RNAi in heterochromatin assembly in S. pombe is established, its role in controlling gene expression is elusive. Here, we report the identification of small RNAs mapped anti-sense to protein coding genes in fission yeast. We demonstrate that these genes are up-regulated at the protein level in RNAi mutants, while their mRNA levels are not significantly changed. We show that the repression by RNAi is not a result of heterochromatin formation. Thus, we conclude that RNAi is involved in post-transcriptional gene silencing in S. pombe. Total RNA from wild type, dcr1Δ and rpd1Δ cells; 3 biological replicates for each strain.

RNA干扰（RNA interference, RNAi）是一类从真菌到哺乳动物均保守存在的基因沉默机制。小干扰RNA（small interfering RNA, siRNA）是RNAi通路的产物与介导因子，在招募效应复合物时作为特异性识别因子发挥功能。裂殖酵母（Schizosaccharomyces pombe）的基因组编码一套核心RNAi蛋白，包括Dicer、Argonaute以及RNA依赖的RNA聚合酶，其编码基因分别为dcr1、ago1与rdp1。尽管RNAi在裂殖酵母异染色质组装中的功能已得到明确证实，但其在调控基因表达中的具体作用仍尚不明确。本研究鉴定出了裂殖酵母中与蛋白编码基因反义匹配的小RNA。我们证实，这些基因在RNAi突变体中蛋白表达水平上调，但其mRNA水平并无显著变化。进一步实验表明，RNAi介导的基因沉默并非通过异染色质形成实现。因此，我们认为RNAi参与了裂殖酵母的转录后基因沉默过程。本研究的样本为野生型、dcr1Δ及rpd1Δ菌株的总RNA，每个菌株设置3次生物学重复。