Habig Jeffrey W, Aruscavage P Joseph, Bass Brenda L
Department of Biochemistry and Howard Hughes Medical Institute, University of Utah, Salt Lake City, Utah, USA.
PLoS One. 2008;3(12):e4052. doi: 10.1371/journal.pone.0004052. Epub 2008 Dec 29.
C. elegans Dicer requires an accessory double-stranded RNA binding protein, RDE-4, to enact the first step of RNA interference, the cleavage of dsRNA to produce siRNA. While RDE-4 is typically essential for RNAi, we report that in the presence of high concentrations of trigger dsRNA, rde-4 deficient animals are capable of silencing a transgene. By multiple criteria the silencing occurs by the canonical RNAi pathway. For example, silencing is RDE-1 dependent and exhibits a decrease in the targeted mRNA in response to an increase in siRNA. We also find that high concentrations of dsRNA trigger lead to increased accumulation of primary siRNAs, consistent with the existence of a rate-limiting step during the conversion of primary to secondary siRNAs. Our studies also revealed that transgene silencing occurs at low levels in the soma, even in the presence of ADARs, and that at least some siRNAs accumulate in a temperature-dependent manner. We conclude that an RNAi response varies with different conditions, and this may allow an organism to tailor a response to specific environmental signals.
秀丽隐杆线虫的Dicer需要一种辅助双链RNA结合蛋白RDE-4来启动RNA干扰的第一步，即切割双链RNA以产生小干扰RNA（siRNA）。虽然RDE-4通常对RNA干扰至关重要，但我们报告称，在存在高浓度触发双链RNA的情况下，rde-4缺陷型动物能够使转基因沉默。通过多种标准判断，这种沉默是通过经典的RNA干扰途径发生的。例如，沉默依赖于RDE-1，并且随着siRNA的增加，靶向mRNA会减少。我们还发现，高浓度的双链RNA触发物会导致初级siRNA的积累增加，这与初级siRNA转化为次级siRNA过程中存在限速步骤一致。我们的研究还表明，即使存在腺苷脱氨酶（ADARs），转基因沉默在体细胞中也会以低水平发生，并且至少一些siRNA会以温度依赖的方式积累。我们得出结论，RNA干扰反应会因不同条件而变化，这可能使生物体能够针对特定环境信号调整反应。
