1Department of Biochemistry, University of Utah, Salt Lake City, Utah 84112, USA.
RNA. 2010 May;16(5):893-903. doi: 10.1261/rna.2122010. Epub 2010 Mar 30.
Years after the discovery that Dicer is a key enzyme in gene silencing, the role of its helicase domain remains enigmatic. Here we show that this domain is critical for accumulation of certain endogenous small interfering RNAs (endo-siRNAs) in Caenorhabditis elegans. The domain is required for the production of the direct products of Dicer, or primary endo-siRNAs, and consequently affects levels of downstream intermediates, the secondary endo-siRNAs. Consistent with the role of endo-siRNAs in silencing, their loss correlates with an increase in cognate mRNA levels. We find that the helicase domain of Dicer is not necessary for microRNA (miRNA) processing, or RNA interference following exposure to exogenous double-stranded RNA. Comparisons of wild-type and helicase-defective strains using deep-sequencing analyses show that the helicase domain is required by a subset of annotated endo-siRNAs, in particular, those associated with the slightly longer 26-nucleotide small RNA species containing a 5' guanosine.
在发现 Dicer 是基因沉默的关键酶多年后，其解旋酶结构域的作用仍然是个谜。本文中，我们证明该结构域对秀丽隐杆线虫中某些内源性小干扰 RNA（endo-siRNA）的积累至关重要。该结构域对于 Dicer 的直接产物或初级 endo-siRNA 的产生是必需的，因此会影响下游中间产物，即次级 endo-siRNA 的水平。与 endo-siRNA 在沉默中的作用一致，其缺失与同源 mRNA 水平的增加相关。我们发现 Dicer 的解旋酶结构域对于 miRNA（miRNA）加工或暴露于外源双链 RNA 后的 RNA 干扰并非必需。使用深度测序分析比较野生型和解旋酶缺陷型菌株表明，该结构域是一组注释的内源性 siRNA 所必需的，特别是那些与含有 5'鸟苷的稍长 26 个核苷酸的小 RNA 物种相关的 siRNA。
