Catalanotto Caterina, Pallotta Massimiliano, ReFalo Paul, Sachs Matthew S, Vayssie Laurence, Macino Giuseppe, Cogoni Carlo
Dipartimento di Biotecnologie Cellulari ed Ematologia, Sezione di Genetica Molecolare, Universita' di Roma La Sapienza, 00161 Rome, Italy.
Mol Cell Biol. 2004 Mar;24(6):2536-45. doi: 10.1128/MCB.24.6.2536-2545.2004.
RNA interference (RNAi) in animals, cosuppression in plants, and quelling in fungi are homology-dependent gene silencing mechanisms in which the introduction of either double-stranded RNA (dsRNA) or transgenes induces sequence-specific mRNA degradation. These phenomena share a common genetic and mechanistic basis. The accumulation of short interfering RNA (siRNA) molecules that guide sequence-specific mRNA degradation is a common feature in both silencing mechanisms, as is the component of the RNase complex involved in mRNA cleavage. During RNAi in animal cells, dsRNA is processed into siRNA by an RNase III enzyme called Dicer. Here we show that elimination of the activity of two Dicer-like genes by mutation in the fungus Neurospora crassa eliminates transgene-induced gene silencing (quelling) and the processing of dsRNA to an siRNA form. The two Dicer-like genes appear redundant because single mutants are quelling proficient. This first demonstration of the involvement of Dicer in gene silencing induced by transgenes supports a model by which a dsRNA produced by the activity of cellular RNA-dependent RNA polymerases on transgenic transcripts is an essential intermediate of silencing.
动物中的RNA干扰（RNAi）、植物中的共抑制以及真菌中的基因压制都是同源依赖性基因沉默机制，其中双链RNA（dsRNA）或转基因的导入会诱导序列特异性mRNA降解。这些现象有着共同的遗传和机制基础。引导序列特异性mRNA降解的小干扰RNA（siRNA）分子的积累是这两种沉默机制的共同特征，参与mRNA切割的RNase复合物的组成部分也是如此。在动物细胞的RNAi过程中，dsRNA被一种名为Dicer的RNase III酶加工成siRNA。我们在此表明，通过在粗糙脉孢菌中进行突变来消除两个类Dicer基因的活性，会消除转基因诱导的基因沉默（基因压制）以及dsRNA加工成siRNA的过程。这两个类Dicer基因似乎是冗余的，因为单个突变体具有正常的基因压制能力。Dicer参与转基因诱导的基因沉默的这一首次证明支持了这样一种模型，即细胞RNA依赖性RNA聚合酶对转基因转录本的活性产生的dsRNA是沉默的关键中间体。
