Small interfering RNAs (siRNAs) and genome-encoded microRNAs (miRNAs) silence genes via complementary interactions with mRNAs. With thousands of miRNA genes identified and genome sequences of diverse eukaryotes available for comparison, the opportunity emerges for insights into the origin and evolution of RNA interference (RNAi). The miRNA repertoires of plants and animals appear to have evolved independently. However, conservation of the key proteins involved in RNAi suggests that the last common ancestor of modern eukaryotes possessed siRNA-based mechanisms. Prokaryotes have an RNAi-like defense system that is functionally analogous but not homologous to eukaryotic RNAi. The protein machinery of eukaryotic RNAi seems to have been pieced together from ancestral archaeal, bacterial and phage proteins that are involved in DNA repair and RNA processing.

中文翻译：

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真核RNA干扰的起源和进化。

小干扰 RNA (siRNA) 和基因组编码的微 RNA (miRNA) 通过与 mRNA 的互补相互作用使基因沉默。随着数以千计的 miRNA 基因的鉴定和多种真核生物的基因组序列可供比较，洞察 RNA 干扰 (RNAi) 起源和进化的机会出现了。植物和动物的 miRNA 库似乎是独立进化的。然而，参与 RNAi 的关键蛋白质的保守表明现代真核生物的最后一个共同祖先拥有基于 siRNA 的机制。原核生物具有类似 RNAi 的防御系统，在功能上与真核生物的 RNAi 类似但不同源。真核 RNAi 的蛋白质机制似乎是从祖先的古菌中拼凑起来的，