Since its discovery in 1998 RNA interference (RNAi), a potent and highly selective gene silencing mechanism, has revolutionized the field of biological science. The ability of RNAi to specifically down-regulate the expression of any cellular protein has had a profound impact on the study of gene function in vitro. This property of RNAi also holds great promise for in vivo functional genomics and interventions against a wide spectrum of diseases, especially those with "undruggable" therapeutic targets. Despite the enormous potential of RNAi for medicine, development of in vivo applications has met with significant problems, particularly in terms of delivery. For effective gene silencing to occur, silencing RNA must reach the cytoplasm of the target cell. Consequently, various strategies using chemically modified siRNA, liposomes, nanoparticles and viral vectors are being developed to deliver silencing RNA. These approaches, however, can be expensive and in many cases they lack target cell specificity or clinical compatibility. Recently, we have shown that RNAi can be activated in vitro and in vivo by non-pathogenic bacteria engineered to manufacture and deliver silencing shRNA to target cells. This new approach, termed TransKingdom RNAi (tkRNAi), has several key advantages. First, tkRNAi may provide a viable means to accomplish therapeutic RNAi since non-pathogenic bacteria have a proven safety record in clinical applications. Second, tkRNAi eliminates the cost of siRNA manufacture since silencing shRNA are produced inside bacteria. Moreover, the intracellular mechanism of shRNA release inherent to tkRNAi may circumvent, or mitigate, the activation of host immune responses. Finally, tkRNAi may facilitate high-throughput in vivo functional genomics screening since bacteria-based RNAi libraries can be easily constructed, stored, reproduced and amplified, thereby allowing for the creation of a stable gene silencing system.

中文翻译：

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TransKingdom RNA干扰：一种应对RNAi治疗和递送挑战的细菌方法。

自1998年发现RNA干扰（RNAi）以来，它是一种有效且高度选择性的基因沉默机制，彻底改变了生物科学领域。RNAi特异性下调任何细胞蛋白表达的能力对体外基因功能的研究产生了深远的影响。RNAi的这一特性对于体内功能基因组学和针对多种疾病（尤其是具有“不可负担的”治疗靶标的疾病）的干预也具有广阔的前景。尽管RNAi在医学上具有巨大的潜力，但体内应用的开发仍遇到了重大问题，尤其是在递送方面。为了发生有效的基因沉默，沉默的RNA必须到达靶细胞的细胞质。因此，使用化学修饰的siRNA，脂质体，正在开发纳米颗粒和病毒载体以递送沉默的RNA。然而，这些方法可能是昂贵的，并且在许多情况下，它们缺乏靶细胞特异性或临床相容性。最近，我们已经表明，RNAi可以在体外和体内被非病原性细菌激活，这些非病原性细菌经过工程改造，可以制造沉默shRNA并将其传递至靶细胞。这种称为TransKingdom RNAi（tkRNAi）的新方法具有几个关键优势。首先，tkRNAi可能为完成治疗性RNAi提供可行的方法，因为非病原细菌在临床应用中已被证明具有安全性记录。其次，tkRNAi消除了siRNA的生产成本，因为沉默的shRNA是在细菌内部产生的。此外，tkRNAi固有的shRNA释放的细胞内机制可能会规避或减轻 激活宿主免疫反应。最后，tkRNAi可以促进高通量的体内功能基因组学筛选，因为基于细菌的RNAi文库可以轻松构建，存储，复制和扩增，从而可以创建稳定的基因沉默系统。