Small interfering RNAs (siRNAs) can be utilized not only as functional biological research tools but also as therapeutic agents. For the clinical use of siRNA as drugs, various chemical modifications have been employed to improve the activity of siRNA drugs, and further chemical modifications are expected to improve the utility of siRNA therapeutics. As the 5' nucleobase of the guide strand affects the interaction between an siRNA and AGO2 and target cleavage activity, structural optimization of this specific position may be a useful strategy for improving siRNA activity. Here, using the in silico model of the complex between human AGO2 MID domain and nucleoside monophosphates, we screened and synthesized an original adenine-derived analogue, 6-(3-(2-carboxyethyl)phenyl)purine (6-mCEPh-purine), that fits better than the natural nucleotide bases into the MID domain of AGO2. Introduction of the 6-mCEPh-purine analogue at the 5'-end of the siRNA guide strand significantly enhanced target knockdown activity in both cultured cell lines and in vivo animal models. Our findings can help expand strategies for rationally optimizing siRNA activity via chemical modifications of nucleotide bases.

中文翻译：

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通过 siRNA 引导链 5' 端核苷酸碱基的化学修饰增强 siRNA 效力

小干扰RNA（siRNA）不仅可以用作功能性生物学研究工具，还可以用作治疗剂。对于siRNA作为药物的临床应用，已经采用了各种化学修饰来提高siRNA药物的活性，并且进一步的化学修饰有望提高siRNA治疗的效用。由于引导链的 5' 核碱基影响 siRNA 和 AGO2 之间的相互作用以及靶标切割活性，因此该特定位置的结构优化可能是提高 siRNA 活性的有用策略。在这里，利用人 AGO2 MID 结构域和单磷酸核苷之间的复合物的计算机模型，我们筛选并合成了一种原始的腺嘌呤衍生类似物，6-(3-(2-羧乙基)苯基)嘌呤 (6-mCEPh-嘌呤) ，比天然核苷酸碱基更适合 AGO2 的 MID 结构域。在 siRNA 引导链 5' 端引入 6-mCEPh-嘌呤类似物显着增强了培养细胞系和体内动物模型中的靶标敲除活性。我们的研究结果有助于扩展通过核苷酸碱基化学修饰合理优化 siRNA 活性的策略。