Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66, Basel 4058, Switzerland.
Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66, Basel 4058, Switzerland.
Mol Cell. 2021 Jun 3;81(11):2388-2402.e8. doi: 10.1016/j.molcel.2021.03.029. Epub 2021 Apr 13.
Small RNA pathways defend the germlines of animals against selfish genetic elements, yet pathway activities need to be contained to prevent silencing of self genes. Here, we reveal a proteolytic mechanism that controls endogenous small interfering (22G) RNA activity in the Caenorhabditis elegans germline to protect genome integrity and maintain fertility. We find that DPF-3, a P-granule-localized N-terminal dipeptidase orthologous to mammalian dipeptidyl peptidase (DPP) 8/9, processes the unusually proline-rich N termini of WAGO-1 and WAGO-3 Argonaute (Ago) proteins. Without DPF-3 activity, these WAGO proteins lose their proper complement of 22G RNAs. Desilencing of repeat-containing and transposon-derived transcripts, DNA damage, and acute sterility ensue. These phenotypes are recapitulated when WAGO-1 and WAGO-3 are rendered resistant to DPF-3-mediated processing, identifying them as critical substrates of DPF-3. We conclude that N-terminal processing of Ago proteins regulates their activity and promotes silencing of selfish genetic elements by ensuring Ago association with appropriate small RNAs.
小 RNA 通路可保护动物生殖细胞免受自私遗传元件的侵害，但通路活性需要受到控制，以防止自身基因沉默。在这里，我们揭示了一种蛋白水解机制，该机制可控制秀丽隐杆线虫生殖细胞中内源性小干扰 (22G) RNA 的活性，以保护基因组完整性并维持生育能力。我们发现，DPF-3 是一种与哺乳动物二肽基肽酶 (DPP) 8/9 同源的 P 颗粒定位的 N 端二肽酶，可加工 WAGO-1 和 WAGO-3 Argonaute (Ago) 蛋白异常富含脯氨酸的 N 端。没有 DPF-3 活性，这些 WAGO 蛋白会失去适当的 22G RNA 组成。随后会出现重复序列和转座子衍生转录物的去沉默、DNA 损伤和急性不育。当 WAGO-1 和 WAGO-3 对 DPF-3 介导的加工产生抗性时，会出现这些表型，这表明它们是 DPF-3 的关键底物。我们得出结论，Ago 蛋白的 N 端加工调节其活性，并通过确保 Ago 与适当的小 RNA 结合来促进自私遗传元件的沉默。
