Piwi-interacting RNAs (piRNAs) constitute a class of small RNAs that bind PIWI proteins and are essential to repress transposable elements in the animal germline, thereby promoting genome stability and maintaining fertility. C. elegans piRNAs (21U RNAs) are transcribed individually from minigenes as precursors that require 5′ and 3′ processing. This process depends on the PETISCO complex, consisting of four proteins: IFE-3, TOFU-6, PID-3, and ERH-2. We used biochemical and structural biology approaches to characterize the PETISCO architecture and its interaction with RNA, together with its effector proteins TOST-1 and PID-1. These two proteins define different PETISCO functions: PID-1 governs 21U processing, whereas TOST-1 links PETISCO to an unknown process essential for early embryogenesis. Here, we show that PETISCO forms an octameric assembly with each subunit present in two copies. Determination of structures of the TOFU-6/PID-3 and PID-3/ERH-2 subcomplexes, supported by in vivo studies of subunit interaction mutants, allows us to propose a model for the formation of the TOFU-6/PID-3/ERH-2 core complex and its functionality in germ cells and early embryos. Using NMR spectroscopy, we demonstrate that TOST-1 and PID-1 bind to a common surface on ERH-2, located opposite its PID-3 binding site, explaining how PETISCO can mediate different cellular roles.

中文翻译：

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秀丽隐杆线虫 piRNA 生物发生过程中 PETISCO 复合物组装的结构基础

Piwi 相互作用 RNA (piRNA) 构成一类与 PIWI 蛋白结合的小 RNA，对于抑制动物种系中的转座因子至关重要，从而促进基因组稳定性和维持生育能力。秀丽隐杆线虫piRNAs (21U RNAs) 作为前体从小基因单独转录，需要 5' 和 3' 加工。这个过程取决于 PETISCO 复合物，它由四种蛋白质组成：IFE-3、TOFU-6、PID-3 和 ERH-2。我们使用生化和结构生物学方法来表征 PETISCO 结构及其与 RNA 的相互作用，以及它的效应蛋白 TOST-1 和 PID-1。这两种蛋白质定义了不同的 PETISCO 功能：PID-1 控制 21U 处理，而 TOST-1 将 PETISCO 与早期胚胎发生所必需的未知过程联系起来。在这里，我们展示了 PETISCO 形成了一个八聚体组件，每个亚基存在两个副本。亚基相互作用突变体的体内研究支持的 TOFU-6/PID-3 和 PID-3/ERH-2 亚复合体结构的测定，允许我们提出一个模型来形成 TOFU-6/PID-3/ERH-2 核心复合物及其在生殖细胞和早期胚胎中的功能。使用 NMR 光谱，我们证明 TOST-1 和 PID-1 与 ERH-2 上的共同表面结合，位于其 PID-3 结合位点的对面，解释了 PETISCO 如何介导不同的细胞作用。