Modification of RNAs, particularly at the terminals, is critical for various essential cell processes; for example, uridylation is implicated in tumorigenesis, proliferation, stem cell maintenance, and immune defense against viruses and retrotransposons. Ribosomal RNAs can be regulated by antisense ribosomal siRNAs (risiRNAs), which downregulate pre-rRNAs through the nuclear RNAi pathway in Caenorhabditis elegans. However, the biogenesis and regulation of risiRNAs remain obscure. Previously, we showed that 26S rRNAs are uridylated at the 3′-ends by an unknown terminal polyuridylation polymerase before the rRNAs are degraded by a 3′ to 5′ exoribonuclease SUSI-1(ceDIS3L2). Here, we found that CDE-1, one of the three C.elegans polyuridylation polymerases (PUPs), is specifically involved in suppressing risiRNA production. CDE-1 localizes to perinuclear granules in the germline and uridylates Argonaute-associated 22G-RNAs, 26S, and 5.8S rRNAs at the 3′-ends. Immunoprecipitation followed by mass spectrometry (IP-MS) revealed that CDE-1 interacts with SUSI-1(ceDIS3L2). Consistent with these results, both CDE-1 and SUSI-1(ceDIS3L2) are required for the inheritance of RNAi. This work identified a rRNA surveillance machinery of rRNAs that couples terminal polyuridylation and degradation.

中文翻译：

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CDE-1通过偶联rURNA的多尿苷酸化和降解来抑制risiRNA的产生。

RNA的修饰，特别是在末端的修饰，对于各种必需的细胞过程至关重要。例如，尿嘧啶化与肿瘤发生，增殖，干细胞维持以及针对病毒和逆转座子的免疫防御有关。核糖体RNA可由反义核糖体siRNA（risiRNA）调控，后者通过秀丽隐杆线虫中的核RNAi途径下调前rRNA。但是，risiRNA的生物发生和调控仍然不清楚。以前，我们显示26S rRNA在3'至5'外核糖核酸酶SUSI-1（ceDIS3L2）降解之前，被未知的末端多尿苷酸聚合酶在3'端尿苷化。在这里，我们发现CDE-1是三种秀丽隐杆线虫多尿苷酸聚合酶（PUP）之一，特别参与抑制risiRNA的产生。CDE-1定位于种系中的核周颗粒，并在3'端尿苷与Argonaute相关的22G-RNA，26S和5.8S rRNA。免疫沉淀后再进行质谱分析（IP-MS）显示CDE-1与SUSI-1（ceDIS3L2）相互作用。与这些结果一致，RNAi的遗传需要CDE-1和SUSI-1（ceDIS3L2）。这项工作确定了rRNA的rRNA监测机制，将末端多尿苷化和降解耦合在一起。