As hubs of metabolism, mitochondria contribute critical processes to coordinate and optimize energy and intermediate metabolites. Drosophila Clueless (Clu) and vertebrate CLUH are ribonucleoproteins critical for supporting mitochondrial function yet do so in multiple ways. Clu/CLUH bind mRNAs and CLUH regulates mRNA localization and translation of mRNAs encoding proteins destined for mitochondrial import. In addition, Clu associates with ribosomal proteins and translation factors, yet whether it is required for fundamental ribosome function in vivo is not clear. In this study, we examine the Clu interactome and probe Clu's requirement in ribosome biogenesis. We previously showed that Clu associates with ribosomal proteins. In this study, we extend these observations to show that clu null mutants display a significant decrease in overall protein synthesis. In addition, Clu associates with ribosomal proteins in an mRNA-independent manner, suggesting Clu's core ribosomal function may be separate from its role in localizing and translating specific mRNAs. We find that Clu is present in the nucleus and associates with the ribosomal RNA (rRNA) processing protein fibrillarin but, surprisingly, that processed rRNA products are normal in the absence of Clu. Furthermore, Clu loss does not affect ribosomal protein levels, but does result in a decrease in 40S and 60S ribosomal subunits abundance. Together, these results demonstrate that Clu is present in the nucleus and required for 40S and 60S biogenesis and global translation in vivo. These results highlight the multifaceted role of Clu in supporting cell function through regulation of mRNA encoding mitochondrial proteins and ribosome biogenesis.

中文翻译：

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果蝇核糖核蛋白 Clueless 是体内核糖体生物发生所必需的。


作为新陈代谢的枢纽，线粒体为协调和优化能量和中间代谢物的关键过程做出了贡献。果蝇 Clueless （Clu） 和脊椎动物 CLUH 是支持线粒体功能的关键核糖核蛋白，但以多种方式发挥作用。Clu/CLUH 结合 mRNA，CLUH 调节编码线粒体输入蛋白质的 mRNA 的 mRNA 定位和翻译。此外，Clu 与核糖体蛋白和翻译因子相关，但尚不清楚它是否是体内基本核糖体功能所必需的。在这项研究中，我们检查 Clu 相互作用组并探测 Clu 在核糖体生物发生中的要求。我们之前表明 Clu 与核糖体蛋白相关。在这项研究中，我们扩展了这些观察结果，以表明 clu null 突变体显示出整体蛋白质合成的显着减少。此外，Clu 以不依赖 mRNA 的方式与核糖体蛋白结合，表明 Clu 的核心核糖体功能可能与其在定位和翻译特定 mRNA 中的作用分开。我们发现 Clu 存在于细胞核中并与核糖体 RNA （rRNA） 加工蛋白原纤维蛋白相关，但令人惊讶的是，在没有 Clu 的情况下，加工的 rRNA 产物是正常的。此外，Clu 丢失不会影响核糖体蛋白水平，但确实会导致 40S 和 60S 核糖体亚基丰度降低。总之，这些结果表明 Clu 存在于细胞核中，并且是体内 40S 和 60S 生物发生和全局翻译所必需的。这些结果突出了 Clu 通过调节编码线粒体蛋白的 mRNA 和核糖体生物发生在支持细胞功能中的多方面作用。