The cell nucleus contains distinct biomolecular condensates that form at specific genetic loci, organize chromosomes in 3D space, and regulate RNA processing. Among these, Cajal bodies (CBs) require key "scaffolding" proteins for their assembly, which is not fully understood. Here, we employ proximity biotinylation, mass spectrometry, and functional screening to comprehensively identify and test the functions of CB components. We document 144 protein interactors of coilin, of which 70 were newly detected, and establish 25 players needed for CB assembly and/or maintenance. Surprisingly, the depletion of nine coilin interactors-mostly constituents of the 60S ribosome (RPLs)-increased CB number and caused subdomains defined by coilin and the survival motor neuron protein (SMN) to merge. These phenotypes were traceable to altered nuclear levels of dimethylarginine. Our data implicate RPL24 and other players in the regulation of CBs by modulating posttranslational modifications. Moreover, the prevalence of transcription factors among the identified components highlights roles for gene activity in CB assembly and nuclear positioning.

中文翻译：

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coilin 相互作用子的鉴定揭示了 Cajal 体数和结构的协调控制。


细胞核包含不同的生物分子凝聚物，这些凝聚物在特定的遗传位点形成，在 3D 空间中组织染色体，并调节 RNA 加工。其中，Cajal 小体 （CB） 需要关键的“支架”蛋白进行组装，这尚不完全清楚。在这里，我们采用邻近生物素化、质谱和功能筛选来全面识别和测试 CB 成分的功能。我们记录了 144 个 coilin 的蛋白质相互作用子，其中 70 个是新检测到的，并确定了 CB 组装和/或维护所需的 25 个参与者。令人惊讶的是，9 个 coilin 相互作用物（主要是 60S 核糖体 （RPL） 的成分）的消耗增加了 CB 数量，并导致由 coilin 和存活运动神经元蛋白 （SMN） 定义的子结构域合并。这些表型可追溯到二甲基精氨酸核水平的改变。我们的数据表明 RPL24 和其他参与者通过调节翻译后修饰来调节 CB。此外，转录因子在已鉴定成分中的普遍性突出了基因活性在 CB 组装和核定位中的作用。