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Abstract：
Inorganic polyphosphate (polyP) is a ubiquitous polymer that controls fundamental processes. To overcome the absence of a genetically tractable mammalian model, we developed an inducible mammalian cell line expressing Escherichia coli polyphosphate kinase 1 (EcPPK1). Inducing EcPPK1 expression prompted polyP synthesis, enabling validation of polyP analytical methods. Virtually all newly synthesized polyP accumulates within the nucleus, mainly in the nucleolus. The channeled polyP within the nucleolus results in the redistribution of its markers, leading to altered rRNA processing. Ultrastructural analysis reveals electron-dense polyP structures associated with a hyper-condensed nucleolus resulting from an exacerbation of the liquid-liquid phase separation (LLPS) phenomena controlling this membraneless organelle. The selective accumulation of polyP in the nucleoli could be interpreted as an amplification of polyP channeling to where its physiological function takes place. Indeed, quantitative analysis of several mammalian cell lines confirms that endogenous polyP accumulates within the nucleolus.
摘要：
无机多磷酸盐(polyP)是控制基本过程的普遍存在的聚合物。为了克服缺乏基因可处理的哺乳动物模型，我们开发了一种表达大肠杆菌多磷酸激酶1（EcPPK1）的诱导型哺乳动物细胞系。诱导EcPPK1表达促进polyP合成，能够验证polyP分析方法。几乎所有新合成的polyP都在细胞核内积累，主要在核仁。核仁内的通道polyP导致其标记物的重新分布，导致rRNA加工改变。超微结构分析揭示了与超浓缩核仁相关的电子致密polyP结构，这是由于控制这种无膜细胞器的液-液相分离（LLPS）现象加剧所致。polyP在核仁中的选择性积累可以解释为polyP通道向其生理功能发生的放大。的确,几种哺乳动物细胞系的定量分析证实内源性polyP在核仁内积累。
