The signal recognition particle (SRP) is a universally conserved non-coding ribonucleoprotein complex that is essential for targeting transmembrane and secretory proteins to the endoplasmic reticulum. Its composition and size varied during evolution. In mammals, SRP contains one RNA molecule, 7SL RNA, and six proteins: SRP9, 14, 19, 54, 68 and 72. Despite a very good understanding of the SRP structure and of the SRP assembly in vitro, how SRP is assembled in vivo remains largely enigmatic. Here we review current knowledge on how the 7SL RNA is assembled with core proteins to form functional RNP particles in cells. SRP biogenesis is believed to take place both in the nucleolus and in the cytoplasm and to rely on the survival of motor neuron complex, whose defect leads to spinal muscular atrophy.

中文翻译：

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真核信号识别颗粒的体内组装：涉及SMN复合体的仍然神秘的过程。

信号识别颗粒（SRP）是一种普遍保存的非编码核糖核蛋白复合物，对于将跨膜和分泌蛋白靶向内质网至关重要。它的组成和大小在进化过程中各不相同。在哺乳动物中，SRP包含一个RNA分子，7SL RNA和六个蛋白：SRP9、14、19、54、68和72。尽管对SRP结构和体外SRP组装有很好的了解，但SRP是如何组装的vivo在很大程度上仍然是个谜。在这里，我们回顾了有关7SL RNA如何与核心蛋白组装以在细胞中形成功能性RNP颗粒的最新知识。SRP的生物发生被认为发生在核仁和细胞质中，并且依赖于运动神经元复合物的存活，运动神经元复合物的缺陷导致脊髓性肌萎缩。