Department of Neurobiology, University of Massachusetts Medical School, Worcester, 01605, USA.
Cell. 2012 May 11;149(4):832-46. doi: 10.1016/j.cell.2012.03.032.
Localized protein synthesis requires assembly and transport of translationally silenced ribonucleoprotein particles (RNPs), some of which are exceptionally large. Where in the cell such large RNP granules first assemble was heretofore unknown. We previously reported that during synapse development, a fragment of the Wnt-1 receptor, DFrizzled2, enters postsynaptic nuclei where it forms prominent foci. Here we show that these foci constitute large RNP granules harboring synaptic protein transcripts. These granules exit the nucleus by budding through the inner and the outer nuclear membranes in a nuclear egress mechanism akin to that of herpes viruses. This budding involves phosphorylation of A-type lamin, a protein linked to muscular dystrophies. Thus nuclear envelope budding is an endogenous nuclear export pathway for large RNP granules.
本地化蛋白质合成需要组装和运输翻译沉默的核糖核蛋白颗粒（RNP），其中一些颗粒非常大。这些大型 RNP 颗粒最初在细胞中的何处组装以前是未知的。我们之前报道，在突触发育过程中，Wnt-1 受体的一个片段，DFrizzled2，进入突触后核，在那里它形成明显的焦点。在这里，我们表明这些焦点构成了含有突触蛋白转录本的大型 RNP 颗粒。这些颗粒通过出芽穿过内核膜和外核膜从核中退出，这一机制类似于疱疹病毒。这种出芽涉及到 A 型层粘连蛋白的磷酸化，A 型层粘连蛋白与肌肉萎缩症有关。因此，核膜出芽是大型 RNP 颗粒的一种内源性核输出途径。
