Numerous surveillance pathways sculpt eukaryotic transcriptomes by degrading unneeded, defective, and potentially harmful noncoding RNAs (ncRNAs). Because aberrant and excess ncRNAs are largely degraded by exoribonucleases, a key characteristic of these RNAs is an accessible, protein-free 5′ or 3′ end. Most exoribonucleases function with cofactors that recognize ncRNAs with accessible 5′ or 3′ ends and/or increase the availability of these ends. Noncoding RNA surveillance pathways were first described in budding yeast, and there are now high-resolution structures of many components of the yeast pathways and significant mechanistic understanding as to how they function. Studies in human cells are revealing the ways in which these pathways both resemble and differ from their yeast counterparts, and are also uncovering numerous pathways that lack equivalents in budding yeast. In this review, we describe both the well-studied pathways uncovered in yeast and the new concepts that are emerging from studies in mammalian cells. We also discuss the ways in which surveillance pathways compete with chaperone proteins that transiently protect nascent ncRNA ends from exoribonucleases, with partner proteins that sequester these ends within RNPs, and with end modification pathways that protect the ends of some ncRNAs from nucleases.

中文翻译：

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非编码RNA监测：目的证明手段

许多监视途径通过降解不需要的，有缺陷的和潜在有害的非编码RNA（ncRNA）来雕刻真核转录组。由于异常核糖核酸酶和过量的ncRNA会被外切核糖核酸酶大量降解，因此这些RNA的关键特征是易于接近的无蛋白质5'或3'末端。大多数外切核糖核酸酶与识别具有可接近的5'或3'末端的ncRNA和/或增加这些末端的可用性的辅因子一起发挥作用。非编码RNA监测途径最初是在发芽酵母中描述的，现在，酵母途径的许多组成部分都具有高分辨率结构，并且对它们如何发挥作用具有重要的机械理解。对人类细胞的研究揭示了这些途径与酵母对应物相似且与众不同的方式，并且还发现了许多在发芽酵母中缺乏等效途径的途径。在这篇综述中，我们既描述了在酵母中发现的经过充分研究的途径，又描述了哺乳动物细胞研究中出现的新概念。我们还讨论了监视途径与伴侣蛋白竞争的方式，该伴侣蛋白可瞬时保护新生ncRNA末端免受外切核糖核酸酶，伴侣蛋白将这些末端隔离在RNP内，以及末端修饰途径可保护某些ncRNA末端不受核酸酶的影响。