Fonds de la Recherche Scientifique (FRS-FNRS), Institut de Biologie et de Médecine Moléculaires, Université Libre de Bruxelles, Belgium.
Biochimie. 2012 Jul;94(7):1521-32. doi: 10.1016/j.biochi.2012.02.001. Epub 2012 Feb 8.
Ribosomal RNAs are produced as lengthy polycistronic precursors containing coding and non-coding sequences, implying that extensive pre-rRNA processing is necessary for the removal of non-coding spacers. Remarkably, this feature is conserved in all three kingdoms of life and pre-rRNA processing has even become more complex during the course of evolution. While the need for such extensive processing remains unclear, it likely offers increased opportunities to finely regulate ribosome synthesis and to temporally and spatially integrate the various components of ribosome synthesis. In this review we discuss our current understanding of pre-rRNA processing pathways in mammals (human and mouse), with a particular focus on the known and putative cleavage sites, and we compare it to budding yeast, the best eukaryotic model, thus far, regarding ribosome synthesis. Based on the emerging research, we suggest that there are likely more pre-rRNA processing sites and alternative processing pathways still to be identified in humans and that a certain level of functional redundancy can be found in the trans-acting factors involved. These features might have been selected because they increase the robustness of pre-rRNA processing by acting as "back-up" mechanisms to ensure the proper maturation of rRNA.
核糖体 RNA 作为包含编码和非编码序列的长多顺反子前体产生，这意味着需要广泛的前 rRNA 加工来去除非编码间隔序列。值得注意的是，这一特征在所有三个生命领域中都是保守的，并且在前 rRNA 加工过程中，甚至在进化过程中变得更加复杂。虽然这种广泛加工的必要性尚不清楚，但它可能提供了更多的机会来精细调节核糖体的合成，并在时间和空间上整合核糖体合成的各个组成部分。在这篇综述中，我们讨论了我们目前对哺乳动物（人类和小鼠）前 rRNA 加工途径的理解，特别关注已知和假定的切割位点，并将其与芽殖酵母进行了比较，芽殖酵母是迄今为止关于核糖体合成的最佳真核模型。基于新兴的研究，我们推测在人类中可能还有更多的前 rRNA 加工位点和替代加工途径有待发现，并且参与的反式作用因子可能存在一定程度的功能冗余。这些特征可能是被选择的，因为它们通过充当“备份”机制来确保 rRNA 的正确成熟，从而增加了前 rRNA 加工的稳健性。
