Department of Genetics, College of Life Sciences, Wuhan University, Wuhan, People's Republic of China.
Mol Biol Evol. 2013 Sep;30(9):2087-98. doi: 10.1093/molbev/mst107. Epub 2013 Jun 5.
Transfer RNAs (tRNAs) play an important role linking mitochondrial RNA and amino acids during protein biogenesis. Four types of tRNA genes have been identified in living organisms. However, the evolutionary origin of tRNAs remains largely unknown. In this article, we conduct a deep sequence analysis of diverse genomes that cover all three domains of life to unveil the evolutionary history of tRNA genes from tRNA halves. tRNA half homologs were detected in diverse organisms, and some of them were expressed in mouse tissues. Continuous tRNA genes have a conserved pattern similar to indels, which is, more closely flanking regions have higher single nucleotide substitution rates, whereas tRNA half homologs do not have this pattern. In addition, tRNAs tend to break into tRNA halves when tissues are incubated in vitro, the tendency of tRNA to break into tRNA halves may be a "side-effect" of tRNA genes evolving from tRNA halves. These results suggest that modern tRNAs originated from tRNA halves through a repeat element-mediated mechanism. These findings provide insight into the evolutionary origin of tRNA genes.
转移 RNA（tRNA）在蛋白质生物发生过程中连接线粒体 RNA 和氨基酸方面发挥着重要作用。在生物中已经鉴定出四种类型的 tRNA 基因。然而，tRNA 的进化起源在很大程度上仍然未知。在本文中，我们对涵盖生命三个领域的各种基因组进行了深度序列分析，以揭示 tRNA 基因从 tRNA 半体的进化历史。在不同的生物体中检测到 tRNA 半体同源物，其中一些在小鼠组织中表达。连续的 tRNA 基因具有类似于插入缺失的保守模式，即更紧密的侧翼区域具有更高的单核苷酸替换率，而 tRNA 半体同源物则没有这种模式。此外，当组织在体外孵育时，tRNA 倾向于分裂成 tRNA 半体，tRNA 分裂成 tRNA 半体的趋势可能是 tRNA 基因从 tRNA 半体进化而来的“副作用”。这些结果表明，现代 tRNA 是通过重复元件介导的机制从 tRNA 半体起源的。这些发现为 tRNA 基因的进化起源提供了新的见解。
