Origin and Evolution of RNA

该研究小组试图阐明功能RNA的产生和进化机制，特别是RNA世界中的机制。为此，我们首先研究了天然催化RNA（核酶）和利用SELEX技术产生的新功能RNA的结构和功能机制，然后从分子水平上研究了参与蛋白质生物合成的tRNA和蛋白质的进化过程，以阐明它们的起源。(1)通过构建一种能自切割的新型核酶，阐明了核糖核酸酶P的M1 RNA的核酶机制。结果表明，连接反应自发发生的RNA分子与末端2 '，3'-环磷酸基团。利用SELEX技术创造了几种新的功能RNA，并讨论了它们在RNA世界中的作用。(2)通过生物化学和遗传学方法，几乎完全确定了大肠杆菌和酵母中tRNA的身份决定簇。许多人类氨酰-tRNA合成酶基因被克隆。因此，合成酶的来源分为古细菌、真核生物和细菌。此外，sme合成酶基因被指示已经从一个生物体水平转移到另一个生物体。两种功能不同的修饰核苷酸，古生菌的古生菌核苷和真核生物和真细菌的古生菌核苷，被意外地发现共享相同的生物合成机制的碱基交换。

This research group tried to elucidate the mechanisms of generation and evolution of functional RNAs, and in particular those in the RNA World. For this purpose, (1) structures and functional mechanisms of the natural catalytic RNAs (ribozymes) and new functional RNAs created by the SELEX techniques were investigated, and (2) the evolutional processes of tRNAs and proteins involved in protein biosynthesis were studied at nolecular level in order to elucidate their origins.(1) The ribozyme mechanism of the M1 RNA of RNase P were elucidated by construction of a novel ribozyme that undergoes self cleavage. It was shown that the ligation reaction spontaneously occurs for RNA molecules with the terminal 2', 3'-cyclic phosphate groups. Several new functional RNAs were created by SELEX,and their roles in the RNA World were discussed.(2) The identity determinants of tRNAs from E.coli and yeast were nearly completely established, by biochemical and genetic methods. Many human genes for aminoacyl-tRNA synthetases were cloned. Thus, the origins of synthetases were classified as archaeal, eukaryotic, and bacterial. Furthermore, sme synthetase genes were indicated to have been horizontally transferred from one organism to another. Two functionally different modified nucleotides, archaeosine from archaea and queuosine from eukaryotes and eubacteria, were found unexpectedly to share the same biosynthetic mechanism of base exchange.