Caprara M G, Lehnert V, Lambowitz A M, Westhof E
Department of Molecular Genetics, The Ohio State University, Columbus 43210-1292, USA.
Cell. 1996 Dec 13;87(6):1135-45. doi: 10.1016/s0092-8674(00)81807-3.
The Neurospora crassa mitochondrial (mt) tyrosyl-tRNA synthetase (CYT-18 protein) functions in splicing group I introns, in addition to aminoacylating tRNA(Tyr). Here, we compared the CYT-18 binding sites in the N. crassa mt LSU and ND1 introns with that in N. crassa mt tRNA(Tyr) by constructing three-dimensional models based on chemical modification and RNA footprinting data. Remarkably, superimposition of the CYT-18 binding sites in the model structures revealed an extended three-dimensional overlap between the tRNA and the group I intron catalytic core. Our results provide insight into how an RNA-splicing factor can evolve from a cellular RNA-binding protein. Further, the structural similarities between group I introns and tRNAs are consistent with an evolutionary relationship and suggest a general mechanism for the evolution of complex catalytic RNAs.
粗糙脉孢菌线粒体（mt）酪氨酰 - tRNA合成酶（CYT - 18蛋白）除了对tRNA（Tyr）进行氨酰化外，还在I组内含子剪接中发挥作用。在这里，我们通过基于化学修饰和RNA足迹数据构建三维模型，比较了粗糙脉孢菌mt LSU和ND1内含子中的CYT - 18结合位点与粗糙脉孢菌mt tRNA（Tyr）中的CYT - 18结合位点。值得注意的是，模型结构中CYT - 18结合位点的叠加揭示了tRNA与I组内含子催化核心之间存在扩展的三维重叠。我们的结果为RNA剪接因子如何从细胞RNA结合蛋白进化而来提供了见解。此外，I组内含子与tRNA之间的结构相似性与进化关系一致，并暗示了复杂催化RNA进化的一般机制。
