Akins R A, Lambowitz A M
Cell. 1987 Jul 31;50(3):331-45. doi: 10.1016/0092-8674(87)90488-0.
The nuclear cyt-18 mutants of Neurospora crassa are defective in splicing a number of group I introns in mitochondria. Here, cloning and sequencing of the cyt-18 gene show that it contains an open reading frame having significant homology to bacterial tyrosyl-tRNA synthetases. Biochemical and genetic experiments lead to the conclusions that the cyt-18 gene encodes mitochondrial tyrosyl-tRNA synthetase, that mutations in this gene inhibit splicing directly, and that mitochondrial tyrosyl-tRNA synthetase or a derivative of this protein is related to the soluble activity that functions in splicing the mitochondrial large rRNA intron and possibly other group I introns. Analysis of partial revertants provides direct evidence that the cyt-18 gene encodes a protein or proteins with two activities, splicing and aminoacylation, that can be partially separated by mutation. Our findings may be relevant to the evolution of introns and splicing mechanisms in eukaryotes.
粗糙脉孢菌的细胞核cyt - 18突变体在线粒体内拼接一些I类内含子时存在缺陷。在此，对cyt - 18基因进行克隆和测序表明，它含有一个与细菌酪氨酰 - tRNA合成酶具有显著同源性的开放阅读框。生化和遗传学实验得出以下结论：cyt - 18基因编码线粒体酪氨酰 - tRNA合成酶，该基因中的突变直接抑制拼接，并且线粒体酪氨酰 - tRNA合成酶或该蛋白质的一种衍生物与参与拼接线粒体大rRNA内含子以及可能其他I类内含子的可溶性活性相关。对部分回复突变体的分析提供了直接证据，表明cyt - 18基因编码具有两种活性（拼接和氨酰化）的一种或多种蛋白质，这两种活性可通过突变部分分离。我们的发现可能与真核生物内含子和拼接机制的进化有关。
