Lavrov D V, Brown W M, Boore J L
Department of Biology, University of Michigan, 830 North University Avenue, Ann Arbor, MI 48109-1048, USA.
Proc Natl Acad Sci U S A. 2000 Dec 5;97(25):13738-42. doi: 10.1073/pnas.250402997.
We determined the complete mtDNA sequence of the centipede Lithobius forficatus and found that only one of the 22 inferred tRNA genes encodes a fully paired aminoacyl acceptor stem. The other 21 genes encode tRNAs with up to five mismatches in these stems, and some of these overlap extensively with the downstream genes. Because a well-paired acceptor stem is required for proper tRNA functioning, RNA editing in the products of these genes was suspected. We investigated this hypothesis by studying cDNA sequences from eight tRNAs and found the editing of up to 5 nt at their 3' ends. This editing appears to occur by a novel mechanism with the 5' end of the acceptor stem being used as a template for the de novo synthesis of the 3' end, presumably by an RNA-dependent RNA polymerase. In addition, unusual secondary structures for several tRNAs were found, including those lacking a TPsiC (T) or a dihydrouridine (D) arm, and having an unusual number of base pairs in the acceptor or anticodon stems.
我们测定了蜈蚣石蜈蚣(Lithobius forficatus)的完整线粒体DNA序列,发现22个推断的tRNA基因中只有一个编码完全配对的氨酰基接受茎。其他21个基因编码的tRNA在这些茎中存在多达五个错配,其中一些与下游基因广泛重叠。由于正常的tRNA功能需要一个配对良好的接受茎,因此怀疑这些基因的产物中存在RNA编辑。我们通过研究来自八个tRNA的cDNA序列来研究这一假设,发现在它们的3'端存在多达5个核苷酸的编辑。这种编辑似乎是通过一种新机制发生的,接受茎的5'端被用作3'端从头合成的模板,推测是由一种RNA依赖性RNA聚合酶催化。此外,还发现了几种tRNA的异常二级结构,包括那些缺乏TPsiC(T)或二氢尿嘧啶(D)臂,以及在接受茎或反密码子茎中具有异常数量碱基对的结构。