Kaçar Y, Beier H, Gross H J
Institut für Biochemie, Bayerische Julius-Maximilians-Universität, Würzburg, Germany.
Gene. 1995 Apr 14;156(1):129-32. doi: 10.1016/0378-1119(95)00079-l.
Six of 13 cloned members of the human tRNA(Val) gene family code for tRNA(Val) pseudogenes, of which all but one are transcribed efficiently in HeLa cell extracts. Due to single or multiple mismatches in stem regions, the corresponding pre-tRNAs are resistant against the action of human 5'- and 3'-processing enzymes and are thus prevented from being converted to mature tRNAs. Surprisingly, all of them are accurately and efficiently processed to mature-sized tRNA in yeast nuclear extract. This is in agreement with corresponding studies of plant pre-tRNAs which are not processed in wheat germ extract but are rapidly processed in yeast extract. These observations imply that the yeast pre-tRNA 5'- and 3'-maturases do not monitor the three-dimensional structure of their substrates as stringently as mammalian and plant enzymes, possibly because tRNA pseudogenes do not occur in yeast.
人类tRNA(Val)基因家族的13个克隆成员中有6个编码tRNA(Val)假基因，其中除一个外，其他在HeLa细胞提取物中均能高效转录。由于茎区存在单个或多个错配，相应的前体tRNA对人类5'-和3'-加工酶的作用具有抗性，因此无法转化为成熟的tRNA。令人惊讶的是，所有这些假基因在酵母核提取物中都能准确、高效地加工成成熟大小的tRNA。这与植物前体tRNA的相应研究结果一致，植物前体tRNA在小麦胚芽提取物中不被加工，但在酵母提取物中能快速加工。这些观察结果表明，酵母前体tRNA 5'-和3'-成熟酶对底物三维结构的监测不像哺乳动物和植物酶那样严格，这可能是因为酵母中不存在tRNA假基因。
