Hanic-Joyce P J, Spencer D F, Gray M W
Department of Biochemistry, Dalhousie University, Halifax, Nova Scotia, Canada.
Plant Mol Biol. 1990 Oct;15(4):551-9. doi: 10.1007/BF00017830.
We have recently described the properties of a wheat mitochondrial extract that is able to process, accurately and efficiently, artificial transcripts containing wheat mitochondrial tRNA sequences, with the production of mature tRNAs (P.J. Hanic-Joyce and M.W. Gray, J. Biol. Chem., in press). Such processing involves 5'-endonucleolytic, 3'-endonucleolytic, and tRNA nucleotidyltransferase activities. Here we show that this system also acts on transcripts containing sequences corresponding to an unusual class of short repeats ('t-elements') in wheat mtDNA. These repeats are theoretically capable of assuming a tRNA-like secondary structure, although stable transcripts corresponding to them are not detectable in vivo. We find that t-element sequences are processed with the same specificity and with comparable efficiency as are authentic tRNA sequences. Because known t-elements are located close to and in the same transcriptional orientation as active genes (18S-5S, 26S, tRNA(Pro)) in wheat mtDNA, our results raise the question of whether t-elements play a role in gene expression in wheat mitochondria.
我们最近描述了一种小麦线粒体提取物的特性，它能够准确、高效地加工包含小麦线粒体tRNA序列的人工转录本，并产生成熟的tRNA（P.J.哈尼奇-乔伊斯和M.W.格雷，《生物化学杂志》，即将发表）。这种加工涉及5'-内切核酸酶、3'-内切核酸酶和tRNA核苷酸转移酶活性。在这里，我们表明该系统也作用于包含与小麦线粒体DNA中一类不寻常的短重复序列（“t-元件”）相对应序列的转录本。这些重复序列理论上能够形成类似tRNA的二级结构，尽管在体内无法检测到与之对应的稳定转录本。我们发现t-元件序列的加工具有与真实tRNA序列相同的特异性和相当的效率。由于已知的t-元件位于小麦线粒体DNA中与活性基因（18S-5S、26S、tRNA(Pro)）相邻且转录方向相同的位置，我们的结果提出了一个问题，即t-元件是否在小麦线粒体的基因表达中发挥作用。
