Choisne N, Carneiro V T, Pelletier G, Small I
Station de Génétique et d'Amélioration des Plantes, INRA, Versailles, France.
Plant Mol Biol. 1998 Jan;36(1):113-23. doi: 10.1023/a:1005988004924.
A comparison of 5'-flanking sequences from 68 different nuclear plant tRNA genes was analyzed to find consensus sequences. Three conserved features stood out, all of which are present in the tRNA(Leu) gene used in this study: (1) a high proportion of A and T residues upstream of all tRNA genes; (2) a region of low duplex stability about 30-35 bp before the coding sequence, often containing a TATA-box like motif; (3) a CAA triplet in the region of the presumed transcription start. The effect of replacement of the AT-rich upstream sequences with GC-rich sequences or unrelated AT-rich sequences was tested by progressive deletions and by inserting randomly cloned sequences upstream of the tRNA gene. GC-rich 5'-flanking sequences were found to be generally incompatible with high levels of expression. The TATA-box like motifs and the CAA triplet were removed or altered by deletion or directed mutagenesis. Mutation of the CAA triplet significantly decreased expression of the tRNA(Leu) gene, suggesting that this CAA triplet is important for transcription efficiency, but mutation or elimination of the TATA-box like motifs generally had little effect. The presence or absence of each of these features in tRNA genes from other organisms is discussed; there are clear and interesting differences between plant tRNA genes and those of yeast and mammals.
对68个不同的植物核tRNA基因的5'侧翼序列进行了比较分析，以寻找共有序列。有三个保守特征很突出，所有这些特征都存在于本研究中使用的tRNA（Leu）基因中：（1）所有tRNA基因上游的A和T残基比例很高；（2）在编码序列前约30-35 bp处有一个双链稳定性较低的区域，通常含有一个类似TATA框的基序；（3）在假定的转录起始区域有一个CAA三联体。通过逐步缺失以及在tRNA基因上游插入随机克隆的序列，测试了用富含GC的序列或不相关的富含AT的序列替换富含AT的上游序列的效果。发现富含GC的5'侧翼序列通常与高水平表达不相容。通过缺失或定向诱变去除或改变了类似TATA框的基序和CAA三联体。CAA三联体的突变显著降低了tRNA（Leu）基因的表达，表明该CAA三联体对转录效率很重要，但类似TATA框基序的突变或消除通常影响很小。讨论了其他生物的tRNA基因中这些特征的有无；植物tRNA基因与酵母和哺乳动物的tRNA基因之间存在明显且有趣的差异。
