Randau Lennart, Schröder Imke, Söll Dieter
Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06520-8114, USA.
Nature. 2008 May 1;453(7191):120-3. doi: 10.1038/nature06833.
The universality of ribonuclease P (RNase P), the ribonucleoprotein essential for transfer RNA (tRNA) 5' maturation, is challenged in the archaeon Nanoarchaeum equitans. Neither extensive computational analysis of the genome nor biochemical tests in cell extracts revealed the existence of this enzyme. Here we show that the conserved placement of its tRNA gene promoters allows the synthesis of leaderless tRNAs, whose presence was verified by the observation of 5' triphosphorylated mature tRNA species. Initiation of tRNA gene transcription requires a purine, which coincides with the finding that tRNAs with a cytosine in position 1 display unusually extended 5' termini with an extra purine residue. These tRNAs were shown to be substrates for their cognate aminoacyl-tRNA synthetases. These findings demonstrate how nature can cope with the loss of the universal and supposedly ancient RNase P through genomic rearrangement at tRNA genes under the pressure of genome condensation.
核糖核酸酶P（RNase P）是参与转运RNA（tRNA）5'端成熟过程的核糖核蛋白，其普遍性在古菌嗜热栖热菌中受到挑战。对该基因组进行的广泛计算分析以及对细胞提取物进行的生化测试均未揭示这种酶的存在。在此，我们表明其tRNA基因启动子的保守位置允许合成无前导序列的tRNA，通过观察5'三磷酸化的成熟tRNA种类证实了其存在。tRNA基因转录的起始需要一个嘌呤，这与以下发现一致：在第1位含有胞嘧啶的tRNA显示出异常延长的5'末端，带有一个额外的嘌呤残基。这些tRNA被证明是其同源氨酰-tRNA合成酶的底物。这些发现证明了在基因组压缩的压力下，自然如何通过tRNA基因的基因组重排来应对普遍存在且被认为古老的RNase P的缺失。
