Department of Chemistry and Biotechnology, Graduate School of Engineering, University of Tokyo, Tokyo, Japan.
Nat Chem Biol. 2016 Aug;12(8):648-55. doi: 10.1038/nchembio.2117. Epub 2016 Jun 27.
Efficient maturation of transfer RNAs (tRNAs) is required for rapid cell growth. However, the precise timing of tRNA processing in coordination with the order of tRNA modifications has not been thoroughly elucidated. To analyze the modification status of tRNA precursors (pre-tRNAs) during maturation, we isolated pre-tRNAs at various stages from Saccharomyces cerevisiae and subjected them to MS analysis. We detected methylated guanosine cap structures at the 5' termini of pre-tRNAs bearing 5' leader sequences. These capped pre-tRNAs accumulated substantially after inhibition of RNase P activity. Upon depletion of the capping enzyme Ceg1p, the steady state level of capped pre-tRNA was markedly reduced. In addition, a population of capped pre-tRNAs accumulated in strains in which 5' exonucleases were inhibited, indicating that the 5' cap structures protect pre-tRNAs from 5'-exonucleolytic degradation during maturation.
tRNA（转移 RNA）的有效成熟对于细胞的快速生长是必需的。然而，tRNA 加工与修饰顺序之间的精确时间协调尚未得到充分阐明。为了分析成熟过程中 tRNA 前体（pre-tRNA）的修饰状态，我们从酿酒酵母中分离了不同阶段的 pre-tRNA，并对其进行了 MS 分析。我们检测到带有 5' 前导序列的 pre-tRNA 的 5' 末端存在甲基化鸟苷帽结构。在 RNase P 活性受到抑制后，这些带帽的 pre-tRNA 大量积累。当 capping 酶 Ceg1p 耗尽时，带帽 pre-tRNA 的稳态水平显著降低。此外，在抑制 5' 外切核酸酶的菌株中积累了一批带帽的 pre-tRNA，表明 5' 帽结构在成熟过程中保护 pre-tRNA 免受 5'-外切核酸酶降解。
