Department of Genetics, University of Georgia, Athens, GA 30602, USA.
Department of Microbiology, University of Georgia, Athens, GA 30602, USA.
Nucleic Acids Res. 2020 Mar 18;48(5):2564-2578. doi: 10.1093/nar/gkz1188.
Ribonuclease P (RNase P) is essential for the 5'-end maturation of tRNAs in all kingdoms of life. In Escherichia coli, temperature sensitive mutations in either its protein (rnpA49) and or RNA (rnpB709) subunits lead to inviability at nonpermissive temperatures. Using the rnpA49 temperature sensitive allele, which encodes a partially defective RNase P at the permissive temperature, we show here for the first time that the processing of RNase P-dependent polycistronic tRNA operons to release pre-tRNAs is the essential function of the enzyme, since the majority of 5'-immature tRNAs can be aminoacylated unless their 5'-extensions ≥8 nt. Surprisingly, the failure of 5'-end maturation elicits increased polyadenylation of some pre-tRNAs by poly(A) polymerase I (PAP I), which exacerbates inviability. The absence of PAP I led to improved aminoacylation of 5'-immature tRNAs. Our data suggest a more dynamic role for PAP I in maintaining functional tRNA levels in the cell.
核糖核酸酶 P（RNase P）对于所有生命领域的 tRNA 5'-端成熟是必不可少的。在大肠杆菌中，其蛋白质（rnpA49）和/或 RNA（rnpB709）亚基中的温度敏感突变导致在非许可温度下无法生存。使用 rnpA49 温度敏感等位基因，该基因在许可温度下编码部分缺陷的 RNase P，我们首次表明，依赖 RNase P 的多顺反子 tRNA 操纵子的加工以释放前 tRNA 是酶的必需功能，因为大多数 5'-不成熟 tRNA 可以被氨酰化，除非它们的 5'-延伸≥8nt。令人惊讶的是，5'-端成熟的失败会引发多聚（A）聚合酶 I（PAP I）对一些前 tRNA 的过度多腺苷酸化，从而加剧了不可知性。缺乏 PAP I 导致 5'-不成熟 tRNA 的氨酰化得到改善。我们的数据表明，PAP I 在维持细胞中功能性 tRNA 水平方面发挥着更具动态性的作用。
