Division of Infectious Diseases, Brigham and Women's Hospital, Boston, MA 02115;
Department of Microbiology, Harvard Medical School, Boston, MA 02115.
Proc Natl Acad Sci U S A. 2019 Jan 22;116(4):1394-1403. doi: 10.1073/pnas.1814130116. Epub 2019 Jan 8.
The factors and mechanisms that govern tRNA stability in bacteria are not well understood. Here, we investigated the influence of posttranscriptional modification of bacterial tRNAs (tRNA modification) on tRNA stability. We focused on ThiI-generated 4-thiouridine (sU), a modification found in bacterial and archaeal tRNAs. Comprehensive quantification of tRNAs revealed that the abundance of some tRNAs is decreased in a Δ strain in a stationary phase-specific manner. Multiple mechanisms, including rapid degradation of a subset of hypomodified tRNAs, account for the reduced abundance of tRNAs in the absence of Through transposon insertion sequencing, we identified additional tRNA modifications that promote tRNA stability and bacterial viability. Genetic analysis of suppressor mutants as well as biochemical analyses revealed that rapid degradation of hypomodified tRNA is mediated by the RNA degradosome. Elongation factor Tu seems to compete with the RNA degradosome, protecting aminoacyl tRNAs from decay. Together, our observations describe a previously unrecognized bacterial tRNA quality control system in which hypomodification sensitizes tRNAs to decay mediated by the RNA degradosome.
细菌中转录后修饰对 tRNA 稳定性的影响
细菌中转录物 tRNA 稳定性的调控因素和机制尚未完全阐明。本研究旨在探讨细菌 tRNA 转录后修饰（tRNA 修饰）对 tRNA 稳定性的影响。研究人员重点关注 ThiI 生成的 4-硫尿嘧啶（sU），这是一种存在于细菌和古细菌 tRNA 中的修饰。通过全面定量 tRNA，研究人员发现某些 tRNA 的丰度在静止期的Δ菌株中以特定方式降低。多种机制，包括部分低修饰 tRNA 的快速降解，导致缺乏时 tRNA 的丰度降低。通过转座子插入测序，鉴定出了其他促进 tRNA 稳定性和细菌存活的 tRNA 修饰。通过对抑制突变体的遗传分析和生化分析，揭示了低修饰 tRNA 的快速降解是由 RNA 降解体介导的。延伸因子 Tu 似乎与 RNA 降解体竞争，保护氨酰 tRNA 免受降解。综上所述，这些发现描述了一个以前未被识别的细菌 tRNA 质量控制体系，其中低修饰使 tRNA 易于被 RNA 降解体介导的降解。
