RNA Biology Laboratory, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Frederick, MD 21702, USA; Department of Cell Biology, Yale School of Medicine, New Haven, CT 06510, USA.
RNA Biology Laboratory, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Frederick, MD 21702, USA.
Cell Rep. 2020 Dec 22;33(12):108527. doi: 10.1016/j.celrep.2020.108527.
Many bacteria contain an RNA repair operon, encoding the RtcB RNA ligase and the RtcA RNA cyclase, that is regulated by the RtcR transcriptional activator. Although RtcR contains a divergent version of the CARF (CRISPR-associated Rossman fold) oligonucleotide-binding regulatory domain, both the specific signal that regulates operon expression and the substrates of the encoded enzymes are unknown. We report that tRNA fragments activate operon expression. Using a genetic screen in Salmonella enterica serovar Typhimurium, we find that the operon is expressed in the presence of mutations that cause tRNA fragments to accumulate. RtcA, which converts RNA phosphate ends to 2', 3'-cyclic phosphate, is also required. Operon expression and tRNA fragment accumulation also occur upon DNA damage. The CARF domain binds 5' tRNA fragments ending in cyclic phosphate, and RtcR oligomerizes upon binding these ligands, a prerequisite for operon activation. Our studies reveal a signaling pathway involving broken tRNAs and implicate the operon in tRNA repair.
许多细菌都含有一个 RNA 修复操纵子，该操纵子编码 RtcB RNA 连接酶和 RtcA RNA 环化酶，由 RtcR 转录激活因子调控。尽管 RtcR 含有一个不同的 CARF（CRISPR 相关的 Rossman 折叠）寡核苷酸结合调节结构域，但调节操纵子表达的特定信号和编码酶的底物都是未知的。我们报告说 tRNA 片段激活操纵子表达。在鼠伤寒沙门氏菌中使用遗传筛选，我们发现当导致 tRNA 片段积累的突变存在时，操纵子会表达。还需要具有将 RNA 磷酸末端转化为 2'，3'-环磷酸的 RtcA。当发生 DNA 损伤时，操纵子表达和 tRNA 片段积累也会发生。CARF 结构域结合以环状磷酸结尾的 5' tRNA 片段，并且在结合这些配体时 RtcR 寡聚化，这是操纵子激活的前提。我们的研究揭示了涉及断裂 tRNA 的信号通路，并表明该操纵子参与 tRNA 修复。
