Masuda Isao, Igarashi Takao, Sakaguchi Reiko, Nitharwal Ram G, Takase Ryuichi, Han Kyu Young, Leslie Benjamin J, Liu Cuiping, Gamper Howard, Ha Taekjip, Sanyal Suparna, Hou Ya-Ming
Department of Biochemistry and Molecular Biology, Thomas Jefferson University, 233 South 10th Street, Philadelphia, PA 19107, USA.
Department of Cell and Molecular Biology, Uppsala University, Box-596, BMC 75124, Uppsala, Sweden.
Nucleic Acids Res. 2017 Apr 20;45(7):4081-4093. doi: 10.1093/nar/gkw1229.
Transfer RNAs (tRNAs) perform essential tasks for all living cells. They are major components of the ribosomal machinery for protein synthesis and they also serve in non-ribosomal pathways for regulation and signaling metabolism. We describe the development of a genetically encoded fluorescent tRNA fusion with the potential for imaging in live Escherichia coli cells. This tRNA fusion carries a Spinach aptamer that becomes fluorescent upon binding of a cell-permeable and non-toxic fluorophore. We show that, despite having a structural framework significantly larger than any natural tRNA species, this fusion is a viable probe for monitoring tRNA stability in a cellular quality control mechanism that degrades structurally damaged tRNA. Importantly, this fusion is active in E. coli live-cell protein synthesis allowing peptidyl transfer at a rate sufficient to support cell growth, indicating that it is accommodated by translating ribosomes. Imaging analysis shows that this fusion and ribosomes are both excluded from the nucleoid, indicating that the fusion and ribosomes are in the cytosol together possibly engaged in protein synthesis. This fusion methodology has the potential for developing new tools for live-cell imaging of tRNA with the unique advantage of both stoichiometric labeling and broader application to all cells amenable to genetic engineering.
转运RNA(tRNA)对所有活细胞都起着至关重要的作用。它们是蛋白质合成核糖体机制的主要组成部分,也参与非核糖体途径的调节和信号代谢。我们描述了一种基因编码的荧光tRNA融合体的开发,它具有在活的大肠杆菌细胞中成像的潜力。这种tRNA融合体携带一个菠菜适配体,在与一种可透过细胞且无毒的荧光团结合后会发出荧光。我们表明,尽管其结构框架比任何天然tRNA种类都大得多,但这种融合体是一种可行的探针,可用于监测细胞质量控制机制中tRNA的稳定性,该机制会降解结构受损的tRNA。重要的是,这种融合体在大肠杆菌活细胞蛋白质合成中具有活性,能够以足以支持细胞生长的速率进行肽基转移,这表明它能被正在进行翻译的核糖体所容纳。成像分析表明,这种融合体和核糖体都被排除在类核之外,这表明融合体和核糖体共同存在于细胞质中,可能参与蛋白质合成。这种融合方法有潜力开发用于tRNA活细胞成像的新工具,具有化学计量标记的独特优势,并且更广泛地应用于所有适合基因工程的细胞。