发布: 2020年06月20日第10卷第12期 DOI: 10.21769/BioProtoc.3646 浏览次数: 3650
评审: Beatrice LiChristian RothLouise Jane Walport
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Abstract
Transfer RNAs (tRNAs) are heavily decorated with post-transcriptional modifications during their biosynthesis. To fulfil their functions within cells, tRNAs undergo a tightly controlled biogenesis process leading to the formation of mature tRNAs. In addition, functions of tRNAs are often modulated by their modifications. Although the biological importance of post-transcriptional RNA modifications is widely appreciated, methods to directly detect their introduction during RNA biosynthesis are rare and do not easily provide information on the temporal nature of events. To obtain information on the tRNA maturation process, we have developed a methodology, using NMR as a tool to monitor tRNA maturation in a non-disruptive and continuous fashion in cellular extracts. By following the maturation of a model yeast tRNA with time-resolved NMR, we showed that modifications are introduced in a defined sequential order, and that the chronology is controlled by cross-talk between modification events. The implementation of this method requires the production for NMR spectroscopy of tRNA samples with different modification status, in order to identify the NMR signature of individual modifications. The production of tRNA samples for the analysis of modification pathways with NMR spectroscopy will be presented here and examplified on the yeast tRNAPhe, but can be extended to any other tRNA by changing the sequence of the construct. The protocol describes the production of unmodified tRNA samples by in vitro transcription, and the production of modified tRNA samples by recombinant expression of tRNAs in E. coli.
Keywords: Transfer RNA (转运RNA)Background
In all domains of life, the synthesis and maturation of RNAs involve post-transcriptional chemical modifications of their nucleotides at specific sites. Among the different RNA families, tRNAs display not only the highest variety of chemical modifications, but also the highest density of modification per transcript (~8-25% of modified nucleotides in tRNAs of various organisms) (Boccaletto et al., 2018). The biogenesis of tRNAs is tightly regulated, and in particular, the introduction of post-transcriptional modifications in tRNAs is controlled and influenced by multiple factors (El Yacoubi et al., 2012; Jackman and Alfonzo, 2013; Barraud and Tisné, 2019). Although all aspects of tRNA biology are controlled and modulated by modifications, methods to directly detect their introduction during tRNA biosynthesis are rare and do not easily provide information on the temporality of modification events. We have developed a methodology, using NMR as a tool to monitor tRNA maturation in a non-disruptive and continuous fashion (Barraud et al., 2019). Briefly, introducing isotope-labeled tRNAs into unlabeled cell extracts containing the cellular enzymatic activities combined with the use of isotope-filters in NMR experiments enables the detection of the tRNA of interest within the complex cell extract environment. This method requires the production of tRNA samples with different modification status, in order to identify the NMR signature of individual modifications (Barraud et al., 2019).
Here we describe the production and purification of two forms of the yeast tRNAPhe differing in their modification content. The first sample corresponds to a yeast tRNAPhe produced by in vitro transcription, which presents no post-transcriptional modifications. The second sample corresponds to a recombinant yeast tRNAPhe produced in an E. coli strain overproducing this tRNA. Since E. coli has a less prolific but related tRNA modification machinery than S. cerevisiae, the modification pattern of this sample resembles that of the fully modified yeast tRNAPhe, but overall exhibits fewer modifications (Barraud et al., 2019). The production and purification of tRNA samples with different modification content is essential to reveal the NMR signature of individual post-transcriptional modifications and correspond to the first steps towards the time-resolved NMR monitoring of tRNA maturation (Barraud et al., 2019). The reported protocol describes the production of unmodified tRNA samples by in vitro transcription, and the production of modified tRNA samples by recombinant expression of tRNAs in E. coli. These productions and purifications will be examplified on the yeast tRNAPhe. Part of the protocol has been published elsewhere (Barraud et al., 2019), but some parts are described here in more detail. Protocol for the expression and purification of active T7 RNA polymerase in E. coli are not detailed here, but have been described comprehensively elsewhere (Rio, 2013; Dégut et al., 2016).
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文章信息
版权信息
© 2020 The Authors; exclusive licensee Bio-protocol LLC.
如何引用
Catala, M., Gato, A., Tisné, C. and Barraud, P. (2020). Preparation of Yeast tRNA Sample for NMR Spectroscopy. Bio-protocol 10(12): e3646. DOI: 10.21769/BioProtoc.3646.
分类
生物物理学 > 核磁共振波谱法 > 体内NMR光谱法
生物化学 > RNA > RNA结构
分子生物学 > RNA > RNA 纯化
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