Hefei National Laboratory for Physical Science at the Microscale, School of Life Sciences, University of Science and Technology of China, 96 Jinzhai Road, Hefei, Anhui 230027, China.
High Magnet Field Laboratory, Chinese Academy of Science, 50 Shushanhu Road, Hefei, Anhui 230031, China.
Nucleic Acids Res. 2019 Jan 10;47(1):495-508. doi: 10.1093/nar/gky1116.
Terminal uridylyl transferase (TUTase) is one type of enzyme that modifies RNA molecules by facilitating the post-transcriptional addition of uridyl ribonucleotides to their 3' ends. Recent researches have reported that Drosophila TUTase, Tailor, exhibits an intrinsic preference for RNA substrates ending in 3'G, distinguishing it from any other known TUTases. Through this unique feature, Tailor plays a crucial role as the repressor in the biogenesis pathway of splicing-derived mirtron pre-miRNAs. Here we describe crystal structures of core catalytic domain of Tailor and its complexes with RNA stretches 5'-AGU-3' and 5'-AGUU-3'. We demonstrate that R327 and N347 are two key residues contributing cooperatively to Tailor's preference for 3'G, and R327 may play an extra role in facilitating the extension of polyuridylation chain. We also demonstrate that conformational stability of the exit of RNA-binding groove also contributes significantly to Tailor's activity. Overall, our work reveals useful insights to explain why Drosophila Tailor can preferentially select RNA substrates ending in 3'G and provides important values for further understanding the biological significances of biogenesis pathway of mirtron in flies.
末端尿苷酰转移酶（TUTase）是一类通过促进尿苷核糖核苷酸在后转录添加到其 3' 末端来修饰 RNA 分子的酶。最近的研究报告称，果蝇 TUTase Tailor 对以 3'G 结尾的 RNA 底物表现出内在的偏好，使其与任何其他已知的 TUTase 区分开来。通过这种独特的特征，Tailor 作为剪接衍生的 mirtron 前体 miRNA 生物发生途径中的抑制剂起着至关重要的作用。在这里，我们描述了 Tailor 的核心催化结构域及其与 RNA 链 5'-AGU-3' 和 5'-AGUU-3' 的复合物的晶体结构。我们证明 R327 和 N347 是两个关键残基，它们协同作用，导致 Tailor 对 3'G 的偏好，并且 R327 可能在促进多聚尿苷酸化链的延伸中发挥额外的作用。我们还证明了 RNA 结合槽出口的构象稳定性对 Tailor 的活性也有很大贡献。总的来说，我们的工作揭示了有用的见解，解释了为什么果蝇 Tailor 可以优先选择以 3'G 结尾的 RNA 底物，并为进一步了解 mirtron 在果蝇中的生物发生途径的生物学意义提供了重要价值。
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