Deep evolutionary origin of nematode SL2 trans-splicing revealed by genome-wide analysis of the Trichinella spiralis transcriptome
Deep evolutionary origin of nematode SL2 trans-splicing revealed by genome-wide analysis of the Trichinella spiralis transcriptome
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DOI：
10.1101/642082
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发表时间：
2019-05
期刊：
影响因子：
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通讯作者：
Marius A. Wenzel;Christopher Johnston;B. Müller;J. Pettitt;B. Connolly
中科院分区：
文献类型：
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作者：
Marius A. Wenzel;Christopher Johnston;B. Müller;J. Pettitt;B. Connolly
剪接前导反式剪接与真核操作子的存在密切相关，允许多顺反子rna加工成单个mrna。我们对剪接先导反式剪接与操纵子基因表达关系的了解大多来自于对秀丽隐杆线虫的研究。在这种生物体中，识别出两个不同的剪接先导反式剪接事件：SL1，用于替换具有新生单甲基鸟苷帽的前mrna的5 '端；SL2，它提供来自多顺反电子rna的无帽前mrna的5 '端。关于其他线虫的操纵子和剪接前导反式剪接的有限数据表明，sl2型反式剪接是一种相对较新的创新，与多顺反子加工效率的提高有关，并且仅限于5个主要线虫分支中的一个，分支v。我们对旋毛虫的剪接前导反式剪接进行了首次转录组分析。我们的工作确定了一组螺旋线虫sl2型剪接先导体，它们专门用于加工多反反电子RNA，这是在进化枝v之外发现的第一个专门剪接先导体的例子。这些螺旋线虫剪接先导RNA具有一个完美保守的茎环基序，以前被证明是秀丽隐杆线虫多反反电子RNA加工所必需的。我们发现该基序存在于广泛分布于线虫门的剪接先导rna的特定集合中。这项工作极大地修正了我们对线虫剪接前导反式剪接进化的理解，表明SL2反式剪接机制在线虫进化过程中的进化比以前所认识的要早得多，并且在线虫门的整个辐射中都得到了保存。
Spliced leader trans-splicing is intimately associated with the presence of eukaryotic operons, allowing the processing of polycistronic RNAs into individual mRNAs. Most of our understanding of spliced leader trans-splicing as it relates to operon gene expression comes from studies in C. elegans. In this organism, two distinct spliced leader trans-splicing events are recognised: SL1, which is used to replace the 5’ ends of pre-mRNAs that have a nascent monomethyl guanosine cap; and SL2, which provides the 5’ end to uncapped pre-mRNAs derived from polycistronic RNAs. Limited data on operons and spliced leader trans-splicing in other nematodes suggested that SL2-type trans-splicing is a relatively recent innovation, associated with increased efficiency of polycistronic processing, and confined to only one of the five major nematode clades, Clade V. We have conducted the first transcriptome-wide analysis of spliced leader trans-splicing in a nematode species, Trichinella spiralis, which belongs to a clade distantly related to Clade V. Our work identifies a set of T. spiralis SL2-type spliced leaders that are specifically used to process polycistronic RNAs, the first examples of specialised spliced leaders that have been found outside of Clade V. These T. spiralis spliced leader RNAs possess a perfectly conserved stem-loop motif previously shown to be essential for polycistronic RNA processing in C. elegans. We show that this motif is found in specific sets of spliced leader RNAs broadly distributed across the nematode phylum. This work substantially revises our understanding of the evolution of nematode spliced leader trans-splicing, showing that the machinery for SL2 trans-splicing evolved much earlier during nematode evolution than was previously appreciated, and has been conserved throughout the radiation of the nematode phylum.