Operon conservation and the evolution of trans-splicing in the phylum Nematoda.
Operon conservation and the evolution of trans-splicing in the phylum Nematoda.
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DOI：
10.1371/journal.pgen.0020198
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发表时间：
2006-11-24
期刊：
影响因子：
4.5
通讯作者：
Blaxter ML
中科院分区：
文献类型：
--
作者：
Guiliano DB;Blaxter ML
线虫秀丽隐杆线虫在模式动物中是独特的，因为它的许多基因被共转录为来自操纵子的多顺反子前mRNA。这些操纵子转录物被分解成成熟mRNA的机制包括反式剪接成SL 2样剪接的前导外显子家族。SL2样剪接前导序列与C.线虫和其他线虫物种。我们调查了另外五种线虫，代表线虫门的五个主要分支中的三个，操纵子的存在和使用反式剪接的领导人在多顺反子前mRNA的分辨率。保守操纵子存在于太平洋棱线虫、巴西日本圆线虫、拉氏圆线虫、马来丝虫和猪蛔虫中。在线虫中，与棒状菌素C关系密切。在线虫中，SL2样剪接前导序列的相关家族用于操纵子转录物解析。然而，在Tylenchine S.使用与SL 1相关的剪接前导序列家族解析ratti操纵子转录物。非操纵子基因在S. Ratti也可能接受这些SL1变体。螺旋线虫B. malayi和A.猪操纵子转录本使用SL1解析。映射这些表型到强大的分子遗传学的线虫表明，操纵子SL 2样剪接的领导人，这是一个进化发明的杆细胞谱系之前演变。秀丽隐杆线虫的基因组是所有动物中第一个被完全测序的。在这种蠕虫的基因组中，一个令人惊讶的发现是，大约五分之一的基因是由两到八个基因组成的，这些基因由同一个启动子表达，类似于细菌的“操纵子”。由这些操纵子产生的前mRNA通过称为SL反式剪接的分子间连接过程进行加工。其他动物基因组，如人类基因组或果蝇基因组，既不含操纵子，也不含SL反式剪接。在这篇文章中，吉里安诺和布拉克斯特研究了基因组组织的这一奇特方面是否是C。线虫和近亲通过检查广泛的寄生和自由生活的线虫的基因组。作者发现操纵子和反式剪接都存在于线虫中，并且操纵子与其他基因组特征一样进化。所有被调查的物种都使用反式剪接将其多基因前mRNA分解为单基因mRNA，但细节与C.优美的特别是，连接到操纵子衍生的mRNA的开始的RNA的短片段在许多线虫组中独立地改变。
The nematode Caenorhabditis elegans is unique among model animals in that many of its genes are cotranscribed as polycistronic pre-mRNAs from operons. The mechanism by which these operonic transcripts are resolved into mature mRNAs includes trans-splicing to a family of SL2-like spliced leader exons. SL2-like spliced leaders are distinct from SL1, the major spliced leader in C. elegans and other nematode species. We surveyed five additional nematode species, representing three of the five major clades of the phylum Nematoda, for the presence of operons and the use of trans-spliced leaders in resolution of polycistronic pre-mRNAs. Conserved operons were found in Pristionchus pacificus, Nippostrongylus brasiliensis, Strongyloides ratti, Brugia malayi, and Ascaris suum. In nematodes closely related to the rhabditine C. elegans, a related family of SL2-like spliced leaders is used for operonic transcript resolution. However, in the tylenchine S. ratti operonic transcripts are resolved using a family of spliced leaders related to SL1. Non-operonic genes in S. ratti may also receive these SL1 variants. In the spirurine nematodes B. malayi and A. suum operonic transcripts are resolved using SL1. Mapping these phenotypes onto the robust molecular phylogeny for the Nematoda suggests that operons evolved before SL2-like spliced leaders, which are an evolutionary invention of the rhabditine lineage. The genome of the nematode worm Caenorhabditis elegans was the first of any animal to be completely sequenced. One surprising finding in this worm's genome was that about one-fifth of its genes were organised as sets of from two to eight genes expressed from the same promoter, similar to bacterial “operons.” The pre-mRNAs made from these operons are processed by an intermolecular ligation process called SL trans-splicing. Other animal genomes, such as the human genome or that of the fruit fly contain neither operons nor SL trans-splicing. In this article, Guiliano and Blaxter have investigated whether this curious facet of genome organisation is peculiar to C. elegans and close relatives by examining the genomes of a wide range of parasitic and free-living nematodes. The authors find that both operons and trans-splicing are present across the nematodes, and that operons evolve as other genome features do. All of the species surveyed use trans-splicing to resolve their multigene pre-mRNAs into single-gene mRNAs, but the details differ significantly from the process in C. elegans. In particular, the short piece of RNA that is attached to the beginning of operon-derived mRNAs has changed independently in many nematode groups.
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