Institute of Bioinformatics, University of Muenster, Muenster, Germany.
Int J Biol Sci. 2012;8(3):344-52. doi: 10.7150/ijbs.3933. Epub 2012 Feb 17.
Most of eukaryotic genes are interrupted by introns that need to be removed from pre-mRNAs before they can perform their function. This is done by complex machinery called spliceosome. Many eukaryotes possess two separate spliceosomal systems that process separate sets of introns. The major (U2) spliceosome removes majority of introns, while minute fraction of intron repertoire is processed by the minor (U12) spliceosome. These two populations of introns are called U2-type and U12-type, respectively. The latter fall into two subtypes based on the terminal dinucleotides. The minor spliceosomal system has been lost independently in some lineages, while in some others few U12-type introns persist. We investigated twenty insect genomes in order to better understand the evolutionary dynamics of U12-type introns. Our work confirms dramatic drop of U12-type introns in Diptera, leaving these genomes just with a handful cases. This is mostly the result of intron deletion, but in a number of dipteral cases, minor type introns were switched to a major type, as well. Insect genes that harbor U12-type introns belong to several functional categories among which proteins binding ions and nucleic acids are enriched and these few categories are also overrepresented among these genes that preserved minor type introns in Diptera.
大多数真核基因都被内含子打断，这些内含子需要在执行功能之前从前体 mRNA 中去除。这是通过一种称为剪接体的复杂机制完成的。许多真核生物拥有两个独立的剪接体系统，分别处理不同的内含子集。主要的（U2）剪接体去除大部分内含子，而少量内含子由次要的（U12）剪接体处理。这两种内含子群体分别称为 U2 型和 U12 型。后者根据末端二核苷酸分为两个亚型。少数剪接体系统在一些谱系中独立丢失，而在其他一些谱系中则保留了少量 U12 型内含子。我们研究了二十种昆虫基因组，以更好地了解 U12 型内含子的进化动态。我们的工作证实了 U12 型内含子在双翅目昆虫中的急剧减少，这些基因组只剩下少数几个案例。这主要是由于内含子缺失，但在一些双翅目昆虫的情况下，次要类型的内含子也被转换为主要类型。含有 U12 型内含子的昆虫基因属于几个功能类别，其中包括结合离子和核酸的蛋白质，而这些少数类别在保留了双翅目昆虫中次要类型内含子的基因中也过度表达。
