Institute of Enzymology, Research Centre for Natural Sciences, Hungarian Academy of Sciences, Budapest, H-1117, Hungary.
Biol Direct. 2019 Jan 16;14(1):2. doi: 10.1186/s13062-019-0231-3.
ᅟ: Animals are known to have higher rates of exon skipping than other eukaryotes. In a recent study, Grau-Bové et al. (Genome Biology 19:135, 2018) have used RNA-seq data across 65 eukaryotic species to investigate when and how this high prevalence of exon skipping evolved. They have found that bilaterian Metazoa have significantly increased exon skipping frequencies compared to all other eukaryotic groups and that exon skipping in nearly all animals, including non-bilaterians, is strongly enriched for frame-preserving events. The authors have hypothesized that "the increase of exon skipping rates in animals followed a two-step process. First, exon skipping in early animals became enriched for frame-preserving events. Second, bilaterian ancestors dramatically increased their exon skipping frequencies, likely driven by the interplay between a shift in their genome architectures towards more exon definition and recruitment of frame-preserving exon skipping events to functionally diversify their cell-specific proteomes." Here we offer a different explanation for the higher frequency of frame-preserving exon skipping in Metzoa than in all other eukaryotes. In our view these observations reflect the fact that the majority of multidomain proteins unique to metazoa and indispensable for metazoan type multicellularity were assembled by exon-shuffling from 'symmetrical' modules (i.e. modules flanked by introns of the same phase), whereas this type of protein evolution played a minor role in other groups of eukaryotes, including plants. The higher frequency of 'symmetrical' exons in Metazoan genomes provides an explanation for the enrichment for frame-preserving events since skipping or inclusion of 'symmetrical' modules during alternative splicing does not result in a reading-frame shift. REVIEWERS: This article was reviewed by Manuel Irimia, Ashish Lal and Erez Levanon. The reviewers were nominated by the Editorial Board.
动物的外显子跳跃率高于其他真核生物。在最近的一项研究中，Grau-Bové 等人（Genome Biology 19:135, 2018）利用 65 种真核生物的 RNA-seq 数据，研究了外显子跳跃的这种高普遍性是何时以及如何进化而来的。他们发现，两侧对称动物的外显子跳跃频率明显高于所有其他真核生物群，而几乎所有动物（包括非两侧对称动物）的外显子跳跃都强烈富集了保框事件。作者假设“动物中外显子跳跃率的增加经历了两步过程。首先，早期动物中外显子跳跃变得富含保框事件。其次，两侧对称动物的祖先极大地增加了它们的外显子跳跃频率，这可能是由于它们的基因组结构向更多外显子定义的转变以及保框外显子跳跃事件的招募，以使其细胞特异性蛋白质组多样化。”在这里，我们提供了一个关于 Metazoan 中外显子跳跃频率高于其他真核生物的不同解释。在我们看来，这些观察结果反映了这样一个事实，即在多域蛋白中，大多数独特于 Metazoan 且对 Metazoan 型多细胞性必不可少的蛋白是通过从“对称”模块（即侧翼为相同相位内含子的模块）进行外显子洗牌组装而成的，而这种类型的蛋白质进化在其他真核生物群中，包括植物，作用较小。Metazoan 基因组中外显子的更高频率“对称”解释了保框事件的富集，因为在选择性剪接中外显子或“对称”模块的缺失或包含不会导致阅读框移位。审稿人：这篇文章由 Manuel Irimia、Ashish Lal 和 Erez Levanon 进行了评审。审稿人由编委会提名。
