Mobile Bacterial Group II Introns at the Crux of Eukaryotic Evolution
Mobile Bacterial Group II Introns at the Crux of Eukaryotic Evolution
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DOI：
10.1128/microbiolspec.mdna3-0050-2014
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发表时间：
2015-02-01
影响因子：
3.7
通讯作者：
Belfort, Marlene
中科院分区：
文献类型：
--
作者：
Lambowitz, Alan M.;Belfort, Marlene
本文综述了最近的事态发展，在我们的理解组II内含子的功能，这些内含子的关系，反转录转座子和剪接体，以及它们的共同特点如何告知思考细菌组II内含子作为真核生物进化的关键因素。逆转录酶介导的和宿主因子辅助的内含子逆转录归巢途径被认为与逆转录转座机制一起沿着到细菌中的新位点，其中II组内含子被认为是起源的。通过靶启动逆转录的DNA靶识别和运动推断II组内含子、非LTR逆转录转座子（如LINE元件）和端粒酶之间的进化关系。此外，II组内含子几乎肯定是剪接体内含子的祖先。它们的深刻相似之处包括延伸到RNA催化的剪接化学、反应立体化学以及在RNA活性位点进行催化的两种二价金属的位置。II组内含子和剪接体的小核RNA（snRNA）之间以及高度保守的核心剪接体蛋白Prp 8和II组内含子样逆转录酶之间也存在序列和结构相似性。有人提出，第二组内含子进入真核生物在细菌内共生或细菌-古细菌融合，核基因组内增殖，需要核膜的进化，和片段化产生剪接体内含子。因此，这些细菌自剪接移动的元件从根本上影响了现存真核基因组的组成，包括人类基因组，其中大部分来自移动的II组内含子的近亲。
This review focuses on recent developments in our understanding of group II intron function, the relationships of these introns to retrotransposons and spliceosomes, and how their common features have informed thinking about bacterial group II introns as key elements in eukaryotic evolution. Reverse transcriptase-mediated and host factor-aided intron retrohoming pathways are considered along with retrotransposition mechanisms to novel sites in bacteria, where group II introns are thought to have originated. DNA target recognition and movement by target-primed reverse transcription infer an evolutionary relationship among group II introns, non-LTR retrotransposons, such as LINE elements, and telomerase. Additionally, group II introns are almost certainly the progenitors of spliceosomal introns. Their profound similarities include splicing chemistry extending to RNA catalysis, reaction stereochemistry, and the position of two divalent metals that perform catalysis at the RNA active site. There are also sequence and structural similarities between group II introns and the spliceosome's small nuclear RNAs (snRNAs) and between a highly conserved core spliceosomal protein Prp8 and a group II intron-like reverse transcriptase. It has been proposed that group II introns entered eukaryotes during bacterial endosymbiosis or bacterial-archaeal fusion, proliferated within the nuclear genome, necessitating evolution of the nuclear envelope, and fragmented giving rise to spliceosomal introns. Thus, these bacterial self-splicing mobile elements have fundamentally impacted the composition of extant eukaryotic genomes, including the human genome, most of which is derived from close relatives of mobile group II introns.