Mechanism for DNA transposons to generate introns on genomic scales.
Mechanism for DNA transposons to generate introns on genomic scales.
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DOI：
10.1038/nature20110
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发表时间：
2016-10-27
期刊：
影响因子：
64.8
通讯作者：
Roy SW
中科院分区：
文献类型：
--
作者：
Huff JT;Zilberman D;Roy SW
40年前发现的内含子是分子生物学中最出乎意料的发现之一。内含子是中断基因的序列，其必须作为mRNA产生的一部分被去除。基因组测序计划已经证明，大多数真核基因含有至少一个，往往是许多内含子。这些基因组的比较揭示了一个长期的进化历史，几乎没有内含子的获得由快速，广泛的获得插曲打断。然而，没有详细的机制，这样的情节内含子生成已实证支持足够的规模，尽管有几个建议。在这里，我们展示了如何短的非自主的DNA转座子独立地产生数百至数千个内含子的prasinophyte微单胞菌pusilla和浮游植物Aureococcus anophagefferens。每个转座子携带一个剪接位点。另一个剪接位点是从转座子插入后复制的基因序列中选择的，允许RNA的完美剪接。可以被增选的序列的分布相对于密码子是有偏向的，并且转座子产生的内含子的定相类似地有偏向。这些转座子插入预先存在的核小体之间，使得多个邻近插入产生核小体大小的插入片段。因此，转座子插入和序列互补可以解释真核生物中观察到的核小体大小的外显子的内含子相位偏差和流行。总的来说，这两个独立的增殖元件的例子说明了一个通用的DNA转座子机制，合理地解释了真核生物进化过程中快速，广泛的内含子获得的事件。
Discovered four decades ago, the existence of introns was one of the most unexpected findings in molecular biology. Introns are sequences interrupting genes that must be removed as part of mRNA production. Genome sequencing projects have documented that most eukaryotic genes contain at least one and frequently many introns. Comparison of these genomes reveals a history of long evolutionary periods with little intron gain punctuated by episodes of rapid, extensive gain. However, no detailed mechanism for such episodic intron generation has been empirically supported on a sufficient scale, despite several proposals. Here we show how short non-autonomous DNA transposons independently generated hundreds to thousands of introns in the prasinophyte Micromonas pusilla and the pelagophyte Aureococcus anophagefferens. Each transposon carries one splice site. The other splice site is co-opted from gene sequence duplicated upon transposon insertion, allowing perfect splicing out of RNA. The distributions of sequences that can be co-opted are biased with respect to codons, and phasing of transposon-generated introns is similarly biased. These transposons insert between preexisting nucleosomes, so that multiple nearby insertions generate nucleosome-sized intervening segments. Thus, transposon insertion and sequence co-option may explain the intron phase biases and prevalence of nucleosome-sized exons observed in eukaryotes. Overall, the two independent examples of proliferating elements illustrate a general DNA transposon mechanism plausibly accounting for episodes of rapid, extensive intron gain during eukaryotic evolution.
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影响因子：
10.7
作者：
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发表时间：
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影响因子：
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