Patthy L
FEBS Lett. 1987 Apr 6;214(1):1-7. doi: 10.1016/0014-5793(87)80002-9.
Exon insertions and exon duplications, two major mechanisms of exon shuffling, are shown to involve modules that have introns of the same phase class at both their 5'- and 3'-ends. At the sites of intronic recombinations exon insertions and duplications create new introns which belong to the same phase class as the recipient introns. As a consequence of repeated exon insertions and exon duplications introns of a single phase class predominate in the resulting genes, i.e. gene assembly by exon shuffling is reflected both by this nonrandom intron phase usage and by the correlation between the domain organization of the proteins and exon-intron organization of their genes. Genes that appeared before the eukaryote-prokaryote split do not show these diagnostic signs of exon shuffling. Since ancestral introns (e.g. self-splicing introns) did not favour intronic recombination, exon shuffling may not have been significant in the early part of protein evolution.
外显子插入和外显子重复是外显子重排的两种主要机制，研究表明，它们所涉及的模块在其5'端和3'端都具有相同相位类别的内含子。在内含子重组位点，外显子插入和重复会产生新的内含子，这些新内含子与受体内含子属于相同的相位类别。由于重复的外显子插入和外显子重复，单一相位类别的内含子在最终形成的基因中占主导地位，也就是说，外显子重排导致的基因组装既体现在这种非随机的内含子相位使用上，也体现在蛋白质的结构域组织与其基因的外显子-内含子组织之间的相关性上。在真核生物与原核生物分化之前出现的基因并未表现出这些外显子重排的诊断特征。由于祖先内含子（如自我剪接内含子）不倾向于内含子重组，外显子重排在蛋白质进化早期可能并不显著。
