Vibranovski Maria Dulcetti, Sakabe Noboru Jo, de Oliveira Rodrigo Soares, de Souza Sandro José
Ludwig Institute for Cancer Research, Sao Paulo Branch, CEP, São Paulo, SP, 01509-010, Brazil.
J Mol Evol. 2005 Sep;61(3):341-50. doi: 10.1007/s00239-004-0318-y. Epub 2005 Jul 18.
Exon-shuffling is an important mechanism accounting for the origin of many new proteins in eukaryotes. However, its role in the creation of proteins in the ancestor of prokaryotes and eukaryotes is still debatable. Excess of symmetric exons is thought to represent evidence for exon-shuffling since the exchange of exons flanked by introns of the same phase does not disrupt the reading frame of the host gene. In this report, we found that there is a significant correlation between symmetric units of shuffling and the age of protein domains. Ancient domains, present in both prokaryotes and eukaryotes, are more frequently bounded by phase 0 introns and their distribution is biased towards the central part of proteins. Modern domains are more frequently bounded by phase 1 introns and are present predominantly at the ends of proteins. We propose a model in which shuffling of ancient domains mainly flanked by phase 0 introns was important in the ancestor of eukaryotes and prokaryotes, during the creation of the central part of proteins. Shuffling of modern domains, predominantly flanked by phase 1 introns, accounted for the origin of the extremities of proteins during eukaryotic evolution.
外显子洗牌是一种重要机制，可解释真核生物中许多新蛋白质的起源。然而，它在原核生物和真核生物共同祖先的蛋白质形成过程中的作用仍存在争议。由于相同相位内含子侧翼的外显子交换不会破坏宿主基因的阅读框，因此对称外显子的过量被认为是外显子洗牌的证据。在本报告中，我们发现洗牌的对称单元与蛋白质结构域的年龄之间存在显著相关性。原核生物和真核生物中都存在的古老结构域更频繁地由0相位内含子界定，并且它们的分布偏向于蛋白质的中心部分。现代结构域更频繁地由1相位内含子界定，并且主要存在于蛋白质的末端。我们提出了一个模型，其中主要由0相位内含子侧翼的古老结构域的洗牌在真核生物和原核生物的共同祖先中，在蛋白质中心部分的形成过程中很重要。主要由1相位内含子侧翼的现代结构域的洗牌解释了真核生物进化过程中蛋白质末端的起源。
