Logsdon J M, Tyshenko M G, Dixon C, D-Jafari J, Walker V K, Palmer J D
Department of Biology, Indiana University, Bloomington 47405, USA.
Proc Natl Acad Sci U S A. 1995 Aug 29;92(18):8507-11. doi: 10.1073/pnas.92.18.8507.
The gene encoding the glycolytic enzyme triose-phosphate isomerase (TPI; EC 5.3.1.1) has been central to the long-standing controversy on the origin and evolutionary significance of spliceosomal introns by virtue of its pivotal support for the introns-early view, or exon theory of genes. Putative correlations between intron positions and TPI protein structure have led to the conjecture that the gene was assembled by exon shuffling, and five TPI intron positions are old by the criterion of being conserved between animals and plants. We have sequenced TPI genes from three diverse eukaryotes--the basidiomycete Coprinus cinereus, the nematode Caenorhabditis elegans, and the insect Heliothis virescens--and have found introns at seven novel positions that disrupt previously recognized gene/protein structure correlations. The set of 21 TPI introns now known is consistent with a random model of intron insertion. Twelve of the 21 TPI introns appear to be of recent origin since each is present in but a single examined species. These results, together with their implication that as more TPI genes are sequenced more intron positions will be found, render TPI untenable as a paradigm for the introns-early theory and, instead, support the introns-late view that spliceosomal introns have been inserted into preexisting genes during eukaryotic evolution.
编码糖酵解酶磷酸丙糖异构酶（TPI；EC 5.3.1.1）的基因，一直处于关于剪接体内含子起源及进化意义的长期争论的核心位置，因为它为内含子早期观点或基因外显子理论提供了关键支持。内含子位置与TPI蛋白质结构之间的假定关联，引发了该基因是通过外显子重排组装而成的推测，并且按照在动物和植物之间保守这一标准，五个TPI内含子位置是古老的。我们对三种不同的真核生物——担子菌灰盖鬼伞、线虫秀丽隐杆线虫和昆虫烟草天蛾——的TPI基因进行了测序，发现了七个新的内含子位置，这些位置破坏了先前公认的基因/蛋白质结构关联。目前已知的21个TPI内含子与内含子插入的随机模型一致。21个TPI内含子中有12个似乎是近期起源的，因为每个内含子只存在于一个被检测的物种中。这些结果，连同它们所暗示的随着更多TPI基因被测序将发现更多内含子位置，使得TPI作为内含子早期理论的范例变得站不住脚，相反，支持了内含子晚期观点，即剪接体内含子是在真核生物进化过程中插入到已有的基因中的。
