Preferential loss and gain of introns in 3′ portions of genes suggests a reverse-transcription mechanism of intron insertion
Preferential loss and gain of introns in 3′ portions of genes suggests a reverse-transcription mechanism of intron insertion
复制标题
DOI：
10.1016/j.gene.2004.05.027
复制
发表时间：
2004-08-18
期刊：
影响因子：
3.5
通讯作者：
Koonin, EV
中科院分区：
文献类型：
--
作者：
Sverdlov, AV;Babenko, VN;Koonin, EV
为了深入了解真核生物蛋白质编码基因中内含子进化的动态，研究了在遥远的同源谱系之间保守的旧内含子和沿着基因长度的新的谱系特异性内含子的分布。在基因的5' -区域中检测到显著过量的旧内含子。新的内含子，当大量分析时，从5'端到3'端几乎呈扁平分布.然而，分析新的内含子在个别基因组中的分布显示显着的谱系特异性功能。而在内含子贫乏的基因组中，特别是在酵母裂殖酵母（Schizosophyomycespombe，Sp）中，基因的5' -部分比3' -部分含有显著更多数量的新内含子，而人类和拟南芥的富含内含子的基因组显示出相反的趋势。这些观察结果似乎与这样的观点相一致，即内含子丢失和插入基因的3'端部分比插入5'端部分更频繁。介导内含子丢失的cDNA中3' -末端序列的过度表达似乎是基因远端部分内含子明显优先丢失的最可能解释。内含子在3' -部分的优先插入表明内含子可能通过逆转录介导的途径插入，类似于内含子丢失所涉及的途径。这种机制可能涉及在逆转录过程中编码区的一部分的复制，随后是同源重组和随后的拷贝中的快速序列差异，成为一个新的内含子。(C)2004 Elsevier B. V.保留所有权利。
In an attempt to gain insight into the dynamics of intron evolution in eukaryotic protein-coding genes, the distributions of old introns, that are conserved between distant phylogenctic lineages, and new, lineage-specific introns along the gene length, were examined. A significant excess of old introns in 5' -regions of genes was detected. New introns, when analyzed in bulk, showed a nearly flat distribution from the 5' to the 3' -end. However, analysis of new intron distributions in individual genomes revealed notable lineage-specific features. While in intron-poor genomes, particularly yeast Schizosaccharomyces pombe (Sp), the 5' -portions of genes contain a significantly greater number of new introns than the 3' -portions, the intron-rich genomes of humans and Arabidopsis show the opposite trend. These observations seem to be compatible with the view that introns are both lost and inserted in 3' -terminal portions of genes more often than in 5' -portions. Overrepresentation of 3' -terminal sequences among cDNAs that mediate intron loss appears to be the most likely explanation for the apparent preferential loss of introns in the distal parts of genes. Preferential insertion of introns in the 3' -portions suggests that introns might be inserted via a reverse-transcription-mediated pathway similar to that implicated in intron loss. This mechanism could involve duplication of a portion of the coding region during reverse transcription followed by homologous recombination and subsequent rapid sequence divergence in the copy that becomes a new intron. (C) 2004 Elsevier B.V. All rights reserved.