An analysis of replacement and synonymous changes in the rodent L1 repeat family.
An analysis of replacement and synonymous changes in the rodent L1 repeat family.
复制标题
啮齿动物 L1 重复家族中替换和同义变化的分析。
DOI：
10.1093/oxfordjournals.molbev.a040386
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发表时间：
1986
影响因子：
10.7
通讯作者：
Edgell,MH
中科院分区：
文献类型：
--
作者：
Hardies,SC;Martin,SL;Voliva,CF;Hutchison3rd,CA;Edgell,MH
L1是哺乳动物中的长散布重复序列家族，包括啮齿动物中的BamHI家族和灵长类动物中的Kpn I家族。先前的研究表明，L1重复序列包含一个长的开放阅读框架，并且该家族协同进化。与32个啮齿类动物的DNA序列是可用的元素，我们使用的替代和同义变化的分布，以确定哪些L1谱系已表达其阅读框架。所获得的证据与已经有少量的L1基因表达功能蛋白是一致的。L1的协同进化主要是由于这些功能性L1基因通过将其转录本衍生的序列重新插入基因组中而不断产生非功能性假基因的趋势。新假基因的增加与半衰期为200万年的旧假基因的损失相平衡。因此，大多数观察到的L1重复序列在L1蛋白的表达或进一步复制自身的潜力方面都处于死胡同。然而，L1假基因的周转足以构成大量序列流入和流出所有细胞基因的侧翼区域。如果侧翼L1假基因的存在影响其他基因的表达，即使是在一个微妙的方式，这一过程应该代表了遗传变异的主要来源。第二个层次的协同进化发生在功能性L1序列中，其模式并不符合我们对自私DNA的预期。此外，尽管替代相对于功能L1基因的同义变化受到显著抑制，但它们的总体进化速度加快到它们自己的假基因水平。
L1 is a family of long interspersed repetitive sequences in mammals that includes the BamHI family in rodents and the KpnI family in primates. Previous studies have shown that L1 repeats contain a long open reading frame and that the family evolves in concert. Working with 32 rodent elements for which DNA sequence is available, we used the distribution of replacement and synonymous changes to determine which L1 lineages had been expressing their reading frame. The evidence obtained is consistent with there having been a small number of L1 genes that have been expressing a functional protein. Much of the concerted evolution in L1 is accounted for by the tendency of these functioning L1 genes to continually create nonfunctional pseudogenes by reinsertion into the genome of sequences derived from their transcripts. The gain of new pseudogenes is balanced by the loss of old pseudogenes with a half-life of 2 Myr. Therefore, most of the observed L1 repeats are at a dead end with respect to either the expression of the L1 protein or the potential to elaborate further copies of themselves. However, the turnover of L1 pseudogenes is sufficient to constitute a vast flux of sequences into and then out of the flanking regions of all cellular genes. If the presence of flanking L1 pseudogenes affects the expression of other genes in even a subtle fashion, this process should represent a major source of genetic variation. A second level of concerted evolution occurs within the functional L1 sequences in a pattern that did not meet our expectations for selfish DNA. Also, in spite of the marked suppression of replacement relative to synonymous changes in functioning L1 genes, they evolve at an overall rate accelerated to the level of their own pseudogenes.