Matveev Vitaliy, Okada Norihiro
Faculty of Bioscience and Biotechnology, Tokyo Institute of Technology, Yokohama, Japan.
Gene. 2009 Apr 1;434(1-2):16-28. doi: 10.1016/j.gene.2008.04.022. Epub 2008 May 22.
Short and long retroposons, or non-LTR retrotransposons (SINEs and LINEs, respectively) are two groups of interspersed repetitive elements amplifying in the genome via RNA and cDNA-mediated reverse transcription. In this process, SINEs entirely depend on the enzymatic machinery of autonomous LINEs. The impact of retroposons on the host genome is difficult to overestimate: their sequences account for significant portion of the eukaryotic genome, while propagation of their active copies gradually reshapes it. In this way, the retropositional activity plays a role of important evolutionary factor. More than 100 LINE and nearly 100 SINE families have been described to date from the genomes of various eukaryotes, and it is salmonoid fishes (Actinopterygii: Salmonoidei) that are particularly noticeable for the diversity of transposons they host in their genomes, including two LINE and seven SINE families. Moreover, this group of ray-finned fish represents an excellent opportunity to study such a rare evolutionary phenomenon as lateral gene transfer, due to a great variety of transposons and other sequences salmons share with a blood fluke, Schistosoma japonicum (Trematoda: Strigeiformes)--a parasitic helminth infecting various vertebrates. The aim of the present review is to structure all knowledge accumulated about salmonoid retroposons by now, as well as to complement it with the new data pertaining to the distribution of some SINE families.
短散在重复序列和长散在重复序列，即非长末端重复逆转座子（分别为SINEs和LINEs），是两组通过RNA和cDNA介导的逆转录在基因组中扩增的散在重复元件。在此过程中，SINEs完全依赖自主LINEs的酶促机制。逆转座子对宿主基因组的影响再怎么高估都不为过：它们的序列占真核生物基因组的很大一部分，而其活跃拷贝的传播逐渐重塑基因组。这样，逆转座活性起着重要进化因素的作用。迄今为止，已从各种真核生物的基因组中描述了100多个LINE和近100个SINE家族，而鲑形目鱼类（辐鳍鱼纲：鲑亚目）因其基因组中所含转座子的多样性而格外引人注目，包括两个LINE家族和七个SINE家族。此外，由于鲑鱼与日本血吸虫（吸虫纲：分体科）——一种感染各种脊椎动物的寄生蠕虫——共享多种转座子和其他序列，这一群硬骨鱼为研究横向基因转移这种罕见的进化现象提供了绝佳机会。本综述的目的是梳理目前积累的关于鲑形目逆转座子的所有知识，并用与一些SINE家族分布相关的新数据对其进行补充。
