Evolution of the Xenopus piggyBac transposon family TxpB:: Domesticated and untamed strategies of transposon subfamilies
Evolution of the Xenopus piggyBac transposon family TxpB:: Domesticated and untamed strategies of transposon subfamilies
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DOI：
10.1093/molbev/msm191
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发表时间：
2007-12-01
影响因子：
10.7
通讯作者：
Kawahara, Akira
中科院分区：
文献类型：
--
作者：
Hikosaka, Akira;Kobayashi, Toshihiro;Kawahara, Akira
在热带爪蟾（Xenopus tropicalis）、非洲爪蟾（Xenopus laevis）和北方爪蟾（Xenopus borealis）中发现了piggyBac超家族的DNA转座子TxpB新家族。在3个种中均发现2个TxpB亚科，分别为Kobuta和Uribo1，在热带蠓中发现Uribo2亚科。对其开放阅读框（orf）的分子系统发育分析显示，TxpB转座子已维持超过100 Myr。Uribo1和Uribo2 orf在每个基因组中都存在多个拷贝，其中一些由末端反向重复序列构成。相比之下，所有的Kobuta orf在每个基因组中都以单一拷贝的形式存在，并表现出高度的进化保守性，表明Kobuta基因被宿主驯化。在一个热带X.物种中观察到Uribo1和Uribo2转座子（非自主型）的基因组插入多态性，表明最近发生了转座子。细胞培养的转染实验表明，完整的Uribo2 ORF的表达载体结构可以精确地从目标载体结构中切除非自主的Uribo2元件，而Kobuta ORF的表达载体结构则没有。目前的结果支持我们的观点，即一些Uribo2成员是天然活跃的自主转座子，而Kobuta成员可能是被宿主驯化的。
A new family, termed TxpB, of DNA transposons belonging to the piggyBac superfamily was found in 3 Xenopus species (Xenopus tropicalis, Xenopus laevis, and Xenopus borealis). Two TxpB subfamilies of Kobuta and Uribo1 were found in all the 3 species, and another subfamily termed Uribo2 was found in X. tropicalis. Molecular phylogenetic analyses of their open reading frames (ORFs) revealed that TxpB transposons have been maintained for over 100 Myr. Both the Uribo1 and the Uribo2 ORFs were present as multiple copies in each genome, and some of them were framed by terminal inverted repeat sequences. In contrast, all the Kobuta ORFs were present as a single copy in each genome and exhibited high evolutionary conservation, suggesting domestication of Kobuta genes by the host. Genomic insertion polymorphisms of the Uribo1 and Uribo2 transposons (nonautonomous type) were observed in a single species of X. tropicalis, indicating recent transposition events. Transfection experiments in cell culture revealed that an expression vector construct for the intact Uribo2 ORF caused precise excision of a nonautonomous Uribo2 element from the target vector construct but that for the Kobuta ORF did not. The present results support our viewpoint that some Uribo2 members are naturally active autonomous transposons, whereas Kobuta members may be domesticated by hosts.