The discovery of new members of the Tc1/mariner superfamily of transposons is expected based on the increasing availability of genome sequencing data. Here, we identified a new DD35E family termed Traveler (TR). Phylogenetic analyses of its DDE domain and full-length transposase showed that, although TR formed a monophyletic clade, it exhibited the highest sequence identity and closest phylogenetic relationship with DD34E/Tc1. This family displayed a very restricted taxonomic distribution in the animal kingdom and was only detected in ray-finned fish, anura and squamata, including 91 vertebrate species. The structural organization of TRs was highly conserved across different classes of animals. Most intact TR transposons had a length of ∼1.5 kb (range, 1,072-2,191 bp) and harboured a single open reading frame (ORF) encoding a transposase of about 340 aa (range, 304-350 aa) flanked by two short terminal inverted repeats (TIRs) (13-68 bp). Several conserved motifs, including two helix-turn-helix (HTH) motifs, a GRPR motif, a nuclear localization sequence (NLS) and a DDE domain, were also identified in TR transposases. This study also demonstrated the presence of horizontal transfer (HT) events of TRs in vertebrates, while the average sequence identities and the evolutionary dynamics of TR elements across species and clusters strongly indicated that the TR family invaded the vertebrate lineage very recently and that some of these elements may be currently active, combining the intact TR copies in multiple lineages of vertebrates. These data will contribute to the understanding of the evolutionary history of Tc1/mariner transposons and that of their hosts.

中文翻译：

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旅行者，一个新的DD35E Tc1 / Mariner转座子家族，最近入侵了脊椎动物。

随着基因组测序数据可用性的提高，有望发现转座子Tc1 / mariner超家族的新成员。在这里，我们确定了一个称为Traveler（TR）的新DD35E系列。系统发育分析其DDE域和全长转座酶表明，尽管TR形成了单系进化枝，但与DD34E / Tc1表现出最高的序列同一性和最亲密的系统发生关系。这个科目在动物界显示出非常有限的分类学分布，仅在包括91种脊椎动物在内的射线鳍鱼，无脊椎动物和鳞状科中才发现。TRs的结构组织在不同类别的动物中高度保守。大多数完整的TR转座子的长度约为1.5 kb（范围1,072-2，191 bp），并带有一个编码约340 aa（范围304-350 aa）转座酶的单开放阅读框（ORF），两侧是两个短末端反向重复序列（TIR）（13-68 bp）。在TR转座酶中还鉴定了几个保守的基序，包括两个螺旋-转-螺旋（HTH）基序，GRPR基序，核定位序列（NLS）和DDE结构域。这项研究还证明了脊椎动物中TRs的水平转移（HT）事件的存在，而TR元素跨物种和集群的平均序列同一性和进化动力学强烈表明TR家族最近入侵了脊椎动物谱系，并且其中一些这些元素目前可能是活跃的，将完整的TR拷贝结合在脊椎动物的多个谱系中。