金鱼hAT家族转座子Tgf2的克隆及其结构

hAT家族转座子以果蝇hobo、玉米Ac和金鱼草(Ceratophyllum demersum L.)Tam3为代表,以"剪切-粘帖"方式进行DNA转座。1996年,日本学者首次在白化青鳉(Oryzias latipes)中发现具有天然活性的脊椎动物hAT家族转座子,即青鳉Tol2转座子,该转座子已在模式生物斑马鱼转基因、基因和启动子捕获方面进行了广泛应用。文章根据玉米Ac与青鳉Tol2转座子序列保守区设计一对引物,在19种不同鱼类物种或品系中进行PCR筛选,最后发现此类hAT家族转座子在我国不同品系金鱼中存在,命名为金鱼Tgf2转座子。金鱼Tgf2转座子全长4720bp,由4个阅读框组成,与青鳉Tol2转座子的相似度为97%。金鱼Tgf2与青鳉Tol2转座子在末端倒位重复和亚末端重复上存在一定差异,此外,金鱼Tgf2转座子的中间反向重复序列(1453bp到2091bp)可形成一种"十"字结构,明显有别于青鳉Tol2转座子形成的茎环结构,这些区域与转座活性密切相关。文章预示金鱼Tgf2转座子可能具有更高的天然转座活性,构建高效金鱼Tgf2转基因元件可供鱼类转基因和基因捕获研究。

Cloning of goldfish hAT transposon Tgf2 and its structure

The hAT transposon family, including hobo of Drosophila, Ac of maize (Zea mays L.) and Tam3 of snapdragon (Ceratophyllum demersum L.), is proposed to be involved in transposition between genomic DNAs in "cut and paste" patterns. In 1996, a transposon of Tol2, the first autonomous transposon in vertebrate, was identified from the genome of albino medaka fish (Oryzias latipes). Since then, a new transgenic and gene trap system based on Tol2 has been developed and widely used in zebrafish. In this study, we designed gene-specific primers based on the conserved regions of amino acid sequences between medaka Tol2 and maize Ac. Meanwhile, PCR was carried out in 19 fish species or strains including goldfish. Finally, another similar hAT transposon, termed as Tgf2, was identified in the genomes from different strains of goldfish. Goldfish Tgf2 is 4720 bp in length including 4 exons and shares an identity of 97% with medaka Tol2. Distinct differences were observed in the terminal inverted repeat (TIR) and subterminal repeat (STR) regions between Tgf2 and Tol2. In addition, the internal inverted repeat (IIR) region of Tgf2 (1453 bp-2091 bp) tended to form a "+" crossing structure, rather than a stem-loop structure in medaka Tol2. The regions, including TIR, STR, and IIR, were supposed to be closely related to the transposing activities of hAT transposon family members. From these sequence differences, we may expect a probably high activity of goldfish Tgf2 in transposition and it could be further used as a tool for transgenesis and gene trap in aquaculture fish in future.