Leung S S, Romans P
Department of Zoology, University of Toronto, Ontario, Canada.
Insect Mol Biol. 1998 Aug;7(3):241-8. doi: 10.1111/j.1365-2583.1998.00068.x.
In order to determine whether there are active genomic copies of the Anopheles gambiae transposon Ikirara, we developed an excision assay based on an internally deleted copy, Ikirara1. This element has 216 bp perfect inverted repeats at its termini, apparently caused a duplication of the dinucleotide TA at its insertion site between vitellogenin genes, and is thought to have been inserted recently at this location. The firefly luciferase gene on the E. coli tac promoter was inserted into Ikirara1 and used as a reporter to assess whether activities in an A. gambiae cell line could cause Ikirara excision. Excisions were observed at a rate of 0.038% in these experiments, but none was detected in controls. The five independent excision products examined gave identical sequences. Excisions were nearly precise, but left behind a footprint of 15 bp of the 3' inverted repeat of Ikirara1 between duplicated TAs. These excisions can be explained by a mechanism formally similar to that proposed for excision of mariner/Tc1 elements with cuts at the transposon ends staggered by 15 bases.
为了确定冈比亚按蚊转座子Ikirara是否存在活跃的基因组拷贝，我们基于内部缺失的拷贝Ikirara1开发了一种切除检测方法。该元件在其末端具有216 bp的完美反向重复序列，显然在卵黄蛋白原基因之间的插入位点导致了二核苷酸TA的重复，并且被认为是最近才插入到这个位置的。将大肠杆菌tac启动子上的萤火虫荧光素酶基因插入Ikirara1，并用作报告基因来评估冈比亚按蚊细胞系中的活性是否会导致Ikirara切除。在这些实验中观察到切除率为0.038%，但在对照中未检测到切除。检查的五个独立切除产物给出了相同的序列。切除几乎是精确的，但在重复的TA之间留下了Ikirara1 3'反向重复序列的15 bp足迹。这些切除可以用一种机制来解释，该机制在形式上类似于为mariner/Tc1元件切除所提出的机制，在转座子末端的切割错开15个碱基。
