Grindley N D, Joyce C M
Proc Natl Acad Sci U S A. 1980 Dec;77(12):7176-80. doi: 10.1073/pnas.77.12.7176.
The kanamycin resistance transposon Tn903 consists of a unique region of about 1000 base pairs bounded by a pair of 1050-base-pair inverted repeat sequences. Each repeat contains two Pvu II endonuclease cleavage sites separated by 520 base pairs. We have constructed derivatives of Tn903 in which this 520-base-pair fragment is deleted from one or both repeats. Those derivatives that lack both 520-base-pair fragments cannot transpose, whereas those that lack just one remain transposition proficient. One such transposable derivative, Tn903 delta I, has been selected for further study. We have determined the sequence of the intact inverted repeat. The 18 base pairs at each end are identical and inverted relative to one another, a structure characteristic of insertion sequences. Additional experiments indicate that a single inverted repeat from Tn903 can, in fact, transpose; we propose that this element be called IS903. To correlate the DNA sequence with genetic activities, we have created mutations by inserting a 10-base-pair DNA fragment at several sites within the intact repeat of Tn903 delta 1, and we have examined the effect of such insertions on transposability. The results suggest that IS903 encodes a 307-amino-acid polypeptide (a "transposase") that is absolutely required for transposition of IS903 or Tn903.
卡那霉素抗性转座子Tn903由一个约1000个碱基对的独特区域组成，该区域由一对1050个碱基对的反向重复序列界定。每个重复序列包含两个被520个碱基对隔开的Pvu II核酸内切酶切割位点。我们构建了Tn903的衍生物，其中一个或两个重复序列中的这个520个碱基对的片段被删除。那些缺少两个520个碱基对片段的衍生物不能转座，而那些只缺少一个片段的衍生物仍然具有转座能力。一种这样的可转座衍生物Tn903 delta I已被选择用于进一步研究。我们已经确定了完整反向重复序列的序列。两端的18个碱基对彼此相同且反向，这是插入序列的结构特征。进一步的实验表明，来自Tn903的单个反向重复序列实际上可以转座；我们提议将这个元件称为IS903。为了将DNA序列与遗传活性相关联，我们通过在Tn903 delta 1的完整重复序列内的几个位点插入一个10个碱基对的DNA片段来产生突变，并研究了这种插入对转座能力的影响。结果表明，IS903编码一种307个氨基酸的多肽（一种“转座酶”），这是IS903或Tn903转座绝对必需的。
