Delius H, Charlier D, Besemer J
Mol Gen Genet. 1980;179(2):391-7. doi: 10.1007/BF00425470.
The isolation and characterization of three unstable and constitutive revertants of mutant galOP-308 of E. coli is described. In this mutant an IS2 element is integrated between the promoter and the first structural gene of the galactose operon, and exerts a strong polar effect on the expression of the three galactose genes. In the three revertants under investigation it was observed that relief of polarity and constitutive expression of the gal-operon were accompanied by the deletion of 90% of the IS2 sequence and of various lengths of the adjacent sequences including the gal-promoter. We conclude from this result that the transcription termination signals causing strong polarity were located on the deleted part of IS2, and that in our revertants the galactose genes are now under the control of a new promoter which is apparently unstable.
本文描述了大肠杆菌突变体galOP - 308的三个不稳定且组成型回复突变体的分离与特性分析。在这个突变体中，一个IS2元件整合在半乳糖操纵子的启动子和第一个结构基因之间，并对三个半乳糖基因的表达产生强烈的极性效应。在所研究的三个回复突变体中，观察到极性的解除和gal操纵子的组成型表达伴随着IS2序列90%以及包括gal启动子在内的不同长度相邻序列的缺失。我们从这个结果得出结论，导致强极性的转录终止信号位于IS2的缺失部分，并且在我们的回复突变体中，半乳糖基因现在受一个新的启动子控制，这个启动子显然是不稳定的。
