Kenyon C J, Walker G C
Nature. 1981 Feb 26;289(5800):808-10. doi: 10.1038/289808a0.
UvrA+-dependent excision repair is one of the most important systems in Escherichia coli for repairing UV-induced pyrimidine dimers and a variety of other forms of DNA damage. The uvrA protein acts in conjunction with the uvrB and uvrC gene products to introduce a nick at the of a DNA lesion and thus initiate the repair process. We have recently used the Mud(Ap, lac) operon fusion vector to identify a set of genes whose expression is induced by DNA damage. One Mud(Ap, lac) insertion mapped at the uvrA locus and made the cells sensitive to UV light. In this fusion strain, beta-galactosidase expression was induced by DNA-damaging agents in a recA+lexA+-dependent fashion. We were surprised by this result because uvrA+-dependent excision repair is observed both in cells in which protein synthesis has been inhibited and in recA- and lexA- cells, findings which have led to the conclusion that the uvrA gene product is constitutively expressed and not under the control of the complex recA+lexA+ regulatory circuitry (see below). We have investigated this possibility further and describe here the generation and characterization of a set of fusions of the lac genes to the promoter of the uvrA gene. We confirm that the uvrA gene product is induced by DNA damage in a recA+lexA+-dependent fashion.
依赖UvrA⁺的切除修复是大肠杆菌中修复紫外线诱导的嘧啶二聚体和多种其他形式DNA损伤的最重要系统之一。uvrA蛋白与uvrB和uvrC基因产物协同作用，在DNA损伤位点引入一个切口，从而启动修复过程。我们最近使用Mud(Ap, lac)操纵子融合载体来鉴定一组其表达受DNA损伤诱导的基因。一个Mud(Ap, lac)插入位于uvrA基因座，使细胞对紫外线敏感。在这个融合菌株中，β-半乳糖苷酶的表达以recA⁺lexA⁺依赖的方式被DNA损伤剂诱导。我们对这个结果感到惊讶，因为在蛋白质合成被抑制的细胞以及recA⁻和lexA⁻细胞中都观察到了依赖UvrA⁺的切除修复，这些发现导致了uvrA基因产物是组成型表达且不受复杂的recA⁺lexA⁺调控电路控制的结论（见下文）。我们进一步研究了这种可能性，并在此描述了一组lac基因与uvrA基因启动子融合体的构建和特性分析。我们证实uvrA基因产物以recA⁺lexA⁺依赖的方式被DNA损伤诱导。
