Ritzenthaler P, Mata-Gilsinger M
Mol Gen Genet. 1983;189(2):351-4. doi: 10.1007/BF00337831.
We have isolated a strain carrying a fusion of the beta-galactosidase structural gene to the promoter of the uxuR regulatory gene with the aid of the Casadaban Mud (Aprlac) phage. Analysis of mutants with deletions that were derived from the uxuR::Mud1 insertion strain confirmed the counterclockwise transcription direction of the uxuR gene. The uxuR-lacZ fusion strain was also used to examine the regulation of expression from the uxuR promoter. It was observed that an increase in the copy number of the uxuR gene results in an increased repression of beta-galactosidase synthesis. Overproduction of the exuR repressor also caused a decrease of the beta-galactosidase level. In all cases, the repression of beta-galactosidase synthesis was accompanied by a stronger repression of uxuB gene product synthesis. These results indicate that the expression of the uxuR gene is repressed by its own product but also by the exuR repressor. The different types of regulation of the two uxu operons are thus identical.
我们借助卡萨达班 Mud(Aprlac)噬菌体分离出了一个菌株，该菌株携带β-半乳糖苷酶结构基因与uxuR 调控基因启动子的融合基因。对源自 uxuR::Mud1 插入菌株的缺失突变体进行分析，证实了 uxuR 基因的逆时针转录方向。uxuR-lacZ 融合菌株也被用于检测 uxuR 启动子的表达调控。观察到 uxuR 基因拷贝数的增加导致β-半乳糖苷酶合成的抑制增强。exuR 阻遏物的过量产生也导致β-半乳糖苷酶水平降低。在所有情况下，β-半乳糖苷酶合成的抑制都伴随着 uxuB 基因产物合成的更强抑制。这些结果表明，uxuR 基因的表达不仅受到其自身产物的抑制，也受到 exuR 阻遏物的抑制。因此，两个 uxu 操纵子的不同调控类型是相同的。
