Cohen-Kupiec R, Zilberstein A, Gurevitz M
Department of Botany, Tel Aviv University, Ramat-Aviv, Israel.
J Bacteriol. 1995 Apr;177(8):2222-6. doi: 10.1128/jb.177.8.2222-2226.1995.
The upstream noncoding region of the Synechococcus sp. strain PCC 7942 (hereafter referred to as Synechococcus 7942) glnA gene was fused to the cat gene in order to study the expression of glnA both in Synechococcus 7942 and in Escherichia coli. The lack of cat expression in E. coli indicated that the glnA promoter was not recognized by E. coli RNA polymerase. The fused construct was integrated into the Synechococcus 7942 chromosome at a neutral site. Expression of the cat reporter gene was regulated under various nitrogen conditions in a way similar to that of the glnA gene. A deletion introduced at the binding site of the NtcA regulatory protein abolished derepression of the glnA promoter during growth in nitrate and under nitrogen starvation. Deletion of the sequence between the transcription and translation start sites of glnA prevented the repression observed during growth in ammonium. These results indicate that the glnA promoter is subject to complex regulation that involves sequences upstream and downstream from the transcription start site.
为了研究集胞藻属（Synechococcus）sp. 菌株PCC 7942（以下简称集胞藻7942）谷氨酰胺合成酶基因（glnA）在集胞藻7942和大肠杆菌中的表达情况，将其上游非编码区与氯霉素乙酰转移酶基因（cat）融合。在大肠杆菌中cat基因不表达，这表明集胞藻7942的glnA启动子不能被大肠杆菌RNA聚合酶识别。融合构建体在一个中性位点整合到集胞藻7942染色体中。cat报告基因的表达在各种氮条件下的调控方式与glnA基因相似。在NtcA调控蛋白结合位点引入的缺失消除了在硝酸盐培养基中生长以及氮饥饿条件下glnA启动子的去阻遏作用。glnA转录起始位点和翻译起始位点之间的序列缺失阻止了在铵培养基中生长时观察到的阻遏作用。这些结果表明，glnA启动子受到复杂的调控，涉及转录起始位点上游和下游的序列。
