Leong S A, Williams P H, Ditta G S
Nucleic Acids Res. 1985 Aug 26;13(16):5965-76. doi: 10.1093/nar/13.16.5965.
Transcriptional regulation of the delta-aminolevulinic acid synthetase gene of Rhizobium meliloti was investigated under conditions of normal vegetative growth and during symbiosis with the legume host alfalfa. S1 nuclease mapping and DNA sequence analysis indicated that transcription originates from two sites separated by 238 base pairs. A deletion analysis of the putative promoter regions P1 and P2, corresponding to the proximal and distal RNA start sites, was carried out with Bal-31 nuclease. Promoter function was monitored as beta-galactosidase activity after fusing the deletions to lac Z and introducing them into Rhizobium on a broad host range plasmid. The data obtained suggest that both regions function equivalently as promoters. The DNA sequences of P1 and P2 show considerable homology in the region between -35 and the start of transcription. Both contain a -35 region that is analogous to the consensus E. coli promoter sequence, while the -10 region is dissimilar. No resemblance was found between either P1 or P2 and the promoter regions of genes under general nitrogen control.
在正常营养生长条件下以及与豆科宿主紫花苜蓿共生期间，研究了苜蓿根瘤菌δ-氨基乙酰丙酸合成酶基因的转录调控。S1核酸酶图谱分析和DNA序列分析表明，转录起始于两个相距238个碱基对的位点。用Bal-31核酸酶对与近端和远端RNA起始位点相对应的假定启动子区域P1和P2进行了缺失分析。将缺失片段与lac Z融合并通过广宿主范围质粒导入根瘤菌后，以β-半乳糖苷酶活性监测启动子功能。获得的数据表明，这两个区域作为启动子的功能相当。P1和P2的DNA序列在-35区和转录起始之间的区域显示出相当大的同源性。两者都含有一个与大肠杆菌启动子共有序列类似的-35区，而-10区则不同。在P1或P2与一般氮控制下的基因启动子区域之间未发现相似之处。
