Frederikse P H, Shapiro L
Department of Microbiology, College of Physicians and Surgeons of Columbia University, New York, NY 10032.
Proc Natl Acad Sci U S A. 1989 Jun;86(11):4061-5. doi: 10.1073/pnas.86.11.4061.
Flagellar and chemotaxis genes are transcribed at a discrete time in the Caulobacter cell cycle. We demonstrate here that the expression of the Escherichia coli chemoreceptor gene tsr, with 2.6 kilobases of its upstream sequence, is temporally controlled in Caulobacter crescentus. The tsr gene was placed on the chromosome in single copy or on a low-copy-number plasmid. It was found that the Tsr protein appeared at the same point in the cell cycle as an endogenous C. crescentus methyl-accepting chemotaxis protein. Nuclease S1 mapping experiments showed that the tsr transcript was also controlled by the cell cycle, suggesting that the E. coli tsr gene is regulated by C. crescentus factors that mediate the timing of transcription initiation. The apparent transcription start site of the E. coli tsr gene was determined in both E. coli and C. crescentus, and we found that in both backgrounds the promoter used conforms to the consensus sequence for the promoters of the flagellar and chemosensory genes of Bacillus subtilis and E. coli. The use of this promoter suggests that C. crescentus has a cognate sigma factor and predicts that other C. crescentus genes are expressed from this consensus promoter.
鞭毛和趋化性基因在柄杆菌细胞周期的特定时间转录。我们在此证明，带有其上游序列2.6千碱基的大肠杆菌化学感受器基因tsr的表达在新月柄杆菌中受到时间控制。tsr基因以单拷贝形式置于染色体上或低拷贝数质粒上。发现Tsr蛋白在细胞周期中的出现时间与内源性新月柄杆菌甲基接受趋化蛋白相同。核酸酶S1图谱实验表明，tsr转录本也受细胞周期控制，这表明大肠杆菌tsr基因受新月柄杆菌中调节转录起始时间的因子调控。在大肠杆菌和新月柄杆菌中均确定了大肠杆菌tsr基因的明显转录起始位点，我们发现在这两种背景下使用的启动子均符合枯草芽孢杆菌和大肠杆菌鞭毛及化学感受基因启动子的共有序列。使用该启动子表明新月柄杆菌有一个同源的σ因子，并预测其他新月柄杆菌基因也从该共有启动子表达。
