Mirel D B, Chamberlin M J
Department of Biochemistry, University of California, Berkeley 94720.
J Bacteriol. 1989 Jun;171(6):3095-101. doi: 10.1128/jb.171.6.3095-3101.1989.
The Bacillus subtilis gene hag, which codes for the flagellin structural protein, was identified by DNA sequence analysis in a collection of DNA fragments bearing in vitro promoters for the sigma 28 form of RNA polymerase. The hag gene and adjacent regions of the B. subtilis chromosome were restriction mapped, and the nucleotide sequence was determined. The hag gene was transcribed at all stages of growth from a single promoter that had sequences in the promoter recognition region characteristic of the consensus sequence for the sigma 28 holoenzyme. Transcription of hag was eliminated by insertion mutations that blocked synthesis of the sigma 28 protein. These findings provide strong support for the previous proposal that the sigma 28 form of RNA polymerase controls transcription of a regulon specifying flagellar, chemotaxis, and motility functions in B. subtilis (J. D. Helmann and M. J. Chamberlin, Proc. Natl. Acad. Sci. USA 84:6422-6424, 1987). The steady-state levels of hag mRNA increased during exponential growth and peaked as the B. subtilis cells entered the stationary phase. The transcript levels then decreased to zero within 4 h after the onset of sporulation. Hence, sigma 28 RNA polymerase function is temporally regulated.
编码鞭毛蛋白结构蛋白的枯草芽孢杆菌基因hag，是通过对一组带有RNA聚合酶σ28形式的体外启动子的DNA片段进行DNA序列分析而鉴定出来的。对枯草芽孢杆菌染色体的hag基因及相邻区域进行了限制性图谱绘制，并测定了核苷酸序列。hag基因在生长的各个阶段都从一个单一启动子转录，该启动子在启动子识别区域具有σ28全酶共有序列特征的序列。hag的转录通过阻断σ28蛋白合成的插入突变而消除。这些发现为先前的提议提供了有力支持，即RNA聚合酶的σ28形式控制着一个调控子的转录，该调控子决定了枯草芽孢杆菌中的鞭毛、趋化性和运动功能（J. D. 赫尔曼和M. J. 钱伯林，《美国国家科学院院刊》84:6422 - 6424，1987）。hag mRNA的稳态水平在指数生长期间增加，并在枯草芽孢杆菌细胞进入稳定期时达到峰值。然后，转录水平在芽孢形成开始后4小时内降至零。因此，σ28 RNA聚合酶的功能受到时间调控。
