Fürbass R, Gocht M, Zuber P, Marahiel M A
Institut für Biochemie und Molekulare Biologie, Technische Universität Berlin, Federal Republic of Germany.
Mol Gen Genet. 1991 Mar;225(3):347-54. doi: 10.1007/BF00261673.
In Bacillus subtilis the abrB gene product negatively affects the transcription of some genes activated during the transition from vegetative to stationary phase of growth. Interaction of AbrB with the promoters of two such genes, spoVG, a sporulation gene, and tycA, an antibiotic biosynthesis gene, was studied by DNase I and hydroxyl radical footprinting. Two binding areas within the leader and promoter regions of tycA were identified. In spoVG the binding site is located at the A + T-rich region upstream of the promoter. Hydroxyl radical footprinting revealed that the AbrB-protected regions, in both the tycA and spoVG promoters, are short A + T-rich regions that are separated by one helical turn, indicating that AbrB binds to one face of the helix. To examine the role of spoOA in the expression of abrB-controlled genes, the levels of AbrB protein in Spo + and in spoOA cells were determined by Western blot analysis. In wild-type cells AbrB was detected only during vegetative growth, whereas in spoOA cells a high level of AbrB was detected during both the vegetative and stationary phases of growth. These findings support a model in which (i) spoOA negatively affects abrB expression, and (ii) the repression of the transition state-activated genes tycA and spoVG in spoOA cells is due to constitutive expression of AbrB, which acts as a repressor.
在枯草芽孢杆菌中，abrB基因产物对一些在生长从营养期向稳定期转变过程中被激活的基因的转录具有负向影响。通过DNA酶I和羟基自由基足迹法研究了AbrB与两个此类基因（一个芽孢形成基因spoVG和一个抗生素生物合成基因tycA）启动子的相互作用。在tycA的前导区和启动子区域内鉴定出两个结合区域。在spoVG中，结合位点位于启动子上游富含A+T的区域。羟基自由基足迹法显示，tycA和spoVG启动子中AbrB保护的区域是由一个螺旋圈隔开的短富含A+T的区域，这表明AbrB结合在螺旋的一个面上。为了研究spoOA在abrB控制基因表达中的作用，通过蛋白质免疫印迹分析测定了Spo+和spoOA细胞中AbrB蛋白的水平。在野生型细胞中，仅在营养生长期间检测到AbrB，而在spoOA细胞中，在营养生长和稳定期均检测到高水平的AbrB。这些发现支持了一个模型，其中（i）spoOA对abrB表达具有负向影响，并且（ii）spoOA细胞中过渡态激活基因tycA和spoVG的抑制是由于作为阻遏物的AbrB的组成型表达。
