Roy C R, Miller J F, Falkow S
Department of Microbiology and Immunology, Stanford University School of Medicine, California 94305-5402.
J Bacteriol. 1989 Nov;171(11):6338-44. doi: 10.1128/jb.171.11.6338-6344.1989.
The bvg region of the respiratory pathogen Bordetella pertussis coordinately regulates the expression of several unlinked virulence determinants in response to environmental signals. The DNA sequence of the bvg region contains three genes (bvgA, bvgB, and bvgC). Transcription of a single-copy fusion consisting of the upstream region of a bvg-activated B. pertussis gene (fhaB) attached to the promoterless lac operon in Escherichia coli requires the entire bvgABC region in trans. Activation of the fhaB::lacZYA fusion is sensitive to the same environmental stimuli in E. coli that modulate the expression of bvg-activated genes in B. pertussis. Our data show that overexpression of the bvgA gene from a strong heterologous promoter results in transcriptional activation of the fhaB::lacZYA fusion even in the absence of the bvgB and bvgC products. Activation of fhaB transcription by bvgA overexpression in E. coli is no longer repressed by environmental conditions. The bvgA product has been identified by maxicell analysis as a 23-kilodalton protein. A B. pertussis mutant containing an in-frame deletion in bvgA was constructed. This mutant was nonhemolytic and no longer produced filamentous hemagglutinin and pertussis toxin. The mutation in this strain was complemented by returning the bvgA gene in trans. Transcriptional chloramphenicol acetyltransferase fusions to the fhaB and ptx promoter regions were returned to both the B. pertussis bvgA deletion mutant and its parental wild-type strain. Analysis of these strains indicated that the deletion mutant was defective in transcription of both ptx and fhaB. We conclude from these data that bvgA, bvgB, and bvgC comprise an operon encoding the components essential for coordinate regulation and sensory transduction. The BvgA protein is a transcriptional regulatory factor. The bvgB and bvgC products may be important in regulating the activity of BvgA in response to the changing environmental stimuli that B. pertussis encounters during the diseases whooping cough.
呼吸道病原体百日咳博德特氏菌的bvg区域可根据环境信号协调调控多个不连锁的毒力决定因子的表达。bvg区域的DNA序列包含三个基因（bvgA、bvgB和bvgC）。由百日咳博德特氏菌bvg激活基因（fhaB）的上游区域与大肠杆菌中无启动子的lac操纵子组成的单拷贝融合体的转录，在反式作用中需要完整的bvgABC区域。fhaB::lacZYA融合体的激活对大肠杆菌中与调节百日咳博德特氏菌中bvg激活基因表达相同的环境刺激敏感。我们的数据表明，即使在没有bvgB和bvgC产物的情况下，来自强异源启动子的bvgA基因的过表达也会导致fhaB::lacZYA融合体的转录激活。在大肠杆菌中，bvgA过表达对fhaB转录的激活不再受环境条件的抑制。通过大细胞分析已鉴定出bvgA产物是一种23千道尔顿的蛋白质。构建了一个在bvgA中存在框内缺失的百日咳博德特氏菌突变体。该突变体无溶血活性，不再产生丝状血凝素和百日咳毒素。通过反式导入bvgA基因对该菌株中的突变进行了互补。将转录氯霉素乙酰转移酶融合体与fhaB和ptx启动子区域导入百日咳博德特氏菌bvgA缺失突变体及其亲本野生型菌株。对这些菌株的分析表明，缺失突变体在ptx和fhaB的转录方面存在缺陷。从这些数据我们得出结论，bvgA、bvgB和bvgC组成一个操纵子，编码协调调控和感觉转导所必需的组分。BvgA蛋白是一种转录调节因子。bvgB和bvgC产物可能在响应百日咳博德特氏菌在百日咳疾病过程中遇到的不断变化的环境刺激来调节BvgA的活性方面很重要。
