Karita M, Tummuru M K, Wirth H P, Blaser M J
Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-2605, USA.
Infect Immun. 1996 Nov;64(11):4501-7. doi: 10.1128/iai.64.11.4501-4507.1996.
Helicobacter pylori strains possessing cagA are associated with peptic ulceration. To understand the regulation of expression of cagA, picB, associated with interleukin-8 induction, and ureA, encoding the small urease subunit, we created gene fusions of cagA, ureA, and picB of strain 3401, using a promoterless reporter (xylE). Expression of XylE after growth in broth culture revealed that basal levels of expression of cagA and urea in H. pylori were substantially greater than for picB. For cagA expression in stationary-phase cells, brief exposure to acid pH caused a significant increase in xylE expression compared with neutral pH. In contrast, expression of xylE in urea or picB decreased after parallel exposure to acid pH (pH 7 > 6 > 5 > 4), regardless of the growth phase. Expression of the CagA protein varied with growth phase and pH exposure in parallel with the observed transcriptional variation. The concentration of CagA in a cell membrane-enriched fraction after growth at pH 6 was significantly higher than after growth at pH 5 or 7. We conclude that the promoterless reporter xylE is useful for studying the regulation of gene expression in H. pylori and that regulation of CagA production occurs mainly at the transcriptional level.
携带cagA的幽门螺杆菌菌株与消化性溃疡有关。为了了解与白细胞介素-8诱导相关的picB以及编码小尿素酶亚基的ureA的表达调控,我们使用无启动子报告基因(xylE)构建了3401菌株的cagA、ureA和picB的基因融合体。肉汤培养生长后XylE的表达表明,幽门螺杆菌中cagA和尿素的基础表达水平显著高于picB。对于静止期细胞中的cagA表达,与中性pH相比,短暂暴露于酸性pH会导致xylE表达显著增加。相比之下,无论生长阶段如何,平行暴露于酸性pH(pH 7>6>5>4)后,尿素或picB中xylE的表达都会降低。CagA蛋白的表达随生长阶段和pH暴露而变化,与观察到的转录变化平行。在pH 6下生长后,细胞膜富集部分中CagA的浓度显著高于在pH 5或7下生长后。我们得出结论,无启动子报告基因xylE可用于研究幽门螺杆菌中的基因表达调控,并且CagA产生的调控主要发生在转录水平。