Membrane Biology Laboratory, Department of Physiology, David Geffen School of Medicine at UCLA, and VA Greater Los Angeles Healthcare System, Los Angeles, California, USA.
J Bacteriol. 2013 Feb;195(3):444-52. doi: 10.1128/JB.01022-12. Epub 2012 Oct 26.
Urease is an essential component of gastric acid acclimation by Helicobacter pylori. The increased level of urease in gastric acidity is due, in part, to acid activation of the two-component system consisting of the membrane sensor HP0165 (ArsS) and its response regulator HP0166 (ArsR), which regulates transcription of the seven genes in two separate operons (ureAB and ureIEFGH) of the urease gene cluster. Recently, we identified a novel cis-encoded antisense small RNA, 5'ureB-sRNA, targeted at the 5' end of ureB, which downregulates ureAB expression by truncation of the ureAB transcript at neutral pH. It is not known whether the truncated transcript is due to transcription termination or processing of the full-length mRNA by codegradation of a ureAB mRNA-sRNA hybrid complex. S1 nuclease mapping assays show that the truncated transcript is due to transcription termination. Further studies using an in vitro transcription assay found that 5'ureB-sRNA promotes premature termination of transcription of ureAB mRNA. These results suggest that the antisense small RNA 5'ureB-sRNA downregulates ureAB expression by enhancing transcription termination 5' of ureB. With this mechanism, a limited amount of 5'ureB-sRNA is sufficient to regulate the relatively high level of ureAB transcript.
脲酶是幽门螺杆菌适应胃酸的重要组成部分。胃酸度中脲酶水平的增加部分是由于由膜传感器 HP0165（ArsS）和其响应调节剂 HP0166（ArsR）组成的两个组件系统的酸激活，该系统调节两个单独操纵子（ureAB 和 ureIEFGH）中脲酶基因簇的七个基因的转录。最近，我们鉴定了一种新型顺式编码反义小 RNA，5'ureB-sRNA，靶向 ureB 的 5'端，在中性 pH 下通过截断 ureAB 转录本下调 ureAB 表达。尚不清楚截断的转录本是由于转录终止还是全长 mRNA 通过 ureAB mRNA-sRNA 杂交复合物的共降解进行加工。S1 核酸酶图谱分析表明，截断的转录本是由于转录终止。使用体外转录测定的进一步研究表明，5'ureB-sRNA 通过增强 ureAB mRNA 转录的 5'终止来促进 ureAB mRNA 的过早终止。这些结果表明，反义小 RNA 5'ureB-sRNA 通过增强 ureB 上游的转录终止来下调 ureAB 表达。通过这种机制，有限量的 5'ureB-sRNA 足以调节相对较高水平的 ureAB 转录本。
