Ruiz Natividad, Silhavy Thomas J
Department of Molecular Biology, Princeton University, Princeton, New Jersey 08544, USA.
J Bacteriol. 2003 Oct;185(20):5984-92. doi: 10.1128/JB.185.20.5984-5992.2003.
Regulation of the sigma factor RpoS occurs at the levels of transcription, translation, and protein stability activity, and it determines whether Escherichia coli turns on or off the stationary-phase response. To better understand the regulation of RpoS, we conducted genetic screens and found that mutations in the pst locus cause accumulation of RpoS during exponential growth. The pst locus encodes for the components of the high-affinity transport system for inorganic phosphate (P(i)), which is involved in sensing P(i) levels in the environment. When the Pst transporter is compromised (either by mutation or by P(i) starvation), the two-component system PhoBR activates the transcription of the Pho regulon, a subset of genes that encode proteins for transporting and metabolizing alternative phosphate sources. Our data show that strains carrying mutations which constitutively activate the Pho regulon have increased rpoS translation during exponential growth. This upregulation of rpoS translation is Hfq dependent, suggesting the involvement of a small regulatory RNA (sRNA). The transcription of this yet-to-be-identified sRNA is regulated by the PhoBR two-component system.
σ因子RpoS的调控发生在转录、翻译和蛋白质稳定性活性水平，它决定了大肠杆菌是否开启或关闭稳定期反应。为了更好地理解RpoS的调控机制，我们进行了遗传筛选，发现pst位点的突变会导致指数生长期RpoS的积累。pst位点编码无机磷酸盐（P(i)）高亲和力转运系统的组成部分，该系统参与感知环境中的P(i)水平。当Pst转运体受损（通过突变或P(i)饥饿）时，双组分系统PhoBR会激活Pho调控子的转录，Pho调控子是一组基因的子集，这些基因编码用于转运和代谢替代磷源的蛋白质。我们的数据表明，携带组成性激活Pho调控子突变的菌株在指数生长期rpoS的翻译增加。rpoS翻译的这种上调依赖于Hfq，这表明涉及一种小调节RNA（sRNA）。这种尚未鉴定的sRNA的转录受PhoBR双组分系统调控。
