Kriner Michelle A, Groisman Eduardo A
Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, CT 06536, USA; Microbial Sciences Institute, Yale University, West Haven, CT 06516, USA.
Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, CT 06536, USA; Microbial Sciences Institute, Yale University, West Haven, CT 06516, USA; Howard Hughes Medical Institute, Chevy Chase, MD 20815-6789, USA.
J Mol Biol. 2015 Dec 4;427(24):3834-49. doi: 10.1016/j.jmb.2015.10.020. Epub 2015 Oct 30.
The bacterial protein Rho triggers transcription termination at the ends of many operons and when transcription and translation become uncoupled. In addition to these genome wide activities, Rho implements regulation of specific genes by dictating whether RNA polymerase terminates transcription within the 5' leader region or continues into the downstream coding region. Here, we report that the Mg(2+) channel gene corA in Salmonella enterica serovar Typhimurium, which was previously thought to be constitutively expressed, is regulated by a Rho-dependent terminator located within its 5' leader region. We demonstrate that the unusually long and highly conserved corA leader mRNA can adopt two mutually exclusive conformations that determine whether or not Rho interacts with a Rho utilization site on the nascent RNA and thereby prevents transcription of the corA coding region. The RNA conformation that promotes Rho-dependent termination is favored by efficient translation of corL, a short open reading frame located within the corA leader. Thus, corA transcription is inversely coupled to corL translation. This mechanism resembles those governing expression of Salmonella's other two Mg(2+) transport genes, suggesting that Rho links Mg(2+) uptake to translational signals.
细菌蛋白Rho在许多操纵子末端以及转录和翻译解偶联时触发转录终止。除了这些全基因组范围的活动外，Rho还通过决定RNA聚合酶是在5'前导区内终止转录还是继续进入下游编码区来实现对特定基因的调控。在此，我们报道，先前认为组成型表达的鼠伤寒沙门氏菌血清型鼠伤寒亚种中的Mg(2+)通道基因corA，受位于其5'前导区内的一个依赖Rho的终止子调控。我们证明，异常长且高度保守的corA前导mRNA可采用两种相互排斥的构象，这两种构象决定了Rho是否与新生RNA上的Rho利用位点相互作用，从而阻止corA编码区的转录。促进依赖Rho终止的RNA构象受位于corA前导区内的一个短开放阅读框corL的有效翻译所青睐。因此，corA转录与corL翻译呈反向偶联。这种机制类似于调控沙门氏菌其他两个Mg(2+)转运基因表达的机制，表明Rho将Mg(2+)摄取与翻译信号联系起来。
