Urban Johannes H, Papenfort Kai, Thomsen Jens, Schmitz Ruth A, Vogel Jörg
Max Planck Institute for Infection Biology, RNA Biology, Charitéplatz 1, 10117 Berlin, Germany.
J Mol Biol. 2007 Oct 26;373(3):521-8. doi: 10.1016/j.jmb.2007.07.035. Epub 2007 Aug 2.
Many bacterial genes of related function are organized in operons and transcribed as polycistronic mRNAs to ensure the coordinate expression of the individual cistrons. Post-transcriptional modulation of such mRNAs can alter the expression of downstream cistrons, resulting in discoordinate protein synthesis from an operon mRNA. Several factors, including small non-coding RNAs (sRNAs), have been described that act collectively as repressors within polycistronic mRNAs. We describe the first case of discoordinated operon expression in which a downstream cistron is activated at the post-transcriptional level. We report that GlmY sRNA activates GlmS synthesis from the Escherichia coli glmUS mRNA without altering GlmU expression. The sRNA is shown to be structurally and functionally conserved in diverse enterobacteria; its transcription may be controlled by the alternative sigma factor, sigma(54). Our data suggest that Gram-negative bacteria evolved a mechanism of glmS riboregulation that is distinct from the glmS riboswitch mechanism of Gram-positive bacteria.
许多功能相关的细菌基因被组织在操纵子中，并作为多顺反子mRNA进行转录，以确保各个顺反子的协调表达。此类mRNA的转录后调控可改变下游顺反子的表达，导致从操纵子mRNA进行不协调的蛋白质合成。已经描述了几种包括小非编码RNA（sRNA）在内的因子，它们共同作为多顺反子mRNA中的阻遏物起作用。我们描述了第一例操纵子表达失调的情况，其中下游顺反子在转录后水平被激活。我们报告说，GlmY sRNA可激活大肠杆菌glmUS mRNA的GlmS合成，而不会改变GlmU的表达。已证明该sRNA在多种肠道细菌中在结构和功能上是保守的；其转录可能受替代sigma因子sigma(54)的控制。我们的数据表明，革兰氏阴性细菌进化出了一种与革兰氏阳性细菌的glmS核糖开关机制不同的glmS核糖调控机制。
