Overgaard Martin, Johansen Jesper, Møller-Jensen Jakob, Valentin-Hansen Poul
Department of Biochemistry and Molecular Biology, University of Southern Denmark, Odense M, Denmark.
Mol Microbiol. 2009 Sep;73(5):790-800. doi: 10.1111/j.1365-2958.2009.06807.x. Epub 2009 Aug 13.
Small non-coding regulatory RNAs in bacteria have been shown predominantly to be tightly regulated at the level of transcription initiation, and sRNAs that function by an antisense mechanism on trans-encoded target mRNAs have been shown or predicted to act stoichiometrically. Here we show that MicM, which silences the expression of an outer membrane protein, YbfM under most growth conditions, does not become destabilized by target mRNA overexpression, indicating that the small RNA regulator acts catalytically. Furthermore, our regulatory studies suggested that control of micM expression is unlikely to operate at the level of transcription initiation. By employing a highly sensitive genetic screen we uncovered a novel RNA-based regulatory principle in which induction of a trap-mRNA leads to selective degradation of a small regulatory RNA molecule, thereby abolishing the sRNA-based silencing of its cognate target mRNA. In the present case, antisense regulation by chb mRNA of the antisense regulator MicM by an extended complementary sequence element, results in induction of ybfM mRNA translation. This type of regulation is reminiscent of the regulation of microRNA activity through target mimicry that occurs in plants.
细菌中的小非编码调节性RNA主要在转录起始水平受到严格调控，通过反义机制作用于反式编码靶mRNA的sRNA已被证明或预测以化学计量方式起作用。在这里，我们表明，在大多数生长条件下沉默外膜蛋白YbfM表达的MicM，不会因靶mRNA的过表达而变得不稳定，这表明小RNA调节因子具有催化作用。此外，我们的调控研究表明，micM表达的控制不太可能在转录起始水平起作用。通过采用高度敏感的遗传筛选，我们发现了一种新的基于RNA的调控原理，即诱捕mRNA的诱导会导致小调节RNA分子的选择性降解，从而消除基于sRNA的同源靶mRNA的沉默。在目前的情况下，反义调节因子MicM的反义调节通过扩展的互补序列元件由chb mRNA进行，导致ybfM mRNA翻译的诱导。这种调节类型让人联想到植物中通过靶标模拟对microRNA活性的调节。
