Reichenbach Birte, Maes Alexandre, Kalamorz Falk, Hajnsdorf Eliane, Görke Boris
Department of General Microbiology, Institute of Microbiology and Genetics, Georg-August University, Grisebachstrasse 8, D-37077 Göttingen, Germany.
Nucleic Acids Res. 2008 May;36(8):2570-80. doi: 10.1093/nar/gkn091. Epub 2008 Mar 11.
In Escherichia coli the glmS gene encoding glucosamine 6-phosphate (GlcN-6-P) synthase GlmS is feedback regulated by GlcN-6-P in a pathway that involves the small RNA GlmZ. Expression of glmS is activated by the unprocessed form of GlmZ, which accumulates when the intracellular GlcN-6-P concentration decreases. GlmZ stabilizes a glmS transcript that derives from processing. Overexpression of a second sRNA, GlmY, also activates glmS expression in an unknown way. Furthermore, mutations in two genes, yhbJ and pcnB, cause accumulation of full-length GlmZ and thereby activate glmS expression. The function of yhbJ is unknown and pcnB encodes poly(A) polymerase PAP-I known to polyadenylate and destabilize RNAs. Here we show that GlmY acts indirectly in a way that depends on GlmZ. When the intracellular GlcN-6-P concentration decreases, GlmY accumulates and causes in turn accumulation of full-length GlmZ, which finally activates glmS expression. In glmZ mutants, GlmY has no effect on glmS, whereas artificially expressed GlmZ can activate glmS expression also in the absence of GlmY. Furthermore, we show that PAP-I acts at the top of this regulatory pathway by polyadenylating and destabilizing GlmY. In pcnB mutants, GlmY accumulates and induces glmS expression by stabilizing full-length GlmZ. Hence, the data reveal a regulatory cascade composed of two sRNAs, which responds to GlcN-6-P and is controlled by polyadenylation.
在大肠杆菌中，编码6-磷酸葡糖胺（GlcN-6-P）合酶GlmS的glmS基因在一条涉及小RNA GlmZ的途径中受到GlcN-6-P的反馈调节。glmS的表达由未加工形式的GlmZ激活，当细胞内GlcN-6-P浓度降低时，未加工形式的GlmZ会积累。GlmZ稳定一种经加工产生的glmS转录本。另一种小RNA GlmY的过表达也以未知方式激活glmS的表达。此外，yhbJ和pcnB这两个基因的突变会导致全长GlmZ的积累，从而激活glmS的表达。yhbJ的功能未知，而pcnB编码聚腺苷酸聚合酶PAP-I，已知该酶可使RNA聚腺苷酸化并使其不稳定。在这里我们表明，GlmY以一种依赖于GlmZ的方式间接发挥作用。当细胞内GlcN-6-P浓度降低时，GlmY积累，进而导致全长GlmZ积累，最终激活glmS的表达。在glmZ突变体中，GlmY对glmS没有影响，而人工表达的GlmZ在没有GlmY的情况下也能激活glmS的表达。此外，我们表明PAP-I通过使GlmY聚腺苷酸化并使其不稳定而在这条调节途径的顶端起作用。在pcnB突变体中，GlmY积累并通过稳定全长GlmZ来诱导glmS的表达。因此，这些数据揭示了一个由两种小RNA组成的调节级联，它对GlcN-6-P作出反应并受聚腺苷酸化控制。
