Viegas Sandra C, Pfeiffer Verena, Sittka Alexandra, Silva Inês J, Vogel Jörg, Arraiano Cecília M
Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Apartado 127, 2781-901 Oeiras, Portugal.
Nucleic Acids Res. 2007;35(22):7651-64. doi: 10.1093/nar/gkm916. Epub 2007 Nov 3.
In pathogenic bacteria, a large number of sRNAs coordinate adaptation to stress and expression of virulence genes. To better understand the turnover of regulatory sRNAs in the model pathogen, Salmonella typhimurium, we have constructed mutants for several ribonucleases (RNase E, RNase G, RNase III, PNPase) and Poly(A) Polymerase I. The expression profiles of four sRNAs conserved among many enterobacteria, CsrB, CsrC, MicA and SraL, were analysed and the processing and stability of these sRNAs was studied in the constructed strains. The degradosome was a common feature involved in the turnover of these four sRNAs. PAPI-mediated polyadenylation was the major factor governing SraL degradation. RNase III was revealed to strongly affect MicA decay. PNPase was shown to be important in the decay of these four sRNAs. The stability of CsrB and CsrC seemed to be independent of the RNA chaperone, Hfq, whereas the decay of SraL and MicA was Hfq-dependent. Taken together, the results of this study provide initial insight into the mechanisms of sRNA decay in Salmonella, and indicate specific contributions of the RNA decay machinery components to the turnover of individual sRNAs.
在致病细菌中，大量的小RNA（sRNA）协同调节对压力的适应以及毒力基因的表达。为了更好地理解模式病原体鼠伤寒沙门氏菌中调控sRNA的周转情况，我们构建了几种核糖核酸酶（核糖核酸酶E、核糖核酸酶G、核糖核酸酶III、多聚核苷酸磷酸化酶）和多聚腺苷酸聚合酶I的突变体。分析了在许多肠道细菌中保守的四种sRNA（CsrB、CsrC、MicA和SraL）的表达谱，并在构建的菌株中研究了这些sRNA的加工和稳定性。降解体是这四种sRNA周转过程中的一个共同特征。多聚腺苷酸聚合酶I介导的多聚腺苷酸化是控制SraL降解的主要因素。核糖核酸酶III被发现强烈影响MicA的降解。多聚核苷酸磷酸化酶在这四种sRNA的降解中显示出重要作用。CsrB和CsrC的稳定性似乎独立于RNA伴侣蛋白Hfq，而SraL和MicA的降解则依赖于Hfq。综上所述，本研究结果为沙门氏菌中sRNA降解机制提供了初步见解，并表明RNA降解机制成分对单个sRNA周转的特定贡献。
