RNase E and RNase J are needed for S-adenosylmethionine homeostasis in Sinorhizobium meliloti
RNase E and RNase J are needed for S-adenosylmethionine homeostasis in Sinorhizobium meliloti
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DOI：
10.1099/mic.0.000442
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发表时间：
2017-04-01
期刊：
影响因子：
2.8
通讯作者：
Evguenieva-Hackenberg, Elena
中科院分区：
文献类型：
--
作者：
Baumgardt, Kathrin;Melior, Hendrik;Evguenieva-Hackenberg, Elena
核糖核酸酶(RNase)E和J分别在大肠杆菌和枯草芽孢杆菌中起主要作用，并在苜蓿中华根瘤菌中共存。我们分析了在相应基因rne和rnj中插入微小Tn5的2011年苜蓿链霉菌突变体，发现了许多重叠效应。我们观察到了类似的mRNA水平的变化，包括运动和趋化相关基因FlaA、flgB和Cher的mRNA水平降低，而ndvA(对葡聚糖输出至关重要)的mRNA水平升高。在两个RNase突变体中，尽管SINI AHL合成酶基因的表达没有增加，但在指数增长过程中，AHL的水平也更高。此外，两个突变体的几个RNA在300V的变性凝胶中发生了异常迁移，但在1300V的较强变性条件下不发生异常迁移。这两个突变体之间的相似之处可以用关键甲基供体S-腺苷蛋氨酸水平的增加来解释，因为这可能导致AHL合成更快，导致AHL积累更高，以及包括RNA在内的大分子的不受控制的甲基化，这可能会加强RNA的二级结构。事实上，我们发现在这两个突变体中，N-6-甲基腺苷的含量几乎增加了三倍，SAM水平至少增加了七倍。通过诱导各自的核糖核酸酶的异位表达来互补，恢复了每个突变体中的AHL和SAM水平。综上所述，我们的数据表明，RNaseE和RNaseJ都是苜蓿链霉菌SAM动态平衡所必需的。
The ribonucleases (RNases) E and J play major roles in E. coli and Bacillus subtilis, respectively, and co-exist in Sinorhizobium meliloti. We analysed S. meliloti 2011 mutants with mini-Tn5 insertions in the corresponding genes rne and rnj and found many overlapping effects. We observed similar changes in mRNA levels, including lower mRNA levels of the motility and chemotaxis related genes flaA, flgB and cheR and higher levels of ndvA (important for glucan export). The acyl-homoserine lactone (AHL) levels were also higher during exponential growth in both RNase mutants, despite no increase in the expression of the sinI AHL synthase gene. Furthermore, several RNAs from both mutants migrated aberrantly in denaturing gels at 300 V but not under stronger denaturing conditions at 1300 V. The similarities between the two mutants could be explained by increased levels of the key methyl donor S-adenosylmethionine (SAM), since this may result in faster AHL synthesis leading to higher AHL accumulation as well as in uncontrolled methylation of macromolecules including RNA, which may strengthen RNA secondary structures. Indeed, we found that in both mutants the N-6- methyladenosine content was increased almost threefold and the SAM level was increased at least sevenfold. Complementation by induced ectopic expression of the respective RNase restored the AHL and SAM levels in each of the mutants. In summary, our data show that both RNase E and RNase J are needed for SAM homeostasis in S. meliloti.