Post-transcriptional control of Crp-cAMP by RNase LS in Escherichia coli
Post-transcriptional control of Crp-cAMP by RNase LS in Escherichia coli
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DOI：
10.1111/j.1365-2958.2008.06504.x
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发表时间：
2008-12-01
影响因子：
3.6
通讯作者：
Yonesaki, Tetsuro
中科院分区：
文献类型：
--
作者：
Iwamoto, Akira;Lemire, Sebastien;Yonesaki, Tetsuro
大肠杆菌核糖核酸酶LS首次被鉴定为噬菌体T4的潜在拮抗剂；大肠杆菌rnlA基因是这种活性所必需的。当rnlA突变体细胞在含有高浓度NaCl的Luria-Bertani琼脂上生长时，其生长受到严重损害，在crp或cyaA中引入突变体可减轻NaCl敏感性。rnlA突变导致Crp过表达5倍。同时，与野生型相比，rnlA突变体中sigma（38）的表达量降低了2 - 3倍，这可能是其对高NaCl浓度敏感的原因。通过删除Crp位点II来消除Crp的过量产生，在异常高浓度的cAMP存在下，Crp与该位点结合以增强其自身的转录。同样，在cyaA中引入突变也消除了Crp的过量产生。事实上，所有的CyaA， cAMP和CyaA转录本积累到高水平，诱导后，与野生型相比，CyaA转录本在rnlA突变体中明显稳定。我们得出结论，RNase LS通过降解cyaA转录本来调节Crp-cAMP浓度。
Escherichia coli ribonuclease LS was first characterized as a potential antagonist of bacteriophage T4; the E. coli rnlA gene is required for this activity. When rnlA mutant cells were grown on Luria-Bertani agar containing a high concentration of NaCl, their growth was substantially impaired, and introduction of a mutation into crp or cyaA alleviated the NaCl sensitivity. A mutation in rnlA caused fivefold overexpression of Crp. At the same time, the expression of sigma(38) was lower by two- to threefold in an rnlA mutant than in the wild type, which probably accounts for the susceptibility to high NaCl concentration. The overproduction of Crp was eliminated by deletion of the Crp-site II, to which Crp binds to enhance its own transcription in the presence of abnormally high concentration of cAMP. Consistently, introduction of a mutation into cyaA also eliminated the overproduction of Crp. In fact, all of CyaA, cAMP and cyaA transcripts accumulated to high levels and, after induction, cyaA transcripts were markedly stabilized in an rnlA mutant compared with the wild type. We conclude that RNase LS regulates Crp-cAMP concentration by degrading the cyaA transcripts.