ExpR, a LuxR homolog of Erwinia carotovora subsp carotovora, activates transcription of rsmA, which specifies a global regulatory RNA-binding protein
ExpR, a LuxR homolog of Erwinia carotovora subsp carotovora, activates transcription of rsmA, which specifies a global regulatory RNA-binding protein
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DOI：
10.1128/jb.187.14.4792-4803.2005
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发表时间：
2005-07-01
影响因子：
3.2
通讯作者：
Chatterjee, AK
中科院分区：
文献类型：
--
作者：
Cui, YY;Chatterjee, A;Chatterjee, AK
N-酰基高丝氨酸内酯（阿勒）是胡萝卜软腐欧文氏菌（Erwiniacarotovora）亚种表达胞外酶和蛋白质以及致病性等多种性状所必需的。以往的研究与E.胡萝卜软腐菌亚种胡萝卜软腐菌的研究表明，阿勒缺乏导致产生高水平的RsmA，RsmA是一种RNA结合蛋白，其作为胞外酶和蛋白质以及次级代谢物的全局负调节剂（Rsm，次级代谢物的调节剂）发挥作用。我们在这里的文件，ExpR，一个假定的阿勒受体属于LuxR家族的监管机构，激活RsmA生产。在没有阿勒的情况下，ExpR（+）E.胡萝卜软腐菌亚种与其ExpR（-）突变体相比，胡萝卜软腐菌菌株产生更高水平的rsmA RNA并更好地表达rsmA-lacZ转录融合体。此外，rsmA-lacZ融合体在大肠杆菌中的表达在expR（大肠杆菌的expR基因）存在下高得多。胡萝卜软腐菌亚种胡萝卜软腐菌菌株Ecc 71）。我们还表明，纯化的MBP-ExpR（71）制剂结合（MBP，麦芽糖结合蛋白）rsmA DNA。相比之下，MBP-ExpR（71）不结合ahlI（阿勒合酶基因）、pel-1（果胶酸裂解酶基因）或rsmB（结合RsmA的调节RNA基因），ExpR（71）也不激活这些基因的表达。这些观察结果有力地表明，rsmA的转录激活由ExpR（71）和rsmA启动子之间的直接和特异性相互作用引起。有证据表明，大肠杆菌产生的主要阿勒类似物N-3-氧代己酰基-L-高丝氨酸内酯（3-oxo-C6-HL）是一种具有生物活性的内酯。胡萝卜软腐菌亚种胡萝卜软腐菌菌株Ecc 71抑制ExpR（71）介导的rsmA表达活化。这些发现首次证实了E.胡萝卜软腐菌亚种胡萝卜软腐菌是通过RsmA，一个转录后调节E。carotovora亚种，阿勒中和这种ExpR效应。
N-acyl homoserine lactone (AHL) is required by Erwinia carotovora subspecies for the expression of various traits, including extracellular enzyme and protein production and pathogenicity. Previous studies with E. carotovora subsp. carotovora have shown that AHL deficiency causes the production of high levels of RsmA, an RNA binding protein that functions as a global negative regulator of extracellular enzymes and proteins and secondary metabolites (Rsm, regulator of secondary metabolites). We document here that ExpR, a putative AHL receptor belonging to the LuxR family of regulators, activates RsmA production. In the absence of AHL, an ExpR(+) E. carotovora subsp. carotovora strain compared to its ExpR(-) mutant, produces higher levels of rsmA RNA and better expresses an rsmA-lacZ transcriptional fusion. Moreover, the expression of the rsmA-lacZ fusion in Escherichia coli is much higher in the presence of expR, (the expR gene of E. carotovora subsp. carotovora strain Ecc71) than in its absence. We also show that purified preparation of MBP-ExpR(71) binds (MBP, maltose binding protein) rsmA DNA. By contrast, MBP-ExpR(71) does not bind ahlI (gene for AHL synthase), pel-1 (gene for pectate lyase), or rsmB (gene for regulatory RNA that binds RsmA), nor does ExpR(71) activate expression of these genes. These observations strongly suggest transcriptional activation of rsmA resulting from a direct and specific interaction between ExpR(71) and the rsmA promoter. Several lines of evidence establish that N-3-oxohexanoyl-L-homoserine lactone (3-oxo-C6-HL), the major AHL analog produced by E. carotovora subsp. carotovora strain Ecc71, inhibits ExpR(71)-mediated activation of rsmA expression. These findings for the first time establish that the expR effect in E. carotovora subsp. carotovora is channeled via RsmA, a posttranscriptional regulator of E. carotovora subspecies, and AHL neutralizes this ExpR effect.