Regulation of the fimB promoter:: a case of differential regulation by ppGpp and DksA in vivo
Regulation of the fimB promoter:: a case of differential regulation by ppGpp and DksA in vivo
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DOI：
10.1111/j.1365-2958.2008.06115.x
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发表时间：
2008-03-01
影响因子：
3.6
通讯作者：
Balsalobre, Carlos
中科院分区：
文献类型：
--
作者：
Aberg, Anna;Shingler, Victoria;Balsalobre, Carlos
通过刺激FIMB转录，1型菌毛的表达依赖于细胞内ppGpp的水平。在这里，我们表明，与前面描述的在ppGpp缺陷株中观察到的减少的菌毛相反，DksA缺乏会导致超灌流状态。体内实验表明，由于FIMB P2启动子转录水平的升高，DksA缺乏对1型菌毛的影响发生在相变水平。相反，我们的体外转录研究表明，ppGpp和DksA可以独立和相互依赖地刺激FIMB P2启动子的转录。我们提供的证据表明，来自体内和体外转录研究的表面上相互矛盾的结果至少部分是由于在体内没有Dks A的情况下，抗暂停因子(GREA和GREB)与RNA聚合酶的关联增加的结果。
The expression of type 1 fimbriae is dependent on the intracellular levels of ppGpp through stimulation of fimB transcription. Here we show that in contrast to the previously described decreased fimbriation observed in a ppGpp-deficient strain, DksA deficiency results in a hyperfimbriated state. In vivo assays show that the effect of DksA deficiency on the type 1 fimbriae occurs at the phase variation level because of elevated transcription from the fimB P2 promoter. In contrast, our in vitro transcription studies demonstrate that ppGpp and DksA can stimulate transcription from the fimB P2 promoter both independently and codependently. We provide evidences that the apparently contradictory results from the in vivo and in vitro transcriptional studies are at least in part a consequence of the increased association of the anti-pausing factors (GreA and GreB) to the RNA polymerase in the absence of DksA in vivo.