Plasticity of a transcriptional regulation network among alpha-proteobacteria is supported by the identification of CtrA targets in Brucella abortus
Plasticity of a transcriptional regulation network among alpha-proteobacteria is supported by the identification of CtrA targets in Brucella abortus
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DOI：
10.1046/j.1365-2958.2002.02777.x
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发表时间：
2002-02-01
影响因子：
3.6
通讯作者：
De Bolle, X
中科院分区：
文献类型：
--
作者：
Bellefontaine, AF;Pierreux, CE;De Bolle, X
CTRA是一种主要的反应调节因子，存在于许多α-蛋白细菌中。在新月桂杆菌和苜蓿中华根瘤菌中，这种调节因子对生存是必不可少的，并且是转录自动调节的。在Crescentus中，它是调节多种细胞周期事件所必需的，如DNA甲基化、DNA复制、鞭毛和菌毛的生物发生和隔膜。在这里，我们报告了阿尔法(2)蛋白细菌布鲁氏菌中CTRA基因同源物的特征，这是一种导致布鲁氏菌病的兼性细胞内病原体。我们检测到CtrA在主要布鲁氏菌中的表达，其过量生产导致了典型的细胞分裂缺陷的表型，与其预期的作用一致。纯化的流产杆菌CtrA重组蛋白(His(6)-CtrA)可以保护流产杆菌CTRA启动子不被DNase I消化，提示转录自我调节，而且CtrA在保守的Asp残基上的磷酸化增强了这种保护作用。尽管流产杆菌和新月弯孢杆菌CTRA有相似之处，但在这两种细菌中，CtrA下游的途径可能是不同的，至少部分是不同的。事实上，除了CTRA本身，在已知的crescentus CtrA靶标的四个流产杆菌同源物中，只有一个(CCRM基因)在体外与磷酸化的流产杆菌CtrA结合。此外，进一步的足迹实验支持这样的假设，即在B.bortus中，CtrA可能直接调节rpoD、Plec、Minc和FTSE同源物的表达。综上所述，这些结果表明，在流产球虫和新月球藻中，相似的细胞过程是由CtrA通过控制不同的靶基因来调节的。这两种细菌中涉及CtrA的调控网络的可塑性可能与它们不同的生活方式有关。
CtrA is a master response regulator found in many alpha-proteobacteria. In Caulobacter crescentus and Sinorhizobium meliloti, this regulator is essential for viability and is transcriptionally autoregulated. In C. crescentus, it is required for the regulation of multiple cell cycle events, such as DNA methylation, DNA replication, flagella and pili biogenesis and septation. Here, we report the characterization of the ctrA gene homologue in the alpha(2)-proteobacteria Brucella abortus, a facultative intracellular pathogen responsible for brucellosis. We detected CtrA expression in the main Brucella species, and its overproduction led to a phenotype typical of cell division defect, consistent with its expected role. A purified B. abortus CtrA recombinant protein (His(6)-CtrA) was shown to protect the B. abortus ctrA promoter from DNase I digestion, suggesting transcriptional autoregulation, and this protection was enhanced under CtrA phosphorylation on a conserved Asp residue. Despite the similarities shared by B. abortus and C. crescentus ctrA, the pathway downstream from CtrA may be distinct, at least partially, in both bacteria. Indeed, beside ctrA itself, only one (the ccrM gene) out of four B. abortus homologues of known C. crescentus CtrA targets is bound in vitro by phosphorylated B. abortus CtrA. Moreover, further footprinting experiments support the hypothesis that, in B. abortus, CtrA might directly regulate the expression of the rpoD, pleC, minC and ftsE homologues. Taken together, these results suggest that, in B. abortus and C. crescentus, similar cellular processes are regulated by CtrA through the control of distinct target genes. The plasticity of the regulation network involving CtrA in these two bacteria may be related to their distinct lifestyles.