Expression of canonical SOS genes is not under LexA repression in Bdellovibrio bactefiovorus
Expression of canonical SOS genes is not under LexA repression in Bdellovibrio bactefiovorus
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DOI：
10.1128/jb.187.15.5367-5375.2005
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发表时间：
2005-08-01
影响因子：
3.2
通讯作者：
Barbé, J
中科院分区：
文献类型：
--
作者：
Campoy, S;Salvador, N;Barbé, J
本文报道的三角变形菌门细菌捕食者Bdellovibrio bacteriovorus的LexA结合序列的鉴定，使得对其LexA调控网络的详细研究成为可能。令人惊讶的是，在这种细菌中，只有lex，4基因和包括dinP和dnaE同源物的多基因盒受到LexA蛋白的调节。体内表达分析证实，该基因盒确实形成了一个多顺反子单元，与lexA基因一样，在B. bacteriovorus中可诱导DNA损伤。相反，像recA、uvrA、ruvCAB和ssb这些构成变形菌群SOS系统典型核心的基因，在该生物体中不受LexA蛋白的抑制，这暗示了维持LexA基因及其对已报道的多基因盒的调控存在持续的选择压力。体外实验表明，B. bacteriovorus的LexA结合序列不能被其他delta-Proteobacteria的LexA蛋白识别，但可以与蓝藻的LexA抑制因子结合。这将B. bacteriovorus LexA置于delta-Proteobacteria LexA家族的基础，揭示了在变形菌门的更深群体中看到的多样化和特化之前，LexA调控序列的高度保守性。
The here-reported identification of the LexA-binding sequence of Bdellovibrio bacteriovorus, a bacterial predator belonging to the delta-Proteobacteria, has made possible a detailed study of its LexA regulatory network. Surprisingly, only the lex,4 gene and a multiple gene cassette including dinP and dnaE homologues are regulated by the LexA protein in this bacterium. In vivo expression analyses have confirmed that this gene cassette indeed forms a polycistronic unit that, like the lexA gene, is DNA damage inducible in B. bacteriovorus. Conversely, genes such as recA, uvrA, ruvCAB, and ssb, which constitute the canonical core of the Proteobacteria SOS system, are not repressed by the LexA protein in this organism, hinting at a persistent selective pressure to maintain both the lexA gene and its regulation on the reported multiple gene cassette. In turn, in vitro experiments show that the B. bacteriovorus LexA-binding sequence is not recognized by other delta-Proteobacteria LexA proteins but binds to the cyanobacterial LexA repressor. This places B. bacteriovorus LexA at the base of the delta-Proteobacteria LexA family, revealing a high degree of conservation in the LexA regulatory sequence prior to the diversification and specialization seen in deeper groups of the Proteobacteria phylum.