LexA-independent DNA damage-mediated induction of gene expression in Myxococcus xanthus
LexA-independent DNA damage-mediated induction of gene expression in Myxococcus xanthus
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DOI：
10.1046/j.1365-2958.2003.03592.x
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发表时间：
2003-08-01
影响因子：
3.6
通讯作者：
Barbé, J
中科院分区：
文献类型：
--
作者：
Campoy, S;Fontes, M;Barbé, J
黄色粘球菌（Myxococcus xanthus）是变形菌门（Proteobacteria delta）的一个成员，具有两个独立的recA基因recA 1和recA 2，但只有recA 2是DNA损伤诱导的。莱克萨基因已从M.通过在Cereon微生物序列数据库中对其基因组进行TBLADNA分析进行序列鉴定后设计的寡核苷酸进行PCR扩增。分枝经证明，xanthus纯化的莱克萨A蛋白与存在于莱克萨A和recA 2上游的共有序列CTRHAMRYBYGTTCAGS特异性结合。在recA 1基因的上游区域可以鉴定出该基序的简并拷贝，但具有重要的差异。已经产生的敲除莱克萨（Def）突变体在形态、生长速率、光诱导的胡萝卜素生成或发育方面与野生型没有显著差异。使用转录lacZ融合和定量RT-PCR分析，它已被证明，莱克萨和recA 2基因的表达是组成性的莱克萨（Def）突变体，而转录的DNA损伤非诱导recA 1基因不受此菌株。recN和ssb在大肠杆菌中的表达受LexA调控，它们在M. xanthus莱克萨（Def）突变体。这些数据揭示了属于不同门的细菌中存在不同的DNA损伤诱导基因的调控机制。
Myxococcus xanthus, a member of the Proteobacteria delta-class, has two independent recA genes, recA1 and recA2, but only recA2 is DNA damage-inducible. The lexA gene has been isolated from M. xanthus by PCR amplification with oligonucleotides designed after sequence identification by TBLASTN analysis of its genome at the Cereon Microbial Sequence Database. The M. xanthus purified LexA protein is shown to bind specifically to the consensus sequence CTRHAMRYBYGTTCAGS present upstream of lexA and recA2. A degenerate copy of this motif but with important differences can be identified in the region upstream of the recA1 gene. A knock-out lexA(Def) mutant that has been generated does not differ significantly from wild type in morphology, growth rate, light-induced carotenogenesis or development. Using transcriptional lacZ fusions and quantitative RT-PCR analysis, it has been demonstrated that expression of both lexA and recA2 genes is constitutive in the lexA(Def) mutant, whereas the transcription of the DNA damage non-inducible recA1 gene is not affected in this strain. recN and ssb, whose expression in Escherichia coli are LexA-regulated, are induced by DNA damage in the M. xanthus lexA(Def) mutant. These data reveal the existence of different regulatory mechanisms for DNA damage-inducible genes in bacteria belonging to different phyla.