Recognition of DNA by three ferric uptake regulator (Fur) homologs in Bacillus subtilis
Recognition of DNA by three ferric uptake regulator (Fur) homologs in Bacillus subtilis
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DOI：
10.1128/jb.185.21.6348-6357.2003
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发表时间：
2003-11-01
影响因子：
3.2
通讯作者：
Helmann, JD
中科院分区：
文献类型：
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作者：
Fuangthong, M;Helmann, JD
枯草芽孢杆菌含有三个毛皮同源物：Fur、PerR和Zur。尽管有显著的序列相似性，但它们对不同的刺激作出反应并调节不同的基因集。DNA靶位比较表明，这三种类似物都识别具有核心7-1-7反向重复的操作符。相应的一致序列在七个确定的位置中的五个或更多位置相同。利用定点诱变，mrgA启动子上的Per盒被改变以模仿Fur和Zur盒的核心7-1-7基序。在体外，含有Zur盒子的mrgA启动子仅被Zur识别，正如DNase I足迹测定所证明的那样。相比之下，Fur和PerR都结合到含有共识Fur盒的mrgA启动子区域。这些启动子的表达分析与体外数据一致，表明每半位点只需1或2个碱基变化就足以改变调控。同样，feuA启动子上的Fur盒子可以通过适当的突变转化为Per或Zur盒子。虽然Fur和PerR都可以识别一些相同的合成操作符序列，但没有已知的自然发生的位点受到双重调节。然而，perr调控的zosA基因是由一个包含Per和Fur盒子的调控区域控制的。虽然纯化的Fur蛋白与候选Fur box结合，但Fur对zosA表达的影响很小，这可能与Fur box相对于zosA启动子的位置有关。总之，我们的研究结果确定了两个核苷酸位置，这对PerR、Fur和Zur区分枯草芽孢杆菌基因组中存在的许多密切相关的操作位点的能力很重要。
Bacillus subtilis contains three Fur homologs: Fur, PerR, and Zur. Despite significant sequence similarities, they respond to different stimuli and regulate different sets of genes. DNA target site comparisons indicate that all three paralogs recognize operators with a core 7-1-7 inverted repeat. The corresponding consensus sequences are identical at five or more of the seven defined positions. Using site-directed mutagenesis, the Per box at the mrgA promoter was altered to mimic the core 7-1-7 motif of the Fur and Zur boxes. In vitro, the mrgA promoter containing a Zur box was only recognized by Zur, as demonstrated by DNase I footprinting assays. In contrast, both Fur and PerR bound to the mrgA promoter region containing a consensus Fur box. Expression analysis of these promoters is consistent with the in vitro data demonstrating as few as 1 or 2 base changes per half-site are sufficient to alter regulation. Similarly, the Fur box at the feuA promoter can be converted into a Per or a Zur box by appropriate mutations. While both Fur and PerR could recognize some of the same synthetic operator sequences, no naturally occurring sites are known that are subject to dual regulation. However, the PerR-regulated zosA gene is controlled from a regulatory region that contains both Per and Fur boxes. Although purified Fur protein bound to the candidate Fur boxes, Fur has little effect on zosA expression-possibly due to the location of the Fur boxes relative to the zosA promoter. Together, our results identify two nucleotide positions that are important for the ability of PerR, Fur, and Zur to distinguish among the many closely related operator sites present in the B. subtilis genome.