SarA, a global regulator of virulence determinants in Staphylococcus aureus, binds to a conserved motif essential for sar-dependent gene regulation
SarA, a global regulator of virulence determinants in Staphylococcus aureus, binds to a conserved motif essential for sar-dependent gene regulation
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DOI：
10.1074/jbc.274.52.37169
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发表时间：
1999-12-24
影响因子：
4.8
通讯作者：
Cheung, AL
中科院分区：
文献类型：
--
作者：
Chien, YT;Manna, AC;Cheung, AL
金黄色葡萄球菌中许多毒力决定簇的表达，包括 α-溶血素、蛋白 A 和纤连蛋白结合蛋白，均受 sar 和 agr 等全局调控位点控制。除了通过agr（例如α-溶血素）控制靶基因表达外，sar位点还可以通过agr独立机制调节靶基因转录。特别是，我们发现 sar 中编码的主要调节蛋白 SarA 与 agr 启动子上的 SarA 结合位点同源的保守序列结合，该序列位于几个靶基因的 -35 启动子盒的上游，包括 hla（α-溶血素基因）、spa（蛋白 A 基因）、fnb（纤连蛋白结合蛋白基因）和 sec （肠毒素C基因）。穿梭质粒中agr和hla启动子区域中SarA识别基序的缺失使得这些基因的转录在agr和hla突变体中分别检测不到。同样，通过 XylE 报告基因融合测定测量，spa（通常被 sar 抑制的基因）的转录活性在含有穿梭质粒的野生型菌株中变得去抑制，其中 SarA 识别位点已从 spa 启动子区域删除。然而，DNase I 足迹分析表明，spa 和 hla 启动子上的 SarA 结合区域比预测的共有序列更广泛，因此提高了共有序列是较大结合区域内的激活位点的可能性。由于 sar 和 agr 调节金黄色葡萄球菌中的各种毒力因子，因此我们根据我们的数据提出了金黄色葡萄球菌中毒力基因激活的统一假设，其中 SarA 是一种调节蛋白，与其共有的 SarA 识别基序结合，以激活（例如 hla）或抑制（例如 spa）sar 靶基因的转录，从而解释了 agr 依赖性和 独立于农业的调节模式。
The expression of many virulence determinants in Staphylococcus aureus including alpha-hemolysin-, protein A-, and fibronectin-binding proteins is controlled by global regulatory loci such as sar and agr. In addition to controlling target gene expression via agr (e.g. alpha-hemolysin), the sar locus can also regulate target gene transcription via agr-independent mechanisms. In particular, we have found that SarA, the major regulatory protein encoded within sar, binds to a conserved sequence, homologous to the SarA-binding site on the agr promoter, upstream of the -35 promoter boxes of several target genes including hla (alpha-hemolysin gene), spa (protein A gene), fnb (fibronectin-binding protein genes), and sec (enterotoxin C gene). Deletion of the SarA recognition motif in the promoter regions of agr and hla in shuttle plasmids rendered the transcription of these genes undetectable in agr and hla mutants, respectively. Likewise, the transcription activity of spa (a gene normally repressed by sar), as measured by a XylE reporter fusion assay, became derepressed in a wild type strain containing a shuttle plasmid in which the SarA recognition site had been deleted from the spa promoter region. However, DNase I footprinting assays demonstrated that the SarA-binding region on the spa and hla promoter is more extensive than the predicted consensus sequence, thus raising the possibility that the consensus sequence is an activation site within a larger binding region. Because the sar and agr regulate an assortment of virulence factors in S. aureus, we propose, based on our data, a unifying hypothesis for virulence gene activation in S. aureus whereby SarA is a regulatory protein that binds to its consensus SarA recognition motif to activate (e.g. hla) or repress (e.g. spa) the transcription of sar target genes, thus accounting for both agr-dependent and agr-independent mode of regulation.