Molecular Insights into the Control of Transcription Initiation at the Staphylococcus aureus agr operon
Molecular Insights into the Control of Transcription Initiation at the Staphylococcus aureus agr operon
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DOI：
10.1016/j.jmb.2011.06.018
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发表时间：
2011-10-07
影响因子：
5.6
通讯作者：
Wigneshweraraj, Sivaramesh
中科院分区：
文献类型：
--
作者：
Reynolds, Jonathan;Wigneshweraraj, Sivaramesh
人类机会致病菌金黄色葡萄球菌的辅助基因调控（agr）操纵子是该细菌的主要致病因子。agr操纵子由两个转录单位RNAII和RNAIII组成，它们分别从趋异启动子P2和P3转录。RNAII编码群体感应系统，包括Agr操纵子的主转录激活因子AgrA。RNAIII是调节许多毒力基因表达的效应RNA分子。由于P2和P3的非典型间隔区长度，人们普遍认为P2和P3的转录仅以严格的AgrA依赖性方式发生。在这里，使用一个完全原生的S。金黄色葡萄球菌体外转录系统，我们提供了第一个分子和机制的特点，转录起始的调节agr操纵子。令人惊讶的是，结果表明，RNA聚合酶（RNAp）可以与P2和P3在AgrA的情况下同样很好地相互作用。然而，当AgrA不存在时，在P2比在P3更容易形成有转录能力的开放启动子复合物（RPo）。将非典型P3间隔区长度减少到17个核苷酸的最佳长度通过促进初始RNAp P3复合物异构化为RPo而显著提高启动子活性，并且P3的延伸的-10样元件是最佳启动子活性所需的。AgrA增加了RNA β对两个启动子的占用，从而增加了P2和P3处起始的转录量。然而，AgrA介导的转录起始的影响是更突出的P3在P2。AgrA在P2和P3的作用似乎仅限于导致RPo形成的事件。在P2和P3的AgrA非依赖性和AgrA依赖性转录起始的相关性是在我们目前对Agr操纵子在S.金黄色的(C)2011爱思唯尔有限公司版权所有。
The accessory gene regulatory (agr) operon of the opportunistic human pathogen Staphylococcus aureus is a prime pathogenesis factor in this bacterium. The agr operon consists of two transcription units, RNAII and RNAIII, which are transcribed from divergent promoters, P2 and P3, respectively. RNAII encodes a quorum-sensing system, including AgrA, the master transcription activator of the agr operon. RNAIII is the effector RNA molecule that regulates the expression of many virulence genes. Owing to the atypical spacer lengths of P2 and P3, it is widely considered that transcription from P2 and P3 only occurs in a strictly AgrA-dependent manner. Here, using a fully native S. aureus in vitro transcription system, we provide the first molecular and mechanistic characterisation of the regulation of transcription initiation at the agr operon. Surprisingly, the results demonstrate that RNA polymerase (RNAp) can interact with P2 and P3 equally well in the absence of AgrA. However, formation of a transcription-competent open promoter complex (RPo) occurs more readily at P2 than at P3 when AgrA is absent. Reducing the atypical P3 spacer region length to the optimal length of 17 nucleotides significantly improves promoter activity by facilitating the isomerisation of the initial RNAp P3 complexes to RPo, and the extended -10-like element of P3 is required for optimal promoter activity. AgrA increases the occupancy of both promoters by RNAp and thereby increases the amount of transcription initiated at P2 and P3. However, the AgrA-mediated effect on transcription initiation is more prominent at P3 that at P2. The effect of AgrA at P2 and P3 appears to be restricted to events leading to the formation of RPo. The relevance of AgrA-independent and AgrA-dependent transcription initiation at P2 and P3 is presented in the context of our current understanding of the role of the agr operon in the pathobiology of S. aureus. (C) 2011 Elsevier Ltd. All rights reserved.