The RpoN-RpoS regulatory pathway in Borrelia burgdorferi

描述（由申请人提供）：伯氏疏螺旋体（Bb），莱姆病螺旋体，当它在不同的蜱虫和哺乳动物宿主之间循环时，经历了巨大的适应性变化。在首席研究员在过去的资助期开展工作之前，人们对调节Bb的适应性变化的遗传调控网络知之甚少，这些变化有助于Bb的传染性和毒力。为此，我们在Bb中发现了一种新的调控途径，其中一种可选sigma因子（CN, RpoN）调节另一种可选sigma因子（Cs, RpoS）的表达，后者反过来控制与Bb毒力相关的关键膜脂蛋白的表达。该通路由一种增强子结合蛋白——反应调节蛋白2 （Rrp2）控制，为了随后的RpoN激活和随后的rpoS转录，必须首先激活rp2。虽然这种在Bb中的调节网络的发现代表了莱姆病领域的重要进展，但它也引发了许多新的问题，如其直接和间接调节作用，该通路如何与其他调节机制交叉，以及Bb的各种基因如何以及在多大程度上受到影响。在下一个供资期间选定的调查领域将继续解决其中一些突出的信息差距。因此，本提案的具体目的是：(1)识别直接受rpo - rpos通路影响的基因。我们将把我们在Bb微阵列方面的专业知识与我们新开发的lac阻遏物/操作员系统结合起来，人为地控制Bb中rpoS的表达。已确定的基因将成为进一步研究的主题（目标4）；(2)探讨rpo - rpos通路调控decorin-binding protein （DbpB/A）操纵子非典型表达的机制。dbpBA操纵子受rpo -RpoS通路控制，但其表达模式不同于其他受RpoS控制的基因（如ospC）。因此，dbpBA可能是受该途径影响的某些基因如何也受到另一层调控的一个模型。重点分析dbpBA启动子和上游顺式元件的主要特征；(3)检测rpoS在Bb虫全生命周期（蜱虫期和哺乳期）的表达；(4)检测选择rpos依赖基因缺失的Bb突变体的表型。这些努力将为进一步表征Bb中新的rpo - rpos调控网络，以及潜在地识别对Bb复杂寄生策略的许多方面有贡献的调控和毒力相关基因提供扩展的基础。了解这些基因的作用可能会导致莱姆病的新干预策略（疫苗，疗法）。

DESCRIPTION (provided by applicant): Borrelia burgdorferi (Bb), the Lyme disease spirochete, undergoes dramatic adaptive changes as it cycles in nature between its diverse tick and mammalian hosts. Prior to work conducted by the principle investigator over the past funding interval, little was known regarding the genetic regulatory networks that modulate Bb's adaptive changes contributing to Bb's infectivity and virulence. To this end, we discovered a novel regulatory pathway in Bb, wherein one alternative sigma factor (CN, RpoN) regulates the expression of another alternative sigma factor (Cs, RpoS) that, in turn, governs the expression of key membrane lipoproteins associated with Bb's virulence. The pathway is controlled by an enhancer-binding protein, response regulator protein-2 (Rrp2), which first must be activated for the subsequent activation of RpoN and the consequent transcription of rpoS. Although the discovery of this regulatory network in Bb has represented an important advance in the Lyme disease field, it also has prompted many new questions regarding its direct and indirect regulatory effects, how the pathway intersects with other regulatory mechanisms, and how and to what extents various genes of Bb are influenced. Selected areas of investigation over the next funding interval will continue to address some of these salient information gaps. Accordingly, the Specific Aims of this proposal are: (1) To discern those genes directly influenced by the RpoN-RpoS pathway. We shall combine our expertise in Bb microarrays with our newly developed lac repressor/operator system to artificially control the expression of rpoS in Bb. Identified genes will become the subject of further studies (Aim 4); (2) To investigate the mechanism by which the RpoN-RpoS pathway regulates atypical expression of the decorin-binding protein (DbpB/A) operon. The dbpBA operon is under the control of the RpoN-RpoS pathway, but it has an expression pattern different from other genes controlled by RpoS (e.g., ospC). As such, dbpBA may be a model of how certain genes influenced by the pathway also are subjected to another layer of regulation. Emphasis will be placed on analyzing key features of the dbpBA promoter and upstream cis-elements; (3) To examine the expression of rpoS over the complete enzootic life cycle (tick and mammalian phases) of Bb; and (4) To examine the phenotypes of Bb mutants deficient in selected RpoS-dependent genes. These efforts will provide an expanding foundation for further characterizing the novel RpoN-RpoS regulatory network in Bb, and for potentially identifying regulatory and virulence-associated genes that contribute to many aspects of Bb's complex parasitic strategy. Understanding the roles of these genes could lead to new intervention strategies (vaccines, therapeutics) for Lyme disease.