Regulation of recombination in Mycoplasma genitalium

摘要 生殖支原体（MG）是一种性传播病原体，被认为是引起几种性传播疾病的重要原因。 男性和女性生殖道疾病综合征。尽管有炎症和特异性抗体 MG感染通常是慢性的，如果不进行有效的治疗， 抗生素治疗我们和其他人已经表明，MG的粘附素MgpB和MgpC经历阶段， 抗原变异，可能导致宿主免疫应答的逃避、持续和再感染。 MgpBC变异是由mgpBC之间独特的节段相互重组系统介导的。 这些基因的表达位点和存档的同源部分拷贝，称为MgPars，位于整个 MG染色体然而，mgpBC/MgPar重组所需的组分和它们的分子量是不确定的。 调节不完全理解，部分原因是难以与这种挑剔的细菌一起工作， MG微小的基因组（580 kb）中缺乏一套完整的重组基因和调控基因。目标 该提议的目的是表征介导mgpBC/MgPar重组的调节机制，以及 从而导致MG的抗原变异。最近，我们发现MG 428正调控重组， 酶（recA，ruvA和ruvB），并确定这种蛋白质是一种以前未表征的， 细胞质外功能（ECF）σ因子。我们还表明，MG特有的RecA表达为 三个不同的异构体产生的替代翻译起始：一个积极的，全长RecA和两个 这种蛋白质的无活性的N-末端截短形式。我们认为，小亚型调节 mgpBC/MgPar重组在MG中通过抑制全长RecA的活性。此外，我们已确定 一种新的未知功能的蛋白质减少了抗原性和相位变异。我们假设这 推定的膜蛋白控制mgpBC/MgPar重组响应环境信号。在 此外，我们已经确定，在低CO2下的生长提高了抗原和相的变化率。建筑 基于这些初步发现，我们寻求资金，以探索截短的同种型在全长 RecA活性（目标1），定义了我们的新方法减少抗原和相位变异的机制。 确定的膜蛋白，包括其假定的相互作用伙伴网络（目的2），并探讨如何 二氧化碳和其他环境条件影响这一过程（目标3）。最后，我们将研究 这些条件对重组基因转录和RecA同种型的表达的影响，从而定义 控制该生物体中mgpBC/MgPar重组的途径。我们预计，这项研究将 揭示了一种新的、复杂的和严格调节的介导存活的抗原和相位变异系统， 在临床上显著且极其挑剔的病原体中逃避宿主免疫应答。

ABSTRACT Mycoplasma genitalium (MG) is a sexually transmitted pathogen, recognized as an important cause of several reproductive tract disease syndromes in men and women. Despite the inflammation and specific antibodies produced by the host, MG infections are often chronic, persisting for many months if not treated with effective antibiotic therapy. We and others have shown that the adhesins of MG, MgpB and MgpC, undergo phase and antigenic variation, likely contributing to evasion of the host immune response, persistence, and reinfection. MgpBC variation is mediated by a unique system of segmental reciprocal recombination between the mgpBC expression site and archived homologous partial copies of these genes, termed MgPars, located throughout the MG chromosome. However, the components required for mgpBC/MgPar recombination and their regulation are incompletely understood, in part due to the difficulty of working with this fastidious bacterium and the absence of a complete set of recombination genes and regulators in MG's tiny genome (580 kb). The goal of this proposal is to characterize the regulatory mechanism(s) mediating mgpBC/MgPar recombination, and therefore antigenic variation, in MG. Recently, we discovered that MG428 positively regulates recombination enzymes (recA, ruvA, and ruvB) and determined that this protein is a previously uncharacterized, extracytoplasmic function (ECF) sigma factor. We have also shown that, unique to MG, RecA is expressed as three distinct isoforms generated by alternative translation initiation: an active, full-length RecA and two inactive, N-terminally truncated versions of this protein. We propose that the small isoforms regulate mgpBC/MgPar recombination in MG by inhibiting the activity of full-length RecA. Further, we have determined that a novel protein of unknown function reduces antigenic and phase variation. We hypothesize that this putative membrane protein controls mgpBC/MgPar recombination in response to environmental signals. In addition, we have determined that growth in low CO2 enhances antigenic and phase variation rates. Building on these preliminary findings, we seek funding to explore the function of the truncated isoforms on full-length RecA activity (Aim 1), define the mechanism by which antigenic and phase variation is reduced by our newly identified membrane protein, including its putative network of interacting partners (Aim 2), and explore how CO2 and other environmental conditions affect this process (Aim 3). Finally we will investigate the effect of these conditions on recombination gene transcription and the expression of RecA isoforms, thereby defining the pathways controlling mgpBC/MgPar recombination in this organism. We anticipate that this study will reveal a novel, complex, and tightly regulated system of antigenic and phase variation mediating survival and evasion of the host immune response in a clinically significant and extremely fastidious pathogen.