Regulation of Virulence Gene Expression in Chlamydia

描述（由申请人提供）：衣原体是导致不育、失明、肺炎的人类病原体，与人类死亡的头号原因——心脏病密切相关。衣原体是专性细胞内细菌，并通过一个与发病机制密切相关的确定的双期发育周期得以延续。发育周期主要受控于转录水平；然而，在我们对衣原体发育调控机制的理解上有一个严重的缺陷。我们研究的长期目标是有助于描述调节衣原体发育和发病机制的关键分子机制。我们在这里提出的研究旨在确定衣原体转录因子ChxR的生物学作用和基本调控机制。ChxR是反应调节因子中OmpR亚家族的非典型成员。我们的中心假设是ChxR在调节中晚期基因表达中起重要作用，其机制与OmpR/PhoB反应调控子亚家族相似，但又不同。主要是由于目前衣原体的遗传难解性，ChxR的生物学作用尚不清楚。为了阐明ChxR的生物学作用并确定其调控机制，本文提出了以下具体目标：1)确定体内ChxR的直接基因靶点；2)描述ChxR转录激活的完整机制；3)确定ChxR功能的完整分子内和分子间相互作用。作为这些研究的结果，我们希望解决这个领域的一个基本问题，“衣原体如何调节它们的生长？”此外，OmpR反应调节因子，如ChxR，在细菌中广泛存在，而在哺乳动物中不存在。因此，它们是开发新的抗菌素的有吸引力的目标。对ChxR发挥正常功能所采用的分子机制的表征，将使未来能够设计出能够中断ChxR和衣原体感染功能的新分子。

DESCRIPTION (provided by applicant): Chlamydia are human pathogens that cause sterility, blindness, pneumonia and are strongly correlated with the number one cause of death in humans, heart disease. Chlamydia are obligate intracellular bacteria and are perpetuated through a defining biphasic developmental cycle that is intimately linked with pathogenesis. The developmental cycle is governed predominately at the transcriptional level; however, there is a critical deficiency in our understanding of developmental regulatory mechanisms in Chlamydia. The long-term goal in our research is to contribute to a delineation of the key molecular mechanisms that function to regulate chlamydial development and pathogenesis. The research we propose here is designed to define the biological role and essential regulatory mechanisms for the chlamydial transcription factor termed ChxR. ChxR is an atypical member of the OmpR subfamily of response regulators. Our central hypothesis is that ChxR has an important role in regulating middle and late stage gene expression and incorporates a mechanisms similar to, but distinct from, the subfamily of OmpR/PhoB response regulators. Largely due to the current genetic intractability of Chlamydia, the biological role of ChxR is not known. To elucidate the biological role and determine regulatory mechanism of ChxR the following specific aims are proposed: 1) define the direct gene targets of ChxR in vivo, 2) delineate the mechanism integral for chxR transcriptional activation, and 3) determine the intra- and inter- molecular interactions integral to ChxR function. As a result of these studies, we expect to address a fundamental question in the field, 'how do Chlamydia regulate their growth?' Furthermore, OmpR response regulators, like ChxR, are widespread in bacteria and absent in mammals. As such, they are attractive targets for the development of new antimicrobials. Characterization of the molecular mechanisms employed by ChxR for proper function will allow in the future for rationale design of novel molecules that interrupt the function of ChxR and Chlamydia infections.