Th17细胞中SOX5介导的RORγt基因启动子和潜在增强子RORCE2间相互作用的分子机制

Th17 cell, RORγt as its key transcription factors (TF), plays an important role in inflammatory diseases. Nowadays, the regulation mechanisms of RORγt expression, especially the roles of enhancers in the regulation of this gene expression, have been not been fully elucidated. In the previous studies supported by my last NSFC, we found and identified a potential enhancer of RORγt gene, named as RORCE2. However the detailed molecular mechanism how RORCE2 enhances RORγt expression needs to be further investigated. After our preliminary results and relevant literatures suggest that after the binding of Sox5 to RORCE2, Sox5 could recruit the Mediator and then interact with a specific subunit of Mediator, which bind to RORγt gene promoter. Finally, the interaction between RORCE2 and RORγt promoter mediated by Sox5 and Mediator will enhance the expression of RORγt gene. In this project, in vitro and vivo models, we will further confirm the function of RORCE2, the key TF and specific mediator subunit mediating the interaction between the RORCE2 and RORγt promoter. The expected results of this project will firstly provide not only a new molecular mechanism of the regulation of RORγt expression but also some new potential targets for the clinical prevention and treatment of Th17-related diseases.

Th17细胞在炎性疾病中具有重要作用。RORγt是Th17关键转录因子，但有关其表达调控机制尚未完全阐明，特别是有关增强子对其调控的研究更是空白。前一个基金在Th17细胞中发现并初步鉴定了一个RORγt基因增强子RORCE2，但其发挥作用的分子机制有待研究。前期实验结果及相关文献提示：可能是转录因子Sox5结合到RORCE2上后，招募并结合Mediator某特定亚基，Mediator再与RORγt基因启动子结合，介导RORCE2和RORγt启动子的相互作用，促进RORγt转录。本课题拟通过体内、外实验，进一步确认RORCE2的增强子功能；证实Sox5是介导RORCE2和RORγt启动子相互作用的关键因素；探寻与Sox5直接结合且参与了RORCE2和RORγt启动子相互作用的特定Mediator亚基。本研究将为RORγt基因的表达调控阐明一种新机制，同时为Th17相关疾病防治提供潜在新靶标。

Th17 (T helper type 17)细胞在炎症和自身免疫性疾病的发病机制以及宿主对病原体的保护中发挥关键作用。视黄酸受体相关的孤儿受体(RORγt)是Th17细胞分化和发挥功能的必要条件。然而，对于RORγt表达的转录调控，尤其是对其增强子的研究，目前尚无报道。在本课题中，基于增强子的表观遗传学研究和双荧光素酶报告实验，我们在Th17细胞中发现了一段全新的RORγt基因的增强子，并命名为RORCE2。增强子RORCE2的缺失可以显著地引起 RORγt的蛋白表达降低，从而影响Th17细胞的分化，导致实验性自身免疫性脑脊髓炎的疾病程度降低。此外，我们还发现在Th17细胞中，增强子RORCE2通过SRY-box转录因子5 (SOX-5)的介导与RORγt启动子区域相互作用形成Loop结构发挥增强子功能。更为重要的是，在RORCE上缺失SOX-5的结合位点，可以完全破坏增强子RORCE2的功能，并影响了RORγt基因的关键激活因子STAT3与RORCE的结合。综上所述，本课题提出了一种全新的调控Th17分化和功能的分子机制，也为Th17细胞相关疾病的治疗提供了新的潜在靶点。

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