p63/YY1通过调控染色质结构激活SULF2介导肝癌的机制研究

染色质结构异常与肿瘤发生密切相关，先锋转录因子能结合并打开封闭染色质。申请人前期证明p53为先锋转录因子，最近发现p63也具备该特性，且其多结合在增强子区域，上调增强子活性。文献及我们预实验均显示部分肝癌组织及细胞系中p63高表达。但“p63是否作为先锋转录因子参与肝癌发生及其机制”尚无报道。围绕这一关键科学问题，我们预实验显示：过表达p63促进肝癌细胞增殖，伴促癌基因SULF2上调；SULF2增强子及启动子区存在多个p63结合位点，过表达p63这些位点附近H3K4me3显著上调(激活)；p63与增强子-启动子互作蛋白YY1存在相互作用，且二者结合位点相邻。由此，我们提出科学假设：p63作为先锋转录因子打开SULF2调控元件染色质结构，召集YY1形成启动子-增强子环，最终上调SULF2表达，促进肝癌发生。本项目拟采用ChIA-PET等方法验证该假设，有望阐明染色质结构重塑介导肝癌的新机制。

Aberrant chromatin structure plays a critical role in tumorigenesis. Pioneer transcription factors can bind to closed chromatin and induce chromatin opening. The applicant previously proved the pioneering capability of p53, and recently found that p63 also has pioneer factor characteristics, which usually binds to enhancer with increased activity. Previous publications and our pilot experiments showed that p63 is highly expressed in a few liver cancer tissues and cell lines. However, "whether p63 functions as pioneer transcription factor in liver tumorigenesis" has not been proved yet. In order to explore this issue, we performed preliminary experiments and found that overexpression of p63 promoted the liver cancer cells proliferation along with up-regulation of SULF2; besides, there were multiple p63 binding sites in the SULF2 enhancer and promoter regions, and p63 overexpression significantly up-regulated H3K4me3 (active histone mark) surrounding these sites; moreover, p63 interacts with YY1 protein which can establish enhancer-promoter interactions, and they also have adjacent binding sites. Therefore, we hypothesized that p63 functions as a pioneer transcription factor, which opens up the chromatin structure of SULF2 regulatory elements, and then recruits YY1 to establish a promoter-enhancer loop, and finally up-regulates SULF2 expression and promotes liver tumorigenesis. Techinques including ChIA-PET will be applied, we aims at providing new insights for the role of chromatin remodeling in liver tumorigenesis.