正常细胞恶性转化过程中，基因组散在CpG位点去甲基化的机制，是甲基化理论的“瓶颈”问题。申请人前期在胆管癌中发现：HP1α和H2A.Z在基因组的分布和锚定位置，对散在CpG位点去甲基化有显著影响，该过程与TET1蛋白密切相关。项目结合国内外研究前沿，提出科学假设：在胆管细胞恶性转化过程中，HP1α和H2A.Z通过转换在基因体和启动子的锚定位置，改变局部染色质构象，募集TET1蛋白并结合辅助因子，识别甲基化CpG位点将其去甲基化。针对科学假设的关键问题，项目拟重点研究：1.证实HP1α，H2A.Z易位对局部染色质构象、TET1蛋白锚定、散在CpG位点去甲基化的调控作用；2.证实TET1是散在CpG位点去甲基化的关键酶蛋白；3.鉴定TET1蛋白去甲基化的辅助因子，阐明散在CpG位点去甲基化的具体机制。项目目的是探讨散在CpG位点去甲基化机制，丰富甲基化理论，完善肿瘤去甲基化干预策略。

The mechanism of demethylation of scattered genomic CpG loci during malignant progression is still a “bottleneck” problem in the theory of DNA methylation. Our previous studies in cholangiocarcinoma have found that the HP1α and H2A.Z binding to specific genomic region is critical to the demethylation of scattered CpG loci, TET1 is indispensable for this process. Combining the national with international foreland, we hypothesize that the transposition of HP1α and H2A.Z in the gene body and promoter alters the local chromatin conformation which recruits TET1 to binds with cofactors and then regulates the demethylation of scarttered genomic CpG loci during malignant transformation. In this project, we will pursue the following specific aims: 1. to determine how HP1α-H2A.Z transposition regulates local chromatin conformation, TET1 recruitment, and demethylation of scarttered CpG loci; 2. to clarify that TET1 is the key enzyme in regulation of scattered CpG demethylation; 3. to identify the co-factors which interact with TET1 and its specific mechanism to leads demethylation at targeted CpG loci. This grant is designed to decipher the mechanism of scattered genomic CpG loci demethylation, to enrich the academic system of DNA methylation, further to explore the strategy of demethylation therapy for cholangiocarcinoma.