UHRF1介导的表观遗传调控网络在肝癌中的作用研究

DNA methylation and histone modifications have emerged as key mechanisms in the tumorigenesis.The interaction between them is paid more attention recently.Recent studies revealed that UHRF1 recognizes both DNA methylation and histone H3K9 methylation and links them, and is considered as one of the few most critical molecules in crosstalk between DNA methylation and histone modifications. In our previous study, we determined the methylation profiling of many tumor suppressor genes (TSGs) in hepatocellular carcinoma, and confirmed that DNA methylation and histone H3K9 trimethylation contributed to the inactivation of several TSGs, the involved enzymes contains of DNMT1, 3a, 3b and HDAC1 (all of them are the components of UHRF1 complexes). These results suggested that UHRF1 may be involved in the development of liver cancer. On this basis, our project is planned to: 1. Screen of methylated TSGs in liver cancer by high-throughput technologies and find the specific target genes of UHRF1; 2. Explore the regulation of target methylated genes by UHRF1-mediated epigenetic network in liver cancer; 3. Knockdown the key genes of this regulatory network and observe the influence on invasion and metastasis of liver cancer cells. This study will have great potential significance in providing early diagnostic marker of liver cancer, interpreting the interaction between DNA methylation and histone modifications and the design of specific epigenetic drugs.

DNA甲基化和组蛋白修饰在肿瘤的发生发展中都起着重要作用，它们之间的相互作用目前备受关注。最新研究发现，UHRF1可双重识别甲基化的DNA和甲基化的H3K9，被认为是DNA甲基化和组蛋白修饰交叉对话中少数最关键的分子之一。我们前期初步制定了肝癌相关抑癌基因甲基化谱并证实，DNA甲基化和H3K9三甲基化可共同导致多个抑癌基因的失活，参与的酶包含了DNMT1,3a,3b和HDAC1（均为UHRF1复合体的组分），提示UHRF1可能参与了肝癌的发生发展。本项目拟在此基础上：1. 高通量筛选肝癌相关甲基化抑癌基因，并在其中寻找UHRF1的靶基因；2. 探讨UHRF1介导的表观遗传网络对肝癌甲基化靶基因的调控机制；3. 敲除该调控网络中的关键基因，观察其对肝癌细胞浸润、转移的影响。本研究将对提供肝癌早期诊断标志物、解读DNA甲基化和组蛋白修饰之间的相互作用以及设计特异的表观遗传药物具有重要的意义。

DNA甲基化和组蛋白修饰在肿瘤的发生发展中都起着重要作用，研究发现两者在基因表达调控通路中并非孤立存在，而是存在着紧密的联系。UHRF1可双重识别甲基化的DNA和甲基化的H3K9，被认为是DNA甲基化和组蛋白修饰交叉对话中少数最关键的分子之一。我们检测了肝癌中的UHRF1表达情况，发现UHRF1在肝癌组织胞核中呈特异性高表达，而癌周肝细胞不表达或呈胞浆弱阳性表达，提示UHRF1可能在肝癌的发生发展中起了重要作用。我们进一步检测了肝癌和癌旁组织中的全基因DNA甲基化情况，制定了肝癌相关基因甲基化谱，同时在大样本中进行了验证，并在其中筛选了UHRF1的靶基因；证实了UHRF1可与PRMT5结合形成复合体，并催化H3R8对称性双甲基化促进肝癌的发生发展，揭示UHRF1不仅在DNA甲基化和组蛋白赖氨酸甲基化之间存在交叉对话，也架起了DNA甲基化和组蛋白精氨酸甲基化之间的桥梁，为DNA甲基化和组蛋白甲基化修饰之间的相互作用提供了新的思路。本课题成功构建了UHRF1的过表达载体和siRNA干扰载体，通过肝癌裸鼠荷瘤模型证实了UHRF1的致癌作用，与体外结果一致。本研究对提供肝癌早期诊断标志物、解读DNA甲基化和组蛋白甲基化之间的相互作用具有重要的指导意义，并为设计肝癌特异的表观遗传药物提供了可能的靶点。