人胚胎干细胞中non-CG甲基化建立的表观遗传学调控机制

哺乳动物基因组通常是CpG甲基化，non-CG(包括mCHG和mCHH)甲基化非常少, 但在人胚胎干细胞（hESC）中，约1/4的甲基化是non-CG甲基化。不像CpG甲基化与基因沉默相关，non-CG甲基化则与基因表达呈正相关，它们是怎样建立的，哪个重新甲基化酶（Dnmt3家族成员）负责，与其它表观遗传机制是否相关，这些仍然未知。本项目拟首先通过功能获得和缺失实验，及细胞外的DNA甲基化实验，在hESC中找出建立non-CG甲基化的酶，继而因植物学领域已经明确，由于H3K9去甲基化酶（ibm1）的缺失可以导致 non-CG甲基化的增加，我们将在hESC中分析H3K9甲基化对于non-CG甲基化建立的影响。除此之外，因植物中DNA甲基化酶可以在非编码RNA的指导下进行non-CG甲基化，我们将研究非编码RNA是否能指导以上发现的non-CG甲基化酶在特定的基因组位置催化non-CG甲基化。

This project is established based on the epigenetic regulation mechanism of the establishment of non-CG methylation in different species, and searched the noncoding RNAs and histone modifications, which play a key direct correlation role with the non-CG methylation in human embryonic stem cells. From two levels of non-coding RNA and histone H3K9 methylation to make a comprehensive and effective non-CG methylation establish mechanism.Specifically, study de novo methyltransferase Dnmt3s in hES cells through loss-of-function and gain-of-function experiments and in vitro DNA methylation assay. Then determine which Dnmt3s are responsible for the establishment of non-CG methylation. Meanwhile, study whether can the Dnmt3s combination of non-coding RNA serve to guide the enzyme created position of non-CG methylation in specific genomic. Due to loss function of H3K9me1,2 demethyltransferase(ibm1) in plant, increase the non-CG methylation, this mechanism will help us to understand whether can loss function of H3K9me1,2 or me3 demethyltransferase influence non-CG methylation. Finially, we make a proposal model that is the epigenetic regulation mechanism of noncoding RNA dependent DNA methylation and H3K9 methylation effect the establishment of non-CG methylation.