组蛋白H3K56单甲基化修饰的动态调节及其对靶基因转录活性的影响

Histone methylation plays pivotal roles in a variety of DNA-based processes including transcriptional regulation, DNA replication, and stem cell differentation by influencing the structural dynamics of chromatin. Residing at the entry-exit site of double-stranded DNA wrapping around nucleosome, H3K56 might be critical to the transcriptional regulation. However, how the methylation state of H3K56 is regulated and its corresponding epigenetic implication and biological function remain elusive. In our preliminary work, we've identified the demethylase KDM56 that selectively removes mono-methyl mark from H3K56, and got the antibody that can specifically recogonize the H3K56me1 modification. Additionally, the distribution profile of H3K56me1 has been described in mouse stem cell by ChIP-seq analysis. Utilizing a combination of biochemical, molecular biological and epigenetic approaches, we aim to further validate the biochemical characteristics of KDM56, uncover the molecular mechanisms underlying dynamic regulation of H3K56 monomethylation and its effect on the transcriptional activity of target genes and chromatin structure. Moreover, we will also investigate the crosstalk between H3K56me1 and other well-defined histone modifications, and finally reveal the biologial function of H3K56me1 in stem cell self-renewal and differentiation.

组蛋白甲基化修饰可以通过影响染色质的高级结构，在基因转录、DNA复制和干细胞分化等诸多方面发挥至关重要的作用。位于核小体entry-exit处的H3K56位点在基因转录调控中可能发挥重要作用，但是该位点的单甲基化修饰H3K56me1研究还有很多未知之处。在前期研究中，我们制备了识别H3K56me1修饰的多克隆抗体并找到了能够特异性去除H3K56单甲基化修饰的组蛋白去甲基化酶KDM56，而且通过ChIP-seq获得了H3K56me1在小鼠干细胞基因组上的分布概貌，本课题将此基础上深入研究KDM56的组蛋白H3K56me1去甲基化酶功能，确定组蛋白H3K56me1的靶基因位点并探究KDM56调控组蛋白H3K56甲基化修饰的分子机制，以及在此过程中组蛋白H3K56me1位点与其他修饰位点之间的互作关系，阐释组蛋白H3K56me1在干细胞自我更新/分化过程中的功能意义。

组蛋白修饰可以影响核小体稳定性，改变染色质结构，在诸多基于染色质的生物学过程中扮演着重要角色。归因于研究技术上的困难和复杂性，尽管组蛋白氨基端众多的赖氨酸修饰被广泛关注，位于DNA进出核小体入口处的组蛋白H3第56位赖氨酸的甲基化几乎很少被关注。本项目利用生化，分子生物学，细胞生物学和表观基因组学等多种研究手段，分别以胚胎干细胞和生殖细胞作为生物学背景，描绘了组蛋白H3K56me在基因组上动态变化的第一张图谱，揭示了H3K56me与其它组蛋白修饰之间的关联性。我们的工作为进一步深入阐释H3K56的表观调控作用和生物学效应打下了坚实的基础。