真核生物基因组DNA通过和组蛋白相互作用形成染色质。核小体是染色质的基本结构单元，对染色质高级结构和基因组功能起着重要的调控作用。核小体由146 bp DNA缠绕在组蛋白八聚体上形成。组蛋白八聚体包括各有两个拷贝的H2A，H2B，H3和H4组蛋白。体外研究表明完整的核小体可以通过打开DNA末端、打开组蛋白互作界面、以及缺失组蛋白等，形成亚核小体结构。细胞内的核小体受到诸多表观遗传因子和DNA代谢过程的影响,如DNA复制和转录，其亚核小体结构风貌可能更加多样。但迄今为止，我们对细胞内的亚核小体结构的存在状态，及其功能和调控机制都还了解的非常少。因此，本项目拟建立一套新的方法来检测体内的亚核小体结构，并通过计算描绘全基因组的亚核小体风貌及其和已有的表观遗传调控因子的关系；并进一步研究组蛋白变体H2A.Z和H3.3对体内亚核小体结构风貌的调控，以及亚核小体结构对染色质高级结构和三维基因组的调控。

In eukaryotes, the genomic DNA interacts with histones to form chromatin. Nucleosome is the basic structure unit of chromatin and is also fundamental for the regulation of high order chromatin structure and genome functions. Nucleosome is formed by wrapping 146 bp DNA on a histone octamer, which is compose of two copies of each of H2A, H2B, H3 and H4 histones. In vitro studies show that an intact nucleosome can transform into subnucleosome through opening DNA ends or the interfaces of octamer, or losing histones. As the nucleosomes in vivo are under intensive regulations by epigenetic factors and DNA metabolism processes，such as DNA replication and transcription, the subnucleosome landscape can be even more diversified. However, we know little about the subnucleosome states in vivo so far, not to mention their regulations and functions. Thus, in this project, we will establish a new method，called MNase facilitated crosslink chromatin immunoprecipitation followed with parallel pair-end sequencing (MNase-X-ChIP-seq), to analyze the subnucleosome structures in vivo, and then mapping the subnucleosome landscape through bioinformatics analyses. We will further study the relationship between the subnucleosome landscape and the epigenetic regulators based on public data. We will also study how the subnucleosome landscape is regulated by histone variants H2A.Z and H3.3, and the function of subnucleosomes in regulating high order chromatin structure and 3-D genome.