染色质在细胞核内三维高级结构包括最底层的核小体、核小体组成的“串珠”结构、螺线管纤维结构、染色质/DNA环结构(chromatin/DNA loop)、拓扑结构域(topologically associated domain, TAD)等多层次结构。其中,TAD因在不同的细胞类型中相对稳定且保守,被认为是染色质三维结构的基本单元。Alu元件是一种哺乳动物基因组中占据了较大比例的短散在重复元件,其广泛存在且种类繁多,目前关于Alu元件功能上的研究尚不透彻。本研究对Alu元件与染色质三维结构的关系进行研究,分析了Alu元件在染色质三维结构形成中的作用,并通过染色质三维结构上的距离关系对Alu元件子族的演化流程进行了探索。结果发现,Alu元件参与的染色质间相互作用在高强度的染色质相互作用中的比例随着强度增加而逐渐增高,表明Alu在染色质三维结构构建的过程中发挥了重要的作用。同时,研究还发现Alu元件在染色质上相互作用的强度与进化上的关系存在着一定的正相关性,表现在一维序列进化距离上比较接近的Alu元件在染色质的三维结构上也会彼此相互靠近。

The interphase chromatin is folded in the nucleus in a hierarchical manner, including the nucleosome, the "beads on a string" structure composed of nucleosomes, the solenoid fiber structure, the chromatin/DNA loop structure (chromatin/DNA loop), and the topologically associated domain (TAD). Among them, TAD is considered to be the basic unit of the 3D structure of chromatin because it is relatively stable and conserved in different cell types. Alu elements occupy a large proportion in the mammalian genomes. There are a wide variety of Alu elements, but their functional characterizations are limited to date. This study investigates the role of Alu elements in the assembly of 3D chromatin conformation. The evolutionary process of the Alu subfamily was explored by the distance relationship of the 3D structure of chromatin. We found that the proportion of Alu elements in high-density chromatin interaction increased with higher similarity, indicating that Alu plays an important role in the construction of chromatin 3D structure. There is a certain positive correlation between the strength of the upper interaction and the evolutionary relationship. In sum, the Alu elements with relatively close distances in the 1D sequence will also be close to each other in the 3D structure of chromatin.