利用冷冻电镜技术解析染色质重塑和组蛋白去乙酰化酶复合物NuRD的高分辨率三维结构

The nucleosome remodeling and histone deacetylase (NuRD) complex plays an important role in epigenetic regulation. DNA is wrapped around the histone octamer and packing as chromatin in eukaryotic cells, the packaging state of chromatin controls whether particular genes are expressed. Previous studies reveal that the NuRD complex regulate DNA transcription by two enzyme activities, NuRD enables to move the position of nucleosomes on DNA by hydrolysis ATP with its CHD3 or CHD4 subunit, and the histone deacetylase (HDAC) subunits are able to deacetylate the modification of key amino acids in histone. However, the details how the NuRD complex interact with chromatin are still unclear as the three dimensional structure of the entire NuRD complex is still unresolved. In this study, we plan to resolve the high resolution structure of the entire NuRD complex in order to elucidate the mechanism of the entire NuRD complex in epigenetic regulation. In our preliminary study, we have purified the entire NuRD complex which expressed in insect cells, and the entire NuRD complex sample showed homogeneities in negative-stain electron microscopy observation. Currently, we have reconstructed the three dimensional structure of the enitre NuRD complex by cryo-electron microscopy at 20 angstrom resolution.

染色质重塑和组蛋白去乙酰化酶复合物NuRD在表观遗传学调控中发挥了重要的作用。在真核细胞中，DNA缠绕在组蛋白八聚体周围并以染色质形式存在，通过改变染色质的高级结构可以对DNA的转录过程进行精确调控。之前的研究表明NuRD通过水解ATP获得的能量来改变核小体的相对位置，并且可以对组蛋白关键位点的氨基酸进行去乙酰化修饰从而实现对基因转录的调控。由于目前完整NuRD复合物的三维结构仍未获得解析，因此NuRD改变染色质高级结构的具体作用机理还不清楚。本研究拟利用冷冻电镜技术解析完整NuRD复合物的高分辨率三维结构，从而了解NuRD复合物在表观遗传学调控中的具体作用机理。在前期研究中，我们已经成功在昆虫细胞中表达了完整NuRD复合物，并通过纯化获得了纯度较高的样品，负染电镜观察结果显示样品具有较好的均一性，利用冷冻电镜三维重构技术解析了完整NuRD复合物约20埃分辨率的三维结构。