School of Biology, Georgia Institute of Technology, Atlanta, Georgia, USA.
PLoS Genet. 2013;9(4):e1003417. doi: 10.1371/journal.pgen.1003417. Epub 2013 Apr 25.
H1 linker histones facilitate higher-order chromatin folding and are essential for mammalian development. To achieve high-resolution mapping of H1 variants H1d and H1c in embryonic stem cells (ESCs), we have established a knock-in system and shown that the N-terminally tagged H1 proteins are functionally interchangeable to their endogenous counterparts in vivo. H1d and H1c are depleted from GC- and gene-rich regions and active promoters, inversely correlated with H3K4me3, but positively correlated with H3K9me3 and associated with characteristic sequence features. Surprisingly, both H1d and H1c are significantly enriched at major satellites, which display increased nucleosome spacing compared with bulk chromatin. While also depleted at active promoters and enriched at major satellites, overexpressed H1(0) displays differential binding patterns in specific repetitive sequences compared with H1d and H1c. Depletion of H1c, H1d, and H1e causes pericentric chromocenter clustering and de-repression of major satellites. These results integrate the localization of an understudied type of chromatin proteins, namely the H1 variants, into the epigenome map of mouse ESCs, and we identify significant changes at pericentric heterochromatin upon depletion of this epigenetic mark.
H1 连接组蛋白有助于高级染色质折叠，对哺乳动物的发育至关重要。为了在胚胎干细胞 (ESC) 中实现 H1 变体 H1d 和 H1c 的高分辨率作图，我们建立了一个敲入系统，并表明 N 端标记的 H1 蛋白在体内与其内源性对应物在功能上可互换。H1d 和 H1c 从 GC 丰富区和基因丰富区以及活性启动子中耗尽，与 H3K4me3 呈负相关，但与 H3K9me3 呈正相关，并与特征序列特征相关。令人惊讶的是，H1d 和 H1c 都在主要卫星上显著富集，与大量染色质相比，主要卫星显示出核小体间距增加。尽管在活性启动子中也耗尽，在主要卫星中富集，但过表达的 H1(0)与 H1d 和 H1c 相比，在特定重复序列中显示出不同的结合模式。H1c、H1d 和 H1e 的耗竭导致着丝粒染色质中心聚类和主要卫星去抑制。这些结果将这种研究较少的染色质蛋白（即 H1 变体）的定位整合到小鼠 ESC 的表观基因组图谱中，并且我们在耗尽这种表观遗传标记时鉴定了着丝粒异染色质的显著变化。
