Together with core histones, which make up the nucleosome, the linker histone (H1) is one of the five main histone protein families present in chromatin in eukaryotic cells. H1 binds to the nucleosome to form the next structural unit of metazoan chromatin, the chromatosome, which may help chromatin to fold into higher-order structures. Despite their important roles in regulating the structure and function of chromatin, linker histones have not been studied as extensively as core histones. Nevertheless, substantial progress has been made recently. The first near-atomic resolution crystal structure of a chromatosome core particle and an 11 Å resolution cryo-electron microscopy-derived structure of the 30 nm nucleosome array have been determined, revealing unprecedented details about how linker histones interact with the nucleosome and organize higher-order chromatin structures. Moreover, several new functions of linker histones have been discovered, including their roles in epigenetic regulation and the regulation of DNA replication, DNA repair and genome stability. Studies of the molecular mechanisms of H1 action in these processes suggest a new paradigm for linker histone function beyond its architectural roles in chromatin.

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接头组蛋白在调节染色质结构和功能中的新兴作用

接头组蛋白（H1）与构成核小体的核心组蛋白一起，是真核细胞染色质中存在的五个主要组蛋白蛋白家族之一。H1与核小体结合形成后生染色质的下一个结构单元，即染色质体，可帮助染色质折叠成更高阶的结构。尽管它们在调节染色质的结构和功能中起着重要作用，但连接子组蛋白却没有像核心组蛋白那样得到广泛的研究。尽管如此，最近已经取得了实质性进展。确定了染色体核心颗粒的第一个近原子分辨率晶体结构和30 nm核小体阵列的11Å分辨率冷冻电子显微镜衍生结构，揭示了有关接头组蛋白如何与核小体相互作用并组织高阶染色质结构的空前细节。此外，还发现了接头组蛋白的几种新功能，包括它们在表观遗传调控，DNA复制调控，DNA修复和基因组稳定性中的作用。对这些过程中H1作用的分子机制的研究提出了一种连接子组蛋白功能的新范式，超越了其在染色质中的结构作用。