Single-molecule study reveals Hmo1, not Hho1, promotes chromatin assembly in budding yeast.
Single-molecule study reveals Hmo1, not Hho1, promotes chromatin assembly in budding yeast.
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接头组蛋白H1在各种生物学过程中发挥着至关重要的作用，包括核小体稳定、染色质高级结构组织、基因表达和真核细胞的表观遗传调节。与高等真核生物不同的是，对酿酒酵母中的连接体组蛋白知之甚少。Hho 1和Hmo 1是芽殖酵母中两个长期存在争议的组蛋白H1候选者。在本研究中，我们在单分子水平上直接观察到Hmo 1而不是Hho 1参与酵母核质提取物（YNPE）中的染色质组装，该提取物可以复制酵母核的生理条件。Hmo 1的存在有利于装配核小体DNA在YNPE中，所揭示的单分子力谱。进一步的单分子分析表明，富含赖氨酸的C-末端结构域（CTD）的Hmo 1的染色质压实的功能是必不可少的，而在C-末端的第二个球状结构域的Hho 1削弱其能力。此外，Hmo 1，而不是Hho 1，通过可逆相分离与双链DNA形成缩合物。在细胞周期中，Hmo 1的磷酸化波动与后生动物H1相一致。我们的数据表明，Hmo 1，而不是Hho 1，具有一些功能类似的接头组蛋白在酿酒酵母，即使Hmo 1的一些属性不同于那些典型的接头组蛋白H1。我们的研究为芽殖酵母中的接头组蛋白H1提供了线索，并为真核生物中组蛋白H1的进化和多样性提供了见解。关于芽殖酵母中连接体组蛋白H1的身份一直存在着长期的争论。为了解决这个问题，我们利用YNPE，它准确地复制酵母细胞核中的生理条件，结合全内反射荧光显微镜和磁镊。我们的研究结果表明，Hmo 1，而不是Hho 1，是负责染色质组装在芽殖酵母。此外，我们发现Hmo 1与组蛋白H1具有某些共同特征，包括在整个细胞周期中的相分离和磷酸化波动。此外，我们发现Hho 1的赖氨酸丰富的结构域被其C-末端的第二个球状结构域掩埋，导致类似于组蛋白H1的功能丧失。我们的研究提供了令人信服的证据表明，Hmo 1股接头组蛋白H1的功能，在芽殖酵母，并有助于我们了解接头组蛋白H1的进化跨越真核生物。
Linker histone H1 plays a crucial role in various biological processes, including nucleosome stabilization, high-order chromatin structure organization, gene expression, and epigenetic regulation in eukaryotic cells. Unlike higher eukaryotes, little about the linker histone in Saccharomyces cerevisiae is known. Hho1 and Hmo1 are two long-standing controversial histone H1 candidates in budding yeast. In this study, we directly observed at the single-molecule level that Hmo1, but not Hho1, is involved in chromatin assembly in the yeast nucleoplasmic extracts (YNPE), which can replicate the physiological condition of the yeast nucleus. The presence of Hmo1 facilitates the assembly of nucleosomes on DNA in YNPE, as revealed by single-molecule force spectroscopy. Further single-molecule analysis showed that the lysine-rich C-terminal domain (CTD) of Hmo1 is essential for the function of chromatin compaction, while the second globular domain at the C-terminus of Hho1 impairs its ability. In addition, Hmo1, but not Hho1, forms condensates with double-stranded DNA via reversible phase separation. The phosphorylation fluctuation of Hmo1 coincides with metazoan H1 during the cell cycle. Our data suggest that Hmo1, but not Hho1, possesses some functionality similar to that of linker histone in Saccharomyces cerevisiae, even though some properties of Hmo1 differ from those of a canonical linker histone H1. Our study provides clues for the linker histone H1 in budding yeast and provides insights into the evolution and diversity of histone H1 across eukaryotes. There has been a long-standing debate regarding the identity of linker histone H1 in budding yeast. To address this issue, we utilized YNPE, which accurately replicate the physiological conditions in yeast nuclei, in combination with total internal reflection fluorescence microscopy and magnetic tweezers. Our findings demonstrated that Hmo1, rather than Hho1, is responsible for chromatin assembly in budding yeast. Additionally, we found that Hmo1 shares certain characteristics with histone H1, including phase separation and phosphorylation fluctuations throughout the cell cycle. Furthermore, we discovered that the lysine-rich domain of Hho1 is buried by its second globular domain at the C-terminus, resulting in the loss of function that is similar to histone H1. Our study provides compelling evidence to suggest that Hmo1 shares linker histone H1 function in budding yeast and contributes to our understanding of the evolution of linker histone H1 across eukaryotes.
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DOI：
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