Abstract：
In addition to replicative histones, eukaryotic genomes encode a repertoire of non-replicative variant histones, providing additional layers of structural and epigenetic regulation. Here, we systematically replace individual replicative human histones with non-replicative human variant histones using a histone replacement system in yeast. We show that variants H2A.J, TsH2B, and H3.5 complement their respective replicative counterparts. However, macroH2A1 fails to complement, and its overexpression is toxic in yeast, negatively interacting with yeast\'s native histones and kinetochore genes. To isolate yeast with macroH2A1 chromatin, we uncouple the effects of its macro and histone fold domains, revealing that both domains suffice to override native nucleosome positioning. Furthermore, both uncoupled constructs of macroH2A1 exhibit lower nucleosome occupancy, decreased short-range chromatin interactions (<20 kb), disrupted centromeric clustering, and increased chromosome instability. Our observations demonstrate that lack of a canonical histone H2A dramatically alters chromatin organization in yeast, leading to genome instability and substantial fitness defects.
摘要：
除了复制组蛋白，真核基因组编码一系列非复制型变异型组蛋白，提供额外的结构和表观遗传调控层。这里,我们使用酵母中的组蛋白替代系统，用非复制型人变异型组蛋白系统地替代个体复制型人组蛋白。我们显示变体H2A。J,TsH2B,和H3.5补充各自的复制对应物。然而,macroH2A1未能补充，它的过度表达在酵母中是有毒的，与酵母的天然组蛋白和动粒基因负向相互作用。为了分离具有大H2A1染色质的酵母，我们解开它的宏观和组蛋白折叠域的影响，揭示这两个域都足以覆盖天然核小体定位。此外，macroH2A1的两个未偶联构建体都表现出较低的核小体占有率，短程染色质相互作用减少（<20kb），中断的着丝粒聚类，增加了染色体的不稳定性.我们的观察结果表明，缺乏典型的组蛋白H2A会极大地改变酵母中的染色质组织，导致基因组不稳定和实质性的适应性缺陷。
