Institute for Systems Genetics and Department of Biochemistry and Molecular Pharmacology, NYU Langone Health, New York, NY 10016, USA; Vilcek Institute of Graduate Biomedical Sciences, NYU School of Medicine, New York, NY 10016, USA.
Institute for Systems Genetics and Department of Biochemistry and Molecular Pharmacology, NYU Langone Health, New York, NY 10016, USA.
Cell Rep. 2024 Jul 23;43(7):114472. doi: 10.1016/j.celrep.2024.114472. Epub 2024 Jul 10.
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.
除了复制组蛋白外，真核基因组还编码了一系列非复制性的变异组蛋白，为结构和表观遗传调控提供了额外的层次。在这里，我们使用酵母中的组蛋白替换系统系统地用非复制性的人类变异组蛋白替换单个复制性的人类组蛋白。我们表明，变体 H2A.J、TsH2B 和 H3.5 可以补充其相应的复制组蛋白。然而，macroH2A1 不能补充，并且其在酵母中的过表达是有毒的，与酵母的天然组蛋白和动粒基因相互作用不良。为了分离具有 macroH2A1 染色质的酵母，我们分离了其宏和组蛋白折叠结构域的效应，结果表明这两个结构域足以克服天然核小体定位。此外，macroH2A1 的两种非偶联构建体都表现出较低的核小体占有率、较短距离染色质相互作用（<20 kb）、破坏着丝粒聚类和增加染色体不稳定性。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严重的适应性缺陷。
