Department of Biochemistry, University of Colorado at Boulder, 80309, Boulder, CO, USA.
Howard Hughes Medical Institute, Chevy Chase, MD, USA.
Nat Commun. 2024 Oct 23;15(1):9138. doi: 10.1038/s41467-024-53364-5.
The organization of DNA into nucleosomes is a ubiquitous and ancestral feature that was once thought to be exclusive to the eukaryotic domain of life. Intriguingly, several representatives of the Nucleocytoplasmic Large DNA Viruses (NCLDV) encode histone-like proteins that in Melbournevirus were shown to form nucleosome-like particles. Medusavirus medusae (MM), a distantly related giant virus, encodes all four core histone proteins and, unique amongst most giant viruses, a putative acidic protein with two domains resembling eukaryotic linker histone H1. Here, we report the structure of nucleosomes assembled with MM histones and highlight similarities and differences with eukaryotic and Melbournevirus nucleosomes. Our structure provides insight into how variations in histone tail and loop lengths are accommodated within the context of the nucleosome. We show that MM-histones assemble into tri-nucleosome arrays, and that the putative linker histone H1 does not function in chromatin compaction. These findings expand our limited understanding of chromatin organization by virus-encoded histones.
DNA 形成核小体的组织是一种普遍存在且古老的特征，曾经被认为是真核生物领域所独有的。有趣的是，几种核质大 DNA 病毒（NCLDV）的代表编码组蛋白样蛋白，在墨尔本病毒中这些蛋白被证明可以形成核小体样颗粒。水螅状病毒属（MM）是一种亲缘关系较远的巨型病毒，它编码所有四种核心组蛋白，并且与大多数巨型病毒不同的是，它还编码一种具有两个类似于真核连接组蛋白 H1 的结构域的酸性蛋白。在这里，我们报告了 MM 组蛋白组装成的核小体的结构，并强调了与真核生物和墨尔本病毒核小体的相似性和差异性。我们的结构提供了对核小体中组蛋白尾部和环长度的变化如何适应的深入了解。我们表明，MM-组蛋白组装成三聚体核小体阵列，而假定的连接组蛋白 H1 不在染色质紧缩中发挥作用。这些发现扩展了我们对病毒编码组蛋白所形成的染色质组织的有限理解。
