Nucleosomes in contact In eukaryotic cells, genomic DNA must be compacted to fit inside the nucleus. A key player in DNA packaging is the nucleosome, which comprises a segment of DNA wrapped around an octamer of histone proteins. During replication and transcription, nucleosomes must reposition themselves on the DNA. In this process, nucleosomes can collide to form a dinucleosome. Kato et al. report a high-resolution crystal structure of a dinucleosome. One of the octamers has lost a histone dimer so that the dinucleosome comprises an octamer and a hexamer. The structure may represent an intermediate during chromatin remodeling. Science, this issue p. 205 An intermediate chromatin structure comprising a dinucleosome may give insight into how nucleosome repositioning occurs. Nucleosomes are dynamic entities that are repositioned along DNA by chromatin remodeling processes. A nucleosome repositioned by the switch-sucrose nonfermentable (SWI/SNF) remodeler collides with a neighbor and forms the intermediate “overlapping dinucleosome.” Here, we report the crystal structure of the overlapping dinucleosome, in which two nucleosomes are associated, at 3.14-angstrom resolution. In the overlapping dinucleosome structure, the unusual “hexasome” nucleosome, composed of the histone hexamer lacking one H2A-H2B dimer from the conventional histone octamer, contacts the canonical “octasome” nucleosome, and they intimately associate. Consequently, about 250 base pairs of DNA are left-handedly wrapped in three turns, without a linker DNA segment between the hexasome and octasome moieties. The overlapping dinucleosome structure may provide important information to understand how nucleosome repositioning occurs during the chromatin remodeling process.

中文翻译：

---

由六体和八体组成的重叠双核小体的晶体结构

核小体接触 在真核细胞中，基因组 DNA 必须被压缩以适应细胞核。DNA 包装中的一个关键参与者是核小体，它由一段 DNA 包裹着一个组蛋白八聚体组成。在复制和转录过程中，核小体必须在 DNA 上重新定位。在这个过程中，核小体可以碰撞形成双核小体。加藤等人。报告了双核小体的高分辨率晶体结构。其中一个八聚体丢失了一个组蛋白二聚体，因此双核小体包含一个八聚体和一个六聚体。该结构可能代表染色质重塑过程中的中间体。科学，这个问题 p。205 包含双核小体的中间染色质结构可以深入了解核小体重新定位是如何发生的。核小体是通过染色质重塑过程沿 DNA 重新定位的动态实体。由开关蔗糖不可发酵 (SWI/SNF) 重构器重新定位的核小体与邻居碰撞并形成中间的“重叠双核小体”。在这里，我们报告了重叠双核小体的晶体结构，其中两个核小体相关联，分辨率为 3.14 埃。在重叠的双核小体结构中，不寻常的“六聚体”核小体由缺少来自常规组蛋白八聚体的 H2A-H2B 二聚体的组蛋白六聚体组成，与经典的“八聚体”核小体接触，并且它们密切相关。因此，大约 250 个 DNA 碱基对被左手包裹成三圈，在六体和八体部分之间没有接头 DNA 片段。