Biology Department, College of Staten Island, City University of New York, 2800 Victory Boulevard, Staten Island, NY 10314, USA.
Biochemistry and Biology Ph.D. Program, Graduate Center, City University of New York, New York, NY 10016, USA.
Cells. 2021 Aug 29;10(9):2239. doi: 10.3390/cells10092239.
The compact nucleosomal structure limits DNA accessibility and regulates DNA-dependent cellular activities. Linker histones bind to nucleosomes and compact nucleosomal arrays into a higher-order chromatin structure. Recent developments in high throughput technologies and structural computational studies provide nucleosome positioning at a high resolution and contribute to the information of linker histone location within a chromatosome. However, the precise linker histone location within the chromatin fibre remains unclear. Using monomer extension, we mapped core particle and chromatosomal positions over a core histone-reconstituted, 1.5 kb stretch of DNA from the chicken adult β-globin gene, after titration with linker histones and linker histone globular domains. Our results show that, although linker histone globular domains and linker histones display a wide variation in their binding affinity for different positioned nucleosomes, they do not alter nucleosome positions or generate new nucleosome positions. Furthermore, the extra ~20 bp of DNA protected in a chromatosome is usually symmetrically distributed at each end of the core particle, suggesting linker histones or linker histone globular domains are located close to the nucleosomal dyad axis.
紧凑的核小体结构限制了 DNA 的可及性，并调节了依赖于 DNA 的细胞活动。连接组蛋白与核小体结合，并将核小体阵列压缩成更高阶的染色质结构。高通量技术和结构计算研究的最新进展提供了高分辨率的核小体定位，并有助于了解连接组蛋白在染色质体中的位置信息。然而，染色质纤维内精确的连接组蛋白位置仍然不清楚。使用单体延伸，我们在与连接组蛋白和连接组蛋白球状结构域滴定后，在鸡成年β-珠蛋白基因的核心组蛋白重建的 1.5kb 长的 DNA 上绘制了核心颗粒和染色质体的位置。我们的结果表明，尽管连接组蛋白球状结构域和连接组蛋白对不同定位的核小体表现出广泛的结合亲和力变化，但它们不会改变核小体位置或产生新的核小体位置。此外，在染色质体中保护的额外约 20bp 的 DNA 通常在核心颗粒的每一端对称分布，这表明连接组蛋白或连接组蛋白球状结构域位于核小体双联体轴附近。
