Kijima Marie, Mizuta Ryushin
Research Institute for Biomedical Sciences, Tokyo University of Science.
Biomed Res. 2019;40(1):51-56. doi: 10.2220/biomedres.40.51.
Oligonucleosomal DNA fragmentation and chromatin condensation are two hallmarks of apoptosis. However, their generation mechanisms are not entirely understood. Histone H1, a positively charged nuclear protein located in the linker region of chromatin, is involved in higher-order chromatin structures and tight chromatin packing. On the basis of the physical and biochemical characteristics of histone H1, we hypothesized that histone H1 plays a role in determining the efficiencies of apoptotic DNA fragmentation and chromatin condensation. Therefore, we examined histone H1 quantity in five human leukemia cell lines and compared the efficiencies. The cell lines were categorized into two groups according to their origins: (i) Ramos and Molt-4 cells of lymphoid origin and (ii) U937, ML-1, and HL60 cells of myeloid origin. Compared to the lymphoid-origin group, the myeloid-origin group had lower levels of histone H1 but more open chromatin. Furthermore, the myeloid-origin group showed marked DNA fragmentation but less chromatin condensation during apoptosis. These results suggested that histone H1 determined chromatin structure and that its quantity affected the efficiencies of DNA fragmentation and chromatin condensation in apoptosis.
寡核小体DNA片段化和染色质浓缩是细胞凋亡的两个标志。然而，它们的产生机制尚未完全明确。组蛋白H1是一种位于染色质连接区的带正电荷的核蛋白，参与高阶染色质结构和紧密的染色质包装。基于组蛋白H1的物理和生化特性，我们推测组蛋白H1在决定凋亡DNA片段化和染色质浓缩的效率中发挥作用。因此，我们检测了五种人类白血病细胞系中的组蛋白H1含量并比较了其效率。这些细胞系根据其来源分为两组：（i）淋巴来源的Ramos和Molt-4细胞，以及（ii）髓系来源的U937、ML-1和HL60细胞。与淋巴来源组相比，髓系来源组的组蛋白H1水平较低，但染色质更松散。此外，髓系来源组在细胞凋亡过程中表现出明显的DNA片段化，但染色质浓缩较少。这些结果表明，组蛋白H1决定染色质结构，其含量影响细胞凋亡中DNA片段化和染色质浓缩的效率。
