Kratzmeier M, Albig W, Hanecke K, Doenecke D
Institute for Biochemistry and Molecular Cell Biology, University of Göttingen, Humboldtallee 23, 37073 Göttingen, Germany.
J Biol Chem. 2000 Sep 29;275(39):30478-86. doi: 10.1074/jbc.M003956200.
H1 histones are involved in the formation of higher order chromatin structures and in the modulation of gene expression. Changes in chromatin structure are a characteristic initial feature of apoptosis. We therefore have investigated the histone H1 pattern of the human leukemic cell line HL60 undergoing programmed cell death, as induced by topoisomerase I inhibition. Histone H1 proteins were isolated and analyzed by high performance liquid chromatography and capillary zone electrophoresis. DNA fragmentation after apoptosis induction was monitored by agarose gel electrophoresis. The patterns of the three H1 histone subtypes extractable from apoptotic HL60 cells significantly differed from those of control cells in showing a decrease of phosphorylated H1 subtypes and an increase of the respective dephosphorylated forms. This dephosphorylation of H1 histones could be observed already 45 min after apoptosis induction and preceded internucleosomal DNA cleavage by approximately 2 h. We conclude that during apoptotic DNA fragmentation, the H1 histones become rapidly dephosphorylated by a yet unknown protein phosphatase.
H1组蛋白参与高阶染色质结构的形成以及基因表达的调控。染色质结构的变化是细胞凋亡的一个典型初始特征。因此，我们研究了人白血病细胞系HL60在拓扑异构酶I抑制诱导下发生程序性细胞死亡时的组蛋白H1模式。通过高效液相色谱和毛细管区带电泳分离并分析组蛋白H1蛋白。通过琼脂糖凝胶电泳监测凋亡诱导后的DNA片段化。从凋亡的HL60细胞中可提取的三种H1组蛋白亚型的模式与对照细胞的模式显著不同，表现为磷酸化H1亚型减少，相应的去磷酸化形式增加。这种H1组蛋白的去磷酸化在凋亡诱导后45分钟即可观察到，且比核小体间DNA切割提前约2小时。我们得出结论，在凋亡性DNA片段化过程中，H1组蛋白被一种未知的蛋白磷酸酶迅速去磷酸化。
