Aviation Medicine Research Laboratory, Air Force General Hospital, PLA, Beijing, 100142, China.
Apoptosis. 2014 Aug;19(8):1281-92. doi: 10.1007/s10495-014-0997-9.
Increasing evidence suggests that histone H2AX plays a critical role in regulation of tumor cell apoptosis and acts as a novel human tumor suppressor protein. However, the action of H2AX in chronic myelogenous leukemia (CML) cells is unknown. The detailed mechanism and epigenetic regulation by H2AX remain elusive in cancer cells. Here, we report that H2AX was involved in apoptosis of CML cells. Overexpression of H2AX increased apoptotic sensitivity of CML cells (K562) induced by imatinib. However, overexpression of Ser139-mutated H2AX (blocking phosphorylation) decreased sensitivity of K562 cells to apoptosis. Similarly, knockdown of H2AX made K562 cells resistant to apoptotic induction. These results revealed that the function of H2AX involved in apoptosis is strictly related to its phosphorylation (Ser139). Our data further indicated that imatinib may stimulate mitogen-activated protein kinase (MAPK) family member p38, and H2AX phosphorylation followed a similar time course, suggesting a parallel response. H2AX phosphorylation can be blocked by p38 siRNA or its inhibitor. These data demonstrated that H2AX phosphorylation was regulated by p38 MAPK pathway in K562 cells. However, the p38 MAPK downstream, mitogen- and stress-activated protein kinase-1 and -2, which phosphorylated histone H3, were not required for H2AX phosphorylation during apoptosis. Finally, we provided epigenetic evidence that H2AX phosphorylation regulated apoptosis-related gene Bim expression. Blocking of H2AX phosphorylation inhibited Bim gene expression. Taken together, these data demonstrated that H2AX phosphorylation regulated by p38 is involved in Bim expression and apoptosis in CML cells induced by imatinib.
越来越多的证据表明组蛋白 H2AX 在肿瘤细胞凋亡的调控中起着关键作用，并作为一种新型的人类肿瘤抑制蛋白发挥作用。然而，H2AX 在慢性粒细胞白血病（CML）细胞中的作用尚不清楚。在癌细胞中，H2AX 的详细作用机制和表观遗传调控仍不清楚。在这里，我们报告 H2AX 参与了 CML 细胞的凋亡。H2AX 的过表达增加了伊马替尼诱导的 CML 细胞（K562）的凋亡敏感性。然而，过表达 Ser139 突变的 H2AX（阻止磷酸化）降低了 K562 细胞对凋亡的敏感性。同样，H2AX 的敲低使 K562 细胞对凋亡诱导产生抗性。这些结果表明，H2AX 参与凋亡的功能与其磷酸化（Ser139）严格相关。我们的数据进一步表明，伊马替尼可能刺激丝裂原活化蛋白激酶（MAPK）家族成员 p38，H2AX 磷酸化也遵循类似的时间过程，表明存在平行反应。H2AX 磷酸化可以被 p38 siRNA 或其抑制剂阻断。这些数据表明 H2AX 磷酸化在 K562 细胞中受到 p38 MAPK 途径的调节。然而，p38 MAPK 的下游分子，丝裂原和应激激活蛋白激酶-1 和 -2，它们磷酸化组蛋白 H3，在凋亡过程中不需要 H2AX 磷酸化。最后，我们提供了表观遗传证据表明 H2AX 磷酸化调节凋亡相关基因 Bim 的表达。阻断 H2AX 磷酸化抑制了 Bim 基因的表达。总之，这些数据表明，由 p38 调节的 H2AX 磷酸化参与了伊马替尼诱导的 CML 细胞中 Bim 表达和凋亡。
