E2F6 inhibits cobalt chloride-mimetic hypoxia-induced apoptosis through E2F1
E2F6 inhibits cobalt chloride-mimetic hypoxia-induced apoptosis through E2F1
复制标题
E2F6通过E2F1抑制氯化钴模拟缺氧诱导的细胞凋亡
DOI：
10.1091/mbc.e08-02-0171
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发表时间：
2008-09-01
影响因子：
3.3
通讯作者：
Yang, Huang-Tian
中科院分区：
文献类型：
--
作者：
Yang, Wei-Wei;Shu, Bo;Yang, Huang-Tian
E2F6是一种有效的转录抑制因子，在细胞周期调控中起重要作用。然而，E2F6在缺氧诱导的细胞凋亡中的作用尚不清楚。在此，我们证明了E2F6在缺氧诱导的细胞凋亡和调节途径中的生物学功能。在缺氧（氯化钴，800 μ M）诱导的人胚肾293细胞凋亡，E2F6表达下调，同时增加E2F1的表达和反式激活。E2F6过表达可消除缺氧诱导的细胞凋亡和E2F1的改变。相反，通过小干扰RNA特异性敲低E2F6具有相反的效果。染色质免疫沉淀实验证实E2F6通过反式阻遏E2F1启动子来调控E2F1的表达。有趣的是，在稳定表达E2F1的细胞中，E2F6过表达抑制E2F1的反式激活和缺氧诱导的凋亡，表明E2F6的抑制作用不仅是通过抑制E2F1启动子介导的。这通过E2F6抑制E2F1的反式激活和通过与E2F1竞争DNA结合位点的凋亡得到证实，E2F6 Delta C（C末端缺失）和E2F6的不同行为证明了这一点。E68（突变DNA结合位点）和E2f6与E2F1蛋白缺乏结合。此外，缺氧上调E2F1反应性促凋亡基因凋亡蛋白酶激活因子1的表达受到E2F6过表达的抑制。总之，这些发现表明E2F6通过调节E2F1在控制缺氧诱导的细胞凋亡中的新作用。
E2F6, a potent transcriptional repressor, plays important roles in cell cycle regulation. However, roles of E2F6 in hypoxia-induced apoptosis are unknown. Here, we demonstrated biological functions of E2F6 in hypoxia-induced apoptosis and regulatory pathways. During hypoxia (CoCl2, 800 mu M)-induced human embryonic kidney 293 cell apoptosis, E2F6 expression was down-regulated with concurrent increases in E2F1 expression and transactivation. E2F6 overexpression abrogated hypoxia-induced apoptosis and alteration of E2F1. Conversely, specific knockdown of E2F6 by small interfering RNA had opposite effects. Chromatin immunoprecipitation assay confirmed that E2F6 regulated E2F1 expression through the transrepression of E2F1 promoter. Interestingly, E2F1 transactivation and apoptosis induced by hypoxia in cells stably expressing E2F1 were inhibited by E2F6 overexpression, suggesting that the inhibitory effects of E2F6 are not only mediated by the repression of E2F1 promoter. This was confirmed by E2F6-inhibited transactivation of E2F1 and apoptosis via competing with E2F1 for DNA binding sites evidenced by the different behaviors of E2F6 Delta C (C-terminal deletion) and E2F6. E68 (mutant DNA binding site) and by the lack of association of E2f6 with E2F1 protein. Moreover, hypoxia up-regulated expression of E2F1-responsive proapoptotic gene apoptosis protease-activating factor 1 was repressed by E2F6 overexpression. Together, these findings demonstrate a novel role of E2F6 in control of hypoxia-induced apoptosis through regulation of E2F1.