Department of Biology, Dulbecco Telethon Institute, University of Rome Tor Vergata, 00133 Rome, Italy.
Cell Death Differ. 2011 Mar;18(3):516-27. doi: 10.1038/cdd.2010.125. Epub 2010 Oct 22.
Apaf1 is a key regulator of the mitochondrial intrinsic pathway of apoptosis, as it activates executioner caspases by forming the apoptotic machinery apoptosome. Its genetic regulation and its post-translational modification are crucial under the various conditions where apoptosis occurs. Here we describe Ku70/86, a mediator of non-homologous end-joining pathway of DNA repair, as a novel regulator of Apaf1 transcription. Through analysing different Apaf1 promoter mutants, we identified an element repressing the Apaf1 promoter. We demonstrated that Ku70/86 is a nuclear factor able to bind this repressing element and downregulating Apaf1 transcription. We also found that Ku70/86 interaction with Apaf1 promoter is dynamically modulated upon DNA damage. The effect of this binding is a downregulation of Apaf1 expression immediately following the damage to DNA; conversely, we observed Apaf1 upregulation and apoptosis activation when Ku70/86 unleashes the Apaf1-repressing element. Therefore, besides regulating DNA repair, our results suggest that Ku70/86 binds to the Apaf1 promoter and represses its activity. This may help to inhibit the apoptosome pathway of cell death and contribute to regulate cell survival.
凋亡蛋白激活因子 1（Apaf1）是线粒体凋亡内在途径的关键调节因子，它通过形成凋亡体（apoptosome）激活执行 caspase。其基因调控和翻译后修饰在各种发生凋亡的条件下至关重要。在这里，我们描述了 Ku70/86，一种 DNA 修复非同源末端连接途径的介质，作为 Apaf1 转录的新型调节因子。通过分析不同的 Apaf1 启动子突变体，我们确定了一个抑制 Apaf1 启动子的元件。我们证明 Ku70/86 是一种核因子，能够结合这个抑制元件并下调 Apaf1 转录。我们还发现 Ku70/86 与 Apaf1 启动子的相互作用在 DNA 损伤时会动态调节。这种结合的效果是在 DNA 损伤后立即下调 Apaf1 的表达；相反，当 Ku70/86 释放 Apaf1 抑制元件时，我们观察到 Apaf1 的上调和细胞凋亡的激活。因此，除了调节 DNA 修复外，我们的结果表明 Ku70/86 结合到 Apaf1 启动子并抑制其活性。这可能有助于抑制细胞死亡的凋亡体途径，并有助于调节细胞存活。
