Department of Pharmacology, College of Medicine, National Taiwan University, Taipei, Taiwan.
National Institute of Cancer Research, National Health Research Institutes, Zhunan, Miaoli County, Taiwan.
PLoS One. 2013 Dec 30;8(12):e84062. doi: 10.1371/journal.pone.0084062. eCollection 2013.
The immediate early gene c-Fos is reported to be regulated by Elk-1 and cAMP response element-binding protein (CREB), but whether nuclear factor (NF)-κB is also required for controlling c-Fos expression is unclear. In this study, we determined how NF-κB's coordination with Elk/serum response factor (SRF) regulates c-fos transcription. We report that PMA strongly induced c-Fos expression, but tumor necrosis factor (TNF)-α did not. In mouse embryonic fibroblasts, the PMA induction of c-Fos was suppressed by a deficiency in IKKα, IKKβ, IKKγ, or p65. By contrast, in human embryonic kidney 293 cells, PMA induced c-Fos independently of p65. In accordance with these results, we identified an NF-κB binding site in the mouse but not human c-fos promoter. Under PMA stimulation, IKKα/β mediated p65 phosphorylation and the binding of the p65 homodimer to the NF-κB site in the mouse c-fos promoter. Furthermore, our studies demonstrated independent but coordinated functions of the IKKα/β-p65 and extracellular signal-regulated kinase (ERK)-Elk-1 pathways in the PMA induction of c-Fos. Collectively, these results reveal the distinct requirement of NF-κB for mouse and human c-fos regulation. Binding of the p65 homodimer to the κB site was indispensable for mouse c-fos expression, whereas the κB binding site was not present in the human c-fos promoter. Because of an inability to evoke sufficient ERK activation and Elk-1 phosphorylation, TNF-α induces c-Fos more weakly than PMA does in both mouse and human cells.
立即早期基因 c-Fos 据报道受 Elk-1 和 cAMP 反应元件结合蛋白（CREB）调节，但核因子（NF）-κB 是否也需要控制 c-Fos 表达尚不清楚。在这项研究中，我们确定了 NF-κB 与 Elk/血清反应因子（SRF）的协调如何调节 c-fos 转录。我们报告说 PMA 强烈诱导 c-Fos 表达，但肿瘤坏死因子（TNF）-α 没有。在小鼠胚胎成纤维细胞中，IKKα、IKKβ、IKKγ 或 p65 的缺乏抑制了 PMA 诱导的 c-Fos。相比之下，在人胚肾 293 细胞中，PMA 诱导 c-Fos 不依赖于 p65。与这些结果一致，我们在小鼠而非人类 c-fos 启动子中鉴定到一个 NF-κB 结合位点。在 PMA 刺激下，IKKα/β介导 p65 磷酸化和 p65 同源二聚体与小鼠 c-fos 启动子中 NF-κB 位点的结合。此外，我们的研究表明 IKKα/β-p65 和细胞外信号调节激酶（ERK）-Elk-1 途径在 PMA 诱导 c-Fos 中的独立但协调的作用。总之，这些结果揭示了 NF-κB 对小鼠和人类 c-fos 调节的不同要求。p65 同源二聚体与 κB 位点的结合对于小鼠 c-fos 表达是必不可少的，而人类 c-fos 启动子中不存在 κB 结合位点。由于无法引起足够的 ERK 激活和 Elk-1 磷酸化，TNF-α 在小鼠和人细胞中诱导 c-Fos 的作用比 PMA 弱。
