Martin Angel G, Trama Jason, Crighton Diane, Ryan Kevin M, Fearnhead Howard O
Apoptosis Section, NCI-Frederick, Frederick, MD 21702, USA.
Aging (Albany NY). 2009 Feb 18;1(3):335-49. doi: 10.18632/aging.100026.
Although the transcription factor NF-kappaB is most clearly linked to the inhibition of extrinsic apoptotic signals such as TNFalpha by upregulating known anti-apoptotic genes, NF-kappaB has also been proposed to be required for p53-induced apoptosis in transformed cells. However, the involvement of NF-kappaB in this process is poorly understood. Here we investigate this mechanism and show that in transformed MEFs lacking NF-kappaB (p65-null cells) genotoxin-induced cytochrome c release is compromised. To further address how NF-kappaB contributes to apoptosis, gene profiling by microarray analysis of MEFs was performed, revealing that NF-kappaB is required for expression of Noxa, a pro-apoptotic BH3-only protein that is induced by genotoxins and that triggers cytochrome c release. Moreover, we find that in the absence of NF-kappaB, genotoxin treatment cannot induce Noxa mRNA expression. Noxa expression had been shown to be regulated directly by genes of the p53 family, like p73 and p63, following genotoxin treatment. Here we show that p73 is activated after genotoxin treatment only in the presence of NF-kappaB and that p73 induces Noxa gene expression through the p53 element in the promoter. Together our data provides an explanation for how loss of NF-kappaB abrogates genotoxin-induced apoptosis.
尽管转录因子核因子-κB（NF-κB）最明显地与通过上调已知的抗凋亡基因来抑制诸如肿瘤坏死因子α（TNFα）等外源性凋亡信号有关，但也有人提出NF-κB是转化细胞中p53诱导凋亡所必需的。然而，人们对NF-κB在这一过程中的作用了解甚少。在这里，我们研究了这一机制，结果表明在缺乏NF-κB的转化小鼠胚胎成纤维细胞（p65基因缺失细胞）中，基因毒素诱导的细胞色素c释放受损。为了进一步探讨NF-κB如何促进凋亡，我们对小鼠胚胎成纤维细胞进行了基因芯片分析，结果显示NF-κB是Noxa表达所必需的，Noxa是一种仅含BH3结构域的促凋亡蛋白，由基因毒素诱导产生并触发细胞色素c释放。此外，我们发现，在缺乏NF-κB的情况下，基因毒素处理不能诱导Noxa mRNA表达。研究表明，在基因毒素处理后，Noxa的表达直接受p53家族基因如p73和p63的调控。在这里，我们表明，只有在存在NF-κB的情况下，基因毒素处理后p73才会被激活，并且p73通过启动子中的p53元件诱导Noxa基因表达。我们的数据共同解释了NF-κB的缺失如何消除基因毒素诱导的凋亡。
