A defect in the p53 response pathway induced by de novo purine synthesis inhibition
A defect in the p53 response pathway induced by de novo purine synthesis inhibition
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DOI：
10.1074/jbc.m304844200
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发表时间：
2003-12-05
影响因子：
4.8
通讯作者：
Moran, RG
中科院分区：
文献类型：
--
作者：
Bronder, JL;Moran, RG
p53被认为在没有DNA链断裂的情况下感知细胞核糖核苷酸的消耗，并通过施加p21依赖性G（1）细胞周期停滞来应答。我们现在报道，在人类癌细胞系中，通过抑制甘氨酰胺核糖核苷酸甲酰转移酶（GART）的叶酸类似物抑制嘌呤的从头合成后，p53依赖性G（1）检查点被阻断。在GART抑制后，p53在HCT 116、MCF 7或A549癌细胞中积累，但令人惊讶的是，包括p21（cip 1/waf 1）在内的几种p53靶点的转录受损。对该缺陷的机理进行了研究。在这些细胞中积累的p53是核的，但在丝氨酸6、15和20处没有磷酸化，在赖氨酸373或382处也没有乙酰化。DDATHF稳定的p53在体外和体内与p21启动子结合，但不激活p21启动子中p53结合位点的组蛋白乙酰化，这是DNA损伤途径介导的转录反应的组成部分。我们的结论是，强大的初始响应的p53途径GART抑制剂是不转录传播的靶基因，由于p53翻译后修饰的缺陷和未能打开染色质结构，尽管启动子结合这种未修饰的p53。
p53 is believed to sense cellular ribonucleotide depletion in the absence of DNA strand breaks and to respond by imposition of a p21-dependent G(1) cell cycle arrest. We now report that the p53-dependent G(1) checkpoint is blocked in human carcinoma cell lines after inhibition of de novo purine synthesis by folate analogs inhibitory to glycinamide ribonucleotide formyltransferase (GART). p53 accumulated in HCT116, MCF7, or A549 carcinoma cells upon GART inhibition, but, surprisingly, transcription of several p53 targets, including p21(cip1/waf1), was impaired. The mechanism of this defect was examined. The p53 accumulating in these cells was nuclear but was not phosphorylated at serines 6, 15, and 20, nor was it acetylated at lysines 373 or 382. The DDATHF-stabilized p53 bound to the p21 promoter in vitro and in vivo but did not activate histone acetylation over the p53 binding sites in the p21 promoter that is an integral part of the transcriptional response mediated by the DNA damage pathway. We concluded that the robust initial response of the p53 pathway to GART inhibitors is not transcriptionally propagated to target genes due to a defect in p53 post-translational modifications and a failure to open chromatin structure despite promoter binding of this unmodified p53.