MYC abrogates p53-mediated cell cycle arrest in N-(Phosphonacetyl)-L-aspartate-treated cells, permitting CAD gene amplification
MYC abrogates p53-mediated cell cycle arrest in N-(Phosphonacetyl)-L-aspartate-treated cells, permitting CAD gene amplification
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DOI：
10.1128/mcb.18.1.536
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发表时间：
1998-01-01
影响因子：
5.3
通讯作者：
Stark, GR
中科院分区：
文献类型：
--
作者：
Chernova, OB;Chernov, MV;Stark, GR
基因组不稳定，包括进行基因扩增的能力，是肿瘤细胞的标志，类似于正常细胞，“不允许的”ref52细胞不会通过扩增靶基因cad而对嘧啶核苷酸合成的抑制剂N-(膦-乙酰基)-L-天冬氨酸(Pla)产生抗药性，而是经历保护性的、长期的、依赖于p53的细胞周期停滞，外源myc的表达阻止了这种停滞，并允许ref52细胞在嘧啶核苷酸受限时进行有丝分裂，这导致dna断裂，导致细胞死亡，很少导致cad基因扩增和pla抗性，用低浓度的PALA预处理REF52细胞，这会减缓DNA复制，但不会触发细胞周期停滞，然后暴露于高选择性浓度的PALA，促进PALA耐药细胞的形成，其中物理连接的cad和内源性N-myc基因被共扩增，在这些经预处理的PALA耐药细胞中，内源性N-myc的激活表达使它们能够绕过未经处理的REF52细胞所特有的p53介导的停滞。我们的数据表明，形成耐PALA的REF52细胞需要两个不同的事件：cad的放大，其产物克服药物的作用，以及N-myc的表达增加。其产物克服了PALA诱导的细胞周期阻滞，这些配对事件只有在基因物理连接的情况下才会以可检测的频率发生，就像N-myc和N-myc一样，在过度表达N-myc的未经处理的REF52细胞中，p53的水平显著升高，但不诱导p21(Waf1)的表达或生长停滞，然而，在DNA损伤后，激活的p53在这些REF52/N-myc细胞中执行快速的凋亡，而不是在REF52细胞中看到的长期保护性停滞，稳定的p53在REF52/N-myc细胞中的主要细胞质定位表明细胞质保留图有助于失活p53的生长抑制功能。
Genomic instability, including the ability to undergo gene amplification, is a hallmark of neoplastic cells, Similar to normal cells, "nonpermissive" REF52 cells do not develop resistance to N-(phosphonacetyl)-L-aspartate (PALA), an inhibitor of the synthesis of pyrimidine nucleotides, through amplification of cad, the target gene, but instead undergo protective, long-term, p53-dependent cell cycle arrest, Expression of exogenous MYC prevents this arrest and allows REF52 cells to proceed to mitosis when pyrimidine nucleotides are limiting, This results in DNA breaks, leading to cell death and, rarely, to cad gene amplification and PALA resistance, Pretreatment of REF52 cells with a low concentration of PALA, which slows DNA replication but does not trigger cell cycle arrest, followed by exposure to a high, selective concentration of PALA, promotes the formation of PALA-resistant cells in which the physically linked cad and endogenous N-myc genes are coamplified, The activated expression of endogenous N-myc in these pretreated PALA-resistant cells allows them to bypass the p53-mediated arrest that is characteristic of untreated REF52 cells, Our data demonstrate that two distinct events are required to form PALA-resistant REF52 cells: amplification of cad, whose product overcomes the action of the drug, and increased expression of N-myc, whose product overcomes the PALA-induced cell cycle block, These paired events occur at a detectable frequency only when the genes are physically linked, as can and N-myc are, In untreated REF52 cells overexpressing N-MYC, the level of p53 is significantly elevated but there is no induction of p21(waf1) expression or growth arrest, However, after DNA is damaged, the activated p53 executes rapid apoptosis in these REF52/N-myc cells instead of the long-term protective arrest seen in REF52 cells, The predominantly cytoplasmic localization of stabilized p53 in REF52/N-myc cells suggests that cytoplasmic retention map help to inactivate the growth-suppressing function of p53.