P53 is involved in regulation of the DNA repair gene O6-methylguanine-DNA methyltransferase (MGMT) by DNA damaging agents
P53 is involved in regulation of the DNA repair gene O6-methylguanine-DNA methyltransferase (MGMT) by DNA damaging agents
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DOI：
10.1038/sj.onc.1202000
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发表时间：
1998-08-20
期刊：
影响因子：
8
通讯作者：
Kaina, B
中科院分区：
文献类型：
--
作者：
Grombacher, T;Eichhorn, U;Kaina, B
DNA修复蛋白O-6-甲基鸟嘌呤-DNA甲基转移酶（MGMT）是可诱导的胁迫。MGMT的诱导是由于MGMT基因的激活，而MGMT基因的激活是对DNA损伤的特异性反应。p53可能参与了MGMT的诱导，因为p53和MGMT都是由DNA断裂激活的。我们比较了基因毒性处理后不同小鼠成纤维细胞和大鼠肝癌细胞系中功能性野生型（wt）和突变型p53的存在与MGMT表达水平。通过MGMT诱导对电离辐射（IR）作出反应的细胞显示功能性p53，而在不表达wt p53的细胞中，未观察到MGMT诱导。此外，克隆的MGMT启动子在转染到p53 wt细胞中后可被IR诱导，但在p53缺陷的细胞中则不然。因此，wt p53的表达似乎是IR诱导MGMT mRNA和蛋白质所必需的。另一方面，与p53一起转染MGMT-启动子-CAT构建体在表达野生型p53的细胞中，野生型或突变型p53的共转染显著降低了MGMT启动子的基础活性，而与p53反义构建体的共转染略微增加了MGMT启动子活性。此外，MGMT启动子与野生型或突变型p53在p53野生型细胞中的共转染减少辐射诱发的MGMT启动子诱导。因此，转染介导的p53高水平表达对MGMT启动子的基础活性和IR对其的激活都具有抑制作用，这一结果为p53参与DNA损伤诱导的MGMT启动子激活提供了证据。
The DNA repair protein O-6-methlguanine-DNA methyltransferase (MGMT) is inducible stress. MGMT induction results from activation of the MGMT gene which Is a specific response to DNA damage, A possible factor involved in triggering MGMT induction might be p53, because both p53 and MGMT are activated by DNA breaks, To study the effect of p53 on induction of the MGMT gene, we compared the presence of functional wild-type (wt) and mutant p53 with MGMT expression level in various mouse fibroblasts and rat hepatoma cell lines upon genotoxic treatment. Cells which responded to ionizing radiation (IR) by MGMT induction displayed functional p53, whereas in cells not expressing wt p53, MGMT induction was not observed. Also, the cloned MGMT promoter was inducible by IR upon transfection into p53 wt cells, but not in cells deficient for p53, Thus, expression of wt p53 appears to be required for induction of MGMT mRNA and protein by IR, On the other hand, transfection of a MGMT-promoter-CAT construct together with p53 (either wt or mutant) in cells expressing wt p53 markedly reduced the basal activity of the MGMT promoter whereas cotransfection with a p53 antisense construct slightly increased MGMT promoter activity. Furthermore, cotransfection of MGMT promoter with wt or mutant p53 in p53 wt cells reduced radiation evoked MGMT promoter induction. Thus, transfection mediated high level expression of p53 has inhibitory effect both on basal MGMT promoter activity and its activation by IR, The results give evidence for involvement of p53 in DNA damage-induced MGMT promoter activation.