Regulation of expression of the DNA repair gene O6-methylguanine-DNA methyltransferase via protein kinase C-mediated signaling.
Regulation of expression of the DNA repair gene O6-methylguanine-DNA methyltransferase via protein kinase C-mediated signaling.
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发表时间：
1998-09
期刊：
影响因子：
11.2
通讯作者：
Istvan Boldogh;C. Ramana;C. Ramana;Zhenping Chen;Tapan Biswas;T. Hazra;Sabine Grösch;T. Grombacher;Sankar Mitra;Bernd Kaina
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文献类型：
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作者：
Istvan Boldogh;C. Ramana;C. Ramana;Zhenping Chen;Tapan Biswas;T. Hazra;Sabine Grösch;T. Grombacher;Sankar Mitra;Bernd Kaina
O 6-烷基鸟嘌呤是烷化剂（包括2-氯乙基-N-亚硝基脲类抗肿瘤药物）诱导的主要致突变性和细胞毒性DNA损伤。这种损伤由O 6-甲基鸟嘌呤-DNA甲基转移酶（MGMT）修复，其表达在正常组织和肿瘤细胞中高度可变。发现人MGMT基因的启动子含有两个推定的激活蛋白（AP）-1位点。在这里，我们发现，MGMT mRNA在HeLa S3细胞中的水平增加3-5倍佛波醇-1,2-肉豆蔻酸-13-乙酸酯（TPA）和1，2-二酰基-sn-甘油（DAG），这是蛋白激酶C（PKC）的激活剂，以及冈田酸，蛋白磷酸酶的抑制剂。PKC抑制剂1-（5-异喹啉磺酰基）-2-甲基哌嗪-HCl消除TPA和DAG对MGMT的激活作用，但不消除OA对MGMT的激活作用。先前PKC的下调消除了TPA或DAG的后续作用。结果表明AP-1参与MGMT表达的调节。这一假设得到了支持，显示AP-1结合到MGMT启动子的两个靶序列和MGMT启动子的反式激活后，在F9细胞中与c-fos和c-jun共转染。TPA介导的MGMT诱导导致细胞对2-氯乙基-N-亚硝基脲的抗性增加，这表明PKC介导的MGMT调节具有治疗意义。
O6-Alkylguanine is the major mutagenic and cytotoxic DNA lesion induced by alkylating agents, including 2-chloroethyl-N-nitrosourea-based antitumor drugs. This lesion is repaired by O6-methylguanine-DNA methyltransferase (MGMT), the expression of which is highly variable in both normal tissues and in tumor cells. The promoter of the human MGMT gene was found to contain two putative activator protein (AP)-1 sites. Here, we show that the level of MGMT mRNA in HeLa S3 cells was increased 3-5-fold by phorbol-12-myristate-13-acetate (TPA) and 1,2-diacyl-sn-glycerol (DAG), which are activators of protein kinase C (PKC), as well as by okadaic acid, an inhibitor of protein phosphatases. The PKC inhibitor 1-(5-isoquinoline sulfonyl)-2-methylpiperazine-HCl eliminated MGMT activation by TPA and DAG but not by OA. Prior down-regulation of PKC abolished subsequent effects of TPA or DAG. The results indicate AP-1 to be involved in regulation of MGMT expression. This hypothesis was supported by showing AP-1 binding to two target sequences of the MGMT promoter and transactivation of the MGMT promoter upon cotransfection with c-fos and c-jun in F9 cells. That TPA-mediated induction of MGMT caused increased cellular resistance to 2-chloroethyl-N-nitrosourea suggests a therapeutic significance for PKC-mediated MGMT modulation.