IN-VITRO METHYLATION OF THE HUMAN O-6-METHYLGUANINE-DNA METHYLTRANSFERASE PROMOTER REDUCES TRANSCRIPTION
IN-VITRO METHYLATION OF THE HUMAN O-6-METHYLGUANINE-DNA METHYLTRANSFERASE PROMOTER REDUCES TRANSCRIPTION
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DOI：
10.1016/0167-4781(94)90027-2
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发表时间：
1994-03-01
期刊：
影响因子：
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通讯作者：
BRENT, TP
中科院分区：
文献类型：
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作者：
HARRIS, LC;REMACK, JS;BRENT, TP
大约20%的人类肿瘤细胞系（称为Mer(-)）缺乏DNA修复酶o -6-甲基鸟嘌呤-DNA甲基转移酶（MGMT； E.C.2.1.1.63）。这种细胞具有MGMT基因和启动子序列，但实际上没有mRNA或蛋白质。基因序列的胞嘧啶甲基化被认为是抑制Mer（-）细胞中MGMT的一种机制；然而，实验证据并不一致地支持这一观点。因此，我们研究了转染到培养的人细胞的报告基因构建体中MGMT启动子的体外甲基化的影响。HpaII或HhaI甲基化酶的DNA甲基化抑制了启动子的活性，尽管这种作用不是绝对的。启动子序列的细胞内部分去甲基化可能是转录不完全抑制的原因。提出了一个模型，试图调和关于胞嘧啶甲基化在MGMT基因表达中的作用的对立观点。
Approx. 20% of human tumor cell lines (termed Mer(-)) are deficient in the DNA repair enzyme O-6-methylguanine-DNA methyltransferase (MGMT; E.C.2.1.1.63). Such cells possess the MGMT gene and promoter sequences but have virtually no mRNA or protein. Cytosine methylation of gene sequences has been proposed as a mechanism by which MGMT could be suppressed in Mer(-) cells; however, the experimental evidence does not uniformly support this idea. We therefore investigated the effect of in vitro methylation of the MGMT promoter in a reporter gene construct transfected into cultured human cells. DNA methylation by HpaII or HhaI methylases suppressed the activity of the promoter, although the effect was not absolute. The occurrence of partial intracellular demethylation of promoter sequences may account for the incomplete inhibition of transcription. A model that attempts to reconcile the opposing views on the role of cytosine methylation in MGMT gene expression is presented.