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首页> 外文期刊>Biochemistry >3-Methyladenine and 7-methylguanine exhibit no preferential removal from the transcribed strand of the dihydrofolate reductase gene in Chinese hamster ovary B11 cells.
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3-Methyladenine and 7-methylguanine exhibit no preferential removal from the transcribed strand of the dihydrofolate reductase gene in Chinese hamster ovary B11 cells.

机译：在中国仓鼠卵巢B11细胞中，3-甲基腺嘌呤和7-甲基鸟嘌呤没有从二氢叶酸还原酶基因的转录链中优先去除。

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摘要

The removal of cylclobutane pyrimidine dimers from cellular DNA occurs preferentially in actively transcribed genes of cells subjected to ultraviolet radiation. In contrast, reports concerning the transcription-dependent repair of N-methylpurines formed in cellular DNA following exposure to methylating agents are quite conflicting, with some studies suggesting that no biased clearance of these lesions occurs and others indicating that preferential removal of these adducts transpires in active genetic loci. Even in the cases where no preferential clearance was demonstrated, a slight but statistically insignificant biased removal of N-methylpurines from the transcribed strand of active genes was often evident. We proposed that these results might be due to the preferential clearance of only one of the two principal N-methylpurines formed, 3-methyladenine, or to the source of the methylating species to which the cells were exposed. Therefore, we investigated the clearance of 3-methyladenine and 7-methylguanine as individual lesions from the amplified dihydrofolate reductase gene of Chinese hamster ovary cells, and we examined the gene-specific removal of N-methylpurines formed by several different methylating agents as well. We observed no biased clearance of 3-methyladenine toward the transcribed strand of the locus being examined. This result indicates that any minor gene-specific preferential repair that has been observed previously for N-methylpurines in toto--which actually reflects the removal of the predominant methylated purine 7-methylguanine--is not due to biased clearance of the transcription-inhibiting 3-methyladenine lesion.(ABSTRACT TRUNCATED AT 250 WORDS)
机译：从细胞DNA中去除环氯丁烷嘧啶二聚体优先发生在受到紫外线辐射的细胞的主动转录基因中。相反，关于甲基化剂暴露后细胞DNA中形成的N-甲基嘌呤的转录依赖性修复的报道则存在很大矛盾，一些研究表明这些损伤没有清除偏差，而另一些研究则表明这些加合物的优先去除在活跃的基因位点。即使在没有证明优先清除的情况下，从活性基因的转录链中去除N-甲基嘌呤也有轻微但统计上不明显的偏见，这是很明显的。我们提出这些结果可能是由于形成的两个主要N-甲基嘌呤中只有一个，即3-甲基腺嘌呤的优先清除，或归因于细胞所暴露的甲基化物质的来源。因此，我们研究了从中国仓鼠卵巢细胞中扩增的二氢叶酸还原酶基因中单个损伤处3-甲基腺嘌呤和7-甲基鸟嘌呤的清除率，并研究了由几种不同的甲基化剂形成的N-甲基嘌呤的基因特异性清除。我们没有观察到3-甲基腺嘌呤朝着被检查基因座的转录链的偏向清除率。该结果表明，以前对N-甲基嘌呤所观察到的任何次要的基因特异性优先修复（实际上反映了主要的甲基化嘌呤7-甲基鸟嘌呤的去除）都不是由于转录抑制性的清除偏差造成的。 3-甲基腺嘌呤病变（摘要截短250字）

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