Role of the Arabidopsis DNA glycosylase/lyase ROS1 in active DNA demethylation
Role of the Arabidopsis DNA glycosylase/lyase ROS1 in active DNA demethylation
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DOI：
10.1073/pnas.0603563103
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发表时间：
2006-08-01
影响因子：
11.1
通讯作者：
Zhu, Jian-Kang
中科院分区：
文献类型：
--
作者：
Agius, Fernanda;Kapoor, Avnish;Zhu, Jian-Kang
DNA甲基化是在包括植物和许多动物在内的各种生物中转录基因沉默的稳定表观遗传标记。与通过甲基转移酶进行良好特征的DNA甲基化机制相反，主动DNA脱甲基化的机制和功能一直存在争议。遗传证据表明，拟南芥的DNA糖基酶结构域ROS1是推定的DNA脱甲基酶，因为功能丧失的ROS1突变会导致DNA高甲基化并增强转录基因沉默。我们在这里报告了ROS1的生化表征及其过表达对靶基因DNA甲基化的影响。我们的数据表明，ROS1的DNA糖基化酶活性从DNA主链中去除5-甲基胞嘧啶，然后其裂解酶活性通过连续的β-固定反应而在5-甲基胞霉素去除的部位裂解DNA主链。转基因植物中ROS1的过表达导致胞嘧啶甲基化水平降低，靶基因表达增加。这些结果表明，ROS1是一种5-甲基环胞嘧啶DNA糖基酶/裂解酶，对于拟南芥中活性DNA脱甲基的重要性很重要。
DNA methylation is a stable epigenetic mark for transcriptional gene silencing in diverse organisms including plants and many animals. In contrast to the well characterized mechanism of DNA methylation by methyltransferases, the mechanisms and function of active DNA demethylation have been controversial. Genetic evidence suggested that the DNA glycosylase domain-containing protein ROS1 of Arabidopsis is a putative DNA demethylase, because loss-of-function ros1 mutations cause DNA hypermethylation and enhance transcriptional gene silencing. We report here the biochemical characterization of ROS1 and the effect of its overexpression on the DNA methylation of target genes. Our data suggest that the DNA glycosylase activity of ROS1 removes 5-methylcytosine from the DNA backbone and then its lyase activity cleaves the DNA backbone at the site of 5-methylcytosine removal by successive beta- and delta-elimination reactions. Overexpression of ROS1 in transgenic plants led to a reduced level of cytosine methylation and increased expression of a target gene. These results demonstrate that ROS1 is a 5-methylcytosine DNA glycosylase/lyase important for active DNA demethylation in Arabidopsis.