中文摘要：

DNA甲基化作为动植物体内一种重要的表观遗传修饰形式,在调控基因表达、维持基因组的稳定性等方面发挥重要的生物学作用。固有DNA甲基化水平和模式的变化会导致生物的表型异常甚至死亡。而5-甲基胞嘧啶的水平和模式是由DNA甲基化和去甲基化共同决定的。DNA去甲基化可以分为主动去甲基化与被动去甲基化,而基因组甲基化模式的形成主要依赖于主动去甲基化。本文综述了生物体内DNA主动去甲基化五种潜在机制：DNA转葡糖基酶参与的碱基切除修复途径、脱氨酶参与的碱基切除修复途径、核苷酸切除修复途径、氧化作用去甲基化与水解作用去甲基化。

英文摘要：

As a significant epigenetic modification,DNA methylation plays a critical role in regulating gene expression and maintaining genomic stability in mammals and flowering plants.DNA methylation level and pattern of change will lead to abnormal phenotype or even death.The level and pattern of 5-mC are determined by both DNA methylation and demethylation processes.Demethylation of DNA can be passive and active.The formation of DNA methylation pattern depends on the active demethylation.Five potential mechanisms of DNA active demethylation are reviewed in this paper： base excision repair involved with DNA glycosylases,base excision repair involved with enzymatic deamination,nucleotide excision repair,oxidative demethylation and hydrolysis.