Ascorbic Acid Enhances Tet-Mediated 5-Methylcytosine Oxidation and Promotes DNA Demethylation in Mammals

作者：Yin, Ruichuan; Mao, Shi-Qing; Zhao, Bailin; Chong, Zechen; Yang, Ying; Zhao, Chao; Zhang, Dapeng; Huang, Hua; Gao, Juan; Li, Zheng; Jiao, Yan; Li, Cuiping; Liu, Shengquan; Wu, Danni; Gu, Weikuan; Yang, Yun-Gui; Xu, Guo-Liang; Wang, Hailin^*

来源：Journal of the American Chemical Society, 2013, 135(28): 10396-10403.

DOI：10.1021/ja4028346

• EMBRYONIC STEM-CELLS
• PATERNAL GENOME
• ACTIVE-DEMETHYLATION
• 5-HYDROXYMETHYLCYTOSINE
• PROTEINS
• DYNAMICS
• 5-CARBOXYLCYTOSINE
• METHYLATION
• MECHANISMS
• GENE

DNA hydroxymethylation and its mediated DNA demethylation are critical for multiple cellular processes, for example, nuclear reprogramming, embryonic development, and many diseases. Here, we demonstrate that a vital nutrient ascorbic acid (AA), or vitamin C (Vc), can directly enhance the catalytic activity of Tet dioxygenases for the oxidation of 5-methylcytosine (5mC). As evidenced by changes in intrinsic fluorescence and catalytic activity of Tet2 protein caused by AA and its oxidation-resistant derivatives, we further show that AA can uniquely interact with the C-terminal catalytic domain of Tet enzymes, which probably promotes their folding and/or recycling of the cofactor Fe2+. Other strong reducing chemicals do not have a similar effect. These results suggest that AA also acts as a cofactor of Tet enzymes. In mouse embryonic stem cells, AA significantly increases the levels of all 5mC oxidation products, particularly 5-formylcytosine and 5-carboxylcytosine (by more than an order of magnitude), leading to a global loss of 5mC (similar to 40%). In cells deleted of the Tet1 and Tet2 genes, AA alters neither 5mC oxidation nor the overall level of 5mC. The AA effects are however restored when Tet2 is re-expressed in the Tet-deficient cells. The enhancing effects of AA on 5mC oxidation and DNA demethylation are also observed in a mouse model deficient in AA synthesis. Our data establish a direct link among AA, Tet, and DNA methylation, thus revealing a role of AA in the regulation of DNA modifications.

• 单位
  中国科学院; 环境化学与生态毒理学国家重点实验室; 分子生物学国家重点实验室; 中国科学院上海生命科学研究院生物化学与细胞生物学研究所; 中国科学院大学; 中国科学院北京基因组研究所