He Weizhi, Yin Xiaotong, Xu Chu, Liu Xiangyue, Huang Yue, Yang Caiguang, Xu Yanhui, Hu Lulu
Cancer Institute, Fudan university Shanghai Cancer Center, Institutes of Biomedical Sciences, Shanghai Key Laboratory of Medical Epigenetics, International Co-laboratory of Medical Epigenetics and Metabolism (Ministry of Science and Technology), Shanghai Medical College of Fudan University, Shanghai 200032, China.
State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China.
ACS Chem Biol. 2024 Jan 19;19(1):129-140. doi: 10.1021/acschembio.3c00567. Epub 2023 Dec 15.
Ascorbic acid (ASC) has been reported to stimulate DNA iterative oxidase ten-eleven translocation (TET) enzymes, Jumonji C-domain-containing histone demethylases, and potentially RNA mA demethylases FTO and ALKBH5 as a cofactor. Although ascorbic acid has been widely investigated in reprogramming DNA and histone methylation status , in cultured cells and mouse models, its specific role in the catalytic cycle of dioxygenases remains enigmatic. Here, we systematically investigated the stimulation of ASC toward TET2, ALKBH3, histone demethylases, and FTO. We find that ASC reprograms epitranscriptome by erasing the hypermethylated mA sites in mRNA. Biochemistry and electron spin resonance assays demonstrate that ASC enters the active pocket of dioxygenases and reduces Fe(III), either incorporated upon protein synthesis or generated upon rebounding the hydroxyl radical during oxidation, into Fe(II). Finally, we propose a remedied model for the catalytic cycle of dioxygenases by adding in the essential cofactor, ASC, which refreshes and regenerates inactive dioxygenase through recycling Fe(III) into Fe(II) in a dynamic "hit-and-run" manner.
据报道，抗坏血酸（ASC）作为一种辅助因子，可刺激DNA迭代氧化酶十一 - 易位（TET）酶、含Jumonji C结构域的组蛋白去甲基化酶，以及潜在的RNA mA去甲基化酶FTO和ALKBH5。尽管抗坏血酸在培养细胞和小鼠模型中对DNA和组蛋白甲基化状态重编程方面已得到广泛研究，但其在双加氧酶催化循环中的具体作用仍不清楚。在此，我们系统地研究了ASC对TET2、ALKBH3、组蛋白去甲基化酶和FTO的刺激作用。我们发现ASC通过消除mRNA中高度甲基化的mA位点来重编程表观转录组。生物化学和电子自旋共振分析表明，ASC进入双加氧酶的活性口袋，并将蛋白质合成时掺入的或氧化过程中羟基自由基反弹产生的Fe(III)还原为Fe(II)。最后，我们通过加入必需的辅助因子ASC，提出了一种双加氧酶催化循环的修正模型，该模型以动态的“即进即出”方式通过将Fe(III)循环回Fe(II)来使无活性的双加氧酶恢复活力并再生。
