Mechanisms for the inhibition of DNA methyltransferases by tea catechins and bioflavonoids
Mechanisms for the inhibition of DNA methyltransferases by tea catechins and bioflavonoids
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DOI：
10.1124/mol.104.008367
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发表时间：
2005-10-01
影响因子：
3.6
通讯作者：
Zhu, BT
中科院分区：
文献类型：
--
作者：
Lee, WJ;Shim, JY;Zhu, BT
本文研究了几种儿茶素和儿茶素对原核SssI DNA甲基转移酶（DNMT）和人DNMT 1催化的DNA甲基化的调节作用。我们发现，每一种茶多酚[儿茶素，表儿茶素，和（-）-表没食子儿茶素-3-O-没食子酸酯（EGCG）]和biflycidine（槲皮素，非瑟酮，和杨梅素）抑制SssI DNMT和DNMT 1介导的DNA甲基化的浓度依赖性方式。儿茶素、表儿茶素和各种类黄酮的IC 50值范围为1.0至8.4 μ M，但EGCG是更有效的抑制剂，IC 50值范围为0.21至0.47 μ M。当表儿茶素被用作模型抑制剂时，动力学分析表明，这种含儿茶酚的膳食多酚在体外很大程度上通过增加S-腺苷-L-同型半胱氨酸（一种有效的DNMTs非竞争性抑制剂）的形成来抑制酶促DNA甲基化，该膳食儿茶酚在儿茶酚-O-甲基转移酶介导的O-甲基化过程中。相比之下，EGCG对DNMT介导的DNA甲基化的强抑制作用不依赖于其自身的甲基化，并且主要是由于其对DNMT的直接抑制。Mg ~（2+）强烈地增强了这种抑制作用。计算建模研究表明，EGCG的没食子酸部分在其与人DNMT 1的催化位点的高亲和力、直接抑制性相互作用中起着至关重要的作用，并且其与酶的结合被Mg 2+稳定。EGCG与人DNMT 1抑制相互作用的精确分子模式的建模数据与我们的实验结果完全一致。
In the present investigation, we studied the modulating effects of several tea catechins and bioflavonoids on DNA methylation catalyzed by prokaryotic SssI DNA methyltransferase (DNMT) and human DNMT1. We found that each of the tea polyphenols [ catechin, epicatechin, and (-)-epigallocatechin-3-O-gallate (EGCG)] and bioflavonoids (quercetin, fisetin, and myricetin) inhibited SssI DNMT- and DNMT1-mediated DNA methylation in a concentration-dependent manner. The IC50 values for catechin, epicatechin, and various flavonoids ranged from 1.0 to 8.4 mu M, but EGCG was a more potent inhibitor, with IC50 values ranging from 0.21 to 0.47 mu M. When epicatechin was used as a model inhibitor, kinetic analyses showed that this catechol-containing dietary polyphenol inhibited enzymatic DNA methylation in vitro largely by increasing the formation of S-adenosyl-L-homocysteine (a potent noncompetitive inhibitor of DNMTs) during the catechol-O-methyltransferase-mediated O-methylation of this dietary catechol. In comparison, the strong inhibitory effect of EGCG on DNMT- mediated DNA methylation was independent of its own methylation and was largely due to its direct inhibition of the DNMTs. This inhibition is strongly enhanced by Mg2+. Computational modeling studies showed that the gallic acid moiety of EGCG plays a crucial role in its high-affinity, direct inhibitory interaction with the catalytic site of the human DNMT1, and its binding with the enzyme is stabilized by Mg2+. The modeling data on the precise molecular mode of EGCG's inhibitory interaction with human DNMT1 agrees perfectly with our experimental finding.