作者:Hao Zhang、Yichen Ge、Ping He、Xushen Chen、Abreu Carina、Yulan Qiu、Diana S. Aga、Xuefeng Ren
DOI:10.1093/toxsci/kfv101
日期:2015.8
In humans, arsenic is primarily metabolized by arsenic (+3 oxidation state) methyltransferase (As3MT) to yield both trivalent and pentavalent methylated metabolites. We recently reported that the putative N-6 adenine-specific DNA methyltransferase 1 (N6AMT1) can biotransform monomethylarsonous acid (MMAIII) to dimethylarsinic acid, conferring resistance of human cells to arsenic exposure. To further decipher the role of N6AMT1 and its interaction with As3MT in arsenic biomethylation, we examined the relative contribution of N6AMT1 and As3MT in metabolizing arsenic using several newly modified UROtsa human urothelial cells, ie, UROtsa cells with either a constant level of N6AMT1 or As3MT in combination with an inducible level of As3MT or N6AMT1, respectively. Our analysis confirmed the involvement of N6AMT1 in MMAIII biomethylation but not for inorganic arsenic. In a comparable level of N6AMT1 and As3MT, the effect of N6AMT1 mediated MMAIII biomethylation was obscured by the action of As3MT. Furthermore, we showed that the levels of N6AMT1 and As3MT proteins varied among and within human normal and cancerous tissues. Overall, the data showed that N6AMT1 has a role in MMAIII biomethylation, but its effect is relatively minor and limited compared with As3MT. In addition, the varied levels and distributions of N6AMT1 and As3MT among human tissues may potentially contribute to the tissue specificity and susceptibility to arsenic toxicity and carcinogenicity.
在人体内,砷主要由砷(+3氧化态)甲基转移酶(As3MT)代谢,生成三价和五价甲基化代谢物。我们最近报告了推测的N-6腺嘌呤特异性DNA甲基转移酶1(N6AMT1)可将单甲基砷酸(MMAIII)生物转化成二甲基砷酸,从而赋予人体细胞对砷暴露的抵抗力。为了进一步阐明N6AMT1的作用及其与As3MT在砷生物甲基化中的相互作用,我们使用几种新修饰的UROtsa人尿路上皮细胞(即N6AMT1或As3MT水平恒定,或As3MT或N6AMT1水平可诱导的UROtsa细胞)研究了N6AMT1和As3MT在砷代谢中的相对贡献。我们的分析证实了N6AMT1参与MMAIII生物甲基化,但不参与无机砷的生物甲基化。在N6AMT1和As3MT水平相当的情况下,N6AMT1介导的MMAIII生物甲基化的作用被As3MT的作用所掩盖。此外,我们表明N6AMT1和As3MT蛋白的水平在人体正常组织和癌变组织之间和内部存在差异。总体而言,数据表明N6AMT1在MMAIII生物甲基