Benzo(a)pyrene induced glycine N-methyltransferase messenger RNA expression in Fundulus heteroclitus embryos.
Benzo(a)pyrene induced glycine N-methyltransferase messenger RNA expression in Fundulus heteroclitus embryos.
复制标题
苯并(a)芘诱导异斜眼底胚胎中甘氨酸 N-甲基转移酶信使 RNA 的表达。
DOI：
10.1016/j.marenvres.2009.10.008
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发表时间：
2010
影响因子：
3.3
通讯作者：
Willett,KristineL
中科院分区：
文献类型：
--
作者：
Fang,Xiefan;Dong,Wu;Thornton,Cammi;Scheffler,Brian;Willett,KristineL
甘氨酸N-甲基转移酶（GNMT）是甲硫氨酸和叶酸循环中的介体，并且负责将甲基从S-腺苷甲硫氨酸（SAM）转移到甘氨酸，形成S-腺苷高半胱氨酸（SAH）和肌氨酸。所有已知的DNA甲基转移酶都使用SAM作为甲基供体，因此，GNMT在DNA甲基化的调节中起着关键作用。GNMT活性的改变与包括肝细胞癌在内的肝脏病理学有关。GNMT的同源四聚体形式具有酶活性，但同源二聚体形式被认为是可能介导CYP 1A表达的4S PAH结合蛋白。为了进一步了解GNMT在苯并（a）芘（BaP）相关毒性中的作用，从成体肝脏中克隆了异盘底菌（Fundulusheteroclitus）GNMT全长cDNA。GNMT的开放阅读框（ORF）长888 bp，编码295个氨基酸，与人GNMT的同源性为74%。用定量RT-PCR法检测GNMT mRNA的表达。未受精、受精后2d和3d胚胎的GNMT组成型高于4d、7 d、10 d和14 d胚胎。胚胎也暴露于10和100μgL−1的水溶性BaP，到10 dpf时，较高的BaP剂量导致GNMT mRNA表达增加。这些结果表明，PAH暴露可能会改变一个重要的生理甲基化介质的表达。未来的工作还需要确定BaP暴露对酶水平的影响。
Glycine N-methyltransferase (GNMT) is a mediator in the methionine and folate cycles, and is responsible for the transfer of a methyl group from S-adenosylmethionine (SAM) to glycine forming S-adenosylhomocysteine (SAH) and sarcosine. All the known DNA methyltransferases use SAM as a methyl donor thus, GNMT is critically involved in regulation of DNA methylation. Altered GNMT activities have been associated with liver pathologies including hepatocellular carcinoma. The homotetramer form of GNMT is enzymatically active, but the homodimeric form has been suggested as the 4S PAH-binding protein which may mediate CYP1A expression. To further understand the role of GNMT in benzo(a)pyrene (BaP)-related toxicity, full length Fundulusheteroclitus GNMT cDNA was cloned from adult liver. The open reading frame (ORF) of GNMT is 888 base pairs long and encodes a deduced protein of 295 amino acids which has 74% identity with human GNMT. Expression of GNMT mRNA was determined by quantitative RT-PCR. In unfertilized, 2days postfertilization (dpf), and 3 dpf embryos GNMT was constitutively higher than in 4, 7, 10 or 14 dpf embryos. Embryos were also exposed to waterborne BaP at 10 and 100μgL−1, and by 10 dpf the higher BaP dose caused increased expression of GNMT mRNA. These results suggest that PAH exposure may alter expression of an important physiological methylation mediator. Future work will be necessary to determine enzyme level effects of BaP exposure as well.