Wainfan E, Dizik M
Carcinogenesis. 1987 Apr;8(4):615-7. doi: 10.1093/carcin/8.4.615.
When male Fischer rats were fed Purina chow supplemented with 2% D,L-methionine and 1% choline chloride, the rapid increase in N2-guanine tRNA methyltransferase II (NMG2) activity otherwise seen in response to cancer-promoting doses (0.02% in the diet) of 2-acetylaminofluorene (AAF) was prevented, and the increase in NMG2 activity otherwise caused by carcinogenic doses of AAF (0.06% in the diet) was decreased by 50%. In addition, the return of NMG2 activity to a normal level after completion of a 3-week regimen of 0.06% AAF was accelerated in animals fed the methionine plus choline supplemented diet. As shown earlier in this laboratory, liver tRNA methylating enzyme activities are shifted rapidly to an onco-fetal pattern in rats receiving methyl-deficient diets. This pattern is characterized by selectively elevated NMG2 activity while the activities of other base-specific tRNA methylating enzymes are relatively unchanged. Our combined results indicate that the exogenous supply of methyl groups is a factor in regulating NMG2 activity and can modulate at least one response of animals to carcinogens.
当给雄性Fischer大鼠喂食添加了2% D,L-蛋氨酸和1%氯化胆碱的普瑞纳饲料时，原本在给予促癌剂量（饲料中0.02%）的2-乙酰氨基芴（AAF）后会迅速增加的N2-鸟嘌呤tRNA甲基转移酶II（NMG2）活性受到了抑制，并且由致癌剂量的AAF（饲料中0.06%）所引起的NMG2活性增加降低了50%。此外，在完成为期3周的0.06% AAF喂养方案后，喂食添加了蛋氨酸和胆碱饲料的动物中，NMG2活性恢复到正常水平的速度加快。如本实验室先前所示，在接受甲基缺乏饮食的大鼠中，肝脏tRNA甲基化酶活性会迅速转变为一种癌胚模式。这种模式的特征是NMG2活性选择性升高，而其他碱基特异性tRNA甲基化酶的活性相对不变。我们的综合结果表明，甲基基团的外源供应是调节NMG2活性的一个因素，并且可以调节动物对致癌物的至少一种反应。
