Differences in the patterns of methylation in rat liver ribosomal ribonucleic acid after reaction in vivo with methyl methanesulphonate and NN-dimethylnitrosamine.
Differences in the patterns of methylation in rat liver ribosomal ribonucleic acid after reaction in vivo with methyl methanesulphonate and NN-dimethylnitrosamine.
复制标题
大鼠肝脏核糖体核糖核酸与甲磺酸甲酯和NN-二甲基亚硝胺体内反应后甲基化模式的差异。
作者：
P. O'connor;M. Capps;A. Craig;P. D. Lawley;S. A. Shah
1.腹腔注射[(14)C]甲磺酸甲酯(50mg/kg)或NN-二[(14)C]甲基亚硝胺(2mg/kg)后，每隔一段时间从大鼠肝脏中分离rRNA。选择这些剂量是为了最大限度地减少毒性影响。 2.[(14)C]甲基化rRNA的水解采用以下方法：pH8酶切为核苷；碱性水解并转化为核苷；酸水解成碱。 3.甲基化产物在Dowex-50(H(+)型)和Dowex-50(NH(4)(+)型)柱上进行色谱分析。 4. 对于两种甲基化剂，甲基化的主要产物是7-甲基鸟嘌呤。然而，次要碱基3-甲基胞嘧啶、1-甲基腺嘌呤和7-甲基腺嘌呤的摩尔比例存在差异。鸟嘌呤 O-6 位的甲基化是从 NN-二[(14)C]甲基亚硝胺处理的动物获得的 rRNA 的一个显着特征，但在用[(14)C]甲基甲磺酸盐处理后的 rRNA 中未检测到。
1. rRNA was isolated from rat liver at short intervals after the intraperitoneal injection of [(14)C]methyl methanesulphonate (50mg/kg) or NN-di[(14)C]methylnitrosamine (2mg/kg). These doses were chosen to minimize the effects of toxicity. 2. The following methods of hydrolysis of [(14)C]methylated rRNA were employed: enzymic digestion to nucleosides at pH8; alkaline hydrolysis and conversion into nucleosides; acid hydrolysis to bases. 3. The methylation products were analysed by chromatography on columns of Dowex-50 (H(+) form) and Dowex-50 (NH(4) (+) form). 4. With both methylating agents the principal product of methylation was 7-methylguanine. Differences were obtained, however, in the molar proportions of the minor bases 3-methylcytosine, 1-methyladenine and 7-methyladenine. Methylation at the O-6 position of guanine was a significant feature of rRNA obtained from the NN-di[(14)C]methylnitrosamine-treated animals but was not detected in rRNA after treatment with [(14)C]methyl methanesulphonate.