1. rRNA was isolated from rat liver at short intervals after the intraperitoneal injection of [14C]methyl methanesulphonate (50mg/kg) or NN-di[14C]methylnitrosamine (2mg/kg). These doses were chosen to minimize the effects of toxicity. 2. The following methods of hydrolysis of [14C]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 (NH4+ 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[14C]methylnitrosamine-treated animals but was not detected in rRNA after treatment with [14C]methyl methanesulphonate.
Differences in the patterns of methylation in rat liver ribosomal ribonucleic acid after reaction in vivo with methyl methanesulphonate and NN-dimethylnitrosamine
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P. J. O'Connor, M. J. Capps, A. W. Craig, P. D. Lawley, S. A. Shah; Differences in the patterns of methylation in rat liver ribosomal ribonucleic acid after reaction in vivo with methyl methanesulphonate and NN-dimethylnitrosamine. Biochem J 1 September 1972; 129 (3): 519–528. doi: https://doi.org/10.1042/bj1290519
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