This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Turkington, R. W. Articles by Riddle, M. Search for Related Content PubMed PubMed Citation Articles by Turkington, R. W. Articles by Riddle, M.

Transfer RNA-methylating Enzymes in Mammary Carcinoma Cells¹

Department of Medicine, Duke University Medical Center, and the Division of Endocrinology, Veterans Administration Hospital, Durham, North Carolina 27705

The activities of specific enzymes for the methylation of tRNA in mammary carcinomas of the C3H mouse and the Fischer rat were compared with those in normal mammary gland. The activities of several of these enzymes were markedly increased above normal values, resulting in an alteration in the enzyme activity profile characteristic of the normal cell. Although the amount of methylase activity in normal mammary tissues is proportional to the cellular content of tRNA, the elevated methylase activities of the carcinoma cells were associated with reduced tRNA contents. The extracts from the carcinomas formed an additional methylated base, 7-methylguanine, which was not formed by normal mammary extracts with an exogenous tRNA substrate. Several other normal tissues can methylate tRNA in the N⁷-guanine position, however, suggesting that the genetic information for guanine 7-methylase has been activated in the neoplastic mammary cells.

¹ This research was supported in part by USPHS Grant CA-10268 from the National Cancer Institute, NIH.

Received 6/ 9/69. Accepted 7/31/69.