The important role of transfer ribonucleic acid (tRNA) in protein synthesis makes it a key molecule in the growth and proliferation of both normal and neoplastic cells. Evidence has also accumulated to suggest that tRNA may have a regulatory function at the level of both transcription and translation. Alterations in its complex structure as well as factors which may affect its various interactions, could have profound effects on its important functions. The most frequently observed structural modification of tRNA is methylation. By in vitro studies, extracts of tumor cells have been shown to have increased tRNA methyltransferase specific activity and capacity using heterologous tRNA when compared to similar extracts of normal control tissues. The tRNA methyltransferases have considerable specificity and react to transfer methyl groups to bases in the preformed macromolecule. Modified degradation products of tRNA are not re incorporated into its structure but catabolized and/or excreted intact. Natural inhibitors of tRNA methyltransferases have been found in specific normal adult tissues. These inhibitors are absent or diminished in amount in neoplastic or embryonic tissues. Stimulators of tRNA methyltransferase activity in particular polyamines, also exist. These various molecules may be factors of importance in influencing changes observed in tRNA methylation between normal and neoplastic cells. Specific, modified pyrimidine and purine end products of tRNA catabolism and in addition polyamines have been identified as urinary excretion products. These compounds have been found to be increased in the urine of animals and humans with malignant tumors. Patients with the more slow growing common solid tumors as well as patients with the rapidly proliferating Burkitt's lymphoma have been studied. Variations have been observed which appear related to the growth characteristics of the individual tumor types.
|Original language||English (US)|
|Number of pages||17|
|State||Published - Jan 1 1976|
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