VARIATIONS IN TRANSFER-RNA MODIFICATIONS, PARTICULARLY OF THEIR QUEUINE CONTENT IN HIGHER EUKARYOTES - ITS RELATION TO MALIGNANCY GRADING

Literature references dealing with the variations in the modification level of nucleosides in total eukaryotic tRNAs as a function of differ ent physiological status and after drug administration as well as in s equenced cytoplasmic tRNAs between normal and tumor cells and in SV40- transformed cells are reviewed. In addition, special attention is give n to guanine replacement of queuine in the first position of the antic odon of tRNAs. A correlation between the level of this undermodificati on in cancer tissues and the malignancy grading could be found in huma n ovarian tumors, confirming the results reported in several laborator ies for lymphomas and lung cancer tissues. Indeed tRNAs from primary a nd metastatic human ovarian malignant tumors are Q deficient as compar ed to tRNAs from normal tissues or benign tumors: thus queuine deficie ncy increases with malignancy and grading of differentiation.