Transfer RNA methylases of normal cells, virus-transformed cells, and tumors derived from transformed cells.

Transfer RNA methylases (rate and capacity) were studied in normal cells and tissues, in RNA and DNA oncogenic virus-transformed cells, and in tumors derived from the transformed cells. The DNA oncogenic virus-transformed cells (SV40 and polyoma) contained greater tRNA methylase capacities than their nontransformed normal cells. In contrast, no difference was observed (capacity or rate) between normal cells and the same cells transformed by RNA oncogenic virus (murine sarcoma virus). However, tumors derived from these murine sarcoma virus-transformed cells, as well as normal fetal tissues, show 2to 3-fold greater activities compared to various normal adult tissues. The results are discussed in terms of a correlation of tRNA methylase derepression with the state of differentiation of the cell.