DIFFERENT EFFECT OF THYMIDINE KINASE LOSS ON TTP POOLS - COMPARISON AMONG HUMAN LEUKEMIA-CELL LINES

Thymidine kinase (TK)-deficient cells were established from six human leukemia cell lines to evaluate the role of TK in maintaining intracel lular TTP pools. The residual TK activities in mutant cells were less than 3% of those of wild-type strains, except for a B-lymphoid cell li ne, Ball-1 (8.7%). In a promyelocytic leukemia cell line (HL-60), a sp lenic B cell line (WI-L2) and Ball-1, a mutational loss of TK resulted in a decrease of TTF pools by 80%, 33% and 54%, respectively. On the other hand, in the T cell lines, Molt-3, Molt-4 and CEM, TTP did not s how any significant differences between parent and TK-deficient cells. TK-deficient HL-60 cells had, however, comparable levels of dATP, dGT P and dCTP with wild-type cells. An analysis of growth characteristics showed that the decrease of TTP was not due to the change of the cell cycle distribution. These results indicate that TK plays a different role in maintaining TTP pools among human leukemia cell lines.