Terminal deoxynucleotidyl transferase in AKR leukemic cells and lack of relation of enzyme activity to cell cycle phase

Summary Terminal deoxynucleotidyl transferase activity in mice, as in other animals, is normally confined to the thymus and the bone marrow (5, 7). In leukemic AKR mice, terminal transferase activity was also detected in leukemic cells. The specific activity of terminal transferase in these cells as a function of cell cycle phase was determined using AKR leukemic cells separated according to their position in the cell cycle by velocity sedimentation through a sucrose gradient at unit gravity. Normalization of enzyme activity to either total number of cells or to total protein in the crude homogenate failed to reveal a relationship of enzyme activity to cell cycle phase.