Changes in ribo- and deoxyribonucleoside triphosphate pools within the cell cycle of a synchronized moused fibroblast cell line

Abstract

Intracellular pool levels of ribo- and deoxyribonucleoside triphosphates were monitored throughout the cell cycle of C3H10T1/2 mouse embryo fibrolast cells synchronized by isoleucine deprivation. Absolute pool sizes of ribonucleoside triphosphates were approximately 30 fold greater than those of the corresponding deoxyribonucleoside triphosphates. Of the ribonucleoside triphosphates, pool sizes of ATP exhibited the greatest change, increasing from a low of 32.7 nmol/10 7 cells during G 1 to a high of 81.6 nmol/10 7 cells 2 h prior to mid S-phase. Levels of ATP subsequently declined to 40.2 nmol/10 7 cells during late S-phase, followed by a second peak of 65.8 nmol/10 7 with the onset of cell division. No significant changes in the pool sizes of UTP and GTP were found throughout the cell cycle. Of the deoxyribonucleoside triphosphates, pool sizes of pyrimidine deoxyribonucleoside triphosphates were approx. 5–10 fold greater than those of purine deoxyribonucleoside triphosphates. Low levels of deoxyribonucleoside triphosphates during G 1 (0.3–1.3 pmol/10 7 cells) increased coordinately with the initiation of DNA synthesis to an initial peak during mid S-phase (0.5–6.4 pmol/10 7 cells). Decling levels of deoxyribonucleoside triphosphates during late S-phase were followed by a subsequent larger second peak (1.7–10.7 pmol/10 7 cells) during G 2-M.