Cell-cycle-dependent variations of deoxyribonucleoside triphosphate pools in chinese hamster cells

Abstract

Variation of levels of the four deoxyribonucleoside triphosphate pools has been examined as synchronized Chinese hamster cells complete mitosis and traverse the cell cycle in preparation for division. The results indicate that; 1. 1. Mitotic cells have the largest pools of dATP, dGTP, and dTTP and that all four deoxyribonucleoside triphosphates are degraded as cells exit from mitosis. 2. 2. The pool of dCTP is maximal in late S-early G 2, and degradation begins in G 2. 3. 3. G 1 cells have little or no deoxyribonucleoside triphosphates. 4. 4. The pool size of all four deoxyribonucleoside triphosphates increases just prior to initiation of DNA synthesis and increases throughout S. 5. 5. Cells treated with hydroxyurea in G 1 accumulate dTTP, dCTP, and dGTP at the time that cells would normally have initiated DNA synthesis, but accumulation of dATP is completely inhibited as is initiation of DNA synthesis. 6. 6. The four deoxyribonucleoside triphosphates are not present in equimolar concentrations, pools in mid-S being 10 pmoles 10 6 cells , 27 pmoles 10 6 cells , 104 pmoles 10 6 cells , and 76 pmoles 10 6 cells for dGTP, dATP, dTTP, and dCTP, respectively. The pools of dGTP, dATP, dTTP, and dCTP are sufficient to support DNA synthesis for 1.0, 1.3, 5.2, and 3.8 min, respectively.