Effects of 5-fluoro-2'-deoxyuridine on DNA metabolism in HeLa cells

5-Fluoro-2'-deoxyuridine at a concentration of 0.1 microM completely inhibited incorporation of radioactivity from [3H]dUrd into DNA in HeLa S3 cells within 5 min of exposure. The dTTP pool size decreased from 800 to 300 pmoles/10(7) cells by 1 hr, and then gradually increased after 3 hr of exposure. Although the incorporation of radioactivity from [32P] H3PO4 into DNA was inhibited, the relative incorporation into smaller fragments compared with larger fragments of DNA was found to be increased in the drug-treated cells. When the cells with [14C]thymidine-prelabeled DNA were exposed to 5 fluoro-dUrd, shifts of labeled DNA peaks to smaller sizes were observed between 5 and 18 hr after exposure, as analyzed by alkaline sucrose gradient centrifugation. Exposure of cells to 1 and 10 microM 5-fluoro-[3H]dUrd caused incorporation of radioactivity into DNA. By high-performance liquid chromatographic analysis of nucleosides, it was confirmed that almost all of the radioactivity was incorporated as 5-fluoro-dUrd.