Biological consequences of incorporation of 5-fluorocytidine in the RNA of 5-fluorouracil-treated eukaryotic cells.

Treatment of HeLa cells with 5-fluoro-[3H]uracil leads to the incorporation into cellular RNA of 5-fluorocytidine to the extent of about 0.2% of the 5-fluorouridine incorporated. In tobacco mosaic virus RNA produced in tobacco leaves this ratio is one order of magnitude lower. Copolymers of cytidylic with 5-fluorocytidylic acids show unchanged template activity with E. coli RNA polymerase, but slightly altered messenger activity in the wheat germ system, compared to poly(C), and it is suggested that some of the biological consequences of 5-fluorouracil treatment of living cells and organisms may be attributed to this mechanism.