Effect of thymidine analogs on tyrosinase activity and mRNA accumulation in mouse melanoma cells

The thymidine analog 5-bromodeoxyuridine (BrdU) has been found to inhibit terminal differentiation of a variety of cell types without significantly affecting the growth of these cells. We have compared the effect of BrdU with two other thymidine analogs, 5-iododeoxyuridine and 5-fluorodeoxyuridine, on the growth, tyrosinase activity, and tyrosinase-mRNA accumulation in BL-6 mouse melanoma cells. We show that all three analogs inhibit growth and tyrosinase activity, but only BrdU significantly inhibits the accumulation of tyrosinase mRNA. We consider these results in the light of current understanding of BrdU action.