Bromodeoxyuridine dependence--a new mutation in mammalian cells.

When cells of a Syrian hamster melanoma were grown in increasing concentrations of bromodeoxyuridine (BrdU), lines of mutant cells able to grow well at high concentrations of BrdU were isolated. The mutant cells were characterized by BrdU dependence. In the absence of BrdU, the cells grew very poorly. The requirement for BrdU was specific for both the bromine and the deoxy sugar. The mutant cells incorporated BrdU into the DNA, replacing about 50% of the thymine residues with bromouracil. The reason for the BrdU dependence is not known.