Excision of bromodeoxyuridine from T4-DNA by an antimutator polymerase of T4 phage.

With gene-43 (DNA polymerase)-ts-mutants of T4 phage, L98 (mutator) and CB121 (antimutator), and the T4 wild type, double labelling of DNA was carried out with (H3)-bromodeoxyuridine (BUdR) and (C14)-thymidine (TdR). Experiments on (C14) TdR for DNA synthesis measurement in the presence of BUdR offered evidence of the ability of the CB121 mutant to excise BUdR from the DNA. This effect took place only at increased temperature. As distinct from DNA synthesis of the host, all T4 phages used preferred TdR rather than BUdR for net synthesis.