Effect of abasic sites on bacteriophage T7 protein synthesis.

We have examined protein synthesis directed by bacteriophage T7 which had been alkylated with methyl methanesulfonate so as to produce apurinic sites in its DNA in vivo. Both repair-proficient and repair-deficient (xth nfo mutant) strains of Escherichia coli served as host cells. In repair-proficient cells, all three classes of phage proteins were synthesized, although with significant delays. In mutant cells, only class I proteins were produced and their synthesis was delayed and reduced, demonstrating a perturbation of protein synthesis and providing the first in vivo indication that transcription is inhibited by abasic sites. However, the proposed effects of abasic sites on transcription appear to be weaker than those on replication.