[Genetic activity of para-aminobenzoic acid. The intensification of DNA polymerase I-dependent repair induced by chemical mutagens in toluene-treated Escherichia coli cells].

Alkylatio of Escherichia coli DNA that have been made permeable to nucleotides by toluene treatment results in the expression of DNA polymerase I-directed repair synthesis. The system only permits measurement of DNA polymerase I-directed repair synthesis. The latter is not observed in mutant cells deficient in this polymerase. DNA ligation is intentionally prevented by the addition of the inhibitor, nicotinamide mononucleotide. MNU, ENU and MMS elicit DNA polymerase I-directed repair synthesis. MNU and MMS are especially potent in this regard, while EMS is a poor inducer of DNA polymerase I activity in permeabilized cells. The natural compound para-aminobenzoic acid itself (0,0002 mM - 20 mM) doesn't induce DNA polymerase I-directed repair synthesis. However, when PABA is used in complex with alkylating agents as the inducers, the repair synthesis increased 2,0, 1,2 and 2,8 times for MNU, ENU and EMS, respectively, as compared to that elicited by "pure" mutagens. The increasing of DNA repair synthesis in permeabilized bacteria in the experiments with PABA may serve as the foundation for its reparagenic activity. The latter was discovered previously by the authors in experiments on mutagenesis of bacterial cells.