Expression of DNA damage-inducible genes of Escherichia coli upon treatment with methylating, ethylating and propylating agents.

Several alkylation-inducible genes have been identified by construction of Mu-d1 (Apr lac) fusions to genes whose expression is increased in response to alkylation treatment, but not UV treatment. We have examined the induction of 4 different alkylation-inducible genes by treatment with a variety of methylating and ethylating agents, and a propylating agent. We have compared the induction of the alkylation-inducible genes with the induction of the sulA gene, which is a component of the SOS response to DNA damage. We find that the Ada-regulated adaptive response genes (ada-alkB, alkA and aidB) are induced primarily in response to methylation treatment. The ada-independent aidC gene is induced upon treatment with agents that alkylate predominantly by SN1 nucleophilic attack. aidC induction occurs only when cells are not aerated during treatment. The SOS response, as indicated by sulA induction, is strongly induced by all types of alkylating agents used.