Gene Expression Caused by Alkylating Agents and cis- Diamminedichloroplatinum(II) in Escherìchiacoli1

Previous work has demonstrated heterogeneous effects of methylating agents on induction of DNA damage inducible genes in Escherìchia coli. These studies employed /:'. coli mutants that have fusions of the lac operon to genes induced by treatment with sublethal levels of alkylating agents. These mutants were selected from random insertions of the Mu di (Ap1lac) phage by screening for induction of /3-galactosidase activity in the presence of methylmethanesulfonate or W-methyl-W-nitro-Nnitrosoguanidine.The current report extends these findings by analyzing gene expression caused by mechlorethamine, chloroethylnitrosoureasand ciVdiamminedichloroplatinum(II) (m-DDP). The results demonstrate heterogeneous effects by these agents on gene expression. While l-(2chloroethyi)-3-cyclohexyI-l-nitrosourea induces ulkA, other nitrosoureas, mechlorethamine, and cis-DDP do not cause expression of this gene. Further, while all nitrosoureas caused expression ofaidC, mechlorethamine and ciVDDP did not. Lastly, c/'.v-l)DPcaused marked expres sion of a su!A fusion mutant while not inducing any of the other /•". coli