Cleavage of lambda repressor and induction of recA protein synthesis elicited by aflatoxin B1 metabolites in Escherichia coli.

In Escherichia coli lambda lysogens incubated with activated aflatoxin B1, the rate of synthesis of RecA protein is markedly increased while lambda repressor is cleaved, but not that of the non-inducible mutant lambdacIind-. Following a 10 min lag period, lambda repressor is almost totally cleaved within 40 min of incubation. Cleavage of lambda repressor is inhibited by chloramphenicol. Synthesis of RecA protein and cleavage of lambda repressor are two characteristic processes induced in E. coil by DNA damaging agents such as u.v. light or mitomycin C. Our results favour the idea that in aflatoxin B1-treated lysogens, DNA lesions activate RecA protein to cleave LexA protein, the repressor of the recA gene, and lambda repressor. DNA damage, which may represent a relatively small fraction of the total cellular lesions, promotes the derepression of specific genes that control epigenetic as well as genetic processes in bacteria.