SOS induction of the recA gene by UV-, gamma-irradiation and mitomycin C is mediated by polyamines in Escherichia coli K-12

Polyamines are involved in a wide range of cellular metabolism. In this stu dy we investigated the effects of polyamines on the SOS induction of the re cA gene by exposure to UV-, gamma-irradiation and mitomycin C employing pol yamine-deficient mutant and wild type Escherichia. coli strains carrying re cA'::'lacZ transcriptional fusion. In the polyamine-deficient mutant, the i nduction factor of the lecA gene by UV-, gamma-irradiation and mitomycin C- treatment are about 3.0-, 2.5- and if-fold lower, respectively, than those of the wild type. The exogenous addition of polyamines restored the reduced induction of the recA gene to the wild type level. Tri-amine spermidine ef fectively restored the recA induction to a level similar to the wild type, while being less restored by the di-amine putrescine. The restoration of le cA induction by polyamines may be accomplished in a dose- and charge-depend ent manner. Our results strongly suggest that polyamines may play an essent ial role as the SOS inducing mediator following exposure to damaging agents in E. coli and provide important information that tackles an interesting q uestion in how cells respond to chemical and physical stresses. (C) 2000 El sevier Science Ireland Ltd. All rights reserved.