Effect of an insertional mutation in the cspA gene encoding the major cold-shock protein on radiation resistance of Escherichia coli

Plasmid pCspA::Km carrying a cloned mutant allele of the cspA gene for the major Escherichia coli cold-shock protein CspA with an insertion of the kanamycin resistance gene cassette from transposon Tn903 into the core region of the coding sequence causes a 2.3-fold increase in radioresistance of wild-type E. coli cells (cspA(+)). The radiation protective effect of this plasmid is abolished or drastically reduced in mutants recA13 and rpoH15 defective in RecA protein and in induction of the heat-shock protein regulon, respectively. Plasmid pCspA:: Km causes a 1.3-fold elevation in the resistance to gamma-irradiation of E. coli mutants with an intermediate level of radiation resistance (Gam(r)445 and KS0160) but slightly diminishes resistance of a highly radiation-resistant Gam(r)444 mutant. In the chromosome of E. coli strain with normal DNA repair systems, the cspA::Km mutation in the homozygous state enhances resistance to the lethal effect of gamma-rays and UV light 2.9 and 1.4 times, respectively. These data suggest that the system of cold-shock proteins can modulate resistance of E. coli cells to the lethal effect of gamma-rays and UV light.