title: Near-ultraviolet radiation blocks SOS responses to DNA damage in Escherichia coli.
abstract: Escherichia coli cells in which the recA promoter is fused to a lac structural gene, (Mu) Mud(Ap,lac)::rec, were irradiated with two far-ultraviolet light wavelengths (254 and 290 nm), selected monochromatic near-ultraviolet (NUV) wavelengths 313 nm, 334 nm, 365 nm, or broad band solar-UV (290-420 nm) from a solar simulator. Irradiation with the two far-ultraviolet wavelengths was followed by high yields of beta-galactosidase, lambda prophage induction, and Weigle reactivation. These end points were not observed after irradiation with the selected NUV wavelengths or the broad spectrum solar-UV. Thus, neither broad spectrum solar-UV nor monochromatic NUV wavelengths resulted in the derepression of the recA promoter. Further, prior exposure of the cells either to the selected monochromatic NUV wavelengths or to solar-UV inhibited (a) the induction of beta-galactosidase by subsequent 254-nm radiation, (b) subsequent 254-nm induction of lambda prophage, (c) Weigle reactivation, and (d) mutation frequency. These observations are consistent with the hypothesis that NUV blocks subsequent recA protease action.
mesh_terms: D010582:Bacteriophage lambda / Q000235:genetics / Q000528:radiation effects; D004260:DNA Repair; D004269:DNA, Bacterial / Q000235:genetics / Q000528:radiation effects*; D004926:Escherichia coli / Q000235:genetics / Q000528:radiation effects*; D005838:Genotype; D009154:Mutation; D011938:Rec A Recombinases / Q000235:genetics; D014466:Ultraviolet Rays; D001616:beta-Galactosidase / Q000235:genetics
chemical_list: D004269:DNA, Bacterial; D011938:Rec A Recombinases; D001616:beta-Galactosidase