title: Increase in UV mutagenesis by heat stress on UV-irradiated E. coli cells.
abstract: When leu- auxotrophs of Escherichia coli, after UV irradiation, were grown at temperatures between 30 and 47°C, the frequency of UV-induced mutation from leu- to leu+ revertant increased as the UV dose and the temperature increased. For cells exposed to a UV dose of 45 J/m2, the mutation frequency at 47°C was 1.9 times that at 30°C; for a dose of 90 J/m2, it was 3.25 times; and for 135 J/m2, it was 4.8 times. Similar enhancement of reversion frequency was observed when the irradiated cells were grown at 30°C in the presence of a heat shock inducer, ethanol (8% v/v). Heat shock-mediated enhancement of UV mutagenesis did not occur in an E. coli mutant sigma 32 (heat shock regulator protein), but sigma 32 overexpression in the mutant strain (transformed with a sigma 32-bearing plasmid) increased the UV-induced mutation frequency. These results suggest that heat stress alone has no mutagenic property, but when applied to UV-damaged cells, it enhances the UV-induced frequency of cell mutation.
authors.affiliation: Department of Biochemistry and Biophysics, University of Kalyani, Kalyani, 741 235, West Bengal, India.
authors.forename: Swati
authors.initials: S
authors.lastname: Saha
authors.forename: Tarakdas
authors.initials: T
authors.lastname: Basu
mesh_terms: D004260:DNA Repair; D004926:Escherichia coli / Q000235:genetics* / Q000528:radiation effects*; D006360:Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D018869:Heat-Shock Response / Q000235:genetics; D016296:Mutagenesis; D009154:Mutation; D012808:Sigma Factor / Q000235:genetics / Q000378:metabolism; D013696:Temperature; D014466:Ultraviolet Rays / Q000009:adverse effects*
chemical_list: D006360:Heat-Shock Proteins; D012808:Sigma Factor; C069774:heat-shock sigma factor 32