title: Induction of protein synthesis in Escherichia coli following UV- or gamma-irradiation, mitomycin C treatment or tif Expression.
abstract: The rate of synthesis of total cellular proteins has been studied by pulse labelling cells at various periods after irradiation with UV or gamma-rays, after treatment with mitomycin C (MMC) or after expression of the temperature sensitive mutation tif. Subsequent gel electrophoresis and autoradiography reveals changes in the rate of synthesis of several proteins. The most striking change is in a protein of molecular weight 40,000, protein X, which has been previously most extensively studied in cells treated with nalidixic acid (Gudas, 1976). Synthesis of large quantities of protein X is induced by UV, gamma-rays, MMC treatment or tif expression in rec+ but not recA cells. A feature of recA cells is that they break down their DNA excessively after irradiation or MMC treatment. However, if protein synthesis following irradiation is prohibited by chloramphenicol, post-irradiation degradation becomes excessive in recA+ cells. This inverse relationship between DNA degradation and new protein synthesis consistent with the hypothesis that an induced protein such as X is responsible for controlling DNA degradation following irradiation. Protein X is not induced in a lexB mutant following MMC treatment. In this respect the lexB mutant behaves like lexA and recA mutants in that the ability to induce protein X can be correlated with excessive DNA degradation. Studies on the induction of proteins in inf, tif and tif sfi mutants fail to reveal any correlation between induction of protein X and either the induction of prophage lambda or septation.
mesh_terms: D001426:Bacterial Proteins / Q000096:biosynthesis*; D004269:DNA, Bacterial / Q000378:metabolism; D004926:Escherichia coli / Q000187:drug effects / Q000528:radiation effects*; D005720:Gamma Rays; D008937:Mitomycins / Q000494:pharmacology*; D009154:Mutation; D013696:Temperature; D014466:Ultraviolet Rays
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D008937:Mitomycins