Bacterial senescence: protein oxidation in non-proliferating cells is dictated by the accuracy of the ribosomes

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Abstract
We have investigated the causal factors behind the age‐related oxidation of proteins during arrest of cell proliferation. A proteomic approach demonstrated that protein oxidation in non‐proliferating cells is observed primarily for proteins being produced in a number of aberrant isoforms. Also, these cells exhibited a reduced translational fidelity as demonstrated by both proteomic analysis and genetic measurements of nonsense suppression. Mutants harboring hyperaccurate ribosomes exhibited a drastically attenuated protein oxidation during growth arrest. In contrast, oxidation was augmented in mutants with error‐prone ribosomes. Oxidation increased concomitantly with a reduced rate of translation, indicating that the production of aberrant, and oxidized proteins, is not the result of titration of the co‐translational folding machinery. The age‐related accumulation of the chaperones, DnaK and GroEL, was drastically attenuated in the hyperaccurate rpsL mutant, demonstrating that the reduced translational fidelity in growth‐arrested cells may also be a primary cause for the induction of the heat shock regulon. The data point to an alternative way of approaching the causal factors involved in protein oxidation in eukaryotic G cells.