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

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(0) cells.