Efficiency and fidelity of cell-free protein synthesis by transfer RNA from aged mice

Function and fidelity of aging tRNA: in vivo acylation, analog discrimination, synthetase binding, and in vitro translation

The liver transfer RNAs for valine and lysine were completely acylated in vivo, as judged by periodate oxidation, at 4 and 24 months of age in male Sprague-Dawley rats. In vitro acylation capacity for whole tRNA populations from rat livers is decreased, but this is evidently not deleterious in vivo. Several halogenated phenylalanines were synthesized and their effects upon acylation capacity for phenylalanine were examined. Synthetases bound to young (3 month) and old (24 month) tRNAs discriminated differently between p-chlorophenylalanine and authentic phenylalanine; synthetase with young tRNA was less able to discriminate than with old tRNA. Purified tRNAphe from old rats did not form ultraviolet-induced crosslinks to purified phenylalanyl tRNA synthetase as well as young tRNAphe. In vitro translation of encephalomyocarditis virus, hemoglobin, and ovalbumin mRNAs was effective, using tRNAs of young or old Sprague-Dawley or Fischer 344 rat livers, although, when the old tRNA was supplied, the product synthesized per unit tRNA was reduced. All of the protein products were synthesized with all tRNAs, as shown by sodium dodecyl sulfate polyacrylamide gel electrophoresis. We conclude that tRNA is capable of normal functions in livers of aging rats, is probably modification deficient, and is unlikely to produce protein errors.

Organ pattern of age-related changes in the aminoacyl-tRNA synthetase activities of the mouse

The specific activities of 17 aminoacyl-tRNA synthetases from liver, lung, heart, spleen, kidney, small intestine and skeletal muscle of young (2 months) and aged (39 months) female Han:NMRI mice were determined under standard conditions of sample preparation and assay. The average reduction of total activity during ageing is 70% for liver, 50% for lung and spleen, nearly 40% for heart and kidney and nearly 20% for intestine and skeletal muscle. Detailed comparison reveals no general, but an organ-specific pattern. Aminoacyl-tRNA synthetases were, furthermore, found to be ribosome-associated in higher proportions in liver tissue from aged mice.