Translational Errors Increase with Age in Some Organs in Mice
Researchers here produce a mouse model incorporating a DNA sequence that produces a luminescent protein only in the case of a readthrough error, where the translation machinery ignores a stop codon in the DNA sequence. This is a way to gauge the degree to which readthrough errors increase with age, producing aberrant RNA molecules and consequent dysfunction. A range of evidence supports an age-related increase in translation errors in the production of RNA from DNA, though as is always the case in these matters understanding how much of degenerative aging results from this sort of dysfunction in gene expression is a challenge. One would have to fix just this one problem without affecting other mechanisms, a difficult prospect.
The accuracy of protein synthesis and its relation to ageing has been of long-standing interest. To study whether spontaneous changes in the rate of ribosomal error occur as a function of age, we first determined that stop-codon readthrough is a more sensitive read-out of mistranslation due to codon-anticodon mispairing than missense amino acid incorporation. Subsequently, we developed knock-in mice for in-vivo detection of stop-codon readthrough using a gain-of-function Kat2-TGA-Fluc readthrough reporter which combines fluorescent and sensitive bioluminescent imaging techniques.
We followed expression of reporter proteins in-vivo over time, and assessed Kat2 and Fluc expression in tissue extracts and by whole organ ex-vivo imaging. Collectively, our results provide evidence for an organ-dependent, age-related increase in translational error: stop-codon readthrough increases with age in muscle (+ 75%) and brain (+ 50%), but not in liver. Together with recent data demonstrating premature ageing in mice with an error-prone ram mutation, our findings highlight age-related decline of translation fidelity as a possible contributor to ageing.