Increased Expression of the S25 Ribosomal Protein Gene Occurs during Ageing of the Rat Liver

BACKGROUND: It appears that consistent changes in the levels of activity of a small cohort of genes (probably <1% of all active genes) occur in all mammalian cells during ageing. Identification of such genes could provide valuable insights into the ageing process. OBJECTIVE: We have studied age-related changes in gene expression profiles in the rat liver. One of the genes which exhibited clear and consistent increases in expression is characterised. METHODS: Analysis of the gene expression profile was carried out using a combination of an optimised form of differential display and single-strand conformational polymorphism (SSCP) gel analysis. Gene expression levels were quantified by Northern blot analysis. The gene's identity was determined by comparing its nucleotide sequence to DNA databases. RESULTS: During this investigation we observed one gene which exhibited an increase in expression in livers from young adult (6 months) to old adult (24 months) rats. The differential expression of this gene was confirmed by SSCP gel analysis and Northern blotting. Densitometry of the latter indicated that expression increased by 165% with age. Characterisation of the isolated polymerase chain reaction fragment demonstrated it to code for the ribosomal protein S25 (RPS25). CONCLUSIONS: This increase in RPS25 expression is further evidence that the composition of ribosomes may alter with age and as a result could have significant effects on protein synthesis.