The effect of aging on the structure and function of liver messenger RNA

The size of the poly(A) segment of poly(A)+RNA extracted from hepatocytes isolated from 4- to 30-month-old rats was determined using polyacrylamide-agarose gel electrophoresis. The average size of the poly(A) segment isolated from newly synthesized poly(A)+RNA was 150 nucleotides, and the average size of the poly(A) segment isolated from the steady state pool of cytoplasmic poly(A)+RNA was 70 nucleotides. No significant age related change in either the size or the heterogeneity of the newly synthesized poly(A) segment was found. The translational activity of poly(A)+RNA isolated from livers of 4- to 30-month-old rats was determined using wheat germ extract and rabbit reticulocyte lysate cell-free systems. No age-related change in the translational activity of the poly(A)+RNA was observed. The effect of aging on the cap structure was also studied by measuring the inhibition of cell-free translation by 7-methyl guanosine-5'-monophosphate. No age-related change in the sensitivity of the poly(A)+RNA preparations to inhibition of translation by 7-methyl guanosine-5'-monophosphate was observed. Therefore, the results of this study demonstrate that no major age-related change occurs in the structure of the poly(A) segment, the translational activity, or the cap structure of poly(A)+RNA from rat liver.