Regulation of protein synthesis in developing mouse brain tissue: in vitro binding of template RNA to brain ribosomes.

Translational control of polypeptide synthesis was measured with ribosomal preparations obtained from brain tissue from mice of various ages. Ribosomal cell-free reaction mixtures were employed to measure the relative activities of the monomeric ribonucleoprotein particles during early neural development. Cell-free protein synthesis was markedly reduced during the first few days after birth and by 18 days of age the incorporation of amino acids was diminished by IO-fold. This over-ah loss in protein synthesis was shown to be the result of an alteration of both the pH 5 enzyme fractions and the ribosomes themselves. The relative inability of ribosomes from more mature brain tissue to participate in polypeptide synthesis was independent of available template RNA or ribonuclease activity. Despite the loss in synthetic activity, RNA to protein ratios and sucrose gradient profiles of young and more mature ribosomal preparations were very similar.