Developmental changes in the translatable mRNA for beta subunit of S-100 protein in rat brain.

The presence of mRNA coding for beta subunit of S-100 protein was demonstrated in polyadenylated RNA from the rat brain in vitro translation in a reticulocyte lysate cell-free system. The products were identified with S-100 protein beta subunit using the immunoprecipitation of the reaction products with the specific antisera, comigration of the isolated, labelled peptide with the purified S-100 protein in SDS-polyacrylamide gel electrophoresis and fluorography and the same retention time of the labelled S-100 protein beta subunit with authentic S-100 beta subunit by high performance liquid chromatography. The size determination of mRNA for S-100 protein on sucrose density gradient centrifugation gave 6-8 S. The assay gave a linear response with increasing amounts of polyadenylated RNA, allowing quantitation of mRNA level for S-100 protein in polyadenylated RNA. During the prenatal period and 10 postnatal days, only minute amounts of mRNA for beta subunit of S-100 protein could be found, however a dramatic increase of mRNA for beta subunit of S-100 was observed within the period of 10 to about 30 days and the mRNA level maintained a plateau from 40 days to adult age. These date indicate that the development changes in the amount of S-100 protein in the rat brain found by other authors is strongly correlated with the changes in the level of its translatable mRNA.