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The Biosynthesis of Transfer Ribonucleic Acid in the Developing Rat Brain and in Cultured Glial Cells
Author(s) -
Sellinger O. Z.,
Der O.
Publication year - 1980
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1980.tb09020.x
Subject(s) - guanosine , transfer rna , biochemistry , guanine , ribonucleoside , astrocyte , biosynthesis , rna , biology , chemistry , microbiology and biotechnology , nucleotide , enzyme , endocrinology , central nervous system , gene
The biosynthesis of tRNA was investigated in cultured astroglial cells and the 3‐day‐old rat brain in vivo . In the culture system astrocytes were grown for 19 days and were then exposed to [ 3 H]guanosine for 1.5–7.5 h; 3‐day‐old rats were injected with [ 3 H]guanosine and were killed 5–45 min later. [ 3 H]tRNA was extracted, partially purified, and hydrolyzed to yield [ 3 H]‐guanine and [ 3 H]methyl guanines. The latter were separated from the former by high performance liquid chromatography and their radioactivity determined as a function of the time of exposure to [ 3 H]guanosine. The findings indicate that labeling of astrocyte tRNA continued for 7.5 h and was maximal, relative to total RNA labeling, at 3 h, while in the immature brain tRNAs were maximally labeled at 20 min after [ 3 H]guanosine administration. The labeling pattern of the individual methyl guanines differed considerably between astrocyte and brain tRNAs. Thus, [ 3 H]1‐methylguanine represented up to 35% of the total [ 3 H]methyl guanine radioactivity in astrocyte [ 3 H]tRNA, while it became only negligibly labeled in brain [ 3 H]tRNA. Conversely, brain [ 3 H]tRNA contained more [ 3 H]N 2 ‐methylguanine than did astrocyte [ 3 H]tRNA. Approximately equal proportions of [ 3 H]7‐methylguanine were found in the [ 3 H]tRNAs of both neural systems. The [ 3 H]methylguanine composition of brain [ 3 H]tRNA was followed through several stages of tRNA purification, including benzoylated DEAE‐cellulose and reverse phase chromatography (RPC‐5), and differences were found between the [ 3 H]methylguanine composition of RPC‐5 fractions containing, respectively, tRNA lys and tRNA phe . The overall results of this study suggest that developing brain cells biosynthesize their particular complement of tRNAs actively and in a cell‐specific manner, as attested by the significant differences in the labeling rates of their methylated guanines. The notion is advanced that cell‐specific tRNA modifications may be a prerequisite for the successful synthesis of cell‐specific neural proteins.