CHARACTERIZATION OF RAT BRAIN RIBONUCLEIC ACIDS BY AGAR GEL ELECTROPHORESIS

Abstract— —The characteristics of total and rapidly-labelled RNAs of rat brain were studied by agar gel electrophoresis. The bulk (more than 90 per cent) of total, nuclear and cytoplasmic brain RNA was represented by the 28 S, 18 S and 4 S RNA components. The 28 S/18 S RNA mass ratio in cytoplasmic RNA was 2·55. Lower values for this ratio were obtained with total and nuclear RNAs. Five minor RNA components were detected in total brain RNA with mobilities in agar gel corresponding to 24 S, 22 S, 14 S, 9 S and 6 S. Two broad rapidly labelled RNA components were detected in total and nuclear (but not in cytoplasmic) brain RNA with mobilities corresponding to about 45 S and 31 S. These fractions were of nuclear origin and resembled ribosomal precursor RNAs of other animal tissues. In cytoplasmic RNA the radioactivity and ultraviolet profiles coincided at all labelling times down to 1 hr. The G + C/A + U ratio of brain RNA was 1·50 for total RNA, 1·39 for nuclear RNA and 1·59 for cytoplasmic RNA. The G + C/A + U ratio of 1 hr-labelled total brain RNA (determined by ³²P-distribution) was 0·94. This ratio rose to 1·31 at 24 hr labelling. The possible significance of these results for the elucidation of ribosomal and messenger RNA metabolism in brain is discussed.