Occurrence and distribution of methylated purines in the ribonucleic acids of subcellular fractions

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Abstract
A procedure is described for the quantitative isolation and estimation of ribonucleic acid ribonucleotides from subcellular fractions. This procedure gave similar yields to salt or phenol extraction for microsomal and mito-chondrial ribonucleic acid, and higher yields for soluble ribonucleic acid. In all tissues examined (mouse liver and spleen, two mouse tumors, rabbit liver, tobacco leaf) the highest proportion of methylated purines was found in the soluble ribonucleic acid. For all subcellular fractions, the highest concentrations of methylated purines were found in fractions from a mammary adenocarcinoma of C3H mice. When soluble ribonucleic acid was fractionated by adjustment to pH 5[center dot]2, the ribonucleic acid in the supernatant fluid contained a higher proportion of methylated purines than that in the precipitate. It is suggested that all the methylated purines are located in soluble ribonucleic acid and that the methylated purines found in microsomal and mitochondrial preparations are due to soluble ribonucleic acid that is not removed from these particles during their isolation.