Isolation and Property of Messenger-like RNA from Rats Liver Polysomes*

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Abstract
RNAs obtained from liver ribosomes (polysomes) of rats administered with Pi32 for various intervals by the method of lithium chloride extraction were fractionated by sucrose gradient sedimentation. A rapidly labeled RNA fraction was observed in a lighter region than the ribosomal RNA (18 and 28 S). This fraction disappeared when the ribosomes were previously incubated with ATP, ATP generating system, amino acids and post microsomal supernatant. Because s-RNAs were eliminated by the lithium chloride method, this rapidly labeled and unstable RNA could not be s-RNA. The nucleotides composition, obtained by measuring the radioactivity of Pi32 incorporated into each nucleotide, was different from ribosomal RNA, s-RNA and DNA of the rat liver. It was found that this RNA was very effective to stimulating the C14-amino acids incorporation into polypeptides in the Nirenberg's E. coli system. These results may suggest this rapidly labeled RNA is messenger RNA or partially degradated of it.