Isolation and Purification of a Nuclear 4.5 S Ribonucleic Acid of the Novikoff Hepatoma

From the recently identified group of low molecular weight nuclear RNA's, a 4.5 S RNA, referred to as 4.5 S RNAi, was isolated, purified, and partially characterized. The 4.5 S RNA was initially obtained from nuclear 4 to 7 S RNA of Novikoff hepatoma cells by electrophoresis on preparative polyacrylamide gels. Chromatography on diethylaminoethyl-Sephadex resulted in the separation of three 4.5 S RNA components. Of these, the 4.5 S RNAi had a purity of approximately 90% as shown by terminal analysis, i.e. the 3'-terminal nucleoside of 4.5 S RNAi is uridine (87%) and its 5'-terminal nucleoside 3',5'-diphosphate is pGp (90%). The Tm of the 4.5 S RNAi is 65° and its nucleotide composition determined by absorbance is 24.8% AMP, 25.6% UMP, 24.6% GMP, and 25.0% CMP. This RNA has been shown to be localized in the extranucleolar portion of the nucleus. The whole 4.5 S nuclear RNA contains at least one more fraction, referred to as 4.5 S RNAiii, which has a blocked 3' terminal. Its nucleotide composition determined by absorbance is 26.6% AMP, 25.8% UMP, 28.5% GMP, and 19.1% CMP. Like the 4.5 S RNAi, this RNA is also localized in the extranucleolar portion of the nucleus.