A Comparison of Polypyrimidine Fragments in 28 S Ribosomal RNA from Rat Liver and the Novikoff Ascites Hepatoma1

The distributions of polypyrimidine sequences have been compared for ribosomal 28 S RNA from the Novikoff hepatoma and normal rat liver. Complete digestion at adenylyl and guanylyl residues by successive treatment with U2 RNase followed by TI RNase released oligonucleotides from highly labeled ribosomaJ RNA. These oligonucleotides were isolated by chromatography according to chain length on diethylaminoethyl Sephadex A-25 at pH 7.6 followed by electrophoresis on cellulose acetate or Whatman No. 3MM paper at pH 3.5. Approximately 60 oligonucleotides with chain lengths of 6 to 17 and with the same compositions and electrophoretic mobilities were isolated individually or in simple mixtures from 28 S ribosomal RNA of normal liver and the Novikoff hepatoma. The data obtained provide further support for the conclusion that large portions of 28 S ribosomal RNA from normal liver and the Novikoff hepatoma have very similar nucleotide sequences.