Modified nucleotides in T1 RNase oligonucleotides of 18S ribosomal RNA of the Novikoff hepatoma

Abstract

The primary structure of 18S rRNA of Novikoff rat hepatoma cells was investigated. Regardless of whether the primary sequence of 18S rRNA is finally determined by RNA or DNA sequencing methods, it is important to identify numbers and types of modified nucleotides. The present study was designed to localize the modified regions in T1 RNase derived oligonucleotides. Modified nucleotides found in 66 oligonucleotide sequences included 2 m62A, 1 m6A, 1 m7G, 1 m1 cap3.psi., 7 Cm, 13 Am, 9 Gm, 11 Um and 38 .psi. residues. A number of these modified nucleotides are now placed in defined sequences of T1 RNase oligonucleotides which are now being searched for in larger fragments derived from partial T1 RNase digests of 18S rRNA. Improved homochromatography fingerprinting of T1 RNase derived oligonucleotides provided a distinctive pattern for 18S rRNA of Novikoff hepatoma ascites cells. The 116 spots obtained by homochromatography contain 176 oligonucleotide sequences.