Marker nucleotides for non-ribosomal spacer segments of preribosomal ribonucleic acid

Abstract

Complete T 1 RNase digestion was carried out on purified nucleolar precursor 45S, 35S and 28S RNA (nRNA) and 18S ribosomal RNA (rRNA) of Novikoff hepatoma ascites cells. Two marker fragments for the spacer segments, having chain lengths of 23 and 19 nucleotides, were isolated from digests of 45S or 35S nRNA by successive chromatography on DEAE Sephadex at pH 7.5 and DEAE Sephadex at pH 3.3. One of the fragments, referred to as the P fragment has a nucleotide composition of AC 13U 8G and is found both in 45S and 35S nRNA. The other fragment, referred to as the Q fragment, has a nucleotide composition of A 2C 11U 5G and is found only in 45S nRNA.