PRIMARY TRANSCRIPT OF THE RIBOSOMAL REPEATING UNIT IN YEAST

Endgroup analysis of 37S ribosomal precursor RNA from Saccharomyces carlsbergensis has revealed that the major 5′ endgroup is pppA-Up, with a molar yield of 0.8. This shows that most, if not all, 37S RNA molecules have preserved a transcriptional initiation sequence. Analysis of the 3′ terminus of 37S RNA has shown the presence of a uridine rich oligo-nucleotide, tentatively identified as U6-8-A-NOH. This long stretch of uridines at the 3′ end of 37S RNA may represent a transcriptional termination site. The two sets of data on the terminal sequences suggest that 37S ribosomal precursor RNA, if not already spliced, is a primary transcription product.Since the 3′ terminus of 26S rRNA, U-U-U-G-UOH, appears to be clearly different from the 3′ end of 37S RNA, we conclude that 37S ribosomal precursor RNA contains additional nucleotides 3′-distal to the 26S rRNA sequence. © 1979 Information Retrieval Limited.