The molecular weights of yeast ribosomal precursor RNAs

Abstract

The molecular weights of the predominant rRNA precursors as well as those of 26-S and 17-S mature rRNA from Saccharomyces carlsbergensis were determined by polyacrylamide gel electrophoresis in the presence of formamide. Mature 26-S+5.8-S rRNA was found to have a molecular weight of 1.24×10⁶ while their immediate precursor, 29-S RNA, had a molecular weight of 1.52×10⁶. Values of 0.70×10⁶ and 0.82×10⁶ were obtained for the molecular weights of mature 17-S rRNA and its 18-S precursor. Finally the 37-S precursor, common to both 29-S and 18-S RNA, was found to have a molecular weight of 2.80×10⁶. Each precursor rRNA, therefore, contains extra sequences not found at the next stage of maturation.