Relationship between sporulation-specific 20S ribonucleic acid and ribosomal ribonucleic acid processing in...

The nature and properties of the 20S ribonucleic acid which accumulates only during the sporulation of Saccharomyces cerevisiae were examined. The 20S ribonucleic acid (RNA) has a base composition considerably different from ribosomal RNA species and is virtually unmethylated. The 20S RNA did, however, exhibit approximately 70% homology with 18S RNA by RNA-deoxyribonucleic acid filter hybridization competitions. The 20S RNA showed a hybridization saturation plateau level 30 to 40% higher than 18S, consistent with measurements of the size difference in polyacrylamide gels. Pulse-chase experiments in the presence and absence of cycloheximide indicate that the 20S RNA has a presumptive relationship to the 20S ribosomal RNA precursor normally observed only in short pulse-labeling in vegetative cells.