Lability of RNA from the Large Cytoplasmic Ribosomal Subunit of the Protozoon Crithidia oncopelti

SUMMARY: Cytoplasmic ribosomal RNA extracted from Crithidia oncopelti and analysed by gel electrophoresis at 4 ° consisted of two components, with molecular weights (relative to E. coli rRNA) of 1.30 x 10⁶ and 0.83 x 10⁶ daltons, present in equimolar amounts. On heating briefly at 51 ° followed by rapid cooling, the 1.30 x 10⁶ RNA completely dissociated into two components of molecular weights 0.70 x 10⁶ and 0.56 x 10⁶ (present in equimolar amounts). Fifty per cent dissociation of the molecule occurred at 28 °. That the integrity of the RNA molecule at low temperatures is maintained by its secondary structure was confirmed by electrophoresis under denaturing conditions (98%, v/v, formamide). To account for these phenomena, latent cleavage of the molecule in vivo is proposed.