Polynucleotide fragments from the 28S ribosomal RNA of insects

If RNA is extracted from the ribosomes which had been isolated from frozen-thawed tissue of Galleria mellonella, the 28 S RNA, when heated or treated with urea, dissociates into seven different species of polynucleotide fragments. They were designated as R1, R2, R3, R4, R5, R6, and R7, whose molecular weights were estimated to be 1.15x10-6, 0.75x10-6, 0.55x10-6, 0.40x10-6, 0.30x10-6, 0.25x10-6, 0.20x10-6 daltons, respectively. It is likely that R1 and R5 arise from a single nick in original 38 S rRNA. Experiments with isolated R1 suggest that it is made up of a hydrogen-bonded complex of R2 and R4. R5 is a complex of R6 and an unidentified species, X. It is suggested that these fragments result from nicks which are introduced, secondarily, in the phosphodiester bonds by an endogenous endonuclease(s). Since the secondary nicks are limited in number and located in specific points of the molecule, it appears that the reaction is quite specific. It was also shown that the 28 S aphid RNA, which apparently lacks the primary nick, is susceptible to nicking.