Effect of point mutations on 5.8S ribosomal ribonucleic acid secondary structure and the 5.8S-28S ribosomal ribonucleic acid junction

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Abstract
Naturally occurring differences in the nucleotide sequences of 5.8S rRNA from a variety of organisms were used to study the role of specific nucleotides in the secondary structure and intermolecular interactions of this RNA. Significant differences in the electrophoretic mobilities of free 5.8S RNA and the thermal stabilities of 5.8S-28S rRNA complexes were observed even in such closely related sequences as those of man, rat, turtle and chicken. A single base transition from a guanylic acid residue in position 2 in mammalian 5.8S rRNA to an adenylic acid residue in turtle and chicken 5.8S rRNA results both in a more open molecular conformation and in a 5.8S-28S rRNA junction which is 3.5.degree. C more stable to thermal denaturation. Other changes such as the deletion of single nucleotides from either the 5'' or the 3'' terminals have no detectable effect on these features. The results support secondary structure models for free 5.8S rRNA in which the termini interact to various degrees and 5.8S-28S rRNA junctions in which both termini of the 5.8S molecule interact with the cognate high MW RNA component.