A component of the large ribosomal RNA molecule that is transcribed in the nucleolus. 5.8S rRNA is the structural equivalent of the 5′-terminal 160 nucleotides of prokaryotic 23S rRNAs. Thus, in eukaryotes, the 5.8S and 28S coding sequences are separated by an internal transcribed spacer that is absent from the rDNA unit that is transcribed into the RNA of the large subunit of prokaryotic ribosomes. The 5.8S and 28S molecules are eventually separated by posttranscriptional excision of the spacer. However, these molecules remain associated by intermolecular base pairing interactions as the large subunit of the ribosome matures. See Miller trees, ribosomal RNA genes, ribosome.
Subjects: Genetics and Genomics.