Selection of sites for pseudouridylation in eukaryotic cytoplasmic ribosomal RNA (rRNA) occurs by base-pairing with specific guide sequences within the RNA components of box H/ACA small nucleolar ribonucleoproteins (snoRNPs). 44 of the 46 pseudouridines (Psis) in the cytoplasmic rRNA of Saccharomyces cerevisiae have been assigned to guide snoRNAs. Here, we examine the mechanism of Psi formation in 5S and 5.8S rRNA in which the unassigned Psis occur. We show that while formation of Psi in 5.8S rRNA is associated with snoRNP activity, pseudouridylation of 5S rRNA is not. The position of Psi in 5.8S rRNA is guided by snoRNA snR43 using conserved sequence elements that also function to guide pseudouridylation elsewhere in the large subunit ribosomal RNA; an internal stem-loop that is not part of typical yeast snoRNAs is also conserved in snR43. The multisubstrate synthase Pus7 catalyzes formation of the Psi in 5S rRNA at a site that conforms to the 7-nt consensus sequence present in other substrates of Pus7. The different mechanisms involved in 5S and 5.8S rRNA pseudouridylation, as well as the multi-specificities of the individual trans-factors concerned, suggest possible roles in linking ribosome production to other processes, such as splicing and transfer RNA synthesis.
|Evidence ID||Analyze ID||Interactor||Interactor Systematic Name||Interactor||Interactor Systematic Name||Type||Assay||Annotation||Action||Modification||Phenotype||Source||Reference||Note|
|Evidence ID||Analyze ID||Gene||Gene Systematic Name||Gene Ontology Term||Gene Ontology Term ID||Qualifier||Aspect||Method||Evidence||Source||Assigned On||Annotation Extension||Reference|
|Evidence ID||Analyze ID||Gene||Gene Systematic Name||Phenotype||Experiment Type||Experiment Type Category||Mutant Information||Strain Background||Chemical||Details||Reference|
|Evidence ID||Analyze ID||Regulator||Regulator Systematic Name||Target||Target Systematic Name||Experiment||Assay||Construct||Conditions||Strain Background||Reference|