Processing of intron-encoded box C/D small nucleolar RNAs (snoRNAs) in metazoans through both the splicing-dependent and -independent pathways requires the conserved core motif formed by boxes C and D and the adjoining 5'-3'-terminal stem. By comparative analysis, we found that five out of six intron-encoded box C/D snoRNAs in yeast do not possess a canonical terminal stem. Instead, complementary regions within the flanking host intron sequences have been identified in all these cases. Here we show that these sequences are essential for processing of U18 and snR38 snoRNAs and that they compensate for the lack of a canonical terminal stem. We also show that the Rnt1p endonuclease, previously shown to be required for the processing of many snoRNAs encoded by monocistronic or polycistronic transcriptional units, is not required for U18 processing. Our results suggest a role of the complementary sequences in the early recognition of intronic snoRNA substrates and point out the importance of base pairing in favoring the communication between boxes C and D at the level of pre-snoRNA molecules for efficient assembly with snoRNP-specific factors.
|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||Reference||Annotation Extension|
|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||Conditions||Strain||Source||Reference|