In eukaryotes, the 40S ribosomal subunit serves as the platform of initiation factor assembly, to place itself precisely on the AUG start codon. Structural arrangement of the 18S rRNA determines the overall shape of the 40S subunit. Here we present genetic evaluation of yeast 18S rRNA function using ten point-mutations altering the polysome profile. All the mutants reduce the abundance of the mutant 40S, making it limiting for translation initiation. Two of the isolated mutations, G875A, altering the core of the platform domain that binds eIF1 and eIF2, and A1193U, changing the h31 loop located beneath the P-site tRNA(i)(Met), show phenotypes indicating defective regulation of AUG selection. Evidence is provided that these mutations reduce the interaction with the components of the pre-initiation complex (PIC), thereby inhibiting its function at different steps. These results indicate that the 18S rRNA mutations impair the integrity of scanning-competent PIC, thereby altering the 40S subunits; response to stringent AUG selection. Interestingly, nine of the mutations alter the body/platform domains of 18S rRNA, potentially affecting the bridges to the 60S subunit, but do not change the level of 18S rRNA intermediates. Based on these results, we also discuss the mechanism of the selective degradation of the mutant 40S subunits.
|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|