Base pairing between U3 and the pre-ribosomal RNA is required for 18S rRNA synthesis.
The nucleolus, the site of pre-ribosomal RNA (pre-rRNA) synthesis and processing in eukaryotic cells, contains a number of small nucleolar RNAs (snoRNAs). Yeast U3 snoRNA is required for the processing of 18S rRNA from larger precursors and contains a region complementary to the pre-rRNA. Substitution mutations in the pre-rRNA which disrupt this base pairing potential are lethal and prevent synthesis of 18S rRNA. These mutant pre-rRNAs show defects in processing which closely resemble the effects of genetic depletion of components of the U3 snoRNP. Co-expression of U3 snoRNAs which carry compensatory mutations allows the mutant pre-rRNAs to support viability and synthesize 18S rRNA at high levels. Pre-rRNA processing steps which are blocked by the external transcribed spacer region mutations are largely restored by expression of the compensatory U3 mutants. Pre-rRNA processing therefore requires direct base pairing between snoRNA and the substrate. Base pairing with the substrate is thus a common feature of small RNAs involved in mRNA and rRNA maturation.
Beltrame
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Gene Expression Programme, European Molecular Biology Laboratory, Heidelberg, Germany.
Tollervey
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D001482:Base Composition; D001483:Base Sequence; D015152:Blotting, Northern; D017931:DNA Primers; D008969:Molecular Sequence Data; D016296:Mutagenesis; D016133:Polymerase Chain Reaction; D012322:RNA Precursors / Q000737:chemistry* / Q000378:metabolism*; D012333:RNA, Messenger / Q000096:biosynthesis*; D012337:RNA, Ribosomal, 18S / Q000096:biosynthesis*; D012342:RNA, Small Nuclear / Q000737:chemistry* / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism
D017931:DNA Primers; D012322:RNA Precursors; D012333:RNA, Messenger; D012337:RNA, Ribosomal, 18S; D012342:RNA, Small Nuclear