Identification of a novel element required for processing of intron-encoded box C/D small nucleolar RNAs in Saccharomyces cerevisiae.
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.
Villa
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Istituto Pasteur, Fondazione Cenci-Bolognetti, Dipartimento di Genetica e Biologia Molecolare, Università di Roma "La Sapienza," 00185 Rome, Italy.
Ceradini
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F
Bozzoni
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I
D000818:Animals; D001483:Base Sequence; D017931:DNA Primers / Q000235:genetics; D004722:Endoribonucleases / Q000378:metabolism; D005095:Exoribonucleases / Q000037:antagonists & inhibitors / Q000378:metabolism; D005816:Genetic Complementation Test; D007438:Introns; D008954:Models, Biological; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D012323:RNA Processing, Post-Transcriptional; D012326:RNA Splicing; D012331:RNA, Fungal / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D020537:RNA, Small Nucleolar / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D043244:Ribonuclease III; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins
D017931:DNA Primers; D012331:RNA, Fungal; D020537:RNA, Small Nucleolar; D029701:Saccharomyces cerevisiae Proteins; C075577:RAT1 protein, S cerevisiae; D004722:Endoribonucleases; D005095:Exoribonucleases; C468367:RNT1 protein, S cerevisiae; D043244:Ribonuclease III