The 3' end of yeast 5.8S rRNA is generated by an exonuclease processing mechanism.
Eukaryotic rRNAs (with the exception of 5S rRNA) are synthesized from a contiguous pre-rRNA precursor by a complex series of processing reactions. Final maturation of yeast 5.8S rRNA involves processing of a 3'-extended, 7S precursor that contains approximately 140 nucleotides of the internal transcribed spacer 2 (ITS2) region. In yeast strains carrying the temperature-sensitive (ts) rrp4-1 mutation, 5.8S rRNA species were observed with 3' extensions of variable length extending up to the 3' end of the 7S pre-rRNA. These 3'-extended 5.8S rRNA species were observed at low levels in rrp4-1 strains under conditions permissive for growth and increased in abundance upon transfer to the nonpermissive temperature. The RRP4 gene was cloned by complementation of the ts growth phenotype of rrp4-1 strains. RRP4 encodes an essential protein of 39-kD predicted molecular mass. Immunoprecipitated Rrp4p exhibited a 3'-->5' exoribonuclease activity in vitro that required RNA with a 3'-terminal hydroxyl group and released nucleoside 5' monophosphates. We conclude that the 7S pre-rRNA is processed to 5.8S rRNA by a 3'-->5' exonuclease activity involving Rrp4p. Homologs of Rrp4p are found in both humans and fission yeast Schizosaccharomyces pombe (43% and 52% identity, respectively), suggesting that the mechanism of 5.8S rRNA 3' end formation has been conserved throughout eukaryotes.
Mitchell
P
P
European Molecular Biology Laboratory (EMBL), Heidelberg, Germany.
Petfalski
E
E
Tollervey
D
D
D000595:Amino Acid Sequence; D001483:Base Sequence; D015152:Blotting, Northern; D002455:Cell Division; D003001:Cloning, Molecular; D017124:Conserved Sequence; D019143:Evolution, Molecular; D005095:Exoribonucleases / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D005656:Fungal Proteins / Q000235:genetics* / Q000378:metabolism; D015966:Gene Expression Regulation, Fungal / Q000235:genetics; D005800:Genes, Fungal; D006801:Humans; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D012322:RNA Precursors / Q000378:metabolism*; D012323:RNA Processing, Post-Transcriptional / Q000235:genetics*; D012340:RNA, Ribosomal, 5.8S / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D012568:Schizosaccharomyces / Q000737:chemistry / Q000235:genetics; D016415:Sequence Alignment; D013696:Temperature
D005656:Fungal Proteins; D012322:RNA Precursors; D012340:RNA, Ribosomal, 5.8S; C098788:RRP4 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D005095:Exoribonucleases