Hypermethylation of the cap structure of both yeast snRNAs and snoRNAs requires a conserved methyltransferase that is localized to the nucleolus.
The m(7)G caps of most spliceosomal snRNAs and certain snoRNAs are converted posttranscriptionally to 2,2,7-trimethylguanosine (m(3)G) cap structures. Here, we show that yeast Tgs1p, an evolutionarily conserved protein carrying a signature of S-AdoMet methyltransferase, is essential for hypermethylation of the m(7)G caps of both snRNAs and snoRNAs. Deletion of the yeast TGS1 gene abolishes the conversion of the m(7)G to m(3)G caps and produces a cold-sensitive splicing defect that correlates with the retention of U1 snRNA in the nucleolus. Consistently, Tgs1p is also localized in the nucleolus. Our results suggest a trafficking pathway in which yeast snRNAs and snoRNAs cycle through the nucleolus to undergo m(7)G cap hypermethylation.
Mouaikel
John
J
Institut de Génétique Moléculaire, IFR 24-CNRS UMR 5535, 1919 route de Mende, 34000 Montpellier, France.
Verheggen
Céline
C
Bertrand
Edouard
E
Tazi
Jamal
J
Bordonné
Rémy
R
D020816:Amino Acid Motifs; D001324:Autoantigens / Q000502:physiology; D002466:Cell Nucleolus / Q000201:enzymology*; D003080:Cold Temperature; D019143:Evolution, Molecular; D006151:Guanosine / Q000031:analogs & derivatives / Q000378:metabolism*; D006836:Hydro-Lyases; D008745:Methylation; D008780:Methyltransferases / Q000235:genetics / Q000502:physiology*; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D009687:Nuclear Proteins / Q000378:metabolism; D010641:Phenotype; D017434:Protein Structure, Tertiary; D012314:RNA Cap Analogs / Q000096:biosynthesis* / Q000502:physiology; D012315:RNA Caps / Q000378:metabolism*; D012326:RNA Splicing / Q000235:genetics; D012331:RNA, Fungal / Q000378:metabolism*; D012342:RNA, Small Nuclear / Q000378:metabolism*; D020537:RNA, Small Nucleolar / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D017411:Ribonucleoproteins, Small Nuclear / Q000502:physiology; D020718:Ribonucleoproteins, Small Nucleolar; D012436:S-Adenosylmethionine / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000502:physiology*; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity; D020798:Two-Hybrid System Techniques
D001324:Autoantigens; D008869:Microtubule-Associated Proteins; C438199:NOP58 protein, S cerevisiae; D009687:Nuclear Proteins; D012314:RNA Cap Analogs; D012315:RNA Caps; D012331:RNA, Fungal; D012342:RNA, Small Nuclear; D020537:RNA, Small Nucleolar; D016601:RNA-Binding Proteins; D011993:Recombinant Fusion Proteins; D017411:Ribonucleoproteins, Small Nuclear; D020718:Ribonucleoproteins, Small Nucleolar; C489392:SMB protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; C405483:U1 small nuclear RNA; D006151:Guanosine; C017778:N(2),N(2),7-trimethylguanosine; C017516:7-methylguanosine triphosphate; D012436:S-Adenosylmethionine; D008780:Methyltransferases; C456271:trimethylguanosine synthase; D006836:Hydro-Lyases; C082278:CBF5 protein, S cerevisiae