Reference : The small nucle(ol)ar RNA cap trimethyltransferase is required for ribosome synthesis an...
Scientific journals : Article
Life sciences : Biochemistry, biophysics & molecular biology
The small nucle(ol)ar RNA cap trimethyltransferase is required for ribosome synthesis and intact nucleolar morphology.
Colau, Geoffroy [> > > >]
Thiry, Marc mailto [Université de Liège - ULg > Département des sciences de la vie > Biologie cellulaire >]
Leduc, Vivian [> > > >]
Bordonne, Remy [> > > >]
Lafontaine, Denis L J [> > > >]
Molecular & Cellular Biology
American Society for Microbiology (ASM)
Yes (verified by ORBi)
[en] Base Sequence ; Cell Nucleolus/metabolism/ultrastructure ; Genes, Fungal ; Methyltransferases/genetics/metabolism ; Microscopy, Electron ; Protein Structure, Tertiary ; RNA Caps/metabolism ; RNA Processing, Post-Transcriptional ; RNA, Fungal/metabolism ; Ribonucleoproteins, Small Nucleolar/chemistry/genetics/metabolism ; Ribosomes/metabolism ; Saccharomyces cerevisiae/genetics/metabolism/ultrastructure ; Saccharomyces cerevisiae Proteins/chemistry/genetics/metabolism ; Sequence Deletion
[en] Nucleolar morphogenesis is a poorly defined process. Here we report that the Saccharomyces cerevisiae nucleolar trimethyl guanosine synthase I (Tgs1p), which specifically selects the m(7)G cap structure of snRNAs and snoRNAs for m(2,2,7)G conversion, is required not only for efficient pre-mRNA splicing but also for pre-rRNA processing and small ribosomal subunit synthesis. Mutational analysis indicates that the requirement for Tgs1p in pre-mRNA splicing, but not its involvement in ribosome synthesis, is dependent upon its function in cap trimethylation. In addition, we report that cells lacking Tgs1p showed a striking and unexpected loss of nucleolar structural organization. Tgs1p is not a core component of the snoRNP proteins; however, in vitro, the protein interacts with the KKD/E domain present at the carboxyl-terminal ends of several snoRNP proteins. Strains expressing versions of the snoRNPs lacking the KKD/E domain were also defective for nucleolar morphology and showed a loss of nucleolar compaction. We propose that the transient and functional interactions of Tgs1p with the abundant snoRNPs, through presumed interactions with the KKD/E domain of the snoRNP proteins, contribute substantially to the coalescence of nucleolar components. This conclusion is compatible with a model of self-organization for nucleolar assembly.

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