Dataset Information

The translation release factor methyltransferase Mtq2-Trm112 is required for ribosome biogenesis

ABSTRACT: The Mtq2-Trm112 methyltransferase is known to modify the translational eukaryotic release factor eRF1 on the glutamine side chain of a universally conserved GGQ motif, which is essential to translation termination. The exact role of eRF1 methylation remains unknown. As the deletion of MTQ2 leads to severe growth impairment in S. cerevisiae, we have investigated its role further. Here we report an unexpected function of Mtq2 in ribosome biogenesis. We reveal that Mtq2 is part of nuclear precursor ribosomes to 60S subunits, and we demonstrate that its catalytic activity is required for the stable production of mature 5.8S and 25S rRNAs and for pre-60S export. Consistently, in the absence of Mtq2 function pre-60S subunits enriched in the export factors Nmd3 and Arx1 accumulate in the nucleus. We conclude that, in addition to its role as a translation terminator modification enzyme, Mtq2 is a ribosome assembly factor which is important for late-stage large ribosomal subunit formation.

INSTRUMENT(S): Q Exactive

ORGANISM(S): Saccharomyces Cerevisiae (baker's Yeast)

TISSUE(S): Cell Culture

SUBMITTER: Nicolas Pythoud

LAB HEAD: Christine Carapito

PROVIDER: PXD018733 | Pride | 2020-10-12

REPOSITORIES: Pride

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The catalytic activity of the translation termination factor methyltransferase Mtq2-Trm112 complex is required for large ribosomal subunit biogenesis.

Lacoux Caroline C Wacheul Ludivine L Saraf Kritika K Pythoud Nicolas N Huvelle Emmeline E Figaro Sabine S Graille Marc M Carapito Christine C Lafontaine Denis L J DLJ Heurgué-Hamard Valérie V

Nucleic acids research 20201201 21

The Mtq2-Trm112 methyltransferase modifies the eukaryotic translation termination factor eRF1 on the glutamine side chain of a universally conserved GGQ motif that is essential for release of newly synthesized peptides. Although this modification is found in the three domains of life, its exact role in eukaryotes remains unknown. As the deletion of MTQ2 leads to severe growth impairment in yeast, we have investigated its role further and tested its putative involvement in ribosome biogenesis. We ...[more]

PMID: 33166396

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Project description:Ribosome biogenesis is a highly complex process in eukaryotes, involving temporally and spatially regulated ribosomal protein (r-protein) binding and rRNA remodeling events in the nucleolus, nucleoplasm and cytoplasm. Hundreds of assembly factors (AFs), organized into sequential functional groups, facilitate and guide the maturation process into productive assembly branches in and across different cellular compartments. However, the precise mechanisms by which these AFs function are largely unknown. Here, we use cryo-electron microscopy (cryo-EM), to characterize the structures of yeast nucleoplasmic pre-60S particles affinity-purified using the epitope-tagged AF Nog2. Our data pinpoint the locations and determine the structures of over 20 AFs, which are enriched in two areas, an arc region extending from the central protuberance (CP) to the polypeptide tunnel exit (PTE), and the domain including the internal transcribed spacer 2 (ITS2) that separates 5.8S and 25S rRNAs. These structural data suggest that the arc-located factors might function to chaperone formation of RNA helices found in the active sites of the subunit, including helices from the CP, peptidyl-transferase center (PTC) and intersubunit bridge. In particular, two regulatory GTPases, Nog2 and Nog1, act as hub proteins to interact with multiple, distant AFs and functional rRNA elements, manifesting their critical roles in structural remodeling checkpoints and nuclear export. Moreover, our snapshots of compositionally and structurally different pre-60S intermediates provide essential mechanistic details for three major remodeling events before nuclear export: rotation of the 5S RNP, construction of the active center, and ITS2 removal. Therefore, our structures provide a framework to understand the molecular roles of diverse AFs, and potentially the atomic information therein constitutes a resource to generalize principles governing the elusive functions of nuclear RNA-binding proteins.

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