title: The methyltransferase adaptor protein Trm112 is involved in biogenesis of both ribosomal subunits.
abstract: We previously identified Bud23 as the methyltransferase that methylates G1575 of rRNA in the P-site of the small (40S) ribosomal subunit. In this paper, we show that Bud23 requires the methyltransferase adaptor protein Trm112 for stability in vivo. Deletion of Trm112 results in a bud23Δ-like mutant phenotype. Thus Trm112 is required for efficient small-subunit biogenesis. Genetic analysis suggests the slow growth of a trm112Δ mutant is due primarily to the loss of Bud23. Surprisingly, suppression of the bud23Δ-dependent 40S defect revealed a large (60S) biogenesis defect in a trm112Δ mutant. Using sucrose gradient sedimentation analysis and coimmunoprecipitation, we show that Trm112 is also involved in 60S subunit biogenesis. The 60S defect may be dependent on Nop2 and Rcm1, two additional Trm112 interactors that we identify. Our work extends the known range of Trm112 function from modification of tRNAs and translation factors to both ribosomal subunits, showing that its effects span all aspects of the translation machinery. Although Trm112 is required for Bud23 stability, our results suggest that Trm112 is not maintained in a stable complex with Bud23. We suggest that Trm112 stabilizes its free methyltransferase partners not engaged with substrate and/or helps to deliver its methyltransferase partners to their substrates.
authors.affiliation: Section of Molecular Genetics and Microbiology and Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, TX 78712, USA.
authors.forename: Richa
authors.initials: R
authors.lastname: Sardana
authors.forename: Arlen W
authors.initials: AW
authors.lastname: Johnson
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism*; D047468:Immunoprecipitation; D009154:Mutation / Q000235:genetics; D011485:Protein Binding; D055550:Protein Stability; D054683:Ribosome Subunits, Large, Eukaryotic / Q000378:metabolism*; D054682:Ribosome Subunits, Small, Eukaryotic / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000201:enzymology*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000378:metabolism*; D012359:tRNA Methyltransferases / Q000378:metabolism*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D029701:Saccharomyces cerevisiae Proteins; D012359:tRNA Methyltransferases; C502205:Trm112 protein, S cerevisiae