The deoxyhypusine synthase mutant dys1-1 reveals the association of eIF5A and Asc1 with cell wall integrity

PLoS One. 2013;8(4):e60140. doi: 10.1371/journal.pone.0060140. Epub 2013 Apr 1.

Abstract

The putative eukaryotic translation initiation factor 5A (eIF5A) is a highly conserved protein among archaea and eukaryotes that has recently been implicated in the elongation step of translation. eIF5A undergoes an essential and conserved posttranslational modification at a specific lysine to generate the residue hypusine. The enzymes deoxyhypusine synthase (Dys1) and deoxyhypusine hydroxylase (Lia1) catalyze this two-step modification process. Although several Saccharomyces cerevisiae eIF5A mutants have importantly contributed to the study of eIF5A function, no conditional mutant of Dys1 has been described so far. In this study, we generated and characterized the dys1-1 mutant, which showed a strong depletion of mutated Dys1 protein, resulting in more than 2-fold decrease in hypusine levels relative to the wild type. The dys1-1 mutant demonstrated a defect in total protein synthesis, a defect in polysome profile indicative of a translation elongation defect and a reduced association of eIF5A with polysomes. The growth phenotype of dys1-1 mutant is severe, growing only in the presence of 1 M sorbitol, an osmotic stabilizer. Although this phenotype is characteristic of Pkc1 cell wall integrity mutants, the sorbitol requirement from dys1-1 is not associated with cell lysis. We observed that the dys1-1 genetically interacts with the sole yeast protein kinase C (Pkc1) and Asc1, a component of the 40S ribosomal subunit. The dys1-1 mutant was synthetically lethal in combination with asc1Δ and overexpression of TIF51A (eIF5A) or DYS1 is toxic for an asc1Δ strain. Moreover, eIF5A is more associated with translating ribosomes in the absence of Asc1 in the cell. Finally, analysis of the sensitivity to cell wall-perturbing compounds revealed a more similar behavior of the dys1-1 and asc1Δ mutants in comparison with the pkc1Δ mutant. These data suggest a correlated role for eIF5A and Asc1 in coordinating the translational control of a subset of mRNAs associated with cell integrity.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Proteins, Signal Transducing / genetics
  • Adaptor Proteins, Signal Transducing / metabolism*
  • Cell Wall
  • Epistasis, Genetic
  • Eukaryotic Translation Initiation Factor 5A
  • GTP-Binding Proteins / genetics
  • GTP-Binding Proteins / metabolism*
  • Gene Expression Regulation, Fungal
  • Lysine / analogs & derivatives
  • Lysine / metabolism
  • Mutation, Missense
  • Oxidoreductases Acting on CH-NH Group Donors / genetics*
  • Oxidoreductases Acting on CH-NH Group Donors / metabolism
  • Peptide Chain Elongation, Translational
  • Peptide Initiation Factors / metabolism*
  • Polyribosomes / metabolism
  • Protein Binding
  • Protein Kinase C / genetics
  • Protein Kinase C / metabolism
  • RNA-Binding Proteins / metabolism*
  • Ribosome Subunits, Small, Eukaryotic / metabolism
  • Saccharomyces cerevisiae / genetics
  • Saccharomyces cerevisiae / growth & development
  • Saccharomyces cerevisiae / metabolism*
  • Saccharomyces cerevisiae Proteins / genetics*
  • Saccharomyces cerevisiae Proteins / metabolism
  • Sequence Deletion

Substances

  • ASC1 protein, S cerevisiae
  • Adaptor Proteins, Signal Transducing
  • Peptide Initiation Factors
  • RNA-Binding Proteins
  • Saccharomyces cerevisiae Proteins
  • hypusine
  • Oxidoreductases Acting on CH-NH Group Donors
  • deoxyhypusine synthase
  • PKC1 protein, S cerevisiae
  • Protein Kinase C
  • GTP-Binding Proteins
  • Lysine

Grants and funding

This work was supported by grants to SRV and CFZ from Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP), Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) and PADC from Faculdade de Ciências Farmacêuticas, UNESP. The authors also thank FAPESP for fellowships awarded to the authors (FCG and DR). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.