Identification and Characterization of rns4/vps32 Mutation in the RNase T1 Expression-Sensitive Strain of Saccharomyces Cerevisiae: Evidence for Altered Ambient Response Resulting in Transportation of the Secretory Protein to Vacuoles

FEMS Yeast Res. 2005 Jun;5(9):801-12. doi: 10.1016/j.femsyr.2005.03.003.

Abstract

We previously reported a genetic analysis of the growth-inhibitory effect caused by the overexpression of the Aspergillus oryzae rntA gene, encoding RNase T1 (Ribonuclease T1), in Saccharomyces cerevisiae. Subsequently, rns (ribonuclease T1 sensitive) mutants with mutations in the rns1 (DSL1), rns2 (UMP1), and rns3 (SEC17) genes, were identified. In the present study, rns4 (VPS32/SNF7) gene mutation was identified by complementation of tunicamycin sensitivity. While the rns4 mutant exhibited sensitivity to ambient stress conditions (200 mM CaCl(2), 1M NaCl and pH 8.0), genome-wide expression analysis revealed a similar pattern of genes up-regulated as was observed under nitrogen depletion condition by Gasch et al. [Mol. Biol. Cell 11 (2000) 4241]. Notably, the genes participating in autophagy (ATG4 and ATG8), the genes encoding a vacuolar protease (PRB1), vacuolar protease inhibitors (PAI3, PBI2 and TFS1) and YHR138c (a PBI2 homolog) were up-regulated in the rns4 mutant. Interestingly, the RNase T1*-GFP fusion protein (*inactive form) expressed in the rns4 mutant strain localized at the ER and vacuole under both stress or no-stress conditions. In contrast, the RNase T1*-GFP fusion protein expressed in the wild-type strain could not be detected under no-stress conditions, however, a stress-dependent localization of the fusion protein was observed at the vacuole. Since, the rns4 mutant exhibited a partial starvation-like response in spite of a rich ambient environment, leading to transportation of the secretory protein to the vacuole and accumulation in the endoplasmic reticulum, the present findings implicate a novel role for Rns4/Vps32 in proper response and adaptation to ambient conditions.

MeSH terms

  • Biological Transport
  • Endoplasmic Reticulum / metabolism
  • Endosomal Sorting Complexes Required for Transport
  • Gene Expression Regulation, Fungal
  • Genetic Complementation Test
  • Genome, Fungal
  • Microscopy, Fluorescence
  • Mutagenesis, Insertional
  • Nuclear Proteins / genetics*
  • Nuclear Proteins / metabolism
  • Nuclear Proteins / physiology
  • Oligonucleotide Array Sequence Analysis
  • Plasmids
  • RNA, Fungal / genetics
  • RNA, Fungal / metabolism
  • Reverse Transcriptase Polymerase Chain Reaction
  • Ribonuclease T1 / genetics*
  • Ribonuclease T1 / metabolism
  • Saccharomyces cerevisiae / enzymology*
  • Saccharomyces cerevisiae / genetics
  • Saccharomyces cerevisiae / physiology
  • Saccharomyces cerevisiae Proteins / genetics*
  • Saccharomyces cerevisiae Proteins / metabolism
  • Saccharomyces cerevisiae Proteins / physiology
  • Vacuoles / metabolism*

Substances

  • Endosomal Sorting Complexes Required for Transport
  • Nuclear Proteins
  • RNA, Fungal
  • SNF7 protein, S cerevisiae
  • Saccharomyces cerevisiae Proteins
  • Ribonuclease T1