Def1 mediates the degradation of excess nucleolar protein Nop1 in budding yeast

Biochem Biophys Res Commun. 2019 Nov 5;519(2):302-308. doi: 10.1016/j.bbrc.2019.09.002. Epub 2019 Sep 7.

Abstract

Nucleolar proteins such as Nop1/fibrillarin are degraded by nucleophagy in nutrient-starved conditions. However, whether and how excess nucleolar proteins are removed in normal conditions is unknown. Here we show that overexpressed nucleolar protein Nop1 is toxic and degraded in nutrient-rich conditions in budding yeast. The degradation was dependent on proteasomes. The CUE domain-containing protein Def1 mediated the degradation via the CUE domain and alleviated toxicity of Nop1 overexpression. Def1 was recruited to overexpressed Nop1 in the nucleolus. Ubiquitin mutants compromised this recruitment. This study revealed that Def1 is a novel factor for ubiquitin-dependent degradation of excess nucleolar proteins.

Keywords: Def1; Nop1; Nucleolar protein; Proteasome; Protein degradation; Ubiquitin.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Chromosomal Proteins, Non-Histone / metabolism*
  • Nuclear Proteins / metabolism*
  • Ribonucleoproteins, Small Nucleolar / metabolism*
  • Saccharomyces cerevisiae / metabolism*
  • Saccharomyces cerevisiae Proteins / metabolism*
  • Ubiquitin / genetics
  • Ubiquitin / metabolism

Substances

  • Chromosomal Proteins, Non-Histone
  • DEF1 protein, S cerevisiae
  • NOP1 protein, S cerevisiae
  • Nuclear Proteins
  • Ribonucleoproteins, Small Nucleolar
  • Saccharomyces cerevisiae Proteins
  • Ubiquitin