Tolerance to thermal and reductive stress in Saccharomyces cerevisiae is amenable to regulation by phosphorylation–dephosphorylation of ubiquitin conjugating enzyme 1 (Ubc1) S97 and S115

Abstract

Ubiquitin conjugating enzyme 1 (Ubc1) is a member of the E2 family of enzymes that conjugates ubiquitin to damaged proteins destined for degradation by the ubiquitin proteasomal system. It is necessary for stress tolerance and is essential for cell survival in Saccharomyces cerevisiae. Ubc1 has five serine residues that are potential substrates for phosphorylation by kinases. However, no data are available to indicate that Ubc1 function or stress tolerance in S. cerevisiae is regulated by serine phosphorylation of Ubc1. We demonstrate that Ubc1 is phosphorylated in serine residue(s). Furthermore, expression of Ubc1 mutants that are 'constitutively phosphorylated' or 'dephosphorylated' in mitogen-activated protein (MAP) kinase serine residues (S97 and S115) affected tolerance to thermal and reductive stress in S. cerevisiae. Specifically, expression of Ubc1S97A and S115D increased thermo-tolerance in both BY4741 and TetO 7 -UBC1ura3Δ cells. Serine phosphorylation of Ubc1 was decreased in BY4741 cells following exposure at 40 C. Tolerance to reductive stress in the same strains correlated with the expression of Ubc1S97A. Ubc1 phosphorylation did not show significant alteration under similar conditions. Both hog1Δ and slt2Δ cells expressing Ubc1S115D and Ubc1S115A were rendered tolerant to thermal and reductive stress respectively. Ubc1 phosphorylation was higher in BY4741 cells compared to hog1Δ cells at 30 C and was significantly reduced in BY4741 cells upon exposure at 40 C. Taken together, the cell survival assays and Ubc1 phosphorylation status in strains and under conditions as described above suggest that tolerance to thermal and reductive stress in S. cerevisiae may be regulated by MAP kinase-mediated phosphorylation of Ubc1S97 and S115.

Structure of an E3:E2∼Ub Complex Reveals an Allosteric Mechanism Shared among RING/U-box Ligases

“…For example, positions that correspond structurally to UbcH5c Asp112 are conserved as either Asp or Ser in a large number of E2s. Yeast E2 Ubc1 Ser115 is a site of reversible phosphorylation associated with a phenotype in which yeast display enhanced tolerance to environmental stresses (Meena et al, 2011). Our E4BU:UbcH5c~Ub model predicts that the phosphorylation of Ubc1 Ser115 would enhance the E2:Ub electrostatic interaction, thereby promoting the activation of Ub transfer.…”

Differential proteomics study of postharvest Volvariella volvacea during storage at 4 °C

“…UBC is reportedly involved in the tolerance of plants to abiotic stresses, including drought, salt, osmotic and water stress 60 . Previous studies have shown that the tolerance of S. cerevisiae to thermal stress might be regulated by dephosphorylation of the MAP kinase serine residues of UBC1 during exposure to this stress, which leads to increased tolerance to thermal stress 61 . Increases in UBC1 expression and proteasome activity elevated cadmium (Cd) tolerance by reducing the Cd levels through the regulation of Cd transporter expression in NtUBC1 tobacco 60 .…”

The UBA domain of conjugating enzyme Ubc1/Ube2K facilitates assembly of K48/K63‐branched ubiquitin chains

“…Ubc1, in turn, is involved in protein turnover and essential for survival of yeast cells deleted for UBC4 (Seufert et al, 1990). It was associated with vesicle biogenesis (Shieh et al, 2001), resistance to proteotoxic stress (Meena et al, 2011), transcription factor shuttling (Jiao et al, 2016), and protein quality control in the endoplasmic reticulum (Friedlander, et al, 2000) and in the nucleus (Ibarra et al, 2016). Furthermore, Ubc1 and Ubc4 were shown to act cooperatively in the degradation of substrates of the anaphase-promoting complex (APC/C; Rodrigo-Brenni & Morgan, 2007).…”