Identification of novel arsenic resistance genes in yeast

Abstract

Arsenic is a toxic metalloid that affects human health by causing numerous diseases and by being used in the treatment of acute promyelocytic leukemia. Saccharomyces cerevisiae (budding yeast) has been extensively utilized to elucidate the molecular mechanisms underlying arsenic toxicity and resistance in eukaryotes. In this study, we applied a genomic DNA overexpression strategy to identify yeast genes that provide arsenic resistance in wild‐type and arsenic‐sensitive S. cerevisiae cells. In addition to known arsenic‐related genes, our genetic screen revealed novel genes, including PHO86, VBA3, UGP1 , and TUL1 , whose overexpression conferred resistance. To gain insights into possible resistance mechanisms, we addressed the contribution of these genes to cell growth, intracellular arsenic, and protein aggregation during arsenate exposure. Overexpression of PHO86 resulted in higher cellular arsenic levels but no additional effect on protein aggregation, indicating that these cells efficiently protect their intracellular environment. VBA3 overexpression caused resistance despite higher intracellular arsenic and protein aggregation levels. Overexpression of UGP1 led to lower intracellular arsenic and protein aggregation levels while TUL1 overexpression had no impact on intracellular arsenic or protein aggregation levels. Thus, the identified genes appear to confer arsenic resistance through distinct mechanisms but the molecular details remain to be elucidated.

Multilevel Regulation of Membrane Proteins in Response to Metal and Metalloid Stress: A Lesson from Yeast

“…Atg1 (Hxt1p) [67], Cdk1 (Hxt1p) [67,68], Npr1p (Hxt1p, Hxt3p) [69] Pho84p (↓) SLC34/SLC20 PM As(V), As(III)? Pho4p [70], Spt7p [71] Pho86p [72], Cdc28p [68], Rsp5p [73] Ftr1p (↓) N/D PM As(V), As(III) Aft1-2p [74] Vta1p [75] Fet3p (↓) N/D PM As(V), As(III) Aft1p [74] Vta1p [75] Vba3 (?…”

“…However, the methionine permease Mup1 has been shown to be upregulated in response to As(III) instead [148]. Moreover, the overexpression of the yeast vacuolar amino acid permease Vba3 has been recently observed to provide the tolerance of yeast cells to arsenate, although the mechanism responsible for the phenomenon seems to not be related to increased As(V) accumulation in the vacuole [72]. In eukaryotes, the TORC1 kinase complex is the master regulator of nutrient response.…”

“…The Dsc complex subunit ubiquitin ligase Tul1 has been demonstrated to promote vacuolar degradation of Ycf1p when overexpressed, suggesting it may be the ligases responsible for its ubiquitylation [77]. At the same time, it has been demonstrated that Tul1p provides tolerance to arsenate when overproduced [72]. Nevertheless, the relationship between the phosphorylation and degradation of Ycf1p remains elusive.…”

“…As for the influx of pentavalent arsenicals, the main proteins responsible for the process are inorganic phosphate transporters, especially the high-affinity phosphate transporter Pho84 [72,109]. Its PM localization is regulated by the Pho86 protein, which conditions proper ER-exit of Pho84p and increases the PM level of Pho84p when overexpressed [72]. Little is known, however, about the regulated degradation of Pho84p, especially in response to arsenic stress.…”