Opi1p translocation to the nucleus is regulated by hydrogen peroxide in Saccharomyces cerevisiae.

During exposure of yeast cells to low levels of hydrogen peroxide (H O ), the expression of several genes is regulated for cells to adapt to the surrounding oxidative environment. Such adaptation involves modification of plasma membrane lipid composition, reorganization of ergosterol-rich microdomains and altered gene expression of proteins involved in lipid and vesicle traffic, to decrease permeability to exogenous H O . Opi1p is a transcriptional repressor that is inactive when present at the nuclear membrane/endoplasmic reticulum, but represseses transcription of inositol upstream activating sequence (UAS )-containing genes, many of which are involved in the synthesis of phospholipids and fatty acids, when it is translocated to the nucleus. We investigated whether H O in concentrations inducing adaptation regulates Opi1p function. We found that, in the presence of H O , GFP-Opi1p fusion protein translocates to the nucleus and, concomitantly, the expression of UAS -containing genes is affected. We also investigated whether cysteine residues of Opi1p were implicated in the H O -mediated translocation of this protein to the nucleus and identified cysteine residue 159 as essential for this process. Our work shows that Opi1p is redox-regulated and establishes a new mechanism of gene regulation involving Opi1p, which is important for adaptation to H O in yeast cells. Copyright © 2017 John Wiley & Sons, Ltd.