title: Induction of the ZRC1 metal tolerance gene in zinc-limited yeast confers resistance to zinc shock.
abstract: Zinc is an essential nutrient but toxic to cells with overaccumulation. For this reason, intracellular zinc levels are tightly controlled. In the yeast Saccharomyces cerevisiae, the Zrc1 and Cot1 proteins have been implicated in the storage and detoxification of excess zinc in the vacuole. Surprisingly, transcription of ZRC1 is induced in zinc-limited cells by the zinc-responsive transcription factor Zap1. We show here that this increase in ZRC1 expression is a novel mechanism of zinc homeostasis and stress tolerance. Zinc-limited cells also express high levels of the plasma membrane zinc uptake transporters. As a consequence, when zinc-limited cells are resupplied with small amounts of zinc, large quantities quickly accumulate in the cell, a condition we refer to as "zinc shock." We show here that ZRC1 and its induction in zinc-limited cells are required for resistance to this zinc shock. Experiments using the zinc-responsive fluorophore FuraZin-1 as an indicator of vacuolar zinc levels indicated that Zrc1 is required for the rapid transport of zinc into the vacuole during zinc shock. We also present evidence that cytosolic zinc rises to higher levels in cells unable to sequester this excess zinc. Thus, the increase in ZRC1 expression occurs prior to the zinc shock stress for which this induction is important. We propose that this "proactive" strategy of homeostatic regulation, such as we document here for ZRC1, may represent a common but largely unrecognized phenomenon.
authors.affiliation: Departments of Nutritional Sciences and Physiology, University of Missouri, Columbia, Missouri 65211, USA.
authors.forename: Colin W
authors.initials: CW
authors.lastname: MacDiarmid
authors.forename: Mark A
authors.initials: MA
authors.lastname: Milanick
authors.forename: David J
authors.initials: DJ
authors.lastname: Eide
mesh_terms: D002352:Carrier Proteins / Q000378:metabolism; D027682:Cation Transport Proteins / Q000235:genetics* / Q000502:physiology; D003600:Cytosol / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects*; D006487:Hemostasis; D026901:Membrane Transport Proteins; D009154:Mutation; D012441:Saccharomyces cerevisiae / Q000737:chemistry / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics* / Q000502:physiology; D015534:Trans-Activators / Q000502:physiology; D014157:Transcription Factors; D014617:Vacuoles / Q000378:metabolism; D015032:Zinc / Q000378:metabolism* / Q000494:pharmacology
chemical_list: C076223:COT1 protein, S cerevisiae; D002352:Carrier Proteins; D027682:Cation Transport Proteins; D026901:Membrane Transport Proteins; D029701:Saccharomyces cerevisiae Proteins; D015534:Trans-Activators; D014157:Transcription Factors; C103264:ZAP1 protein, S cerevisiae; C088843:ZRC1 protein, S cerevisiae; C017800:zinc-binding protein; D015032:Zinc