War1p, a Novel Transcription Factor Controlling Weak Acid Stress Response in Yeast

Abstract

The Saccharomyces cerevisiae ATP-binding cassette (ABC) transporter Pdr12p effluxes weak acids such as sorbate and benzoate, thus mediating stress adaptation. In this study, we identify a novel transcription factor, War1p, as the regulator of this stress adaptation through transcriptional induction of PDR12. Cells lacking War1p are weak acid hypersensitive, since they fail to induce Pdr12p. The nuclear Zn 2 Cys 6 transcriptional regulator War1p forms homodimers and is rapidly phosphorylated upon sorbate stress. The appearance of phosphorylated War1p isoforms coincides with transcriptional activation of PDR12. Promoter deletion analysis identified a novel cis-acting weak acid response element (WARE) in the PDR12 promoter required for PDR12 induction. War1p recognizes and decorates the WARE both in vitro and in vivo, as demonstrated by band shift assays and in vivo footprinting. Importantly, War1p occupies the WARE in the presence and absence of stress, demonstrating constitutive DNA binding in vivo. Our results suggest that weak acid stress triggers phosphorylation and perhaps activation of War1p. In turn, War1p activation is necessary for the induction of PDR12 through a novel signal transduction event that elicits weak organic acid stress adaptation.

Novel stress responses facilitate Saccharomyces cerevisiae growth in the presence of the monocarboxylate preservatives

“…Resistances are induced to Acetic, but not propionic, sorbic or benzoic acids [19] Propionic, sorbic, benzoic acids, but not acetic acid [1,7] Key induced signalling pathway and activity HOG pathway signalling, leading to Hog1p MAP kinase activation [19] No evidence for a signalling pathway involvement; acid anion may act directly on the War1p transcription factor [13] Key action/target of the induced activity needed for the acquisition of resistance Phosphorylation of Fps1p, leading to Fps1p endocytosis [20] PDR12 gene induction, leading to an elevated plasma membrane level and activity of the Pdr12p ABC transporter [23,28] Probable related stress response Hog1p-directed downregulation of metalloid entry through the Fps1p channel [40] War1p activation in media containing leucine, methionine or phenylalanine as sole nitrogen source [9] Normal physiological function of the major target of the response Fps1p is the major glycerol channel of the plasma membrane, important for osmoadaptation [10,22,38] Pdr12p is also involved in export of the potentially toxic aromatic and branched-chain organic acids produced during amino acid catabolism [9] (2), a MAP kinase constitutively bound to, and that directly phosphorylates, Fps1p (3). This phosphorylation provides the signal for Fps1p endocytosis and degradation, eliminating this source of the acetic acid entry to the cell.…”

“…Acquisition of resistance to these larger acids appears to involve, not the loss of a membrane pore, but the induction of an activity catalysing active efflux of the acid anion from the cell (Figure 2b). Inhibitory amounts of propionic, sorbic and benzoic acid induce the activity of a zinc-finger transcription factor, War1p [7,13,28] (Table 1). Only a small number of genes are subject to War1p regulation and, of these, it seems that just a single gene -that encoding the Pdr12p plasma membrane ATP binding cassette (ABC) transporter -is of any major importance for weak organic acid resistance.…”

“…This is an ABC transporter that provides resistance to those carboxylate compounds that can, to a reasonable extent, partition into both lipid and aqueous phases. [7,11,13,23,28] It may therefore initially bind acid anions that have become incorporated within the inner leaflet of the plasma membrane, anions orientated with their polar carboxylate groups exposed on the cytosolic surface of this membrane, then act by transporting these to the opposite (periplasmic) side of the membrane (i.e. act as a 'flippase'; Figure 2b).…”

Yeast ABC transporters – A tale of sex, stress, drugs and aging

“…War1p controls a rather small regulon [73], forms homodimers, is activated by stress-triggered hyper-phosphorylation (Frohner et al, in preparation), and decorates a cis-acting weak acid response element in the PDR12 promotor [72,73].…”

Acetate but not propionate induces oxidative stress in bakers’ yeastSaccharomyces cerevisiae

“…It is well documented that S. cerevisiae is capable of growing in the presence of sorbate due to induction of Pdr12p via War1p transcriptional factor-dependent pathway. 17 Pdr12p is responsible for the active extrusion of benzoate, propionate, fluorescein, catabolic products of amino acids, and multicyclic compounds such as caffeine. [18][19][20] However, possible role of the involvement of the pump in acetate efflux from S. cerevisiae cells is still debated.…”