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 Zn₂Cys₆ 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.

ACKNOWLEDGMENTS

We thank Chantal Schwartz and Gerd Krapf for expert technical assistance. Michael Schuster is acknowledged for help with computers and software.

This work was supported by grants from the Fonds zur Fürderung der wissenschaftlichen Forschung (P-12661-BIO and P-15934-B08) and in part by funds from DSM Life Sciences and the Herzfelder'sche Familienstiftung. P.P. was supported by BBSRC grants 31/D10371 and 31/D13918.

The first two authors equally contributed to this work.