BACKGROUND: Exposure of the budding Saccharomyces cerevisiae to an alkaline environment produces a robust transcriptional response involving hundreds of genes. Part of this response is triggered by an almost immediate burst of calcium that activates the Ser/Thr protein phosphatase calcineurin. Activated calcineurin dephosphorylates the transcription factor (TF) Crz1, which moves to the nucleus and binds to calcineurin/Crz1 responsive gene promoters. In this work we present a genome-wide study of the binding of Crz1 to gene promoters in response to high pH stress. RESULTS: Environmental alkalinization promoted a time-dependent recruitment of Crz1 to 152 intergenic regions, the vast majority between 1 and 5 min upon stress onset. Positional evaluation of the genomic coordinates combined with existing transcriptional studies allowed identifying 140 genes likely responsive to Crz1 regulation. Gene Ontology analysis confirmed the relevant impact of calcineurin/Crz1 on a set of genes involved in glucose utilization, and uncovered novel targets, such as genes responsible for trehalose metabolism. We also identified over a dozen of genes encoding TFs that are likely under the control of Crz1, suggesting a possible mechanism for amplification of the signal at the transcription level. Further analysis of the binding sites allowed refining the consensus sequence for Crz1 binding to gene promoters and the effect of chromatin accessibility in the timing of Crz1 recruitment to promoters. CONCLUSIONS: The present work defines at the genomic-wide level the kinetics of binding of Crz1 to gene promoters in response to alkaline stress, confirms diverse previously known Crz1 targets and identifies many putative novel ones. Because of the relevance of calcineurin/Crz1 in signaling diverse stress conditions, our data will contribute to understand the transcriptional response in other circumstances that also involve calcium signaling, such as exposition to sexual pheromones or saline stress.

Departament de Bioquímica i Biologia Molecular Universitat Autònoma de Barcelona Cerdanyola del Vallès 08193 Barcelona Spain

Departament de Bioquímica i Biologia Molecular Universitat Autònoma de Barcelona Cerdanyola del Vallès 08193 Barcelona Spain Institut de Biotecnologia i Biomedicina Universitat Autònoma de Barcelona Cerdanyola del Vallès 08193 Barcelona Spain

Departament de Bioquímica i Biologia Molecular Universitat Autònoma de Barcelona Cerdanyola del Vallès 08193 Barcelona Spain Institut de Biotecnologia i Biomedicina Universitat Autònoma de Barcelona Cerdanyola del Vallès 08193 Barcelona Spain Present Address Transgenic Models of Diseases and Transgenic Unit Institute of Molecular Genetics of the ASCR v v i BIOCEV Průmyslová 595 Vestec CZ 252 42 Czech Republic

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