title: The yeast transcription factor Crz1 is activated by light in a Ca2+/calcineurin-dependent and PKA-independent manner.
abstract: Light in the visible range can be stressful to non-photosynthetic organisms. The yeast Saccharomyces cerevisiae has earlier been reported to respond to blue light via activation of the stress-regulated transcription factor Msn2p. Environmental changes also induce activation of calcineurin, a Ca(2+)/calmodulin dependent phosphatase, which in turn controls gene transcription by dephosphorylating the transcription factor Crz1p. We investigated the connection between cellular stress caused by blue light and Ca(2+) signalling in yeast by monitoring the nuclear localization dynamics of Crz1p, Msn2p and Msn4p. The three proteins exhibit distinctly different stress responses in relation to light exposure. Msn2p, and to a lesser degree Msn4p, oscillate rapidly between the nucleus and the cytoplasm in an apparently stochastic fashion. Crz1p, in contrast, displays a rapid and permanent nuclear localization induced by illumination, which triggers Crz1p-dependent transcription of its target gene CMK2. Moreover, increased extracellular Ca(2+) levels stimulates the light-induced responses of all three transcription factors, e.g. Crz1p localizes much quicker to the nucleus and a larger fraction of cells exhibits permanent Msn2p nuclear localization at higher Ca(2+) concentration. Studies in mutants lacking Ca(2+) transporters indicate that influx of extracellular Ca(2+) is crucial for the initial stages of light-induced Crz1p nuclear localization, while mobilization of intracellular Ca(2+) stores appears necessary for a sustained response. Importantly, we found that Crz1p nuclear localization is dependent on calcineurin and the carrier protein Nmd5p, while not being affected by increased protein kinase A activity (PKA), which strongly inhibits light-induced nuclear localization of Msn2/4p. We conclude that the two central signalling pathways, cAMP-PKA-Msn2/4 and Ca(2+)-calcineurin-Crz1, are both activated by blue light illumination.
authors: Department of Applied Physics, Chalmers University of Technology, Göteborg, Sweden. kristofer.bodvard@chalmers.se
authors: Kristofer
authors: K
authors: Bodvard
authors: Anna
authors: A
authors: Jörhov
authors: Anders
authors: A
authors: Blomberg
authors: Mikael
authors: M
authors: Molin
authors: Mikael
authors: M
authors: Käll
mesh_terms: D019703:Calcineurin / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005110:Extracellular Space / Q000378:metabolism; D008027:Light; D021381:Protein Transport; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D015398:Signal Transduction; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: C109868:CRZ1 protein, S cerevisiae; D004268:DNA-Binding Proteins; C081935:MSN2 protein, S cerevisiae; C081937:MSN4 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D017868:Cyclic AMP-Dependent Protein Kinases; C534502:CMK2 protein, S cerevisiae; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D019703:Calcineurin; D002118:Calcium