Negative regulation of calcineurin signaling by Hrr25p, a yeast homolog of casein kinase I.
Calcineurin is a Ca2+/calmodulin-regulated protein phosphatase required for Saccharomyces cerevisiae to respond to a variety of environmental stresses. Calcineurin promotes cell survival during stress by dephosphorylating and activating the Zn-finger transcription factor Crz1p/Tcn1p. Using a high-throughput assay, we screened 119 yeast kinases for their ability to phosphorylate Crz1p in vitro and identified the casein kinase I homolog Hrr25p. Here we show that Hrr25p negatively regulates Crz1p activity and nuclear localization in vivo. Hrr25p binds to and phosphorylates Crz1p in vitro and in vivo. Overexpression of Hrr25p decreases Crz1p-dependent transcription and antagonizes its Ca2+-induced nuclear accumulation. In the absence of Hrr25p, activation of Crz1p by Ca2+/calcineurin is potentiated. These findings represent the first identification of a negative regulator for Crz1p, and establish a novel physiological role for Hrr25p in antagonizing calcineurin signaling.
Department of Biological Sciences Stanford University, Stanford, California, 94305-5020, USA.
Kimberly A
KA
Kafadar
Heng
H
Zhu
Michael
M
Snyder
Martha S
MS
Cyert
D019703:Calcineurin / Q000378:metabolism*; D047389:Casein Kinase I; D047388:Casein Kinases; D004268:DNA-Binding Proteins; D015966:Gene Expression Regulation, Fungal / Q000502:physiology*; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism*; D021381:Protein Transport; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*; D015534:Trans-Activators / Q000378:metabolism; D014157:Transcription Factors
C109868:CRZ1 protein, S cerevisiae; D004268:DNA-Binding Proteins; D029701:Saccharomyces cerevisiae Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D011494:Protein Kinases; D047389:Casein Kinase I; D047388:Casein Kinases; C070775:HRR25 protein, S cerevisiae; D019703:Calcineurin