Calcineurin-dependent regulation of Crz1p nuclear export requires Msn5p and a conserved calcineurin docking site.
Calcineurin, a conserved Ca(2+)/calmodulin-regulated protein phosphatase, plays a crucial role in Ca(2+) signaling in a wide variety of cell types. In Saccharomyces cerevisiae, calcineurin positively regulates transcription in response to stress by dephosphorylating the transcription factor Crz1p/Tcn1p. Dephosphorylation promotes Crz1p nuclear localization in part by increasing the efficiency of its nuclear import. In this work, we show that calcineurin-dependent dephosphorylation of Crz1p also down-regulates its nuclear export. Using a genetic approach, we identify Msn5p as the exportin for Crz1p. In addition, we define the Crz1p nuclear export signal (NES) and show that it interacts with Msn5p in a phosphorylation-dependent manner. This indicates that calcineurin regulates Crz1p nuclear export by dephosphorylating and inactivating its NES. Finally, we define a motif in Crz1p, PIISIQ, similar to the PxIxIT docking site for calcineurin on the mammalian transcription factor NFAT, that mediates the in vivo interaction between calcineurin and Crz1p and is required for calcineurin-dependent regulation of Crz1p nuclear export and activity. Therefore, in yeast as in mammals, a docking site is required to target calcineurin to its substrate such that it can dephosphorylate it efficiently.
Boustany
Leila M
LM
Department of Biological Sciences, Stanford University, Stanford, California 94305-5020, USA.
Cyert
Martha S
MS
D021581:Active Transport, Cell Nucleus; D020816:Amino Acid Motifs; D001665:Binding Sites; D019703:Calcineurin / Q000378:metabolism*; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism*; D017124:Conserved Sequence; D004268:DNA-Binding Proteins; D028884:Karyopherins; D009154:Mutation; D011485:Protein Binding; D021382:Protein Sorting Signals; D012441:Saccharomyces cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D017384:Sequence Deletion; D015534:Trans-Activators / Q000378:metabolism*; D014157:Transcription Factors
C109868:CRZ1 protein, S cerevisiae; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D028884:Karyopherins; C401306:MSN5 protein, S cerevisiae; D021382:Protein Sorting Signals; D029701:Saccharomyces cerevisiae Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D019703:Calcineurin