Calcineurin-dependent nuclear import of the transcription factor Crz1p requires Nmd5p.
Calcineurin is a conserved Ca2+/calmodulin-specific serine-threonine protein phosphatase that mediates many Ca2+-dependent signaling events. In yeast, calcineurin dephosphorylates Crz1p, a transcription factor that binds to the calcineurin-dependent response element, a 24-bp promoter element. Calcineurin-dependent dephosphorylation of Crz1p alters Crz1p nuclear localization. This study examines the mechanism by which calcineurin regulates the nuclear localization of Crz1p in more detail. We describe the identification and characterization of a novel nuclear localization sequence (NLS) in Crz1p, which requires both basic and hydrophobic residues for activity, and show that the karyopherin Nmd5p is required for Crz1p nuclear import. We also demonstrate that the binding of Crz1p to Nmd5p is dependent upon its phosphorylation state, indicating that nuclear import of Crz1p is regulated by calcineurin. Finally, we demonstrate that residues in both the NH2- and COOH-terminal portions of Crz1p are required for regulated Crz1p binding to Nmd5p, supporting a model of NLS masking for regulating Crz1p nuclear import.
Polizotto
R S
RS
Department of Biological Sciences, Stanford University, Stanford, CA 94305, USA.
Cyert
M S
MS
D021581:Active Transport, Cell Nucleus / Q000502:physiology; D000595:Amino Acid Sequence; D019703:Calcineurin / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism*; D004268:DNA-Binding Proteins; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D017930:Genes, Reporter; D006160:Guanosine Triphosphate / Q000378:metabolism; D015151:Immunoblotting; D008969:Molecular Sequence Data; D020559:Monomeric GTP-Binding Proteins / Q000235:genetics; D019913:Nuclear Localization Signals; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D021382:Protein Sorting Signals; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors; D015003:Yeasts / Q000502:physiology; D016335:Zinc Fingers
C109868:CRZ1 protein, S cerevisiae; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; C080324:GSP1 protein, S cerevisiae; D019913:Nuclear Localization Signals; D009687:Nuclear Proteins; D021382:Protein Sorting Signals; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D006160:Guanosine Triphosphate; D019703:Calcineurin; D020559:Monomeric GTP-Binding Proteins