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Calcineurin-dependent nuclear import of the transcription factor Crz1p requires Nmd5p

R S Polizotto1, M S Cyert

  • 1Department of Biological Sciences, Stanford University, Stanford, CA 94305, USA.

The Journal of Cell Biology
|September 6, 2001
PubMed

Insights

Calcineurin regulates yeast transcription factor Crz1p nuclear import. This occurs via a novel nuclear localization sequence (NLS) and karyopherin Nmd5p, controlled by Crz1p phosphorylation.

Area of Science:

  • Cellular signaling
  • Molecular biology
  • Yeast genetics

Background:

  • Calcineurin is a calcium/calmodulin-dependent serine-threonine phosphatase.
  • It regulates numerous Ca2+-dependent signaling pathways.
  • In yeast, calcineurin dephosphorylates the transcription factor Crz1p, affecting its nuclear localization.

Purpose of the Study:

  • To investigate the mechanism of calcineurin-mediated nuclear import regulation of Crz1p.
  • To identify novel regulatory elements and factors involved in Crz1p nucleocytoplasmic transport.

Main Methods:

  • Characterization of a novel nuclear localization sequence (NLS) in Crz1p.
  • Assays to determine the role of karyopherin Nmd5p in Crz1p nuclear import.
  • Phosphorylation-state dependent binding studies between Crz1p and Nmd5p.

Main Results:

  • A novel NLS in Crz1p was identified, requiring both basic and hydrophobic residues.
  • Karyopherin Nmd5p is essential for Crz1p nuclear import.
  • Crz1p binding to Nmd5p is regulated by its phosphorylation state, controlled by calcineurin.
  • Both N- and C-terminal residues of Crz1p are involved in regulated Nmd5p binding.

Conclusions:

  • Calcineurin regulates Crz1p nuclear import through phosphorylation-dependent masking of its NLS.
  • Nmd5p acts as the karyopherin mediating Crz1p import.
  • This mechanism provides insight into the spatial control of gene expression in response to calcium signaling.

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