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SCF(Pof1)-ubiquitin and its target Zip1 transcription factor mediate cadmium response in fission yeast

Clare Harrison1, Satoshi Katayama, Susheela Dhut

  • 1Laboratory of Cell Regulation, Lincoln's Inn Fields Laboratories, Cancer Research UK, London Research Institute, London, UK.

The EMBO Journal
|January 22, 2005
PubMed

Insights

Fission yeast

Area of Science:

  • Cellular biology
  • Molecular biology
  • Genetics

Background:

  • Ubiquitin-dependent proteolysis regulates gene expression in eukaryotes.
  • Pof1, an F-box protein in fission yeast, is crucial for cell growth.
  • Pof1 mutants exhibit growth arrest and small cell size.

Purpose of the Study:

  • To identify and characterize the targets of the fission yeast F-box protein Pof1.
  • To elucidate the role of Pof1 and its target in cellular responses to environmental stress, specifically cadmium exposure.
  • To understand the mechanism of growth regulation mediated by Pof1 and its substrate.

Main Methods:

  • Genetic analysis of temperature-sensitive pof1 mutants.
  • Identification of Zip1 as a Pof1 target through suppressor analysis.
  • Biochemical assays to study Pof1-Zip1 interaction and Zip1 ubiquitylation.
  • Genome-wide DNA microarray to assess gene expression changes.
  • Phenotypic analysis of zip1 mutants under cadmium stress.

Main Results:

  • Zip1, a bZIP transcription factor, is a substrate of SCF(Pof1) and is stabilized in pof1 mutants.
  • Pof1 specifically binds to phosphorylated forms of Zip1, leading to its ubiquitylation and degradation.
  • Zip1 controls the expression of cadmium-induced genes and is essential for cadmium response.
  • Zip1 mutants are hypersensitive to cadmium, exhibiting loss of cell viability.
  • Cadmium exposure upregulates Zip1, causing growth arrest and reduced cell size in wild-type cells.

Conclusions:

  • Zip1 mediates a crucial growth arrest response to cadmium stress, essential for maintaining cell viability.
  • SCF(Pof1) normally regulates cell growth by constitutively ubiquitylating and degrading Zip1.
  • This study reveals a novel regulatory pathway involving Pof1, Zip1, and ubiquitin-dependent proteolysis in cadmium stress response and cell cycle control.

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