Inactivation of the Cdc25 phosphatase by the stress-activated Srk1 kinase in fission yeast

Mol Cell. 2005 Jan 7;17(1):49-59. doi: 10.1016/j.molcel.2004.11.043.


The mechanisms by which environmental stress regulates cell cycle progression are poorly understood. In fission yeast, we show that Srk1 kinase, which associates with the stress-activated p38/Sty1 MAP kinase, regulates the onset of mitosis by inhibiting the Cdc25 phosphatase. Srk1 is periodically active in G2, and its overexpression causes cell cycle arrest in late G2 phase, whereas cells lacking srk1 enter mitosis prematurely. We find that Srk1 interacts with and phosphorylates Cdc25 at the same sites phosphorylated by the Chk1 and Cds1 (Chk2) kinases and that this phosphorylation is necessary for Srk1 to delay mitotic entry. Phosphorylation by Srk1 causes Cdc25 to bind to Rad24, a 14-3-3 protein family member, and accumulation of Cdc25 in the cytoplasm. However, Srk1 does not regulate Cdc25 in response to replication arrest or DNA damage but, rather, during a normal cell cycle and in response to nongenotoxic environmental stress.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • CDC2 Protein Kinase / chemistry
  • CDC2 Protein Kinase / genetics
  • CDC2 Protein Kinase / metabolism
  • Cell Cycle
  • Cell Cycle Proteins / genetics
  • Cell Cycle Proteins / metabolism
  • Cytoplasm / metabolism
  • DNA Damage
  • DNA Replication
  • Fungal Proteins
  • Genes, Fungal
  • Intracellular Signaling Peptides and Proteins
  • Mitogen-Activated Protein Kinases / chemistry
  • Mitogen-Activated Protein Kinases / genetics
  • Mitogen-Activated Protein Kinases / metabolism*
  • Mitosis
  • Phosphorylation
  • Protein Structure, Tertiary
  • Recombinant Fusion Proteins / chemistry
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism
  • Schizosaccharomyces / cytology
  • Schizosaccharomyces / enzymology*
  • Schizosaccharomyces / genetics
  • Schizosaccharomyces pombe Proteins / chemistry
  • Schizosaccharomyces pombe Proteins / genetics
  • Schizosaccharomyces pombe Proteins / metabolism
  • Tyrosine / chemistry
  • cdc25 Phosphatases / antagonists & inhibitors*
  • cdc25 Phosphatases / chemistry
  • cdc25 Phosphatases / genetics
  • cdc25 Phosphatases / metabolism


  • Cell Cycle Proteins
  • Fungal Proteins
  • Intracellular Signaling Peptides and Proteins
  • Recombinant Fusion Proteins
  • Schizosaccharomyces pombe Proteins
  • rad24 protein, S pombe
  • Tyrosine
  • SRK1 protein, S pombe
  • CDC2 Protein Kinase
  • cdc2 protein, S pombe
  • Mitogen-Activated Protein Kinases
  • cdc25 Phosphatases