Article
- The EMBO Journal (1997) 16, 6162 - 6170
- doi:10.1093/emboj/16.20.6162
Multiple modes of activation of the stress-responsive MAP kinase pathway in fission yeast
Itaru Samejima1, Shaun Mackie1 and Peter A. Fantes1
- Institute of Cell and Molecular Biology, University of Edinburgh, Mayfield Road, Edinburgh EH9 3JR, UK
Correspondence to:
Peter A. Fantes, E-mail: p.fantes@ed.ac.uk
Received 24 December 1996; Revised 18 July 1997
Abstract
The Schizosaccharomyces pombe wis1+ gene is essential for cell survival under stress conditions. The MAPKK homologue Wis1 is required for activation of the MAPK homologue Spc1, and integrity of the Wis1–Spc1 pathway is required for survival in extreme conditions of heat, osmolarity, oxidation or limited nutrition. We show here that Wis4, a protein kinase of a new MAPKKK class, phosphorylates Wis1 in vitro and activates it in vivo. Win1 is also required for full activation of Wis1, and Win1 rather than Wis4 mediates the osmotic stress signal. Surprisingly, the pathway can still be activated by heat or oxidative stress independently of the phosphorylation of two conserved Wis1 residues. Evidence is presented that the Pyp1 protein tyrosine phosphatase, which dephosphorylates Spc1, is central to this alternative activation mechanism.
Keywords:
- cell cycle control,
- fission yeast,
- MAP kinase signalling pathway,
- protein tyrosine phosphatase,
- stress response
