Wsh3/Tea4 is a novel cell-end factor essential for bipolar distribution of Tea1 and protects cell polarity under environmental stress in S. pombe.
BACKGROUND
The fission yeast Schizosaccharomyces pombe has a cylindrical cell shape, for which growth is strictly limited to both ends, and serves as an excellent model system for genetic analysis of cell-polarity determination. Previous studies identified a cell-end marker protein, Tea1, that is transported by cytoplasmic microtubules to cell tips and recruits other cell-end factors, including the Dyrk-family Pom1 kinase. The deltatea1 mutant cells cannot grow in a bipolar fashion and show T-shaped morphology after heat shock.


RESULTS
We identified Wsh3/Tea4 as a novel protein that interacts with Win1 MAP kinase kinase kinase (MAPKKK) of the stress-activated MAP kinase cascade. Wsh3 forms a complex with Tea1 and is transported to cell tips by growing microtubules. The deltawsh3 mutant shows monopolar growth with abnormal Tea1 aggregate at the non-growing cell end; this abnormal aggregate fails to recruit Pom1 kinase. Consistent with the observed interaction between Win1 and Wsh3, cells lacking Wsh3 or Tea1 show more severe cell-polarity defects under osmolarity and heat-stress stimuli that are known to activate the stress MAPK cascade. Furthermore, mutants of the stress MAPK also exhibit cell-polarity defects when exposed to the same stress.


CONCLUSIONS
Wsh3/Tea4 is an essential component of the Tea1 cell-end complex. In addition to its role in bipolar growth during the normal cell cycle, the Wsh3-Tea1 complex, together with the stress-signaling MAPK cascade, contributes to cell-polarity maintenance under stress conditions.
Tatebe
Hisashi
H
Section of Microbiology, Division of Biological Sciences, University of California, Davis, Davis, California 95616, USA.
Shimada
Koichi
K
Uzawa
Satoru
S
Morigasaki
Susumu
S
Shiozaki
Kazuhiro
K
D016764:Cell Polarity / Q000502:physiology*; D005982:Glutathione Transferase; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism*; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D021381:Protein Transport / Q000502:physiology; D012568:Schizosaccharomyces / Q000235:genetics / Q000502:physiology*; D029702:Schizosaccharomyces pombe Proteins / Q000235:genetics / Q000378:metabolism*; D020798:Two-Hybrid System Techniques
D008869:Microtubule-Associated Proteins; D029702:Schizosaccharomyces pombe Proteins; C432671:Tea1 protein, S pombe; C501888:Tea4 protein, S pombe; D005982:Glutathione Transferase; C109170:win1 protein, S pombe; D020929:Mitogen-Activated Protein Kinase Kinases