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Updated: May 3, 2026
Assay for Adhesion and Agar Invasion in S. cerevisiae
Published on: November 8, 2006
Polo kinase links the stress pathway to cell cycle control and tip growth in fission yeast
1Cancer Research UK Cell Division Group, Paterson Institute for Cancer Research, Wilmslow Road, Manchester M20 4BX, UK.
Abstract:
Stress-activated mitogen-activated protein kinase cascades instigate a range of changes to enable eukaryotic cells to cope with particular insults. In Schizosaccharomyces pombe these responses include the transcription of specific gene sets and inhibition of entry into mitosis. The S. pombe stress response pathway (SRP) also promotes commitment to mitosis in unperturbed cell cycles to allow cells to match their rate of division with nutrient availability. The nature of this SRP function in cell cycle control is unknown. Entry into mitosis is controlled by mitosis-promoting factor (MPF; Cdc2/cyclin B) activity. Inhibitory phosphorylation of Cdc2 by Wee1 kinase inactivates MPF until Cdc25 removes this phosphate to promote mitosis. The balance between Wee1 and Cdc25 activities is influenced by the recruitment of polo kinase (Plo1) to the spindle pole body (SPB). The SPB component Cut12 mediates this recruitment. Hyper-activating mutations in either cut12 or plo1 enable Cdc25-defective cells to enter mitosis. The hyperactive cut12.s11 mutation suppresses cdc25.22, as it promotes recruitment of active Plo1 to interphase SPBs. Here we show that the SRP promotes phosphorylation of Plo1 on Ser 402. In unperturbed cell cycles, SRP-mediated phosphorylation of Ser 402 promotes Plo1 recruitment to SPBs and thus commitment to mitosis. Ser 402 phosphorylation also ensures efficient reinitiation of cell tip growth and cell division during recovery from particular stresses. Thus, phosphorylation of Plo1 Ser 402 not only enables SRP signalling to modulate the timing of mitotic commitment in response to nutrient status in unperturbed cycles, but also promotes the return to normal cell cycle control after stress.
Insights
The stress response pathway (SRP) in Schizosaccharomyces pombe regulates cell division timing by phosphorylating polo kinase (Plo1). This phosphorylation controls Plo1 recruitment to the spindle pole body (SPB), impacting mitotic entry and recovery from stress.
Area of Science:
- Cell Biology
- Molecular Biology
- Genetics
Background:
- Stress-activated protein kinase cascades orchestrate cellular responses to environmental insults.
- In Schizosaccharomyces pombe, the stress response pathway (SRP) regulates gene transcription, inhibits mitotic entry under stress, and promotes mitotic commitment in unstressed conditions.
- Mitotic entry is tightly controlled by the balance of Wee1 kinase and Cdc25 phosphatase activities, which regulate the phosphorylation state of Cdc2/cyclin B (MPF).
Purpose of the Study:
- To elucidate the role of the SRP in controlling cell cycle progression, specifically its function in regulating mitotic commitment.
- To investigate the molecular mechanism by which the SRP influences the balance of Wee1 and Cdc25 activities.
- To determine how SRP signaling impacts Plo1 kinase activity and its localization.
Main Methods:
- Genetic analysis of Schizosaccharomyces pombe mutants, including hyper-activating mutations in cut12 and plo1.
- Investigating the interaction between the SRP and the cell cycle regulatory machinery.
- Phosphorylation site analysis of Plo1 kinase, specifically focusing on Serine 402.
Main Results:
- The SRP signaling pathway promotes the phosphorylation of Plo1 at Serine 402.
- SRP-mediated phosphorylation of Plo1 Ser 402 is crucial for Plo1 recruitment to the spindle pole body (SPB) in both unperturbed and stressed cell cycles.
- This phosphorylation event facilitates commitment to mitosis and ensures timely reinitiation of cell growth and division after stress recovery.
Conclusions:
- Phosphorylation of Plo1 Ser 402 by the SRP is a key regulatory mechanism linking stress signaling to cell cycle control.
- SRP-dependent Plo1 phosphorylation modulates the timing of mitotic entry in response to nutrient availability during normal growth.
- This pathway is essential for efficient adaptation and return to normal cell cycle progression following cellular stress.
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