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Phosphorylation of RNA-binding protein controls cell cycle switch from mitotic to meiotic in fission yeast
Y Watanabe1, S Shinozaki-Yabana, Y Chikashige
1Department of Biophysics and Biochemistry, Graduate School of Science, University of Tokyo, Japan.
Abstract:
Meiosis generates haploid gametes from diploid cells and is an almost universal feature of eukaryotic organisms. But little is known about how the switch from mitotic to meiotic cell cycles is molecularly controlled. In the fission yeast Schizosaccharomyces pombe, inactivation of the protein kinase Pat1(Ran1) upon nutrient deprivation triggers entry into the meiotic cell cycle. Here we show that the RNA-binding protein Mei2 is a substrate of Pat1 kinase and that dephosphorylation of Mei2 is sufficient to switch cells from the mitotic cell cycle into meiosis. Mei2 is localized mainly in the cytoplasm of proliferating cells but is seen as a single spot close to the microtubule organizing centre in prophase nuclei during meiosis. Our results, and others from a metazoan, emphasize the crucial role of RNA-binding proteins in the initiation and execution of meiosis.
Insights
The protein kinase Pat1 inactivates Mei2, an RNA-binding protein, triggering meiosis in fission yeast. Dephosphorylating Mei2 is key to switching from mitotic to meiotic cell cycles.
Area of Science:
- Molecular Biology
- Cell Biology
- Genetics
Background:
- Meiosis is essential for sexual reproduction in eukaryotes, producing haploid gametes from diploid cells.
- The molecular mechanisms controlling the transition from mitotic to meiotic cell cycles remain largely unknown.
- Fission yeast (Schizosaccharomyces pombe) uses nutrient deprivation to trigger meiosis, involving the inactivation of protein kinase Pat1.
Purpose of the Study:
- To elucidate the molecular control of the mitotic to meiotic cell cycle switch in fission yeast.
- To identify the role of the RNA-binding protein Mei2 in meiosis initiation.
- To investigate the relationship between Pat1 kinase and Mei2.
Main Methods:
- Biochemical assays to determine substrate relationships between Pat1 kinase and Mei2.
- Cell cycle analysis to observe the effects of Mei2 dephosphorylation on cell cycle progression.
- Fluorescence microscopy to track Mei2 localization during different cell cycle stages.
Main Results:
- Mei2 is a direct substrate of the Pat1 kinase.
- Dephosphorylation of Mei2 by Pat1 is sufficient to induce entry into the meiotic cell cycle.
- Mei2 exhibits distinct subcellular localization patterns during proliferation and meiosis.
Conclusions:
- The Pat1-mediated dephosphorylation of Mei2 is a critical regulatory step initiating meiosis in fission yeast.
- RNA-binding proteins, like Mei2, play a vital role in the initiation and progression of meiosis.
- These findings contribute to understanding the conserved mechanisms of meiotic regulation across eukaryotes.