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Activation of p34cdc2 protein kinase activity in meiotic and mitotic cell cycles in mouse oocytes and embryos
1Department of Animal Breeding, Faculty of Agriculture, University of Tokyo, Japan.
Abstract:
p34cdc2 protein kinase is a universal regulator of M-phase in eukaryotic cell cycle. To investigate the regulation of meiotic and mitotic cell cycle in mammals, we examined the changes in phosphorylation states of p34cdc2 and its histone H1 kinase activity in mouse oocytes and embryos. We showed that p34cdc2 has three different migrating bands (referred to as upper, middle and lower bands) on SDS-PAGE followed by immunoblotting with anti-PSTAIR antibody, and that the upper and middle bands are phosphorylated forms since these two bands shifted to the lower one by alkaline phosphatase treatment. In meiotic cell cycle, only germinal vesicle (GV) stage oocytes had the three forms. The phosphorylated forms decreased gradually in oocytes up to 2 h after isolation from follicles, and thereafter the phosphorylation states did not change significantly until metaphase II. However, the histone H1 kinase activity oscillated, being activated at the first and second metaphase in meiosis and inactivated at the time of the first polar body extrusion. These results suggest that changes in phosphorylation states of p34cdc2 triggered its activation at the first metaphase, but not inactivation and reactivation at the first and second metaphase, respectively. In mitotic cell cycle, phosphorylated forms appeared at 4 h after insemination, increased greatly just before metaphase, and were dephosphorylated in metaphase. Histone H1 kinase activity was high only at metaphase. This kinase activation is probably triggered by dephosphorylation of p34cdc2.
Insights
The study reveals how p34cdc2 protein kinase regulates mammalian cell division. Changes in its phosphorylation state control key events in meiotic and mitotic cell cycles, impacting histone H1 kinase activity during oocyte and embryo development.
Area of Science:
- Cell Biology
- Molecular Biology
- Developmental Biology
Background:
- The p34cdc2 protein kinase is a critical regulator of the M-phase in the eukaryotic cell cycle.
- Understanding its regulation is crucial for comprehending mammalian meiotic and mitotic cell division.
Purpose of the Study:
- To investigate the regulation of meiotic and mitotic cell cycles in mammals.
- To examine the changes in phosphorylation states of p34cdc2 and its histone H1 kinase activity in mouse oocytes and embryos.
Main Methods:
- Utilized SDS-PAGE and immunoblotting with anti-PSTAIR antibody to analyze p34cdc2 phosphorylation states.
- Assessed histone H1 kinase activity in mouse oocytes and embryos during meiotic and mitotic progression.
- Employed alkaline phosphatase treatment to identify phosphorylated forms of p34cdc2.
Main Results:
- p34cdc2 exhibits three distinct migrating bands on SDS-PAGE, with upper and middle bands representing phosphorylated forms.
- In meiosis, p34cdc2 phosphorylation states changed gradually, while histone H1 kinase activity oscillated, activating at metaphase and inactivating during polar body extrusion.
- In mitosis, p34cdc2 became phosphorylated before metaphase and dephosphorylated during metaphase, coinciding with high histone H1 kinase activity.
Conclusions:
- Changes in p34cdc2 phosphorylation states appear to trigger its activation at the first metaphase in meiosis.
- Dephosphorylation of p34cdc2 likely triggers histone H1 kinase activation during mitotic metaphase.
- The study elucidates the dynamic regulation of p34cdc2 activity during mammalian gametogenesis and early development.