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Xenopus M phase MAP kinase: isolation of its cDNA and activation by MPF
Y Gotoh1, K Moriyama, S Matsuda
1Department of Biophysics and Biochemistry, Faculty of Science, University of Tokyo, Japan.
Abstract:
MAP kinase is activated and phosphorylated during M phase of the Xenopus oocyte cell cycle, and induces the interphase-M phase transition of microtubule dynamics in vitro. We have carried out molecular cloning of Xenopus M phase MAP kinase and report its entire amino acid sequence. There is no marked change in the MAP kinase mRNA level during the cell cycle. Moreover, studies with an anti-MAP kinase antiserum indicate that MAP kinase activity may be regulated posttranslationally, most likely by phosphorylation. We show that MAP kinase can be activated by microinjection of MPF into immature oocytes or by adding MPF to cell-free extracts of interphase eggs. These results suggest that MAP kinase functions as an intermediate between MPF and the interphase-M phase transition of microtubule organization.
Insights
Mitosis-promoting factor (MPF) activates MAP kinase in Xenopus oocytes, regulating cell cycle transitions. This MAP kinase activity is controlled post-translationally, likely via phosphorylation, acting as a key intermediate.
Area of Science:
- Cell Biology
- Molecular Biology
- Developmental Biology
Background:
- The M phase of the cell cycle involves critical transitions in cellular organization.
- Microtubule dynamics are essential for cell division and are regulated during the cell cycle.
- MAP kinase is a key signaling molecule implicated in cell cycle regulation.
Purpose of the Study:
- To clone and characterize Xenopus M phase MAP kinase.
- To investigate the regulation of MAP kinase activity during the cell cycle.
- To elucidate the role of MAP kinase as an intermediate in MPF signaling.
Main Methods:
- Molecular cloning of Xenopus M phase MAP kinase.
- Analysis of MAP kinase mRNA levels during the cell cycle.
- Western blot analysis using anti-MAP kinase antiserum.
- Microinjection of MPF into oocytes and addition to cell-free extracts.
Main Results:
- The complete amino acid sequence of Xenopus M phase MAP kinase was determined.
- MAP kinase mRNA levels remain constant throughout the cell cycle.
- MAP kinase activity is regulated post-translationally, primarily through phosphorylation.
- MPF activates MAP kinase in both intact oocytes and cell-free extracts.
Conclusions:
- MAP kinase is activated during the M phase of the Xenopus oocyte cell cycle.
- MAP kinase activity is regulated post-translationally, independent of mRNA levels.
- MAP kinase acts as a crucial intermediate linking MPF to the regulation of microtubule organization during the cell cycle.