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Published on: November 8, 2006
Preliminary characterization of maturation-promoting factor from yeast Saccharomyces cerevisiae
K Tachibana1, N Yanagishima, T Kishimoto
1Department of Developmental Biology, National Institute for Basic Biology, Okazaki, Japan.
Abstract:
It has been known for some time that maturation-promoting factor (MPF) appears in a wide variety of eukaryotic cells at M phase and exerts equal M-phase-promoting activity in both meiotic cells and mitotic cells in a non-specific manner. MPF was extracted from cdc20 mutant cells of the yeast Saccharomyces cerevisiae synchronized at M phase by incubation at the restrictive temperature. When injected into immature oocytes of Xenopus laevis, yeast MPF caused meiosis reinitiation in a dose-dependent manner and even in the presence of cycloheximide. Yeast MPF exerted its activity in starfish oocytes as well. MPF activity was obtained only from cells in M phase and not from G1, S or G2 phase cells, indicating cyclical changes during the yeast mitotic cell cycle. Preliminary characterization of yeast MPF revealed that its activity was associated with a heat-labile protein having a sedimentation coefficient value of 6 S. In contrast to the current assumption that MPF is a Ca-sensitive phosphoprotein stabilized by phosphorylated small molecules, such as ATP and Na-beta-glycerophosphate, the present study revealed that yeast MPF was still active even after treatment with either Ca2+ or alkaline phosphatase. Furthermore, it was found that yeast MPF and these phosphorylated small molecules were complementary in inducing reinitiation of meiosis, since the meiosis-reinitiating activity was detected only when both were present simultaneously and almost undetectable when either of them was present alone.(ABSTRACT TRUNCATED AT 250 WORDS)
Insights
Yeast maturation-promoting factor (MPF) triggers meiosis reinitiation in Xenopus oocytes, demonstrating conserved M-phase regulation across species. This study characterizes yeast MPF, revealing its protein nature and novel interactions.
Area of Science:
- Cell Biology
- Molecular Biology
- Yeast Genetics
Background:
- Maturation-promoting factor (MPF) is crucial for M-phase progression in eukaryotic cells.
- MPF activity is conserved across diverse species and cell types.
- Previous assumptions suggested MPF is a Ca-sensitive phosphoprotein.
Purpose of the Study:
- To investigate the properties and activity of MPF extracted from yeast.
- To determine if yeast MPF can induce meiotic maturation in non-yeast cells.
- To challenge existing models of MPF regulation and composition.
Main Methods:
- Extraction of MPF from synchronized Saccharomyces cerevisiae (yeast) cdc20 mutant cells.
- Microinjection of yeast MPF into immature Xenopus laevis oocytes.
- Assay of MPF activity in starfish oocytes.
- Biochemical characterization including heat treatment and phosphatase treatment.
Main Results:
- Yeast MPF induced dose-dependent meiosis reinitiation in Xenopus oocytes, even with cycloheximide.
- Yeast MPF exhibited activity in starfish oocytes, indicating cross-species function.
- MPF activity was strictly confined to M-phase cells.
- Yeast MPF was associated with a heat-labile 6S protein.
- Yeast MPF retained activity after Ca2+ or alkaline phosphatase treatment.
- Yeast MPF and phosphorylated small molecules showed complementary activity for meiosis reinitiation.
Conclusions:
- Yeast MPF possesses conserved M-phase-promoting activity functional in other eukaryotic systems.
- Yeast MPF is a proteinaceous factor, not solely dependent on Ca2+ or specific phosphorylated small molecules.
- The findings challenge the established model of MPF as a Ca-sensitive phosphoprotein and highlight complementary roles in meiosis.
- This research provides new insights into the fundamental mechanisms of cell cycle control and meiotic maturation.
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