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Mitogen-activated protein kinase kinase is required for the mos-induced metaphase arrest
1Department of Genetics and Molecular Biology, Kyoto University, Japan.
Abstract:
The product of the c-mos proto-oncogene functions not only as an initiator of oocyte maturation but also as a component of cytostatic factor that causes the natural arrest of the unfertilized egg at the second meiotic metaphase. It has been shown that Mos can phosphorylate and activate mitogen-activated protein (MAP) kinase kinase (MAPKK) in vitro, leading to activation of MAP kinase. In this study, by using an anti-MAPKK antibody that can specifically inhibit Xenopus MAPKK activity, we have shown that MAPKK mediates the cytostatic factor activity of Mos. Coinjection of this anti-MAPKK antibody with the bacterially expressed Mos protein into a two-cell embryo prevented the Mos-induced cleavage arrest as well as the Mos-induced MAP kinase activation. The analysis of individual embryos indicated that the degree of the cleavage arrest was correlated with the extent of the MAP kinase activation in the Mos- and the Mos/antibody-injected embryos. These observations suggest the involvement of a signal transmission pathway consisting of Mos, MAPKK, and MAP kinase in the metaphase arrest.
Insights
The c-mos proto-oncogene product initiates oocyte maturation and causes egg arrest. This study shows MAP kinase kinase mediates c-mos
Area of Science:
- Cell Biology
- Molecular Biology
- Developmental Biology
Background:
- The c-mos proto-oncogene product is crucial for oocyte maturation and egg arrest.
- Mos protein activates mitogen-activated protein (MAP) kinase kinase (MAPKK), which in turn activates MAP kinase.
Purpose of the Study:
- To investigate the role of MAPKK in mediating the cytostatic factor activity of Mos.
- To elucidate the signal transmission pathway involving Mos, MAPKK, and MAP kinase in metaphase arrest.
Main Methods:
- Utilized an anti-MAPKK antibody to specifically inhibit Xenopus MAPKK activity.
- Coinjected bacterially expressed Mos protein and anti-MAPKK antibody into two-cell embryos.
- Analyzed cleavage arrest and MAP kinase activation in injected embryos.
Main Results:
- Inhibition of MAPKK activity prevented Mos-induced cleavage arrest and MAP kinase activation.
- A correlation was observed between the degree of cleavage arrest and MAP kinase activation.
- These findings confirm MAPKK's role in mediating Mos's cytostatic factor activity.
Conclusions:
- MAP kinase kinase (MAPKK) is a key mediator of the cytostatic factor activity of Mos.
- A signal transmission pathway involving Mos, MAPKK, and MAP kinase is implicated in metaphase arrest.
- This pathway is essential for regulating the natural arrest of unfertilized eggs.