| Research Abstract |
This study was undertaken to investigate molecular mechanisms of the initiation of cyclin BETA mRNA translation during oocyte maturation, with special reference to the following three subjects.
1) Significance of cyclin BETA translation during oocyte maturation
Our previous finding that cyclin BETA mRNA translation is necessary for initiating goldfish oocyte maturation has been also confirmed for other species, including fishes other than goldfish and amphibians (frog, toad and newt) except for Xenopus laevis, suggesting the general adoption of this mechanism in lower vertebrates.
2) Identification of cyclin BETA mRNA-binding proteins and the effect of hormone on translation.
An attempt to identify cyclin BETA mRNA-binding protein purified with a biotin-labeled RNA affinity chromatography was unsuccessful because of the poor yield. To examine the effect of hormonal stimulation on the translational control, we injected cyclin BETA mRNA into honnone-treated oocytes. We found that the progression of oocyte maturation induced by the injection of cyclin BETA mRNA occurred earlier than that induced by the hormone, but later than that induced by the injection cyclin BETA protein. These results indicate that the hormonal treatment enhances the synthesis of cyclin BETA protein from the injected mRNA.
3) Involvement of known proteins in cyclin BETA mRNA translational initiation
To investigate the functions during oocyte maturation of proteins that have been already suggested to be translational regulators in other systems, we have isolated cDNA clones and produced antibodies against their products. Those include cytoplasmic polyadenylation element-binding-protein (CPEB), Nanos, Pumilio, poly(A) polymerase, poly(A) binding proteins, Y-box proteins. We have shown that Y-box proteins and Pumilio are a cyclin B mRNA-binding protein, suggesting the involvement of these proteins in the translational control during oocyte maturation.
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