Dispersion of cyclin B mRNA aggregation is coupled with translational activation of the mRNA during zebrafish oocyte maturation.
Cyclin B mRNA stored in immature zebrafish oocytes is translationally activated upon the stimulation of 17alpha,20beta-dihydroxy-4-pregnen-3-one (17alpha,20beta-DP), an event prerequisite for initiating oocyte maturation in this species. We investigated localization of cyclin B mRNA in zebrafish oocytes. Cyclin B mRNA was found to be exclusively localized as an aggregation along the cytoplasm at the animal pole of full-grown immature oocytes. When oocytes were treated with 17alpha,20beta-DP, a meshwork of microfilaments in the oocyte cortex disappeared and the aggregation of cyclin B mRNA dispersed just prior to the initiation of cyclin B synthesis and germinal vesicle breakdown (GVBD). Cytochalasin B, but not nocodazole or taxol, deformed the aggregation of cyclin B mRNA, indicating the involvement of microfilaments in organizing this form. Like 17alpha,20beta-DP, cytochalasin B (10 microg/ml) induced both complete dispersion of the aggregation and translational activation of cyclin B mRNA, forcing the oocytes to undergo GVBD without 17alpha,20beta-DP. Conversely, disturbance of the aggregation of cyclin B mRNA with a low concentration (1 microg/ml) of cytochalasin B inhibited 17alpha,20beta-DP-induced GVBD. These results suggest that the direct change in cyclin B mRNA from the aggregated form to the dispersed form is responsible for translational activation of the mRNA during zebrafish oocyte maturation.
Kondo
T
T
Laboratory of Molecular and Cellular Interactions, Graduate School of Science, Sapporo, 060-0810, Japan.
Kotani
T
T
Yamashita
M
M
D000818:Animals; D016203:CDC2 Protein Kinase / Q000378:metabolism; D019926:Cyclin B / Q000235:genetics*; D003571:Cytochalasin B / Q000494:pharmacology; D005260:Female; D018507:Gene Expression Regulation, Developmental; D006908:Hydroxyprogesterones / Q000494:pharmacology; D009865:Oocytes / Q000187:drug effects / Q000502:physiology*; D014176:Protein Biosynthesis / Q000187:drug effects; D012333:RNA, Messenger / Q000187:drug effects / Q000378:metabolism*; D014158:Transcription, Genetic; D015027:Zebrafish
D019926:Cyclin B; D006908:Hydroxyprogesterones; D012333:RNA, Messenger; C021012:17 alpha,20 beta-dihydroxypregn-4-en-3-one; D003571:Cytochalasin B; D016203:CDC2 Protein Kinase