Localization and dynamics of Cdc2-cyclin B during meiotic reinitiation in starfish oocytes.
The Cdc2-cyclin B kinase has a central role in regulating the onset of M phase. In starfish oocytes, Cdc2-cyclin B begins to be activated approximately 10 min after application of maturation hormone, followed by accumulation in the nucleus then nuclear envelope breakdown. By immunofluorescence and by expressing a green fluorescent (GFP) chimera of cyclin B, we find that cyclin B is present in aggregates in the cytoplasm of immature oocytes. The aggregates disperse at approximately 10 min, suggesting that the dispersal is closely related to the activation of the kinase. Using cyclin B-GFP, the dispersion begins from the region containing the centrosomes. Extractability of Cdc2-cyclin B changes with similar kinetics during maturation. Active Cdc25 phosphatase released Cdc2-cyclin B from the detergent-insoluble fraction independently of its phosphatase activity. Live cell imaging also showed that Cdc2-cyclin B begins to accumulate in the nucleus before changes in nuclear pore permeability, consistent with Cdc2-cyclin B-induced disassembly of the pores.
Terasaki
Mark
M
Department of Physiology, University of Connecticut Health Center, Farmington, Connecticut 06032, USA. terasaki@neuron.uchc.edu
Okumura
Ei-Ichi
E
Hinkle
Beth
B
Kishimoto
Takeo
T
D000818:Animals; D016203:CDC2 Protein Kinase / Q000378:metabolism*; D002458:Cell Fractionation; D002467:Cell Nucleus / Q000378:metabolism; D019926:Cyclin B / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism*; D049452:Green Fluorescent Proteins; D008164:Luminescent Proteins; D008845:Microinjections; D008856:Microscopy, Fluorescence; D008938:Mitosis; D009865:Oocytes / Q000166:cytology / Q000378:metabolism*; D013215:Starfish / Q000196:embryology / Q000378:metabolism*; D020687:cdc25 Phosphatases / Q000378:metabolism
D019926:Cyclin B; D008164:Luminescent Proteins; D049452:Green Fluorescent Proteins; D016203:CDC2 Protein Kinase; D020687:cdc25 Phosphatases