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BOR - Papers in Press, published online ahead of print May 19, 2004.
Biol Reprod 2004, 10.1095/biolreprod.104.029611
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BIOLOGY OF REPRODUCTION 71, 894–900 (2004)
DOI: 10.1095/biolreprod.104.029611
© 2004 by the Society for the Study of Reproduction, Inc.

Ovary

Cdc2-Cyclin B–Induced G2 to M Transition in Perch Oocyte Is Dependent on Cdc251

Dipanjan Basu3, A.K. Navneet4, Subrata Dasgupta3, and Samir Bhattacharya2,4

Department of Zoology,3 School of Life Science, Visva-Bharati, Santiniketan 731 235, India Molecular Endocrinology Division,4 Indian Institute of Chemical Biology, Jadavpur, Kolkata 700 032, India

The G2 to M phase transition in perch oocytes is regulated by maturation promoting factor (MPF), a complex of Cdc2 and cyclin B. In Anabas testudineus, a fresh water perch, 17{alpha},20ß-dihydroxy-4-pregnen-3-one, the maturation inducing hormone (MIH), induced complete germinal vesicle breakdown (GVBD) of oocytes at 21 h. An unusual cyclin, p30 cyclin B, has been identified in oocyte extract using both monoclonal and polyclonal antibodies. Surprisingly, Cdc2 could not be identified, although a Northern blot with Cdc2 cDNA demonstrated expression of the gene. Purification of MPF through an immunoaffinity column followed by SDS-PAGE showed three proteins, Cdc2, cyclin B, and a 20 kDa fragment, indicating earlier failure in immunodetection may be due to the interference by this fragment. In uninduced oocytes, p30 cyclin B was present, and its expression was increased by MIH. MIH increased p30 cyclin B accumulation at 3 h, a high level which was maintained between 9 and 21 h, but an effective increase in GVBD and H1 kinase activation could only be observed between 15 and 21 h. This delay in active MPF formation was found to be related to the activation of Cdc25, phosphorylation of which was detected at 12 h, and a substantial increase occurred during 15–18 h. Sodium orthovanadate, a tyrosine phosphatase inhibitor, inhibited H1 kinase activity and GVBD, suggesting the requirement of Cdc25 activity in MPF activation. Our results show occurrence of pre-MPF in uninduced oocytes and its conversion to active MPF requires dephosphorylation by Cdc25, the existence of which has not yet been shown in fish.

1 Supported by the Department of Biotechnology, Government of India, and the Council of Scientific and Industrial Research, New Delhi, India.

2 Correspondence. FAX: 91 33 2473 0284; samir{at}iicb.res.in






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Copyright © 2004 by the Society for the Study of Reproduction.