Cyclin A2 is phosphorylated during the G2/M transition in mouse two-cell embryos.
In the present study, we investigated the expression of cyclin A2 in mouse two-cell embryos to elucidate the role of cyclin A2 at the G2/M transition. Two forms of cyclin A2 on SDS-PAGE (an upper and a lower band) were detected in two-cell embryos synchronized at the M phase by nocodazole. To investigate the nature of this shift, embryos synchronized at the M phase were treated with alkaline phosphatase (AP). The upper band of cyclin A2 was fainter in AP-treated embryos than in nontreated embryos. This result indicates that cyclin A2 in mouse two-cell embryos is phosphorylated and the band on SDS-PAGE shifts up during the G2/M transition. In addition, we examined the sequential expression of cyclin A2 in two-cell blocked embryos after OA treatment. The upper band of cyclin A2 was first detected at 2 hr after the treatment, corresponding to the timing of Cdc2 kinase activation. In two-cell embryos after removal from nocodazole treatment, the phosphorylated form of cyclin A2 protein decreased abruptly just before cytokinesis. These results suggest that the mechanism of cyclin A2 degradation in mouse two-cell embryos may be different from that in somatic cells.
Laboratory of Reproductive Biology, Graduate School of Agriculture, Kyoto University, Kyoto, Japan.
Akihiro
A
Ohashi
Hiroshi
H
Imai
Naojiro
N
Minami
D000818:Animals; D016203:CDC2 Protein Kinase / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects; D019925:Cyclin A / Q000378:metabolism*; D004622:Embryo, Mammalian / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D016195:G2 Phase / Q000187:drug effects; D051379:Mice; D008938:Mitosis / Q000187:drug effects; D015739:Nocodazole / Q000494:pharmacology; D019319:Okadaic Acid / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects
D019925:Cyclin A; D019319:Okadaic Acid; D016203:CDC2 Protein Kinase; D015739:Nocodazole