EXPRESSION OF THE CELL-CYCLE CONTROL PROTEIN CDC25 IN CLEAVAGE STAGE BOVINE EMBRYOS

We have examined the synthesis and expression of a homologue of the ce ll cycle control protein cdc25 by early cleavage stage bovine embryos. cdc25 is the protein phosphatase responsible for activating p34(cdc2) by dephosphorylating the threonine 14 (Thr 14) and tyrosine 15 (Tyr 1 5) residues of p34(cdc2) Human cdc25 antibody was utilised in western blots and immunoprecipitations to examine the presence and synthesis o f cdc25 in bovine embryos. cdc25 is present as a 52 kDa non-phosphoryl ated and a 66 kDa presumably phosphorylated form in bovine 1-, 2-, 4- and 8-cell embryos. However, cdc25 is actively synthesised only in 8-c ell embryos, indicating that the cdc25 present prior to this stage is inherited from the oocyte. In addition, the synthesis of cdc25 was ind uced in 2-cell embryos in which cleavage was blocked with the DNA synt hesis inhibitor aphidicolin.