PROTEIN-PHOSPHORYLATION PATTERNS DURING IN-VITRO MATURATION OF THE GOAT OOCYTE

Protein phosphorylation patterns were studied by radiolabelling goat c umulus oocyte complexes with [P-32] orthophosphate for various periods of time. The radiolabelled denuded oocytes were assessed for nuclear status and were used individually for gel electrophoresis. This study demonstrated that specific changes in protein phosphorylations were pr ogrammed during goat oocyte maturation. One of the most prominent chan ges was a general increase in the phosphorylation rate at germinal ves icle breakdown (GVBD). From 8 hr of culture, dominant phosphoprotein b ands with apparent molecular weights of 27, 31, 40, and 50 kD were obs erved; they remained at this level until the metaphase II stage. In th e molecular weight range of 65-80 kD, the protein phosphorylation patt ern exhibited characteristic differences, with a complex series of pho sphoproteins appearing and disappearing, during maturation. Addition o f 6-dimethylaminopurine (6-DMAP) at the onset of culture blocked the m aturation process after GVBD and induced a dramatic condensation of ch romatin. When added at different times after GVBD, 6-DMAP invariably i nduced chromosome condensation. This inhibition was partly reversible; i.e., after removal of the drug, oocytes were able to progress only u ntil metaphase I. (C) 1993 Wiley-Liss, Inc.