ASSOCIATION OF P34(CDC2) AND CYCLIN B1 DURING MEIOTIC MATURATION PORCINE OOCYTES

The relative levels and association of p34(cdc2) and cyclin B1 have be en determined in pig oocytes during meiotic progression from G2 to met aphase II (MII). Fully grown G2-arrested porcine oocytes contained lar ge amounts of free p34(cdc2) and extremely small amounts of p34(cdc2)- cyclin B1 complex which did not increase in amount during the GV stage . Cyclin B1 is not synthesized in measurable quantities until 23 hr af ter the start of maturation. During the first metaphase (MI) the amoun t of both cyclin BI and the p34(cdc)-cyclin B1 complex increased sharp ly until 35 hr. Thereafter the amount of the p34(cdc2)-cyclin B1 compl ex increased again to 45 hr, resulting in higher levels of the complex in MII than in MI. Moreover, three distinct migration forms of p34(cd c2) Were detected in pig oocytes by immunoblotting with anti-PSTAIRE a ntibody, and most of the cyclin B1-associated p34(cdc2) was detected i n the lower band in MI oocytes but migrated in the second band during MII. These results suggest that cyclin B1 levels in porcine oocytes di ffer from those in starfish, clam, and Xenopus oocytes in which consid erably higher concentrations of cyclin B1 appear to be present during the GV stage and that the nature of the association between p34(cdc2) and cyclin B1 changes between the first and the second metaphase. (C) 1995 Academic Press, Inc.