Meijer Laurent

Hepatocytes: A suitable cell system for studying the control mechanisms of cell cycle progression in mammalians

Dur ing f i rs t meiot ic cell cycle cycl in B is the most p r o m i n e n t l y syn the s i zed pro te in , a l though an impor t an t s tockpi le of cyclin was already present in the oocyte and meios is re in i t ia t ion does not require cycl in synthes is . At the t ime of first polar body emission the whole amount of cycl in has been destroyed, what does not support the view that cycl in B could be synthesized in advance during first cycle to allow a rapid entry into second cycle. As stockpile cycl in B begins degrada t ion long before IVletaphase, the p rominen t neosynthes is al lows to maintain a mitot ic state and gives the cell t ime enough to bring about events of d iac ines i s , p rome taphase and metaphase entry. We have shown that a nuclear factor, different from cyclin B mRNA, is r equ i r ed for e n h a n c e d cyc l in B n e o s y n t h e s i s af ter Germinal Vesicle Breakdown. REGULATION OF CYCLIN PI~,OTEOLYSIS