Protein synthesis is not involved in initiation or amplification of the maturation-promoting factor (MPF) in starfish oocytes

Abstract

1-Methyladenine (1-MeAde) induces the appearance in cytoplasm of starfish oocytes of an autocatalytic and amplifiable factor (MPF: maturation promoting factor) which brings about meiosis reinitiation when transferred in immature oocytes. Although previous work demonstrated that full amplification of MPF does not occur in the absence of germinal vesicle material, and that significant enhancement of protein synthesis due to hormone application begins just after germinal vesicle breakdown (GVBD), it was found that 1-MeAde induces GVBD even in the absence of protein synthesis. On the other hand, 1-MeAde readily stimulates protein synthesis even in anucleate fragments obtained from immature oocytes. MPF already reaches its maximal activity at the beginning of GVBD, thus before significant enhancement of protein synthesis. Finally MPF is amplified to the same extent in Marthasterias glacialis oocytes treated or not with 100 μg/ml cycloheximide, which completely suppresses protein synthesis. These findings make very unlikely that protein synthesis might be involved in either initiation or amplification of MPF in starfish oocytes.