Temporal relationship between histone H1 kinase activity and maturation promoting factor activity during mouse oocyte maturation

Abstract

The present study examines whether the histone Hl kinase activity may alter as a function of specific stages of mouse oocyte meiotic maturation and whether changes in histone Hl kinase activity are associated with those in maturation promoting factor (MPF) activity. The histone Hl kinase activity was determined in 20 pl of final volume containing 10 |jl of oocyte extracts, 1 pg/ml histone Hl as substrate and 2-5 gCi [y-32P]ATP in 100 mM non-radioactive ATP. Samples were loaded on 18% SDS-polyacrylamide separation gel, and the phosphorylated histone Hl was visualized by autoradiography. The MPF activity in vivo was determined by microinjection of cytoplasmic fractions (？ 10 pl) taken from donor oocytes into germinal vesicle (GV)-arrested oocytes, and then the percent (%) of germinal vesicle breakdown (GVBD) was scored at 2 and 4 h after culture in vitro. Donor oocytes were oocytes with GV, GVBD, nuclear membrane produced by puromycin treatment (50 |ig/ml) and nuclear membrane dissolution (NMD). The MPF activity appeared at the time of GVBD and increased during metaphase. The profiles of MPF activity change during metaphase II and NMD were similar to those of GVBD. The histone Hl kinase activity of mouse oocytes in vitro also increased in GVM phase transition and decreased after M-phase. These data indicate that the alteration in histone Hl kinase activity appears to be in parallel with that of MPF activity during mouse oocyte maturation.