Int. J. Dev. Biol. 37: 595 - 600 (1993)

Vol 37, Issue 4

Kinetics of MPF and histone H1 kinase activity differ during the G2- to M-phase transition in mouse oocytes

Published: 1 December 1993

T Jung, R M Moor and J Fulka

Department of Molecular Embryology, Institute of Animal Physiology and Genetics Research, Cambridge, United Kingdom.

Abstract

Maturation promoting factor (MPF) is universally recognized as the biological entity responsible for driving the cell cycle from G2- to M-phase. Histone H1 kinase activity is widely accepted as a biochemical indicator of p34cdc2 protein kinase complex activity and therefore MPF activity. In this paper we present results which indicate that during the G2- to M-phase transition in mouse oocytes the dynamic of p34cdc2 related histone H1 kinase activity differs markedly from the biological activity of MPF as measured by classical cell fusion procedures. MPF is activated just before germinal vesicle breakdown (GVBD) whereas histone H1 kinase is activated 5-7 h later coincident with the formation of the definitive first metaphase plate. The biological activity of MPF is merely reduced to about 50% of control levels by a short period of protein synthesis inhibition (1-2 h) and completely suppressed after a prolonged period of inhibition (4-5 h). By contrast, inhibition of protein synthesis in mouse oocytes results in a rapid and complete suppression of histone H1 kinase activity. Therefore, biological MPF and histone H1 kinase activity should not be used in an interchangeable manner during the G2- to M-phase transition in mouse oocytes.