Meiotic initiation by the mos protein in Xenopus

Nature. 1992 Feb 13;355(6361):649-52. doi: 10.1038/355649a0.


When fully grown Xenopus oocytes are stimulated by progesterone, a period of protein synthesis is necessary for maturation. Synthesis of the mos proto-oncogene product, pp39mos, is necessary for the activation of M-phase promoting factor (MPF) in meiosis I. On the basis that mos is translated de novo on hormonal stimulation of Xenopus oocytes and that injecting mos RNA into oocytes induces their maturation, we have proposed that the mos protein is a candidate initiator of oocyte maturation, needed to trigger the conversion of precursor MPF into its active form. To determine whether mos is the only protein required for initiating maturation, we have produced a soluble, active recombinant mos protein and injected it into Xenopus oocytes. We report here that in the absence of protein synthesis that mos protein efficiently induces germinal vesicle breakdown and the activation of MPF. The oocytes, however, do not proceed into meiosis II. Thus, the mos protein fulfills the requirements of an initiator protein, but the synthesis of one or more additional proteins may be necessary to complete oocyte maturation.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Cycloheximide / pharmacology
  • Female
  • Genetic Vectors
  • Humans
  • In Vitro Techniques
  • Infant, Newborn
  • Isopropyl Thiogalactoside / pharmacology
  • Maturation-Promoting Factor / physiology
  • Meiosis / physiology*
  • Oocytes / drug effects
  • Oocytes / physiology
  • Oogenesis / physiology
  • Progesterone / pharmacology
  • Promoter Regions, Genetic / drug effects
  • Promoter Regions, Genetic / physiology
  • Proto-Oncogene Proteins / physiology*
  • Proto-Oncogene Proteins c-mos
  • Recombinant Fusion Proteins / pharmacology
  • Xenopus


  • Proto-Oncogene Proteins
  • Recombinant Fusion Proteins
  • Isopropyl Thiogalactoside
  • Progesterone
  • Cycloheximide
  • Proto-Oncogene Proteins c-mos
  • Maturation-Promoting Factor