Translocation of a store of maternal cytoplasmic c-myc protein into nuclei during early development.
The c-myc proto-oncogene is expressed as a maternal protein during oogenesis in Xenopus laevis, namely, in nondividing cells. A delayed translation of c-myc mRNA accumulated in early oocytes results in the accumulation of the protein during late oogenesis. The oocyte c-myc protein is unusually stable and is located in the cytoplasm, contrasting with its features in somatic cells. A mature oocyte contains a maternal c-myc protein stockpile of 4 x 10(5) to 6 x 10(5) times the level in a somatic growing cell. This level of c-myc protein is preserved only during the cleavage stage of the embryo. Fertilization triggers its rapid migration into the nuclei of the cleaving embryo and a change in the phosphorylation state of the protein. The c-myc protein content per nucleus decreases exponentially during the cleavage stage until a stoichiometric titration by the embryonic nuclei is reached during a 0.5-h period at the midblastula stage. Most of the maternal c-myc store is degraded by the gastrula stage. These observations implicate the participation of c-myc in the events linked to early embryonic development and the midblastula transition.
Gusse
M
M
Institut Jacques Monod, Centre National de la Recherche Scientifique, Paris, France.
Ghysdael
J
J
Evan
G
G
Soussi
T
T
Méchali
M
M
D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism; D004625:Embryo, Nonmammalian / Q000502:physiology*; D005260:Female; D007124:Immunoenzyme Techniques; D009865:Oocytes / Q000378:metabolism*; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational; D011505:Protein-Tyrosine Kinases / Q000235:genetics; D011518:Proto-Oncogene Proteins / Q000032:analysis / Q000235:genetics*; D016271:Proto-Oncogene Proteins c-myc; D011519:Proto-Oncogenes; D014982:Xenopus laevis
D011518:Proto-Oncogene Proteins; D016271:Proto-Oncogene Proteins c-myc; D011505:Protein-Tyrosine Kinases