Gusse M, Ghysdael J, Evan G, Soussi T, Méchali M
Institut Jacques Monod, Centre National de la Recherche Scientifique, Paris, France.
Mol Cell Biol. 1989 Dec;9(12):5395-403. doi: 10.1128/mcb.9.12.5395-5403.1989.
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.
在非洲爪蟾的卵子发生过程中，即非分裂细胞中，原癌基因c-myc作为母源蛋白表达。早期卵母细胞中积累的c-myc mRNA延迟翻译导致该蛋白在卵子发生后期积累。卵母细胞中的c-myc蛋白异常稳定，位于细胞质中，这与其在体细胞中的特征形成对比。成熟卵母细胞中母源c-myc蛋白的储备量是体细胞生长细胞中水平的4×10⁵至6×10⁵倍。这种c-myc蛋白水平仅在胚胎的卵裂阶段得以保留。受精触发其迅速迁移至卵裂胚胎的细胞核中，并导致该蛋白磷酸化状态发生变化。在卵裂阶段，每个细胞核中的c-myc蛋白含量呈指数下降，直到在囊胚中期的0.5小时内达到胚胎细胞核的化学计量滴定。大部分母源c-myc储备在原肠胚阶段被降解。这些观察结果表明c-myc参与了与早期胚胎发育和囊胚中期转变相关的事件。
