Elongation factor 1α (EF-1α) is concentrated in the Balbiani body and accumulates coordinately with the ribosomes during oogenesis of Xenopus laevis

Abstract

In Xenopus laevis oocytes two distinct systems catalyze the mRNA-dependent binding of aminoacyl tRNA to the A site of ribosomes. These systems are elongation factor 1α (EF-1α) and the 42S nucleoprotein particle. This particle is also implicated in the long-term storage of 5S RNA and aminoacyl tRNA during early oogenesis. We report here that the ribosomes and the storage particles are distributed uniformly in the cytoplasm of previtellogenic (stage I) oocytes. In contrast, EF-1α is concentrated in a small region of the cytoplasm, known as the mitochondrial mass or Balbiani body. When the Balbiani body disperses in early vitellogenic oocytes (stage II), EF-1α becomes evenly distributed in the cytoplasm. The main phase of EF-1α accumulation follows the disappearance of the 42S particles (stage II), but coincides with the main phase of ribosome accumulation (stages III and IV).