p70S6K Controls Selective mRNA Translation during Oocyte Maturation and Early Embryogenesis in Xenopus laevis
AUTOR(ES)
Schwab, Markus S.
FONTE
American Society for Microbiology
RESUMO
In mammalian cells, p70S6K plays a key role in translational control of cell proliferation in response to growth factors. Because of the reliance on translational control in early vertebrate development, we cloned a Xenopus homolog of p70S6K and investigated the activity profile of p70S6K during Xenopus oocyte maturation and early embryogenesis. p70S6K activity is high in resting oocytes and decreases to background levels upon stimulation of maturation with progesterone. During embryonic development, three peaks of activity were observed: immediately after fertilization, shortly before the midblastula transition, and during gastrulation. Rapamycin, an inhibitor of p70S6K activation, caused oocytes to undergo germinal vesicle breakdown earlier than control oocytes, and sensitivity to progesterone was increased. Injection of a rapamycin-insensitive, constitutively active mutant of p70S6K reversed the effects of rapamycin. However, increases in S6 phosphorylation were not significantly affected by rapamycin during maturation. mos mRNA, which does not contain a 5′-terminal oligopyrimidine tract (5′-TOP), was translated earlier, and a larger amount of Mos protein was produced in rapamycin-treated oocytes. In fertilized eggs rapamycin treatment increased the translation of the Cdc25A phosphatase, which lacks a 5′-TOP. Translation assays in vivo using both DNA and RNA reporter constructs with the 5′-TOP from elongation factor 2 showed decreased translational activity with rapamycin, whereas constructs without a 5′-TOP or with an internal ribosome entry site were translated more efficiently upon rapamycin treatment. These results suggest that changes in p70S6K activity during oocyte maturation and early embryogenesis selectively alter the translational capacity available for mRNAs lacking a 5′-TOP region.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=84041Documentos Relacionados
- Identification and early activation of a Xenopus laevis p70s6k following progesterone-induced meiotic maturation.
- Cap ribose methylation of c-mos mRNA stimulates translation and oocyte maturation in Xenopus laevis.
- A novel regulatory element determines the timing of Mos mRNA translation during Xenopus oocyte maturation
- Rabies mRNA translation in Xenopus laevis oocytes.
- The Mitogen-Activated Protein Kinase Signaling Pathway Stimulates Mos mRNA Cytoplasmic Polyadenylation during Xenopus Oocyte Maturation