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Mol Cell Biol 1995 Dec 01;1512:6686-93. doi: 10.1128/MCB.15.12.6686.
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Regulation of Raf-1-dependent signaling during early Xenopus development.

MacNicol AM , Muslin AJ , Howard EL , Kikuchi A , MacNicol MC , Williams LT .

The Raf-1 gene product is activated in response to cellular stimulation by a variety of growth factors and hormones. Raf-1 activity has been implicated in both cellular differentiation and proliferation. We have examined the regulation of the Raf-1/MEK/MAP kinase (MAPK) pathway during embryonic development in the frog Xenopus laevis. We report that Raf-1, MEK, and MAPK activities are turned off following fertilization and remain undetectable up until blastula stages (stage 8), some 4 h later. Tight regulation of the Raf-1/MEK/MAPK pathway following fertilization is crucial for embryonic cell cycle progression. Inappropriate reactivation of MAPK activity by microinjection of oncogenic Raf-1 RNA results in metaphase cell cycle arrest and, consequently, embryonic lethality. Our findings demonstrate an absolute requirement, in vivo, for inactivation of the MAPK signaling pathway to allow normal cell cycle progression during the period of synchronous cell divisions which occur following fertilization. Further, we show that cytostatic factor effects are mediated through MEK and MAPK.

PubMed ID: 8524233
PMC ID: PMC230921
Article link: Mol Cell Biol

Species referenced: Xenopus laevis
Genes referenced: mapk1 raf1

References [+] :
App, Epidermal growth factor (EGF) stimulates association and kinase activity of Raf-1 with the EGF receptor. 1991, Pubmed