Raf-1 protein kinase is important for progesterone-induced Xenopus oocyte maturation and acts downstream of mos.
In somatic cells, the Raf-1 serine/threonine protein kinase is activated by several polypeptide growth factors. We investigated the role of Raf-1 in progesterone-induced meiotic maturation of Xenopus laevis oocytes. Raf-1 enzymatic activity and phosphorylation (reflected by a mobility shift on sodium dodecyl sulfate gels) were increased in oocytes following progesterone stimulation. The increase in Raf-1 activity was concurrent with an elevation in the activity of mitogen-activated protein (MAP) kinase. When RNA encoding an oncogenic form of Raf-1 (v-Raf) was injected into immature oocytes, MAP kinase mobility shift, germinal vesicle breakdown, and histone H1 phosphorylation increased markedly. When RNA encoding a dominant-negative version of Raf-1 was injected, progesterone-induced oocyte maturation was blocked. When RNA encoding Xenopus mos (mosxe) was injected into oocytes, Raf-1 and MAP kinase mobility shifts were observed after several hours. Also, when antisense mosxe oligonucleotides were injected into oocytes, progesterone-induced Raf-1 and MAP kinase mobility shifts were blocked. Finally, when antisense mosxe oligonucleotides were coinjected with v-Raf RNA into oocytes, histone H1 kinase activation, germinal vesicle breakdown, and MAP kinase mobility shift occurred. These findings suggest that Raf-1 activity is required for progesterone-induced oocyte maturation and that Raf-1 is downstream of mosxe activity.
Muslin
A J
AJ
Howard Hughes Medical Institute, Department of Medicine, University of California, San Francisco 94143-0130.
MacNicol
A M
AM
Williams
L T
LT
D000818:Animals; D003001:Cloning, Molecular; D005260:Female; D008540:Meiosis; D051379:Mice; D016297:Mutagenesis, Site-Directed; D009865:Oocytes / Q000254:growth & development*; D010766:Phosphorylation; D011374:Progesterone / Q000502:physiology*; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D017231:Proto-Oncogene Proteins c-mos / Q000235:genetics* / Q000378:metabolism; D019908:Proto-Oncogene Proteins c-raf; D014982:Xenopus laevis
D011518:Proto-Oncogene Proteins; D011374:Progesterone; D017346:Protein Serine-Threonine Kinases; D017231:Proto-Oncogene Proteins c-mos; D019908:Proto-Oncogene Proteins c-raf