Mos proto-oncogene function during oocyte maturation in Xenopus.
The function of the Xenopus c-mos proto-oncogene product (Mos(xe)) has been investigated during oocyte maturation. Experiments with a new antibody able to immunoblot Mos(xe) demonstrated the time course of MAP kinase (MAP K) activation in oocytes paralleled Mos(xe) accumulation, and in activated eggs the deactivation of MAP K paralleled the degradation of Mos(xe). Ablation of Mos synthesis by microinjection of antisense oligodeoxynucleotides abolished activation of MAP K by progesterone, but microinjection of GST-Mos fully restored both MAP K activation and germinal vesicle breakdown (GVBD). The Mos(xe) level at metaphase of Meiosis I (MI) was 2 - 3-fold less than that at metaphase of Meiosis II (MII), but MAP K activation was maximal at metaphase in both MI and MII. In the transition between MI and MII, both cyclin B and Mos(xe) levels rapidly declined in the presence of cycloheximide and injection of exogenous GST-Mos(xe) did not prevent degradation of either protein, although MAP K was activated. Microinjection of GST-Mos(xe) into oocytes was able to activate MAP K before GVBD and H1 kinase activation, and microinjection of constitutively-activated thiophosphorylated MAP K induced de novo synthesis of Mos(xe) before H1 kinase activation, suggesting the existence of a positive feedback loop between MAP K and Mos(xe) accumulation.
Roy
L M
LM
Howard Hughes Medical Institute, University of Colorado School of Medicine, Denver, 80262, USA.
Haccard
O
O
Izumi
T
T
Lattes
B G
BG
Lewellyn
A L
AL
Maller
J L
JL
D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D004789:Enzyme Activation; D005260:Female; D016258:Genes, mos; D008540:Meiosis / Q000502:physiology; D008677:Metaphase / Q000502:physiology; D017232:Oncogene Proteins v-mos / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D009865:Oocytes / Q000166:cytology / Q000201:enzymology / Q000502:physiology*; D014982:Xenopus laevis
D017232:Oncogene Proteins v-mos; D017871:Calcium-Calmodulin-Dependent Protein Kinases