The cyclin B2 component of MPF is a substrate for the c-mos(xe) proto-oncogene product.
Previous studies from this laboratory have shown that purified MPF from Xenopus eggs contains cyclin B2 complexed with cdc2 kinase. The activation of MPF during oocyte maturation is known to require expression of the c-mos(xe) proto-oncogene. We show here that immunoprecipitates of either v-mos from Moloney murine sarcoma virus-transformed NIH 3T3 cells or c-mos from Xenopus eggs phosphorylate cyclin B2 in vitro. Phosphopeptide analysis reveals a pattern similar to that observed with cdc2 kinase. Moreover, ablation of c-mos(xe) from oocytes by antisense oligonucleotide injection reduces the rate of cyclin B2 phosphorylation in oocyte extracts by 40%. These results suggest that the mechanism of activation of MPF by c-mos(xe) involves phosphorylation of the cyclin component.
Roy
L M
LM
Department of Pharmacology, University of Colorado School of Medicine, Denver 80262.
Singh
B
B
Gautier
J
J
Arlinghaus
R B
RB
Nordeen
S K
SK
Maller
J L
JL
D000818:Animals; D002453:Cell Cycle / Q000502:physiology; D016213:Cyclins; D006133:Growth Substances / Q000378:metabolism*; D007447:Invertebrate Hormones / Q000378:metabolism*; D016200:Maturation-Promoting Factor; D009841:Oligonucleotides; D016376:Oligonucleotides, Antisense; D017232:Oncogene Proteins v-mos; D009865:Oocytes / Q000378:metabolism; D010766:Phosphorylation; D011494:Protein Kinases / Q000502:physiology*; D011518:Proto-Oncogene Proteins / Q000502:physiology*; D017231:Proto-Oncogene Proteins c-mos; D015682:Retroviridae Proteins, Oncogenic / Q000502:physiology; D014981:Xenopus
D016213:Cyclins; D006133:Growth Substances; D007447:Invertebrate Hormones; D009841:Oligonucleotides; D016376:Oligonucleotides, Antisense; D017232:Oncogene Proteins v-mos; D011518:Proto-Oncogene Proteins; D015682:Retroviridae Proteins, Oncogenic; D011494:Protein Kinases; D017231:Proto-Oncogene Proteins c-mos; D016200:Maturation-Promoting Factor