Human retinoblastoma protein (Rb) is phosphorylated by cdc2 kinase and MAP kinase in Xenopus maturing oocytes.
Xenopus oocyte meiotic maturation combines features of G0/G1 and G2/M transitions of the cell cycle. To study the in ovo Rb kinase activity, we have microinjected human Rb into oocytes. Microinjected human Rb localizes into the nucleus, is hypophosphorylated in prophase oocytes, becomes hyperphosphorylated during meiotic maturation and is dephosphorylated as the cell reenters interphase. Inactivation or overexpression of the cyclin D-cdk4/6 complex in an oocyte extract does not affect the Rb kinase activity. This kinase activity could be attributed to both cdc2-cyclin B and MAP kinase, opening new perspectives of investigation in somatic cells.
Taieb
F
F
Laboratoire de Physiologie de la Reproduction, INRA/URA-CNRS 1449, Université Pierre et Marie Curie, Paris, France.
Karaiskou
A
A
Rime
H
H
Jessus
C
C
D000818:Animals; D016203:CDC2 Protein Kinase / Q000378:metabolism*; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D002453:Cell Cycle / Q000502:physiology; D019926:Cyclin B / Q000502:physiology; D056741:Cyclin D; D016213:Cyclins / Q000378:metabolism; D004789:Enzyme Activation / Q000502:physiology; D005260:Female; D006657:Histones / Q000378:metabolism; D006801:Humans; D008540:Meiosis / Q000502:physiology; D008845:Microinjections; D004676:Myelin Basic Protein / Q000378:metabolism; D009865:Oocytes / Q000201:enzymology / Q000502:physiology*; D010766:Phosphorylation; D011494:Protein Kinases / Q000502:physiology; D011994:Recombinant Proteins / Q000378:metabolism; D016160:Retinoblastoma Protein / Q000378:metabolism*; D014982:Xenopus laevis
D019926:Cyclin B; D056741:Cyclin D; D016213:Cyclins; D006657:Histones; D004676:Myelin Basic Protein; D011994:Recombinant Proteins; D016160:Retinoblastoma Protein; D011494:Protein Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D016203:CDC2 Protein Kinase