Cyclin B/p34cdc2 triggers phosphorylation of DNA ligase I during Xenopus laevis oocyte maturation.
Phosphorylation of DNA ligase I has been analyzed during Xenopus laevis early development. The enzyme, which is involved in DNA replication and DNA repair events, is accumulated during oogenesis to reach a maximum in the stage VI oocyte, and remains at a constant level during maturation. When maturation of the oocyte is induced (in vivo or in vitro), this leads to a post-translational modification of the protein. In stage VI oocytes, a DNA ligase I of apparent molecular mass 180 kDa is detected immunologically whereas a 190-kDa form is found in unfertilized eggs and persists until the tadpole stage. This modification is due to phosphorylation performed by a protein kinase that is turned on 3-4 h after induction of the maturation. Activation of the kinase requires protein synthesis, and appearance of phosphorylated DNA ligase coincides with activation of histone H1 kinase activity. Induction of DNA ligase I modification and maturation are induced in the absence of protein synthesis following injection of maturation promoting factor into oocytes. Immunoprecipitated oocyte DNA ligase I is phosphorylated and its molecular mass modified by purified cyclin B/p34cdc2 in vitro. DNA ligase I phosphorylation is not induced in oocyte extract where only mitogen-activated-protein kinase is induced. Phosphorylation of DNA ligase I induced by cdc2 kinase occurs at the time new DNA replication and recombination activities appear in eggs.
Aoufouchi
S
S
Département de Biologie et Génétique du Développement, CNRS URA 256, Université de Rennes 1, France.
Prigent
C
C
Ford
C
C
Thiebaud
P
P
Philippe
M
M
Theze
N
N
D000818:Animals; D016203:CDC2 Protein Kinase / Q000502:physiology*; D016213:Cyclins / Q000502:physiology*; D000072481:DNA Ligase ATP; D011088:DNA Ligases / Q000378:metabolism*; D005260:Female; D007814:Larva / Q000254:growth & development; D009865:Oocytes / Q000166:cytology / Q000201:enzymology*; D009866:Oogenesis; D010766:Phosphorylation; D014982:Xenopus laevis
D016213:Cyclins; D016203:CDC2 Protein Kinase; D011088:DNA Ligases; D000072481:DNA Ligase ATP