Geminin stabilizes Cdt1 during meiosis in Xenopus oocytes.
During the mitotic cell cycle, Geminin can act both as a promoter and inhibitor of initiation of DNA replication. As a promoter, Geminin stabilizes Cdt1 and facilitates its accumulation leading to the assembly of the pre-replication complex on DNA. As an inhibitor, Geminin prevents Cdt1 from loading the mini-chromosome maintenance complex onto pre-replication complexes in late S, G(2), and M phases. Here we show that during meiosis Geminin functions as a stabilizer of Cdt1 promoting its accumulation for the early division cycles of the embryo. Depletion of Geminin in Xenopus immature oocytes leads to a decrease of Cdt1 protein levels during maturation and after activation of these oocytes. Injection of exogenous recombinant Geminin into the depleted oocytes rescues Cdt1 levels demonstrating that Geminin stabilizes Cdt1 during meiosis and after fertilization. Furthermore, Geminin-depleted oocytes did not replicate their DNA after meiosis I indicating that Geminin does not act as an inhibitor of initiation of DNA replication between meiosis I and meiosis II.
Narasimhachar
Yadushyla
Y
Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, Lubbock, Texas 79430, USA. yadushyla.narasimhachar@ttuhsc.edu
Coué
Martine
M
D000818:Animals; D018797:Cell Cycle Proteins / Q000737:chemistry / Q000378:metabolism*; D003513:Cycloheximide / Q000494:pharmacology; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D005306:Fertilization; D064248:Geminin; D007267:Injections; D008540:Meiosis; D009865:Oocytes / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D055550:Protein Stability / Q000187:drug effects; D011994:Recombinant Proteins / Q000008:administration & dosage / Q000494:pharmacology; D013997:Time Factors; D014981:Xenopus / Q000196:embryology / Q000378:metabolism*; D029867:Xenopus Proteins / Q000737:chemistry / Q000172:deficiency / Q000378:metabolism*
C406819:Cdt1 protein, Xenopus; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; C577998:GMNN protein, Xenopus; D064248:Geminin; D011994:Recombinant Proteins; D029867:Xenopus Proteins; D003513:Cycloheximide