title: 14-3-3 epsilon prevents G2/M transition of fertilized mouse eggs by binding with CDC25B.
abstract: BACKGROUND
  The 14-3-3 (YWHA) proteins are highly conserved in higher eukaryotes, participate in various cellular signaling pathways including cell cycle regulation, development and growth. Our previous studies demonstrated that 14-3-3ε (YWHAE) is responsible for maintaining prophase | arrest in mouse oocyte. However, roles of 14-3-3ε in the mitosis of fertilized mouse eggs have remained unclear. Here, we showed that 14-3-3ε interacts and cooperates with CDC25B phosphorylated at Ser321 regulating G2/M transition of mitotic progress of fertilized mouse eggs.
  
  
  RESULTS
  Disruption of 14-3-3ε expression by RNAi prevented normal G2/M transition by inhibition of MPF activity and leaded to the translocation of CDC25B into the nucleus from the cytoplasm. Overexpression of 14-3-3ε-WT and unphosphorylatable CDC25B mutant (CDC25B-S321A) induced mitotic resumption in dbcAMP-arrested eggs. In addition, we examined endogenous and exogenous distribution of 14-3-3ε and CDC25B. Endogenous 14-3-3ε and CDC25B were co-localized primarily in the cytoplasm at the G1, S, early G2 and M phases whereas CDC25B was found to accumulate in the nucleus at the late G2 phase. Upon coexpression with RFP-14-3-3ε, GFP-CDC25B-WT and GFP-CDC25B-S321A were predominantly cytoplasmic at early G2 phase and then GFP-CDC25B-S321A moved to the nucleus whereas CDC25B-WT signals were observed in the cytoplasm without nucleus accumulation at late G2 phase at presence of dbcAMP.
  
  
  CONCLUSIONS
  Our data indicate that 14-3-3ε is required for the mitotic entry in the fertilized mouse eggs. 14-3-3ε is primarily responsible for sequestering the CDC25B in cytoplasm and 14-3-3ε binding to CDC25B-S321 phosphorylated by PKA induces mitotic arrest at one-cell stage by inactivation of MPF in fertilized mouse eggs.
authors: Cheng
authors: C
authors: Cui
authors: Xiuli
authors: X
authors: Ren
authors: Dajun
authors: D
authors: Liu
authors: Xin
authors: X
authors: Deng
authors: Xin
authors: X
authors: Qin
authors: Xiangyu
authors: X
authors: Zhao
authors: Enhua
authors: E
authors: Wang
authors: Bingzhi
authors: B
authors: Yu
mesh_terms: D048948:14-3-3 Proteins / Q000235:genetics* / Q000378:metabolism*; D000818:Animals; D002453:Cell Cycle; D002467:Cell Nucleus / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D046149:Embryo Culture Techniques; D004622:Embryo, Mammalian / Q000166:cytology; D005260:Female; D008297:Male; D000090204:Mesothelin; D051379:Mice; D010766:Phosphorylation; D034622:RNA Interference; D015053:Zygote / Q000378:metabolism*; D020687:cdc25 Phosphatases / Q000378:metabolism*
chemical_list: D048948:14-3-3 Proteins; C000715528:Msln protein, mouse; C576823:Ywhae protein, mouse; D017868:Cyclic AMP-Dependent Protein Kinases; C517006:Cdc25b protein, mouse; D020687:cdc25 Phosphatases; D000090204:Mesothelin