14-3-3 epsilon prevents G2/M transition of fertilized mouse eggs by binding with CDC25B

Abstract

BackgroundThe 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.ResultsDisruption 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.ConclusionsOur 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.

Response of Mouse Zygotes Treated with Mild Hydrogen Peroxide as a Model to Reveal Novel Mechanisms of Oxidative Stress‐Induced Injury in Early Embryos

“…Those remind us that γ H2AX may involve in DNA damage response to regulate cell cycle in zygotes with oxidative-stress damage, too. We may learn that normal zygotes mediate G2/M by protein kinase A (PKA), WEE1B, 14-3-3 ε , and M-phase promoting factors [ 39 – 41 ]. But the specific molecular pathways regulate cell cycle of normal zygotes and zygotes with oxidative-stressed damage are unclear, and whether DNA damage in zygotes activates cascade of ATM → Chk1 → Cdc25B/Cdc25C during G2/M to repair the damage depends on our further study.…”

Low-dose radiation differentially regulates protein acetylation and histone deacetylase expression in human coronary artery endothelial cells

“…14-3-3 proteins form a family of highly conserved proteins capable of binding to more than 200 different, mostly phosphorylated proteins, involved in cellular processes such as cell cycle, apoptosis, and cellular adhesion (Cui et al 2014, Heverin et al 2012, Niemantsverdriet et al 2008, Zuo et al 2010. Acetylation of conserved lysine residues in 14-3-3 proteins is necessary for the binding of phosphoproteins and thereby for proper functioning (Choudhary, et al 2009).…”

YWHA (14-3-3) protein isoforms and their interactions with CDC25B phosphatase in mouse oogenesis and oocyte maturation

“…It is necessary to examine all YWHA isoforms when examining the regulation of CDC25B. Some previous reports on oocyte and egg YWHA protein interaction with CDC25B have examined only several of the YWHA isoforms [43, 59]. We also note here, that by FRET analysis, that there is a strong interaction between exogenously expressed mouse YWHAH and CDC25B, that suggests binding between the two proteins.…”