FBXO34 Regulates the G2/M Transition and Anaphase Entry in Meiotic Oocytes.

Bing-Wang Zhao,Ying-Chun Ouyang,Zhen-Bo Wang,Wen-Long Lei,Ke Xu,Qing-Yuan Sun,Yuan-Yuan Li,Li Li,Sai-Li Liu,Si-Min Sun

doi:10.3389/fcell.2021.647103

Abstract

There are two important events in oocyte meiotic maturation, the G2/M transition and metaphase I progression. Thousands of proteins participate in regulating oocyte maturation, which highlights the importance of the ubiquitin proteasome system (UPS) in regulating protein synthesis and degradation. Skp1–Cullin–F-box (SCF) complexes, as the best characterized ubiquitin E3 ligases in the UPS, specifically recognize their substrates. F-box proteins, as the variable adaptors of SCF, can bind substrates specifically. Little is known about the functions of the F-box proteins in oocyte maturation. In this study, we found that depletion of FBXO34, an F-box protein, led to failure of oocyte meiotic resumption due to a low activity of MPF, and this phenotype could be rescued by exogenous overexpression of CCNB1. Strikingly, overexpression of FBXO34 promoted germinal vesicle breakdown (GVBD), but caused continuous activation of spindle assembly checkpoint (SAC) and MI arrest of oocytes. Here, we demonstrated that FBXO34 regulated both the G2/M transition and anaphase entry in meiotic oocytes.

Highlights

The life of sexual reproduction originates from fertilized egg, the zygote of oocyte, and sperm after fertilization (Stitzel and Seydoux, 2007)
Mammalian oocytes mature with the involvement of thousands of proteins, many of which later follow the cytoplasm into the fertilized egg and participate in the subsequent life activities, such as zygotic gene activation and embryogenesis (Zhang et al, 2009; Wang et al, 2010)
F-box protein family contains almost 70 members (Skaar et al, 2009) that consist of cell-cycle regulators, DNA replication factors, cyclin-dependent kinase inhibitors, transcription factors, and so on (Kipreos and Pagano, 2000)

Summary

Introduction

The life of sexual reproduction originates from fertilized egg, the zygote of oocyte, and sperm after fertilization (Stitzel and Seydoux, 2007). Oocytes provide almost all cytoplasmic components for fertilization (Matzuk et al, 2002). With the separation of homologous chromosomes, the oocytes accomplish the progression of the first meiosis, and after the first polar body extrusion, oocytes stagnate in the metaphase of the second meiosis (MII) (Jones, 2004; Tripathi et al, 2010; Fabritius et al, 2011), awaiting the arrival of the sperm and the occurrence of fertilization. The G2/M transition of meiosis, which is the resumption of meiosis, requires activation of maturation promoting factor (MPF) (Adhikari et al, 2012). There are two important components of MPF, the regulatory subunit CCNB1 ( known as cyclin B1) and the catalytic subunit CDK1

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Conclusion