The Function And Regulation Of Nucleolar Protein DCAF13 During Oocyte Growth And Meiotic Maturation

In clinic,premature ovarian failure(POF)is one of the common causes of infertility.The qulity of oocytes and follicular development was important for female fertility.However,the molecular mechanisms that regulate the follicular development and survival are not well known.In this study,we used oocyte-expressed Cre to specifically delete Dcaf13 in oocytes to investigate the protein accumulation in oogenesis,oocyte meiotic maturation,to demonstrate the mechanisms of oocyte maintenance and female fertility.During mammalian oocyte growth,ehromatin configuration transition from the nonsurrounded nucleolus(NSN)to surrounded nucleolus(SN)type plays a key role in the regulation of gene expression and acquisition of meiotic and developmental competence by the oocyte.Nonetheless,the mechanism underlying chromatin configuration maturation in oocytes is poorly understood.Here we show that nucleolar protein DCAF13 is an important component of the ribosomal RNA(rRNA)-processing complex and is essential for oocyte NSN-SN transition in mice.A conditional knockout of Deaf13 in oocytes led to the arrest of oocyte development in the NSN configuration,follicular atresia,premature ovarian failure,and female sterility.The DCAF13 deficiency resulted in pre-rRNA accumulation in oocytes,whereas the total mRNA level was not altered.Further exploration showed that DCAF13 participated in the 18S rRNA processing in growing oocytes.The lack of 18S rRNA because of DC AF13 deletion caused a ribosome assembly disorder and then reduced global protein synthesis.DCAF13 interacted with a protein of the core box C/D ribonucleoprotein,fibrillarin,i.e.,a factor of early pre-rRNA processing.When fibrillarin was knocked down in the oocytes from primary follicles,follicle development was inhibited as well,indicating that an rRNA processing defect in the oocyte indeed stunts ehromatin configuration transition and follicle development.We have proved that DCAF13,as a nucleolar protein,plays a key role for follicle growth.It also as a cullin ring-finger ubiquitin ligase 4(CRL4)adaptor ensures preimplantation embryonic development.Then we carefully investigated the meiotic maturation process in Dcaf13-deleted oocytes.Dcaf1 3 knockout in oocyes caused decreased MPF activity and impaired meiotic cell cycle progression including GV arrest,delayed GVBD,and chromosome condensation defects.As a result,chromosomes fail to be properly aligned at the spindle middle plate,the spindle assembly checkpoint is activated,and most Deaf1 3 null oocytes are arrested at the prometaphase Ⅰ.In addition,insufficient accumulation of CDC20 proteins also impairs the activation of anaphase promoting complex(APC)and prevents the metaphase-to-anaphase transition in meiosis I,We also found that CRL4BDCAF13 E3 ligase could target PTEN for polyubiquitination and degradation during meiotic resumption,which can improve the activation of AKT that is involved in CDK1 activation.Our research reveals that nucleolar protein DCAF13 plays a vital role for protein accumulation during oocyte grouth.We also invesgated that the function of CRL4DCAF13 in meiotic maturation.It provides the physiological proof for exploring the meehanism of rRNA processing and a theoretical support for clinical research on the mechanism and treatment of POF.