Aneuploidy in Oocytes Is Prevented by Sustained CDK1 Activity through Degron Masking in Cyclin B1.
Successful mitosis requires that cyclin B1:CDK1 kinase activity remains high until chromosomes are correctly aligned on the mitotic spindle. It has therefore been unclear why, in mammalian oocyte meiosis, cyclin B1 destruction begins before chromosome alignment is complete. Here, we resolve this paradox and show that mouse oocytes exploit an imbalance in the ratio of cyclin B1 to CDK1 to control CDK1 activity; early cyclin B1 destruction reflects the loss of an excess of non-CDK1-bound cyclin B1 in late prometaphase, while CDK1-bound cyclin B1 is destroyed only during metaphase. The ordered destruction of the two forms of cyclin B1 is brought about by a previously unidentified motif that is accessible in free cyclin B1 but masked when cyclin B1 is in complex with CDK1. This protects the CDK1-bound fraction from destruction in prometaphase, ensuring a period of prolonged CDK1 activity sufficient to achieve optimal chromosome alignment and prevent aneuploidy.
['Levasseur|Mark D|MD|', 'Thomas|Christopher|C|', 'Davies|Owen R|OR|', 'Higgins|Jonathan M G|JMG|', 'Madgwick|Suzanne|S|']
D000782:Aneuploidy D000818:Animals D016203:CDC2 Protein Kinase D018797:Cell Cycle Proteins D056744:Cyclin B1 D018844:Cyclin-Dependent Kinases D005260:Female D008540:Meiosis D051379:Mice D008938:Mitosis D009865:Oocytes D008941:Spindle Apparatus
aneuploidy oocyte degron cyclin B1 meiosis APC/C Cdc20 chromosome segregation proteostasis spindle checkpoint