CDK1-PP2A-B55 interplay ensures cell cycle oscillation via Apc1-loop300

Cell cycle control relies on a delicate balance of phosphorylation with CDK1 and phosphatases like PP1 and PP2A-B55. Yet, identifying the primary substrate responsible for cell cycle oscillations remains a challenge. We uncover the pivotal role of phospho-regulation in the anaphase-promoting complex/cyclosome (APC/C), particularly through the Apc1-loop300 domain (Apc1-300L), orchestrated by CDK1 and PP2A-B55. Premature activation of PP2A-B55 during mitosis, induced by Greatwall kinase depletion, leads to Apc1-300L dephosphorylation, stalling APC/C activity and delaying Cyclin B degradation. This effect can be counteracted using the B55-specific inhibitor pEnsa or by removing Apc1-300L. We also show Cdc20’s dynamic APC/C interaction across cell cycle stages, but dephosphorylation of Apc1-300L specifically inhibits further Cdc20 recruitment. Our study underscores APC/C’s central role in cell cycle oscillation, identifying it as a primary substrate regulated by the CDK-PP2A partnership. [Display omitted] •PP2A-B55 opposes CDK1 by dephosphorylating the Apc1-loop300 domain on the APC/C•Premature activation of PP2A-B55 during mitosis stalls APC/C activity•Cdc20 dynamically interacts with mitotic APC/C, essential for its activation•Dephosphorylated Apc1-loop300 domain prevents dynamic association of Cdc20 to APC/C Chia et al. reveal PP2A-B55’s crucial role in APC/C phospho-regulation, showing that its mitotic activation leads to APC/C inactivation by blocking Cdc20’s binding via Apc1-loop300 dephosphorylation. This discovery emphasizes the CDK-PP2A axis’s pivotal role in controlling cell cycle oscillation through APC/C regulation.