Molecular mechanism of APC/C activation by mitotic phosphorylation

摘要: In eukaryotes, the anaphase-promoting complex (APC/C, also known as cyclosome) regulates ubiquitin-dependent proteolysis of specific cell-cycle proteins to coordinate chromosome segregation in mitosis and entry into G1 phase. The catalytic activity APC/C its ability specify destruction particular at different phases cell cycle are controlled by interaction with two structurally related coactivator subunits, Cdc20 Cdh1. Coactivators recognize substrate degrons, enhance affinity for cognate E2 (refs 4-6). During mitosis, cyclin-dependent kinase (Cdk) polo-like (Plk) control Cdc20- Cdh1-mediated activation APC/C. Hyperphosphorylation notably Apc1 Apc3, is required activate APC/C, whereas phosphorylation Cdh1 prevents association Since both coactivators associate through their common C-box Ile-Arg tail motifs, mechanism underlying this differential regulation unclear, role sites. Here, using cryo-electron microscopy biochemical analysis, we define molecular basis how human allows Cdc20. An auto-inhibitory segment acts a switch that apo unphosphorylated interacts binding site obstructs engagement Phosphorylation displaces it from C-box-binding site. Efficient segment, thus relief auto-inhibition, requires recruitment Cdk-cyclin Cdk regulatory subunit (Cks) hyperphosphorylated loop Apc3. We find small-molecule inhibitor, tosyl-l-arginine methyl ester, preferentially suppresses APC/C(Cdc20) rather than APC/C(Cdh1), sites motifs. Our results reveal mitotic provide rationale development selective inhibitors state.