Juxtaposition of Bub1 and Cdc20 on phosphorylated Mad1 during catalytic mitotic checkpoint complex assembly

• DOI: 10.1101/2022.05.16.492081
• Publication Date: 2022-05-18T09:20:17Z
• Authors: Elyse S. Fischer; Conny W.H. Yu; Johannes F. Hevler; Stephen H. McLaug...; Sarah L. Maslen; Albert J.R. Heck; Stefan M.V. Freund; David Barford
• Keywords: Mad2; Spindle checkpoint; CDC20; BUB1

Abstract In response to improper kinetochore-microtubule attachments in mitosis, the spindle assembly checkpoint (SAC) assembles mitotic complex (MCC) inhibit anaphase- promoting complex/cyclosome, thereby delaying entry into anaphase. The MCC is a of Mad2, Cdc20 and BubR1:Bub3. Its catalysed by unattached kinetochores on catalytic Mad1:Mad2 platform. Mad1-bound closed-Mad2 (C-Mad2) recruits open-Mad2 (O- Mad2) through self-dimerization. This interaction, combined with Mps1 kinase-mediated phosphorylation Bub1 Mad1, accelerates assembly, process that requires conversion O-Mad2 C-Mad2 concomitant binding Cdc20. How Mad1 catalyses poorly understood. this study we characterized obtained structural insights phosphorylation-specific Mad1:Cdc20 interaction. together Mps1-phosphorylation dependent association generates tripartite onto C- terminal domain (Mad1 CTD ). We additionally identified folded state suggests how Cdc20:Mad1 interaction brings Mad2- interacting motif (MIM) (Cdc20 MIM ) close proximity O-Mad2. also show sufficient catalyse Mad2 its entrapment safety- belt. Thus, Mps1-dependent formation MCC-assembly scaffold functions position orient near O-Mad2, catalysing C-Mad2:Cdc20.