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Molecular mechanism of Mad1 kinetochore targeting by phosphorylated Bub1.

Published version
Peer-reviewed

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Abstract

During metaphase, in response to improper kinetochore-microtubule attachments, the spindle assembly checkpoint (SAC) activates the mitotic checkpoint complex (MCC), an inhibitor of the anaphase-promoting complex/cyclosome (APC/C). This process is orchestrated by the kinase Mps1, which initiates the assembly of the MCC onto kinetochores through a sequential phosphorylation-dependent signalling cascade. The Mad1-Mad2 complex, which is required to catalyse MCC formation, is targeted to kinetochores through a direct interaction with the phosphorylated conserved domain 1 (CD1) of Bub1. Here, we present the crystal structure of the C-terminal domain of Mad1 (Mad1CTD ) bound to two phosphorylated Bub1CD1 peptides at 1.75 Å resolution. This interaction is mediated by phosphorylated Bub1 Thr461, which not only directly interacts with Arg617 of the Mad1 RLK (Arg-Leu-Lys) motif, but also directly acts as an N-terminal cap to the CD1 α-helix dipole. Surprisingly, only one Bub1CD1 peptide binds to the Mad1 homodimer in solution. We suggest that this stoichiometry is due to inherent asymmetry in the coiled-coil of Mad1CTD and has implications for how the Mad1-Bub1 complex at kinetochores promotes efficient MCC assembly.

Description

Funder: Gates Cambridge Trust; Id: http://dx.doi.org/10.13039/501100005370

Keywords

Bub1, Cell cycle, Mad1, Mitotic checkpoint complex, Spindle assembly checkpoint, Cell Cycle Proteins, Chromosome Segregation, Kinetochores, Mad2 Proteins, Phosphorylation, Signal Transduction, Spindle Apparatus

Journal Title

EMBO Rep

Conference Name

Journal ISSN

1469-221X
1469-3178

Volume Title

Publisher

Springer Science and Business Media LLC
Sponsorship
UKRI | Medical Research Council (MRC) (MC_UP_1201/6)
Cancer Research UK (CRUK) (C576/A14109)