The spindle checkpoint prevents aneuploidy by delaying anaphase onset until all sister chromatids achieve proper microtubule attachment. The kinetochore-bound checkpoint protein complex Mad1-Mad2 promotes the conformational activation of Mad2 and serves as a catalytic engine of checkpoint signaling ...
The spindle checkpoint prevents aneuploidy by delaying anaphase onset until all sister chromatids achieve proper microtubule attachment. The kinetochore-bound checkpoint protein complex Mad1-Mad2 promotes the conformational activation of Mad2 and serves as a catalytic engine of checkpoint signaling. How Mad1 is targeted to kinetochores is not understood. Here, we report the crystal structure of the conserved C-terminal domain (CTD) of human Mad1. Mad1 CTD forms a homodimer and, unexpectedly, has a fold similar to those of the kinetochore-binding domains of Spc25 and Csm1. Nonoverlapping Mad1 fragments retain detectable kinetochore targeting. Deletion of the CTD diminishes, does not abolish, Mad1 kinetochore localization. Mutagenesis studies further map the functional interface of Mad1 CTD in kinetochore targeting and implicate Bub1 as its receptor. Our results indicate that CTD is a part of an extensive kinetochore-binding interface of Mad1, and rationalize graded kinetochore targeting of Mad1 during checkpoint signaling.
Related Citations:
Protein metamorphosis: the two-state behavior of Mad2. Luo, X., Yu, H. (2008) Structure 16: 1616
The Mad2 spindle checkpoint protein has two distinct natively folded states. Luo, X., Tang, Z., Xia, G., Wassmann, K., Matsumoto, T., Rizo, J., Yu, H. (2004) Nat Struct Mol Biol 11: 338
The Mad2 spindle checkpoint protein undergoes similar major conformational changes upon binding to either Mad1 or Cdc20. Luo, X., Tang, Z., Rizo, J., Yu, H. (2002) Mol Cell 9: 59
Organizational Affiliation:
Department of Pharmacology, University of Texas Southwestern Medical Center, 6001 Forest Park Road, Dallas, TX 75390, USA.
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