p31comet blocks Mad2 activation through structural mimicry.
The status of spindle checkpoint signaling depends on the balance of two opposing dynamic processes that regulate the highly unusual two-state behavior of Mad2. In mitosis, a Mad1-Mad2 core complex recruits cytosolic Mad2 to kinetochores through Mad2 dimerization and converts Mad2 to a conformer amenable to Cdc20 binding, thereby facilitating checkpoint activation. p31(comet) inactivates the checkpoint through binding to Mad1- or Cdc20-bound Mad2, thereby preventing Mad2 activation and promoting the dissociation of the Mad2-Cdc20 complex. Here, we report the crystal structure of the Mad2-p31(comet) complex. The C-terminal region of Mad2 that undergoes rearrangement in different Mad2 conformers is a major structural determinant for p31(comet) binding, explaining the specificity of p31(comet) toward Mad1- or Cdc20-bound Mad2. p31(comet) adopts a fold strikingly similar to that of Mad2 and binds at the dimerization interface of Mad2. Thus, p31(comet) exploits the two-state behavior of Mad2 to block its activation by acting as an "anti-Mad2."
Yang
Maojun
M
Department of Pharmacology, The University of Texas Southwestern Medical Center, 6001 Forest Park Road, Dallas, TX 75390, USA.
Li
Bing
B
Tomchick
Diana R
DR
Machius
Mischa
M
Rizo
Josep
J
Yu
Hongtao
H
Luo
Xuelian
X
D048868:Adaptor Proteins, Signal Transducing / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D000494:Allosteric Regulation; D000595:Amino Acid Sequence; D000818:Animals; D002135:Calcium-Binding Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D002453:Cell Cycle / Q000502:physiology; D018797:Cell Cycle Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D018360:Crystallography, X-Ray; D006801:Humans; D064246:Mad2 Proteins; D008958:Models, Molecular; D018716:Molecular Mimicry; D008969:Molecular Sequence Data; D046912:Multiprotein Complexes / Q000737:chemistry / Q000378:metabolism; D015739:Nocodazole / Q000378:metabolism; D009687:Nuclear Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D012097:Repressor Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment; D050257:Tubulin Modulators / Q000378:metabolism
D048868:Adaptor Proteins, Signal Transducing; D002135:Calcium-Binding Proteins; D018797:Cell Cycle Proteins; C577697:MAD2L1 protein, human; C470309:MAD2L1BP protein, human; D064246:Mad2 Proteins; D046912:Multiprotein Complexes; D009687:Nuclear Proteins; D012097:Repressor Proteins; D050257:Tubulin Modulators; D015739:Nocodazole