title: BUBR1 and closed MAD2 (C-MAD2) interact directly to assemble a functional mitotic checkpoint complex.
abstract: The mitotic checkpoint maintains genomic stability by ensuring that chromosomes are accurately segregated during mitosis. When the checkpoint is activated, the mitotic checkpoint complex (MCC), assembled from BUBR1, BUB3, CDC20, and MAD2, directly binds and inhibits the anaphase-promoting complex/cyclosome (APC/C) until all chromosomes are properly attached and aligned. The mechanisms underlying MCC assembly and MCC-APC/C interaction are not well characterized. Here, we show that a novel interaction between BUBR1 and closed MAD2 (C-MAD2) is essential for MCC-mediated inhibition of APC/C. Intriguingly, Arg(133) and Gln(134) in C-MAD2 are required for BUBR1 interaction. The same residues are also critical for MAD2 dimerization and MAD2 binding to p31(comet), a mitotic checkpoint silencing protein. Along with previously characterized BUBR1-CDC20 and C-MAD2-CDC20 interactions, our results underscore the integrity of the MCC for its activity and suggest the fundamental importance of the MAD2 αC helix in modulating mitotic checkpoint activation and silencing.
authors.affiliation: Department of Biological Sciences, University of Toledo, Toledo, Ohio 43606, USA.
authors.forename: Aaron R
authors.initials: AR
authors.lastname: Tipton
authors.forename: Kexi
authors.initials: K
authors.lastname: Wang
authors.forename: Laura
authors.initials: L
authors.lastname: Link
authors.forename: John J
authors.initials: JJ
authors.lastname: Bellizzi
authors.forename: Haomin
authors.initials: H
authors.lastname: Huang
authors.forename: Tim
authors.initials: T
authors.lastname: Yen
authors.forename: Song-Tao
authors.initials: ST
authors.lastname: Liu
mesh_terms: D000705:Anaphase; D064173:Anaphase-Promoting Complex-Cyclosome; D002135:Calcium-Binding Proteins / Q000378:metabolism*; D018797:Cell Cycle Proteins / Q000378:metabolism*; D019281:Dimerization; D005786:Gene Expression Regulation; D020868:Gene Silencing; D006367:HeLa Cells; D006801:Humans; D064246:Mad2 Proteins; D008297:Male; D008938:Mitosis; D011467:Prostate / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D012097:Repressor Proteins / Q000378:metabolism*; D008941:Spindle Apparatus / Q000378:metabolism; D014162:Transfection; D043743:Ubiquitin-Protein Ligase Complexes / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism
chemical_list: D002135:Calcium-Binding Proteins; D018797:Cell Cycle Proteins; C577697:MAD2L1 protein, human; D064246:Mad2 Proteins; D012097:Repressor Proteins; D043743:Ubiquitin-Protein Ligase Complexes; D064173:Anaphase-Promoting Complex-Cyclosome; D044767:Ubiquitin-Protein Ligases; C584277:BUB1 protein, human; C090464:Bub1 spindle checkpoint protein; D017346:Protein Serine-Threonine Kinases