title: Dissecting the roles of human BUB1 in the spindle assembly checkpoint.
abstract: Mitotic chromosome segregation is initiated by the anaphase promoting complex/cyclosome (APC/C) and its co-activator CDC20 (forming APC/C(CDC20)). APC/C(CDC20) is inhibited by the spindle assembly checkpoint (SAC) when chromosomes have not attached to spindle microtubules. Unattached kinetochores catalyze the formation of a diffusible APC/C(CDC20) inhibitor that comprises BUBR1 (also known as BUB1B), BUB3, MAD2 (also known as MAD2L1) and a second molecule of CDC20. Recruitment of these proteins to the kinetochore, as well as SAC activation, rely on the mitotic kinase BUB1, but the molecular mechanism by which BUB1 accomplishes this in human cells is unknown. We show that kinetochore recruitment of BUBR1 and BUB3 by BUB1 is dispensable for SAC activation. Unlike its yeast and nematode orthologs, human BUB1 does not associate stably with the MAD2 activator MAD1 (also known as MAD1L1) and, although required for accelerating the loading of MAD1 onto kinetochores, BUB1 is dispensable for the maintenance of steady-state levels of MAD1 there. Instead, we identify a 50-amino-acid segment that harbors the recently reported ABBA motif close to a KEN box as being crucial for the role of BUB1 in SAC signaling. The presence of this segment correlates with SAC activity and efficient binding of CDC20 but not of MAD1 to kinetochores.
authors.affiliation: Molecular Cancer Research, University Medical Center Utrecht, Utrecht 3584 CG, The Netherlands.
authors.forename: Mathijs
authors.initials: M
authors.lastname: Vleugel
authors.affiliation: Molecular Cancer Research, University Medical Center Utrecht, Utrecht 3584 CG, The Netherlands.
authors.forename: Tim A
authors.initials: TA
authors.lastname: Hoek
authors.affiliation: Molecular Cancer Research, University Medical Center Utrecht, Utrecht 3584 CG, The Netherlands Theoretical Biology and Bioinformatics, Department of Biology, Science Faculty, Utrecht University, Utrecht 3584 CH, The Netherlands.
authors.forename: Eelco
authors.initials: E
authors.lastname: Tromer
authors.affiliation: Molecular Cancer Research, University Medical Center Utrecht, Utrecht 3584 CG, The Netherlands.
authors.forename: Tale
authors.initials: T
authors.lastname: Sliedrecht
authors.affiliation: Molecular Cancer Research, University Medical Center Utrecht, Utrecht 3584 CG, The Netherlands.
authors.forename: Vincent
authors.initials: V
authors.lastname: Groenewold
authors.affiliation: Molecular Cancer Research, University Medical Center Utrecht, Utrecht 3584 CG, The Netherlands.
authors.forename: Manja
authors.initials: M
authors.lastname: Omerzu
authors.affiliation: Molecular Cancer Research, University Medical Center Utrecht, Utrecht 3584 CG, The Netherlands Cancer Genomics Netherlands, University Medical Center Utrecht, Utrecht 3584 CG, The Netherlands g.j.p.l.kops@umcutrecht.nl.
authors.forename: Geert J P L
authors.initials: GJ
authors.lastname: Kops
mesh_terms: D064199:Cdc20 Proteins / Q000235:genetics* / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D020090:Chromosome Segregation / Q000235:genetics; D006801:Humans; D018386:Kinetochores / Q000378:metabolism; D059566:M Phase Cell Cycle Checkpoints / Q000235:genetics*; D008938:Mitosis / Q000235:genetics; D009687:Nuclear Proteins / Q000235:genetics; D000075223:Poly-ADP-Ribose Binding Proteins; D017346:Protein Serine-Threonine Kinases / Q000235:genetics* / Q000378:metabolism; D008941:Spindle Apparatus / Q000235:genetics
chemical_list: C489444:BUB3 protein, human; D064199:Cdc20 Proteins; D018797:Cell Cycle Proteins; C501384:MAD1L1 protein, human; D009687:Nuclear Proteins; D000075223:Poly-ADP-Ribose Binding Proteins; C577488:CDC20 protein, human; C584277:BUB1 protein, human; D017346:Protein Serine-Threonine Kinases
keywords: BUB1; Kinetochores; Mitosis; Spindle assembly checkpoint