title: The Bub1-Plk1 kinase complex promotes spindle checkpoint signalling through Cdc20 phosphorylation.
abstract: The spindle checkpoint senses unattached kinetochores and inhibits the Cdc20-bound anaphase-promoting complex or cyclosome (APC/C), to delay anaphase, thereby preventing aneuploidy. A critical checkpoint inhibitor of APC/C(Cdc20) is the mitotic checkpoint complex (MCC). It is unclear whether MCC suffices to inhibit all cellular APC/C. Here we show that human checkpoint kinase Bub1 not only directly phosphorylates Cdc20, but also scaffolds Plk1-mediated phosphorylation of Cdc20. Phosphorylation of Cdc20 by Bub1-Plk1 inhibits APC/C(Cdc20) in vitro and is required for checkpoint signalling in human cells. Bub1-Plk1-dependent Cdc20 phosphorylation is regulated by upstream checkpoint signals and is dispensable for MCC assembly. A phospho-mimicking Cdc20 mutant restores nocodazole-induced mitotic arrest in cells depleted of Mad2 or BubR1. Thus, Bub1-Plk1-mediated phosphorylation of Cdc20 constitutes an APC/C-inhibitory mechanism that is parallel, but not redundant, to MCC formation. Both mechanisms are required to sustain mitotic arrest in response to spindle defects.
authors.affiliation: Department of Pharmacology, Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, 6001 Forest Park Road, Dallas, Texas 75390, USA.
authors.forename: Luying
authors.initials: L
authors.lastname: Jia
authors.affiliation: Department of Pharmacology, Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, 6001 Forest Park Road, Dallas, Texas 75390, USA.
authors.forename: Bing
authors.initials: B
authors.lastname: Li
authors.affiliation: Department of Pharmacology, Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, 6001 Forest Park Road, Dallas, Texas 75390, USA.
authors.forename: Hongtao
authors.initials: H
authors.lastname: Yu
mesh_terms: D064173:Anaphase-Promoting Complex-Cyclosome / Q000378:metabolism*; D064199:Cdc20 Proteins / Q000235:genetics / Q000378:metabolism*; D018797:Cell Cycle Proteins / Q000235:genetics*; D045744:Cell Line, Tumor; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D006367:HeLa Cells; D006801:Humans; D015151:Immunoblotting; D047468:Immunoprecipitation; D066298:In Vitro Techniques; D018386:Kinetochores / Q000378:metabolism; D059566:M Phase Cell Cycle Checkpoints / Q000187:drug effects / Q000235:genetics*; D064246:Mad2 Proteins; D009154:Mutation; D015739:Nocodazole / Q000494:pharmacology; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000235:genetics*; D011518:Proto-Oncogene Proteins / Q000235:genetics*; D015398:Signal Transduction; D050257:Tubulin Modulators / Q000494:pharmacology; D054875:Ubiquitination; D000097869:Polo-Like Kinase 1
chemical_list: D064173:Anaphase-Promoting Complex-Cyclosome; D064199:Cdc20 Proteins; D018797:Cell Cycle Proteins; D064246:Mad2 Proteins; D015739:Nocodazole; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D050257:Tubulin Modulators; D000097869:Polo-Like Kinase 1; C577697:MAD2L1 protein, human; C577488:CDC20 protein, human; C584277:BUB1 protein, human