title: Recognizing chromosomes in trouble: association of the spindle checkpoint protein Bub3p with altered kinetochores and a unique defective centromere.
abstract: Spindle checkpoint proteins monitor the interaction of the spindle apparatus with the kinetochores, halting anaphase even if the microtubule attachment of only a single chromosome is altered. In this study, we show that Bub3p of Saccharomyces cerevisiae, an evolutionarily conserved spindle checkpoint protein, exhibits distinct interactions with an altered or defective kinetochore(s). We show for the first time that green fluorescent protein-tagged S. cerevisiae Bub3p (Bub3-GFP) exhibits not only a diffuse nuclear localization pattern but also forms distinct nuclear foci in unperturbed growing and G(2)/M-arrested cells. As Bub3-GFP foci overlap only a subset of kinetochores, we tested a model in which alterations or defects in kinetochore or spindle integrity lead to the distinct enrichment of Bub3p at these structures. In support of our model, kinetochore-associated Bub3-GFP is enriched upon activation of the spindle checkpoint due to nocodazole-induced spindle disassembly, overexpression of the checkpoint kinase Mps1p, or the presence of a defective centromere (CEN). Most importantly, using a novel approach with the chromatin immunoprecipitation (ChIP) technique and genetically engineered defective CEN [CF/CEN6(Delta31)], we determined that Bub3-GFP can associate with a single defective kinetochore. Our studies represent the first comprehensive molecular analysis of spindle checkpoint protein function in the context of a wild-type or defective kinetochore(s) by use of live-cell imaging and the ChIP technique in S. cerevisiae.
authors.affiliation: Genetics Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, 8901 Wisconsin Avenue, Bethesda, MD 20889-5101, USA.
authors.forename: Oliver
authors.initials: O
authors.lastname: Kerscher
authors.forename: Luciana B
authors.initials: LB
authors.lastname: Crotti
authors.forename: Munira A
authors.initials: MA
authors.lastname: Basrai
mesh_terms: D001483:Base Sequence; D002453:Cell Cycle / Q000187:drug effects / Q000235:genetics*; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D002467:Cell Nucleus / Q000235:genetics / Q000378:metabolism; D002503:Centromere / Q000235:genetics / Q000378:metabolism*; D015825:Chromosomes, Fungal; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D015966:Gene Expression Regulation, Fungal; D049452:Green Fluorescent Proteins; D018386:Kinetochores / Q000378:metabolism*; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D015739:Nocodazole / Q000494:pharmacology; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D008941:Spindle Apparatus / Q000378:metabolism / Q000502:physiology
chemical_list: C070352:BUB3 protein, S cerevisiae; C081071:CBF2 protein, S cerevisiae; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D008164:Luminescent Proteins; D011994:Recombinant Proteins; D029701:Saccharomyces cerevisiae Proteins; D049452:Green Fluorescent Proteins; D011494:Protein Kinases; D011505:Protein-Tyrosine Kinases; C090464:Bub1 spindle checkpoint protein; D017346:Protein Serine-Threonine Kinases; C093416:MPS1 protein, S cerevisiae; D015739:Nocodazole