title: Sgt1 associates with Hsp90: an initial step of assembly of the core kinetochore complex.
abstract: The kinetochore, which consists of DNA sequence elements and structural proteins, is essential for high-fidelity chromosome transmission during cell division. In budding yeast, Sgt1, together with Skp1, is required for assembly of the core kinetochore complex (CBF3) via Ctf13 activation. Formation of the active Ctf13-Skp1 complex also requires Hsp90, a molecular chaperone. We have found that Sgt1 interacts with Hsp90 in yeast. We also have determined that Skp1 and Hsc82 (a yeast Hsp90 protein) bind to the N-terminal region of Sgt1 that contains tetratricopeptide repeat motifs. Results of sequence and phenotypic analyses of sgt1 mutants strongly suggest that the N-terminal region containing the Hsc82-binding and Skp1-binding domains of Sgt1 is important for the kinetochore function of Sgt1. We found that Hsp90's binding to Sgt1 stimulates the binding of Sgt1 to Skp1 and that Sgt1 and Hsp90 stimulate the binding of Skp1 to Ctf13, the F-box core kinetochore protein. Our results strongly suggest that Sgt1 and Hsp90 function in assembling CBF3 by activating Skp1 and Ctf13.
authors.affiliation: Department of Molecular Pharmacology, St. Jude Children's Research Hospital, 332 N. Lauderdale St., Memphis, TN 38105, USA.
authors.forename: Parmil K
authors.initials: PK
authors.lastname: Bansal
authors.forename: Rashid
authors.initials: R
authors.lastname: Abdulle
authors.forename: Katsumi
authors.initials: K
authors.lastname: Kitagawa
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D016227:Benzoquinones; D025141:Drug Resistance, Fungal / Q000235:genetics; D044783:F-Box Proteins / Q000378:metabolism; D018841:HSP90 Heat-Shock Proteins / Q000378:metabolism*; D006360:Heat-Shock Proteins / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D018386:Kinetochores / Q000378:metabolism*; D047029:Lactams, Macrocyclic; D008954:Models, Biological; D018832:Molecular Chaperones / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D009687:Nuclear Proteins / Q000378:metabolism; D010641:Phenotype; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011809:Quinones / Q000494:pharmacology; D012097:Repressor Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D044843:SKP Cullin F-Box Protein Ligases / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D016227:Benzoquinones; C081354:CTF13 protein, S cerevisiae; D044783:F-Box Proteins; C074510:HSP82 protein, S cerevisiae; D018841:HSP90 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D047029:Lactams, Macrocyclic; D018832:Molecular Chaperones; D009687:Nuclear Proteins; D011809:Quinones; D012097:Repressor Proteins; C470726:SGT1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D044843:SKP Cullin F-Box Protein Ligases; C120507:SKP1 protein, S cerevisiae; C001277:geldanamycin