title: Hsp90-Sgt1 and Skp1 target human Mis12 complexes to ensure efficient formation of kinetochore-microtubule binding sites.
abstract: The formation of functional kinetochores requires the accurate assembly of a large number of protein complexes. The Hsp90-Sgt1 chaperone complex is important for this process; however, its targets are not conserved and its exact contribution to kinetochore assembly is unclear. Here, we show that human Hsp90-Sgt1 interacts with the Mis12 complex, a so-called keystone complex required to assemble a large fraction of the kinetochore. Inhibition of Hsp90 or Sgt1 destabilizes the Mis12 complex and delays proper chromosome alignment due to inefficient formation of microtubule-binding sites. Interestingly, coinhibition of Sgt1 and the SCF subunit, Skp1, increases Mis12 complexes at kinetochores and restores timely chromosome alignment but forms less-robust microtubule-binding sites. We propose that a balance of Mis12 complex assembly and turnover is required for the efficient and accurate assembly of kinetochore-microtubule binding sites. These findings support a novel role for Hsp90-Sgt1 chaperones in ensuring the fidelity of multiprotein complex assembly.
authors.affiliation: The Section of Molecular and Cellular Biology, University of California, Davis, Davis, CA 95616, USA.
authors.forename: Alexander E
authors.initials: AE
authors.lastname: Davies
authors.forename: Kenneth B
authors.initials: KB
authors.lastname: Kaplan
mesh_terms: D001665:Binding Sites; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D002868:Chromosomal Proteins, Non-Histone / Q000235:genetics / Q000378:metabolism; D018841:HSP90 Heat-Shock Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D018386:Kinetochores / Q000378:metabolism* / Q000648:ultrastructure; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism*; D008870:Microtubules / Q000378:metabolism*; D046912:Multiprotein Complexes / Q000378:metabolism*; D011485:Protein Binding; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D044843:SKP Cullin F-Box Protein Ligases / Q000235:genetics / Q000378:metabolism*
chemical_list: D018797:Cell Cycle Proteins; D002868:Chromosomal Proteins, Non-Histone; C532764:DSN1 protein, human; D018841:HSP90 Heat-Shock Proteins; C492664:MIS12 protein, human; D008869:Microtubule-Associated Proteins; D046912:Multiprotein Complexes; D034741:RNA, Small Interfering; D011993:Recombinant Fusion Proteins; C490164:SUGT1 protein, human; D044843:SKP Cullin F-Box Protein Ligases
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