title: Ectopic expression of plasma membrane targeted subunits of the Ndc80-complex as a tool to study kinetochore biochemistry.
abstract: Genomic stability depends on the normal function of the kinetochore, a multi-protein assemblage, which consists of over 80 molecules including both constitutive and transiently binding components. Information regarding the spatial-temporal assembly of kinetochore subcomplexes is often limited by technical difficulties in their isolation. To study kinetochore subcomplex formation, we targeted separately Hec1 and Spc24, two subunits of the Ndc80 kinetochore compilation, to the plasma membrane by fusing them with the amino-terminal palmitoylation and myristoylation (pm) sequence of the receptor tyrosine kinase Fyn. We found that in early mitotic cells, pm-GFP-Hec1 and pm-GFP-Spc24 fusion proteins localised to the plasma membrane and were able to recruit all subunits of the Ndc80 complex (Ndc80/Hec1, Nuf2, Spc24 and Spc25) to these foci. In interphase cells, only Hec1-Nuf2 and Spc24-Spc25 heterodimers accumulated to the plasma membrane foci. The results propose that the assembly of Ndc80 tetramer can take place outside of the kinetochore but requires co-factors that are only present in mitotic cells. These findings provide the first experimental evidence on the successful employment of the plasma membrane targeting technique in the study of kinetochore biochemistry.
authors.affiliation: State Technical Research Centre VTT, Medical Biotechnology, 20521 Turku, Finland; Centre for Biotechnology, University of Turku, 20520 Turku, Finland.
authors.forename: Tim H
authors.initials: TH
authors.lastname: Holmström
authors.forename: Jonathan
authors.initials: J
authors.lastname: Rehnberg
authors.forename: Leena J
authors.initials: LJ
authors.lastname: Ahonen
authors.forename: Marko J
authors.initials: MJ
authors.lastname: Kallio
mesh_terms: D002462:Cell Membrane / Q000235:genetics / Q000378:metabolism*; D003598:Cytoskeletal Proteins; D015870:Gene Expression; D042822:Genomic Instability / Q000235:genetics; D006367:HeLa Cells; D006801:Humans; D018386:Kinetochores / Q000378:metabolism*; D054878:Lipoylation / Q000235:genetics; D008938:Mitosis / Q000235:genetics; D046912:Multiprotein Complexes / Q000235:genetics / Q000378:metabolism*; D009687:Nuclear Proteins / Q000096:biosynthesis* / Q000235:genetics; D055503:Protein Multimerization
chemical_list: D003598:Cytoskeletal Proteins; D046912:Multiprotein Complexes; C120529:NDC80 protein, human; D009687:Nuclear Proteins